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CONSTRUCTORS1 DESIGNS OF SEVERAL
NUMBER ^ NEW RECEIVERS
Who Owns Our Radio Sets?
How A Broadcasting Station Is Run
Doubleday, Page & Co.
Garden City, N. T.
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RADIO
TUBES
Since 1915 — Standard for All Sets
TYPES, C-3OIA-C-299-C-3OO-C-11-C-12,
IN THE ORANGE AND BLUE CARTON
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Chicago
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if Tested and approved by RADIO BROADCAST
New York
Bound
MA 13 '26
RADIO BROADCAST
VOLUME VIII
NOVEMBER, 1925, to APRIL, 1926
GARDEN CITY NEW YORK
DOUBLEDAY, PAGE & COMPANY
1926
INDEX
("Illustrated Articles. Editorials in Italics)
* A . C. Receiver and Power Amplifier,
-fl An (James Millen) 57
Additional Opinions About the Naval
Radio Service 552
*All-Purpose Coil Winder, An (Edward
Thatcher) 582
*" Aristocrat":
*" Aristocrat," The Radio
Broadcast (Arthur H. Lynch) 28
*" Aristocrat" Receiver, The. . . 664
*" Aristocrat" Receiver, The:
Resistance-Coupled Amplifi-
cation 196
*As the Broadcaster Sees It (Carl
Dreher) 45, 191, 326, 467, 568, 672
*Audio Amplification, Better (Kendall
Clough) 308
Australian Broadcasting Stations, A
List of 224
BEST in Current Radio Periodicals,
The (E. G. Shalkhauser) 88
*Better Audio Amplification (Kendall
Clough) 308
Blooper? Is Your Set a 238
Book Reviews:
"Economics of the Radio In-
dustry" 514
"Radio: Beam and Broadcast". 388
Booklet of Foreign Broadcasting Sta-
tions, "Radio Broadcast's" (Law-
rence W. Corbett) 465
Broadcast Listeners Organize 555
*Broadcast Receiver, A Model 1926
(Me Murdo Silver) 36
Broadcast Relaying, The Progress of. . .. 24
*AN We Forecast Radio Reception
from the Weather? (J. C. Jen-
sen) 558
Canada As Our Instructor 170
Canada, How They Run Radio in 655
*Cone Loud Speaker, Improving the. . . 50
Conferences, A Year of 26
"•Controlling Oscillation in Radio Fre-
quency Circuits, Methods of (John
Bernard) 350
Convention, The Institute of Radio En-
gineers 653
Current Radio Periodicals, The Best in
(E. G. Shalkhauser) 88
*Current Supply Unit, An Improved
(Roland F. Beers) 186
"Cutting Out the Locals (H. E. Rhodes) 686
iESIGN of Radio Inductances (W.
W. Harper) 436
Detroit Has a Good Radio Supervisor . . . 433
ECONOMICS of the Radio Indus-
try" (Book Review) 514
*Ether Waves You Cannot Hear (James
Stokley) 295
Ethics of Radio Advertising, The 434
ACTS About the Farmer and Radio,
The 170
"Filament Resistance, The Use of the
(John Brennan) 682
*First Report on the International
Tests, The (Willis K. Wing) 588
$500 Short Wave Receiver Contest, The 657
"Five-Tube Receiver for the Inexperi-
enced Constructor, An Improved
(A. H. Fulton, Jr.) 51
"Five-Tube Receiver of Dual Efficiency,
A (Glenn H. Browning) ............
Fourth National Radio Conference, What
Happened at the ................... 431
172
, The:
VJ Aristocrat Values ........ 376
C Batteries in the Detector Cir-
cuit ...................... 484
Coil Placement in an R. F.
Amplifier ................. 226
Condensers in Series and Paral-
lel ........................ 698
Eliminating the Reflex in the
Roberts Circuit ............ 696
Explaining Static and Fading. . 72
Explanation of Tuning, An .... 482
How to Charge Storage Batter-
ies from D. C .............. 596
How to Obtain Better Regen-
eration .................... 482
Impedance Amplifiers ........ 378
Impedance Coupled Amplifier,
An ....................... 700
Loop Construction ........... 84
Making Your Own Grid Leaks 596
Measuring the Resistance of
Coil Units ................. 228
New Tubes and Their Charac-
teristics ................... 596
Noises and Their Causes ...... 376
One Dial Loop Receiver ....... 594
Precautions in Antenna Erec-
tion ...................... 226
Protecting the Loud Speaker. .. 484
Receiver Coil Resistance ...... 84
Separate R. F. Tube Voltage
from B Battery Eliminator ... 594
Substituting Toroid Coils in
Neutrodynes .............. 86
Tubes and R. F. Coils: How
They Should be Matched in a
Receiver .................. 228
"Universal" Receiver Coils. . . . 696
"Grimes Inverse Duplex, How to Build
a (Florian J. Fox) ................. 439
HIGH-SPEED Fading ............. 392
History of the Vacuum Tube,
The Fascinating .................. 300
"Home Laboratory, Standards for the
(Keith Henney) ................... 573
"How a Portable B Battery Transmit-
ter Works (Laboratory Staff) ....... 678
""How Long Will My B Batteries
Last?" (George C. Furness) ........ 452
"How Radio Grew Up (Robert H. Mar-
riott) .......................... 159,643
How Radio Has Improved ............ 303
How They Run Radio in Canada ...... 655
"How to Build a Grimes Inverse Duplex
(Florian J. Fox) ................... 439
"How to Eliminate Local Interferencel02, 212
"How to Use Meters in Your Receiver
(James Millen) ................... 198
"How to Use Vacuum Tubes (Keith
Henney) ......................... 456
IF YOU Seek Economy, Buy the Best
(Harold Jolliffe) ................. 360
"Improved Five-Tube Receiver for the
Inexperienced Constructor, An (A. H.
Fulton, Jr.) ....................... 51
"Improved Plate Current Supply Unit,
An (Roland F. Beers) .............. 186
PAGE
"Improving the Cone Speaker 50
Institute of Radio Engineers Convention,
The 653
Interesting Things Said Interestingly
27, 171, 304, 435, 557, 656
International Tests:
"First Report on the Interna-
tional Tests, The (Willis K.
Wing) 588
"International Radio Broadest-
ing Tests, The 1926 (Willis K.
Wing) 462
"Plans for the Third of the In-
ternational Radio Broadcast
Tests (Arthur H. Lynch) .... 185
Recent International Radio
Broadcast Tests, The 654
What Happened During the
1926 International Tests
(Willis K. Wing) 647
Is the Loop or Antenna Receiver More
Popular! 433
Is Your Set a Blooper? 238
K
EY to Recent Radio Articles, A
(E. G. Shalkhauser)
88, 232, 380, 504, 608, 710
555
T ANGMUIR Patent, A Note on the . . .
•I-* Late News on the International
Tests (Willis K. Wing) 299
Legal Test Case for our Radio Laws, A.. 652
"Light Keepers, Radio Sets for 666
List of Australian Broadcasting Sta-
tions, A 224
"Listeners' Point of View, The (Kings-
ley Welles) 32, 177
"Listeners' Point of View, The (John
Wallace) 317, 445, 577, 667
"TV/TAN and His Hobby, A (E. E.
ivi Horine) 547
"March of Radio, The (J. H. More-
croft) 23, 167, 300, 431, 552, 652
"Methods of Controlling Oscillation in
Radio Frequency Circuits (John
Bernard) 350
"Model 1926 Broadcast Receiver, A
(Me Murdo Silver) 36
Month in Radio, The
26, 170, 304, 434, 556, 656
More Information on Super Power 169
More Millions for Radio 555
"Multiple Regeneration Can Do For
Your Tuned R. F. Amplifier, What
(V. D. Landon) 563
T^TATIONAL Association of Broad-
•L V casters 168
National Radio Council? Shall We
Have A 23
Naval Radio Service, Additional Opin-
ions About the 552
Naval Radio Service? What is the Mat-
ter With the 167
*New Fields for the Home Constructor
(Keith Henney) 201
"New in Radio? What's (Austin C.
Lescarboura) 305
New Short Wave Ray Is Discovered, A.. 433
"New Way to Make Money in Radio, A
(D. C. Wilkerson) '. 606
News on the International Tests, Late
(Willis K. Wing) 299
Note on the Langmuir Patent, A 555
INDEX— Continued
*Notes on the Model 1926 Receiver
(Ernest R. Pfaff) 313
*"Now, I Have Found":
Better Reproduction in Cone
Speakers (William C. Morrill) 702
Checking Up On B Battery
Leakage (Claude Schuder). . . 210
Coil Design Data (Boris S.
Naimark) 488
Coupling Device for the Roberts
Circuit, A (Clarence J.
Frenck) 208
Cylindrical Coils for the Knock-
out Set (L. O. Doran) 374
Description of a New NP Coil
for the Roberts Receiver
(Ralph D. Tygert) 66
Economical Sub-Panel Brackets
(R.L.Douglas) 706
Efficient Coil Covering the
Broadcasting Frequencies
(W. H. Mayfield) 70
File for Ideas, A (F. E. Kunkel) 208
Good Audio Amplifier, A (Ed-
ward T. Werden) 490
Good Audio By-Pass Method,
A (Jerome Kidder) 600
Good Neutralizing Condenser
for the Roberts Circuit, A
(H. A. Franchere) 68
Handy Battery Throw-Over
Switch (Bernard Salzberg) ... 706
Home-Made Coil Winder for
Diamondweave Coils (R. S.
Hart) 704
Home-Made Loud Speaker, A
(J. T. Carver) 364
How to Make Balloon Coils
(John L. Lee) 600
How to Obtain Improved Loud
Speaker Reproduction (Boris
S. Naimark) 602
How to Provide a Counterpoise
System (J. B. Greenman) .... 702
Improving the Volume of the
Two-Tube Roberts Circuit
(J. W. Teale) 492
Lead-in Problem, A (G. A.
Luers) 70
Low Loss Coil, A (Everett Free-
land) 602
Measuring High Resistance
(Claude Schuder) 66
One Use for a Bypass Condenser
(K. B. Humphrey) 604
Ratchet Coil Winder Prevents
Unwinding, A (G. A. Luers). 206
Roberts Circuit and Audio
Amplifier Without a Storage
Battery, The (J B. Clothier,
Jr.) 362
Short Waves on the Hanscom
Super-Heterodyne (A. T.
Hanscom) 68
Simple Long- Wave Receiver, A
(H. H. Buckwalter) 490
Some Notes on Silver's Model
1926 Receiver with Choke
Amplification (Davenport
Hooker) 702
Storage Battery, The (J. B.
Clothier, Jr.) 362
Tracing Radio Noises (A. H.
Klingbeil) 206
Using a Voltmeter As a Milliam-
meter (Claude Schuder) 488
Variometer to Tune Antenna
Circuit of the Roberts Set, A
(John L. Lee) 210
Winding Spider Web Coils
(H. Edward Knies) 492
O
,FFICIAL Indiscretion, An" . . 653
PHOTO-ELECTRIC Cell? Who
Invented the 555
*Plans for the Third of the International
Radio Broadcast Tests (Arthur H.
Lynch) 185
*Portable B Battery Transmitter
Works, How a (Laboratory Staff) ... 678
Praiseworthy Bit of Radio Research, A.. . 431
Prize Contest Announcement 444
Progress of Broadcast Relaying, The .... 24
Progress of Radio in 1925, The 553
Pure Science Becomes Practical 302
*"DADIO Broadcast "Aristocrat,"
IV The (Arthur H. Lynch) 28
Radio Broadcast's Booklet of Call Sig-
nals (Lawrence W. Corbett) 337
Radio Broadcast's Booklet of Foreign
Broadcasting Stations (Lawrence W.
Corbett) 465
Radio Broadcast's Universal Receiver
(Arthur H. Lynch) 332
Radio Broadcast's Universal Receiver.. 450
Radio Business As Others See It, The. . . 25
*" Radio Central" — Conqueror of Time
and Distance (Fred. J. Turner) 41
Radio Control for Railroads 432
Radio for 1926: A Forecast 24
*Radio Grew Up, How (Robert H. Mar-
riott) 643
*Radio Sets for Light Keepers 666
*Radio: The Jungleman's Newspaper
(John W. Swanson) 427
Recent International Radio Broadcast
Tests, The 654
C<HALL We Have a National Radio
O Council? 23
Short Wave Ray Is Discovered, A New. . 433
Short Wave Receiver Contest, The $500 640
Short Wave Stations 9f the World 708
*Short Wave Transmitter, A Universal
(Nicholas Hagemann) 321
*Short Waves — A New Paradise for the
DX Fan (Edgar H. Felix) 182
Short Waves Are Growing Shorter 303
Standards for the Home Laboratory
(Keith Henney) 573
"Straight Line Frequency" Condenser
Means, What the 23
*Super-Heterodyne Construction (Har-
old C. Websr) 589
*'T>HEY Shut the Door on Fortune
-1- (C. S. Thompson) 19
"Tube and Its Best Uses, The (Keith
Henney) 658
"TTNIVERSAL RECEIVER, Radio
U Broadcast's (Arthur H. Lynch) 332
"Universal Receiver, Radio Broadcast's 450
*Uniyersal Short- Wave Transmitter, A
(Nicholas Hagemann) 321
*Use of the Filament Resistance, The
(John B. Brennan) 682
TSACUUM Tube, The Fascinating
r History of the 300
*Vacuum Tubes, How to Use (Keith
Henney) 456
^WAVELENGTH-FREQUENCY
VV Chart 472
'Wavelength-Frequency Conversion
(Homer S. Davis) 471
What Constitutes a Radio Patent? (Leo
T. Parker) 494
*What Do We Know About Short
Waves? (Keith Henney) 54
What Happened at the Fourth National
Radio Conference 431
*What Happened During the 1926 In-
ternational Tests (Willis K. Wing) . . . 647
*What's New In Radio (Austin C. Les-
carboura) 305
What Is the Matter With the Naval Radio
Service? 167
*What Multiple Regeneration Can Do
for Your Tuned R. F. Amplifier (V.
D. Landon) 563
What Our Readers Write Us
110, 244, 394, 518, 618, 716
What the Australians Think of Their
Broadcasting 653
What the "Straight Line Frequency" Con-
denser Means 23
*When the Doctor Came to the Faral-
lones — by Radio (Lewis N. Waite) ... 63
Who Invented the New Photo-Electric
Cell? 555
*Winner of Our $500 Prize Cover Con-
test, The 100
PORTRAITS
(*Portraits in "The March of Radio")
*Arlin, H. W 24
Arnoldi, Florence Long 33
Branly, Edouard 643
Brees, Anton 445
Cadman, S. Parkes 319
Damrosch, Walter 667
De Forest, Lee 21
Diefendorf, William 669
*Dill, C. C 171
*Dubilier, William 304
Eckersley, E. P. . 434
Elliott, Frank W 177
*Fessenden, Reginald A 656
Golden, Ernie 34
*Hammond, John Hayes, Jr 303
Hansen, Cecilia 667
"Hayes, Cardinal 171
*Hazeltine, L. A 27
*Hogan, John V. L 27
Homer, Louise 178
*Housekeper, William G 25
Kemp, C. S 645
Kent, A. Atwater 178, 556
*Kordi, I. H 303
*Langmuir, Irving 304
Lopez, Vincent
Ludlow, Godfrey 34
McLeod, Keith 34
MacNamee, Graham 319
Marconi, Guglielmo 644
Marriott, Robert H 159
Maude, Cyril 578
Mazarin, Mariette 32
Miura, Tamaki 579
Ryan, Quin A 319
*Saltzman, Charles Me K 557
Sargent, Jean 33
Seidel, Toscha 178
*Shaw, Charles Gray 435
Smith, Fred 669
Stock, Frederick 579
Tesla, Nikola 644
Walsh, Edmund A.. . 447
Werrenrath, Reinald 178
*West, A. G. D 656
Wiley, Louis 181
Zendonini, Elizab3th 22
*Zworykin, V. K 302
AUTHORS
Beers, Roland F 186
Bernard, John 350
Brennan, John B 682
Browning, Glenn H 172
Buckwalter, H. H 490
Clothier, John B. Jr. . . 362
INDEX.— Continued
Clough, Kendall 308
Corbett, Lawrence W 337, 465
Davis, Homer S 471
Doran, L. 0 374
Douglas, R. L 706
Dreher, Carl 45, 191, 321, 467, 568, 672
Felix, Edgar H. . . 182
Fox, Florian J 439
Franchere, H. A 68
Freeland, Everett 602
Frenck, Clarence J 208
Fulton, A. H., Jr 51
Furness, George C 452
Carver, J. T 364
Greenman, J. B 702
Hagemann, Nicholas ' . . . 321
Hanscom, A. T 68
Harper, W. W 436
Hart, R. S 704
Henney, Keith. . . .54, 163, 201, 456, 573, 658
PAfiE
Hooker, Davenport 702
Humphrey, K. B. . . 634
Jensen, J. C. . . 558
Jolliffe, Harold 360
Kidder, Jerome . . 600
Klingbeil, A. H. 206
Knies, H. Edward 492
Kunkel, F. E 208
Landon, V. D. . . 563
Lee, John L 210, 600
Lescarboura, Austin C 305
Luers, G. A 70, 206
Lynch, Arthur H 28, 185, 332
Marriott, Robert H.. . ..159,643
Mayfield, W. H 70
Millen, James 57, 198
Morecroft, J. H.
23, 167, 300, 388, 431, 552, 652
Morrill, William C 702
Naimark, Boris S.. . . .488, 692
PACE
Parker, Leo T 494
Pfaff, Ernest R 313
Rhodes, H. E 686
Salzberg, Bernard . . 706
Schuder, Claude 66, 210, 488
Shalkhauser, E. G.88, 232, 380, 504, 608, 710
Silver, McMurdo 36
Stokley, James 295
Suggs, I.T 210
Swanson, John W 427
Teale, J. W. . . 492
Thatcher, Edward 582
Thompson, C. S 19
Turner, Fred J 41
Tygert, Ralph D 66
Waite, Lewis N. . . 63
Wallace, John 317, 445, 577. 667
Weber, Harold C 589
Welles, Kinsley 32, 177
Werden, Edward T 490
Wilkerson, D. C 606
Wing, Willis K 299, 462, 588, 647
Copyright, 1926, by
DOUBLEDAY, PAGE & COMPANY
RADIO BROADCAST ADVERTISER
13
ai the Loos Brothers
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Tested and approver) bv RADIO BROADCAST
RADIO BROADCAST
ARTHUR H. LYNCH, Editor
WILLIS K. WING, Associate Editor
JOHN B. BRENNAN, Technical Editor
NOVEMBER, 1925
Vol. VII, No. 1
BEHIND THE EDITORIAL
Cover Design - From a Painting by Fred J. Edgars
England's Greatest Broadcasting Station Frontispiece
They Shut the Door on Fortune - C. S. Thompson
The March of Radio - - - - - J. H. Morecroft
The Radio Broadcast "Aristocrat"
Arthur H. Lynch
The Listeners' Point of View - - Kingsley Welles
A Model 1926 Broadcast Receiver McMurdo Silver
"Radio Central" — Conqueror of Time and Distance
Fred /. Turner
As the Broadcaster Sees It - - - - Carl Dreher
Improving the Cone Loud Speaker - - - - - -
An Improved Five' Tube Receiver for the Inexperi-
enced Constructor - - ' - A. H. Fulton, Jr.
What Do We Know Aboxit Short Waves?
Keith Henney
An A. C. Receiver and Power Amplifier
James Millen
When the Doctor Came to the Farallones — by Radio
Lewis 7S[. Waite
"Now, I Have Found ..."
Measuring High Resistance — A New NP Coil for the Roberts Receiver —
A Good Neutralising Condenser — Short Waves on the Hanscom Super-
Heterodyne — Solving a Lead-in Problem— An Efficient Coil
The Grid — Questions and Answers ''"'*'
Some Facts About Static and Fading — Why Coils Work on One Fre-
quency Better Than Another — How to Build a Loop — Substituting Toroid
Coils in Neutrodynes
The Best in Current Radio Periodicals
E. D. Shalfyuser
The Winner of Our $500 Prise Cover Contest -
How To Eliminate Local Interference - - * * *
What Our Readers Write Us
72
88
100
102
110
A~\ TE ARE proud to present the new RADIO BROADCAST which
"' in quality of appearance and contents speaks for itself,
and we are confident that all our readers will feel the same as
one enthusiastic subscriber who was in the office the other day
and to whom we showed the plans of the new RADIO BROADCAST.
"Why," said he, "there is nothing in the radio field to equal
RADIO BROADCAST now that you have increased its size and suc-
ceeded in turning out a magazine of the splendid quality of this
November number."
In this issue are described four complete receivers, any or all of
them good enough to please the heart of the most discriminating of
constructors. The RADIO BROADCAST "Aristocrat" is a single-
control set with resistance coupling; Mr. Millen's receiver and
power amplifier is the first one to be described employing impor-
tant new developments with a.c. audio power amplifiers for the
home constructor. The other articles are worthy of distinct
attention each on its own merits.
TV/f R- C. S. THOMPSON, the author of the interesting piece
•"•*• about Doctor Deforest, was for many years closely as-
sociated with him and knows whereof he speaks. Mr. Fred
Turner, whose '"Radio Central' — Conqueror of Time and Dis-
tance" appears in this number, is a broadcast speaker whose
"Trips and Adventures" are familiar to WEAF and wjz listeners.
Readers who have been following the interesting discussion in
Carl Dreher's department regarding the merits of so-called "super
power" will read with great interest the concluding arguments in
this word-battle. Those who have been curious about the
internal human machinery of a great broadcasting station should
read Mr. Dreher's leading article on page 45.
In the following numbers of the magazine, there will be
articles of great interest to every one who follows radio. To
make a confession, because of lack of space for many months,
the editors have had to leave out almost as much material as ap-
peared in the magazine. That embarrassment of riches means
that the reader can be confident of some mighty good mater al in
every number. One of the" most interesting of the articles due to
appear as soon as space can be made is by Roland F. Beers on "How
to Build an Improved Plate Supply Unit" employing the new
Raytheon tube, an improved "S" tube. The article is very
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RADIO BROADCAST ADVERTISER
17
"Quality Is Season's Watchword"
"Fidelity of Tone Production Will Be Greatest Public Demand
this Fall"— Radio Retailing, issue of August, 1925.
Radio Retailing asked one
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A graph from August issue of Radio Retailing,
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ENGLAND'S GREATEST BROADCASTING STATION
Three unusual views of the new high-power station of the British Broadcasting Company at Daventry. The top view (© Barratt's)
shows the twin 500-foot masts with the station building in the center, silhouetted against the cloudy English sky. The illustra-
tion in the oval insert, which at first sight might be mistaken for the interior of the great hall in a castle, shows a corner of the
transmitter house. The illustration below shows the eight generators necessary to supply the 25,000 watts for the transmitter.
Programs are sent out on 187 kc. (1600 meters) and can be heard throughout a large part of England with only a crystal receiver
RADIO BROADCAST
VOLUME VIII
NUMBER 1
NOVEMBER, 1925
IKS*
They Shut the Door on Fortune
"Only a Toy," said the Wise Ones, of the Audion, and They Gave No Support to
the "Aladdin's Lamp" of Radio — Some Important Incidents Hitherto Unpublished
in the Life of Dr. Lee DeForest, Inventor of the Three-Element Vacuum Tube
By C S. THOMPSON
O
N THE sands behind the coral
reefs of Washington Island, in
the Pacific South Seas, a thou-
sand miles southwest of Hono-
lulu, an audion bulb was picked up some
years ago. Bits of water-soaked wood, a
rusty spike, a length or so of frayed rope
were not uncommon on the beach, but the
audion bulb was something new in flot-
sam. Here the audion turned up on the
shore of an island 900 miles west of the
nearest steamer lane.
There was a radio telegraph station at
Washington Island. R. A. Travers was
the operator. He saw the audion bulb and
recognized the handiwork of the inventor,
and that night put the bulb in the mail,
with the following letter:
Washington Island,
Via Honolulu and Fanning Island.
Decembei I, 1919.
"Dr. Lee DeForest,
New York City,
U. S. A.
DEAR DR. DEFOREST:
I am sending you by parcels post an interest-
ing valve 1 believe to be one of your pre-war
types. . . . This valve traveled many miles
through the Pacific ocean, bobbed over a coral
reef, and came to rest on the sands of this is-
land. . . . Washington Island is a wee
spot in the wide Pacific, having less than a
dozen miles of coast. . . . From wreck-
age picked up from time to time, it appears
drifting objects come from the eastward. . . .
I believe this valve will be of interest in your
collection.
R. A. TRAVERS."
Doctor DeForest, at his laboratory, did
find the bulb to be one of his own pre-war
types. The story of this "lost audion" set
his imagination working.
"If I could spend a couple of months,"
he said, "away from all cares on a paradise
> Paul Thompson
THE DEFOREST
AUDION
The three-element tubes
familiar to every radio
listener to-day look
much different from this
early commercial form of
the "audion." The per-
fection of this innocent-
appearing little bulb
brought the only real
"revolution" that radio
has ever enjoyed. It
brought fame to the ex-
perimenters who discov-
ered its possibilities, for-
tune to others — and
lawsuits without num-
ber, and the end is not yet
island in the South Seas, 1 could doubtless
compose my soul sufficiently to write a
poem worthy of the theme, but our New
York subway is not conducive to poetic
rhapsodies. There has been altogether too
little poetry on radio from its beginning,
but perhaps the poetry has been in the ac-
complishment itself."
The frail glass bulb, safe on the labora-
tory table at Highbridge, incidentally
suggested to DeForest the story of his
invention for so many dark years laughed
at and scorned as a useless toy by in-
vestigating lawyers, telephone experts,
men of science, engineers, captains of in-
dustry and their capitalists. Doctor De-
Forest's early experiences merely repeated
the story of the flying machine, the loco-
motive, the moving pictuie, the talking
machine, the power-driven car, the sub-
marine, all, in their early stages, merely
wild tales of the imagination fit only for
the readers of a Jules Verne.
It was in the summer of 1912, already
having lost two fortunes, that DeForest,
at work on a meagre salary in California,
went to the president of the company to
borrow $125. DeForest wanted
the money to perpetuate the life
of audion patents held by him in
France. In payment, he offered
half his interest in the French
rights. The president heard the
offer but thought it too much of a
gamble and then, to the despair
of the inventor, the rights reverted
to the French Government. Then
came the war, and the audion took
its place as the very heart of radio
communication. Countless bulbs
were supplied to the allied armies
in France.
"One million dollars is a con-
servative estimate of the royalties
20
RADIO BROADCAST
NOVEMBER, 1925
which would have been paid us by the
manufacturers during the period of the
war alone," said DeForest recently. "But,
unfortunately in 1912, my friend the presi-
dent, thinking that I was only dreaming,
withheld his one hundred and twenty-
five."
Was it lack of faith in the dream of the
young inventor, or failure to see the march
of progress? The name of the president
will not go down to future generations.
Nor is it fair to put him in a class by
himself. With him may be named a score
of others who blindly shut the door on
fortune appearing in the guise of our
rather ambitious young inventor. We
might include in this group of mentally
near-sighted the following:
The eminent directors of an early wire-
less telegraph company.
Telephone experts of 1908, 1909, 1910,
1911.
An eminent professor of electrical en-
gineering instructing the student, De-
Forest.
Some well-to-do college classmates.
The executives and attorneys of a leading
American telephone company.
A learned district attorney who solemnly
proclaimed the audion to be a worthless
"piece of glass."
MAKING MODERN VACUUM TUBES
The name of Doctor DeForest is always linked in the mind of the radio man
with the three-element tube, although he was responsible for many other develop-
ments and perfections in radio, most of which had hard financial sledding, as Mr.
Thompson suggests in this article. The early vacuum tube was made in small
quantities and no two of them were electrically alike. This illustration shows how
the more modern types of transmitting tubes are made. The tubes are slowly
pumped out, so that almost no gas remains
It was early in the history of the wireless
telegraph that worldwide recognition was
given DeForest as a pioneer. In this
period of invention came the birth of the
audion. The audion was a lamp about the
size of an Edison bulb.
HOW THE AUDION WAS NAMED
THE tube contained a filament, a grid,
and a plate. DeForest made up a name
for it, he took the word "audio," to hear;
and "ion" meaning one or more electrons,
and combined them into the one word —
"audion," the three-electrode vacuum
tube. It is the "talking" or "listening"
lamp.
The first patent on the audion was as-
signed by DeForest to an early American
wireless company. But this company got
into trouble. Rather than have anything
more to do with them, the inventor turned
in his stock holdings and took in exchange
certain patents which the company con-
sidered of no particular value. Among
these were the first audion patent applica-
tions. How much are the exclusive rights
to these patents worth to-day? Ask these
former directors of the early American
wireless company, or the corporations to-
day operating under the audion patents!
Just about this time, when "some care-
less hand was
tossing aside
the audion"
DeForest ap-
peared before
the New York
Electrical So-
ciety to report
on the devel-
opment of his
lamp. Tele-
phone com-
munication,
in those days,
was limited to
a compara-
tively few
miles. The
Electrical So-
ciety meeting
was widely
advertised,
and among
those present
were tele-
phone engi-
neers. Their
company at
this time had
paid $400,000
for another
device which
they hoped
would aid long
distance oper-
ation. But
this other de-
vice failed to
do the job.
''My ad-
dress," says
DeForest, in
recalling this experience, "included a detailed
description of my numerous patents, even
including one taken out in January, 1907,
for amplifying weak telephone currents.
The audion amplifier patent indicated very
clearly the service that the audion could
perform as a telephone relay or repeater,
the result of experiments which I had been
conducting in the summer of 1906 on the
top floor of the old Parker Building on
Fourth Avenue, in New York. The tele-
phone engineers heard my story but were
skeptical — too skeptical for words. One,
two, three, four years elapsed — years
thrown away. It was not until 1912 that
I at last succeeded, through a friend, in
getting an opportunity to demonstrate
the audion relay before the telephone
company. With the audion, in less than
two years, they opened telephone service
across the continent."
So much for the telephone engineers of
1908, 1909, 1910, and 191 1. Butthesemen
of science were not alone in shutting the
door on the efforts of the young inventor.
"HE WILL NEVER AMOUNT TO ANYTHING"
MANY years earlier along came the
professor of electrical engineering in
the university where DeForest had set
out to write his thesis on the " Reflection
of Hertzian Waves Along Parallel Lines."
One night, while the student was working
in a basement laboratory, the lights in a
classroom went out. DeForest was sus-
pected of having removed the wrong fuse.
Shortly afterwaid the professor discovered
that DeForest had committed the grave
crime of nailing his apparatus to a labora-
tory table. That was too much.
"Any student who will spoil a table like
that," said the professor, "will never
amount to anything."
DeForest pleaded the value of his work
and what he hoped to accomplish, but the
professor was firm, and out went the stu-
dent. He wanted his Ph. D. and at length
succeeded in being enrolled in another de-
partment of the university, where, inci-
dentally, Morse did his early work on the
telegraph. But at least the table was
saved from the earmarks of the "worthless
student."
Recently DeForest, attending a class
reunion, was approached by a friend of
earlier days.
" Is there still any money to be made in
radio?" asked the classmate.
DeForest smiled. "Have you for-
gotten," he said, "not so many years ago
I came to you for the loan of a few hundred
dollars saying there was a fortune to be
made in putting the audion on the mar-
ket?"
"No, Lee," replied the other, ruefully,
" I certainly slammed the door on fortune."
In the year 1917, the telephone com-
pany which paid the first $140,000 for rights
to the audion entered into negotiations for
further patents. The audion in the mean-
time had grown from a mere child of imag-
ination to a good-sized boy. It was being
used in many different ways. It picked up
NOVEMBER, 1925
THEY SHUT THE DOOR ON FORTUNE
21
radio. Last yearthe"amateurtrade"
— so-called — spent nearly four hun-
dred million dollars on "the joke."
"A PIECE OF GLASS — WITHOUT
MERIT"
DERHAPS the first prize in this
* competition for those who blindly
shut the door on the young inventor
should go to that eminent gentleman
who many years ago occupied the
position of district attorney in one of
the Eastern courts. The device con-
ceived by the young inventor chanced
to be an exhibit in a trial of some
corporation directors who proclaimed
it to be a wonderful invention.
They were selling stock in order to
promote the use of the audion in the
world of art, industry, and com-
munication. They had been in-
dicted by the grand jury, together
IN A BROADCASTING STATION
Three-element tubes, whose use was originally discovered by Doctor
Deforest, are used at every stage of both sending and receiving
wireless dots and dashes across the seas.
It carried the human voice on the telephone
wires across continents. It had also en-
tered the business arena as an oscillator.
In other words, it had almost become
a competitor of the huge alternating gen-
erator of our modern power houses. The
sum of $250,000 was finally agreed upon
for the additional rights.
At last the attorneys and officials of the
telephone company were satisfied. One of
them said to the writer:
"We have all there is to have now under
the audion patents."
"Yes," I interposed, "but
not the exclusive right to sell
radio sets to the public. De-
Forest retained that right."
" But what dd^frfii't amount
to?"
To be sure, in 1917, the right
to sell to the "amateur" as it
was designated, meant very
little. In those days radio
broadcasting was a joke. But,
in less than three years, the
country was inoculated with
© Western Newspaper Union
DR. LEE DEFOREST AND HIS "WIRELESS TELEPHONE"
As long ago in radio history as 1919 this outfit was announced to the public as the "last word in wire-
less telephony . . . destined to become quite popular in these uncertain days of telephonic ills."
The vacuum tubes used in this model can be clearly seen. The sketch to the right, above, is a charcoal
drawing of early wireless telephone and telegraph apparatus used by Doctor DeForest at a station in
Washington. Its appearance is quite different from the large broadcast transmitter of to-day
with the inventor, and stood facing a
term in Atlanta.
But listen to the District Attorney:
"They would have us believe," said
he in summing up, "that this little
thing is a wonderful instrument of
science. They are appealing to the pub-
lic to subscribe to their stock. But let
me tell you, gentlemen of the jury,
they are preying on the minds of ignorant
and simple people. This device is with-
out merit. It is not a wonderful inven-
tion. It fails to perform the many mar-
vels they claim for it. It is a piece of
glass which has been built into the form
of a lamp, not to perform scientific
wonders, but to sell stock. I ask, there-
fore, that you bring in a verdict of guilty
for all those who have been concerned
with this palpable fraud."
One or more of the defendants were
found guilty and actually went to the
penitentiary, not altogether, perhaps,
upon the question of the merit of the
"piece of glass" but more likely because
of their misuse of the mails in selling
the stock of the corporation. The in-
ventor was acquitted.
"In the audion," said Edison some
years after the courtroom scene, "De-
22
RADIO BROADCAST
NOVEMBER, 1925
HISTORIC WIRELESS APPARATUS
This view was taken in the DeForest laboratory and shows some early experimental
apparatus. At the left is an early model of a wireless telephone, using an arc instead
of vacuum tubes for power. In the center is a model of a "picture machine" and
at the right a crude receiver. A vacuum tube (inverted) can be seen on the top of
the cabinet
Forest has invented a device which amplifies sound so much
that if a fly were to walk across the transmitter, the noise
at the receiver would shatter your eardrums!"
Had. these various gentlemen no prophetic inkling to stir
their imaginations? Publicly the first radio broadcasting
took place at Put-In-Bay on Lake Erie, July 15, 1907, at
the regatta of the Inter-Lake Yacht Association, when the
reports of the yacht race together with gramophone selec-
tions were reported by radio. Not many months later,
audion bulbs were installed on the radio telephone receiving
apparatus used by the fleet of Admiral "Fighting Bob"
Evans in his noteworthy cruise around the world. Even
as early as 1907, we had plenty of demonstrations of what
might be accomplished in the transmission of news and
music by radio. In May of that year the inventor an-
nounced: "Church music, sermons, lectures, etc., can be
spread abroad by the radio telephone. In rural districts
scores of individual radio telephone services can be main-
tained between widely separated farms, ranches, cross-
road stores, etc. For the distribution of music, the
radio telephone means an enormous increase of patron-
age among music lovers. It will very soon be possible
to distribute grand opera music from transmitters
placed on the stage of the Metropolitan Opera House by
a radio telephone."
Such, in brief, is the tale of "The Lost Audion."
The lamp which to-day, developed by engineering,
makes it possible for your voice to span continents, for
your ear to listen-in to nightly entertainments, or the
spoken words of your president. The lamp which
has made possible multiplex telephony or "wired wire-
less," the transmission of photographs by wire, the
"talking picture," and a thousand and one other mar-
vels of science and industry, eliminating the distance be-
tween nations and making us all one bigger human family.
The first modest "audions" did their work quietly
and well, and no one had the slightest inkling that
the queer little bulb would some day expand radio, in
all its branches, far beyond the sober plans of the
IN AMATEUR STATIONS
Three-element vacuum tubes are widely used. Years ago, in 1912, an employer refused Doctor DeForest
$125 to renew his "audion" patents in France so the rights reverted to the French Government, and perhaps
a fortune was lost. Elizabeth Zandonini, owner of station 3 CDQ, Washington, is shown at her set. She is a
radio aide at the Bureau of Standards
IN THE EXPERIMENTAL DAYS
A portable wireless telephone transmitter
being tested in the fields near Newark,
New Jersey. The operators were never
certain in those days just how far their
signals would travel; uncertainty was the
one certain thing about wireless then. The
outfit is one built by Doctor De Forest
early radio experimenters. Now at
last we may well sing with the poet
of the Pacific:
FLOTSAM
Wave-borne, a fragile thing of glass and
wire
Past the grim reefs that guard a lonely
land
The audion drifted. Balked of its desire.
The spent sea washed it on the level
sand,
But we can fancy countless days you
watched the ships go by —
The months, in idle drifting spent be-
neath a tropic sky!
THE MARCH OF RADIO
Past President, Institute of Radio Engineers
Shall We Have A National Radio Council?
W!
'E HEAR so much about
various organizations nowa-
days, with their innumer-
able committees and sub-
committees, that our natural reaction
toward bringing into existence a new society
is negative. Most of the hours that can be
spared from our necessary daily tasks seem
to be used up in committee meetings and
discussions of one sort or another.
" Don't do it " was our first reaction to a
suggestion for a national radio council
made by the Radio Manufacturers Asso-
ciation. The society is active and in-
fluential; its members constitute many
dependable radio manufacturers. Natur-
ally any activities which bring about an
increased interest in radio will be reflected
in greater sales of apparatus, and it is un-
doubtedly the prime object of the Radio
Manufacturers Association to bring about
just this result.
We can look at the proposal of the Radio
Manufacturers Association in just the same
spirit as we consider the activities of the
National Automobile Chamber of Com-
merce while primarily they are looking out
for their own good, their vision may be
broad enough to take in the idea that any
movement which makes radio more pleasur-
able for the listeners increases their sales to
just the same degree. The elimination of
interference, the improvement of pro-
grams, and all such activities might well be
forwarded by the manufacturers association.
The report of the R. M. A. was evidently
drawn up in the liberal spirit we have al-
luded to. A national radio council is rec-
ommended, whose function is not primar-
ily to bring about increased sales for the
manufacturers but rather to improve the
radio situation as a whole. Among other
things, Mr. Frank Reichmann, chairman of
the R. M. A. committee, says, "We recom-
mend the establishment of a National Radio
Council to be composed of representatives
of the Radio Manufacturers Association,
dealers and jobbers, manufacturers' agents,
the broadcasters, radio publications, and
the listeners.
We are advised that the National Radio
Trades Association, which has done much excel-
lent work in the past, is anxious that the manu-
facturers get behind an organization of the
dealers and jobbers. We understand that the
National Association of Broadcasters is willing
to help in organizing a central council, and we
are assured that we will have the active support
of the two leading listeners' organizations — the
American Radio Association and the Broadcast
Listeners Association of America.
We are also of the opinion that the American
Radio Relay League should be invited to become
a member of the council and we can promise
that the Farm Radio Council will join.
This committee also recommends that the
association take up the matter of further en-
couraging the teaching of radio in all manual
training classes in all public and private schools.
This committee believes that by careful,
conservative action during the coming year a
great deal can be done to cement together all
those interested in radio, to the end that the
industry will be better prepared to repel legisla-
tive and other attacks, and that even greater
public interest in radio will be assured.
What the "Straight Line Fre-
quency" Condenser Means
WI TH the increase in use of the term
frequency, rather than wavelength
in radio broadcasting ideas and
practice, the straight line frequency con-
denser has appeared on the market and
there seems to be considerable misunder-
standing as to what and why it is.
It is not long since we made comment on
the "low loss" condenser, a term which was
invented by some astute radio business man
to increase his sales. As we pointed out at
that time "although some condensers do
actually have lower electrical losses than
others, due to better materials used for
plates and insulation, the difference is so
slight that any one of a dozen reputable
condensers would show up equally well
when connected in a receiving set." The
24
RADIO BROADCAST
NOVEMBER, 1925
H. W. ARLIN
Chief Announcer at station KDKA, East Pittsburgh, holding a
large water-cooled ten kw. transmitting tube in contrast
to the piezo-electric crystal. This quartz crystal has the prop-
erty of vibrating when properly excited at radio frequencies.
It is inserted in the KDKA transmitter and holds the transmitted
frequency very accurately on the proper adjustment
difference in loss of various standard con-
densers is so slight" that accurate 'laboratory
measurements are required to show it.
Not so, however, with the straight line
frequency condenser; the use of such a con-
denser in radio sets is a real advance in the
radio art. The assignment of various
channels to different
broadcasting stations
is made because each
station requires a
definite number of
cycles for its own use;
the proper number
depends upon the
quality of the broad-
cast material, but in
general it may be said
that no station should
be assigned a fre-
quency within ten
kilocycles of another
located sufficiently
close to interfere with
the one in question.
Thus if there were ten
stations in one dis-
trict they would na-
turally be assigned
channels equally
spaced in frequen-
cies, say twenty kilo-
cycles apart, and if
the set being used is
equipped with
straight line fre-
quency condensers
these stations will be
found at equally
spaced points on the
tuning dials. With ordinary
condensers of course this is by
no means possible, for only
one or two stations are found
at the higher points of the
scale, where at the lower end
of the scale the different sta-
tions come in at points so close
together that it is difficult to set
accurately for them. These
new condensers, however, show
one station at 5, another at 10,
another at 15, etc., all the way
up the scale, and their use
makes a set considerably easier
to manipulate.
The Progress of Broad-
cast Relaying
A! ANNOUNCEMENT
from KDKA confesses
that what they call a
new scheme of relaying has
been tried out and found to
be satisfactory. The West-
inghouse station at Hastings,
KFKX, which has been used as
a relay outfit for quite some
time, has ordinarily been oper-
ated on a different frequency
from KDKA, so that any one
midway between Pittsburgh and Nebraska
might receive the same program from either
station, providing he retuned as he wanted
to listen to one station or the other. To
operate both stations at the same fre-
quencies brings in some technical difficul-
ties, according to the engineering staff of
the Westinghouse Company, but recent im-
provements have overcome these troubles
and now they say that both stations may
be operated at the same frequency. The
feat may have more promise than we now
think it has.
It also said that the frequency of KDKA is
now being held constant by the use of a
piece of piezo-electric quartz. As we have
related in these columns before, a small
piece of good quartz crystal, properly cut
and arranged in an electric circuit, will hold
the frequency of oscillation so constant that
no present methods can detect any change.
The use of this frequency fixing scheme of
KDKA seems much more important to us,
as far as the March of Radio is concerned,
than the rebroadcasting stunt mentioned
above and about which such sweeping
claims are made. We are interested to
note that the other Westinghouse stations
are soon to be equipped with quartz fre-
quency stabilizers. This technical advance
might well be followed by many other sta-
tions which evidently experience some
difficulty in maintaining their frequency.
Radio for 1926: A Forecast
c
ARL BUTMAN has just completed
an extensive survey of what the
radio listener wants for 1926. His
findings are in accord with what we have
urged on our readers for quite some time.
The DX fan, the man who continually
manipulates dials to see if he cannot catch
the last letter perhaps of a station 500
miles farther away, is rapidly disappearing.
He was ever a nuisance, this distance seek-
© Harris & Ewing
RADIO DETECTIVE EQUIPMENT ABOARD A RUM CHASER
The radio direction finder installed on the bridge of the CGigS. It is said that many of the rum runners off the American
coast are using radio to help them in their operations. The direction finder, as used by the "Dry Navy," is expected to be
of great aid in locating the rum ships. The large carboy in the foreground supposedly contains distilled water
NOVEMBER, 1925
THE CHANGING RADIO FASHIONS
25
ing fanatic; no sooner had the radio set been
tuned to one station and the call letter
heard than he was off for another. A kind
of sport it was, to be sure, but in the main,
radio is to give entertainment to the family
from stations close at home.
With the slow disappearance of the DX
listener, the survey finds an ever-increasing
demand for quality reception. Many
people are just awakening to the realiza-
tion of how very poor is the quality the
loud speaker delivers and this has resulted
in an insistent demand for faithful repro-
duction. As was said in these columns
many months ago, it is very seldom that a
radio loud speaker leads us to believe that
the speaker is actually in the room and
until this is so the goal, an attainable one,
has certainly not been reached. Any
skilled radio engineer can, if he has suitable
laboratory facilities, develop a set which
will amplify properly throughout the whole
audible scale and from such a set, after the
loud speaker manufacturers have much
improved their product, reasonable quality
may be expected. The present horn is
eventually doomed to the radio scrap pile,
we believe and the diaphragm type or pos-
sibly something better will take its place.
A growing tendency toward simple con-
trol is shown in the new sets and it seems
that two-dial sets will soon predominate in
the market. The simple regenerative re-
ceiver is on the down grade and the tuned
radio frequency five-tube receiver seems to
be the one most favored. It is well to
point out that to get good quality with
loud speaker reception, the ordinary small
tube as used to-day must be done away
with; it cannot possibly deliver enough
power for the ordinary loud speaker to han-
dle. In the new sets we are glad to see a
new typeof tube used in the last audio stage.
Quality is undoubtedly the keynote of
progress for the sets of 1926.
The Radio Business as Others
See It
THE Copper and Brass Research
Organization, whose function is to
compile all information useful to
companies dealing in copper and brass
products, has recently given out a summary
of its investigations of the radio business.
It is interesting to note that the estimate
of the value of the coming year's radio busi-
ness, and number of sets already in use, etc.,
compare quite closely with some other fig-
ures at hand compiled from the past reports
of the Bureau of the Census. The Bureau
reports are not brought up to date because
compilations are made only every two
years.
According to the Copper and Brass As-
sociation, "Manufacture and sale of radio
receivers has established a record for rapid
industrial expansion. In 1922 there were
hardly 100,000 radio sets in use; in 1923
the number had grown to 2,000,000; in
1924 to 3,750,000, and by the end of 1925
it is estimated that the number of sets in
use will reach a total of 5,000,000. The re-
tail value of sets and parts has grown from
$50,000,000 in 1922 to an estimated
$500,000,000 in 1925.
Public interest in radio has gained rapidly
and apparently has continued unabated. Only a
year and a half ago the consumer demand was
far in excess of the manufacturers' ability to
supply. At that time the number of home-made
sets exceeded the factory-made, and there was a
correspondingly large retail market for radio
parts of every description. The last year has
seen the beginning of something like stabiliza-
tion in the industry. The trend of sales is now
away from the home-made set and toward the
set purchased as a complete unit.
The present rate of manufacture, ac-
cording to the Association's survey, indi-
cates that 1925 production will be 2,000,000
sets in which the consumption of copper and
brass will be about 7,750,000 pounds.
These metals are used for antennas, ground
connections, coils, condensers, tube sockets,
panels, and miscellaneous small parts.
The interesting report continues:
Radio now appears to be as universal in its
appeal and as much a necessity as the automo-
bile, so there is no reason to look for any falling
off in sales in the next few years. The radio
purchaser is not only a good customer for tubes,
batteries, plugs, jacks, and other miscellaneous
parts, but almost generally he is ready, after
using a set a year or two, to scrap it and replace
it with another which has a more stylish cabinet
or a newer "hook-up" or more tubes. Conse-
quently both replacement and new set markets
increase together with the market for parts and
accessories.
A review by Mr. Carl Butman of Wash-
ington suggests the interesting note that in
1923 the average price of a radio outfit was
$16, in 1924 it was $50, and to-day it is a
hundred dollars or more. This higher
priced equipment is not going to the high-
salaried city dweller only, but the agri-
cultural communities also show the same
evidence of giving up the old five-dollar
home-made set in favor of one which per-
forms more reliably and has a more pleas-
ing appearance.
Both of the reports place the probable
number of receiving sets in the United
States for 1926 as five million or over.
When nation-wide broadcasts are carried
out next year, therefore, it is evident that
the potential audience is certainly measured
in the millions, possibly ten or even more.
© Bell Telephone Laboratories
WILLIAM G. HOUSEKEPER
An engineer of the Bell Telephone Laboratories who was recently awarded the John Scott Medal
by the City of Philadelphia for his contribution to technical progress. The award carried with
it a f 1000 prize. Mr. Housekeper was responsible for the metal-glass seal in large vacuum
tubes. Previous to his discovery, it had been almost impossible to make large vacuum
tubes because of the difficulty of bringing out large leads through the glass. Mr. Housekeper
is here shown in his laboratory with one of the large tubes. Note how small the lead wire is made
just where it passes through the glass
26
RADIO BROADCAST
NOVEMBER, 1925
A Year of Conferences
THE International Radio Conference,
many times delayed, is now to be held
in Washington next spring. Not
since the last international conference was
held in London in 1912 have the various
nations interested in radio met to discuss its
problems. Invitations have now been sent
out to forty-two different governments,
asking them to send delegates to America
in the spring of 1926. Congress has ap-
propriated $92,000 to defray the expenses
of the conference, and outlines of the work
to be covered have already been laid out.
The subjects to be discussed include the
revision of the International Radio Tele-
graph Convention and Regulations, the dis-
cussion of measures for the international
supervision of communication by radio
between large fixed stations, broadcast-
ing, measures for elimination of interfer-
ence, distress messages, radio aids to
navigation, and other developments of the
art which have come into being since the
1912 conference.
As this is written there is being held
in Paris the International Telegraph Con-
vention. The United States is not offi-
cially a party to this conference and our
delegates will be seated as observers only.
Three attended. In addition to these,
certain of the government technical men
are being sent and the telephone, telegraph,
and cable companies of America have
many representatives in Paris to advise
with the government representatives and
their aids.
In addition to these two conferences,
Secretary Hoover will probably call the
regular annual national conference for some
time in November. He rightly feels that
the previous Washington conferences have
been of value to the department in framing
new policies and that this year especially,
when there are many stations increasing
their power, it will be well to test public
feeling toward these more powerful stations.
One station is already operating experi-
mentally with fifty kilowatts, another is
prepared to do so, and there are several
operating at five kilowatts. The use of
these greater powers has by no means re-
sulted in the confusion and interference
which many panic-stricken listeners pre-
dicted and it seems quite likely that this
national conference will put its stamp of
approval on the super-power channels.
The radiating receiver should get its
share of adverse comment at the Wash-
ington conference. Listeners continually
complain of these miniature broadcasting
stations. We strongly urge the Depart-
ment to put its official stamp of disap-
proval upon this prolific source of radio
discomfort.
The Month in Radio
1
THE FIRST AMERICAN " SUPER POWER" BROADCASTING STATION
The 50 kw. transmitter at station WGY, Schenectady. Recent tests were made to determine
whether better program service could be given listeners if the power of the transmitting
station were greatly increased
PRELIMINARY reports of the opera-
tion of the 50 kw. WGY transmitter
give some very interesting, though not
startling, information. Comparative tests
were recently carried out first with 2.5 kw.
and then with 50 kw., that is, twenty times
as much power as the first. Many listeners
had expected that so much power would
completely blanket other stations, but
was not found to be the fact; the results so
far obtained show that theory is able to pre-
dict what will happen at the higher powers
and in this case the theory indicated that
the blanketing effect would be pronounced
only when close to the high-powered sta-
tion. Listeners fifty miles away from one
of these high-powered stations will probably
be disappointed to find out how strong the
signals really are; the signal will be about
the same strength as from an ordinary sta-
tion about ten miles away.
The useful area of transmission of the
super power station is very much increased
over the low powered station of course, and
the quality of reception is improved because
of the higher ratio of signal strength com-
pared to static.
Much trouble is experienced by the
average listener fifty miles or more away
from a station due to the now well-known
fading effects; the rapid waxing and waning
of signal strength makes many radio eve-
nings very disappointing. It had been
supposed by some that fading would be
lessened when the high power was used
but such proved not to be the fact. The
signal is of course much more audible with
the higher power but its fading is just as
pronounced as with the older lower pow-
ered sets.
THE cruise of our fleet through the
southern Pacific has given rise to some
remarkable distance events. The U. S. S.
Seattle in the harbor at Wellington, New
Zealand, has heard telephone conversations
with a London amateur with remarkable
regularity. The distance, slightly more than
12,000 miles, is as far as a radio telephone
message can be transmitted on this earth.
The operator on the Seattle has also main-
tained two-way communication with the
naval experimental station at Bellevue as
he crossed the Pacific from Honolulu
to Australia. The Laboratory of RADIO
BROADCAST station 2 GY communicated
with the Seattle while she was leaving
Tahiti. Our station used only a 5-watt
tube, which is thought to establish a record
for j-watt transmission.
THE American consul in Paris, report-
ing to the Department of Commerce,
sees but little market for American receiv-
ing sets in that country. So far, he says,
broadcasting in this section has become
popular only in a small degree compared
to the situation in America. There are
only four stations broadcasting, all of
WHAT PEOPLE SAY ABOUT RADIO
27
JOHN V. L. HOGAN
—New York; Consulting Radio Engineer
" The report, recently made public by
Secretary of the Navy Wilbur, relating to the
work of the Naval Laboratories, which
seemed to point to the possibility of the ex-
pensive high-powered, long wave stations now
used for inter-continental radio communica-
tion being replaced by less expensive short
wave, lower powered stations is especially
interesting. The conclusions are quite in
line with the recent reports on the same sub-
ject made by Dr. Alexanderson, of the
General Electric Company at Schenectady.
It is difficult to say definitely that the present
high power, long wave stations will be re-
placed by the short wave transmitter because
the short waves are not always reliable.
However, there seems to be no doubt that they
will be valuable adjuncts to the powerful long
wave stations."
hem in Paris, and the number of listeners is
probably less than we have in one good-
sized city. The radio trade in France is of
the opinion that from fifteen to twenty
stations will be required to cover the coun-
try properly and that until such stations are
erected and put into operation the number
of broadcast listeners will remain compara-
tively small.
I AST year we exported close to $6,000,000
p* worth of radio apparatus and this
year shows a very decided increase. Judg-
ing by the value of the first half of the year's
business it appears that our total radio ex-
ports for this year will exceed §13,000,000.
A GERMAN court has recently held that
not only has a tenant a right to erect
an antenna on a housetop but that, owing
to the importance of broadcasting, it is the
duty of the proprietor to see that the tenant
is enabled to put up an antenna on a house.
E of the flight sergeants of the R. A.
F. was recently killed while conduct-
ing some radio experiments over the
aerodrome at Andover, England. For
some time his death was regarded as a
mystery, but careful examination of the
radio installation on his plane indicated
that defective insulation in the headphones
and other parts of the transmitting set had
permitted a shock of over one thousand
volts to pass through his head. As a
shock of only twenty or thirty volts around
the head is extremely painful it is no wonder
that the leakage of the thousand volt cur-
rent into his ears was fatal.
IN BRITISH India, the government re-
* tains the right to supervise and inspect all
broadcasting stations, censoring them and
taking them over in emergencies. It is also
required that each station, as in the United
States, shall have a receiving set in continual
service while broadcasting. Government
matter, such as weather reports, educa-
tional lectures, and emergency dispatches
must be handled free. No program can have
more than ten per cent, of its time used for
advertising purposes.
Interesting Things
Said Interestingly
JOHN McCORMACK (London; Irish tenor):
J " I shall retire at 50 and from now on shall
come to London each year to sing in the Al-
bert Hall. However. I emphatically refuse to
broadcast. I tried it once in New York and dis-
liked it thoroughly."
A .L. RUBENSTEIN (New York ; chief opera-
*• tor of the S. S. Arcturus with the recent
William Beebe scientific expedition): "While
we were in the Galapagos the broadcasting
station that came in best was WMBF, at Miami
Beach, Fla. Ordinarily we couldn't get New
York. But on one occasion we asked the East
Moriches station to request a certain concert
from an orchestra in a Greenwich Village
restaurant. The music we asked for was put
on the air by WGBS, and came through with
remarkable clarity, considering the distance and
atmospheric conditions."
LJERBERT H. FROST (Chicago; president
1 Radio Manufacturers Association): "In
the early part of 1917 I was assigned to the
command of a radio company of one of the
Regular Army Field Signal Battalions, and
found that out of a total strength of seventy-six
men in this company, 52 of them were licensed
amateur operators who had enlisted at the first
call, and 1 know of one town in Pennsylvania
that gave 1 1 amateurs to the Signal Corps out
of a total of 13 licensed members who were
residents of that city. The American amateur
and the American Radio Relay League have
made their bid for fame, and stand before us to-
day richly endowed with a past record in both
peace and war. It is not too much to say that
the experimental work they are now doing on
short waves will revolutionize our present sys-
tems of transmission and reception over great
distances.
JOSEPH D. R. FREED (Brooklyn; president
J Freed-Eisemann Radio Corporation): "I
firmly believe that all kinds of freak
circuits will be exploited within the next two
months. The public should be warned against
L. A. HAZELTINE
Hoboken; Professor of Electrical
Engineering
"/ would not advise any young man to
attempt a short cut into radio engineering.
The ordinary electrical engineering course
should be sufficient, if followed by practical
experience preferably with a large organiza-
tion, or by post graduate work at college, the
latter more especially for the man having a
a taste for research. My own collegiate work
was simply the mechanical engineering course
given by Stevens, and I found it quite sufficient
to build on by studying in my spare time.
While one cannot expect the present excep-
tional demand for radio engineers to continue
indefinitely, it would be equally a mistake to
consider radio as a fad or in any way transi-
tory. There should continue to be good op-
portunities/or experience and advancement in
radio fields, perhaps more than in other
branches of electrical engineering. I still bave
the same feeling that caused me to take up
radio as a specialty, that it is especially at-
tractive to men having a fondness for math-
ematics and its practical application."
high-sounding phrases and the mass of adjectives
that will accompany reports of these circuits,
such as used in hundreds of thousands of receiv-
ing sets, and the variations are only good for
publicity, not as far as efficiency in reception is
concerned. With so many receivers and with
so many claims as to their merits, the public
should study the situation very carefully.
Surely, if freak circuits were really better, the
leading manufacturers would be only too happy
to use them in their regular lines, and to use the
funds devoted to advertising these standard •
sets toward the boosting of the 'freaks'."
DOXY" (in Broadcasting: Its New Day,
*^ written in collaboration with R. F. Yates):
"At the present time there are two changes that
would rescue broadcasting from the shadow of
disaster and place it on the solid footing it
deserves. If half our better studios would cut
down their broadcasting time and concentrate
more upon quality than upon quantity, a very
pleasing result would be the outcome. The
second change would be that of converting
some of the studios to a class basis."
RADIO BROADCAST Photograph
FIG. I
Here are a few of the resistance units tried out in the RADIO BROADCAST Laboratory in conjunction with the development of the RADIO BROADCAST
"Aristocrat." They include assemblies made by the Arbee, Electrad, Daven, Heath, and Crescent, as well as units from Cole, Brach, Muter,
Dubilier, and Durham
How to Build a Five-Tube Receiver Which Has Extremely
High Quality, Especially Fine Selectivity and Sensitivity
By ARTHUR H. LYNCH
\OR a very long time we have been
looking for the kind of receiver
that would be easy to build, easy
to operate, and at the same time be
comparatively economical. In the receiver
described here, we have found what we
consider a solution to the problem. There IN COMBING over the possible circuits
is but one main tuning control which makes I nf rpal wnrth tn thp hnmp hnilHpr WP
up to the present time have felt that radio
reproduction was not sufficiently free from
flaws to reproduce with true fidelity the
music they love.
WHAT THE RECEIVER IS
the finding of stations so simple that the
most inexperienced can secure surprising
results. In an actual demonstration, we
have been abletoshowthatby means of this
single control and no other adjustments
whatever we were able to hear sixteen sta-
tions in less thanthreeminutes, withasingle
turn of the tuning dial. When other adjust-
ments were made — and where is the DX fan
who will not want to be certain that he is get-
ting the last drop of energy out
of his set? — we have been able *9I
to procure distance with volume,
which few receivers other than
a super-heterodyne could have
accomplished. And above all
we have been able to secure tone
quality which has been char-
acterized by many of the radio
designers and enthusiasts who
have come to Garden City to
witness the performance of our
new outfit, as being far superior
to most receivers they have seen
of real worth to the home builder we
have come to the conclusion that there are
but three that possess the merits we
sought, namely: the super-heterodyne, the
neutrodyneinmany of its advanced models,
and the combination of a stage of tuned,
neutralized radio-frequency amplification
in combination with a regenerative detector
and some more than ordinarily good system
of audio-frequency amplification. After
considerable thought to each of these we
or heard. We believe this re-
ceiver will do much to endear
radio to those music lovers who
^ HIS article is one of the features we have worked on to produce for
RADIO BROADCAST in its new form. In changing the si%e and improv-
ing the general appearance of the magazine we are at the same time making
great efforts to improve the quality of every single contribution in it. This
receiver, frankly, is one of the first to he presented anywhere to the home
constructor which unmistakably takes the lead in what is destined to be the
whole progress of radio fashion. The receiver described here, although it is
not difficult to build, has practically but one control, and is extremely economi-
cal in battery consumption, has the crowning merit of delivering a signal of
unusually good quality. Radio constructors are no longer content to assemble
a receiver which has merely the merit of great sensitivity or selectivity, or some
other familiar point of superiority. The constructor is demanding, and
rightly, that his receiver give the most faithful reproduction possible of the
transmitted voice and music. That is the keynote of radio fashion for 11)26,
and that keynote the RADIO BROADCAST "Aristocrat" strikes. — THE EDITOR.
decided in favor of the last, not because we
thought the others less valuable but be-
cause the combination of price, distribution,
ease of building, operating, and low upkeep
cost seemed to be best carried out in the
receiver we are now to describe.
So, in the RADIO BROADCAST "Aristocrat,"
we have one stage of tuned, neutralized,
radio-frequency amplification, a regenera-
tive detector, and three stages of resistance-
coupled amplification. Before going further
let it be said that the resistance-coupled
amplification we are using should not be
confused with similar systems described in
the past because it is now possible to main-
tain tone quality, for which this type of
amplifier is famous, together with great
volume, because of the foresightedness of
some of the tube manufacturers
WV who are now marketing what
are known as high-Mu tubes.
These tubes are designed for
resistance-coupled amplification.
The amplification per stage that
is obtainable with them is far
greater than has heretofore been
generally possible.
Then, too, in the "Aristocrat"
there are no rheostats whatever
and the number of binding posts
has been reduced to a mini-
mum. In order to make the
design, building, and operation
of this type of receiver quite
clear, and in order to demon-
NOVEMBER. 1925
THE RADIO BROADCAST "ARISTOCRAT"
29
FIG. 2
In this assembly each unit is made with individual mounting. The
antenna switch is behind the panel and .5 mfd. condensers are used in
the resistance-coupled amplifier, and a short-circuiting switch is used
on the ballast for the last tube to allow for use of either 5- or 6-volt
tubes at will. The regeneration is controlled by a variable resistance
across the tickler. A Cabelug is used for the battery wiring. For the
experimenter who wishes to make frequent changes in his circuit this
arrangement is just about ideal. The panel, by the way, is 7 x 21"
RADIO BROADCAST Photographs
FIG. 3
This receiver was made on a 7 x 18" panel and is intended to illustrate
the method of using a complete resistance-coupled amplifier unit in
connection with two additional tubes for the complete assembly. When
6-volt tubes such as Daven MU-ZO, and Mu-6 are used, there is no need
of making any alteration in the filament circuit of the amplifier, and the
wiring is thus materially simplified. In this receiver we have used the
regular Sickles Knockout coils. The ballast resistors for the first two
tubes are shown beneath the sub-panel
strate the variations that may be incor-
porated in it at the discretion of the home
builder, we will describe at length but one
of the group we have made, and will
point out the differences between it and the
others by means of the captions under the
illustrations.
THE DESIGN AND ASSEMBLY
BY REFERRING to Fig. 5, it will be
observed that there is but a single dial,
in the center of the panel. This dial is
usedtocontrolaHanscomsinglecontrol unit
(first described in this magazine forOctober,
1925) and is the main tuning control. It
is a unique arrangement of two Remler
condensers geared together in a manner
that makes tuning of the antenna and
radio-frequency circuits simultaneous.
The small knob below and to the left of the
main dial is the vernier which is used to
compensate for any slight variations be-
tween the windings of the circuits tuned by
the two condensers. The knob below and
to the right of the tuning dial is the filament
switch. By referring to the circuit dia-
gram, it will be observed that the filament
switch is placed in a position in the circuit
that cuts out the by-pass condensers across
the batteries, which would ordinarily form
a high resistance leak and result in a drain
on them even when the receiver was not
actually in operation. The small knob at
the left of the panel is used for the tap
switch, connected to the primary of the
antenna coupler, to compensate for an-
tennas of different lengths. Once this
switch has been set for a given antenna it
need not be touched, except for ultra-fine
tuning, when extreme selectivity or ex-
tremely long distance is desired. The
knob on the right controls the regeneration,
and may be considered a volume control.
Before passing on to the consideration of
the remainder of the receiver it would be
well to look over the accompanying illus-
trations and observe the variations that
have been made in the panel design, the
layout of the apparatus, and the different
systems of tuning and regeneration control.
There is very little difference in the actual
performance of any of the models we have
made and the selection
you make may well be
considered from a con-
venience standpoint rather than one of net
results obtainable. Bear this in mind, how-
ever: you cannot expect to get the results we
are getting if you buy your parts on noth-
ing but a price basis. We have spared no
expense in attempting to bring only the
best to your attention and suggest that
you make an attempt to get the best — not
necessarily the most expensive. And when
you are all through getting the best of
parts and have done a thorough job in your
building don't blame poor reception on the
receiver if you hook some poor loud speaker
to it.
But to continue, we may as well point
out some of the other important points in
the actual construction of this receiver.
The panelof what we may consider our main
model is 7 x 18 inches and there is plenty of
room on it for all the equipment necessary,
when a sub-base is employed. In this
model we have used large-size inductances,
in order to illustrate how the entire assem-
bly may be housed in a standard cabinet.
When other types of inductances are em-
ployed, as is the case in some of the other
models, there will be a little more room in
the cabinet.
It will be observed that the tuning in-
FIG. 4
On a recent visit to our laboratory Mr. McMurdo Silver built this
receiver from the ground up in less than four hours. It is his version of
the RADIO BROADCAST "Aristocrat." The single control feature is accom-
plished by belting two of his condensers together with fish line, letting one
dial do all the moving. When it is desired to change the capacity in
one circuit without altering the other, one condenser is held in place and
the other turned. We are not as enthusiastic about this scheme as that
devised by Hanscom, but it has enough merit to warrant attention.
In this 7x18" receiver there is plenty of room, even with the large solenoid
coils. The parts used include Hoosick sockets, A. B.C. panel, Accuratune
vernier dials and knobs, Silver Knockout coils, .0005 S.L.F. variable
condensers and .005 coupling condensers, Micamold coupling resistors,
Muter mountings and grid leaks, Daven mountings and ballast resistors,
Carter switch and jack and Belden battery cable
RADIO BROADCAST Photographs
FIG. 5
Front view of RADIO BROADCAST'S "Aristocrat" made to fit in a cabinet
providing for 37x18" slanting panel. In this receiver, as the accompany-
ing article will show, we have gone a long way afield and produced what
we believe is a true departure from conventional design electrically,
artistically, and mechanically. It will operate over comparatively long
distances, produce music with great volume and fidelity with the ad-
vantage of one major tuning control and remarkable economy.
30
RADIO BROADCAST
NOVEMBER, 1925
ductances and the variable condenser
assembly antenna switch and battery
switch are mounted on the main panel,
while all the remaining equipment is either
on the top or bottom of the i\ x ly^-inch
sub-panel, which is suspended from the
main panel by means of Benjamin No. 8629
brackets.
On the upper side of the sub-panel
will be found the five tube sockets, the
threeresisto-couplers, the grid condenser
and leak mounting, and the variable neu-
tralizing condenser. It is also possible to
find room for all the binding posts, includ-
ing those for the three connections for the
C battery, if they are thought to be desir-
able.
On the under side of the sub-panel there
are five mountings which are used for the
filament ballast resistors, when they are to
be used. When they are to be taken out
of the circuit, as explained a little later on,
it is but necessary to make a direct con-
nection between the two spring clips of the
mounting.
LIST OF PARTS
HPHE list of parts used in the model we
*• are considering is as follows. The
variation in material that is possible is
indicated in the accompanying illustrations.
i 7 x i8-inch panel, i 2j x iyj inch sub-panel,
Hanscom S. C. Condenser Unit, i set East-
ern Knockout Coils, i Carter filament switch,
2 Apex knobs, 5 Benjamin sockets, 3 Daven
resisto-couplers with 3-.! megohm resistors and
i each, i meg., .5 meg., and .25 meg. resistors,
I Hammarlund neutralizing condenser. 2 .004
Sangamo fixed condensers, i Dubilier .5 mi-
crofarad by-pass condenser. 6 Daven No. 50
mountings, i Daven Leakandenser (a new unit,
which combines the grid condenser and leak),
5 Daven Ballast Resistors. (The capacity of
these resistors depends on the type of the tube
used and the values for various tubes are given
in that part of this article which deals with
the circuit and its characteristics.) I Belden
Standard Color, five wire, cable. 2 Benjamin No.
8629 brackets, 2 to 6 Eby binding posts. 2 dozen
6 or 8-32 round head, brass machine screws,
f inch long. About 6 two-foot lengths of bus
bar.
THE CIRCUIT AND ITS CHARACTERISTICS
IN DESIGNING this receiver we have
1 attempted to keep in mind the diffi-
culties encountered by some of our readers,
who sometimes find that their local dealer
does not carry a stock of a particular item,
for use in a receiver, whatever kind it may
be, and for this reason have endeavored
to indicate what we believe to be intelligent
substitution and variation in design to ac-
commodate units of different size without
materially altering the performance of the
circuit. By referring to the circuit dia-
gram and the illustrations of the models
we have made, you will be able to see how
the various units may be made to fit in
whatever space you have available and
how they will conform to whatever type of
construction you may prefer. If we go
over the entire circuit and consider each
unit individually, this may be a little more
comprehensive. So we may as well start
with the antenna coupler.
There are now many sets of coils on the
market, designed for use in the now famous
series of Knockout Receivers, which have
been described in RADIO BROADCAST.
Any of these coils may be used in the "Aris-
tocrat".
The tuning condensers used do not by
any means have to be those we have chosen
to use. Any good pair of .0005 mfd.
variables will do, but what we wanted was
single control, and in the "Aristocrat" we
have it in a very practical manner. The
only remaining requisites are the ballast
resistors and the units which comprise the
resistance-coupled amplifier system.
Let us consider the ballast resistors first.
They are shown in the diagram as, R
1-2-3-4-5. Now the selection of these
resistors will depend entirely upon the types
of tubes used and we have found what we
consider an ideal combination in two of the
standard storage battery tubes for the
radio-frequency amplifier and the detector
with two high-Mu tubes in the first two
stages of the resistance-coupled amplifier
and a semi-power tube in the last stage of
the amplifier. Some tubes, such as the
Daven MU-2O, and Mu-6; the Western
Electric 2i6-A and the new Radiotron
ux-2io will operate directly from a 6-volt
storage battery without requiring any re-
sistance in the filament circuit. Where
tubes of this character are employed the
ballast resistors and their mountings may
be left out of the circuit entirely, or a direct
connection may be made across the mount-
ing, as shown in Fig. 2. In this receiver a
ballast of \ ampere capacity has been used
with a Harvey Hubbell toggle switch con-
nected directly across it. This makes it
possible to use either 5- or 6-volt output
tubes and either is thus assured the proper
filament voltage. Most other high-Mu
tubes are designed for use on 5 volts and
where they are employed a j-ampere ballast
should be used with each, or a single ballast
of \ or f-ampere rating may be used with
two or three of them, in multiple.
That should clear up the resistance ques-
tion, though it may be well to say in passing
that filament rheostats may be used if they
are on hand, and for extremely sensitive
operation it will be found that a rheostat in
the filament circuit of the radio-frequency
amplifier tube provides greater flexibility
than the ballast resistor method.
THE RESISTANCE-COUPLED AMPLIFIER
IN CHOOSING the system of construction
1 for our principal model we have had in
mind the idea that a certain balance may
well be obtained between first cost and
simplicity of assembly. For the inveterate
experimenter we recommend the mode
Regeneration may be Obtained Either by Variable
•' Tickler or Resistance Shunted AcrossA Fixed Tickler
Circuit Enclosed Herein Comprises Resistance Coupled
«t Amplifier which may be Obtained as a Complete Unit
Separate Resistor Units may be Employed in the Audio Amplifier
f where the Complete Manufactured Amplifier is not used
r*- - -i r-^1 i— *-
I P II G i ! P II G i i p
THE CIRCUIT DIAGRAM OF THE "ARISTOCRAT'
NOVEMBER, 1925
THE RADIO BROADCAST "ARISTOCRAT11
31
shown in Fig. 2. In a layout of this kind
there is all the room necessary for experi-
menting with various units designed for
the same purpose. This arrangement is a
delight for the experimenter. For the
average individual we believe our principal
model will be more in keeping with his re-
quirements and desires, for it permits him
to make about all the changes he could
desire without requiring an undue amount
of wiring, as much of that has been done
for him. For the third type of home
builder, who desires to have as much of the
building of a receiver as possible done in
the factory, we suggest the model in Fig, 3
where a complete three-stage resistance-
coupled amplifier unit has been shown.
One of the principal things to remember
in connection with the building of a re-
ceiver in which a resistance-coupled am-
plifier is used is that it depends for its
operation to a great extent on the actual
resistance of the units employed. If, for
instance, in one of the plate circuits where
we have specified a resistance of .1 megohm
(100,000 ohms) you use a mounting made
of some material which in damp weather
will absorb moisture, a measurement of the
resistance in such a plate circuit will indi-
cate that there is less resistance in the
mounting itself than in the resistor used in it .
There are many such devices being peddled
about and you will do well to be certain
that the units you procure do not suffer
from such a defect. In other types of
mountings which have been submitted to
our laboratory for test we have found that
the clips for holding the resistors are held
to the insulating base by machine screws
and locknuts. Obvi-
ously, if the heads of
the screws are not
thoroughly counter-
sunk and the mount-
ing is placed on top of
a condenser with a
metal case, a short
circuit is almost in-
evitable. Where you
do your mounting on
a wood base it is well
to keep the wiring off
the wood itself, as
this will prevent
leaks occurring in un-
expected and unde-
sired places. Some
cheap condensers
have been found to have a very low resist-
ance in damp weather.
Another thing about resistance-coupled
amplification, which has not been given
the attention it deserves, is the size of the
coupling condensers. We have found that
they should be much larger, for the best
tone quality, than is ordinarily suggested.
The mathematical and experimental back-
ground for this assertion is sound. Do not
use condensers in your coupling units of
less than .1 mfd. if you want to procure
better than average quality.
When you have finished building this
receiver and you want to make an actual
test of its quality, in comparison with other
receivers, connect first one and then the
other to a Western Electric cone speaker.
If the receiver is right, the cone can be
worked with tremendous volume with-
RADIO BROADCAST Photograph
FIG. 7
Bottom view of the "Aristocrat". Illustrating the wiring under the sub-
panel. The only units not shown in Fig. 6 are the two Eby posts on the
extreme left, for antenna and ground, the Amperite and Daven ballast
for the filament circuit of each tube and the Belden battery cable
out rattling. The rattle, as a rule, is
not an inherent fault in the cone; it is the
result of imperfect amplification. In using
a Western Electric cone, it should be re-
membered that the impedance of the cone
is much lower than most other speakers and
the output tube used with it should be one
with a plate impedance that matches the
cone, such as the new semi-power tubes to
which we have previously referred. If an
ordinary tube is used with the cone, an out-
put transformer should be used which will
make up for the unbalanced condition
that would otherwise result.
If you consider the little things in con-
nection with the building of RADIO BROAD-
CAST'S "Aristocrat" you will produce a re-
ceiver which you will be proud to exhibit to
your friends. You will enjoy radio as it
is but verv seldom heard.
FIG. 6
RADIO BROADCAST Photograph
The "Aristocrat." Left to right on the sub-panel we have the Daven leakandenser, Benjamin socket, Sangamo .004 bypass condenser, Daven
resisto-coupler with . i and i meg. resistors, socket, resisto-coupler with . i and 5 meg resistors, socket, resisto-coupler with . i and .25 meg resistors,
socket. The .1 microfarad condensers are within the resisto-couplers. The two Eby posts on the upper strip are for the loud speaker. The
three posts on the lower side are for the C battery and the small knob is for the Hammarlund variable neutralizing condenser. Left to right on
the main panel are the Benjamin bracket, Dubilier .5 by pass condenser, Eastern Knockout r. f. coupler with Apex knob, Hanscom single control
unit with Marco dial, Yaxley filament switch. Eastern Knockout antenna coupler with Carter antenna switch and another bracket
' Point
ortdn&ed by KJmJsleij UQelles
i Who -Are the Owners of Our (f(adio Sets? I
Wl
rHEN the broadcast announcers
tell you over the air that
two million people are hear-
ing the "program now being
broadcast," it is breaking no confidences
to say that they do not really know
how many listeners they are actually
reaching. Almost everyone who has had
the opportunity has played fast and free
with statistics dealing with radio, partic-
ularly the number of radio receivers and
their owners. There is no positive way to
tell just how many sets are in use. The
question, "Have you a radio set?" might
well be added to the already long list asked
by the United States Census, although we
should have to wait until 1930 before these
now occult facts could be made public.
It is an excellent maxim not to take any
statistics too seriously, for like the Scrip-
tures, the Devil can (and probably does)
quote them for his own purposes.
But slices of the radio listening group
have been visited by the equivalent of the
Inquiring Reporter, and the results, while
they prove nothing but facts about the
given group, are interesting. The figures
give one a pretty fair idea of what sort
of an individual the composite radio
listener is.
Two thirds of those interviewed owned
receivers and nearly 72 per cent, were
men. Ages varied from under 20 to the
ripe age of 71. The group between 21
and 30 years old were most attached to
radio. Men were more anxious to have
a set installed than women, for more
than 58 per cent, of those approached
in the survey were men and responsible
for the purchase of the equipment. Wives
came second with a percentage of 22,
while the clamor of the children in 20
per cent, of the total succeeded in secur-
ing the set.
Out of 1 200 homes investigated in one
survey, 66 per cent, were operating their
first sets. The remaining third had
owned radio equipment previously. Some
families had owned as many as nine
outfits; in fact, this group represented 5
per cent, of those interrogated. And 45
per cent, were using their second receiver,
while 21 per cent, had purchased three.
One home confessed to having six sets on
hand; five others had five receivers apiece,
and 1 10 households had two or more.
The investigators were much interested
in learning why a particular make of re-
ceiver was bought. It was found that
46 per cent, of the owners purchased their
set because they thought it the best make,
while 17 per cent, acted on the advice of
friends, and a lagging 12 per cent, bought
because of low prices. Some were in-
fluenced by advertisements, but almost as
many were convinced by a personal dem-
onstration in their homes.
Radio receivers appear to be regarded by
these groups as a necessity rather than a
mere convenience, as some of the un-
convinced seem to think. Out of 1166
set owners asked the price paid for their
equipment, 24 per cent, did not know what
it cost, although 12 per cent, bought be-
THE FIRST OPERATIC BROADCASTER — 1908
Mme. Mariette Mazarin, operatic soprano under
the management of Oscar Hammerstein, who came to
New York to create the role of "Elektra," shown in
an old photograph singing in the microphone of an
early Deforest arc radio telephone transmitter.
A few earnest experimenters heard Mme. Mazarin
then, but what an audience she would have to-day!
cause the cost was low. The initial cost of
the sets varied from $2 to $650. The
average cost of the receiver was $100.
The manufactured set cost more than the
home-assembled receiver, which was found
to cost about $40. The survey indicated
quite definitely that most of the present
owners are willing and expect to pay more
for their next set. Some 40 per cent,
expect to pay between $150 and $200 for
their new receiver.
Out of 1280 homes investigated in one
census, nearly 36 per cent, had five-tube
sets in operation, 9 per cent, used more
than five tubes, and 19 per cent, used re-
ceivers with three tubes. Crystal and
one-tube receivers accounted for 8 per
cent. each. In England, by far the
greatest number of listeners use crystal
receivers, which are naturally not at all
selective and their range is limited to about
five or ten miles. One of these American
surveys showed that 47 per cent, of the
owners bought their sets in order to re-
ceive programs from distant stations.
Selectivity was considered the most im-
portant factor by 42 per cent.
In Seattle, whose population by the
last census is given as 237,000, a kind of
radio census was taken, which showed
that 18,000 radio receivers were in use
in that area. Three years ago, the crystal
set was very much in the majority in that
city, as it was in almost every other.
Now only 21 per cent, of the Seattle
listeners use crystal receivers. Thirty-
seven per cent, of the sets are single-tube
ones — usually home made. Forty-eight
per cent, of the tube receiving sets are
either five- or six-tube affairs. Seattle is
probably reasonably representative of the
country, although it is highly doubtful
that 21 per cent, of the outfits of the
nation are crystal receivers.
Probably the most interesting part of
the surveys is found in the answers to the
question, "Who runs the set?" In 455
cases out of 644 it was the man of the
house — 71 per cent. Women did the
tuning in 6 per cent, of the total and
the children in 3 per cent.
NOVEMBER, 1925
WHAT WE CAN EXPECT IN BROADCASTING
33
What Hope for Programs?
The response of the radio audiences to the con-
certs of the New York Philharmonic Orchestra
is very significant. It is not improbable that
several hundred thousand persons listened to
these concerts over the air during the summer.
That their appreciation is keen may be judged
from the fact that wjz and WCY — fully alive to
the public's wishes — have seen fit to give the
concerts such prominence on their schedules.
This in itself is encouraging. Even more so is
the interest of the public in the best class of
music. Broadcasting stations reported a year
ago that there was a notable increase in the
number of letters asking for more concert music.
The experience in this broadcasting
shows that there is a much larger audience of
music lovers in this country than was thought to
exist. . . . What the Philharmonic has done,
others can do. What we have lacked (in this
country), save in the big cities, is the opportunity
to hear good things. This the radio now gives
us. — Editorial in the New York Times.
By FAR the outstanding event of'the
summer radio season was the
broadcasting of the Philharmonic
Orchestra at the Lewisohn Stadium in
New York. Aside from the fact that this
broadcasting was technically the finest bit
of broadcasting we have ever heard, the
Philharmonic programs were noteworthy
because of the high musical standard of the
selections and their rendering. One hour
of a Philharmonic concert is worth, by
actual calculation, 2027 hours of any jazz
band you can mention.
There are mutterings against jazz, and
they are none too faint. We venture the
prediction that the stations who want to
stay in the van will have to rearrange their
schedules so that jazz takes a secondary
place on their programs — if for no better
reason than variety. Who would attend
a vaudeville performance where 50 per cent,
of the program was devoted to dance music?
The wire links of WEAF to the outlands
will furnish much excellent program ma-
terial. The recent announcement by A. A.
Kent that Metropolitan Opera stars have
signed for a series of concerts, to be broad-
cast through WEAF and a chain of Middle
Western stations begining October 4, is the
first good omen in the Fall Season.
The WEAF Grand Opera Company will
furnish tabloid grand opera to a large
group of stations. We have heard many
listeners say, and not a few have written us,
that they think this feature one of the best
to be found in the air lanes. There is now
a pleasing tendency among program direc-
tors to arrange radio speeches which have
some justification for their being. Pro-
gram directors will never learn, however,
that there is no possible justification for
broadcasting an entire banquet. It is bad
enough to be forced to attend a banquet,
but when one has to listen to the rumble
of moving dishes, the distorted sounds of an
orchestra perhaps, and the hollow echoes
of "speeches of the evening" which re-
verberate in the banquet hall despite the
best efforts of the microphone to ensnare
them — then the limit of something has
been reached.
But in the main, the start of the fifth
year of radio broadcasting is good. In a
hundred little ways programs are being
improved and more able individuals are
coming to the studios, in the persons of
both performer and director.
Church Broadcasting: A Failure
{THOUGHT, as a matter of course,"
writes Charles Magee Adams, of
Milford, Ohio, "that a considerable
majority of my neighbors picked up church
services regularly. They tune-in every
other radio offering, and religion, regard-
less of creed, is something whose appeal is
universal and fundamental. But I find
that, on the contrary, the overwhelming
majority of my neighbors' sets either stand
idle during church hours or pick up a pro-
gram of some other type if one is within
range. They began listening zealously
enough when the sets were new, these
friends of mine (and I am sure they are
representative of the radio audience), but
gradually discontinued the practise, for-
reasons hinted at rather than explained.
There were vague remarks, such as ' I don't
care much about it.' From this and
similar remarks and my own convictions, I
came to the conclusion that something is
wrong with church broadcasting."
In the September "Listeners' Point of
View," issue was taken with the arrange-
ment of Sunday programs in general and
it was mentioned that broadcasting from
churches is not very successful. Mr.
Adams develops the point. "The Church
thinks of broadcasting," he continues,
"simply as a means of bringing its services
to shut-ins and as a sample to interest
prospects; in other words, broadcasting is
an auxiliary to and substitute for attendance
at services in person. This is not to say
that these aims are not legitimate and
laudable. Bringing help and comfort to
dwellers in remote places or to invalids is a
fine service; and attracting more people
into church membership is altogether worth
while.
Radio has placed at the disposal of the church
an instrumentality for multiplying its usefulness
to an extent that leaves possibilities difficult to
grasp. Yet the church classifies radio as an
auxiliary, a substitute; and continues to place
the emphasis on assembling in congregations.
GOLDY AND DUSTY
FLORENCE LONG ARNOLDI who ^1e p MISS JEAN SARGENT
Coloratura soprano, a regular artist at station chain of stations, in an "indirect advertising" Who was for four years with WNAC, Boston, and
WOAW, Omaha. Her voice has thrilled and program. It is darkly hinted that they are two now is in charge of women's programs at WHT,
delighted many an evening's radio audience, well-known concert singers, well known to buyers Chicago. Miss Sargent is said to be the first
One might add that her costume is fully as charm- of phonograph records, who have turned their woman announcer. Her voice is frequently
ing as her voice talents to broadcasting heard over WHT
34
RADIO BROADCAST
NOVEMBER, 1925
LOPEZ SPEAKING
This concert, by Vincent Lopez and his orchestra,
is being broadcast through the courtesy of station
W-E-A-F direct from the Pennsylvania Hotel Grill.
The next number . . . On the Radio"
This is much the same as if, during the last
presidential inauguration, the nation-wide radio
audience had been told that it might listen-in at
home, but that attending the ceremonies in
person was vastly to be preferred.
Mr. Adams goes on to enumerate the
disadvantages of this widespread attempt
to adapt the service designed for attendance
in person to the special requirements of
broadcasting. "The acoustics of church
auditoriums result in cavernous boomings
and reverberations . . . and it is im-
possible for the preacher to adapt his deliv-
ery both to the radio audience and to his
congregation. Much the same is true of the
incidental music. Announcements of in-
terest only to the congregation must be
made from time to time. These strike the
listener as wholly irrelevant and are
psychologically very important.
"The Church should arrange a special
service, with universal appeal, conducted
in a broadcasting studio according to the
KEITH MCLEOD
Accompanist and musical director of stations wjz
and WJY, New York. He accompanies Mr. Godfrey
Ludlow in the popular Sunday night recitals from
wjz and is a pianist of great talent. Mr. McLeod
is a Westerner, coming from Denver, Colorado
best radio practise. Sermons should be
cut to somewhere near ten minutes — the
length of maximum radio listener atten-
tion. (The closing speeches broadcast in
the last presidential campaign by President
Coolidge and Mr. Davis — the most effec-
tive radio addresses delivered by either —
were n and 13 minutes long.) Radio
has placed before the Church an opportun-
ity for usefulness greater than any other
single one in all its long history. The
Church has failed so far to make the most
of this opportunity, not because technical
facilities are undeveloped, but because the
Church has not chosen to adapt itself to
this new potentiality." With all of which,
needless to say, we heartily agree.
Do Women Know What They
Want In Radio Programs?
IN ENGLAND recently, a woman
graduate of Cambridge debated before
the microphone with a woman who
had been in charge of various canteens dur-
ing the war on what subjects appeal most
to women listeners. The Cambridge
graduate favored amusing and intellectual
talks of a non-domestic character, and the
ex-canteen manager declared she wanted
talks on practical subjects and "ultra-
feminine topics" — whatever they are. Lis-
teners were asked to express their views,
and some 80 per cent, of the letters sided
with the Cambridge woman. Cookery,
child welfare, and household management
talks were not wanted. The general cry
was: "Take us out of the kitchen and take
us out of ourselves!" The letter writers
wanted talks on music, literature, travel,
women's movements, etc., with an occa-
sional fashion talk or humorous reading.
Almost without exception American
broadcasting stations, when they have a
program for women, have limited it to the
obvious domestic things. No broadcaster
has had the courage or the intelligence to
arrange a program to appeal to the intelli-
gence of women. One wonders whether
this failure is due to a belief that it would
be useless to make the attempt or because
the program designers simply fail to ap-
preciate the necessity.
However, a new feature for women has
been started by the Washburn Crosby-
Company with the talks by Betty Crocker,
on Monday, Wednesday, and Friday morn-
ings through WEEI, Boston; WEAF, New
Yorkjwpi, Philadelphia; WCAE, Pittsburgh;
WGR, Buffalo; WEAR, Cleveland; wwj, De-
troit; WHT, Chicago; KSD, St. Louis; WDAF,
Kansas City; KFI, Los Angeles; and wcco,
St. Paul-Minneapolis. This is a genuine
forward step in broadcasting, for it is the
first time a national wire link has been
employed for a program of "service."
It is frankly commercial broadcasting, and
that of the most defensible sort. Perhaps
this national effort will awaken the pro-
gram directors, and they will now busy
themselves and arrange women's programs
of broader appeal.
ERNIE SPEAKING
I want to thank all my radio friends for the wonder-
ful letters they have sent me. 1 will be pleased to
send a log book with a picture of my orchestra on
it to everybody writing for one. The next numbaah
played by Ernie Golden and his Hotel McAlpin
Orchestra will be 'The Farmer Took Another Load
Away'"
The Shy Radio Minstrel
"A wandering minstrel I,
A thing of rags and patches. . . ."
MINSTRELS have quite gone out of
fashion except as one reads of them
in good old classical ballads, or
hears the lines quoted above floated out at
one during a "Mikado" performance.
The fact is that the automobile — and we
almost said radio — has made the minstrel
business a bit superfluous, and probably
unprofitable. To come out with a startling
truth, radio broadcasting has brought the
minstrel back again. Most of our modern
minstrels travel on the best trains instead
of a slow and probably underfed horse and
are well paid for their time, as witness the
favorite Wendell Hall — in the employ of the
National Carbon Company, who only last
GODFREY LUDLOW
Staff violinist at station wjz getting his fine Stradi-
varius — the de Rougement, dated 1703 — ready fora
recital.- Mr. Ludlow is an artist of high ability, and
through his Sunday night concerts through wjz and
WGY has won a very large following
NOVEMBER, 1925
NEWS AND COMMENT ABOUT BROADCASTING
35
year shadowed the microphone of most of
the important broadcasters of the country.
He sent this department, we recall, a postal
card from Cuba while he was on his lyrical
mission there.
There are a host of others who travel
about, some who are paid for their services
and others — a majority of the number, in
all probability — who give their services to
the broadcasters for the pure love of the
thing, which, being translated, means for
the "publicity value." The management
of station KGO admits that within the past
thirty days five radio minstrels reported
to the studio manager, ready to do their
bit "entertaining the silent audience of the
day and night." One was armed with a
harmonica, another played a Tyrolean
zither, another carried a set of "sweet
potatoes," while a fourth drove to the
station in a Ford and unloaded his "kitchen
piano" or dulcimer, which is stringed, and
as a WEAF announcer phrased it the other
night, is "the grandfather of the piano."
"We are only observing the old Biblical
injunction," admitted one of the minstrels.
"We cast our music on theair, and, brother,
it works! As I travel, I meet friends
everywhere — and chicken dinners, too."
The electrical wanderlust has spread to
broadcast announcers, too, for we have
heard from a number of stations during the
lately concluded summer, elaborate and
flowery introduction of this well-known
announcer, and that being presented over a
rival but friendly microphone.
^Broadcast Miscellany
WHEN broadcasters close their
program, it is usual for them to
announce the time. "Station
xxx now signing off at 10:10 p. M.,
Central Standard Time. . . ." We
took the trouble to check the announced
time from a number of stations recently,
and the variations from the actual
minute were fearful to behold. It is a
small matter, but if the broadcaster
really means what he so often says
about "service" we suggest he take
care his clocks are right. We will wager
that a good many trains are missed
because of carelessness of this sort.
THE bubbling Ernie Golden, radio
good fellow par excellence, an-
nounced from WMCA, New York, the
other night that a certain performer
would "now whistle 'To a Wild Rose.'"
A curious occupation for a grown man,
but perhaps less futile than the not un-
common announcement of this or that
hopeful "broadcasting to listening rela-
tives in Brest-Litovsk."
only knows how many times each evening.
This gracious compliance with wishes never
fails to remind us of that ultra-complier,
Josephus, whose fame is sung in a good old
ballad:
Now these two boys are dead and gone.
Long may their ashes rest.
Bohunkus of the cholera died,
Josephus, by request.
IT IS the common practise among wire
and radio telegraphers to use their
initials or some other cabalistic set of let-
ters to indicate their presence at the sta-
tion, chiefly because it takes too much
time to send with each message, "sent by
operator Charles B. Smith," or the equiva-
lent. When the radio operators became
radio announcers, as many did in the early
days of broadcasting, before the present
age of specialization where every station
with any claim to pretension has its staff
of announcers, its program and publicity
force, and its group of operators — they
took with them the practise of giving their
initials during the announcing. The orig-
inal purpose of the abbreviation was to
save time, but now there is no possible
justification for the practise. The an-
nouncer is — if he is even moderately
talented — an asset to his station, and in
many ways he is as important as the event
or the artist he introduces. Why, then,
should he not give his name? The practise
was begun by WEAF. Millions, probably,
heard the name of Graham McNamee, and
werecharmed by his easy graceand high tal-
ent for description. But some power above
gave his orders and no>v no longer do the
Bell System announcers reveal their iden-
tity. The Radio Corporation group do,
however, and if you don't believe that the
name of the announcer adds a necessary
touch to the broadcast proceedings, com-
pare some night the offerings of a station
representing each group. When the lis-
tener knows the name of the announcer
serving him, an indefinable something is
added which is highly desirable. It makes
for better announcing, too; Milton Cross
of wjz probably felt a greater responsibility
and approached the task of preparing those
extraordinarily able program notes he
gave for the New York Philharmonic Con-
certs (given through WGY, wjz, and WRC)
with considerably more enthusiasm since
he knew that large numbers of listeners-in
looked to him for his interpretations.
And, contra, the WEAF announcer who
handles the Hotel Bossert orchestra several
nights a week might make more certain
that what he says by way of "fill in" is
really funny, if his name were aerially
signed to his remarks.
THE late Walter Camp and his system
for the glorification of the American
physique, known familiarly as the "Daily
Dozen" is probably responsible for the
radio popularity of the setting-up exercises.
Aided by a bugle, and the less military
piano, unseen physical training instructors
dispense musically accompanied instruc-
tions for health exercises from a great
many stations. Though there is no sure
way of estimating, the number of exer-
cises must be very large. We hope that
this new addition to the radio program may
become such a fixture that it entirely dis-
places the bedtime story — misguided ju-
venile sentimentalism which everyone, in-
cluding the children, could well do without.
THE next number will be played by IN THE VILLAGE OF JUAN DIAZ, PANAMA
*• request." Similarly worded confi- The natives hear a program from a Cuban broadcasting station. The radio receiver is part of the "on
j-_ ' •• , • . , location" equipment of the company filming the picture "Spaces Beyond" in Panama. It is a question
dences are whispered into many a de- whether the natives Hvjng on the calm ,ittle Tapia River jn ^ backgVound were more impressed with the
tenseless microphone, the good Marconi radio concerts or the strange behavior of the cameramen and directors
A Model
Designed to Meet Present Requirements of Great Selectivity on All Frequency
Bands, This Set Is Highly Satisfactory in Operation and Decidedly Easy to Build
By McMURDO SILVER
OR some time past, the writer has felt
that it should be possible to design a
radio receiver possessing all of the valu-
able features of the best super-
heterodynes, yet going a step beyond in dealing
with the coming seasons' radio problems in a man-
ner not possible with any previous systems, since
none of the present aggravated reception condi-
tions were even imagined during the past year.
Before examining this system in detail, it may
be interesting to consider a few of the facts con-
cerning present, and probably future, broadcast-
ing conditions, which, incidentally, will explain in
a measure the writer's apparent abandonment
of the super-heterodyne school of thought. In
a nutshell, a simpler system has been so improved
that it is now nearly the equal of the super-
heterodyne.
BROADCASTING CONDITIONS — TO-DAY AND
YESTERDAY
I AST year at this time, the entire range of
^ available broadcasting channels may have
been occupied by transmitting stations, but any
listener of a year's standing knows that in actual
operation this was not so. Channels could often
be found where stations were not transmitting,
and it was seldom indeed that a fan could pick
up the full quota of approximately 95 stations
that would be required to fill properly the
broadcast frequency range of 1500-550 kc. (200
to 546 meters), a range of some 950 kc.
Obviously, there will be far more stations
operating simultaneously than there were last
year. Equally obviously, we require far more
selective receivers this year than last.
To-day the range of the broad-
cast frequency is from 1500 to Cftfjj^— ^—
550 kc. '200-546 meters). Re-
broadcasting goes up to 5996
kc. (50 meters) in some cases, and
it is quite possible that the regu-
lar broadcasting range may be
extended above 1 500 kc. (200
meters). Foreign super-power
broadcasting takes place in many
instances on long waves, running
up to several thousand meters.
Of what value, then, is last year's
receiver, with its satisfactory
operating range generally from
1330 to 520 kc. (225 to 575
meters)? This year, and future
years, sets must be capable of
covering a wide wavelength range
— far wider than any existing de-
signs will rover.
ceiver itself is shown in the accompanying
illustrations, which bring out the mechanical
details of panel design, instrument arrangement,
and wiring.
At first glance, the set does not seem at all
original, since it consists merely of two stages of
tuned radio frequency amplification, followed by
a detector tube and two audio amplifiers. The
circuit is a combination of the best points of all
receivers, carefully executed with regard for the
most recent discoveries, and the fund of informa-
tion gained by the writer and his assistants
through contact with many thousands of ex-
perimenters— men whose judgment of receiving
equipment was based solely upon one thing, per-
formance.
Since one of the first requirements was wave-
length flexibility, it was necessary to devise a
method of shifting inductances for different
frequency bands. This made necessary the
designing of interchangeable coil forms possessing
a form factor suitable for all frequencies to be
handled. For the higher frequency bands, the
turns are spaced, while the coils for waves
longer than the present broadcast band, the
coils may be bank wound. Six contacts are
provided on a reinforced ring at the bottom of
each coil, upon which are mounted six studs in
which the ends of the windings terminate, and
which in turn make contact with springs in a
special six-contact socket, so keyed that a coil
cannot be inserted incorrectly. In order to
change a frequency band, it is necessary only to
remove the coils from their sockets and insert
ones of different inductance values — an operation
consuming about 10 seconds.
A RECEIVER TO MEET PRESENT
CONDITIONS
IT IS felt that the receiver to
* be described adequately solves
the problems encountered, with
fewer tubes and less equipment
than a super-heterodyne, yet is cap-
able of equalling super-heterodyne
selectivity and sensitivity — a goal
indeed worth aiming at. The re-
and again, readers of RADIO BROADCAST have asked us why
we did not publish more information on the familiar five-tube,
tuned radio frequency receiver. Our position was that as soon as we
found a receiver sufficiently good and sufficiently off the beaten path, a
description would find its way into the pages of the magazine. RADIO
BROADCAST has published many articles on the neutrodyne (December,
1923, January, and February, 1924, and August, 1924), and many
more on applications of tuned radio frequency circuits. The receiver
here described involves no "revolutionary circuit," but it contains
other features which are certain to be of positive interest to the con-
structor. These departures in design are used which give ease of con-
trol, adjustment to various frequencies, and well-nigh perfect selectivity:
1 Plug-in coils for covering all broadcast frequencies.
2 Straight line frequency condensers, insuring even spacing of received
frequencies along the dial. The exact dial location of a given
station can be precalculated after referring to published programs.
3 Proper detector grid biasing instead of the conventional grid leak
and condenser.
4 A new system of regeneration control achieved by shunting the r. f.
secondary coil with a variable $oo,ooo-ohm resistance.
This excellent article is another of the special features promised our
readers in the new RADIO BROADCAST, and we think it well justifies its
place. — THE EDITOR.
STRAIGHT LINE FREQUENCY CONDENSERS
'"THE condensers used with these inductances
' are of the type giving an approximately
straight line frequency variation, or a uniform
kilocycle variation for each dial division.
A very important factor for broadcast recep-
tion, particularly on short waves, is the ratio of
inductance to capacity in a tuning circuit. The
500 mmf. (.0005 mfd.) condensers, which are com-
monly used, prove rather large for use above
1500 kc. (200 meters). Even above this, the in-
ductance capacity ratio resulting from their use
is not as good as with 350 mmf. (.00035 mfd.)
condensers. In order that maximum signal
strength may be obtained, the condenser
capacity should be kept as low as possible. For
another reason, this is of vital importance at
short waves where tuning is practically impos-
sible with large condensers. Above 6000 kc.
(below 50 meters) tuning capacities should be
on the order of 150 mmf. (.00015 mfd.) although
below this, 350 mmf. seems quite satisfactory.
Neutralization, which is nothing more than
fixed oscillation or regeneration control, could
not be used. This is because the r. f. amplifier
for a given frequency band, would have to be
neutralized at the shortest wave to be received in
that band so that the amplifier would not oscil-
late. Sensitivity would be obtained then only
at the lower end of the wavelength band, while
the receiver would be as inefficient and as little
sensitive as the average neutrodyne at the longer
waves. In this connection, the now popular
circuits employing a stage of tuned neutralized
r. f. amplification and a regenerative detector
were considered. In them, due to
^^—4^3 reaction, regeneration in the de-
tector circuit tends to assist the
neutralized r. f. amplifier. This
being at best an indirect solution
of the problem, the r. f. ampli-
fier in this design was made highly
regenerative, with an increase in
sensitivity, since a much stronger
signal could then be delivered to
the detector tube, the efficiency of
which varies with the square of the
applied voltage. This means that,
with a given signal applied to the
detector, doubling the strength of
the signal will increase the detector
response four times. In the new
receiver, due to reaction, the de-
tector circi'it is rendered practi-
cally as sensitive as if direct re-
generation were employed (see the
writer's article in the March, 1925,
issue of RADIO BROADCAST)
through the reactive effect of
regeneration in the r. f. amplifier.
NEW REGENERATION CONTROL
' I *HE actual method of regener-
* ation control employed is new,
practically, and consists of a vari-
able high resistance in shunt
with the grid circuit of the
NOVEMBER, 1925
A MODEL 1926 BROADCAST RECEIVER
37
RADIO BROADCAST Photograph
FIG. I
Front panel view of the five-tube receiver described in this article. The three tuning dials
may be linked together as one if desired. The plug-in coils are shown at the right
second r. f. tube. Customarily, a grid bias-
ing potentiometer is employed which is ex-
tremely inefficient at short waves although
satisfactory at long waves as in a super-
heterodyne, or a series B battery resistance.
The latter, the most popular method, is ex-
tremely unsatisfactory, as it merely controls
oscillation by reducing the effective amplifier
plate voltage. This process is bound to' detune
the set in a measure, as well as throw the ampli-
fier tubes entirely off their proper operating
characteristic if a C battery is employed, as
should be done. In the system used, a variable
resistance of 500,000 ohms is shunted across one
tuned circuit feeding into the tube's grid circuit.
The probable average operating resistance of the
tube is about 1 50,000 ohms, so that the resistance
is so far in excess of this that selectivity is not
affected. Due to careful design of the circuit,
it is only necessary to decrease the value of shunt
resistance to not less than 300,000 ohms to get
excellent oscillation control. Obviously, this
method will not affect selectivity to the detri-
mental extent that any other method would.
Due to the extremely low losses of the three
tuned circuits, the overall amplification curve
resembles that of a band-pass filter, such as is
used in carrier telephone work; in some cases for
separation of carriers — not 10 kc. apart as in
radio — but only 3 kc. apart. This is the ideal
response curve and can only be obtained by other
systems after they have gone beyond the limits
of practicability; or practically by the super-
heterodyne. The next most satisfactory curve
would probably result from the single r. f. ampli-
fier and regenerative detector mentioned above.
The efficiency of the receiver decreases rapidly
at frequencies greater than 2000 kc. (i 50 meters),
so that at 6000 kc. (50 meters) it will probably
only work slightly better than a regenerative
detector and the same number of audio stages.
This is true of all r. f. amplifiers, but it must be
remembered that it is practically impossible to
improve upon a regenerative detector at short
waves. This is not because more sensitive sys-
tems cannot be built; rather, that they are not
required — transmission efficiency renders the Use
of a terrifically sensitive receiver unnecessary.
AUDIO AMPLIFICATION
HpHE audio amplifier shown uses two standard
' 3^:1 transformers, and will be found to give
most excellent reproduction. However, resist-
ance coupling may be used where practically per-
fect quality is desired. Unless high-Mu tubes
are used in the first two stages, and a low-
impedance tube (suchasuxi 12, ux 120, ux 210 or
the Daven), in the last stage, resistance coupling
is not worth while. The only high-Mu tubes
generally available for standard sockets are made
by Daven. However, using ordinary tubes,
choke-coupled amplification will about equal re-
sistance coupling, using the new 35o-henry
Thordarson autoformers. Three stages will be
required, with but 90 volts of B battery rather
than 135, as with the resistance audio amplifier.
The current consumption of the receiver is
astonishingly low. With six tubes, three in a
resistance amplifier operating on 135 volts, it was
but seven milliamperes as against the general 1 5
to 20 for neutrodynes and 15 to 30 for supers.
Despite the fact that storage battery tubes were
used throughout, this was made possible by
biasing all grids 4^ volts negative. Thus, the
amplifiers all have the correct bias for 90 volts,
while the detector bias is correct for 45 volts.
This practice, unusual in the case of the detector,
results in an increase in overall efficiency due to
lower detector input losses, plus the greater
handling power for strong signals, unobtainable
with the customary grid-condenser-leak method
of obtaining rectification.
SINGLE, DOUBLE, OR TRIPLE CONTROL
npHE receiver may be tuned either as a single,
* double, or triple control outfit at will.
Each condenser is provided with a pulley collar
on its shaft, which may be connected with all the
others by means of fish-line. While at first this
idea may seem impracticable, it is well to remem-
ber that the builder of one of the country's finest
commercial receivers has used the method for
years. This season it will be found on the Bosch,
Grebe, and Zenith receivers, not to mention
others. It is, to the writer's mind, the most
practical single-control scheme yet devised, be-
cause of its flexibility. Thus, the builder of a
set may test it out carefully, determine just how
it logs, then put the fish-line in place and realize a
RADIO BROADCAST Photograph
FIG. 2
The five-tube receiver from the rear. Note the three interchangeable coils and their
sockets. The battery cord leading away from the left end carries all battery supply wiring
38
RADIO BROADCAST
NOVEMBER, 1925
Photograph
FIG.
This photograph should be studied carefully before laying out the baseboard, since no dimensions are given. This is because different
types of instruments may be substituted, so the layout can only be approximately followed with respect to spacing of the parts
true uni-control set without the fear that all the
circuits may not be properly adjusted, as in the
case of gang condensers. The use of external
compensating capacities, often suggested with
gangc ondensers, is not particularly to be recom-
mended.
Further, a multiple range, uni-control receiver
cannot be built practically. It might be possible
to build it for one frequency range, but if coils
"must be interchanged, the circuits must be com-
pensated for errors that cannot be overcome.
This is where the beauty of the fish-line control
comes in — it is merely necessary in logging at
first to determine how many degrees apart the
three dials may run for one set of coils, then when
they are used, adjust the dials to this relation
and go ahead tuning with but one or two controls
as desired, since holding one or two dials with the
fingers and turning the other merely causes the
fish-line to slip, only to grip tightly again when
but one dial is turned alone. Yet the arrange-
ment is totally without play or backlash.
TUBES AND RHEOSTATS
THE receiver illustrated uses two rheostats,
one for both r. f. tubes and detector, and
one for the a. f. tubes. This permits the use of
small tubes up to the detector, and larger or
power tubes from there on. It is suggested that
uv-2oiA and UX-2OIA (identically the same
except for bases) be used throughout, up to the
last stage, where a ux-ii2 or a uv-2io for ex-
treme volume be used. Dry battery tubes may
be employed if desired, but uv-2oiA's will be
found to give about 15 per cent, greater volume.
Rheostats are not vitally necessary, with tubes
coming through with their present uniformity.
There is no reason at all why Daven ballast
resistors or Amperites may not be used for
permanent filament control.
FLEXIBILITY
ONE feature of the set is its flexibility. It
may be used on antenna or loop with
either only a detector, one r. f. or two r. f.
amplifiers. Suppose an antenna is to be used,
the antenna coil with its adjustable rotor for
maximum selectivity is inserted in the socket
at the left end of the set. Then the r. f. coils are
put in their sockets and the antenna and ground
connected to posts I and 2 of the antenna socket.
Thus, we have detector and two r. f. stages. If
only one r. f. stage is desired, the first tube is
removed, the antenna coil moved to the middle
socket with antenna and ground connected to i
and 2 of this socket, and the set tuned with the
two right-hand dials. To use only the detector,
the antenna coil and antenna and ground leads
are moved to the socket nearest the detector,
and all tuning is done with the right-hand con-
denser. If a loop is to be used, the antenna coil
is removed, and the loop leads connected to 3
and 4 of the socket from which the coil is re-
moved, depending upon the number of r. f.
stages desired. The a. f. amplifier i? controlled
by- jacks, one for the first and one for the second
stage. Thus the set may be changed from a
two to a five tube set at will. The volume resist-
ance serves as a smooth, even control of loud-
speaker volume, by means of which any desired
ntensity of sound may be obtained at will.
RESULTS OBTAINED DURING AUGUST
P\URING the latter part of August, the re-
^-* ceiver was tested in the center of the
Chicago loop district, among steel buildings, and
in comparison with a completely shielded seven-
tube super, capable of cutting side-bands, a
neutrodyne and several other types of com-
mercial tuned r. f. sets. The "super" gave, us-
ing a loop, slightly greater sensitivity. This
could be made up by attaching a 2O-foot wire to
the grid side of the loop on the r. f. set. This
was seven tubes against five of similar type. The
other receivers were practically worthless on a
loop. On a 4o-foot antenna, the r. f. set and
"super" were even — the point had been reached
where the additional sensitivity of the "super"
was useless. The other sets tested failed signally
to equal the "super" or r. f. set — even to the
point of the number of stations heard. Fre-
quently DX stations would operate a speaker on
the super or r. f. set, yet could not be heard on
the other factory-built sets. The results in
selectivity were similar. Either the "super"
or r. f. set would eliminate some ten local broad-
casters, a few less than 500 yards distant, which
completely blanketed the other sets. Side-bands
could be cut on any station at will with either
"super" or r. f. set, but not with the others. On
local broadcasters within one mile, the "super,"
shielded, was more selective than the r. f. set.
Shielding the r. f. set evened things up. This
would never be necessary, however, except where
the set was but a few yards from a transmitter.
Then a sample receiver was tested in Garden
City, Philadelphia was brought in in daylight
with plenty of volume to be heard all over the
house.
CONSTRUCTION OF THE SET
IN BUILDING the receiver, the following ma-
* terial was used. It is suggested that sub-
stitution be not indulged in, since many of the
items have been designed for the set. If one sub-
stitutes without proper knowledge of the elec-
trical details he is almost courting disaster with
the finished receiver.
3 Silver-Marshall 350 mmf. S. L. F. condensers
3 Silver-Marshall six-contact coil sockets
Silver-Marshall coil forms or wound coils as
required, three to one frequency range
5 Naald, Silver-Marshall, or Benjamin cush-
ioned ux or uv sockets
2 Thordarson audio transformers, 3^:1
2 Carter, U. S. L. or Pacent 6-ohm rheostats
Centralab 500,000 ohm modulator
Carter or Pacent 2-spring jack
Carter or Pacent I -spring jack
Carter or Cutler-Hammer on-off switch
Muter or Dubilier .002 mfd. condenser.
2 Dubilier or Silver-Marshall .5 mfd. bypass
condensers
3 Kurz-Kasch moulded, Ezytoon or plain 4-
inch dials, zero-left
i Belden s-lead color cable
I 7x24-^3 inch bakelite panel
i 7X23-|inch oak baseboard
15 Bus-bar lengths
13 i-inch No. 6 R. H. N. P. brass wood
screws
10 |-inch No. 6. R. H. N. P. brass wood screws
6 J-inch No. 6 R. H. N. P. brass wood screws
i Rosin core solder
i Spaghetti
27 Tinned lugs
Tools required: Screw-driver, side-cutting
pliers, soldering iron and non-corrosive solder-
ing paste, hand drill with drills and counter-
sinks
ASSEMBLY
THE panel is first laid out with the positions
of the instrument centers as given in the
pictorial diagram. These dimensions may be
supplemented with the individual templates
furnished with each instrument. The holes
should be drilled and countersunk where re-
quired. The panel may be grained by rubbing
lengthwise only with very fine sandpaper and
lemon oil, it being finished off with steel wool so
that no shiny spots appear. If engraving
facilities are available, it may be engraved as
shown in the photographs.
While the volume control resistance is shown
above and between the two rheostats, it would
be better to locate it below and between the
middle dials. This would give shorter leads,
and leave the space occupied by it in the set
photographed free for a voltmeter, which is
absolutely essential with 3-volt tubes unless
fixed control resistances are used, such as
Davens or Amperites.
Each separate part should be examined, and
NOVEMBER, 1925
A MODEL 1926 BROADCAST RECEIVER
39
every nut, screw, and spring adjusted and
tightened before proceeding further. Lugs
should be put on the sockets, rheostats, and
wherever necessary. Then the hole locations
may be laid out on the oak baseboard from the
pictorial drawing, and each one started with a
nail and hammer. All parts should be screwed
down firmly in position, using the short screws
for by-pass condensers and transformers, the
medium ones for the sockets and the long ones
for inductance sockets.
The wiring of the set is the simplest of as-
sembly operations. The soldering iron should
be heated, the point filed bright, rubbed in
paste, and then in solder so that it will acquire a
coat of tin, without which it would be impossible
to solder. Each lug to be soldered should
have the point of a pin carrying a little paste
rubbed over it, the iron held to it and the end of
the length of solder rubbed on the lug itself, not
the iron. This will tin the iron. Another
method is to pick up a drop of solder on the iron
and deposit it on the lug by rubbing the lug with
the iron tip until it is heated sufficiently to cause
the solder to flow to it. This makes for neater
work, but requires more skill. Rosin on a joint
does not hurt it, providing there is solid solder
underneath. Do not try to wire with anything
but perfectly straight bus bar rolled flat between
two boards. Then measure it carefully, cut and
bend it to size, tin the ends, and finally solder it in
place.
Many constructors prefer to use flexible wire
in connecting up sets. In this particular re-
ceiver, this is permissible only for the filament,
battery, and audio amplifier sections. All r. f.
amplifier wiring should be of stiff bus bar, as il-
lustrated, in order not to interfere with the
satisfactory operation of the simplified control
feature.
So far the panel has not been touched, only the
baseboard having been wired. The proper parts
should be mounted on the panel. After adjust-
ing the condensers for the desired tension, the
panel is screwed to the baseboard and the re-
maining wiring put in, after which the receiver is
completed with the exception of the battery
cable. This should have its short ends con-
nected to the wiring where it terminates in
instrument binding posts, say at the switch,
rheostats, and transformers.
INDUCTANCES
IT IS probably simplest to buy machine wound
' coils, since any variation in wire tension,
spacing, insulation, or impregnation will affect
the operation of the single control feature
slightly.
Using standard ribbed forms, the coils are
wound as follows: Starting at the topof each tube
with end 3, terminating this winding in 4, begin-
ning again in 5, and ending in 6; I and 2 lead to
the rotor, used only in the antenna coil. All
coils are wound in the same direction with No. 26
d. s. c. wire, except the rotor, which is wound with
No. 32 d. s. c.
ANTENNA COILS
1578- 545 kc. (190-5 50 meters)
3331-1428 kc. (90-210 meters)
5996-2726 kc. (50-1 10 meters)
R. F. TRANSFORMERS
1578-545 kc. (190-550 meters)
331-1428 kc. (90-210 meters)
5996-2726 kc. (50-110 meters)
I to 2
30 turns
16 turns
6 turns
I to 2
3 to 4
42 turns
16 turns
7 turns
3 to 4
84 turns
32 turns
14 turns
5 to 6
42 turns
i 6 turns
7 turns
5 to 6
1 8 turns
7 turns
4 turns
In the r. f. transformers, the winding 5—6, or
primary, may be wound just over the lower
end of winding 3-4, so that end 6 is just
over 4. In the commercial forms, this smaller
primary is located under instead of on top of
the grid coil.
TESTING
AFTER the receiver has been completed,
and the wiring checked against the circuit
diagrams, it may be connected up, using one
standard A battery as required, say a 6-volt,
go-ampere storage battery for uv-2oi A'S, one
4^-volt C battery and 90 volts of B battery,
consisting of large 22^ or 45 volt blocks. The
ends of the color cord are terminated at the bat-
teries, with the exception of the 645 and 690
leads. With these unconnected, a tube inserted
in a socket should light, if the switch is on, and
the rheostats turned on. If this happens, re-
move the plus A lead from the A battery, and
substitute for it the 645 and then the 890
leads. The tube should not light — if it does,
the circuit is incorrect and should be checked
for errors. Assuming the tube not to light,
all batteries should be connected properly
to the set.
With a water-pipe ground connected to either
i or 2 of the left coil socket, and a 25 to 5o-foot
single wire indoor or out-
door antenna connected to
whichever post (i or 2) the
ground has not been connected
to, the set may be tuned, us-
ing the three dials. It should
first be operated with head-
phones. The modulator or
volume control should b£
turned all the way to the
right, or at maximum. The
antenna coil rotor should be
so adjusted that its axis is
parallel to those of the stator
coils. All three dials will read
practically alike — that is, they will all be set
at within one or two degrees of each other for
a given station. Since each dial division may
be assumed to represent approximately 10 kc.
with s. 1. f. condensers, a station might be easily
located.
890+ C- B45 +
FIG. 4
In this diagram are combined a panel drilling layout, base-board layout to scale for the parts used, and a pictorial wiring diagram
40
RADIO BROADCAST
NOVEMBER, 1925
FINDING UNKNOWN STATIONS
FOR simplicity, let us assume that zero on the
dials equals 1500 kc. (200 meters) and 100
degrees equals 500 kc. Thus, we have 10 kc. per
dial division. Suppose we want WHT, 750 kc.
(400 meters) (we get this information from the
call book or daily paper). Then 500 kc., our
lower limit, subtracted from 750 kc.— WHT'S
frequency — gives us 250 kc., which, divided by
10 kc. — the frequency variation per dial degree —
gives us 25. Thus, setting the dials at 25 degrees
plus or minus one or two divisions will tune the
set to 750 kc. (400 meters).
Suppose we were using straight line wave-
length condensers. The process is different.
Our wavelength range covered by 100 dial de-
grees may be assumed to be 200 to 550 meters, or
a range of 350 meters. Thus, each dial division
represents 3.5 meters. Suppose we want WHT
again, at 400 meters. Then 200 — our low wave-
length limit — subtracted from 400 — WHT'S wave
—gives 200, which, divided by 3.5 — the number
of meters per dial division — gives us approxi-
mately 57 — the setting at which the set will be
tuned to 400 meters.
It must be remembered that these figures are
at best but approximate, due to unavoidable
variation in individual receivers and tubes.
LEARNING TO TUNE
SUPPOSE we want to tune-in some particular
station, the proper dial setting for which
has been found in the manner previously sug-
gested. It is merely necessary to set the center
dial at the figures found, and rotate the remain-
ing two slowly through a range slightly above
and below the setting of the other. No doubt a
click will be heard indicating oscillation, which
will prevent satisfactory reception of stations as
they will be heard only as a squeal. This is
eliminated by retarding the volume control about
one quarter of an arc. If the click is then no
longer heard as the dials are rotated, tuning will
be found to be quite simple, stations coming in
with all three dials set approximately alike.
The system will oscillate only when all three
tuned circuits are in approximate resonance —
the condition indicated by the click. It should
be possible to make the amplifier oscillate when
the volume control is retarded not over one
quarter. If this cannot be done, the rotor coil
of the antenna inductance should be turned out
in small steps until this is possible. The volume
control regulates the volume of the receiver, as
well as the selectivity, in that by means of it it
is possible to vary the width of the frequency
band passed from about 3 kc. on through the
10 kc. band required for good reception, and
then to 25 kc. At this last adjustment, tuning
will be found quite simple, as the set will be
rather broad — with the volume control set from
one half to full left position.
The size of the antenna will affect the position
of the antenna rotor. A small antenna requires
tight coupling — a long one almost right angle
coupling. This adjustment must be found for
each particular installation, but once ascertained
need not be changed. Under all conditions of
satisfactory operation, this antenna coupling will
be so loose as effectively to prevent radiation,
which could occur only with the amplifier oscil-
lating— a condition not permitting of satisfac-
tory reception. Further, the antenna coupling
will also generally be sufficiently loose to elimi-
nate the reactive effect of the antenna-ground
system characteristics upon the first tuned grid
circuit.
SINGLE OR DOUBLE CONTROL
THIS latter feature is what allows the three
dials to read practically alike over their
entire scale for different wavelengths. If the
first dial is out of relation with the two right-
hand ones, the remedy is to turn the rotor until
it is nearly at right angles with the antenna
stator coil. Suppose we find that throughout
the range of the large coils our dials are separated
by, say, two degrees each. The correction is
simple. They must be turned on the condenser
shafts so that they read alike.
It will probably be most satisfactory to use the
receiver as a dual control set, combining the two
r. f. dials. To do this, a piece of heavy braided
fish-line is necessary; this should be long enough
to go around the pulleys on the two condenser
shafts without the ends quite meeting. To the
ends are spliced short pieces of magnet wire.
Then, when the pulleys are joined with the fish-
line, the two wire ends may be twisted together
and gradually tightened up until all play is gone
from the line, and turning one dial causes the
other also to rotate. The wire provides a take-
up in case the line stretches — since the ends can
be twisted at any time with a pair of pincers.
It will be found quite simple to release either dial
at will, since the drive is purely due to friction.
It is merely necessary to turn one dial while
holding the other dial steady with a finger.
Thus, a full advantage of individual circuit ver-
niers are obtained, yet with a simple, efficient
arrangement and no extra equipment.
To connect all three controls, the line is merely
lengthened sufficiently to go around both end
pulleys, and once completely around the middle
pulley. It is fastened in the same manner as
previously. Tuning is simpler, although either
dial can be released at will by merely placing
a finger on the other two to prevent their follow-
ing the one rotated. If this is done, the sim-
plicity of the panel may be enhanced by using
small knobs on two of the condensers, and a large
dial on one, since the small knobs serve merely
as verniers, and need seldom be touched once the
builder has become familiar with the operation
through preliminary logging of the set without
the simplified control feature.
It is hardly necessary to say that the builder
will be well repaid for this effort in building the
set — he will be, since it is about impossible to
build a practical receiver, equally simple, cap-
able of delivering better results. A hundred
stations will not be heard the first night of opera-
tion— the set is far too selective for that. It
will require several nights of patient tuning be-
fore the builder will realize that he really has a
better set than his friends.
R.F.T.
FIG. 5
This is the regular schematic diagram of Mr. Silver's new receiver. This should always be fol-
lowed in wiring rather than the pictorial diagram, where the fan's knowledge of symbols is adequate.
'• -;-•" ~-f*m?» sgS*' K£--;jZ!^ir^'"fl^ */"^v^'^ _ ^'' - '
3K^^*"^(|p^^^<^^r|..^. yj ^ . «. ZJiriilSr -r1^*^^
ipK:.-:^>.T ^i.,. ,. .., lAl'v^f-^s^
^Sgh^x^^- /•* '*'* •"• .- i i I , i * -i 7 i^^r^^ •^•^'^'^::^?'yV:-r>v
BiHfc«jg^^ •/' i i ' i i li^-Eii •- )• «"*\\ -^v j^?^--^-''^
&mif i 1 r * *, r r'^«». Li [j\ ..^^vv. ^3F^E
111 ii^«Eri r • ' -*1* »»«w>w« *~*^«&-
^**l|S^****l*« I ^s^*" t 1
'I'' *Hfc«, '• ""'V^ Via* :••-.:-. \
,^* ^^'Tfc^^rt'* •»». V-..^-^-
fc^*'*»*fc*.«r Tr"<»*V^te»\ -,.*"' -~- -^- ' "
THE LOCATION OF THE GREATEST RADIO TELEGRAPH STATION
On the American continent. The antennas and transmitting apparatus are located at Rocky Point, about sixty miles from New York. The
operators who control the power of this huge station sit at tables in a building in Broad Street, New York. The messages are punched out on a
mechanical tape sender and forwarded out over a wire line to the transmitters
Visit to the Great Radio Telegraph Station at Rocky Point, Long Island — the Radio Link
With England, France, Norway, Sweden, Holland, Germany, Poland, Italy, and South America
By FRED J, TURNER
I VERY minute of the twenty-
four hours of the day, eveiy
day of the full 365, the dit-
dit-da-das of the radio code
are shooting through space. And in
England, France, Italy, Germany,
Norway, Sweden, Poland, Holland,
the Argentine, these code characters
are being received and translated
into messages.
For this, a great human and me-
chanical organization is needed.
Powerful stations are required. Such
an organization is the Radio Corpor-
ation of America and such a station
is the one at Rocky Point, Long
Island.
To the average man, an antenna is
generally thought of as being a
single wire 100 feet long supported
from 40 to 60 feet above the ground.
The voltage he thinks of in most
radio work is seldom higher than 130
HOW THE GREAT ANTENNAS ARE CONNECTED
and he is, for the main, interested
only in wavelengths of from 200 to
600.
Picture two antennas each one
and one half miles in length, each
consisting of twelve wires having a
total length of 18 miles. And then
picture the supports of these huge
antennas, twelve in all, each 440 feet
in height with cross arms 150 in
length. Then try to understand the
tremendous power that sends the
messages, 800 amperes and 120,000
volts, and you begin to appreciate
what a remarkable thing a great
radio telegraph station is.
Arriving at the station, my first
impression was that this was a lone-
some spot. No houses were visible.
Only one other passenger left the
train. An automobile was in waiting
and we climbed in. A drive of sev-
eral miles over a fine, macadamized
42
RADIO BROADCAST
NOVEMBER, 1925
OUTSIDE THE POWER HOUSE
The water cooling tanks are shown in action. Some of the water
is used in the specially built water rheostats The 44o-foot
towers look strangely dwarfed in the picture
The other, WQK, sends its
messages through the air
on 18.22 kilocycles (16,-
465 meters).
Both antennas can be
connected in an amaz-
ingly brief time, when-
ever it is found necessary,
thus giving one or the
other station a three-
mile antenna containing
fully thirty-six miles of
over- head wire. With
this great unit messages
can be driven through
space in an astounding
way.
The ground around
the station is flat as far
as one can see. The ab-
sence of trees is also
noticeable. This part of
Long Island was a forest
when it was taken over
by the company and
thousands of trees had
to be removed to provide
the cleared space re-
quired. The Radio Cor-
poration now owns nine
road, a turn into a graveled driveway and
our machine came to a stop in front of a
long one-storied building. Here I was met
by W. H. Graff, the engineer in charge,
to whom I presented my pass.
The house I was invited into is called the
Community House. It is also known as
"Bachelors' Hall," for it is here that the
single men employed at the station are
housed. The great, long room I saw was
both the dining and recreation room. To
the right was a billiard table and also a
pool table. Dining tables, with their
clean white linen and other table equip-
ment, occupied the major part of the left
side of the room. A radio set, one of the
finest, was near the window. Roomy,
restful chairs and settees. A big, open
fireplace. The room had much the ap-
pearance of a country club.
MASSIVE TOWERS
MY FIRST close-up view of one of the
great supporting towers was a sur-
prising one. What had looked like tall,
slender things, proved to be massive
things of steel. Each tower, known as the
self-supporting type, is fifty-four feet
wide at the base. Each leg rests on huge
blocks of concrete. The height of the
towers is 440 feet, and the length of the
cross pieces, ten feet wide, is 1 50 feet, or
seventy-five feet in each direction from
the center of the upright.
There are twelve of these towers. These
are divided into two groups, of six each,
set 1250 feet apart. They support an
antenna containing twelve three-eighth
inch copper-clad steel cables, running
parallel. Rocky Point is in reality two
stations. One is known as WQL and it trans-
mits on 17.15 kilocycles (17,500 meters).
square miles in this section.
A tablet on the front of the building
stated that this "Radio Central" station
was built in 1920. Now, inside the build-
ing, and what a sight! Great motors and
generators. Tall and wide panels with
many switches, meters, lights, indicators
and other things so familiar to those who
have visited the control rooms of big elec-
tric companies. A caged section to the
right could be seen with equipment of vary-
ing sizes and shapes set row on row, all
connected with copper wires and bars of
different thicknesses. Something to one
side spitting out big blue, electric flashes.
The familiar sound of dots and dashes.
Something about the entire room that be-
spoke power and mystery.
EIGHT THOUSAND DOLLARS FOR ELECTRICITY
EVERYTHING in the station, so I
was told, had been designed with
but one thought in mind, and that was to
obtain the maximum of results with the
minimum of waste. And it had to be so,
for it costs a huge sum to operate a station
like this. I understand that the cost of
the current used here in one month is in
excess of $8000.
The current used to drive the great
motors which in turn operate the powerful
generators is taken from the Long Island
Lighting Company's generating station lo-
cated at Northport. It is transmitted over
high-tension lines at a voltage of 22,000
at 60 cycles and stepped down after it
reaches the radio station to 2200 volts,
60 cycles. As is well known to students of
electricity, it is more economical to send
electricity along at a high voltage and
small amperage, because wires of a small
diameter can be used to carry it.
The generators, which are one behind the
other, are remarkable machines. Each is
known as an Alexanderson 200 kilowatt
high frequency generator. The one seen
first as you enter the plant operates at
1 7, 1 30 cycles per second and is used to send
messages on 17.1 kilocycles (17, 500 meters).
In these generators, which are known
as inductor type alternators, there are 976
poles. Generators used for ordinary com-
mercial work have only from 8 to 12 poles.
The motors are each of 500 horse-power
and are known as induction motors. Each
makes some 800 revolutions per minute.
Through a set of step-up gears of a ratio of
two and three quarters to one, the steel
INSIDE ONE OF THE OPERATOR S COTTAGES
The company has built living quarters for the staff attached to the station. The married
men live in homes like the one shown, while the bachelors have a kind of club, with a dining
room, and every convenience
NOVEMBER, 1925 "RADIO CENTRAL"— CONQUEROR OF TIME AND DISTANCE
43
rotor of the generator is driven by the
motor at the required number of revolu-
tions.
Just as the two antennas can be joined
and used as one, so can both generators be
operated in unison. And there are times
when this is done, especially in sending
messages over very great distances.
Seeing that my attention was being
constantly attracted to a set of long,
vertical metal arms which were constantly
emitting big, blue, electrical flashes, like
dots and dashes, I was told that they were
the compensation relays. They were do-
ing for the generator what the steam gov-
ernor does for an engine. Without those
relays there would be all kinds of trouble.
When each dot or dash is sent the alter-
nator is called upon to deliver a full load
to send it up and through the antenna and
out into space. Between each dot and dash
the load is released and thus the motor
would tend to run faster. In order that
the generator can run at a constant speed
at all times, these compensation relays
close at each dot or dash, allowing the
motor to draw from the line the amount
of power required to drive the loaded alter-
nator. In the interval between the dots
and dashes, the compensation relays open
and the motor receives only enough power
to drive the unloaded alternator at normal
speed. For those who like precision it will
be interesting to know that if there is a
variation of one tenth of one per cent, in
the frequency of the generator it is not con-
sidered to be working properly.
Down at 64 Broad Street, miles away,
in New York, operators are seated in front
of typewriters punching the dots and dashes
on long ribbons of tape. This tape is run
through a machine which causes the dots
and dashes to be sent along great land
cables to this station. They are started
from Broad Street with
a power of only 50
miliamperes at 120
volts and instantane-
ously sent through the
air by this station with
the tremendous forceof
nearly 800 amperes at
125,000 volts.
One of the very in-
teresting things to see
is a water rheostat.
Yes, that is what each
of the four big box-like
affairs really are. As I
looked into one of
them, and I had to
stretch quite a bit to
do so, I saw water rushing over a sort
of a dam, set in front of a number of
uprights. That dam, I was told, is raised
and lowered at the will of the engineer.
The higher the dam, the more deeply
the uprights, or electrodes, are immersed
in the water and the greater, therefore,
the amount of current which flows be-
tween the electrodes through the water.
This water constantly circulates through
the electrode compartment and then
past cooling coils to keep it from boil-
ing.
A CLOSE-UP OF ONE OF THE MASTS
And back view of the transmitter house at the great Rocky Point Station of the Radio Corporation of America. The power is fed to the antennas from
the wires supported on the quartet of insulators. The insert shows one of the multiple tuning inductances employed in adjusting the wavelength of the
antenna. A man's head would come up a bit above the concrete base of the coil support, which gives some idea of its size
44
RADIO BROADCAST
NOVEMBER, 1925
A FOREST OF METERS
by, I saw a number of air blow-
^-> ers which were being used to send
their cooling draughts along to the relays.
It was by this means that the contacts
were cooled and the arcs extinguished.
(The arcs form when the relays are opened.)
The many meters, as one can see, are so
arranged that they are visible from almost
every part of the power house. Some of
these were pointed out to me. One, a
graphic meter, recorded all the variations
in generator frequency. Another, close
by, showed the frequencies and voltages
of the incoming current supply.
Another look at the generators brought
forth further information. They are the
biggest of their type in the world. The
armatures and fields are stationary and the
high frequency is generated by large slot-
ted steel rotors. The weight of each is
two and one half tons. Each generator
has two armature sections, one on each
side of the rotor. There are 32 armature
coils in each section and each armature
coil is connected to the separate primary
coil of one of the two air core generator
output transformers belonging to each
generator.
From the generator the current is passed
along into the instruments which 1 had
noticed in the caged section. Signs of
brilliant red and big white letters warn of
"Danger, High Voltage." A number of
big, barrel-shaped things, with regular
windings of three-eighth inch .wire, 1 was
told, were transformers. A giant variome-
ter caught my eye. What a size! More
than three feet in diameter. It, together
with others of a similar size, is regulated
from the engineer's position, much like we
who are broadcast fans regulate those in
our sets. A number of big steel tanks close
to the floor were pointed out and I learned
that they were the variable impedances
that actually controlled the flow of current
from the generator output transformers to
the antenna. Each of the variable im-
pedances is oil insulated and water cooled.
The impression of bigness grows the
longer one remains in the power house. In
one section I saw hundreds and hundreds
of fixed condensers joined together by ever
and ever so many wires. The same kind
of condensers used in our sets, but truly
monsters when compared with ours.
Now, outside, the first thing I saw was a
big coil on a platform. Its height was
fully fifteen feet above the platform on
which it stood. It is an antenna tuning
coil. The current enters this at 7000
volts and leaves it at the top at 125,000.
The men here are never careless. Each
knows just what he is going to do before he
does it. So great is the amount of elec-
tricity thrown out by those huge antennas
that none of the workers attempts to crank
their automobiles until they have grounded
the handles by laying a long piece of steel
against them. The metal of the automo-
bile takes up the current which is prevented
from reaching the ground by the rubber
tires.
The insulators which look big from where
I stood, I learned were really big. They
are of the finest glazed porcelain, each
being a hollow tube 72 inches long, three
TWO ALEXANDERSON ALTERNATORS
Each of 2oo-kw. capacity, used to furnish power to the antennas. These machines, developed by Dr. E. F W.
Alexanderson of the General Electric Company, are much different from the usual commercial type of alterna-
tor in that they develop radio frequency current which is fed directly to the antenna. The armature and
field coils are stationary and a carefully balanced rotor causes the magnetic fluctuations necessary to pro-
duce the current
and one half inches in diameter, with walls
one inch thick. At the lower end, looking
much like the steering wheels of automo-
biles, are the corona shields. Dropping
over the insulators are the rain shields,
called by the men, "petticoats."
At one side of the power house are small
structures of metal on elevated platforms.
Into each of these structures each of the
twelve wires of the antenna terminate.
At this point the twelve are converted into
one by a series of switches, and as one wire
is carried to the big antenna tuning coil.
From there it goes to the power house. In
the winter these metal structures are used
for melting the ice and sleet which form
on the antenna wires. If this were not
done, the tremendous weight would cause
them to fall to the ground. By sending a
60 cycle current through each wire, suf-
ficient heat is created to melt the ice.
Looking up at those giant supports and
meeting the long straight ladders that lead
to the top, a platform at each 100 foot
level breaking the climb, one cannot help
but admire the nerve and skill of the rig-
gers who work away up there.
There are five more huge tuning coils,
one connected to each antenna at regular
intervals throughout its length, in addition
to the one just outside the power house.
These insure the most efficient distribution
of current over the entire antenna and
ground system. This system is known as
the multiple tuned antenna.
The ground system of this station is
extremely interesting. Running parallel
with the antennas, one on each side, are a
number of telegraph poles, supporting a
dozen or more wires. These, of
course, are the same length as the
antennas. Around each pole, about
one third the distance from the
ground, is a wire coil. Each coil is
smaller the further away it is from
the power house. Direct contact to
the ground is made from them.
It can now be understood how
this ground system is used. With a
single ground connection, all the
current would be concentrated in
one spot and a great deal of energy
would be wasted. A large number
of ground connections, each receiv-
ing only a fraction of the total cur-
rent, ensures low resistance and
maximum efficiency. It will no
doubt surprise many to know that
two hundred and forty miles of
bare copper wires are buried in the
earth under the antennas for ground
connections.
Before leaving I could not help
stopping to look at the power house
again and I got quite a thrill think-
ing that at that moment messages
were being sent from New York
over great land lines, through the
many instruments inside the build-
ing and out into space to England,
France, Italy, Holland, and the
other countries almost as quickly
as I could wink my eye.
M '
AS THE
Drawings by Fran\lyn F. Stratford
The Complicated Business of Running a Broadcasting Station
i
N GENERAL the work of a broadcast-
ing station falls naturally into two
divisions, getting the programs, and
broadcasting them. A third and indi-
rectly connected function is that of securing
publicity for the station's programs and
achievements in newspapers and other
publications. Three sorts of people, there-
fore, work at a broadcasting station: the
program organizers, engineers, and pub-
licity representatives. Musicians should
be added as a fourth class, for, as we shall
see, musicians as well as engineers are
needed for the actual broadcasting, as well
as in arranging the programs. The musi-
cians function in the no man's land between
the program and engineering departments.
I refer, of course, to the musicians at-
tached to the station staff, not to the artists
or performers, with whom this article is
not directly concerned.
Fig. i shows one possible organization
chart of a good-sized broadcasting station.
The great mogul on top is not the same in
every station. On a newspaper which has
gone in for broadcasting he may be one of
the editors or the pro-
motion manager. He
may be the president
or the vice-president
of a radio company or
any other organiza-
tion that has entered
the radio field. In
the case of a univer-
sity he may be a pro-
fessor or dean. What
happened in all these
instances was the in-
trusion of a new ac-
tivity into a more or
less settled organiza-
tion, engaged in sell-
ing chewing gum or
operating a telephone
system or in teaching
or what not. Some
executive, with or
without qualifications
for the task, was en-
trusted with the job
of broadcasting.
Often the head of the enterprise took the
new responsibility for himself. At any
rate, this "manager or other executive"
is the man who makes the ultimate deci-
sions, who decides how much money shall
be spent, what the policies of the station
shall be, and other matters of that sort.
He may not be found at the offices of the
station, and he may have a lot of other
things to do besides broadcasting, but his
is the guiding hand, and, if he is not him-
self one of the chief executives or owners of
the enterprise, he reports directly to them.
From this officer, the organization line
splits into a number of divisions: program,
publicity, and technical. There may be
some variations. For example, if the sta-
tion broadcasts for toll, and has an in-
come, there may be a head accountant or
bookkeeper. Again, the publicity man
may not report directly to the executive;
he may be a member of the program de-
partment. And often, of course, various
diverse functions may be assigned to one
man, complicating the chart in ways which
need not be taken up here. If the station
IT TAKES ALL KINDS OF PEOPLE TO RUN A BROADCASTING STATION
is large, instead of one position shown on
the chart, there may be a number with the
same title. For example, there might be
two music critics instead of one, as shown
in Fig. i. In presenting this chart, the
object has been to make it inclusive enough
for large stations and yet as simple as pos-
sible. Thus stenographers and general
office workers are not included, and special
workers, such as statisticians, who may be
employed in some instances, are also
omitted.
The work of the publicity representative
is probably the least unfamiliar to the
general reader, since press agents antedated
broadcasting. However, it is not quite
the same job in a broadcasting station as in
a theatre or hotel. The publicity man goes
around to the various radio editors in his
town and tries to keep on amicable terms
with them. They are necessary to him
and he is also necessary to them, for he
supplies them with material for their
pages, material which may be written by
a copy writer or by the press representa-
tive himself. The members of the pub-
licity staff are also in
contact with the art-
ists, who give them
photographs and data
for articles, which, if
they are interesting
enough, get into the
newspapers. Part of
the publicity man's
duty, also, is to attend
to the printing of pro-
grams well in ad-
vance, sending them
to newspapers, and
calling up those in
his own town, on all
broadcasting days, to
make corrections in
these lists, for there
is many a change in
the programs between
booking and modula-
tion of the carrier.
This information the
press man secures
from the booking de-
46
RADIO BROADCAST
NOVEMBER, 1925
MANAGER, or other EXECUTIVE
DUOOEAM DIRECTOR
I I
Assistant Musical Chief Assistant Studio
Prt^ram Director .Announcer rrcgr<am Director
Director adage «• Director
incJiiagt of Assistant
afuJKifing 4MNMMT
*"&*»*
PUBLICITY REPRESENTATIVE.
Copy Wriler
Assistant
I
Pw<ram Proinun
Sdkitor S^jtor
Director
*v
Chief Transmitter Chief Control Chk f Reid
Operator Operator Operator
. .
Twins- Irans- Trans- Control Control Control Field Field Field,
initter mitter mitter Operator Opoaior Operator Opr Opr Opr
Opr. Opr Opr
Jtanmnx«r Announcer Announcer
FIG. I
"Organization chart" of a typical large broadcasting station. Mr. Dreher explains how the affairs of a typical station proceed — from the inside.
A broadcasting station is a business organization, frequently one of some size, but the public knows very little about broadcasting except the impression
gained from whatever they hear from the announcer
partment of the station. Publicity activi-
ties include photographing, of course, this
being handled, ordinarily, by a professional
photographer who does such work for the
station as the publicity representative may
direct. A scrap book is also kept, and the
publicity representative may hand in oc-
casional reports on the amount of space he
has been able to secure, since the object of
every station is to be well known, and a
good press agent helps in that endeavor as
much in broadcasting as in saving souls or
governing the country.
The program director, like the chief
executive to whom he reports, may have
come into broadcasting from anywhere.
Some of them are ex-concert managers,
with a wide acquaintance among musicians.
Others are ex-newspaper men. Still others
are musicians, theatrical booking agents,
actors, clergymen, to name a few of the
vocations which might be mentioned.
The oldest program manager in the New
York district, in point of experience, is a
mechanical engineer. What a program
manager was doesn't matter; his duties are
to keep in touch with the public and its
desires, to see that the station gets the
best program material available, to mould
the programs in accordance with station
policy, to coordinate the work of his
department, to report to the management
and to exercise various other special and
executive powers. In a large station, if
he saw everyone who tries to see him, he
would hold his job about a week before the
hospital claimed him. His assistants pro-
tect him to some extent.
Among these assistants there may be a
subordinate program director in charge of
soliciting programs. He may have a squad
of program solicitors under him, or he
may do all the work himself. If so, he is
primarily an outside man, going around
interviewing prospective broadcasters. He
keeps a sharp watch on the newspapers for
reports of what may turn out to be "fea-
tures." If the station is one which sells
time, he is a sort of advertising solicitor,
seeking customers, aiding them to arrange
suitable programs, etc.
Just as a magazine gets a certain num-
ber of unsolicited contributions from writ-
ers, so a good many artists, some very good,
some very bad, visit a broadcasting studio
to volunteer their services. Hence a mu-
sician must be attached to the staff to give
these people auditions and weed out the
poor ones. He may do this at a time when
the station is not on the air, and serve as
the accompanist of the station when it is
broadcasting. He disposes of the aspirant
he cannot use as tactfully as possible, and
sends the remainder to the booking agent
of the station, who is in a position to ar-
range for a definite time when they may
broadcast. The musical critic should, if
possible, be equipped with a suitable mi-
crophone pick-up, audio frequency ampli-
fier, and loudspeaker, so that he may hear
applicants about as they will sound on the
air, for some people with satisfactory con-
cert voices do not transmit well, owing
to the limitations of present-day electrical
reproduction.
The booking agent of the station may
be an assistant program manager, or
the program director's secretary. He
or she must be in close touch with the
director in order to carry out his wishes in
making up the program, assigning desirable
times in accordance with the importance of
events, and so on. Generally, the booking
official knows pretty well what the program
director will approve, and does not have to
ask him in the majority of cases. The
system of booking programs works with
the program book as its basis, which is
marked in quarter-hour intervals for all
the time the station has on the air. When
an event is booked, the appropriate spaces
are filled in several weeks ahead of time, as
a rule, and the program people can tell at
a glance what time is still free. Thus a
program solicitor may come to the booking
clerk and ask, "What time have you free
after 8 p. M. on November 3rd?" if he has
something in mind for that date. The
booking agent is also responsible, as a rule,
for making sure, on the day of broadcast-
ing, that none of the performers have
forgotten their dates or will be unable to
appear for one reason or another. He has
another job — that of furnishing lists of
events booked to the publicity man, engi-
neer, and announcers, so that suitable ac-
tion may be taken, schedules made out,
etc. And, every day, the program for the
day, correct in every detail, is issued to all
the operating and announcing forces con-
cerned.
So far we have been more concerned with
making up the programs than with broad-
casting them. The latter job is princi-
pally in the hands of the technical force,
and it will be taken up in more detail
in our next issue, when we expect to
print an article on "Technical Routine in
a Broadcasting Station." The operating
personnel is headed by a technical man,
styled variously as "Chief Operator,"
" Engineer-in-Charge," "Chief Engineer,"
or blessed with some other mellifluous title.
Sometimes he is a graduate electrical engi-
neer, sometimes he is not; but in any case
his function is to see that the amperes flow
NOVEMBER, 1925
SOME THOUGHTS ON "SUPER-POWER"
47
in the antenna, when needed, and that
they are modulated as accurately as may
be. on whatever speech and music the sta-
tion is supposed to broadcast. The actual
work of broadcasting, in the larger stations,
is handled by a squad of operators or junior
engineers, and the technical man in charge,
like the program director, is something of
an executive in addition to his specialized
functions. But in most stations, probably,
the engineer wears headphones and turns
knobs. Assuming, however, that the sta-
tion is a big one, the technical work is
divided into outside or field pick-up, and
internal station jobs. The field work is
usually handled by a Chief Field Operator,
who may have a considerable number of
assistants, up to a dozen in some cases.
He makes up the schedules for these men
and usually handles some of the important
jobs himself. The inside work may also
be directed by a Chief Inside Operator,
but frequently the control room of the sta-
tion is separated from the power plant, so
that a Chief Control Operator and a Chief
Transmitter Operator are separately re-
sponsible for the work in these two de-
partments. The control room is in close
association with the studios, while the
power plant is isolated; the former
handles only relatively weak currents,
while the latter deals with dangerous
voltages and powers. Thus the qualifica-
tions for the various technical positions,
inside and outside, vary widely. The
operation of a good-sized station, with
perhaps a score of engineers and operators
on its staff, is quite a complicated enter-
prise, and the complications increase in
proportion to the number of outside events
where program material is carried to the
station proper by wire lines. The routine
and methods of technical broadcast opera-
tion will be taken up in detail in later
issues, together with the tasks of the studio
director and announcers, who work with
the engineers in the actual broadcasting of
the programs.
A Forgotten Romance: German
Radio in Africa
POSSIBLY it should be called a
tragedy. It is one of the stories
of the war, of radio in war. As far
as I know, it was never printed in the
United States. A German radio and tele-
graph engineer, Doctor Roscher, wrote it
for Archivfur Post und Telegraphic, August,
1920.
Before the war the Germans had a col-
ony, Togoland, in West Africa. As early
as 1909 they decided to place a wireless
station there for communication with
Berlin. The site chosen was Kamina, four
miles from the terminus of the Hinterland
Railroad.
"At last, on the night of the yth of June,
1911," says Dr. Roscher, "after some
two years' trying, signals were picked up
for five minutes from the great station at
Nauen. But before this was achieved mast
after mast had been destroyed by torna-
does, and when the first signals from Nauen
reached them it was through a captive
balloon some 450 feet up, as substitute.
At the same time they heard Poldhu, Corn-
wall, talking." This "talking" was in tele-
graphic cftde, of course.
After prodigious labor in the tropical
jungle, the station was completed on June
20, 1914. It had three steel masts 225
feet high, and six 360 feet high. The
power was supplied by two 500 hp. tur-
bines and two of 120 hp. By day it
transmitted to Nauen on 6000 meters, by
night on 4500. During the night it re-
ceived, when it could, through the appall-
ing equatorial static.
A few weeks after completion of the
station the war broke out. It is said that
800,000 tons of German shipping were
saved through the activities of this trans-
mitter. It handled traffic from South
America and Germany. Naturally, it was
not left alone for long. The French ad-
vanced against it from Dahomey, the
British from the Gold Coast Colony.
On August 2yth the station was de-
stroyed by its own personnel, in a few
hours, by "explosions and smashing," in
accordance with contingent instructions
from Berlin. The enemy was then 30
miles away, in such numbers that success-
ful resistance was out of the question.
"Finally," the account reads, "they pro-
ceeded to overthrow the nine towering
masts by loosening the couplings at the
foundation blocks. Like a row of gigantic
ninepins they went down, one after an-
other, with a terrific metallic ringing noise,
heard, it appeared later, far away in the
silence of the night."
Five years of research, five weeks of
service, and suicide. That was the career
of the German station at Kamina in Togo-
land, which began and ended long before
radio waves received their modern burden
of jazz, grand opera, and inspirational talks.
Rebuttal in the Discussion of
Super-Power
In the October magazine, Mr. Dreher and Pro-
fessor Williams aired out the question of super-
power broadcasters as opposed to the service which
can be rendered by $oo-watt stations. Professor
Williams, of station WHAZ, Rensselaer Polytechnic
Institute, Troy, New York, has accepted the op-
portunity to reply to Mr. Dreher' s remarks in the
October RADIO BROADCAST and they appear below.
The views of Professor Williams and Mr. Dreher
are not necessarily those of the editors. Professor
Williams said, on page 764 of our October issue,
that this magazine had " reversed its position on
5oo-watt stations." That is not the case. We
are simply giving a hearing to both sides. Inso-
far as the present discussion is concerned, the
debate is now closed. — THE EDITOR.
IN THE articles appearing in the September
and October numbers of your magazine on
the subject of super-power broadcasting
stations, Mr. Dreher, unable to meet the facts
brought out in the fields of electrical engineering,
automobiling, and cash register use, all of which
were selected by him, jumps into the field of
• RAOV
SOME ONE IS ALWAYS EXPLAINING THE MYSTERIES OF RADIO
48
RADIO BROADCAST
NOVEMBER, 1925
RADIO INVESTIGATION IS AS FASCINATING AS THAT IN OTHER FIELDS
physical optics, drags Galileo and his telescope
into the argument, and ends — 1 am sorry to say
— by a rather harsh criticism of his opponent.
If radio broadcasting were carried on between
two perfectly definite power levels, radio
receiving sets could be designed to function
satisfactorily in the hands of the radio public
between those limits. This does not exclude
the super-sensitive sets for scientific and indus-
trial use any more than the fact that the human
being has eyes excludes the use of the telescope
or microscope in similar fields.
I do not know how much experience Mr.
Dreher has had with the difficulties of properly
adjusting telescopes and microscopes, but, from
my own experience, I am thankful that my eyes
function satisfactorily for most purposes without
the aid of these complicated instruments which
require so much skill for their satisfactory use,
and at the same time are very expensive.
Similarly, I am for a broadcasting system
which will operate between fixed power levels
so chosen that a relatively simple and inex-
pensive receiving set will function between these
levels satisfactorily for general use, and will not
require a great amount of technical skill on the
part of the listener to operate it. While Mr.
Dreher is unwilling to grant a high order of
technical intelligence to the listener, he advo-
cates putting in his hands the type of instru-
ment which requires a maximum of technical
intelligence to operate. This simply proves that
he misunderstands the radio public, and does
not know that the present trend in the manu-
facture of receiving sets and tubes is in the
direction of making the complete receiver as
near fool-proof as possible.
Nature has been very kind in not placing the
sun in the direct line of vision at the time when
the light rays from the sun are most intense and
by placing the sun behind the earth at night in
order that the earth's inhabitants may enjoy
the moon or star-lit heavens without any in-
terference from the sun's rays. If Mr. Dreher
can devise some scheme whereby he can shut
down his super-power stations altogether, or
remove them so far in space, time, or wavelength
from the other broadcasting stations so that
they will interfere as little — with the programs
now being broadcast — as the sun interferes with
our enjoyment of the heavens at night, I do
not believe that any one will object, and he can
enjoy his super-power stations to his heart's
content.
My opponent accuses me of not being courage-
ous enough to enter the radio field against him.
It was not lack of courage, but lack of a mean
disposition, and, even now, after a second chal-
lenge, 1 would rather not do it. However, let
us look into this little computation of his. He is
a very clever and interesting writer and uses a
lot of words to prove simply this: If you have
500 watts and increase it to 50,000 watts, every-
thing else remaining constant (presumably,
including the science of mathematics) you have
one hundred times as much power on the an-
tenna, and therefore one hundred times as
much power at all other locations. Now, if he
had had as much experience as I have had dur-
ing the last fifteen years trying to transmit
energy at different power levels to the points
where you want it to go, instead of into copper
roofs, water-pipes, steel buildings, etc., he would
never have penned that article and misled his
readers into believing that they were going to
receive one hundred times the volume from
WGY'S 5o,ooo-watt transmitter, on its first test,
that they receive from our 5OO-watt transmit-
ter. This is no argument against super-power,
but against the deplorably misleading state-
ments one reads in the radio press. Station
WHAZ stood by on August 24, 1925, to allow WCY
to complete their transmission tests, and our
staff was as disappointed as the WGY staff
with the results. It was my good fortune to be
listening in at one of our test stations and the
increase in power level at that location was
almost nothing.
The set I was operating is one we are at present
using for field strength measurements. It
makes one of the best receiving sets (I did not
make it) I have ever had. On several occasions
1 have loaned this set to B. C. L.'s and they
have been invariably dissatisfied with it, the
reason being that it requires as fine and delicate
adjustment as a high-grade microscope and when
not properly handled will absolutely ruin the
best program beyond recognition.
Mr. Dreher's other contention regarding the
advantages of one or two steps of amplification
at the transmitter rather than at the receivers
reads as easily as the one just discussed and is
as misleading. Here again he assumes ideal
conditions which do not exist. The simple
fundamental error made in his assumption is
that a receiving set receives energy only at the
frequency for which it is tuned. He intimates
that I have never listened to DX. Well, I have,
and 1 have not only amplified DX signals to loud
speaker value but have sent them out through
our experimental station 2 XAP with sufficient
power and clearness to be heard in California
without appreciable distortion. These re-
broadcasting experiments were carried out in
connection with other experiments, the primary
purpose of which was to determine the facts
regarding the sensitivity and selectivity of the
most widely used receiving sets already owned by
the B. C. L.'s. Station 2 XAP was used as an in-
terfering station with different amounts of
power in the antenna and at different frequencies
(wavelengths). The receiving sets were lo-
cated at various points at different distances
from 2 XAP. These experiments proved con-
clusively that increasing the power level of the
interfering station, which is usually a local
station, by as much as one or two step? of ampli-
fication prevented us from receiving stations
which could be received at the lower power
levels of 2 XAP with good enough quality for re-
broadcasting purposes. It could not be ex-
pected that conclusions drawn from radio
engineering experiments carried out through two
cold winters would agree with opinions formed
in a steam-heated New York City office. You
must decide for yourselves which are of greater
value.
Space will not permit me to tell you the little
I know about transatlantic radio telephony and
telegraphy and how international broadcasting
will be accomplished. I will content myself
with the statement that our station has already
been rebroadcast on the other side of the At-
lantic, and I am not really as ignorant on the
subject as Mr. Dreher would have you believe.
I cannot agree with my opponent in his final
conclusion to the effect that talk on this subject
is of no value. If he really has a set that can be
interfered with by a cat rubbing his back against
the fence and cannot pick up a joo-watt station
only one hundred and fifty miles away, we have
learned something from his side of the argument,
granting my points sum up to zero.
The Memoirs of a Radio Engineer
VI
IN 1910 I graduated from the elementary
school, and a little later my family
moved to another house, where I started
what may not have been an innovation,
but it was certainly an early use of an ex-
pedient now very common — the resort to
an indoor antenna where it is not feasible
to erect one outdoors. The landlord ob-
jected to my trespassing on the roof of his
three-story treasure, on the ground that I
would wear through the sheet iron and
cause the roof to leak, that I might fall off,
that an antenna would be unsightly, that
it would attract the unchained lightnings,
etc., etc. So I strung two wires about
fifty feet through our apartment and, as
the neighborhood was one of frame struc-
tures, obtained satisfactory results, as the
times went. I had a crystal detector, con-
sisting of a piece of silicon, ground flat
and smooth on one surface — God knows
why, but the current superstition was that
silicon should be used in that way — and
imbedded in solder, with a blunt brass
point pressing down on it. This was at-
tached to the antenna and a gas pipe
ground, and a 75-ohm receiver, swiped
from some telephone desk set, connected
in parallel with it. Once in a while this
combination picked up signals very faintly.
They were probably those of near-by ama-
teurs. After a while I got together a
tuner — a cardboard mailing tube about
NOVEMBER, 1925
ANTENNAS WERE UNFAMILIAR IN 1912
49
two inches in diameter, wound with No.
24 enameled wire, and provided with two
sliders making contact with a bare swath
the length of the winding. This consti-
tuted a conductively coupled system, with
a tuned antenna and approximately tuned
secondary or detector circuit. It was
quite effective, remarkably so in compari-
son with the untuned set, and it was
further improved by the substitution of a
alena — cat whisker detector for silicon.
Dicking up a signal was no longer an
achievement; it could be accomplished
almost any time. The United Wireless
tation at 42 Broadway, New York City,
ame in fairly loud, although about eight
liles away. There was also the Wana-
laker station, MHI, in New York, com-
lunicating with MHE in Philadelphia —
erhaps this was a little later; it is rather
tiard to remember down to a year after
;ifteen of them have rolled by. The rest
vere largely amateurs. 1 also had a
transmitting station. My parents had
aught me a quarter-inch spark coil, in a
quartered oak case. In my own room,
vhich measured about eight by ten feet,
strung up an antenna of aluminum wire,
vhich was popular at that time, consisting
}f about a dozen wires forming a grid which
Dvered the whole ceiling. The spark coil,
perated from dry cells and keyed by some
crude spring and knob arrangement, when
onnected to this antenna and a ground,
vas heard by an amateur about five blocks
away-, we engaged in conversation, and he
paid me a visit, declaring that I came in
louder than some of the boys with outdoor
antennas. The spark gap, I recollect,
consisted of zinc electrodes turned out for
me by a boy who attended Stuyvesant
High School and had access to the machine
shop there. Among other amateurs in
the neighborhood, some were using long
single wire antennas at a time when multi-
wire ones were all the fashion, until, on
the advent of broadcasting, the single wire
antenna for reception came into its own.
Many quaint superstitions regarding an-
tennas and other radio subjects raged among
these innocents. For example, it was de-
clared, on the strength of an article in a
periodical, that "the wavelength of an
aerial was four times its mean height
above the instruments." There was one
comrade, it happened, who had a sloping
antenna running from his roof to a clothes-
pole, with a horizontal lead to the set,
the lower end of the antenna being about
as far below the apparatus as the upper
end was higher. In a discussion on wave-
lengths, in which everyone boasted of the
great length of his own wave, one of his
rivals taunted this fellow, saying, "You
ain't got no wavelength," and backing
his argument with the article in ques-
tion. Confronted with the fact that the
antenna radiated audible signals, he merely
shrugged his shoulders and admitted that
there might be signals, but, properly
speaking, no wavelength existed. I do
not remember the name of this dialecti-
cian, but he deserves high honors, for he
is the forbear, in the radio field, of a great
multitude who substitute words for sense,
and they should keep his memory green.
It was in the early part of 1912 that 1
wrote my first radio article, for which I
received the sum of 65 cents. It was a
description of a Tesla coil, fed from the
quarter-inch spark coil which also fur-
nished the oscillations for my transmitting
set, and it was certainly one of the smallest
Tesla coils ever made. The secondary or
high frequency winding covered an or-
dinary small test tube, the turns being
No. 30 silk-covered wire carefully spaced
by hand and dipped in wax. Over this
were wound a few turns of heavy weather-
proof wire, in parallel with a leyden jar
across the spark gap of the induction coil.
The secondary of the Tesla converter gave
a one half inch high frequency spark,
which, being confined to the surface of the
body, could be taken without sensation —
a great opportunity for fooling other boys
who believed that an electric spark always
meant a severe shock to any one monkey-
ing with it. The same credulity was being
exploited by some vaudeville acts built
around large Tesla transformers, throwing
sparks several feet long, which enabled the
actors or "professors" to announce that
they could withstand potentials of millions
of volts where a mere 1800 would kill an
ordinary man in the electric chair. The
distinction between high frequency cur-
rents and d. c., and the matter of the num-
ber of amperes actually flowing through
vital tissues, were of course unmentioned
in these acts.
For the July, 1913, issue of Modern
Electrics 1 also wrote an article on "indoor
aerials," which won the third prize of
$1.00. Recently, in looking up this pub-
lication, I was amused to note that the
second prize in that issue ($2.50) was cap-
tuied by Harold Beverage, who was
probably at that time a student at the
Universityof Maine,
or, more likely, pre-
paring for his college
course, as I was. He
was not wi i t ing
about antennas, in
fact, his contribu-
tion was electrical in
nature and really
had nothing to do
with radio. About
six years later this
boy was to invent a
new type of anten-
na, the "wave an-
tenna," whose
highly directional
properties, eliminat-
ing the bulk of the
static on trans-
oceanic reception,
marked a great step
forward in high
power commercial
radio.
In 1912, however,
antennas were not
yet familiar objects, and the indoor vaiiety,
particularly, seemed very strange to most
people. They could not conceive of waves
penetrating wood and glass and other solid
objects. One friend of my father's came
to the house and listened attentively to
the wireless signals, but when he asked
whether I had an antenna on the roof, and
I pointed to my indoor wire, he declared
vehemently that I was hoaxing him, and
that the signals were being cooked up
somewheie in that room. I argued with
him for a long time, and grew very angry,
for I was young and it irritated me to be
accused of fraud when I knew that the
signals were genuine and there was nothing
extraordinary in such reception. I had
not yet learned the truth of Schiller's say-
ing, "Against stupidity the gods them-
selves fight in vain," an aphorism which
the progress of the engineering arts has
not affected in any way.
The Country Is Saved! Advertisement
of a manufacturer of automobile accessories
entering the radio field:
HICCOUGH & Co. Radio — the ensemble
radio — is now ready!
The good news has been hard to keep!
Extreme secrecy has guarded every move and
discovery of Hiccough engineers, who have for
more than two years been engaged in the solu-
tion of a tremendous problem — the perfection of
radio! Yet for months the radio world has been
atremble with the rumor that "something
revolutionary in radio is about to be an-
nounced."
So the announcement of Hiccough & Co. is
not a surprise because everybody has been ex-
pecting it. You know you yourself have been
waiting for a concern like Hiccough & Co. to
take the uncertainties, disappointments, and
troubles out of radio and give you only real re-
sults.
Italics and exclamation marks not ours. At
last! Radio is to be made perfect — by a man-
ufacturer of automobile accessories.
^^^^^••^•••••••••••••••i
FI^B
THE LANDLORD OBJECTED TO TRESPASSING ON HIS TIN
TREASURE
IONE-TYPE loud
speakers, particu-
larly the Western
Electric Loud Speaking
Telephone No. 54oAW,
when used with a receiver
not designed especially
for use with them, may
be greatly improved by a
few simple adjustments.
If these suggestions are
followed with care, a
greatly improved signal
will result, and the
speaker itself will not be
harmed. It is no es-
pecial secret that many
Western Electric engineers make
these adjustments on speakers used
on their own radio sets. This is the
first time that information for doing
the trick has been made public. The
operation, in the parlance of the
engineers, is called loading.
The first operation necessary is
to loosen the small thumb screw
at the apex of the cone. It is well
to wind a rubber band around it
after loosening, to prevent its becom-
ing lost.
The second operation (see Fig. i),
is the removal of the five screws
nearest the center, at the rear of
the speaker. Removing these
FIG. I
FIG. 2
FIG. 3
screws permits the metal ring,
the composition ring, and the
metal shield which they hold in
place, to be removed and leaves
the mechanism open to view.
The third operation is the re-
moval of the three screws which
hold the mechanism in place on
the main frame.
The fourth step in the proce-
dure is to remove the small screw
to which the screw driver is point-
ing in Fig. 2, and to place a small
piece of friction tape between the
two metal parts the screw holds
together. Of course, a
small hole must be cut in
the tape to permit the
screw to pass through.
Then the piston of the
driving mechanism (see
Fig. 4) is wound with
rubber tape which is
tightly stretched. In ap-
plyingthe tape tothe pis-
ton, great care must be
used to avoid bending
the pin.
After the driving pin
has been wound with rub-
ber tape as shown in Fig.
3, the tape should be vul-
canized by burning a match under
it. After the tape is vulcanized (see
Fig. 4) it will not loosen while the
speaker is in operation. With this
step, the alterations to the cone are
complete and re-assembly is begun.
First, place the driving mechanism
back in place and hold it there tem-
porarily by bringing up the three sup-
porting screws with their lock washers.
This mechanism must be centered, and
that may be accomplished by shifting
it onewayand another before the sup-
porting screws are brought up tightly.
Following this, it is but necessary to
replace the parts removed and tighten
the thumb screw and the job is done.
The sound produced by the remodeled
cone is greatly improved.
FIG. 4
FIG. I
A rear illustration. By means of small bushings, the audio-frequency transformers are underslung from
the bottom of the shelf. In order from right to left the tube sockets are, first audio-frequency amplifier,
radio-frequency amplifier, detector, and the last two are the two parallel tube sockets of the second stage
audio amplifier
Improved Five-Tube Receiver for the
The Crystallization of Modern Improvements in Receiver De-
sign— Especially Arranged for Ease of Assembly and Operation
By ARTHUR H. FULTON, Jr.
ALONG with the developments in
/\ receivers to be made public for
£ \V the fall radio season comes one
which, in the estimation of its
designers, is very high up in the scale.
A great deal of time and study and many
hours have been spent in the laboratory to
produce a five-tube receiver — improved
electrically especially in the unseen parts
that are so important — that would give
to the inexperienced constructor a
receiver which would contain the
best results of design and at the
same time have a finished com-
mercial appearance. A receiver
has been designed which is very
easy to assemble. All the con-
structor needs is a soldering iron,
a few other tools, the parts, and
the ambition to complete the
job.
The term assembly is used
advisedly because it can hardly be
said that the receiver to be de-
scribed entails either elaborate
construction or detailed layout, dimen-
sioning, or the necessity of machine shop
equipment.
Electrically, the circuit embodies and in-
corporates every important and worth-
while refinement of control and accuracy of
coil design that can be approached in
factory-made jobs. Here is a receiver em-
ploying a tuned, neutralized radio-
frequency amplifier which has unusually
CT* HERE is a story behind the development of the receiver described
•*• in this article. It was felt that there were a large number of
radio enthusiasts, not especially gifted mechanically, who would
welcome the design of an outfit which would take the guesswork out of
home receiver construction. It would be possible, thought the designers,
to produce a highly efficient five-tube non-radiating receiver embodying
all the best points of the Roberts Knockout receiver — which, month in and
month out, continues to be the most popular receiver for home construction
in use in the United States to-day — and to select a group of the best parts
obtainable on the market, even to the panel. So the result is a design
which we can heartily commend to any constructor who wants to build
an efficient receiver with as few mechanical difficulties as possible, and
who, when the thing is completed, will have a set whose appearance is as
finished as a factory-made product.
— THE EDITOR.
high "gain", a regenerative detector fol-
lowed by a straight stage of audio-frequency
amplification, and that in turn followed by
a special power amplifier consisting of two
tubes arranged with their elements con-
nected in parallel.
No reflex feature is employed in the cir-
cuit, which sets this design off from the
conventional Roberts Knockout circuit,
which is, in many ways, similar. The high
degree of selectivity and sensi-
tivity of the five-tube set may be
attributed to these modern im-
provements and changes.
Going one better than the
orthodox kit idea, the designers
of this receiver so arranged its
construction that with the aid of
a basic unit consisting of the
panel, shelf, and miscellaneous
hardware, it is possible for trie
builder to patronize his local
radio dealer in the choice of
the various other elements
necessary for the construction of
52
RADIO BROADCAST
NOVEMBER, 1925
FIG. 2
The apparatus behind the panel. This view clearly shows the location and placement of the sockets,
ballast resistances, and pin jacks on the shelf. Note that the coil units are at right angles to each other
the set. Instead of working from a set of
blue prints on to a panel, the constructor
has the opportunity of buying the panel
ready-drilled, together with the other es-
sentials, and merely assembles the rest of
the material which goes to form the com-
pleted receiver. Brackets, cut and bent to
shape, support a shelf upon which a majority
of the apparatus, such as tube sockets, audio-
frequency transformers, ballast resistances,
and the neutralizing condenser are mounted
in the completed job.
THE APPARATUS USED
IN ITS mechanical and electrical design,
1 consideration has been given seriously to
the employment of none but the best ap-
paratus obtainable (all of which has been
tested and approved by the Laboratory of
RADIO BROADCAST). In its present form,
the construction and operation of the re-
ceiver has been modified to simplicity with
the inclusion of ballast resistances for all
but one tube, one output jack for the loud
speaker, and pin jacks for battery terminals
mounted on the rear of the tube shelf.
Following the trend of modern design, the
receiver has been constructed on a slanting
panel and is entirely self-contained thereon,
the apparatus being mounted either directly
on the panel or on the shelf supported by
the brass brackets which are fastened to the
panel.
High grade audio-frequency transformers
employed in the audio amplifier, together
with the peculiar parallel arrangement of
the last two tubes, insure distortionless
quality output.
In this receiver the tubes are not situated
in the conventional manner, but in order
from left to right looking over the top
of the receiver are: fust audio, radio fre-
quency, detector, second audio (this last
named consists of two tubes connected in
parallel).
Volume is controlled by means of the
filament rheostat connected in series with
the filament of the radio-frequency tube.
The tuning coils used permit of the re-
ception of signals from those stations which
operate on the higher frequencies (low
wavelengths) and will amply cover those
stations situated at the other end of the
scale.
The tuning is reasonably sharp on the
antenna coil control due to the absence of
reflexing. Tuning in the detector circuit
is the same as before and is comparable to
tuning a regenerative receiver by the squeal
method. Briefly, to tune with this method,
the tickler is well advanced to produce re-
generation and by rotating the detector
tuning condenser, squeals will be heard
every time the circuit beats with the carrier
wave of a station transmitting at that time.
Once a desired station is located in this
manner, the squeal can be eliminated by
loosening the coupling between the second-
ary and tickler. While, in the standard
three-circuit regenerative receivers this
system would play havoc with other re-
ceivers in the neighborhood, in this re-
ceiver, due to the use of the Roberts
system of neutralization which is a positive
preventive, no squeal is passed along to the
antenna to cause disturbance.
Three views of the receiver shown here
indicate its commercial appearance and
mechanical design, and by means of the pre-
pared parts, duplication in design by all
those attempting its construction is as-
sured. The models shown differ in some
points of mechanical refinement from the
receivers it will be possible to construct
from the commercially available units.
Considering the individual variations in
the construction of receivers described in
radio periodicals, and realizing the troubles
encountered by constructors in modifying
original designs to suit their own fancies,
it is not difficult to appreciate the special
attractions and favor of a plan which will
minimize the detailed dimensioning, layout,
and assembly of receivers.
Analyzing the circuit in Fig. 4 the salient
features herewith described are apparent.
ELECTRICAL DETAILS OF THE CIRCUIT
TN THE receiver illustrated, the variable
*• condensers Ci and C2 are shunted across
their respective secondary coils, the first
secondary functioning as a combined pri-
mary-secondary, in auto-transformer fash-
ion, but in the finished mode!, a separate
antenna coil has been provided. These con-
densers are of the standard .0005 mfd. value.
The condenser Cj is that with which
neutralization is obtained and is of the
value of .000032 mfd. Two by-pass con-
densers, 05 and C6, are employed, one
across the primary of the first audio trans-
former, and B battery in its circuit, its value
being .001 mfd. and the other a .006 mfd.
one, connected from the minus A to the
NOVEMBER, 1925
AN IMPROVED FIVE-TUBE RECEIVER
53
lower end of the plate coil in the radio-
frequency tube circuit.
A tickler having variable coupling with
the detector secondary provides regenera-
tion. The grid leak condenser €4 is
.00025 mfd., shunted by a grid leak of 2
megohms. The value of the grid leak will
vary with the particular detector tube used.
Low ratio audio-frequency transformers
of the latest design, having large iron cores
upon which are wound large coils, should
be used. This sort of transformer gives
equal response on all the audio frequencies,
insuring good quality of signal.
The unusual system of parallel tube am-
plification is practically new to the radio
broadcast field, and is intended for the pre-
vention of overloading in the last audio
amplifier.
Two major controls afford tuning over
the entire broadcast range. These are the
tuning condensers; the detector circuit is so
designed that its tuning is slightly sharper
than the antenna circuit. As previously ex-
plained, regeneration adds to the simplicity
of tuning, and the control for the tickler coil
is located in the top center of the panel.
FIG. 3
A clear representation of the method of supporting the coils, shelf, and brackets.
The audio-frequency transformers are mounted at right angles to each other to
minimize magnetic coupling effects
This improved five-tube receiver employs the following parts, others, similar,
can be selected from apparatus approved by RADIO BROADCAST:
| i. 80
18.00
2 Condensers ooo5mfd (Hammarlund), @ $5.00 ea
10.00
2 Dials, 4 inch, Na-ald, @ $.75 ea
1.50
I Dial if inch Na-ald
.25
4 Ballast Resistances, Amperite, @$i.ioea
4-4°
. . 6.00
5 Sockets Na-ald @ $ 75 ea
3.75
Rheostat 25 ohms Carter
1 .00
65
1.25
.70
Grid Condenser ooo25mfd , Dubilier
.50
.40
.45
65
9-4°
$60.70
Tuned Radio
Frequency Amplifier X
Power Audio
Frequency Amplifiei
o
A
45
67
B FIG- 4
The circuit diagram of the final receiver differs slightly with the diagram here in that a separate antenna coil is provided in place of the auto-
transformer arrangement shown. This antenna coil has three leads, the two ends and a center tap which allows of correct adjustment of the
antenna coupler with the particular length of antenna used. The values of the various apparatus employed are: Ci and C2= .0005 mfd.;
C3 = .000032 mfd.; C4 = .00025 mfd.jCj = .002 mfd.; C6 = .006 mfd.; Ri = 25 ohms, R2, R3, R4, R$ = J-ampere filament ballast resistances;
R6 = 2 meg; AFTi and AFT2 = 2 to i audio-frequency transformers. Note the parallel arrangement of the last two tubes. The neutralizing and
primary windings of the r.f. coupler are indicated as a double-wound coil, but in reality it is a single-wound coil with a tap taken off the middle turn
RADIO BROADCAST Photograph
THE TRANSMITTER HOUSE AND ANTENNA AT 2 GY
Where the RADIO BaoADCAST-Eveready short wave experiments are in progress.
The "driver" antenna can be clearly seen above the small operating house in
the right foreground. The main 4o-meter antenna is suspended vertically from
the supports between the two 85-foot masts
Wi
'HEN radio amateurs first
explored the region of the
very high frequencies, say
beyond 2000 kilocycles (100
meters and lower) the phenomenal dis-
tances covered with low power were at-
tributed to the total lack of interference
encountered there. Then as these high
frequency ether lanes became the common
property of thousands of amateurs, it was
realized that the results obtained there were
due to other causes than freedom from
interference.
What these other causes are has been the
subject for considerable speculation among
the radio learned, and the experimental
work carried out to discover the laws gov-
erning transmission at high frequencies has
been very valuable. To aid in this ex-
perimental work, the Laboratory of RADIO
BROADCAST has in operation a station work-
ing on high frequencies under
the amateur call of 2 GY.
This work will be prosecuted
during the coming winter
with the cooperation of the
National Carbon Company
in an endeavor to learn all
that is possible of what goes
on on the higher frequency
bands.
To see what happens at
these higher frequencies, let
us perform a hypothetical
experiment at our trans-
mitting station. Starting
with 1500 kilocycles (200
meters) — the wave used by
all amateurs in the "good old
days" — let us see how far, on
the average, we may transmit
with a given power.
What Do We Know
The Fascinating New Problems of Radio
High Frequencies — A Distinct Branch of
Are Yet to Be Discovered — How Radio
By KEITH
Director, Radio
Aside from the frequency and the power used, the
other factors limiting our transmission are the time of
day, the type of antenna, and nature of the country
between the transmitting station and the receiver. At
night, conditions are vastly different than during day-
light— as all radio enthusiasts know. The effect of
intervening objects has not been completely investigated.
Other conditions theoretically remaining the same,
increasing the transmission frequency (decreasing wave-
length) widens the radius over which signals from our
station may be heard. If the frequency is increased we
find that our range increases accordingly until at 7000
to 12,000 kilocycles (40 to 20 meters) we can communi-
cate during the daytime over distances that are con-
sidered very good at night on the lower frequencies
(longer wavelengths). At the same time, we seem to
find that our signals are not heard near by, but that
they take a peculiar jump and come down again at
some greater distance. This view is maintained by sev-
eral experimenters, notably John Reinartz, and yet
remains to be proved or disproved.
THE CLOCK IS IMPORTANT IN SHORT WAVE WORK
A LTHOUGH greater distances may be covered with
*• medium power, the reliability of communication
suffers, for fading and other disturbing effects become
quite noticeable. At still higher frequencies, the time
of day is of great importance, but so little is known of
transmission on the highest amateur band, 60,000 kilo-
cycles (5 meters), that it is unsafe to make any definite
assumptions of what actually happens.
The MacMillan Arctic expedition of last year was out
of touch with civilization for many weeks because the
operators were not equipped to route their traffic over
the very high frequency (short wavelength) bands.
The expedition this year has been in continual touch
with amateurs in this country as well as those in Eng-
land, Australia, and other far distant lands. The com-
munication last year was accomplished on 1500 kc.,
while this year it was chiefly accomplished at 7000 kc.
While the expedition was in continual daylight this year,
it was necessary to use still higher frequencies, and suc-
cessful communication was carried out with amateur sta-
tion 9 cxx in Cedar Rapids, Iowa, on the extremely high
frequency of approximately 20,000 kilocycles (16 meters).
(. l^ HERE are a surprisingly large number of broadcast
•*• listeners who are able to understand what goes on in the
always interesting amateur radio channels. The fact that
the amateurs use code almost exclusively has not prevented
these ambitious ones from buckling down and learning the code,
setting up equipment — which costs less than many a home-
assembled super-heterodyne — and reaching out themselves over
astonishingly great distances. This article announces ex-
periments which are bound to be of interest to "transmitting
amateurs" and the many broadcast listeners whose interest
in radio is broadening out. The RADIO BRO\DCA$r-Eveready
Transmission and Reception on Very
Radio Investigation in Which Many Facts
Enthusiasts Can Join the Experiments
HENNEY
Broadcast Laboratory
Communication between the S. S. Peary at Etah,
Greenland, and 2GY has been successful at night on 7000
kilocycles, but not a sound could be heard from the ex-
pedition in daytime until our receivers were tuned to the
higher frequencies.
What takes place along the high frequency bands?
How far may one expect to carry out reliable communica-
tion in daylight, and at night, with a given amount of
power and at a given frequency? Do signals actually
jump over near-by stations to reappear at some much
greater distance? What is the relation between time of
day and distance of transmission? What of seasonal
differences? Of increase in power? Are some frequencies
good at certain hours and not at others?
These and other questions are assailing every true
radio investigator. Station 2 GY was established to work
on the high frequency bands, and considerable time and
energy will be devoted to the solution of certain partic-
ular aspects of these broad problems.
T
AID OF EXPERIMENTERS IS WANTED
O AI D in this work, the staff of the RADIO BROADCAST-
Eveready short wave experimental station are com-
pelled to call upon other amateurs. To this end the Staff
is desirous of hearing from all amateurs who may be able
to aid, either by listening to transmissions from 2 GY at
definite periods or in other ways to be arranged.
At the present time, the station is experimenting in
two directions. One has to do with antenna systems and
the other is the relation between power and reliability of
communication.
A brief description of the antenna now in use at 2GY
will explain the manner in which other amateurs may
aid in this work. A single vertical wire, one half wave-
length long (about 65 feet) is "fed" by a transmission
line from the transmitter which is working on the so-
called yooo-kilocycle (4O-meter) band.
The questions to be answered are, what is the proper
length, one half wavelength, or more or less? At which
point along the antenna should the driver wire be attached?
What are the best methods of indicating resonance? What
is the effect of using two or more parallel vertical wires,
each tuned to the transmitting frequency? Should the
wire be vertical or horizontal?
Those who have studied the classical wave theories in
experiments will give all interested experimenters an oppor-
tunity to take a personal share in as interesting an experiment
as we know of and this article tells something of the problems
which have to he solved. High frequency (short wave) trans-
mission in the last two years has set the radio world by the ears
and the more that can be found out about the strange phe-
nomena the faster will radio advance. Succeeding articles in
this series will tell more about the progress of the experiments,
which will, we think, be of great service to all the experimenters
in this field, and which will, we hope, further the interest of
the veriest of fans in this engrossing subject. — THE EDITOR.
CHAPTER IX
EXPERIMENTS ON THE IDENTITY OF ELECTRIC WAVES
AND LIGHT
Hertz's Apparatus for Shorter Electric Waves. — After Hertz had
succeeded in proving that the action of an electric oscillation spreads
out as a wave into space, he planned experiments with the object
of concentrating this action and making it perceptible to greater
distances, by putting the oscillator in the focal line of a large con-
cave cylindrical mirror. In order to avoid the disproportion between
the length of the waves and the dimensions he was able to give to the
o
o
FIG. 28. Hertz's rec-
tilinear oscillator.
Fi<*. 29. Hertz's cylindrical mirrors. Oscillator
is at left; resonator, at right.
mirror, Hertz made the oscillator smaller, so that the length of the
waves was less than one-tenth of those first discovered.
The form of oscillator used in these experiments is shown in
Fig. 28. The two halves, of the oscillator were cylindrical bodies
3 cm. in diameter, terminating in spheres 4 cm. in diameter. The
total length of the oscillator was 26 cm., and the spark gap was
usually about 3 mm.
For a receiving circuit, the circle of wire used in the previous
experiments was replaced by a linear resonator, consisting of two
straight pieces of wire, each 50 cm. long and 5 mm. in diameter,
adjusted in a straight line so that their near ends were 5 cm. apart.
51
THE HERTZ OSCILLATOR SYSTEM
A page from the text book (copyright by McGraw Hill Book Company), Prin-
ciples of Wireless Telegraphy, by Prof. George W. Pierce of Harvard University.
As early as 1888, Professor Hertz, at Bonn, Germany, performed experiments in
directive radio transmission, using waves of about 66 centimeters. Some of the
methods used by Professor Hertz are being revived at the present time, a curious
instance of a technical "swing around the circle"
the older texts will see the
similarity between this
single wire to the original
oscillators of Hertz. One
half of the wire is the an-
tenna, and the remainder
is the counterpoise of the
usual antenna installation.
The advantages of such
an antenna are several. In
the first place, it may be
situated some distance from
the transmitter proper with
the result that all absorbing
material may be removed
from the field of the an-
tenna. The single wire
operated very near its fun-
damental frequency (wave-
length), or at a harmonic of
it will have a very high
radiation resistance with
the result that a given
amount of power put into it will be effi-
ciently radiated into space. The only dis-
advantage discovered to date is that it is
somewhat "tricky" to get into actual
operation.
Amateurs who have experimented with
such an antenna system are invited to
write of their work to the Laboratory.
Actual measurements of course are greatly
to be desired.
WHAT RELATION EXISTS BETWEEN POWER
AND DISTANCE?
\ A/TTH regard to the relation between
' * power and distance, the experiments
already under way will reveal the ques-
tions the RADIO BROADCAST-Eveready ex-
perimenters would like to answer.
For several months the power used at
2 GY consisted of a battery powered 50-
watt tube. About 120 watts input to the
plate was used. Occasionally 1500 volts
"raw" a. c. was placed on the plate and
56
RADIO BROADCAST
NOVEMBER, 1925
at times the 1 500 volts were
rectified by means of an
"S" tube rectifier.
The daylight range that
could be expected from such
an installation seemed to be
from 800 to 1000 miles since
stations in Florida, Ohio,
and Illinois were worked
without difficulty in broad
daylight with considerable
reliability.
When the 50 "watter"
suddenly burned out, a 5-
watt power tube was in-
stalled in its place and with
about 40 watts input to the i __ _
plate, the same range was
obtained as with the larger tube. At night
several communications were carried out
with very low power. Notable among this
work was that done with 4 JR in Gastonia,
North Carolina, and 4 KW in Jacksonville,
Florida. With the latter station communi-
cation was established when about 25 watts
were used. Then the plate voltage was
steadily reduced until finally only 100 volts
were used with a plate current of 12 milliam-
peres. This represents a power input of i .2
watts — and still 4 KW answered all of the
questions that were sent to him from 2 GY.
In other words, successful and reliable
communication had been carried out with
a power-mileage ratio of more than 800
miles per watt. This was not freak trans-
mission nor was it due to excessive fading,
Some Important Radio Questions to Be Answered
— Wlnat takes place along the high frequency bands?
— How far may one expect to carry on reliable communication
in daylight, and at night, with a given amount of power
and at a given frequency?
— Do signals actually "jump over" near-by stations, to re-
appear at some much greater distance?
— What is the relation between time of day and distance of
transmission?
— What difference do the seasons make in short wave trans-
mission and reception?
— Are some frequencies good at certain hours and not at others?
since the transmission lasted for nearly an
hour, and followed similar work with 4 JR.
While it is realized that it is one thing
actually to exchange signals with a station
and another to send and receive messages
from it, it is believed that this "800 miles
per watt" can be repeated or bettered.
Recently 2 GY established communication
and received several messages from the
U. S. S. Seattle when she was leaving Tahiti
in the South Seas. This is a distance of
about 7000 miles and the communication
was carried out on 97.5 watts. A still
better record is the work with 7 uz, Seattle,
Washington, two days in succession with a
power of 5.4 watts. Station 2 GY has com-
municated with a number of amateurs who
were using receiving tubes for transmitters.
There is the recent per-
formance of Canadian 9 CK
on Vancouver Island, Brit-
ish Columbia, who worked
for an hour with an Aus-
tralian amateur when using
a 5-volt receiving tube with
400 B battery volts on the
plate.
The Staff would like to
hear from amateurs who
have records of successful
low-powered transmissions
especially when the time of
day, distances covered, and
power used are known. If
communication is attained
on very low power, it is
suggested that a long message, copied per-
haps from a magazine, be transmitted and
checked back to see whether the communi-
cation was sufficiently dependable for the
carrying out of traffic.
Amateurs who care to aid the Staff in
the RADIO BROADCAST-Eveready experi-
ments in their short wave, low-powered work
are invited to write to the Laboratory of
RADIO BROADCAST indicating in what man-
ner they may best be able to help. Inter-
esting experiments and experiences of ama-
teur operators are always appreciated.
Amateurs who care to take part in the
winter's tests from 2 GY are requested to
communicate with this station, and inter-
esting experiences of any operators will
be appreciated at all times.
THE KDKA SHORT WAVE ANTENNA
Where the "driver" principle is employed to energize the antenna. One of the
high frequency antennas can just be seen behind the station house at the right
of the photograph. The driver system is in use on the longer antenna. Note
the coupling coil at the base of the wooden mast. The wires suspended from the
short pole are the counterpoise and take the place of a " ground." Signals radiated
from this antenna have been received in Europe and Africa and are much more
consistent than these sent out on the lower frequency
A TYPICAL AMATEUR SHORT WAVE OUTFIT
This one is owned by Mr. Leo Johnson, of New York City. His
station call is 2 CTQ. Although many amateur stations are not
famous for their scrupulously neat appearance, these experi-
menters have been able to reach out with their short wave
signals to surprising distances. Amateur signals have been heard
over a distance of 12,000 miles, which is as far in one direction
as it is possible to transmit a radio signal
An A. C* Receiver
Design and Assembly of a New High Quality Amplifier Operating from Alternating
Current Together with a High-Efficiency Four-Tube Receiver with an A. C. Plate Supply
IT HAS been suggested by a number of
radio authorities that one of theessen-
tials for good audio quality is high
plate voltage. The most practical way
in which to obtain this high plate voltage
is from a current-tap operated from the a.
c. electric light socket. Such a system also
permits lighting the filament of the last
tube with a. c., so that the use of a 5- watt
power tube for this purpose is made pos-
sible.
Until now, the construction of a quality
audio amplifier which would operate from
the a. c. line has been almost impossible
as many of the essential parts were un-
obtainable in the open market.
Realizing the advantages of an amplifier
which would require neither A, B, or C
batteries, and which at the same time would
give amplification with an unusually high
quality, RADIO BROADCAST has done much
experimental work in order to determine
the best design for the parts required.
Regardless of how fine an amplifier one
has, if the loud speaker is poor, the received
signal will probably sound no better, if as
good, as from a poor amplifier connected to
the same poor speaker. A number of good
speakers are now obtainable on the radio
market. Of particular merit are the cones.
In order to obtain quality output with a
quality speaker, it is necessary that all
the apparatus along the line be of high
quality. The broadcasting station must
produce high quality signals, the receiver
must supply the power amplifier with high
quality input and so on to the speaker.
In this paper will be described the con-
By JAMES MILLEN
struction of a complete receiver operated
mainly from the lamp socket. The re-
ceiver employs one stage of radio fre-
quency amplification with a regenerative
detector, and an audio-frequency amplifier
embodying all the requirements for high
quality.
The requirements are: i. Use proper
D ADIO constructors are watching with
•*• *" eagle eye to see what the fall season brings
out in new design. The receiver and power
amplifier described here so completely by Mr.
Millen combines ideas far in the forefront of
radio progress. The audio amplifier is a
particularly interesting bit of design. Mr.
Cram's article in RADIO BROADCAST for
October, 1925, laid down some theories of the
audio amplifier and Mr. Millen s design puts
his suggestion into definite form. And — per-
haps most important of all — the plate supply of
the entire receiver is drawn from alternating cur-
rent; and in addition, the filament of the
power amplifier is heated by A.C. The quality
of the received signal, using this set-up with
a cone type loud speaker, is almost beyond
reproach. — THE EDITOR.
value of C battery for the signal voltage
at the grid of each tube. 2. Use plate
voltage which corresponds to this C volt-
age. 3. Use transformers with proper
primary inductances. 4. Use a. f. by-pass
condensers. 5. Cable filament and plate
leads. 6. Burn tubes so as to secure
proper electron emission. 7. Employ an
output device to keep the d. c. component
of the space current on the last tube from
flowing through the loud speaker.
Since many of the readers of RADIO
BROADCAST already have receivers of
various kinds which they do not care to
change, the construction of a power ampli-
fier and power supply unit which will en-
able them to improve their present outfit
will also be described.
The quality of output that will be ob-
tained from the power amplifier does not
materially differ from that obtained from a
good resistance-coupled amplifier with a
low impedance tube (so as better to match
impedance of the cone type speakers) in
the last stage. The main difference is
that one power stage will do what three
resistance stages will, and at the same
time eliminate the batteries.
As the two tubes in a push pull ampli-
fier are operated 180° out of phase, distor-
tion due to insufficient C and B voltage
cancels out, and good quality is thus ob-
tained with low voltage.
THE CONSTRUCTION OF A KNOCKOUT SET
WITH QUALITY POWER AUDIO AMPLIFICATION
THE set proper employs the standard
Roberts Knockout circuit. The writer
made a number of experimental models and
in some, reflexed the first audio through the
radio tube. The sets shown in Figs, i, 2,
and 3 are not reflexed, and, though the
elimination of the reflex requires an addi-
tional tube, such a set will give more volume
without danger of overloading the first
audio tube, which may happen with the
reflex model on loud signals.
RADIO BROADCAST Photographs
FIGS. I AND 2
Fig. i (Top of sub-base views), The receiving set with power amplifier. The a. c. power supply unit is contained in a separate cabinet. Fig. 2 (Under
sub-base) Note the output transformer, which serves the double purpose of keeping the d.c. component of the plate current out of the loud speaker and
making possible the use of a low impedance speaker
58
RADIO BROADCAST
NOVEMBER, 1925
RADIO BROADCAST Photograph
FIG. 3
An experimental receiver with a high quality audio amplifier. Audio frequency
by-pass condensers, an output transformer, and high C and B voltages are employed.
The power supply unit is contained in a separate cabinet, but in order to reduce the
number of leads between the power unit and the set, the voltage dividing resistors
are mounted in the set as shown
The only batteries required with this set
are one small 4^-volt C battery and three
dry cells.
The first three tubes may be three-,
one and a half-, or five-volt. Although the
amplification obtained with the smaller
tubes is somewhat less than that obtainable
with storage battery tubes, thefe are several
advantages to be gained by the use of the
small tubes. First, the maximum output
obtained from the small tubes will not be
great enough to overload the power tube
and thus cause it to distort. In other
words, in order not to overload the power
tube, the maximum signal voltage applied
to the grid of this tube must not be greater
than the C battery voltage. In this am-
plifier, therefore, a signal voltage in excess
of about 22 to 24 volts (with a uv-2O2 or
27-28 volts with ux-2io) will very likely
cause distortion. As most of the input
transformers, which are recommended for
use with the last stage in this amplifier,
have a ratio of 2:1, the output signal
voltage from the first audio stage should
not exceed 12 volts. Measurements made
in the RADIO BROADCAST Laboratory
showed that output peak signal voltages
(measured with a vacuum tube voltmeter)
obtained from the first audio tube using a
uv-igg were never likely to exceed the 12-
volt limit.
Should overloading take place in your
amplifier, it will readily be detected by the
plate circuit milliameter needle movement
as described by Mr. Crom in his article
in the October RADIO BROADCAST. In
order to remedy the trouble, connect a
variable resistance, such as Bradleyohm
No. 10, a Clarostat, Royalty No. B, or simi-
lar resistance across the secondary of the
first audio transformer and adjust it until
the distortion is eliminated. The effect of
this resistance is to reduce the signal volt-
age which will be applied to the grid of the
last tube and incidentally that which will be
applied to the grid of the first tube. If this
resistance were connected across the secon-
dary of the second transformer, it would ac-
complish the same results, as far as the
power tube is concerned, but it would not
have eased the load on the first audio fre-
quency tube, and, as this amplifier has been
designed so that overloading (when three
volt tubes are used) will start in the first
stage slightly before (if at all) it will in the
, NOTE : It may be necessary with some transformers and layouts
to insert an R F choke here. Such a choke consists of 200 turns'
dfNo26DSCon 1'dia.tube
FIG. 4
The circuit diagram of the complete receiver
NOVEMBER, 1925
AN A. C. RECEIVER AND POWER AMPLIFIER
59
power stage, the proper way is to reduce
the load on all tubes by means of a resist-
ance across the first transformer secon-
dary. Such a variable resistance also
serves as an excellent volume control.
Instead of the variable tickler to control
the regenerative detector, frequently in a
receiver employing a circuit of this sort
a fixed tickler and variable by-pass con-
denser are employed. With this arrange-
ment, the tuning of the detector condenser
is not affected by the regeneration control.
Another satisfactory method of controll-
ing regeneration when a fixed tickler is
employed, is by means of a variable resist-
ance connected across the tickler coil.
The coils may be the standard coils made
for the Roberts circuit, such as the Super-
coils, Sickles diamond weave, etc., or they
may be home made. The two tuning, con-
densers have a maximum capacity of .0005
mfd., and with the coils described above
cover a frequency range of from 1363 to 545
kilocycles (220-550 meters). A rheostat is
provided for the detector and another for
the two amplifier (r. f. and a. f.) tubes.
If three-volt tubes are to be used (and
their use is highly recommended) it will be
better to use them in sockets designed for
them rather than using adapters in large
sockets, as shown in the photographs.
All filament and plate leads are "cabled."
Furthermore, large by-pass condensers
are provided in all the amplifier circuits.
As the construction, neutralization, and
BROADCAST Photograph
FIG.
A power supply unit employing an S tube as a rectifier. The transformer
and the chokes are contained in separate iron boxes with bakelite panels
operation of sets with neutralized r. f. am- THE POWER AMPLIFIER
plifiers and regenerative detectors has been
dealt with so many times in previous issues '""THE necessary components of the power
of RADIO BROADCAST, the subject will not be *• amplifier are input transformer, power
further discussed here. Those who are not
already familiar with circuits of this type are
referred to the article by Mr. Keith Henney
in the April,
1925, RADIO
BROADCAST
or to any of
the articles
by Mr.J. B.
tube, by-pass condensers, and output trans-
former.
The input transformers may be any high-
[o BROADCAST Photograph
FIGS, b AND 7
Interior of the power supply unit shown in Fig. 7 is in the insert at the upper right. The large photograph shows an experimental layout with the high-
quality amplifier and power supply unit connected to a two-tube Knockout receiver. An impedance-capacity output device is employed in the amplifier
60
RADIO BROADCAST
NOVEMBER, 1925
grade lov ratio audio transformer. Those
successfully tried out by the writer in his
amplifier were Rauland Lyric, Amertran
(35:1), and General Radio No.285A. They
should have a turn ratio of from 2 to 35
to i , not higher.
The power tube may be a uv-2O2 or a
UX-2IO.
The UX-2IO and the uv-2O2 operate
from the transformers without rheostats.
The uv-2O2 is most easily obtained by
writing direct to Amateur Sales Division
Radio Corporation of America, 233 Broad-
way, New York. It sells for $3.50. The
ux-2io lists at $9.00 and is obtained from
any Radio Corporation or Cunningham
dealer.
Several of the independent tube manu-
facturers are now making power tubes
with 5-volt filaments. Double rheostats,
as shown in Fig. 13, will have to be used
with them.
The grid return condenser may be any
of the paper condensers. About one mfd.
is a satisfactory size. The plate by-pass
condenser, however, must be capable of
continuously withstanding the full plate
voltage (about 400 volts). Most of the
small paper condensers, such as the No.
765 Dubilier, will not stand up when put
to this use. The Dubilier No. 769, W. E.,
Tobe, Acme No. 750 volt, or four of the
lower voltage condensers connected in a
series-parallel arrangement will be neces-
sary.
The output device serves two purposes.
The first is that it keeps the direct current
from going through the speaker, and,
second, it "matches" impedances. Thus,
if a transformer is used the primary must
have the proper impedance to work with
the power tube and the secondary must be
designed to fit the speaker. The plate
impedance of the power tubes available
for use in the set is the same. The im-
pedances of some of the high-grade loud
speakers, however, are quite different, and
they may be grouped into two classes,
high and low impedance. The Western
Electric cone is a low impedance speaker,
whereas the Farrand-Godley has a high
"S'Tube
impedance. Therefore, in purchasing an
output transformer, the type of speaker
that it is to be used with must be kept in
mind.
Some constructors may have a pair of
push-pull transformers on hand. An out-
put push-pull transformer can be used as
an output transformer for the amplifier.
The mid tap on the primary should be dis-
regarded and the plate of the power tube
connected to one of the terminals marked
P (or plate) and the plus B to the other
terminal marked P (or plate). The loud
speaker (which, for most push-pull trans-
formers, excepting the Western Electric,
should be of fairly high impedance) is con-
nected to the "output" or "speaker" posts.
There is another method of connecting
the loud speaker which does not require a
transformer. It is illustrated in Fig. 12,
and employed in the amplifier shown in
Fig. 6. The "Amerchoke" and the Thor-
darson Autoformer make ideal impedances
for this use.
When these parts have been wired up
as shown in Figs. 11 and 12 the receiver
itself is complete. There then remains the
construction of the power unit for operating
it from the house current.
CONSTRUCTION OF POWER UNIT
THE power unit is merely an "over-
grown" B-substitute with an addi-
tional transformer winding. The rectify-
ing device should be either a thermionic
or an S tube. Both have been very suc-
cessfully employed. The parts required for
the construction of the power unit are
transformer, tube and socket, chokes, con-
densers, and resistance units.
Transformers suitable for this purpose
are the General Radio, Amertran, Acme,
Dongan, and Jefferson. A suitable trans-
former must have at least one 7. 5-volt
secondary (with mid tap), and at least one
450- to joo-volt winding.
The transformer must also have a 110-
volt primary, or better yet, have taps to
take care of variations in line voltage from
105 to 120. If a thermionic tube (Kenotron,
uv-202, ux-2io, ux-2i6B) is to be employed
as a rectifier, then two 7. 5-volt windings
will be required. An S tube has no filament
and, consequently, requires no filament
heating winding.
Either double- or single-wave rectifica-
tion may be employed. Both give excel-
lent results, but the double-wave rectifier
has the advantage of not requiring quite
as elaborate a filter system as the single
wave. However, for double wave rectifi-
cation two rectifying tubes are required and
two high-voltage transformer secondaries.
The power supply units described in this
paper are of the single-wave rectification
type, requiring but one rectifier tube and
one high-voltage transformer secondary.
The transformer should be rated at about
50 watts.
If a power tube (uv-2O2, ux-2io, etc.)
is employed as the rectifier, it is highly im-
portant that the grid and plate be con-
nected together. The Kenotron, uv-2i6,
which is the same as a uv-2O2 but de-
signed only for rectifying and, therefore,
having no grid, may_ be obtained from the
Amateur Sales Division, Radio Corpora-
tion of America, 233 Broadway, New York.
The ux-2i6 B, which is the rectifier pat-
terned after the ux-2io, is carried by all
R. C. A. and Cunningham dealers.
Two chokes of about 50 henries each
are required for the filter system. They
must be designed for a total current of
about 30 milliamperes and have as low a
d. c. resistance as is economically practical.
Such chokes may be obtained from Amer-
tran, Jefferson, Dongan, Molliformer, Apco,
or General Radio Companies, or they may
be made at home as described by the writer
in the June and October issues of RADIO
BROADCAST.
The filter condensers must be capable of
continuously withstanding the high voltage.
There is generally quite a difference be-
tween "flash" voltage and "Maximum
working" d. c. voltage. It is this last rat-
ing that is important and it must be at
least 500 and preferably 750 volts in order
to be satisfactory for use in the filter.
Condensers which meet this requirement
are manufactured by Dubilier (No. 769
<=
110*
4 Mfd.
2Mfd.
12,000 to
9,000
U)
0 90
p
R3
Fil.
UV 202
or
UX210
FIG. 8
The circuit diagram of the power supply unit shown in Fig. 5
NOVEMBER, 1925
Filament Winding
on Transformer
FIG. 9
The C bias is obtained by means of the
voltage drop across the resistance R3
but not No. 765), Acme, Tobe Dutschmann
and Western Electric. W. E. condensers
may be obtained from C. E. Jacobs, 2802
N. Kedzie Ave., Chicago.
Several resistance units are required in
order to secure the proper B voltages for
AN A. C. RECEIVER AND POWER AMPLIFIER
the detector, r. f. tube, and first a. f. tube
as well as the negative C voltage for the
grid of the power tube. The values and
connections for these units are indicated
in Figs. 4 and 8. They may be of Ward-
Leonard, Crescent, or Allen-Bradley make.
In place of the fixed i25O-ohm unit
employed for obtaining the proper nega-
tive bias on the power tube, a C battery of
about 22^ volts (for uv-2O2 or 28 volts for
ux-2io) may^be employed. The voltage
should in that case be adjusted for best
results as indicated by the milliammeter
tests outlined by Mr. Crom in RADIO
BROADCAST for October.
Another way of varying the negative
bias to the power tube which does not re-
quire a separate C battery, is the use of a
variable resistance such as the Clarostat
or Electrad Royal. We believe this to be
the best method, as the proper C bias may
be obtained by varying the resistance while
observing the
61
Transformer ,'''
Filament Winding
- B
._ Transformer
Filament Winding
mum ...... niamiiiiiiiiiiiB ...... i
MAXIMUM PRICE
8.00
5.00
7.00
COST OF MATERIAL
Used in the Complete Receiver
The Receiver
Panel
Base Board
3 General Radio, Silver, Hammarlund, or other good condensers,
max. cap. 500 mmfd $15.00
3 Dials
I i Set Robert Coils
1 i A. F. Transformer Ti (7 General Radio, No. 285, $6; i Amerlran
No. AF6,$7).
I i Neutralizing Condenser C,
| 3 Sockets
1 2 Rheostats R, and Rj
| i Volume Control R5 (Clarostat, $2.25; Bradleyobm No. 10, $2.00;
Royalty (Electrad) No. B, $7.50)
i Grid Condenser and Leak G>
4 i mfd. By-pass Condensers C,
The Power Amplifier
Input Transformer T2 (General Radio, No. 28s-A, $6; Amertran,
No. A F 7, $7).
Output Device
General Radio Transformer No. 367, T3 (for W. E. Cone)
Output push-pull transformer (for high Impedance Speakers)
or
Impedance-Output (for either high or low Impedance Speakers),
Thordarson Auto-former. I, $5; Amer-choke No. 154, I, $6;
1-4 mfd. condenser (or total of 4 mfd., $5).
Socket
i Mfd. By-pass Condenser Cs (Tobe Deutschmann, $7.25;
Dubilier No. 678, $1.75).
Power Supply Unit
Power Transformer T< (Amertran No. PF 45, $12; General
Radio No. 365 (for "S" tube), §72; General Radio No. *7}M
(Additional filament winding for rectifier tube.) £72).
Chokes I, (2 Amer-cbokes No. 854 at $6, $12; 2 Molliformers at
$6, $12; 2 apco chokes at %6, $12; i General Radio double
choke No. )66, $12).
Filter Condensers (500 volt) C«, C-, (4 Dubilier No. 764, $^.50.
$14; 4 Tobe Deutschmann No. 709 2 mfd., $7.75, $7; 4 W. E 2
mfd.,%,.65,$6.6o).
Socket
Milliammeter (0.25 m.a.), (Jewel, Weslon, $8.)
Jones Cable (or Belden)
Resistance Units (Bradley Units, 2 12,000 ohms; i 10,000 ohms; i
25,000 ohms, $.75 each; Ward Leonard H S Units; Crescent,
2 12,000 ohms; i p,ooo ohms; i 24,000 ohms, $2.50 each (All
special) $10).
Grid Bias Resistance R., (Ward Leonard (fixed) (L S 7250), $.§5;
Clarostat, $2.25; Royalty, $7.50).
Tubes
ux 210
uv 202
KENOTRON
RECTRON 2l6B
Speaker
Switches, Screws, Lamp Cord and Plug, Box or Base Board for
Power Supply Unit.
The completed receiver, including tubes but not speaker, will
cost approximately $100.
9.00
3.50
3.00
7.50
rnililliiinillinromil
plate milliam-
meter.
The power
supply unit is
generally most
conveniently
located under
the table on
which the set is
placed. The
several leads
from the power
unit to the set
should be
"bundled" to-
gether into a
cable; one of
the standard
battery cables
such as the
Jones or Belden
may be used for
the purpose.
The i lo-volt
a. c. cord is
thus kept a fair
distance away
from the set
proper. This is
of slightly more
importance in
reflexed sets.
If the power
unit is placed in
a cabinet, such
as the one in
Fig. 7, it is im-
portant to pro-
vide proper
ventilation so
that the heat
generated by
the rectifier
tube will be dis-
sipated. The
plate milliam-
meter (0-50
m. a.) may also
be conveniently
located if de-
Center Tap on Transformer
Filament Winding
FIG. 10
A C battery may be employed with the power
amplifier, if desired, instead of obtaining the
grid bias from the power supply unit
sired, on the panel of the power supply
unit. This is also a good place for the 1 10-
volt switch.
OPERATION OF THE SET
AS THE operation and neutralization of
** receivers employing this circuit have been
covered in a number of previous articles in
RADIO BROADCAST, they will not be taken up
again.
The adjustment of the power amplifier, how-
ever, will no doubt present some new problems
to many of the readers. The filaments of both
the power amplifier and the rectifier tubes must
be operated at exactly the right voltage. This
is particularly true of the uv-202 when used as
an amplifier. If the filament voltage is too low,
it will cause a great deal of distortion. On the
other hand, if it is too high, the life of the tube
will be materially shortened. The filament
voltage of the 210 is not as critical as the 202.
Ordinarily the only way to adjust the filament
voltage properly is with an a. c. voltmeter, but
the use of such an instrument will not be neces-
sary with the transformers recommended in this
article, as the voltage supplied is just right,
providing sufficiently heavy wire, such as No.
16 or No. 18 flexible lamp cord or the equivalent
solid wire is employed in connecting the tube
socket to the filament winding on the trans-
former. Furthermore, the length of the fila-
ment line should preferably not exceed three
feet. It is also highly important, especially with
the uv-2O2, that the tube makes very good con-
tact in the socket.
When a 6-volt tube is to be used, or if 'the
Acme 75-watt c. w. transformer (which has a
10 instead of 7.5 volt filament winding) is used
with either a 6- or 7^-volt tube, it is necessary
to employ two rheostats, one in each filament
lead; they must both be adjusted simultane-
ously in order that the resistance in each fila-
ment lead will be about the same. See Fig. 130.
When rheostats are employed to adjust the
FIG.
The circuit diagram of the power
amplifier using an output transformer
62
RADIO BROADCAST
NOVEMBER, 1925
400
FIG. 12
The circuit diagram of the power amplifier
using an impedance-capacity output device
filament voltage, it is strongly recommended
that a good a. c. voltmeter be used as an aid to
securing the proper adjustment. To dispense
with the use of such an instrument is not
economy. The life of a tube is very materially
reduced when operated at higher than rated volt-
ages.
Rheostats for this use must be capable of
carrying about 2\ amperes. The resistance may
be one or two ohms. Such rheostats are manu-
factured by Amsco, Acme, Fada, Pacent, and
General Radio. If a variable resistance is em-
ployed for obtaining the grid bias, it should be
adjusted so that the milliammeter in the plate
circuit of the power tube remains reason-
ably still when receiving signals of varying
intensity.
The plate current drawn by the power tube
should not exceed about 20 mils. Seventeen or
eighteen is about correct for most 202'$ and
about 20 for the 2io's.
If an Acme c. w. transformer is employed, it
will be necessary to use an S tube as the rectifier;
there being no rectifier filament winding provided
on this transformer (the S tube has no filament).
The No. 5000 S tube is best suited for this pur-
pose, although the No. 4000 may be employed
if desired. The No. 5000 only costs $6.50,
whereas the other costs $10.00. S tubes are
best obtained direct from the factory.
The voltage of one half of the split high
voltage secondary on the Acme transformer is
too low and the entire voltage is too high
Therefore, it is necessary to use the entire
FIG. 13
The way in which rheo-
stats must be connected
when a 6-volt tube is
to be operated from a
higher voltage trans-
former winding
secondary and connect a resistance of from 5000
to 6000 ohms in series with the plus lead as shown
in Fig. 14. The drop in voltage across this
resistance results in the proper output voltage.
A POWER AMPLIFIER FOR YOUR
RECEIVER
EPICURES 7, 11, 12, show the power
1 amplifier, similar to the one used in
the complete set, mounted on a small board
by itself. The same power unit as is em-
ployed to operate the complete set (Figs,
i, 2, 3) is used to operate this amplifier as
'S'lube
<o
o
110V. §
A.C. C=l
R R3
FIG. 14
Circuit diagram showing proper connections for
employing a standard Acme c. w. transformer
well as supply the B voltages to the small
outfit to which it is connected. Such a
combination possesses most of the advan-
tages of the complete set (for it is practi-
cally the same thing) and at the same time
makes it unnecessary to discard the small
set.
In most cases it will be necessary to
connect a variable resistance such as a
Bradleyohm No. 10, Royalty B, or Claro-
stat across the secondary of the reflex trans-
former. It is also necessary to keep the
a. c. lines as far as possible from the reflex
amplifier in order that a. c. "hum" will not
be picked by induction, and, most impor-
tant of all, ground the negative B.
Such a combination as shown in Fig. 6
results in a considerable "gain" in volume
without the loss of any of the high quality
for which the Roberts Knockout receiver is
so well known.
RADIO BROADCAST Photographs
FIG. 15
There are a number of excellent transformers and chokes now obtainable in the radio market. Some
which have been successfully used, but which are not shown in the other photographs, are grouped here
How Broadcasting Has Brought the Advantages of City Life to a Barren Pacific Island
JHE following episode, a little
drama of modern science, has an
interest which reaches far beyond
the small group of persons it con-
cerns, and it is for this reason that it is
told.
The incident occurred some few months
ago on the lonely Farallone Islands, which
are situated off the mid-northern coast of
California. A young child belonging to
one of the half-a-dozen families then living
on the island was taken seriously ill.
There was no physician available on the
Farallones, none nearer than San Francisco,
twenty-five miles distant over the ocean.
The condition of the child indicated that its
illness was no ordinary one, and the services
of a skilled physician were urgently re-
quired.
To carry the child to San Francisco or to
summon a specialist to the Island seemed
the only possible things to do, but both
these plans involved hours of delay.
Those at the bedside realized that such delay
might prove costly or even fatal. It was
at this point that science stepped in with
an alternative plan.
On the I sland.theGovernment maintains,
together with other devices for the assis-
tance of navigation, a radio signal station,
and so once again it fell to the lot of wireless
to serve humanity in an hour of distress.
Within a few moments after it had been
decided to make wireless serve as a physi-
cian, the operator on duty was in touch
with San Francisco and the San Francisco
radio office was telephoning to locate a
specialist in children's diseases. Less than
half an hour passed before the specialist
and the father of the child were in direct
communication, aided by the long arm of
the radio telegraph. Then followed a long
series of questions and answers, while the
doctor, thirty miles away, familiarized
himself with the case, made his diagnosis,
and, finally, prescribed a course of treat-
ment. It was an illness that required im-
mediate attention along a particular line;
a delay of a dozen hours might have
proved fatal.
THE RADIO DOCTOR SAVES LIVES
'"p'HE instructions given over the radio
* were scrupulously followed in the sick
room, and the next day reports from the
Island were so encouraging that the doctor
pronounced his radio patient out of danger.
In a week, the child's recovery was com-
plete.
This incident serves to illustrate in a
By LEWIS N. WAITE
striking way how modern inventiveness is
changing very materially the lives of those
who live in remote and inaccessible places.
New methods of communication are
drawing scattered communities closer to-
gether, and, perhaps, gradually fusing the
thought and interests of the country into
a homogeneous whole.
More than in most communities, radio
has influenced the lives of those on the
Farallone Islands. Only here, and in
other similarly isolated colonies, can the
change be truly called revolutionary.
FARALLONE LIGHT
Whose beam at night is the first suggestion to sea
travelers bound for San Francisco that they are ap-
proaching the western coast of the United States.
Recently, radio brought aid to a child on the coast
who was seriously ill. A physician in San Francisco
was reached through the Naval radio station and
gave a diagnosis and suggestion for treatment which
cured the child. Broadcasting has brought the
Islanders close to the entire western half of the
country and has altered the monotony of their lonely
existence
Where formerly the two or three dozen
isolated citizens who live on the Islands
derived their sole contact with the outer
world from the infrequent visits of govern-
ment supply boats, and their own still
less frequent visits to the mainland, the
broadcasting stations now have placed at
their disposal a variety of entertainment
that must make their lives, in comparison
with their former existence, almost un-
believably pleasurable. All of the Pacific
Coast and many of the inland broad-
casting stations are within range of the
Farallone receiving sets. Frequently now,
of an evening, these people dance to the
music of the jazziest of metropolitan or-
chestras, or listen to a lecture or a play.
They hear news items that otherwise
would not have reached them until after
the arrival of the government tug, perhaps
days later. The radio has at last beaten
down the barrier of the Pacific and made
these lowly inhabitants of the Farallones
sharers in the bustle and activity of life
on the mainland.
THE ISLAND STAGE WHERE RADIO PLAYS
THE Farallones are as bleak and rugged
a group of islands as may be found
anywhere in the world. There is nothing
about their steep cliffs and rocky crags,
and their inhospitable, reef-fringed shores,
to attract settlers. The fact that they are
inhabited at all is due to an accident of
location. For the Islands lie due west of
San Francisco Bay, twenty-five miles
from the Golden Gate.
Standing thus directly in the path of
steamers plying to and from the Orient, the
Farallones were so serious a menace to
navigation that the Government was forced
many years ago to establish a lighthouse
there. The lighthouse, one of the most
powerful and important on the Pacific
Coast, is perched on top of one of the
rocky summits, 350 feet above the sea.
To many hundreds of travelers from the
Orient, this flashing light, visible for 26
miles, is the first welcoming signal from
America, the first intimation of land after
weeks at sea.
Other means of safe-guarding shipping,
supplementing the lighthouse, were pres-
ently established on the Farallones. For
use during foggy weather — frequent in this
district during certain seasons — a powerful
siren was installed, its intermittent blast,
audible for miles, announcing that danger
of running on the rocks was imminent for
any ship that might be groping about in
64
RADIO BROADCAST
NOVEMBER, 1925
'V,
NEVADA
\
\
THE FARALLONES
Are lonely barren islands, about twenty-five miles
due west of San Francisco Bay. It is the fashion
to speak of radio revolutionizing domestic life be-
cause of the new and varied entertainment it intro-
duced into the home. That is rarely true, but in
isolated spots such as these islands, broadcasting
does bring many of the municipal advantages to
the door step of isolated people
the vicinity. More recently, as the science
of marine signalling has developed, other
safety devices have been added, among
them submarine bells. The radio compass
signal station, installed for the purpose of
assisting ships at sea in checking
their positions, was one of the earliest
additions to the Islands' safety
equipment.
With the installation of these va-
rious devices, the population of the
Islands, which at first consisted only
of the lighthouse keepers, has steadily
increased. To-day the government
employees and their families alone
make up a considerable community.
They are adequately housed and
cared for with materials brought from
the mainland. Naturally, reserve
stores of supplies are maintained on
the Islands, and these supplies are
carefully checked and frequently re-
plenished.
The normal, matter-of-fact com-
munity life which the inhabitants
lead is not notably different from
that of little settlements elsewhere.
But an example of the ingenuity
employed in overcoming difficulties
that ordinarily would be considered
insurmountable is shown by the way
in which the inhabitants of the Islands
obtain their water supply. The
Islands have no natural supply of
fresh water. The task of shipping
waterfrom the mainland was imprac-
ticable, both because of the large
quantity required and the difficulty
of transporting it from the vessel to
the Islands, which difficulty is due to
the currents and reefs that make the
landing of supplies a difficult feat.
The solution to the problem was
that the Islands, while they contain no
sub-surface water, have a very heavy
rainfall, which, it was decided, should be
gathered and conserved. The top of the
largest building of the Islands was made
to serve as a shield in which the water
was collected and then drained off into
storage tanks. By an admirable com-
bination of pleasure and utility, the
inhabitants use the concrete roof of this
building during dry weather for a tennis
court.
NOW THE FINGER OF ATTENTION POINTS
NORMALLY, the Farallones receive
but little attention from the out-
side world. The inhabitants go about
year after year performing their mo-
notonous task of issuing warnings to
shipping and keeping their signals in
order, and they neither expect nor want
attention from those who live on the
mainland. But occasionally something
happens that brings the Islands before
the public.
Recently the Farallones figured prom-
inently in the newspapers of the Pacific
Coast, and in a very curious way. A
Coast Guard cutter, cruising about in
search of rum-runners, sighted such a vessel
off the Farallones and, after a chase, suc-
ceeded in capturing it and bringing it into
San Francisco Bay. The steamer and its
cargo, valued at several hundred thousand
dollars, was held by the prohibition au-
thorities and confiscation proceedings were
begun.
At this point attorneys representing the
owners of the vessel put forward a novel
defense. They advanced the argument
that the seizure was illegal because the
vessel, at the time of its capture, was more
than twelve miles from United States
territory — the maximum distance at which
arrest for violation of this law can take
place. This statement the prosecution
emphatically denied and proceeded to
prove that the capture was made only a
mile or two off the Farallones. The at-
torneys for the defendants then made the
statement that the Farallones, never hav-
ing been formally annexed to the United
States, were not in reality a part of this
country, and that the arrest was therefore
an illegal one.
So surprising a charge naturally created
widespread interest and led to a careful
search in musty, long-forgotten records.
Whether or not these lonely rocky islands
will be proved to be ownerless has not yet
been determined. But in the meantime
the little group of lighthouse keepers and
signal station operators go unconcerned
about their tasks, conducting quietly the
affairs of the community in which they
live, and gathering about their radio sets
in the evening to listen to the grand opera
or the jazz orchestras of the outside world.
SOUTH ISLAND
In the Farallone group, off the California coast, showing the combination watershed and tennis court in the
lower left. The radio tower is part of the Navy radio installation which forms the sole link to the mainland.
The Farallones are about twenty-five miles off the coast, almost opposite San Francisco, and are barren and
storm-swept. The population is very small
EADIO BROADCAST ADVERTISER
65
3 1 76 Trained
Factory
Representatives
Are Now Entitled
toViear That ^
Radio
With Service
ZARKA radio instruments aredemonstrated,
sold, installed and serviced by direct fac-
tory representatives only. These men have been
thoroughly train-d by our own engineers who
designed and perfected the Ozarka.
The success of any radio instrument, like the auto-
mobile, depends on the quality of service rendered.
No matter how perfectly any radio instru-
ment leaves the factory, little things may
sometimes go wrong. You've no doubt
learned, by costly experience, that the
ordinary handy man cannot properly service
>ur automobile. The same is true of Radio.
roubles are generally caused by very liltle
things which are exasperating to the owner,
but are quickly corrected by the man who is
trained on that instrument.
Today 3176 factory representatives are
authorized to wear th e Ozarka button. These
men know Ozarka perfectly; more are now
being trained; soon there'll be one in every town.
Without obligation to you, the Ozarka representative
will set up an Ozarka in your home on trial. He won't
claim that it is better than othe-s. All he asks is the
opportunity of letting the Ozarka do its own selling.
"With your own operating you must satisfy jyrtMrs*"/that
it has no equal for volume, tone, distance and ease of
operation.
Let us send you the sto jes of Ozarka long distance reception — from many people who have
heard London and Manchester, England; Cardiff, Wales; GUseow, Scotland; Buenos Aires. South
America; and even Honolulu, H. I. Write for jree illustrated book No. 200. Please give name of
your county.
Ozarka Offers Real Opportunities
for Sales Representatives
It is not exaggerating to state that hundreds of thousands
of homes are waiting for "Radio with Service."
In other words they are waiting for the Ozarka trained man. Already
we have 3176 such representatives, and the field is barely scratched.
Ozar^'a training is very thorough, intensely interesting, and quickly
absorbed through study in spare time, by any man who is mechanically
inclined.
12 FREE Selling Lessons
Three other qualifications are necessary: the desire to bet*
ter your condition, willingness to work, and at least a little
capital.
You may not think that you possess the necessary selling
ability, but •with the qualifications just mentioned, plus
Ozarka training, you can and will talk convincingly or what
Ozarka will do — and you can set up the Ozarka instrument
in the approved manner that insures satisfaction.
FREE BOOK!
The Ozarka plan is fully described in a large illustrated book. A copy
will be sent to men who are willing to tell us fully about themselves.
Unlike any book you have ever read, the Ozarka book is a true story of
life, of men, of why they fail, and how they succeed. It is founded on the
principle that nothing is impossible to the man who is determined and
willing to try.
In territory not now covered, the right man is wanted. The invest*
ment in money is small, but investment in time and study is considerable*
If you are willing to put forth the necessary effort to obtain a splendid,
profitable business (of your own, write and say "Send me your Ozarka
Plan Book No. 100." It maybe the turning point in your life. Don't fail
to mention the name of your county. Use the coupon!
120 Austin Avenue M
Chicago, Illinois
Gentlemen: V/ithout obligation send book "Ozarka Instru
ments No. 203" and name of Ozarka representative.
120 Austin Avenue M
Chicngo, Illinois
Ask the Man Who
Wears this Button
Gentlemen: I am prreatly interested in the FREE book "The
Ozarka Plan" No. lOO.whereby I can sell your radio instruments.
Name
Address City
County State
66
RADIO BROADCAST ADVERTISER
The Trimrn Home Speaker is the
biggest value in radio today. It
out-performs other speakers cost-
ing twice as much. Model No. 25
has large Volconite horn, 18 inches
high with a 12 inch bell and pre-
vents tinny, scratchy noises, giving
a full, well rounded tone.
Factory regulated adjustment as-
sures maximum volume without
blasting or distortion. Carries the
Trimm Lifetime Guarantee of per-
fect satisfaction. Have your dealer
demonstrate the Home Speaker to
you before you buy.
Trimm Headsets, Speakers and
Units give radio fans the utmost
in performance for their money.
Dealers who wish to be shown,
write for details.
TRIMM
Superior Reproducers
HEADSETS
Professional - - $$.$O
Dependable - - - 4.40
PHONODAPTERS
Giant Unit - - $1O.OO
Little Wonder - 4. SO
SPEAKERS
Home Speaker
Entertainer •
Cabinette • •
Concert - -
Chello . .
$10.00
- 17.50
- 17.50
- 15.00
3O.OO
US. A.
"Now, I HAVE FOUND . . ."
A Department Where Readers Can Exchange Ideas and Sug-
gestions of Value to the Radio Constructor and Operator
/N THE August RADIO BROADCAST it was announced that a pri^e of
twenty-five dollars would be given to the reader who submitted the best idea
for the " Now, I Have Found . . " department, during each three months'
period. The best suggestion published during the last quarter is that of Mr.
Welsford A. Wesi, whose two ideas were published in the September number,
on page 660. This award will be continued and announcement made every
three months. All used manuscripts will be paid for at the usual rates, that
is, from two to ten dollars each. Those submitted should be no longer than
about three hundred words, and should be typewritten. Address your letters
to this department, RADIO BROADCAST, Garden City, New York
T
FIG. I
MEASURING HIGH RESISTANCE
WHEN the experimenter constructs
a resistance-coupled audio ampli-
fier and doesn't get proper results,
he often wonders if the resistances used are
in good condition and of correct values.
Such resistances may be measured with a
good-grade voltmeter of known resistance
having about a zero to eight scale or less.
If you don't know your meter's resistance,
write to the maker. The use of good B
batteries of about 90 volts is essential as
using partly run down batteries will affect
the results obtained.
Make connections as shown in the sketch,
Fig. i, the resistance under test being
shown at X. Note voltmeter reading.
In a test made with some .1 megohm re-
sistances, the B voltage was 90, meter re-
sistance 496 ohms,
reading .42 volts.
Substituting, X =
90 x 496-*-. 42 =
106285 ohms = .io6
megohms.
Precaution : Test
only high resistances
such as used for the
above purpose.
Testing low resistances will damage the
meter.
The above formula is not absolutely cor-
rect according to theory, but error may be
disregarded for practical purposes such as
this test is suggested for.
CLAUDE SCHUDER, Sumner, Illinois.
DESCRIPTION OF A NEW NP COIL
FOR THE ROBERTS RECEIVER
THERE have been written reams and
reams of information on the wonders
and drawbacks of the now justly
famous Roberts circuit. However, one
very important point has been overlooked.
The big question usually asked was,
"Why is my set dead on certain frequencies
(wavelengths)?" This question being a
serious one, every possible reason for this
undesired condition was considered and an
organized search for the cause of the trouble
instituted. Transformers spaced top close
to coils, coupling effects, high resistance
condensers, open-circuited or defective
coils, and a thousand and one other things
suggested themselves at the time. After
spending considerable time on this problem,
a Roberts set which extended for over three
feet on an old super-heterodyne panel,
resulted from the experiments. The reason
for this lengthy arrangement was to keep all
instruments as far away as possible from
fc- Tested and approved by RADIO BROADCAST -
each other, and to avoid any detrimental
feedback or absorption which might take
place in a more congested layout. But the
outfit still showed the same symptoms, and
the only place left to look for trouble was
in the design of the coils. Here was found
the secret of the difficulty.
All descriptions of the NP coil have ad-
vised that this winding should be done in a
rather peculiar fashion. That is, two
parallel wires are wound at the same time
over the same form, and are connected top
to bottom in such a way that they form a
continuous wire with a tap in the center.
The reason for this peculiar type of winding
is that it makes neutralization much
easier. Be that as it may, it certainly
does make everything else much more
difficult.
Probably the reader of this article knows
something about distributed capacity and
perhaps he is a little uncertain as to what it
is all about and why it is one of the things
to be avoided in a radio receiver.
The electrical energy which flows through
the coils of your radio set is much the same
as water in a pipe, and the insulation of the
wire in your coils forms the piping which
holds in the current. The tendency of the
electrical energy is to leak through the
insulation. This tendency is altogether
governed by the distributed capacity or
leakage area and the amount of pressure.
The leakage action generally takes place
from one turn to the next and, as only a
small amount of voltage builds up in one
turn, the effective loss is very small.
However, the regular Roberts NP coil is
wound so that the potential difference be-
tween adjacent turns varies from zero to
forty volts, which may be seen in B, Fig. 2.
We can very easily calculate the mean
voltage between windings or across the
condensers. It is 20 volts. Therefore
we have approximately twenty times the
loss which we have in a coil of proper
design.
To Grid Neutralizing
Condenser ,
To Plate of
FiratTube
10 Turns
::
8 Turns
6 Turns
4 Turns
S-
FIG. 2
RADIO BROADCAST ADVERTISER
67
(Conception of
Jlew/Qnd of Deceiver
flo Dials -Jfo Panel
\ Built-in (budspeaker
lira Simplicity <
tastefully Unobtrusive
CT*HIS new kind of radio-musical instrument marks the
-*• mastery of technicalities to the point where the whole
range of radio's resources are literally at your instant
command.
The Ultradyne, Model L-3 is a six-tube re-
ceiver employing the fundamental principles
of the best circuits, greatly refined and mar-
velously simplified. No dials — no panel:
Just two inconspicuous levers which consti-
tute a station-selector. Duco finished, two-
toned mahogany cabinet.
Designed by R. E. Lacault, E. E., Chief
Engineer of this Company, and formerly
Radio Research Engineer with the French
Signal Corps Research Laboratories.
To protect the public, Mr. Lacault's per-
sonal monogram seal (R. E. L.) is placed
on the assembly lock bolts of all genuine
ULTRADYNE" Model L-3 Receivers. All
Receivers are guaranteed so long as these
seals remain unbroken.
The Ultradyne, Model L-3, sup-
plants the usual "laboratory ma-
chine." It is a new artistic table-
piece that makes the entrance of
radio into the well-appointed
home unobtrusivej inconspicuous.
It represents the triumph of art
over mere mechanics.
The Ultradyne Receiver is
worthy of the place of honor in
luxurious homes.
The Ultradyne Model L-3
fulfills everything that the crit-
ically-minded have demanded of
radio. Why wait any longer,
why deny yourself the infinite
treasures of radio? The ideal
has at last been attained!
Skepticism will vanish if you
will let your local dealer demon-
strate this new modern radio
receiver.
Illustrated folder on request.
PHENIX RADIO CORPORATION, n6-C EAST 25™ ST., NEW YORK
MODEL L-3
Tested and approved by RADIO BROADCAST
68
RADIO BROADCAST ADVERTISER
We Sold
4000 Sets
Had 4000 Favorable Reports
Before We Felt
Justified to Say
Quality Radio
Apparatus
Now we invite you to go
to your ApexDealerwho
will be glad to make a
personal demonstration
for you in your home or
in his store. A demon-
stration will prove to you
that Apex Radio Receiv-
ers will give you every-
thing you can possibly
wish for in a radio re-
ceiver from standpoint
of selectivity, clarity, vol-
ume, distance and attrac-
tiveness of design.
The APEX Super Five
without accessories. .
The APEX De Luxe
without accessories. . .
The APEX Baby Grand
Console without acces-
135
225
75
The APEX Utility Radio
Table
The APEX Entertainer
(Loud Speaker)
The APEX Console En-
tertainer
Upon request we will gladly
mail you descriptive Folder
APEX ELECTRIC
MFG. COMPANY
Dept. 1104
1410 W. 59th St. Chicago
Price* Wett of Kockiet slightly higher
Canadian price* approximately
40% Higher
There are also other factors which tend
to make this type of winding unsuitable for
use in a radio receiver, such as the high
natural period of the coil and its inability
to respond to different frequencies (wave-
lengths). However, we will not go into a
discussion of these matters as they are
largely dependent upon the master offender
— distributed capacity.
Several different experiments were tried
with this coil, and by removing turns enough
to reduce the natural period to about two
thousand kilocycles (150 meters), very
satisfactory reception was had over the
entire frequency band. However, the effi-
ciency dropped very slightly at the lower
frequencies (longer wavelengths), but this
was expected as there were now too few
turns for efficient transformation on the
lower frequencies.
After trying several different styles of
NP coils, the design which seemed most
efficient for all around use consisted of an
ordinary diamond weave coil containing
forty turns of wire tapped at the 2oth turn
and connected in the following manner:
inside lead to plate, center tap to B battery
positive and outside lead to the neutralizing
condenser. See C, Fig. 2.
A great many of these coils have been
installed in Roberts receivers which had
not been giving the best of results. This
new style of NP coil has in every case
shown far superior results to the old-style
coils.
RALPH D. TYGERT,
Springfield, Massachusetts.
A GOOD NEUTRALIZING
CONDENSER FOR THE ROBERTS
CIRCUIT
ATER experimenting with several
types of neutralizing condensers on
the market, from plate condensers
to sliding condensers, it was found that the
average type was either too large or too
small, either in size and capacity, or that
they were not efficient in operation. In
making adjustments they were not pro-
tected against body capacity.
The condenser used in my laboratory for
this purpose can be constructed in a few
minutes from material to be found in any
home laboratory. As Fig. 3 shows, the
condenser is made by taking a piece of
one quarter-inch copper tubing, one and
one-half inches long, a piece of cambric
spaghetti, two and one-half inches long,
which is passed up into the copper tube
at one end, and a three sixteenths-inch
threaded binding post screw with the head
cut off, to be soldered at the upper end of
the copper tube. A bakelite binding post
thumb grip is to be placed on this screw,
which acts as a handle for making adjust-
ment. A piece of insulated copper wire
(flexible preferred) is soldered to the upper
surface of the copper tube, which is to be
connected to the N lead of the NP coil. The
condenser is now nearly completed and the
last step is to cut a piece of No. 14 copper
bus bar wire long enough to pass into the
cambric tubing two and one fourth inches,
leaving enough to attach to a lug which is
placed on the binding post of the tube
socket marked G. The neutralizing con-
denser is now completed and when mounted
on the tube socket as indicated in the draw-
ing, should stand parallel to it. Neutralize
in the usual way by simply sliding the tube
back and forth on the bus bar.
H. A. FRANCHERE,
Lake Crystal, Minnesota.
Shaded Section
of Fixed Plate
to be Cut off B
Flexible Connector/
Soldered to Copper
Tubing
I
Binding Post Top
-6/32" Screw Cut &
Soldered to Tubing
„ Copperor
Brass Tubing
-- Spaghetti
Tubing
.—Copper Bus-bar
/Connecting Lug
FIG. 3
Tested and approved by RADIO BROADCAST
FIG. 4
SHORT WAVES ON THE HANSCOM
SUPER-HETERODYNE
SOME builders of this set have noticed
that the volume on the high-frequency
(short-wave) stations is not as great
as from stations operating on lower fre-
quencies (longer waves.) Theoretically,
the super-heterodyne should give uniform
amplification throughout the entire range
of frequencies, but the Hanscom circuit
makes use of regeneration in the first tube,
thus making possible the great volume
which the set possesses for loop reception.
The diagram A. Fig. 4, shows the circuits
of the first tube. The condenser N is
usually of the midget variable type. It
will be noticed that as its capacity is de-
creased the signal strength increases rapidly
until the first tube breaks into oscillation.
The radio frequency output of the first tube
goes through the iron core radio-frequency
transformer R. The action of the condenser
N, is to prevent a tuned plate feed back by
by-passing radio frequency through itself
and the fixed condenser C. At the same
time as N is increased, there occurs a feed-
back through the coil D which acts as a
tickler at intermediate frequency.
On the short waves it will be noticed that
there is no tendency for the first tube to
oscillate and this is caused by the residual
capacity of the condenser N even though
set at zero. To prove this, it is only neces-
sary to disconnect the wire from the plate of
the tube to N and a great increase in signal
strength will be noted.
With N set at zero, the first tube will
oscillate as we go up the scale, usually at
about 750 kilocycles (400 meters) but with
RADIO BROADCAST ADVERTISER
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Worthy to Bear the KELLOGG Name
The Wave Master
Console Model
A handsome genuine maho-
gany design with battery compartments
and inbuilt horn. Price. <C7'7C C\C\
Without battery
table, price - •
Also made in the beautiful Con-
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gnny, price.
A Year Ahead! The WAVE MASTER, S'Tube Standard Model
Cabinet of solid, Genuine Mahogany, beautifully finished,
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Kellogg
Symphony
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A Separate Circuit for Each
40 Meter Wavelength Band
One -Dial Control, Yet Greater SeltclMtu.
'I never dreamed it was such fun'9
"I used to be content to enjoy radio merely as a listener,
never realizing how much greater pleasure I was mis-
sing. I had no idea of the fascinations of radio tuning
— the fun of going after any station and getting it."
WHEN you make a telephone call, the operator con-
nects you first with the "exchange" and then with
the desired number of that group or division.
To "connect" the WAVE MASTER instantly with any de-
sired broadcasting station, you first set the pointer for the
"Exchange" or wave zone group to which the station be-
longs and then merely turn the Station Selector dial. "Ex-
pert" tuning becomes child's play. To separate stations very-
close together in their wavelengths, is astonishingly easy..
When buying any radio set, protect yourself by learning:
something about the firm that produced it— their reliability-
and experience. For 28 years Kellogg has produced the
finest of telephone apparatus. Since radio began Kellogg:
has built the highest quality parts.
If you do not know where you can see, try and hear the WAVE
MASTER in your neighborhood, write us. We'll give you the name
of your nearest dealer, and, if you wish it, a full technical explanation
of the Wave Master Circuit. Ask for Folder No. 5-K
Radio Dealers and Jobbers
The WAVE MASTER franchise backed by Kellogg resources
and our powerful advertising campaign, is most valuable.
Open territories are being rapidly taken up. If interested,
wire or call on us promptly for our money-making proposition.
Kellogg Switchboard &. Supply Company
1066 West Adams Street, Chicago, Illinois
Tested and approved by RADIO BROADCAST -jr
70
RADIO BROADCAST ADVERTISER
BURGESS
RADIO BATTERIES
Win Aga in
The illustration pictures the take-off of the winning
flight and in the insert is the radio equipment carried.
(Burgess 'A', 'B' and 'C' Batteries furnished the
electrical energy to operate the set.)
When the Goodyear III won the right
to represent the United States at Bel-
gium, Burgess Radio Batteries supplied
the electrical energy for the operation
of the balloon's radio equipment.
Almost every day from somewhere
in the world news comes to us of new
Burgess adventures.
And that Burgess Batteries have con-
tributed their bit in so many interesting
events of sport, commerce and science re-
flects the esteem in which they are held.
"Ask Any Radio Engineer"
Your own radio dealer down the street
•ells Burgess Batteries. He probably
sells the famous Burgess Flashlights, too.
BURGESS BATTERY COMPANY
GENERAL SALES OFFICE: CHICAGO
Canadian Factories and Offices:
Niagara Falls and Winnipeg
the above mentioned wire disconnected,
the first tube will oscillate at about 1000
kilocycles (300 meters). Unfortunately
there is no small variable condenser avail-
able with a minimum capacity sufficiently
low to function on the snorter waves with
maximum efficiency. To those who are ex-
perimentally inclined, we suggest the cut-
ting of the fixed plates of a three-plate
vernier as indicated in B, the point being
Drilled Hole
Through
Window Glass
Protected ^
Porcelain'''
Through Window
Casing
Metal
Funnel
FIG. 5
to make a condenser with a wide separation
between the edges of the fixed and rotating-
plates at zero setting. It is also possible
to connect a single point switch so that
the condenser N may be cut out of the
circuit as indicated in C. Needless to say,
the leads to the condenser N from the set
should be as short and direct as possible,
particularly the lead from the plate of the
tube.
A. T. HANSCOM,
Woonsocket, Rhode Island.
A LEAD-IN PROBLEM
A RADIO friend of the writer, erected
an antenna some hundred and
twenty-five feet in length, about for-
ty feet above ground, brought the lead wire
down past the drain spout, and under the
lower sash of the window directly in contact
with the stone sill.
Results; a strangled band and gagged call
letters, with other muffled sounds, were
received with the aid of five tubes in a high-
priced receiver.
It took one radio expert about ten min-
utes to fix up the antenna and about three
hours explaining to this friend why his
antenna failed, even though at this time
the latter is hardly convinced of having
made any grave error in running the wire
as he did.
The manner of leading in an antenna
wire, which was used to correct this afore-
mentioned mistake, is illustrated in the
attached sketch, Fig. 5, and is about the
cleverest and most practical of any which
the writer has observed. A single small
hole is drilled through the center of the
window glass. The antenna lead passes
through this hole obtaining insulation of the
Tested and approved by RADIO BROADCAST if
most desirable type, and at the same time
providing a support for the wire. The
same idea can be further improved by the
use of a small threaded rod having screw
terminal nuts at each end to attach or de-
tach the lead wire. In drilling through the
glass, it is advisable to use a small hard
drill with turpentine as a drill lubricant,
turning the drill quite fast and giving only
enough pressure to cause the drill to cut.
In another illustration shown in the same
sketch, a method of leading the antenna
through the window casing is shown. The
antenna wire leads through a porcelain
tube, placed through a bored hole in the
wood. Surrounding the lead through the
porcelain, is a small metal funnel, secured
with tape as shown in the sketch. The
funnel not only prevents the water following
through the tube, but it also keeps the lead
dry below this point, preventing a leak
which would be found detrimental to recep-
tion.
G. A. LUERS,
Washington, District of Columbia.
AN EFFICIENT COILCOVERING THE
BROADCASTING FREQUENCIES
I HAVE found that with the 35-turn coil
which is illustrated in Fig. 6 and shunted
by a good .0005 mfd. variable con-
denser, frequencies from 1 500 kilocycles (200
meters) to 545 kilocycles (550 meters) may
be covered, and I know of no other winding
in which 35 turns will cover this range.
This coil is wound on a form 3 inches in
diameter, with 25 pegs equally spaced, and
is wound over two and under two, and
sewed as shown in the photograph, Fig. 6.
W. H. MAYFIELD, Miami, Arizona.
About Contributions
CT"HIS department particularly welcomes short
manuscripts relating to all matters pertain-
ing to workshop practice, such as the handling
of tools, and general hints of a constructional
nature. These, as in the one of other contribu-
tions for the "j^pw I Have Found . . ."
section, should not be longer than about 300
words and should be typewritten.
RADIO BROADCAST ADVERTISER
EVEREADY HOUR
EVERY TUESDAY AT » P. M.
Eastern Standard Time
For real radio enjoyment, tune in the
"Eveready Group." Broadcast through
stations —
WEAF New York WCAE Pittsburgh
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*«. RADIO DRV
INSPECTED
TESTED
RELIABLE
"**»«. CARBON CO-"
"
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Large
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Price
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ALWAYS
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EVEREADY Radio Batteries are
always uniform and reliable!
Evereadys perform the same,
everywhere, for everybody, need-
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There is an Eveready dealer
nearby.
Manufactured and guaranteed by
NATIONAL CARBON COMPANY, INC.
New York San Francisco
Canadian National Carbon Co., Limited, Toronto, Ontario
Radio Batteries
-they last longer
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fe,r-»_ "<n
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45 -volt
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Extra-
Large
Vertical
Price
$5.50
RADIO BROADCAST ADVERTISER
A practical,
authoritative book on
RADIO
I.C.S.
RADIO
HANDBOOK
100,000 SOLD
514 PAGES
Compiled By
HARRY F. DART, £.£.
Formerly with the
Weitern Electric
Co., and U. S.
Army Instructor of
Radio. Tech-
nically edited by
F. H. DOANE.
BE A RADIO EXPERT— it's easy
for the 100,000 who own this com-
pact, complete Radio Handbook. Writ-
ten in good, plain, understandable lan-
guage. Crammed full of facts, every
one useful and important. Explains
how receivers and transmitters work,
how to build and operate them. What-
ever you or your friends want to know,
it's here. Will save you many times its
small cost.
TELLS ALL ABOUT: Electrical terms
and circuits, antennas, batteries, gen-
erators and motors, electron (vacuum)
tubes, most receiving hook-ups, radio
and audio frequency amplification,
broadcast and commercial transmitters
and receivers, super-regeneration, codes,
license rules. Many other features.
Nothing else like it. Make this ex-
traordinary book your radio library —
just this one little giant is all you need.
Everything in one index, under one
cover, in one book, for one dollar. The
biggest dollar's worth in radio today.
Combines the knowledge of many ex-
pensive works. Buy this and save the
difference.
Just mail the coupon with a dollar
bill and your name and address, and
this 514-page I. C. S. Radio Handbook
will be sent to you by return mail. Note
the other good books listed below at
low prices.
International Correspondence Schools
Box 8295-E, Scranton, Penna.
I enclose I for which send me, post-paid,
the Handbooks marked X. at $1 each. It Is under-
stood that if I am not entirely satisfied I may
return them within flve days and you will refund
my money.
Q RADIO HANDBOOK, 514 PAGES, $1
Automobile Handbook, 354 pages - - - $1
Electrical Handbook, 414 pages - - - - $1
Chemistry Handbook, 3 8 pages - - - )
Pharmacy Handbook, 324 pages - - - 3
Traffic Handbook. 386 pages - - - - )
Building Trades Handbook, 409 pages - - $1
Machine Shop Handbook, 335 pages - - I
Salesman's Handbook, 352 pages - - - 1
Advertising Handbook. 445 pages - - - »1
Bookkeeper's Handbook, 302 pages - - 1
Civil Engineer's Handbook, 411 pages - - !
Steam Engineer's Handbook, 298 pages - Jl
Name..
Address
Kncloie $1.50 instead ol $1 lor each look if
you want the lentheroid binding. *ll ol the
above books can be had in this binding except
I «»« Traffle Handbook and the Building Trades I
• Handbook. I
THE GRID
A Department Devoted to Solv-
ing the Problems of our Readers
QUERIES ANSWERED
1 . WILL YOU GIVE ME A CLEAR, NON-TECHNICAL
EXPLANATION OF STATIC AND FADING?—
A. R. S— Yonkers, New York.
2. ON THE LONGER BROADCAST WAVELENGTHS
MY RECEIVER PRODUCES POOR VOLUME.
WHAT is THE CAUSE? — A. C. P. — Grove
City, Pennsylvania.
EXPLAINING STATIC AND FADING
MANY times have the questions been
asked, what is static; what causes it;
what is fading?
At the present time much attention is being
given to the subject of static and in answer to
the specific question of our correspondent,
nothing could be more timely in answer than
the paper prepared by Dr. A. F. Van Dyck,
on this very interesting topic. Dr. Van Dyck
is a former General Electric engineer and at
present is connected with the Radio Corpora-
tion of America. His recent researches on the
static problem admirably qualify him to speak
on the subject:
" First, let us consider what radio transmis-
sion is. We know that a radio sending station
sends out from its antenna, in all directions,
a disturbance of electric forces. We cannot see
or hear or otherwise observe with our senses
just how this disturbance behaves, as we can
with light waves and sound waves. We con-
sider it quite natural that a stone wall stops
the light beam from a searchlight, or that a
bugle call can be heard much farther over water
than through a forest, or that under certain air
conditions on a desert the mirage phenomenon
is observed. So to know what to expect in
radio, we need only to remember that some
things in space will stop, or reflect, or perhaps
absorb the traveling radio waves, just as some
other things in space stop or absorb or reflect
light waves or sound waves.
"Substances which are obstructions to light or
sound waves are not necessarily such to radio
waves. For example, we know that radio waves
pass through the walls of a house with only
slight loss. But there is some substance in the
space around the earth which does have effect
upon radio waves. This substance is not uni-
formly distributed through space but is present
here and there, is continually changing location
and magnitude, and consequently has very er-
ratic effects on the passage of radio waves. The
condition is quite similar to the use of a search-
light in a fog which might be varying rapidly in
density or location, or both. This radio fog is
commonly supposed to be made of ionized air,
that is, air which by some influence has become
a partial conductor of electricity. Of course
it never stands still and is changing from mo-
ment to moment under the influence of the
complicated conditions of our atmosphere, and
so the radio wave passing through space has an
adventurous journey because it meets electri-
cally charged clouds, patches of ionized air, and
perhaps other obstacles of which we know
nothing.
" It is a fact, often observed, that it is possible
to work radio communication over much greater
distances at night than in the daytime. This
(Continued
3. WILL YOU DESCRIBE THE CONSTRUCTION
OF BOX AND SPIRAL LOOP ANTENNAS? —
R. M. C.— Oak Park, Illinois.
4. HOW MAY THE NEW TOROID COILS BE SUB-
STITUTED FOR THOSE NOW CONTAINED IN
NEUTRODYNES AND OTHER TUNED RADIO-
FREQUENCY RECEIVERS? — T. J. Me G. —
Hartford, Connecticut.
may be explained by the effect of the sun upon
the air, which causes ionization of it, and is
most active in the daytime, and practically
absent at night. The sun seems to be re-
sponsible, without question, in view of the
fact that very erratic results in long distance
reception are always noticed at sunrise and
sunset.
"With the preceding statements in mind it
should be clear that when one is receiving over
long distances — several hundreds of miles —
it is natural for the waves to come through
strong at one moment, and to fade away con-
siderably the next moment, as some obstacle to
radio waves comes between the transmitter and
receiver. This explains, too, why one trans-
mitting station, of two or more which are being
heard, may get weaker, while the others do
not. These effects are much more frequent
in the summer than in the winter season, pre-
sumably because of the greater influence of the
sun on earth and its atmosphere during that
season.
"These ionized clouds sometimes reflect the
waves, much as a mirror does a light wave, and
very peculiar reception effects are sometimes
noticed. Sometimes the signals are made
stronger instead of weaker, sometimes they may
be lost altogether, as the several effects of re-
flection and absorption combine.
"And now, let us consider that arch enemy of
radio — static. When Marconi first began to
receive messages over distances of a few miles
he noted, besides the signals he was listening
for, noises which had nothing to do with the
signals.
"These noises have been called strays, or
atmospherics, or static, and their elimination
is the most important problem in radio com-
munication to-day. The intensity of this dis-
turbance is different at different parts of the
earth's surface, being progressively worse from
the temperate to the tropical zones. The in-
tensity of static varies greatly with the seasons
of the year. For example, in the northern part
of the United States, it is practically absent
during the winter months, increases during the
spring, and is most severe during the summer.
There are at least two or three kinds of static,
but the most troublesome kind is the one which
is due to traveling electric waves, in nature just
like radio waves, and caused by electrical dis-
turbances somewhere in space. A lightning
flash produces a traveling electric-wave, much
like a radio wave, and if we can assume that
lightning flashes, large and small, are occurring
continuously somewhere we have a reasonable
explanation of static. Of course, these dis-
charges do not always manifest themselves by
a display of lightning, the majority in fact
being small discharges inside of or between
clouds. Also it is probable that the continuous
on page 84)
RADIO BROADCAST ADVERTISER
83
• f -
Ifou*
Radio
Arl.
MICARTA
YOUR radio will be built of the best only when a Micarta
panel adds efficiency and beauty to careful building.
It is the easiest of materials to engrave and machine. Smooth
holes may be drilled without the slightest sign of a chip. It
is not affected by temperature changes, water or oil,
Micarta panels are now available in the soft, deep gloss of
mahogany and walnut as well as in black. You will find them
at your dealer's packed in the orange and black envelopes.
Westinghouse Electric & Manufacturing Company
East Pittsburgh Pennsylvania
Sales Offices in All Principal Cities of
the United States and Foreign Countries
ibttse
•i^^^^
Tested and approved by RADIO BROADCAST
84
RADIO BROADCAST ADVERTISER
of all radio trouble
can be traced to
weak or poor batter'
ies. This is not a
guess but the actual
percentage shown
by an extensive sur-
vey made by a large
manufacturer of ra-
dio sets.
| Don't guess — -Be .sure
—Be accurate — Test
your batteries fre-
quently. Save time
and expense and get
the best results and
greatest pleasure out
of your set.
H
J There is a Jewell radio testing
instrument to meet every
need or pocketbook ($2.00
to $75.00). The No. 98
Voltmeter shown above is
being used by dealers to
test batteries as customers
buy them.
Send for our 15-B Radio Catalog
Jewell Electrical Instrument
Company
1650 Walnut St., Chicago, HI.
atmospheric changes above the surface of the
earth, such as the formation of water vapor
clouds, are accompanied by electrical disturb-
ances which travel to the earth.
"We know that static is worse in the summer
when variations in the atmosphere are greater
and more frequent. Also it is often observed
in the winter time that the formation of snow
causes static. Without knowing definitely the
origin of this disturbance, it seems safe to as-
sume that the actions which take place in our
atmosphere, due to the air, the sun, sun spots,
water vapor, etc., are responsible for the creation
of these irregular, irresponsible, and very
troublesome waves which we call static. Since
they are so much like the radio waves in nature,
no way has yet been found of eliminating them
completely. Progress has been made in the
last few years, however, and the transoceanic
stations are much more free of this interference
than formerly. The problem of complete
elimination of static is the most difficult one
in radio, and if solved, we shall have a new
epoch in radio because it will then be possible
greatly to reduce the power of transmitting
stations and the reliability of communication
increased."
RECEIVER COIL RESISTANCE
MANY owners of radio receivers observe
that their sets will respond quite satis-
factorily on the lower end of the scale of
the condenser dial, but above a certain set-
ting the volume produced will decrease con-
siderably and the selectivity is not as sharp as is
desirable.
Granting that a thorough inspection of a
receiver has disclosed no error in circuit wiring
or defect in coils, tubes, etc., it is fair to assume
that this condition is due to the use of coil
units which, while otherwise O. K., have an
exceedingly high resistance at the higher end of
the condenser scale.
Resistance in a coil may be attributed to i.
insulation within the field of the coil, such
as tubing, panels, and other nearby objects; 2.
the use of "dope" which is used as a binder to
hold the coil together; 3. the use of fine wire (or-
dinarily circuits should employ coils wound with
wire not smaller than No. 28 wire or larger than
No. i8d. c. c.)
Resistance here should not be confused with
the ordinary use of the term where it is em-
ployed to indicate the direct resistance of a
piece of wire. Rather, it is a value which
changes with each change in frequency to which
the circuit may be tuned. This is brought out
quite clearly in the table of measurements which
follows. These measurements were obtained by
a regular laboratory procedure.
tofore discussed. Broadcast listeners do not
usually have the means to make these measure-
ments, however, and it is necessary for them to
judge entirely by ear and eye in the matter of
volume and selectivity. But for those who do
have means for making these measurements,
the following table of measurements of a coil
which has proven satisfactory is given for com-
parison.
FREQUENCY
IJOO KC. (2OOM)
1 2OO KC. (25OM)
looo KC. (}OOM)
75O KC. (4OOM)
600 KC. (JOOM)
5OO KC. (600M)
RESISTANCE
75-5 ohms
38. t "
24.5
16.5 "
35-S "
10.5
COIL NO. 2
95-5
108.5
300.0
72.0
18.5
12.5
From the above it will be observed that in
coil No. 2 the resistance gradually rose from
95.5 ohms at 1500 kc. (200 meters) to 300
ohms at 1000 kc. (300 meters) and then
gradually decreased to 12.5 ohms at 500 kc.
(600 meters). In all receiving circuits it is es-
sentia-Mhat the resistance of the tuner circuits
be kept as low as possible. Where this is not
thi case, poor selectivity, with a loss in volume,
is sure to result.
Obviously the solution to this problem lies in
the use of coils having a minimum of resistance
which depends upon the several points as here-
Tested and approved by RADIO BROADCAST -A
FREQUENCY
IJOO KC. (2OOM).
1 2OO KC. (25OM).
IOOO KC. (30OM).
750 KC. (400M).
6OO KC. (5OOM).
500 KC. (600M).
RESISTANCE
. . 20.5 ohms
. . 12.5
. . 12.5
. . .0.5 "
. . 8.5
. . 7-5
FIG. 1
LOOP CONSTRUCTION
IN THE main, two types of loops are used
for reception. The spiral type, more com-
monly known as the pancake type, is the
easier of the two to build. It has marked di-
rectional effects and may be used successfully
in a direction-finding station. See Fig. i.
To construct this type of loop two pieces of
one inch square wood are required, one thirty
inches long, the other twenty-four inches long.
The shorter of the two is the horizontal piece
while the other is the vertical piece, to which
may be fastened an appropriate base. By
means of a half lap joint, the two sticks are
fastened together to form a cross.
The two pieces are so crossed that three of
the arms will measure 12 inches from the point of
intersection, while the fourth, which is fixed
to the base, measures 18 inches.
Five inches out from the centre, on each of
the four arms, is placed a No. 4 round head brass
wood screw 5 inch long. Fifteen more screws
of the same size are located on each of the four
arms, each screw being placed f of an inch apart.
The winding of the wire is begun on the
inside screws and outward, the two ends of the
wire being made fast to binding posts located
at the lower end of the vertical arm. Stranded
wire having double silk or cotton covered insula-
tion will be found best.
In Fig. 2 is shown the box type of loop which
consists of a specially constructed frame upon
which is wound the wire in a horizontal plane.
Its constructional details are apparent from
reference to the illustration. The depth of th<
h
^
RADIO BROADCAST ADVERTISER
85
^Another
BOSCH
RADIO
PRICE
$1/150
JuniorAMBOTONE
A NOTHER Bosch Radio triumph. The
-**• announcement and immediate nation-
wide acceptance of the Bosch Radio Receiver,
and the Bosch Reproducer, the Ambotone,
is now followed by another Bosch Radio
product.
Bosch now announces the Junior Ambotone. The Junior
Ambotone is a radio reproducer with an unusual tonal
quality built to the famous Bosch standard of precision.
Following the Ambotone principles of reproduction, the
Junior Ambotone gets its mellowness from wood.
The Bosch ability to manufacture to precision standards,
accounts for the tone quality. The Bosch ability to build
with accuracy in quantities accounts for the remarkably low
price. The greatest value in radio — the Junior Ambotone
—at $14.50.
TRADED r^MAWK
American Bosch Magneto Corporation
SPRINGFIELD, MASS.
Tested and approved by RADIO BROADCAST
86
RADIO BROADCAST ADVERTISER
Rhamstine*
TUBE BOOSTER
Your radio en-
joyment depends
largely on t h e
tubes. If they do
not function prop-
erly you can not get
a full, clear tone.
They can be made
"just like new" —
Rhamstine* Tube
Booster renews
their youth with all
(that the word im-
plies — pep, fresh-
ness, a true, full,
round tone which
carries the message
as "clear as a bell."
Why buy new
tubes when the
Rhamstine* Tube
Booster assures
you of perfect radio enjoyment. Works on
any alternating current 110-120 volts, 50-
133 cycles, it matters not whether you
use 2OI-A or 199 Type Tubes.
Send no money — check the coupon below
— pay on delivery.
Khamslinc*
Tube Booster
Only
!.(. I »«!? T> . • (* Elimina
B Kectmer B Bat,
tm
ttery
Rhamstine* "B" Rectifier
Only
The Rhamstine* "B" Rectifier is a quality
product which furnishes an always depend-
able source of "B" power. It eliminates
"B" Battery troubles such as chemical
action, dead cells, recharging, and gives a
continuous and uniform current, reproduc-
ing perfectly the original sound.
The cost is nominal compared to the
pleasure and satisfaction derived from the
service it performs.
Send no money — just check the coupon.
The "B" Rectifier is shipped on 5-day
approval. If not satisfied, your money will
be refunded as cheerfully as the sale is
made.
Mail the Coupon To-day
J. THOS. RHAMSTINE' (n)
506 E. Woodbridge, Detroit, Mich.
Please send me
D your Tube Booster at $6
D your "B" Rectifier at $25
by express C. O. D. subject to inspection. If I am
not entirely satisfied with the "B" Rectifier I will re-
turn it to you in five days and receive a refund of the
full purchase price.
Name.
Address .
J. THOS. RHAMSTINE*
Radio and Electrical Products
506 E. Woodbridge St., Detroit, Mich.
FIG. 2
box is 95 inches and the diagonal pieces are 36
inches long. Sixteen turns of loop wire are
wound on the frame, the turns being separated
J inch.
SUBSTITUTING TOROID COILS IN NEUTRODYNES
CTELY the toroid type of coil, under
many different trade names, has come
to the front as a promising substitute
for the coil unit in receivers where inherent
neutralization was not possible. This new type
of coil possesses the property of confining its
electro-magnetic field within itself. With other
coils the field usually shapes itself outward and
around the coil, thus interlinking with the
Coils Parallel and Adjacent .,
MO?
Fields Interlinking
FIG. 3
fields of nearby coil units and causing uncon-
trolled oscillation due to energy feedback.
See Fig. 3.
To replace the older type of cylindrical coil
with a toroid in a neutrodyne, for instance, is
not a difficult matter. The toroids have four
binding posts as terminals for their windings.
These are P, B, G, and F, not unlike those mark-
ings for audio-frequency transformers.
When the toroid coil is used as an antenna
coupler, the terminals P, B constitute the an-
tenna-primary coil to which are connected the
- B
FIG. 4
antenna and ground leads. When used as an
inter-stage coupler, in a radio-frequency circuit,
the terminals P, B constitute the plate (primary)
winding, terminal P connecting to the plate of
the preceding tube and terminal B connecting
to the positive B battery lead.
In both instances the secondary terminals G
and F connect to the grid and filament leads of
the next tube. The several points brought out in
this discussion are evident in Fig. 4. The above
is true only of coils having two distinct windings,
primary to secondary, and does not hold when a
tap is taken off the coil for antenna use.
GRID INQUIRY BLANK
Editor, The Grid
RADIO BROADCAST
Garden City, Tvjeu/ Tor);
DEAR SIR,
Please give me the fullest information on the attached questions. I enclose a stamped
envelope.
O I am a subscriber to RADIO BROADCAST and therefore will receive this information free
of charge.
C] I am not a subscriber and enclose $1 to cover cost of answers.
NAME .
ADDRESS .
G. N.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
87
The Empire Model
Baby Grand Model
Enclosed in a 17th Century
solid mahogany French Cabi-
net with hand carved figures,
housing all batteries $100
(without accessories)
The David Grimes Inverse
Duplex Empire and Renais-
sance models are in reality
six-tube sets, utilizing only
four UV 199 tubes. This
is accomplished by inverse
duplexing which permits the
dual operation of vacuum
tubes, at the same time de-
livering a natural tone qual-
ity which is so noticeably
lacking in most present day
receivers. Incorporated in
these models are two stages
of sharply tuned radio fre-
quency amplification, vac-
uum tube detector, and
three stages of audio fre-
quency amplification. A con-
veniently located super-power
switch gives tremendous re-
serve power on distant sta-
tions when necessary. Re-
markable selectivity is gained
by the use of straight line
condensers and a new form of
inductance, the twin cylinder
coil, which was developed in
our laboratory after months
of research.
The Renaissance
Model
Enclosed in an Italian Ren-
aissance Cabinet of a beauti-
ful two tone mahogany and
walnut, housing all batteries
$100
(without accessories)
The supreme achievement of the world
famed Radio Engineer, David Grimes —
sharply selective sets that tune in the sta-
tions you desire and hold out all others.
Distant or local programs are sustained
with marvelous clearness and superb
tone, just as they are broadcasted, with-
out annoying interference.
Built on the Grimes Inverse Duplex prin-
ciple in which there is a dual operation
of the vacuum tubes.
You've expected something new, some-
thing that would give real pleasure — by
all means hear these instruments!
Look for this Emblem
It identifies your authorized Grimes dealer
who will gladly demonstrate any of the in-
struments pictured herein.
Products of the
DAVID GRIMES RADIO and
CAMEO RECORD CORPORATION
1571 Broadway, New York, N. Y.
SUPER SELECTIVE SERIES
•4r Tested and aooroved bv RADIO BROADCAST
A three-tube duplex receiv-
ing set that uses UV 199
tubes. Incorporates one stage
of tuned radio frequency am-
plification, tube detector and
two stages of audio frequency
amplification. A powerful,
super selective set that gives
exceptional volume and an
excellent distant range. In
two tone mahogany cabinet,
housing all batteries. $59. 50
(without accessories)
All of the essential units of
the various instruments are
developed and built within
the Grimes plant. The sets
are factory tested, sealed and
guaranteed before they are
put on the dealer's shelves.
The Grimes
Super Tone
Loud Speaker
$25
A really real-
istic repro-
ducer - - non-
metalic in
composition with a mica dia-
phragm that eliminates dis-
tortion.
Whether the deep mellow
notes of the cello or the flut-
tering notes of the gifted so-
prano are taken from the air
— a sweet clear rendition of
the voice or music is always
secured.
88
RADIO BROADCAST ADVERTISER
The
New
PRECISE
Syncrodenser
A scientific combination of
straight line frequency where
that is vital, with straight
line capacity where that is
superior.
By use of the Syncrodenser the
lower half of the dial range has
fewer stations, while the upper
half contains many stations found
between 0 and 50 on ordinary con-
densers. This absence of crowded
stations on the lower half of the
dial permits finer tuning and tre-
mendously increases the selec-
tivity of any set. The Syncro-
denser is strongly built and can be
mounted on panel or subpanel in
any position. Prices, .0005 mfd.
cap. $4.50; 00035 mfd. cap. $4.00.
THE MONSTER
PRECISE No. 480
A master transformer, designed
for radio reception in a concert hall
or ballroom if necessary. It brings
forth the deep, rich tones as well
as the high clear tones with perfect
amplification. Made in two ratios,
l\ to 1, and 5 to 1. Price, $7.50,
either ratio.
PRECISE MFG. CORP.
ROCHESTER, N. Y.
THE PRECISE SUPERSIZE
No. 480 AUDIO TRANSFORMER
THE BEST
The First Installment of a Useful Classified Sur-
vey of Material Appearing in the Radio Press
By E. D. SHALKHAUSER
How This Survey Can Help Ton
~LJOW often have you looked for information contained in some article which you recall having
•*• •*• read months ago — the description of the Browning-Drake receiver, or the measurement of
losses in inductance coils, for example? After looking through probably several issues of a do^en dif-
ferent publications you either give up or become interested in something altogether different.
When data is wanted on some particular subject, a systematic fie of subjects and titles becomes a
real radio encyclopedia. Instead of having merely the title of an article given, which often is misleading,
a summary of the contents gives all the information. These surveys cover the radio field as gleaned from
material in to-day's periodicals. They will always serve as a future reference-guide to all who are
interested in the science of radio, whether engineer, manufacturer, dealer, experimenter, or listener.
To be of practical value and easily accessible, these surveys should either be filed in a scrap book,
or pasted on individual cards and filed according to numbers, or alphabetically. In the matter of
classification of articles, the Bureau of Standards circular No. i )8 has been followed. This may
be obtained from the Government Printing Office, Washington, District of Columbia, for ten cents.
In addition, each abstract has certain key-words placed at the upper right, which may be used for
the purpose of filing articles alphabetically.
With this series of surveys we hope to aid our readers and help them through many difficulties
which they no doubt have often experienced. In future we will give information and references to
articles previously surveyed upon receipt of a stamped and self-addressed envelope.
Following is a brief outline of the Dewey Decimal System used in the Bureau of Standards circular
No. ij8:
Rooo RADIO COMMUNICATION IN GENERAL.
Under this heading will appear all subject
matter pertaining to laws, regulations, history,
publications, etc., which deal with radio in a
general way.
Rioo PRINCIPLES UNDERLYING RADIO COM-
MUNICATION.
Here will be given the phenomena of radio
waves, their underlying theory of propagation,
the principle of antenna and counterpoise, de-
sign and characteristics of vacuum tubes and
their behavior in circuits, types of circuits, trans-
mitting and receiving apparatus and their prin-
ciples of operation.
R2oo RADIO MEASUREMENTS AND STANDARDIZA-
TION METHODS.
The various known methods which have been
used in measuring frequency, wavelength, reson-
ance, capacity, inductance, resistance current,
voltage, dielectric constants, and properties of
materials, will be mentioned here.
R3OO RADIO APPARATUS AND EQUIPMENT.
A description of various types of antennas
and their properties, the use of the electron tube
in various types of receiving and transmitting
sets, other methods of transmission of signals,
various detecting devices used in reception,
instruments and parts of circuits, come under
this heading.
R4oo RADIO COMMUNICATION SYSTEMS.
The spark, modulated wave and continuous
wave systems in transmission, beat and other
methods of reception, wired wireless, automatic
printing, the buzzerphone and Fullerphone, will
be given here.
Rjoo APPLICATIONS OF RADIO.
To aviation, navigation, commerce, military,
private and broadcasting, and the specific infor-
mation under their headings, are referred to here.
R6oo RADIO STATIONS.
The operation, equipment, and management
of radio installations, both transmitting and re-
ceiving, the testing, the rules and regulations
concerning stations, the reports and bulletins
issued, will follow under this heading.
Ryoo RADIO MANUFACTURING.
Data relative to costs and contracts of radio
equipment from raw material to finished product,
including factories, tools, equipment, manage-
ment, sales and advertising, follows here.
R8oo NON-RADIO SUBJECTS.
The matter of patents in general; the mathe-
matics and physics, including chemistry, geology
and geography; meters of various kinds; all in-
formation not strictly pertaining to radio,
but correlated to this subject, will be found
under this heading.
Rgoo MISCELLANEOUS MATERIAL.
A Key to Recent Radio Articles
R343. ELECTRON TUBE RECEIVING SETS. RECEIVER,
Radio-frequency.
RADIO BROADCAST. Sept. 1925, pP- 581-585.
"An All-Wave Tuned Radio Frequency Receiver."
Zeh Bouck.
To make broadcast reception possible from foreign as
well as domestic stations, a receiver should be able to cover
a band of from 200 to 2600 meters. Ordinary tapped in-
ductances entail too great losses when used for wide wave-
length ranges. By using the well-known honeycomb coils,
the desired range can be obtained. The list of parts re-
quired, the circuit diagram and construction data is very
completely given. A list of foreign broadcasting stations is
appended.
R43O. INTERFERENCE ELIMINATION. INTERFERENCE.
RADIO BROADCAST. Sept. 1925, pp. 586-590.
"When Broadcast Stations Interfere." C. B. Jolliffe.
The cause of so-called heterodyning of broadcast stations
is explained by diagram and found to exist when broadcast
stations deviate somewhat from their assigned frequencies.
Some interference with programs broadcast from other
stations is due to beat note produced when frequencies come
too close together. The author describes how stations
must constantly be checked by station operators and radio
supervisors in the various government districts in order
to maintain their assigned frequency.
Tested and approved by RADIO BROADCAST -jr
R343- ELECTRON TUBE RECEIVING SETS. RECEIVER
Super-pliodyne.
RADIO BROADCAST. Sept. 1925, pp. 620-622.
"A Single-Control Receiver," C. L. Farrand.
A receiver, known as the super-pliodyne, is described,
giving more detailed information on the operation and ad-
justing of the circuit, also described in July RADIO BROAD-
CAST, pp. 387-392. Although a single control receiver, it
gives just as great selectivity as a good super-heterodyne be-
cause the individual circuits are matched. The exact
operation of this set, using a two-stage radio-frequency
amplifier, is described technically, the circuit diagrams
giving the necessary detail.
R375. DETECTORS AND RECTIFIERS. RECTIFIERS,
Tun gar tube.
RADIO BROADCAST. Sept. 1925, pp. 640-650.
" How to Make a Universal Battery Charger," Roland F.
Beers.
The author reviews briefly the theory of a. c. rectification
by various methods, and proceeds to describe the construc-
tion and operation of a tungar charger which can be used
for a frequency range of from 25 to 70 cycles. Consider-
able detail in the assembly of this charger, parts required,
and final instructions for operation, leave no opportunity
for guesswork. Only 150 watts are consumea by this
2-ampere charger.
RADIO BROADCAST ADVERTISER
93
The 1925-26 Radio Dealer
a catalog of radio apparatus and trade
marks now available to the trade
at
$1.00 per copy, or
FREE
with One Year's subscription
to
The RADIO DEALER
the Pioneer (B^adio Trade Journal
The Radio Dealer Publications
1133 Broadway New York City
If you are in need of apparatus get in touch with our FREE Service Bureau
Tested and approved by RADIO BROADCAST
94
RADIO BROADCAST ADVERTISER
Howling and distortion both
result frequently from running
transformer leads too close to-
gether.
The case and brackets on B-T
Euphonic Transformers are so
designed to allow mounting in any
position, on baseboard, sub-panel,
or side — with the terminals always
in position for short leads, and
no crossed wires.
B-T "Euphonic"—
Pleasing to the Ear
More and more is popular judgment of radio directed toward
quality. Fidelity to speech or music as given in the studio is the
requirement of to-day.
Convinced that better audio transformers were necessary to se-
cure the full benefit of B-T circuits and apparatus, B-T engineers
tackled the transformer problem. The result of their long effort
is the B-T Euphonic, a superior transformer. As its name im-
plies it is "Pleasing to the Ear." We believe it the best audio trans-
former available to-day.
Ratio 2.2 to 1, Price, $5.00 Ratio 4.7 to 1, Price, $5.75
Before You Buy Condensers —
No condenser is better than its bearings, and
there is no bearing in radio that compares with
the B-T "Lifetime."
Examine this feature before you buy.
The Straight Line Frequency type is illustrated.
The 17-plate, .00035 is $5.75. It covers 200 to
550 meters with Torostyle coils, giving absolute S. L. results.
The "LIFETIME" is also furnished in straight line wave length
as well as Tandem.
The New B-T Set,— TheCounterphase-Six
A B-T patented circuit with B-T parts and built in the B-T fac-
tories with typical B-T craftsmanship.
Six tubes, three stages of radio frequency enable it to receive dis-
tant stations with only a short indoor antenna. Only two tuning
dials.
Write for full information
BREMER.TULLY MFG. co.
532 S. Canal Street
Chicago, 111,
R344- ELECTRON TUBE GENERATORS.
OSCILLATOR,
Modulated
RADIO BROADCAST. Sent. 1925, pp. 604-609.
"What is to Become oi the Home Constructor?"
Henney
Keith
Henney.
The radio field for the "home constructor" goes beyond
mere set building if he is at all interested in the science of
radio. In this article, RADIO BROADCAST makes the first
attempt to bridge the gap between the larger scientific
laboratories and the home workshop by guiding the con-
structor in the building and testing of apparatus for ex-
perimental purposes. The first instrument described is a
modulated oscillator comprising a high frequency and a
low frequency oscillator in one. Its construction is simple
and can be used as an audio oscillator, radio oscillator, and
modulated oscillator, for a variety of purposes.
R385-5 MICROPHONES. MICROPHONE.
RADIO BROADCAST. Sept. 1925, pp. 612-615.
"Microphone Placing in Studios." Carl Dreher.
The microphone in a broadcasting studio is very sensitive
to air vibrations and its proper operation and placing is
quite important. How it is connected and set for receiving
sound waves properly for transmission is explained and il-
lustrated. Depending upon the type of musical instru-
ment used, the microphone must be placed so as to receive
a proportionate amount of sound energy. Blasting or
reflection from walls causes distortion in the received wave.
Rj82. TRANSMISSION OF PHOTOGRAPHS. PHOTOGRAPH
TRANSMISSION.
Popular Radio. Aug. 1925, pp. 107-113.
"Motion Pictures by Ether Waves," Charles Allen
Herndpn.
The transmission of shadow pictures has been accom-
plished by C. Francis Jenkins. With his teloramaphone.
using four photo-electric cells and a rotating disc of lenses,
he has been able to build up pictures at the rate of 1 5 per
second and throw them on an illuminated screen, thus
giving the effect of true moving pictures. The bulb used
in bringing the pictures out clearly on the screen has a well
of gas instead of the common filament. This light will
go on and off instantaneously with the current. Photo-
graphs of the inventor and his machine in detail illustrate
the system used.
R36o. ELECTRON TUBE RECEIVING SETS. RECEIVER,
Grebf
Syncbropbasc.
Popular Radio. Aug. 1925, pp. 116-127.
" No. 7. The Grebe Synchrpphase," S. Gordon Taylor.
In this yth of a series of articles, explaining the theory,
operation, equipment and care^ of manufactured receivers,
the Grebe synchrophase is discussed. This is a tuned
radio frequency receiver of five tubes. The wiring diagram
is shown complete, while the exterior and interior views of
the set illustrate the placing of the various parts, including
the "binocular" coils. The battery connections for the
complete equipment, and the proper method of tuning, are
described in detail. The receiver can be easily charted
because the straight-line frequency condensers give equal
spacing on the dials between stations.
R376-3- LOUD SPEAKING REPRODUCERS. LOUD-SPEAKERS
Popular Radio. Aug. 1925, pp. 128-120.
" A New Type of Hornless Loudspeaker," W . T. M eenam.
A brief description of the operating principles of a new
loud speaker, having several new features. A small
paper cone is used as a horn, the field winding of the coil
moving the voice-current coil is obtained from ad. c. source.
A diagram of the working principles is given.
R532. APPLICATION OF RADIO TO THE PRESS. PRESS.
RADIO BROADCAST. Sept. 1925, pp. 575-580.
" Is the Radio Newspaper Next?" James C. Young.
The effects of radio on newspaper work is felt not only
in the matter of disseminating news, but also is becoming
really a part of the press. In broadcasting happenings as
soon as they occur, following a regular schedule, newspapers
will likely change somewhat from their present practice of
flashing news in glaring headlines and settle down to a
practice similar to that of magazines. Some of the larger
papers have installed their own stations both for trans-
mission and reception of news, and the radio newspaper
will before long become another of the many innovations of
our present-day life.
R48o. RELAY SYSTEMS. PORTABLE
STATIONS.
Popular Radio. Aug. 1925, pp. 130-135.
"A Mobile Radio Relay Station." David Lay.
The 63-meter mobile radio relay station of the A. H.
Grebe Company, WGMU, is shown and described in detail.
Fig. 5 represents the circuit diagram of the transmitter.
Fig. 7 the microphone control. Photographs of the receiver
and transmitter give an idea how relay stations pick up
programs at remote points and relay them to the main
station for rebroadcasting. This outfit is mounted in an
automobile. It uses four5O-watt tubes as oscillators with a
motor generator of 1 500 volts furnishing the plate energy.
R38i. CONDENSERS. CONDENSERS.
Proceedings I. R. E. Aug. 1925, pp. 507-509.
"The Straight-line Frequency Variable Condenser,"
H.C.Forbes.
The equation for the shape of the rotary plates in a ro-
tary variable condenser is developed so that the frequency-
angular setting characteristic is a straight line. The equa-
tion for the capacity of this condenser at any angular
setting is also given.
R383.I. GRID LEAKS. GRID LEAKS.
Popular Radio. Aug. 1925 pp. 154-158.
"Important Trifles m Radio: The Grid Leak," R. F.
Yates.
Though very insignificant physically, the grid leak s a
very vital part in a receiver. Although of specific resistaii f
when new its value changes considerably with age. The
best kind of a grid leak would be a two-element vacuum
tube with battery and rheostat connected as in Fig. i
Several standard' types of variable leaks are good when
properly used.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
p
mni
Music MASTER SUPREME
— as in Reproduction, so in Reception
Played, Sung or Spoken before the Microphone
Music Master's Sensitive Mechanism Receives,
Endures with Power, Clarity and Volume.
)ETWEEN broadcasting station and Music
"Master Reproducer stands Music MASTER Re-
ceiver to bring in today's wonderful New Era super-
program with splendid fidelity of effect and natural-
ness of tone.
Music Master Radio Receivers incorporate every
demonstrated principle of standard radio reception
and reproduction.
Music Master Receivers furnish radio reception
equal in efficiency to the world-standard quality of
radio reproduction achieved in Music Master Re-
producer. Perfectly balanced radio reception and re-
production are thus available to discriminating radio
lovers.
Ask any authorized dealer to demonstrate for you
what clarity in reception may really be — what dis-
tance range is really available — what selectivity
really means.
See Music MASTER — hear — com-
pare— before you buy any radio set.
TYPE 60
Five Tubes. Special
Music Master design.
Full, round, natural
tone. Three selectors
for precise tuning.
Without equip-
ment
Ten Models — $50 to $460 — Unconditionally Guarantee^
TYPE 100 .-"'
FiveTubes, Resonant
reproduction. Excep-
tional range. Massive
mahogany console
cabinet. "B" battery
compartments in
cabinet. With-
out equip- $1 C\f\
ment ..... IvA/
Music Master Corporation
Makers and Distributors of High-Grade Radio Apparatus
Music Master Resonant Wood Insures Natural Tone Quality CHICAGO NEW YORK PHILADELPHIA PITTSBURGH MONTREAL
Canadian Factory: Kitchener, Ontario
PRODUCTS
E
Tested and approved by RADIO BROADCAST
96
RADIO BROADCAST ADVERTISER
"As efficient
as Radion Panels"
The best recommendation for
these Radion low- loss parts
NEW!
Practical types of low-
loss Radion sockets for the
new tubes and a collar
adapter, if you like, for
the old style bayonet type
tube.
No. 2 Socket for new
UX tubes with collar
adapter for old type tubes.
No. 3 same as No. 2 with-
out binding posts.
No. 4 Sockets for new
UX tubes. No. 5 same
as No. 4 without binding
posts.
RADION
^Jic Supreme Insulation
Made to order for radio
Purposes exclusively
THE very latest devel-
opments in radio are
embodied in the complete
line of Radion low-loss parts
—moulded of Radion, the
insulation made to order for
radio purposes exclusively.
Leading set manufacturers
and thousands of amateurs
know by experience that Radion
Panels are most effective in re-
ducing surface leakage and leak-
age noises. This means lowest
losses and greater efficiency,
especially noticeable in super-
sensitive circuits. All the Ra-
dion low-loss parts have the
same high -resistant character-
istics of Radion Panels.
You can now get Radion Sock-
ets, Dials, the new Radion Loud
Speaker Horn, Tubing, Binding
Posts, Strips, Insulators, etc.
Radion Panels in black and
Mahoganite come cut in stand-
ard sizes for whatever set you
wish to build.
Send for booklet, "Building
Your Own Set." Gives wiring
diagrams, front and rear views,
shows new set with slanting
panel, lists of parts and direc-
tions for building popular cir-
cuits. Mailed for 10 cents.
AMERICAN HARD RUBBER CO.
Dept. C-ll, 11 Mercer St., New York City
r
AMERICAN HARD RUBBER COMPANY
Dept Cll, 11 Mercer St., New York City
Please send me your booklet, "Building Your
Own Set," for which I enclose 10 cents in stamps.
Name _
Address .
Tested and approved by RADIO BROADCAST
R343- . ELECTRON TUBE RECEIVING SETS. RECEIVER.
Radio. Aug. 1925, pp. 35ff. 5-100 meters.
A 5 to 100 Meter Radio Receiver," D. B. McGown.
For high frequency telegraph reception the simple re-
generative feedback circuit gives very good results. The
construction and operation of such a receiver is delicate
and must be done properly. A series of coils are necessary
to cover the band of frequencies. The construction data
include number of turns, diameter and approximate wave
length covered by coils, and method of mounting.
R3I3 ELECTRON TUBE RECEIVING SETS. RECEIVER,
QST. Aug. 1925, pp. 11-14. , 5-200 meters.
Plug-m-Coil Receivers." John M. Clayton.
A short wave receiver covering the present amateur bands
within 15-200 meters must have rapidly interchangeable
coils to be of any value in good operation. Space wound
plug-in coils of various sizes serve the purpose well. The
views of circuit diagrams and receiver show the arrange-
ment of parts, and data for constructing the coils is given
General Radio coils of the plug-in type can be used also
The two receivers described make use of either the manu-
factured coils or the home made ones. Both receivers
are one-tube sets; amplifiers can be added.
R369. ELECTRON TUBE RECEIVING SETS. RECEIVER
QSr. Aug. 1925, pp. 16-19. DeForest D-lj.
• The DeForest D-17 Receiver," E. A. Livingstone.
This receiver is a five-tube refjex set covering a band
from 220 to 550 meters. The circuit diagram is shown
complete, also internal views of the finished receiver. The
data covering the set is very complete, even giving size of
condensers, transformer ratios and gauge of wire used in
them, and their characteristics, including those of the re-
maining parts of the instrument. Real information for the
owner of one of these receivers.
R342.I5 AMPLIFIER TRANSFORMER. TRANSFORMERS.
QST- Aug. 1925, pp. 24-25. yollage ratio.
Measurement of Voltage Ratio of Audio and R. F.
Transformers." R. R. Ramsey.
The article presents a mathematical discussion of audio
and radio frequency transformer-ratios and how to measure
them. The application of the method outlined is applied
to the neutrodyne circuit in the case of radio-frequency
transformers.
R355. HIGH-VOLTAGE GENERATORS. GENERATORS.
QST. Aug. 1925, pp. 26-27.
"The Bowdoin's Generators," E. \V. Berry.
A new type of generator built by the Electrical Specialty
Company has been designed for use on the ship Bowdoin.
This machine gives almost a perfect sine wave, excellent
commutation and has a greater capacity to size than
former types, due to material changes made infield construc-
tion and winding. It is also remarkably free from ripple
effects
R386. FILTERS. FILTER CIRCUIT.
QST. Aug. 1925, pp. 33-34.
"Smoothing Circuits for Half-Wave Rectification." F. S.
Dellenbaugh, jr.
In smoothing out rectified a. c. voltage for plate supply,
both capacity and inductance must be used in order to
obtain steady output. What effect mere inductance or
capacity will have, and how the combination is used to best
advantage, is simply explained in this discussion and illus-
trated with diagrams.
R240. RESISTANCE; DECREMENT;
PHASE DIFFERENCE; POWER Loss.
QST. Aug. 1925, pp. 37-38.
" Loss Comparisons," W. L. Seibert.
In the discussion, the author describes a convenient
method of comparing losses in variable air condensers and
other parts of radio frequency receiving circuits. By this
scheme, using a standard one-tube receiving circuit, "other
instruments may be compared, so that the best apparatus
can be selected for radio purposes. It is a very simple
method and can be applied in any experimenter's work-shop.
R8oo (535.3)- PHOTO-ELECTRIC PHENOMENA. SELENIUM
Radio Engineering. July, 1925, pp. 346-349.
"Selenium and Photo-Electric Cells," Samuel Wein.
Selenium was discovered about 100 years ago. It is
found in various minerals as listed in this discussion. How
it is extracted, the amount annually produced, the methods
used in purification, and its chemical and physical char-
acteristics are given in detail. Just as it was discovered by
accident, so also the fact that its light sensitivity is very
great was determined accidentally. A non-conductor of
electricity when not subjected to light, its conductivity is
materially great when light waves strike it, the difference
being from 15 to 20 per cent. A list of references to other
authors on the subject is appended.
R8oo (535.3). PHOTO-ELECTRIC PHENOMENA. SELENIUM
Radio Engineering. July, 1925, pp. 300-392.
"Selenium and Photo-Electric Cells." Samuel Wein.
In this second chapter on Selenium Cells, Mr. Wein dis-
cusses the essentials of their construction, and the various
forms of cells used to-day. The methods employed in
fixing the selenium to the conducting wires is simple
yet delicate. The seven diagrams show the various types
of cells which have been made and used in experimental
laboratories. A list of references to other articles on the
subject is appended.
R333. ELECTRON TUBES; THREE ELECTRODE.
TUBES,
Radio. Aug. 1925, pp. iTff. AC. receiving.
" Principles of Alternating Current Tubes," E. E. Turner.
A tube for receiving sets operating on alternating current
for both filament and plate supply, has been designed and
is destined to relieve the listener of the troublesome wet
cell batteries. The tube has been developed by the General
Electric Company and its operating features are illustrated
in the article. The A. C. hum has been practically elim-
inated by the use of filter-systems in the plate circuit.
The electron emission is obtai'ned through indirect heating
of an oxide coated cylinder. This tube is by no means
perfected, but represents a step in the right direction.
LOSSES IN
APPARATUS.
RADIO BROADCAST ADVERTISER
97
COILS
eme.'
REALIZE the best possible results from your circuit.
Do not be satisfied with less!
The utmost efficiency obtainable from your set is guar-
anteed in using Eastern Pickle Bottle Coils because
they represent the greatest advance in low loss coil design,
and are the most efficient coils it is possible to make.
In Eastern Pickle Bottle Coils dielectric losses are neg-
ligible. All wires are kept free of any collodion or other
injurious substance. They have less insulating material
in the field than any other type of coil, and are designed
with a view to mechanical and electrical perfection in
every detail.
Elimination of losses keeps the high frequency resistance
at the minimum, insuring increased selectivity, volume,
and natural tone quality.
EASTERN
KNOCKOUT COILS
(TYPE R)
are designed and guaranteed for perfect performance in
any Radio Broadcast Roberts Knockout Circuit (reflexed
or non-reflexed). Minimum of capacity between N. P.
winding and secondary; mid-tap on single-wound N. P.
coil — makes it easy to neutralize and tune, d* Q r* f\
and brings in the lower wave length sta- *P O • O \J
tions as never before. Price
per set
Endorsed by
Radio
Broadcast
EASTERN PICKLE BOTTLE COILS
ARE ALSO DESIGNED FOR THE
BROWNING-DRAKE Circuit
(Type B-D) Price $8.00 per set
DX SUPERDYNE (Type S) $8.00 per set
RX-1, the new revolutionary
M. B. Sleeper Circuit
(Type RX-1 coils) $6.00 per set
O'CONNOR FREQUENCY CHANGER
A one-tube outfit which converts
any set into a super-heterodyne
(Type F C Coupler) $6.00
TUNED R. F. Circuits
(Type A) For .0005 condensers;
(Type B) For .00035 condensers $2.00 per coil
THREE CIRCUIT SET (Eastern Low Loss Coupler)
Broadcast Wave (Type 3d 200-600 meter $6.00
Medium Wave (Type M3C) 60-240 meter $6.00
Low Wave (Type L3C) 19.7-81 meters $6.00
At your dealer's or direct, postpaid
EASTERN COIL CORPORATION
22 Warren Street Department R. B. New York
EESSgSg^fr^
•A- Tested and approved bv RADIO BROADCAST -A-
98
RADIO BROADCAST ADVERTISER
Striking Lines and
Vigorous Proportions
cNew and Improved
Complete
With Console
Vable
as Illustrated
FRANKLIN CONSOLE
is a dignified piece of furniture, built entirely
of carefully selected five-ply genuine mahogany
in a two-tone effect of soft and alluring beauty.
It Is Composed of Two Separate
and Distinct Units
[1] the actual receiving set with built-in
loud speaker.
[2] the console cabinet with compartments
for batteries, eliminator, charger and
oth:r accessories, not a single wire be-
ing visible.
Write for illustrated booklet (in seven colors')
describing our entire line of radio receivers.
For Sale by Authorized FRESHMAN DEALERS Only
Phas. Freshman fb.lnc.
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R8oo (537.65) PIEZOELECTRIC PHENOMENA. CRYSTALS,
Pie^o-electric.
Radio News. Aug. 1925, pp. i42ff.
"The Piezo-Electric Oscillograph," C. B. Bazzoni.
When current passes through a circuit certain effects are
observed, known primarily as thermo-electric, Seebeck,
Peltier, Thompson, Nerst, Hall, Leduc, and others which
are of interest. These effects are explained briefly. Elec-
tric currents may also be produced with the aid of crystals.
Two effects, the pyro-electric and piezo-electric, are of
special interest in the study of crystals, and are described.
Because of the piezo-electric effect, oscillographs may be
constructed with very little cost, which, when suitably
mounted, record frequencies up to 5000 cycles. The Ro-
chelle salt crystals can easily be made with the aid of the in-
formation given. Other uses for the oscillograph suggest
themselves after the apparatus has been constructed and
used.
R?8i. CONDENSERS. , CONDENSERS.
Radio News. Aug. 1925, pp. ]88ff.
"Straight-Line Frequency Condensers," Sylvan Harris.
A detailed discussion covering straight-line wave-
length, capacity, and frequency condensers and how they
are mathematically designed and constructed. The curves
show the comparison of the three types of condensers, dial-
setting vs. kilocycles. Since broadcasting stations are
separated according to kilocycles, this frequency should
form the basis for condenser construction. All stations
would then be equally separated on the dial. The article
is very complete, in illustrations as well as information.
R420. CONTINUOUS WAVE SYSTEMS. TRANSMITTERS
/ 00-200 m.
Proceedings I. R. E. Aug. 1925, pp. 413-436
" Recent Commercial Development in Short Wave-Trans-
mitters and Receivers," by S. E. Anderson, L. M. Clem-
ent, and G. C. DeCoutouIy.
This paper describes the transmitter and receiver recently
developed for use by the United States Coast Guard. This
apparatus is for operation on wavelengths between 100 and
200 meters. A short summary of the various circuit con-
siderations is included. The actual transmitter finally
developed is also described together with its operating char-
acteristics. In considering the radio receiver, the various
problems to be met in the design of a radio receiver of this
character are dealt with at some length. The frequency
characteristics of the radio receiver, as developed, are
shown, and the method of determining them is described
in detail. The transmitter and receiver performed very
satisfactorily under conditions considerably more severe
than will be met in actual service.
R376.3. LOUD-SPEAKING REPRODUCERS.
LOUD-SPEAKERS.
Proceedings I. R. E. Aug. 1925, pp. 437-460.
" Design of Telephone Receivers for Loud-Speaking Pur-
poses," C. R. Hanna.
A discussion of the advantages and disadvantages 'of
various present day electro-magnetic receivers is given in
a mathematical outline. A new type, called the balanced
diaphragm receiver, is described and the details of design
worked out. The experimental work includes resistance
and reactance curves and a verification of the theory
covering the design.
R387.1 . SHIELDS. SHIELDING.
Proceedings I. R. E. Aug. 1925, pp. 477-505.
"The Shielding of Electric and Magnetic Fields,"
J. H. Morecroft, A. Turner.
An experimental investigation of the shielding of electric
and magnetic fields is reported, for both constant and
changing fields.
The effect of using iron shells, or sheets, for shielding
against the fields of permanent magnets, as well as those set
up by electric currents, is considered; the best form for the
iron sheets is deduced and an expression for a measure of
the shielding action suggested.
The reason for the leakage of magnetic and electric
fields is shown to be due to differences of magnetic or elec-
tric potentials in the circuit in which the fluxes are being
set up; several cases are cited in which no external fields are
set up, as the circuits exhibit no differences in potential.
An expression for the shielding effect of a short-circuited
coil is deduced and experimental verification is offered for
frequencies between io^ and lo6 cycles per second.
Finally the shielding effect of metal sheets against chang-
ing magnetictfields is analyzed, and experimental results are
given to show how the action depends upon the character-
istics of the material of which the shielding plate is made,
its thickness, and upon the frequency used. The effect of
slits in the metal sheet, and the value of wire mesh, is in-
dicated.
R235. MUTUAL INDUCTANCE.
MUTUAL
INDUCTANCE.
Proceedings I. R. E. Aug. 1925, pp. 511-512.
"Calculation of the Mutual Inductance of Co-axial
Cylindrical Coils of Small Radial Depth." F. B. Vogdes.
This article shows how the mutual inductance of co-axial
cylindrical coils of small radial depth may readily be ob-
tained by the use of curves of a type recently described by
the United States Bureau of Standards. These curves cover
the mutual inductance between coaxial circles, and by a
very simple process of summation their usefulness can be
extended to coils of small radial depth.
R343. ELECTRON TUBE RECEIVERS. SUPER-HETERODYNE,
Radio. Aug. 1925, pp. i iff. Modified Best.
"The Modified Best Super-heterodyne," G. M. Best.
The Best Super-heterodyne has been redesigned by the
author to coyer wavelengths from 40 to s8o meters. In
this first article a shielded model using dry cell tubes is
described. Three controls are needed. The oscillator coil
can be removed and exchanged for one covering a different
band of frequencies. A complete description of con-
struction and operation is given, including diagrams and
panel layouts.
Ri42. COUPLED CIRCUITS. COUPLING.
Radio. Aug. 1925, pp. 30 ff.
"Coupling/ L. R. Felder.
How energy is transferred from one circuit to another is
discussed by the author in an elementary way. Resistance,
inductance and capacity coupling are taken up in turn
and explained with the aid of diagrams.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
99
Worth in I\aMo
that li/irf 10 0/jferj
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But combining as it does the ultimate in good per-
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the LOGODYNE Big Five expresses the perfection re-
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Send for the new edition of our free booklet "The
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THE KODEL
505 East Pearl Street
CORPORATION
Cincinnati, Ohio
LOGODYNE >'Big Five" Con-
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Console Model — beautiful brown
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Owners of Kodel Broadcasting Station WKRC
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*
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Two Tube "Gold Star" Model. . $20
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100
RADIO BROADCAST ADVERTISER
^Announcing
*
the ^ew Type 334
GENERAL RADIO
Straightline Wavelength Condenser
In certain instances of radio construction the shielding
effect of a metal end plate condenser is particularly desirable.
To meet the popular demand for this type of condenser
the new type 334 has been developed and is now available
at popular prices in all standard capacities both with and
without vernier.
In designing these condensers points that have been
stressed particularly are ruggedness, permanence of calibra-
tion, and uniformity between individual condensers of the
same capacity.
These are the factors so essential to the successful opera-
tion of modern radio sets.
Rotor and Stator units are similar to those used in the
well known type 247 condensers and good interplate
conductivity is assured through solder-sealed contacts.
All General Radio condensers are rigidly inspected be-
fore leaving the factory and are thoroughly guaranteed
electrically and mechanically.
Type
334-H
334-P
334-M
With Vernier
Capacity
.0005 MF.
.00035 MF.
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Price
#5.25
5.00
4.75
With Counterweight
Type Capacity Price
334-F .0005 MF. #4.25
334-N .00035 MF. 4.00
334-K .00025 MF. 3.75
As\ to see them at ydur local dealer's
or twite for our new Catalog 922-B.
GENERAL RADIO Co.
Cambridge, Mass.
R402. SHORT WAVE SYSTEMS. SHORT WAVE
Radio, Aug. 1925, pp. toff. STATIONS.
"Short Wave Work at Naval Research Laboratory,"
S. R. Winters.
Tests on 20 meters have shown that great distances can
be spanned with comparatively low power transmitters.
This fact has been established at the Naval Research
Laboratory under the supervision of Dr. A. H. Taylor.
With the transmitter, receiver and antenna as illustrated,
communication was carried on with stations in England
and Australia.
R2io. FREQUENCY; WAVELENGTH. KILOCYCLES.
Radio. Aug. 1925, pp. 24ff.
" Ideal Tuning in Kilocycles," E. E. Griffin.
The advantages of using kilocycles in preference to wave-
lengths are many. With a more general use of the term,
kilocycle, eventually all apparatus will be constructed on
this new basis. Using frequency designation simplifies
tuning and leads to clear understanding of the principles
involved. The author illustrates this point very clearly.
Since most receivers use a variable condenser in tuning, it
is of course desirable to employ a condenser of the straight
line frequency type, not straight line wavelength or straight
line capacity as shown.
Ri62. SELECTIVITY IN RECEIVERS. SELECTIVITY.
Radio. Aug. 1925. pp. 27ff.
"Selectivity Versus Distortion in a Super-heterodyne,"
J. E. Anderson.
A minute analysis of the part that the intermediate
filter plays in a super-heterodyne is given. What fre-
quency ratios are best in obtaining all-around good results
when tuning in on certain stations can best be determined
by using some definite intermediate frequency to which the
filter is tuned, and determining by illustration what beat
notes are set up. This the author brings put very clearly.
Since selectivity and distortion increase with a lowering in
frequency for the filter circuits, some value must be chosen
which gives the minimum for both. Curves showing the
distortion ratios illustrate the points discussed. By proper
selection of audio frequency transformers much of the dis-
tortion introduced through the filter circuit can be elimi-
nated.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVERS,
Radio. Aug. 1925, pp. 2off. Browning-Drake
" More Miles to the Dollar," V. G. Mathison.
Directions are given for the construction of a cheap and
selective three-tube Browning-Drake receiver, employing
several novel modifications in coil construction and ar-
rangement. Diagrams of winding and setting complete
the information.
The Winner of Our $500 Prize
Cover Contest
OUR new cover, which, as the reader will read-
ily see, is an entirely distinct departure from
anything else we have heretofore done in this
respect, and is the design of Mr. Fred J. Edgars
of Tenafly, New Jersey. Out of nearly a hun-
dred cover designs submitted, his was chosen by
the judges as being the most original and gener-
ally attractive.
Mr. Edgars was born in Dover, a seaport on
the southeast coast of England, and is descended
from a long line of ar-
tisans and shipbuild-
ers. Very early in life
he felt the urge to
paint, and in fact, sold
his first landscape
when only nine years
old. After this he
spent some time study-
ing at Kensington, in
London, and was able
there to develop fully
his desire to paint sub-
jects from nature and
other natural subjects.
Mr. Edgars is probably
more American than
MR. FRED J.
EDGARS
English now, for he has
been in this country
for more than forty years, since 1881. He spent a
number of years doing theatrical scenery paint-
ing and was very successful at this, but later
branched out into doing illustration work for
national advertisers. He has been employed in
this branch of creative work for some twenty
years now.
Throughout all his painting he strives to use
the colorful effects of natural subjects and is
largely inspired by the many flowers which
bloom in his garden, a view of which is obtained
through his studio window. His hobbies are
carpentry and farming.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
101
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Chipping
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Fifty-five years of rubber manufacturing
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Goodrich has built for radio —
Qoodrich V. T. Sockets Spaghetti Tubing
Qoodrich Variometers Unwound Battery Mats
Qoodrich Radiophone Ear Cushions
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102
RADIO BROADCAST ADVERTISER
Fifty Years for Stability
Discriminating people must have assurance of unquestioned
stability back of every piece of merchandise they pur-
chase.
This year, the fiftieth anniversary of the Holtzer-Cabot
Electric Company, is an opportune time to bring before the
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Rapid Engraving Machine
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Will tarn several dollars an hour engraving
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FROST-RADIO
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Tested and approved by RADIO BROADCAST -
Local Interference
Parti
How the Interference Originating
in Electrical Apparatus Reaches
Your Radio Receiver
R the past year, the Research Council oj
Canada, on behalf of the Department oj
Marine and Fisheries, has been conducting an in-
vestigation into the cause of and means of locating
and suppressing radio inductive interference.
This series of articles, of which this is the first, is
reprinted from an excellent little pamphlet,
published by the Radio Branch of the Depart-
ment of Marine and Fisheries of the Do-
minion of Canada Government. The book is
entitled "Radio Inductive Interference, Bulletin
Number i ." Many of the suggestions contained
in this series have not been offered in other quarters,
and we are sure that radio listeners who have been
cursed with artificial interference of one sort or
another will welcome the help this series offers.
— THE EDITOR.
HOW THE INTERFERENCE ORIGINATING IN ELEC-
TRICAL APPARATUS REACHES YOUR RADIO RE-
CEIVER
ALL electrical conductors carrying current
are surrounded by an electromagnetic
field. When the current in a conductor
changes, the electromagnetic field also changes
in a similar way and will induce a voltage in any
radio receiving antenna close to it.
There is also another field, called the electro-
static field, surrounding all electric conductors at
high voltage. A change in this electrostatic
field also induces a voltage in the antenna of any
radio receiver which is close to the power wires.
Under normal operating conditions on electric
power lines, this electromagnetic and eletrostatic
field which surrounds the conductors does not
extend more than a few yards from the power
line. In some cases, however, where the
change of current or the change of voltage is of a
very sudden nature, called an electrical surge, a
radio receiving antenna situated at a considerable
distance from the power line may be affected.
An electrical surge may travel many miles along
a power line, and produce a radiation which may
be picked up on radio receivers.
In cases where it is not practicable to get far
enough away from the power lines, the antenna
should be run as nearly as possible in a direction
at right angles to the power line, as the induction
from power lines is very much greater on antennas
which run parallel to them.
In no case should an antenna be erected above
a power wire in such a way that it would be possi-
ble for it to come in contact with the power wire
in case it should accidentally fall. Many acci-
dents have been caused in the past by antennas
accidentally coming in contact with power wires.
CHARACTERISTICS OF RADIO INDUCTIVE INTER-
FERENCE
PHE following characteristics of the radio
"• inductive interference from some sources
may provide useful clues in the investigation.
I. Battery chargers of the vibrator type cause
an electrical surge which may travel along the
supply wires of the secondary distribution sys-
tem and cause radio interference to all receivers
near these wires. This interference is very
staccato in character and consists of a regular
series of clicks corresponding to the frequency
RADIO BROADCAST ADVERTISER
103
The real solution
to the tuning problem!
MAKE your radio a 1926 model. Replace your present Dials
with Rathbun Straight Line Frequency Converters which spread
all stations within the range of your receiver uniformly around the
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Why be satisfied with Dials or Condensers which are limited to
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in the circle? No gears with their back lash, no friction with its
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The Rathbun Straight Line Fre-
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Don't forget that we build the Rathbun
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Rathbun
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Jamestown, New York
Stations indicated in kilocycles
and wave lengths showing crowd-
ing -with an ordinary capacity
condenser
Practically even separation over
half the dial with a Straight Line
Frequency Condenser
I
Stations partially separated and
tuning slightly improved -with a
Straight Line Wave Length Con-
denser
Complete and equal separation of
Stations over the entire dial with
the Rathbun Straight Line Fre-
quency Converter
Tested and approved by RADIO BROADCAST
104
RADIO BROADCAST ADVERTISER
JOT down the call
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c°
CLEVELAND. OHIO.
of the alternating current supplying the charger.
2. Commutator motors in some cases cause
radio interference due to sparking of the brushes,
and may often be recognized by the sound in
the radio receiver. The interference noise will
rise in pitch as the motor speeds up. In cases
of motors running at less than 300 revolutions
per minute it is sometimes possible to count the
speed of the motor by listening to the radio
receiver and observing the second hand of a
watch.
With practice an observer may learn to count
much higher speeds by listening to the run of the
sounds by fours and counting only the beginning
of each group of four. To acquire this ability
it is suggested that at first the hand be moved
down at the beginning of each group, and when
this can be done easily the motions of the hand
may be counted.
FAULTS OF HIGH VOLTAGE LINES
A FAULTY insulator on a transmission line
*• of 30,000 volts or more may sometimes
cause an electrical surge which travels along the
transmission line for many miles and causes
radio interference to receivers situated within a
few hundred yards of this line. This radio
interference may be induced into other lines
which run parallel to it and thus be distributed
over a wide area, possibly throughout the entire
city. This interference is usually continuous,
but may under some conditions be intermittent
and very erratic. The number of cases of such
interference, however, is very small, as faulty
insulators usually cause the shut down of the
transmission line for repair.
4. A transmission line which sparks to some
insulated conductor, such as an insulated guy
wire or an ungrounded conduit, may cause
radio interference of a similar nature to that
described as originating on a faulty insulator.
In this case, however, the interference may con-
tinue for weeks or months without causing any
power shut down, as the amount of current
flowing is only sufficient to charge the un-
grounded metal and not sufficient to indicate at
the power house. In case such a fault is caused
by a line swinging into contact with a guy wire,
it is usually noticed to be intermittent during
windy weather.
FAULTS IN TRANSFORMERS
| NTERFERENCE which is caused by defective
* insulation in conduit or in electrical apparatus,
is sometimes intermittent and comes on when the
apparatus is vibrated or subjected to strain by
expansion due to a change of temperature. For
example: A faulty bushing on the primary of the
transformer may cause radio interference by
sparking to the ungrounded frame of the trans-
former when the transformer is subjected to
vibration by the passing of a truck along the
road.
Transformers which produce an audible hum
do not necessarily cause radio interference, as
this hum is usually produced by the vibration of
the laminations of the core.
6. Charging of lightning arresters is heard in
the radio receiver as a very loud roar, but only
lasts for a few seconds. Sometimes this is re-
peated a number of times as a series of lightning
arresters are charged at one station. Most
power companies charge their arresters at times
outside the broadcasting period, such as noon
or 2:00 or 3:00 o'clock in the morning. The
interference from lightning arresters may be
heard for many miles from the source.
7. Cottrell Precipitators sometimes cause
radio interference which may be heard at a dis-
tance of 15 miles, but when proper means are
taken to reduce this interference at its source
they cannot be heard at a distance of more than
one mile.
•jr Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
105
Radio
Receiver
Radio evenings are complete
If you have a Valleytone
Appearance
The Valleytone is mounted in a solid walnut
cabinet, finished in two tones with inlaid
gold stripes. It may also be procured in
beautiful console models. Special Valley
tables with built-in loud speaker may be
obtained for the cabinet model.
Valleytone
Console
Model
Valley table
with built-in
loud speaker
You can always count on a full evening's entertainment if
you have a Valleytone Radio Receiving Set.
Music with your dinner ' » / bedtime stories for the children
» t * a play, an opera, or a concert » * * jazz, mammy songs,
spirituals * * * the whole range of radio broadcasting can be
yours.
With the Valleytone, you can choose your programs by the
clock and hear them all the evening through.
For the Valleytone is selective. It will separate and bring in
stations only four or five meters apart and will easily separate
local and distant stations.
Valleytone selectivity gives a new meaning and puts a new
pleasure in radio.
And with the balanced tone of the Valleytone when you
hear a station you marvel that any reproducing mechanism
can really achieve such faithfulness and such natural results.
The superiority of the Valleytone can be demonstrated.
The Valleytone thrives on comparison. Wherever it is judg-
ed by results and performance, it wins a new owner.
Any authorized dealer will be glad to demonstrate the
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VALLEY ELECTRIC COMPANY, Radio Division, ST. Louis, U.S.A.
Branches in Principal Cities
Vallevtone
Receiving Sets
Valley
Battery Chargers
Valley
B-Eliminators
Valley Electric
•A- Tested and approved by RADIO BROADCAST if
106
RADIO BROADCAST ADVERTISER
ANOTHER RAD I O TRIUMPH
AUDIO COUPLER
An Improved Resistance Coupler
Here is the result of months of experimentation in the Brach
Laboratories. Unusual features such as standardization and
interchangeability for all stages have been accomplished by the
use of a 1-micro-farad condenser and specially designed resistors
that are non microphonic and capable of withstanding high volt-
ages. To insure permanent uniformity all connections are either
soldered or held by screw pressure instead of the usual spring
contact.
These features have been at once recognized by Radio Engi-
neers of national repute who have replaced resistance couplers
with Brack Pur-A-Tone Audio Couplers in order to obtain maxi-
mum results.
BRACH -STAT
AUTOMATIC
Filament Control
The Ultimate Standard for Fine Receivers
Brach-Stats completely eliminate the need for hand rheostats, on all amplified circuits —
fewer controls — better operation.
The uniformity of control of the filament current obtained by the use of Brach-Stats has
far exceeded the greatest expectations of noted Radio Engineers.
All set constructors should provide for their use.
Brach Pur-A-Tone Audio Couplers and Brach-Stats are notable contributions
to the successful Roberts Circuit featured in this issue of Radio Broadcast.
L. S. BRACH MFG. CO., NEWARK, N. J.
Electrical Specialists for Over 20 Years
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FORMICA *
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RADIO BROADCAST
For December
will be a better magazine
than this. Make sure of it
by telling your newsdealer
to hold one for you — or
better still, subscribe through
him or direct.
RADIO BROADCAST
Garden City New York
Tested and approved by RADIO BROADCAST
PRELIMINARY TEST TO INVESTIGATE
RADIO INDUCTIVE INTERFERENCE
FIRST TEST:
To determine if the noise in the radio receiver is
due to a fault in your receiver or is actually inter-
ference coming in on the air.
Disconnect your antenna and ground wires and
if there is no reduction in the intensity of the
noise while the broadcast music is stopped by
the disconnection, the probability is that the
source of the noise is in your own receiving
set, in the form of a loose connection, faulty
batteries, or defective tube.
Also shake your ground wire near the ground
connection to make sure that the noise you hear
is not caused by a bad connection at this point.
SECOND TEST:
To determine whether the interference originates
in your own house lighting circuit.
From cases of interference investigated it has
been found that a great number of these are of a
purely local nature, originating in such sources
as a lamp loose in its socket, or a loose plug of a
heater, or from faulty household apparatus.
While the interference is apparent, have some-
body open your main house-lighting switch for a
few seconds while you listen in on the radio re-
ceiver. If the interference stops when the switch
is open, the source of the interference is probably
in your own circuit. This test should be repeated
several times, however, as there may have been a
misleading coincidence with something occurring
outside at the instant this switch was opened.
Many sources of interference do not start again
immediately the switch is closed, so that observa-
tions taken at the instant of opening the switch
are more reliable than those taken at the instant
of closing it.
THIRD TEST:
To determine the extent of the area affected by this
interference.
When you are assured that the interference
comes in on the air and does not originate in
your own set or in your own house lighting cir-
cuit, you should cooperate with others in
your district who have radio receivers. Great
care should be taken in making this test to avoid
the danger of confusing the interference which
originates from different sources, which may
appear similar in the radio receiver. The most
satisfactory way of making this test is for one
observer to listen to the interference received
on two radio receivers at different points at the
same time by means of the telephone system.
To carry out this test, an assistant at the distant
radio receiver should place his head-phones (or
preferably his loud speaker) near the transmitter
of the telephone in order that the observer at the
other radio receiver may listen at the same time
to the interference heard on his own receiver at
his right ear, while listening to the interference
heard at the distant radio receiver by means of
the telephone to his left ear. This test should be
continued for a sufficient length of time to ob-
serve a number of variations in the nature of the
interference.
In cases where it is not convenient to use the
telephone system for this test, the two observers
at distant radio receivers may keep an accurate
log of the interference, but in this case they
should first synchronize their watches and record
any characteristic change in the interference
heard, noting the time accurately to within a
few seconds.
FOURTH TEST:
To determine if any suspected source actually
causes radio interference.
In carrying out this test either of the two
RADIO BROADCAST ADVERTISER
107
KNOCK-OUT for the Knock-out!"— that's what a prominent
engineer said when he saw the CLAROTUNER in action. And the
moment you lay eyes on this latest creation, the moment you discover how
miraculously sharp is its tuning, you will be just as enthusiastic. You will
realize why Radio Broadcast experts recommend it, and use it in the
Radio Broadcast Knockout, Roberts, Phonograph Model and similiar
hook-ups.
Low-loss coils, sturdy compactness, and absolute one hole mounting are
only a few of the features. The biggest thing is the precision control —
as smooth as velvet. The antenna coupler, by the way, is one hole
mounting too, and eliminates all extra switch points and levers. Ask
your dealer!
CLAROTUNER, model 2RK (two units as shown). . . ,
(In case distribution has not reached your dealer, send
your remittance direct to the address given below.)
*
The famous
CLAROSTAT,
heart of the
CLAROTUNER.
$2.25
American Mechanical Laboratories, Inc., 285-287 North 6th St., Brooklyn, N. Y.
Tested and approved by RADIO BROADCAST
108
RADIO BROADCAST ADVERTISER
THE KODEL MICRO-
PHONE LOUD SPEAKER
is an exact replica of the
transmitting microphone
used in broadcasting.
The eff ecient Kodel reproducing
unit, with an ingenious new
snail-shell horn, mounted inside
the microphone case, produces
a remarkably clear, full-toned
volume. Non-vibrating tone
chamber eliminates distortion.
The $15 model incorporates the
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Radio Jtalrri tverywhtre hmt them
THE KODEL RADIO CORP.
SOS E. Pearl St., Cincinnati, O.
LOUD SPEAKER
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DOUBLED AY, PAGE 6? CO. wish to enlist earnest and reliable
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This is no ordinary subscription proposition. You can't afford to
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Write Agents' Service Division
DOUBLEDAY, PAGE & CO. Garden City, N. Y.
systems referred to in Test No. 3 is suitable.
Great accuracy is required in these tests, for it
has been found that many misleading reports
have been received from observers who were not
sufficiently accurate in their observations. For
instance, interference has been reported to be
associated with the switching on of the street
lights in cases where the interference actually
was produced by another circuit which was
switched on every evening about dusk. If the
observers in this case had noted the time very
accurately, the source of the interference could
have been located much more readily.
FIG. I
This circuit, in conjunction with a loop may be
satisfactorily employed to locate some sources of
interference
FIFTH TEST:
To determine where the interference radiates
front, by means of a portable radio receiver.
In cases where a portable radio receiver is
available the source of interference may be very
often traced by this means. In cases where the
radio interference is of such a weak nature that it
only interferes with the reception of distant
broadcast signals, a very sensitive loop receiver
is required to pick this up. A portable super-
heterodyne receiver complete with batteries
thoroughly shielded is best for this purpose. A
much less sensitive receiver may, however, be
used in connection with the loop which will be
suitable for determining the conductors from
which the interference radiates. In cases
where the interference is coming in along the
conductors of the electric light or power system,
a single circuit regenerative receiver having two
stages of audio frequency amplification is
sufficiently sensitive to give indication when the
loop of the receiver is placed within a few yards
of the conductor radiating the interference.
A detailed description of more elaborate
apparatus used by Canadian Government Radio
Inspectors and suitable for investigation in
power houses will be published in another
pamphlet now in course of preparation.
GENERAL NOTES
IN MAKING all these tests it is important to
approach the subject with an unprejudiced
mind as to the source of the interference, and
before concluding that the interference is caused
by any given source, it is well to consider all
possible conditions in which the interference may
have originated from some other unknown cause.
Investigating interference is a very fascinating
detective game and one would sometimes sup-
pose that the source of the interference had a
sense of humor and was trying to evade detection
in a manner similar to that of the most clever
criminal.
The obvious and only satisfactory method of
suppressing radio inductive interference that is
caused by electrical apparatus which is defec-
tive, is to put this apparatus in good condition.
The owners of such electrical apparatus are
usually very pleased to have their attention
drawn to the fact that their apparatus is in need
of repair.
if Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
109
Constant vigilance
is the price
u niFor m i tt|
and constant vigil-
ance is maintained
over Magnatrons.
That is why Magna-
trons are uniPorm.and
uniformly
The Magnatron DC-201A, DC-199, and
DC-199 (large base) now list for only
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Connewey Electric Laboratories
Magnatron Bldg. Hohokcn, N. J.
MACNATRONS
if Tested and approved by RADIO BROADCAST
110
RADIO BROADCAST ADVERTISER
^AMSCO
ALLOCATING
CONDENSER
(STRAIGHT LINE FREQUENCY)
. \ \ I 1 ,
\ •*. . * 1 1 1 1 1 1 1 1 / 1 1 .'. % ./
Spreads the Stations
Over the Dial — The new
AMSCO Allocating Condenser is the
triumphant combination of electrical
engineering and mechanical inge-
nuity. Electrically efficient in un-
scrambling the stations on your dials.
Each dial degree from 1 to 100 will
be found to represent 10 broadcast-
ing kilocycles accurately over the en-
tire scale — "a station for every degree".
Mechanically ingenious in correcting
the fault of other S. L. F. Conden-
sers— it conserves space I Scientific
low-loss construction. Rigidity with
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Made in three capacities — Single or Siamese.
Ask your dealer, or write for details of the
entire AMSCO Line of engineered radio parts.
AMSCO PRODUCTS, INC. Dept.E
Broome and Lafayette Streets,N.Y.C.
LJZ — a hand-
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Write: Agents' Service Division
DOUBLEDAY, PAGE 6? CO. Garden City, N. Y.
Tested and approved by RADIO BROADCAST
READERS WRITE
US
J . H . Dellinger Praises Our
Frequency-Wavelength Policy
A S WE stated in our August number, RADIO
** BROADCAST will no longer use the term
wavelength except in parentheses after its
equivalent in kilocycles. It is probable that every-
body ultimately will fall in with this idea, and
already condenser manufacturers are realizing
this is so, and are designing new instruments
giving a straight-line frequency reading. These
latter have specially shaped plates designed so
that any movement of the dial will give a reading
in degrees directionally proportional to the
frequency, all the way around the dial. We
recently had a letter from Dr. J. H. Dellinger,
the president of the Institute of Radio Engineers,
in which he commends us upon our step.
Editor, RADIO BROADCAST,
Doubleday, Page & Company
Garden City, New York.
SIR:
Ever since the Second National Radio Con-
ference, held in 1923, there has been an increasing
use of the concept of frequency and its expres-
sion in kilocycles in place of the use of wave-
lengths in meters. The realization has rapidly
spread that the use of wavelengths in radio is
unnecessary and that its original introduction
was a mistake. I have noted with pleasure the
statement of policy on page 499 of the August
RADIO BROADCAST, namely, that in future issues
of the magazine frequencies will be used as
standard, with wavelengths given thereafter in
parentheses. Not only was this policy stated
but succeeding issues of the magazine have
proved that the editorial staff intend to abide
by this announcement. With convenient con-
version tables freely available and with excellent
articles like that of Professor Morecroft's in
your August issue explaining the superiority of
frequencies in kilocycles, there is no longer any
reason why this change of practice should con-
fuse anyone. I congratulate you on assuming
a position of leadership in this change to a mo-
dern and rational basis of radio expression.
Very truly yours,
J. H. DELLINGER
President, Institute of Radio Engineers.
What a Foreign Reader Thinks of
"Radio Broadcast"
THE following congratulatory letter was
received recently from the Count de Warn,
who was a High Commissioner of the Inter-
national Amateur Congress of 1925 held in Paris.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
1 have just come across a copy of RADIO
BROADCAST. Allow me to congratulate you for
your very excellent magazine which I did not
know of before. Although I am a bit late, please
put me down for a five years subscription for
which I enclose my cheque. I intend to try a
super-heterodyne of American make and hope
that you will advise me on this question.
Yours faithfully,
COUNT DE WARN,
Alpes Maritimes, France.
The Causes of Fading
THE late discussions of the fading of radio
signals at the time of the total eclipse of
the sun have revived interest in the popular
RADIO BROADCAST ADVERTISER
111
-YJineJladto
FILTER CONDENSERS
.1 M.F.D.
Type 705
Price $ .70
1. M.F.D.
Type 708
Price 1.25
2. M.F.D.
Type 709
Price 1.75
4. M.F.D.
Type 711
Price 3.75
ADIO BROADCAST'S article in this issue on 'B'
battery eliminators shows that the following TOBE
condensers can be used in building the set: 5 type
708 and 7 type 709.
Any 'B' battery eliminator circuit depends very large-
ly for its operating efficiency upon the filter condensers
used. TOBE condensers alone possess all of the follow-
ing favorable characteristics:
Will operate at voltages up to 700 D. C. without break-
down or overheating.
High megohm resistance — indicating perfect insulation.
Capacities guaranteed to be within 5% of accuracy.
Extreme heat or cold has no effect on TOBE condensers.
Compact and handsome in appearance.
Tobe condensers are better condensers — distinguisha-
ble by their silvered finished case. Ask your dealer
for them by name "TOBE."
-
CORNHILL
BOSTON, MASS.
if Tested and approved by RADIO BROADCAST
112
RADIO BROADCAST ADVERTISER
$„ "betigMulty dear tone
*» -v with Amazing Volume
"Gets 200 to 600 meter
Stations coaft to coafl
/A great fa*
****tfflOJtt*
BUILT LIKi: LOOKS LIKK PKHFORMS LIKK A #'iOO SKT
NOTICEI Enormous demand for the celebrated Miraco Ultra-5 (resulting from its many enthusiastic u^ers so
highly recommending it to their friends) has enabled us to add hosts of costly new features, refinements and improvements
such as you might expect to find only on the newest sets selling
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RADIO
GETS'EM
COAST P>
COAST
Report* from
Ultra-5 iiffrx
everywhere
leave little for
UK to add. These
t/iiral of
PENNSYLVANIA HEARS CALIFOR-
NIA VERY LOUD
I received the Ultra-5 Set. set it up
as directions called for, and re eived
Dallas. TEXAS firsi station. Will list
a few of the stations reci-ived in two
hours: KDKA, WHArf. WOR.WOAW,
WOS, WTAM, WCAff, WLW. WOO.
WJY. WJS. kFI. KSI. WWJ, WHN,
WHX. It is very easy for me to receive
Los Angeles, California, loud enough
to be heard in any room in the house.
W. E.. . Uniontown. Penna.
CALIFORNIA GETS NEW YORK
ON LOUDSPEAKER
I have got stations f, om coattt to e«ast
without any trouble at all on the Ultra-
6. WTAM, Cleveland, Ohio, c> mua in
on loudspeaker nearly aa loud aa the
nearby stations do. I have brought in
on loudspeaker with ample volume to
hear all over the room stations WEAK,
N. Y.. KDKA, Pittsburg. Pa.. WGY.
N. Y., CHOX. Ottawa. WSAI. Cincin-
nati, WCCO, St. Pauf. Minn.. WLS,
Chicago. S. S Dorria, California.
NEW JERSEY HEARS CALIFORNIA
ON LOUDSPEAKER
MIRACO Ultra-5 working fine. Have
received Western coast. Had two
stations in California on same night.
Have had many other stations. Receive
all other stations with loudspeaker.
NivUon Van Freehold. N. J.
MONTANA HEARS BOTH COASTS
Ultra-5 Set is O. K. Have got New
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stations in two weeks. W. H
Poison, Montana.
RADIO EXPERT SPEAKS FROM
EXPERIENCE
As I sell almost all kinds of aets, I have
operated all of them and will state that
the Miraco Ultra-5 is as go >d if not
better than any other set in the market
todty, Felix J...., Paw tucket. Rhode
Island.
PREFERS IT TO $150 SETS
1 received your Miraco Ultra-5 Radio
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William I tyracuse. N. •'.
ILLINOIS HEARS ALASKA
Theni^ht I received the Ultia-5 I luned
in New York City. The second day I
tuned in KFI. Los Angolea. Calif., and
KK.J. ,'uneau, Alaska. Can get any-
thing in the United States. I will put it
Kainst any set I have ever heard.
U Aahkum, Illinois.
GOT CALIFORNIA BETTER THAN
Received the Miraco Ultra-5 the
other day and it is a big surprise
Compared it with my friends'
$263.00 and could bring them
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Ultra-5. Really 1 brought in Loa
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louder than he did. Am more than
I pleased. Kyle New Albany.
I
SEND FOR SPECIAL OFFER.'
e
[FIVE TUBE OUTFIT IN BEAUTIFUL,. MAHOGANYCttE]
Let the testimony of its many users
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Completely built, carefully tested and
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oscillations are easily controlled on all
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the "Counter-Balancer" (patented); flex-
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is the title of an article by Keith Henney, Director of the
Radio Broadcast Laboratories, to be printed in the December
Special attention is given to the new tubes by the
issue.
Radio Corporation of America. Much help will be given on
how to use the best tube for the best purpose.
Reserve a copy of December Radio Broadcast at your
news dealer or radio supply store.
mind about this peculiar and little-known peculi-
arity of radio transmission. It is probable that
scientific and popular interest in the fading of
signals is more acute now than it ever has been
before. The suggestions below were written
by an electrical engineer whose theories are
certainly interesting. Elsewhere in this issue
the probable causes of fading are ably discussed
but so interesting is the letter below that we
make no apology for covering the subject in two
separate departments.
Editor, RADIO BROADCAST,
Doubleday, Page & Company
Garden City, New York.
SIR:
It is generally recognized that air molecules
are ionized by the sun's rays and that the result-
ing charged air dissipates the energy of radio
waves, since it is a partial conductor of electric-
ity. Likewise an ionized layer of air, being a
conductor, will act in the same manner as a met-
al reflector, though in less degree, to reflect the
radio waves. As night approaches, the air be-
comes less and less conductive with consequent
increase of signal strength, but it is highly prob-
able that the air is always slightly ionized, even
in the absence of the sun's rays. This may be a
result of light from the stars and moon, or the air
may retain some of its charge for long periods
after the ionizing rays of the sun have been re-
moved. Even if the lower layers of air between
two stations are completely neutral, electrically,
there is the possibility that the upper layers are
acted upon by sunlight, especially if the stations
are in an east-west line. It has been stated by
observers that the worst fading occurs in such a
direction.
Now as to the real causes of fading, there are
possibly three, which may be: (i) at the sending
station, (2) at the receiving station, and (3) be-
tween the two stations. It is possible that there
may be a cyclic variation in the electrical state or
condition of either the sending or receiving ap-
paratus (tubes), but this is rather doubtful. Of
course an antenna system swayed by the wind will
become detuned, and there is an additional
probable cause, in that layers of air of varying
density may pass under the antenna and thus
alter its capacity. If either of these two factors
just mentioned were the contributing cause, it
would be possible to tune the station in again by
adjusting the controls. However, in all too
many cases no amount of tuning will bring in
the station. We must wait a few minutes until
the signal increases in strength of its own accord.
Generally this is a gradual increase.
The facts seem to indicate that fading is due to
variable conditions existing between the sending
and the receiving station. We know that there
are always layers of air of different densities,
temperatures, and humidities, and if we grant
that these layers are always slightly ionized,
which is likely, we have at once a plausible
explanation for fading. For suppose that a
station is receiving with good audibility at any
one moment, and suppose, then, that an ex-
tended layer of ionized air drifts between the
sending and receiving station. The signal
waves will then be both reflected and absorbed
by the conducting "sheet" of air, and there-
fore the signal strength at the receiving station
will be materially reduced until the ionized body
of air has drifted past the path between the
two stations. There are, of course, many mov-
ing layers of air between two stations widely
separated, and consequently it would be ex-
pected that fading would be worse for such
stations.
The varying ionization of the layers of air
would result from the varying factors such as
temperature, density and humidity, when the
air is exposed to the same ionizing source such
as sunlight. A further cause of ionization is the
friction of the various air streams.
There is still another possible cause of fading
in that the numerous ether waves may interfere
to cause partial neutralization, but the air
layer explanation seems more plausible.
Yours very truly,
A. G. THOMAS,
Lynchburg, Virginia.
RADIO BROADCAST ADVERTISER
153
f?Ri^JNc7
u
XXX
Siss.?*?*'
_1L ,,irrfaTf I
cfhe New Improved
5 AMPnAL 6- B
GO
Over 500,000 already in use
Charges in OneJhirdthelime!
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New micrometer adjustment,
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Beautiful cabinet in maroon
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Write for new edition of
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radio operation "The
Secret of Distance and
Volume in Radio."
It takes only one-third as long to fully charge
your battery with the New Improved 5 -ampere,
GOLD SEAL HOMCHARGER.
No more of the long, bothersome waits that were neces-
sary when the slow inefficient 2-ampere charger was
the best that radio offered. The New Improved GOLD
SEAL HOMCHARGER charges 150% faster— fully
charges the average battery overnight — and it charges
both A and B batteries without additional equip-
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Before you buy any charger be sure it charges at
5-amperes. To be absolutely sure insist on the GOLD
SEAL HOMCHARGER.
The Kodel Radio Corporation
505 East Pearl Street Cincinnati, Ohio
Owners of Kodel Broadcasting Station WKRC
on the Alms Hotel. Send for program.
Tested and approved by RADIO BROADCAST if
RADIO BROADCAST
ARTHUR H. LYNCH, Editor
WILLIS K. WING, Associate Editor
JOHN B. BRENNAN, Technical Editor
DECEMBER, 1925
Vol. VIII, No. 2
Cover Design - From a Painting by Fred J. Edgars
Radio Enters the Club - Frontispiece
How Radio Grew Up Robert H. Marriott
Tubes: Their Uses and Abuses - - Keith Henney
The March of Radio - - - - J- H- Morecro/t
A Five'Tube Receiver of Dual Efficiency
Glenn H. Browning
The Listeners' Point of View Kingsley Welles
Short Waves — A New Paradise for the DX Fan
Edgar H. Felix
Plans for the Third of the International Radio Broad'
cast Tests *•*.**•• Arthur H. Lynch
An Improved Plate Current Supply Unit
Roland F. Beers
As the Broadcaster Sees It - - - - Carl Dreher
The "Aristocrat" Receiver: Resistance'Coupled
Amplification '»*»..*•' -
How to Use Meters in Your Receiver James Millen
New Fields For the Home Constructor
Keith Henney
"Now, I Have Found"
Tracing Radio Noises
A Ratchet Coil Winder
A Coupling Device for the Roberts Circuit
A File for Ideas
Super-He'erodyne Noises
Checkii t* up on B-Battery Leakage
A Vark meter for the Roberts Set
How to Eliminate Local Interference - -
A List of Australian Broadcasting Stations
The Grid — Questions and Answers - -
Coil Placement in an R. F. Amplifier
Precautions in Antenna Erection
Measuring the Resistance of Coil Units
Matching Tubes and R. F. Coils
A Key to Recent Radio Articles E. G. Shalkhauser
159
163 *
167
172
177
182
185
186
191
196
198
201
206
Is Your Set a Blooper? - - -
What Our Readers Write Us
212
224
226
232
238
244
BEHIND THE EDITORIAL
SCENES
THE new and enlarged RADIO BROADCAST has met with almost
universal favor and its reception was even more hearty than
the publishers had dared hope. In New York City alone, the
supply of the November number was exhausted four days after
it was placed on sale. Copies of the number are so rare that we
haven't more than three copies in the editorial offices for our own
use. Letters from readers all over the country have been most
generous in praising the appearance and contents of the November
number.
ROBERT H. MARRIOTT, whose article, "How Radio
Grew Up" leads this issue, is one of the old men of wireless
in the United States. He was the first president of the Insti-
tute of Radio Engineers, was one of the first radio inspectors to be
appointed after the radio law of 1912 was passed. For a long
time he was expert radio aide at the Bremerton Navy Yard,
Washington, and is now a consulting radio engineer in New
York. . . . Edgar Felix, who writes about short waves in
this number, was for several years publicity representative of
station WEAF in New York. Glenn H. Browning, who with his
inseparable technical partner, Mr. F. H. Drake, has become
nationally known for the Browning-Drake receiver, describes a
great improvement over the early model in this number. Both
Mr. Browning and Mr. Drake are familiar figures around the
famous Cruft laboratory at Harvard University, where much of
their work has been done. The valuable current periodical
surveys, made by E. G. Shalkhauser, the first of which appeared
in our November issue, are continued in this number. Many
readers have written us saying that these condensed surveys of
the important articles appearing in this magazine and in our
contemporaries are of great value to them.
THE January RADIO BROADCAST will contain an article by
Arthur H. Lynch telling how to build "RADIO BROADCAST'S
Universal Receiver." The set he describes is an unusual and
very efficient combination of standard parts and it is doubtful
if there is any receiver its superior in point of sensitivity and
quality. It is not a "freak" outfit in any sense. Kendall
Clough of Chicago will have an article about the principles of
audio amplification which is of particular interest. The author
weighs and casts aside some of the commonly accepted theories
of amplification. We believe the article will attract a great deal
of attention. Mr. John Wallace of Evanston, Illinois, will from
now on write the "Listeners' Point of View." With his
central location, Mr. Wallace is able to hear broadcast offerings
in almost every part of the United States and Canada. Our new
broadcast critic is an unusually versatile person, for he is a writer
of great charm and not a little wit. as well as an artist of consider-
able ability. In his college days, his drawings and humorous
"pieces" appeared in the Cornell Widow.
rT"(HE advertising pages of the magazines of the "Quality
JL Group," that is, the Atlantic Monthly, Harpers, Review of
Reviews, Scribners, and the World's Worf; now contain only the
announcements of those radio manufacturers whose products
have been tested and approved by the Laboratory of RADIO
BROADCAST. Readers of those magazines who are not well versed
in matters radio have the privilege of calling on the technical
staff of this magazine for help and advice.
Doubltday, Page fir Co.
MAGAZINES
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'54
RADIO BROADCAST ADVERTISER
157
//
**»> V.VG
.
oa
in <Madio
Emphatically Yes!
Radio IS marching forward, this season as before.
But it is marching in a new direction.
Quality of Reception.
That is the big, new theme. And the new Jewett
Receiver is its inspiration.
At last Radio commands a Receiver that is truly a
Musical Instrument, by a manufacturer of experience
in the musical instrument field.
Mere words cannot describe this new Jewett Quality
of Reception. You must hear and understand.
So just visit an authorized Jewett Dealer and let him
prove to you that here is a new kind of Radio — so
.different from the old as to create new standards and
ideals.
For the first time, B-Battery current and resulting dis-
tortion have been completely barred from the speaker
circuit.
You should know the story of this epoch-mark-
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straight-thinking young engineers who refused
to admit that it couldn't be done. Ask us for it.
"There Is No Substitute For The Best"
JEWETT RADIO & PHONOGRAPH CO.
5672 TELEGRAPH ROAD PONTIAC, MICHIGAN
Factories: Allegan, Michigan— Pontiac, Michigan
In Canada: Jewett Radio-Phonographs, Ltd., Walkerville, Ontario
Export Sales Offices: 116 Broad Street, New York City
Special Wednesday
WJR feature— The
Burroughs Hour, 9
to 10 p. m.
The Jewett Receiver
— Three simple controls provide dis-
tortionless reception and eliminate all
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The Jewett Superspeaker
— All that the name implies. Recom»
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The Jewett Superspeaker
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— A handsome cabinet with Super-
speaker performance.
The Jewett Cone
— Faithful in tone and pitch regardless
of heat, cold, or dampness. Semi-ad-
justable.
The Jewett Vemco Unit
—Makes a loud speaker out of your
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The Jewett Parkay Cabinet
— Puts the amateur on a par with the
most exclusive cabinet worker.
The Jewett Micro-Dial
—Makes tuning 50 times as accurate.
Fits any standard receiver.
The Jewett Superspeaker
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"Quality Broadcasting to
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—Station WJR"
©1925 Jewett Radio & Phonograph Co
Tested and approved by RADIO BROADCAST
RADIO ENTERS THE CLUB
The installation at the Cornel! Club in 'Nfw Tor); City. The Western Electric super-heterodyne tfith peanut tubes is shown in
the top view at the left. A four-tube amplifier below intensifies the energy which is supplied to the loud speakers on the panelled
uialls of the various rooms. Employees of the Club are shown listening to the first test of the equipment. A public address
system is also installed. Microphones picf( up the speeches mhich are carried to all parts of the club through the loud speakers
RADIO BROADCAST
VOLUME VIII
NUMBER 2
DECEMBER, 1925
Grew Up
Many Little Known Facts About Radio Development are Related — Here Is the
First of a Series of Articles on This Subject Written by a Pioneer in Wireless
By ROBERT H. MARRIOTT
EPEATEDLY during the last one
hundred years, radio has been
referred to as new, which has
had the result of making people
come to the conclusion that it must be new.
This is, of course, very confusing, and is
due no doubt to the fact that certain in-
ventions and inventors have been overrated
while others have been forgotten. Human
love of fairy tales makes it easy for a
man or a corporation with money to
refer to a certain individual as the
great one who has done all of the*
wonderful things that have been
done. Money getters, too, take ad-
vantage of that love of fairy stories
to fill their pockets.
Haywire, halos, and haymakers
have characterized many of the early
careers in radio. Inventors and
would-be inventors built haywire
apparatus. Promoters built press
agent halos around the alleged in-
ventors and their haywire products.
Some of the hay went to develop
radio and a lot of it went to whoever
received the stock jobber's money.
Sometimes promotors became so ex-
travagant in the claims about an
invention that the inventor himself
would be found to disclaim some of
the things that he was purported to
have done, and to give the credit to
others. Such a procedure was, of
course, just what the promoters
wanted, and they immediately got
their press agents and after-dinner
speakers on the job, in order that
they might tell how modest and gen-
erous the inventor was, and thereby
stud his halo with the pearls of
modesty and generosity.
Homage is due to many rather
than to a few. Many radio develop-
First President Institute of Radio Engineers
ers have received little compensation for
their work in the past and they are not in
a position to collect now. The public
owes a debt to many people which it cannot
A PORTABLE SET, IQOI MODEL
Mr. Marriott operating a portable transmitting set. Note
the ground plate on the floor. With an outfit about the same
size as this, using vacuum tubes as the radio generating device,
signals are being sent by amateurs using code, for tremendous
distances. The Laboratory of RADIO BROADCAST recently
communicated with the U. S. S. Seattle as she was leaving
Tahiti in the Pacific ocean. A five-watt tube was used as a
transmitter for this remarkable communication
pay. Some of those people need the money,
others do not; some are dead while those
still alive do not expect to realize anything
on their past labors.
The changes in radio development may
often be traced to unexpected causes.
For example, the United States Prohibition
Act seems to have played a somewhat
important role in the recent stimulation
of radio broadcasting. Volstead's
unintentional creation of laborious
home brewing and the attendant
substitution of inconvenient boot-
leggers for bar tenders, has appar-
ently been an important step in the
development of radio, because it
suddenly has shut off from the public
a very convenient means of spending
their money. Now these baffled
people are looking for other outlets.
Broadcast receiving has supplied
that demand, and its problems pres-
ent a new field in which alcohol-free
brains may engage.
Not only is radio history valuable
as a thing of interest, as educational,
and as a precedent for use in plan-
ning the future, but it is valuable in
other ways. I was recently examined
and cross-examined for three days
about historical radio devices, for
evidence in a radio suit. I believe
the suit was for several millions of
dollars. At any rate the amount was
so interesting that two lawyers and
an expert traveled across the United
States and back to get my testimony.
The lawyers' questions and my
answers in that testimony took up
more words than 1 am using in this
whole series of articles. The testi-
mony was relative to only a few
historical devices which had their
origin from 1899 on, while I am striv-
160
RADIO BROADCAST
DECEMBER, 1925
U.S.
RADIO
DEVELOPMENT
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HOW WIRELESS DEVELOPED
One of a number of charts presented by Mr. Marriott in a paper published in the
Proceedings of the Institute of Radio Engineers for June, 1917, showing graphically
the rise and decline of the various radio factors. For example, the electrolytic
detector, No. 3 in the charts, came into use about 1902, was the leading detector
about 1905 and then gave way to crystal detectors, No. 4
ing in these articles to outline the more
interesting points in the development of
radio since about 1790.
Starting on our outline of radio history
then, we find that Galvani got a "radio
kick" out of frogs' legs even before 1790;
De Salva wrote a recipe for a "wireless"
in 1795; Morse built a "wireless" which
worked across narrow bodies of water
in 1842; Maxwell wrote a theory for radio
in 1867; Loomis patented a "wireless" in
1872; Hughes made and used a radio in
about 1879, but he only let a few friends
in on it; Professor Dolbear patented one
in 1886; Hertz made a tuned radio system
according to Maxwell's recipe in 1886, and
that development led
others in our radio of to-
day.
MARCONI EXPLOITS RADIO
RADIO had been thus
brewing since the
1 8th century. By 1895 it
was ready for exploitation,
by which I mean that it
was ready for sales engi-
neers, exploiters, promot-
ers, advertisers, and
others. Marconi demon-
strated the more or less
academic radio instru-
A VERTICAL ANTENNA
About the year 1900, vertical antennas were quite popular for
land stations, but as wireless became more general and the in-
stallations more elaborate, the flat top horizontal type was
almost universal. It is interesting to note that now, for short
wave transmissions, amateurs and others are returning to the
vertical antenna
ments to some politicians, army men, and money getters
at this time. He played the part of a demonstrator and
sales engineer. A money getting company was then formed
AT ANNAPOLIS
How the wireless towers looked when the picture was taken
on October 25, 1902. On this day, some history was made,
for, using this equipment, the Navy made its first record of
about 50 miles by wireless from this equipment to a ship.
Fifty miles, with the equipment known then was an extraor-
dinary distance
DECEMBER, 1925
HOW RADIO GREW UP
161
which, in attempting to obtain a monopoly, set out to ad-
vertise to everybody that Marconi was the inventor and
that they owned that patent on wireless which entitled
them to a monopoly in America and other places. That
was not, of course, true, but he did advertise wireless and
to him is due the credit for having started the development
of radio in many different parts of the world.
By 1900 radio had edged itself into the market as a
mild public service. It continued as a tonic and stimulant
for business, for military purposes, and for life saving.
To obtain plenty of radio equipment for recent war pur-
poses greater quantities of money and effort were sud-
denly put forth. In 1921 a radio by-product called broad-
casting began to take on. Now it is a principal product,
a product that sold for about $3 50,000,000.00 last year.
That is a very brief outline of some of the more important
events in the history of radio.
Luigi Galvani was an Italian anatomist and he got the
kicks from frogs' legs when he put them near an electric
spark. Nowadays we would call his spark maker a radio
transmitter while the detached frogs' legs acted as the
radio detector. Therefore he must be credited with having
made a genuine radio experiment one hundred and thirty-
five years ago. The distance between the spark gap and
legs must have been only a few inches or, at most, a few
feet, and at that time the whys and wherefores probably
were not realized.
On December 16, 1795, De Salva, a Spanish physicist,
read a paper before the Academy of Sciences at Barcelona
in which he said: "One could, for example, arrange at
Mallorca an area of earth charged with electricity, and at
Alicante a similar space charged with opposite electricity,
with a wire going to, and dipping into, the sea. On lead-
INTER.IOR OF THE OLD ANNAPOLIS STATION
ing another wire from the
sea shore to the electrified
spot at Mallorca, the com-
munication between the two
charged surfaces would be
complete, for the electric
fluid would traverse the sea,
which is an excellent con-
ductor, and indicate by the
spark the desired signal."
If Salva's scheme had
worked as he said, it would
have been wireless, but not radio. He
specified for the flow of a direct current
from one station to the other, rather than
waves composed of combined magnetic
fields and condenser fields such as are
radiated from one radio station to another.
However he had the idea of establishing
wireless communication. Therefore the
idea of wireless communication by elec-
trical means must be at least one hundred
and thirty years old.
In 1831, Faraday demonstrated electro-
A GALLERY OF TRANSMITTING APPARATUS
In use between 1899 ar>d '9' 5 set up in the Brooklyn Navy Yard. Mr. Marriott, at the left in the photograph, was the expert witness in a case tried
before a United States judge in 1915. In the foreground, to the right, is a ten-inch induction coil, with separate vibrator. This was connected
directly to the antenna and was popular until about 1906. Various kinds of glass jar transmitting condensers can be seen. The inductances, of
large wire, are "oscillation transformers" and coupled the oscillating circuit, consisting of spark gap and condenser, inductively to the secondary
circuit which had taps leading to antenna and ground. This is a most unusual historical photograph
162
RADIO BROADCAST
DECEMBER, 1925
magnetic induction. He showed that
making current start and stop in one cir-
cuit would cause currents to flow in a cir-
cuit parallel to it, although there be no
connecting wires between the two circuits.
That was a kind of wireless, but it is not
classed as the kind of wireless we call
radio.
Professor Samuel F. B. Morse, of the
United States, telegraphed across narrow
bodies of water in 1842, by installing a
ground return transmitter circuit along
one bank and a ground return receiver cir-
cuit along the other, without any wires
between the sender and receiver. His,
again, was not radio communication but
it was wireless communication. He not
only had the idea of communicating
without using wires between the trans-
mitter and receiver, but he did actually
telegraph with success that way. The
currents between the points at which
he connected his transmitter are sup-
posed to have wandered across the stream
and through the wire that connected the
two points of ground or water contact of
his receiver. That was a kind of wireless
that worked, and it worked more than
eighty years ago.
The electromagnetic theory, which is
our present accepted theory of radio
wave propagation, is said to have origin-
ated with William Clerk Maxwell, a noted
Scotch physicist in about 1867, and it was
published shortly after that time.
LOOMIS UTILIZES STATIC FOR SENDING
JULY 3Oth, 1872, patent number 129,971,
was issued to Mahlon Loomis, dentist,
of Washington, District of Columbia.
The following is quoted from the patent.
What I claim as my invention or discovery,
and desire to secure by Letters Patent, is —
The utilization of natural electricity from
elevated points by connecting the opposite
polarity of the celestial and terrestrial bodies
of electricity at different points by suitable
conductors, and, for telegraphic purposes,
relying upon the disturbance produced in the
two electro-opposite bodies (of the earth and
atmosphere) by an interruption of the continuity
of one of the conductors from the electrical
body being indicated upon its opposite or corres-
ponding terminus, and thus producing a circuit
or communication between the two without
an artificial battery or further use of wires
or cable to connect the cooperating stations.
Stating the Loomis claim briefly and in
present day language; if you put up an
antenna where it will get atmospheric
charges, and interrupt the flow of current
from the antenna to ground, you can
send messages. If the atmospheric vol-
tage is high enough so that the sparks
from antenna to ground will jump a gap
of one inch, it would be possible to send
messages more than a hundred miles
to a present day receiver. However,
the atmospheric voltage is not reliable
for telegraphing, because conditions vary
widely in different locations and at different
times. Unless you use a sensitive galvan-
ometer you might be unable to detect any
voltage on your antenna, the day you read
this. On the other hand, it is not a safe
thing to try, carelessly, because you might
get too much voltage, especially just before
a rain storm.
That arrangement as described by
Loomis, has worked for me many times
in years past and in fact I am experimenting
with such a device at present. I am using
the system to find out things about the
unidentified noises that interfere with
radio receiving, and about fading and
static. The one I am working with now
is interrupted by a little copper water
wheel. When the voltage is low the
current only discharges from the antenna
through the longest paddle of the wheel.
When the voltage is high it jumps to all
four. Some of us can hear it click at our
receiving stations and get an idea of what
is happening in the atmosphere.
An observer might record the area
and movement of high
voltage atmosphere by
setting up numerous
Loomis antennas, with
clock operated spark
gaps having differently
timed interruptions, in a
large circle around him and his receiving
apparatus. Weather scientists may find
this suggestion useful.
From observations made with this kind
of an arrangement, it seems that some of
the interference one hears on a broadcast
receiver is probably due to the atmosphere
charging insulated conductors to such a
high voltage that the charge jumps over
to earth in one spark which produces
a click, or many sparks, that produce
grinding, buzzing, or sizzling noises. The
conductor in question might be a guy wire,
fence wire, power wire, or something else.
If electric power follows those pilot sparks
to earth, you may hear an alternating
current or commutator hum. Falling rain
may contribute both voltage and moisture,
causing a power circuit to leak over in-
sulators.
I am not an inveterate story reader, but
so far as I know, fiction writers have
overlooked the possibilities of the Loomis
antenna. All their hero or heroine needs
for wireless salvation are the right weather
conditions, an elevated conductor and the
radio code. The villain might even grab
the conductor and get a static knock-out.
Loomis was away ahead of his time. His
patent was not only for communicating
without wires, but for taking the electricity
to do it with from the atmosphere. He
apparently did not reason according to the
radio theory, but the idea he patented
certainly works that way. He wanted to
make static send messages. He probably
imagined wonderful possibilities "via
static," but I daresay he didn't go so far as
to imagine then that the new baby
across the street was destined to
make money from automobiles; move
(he might even fly) to Southern'
California to a place called Los
Angeles and there buy a winter home
for a fabulous sum,
retire and spend his
time playing Mah
Jongg or working
cross word puzzles,
and maybe even
drinking home brew
while listening to
Washington jazz
delivered without
"wires," in 1925.
HIGH POWERED EQUIPMENT — IN 1903
The ten-inch induction coil which was standard during the early years of wireless as the trans-
mitter. Nothing was simpler than the circuit used. About twenty volts was supplied to the
primary of the coil and some eighty or a hundred thousand volts were produced between the
electrodes the operator is adjusting. Ships and shore stations alike used the coils and sharp
tuning was unknown. Those were the days when no one knew exactly what wavelength he was
using and didn't care. The few wavemeters in existence were objects of curiosity in almost
inaccessible laboratories
FIG. I
A collection of modern tubes, nearly all of which are designed for the second audio stage where so much distortion due to overloading now occurs.
The power tubes illustrated in this photograph are Western Electric 2i6-A, ux-i 12, ux-2io, ux-iao, uv-2O2, Cleartron, and Heliotron. The small
"peanut" tube is the Western Electric "N" tube, and in the photograph are two tubes designed for resistance-coupled amplifiers, the Daven "MU-2O"
and the High Constron. Daven also makes a power tube known as the Daven "MU-6."
Tubes: Their Uses and Abuses
How to Use the Standard and the Latest Tubes to Attain High
Quality in the Radio Receiver — Some Little Known But Easily
Applied Facts of Increasing Importance About Audio Amplification
By KEITH HENNEY • "• < ;
Director, "Radio Broadcast" Laboratory
E development of the vacuum tube
has placed in the hands of engineers and
scientists — and radio listeners — one of
the most versatile and useful devices
that has resulted from man's ingenuity. The
applications of the vacuum tube device are so
diverse and so important that it is indeed the
modern "Aladdin's lamp."
Vacuum tubes in the early days were not what
they are to-day. Any one who remembers trying
to hook up two of the old "tubular" tubes into
a two-stage amplifier knows that. Amplifiers
in those days were practically unknown. Tubes
did nothing but oscillate, and quite often not
much of that. All receiving was done by
"beats." that is with the tube oscil-
lating and the circuit tuned so that
a slight difference of frequency ex-
isted between the incoming signals
and those generated in the tube it-
self. Operators read the signals by
these difference notes.
Tubes were not pumped (as
highly evacuated) as hard as they
are to-day. No two were alike.
Some had grids on the outside of
the glass bulb. Often amateurs
used a complicated system of per-
manent magnets placed about the
tube so that the electrons
would be drawn from the filament
at a faster pace. All in all, mod-
ern radio listeners have a lot to
be thankful for.
Tubes to-day are fairly uniform.
If you buy a 5-volt tube you know that its char-
acteristics will be such and such within fairly nar-
row limits. This means that you can interchange
tubes with out "spilling the beans." Some manu-
facturers of tubes take particular precautions to
have their tubes all alike and in RADIO BROAD-
CAST Laboratory, a consignment of tubes from
one manufacturer have been tested that were all
alike — all twelve of them — and they were not
specially picked, either.
Tubes in radio communication serve several
special purposes, but to the listener there
are two services which are of paramount im-
portance, detection and amplification. And like
all delicate apparatus, there are certain con-
SINCE the basic patents on the vacuum lube expired some months ago, there
las been feverish activity among many manufacturers, and many new names
have appeared on the market. The result is that a goodly number of experi-
menters are a bit at sea.; tubes with capabilities quite beyond any of tbe previous
well known types are available and many fans are groping for real information
about them. Tbe far sighted manufacturers who brought out the new tubes, the
power type in especial, deserve much praise, for they have added infinitely to the
acoustical refinement of radio. This article, we believe, contains some sug-
gestions which will be highly valued by those experimenters who follow them. It
is a plea, in short, for our audio amplifiers to be properly planned. By far the
greatest number of radio experimenters use every tube they have in the con-
ventional way: go volts on the plate and the rated filament voltage. Tbe author,
who by tbe way, knows a great deal about high quality in audio circuits, shows
how the amplifier can be correctly planned — which appears almost to be a new
idea. — THE EDITOR
ditions under which they must be operated to get
best results. It is the purpose of this article
to deal with those best operating conditions and
to attempt to point out a few noteworthy ideas
in the design of radio receiving equipment that
utilizes vacuum tubes as the central piece of
apparatus.
HOW THE TUBE OPERATES
TT IS not necessary for the reader to know
*• much of the theory of vacuum tube operation.
It is sufficient if he knows that within the glass
tube there are three metallic elements, a filament
which lights up when you turn on the A battery,
a grid which acts as a controlling valve for the
plate current which flows from the
^_^^ia^ third element, the plate, around
through the B battery and back
to the filament.
The filament emits electrons,
according to the language of the
physicist, but in ordinary terms,
these building stones of all matter
are actually boiled off the metallic
filament when it is heated to a
certain temperature.
These electrons are negatively
charged and move toward the
positively charged plate with a
certain velocity depending on
various controlable factors.
The grid is situated between the
filament and the plate and is made
of a mesh arrangement so that the
electrons can go between its meshes
164
RADIO BROADCAST
DECEMBER, 1925
on their way toward the plate. If the grid is
negative it repels electrons and less plate current
flows; if it is positive, it draws more electrons
from the filament out into the space of the tube
and the plate current increases. In this way
the grid is essentially a controlling element.
DETECTOR THEORY AND PRACTICE
*~pHE theory of detection is complicated and
^ will not be described here. It is only neces-
sary to say that 41 volts on the plate of the de-
tector is about the correct value with modern
highly pumped tubes; that the grid return should
be connected to the positive side of the filament;
that for grid condenser-leak detection, the proper
values seem to be about .00025 mfd. capacity and
two megohms, although other values may be
used; that there is little use in using a C battery
detector unless very powerful signals are to be
I
r
Speaker
FIG. 2
Signals from an antenna go through several
electrical devices before they finally emerge
from a loud speaker. This illustration shows
the path of these signals. At the input and
output of each amplifier the voltages and
power levels differ, increasing as the signal
approaches the loud speaker
received, say in the second super-heterodyne de-
tector.
Often a detector that will not work on 45 or
even 225 volts B battery will work very well
indeed on 12 or thereabouts. If regeneration
is not smooth, that i«, if advancing the tickler,
or the condenser in capacity feedback sys-
tems, is accompanied with growls and low fre-
quency clicking noises, the trouble lies in too
much tickler, wrong grid leaks, or too much B
battery. The tube should slide into operation
without fuss, and if it does not, something is
wrong. With low loss receivers, not much tickler
is needed. The higher the resistance of the coil
into which regeneration is being introduced, the
more tickler will have to be used and the more
erratic will be the operation.
There is one point that may be mentioned
here. It is a common statement that there is no
necessity for low loss circuits in regenerative
receivers since the addition of regeneration re-
duces the resistance of the circuit. Regeneration
does reduce the effective resistance, making
tuning sharper, and receiving more selective.
If the receiver suddenly begins to oscillate after
the regeneration has been set say when a crash
of static comes along, or some loud signal, the
Hill-
operator can look for a high
resistance circuit in which the
tuning is broad until much
regeneration is added. Then
it is time to read up on low
loss circuits.
The use of low resistance
grid leaks, say one half
megohm, will improve the
quality of music received but
on the other hand, low valued
grid leaks will cause some loss
in volume — which maybe
made up in the audio amplifier.
Various methods of obtain-
ing regeneration in a detector
circuit have been described
(see RADIO BROADCAST for
October) and all produce the same results. In-
creased signal strength, increased selectivity,
and, if it is pushed too far, decreased quality.
AMPLIFIERS: RADIO AND AUDIO
""THERE is little that one can do to a detector
^ tube or detector circuit beyond what has
been mentioned above. When it comes to
amplifiers, however, there is much to be said,
and many false notions to be discussed.
There are two kinds of amplifiers in the usual
radio receiver, those which are working at very
high frequencies, and those which work at low
audible frequencies, and there is a league and a
half of distance between them.
In the first place there are two things to con-
sider, voltage, and power amplification. These
are two different things, and until quite recently
little attention has been paid to the difference
between them. Now that we have semi-power
tubes appearing on the market from several tube
manufacturers, we shall be able to plan our
amplifiers with a little more engineering and a
little less guess work.
Fig. 2 is a diagrammatic method of showing a
receiver with its component parts. We shall
begin at the loud speaker and work up toward the
antenna circuit.
The speaker requires power — and there is a
certain amount of power that is required by
every good one to give a good, well-behaved
sound. For example, the Western Electric
2i6-A tube, which until recently was the only
semi-power tube available, has an output of .06
watts under the proper operating conditions, and
if this is placed upon a good speaker, plenty of
volume will result. Such volume will not be
sufficient for a large auditorium, it will not be
heard a mile or so up the street, nor will it drive
any one out of the house — but who nowadays
wants such volume?
Let us say, then, that a good signal requires .06
watts and since this figure represents power, the
last tube in the receiver should supply power.
Now there is an expression, due to Van Der Bijl,
which amplifier designers seem
to have overlooked, that says
that the power output of any
tube will be as follows.
(mu X input voltage)2
FIG. 5
Transformers are used to "match" impedances. In the case
shown here, for maximum transfer of power from tube to load,
the turns ratio of the transformer must be
/Zp
VzL
FIG. 3
A two-stage audio amplifier and the voltages that must appear
at various points along the circuit if the full output of the last
tube is to be delivered to the loud speaker. If lower voltages
are delivered the volume will be "down." If more than nine
volts peak are applied to the grid of the last tube, overloading
will occur and a cone type loud speaker will, in popular par-
lance sound, "awful"
power =
8 X plate impedance
Now, using this formula, let
us figure out the maximum
power obtainable from several
tubes under the usual operat-
ing conditions, namely, 90 volts
B battery, minus 4.5 volts C
battery, and assuming that the
input voltage peak is just equal
to the C battery voltage. In
other words we are working
the tube up to the limit of distortionless am-
plification.
Under these conditions the following table
gives the power obtainable,
3-VOLT TUBE
.0066
5-VOLT TUBE UX 1 12
.0135 .0184
Thus it is seen that none of the tubes ordinarily
used will give sufficient output to operate a loud
speaker at the desired level of .06 watts.
The following table gives the powers obtain-
able from tubes under conditions of greater
input and plate voltages.
J-VOLT UX-I 12 2I6-A
.0135
B-VOLTS
90
90
'35
'57-5
4-5
6.0
9
10.5
.058
.0328
.118
.185
.059
From this table it may be seen that sufficient
power is not obtainable for satisfactory reception
with a 5-volt tube until 135 volts are used on the
plate and until 9 volts are placed upon the input
to the last tube. Under the same conditions, the
newer j-volt, one-half ampere filament tubes,
such as the ux-H2, and similar tubes foi the
same purpose, will deliver nearly twice as much
power as is actually needed, and with 157.5 volts
on the plate and 10.5 volts C bias will have an
output that is still more favorable.
These figures mean that it will not be neces-
sary to crank up a receiver to the top notch to
hear the average level of an orchestra; and to
endure distortion, or to turn down the set when
a player bangs down on his kettle drums un-
expectedly, or when the orchestra rises to a
maximum output level.
In other words, a receiver properly operated
with one of these semi-power tubes in the last
— HI
FIG. 4
The last tube in a receiver must deliver power
to the load which is usually a loud speaker. If
the impedances of the tube, Zp. and the load, ZL
are alike, maximum power will be delivered
stage may always be somewhere short of the
overloading point, and the range in volume, with-
out the distortion due to overloading, will be
much greater. For practically the first time in
radio broadcasting reception it is possible to
avoid overloading distortion without going to the
bother of installing power tubes and high voltage
DECEMBER, 1925
TUBES: THEIR USES AND ABUSES
165
TABLE I
TUBE
USE
PLATE VOLTS
GRID VOLTS
PLATE RES.
POWER OUTPUT
WATTS
WD-II
( Amplifier
1 Detector
90
4-5
14OOO
.0057
UV-I99
( Amplifier
1 Detector
90
4-5
IJOOO
.0066
UV-2O1-A
UX-I 12
( Amplifier
< Detector
( Amplifier
90
'35
90
4-5
9.0
6.0
12OOO
I1OOO
8800
.0135
.058
•033
112.5
7-5
8400
.054
'35
9.0
5500
.118
'57-5
10.5
4800
.185
UX-I20
Amplifier
'35
22.5
66OO
. 101
2l6-A
Amplifier
'35
9
6OOO
.059
UX-2IO
Amplifier
90
4-5
9700
.015
'35
9
8000
.07I
'57-5
10.5
7400
.105
250
18
5600
•41
350
27
5IOO
1. 08
425
35
5000
1.84
Daven MU-6
( Amplifier
I2O
7-5
6lOO
.0625
Cleartron
t Amplifier
I2O
7-5
6260
.O3I2
Goldentone
Amplifier
120
7-5
557°
.058
B batteries. Tube builders who have had the
initiative to bring out these new tubes deserve a
large vote of thanks from the part of the radio
public that really enjoys high quality.
In Fig. 3 is the conventional two-stage audio
amplifier with the voltages marked as they
appear at various points, considering that 9 volts
at least are to be used as a C bias on the last tube,
and that transformers of 3 to I ratio are used,
and that the amplification factor, " Mu", of each
tube is 8. It is seen that .125 volts must appear
across the primary of the first audio frequency
transformer, this must be the output voltage of
the detector.
At the present time, nearly everybody has his
receiver too near the point where the C battery
voltage on the last amplifier is exceeded by strong
signals. On a cone speaker this is signalized by
a peculiar rasping, scraping, or rattling, and the
user of the speaker believes the fault lies there
when the trouble really exists in his amplifier.
No loud speaker can be operated at sufficient
volume from a 3-volt tube without overloading.
This fact cannot be avoided.
One method of avoiding the semi-power tube
problem is to use two s-volt tubes in parallel
in the last audio amplifier, that is, with their
grids and plates connected together. From the
above formula, the resultant output power with
negative 4.5 volts on the grid and 90 volts on the
plate is .027 watts and with 135 volts B battery
and 9 volts C battery, the result is .117 watts.
In other words, a single ux-i 12 will equal two 5-
volt tubes in parallel.
All of these figures assume that the detector is
turning out .125 volts — and if it does not, of
course the C volts assumed above will not be
available, and the power output will drop.
IMPEDANCE CONSIDERATIONS
are other considerations in the audio
amplifier end of a receiver that are im-
portant. One is the impedances of the loud
speakers used with respect to the plate im-
pedances of the tubes used. The layman need
not know what these terms mean, but it is not
difficult for him to see their importance. Fig. 4
represents a tube working into a load of some
sort, say a loud speaker. Now it is an axiom
among electrical power workers that any device
will put the maximum power into a load when
the impedances of the two are alike. When
these impedances differ, the power dropsA
Now, the impedance of a tube varies with the
B battery applied, dropping as the battery volt-
age increases. The impedance of a loud speaker
is under control of the designer, he can make it
have, at a given frequency, practically any
desired impedance. Therefore, let him design
it so that the impedance of the
speaker and that of the tube are
alike, or as an engineer would say,
let them "match" the impedances.
This sounds easy but it is not.
The difficulty lies in the fact
that the impedance of the loud
speaker differs with each fre-
quency, so that the designer
must pick out some particular frequency and
match his impedances there.
Suppose that a manufacturer desires to place
on the market a very high grade loud speaking
device. He makes a number of experimental
models and finally finds one that seems to be
worth producing. He measures its impedance
at various frequencies, finding that at low fre-
quencies it has a low impedance and at high
frequencies it becomes very high in impedance.
Then he selects a number of people to listen
to the device, people who know music and who
have a feeling for tone value. He starts at the
low frequencies, matches his speaker to the tube
impedance at say 200 cycles by means of trans-
formers, as in Fig. 5. Then he matches the
impedances at higher frequencies, and asks his
audience to say which of the many impedance
matches seems the best.
Perhaps they decide upon a certain impedance,
knowing that the answer must be a com-
promise, for if the device is matched at 100
cycles the tube will transmit to the speaker a
maximum of power at too cycles but very little
at 10,000 cycles, and vice versa.
For example, the nominal impedance of the
54O-AW Western Electric speaker happens to be
in the neighborhood of 4000 ohms, and for the
best transfer of power from tube to cone, the
output impedance of the tube should be about
4000 ohms. Thus the ux-i 12 tube with 157.5
volts on the plate has an impedance of 4800
ohms, a good impedance match, while a uv-199
tube with 90 volts on the plate has an impedance
of 15,000 ohms, a terrible match — all of the low
frequencies would be lost no matter how good
the transformers are.
From the standpoint of quality then, tubes
should be worked below the overloading point,
that is below the place where the available C
battery voltages are exceeded, the loud speaker
should have the same nominal impedance as
the power tube, and the output tube should have
sufficient power output to actuate the speaker
FIG. 6
As shown in the table of tube characteristics in this article, one ux-i 12 will have approximately the same output as two uv-2Oi-A tubes in parallel.
In receiving sets such as the Freed-Eisemann illustrated here power tubes may be used in place of the two parallel tubes ordinarily used1-
166
RADIO BROADCAST
DECEMBER, 1925
FIG. 7
Curves showing the relation between grid volts and plate current of three
power tubes. These curves were made at a plate voltage of 120, and
show that a C bias of about 73 could be used on the Daven Mu-6 and
the 2i6-A while for the Cleartron, and the u\-U2, a bias of about
6 would be required at 120 volts of B battery
without forcing. Goodness knows what the
impedance of loud speakers now on the market
may be. There is no standard, for there has
been no standard in tubes. Many people try
to work cone type speakers on j-volt tubes, and
it cannot successfully be done without some dis-
tortion. Manufacturers of speakers should set
upon some value of nominal impedance, say
5000 ohms and stick to it. Otherwise some care-
ful designer should bring out an output trans-
former which will connect a high impedance loud
speaker with a low impedance tube, and a low
impedance speaker with a high impedance tube.
At the present time, the best combination
for a transformer-coupled amplifier seems
to be a standard 3- or j-volt tube for the
first audio amplifier, and a semi-power tube
in the last amplifier. Since the amplification
of 5-volt tubes is considerably above that of
dry cell tubes, those who wish the best in quality
and volume should use the larger tubes. As a
final tube, the v\-\\2, the 2i6-A, the Daven
MU-6, the Cleartron semi-power tube, the
Heliotron power tube — all are excellent choices
for that last audio stage. And of course for good
quality, good transformers must be used.
TRANSFORMER RATIOS
""THERE are several strange ideas prevalent
^ regarding the ratios of transformers. There
is no reason why good transformers must be
low ratio affairs. In fact one of the best trans-
formers on the market has a comparatively high
ratio and for several years before the present
broadcasting era, the telephone industry had a
high ratio transformer with an essentially flat
characteristic.
The difficulty is expense, and until people will
pay for high ratio, [high quality transformers
they will have to be content with low ratio
high quality ones.
With regard to the overloading of tubes, there
is no difference whether a high ratio transformer
comes before a low ratio instrument or not. It
is overall amplification that causes overloading,
and it is seldom indeed that the first audio
amplifier overloads.
From the standpoint of
quality, however, the
prevailing system of
having high ratio trans-
formers first and low
ratios second is wrong.
High ratio transformers
will probably have a
lower primary imped-
ance than will low ratio
instruments. A detec-
tor has a high plate
impedance while an am-
plifying tube has a much
lower impedance. If
these impedances are to
be matched at all, the
higher impedance trans-
former (low ratio) should
come next to the de-
tector.
RADIO-FREQUENCY AM-
PLIFIERS
IT IS probable that the
' standard practice of
using 90 volts B bat-
tery and negative 4.5
volts C battery is about
correct for radio fre-
quency amplifiers. It
is true that somewhat
greater amplification
will result from the use
of higher plate voltages, but at the same time it
is more difficult to control such an amplifier.
As a matter of fact, a five-tube set, with two
stages of radio-frequency amplification which are
working properly will have all the voltage
amplification that can be handled. If a potentio-
meter controlled amplifier is used, and many of
the tuned "r. f." sets use this means of stabiliz-
ing, a large B battery current will be drawn when
the potentiometer is swung to the positive side.
There is no remedy for this, since such sets cannot
under existing patent arrangements use C
batteries and cannot be neutralized.
RESISTANCE-COUPLED AMPLIFIERS
A S LONG as radio constructors were limited
•• to the usual 3- and 5-volt tubes, resistance-
and impedance-coupled amplifiers were not to
be advised. Due to the high resistances used as
coupling devices, the voltage actually on the
plates of tubes is very low, and no amplifier tube
will work satisfactorily unless a certain voltage is
maintained on the plate. This meant that at least
double the ordinary B voltages must be used.
High "Mu" tubes, however, are a distinct
boon to resistance- and impedance-coupled ampli-
fiers. Curves taken by Mr. G. H. Browning
are illustrative of the effect of using these new
tubes and may be seen in his article on the
Browning-Drake receiver in this number of
RADIO BROADCAST.
Owing to the very high plate impedance of
these tubes, they will not act as power amplifiers
at all, and in the third stage of a resistance- or
impedance-coupled audio amplifier a semi-power
tube should be used. To get the same amplifi-
cation— and the same power into a speaker —
from such an amplifier as is obtainable from a
good two-stage transformer-coupled amplifier, at
least three stages must be used, the last of which
should be a semi-power tube as indicated before.
Unless large capacities are used as the coupling
units, at least o. i-mfd., the low frequencies will
be dropped out and the user is no better off than
if he had used transformers.
Two "high Mu" tubes have come to the
Laboratory of RADIO BROADCAST which may be
recommended. These are made by Daven and
by Cleartron. The former are known as "MU-
20" tubes and the latter as the "High Constron."
Both have an amplification constant of 20, have
proven to be very uniform, and have a plate
impedance at 90 volts B of about 30,000 ohms.
Daven tubes are designed to operate on 6 volts
without the use of rheostats. Since storage
batteries retain their voltage output until nearly
discharged, the full 6 volts is obtainable.
These high impedance tubes cannot be used
with profit, in a radio frequency stage of presen
receivers. Their field is in the usage discussec
above, and Mr. Browning's curves show con
clusively that they are of great value in thi
connection.
OTHER POWER TUBES
'IP HE ux-i2o, a dry cell tube to be used to feec
into loud speakers, has an amplification
factor of 3.3, a plate impedance of 6600 ohms
and should be used with a plate voltage of 135
and a negative C bias of 225 volts. The powe
output under these conditions should be .1 wat
which is sufficient for high quality high volum
operation, but owing to the curved characteristic
of this tube it is doubtful of this power output
may be approached. This will be an excellent
tube for use in super-heterodynes which at
present use the ordinary 3-volt tube which has
not the output required.
The ux-2io tube is essentially a power tube
and should be operated from a source of alter-
nating current by means of a step down trans-
former, as was described in November RADIO
BROADCAST by James Millen. Only where
considerable power is desired should this tube
be necessary. In the Laboratory it has proved
to be an excellent transmitting tube, and more
than 30 watts have been applied to it without
difficulty.
At the present time, the proper arrangement
of tubes in a five-tube set seems to be as follows,
3- or j-volt tubes for everything but the last
where a ux-i2o, a ux-ii2, Daven Mu-6, Clear-
tron 112, Heliotron power tube, WE 2i6-A, Sea-
gull type t, or Goldentone, should be used.
If more power is desired, two tubes may be
used in parallel, two may be used in a push-
pull arrangement, or the ux-2io type may be
used.
In a future article the new Radio Coporation
ballast and rectifying tubes will be described.
The data given in the table in this article must
not be misunderstood. It gives the maximum
undistorted power in watts that certain tubes
will deliver under certain conditions, those con-
ditions having to do with the plate voltage used
and the variation in grid volts being applied to
the tube. If these grid volts are not applied,
less power will be delivered.
For instance, there is an idea prevalent, since
the appearance of semi-power tubes, that the
substitution of such tubes for standard 3- or
5-volt tubes will result in a marvelous increase
in volume. Such is not the case although some
increase will be noted due to the lower output
impedance of these tubes over these in standard
use. Under the same operating conditions, a
standard tube and a semi-power tube will de-
liver about the same power. The great advan-
tage of the newer type of tube is that it will
handle more power, that is, a greater input volt-
age and corresponding greater output, than the
3- or 5-volt type. In other words, the substitu-
tion of a 112 type or 210 type tube will enable
the user to use greater voltage amplification up
to the last stage and by the proper use of C, and
B batteries, distortion due to overloading will
be less likely to result.
OF RADIO
?
Past President, Institute of Radio Engineers
What Is the Matter With the Naval Radio Service?
o
NLY a short time ago radio had
one of the best opportunities
in its history to prove its worth
to the mariner in distress — and
failed. It is not in a spirit of
cynical criticism that we bring up this in-
cident but rather with the purpose of in-
quiring whether something cannot be done
to prevent similar occurrences in the
future.
The whole country was enthusiastic
several months ago over the idea of our
naval aviators hopping from California
to Hawaii. Three of the planes were to
go, but due to mishaps only one made a
serious attempt at the long flight. This
trip had been planned very carefully and it
seemed as if nothing could happen to pre-
vent the goal being reached. Destroyers
were used to mark the course and were
ready to render assistance should the
planes come to grief; every two hundred
miles along the two-thousand mile course
a destroyer or a supply ship was stationed
to give the planes the proper direction and
to record their progress.
The radio equipment of these planes
was supposed to be of the very best. With
a sending radius assumed to be in the
hundreds of miles, and reliability of opera-
tion never before attained (as the descrip-
tion of the radio outfits specified), it was
confidently assumed that the operators of
these seaplanes couldn't help knowing ex-
actly where they were, and could keep in
constant communication with the marking
vessels. The radio signals were to be used
for compass bearings as is the case every
day with hundreds of ocean-going ships,
and altogether the planes were considered
as safe as though they were close to their
own home port.
One of the planes had mishaps and had
to give up the trip after covering a short
distance, another never even started. The
third flying boat however, PN-g No. i,
in charge of Commander Rodgers, got well
away and picked up the first of the mark-
ing ships almost on schedule. The wind
was not quite as favorable as had been
hoped, so that the speed was considerably
less than that reckoned on. Thus the
gasoline supply was not quite sufficient
to cover the two thousand miles and Com-
mander Rodgers decided to come down
near the Aroostook, two hundred miles
from the end of his trip, to renew his gaso-
line supply.
And now, probably the only time during
his trip that the radio channel was really
needed, it failed. The radio compass
bearings should have enabled the PN-g
No. i to proceed at once to her supply ship,
but the plane missed her completely. The
compass bearings indicating that the PN-g
No. i was south of the Aroostook, her
commander flew north until his gasoline
supply gave out and he had to drop to
the ocean. The plane's position was then
calculated by her commander as fifty
miles north of the Aroostook.
Having thus failed in its important work
of keeping the plane on her course, the
Naval radio now scored an even worse
failure. With no gasoline to run her en-
gines, the only thing the Commander of
PN-c) No. i could logically do was to call
for help and supplies. It is exactly in
emergencies of this kind that radio is sup-
posed to be the mariner's most useful
agency, but this failure was nothing short
of dismal. Only fifty miles from the wait-
ing patrol ship, the PN-g No. i was for
some inexplicable reason helpless as far
as radio communication was concerned.
And to add, to its ignominious failure,
radio served to agonize the souls of the
crew by letting them hear all of the radio
messages with which the air was filled.
Gradually, their receiving set told them,
the searchers were giving up hope of finding
them; each succeeding day their would-be
rescuers were becoming more discouraged
and evidently soon would give up the
search. And all this time their rescuers
were only a couple of hundred miles away !
168
RADIO BROADCAST
DECEMBER, 1925
There is no good reason why a
single circuit regenerating receiver
could not have been used as a trans-
mitter for the short distance to be
covered, if no other means were at hand.
But why wasn't there a transmitter which
would work if the plane was forced down?
According to the plane's commander, a per-
fect landing on the ocean was made and
nothing happened to interfere with the
radio apparatus performing as it was in-
tended to do. Why didn't it perform?
Was there no emergency apparatus able to
operate if the plane was forced down?
RADIO PICTURES OF THE CALIFORNIA-
HONOLULU AIR FLIGHT
Sent from Honolulu to New York on Sunday, September
13, by the Ranger photoradiogram system. The dis-
tance is 5116 miles. Left: Commander John Rodgers
of the PN-Q No. i as he looked when he landed at
Liuhui, Kauai Island, after his rescue from the disabled
plane shown in the view above. The ship was adrift
for nine days, owing tofailureof radio compass bearings
when the ship was only about 200 miles from her goal.
When she landed on the sea, there was no emergency
transmitter to signal the rescue vessels. The operator
of the plane was forced to hear all the conversations
relating to the rescue work
Favorable weather and fortunate winds
enabled these trans-air travellers finally to
reach land after nine days of hazardous
drifting in their tiny craft. And with that
loyalty to the service which the Navy
officer feels to be his first duty, Commander
Rodgers stated that "there was no failure
of material at any time in the air or the
water."
We are not under the restraint that
Commander Rodgers is, and we can say
frankly that there was a failure, one of the
worst that radio has scored. Some ex-
planation should be forthcoming from those
responsible in the Naval Radio Service
for this blot on their reputation.
It transpired in the hearing which fol-
lowed the disaster several years ago, when
six Naval destroyers were wrecked off Point
Arguello, that the compass bearings given
to the leading destroyer by the Naval
radio station were incorrect. The radio
weather intelligence furnished the Sloenan-
doab on her recent disastrous trip was
incomplete or entirely lacking — to which
one might lay a large share of the blame
for the failure of her navigating officers
to avoid the storm which destroyed the
ship. Listeners who have heard the way
in which sos traffic has been handled re-
cently around the New York territory
have observed that the Naval stations have
handled that traffic in a singularly inexpert
fashion. Taken all in all, there are un-
mistakable signs that there is something
radically wrong with the Naval Radio
Service. Who is to blame?
National Association of Broad-
casters
A THOUGH the average broadcast
listener probably knows nothing
about it, their purveyors of enter-
tainment have been organized for some
time. The National Association of Broad-
THE NEW MARCONI DIRECTIONAL BEAM STATION AT DORCHESTER
About 120 miles from London. This is a new and exclusive photograph published for the first time in the United States. The picture shows five of the
masts which are 277 feet high, and 750 feet apart. The masts are at right angles to the direction in which communication is to be established. The
cross arm at the top is 90 feet across. The antenna wires, which are not yet in place, will be attached to triatics at one end of the cross arm and the
reflector wires to the other. The distance between the antenna wires, reflector wires, and the number and distance apart of the separate wires making
the antenna and reflector will depend on the transmitting frequency used. The installation shown is expected to communicate with New York. Others
•ow in process of construction and test will connect England with Australia and the Dominions. On a recent four-day test, Senator Marconi announced
that he had been in uninterrupted communication with Australia, using the beam system
i DECEMBER, 1925
GOOD WORK BY THE ORGANIZED BROADCASTERS
169
Be It Resolved that, it is the sense of this meeting that
any agency of program censorship other than public
opinion is not necessary and would be detrimental to
the advancement of the art."
More Information on Super Power
A i THE first experiments on higher broadcasting
power continue, the public is beginning to see that
those engineers who advised caution in drawing
conclusions as to what effect this increased power would
have were wise. Many were the broadcast listeners who
said 50 kw. for one station would blanket all that part
DETAILS OF THE RADIO "BEAM" LIGHTHOUSE AT
SOUTH FORELAND, ENGLAND
Senator Marconi recently conducted tests with this installa-
tion from his yacht Eletlra. The beam flashes signals ac-
-— _,. .. -
cording to a schedule from all points of the compass. The
loud speaker announced a letter at intervals, and the position
of the ship was determined according to 'the letter heard. By
means of a chart, it was possible to tell just where the ship was.
The frequency was 49,970 kc. (6 meters). The heading for
this department this month shows the lighthouse and the re-
volving antenna and this view shows the details of the antenna
casters had its annual meeting this month
and its transactions are indirectly of in-
terest to us all. The object of the society
is to promote generally the welfare of our
broadcasting stations through various co-
operative arrangements.
It was started by a small but active
group in the Middle West, with the able
Mr. Paul B. Klugh as Executive Chairman.
Its activities proved so worth while that
the membership rapidly increased and now
it bids fair to justify its name.
Among the members elected at this meet-
ing was WEAF, representing the American
Telephone and Telegraph Company. When
this company goes into an association of
this kind it is undoubtedly a sign of its
promised or accomplished success.
The question of broadcasting copy-
righted material has been more troublesome
to the National Association of Broadcast-
ers than any other problem in their opera-
tions. At first the organization was averse
to paying royalties for the privilege of
putting music and songs on the air (the
copyright law, of course, contains no pro-
viso for such an exigency). Now this
association has changed its point of
view. Among other resolutions passed was
one which would put the broadcasting of
copyrighted material on the same basis
as the mechanical reproduction of such
pieces (by player piano and phonograph)
in so far as royalties are concerned.
Another matter which received consider-
ation was that of the method of introducing
the paid features of the program. One of
our congressmen has advocated the com-
plete separation of paid channels from the
others. That attitude seems unnecessary
and inadvisable. The broadcasters took this
view of the matter and decided that paid
programs could be "gently" introduced.
On the question of censorship, the society
declares that "Whereas it is universally
agreed that the success of radio broad-
casting is founded upon the maintenance
of public good will and that no broadcast-
ing station can operate successfully without
an appreciative audience, and Whereas the
public is quick to express its approval or
disapproval of broadcast programs
of the broadcast range, that it would be
impossible to receive other stations which
sent signals of anywhere near the same
frequency. Some months ago we got sev-
eral petitions (with requests to sign) directed
to Mr. Hoover, requesting that he prohibit
broadcasting stations using a greater power
than 5 kw. The petitions stated what
troubles were to be encountered if the
Department did not block this anticipated
move by the "Trusts."
Schenectady has carried on many tests
with a 50 kw. outfit, and at the time this
is written, very few complaints have been
received. Many replies have been re-
ceived to questionnaires sent out, and they
are still being classified and compiled.
It is interesting to note that the public
must be depended upon to answer the
question as to how much power the broad-
casting agencies should use. All question-
naires received should be carefully an-
swered, for it is the facts in the compila-
tion of these answers that Mr. Hoover will
depend on to determine his future policy
regarding high power stations.
170
RADIO BROADCAST
DECEMBER, 1925
Although many of the letters received
by WGY are contradictory, the average
listener seems to think that a 50 kw. signal
is two or three times as loud as a 25
kw. signal. In the recent tests, the two
powers were alternated so that repeated
comparisons could be made and but few
of the reports say that one signal is more
than ten times as strong as another. As
a matter of fact, theory would indicate
that the 50 kw. signal is twenty times as
strong as a 2^ kw. signal, yet most of the
listeners say it is about twice as strong.
Probably the signal is actually twenty
times as strong and the factor ten by which
the average listener misses the truth is
due to his lack of skill in comparing noises
of different strengths.
The unexpected absence of complaint
regarding interference by the high power
channel has encouraged the General Elec-
tric engineers to continue their tests and
the Department of Commerce has given
WGY permission to use 50 kw. regularly on
Saturday and Sunday evenings. If this
much power is found to give to the broad-
cast listeners more trouble than benefit
it will be discontinued, but it is almost sure
that such will not be the case. A few
listeners near the station who want to hear
other stations thousands of miles away,
whose frequency is nearly the same as
Schenectady's, will of course report inter-
ference. This can be predicted without any
further tests. But as radio broadcasting de-
velops the complaints of the distance hound
will fall upon less sympathetic ears. High
quality reception for the most listeners is
what radio must eventually supply and
increased power, properly controlled, will
help in the solution of this problem.
Canada as Our Instructor
WE MUST congratulate our Cana-
dian friends on the way their gov-
ernmental radio activities are
conducted. It has been noted before in
these columns that many radio questions
were tackled in an intelligent and reason-
able manner by our northern neighbors,
even though some of their procedure (such
as the licensing of receiving sets at one
dollar a year) may not meet with our
approval.
There has just come to hand a pamphlet
put out by the Radio Branch, Department
of Marine and Fisheries, Ottawa, which
takes up the question of regenerative re-
ceivers. It is a circular letter addressed
to all broadcast listeners and is written in
a manner which will appeal to the average
non-technical man. The letter starts with
the paragraph "When using a receiver of
the regenerative type for the reception of
radio telephone programs, please avoid in-
creasing regeneration to the point at which
the receiver begins to oscillate, otherwise
you will cause interference with neighbor-
ing receiving equipment." Are you doine
your best to observe this?
The letter then proceeds to give an
elementary, but clear and correct analysis
of what regeneration is and why it causes
interference, ending
with easily followed
instructions as to how
to avoid spoiling
neighbors' reception.
With the govern-
ment list of listeners
available, as a result
of the licensing fea-
ture of radio recep-
tion in Canada, this
circular should reach
the owners of nearly
all the radio sets in
that country and
should do a deal of
good.
The Facts About the Farmer and
Radio
THE benefits which radio confers
on the farmer have been repre-
sented to him repeatedly, but it is
a fact that no one has really known whether
the average farmer profited by broadcast-
ing or not. A recent survey by the De-
partment of Agriculture among the coun-
try's farms yields the information that
there are 553,003 sets on farms, not as
many as we had expected. This repre-
sents only 85 per cent, of the country's
farms, so there is still a large virgin market
for the active radio manufacturer.
A questionnaire was sent out and the
returns for the State of Pennsylvania
have been sent us by Mr. George F.
Johnson of the Department of Agriculture
at Harrisburg. Of 343 answers received,
two thirds used tube sets with loud speak-
ers. To the question "Have market re-
ports ever made or saved you money?"
exactly half answered "Yes." and half
"No." We hasten to encourage the pro-
moter of "radio for farmers" after this
answer, because while it looks at first as
though radio was not functioning very well
here; that is really not the significance of
the return. That fifty per cent, of the
farmers saved money from the information
conveyed over the radio channel is in-
controvertible evidence of its utility.
The Month in Radio
ENGLISH employment agencies are
finding that domestic help appre-
ciates radio possibly even more
than does the mistress of the house. Bast-
ing the roast beef in tune with the wedding
marches, or washing dishes to the time of
modern jazz proves to be so appealing that
the agencies are said to be actually classify-
ing the vacant positions as radio and non-
radio, much to the detriment of the latter.
THE first attempts experimentally to
determine the proper allocation of
frequencies to the various European sta-
tions resulted in ethereal pandemonium,
HOW THE CANADIAN RADIO SERVICE HELPS THE LISTENER
The "Inductive Interference" car maintained by the Radio Service of
the Canadian Government. The annual license fee of one dollar, paid by
every Canadian listener is used to maintain a corps of inspectors. A
specially trained "induction squad" operates with this car to locate
interference hard to detect by the ordinary methods. The car is especi-
ally made for this purpose, with a body of insulating material and care-
fully screened ignition system. Two special super-heterodynes, several
portable receivers, a sledge hammer, condensers, jand chokes form the
equipment of the trouble car. The chokes and condensers are applied to
cure trouble when found. The sledge hammer is often used to tap
electric light poles in a suspected territory, and the trouble is quickly
located by a listening inspector
DECEMBER, 1925
WHAT PEOPLE SAY ABOUT RADIO
171
© Harris & Ewing
SENATOR C. C. DILL
—^Washington; United States Senator——'
for Washington
" The organisation of a Government Com-
mission on Communications to act for the
telephone, telegraph, and radio, such as has
been proposed, would probably end in disaster
for broadcasting.. It would be the beginning
of the end of freedom of action in the radio
business. I also wish to emphasise the neces-
sity of immediate action on the part of the
United States Supreme Court to arrive at a
decision regarding the broadcasting of copy-
righted musical numbers. If it is decided
that such broadcasting is done for profit,
and therefore a fee is due to the publishers of
the music, I intend to introduce a bill to
regulate the payments, so that radio broad-
casting will not be at the mercy of any one
group of men."
according to a dispatch from London.
About sixty stations going at once in an
expanse of territory perhaps less than a
quarter the area of our country proved too
much. The interference was truly inter-
national. Newcastle, England, heterodyn-
ing with Gratz, Austria, and Norway sta-
tions beating with some in England, Ger-
many and France, show us what a difficult
question the Europeans have compared to
ours. The radiophone center in Geneva
was notified of all the interference and in
the next test period changes will be made
to keep the interfering stations farther
apart in frequency.
""PHE research laboratory of the West-
* inghouse Company announces that the
metal, thorium, is now available in such
quantities that the filaments of vacuum
tubes may be made of pure thorium instead
of thoriated tungsten as is now the practise.
The present tubes have a layer of thorium
on the surface of tungsten filament, the
layer being only about one atom deep.
If the filament is improperly used, this
thin layer of thorium disappears and the
electron emission practically stops, the
tube is useless. By considerably overheat-
ing the filament, without B batteries, a new
layer of thorium will appear, this new
thorium diffusing to the surface from in-
side the filament.
Now, it is announced, solid thorium fila-
ments will soon be available. This is a real
advance because the possibility of the dis-
appearance of the thorium atom-deep
layer no longer threatens. The new tubes
will very likely have much longer life than
the present ones and not be so sensitive to
improper adjustments.
A RECENT discussion in the semi-
•'* popular press, having to do with the
use of super-power, ventured the statement
that if a 5 kw. station was audible on a
crystal set at twenty-five miles distance,
the 50 kw. station would be audible on the
same crystal set for a distance of "several
hundred miles." It seems that if we
interpret "several hundred" as five hun-
dred miles, the power of the 5 kw. station
would have to be increased to at least 250
kw. to increase the crystal set range as
much as the writer suggested — and then
it would probably fall short. Schenectady's
tests should soon give us some reliable
information on this point.
ACCORDING to the Department of
*» Commerce, Japan's long distance
radio telegraph stations are to pass from
the control of the government into the
hands of a private company which expects
to erect two new stations in addition to
the two now in operation and that when
their four stations are in operation the com-
pany will communicate directly with the
United States, Germany, and France. With
the 50 kw. of power which the new stations
are to have it seems very unlikely that
signals can be sent directly to Europe
except under most favorable conditions.
Most of the time one or two relay stations
will undoubtedly be required if any relia-
bility is to be obtained.
Interesting Things
Said Interestingly
DOWEL CROSLEY, Jr. (Cincinnati; presi-
dent Crosley Radio Corporation): "Very
few broadcasting stations are operating with
any direct profit. No broadcasting station in
the country is making money to-day. Some
handle indirect advertising with some source
of revenue; so far, I believe, no stations have
been able to meet expenses with this income.
Our own revenue at WLW from this source would
not pay for the direction of the studio. We have
a large investment in broadcasting equipment —
whether it is profitable for us to broadcast is a
question; whether the good will created by a
broadcasting station justifies its continued
existence is merely a matter of opinion. No one
can check the results. If all broadcasting
stations face an additional expenditure of from
$5,000. to $50,000. per year, due to the royal-
ties imposed by the Society of Composers,
Authors and Publishers, and perhaps more, be-
cause no limit has yet been set — how many of
these stations will continue? Imagine the
feelings of a man who appreciates the serious-
CARDINAL HAYES
—New York; Speaking at the opening ,
of station WLWL:
"Among the most recent and wonderful
gifts of science comes the radio. As Cardinal
Archbishop of New York, I congratulate the
Paulist Fathers upon the great work they
have undertaken in opening up station WLWL.
/ congratulate also the people of this immense
city and of this whole country of ours upon
the inauguration of an enterprise so admir-
able. May I add that in the building of this
station, the Paulists have shown themselves
worthy sons of their founder, for nothing was
more characteristic of the first Paulist, Isaac
Hecker, than this readiness to utilise every
•new instrument of good. How his noble
soul would rejoice to witness this scene, the
dedication of the twin towers of steel that over-
look the Paulist Church here at Fifty-ninth
Street, as an agency for the spread of truth
and wisdom. We who employ radio are
responsible for our use of it. We must take
care that we use it not for harm. But, further,
we are strictly bound to use it for good,
to make it fruitful. Whoever would be great,
must serve. He who has power must turn it
to the welfare of his fellows."
ness of this situation, playing a gambling game
in which no limits are set — where the more he
pays the more he will have to pay — and you will
appreciate how serious the situation is."
GOVERNOR ALFRED E. SMITH (Albany,
^-* New York): "Radio broadcasting has
revolutionized political campaigning. It makes
it possible for a candidate to reach the by-ways
of politics. The stay-at-home gets your message
as clearly and intelligently as the man who is
able to come out to the meetings. A great
event can be recorded at the fireside. The
opening of the extraordinary session of the
New York State Legislature this year is an
example. It brought to the people young and
old an important lesson in civics and gave them
exactly the procedure which occurs when a
session of the Legislature is opened. Radio
gives you the widest possible audience and also
the benefit of public opinion. I have had oc-
casion to use the radio on many important
occasions including my inauguration as Governor
and in making an appeal for public support
of important and vital policies. Just as it has
served my needs and opened up a tremendous
avenue for political education, I am glad to have
the opportunity to say so to the radio public."
A Five-Tube Receiver of Dual Efficiency
A Late Development of the Famous Browning-Drake Receiver Employing Impedance-
Coupled Audio Amplification Producing the Highest Quality — Some Valuable New
Data on Radio-Frequency Transformers and a New Method of Balancing Them
By GLENN H. BROWNING
UESTIONS are frequently being
asked concerning the necessary
requirements of the ideal radio
receiver. The answer pictures a
set which is sensitive enough to
receive great distance, gives perfect repro-
duction of the program being broadcast,
tunes sufficiently sharp to separate trans-
mitting stations, does away with interfer-
ence, and accomplishes all
this without batteries, tubes, ^ _
or other trouble making de-
vices. At the present time,
our ideal seems far from the
realm of realization, but at
least we may take a step in
the right direction, by scien-
tifically investigating radio
and audio frequency ampli-
fication.
The receiver to be de-
scribed, which consists of one
stage of balanced, tuned radio
frequency amplification, re-
generative detector, and three
stages of impedance-coupled. audio ampli-
fication, is still far from perfect, but it is
sensitive enough to do DX work, selective
enough to cut through locals, is properly
designed for good quality reception, and
does not radiate.
Let us consider the component parts
separately. The tuned radio-frequency
transformer is probably the most important
part of the receiver, for into its develop-
ment went almost a year of theoretical
and laboratory work by Mr. F. H. Drake
and the writer, with a result that a piece of
apparatus was designed, which gave almost
90 per cent, of the amplification predicted
by mathematical calculations.
Several interesting discoveries were made
during this time, among which was the
fact that the "turn ratio" of a tuned
radio-frequency transformer was not so
A L THOUGH Mr. Browning lias made Jew fundamental changes in the origi-
•*• ^ nal design of the justly famous Browning-Drake receiver which was originally
described in RADIO BROADCAST for December, 1924, the reader will find that the re-
ceiver described here contains some distinct improvements which place this model in
the vanguard of current receiver design. The improvements are in the audio circuit,
and impedance-coupled amplification has been chosen. The four-tube model of the
Browning-Drake receiver does frequently overload, but the set described below is
almost free from that disadvantage. In this article, the author presents some inter-
esting data on comparison between transformer-, resistance-, and impedance-coupled
amplification, and suggests a new method of balancing the radio-frequency trans-
former. It should be read with much interest. — THE EDITOR.
regeneration is present in any radio-
frequency amplifier to a greater or less
extent, and the necessity of providing a
method of controlling it arises sooner or
later. A little experimenting showed that
greater signal strength could be obtained
by balancing the radio tube and regenera-
ting on the secondary of the radio frequency
transformer, rather than regenerating di-
rectly on the antenna tuning
javj system. The former course,
besides giving greater signal
strength, has the added ad-
vantage that it does away
with any radiation tendencies
the receiver might otherwise
have.
SELECTING THE AUDIO
AMPLIFIER
important as the resistance of the secondary
circuit, and the relation between primary
and secondary. It was also found that
any capacity between these two windings
tended to decrease the efficiency, so that
the final design consisted of a "bunched"
primary winding coupled closely to a
low resistance secondary coil. Having de-
signed the radio frequency part of the cir-
cuit, the question of regeneration was then
encountered. As most radio fans know,
TN CHOOSING an audio
1 amplifier for the circuit,
tstf some experimenting was
necessary, as one can use
transformer, resistance-, or impedance-
coupled systems with varying results. Two
stages of, say, 4 to i transformers will un-
doubtedly give sufficient volume, but the
quality or naturalness of the received pro-
gram must, in some measure, be sacrificed.
Three stages of impedance-coupled am-
plification has as good quality as resistance,
and, if properly built and operated, gives
greater volume and does not require an
abnormal B battery voltage. It was con-
OltolOmfd. O.ltol.Omfd. O.ltol.Omfd.
DAVENTUBE ., DAVENTUBE II DAVENTUBE
67!sV.or90V.
FIG I
[] 'i Amp. Ballast for 5VoltTubes
ti % Amp. Ballast for Power 5 VoltTubes
The schematic diagram of the circuit employed in the receiver. The several battery terminals of similar markings are paralleled and connected to
the terminal of the indicated polarity of the battery in question. For instance, there are four minus A posts. This group is connected together as one
terminal, thence connecting to the proper battery. The same holds true of the two plus B 45-volt terminals, and the three plus B 6yj-volt
or go-volt terminals. However, in the case of the minus C battery terminals, the last audio stage will require more voltage than the first two
DECEMBER, 1925
A FIVE-TUBE RECEIVER OF DUAL EFFICIENCY
173
FIG. 2
Details of the winding of the radio frequency
coupler. L} is the primary; La the secondary,
and Lp the variable tickler coil. The actual
winding specifications are contained in the ac-
companying article
sequently chosen for the receiver to be
described.
For those who are interested in labora-
tory measurements, a comparison between
the three systems is shown in the accom-
panying chart, where signal strength is
plotted for frequencies ranging from 100
to 10,000 cycles per second. It will be
seen that the more constant the amplifica-
tion for the frequencies shown, the better
is the quality of the received signals.
The conclusion to be drawn from this
data has lead us to choose three-stage
impedance-coupled amplification with high-
Mu tubes.
The parts listed below were used in build-
ing the set. Whether or not the builder
follows the exact list given, he will need the
parts listed below or their equivalent.
One panel — 21 x 7 inches.
x Shaft Threaded with
10-32 Die
Split and Tapped
For 10-32 Thread
Brass Bushing ,-''
10-32 Thread
FIG. 3
Shows the mechanical arrangement of the bal-
ancing condenser plate and mount. It is to
be mounted on the sub- panel in the rear of the
radio frequency secondary coil
One sub-panel (bakelite) 18 x 7 inches.
One National Kit (containing the two variable
condensers and Browning-Drake coils.) i
Five Na-ald sockets (2 uv-igo, and 3 uv-2oi A).
One Daven Leakandenser (the leak shot) Id
have a resistance of 6 to 8 megs.)
Use No. 19 Drill for Holes not Specified
-.
_._,_*.
•£ y_
-- 10 V2"
21'
— -\
H
FIG. 4
The panel layout. There is room enough between the two tuning condensers to include a filament voltmeter which would not only
add to the appearance of the receiver, but prove exceptionally advantageous in knowing the value of voltage delivered to the tubes
RADIO BROADCAST Photograph
FIG. 5
Looking down on the sub-panel, the position of the balancing condenser may be observed. Much of the wiring is below the sub-panel
174
RADIO BROADCAST
DECEMBER, 1925
FIG. 6
RADIO BROADCAST Photograph
The simplicity of assembly is evident from this view. Note that the two coil units are at right
angles to each other and on the same plane. This is necessary to prevent uncontrolled oscillation
Three Daven .1
megohm grid leaks,
and mounts.
Three loo-henry
National chokes.
One Yaxley filament
control jack.
One .001 mfd. fixed
by-pass condenser.
One .0001 mfd. fixed
condenser.
One balancing de-
vice.
Nine binding posts.
.
- * 1 ,
Fig. i shows the
schematic diagram
of the circuit used. The antenna tuning coil
Li consists of 46 turns of No. 20 d.s.c. wire
on a three-inch bakelite form with a center
tap taken off. The radio-frequency trans-
former, commercially familiar as the
" regenaformer," consists of three windings,
a primary, a low resistance secondary, and
a rotor coil. The details of its mechanical
FIG. 8
The panel appearance of the completed receiver: simplicity itself
construction are given in Fig. 2. The
primary, L3, consists of 24 turns of No. 28
or 30 d.c.c. wire, wound in a groove and
placed at the low potential end of the
secondary coil (under the first few turns of
the secondary at the filament end). The
secondary, L2, is a single-layer solenoid
made by winding 75 turns of No. 20 d.s.c.
wire on a three-inch
bakelite tube. As
has been mentioned
before, the resis-
tance in this circuit
is important, and a
great quantity of
data has been col-
lected which would
indicate that the re-
sistance of a single-
layer solenoid is
somewhat lower
than those wound in
a so-called "low
loss" manner. The
rotor coil Lp is made up of 20 turns of No.
28 d.s.c. on a 2|-inch form and so mounted
that it may be rotated with respect to the
secondary of the tuned radio-frequency
transformer. The condensers chosen to
tune the two circuits are of such construc-
tion as to separate the high frequency
(short wavelength) stations considerably
RADIO BROADCAST Photograph
FIG. 7
An under-view of the sub-panel where most of the wiring is placed. Convenient holes in the
sub-panel allow the passage of wires connecting parts above the sub-panel with those below it
RADIO BROADCAST Photograph
DECEMBER, 1925
A FIVE-TUBE RECEIVER OF DUAL EFFICIENCY
175
more than the ordinary condenser, and
their sizes are such as to cover a frequency
spectrum from 600 kilocycles to 545 kilo-
cycles (200 to 550 meters).
The construction of the choke coils is
not described because of the difficulty of
making them at home. The National 100-
henry choke was used in "the model de-
scribed. However, any standard choke
coil for audio frequency work may be em-
ployed, such as those made by Acme, the
General Radio Company, AmerTran, and
Thordarson.
CHOICE OF TUBES
IN EXPERIMENTING with the re-
1 ceiver, it was found that a uv-igg was
much easier to balance than the larger
tubes, and was consequently used as the
radio-frequency amplifier tube. As most
fans know, a uv-igg is also a good detector,
so at the suggestion of Mr. Arthur Lynch,
the two uv-igg tubes were put in series
and three Daven six-volt tubes employed
so that the set operates directly from a
six-volt storage battery without the use of
rheostats. Two Daven MU-2O tubes may
be used in the first two stages of impedance
with a Mu-6 in the last stage. The con-
structor may use other tubes by placing the
correct filament ballast such as Amperite,
Brach, or Daven type in the battery leads
of the respective tubes. A five-volt, J-
ampere tube would take a j-ampere ballast,
and a five-volt, ^-ampere tube would take a
^-ampere ballast, etc. The new power tube,
ux-i 12, may be used in the last audio stage
with about 1 3 5 volts on the plate and g volts
C battery. A separate C battery binding
post is provided so the last audio tube may
have an independent bias battery. When
the Mu-2o tubes are employed in the two
intermediate stages of audio, little or no
bias is needed with go volts plate battery,
but when higher voltages are used a C
battery of 15 to 3 volts should be employed
for good quality recep-
tion.
Forty-five volts is rec-
ommended on both the
radio-frequency ampli-
fier and detector, as this
voltage has been found
more efficient on the de-
tector and sufficient for
the radio frequency tube.
With 45 volts on a radio-
frequency amplifier, no
C battery is needed and
the grid return is run
directly to the negative
side of the filament.
In laying out the ap-
paratus so that the set
would be compact, the
tuning condensers are
placed symmetrically on
the panel with the tube
sockets arranged as
shown in the photo-
graph, the radio fre-
quency tube being the
one on the extreme left
with the detector on the
extreme right, and the
audio tubes between the
two.
CONSTRUCTION DETAILS
700
600
500
z
o
<
_
A
•
VOLTAGE AMPLIFIC
^
S^
^
\
^
D
\
\
1
X) 200 ' 500 1.000 2.000 5.000 IftO
FREQUENCY
FIG. IO
Curves for various types of audio amplification compared in this
article. Curve A. Three stages of impedance-coupled audio ampli-
fication, using two Daven MU-SO tubes and one Daven MU-6 in the
last stage. One hundred-henry chokes, i-mfd. condensers and o. i
meg. grid leaks were used. Curve B. Three stages of resistance-
coupled amplification, with two Daven Mu-2O tubes and a Daven
MU-6 in the last stage. In the plate circuit was o.i meg. resistance.
The grid leaks were o. i meg. and o. i mfd. condensers were employed.
Curve C. Two stages of transformer-coupled audio amplification
were measured. The first transformer was a 6:1 and the second a
2:1 ratio. The tubes used had a voltage amplification of 8 which is
standard for the 5-voIt type of tube. Curve D. The curve of a
three-stage impedance-coupled amplifier using tubes of a voltage
amplification of 8; other constants the same as with curve A. Curve
E. Three stages of resistance-coupled amplification, with similar
constants. Curve B used with tubes whose amplification factor was 8
1 1 ""HE balancing of the first tube is ac-
* complished by placing a f-inch metal
disc, connected to the grid of the first tube,
in the rear of the radio frequency trans-
former (about in the middle of L2) and
moving it toward or away from the secon-
dary winding. This method of balancing,
though not generally known, is simple and
effective. The details for constructing this
balancing device are shown in the accom-
panying diagram, Fig. 3.
The drilling template for both front
and sub-panel are shown, together with
photographs of the complete set, so that
there is little need for lengthy construc-
tional details. However, the buildei
should be cautioned to keep his grid and
plate leads as short as possible and well
separated from each other. Most of the
radio frequency leads are above the. .sub-
panel, with the exception of the plate lead
from the first tube to the primary of the
radio-frequency transformer which is long,
and should be kept well away from all
other wires. The lead from the grid of the
first tube to the balancing device should
-
»<-- !V'
No. 20 Drill on Holes not Specified
,
rf\ _ fi\ /T\ ^K
' vl/~ * t±7 tt/ ' vp
FIG. 9
The sub-panel drilling specifications which are self-explanatory. As you look at this layout the
top is the front of the sub-base, and the bottom is the back which supports the binding posts, etc.
176
RADIO BROADCAST
DECEMBER, 1925
g
§
§5
. I - Calculated Radio Amplification
II - Measured Radio Amplification
Ill-Measured Radio Amplification
of Transformer with 8 Turn Primary
400
FIG. I I
Three curves which are both interesting and instructive. Note how
approximately correct in comparison is the calculated and measured
radio frequency amplification while manifestly the 8-turn primary
is not as good
also be kept well away from other con-
nections. A center tap is provided on the
first coil, L,, to be used with a long antenna
of loo feet or over, but as some antennas,
which are even much shorter than this,
have a large amount of capacity, it is well to
make the connection from the .0001 mfd.
stations on the head-
phones, is absent with
the impedance ampli-
fier. Instead of us-
ing a filament switch,
the jack is made to do
double duty, so that
placing the plug in
the jack lights the
tubes.
BALANCING AND
OPERATING THE
RECEIVER
THE first thing to
do after the re-
ceiver has been con-
structed as shown, is
to balance the first
tube so that no radi-
ation will occur, and
in such a way that greatest signal strength
will be obtained
Connect batteries, phones, and ground to
the set, but do not connect the antenna.
Turn the rotor or tickler coil to a point
where placing a finger on the stator plates
of the condenser, Q, gives a loud "pluck"
condenser to the point of the coil which in the phone. This shows the secondary
makes the two dial settings most nearly
coincide at mid-scale. Only one jack is
used, as most radio enthusiasts use a loud
speaker except when tuning for extremely
distant stations, and then it has been
found that three stages of impedance-
coupled amplification can be used conve-
of the radio-frequency transformer is
oscillating. Now rotate the coil until
oscillations cease, as determined by the
finger test. The first condenser should
then be turned through its range, and if,
at any setting of this condenser, the secon-
dary of the radio-frequency transformer
niently with head phones. This is due to oscillates, the balancing device should be
the fact that the noise which is apparent
with transformer coupling, and which tends
to draw comfortable reception of distant
adjusted until this test is satisfactory, and
the two tuning circuits are entirely inde-
pendent of each other.
FIG.
RADIO BROADCAST Photograph
A compactly built modification of the Browning receiver, which could be made to fit in a phonograph
cabinet as described in this magazine for June, July, and August 1925. This one employs re-
sistance-coupled audio amplification. The amplifier units are situated below the sub-panel
A few notes on tuning may be helpful,
though actually operating the set is the
only way one can acquire the knack of
doing DX work. If the set is performing
normally, the volume coil, Lp, can be turned
to such a position that placing a finger on
the stator plates of the .00025 mfd. con-
denser gives a "pluck" in the receivers.
This means circuit L,, Q, is oscillating.
With the volume coil in that position,
turn the dial of the .00025 mfd. condenser
until this whistle is loudest and adjust the
volume coil until the whistle disappears,
and by slightly retuning, the station
should come in. If the detector tube has
a tendency to "snap" into oscillation in-
stead of going in gradually, the resistance
of the grid leak should be increased.
The receiver described is capable of
extraordinary results, for not only is it a
fine distance getter, but quality of the re-
ceived concerts is almost above reproach.
Combined with this is its non-radiating
property, and the fact that an extremely
short antenna of only ten or twelve feet of
wire may be used with satisfaction.
-tev
Concerning the Receiver Which
Are Commonly Asl^ed
Q.
Q.
A.
Q.
What is the trouble if the receiver tunes
broadly?
The .0001 mfd. condenser in series with the
antenna may be of incorrect value or an
excessive amount of loss would give this
effect. The blame might also be laid to
poorly soldered connections to the two coils,
Li and La.
What makes the detector tube go into
oscillation with a "snap" instead of going
in gradually?
The grid leak is not the correct size. Try
one whose resistance is higher. The grid
condenser might be larger than .00025
mfd. (It is much better to use a condenser
smaller than .00025 mfd- rather than one
larger).
What length and type of antenna works
best with the receiver?
A 50 to yo-foot antenna is usually ample
with as much of this vertical as possible.
Very good results have been obtained with
a piece of wire about 30 feet long extending
from a pine tree down vertically to the
receiver.
Will the set work with a loop?
Yes: but even an antenna of fifteen feet
located in the same room as the receiver
has been found to give better results, and is
easier to erect.
ondiuFted by
Point or Vieuu-
KJndsleu tHcllcs
o *
Is the Popularity of Jazz Music Waning?
wi
"HEN radio broadcasting was
a novelty and one called in
the neighbors to hear the
voices coming in "right out of
the air," little or no attention was paid to
what the voices were saying. "Radio is a
marvellous instrument, a tremendously
potential medium, but what difference does
it make if it is being used to give currency
to worse than second-rate stuff," is about
the gist of the very vocal objections made
by these observers. George Jean Nathan,
the rapier-worded dramatic critic of The
American Mercury said in a recent issue of
that green-jacketed organ of dissent:
Nightly the front parlors of the proletariat re-
sound to the strains of alley jazz pounded out by
bad hotel orchestras, to lectures on Sweden-
borgianism by ex-veterinary surgeons, to songs
ibout red hot mammas, and Beale street melan-
cholias by hard-up vaudeville performers. . .
Now all the criticism of radio programs
made along these lines is true in that it is
possible to hear the thing described from
some radio station or other at one time or
another. We should not judge broadcast-
ing by that method any more than we
should judge the thinking processes of the
American citizenry by what we hear a '
chance street orator mouth. Broadcasting
is not nearly as badly off as its hostile critics
would have you think, and the aerial
offerings of the radio season now upon us
are daily justifying that belief.
" If it weren't for the constant stream of
jazz flowing from nearly every broadcast-
ing antenna," remarked a listener to us the
other day, " I would enjoy radio a lot more.
These jazz orchestras from every, station
in the country, all practically banging away
at the same piece at practically the same
time are much more than annoying." The
trouble with a criticism such as this is that
it groups all dance music ,as jazz, which is
only true because we have no term which
allows us to distinguish between the grades
of jazz. We use the same term to describe
the soft symphonic effects of Art Hickman,
Ben Bernie, and Vincent Lopez as we use
for the fifth rate Five Melody Kings of
Four Corners, Oklahoma.
" 1 believe," writes D. M. Craig, of La-
mar, Missouri, "that the universal con-
demnation of jazz is contrary to the true
feeling of a majority of radio listeners, if
all music is classified as jazz. Would these
objectors want to stop the broadcasting of
such organizations as those of Paul Whit-
man, Vincent Lopez, Jean Goldkette, and
many others?" Decidedly not. While
there are those who are utterly opposed to
jazz whatever its origin, the more liberal
among us recognize that jazz music has a
very strong hold on a large percentage of
the public of several continents, that it is
not wholly as bad as it is pictured, and that,
in moderation, jazz is excellent entertain-
ment.
The trouble with broadcasting programs,
and up to the past six months this has
been true of almost every American sta-
tion, is that they have been too heavily
loaded with this orchestra and that, play-
ing the currently popular tunes. Too
much of the program has been devoted to
FRANK \V. ELLIOTT
The new president of the National Association
of Broadcasters, who succeeds Eugene F.
McDonald, of Chicago. Mr. Elliott is business
manager of station woe at Davenport
dance orchestras, or to soloists who ha<
nothing on their repertoire but whateve
numbers were being sold in the musii
shops as "the latest thing" or, worse, t<
song " pluggers " in the employ of the musi
publishers. This practise of the broad
casters, we firmly believe, has shortene<
the life of many moderately good popula
numbers, which otherwise might have re
tained popularity for a considerably longe
time.
Mr. Frank McEniry, of station KOA a
Denver, in answering a recent inquiry o
ours about this subject replied:
On the whole, 1 believe listeners tire of jaz
much more quickly than they do of the classics
or semi-classical presentations. This belief i
of course, wholly a personal one, but it is base<
on a daily study of mail from our listeners. Her
is an excerpt from the letter of a Western listene
which seems typical of a great mass of mail w
are receiving on the subject: "One cannot b
unmindful of the lovely entertainment last even
ing; especially beautiful was the Floradora Sex
let by the Municipal Band. Likewise, the sam
selection with the lullaby on the saxophone. I
was such a relief from the slap-stick stuff one get
from many stations." That letter was fror
Charles G. Hickman of Forsyth, Montana.
And here is another from Mrs. Walter Burk
of New Plymouth, Idaho: "Almost without ex
ception, we like the better class of music. Jaz
ceases to have any appeal after the first two o
three selections — it is all alike. . . -."
They are doing some good things a
KOA, and by the time this magazine is ii
the hands of the reader, the competitivi
program of classical music as opposed t<
jazz music will have been given from tha
station. All the listeners will have ;
chance to express their opinion and a com
plete record will be made of the results
We hope to announce the findings in ai
early number. There should be some in
teresting letters after this contest.
Mr. Freeman H. Talbot, that abli
musician responsible for the programs o
KOA set down some of his thoughts aboui
the subject of jazz especially for this de
partment. "For many years," he says
music critics have been periodically an-
nouncing the death of jazz. Probably th(
178
RADIO BROADCAST
DECEMBER, 1925
so-called music of jazz is largely responsible
for the belief that it is moribund. To
those who would shed no tears over its
demise, jazz displays a most disheartening
vitality. Phoenixlike, it arises fresh after
each reputed annihilation." Mr. Talbot
continues:
Jazz has been called primitive, uncouth, banal.
It has been charged with disrupting homes,
weakening Church ties, and undermining the
morals of the nation. Personally, 1 feel that jazz
is not all bad — it is not clever enough for that.
It may be banal, and at times it is discouragingly
stupid, but it is not essentially bad. Lately,
jazz has gathered to itself some notable defend-
ers among the musically correct. Serious
minded musicians have perceived under the bat-
tered and tattered appearance of jazz, evidence
of a new vitality in music, a struggle after a new
form of expression, crude as the hieroglyphics of
Cubism, but genuine art, nevertheless.
The moans, shrieks, cat calls and sobs of jazz
will eventually disappear, but the vibrancy of its
stimulating rhythms will remain to be caught
some time by a master composer on a new work
or series of works as revolutionary as the caco-
phonies of Wagner.
How do all these remarks apply to pre-
sent programs? Well, they are some of the
signs — if indeed any are needed — which
show that the old preponderance of jazz
on programs is greatly lessening. For some
time, one of the two outstanding stations
in New York City has had a rule, somewhat
flexible, it is true, that no dance music can
be broadcast until after ten thirty in the
evening. Mr. Carl Dreher discusses this
matter more fully on another page of this
number. The fact that the musical parts
of programs are being more devoted to more
serious efforts by stations in nearly every
part of the country except Chicago, simply
means that there is less time left for jazz.
To mention a specific type of program
which has brought improvement in its
tone, consider some of the "indirect adver-
tising" programs put on through the WEAF
chain of stations. Here is what the direc-
tor of broadcasting for that station, Mr.
J. A. Holman, says about them: "Pro-
grams have been presented of a type that
previously would have been considered im-
possible by radio — impossible in the sense
that they assumed too high a degree
of musical and general culture on the
part of the radio audience. The' public
accepted them at their real value and en-
thusiastically availed itself of their educa-
tional activities. . . . No music was
too "highbrow." For example, George
Barrere's Little Symphony Orchestra pre-
sented a series of chamber music recitals,
which while beautiful and perfect gems of
instrumental music, are generally con-
sidered above the understanding and ap-
preciation of the average music lover.
The interesting fact is that the American
public welcomed the innovation. . . ."
The radio audience is not required to listen
altogether to the sad stuff outlined by Mr.
Nathan. The signs are unmistakable that
T;
the taste of the radio public is changing,
and for the better.
A New Note in Broadcasting:
Cooperation
O MOST listeners in this country
east of the Mississippi River who
heard the broadcasting of the radio
industries dinner from the Commodore
Hotel not so long ago, it probably seemed
as if very little was occurring except the
presentation of an exceptionally fine purely
entertainment program announced by the
active Major J. Andrew White. A good
program it was, too, with some of the Capi-
tol radio family, the Happiness Boys, the
shy Will Rogers, busy explaining why he
was not there, Rudy Weidoeft, Vincent
Lopez and his Orchestra, and several
speakers, including Senator Dill. The
radio lambs and lions, however, were lying
down together and at executive sessions
before and after the dinner, various as-
sociated organizations arrived at some
decisions whose effect may be far reaching.
The National Association of Broadcast-
ers, whose member-stations include a good
proportion of the broadcasters of the
country, elected Dr. Frank Elliott of station
woe at Davenport, president, succeeding
E. F. McDonald, Jr., of station WJAZ.
And among other applicants, station
WEAF, New York, was admitted to mem-
bership. This is somewhat important, be-
cause thus far, WEAF has played a lone
hand in broadcasting. It probably means
that broadcasters are going to cooperate
to a greater degree than ever before, with
inevitable benefit to the listener.
Ever since the first broadcaster was li-
censed, there has been a quarrel on be-
tween the owners of the radio stations and
REINALD WERRENRATH, MME. LOUISE HOMER, TOSCHA SEIDEL, AND A. ATWATER KENT
The Atwater-Kent Manufacturing Company has arranged a series of Sunday evening concerts given at 9:15, Eastern Standard time through WEAF,
WCAP, WJAR, WEEI, WCAE, wsAi, wwj, woo, wcco, WGR, woo, Kso, and WTAG. The series presents some of the best-known artists familiar to concert-
goers and is regarded by radio listeners as one of the real treats of the Fall and Winter radio season. There will be thirty concerts and the last will be
given some time in May, 1926. Mr. Werrenrath, baritone, gave the first concert on October 4th, and was followed by Mr. Seidel, the well known Rus-
sian violinist. Mme Homer, the contralto of the Chicago Civic Opera Company, presented a popular program as the third concert of the series.
Mr. Kent is shown in the photograph at the top
DECEMBER, 1925
179
JEAN GOLDKETTE AND HIS LITTLE SYMPHONY ORCHESTRA — AT WJR
The photograph at the left shows one of the orchestras heard regularly from station WJR. Left to right: J. Schwatzman, celle; Gaston Brohan, bass;
M. Shapiro, violin; Victor Poland, violin; Jean Goldkette, pianist and conductor; Joseph Corner, violin. The Book-Cadillac Hotel is shown at the
right and houses the Detroit studios of WJR-WCX. The transmitting apparatus of the two stations operating on 580 kc. (517 meters) is located at
Pontiac, Michigan
the organization which claims to have con-
trol of most of the copyrighted musical
numbers, both popular and more classical —
the American Society of Authors, Compos-
ers, and Publishers. This Society to the
outsider appears to have what amounts
to a monopoly in the control of the per-
formance of copyrighted music. And also
to the outsider they seem to have exercised
that control in a most arbitrary fashion.
Whatever the merits of the disputes be-
tween the two opposed parties may be,
the situation now seems to be that the
broadcasters are unwilling to pay for a
yearly license from the Society for the
simple reason that they have no assurance
that they will be fairly treated from year
to year. The broadcasters have taken the
sensible position (to use their own phrase-
ology): "we desire to see that the writer
of the songs as well as their assignees
shall be paid a fair sum. . . . Re-
solved, that the principle involved in the
reproduction of music by mechanical means
now embodied in the present copyright
law be extended to the reproduction of
music by radio. . . ."
This means, simply put, that the listen-
ers will benefit, for after the smoke of legal
battle clears away, it will undoubtedly be
possible for more stations to broadcast
much good music which is barred to them
now by the provisions of the copyright. It
also means that radio is advancing toward
a firmer and sounder basis, for there is no
doubt that the dispute over payment and
copyright has hampered the arrangement
and presentation of programs.
Radio Plums for the Present
Season
WHILE the optimistic estimate of
Mr. W. E. Harknessof the Ameri-
can Telephone and Telegraph
Company that the largest of the WEAK
wire tie-ups reached sixty-five per cent, of
the listeners of the United States may be
viewed with the raising of an slightly
doubting eyebrow, it is certainly true that
the new concerts of the Atwater Kent
Company which began on October fourth
have jumped into immediate popularity
with a great number of listeners. When the
Victor and Brunswick Companies broad-
cast their concerts last year, the radio
audience sat up before its assorted loud
speakers and wondered if something new
hadn't happened in broadcasting. It had.
The tone of all broadcasting was raised
and it is our belief that it will never be
lowered. The first concert of the Atwater
Kent series with Reinald Werrenrath, one
of the best of American baritones, set
the pace for the rest of the series. Other
artists who will be heard in the thirty
concerts, which begin at 9:15 p. M. Eastern
Standard time, on Sunday evenings, are
among the foremost opera and music
stars of the world: Louise Homer, Edward
Johnson, Mabel Garrison, Maria Kurenko,
Salvatore de Stefano, Alexander Brai-
lowsky, Leo Luboshutz, Charles Hackett,
Florence Austral, Albert Spalding, Benno
Moiseiwitch, Toscha Seidel, Felix Salmond,
Vincente Ballester, John Powell, Eva
Gauthier, Anna Case, Freida Hempel,
Paul Althouse, Arthur Middleton, May
Peterson, Paul Kochanski, Mischa Levit-
ski, and Hulda Lashanska.
Then there are the concerts of the Victor
and Brunswick Phonograph Companies
which will be heard from the Radio Cor-
poration group of stations, which will pre-
sent other opera stars. It looks like an
embarrassment of riches for the radio audi-
ence. Whatever the internal politics
among the broadcasters and however
strong the grimly competitive spirit, the
listener is sure to benefit.
Learning, Via the Loud Speaker
THOSE who have a burning desire to
increase their store of knowledge can
accomplish a good part of that end
by radio if they are so minded during the
radio season now upon us. During the
last two years, many radio "extension
courses" have been offered over the air,
and the State University of Iowa was prob-
ably the first higher educational institution
to offer a regular air course, which was be-
gun last year. Station wsui, 620 kc. (484
meters) is broadcasting a course of lectures
on Monday and Wednesday from seven
thirty to eight fifty P. M., Central Standard
time. On Mondays lectures on "Early
Iowa History," "American Literature,"
"Iowa Flora" and "Population Problems"
On Wednesdays wsui offers lectures on
"The Teaching of English," "Political
Parties in the United States", and "Ele-
mentary Psychology." Actual university
credit is offered to those radio listeners
180
RADIO BROADCAST
DECEMBER, 1925
who complete the requirements of the
course. Full information can be secured
from Edward H. Lauer, director, extension
Division, State University of Iowa, Iowa
City. In Pittsburgh, station KDKA will
resume its extension courses in cooperation
with the University of Pittsburgh and the
Pennsylvania State College. In Spring-
field, WBZ is laying plans for another ex-
cellent series of extension lectures. In
Oakland, KGO, is broadcasting regularly
to the grade schools of the city according
to a very well worked out and ambitious
plan. Throughout the country, educa-
tional programs, most of them well planned
out and presented can be regularly heard
with little more trouble than a reference to
the newspaper programs and the effort of
revolving a dial.
Why the Farmer Likes Radio
VERY early in its experience with
radio in the broadcasting of eco-
nomic information, the Depart-
ment of Agriculture proceeded on the
theory that radio broadcasting, when es-
tablished as a regular part of the machin-
ery of our present day living, would render
a greater measure of service to the farmers
than any other group or section of society,"
writes J. C. Gilbert, the Marketing Special-
ist of the Department of Agriculture. "The
THE AIR COLLEGE FACULTY AT WSUI
At the State University of Iowa, Iowa City. A series of lecture courses, of college standard are
broadcast from wsui throughout the winter, and college credit is given to those who comply with the
requirements. Left to right: Edward B. Reuter, Frank Luther Mott, Bruce E. Mahan, Christian
A. Ruckmick, Helen Williams, M. F. Carpenter, Kirk H. Porter, Bohumil Shimek, and Edward H.
Lauer
Department is firm in its belief that radio
is a permanent fixture on the farm, as
strongly entrenched, perhaps, as the Ford.
WEAF AND TWELVE OTHER STATIONS.
The "speech input equipment" of the Bell System at 195 Broadway, New York where the program, originat-
ing at the WEAF studio is sent to the stations connected to it by wire. On some programs as many as
thirteen stations — as far west as Davenport and St. Louis — are connected. At the control board shown,
much of the wire "routing" is done. The second panel from the left contains the board on which the pro-
gram comes from the microphones in the studio. The small hooded lamps are speech amplifier tubes,
which increase the strength of the energy before it is sent out by wire to the distant broadcasting station.
The three switchboards at the right take the programs for the various wire lines to the Middle West. Two
complete "set-ups" are always maintained — one wire for broadcasting, called the red layout, and another,
the "order wire," so that instructions can go out independently between the control office and the various
stations. If the broadcasting line should go bad, it is possible to swing in the "order wire" and so the pro-
gram continues without interruption. No other traffic goes out over the broadcasting wires — contrary
to regular long distance telephone practise, some lines carrying many other telephone and telegraph messages
The experts of the Department estimate
that there are 553,003 radio sets in use
on the farms of this country, as against
an estimated total of 364,800 re-
ceivers in use in 1924. While most
of us depend on radio broadcasting
for entertainment and perhaps a
bit of news, the farmer is growing
to think of his radio set as a source
not only of pleasure but of genuine
profit.
(One of the most interesting letters
among a large number written by
the farmers to show just what radio
is doing for this interested class of
listener was written by Fred Bu-
chanan of Granger, Iowa who said:
As early as 8:30 in the morning we
get livestock market report and from
10 o'clock on, grain reports. The
market reports will revolutionize the
farming business. The farmer gets the
news about markets right off the bat
— he does not have to take the buyer's
word for anything, and knows as much
about them as the man at the principal
market points. ... If everything
in broadcasting is cut out, save the
market reports, for they are bread and
butter to us out here.
The increasing number of radio
sets on farms, suggests the De-
partment of Agriculture, places a
responsibility upon those who con-
duct broadcasting stations and
those who have information to dis-
tribute. When half a million farm-
ers turn a listening ear toward the
broadcasting stations of the coun-
try, they expect to hear something
worth while. They expect the
weather reports, market reports,
agricultural lectures, instruction
DECEMBER, 1925
181
LOUIS WILEY
Business Manager of the New York Times who
recently spoke over WMCA, New York. "The
daily newspapers published in English on
Manhattan Island," said Mr. Wiley, "exclusive
of trade newspapers, have the astounding total
daily circulation of 4,039,286 copies. The
total is approximately twice the number of
families in the entire metropolitan district.
There is no other cohesive force, not even our
schools, which is so important in the life of our
community as the newspaper."
on various subjects from their agricultural
colleges and experiment stations. The
Kansas State Agricultural College at
Manhattan, Kansas, station KSAC, ever
since 1923 has taken the lead in broad-
casting air courses for rural residents
on agriculture, engineering, home econo-
mics, and general science. Those who
have heard the lectures in these excellent
courses will agree that they are well worth
an hour's listening.
'Broadcast Jftiscellany
IT IS sometimes fortunate that the radio
artists do not hear all the remarks —
well intentioned enough for the most
part — made by the radio announcers. It
was only the other night that a soloist
failed to appear at a certain large station.
"However," vocally beamed the announ-
cer, " Mr. Edward Gumph, a very depend-
able artist, will entertain you." Memo for
the desk pad: "Be sure to tune-in radio
to-night to hear "dependable artist."
THE publicity man of WNYC was doing
his best to drum up interest — on paper
— about the broadcasting of recent munici-
pal election returns from the station.
Quoth he, "The first official election figures
available will be heard from this station,
since it will operate in conjunction with the
Police Department. As votes are counted
at the poles, each district reports to its
Police precinct. . . ." Italics ours, or
is it "our'n?" It is so hard to remember
these days when spelling books are out of
print.
EO FITZPATRICK, the "Merry
Old Chief" of the Kansas City Star
station WDAF has left Kansas City and will
now be heard from WJR, Detroit. He was
the organizer of the phenomenally popular
"Nighthawks" whose membership is said
to reach 200,000.
NEXT to WGY, now licensed to use
50,000 watts on Saturday and Sun-
day nights, KDKA with a license to use as
much as 10,000 watts is the most powerful
broadcaster in the country. There are
ten jooo-watt stations, WSAI, WLW, woe,
WCCO, WCBD, WORD, KOA, WOK, WHO, and
WEAF. Stations WGY, and WTAM follow
with 3500 watts each, and KFI and KGO
each, with 3000 watts are next in power
rating. Station WTAS and WJR-WCX use
2500 watts. There are now three stations
employing 1500 watts, 25 using 1000, and
seven with 750 watts.
THE present conductor of this depart-
ment is relinquishing his duties with
this number of RADIO BROADCAST because
of his heavy duties in other departments
of the magazine. His successor, Mr. John
Wallace, of Chicago, a writer and critic
of more than ordinary ability, will continue
"The Listeners' Point of View" in the
January number.
THE new station, WLWL, 1040 kc. (288.3
meters) operated by the Paulist Fath-
ers, in New York went on the air with its
first program not so long ago. A frankly
religious station, operated by a branch of
the Catholic Church, its first programs
have been all that one could ask for in the
matter of dignity and high quality. The
work of WLWL is being watched with some
interest by listeners in the Eastern part
of the country. Those who can hear the
station on its high frequency band are
missing a rare treat if they do not hear the
Paulist Choristers, frequently broadcast
from this station, which is on the air be-
tween 8 and 10 p. M., Eastern Standard
Time, on Sunday, Tuesday, and Friday
nights.
ANEW broadcasting station is sched-
uled for St. Louis which will be
sponsored by sixteen firms in that city,
the St. Louis Globe-Democrat, the Colin
B. Kennedy Corporation among them. It
will be a jooo-watt installation, located, as
is the growing practise, a number of miles
outside the city. This is the second large
station to be installed by a group of busi-
ness interests and operated cooperatively
by them. The first station of this kind was
the excellent wcco, Minneapolis-St. Paul.
Nashville, Tennessee, has a new station,
WSM, which took the air early in October
on a frequency of 1060 kc. (282.8 meters).
IT IS reported that Liberty has bought
' the erstwhile WTAS at Elgin, Illinois
and will soon come on the air with its own
programs. It is to be hoped that the pub-
lishers of Liberty will be enabled to present
programs of a better type than WTAS
The mental level of WTAS is best indicated
by their slogan, "Willie, Tommy, Annie,
Sammy." The writer defies any one to
distill sense out of that. Liberty is owned
by the same group which publishes the
Chicago Tribune and the new station, WLIB,
will thus join WGN, making two stations in
the Chicago area owned by the same in-
terests.
THE COON-SANDERS NIGHTHAWKS
Frequently heard from station KYW, playing from the Congress Hotel in Chicago
* 76. Salitbury Strtet, Bedford. England
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hort Waves — A New
When the Stations Come Rolling In
Reception Is Renewed for the Broad
paritively Inexpensive — Learning the
By EDGAR
TH E twirling dial has captivated the
imagination of the world and the
prophecy of the Arabian Magic
Carpet has been more than ful-
filled, as we flit from city to city,
by a mere turn of our tuning control. The
thrill of DX reception is still with us, but
its captivating novelty, strangely enough,
is already wearing off.
That the popularity of DX broadcast
reception should occupy the center of the
stage for so short a period in the interest
of the average broadcast listener is sur-
prising, when we consider the marvel of
that scientific conquest. But it cannot
be denied that those who have tasted a
season or two of DX are to-day concentrating
in the search for better quality of tone
reproduction so that they may receive the
local stations with truthful fidelity of re-
creation. The DX hound of yesterday is
the stickler for high quality of to-day.
Not that we forget those proud mo-
ments "when the stations come rolling
in," with the aid of a newly built receiver
— when New York, Philadelphia, Pitts-
burg, Cleveland, Chicago, Minneapolis,
Atlanta, Hastings, Denver, Los Angeles,
Seattle, Oakland, Montreal and Mexico
City were heard all in one evening! But
even such accomplishments may become
commonplace.
To him, who would again enjoy these
thrills, we say, take heart, for short wave
amateur transmission and reception has
brought us new fields to conquer, more
fascinating than the old. There is no
exhausting the novelty of amateur com-
munication until we have established per-
sonal friendships in every corner of the
globe! The construction of a simple but
efficient short wave receiver brings the
whole world within range of the dial.
When the stations come rolling in on
7500 kc (40 meters), our magic carpet is
not delimited in its journeyings to the
confines of a mere continent. We begin
at the remotest border of our broadcast DX
range as the appetizer for an international
evening. First, it's England, France, Bel-
gium, Holland, Switzerland, Spain, and
Italy. Slowly, we move on as the radio
night advances, picking our way through
myriads of American amateurs for the
foreign stations to which our short wave
receiver makes us host. Next, it is Brazil,
Argentina, Chile, Alaska, Hawaii, as the
shades of radio night advance westward.
In the early morning hours, New Zealand,
Australia, the Philippine Islands and
Japan reward our zealous dial twisting.
A diet fit for a DX king!
WHO "BOILED OWLS" ARE
NOR is it unusual, as the first inkling of
fleeting time, to have the bright
rising sun break into our international
reveries and remind us that once more
we must resume our daily tasks. For
such is the lure of the new DX that its
first tastes have led many a new recruit
to sit attentive before his receiver the
long night through. Such ardent devo-
tees of the dial are rewarded with the
honored title of "boiled owl" — a fitting
designation for one whose long distance
work has been unexpectedly interrupted
by the rising sun. Increasing numbers
of broadcast listeners are being in-
trigued into this fascinating field of
radio reception, permitting, as it does, a
much greater scope for their DX abilities.
The requirements to admission are few.
The receiver used is of a much less elabor-
ate type than that needed for good broad-
cast reception. Two tubes at the most are
usually employed. Tuning is so sharp on
the high frequency (short wave) amateur
bands, that but one tuning circuit is re-
quired. Another control adjusts regener-
ation, which plays an important part in
short wave reception. There is nothing
startling in the way of special equipment
needed.
It is needless to describe in detail a suit-
able receiver, because extensive experi-
ments are under way, leading to the de-
velopment of short wave receivers for the
needs of new recruits to this new field.
Simple receivers and small battery powered
transmitters will soon be described in
RADIO BROADCAST, and these can be built
at costs ranging from $20 to $50, including
vacuum tubes. These experiments are
being conducted at the RADIO BROADCAST
T WAS talking to a chap in Australia last night "
•*• is not an uncommon report from a well equipped
amateur radio operator in these days of short wave,
low power transmitting. The Navy, in 1902
were gleeful over a record of established communica-
tion from Annapolis, Maryland to a ship off the
coast, 50 miles away. But to-day, even the
lowliest amateur would consider a ^o-mile trans-
mission as nothing. Of course all this short wave
communication is accomplished by radio telegraph
and one has to have a working knowledge of the
Continental code in order to share the thrills of this
long distance work. But learning the code is not
HOW SHORT WAVE HIGH POWER —
A section of tape, part of a message received at the Broad Street offices of the Radio Corporation of America from station SAQ at Gothenburg, Sweden.
The message reads: " Favor creditbank Oslo 2." The effects of static can be seen in several places appearing as a sharp .pointed mark much narrower
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Paradise for the DX Fan
on Forty Meters the Thrill of Distance
cast Listener — The Apparatus Is Com-
Code Is Necessary But Not Difficult
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H. FELIX
laboratories with the cooperation of the
National Carbon Company.
Amateur transmission is carried on
largely on a frequency of 7496 kc. (40 me-
ters). Some stations work on about 60,000
kc. (5 meters) and a great many others on
3750 kc. (80 meters). Another group,
employing radio telephony and continuous
wave telegraphy, work on 1666 kc. (180
meters). A 7496 kc. (40 meter) receiver,
however, gives ample opportunity for DX
work because amateurs in all countries of
the world where the contagion has spread
are permitted entrance to the ether on or
about this frequency.
WHO'S WHO ON SHORT WAVES
THERE are also other ethereal attrac-
tions available to the possessor of the
short wave receiver. Considerable com-
mercial transoceanic communication is
carried on by new experimental short wave
transmitters, which may some day sup-
plant the immense high power, long wave
equipments erected prior to the debut of
such a chore as it is commonly reported to be, and
more than one broadcast li<tener, to whom DX re-
ception is almost essential, is buckling down with
key and bu^er to learn the code and take part in
the fascinating short wave communication. We
shall publish articles in later numbers, describing
the construction of simple transmitters and re-
ceivers which will operate on these bands. We
believe with many of our readers who have written
us since articles about short wave communication
have appeared in this magazine, that this is a fas-
cinating new field to which many broadcast listeners
will glady come. — THE EDITOR.
the short wave. Among these stations are
Nauen, Germany, POZ, operating on 15,000
kc. (20 meters); 2YT, Poldhu, England,
12,000 kc. (25 meters); LPZ, Buenos Ayres,
8333 kc. (36 meters); i XAO, Belfast, Ire-
land, 4997 kc., (60 meters); SFR, Paris,
France, 4614 kc. (65 meters); WCM, Rocky
Point, Long Island, 4000 kc. (75 meters) and
ROW, Moscow, Russia, 3614 kc., (83 meters.)
Another service, which lends enchant-
ment to the short wave territory, are
special rebroadcasting links used to inter-
connect chains of stations or to furnish
programs to permanent stations. The pro-
grams of WGY are broadcast on 8570 kc.
(35 meters); KFKX, Hastings, Nebraska,
5357 kc. (56 meters) and KDKA, Pitts-
burgh, 4838 kc. (62 meters.) Oftentimes
these programs can be heard with great
volume on the short wavelengths while
the broadcast receiver is incapable of
picking them up on their regular broad-
casting channel.
The MacMillan expedition also used
short wave transmission for code and radio
telephone communication, during its
recent exploration voyage. Short wave
enthusiasts were privileged to hear the
transmitters installed on the two prin-
cipal ships of the expedition.
The Navy Department has taken cog-
nizance of the possibilities of the short
wave in its recent Pacific cruise by the
installation of short wave station NRRL
aboard the U. S. S. Seattle, flagship of the
fleet. It selected Mr. F. H. Schnell, Traf-
fic Manager of the American Radio Relay
League, to take charge of the transmit-
ter. The extraordinary success of his
work is one of the most interesting chap-
ters of amateur short wave history, pro-
ducing as it did convincing evidence to
naval officials of the practicability of ex-
tremely long range transmission on low
power. The experimental station of this
magazine, 2GY, communicated with NRRL
while she was leaving Tahiti in the South
Pacific Ocean. Forty meters and five
watts of power were used at the Garden
City end.
Two difficulties of broadcast DX are not
encountered to a great degree in short
wave reception. First, interference is min-
imized because of the very much sharper
tuning on the high frequencies (low wave-
lengths.) Second, the difficulty of identi-
fying stations is greatly reduced because
amateurs sign their call letters frequently
and freely.
THE CODE: OPEN SESAME
ON THE other hand, the broadcast
listener must spend some patient eve-
nings in learning the code, for amateur com-
munication is carried out by the dot and
dash method. Not that this is a tremen-
dous undertaking, although the first few
hours of code education are usually quite
bewildering. It is something like learning
to operate a typewriter. If you do not
know the location of a single letter on the
keyboard, your progress is very slow. But
as soon as you are familiar with the position
of a few letters, progress is quite rapid.
Amateur communication is carried on
at a much slower rate of sending than that
used in commercial traffic. By the use of
abbreviations, representing an efficiency
comparable only to that of short wave
transmission itself, the amateur compresses
—RADIO MESSAGES ARE RECEIVED
than the characters of the code. The Radio Corporation maintains several short wave stations, some operating on frequencies as high as 1 5,000 kc.
<20 meters), mainly as an adjunct to their long wavelength stations. German and Argentine stations are also using short waves for telegraphic traffic
184
RADIO BROADCAST
DECEMBER, 1925
into a few letters messages of considerable
import and significance. A few samples
of this esoteric language will serve to indi-
cate the principles upon which it is founded.
First amateur:
CQ CQ CQ CQ CQ CQ UIAQR U I AQR
UIAQR UIAQR . CQ CQ
CQ CQ UIAQR UIAQR UIAQR
Second amateur:
UIAQR UIAQR UIAQR G2BAO G2BAO
G2BAO G2BAO QRA?
First amateur:
G2BAO G2BAO G2BAO UIAQR UIAQR
UIAQR QRA WALTHAM MASS GE OM
U VY QSA HR BUT QRM FM u6ciX
WL WK U LATER HV 2 MSGS 4 CUL 73
OM
Second amateur:
R R UR SIGS CD BUT QSS CUL
This seemingly cryptic communication
is pregnant with information and good
manners. CQ is a general invitation to
communicate. CQD, the predecessor of the
now universally adopted sos distress call,
is derived from CQ, the D being added to
signify "danger."
UIAQR is the first amateur's official call.
The letter prefix designates him as a resi-
dent of the United States. The figure i
indicates his location in the New England
district. The United States is divided
into nine districts, each headed by a radio
inspector. AQR are the letters assigned to
this particular amateur by the Depart-
ment of Commerce.
The acknowledgement of the second
amateur consists of the first amateur's call,
followed by that of the second amateur's.
The letter G — called in amateur parlance,
the intermediate — indicates him to be a
resident of the British Isles. The prefix
A indicates an Australian amateur; B,
Belgian; BZ, Brazilian; c, Canadian; CH,
Chilian; D, Danish; i, Italian; j, Japanese;
M, Mexican; o, South African; PI, Philip-
pine Islander; R, Argentinian; Y, Uru-
guayan; and z, New Zealander. The
QRA? means, "Where are you located?"
The answer of the first amateur consists
of the usual acknowledgement followed by,
"My location is (QRA without question
mark) New Britain, Connecticut. Good
evening, old man (GE OM). You are very
loud here (u VY QSA HR) but I am having
interference from u6cix an American ama-
teur on the Pacific Coast (BUT QRM FM
u6cix) I will work with you later (WL WK
u LATER). I have two messages for you
(HV 2 MSGS 4 u). I'll see you later (CUL)
Best wishes, old man (73 OM)."
The reply means : " I received your mes-
sage satisfactorilay. (RR) Your signals
are good (UR SIGS GD) but they fade in and
out (QSS). I'll see you later (CUL)."
Eavesdropping on short wavelengths
has its fascination but almost invariably,
it serves only as an introduction to the
creation of a "dyed-in-the-wool ham."
The term "ham" is used to describe the
owner of an amateur transmitting outfit.
Possessed of a transmitter, amateur radio
becomes a personal and living thing. It
is no longer an external world which you
visit as an onlooker. You too can press
the key and become a part of the inter-
national dot-and-dash whirl.
Those of you who have seen giant trans-
This is Station
2GY
pnpral Headquarters
INTERNATIONAL
RADIOBROADCA-ST TESTS
TWO ESSENTIALS FOR AMATEUR TRANSMITTING
The regulations of the Department of Commerce, the Bureau in charge of radio in this country,
are that for a transmitting station capable of sending signals outside of the state in which the set
is located, a license is necessary. The operator of the station must have a license also. The
amateur station license is the long one in the center and the operator's license is shown at the right
of that. There is no fee for either license and the examination is not difficult. Licenses are
granted to those who can send and receive ten words per minute in the Continental code and who
can pass a simple theoretical examination, dealing with the theory and operation of amateur
apparatus
oceanic radio stations, with their immense
and stately towers, overshadowing power
houses, and buildings filled with trans-
mitting and receiving apparatus, may hesi-
tate to believe that tiny miniatures of these
imposing equipments have sent their mes-
sage half way 'round the world. But the
remarkable feature of short wave trans-
mission is the fact that only very minute
power is required to set up ether waves
which radiate for thousands of miles.
Recently an amateur in British Columbia
maintained a regular schedule of trans-
mission and reception for fourteen succes-
sive nights with a radio-found friend in
Australia, using only a five-volt receiving
tube, powered by heavy duty B batteries,
designed for use with receiving sets! Think
of it, you owners of five-tube sets — one
receiving tube, efficiently used, is capable
of transmitting half way round the world.
SIMPLE APPARATUS IS USED
THE circuits used in these diminutive
transmitters are very simple. The
all-important thing is the correct arrange-
ment and placement of high grade com-
ponents. In a characteristic way, RADIO
BROADCAST is leading the way to the new
field, by collecting data and designing
transmitters and receivers for the special
benefit of broadcast listeners. As rapidly
as the engineers conducting the RADIO
BROADCAST-Eveready short wave experi-
ments progress with their work, descrip-
tive articles will be printed in the maga-
zine, giving full details of construction and
operation.
Although primarily a sport and hobby,
there are serious aspects to amateur trans-
mission. Feelings of sectionalism and
nationalism vanish when personal friend-
ships are built up between amateurs in the
four corners of the globe. As the bound-
aries of friendship have been extended
through the ages by means of easy com-
munication and transportation, from tribe
to community, community to state, and
state to nation, we have gradually acquired
a unified national consciousness. Tribes
no longer fight tribes; rivalries between
cities, as that of Carthage and, Rome of
old, no longer result in bloody warfare, as
the telegraph, telephone, railroad and
steamship have cemented friendships and
demonstrated powerful common interests.
Now we have short wave, low power
radio, producing the citizen of the world,
with friends whom he calls by name
through the radio night, in Melbourne,
Paris, Tokio, and Rome! If short wave
radio spreads as rapidly as has broadcast-
ing during its first five years, international
peace will have a recruit and ally of signi-
ficant influence. Predictions seem vision-
ary, but we need contemplate only the
influence of the telegraph and telephone,
which has lifted us out of community in-
terest to a true national consciousness, to
lend the color of realism to the hope that
the seeds are firmly planted for a new recog-
nition of international bond, established
through the agency of short wave radio!
Plans for the Third of the International
Radio Broadcast Tests
The First Announcement of the Tests Which This Year Will Take
Place in January — Cooperation in All Branches of the Radio Industry
Will Make the Third Yearly Test More Successful Than Ever
By ARTHUR H. LYNCH
Director, International Radio Broadcast Tests
JOR two years, now, we have, during
the early part of the winter, had
an opportunity to listen to foreign
stations with American broadcast-
ers off the air. Listeners in the far
West have heard programs directly from
France, England, Spain, and other coun-
tries. Our European neighbors have lis-
tened to our concerts, and many reports
have reached us from South America,
Australia and, in fact, almost every nook
and corner of the globe.
But every effort which has been made in
the past is to be outdone this year. Prep-
arations are now being undertaken to as-
sure some very worth while features on the
programs themselves, as well as for the
immediate check-up of the origin of certain
numbers broadcast, which will make it a
simple matter to recognize a station, even
when the call letters cannot be understood.
The great difference between this year's
tests and those we have formerly con-
ducted, however, lies essentially in the
period we have selected. The matter was
put to a vote at the Associated Manufac-
turers of Electrical Supplies Convention at
Hot Springs several months ago; at the
Radio Manufacturers Association Conven-
tion at Atlantic City; the National Radio
Trade Association Convention at New York
in September; and a referendum was re-
cently taken by mail. In every instance
the majority was in favor of the lat-
ter part of January, when receiving condi-
tions would be better than at any other
time during the year.
Many of the trade
associations have al-
ready signified their
intention of cooperat-
ing, and during the
annual meeting of the
National Radio Trade
Association, a fund of
several thousand dol-
lars was raised to
assist in letting the
public know about
International Radio
Week. Powel Cros-
ley was re-elected
Chairman of Inter-
national Radio Week
and L. A. Nixon was
put in charge of the publicity and other
matters of a kindred nature.
Among those whose aid has been se-
cured are Mr. F. N. Doubleday, President
of Doubleday, Page & Co., who is now in
England, where with the assistance of his
friend, Rudyard Kipling, he hopes to ar-
range for the King to address a few words
to President Coolidge while millions of us
radio-eavesdrop.
Our Canadian friends, under the direction
of Jacques Cartier, who is in charge of the
week for Canada, are also attempting an
exchange of greetings between the King
and his Western Dominion representatives.
Radio organizations which for the last
two years have been tolerant spectators, are
now enthusiastic supporters of the Interna-
tional Test idea and many such groups are
taking it upon themselves to see that the
entertainment provided for our foreign
friends will be of a superior nature.
Nor are we forgetting about the folks
at home. Even though the programs
are being specially designed for our foreign
listeners, they will be of such high quality
as to meet the demands of the most sophis-
ticated dial twisters.
The success of the tests this year is made
doubly secure, because in Europe and
America there are more high-power broad-
casters than heretofore, and there will be,
by the time the tests are under way, a
direct short wave tie-up between our head-
quarters at Garden City and most of the
countries taking part.
THE COMMITTEE IN CHARGE OF THE TESTS
Powel Crosley Jr., is at the head of the table; at his left is Arthur H. Lynch; others in the group
include L. A. Nixon, second from Mr. Crosley's right, R. W. Demott of Radio News, third from
Mr. Crosley's left; H. S. Fraine, of RADIO BROADCAST next to Mr. Demott on his left. Mr.
George Furness of the National Carbon Company is in the right foreground
From our experience during the last two
years, we have learned much and hope to
eliminate some of the difficulties by apply-
ing what we have learned. One of our
greatest troubles was caused by lack of
accurate knowledge of what was being
broadcast by the foreigners. This year
we hope to overcome this bothersome ob-
stacle by having the foreign programs well
in advance so as to be able to send them to
the press. We are going to arrange to
have to-night's program appear in to-
morrow morning's paper and in this way
make it possible for the listeners in any
part of the country to make a check-up
for themselves, instead of writing to us,
or telephoning us from San Francisco or
Houston, to verify a program, as has been
the case heretofore.
In the past, many imaginative listeners
heard all sorts of things, some of them
based on fact. This year we are going to
arrange to mislead the misleaders by in-
serting one or two false numbers in the
programs. These numbers will appear in
the newspapers, but will not actually be
played. Thus, when we get a report from
some listener who claims to have heard a
number which we know was not broadcast,
we will see that his membership in the
Ananias Club be entered at once.
For the serious listener, however, who
wants to enjoy the thrill of personal con-
tact with many foreign nations within a
single short hour, or the scientist who, by
properly co-relating data from various
sections of the world,
taken during the
tests, a golden oppor-
tunity will be pro-
vided.
Months of prepar-
ation will result, this
year, we feel certain,
in European and other
foreign stations being
heard in every corner
of our country and
vice versa. Every
listener in America is
invited to take part in
these tests and assist
in making them the
greatest we have had
thus far.
An Improved Plate Current Supply Unit
How to Build a Universal B Battery Substitute Which Is Highly Satisfactory in
Operation and Low in Cost — The Parts Are Readily Obtainable — A Description of
the New Raytheon Rectifier Tube Which is the Essential Feature of This Device
|O MUCH has been published in
the last six months with regard to
B-battery substitutes that the aver-
age broadcast listener is in doubt
as to what type will give him the
most satisfaction. It is natural that cer-
tain prevailing types of eliminators will be
suited for particular types of receivers,
while they are entirely unsuitable for
use on others. In order to make an in-
telligent choice between these various de-
signs, the broadcast listener has had to try
out one after another until he has obtained
satisfaction. Even after a comparatively
thorough test, he may find that the short
life of the rectifier elements will cause an
expense equal to that of maintaining B
batteries.
It is the purpose of this article to describe
the theory and construction of a universal
B-battery substitute having excellent oper-
ating characteristics on all types of re-
ceivers, and an unusually long life. The
cost of construction will not exceed twenty-
30 Henries
By ROLAND R BEERS
underlying the design of eliminators that
are appearing this fall have brought forth
new facts which are extremely important
for the attainment of high quality perform-
ance. Many weaknesses were present in
the designs of last year's models: but the
research of the last twelve months has
succeeded in building up units of recog-
nized quality and dependability.
30 Henries
2-4 mfd
2-4 mfd.
28 mfd.
28 mfd.
FIG, I
Two types of filter circuits. That shown in
Fig. i A is the "smoothing" filter popular in
1924 while the circuit, shown directly above,
is the "brute force" or reservoir type so
highly efficient
five dollars, and, as all parts are readily
available, the entire unit may be con-
structed at home. Several ad-
vanced features are present in *3M
the design described below.
Battery eliminators gener-
ally consist of three major ele-
ments: A Transformer to con-
vert the 1 10 volt a.c. supply to
the required voltages; a rectifier
which converts the a.c. into
pulsating d.c. and a filter cir-
cuit which smooths out the
irregularities of the rectified
voltage into a uniform d.c.
Most of our readers are al-
ready familiar with these ele-
ments from previous articles
in this magazine. However,
the study and development
FIG. I A
In the discussion given below, the reader
will find complete instructions and draw-
ings for making a B battery substitute. The
general design is similar to that developed
by several manufacturers of new B battery
substitutes that will be marketed this fall.
Complete dimensions, list of materials, size
and turns of wire, etc., are given for those
who want to make up a complete unit
at home. This construction can be very
easily accomplished, but for the conven-
ience of those who prefer to use factory-
made transformers and choke coils, units
are described wherein use is made of these
parts manufactured by the Acme Appara-
tus Company, General Radio Company,
Dongan Electric Manufacturing Company,
and Jefferson Electric Manufacturing Com-
pany. On 6o-cycle supply, any of these
manufactured parts may be employed with
excellent results, and the appearance of the
O INCE our September, 1924, number RADIO BROADCAST has printed the
*J best and almost without exception the only material on chemical and tube-
rectified plate supply units. The present article invokes nothing startlingly
new, but it does describe a new rectifier lube which should have a very wide appli-
cation and popularity for this type of service. The Raytheon tube, whose use is
described here, has no filament. This simplifies the step-up transformer wind-
ing, since no extra tap-off from that winding is necessary to supply current for a
filament. This unit is also a full-wave rectifier which produces a much smoother
potential supply than the other types and simplifies the problem of filtering the
output. One of the features of construction of the transformer in this unit is a
shield around the primary of the transformer which effectively prevents any stray
noises present in the power line from reaching the secondary and being com-
municated to the rest of the radio circuit. Such a device has never been described
before. The problems of construction and assembly are unusually few.
— THE EDITOR.
unit using them will certainly surpass that
of the home-made model. The photo-
graphs, Figs. 4 and 6, show the construction
of models employing factory parts.
THE RAYTHEON TUBE
'T'HE very heart of this device is the
*• new Raytheon rectifier tube, which
has been developed for this specific purpose.
The characteristics of this tube are quite
revolutionary in their nature.
In the construction of this tube, two
anodes are provided, so that the tube
rectifies both halves of the alternating
current wave. This feature is of first im-
portance because it greatly simplifies the
problem of filtering to obtain a pure d.c.
supply. An additional feature made pos-
sible by the small anode area is that it
permits but a minute fraction of the current
to flow during the reversed voltage period
of the current-flow cycle. Many rectifiers
operating on the gaseous conduction
principle give forth an extraordinarily
high "back current", as it is called, which
-WWW"
3040 Henries
4 mfd.
J WWW1-
30-40 Henries
2 mfd. 8-16 mfd..
FILTER CIRCUIT COMMON IN NEW MODELS
FIG. 2
A filter circuit common in new models. The
intelligent use of chokes and filter condensers
here insures smooth output
frequently rises to such a value as to be-
come of great danger to the life of the tube
and unnecessarily complicates the filter
circuit problem. In the Raytheon tube
it is extremely difficult to de-
^^^~|6v tect the back current by even
the most sensitive measuring
instruments.
The Raytheon rectifier has
been designed to meet the re-
quirements of most of the
standard B-battery substitutes.
Its starting voltage is very low
— approximately 155-160 volts
— and its current carrying
capacity is high. The Ray-
theon tube type B is rated at
60 milliamperes at 150 volts
d.c. output. As there is no
filament to burn out, the life
of the rectifier is extremely long.
Standard Raytheon tubes
DECEMBER, 1925
AN IMPROVED PLATE CURRENT SUPPLY UNIT
187
150
50
have been on test at maximum
output for more than 4000 hours,
and have not yet shown signs
of deterioration. It is doubtful
if the maximum life of these
tubes can be determined at
intermittent operating periods
such as they would receive in
the ordinary operation of a cur-
rent tap. If they were not
abused by overload or continued
short-circuit, they should last
for years.
The operation of the Raytheon
tube in a B-substitute is unusu-
ally quiet. The reason for this is
that the gaseous discharge is en-
tirely enclosed. There cannot
be any sputtering of the dis-
charge which might occur if the
elements were exposed to the glass tube or
insulators. This act conserves the helium
gas with which the tube is filled, and greatly
prolongs the tube life.
The operation of a properly designed
current tap employing the Raytheon
rectifier tube has unusually good charac-
teristics. Some of these will be pointed
out in connection with
points previously explained.
First of all, we have excep-
tionally good "regulation."
The impedance of the Ray-
theon tube increases with
load, causing an upward
curve in the load character-
istic, in distinction to the
usual straight line falling
curve that gives low volt-
age at full load current.
The fact that the output
voltage does not fall off as
rapidly as usual obviates
the necessity of providing
an excessively high trans-
former secondary voltage.
The lowered a.c. voltage is an important
contribution to the safety of operation of
the device.
The current and power capacity of the
Raytheon tube are sufficient to supply the
greater majority of radio receivers. The
current output is rated at 60 milliamperes
at 1 50 volts and it has been found from
measurements of the plate current con-
sumption of large numbers of receivers that
Regulation Curve of B- Eliminator
Using Raytheon Rectifier
Dashed Straight Line Shows
Equivalent Regulation Without
Decrease of Impedance in Tube
Which Occurs with Increasing Load
10 20 30 40 50
OUTPUT CURRENT IN MILLIAMPERES
FIG. 3
this value is more than sufficient for the
demands of most receivers.
The filtering problem in plate current
supply units is usually one of high cost
and considerable difficulty. When the
Raytheon tube is employed, as it gives
rectification of both halves of the a.c. wave,
the filtering requirements are much simpler.
60
Another 'important feature
presented by the Raytheon rec-
tifier is that it requires no power
for lighting a filament. This
power very often demands a
large transformer supply, the
cost of which is an item of great
importance. With the use of the
Raytheon tube, a complete B-
substitute can be made up in a
space no larger than a heavy
duty B-battery.
After a consideration of the
foregoing remarks, we may write
a set of specifications for the ideal
B battery eliminator of to-day:
HOW TO BUILD THE APPARATUS
w:
LIST OF RAW MATERIALS REQUIRED
6 Ibs. Silicon Steel ? 1.20
28075. No. 31 d.c.c. wire 2.19
12 ozs. No. 32 d.c.c. wire .94
y-2-Mfd. Condensers • 12.25
1-0.5 Mfd. Condensers .90
2-0.1 Mfd. Condensers 1.40
i Bradleyohm No. 10 2.00
i Raytheon tube 6.00
i Standard socket .25
i-io,ooo-ohm resistance i.oo
I28..3
The prices quoted above are maximum retail prices. In some cases sub-
stantial reductions can be obtained from the costs given.
Here one tube does the work of two at a
great saving in cost, and at a higher
efficiency. As indicated previously, there
is no back-current perceptible. Back-
current is a bad feature from a filtering
standpoint, as it complicates the filtering
problem, and heats up the choke coil wind-
ings often to an injurious degree.
E WILL now proceed with
the building of the elim-
inator. Figs. 4 and 6 show the arrange-
ments of the parts when the unit is assem-
bled from factory models. The basis of
these models lies in the circuit diagram, a
schematic drawing of which is shown in
Fig. 7. The values of capacity, inductance,
and resistance shown in this diagram have
been determined after considerable inves-
tigation, and the builder will
do well to adhere to these
quantities as strictly as pos-
sible. These instructions
also apply to the construc-
tion of the home-made
transformer and chokers
described below.
Dimensions for the trans-
former used in this elimina-
tor are shown in Fig. 8. The
reader will do well to refer
to pages 640-650 of the Sep-
tember RADIO BROADCAST
for a general discussion on
the proper method of wind-
ing and assembling trans-
formers. For the benefit of
those who cannot secure copies of this
number, a brief discussion of the general
procedure will be helpful.
The transformer is made up of three coils
of insulated copper wire wound over a
core composed of a large number of strips
of No. 29 gauge Apollo special electrical
steel. These strips are carefully cut by
hand from an old power transformer or
RADIO BROADCAST Photograph
FIG. 4
A compact model of the battery eliminator described here. Note the large con-
densers which are employed in the filter circuit to insure a smooth d. c. output
188
RADIO BROADCAST
DECEMBER, 1925
110
Volts
A.C.
Transformer
cnoKe j
H® VJY"^ ~^P^ ^ 1 i-c»l "^ ^~
! ' mfd i^ — K 4i«* i-*1 'vn r«" 4=^ K»
i i
2 mfd. j
Condenser
C»i— i «"— ' ' "
Li'-Crj "---CU C3S»i J
High Low
Switch"'
t
10,000 Bradleyohm
to _,-•
100,000 ~v' //'
Dhm ' I .
r.j DC eter- ~"S®
Sjjl J | c%^.-:rzrz^p
v Bradley unit
15,000 Ohms
FIG. 5
A picture diagram and wiring layout of the eliminator whcse circuit is embodied in the diagram Fig. 7
from sheets of the proper material, and
shaped into the forms shown in Fig. 8.
Enough pieces are cut out to make up a
complete core of the dimensions given in
Fig. 8, when they are assembled and
clamped together in a vise to determine
if the required amount of steel has been
prepared. All rough edges must be re-
moved, and the dimensions shown must
be uniformly attained.
There are three windings on the trans-
former which are wound in place on the
winding form illustrated in Fig. 9. The
winding spool may be assembled on a long
stove bolt with nut and clamped in a hand
drill, carpenter's brace, or in the chuck of a
lathe for convenience in winding the coils.
Some means should be provided for count-
ing the turns exactly as they are applied.
If the ratio of turns of the hand drill is
known for one turn of the handle, it is a
very simple matter to use this factor in
counting the turns as they are applied.
Care should be used to obtain within one
per cent, of the specified number of turns
on each winding. The primary winding is
applied first over the entire length of the
winding form, and consists of 1250 turns
of No. 31 enameled copper wire, with a
tap taken out and insulated at the loooth
turn. Two layers of Empire cloth are
placed over the primary winding, then the
two separate secondary windings are
wound, each of which consists of 2900 turns
of No. 32 enameled copper wire, These
two secondary windings are insulated from
each other at the middle of the winding
form by means of a rectangular separator
of .oio-inch fiber. This separator is cut
out after the primary insulation has been
applied, and is put in place by means of a
slot cut in one face of the separator. See
Fig. 9.
While the first secondary is being wound,
the remaining winding space is tightly
filled up with a number of strips of cotton
muslin or cotton tape, in order to prevent
the wire from crowding the winding separa-
tor out of place. In all cases, insulated
leads 8 inches long, of flexible stranded
wire (six No. 30 d.c.c. wires twisted to-
gether are satisfactory) are soldered to the
ends of the windings for terminals, before
the ends are brought out from the winding.
Each terminal is tied in place in order to
prevent its being ripped from the coil by
accident. If it is necessary, thin strips
of paper may be laid over each layer of
wire as it is completed, in order to insure
smooth layers in the winding. When the
coils are completed, the outside is wrapped
with two layers of Empire cloth or heavy
manila paper as a protection and an insula-
tor.
The steel laminations are now inserted
one by one in the completed winding, as
shown in Fig. 8 and the transformer is
bolted together. If it is not convenient
to drill holes in the laminations for the
clamping bolts, the builder may cut out
clamping plates from hard wood or angle
iron. In such case, the bolts will pass
through the ends of the clamping plates
at the ends of the core, instead of through
the holes therein. Fig. 1 2 shows the method
of clamping adopted by the author in pref-
erence to drilling holes in the core. If the
builder desires, he may put mounting
FIG. 6
A different view of the eliminator employing manufactured parts
DECEMBER, 1925
AN IMPROVED PLATE CURRENT SUPPLY UNIT
189
Ll
2 mfd
8 to 10 mid
°5
-Ol
TRANSFORMER
Resistances Rj& R2-15,OOOOhms
R1-NolOBradleyohm
Condenser C-0.5uld.
Reactance Coils Li 4 L2
sary under the operating conditions. When
this has been accomplished, the clamping
plates are secured as described above.
The filter condensers, shown in Figs. 4 and
6 were procured from Tobe Deutschmann,
Cornhill, Boston, Massachusetts, and have
passed themost severe operating conditions.
They were subjected to repeated charging
and discharging at 700 volts d.c., and
FIG. 7
The circuit diagram of the entire eliminator unit. The trans-
former at the left steps up the line voltage, passes it to the
double-wave tube which rectifies both halves of the cycle.
Thence it is passes to the filter where it is smoothed out into
pure d. c. The resistances permit the tap-off of the desired
voltages necessary to the operation of the receiver
brackets on the base of the transformer to aid in se-
curing the instrument to the base board.
NEXT, THE CHOKE COILS
THE choke coils, shown at L, and U, Fig. 7 are
constructed in a manner similar to that employed
in the making of the transformer. Each of these coils
will have an inductance of approximately 20 henries
if care is taken in constructing and assembling the
cores. All rough edges should be removed and the
cores should be assembled in an orderly manner.
The winding on each choke coil consists of 5000
turns of No. 3 1 enameled copper wire, wound in smooth
layers with the necessary interleaving papers. The out-
side of the completed coil is wrapped with one layer of
heavy manila paper as a protection. The laminations
shown in Fig. 10 are inserted in the completed wind-
ings, and the entire coil is assembled in accordance with
the description of the power transformer above. A piece
of .ooj-inch paper is inserted in the air gaps of the
choke coil cores, to insure the magnetic stability neces-
, Mounting Holes to Pass y,J Bolt-,
6
\^
I *
1
1
t '
-J .'
*"*t Ol
O rg
Y i
o
O
! 1
,i
+ j
UU25"->1
1
< 2.75" ...
•c-U25"->
ASSEMBLED TRANSFORMER CORE
•"]
,
tflt*
K
^ «•
1
I
C* |
1
L 1
., 1
C
WINDING FORM FOR TRANSFORMER COILS
Jz
I~.l
FIG. 9
it-
-}g°Slot Cut Through
0
A A
I
•
O
<-1.125->
• •
O\ t*>
Csj 0
t
f
O
^
O
LAMINATIONS FOR TRANSFORMER CORE
Material: No 29 Gauge Apollo Special
Electrical Steel.
Required Approx. 80- Pieces of each Type
Total Core Weight:Approx.3Lbs.
ASSEMBLED TRANSFORMER WITH WINDINGS IN PLACE
FIG. 8
~ransformer core details
WINDING SEPARATOR FOR SECONDARY WINDINGS-^g FIBRE
withstood the strain upon the
dielectric successfully. None of
the samples examined in this
way were found to break down.
The equivalent series resistance
was found to be low enough to
give excellent results in connec-
tion with the B battery filter
circuit. The particular arrange-
ment of the filter circuit shown
in Fig. 7 requires a total capac-
ity of 14 mfd. and the distribu-
tion of this quantity is more im-
portant than the absolute value.
If this circuit does not meet with
the requirements of the attached
receiver and loud speaker, a
slight improvement will be ef-
fected by increasing the value
of C3 to 12 or 1 6 mfd. Increas-
ing this capacity beyond 20 mfd.
does not add greatly to the stand-
ard of quality already established
and, for average conditions, this
capacity need not exceed 8 mfd.
The arrangement of the detec-
tor voltage control shown in Fig.
7 is unique in some respects,
and is an improvement over the
usual series resistance method.
A 0.5 mfd. condenser is used
to by-pass any disturbance that
might reach the detector through
other paths. The amplifier volt-
-Transformer Coil
Primary Winding 1250 Turns No.31 Enamel
2-Secondary Windings each 2,750Turns
No.32 Enamel
.005" Copper Shield between
Primary and Secondary
190
RADIO BROADCAST
DECEMBER, 1925
,3/ie ,-
Copper • 10 oz. Steel • 1!< U)S
2 9" _ %2 R.H. Iron Mach. Screws
4-R«
0.45"
I- Required with Hex. Nuts
- •+' -4 0.45"
-H* - •+'
T°-55T
0.45
0.45"
O.OlORed Fibre Strip
,' 0.9"x 29"
Material: No 29 g.
Apollo Special Electrical
Steel. Required:Approx.
48 Pieces each Type
FIG. IO
Here are given all the specifications
necessary for the construction and
assembly of the choke coil cores
Separate Spool Heads
0.45°
LAMINATION FOR TYPE B REACTANCE COIL
ASSEMBLED REACTANCE COIL TYPE B
age is controlled by means of the switch shown at S, Fig.
7. The blade of this single pole, double throw switch is
connected to one side of the 1 10 volt a.c. line; one lug goes
to the loooth turn tap on the primary, the other lug goes
to the full secondary terminal at 1250 turns. When the
switch is thrown to the loooturn tap, the output voltage
will be from 30 to 50 volts higher than on the 1250 tap,
depending upon the connected load.
The Raytheon rectifier tube will ordinarily run at a tem-
perature in the neighborhood of 200 degrees F. In case
the cup should become red hot, there is evidence that the
circuit is being overloaded. Although no permanent dam-
age will be done, it is not advisable to continue this load for
more than a few minutes. Continued overloading will
soon saturate the cores of the choke coils and render them
useless as filter chokes.
In order to prevent the transmission of power line noises
through the eliminator circuit, a coppershield has been placed
between the primary and secondary windings, and thoroughly
insulated therefrom. This consists of a strip of .oo5-inch cop-
per carefully wrapped over the Empire cloth insulation, and
extending within \ inch of the entire periphery of the primary
winding. A flexible lead is soldered to the shield, brought
out from the winding, and later connected to the ground ter-
minal of the eliminator. All cores of the instrument should
be connected together and to the ground terminal. The
homemade unit should be placed in an iron or steel case which
completely encloses the unit. In the case of the factory
units, each part has been placed in an iron magnetic shield,
and this is connected to ground to prevent induction of hum
in the receiver. Another means for preventing the transmis-
sion of line noises through the eliminator is the use of the
buffer condensers, shown shunted across the mid-tap and
outer leads of the secondary of the transformer, Fig. 7. These
„.__,$•—-.»
2*"
jh
Hf
O
.>U- 1"— 4* i
t 2X" — -
WINDING FORM FOR CHOKE COILS
Material: Wood Winding: S.OOOTurns No31 Enamel CopperWire
FIG. I I
2.
3-
Specifications for the Design of Ideal B Battery Substitute
i. TRANSFORMER
Power loss should not exceed 10 watts.
Should operate on 25 to 75 cycles a.c.
Secondary voltage should not exceed 300 volts for safety.
Should be shielded in magnetic shield.
Should have electrostatic shield between primary and secon-
dary windings to prevent transmission of line noises to
radio receiver. Secondary winding should be balanced
for inductance and capacity.
II. RECTIFIER
Should have life of at least 5000 hours.
deliver sufficient current at all times,
have low impedance, preferably rising characteristic.
(See Fig. 3).
Should rectify completely with no reverse current, and with
quiet performance at all times.
Should rectify both waves of cycle.
Should have low starting voltage — i.e. not greater than 160
volts.
III. FILTER CIRCUIT
Should filter perfectly, leaving no hum in headphones.
D.c. resistance should not exceed 750 ohms.
Should consist of two or more sections instead of one section.
IV. MISCELLANEOUS
Should give complete control of amplifier and detector voltages.
Should be small and light in weight.
Should be capable of being installed in receivers without
producing interference.
Cost of construction and maintenance should be low.
each have a capacity of o. i mfd. and
serve the purpose of balancing the ad-
mittance of each secondary to the neu-
tral or ground side of the line. There is in
this way an easy path to ground provided
for any disturbing unbalance that might
arise in any part of the circuit. The in-
clusion of these condensers is an important
feature, and one that will more than repay
their cost.
FIG. 12
A made-up transformer
with its tin-can shield
AS THE BROADCASTER SEES IT
CARL DREHER^,
Drawings by Fran\lyn F. Stratford
In Defense of Broadcasting
IN THE September issue of the American
Mercury, under the rubric of his monthly
department, "The Theatre," Mr. George
Jean Nathan pays his respects to broad-
casting in terms which will descend
harshly on the ears of radio impresarios who
were beginning to believe what their own
publicity representatives write about them.
Supporting the cheap magazines and moving
pictures in their campaign to moronize the
country, writes Mr. Nathan, we now have the
radio. The roofs of houses from the Atlantic
to the Pacific presently take on the aspect
of so many sailless schooners. And nightly
the front parlors of the proletariat resound
to the strains of alley jazz pounded out by bad
hotel orchestras, to lectures on Swedenborgian-
ism by ex-veterinary surgeons, to songs about
red hot mammas and Beale Street melancholias
by hard-up vaudeville performers and to the
names of the notables who have just come
into Reuben's delicatessen restaurant.
Where a few years ago, a family living in
the hinterland occasionally after dinner read
a book or at least looked through an album
of "Famous Masterpieces of Painting," it
presently glues receivers to its ears and is
thrown into wild aesthetic transports by
some Harlem coon's recitative on his Heimweh
for Alabamy or some two-a-day De Pach-
mann's interpretation of Mozart on a saw.
There are two radio broadcasting stations,
one in New York and one in Philadelphia,
that have made an effort periodically to give
their customers something better in the way
of music than that which, for its finest effect,
must be played on kitchen utensils and cow-
bells and something better in the way of
educational talks than lectures on hygiene
by press agents for new mouth-washes, but
I understand that they have found the going
rough and, in self-preservation, have been
forced to fall back more and more on the
gibberish and caterwauling that the aerial
connoisseurs admire.
Readers who have never before encoun-
tered Mr. Nathan's mode of expression will
observe that he does not deal in weasel
words. He makes it plain that no high-
pressure salesman is going to sell him a
1575. radio set. Not that Mr. Nathan has
anything against broadcasting in partic-
ular. In the article from which 1 have
quoted he rends and tramples on the twenty
cent magazines, the movies, tabloid news-
papers, and other such agencies of popular
enlightenment. If you were the editor of a
tabloid newspaper, how would you like this
projectile: "A tabloid newspaper, you need
not be told, is a newspaper reduced in size,
sense, taste, and decency." Mr. Nathan lets
radio off easy, comparatively speaking.
Many broadcasters, unused to criticism
along old fashioned football lines, will roar
indignantly and let it go at that. That
attitude possesses neither maturity nor good
sense. If the critic has no case, what he says
will in time dissipate itself, like gasolene
vapor on a boulevard, and there is no need to
get het up about it. If what he says is true,
wholly or partially, we might as well let him
rub our noses in it and then see what we can
do about it. And then, criticism is adver-
tising, and no one can tell me that broad-
casters don't like advertising. In this they are
WHEN IN DOUBT, THEY WIELD THE BLUE
PENCIL
like George Moore, who used to say, according
to Frank Harris: "Attack me as you please;
slang me, but write about me. I'd rather
have a libelous article than silence; indeed,
I think slander more effective than eulogy. If
you hate my books, say so, please, at length;
that will get me readers."
As for me, I can discuss this subject in a
serene and unprejudiced spirit. While I am
a professional broadcaster and derive most
of my income from radio, my responsibilities
are purely technical. I am an engineer and
I put out on the air what is given to me, just
as a telephone installation man wires up
equipment indiscriminately for crooks, phil-
anthropists, theatrical ladies who drive
Minerva cars on an apparent income of $35.
per week, and gentlemen of the cloth. The
gentle rain falls alike on the just and the un-
just, and I don't care what I broadcast.
It's no skin off my back if the programs are
rotten. As long as the transmission is
good, I get my check and the V.P. & G. M.
smiles on me. So much for the benefit of
those spectators who might imagine that I
am moved in my defense of broadcasting —
to the extent that I feel called on to defend
it — by my need for Hungarian goulash and
French pastry.
Mr. Nathan's indictment is true enough,
alas, but it should be added that he has
selected the holes in the cheese for his dis-
cussion. There is considerable nourishment
in the solid portions. Among some 600
broadcasting stations in operation in the
United States, at any given time, some will
be radiating respectable stuff, others will
be carrying a load of aspiring sopranos and
so-so material, still others will be engaged
in purveying aerial garbage for the listeners
who like that sort of thing. A cross-
sectional view of the burden of the ether
waves would show as great a variety in
quality as the same process applied to peri-
odical publishing, say. If one. walked
blindfolded up to the newsstand at the
corner of Sixth Avenue and Forty-Second
Street in New York, picked out a magazine,
opened it at random, and analyzed the pages
exposed for ideas, the percentage revealed
would probably run even with the birth rate
among mules. And that newsstand, be it
noted, carries all the respectable magazines
192
RADIO BROADCAST
DECEMBER, 1925
as well as the cash girl trade; at most magazine
stores the chances of lighting on something in
the cultural Class A would be even less. If
you are after intellect and good taste, you
must pick it out from amid the rubbish.
Likewise in radio. If you want jazz issuing
from your loud speaker, there are certain
wavelengths in every radio locality where you
can get it at any time. If you want something
better, you may be able to get it if you have
learned to discriminate between stations.
You may not be able to get it just when you
want it. But there is just as wide a range
between the best and the worst broadcasters
as that between the most estimable and the
most trashy books or magazines. And, owing
to the vast and, perhaps, excessive amount
of broadcasting, there is also a great variation
with respect to time in the case of any given
station. In order to arrive at a fair judgment,
one would have to assess a lot of broadcast
material and to do far more listening than
Mr. Nathan has either the time or the
inclination for, in all probability. As one of
his customers in his present vocation, I
should lament his engaging in any such
Augean task. But I, perforce, have done
something of the sort. In the last two and
one half years, equipped, gratis, with a very
fine receiving set, I have put in some 3000
hours listening to my own stations and others.
Some of the stuff was not fit to inflict on an
ursine howler. Most of it, culturally, was
neither here nor there, like the columns of a
newspaper or the counters of a five-and-ten-
cent store, it had nothing to do with learning
the arts, or civilized taste. It neither assisted
nor came into conflict with these things.
Some of it, the cream, required no apologies
to any one. For three summers, now, any one
who cared to tune to 600 kc. (455 meters) could
hear the New York Philharmonic on the air two
or three nights a week, absolutely "without
concessions", as the management puts it,
to the popular taste for operatic selections,
easy overtures, and the like. Having thus
thoroughly sampled the etherial waves, and
emerged sound and articulate, I depose and
say that the average metropolitan broad-
casting performance is no more offensive to
good taste than the average printed book
or magazine, not half as disturbing to the same
as the average city newspaper, and not one
quarter as flagrant as the average big time
vaudeville show or moving picture. As for
the tabloid newspapers and other such dung-
hill enterprises, broadcasting, with all its
glaring faults, is positively a civilizing influ-
ence; by contrast, its entrepreneurs and
managers become so many Schopenhauers,
and Sidney Laniers.
It is true that a great many silly and obvious
talks get a hearing via radio, and that not a
few of the lectures have an unpleasantly
sanctimonious and oily tone. The second
fault is caused partly by the influx of people
quite without qualifications for radio lecturing,
who try to compensate for their deficiencies
by slobbering over the listeners. On the other
hand, one hears more than a few people on the
air whose natural frankness and sincerity
manages to get through to the orifices of the
loudspeakers. Dr. John H. Finley is one
such engaging speaker; even if one does not
agree with what he says it is pleasant to listen
to him. As for the content of the talks, it
varies all over the map. I have heard every-
thing from an inspirational speaker (he broad-
cast in a frock coat, incidentally) declaring,
"All the evils of the world are due to incorrect
thinking," to a lecture on Whitman by such
a recognized authority as Prof. Emory Hol-
loway, the reading of a story by Sherwood
Anderson, and performances of one act
Provincetown plays.
The trouble with radio talks is mainly that the
owners and program managers of the stations
feel it incumbent on them not to offend anyone.
They are in a constant stew about "adverse
publicity." A few letters from irate listeners
give them the horrors. They run their stations
for advertising or good will, and as soon as
any one looks at them cross-eyed their knees
shake. When in doubt, they wield the blue
pencil, and any one who tries to please the whole
world is in doubt most of the time. In such
large audiences as those they figure they are
catering to, there are thousands of inferiority
complexes ready to be triggered off. Eddie
Cantor once delivered a first-rate humorous talk
RADIO IS TRYING TO PLEASE ALL BETWEEN EIGHT AND EIGHTY
over the radio, and at one point he remarked
extemporaneously, " For all 1 know a lot of
Polacks are listening to me." The comedian,
of course, had no offensive intention, but during
the next few days he received twenty protests
from Polish listeners, including a formal de-
nunciation from a society. If I wrote a story
containing some reference to an elderly Jew in a
green sport suit, and there was nothing else the
matter with it, there would be no difficulty in
getting it published and receiving payment for
it. But broadcasting that phrase, at the present
stage, would be out of the question. No pro-
gram manager would touch it. In his audience
of several hundred thousand there must be
several elderly Jewish gentlemen who wear
green sport suits, and he wouldn't make them
sore for the world. No one must be offended,
no one's morals must be impaired, a thousand
dignities must be tenderly preserved, the lecture
must be fit for everyone between the ages of
eight and eighty. If, under these conditions, the
content of the talk is also to be mature and
significant, you have a large order.
Even controversy is often frowned upon.
Admiral William Ledyard Rodgers and General
Tasker Howard Bliss recently broadcast a debate
on "Shall America Arm for War?" under the
auspices of the Forum. The debaters did not
come to blows, no riots were reported, and the
more thoughtful among the listeners spent a
profitable half-hour. The magazine next wanted
to put on the air a debate between Professor
Osborn and Mr. Bryan on the subject of Evo-
lution. But this was declared to be "too
controversial" by all the station managers
interviewed. So it was not broadcast.
Mr. Nathan's conclusion that jazz is the staple
radio musical diet does not jibe with my ob-
servations. There is a great deal of jazz on the
air, and a few stations emit almost nothing else,
but they are decidedly atypical. The average
musical radio offering is rather something on
the order of the Silvestri-Toselli "Rimpianto"
serenade — pretty and obvious. In short, the
sort of thing all dining room orchestras in big
hotels turn out. Some of the hotel "ensembles"
are very good, incidentally. They broadcast
popular classics. If 1 have heard " Mon coeur
s'ouvre a ta voix" once, I have heard it a hun-
dred times. There is a lot of Old Black Joe-ing
and Silver Threads Among the Gold on the air,
but, after all, these are decent folk songs, ob-
jectionable only when overdone. Down another
pegare college things like " Rolling Down to Rio,"
and the bombastic "Invictus." Not over a
third of the total is jazz, and on top you have
beautiful Lieder, the best symphonies, including
all the Brahms, the tone poems (I have heard
Don Juan on the air in its entirety seven times)
and the Strauss waltzes. At one station in
New York, for example, absolutely no dance
music is allowed on the air until after 10.30 in the
evening. All in all, not so bad.
Such inventions as the motion picture and the
radio telephone have cultural and artistic
possibilities, which are rarely realized because,
with a large initial investment and heavy oper-
ating expenses, the only way to get a return on
the money is to produce something attractive to
the masses. The result is what we know. Only
two copies of Thomas Hardy were sold in Boston
in the six months from January i to July i,
Mr. Nathan points out. Still, the movies could
do something even for Hardy's art. Need-
less to say, I don't mean any such shameful bur-
lesque as the movie version of Tess of the d'Urber-
villes which appeared a while ago. But if I
had a few million dollars, I'd make a moving
picture of Hardy's The Dynasts and perform
it, serial fashion, a competent actor, to be
DECEMBER, 1925
HOW OUTSIDE PROGRAMS ARE PICKED UP
193
selected by Mr. Nathan, intoning the lines,
to the accompaniment of a first class symphony
orchestra. 1 should do this, not to improve
the movies, which can go straight into the sewer
for all I care, but purely for the benefit of the
few who care for that sort of thing. The Na-
poleonic wars forming the background of Hardy's
great epic, the transparent tentacles of the
Immanent Will, moving irresistibly those great
columns of soldiers wearing the expression
of men in a dream, could only be portrayed in
the medium of the cinema.
Similarly, some day, somewhere, a millionaire
with American Mercury tastes may endow a radio
broadcasting station to disseminate material
which is agreeable to him. If so, I shall be
pleased to oil the generators for same, and
to be counted among its listeners. Mr. Nathan
might buy an eight-tube "super" on that remote
to-morrow. In the meantime, radio is neither
as good as the publicity artists would have us
believe, nor as bad as Mr. Nathan has painted it.
Technical Routine in Broadcasting
Stations
i. Wire Lines
¥ AST month, in our discussion of "Per-
sonnel and Organization in Broadcast-
•1 — ' ing," we took up in some detail the
responsibilities and functions of the various
employees, program and technical. However,
the bulk of the discussion was on the problem
of securing programs, rather than broadcasting
them. In this issue we shall get down to the
actual business of putting the program material
out on the air. with all the technical preliminaries
involved.
The technical staff, as we have seen, is divided
into transmitter, control, and field divisions,
all reporting to an engineer-in-charge or chief
technician of some sort. These men work with
the announcers and the studio manager during
the actual broadcasting. First, however, we shall
take up the technical routine which precedes it.
This technical routine, in many respects, is
not radio at all. For example, the testing of
wirelines is no more characteristic of broadcasting
than of wire telephony, but it is equally import-
ant in both. Practically every large broadcast-
ing station finds it necessary to go after its
programs by means of telephone lines. These
lines are in a few cases owned outright by the
broadcasting company, but as a rule they are
leased from some pre-existing telephone or
telegraph company. Lines are costly and one
does not generally buy them out-
right, any more than one buys a
railroad in order to commute.
When the lines are leased from
some public service corporation,
they are usually maintained by the
owners. Such a system will con-
sist of certain trunks running
through the principal part of the
town, possibly in the form of a
ten-pair cable devoted exclusively
to radio, for it is important that
these wires should not be subject
to inductive disturbances and that
they should not interfere, in turn,
with other public services.
A week or more before the time
scheduled for broadcasting, the
program department sends a list
of projected field events to the
line company. On a certain day,
for example, a musical comedy is to
be broadcast from a theatre. The
wire company then runs a twisted pair from a
convenient terminal box on the nearest trunk,
over housetops and streets, to the theatre in
question. This lead is called a "lateral." If
the broadcasting company is leasing an adequate
wire system these laterals are normally only a
few blocks long. The expense of work and
material is charged to the broadcasting company,
so it is wise for the latter to balance trunk costs
against additional construction in order to get a
minimum total for the two. When the wire
is placed in the theatre, with a long lead left
in a coil so that the broadcasting operators can
set up at a convenient point in the house, the
telephone or wire company's lineman calls
up the station, using an ordinary portable
telephone, and tests through. He rings the
station with a magneto, causing a telephone
relay to release a drop on the station switch
board, and says to the control operator who
answers. " This is at the Criterion Theatre.
Will you test this loop?" The operator then
puts no volts on each side of the line through
a voltmeter to ground. If the loop is properly
insulated the meter will read only a few volts, the
resistance in series with it being of the order of
many megohms. The ends of the pair are then
short-circuited at the theatre and a continuity
test is made to locate high resistance joints and
the like. If the line is in good shape, the meter
will read practically full voltage, the line resis-
tance being negligible compared to the resistance
of the voltmeter. So far we have merely the
standard procedure which thousands of wire
chiefs go through every day on telephone and
telegraph lines. However, a further test is now
made in which radio standards are rather more
critical than those of the older services. The
men on the line listen for noise. If they can
hear any noise at all with an ordinary pair of
telephones bridged across the line, they are apt
to run into trouble during quiet intervals in the
broadcasting.
Noise comes in from various sources, such as
stock-tickers, parallel Morse circuits, elevator
motors, etc. Each of these machines has a
characteristic sound, and men who work on
lines become familiar with the various types.
Usually noise interference is due to some un-
balance of the line. It is necessary to have
the circuit accurately symmetrical, electrically,
about an imaginary reference line in the middle.
Fig. i shows this condition, the line terminating
at either end in repeating coils, or 1:1 trans-
formers, with grounded midpoints. Each side
is assumed to measure 60 megohms to ground.
If, now, one side of the line should be opened
or grounded, a roar of noise would probably
come in, although in the balanced condition the
circuit might be perfectly quiet. But it is not
sufficient to have the two sides of the line equal
in insulation resistance. It is also necessary
to transpose or interchange the two wires fre-
quently, so that induction picked up in one
stretch is neutralized in the next stretch of equal
length. On an open wire line running on cross-
arms fastened to poles, each pair of wires will
be transposed at, say, every tenth pole. Like-
wise, in a cable, the various wires must be
"paired." "Twisted pair" is used, never
simply a pair of wires lying side by side. In
a properly paired cable several miles long, a few
hundred feet of "straight-laid" conductor will
ruin the entire circuit for broadcasting purposes,
because of the excessive noise picked up. The
telephone engineers put it this way: "A tele-
phone circuit balanced in all respects, including
balance to other circuits, is immune to inductive
interference."
When trouble is encountered on wire circuits,
it is hunted down by the process of "localizing."
On long lines it is necessary to use special tests
which show the distance of the fault from the
testing point, but on short local circuits the
lineman simply cuts out a section and by pro-
ceeding in this way sooner or later reduces the
trouble to one section. He usually knows the
weak spots in each section — here the wire runs
through a damp cellar, and there it rubs against
a roof coping, and so on; and sooner or later he
finds the particular spot which is causing the
trouble.
Of course no circuit of any length is ever
exactly balanced, in practice, and in the presence
of very powerful inductive fields noise will
inevitably be picked up. For example, nearby
lightning will register on the best lines; high
tension leaks, power plant troubles, certain
types of automatic and multiplex telegraph
circuits, will interfere on almost any loop near
them. Even if a man has armor on, you can
probably kill him with a sledge-hammer or an
elephant rifle. The only answer is to keep
away from trouble-making types of service as
much as possible. However, various devices,
such as shielded, paired cables; anti-noise sets,
which slow down electrical impulses to a point
where they no longer interfere, have been used
with considerable success. Again, some types
of interference clear themselves through the
cessation of business activity in the early evening.
Ticker noise encountered on a morning test
of a certain circuit, which is to be used in the
evening for broadcasting, may be ignored if it
O
O
To Reid O
.Amplifier
ol
Mid-point
Ground
60 tn^ohnw
Mid-point
(ground \ ^.
O
To
TrABsmiHer
3
Repeating'
Coil
Coil
FIG.
Electrically symmetrical lines are necessary in outside "pick-ups." The diagram shows the cir-
cuit used. The field amplifier is controlled by an operator at the actual point of broadcasting
194
RADIO BROADCAST
DECEMBER, 1925
is known to come from certain financial houses
which close down at 4 p. m. In case of emer-
gency, it is sometimes possible to shut down
parallel, interfering circuits during the period
of broadcasting.
Broadcast operators and the lineman who
work with them know all these kinks and utilize
them in their work. The organization chart
shown last month did not include a lineman
among the technical employees, but as a matter
of fact, although this man is usually not on the
broadcasting station's payroll, he works in the
closest cooperation with the station staff and
is to all intents and purposes a member of it, and,
if he knows his business, no mean asset.
Regardless of previous tests, it is important
that every wire circuit which is to be used on a
certain day for broadcasting, should be tested
on that day some hours before the event is
scheduled. Accidents often happen at the last
minute. If the event is a very important one,
such as a presidential broadcast, or a major
prizefight, if may even pay to have the lineman
around till the job is done on the air. For these
occasions, also, it is quite necessary to have two
or three pairs, one for broadcasting, one as a
breakdown pair, and one for an "order wire."
For ordinary jobs a single pair is generally
sufficient. The operators talk over it until it is
time to take the air, and use it for post-mortems
afterward. Sometimes the wire is simplexed or
used for telegraph conversation during the
broadcasting without interference between the
two functions. This is not very common in
local work, but it is the usual thing on long
out-of-town circuits, where the cost of the line
is so great that all its potentialities must be
utilized.
Wire tests must not be left to any one's mem-
ory, but a log book, as shown in Fig. 2, is kept,
showing the condition of the circuit at the time
tested, and who is responsible for. the obser-
vations.
It is possible to have one control operator in
the station who is exclusively detailed for wire
line work, but the usual procedure is to have
the men rotate, so that everyone takes a turn at
it. Often the station is on the air in the morning
and the operator who runs the control room
at that time also takes care of the wire line
tests for the day, since as a rule the observations
are quickly made, and there are long intervals
between tests while the lineman goes from one
remote point to another. In a large station
one operator may be "on the channel," as
the saying is — watching what goes out on the air
and making necessary adjustments — while an-
other man handles the wire tests and does
maintenance work in the intervals.
One point that should not be neglected is the
removal of all laterals not in use on any given
trunk. Otherwise the laterals pile up, increasing
the capacity of the line to the point where the
higher frequencies are lost and quality of trans-
mission is adversely affected. These sections
hanging on uselessly may also bring in noise.
In a properly maintained wire system the trunks
are stripped of laterals at frequent intervals — •
and that does not mean every few weeks.
If the lines pass through telephone exchanges
or telegraph offices
the utmost care
must be taken to
avoid interference
by employees who
don't know what is
going on. The broad-
casting lines should
be red-tagged and a
special notice sent
around cautioning
all unauthorized peo-
ple to keep away.
Most telegraph and
telephone men have
little notion of what
broadcasting quality
is and they will some-
times innocently
break up a circuit in
order to get a little
amusement during
idle periods. At one
station it was noticed
that music coming
over a long line (some
five miles) was curi-
ously tinny — lacking
in the lower fre-
quencies. This was
just the opposite of what one would expect — the
suppression of the higher frequencies by the line
capacity. The engineers were somewhat puzzled
until one day one of them happened to be at the
main telegraph office in the city in question
and saw an idle operator plug a 6o-ohm telephone
into the jack panel of the broadcasting station,
in order to listen to the music. The circuit
was one terminating in joo-ohm impedances, so
this low inductance was effectively by-passing
all the lower frequencies. The engineer sent
a 2OOO-ohm headset down to the telegraph
office with a polite note to the wire chief suggest-
ing that if the operators wanted to listen in they
could use the high impedance telephones without
ruining quality on the air. But the wire chief,
receiving this epistle, flew high up in the air,
returned the 2OOO-ohm phones with thanks and
apologies, and posted a notice informing his
staff that any one who plugged anything into
those circuits without authority would be sum-
marily fired. Then there was peace.
Radio Lingo, Past and Present
SOMEWHERE in his writings or conver-
sations Anatole France compares a syn-
thetic language to a doll, while a natural
language, with its centuries of use, growth, and
development, he likens to a living woman. On
a more modest scale, the technical terminology
of an art or science, as it reflects the achieve-
ments and changes of years of effort on the part
of many men, takes on an almost organic mean-
ing and color. We usually think of objects like
antennas and microphones as purely inanimate
and lifeless, forgetting that they are the tools of
human aspirations and carry with them an eman-
ation of human emotions. The names of these
tools, and of the scientific ideas which they em-
THE WIRE CHIEF WENT UP IN THE AIR
body, and the way in which people talk about
them, all change with time. Not only do they
change, but they show a tendency toward poetic
figures of speech, and many terms which we use
daily in the most matter of fact way, if we stop
to examine them, show an interesting technical
and literary history. This is particularly the
case with radio terms, and I purpose to classify
and discuss some of these| now popular expres-
sions in the light of their origin and history.
Radio, contrary to the notion of many of its
devotees, did not start in 1920. It had its period
of development in the minds of men like Maxwell,
Henry, Heaviside, and Hertz, it was born three
decades ago, and it is now past its infancy. It
has borrowed from all the older engineering
arts both words and ideas. If, as someone has
asserted, one can understand a thing only by
understanding how it became what it is, an
examination of the technical jargon of radio
should be as instructive as an article on hook-ups
and super-circuits — and a little more out of the
ordinary.
Physical Characteristics
As in every field, the obvious physical char-
acteristics of objects suggest suitable names.
We speak of cat-whisker detectors, bulbs, tubes,
condenser plates, plugs, knobs, etc. Position
in space acts in the same way; aerial is the most
prominent instance. The types of aerials are all
named in the same way: umbrella, harp, fan,
V, inverted-V, flat-top, inverted-L, and T.
In these cases the name, or the figure of speech,
was suggested by the physical appearance.
Somewhat the same process occurs with in-
ductance coils. We refer to inductance spirals
and helices, and to honeycomb, latticework,
basket-wound or cellular coils where the criss-
FIG. 2
A typical test report made by broadcast operators on the condition of an outside wire used for picking up programs
LOOP NUMBER
TO
LEAKS TO GROUND
CONTINUITY
DATE
OPERATOR
465
Criterion Theatre
Tip Sleeve
8 8
118
9/15/2?
GN
DECEMBER, 1925
EARLY TRIUMPHS OF "WIRELESS"
195
crossing of the turns results in a cellular struct-
ure. This is the simplest and least imaginative
portion of radio philology.
Figurative Expressions
If to call an aerial by that name is an obvious
procedure — as well as a trifle out of date in those
instances where the aerial has been taken in out
of the wet to share the rarified atmosphere
with the vases and porcelain dogs on the Dutch
shelf of the living room — the term antenna is
a step higher in the literary if not in the physical
sense. This was originally a zoological name,
applied to the organs of feeling with which
lobsters, cockroaches, and other noble animals
poke their way. No one who has seen an insect
waving his antennae around when in an un-
certain situation, confronted, for example, by
an angry housewife with a mop, could have
overlooked the analogy with a crystal set owner
striving to receive Los Angeles from the Eastern
coast. A radio antenna is, in fact, an artificial
feeler or organ of sensation.
We speak of a "phantom" or "dummy"
antenna, as used for testing purposes where
radiation must be suppressed. Another figu-
rative expression in connection with antennas
is "counterpoise" — literally a counterweight —
applied to a network of wires beneath an an-
tenna, the purpose being to keep the electric
field away from poor conducting materials, such
as dry earth, and thereby to reduce the losses
of the transmitting system. It might really
be called a "counter-capacity."
The Memoirs of a Radio Engineer
VII
NOWADAYS radio gets the bulk of its
publicity through broadcasting. Some
famous opera singer performs for the
radio, or the President delivers a speech, and the
headline writers get busy. In the pre-broad-
casting era, maritime disasters in which radio
played a part were the principal source of pub-
licity for the art. Of course, at that time there
was a novelty about the whole business which
has largely disappeared since, so that incidents
like two stations exchanging messages over a
distance of a few thousand miles, would get into
the newspapers, while now no one pays any
attention to them. But anything that saves
human lives interests everybody, and it was in
connection with accidents at sea that many
people first heard of radio or had it called strik-
ingly, often unforgettably, to their attention.
It must be remembered that at this time, around
1910, communication with a vessel at sea was still
a novelty. The act requiring passenger-carrying
vessels making sea voyages more than 100
miles in length to be equipped with "wireless"
was passed by the United States Congress in
that year. 1 1 was not much more than ten years
before that the first radio set had been installed
on a ship. Along in the early part of the first
decade of the Twentieth Century, it was still
the usual thing for vessels carrying hundreds of
passengers to leave land and not be heard from
again till they reached their destination, or,
in some instances, not to be heard from again
at all. The sea swallowed them up, and that
was all. After radio was introduced, such
episodes became rare. Radio cannot prevent
shipwrecks altogether, but a great percentage
of them may be avoided by its use, and practi-
cally always help can be summoned when needed.
That help may be only partially effective, or it
may arrive too late, for, unfortunately, men and
ships cannot be transported with the speed of the
ether waves, and there are storms and situations
in which every ship has all it can do to take care
of itself, but at least one has the consolation of
knowing that what man can do was done.
Before radio got into the picture, a vessel could
burn up or founder with hundreds of people on
board, and another ship near by might go on its
way oblivious of what was happening. There
is no tragedy like an avoidable tragedy.
It was in 1909 that through the intervention
of radio such a tragedy was averted. The
White Star passenger steamship Republic collided
near Nantucket Light with the freighter Florida
and sank some hours later. But before she went
down she called for help on her wireless set,
operated by Jack Binns. That call, picked
up at Siasconsett, Massachusetts and by various
other coast and ship stations, resulted in all the
passengers and crew being taken off the Re-
public before she sank, and what would probably
have amounted to a loss of hundreds of lives
was limited to the six casualties which had
occurred during the actual collision. The
world sat up and took notice. Mafiy people
who had thought of the wireless telegraph as
merely an interesting scientific toy, changed
their minds overnight. Some of them bought
stock in radio companies, not all of it good.
Three years passed, with the number of wire-
less stations and activities in general increasing
rapidly. Then, once more, the aerial telegraph
played its part, effectively enough, and yet it was
not sufficient to obviate a great loss of life when
the S. S. Titanic, then the largest ship in the
world, sank 800 miles off the Grand Banks of
Newfoundland, at 2 a.m., April 15, 1912, after
striking an iceberg. The Titanic was driving
through the night on her maiden trip, trying to
make a record for the crossing (Those were the
days of rivalry between British and German
shipping interests) when her nose crashed into a
"growler" of moderate size, but large enough
to open the liner's compartments, so that she
sank only a few hours later. Although the
accident occurred in midocean, many vessels
were near, and if the Titanic could have managed
to stay afloat six or eight hours almost everyone
might have been saved. The nearest ship was
the Carpatbia and it was she who sped 58 miles,
under forced draught, in three and one half
hours, arriving at the scene of the disaster
at 4. 10 in the morning, to find lifeboats filled with
survivors dotting the icy sea. The dead num-
bered 1635, among them Jack Phillips, the
senior wireless operator, to whom the surviving
700 owed their lives, for it was his CQD and sos
calls that summoned the Carpatbia to the
rescue. Other vessels, the Olympic, the Birma,
the Virginian, and the Baltic, were on their
way, but turned around on hearing that the
Carpatbia had already done all that human
sailors in iron ships could do.
Great as the service of radio proved on this
occasion, luck and uncertainty played too great
a part in what followed the collision of the ship
and the iceberg. The Titanic carried an ade-
quate transmitting set, with a day range of more
than 400 miles and a night range which carried her
cry of distress far over the sea, and yet she might
easily have missed altogether the Carpathia,
the one ship near enough to give quick assistance.
It was also rumored at the time that one
freighter, unequipped with radio, was even
closer and might have taken off passengers
who could not find a place in the lifeboats and
whose lives ended shortly in the cold water.
The fact was that the Carpathia's one operator,
H. T. Cottam, was going to bed before the
Titanic smashed her nose on the iceberg, and
it was only by chance, or, if you please, the
intervention of Providence, that he stayed up
a little longer to get off some messages, and
heard the Titanic's CQD buzzing into his head-
phones, at 12:35 in the morning. Cottam
already had his coat off. Had he taken off
the phones and grounded his antenna a few
minutes earlier, the Carpatbia would have
continued tranquilly on her course while 2000
people were perishing 60 miles away. The
necessity of a continuous watch by two or more
operators was impressed on everyone
( To be continued)
MARINE RADIO GAVE THE ART ITS FIRST PUBLICITY
"ARL
A Gallery of Interesting Models of the RADIO
BROADCAST "Aristocrat" Receiver, Espe-
cially Adapted for the Phonograph Cabinet
— the High Quality Audio Channel is Assured
by Resistance- Coupled Amplification
FIG. 1
One of the Phonograph Receivers described in RADIO BROADCAST for June,
July, and August, converted into a RADIO BROADCAST "Aristocrat" by the
addition of one tube and by replacing the transformers with Dubilier con«
denser and resistance units for making a resistance-coupled amplifier
FIG. 2
This is a bottom view of the receiver shown in Figs. 5 and 8. The filament
circuit in this receiver has been somewhat altered in that j-ampere ballasts,
one each, have been used in the detector and radio-frequency amplifier filament
circuits. A half-ampere ballast is used in the first two audio tube circuits and
another is used in the output tube circuit. Where six-volt tubes are used
instead of the five-volt type, short pieces of bus wire may be employed in
place of the ballast resistors as indicated at the left hand side of the illustration,
where two such base connections have been made. It will be noted that
in this receiver Brach resistance coupling units and Brach ballast resistors
have been used
FIG. 3
Another RADIO BROADCAST Phonograph Receiver converted into an " Aris*
tocrat" by the use of a three-stage Muter resistance-coupled amplifier
FIG. 4
This RADIO BROADCAST "Aristocrat" was made by Radio Research Laboratories, New York, and they have incorporated some slight modifications of their own,
which are to be commended. For instance, the General Radio variocoupler used in the antenna circuit makes it possible to compensate for various antennas
without tap switch. The voltmeter has a multiplier in series as it is one of the double scale type. Victor coils have been used in the radio frequency unit,
and they have been found very satisfactory. Two Pacent lo-ohm rheostats are employed, one in the detector circuit and one in the radio-frequency amplifier
circuit. The latter makes a particularly good volume control. The entire assembly is an example of the kind of workmanship that any home constructor may
accomplish if he will devote himself sincerely to the job
FIG. 5
This is a rear view of the receiver shown in Fig. 8. The simplicity of the
layout is brought out thoroughly from this viewpoint. It will be noted that
the sockets extend far enough beneath the sub-base to allow wiring to be made
at approximately the level of the socket prongs. The manner of fastening
the sub-base and binding post strip to the Bruno bracket is very satisfactory
and very substantial
FIG. 6
A Phonograph Receiver using the National Regenoformer Kit and the
Browning-Drake circuit with a Heath resistance coupled amplifier unit. A
199 tube used in the radio frequency part of the circuit to save current and
facilitate neutralization
FIG. 7
This is the under side of Fig. 6. The small resistance in series with the right
hand rheostat is used to reduce the current from the borage battery to a point
where operation of the 199 tube is possible without overloading. The use of
a three-Sage resistance-coupled unit in receivers of this kind makes the entire
wiring job a simple one. The arrangement illustrated in Figs. 6 and 7 is very
neat and the performance of the receiver is such that we do not hesitate to
recommend it for those who desire a really good receiver for installation in
their phonographs
FIG. 8
Another RADIO BROADCAST "Aristocrat" receiver. The panel itself is but 18
inches in length and there is plenty of room left at either end. Specially de'
signed coils for the "Aristocrat" receiver, made by the American Mechanical
Laboratories, have been incorporated in this model and the movable tickler is
replaced by a variable resistance. This unit with the primary and secondary
radio frequency coils is called a Clarotuner. Bruno brackets have been used
and the sub-base has been made to our design by the Osborne Company of
Boston, Massachusetts.
Regeneration may be Obtained Either by Variable
'Tickler or Resistance Shunted Across A Fixed Tickler
Circuit Enclosed Herein Comprises Resistance Coupled
f Amplifier which may be Obtained as a Complete Unit
Separate Resistor Units may be Employed in the Audio Amplifier^
' where the Complete Manufactured Amplifier is not used
«/ **
~l
.002 to .004
Determine by
experiment,
the necessity
for the use of
this Condense
FIG. 9
This is the circuit diagram of the RADIO BROADCAST "Aristocrat". Note that the connections of C3 have been altered. They were incorrectly shown
in the diagram accompanying the constructional article on this circuit on page 30 of RADIO BROADCAST for November. A .5 mfd. condenser should
be tried across the B battery, which may improve the tone. Amperite ballasts may be used for filament control in each of the tubes
How to Use Meters in Your Receiver
The Meter is a Comparatively Inexpensive and Valuable Refine'
merit — How Meters Work and How to Use Them for Best Results
N
*OT a few broad-
cast listeners have
the idea that
meters in a radio
receiver, if they are built in at
all, are there forappearance and
not for any good they may do
in enabling the operator of the
set to use his receiver more
effectively. Of course, every-
body knows that a set will
work without a meter, but few
know how much the proper
meters will help in obtaining economy
and quality performance.
A small voltmeter, connected in the
filament circuit enables one quickly to
turn the control rheostats to the proper
point so that enough current is flowing
By JAMES MILLEN
article might have an alternative title, "How to Get More Out of Your
Receiver," for that is exactly what will happen if Mr. Millen's suggestions
are followed. It is easy enough for anyone to tell how a radio receiver is operat-
ing acoustically, but electrically, meters are required to tell the operator how the
circuits are functioning. The addition of the proper meters to any set is neither
an inordinately expensive matter nor a very difficult one. The mere assurance
that one is using his tubes at the proper filament voltage is enough reason for
installing the meters. In addition, the use of a plate current milliameler will
register instantly the slightest distortion occuring in the audio circuit, after the
fashion described by Mr. Crom in his article in RADIO BROADCAST for October.
Mr. Millen's excellent suggestions can aid every home constructor and net a few
of those who have manufactured sets which they would like to improve.
— THE EDITOR.
used. Should the needle
fluctuate violently in both
directions, the tube is very
much overloaded and both B
and C voltages must be
materially increased.
MANY USES FOR METERS
THERE are also a number
of other uses for meters
I
1
•IT
•tl
(Multiplier)
\*r\ Galvanometer
* I "*!
FIG. I
This diagram shows how a resistance and a
current measuring device are employed to
determine voltage
through the circuit to heat the filament
wire to insure emission of electrons in
the proper quantity. This is one of the
conditions for the production of good
quality. At the same time, the fila-
ment is not operated above its rated volt-
age. This prolongs the life of the tube.
When a tube is used with a very slight
increase over its rated voltage, its life is
greatly reduced.
Depleted B batteries are frequently a
source of noise and distortion in radio
- Galvanometer
t
t
^<Lr
u
'2
(Shunt)
FIG. 2
A shunt resistance is employed in order that only
a small percentage of the total current in the
circuit passes through the meter
receivers. And when, as is frequently
the case, the B batteries are located in the
cellar or some out-of-the-way place, it is
inconvenient to test them frequently with
a pocket voltmeter. So they are often
neglected and as a result the quality of
reception becomes poorer, all unnoticed
by the owner, because the process is grad-
ual. But some evening, when the receiver
is put into operation it refuses to work.
Had the set been provided with a con-
veniently arranged panel voltmeter, the
operator could have made a frequent and
easy check on the condition of the batteries.
The third meter which helps toward
good quality and economical operation
is a plate-current milliammeter. A plate
milliammeter primarily indicates the rate
at which energy is being drawn from the
B batteries. If this plate current is ex-
cessive, the life of the batteries and the
tubes will be seriously impaired. By
means of proper C voltages it is possible
to vary the plate current and thus secure
the value specified by the manufacturers
of the tube for any given plate voltage.
A second, but not a lesser important
function of the plate milliammeter, is to
indicate how an amplifier tube is "modula-
ting." For quality reception it is abso-
lutely essential that the d. c. component
of the space current of a tube, as indicated
by a d. c. milliammeter does not vary.
If the needle on the milliammeter drops
down on a strong
signal, the tube is said
to be "modulating
down" and the C
voltage must be in-
creased. If, on the
other hand, the needle
advances on a strong
signal, the amplifier is
said to be "modulat-
ing up," which indi-
cates that the C volt-
age is too high for the
plate voltage being
in connection with radio re-
ceiving sets, but with the
equipment as available at pre-
sent, their use is of value mainly in the
laboratory. Such a meter is an ammeter
for indicating the rate at which a storage
battery is being charged. As the charg-
ing rate on the majority of home battery
chargers is not variable, there is little to
be gained by the use of a meter in such
cases.
Scale
Permanent
' Magnet
Non-Magnetic / -*-" "-»- AirGap
Support '
FIG. 3
The most accurate meters are of the moving-coil
type, such as shown in this diagram. The photo-
graph below shows a meter of the moving coil
type, apart. The D-shaped piece on the base of
the meter, center, is the permanent magnet
RADIO BROADCAST Photograph
FIG. 3A
DECEMBER, 1925
HOW TO USE METERS IN YOUR RECEIVER
199
RADIO BROADCAST Photographs
FIG. 4
There are a number of different concerns making meters for radio use. The products of Hoyt (Burton and Rogers), Dongan, Jewell, and Cellokay are shown
Another such meter is a wavelength or
frequency meter, but this too may be dis-
pensed with in the modern radio broadcast
receiver by the simple expedient of cali-
brating the dials on the receiving set.
All of the meters referred to above with
the exception of the wavemeter are funda-
mentally the same — that is, they are
essentially galvanometers, or devices for
indicating current flow. If a voltage is to
be measured, then a high resistance unit,
called a multiplier, is connected in series
with a galvanometer and the combination
connected to the source whose voltage is to
be measured. This arrangement is shown
in Fig. i. A small current will flow
through the resistance and galvanometer.
The galvanometer will indicate the value
of this current. Now, by means of one of
the fundamental laws of electricity, it is
possible to compute the voltage readily
across the terminals A, B, Fig. i, as the
value of the resistance, R, and the current
I, are known. This, known as "Ohm's
Law," says that the voltage across a resis-
tance due to current flowing through the
FIG. *,
External cased meters may be placed
as shown on a previously built set.
The voltmeter at the left shows
filament volts, and the milliam-
meter at the right indicates B
battery consumption. Both are
Weston meters
resistance is equal to the product of resis-
tance in ohms and the current in amperes,
which, in symbols is E = IR.
Of course, it is not convenient to make
even this simple calculation every time
one wants to know the voltage of his
batteries, so the manufacturers put a
special scale on the galvanometer which
reads directly in volts. Then they go
still another step farther and build meters
having an inherent resistance of such a
magnitude that, for voltages under say
50 volts, the use of an external resistance
or multiplier is dispensed with. For higher
voltages, such as B battery voltages, it is
generally customary for the meter manu-
facturers to take a lower voltage meter,
such as one having
a range of 10 volts
and making a mul-
tiplier which will
give a range of
100 volts. The
scale on the meter
is then frequently
a double one, so
that either the o-io, or o-ioo-volt scale
may be referred to depending upon whether
or not the multiplier is being used.
Ammeters are also fundamentally galvan-
ometers, which would be burned out if a
heavy current were to be passed through
them. In order that they may be used
to measure heavy currents, resistances
are connected across them so as to "by-
pass" most of the current and thus let
only a small fraction of the total current
pass through the meter. This "by-pass" re-
sistance is known as a shunt and in the case
of the small panel mounting typeof milliam-
meters used for radio work, the shunt
generally consists of a small piece of resist-
ance wire contained within the meter case.
200
RADIO BROADCAST
DECEMBER, 1925
(
t*
H
J
n
i
)
Multiplier
i/vwvw-
^/VW
liH
—
filamsntVolts .,.
Open Circuit Jack
Jl Plug
ia
Plate C
Closed Ci
a, L
ircuit '
rcuitJack
^- Plate Volts
nOpen Circuit Jack
FIG. 9
This is the panel view of the "Aristocrat" receiver shown in Fig. 4 on page 196 of this issue.
The
switch below the meter at the right side of the panel allows the meter to read either filament or
plate voltages
FIG. 7
By connecting three jacks in each tube circuit, it
is possible to use one meter for many different
purposes, in order that several different multi-
pliers will not be required, one multiplier may
be arranged with a short-circuiting switch in the
plug circuit
HOW THE METER WORKS
THE galvanometer units generally,
in the higher grade instruments,
consists of a movable coil, to which is
affixed a pointer, pivoted in a strong
magnetic field set up by a permanent
magnet of the "horseshoe" type. This
arrangement is illustrated in Fig. 3. When
a current passes through the coil, an elec-
tro-magnetic field is set up which reacts
with that set up by the permanent magnet
and the coil tends to rotate. It is held back
by a small hair spring. The force (or as
it is technically called, torque) tending to
rotate the coil is directly proportional to
the current f. owing through the coil.
Furthermore, the deflection of the coil is
governed by the spring, whose deflection
with certain limits, is directly proportional
to the torque. Thus the deflection of the
galvanometer is directly proportional to
current.
Instruments, such as the Weston and
the Jewel employ the movable coil type
of movement illustrated in Fig. 3. The
less expensive meters, especially the small
pocket volt and ammeter used for testing
dry cells are of what are known as either
the plugger, and iron vane type* The iron
vane type consists of a small electro-
magnet with a soft iron core. When a
current is passed through the winding of
the electro-magnet a small iron "vane,"
which is mounted on a shaft, is attracted.
The vane is held back by the permanent
magnet, and a pointer is affixed to the shaft
so as to indicate the deflection.
The electro-magnet in an ammeter of
this type consists of a half dozen turns
of very heavy wire, whereas the voltmeter
elec.ro-magnet is wound with many turns
of very fine wire.
In the past, instruments of the iron vane
type have not been considered very accur-
ate for high grade work. Furthermore,
they consumed considerable power, and
-B
VF = 0-7.5 Volts
VB • 0-1 50 Volts
MA= 025 Milliamperes
FIG. 6
This circuit diagram shows how to connect a filament voltmeter, a plate voltmeter,
and a plate milliammeter in a RADIO BROADCAST Four-tube Knockout receiver
thus could not be left in a circuit for any
length of time, as they would run the
batteries down. This is especially true
of voltmeters since they are shunted across
the supply and if left in circuit would
deplete the batteries very rapidly.
At present, however, there are at least
two well-known concerns manufacturing
improved instruments of this type which
are well suited for radio use, particularly
for measuring B battery voltages. Such
a meter mounted on the panel of a tuned
radio frequency receiver is shown in Fig. 8.
Two push buttons are provided so that
either the detector or the amplifier B
voltages may be instantly read with the
same meter. When push-buttons are
used for this purpose there is no danger
of the meter remaining connected to the
B batteries for long periods and thus un-
necessarily running them down.
Fig. 4 shows a group of different meters
for mounting on the panel of a radio
receiving set. The meters may be mounted
in small cases, and connected to the set
with flexible lamp cord. Such an arrange-
ment is shown in Fig. 5.
Fig. 6 shows how these meters are con-
nected in a RADIO BROADCAST Four-Tube
Knockout receiver. By carefully examin-
ing the way in which the meters are con-
nected in this circuit, the manner in which
they should be connected in any circuit will
be evident.
If a meter is equipped with an ordinary
phone plug and flexible cord, jacks may
be arranged on the panel of the receiver so
that it may be plugged into any part of the
circuit. Fig. 7 indicates how to connect
the jacks in a circuit.
Instead of having three separate meters
—A voltage, B voltage, and plate current —
for use with the set in Fig. 7, one meter
may be made to serve the purpose most
excellently. If a o to 7.5 voltmeter is
available it may be used directly to read
filament volts, with a resistance in series
(8825 ohms for Weston o-7.5-volt No. 301)
to read up to 150 volts (multiply scale
readings by 20) and without any attach-
ments, as a milliammeter. For the model
3t)i Weston meters, a full scale deflection
requires 16.1 milliamperes or for the o
to 7.5 volt Weston meter, each division
is equal to 2.146 milliamperes or approxi-
mately 2 milliamperes.
Home Constructor
The Second of a Series of Articles — Each Complete in Itself — Showing the
Jaded Home Builder How He Can Use His Present Equipment to Make
Valuable and Useful Measurements and Experiments in His Own Home
- By KEITH HENNEY
Director, "1(adio Broadcast" Laboratory
IHERE can be little doubt that
radio is one of the most attractive
fields for home experiment that
has ever offered itself to the
average layman. The ramifica-
tions of this specialized part of electrical
engineering are so many and so varied
that "that tired feeling" of having solved
all is always far in the distance, and the
home experimenter, with inexpensive and
not too complicated apparatus, can ap-
proach so closely to actual scientific
research that he cannot help attaining a
distinct feeling of having accomplished
something of value at the end of each
day's experiment.
For a long time the Editors have been sure
that there were many who felt they had
built enough receivers, but who still had a
craving to construct something with their
own hands that would work in some useful
way. Tools accumulated through days of
receiver building cannot lay idle; radio
junk collected during those same days, is
always too good to throw away; experience
in radio matters causes a yearning for more
experience — and yet, to build one more
receiver might be the breaking of the
proverbial camel's back. What is the home
constructor to do?
This series of articles, of which this is
the second, has been planned with but one
object in view, to lead these jaded souls
into a field where there is endless variety,
and where each thing accomplished leads
to something else. And for those who
really want to know more about radio,
who want to find out for themselves what
is going on behind laboratory doors, these
articles will be written so that they will be
in some degree helpful. The
home constructor naturally fits (gst ;
into the field of radio experi-
ment since he has already
tasted the joys of building
successful apparatus, and in
this way he has learned the
"feeling" of electrical equip-
ment
The first article, in the Sep-
tember number, described a
simple piece of laboratory
equipment that is efficient
enough to grace the best lab-
oratory, useful enough to make
it worth while for any one to
build, and at the same time
inexpensive and not compli-
cated. It is a two-tube oscillator, one of
the tubes working at broadcasting radio
frequencies, and the other at a fixed audio
frequency. Either tube may be used alone,
or the two may be operated together as a
source of modulated high frequency energy.
USES OF AN AUDIO OSCILLATOR
FOR example, the audio part of the
oscillator referred to above is used in
the Laboratory of RADIO BROADCAST for
the following purposes:
1 . Source of tone for testing open circuits.
2. Tone for measuring capacity, inductance,
or resistance.
3. Measuring the characteristics of audio
instruments, such as audio-frequency transform-
ers, loud speakers, etc.
It is common practice among radio
workers to use a battery and a pair of head
phones to test open circuits, and at times
a dry-cell operated buzzer is used. For
example in a receiver which is inoperative
due to a broken connection, the wiring
may be traced until the break is found.
In testing audio frequency circuits in
which transformers are used, it is extremely
bad practice to use direct current for
testing. After such a test it may be
found that the iron cores are magnetized
with the result that distortion occurs
when the amplifier is again placed in
operation. In the laboratories of the
telephone companies, where hundreds of
telephone transformers are used, it is
strictly against the rules for laboratory
assistants to "buzz" out circuits either
with the phones and dry cell or with a
buzzer.
The iooo-cyc!e tone emitted by the any large
CT*O SHOW bow the home constructor can go on in radio after be has built the
•*• radio sets that to bint are satisfactory, is the purpose of these articles. The
first " What Is to Become of the Home Constructor? " appeared in this magazine
for September and has created a phenomenal amount of interest. Each of these
articles really gives a complete set of experiments and useful tests which may be
made by any experimenter who is properly equipped. The apparatus, most of
it at least, in the form of parts, is in the radio "junk pile" of almost every
constructor. Each article is complete in itself, the experiments are related and
they have a very definite use in any one of a number of ways. Using the audio
oscillator to test receivers and the radio oscillator to calibrate them, is, for ex-
ample, of great use to radio dealers who take pride in their repair and service
departments. The uses of the radio oscillator suggested here are novel and in-
genious and bound to be helpful. Those who are interested in laying out a
modest little "lab." of their own will be interested in the suggestions given at the
end of this article. — THE EDITOR.
audio oscillator described in the September
article, is an alternating current of small
amplitude which cannot magnetize the
cores of any transformers. Fig. i shows
the usual method of testing open circuits
with battery and headphones, as well as
the correct method of using the audio
oscillator as a tone tester. The jack in
the oscillator provides an outlet for the
looo-cycle tone and a plug in this jack
will have the alternating voltage across
its terminals. One terminal should go
to the receivers, and the remaining wires,
one from the oscillator and the other from
the phones, should go across the sus-
pected broken connection.
Capacity and inductance, as well as al-
ternating current resistance, are measured
by what is known as an "impedance
bridge" which operates from a source of
alternating current. The audio part of
this oscillator is again useful here, and
Fig. 2 shows how it is used in the Labor-
atory. It is not necessary to have much
power for work of this kind, and if extrane-
ous noises make it difficult to get proper
balance on the bridge, a one- or two-stage
audio amplifier is connected to the bridge
and thence to the receivers. For example,
in the Laboratory, the noise and vibration
from presses, in action several floors below,
makes it difficult to obtain correct mea-
surements, without the aid of the amplifier
shown in Fig. 2.
A simplified form of bridge will be
described soon in this series and, with the
aid of the audio oscillator, will enable the
experimenter to measure his own induct-
ances and capacities just as is done in
and well equipped laboratory.
This will eliminate much of the
cut-and-try method that is
now in order when the radio
builder decides to make new
coils, or to try different sizes
of condensers to tune to cer-
tain frequencies. The bridge
shown in Fig. 2 is made by
the General Radio Company.
By varying the tuning con-
denser across the secondary of
the oscillator, notes may be
secured varying from about
200 cycles to the natural fre-
quency of the transformer
itself, which is usually around
5000 cycles. These tones
may be amplified if necessary,
•t&f
202
RADIO BROADCAST
DECEMBER, 1925
and used to determine the characteristics
of audio-frequency transformers as well
as the resonance peaks which exist in
many loud speakers. Methods of testing
these low frequency instruments will be
described later. Calibrating the oscillator
is not difficult provided access is had to a
musical instrument that is accurately
tuned.
Middle C on a properly tuned piano cor-
responds to a frequency of 256 cycles per
second, and is a good starting point for the
calibration of an audio oscillator. The
tuning condenser should be varied until
the sounds emitted by the piano string and
the oscillator are the same. Other fre-
quencies may be obtained in the same
manner. The relation between
frequency and the piano scale
will be shown graphically in the
January RADIO BROADCAST.
Tuning forks may be pur-
chased from musical supply
houses and a small set, say,
those of 256, 512, 1024, and 4196
cycles, will enable any one to
calibrate an oscillator.
FIG. I
A source of pure alter-
nating current is useful
in testing audio -fre-
quency transformers.
There is no danger of
magnetizing the cores
when such a tone source
is used. The battery
"click" method is dan-
gerous. An Erla cru-
ciform audio trans-
former is being test-
ed in this view
USING THE RADIO OSCILLATOR
In the Laboratory, the radio
FIG. 2
An impedance bridge for measuring induc-
tance or capacity requires a source of alter-
nating current. In this laboratory arrange-
ment, the modulated oscillator furnishes the
tone, and a General Radio Inductometer is
used as a standard of inductance by which
the toroid is being measured. The other ap-
paratus is a two-stage audio amplifier and
telephone receivers for obtaining an audible
balance. The picture diagram above shows
how the apparatus is connected
part of this simple device is used for the
following purposes:
1. Calibrate receiving sets.
2. Set receiver for a given frequency.
3. Measure the frequency of incoming signals.
4. As a separate oscillator for super-
heterodynes.
5. Source of radio frequency energy for
measuring losses in coils, etc.
6. Wavemeter.
7. Energy for neutralizing receivers.
As an example, let us suppose that a
new receiver is constructed and we are
desirous of finding out what frequency
band it will cover. We crank up the oscil-
lator and tune the receiver to it. Noting
the dial numbers of the receiver, we change
the frequency of the oscillator and again
tune the receiver. In this manner we
RADIO BROADCAST Photograph
DECEMBER, 1925
NEW FIELDS FOR THE HOME CONSTRUCTOR
203
1,500
1,400
1,300
1,200
1,100
1,000
900
800
700
600
500
400
RAD
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IODU1
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.ATEI
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> OSC
.ABO!
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600
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10 20 30 40 50 60 70
CONDENSER DEGREES
80 90 100
FIG. 3
A calibration of the Laboratory's oscillator. Both frequencies
and wavelengths are plotted against condenser settings. This
calibration will be true only of the coil and condenser used in this
particular case. All other combinations must be calibrated
against standard frequency signals either from a known broadcast
station or from the standard frequency signals sent out by the
Bureau of Standards
may have an exact tuning curve of the
receiver before a single station is heard.
Fig. 3 shows a calibration of the radio part
of the Laboratory's oscillator. This of
course will differ for each coil and con-
denser used and the effect of connections
will not be negligible.
This means that each constructor will
have to calibrate his own oscillator, but at
night this is not a difficult task. With
both tubes functioning it is only necessary
to tune a receiver to a known station.
Then the oscillator is varied until the tone
is heard in the receiver. Now that radio
stations stay closely to their required
frequencies, it is possible to own a very
accurate wavemeter using this simple
means of calibrating it.
Incoming signals on any receiver may
be measured for their frequency by tuning
the oscillator until it is heard together with
the stations signals. A glance at the
calibration will show what station is being
received.
The receiver may be set at a required
frequency by setting the oscillator for this
frequency by means of its calibration curve,
and then tuning the receiver until the sound
is heard. In other words, the modulated
oscillator will make a good wavemeter,
and due to the fact that both audio and
radio waves are tube-generated they will
be very sharp. The old time buzzer with
sparking contacts is notoriously broad in
the frequency spectrum it turns out.
USE IN NEUTRALIZING RECEIVERS
'"THERE is another use of the radio
' part of the apparatus that is very
important, and in the Laboratory it has
been used many times for
this purpose and may easily
find the same use in
many home laboratories.
This is the neutralization
of radio-frequency ampli-
fiers. Tuning-in a signal
and then, with the radio
frequency tubes turned out,
to adjust the neutralizing
condenser until no sound is
heard is one method, and
the modulated oscillator,
with both tubes burning,
provides a good source of
energy for this purpose.
There is another method
that may be used, especially
where a regenerative detec-
tor is in the circuit, and it is
somewhat more accurate.
This is particularly true if
high gain amplifiers are
used, characterized by many
plate turns in the amplifier
coils, and correspondingly
large fields.
The detector is made to
oscillate, and with the radio
frequency tube of the oscil-
lator set at some frequency
in the middle of the broad-
cast band, the detector tun-
ing condenser is varied until a beat note be-
tween the detector current and that emitted
by the oscillator is heard. Then the radio-
frequency amplifier condenser is varied.
If the amplifier is not properly neutralized,
the beat note will change pitch rapidly as
the amplifier is tuned. If far from the
neutralizing point, the amplifier may oscil-
late, or reaction between the amplifier
and detector may be so great that the
detector will refuse to oscillate.
The neutralizing condenser is then varied
until changing the amplifier tuning has
little or no effect upon the detector circuit.
This balanced condition will be noted
when the beat note between detector and
oscillator does not change appreciably when
the radio-frequency amplifier is tuned.
Since it is not always possible to pick up
broadcasting stations, especially where
constructors are out of the daytime range,
the oscillator provides an excellent source
of both pure radio and modulated radio
frequency energy for neutralizing purposes.
TO GET GREATER ENERGY FROM THE
OSCILLATOR
FOR some purposes it is necessary to
have greater power than is turned
out by the wo-12 tubes used in the Labora-
tory oscillator. In this case it is only
necessary to use standard 5-volt tubes, or
better yet, the new one-half ampere, 5-volt
tubes, such as the ux-i 12, the Daven MU-6,
Cleartron 1 12, etc., and to push up the B bat-
tery voltage until the required power is ob-
tained. It will be necessary to recalibrate
the set owing to the changed grid-filament
capacity, but the differences will be small
and unless very accurate work is to be done,
recalibration will not really be necessary.
The audio output may be sent through
an audio-frequency amplifier such as is
illustrated in Fig. 2 if greater tone volume
is needed.
Another method of getting greater volt-
ages out of the radio part of the device is
shown in Fig. 4, which gives the entire
circuit. Currents in tuned resonant cir-
cuits are usually high, and this is particu-
larly true when those circuits are of low
resistance. Thus the output of the oscilla-
tor may be coupled to a tuned circuit and
part of the voltage of that circuit used for
whatever purpose is necessary, such as for
measuring the resistance of coils and other
radio frequency apparatus.
The oscillator is first tuned to the re-
quired frequency. Then the output circuit
is tuned, and finally the circuit to be driven.
Unless considerable power is required, it is
not necessary to tune the output circuit
which is then acting as an untuned "trans-
mission line," and serves simply to transfer
energy from one circuit to another.
Little current will flow through the
transmission line, if it is untuned, but in
the tuned circuit at the end there will be
heavy currents.
Fig. 5 shows the apparatus required for
measuring the high frequency resistance of
coils. With the addition of a vacuum tube
voltmeter, such as was described in RADIO
FIG. 4
A use for the radio frequency part of the oscillator. By use of a coupling coil, energy may be
transferred from the oscillator to some other circuit. If this intermediate circuit is tuned by
means of the condenser, much more current will flow in it and correspondingly greater voltages
may be transferred to the circuit under test
204
RADIO BROADCAST
DECEMBER, 1925
.00025 mfd.
.00025 mfd.
Output Coil
• Feeder Wire
1,000^ Output
FIG. 6
A method of tuning
the intermediate cir-
cuit connecting the
oscillator and the
apparatus being
measured
'uning Condenser
BROADCAST for February, 1925, page 1 101,
the gain of radio-frequency amplifiers may
be measured.
Many experiments are now being simpli-
fied in RADIO BROADCAST Laboratory for
inclusion in this series. A simple and
fairly accurate impedance bridge will be
described, methods of measuring the am-
plification of both audio- and radio-
frequency transformers and the losses in
coils will be explained, and among other
apparatus described there will be a vacuum
tube voltmeter with which many important
experiments can be performed. Wherever
possible references to current literature
will be cited as well as to standard texts.
Readers are invited to write of their ex-
periences or difficulties or to state what
particular problems they would like to see
treated in this series.
WHAT SHOULD THE HOME "LAB" BE?
IT SEEMS to the writer that there are two
methods by which the experimenter
may carry out his work. He may have a
regular place for his apparatus and for his
work, or he may not. Naturally, the
laboratory should be a fixed place, where
apparatus may be set up and not disturbed
until the experiments in progress are fin-
ished.
In this place there should be a work
bench and a laboratory bench, and the
latter should be kept free for the actual
work at hand. It often happens that a
certain set-up of apparatus will be used for
some time, for instance where one is meas-
uring the gain of radio-frequency amplifiers,
and it is a waste of time and energy to tear
down and set up the equipment each time
an experiment is completed. Added to
the nuisance of such movement there is the
likelihood that readings taken on succes-
sive days will not check — for radio fre-
quency circuits are tricky affairs.
The tools that are needed are no more
than are required for constructing receivers,
but, like the electrical equipment, they
should be of the best make possible. A
good drill, a pair of long nose pliers, a pair
of cutters, and a long, narrow screw driver
are vitally necessary. Added to these may
be the usual wood working tools, such as
a hammer, a saw, and a plane.
Electrically speaking, the home experi-
menter should begin his collection of
apparatus by purchasing a good voltmeter
and a good milliammeter. The meters
may be of the Weston 301 type installed
in student bases, or corresponding meters
made by Jewell, Roller-Smith, General
Radio, etc. The voltmeter should have a
range of o to 10 volts and an ammeter
which will be found to have many con-
venient uses should read from o to 10
milliamperes. This will read the plate
currents of 5-volt tubes under ordinary
conditions, and with some simple acces-
sory apparatus will enable the experi-
menter to measure the constants of tubes
as well as to check up on the other ex-
periments that go on.
Such meters can be purchased for about
$10 each with base, and are the first equip-
ment that the experimenter should possess.
Additional equipment will be cited in
future articles.
RADIO BROADCAST Laboratory wishes
success to prospective home laboratory
owners, and will be glad to hear from
readers who are interested in the experi-
ments described here.
RADIO BROADCAST Photograph
FIG. 5
A photograph of apparatus actually being used to measure the high frequency resistance of coils. The oscillator supplies the energy, a Weston galvano-
meter, Model 425, measures the current flowing, and a Genial Radio Laboratory condenser and resistance box aid in the actual measurement. In
this case the intermediate coupling circuit is not tuned, consisting merely of two very small coils, one coupled to the oscillator, one to the coil under test.
Later articles will contain descriptions of simple apparatus which is capable of performing similar experiments to those described in this article
RADIO BROADCAST ADVERTISER
205
Ozarka Senior Console £197.50
Complete with Tubes, Batteries and Speaker
If Your Radio is Bought Right
It will be a Life-Long Pal
A LITTLE more time, a little more care in making the
** selection in the first place generally tends to more
lasting satisfaction.
Out of every 100 Ozarka's sold in
1922 only eight are not today in the
hands of the original owners — this
does not include 17 out of each 100
who have purchased later Ozarka
models in newer type cabinets. If
there is a single Ozarka that is not in
active service today, we have never
heard of it.
Without the Ozarka Service in
charge of direct factory trained repre-
sentatives, such a record would not be
possible. Ozarka service can be had
today in almost every country. Pur-
chasers in South Africa, Alaska, Swe-
den, Newfoundland, New Zealand,
and Japan all receive the same prac-
tical service as those in Canada, United
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you find the sign of the Ozarka long
distance goose, you'll find a man who
knows Ozarka instruments perfectly.
If such service added more to your
cost price it might be a matter to con-
sider, but it doesn't. Quality for quality
you'll find Ozarka prices lower — four
tube Ozarka's with built-in loud
speakers retail for $58.00 — five tube
with built-in speaker $64.00, up to
solid walnut console design, $160.50.
Our nearest representative will
gladly set up an Ozarka in your home,
without any obligation whatever. He
won't tell you what it will do — he will
let you do all the tuning. With the
Ozarka you must satisfy yourself, as
to distance, tone, volume, ease of
tuning and selectivity.
More than this you will be very
agreeably surprised at Ozarka prices
— selling as we do, thru our own direct
factory representatives, our selling
expense is very low — we give Ozarka
purchasers the benefit of it.
Where is there a value to compare
with the one shown above — - solid
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veneer), imported English loudspeaker
of a marvelous tone, five tube instru-
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battery, 90 volts of Eveready "B"
battery, 5 tubes, aerial equipment all
erected and the price is only $197.50.
A Few More Men
are Needed to
Sell Ozarka
In a great many counties we have the
man we want. He is rapidly building up a
permanent and profitable business of his
own because he has an instrument that will
more than meet all competition. More than
this, he is trained to back up his sales with
the kind of service that counts.
Many well established Ozarka representa-
tives started by giving us only their spare
time — their evenings. If your county is open
you can do the same.
The investment in cash is very small.
The investment in time necessary for study
is considerable. It requires patience, but
the results have enabled many men to get
out of the salary and time clock class.
Any previous sales experience is helpful
but not necessary. We can and will teach
you how to sell.
Send for 84 Page Book —
"The Ozarka Plan"
This book is entirely too expen-
sive to be sent out on postal card
requests. It will be sent FREE to
any man who mails the coupon
below and who is really anxious
to improve his condition. Tell us
about yourself — ask for Ozarka
Plan No. I OOand don't fail to give
the name of your county.
122 Austin Avenue B
Chirao-o Illinois
Gentlemen: Without obligation send book "Ozarka Instru-
ments No. 200" and name of Ozarka representative.
Name
Address City.
County ...State.
122 Austin Avenue B
Chicago, Illinois
Gentlemen: I am greatly interested in the FREE book "The
Ozarka PlanNo. 100,"whereby I can sell your radio instruments.
Name
Address....
County
Tested and approved by RADIO BROADCAST if
Ask the Man Who
Wears this Button
....City.
.State...
206
RADIO BROADCAST ADVERTISER
There's Economy
and Satisfaction
in these Valley units
You will find both economy and satis-
faction in the use of the Valley B'
Eliminator and the Valley Battery
Charger.
Economy in the B-Eliminator because
it stops forever the expense of buy
ing new B batteries. . .
Economy in the charger because it
recharges your own storage battery
at home overnight at one-tenth the
cost of service station charging. . .
And satisfaction in both because, by
using them, you need never miss a
program on account of low or worn-
out bat'
teries.
THE VALLEY B 'ELIMINATOR operates
from ordinary light socket; provides
a steady, noiseless flow of B current
at a constant voltage all the time.
With it, there can never be any de'
crease of signals or frying noises due
to low B batteries. Volume is main-
tained. Reception is uniformly good.
For receiving sets of from one to
eight tubes. Costs less at the start
than wet B batteries. Costs less in
the long run than dry cells. Much
more sat- ..., -
isfactory ,
than -'
both.
THE VALLEY BATTERY CHARGER is
the only charger needed for all radio
storage batteries. Its correct 6-am-
pere charging rate makes overnight
charging a possibility.
The Valley Charger also functions
on any^lamp socket. It takes about
a dime's worth of current for an
average charge. Quiet in operation.
Most radio dealers handle the Valley
B- Eliminator and Valley Charger.
Any one of them will be glad to
show you these units and explain
their advantages.
Radio Division
VALLEY ELECTRIC Co. ST. Louis, u. s. A.
Branches in Principal Cities
Valley Electric
:Now, I HAVE FOUND
A Department for the Exchange of Ideas and Sugges-
tions of Value to the Radio Constructor and Operator
CONTRIBUTIONS to this department are welcome and those used will be
paid for at the usual rates, that is from two to ten dollars each. A pri^e
of twenty-five dollars is given for the best idea used during each three-month
period. The prizewinner for the last period was announced in the November
RADIO BROADCAST. All manuscripts intended for this department should not
exceed about three hundred words and should be typewritten. Little consider-
ation can be given to manuscripts not typewritten. Envelopes should be
addressed to this department, RADIO BROADCAST, Garden City, New York.
TRACING RADIO NOISES
MANY radio listeners have been led
to believe that certain objection-
able noises accompanying reception
were caused by power-line interference, or
other neighborhood operated devices, from
the advice, "if the noise ceases when the
antenna is disconnected, it is an indication
of outdoor interference," and as such, was
largely beyond the individual efforts of the
set owner to control. This is not always
true.
A particularly bad case of interference,
which had the characteristics of outdoor
interference, was discovered to be coming
from the residence main switch and branch
terminal cabinet, which was located four-
teen feet from the receiver, in the same
room.
The switch cabinet and receiver were
installed on op-
posite sides of this
room, and the lead-
in wire paralleled
the house wiring
through the adjoin-
ing rear room at a
distance of five feet,
for fifteen feet, and
did not enter nearer
to the switch than
the width of the
room.
The receiver, a
five-tube neutro-
dyne, with loud
speaker, was ad-
justed until noises
were loudest. The
time selected for
test was 2 a. m.
when no interference
was encountered
from street cars,
regenerative sets,
or neighborhood
electrical devices.
Disconnecting the antenna produced si-
lence. Replacing the antenna and oper-
ating the room switches, the noise was
still present in full volume.
Next, the residence main switch was
opened, and the mystery was solved,
for the noises could be produced and made
to disappear by closing and opening this
switch.
The continuous "crackling" or "frying"
noises, similar to that produced by bad
tubes, were caused by loose connection
screws of the main switch, branch ter-
minal fuse blocks, and bad contact of plug
fuses.
An occasionally loud "zip," or "buzz,"
similar to nearby code interference, or
arcing of defective receiver jacks, was
caused by loose rivets fastening the main
•if Tested and approved by RADIO BROADCAST
switch blades to the switch block and was
traced through applying test loads using
heater coils, although arcing was not visible
to the eye. Thus, all noises present at this
time of day were eliminated. The remainder
heard during usual broadcasting hours,
such as code, sparking trolley wheels, and
during heavy rain or snowfall were satis-
factorily reduced to a minimum by various
methods which have often been described
and which will not be gone into here.
A. H. KLINGBEIL,
Ashtabula, Ohio
A RATCHET COIL WINDER
PREVENTS UNWINDING
O1
Means for Restraining the
Wire While Winding -,
Handle-'
Wire
FIG.
FTEN in the middle of the winding
of a coil, the hold will be released
momentarily to straighten out the
wire, and as a result the carefully arranged
turns of wire may
loosen, and the work
has to be done over
again.
A method of im-
proving the usual
winder, is shown in
the sketch, Fig. i,
involving an ordi-
nary ratchet type
screw driver, which
many radio experi-
menters have in
their tool equip-
ment. As shown, the
handle of the tool is
gripped in a vise, or
held stationary by
other means. The
spindle of the winder
is fixed to the barrel,
and the ratchet is
set so as to prevent
unwinding. A rat-
chet type of brace
bit obviously has
the same advan-
tages for this use, and the spindle is
gripped in the jaws in the same manner as
is the screw driver method.
The best method of restraining the wire
while winding, may not be available to radio
workers, for which reason the restraining
reel, shown in the lower section of the
sketch, will solve their problem.
Make this up of four ordinary spools,
used for thread. Mount these spools on
nails or screws, so that the wire will feed
through with enough tension to make it
tight when wound on the coil. This reel
will not only restrain the wire, but will also
take out kinks and make it uniform and
even throughout the length of the wound
coil.
G. A. LUERS,
Washington, District of Columbia.
RADIO BROADCAST ADVERTISER
207
JVo Dials, JVo Panel, Built-in loudspeaker
Designed by R. E. Lacault, E.E.,
Chief Engineer of this Company,
and formerly Radio Research Engi-
neer with the French Signal Corps,
Radio Research Laboratories.
To protect the public, Mr. Lacault's
personal monogram seal (R.E.L.)
is placed on the assembly lock bolts
of all genuine ULTRADYNE
Model L-3 Receivers. All Ultra-
dyne Receivers are guaranteed as
long as these seals remain un-
broken.
$135.00
The Quiet Manner and
The Eloquent Tone
UNOBTRUSIVENESS with sufficiency— the rule of good taste
—is the distinguishing grace of the ULTRADYNE Model L-3
Radio Receiver. Ushers in a new era of radio reception — a new,
easier command of the air's treasures.
A new artistic form of a radio receiver that blends happily with every
scheme of interior decoration. Pleases the eye with itscharrning lines,
its beautiful two-tone mahogany cabinet, its fine proportions. Has
the appearance of a decorative tablepiece. Utter simplicity with
superb receptive and reproductive qualities. Your local radio dealer
will gladly give you a demonstration of this new modern receiver.
The Ultradyne Model L-3 is a six-tube receiver employing the
fundamental principles of the best circuits greatly refined and
marvelously simplified. No dials — no panel; just two inconspic-
uous levers, which constitute a station-selector. Volume adjust-
ment the only other control.
Write for descriptive folder
MODEL L-3
PHENIX RADIO CORPORATION, ii6-C E2sth St., N.Y.
Tested and approved by RADIO BROADCAST
208
RADIO BROADCAST ADVERTISER
Carol
Far out over hill and valley
— into the homes of rich and
poor alike — come the waves
that carry the glad tidings of
the Savior's birth. Little does
it matter whether the set is
of new mahogany and gold or
of humble cardboard coils.
Tonal beauty in the amplifier
is the one indispensable need
for the real joy of radio. Happy
indeed is the owner of
Rauland'Lyric!
^ A New Gift
for Every Radio Listener
Two Rauland-Lyricsin this beautiful
holiday box (fully sufficient for any
radio set). Sec it at your dealer's I
ALL-AMERICAN RADIO CORPORATION
4201 W. Belmont Ave.. Chicago
TRANSFORMER
The Choice of Noted Music Critics
A COUPLING DEVICE FOR
ROBERTS CIRCUIT
A SIMPLE device for varying the coup-
ling between the tickler and second-
ary coils is presented here for the ben-
efit of builders of receiving sets using the
Roberts circuit. This device provides a
go-degree coupling, or less, with a 180-
degree turn of the dial. The rotation may
be in either direction to provide the same
effect, and the dial may be turned more
than one revolution without altering con-
ditions.
From Fig. 2 B, it may be seen that the
Dial
2 E.
FIG. 2
whole idea of the device rests in the use of a
brass rod bent as shown in Fig. 30, and a
slotted fibre block as shown in Fig.
The slot takes up all the up-and-
down motion of the bent rod and
makes use of the side motion as
the rod is rotated. Bending the
rod at an angle of less than 45 de-
grees will produce a coupling of
less than 90 degrees. The angle of
coupling will be twice the angle to
which the rod is bent.
The materials used are shown in
the sketches, which are self-explan-
atory. The same materials and
dimensions need not necessarily be
used however. The fibre block is
shown with square corners but
these may be bevelled off so that
other positions of the tickler may
be obtained. The center lines of
the rod and block must coincide
to produce smooth operation.
CLARENCE J. FRENCK,
Wauwatosa, Wisconsin.
A FILE FOR IDEAS
T DEAS are elusive. They come
and go.
* Some means should be found
for catching and using them.
Memory is short-lived, not always
•jr Tested and approved by RADIO BROADCAST if
THE dependable, and ideas that are worth re-
membering are also worthy of preservation.
By having a well-organized plan for
systematically preserving and storing away
the best ideas constantly appearing in the
pages of magazines one does not have to
depend upon memory, since an idea-file
will always keep them on tap, available at a
moment's notice when you want them. The
necessity of having to remember where
you last saw such and such an idea, and
having to spend a lot of unnecessary
time trying to dig it up is obviated by
the use of a good file.
The idea-finder saves you this an-
noyance and bother. It also
saves time and labor, for if you
have filed away your material
for safe keeping, it is always go-
ing to be on hand, right at your
finger tips, ready for instant use.
Good ideas are always finding
their way into print. Plans are
being constantly evolved by
others and heralded in the pages
of magazines. There is always
a wealth of various kinds of in-
formation at hand, simply await-
ing collection, coordination, and
preservation in organized form.
By starting such an idea-store-
house you can have within elbow
reach the most useful data that
can be obtained from literature
of all kinds — data which might
otherwise, for want of assimila-
tion and organization, go to seed,
be forgotten or neglected.
As you read a magazine you
can mark articles of particular
interest which suggest fruitful
ideas for future application, and
index them in synopsis form on a
3x5 inch card, which is filed in
a card tray, with alphabetic
guide cards. These are arranged
according to subjects in which
you are vitally interested.
Then again, you can clip these
articles and file them away,
either in filing folders, or in a
desk-book file, with pocket pages, an old
time bill file, or a work-organizer. Any of
these simple accessories may be obtained
from a local sta-
tionery store at
small cost.
If you want to
put yourown ideas
to work immedi-
ately, you scrim-
mage through
your file and find
data already in
your idea-store-
house which en-
ables you to carry
out yourown plans
effectively, and
with greater assur-
ance of success.
Or, your own ideas
may start you on a
scouting expedition
for similar plans in
the magazines to
which you regular-
4 ly subscribe, and
45° so open up a new
— i subject for further
investigation and
data-gathering.
F. E. KUNKEL,
Washington, D. C.
Primary-,
Dial
TOP VIEW
A
BRASS ROD Vil DIAM. 3^' LONG
D
FIG. 3
RADIO BROADCAST ADVERTISER
209
mfherafm
ZONE-8
wcx fowoc
ZONE-3
WJAR to WNAC
ZONE-6
WSB to WHAS
ZONE -7
WFAAfo WOS
ZONE-4
WWJ fc> KDKA
ZONE -5
WFI io KGO
ZONE-2
WORD to KFVG
ZONE- 1
KFOTfo 200 aw/ere
WAVE- MASTER
Standard Model
$125.00
WAVE- MASTER
Brotvn Walnut Console
with inbuilt horn
$275.00
A Separate Circuit for Each
40 Meter Wavelength Band!
Kellogg — • for 28 years makers of precision telephone instruments and
equipment — producers of quality parts since radio began — Kellogg has
perfected a radio receiver worthy to bear the Kellogg name.
In the illustration we visualize this
wonderful engineering achieve'
ment.
In the new WAVE-MASTER
there are nine separate circuits —
one for each 40 meter wavelength
band. Each circuit gives that max-
imum efficiency heretofore found
only in one short section of the
dials of ordinary radio frequency
sets. Each circuit brings within
the range of the tuning dial a dif-
ferent group of stations.
How wonderfully simple tuning
becomes! Merely set the pointer
to the wave zone in which you are
interested and bring in the desired
station with the single Selector dial.
This remarkable tuning dial actu-
ally has a tuning range of 540 de-
grees— equal to 1/4 times around
a complete circle — over three times
the station finding range of any
other set.
All other radio frequency sets have
variable capacity which must be
tuned, usually with three different
dials, to balance with their in-
ductance coils.
The WAVE-MASTER'S induc-
tance is not fixed but variable and
is easily and quickly tuned, with
the one Station Selector dial, to
balance the fixed capacities.
Write us for the name of your near-
est dealer. We will also send on
request, a complete explanation of
the WAVE-MASTER circuit.
Ask for Folder No. 5-L.
Kellogg Switchboard & Supply Company
1042 W. Adams St., Chicago, 111.
Radio Dealers and Jobbers
The WAVE-MASTER franchise, backed by Kellogg
resources and our powerful advertising campaign,
is most valuable. Open territory is being closed
rapidly. Wire us, or get into Chicago, quick, and
tec us.
nnH annrmrprl Kv T? 4nir»
210
RADIO BROADCAST ADVERTISER
Radian Panels in black and Makoganite
come cut in standard sixes for all sets.
Be Sure of
Lowest Losses
RADION Panels are most ef-
fective in reducing surface
leakage and leakage noises be-
cause they are moulded from the
insulating material made to
order for radio purposes ex-
clusively.
No. 2 Socket for new UX
tubes with collar adapter
for old type tubes. No. 4
same as No. 2, without
collars, for new UX tubes
exclusively.
Tests after tests have proved
that Radion insures lowest losses
and highest efficiency. Radion
Sockets, Dials, Insulators and
Tubing have the same high-
resistant characteristics as Ra-
dion Panels. They embody the
latest developments in radio.
Ask your dealer to show you the
complete line of Radion low-loss
parts.
Send 10 cents for booklet,
"Building Your Own Set"
AMERICAN HARD RUBBER COMPANY
Dept.C-12 11 Mercer Street New York City
Chicago Office: Conway Building
Pacific Coast Agent: Goodyear Rubber Co.
San Francisco Portland
New No. 10 4-inch Radion Dial. Nine other
styles in several sizes to meet all requirements.
^Ihc Supreme Insulation
Made to order for radio purposes exclusively
AMERICAN HARD RUBBER CO.
Dept- C12. 11 Mercer St.
New York City
Please send me your booklet for which I en-
close 10 cents in stamps.
Name
Address
SUPER-HETERODYNE NOISES
I HAVE been troubled at times with a
peculiar sort of throbbing, spluttering
noise which was sometimes accom-
panied by a low whine which sounded as
if it was under a strain, on my super-
heterodyne.
I tried almost everything to obviate
this trouble and inquired of several radio
men as to the cause — without result, and
was almost baffled. I finally discovered
that it was due to corroded A and B battery
terminals.
I used battery clips to connect to the
battery and when the clips all happened to
bite through the corrosion I did not get
the noise. "How simple!" the reader
will probably say, but I will confess that
it bothered me at times for two months
before I finally ran it down.
I hope that this may be of benefit to some
other fan.
I. T. SUGGS,
St. Paul, Minnesota.
CHECKING UP ON B BATTERY
LEAKAGE
MANY magazines are advising the use
of incandescent lamps in series
with the B battery to protect tube
filaments, and to lengthen the life of
such batteries, by lighting up to indicate
shorts.
When such a lamp is used with a multi-
Lamp-
•OB +
Receiver
-OB-
A
(WRONG)
-OB+
Receiver
-OB-
(RIGHT)
FIG. 4
tube set having no by-pass condenser, or
else a very small one, oscillations and howl-
ing often result. The effect is the same as
using a B battery partly run down — it adds
resistance to the circuit. Therefore put a
large condenser directly across the B bat-
tery as shown in Fig. 4 B.
If the lamp lights dimly when the set is
turned on, of course a short circuit exists in
the set and can usually be easily located. .00025
But the fact that the lamp does not light is mfd.
no indication there is no B battery leakage
in the set — a small leak wouldn't pass
sufficient current to light the lamp. So it
is advisable, before any home-made set is
put in use, and after making tests for shorts
and remedying any found (a short would
ruin the meter in the next test), to connect a
high resistance voltmeter in place of the
lamp in B. Turn up the rheostats, when a
small deflection on the meter should result.
Then turn the rheostats completely off and
the meter should read zero. If it reads
even slightly past zero, there is a leak in the
set which will run the B batteries down even
when the set is not in use.
For example, one set checked this way
showed a very small deflection, which,
measured with a milliammeter, amounted to
only | milliampere. The set required seven
milliamperes in operation, but because such
a leak goes on whether the set is in use or
not, this one would cut the B battery life
in half where average use of the set was one
and a half hours per day. The trouble in
this particular set was traced to a by-pass
condenser of .002 mfd. size (of reliable
make, probably damaged by soldering), and
replacing it stopped the leakage. Another
leak of this sort was located between the
windings of one long-wave transformer in a
super-heterodyne outfit.
The measurement by a milliammeter was
not necessary to locate the leakage, it was
made merely to show by calculations how
serious such troubles might be. Where the
B battery life is short in any set, the above
test is certainly advisable.
CLAUDE SCHUDER,
Sumner, Illinois
A VARIOMETER TO TUNE ANTENNA
CIRCUIT OF THE ROBERTS SET
A VARIOMETER can be used to re-
/-\ place the two antenna coils, variable
•f »• condenser, and switch, in the Roberts
circuit. It is much simpler to construct
than the standard arrangement, is easier to
tune, just as selective, takes up less space,
and makes a neat panel appearance, and
there are fewer possibilities of losses. 1 f you
are mechanically inclined, you can easily
make a variometer.
The sketch, Fig. 5, shows the part of the
set that is changed. From the grid of the
amplifying tube and the plus terminal of
theC battery, the hookup is the same as in
the original circuit diagram. Connect the
stator terminal to the antenna binding post.
The rotor goes to the ground post. Some
variometers may work better with the rotor
terminal connected to the antenna post
and stator to the ground. Connect the
terminal of the variometer that is connected
to the antenna, to the grid terminal of the
amplifier tube as shown. Connect the
ground terminal of variometer to the
negative post on the C battery. A small
fixed condenser of about .00025 mfd. will
probably be needed in series with the an-
tenna as shown, otherwise the average
variometer will not reach below 999 kilo-
cycles (300 meters) when used this way,
especially if you have a long antenna. It
is interesting to experiment with a variable
condenser in series with the antenna.
There have been many interesting sug-
gestions on improving the Roberts set and
FIG. 5
the variometer will work equally well with
two or four tubes. A set in Washington,
District of Columbia, using four dry cell
tubes, gave good loud speaker volume on
KHJ. With two tubes, KHJ was easily
heard on head phones. I logged seventy-
five stations on a loud speaker in one
month.
JOHN L. LEE,
Washington, District of Columbia.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
EVEREADY HOUR
EVERY TUESDAY AT 9 P. M.
Eastern Standard Time
For real radio enjoyment, tune in the "Ever-
eady Group," broadcast through stations —
WEAF New York WCAE Pittsburgh
W J A R Providence W S K I Cincinnati
WEE I Boston WWJ Detroit
WTAG Worcester
W F I
W G R
Philadelphia wcco
liutTalo WOC
KSO St. Louis
Minneapolis
St. Paul
Davenport
RADIO DRY
No. 764
Portable
22y,-volt
Vertical
Price
$1.75
Evtready
Columbia.
Ignitor
"A"
Battery,
the proven
dry cell
jor all
radio
dry cell
tubes
volts
No. 779
22'A-volt
Large
Vertical
Price
$2.00
For radio economy
EVEREADY Radio Batteries are noted for their long
service and economical operation. They are made in
different sizes and types so that every radio user can
enjoy the economy and convenience to be had by
fitting exactly the right Eveready to his receiver.
The five dry cell types of Eveready Radio Batteries
are here illustrated and described to make it easy
for you to decide just which will give the longest
and most economical service on your set. A dealer
near you sells Evereadys.
Eveready Heavy-duty "B" Battery for four
or more tubes
No. 486. Extra-large Layerbilt. 45 volts. Vertical.
Eveready's latest contribution to radio. The new Layerbilt
construction which gives much greater service. Same
size as No. 770. Price $5.50.
Eveready "B" Battery for one to three tube sets
No. 779. Large. 2V/2 volts. Vertical. Especially adapted
for Radiola 25, DeForest D-17 and Operadio receivers.
Same capacity as No. 766, and suitable wherever variable
taps are not required. Price $2.00.
Eveready "B" Battery for portable sets
No. 764. Portable. 22l/z volts. Vertical. For portable
sets where medium weight and size are permissible.
Price $1.75.
Eveready "A" Battery
Eveready Columbia Ignitor Dry Cell Radio "A" Battery
for all dry-cell tubes. V/2 volts. The dry battery used
by vacuum-tube engineers in developing the dry-cell tube.
Eveready "C" Battery
No. 771. 4^2 volts. Saves "B" Batteries, improves tone.
Price 60 cents.
Manufactured and guaranteed by
NATIONAL CARBON COMPANY, INC.
New York San Francisco
Canadian National Carbon Co., Limited, Toronto, Ontario
EVEREADY
Radio Batteries
- they last longer
Tested and approved by RADIO BROADCAST
212
RADIO BROADCAST ADVERTISER
for Christmas
A set of NA-ALD
Colored Dials
to dress up your radio
Give 'em to your wife and
get the benefit yourself!
TXTHEN fans first built radio sets,
" • the womenfolk registered silent
objection to their ugly appearance but
they endured the clutter because radio
was such a novelty and because they
thought maybe you'd soon get over
the craze.
But scon as they saw your craze was a
permanent obsession, they began ask-
ing for better-looking sets.
The latest, up-to-the-minute advance-
ment in making a set harmonize with
its surroundings is represented by the
New Alden Colored Dials. They will
make your old set most attractive. To
the new set they will add the pleasing
qualities of color and beauty.
The colors are Garnet; Malachite
Green, like mottled green and white
marble; Brilliant Tortoise, that blends
with every color combination; or in
beautiful Grained Mahogany. $5.00 a
set, any color, in hardware, electrical,
radio or department stores and in gift
shops.
Give a set to someone in your family
and then — all of you can enjoy their
beauty! Or here's a stunt. Leave this
magazine open on the living room table
at this page, with a big pencil check
mark beside this ad, and see if the fam-
ily doesn't take the hint and buy a set
for you. If the wife of one of your
radio fan friends asks you what to give
her husband for Christmas, you might
mention Alden Colored Dials.
Mail the coupon below if you'd like
some free but worthwhile information
on the New Colored Dials.
ALDEN MFG. CO.
Dept. B13. Springfield, Mass.
Alden Processed
ALDEN MFG. CO.
Springfield, Mass. Dept. 613.
Please send me "What to Build'* information together
with information on Na-Ald Colored Dials.
HOW TO ELIMINATE LOCAL
Part 2
Some Practical Information Based on the Results of
an Investigation on Radio Inductive Interference
T AST month's RADIO BROADCAST presented the first of two articles to be
•*-' printed herein on the above subject. The information has been taken
from a very excellent little pamphlet which has been specially prepared by the
Radio Branch of the Department of Marine and Fisheries of the Dominion of
Canada Government, and which is entitled "Radio Inductive Interference,
Bulletin Number One." The previous article was devoted chiefly to determining
the source of various forms of interference while this concluding part fives much
practical information for the elimination of the trouble once it has been found.
MEANS OF SUPPRESSING RADIO INDUCTIVE INTER-
FERENCE
IN CASES where electrical apparatus sus-
pected of causing interference appears to be
in good mechanical and electrical condition,
it is very often possible to supply some means of
preventing electrical surges, originating in the ap-
paratus, from getting out to the power line where
they would radiate and cause radio interference.
These electrical surges have the property of
passing through condensers more readily than
through inductances. The method employed,
therefore, in preventing electrical surges from
traveling along the power lines and thus causing
radio interference, is to provide a path to ground
sufficient insulation to withstand the voltage of
the line. These installations should be approved
by the local electrical inspector to ensure that
there are no fire or accident hazards introduced
by the installation.
It is important in the design of these choke
coils that they should have low distributed
capacity in order to prevent the electrical surge
passing through the choke coil by means of this
capacity.
CHOKE COIL
A TYPE of choke coil recommended for
*• cases where the current is less than three
amperes, is constructed according to Fig. i. It
consists of a hundred turns of No. 18 double cot-
ton-covered copper wire in a single
layer, wound on a fiber tube 3
inches in diameter, \ inch thick.
Leads are soldered to each end and
made from No. 14 flexible rubber-
insulated braid-covered copper
wire, making one turn around
the tube then through a hole in
the tube and extending through
the inside of the tube. The
burrs are carefully removed from
the hole in the fiber tube so as not
to cut the insulation. End rings
or fillers are mounted at the end of
the winding to build up the same
diameter as the outside diameter
RADIO BROADCAST Photograph
AN INTERFERENCE FINDER
Of typical form. This was made in the RADIO BROADCAST Laboratory. One Duplex variable
condenser tunes both loop and the R. F. secondary, which feeds into a crystal detector
in the form of a condenser to filter or drain off
this surge. In order to make this filter more
effective, it is often advisable to introduce be-
tween the line and the source of the disturbance
a trap, which will make the passage of the surge
more difficult. This trap preferably takes the
form of a choke coil which consists of a number
of turns of wire of sufficient size to carry the
required current without overheating, and
Tested and approved by RADIO BROADCAST i
of the winding. These may be made of tape
or a suitable size of fiber tube. The whole
coil is then covered with five layers of Empire
cloth and then taped with black friction tape
and painted with insulating varnish. Mounting
lugs made of fiber are then attached to each
end of the coil.
This coil should be mounted on a board
covered with asbestos i inch thick and the leads
RADIO BROADCAST ADVERTISER
221
ATWATE R KENT
Model R,$IZ
Model II, Jll
Model 12 (without lubes), $100
Model I9,f<i
fricei slightly higher from the
Rockies ivesty and in Canada
"But why
he go?"
WHEN they struck oil on the Indian lands in Oklahoma
many of the Indians became suddenly rich. One of
them, anxious to begin his life of luxury, went to buy
an automobile.
The salesman launched into a description of the car
in detail. Technical term followed technical term in a
bewildering stream. Finally the salesman thought his work
was done. He produced an order blank and paused.
"Now," he asked, "is there anything else I can tell
you?" The Indian scratched his head.
"Urn," he said. "You tell me: He no have horse.
Why he go?"
We could give you a description of the Atwater Kent
Radio Receiving Sets and Speakers that would fill hun-
dreds of pages.
But what would be the use? You would still judge
an Atwater Kent, as you should, by its performance.
We want you to judge it that way, to compare it with
any other radio you are considering.
By looking at it and listening to it, you will get some
of its technical perfection. When you have owned it and
lived with it, you will know how good it is.
Hear the Ativatcr Kent Radio Artists every Sunday evening at
9.15 o'clock (Eastern Standard Time) through stations:
WEAK . Neiv York WEEI .... Boston WCAE . . Pittsburgh
WFI ) Philadelphia WGR Buffalo woe . . . Davenport
woo ^ alternating wwj .... Detroit WSAI. . . Cincinnati
WJAR . Providence KSD .... St. Louis WTAG . . Worcester
WCAP . . . Washington wcco . . . Minneapol:s-St.Paul
Write for illustrated booklet of Atwater Kent Radio
ATWATER KENT MANUFACTURING COMPANY
A. At-wattr Kent, President
4.726 WIS&AHICKON AVENUE . PHILADELPHIA, PA.
-^ Tested and approved by RADIO BROADCAST ^
Model M,$z8
Model 10 (without tubes), $80
Model 20 Compact, $80
Model 24, $100
Prictt t light fyhightr from th*
Rotkitf wtit, and in Canada
RADIO BROADCAST ADVERTISER
For EVERY
Radio Set
A stunning piece of furniture that
restores order in the room where
you have your Radio! No more
cluttered table-tops, nor litter of
equipment un-
der-foot.
No unsightly
horn in evidence,
either! This con-
sole has its own
loudspeaker, in-
built. It's out of
sight, but with
very apparent
tonal SUperiori-
«-i»o T?/-,«- it Uoo
ies. t*or it nas
the highest -de- Position which defeats
,- vibration.
veloped type of
unit. With horn built of special
non-vibrating,extra-hard,ceramic
material. Produces clear non-vi-
brant tone.
There's ample room for every-
thing; space for largest A and B
wet batteries — or battery elimi-
nator—required for any home set;
and for a big charging outfit, too.
Finished in mahogany, or walnut color.
Dainty design of parqueterie on two front
panels. Top, 38 in. x 18 in. Substantially
built; the product of a 40-year-old furni-
ture maker.
The price, forty dollars, is for the complete
console and includes the loudspeaker horn
and unit. Thousands of dealers are show-
ing this artistic addition to home radio
equipment.
Rear View— Set Hooked Ul>
Non-Vibrant Ceramic
Horn
The clearest tone pro-
ducer on the market.
Made of special com-
Prict, tlO
West of Koch Mis., t42.SO
Windsor Furniture Co
soldered and thoroughly taped according to
standard wiring practice. Another type of
choke coil which
^^••^^MI^^H^^ w'" be found emi-
nently satisfactory
for use in motor
lines, telephone
bell-ringing lines,
etc., is that de-
scribed on page 438
of September
RADIO BROADCAST,
in the columns of
the Grid (and pre-
viously in the May
issue of 1924). It
was originally de-
scribed by Mr. Van
Dyck in his article
entitled "Man-
Made Static."
RADIO BROADCAST Photograph
A PORTABLE INTERFERENCE FINDER
Consisting of a stage of radio frequency amplifi-
cation followed by a crystal detector. A col-
lapsible loop will greatly improve the portability
possibilities
INSTRUCTIONS FOR MOUNTING CONDENSERS
/CONDENSERS which will stand a test
^-> voltage of 1000 volts d. c. may be con-
nected across an alternating current or direct
current circuit of 250 volts or less. On circuits
which are protected by fuses of not more than
15 amperes capacity, no additional fuse is re-
quired for the condenser. On circuits protected
by fuses of greater than 15 amperes capacity, a
separated cutout base and small fuse (of ap-
proved type) not exceeding 15 amperes, must be
installed between the condenser and each un-
grounded power wire. Where condensers are
not installed in metal boxes and are to be placed
on wooden surfaces, they should be mounted on
pads of asbestos at least \ inch thick, and these
pads should be sufficiently large to extend be-
yond the clamps used for holding the condenser
in place.
Where condensers are to be used on 550 volt
circuits, two condensers of the approved type
must be connected in series between the lines
and the common point may be grounded. In
such installations, the condensers are to be pro-
tected by 6oo-volt fuses not greater than 10
amperes in each live line, and both the con-
densers and fuses are to be enclosed in a grounded
metal case. Where the condensers are to be
connected to two-phase or three-phase circuits
not greater than 600 volts, one condenser may
be connected from each live line to ground and
installed with fuses in boxes as stated above.
As these condensers contain wax, they should
not be placed where they may be subjected to
excessive heat.
Condensers when connected to a circuit as
stated above have no objectionable effect on the
circuit or the operation of any electrical appara-
tus and they do not consume any power.
APPROVED TYPES OF CONDENSERS
HpHERE are now many condensers on the
* market suitable for the purposes detailed in
this article. Those chosen must be capable of
standing a test voltage of 1000 volts d. c. At
r Tested and approved by RADIO BROADCAST -J
the time of the publication of this bulletin by the
Department of Marine and Fisheries of the
Dominion of Canada Government, special
condensers having No. 14 rubber-insulated leads
suitable for installing without metal boxes, were
obtainable from the Radio Branch of the above
Department, at cost.
TREATMENT OF TYPICAL CASES
IN MANY cases it is possible to make slight
• changes in the connections of the electrical
apparatus causing the surge in order to use some
existing apparatus as a choke coil and thus pre-
vent the necessity of adding additional choke
coils to the system.
A series commutator motor causing a surge by
sparking at the brushes may have its leads
reversed to reduce the radio interference. Where
one wire is grounded, radio interference from
such a motor is sometimes reduced by reversing
the leads supplying the motor, so that one of
the brushes is connected to the ground side of the
line and the field coil is connected to the live side
of the line. In this case, the field coil is used as
a choke. It may also be necessary to place a
, Friction Tape and
Varnished Cambric
End Ring
-FibreTutw
FIG. I
Details for the choke construction. It consists
of one hundred turns of No. 18 d. c. c. copper wire
on a three-inch tube
condenser of one or two microfarads capacity
across the brushes. This is shown in Fig. 3.
In cases where neither side of the line is
grounded, a choke may be inserted on the line
connected directly to one of the brushes, while
the field coil may act as a choke in the other line.
In this case it is recommended to use two 2-
microfarad condensers in series and ground the
middle point according to the diagram.
In cases where it is not convenient to make
connections with the brushes of a motor, the
condenser may be placed across the line as near
the motor as possible, and a choke coil may be
RADIO BROADCAST Photograph
FIG. 2
Showing condenser connection across
vibrating contacts of a battery charger
inserted in the live line when necessary. See
the instructions above regarding approved con-
densers and the use of fuses.
RADIO BROADCAST ADVERTISER
The S. L. F. that
doesn't "hog" panel space
The principal objection to many Straight line Frequency con-
densers now on the market is that they "hog" too much panel
space; thus making it necessary to re-arrange other instru-
ments on the panel or rebuild the set entirely to allow enough
room for the scythe-like sweep of the S. L. F. rotor.
The new General Radio type 374 S. L. F. condensers eliminate
entirely all such difficulties. They occupy the same panel
space as the well known types 247 and 334 condensers — and
no more. In fact they may be used interchangeably with
those condensers since the mounting holes are the same.
By using smaller rotor plates of correct shape and double the
number of plates General Radio condensers have a straightline
frequency calibration curve without the mechanical disadvan-
tages encountered in the average S. L. F. with fewer plates of
larger area. The assembly of the type 374 condensers with
respect to bearings, soldered-plates, and correct spacings are
the same as the types 247 and 334.
For further description and prices ask to see them at your
local dealer's or write for our latest Bulletin 923-R.
GENERAL RADIO COMPANY
30 State St. Cambridge, Mass.
For over a decade General Radio
parts have been the universal stand-
ards of quality.
They have been developed by the
same engineers who designed the pre-
cision apparatus now used as stand-
ard equipment in nearly all the lead-
ing commercial and technical school
laboratories throughout the entire
world.
Since 1915 the General Radio Com-
pany has supplied scientific instru-
ments in ever increasing quantities to
such prominent institutions as the
General Electric Company, Westing-
house, Bell Telephone System, and
the Bureau of Standards for use in
electrical and radio research.
No one company in the history of
radio has contributed more in labora-
tory equipment than the General
Radio Company.
The same outstanding skill, mate-
rials, and workmanship are embodied
in General Radio parts for use in the
construction of broadcast receivers.
Through the merits of design, per-
formance, and price General Radio
instruments for the scientist or set-
builder are universally recognized as
the Standards of Excellence.
Every instrument made by the
General Radio Company is thorough-
ly guaranteed.
GENERAL RADIO
Behind the panels of Better Built Sets"
Tested and approved by RADIO BROADCAST
224
RADIO BROADCAST ADVERTISER
Cfjrtetma*
On the Air!
Are Your Tubes in Shape?
At Christmas Tide! Listen to sweeter
"Christmas Carols" — clearer chimes and
more celestial music broadcast by the great
cathedral choirs throughout the land.
A Rhamstine*
TUBE BOOSTER
Rhamstine'Ar
Tube Booster
Only
will renew your old
tubes with all the
pep and freshness
of new ones. Just
put them in the
socket and turn on
the current — do it
once a month — it
will treble the life
of your tubes and
give you better dis-
tance, volume, and a
tone as clear as a belt
at all times. It will pay
for itself in a few days.
Works on any alter-
nating current 110-120
volts, 50-133 cycles. It
matters not, whether
you use 2OI-A or 199
Type Tubes.
Send no money — check
the coupon below — pay
on delivery.
-- 1 *** I ft • •/*
B Rectifier
Eliminates
B" Battery
Rhamstine* "B" Rectifier
Only
(Tube not included)
£liminatfS all your "B" Batt*ry troubles such as
recharging, dead cells, and chemical action. A
Rhamstine* "B" Rectifier will more than take the
place of a "B" Battery — tt will give a continuous
and uniform current year in and year out with abso-
lutely no trouble at all. Small, compact, good look-
ing, endorsed by the leading radio manufacturers,
and reasonably priced. You should have one.
Send no money — just check the coupon.
Tube Boosters are Trade Boosters.
DEALERS write for our attractive proposition.
Mail the Coupon To-day
J. THOS. RHAMSTINE* (12)
506 E. Wood bridge, Detroit, Mich.
Please send me
D Rhamstine* Tube Booster at $6
D Rhamstine* "B" Rectifier at $25
by express C. O. D. subject to inspection. If I am
not entirely satisfied with the "B" Rectifier I will re-
turn it to you in five days and receive a refund of the
full purchase price.
Name. . .
Address .
J. THOS. RHAMSTINE*
Radio and Electrical Products
506 E. Woodbridge St., Detroit, Mich.
The live side of a low voltage lighting circuit
may be determined by means of a test lamp con-
nected from ground first to one wire and then to
the other. The lamp will light when connected
from the live line to ground.
Battery charger of the vibrator type may be
prevented from causing radio interference by
connecting a condenser of \ microfarad capacity
across the vibrating contacts. This is illustrated
in Fig. 2 on the previous page. In the case of
battery chargers it is useless to put condensers
2 Mid. Condenser
1000 Volts
FIG. 3
Method of connecting a large capacity con-
denser across the brushes of a small motor
across the mains, as it is necessary to make use
of the choke consisting of the wire and coil within
the battery charger, to prevent this surge from
getting out on the line.
Flashing electric signs may usually be prevented
from causing radio interference by connecting
condensers of from 5 to 2 microfarads capacity
across the contacts of the circuit breaker. It is
sometimes necessary, however, to add a choke
coil at the line side of the circuit breaker and also
connect the condenser across the contacts of the
circuit breaker. As the radio interference from
such sources depends upon the conditions of the
installation it is necessary to make these few
experiments, as suggested above, in each case in
order to reduce the radio interference most
effectively.
Sometimes the radio interference from a flash-
ing sign installation is caused by sparking at the
commutator of the motor which drives the
flasher. This may readily be determined by the
nature of the sound in the radio receiver and may
be remedied by the method described for dealing
with interference from commutator motors.
Internal combustion engine ignition systems
may cause radio interference, but this is usually
of a very local nature. Such interference may be
considerably reduced by making the leads from
the magneto or spark coil to the engine as short
as possible and running them in a grounded
shield, such as metal conduit or lead-covered
cable. The frame of the engine, magneto, and
all shields, should be thoroughly grounded.
Rotary converters sometimes cause radio
inductive interference by producing a surge
which travels out both on the alternating and
direct current lines. In some such cases it
may be necessary to introduce choke coils into
the alternating current lines and put condensers
across the lines between the choke coils and the
converter. Before putting these choke coils
in the alternating current lines, it is recom-
mended to try the effect of condensers across the
brushes as described previously for the case of
commutator motors.
Electric oionators which are used for purifying
the air in large buildings and for bleaching pur-
poses in flour mills, sometimes cause radio
inductive interference by producing a surge
which travels along the primary lines supplying
the ozonator.
This interference may easily be eliminated by
connecting two choke coils of the cylindrical
type previously described, one in each of the
low voltage lines placed as near as possible to the
ozonator.
less than 600 Volts
Ungrounded
If Motor Fuses are
Large/than 1 5 Arnps.
- Inserts Ampsfuses Here,
1
L — ii---. — n
'.' " * ".'
Dotted Lines Show Addition
of Condensers Across Motor
or Generator Brushes
FIG. 4
Connection for two condensers in series across
the brushes of a motor generator. The position
for extra fuses, if the motor fuses are larger than
1 5 amps., is clearly shown
A List of Australian Broadcasting Stations
Here is a complete list of Australian broadcasting stations now active in that country. It is not gen-
erally known that one of these stations, that at Brisbane, Queensland, can vie with some of the important
American stations as far as power is concerned, for they use 5000 watts. As will be seen by the list,
three of the seven other stations use as much as 3000 watts. American stations are often heard in Aus-
tralia, especially those ;..::aicl on the Pacific Coast. We are indebted io Mr. A. W. Watt, editor of
Australian Wirtless Weekly, for the appended list.
LOCATION
Sydney, New South Wales
Sydney, New South Wales
Melbourne, Victoria
Melbourne, Victoria
Adelaide, South Australia
Perth, West Australia
Hobart, Tasmania
Brisbane, Queensland
Farmer and Company Ltd.
Broadcasters, Ltd.
Australian Broadcasting
Co. Ltd.
Associated Radio Co., Ltd.
Central Broadcasters Ltd.
West Australian Farmers
Ltd.
Associated Radio Co., Ltd
Government Radio Service
CALL
2FC
2BL
3LO
3AR
5CL
6WF
7ZL
4QG
FREQUENCY
IN KC.
26l
857
809
789
937
240
769
779
WAVELENGTH
IN METERS
350
37"
380
320
1250
390
385
POWER
IN WATTS
30OO
5OO
3OOO
JOO
500
30OO
5OO
50OO
The broadcasting from the above stations is usually divided into four sessions, morning, afternoon,
early evening, and evening. The exact times of these sessions, taking jlo as an example, are as
follows: Morning, from 1 1 a.m. to 2 p. m.; afternoon, from ) p.m. to 5.75 p. m.; early evening, from 6
to 7.75 p. m.; evening, from j.i^to up. m., the program always concluding with "Cod Save the King."
The difference between New York and Melbourne time is fifteen hours, thus, when it is midday in New
York on a Monday, it is 3 a. m. Tuesday in Melbourne. Appropriate allowances must be made when
comparison is being made between Melbourne time and United States time in points west of New York,
and also for Australian points west of Melbourne.
if Tested and approved by RADIO BROADCAST *
RADIO BROADCAST ADVERTISER
225
THE • PERFECT • UNION • OF • ART • ANO • SCIENCE
DE FOREST W 6
n F TV A TfifiA KC.E TYPE
DE FOREST AUDION
\B the world standard in tubes. De Forest
created the first successful radio tube, and
his Invention made broadcasting possible.
The De Forest policy o f a specific type tube
for each socket Insures finer reception and
greater distance. Price. $3.
DE FOREST F-5 AW
A compact, powertu 1 set I n polished walnut
that will bring joy to many a household.
Gives rich volume, and has the capacity to
separate stations positively so that you can
pick the broadcast gems without Interfer-
ence. Extremely easy to operate. Price
(minus tubes, loud speaker and batteries)
$90.
DE FOREST F-5 M
A superfine 5-tube set in two color mahog-
any cabinet with built-in loud speaker and
concealed compartments for "A" and "B* '
batteries. A great distance-getter, with un-
canny power to tune in and out stations at
will, and gifted with splendid tonal quali-
ties. Extremely simple to operate. No
howling or hissing in tuning In. An unsur-
passed value at $110.
De Forest Radio Sets can be bought
at prices ranging from $85 to $450.
De Forest Genius now Humanizes Radio!
But Tonal Supremacy is Not All —
Elbert McGran Jackson, renowned sculptor,
architect and painter, put into this hand-
wrought, hand-carved cabinet the spirit of
radio, in design, in motif — it is not an adap-
tation of a phonograph. An image of charm-
ing individuality, it harmonizes with the set-
ting of any home.
One unit, everything self-contained — not a
wire in sight, nothing to connect . . . and
portable; move it any place! Only charm and
beauty for the eye.
The artistic conical reproducer is an insepa-
rable part of the cabinet and its tonal mecha-
nism peerlessly attuned to that of the Weagant
circuit. There are just two controls for tuning,
and these operate on one dial, which makes
the normally perplexing task of "tuning in"
extremely simple. There are special power
tubes in the fifth and sixth sockets which can
give you volume to flood an auditorium, if
you desire it. And, at your fingers' tips, the
means to tune in a far-distant station you
want no matter how powerful nearby stations
may be.
See the incomparable De Forest Wj and W6
at your De Forest dealer's or write for an in-
teresting booklet describing these master-
pieces in detail.
DE FOREST RADIO CO., Jersey City, N. J.
9Ae Qraite&
J\famt in'Radio
DEALERS IN ALL CITIES AND RADIO COMMUNITIES
THE EPOCH-MAKING ACHIEVEMENT WHICH MAKES ORDINARY RADIO RECEPTION A THING OF VE5TERDA
CTy^ARVELOUS new circuit, just
C_X 0 L perfected, reproduces flawlessly
the mellow, sort modulations of
the human voice and captures the
hitherto elusive overtones of the
musical register .... tuning sim-
plified .... a new ease in opera-
tion .... all embodied in the new
and beautiful De Forest W5 or W6
Radiophones.
^ ^> ^>
The voice of radio is no longer flinty and me-
tallic, but mellow, human and musical —
thanks to the development by Roy A. Wea-
gant, Vice-President and Chief Engineer of
the De Forest Radio Company, of a new and
marvelous circuit.
This ingenious circuit, and all the joy it
means to radio lovers, makes its first public
appearance in the De Forest W5 and W6 Radio-
phones, masterpieces of cabinet art worthy
only of a scientific development so outstanding.
So wonderful is the reproduction of tone in
the De Forest W5 or W6 that only the presence
of the lovely instrument dispels the illusion
that the living artist is in the rooms.
Piano chords come to you with their full
rich resonance — true piano tone. High notes
dance, ripple and sparkle . . . clearly, dis-
tinctly. . . musically! Those brooding low notes,
never caught in average reception, are heard
distinctly — as though from the next room.
In the reproduction of orchestral music the
full importance of the De Forest achievement
stands out. For the first time you get the over-
tones as well as the middle tones . . . the ma-
jestic roll of the kettle drums, the crooning
of the bass viols, the strident crash of the
brasses and the piping heraldry of the cornets
and trombones. A symphony orchestra heard
over the De Forest W5 or W6 stirs the soul.
No incoherence, no oscillating jumble of
noise — every instrument, every octave, in its
true value. A ma&ic achievement'.
To the lover of dance music the De Forest
W5 or W6 brings more sprightliness, more
beauties of syncopation . . . you should hear
Vincent Lopez, Joseph Knecht, The Night
Hawks, or any others over either of these in-
struments!
All the tenderness of song, every shading of
the soprano's voice, all the pathos of the folk
song — exquisite but elusive elements so much
desired but lost in practically all present-day
reception, are captured by these De Forest
masterpieces.
To everything that is broadcast, the De
Forest Radiophone gives animation, life and
humanness.
226
RADIO BROADCAST ADVERTISER
BE SAFE-
—the Fire Under-
writers Radio Code calls
for the installation of a
lightning arrester where-
ever an outside antenna
is used.
The Jewell
Arrester —
—has been approved by
the Underwriters (see their
Certificate No. E-5403) for
both indoor and outdoor in-
stallations. It is mounted
in an attractive brown por-
celain case and is easily in-
stalled.
Radio
Instruments —
ask your dealer for a
Jewell 15-B Radio Catalog
— or write to us.
Jewell Electrical Instrument
Company
1650 Walnut St., Chicago, 111.
Making Good Instruments
for 26 Yean
THE GRID
A Department Devoted to Solv-
ing the Problems of our Readers
QUERIES ANSWERED
1. WHAT IS THE PROPER METHOD FOR PLACE-
MENT OF COILS IN A TUNED RADIO-FRE-
QUENCY AMPLIFIER? — F. H. J. — Houston,
Texas.
2. WHAT ARE THE PRECAUTIONS THAT SHOULD
BE OBSERVED IN ERECTING AN ANTENNA
NEAR POWER LINES?
C. A. C— Buffalo, New York.
COIL PLACEMENT IN AN R. F. AMPLIFIF.R
IN A receiver employing one or more stages
of radio-frequency amplification, satisfactory
results depend largely upon whether or not
these amplifiers are properly neutralized. Now,
neutralization depends upon several things.
The internal capacity of the amplifier tube must
be balanced ; the wiring to the tube must be such
that no coupling effects are obtained; and the
Swivel -
with Set Screw
FIG. I
several radio-frequency transformers should be
so placed and located that there is no electro-
magnetic coupling between them. It is this
last point which we will discuss here.
Most of us have had an opportunity to view the
inside of a neutrodyne and to observe the pecu-
liar angle at which the coil units are turned.
At such a setting there is a minimum of coup-
3. WILL YOU DESCRIBE A METHOD OF MEASUR-
ING THE RESISTANCE OF COIL UNITS TUNED
TO PREARRANGED FREQUENCIES? — B. H. R.
— Utica, New York.
4. WHEN I REPLACE THE 3-VOLT TUBES IN MY
SET WITH 5-VOLT TUBES, THE SET OSCIL-
LATES. WHY?
T. M. B. — Boston, Massachusetts.
right angle coupling between the coil units be
employed. See Fig. 2.
It is most important that, in the construction
of a radio-frequency amplifier, or a receiver con-
taining one or more stages of radio frequency
amplification, the tube sockets be so placed
that the grid leads are as short as possible.
PRECAUTIONS IN ANTENNA ERECTION
THE other day a serious accident occurred
in Waltham, Massachusetts, caused by
a young man drawing an antenna wire
across an electric power line. The fact tha*
the line was insulated did not matter as his
antenna wire soon cut through the insulation,
and thus the current was communicated to his
body. The problem of antenna installation has
caused carelessness on the part of a great many
fans throughout the country, and it has been
the cause of many fatalities. The following
general " Don'ts" relating to antenna erection
are given in a paper by Mr. Clarence V. Purcell,
of the Boston Edison Company, for the benefit
of those who would profit by the example of
others who have been unfortunate enough to
become involved in some needless mishap:
Don't run an antenna over or under any other
wires carrying an electric current of any sort,
ling between the coils. This placement can be
approximated by the home experimenter in his
own construction. Individual test must be
made to determine the point at which satisfac-
tory neutralization is obtained in the regular
manner.
As an aid in obtaining the desired results, it is
suggested that in the construction of a receiver
the coil units be only temporarily fastened to
permit ready change and variation in the angle
at which they are to be set. See Fig. i. If it is
not possible to approximate this angle, which
is about 55 degrees from the horizontal, or
if there is plenty of space in which to con-
struct the amplifier, then it is suggested that a
f Tested and approved by RADIO BROADCAST -f
whether these wires be high tension wires,
service wires, or telephone lines.
Don't attach an antenna to any pole or tower
to which other wires are attached, or climb or
attempt to climb such poles or towers for any
purpose.
Don't run an antenna over or across any
public highway.
Don't attach an antenna to any electric light,
telephone or telegraph pole, even though no
other wires are attached thereto. If using an
outside antenna, always comply with the regula-
tions governing the installation of an approved
lightning arrester. Such a device is inexpensive
and easily installed.
RADIO BROADCAST ADVERTISER
227
Radio
Receiver
This new principle of radio
is exclusive in the Valleytone
Appearance
The Valleytone is mounted in a solid walnut
cabinet, finished in two tones with inlaid
gold stripes. It may also be procured in
beautiful console models. Special Valley
tables with built-in loud speaker may be
obtained for the cabinet model.
Valleytone
Console
Model
Valley table
with built-in
loudspeaker
Set the dials of a Valleytone for any station you choose. Bring in the
signals strong and clear.
Then turn the dials one point beyond or back from the correct
tuning. You merely diminish volume. The quality of the signals re-
mains the same. There is no incoherent babble of noises.
Turn the dials two or three points either way from the correct
tuning. Your program is gone.
Such tuning is possible only in the Valleytone. It is due to the
potential balance method of preventing distortion and oscillation. . .
a new principle for radio which is exclusive in the Valleytone 5-Tube
Radio Receiving Set.
The potential balance gives a balanced tone to the Valleytone. The
results are an amazing clearness and naturalness of reproduction. If
you have never heard the Valleytone, a new experience in radio
reception awaits you.
The Valley Toroidal Coils make possible a selectivity not previously
achieved. Stations four or five meters apart can be brought in clearly
and distinctly one after the other whether they are distant or local
stations.
Before you buy a radio, hear the Valleytone. Judge it by results.
Avoid regrets later by listening to the Valleytone now. Any
authorized dealer will be glad to demonstrate the Valleytone for you.
*
, Radio Division, ST. Louis,u.s. A.
Branches in Principal Cities
Valleytone
Receiving Sets
Valley
Battery Chargers
Valley
B-Eliminators
Valley Electric
TV«H>H nnrl annrm
R »nin Rurn
228
RADIO BROADCAST ADVERTISER
WITH ONE OF THESE 3 DIALS
ACCVRATUNE
M I C & OM ETE.K CO NT R OILS
ACCURATUNE dials
x~V. not only enhance im-
measurably the attractive
appearance of your set but
they insure clear and pre-
cise reception of programs,
and with even those
stations now so closely
grouped on the lower wave
lengths easily and readily
segregated. This type rec-
ommendedfor Neutrodyne
and Radio Frequency sets.
Priced at $3.50
A. J. VERNIER
T7OR use on Super-Heter-
JT odyne and Regenerative
receiving sets, the A. J. of-
fers a degree of tuning
efficiency not usually as-
sociated with dials that sell
at this price. Beautifully
constructed of genuine
Bakelite, the A. J. possesses
a dignity of appearance
that lends an air of rich-
ness to your receiver.
Priced at $2.25
Recording Dial
ON this new style record-
ing dial, ample space
has been provided to jot
down call letters, thus in-
suring a permanent record
of dial settings. The dial
itself is beautifully propor-
tioned, made of genuine
Bakelite with handsome
embellishments on a mat-
ted background. Truly a
product of master crafts-
men who specialize in the
manufacture of dials.
Priced at $1.75
MYDAR RADIO CO.
3 CAMPBELL ST.
NEWARK, -N.J.
Tested and approved by RADIO BROADCAST
Don't borrow your neighbor's antenna by
attaching your lead-in to the far end of his wire.
You don't know what he is doing and besides,
antenna wire is cheap and serves the purpose
far better.
Don't attach your antenna to a kite. Don't
use your telephone line for an antenna. Connec-
tion to an electric light socket is not encouraged
or recommended; light socket attachments are
approved.
MEASURING THE RESISTANCE OF COIL UNITS
HERE is described a method whereby those
having the proper facilities may measure
the resistance of coils tuned successively
to several prearranged frequencies.
With the aid of a radio oscillator, a thermo-
galvanometer and a resistance box, a curve,
plotting resistance against frequency, may be
Intermediate Coupling Circuit
FIG. 3
made from the several readings obtained. The
circuit diagram for the layout is shown in Fig.
3. To measure the resistance of a coil, the pro-
cedure is as follows, assuming that readings are
to be taken at 1500 kc. (200 meters) 1200 kc.
(250 meters) 1000 kc. (300 meters) and so on, for
every 50 meters up the scale to 545 kc. (550
meters.)
Put the oscillator into operation setting its
frequency control at 1500 kc. (200 meters).
Couple the coil to be measured, Li, to the os-
cillator output coil \_2. This will cause a
deflection of the needle of the thermo-galvano-
meter. Now by varying the coupling between
Li and L.2, the galvanometer reading may be
varied to one of the numbered markings of the
meter scale such as 20-40-60-70-80, etc.
Since the next step requires the addition of
resistance to the measured circuit, until the read-
ing of the meter drops to one-quarter of its ori-
ginal value, it is well to vary the coupling to a
point where this division will be simple. At an
original reading of 60 or 80, it is quite easy to
add resistance to the circuit until the reading
falls to 15 or 20. Resistance is added to the
circuit by means of the controls on the resis-
tance box which, until this time, had been set
at zero. When the one quarter reading is ob-
tained, reference is made to the resistance box
and the resistance noted. This constitutes the
resistance of the coil and the meter at that par-
ticular frequency. Usually the resistance of the
meter is known and its value may be deducted
from the reading obtained.
This whole system is repeated for each fre-
quency point to be measured.
TUBES AND R.F. COILS: HOW THEY SHOULD BE
MATCHED IN A RECEIVER
TO OBTAIN maximum efficiency in a
receiver using radio frequency amplifi-
cation, it is necessary to have transformers
designed for the type of tube used in the set.
This statement has been amply justified as
the result of exhaustive tests made by indepen-
dent engineers who were interested in the
problem.
If a receiver is using the 0-299 °r uv-igg type
of dry cell tubes, with proper transformers, and
is changed over to the C-3OI-A or uv-2oi-A
RADIO BROADCAST ADVERTISER
229
DISTANCE
THE OBEDIENT SLAVE TO YOUR DESIRES
*
Upon request, we
will gladly mail
descriptive folder
Quality Radio Apparatus
Apex
Entertainer
Price 122.50
APEX mastery over the most advanced radio
engineering principles makes distance the obedi-
ent slave of your desires and places at your in-
stant command the whole continent of radio
enjoyment.
The infinite care and skill employed in perfect-
ing the mechanical construction of APEX Radio
Apparatus is radiantly reflected in the rich
beauty of design, harmony of proportion and
elegance of finish that stamp all APEX sets with
an unmistakable mark of master craftsmanship.
You are cordially invited to inspect this com-
plete showing of Quality Radio Apparatus. Only
a dependable merchant is given the APEX
dealer franchise. Your APEX dealer will gladly
make a personal demonstration of APEX Quality
Radio Apparatus.
APEX ELECTRIC MFG. CO.
1410 W. 59th St., Dept. 1204 CHICAGO, ILL.
Also makers of the famous APEX Vernier Dials
and APEX Rheostat Dials which are sold
by every good dealer in Radio.
Apex Super Five
Price $95 — without accessorie
Apex
Console
Entertainer
Price $27.50
Prices West of Rockies Slightly Higher
Canadian Prices Approximately 40 % Higher
if Tested and approved by RADIO BROADCAST
280
RADIO BROADCAST ADVERTISER
Helps to Land
Everything
You Catch
The "Electrad" Lead-in meets that high
quality standard set by all "Electrad's"
products. There is a difference.
The convenientlead'in. Now you need
not scar or mar your walls or sash with
unsightly holes or ugly porcelain tubes.
This flat, highly insulated and water-
proofed lead-in fits
under locked win-
dows and doors.
The windows may
be closed tightly
— there need be no
loss of heat in the
room. Pliable, it
bends into any
shape — meeting
your every need. Price 40c.
Other Guaranteed Electrad
Radio Products
which simplify construction, facilitate
installation and improve reception of radio sets — Van-
ohms, Lamp Socket Antenna, Certified Grid Leaks,
Resistance Coupled Amplifier Kits and many others.
At your dealer's, if he can't supply, write us.
ELECTRAD, Inc.
428 Broadway New York City
"ELECTRAD" AUDIOHM
A necessary tone and quality controlling
device. Placed across secondary of 6rst
audio transformer it eliminates distortion
and transformer noises. Requires no
drilling, soldering or tools to attach. Fits
any transformer. $1.50 each.
*
ELECTRAD" LIGHT-
NING ARRESTER
Price 50c. Indoor type.
Approved by Under'
writers. Should fire
occur from lightning you
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culties unless you have
an approved arrester.
ELECTRAD
The Six Point
Pressure Condenser
The "Electrad" Certified Fixed
Condenser is a revelation in accuracy
and design. Ingenious, rigid binding
and firm riveting fastens parts securely
at Six different points insuring positive
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Value guaranteed to remain within 10%
of calibration. Standard capacities, 3
types. Licensed under Pat. No. 1,181,623
May 2, 1916 and applications pending.
Price 30c to 75c in sealed dust and mois-
ture proof packages.
type of tubes, it will be necessary to change the
radio-frequency transformers also, if equally
efficient results are to be obtained.
This is made necessary by the fact that the
characteristics of the tubes vary according to
their internal construction. In the uv-igo.
tube, the elements are very close together, mak-
ing it possible and advantageous to use more
wire on the primary of the transformer. The
tendency for a vacuum tube having a tuned in-
put circuit to oscillate, is proportional to the
inductive load or the number of turns on the
primary of the transformer in the plate circuit.
If the tubes were replaced with the C-3OI-A
or uv-2oi-A type, the circuit would become
unstable and oscillate readily, due to the dif-
ference in construction of the elements of the
latter type of tube. Fewer turns of wire should
be used on the primary of the transformers.
The curve of the transformer will fall off at one
end of the scale and result in poor amplification
of either the high or low waves, if the proper
type of tube is not used. This is due to the
capacity of the input circuit of the tube, which
varies in different tubes. As this is shunted
across the secondary winding, it has sufficient
tuning effect on that winding to shift the area
of maximum amplification from the desired
band.
When the tube characteristics are matched
up with the correct amount of wire on the
primary of the transformer, then the circuit
will cover the whole wave band evenly, with
good amplification. In some types the core of
the transformer is filled with finely powdered
iron or iron laminations. The use of iron in the
core broadens tuning so that the transformer
may be used over the entire wave band, without
the need of a variable condenser for tuning.
When Writing to the Grid —
A TYPEWRITTEN letter, written on one
side of the paper only, is to be preferred.as it
aids in the quick formation of a satisfactory reply.
Don't fail to send a stamped addressed envel-
ope with your inquiry.
Don't send a second inquiry about the first.
Don't include questions on subscription orders
or inquiries for other departments of Doubleday,
Page & Company.
In asking questions give us all the information
that will aid in advising you. If the question
relates to apparatus described in RADIO BROAD-
CAST, give the issue, page number, and figure
number of the circuit diagram, etc.
Be explicit yet brief.
GRID INQUIRY BLANK
Editor, The Grid
RADIO BROADCAST
Garden City, J^ew
DEAR SIR,
Please give me the fullest information
on the attached questions. I enclose a
stamped envelope.
EH I am a subscriber to RADIO BROADCAST
and therefore will receive this information
free of charge.
EH I am not a subscriber and enclose $1
to cover cost of answers.
NAME . . .
ADDRESS .
G. D.
Tested and aooroved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
231
What to give the radio fan
The Tungar is a G-E prod-
uct, developed in the Re-
search Laboratories of Gen-
eral Electric.
The new Tungar charges
any make and size of storage
battery: radio "A" and auto
batteries, and "B" batteries
as high as 96 volts in series.
Prices
Two ampere size . $18.00
Five ampere size . $28.00
60 cycles . . 110 volts
Give him a two- ampere Tungar if he has a storage bat-
tery of any kind. It will charge all his radio batteries and
his auto battery, too.
Or, for bigger jobs, give him a five-ampere Tungar — built
to do the same work but to do it more than twice as fast.
Every man who has a storage battery wants a charger.
And every man who wants a charger wants the original
General Electric bulb charger— the Tungar.
Tunar
REG. U.S. 5J^^^
OFR
IB ATT E RY _CHARG E.R
Tungai — a registered trademark — is found on]}!
on the genuine. Look for it on the name plate.
Merchandise Division
General Electric Company, Bridgeport, Connecticut
GENERAL ELE
•Jr Tested and approved bv RADIO BROADCAST
RADIO BROADCAST ADVERTISER
B-T "COUNTERPHASE-SIX" (Built from Kit)
System of Instructions
Simplify Building the
COUNTERPHASE r
THE B-T "Counterphase" is a combination of the best
apparatus ever put in a receiver and the exclusive patented
B-T method of oscillation control which gives maximum
efficiency on all wave lengths.
You can build the "Counterphase" with one, two or three
stages of R. F. or buy a complete factory built 6-tube receiver.
Two tuning controls give the most simple as well as sensible
tuning.
"Counterphase" kits for the home builder include a complete
set of instructions with progressive circuit charts in nine colors
(the same colors as wires furnished.) There's no excuse for
error.
Ask your dealer, he'll tell you about B-T performance.
"The Best We Ever Tested—"
says a leading laboratory of the B-T "Euphonic" Audio
Transformers.
Listen to a set equipped with "Euphonies" and you'll appreciate
the improvement on both high and low notes.
The B-T "Euphonic" is the
only transformer designed
to permit mounting in such
manner that terminals may
always be brought where
they are needed to prevent
crossed wiring, a frequent
cause of howling and dis-
tortion.
Compare the tone and you'll
use only "Euphonies."
Because It's Different
You Should Read
Better Tuning
RADIO: 2.2 to 1
4.7 to 1
before you buy a set or
parts. 80 pages of facts,
hook-ups, tuning hints, dis-
cussions of latest radio topics. Postpaid, 10 cents.
Literature describing B-T products free on request.
BREMER-TULLY MFG. CO.
532 S Canal Street Chicago, 111.
A KEY TO RECENT
RADIO ARTICLES
By E. G. SHAULKHAUSER
THIS is the second instalment of references to
articles which have appeared recently in var-
ious radio periodicals. Each separate reference
should be cut out and pasted on cards for filing,
or they may be pasted in a scrap book either
alphabetically or numerically. A brief outline
of the Dewey Decimal System (employed here)
appeared in the November RADIO BROADCAST.
the
R 1 1 3. TRANSMISSION PHENOMENA. TRANSMISSION
Popular Radio, Sept. 1925, pp. 199-206. PHENOMENA.
" How the Air Affects Radio," E. E. Free.
In a simple non-technical way the author tells us how
the two theories of wave propagation, the Heaviside Layer
theory and the Gliding Wave theory, may affect radio trans-
mission. Probably both theories are correct. Apparently
the ions and free electrons in the air account for fading,
bending, and absorption. Sir Joseph Larmor, on October
27, 1924, stated that he believes most of the phenomena
pertaining to wave reflection occurs about fifty miles above
the earth's surface. How free electrons may affect radio
energy distribution is explained in greater detail.
Ri 13. TRANSMISSION PHENOMENA. ABSORPTION.
Popular Radio. Sept. 1925, pp. 207-21 1.
"How Radio Dead-Spots are Found by a Wandering
Broadcasting Station," J. p. Perrine.
The distribution of radio wave energy about a broad-
casting station located in a city, has been determined with
the aid of a mobile receiving set. Energy received is com-
pared with that given out by a local oscillator, and field
strength is recorded in microvolts per meter. The area
about the Washington, District of Columbia station, WCAP,
within a radius of 50 miles, is shown in diagram with contour
lines. These tests have given very valuable and inter-
esting results, showing effect of ground condition, build
ings, hills, and various conducting materials found in th<
earth, on the direction and intensity of the wave.
Ro8o. COLLECTIONS, TABLES, MISCELLANIES. TABLES
Popular Radio, Sept. 1925, pp. 221-226.
"Useful Charts for Amateurs," Lieut. C. C. Todd. jr.
Simple and valuable information to guide the constructor
in designing coils and determining proper size condensers
to cover certain wavebands, is contained in this article.
Eight charts show the relation between capacity, induc-
tance, wavelength, and col! turns, to cover both short and
long wavelengths. The information is very well presented
and the diagrams are clear.
RSoo (530) PHYSICS ATOMS
Popular Radio, Sept. 1925, pp. 232-236.
"The Atom," Sir William Bragg.
Article No. 2 deals with the nature of gases. The ar-
rangement of the electrons in various atoms, their number,
and how the various combinations account for the different
elements, is described. Models illustrate the facts out-
lined in a very simple way. The author relates the theory
of the electrons and atoms and the part they play in our
present day research, in simple language.
R36o. RECEIVING SETS FREED-
Popular Radio. Sept. 1925, pp. 244-254. EISEMANN.
"How to Get the Most out of Your Ready-Made Re-
ceiver," S. G. Taylor.
The new Freed-Eisemann five tube receiver, NR2O, is
discussed, illustrated, and described in great detail, A de-
scription of the theory, operation, and equipment, with
plenty of photographs and diagrams, give the set owner all
the desired information. The B battery life for this set,
using various sizes of B batteries, is shown in a table,
R 304.1 WAVEMETERS. WAVEMETERS.
Popular Radio, Sept. 1925 pp. 267-271. Oscillating,
"An Oscillating Wavemeter/ S. G. Taylor.
A description of an oscillating wavemeter, using a vacuum
tube in a simple oscillating circuit, is given. Parts required,
and size of coils to use in order to cover frequencies from
9091 kc. (33 meters) to 498 kc. (602 meters), are listed. The
instrument is valuable in measuring capacities and induc-
tances. The circuit diagram shown is the modified Hartley.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVER,
Radio Engineering. Sept. 1925, pp. 433-441. RX-l.
"How to Build the RX-i."
This receiver is one especially developed in the Darien
Laboratory. It is a non-regenerative four-tube set known
as the RX-I receiver. The receiver was designed to give
easy control, good quality, and precise tuning, together with
plenty of volume. Diagrams and data are ample to permit
the constructor to build this receiver. The best parts
available are listed, the cost of these being only about $32.
R72O. PROCESSES. MOULDING
Radio Engineering. Sept. 1925, pp. 455-458. BAKELITE.
"Why Not Do Your Own Moulding."
The article describes the equipment necessary for mould ing
bakelite parts on a rather small scale. The process is not
difficult and the equipment can be installed in small estab-
lishments without excessive cost. The method used in
making molded parts is described in detail. Photographs
of the machinery are shown.
R384.I. WAVEMETERS. LECHER WIRES.
QST. Sept. 1925, pp. 11-12.
"Practical Lecher Wires," E. C. Woodruff.
Description and arrangement of Lecher wires with con-
stants of construction are given in detail, showing diagram.
In making measurements of waves the wires are connected
to a vacuum tube circuit as shown in Fig. i, and a milli-
ammeter in the plate circuit indicates resonance. A calibra-
tion chart and graph show the method of using these parallel
wires.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
233
Imagine a Radio Set
stripped of these parts
What a useless collection of
wood, wire and metal it would
be. Realizing that the parts and
accessories shown here are wholly
or partly of Bakelite, gives you
a vivid picture of its importance
to Radio.
To-day Bakelite is used in a
greater variety of radio parts
than ever before — and the num-
ber grows constantly. This
dominance of Bakelite in radio
reflects the experience and the
opinions of radio manufacturers,
great and small.
Radio set and parts manufac-
turers have every facility for
testing all insulation materials
and over 95% have standardized
on Bakelite. This indicates how
really important it is for you to
make sure that the set or parts
that you buy are Bakelite in-
sulated.
Write for Booklet 29
BAKELITE CORPORATION
247 Park Avenue, New York, N. Y.
Chicago Office: 636 West 22d Street
Bakelite is an exclusive
trade mark and can be
used only on products
made from materials
manufactured by the
Bakelite Corporation.
It is the only material
which may bear this
famous mark of excel-
lence.
BAKELITE
REG. U.S. "AT. OFF:.
BAKELITE
is the registered trade
mark for the phenol
resin product manu-
factured under pat-
ents owned by the
Bakelite Corporation.
THE MATERIAL OF A THOUSAND USES
•jf Tested and approved by RADIO BROADCAST -^
234
RADIO BROADCAST ADVERTISER
A BRISTOL Loud Speaker will bring everlasting Christ-
•**• mas joy to the whole family.
It has all the volume you will ever wish, but its fine
point, — its outstanding claim for distinction, is its tone,
a true, clear, natural reception of voice or instrumental
music. This is because it is a true musical instrument
not merely a phone unit in a horn.
Bristol Loud Speakers have highly developed electro-
magnetic tone mechanisms, and non-metallic horns with
long, freely vibrating sound chambers.
The super S and super C models are equipped with the
Super-Unit which contains a specially designed diaphragm
of broad pitch range. It reproduces not only the low
pitched notes but the high as well.
There are four Bristol Speakers, horn or cabinet type,
priced at $15.00 to $30.00. If not at your dealer's, send
for our new booklet. "How to select your loud speaker."
THE BRISTOL COMPANY, RadA°HDiv- WATERBURY, CONN.
For 36 Years Makers of highly accurate and sensitive Bristol Recording Instruments.
BRISTOL AUPI^pNELoud Speaker
Tested and approved by RADIO BROADCAST
Ro84. TABLES. CHARTS.
QST . Sept. 1925, pp. 16-17. Ind. Sr w. I.
" Designing the Secondary Coil," G. H. Burchill.
Using double cotton covered wire, the inductance and
wavelength of cylindrical coils, closely wound, can readily
be determined with the aid of the chart in the form of a
graph. A simple description of coil design and method of
procedure is given.
R8oo (535.3). PHOTOELECTRIC SELENIUM CELLS.
PHENOMENA
Kadio Engineering. Sept. 1925, pp. 442-443.
"Selenium and Photoelectric Cells, S. Wein.
The third chapter on selenium cells gives the construc-
tion of different types of cells by various scientists: Tainter,
Bell, Mercadier, Townsend, and Cherry. Keferences are
listed.
R356. TRANSFORMERS. TRANSFORMERS.
QST. Sept. 1925, pp. 21-24.
"Transformers and Reactors in Radio Sets," R. H. Chad-
wick.
In the first article on transformers and reactors, the author
takes up the general theory, regulation, and efficiency, and
describes the construction and operating principles of
various types of commercial transformers. The leakage
reactance is a governing factor in proper transformer de-
sign. Useful information for users of these instruments.
R342.I5. AMPLIFIER TRANSFORMER.
AMPLIFYING
QST. Sept. 1 92 5, pp. 27-29. TRANSFORMERS.
High Ratio and High Amplification," R. S. Kruse.
Some misunderstood principles about audio and radio-
frequency transformers are cleared up by the author.
Stage to stage amplification depends on the regeneration
as well as the transformation ratio and the tube constants.
When the transformer is largest, both regeneration and
amplification are strongest. A 2:1 transformer may give
much better amplification than a 6:l, depending upon
design. Diagrams illustrate the points under consideration.
R402. SHORT WAVE TRANSMITTERS. SHORT WAVE
QST. Sept. 1925, pp. 30-32. TRANSMITTER
A Power-Amplifier Transmitter for the Low Waves "
W. H. Huffman.
The circuit arrangement in a Colpitts oscillator, using an
added power amplifier, is described. The transmitter
operates well on very short wavelengths. It transmits a
very steady frequency and with the apparatus recom-
mended, has a tuning range from 14990-3894 kc. (20-77
meters). Since the set uses uv-2O2 tubes it can be operated
on storage or dry batteries, and used as an emergency
layout. Operating adjustments and list of parts required,
including circuit diagram, give complete construction data.
Rii3.4. IONIZATION; HEAVISIDE LAYER. HEAVISIDE
QST. Sept. 1925, pp. 33-34. LAYER THEORY.
Is There a Heaviside Layer?" G. W. Pickard.
A brief discussion concerning some of the transmission
phenomena, with particular reference to various theories
on reflection and refraction, is contained in a letter to QST
by the writer.
RSI 2. RADIO BEACONS. LIGHTHOUSE,
RADIO BROADCAST. Oct. 1925, pp. 710-724. Radio.
"And Now — The Radio Lighthouse," J. C. Young.
Radio service to ships at sea has become absolutely
necessary. Radio signals help guide ships when near the
coast and give bearings when needed. What advances have
been made in guarding against danger, what pleasure and
enjoyment has been derived through the use of radio to
those sailing the waters, is well pictured in this article.
Ri40. RADIO CIRCUITS. ROBERTS
RADIO BROADCAST. Oct. 1925, pp. 725-731. CIRCUIT.
"New Developments and Experiments with Receiving
Circuits," K. Henney.
The Roberts Knockout receiver offers possibilities for
development along many lines. In this article some of the
experiments carried on at the RADIO BROADCAST Laboratory
with this circuit, are discussed. How a fifth tube may be
added, how the reflex stage may be eliminated, how the
circuit is neutralized, how regeneration may be employed
in either detector or amplifier, are changes that may be
tried with success.
Rooy. 2. U. S. RADIO INSPECTION SERVICE. RADIO
RADIO BROADCAST. Oct. 1925, pp. 743-744. CONDITIONS.
"Guiding the Good Ship Radio," D. K. Tripp.
An interview with W.ID. Terrell, Chief Supervisor of Radio,
concerning radio conditions in the U. S. at present, reveals
his views about the department's attitude toward the
amateur, the broadcaster, and the service both can render
toward bettering conditions in radio.
Rija. AMPLIFYING ACTION. AMPLIFYING
RADIOBROADCAST. Oct. 1925, pp. 745-750. PRINCIPLES.
"Some Remarks on Audio Amplification," G. C. Crom
Jr.
Good radio reception depends upon proper amplifier
design. The functions of each part in the amplifier circuit
are discussed in detail. Good parts must be used for best
reproduction. Distortion may be produced by any one
of four things as stated. High plate voltages are recom-
mended and are of ad vantage when proper C battery voltages
and by-pass condensers are inserted, as shown in Fig. 2.
R373. 2. MICROPHONES. MICROPHONE
RADIOBROADCAST. Oct. 1925, pp. 769-770. PLACING.
" More About How to Place the Microphone."
Methods of placing microphones for picking up band and
orchestra music in and put of the station studio, are shown.
In particular, the placing of several microphones at the
Lewisohn Stadium in New York City and on the campus
of New York University, in order to broadcast music from,
large organizations, is of interest.
R375.3 ELECTROLYTIC RECTIFIERS. RECTIFIERS.
RADIOBROADCAST. Oct. 1925, pp. 774-780. Chemical.
"Notes On Chemical Plate Supply Units," J. Millen.
The chemical rectifier here described, employs two or
more jars in order to handle output voltages up to 1 50 volts
and enough current for the receiver, at the same time giving
absolutely no line hum in the output circuit. The dis-
cussion covers all phases of construction and operation
in a very thorough manner. List of parts and diagrams of
circuits and complete unit are added.
RADIO BROADCAST ADVERTISER
235
FILTER CONDENSERS
.1 M.F.D.
Type 705
Price $ .70
1. M.F.D.
Type 708
Price 1.25
2. M.F.D.
Type 709
Price 1.75
4. M.F.D.
Type 711
Price 3.75
ADIO BROADCAST'S article in this issue on
Improved Plate Current Supply Unit" shows that the
following TOBE condensers can be used in building
the set: 5 type 708 and 7 type 709.
Any 'B' battery eliminator circuit depends very large-
ly for its operating efficiency upon the filter condensers
used. TOBE condensers alone possess all of the follow-
ing favorable characteristics:
Will operate at voltages up to 700 D. C. without break-
down or overheating.
High megohm resistance — indicating perfect insulation.
Capacities guaranteed to be within 5% of accuracy.
Extreme heat or cold has no effect on TOBE condensers.
Compact and handsome in appearance.
Tobe condensers are better condensers — distinguisha-
ble by their silvered finished case. Ask your dealer
for them by name "TOBE."
CORNHILL
BOSTON, MASS.
Tested and approved by RADIO BROADCAST
236
RADIO BROADCAST ADVERTISER
JN O W you can
buy Matched Tubes
and be certain your reception will be
clear, smooth, loud and uniform
Blue Specials
cost a trifle more and
are worth it. Try them,
and you'll never again
bother to try to match
tubes yourself; 501 -A
is for storage batteries,
and is packed singly
and in kits of three
and five matched tubes.
499 is for dry cells,with
peanut base and is
packed singly and in
kits of four and six
matched tubes.
Price $2.75 each
Buy them by the box
for best reception.
500
Matched
Blue Tubes
(Peanut or Standard Types)
mark a new step in Radio. They are what
every radio "bug" has been looking for
and wondering when and where they
could get them.
It is most important to gooa radio reception that
your tubes are matched — and pull in harmony.
Equal pull in the tubes means smoothness of re-
ception — sweetness of sound — full throated vol'
ume — resonant clarity.
BLUE SPECIALS are matcned tubes. After care-
ful selection by actual test the individual charac-
teristics are plainly indicated and they are packed
in kits of three and five matched tubes — ready for
immediate use. Made for storage batteries only.
This process of selection enables us also to discard
all inferior tubes and retain only the first grade.
BLUE SPECIALS give wonderful results.
Try them. Find out for yourself what a big
advantage it is to have matched tubes. Re-
member they are unconditionally guaranteed.
See the Sylfan line Booth No. 34
Chicago Radio Exposition
Manufactured and Marketed Exclusively Thru Jobbers by
BAKER- SMITH CO., Inc.
New Call Building, San Francisco
Branch Office Addresses
Portland, Ore., Henry Bldg. New York City, 1270 Broadway
Salt Lake City, Atlas Bldg. Chicago, 30 N. Dearborn St.
Seattle, L. C. Smith Bldg. Denver, McCHntock Bldg.
Los Angeles, 443 South San Pedro Street
Vancouver, B.C., 179 Fender Street, West
Tested and approved by RADIO BROADCAST
R550. BROADCASTING. SUPER-POWER
RADIOBROADCAST. Oct. 1925, pp. 761-768. STATIONS.
"A Debate: Resolved, That 5OO-watt Stations Are Not
Sufficient for Program Service," Affirmative: Mr.
Dreher. Negative: Prof. Williams.
The pros and cons of so-called super-power stations, is
given in two articles. Much information is contained in
both, especially in regard to power and noise level.
Rii3.i. FADING.
FADING
ALS.
Radio News. Sept. 1925, pp. 278ff. SIGNA
"Concerning the Nature of Fading," J. H. Dellinger.
The problem of fading has become more serious than
the problem of static, primarily because so much fading
occurs on the high frequencies (1500 kc. and up) where
much research is being done at present. The Bureau of
Standards has undertaken a series of tests to determine
the cause of fading. It is probably due to the shifting
of the upper atmospheric conducting surface.
Rs82. TRANSMISSION OF PHOTOGRAPHS. PHOTOGRAPH
Radio News. Sept. 1925, pp. 278ff. TRANSMISSION.
"See With Your Radio," W. B. Arvin.
The Jenkins-Moore system of television is described.
A photoelectric cell converts the black and white of a pic-
ture into electric currents while a lighting device, the Moore
lamp, picks up these currents and changes them back to
light and shadow on the screen. The breaking up of the
picture for transmission is done with the prismatic disc,
a very simple method. Synchronism is accomplished with
synchronous motors at both ends. This system is said to
be the best one developed to-day, and was demonstrated
at Washington last June.
R323. GROUND AND UNDERGROUND UNDERGROUND
ANTENNAE ANTENNAE
Radio News. Sept. 1925, pp. 3oiff.
"Underground Radio." W. H. M. Watson.
Experiments with underground antennas with frequencies
of from 5996 kc. (50 meters) to 1666 kc. (180 meters) are
described in detail, with varying results. Good transmission
distance is possible with low power input after proper ad-
justments are made and antenna placed properly. The
antenna is very directional. — An article on underground and
under-water antennas, is reprinted from Dec. 1919, Radio
News showing what was accomplished along this line
several years ago.
R38i. CONDENSERS. CONDENSERS,
Radio News. Sept. 1925, pp. 3o8ff. S. L. F.
" More About Straight Line Frequency Condensers," S.
Harris.
A general discussion concerning condensers, in particular
the straight line frequency condensers, is presented to clear
up certain points. The question of low minimum capacity
for definite sized condensers, of condenser resistance when
plates are nearly all the way out, and of tuning with
straight line frequency condensers, is considered.
Ri4o. RADIO CIRCUITS. REGENERATIVE
Radio News. Sept. 1925, pp. jioff. CIRCUITS.
"Single-Tube Circuits," L. W. Hatry.
The author reviews regenerative circuits, inductive and
capacitive, using one tube. All other circuits are merely
combinations of these simple circuits. A good understand-
ing of these, makes the "dynes " and " plexes " comparatively
simple. The Reinartz, the ultra-audion, the Cockaday,
and others, receive considerable attention in this discussion.
R43O. INTERFERENCE ELIMINATION. INTERFERENCE
Radio News. Sept. 1925, pp. 2ooff. REDUCTION.
"Directional Reception Reduces Interference," P. C.
HoArnt1'
A
the two loops, the latter are mounted on a long turntable
at some distance apart (depending on wavelength). Fig. 3
shows the general form of the directional characteristics,
and Fig. I the circuit used. Several photographs give an
idea of the general layout. The tuning is simple and the
results obtained were very good. Amateurs and experi-
menters can amplify along these lines.
R375. DETECTORS AND RECTIFIERS. RECTIFIER
Radio News. Sept. 1925, pp. 293ff. TUBE.
"A New Neon-Filled Rectifier Tube," J. Riley.
The tube used as rectifier for B battery eliminators has
two electrodes of aluminum, a rod and a cylinder, and con-
tains neon gas at a pressure of six millimeters of mercury.
Its action in d. c. and a. c. circuits is discussed in detail
and illustrated by diagrams. Other possibilities of the
neon lamp are enumerated and offer a field of research.
R35I. SIMPLE OSCILIATORS. OSCILLATOR.
Radio Journal. Sept. 1925, pp. 12-15.
"A Laboratory Oscillator," H. W. Leighton.
The author describes the construction of a laboratory
oscillator and gives some of its uses. The circuit is shown
in Fig. i. Calibration of the oscillator is simple when a
standard wavemeter is available. Measurements of trans-
formers and filter for use in super-heterodynes are made
according to Fig. 2, and curves plotted showing how one
can determine just how to select the proper apparatus to
match. Small fixed, condensers can also be measured with
this oscillator.
R343. ELECTRON TUBE RECEIVING SETS.
Radio Journal. Sept. 1925, pp. 14.
RECEIVER,
Brownjng-
Drakf.
"New Type Browning-Drake," Bill Massaggee.
The constructional details of the Browning-Drake re-
ceiver are described, particular attention being called to
several minor details which nevertheless are essential if the
set is to operate well. A proper design of the coils used is
essential. Extreme selectivity and sensitivity is claimed
for the 4-tube set in comparison to other sets of similar
size. (Further details in Oct. issue)
R3&0. RECEIVING SETS. GREBE CR. 17
Radio Journal. Sept. 1925, pp. 15.
"The New Grebe CR-i7," M. Best.
Photographs and wiring diagram of the Grebe short wave
receiver, including a short description of the operating
principles, is given.
RADIO BROADCAST ADVERTISER
237
\^*^^>»» s
ttetiimwuftr^*
%-
oJOl iUU .|JTrr KARAS o*HOMETR,CCOHDENSER/tangement
Ordinary Condenser Arrangement of Wavelengths Straight Line Wavelength Condenser Arrangement Of Wavelengths on Dial
Ordinary straight capacity con-
densers crowd 70 of the 100 wave-
lengths into the first 30 points
of the dial.
With straight-line-wavelength con-
densers 57 of the 100 wavelengths
are crowded into the first 30 points
of the dial.
The New, Scientific Karas Orthometric
Condensers insure absolutely equal sep-
aration on the dial of all wavelengths
throughout the entire broadcasting range.
Tuning Marvelously Simplified with
Karas Orthometric Condensers
The condenser that brings in KDKA where it be-
longs— at 53 on the dial. Remember, 52 of the 100
allotted wavelengths must come in below KDKA. '* p°ate»
Mtt
0 10 20 30 40 50 60 70 60 90 100
Spreads Stations Evenly Over the Dial —
No Crowding Whatever
T
I HE Karas Orthometric Condenser positively separates all adjoining wave-
lengths by EQUAL distances on the dial, giving you the full benefit of the
10 Kilocycle frequency separation fixed by the Government.
Ordinary condensers jam 70 of the 100 Government
allotted wavelengths into the first 30 points of the dial
— even straight -line -wavelength condensers crowd 57
of them below 30.
With Karas Orthometrics, each point on the dial cor-
responds exactly to one of the 100 allotted wave-
lengths. The result is marvelous simplicity in tuning
— better, clearer reception — you get all the side bands
without interference.
The Karas Orthometric stands absolutely alone! — an
eccentric condenser, scientifically designed for present
day broadcast receiving sets — the Last Word in making
REAL SELECTIVITY POSSIBLE.
The Karas Orthometric is a "job" that will delight
the eye of the mechanical critic. It is made entirely
of brass — frame and plates all die stamped — plates,
patent leveled and solidly bridged to insure permanent
rigidity and alignment. Every joint throughout is sol-
dered. Grounded frame and rotor, with stator plates
supported on hard rubber insulation. Tapered adjust-
able cone bearings, spring copper pigtail connection,
automatic stops — in short, a condenser that is both
theoretically and mechanically perfect.
If Your Dealer is Not Yet Supplied, Order on this Coupon
We are supplying Jobbers and Dealers as fast as the output of
our factory permits. If your dealer is not yet supplied, order
direct on the coupon. You need send no money with your
order. Condensers will be delivered C. O. D., and you receive
them subject to our unconditional guarantee of satisfaction.
Why run the risk of delay? Order NOW!
Money Back Guarantee
Karas Orthometric Condensers are uncon-
ditionally guaranteed to give you absolute
satisfaction. They may be returned for full
refund any time within 30 days.
SIZES AND PRICES
23 plate, .0005 Mfd.,$7.00
17 plate, .00037 Mfd., 6.75
11 plate, .00025 Mfd., 6.50
Karas Electric Co., 4042 Rockwell St., Chicago
For OverSO Years Makers of PRECISION Electrical Apparatus
Send No Money With this Coupon —
Karas Electric Co., 4042 N. Rockwell St., Chicago
Please send me Karas Orthometric Condensers,
size— at $ each. I will pay
the postman the list price, plus postage, on delivery. It is understood
that I have the privilege of returning these condensers any time
within 30 days if they do not prove entirely satisfactory, and you will
refund my money at once.
Name-
Address-
Dealer's Name
If you send cash with order, we'll send condensers postpaid.
Tested and approved by RADIO BROADCAST •£
238
RADIO BROADCAST ADVERTISER
GUARANTEED I
To increase the effi-
ciency of a receiver
employing Resist-
ance-Coupled Amplification, and
to get the full measure of tone
purity and faithfulness of repro-
duction, for which this method of
amplification is noted, use Clear-
tron Hi-Constron Tubes — Type
101A.
RADIO TUBES
I RON -CLAD
GUARANTEE
All Cleartron Tubel ut guaranteed
to deliver positively perfect
service and we authorize our
distributors to' mike replacement
o* *ny Clcamoa Tube which proves
unsatisfactory to the user ~ "
The only requirement ts thai the
tube must not have been bunted out
Clevtron Vacuum Tube Co
28 Wt.t 44th Si
The Cleartron Hi-
Constron is a Hi-
Mu Tube with an
amplification constant of 20,
especially designed for Resistance-
Coupled and Reactance-Coupled
Amplifiers. It is the result of
years of research work and is
the original and genuine Hi-Mu
Tube.
The Following Types $2.50
C-T 201 A
C-T 199 Standard
Base
C-T 199 Small Base
CTX 120
C-T 400 Rectron Tube
for "B" Battery Elimi-
nators
CTX 112 Power Tube $6.50
All Types Equipped With Genuine Bakelite Bases
At All Reliable Dealers if
Write for FREE six-page folder giving valuable
information regarding radio tubes
Cleartron Vacuum Tube Company
Executive Offices
28 West 44th Street
New York City
West New York, N. J., U. S. A.
Birmingham, England
ORIGINAL
R§ sist ance-CoupIed
$3 22 ~"**~ Amplifiers
FOR BETTER RECEPTION
Is Your Set A
How to Prevent Your Receiver
Causing Interference and Thus
Spoiling Your Neighbor's Re-
ception
are still many single-circuit bloopers
in use, although the general trend in design, as
far as commercially made receivers are concerned,
seems to be toward receivers which are almost
incapable of causing interference, however carelessly
handled. The excellent instructions appearing be-
low have been specially prepared by the Radio
Branch of the Department of Marine and Fisheries
of the Dominion of Canada, for circulari^ation
among all Canadian broadcast listeners. On the
back of all Canadian receiving licenses is the follow-
ing note. " When using a receiver of the regenera-
tive type for the reception of radio telephone
programs, please avoid increasing regeneration to
the point at which the receiver begins to oscillate,
otherwise you will cause interference with neighbor-
ing receiving equipments. Are you doing your
best to observe this?" The point is that many
owners of receiving sets capable of radiating squeals,
cause such interference purely from inadequate
knowledge of the handling of their sets, and it was
for their benefit that this circular was printed.
These instructions should help many readers of
RADIO BROADCAST who are looking for clear
directions on how properly to use their regenerative
sets. — THE EDITOR.
HOW MUCH INTERFERENCE A RECEIVER CAN CAUSE
A RECENT survey of radio broadcast
reception conditions in the more popu-
lated centers of the Dominion of Canada
indicates that approximately fifty per cent, of
the "preventable interference" which prevails.
is caused through the incorrect operation ot
regenerative receiving sets by the broadcast
listeners themselves.
The survey further indicates that most of the
interference is due to a lack of knowledge of
correct methods of adjusting a regenerative
receiving set, and it is accordingly hoped that a
material reduction in the same way may be
effected if the broadcast listeners can be per-
suaded to cooperate in an endeavor to clear the
air of regenerative whistles, and, with this end
in view, the following instructions for operating
this class of receiving set have been drafted.
WHAT IS REGENERATION?
'"THE principle of regeneration, as used in
*• radio receiving sets, is that a part of the
output of the detector vacuum tube feeds back
into its own input and thus greatly increases the
volume of the signal.
The electric waves reaching the receiving
set from the transmitting station travel down
the antenna wire through the primary coil in the
set and so to earth down the ground wire. The
weak electric current resulting from this influ-
ences the vacuum tube in such a way as to set it
functioning.
The resulting output from the plate circuit of
this tube is fed back in such a manner as to set
up a "field," or "influence," in the part of the
circuit connected to the input (the grid) of the
tube. This "field" induces in the input circuit
a current of electricity of the same frequency as
that of the received electric waves. The energy,
therefore, which comes down the antenna wire
is automatically strengthened by an impulse
from the output of the detector tube.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
239
NATIONAL Velvet Vernier DIAL
Type B, Variable
(Patents Pending)
Positive Control
Easily Mounted
Gearless
Variable Ratio
Velvety Smooth
Graceful Design
*
With This NEW National Type B, Velvet Vernier Dial,
YOU Control the Reduction Ratio!
WHAT a difference in the tuning of your
set when you replace your plain dial
with a new NATIONAL Type B Variable
(patents pending). You'll be astonished.
Any ratio you desire, from a minimum of
6 to 1 to a maximum of 20 to 1 is instantly
obtained by shifting a small lever. Note how
it separates the stations operating on the
lower wave lengths.
Easily mounted on the \" shaft of any stand-
ard type of variable condenser. The only
tool you need is a screw driver.
The same velvety smoothness, the same free-
dom from backlash, the same mechanical drive
as the famous Type A Velvet Vernier Dial,
(patents pending). Price $2.50.
NATIONAL Tuning Unit
Type B D-2
The NATIONAL KIT
for the popular circuits and hook-
ups gives amazing results to am-
ateur set -builders.
Comprises the NATIONAL
CONDENSER and the wonderful
BROWNING-DRAKE TRANS-
FORMER. Complete in one
package, Price $2 2. Makes a most
welcome Christmas Gift.
Write for Bulletin 106 R. B.
NATIONAL CO., INC.
W. A. READY, President
110 Brookline St. CAMBRIDGE, MASS.
NATIONAL Tuning Unit
Type B D-l
Tested and approved by RADIO BROADCAST
240
RADIO BROADCAST ADVERTISER
ACME WIRE RADIO PRODUCTS
Stranded Enameled Antenna
The best outdoor antenna you can put up. 7 strands
of enameled copper wire; maximum surface for recep-
tion. Enameling prevents corrosion and consequent
weak signals. 100, 150 or 200 ft. coils, boxed.
Loop Antenna Wire
You can make a good loop with Acme wire made of 65 strands of fine copper
wire, green silk covered. Flexible; non-stretching, neat.
The Original Celatsite Wire
Celatsite is a tinned copper bus bar wire with a non-inflam-
mable "spaghetti" insulation in five colors. Supplied in 30
inch lengths.
Flexible Varnished "Spaghetti"
A perfect insulation tube for all danger points in set wiring.
Costs little more and is worth a lot more than the cheaper sub-
stitutes offered. Black, yellow, red, green, brown; for wires No.
10 to No. 18. 30 inch lengths.
Flexible Celatsite
Flexible stranded wire for "point to point" and
sub-panel wiring — latest method of wiring sets.
5 colors, black, yellow, green, red and brown,
one for each circuit. 25 foot coils.
Celatsite Battery Cable
For connecting A and B Batteries (or current supply) to
radio set. Silk braid covering 5 flexible Celat-
site wires — 5 feet long — a different color for
each terminal. Prevents mess^ wiring and
"blown" tubes. Adds greatly tpv the appear-
ance of your set. A* v ^
jp .$*oend for Folder
V
WIRE CO., Dept. B
New Haven, Conn.
FROST RADIO
TUBE *
CONTROL
UNIT
*]21
(6, 25 or 35 ohms)
COMBINES Vernier Rheostat and Poten-
tiometer. Single hole mounting. 6, 25
or 35 ohm rheostat, 400 Potentiometer. Gen-
uine Moulded Bakelite.
List; $1.75. Pacific Coast
price slightly higher,
HERBERT H. EROST, inc.
314-324 WEST SUPERIOR STREET, CHICAGO
New York City Cleveland Kansas City Los Angeles
22l/2 Volt
un-acid
everlasting
rechargeable
"B"
Storage Battery
$2.95
includes
chemical
45 volts $5.25. 90
volts*10.00. 112%
volts J12.50, 135
volts tit. 75, 157!4
v o i t B tie. so.
Truly the biggest buy today. Easily charged on any current includ-
ing 32 volt systems. Any special detector plate voltage had. Tested
and approved by leadim: authorities such as Popular Radio labora-
tories. Over 3 years sold on a non-red tape 30 day trial offer with
complete refund if not thoroughly satisfied. Further guaranteed 3
yfars. Knock-down kits at greater savings. Complete "Haw ley"
"B" 3attery Charger $2. 75. Sample cell 35c. Order direct— send no
money— simply pay the expressman cost on delivers-. Or write for
my free literature, testimonials and guarantee. Same day shipments.
B. Hawley Smith, 312 Washington Ave., Danbury , Conn.
WHAT IS OSCILLATION?
I JNLESS controlled, this action will continue
'••' until the saturation point or climax is
reached, the tube then being said to be in a state
of oscillation. When a receiving set is in oscilla-
tion, it causes howling and squealing in your own
and your neighbor's receiving sets. Regenera-
tion should therefore never be allowed to proceed
to this point as it then constitutes a public
nuisance. On commercial receivers, regenera-
tion is not always described by this name, and
the dial which controls this feature of the equip-
ment may be designated by any of the following
terms: Regeneration; Reaction; Tickler; Feed-
back: Amplification; Varind; Sensitivity, etc.
When a radio receiving set in a state of oscilla-
tion is being tuned to a broadcast station:
(1) It causes whistles in radio receiving sets,
of all types, which are tuned to the same station.
This interference may be heard up to a distance
of several miles.
(2) It distorts the quality of your own music.
(:)) It uses more B battery power and
therefore the life of the B battery is reduced.
(4) It tends to reduce the life of the detector
tube.
When a radio receiving set, in a state of oscilla-
tion, is exactly tuned to a broadcast station, it
is said to be in the state of zero beat. This
distorts the broadcast reception and also in-
terferes with neighboring receiving sets which
are tuned to the same station.
In a word, regeneration carried to oscillation
causes great annoyance to your neighbors,
poor reception and expense to yourself, and has
no advantages whatever.
DOES YOUR RADIO RECEIVING SET CAUSE
INTERFERENCE?
'T'HE interfering whittle which you hear in
* your receiving set may originate in your
own set or it may be interference caused by your
neighbor. In order to determine this point
you may make the following test:
Leave the regeneration control in a fixed
position, slowly rotate the tuning dial, and
note particularly the change in sound of the
whistle. If the whistle rises and lowers in pitch
sympathetically with the movement of your
tuning dial it indicates that your receiving set is
in a state of oscillation and probably causing
interference to other sets. On the other hand,
if the whistle does not change in pitch cor-
responding to each movement of your tuning
dial, but simply varies in volume, the whistle
is not caused by your receiving set, but is inter-
ference produced by some other oscillating re-
ceiving set in the neighborhood.
Many so-called non-radiating receivers will,
under certain conditions, radiate and thus cause
interference. Make it your business to see that
your set is not causing trouble.
If you are in doubt as to whether your set can
cause interference you can check the same by
making the following test, but be careful to do
so at a time when only a few people are listening
in, so as not to cause annoyance:
Call a neighbor on the telephone and ask him
to listen in on a particular station at a pre-
arranged time and then tune your own set to the
same station. Turn up your detector tube fila-
ment to normal and put the regeneration control
to its maximum ; move your tuning dial five times
slowly across the point corresponding to the
tuning of that station, then telephone your
neighbor and ask him if he heard the interference
corresponding to these five movements of the
dial on your receiving set. If he heard your
interference, the probability is that hundreds
of others have also been annoyed at times by
radiation from your receiving set. You should
RADIO BROADCAST ADVERTISER
241
Employs no fluids of any kind. Uses only one rectifying lube. Separate adjustment for detector and amplifier tubes. Handsomely finished in
rich velvet-green Duco with solid walnut, satin finish top and bottom. Ample continuous "B" current for one to ten-tube sets.
Remarkable Tone Quality *-* ^ Amazing
Volume and Selectivity^ without "B" Batteries
, in place of "B" Batteries, is guaranteed to improve the overall efficiency of your set.
It provides constant "B" current at proper potential for your particular receiver circuit, tubes
and loud speaker.* DIS-TON is noiseless in operation — no crackles and popping such as you
get with run down "B" Batteries — no hum of any kind to distort the finest aria or drown
out the faint signals from distant stations.
A self-contained electrical instrument using A C
DIS-TON is trouble free — the special Trans-Filter Unit is sealed
in, protected against tampering and deterioration. It can't wear
out. Consumes only eight watts from the nearest lamp socket
and puts your "B" load on the big, powerful, carefully watched
generators of your central station. You can rely upon DIS-TON
to give you the best from your receiver.
Without attention of any kind after simple initial adjustment to
your set — DIS-TON insures you the equivalent in performance of
new "B" Batteries every time you listen in.
DIS-TON requires no change in the internal wiring of your set to
secure either utmost efficiency or entire safety. Accidental im-
proper connections can't result in tube "burn outs."
DIS-TON
complete
ready for
operation
110 volt, 60 cycle
$10.00
Other voltages and
cycleson application
Know how much DIS-T5N adds to radio
The advantages that DIS-TON will give you are outstanding and unusual. You
have the opportunity to verify them -all on your present receiver. A DIS-TON
demonstration is yours for the asking. Send for Leaflet B and full details as the
first step to greater radio enjoyment this season.
RADIO PRODUCTS, Inc.
Dept. RB Richmond, Ind.
DIS-TON KITS
Essential Parts
for
Home Builders
110 volt, 60 cycle
$28.50
Other voltages and
cycleson application
*Dis-TON will not make a "single tube" into a "super-het," but it will modernize the performance of any
of the good, older receivers in an amazing fashion.
if Tested and approved by RADIO BROADCAST
242
RADIO BROADCAST ADVERTISER
Smallest Uniform Frequency Condenser
Easily Fits Into Present Sets
FULL size illustration above shows Samson Condensers are but
z1/*" diameter with plates fully extended — half to a third the
size of others.
You can easily increase the selectivity of your present receiving set having
ordinary condensers, and do away with the crowding of station readings —
where 85 out of 100 come in below 50 on dial — by using
Damson
^^ l/ni form frequency
\Jondensers
Samson Uniform Frequency Condensers are built to a tolerance of 1/1,000
inch, silver plated all over for high surface conductivity, and — in addition
— have gold plated rotor and stator plates to prevent oxidization.
These grounded rotor type instruments have losses lower than the average
laboratory standards. This condenser, due to its design does not have the
defects caused by either solid metal or dielectric end plates. 500 mmf.,
$7.00; 350 mmf., $6.75; 250 mmf., $6.50.
SAMSON ELECTRIC COMPANY
Manufacturers Since 1882
Canton, Mass.
Salt* Representatives in Thirty Leading American Citie* i
Why not subscribe to Radio Broadcast? By the year only $4.00; or two
years, $6.00, saving $2.40. Send direct to Doubleday, Page & Company,
Garden City, New York.
ACME CHARGERS
Best by Test
$Q50
^— minus bulb
Your dealer can get it for you
THE ACME ELECTRIC & MFG. CO.
1410 Hamilton Avenue
Cleveland, O.
therefore learn how to operate without causing
this interference.
ADJUSTING A REGENERATIVE SET
IF YOU will take the trouble to observe the
* rules which follow, you will obtain greater
satisfaction and enjoyment from your radio
receiving set, and at the same time cause mini-
mum annoyance to your neighbors.
(1) Practise on tuning powerful stations first
and do not try to pick up weak distant stations
until you become expert.
(2) Use both hands, one hand for the regenera-
tion control and the other hand for the tuning
control.
(3) Keep the regeneration control always just
below the point of oscillation, your set is then
in the most sensitive condition. This is the
reason for using your two hands for tuning.
(4) If your set then accidentally breaks into
oscillation, turn back the regeneration control
at once.
(5) Do not try to find a station by the whistle.
If your set is tuned just below the whistling
point, the signals will come in clear and your
regeneration control can then be tuned a little
further to increase the volume.
(6) Do not force regeneration in an attempt to
obtain loud speaker volume from a set not
designed for the purpose.
(7) Do not force regeneration in an attempt to
hear stations beyond the range of your set; be
content with those you can really hear.
The fact that you once heard a distant station
on your receiving set is no indication that you
can hear this station regularly, for occasionally a
radio broadcast from a distant station is re-
ceived with extra strength due to some freak
condition. When you have tried to tune-in to a
station in the correct manner for a minute or
two and are not able to hear it, do not unduly
increase your regeneration and persistently
wiggle your dials, for in so doing you may be
causing annoyance to some other broadcast
listener who would otherwise be able to hear
this distant station on his multi-tube set.
If you are not satisfied with the range your
present receiver is giving you and providing local
conditions are satisfactory, the only remedy is a
more sensitive receiver or the addition of more
tubes to your exisiting set. Don't at your
neighbors' expense, try to force your receiver.
Besides being unfair to your neighbors, you are
also spoiling your own quality.
You can accordingly assist in eliminating
these whistles by:
(a) Learning to operate correctly yourself.
(b) Not allowing children, who are not old
enough to understand the correct method of
operation, to cause interference from your set.
(A crystal set causes no interference).
THE LICENSE
A LL radio receiving sets in Canada are re-
«• quired, by law, to be licensed. Licenses
are issued yearly and are required to be renewed
on the first of April each year. They may be
obtained for one dollar from local Radio In-
spectors, many Post Offices, many Radio Dealers,
or from the Radio Branch, Department of
Marine and Fisheries, Ottawa, Canada.
The proceeds of the license fees are used to
maintain an inspection staff for the administra-
tion of radio and for the improvement of radio
conditions in the Dominion.
For the benefit of listeners who are desirous of
obtaining this article in circular form, it should be
stated that copies may be had, on request, from
the nearest Canadian Radio Inspector, or direct
from the Radio Branch, Department of Marine
and Fisheries, Ottawa, Ontario, Canada.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
243
"SELF-ADJUSTING" Rheostat
A BASIC Need
in Every Circuit
BECAUSE— AMPERITE not only modernizes any
set— it keeps it modern.
1 — Eliminates Hand Rheostats, thereby
simplifying control.
2 — Permits use of the latest types of
tubes or any combination of tubes.
3 — Simplifies and reduces set-wiring,
thereby making for greater
pactness and avoids losses.
4 — No moving parts, hence no grinding
clear and full tones.
5 — Prolongs tube-life by keeping fila-
ments at a constant temperature.
6 — No filament meters needed.
7 — Brings the most out of each indi-
vidual tube — automatically — no
guessing.
8 — Makes every set-owner a master
operator, no knobs to turn.
Write today for
FREE
Hook-Ups
Obsolete
Sold Everywhere
. 1 0 complete with mounting
AMPERITE is used in every popular present-day construction
set. Why? Because of its many outstanding exclusive features,
and because it solves the perplexing problem of tube-control —
COMPLETELY and AUTOMATICALLY.
For the new tubes:
Amperite No. 112— for the UX-112 and CX-112
Amperite No. 120— for the UX-120 and CX-120
(Company
Depi. R.B.-13 50 Franklin Street New York City
Mf's of "TUNE-RITE" Straight-Line-Frequency Dial
Be sure that the set you buy or build is equipped with AMPERITE.
Tested and approved by RADIO BROADCAST
244
RADIO BROADCAST ADVERTISER
ifiC
Amplion pedigree
Thirty-eight years ago —
Created by the actual
originators and world 's
oldest makers of loud
speakers, it is only logi-
cal that the Amplion
should be unrivaled for
clarity of tone. Some
of the countries in
which Amplions rule
as favorites:
UNITED STATES
CANADA
ENGLAND
SCOTLAND WALES
IRELAND
NORWAY SWEDEN
DENMARK
HOLLAND BELGIUM ,
FRANCE SPAIN
SWITZERLAND
ITALY JAPAN
SOUTH AFRICA
NEW ZEALAND
AUSTRALIA
In 1887 Mr. Alfred Graham
invented and dem-
onstrated the first
practical loud speak- v
er which the world had ever heard (illustrated above).
In 1893 -- *UB^ Graham Loud
Speakers placed
upon market. In 1 894 GrahamLond
Illustration shows Speakers first used in
the "1893 model." British Navy. Graham
transmitters applied to
phonographs for loud
speaker reproduction.
In 1896 Graham Loud Speaking Naval Telephones developed and
adopted by British Admiralty.
In 1898 Graham Watertight Loud Speakers patented. Placed on many
warships and mercantile vessels, throughout world.
In 1903 Complete Graham Loud Speaker installations, on central bat-
tery plan, erected on warships as sole means
of communication.
In 19OO The most extensive loud speaking naval in-
stallation to date was made by Grahams.
Included a Graham exchange system fitted to
H. M. S. Dreadnought.
Onwards Graham Loud Speakers applied to all sorts
and conditions of service at home and abroad,
ashore and afloat.
By 1919 No less than 12,OOOGraham loud speaking installations in oper-
ation on ships alone.
19!
Mui
In 193O (before radio
loud speakers were in
common use) "AMP-
LION" Loud Speakers
produced for radio by
Alfred Graham & Co.
"AMPLION" trade-
mark registered.
In 1923 Amp-
lions adopted as
standard equip-
ment by leading
makers of radio
sets abroad.
The Amplion
of!926
To hear this new cAmplion '•Dra-
gon AR-io, if to appreciate why
cAmplions, year after year, inter-
nationally lead in stiles. Six mo-
dels, including phonograph units,
$1210 $42.10. Write for interest-
ing literature and dealer's address.
^•Vr
In 1933 Amplions introduced into United States, Canada and other
countries. Quickly attained largest throughout-the-world sale
of any loud speakers.
In 1934 To supply demand The Amplion Corporation of America was
formed to market and manufacture Amplions here.
In 1935 More Amplion companies formed and agents appoint- il^TI
ed throughout world to keep pace with international Jilll^
demand. The Amplion Corporation of Canada, Lim-
ited, organized.
^|j00nBME4vrrax)nnMWfOT
Alf L ON
(gudSpeaker
Alfred Graham & Co.
London, England
Patentees
THE AMPLION CORPORATION OF AMERICA
Executive Offices: Suite L, 280 Madison Are., New York City
Canadian Distributors: Burndept of Canada, Ltd., Toronto
Associated Companies and Agents : Alfred Graham & Co., London, England; The Amplion Corpora-
tion of Canada, Limited, Toronto; Compagnie Francaise Amplion, Paris, France; Compagnie Conti-
nentale Amplion, Brussels, Belgium; Amalgamated Wireless (Australasia), Ltd., Sydney and Mel-
bourne; British General Electric Company, Ltd., Johannesburg and Branches; Indian States and
Eastern Agency, Bombay and Calcutta; C. J. Christie E. Hijo, Buenos Ayres; David Wallace &, Co.,
, Valparaiso; Mestre Qc Blatge, Rio de Janeiro; F. W. Hammond & Company, London and Tokio.
This is a good time to subscribe for
RADIO BROADCAST
Through your dealer or direct, by the year only $4.00
DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORK
RADIO WIRES
We manufacture all types.
Round braided antenna wires
Flat braided antenna wires
TRADE MARK REG. Round stranded antenna wires
Above types in copper — tinned copper — enameled copper — tinned bronze.
Loop wires in silk or cotton covered. Antenna supporting springs.
Litz wires. Cotton and silk covered wires for set
Enameled wires. wiring. j
Write us for descriptive catalogue. ™
ROSS WIRE COMPANY 69 Bath St., Providence, R. I
READERS WRITE
US
Say "Pico" Instead cf "Micro-
Micro-Farad"
\A7HY not adopt and familiarize the prefix
T * 'pico' for 'micromiker'" wrote Mr. F. I.
Anderson in the September RADIO BROADCAST
(page 662). "Thus, instead of saying a 'triple-
o-five' condenser, for an instrument of 500
micro-micro-farads, let us say 500 picos, which
is correct and simple, if we once get used to it.
To be precise, we should say pico-farads, but we
could drop the farads once we get used to the
pico end of it." From Robert S. Kruse, techni-
cal editor of QST, comes a letter informing us that
he is heartily in agreement with this idea and
has already taken steps to make it take on
definite shape.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
1 want to enter an enthusiastic endorsement
of the idea expressed by Mr. F. 1. Anderson on
page 662 of your September issue. By a
strange coincidence we received this issue on the
exact day when we had been discussing the
extremely unsatisfactory nature of the micro-
micro-farad. This letter is only to offer you
my personal cooperation in anything you would
care to do along this line, although we have al-
ready half formed a plan of more general techni-
cal cooperation. This plan has now been sub-
mitted to our Executive Committee which is
investigating its practicality.
Very truly yours,
ROBERT S. KRUSE.
Technical Editor, QST.
Radio Developments in New Zealand
VA/E ARE always pleased to hear from our
' ' readers abroad and we think that fans in
this country are interested to know what pro-
gress is being made in foreign parts too. There
is a certain amount of satisfaction in knowing
that one's local station is heard regularly in
some remote spot of the globe, and perhaps a
certain amount of chagrin when one reads that
such and such a station may be heard very well,
in New Zealand for example, while the native
fan, who may be merely two or three thousand
miles nearer, is unable to receive it. We wonder
what percentage of East Coast fans have
received KGO, KFI, and KPO, as often as Mr.
Haggett has?
DOMINION RADIO COMPANY
WELLINGTON, NEW ZEALAND
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
Just a few lines to express my appreciation
of your excellent magazine. I have always
found it an ideal publication in every way. I
have just received the July issue and I think it
is the best yet. I was very sorry to learn of the
death of Miss Mix, as her column was of great
interest to us. Broadcasting here is not of a
very high order just yet, but this year will see
New Zealand with one of the best broadcasting
services in the world. Parliament is making
provision this session for the erection of several
main stations and several satellite relay sta-
tions. The revenue is derived from fees to be
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
245
J
Radio technicians and engineers as well as seasoned amateurs know that
"General Instrument" is satisfied with nothing short of perfect precision.
For example: The General Instrument laboratories developed the eccentric
type straight line frequency condenser at great expense — only TO
ABANDON IT!
Try to rotate an eccentric type straight line frequency condenser and note
the effect on the bearing and then you will realise why "General Instni'
ment" discontinued the eccentric type and created the CONCENTRIC
straight line frequency condenser.
CONCENTRIC straight line variable condensers represent the latest
development in condenser engineering. Observe the even
distribution of weight of the rotor plate.
"General Instrument" thinks more of its reputation than the
cost involved in creating a perfect instrument. Hence—
the CONCENTRIC straight line frequency condenser.
CONCENTRIC Straight Line
Frequency Condenser
(Pyrex Insulated)
The perfect instrument created by
General Instrument. Type 80.
STATOR
PATENTED
TYPE 40
THE INIMITABLE RHEOSTAT
Built only by General Instrument, this rheostat can
NOT be imitated. To get it, you must make sure
of the name "General Instrument."
OBTAINABLE AT BETTER CLASS RADIO DEPARTMENTS
^Manufacturers of Laboratory Equipment
423 Broome Street New York City
•if Tested and approved by RADIO BROADCAST -fa
V .
246
RADIO BROADCAST ADVERTISER
Superadio Receiver
5 Tubes
2 Dials
$56
Licensed Under
Reactodyne Agreement
At last — true beauty is combined with scientific design so that results
never before expected are now easily achieved. Loose, extravagant
claims are not made for this set, which must be seen and heard to be
appreciated.
Results Undreamed of Now Secured
Employs a radically new principle — inductive reaction. Housed in a handsome,
compact, solid walnut cabinet with black bakelite panel engraved in deep gold-
Produces full rounded tones with all their color and shading. Oscillations
automatically controlled. Use of low loss S. L. F. Condensers and highly
developed Solenoid R. F. Transformers results in tremendous power without
disturbing squeals, while simple controls, only two, regulate the thunderous
volume to fairylike whispers, if desired.
Send for circular giving engineering details why the Superadio
is so far ahead of present day conceptions.
Tested Tubes Now Possible
With the Superadio Dynometer
Remember — you can now buy TESTED tubes —
where the Superadio Dynometer is on the job.
This meter is direct reading. Measures the ampli-
fication factor, plate impedance, and mutual con-
ductance of any radio tube. Extremely easy to
operate. Tests three tubes per minute.
Special Model S-2 Amplifier $30.
Jobbers and Dealers
Write for details on the Dynometer, and our
liberal selling proposition. Be the first in your
town to sell TESTED tubes.
Superadio Dynometer equipped
with phones and plug. Price $120.
(Patents Pending)
DeWITT-LaFRANCE CO., Inc.
54 Wash burn Ave., Cambridge, Massachusetts
Boston Representative:
Martin, Hartley & Dewitt Sales Co., 99 Bedford St.
Chicago Representative:
William A. Welty & Co., 36 So. State St.
This is a good time to subscribe for
RADIO BROADCAST
Through your dealer or direct, by the year only $4.00
DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORK
Mexican Crystals
"The Catwhisker's Delight"
The BEST, bar none.
For Crystal sets, "Sil-
ver Galena.'' For Re-
flex sets, "Placerite."
Once tried, always used.
A 40c Each, 3 for $1.00
^ Special for DeForest, joe
70,000 users. You are next.
Dealers write
H. D. HATFIELD & SON
1762 Vermont Ave.
Hollywood California
FREE
Diagram for
ultra-selective
Crystal circuit
free with 3
crystal! at $1.
BROADCAST CONTROL OPERATORS
who read Carl DreherVs discussion in the September RADIO
BROADCAST on "Microphone Placing in Studios," should not
miss "Additional Notes on Microphone Placing" to be printed
in the January magazine.
DEALERS!
Send for our big new live
Catalog. Contains hun-
dreds of standard nation-
ally advertised sets,
kits and parts.
Use your letterhead
charged listeners-in which will be the equivalent
of nearly five dollars. At the present time my
company is running the broadcasting stations
in this city and local companies are doing the
same in the other towns, but that will cease of
course when the new Broadcasting Company
(now in course of formation) is ready. The
reception of American stations here is achieved
nightly using only single "valve" sets, and loud
speaker volume using one stage of radio, de-
tector and two of audio. I have heard KGO,
KPO, KFI, and others using a Kennedy Model XV
Receiver and have logged any number of
"Yanks" on a low loss set of my own construc-
tion. I am at the present time building a RADIO
BROADCAST Phonograph receiver as described in
your paper. 1 expect great results from it and
no doubt you will be pleased to hear how I get on
with it. This quarter of the globe is excellent
for reception as is evident by the long distance
records made by New Zealanders. At the
time of writing we are expecting the arrival of
the American Fleet here and I have already
heard their "sigs." from Lieutenant Schnell's
short wave set.
The "star" on your advertisements means a
lot to us here in New Zealand. We cannot tell
what is the latest apparatus and whether all the
goods one sees advertised are what they are sup-
posed to be, but in buying for this firm I have
never once fallen in when guided by the "star."
We have up to the present only handled small
quantities of goods but we anticipate an in-
creased volume of business this year. Thordar-
son, Belden, Na-ald, Peerless, Daven, Bell,
Walnart, and Federal are amongst the lines we
handle and we are satisfied that they are the best.
So you can see what a valuable guide your paper
is to us who "have no mother to guide us", as it
were. We all enjoy your column "As The
Broadcaster Sees It" — it is a scream.
Wishing you all the success you deserve with
your excellent paper.
Very truly, yours,
R. J. HAGGETT
Wellington, New Zealand.
The O'Connor Frequency-Changer
THE O'Connor Frequency-Changer,
which was described fully in the J une and
August, 1925, RADIO BROADCAST, hascaused
much comment, and we have received num-
erous letters from readers who have had
success with this circuit. By its use it is
possible to convert any existing receiver to
a super-heterodyne, and thus increase
range and selectivity. Used in combina-
tion with a neutrodyne receiver it is possible
to efficiently reduce the number of tuning
controls to two, instead of the usual three.
Here is a letter from an enthusiastic con-
structor.
Editor, RADIO BROADCAST
Doubleday, Page & Company,
Garden City, New York.
SIR:
I have read with interest the controversy re-
lative to the O'Connor Frequency-Changer, and
as to its being a dud I can give evidence to the
contrary.
1 have one of the first ones made in this terri-
tory and what it did to my five-tube neutrodyne
is more than satisfying, in selectivity and volume
and distance, and I had what was considered an
exceptional set before.
Atlantic City, Elgin, Providence, and Pittsburg
come in between two degrees on the dial, and
with no interference.
Detroit and Toronto come in within half a
degree on the dial, also with no interference. 1 am
getting Fort Worth nightly now, and practically
all stations above 500 watts in power.
Very truly, yours,
C. F. RODGERS,
Conneaut. Ohio.
"if Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
/rety/mrtj l/m E
Marks a new era in Radio progress —
Sweeping country like a tornado —
Fans welcome it with open arms —
Irresistible demand growing by leaps and bounds —
*
KAR AS Started It
- and KAR AS Is Carrying On ! !
When we sprung the Karas Orthometric Condenser on a
restless, hungry radio public — we knew we had started
something. But we scarcely expected to be snowed under
with such a literal avalanche of orders.
We inaugurated Straight Frequency Line Tuning at the
psychological moment. Radio Fandom was waiting hun-
grily for something new. And here was something — not
only new — but so perfectly simple — so thoroughly scien-
tific—so downright sensible, that everyone wanted KARAS
Orthometric Condensers at once.
Our scheduled production was like a drop in the bucket.
Buyers pleaded — cajoled — even threatened. Our plans
were doubled, trebled, quadrupled. But it all took time.
KARAS Orthometric Condensers could not be thrown
together. It took months to train gangs to build them
with the absolute precision KARAS demands. So tens of
thousands had to wait or buy other makes, hurriedly
assembled to supply the demand we had created.
NOW — after months of preparation we are able to pro-
duce enough KARAS Orthometric Condensers to take
care of at least a fair share of the demand. This an-
nouncement is an apology to those who were disappoint-
ed. A note of thanks to those who have waited. And a
promise of revelation to those who have not yet discov-
ered the marvelous advantages of Straight Frequency-
Line Radio Tuning.
How KARAS Orthometric Condensers
Simplify the Tuning of any Radio Set
\o to
"'
Culinary Condenser Arrangementof Wavelenglhs Straight Line Wavelength CondenserArrangement
Ordinary straight capacity condensers
crowd 70 of the 100 wave lengths
into the first 30 points of the dial.
With straight -line -wavelength con-
densers 57 of the 100 wavelengths are
crowded into the first 30 pointsonthediaL
of Wavelengths on Dial
Sizes and Prices —
23 plate, .0005 Mfd., $7.00
17 plate, .00037 Mfd., 6.75
11 plate. .00025 Mfd., 6.5O
5 plate, .0000972 Mfd., 6.50
Note the
long
eccentric
plates
The New Scientific Karas Orthometric
Condensers insure absolutely equal sep-
aration on the dial of all wavelengths
throughout the entire broadcasting range.
Government regulations separate all stations by an equal interval of 10 kilocycles. Old type
condensers — straight line capacity and straightline wavelength — warped this uniform arrange-
ment — crowding a lot of low wavelength stations into the first few degrees on the dial. Diffi-
culty in tuning — confused heterodyning interference — garbling of programs — these were the
results. KARAS Orthometric Condensers give low wavelength stations the same equal sepa-
ration as the high ones. It is the last word in making real selectivity possible. The illustra-
tions above tell the story better than words.
Karas Orthometric Condensers are both theoretically, and mechanically perfect. Made entirely of brass— plates
patent leveled and securely bridged to insure permanent rigidity and alignment. Every joint soldered. Grounded
frame and rotor. Adjustable cone bearings. Spring copper pigtail. In short, so beautiful a job that one engineer,
on seeing the condenser for the first time, smilingly inquired. How many jewels?" As proof of their mechanical
and electrical efficiency, Karas Orthometric Condensers will hold a charge for from 6
to 8 hours, as against one hour to an hour and fifteen minutes for ordinary condensers.
If your dealer hasn't secured a stock of Karas Condensers
Order on this
Coupon !
Most good dealers every-
where. sell Karas Orthomet-
ric Condensers. If your
dealer happens to be one who
hasn't secured them, we will sup-
ily you direct on our 30-day
oney-Back Guarantee. Just fill
in and mail this coupon at once.
Send no money. Pay your post-
man on delivery.
KARAS ELECTRIC CO.,
_ For more than 30 years makers of PRECISION Electrical Apparatus
4043 N. Rockwell St., Chicago
Please send me Karas Orthometric Con-
densers, size at $ each.
I will pay the postman the list price, plus postage, on deliv-
ery. It is understood that I have the privilege of returning
these condensers any time within 30 days if they do not prove
entirely satisfactory, and you will refund my money at once.
Name —
Address _,
Dealer's Name... —
If you send cash with order.we'll »end pat
ag«po«tpald
Tested and approved by RADIO BROADCAST
RADIO BROADCAST
ARTHUR H. LYNCH, Editor
WILLIS K. WING, Associate Editor
JOHN B. BRENNAN, Technical Editor
JANUARY, 1926
Vol. VIII, No. 3
Cover Design - From a Painting by Fred }. Edgars
Telephoning Photographs *•*'**.- Frontispiece
Ether Waves You Cannot Hear - - - James Stotyey
Late News on the International Tests Willis K. Wing
The March of Radio J. H. Morecroft
What's New in Radio - - - Austin C. Lescarboura
Better Audio Amplification - Kendall Clough
Notes on the Model 1926 Receiver Ernest R. Pfaff
The Listeners' Point of View - - John Wallace
A Universal Short' Wave Transmitter
Nicholas Hagemann
As the Broadcaster Sees It - - - ' Carl Dreher
"Radio Broadcast's" Universal Receiver
Arthur H. Lynch
"Radio Broadcast's" Booklet of Call Signals
Lawrence W. Corbett
Methods of Controlling Oscillation in Radio Fre'
quency Circuits - - - - - - - John Bernard
If You Seek Economy, Buy the Best Harold Jolliffe
"Now, I Have Found" - - - - '
An A. C. Amplifier with the Robert!
The Roberts Set with Cylindrical Coil*
A Home-Made Loud Speaker
The Grid — Questions and Answers •»'•**»
Component Values for the "Aristocrat "
Noises and Their Causes
Impedance Amplifiers
A Key to Recent Radio Articles E. G. Shaltyiauser
Book Review *.••'_• - - J. H. Morecroft
"RADIO: BEAM A>{D BROADCAST"
High-Speed Fading - - ' - - -
What Our Readers Write Us ........
295
299
300
305
308
313
317
321
326
332
337
350
360
362
376
380
388
392
394
EDITORIAL SCENES
TAMES Stokley. who writes "Ether Waves You Cannot
I Hear" is an associate of Dr. Edward E. Slosson, the di-
rector of Science Service in Washington. Science Service is
a most interesting and unusual organization, devoted to present-
ing in an able fashion the facts about science in any of its
branches. The board of directors of the organization number
some of the greatest scientists now living in America. For
the benefit of those readers who do not know, Professor J. H.
Morecroft whose "March of Radio" has appeared in RADIO
BROADCAST ever since its first issue is a professor of electrical
engineering at Columbia University, where he has trained many
a radio engineer. Austin Lescarboura, the writer of'What's
New in Radio" was formerly Managing Editor of the Scientific
American. He is now a free lance writer. Some interesting
slants — as the baseball writers put it — on broadcasting are
offered by the new conductor of "The Listeners" Point of
View," John Wallace, whose first department appears in this
number. The changes in call letters, and frequency of Cana-
dian and American broadcastings tations during the past few
months have been many and we have made every effort to have
the list appearing on page 337 the most accurate to be found
anywhere. Readers who have access to a razor blade and a pin
can quite easily make up a sixteen-page booklet from the list.
Some misunderstanding has arisen about the description of
a new N-P coil for the Roberts Knockout receiver printed on
page 66 of RADIO BROADCAST for November. The author was
Ralph D. Tygert, an engineei on the staff of the F. W. Sickles
coil company at Springfield, Massachusetts. Mr. Tygert's
findings have been incorporated in the new coils now being
marketed by that company for the Knockout receiver.
OCTOBER and November have been the months of radio
shows throughout the country; November especially was
a red letter month in American radio affairs, for the third of
Secretary Hoover's radio conferences was held in Washington
and everyone agrees that the policies recommended for radio
are most wise and calculated for the best interests of radio in this
country. Too much credit can not be given to Mr. Hoover for
his ability and foresight in causing the varied and sometimes
sharply competitive interests of radio to settle their complex
problems by amicable conference where reason has almost al-
ways prevailed.
MUCH activity is seen in the Laboratory these days. The
staff is experimenting with three distinct receiver cir-
cuits, all of which have great merit and technical interest.
If the receivers are proved worthy, each one will be described
in an early number of the magazine. The Laboratory is col-
lecting data on radio tubes and Keith Henney, director of the
Laboratory, will have an article showing curves on all the popu-
lar tubes with a mass of highly valuable information for every
radio user, which, as far as we know, has never been put to-
gether in one article before. The February number will also
present "How Long Will My B Batteries Last?" by George
C. Furness, an engineer who probably knows as much about
radio batteries as anyone in the business. We shall also give
the latest plans for the 1926 International Radio Broadcast
Tests which will occur one week after the February magazine
is on sale. Those Tests, by the way, give promise of being
more interesting and successful than either of the two which
have so far been held.— W. K. W.
Doubleday, Page & Co.
MAGAZINES
COUNTRY LIFE
WORLD'S WORK
GARDEN & HOME BUILDER
RADIO BROADCAST
SHORT STORIES
EDUCATIONAL REVIEW
LE PETIT JOURNAL
EL Eco
THE FRONTIER
WEST
Doubleday, Page &• Co.
BOOK SHOPS
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I PENNSYLVANIA TERMINAL (2 Shops)
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TOLEDO: LASALLE & KOCH
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ST Louis-
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OFFICES
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TORONTO: OXFORD UNIVERSITY PRESS
Doubleday, Page &" Co.
OFFICERS
F. N. DOUBLEDAY, President
A. W. PAGE, Y ice-President
NELSON DOUBLEDAY, Vice-President
RUSSELL DOUBLEDAY, Secretary
S. A. EVERITT, Treasurer
JOHN J. HESSIAN, Assi. Treasurer
Co,
DOUBLEDAT, PAGE & COMPACT, Garden Qity, ^e
jpyright, 1925, m the United States, Newfoundland, Great Britain, Canada, and other countries by Doubleday, Page & Company. All rights reserved.
TERMS: $4.00 a year; single copies 35 cena.
29O
RADIO BROADCAST ADVERTISER
293
Single
Dial Tuning
Yet
Greater
Selectivity
The Wave Master
Consolette
A beautiful genuine
mahogany model with
inbuilt horn,
$235.00
Also made
in a handsome Console
Model. Price
$275.00
"NOW
I Get What
I Want
When I Want It"
KELLOGG
Found the Way!
Standard Model
5-Tube Wave Master
in beautifully finished
cabinet of solid genuine
mahogany. Price,
$125.00
HERE, at last, is a radio set that is REALLY easy
to tune. Just one tuning dial — but what a magic
dial it is! For it actually has a range of 540
degrees— over three times more station finding range
than the ordinary dial.
A dial that gives lots of room
for a wide separation of stations.
Makes it easy to tune in the
one you want and to completely
blot out the others.
In fact, this remarkable new Kel-
logg receiver is exactly the set
busy men and women every-
where have been asking for. A
set that brings in what you want
when you want it — without fus-
sing, without "hushing" the rest
of the family, without any need
of knowing what is going on in-
side the handsome cabinet. Sim-
ply superb is the musical quality
of WAVE MASTER reception.
This masterpiece of receiving
sets is the product of a manu-
facturing company that would
naturally be expected to design
a great set. For 28 years, the
Kellogg Switchboard & Supply
Company has been making pre-
cision electrical instruments —
telephones, switchboards, and
apparatus. Ever since the be-
ginning of radio we have been
making radio parts of highest
quality. But not until now have
we been able to perfect a radio
receiver that we felt was worthy
to carry the Kellogg name.
The Kellogg WAVE MASTER
has little in common with other
five-tube sets. It operates on a
new, better and more efficient
principle. By using a new sys-
tem of amplification and detec-
tion, we have solved the difficult
problem of single dial tuning.
We have done it without any
sacrifice of selectivity; instead,
we have INCREASED selectiv-
ity as greatly as we have in-
creased simplicity.
Would you know more about
the WAVE MASTER? It is our
aim to make it easy for folks
to test the WAVE MASTER
wherever they may be located
— the country over. If you do
not know the Kellogg dealer in
your vicinity, write us at once
for his name and a full descrip-
tion of the WAVE MASTER
circuit. Ask for Folder No. 5-A.
Kellogg
Symphony
Reproducer
A Separate Circuit for Each
40 Meter Wavelength Band
One-Dial Control, Yet Greater Selectivity.
Radio Dealers and Jobbers!
We are now closing sales franchises in open
territory which is fast being taken up, The
WAVE MASTER franchise, backed by
Kellogg resources and our powerful advertis-
ing campaign is most valuable. Wire us if in-
terested—«r get into Chicago quickly and see
us regarding this money-making proposition.
Kellogg Switchboard & Supply Company
1066 West Adams Street, Chicago, 111.
*
TER
Tested and approved by RADIO BROADCAST
IDENTIFICATION
"'ANTED
HOW "TELEPHONED" PHOTOGRAPHS LOOK
Radio men have been interested in the announcement of the Amercian Telephone & Telegraph Company of the successful sending of photographs by wire.
The center oval shows a transmitted piAure of the parade a President Coolidge's inaugural. Note the great detail preserved. Checks and business papers
are frequently sent by wire. The check shown was sent from New York to Chicago in seven minutes. The finger print is shown upper left, as received
in Chicago after it was sent from the files of the Police Department in New York to the Chicago police, for indentificaton, which was made and confirmed
in three minutes after reception. Diredtly above is shown the picture receiving device. On the left is the 'amp house, next the "light valve," operated
by electric impulses received from the sender The rolled unexposed film is shown on the drum in the foreground; behind it is the synchronous motor.
When pictures are received, the room is kept dark. The only light on the receiving film is that which passes through the light valve
RADIO BROADCAST
VOLUME VIII
NUMBER 3
JANUARY, 1926
V8I- ' "•
Ether Waves You Cannot Hear
The Few Isolated Facts Known About the Ultra Short Waves of Heat and Light
—The Characteristics of* X- and Radium Rays — Taking Photographs Through Dense
Mists by Aid of Infra-Red Rays — How the Gap in Knowledge is Being Bridged
Between Radio Waves and the Much Shorter Ones Familiar as Heat and Light
M
"OST radio enthusiasts are a-
ware that when they listen to
a broadcast concert or lecture,
the ether is frequently full of
commercial messages in code
sent from ships or land stations, yet, in the
best receiving sets, these are not heard be-
cause their wavelength is much greater than
that to which the sets are tuned. Likewise
short-wave transmission, using wavelengths
down to a few meters, which has been so
much discussed as making possible the
sending of messages over great distances in
daytime, does not affect the ordinary set,
but requires a special one that is tuned to
these waves.
Even a short-wave receiv-
ing set, however, will not
make audible the multitude
of still shorter waves that are
continually fleeting through
space, for radio waves are not
the only kind of ether waves.
Thousands of times shorter
but otherwise identical with
them, are the waves of light,
and still shorter are the X-
rays, and the rays of radium.
Thus there is a complete
range of vibrations, all the
way from those with waves
whose lengths are measured
by the millionths of an inch,
to others whose waves are
miles long. Some occur in
nature, some are produced by
man with his various pieces
of scientific apparatus, and
still others are yet to be pro-
duced. . There are undiscov-
ered gaps in the series which
have not yet been filled, but
By JAMES STOKLEY
physicists and many other tireless workers
in allied fields in many countries are busily
engaged in closing these gaps, and making
the series an unbroken one.
Most familiar to us, more familiar even
than the radio waves, are those which make
up visible light. The wavelengths of these
are between ^i^ and TnrW of an
inch, the shortest making up violet light
and the longest red. Between these are
the wavelengths of the other colors, but
longer than the longest red waves, and
shorter than the shortest violet ones, are
the waves which make up what is often re-
ferred to as "invisible light." Those that
TWO EXAMPLES OF X-RAY TUBES
The largest and smallest ones made. These tubes have been invaluable for
surgical work during the past few years. By placing the hand, in which, let us
suppose, a piece of metal has become lodged, between the tube and a phosphores-
cent screen, the flesh will be found to cast a very faint shadow; the bones, a
stronger one; while the embedded metal object will show a clear defined shadow
are too long to see are called infra-red, and
the short ones ultra-violet.
When a beam of white light is passed
through a prism, the familiar rainbow-like
spectrum is the result, a band of colors
varying from red at one end to violet at the
other. But the red and violet parts are not
really the ends; the fact that they seem so is
only because our eyes are not as sensitive as
some scientific instruments. Take a radio-
meter, the little device consisting of small
vanes, black on one side and silvered on the
other, inside a glass bulb, which is often
seen in an optician's window, and spins
merrily when the sun shines on it. This is
operated by the heat rays,
and if it is placed a little be-
yond the red end of the spec-
trum, it will twirl, thus
showing the presence of heat
waves, which are identical
with the infra-red.
On the other hand, if we
allow the spectrum, and the
part of it beyond the violet,
to fall upon a photographic
film, the most impression on
the film will be made not by
the yellow part of the spec-
trum, which appears bright-
est to the eye, but by the
darker blue, and there will
be a prominent image caused
by the presence of the short
waves called the ultra-violet.
In the realm of invisible
light, things are not always
what they seem. During the
World War, several allied air-
planes arose from their own
lines bearing what was ap-
parently an enemy insignia,
296
RADIO BROADCAST
JANUARY, 1926
and they could easily have flown over the
German lines without molestation from
anti-aircraft guns. Neither did any of
the allied soldiers attempt to capture the
occupants of the planes when they landed,
nor were any bombs dropped before the
planes came down, for although to the un-
aided eye they bore a strange insignia it
was transformed to the familiar design of
an allied craft when observed through red
color screens provided the allied observers.
The enemy insignia was painted on the
airplane in paint that reflected visible light,
but that of the allies was painted with
pigment that reflected its shape and form
only in deep red light.
i Even the secrets of the spheres are re-
vealed through astronomical photography
with invisible light. Last summer at the
Mt. Wilson Observatory, in California,
when Mars made a close approach to the
earth, it was found possible for the first
time to measure the extent of the planet's
atmosphere, and indeed, to prove to a cer-
tainty that it has an atmosphere. These
pictures were made with the great loo-inch
telescope, the largest in the world. Two
sets were made, one by blue light, and the
other by infra-red. Not only did the latter
exposures show numerous markings on the
planet, which were completely obscured in
the blue set, but they also showed the dia-
meter of the planet appreciably smaller!
This, of course, is what we would expect if
Mars had an atmosphere like the earth's.
The blue light photographs could not pene-
trate the Martian layer of air, but the infra-
red ones did, and enabled us to see the
planet's surface.
This same principle also permits photo-
graphs to be made on the earth through
great depths of atmosphere, and even
through mists so dense that the human eye
cannot see through them. Airplane photo-
graphs from great heights are made in his
manner, and the special plates used reveal
all the detail on the ground below. The
photographer ordinarily uses a red light in
his dark room because light of that color
does not affect his sensitive emulsions, but
by bathing the plates before use in special
dyes, they becomesensitiveto this part of the
spectrum, and may be used with sufficiently
fast shutter speeds to permit aerial photo-
graphy with red, or even infra-red light.
The bathing beauties and the brave life
guards browned by the sun have ultra-
violet rays to thank for their coloration.
For sunburn is largely due to light waves
shorter than the visible spectrum. Babies
are endangered when they lack this sort of
light, for it is necessary to their health.
One of the most important recent discover-
ies in the field of nutrition is that foods,
such as milk and even lard, when exposed
to ultra-violet rays, develop properties that
prevent and cure rickets in animals and
human beings.
The sun is the greatest and best ultra-
violet ray machine we have. The sun is a
great doctor. Mercury, vapor lamps can,
of course, substitute for the sun, when days
are dark or short. Moreover, there should
be little or nothing between the sun and the
patient for the most effective treatment
MODERN X-RAY APPARATUS
Which is due to the discoveries of Rontgen, in 1895, of certain rays called X- or Rontgen rays. These rays are invariably produced by the sudden
stoppage of cathode rays by a solid obstacle. In modern X-ray tubes, the rays are as a rule allowed to impinge on a tungsten target placed in the
center of the bulb. X-rays are then emitted only on the side of the bulb facing the tungsten. These Rontgen rays, like cathode Rays, excite fluorescence
when they strike a suitable object. The exact nature of X-rays is still a matter of controversy, but most people now maintain that they are simply
ultra-short light waves
JANUARY, 1926
ETHER WAVES YOU CANNOT HEAR
297
TWO EXHIBITS AT THE NATIONAL ACADEMY OF SCIENCES, WASHINGTON
To the left is shown an ultra-violet lamp which has been photographed by means of its own light. The photograph to the
right shows another picture of this instrument. The mercury-vapor lamp, as it is termed, is rich in ultra-violet light
For most substances, glass among them, are
opaque to these short rays. A sun bath
behind a window pane would be ineffectual
and for the same reason many violet-ray
machines with lamps housed in glass, are
valueless.
WHAT CAUSES LIGHT
DUT what causes light, or other ether
L* waves, and how are they trans-
mitted? Many years ago it was supposed
that a luminous body gave off myriads of
tiny particles, or "corpuscles," which tra-
veled in straight lines, and when they en-
tered the eye, produced a physiologic effect.
This, however, gave way to the wave theory
which is still held, though with some modi-
fications. In studying light, one of the
most useful instruments has been the spec-
troscope.
When light is passed through a prism and
the proper combination of lenses, a band of
colored light, the familiar spectrum, is the
result, and if the prism and lenses are prop-
erly adjusted, there appears, when sun-
light is being analyzed, a number of dark
bands or lines which cross the spectrum at
right angles. These were long ago shown
to be due to incandescent gases, and by
their use, astronomers have been able to
tell what substances the sun contains, al-
most as well as if they had a piece of it in
the laboratory to study.
Each element has certain lines in the
spectrum. Thus many thousand are
known for iron, while others do not have so
many. Hydrogen has a number in various
parts of the spectrum, and corresponding to
the color, or wavelength of the part that
they occupy. In 1885, Balmer found that
a simple law would give the wavelengths of
the lines of one of the series due to hydro-
gen. Since then, similar series have been
found for other series of hydrogen lines,
and also for other elements.
This, then, showed that there must be
some order in the structure of these ele-
ments, but it is a different thing to find,
by trial and error, a law that fits a series of
cases, and to work out the reason that
such a law is followed. But the talent was
not lacking to find such a reason, and the
best explanation, and the one that is most
generally accepted by physicists, is that
given by Prof. Niels Bohr, of Copenhagen,
Denmark. It explains not only the series
spectra of hydrogen, but also of the other
elements for which such spectra have been
determined.
According to the Bohr theory, the atom
consists of electricity. At the center is a
charge of positive electricity called the
proton, and around it revolve one or more
negative charges, which the physicists calls
electrons. These resemble the planets of
the solar system, while the proton is similar,
in its relative position, to the sun, around
which theelectrons revolve indefmiteorbits.
But here is an important difference between
the celestial and atomic cosmogony.
While the planets in the sky always move
in the same orbit, the electrons have the
power of jumping from one orbit to another,
and every time that such a change occurs,
either visible or invisible light, or possibly
one of the other forms of radiation, is given
off.
The simplest atom is that of hydrogen,
and thus it is understood why the spectral
series of that element was first determined.
Its atom consists of a single proton, or
nucleus, around which revolves a single
planetary electron. Every time the planet-
ary electron changes its path, a radiation is
given off. But, one asks, how is it that
there are so many lines in the spectrum of
hydrogen, when a single wavelength is
given off with each change? As a matter of
fact, if it were possible to isolate a single
hydrogen atom, it would not radiate light
of the entire hydrogen spectrum. But
when there are a great number of atoms to-
gether, as there are in even the smallest
298
quantity of hydrogen that we
can work with, there are so
many that at any instant every
possible change is going on in
one or more atoms, and the
combination produces the
spectrum.
X-RAYS USED TO ANALYZE
THE ATOM
RADIO BROADCAST
JANUARY, 1926
Invisible Limit of Violet Blue Blue-
Ultra-Violet Visibility Green
Yellow- Orange Red Deep Limit of
Green Red Visibility
\A/ITH the shortest ultra
"" violet waves about
^oo!ooo °f an incn '" length,
and the atoms so much smaller
than that, it would seem hope-
less to expect to study them by that means,
but here the X-rays came into use. Much
like lifting one's self with one's boot straps
is this method, for the X-rays have been
used to analyze the atom, and at the same
time the study of the structure of matter
has thrown light on the nature of the X-
rays. In 1895, on the 8th of November,
Prof. W. K. Rontgen, at Wurzburg, Ger-
THE SOLAR SPECTRUM
As defined by the spectroscope and photographed on a sensitive plate. The
ray to be analyzed is passed through a narrow slit before the prism. The
slit tends to prevent overlapping of the various colors. Note that the photo-
graph shows, at the violet end, a part of the spectrum beyond the limit of
human visibility
SIR ERNEST RUTHERFORD
An English physicist, born in New Zealand in
1871. He has been responsible for much de-
velopmental work in radio-activity, and pub-
lished papers on the subject as early as 1904.
He has done a lot of useful work in bre aking up
atoms by means of radium rays, and was awarded
the much coveted Nobel Prize in 1908
many, discovered these rays which bear
his name, and as their nature was not
known, they were also called X-rays.
In 1912, however, another German
scientist, Laue, found that by passing a
beam of X-rays through a crystal they
were deflected, in much the same way as a
beam of light is deflected when it passes
through a grating consisting of fine lines
ruled on a glass plate, thousands to the
inch. This effect is called "diffraction,"
and will only take place when the distance
between the lines is not very much greater
than the wavelengths of the light waves
themselves.
Laue thought that X-rays
were really light waves of very
short wavelength, and that the
reason they could not be dif-
fracted was because the dis-
tance between the lines on
even the finest grating that
can be made artificially, some
15,000 to the inch, was so much
greater than the wavelengths
of the X-rays that the effect
was not appreciable, So he
set to work to use a natural
grating, and he chose a crystal
which, according to the ac-
cepted ideas, consisted of molecules
arranged in layer fashion.
Many facts previously observed made
this theory of the structure of crystals the
accepted one. When Laue passed X-rays
through a crystal and found them deflected,
the molecular layers themselves acting as
a very fine grating, he investigated the
nature of crystals and of X-rays at the
A RADIOMETER
The device invented by Sir William Crookes to
exhibit motion caused by action of light. It
consists of a light horizontal vane formed of four
metal discs, supported by cross arms at right
angles, on an easily moving pivot. The whole
is mounted in a highly exhausted glass bulb.
The four metal discs are polished and blackened
on alternate sides. If light rays are concentrated
on the instrument, what little gas remains therein,
is heated, and the discs are affected, the black
ones becoming the hotter. The gas molecules
acquire a greater velocity when flying off the
black discs than they do off the bright ones, and
the difference of velocity causes motion. The rate
of rotation depends on the brightness of the light
PROFESSOR R. W. WOOD
Of Johns Hopkins University, Baltimore, who
has interested himself in spectrology. While a
Major in the United States Army (1917 to 1919),
he developed a system of secret signalling, em-
ploying both visible and invisible light. One of
his earlier inventions, curiously enough, can
hardly be compared even remotely with his
present work. It was a device for thawing
frozen pipes by means of electricity
same time, and we now know the X-rays
to be short waves, about ^^0 J0i0 0 0 of an
inch long.
Since then, Sir William Bragg, of the
Royal Institution of London, and his son,
W. L. Bragg, who is now professor of
physics at the University of Manchester,
England, collaborated on a remarkable
piece of research, which in 1915 won for
JANUARY, 1926
THE JANUARY INTERNATIONAL TESTS
299
them the Nobel prize in physics, probably
the highest honor that can be given a scien-
tist. They made an exhaustive study of
the way crystals deflected X-rays, and from
their results were able to deduce many facts
about the very structure of the molecules
of which the crystals were made.
Another Englishman, Sir Ernest Ruther-
ford, also a Nobel prize winner, has since
carried the work into the very heart of the
atom. According to the Bohr theory, the
atom consists of electrons revolving around
a central nucleus, and if we could hit the
nucleus hard enough, somethingshould hap-
pen. This seems impossible, at first sight,
because there is apparently no instrument
small enough to get into the atom. Such a
devicewould have to be as small as the atom
itself, and as every kind of known matter
is itself made of atoms, it is hard to imagine
how we could knock an electron out of its
orbit.
Here Sir Ernest made use of that wonder-
ful element, radium, which is continually
changing into another element. A small
particle of radium constantly emits atoms
of helium at a speed which would take them
half way around the world in a single
second. Actually, they cannot travel more
than a few centimeters, but by placing the
material — he used nitrogen — the atoms of
which it is desired to knock apart in close
contact with the radium, the alpha parti-
cles, as the helium atoms are called, hit
with a high velocity. They are so small
themselves that they can enter the atom,
and, when one hits the nucleus of an atom,
its high speed can do a lot of damage.
This is not quite so easy to accomplish
as it sounds however. Even in the mosf
solid matter, the atoms are so spread out
that, in proportion to size, there is as much
empty space between the electrons and
those of their neighbors as there is between
the stars in the heavens. As there is no
known way of aiming the alpha particles at
the nucleus, the only possible procedure is
to shoot a great many, by letting the radium
act for a long time, and then waiting for an
accidental hit. The process has been well
compared with throwing keys at a door
and waiting for one to lodge right in the
keyhole.
But while the English scientists have
been working on the problem, our American
scientists have not been idle. Chief among
those active in this branch of scientific re-
search is Dr. Robert A. Millikan, of the
Norman Bridge Laboratory of the Cali-
fornia Institute of Technology, at Pasa-
dena, California. Within the past year, by
means of what he calls high vacuum, hot
spark spectrometry, he has been able to re-
move some of the electrons from an element
and to detect the difference with the
spectroscope.
Although it represents probably the
greatest achievement of physical science in
recent years, the study of the atom and the
forces within it, is barely beginning. Now
we have but a glimmering of the time when
atoms can be changed from one element to
another at will, and when the tremendous
forces that hold the atoms together can be
utilized in our daily work. One difficulty
has been suggested that may arise when this
is accomplished. If we start the atoms
disintegrating, will we be able to stop them,
or will the disintegration continue until the
entire world has been reduced to hydrogen,
perhaps, and, like Icarus, our efforts result
in our own annihilation? Whether this
will happen cannot be foretold, but it seems
likely that the physicists of the future who
succeed in breaking up the elements at
their pleasure, will not be without a means
of controlling their efforts.
LATE NEWS ON THE INTERNATIONAL TESTS
kLANS for the third International Radio
Broadcast Test are progressing so rapidly
that it is impossible to make a complete
and accurate announcement in RADIO BROAD-
CAST at this time because this is written about a
month before the magazine appears on the news-
stands. The last week in January, 1926, is the
time fixed for the tests. American, Canadian,
Mexican, and Cuban broadcasters will transmit
from 10 to 11 p. M. Eastern Standard time
beginning on the evening of January 24 (Sun-
day), and running throughout the week. Eng-
lish and Continental broadcast stations will be
on the air during the same week from 1 1 to 12
p. M. Eastern Standard time.
Although the arrangements are not completed
at the moment of going to press, it is probable
that on Friday night, of that week, American
listeners especially will have the opportunity of
sharing in a most unusual broadcast experiment.
During the first fifteen minutes of the American
transmitting period, broadcasters in the Eastern
time zone will broadcast while all other North
American stations are silent. During the second
fifteen minutes, stations in the central time zone
will send, while all others are silent. And during
the third fifteen-minute period, all the broad-
casters in the mountain time belt will be on the
air and every other station silent. During the
last fifteen-minute period, the stations in the
Pacific time belt will send out their programs
under the same conditions.
It is expected that British and Continental
stations will engage in a similar north and south
broadcasting experiment during their trans-
mitting hour on the next to the last night of
the test. The transmissions for the first fifteen-
minute period will begin with the English sta-
tions in the Greenwich Mean Time zone and
progress across the Continent, if the present
plans go through.
On the final night of the test, the British and
Continental stations are expected to engage in a
By WILLIS K. WING
north and soutn broadcasting test, which will be
similar to the one in which the North American
broadcasting stations will take part. The
north and south schedule for American stations
follows:
EASTERN STANDARD TIME
From 1 1 to 1 1:15 p. M., Canadian stations will
transmit.
From 1 1 :i 5 to 1 1 30 p. M., stations in the north-
ern half of the United States will transmit.
From 1 1 30 to 1 1 :45 p. M., stations in the south-
ern half of the United States will transmit.
From 1 1 :45 to 12 M., stations south of the United
States will transmit.
This schedule will not only give American
listeners a chance to hear stations in this country
never heard before because of the station
operating on a frequency used by some near-by
station, but this arrangement will also give the
overseas listeners a chance to pick up some
American stations that are more distant from
them than the stations almost on the edge of the
Eastern seaboard. The arrangement of the
American tests so that on the first night (Friday,
American time) the stations will progressively
transmit from east to west, and on the second
night of those tests (Saturday, American time)
transmit north and south, will give American
listeners a chance to experiment with DX
reception such as they have never before had.
The Continental and British stations, if they
follow the same plan for their territory, on the
last two nights of the test, will be on the air just
one hour earlier than the American stations.
This will keep the air clear for the American
transmissions which follow. The British and
Continental broadcasters will undoubtedly
appreciate this arrangement, for it will give them
a chance to get a bit more rest. Since the trans-
missions from abroad come at from three to four
o'clock in the morning, London time, the physi-
cal strain on the various station staffs is bound
to be quite heavy by the end of the test week
The time chosen, which is a distinct hardship
on the foreign broadcasters, is necessary because
only during those hours is there a complete band
of darkness clear across the Atlantic and as far
as the Pacific coast of this country. It was
hoped at one time, to interest the Australian
broadcasters in joining the experiments, but the
serious difference in time made that simply out
of the question.
In every city of importance in the United
States and Canada, one official "International
Radio Week newspaper" will be chosen by the
International Radio Week Committee. That
paper will print the official, verified programs
as transmitted from the overseas broadcasters.
This will allow every listener to verify his
reception the day after he has heard a foreign
station. Newspapers throughout the country
will carry frequent announcement of the latest
development in the plans for the International
Radio Broadcast Tests of 1926.
But if all those who had verified reports last
year will send a description of their apparatus and
something about the results they have with their
receiver, to " International Radio Broadcast Test
Committee, RADIO BROADCAST magazine, Garden
City, New York" the Committee will pass on
their equipment and wherever possible, appoint
them as an official listening post for the Tests.
Results of successful reception can be sent to
the Test Committee by mail, telegraph, and
telephone. We can then verify reception. Re-
ports of successful reception of the overseas sta-
tions can also be forwarded to the Test Com-
mittee by amateur radio. Station 2 CY, operated
by RADIO BROADCAST Laboratory will be in con-
tinual operation and will receive and acknowledge
all messages which outside listeners file with
amateur radio stations in their home localities.
Past President, Institute of Radio Engineers
The Fascinating History of the Vacuum Tube
BOUT a year ago the question of
vacuum tube patents was dis-
cussed in these columns and the
occasion was the expiration of
the seventeen-year life of De Forest's
"third electrode" patent. This patent of
De Forest's, combined with the Fleming
valve patent, completely tied up the vacuum
tube industry for years, and during those
years, six dollars was the price we had to
pay for even the poorest type of tube.
The De Forest patent had been acquired
by the Radio Corporation and for years
the price stayed where it had been put by
De Forest when his output was measured
in the hundreds and the cost of his hand
made article was necessarily high.
The Radio Corporation had a complete
monopoly of the manufacture of triodes
and could fix the price as they chose.
But in the last year or two with the rapidly
expiring life of the De Forest patent,
independently made tubes began to appear
in large numbers and coincidentally, the
price of RCA tubes began to fall to some-
where near a reasonable value. Whether
the possible competition forced the RCA
price down or whether it was purely an act
of thoughtfulness for the good of the public
on the part of this corporation, the broad-
cast listener can probably best judge.
At any rate, we do know that when there
was no competition, the price remained
very high.
Because of this very recent situation, we
are somewhat perturbed to see that the
"high vacuum" patent has finally been
granted to Dr. Irving Langmuir of the
General Electric Company — -which means
also the Radio Corporation of America.
This basic patent has had a checkered
career since the application was made in
1913. Almost allowed by the patent ex-
aminer at one time, and then withdrawn to
permit interference proceedings in behalf
of Arnold of the Bell Telephone Labora-
tories, the patent has been the subject of
most exhaustive and expensive litigation.
A decision by one authority in favor of
Dr. Langmuir was nullified by a reverse
decision by another and only during the
last month has the patent been adjudged
Langmuir's by the Court of Appeals of the
District of Columbia.
This patent may prove to be so impor-
tant in the development of radio apparatus
that it well behooves us to know just what
it is; and in deciding upon the possible ef-
fect of a renewed monopoly in the vacuum
field we have only to remember that not
longer ago than a year or two, companies
making receiving sets were actually being
sued by the Radio Corporation on the
basis of their tube patents. The conten-
tion was that a radio receiver was evidently
intended to be used with tubes and that
therefore the set manufacturer should pay
tribute, and turn in a percentage of his
income to the Radio Corporation! The
percentage was demanded not because he
was making tubes but because he was
making sets for which tubes were required!
In the half dozen years before 1912,
vacuum tubes were obtainable only in the
form manufactured by De Forest; modified
small electric lamps is all they pretended
to be. Their degree of vacuum was only
as good as the commercially available
methods permitted at that time. The
tubes were far from uniform. One con-
tained little gas and another had ten
times as much, so that the performance of
the tubes as detectors and amplifiers was
erratic and unreliable. De Forest ap-
parently didn't know why his wonderful
devices were so variable in character, so
that the ground was prepared for the
procedure which started shortly after.
It was not long before the Western Electric
and General Electric Companies began to
appreciate the significance of the De
Forest audion, and to perceive its possi-
bilities. Their research staff was put to
work to find out why it was so variable and
how to make the tubes more uniform.
The American Telephone and Telegraph
JANUARY, 1926
CAN "HIGH VACUUM" BE PATENTED?
301
Company was already using vacuum tubes
as "repeaters" in its long distance lines
and the General Electric Company had
been for years greatly interested in vacuum
devices so that both groups of research
workers began intensive experimentation
on the problem. The Western Electric
engineers in their work of improving De
Forest's relay (as they were using it)
didn't consider their improvements in
evacuation as anything really novel, al-
though the improvement in the vacuum
was the one thing De Forest's audion
needed to change it from a toy to a reliable
and most important piece of engineering
apparatus. If a vote were taken to-day
in one of our national societies of scientists
as to whether the improvement in vacuum
of De Forest tubes could be considered an
invention, the result of the vote would un-
doubtedly be negative; the General Elec-
tric Company nevertheless had Langmuir
apply for a patent on a new kind of audion.
The patent claimed that the General Elec-
tric tube, evacuated better than De For-
est's had been, was sufficiently novel and
new to be patentable. •
At first the American Telephone and
Telegraph engineers maintained (as would
any reasonable scientist) that there was
no patentable idea involved — that Lang-
muir had simply done a little bit better
than De Forest had been doing for years.
Langmuir contributed to the problem no
really new ideas but simply brought the
facilities of a great laboratory to help do
the work De Forest's incompetent work-
men had been trying their best to accom-
plish.
When it was finally decided by the patent
office that these highly evacuated audions
(given "Greco-Schenectady" names, to
quote De Forest) actually constituted an
invention, the American Telephone and
Telegraph engineers started proceedings to
show they had achieved the improvement
of the vacuum first. Testimony was taken
from the best scientists in England as well
as America, the court was treated to ela-
borate laboratory demonstrations on the
methods and results of getting high
vacuum. Altogether the report of the
proceedings covered some thousands of
pages.
The upshot of the proceedings is now
before us. The Government says that to
improve the evacuation of De Forest's
audion does constitute a patentable idea
and that the General Electric Company is
entitled to the patent. This means, evi-
dently, that every highly evacuated tube is
subject to Langmuir's patent. But nowa-
days we use nothing but highly evacuated
tubes so that we must conclude that every
tube we have to-day is subject to this new
Langmuir patent. This constitutes a
most dangerous situation, one which the
Radio Corporation of America can ap-
parently freely use to their advantage if
they desire. If we read the patent aright,
it appears that now, and for the next
seventeen years, all of our tubes are legally
produced only by RCA so that the price is
again at the mercy of this radio trust.
Possibly the RCA will not now push
their advantage as they might have done
had the patent been granted three years
ago. The present Federal Trade Com-
mission inquiry will probably effectually
prevent the Radio Corporation from at-
tempting crude monopoly. Seventeen
years is a long time, and if the Radio Cor-
poration lasts that long (a matter open to
some doubt) it may still exert a strangle-
THE SHORT WAVE EXPERIMENTAL STATION
Of the Burgess Laboratories at Madison, Wisconsin, operating under the calls 9 EK and 9 XH. This elaborate station contains three distinct trans-
mitters, one, in the immediate foreground operating on 3748 kc. (80 meters), another, directly above it tuned to 7496 kc. (40 meters), and a third,
next to the 7496 kc. transmitter adjusted to 14,990 kc. (20 meters). A 7o-foot telephone pole, three feet from the window shown at the right in this
view, supports a rigid vertical antenna. The receiver at the left has a range of from 19,990-2998 kc. (15-100 meters). The next one to it works on
4997 kc. (60 meters). This is an example of a very well planned station, although it is considerably more elaborate than many successful amateur
stations whose short wave signals bridge distances on the map as easily as a navigator does with a pair of dividers. One of the low powered trans-
mitters here is operated entirely from heavy duty B batteries
302
RADIO BROADCAST
JANUARY, 1926
hold on America's radio before the expira-
tion of the life of this patent.
We believe that the Court was unfortun-
ately advised in deciding that any man is
entitled to a patent on the improvement
in vacuum of a well known device. Un-
fortunately our opinion does not affect the
legality of the situation. If Jones con-
ceives a new and novel device and builds it
to the best of his ability it appears that
Smith may take one of Jones' devices and
improve it by the help of better tools and
thereby get a patent on it. Smith's patent
represents no real inventive genius on his
part but simply the application of better
tools, which Jones would probably have
used if he had access to them.
It may be that some legal step yet re-
mains by which this threatened strangle
hold of the Radio Corporation on the tube
situation may be broken, but just what
means are to be employed are not quite
evident.
Pure Science Becomes Practical
TO THE scientist it is most fascinat-
ing and gratifying to see the ap-
paratus and phenomena which he
studies as his life-work, coming to be of
general service to mankind. And in the
last few years, many are the cases in which
this has come to pass.
Twenty-five years ago, most of the people
who are broadcast listeners would have
classed Richardson as a crazy visionary,
not dangerous to be sure, but certainly
unbalanced, when he dared to speak of
evaporating electricity from a hot metal. To-
day the Radio Corporation makes millions
of dollars each year in the utilization of
this idea.
Ten years ago,
some American and
European investiga-
tors had to delve
through ancient and
unused textbooks to
find out what was
known regarding
piezoelectricity. The
older textbooks said
that if certain crys-
talline substances
were properly
squeezed, their sur-
faces developed elec-
tric charges; the
amount of electricity
which thus became
available was so in-
finitesimal that engi-
neers would have
laughed at the idea
of applying these
crystals to useful
service. Yet to-day
these very piezo-elec-
tric crystals are being
used in the broadcast
stations to maintain
the frequency con-
stant. Furthermore
this same piezo crys-
tal has been found to
be the most efficient
sound producer we have for sounds above
the audible range. As a submarine detector
these piezo-electric sound generators gave
more promise than any other device, and
intensive development was carried on dur-
ing the war to push the piezo-electric de-
tection scheme to completion.
Now another discovery from the realm
V. K. ZWORYKIN AND HIS THERMIONIC PHOTO-ELECTRIC TUBE
Which was recently developed at the research laboratories of the Westinghouse Company at Pitts-
burgh. The large illustration shows a special set-up to demonstrate the capabilities of the tube. A
75-watt bulb is at the extreme right; next to it is the photo-electric cell, which is really an improved
vacuum tube, showering millions of electrons when light falls on an electrically sensitive substance,
inside the tube. This light-sensitive substance in turn operates a relay. In the demonstration,
the smoke of a cigarette, coming across the plane of the light caused a bell to ring, and the slightest
shadow caused the cell to howl. The cell may be used to measure the light of the stars, through com-
bination with a device developed by Dr. R. A. Millikan
Radio Times, London
Householder (to departing burglar) : " Er, would it be too much
to ask you to take the loud speaker from the flat below?"
of pure science promises to push itself into
the purview of the layman. It has been
known for years that if light, especially
that toward the blue end of the spectrum,
is allowed to fall on the fresh surface of such
a metal as sodium, the surface being in
vacuum, electrons will pull loose from the
metal surface in some way by the action
of the light waves. Small indeed was the
amount of electricity thus set free, but to
the scientist it was all important — as it
allowed him to check his theories dealing
with the constitution of matter. But now
this photo-electric effect, as it is called, is
to be used to check the stationary fireman
to see how much smoke he sends up his
chimneys.
The possibilities of the photo-electric
cell have been realized for many years.
Many experimenters in university labora-
tories have spent long hours of research
and investigation to discover and formulate
the laws governing its action. It has been
used in talking movies to change light
impulses into electric currents which could
then be amplified by the vacuum tube
amplifier It remained for one of the
Westinghouse engineers, V. K. Zworykin,
however, to combine the photo-electric
cell and the triode to make a more com-
pact, and possibly more reliable, piece of
apparatus. The electrons freed from the
photo-electric cell in the tube are made to
affect the potential of the grid of the tube
and thus the plate current; this in turn
opens or closes relays or performs other
similar services.
As the light falling on the photo-electric
surface varies, so does the plate current of
JANUARY, 1926 THE GRADUAL IMPROVEMENT IN RADIO EQUIPMENT
303
the triode; by arranging an incandescent
lamp to throw its light on the sensitive sur-
face of sodium, the smoke recording device
became possible. The smoke, passing
between the incandescent light and the
sensitive surface of the photo-electric cell,
perhaps one hundred feet away, cuts off
part of the Tight, thus operating proper
relays to record the event. At one of his
demonstrations, Mr. Zworykin showed
that if the smoke from a cigarette passed
between the lamp and his sensitive cell
the latter was sufficiently activated to
•cause the opening or closing of a switch.
Short Waves Are Growing Shorter
THE daily press recently gave con-
siderable space to an announcement
of John Hays Hammond, Jr., that
he had perfected a scheme for sending as
many as eight radio messages on the same
wave. The frequency of his carrier wave,
30,000 kilocycles, shows how short these
short waves are becoming.
It is not evident that the Hammond
transmitter has anything of real merit in
it or that any new ideas are involved.
Patents have apparently been granted on
the method, but that indicates very little
nowadays. To the best of our knowledge,
Mr. Hammond has not yet explained the
merits and new features of his scheme to
any of the engineering societies, and we
•cannot help but feel that announcements
of engineering accomplishments which are
first divulged through the daily press in-
stead of through the transactions of an
engineering society, the members of which
are able to judge its real merits and rate it
JOHN HAYES HAMMOND, JR.
With a bit of apparatus from his laboratory. Mr. Hammond,
whose inventive talents are active in many fields beside radio,
is probably best known for his secret system for radio control
which several years ago was sold to the United States Govern-
ment. The inventor recently sold certain rights on a directive
and secret "broadcasting" system to the Italian Government.
Many of Mr. Hammond's radio experiments have been carried
on at Cruft Radio Laboratory at Harvard
at its proper worth are decidedly
open to question.
A wireless dispatch to the New
York Times from Berlin states that
Professor Esau of Jena University
has invented a wireless sender us-
ing a frequency so high that the
wavelength is only two meters.
It is reported that Professor Esau
finds these very high frequency
waves are not affected by the
conditions which give absorption
and fading on the longer waves
and that he expects to telephone
to America with his set "before
Christmas."
Another report tells of experi-
ments at the University of Iowa,
in which wave-lengths of only 74
centimeters were used. Just what
was done with these short waves,
we do not know.
Before anyone else "invents"
more of these short waves, we
hurry to say that waves much
shorter than any of these re-
cently reported have been experimented
with and measured years ago. Radio
seems to be a field in which things are
continually re-invented. At Columbia
University, Professors Nicols and Webb
years ago performed a number of striking
experiments with short waves — really short
ones. It is our recollection that they went
as low as two centimeters, that is, about
one inch. These waves were measured for
length, were focused by mirrors and lenses,
and reflected back and forth across the
laboratory. Later Professor Nicols worked
with waves much shorter, so short that his
waves practically joined the
spectrum of heat waves, which
also are electro-magnetic.
If anyone else thinks of
"inventing" some other short
waves he had better look up
scientific papers recording the
work of earlier experimenters
and then go back to the fa-
ther of them all, Hertz. In
his book on electric waves,
Hertz describes practically all
the phenomena which the re-
cent inventors have been giv-
ing us. Some of these recent
announcements of short wave
"inventions" read almost like
sections of Hertz's book; pub-
lished thirty-five years ago.
How Radio Has Im-
proved
THREE general moves in
the direction of improve-
ment in the broadcast
field we have consistently ad-
vocated and it is a pleasure to
see them all coming to pass.
The single-circuit regenerative
receiver has come in for the
universal condemnation it
deserves and for which
I. H. KORDI, EGYPTIAN RADIO ENGINEER
Sent to the United States by King Fuad to study Ameri-
can radio methods. M. Kordi is shown inspecting a ijkw.
arc telegraph transmitter at station WCG, New York
these columns called years ago. Im-
proved quality of reproduction was the
next general suggestion RADIO BROADCAST
called for — hornless speakers, improved
transformers, and power tubes for loud
speaker operation. All of these are featured
to-day in the best radio sets. Next we re-
peatedly called attention to the absurdity of
continuing with batteries as the only source
of power supply for radio sets. The crudest
devices of the home use power from the
light socket, yet radio outfits, the most
scientific piece of apparatus the average
home will ever have, continued with the
crudest form of power supply. Only this
year have the A and B batteries both been
eliminated fiom any standard set and even
now the price of such a set is absurdly
high. The man with two hundred dollars
to spend for radio, still has to depend upon
batteries for his power, and how many
times he runs into trouble as a result of this
power supply! Dry batteries give out
altogether, or become noisy; storage bat-
teries call for a charging outfit and are
troublesome to some listeners: all this
time the light socket has unlimited power
supply at negligible cost.
Commander Elmer Langworthy, U. S.
N., who designed and built sets for the
White House says, "About ninety-five
per cent, of the trouble fans have with
reception is due to their power supply."
When called upon to diagnose reception
troubles (for the President, we suppose)
the Commander "usually finds dead or low
low B batteries, defunct C batteries, and
broken or loose battery leads." These
troubles with the vexatious performances
of the radio outfit, or no performance at
all, will disappear when radio tinkering
changes to radio engineering. An engineer
depends upon batteries for power only
when absolutely necessary, but in radio
reception this is not so. The greatest
need of the radio listener to-day, who is
eager enough to get good quality without
304
RADIO BROADCAST
JANUARY, 1926
WILLIAM DUBILIER
New York; Quoted in the British
press on his recent European tour
" Radio broadcasting is only four years old
in America, yet the radio industry there is the
sixth largest in America, and equals the auto-
mobile industry. The sales in America
alone this year will be at least £100,000,000.
As regards broadcasting, it may interest those
who are continually criticising broadcasting
methods in Great Britain to know that in this
connection you are in a much better position
here than we are in America. The conditions
in New York are intolerably worse than those
of London. In my opinion, the British
system is easily the better of the two. I am
certain that good broadcasting is the key not
only to international amity, but to world
peace."
further urging, is a reliable and reason-
ably cheap apparatus for supplying the
power to his set from the light socket.
The Month In Radio
EVER since the development of broadcast-
ing on an important scale, the Commerce
Department has been deluged with
complaints from owners of radio sets relative
to the great interference encounted from ship
signals. Fans will be delighted to hear therefore
that the Department of Commerce has agreed
with British and Canadian authorities to pro-
hibit the vessels of the three countries from using
frequencies in the broadcast band when within
250 miles of the United States, Canada, or the
British Isles.
(~\ N E of the most famous American stations has
*— ' outlived its usefulness and has been retired.
After the outbreak of the war in Europe, all of
Germany's communications to this country had
to be carried out through their Sayville station
on Long Island. Many an amateur listened-in
on the dot and dash signals which went out over
this channel — and so did Uncle Sam. Although
United States officers were stationed there as
censors, it was said that "contraband" messages
were continually coming and going over Say-
ville's channel. We now know through an arti-
cle in World's Work (Nov. 1925) that the famous
Zimmerman telegram inviting Mexico to take
whatever of our Southwest territory she desired,
with the additional suggestion that Japan join
her, traveled by way of Sayville in one of its
routes to Mexico City. When we entered the
war, the station was, of course, taken over and
the Navy has operated it ever since. Now it
has been decided that Sayville's traffic can well
be routed over other Navy channels. The
famous Sayville station will now be held for
reserve duty only.
THE Columbus (Ohio) Dispatch, has just
issued a most interesting compilation of
statistics for the radio dealers of that State.
All information of any value about prospective
radio buyers is contained in the folder. How
many buyers there are, percentage of male and
female owners, number in family, character
and earning capacity of the people in the differ-
ent towns of Ohio, how many own automobiles,
etc. We find the number of radio sets bought
last year, number of radio dealers, number of
clerks and employees, whether parts or sets
satisfied the average buyer, whether the dealers
serviced their sets and how it is done, how much
advertising the radio trade does and where it
is placed. This is the best piece of statistical
work of value to radio manufacturers that we
have seen.
THE Radio Corporation is in for a thorough
airing. The Corporation will have to con-
vince the Federal Trade Commission of their
fair and just treatment of competitors and the
radio public in general. There are one or two
unsavory reports of the Corporation's activities
still in our minds and it is to be hoped that no
more will be brought to the light.
The companies being investigated by the
Federal Trade Commission in addition to the
Radio Corporation are The General Electric
Company, American Telephone and Telegraph
Company, Western Electric Company, Westing-
house Electric and Manufacturing Company,
International Telegraph Company, the United
Fruit Company, and the Wireless Specialty
Company. The Federal Commission expects
to bring out that a monopolistic trust exists
in the radio field. It is possible they will prove
such to be the fact. That isn't the thing that
really counts, however; the question is, Has the
trust (if such exists) been reasonable in the
prices it has charged for its wares ?
Interesting Things
Said Interestingly
LJASKELL COFFIN (New York; artist):
' "Men have good color and they don't put
anything on their faces. For youth to rouge and
paint is just like gilding refined gold and losing
the perfection and modesty of a sweet girl. A
couple of glasses of cold water, a good walk in
the park, or exercise in the morning by radio are
a great deal more efficient in assisting beauty."
TORD GAINFORD (London; chairman of the
*•* British Broadcasting Company): "On a
conservative basis it is estimated that ten
millions of the inhabitants of these islands listen
to our programs either regularly or occasionally.
The peculiarly intimate character of this
medium — the fact that the programs are re-
ceived at the fireside — adds greatly to the burden
of our responsibility. In a little more than two
years, broadcasting has not only been estab-
lished as a necessary part of the machinery of
DR. IRVING LANGMUIR
—— "Schenectady: Research Engineer,—"—
General Electric Company
"No branch of electrical engineering has had
more interest for the physicist than radio.
Hertzian waves, the vital element of radio,
were discovered in a physical laboratory.
Electrons, the discovery of another great \
physicist, J . J . Thompson, found their first
engineering application in the form of a pure
electron discharge in the hands of the radio
engineer. Studies in the physical laboratory
of phenomena in high vacuum, such as \
"clean-up" effects of electron emission, of
diffusion of one metal through another, of
contact potential, and of other interesting
physical phenomena, have all contributed to
the development of the vacuum tube, which
has been called the 'heart of the radio system.'
"Now, when a high stage of development
has been reached in transmitting and receiving
apparatus, the problems of the transmitting
medium become more fascinating than ever.
We are just beginning to understand the na-
ture of the much-discussed Heaviside layer,
and something of the polarisation, reflection,
absorption, and interference of radio waves."
I
civilization, but it has come to exert a definite
influence on the minds of the people. It is
something that so far we have built this in-
fluence on definite ideals and standards of public
service. But it is of greater importance that in
future the medium of broadcasting should
exercise no increasingly beneficent influence,
and that nothing be done to endanger this
influence."
p\R IAGO GALDSTON (New York; New
*-^ York State Medical Society): "Five of the
largest broadcasting stations in and near New
York City are now cooperating with the Medical
Society of the County of New York in its en-
deavor to present authentic health information
to the public, to the extent of accepting volun-
tary supervision of all health talks going out
over their wires. . . . There are still,
however, certain agencies, both radio and
journalistic which, to our great regret, have not
closed their avenues of publicity to the insidious
propaganda disseminated by persons whose
ignorance of medical science is unbounded.
They employ gross falsehoods daily in their
attempts to discredit scientific medicine, and
they advocate healing theories whose fallacies
are largely veiled by the plausible manner in
which they are presented. The medical profes-
sion has been unable to stem the flow of this
propaganda."
What* s New in Radio
Many Interesting Refinements were Exhibited at the Fall Radio Shows, Which Started
the Radio Season Off, But No Startling Developments Were Shown — Improved Quality
Striven for by Nearly All — The Artistic Appearance of the Receiver Is Improving
By AUSTIN C. LESCARBOURA
A SIX-TUBE SUPER-HETERODYNE
The second harmonic principle is embodied and
a loop is used. While this type of receiver is not
absolutely new. it has been redesigned and its
appearance considerably enhanced. It is manu-
factured by the Radio Corporation of America
A FINE T. R. F. RECEIVER
Made by the Pathfe Company. Such an instru-
ment would not disgrace the appearance of any
living room. The built-in loud speaker should
gratify the most descriminating of tastes
TWO radio shows recently held in New
York and those in other cities have
served the usual ends. There has been
the institutional round of handshaking,
banquetting, chinning, praising, knocking, argu-
ing, and agreeing — the social business of any
gathering, radio or otherwise; and there has
been the business of laying the radio cards on
the table, in the form of new offerings to the
radio public — the real, honest-to-goodness ex-
cuse for a radio show or exposition, and the
very thing which attracts the crowds. These
shows have well served as the national window
display of the radio industry.
NO STARTLING CHANGES BUT NO END OF REFINE-
MENTS
pHERE isn't a single genuinely startling
* change among this season's offerings — at
least, if there is, it hasn't been exhibited at the
radio shows thus far. Of refinements, how-
ever, there are many, indicating that radio
engineers and manufacturers are keen to keep
apace with the radio march of progress, devoting
their attention to details when there are no pros-
pects of immediate changes in fundamentals of
radio reception.
Indeed, the whole atmosphere of this season's
offerings is a happy one. Thus the fellow who
bought a receiver a year or so ago, can feel
happy in the assurance that he hasn't been
"stung," because the same fundamentals that
were included in his receiver are still being em-
ployed in the latest offerings. For the fellow
who has waited until now, there is likewise much
satisfaction; because, while the fundamentals
may remain unchanged, there have been numer-
ous refinements which go to produce greater se-
lectivity, simpler operation, better tonal quali-
ties and, in a few instances, more volume. For
the manufacturer, too, there is much happiness
in the stability of radio engineering. The more
critical radio enthusiasts are bound to want the
very latest refinements and will therefore pur-
chase the new receivers, happy that these re-
finements have been made. So everyone is happy
with the present state of affairs.
THE PRIME CONSIDERATION IS TONAL QUALITY
*pHE keynote of this season's offerings is tonal
* quality. A year ago, the general trend
among radio receivers was toward sensitivity,
selectivity, and volume; but to-day the prime
consideration is tonal quality, which, like charity,
begins at home with the radio receiver itself.
In other words, the radio enthusiast now realizes
that tonal quality is not a matter of trying one
loud speaker after another, always in the fond
hope that some day, somewhere, a suitable one
will be discovered, which will produce the long
desired realism. Distortion and poor tonal
qualities originate in the radio receiver, and more
particularly in the audio-frequency transformers
and in the amplifying tubes. Poorly designed
audio-frequency transformers fail to amplify with
equal volume the wide range of audio frequencies.
THE CAMPBELLS ARE LISTENING: TRA
LA, TRA LA!
An interesting photograph showing two instances
of being all dressed up. The general trend at
the recent radio exhibition was not toward any-
thing revolutionary in design but rather toward
improvement of existing models, both in general
design and outward appearances. The receiver
depicted is a Premier
Also, transformers constructed with poor quality
of iron for their cores, are unable to keep up with
the rapid magnetic changes caused by the audio
frequency currents, with the result that the tonal
qualities are blurred.
Until recently, the audio frequency end of
A NEW PARAGON RECEIVER
Of particularly handsome appearance. Its oper-
ation is quite simple, two main controls accom-
plishing the tuning. There is plenty of room in
the cabinet for the inclusion of batteries
306
radio reception has been sadly neglected in the
merry chase after new circuits. The audio-
frequency transformers employed have often
been the same as those originally intended for
radio telegraph work, in which it is desirable to
have a definite amplifying peak at 500 to 1000
cycles, so as to produce the utmost strength of
signal at the usual audio frequencies employed
in signaling. However, with radio telephony it is
quite different. A flat amplifying curve, provid-
ing uniform amplification of signals from at least
100 to 8000 cycles, is absolutely essential if real
tonal quality is to be had from the loud speaker.
So it is to be expected that this season's
offerings stress the audio-frequency end. All
sorts of queer terms are heard in this connection,
such as acoustical synchronization, omni-tonal,
ortho-sonic, polytonal and so on, which, reduced
to plain English, mean improved audio-frequency
amplification so as to produce loud speaker re-
sults comparable with those obtained from the
simple crystal detector receiver and head set — •
the cheapest yet highest acoustic development in
radio telephone reception ! A glance at the work-
ing parts of the new offerings discloses larger
audio-frequency transformers. In some in-
stances, the transformers have been replaced by
resistance-coupled stages of amplification; in
other instances, the transformers are employed
in conjunction with special by-pass condensers
and special resistances designed to aid the tonal
qualities.
THE HORN VS. THE HORNLESS LOUD SPEAKER
"TpHE radio shows have indicated a decided
* swing in favor of the hornless loud speakers,
although, truth to tell, the horn type still is in
the majority in numbers by a very comfortable
margin. The hornless type is represented by a
number of exposed parchment cones, all more or
less alike in design and mechanism; by an ex-
posed cone of wood veneer — a very beautiful
thing to gaze upon and presumably of excellent
tonal qualities; and by enclosed or concealed
parchment cones, which are provided with
wooden cabinets or metal barrels.
With the present state of the radio acoustic art
as applied to loud speaker horns, it is safe to say
that the cone type of loud speaker has advan-
tages which are not to be denied. However, the
RADIO BROADCAST
last word has not been said in connection with the
horn type of loud speaker, although the radio
shows failed to promise anything startlingly
new in that line. There are some interesting
horns of moulded construction — veritable pret-
zels, designed to produce deep, mellow notes, yet
fitting in a surprisingly small space.
Just what the latest loud speakers can or can-
not do was not demonstrated at the radio shows.
One cannot think about the early radio shows
without recalling the bedlam of shrieks and
groans and distorted music from hundreds of
loud speakers all going at once. Fortunately,
most radio shows to-day do not attempt to emu-
late the Tower of Babel, although it has always
seemed to us that a radio show ought to demon-
strate what a radio receiver can do. Individual
sound-proof booths provided for the various ex-
hibitors with something to demonstrate in the
way of loud speaker performance, would solve
this perplexing problem. However, at the
Grand Central Palace exposition, excellent radio
music was provided by Hewlett induction loud
speakers, two of which were employed for the
entire vast hall.
AND NOTHING NEW IN THE WAY OF HOOK-UPS
/"* ETTING down to the real fundamentals of
'-* radio — the hook-ups — there is nothing new
to report, so far as the present season's offerings
are concerned. There is an overwhelming ma-
jority of receiving sets employing the five-tube
radio-frequency layout, with two tubes for radio
frequency, one for detector, and two for audio
frequency amplification, and with the usual three
tuning controls so much like the neutrodyne re-
ceiver that there is often some confusion in the
lay mind. I n some instances the number of con-
trols have been reduced from three to two, and
even to one, either with a single fixed means of
tuning the circuits in combination, or with a fixed
means and an optional means, so that each circuit
may be tuned in combination or individually for
maximum efficiency. In the simpler tuned radio
frequency receivers, various means are employed
to prevent regeneration.
Even though radio frequency receivers com-
prise the greater number of offerings, particu-
larly in the low-priced group, this must not be
taken to mean that this circuit is preferable to
JANUARY, 1926
NO A B OR C BATTERY
Is required for this receiver. It is connected directly to the house electric light socket — its
only source of power. There is nothing unusual about the circuit itself, it being of standard radio
frequency pattern. It is made by the Batteryless Radio Corporation, New York
SIMPLICITY OF CONTROL
Is the keynote of this Ferguson receiver. The
two controls are for volume and sensitivity,
while a numbered revolving dial behind the face
of the panel enables one to write down the set-
tings for the various stations
others. It should be remembered that the
patent situation has no little influence on the
choice of circuits by manufacturers, and that the
regenerative, reflex, and super-heterodyne circuits
are more or less dangerous ground to tread upon.
As a matter of fact, a well designed three-tube
regenerative receiver will usually do as well, if
not better, than a five-tube radio frequency re-
ceiver, although its operation is more critical
and is not so well suited to lay operation.
There is little change in the reflex circuit, as the
original arrangement has been found quite satis-
factory. The number of tubes for commercial
reflex receivers is five or six, with two or three
control dials. The reflex receivers are arranged
for either antenna or loop operation. Some still
employ the crystal detector, while others have
gone to the tube detector which is simpler and
more stable in its operation.
XVhile the neutrodyne circuit remains basically
the same, with the familiar three tuning dials,
numerous refinements have taken place in pro-
ducing the present season's neutrodyne receivers.
The standard layout of five tubes has, in several
instances, been increased to six, with the addi-
tional tube employed either in the radio fre-
quency end or the audio frequency end. One
neutrodyne receiver now employs three stages
of tuned radio frequency, a detector, and two
stages of audio frequency, with but two tuning
controls. The antenna coupler tuning condenser
operates on one tuning control, while the three
remaining interstage condensers are ingeniously
coupled together and operated by a single tuning
control. The four radio frequency sections are
individually shielded, to prevent the interplay of
energy and to permit of increased voltage ampli-
fication. One neutrodyne manufacturer offers
a six-tube set, with the extra tube used in the last
stage of audio-frequency amplification, so as to
have two tubes in parallel to handle the increased
energy without distortion, even when employing
standard vacuum tubes.
The regenerative circuit has all but disap-
peared in present offerings, being retained only in
connection with the lowest-priced offerings.
The super-heterodyne is represented by just a
few offerings. This circuit, in its highly devel-
oped commercial form, is now offered in two
popular models, a six-tube receiver and an eight-
tube receiver, both employing a decorative loop.
Also, there is an elaborate decorative set con-
taining an eight-tube super-heterodyne receiver
and enclosed loop, together with concealed cone-
type loud speaker and battery eliminator. This
radio receiver, as it stands, is beyond doubt the
greatest achievement so far scored in radio re-
ception. Operating from the standard alternat-
ing current socket, without batteries of any
kind, this radio receiver produces remarkable
tonal quality in any volume from a mere whisper
to a beautifully modulated output that will fill
the largest hall. Antenna-operated receivers
still lead by a big margin, despite the large
number of loop type receivers.
JANUARY, 1926
WHAT'S NEW IN RADIO
307
the special vacuum
tubes now avail-
able for resistance-
coupled amplifi-
cation. More and
more it is coming
to be recognized
that the vacuum
tube is part and
parcel of a radio
circuit, and must
therefore be de-
signed for the
specific purpose in-
tended. There is
no such thing as a
universal tube.
The A. C. tube
has not as yet re-
ceived wide recog-
nition, although a
few sets have been
designed specific-
ally for it.
THE IMPORTANCE
OF LITTLE THINGS
IN LITTLE
' things as well
as big things, the keynote of the present radio
season is improved reception. With no startling
developments to monopolize attention, the radio
engineers and the radio manufacturers have
found time to concentrate on the numerous
details of radio.
Even a hasty survey of radio parts and acces-
sories discloses no end of refinement and
improvement. Condensers have undergone
marked changes, particularly toward the
straight-line frequency type of plate, which pre-
vents the crowding of radio stations at the lower
end of the tuning dial. Sockets have been
improved not only in mechanical details but also
toward better insulation, with the former metal
shell replaced by dielectric material. There is
a definite trend toward broken-away bases,
with the object of forming an air gap between
plate and grid to reduce possible leakage.
A CABINET-MAKER S BOOTH
Unless the trend in present day design was toward a more beautiful receiver
outwardly, it is obvious that the above exhibitor would not waste time and
money at the show. Now the public wants a good cabinet for the receiver
BATTERIES OR NO BATTERIES — THAT IS THE
QUESTION
A VERY definite phase of this season's
•*•• offerings, as reflected in the New York
radio shows, is battery elimination. There are
many offerings which have for their object the
simplifying of storage battery operation, on the
one hand, and the total elimination of batteries
on the other. Some offerings are in the form of
complete receivers with self-contained battery
eliminators, but most of them are presented as
accessories, intended for use with any receiver.
Again, some offerings eliminate both A and B
batteries, and even the C battery; but for the
most part, merely the B battery is eliminated,
because, after all, that is more readily achieved
with satisfactory results than the elimination of
the filament battery.
Due to ingenious methods of recharging the
storage battery, this old-time radio device has
received a brand new lease of life. This season's
offerings include various combinations of storage
battery and recharger, which do away with the
usual storage battery. An interesting develop-
ment is the trickle recharger, through the use
of which a storage battery is constantly on charge
at a very slow rate so that the current consump-
tion is virtually negligible. Certain it is that
these automatic storage battery outfits, if such
they can be called, restore the storage battery in
the good graces of the radio fan because of their
steady output of current and their relatively low
upkeep.
MORE AND BETTER TUBES THAN EVER
IT IS with keen satisfaction that we note the
' tube developments for the coming season.
Instead of being limited to just a few types of
tubes for the various purposes encountered in
modern radio reception, the radio enthusiast now
has a wide range of vacuum tubes to choose from.
To the former standard tubes, now appearing
with the new standardized base, there have been
added power tubes for taking care of the last
stage of amplification in storage-battery as well
as dry-battery receivers. The growing use of
battery eliminators and power amplifiers has
also called for special tubes, such as rectifiers,
ballast tubes, special power amplifier tubes and
so on. To what extent the radio industry aims
to give the very best it possesses, is exemplified in
And so it goes with all other parts, such as
rheostats, potentiometers, plugs, jacks, fixed
condensers, grid leaks, and binding posts, No
radical changes, please understand, but plenty of
evidence to prove that engineers and manu-
facturers have been hard at work.
LESS ACCESSORIES AND MORE SELF-CONTAINED
RECEIVERS
H E order of the day, if we read the signs
correctly, is a steady move toward self-
contained receivers. More and more the radio
manufacturers are coming round to the practice
of a single cabinet v, ith batteries, loud speaker,
and, in some cases, wave interceptor, complete.
Thus what were once accessories now become
integral parts of the self-contained receiver, not
only making for greater efficiency, since all com-
ponents must obviously be better balanced in
such an arrangement, but also making for re-
markably attractive radio cabinets.
Then, too, there is a definite tendency toward
beautiful appearance, with all signs of radio
mechanism artfully submerged in the more ad-
vanced offerings. Thus the insulating panel
with its dials, rheostat knobs and jacks, has been
giving way to decorative wood fronts, with the
radio controls artfully blended with the general
decorative scheme so as to be inconspicuous.
The standard tuning dial and knob have dis-
appeared in many receivers, and in their place
we have ingenious controls in the form of drums
or rims which protrude through decorative slots;
or, again, we have small knobs which control
dials placed behind the panel, with just the
immediate readings appearing through small
windows. Some receivers have the tuning
controls entirely concealed from view, until they
are exposed by a drop front or other means.
Fortunately, however, this move toward
camouflaged radio is devoid of freak effects.
There are no radio receivers made to look like
pianos or ice boxes or reading lamps. The move
is a safe and sane one, which must go far to con-
vince Milady that she should have the finest
radio obtainable for that corner of the living
room. It certainly makes things lots easier for us
men who must sell the radio idea to Friend Wife!
BLACK BEAUTY
Is a title befitting the new Bosch Amborola receiver. The cone type loud speaker shown in this
photograph, and exhibited at recent radio expositions, is the first of its kind to be made of wood
FIG. I
The set-up of apparatus which is required to take accurate readings of audio transformer amplification over the audible frequencies. At the left is
shown the audio oscillator which grinds out the signal whose frequency is known. In the center of the picture may be observed several sizes of tuning
forks which, when struck, produce an audible signal whose frequency depends upon the mechanical make-up of the fork. At the right of the picture
is the recording apparatus for measuring the degree of amplification of the audio transformer under test
The Requirements for Better Audio
How to Tell a Good Transformer by Its Curve — Comparing
Resistance and Transformer Coupling — The Right Tubes to Use
By KENDALL CLOUGH
IN SPITE of the fact that the audio-
frequency amplifier is one of theoldest
units of radio and telephonic recep-
tion, it is still the subject of much
controversy, and conflicting ideas are just
as prevalent now as they ever were. The
purchaser of coupling units for the audio
amplifier is confronted with a variety of
products to choose from, which are ac-
companied by as many different curves
taken under as great a diversity of condi-
tions. Then, after examination of the
characteristic curves, he decides on a par-
ticular transformer, resistance unit, or
choke, and installs it in his own receiver
where it operates either to his pleasure or
dissatisfaction.
There is just one sad thing about the
whole affair and that is that he is usually
satisfied with his arrangement, chiefly be-
cause the theory of the thing is right. The
ear is rather untrustworthy to some minds
and even though things may not sound just
right, the unsophisticated listener is apt to
recall the curves that he has seen on the
device, or some particular theory that he
has heard regarding it, and conclude that
the theory must be right and that his ears
Research Engineer, Electrical Research Laboratories
arf* wrong. As a consequence, too many of
our homes are blessed with radio melodies
of a nature that would make the composers
as well as the artists blush with shame.
One of the first applications of the audio
amplifier was its use in telephone systems
for the amplification of the voice frequen-
cies. In this capacity, it was considered
necessary that the repeating devices used
between tubes should handle with equal
facility all frequencies between 200 and
2000 cycles per second. It has been recog-
nized that the transmission of music re-
quires a still greater frequency range, but
how much greater, the manufacturers'
curves do not seem to agree. It seems
that, to date, few of them have considered
the performance of their transformer or
other devices below 100 cycles per second,
and in some cases not that low. On the
upper range, we see some carrying their
curves up to 3000 cycles and some to as
high as 8000 or 10,000 cycles.
The chart shown in Fig. 2 may shed a
little light as to how great this frequency
range actually should be. Here the piano
keyboard is shown in full lines correspond-
ing to actuality, while an additional oc-
tave, which will be discussed later is
shown dotted. The heavy lines opposite
the names of the various instruments are
indicative of their frequency ranges.
The important point of this chart is the
fact that the piano notes involve frequen-
cies as low as 30 cycles. In addition, such
instruments as the bass viol and the tuba
have their entire ranges in the lower fre-
quencies thus making it imperative that
the audio amplifier be capable of magnify-
ing such frequencies if it is to be properly
designed. There are a few instruments,
such as certain kettle drums and organ
pipes, that sound at frequencies lower than
those shown on the chart, but these notes
are so exceptional that it is hardly necessary
to consider them for the average broadcast
program.
In the upper range of frequencies, the
piano continues to represent the extreme,
having a frequency of more than 4000
cycles at the highest note. It might appear
on first thought that it would be unneces-
sary to measure amplification at higher fre-
quencies, although, as mentioned previously,
some transformers will amplify efficiently
at considerably higher frequencies.
JANUARY, 1926 THE REQUIREMENTS FOR BETTER AUDIO AMPLIFICATION
309
It is a fact well known to musicians and
physicists that when an orchestral instru-
ment is sounded, there is emitted, not only
the fundamental note, but also frequencies
of double, triple, etc., the frequency of the
fundamental. These are ordinarily called
overtones by the musicians, and harmonics
by engineers. For example, suppose that
the note C, frequency 256, is struck on the
piano. Frequencies of 512, 1024, 2048,
etc., together with combinations of these
frequencies, will be present in the resultant
note. In general, the intensity of these
overtones will decrease in the order named,
but for a given instrument they will bear
a definite amplitude relative to the funda-
mental note played. It is the number
and intensity of these harmonics that en-
able the ear to distinguish between the
violin and the piano playing the same note.
These harmonics aid the highly trained ear
to tell the Stradivarius violin from others.
In other words, the harmonics and their rel-
ative intensities determine the tone quality
or color of the individual note. Experience
has shown that in order to retain with
fidelity the characteristics of the upper
notes that at least one harmonic must be
provided for in the design of the amplifier.
For that reason we will need to consider cer-
tain notes that are not actually on the piano
keyboard although they are heard. They
are shown in the chart by the dotted line
portion and by the notes of the staff above.
So the first point that we will want to
assure ourselves of in the purchase of ampli-
fying devices is that the characteristic is
desirable from 32 to 8192 cycles or more.
WHAT CURVES AND CHARTS MEAN
THERE is a considerable variation in
the appearance of response curves ac-
cording to the type of coordinate paper
that is used in plotting the results of tests,
so that it is well when reviewing curves to
note what type of paper is used. To il-
lustrate this point, curves on two different
transformers have been plotted on three
different scales, such as have been used by
various firms. The full line in each chart
is the characteristic of a very good audio
transformer while the dotted line repre-
sents a poor instrument. It will be noted
immediately that there is very little ap-
parent difference between the two as
plotted in Fig. ^a. while a decided difference
is shown in Figs. 3b and 3c. The first
curve is plotted in the usual regular co-
ordinates and the third in what is called
logarithmic scale. The second, Fig. 3b,
is a combination of the two, frequencies
being plotted on the logarithmic scale and
the response or amplification in regular
scale.
There can be no doubt but that the scale
of frequencies should be plotted in logarith-
mic scale. The "C's" of the musical scale
have been marked off on the three charts
to show the absurdity of the use of regular
coordinates for this purpose. Note in the
curve, Fig. 33, how the octaves are crowded
at the lower end of the scale and spread out
at the upper end. In logarithmic scale,
however, the various octaves of the musical
scale are each given equal importance and
are actually illustrative of physical fact.
There is yet some doubt as to the proper
scale to use in the plotting of amplification
in these characteristics. While the semi-
logarithmic scale is capable of differentiat-
ing between the good and the poor in trans-
formers, it would seem that the double
logarithmic paper gives a more accurate
picture of what may be expected in the
actual performanceof the instrument. This
opinion is based on Fechner's Law which
states that "physiological response is pro-
portional to the energy involved in the
phenomena." This means simply that a
sound pressure of 1000 dynes, for example,
will produce only three times the sensation
to the ear as would a sound pressure of 10
dynes, 1000 being the cube or third power
of 10. It would not produce 100 times as
great a sensation as might be expected.
Hence a full logarithmic scale in the plot-
ting of representative characteristics is
considered best.
Now, unfortunately, a given transformer
does not show the same characteristic
under a variety of conditions. Thus, not
only will the characteristic be altered by a
change in tubes but also by changes in grid
and plate voltages with the same tube.
Furthermore, tubes of the same type do
not have the same characteristics at the
same voltages, so it is important that curves
for purposes of comparison bear a notation
of the types of tube used, the voltages at
which it was used in the test, and the ampli-
fication factor and the plate resistance of
the tube at those voltages.
This variation of amplification charac-
teristic with change in tube constants is
a subject that holds remarkable possibili-
ties for the listener who is striving toward
perfection in reproduction.
The characteristic of a given transformer
is influenced by the amplification constant
of the tube only in the matter of degree.
That is, the amplification is high or low
in proportion to the amplification factor
of the tube provided the plate resistance
of the tube is unchanged. This explains
the fact that greater volume is obtained
from the use of the 2OI-A type tube, with its
amplification factor of 7.5 than from the 199
type with a factor of 6.0. It should not be
thought that the use of some of the new
.,i 'ill!
Flute
Piccolo
Oboe
English Horn
Clarinets
Bassoon
.French Horn
Trumpet
Cornet
Trombone
Bass Clarinet
Bass Tuba
STRINGS
Violin
Viola
Cello
Bass Viol
HUMAN VOICE
Tenor
Baritone
Soprano
Bass
Alto
FIG. 2
A most interesting graphical comparison of the frequency range of a piano and other musical instru-
ments. Even though there is overlapping of the ranges covered by these instruments, the particular
tone by which a certain type of instrument may be identified is produced by a combining of the
overtones emitted with the fundamental tone
310
RADIO BROADCAST
JANUARY, 1926
high-Mu tubes would be desirable with
transformers on this account, however,
for there is another consideration in the
case.
That consideration is the plate resistance
of the tube. It is a difficult if not im-
possible thing in vacuum tube design to
produce a tube having a high amplifica-
tion constant and a low plate resistance.
Hence we find that the high-Mu tubes have
an almost correspondingly high plate im-
pedance which produces an exaggeration
of the effect illustrated in Fig. 4. Here
are shown curves of the transformer pre-
viously referred to with a tube having an
amplification factor of 7.5 and values of
plate resistance of 5000, 10,000, and 15,000
ohms as marked. This instrument has a
remarkably high primary inductance which
causes it to produce high amplification at
to increase the bias on the first stage to
45 volts, the curve would be modified to
that marked 15,000 ohms, for we have in-
creased the plate resistance to that value
by the use of a high bias.
It would not be wise to increase the bias
beyond i| volts unless required to by the
tests described by Mr. Crom, for we would
only be impairing the quality at the low
frequencies.
On the other hand we might decide, after
listening very analytically to our speaker,
that the low frequency instruments cannot
be heard with quite the volume relative to
the other instruments that we would hear
them if actually in the studio. In this case,
unless the loud speaker has a decided dis-
crimination against the low frequencies
there will be some advantage in operating
two 20 1 -A tubes in parallel as shown in
Fig. 5. The combined plate
cv impedance of the two tubes
would be reduced to 5000
ohms and we would obtain
TUBE 201-A
Amplification Factor 7.5
Plate Resistance 10,000 Ohms
Filament Voltage 5.0
Plate Voltage 90.0
Grid Voltage -0.5
2.000 3,000 4.000 5,000 6,000
FREQUENCY-CYCLES PER SECOND
such proportions that a single aoi-A will
not handle it without some tube distort ion.
Therefore, the low plate resistance of two
tubes or of a power tube in the last stage
will allow the plate circuit to deliver more
energy to the loud speaker at the low fre-
quencies.
RESISTANCE-COUPLED AMPLIFICATION
/CONSIDERABLE material has been
^ published on the improvement o,"
reproduction at the low frequencies to-
gether with various means for attaining it.
Among these the claims of the various
manufacturers of resistance couplings are
predominant. While it is true that the
theory of the resistance-coupled amplifier
attributes to it the property of uniform
amplification at all audible frequencies it
can be shown by test that the average
resistance-coupled amplifier, as merchan-
dised, does not do very well with the low
notes. This is due principally to the low
capacity of the coupling condensers advo-
7,000 8,000
FIG. 3
Here are three curves, A, B, and C. They are all for the same two transformers. It is
evident that by using one kind of cross section paper, the curve can be made to look as
though the transformer measured was very good and amplified well over the frequencies
desired. From an inspection of the three ways in which a transformer curve may be
indicated as presented here, it is obvious that the curves in Fig. }A are not honest in
comparison to those shown in B and C. In Fig. 2 we saw that the tones and sounds we
are most interested in ranged from about 32 to 4000 cycles. Yet by presenting a curve
as in A, attention is subtly centered upon the flat portion of the curve which deals
mostly with the high notes. The amplification at the lower frequencies is negligible
compared to the higher frequencies. In B this condition is corrected somewhat by the
use of logarithmic cross section paper where the frequency is plotted on a logarithmic or
octave scale. However, the amplification indication is not of the same scale. I he scale
employed in C is favored by many as the true way to represent response curves for
audio transformers. Here the frequency increases on the logarithmic or octave scale,
as it is played on a musical instrument. Also the amplification in }C is plotted logarith-
mically which is probably the way in which the ear hears sounds
FIG. 3-A
the low frequencies, but note that the
amplification falls off at these fre-
quencies as the plate resistance
increases, due to lack of balance
between the plate resistance and the
transformer impedance at those fre-
quencies. This slump of amplifica-
tion on the low notes would be
aggravated with the high amplifica-
tion tubes and, while the over-all
amplification would be very good at
the high frequencies the low notes
would receive almost no amplifica-
tion with consequent unnatural re-
production.
Our particular interest in these curves
lies, however, in the fact that they repre-
sent particular possibilities in regard toselec
tion of tubes. The curve, Fig. 4, marked
10,000 ohms would be indicative of the per-
formance of this transformer when used
with a 2OI-A tube with 90 volts on the
plate and a negative grid bias of half a
volt. This tube and these voltages would
be very satisfactory for operation in the
first stage as the grid of the tube would
never become sufficiently positive on
moderate signals, to introduce the kind of
distortion discussed by Mr. Crom in the
October RADIO BROADCAST. If we were
C.'
AMPLIFICATION
o u, S S 8 S
^
^-
:•;
^*
^-
-— •
— -
• 1 •
,,^
^x
1
/
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/
A
TUBE 201-A
•nplification Factor 7.5
ate Resistance 10,000 Ohms
lament Voltage 5.0
tleVoltage 90.0
id Vuluwe -0.5
/
P
F
P
G
x
II! ! 1
1
0 20 3040506080100 2 34 56781,000 234 567810.000
FREQUENCY-CYCLES PER SECOND
cated in such amplifiers, whose im-
pedance at 30 to 60 cycles becomes
so high as to prevent an effective
transfer of voltage to the succeeding
tube. The only remedy for this,
condition is in the use of larger
condensers of from one half to one
microfarad, and even then there are
often certain limitations that make
it nearly impossible to obtain the
quality of reproduction possible in
a well designed transformer-coupled
amplifier.
FIG. 3-8
the curve shown for that figure
on the chart. Or, we might use
a single 2i6-A tube with some
sacrifice in amplification (am-
plification factor 5.6) but with
the same quality. The grid bias
in the second stage should not
be omitted due to the risk of the
grid becoming positive and
drawing current as described in
Mr. Crom's article. Here, how-
ever, the use of semi-power tubes
is desirable, for the output signal
from the first stage has reached
100
=3
C2
C
C
,1
C' <
,:;
•IV
E'
60
50
40
30
20
10
a
«*
•IT-*-
"
——
— •—
• •
*
*
X
*"•"
**
—
8
6
5
4
3
2
1
1
---»* —
TUBE 201-A
jlification Factor 7.5
e Resistance 10,000 Ohms
ment Voltage 5.0
e Voltage 90.0
Voltage -0.5
Pint
t
Fi!t
/
/
Grid
~'_
0 20 3040506080100 2 3 456781.000 2 3 4567810.1
FREQUENCY CYCLES PER SECOND
FIG. 3-C
JANUARY, 1926 THE REQUIREMENTS FOR BETTER AUDIO AMPLIFICATION
311
The principle of these limitations is the
inability of the resistance amplifier to over-
amplify the high frequencies. It has been
the writer's experience that the average
loud speaker discriminates against the high
frequencies in such manner as to make it
desirable that the amplifier supply a little
more energy at these frequencies than at
the low or medium frequencies.
In addition, in the more selective receiv-
ers the detector output shows a falling char-
acteristic, that is the low frequencies are
louder than the high, due to the tuned cir-
cuits of the radio amplifier cutting the side-
bands of the transmission. This effect is
illustrated roughly in Fig. 6, showing the
output characteristic of a regenerative
detector. Hence the desirability of being
able to amplify the high frequencies to a
greater degree than the low tones.
It is not the contention of the writer that
all transformers are good in this respect.
The majority of the transformers on the
market show such ineffectiveness at the
low frequencies that it is impossible to
offset their characteristics. One particu-
lar transformer on the market
is very poorly designed as
evidenced by the fact that
at 125 cycles it ceases am-
plifying entirely and from
there down is actually nulli-
fying the amplification ob-
tained from the tube. From
30 to 60 cycles, an octave in
the bass of the piano, it ac-
tually attenuates the signal
to a greater extent than the
tubes' ability to amplify, so
that any note in this octave
would actually be louder at
the detector output than at
the output of the amplifier.
Unfortunately there are sev-
eral transformers on the mar-
ket that have similar char-
acteristics, so the necessity of
knowing the characteristics of
1,000 2,000 3.000
4,000
CYCLES
5.000 6.000 7,000 8.0*
FIG. 6
Briefly, this curve shows that as regeneration is
increased the response on the higher frequencies
is reduced
a transformer over the entire frequency
range of the piano becomes very evident.
There are several transformers on the
market suitable for low frequency repro-
duction and among these is the transformer
whose characteristic is shown by the solid
line in Fig. 30 The extremely good ampli-
fication obtained at the low frequencies is
made possible by the use of a novel core con-
FIG. 5
By paralleling the elements of tubes as shown, the effective
plate impedance is reduced to one half the value of one tube.
However, this arrangement does not increase the amplification
but does increase the power output of the amplifier
c1 c« C" c" c»
30 40 50 60 80 100 2 3 456781,000
FREQUENCY-CYCLES PER SECOND
2 345 67810,000
FIG. 4
Simply because a tube is called high-mu it does not follow
that better amplification will result. It is difficult, in high-mu
tubes, to obtain a low plate impedance. As the value of mu,
shown here, increases, the plate impedance increases. From
the curves shown above it will be observed that as the plate
impedance is increased the amplification falls off correspond-
ingly. However, when high-mu tubes are used in a resistance
audio amplifier, the story is entirely different
struction known among power
engineers as the cruciform.
The advantage in this type
of construction is the fact
that the magnetic flux de-
veloped by the windings is
almost completely confined
to the iron core, with the
result that the primary in-
ductance obtainable with a
given amount of iron is
higher with consequent bet-
ter transformation at the
low frequencies. Fig. 7 shows
the manner in which the flux
leaks out into the surround-
ing space with the more usual
core construction, while with
the cruciform construction
the coil is so completely sur-
rounded by iron that the
leakage is negligible.
EDITOR'S
IN THE October, 1925, RADIO BROAD-
CAST, an article by George C. Crom
reviewed certain considerations of
audio frequency amplification which are
quite fundamental. Some of the readers
of this article may not have seen Mr.
Crom's remarks, and so, reprinted below
are several paragraphs dealing with the
requirements, as Mr. Crom sees them, for
distortionless amplifier operation. These
conditions apply to the amplifier tube it-
self:
First — The filament of the tube must be
operated at a temperature high enough to
supply all the electrons resulting from the sum
of the direct plate current and its audio fre-
quency component. The majority of good
tubes give this necessary electron emission at
low temperatures such as that resulting from
4.5 to 5.5. volts across the filament of a five- volt
tube.
Second — The plate circuit should have suffici-
ently high impedance. This high impedance
straightens out the curve which is usually re-
ferred to as the operating characteristic, and is
explained in Paragraph 60 of Thermionic
Vacuum Tubes, by Van Der Bijl. The dis-
cussion there is too involved to be detailed here.
Third — The grid must be maintained negative
with respect to the filament so that at the posi-
tive peaks of the signal-voltage wave, apprecia-
ble current does not flow to the grid. If current
does flow to the grid, it pulls down the plate
f* — Laminated Core
*~- Coil
FIG. 7
The lower illustration shows the flux leakage
prevalent in most transformers. This condition
can be remedied by the intelligent use of iron
cores situated as shown in the upper sketch
Laminated Core
Coil —
312
RADIO BROADCAST
JANUARY, 1926
FIG. 9
This is a detailed view of the audio-frequency oscillator. The dial and
switches on the front of the panel allow the adjustment of the instrument
to frequencies ranging from 30 to 100,000 cycles with three inductance
coils. The large white coil at the right is the coil for the medium range
frequency. Note the phones attached to the small pick-up coil used for
picking up the tone of the oscillator for comparison with the standard
fork. The large fork at the left has a pitch of 32 cycles and near it is a
fork of 64 cycles
current and causes a bend in the operating
characteristic curve, that is, the positive peaks
of the plate current waves are cut off. As cur-
rent flowing to the grid must pass through the
transformer secondary with its many turns, it
may saturate the transformer core, pull down its
amplification, and thus cause distortion in the
transformer. The value of the C battery neces-
sarily depends on the structure of the tube used
and upon the signal voltage. This is not
CALIBRATION RESISTANCE
FOR VACUUM TUBE
VOLTMETER.
necessarily true, for
individual tubes vary
widely.
Fourth — the plate volt-
age must be high enough
so that the plate current
can faithfully follow the
grid voltage. The plate
voltage must force the
plate current through
the resistance of the ap-
paratus in the plate cir-
cuit and still apply
enough voltage to the
tube, so that on the
maximum negative sig-
nal voltage on the grid,
some plate current will
still be flowing. 1 n other
words, the negative
peaks of the plate cur-
rent waves must not be
cut off.
These conditions
sound complicated,
but they are not when
stated simply. The
first is: use good
tubes and keep your
The second is: use good
third and fourth are:
A battery charged.
transformers. The
use the proper value of C battery for the
signal voltage at the grid of each tube,
and a plate voltage which corresponds to
this C voltage.
The most satisfactory method, and also
the easiest, for determining these last two
conditions is to put a milliammeter (d. c.,
of say, o-i 5 milliamperes range) in the plate
circuit of the amplifier tube under investi-
gation and observe the plate current while
the strongest signal that is to be received
is going through the amplifier. If the C
battery voltage is not high enough and
positive peaks of the plate current are cut
off (and current is flowing in the grid circuit),
the plate current will decrease with a strong
signal. Increasing the C battery will pre-
vent the grid from going too much positive.
If the plate voltage is too low (in the
opinion of the writer, it usually is) and the
negative peaks of the plate current are
being cut off, the current will rise on a
strong signal. Increasing the plate volt-
age will remove this difficulty."
In an early number, we expect to publish
an article about audio frequency trans-
formers which should be of deep interest to
everyone in the radio field. We shall
show many curves of the electrical charac-
teristics of audio transformers, taken in
RADIO BROADCAST'S Laboratory. This
feature alone should be very interesting
because with so many transformers on the
market, it is difficult for the untutored
buyer to know just what transformers have
the characteristics he wants. The article
will explain how the transformers are
measured. Some needed light will be
cast on the disputed effect of the use of
shunt condensers and resistances in audio
transformer circuits. The effect of the C
battery on transformer operation will be
carefully covered.
INPUT
THERMOCOUPLE
RESISTANCE TO
CONTROL INPUT
TO TEST SET
O.C MILL. VOLTMETER
(INPUT METER.)
DUMMY
RESISTANCE RP.
FILAMENT
VOLTMETER
TRANSFORMER
UNDER TEST
.VOLTMETER
TUBE
-LOAD IN PLATE CIRCUIT
METER IN OUTPUT
- OF VOLTMETER
TUBE
FIG. 8
A close-up which is self-explanatory of the recording apparatus
Additional Notes on the Model 1926
How to Employ Impedance- or Resistance- Coupling in the All- Wave
Receiver — How Quality in the Loud Speaker Can Be Bettered by Coup-
ling the Output Tube to the Speaker Through an Auto-Transformer
By ERNEST R. PFAFF
WIS year we find attention con-
centrated upon the improvement
of the reproducing quality of the
radio receiver, rather than upon
its sensitivity and selectivity as in past
years. There is very little reason why this
problem should require any very great
concentration or experiment upon the part
of the enthusiast or listener desirous of
building his own, since equipment is avail-
able upon the market for audio amplifica-
tion purposes which will permit of nearly
perfect reproduction.
In the November, 1925, RADIO BROAD-
CAST there appeared a description of a re-
ceiver developed by McMurdo Silver which
possessed ample selectivity and sensitivity,
and consequently was admirably fitted for
the incorporation of any type of audio
frequency amplification desired by the
individual builder. In this article, a
standard two-stage transformer-coupled
audio amplifier was considered, while in
the present article, methods of improving
this amplifier, the use of resistance and
choke coupling, and the application of the
new power tubes are considered.
THE ORIGINAL AUDIO AMPLIFIER
IN THE November article, the receiver
was shown with a two-stage audio ampli-
fier using Thordarson 3^:1 audio trans-
formers. These transformers are remark-
ably satisfactory, though they do not
wholly satisfy one
condition necessary
for distortionless
amplification —
which is that the
primary impedance
of the interstage
transformer should
exceed by t hree
times the output
impedance of the
tube feeding into it
at the lowest fre-
quency to be han-
dled. The primary
impedance of the
35:1 Thordarson
transformer at 50
cycles, which may
be considered as the
lowlimit of frequen-
cies to be repro-
duced is a bit less
than 10,000 ohms, while the lowest frequency
at which the condition stated above is
satisfied will be in the neighborhood of 175
cycles, since the tube impedance for a uv-
20 1 A is approximately I2,oooohms. There-
fore, it is obvious that above 175 cycles,
substantially distortionless amplification
will be obtained, while below this frequency
the gain will fall off rapidly, until some of
the lower notes below 50 cycles suffer
badly.
The reproduction from practically any
audio transformers used in an amplifier
can be very appreciably improved by care-
ful and judicious attention to small de-
tails, such as by-pass condensers, proper
operating voltages for the tubes used,
shunt resistances and shunt plate feed ar-
rangements. A most excellent discussion
of such features will be found in Mr.
Crom's articles in the October, 1925, RADIO
BROACAST.
A point not stressed by Mr. Crom is the
use of shunt resistances across audio trans-
formers secondaries, as well as small by-
pass condensers across these windings.
Grid leaks of from .05 megohms on up to
.5 megohms shunted across audio trans-
former secondaries will invariably help to
stabilize an amplifier, and at times will tend
to improve its quality of reproduction.
Small condensers ranging from .0001 to
.0005 mfd., shunted across the secondaries
of audio transformers will tend to bypass
A-
B-
C +
FIG. I
The circuit of a transformer-coupled audio amplifier showing how the output coil and con-
denser constitute a separate unit which insures correct functioning of the loud speaker
some of the higher frequencies, with the
net result that in many cases the reproduc-
ing qualities of the amplifier for low notes
seem materially improved. This, how-
ever, is only apparent improvement since
it amounts to decreasing the high fre-
quencies to the same volume as the low
notes. A combination of resistance and
capacity shunt is also frequently helpful.
Where a high plate voltage is used on an
audio amplifier, the last stage should not
include the loud speaker directly in the
plate circuit of the tube. This is because
the normal direct plate current would flow
through the speaker, to which would be
added the alternating signal component.
In many cases the handling capacity of
loud speakers is decreased to one-half or
one-quarter what it would normally be by
this arrangement. A much more satis-
factory arrangement is to feed the plate
supply directly to the plate of the tube
through a high inductance choke, such as a
Thordarson autoformer, and then shunt the
loud speaker in series with a .5- or i.o- mfd.
condenser from plate to filament. In this
way, the direct current component is fed
through the choke and kept out of the
speaker; only the alternating signal com-
ponent reaching the speaker windings.
Thus, the value of signal required to satur-
ate the speaker is that normally required,
instead of, with the usual connection, the
normal value minus the direct plate current
— often several
times the alternat-
ing component.
If it is desired to
use a shunt feed
system in several
different stages of a
receiver, the choke
and condenser can
be permanently
connected to the
speaker and set,
and one side of the
speaker plugged
into the different
stages at will. Fig.
i illustrates a mode
of connection which
can be applied to
any amplifier.
In this case, the
join between the
choke and conden-
Speaker Cord and
Condenser Permanently
Connected
314
RADIO BROADCAST
JANUARY, 1926
R.F.T.
ANT.
6 Ohms
B+90 B+45 A-B-C+ A+ C-4>i
GND. 2
0
FIG. 2
That part of the circuit to the left is the tuner section of the receiver described by Mr. Silver in November RADIO BROADCAST. To the right is shown
two types of audio amplification, the lower is resistance coupling while that above is the regular transformer audio amplification described last month.
This circuit shows how one may be substituted for the other
ser connects to the tip of a phone plug
only, the sleeve being left free. The ar-
rangement will be found quite helpful.
RESISTANCE COUPLING
WHILE resistance coupling has been
popular for quite some time, this is
the first season where indications point to
a general appreciation of the merits of this
system by the listening public. Unques-
tionably, resistance-coupled audio amplifi-
cation will give as fine quality of repro-
duction as it is possible to obtain, and
contrary to general opinion, it is not ex-
tremely wasteful, either from the power
consumption standpoint, or the quantity
of apparatus necessary to render this sys-
tem the equal of a good transformer am-
plifier so far as voltage gain per system
goes.
A three-stage resistance-coupled ampli-
fier made up of standard parts, operated on
135 volts, using proper tubes, will give
about the same amplification that may be
obtained with two transformer stages
operated on 90 volts. The actual B bat-
tery consumption figured over a period of
time is no greater than that of the trans-
former amplifier, though it is true that the
initial battery cost is higher by 50 per cent.
Mr. Silver's six-tube receiver with a re-
sistance amplifier is at its best, for the
quality of reproduction is truly splendid.
R.F.T.
AUTOFORMER
.5 mfd.
AUTOFORMER
.5 mfd.
FIG.
A complete circuit diagram of the receiver employing impedance-coupled audio amplification. The various features described
in the text, such as modulation control on the r. f. secondary and impedance amplifier coil, are brought out here prominently
JANUARY, 1926 ADDITIONAL NOTES ON THE MODEL 1926 RECEIVER
315
RADIO BROADCAST Photograph
FIG. 4
A view of a model showing the disposition of the resistance coupling units. In all three types, the audio amplifier occupies the same location
and the ease of tuning is surprising con-
sidering the extreme sensitivity and selec-
tivity of the set. However, in incorporating
this type of audio amplifier, there are a
few cautions to be observed.
The detector of the set operates with a
negative grid potential of 45 volts, which
is substantially correct in order to obtain
satisfactory rectification using a plate
potential of 45 volts. This assumes that
in series with the B battery is a transformer
primary winding of only one to two thous-
and ohms resistance — so low as to have
hardly any effect upon the actual plate
potential. However, with resistance coup-
ling, a resistance of about 100,000 ohms
will be in this plate circuit. If the de-
tector plate voltage is increased to 90,
rectification will still occur in an efficient
manner with a 4j-volt negative grid po-
tential. Since the resistance amplifier
requires 135 volts, two B battery positive
leads will come out of the set — one 90 volts
plus, for the r.f. amplifiers and detector,
and one, 135 volts plus for the three a. f.
amplifiers. Due to the low actual operat-
ing potential of the first two resistance
amplifiers because of the high resistances
in their plate circuits, no C battery will be
required for these two tubes, their grid
leaks terminating directly in the negative
filament line. The last audio stage has
only the loud speaker resistance in its
plate circuit — a matter of several thou-
sand ohms, and so should have its grid
biased for 135 volts. With a UV-2OIA this
bias would be about 9 volts, although 45
will be satisfactory as a basis for test
observation.
Coupling units are available made by
Muter, Daven, Brach, Dubilier, Polymet,
and others, which provide clip mountings for
grid leak, plate resistor and coupling con-
denser— thus but one unit is required to a
stage. With uv-2oiA tubes, the coupling
resistances should be 100,000 ohms, the first
grid leak one megohm, the second one half
and last one quarter. In no case should
the" coupling condensers be below .01 mfd.,
or distortion will be evident, and all the
advantages of the system will be lost.
Going to the opposite extreme will provide
better quality, up to the point where the
time constant — the discharge period of the
condenser and resistance combination —
becomes so low as to interfere with repro-
duction and cause blocking of the amplifier
• — .5 mfd. is a satisfactory maximum capa-
city, though for convenience and general
practicability, the writer prefers .01 mfd. at
least.
A circuit and layout drawing showing the
substitution of three resistance-coupled
stages for the transformer-coupled audio
amplifiers accompanies this article. See Fig.
2. It might be well to mention the matter
of sockets. Those are combination ux or uv
sockets — that is, either a uv-2oiA or a
ux-2OiA tube may be used in them, or for
RADIO BROADCAST Photograph
FIG. 5
Another view of the resistance-coupled receiver. The wiring of such a set is very easy as can be attested by close observation of the above
316
RADIO BROADCAST
JANUARY, 1926
that matter, any other type of ux tube.
With the uv bases, the tube pins are in-
serted in holes in the socket, with the
bayonet pin over a corresponding mark on
the socket. With other makes of ux
sockets, uv-2oiA tubes may not be used —
that is, ux or uv tubes may not be inter-
changed at will, except in a few cases.
Therefore, the builder, if he uses ux sock-
ets, should be sure that his tubes are ux
bases.
IMPEDANCE AMPLIFICATION
DURING the war, "choke" or imped-
ance amplification was quite popular,
and was used in various airplane, ground
and ship low powered telephone transmit-
ter stations where quality of reproduction
was important. The first practical chokes
available are the Thordarson autoformers.
which are inductances of 350 henrys,
tapped so that there is a voltage step-up
of i:ij. These chokes satisfy the im-
pedance requirements of a distortionless
amplifier very nicely, and will give greater
amplification per stage than a resistance-
coupled amplifier but not quite as much as
a transformer amplifier. They require but
90 volts for their operation, in this respect
being similar to transformers.
A three-stage choke amplifier added to a
receiver described by Mr. Silver in the
November issue is shown in the circuit dia-
gram, Fig. 3. While .5- mfd. coupling
condensers are shown, those of .01- mfd.
will probably be more practical, due to
the tendency of the amplifier to block
with higher capacities, for reasons pre-
viously given. One interesting feature of
this amplifier is the use of the modulator
to control its volume. Instead of the con-
ventional shunt resistance which is not
entirely satisfactory for audio volume con-
trol, the modulator consists of a 500,000-
ohm resistance across the output circuit
of the second stage. The grid of the tube
into which this circuit normally feeds is
then tapped in at any desired point on the
resistance, thus giving a smooth even
volume control from zero to the maximum
available. The modulator may be used
on an amplifier, of any type, and is to be
recommended as a volume control instead
of the conventional jack arrangement. It
also serves, in this instance, as a grid
leak.
POWER TUBES
"THE use of ux-i 12 tubes in both stages
*• of a transformer amplifier will improve
quality considerably, since, in the case of
the Thordarson 35:1 transformers, at 50
cycles, the tube impedance is about one-
third that of the transformer primary.
However, it is doubtful if any increase in
volume will result from the use of ux-H2
tubes instead of uv-2OiA's. Other than
improved quality, increased handling power
will be obtained. This means that with a
very strong signal, the ux-i 12 will function
only without distortion, whereas a UV-2OIA
would probably overload and distort.
This is true, provided the proper C battery
voltage is used.
ux-i 12 tubes should really be used with
135 volts plate potential, and about 9
volts negative grid bias. They will func-
tion moderately well at 90 volts plate poten-
tial with the conventional bias, however.
For resistance amplification, Daven and
Cleartron make high-Mu tubes which are
ideal for interstage use, and both make
a power tube which is excellent for
use in the last audio stage. The use
of these tubes cannot be too highly rec-
ommended, as they will do much to
bring resistance amplification into its own,
for the improved volume resulting from the
use of two high-Mu and one output tube is
surprising when compared with the output
of three standard tubes.
If Daven tubes are used, no rheostat
will be required for them. Thus, the rheos-
tat or ballast resistor if used would be
connected in the filament circuits of the
first three tubes, while the last three, being
Daven tubes designed for 6 volts, would
connect directly across the battery.
ux-i 99 tubes may be used throughout
the set if it is intended to operate it on dry
cells. If this is done, the ux-iao should
be used for the output stage, or entirely
in the audio amplifier if transformer coup-
ling is used.
OPERATION
IT APPEARS that in preliminary opera-
tion, builders have experienced some
difficulty in getting distance until they were
familiar with this receiver's operating pe-
culiarities. It might therefore be well to
go over the mode of operation again.
Assuming locals to be received properly,
the antenna coupling coil should gradually
be turned out until the desired degree of
selectivity on the first, or left, dial is ob-
tained. This setting will react on the vol-
ume control, and may be found by tuning-in
a high frequency (short wave) station, set-
ting the volume control so that the arrow
points straight to the right, and gradually
loosening the antenna coupling until the
set breaks into oscillation. This is a
proper operating position for the antenna
rotor, where it may be left permanently
set. If the volume control is then turned
counter-clockwise, the set will stop oscil-
lating and it may be tuned as one would a
neutrodyne — that is, all three dials will be
set about alike for a given station.
If maximum sensitivity is desired, the
volume knob should be turned clockwise
until, with all three dials set in resonance,
i. e., in a position where a station would
come in, the set breaks into oscillation.
Then, if one dial is moved, it will click out
of oscillation, but if both dials are moved
after the first a corresponding amount,
oscillation will start again.
In this fashion the three dials may be
moved up the entire scale in hunting for a
station in steps of one or two degrees at a
time. Using this method, a station will
come in as a squeal. To tune-in properly,
the first and third dials should be set right
on the squeal — that is, so moving either
one in either direction will cause the pitch
to increase. Then, with the middle dial
set dead on the squeal, the volume knob
should be retarded until the squeal stops
and the signal is audible.
No squeals will be heard if tubes or bat-
teries are not good, or if too long an an-
tenna is used. In some cases it may be
necessary to add two or three turns to
windings 5-6 of the radio frequency trans-
formers. They were described in the
November, 1925, RADIO BROADCAST.
In case too short an antenna is used, it
may have to be connected to point 4-5
of the antenna coil socket, with the ground
to the minus filament line. If one stage
of r. f. amplification is to be cut out, the
antenna connects to No. 5 of the middle
socket, with the ground to the filament,
and the antenna coil removed.
To use a loop, the antenna coil is re-
moved and the loop connected to points 3
and 6 of the coil socket.
SINGLE OR DUAL CONTROL
C INGLE control will not be found en-
^ tirely satisfactory in this receiver,
but dual control will work quite nicely.
This is because of the extreme selectivity
of the outfit, which renders each circuit so
sharp that minor variations which cannot
be overcome cause trouble. The second
and third controls may be connected so
that they will work together if only one
knob is turned by tying a piece of heavy
braided fishline around the pulleys on the
two condenser shafts. The ends of the line
should meet in a light coil spring which
can be gotten from a hardware store, and
which serves to take up any play. It also
allows either dial to be turned indepen-
dently by loosening up whenever pressure
is applied to either dial separately. With
this arrangement, only the first and second
dials need be manipulated for tuning, and
operating the set becomes a real pleasure.
The Listeners' Point of View
Conducted by - John Wallace
Bb^milllllllllllllllllllllimillllNIIIIIIIIIIIIIIINIIMIIIIIIIIIIIMMIIIIIIIIIIIIW
i The Design of Receiving Sets i
^^iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiimiiiiiiiiiiiimiiiiiiiiiiiNiiiiiiiiiiiiiiiiiiiiiiiu
THE one phase of the radio industry
which, as far as we have observed,
has received no adulation in the
public prints, and which, we are
convinced, is the one and only phase of the
whole phenomenon that is worthy of un-
stinted praise is the astounding excellence
of design of receiving sets.
Almost every new invention has spent its
infant years decked in the most ugly of
habiliments. It has been the good for-
tune of radio to be swaddled from the start
in a manner to make Velasquez' Infantas
look dowdy.
The early talking machines were un-
gainly looking eye-sores, with great over-
size cranks, and hideously decorated and
uncouthly proportioned horns.
The first automobiles were a laugh.
They strove valiantly to keep up the ap-
pearance of their horse drawn predecessors,
and succeeded only in being
a silly travesty on the same.
The history of automobile
design in America, if we may
digress, has been an interest-
ing one, and a supreme testi-
monial to theGreat American
jod, Standardization. After
its shamming days were over
and the automobile had de-
cided to "be itself," there
was a constant and rapid im-
provement in its appearance.
This improvement continued
until a very few years ago,
when disaster suddenly over-
took it.
In their endless struggle to
go their competitors one bet-
ter, the manufacturers called
in Professional Designers to
supervise their coach work.
Now, designers worthy of the
name simply do not exist in
America. The fact that the
United States was the only
great nation of the world
that found herself unable to
participate in the Industrial
Arts exhibit lately held in Paris, would
seem to support this contention.
What the Professional Designer did to
the automobile body can be only too
quickly perceived by a casual glance to-
ward the nearest boulevard. Past us they
ooze — a flock of elegant black seals — as
diversified in appearance as the well known
peas in the pod — sleek and elegant, but
with no vestige of individuality.
The error into which they have fallen is
one of over-refinement. All accessories are
concealed in one svelt ensemble. Refine-
ment is desirable but, gosh, not so much of
it! Structural lines may be emphasized or
subordinated, but they cannot be annihi-
lated if the result is to be design in good
taste. The Packard's design seems to have
been the goal of the imitators. Cadillac
held out nobly, but it, in its last edition,
succumbed and now is as characterless as
DR. S. PARKES CADMAN
Pastor of the Central Congregational Church, Brooklyn, New York. Doctor
Cadman's afternoon talks before the Bedford Branch Y. M. C. A. Brooklyn,
every Sunday at 3:45 p. M., are broadcast by WEAF, WEEI, WTAG, WCAE,
and WSAI. In addition to his very large following, gained by the sheer
force of his preaching in his own church, his broadcasting activities in the
past few years have made him one of the most popular preachers ever
to appear before the microphone
the rest of them. The old game of "What
make of car is that?" has ceased to be a
game and reduces itself into a guessing
contest. Certainly the automobile was
more fortunate when its body was designed
by one of the plant engineers in his off
hours.
In fact probably the best, and certainly
the most American, design in this land at:
the present day is the work of the engineer.
The engineer goes directly and efficiently
to his goal, makes his designs to suit his
purposes, and having attained them, adds
no superflous and meaningless adornments,
nor attempts to cover up what he has done
with sham work. So his products are in-
evitably beautiful — beautiful in their sim-
plicity and in their adaptation to their pur-
pose.
Certain radical French artists, notably
the late, unlamented Dadaists, have been
so obsessed by the beauty of
mechanics that they have
smeared vast quantities of
canvas with their interpreta-
tions of turbines, and girders,
and egg beaters, and what
nots. A pretty tribute in-
deed; if hardly a justifiable
procedure in a supposedly
creative art.
It is improbable that the
radio engineer when he set
about devising a container
for his half bushel of parts,
had in mind the making of
a definite and important con-
tribution to industrial art.
He simply went ahead and
made the most practical and
efficient case he knew how.
But, whatever his inten-
tions were, he succeeded in
creating a "thing of beauty."
We know of few merchandise
displays out of which we get
a more definite and legiti-
mate aesthetic kick than a
window full of first class radio>
receiving sets.
318
RADIO BROADCAST
JANUARY, 1926
All are housed in simple wooden cabinets
of pleasing proportion. And their panels
are enough to make any one with any sensi-
tivity to design whoop with joy. The
regular arrangement of gleaming dials,
with here and there smaller circles artlessly
placed, is an application of one of the
fundamental principles of good design —
the repetition with variation of geometric
forms.
Now please don't reduce this eulogy to
absurdity by suggesting that if that's the
way we feel about it, we forthwith white-
wash our Rembrandt and cover its gilt
framed canvas with assorted radio dials
neatly glued on. It's the fact that the
dials have a raison d'etre on the radio panel
that makes them beautiful. The same set
of dials applied to the front door would be
meaningless and ugly.
Some of the cone type loud speakers are
as pleasing in form as a Greek vase (as to
the goose neck horns, we'll never admit
them to be other than unsightly). And
an outside loop never ceases to delight us
with its concentric, diamond-shaped wiring.
The innards of our set we likewise find
intriguing (though we confess here and now
we don't quite know what they are all
about). Anyway we like the way those
wires run around in neat little parallel lines,
dodging tubes, and coils, and miscellaneous
gadgets.
More power to the engineer ! Would that
his kind made up the membership of our
lamentable "Civic Art Commissions."
But, alas and alack! even as we write,
the so-called Designer is getting in his dirty
work in the field of radio, and we are more
and more frequently being pasted in the
eye by receiving sets masquerading as
Chinese pagodas, lamps, canary cages,
electric heaters, fish bowls, and Louis XVI
medicine chests.
What Sort of Fellow Should the
Announcer Be?
O EATED in the theater awaiting the
^S rise of the curtain on what was
^^ declared by all the critics to be the
best show in town, we were presently
brought to our feet by the arrival of a
portly gentleman accompanied by his
multitudinous family. We hitched in a
reluctant patella and they squeezed
through to their seats. Following them,
the usher's hand, laden with programs,
brushed by our nose. These were distri-
buted to everybody down to little Willie,
and all immediately buried their noses in
them. At once a buzz of indignation
began.
"I don't think much of the picture on
the cover," growled Pa.
"There aren't any beauty hints or fire
rules," whined Gerty.
"Shucks, where are the jokes?" wailed
Willie.
"The program is rotten," said Pa with
finality, "Let us depart!"
We hitched in a willing patella and they
filed out, doubtless to seek some theater
which presented a program of more at-
tractive format and content.
But what we started out to say before we
got side-tracked on the above fable was:
Why the importance attached to radio
announcers? Why are their photographs
continually staring us in the face in the
public prints? Why have their names
become household words?
Announcers are — or should be — simply
substitutes for the printed program.
How they part their hair or what they
thought of the last selection is of no concern
to us. We will not lament with little
Willie if they offer no jokes.
The announcer par excellence, in our
opinion, is the one who is only slightly
more human than an automaton; who
conveys the desired information in the
minimum of words and intrudes no more of
his personality than would a column of
8-point Caslon.
And, while we're on the subject, do they
say "This is radio station XYZ" to keep us
from falling into the error of suspecting it
to be Post Hole Factory XYZ, Cumulus
Cloud XYZ, or Choir of Angels XYZ?
From Ten P. M. to Two A. M.
IF EVER the disciples of Mercury crave
substantiation of their suspicion that
this is a nation eighty per cent, moron,
they have only to plug in on the air any
time between 10 p. M. and 2 A. M. Shades
of Euterpes! What manner of cacophony
greets the ear? You, little boy in the back
row? Correct !
Now this department hereby declares it
has no quarrel with jazz as such. But
what does make it stand up on its hind
feet and yowl desolately is the insufferable
punkness of present jazz.
Popular music always was and always
will be, and we contemplate no diatribe
against it. In fact, to give it due credit,
it should be remembered that the serious
music of the present owes considerably
more to the popular music of the past times
than, say, to the classic polyphony of the
church.
But the rhythmic caterwauling that is
spewed forth by a hundred-odd (very)
dance orchestras every night can only by
courtesy be called popular music. "Popu-
lar" no doubt; but "music" . . . no!
If memory serves us right, we used to
have a rather respectable brand of dance
music in this country five or ten years ago.
The tango brought with it no end of de-
lightful pieces of melodic interest and
colorful Spanish trimming. But melody
and color have been consigned to the pup-
pies. The only goal of present terpsi-
chorean thrumming seems to be the main-
tenance of a rhythm. And this a hundred
banjos do every night, with dogged and
monotonous persistance. The result may
be satisfactory for dancing but is far from
delectable to the listener-in who is not, at
the moment, imitating a kernel of corn in a
popper.
Imagine, if you can, the music lover of a
couple hundred years hence, collecting
the "quaint old fox trot melodies of the
twentieth century" as we do the charming
old gigues, sarabandes, minuets, and
polkas.
The trouble with modern jazz is not that
it is jazz, but that it is poor jazz. Our
high-hat friend who comes out flat-footed
with the statement that he cannot bear
popular music in any shape or form can,
nine times out of ten, be labeled a four-
flusher. Of course there is that rare tenth
person who really understands music, and,
understanding it, realizes that popular
music is a very hollow echo of the real
thing. But even an epicure occasionally
enjoys a fried egg.
The line of demarcation between popular
and serious music is not as exactly defined
as some would have us suspect. At last
reports the savants had not yet voted a
unanimous ballot as to which rank claims
M. Igor Stravinski. But, even as jazz
can approach perilously near to being
music, so it can likewise move a long way
from it. Jazz, as is, has retreated to the
limit. The tom-tomery of the aboriginal
head hunter must have been less obnoxious
than that which delights the present day
sheik, if for no other reason than that the
savage had fewer instruments — and no
saxophones — with which to perpetrate it.
Popular music has been defined as differ-
ing from the serious by a diminution of the
intellectual content. If the entire intel-
lectual content of the see-lections that
pollute the air from 10 p. M. to 2 A. M.
were stood on end it would about equal the
intellectual content of the third act of
Abie's Irish Rose — or, if you must have
your statistics stated graphically, it would
be slightly higher than the grasshopper's
instep.
In the aforementioned epic of the Ameri-
can stage, not an event transpires which
can not be anticipated twenty minutes in
advance by any normal fourth-grader.
So in our modern dance music, the unex-
pected never happens. One piece is the
Siamese sister of the other. The tunes are
the same; the orchestration is the same; the
banality is the same. You, gentle reader,
could sit down at the piano now and write
something better, and — so could the jazz
composers !
But if the dance music that clutters up
the long suffering ether from 10 p. M. to
2 A. M. is about as entertaining as a game of
three handed bridge played with isinglass
cards, what can be said of the songs that
adorn those sad four hours? They are all
cut from a pattern: either riotously
"peppy" or lugubriously sad. Of the
two, we most abhor the latter. " I want
some bah-ha-dy. . . ." we hear a
sacharine barytone imploring from XYZ at
a speed of 25 miles per hour. And from
ZXY, a tearful and flat soprano wails:
"Like a rose-uh, I'm all, alone-uh!" And
JANUARY, 1926
WHAT HAPPENS ON THE AIR AFTER 10 P.M.
319
QL'IN A. RYAN
Director of WON, Chicago. He reported the
Big Ten football games. Mr. Ryan's sports
reporting is exceptionally graphic and manifests
a very complete and thorough preparation of
material. He also reported the Kentucky
Derby, Indianapolis Auto Races, and World
Series. Inclined to rhapsodize poetically — but
the stuff is poetical !
we are all but overcome by a wild urge to
call up their respective stations and ar-
range for a get-together. Continuing with
our statistics: if all the sickly, sentimental
ballads broadcast of an evening were placed
end to end they would reach from Athol,
Mass., to the Pacific Ocean. That statis-
tical end attained, we would place ourself
at the eastern end of
said column and
push.
"But," it is pro-
tested, " that is what
the pee-pul want,
and what the pee-
pul want they
should have!"
With both these
propositions we take
exception. I n the
first place, we are
not convinced that
such a large number
of individuals as is
imagined want this
juvenile sort of
musical substitute.
There exist a goodly
number of persons
who are satisfied
with this tastelesj,
diet because they
have known no
other, but who,
nevertheless, are
capable of gustating
something at least a
little more meaty.
Take some igno-
rant looking yokel
in the lowest ranks
of the army of list-
eners - in. Suppose
it is discovered that
he has assembled his
own receiving set. Then, say we, if he has
brains enough to know what is inside that
mysterious box that brings him in his radio
entertainment, he, by that sign, has brains
enough to appreciate to some extent the
content of music. IF he gets a chance.
If, for instance, we were to ask him: "The
song of what small bird, frequently found
in clocks, furnishes the motif of Japanese
Sandman, Carolina in the Morning and
Berlin's Pack Up Your Sins?" we will
wager he could discover the answer, and in
so doing he would have, after a fashion,
discovered some of their "content." But
it is to the second proposition — "what the
pee-pul want they should have" — we take
the most violent exception. Let them,
say we, go without it!
A cursory glance at this mortal coil dis-
closes it to be populated by two principal
classes of beings: the common pee-pul,
and those existing to serve the common
pee-pul.
"Pity the poor masses!" we hear con-
stantly reiterated. Pity, rather, the poor
"classes," we shout. They are the ones
who are getting the rotten deal in this age
of the proletariat.
Everywhere the low-brow turns, he finds
someone waiting to serve and entertain
him, to supply at a moments' notice his
slightest want. While the poor high-brow
searches about taking his scant pleasures
where he may. What's more, the high-
brow's entertainment comes high (unless
it be communion with books) and more
A presentation of
KGO, at Oakland.
THE RADIO PLAYERS AT KGO
William Archer's "The Green Goddess" before the microphone of
This is the way the radio villain loses his life — under protest (his own)
GRAHAM MACNAMEE
of WEAF, who, with Phillips Carlin, reported
several important games played in the East.
Among them were the Chicago-Pennsylvania,
Yale-Army, and Cornell-Penn games. The cup
Mr. MacNamee is gazing at is a popularity tro-
phy awarded him some moons ago. Inclined to
improvise comically — but the stuff is comical
often than not he has less money than his
slanty-domed, ditch-excavating neighbor.
With half the world catering to the
masses' whims, we often wonder why
existence does not become a surfeit and a
bore to said masses. If Fu^y Wuny Baby
played on a tomato can is the summum
bonum in music to them, imagine how con-
stantly they are surrounded by art!
Imagine a world in
which every open
cafe door emmited
strains of Brahms
and DeBussy, and
passers-by whistled
airs by Palestrina
(are they whistle-
able?). A world in
which every bill-
board bristled with
El Grecos and Ti-
tians, and every
vaudeville skit dis-
played the artistry
of a Strindberg or a
Synge!
Well now that
we've quite com-
pletely disposed of
the issue — whether
the public should
get what it suppos-
edly wants, let's get
back to the subject,
which, if we remem-
ber, was jazz.
A little jazz is rel-
ished by the best of
men (now and then)
but there's no relish
in the variety on the
present market.
Even the redoubt-
able Paul Whiteman
is dishing out the
same monotonous
320
RADIO BROADCAST
JANUARY, 1926
stuff as the rest of them, the while riding
on a reputation created by mob hysteria
and which he has long ceased to deserve.
In conclusion: give us jazz, Oh Mister
Popular Music Composer! We can stand
our share of punishment. But, frevvens
sakes, give us a better brand of it. We will
trade seventeen Yes, Sir, That's My Baby's
for one Allah's Holiday ... or what
have you?
Broadcasting Funeral Services
A ONE of the outstanding examples
of bad taste in broadcasting that
has come to our attention during
the past month, we submit the broadcast-
ing by a Mid-Western station of funeral
services for one of its departed minstrels.
Certainly the man was a most excellent
entertainer and his death was regretted
by those who had come to know him
through the air. But we question whether
their grief was so sincere as to justify their
being, not merely invited, but forced, to
attend his obsequies. And of course
thousands of listeners-in had never even
heard of him before. It is a doubtful
mark of respect to the deceased to intrude
his funeral eulogy into what may be a
dancing party, a convivial dinner, or a
poker session.
Assuming that the whole nation was
genuinely "bowed in grief" over the death
of some great statesman or outstanding
leader, a radio funeral service might be not
only appropriate but almost imperative.
In the instance cited the service was given
an importance out of all proportion to the
importance of the deceased.
'Broadcast ^Miscellany
DOUBTLESS ere this appears in
print the results of KOA'S aerial
battle, "Jazz vs. Classical Music"
will have been published. And the statis-
tical lore of radio will have been enriched
by an impressive array of figures tabulating
the judgment of the populace as to which
was the winner.
But as to the possibility of this musical
debate having lured the army of jazz
lovers over to the enemy camp, or vice-
versa, we are inclined to believe that the
prophetic utterances here appended will
have been realized:
—AND MAKES NIGHT HIDEOUS—
Jazz and classical music are to fight it out in
the air. KOA will stage the battle in Denver on
November 6. The ringside is the continent —
or where you will. Seats are free. The betting
is heavy on both sides.
The ethereal, soul-stirring sonata will spar
with the sole-tickling slide of the trombone.
The thunder of the Mountain King's Ball will
roar defiance at the comic saxophone simulating
a psychic jackass extemporizing during the ver-
nal equinox. The graceful minuet pirouetting
on the gossamer of imagination must hurl the
lance at the primitive pom pom moving to fleshly
ecstasy the "fat black bucks in a wine-barrel
room." The flute, capturing bird notes still
fresh with the dew of morning, must fence with
the piccolo harmonizing feline infelicities at
2 A. M. Faust, meditating divinely on Mar-
garita's dwelling, must come to vocal blows with
a "gent" in rainbow linen and checkerboard
socks snapping out " Yes, Sir, That's My Baby."
Beethoven, Bach, Handel, Gounod and all
the other masters who are doing their harmon-
izing among the celestials will descend as an
awful nightmare upon the living hip-wigglers
and will utterly demolish Polasek's "Spirit of
Music." The boys in the pool-room will say
"That was some jazz." The girls in the School
of Music will buy tickets for the Spring Fes-
tival. That's how the world of music will be
changed.
News— Index
Evanston (Illinois)
LET the calamity howlers take note:
radio has added several things to the
credit side of its somewhat unbalanced
ledger since last writing.
First and foremost on its list of achieve-
ments we place the broadcasting of the
autumn's football games. Here is radio
at its best — performing a unique service
that no other existing agency can do.
Music we can get, after a fashion, on rec-
ords; speeches can well wait perusal in the
morning paper; but a football game to be
properly enjoyed has to be lived through.
Certainly the broadcasters made us feel
as though we were right down on the side-
line bench with the water boys and the
coach's relations.
A close second on the list is the epochal
undertaking of WEAF — the weekly broad-
casting of first rate artists. And paid
artists at that! Not pluggers for Whoozis
Garters or Whatzis Shaving Cream.
Mr. A. Atwater Kent is the sponsor of
this concert series, which has been broad-
cast by WEAF, and connected stations,
Sunday nights since October 4. The list
of singers and musicians who have already
been heard and those yet to come reads
like a roster of Who's Who in Musical
America.
Other isolated instances of genuine
musicians performing via radio could be
mentioned. Station fico's Tito Schipa
concert, and KFI'S program by Mme.
Schumann-Heink come to mind.
And all these events presage a brighter
future for radio programs. A small be-
ginning, perhaps. An hour of music is a
small drop in the bucket of several hundred
hours of mediocrity. But vastly important
because it is a beginning.
FORD AND GLENN
Ford Rush and Glenn Howell ; which is which we don't know. As entertaining a pair of comedians
as have ever been heard by radio. They were recently broadcast by WFAA, Dallas, to whom they
were loaned by WLS. They are versatile humorists appealing to domes of all dimensions
A Universal Short Wave Transmitter
How to Build a Five- Watt Transmitter of Extraordinary Range
and Steadiness which Can Be Used with Receiving B Batteries as
a Source of Plate Supply — The Cost is Not More Than Fifty Dollars
By NICHOLAS HAGEMANN
Station 2 KP, Mitchel Field, Long Island
A one who has listened to signals
on the very high frequencies, on
the so-called amateur 40 meter-
band, for example, will know
that strange things occur there. In the first
place, signals do not stay put, but they
wobble around, fading in and out, changing
in frequency and strength. It is one of the
discouraging things about high frequency
transmission — but on the other hand it is
one of the joys, for one never knows what is
going to happen next. The next signal
may be from China or Indiana, no one
knows. And no one can tell whether the
station will sign before he fades out.
Once in a great while a station can be
heard that in a steady, unvarying pure note
pounds away, perhaps not very loud, but
Cc
:c0
FIG. I
A conventional input circuit to a vacuum tube
wavemeter. The frequency to which such a
circuit will tune depends upon the inductance
and three capacities as indicated. The resultant
frequency is a function of L X (C0 + Ce + Cc)
unceasingly. Among the medley of notes
that fill the y-megacycle (yooo-kc.) band,
notes of all sorts, some coarse and raw,
practically all of them varying, a clean
steady note is like a beam from
a lighthouse on a thick night. c^r,^—
It gives the receiving operator
confidence, for he knows that
the signal will not leave him
in the middle of a message.
There are several reasons
why signals of this sort vary.
One reason is fading; no one
yet knows how to conquer that
natural phenomenon. Another
is a swinging antenna, some-
times fifty feet from the ground,
at other times nearer or farther
from earth. This swinging
changes the antenna capacity
and naturally changes the
emitted frequency. Another
reason lies in a transmitter whose filament
or plate supply is not steady. With every
change in the conditions under which the
tube is operating, the frequency emitted
changes.
A transmitter whose frequency is inde-
pendent of filament or plate voltages is a
great boon, and if attached to it is an an-
tenna that is rigidly fixed, unvarying signals
will be emitted that will attract any receiv-
ing operator's attention at once, especially
if it is battery operated so that a pure
steady d. c. note is emitted.
The transmitter described in this article
has several noteworthy features that should
appeal to any constructor of amateur equip-
ment, whether he already possesses a trans-
mitting station or whether he
is about to enter this fascinat-
ing field.
The great advantage of the
present circuit lies in its sta-
bility with regard to the fre-
quencies it turns out to an
antenna or other load. A little
of the history behind its devel-
opment will reveal its possi-
bilities in this direction.
In connection with other
precision radio instruments
developed by the Signal Corps
for the various branches of
the United States Army, a
need arose for a frequency
meter whose calibration
would be independent of
many factors, notably tube
capacity, differences in plate and filament
voltages, etc. In other words, the Army
needed a heterodyne frequency meter that
could be calibrated with one tube and at
CT" HIS article will primarily interest those who already have a short wave
•*• receiver and are anxious to build a good transmitter for the high frequencies.
This set has the great advantage that the note produced is unwavering and very
steady. It should appeal strongly to the amateur experimenter located in the
country, where it is difficult to get a dependable source of current supply. The
set described here is entirely operated from batteries, an unusual design in short
•wave transmitters. For those who are interested, a short description of the
short wave receiver at present in use at our station 2 GY is shown. We expect
to describe a good short wave receiver in an early number. The author has
used the term megacycle in referring to transmission frequencies because it
simplifies terminology. A megacycle is one thousand kilocycles. It is custom-
ary to refer to the frequency of broadcasting and short wave stations in kilocycles,
but in short wave work, where the frequency is often of the order of 10,000 kilo-
cycles, the term megacycle is more satisfactory. A government license is, of
course, necessary before this transmitter can be used. — THE EDITOR.
certain filament and plate voltages with the
certainty that this calibration would not
differ materially when other tubes or volt-
ages were used.
Fig. i shows the usual tuned circuit that
is used in a vacuum tube frequency meter
(wavemeter). The apparatus consists of a
coil and a condenser, which is usually
variable, the tube, and a grid milliammeter.
There are three capacities as shown in this
Figure, all of which must be accounted
for in the tuning. The coil capacity Cc
is small, of the order of a few micro-micro-
farads, the condenser capacity Co is
usually quite large, and the tube capacity
Cg is of the order of several micro-
microfarads. Naturally a change in any
OA-
OB*
f FIG 2
The circuit diagram of this new transmitter. It is distinct in
that the inductance in the tuned circuit is very small and the
capacity is very large. For this reason small variations in grid-
filament capacity will have little effect upon the resultant
frequency. The key is inserted in the B battery negative lead
of these capacities affects the frequency
to which the circuit will tune.
The task of developing a new type of
frequenty meter was undertaken at the
Signal Corps Radio Labora-
tat, tories, Fort Monmouth, New
Jersey. The circuit described
in this article is based upon
the results of the work there.
This meter was remarkably
stable as regards frequency,
due chiefly to the fact that the
small grid-filament capacity of
the tubes used was bridged
across a very large capacity so
that variations in the small ca-
pacity had little effect upon the
total capacity in the circuit.
The circuit performed so
creditably as a frequency meter,
and it was found that such high
voltages and currents existed
322
RADIO BROADCAST
JANUARY, 1926
20 Turns
.
0 If"
W999***
FIG. 4
Details of the filament choke coils. There is
no trick whatever about the construction. Both
coils are on this tube, one to be inserted in each
filament lead
in the tuned circuit, that its value as a
transmitting circuit soon became evident.
It was then designed to operate at 3748-
2998 kc. (80-100 meters), on low power.
At these frequencies, a change of 150-400
volts on the plate of the tube produced no
greater change in frequency than 800 cycles
and corresponding differences in grid-
filament capacity and filament voltage pro-
dused very little difference in the frequency
of the tuned circuit.
AN EXCELLENT TRANSMITTER CIRCUIT
A^Y one who has listened on the high
frequency amateur bands 3.5, 7, and 10
megacycles, (3500-10,000 kc., 80-30 me-
ters) will appreciate this advantage.
With a d. c. plate supply, say from B bat-
teries, a pure unvarying note will arrive at
a receiving station and where is the amateur
who would not pass by a dozen powerful
but fluttering notes for one that is steady
though not so powerful?
As actually designed for transmitting
service, the coil in Fig. 2 is a single loop
of heavy wire and, with a five-watt tube,
currents as high as eight or more amperes
were obtained in the loop. As designed
here for amateur use, the coil L consists
of a few turns of heavy wire coupled
to an antenna-counterpoise system. With fundamental frequency of the antenna and
medium power, large currents are induced the actual frequency used for transmission,
in the antenna, the actual value of course as well as upon other factors,
depending upon the relation between the As constructed by the writer, a consis-
"-Two halves of coil form for inductance '
FIG. 5
Details of the Lg-Lp coil and its construction. This is somewhat different from the
usual transmitter inductance. A good view of it is shown in Fig. 3 and in Fig. 6
FIG.
BROADCAST Photograph
A view of the transmitter from below the sub-panel showing the disposition of the choke coil and the
criss-cross inductance. The short, direct, and heavy leads for the radio frequency paths are clearly
shown. The variable condensers shown are a General Radio 247 .ooo44-mfd. and DXL .oooj-mfd.
FIG. 3
The first experimental model of
the transmitter. The General
Radio o.5-ampere meter was in
the closed circuit and with a
20 1 -A tube with 90 volts on the
plate it went up in smoke.
The details of the "criss-cross"
inductance are clearly shown.
The condenser used here was
an X-Laboratory .ooi-mfd.
RADIO BROADCAST Photograph
tent day range of 800 miles was obtained
in the so-called 4o-meter band with a ux
-2 10 tube with 350 B battery-volts supplied
on the plate. The currents and voltages in
the loop circuit are so high that higher
powers require great care, and at the
present time, the writer is not prepared to
give dimensions of the parts to be used if
more than 50 watts input to the tube are
employed.
The constants of the various condensers
are shown on the diagram of connections
in Fig. 2 and the general layout of such a
transmitter may be seen from the photo-
graphs accompanying this article. The
tuning condenser must have wide spacing
between plates and have a large capacity,
since the inductances used in the set are
quite small. The larger this condenser C,
the smaller will be the detuning effect of
varying tube capacities. The by-pass
condensers and .04 mfd. stopping conden-
ser in the L-C circuit must be able to stand
JANUARY, 1926
A UNIVERSAL SHORT WAVE TRANSMITTER
323
at least 1000 volts, and for this
reason transmitting condensers,
are suggested. In the writer's
opinion it always pays to buy
good by-pass condensers since
the life of tubes frequently de-
pends upon them. Mica con-
densers of the correct capacity
may be found in many automo-
bile spark coils.
Coil L consists of three turns
of No. 10 bare copper wire
wound on the cardboard case
of a dry cell and then allowed
to expand until the diameter of
the coil is about 35 inches. The
antenna coupling coil is a single
turn of the same wire and about 25
inches in diameter.
The filament choke coil is wound
in two layers on a bakelite or hard
rubber tube I x 2j inches. The
bottom layer has 22 turns, the top
20 and any size of wire may be used,
although No. 18 d. c. c. is about the
best from the standpoint of resis-
tance. One layer is wound on over
the other as shown in Fig. 4 and the
connections to the tube as illustrated
in the figure should be short.
The other inductance, Lg — Lp, is
constructed of two hard rubber cross
pieces as shown in Fig. 5 and in the
set illustrated about 17 turns are
correct for the 7-mcgacycle (40 me-
ter) band. Varying the tap along
this coil controls the plate current
taken by the tube and with a given
antenna current, this plate current
should naturally be as small as possi-
ble. The tap with a ux-2io tube
should lie about six turns from the
RADIO BROADCAST Photograph
FIG. 7
The panel view of the completed transmitter
FIG. 8
A method of indicating when the transmitter is in resonance
with the antenna-counterpoise system. The length of the shunt
varies with the current passing into the antenna and with the
amount of current that the indication device will stand without
burning up. About one foot may be used and one point of con-
nection made variable so that more or less antenna is included
plate end. The actual construc-
tion of such a transmitter is re-
markably simple. There are few
pitfalls to avoid, the chief one
being long, poorly made connec-
tions and condensers that will
not stand the voltage.
After the instruments are
wired up, a receiving tube should
be placed in the socket and
about 90 volts used on the plate.
Then the transmitter should be
brought near a receiver that
will tune to the frequencies to
be covered by the transmitter
and the latter tuned. It will be
found that, with the constants
used in the diagram in Fig. 2, that
the entire 7-megacycle band can be
covered with the tuning condenser C
at from 80 to 100 degrees. This is
purposely done so that the condenser
will be used at its maximum value.
If desired, a fixed air condenser may
be made with a small two- or three-
plate variable placed across it. Then
the frequency band may be covered
with more degrees of dial rotation.
The variable condenser, C, should
be turned to maximum and the lowest
frequency found by tuning the re-
ceiver to it, and then the condenser
capacity decreased until the tube
stops oscillating or until the con-
denser approaches its minimum ca-
pacity. The transmitter illustrated
in Fig. 3 oscillated perfectly until 10
megacycles (10,000 kc., 30 meters),
was reached. It is probable that a
given set could be made to cover two
of the amateur bands, either the 15-
to 7-megacycle (15,000 to 7000 kc.,
FIG.
RADIO BROADCAST Photograph
Looking behind the panel of the transmitter, the three turn coil L and the single turn of antenna coupling inductance are very much in evidence
324
RADIO BROADCAST
The Facts About This Transmitter
JANUARY, 1926
FREQUENCY RANGE: 6.5 to 8.5 megacycles
WAVELENGTH: 35 to 40 meters
ANTENNA: Single Wire, 35 feet long
COUNTERPOISE: Single Wire, 35 feet long, as near to the
ground as possible
SOURCE OF PLATE CURRENT SUPPLY: Receiving B Batteries
Rectified a.c.
Motor generator
TUBES WHICH MAY BE USED
A VOLTAGE B VOLTAGE
uv-aoiA or similar inde-
pendently made tube 6 200
UX-II2 6 2OO
ux-2io 7.5 400
SENDING
RANGE
(MILES)
50
IOO
800
If B batteries are used, so-called "heavy duty" cells should
be purchased. This transmitter when properly operated, will
have a current drain of about 35 milliamperes, which is about
equivalent to the demand made by an 8-tube super-hetero-
dyne. Owing to the fact that, in the transmitter, the keying
of the circuit interposes an intermittent drain on the B bat-
teries, the drain on them is not nearly as heavy as would
ordinarily be supposed.
LIST OF PARTS USED IN CONSTRUCTING THIS TRANSMITTER
One panel, 7 inches by 14 inches by ^ ... 1.25
One General Radio condenser .ooo5-mfd. without gears 3.25
(or other good receiving condenser)
Two General Radio dials with verniers .... 5.00
One Centralab ioo,ooo-ohm variable resistance . . 2.00
(Bradleyohm or Royalty B may be used)
Two Benjamin brackets, .70
One .ooo25-mfd. variable condenser (any reliable make) 3.00
One socket for ux tubes .65
Two Dubilier .oi-mfd. condensers type 577 . . . 5.50
One Dubilier .ooj-mfd. condenser type 577 . . . 2.25
One General Radio or Weston radiation meter . . 8.00
One General Radio rheostat 2.25
(or similar which will handle up to 2>£ amps
Eight heavy duty binding posts .56
One sub base 3 1 inches by 1 1£ inches .... .75
Two hard rubber cross pieces
One bakclite choke coil tube i inch by 2j inches
One Dubilier .o4-mfd., looo-volt stopping condenser. 2.75
One plate milliammeter, range o-ioo (Weston or Jewell) 8.00
One ux tube 2.50-6.50
Total not over $50.00
20-40 meters), or the 7- to 3.5- megacycle
(7000-3500 kc., 40-90 meters) band.
After the maximum frequency range
has been determined, the constructor can
calibrate the condenser in megacycles,
kilocycles, or wavelengths as desired.
THE ANTENNA
OROBABLY the simplest antenna to be
' used with this transmitter is a single
wire 1 5 to 25 per cent, lower in fundamental
frequency than the actual frequency to be
emitted. A series condenser is then used to
bring the frequency to the desired value.
For example, on the 4O-meter band, a single
wire 12 meters (37 feet) long and a similar
counterpoise will have a fundamental
wavelength of about 50 meters which can
easily be reduced to 40. The antenna
current will be lower under these condi-
tions than if the antenna were being ex-
cited at its fundamental frequency, but
rn
RF.Choke
10 '-I
Short circuiting
Switch
1.00025
mfd
00025
mfd
Ant
tA&B-
O
A-
FIG. I I
The connections for the receiver. Interchangeable coils
enable this receiver to cover all of the amateur bands
FIG.
A photograph of a receiver now in use at 2
amateurs, known as the capacity feed-back,
and the interchangeable coils are wound on
American,
RADIO BROADCAST Photograph
GY which employs the circuit familiar to all
The condenser is a five-plate Bremer-Tully
Bruno forms. The transformer is an All-
ratio 10: i
since the radiation resistance is higher
above the fundamental frequency, greater
efficiency is obtained.
Ribbon antenna wire will .lower the
ohmic resistance and if the wire is twisted,
motion caused by the wind will have little
effect on the frequency transmitted. Good
copper ribbon may be obtained from an old
Ford spark coil primary. It is highly
important that the antenna be thoroughly
insulated, preferably with Pyrex and that
it be taut.
In the photographs illustrating this
transmitter, a General Radio half-ampere
radiation meter is shown. This will
handle the output of a 2OI-A, a ux-H2 or
even a ux-2io type tube, unless a very
small antenna or greater plate voltages are
used. Then a copper wire should be
shunted across the meter so that it will not
be burned out.
In actually tuning the transmitter to the
antenna, the antenna series condenser
JANUARY, 1926
A UNIVERSAL SHORT WAVE TRANSMITTER
325
and the tuning condenser C should be
varied until the greatest radiation on the
desired frequency is secured. At this
point, the plate current should be adjusted
by varying the tap on the Lg-Lp coil until it
is smallest, consistent with good radiation.
If the constructor desires only one meter,
and only one is really necessary, he may
use a plate milliammeter with a range of
o-ioo and a flash light bulb. The milli-
ammeter is placed in the negative B battery
lead, and the flash light is placed in the
antenna-ground lead. When maximum
current flows in the antenna, the lamp will
be brightest. Here, again, care must be
taken not to burn out the indicating device.
A 6-volt lamp or smaller with a shunt wire
may be used for this purpose. Fig. 8
shows the proper position of the indicating
device.
After the constructor is thoroughly
familiar with the operation of the trans-
mitter, greater power may be applied to
the receiving tube, or a power tube can be
employed. It must be understood, how-
ever, that the voltages in the tuned circuit
are very high and that as soon as heavy
currents begin to flow, both condensers
must be able to stand up. If the mica
condenser passes more than five amperes
it will probably get hot and then trouble
begins. The remedy is to use more con-
densers in a series parallel arrangement —
but before that time, enough distant sta-
tions should be worked to satisfy any one.
In the writer's station 2 KP at Mitchel
Field, Garden City, Long Island, and at
2 GY, located in the Radio Broadcast-
Eveready experimental station, no diffi-
culty at all has been had in maintaining
schedules with stations 800 or more miles
away. On several occasions, a 201 -A tube
has been used, and with 180 volts of stand-
RADIO BROADCAST Photograph
FIG. 12
A short wave receiver used at 2 GY on the so-called 8o-meter band. Karas orthometric condensers
are used for both feed-back control and for tuning. The coils shown are made by Hammarlund
Manufacturing Company. Other coils may be quickly inserted in the circuit so that higher or
lower frequencies may be received
ard receiving B batteries on such a tube,
successful transmission of several mes-
sages to Philadelphia, 100 miles away,
has been accomplished. This represents
a power input of less than one-half watt!
At the Mitchel Field station, a standard
input of 19 watts has been used on a five-
watt tube and all districts in the United
States have been worked.
The transmitter illustrated in this article
is now operating at 2 GY, and the operators
there would appreciate reports on signal
reception.
THE RECEIVER
*~P H E receivers used at 2 KP and
* at 2 GY are very simple and
are fashioned according to the
well known amateur capacity-
feedback circuit shown in Fig. 1 1 and il-
lustrated in Figs. 10, and 12. Complete
description of such a receiver will be in-
cluded in the Radio Broadcast-Eveready
short wave experiments series of articles.
The photographs and circuit diagram show
enough detail so that the home constructor
should have little difficulty in actually
constructing such a receiver. A fixed
condenser is placed in series with the tuning
condenser so as to spread out the stations
over a greater number of degrees on the
dial. This may be shorted when not
wanted. The switch is shown in Fig. 12.
FIG.
RADIO BROADCAST Photograph
Twelve miles from the home station 2 GY. This transmitter with an input of about 6 watts on an antenna 7 feet above ground put
strong signals into the receiver at 2 GY. The oval insert shows a close-up of the automobile installation, operated from B batteries
Drawings by Fran^lyn F. Stratford
Who Shall Judge the Quality of Our Broadcasting Stations?
THE years of broadcasting reach
a dignified sum, and similarly the
money expended on programs, the
question, "Who shall be responsible
for the musical quality of the station output?"
is being raised at more than one station. That
is, who shall say that there is not quite enough
cello in this trio or that quartet, or that the
woodwinds are a trifle too prominent in some
symphony orchestra (as broadcast), or that the
accompaniment to a vocal solo might be a little
less prominent without injury to
the pianist or his relatives. Shall
it be the operators, who have been
doing it heretofore? Or shall the
job be handed over to profes-
sional musicians?
The opinion among the best
informed and forward looking
broadcasters seems to be that this
responsibility should be loaded
on to the shoulders of the musi-
cians, rather than the operators,
but with certain qualifications.
Not to any old musicians, but to
men trained in both music and
broadcasting. And to these, with
reservations as to the no man's
land between the program side of
an event and the technical aspects
of transmission.
For example, when carbon mi-
crophones are used, there is always
liability to blasting. This phe-
nomenon is a technical matter.
(See "Microphone Placing in Stu-
dios," September, 1925, RADIO
BROADCAST.) The operators and
engineers of broadcasting stations
know more about it than the
average musician does. Further-
more, they have instruments (d.c.
milliammeters in the battery cir-
cuits of carbon transmitters),
which afford an additional check,
showing up both incipient and
severe blasting. Some micro-
phones are more susceptible to this
difficulty than others. Clearly,
therefore, this is a matter wherein
the musical critics in the studio
need the aid and counsel of the
technical experts.
As a matter of logical expecta-
tion, skilled musicians should be
better able to balance an orchestra
to the utmost nicety, and to per-
form similar delicate musical tasks, than men who
grew up with voltmeters and R. M. S. voltages
and curves of tube characteristics. That is, as
a class. There will be exceptions, of course.
Some broadcast operators with exceptional
musical taste or experience are capable of turn-
ing out a better job on the air than all but a few
musicians. The ideal combination is a first-
rate engineer who is also a first-rate musician,
a sort of fusion of Charles P. Steinmetz and
Jean De Reszke, for example. Try and get
'IF
MISS AMERICA ARRIVED, HE WOULD NOT STOP
LISTENING"
him. Having done that, try to make him work
in a broadcasting station for $3000 a year.
When we poor devils who, for our sins, have
been set to running broadcast stations — when
finally we have completed our penance, and the
last milliampere has quivered through our
nerves, then, operating the broadcasting sta-
tions of heaven, we shall have paragons like that
working with us. Oh for those celestial studios
and control rooms, where sopranos shall never
shriek, where the "mikes" shall cease from blast-
ing, and the grid milliammeter be
at rest! But here on earth we
must take men and materials as
we find them, and there is no use
looking for such engineer-musical
genius combinations as those we
have been dreaming about. Their
very qualities are antipathetic.
The basis for employing musi-
cians in this phase of radio trans-
mission is simply the old motto:
Shoemaker, stick to thy last. But
in citing that phrase — and 1 do so
with approval and have thrown
what influence 1 have toward the
musicians in this friendly contro-
versy— 1 want to add that 1 am
proud of the part engineers and
operators have played in the mu-
sical development of radio broad-
casting. Lifted abruptly, most of
them, out of the purely techno-
logical and non-artistic labors of
radio telegraphy, they quickly
adapted themselves to unfamiliar
conditions, learned what was
needed, developed new aptitudes,
and turned out a good job in many
cases, and a brilliant one in some.
And a rotten job in other instances,
it must be added, but to the custo-
dians of the tin horn and dishpan
stations 1 refuse to grant the name
of radio operators and engineers.
It was a fine example in adapta-
tion. Radio men are not a sta-
tionary lot and they move fast
when necessary. If they ever have
to do it again, in some other con-
nection, depend on it that you
will not find them lacking. Those
of us who live to see the complete
development of radio motion pic-
tures may view a similar incursion
of radio men into the field of pic-
torial art. But inherently such in-
JANUARY, 1926
MUSIC JUDGES FOR BROADCAST STATIONS
327
vasions are self-limiting in their nature. In-
variably the investigators and research men im-
prove the equipment to such an extent that the
most artistic interpretations become possible,
and the aid of men with an artistic background
becomes essential for the best possible results
And in broadcasting we are not going to be satis-
fied until we get to the point where a man listen-
ing to a loud speaker will not be able to tell for
the life of him whether he is hearing the original
performance or a reproduction. That point
we may not be able to reach, but we shall cer-
tainly aim at nothing less. And anybody who
can help us, whether he is a musician or a street-
cleaner, is welcome.
The musician who undertakes work in broad-
casting should realize, on his part, that he must
add something to his technique, as the operators
have added something to theirs. I have myself
seen competent orchestra leaders and soloists
— competent, that is to say, as leaders of orches-
tras or performers on special instruments — whom
I would not trust on the musical end of a lo-watt
station with an audience of two dozen. They
were incapable of listening closely, in the first
place. Have you ever seen a good broadcast
technician listening to the output of some piece
of equipment? He goes into a kind of trance.
If Miss America came and pirouetted before him
in a one-piece bathing suit, it is doubtful if he
would pay any attention to her. Frequently he
stops breathing. With such concentration one
is likely to know what one is hearing, These
musicians I am writing about did not go to all
this trouble. They would listen for a few
seconds, snatch the phones off their ears, rush
over to the orchestra, and make some change.
After touching the telephones to their ears once
more, they found it necessary to alter something
else. With the third trial, the orchestra — the
men by now in active rebellion, was returned to
the first position. This was now pronounced,
"Excellent!" "Wonderful!" which it was not.
After a few minutes the virtuoso realized this,
although he was quite incapable of making the
correct diagnosis. Once again he began making
changes. By this time every man in the en-
semble was ready to come to blows with
him. In anotherminute the tension would
have risen to that point, but at this junc-
ture the operator took charge, moved the
microphone a foot back in the right di-
rection, getting rid of the violin blasting
which was causing all the trouble, and
ended the argument.
Why should some musicians, who are
perfectly competent to read a score, give
their individual interpretation, control an
orchestra, and play a few instruments,
be unable to listen to a loud speaker |
giving a fairly faithful reproduction and
tell how it can be improved? I don't
know, but presumably they overlook the
differences between even the best repro-
duction and the original in the present
state of the art, and, in an unfamiliar
situation, they are unable to concentrate
to the necessary degree. There are also
temperamental obstacles. I am not one
of those who look on all artists, writers,
poets, and musicians as subjects for the
psychopathic ward; I believe that as a
class they do not go crazy much oftener
than manufacturers of corrugated ashcans
and cheese-paring machines, and that in
any state they are more interesting to
talk to. But I presume that the average
musician is somewhat more nervous than
the average engineer, because in his pro-
fession nervousness is not discouraged as
much as in engineering. And there is not
much room for nervousness in broadcasting.
The business itself contains enough tension
without any contributions from the partici-
pants. One needs sharp ears and a cool head.
It is to be hoped that no personal rancor will
enter into any readjustments that must be made.
It is merely a matter of doing the best possible
job. There is room enough for everybody in-
volved. If it were not for music and musicians
there would be little use for radio broadcasting,
and if it were not for broadcasting some musi-
cians would be out of jobs. There is also dignity
enough to clothe everyone, it is to be hoped.
The operator's function can never be relegated
to a place of unimportance. Some people seem
to think that the term "operator" is applied
only to persons of no great consequence or skill.
This is a mistake. The term is a very broad one,
applied to a variety of workers. Some are un-
skilled and others must be extremely intelligent
and capable. It is not generally known that
in medical literature the surgeon who performs
an "operation" is referred to as the "operator."
If a man who daily holds the lives of other men
in his hands does not mind being called an "oper-
ator," surely there is nothing invidious about the
expression. But why dwell on such trivialities?
Radio men are more interested in radio.
Credit Where Due
MANY a time and oft I have felt called
upon to comment sourly on the contents,
make-up, and editing of the newspaper
supplements devoted to radio, especially those
in New York, which meet my dour eye most
often. As a whole, they seem to me to foster
superstition, sensationalism, and questionable in-
formation, to emphasize all that is transitory,
childish, and unoriginal, and to neglect the sub-
stantial and scholarly elements in the art. There
are, of course, some exceptions. Mr. Zeh
Bouck's weekly column, "What Are the Air
Waves Saying?" in the New York Sun, stands
out in this group. But it is an oasis in the
desert. Most of the sheets are dull, obvious,
full of unchallenged press agents' concoctions,
I SWEAR — WITH MY HAND ON A COPY OF
ZENNECK"
and perhaps dubious advertisements. Heaven
knows I have a lot to learn about radio, but, with
my right hand raised and my left laid solemnly
on a copy of Zenneck, I declare that I have never
learned anything from newspaper radio sections,
with lamentably few exceptions.
It is with the more pleasure, therefore, that
I would call attention, somewhat belatedly, to
the New York Times Sunday Radio Section of
September 13, 1925. It was a first class journal-
istic job. It was brought out during the week
of the two big radio shows in New York, with,
presumably, the same fundamental objects as
those of other radio sections and supplements.
But this one set about its task by filling the
space not occupied by advertisements with useful
information, authoritative articles, and good
sense. Among the authors who contributed
were Orrin E. Dunlap, Jr., A. Hoyt Taylor, E.
F. W. Alexanderson, E. E. Free, J. A. Holman,
David Sarnoff, Alfred N. Goldsmith, Kolin
Hager, C. B. Popenoe, E. H Jewett, Lee De
Forest, J. H. Dellinger, E. C. Mills, Martin P.
Rice, H. P. Davis, W. H. Priess, David Grimes,
J. D. Freed, and J. H. Morecroft. I spent
several hours reading it, and they were profitably
spent. I have never met the editor of the Times
weekly radio section, nor does the paper sub-
sidize me, but, having knocked radio newspaper
supplements in general, I feel bound to con-
gratulate that editor and that paper for their
achievement
Among the Broadcasters
WHAZ
A CORDING to all accounts and evidence
on hand, WHAZ, the broadcasting station
of the Rensselaer Polytechnic Institute
at Troy, New York, has started its fourth year
on the air without showing the effects of age.
WHAZ, it will be remembered, is under the direc-
tion of Prof. W. J. Williams, who defended the
low power side in the super-power debate which
lately raged in these columns. Mr. Rutherford
Hayner is program director and announcer.
Station WHAZ is housed in the Russell
Sage Laboratory of the Institute, with
the towers on the roof. The location
overlooks the Hudson River at the head
of tidewater navigation, 1 50 miles north
of New York, and it appears to have elec-
trical as well as scenic advantages, for the
station has attained enviable ranges for a
standard 5oo-watt installation. No doubt
a part of this is also due to the operating
personnel and management, which, in an
engineering school, may be expected to
turn out a top-notch technical job. As
early as February, 1923, the station was
heard in New Zealand, two-fifths of the
way around the earth. It has also been
picked up repeatedly in France, Belgium,
Scotland, England, Alaska, Panama,
South America, the Pacific Islands, the
Far East, and of course all over the
United States and points near by.
The R. P. I. station is on the air but
once a week, on Monday evenings. It
is the gift of the Roebling family to the
Institute, and is operated naturally, on
strictly, non-commercial lines, in contrast
to the blatant advertising of some of the
smaller and irresponsible stations in the
state. There are popular monthly pro-
grams by the students' symphony and
dance orchestras, and musical clubs. The
first minstrel show is said to have been
broadcast from WHAZ'S studio. One of
its programs that is well and favorably
328
RADIO BROADCAST
JANUARY, 1926
THE ANTENNA AT STATION WHAZ
remembered is the commemorative Joseph
Henry broadcast, in honor of the American elec-
trician and physicist, whose work in electro-
magnetism prepared the way for many later
developments of the telegraph, telephone, and
radio. Other educational broadcasts have found
a place in the programs, including practical and
non-technical talks by members of the faculty
on subjects of current interest in the scientific
and engineering field.
Of course Rensselaer does not limit its radio
activities to the operation of WHAZ on its fre-
quency of 790 kc. (379.5 meters). As an engi-
neering college in which electrical and com-
munication engineering are among the major
courses, the school employs numerous trans-
mitting and receiving sets covering a very wide
range of frequencies. Among the curiosities
are a DeForest radiophone set which Professor
Williams demonstrated to the students in his
courses as long ago as 1910, and a Marconi
wireless telegraph set dating back to 1902, con-
taining one of the original coherers.
Many radio amateurs both in this country
and abroad are familiar with the call letters of
the Rensselaer experimental stations, 2 XAP,
a sz, and 2 CDC.
WIBO
NEWSPAPER reports tell of an accident in
the generator room of WIBO in Chicago,
when L. G. Rasmussen came into contact with
a high tension wire during the evening program
on September 171(1, and was severely injured. He
was taken to St. Francis Hospital in Evanston.
The operator's injuries were sustained when
the gold frame of his eyeglasses came into contact
with a live lead. The frame of the glasses fused
immediately and the resulting arc burned the
face, hands, and chest, of the victim. The sta-
tion had to be shut down before he could be
released.
This unfortunate occurrence should be a
warning to other broadcast operators who have
so far escaped. Familiarity breeds contempt,
and men who handle high tension machinery
every day are apt to forget that contact with it
at the wrong time may prove fatal. Particularly
with the higher powers and voltages which are
coming into use in broadcasting, additional pre-
cautions are the order. One good trick is to work
on the equipment, where possible, with only the
right hand, leaving the left in the hip pocket on
that side. The logic of that is the fact that if one
is caught, the current will pass down the right
side of the body to ground, instead of through the
relatively low resistance arm-to-arm path which
includes the heart region, the great splanchnic
ganglion, and other primary
nerve centers and organs.
Secondly, never lay a hand
heavily on a portion of a
circuit which may be alive,
without first flicking it
lightly with one finger,
which will give you a chance
to disengage if there is any-
thing wrong. The same pre-
caution should be used in
connecting two wires which
may cause a short-circuit.
Incidentally, the arc follow-
ing a short circuit, if the
potential difference is not
too high, may be blown out
with a puff of breath.
Thirdly, every station
should contain red fibre
signs " Man working on
this circuit — do not close,"
or some similar formula, to
be attached to open switches
when an opera tor is working
on a "killed" circuit. These
tags should be signed, and
the rule is that no one but
the man who attached the
tag may remove it.
Fourthly, keep away from
the sets when there is a
local lightning storm. And
finally, all operators should
be familiar with first-aid
practice and methods of
resuscitation, and in the
larger stations it is a good
thing to have a drill along
these lines once a month.
KFI
ACCORDING to some-
what vague reports
experimenting with varying amounts of acous-
tic damping in the studio. They started, it
seems, with the usual idea that a studio
should be made as "dead" as possible, the
ideal studio being one with entire absence
of reverberation. This opinion is now being
modified, and the object of the experimentation
at KFI is to ascertain how much reverberation is
to be allowed for best results on the air. This
quality seems to be like salt; you don't want
much of it in the goulash, but a little is almost
indispensable.
KGO
STATION KCO in San Francisco tackled a
big job at the Municipal Auditorium,
broadcasting the oratorio "Creation," given by
the city of San Francisco with a chorus of 300,
65 players in the orchestra, and three soloists
This was possibly as big a pick-up undertaking as
any one in the West has tried. There was also
an organ, we must not forget to mention.
The space occupied by the chorus and musi-
cians was 48 by 80 feet, and the organ pipes rose
50 feet in the rear. The solution of the pick-up
problem was found in the use of condenser
microphones, which have no hiss or internal
noise, when they are in proper working order,
and can be used to pick up sounds within an
extreme range of volume. One of these mechan-
isms, about three inches in diameter and ten
inches long, was suspended twenty feet over the
heads of the performers, carrying most of the
orchestral and choral tone. A second condenser
was used for the soloists, about five feet in front
which have reached us, the
engineers at KFI have been
'HIGH TENSION EQUIPMENT . .
HANDLED GINGERLY'
MUST BE
JANUARY, 1926
WHERE SHOULD THE MICROPHONE BE PLACED?
329
of them. As the soloists stood in front of all
the other performers, this microphone was well
removed from the rest of the musicians and
singers.
By all accounts the transmission was first-
class. Even the slight rustling sound as the
audience turned the pages of the programs in
unison, while reading the words of Haydn's
masterpiece, was distinctly heard on the air.
Some years ago WEAF broadcast the "Mes-
siah" oratorio from Carnegie Hall in New York,
also turning out an excellent piece of work. And
wjz in the same city did Beethoven's Ninth and
Verdi's "Requiem" last summer, outdoors,
with an orchestra of no men, five soloists, but
with a smaller chorus — 200 in number. We
should like to hear from other broadcasters re-
garding large pick-ups they may have tried,
and their estimate of the results.
CKCO
DR. G. M. GELDERT of Ottawa, the presi-
dent of the Ottawa Radio Association of 600
members which operates CKCO out of pure interest
in broadcasting, was in New York during the
week of the radio expositions, looking over the
field and visiting the metropolitan broadcasters.
The Doctor is a prominent physician of Ottawa.
If I knew as much about cyanosis and strepto-
cocci as he knows about microphones and audio
frequency, I should feel proud of myself.
Studio Microphone Placing — Fur-
ther Consideration
THE interest shown in the problems of
microphone placing in the studio has
been sufficiently marked to warrant in-
terrupting the progress of our technical series
for broadcasters to give further discussion of
this important subject.
Among the letters received is one from Mr.
Ralph S. Hayes, of Ardmore, Pennsylvania,
"reading as follows:
While I have never had anything to do with
broadcasting, nevertheless, from a study of
speech, music, and acoustics, 1 would like to
submit some ideas relevant to the article, "Mi-
crophone Placing in Studios." (In the Septem-
ber issue.)
1 . I notice the basses and percussion instru-
ments are placed comparatively far from the
microphone. Should it not be just the opposite
on account of the fact that the bass tones are
invariably attenuated more in their transmission
through the station amplifiers and receiver
amplifiers?
2. It is a proved fact that the basses carry
much of the pleasant roundness of music — as well
as the energy.
3. The excess of energy in the lower pitches
— isn't it the usual cause of the "blasting"
mentioned?
4. Wouldn't a better placement be —
(a) microphone farther away from or-
chestra;
(b) basses closer to microphone than
trebles.
5. A possible objection to such an arrange-
ment would be carbon frying, but it either need
not be carried to such extremes, or a condenser
transmitter could be used. At any rate shouldn't
you aim toward "basses front" instead of
"basses rear?"
As to Mr. Hayes's first point, 1 believe the
general feeling among broadcast engineers is
against trying to compensate for losses of essen-
tial frequencies in the audio channels of trans-
mitters and receivers, by exaggerations in the
pick-up or elsewhere. As far as the transmitter
is concerned no such losses should be tolerated
in any considerable degree. Plenty of stations
find it possible to send out their stuff flat be-
tween 60 and 6000 cycles, and those
who haven't learned how, should
acquire that ability quickly, while
they still have an audience. As
for receivers, what degree of de-
ficiency is to be taken as a cri-
terion? In some cases the loss of
low frequencies is so complete that
a slight gain in bass at the start
wouldjnot help appreciably. Again,
just as many receivers lose the
higher frequencies as well as the
lower, passing only a band of
three octaves or so in the middle.
Following out Mr. Hayes's theory,
there is just as much reason for
emphasizing the violins at the
start in order to retain the nat-
ural quality of the treble strings
with their wealth of overtones.
This brings us to the second point.
It is true that loss of bass notes
makes music sound "tinny," "canned," and
disagreeably sharp, and strident. But drop-
ping the band from 3000 cycles up is quite
as bad. All the instruments merge into a
dull, soft, lifeless harmony, like a bad orj;an
heard with one's ears stuffed full of cotton.
Finally, receiving sets are now on the mar-
ket which are capable of reproducing sounds
sensibly as they are broadcast, and the number
of these sets will naturally increase. They are
the only safe criterion. It is obviously a saner
procedure to work with a horizontal frequency
characteristic all along the line.
Answering the third point, I believe that blast-
ing is most frequent with instruments possessing
a steep wave front. The cornet is about the worst
offender. Cutting off the higher frequencies
tends to reduce blasting. One type of carbon
microphone, which cuts off on the high end at
about 2500 cycles, is relatively free from blasting,
but the loss of intelligibility and tone brilliancy
makes the net result undesirable in high quality
work.
To point 4a, I should answer "No," for reasons
well stated by Mr. Julius Weinberger, one of
the leading electro-acoustic and broadcast engi-
neers in the East. (" Broadcast Transmitting
Stations of the Radio Corporation of America."
Proc. Institute of Radio Engineers, Vol. 12,
No. 6, December, 1924.). Mr. Weinberger
writes:
It may appear that less work would have to
be done with regard to proper placing of the
performers if the microphones were not used
relatively close up, being placed instead, for
example, at the opposite end of the studio.
In the latter case, the relative distance of the
microphone from each of the several performers
would be nearly the same and there would ap-
parently be less of a problem so far as proper
"balance" is concerned. However, it has been
found that this cannot be done for a number of
reasons. First, the farther away the microphone
is from the performers, the greater is the propor-
tion of sound which reaches it by reflection from
the room walls, compared with that reaching
it directly from the source of sound. These
reflected sounds are generally distorted, since
they not only are reflected in a variable fashion
with respect to frequency, but interference phe-
nomena occur between reflected sounds coming
from various reflection points. Thus, it is found
that the sounds as heard from a microphone
located, say, twenty feet from the source, are more
distorted than those heard when the microphone
is placed relatively close.
Secondly, the sounds reaching the microphone
must be strong enough to give an output far
exceeding the hiss due to the use of carbon,
and this again necessitates fairly close placing
with all performers except orchestras or large
choruses.
Wave
Broad \Jswe
\riXh Double Hump
FIG. I
It will be observed that I am not attempting
to controvert Mr. Hayes's idea that the bass
instruments may advantageously be moved
closer to the microphone. No doubt in some
studios something might be gained by work in
this direction. I do not believe, however, that
some of the theories on which Mr. Hayes bases
his conclusion, would work out in practical
broadcasting.
There is no doubt that the carbon micro-
phone is not .the final answer to the pick-up
problem. What is needed is an • inherently
hissless and noiseless transmitter, reasonably
flat from say 50 to 6000 cycles, if not better,
and insusceptible to blasting. Preferably, also,
it should be a low impedance instrument, so
that it can be used with a long, relatively high
capacity lead. Finally, it should be capable
of producing a voltage output comparable to
that of a good carbon microphone, which is,
incidentally, a fine amplifier in itself. Such
an outfit would simplify many of our pick-up
problems, and personally I pray for it night and
day. If someone will invent it, I hereby offer
$25 in gold, out of my own pocket, toward a
statue of the great man, to be erected at the site
of his labors, be it East Pittsburgh; 463 West
Street, New York; Schenectady; Van Cortlandt
Park South, New York, or any other place.
Radio Lingo, Past and Present
IN THE December issue of this magazine, the
writer considered the source of some of the
terminology of radio. In the group of figura-
tive expressions we considered were phantom and
dummy antennas, and the counterpoise.
Numerous figurative expressions along the
same lines will occur to the reader. We speak
of the "fading" and "swinging" of distant
signals as they vary in strength in their journey
over great distances. A reactance coil is termed
a "choke" for alternating currents. Interrupted
continuous wave signals are sent with a "chop-
per." A transmitting station has a "broad"
wave or a "sharp" wave; it is violating the
radio regulations if it has a "double hump"
or "peak." These terms are derived from
the curve of response of a wavemeter or receiver
to such a transmitter, as shown in Fig. i. The
word "wave" with its combinations, as used
in radio, is itself in the nature of a simile, for
an electric wave is some sort of displacement
or stress in a figurative medium, quite incon-
ceivable to the non-mathematical mind, and
the comparison with the waves of the sea and
other material wave motions is simply a con-
venient but rather inaccurate means of tuition.
The same hydraulic analogy persists when we
330
RADIO BROADCAST
JANUARY, 1926
refer to wave "filters" — networks of resistance,
inductance, and capacity which allow only a
certain "band" of frequencies to pass. But
we are also familiar with wave "traps," used to
eliminate a narrow range of frequencies, and
here apparently we think of the wave as a small
animal — a rat or mouse — while when we speak
of "carrier" waves or "carrier" telephony the
wave has become a beast of burden. The term
"trap," incidentally, is one of those ubiquitous
comparisons which can be found in almost every
trade; the bend in a drainpipe to prevent gases
coming back along the tube is called a "trap"
by plumbers, for example.
The "regeneration" of Armstrong is a dis-
tinctly figurative term, carrying a theological
connotation, although it was used in connection
with gas engines and other prime movers long
before the vacuum tube was invented. There is
also a physiological reference in the name "tick-
ler" applied to a "feed-back" inductance in the
plate lead of the amplifier-rectifier tube of a
receiving set. The early workers in this field
must have been struck by the extraordinary
increase in volume as the tickler coupling was
brought up, and the sudden break into oscil-
lation; and they compared these phenomena
to the peculiar spasmodic reactions of human
beings to a tickling stimulus. Nor must we
overlook the word "feed-back" in this con-
nection. Why should we speak of the oscil-
lations in the plate circuit as being "fed" back
to the grid, instead of merely saying "brought"
back? This figure has a practically universal
utility. It is used in transportation, in reference
to railroads and waterways, as, the Morris Canal
Feeder. In communication, as "feeder" tele-
graph offices. In electrical engineering —
"feeder" conductors, generating stations, etc.
In sport: basketball players speak of "feeding"
a team-mate when he is in position to shoot for
the goal. And it is all based on the nutritional
instinct, of course, and the comparison is wide-
spread because that instinct is shared by all
living creatures.
It is hardly possible to go through the list
of metaphorical expressions which have invaded
the radio field, but a few more typical ones may
be mentioned briefly. Electricians talk of
"juice," apparently a survival of the early
fluid theories of electricity. The flow of high
frequency oscillations on the surface of a con-
ductor is called "skin-effect." Irregular inter-
ference of arc transmitters on low wavelengths
is termed "arc-mush." Transient interference
with radio reception, both natural,
as from lightning, and artificial, as
from arc lamps, lightning circuit
grounds, sparking commutators,
etc. is referred to as "strays."
We talk of "shielding" a panel
with metal. Spark interference is
"jamming," a graphic expression
which originated in the English Channel, although
familiar in a related sense to the riders in the
New York City subways during the rush hours.
(To Be Continued)
Memoirs of a Radio Engineer,
VIII
IN OUR last issue I gave a brief account of
the Titanic tragedy of 1912. For some
days after the disaster all was confusion.
Commercial stations and ships interfered with
each other, some of the amateurs, it was charged,
interfered with commercial stations, and no
reliable list of survivors could be obtained. As
the Carpathia neared New York with the sur-
vivors, communication improved, and the names
came through in the rescue ship's mournful 60-
cycle spark. Most of the shore copying was
done, 1 believe, by the Wanamaker station, WHI.
The amateurs shut down voluntarily, setting a
good example which they have followed on other
occasions since that time, although now, with
commercial and amateur wavelengths so far
separated, the necessity for it has disappeared
as far as sos calls are concerned. They listened
on their double-slide tuners and loose couplers
to the long fateful strings of names. The com-
mercial operators worked heroically, some of
them standing continuous watches until they
were ready to drop.
I have referred before to the anarchy which
prevailed in the ether lanes in those days.
Everybody transmitted on any wavelength
which pleased him, or, for that matter, without
knowing what his wavelength was or giving
any signs that he cared. Amateurs interfered
with paid commercial traffic, and refused to
shut down when sworn at in code. Profanity
on the air was the rule rather than the exception.
The caution of Y. M. C. A. broadcasting phrase-
ology was as yet unknown. Call letters were
self-assigned, according to fancy; initials were
used, or simply what was known as a "good"
call — one that had a pleasing rhythm and lilt
to it in the Continental or American Morse
code. Both codes were used, with American
Morse as yet more prevalent. The Britishers
used Continental, and there was a strong
prejudice against it among the Americans.
Morse, with its spaced letters, such as c (two
dots, space, dot) was harder to copy than Con-
tinental, but faster, and the Morse operators
were very contemptuous of the newer symbols.
The New York Herald, which maintained a
wireless station, OHX, in connection with its
excellent shipping news department, sent press
every night at 9 o'clock, first in Morse, then in
Continental, but traffic was generally sent in
Morse, and my recollection is that the election
returns of November. 1912, were sent in Morse
only. All this confusion could not last. Soon
after the Titanic catastrophe, the government
took hold. In 1910 a law had already been
passed providing for radio equipment on certain
steamers. This was not taken very seriously
until 1912, when it was amended to apply to
all vessels licensed to carry fifty or more persons
on the ocean or the Great Lakes, and to provide
for auxiliary apparatus covering failure of the
main set, continuous watches, and penalties in
case of failure to observe the law. A little
later, on August 13, 1912, the Senate and House
of Representatives passed "An Act to Regulate
Radio Communication," under which the present
licensing system for stations and operators was
instituted. By an international convention
signed at London on July 5, 1912, and ratified
by the United States Senate early in 1913,
initial call letters were allocated to the several
nations. Those two years, 1912 and 1913, were
the great legislative years of radio. In fact,
so much legislation went through that this
country has not experienced any since, and has
gone twelve years without altering the radio
laws themselves. What adjustments have been
made the Department of Commerce has taken
care of by regulations under the administrative
power which it was granted by the law of August,
1912.
These momentous changes percolated down to
even the lowest strata of amateurs. Some of
my friends lost their call letters. Such amateur
calls as MHS, NSE, DSE, su, JR, AY and, YF, became
taboo. M calls belonged to British stations;
D was allocated to the Germans; N to the Ameri-
can Navy. Amateurs were to be licensed, and
to receive calls beginning with numbers, de-
noting the radio district in which the applicant
happened to find himself. All stations, from the
largest down to the most insignificant which
might interfere with reception over a State line
(the necessary limitation of Federal authority),
were subject to the new regime. It was like the
lines in the Agamemnon:
None who was mighty then, and none so small
But in the sack of doom is borne away.
All the amateurs, formerly so
reckless and carefree, went about
with worried faces, wondering if
they could pass the examination,
and trembling in fear of a new
ogre, the Radio Inspector.
(To be Continued)
'THE AMATEURS . . . TREMBLED BEFORE A NEW
OGRE— THE RADIO INSPECTOR"
Being the Study of Several of the Most Popular and Most Efficient Circuits for
Home Construction With a View to Adapting Them to Fit Our Individual Needs
By ARTHUR H. LYNCH
H
'AVE you noticed that within
the past few months the new
Flexes, Dynes, and Supers
described in the radio press
have been extremely conspicuous by their
absence? For some time, the passing of
the trick circuit and its capitalization by
the crafty and sometimes not too scrupu-
lous publicist and manufacturer has been
considered, by those who really understood
the radio business, as a foregone conclusion.
In passing on this interesting angle of the
radio business, some of the older readers of
RADIO BROADCAST will recall Zeh Bouck's
article, entitled "The Truth About Trick
Circuits" which appeared in our March,
1924, number. Some others may remember
that we defended ourselves successfully in
a libel suit for $100,000 which was brought
against us as a direct result of the publica-
tion of this article and our refusal to make
public apology for the things we said.
We hope that article was instrumental in
bringing about the situation with which the
radio parts business is now blessed. Cer-
tainly, it is in better shape now than it has
ever been before, even though there are
those who would have us believe that,
because the business in completed receivers
has flourished so greatly, there is little or
no parts business going on.
And before going directly to the subject
at hand, perhaps a few words about the
parts business will be of interest to the
home constructor and others. On the
magazine, we are in direct contact with
thousands of the listening public by mail
who express their likes and dislikes to
us in no uncertain terms. Through our
short wave transmitting station in our
Laboratory at Garden City (2 GY) we
are in direct communication with amateur
radio enthusiasts in all parts of the world.
Many manufacturers avail themselves of
our laboratory services and from them we
learn much of what is going on in their
particular fields. Then, too, our labora-
tory has been chosen to pass on the quality
of the products radio manufacturers desire
to advertise in The World's Work, The
Atlantic Monthly, Harper's Magazine, Review
of Reviews, Scribner's Magazine, and
Country Life. From these contacts, we
come in still closer contact with many
sides of the radio business.
There has been a considerable slackening
.00025
mfd.
DETECTOR
off of the general parts business and there
is no contradicting that fact. There are
far fewer varieties of parts now to be had
than there were a year ago. Allah be
praised for that! Much of the older kind
of parts business was little more than
traffic in junk. Much of the junk has now
been cleared out and it will not be long
before the rest will have found its way to
the scrap heap. Many of the junk dealers,
who, a few months ago, believed themselves
to be in the radio parts business have
gone broke or have gone back to their
old jobs, whatever they were. The parts
merchant of to-day and to-morrow is not
the fellow who attempts to unload a lot
of radio jimcracks on credulous but mis-
informed radio buyers, but he is rather
the man who understands the reason for
every part he sells and is able to render
the home constructor the sort of service he
is reasonably entitled to expect. If more
dealers would study some of the existing
radio circuits and determine from actual
performance just which is suited to their
particular needs and then have samples
made, which could be displayed in their
stores and operated if need be, they would
SECOND
AUDIO STAGE
Loud Speaker
Jack
FIG. I
This is the circuit diagram of the Universal Receiver. It consists of one stage of tuned radio-frequency amplification utiliz ing the Rice method of
neutralization, a regenerative detector, and two low ratio stages of audio-frequency amplification. The wiring of the assembled receiver takes the
same form followed in this diagram. For instance, the lower terminal of the radio frequency coupling unit is the lower end of L4 in the diagram
332
RADIO BROADCAST
JANUARY, 1926
OH SUPPORTS
Matenai Bras^Bafcelne or wood ,
2 Required
U.-V-H
Hole
T
'jf
,No 18 Hole
*
;rv1
NEUTRALIZING CONDENSER
SUPPORT
Material Brass
1 Required
©
ANTENNA COIL SUPPORT
Material -Brass Strip i}*1 l/"
1 Required
FIG. 2
The dimensions and other specifications for the
angles and other hardware used to assemble the
receiver are given here. In the case of the bush-
ings, bakelite or wood will do as a substitute for
brass
find a harvest in the parts business far
beyond their most optimistic expectations.
In fact, those dealers who are following
this plan, and there are a great many of
them, are finding the parts business to be
anything but dead.
Every home constructor is actually a
HOW THE SET STARTED . . .
The embryo "Universal." By laying out the parts on the base-board, it was possible to experiment
with changes in location of the various coil and condenser units to observe any improvement in
results obtained. This system of experimental construction is to be highly recommended
t
i
-e-
f
No 18 Holes foi Mounting
«...
-f
Bue to Supports
V?
rf>
*r
1
-i V
•t
4
i I
Y
t'
j
,
,- ,
M*un»l k'wgod
radio salesman in his neighborhood. If
his receiver works well, and homemade
receivers usually do, the builder generally
proclaims from the housetops, first the
wonders of his outfit and then the wonders
of radio in general. Many of his auditors
wouldn't give a red apple to duplicate his
accomplishment, but many of them would
like to be able to hear the things he hears
and the rapid growth of the radio business
to-day may well be credited to the home
constructor.
FIG. 3
The baseboard layout. Especial care should be exercised in
cutting out the section to be removed so as to prevent splitting
the wood. The use of this type of baseboard insures easy
assembly and wiring
r
No. 18 Hole'
dU-No.18
Hole
space m
THE PROBLEM
ALL of the foregoing was
brought to mind by a.
moment's consideration of the
problem at hand and our rea-
sons for dealing with the sub-
ject of the universal receiver.
First of all it was necessary for
us to determine on a particular
circuit. It is almost impos-
sible to think of circuits at all
without thinking of all the
dynes and whosits and so forth
which were given so much free
the newspapers a few short
tried and true circuits, so the matter of
selecting the proper one for our individual
use, is not such a difficult job, even for
the uninitiated. There are many we could
attack and use to good advantage, but
when all the smoke has cleared away
and the shouting is all over and we get
back to a peace time basis, there is but one
real type of circuit which may be called
universal and that is the combination of
one stage of tuned, neutralized radio fre-
quency amplification, a regenerative de-
tector and some kind of audio-frequency
amplifier which will produce good quality.
To explain the kind of a circuit we are
describing, each time we have some varia-
tion of this circuit to contend with is indeed
embarrassing and the name "Universal"
is about as near the correct characterization
as we have been able to find.
All No.18 Holes
months ago. Most of them have met
a natural death. There remain but a few
--------------- 10 ^ -------------- •*!
FIG. SA
This is the layout for the binding post terminal
strip. Bakelite, hard rubber, or formica f"s-
inch thick is satisfactory for use here
No.18
Hole
SUB-BASE SUPPORTS
Material:- J$'x \& Strip Brass.
2 Required
FIG. 4
Two brackets, made as shown here, support the
baseboard assembly. Approximately 32 inches
of 5 x i*s-inch strip brass are required to make
the two brackets
See F,g.3
.Bracket
terminal strip'1
SeeFig.4
SeeFig.5A'
FIG. 4A
The baseboard is mounted on the brackets and
panel in the manner shown above. Two brackets
for the terminal strip are required. The vertical
part is 1 1 inches long and the hole for the strip
is located i of an inch from the bottom
1_
Hoie
5V'
^ Hole J*
Hole
M» Holes -
--- 3"
——3% —
-r-4
•18-
.JL
FIG. 5
The panel layout. Only center holes are shown so as to enable the builder to use parts that he may
have on hand which differ in make from those recommended. In any case, before these center holes
are drilled it is well to spot off the other mounting holes
JANUARY, 1926
RADIO BROADCASTS UNIVERSAL RECEIVER
333
FIG. 7
Here Is a view of the Universal employing the new ux sockets. With this arrangement there is a generous spacing of the parts and it is possible to
employ any of the ux type of tubes such as the ux-igg, ux-2Oi A, wx-12, or ux-i 12 tubes in these sockets. The advantage of building the receiver
with these sockets is apparent as there is not the necessity for using adapters when other voltage tubes are to be employed. Leads are short and direct.
another obvious advantage
DETECTOR CIRCUIT
8»90 B»45to67
Volts
FIG. 6
This is a picture of the Universal receiver employing, in the main,
General Radio Company parts. Standard uv type sockets are provided.
This allows the use of either the ux or uv2oi A type of tube in this set.
Note the position of the neutralizing condenser between the first two
sockets at the right. The grid leak and Amperite mountings are easily
accessible if replacement ever becomes necessary. The binding post
terminal strip serves also as a support for the rear of the wooden sub-
base
FIG. 9
Still another highly
efficient way in which
to control regeneration
by a variable resist-
ance. It is necessary
to experiment with dif-
ferent values of capac-
ity shunted across the
resistance to obtain
smooth control of re-
generation. Such re-
sistance units as the
Bradleyohm No. 10,
the Centralab, and the
Royalty may be em-
ployed successfully
T ©
FIG. 10
With the use of the cut-out baseboard, the wiring and assembly of the
parts employed in the construction of the receiver is made amazingly
simple. Unlike a bakelite sub-base it is possible to screw down on to
the wood the sockets, transformers, and other material without previously
drilling it to admit the screws
FIG. 8
Several systems of regeneration which may be incorporated in the circuit of
the Universal receiver. In A, the resistance R shunts the tickler coil which
is closely coupled to the secondary. This system is employed in the receiver
described. Regeneration is obtained and then controlled by varying the
resistance. In B, a condenser feedback system is employed which will func-
tion remarkably well when care is taken to include in the circuit a suitable
r. f. choke-coil. In C is shown the usual tickler feedback system. When
General Radio coils are used in the receiver and it is desired to employ
tickler feedback, a mechanical arrangement must be provided so that the
tickler may be coupled to the secondary of the detector coil unit. This
puts another control on the panel
334
RADIO BROADCAST
JANUARY, 1926
A circuit which would perform
satisfactorily in city and coun-
try on dry cells or with a storage
battery, without wasting B bat-
teries, which would give more
than ordinarily good quality of
reproduction on a loud speaker
over comparatively long dis-
tances, which was easy to build
and easy to operate after it was
built, and, last, but not least a
circuit for which the parts could
be procured in any town of any
size in any part of the world; that
was our notion of what the " Uni-
versal" should be. We believe we have
found it. It is not a new circuit, by any
manner of means. Fundamentally it was
used in slightly modified forms in such pop-
ular receivers as the Teledyne, the Browning
Drake, The Roberts, RADIO BROADCAST'S
Four-Tube, Three-Tube, and Two-Tube
Knockout Receivers. Hammarlund-
Roberts, RADIO BROADCAST'S Aristocrat,
the Samson T. C. Receiver and the Silver
Knockout. But since the appearance of
most of these receivers in RADIO BROAD-
CAST, improvements have been made in the
design of many of the integral parts and
this improvement is particularly evident in
the matter of tubes.
In order to show how various parts may
be used in this circuit with satisfaction,
we are illustrating with this article, a
receiver employing just about the same
circuit and sold in kit form by the Samson
Company of Cambridge, Massachusetts,
and another built to our desrgn by the
American Mechanical Laboratories of
Brooklyn, New York. Other variations
on the same theme may be seen by looking
over the article by Allan T. Hanscom in
our October, 1925, number and the descrip-
FIG. I I
A panel view of the Universal. Symmetrical layout has been one
of the prime considerations in the construction of this receiver.
tion of RADIO BROADCAST'S "Aristocrat,"
by the present writer, in our November
number. We are very anxious to have the
fact understood that intelligent substitu-
tion of parts for those we have used will
not detract from the performance of the
receiver. It is impossible for us to list
all those which can be used, but we wish
to show no favoritism in the matter of
recommending parts for the RADIO BROAD-
CAST Universal Receiver.
So, then, as an example of what may be
done, let us first consider the circuit and
then the components of a single manufac-
turer which may be used to advantage in
it. From a study of Fig. i it will be seen
that there are two coil assemblies, one, a
primary and secondary in the antenna
circuit (L, and L2; the latter tuned by the
variable condenser C,) the other, a tuned
radio-frequency transformer of the auto
transformer type and a tickler coil, which is
fixed in position but adjusted electrically
by means of the 500- to jo.ooo-ohm
resistance, Rj shunted across it. These
coils are indicated in the diagram by L3 and
L4. By properly using the windings already
provided on the General Radio Company's
coils, No. 2770, both these coil
units are instantly provided. No
changes whatever need be made
as the coils are of solenoid type
with two windings on a single
form. Two such forms are nec-
essary. On each form there is a
small and a large winding. The
small ones are used for L and L4
while the large ones are used for
L, and L3. The tap indicated on
L3 is easily provided by picking
up a turn of the large coil, and
scraping clean . 1 1 is merely nec-
essary to solder the proper wire
to it to carry out the correct circuit ar-
rangement. In LI this tap is made 39
turns from the grid end and the tap on L-,
is made in the exact center of the coil.
These coils may be used with .00035 mW-
variable condensers to cover the broadcast
frequency range and the results obtained
in our laboratory tests of the completed
receiver indicate that they will go well be-
low the lowest and well above the highest
frequencies transmitted by the broadcast-
ing stations now on the air. Let us now
consider the remainder of the parts used
for storage battery operation and once hav-
ing done that we will study the few changes
necessary for using the same circuit ar-
rangement with dry cell tubes.
PARTS USED IN R. B. LAB MODEL OF THE
UNIVERSAL RECEIVER
THE parts employed are: i Panel, 7x 18,
i Wood sub-base 7 x 17^, cut as shown
in Fig. 3 and for simplicity of mounting
and wiring we recommend the use of wood
not more than ^ inch thick, 2 sub-base
supports, made as shown in Fig. 4, from
\ x -jV inch brass strip (the approximate
length of this strip required for the re-
FIG. 12
A base view of the receiver. Note that the coil units are in line with and at right angles
to each other. This is absolutely necessary for obtaining proper neutralization
JANUARY, 1926
RADIO BROADCAST'S UNIVERSAL RECEIVER
335
In this end view the use of other brackets is
Ehown. The builder may use either type accord-
ing to his own desires
ceiver is 32 inches); 2 Detector coil sup-
ports, as illustrated in Fig. 2A; i Antenna
coil support, as shown in Fig. 28; i Neu-
tralizing condenser support, as shown in
Fig. 2C; i Royalty, 500- to 5O,ooo-ohm
variable resistor; i each Electrad, .00025-
.002- and .oooj-mfd. fixed condensers, and
the following General Radio parts: 2
coils, type 2yyD; 2 variable condensers
with vernier attachment, .00035 mfd.
capacity, either S.L.W. or S.L.C., type
247?; 2 Dials type 310; i neutralizing
condenser, type 368; 2 audio-frequency
transformers, 2:1 ratio, type 285!.; 4
sockets, type 156 for use with tubes having
uv base, or type 349 ux sockets for tubes
with t'x bases, as explained further along;
i binding post strip, with 8 posts, type
I38Z; 2 rheostats, 10 ohms, type 301;
i Yaxley filament switch and phone jack
and one Electrad grid leak resistor, 2
megohm; and the large \ to i mfd. con-
denser across the B batteries is optional,
but advisable. One each \ and \ ampere
Brach or Amperite filament ballasts and
mountings.
BEFORE BUILDING THE RECEIVER
TO BEGIN with, the combination which
we have found to meet nearly every
occasion, except where the storage battery
is impossible for one reason or another,
is the circuit in which 201 -A type tubes
are used in all sockets except the output of
the amplifier and here we have found
the ux-ii2 very satisfactory, when oper-
ated with 135 volts on the plate and a
negative bias of approximately minus 9,
as shown in the diagram, Fig. i With
this arrangement, using the proper plate and
biasing voltage (B and C) on the radio fre-
quency tube as indicated in the same
diagram the plate current consumption
is in the neighborhood of five milliamperes
and should not be above seven. The
ux-ii2 will increase this figure somewhat.
This sum is very low for a receiver of this
general type and is one of the outstanding
features of the RADIO BROADCAST Univer-
sal. If your receiver is to be located more
than fifty miles from a broadcasting station,
you may find that one low and one high
ratio transformer will give you more
volume and in such cases it is advisable to
use it. It should not be more than 6:1,
however. If this combination of trans-
formers is to be used, be suYe the high ratio
transformer is used last and not first as is
common practise. The reason for this
change is well covered by Mr. Keith
Henney, Director of RADIO BROADCAST'S
Laboratory, in his article, Tubes: Their
Uses and Abuses, in our last number.
The matter of sockets is a rather im-
portant one, in view of the great number
of tubes already on the market and those
which will probably follow. We have
found that the standard socket is just
about as satisfactory at the present time
as any, because the standard tubes will
fit in them and so will the tubes with the
new ux bases. Where either the WD-I i
or the uv-igg types
of tube are to be used,
they may be placed in
the standard sockets
by means of adapters.
So much, for the
receiver, when the
tubes to be used are
those with which we
have become quite
familiar.
Now for the dry
cell operation. We
have found the com-
bination of three 199
and one 120 tubes,
or their equivalent, to
be very satisfactory and, if you contemplate
the building of this receiver without using
any of your present stock, we suggest that
you use the new type of socket because it
may be used with any of the new tubes and
it will be remembered that both these
tubes are soon to be on the general market
with the new ux bases, and by using the ux
sockets, it will be possible to convert
your receiver from dry battery operation
to one which may be used with a storage
battery by going to no greater bother than
changing the tubes. Many of the inde-
pendent tubes have been found to be very
satisfactory and most of them will be on
the market within a short time, probably
before this article gets into circulation,
with the new type bases. In order that
you may have a direct comparison of the
two types, we illustrate in Figs. 6 and 7,
just how they will look when completed.
The proper use of any type of tube in
any receiver is one of the greatest factors in
determining its performance and we can
not urge too strongly the careful reading
and then putting into application the in-
struction sheets which accompany the tubes
now on the market.
BUILDING THE RECEIVER
AFTER procuring all the necessary
parts and properly bending and drill-
ing all the brass fittings and the wood sub-
base, the drilling of the panel can be under-
taken and the layout shown in Fig. 5
FIG. 14
This view of the rear of the Universal gives a pretty good idea of the
disposition of the various parts. In this particular receiver, larger tun-
ing condensers have replaced the .00035 mfd. variables. However, for
the broadcast range the .00035*5 are entirely satisfactory
will be found helpful in this connection.
Next, all the parts which are to be directly
attached to the panel should be put in
place as should those which are to be
attached to the sub-base. From this point
on, the work of assembly is a very simple
matter and it is but necessary to fasten
the sub-base and the panel together by
means of the brass supports and attach
the binding post strip, which acts as the
rear support for the receiver and then go
ahead with the wiring. The dimensions
of the entire assembly are such that the
completed receiver will fit into a standard
7 x i8-inch cabinet and the use of a cable
lead to the batteries is handy and is
FIG. I 5
So much equipment in such small space is, in itself, an accomplishment. This layout of the Samson
TC Receiver is a little difficult to approximate but when you have it finished it's a real receiver.
The tests run on it in our laboratory revealed it as one of the best receivers we have ever used. It
is compact, easy to handle, economical to use and the tone quality is far above the average. On
the second stage audio it performs very well with a cone speaker which is saying much for a
transformer-coupled audio receiver
336
Hard Rubber
or Bakelite
To keep radio frequency currents where they are
useful, a choke coil is shown in use in Fig. 8B.
Such a coil is illustrated above and may consist
of No. 30 wire wound 100 turns to the slot.
With such a coil the feed-back condenser may
be a small " midget " condenser
recommended. Furthermore, the dimen-
sions on the sub-base are large enough to
allow the use of any sockets or transformers
now on the market, without making
necessary any changes in design.
Perhaps there are those who would like
to improve on the general design of this
receiver in one way or another and the
point which might well be expected to be
attacked is the control of regeneration by
the resistance across the tickler. Some of
the attempts at this which were made in
our laboratory, during the development
of this receiver are indicated in Fig. 8, but
for a number of reasons we have found the
system finally employed here to be most
practicable with the type of coils employed.
Since the inductive relation of the tickler
to the secondary of the radio-frequency
transformer, that is coil L4 to coil L3, is
always the same there is no change in wave-
length or detuning in the radio frequency
circuit, which is sometimes noticeable to a
marked degree in receivers where a tickler
of the rotary type is employed. Then,
too, the number of moving wires and the
breaking of connections they sometimes
cause has been eliminated and with the
proper detector plate voltage and the proper
RADIO BROADCAST
variable resistance, the control of regenera-
tion is remarkably smooth, which is a
distinct advantage.
CONDENSER FEED BACK
A VARIATION of the resistance control is
•*>• the condenser feedback, probably due
to Weagant and used commonly in the
Reinartz circuit. A fixed coil is placed near
the detector secondary and coupling to the
plate is effected by means of a series con-
denser. The condenser and coil is then a
shunt path for the radio frequency currents,
and a choke coil may be necessary to keep
these currents from escaping through the
phones or amplifier primary. The circuit
is shown in Fig. 8B and a drawing of a choke
in Fig. 1 6. There should be no condenser
across the output in this arrangement. This
method of adding regeneration is partic-
ularly smooth in operation, and it avoids
the movable tickler with its varying field.
And now there is little to do but the
soldering and wiring. Wherever possible,
the home constructor should fit himself
out with a good soldering outfit, and a set
of those small wrenches which comes in so
handy in getting the nuts on and off trans-
formers, tube sockets and such places.
He should have a good supply of bus bar
and spaghetti or flexible rubber-covered
wire and a goodly supply of small sized
lugs which may be directly fastened to the
various units which go to make up the cir-
cuit and to which the soldering is actually
done, rather than to the units themselves.
By using this method of construction, it
is possible at any later time to remove
the holding nuts and off comes the wire
with no fuss whatever. Then it should
also be remembered that a good small
screw driver is valuable in placing the
soldering lugs under the heads of the screws
in those units provided with screws instead
FIG. 17
A typical example of the Universal circuit worked into the small dimensions of RADIO BROADCAST'S
Phonograph Receiver. A Hanscom single-control unit with model 2 RK Clarotuner coils provides the
tuning system, and the sub panel with special sockets was supplied by Osborne & Company of
Boston to our dimensions. Note the freedom from visible wiring
JANUARY, 1926
of binding posts, and there are a great
many of them on the market. That's
about all there is to the building, and now
we come to the point of putting our prize
on the air.
OPERATING THE UNIVERSAL
THE antenna used with RADIO BROAD-
CAST'S Universal Receiver should be
about 1 50 feet long, from the receiver itself
to the outside insulator, including the
length of the lead-in wire. With such an
antenna, if you are located within 25 miles
of a powerful broadcasting station you may
find that the receiver is not selective enough
to permit you to cut out the local station
and bring in distant stations on frequencies
near that of the local. This objection
may be overcome by inserting a .oooi-mfd.
fixed condenser in series with the antenna
or by reducing the length of the antenna a
little. The former method is easier and
usually more effective.
It will be found that the two dials will
run just about even over the entire scale,
if they are properly set when they are
attached to the shafts. If the wiring is
correct the receiver should respond as soon
as it is put on the air, if there is any broad-
casting going on. The only adjustment
other than that which usually characterizes
tuning is the setting of the neutralizing
condenser and that is a simple matter,
which once taken care of need cause no
further worry. In order to set the neutral-
izing condenser properly, some broad-
caster whose frequency is about 1000 kc.
(300 meters) and whose volume is not very
great should be tuned-in with the detector
oscillating. The detector condenser should
be tuned until the whistle from the station
is quite loud. Then the first, or antenna,
condenser, should be tuned. It will be
noted that the whistle will change in pitch
as this condenser is varied. When the
set is exactly neutralized, this whistle
will not change, and the problem is to
adjust the neutralizing condenser until
such a state of affairs exists. The neutral-
izing condenser should be varied a little
at a time, each time noting the change in
pitch of the whistle. On one side of the
neutralization point, the pitch will rise in
frequency; when the neutralizing point
has been passed, the pitch will lower in
frequency. By listening for these changes
in pitch, the listener can tell on which side
of the actual balance point he is.
The usual method of turning out the
first tube and adjusting the neutralizing
condenser until no sound is heard is not
satisfactory. The grid-plate capacity of
tubes differs by a large factor in the two
conditions of tube unlighted and tube
lighted. In other words, the tube wiH
not be neutralized when it is lit if it is
balanced with the filament turned out.
It should be neutralized under actual oper-
ating conditions.
A more practical all-round receiver than
RADIO BROADCAST'S Universal will be hard
to find.
JANUARY, 1926
RADIO BROADCAST
337
MILES
FROM TO— >
Atlanta, Ga ...........
Baltimore, Md ........
Birmingham, Ala ......
Buffalo, N. Y .........
Calgary, Alta ..........
Dallas, Tex ...........
Davenport. la .........
Denver, Colo ..........
Des Moines, la ........
Elgin. Ill .............
Galveston, Tex ........
Hastings, Neb .........
Havana, Cuba ........
Houston, Tex .........
Indianapolis, Ind ......
Iowa City, la .........
Joliet, 111
Kansas City, Mo
Lancaster, Pa .
Lansing, Mich
Lincoln, Neb
Los Angeles, Cal
Louisville, Ky
Madison, Wise
Memphis, Tenn
Mexico City, Mex
Miami, Fla
Milwaukee, Wise
Minneapolis, Minn ....
Montreal, P. Q
Oakland, Cal
Ottawa, Ont
Providence, R. I
Rochester, N. Y
Salt Lake City, Utah. . .
San Francisco, Cal
Schenectady, N. Y
Scranton, Pa
Seattle, Wash
Shenandoah, la
Springfield, Mass
Tampa, Fla
Toronto, Ont
Valparaiso, Ind
Vancouver, B. C
Washington, D. C
Winnipeg, Man
Worcester, Mass
Zion, 111
930
350
1050
400
20HO
1515
990
1750
1135
870
1585
1400
1500
1575
790
1045
870
1225
310
680
1320
2560
815
925
1120
2300
1280
840
1110
260
2650
315
40
340
2070
2650
145
240
2500
1240
80
1160
440
815
2500
390
1350
40
850
590
600
580
450
1370
800
160
900
300
35
945
560
1315
925
160
200
35
400
600
170
465
1730
270
120
480
1675
1180
80
360
740
1820
640
825
500
1245
1820
700
615
1710
400
760
1060
425
45
1760
590
710
800
45
375
420
415
395
1620
795
360
1080
500
280
880
740
1100
875
100
405
250
545
430
240
650
1875
90
370
410
1600
950
320
590
700
2000
620
700
450
1440
2020
600
490
1950
590
645
775
400
200
2000
400
970
700
285
J_
550
315
615
175
1645
1000
455
1200
605
335
1100
865
1250
1085
255
505
330
690
295
170
775
2020
300
405
620
1800
1085
335
620
490
2115
410
525
240
1550
2140
400
315
2000
700
460
925
190
270
2040
300
940
500
320
595
405
640
215
1555
990
390
1140
540
260
1090
795
1325
1080
230
435
260
640
390
85
700
1950
310
325
615
2120
1150
255
545
515
2030
425
585
280
1475
2065
460
390
1920
635
525
985
200
210
1950
390
850
570
240
745
170
855
295
2000
1350
860
1600
1010
740
1400
1265
1300
1400
630
900
730
1080
130
550
1175
2420
645
800
950
2115
1100
725
1005
335
2500
335
150
250
1950
2540
150
100
2400
1110
120
1000
350
670
2400
200
1295
155
720
IE
660
85
775
280
1200
1280
800
1550
965
690
1315
1215
1270
1310
575
860
680
1025
65
520
1120
2360
570
760
870
2035
1025
690
980
400
2490
380
235
260
1900
2500
210
105
2385
1050
200
930
340
625
2385
125
1275
235
675
il
0. 03
520
200
610
180
1755
1060
560
1310
710
440
1125
965
1215
1120
325
600
430
775
200
280
875
2110
345
520
655
1860
1010
450
750
470
2240
410
450
225
1650
2240
350
230
2115
800
395
870
225
370
2150
190
1050
435
420
470
730
400
655
1950
540
200
775
265
255
690
445
1165
660
230
210
225
230
750
400
365
1565
245
300
240
1420
1050
325
465
970
1705
875
1000
720
1145
1715
900
790
1695
310
960
855
640
255
705
845
985
290
Sixteen
RADIO BROADCASTS
Booklet of
and
Canadian
Broadcasters
December 15, 1925
CALL
SIGNAL
WSAI
WSAJ
WSAN
WSAR
WSAU
WSAV
WSAX
WSAZ
WSB
WSBC
WSBF
WSBT
WSDA
WSKC
WSM
WSMB
WSMH
WSMK
WSOE
WSRF
WSRO
WSUI
WSY
WTAB
WTAC
WTAD
WTAF
WTAG
WTAL
WTAM
WTAP
WTAQ
WTAR
WTAS
WTAT
WTAW
WTAX
WTAY
WTAZ
WTG
WTHS
WTIC
WWAD
WWAE
WWAO
WWGL
WWI
WWJ
WWL
LOCATION
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
Mason, Ohio
Grove City, Pa
Allentown, Pa
Fail River, Mass
Chesham, N. H
Houston, Tex
Chicago, 111
Pomeroy, Ohio
Atlanta, Ga
Chicago, 111
St. Louis, Mo
South Bend. Ind
New York, N. Y. (Shortly to re-open)
Bay City, Mich
Nashville, Tenn
New Orleans, La
Owosso, Mich
Dayton, Ohio
Milwaukee, Wis
Broadlands, 111
Hamilton, Ohio
Iowa City, la
Auburn, Ala
Fall River, Mass
Johnstown, Pa
Carthage, 111
New Orleans, La
Worcester, Mass
Toledo, Ohio
Cleveland, Ohio
Cambridge, 111
Osseo. Wis
Norfolk, Va
Elgin, 111
Boston, Mass, (portable)
College Station, Tex
Streator, 111
Oak Park, 111
Lambertville, N. J
Manhattan, Kan
Flint, Mich
Hartford, Conn
Philadelphia, Pa
Plainfield, 111
Houghton, Mich
Richmond Hill, N. Y
Dearborn, Mich
Detroit, Mich
New Orleans, La
920 325.9 5000
1310 229 250
1310 229 100
1180 254 100
Ceased activities October, 1925
1210 248 100
Ceased activities June, 1925
1230 244 50
700 428.3 1000
1430 209.7 500
1100 273 250
1090 275 250
1140 263 250
1150 261 100
1060 282.8 1000
940 319 500
1250 240 10
1090 275 500
1220 246 500
1290 233 10
1190 252 100
620 483.6 500
1200 250 500
1130 266 10
1120 268 100
1270 236 50
Call signal changed to WOWL
1120 268 500
1190 252 10
770 389.4 2500
1240 242 50
1180 254 100
1150 261 100
Call signal changed to WLIB
1230 244 100
1110 270 250
1300 231 50
Call signal changed to WGES
1150 261 15
1100 273 50
Ceased activities October, 1925
860
1200
1240
1140
1410
1130
850
1090
348.6
250
242
263
212.6
266
352.7
275
500
100
500
250
500
500
1000
100
To make these pages into a booklet, cut through the center, horizontally along the
rule, and along the outside of the page. It will then be easy to fit the pages in or-
der, as numbered. They may be bound with a pin or sewed with several stitches.
Fourteen
CALL
SIGNAL
KFJB
KFJC
KFJF
KFJI
KFJM
KFJR
KFJX
KFJY
KFJZ
KFKA
KFKB
KFKQ
KFKU
KFKX
K.FKZ
KFLB
KFLP
KFLR
KFLU
KFLV
KFLX
KFLZ
KFMB
KFMQ
KFMR
KFMT
KFMW
KFMX
KFNF
KFNG
KFNJ
KFNL
KFNV
KFNY
KFOA
KFOB
KFOC
KFOJ
KFON
KFOO
KFOR
KFOT
KFOX
KFOY
KFPG
KFPL
KFPM
KFPR
KFPV
KFPW
KFPY
KFQA
KFQB
LOCATION
FREQUENCY
WAVE-
LENGTH
POWER
Marshalltown, la.
Junction City, Kans.
Oklahoma, Okla. . .
Astoria, Ore. .
Grand Forks, N. Dak
Portland, Ore. . .
Cedar Falls, la. . .
Fort Dodge, la. .
Fort Worth, Tex.
Greeley, Colo.
Milford, Kans. .
Conway, Ark.
Lawrence, Kans.
Hastings, Neb. .
Kirksville, Mo. .
Menominee, Mich. .
Cedar Rapids, la.
Albuquerque, N. Mex.
San Benito, Tex.
Rockford, 111. . .
Galveston, Tex. .
Atlantic, la. .
Little Rock, Ark.
Fayetteyille, Ark
Sioux City, la.
Minneapolis, Minn. .
Houghton, Mich.
Northfield, Minn.
Shenandoah, la. .
Coldwater, Miss.
Warrensburg, Mo. .
Paso Robles, Cal. • .
Santa Rosa, Cal.
Helena, Mont.
Seattle, Wash. . .
Burlingame, Cal.
Whittier, Cal. . .
Moberly, Mo.
Long Beach, Cal.
Salt Lake City, Utah
David City, Neb.
Wichita, Kans. . .
Omaha, Neb.
St. Paul, Minn. . .
Los Angeles, Calif. .
Dublin, Texas . .
Greenville, Tex. . .
Los Angeles, Cal.
San Francisco, Cal. .
Carterville, Mo. .
Spokane, Wash. .
St. Louis, Mo.
Fort Worth, Texas .
IN KCYS. IN METERS IN WATTS
1210 248 10
1370 218.8 10
1150 261 225
1220 246 10
1080 278 100
1200 250 10
1160 258 50
1220 246 50
1180 254 50
1100 273 50
Ceased Activities June, 1925
1200 250 100
1090 275 500
1040 288.3 20CO
1330 226 5
Ceased activities June, 1925
1170 256 20
1180 254 200
1270 236 10
1310 229 100
1250 240 10
1 100 273 100
Changes pending
1000 299.8 500
1150 261 100
Can signal changed to WHAT
1140 263 50
890 336.9 750
1130 266 500
1180 254 10
Ceased activities June, 1925
Ceased activities June, 1925 -
1310 229 50
Ceased activities June, 1925
660 454.3
1330 226
Changes pending
1240 242
1290 233
1270 236
1330 226
1300 • 231
1210 248
1190 252
1260 238
1190 252
1240 242
1300 231
Changes pending
1160 258
1130 266
1150 261
1140 263
500
10
100
250
100
50
100
50
500
15
10
500
20
100
100
150
Three
338
RADIO BROADCAST
JANUARY, 1926
CALL
SIGNAL
KDKA
KDLR
KDPM
KDYL
KDZB
KFAB
KFAD
KFAE
KFAF
KFAJ
KFAN
KFAU
KFAW
KFBB
KFBC
KFBG
KFBK
KFBL
KFBS
KFBU
KFCB
KFCC
KFCF
KFCY
KFCZ
KFDD
KFDH
KFDJ
KFDM
KFDX
KFDY
KFDZ
KFEC
KFEL
KFEQ
KFER
KFEY
KFFP
KFFV
KFFY
KFGC
KFGD
KFGH
KFGQ
KFGX
KFHA
KFHL
KFI
KFIF
KFIO
KFIQ
KFIU
KFIZ
LOCATION
East Pittsburgh, Pa. ...
Devils Lake, N. Dak.
WAVE- POWER
FREQUENCY LENGTH IN WATTS
IN KCYS. IN METERS
970 309.1 10,000
1300 231 5
1200 250 500
1220 246 50
1430 209.7 100
800 340 500
1100 273 100
860 348.6 500
1380 217.3 50
1150 261 100
Ceased Activities October, 1925
1060 282.8 750
1400 214,2 . 10
1090 275 50
1340 224 10
1200 250 50
1210 248 100
1340 224 50
1260 238 15
1110 270 500
1260 238 100
1210 248 10
1170 256 100
Call signal changed to KWUC
1160 258 50
1080 278 50
1160 258 50
1060 282.8 750
950 315.6 500
1200 250 100
1100 273 100
1300 231 10
1210 248 50
1180 254 50
1120 268 500
Changes pending
1290 233 10
1240 242 50
1200 250 100
1090 275 50
1120 268 100
Call signal changed to KOCW
1110 270 500
1330 226 10
1200 250 500
1190 252 50
1250 240 10
640 468.5 3000
1210 248 100
1130 266 100
1170 256 100
1330 226 10
1100 273 100
CALL
SIGNAL
CFAC
CFCA
CFCF
CFCH
CFCK
CFCN
CFCQ
CFCU
CFCT
CFCY
CFKC
CFQC
CFRC
CFXC
CFYC
CHCS
CHIC
CHNC
CHSC
CHUC
CHXC
CHYC
CJCA
CJCD
CJGC
CJKC
CJSC
CJWC
CKAC
CKCD
CKCK
CKCL
CKCO
CKCW
CKFC
CKOC
CKY
CNRA
CNRC
CNRE
CNRM
CNRO
CNRR
CNRS
CNRT
CNRV
CNRW
Canadian Broadcasting Stations
WAVE-
LOCATION FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
Calgary, Alta 6EO 434.5 500
Salt Lake City, Utah . . .
Bakersfield, Cal
Toronto, Ont
Montreal, P. Q
Iroquois Falls, Ont
Edmonton, Alta
Calgary, Alta
Vancouver, B. C. (Not Active) .
Hamilton, Ont
Victoria, B. C
840 356.9 500
730 410.7 1650
600 499.7 250
580 516.9 100
690 434.5 750
730 410.7 5
880 340.7 500
910 329.5 500
960 312.3 50
1210 247 8 75
Pullman Wash
Boulder, Colo
Havre, Mont
San Diego, Cal
Tacoma, Wash
Sacramento, Cal
910 329.5 500
1120 267.7 500
1030 291 . 1 20
730 410.7 500
880 340 7 10
840 356.9 500
840 356.9 500
840 356.9 250
910 329.5 50
690 434.5 250
730 410.7 850
580 516.9 500
840 356.9 50
910 329.5 50
730 410.7 500
840 356.9 500
910 329.5 250
730 410.7 1200
730 410.7 1000
630 475.9 500
840 356.9 500
690 434.5 100
910 329.5 5000
730 410.7 50
880 340 . 7 50
780 384 . 4 500
960 312.3 500
Uses stations CFAC or CFCN
New Westminster, B. C. . . .
Burnaby, B. C
Trinidad, Colo
Laramie, Wyo
Phoenix, Ariz
Helena, Mont
Hamilton, Ont. (Not Active) .
Toronto, Ont
Toronto, Ont
Unity, Sask
Walla Walla Wash
Le Mars, la
Ottawa, Ont. . .
Montreal, P. Q
Tucson, Ariz
Toronto, Ont
Beaumont, Tex
Shreveport, La
Brookings, S. Dak
Burnaby, B. C
Minneapolis, Minn
Portland Ore
Montreal, P. Q
Vancouver, B. C
Oak, Neb
Fort Dodge, la
Ottawa, Ont
Durham Co., Ont. (Not Active) .
Lamoni, la
Alexandria, La
H "It Ont
Baton Rouge, La
„,. . ' ,,
Chickasha, Okla
Stanford University, Cal. .
Boone, la
Orange, Texas
Uses station CHYC, CKAC
or CFCF
690 434.5 500
Uses station . . . CKCK
Uses station . . . CFQC
Uses station . . . CFCA
1030 291.1 500
Uses station . . . CKY
Oskaloosa, la
Los Angeles, Cal
Portland, Ore
Spokane, Wash
Vancouver, B. C
Juneau, Alaska
Fijtos*
Two
CALL
SIGNAL
KFQC
KFQH
KFQP
KFQR
KFQT
KFQU
KFQW
KFQY
KFQZ
KFRB
KFRC
KFRH
KFRL
KFRM
KFRQ
KFRU
KFRU
KFRW
KFRX
KFRY
KFRZ
KFSG
KFSY
KFU
KFUJ
KFUL
KFUM
KFUO
KFUP
KFUR
KFUS
KFUT
KFUU
KFUV
KFUY
KFUZ
KFVC
KFVD
KFVE
KFVF
KFVG
KFVH
KFVI
KFVJ
KFVK
KFVL
KFVN
KFVO
KFVR
KFVS
KFVU
KFVW
KFVX
LOCATION
Taft Cal
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
1300 231 100
Call signal changed to KFOB
1340 224 10
Changes pending
1190 252 20
1380 217.3 100
1390 215.7 50
Ceased activities August, 1925
1330 226 50
1210 248 250
1120 268 50
Changes pending
Ceased activities October, 1925
1240 242 50
Ceased activities June, 1925
Ceased activities October, 1925
600 499 . 7 500
1370 218.8 50
1380 217.3 10
1130 266 50
1350 222 15
1090 275 500
Ceased activities October, 1925
CALL
SIGNAL
WOAX
woe
WOCG
WOCL
WODA
WOI
WOK
WOKO
WOO
WOQ
WOR
WORD
WOS
WOWL
WOWO
WPAK
WPAZ
WPCC
WPDQ
WPG
WPRC
WPSC
WQAA
WQAC
WQAE
WQAM
WQAN
WQAO
WQAS
WQJ
WRAA
WRAF
WRAK
WRAM
WRAV
WRAW
WRAX
WRBC
WRC
WREO
WRHF
WRHM
WRK
WRM
WRMU
WRNY
WRR
WRST
WRVA
WRW
WSAC
WSAD
WSAG
LOCATION
Trenton N J
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
1250 240 500
620 483.6 5000
1460 205.4 10
1090 275 15
1340 224 250
1110 270 750
1380 217.3 500
1287 233 50
590 508.2 500
1080 278 1000
740 405.2 500
1090 275 5000
680 440.9 500
1110 270 100
1320 227 500
1090 275 50
Changes pending
1160 258 500
1460 205.4 500
1000 299.8 500
1390 215.7 100
1150 261 500
1360 220 500
1280 234 100
1220 246 50
1120 268 100
1200 250 100
833 360 100
Changes pending
670 447.5 500
Changes pending
1340 224 100
1170 256 100
1230 244 100
1140 263 100
1260 238 10
1120 268 250
1080 278 500
639 469 1000
1050 285.5 500
1170 256 50
1190 252 50
1110 270 200
1100 273 500
1270 236 100
1160 258 500
1150 261 350
1390 215.7 250
1170 256 1000
1110 273 500
Ceased activities October, 1925
Ceased activities June, 1925
Ceased activities August, 1925
Oklahoma Okla
Paterson N J
Holy City, Cal
North Bend Wash.
Homewood, 111. .
New York N Y
Belden Neb
Hollywood Cal
Philadelphia, Pa
Beeville Tex
Newark, N. J
Batavia, 111
Grafton, N. Dak
Grand Forks, N. Dak. . . .
Fort Sill Okla
Jefferson City, Mo
New Orleans, La
Fort Wayne, Ind
Agricultural College, N. Dak. .
Charlestown, W. Va
Chicago, 111.
Buffalo, NY
Portland Ore
Bristow Okla
Pullman, Wash
State College, N. Mex. . . .
Atlantic City, N. J
State College Pa
Helena, Mont
Amarilla, Tex
Springfield, Vt
1240 242 50
1160 258 10
1240 242 100
550 545.1 500
1280 234 50
1340 224 50
1170 256 50
1150 261 100
1340 224 50
Ceased activities October, 1925
Ceased activities August, 1925
Ceased activities October, 1925
Ceased activities August, 1925
1460 205.4 50
1250 240 500
1440 208.2 250
1270 236 10
1370 218.8 15
1210 248 10
1330 226 500
Galveston, Tex
Colorado Springs, Colo
St. Louis, Mo. . ...
Denver, Colo.
Ogden, Utah ....
Oakland, Cif.
Scranton, Pa
New York, N. Y
Chicago, 111
Salt Lake City, Utah . . .
Butte Mont
Yellow Springs, Ohio ....
Virginia, Minn
San Pedro, Cal
St. Louis, Mo
Washington D C
Hollywood, Cal
Independence, Kans.
Lansing, Mich
Washington, D. C
Minneapolis, Minn
Urbana, 111.
New York, N. Y. (portable) . .
New York NY ....
Vancouver, Wash
Welcome, Minn
Ceased activities August, 1925
1320 227 10
Dallas Tex
Call signal changed to KFKZ
Bay Shore, N. Y
Richmond, Va. ,
Tarrytown, N. Y. ...
Clemson College, S. C
Denver, Colo. ....
Cape Girardeau, Mo.
Eureka, Cal
San Diego, Cal
1220 246 50
1340 224 50
1430 209.7 5
1200 246 500
1270 236 10
Four
Thirteen
JANUARY, 1926
RADIO BROADCAST
339
CALL
SIGNAL
WJZ
LOCATION
New York, N. Y
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
660 454.3 1000
CALL
SIGNAL
KFVY
LOCATION
Albuquerque. N. Mex. .
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
1200 250 10
WKAA
1080 278 500
KFWA
Ogden, Utah
1150 261 500
WKAD
1250 240 20
KFWB
1190 252 500
WKAF
1150 261 250
KFWC
Upland, Cal
1420 211.1 50
WKAP
1280 234 50
KFWF
St. Louis, Mo.
1400 214.2 250
WKAQ
WKAR
WKAV
WKBB
San Juan, Porto Rico ....
East Lansing, Mich
Laconia. N. H. (portable) .
Joliet III
880 340.7 500
1050 285.5 1000
1430 209.7 50
1400 214 2 100
KFWH
KFWI
KFWM
KFWO
Chico, Cal
South San Francisco, Cal. .
Oakland, Cal
Avalon, Cal
1180 254 100
1330 226 500
1430 206.8 500
1420 211.1 250
WKBE
1300 231 100
KFWP
1400 214.2 10
WKBG
Chicago 111
1390 215 7 100
KFWU
Pineville, La.
1260 238 100
WKBK
WKRC
WKY
WLAL
WLAP
WLAX
New York, N. Y
Cincinnati, Ohio
Oklahoma, Okla
Tulsa, Okla
Louisville, Ky
1430 209.7 500
920 325.9 KXK)
1090 275 100
1200 250 150
1090 275 20
1300 231 10
KFWV
KFXB
KFXC
KFXD
KFXE
KFXF
Portland, Ore
Big Bear Lake, Cal. . . . . ,
Santa Maria, Cal
Logan, Utah
Waterloo, la
Colorado Springs, Colo.
1410 212.6 50
1480 202.6 500
1430 209.7 100
1460 205.4 10
1270 236 10
1200 250 560
WLB
1080 278 500
KFXH
El Paso, Tex
1240 242 50
WLBL
1080 278 500
KFXJ
1390 215.7 10
WLIB
Elgin (near) III
990 3028 1500
KFXM
1320 227 10
WLIT
760 394 5 500
KFXY
Flagstaff Ariz
1460 205 4 50
WLS
Chicago 111
870 344.6 1500
KFYD
Muscatine, la
1170 256 250
WLTS
Chicago 111 . .
1160 258 100
KFYF
Oxnard, Cal
1460 205.4 10
WLW
710 422 3 5000
KFYJ
1260 238 10
WLWL
New York, N. Y
1040 288.3 1000
KFYR
Bismarck, N. Dak
1210 248 10
WMAC
1090 275 100
KGB
Tacoma Wash
1200 250 50
WMAF
680 4409 1000
KGO
Oakland, Cal. ....
830 361.2 3000
WMAK
Lockport N Y
1130 266 500
KGTT
1280 234 50
WMAL
WMAN
Washington, D. C
1410 212.6 15
1080 278 50
KGU
KGW
Honolulu, Hawaii ....
Portland, Ore
1110 270 500
610 491.5 500
WMAQ
Chicago, 111
670 447.5 500
KGY
Lacey, Wash
1220 246 5
WMAY
1210 248 100
KHJ
740 405.2 500
WMAZ
1150 261 500
KHQ
Spokane, Wash
1100 273 500
WMBB
Chicago 111
1200 250 500
KJBS
1360 220
WMBC
1170 256 100
KJR
Seattle, Wash
780 384 4 1000
WMBF
780 384 4 500
KLDS
680 440 9 1000
WMC
600 4997 500
KLS
Oakland Cal
1200 252 250
WMCA
Hoboken N J
880 340 7 500
KLX
Oakland Cal
590 5082 500
WNAB
1200 250 100
KLZ
Denver Colo
1130 266 250
WNAC
1070 280.2 500
KMA
Shenandoah, la
1190 252 500
WNAD
1180 254 250
KMJ
1280 234 50
WNAR
WNAT
Butler, Mo
Philadelphia Pa
1300 231 20
1200 250 100
KMO
KNRC
Tacoma, Wash
1200 250 100
WNAV
1290 233 500
KNX
890 3369 500
WNAX
WNBH
WNJ
Yankton. S. Dak
New Bedford, "Mass
1230 244 100
1210 248 250
1290 233 100
KOA
KOB
KOCH
Denver, Colo
State College, N. Mex
930 322.4 2000
860 348.6 750
1160 258 250
WNOX
1120 268 500
KOCW
Chickasha, Okla.
1190 252 200
WNYC
New York N Y
570 526 1000
KOIL
Council Bluffs, la
1080 278 500
WOAC
1150 261 10
KOP
Detroit Mich
1080 277 6 500
WOAI
760 394.5 2000
KPO
700 428 3 1000
WOAN
1060 282 8 500
KPPC
1310 229 50
WOAW
570 526 1000
KPRC
1010 296 9 500
Twelve
Five
CALL
SIGNAL
WGBS
WGBT
LOCATION
New York, N. Y.
Greenville S C
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
949 316 500
CALL
SIGNAL
WARC
WBAA
LOCATION
Medford Hillside, Mass.
West Lafayette Ind
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
1150 261 100
1 100 273 C00
WGBU
WGBW
Fulford-by-Sea, Fla
Spring Valley 111
1080 278 500
1170 256 10
WBAK
WBAO
Harrisburg, Pa
Decatur 111 '
1090 275 500
1110 270 100
WGBX
1190 252 |100
WBAP
Fort Worth Tex
630 475 9 1500
WGBY
WGCP
New Lebanon, Ohio ....
Ceased activities August, 1925
1190 252 500
WBAV
WBAX
Columbus, Ohio
Wilkes-Barre, Pa
1020 293.9 500
1170 256 100
WGES
WGHB
Oak Park, 111
12(X) 250 500
1 130 266 500
WBBG
WBBL
Mattapoisett, Mass.
1210 248 100
1310 229 100
WGHP
Detroit, Mich
1110 270 1500
WBBM
Chicago 111
1330 226 1500
WGMU
Richmond Hill, N. Y. (portable) .
1270 236 100
WBBP
1260 238 200
WGN
WGR
Chicago, 111
Buffalo, N. Y
810 370.2 1000
940 319 750
WBBR
WBBS
Staten Island, N. Y
New Orleans, La
1100 273 500
1190 252 50
WGST
Atlanta, Ga
1110 270 500
WBBU
Monmouth, 111
1340 224 10
WGY
Schenectady NY
790 379.5 5000
WBBV
WHA
560 535 4 750
WBBW
Norfolk Va
1350 222 50
WHAD
Milwaukee, Wis.
1090 275 500
WBBY
1120 268 10
WHAG
1300 231 100
WBBZ
WHAM
WHAP
Rochester, N. Y
New York, N. Y
1080 278 500
1250 240 100
WBBZ
WBCN
Chicago, 111. (Portable) . .
Chicago, 111
1390 215.7 50
1130 266 500
WHAR
Atlantic City N J
1090 275 500
WBDC
1 1 70 256 50
WHAS
750 399 8 500
WBES
Takoma Park ' Md
1350 100
WHAT
WHAV
Minneapolis, Minn
500
1130 266 100
WBNY
WBOQ
New York, N. Y. .
Richmond Hill N Y
1430 209.7 500
1270 236 100
WHAZ
Troy, N. Y
790 379.5 1000
WBRC
1210 248 10
WHB
820 3656 500
WBRE
Wil'ces Barre Pa
1300 231 10
VVHBA
Oil City, Pa
1200 2M 10
WBS
Changed to WGCP
WHBB
Stevens Point, Wis
Ceased activities October, 1925
WBT
Charlotte N C
Ceased activities October 1925
WHBC
Canton, Ohio
1180 254 10
WBZ
900 333 I 2000
WHBD
Bellefontaine, Ohio
1350 222 20
WBZA
1240 242 250
WHBF
Rock Island, 111
1350 222 100
WCAC
1090 275 500
WHBG
1300 231 20
WCAD
Canton N Y
1 1 40 263 250
WHBH
1350 222 10
WCAE
650 461 3 500
WHBI
Chesaming, Mass
Ceased activities June, 1925
WCAG
WHBJ
1280 234 10
WCAH
1130 266 500
WHBK
1300 231 10
WCAJ
1180 254 500
WHBL,
1390 215.7 50
WCAL
Northfield Minn
890 336 9 500
WHBM
WHEN
Chicago, 111. (portable) . | . . .
1290 233 20
1260 238 10
WCAO
WCAP
Baltimore, Md. .
1090 275 100
640 468 5 500
WHBO
Pawtucket, R. I
Changes pending
WCAR
1140 263 500
WHBP
1170 256 100
WCAT
1250 240 50
WHBQ
Memphis, Tenn
1290 233 50
WCAU
Philadelphia Pa
1080 278 500
WHBR
Cincinnati, Ohio
1390 215.7
WCAX
1200 250 100
WHBS
WHBT
Mechanicsburg, Ohio ....
Downers Grove, 111
Changes pending
Ceased activities June, 1925
WCAY
WCAZ
Milwaukee, Wis. ....
Changes pending
1220 246 50
WHBU
1370 218 8 10
WCBA
WHBV
WCBC
WHBW
Philadelphia, Pa
1390 215.7 100
WCBD
Zion 111
870 344 6 5000
WHBX
Punxsutawny, Pa.
WCBE
1140 263 5
WHBY
West De Pere, Wis
1200 250 50
WCBG
1120 268 10
WHDI
1080 278 500
WCBH
1240 241 19
WHEC
Rochester, N. Y
1160 258 100
WCBI
WHK
Cleveland, Ohio
Ceased activities October, 1925
WCBJ
Ten
Seven
340
RADIO BROADCAST
JANUARY, 1926
CALL
SIGNAL
KPSN
KQP
LOCATION
Pasadena, Cal . . .
Portland, Ore
WAVfc;
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
950 315.6 1000
1410 212.6 500
CALL
SIGNAL
WHN
WHO
LOCATION
New York, N. Y. .
Des Moines, la. .
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
830 361.2 500
570 526 500
KQV
Pittsburgh, Pa. . . . .
1090 275 500
WHT
Deerfield, 111.
750 400 1500
KQW
KRE
KSAC
San Jose, Cal. . . . . .
Berkeley, Cal. . . . . .
1300 231 500
1170 256 50
880 340 7 500
WIAD
WIAK
WIAS
Philadelphia, Pa
Omaha, Neb
1200 250 100
Changes pending
1180 254 100
KSD
St. Louis, Mo
550 545 1 750
WIBA
1270 236 100
KSL
Salt Lake City, Utah . . . .
1000 299 8 1000
WIBC
1350 222 100
KSO
1240 242 500
WIBD
Joliet 111
Ceased activities October 1925
KTAB
KTBI
Oakland, Cal
Los Angeles, Cal
1250 240 1000
1021 293.9 750
WIBE
WIBF
Martinsburg, W. Va.
Wheatland, Wis
Ceased activities August, 1925
KTBR
Portland Ore
1140 263 50
WIBG
Elkins Park Pa
1350 222 50
KTCL
Seattle, Wash
980 305.9 1000
VVII'.H
1430 209 7 5
KTHS
800 274 8 500
WIBI
Flushing N Y
1370 218 8 50
KTW
Seattle Wash
660 454 3 1000
WIBJ
1390 215 7 50
KUO
San Francisco, Cal. . . . . .
1200 250 150
WIBK
Ceased activities October 1925
KUOM
1230 244 250
WIBL
Chicago 111 (portable)
KUPR
1110 270 50
WIBM
1390 2157 10
KUSD
1080 278 100
WIBO
1330 226 1000
KUT
1300 231 500
WIBP
KWG
Stockton Cal
1210 248 50
WIBO
1 460 205 4 5
KWKC
1270 236 100
WIBR
Weirton W Va
1220 246 50
KWUC
1190 252 50
WIBS
Elizabeth N J
1480 202 6 20
KWWG
Brownsville, Tex
1080 278 500
WIBU
Poynette, W s . .
1350 222 20
KYW
Chicago, 111
560 535.4 1500
WIBV
Henderson, N C
1140 263 25
KZKZ
Manila, Philippines
1110 270 100
WIBW
1360 220 100
KZM
Oakland, Cal
1250 240 100
WIBX
Utica, N. Y. ...
1460 205 4 5
KZRQ
Manila, Philippines
1350 222 500
WIBZ
1300 231 10
WAAB
New Orleans; La. .
1120 268 100
WIL
1 100 273 250
WAAC
New Orleans, La. .
1090 275 100
WIP
Philadelphia. Pa
590 508 2 500
WAAD
Cincinnati, Ohio
1160 258 25
WJAD
850 352 7 500
WAAF
Chicago, 111
1080 278 200
WJAG
Norfolk, Neb. . . .
1110 270 250
WAAM
Newark, N. J
1140 263 500
WJAK
1180 254 100
WAAW
Omaha, Neb.
770 389.4 500
WJAM
1120 268 100
WABA
Lake Forest, 111
Ceased activities October, 1925
WJAR
980 305 9 500
WABB
WABC
Harrisburg, Pa
Asheville, N. C
Ceased activities October, 1925
1180 254 10
WJAS
WJAZ
Pittsburg, Pa
930 322.4 1500
1120 268 100
WABI
1250 240 100
WJBA
Joliet 111
1450 206 8 50
WABL
Changed to WCAC Mans-
WJBB
1450 206 8 10
field, Conn.
WJBC
La Salle, 111. .
1280 234 100
WABO
Rochester, N. Y
1080 278 100
WJBD
Ashland, Wis
1290 233 100
WABQ
Haverford, Pa
1150 261 100
WJBG
Charlotte N C
1340 224 10
WABR
Toledo, Ohio
1140 263 50
WJBI
Red Bank, N. J. ...
1370 218.8 250
WABW
Wcoster, Ohio
1450 206.8 50
WJBI
Joliet, 111
Call signal changed to WCLS
WABX
Mount Clemens (near), Mich. .
1220 246 500
WJBK
1290 233 10
WABY
Philadelphia, Pa
1240 242 50
WJBL
Decatur 111
1110 270 500
WABZ
1090 275 50
WJBN
1170 256 10
WADC
1160 258 100
WJBP
Buffalo N Y
1370 2188 50
WAFD
1090 275 500
WJBQ
1420 211 1 100
WAHG
Richmond Hill, N. Y. . . .
950 315 6 500
WJD
1380 2173 10
WAIT
1310 229 10
WJJD
Mooseheart 111
990 302 8 500
WAMD
1230 244 500
WJR
580 517 1500
WAPI
1210 248 500
WJY
New York N Y
740 405 2 1000
Six
Eleten
CALL
SIGNAL
WCBM
LOCATION
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
1310 229 50
CALL
SIGNAL
WEBD
LOCATION
WAVE-
FREQUENCY LENGTH POWER
IN KCYS. IN METERS IN WATTS
1220 246 10
WCBQ
Nashville, Tenn
1270 236 100
WEBE
1280 234 10
WCBR
Providence, R. I. (portable)
1460 205 30
WEBH
Chicago, 111 ...
810 370 2 1000
WCBU
Arnold, Pa
Ceased activities October, 1925
WEBJ
New York, NY . .
1100 273 500
WCCO
St Paul, Minn. .
720 416 4 5000
WEBK
1240 242 20
WCEE
Elgin (near). 111
1090 275 1000
WEBL
United States (portable)
1330 226 100
WCK
Call signal changed to WSBF
WEBM
1330 226 100
WCLO
Camp Wis
1300 231 50
WEBQ
1330 226 10
WCLS
Joliet, 111
1400 214.2 100
WEBR
Buffalo, N*. Y. ... . .
1230 244 100
WCM
Austin, Tex
1120 268 250
WEBT
1170 256 5
WCSH
Portland, Me
1170 256 500
WEBW
Beloit Wis
1120 268 500
WCTS
Worcester, Mass
Call changed to WTAG
WEBZ
1140 263 50
WCUW
Worcester, Mass.
1260 238 250
WEEI
630 475 9 500
WCWS
1430 209 7 100
WEHS
1480 202 6 20
WCX
Detroit Mich
WEMC
R ' *^' ' ' Matft
1050 285 5 500
WDAD
Nashville, Tenn
with WJR
1330 226 150
WENR
WEW
Chicago, 111. .
1130 266 1000
1210 248 100
WDAE
Tampa Fla
1 100 273 250
WFAA
Dallas Tex
630 475 9 500
WDAF
820 365.6 1000
WFAM
St Cloud Minn
1100 273 10
WDAG
Amarillo, Tex
1140 263 100
WFAV
1090 275 5OO
WDAH
El Paso
Ceased activities August, 1925
WFBB
Eureka, 111
Ceased activities June, 1925
WDAY
Fargo, N. Dak
1150 261 50
WFBC
1200 250 50
WDBC
1 160 258 50
WFBD
Philadelphia Pa
1280 234 5
WDBE
Atlanta, Ga
1110 270 100
WFBE
1330 226 20
WDBJ
Roanoke, Va
1310 229 50
WFBG
1080 278 100
WDBK
Cleveland, Ohio
1320 227 100
WFBH
New York NY
1100 273 500
WDBO
Winter Park, Fla
1250 240 100
WFBI
Camden N J .
1270 236 250
WDBP
WFBJ
1270 236 50
WDBQ
Salem, N. J
1280 234 10
WFBK
WDBR
Boston, Mass
1150 261 100
WFBL
1190 252 100
WDBS
Call signal changed to WSMK
WFBM
1120 268 250
WDBW
Columbia, Tenn
Ceased activities June, 1925
WFBN
WDBX
New York, NY. ...
Call signal changed to WOKO
WFBQ
Raleigh N C
1190 252 50
WDBY
Chicago, 111 ...
Call signal changed to WPCC
WFBR
1180 254 100
WDBZ
Kingston, NY. ...
1290 233 10
WFBY
WDCH
Hanover, N. H
1170 256 100
WFBZ
Galesburg, 111. ......
1180 254 20
WDM
Washington, D. C
Changes pending
WFDF
1280 234 100
WOOD
Chattanooga, Tenn
1170 256 50
WFI
Philadelphia Pa
760 394 5 500
WDWF
Cranston, R. I
680 440.9 500
WFKB
Chicago 111
1380 2173 200
WDZ
Tuscola, 111
1080 278 100
WFRL
Brooklyn NY ....
1460 205 4 100
WEAA
Flint, Mich
Call changed WFDF
WGAL
1210 248 10
WEAF
New York, N. Y
610 492 5000
WGAZ
WEAH
Wichita, Kans.
1120 268 100
WGBA
1180 254 100
WEAI
WEAJ
Ithaca, N. Y
Vermilion, S. Dak
1180 254 500
Call signal changed to KUSD
WGBB
WGBC
Freeport, N. Y
1230 244 100
1080 278 10
WEAM
North Plainfield, N. J. . . .
1150 261 250
WGBF
1270 236 100
WEAN
Providence, R. I
1110 270 250
WGBH
Fall River Mass (portable)
WEAO
1020 294 500
WGBI
1250 240 50
WEAR
Cleveland, Ohio
770 389.4 1000
WGBK
1210 248 5
WEAU
Sioux City, la
1090 275 100
WGBL
1320 227 10
WEAY
Houston, Tex
Ceased activities October, 1925
WGBM
1280 234 5
WEBA
Highland Park, N. J. . . .
1290 233 15
WGBQ
1280 234 100
WEBC
Superior, Wis. - ...
1240 242 100
WGBR
Marshfield Wis
1310 229 10
Eight
Nine
RADIO BROADCAST ADVERTISER
349
V
Illustrated: 5-tube Thorola Islo-
dyne in Burled Wai- $-| (\(\
nutwithCircasaiantop _L \J \J
JewModein.GenuineMa- $QC ^
oeany Cabinet .... O^
. $225
Coniole Model
5-tube Thorola I«lodyne
in smart Tborocco Finish ....
sr?H2
[slodyne action is based
on Thorola Low- Loss
Doughnut Coils. They
bring many Thorola
advantages to other re-
ceive rs
Per $A
Coil *T
Thorola Low-Loss Straight Line Frequency
Condensers can also be bought separately
Thorola Golden Audio Reproduo $ + 59
ing Transformer ••••••••
*
Most-Demonstrated
Set of the Season
From radio as you have known it, to Thorola
Islodyne is as great a change as could happen,
even in radio! Here is so much of an ad-
vance that it seems to put final highest de-
velopment into view. Thorola Islodyne now
brings you radio safe from being surpassed.
Only the Thorola Islodyne principle of Iso-
lated Power makes it all possible. Based on
the epochal discovery of Thorola Low-Loss
Doughnut Coils, Islodyne action literally
isolates the radio impulses — keeps them from
interfering with each other— from tangling up
— from weakening themselves — keeps all un-
wanted stations out.
Sharpest selectivity is certain, wherever you
are. Tone is unbelievably pure, since inter-
ference is defeated. Superabundant volume
is available at extreme distances because
power, instead of being wasted, neutralized,
or damped, is put fully behind the broad-
casting of the one chosen station only.
These amazing results, free from mysterious,
unmanageable, disappointing old elements
of radio reception, are the regular perform-
ance of Thorola Islodyne receivers. Excel-
lence is uniform in all Thorola sets, and
throughout the range of reception. Your
radio parties proceed as scheduled. Stations
come in as logged. Words and music come
in as broadcast!
It is the latest proof of Thorola eminence, first
established by the matchless tonal accuracy
of Thorola Loud Speakers. Now there is a
complete receiver, Thorola Islodyne, even
further ahead. At the Thorola store you can
listen to the most- demonstrated radio set.
REICHMANN COMPANY, CHICAGO
ISLODYNE
Tested and approved by RADIO BROADCAST
R. K Circuits
The Systems at Present in Use for Neutralizing Radio-Frequency Amplifiers and a Dis-
cussion of the Recently Developed "Counterphase" Method for Controlling Oscillations
EFORE looking into the future
and ascertaining what is in store
for the dyed-in-the-wool experi-
menter and builder of radio cir-
cuits, it is well to pause for a moment in
consideration of what has gone before.
Without any question, tuned radio fre-
quency amplification, that discarded sys-
tem of reception of years ago, has again
come into its own and is now_ the gen-
eral mainstay and backbone of receiver
design.
But even up to the present time, the
especial and particular difficulties which
have accompanied this system of reception
are far from being satisfactorily controlled.
Constantly, the birth of a new method
for the successful handling and control
of radio frequency amplication is heralded
as the last word in efficiency and per-
formance— and still we search on.
In brief reconsideration of the many
methods of control of radio-frequency am-
plifiers, it is worthy of mention to restate
the particular advantages and disadvan-
tages of this system of amplification.
By JOHN BERNARD
In the application of Ohm's law, we find
that, if for a given voltage, the resistance
of a certain circuit be reduced, then a
greater current will flow. And conversely,
if the resistance be increased then the cur-
rent will be decreased.
In a radio circuit where a coil is tuned
by a variable condenser, a maximum of cur-
rent will flow in the circuit when the con-
denser adjusts the circuit to resonance with
^\~TE/IRLY every multi-tube receiver in use to-
<* X. day employs some form of radio frequency
amplification, and the matter of controlling oscil-
lations in such circuits has always been a serious
•problem. In this article, the various popular
methods art reviewed, and a description is offered of
a method which differs from the conventional
"losser" and from neutralising schemes. The pres-
ent arrangement combines resistance and capacity
as a method of control, and should arouse a consider-
able amount of interest, for the idea may have
wide application in r.f. circuits. — THE EDITOR
the transmitted frequency. Where, in a
vacuum tube circuit the grid and plate cir-
cuits are in resonance, a maximum of cur-
rent will flow in each one and the only
coupling agent between them is the tube
capacity. When such a state of affairs ex-
ists, the entire circuit oscillates.
Where high-grade apparatus is employed
to cut down the actual resistances of the cir-
cuit, sharp tuning of the circuit by the
variable tuning element, as shown in Fig. 2,
is obtained.
Now if it were possible to utilize such a
circuit with its advantage of extra-fine
tuning, there would be no obstacle to be
overcome or problem to be solved. How-
ever, this is not the case. Whenever a
circuit is in oscillation, it produces radio fre-
quency energy which, when adjusted in fre-
quency to the frequency of an incoming
signal, produces distorted reception, some-
times unintelligible. It is as though two
broadcasting stations were transmitting on
the same frequency adjustment and were
received simultaneously.
Yet if it were possible to prevent the
DETECTOR
DUAL
RESISTANCE
RADIO BROADCAST Photograph
2 1£
A?
FIG. i STAGE
A base-board layout of the Bremer-Tully "Counterphase" receiver. The rectangular blocks shown above the tube sockets and between the toroidal
coils, are the condensers, by means of which the tubes may be adjusted to the correct oscillating point. Note also the extra midget or trimming con-
densers, which are a part of the large tandem tuning condensers
RADIO BROADCAST ADVERTISER
351
NO DIALS
NO PANEL
BUILT-IN
LOUDSPEAKER
$
135
.00
West of the
Rocky Mountains $140
the ^Well Appointed JJome
PEOPLE of taste will instantly recognize in the
ULTRADYNE, Model L-3, the long-awaited
perfection in radio-musical instruments. This new
receiver offers complete mastery of the air's riches;
effortless operation — as simple as playing a phono-
graph ; and a new artistic form that blends harmoni-
ously with its environment.
Better than the most exacting critics of radio ever demanded, more
than the radio authorities themselves predicted. Complete freedom
from entangling technicalities. "Belongs" in almost any scheme of
furnishings. The perfect harmony of scientific skill and artistic
genius.
Radio never held out more attractions for you than this new kind
of receiver makes possible. See and hear it demonstrated at the
higher standard radio shoos and department stores.
The ULTRADYNE, Model L-3,
is a six-tube receiver employing
the fundamental principles of the
best circuits greatly refined and
marvelously simplified. No dials —
no panel; just two inconspicuous
levers which constitute a station-
selector. Volume adjustment, the
only other control. Beautifully duco
finished, duo-toned panelled mahog-
any cabinet.
Designed by R. E. Lacault, E.E.,
Chief Engineer of this Company,
and formerly Radio Research
Engineer with the French Signal
Corps, Radio Research Labora-
tories.
To protect the public, Mr. Lacault's
personal monogram seal (R.E.L.) is
placed on the assembly lock bolts of
all genuine ULTRADYNE Model
L-3 Receivers. All Ultradyne Re-
ceivers are guaranteed so long as
these seals remain unbroken.
Write for illustrated descriptive folder
OLTR3DXne *
MODEL J.-3
PHENIX RADIO CORP., 116-C East 25th St. NEW YORK
Tested and approved by RADIO BROADCAST
352
RADIO BROADCAST
JANUARY, 1926
Represents,. ^
Tube Capacity
C Is a Sharply Tuned Circuit
B Is Average in Selectivity
A Is Broad
FREQUENCY
FIG. 2
The circuit above depends, for selectivity, upon the resistance
of the tuned portion, represented by the coil L and the vari-
able condenser shunting it. If the resistance is high, the tuning
response will be broad as in the curve A. As the resistance is
decreased the selectivity becomes sharper, as depicted on curves
B, and C. Also, as the resistance of the circuit is decreased,
more current will flow in the grid and plate circuits and oscilla-
tions will be produced due to the coupling between these two
circuits by the inherent capacity of the tube
in question. The
well known neut-
rodyne system is
shown in Fig. 3.
Another system
worthy of compar-
ison is that devel-
oped by Walte'r
Van B. Roberts.
It is shown in Fig.
4. Here, any po-
tential set up in
the plate coil P is
set up also in the
plate coil N, but in
opposite relation to that flow-
ing in P. Then through the
capacity C, which balances out
the tube capacity, this poten-
tial is applied to the grid of
the tube, effectively preventing
any possibility of oscillation
because it is equal in potential,
and opposite in phase, to that
Ntutralizin» .
Condensers
oscillation, but keep the circuit as
sharply tuned to that particular fre-
quency as before, then a distinct and
worthwhile advantage would result.
The various systems for stopping
this oscillation are known as neu-
tralization methods.
The word itself carries a world of
meaning, and implies an equalization
or neutralization of the capacity of
the tube which is the coupling agent
producing the oscillation. In effect,
neutralization is the setting up of an
equal and opposing voltage which,
due to its opposition, prevents un-
wanted oscillations from taking place
in the grid-plate circuit of the tube
Neutralizing — .
Capacity
1ST R.F.
2NDR.F.
FIG. 4
The Roberts system of neutralization. The coil in series with
the neutralizing capacity is connected counter to the plate coil,
and produces an effect on the grid, through the neutralizing
capacity, equal and opposite to that produced by the plate coil
acting through the grid-plate capacity of the tube
3soR.F
FIG. 3
Professor L. A. Hazeltine is responsible for the neutralization,
or balancing-out system shown above. A goodly portion of
all the manufactured receivers sold during the past few years
incorporated this system using licenses granted under the
neutrodyne patents
which might be fed back to the grid of
the tube by the coil P through the tube
capacity. Yet, even this method is not
possible of adjustment independent of
frequency.
Absorption systems, still another way,
never were regarded as truly a satisfactory
neutralization method, and were more cor-
rectly termed "losser" systems.
OSCILLATION CONTROL METHODS
ONE of the most simple and com-
mon methods is to add sufficient
resistance to the grid or plate circuit
to prevent the possibility of oscilla-
tion. Considering the efforts that
have been made to reduce resistance
in coils and condensers, and the value
attributed to such efforts, the fallacy
of again deliberately introducing such
losses into a circuit is evident. Were
it not for the popular delusions, how
much more simple it would be to use
high-loss coils and condensers in the
first place.
' Eddy current losses result from
placing condensers within the field
2NDA.F
FIG. 5
In the "Counterphase" circuit shown here, the tendency of the radio frequency stages to oscillate is prevented by the separate circuits comprising the
inductances M-R and the condensers Cn. It is necessary to adjust the condensers Cn, the variable part of this circuit, to suit the tube employed. On the
high frequency end of the tuning scale, the tendency of a circuit to oscillate is greater than at the other end of the scale, the lower frequencies, so a
panel adjustment is provided in the dual resistance control to compensate for these changes, thereby obtaining maximum efficiency on all frequencies
within the tuning range
RADIO BROADCAST ADVERTISER
353
These Eveready Patterns are the correct
size for your set. With average use they will last
you a year or longer"
"You have been one of the
many who use 'B' batteries
that are too small in capacity
for their receivers. That is not
economical. It makes you buy
'B' batteries twice as often as
necessary. Fit the right size
Evereadys to your set and add
a 'C' battery,* if you haven't
one, and you'll get the maxi-
mum of service at the mini-
mum of cost."
The life of your Eveready
"B" Battery depends on its
capacity in relation to your
set and howmuch you listen in.
We know, through a careful
investigation, that the aver-
age year-round use of a set is
two hours a day. Taking that
average we have proved over
*NoTE: In addition to the increased life
which an Eveready "C" Battery gives to
your "B" batteries, it will add a quality of
reception unobtainable without it.
and over that on sets of one to
three tubes the No. 772 Ever-
eady "B" Battery used with a
"C" battery will last a year or
longer. On sets of four and five
tubes, the larger heavy duty
Eveready batteries used with
a "C" battery will last eight
months or more.
The secret of "B" battery
satisfaction and economy is:
With sets of from I to 3 tubes,
use Eveready No. 772.
Layerbilt"B"Bat-
tery No. 486. 45
colts, for maximum
economy on tour,
five or more tubes.
K I a H T-Eveready
DryCellKadio"A"
Battery, 1 % colti.
The battery built
especially for dry
cell tubes.
EVERErVDY
Radio Batteries
-they last longer
With sets 0/4 or more tubes, use
either of the heavy duty batteries,
No. 770 or the even longer-lived
Eveready Layerbilt No. 486.
We have prepared for your
individual use a new booklet,
"Choosing and Using the
Right Radio Batteries," which
we will be glad to send you
upon request. This booklet
also tells about the proper bat-
tery equipment for use with
the new power tubes.
Manufactured and guaranteed by
NATIONAL CARBON CO., INC.
New York San Francisco
Canadian National Carbon Co., Limited
Toronto, Ontario
EVEREADY HOUR
EVERY TUESDAY AT 9 P. M.
Eastern Standard Time
For real radio enjoyment tune in the "Eveready
Group." Broadcast through stations —
WEAF-AVtt- York v/fi-Pkiladflpkia WSAI - Cincinnati
wjAK-Providtnce wrjt-Ruffa!n wwj-Detroit
vtEEi-Boston woe- Davenport
WT \c-rVorctster we AE -Pittsburgh KSD-St. Louis
wcco-Minwapolis, St. Paul
Tested and approved by RADIO BROADCAST
354
RADIO BROADCAST ADVERTISER
What You COULD
Get From Your Set
IT isn't what you're getting now. It's
how much more you could get from
your present set.
Your set may be one of the finest in
the world but it can be no better than
its Dials.
The human hand cannot tune ordinary
dials sufficiently accurate to bring in all
the stations within scope of your set.
That's where Science has stepped in
with the two dials shown above.
MYDAR Recording Dial shown at the
left above, offers a degree of tuning
efficiency not usually associated with
this price. Ample space for call letters
insures permanent logging of all stations.
Genuine Rakelite, handsomely embel-
lished—12 to 1 Ratio. Price $1.75.
The A.J. (Vernier) shown at the right
above, geared at 150 to 1, brings tones
into sharp focus like a fine camera lens.
Beautiful, dignified. Genuine Bakelite.
A master product of master craftsmen
-Price $2.25.
Accuratune (not shown) geared 80 to 1
is admirably suited to every type of
tuning requirements.
No panel drilling necessary to substitute
any one of these dials.
^ MYDAR Radio Company
3 CAMPBELL STREET
NEWARK, N. J.
of a coil, and this is another method that
has been used and probably will be again.
It is evident also that if one circuit were
slightly detuned, the tendency toward oscil-
lation would be reduced. Another method
has likewise been employed, oscillations
being prevented by reducing the plate load
or number of turns in the primary circuit
of the transformer, which cuts down the
coupling between primary and secondary.
This latter method increases selectivity,
but unfortunately the energy transfer be-
tween tubes is thereby reduced, and if the
coupling is cut down sufficiently to prevent
oscillation on the higher frequencies
(shorter wavelengths), this same insuffi-
cient coupling results in very unsatisfac-
tory response on the longer waves.
CAUSE OF TROUBLE ON SHORTER WAVES
AT 5 50 meters, the upper end of the pres-
ent broadcasting band, the frequency
per second is only 545,100, but at 200 me-
ters, or the lower limit, the frequency per
second reaches the enormous number of
1,500,000 cycles. The resultant increase in
tendency to oscillate on the higher fre-
quencies (shorter wavelengths) has worried
circuit designers from the earliest days of
radio. It creates the problem that has been
fought over, avoided, evaded, neglected, or
ignored, according to the varying degrees
of intelligence or intention involved.
Regardless, however, of what last year's
arguments may have been, it is now quite
generally agreed that when primary to se-
condary coupling is reduced to the extent
that oscillation is prevented, the set will be
satisfactory on the higher frequencies
(shorter wavelengths) only. Within a
narrow broadcast range 750 kc. wide (200
to 400 meters), such a set would be accept-
able, but from 1 500 kc. (200 meters) to
545 kc. (550 meters) gives a band 955 kc.
wide, — greater than has been handled with
satisfaction.
Some difficulty was avoided by the manu-
facture of sets and parts which would not
reach the higher frequencies (shorter wave-
lengths), but this did not solve the problem
for the user. When there were no stations
assigned at the lower frequency end, the
omission was not generally noticed, al-
though undoubtedly part of the reason why
stations were not assigned to this band was
because of the trouble the Government
knew would have ensued, and because of
the complaints that would have arisen
among those whose sets would not receive
satisfactorily the full range in effect at the
time they were made.
SYSTEMS OF NEUTRALIZATION
OINCE the reduction of coupling to the
^ point of complete avoidance of oscil-
lation gives acceptable results over part of
the range, it follows that increasing the
coupling somewhat by a few more primary
turns will bring the point of complete sup-
pression farther up the wavelength scale,
and while oscillations will occur below that
point, the middle range will respond favor-
ably, and the upper range to a slight extent.
Similar results are obtainable under the
other methods mentioned by varying the
amount of resistance or losses, or by fixed
Tested and approved by RADIO BROADCAST -jr
RADIO BROADCAST ADVERTISER
355
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AUDIO FREQUENCYATRANSFORMER
TYPE R-SOO SERIAL N°
ALL-AMERICAN RADIO CORP. CHICAGO, U.S.A.
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When a Finer Transformer Is Made
It Will Bear This Name-Plate
iiiiiiiiiiiiliijlijj
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Radio moves rapidly. Perhaps some time there
may be seen a better transformer than what we
II
EE
;
now know as Rauland'Lyric. It may sell
at $9,
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:
or $10, or $15, or $7. But the careful observer
|E !
— —
of the past year's developments will entertain
not a moment's doubt of one thing: when the
EEE !
«
1;
better transformer comes it will come beneath
— _ .
—
'•'-
the famous Rauland'Lyric name'plate. Behind
this as a pledge rests the entire organization and
resources of the All' American Radio Corporation
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Raukmd'Lyric is easily obtain- Rauland'Lyric tone quality is
abk from better 'class dealers now; available in a complete
everywhere. The price is nine receiver: the new A JJ- American
dollars. Descriptive circular . Model R (a/ive-tube tuned-
untfi technical data may be had ' radio'frequency set) now being
on request to All' American §k shown. If your preferred dealer
Radio Corporation, 4201 «r/S ''•• does not display it, send to us
Beimont Avenue, Chicago - S^ for descriptive booklet
EE :
TjTmTjl ; (
^
^
: =.-
I
if Tested and approved by RADIO BROADCAST
354
RADIO BROADCAST ADVERTISER
What You COULD
Get From Your Set
IT isn't what you're getting now. It's
how much more you could get from
your present set.
Your set may be one of the finest in
the world but it can be no better than
its Dials.
The human hand cannot tune ordinary
dials sufficiently accurate to bring in all
the stations within scope of your set.
That's where Science has stepped in
with the two dials shown above.
MYDAR Recording Dial shown at the
left above, offers a degree of tuning
efficiency not usually associated with
this price. Ample space for call letters
insures permanent logging of all stations.
Genuine Bakelite, handsomely embel-
lished—12 to 1 Ratio. Price $1.75.
The A.J. (Vernier) shown at the right
above, geared at 150 to 1, brings tones
into sharp focus like a fine camera lens.
Beautiful, dignified. Genuine Bakelite.
A master product of master craftsmen
-Price $2.25.
Accuratune (not shown) geared 80 to 1
is admirably suited to every type of
tuning requirements.
No panel drilling necessary to substitute
any one of these dials.
if MYDAR Radio Company
3 CAMPBELL STREET
NEWARK, N. J.
V
of a coil, and this is another method that
has been used and probably will be again.
It is evident also that if one circuit were
slightly detuned, the tendency toward oscil-
lation would be reduced. Another method
has likewise been employed, oscillations
being prevented by reducing the plate load
or number of turns in the primary circuit
of the transformer, which cuts down the
coupling between primary and secondary.
This latter method increases selectivity,
but unfortunately the energy transfer be-
tween tubes is thereby reduced, and if the
coupling is cut down sufficiently to prevent
oscillation on the higher frequencies
(shorter wavelengths), this same insuffi-
cient coupling results in very unsatisfac-
tory response on the longer waves.
CAUSE OF TROUBLE ON SHORTER WAVES
AT 550 meters, the upper end of the pres-
ent broadcasting band, the frequency
per second is only 545,100, but at 200 me-
ters, or the lower limit, the frequency per
second reaches the enormous number of
i, 5 00,000 cycles. The resultant increase in
tendency to oscillate on the higher fre-
quencies (shorter wavelengths) has worried
circuit designers from the earliest days of
radio. It creates the problem that has been
fought over, avoided, evaded, neglected, or
ignored, according to the varying degrees
of intelligence or intention involved.
Regardless, however, of what last year's
arguments may have been, it is now quite
generally agreed that when primary to se-
condary coupling is reduced to the extent
that oscillation is prevented, the set will be
satisfactory on the higher frequencies
(shorter wavelengths) only. Within a
narrow broadcast range 750 kc. wide (200
to 400 meters), such a set would be accept-
able, but from 1 500 kc. (200 meters) to
545 kc. (550 meters) gives a band 955 kc.
wide, — greater than has been handled with
satisfaction.
Some difficulty was avoided by the manu-
facture of sets and parts which would not
reach the higher frequencies (shorter wave-
lengths), but this did not solve the problem
for the user. When there were no stations
assigned at the lower frequency end, the
omission was not generally noticed, al-
though undoubtedly part of the reason why
stations were not assigned to this band was
because of the trouble the Government
knew would have ensued, and because of
the complaints that would have arisen
among those whose sets would not receive
satisfactorily the full range in effect at the
time they were made.
SYSTEMS OF NEUTRALIZATION
SINCE the reduction of coupling to the
point of complete avoidance of oscil-
lation gives acceptable results over part of
the range, it follows that increasing the
coupling somewhat by a few more primary
turns will bring the point of complete sup-
pression farther up the wavelength scale,
and while oscillations will occur below that
point, the middle range will respond favor-
ably, and the upper range to a slight extent.
Similar results are obtainable under the
other methods mentioned by varying the
amount of resistance or losses, or by fixed
Tested and approved by RADIO BROADCAST -jr
RADIO BROADCAST ADVERTISER
355
E3
AUDIO FREQUENCY TRANSFORMER
TYPE R-500 SERIAL N2
ALL-AMERICAN RADIO CORP. CHICAGO, U.S. A.
When a Finer Transformer Is Made
It Will Bear This Name-Plate f
Radio moves rapidly. Perhaps some time there
may be seen a better transformer than what we
now know as Rauland'Lyric. It may sell at $9,
or $10, or $15, or $7. But the careful observer
of the past year's developments will entertain
not a moment's doubt of one thing: when the
better transformer comes it will come beneath
the famous Rauland'Lyric name "plate. Behind
this as a pledge rests the entire organisation and
resources of the All' American Radio Corporation
Rauland'Lyric is easily obtain'
able from better'dass dealers
everywhere. The price is nine
dollars. Descriptive circular
with technical data may be had
on request to All' American
Radio Corporation, 4201
Belmont Avenue, Chicago
Rauland'Lyric tone quality is
now available in a complete
receiver: the new All' American
Model R (afive'tube tuned'
radio-frequency set) now being
shown. If your preferred dealer
does not display it, send to us
for descriptive booklet
Tested and approved by RADIO BROADCAST
356
RADIO BROADCAST ADVERTISER
Wade Tuning Unit Includ-
ing Condenser and Dial
The Wade Tuning Unit con-
sists of a Wade Condenser
geared to a four- nch 360 de-
gree vernier dial of 16 to 1
ratio. Finest possible control
with no backlash. Prices be-
low are for the complete unit.
Capacity .0001 25 mfd. #6.00
Capacity .00025 mfd. 6.25
Capacity .00035 mfd. * 6.35
Capacity .0005 mfd. 6.50
Viking Tool and Machine Co.
Why dime
With Only
UalfaDial?
T TNIQUE design of Wade Condensers
^ spreads stations over our entire
360 degree dial. The Wade is a complete
tuning unit built with specially designed
vernier dial. This means twice as much
space between stations for close tuning
adjustment; even wider separation of
stations than the rotor plate types of
straight line frequency condensers using
standard 180 degree dials. None of the
annoyance of overlapping stations and
jumbled reception. The Wade Conden-
ser gives the lowest minimum capacity
and wider tuning range. Covers the
whole broadcast range and down below
200 meters.
No Body Capacity Effects
A separately grounded frame insulated from
both sets of plates shields the condenser from
all body capacity effects — an important feature,
exclusively in Wade Condensers.
745-A 65th Street, Brooklyn, N. Y.
Have your favorite circuit
Built or Repaired by experts
We are recommended by
Harnmarlund-Roberts
Radio Broadcast Aristocrat
Sampson
Browning-Drake
Bremmer-Tully
To render this service ^L.
These kits always in stock *
— Prompt Mail Order Service —
Radio Construction Laboratories
71-73 West Broadway New York City
Blackburn Ground Clamps
Telephone companies using
MILLIONS. Adjustable — fits
any size pipe. Requires no pipe
cleaning — screw bores through
rust and scale. Send 12 cents
for sample and postage.
Blackburn Specialty Company
1960 E.66th St. Cleveland, 0.
Books by Telegraph
between
New York
Cleveland
Kansas City
Springfield
Toledo
St. Louis
Doubleday, Page Book Shop
neutralization on some wavelength below
the mid-scale, but none of these methods
give results over the entire scale. Should
the wavelength be increased by dropping
the lower limit, there is still less possibility
of satisfactory operation.
EXTERNAL CIRCUIT REQUIRED
EVIDENTLY some other arrangement
*-' must be found to compensate for the
inherent feedback of the present-day tube.
A logical solution is an external circuit de-
signed to feed back energy of opposite po-
tential in such manner and amount as to
overcome or neutralize the regenerative
action of the tube. It must also be efficient
over the entire tuning range of the receiver
to which it is applied.
It is also evident that the adjustment of
this external circuit should not remain
constant for all broadcast frequencies.
The sensitivity of a receiver is always great-
est just below the point of oscillation of
both r. f. and detector tubes. The action
of a sensitive r. f. amplifier is therefore very
similar to the regenerative circuit in which
a regenerative control, or tickler, is always
used to bring regeneration up to the point of
oscillation. The difference is that, in a
radio-frequency amplifier, this action is re-
duced below the point of oscillation.
Panel control of sensitivity is just as im-
portant and desirable, for example, as the
panel control of a tickler in the well-known
three-circuit regenerative receiver. Per-
manent neutralization, on the other hand,
is to all practical purposes similar to what
we would find with a permanent adjust-
ment of the tickler in the circuit mentioned.
Only recently a new method of control-
ing oscillation has been brought forward by
the Bremer-Tully Company of Chicago, and
has been secured by patent. This system
has been termed the "Counterphase," and
an explanation of its function is of interest.
The Bremer-Tully "Counterphase" cir-
cuit includes a bridge between the output
and the input circuits. Counter potential is
derived from a coil coupled inductively to
the plate circuit, and fed, through an adjust-
able capacity, to a coil inductively coupled
to the grid circuit. Any connection made
between plate and grid circuits must to
some extent increase grid-to-plate capacity,
which in turn tends to increase oscillation.
The most careful design is necessary, there-
fore, to avoid such increase as to make
neutralization impossible in any neutraliz-
ing circuit at the high frequencies (shorter
wavelengths) of the broadcasting range. In
the Bremer-Tully "Counterphase" method,
this capacity effect is overcome to such an
extent that neutralization on as high fre-
quencies as 1 500 kc. (200 meters) is easily
accomplished.
As compared to any fixed method of
neutralization, it will be noted that the link
circuit between each r. f. stage includes
a small adjustable condenser. The method
of controlling two or more stages of r. f.
amplification is extremely simple.
The circuit is shown in Fig. 5.
It is well known that the variation of a
resistance in series with a condenser var-
ies the effective capacity of the condenser.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
357
Employs no fluids of any kind. Uses only one rectifying tube. Separate adjustment for detector and amplifier tubes. Handsomely finished in
rich velvet- green Duco with solid walnut, satin finish top and bottom. Ample continuous "B" current for one to ten-tube sets.
Give your Radio Set a "B" Current
Supply-— for life!
, using alternating current from your lamp socket, in place of "B" Batteries, is guaran'
teed to improve the overall efficiency of your set. It provides constant "B" current at proper
potential for your receiver circuit, tubes and loud speaker.* DIS'TON is noiseless in operation-
no crackles and popping such as you get with run down "B" Batteries — no hum of any kind
to distort the finest aria or drown out the faint signals from distant stations.
Remarkable Clarity -Amazing Volume and Selectivity
DIS-TON is trouble free — the special Trans-Filter Unit is sealed
in, protected against tampering and deterioration. It can't wear
out. Consumes only eight watts from the nearest lamp socket
and puts your "B" load on the big, powerful, carefully watched
generators of your central station. You can rely upon DISTON
to give you the best from your receiver.
Without attention of any kind after simple initial adjustment to
your set — DIS-TON insures you the equivalent in performance of
new "B" Batteries every time you listen in.
DISTON requires no change in the internal wiring of your set to
secure either utmost efficiency or entire safety. Accidental im-
proper connections can't result in tube "burn outs."
DIS-TON complete
ready for operation
110 volt, 60 cycle
$40.00
Special 3 Voltage
DIS-TON, 60 cycle
110 volt, $45.00
Other voltages and
cycleson application
Know how much DIS-ToN adds to radio
The advantages that DIS-TON will give you are outstanding and unusual. You
have the opportunity to verify them all on your present receiver. A DIS-TON
demonstration is yours for the asking. Send for Leaflet B and full details as the
first step to greater radio enjoyment this season.
RADIO PRODUCTS, Inc.
Dept. RB Richmond/Ind.
*Regular DIS-TON will modernize the performance of any of the good, older receivers in an amazing fashion.
Three voltage DIS-TON is the only AC current supply adapted to the newest circuit where different detector,
radio frequency and audiofrequency ".B" potential is required.
DIS-TON KITS
Essential Parts
for
Home Builders
110 volt, 60 cycle
$28.50
Other voltages and
cycleson application
Tested and approved by RADIO BROADCAST
358
RADIO BROADCAST ADVERTISER
TONE
SUPER S $25.00
Rubber horn I4i" diameter. Black
mat finish. Gold decorated base.
Equipped with new Super-Unit.
clear — natural — pleasing — musical
HpHE latest Bristol refinement, the Super-Unit, contains a large, low-pitch dia-
*• phragm which brings in, not only the middle and upper registers, but all
those deep bass notes heretofore only imperfectly heard if at all. With a Bris-
tol, either Super S or Super C, you hear all the concert; with it all tones are dis-
tinguished in their proper qualities, in all selections.
Have Your Dealer Send One Out On Christmas Eve
He will be glad to have you try any one of the Bristol models in your
home. It's an ideal way to appreciate Bristol tone quality and judge
for yourself. There are four Bristol Speakers: Super S at $25.00, Su-
per C, the Cabinet, at $30.00 and horn types at $15.00 and $20.00.
Send for Booklet "How to Select Your Loud Speaker"
Easily understood and explains the " how" and "why" of mechanisms
and materials in loud speaker construction.
BRISTOL SPEAKER
[The AUDIOPHONE]
THE BRISTOL COMPANY Radio Div. AH WATERBURY, CONN.
for 36 years makers of the highly sensitive and accurate Bristol's
Recording Instruments.
Therefore, by placing one resistance in
series with and common to all the neutraliz-
ing circuits, the capacity of each can be
changed by varying this common resistance.
The effect is to unbalance these circuits,
permitting an increased sensitivity, easily
variable over all frequencies within the
range covered.
Here again we find a fortunate factor
operating in our favor. Aside from the
advantage of enabling us to control several
stages with one knob, this resistance does
not introduce losses or interfere with se-
lectivity, and in addition to that it does not
affect dial readings by detuning the circuit.
DUAL RESISTANCE-CONTROL AN ASSET
INASMUCH as sensitivity is not required
1 on stations where it is desirable to reduce
volume, the same knob can be used to oper-
ate a separate resistance in the B battery
circuit to control volume.
This is accomplished by a dual resistance
containing two distinct resistance elements,
each operable over an arc of 240 degrees.
When sensitivity is the objective, no
reduction in volume is desired. When a
decrease in volume is wanted, there is no de-
mand for sensitivity. Therefore, in opera-
tion, it is necessary only to turn one knob
to the right or left to secure either one or
the other as desired.
LjH^*addition to the simultaneous un-
balancing feature which makes it possible
to secure sensitivity over the full range, the
"Counterphase" method makes it possible
to control three stages of tuned radio
frequency efficiently with but two tuning
controls.
In design the circuit is distinctly new
and will no doubt appeal to those who are
of that jaded group of circuit seekers and
dyed-in-the-wool experimenters who are
always on the look-out for "something new
under the sun."
VALUES OF PARTS EMPLOYED IN CIRCUIT
E coils employed in the "Counter-
* phase" circuit are toroids, each wound
on a frame if -inches square. The secon-
dary consists of 1 68 turns of No. 24 double
silk covered wire and is tapped at the I24th
turn from the filament end. It has an
inductance value of 220 millihenries. The
primary is spaced inside the secondary at
the filament end, and consists of 52 turns
of No. 36 d.c.c. or d.s.c. wire.
The "Counterphase" coil is wound with 96
turns of the No. 36 wire, its turns being
spaced between the turns of the primary.
The antenna secondary is tapped at the 2nd,
8th, 25th, and 4Oth turn from the filament
end of the coil. The tuning condensers
are .00035 mfd; the trimmers .000024 mfd.
The "Counterphase" condensers Cn have a
minimum of i mmf. and a maximum of 30
mmf.
The dual resistances are variable, the one
located in the Counterphase part of the
circuit is 3000 ohms and that in the plate
circuit 500,000 ohms.
The by-pass condensers are as follows: — •
A .00 1 -mfd. across the first audio trans-
former primary; a i-mfd. across the C
battery, and a i-mfd. across the B battery.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
359
Separate All Stations Evenly
IT is not necessary to tear down and rebuild your present
set in order to separate the stations evenly on the dials.
By merely substituting Rathbun Straight Line Frequency
Converters for your present dials — you will be able to se-
cure real S. L. F. tuning.
Here is a variable vernier control that provides a ratio of
50 to 1 down where the stations are crowded — gradually
and smoothly decreasing in uniform ratio over the full
360° of the dial. The stations are evenly separated around
the entire circle. There are only two moving parts— a cam
and a lever. The action is dependable and accurate — with-
out a particle of backlash. Easier tuning and immeasur-
ably better logging are obtainable from straight line capac-
ity condensers with these new converters.
Remember that we build the Rathbun Single Hole Mounting Condenser
with genuine Bakelite ends. This year's models are enclosed with
transparent pyralin dustbands which preserve their high efficiency
for life. They are small, light and rugged — always reasonably priced.
Ask your dealer for Rathbun Straight Line Frequency Converters
He has them in stock or will get them for you promptly
PRICE $3.50
*
RATHBUN MANUFACTURING CO., INC.
JAMESTOWN, N. Y.
Tested and approved by RADIO BROADCAST
360
RADIO BROADCAST ADVERTISER
dion Panels in
black and Mahoga-
nite come cut in
alt standard sixes
The double advantage
of RADION
SUCCESSFUL set manufac-
turers and experienced ama-
teurs know that there are two
important requirements for any
set:
1. Efficient reception.
2. Good appearance.
The selection of RADION goes
far toward fulfilling both these
requirements. RADION Panels
possess superior insulating qual-
ities not equaled in any other
panel made. And RADION has
such a beautiful surface finish
that it noticeably enhances the
appearance of any set.
New No. 10 4-inch
Radian Dial, built
to conform to the
fingers, helping you
to get close tuning.
This double advantage of RADION is
due to the fact that it is the only in-
sulation that was made to order for
radio purposes exclusively.
The high-resistant characteristics of
RADION Panels mark all RADION
low-loss parts — Sockets, Dials, Insula-
tors, Tubing, etc. Adopted by leading
manufacturers and sold universally by
radio dealers.
No. 2 Ration Socket for
new UX tubes with collar
adapter for old type tubes .
No. 4 same as No. 2,
without collar adapter for
new UX tubes exclusively.
Send for booklet, "Building Your
Own Set." Mailed for 10 cents
Man ufact urers: Our facilities and equipment
for the manufacture of moulded parts are sec-
ond to none. Write us for prices on quantities.
AMERICAN HARD RUBBER COMPANY
Dept. C-13 11 Mercer Street New York City
Chicago Office: Conway Building
Pacific Coast Agent: Goodyear Rubber Co.
San Francisco Portland
Gflic Supreme Insulation
Made to order for radio purposes exclusively
If You Seek Economy, Buy the Best!
By HAROLD JOLLIFFE
The time has come, the Walrus said,
To talk of many things;
Of shoes and ships and sealing-wax,
Of cabbages and kings.
— CARROLL.
THE fellow who came out with that clever
remark about economy, certainly was a
wise old bird; his head was in the right
place, and he knew what he was talking about.
We do not know who the originator of this bright
little maxim was; he probably dates 'way back
down the dim corridors of time to the obscure
and misty past, when the ancient Phoenicians
dauntlessly set forth in their little vessels to
invade the shores of distant Britain with their
varied trade. Quite likely it had its inception
at a far earlier date than that; maybe it was
around about the time when that little fellow,
David, got peeved and knocked his enemy, the
great and husky Goliath, for a home run, with a
well-directed stone from his sling.
But no matter when, where, or how. It is
an axiom that applies now as ever; and it holds
just as forcefully in radio as in anything else
under the sun. You can't get away from it.
Take vacuum tubes, for instance. As every-
one knows, for the standard price of two and a
half dollars you can walk into any radio dealers'
and purchase a good tube; a tube of recognized
quality; a tube which is the result of the con-
stant efforts of many of the greatest scientists
of the age, and years and years of tireless study
and ceaseless experiment. Millions and millions
of dollars have been expended to bring it up to
its present high state of perfection, and it has
embodied in its construction all those desirable
and necessary qualities which make for an effi-
cient, serviceable tube, it is rated at a certain
voltage and current consumption, and is guaran-
teed to perform exactly as indicated by the man-
ufacturer when his directions, regarding its use
and care, have been followed carefully, and pro-
vided it is not abused. Therefore, such a tube
may be expected to do all that is claimed for it.
And yet, there are those who will waste one
dollar — yes, one buck's the price! Can you beat
it? — on a tube which, in the first place, is proba-
bly a "second" of a so-called independent manu-
facturer; a tube which, if rated as consuming .25
amps., will more than likely draw considerably in
excess of that amount; a tube which may not
even fit its socket, for that is exactly the case
with some of the three-volt variety. You have
to take a file and rub down what appears to be a
small brass rivet projecting from one side of the
base, before it can be inserted into a socket;
others sit wobbly in their sockets because their
bases have a diameter of one-sixteenth inch less
than the internal diameter of the shell of the
socket, which results in uncertain contact.
The writer knows of a case where an elderly
couple had a four-tube receiver, and the tubes,
having become worn out through continued use,
needed replacement. Despite warning, they
bought four tubes of the above-mentioned type,
and without a word of exaggeration, these tubes
gave absolutely no satisfaction. They ate very
heavily into the dry A batteries — the tubes were
of the three-volt class — and produced a most
annoying whining sound which could not be
eliminated and which was not due to any fault of
the receiver, which was pulled apart and re-wired
in an attempt to locate the trouble. In the end,
they had either to buy four good tubes or let
the receiver sit on the table and collect dust.
Being devout fans they purchased the tubes, and
presto! — the set worked like a charm.
It therefore cost them sixteen dollars to re-
place the tubes instead of twelve. But they
were attracted by the low price. False economy!
They might just as well have thrown the cheap
tubes into the ash can.
What is the good of buying such tubes and
taking a chance as to whether they will be any
good? Admittedly, you will strike some good
ones now and again, but at the most, they are
good for but a fraction of the service you would
get from the better class.
•if Tested and approved by R VMO BROADCAST -A-
The writer, with the help of a certain dealer,
tested several of these tubes with a device which
registers the current in the plate circuit when the
filament is heated to a certain temperature. If
a recognized make of 201 -A tube was inserted in
the socket, and the customary five volts applied
to the filament, the milliammeter indicated a
current of anywhere between i.i to 1.4 mil-
liamps. But if one of the dollar variety were
tried, it was seldom indeed that a reading of
more than one milliamp. was obtained; many
went as low as .75 milliamps., but only once in a
while would the meter indicate a good tube.
Then again many of them will not oscillate.
The writer has three such tubes of the 201 -A type
which were loaned him for testing purposes.
One will oscillate very strongly if a pressure of
no less than 5.5 volts is applied to the filament.
The remaining two will not oscillate at all,
which, of course, renders them useless as detec-
tors in a regenerative circuit. And do they play
havoc with the A battery! I'll tell the world!
AND TRANSFORMERS!
/CONSIDER audio frequency transformers.
v-< These, next to vacuum tubes, are probably
the most delicate of all radio receiving apparatus.
They must be designed and constructed with the
greatest thought and care, for it is upon the de-
sign and construction of the audio amplifier that
the quality of the received music depends. Oh,
yes; the loud speaker does have a lot to do with
it, but the audio amplifier first. Now, if there is
anyone who believes it possible to produce a
good transformer, one that will really do the
work, for $1.50, let him take the floor and show
us how! It simply can't be done, after the
middlemen have taken their profits.
Yet, a rather doubtful looking affair can now
be purchased at that price at certain cut rate
stores — one dollar for the winding and fifty cents
for the core, is the way they advertise them.
A socket for twenty-five cents, and not such a
bad-looking affair at that. Cheap? Sure it is,
until you apply the soldering iron and melt half
of it. Nothing but "mud"!
Radio fans! If you wish to build a good re-
ceiver, one that will reward you with the great-
est possible clarity and distance for a given
number of tubes, one that will be easy to work
with during construction, one that you can pull
apart without damaging the apparatus when you
wish to switch over to another circuit — then
purchase, steal, or otherwise acquire good, de-
pendable apparatus. There's a reason!
Take the case of John Brown, for instance.
The radio bug bit Johnny good and hard; so
having a nice little work bench and all the
necessary tools down the cellar, he decided to
" roll his own." Being a sensible sort of a fellow,
he went out and bought the best he could afford,
and since he didn't know much about it, he took
someone along with him to show him what was
what, and why. Johnny now has a fine outfit if
there ever was one, a real low loss set, and he is
justly proud of it. He gets splendid results:
night after night the old stations come pounding
in with a roar; and Johnny sits back in the old
easy chair with a contented look on his face, and
enjoys real radio satisfaction.
His neighbor, just a few doors down, is always
tinkering around, fixing this and changing that
and wondering why in heck his set won't work as
well as Johnny's. The answer is simple. Al-
though he could afford it, he wouldn't spend the
necessary cash to buy the good parts that char-
acterized Johnny's purchase. Disregarding the
reliable dealer down at the corner, he went to
the other store where "a real low loss" variable
condenser sells for a dollar and a quarter, and
bought a lot of cheap stuff that Johnny and his
experienced friend passed up with a grin of
derision. He now has more sense, and is think-
ing of junking the entirety of his original pur-
chase and starting in all over again with good
apparatus.
johnny Brown doesn't have to do that, so he
is just that much money to the good.
RADIO BROADCAST ADVERTISER
361
362
EADIO BROADCAST ADVERTISER
ASK . . ANY . . RADIO . . ENGINEER
An every-night
adventure of Burgess
Radio Batteries
ONE of the reasons why
you should always buy
Burgess Radio Batteries is
that the batteries used by air'
mail pilots — battleships — ex'
plorers— and the majority of
recognised radio engineers—
are evolved in the Burgess
Laboratories and manufac'
tured in the Burgess factory.
These batteries are identi'
cal with the batteries sold
by your dealer and thousands
of other good dealers every
where.
BURGESS BATTERY COMPANY
GENERAL SALES OFFICE: CHICAGO
Canadian Factories and Offices:
Niagara Falls and Winnipeg
BURGESS
RADIO
BATTERIES
:Now, I HAVE FOUND
A Department for the Exchange of Ideas and Sugges-
tions of Value to the Radio Constructor and Operator
CONTRIBUTIONS to this department are welcome and those used will be
paid for at the usual rates, that is from two to ten dollars each. A pri^e
of twenty-five dollars is given for the best idea used during each three-month
period. The prizewinner for the last period was announced in the November
RADIO BROADCAST. All manuscripts intended for this department should not
exceed about three hundred words and should he typewritten. Little consider-
ation can be given to manuscripts not typewritten. Envelopes should be
addressed to this department, RADIO BROADCAST, Garden City, New York.
THE ROBERTS CIRCUIT AND AUDIO
AMPLIFIER WITHOUT A STORAGE
BATTERY
THE circuit about to be explained
consists of the well-known Roberts
two-tube circuit plus one stage of
audio amplification. One five-volt tube
and two three-volt tubes are employed.
The filament supply for the three-volt tubes
consists of a battery of dry cells, while the
five-volt audio amplifier tube is supplied
through a transformer by the oo-cycle a. c.
lighting system. In this way the expense
and inconvenience of a storage battery are
eliminated without sacrificing any of the
good points of the set.
In order to eliminate the a. c. hum from
the amplifier, a potentiometer and grid bias
are necessary. By connecting the grid re-
turn of the amplifier to the negative ter-
value and the switch used for making and
breaking the filament circuit.
A transformer with a secondary voltage
of at least six, is used. This steps down
the house lighting circuit voltage from 1 10
volts. A toy transformer is being used on
my set at present. A bell ringing trans-
former which gives the required secondary
voltage may be used. Do not burn the
tube at greater brilliancy than is necessary
to obtain good, clear tone quality.
The filament rheostats of the three-volt
tubes are each of 25 ohms resistance. It is
important that the negative terminal of the
filament battery be grounded; otherwise a
hum will be heard in the phones.
The adjustment of the amplifier consists
merely in lighting all the tubes, plugging-in
on the amplifier, and adjusting the poten-
tiometer arm until the hum heard in the
phones is at a minimum. The position of
A.C Output of Step-down
Transfotmef
FIG. I
minal of the filament supply for the three-
volt tubes, and connecting the potentio-
meter arm to the positive terminal of this
battery, the grid of the amplifier acquires
a 45-volt negative bias.
I have found by operation that a vernier
is not necessary on the grid circuit tuning
condenser of the first tube. However, on
the second tube, a vernier condenser greatly
facilitates tuning. Two jacks are so ar-
ranged that the loud speaker may be plug-
ged-in on the output of the three-volt or on
the amplifier output. A filament switch
is used to control the filament circuits of
the three-volters. In this manner the fila-
ment rheostats may be set at the proper
f Tested and approved by RADIO BROADCAST -
the arm should be midway between its ex-
treme end positions. If the hum is not re-
duced to low audibility when the potentio-
meter arm is near its mid-position, check
over the amplifier connections and examine
the potentiometer itself for broken wire or
loose contacts.
The circuit as shown in Fig. i is correct
for two three-volt tubes and one audio
amplifier tube. This latter tube may be
of any type capable of handling the out-
put of the preceding tubes. The ohmic
value of its rheostat is determined by the
filament current and voltage, and by the
output voltage of the filament transformer.
For a tube requiring a filament current of
RADIO BROADCAST ADVERTISER
363
NATIONAL Velvet Vernier DIAL
Type B, Variable
(Patents Pending)
Positive Control
Easily Mounted
Gearless
Variable Ratio
Velvety Smooth
Graceful Design
*
With This NEW National Type B, Velvet Vernier Dial,
YOU Control the Reduction Ratio!
WHAT a difference in the tuning of your
set when you replace your plain dial
with a new NATIONAL Type B Variable
(patents pending). You'll be astonished.
Any ratio you desire, from a minimum of
6 to 1 to a maximum of 20 to 1 is instantly
obtained by shifting a small lever. Note how
it separates the stations operating on the
lower wave lengths.
Easily mounted on the \" shaft of any stand-
ard type of variable condenser,
tool you need is a screw driver.
The only
The same velvety smoothness, the same free-
dom from backlash, the same mechanical drive
as the famous Type A Velvet Vernier Dial,
(patents pending). Price $2.50.
NATIONAL Tuning Unit
Type B D-2
The NATIONAL Tuning Unit
for the popular circuits and hook-
ups gives amazing results to am-
ateur set -builders.
Comprises the NATIONAL
CONDENSER and the wonderful
BROWNING-DRAKE TRANS-
FORMER Complete in one
package,Price $22. Makes a most
welcome Christmas Gift.
Write for Bulletin 106 R. B.
NATIONAL CO., INC.
W. A. READY, President
110 Brookline St. CAMBRIDGE, MASS.
NATIONAL Tuning Unit
Type B D-l
Tested and approved by RADIO BROADCAST
364
RADIO BROADCAST ADVERTISER
Better Tone!
with Dry Cells
and UX 120
than with Storage Batteries
Note: The UX 120
is a new three-volt dry
battery power tube.
Used for audio fre-
quency amplification,
this tube will produce
better quality and great-
er loud speaker volume
than regular storage
batterv lubes.
Any set owner can easily install a UX 120
tube in his set in a few minutes by using the
new Na-Ald Number 120 Connectorald. It
is a simple, efficient means of introducing the
necessary additional "B" and "C" voltage
required for this tube into the plate and grid
circuit without rewiring the set. As easy
to use as an adapter.
Just slip the Connectorald onto the UX 120
tube and put the tube in the socket. Connect
the batteries — and — well, that's all there is
to it. Except to enjoy a quality and volume
you would not have believed possible. No
need to fuss with charging batteries. The
simplicity, economy and freedom from atten-
tion characteristic of dry cells is now com-
bined with the real volume and quality
previously obtainable only with storage
battery tubes.
The No. 120 Connectorald is suitable for
all sockets — metal neck as well as insulated.
For sale at radio, electrical and hardware
stores. Price, $1.25.
NA-ALD ADAPTERS
Na-Ald Adapter 419-X
With this adapter the Na-Ald df
Luxe Socket will take the new UX 199
small base tube. Price, 419-X, 35
cents.
Na-AId 420
Connectorald
No. 420, equipped with
cables, enables owners of
Radiola Snper-Het to get the
great increase in volume and
clarity the new UX-120 tube
develops. Price, 420, $1.25
Na-Ald Adapter 421-X
No. 421-A" makes possible the shift
from WD-U to UX lubes. Especially
designed to enable owners of Radiola
III, and III-A to enjoy the improved
operation the new tubes provide.
Price, 75 cents.
All Na-Ald products are for sale at radio,
electrical and hardware stores, everywhere.
Send for complete data on adapters for new
tubes.
ALDEN MANUFACTURING Co.
Also makers of the Famous Na-Ald
Sockets and Dials
Dept. B14 Springfield, Mass.
Alden Processed
IA-ALI
Sockets and Dials
i ampere, use a 6-ohm rheostat for a secon-
dary voltage of 6 volts; use about a 25-ohm
rheostat for any voltage between 6 and 10
volts.
For a tube requiring a filament current of
one ampere, a 6-ohm rheostat may be used
for any voltage up to 10 volts.
I have used plate voltages as low as 67
volts on both amplifier tubes with satis-
faction. The optimum value of plate
voltage for the detector tube can best be
found by experiment, and for the three-volt
tube will be about 40 volts.
JOHN B. CLOTHIER, JR.,
Lansdowne, Pennsylvania.
A HOME-MADE LOUD SPEAKER
THE main difficulty in loud speaker
horn construction lies in cutting the
parts to fit, and in obtaining well
proportioned lines and acoustics, which will
be a credit to the finished product.
A brief study of the patterns and details
given below, will enable anyone to build
easily a horn which will be very satisfactory
with an audio-frequency amplifier.
It is constructed almost entirely of rs
inch fibre or cardboard, and the dimensions
for the various pieces are outlined in Fig. 2.
The back, A, is cut from a piece 9 inches
wide and 24 inches long. A line drawn
through the center and perpendicular to
the 9-inch side, will aid in making the nine
measurements, one every three inches, to
secure the curves indicated. The two sides,
B, and back, C, are likewise laid out and
cut with a sharp knife.
The four parts are fitted together by
lapping A and C over the two sides, B, be-
ginning at the bell end and taking one cor-
ner at a time and bending to conform to
the curves and fastening, wherever neces-
sary, with a few stitches of No. 26 copper
wire, which is threaded through perforations
near the edge.
After all corners are fastened, four strips
of strong paper, 4 inches wide, are cut to fit
each corner. These are creased lengthwise,
THE FINISHED SPEAKER
scored where bends cause wrinkles, and
pasted on smoothly.
To assist in making the base, D, a circle
14 inches in diameter is drawn on a piece
of cardboard. This is then marked, cut,
scored on the dotted lines, bent over a
sharp edge and the seven 5-inch woodstrips
tacked in at the corners. Four of these
may be used if desired. A f-inch hole is
cut in the center of the base for a No. 522
CW Western Electric Loud Speaker Unit.
The base and horn are then fastened to-
gether with moulding and small brass
screws, and the whole given four coats of
paranite. Paranite can be made by dissolv-
ing parts of an old phonograph record in de-
natured alcohol. It strengthens the horn
and gives it a very desirable velvet black
finish.
The unit is fastened in the base by first
inserting the rubber bushing to a tight fit.
(Continued on page 174)
J£ Moulding
and Bottom Strips
-1%
FIG. 2
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
373
if- 41
Operates WMAQ
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WMAQ. My income prac-
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KEITH KIMBALL, Chicago.
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Dept. AU5, Washington, D. C.
Instruments
Given with Course
All instruments shown here
and many others given to
students for practice work
while learning. Receiving
sets, from simplest kind
to thousand mile re-
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LARGEST RADIO SCHOOL IN THE WORLD
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Without obligating me in any way, send me your free book,
"Rich Rewards in Radio," and all information about your prac-
tical, home-study Radio course.
Name ,
Address
Town State.
374
RADIO BROADCAST ADVERTISER
ANOTHER
JEWELL
DEVELOPMENT—
— Jewell
Engineers are constantly
studying the latest devel-
opments in radio :— where
there is need for a new
instrument we are the
first to design it.
The Jewell No. 109
Super-Heterodyne
Voltmeter
—Shown above
was designed for owners
of Radiola portable Super-
heterodyne sets. It is
mounted in a panel which
is an exact duplicate of
those in the set.
SAVE YOUR TUBES
ASK FOR JEWELL
15-B RADIO CATALOG.
Jewell Electrical Instrument
Company
1650 Walnut St., Chicago, HI.
26 Years Making Good Instruments
The insertion of the nipple into this rubber
under considerable force holds it perman-
ently, while the cord is brought out through
a small perforation in the side. The dia-
phragm of the unit is adjustable, and in
conjunction with this horn and 90 volts on
theplateof a two-stage amplifier, it brings in
distant stations with as good definition and
volume as many more expensive speakers.
J.T. CARVER,
Huntington, Tennessee.
CYLINDRICAL COILS FOR THE
KNOCKOUT SET
THIS letter is in response to your
request in RADIO BROADCAST regard-
ing the use of cylindrical coils in the
Roberts.'circuit. (Incidentally, I bought this
particular issue at a newsstand in Singa-
pore.)
I built a three-tube Roberts outfit last
summer, using cylindrical coils, and con-
sider it a very satisfactory set. I find that
some distortion is present when receiving
local or near-by stations, but on the DX
stuff the reproduction is all that could be
desired. The distortion on locals can be
eliminated by slightly detuning the left
hand condenser.
The circuit is shown in Fig. 3 while the
arrangement of coils may also be seen in
this diagram. Tubes of the UV-2OIA type,
daylight cut them off. It is interesting to
note that all of the stations east of the
Rockies suddenly fall off at about 3200
miles west of San Francisco, in longitude
173 East. The same effect is noticed on
the 4200-^3700 kilocycles-(75-8o meter)
amateur signals which are very strong one
night and unreadable the next as we go
farther east. At the same time there is no
decrease in the signal strength of the west
coast stations.
I found that the use of No. 24 d.s.c. wire
for the coils was satsifactory, and used this
wire throughout. The dimensions of the
coils and the data for their construction is
perfectly simple, and is as follows: S-i
consists of forty-five turns wound in single-
layer fashion, on a suitable tube of three-
inch diameter; A, which is the primary
coil, is next wound on the same tube and
on top of S-i, in the center. It consists of
25 turns of the 24 d.s.c. wire, and is tapped
at every fifth turn; N-P is the next con-
sideration. It is formed of two 2o-turn
coils wound on top of each other, on a tube
with a diameter of 2f inches; S-2 is bank
wound, and is composed of 45 turns. Its
cylindrical form is also 2f inches diameter;
T, the tickler coil, is made by winding 20
turns on a 2-inch tube. The tickler coil is
so arranged that it may be variably coupled
to S-2, as shown by the dotted lines in Fig.
3. I have found this arrangement gives
better results than if the tickler is mounted
+45 +90
FIG. 3
and General Radio audio transformers are
used throughout.
This set has brought in KGO Oakland at
820 miles west of San Francisco, in broad
daylight, and practically every important
station in the country at night, until we
were so far west of San Francisco that the
to rotate within S-2. N-P should be placed
about f-inch from S-2 for best results.
Ci and C2 were found necessary, as without
them the receiver was found to be very
unstable.
L. O. DORAN,
San Francisco, California.
( " As stated elsewhere in this department, a $25 prize is
awarded each three months for the best contribution pub-
lished. The winner for the December, January and Feb-
ruary period will be announced in the next number of
RADIO BROADCAST.
Tested and approved by RADIO BROADCAST -jr
RADIO BROADCAST ADVERTISER
375
It works better than a Jot of sets that sell for
twice the price. I have owned four other sets ana
heard many more - and none beats this
Built like— looks like—performs like a $200 set!— 27 inches long.
Demand Breaking All Records-More User Agents Wanted-Get Wholesale PricesQuick
Notice!
RADIO
GETS'EM
COAST fr
COAST
Enormous demand for the celebrated Miraco
Ultra 6 (resulting from itB many enthusiastic
users so highly recommending it to their
frienda) enabled us to add boats of coatly
new features. latest refinements and up.-to-
expect to find only onThe newest se^selli^K a!
much higher prices. So the Improved Ultra
p tor 1926 is even a better set— a more beaut-
iful set— a more selective and more powerful
set— incredible BS thia may aound' — for less
money than ever before.
COAST TO COAST RECEPTION VERIFIED BY USERS
MANY SAY IT'S BEST THEY'VE
"Ultra 6" more than meets my
expectations of a gnod radio set.
Many think it is the best that they
have heard. For volume, selec-
tivity, clearness and long distance
u is unsurpassed in my estimation
s, Auto Supply. Allentown.
i>nna,
.PRAISES THE FINE TONE AND
The Ultra-5 has a fine tone and trood
volume; last night had 24 different
Stations from 8 to 10-aIl on loud
speaker. O. T Malone, Ne<
York.
THE TONE IS "WONDERFULLY
CLEAR AND POWERFUL"
"T1 m."re tnan PIe*««d with my 6
tube Miraco. Tone wonderful lye [ear
and powerful. D. C Detroit,
Michigan.
MORE PRAISE FOR MIRACO
, TONE QUALITY
The Ultra-6 received from you is
the best lever heard. It is just as
clear as a crystal. Raymond W.
Massback. III.
ONE OF THE^CLEAREST EVER
All who have heard ray Ultra-5 set
-jronounce it one of the clearest
Jiey have heard, and I must say
that the MIRACO is In every way as
represented by you George . .
Colville, Washington.
MONTANA HEARS BOTH
COASTS
IJltra-R wet is O. K. Have got them.
New York to Los Angeles, Winni-
peg to Dallas. Texas. W. H
rolson, Montana.
OHIO GETS 'EM COAST TO
COAST
We are enjoying the Ultra-5 Radio.
It is all you recommended. We get
stations on the east coast, south
and west coast. Walter ..... Van
Buren, Ohio.
CALIFORNIA THE FIRST NIGHT
Headphi.nea are not necessary with
the Ultra-5 I bad KFI, California,
the first night with same volume as
Pittsburgh. Fred G Liver-
pool, Ohio.
K
With Miraco' five" "tube "set am get-
ting stations on the Pacific and At-
WKWt1"*1 paulB
^COAST TO COAST" A REALITY
The two Miraco-6's have been work-
ing fine, in fact far beyond our
expectations, four statement of
'coast to coast" reception proved
absolutely a reality. T. D
Houston, Texas.
MICHIGAN GETS COAST TO
COAST
I am overly pleased with the Miraco
Ultra-5. Can get stations from coast
to coast and from Texas to Canada.
Geo. O' Gordon, Michigan.
LOTS OF VOLUME - 20 STATION FIRST NIGHT
Will drop yoa a few lines to let you know that I re-
ceived my Miraco Ultra-5 and that it works fine. Had
20 stations the first night — it has lots
ofvolume. Fred Versailles, III.
The reports we print are
from UNSOLICITED letters
sent us by pleased users.
INDIANA HEARS BOTH COASTS
Miraco Ultra-5 is a first-class set
In every respect. It can't possibly
be beat for the price. The first night
1 received over twenty stations
from both coasts. Adolpb M
Indianapolis. Indiana.
MINNESOTA HEARS COAST TO
COAST
Received Ultra-5 in fine condition.
Have received programs from sta-
tions all over the Ui.ited States and
Canada. We find it is one of the best
sets in this locality. We are well
pleased with the wonderful results.
Clarence ,..,.' Nashwauk, Minn,
HEARS CALIFORNIA TO EUROPE
Enclosed is a partial list of the sta-
tions I received with the Miraco
Ultra-B: KSD, WEUH WHAV
WEAF. WLW, WCHD WHIT
WOR. WJAZ, WOC. WHAS WWj'
CKAC, KKIX. WCK.WHAZ'
KPAB WllAA, WAS!, WCAP
WTAfc. WC1J, KFKX ,'WAAW
WTAM. WOAI, WSOri. WCCO
KDKA. WIJAr*. WMO. CNRO,
WLS, WHJ, WBZ. WNH KFNF
Carl H.
Ine.), Paris
. . Waukeaha. V. is.
MONTANA HEARS CALIFORNIA
TO IRELAND
am more than pleased with the
ltra-6 Receiver. I have 90 stations
my record in 20 days' time in-
[a
Ultr
.
»T v *-t. n\ifi tj, w n \j, WUUA
^kCp?UA,UkBT°KAp£ &$£
%ttVM£F**u?.'(l&
WM<1. WJJ^VVGAN: KKU.'WGW:
- Jlock I received Ireland, the dis-
tance being several thousand miles
Richard Coniertown. MontJ
WEST VIRGINIA HEARS
AUSTRALIA
Got2-XBWellinBton,Australla.plain
,a»t rnnht at 12:46 A.M. over the
U ltra-5 Miraco von Bold me. I am
delighted and would not trade for
any instrument in town. Geo
'•'-- Ferris. West Va.
Se
ALL WE CLAIM ... AND MORE
Miraco Ultra "5" r ' '
stalled yesterday ev
—had wonderful n
last night. Think I
tra "6 ia
claim and _.
V. A
Hampshire.
Tenneaaea .
Guaranteed by _
One of the Oldest
Radio Builders
[ULTRA SELECTIVE FIVE TUBE SET IN ^J MAHOGANY CABINET]
You can ei
lot of money on sets and sup-
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for our Amazing Special
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Big profits easy — accepting
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demonstrateinyourhome. No
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formance of Miraco Sots
does the selling. Greatest de-
mand in the six years we have
been building sets — we need
Tested and Approved
by Radio's
Highest Authorities
In the opinion of radio ex-
perts. Selectivity, long dis-
tance reception, clarity of
tone, power and volume have
been amazingly increased —
"B" battery consumption is
minimized — oscillations are
easily controlled on all wave-
lengths, through use of latest
radioinventions.Among these
are: Duoformers" (ultra low-
loss inductance coils); the
Counter-Balancer" (patent-
ed); flexible wiring which
prevents broken or noisy con-
OfherMiracoLongVistcmjceSets ^/?75up
Wonderfully improved new models in one-tube and
three-tube Miraco Long Distance Seta also ready at
lowerpnces! New Miraco R-3atonly$27.36 (retail) oper-
ates loud speaker on distant stations. New
one- tube Model R is also a record-breaker
Get Special Offer! „„.,„. „_„„_
sets work on storagre or dry batteries, are easily
connected and operated. Unmatched values!
Let testimony of users convince you. Write for
literature and Special Offer — use coupon.
Jftl theThoofyou want is waiti
Reports from hosts of users in every state prove Miraco sets— at rock-bottom factory prie
outperform seta costing up to three times as much. Send for latest literature, SPECIAL
! of additional testimony leaving no doubt that
•eta *em Coast to Coast.
'ER and plenty c
"iraco Radio Get
RADIO
GETS'EM
COAST ft
COAST
big
[] Agent
NAME.
ADDRESS ........
376
RADIO BROADCAST ADVERTISER
TONE
Full, sweet, mellow and
natural, without the
slightest indication of
distortion, is another
achievement that is mak-
ing the APEX SUPER
FIVE the most popular
of all receiving sets.
A
VOLUME
That supplies dance mu-
sic or entertainment
without any loss, is a fea-
ture for which the APEX
SUPER FIVE is world
famed.
A
DISTANCE
Lends added enjoyment
to radio with an inde-
scribable fascination of
tuning-in far away sta-
tions, which is always
possible with the APEX
SUPER FIVE.
Ask your dealer for a demonstra-
tion. Your eyes and your ears will
tell you that APEX stands at the
high point of perfection in both
performance and appearance. $80
without accessories.
Apparatus
SUPERS
APEX ELECTRIC
MFG. CO.
1410 W. 59th Street
Dept. 104
CHICAGO
THE GRID
A Department Devoted to Solv-
ing the Problems of our Readers
QUERIES ANSWERED
WHAT ARE THE VALUES OF THE CONDENS-
ERS, RESISTANCES, AND BALLASTS ETC., FOR
THE RADIO BROADCAST "ARISTOCRAT"?
T. J. L. Lansing, Michigan.
2. WHAT ARE THE CAUSES OF SOME OF THE
NOISES PRODUCED IN MY RADIO SET? CAN
THESE ORIGINATE AT THE STUDIO?
A. W. T. — Pompton Lakes, New Jersey.
3. WHAT is THE THEORY OF OPERATION OF IM-
PEDANCE AUDIO AMPLIFIERS?
W. S. Burlington, Vermont.
"ARISTOCRAT VALUES"
THE following values apply to the "Aristo-
crat" receiver which is shown diagramati-
cally in Fig. i: Ci and C2, .0005 mfd.;
€3, .002 mfd.; €4, .0005 to .002 mfd.; C6, .00025
mfd.; €7, C8, and €9, not less than .01 mfd.
Cj is a midget variable condenser and its capacity
approximates .000032 mfd. The values for the
various resistances shown in the diagram, are as
follows: Ri, R2, R3, R4, and R5 are filament
ballasts, and their size will vary with the differ-
ent types of tubes employed. Thus, for tubes
consuming .25 amperes, j amp. ballasts are nec-
essary, etc.; R6, 2 to 4 megohms; Ry, Rg, and
Rn, 100,000 ohms each; R8, approximately I
megohm; R.IOJ megohm; Ri2,j megohm. The
use of condenser Cio often improves the results
but its use may not be essential. Its capacity
will be in the neighborhood of .002 to .004 mfd.
A large capacity condenser of about half a mi-
crofarad will often improve the tone if connected
across the B battery binding posts. In the ori-
ginal RADIO BROADCAST "Aristocrat," single
broadcasting, are often excessively noisy by
induction from neighboring wires. A steady
rushing sound, especially noticeable when the
receiver is tuned to resonance, is often caused
by the generator which supplies the plate po-
tential to the transmitter tubes. This noise is
more or less pronounced on all stations and
continues until the broadcasting is finished and
the stations sign off.
Noise contributed by the ether medium may
be defined as those sounds which are caused by
electrical disturbances between the broadcasting
station and the receiver itself. In this group
are found the disturbing influences of high
tension power lines, violet and X-ray machines,
leaky transformers, electrically operated ele-
vators, sparking motors and generators, trolley
and elevated systems, railway systems and tele-
phone and telegraph wires, and a host of other
electrical contrivances. Electrical impulses from
those undesirable sources usually occur at short
wavelengths and are picked up by sensitive
receivers. Static also comes in this class and is
Regeneration may be Obtained Diner by Variable
l' Tickler or Resistance Shunted Across A Fixed Tidder
SSOO-50.000A
Circuit Enclosed Herein Comprises assistance Coupled
' Amplifier wtifch may be Ottatred a* a Complete Unit.
Separate Resistor units may be Employed in the Audio Amplifier
' wherethe Complete Manufactured AmpUfwr n not used
"1
H-
Cj
"9
»2
1
j
B F
L.
-r
L
B F
L
R4
L
"1!
B F
1
1
i
L
Rs P —
.002(0.004
j
the necessity
for the use or
this Condense,
i
;
1
_
1
FIG. I
units consisting of two resistances and a coupling
condenser all in one piece were, among other
arrangements, tried out. It is for this reason
that the two resistances and coupling condenser
preceding each audio amplifier tube are sur-
rounded by dotted lines.
NOISES AND THEIR CAUSES
IT IS possible that various noises heard
through one's loud speaker can have ori-
ginated at the transmitting station, but
generally speaking the trouble can be traced to
either the receiving equipment or the interme-
diate medium — the ether. Noisy microphones
cause a steady hiss which often blurs the voice
of the artist, while programs picked up outside
of the studio and carried overland by wire for
Tested and approved by RADIO BROADCAST i
more prevalent throughout the summer months.
Many satisfactory programs are suddenly broken
up by a series of unfamiliar clicks, and in many
cases are interrupted entirely for short periods.
Those may be caused by key clicks from con-
tinuous wave transmitters and by improperly
operated regenerative and super-heterodyne
receivers.
In another class are the noises which are
caused by the receiver itself or by the equipment
which is used in connection with it. Dis-
charged B batteries become noisy and are
usually the cause of a high pitched squeal when
the receiver is operating on the second audio
stage. These batteries should be discarded when
their voltage drops below about thirty-four.
Storage B batteries often cause the same trouble
RADIO BROADCAST ADVERTISER
377
Made to Last
RADIO tubes will continue
to be used for many years,
and with careful, intelligent
handling and periodic flashing
with the Burton and Rogers
Tube Flasher they will last for
many years.
So will the Burton and Rogers
Tube Flasher. It is made to
last. I ts genuine Bakelite pan-
els, resistances accurate under
all conditions and wound on
porcelain, baked green enamel
sides; proclaim its quality and
insure its durability.
Electrically its design is based
on fundamental principles and
long experience and experimen-
tation. It is the scientific de-
velopment of an idea — not an
unintelligent imitation of some-
thing else. And because what
is made right, loo^s right, it is an
ornament to the accessories of
the most particular radio owner.
YOU CAN DO IT YOURSELF
WITH A
FL-ASHE.R
50
One Model for D. C. or A. C. all cycles
For tubes with thoriated filaments.
BURTON & ROGERS MFG. CO.
755 Boylston Street, Boston, Mass.
If Your Set Won't
Percolate
write us about it. RADIO
BROADCAST is establishing a
special repair department to assist
set builders in getting the best
out of the receivers they build
from plans published in the mag-
azine. Write for complete infor-
mation about this new depart-
ment established for your benefit.
Volume— with True Quality!
The value of radio as an entertainer increases only with the realism and quality of
reception. This requires good broadcasting— reception and amplification equal to, or
better than, the broadcast range of audio frequencies— and a loudspeaker of uniform
response over the same range. Heretofore one of the weak links in this chain has been
the audio amplifier.
But it is now possible with AmerTran DeLuxe audio transformers to obtain faithful,
strong reproduction over a range of frequencies down to the lowest pitched audible
sound. This is nearly three octaves lower than that previously obtained. The deep boom of
the drum, the thrum of the base viol, and the thunder of the pipe organ are reproduced
with startling realism— and at no sacrifice of the highest notes within the audible range.
Once tried, the AmerTran DeLuxe will be recognized as setting a new high standard of
excellence in audio amplification.
AmerTran DeLuxe requires no special circuit other than the use of a large
tube in the last stage to prevent overloading at the low frequencies brought
out. It is made in two types.
Price, either type, #10.00 .
We have prepared a booklet describing these and other ^mf
AmerTran products, together with recommendations for
their use. We shall be glad to send you a copy upon request.
AMERICAN TRANSFORMER COMPANY
178 Emmet Street, Newark, N. J.
"Transformer builders for over twenty-four years"
SOLD ONLY AT AUTHORIZED AMERTRAN DEALERS
AmerTran Audio Transformers type AF6 (turn
ratio 5) and AF7 (turn ratio 3H) have been sub-
stantially reduced in price. As before, they are
today the leaders in their class. No changes
have been made in the electrical characteristics
since they were first sold. Either type now $5.00.
Be sure to see the other Amer-Tran ad on page 383
Why not subscribe to Radio Broadcast? By the year only $4.00; or two
years, $6.00, saving $2.40. Send direct to Doubleday, Page & Company,
Garden City, New York.
Write {or information
The new and improved line of
ELDREDGE *
Pocket and Panel
Ammeters - Voltmeters - Voltammeters
ELDREDGE ELECTRICAL CORPORATION
Springfield, Mass.
Established 1892
Dealers: --Address Dept. 5, for information
Tested and approved by RADIO BROADCAST
378
RADIO BROADCAST ADVERTISER
Do you know about the
"SUPERUNIT"
FAMILY?
They are all tested assemblies
which make possible the construc-
tion of various sets with no worry
about the location of the parts.
They are all equipped with cushion
sockets and nickeled brackets.
They solve the problem for the
folks who like to build their own
sets.
4-Tube "Superunit
"
Type A for |Standard base,
Type B for UV199, Type C
for UX tubes. Add two
stages of audio for 6 tube
set ............................
f\ fj
% /
ij 9
tn
"Superunit-6"
The same as the standard
type, but with two stages
of Thordarson audio
mounted and connected.
Size 5x15 inches
$
50
,00
"Superunit" Jr.
4 tubes with low loss plug
in coils, R. F., detector and
two stages of Thordarson
audio '. ....
$
37
.50
Any "SUPERUNIT" can be used
with the S-C Capacity Element
which we manufacture.
NOTE: The S-C Capacity Element is
indicated by Mr. Arthur H. Lynch for the
Radio Broadcast Aristocrat Receiver.
^^ Bulletins on request
Hanscom Radio Devices
WOONSOCKET, R. I., U. S. A.
even when the voltmeter reading is high. Squeals
in this case are caused by one or more dead cells
which are usually not detected unless a volt-
meter reading is taken of each individual cell.
Noises are sometimes caused by the vacuum
tubes themselves. While outwardly they appear
quite satisfactory, it sometimes happens that
their internal elements are not rigidly supported,
and any disturbance in the vicinity of the re-
ceiver may cause these elements to vibrate. This
defect in construction produces a bell-like sound
which has been known to build up in volume and
drown out the program.
A somewhat similar sound may possibly be
produced by placing the loud speaker on top
of the receiver or by pointing the horn in the
direction of the receiver. This may be reme-
died by a slight change in the position of the
horn.
Noises are also caused by dirty prongs of
vacuum tubes or by sockets which do not make
perfect contact. These noises may be over-
come by sandpapering the prongs of the tubes
or by bending up the spring contacts of the
tube sockets.
IMPEDANCE AMPLIFIERS
THE desire for quality of tone, rather than
excessive volume, is the dominant factor
causing widespread investigation and re-
search work in the quest of an audio amplifier
that will entirely satisfy the critical tastes of the
modern broadcast listener.
Up to recent times, transformer audio ampli-
fiers have been accepted because very little was
known about alternatives. The activity of in-
dependent investigators, however, led to very
fine accomplishments as regards resistance-
coupled amplifiers, yet there is still much to
be found out about this very interesting phase of
amplification work.
Now radio is repeating itself in a swing around
VT-1
VT2
FIG. 2
the circle, and the old-time choke or impedance
audio amplifier is coming into its own again.
Claims are being advanced to prove its partic-
ular advantages and superiority over other forms
of amplification, and improvement has led to the
development of a type of choke coil which has a
satisfactory voltage step-up. Ordinarily, such
amplifier units consisted of a single coil of wire
having an iron core.
Such a coil is shown applied to an audio ampli-
fying circuit in Fig. 2.
To-day, by means of a tap-off on the choke
coil, it is possible to obtain a step-up ratio suffi-
cient to overcome any drop that might take
place in the condenser C. Commercially this
type of choke coil is known as an "Autoformer."
Explaining the function of the circuit in
Fig. 2, the variations in a.c. current in the plate
circuit of the first tube set up a varying electro-
magnetic field in the choke coil; the e.m.f. pro-
duced is impressed upon ihe grid of the succeed-
ing tube through the condenser C, which pre-
vents the B battery potential from reaching the
grid of the second tube.
Note the similarity in this type of amplifier
f Tested and approved by RADIO BROADCAST •
to the standard resistance type. In the latter, a
plate resistance unit replaces the choke coil.
Some claim that the resistance amplifier requires
higher B battery voltage to be applied to the
plates of the amplifying tubes, because of the
drop in voltage through the high plate resistance.
However, all tests conducted at the RADIO BROAD-
CAST Laboratory tend to indicate that as low as
ninety volts on the plate of the last stage resis-
tance-coupled amplifier will operate entirely
FIG. 3
satisfactorily. Of course, with the new high-Mu
tubes, greater plate voltages are required.
The new type of choke coil, or impedance am-
plifier, as it is correctly called, employs the auto
transformer system to obtain the desired step-
up. In Fig. 3, P-B indicates the primary or
plate winding of the coil, while G-B constitutes
the secondary. Any variations of the electro-
magnetic field in P-B will cause corresponding
but stronger variations in G-B. The resistance
R, in both types of choke amplifiers, prevents
excessive negative charges from piling up on the
grid of the tube, by providing a leakage path
back to the negative side of the filament. Or-
dinarily, the grid should be maintained at a
negative potential in respect to the filament, and
often a C battery is employed for this purpose;
this, so that the tube may function on the proper
part of its characteristic curve.
Several types of impedances suitable for use
in an amplifier of this type, are finding their way
to the radio market, and there are some com-
panies, such as the Acme, General Radio, Don-
gan, Amertran, Thordarson, and National, that
are either making such coils or have on stock a
coil which may readily be employed in this
capacity.
The experimenter may have an old trans-
former whose primary is burned out, in which
case the secondary may be connected as in Fig. 2
to form quite an efficient choke coil for such an
amplifier.
An important feature of the choke amplifier is
the selection of a suitable isolating condenser,
as C i is termed. If this condenser is too
small, it will by-pass some of the higher frequen-
cies. One on the order of .5 or i mfd. should be
employed for satisfactory reproduction.
WHEN WRITING TO THE GRID—
A TYPEWRITTEN letter, written on one
•* side of the paper only, is to be preferred.as it
aids in the quick formation of a satisfactory reply.
Don't fail to send a stamped addressed envel-
ope with your inquiry.
Don't send a second inquiry about the first.
Don't include questions on subscription orders
or inquiries for other departments of Doubleday,
Page & Company.
In asking questions give us all the information
that will aid in advising you. If the question
relates to apparatus described in RADIO BROAD-
CAST, give the issue, page number, and figure
number of the circuit diagram, etc.
RADIO BROADCAST ADVERTISER
379
Technical Booklets
Worth Reading
Cardwell Quality Radio Parts are
standard. Write for Bulletins on
any or all of the following. They
give a liberal education on radio
theory and practice:
51 Variable Condensers
52 Special Condenser Types
55 Cordweve Coils (on press)
56 Transmitting Condensers
71 Equitrol Dials
36 Engineering Service
37 Audio Transformers
82 Professional Set Builders Plan
85 Straight-Line Condensers
60 Dealer Electrotypes
72 Exclusive Dealer Agencies
PLEASE BE SURE TO CHECK BULLETINS
IN WHICH YOU ARE INTERESTED.
ALLEN D. CARDWELL
Manufacturing Corporation
81 Prospect St.
Brooklyn, N. Y.
Antiques
interiors, houses,
gardens, travel,
sports, horses, dogs,
blooded cattle —
all these are in
Country Life
A Doubleday, Page Magazine
Limited Supply at Newsstands
FAHNESTOCK
CONNECTORS
Popular Wherever
Radio is Used!
Antenna Connector
Eliminates splicing
and soldering of
wires. Snap larger
connector over an-
tenna wire ; insert
lead-in wire into
smaller clip and a
perfection connection
is the result.
Made of the finest
quality Phosphor
Bronze.
PRESS v
Ground Clamps
Eliminates solder-
ing, easily attached.
Made from soft
copper % it wide with
a phosphor bronze
spring binding post,
also a screw and nut
attached.
FAHNESTOCK
ELECT.CO-
N.Y.
9&e AMSCO
ALLOCATING
CONDENSER
IT SAVES SPACE/
This straight line frequency condenser is a space-saver in the radio
cabinet ... It can usually be substituted for the old time conden.
sers in existing sets ... Once installed, it revolutionizes your
ideas about tuning ... Those Amsco half-a-heart-shaped
plates add Kilocycles at the rate of ten to each dial divis-
ion— giving "a station for every degree". . . AH wave-
lengths— high or low on the scale— tune in with
equal ease . . . Amsco allocation of the sta-
tions is uniform and correct to within a
fraction of 1% ... Insist on Amsco
Allocating Condensers ... Made
in six space-saving models, three
Single and three Siamese, at
very reasonable prices.
Amsco Products, Inc.,
Dept. E
Broome &. Lafayette Sts.
New York, N. Y.
AMSCO PARTS
Write for our booklet, "The Heart of
the Hook-up" for full details and prices
of the entire Amsco line. Amsco for
Excellence.
DEAFNESS IS MISERY
GOOD HEARING A JOY
Millions of people know that, but Multitudes of
, persons with defective hearing and Head Noises
" are again enjoying conversation, go to Theatre and
Church because they use Leonard Invisible Anti-
' septic Ear Drums, which are Tiny Megaphones
fittingin the Ear entirely out of sight. Nowires.no
», batteries, no head piece. They are Unseen Comforts,
and inexpensive. Write for booklet and sworn
statement of the inventor who was himself deaf.
&. O. LEONARD, Inc., Suite 151 70 5th Ave., New York
RADIO RENCH
Piv* II tone
«nd . hind]
22'/2 Volt
un-acid
everlasting
rechargeable
"B"
Storage Battery
$2.95
includes
chemical
illlllf •>' H ,,!«> »»•!>«• I'lIP
IttWtFV STOW6E
45 volts 15.25, 90
volts $10.00, 1125$
volts $12.50, 135
volts |U. 75, 157%
volts $16.80.
Truly the biggest buy today. Easily charged on any current includ-
ing 32 volt systems. Any special detector plate voltage had. Tested
and approved by leading authorities such as Popular Radio labora-
tories. Over 3 years sold on a non-red tape 30 day trial offer with
complete refund if not thoroughly satisfied. Further guaranteed 2
years, Knock-down kits at greater savings. Complete "Hawley"
"B" Battery Charger $2.75. Sample cell 35c. Order direct— send no
money— simply pay the expressman cost on delivery. Or write for
my free literature, testimonials and guarantee. Same day shipment*.
B. Hawley Smith, 312 Washington Ave., Danbury, Conn.
Tested and approved by RADIO BROADCAST
380
RADIO BROADCAST ADVERTISER
3&tng tn tjje
Jgeto fear!!
Listen to the clear tinkling bells on the
frosty midnight air — at the stroke of 12.
Why Not Use
the "B" Rectifier?
Rhamstine* "B" Rectifier
$<
525
Only
(Tube not included)
A Rhamstine* "B" Rectifier eliminates "B"
Battery troubles, converts alternating cur-
rent ( 1 10 volts) into direct current, and
assures a continuous flow of power through
Radio receiving set at a constant voltage.
The "B" Rectifier gives you better reception
and reproduces the original sound in all its
natural fullness. Its efficiency will amaze
you. Endorsed by Radio Manufacturers and
Dealers. Why not get one? Sold on assured
satisfaction — you can depend upon Rhams-
tine* quality and performance. Send no
money. Just check the coupon.
Why Buy New Tubes?
A Rhamstine*
Tube Booster will
re-energize the fila-
ment and repro-
duce the clear tones,
and give better
volume and recep-
tion. A few min-
utes, once a month,
will re-create the
energy in the old
tubes and make
them just like new.
Tube Booster
Only
Works on any
A.C. no- 1 20 volts,
50-133 cycles-2OiA
or 199 type tubes.
Mail the Coupon To-day
J. THOS. RHAMSTINE* (i)
506 E. Wood bridge, Detroit, Mich.
Please send me
D Rhamstine* Tube Booster at $6
D Rhamstine* "B" Rectifier at £25
by express C. O. D. subject to inspection. If I am
not entirely satisfied with the "B" Rectifier I will re-
turn it to you in five days and receive a refund of the
full purchase price.
Name. .. ,
Address . .
City . . . .
J. THOS. RHAMSTINE*
Radio and Electrical Products
506 E. Woodbridge St., Detroit, Mich.
THE BEST IN CURRENT RADIO
PERIODICALS
The Third Installment of a Useful Classified Sur-
vey of Material Appearing in the Radio Press
By E. G. SHALKHAUSER
How This Survey Can Help You
HOW often have you looked for information contained in some article which you recall hating
read months ago — the description of the Browning-Drake receiver, or the measurement of
losses in inductance coils, for example? After looking through probably several issues of a do^en dif-
ferent publications, you either give up or become interested in something altogether different.
When data is wanted on some particular subject, a systematic file of subjects and titles becomes a
real radio encyclopedia. Instead of having merely the title of an article given, which often is misleading,
a summary of the contents gives all the information. These surveys cover the radio field as gleaned from
material in to-day's periodicals. They will always serve as a future reference-guide to all who are
interested in the science of radio, whether engineer, manufacturer, dealer, experimenter, or listener.
To be of practical value and easily accessible, these surveys should either be filed in a scrap book, or,
better still, be pasted on individual cards and filed according to numbers, or alphabetically. In the
matter of classification of articles, the Bureau of Standards circular No. i )8 has been followed. This
may be obtained from the Government Printing Office, Washington, District of Columbia, for ten cents.
In addition, each abstract has certain key-words placed at the upper right, which may be used for
the purpose of filing articles alphabetically.
With this series of surveys we hope to aid our readers and help them through many difficulties
which they no doubt have often experienced. In future we will give information and references to
articles previously surveyed upon receipt of a stamped and self-addressed envelope.
Following is the series of headings, made up according to the Dewey Decimal System used in the
Bureau of Standards circular No. 138:
VSt
Rooo RADIO COMMUNICATION IN GENERAL.
Under this heading will appear all subject
matter pertaining to laws, regulations, history,
publications, etc., which deal with radio in a
general way.
Rioo PRINCIPLES UNDERLYING RADIO COM-
MUNICATION.
Here will be given the phenomena of radio
waves, their underlying theory of propagation,
the principle of antenna and counterpoise, de-
sign and characteristics of vacuum tubes and
their behavior in circuits, types of circuits, trans-
mitting and receiving apparatus and their prin-
ciples of operation.
Raoo RADIO MEASUREMENTS AND STANDARDIZA-
TION METHODS.
The various known methods which have been
used in measuring frequency, wavelength, reson-
ance, capacity, inductance, resistance current,
voltage, dielectric constants, and properties of
materials, will be mentioned here.
Rjoo RADIO APPARATUS AND EQUIPMENT.
A description of various types of antennas
and their properties, the use of the electron tube
in various types of receiving and transmitting
sets, other methods of transmission of signals,
various detecting devices used in reception,
instruments and parts of circuits, come under
this heading.
R400 RADIO COMMUNICATION SYSTEMS.
The spark, modulated wave and continuous
wave systems in transmission, beat and other
methods of reception, wired wireless, automatic
printing, the buzzerphone and Fullerphone, will
be given here.
R5Oo APPLICATIONS OF RADIO.
To aviation, navigation, commerce, military,
private and broadcasting, and the specific infor-
mation under their headings, are referred to here.
R6oo RADIO STATIONS.
The operation, equipment, and management
of radio installations, both transmitting and re-
ceiving, the testing, the rules and regulations
concerning stations, the reports and bulletins
issued, will follow under this heading.
Ryoo RADIO MANUFACTURING.
Data relative to costs and contracts of radio
equipment from raw material to finished product,
including factories, tools, equipment, manage-
ment, sales and advertising, follows here.
R8oo NON-RADIO SUBJECTS.
The matter of patents in general; the mathe-
matics and physics, including chemistry, geology
and geography; meters of various kinds; all
information not strictly pertaining to radio
but correlated to this subject, will be found
under this heading.
Rooo MISCELLANEOUS MATERIAL.
A Key to Recent Radio Articles
R333- THREE-ELECTRODE TUBES. VACUUM TUBES,
Life Testing
Proceedings I.R.E. Oct., 1925, pp. 625-645.
"Life Testing of Tungsten Filament Tnodes," W. C.
White.
Triodes are life-tested primarily as an aid to the manu-
facturers in proving their performance and useful length
of service rather than to obtain any average life figure.
The apparatus employed and its method of operation,
together with the procedure in handling the data, is next
described. Actual results obtained are given to illustrate
the methods used. These results are outlined in the form
of tables and curves. One point emphasized throughout
the paper is that triode life is just as much a variable factor
as other factors, such as electron emission or impedance.
R43O. INTERFERENCE ELIMINATION INTERFERENCE,
Popular Radio. Oct., 1925, pp. 318-323. General.
"How to Improve Broadcast Reception," (. V. Hogan.
Part VII.
The question of interference in broadcast reception is
taken up from the receiver standpoint. _ The receiving
set can be made very selective by proper choice of apparatus
and good arrangement of parts. Various primary and
secondary circuits are discussed in detail, and their advant-
ages and disadvantages noted.
*tr Tested and approved by RADIO BROADCAST
Ruo. RADIO WAVES. MAGNETISM OF
EARTH AND WAVES
Popular Radio. Oct., 1925, pp. 309-316.
"How Earth Magnetism Affects Radio Waves," H.
Nichols and J. Schelleng.
The discrimination made against waves of different fre-
quencies by the medium through which they travel, has
changed our ideas of wave propagation within recent years.
The atmosphere is supposed to have a marked effect on
electromagnetic waves, much as a glass prism has on light
waves. Because electrons move in the magnetic field of
the earth, we would expect them to be affected by this field.
Such an effect seems to be particularly noticeable at about
1199 kilocycles (250 meters), and the much-discussed
question of fading may be explained in this way.
Ri34-4 REGENERATIVE ACTION OSCILLATIONS
Popular Radio. Oct., 1925, pp. 388-300. AND
REGENERATION.
"The Prevention of Oscillation and Control of Regenera-
tion in R. F. sets."
Radio frequency receivers usually have the tendency to
oscillate at some frequency, especially if more than one
stage is used. Several methods are described which can be
used to prevent such undesirable noises. Diagrams are
added to aid in applying these remedies
RADIO BROADCAST ADVERTISER
381
A new line of
COIL UNITS
USING
HEXCELL COILS
Complete set of coils for
Roberts circuit, List Price $6.
List Price
3 circuit HEXOELL tuner 200-575
meters $3.00
Complete set of HEXOELL coils
for Roberts circuit 6.00
Complete set of HEXCELL coils
for Browning-Drake circuit
with new improvements 6.00
Short wave HEXCELL extra low
loss 3 circuit tuner 40-115 me-
ters .. .3.50
We have put real electrical and mechanical
engineering into our inductances. Partic-
ular attention is given to efficient operation
at the lower end of the Broadcast Wave Band.
Our coils are finished in beautiful silk
shades, each coil having a different color.
Highly polished bakelite and nickel mount-
ing parts used. Merchandise packed in at-
tractive boxes.
A live line for live dealers
Liberal jobber and dealer discounts
Write for information
EASTERN ELECTRIC Si MAN-
UFACTURING COMPANY
Providence, Rhode Island
Licensed manufactures of Zig-Zag Coils
Antiques
interiors, houses,
gardens, travel,
sports, horses, dogs,
blooded cattle — .
all these are in
Country Life
A Doubleday, Page Magazine
Limited Supply at Newsstands
ACME WIRE RADIO PRODUCTS
Flexible Celatsite
Flexible stranded wire for "point to point"
and sub-panel wiring latest method of wir-
ing sets. Five colors, black, yel-
low, green, red and brown,
one for each circuit.
Twenty-five foot coils.
Stranded Enameled Antenna
The best outdoor antenna you can put up. 7 strands
of enameled copper wire; maximum surface for recep-
tion. Enameling prevents corrosion and consequent
weak signals. 100, 150 or 200 ft. coils, boxed.
t i,
Original Celatsite Wire
Celatsite is a tinned copper buss bar wire with a non-inflam-
mable "spaghetti" insulation in five colors. Supplied in 30
inch lengths.
Flexible Varnished "Spaghetti"
A perfect insulation tube for all danger points in set wiring.
Costs a little more and is worth a lot more than the cheaper
substitutes offered. Black, yellow, red, green, brown; for wires
No. 10 to No. 18. 30 inch lengths.
Celatsite Battery Cable
For connecting A and B Batteries (or current
supply) to radio set. Silk braid covering 5
flexible Celatsite wires — 5 feet long — a differ-
ent color for each terminal. Prevents messy
wiring and "blown" tubes. Adds greatly to
the appearence of your set.
Send for Folder
THE ACME WIRE CO., Dept. B
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Tested and approved by RADIO BROADCAST
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RADIO BROADCAST ADVERTISER
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R56o. MILITARY. WAR AND RADIO.
Popular Radio. Oct., 1925, pp. 301-308.
"Radio and the War Menace," Bruce Bliven.
Radio is considered as being one of the most powerful
agencies either for war or peace among nations. The sooner
it is harnessed for the purpose of maintaining peace the
less likely are we to use it as a means of destruction. A
common language is sought among nations so that broad-
cast programs will be understood by all. Radio should be
used to help in disseminating new ideas and to foster a
proper attitude among constituents. On the contrary,
it may serve as a spreader of much wrong propaganda and
be able to do much harm. Thus radio exists as a great
force ready to be used either for good or evil.
R382. INDUCTORS.
COILS,
Low Loss,
Popular Radio. Oct., 1925, pp. 326-329.
"What Makes a Low Loss Coil?" Charles Burke.
A comprehensive discussion on the relation of inductance
to high frequency resistance is presented. What size wire
is best to use at definite frequencies, what shape of coil
is best and how it shou|d be constructed — these are questions
considered. The specifications for coils of highest efficiency
are presented, various forms of coils being shown in photo-
graphs.
VJ
P
. BROADCASTING.
opular Radio. Oct., 1925, pp. 334—339.
STUDIO
SECRETS
"Secrets of the Studio," Paul Godley.
Much effort is being expended in improving the quality
of programs coming from the broadcast studio. To secure
good reproduction at the receiver, both transmitter and
receiver must show little or no distortion. At the studio
much intensive work is done to insure the best transmission
possible from the artists. Better microphones, better
circuits, and better apparatus for modulation, have im-
proved broadcasting.
CONDENSERS.
CONDENSER
Popular Radio. Oct., 192^, pp. 340-345. LOSSES.
"How to Compare Losses in Condensers," S. Harris.
The question of condenser losses, and the method of
testing condensers, is discussed. Various tests used in
making comparisons of condenser losses have resulted in
the drawing of wrong conclusions. The curve showing
effect of resistance with change in frequency for a 500 mfd.
condenser emphasizes the point to be considered. Con-
densers should be tested for fosses not at a thousand cycles,
but at frequencies for which they are to be used, in order
to determine their efficiency and characteristics.
R 1 34. 75. SUPER-HETERODYNES. SUPER-HETERODYNES
Popular Radio. Oct., 1925, pp. 350-363. Single Control.
" How to Build the New Super-Heterodyne With a Single
Control," J. McLaughlin.
The operation of an eight-tube super-heterodyne from
a single dial is here described. Complete details include
circuit diagram, parts to be used, layout of the set, and
instructions for wiring and testing.
R5I4- RADIO COMPASS. COMPASS,
Radio. Oct., 1925, pp. loff. Radio
"Piercing Neptune's Shroud," V. G. Mathison.
A sketch of an actual occurrence aboard an American
liner, is given, showing the extreme value of the radio
compass. The author then goes into details concerning
theory and the practical uses of the radio compass during
fogs at sea. The compass designed by Roister, and built
by the Federal Telegraph Company, is shown. Many
difficulties had to be overcome in order to obtain absolutely
reliable results under any and all conditions, and some of
these are mentioned. Diagrams of the set and photographs
of the compass are shown.
R 376.3. LOUD-SPEAKING REPRODUCERS. HORNS.
Radio. Oct., 1925, pp. i8ff.
" Limitations of Horn Type Loud Speakers," Dr. J .
Minton.
A series of curves showing the relation of frequency of
sound waves and sound pressures coming from horns of
various shapes and sizes are presented. The curves are
interpreted by the author. These so-called "response-
frequency" curves show considerable variation, the best
kind of a horn giving a high flat curve.
R34i. DETECTORS, RECTIFIERS. DETECTORS.
Proceedings I.R.E. Oct. 1925, pp. 611-623.
"Detecting Characteristics of Electron Tubes," H. M.
Freeman.
It is pointed out that, owing to the progress of the radio
art, the opinions heretofore held as to the importance of the
part played by detector efficiency in a receiving set are in
need of revision.
Taking the well-known analysis of the operation of a
detector tube with condenser and grid leak, curves are
derived from the static characteristics of a typical general
purpose tube, showing the performance of the tube as a
detector under certain conditions of operation.
A method is described of measuring the output of a
detector tube with a standard incoming signal, and experi-
mental results obtained with the tube used for deriving the
curves are compared with those obtained from theoretical
considerations, showing that the method can be used to give
a true picture of the effect on detector efficiency of variations
in operating conditions.
Sample curves are given, showing the wide variations
obtained in the efficiency of certain types of standard
tubes by relatively slight changes from the customary
operating conditions, ami also the variations in efficiency
of a number of similar tubes under normal operating
conditions.
R6n. LONG WAVE STATIONS. STATIONS,
Proceedings I.R.E, Oct 1925, pp. 570-588. Warsaw,
"Transoceanic Radio Station, Warsaw, Poland," W. G.
Lush.
A brief history and description of the Warsaw trans-
oceanic radio station, as constructed and installed for the
Government of Poland by the Radio Corporation of
America, is given. A technical description of the details
of the system used is not presented, as the system is similar
in all respects to that in use in the United States by the
Radio Corporation. Several photographs show the gen-
eral plan of the station and the equipment.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
383
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A Real Power Transformer
The modern home may now utilize its electric service for the operation
of a Radio Receiver. Reception is greatly improved when efficient B and
A eliminators are employed to use this steady power.
The AmerTran Power Transformer Type PF-45, 65 VA— 60 cycles 110 volts primary,
450-8/4-8/4 secondary, is intended for use in converting the standard 110 volt, 60 cycle
alternating house lighting current to a higher voltage for the plate and low voltages for
filament supply. It can be depended upon to give good results when used in connection
with the different tubes now available and is designed with the usual margin of safety.
It is a real power transformer, in design, construction and usefulness.
The AmerTran Power Transformer Type PF-52 is another transformer of
the AC Power Type similar to Type PF-45 except that it has a plate wind-
ing for 525 volts AC and a metal ground shield between the primary and
secondary windings.
PRICE, Type PF-45, £15.00— Type PF-52, #18.00
We have prepared a booklet describing these and other
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their use. We shall be glad to send you a copy upon request.
AMERICAN TRANSFORMER COMPANY
178 Emmet Street, Newark, N. J.
"Transformer builders for over twenty-four years"
SOLD ONLY AT AUTHORIZED AMERTRAN DEALERS
I
The AmerChoke Type 854 is a choke coil or im-
pedance of general utility designed primarily for
use in filter circuits. It hasa current capacity up to
60 milliamps. and a no load inductance of approxi-
mately 100 henrys at 60 cycles. Price $6.00 each
Be sure to see the other Amer-Tran ad on page 377
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favorite radio store does not stock the magazine
write us giving name of radio dealer and address.
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As transmitting Grid leaks, they are made in
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Special resistances $2.50 each.
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THE OMNIGRAPH is not an experiment. For more than 15 years, it has been sold all over the world
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Tested and approved by RADIO BROADCAST
384
RADIO BROADCAST ADVERTISER
Whether You
Buy or Build
Insist on EBY Cushion Sockets
most important elements in any set are
the tubes. There's no getting around that!
And what else but the sockets are responsible for
the life and efficiency of those tubes? Whether
you build or buy see to it that the tubes in your
set are mounted on EBY Cushion Sockets.
The design of this revolutionary socket provides
a three-point wiping contact on each of the four
tube prongs. Each spring clip acts as a shock-
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R431. STRAYS.
Radio.
INTERFERENCE.
Oct., 1925, pp. lyff.
"How to Reduce Interference," L. W. Hatry.
Most receivers in use to-day employ the untuned primary
method of reception. This is undesirable from several
standpoints. A method whereby greater selectivity can
be obtained, is described, by adding a loading coil to the
antenna circuit. This will permit rough tuning of the
antenna circuit and insure much better reception.
Ri27. ANTENNA CONSTANTS. ANTENNA
Radio. Oct., 1925, pp. 2ofT. CONSTANTS
"How Antenna Characteristics Affect Reception,"
K. B. Morcross.
A description of the effect of resistance, capacity, in-
ductance, direction, height, length and surroundings, of an
antenna on transmission and reception of ether waves, is
given. Various types of antennas are discussed, and
equations are presented and interpreted for the benefit of
the less experienced in the radio art.
Rn4-4. REGENERATIVE ACTION. OSCILLATIONS
Radio. Oct., 1925, pp. 22f. IN SETS.
" Elimination of Oscillations in R. F. Amplifiers,"
Dr. Buchbinder.
An analysis of the causes of oscillations and several of
the methods used in preventing oscillations in radio-
frequency amplifiers is given. Three general methods
are employed usually: i. Decreasing the amplification
efficiency through losses; 2. Reducing stray magnetic
and electro-static fields; 3. Using balancing-out arrange-
ments. The last method is suggested as being the best be-
cause it leads to sensitive and selective receiving.
Ri45. REACTANCE
145. KEACTANCE
Radio. Oct., 1925, pp. 24f.
"How Radio Circuits Work," G. F.
Lampkin.
REACTANCfc
DIAGRAMS
inductance in radio circuits is presented. Graphs and
concrete examples of the application of various equations
to typical radio circuits brings this much misunderstood
and difficult information within the grasp of the average
experimenter.
R384- 1 . WAVEMETERS
WAVEMETER.
Radio. Oct., 1925, pp. 2gff.
"A Detecting, Oscillating and Modulating Radiocast
Wavemeter," E. E. Griffin.
The construction and operation of a simple wavemeter.
which may be used as a receiver, a modulator, or an oscilla-
tor, is given. In design and general arrangement it
resembles any ordinary one-tube receiving set, but its uses
are many. Method of calibration and testing is given.
Its many uses in measuring constants of radio apparatus
make this one of the best laboratory instruments for any
radio worker.
R42O. MODULATED WAVE SYSTEMS. MODULATING
Radio. Oct., 1925, pp. 31-32. SYSTEMS.
"Plate and Grid Modulation Systems," L. Grignon
and F. Jones.
A constant carrier frequency is modulated by either a
decrease in antenna current (Heising system) or a decrease
or increase in antenna current (grid modulation system).
The theory underlying these two methods, their advantages
and disadvantages on the broadcast range of wavelengths,
as discussed, lead the authors to believe that the grid
system of modulation is the better. Circuit diagrams and
data are given for the benefit of those wishing to try out
these two systems for comparison.
R35i. SIMPLE OSCILLATORS. OSCILLATOR.
Radio. Oct., 1925, pp. 33~34- Quart;.
"A Quartz Crystal Oscillator," D. B. McGown.
A description of this new form of instrument, used as a
standard of wavelength, and information on the construc-
tion of such an instrument, is given. The Hartley circuit
is used. The parts that enter into the building of this
oscillator are all standard and easily obtainable. It can be
used as any other oscillator. Its accuracy is said to be
much greater than ordinary forms of oscillators.
R342.6. RADIO-FREQUENCY AMPLIFIERS. RECEIVER,
QST. Oct. 1925, pp. 8-11. Fellogg-RFL.
"A True Cascade R. F. Amplifier," Dr. L. M. Hull.
According to Mr. H. Snow's experimental study, the
so-called intermediate-frequency amplification in super-
heterodynes, using three tubes, will not give a voltage
gain of more than from 800 to 1000. A marked "tapering-
ofT" effect is usually apparent. Straight cascade one-way
stages were tried at 750 kc. with a voltage gain, starting
with seven, of seven times for each tube used. Five tubes
gave an amplification of more than 16,000. A description
of the set, its peculiarities of construction, and a circuit
diagram are given. The instrument is very selective and
has but two controls.
Rii3- TRANSMISSION PHENOMENA. SHORT WAVES.
QST, Oct. 1925, pp. 12-21. Characteristics of
"Wave Propagation at High Frequencies," Dr. A. H.
Taylor and E. Hulbert.
This article contains a detailed discussion concerning'! he
probable condition of the upper ionized atmosphere and
its effect on the propagation of waves at high frequencies,
lonization, de-ionization, wave-energy losses, absorption,
skipped distances and their cause, effects due to frequency
changes, day and night transmission — these are subjects
taken up in turn and discussed in a very clear manner.
Experimental evidence substantiates most of the statements
made, curves and diagrams serving to illustrate points in
question.
Roo5- EXECUTIVE, ADMINISTRATIVE.
PERSONNEL. AMATEURS LINKED
QST. Oct. 1925, pp. 22-24. WITH THE ARMY.
"The Army links up with the Amateur."A.R.R.L Plan.
A plan whereby amateur stations located in the United
States will cooperate with the United States Signal Corps
for a four-fold purpose: i. To have channels available in
case of emergency; 2. To have channels available for
civilian components of the army; 3. To have operators
available trained in army methods; 4. To have contact
available between operators and Signal Corps for the
exchange of new ideas in experimental work. The plan of
affiliation is given verbatim.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
38.)
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T TF.RF. ARE SOME of the topics discussed in this
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RADIO BROADCAST ADVERTISER
Superadio Receiver
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R383. RESISTORS RESISTORS.
QST. Oct. 1925, pp. 25-28.
"High Frequency Resistance Standards," J. M. Clayton.
In measuring frequencies above 2000 kc. the ordinary
resistance units are inaccurate, either adding inductance,
capacity, or both to the circuit being tested. A new form
of resistance made of magnesium wire is described, which
can be used for much higher frequencies with extreme
accuracy. The method of construction is given. Diagrams
illustrate method of mounting and adjusting.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVER,
QST. Oct. 1925, pp. 33-36. SHORT-WAVE,
"Short-Wave Receivers," R. R. Batcher. Grebe CR-i?.
Valuable pointers concerning construction of short-wave
receivers are brought out in this discussion, with particular
reference to the Grebe CR-iy. A short-wave tuner chart
is used for inductance and capacity calibrations.
R356. TRANSFORMERS. TRANSFORMERS.
QST. Oct. 1925, pp. 37-39.
"Transformers and Reactors in Radio Sets," R. H.
Chadwick. Part II.
Audio-frequency transformers are discussed, more or
less theoretically, with particular emphasis on the ampli-
fication factor at various frequencies. At low and high
values of frequency, the amplification is less, due to effects
noted in diagram. Fig. 10. Filter reactors are used for the
purpose of introducing opposition to the flow of alternating
current. Depending upon the circuit they are to serve,
their construction will be determined. The discussion
brings out the general principles involved in reactor design.
RIIO. RADIO WAVES. SHORT WAVES,
Radio News. Oct. 1925, pp. 41 off. Phenomena of
"The Behavior of Radio Waves," Dr. E. F. W. Alex-
anderson.
Little is known concerning the radiation of energy from
antennae. Our conception of the ether and the electron
is more or less vague at present. Experience points towards
the fact that short waves are reflected according to the
Larmor Theory of propagation, herein described. A new
phenpmenon was noted recently, namely that of horizontally
polarized waves when sent from a horizontally mounted
multiple-tuned loop. The plane of polarization changes
as the wave progresses. The method used for analysis, and
the construction of the loop, are shown in photographs.
R594. GERMANY GERMAN RADIO
Radio News. Oct. 1925, pp. 41 2ff. DEVELOPMENTS.
"Radio in Germany," Dr. E. Nesper.
Radio developments in Germany have been making
great strides, as is indicated by the interest shown in recent
radio exhibits. Since September ist, the German radio
laws and regulations have been greatly modified, so that
experimenters have about the same range of freedom that
we, here in America, enjoy. Interest in broadcast pro-
grams is keen. The broadcast system is owned by the
Postal Company and licenses are issued for receivers.
Photographs of several home-made receivers are shown.
R?so. BROADCASTING. SUPER STATIONS
Radio News. Oct. 1925, pp. 4l8fT.
"Super-power Broadcasting."
This article describes the new WGY 5O-kilowatt broad-
casting station. The accompanying photographs give a
very clear idea of the size and scope of the equipment.
The circuits used in the many transmitters at Schenectady
are of the master oscillator type. Much of the work is
experimental, for little is known regarding the use of super-
power on the various frequencies. The stations are operat-
ing primarily for the purpose of learning more about the
"attenuation constant" of transmitters.
R8oo(535.3) PHOTOELECTRIC PHENOMENA PHOTOELECTRIC
Radio News. Oct. 1925, pp. 426fT. CELL, Its use.
"The Vacuum Tube and Photoelectric Cell," General
G. Ferric.
A method whereby the photoelectric cell is used in con-
junction with three and four electrode tubes, to detect and
amplify extremely small currents set up bv light waves
(particularly ultra-violet), is here given. This principle
has many applications in astronomy. It is a|so used in
determining the period of a pendulum, a mirror being
attached to the swinging arm, and light reflected into the
cell.
Ri30. ELECTRON TUBES. VACUUM TUBES.
Radio News. Oct. 1925, pp. 434ff. Detecting and Amplifying
"Hard Tubes and Soft Tubes as Amplifiers and Detec-
tors," Prof. C. Bazzoni. Part I.
An elementary but nevertheless very thorough and com-
prehensive discussion on the operation of vacuum tubes
is presented. Emission, space charge, degree of vacuum
and the action of gas atoms and electrons, determine de-
tector and amplifier action in vacuum tubes. Graphic
diagrams help to form a mental picture of the action within
the tube.
R38i. CONDENSERS. CONDENSERS,
Radio News. Oct. 1025, pp. 447ff. S.L.F.
"Does a Straight Line Frequency Condenser Exist?"
S. Harris.
The question of obtaining straight line frequency cali-
bration curves with a so-called straight line frequency
condenser, is a point much discussed. The author shows
the relation between condenser capacity and coil at various
frequencies. There is practically no deviation from the
straight line even with coils of a jarge distributed capacity
when connected to a straight line frequency condenser.
So for all practical purposes the instrument does exactly
what it is supposed to do.
Ri49. RECTIFICATION. FILTERS.
Radio News. Oct. 1925, pp. 452ff.
"All About Filters," E. W. Berry.
In order to obtain a source of good direct current for plate
supply, either a generator or alternating current rectifier
is often employed. Both need considerable filtering. The
article describes in detail the effect of choke coils and
condensers in a circuit. Concrete examples serve to illus-
trate the points brought out. A series of graphs show
the result of tests made with series, parallel, and series-
parallel cpnnections of chokes and condenses. A thorough
presentation of the subject for experimenters.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
387
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3— S-M 311 .00035 S. L. F. Condensers
3 — 4- in. Na-ald moulded dials
3— S-M 515 Coil Sockets
2 — S-M 112A Inductances
1 — S-M 110A Inductances
6— S-M 510 Sockets
1 — Carter 6-ohm imp. Rheostat
1 — Central Laboratory 500,000 ohm Modulator
3 — Muter or Daven Resistance couplers complete
1— Carter 101 Jack
I— Carter 102A Jack
— Benjamin On-off Switch
—.002 M. F. Condenser
—S-M .5 M. F. By-pass Condensers
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NOVEMBER RADIO BROADCAST
The engineers _of the leading manufacturers who make these parts en-
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Unit No. I. 2 Rauland-Lyric Transformers @ $9.00 £18.00
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Unit No. 3. 2 Hammarlund .0005 mfd. Model "C"
or S. L. F. Condensers @ 5.00 1000
Unit No. 4. I Set Hammarlund-Roberts Coils @ 6.00 6.00
Unit No. 5. 2 Na-ald "Super DeLuxe" 4 in. Bakelite
Dials @ .75 1.50
Unit No. 6. 5 Na-ald "DeLuxe" Sockets @ .75 3.75
Unit No. 7. 1 Na-ald K3844 — \% in. Dial @ .20 .20
Unit No. 8. 4 Amperites No. 1-A @ 1.10 4.40
Unit No. 9. 5 Prs. Union Phone Tip Jacks, per pair @ .25 1.25
Unit No. 10. 1 Carter 25-ohm "Imp" Rheostat @ 1.00 100
Unit No. 11. 1 Carter Single Circuit No. 101 "Hold-
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Unit No. 12. 1 Carter "Imp" Battery Switch @ .65 .65
Unit No. 13. 1 Dubilier Type 640-G .00025 mfd.
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Unit No. 14. i Dubilier Type 640 .002 mfd. Fixed
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Unit No. 15. 1 Dubilier Type 640 .006 mfd. Fixed
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Unit No. 16. 1 Durham Metallized Resistor @ .40 .40
Unit No. 17. 1 Hammarlund-Roberts Foundation Unit
(contains engraved bakelite Westing-
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9.40 9.40
$57.50
HAMMARLUND MFG. Co., INC.
Complete Parts as specified
Cabinet $10.00 extra
Booklet "How to Build the Hammarlund-Roberts Receiver" with complete
diagram and illustiations — Postpaid, 3.25.
We Also Have Specified Parts For The New
L. C. 1926 MODEL RECEIVER
HEINS & BOLET, 46 Park Place, New York
Tested and approved by RADIO BROADCAST if
388
RADIO BROADCAST ADVERTISER
Product of over 30 years' experience
^fnemvorite
J/6ice o
O hear an Amplion
in comparison with
any or all other loud
speakers is to appre-
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are the largest selling radio re-
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world — favorites of music
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The actual originators and old-
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Alfred Graham & Co., Lon-
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Amplion. Its superbly life-like
THE AMPLION CORPORATION OF AMERICA
executive Offices: Suite L, 280 Madison Ave., Nev York City
Canadian Distributors: Burndept of Canada, Ltd., Toronto
Associated Companies and Agents: Alfred Graham £ Co., London, England, Patentees;
Amplion Corporation of Canada, Limited, Toronto; Compagnie Francaise Amplion,
Paris, France; Compagnie Continentale Amplion, Brussels, Belgium; Amalgamated Wire-
less (Australasia), Ltd., Sydney and Melbourne; British General Electric Company, Ltd.,
Johannesburg and Branches; Indian States and Eastern Agency, Bombay and Calcutta;
C. J. Christie E. Hijo, Buenos Ayres; David Wallace Si Co., Valparaiso; Mestre & Blatge,
Rio de Janeiro; F. W. Hammond & Company, London and Tokio.
reproduction and supreme
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Bring out the full musical
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BLUE PRINTS FOR THE "ARISTOCRAT1
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YOU SEND US HIS NAME AND ADDRESS.
Price one dollar for complete set.
BOOK REVIEW
A History of Radio Men and
Their Contributions to Radio
Progress
RADIO: BEAM AND BROADCAST. By A
H. Morse, Published by Ernest Benn, Ltd.,
London. In New York, by D. Van Nostrand
Company. 186 •pages. $4.
I HIS recent book on radio is well worth
while the attention of any who expect to
do developmental work in radio, or in any
of its allied fields. While it is entirely
different from what we had expected to find, it
proved to be of sufficient interest that we stayed
with it on the first reading until the last page
had been covered.
Instead of being as we had supposed, a book
written more or less in the manner of a text, it
proved to be an interesting and continuous his-
tory of the art of radio as a whole, having no
special connection with either beam or broadcast
methods of communication. The author's in-
tentions are perhaps best given in his own words.
Says he in the introduction: "Within the last
few years, the radio field has been invaded by
many thousands of persons who know nothing
of its evolution, and are therefore sometimes un-
able to distinguish between what is new and what
is old. The consequence is that they waste
much time and money in re-inventing old devices
and in developing others to circumvent imagined
patents, or inventions, long since in the public
domain. The case of the spider-web coil may
be cited as an example. This will be found to
have been illustrated and described several years
before the Great War, but was heralded as a
novelty two or three years ago. It is one of the
author's objects to help to create the perspective
of these newcomers, and it is hoped that this
book will be of some assistance to British and
American patent agents' attorneys (new to the
art), inventors, experimenters, journalists, radio
enthusiasts, and 'why men' generally, on both
sides of the Atlantic.
"The evolution of the radio art is traced herein
mainly through the Patent Office records of
inventions in use to-day, or their lineal forebears.
As a consequence, many inventions of great
merit and one time promise, receive little or no
mention; and except in a few cases where inven-
tions are cited merely as evidence of the con-
temporary knowledge of the art, a selection has
been made, not by the author but by the test
of utility. It may be observed that this test
has proved too much for some of the most her-
alded inventions."
The first chapter of the book briefly relates
the accomplishments of the early workers in the
radio field, starting with Christian Huygens.
who first propounded the undulatory theory of
light in 1678, and ending with the year 1912.
The author has been at a deal of trouble evi-
dently in consulting original writings, and has
given in an interesting manner a story of the
high spots of radio's development during this
period. To indicate the scope of the material
given, there is a note that in 1843 Professor
Joseph Henry succeeded in magnetizing needles
two hundred and twenty feet distant from his
energizing apparatus. In the opinion of one of
America's foremost physicists, these experiments
of Henry really constitute the first disclosure of
radio communication, but they apparently were
not appreciated as such by Linsely, and his work
had no important commercial outcome. In 1879,
Professor Hughes, an Englishman, succeeded
in sending radio signals a distance of about sixty
feet. Among those present were some of the
most noted English scientists and engineers,
Tested and approved by RAHTO BROADCAST
RADIO BROADCAST ADVERTISER
389
dA Hookup for Dealers
that Eliminates Interference
- ^»/"< +J
When a Radio Dealer "hooks up"with the
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The numerous user inquiries referred to
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equipment carried at all times for im-
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that are responsible for the reputation
and success of the Hommel organization
to-day.
Hommel's Encyclopedia No. 466-6 tells the story in detail — write for your copy to-day.
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929 PENN AVENUE
PITTSBURGH, PA.
You can do it right in your
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Makes use of
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OVERNIGHT
Model "A" — for radio "A" and 6 volt automobile batteries.
A.C. line, 40 to 60 cycle, 110-120 volts. Battery
— 6 volts 6-8 amperes. Comes complete with $ J §'00
cords, plug and leaded clips.
Price East of the Rockies
Model "A-B" — for charging radio "A" and "B" batteries sim-
ultaneously. A.C. line, 40 to 60 cycle, 110-120
volts. Battery — "A," 6 volts 3-4 amperes; "B,"
48 to 96 volts in series, 1/10 ampere, up
Price East of the Rockies
Pays its cost in a short time
by what it saves you
Ask your dealer to show it to you — or write for booklet.
LIBERTY ELECTRIC
RADIO
BATTERY CHARGER
HE ordinary charger uses only half the electric
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Ful-Wave, by a new and better principle, uses the full
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Because of this and other reasons Ful-Wave takes only
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- 342 Madison Ave NewYorR
Tested and approved by RADIO BROADCAST
390
RADIO BROADCAST ADVERTISER
The First
radical improvement in
radio SLF condensers
AT LAST ! A new era in vari-
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But now — professionals recognise
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Simplicity is the keynote of prog-
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36O° TAPER COIL
CONDENSERS
but Hughes apparently did not really appreciate
how important and real his work was, and so was
discouraged by the comments of a fellow scient-
ist. They took the romance out of Hughes's ex-
periments by telling him that the ordinary laws
of mutual induction might be used to explain
all of his experiments. In 1899, Sir William
Crookes, commenting on Hughes' work, said:
" It is a pity a man who was so far ahead of all
other workers in the field of wireless telegraphy
should lose all the credit due to his great in-
genuity and prevision."
Of course every radio enthusiast now knows
that in 1888 Professor Hertz succeeded in show-
ing that electro-magnetic waves and light waves
are the same thing, and that he actually did
carry on radio experiments in his laboratory
with such skill and perseverance that one may
read in his laboratory reports a description of
practically all of the radio schemes which it has
taken us thirty-five years to develop. For those
who have not read Hertz's book, a real treat is
in store, for one may see pictures and read
about experiments disclosing the whole idea of
radio beam communication, which many people
believe originated in the comparatively recent
experiments of Marconi.
The author takes us through the work of
Branly (who recently received the Nobel prize
for the work he carried out during this period),
Thomson, Lodge, Popoff, Rutherford, Marconi,
and Fessenden. In 1906 DeForest put the B
battery in the plate circuit of the Fleming valve
and, in 1907, introduced the third electrode,
giving us the now famous audion. In the same
year, in Italy, Bellini and Tosi were showing the
possibilities of direction finding by radio, and
in Germany von Lieben and Reisz were experi-
menting with the three electrode tube. This
brings us up to 1912, when the regenerative cir-
cuit was patented in England by Franklin, in
Germany by Meissner, and in America by Arm-
strong. Here the author expands greatly his
previously brief presentation of the subject to
show that DeForest should be credited, at least
in America, with the regenerative and oscilla-
tory features of the audion. He cites the recent
decision of the United States Court of Appeals
of the District of Columbia, which gives prece-
dence regarding the invention of the oscillating
audion to De Forest, whereas the public is accus-
tomed to think that Armstrong was the first
to develop this idea.
As we read over this part of the book, and
again read over the comparison of the work of
Fleming and De Forest, we were urged to look
up the former connections of the author, and
found on the title page that he was formerly as-
sociated with De Forest as superintendent of one
of the De Forest wireless telegraph companies.
In reading certain parts of the book this fact
should be kept in mind.
Chapters II and III deal with radio between
1912 and the present time, and the prediction as
to future development. It is not apparent why
the prediction should be inserted in Chapter
III, as this chapter is followed by others on such
subjects as the Poulson arc, broadcasting, re-
generation in reception, the triode as generator,
one on beam and short wave radio, ending up
with the ninth chapter entitled "Conclusion."
An interesting paragraph in the final chapter
calls our attention to the fact that many in-
ventors fail to get the credit which is due them.
In this place the author writes as follows:
" Prior to 1896, Preece had in operation a system
of inductive wireless telegraphy, and it was just
when he was smarting under the failure of this
system to provide communication with East
Goodwin lightship, that Marconi came to him
with a letter of introduction from Mr. A. A.
Campbell-Swinton. Both Lodge and Ruther-
ford had already shown that wireless telegraphy
was practicable, and by the same essential
Tested and approved by RADIO BROADCAST
Jo-day
-in every
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a MASTER
OPERATOR"
AMPERITE neverdistinguishes between
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There it an AMPERITE for every tube
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DepL R. B.— 1 SO Franklin St., N. Y. City
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RADIO BROADCAST ADVERTISER
391
TUBE SERVICE
Your set is no better than your poorest tube
They must be uniform
A good tube must
have:
1. Good Tone
Quality.
2. Impedance not
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3. Low filament
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4. Long life.
Pingree Tube
Characteristics
Plate impedance
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Amplification fac-
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Filament consump-
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Filament voltage
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PROTECTION
Each tube is tested rigidly on a Superadio Dynometer before
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TRIAL OFFER
Try these tubes 10 days at our expense. If they are not what
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PINGREE RADIO SERVICE, INC.
170 Summer Street Boston, Mass.
Dealer inquiries solicited
5 WIRE BATTERY CABLE
with heavy leaded terminals, soldered to stay. Conductors are
insulated with rubber, preventing short circuits and blown tubes.
Cable with storage battery clips
Without clips
Without terminals .
#1.00
Each wire is coded so that wrong connections are impossible.
PREMIER 20 foot extension cord with new connector, $1.75,
longer lengths also. PREMIER JR., $1.25.
Take your loud speaker anywhere.
At your dealer or write us
CRESCENT BRAID CO., Inc. -£
Providence Rhode Island
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On to Success
in RADIO!
1
Mr. R. L. Duncan
Director of the
Radio Institute
of America
R\DIO is a profession well worth
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strong.
You can embark, right now, on a suc-
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you can pass your U. S. Government
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Study in spare time
There's no need to give up your present
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RADIO INSTITUTE OF AMERICA
Formerly Marconi Institute Established in 1909
328 Broadway New York City
—.CUT HERE— .. .
RADIO INSTITUTE OF AMERICA
328 Broadway, New York City |
Please send me lull information about your Home Study '
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Tested and approved by RADIO BROADCAST
392
RADIO BROADCAST ADVERTISER
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THE KODEL RADIO CORPORATION
505 EAST PEARL ST. CINCINNATI, OHIO
Owners of Kodel Broadcasting
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Through your dealer or direct, by the year only $4.00
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BADIO
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t Tested and approved by RADIO BROADCAST •
method that was used by Marconi, but ap-
parently they did not see, or were not interested
in, its commercial potentialities, or were too
much engrossed in other activities to endeavor
to exploit them. This circumstance has no
doubt contributed to the fact that to-day the
layman regards 'Marconi' and 'Wireless' as
interchangeable terms, while the credit which is
due to Hughes, Lodge, Popoff, Braun, Fessen-
den, Stone, and others, is in danger of being
forgotten, except by technicians."
The author's views on monopoly are especially
interesting in light of the investigation now
being carried on by the Federal Trade Com-
mission regarding the activities of the Radio
Corporation of America. Quoting Sir William
Crookes, regarding the activities of the Mar-
coni Company, the author says: "The whole
effect of the operations of the Marconi Company
has been to check and really stop the growth of
wireless telegraphy as a convenience to naviga-
tors as well as a commercial undertaking."
This comment, it is to be borne in mind, is
made regarding the British Marconi Company,
and quite possibly Sir William Crookes might
not have expressed the same thing regarding an
American monopoly.
In the appendix, which occupies the second
half of the book, there are given copies of the
important patents which have been granted in
the radio field since its inception.
The material given in the book, although not
presented in very carefully thought out manner,
is extremely interesting, and is well worth the
attention of anyone who wishes to appreciate
the development of radio and its growth.
J. H. MORECROFT
HIGH-SPEED FADING
MUCH experimental work is being carried
out by British "hams" with a view to
finding some feasible explanation, and a suitable
cure, for high-speed fading. This phenomenon
manifests itself, at nearby receiving stations, by
distortion and very ragged modulation. As an ex-
ample of the far-reaching effect of high-speed fad-
ing, it is interesting to cite a case experienced by
that well known British "ham" Mr. Gerald Mar-
cuse, who operates station 2NM, and whose tele-
phony transmissions are often heard in this coun-
try on 6663 kc. (45 meters). He states that, while
his short-wave telephony tests, carried out on Sun-
day evenings with Iraq and India, are reported as
being received with crystal purity in those coun-
tries, nearby listeners (within a hundred miles
or so) write and tell him that his modulation
is terrible; nothing can be received intelligibly.
Often this condition is far less troublesome
during the hours of daylight, and in this instance
we might mention an interesting fact about the
short-wave transmissions of KDKA. Listeners in
the city of Washington state that it is impossi-
ble to receive this station's short-wave emission
with anything like good quality during the night
hours. However, during the daylight hours,
the Pittsburgh programs are perfect.
High-speed fading is only one of the many
short-wave telephony problems with which the
amateur has to cope, and it is hoped that the
recommendation by the recent Washington
Radio Conference, that amateurs should be per-
mitted the use of a short-wave band for telephony
experiments, will materialize. Already, we under-
stand, the United States Navy Department have
concentrated their attention in an effort to over-
come this and other short-wave difficulties.
If, then, the American amateur is permitted
the use of the short waves for his radio vocal
efforts, it is more than likely that the data al-
ready collected by the Navy Department, will
be greatly supplemented, and at least, the many
short-wave problems greatly mitigated.
RADIO BROADCAST ADVERTISER
393
Model 2 RK, antenna
coupler and regenera-
tive tuner for Rob-
ert's, Radio Broad-
cast Knock-out, etc.
$7.50
Model TCH, for
straight three cir-
cuit hook-ups and
Radio World's
Thoroughbred
$4.50
FOR THE "KNOCK-OUT" BECAUSE-
Knock-out Receiver using model 2 R.K. Clarotuners and Clarostat as tone modulator
they are easier to mount (requiring only one hole)
they are easier to connect (all terminals are designated)
the antenna coil is tapped, making for greater selectivity
the regenerative tuner is easier to control because its fixed tickler arrange-
ment affords a more even approach to the point of maximum amplification.
If your local dealer cannot supply you, send your remittance direct to us.
AMERICAN MECHANICAL LABORATORIES INC.
285 North Sixth Street, Brooklyn, N. Y.
CLAROSTAT, the heart of the Claro-
tuner, is the most accurate variable resis-
tance ever placed on the market. It has
a continuously variable resistance rang-
ing from practically zero to five million
ohms — and all this without a single
abrupt step! — $2.25.
The COMPLETE radio
guide — 96 pages, com-
piled by radio experts
and crammed full of
interesting data for
radio enthusiasts.
From the first to the
last page, it's a review
of the newest, finest in
radio; EVERYTHING
listed is standard,
nationally known,
merchandise; Sets
parts, equipment,
apparatus, cabinets,
etc. 1 - 3 - 5 and multi-
tube circuits, kits as
well as ready-built
outfits.
FREE
EXAMINATION
Everything you order
from WRS is sent with
the privilege of free
examination. You do
not risk a single
penny, you MUST be
satisfied or the sale is
NOT complete!
•ir Tested and approved by RADIO BROADCAST ~ir
394
RADIO BROADCAST ADVERTISER
For EVERY
Radio Set
A stunning piece of furniture that
restores order in the room where
you have your Radio! No more
cluttered table-tops, nor litter of
equipment under-foot.
N o unsightly
horn in evidence, i
either! This con-
sole has its own
loudspeaker, in-
built. It's out of
sight, but with
very apparent
tonal SUperiori- Non-Vibrant Horn
ties. For it has The clearest tone pro-
., i_-i .1 i ducer on the market.
the nignest-devel- Made of special com
oped type of unit. ^S™, which defeats
With horn built
of special non-vibrating, extra-
hard material. Produces clear
non-vibrant tone.
There's ample room for every-
thing; space for A and B wet bat-
tries — or battery eliminator —
and for a charging outfit, too.
Finished in mahogany, or walnut col-
or. Dainty design of parqueterie on
two front panels. Top, 38 in. x 18 in.
Additional pattern No. 128 (Special
for Radiola No 125) in two-tone fin-
Fsh. Top, 21 in. x 31 in. Fitted with
doors for access to control switches of
combination eliminator-charger.
The price, forty dollars, is for the
complete console and includes the loud-
speaker horn and unit. Thousands of
dealers are showing this artistic ad-
dition to home radio equipment.
Rear View— Set Honked Ut
Price, $40
West of Rocky Mt:.. M.50
Windsor Furniture Co
READERS WRITE
US
Wlnat Some Famous Radio Men
Think of the New "Radio
Broadcast"
HERE are a few extracts from letters of
radio men known to all of our readers,
telling us what they think of the new RADIO
BROADCAST.
DE FOREST PHONOFILMS, INC.
NEW YORK CITY
Edi'or, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
I have just had time to look over the last issue
of RADIO BROADCAST. 1 am highly pleased
with its appearance and contents. The new is
certainly a distinct advance over the old style.
Mr. Thompson certainly succeeded in making
another live, interesting story on the "Audion"
— full of the personal touch which surely appeals
to the average reader. Congratulations and
continued success to RADIO BROADCAST.
Very truly yours,
LEE DEFOREST.
President
DEPARTMENT OF COMMERCE
WASHINGTON
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
The November number of RADIO BROAD-
CAST makes a very fine appearance in its new
form. ... 1 wish you the best of fortune
in the further development of your very excellent
periodical.
Very truly yours,
J. H. DELLINGER.
Physicist.
RADIO CORPORATION OF AMERICA
NEW YORK CITY
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
On my return to the city, after a week's
absence, I had brought to my attention the new
RADIO BROADCAST. . . . It is a well pre-
pared magazine and should meet with the
public's approval.
Very truly yours,
J. G. HARBORD.
President.
NATIONAL ASSOCIATION OF BROADCASTERS
NEW YORK CITY
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
I am very happy to see the recent changes in
RADIO BROADCAST. It augurs well for a con-
tinued advancement in publications dealing with
radio. We have always considered RADIO
BROADCAST a foremost radio magazine of the
country, and hope that it will always continue to
be so.
Very truly yours,
FRANK W. ELLIOTT.
President.
Tested and approved by RADIO BROADCAST -
EASTERN
KNOCKOUT COILS
TYPE R
Designed in strict accordance with
Radio Broadcast specifications and ap-
proved for the "Aristocrat" and for all
Roberts Knockout Circuits, reflexedor un-
reflexed. Latest design — mid-tap on sin-
gle layer wound N. P. Coil — simplifies
neutralization and tuning. Per set, $8.50
All Eastern Coils are in the efficient
low loss pickle bottle form of winding,
guaranteed incomparable for the
BROWNING-DRAKE (Type B-D,
$8.00 per set), O'CONNOR FREQUEN-
CY CHANGER (Type FC Coupler,
$6.00). OSCILLATOR COILS (Type O
C), for same, with special .00013 mfd.
fixed condenser ($4.75). THREE CIR-
CUIT SET (Type 3C Coupler, $6.00),
and for other leading circuits.
At your dealers
or direct postpaid
EASTERN COIL CORPORATION
22 Warren Street Dept. R. B
New York
ALL STANDARD
TYPES $2.50 -•-
GUARANTIED
RADIO TUBES
™ Why spoil your enjoyment of radio with ••
*« inferior tubes when Cleartrons are guar- •}
5 anteed to give perfect service — clearer "~=
5 tone, more volume, greater distance and •«»
••• sharper selectivity. Buy quality and 5
'• service — Cleartrons. ™
At All Reliable Dealers '--
^ Write for free six page tube folder. «
CT 101A, the original Hi-Mu tube ~
for Resistance-Coupled Amplifiers $3.00
E CLEARTRON VACUUM TUBE CO. =
28 West 44th Streel, New York City —
- FactoriesrWeslNew York, N.J,, Birmingham, Eng. —
iiiiiiiriniiiiiiiiiiiiiiiiiiiiiiiiiiii
FOR. BETTER. RECEPTION
immiimiiiiiiiiiiiiiiiiiiiiiiiiiii
RADIO BROADCAST ADVERTISER
395
CONDENSERS
"Made of Mica and Moulded
in Genuine Bakelite."
Capacities of Resistors and Con-
densers guaranteed within 5% and
constant in value.
They are indestructible and Mois-
tureproof.
At all good Radio Stores
Micamold Radio Corp.
Flushing & Porter Ave.
BROOKLYN, N. Y. JL
ACCURACY GUARANTIED
-VALUES RSMAIN CONSTANT
RUDYARD
KIPLING
A set of KIPLING in
the home is read by
every member of the family.
Buy KIPLING'S books.
AT ALL BOOK STORES
FOR CLEAR, QUIET "B" POWER
RADIO
Storage "B" Battery
Lasts Inde/imtely-Pays /or Itself
Kible cost, 1'elivers unfailing power that is clear, pure and quie
Approved an I listed as Standard by leading Ka> io Authorities includ-
ing i'op. Ridio Laboratories, Pop. Pci. Inst. Standards, Kadio News
Lab.. Lefax. Im., and other Important institutions. Equipped with
Solid Rubber Caae^ rn insuranr-e aKainsc acid ard leakage. Extra
heavy pla
«e, 0n Insurance aftainsc acid aid leakage
_. Heavy ru^Ked plates. Order yours today 1
I XTO \/f OXIT7V Just state number of batteries
1 JNU MUfMtl wanted and wev.il! ship day order
isreceived. Extra ofler: 4 batteries in series (96 volts), $10.00. "
>T psv
ining batteries. 6 per cent discount for cash
ur order now!
WORLD BATTERY COMPANY
i.WabashAve., Dept. 24 Chicago, IU.
Maters of the Famma World Radio " A' • Storage Battery
i.tll.SS; !SOAmp.$lfl.S5;lltOAltlv.Sllt.OO*
1219 So. Wabash Ave.,
Prices; 6-valt, 100 Amp. tit
AH equipped
'5; IWAm-p. $1.1.25: 140
nth Solid Rubber Cafe.
STORAGE BATTERIES
Set your Radio Dials at 210
metera for the new 1000
u World Storage Battery
The Best in the World
No Batteries
are required even
to operate the
most powerful
10- tube receiver
pictured above, if
you use the new
laboratory type
Model A
Power Unit
One Customer Telegraphs:
"Receiver assembled, per-
forming like a thorobred."
The Amateur or Experimenter
with his ultra-modern high-
powered receiver is years ahead
of Commercial Radio.
It is significant that unsolicited testimonials are
constantly being received from even the far corners
of the earth, where Norden-Hauck Engineers
have furnished the finest radio apparatus known
to the art today.
Quotations gladly furnished on radio parts and
apparatus having non-infringing uses.
Write for Literature
NORDEN-HAUCK, Inc.
Engineers
1617 Chestnut Street, Philadelphia, Pa.
RADIO BROADCAST
For February
will be a better magazine than this. Make sure of it by
telling your newsdealer to hold one for you — or better
still, subscribe through him or direct.
RADIO BROADCAST
Garden City New York
Jty&rtkur&Qile &&
sent post-paid on receipt of /Of
in stamps or com
COLE RADIO MFC.CORP.
BLOOMFIELD.NEW JERSEY
Tested and approved by RADIO BROADCAST
RADIO FANS, a one-year's subscription to Radio Broadcast will cost
you four dollars, two years six dollars. Consider this expenditure
as being a necessary investment on your part for the future develop-
ment of your own knowledge of Radio.
in a weeK
your Buescher Saxophone
You can do it — easy, 3 leseons free with each
new instrument give you a quick start. Prac- A
ticing is fun because you learn so fast. And itf
will make you popular, in demand, the center
of attraction everywhere you go. Always a hit.
Even if you have failed with some other instru-
ment, you can learn the simplified Buescher
Saxophone. Don't delay. Get into the big fun.
Any instrument sent for 6 days' free trial. Easy
terms if you decide to buy. Write now for
beautiful, free literature. Address:
Buescher Band Instrument Co. "'
1218 Buescher Block Elkhart, Indiana
396
RADIO BROADCAST ADVERTISER
Centralab Radiohm
for oscillation control
The Centralab Radiohm gives you perfect
oscillation control — enables you to get full
efficiency from your radio set.
By controlling oscillation with this little
unit, you can hold that sensitive regenera-
tive position which immediately precedes
the oscillation point, without distortion or
loss of selectivity. Think what a boon to
clear, true-tone reception this is!
The Radiohm provides smooth variation of resistance
from zero to 200,000 ohms. Ideal for plate circuit con-
trol of oscillation. Used as a standard unit in many lead-
ing commercial sets. Price: $2.00.
Centralab Modulator
for volume control
This improved type of potentiometer takes the
"rough spots" out of volume — smooths out
powerful "locals" as well as difficult "DX."
It provides noiseless control of tone volume
without in any way affecting the tuning of
your set. Has a maximum resistance of 500,000
ohms, specially tapered to give smooth, even
control from a whisper to full volume — or
vice versa — without de-tuning.
Used in the "Silver Six" set! also in audio
circuits with any transformers or with Thordarson
Price: $2.00.
"Autoformers."
CENTRAL RADIO LABORATORIES
22 Keefe Avenue Milwaukee, Wis
Mail the coupon
CENTRAL RADIO LABORATORIES 14 Keefe Ave., Milwaukee, Wlo.
( ) Send me literature describing Centralab controls. Enclosed find
% for which please send me the following:
( ) Centralab Modulator, at $2.00 each. ( ) Centralab Radiohm,
at S2.00 each.
This is a good time to subscribe for
RADIO BROADCAST
Through your dealer or direct, by the year only $4.00
DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORK
If you are the type of dealer who hustles after business, who
isn't content to wait for trade to com*- in hut who takes sots out
to demonstrate, can talk and sell quality merchandise, and
knows Radio values, we have a big proposition for you. Are
you that dealer?
SO% Discount to Dealers
We manufacture a complete line of high
grade receivers and sell to dealers at 50#
discount. We are distributors for more than
225 Nationally advertised lines.
FREE Write today for amazing offers, new
112- page catalogand regular month-
ly catalogs quoting below- the- market prices
on latest merchandise — all free. Everything
in Radio for less.
AMERICAN RADIO MFG. CO.
1436 McGee St.. Kansas City. Mo.
GRID INQUIRY BLANK
Editor, The Grid
RADIO BROADCAST
Garden City, ~Nfw for\
DEAR SIR:
0 I am a subscriber to RADIO BROADCAST
and therefore will receive answers to my
queries free of charge.
1 I I am not a subscriber and enclose $1
to cover cost of answers.
NAME .. .
ADDRESS .
G. D.
THE CROSLEY RADIO CORPORATION
CINCINNATI, OHIO
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
1 wish to compliment you on the beautiful
copy of RADIO BROADCAST which has just come
to my desk. . . . It is certainly attractive,
and 1 feel sure that in its new form it is destined
to greater accomplishments than ever before.
Very truly yours,
POWEL CROSLEY, JR.
President.
A Remedy for Congestion
COMETH ING will have to be done to
>-J reduce the congestion of broadcasting
stations, which is probably felt more in
New York than in any other city. Even in
Europe trouble is being met with in this re-
spect, and it is suggested that some of the
British relay stations will have to be closed
down to make room in the ether. Here is
a reader's suggestion to alleviate the con-
gestion in New York.
Editor, RADIO BROADCAST
Doubleday, Page & Company,
Garden City, New York.
SIR:
Regarding the congested condition of avail-
able wavelengths for broadcasting, particularly
in this vicinity, 1 would like to state my views in
the nature of constructive criticism. I believe
that a mistake is being made in granting so many
New York stations exclusive Class B wave-
lengths. There are now nine Class B stations
operating in and around this city on seven dif-
ferent frequencies, only four stations dividing
time, namely, WOR and WJY on 740 kc. (405
meters) and WCBS and WAHG on 949 kc. (316
meters), and now, another station, WLWL, has
been granted a license to operate on an exclusive
frequency, 1041 kc. (288 meters). When there
is already a shortage of wavelengths, I cannot
understand why every new New York station is
given its own wave instead of dividing time with
some other station, particularly when such fine
stations aswcApand WRC in Washington are com-
pelled to share time. Each of these two stations,
I believe, deserves its own wavelength as they
both give the highest grade of programs. Here
in New York only two stations, WEAF and wjz,
are in my opinion rendering the type of service
which justifies an exclusive wave.
I have no grievance against any particular
station, but 1 fail to see any good reason for
stations WHN, WMCA, and WNYC not dividing
time. The latter, especially, could easily re-
arrange its programs and allow some other sta-
tion to share its wavelength. At present it is
only on the air for three or four hours a day,
seldom starting before 7 p. M. and usually signing
off by 10:30 or 1 1 p. M. If these three stations
and the new one, WLWL, were put on a part time
basis (WEAF, wjz, WOR, WJY, WGBS and WAHG
continuing as at present), New York would still
have six Class B channels which, with the Class
A stations in operation, should be enough to
satisfy any listener. This would leave two waves
available for other eastern cities, one of which
should be assigned to Washington and the other
reserved for future use.
In Chicago, every station divides time with
another and 1 believe this arrangement has been
satisfactory to all concerned, while the programs
broadcast from that city are in most cases of the
highest caliber. If such a plan were put into
effect here, while no doubt it would not meet
with the approval of the owners of the stations
concerned at once, it would enable them to con-
centrate more on the time they would be on the
air and thus furnish better programs.
Yours very truly,
GEORGE W. CLINCHY,
New York City.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
397
The VEBY
Itgsistance Qoupied
Amplifier
A REVELATION to Music Lovers—
•**• amplifies all frequencies alike, thereby
producing the radio concerts with utmost
fidelity. Size 5x7 inches — fit
within any receiving set. Price $12.00
A. F. 20 High Mu Tubes for R. C.
Amplifiers $3.00
A. F. 6 Power for the last stag e. . . 4.50
A. F. 30 Super High-Mu Tube. ... 6.50
VEBY PRODUCTS are uniform at
all times — you can depend on them.
Manufacturers, Distributors and Dealers
write or wire for particulars.
VEBY RADIO COMPANY
"Quality Resistors"
47-51 Morris Avenue
NEWARK N. J. .
TF you like this magazine
with its coated paper and
enlarged siz,e — then why not
subscribe and get it regularly
-by the year, $4.00, Six
months, $2.00.
Doubleday, Page & Co.
Garden City New York
' * a new 5-Tub«
Set with all the
power and none
of the grief of
the Supers*' —
so wrote Henry
M. Neely, Edi-
tor of Radio in
the Home,
Philadelphia.
Get This Book
Write to-day for this big fasci-
nating 32-page booklet which
tells how you can build the
truly amazing new QUADRA-
FORMER receiver. Based on
a new radio principle, five
tubes give remarkable results.
Enclose lOc and you'll have it by return mail
Gearhart-Schlueter Radio Corp'n.
713 Voorman Avenue, Fresno, California
A receiving set is no better than its tubes.
With other parts and connections right a set may be
as good as its tubes — no set can be better.
That's why you want CECO Tubes. They stand up
and deliver. With them your set works at its maxi-
mum. Clarity of tone, rich volume, long life — CECO
has them all to a superlative degree.
Our charted tests (results confirmed by laboratories
of national reputation) PROVE CECO TUBE SU-
PERIORITY— whether used as detectors, audio or
radio frequency amplifiers.
CECO Tubes make a Good Receiver BETTER. Try
them and you'll BUY them always — for results.
Now Ready! CECO Tubes with new type Long
PRONG BASES. Also, Power Amplifier Tubes, E
(Dry Cell Type), F (Storage Battery), for last stage
of Audio Frequency.
Dealers write giving jobbers name.
C E. Mfg. Co., Inc.
702 Eddy Street, Providence, R. I.
This is a good time to subscribe for
RADIO BROADCAST
Through your dealer or direct by the year, only $4.00
DOUBLEDAY. PAGE & CO. GARDEN CITY, NEW YORK
RADIO WIRES
We manufacture all types.
Round braided antenna wires
Flat braided antenna wires
TRADE MARK ftEG. Round stranded antenna wires
Above types in copper — tinned copper — enameled copper — tinned bronze.
Loop wires in silk or cotton covered. Antenna supporting springs.
Litz wires.
Enameled wires.
ROSS WIRE COMPANY
Cotton and silk covered wires for set
wiring. A
Write us for descriptive catalogue. ft
69 Bath St., Providence, R. I.
Tested and approved by RADIO BROADCAST
398
RADIO BROADCAST ADVERTISER
ELECTRAD
Royalty
Variable High
Resistances
They provide all the flexibility
of the throttle of a twin-six — bet'
ter control of volume — complete
control of tone quality and smooth
variation of resistances.
Specially designed as a compensa-
tor or a volume control in audio
amplifiers wherever a high resis-
tance is specified. Neatly wire
wound, indestructible, and the same
setting provides the same resistance
at all times. Bakelite moulded and
provided with holes of standard
spacing for panel or base board
mounting.
Type A— Variable Grid Leak, -fr to 7
megohms.
Type B— 1,500 to 100,000 ohms.
Type C— 500 to 50,000 ohms.
Price $1.50
Type D — Specially designed for con-
\l of detector plate current in B-
Sattery Eliminators. 10,000 to
700,000 ohms. Price $2.00.
The Six Point
Pressure Condenser
The "Electrad" Certified Fixed Mica Con-
denser is a revelation in accuracy and design.
Ingenious rigid binding and firm riveting
fastens parts securely at Six different points
insuring positive electrical contact. Value
guaranteed to remain within 10% of cali-
bration. Standard capacities, 3 types. Price
30c to 75c in sealed dust and moisture proof
packages.
ELECTRAD, Inc.
428 Broadway New York City
Is All Broadcasting Advertising?
WHETHER advertising should or
should not be permitted is a question
which the radio public will ultimately have
to decide for itself. It is a much-mooted
question and one in which most of the
readers of RADIO BROADCAST have a deep
interest. As long as broadcasting stations
are owned and operated by private indivi-
duals they will be advertising, regardless
of whether they are or are not doing so in
the abstract. When an announcer states
that "This is station WPY, broadcast-
ing from Bambelf Brothers Store, West
Oskaloosa," he is placing the name of
that concern before the public in a manner
which defies competition. Yes, after that,
it is advertising, regardless of whether or
not he broadcasts grand opera or education
or economics. The letter printed below
sets forth some very interesting ideas on
the subject.
Editor, RADIO BROADCAST
Doubleday, Page & Company,
Garden City, New York.
SIR:
Referring to the invitation to express views on
the matter of advertising matter being broad-
cast, I venture to ask if all broadcasting is not
advertising? What difference does it make to
the listener whether he is told that Miss Jones
will sing from station woe, the Palmer School
of Chiropractic, etc., or that the A & P Gypsies
will play from station WEAF? In either case it
will be a good number, well worth hearing. The
number from woe advertises the Palmer School,
the one from WEAF advertises the little red store.
Or take for illustration the stations operated by
educational institutions; is the purpose for which
they are conducted to furnish laboratory facili-
ties for their students or to make the college
better known, that is, to advertise the college?
Speaking only from recollection, 1 am of the
opinion that the newspapers were among the
first to install broadcasting stations. In any
event several good stations are still operated by
newspapers. What purpose is there for the
operation of stations by newspapers except ad-
vertising?
It seems to me that advertising is the logical
support of a broadcasting station the same as it
is the support of periodicals, and that there can
be no more objection to advertising in connec-
tion with broadcasting than there is in connection
with publishing. Any owner of a receiving set,
except possibly a crystal set, is within range of
more than one station and as free to make his
choice of the station to which he listens as he is
to read the newspaper he prefers. Any news-
paper that cannot make its news pages of suffici-
ent interest to have enough readers to make its
advertising space valuable loses money and in
time goes out of business. If a broadcasting
station does not make its programs interesting
it will have few regular listeners, it will have no
advertising value and in time it will go out of
business. If we could have a frank expression
from the owners of the broadcasting stations that
have been discontinued we would find that these
stations were discontinued because they did not
pay, in other words that they did not have
sufficient advertising value to warrant the cost of
operation.
The use of broadcasting for advertising pur-
poses seems to be the logical way to maintain
good broadcasting; the broadcasting has to be
good to make the advertising worth while. Even
the talks which are purely advertising, such as
those given some time ago regarding tea and
surety bonds, are in no way objectionable because
such talks must be of sufficient interest to hold
the attention of listeners, or they would dial an-
other number.
Very Truly Yours
B. O., New York.
if Tested and approved by RAIIP BROADCAST if
Building
Better
Service into
RADIO PARTS
Aside from recognized
radio uses in which no
other metals can be
substituted, COPPER
and its alloys help you
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Without Penetrola the scientifically meas-
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RADIO BROADCAST
ARTHUR H. LYNCH, Editor
WILLIS K. WING, Associate Editor
JOHN B. BRENNAN, Technical Editor
FEBRUARY, 1926
Vol. VIII, No. 4
426
427
431
436
439
Cover Design - - From a Painting by Fred }. Edgars
The Hamilton Rice Expedition - - Frontispiece
Radio: The Jungleman's Newspaper
John W. Swanson
The March of Radio » * •* J. H. Morecroft
Design of Radio Inductances - W. W. Harper
How to Build a Grimes Inverse Duplex
Florian J. Fox
Prize Contest Announcement 444
The Listener's Point of View - - John Wallace 445
"Radio Broadcast's" Universal Receiver - 450
"How Long Will My B Batteries Last?"
George C. Furness
How to Use Vacuum Tubes Keith Henney
The 1926 International Radio Broadcasting Tests
Willis K. Wing
"Radio Broadcast's" Booklet of Foreign Broadcasting
Stations - * < * - - Lawrence W. Corbett
As the Broadcaster Sees It - - - - Carl Dreher
Wavelength'Frequency Conversion Homer S. Davis
Wavelength-Frequency Chart - - -
452
456
462
465
467
471
472
The Grid — Questions and Answers
An Explanation of Tuning
How to Obtain Better Regeneration
Protecting the Loud Speaker
C Batteries in the Detector Circuit
"Now, I Have Found" - - - -
482
488
Quarterly Prize Award Announcement
Using a Voltmeter as a Milliammeter
Coil Design Data
A Simple Long- Wave Receiver
A Good Audio Amplifier
Improving the Volume of the Two-Tube Roberts
Winding Spider Web Coils
What Constitutes a Radio Patent? - Leo T. Parser
A Key to Recent Radio Articles £. G. Shaltyiauser
Book Review *.»**•* -
"ECONOMICS OF THE RADIO INDUSTRY"
What Our Readers Write
494
504
514
518
BEHIND EDITORIAL SCENES
"OROBABLY one of the most interesting numbers of RADIO
Ji BROADCAST presented to our readers in a long time is this
February magazine. To start it off, Mr. John W. Swanson, who
is now a radio inspector for the Department of Commerce, with
headquarters at Norfolk, Virginia, tells of the unusual experi-
ences he and his comrades had on their trip to the headwaters
of the Amazon and shows how short waves saved the day*.
Mr. W. W. Harper, who wrote "Design of Radio Inductances"
on page 436, is a consulting radio engineer in Chicago who has
practically lived with coils in his laboratory for the past year.
His conclusions should excite considerable comment and, in addi-
tion, prove very valuable to every home constructor. Florian
J. Fox, who prepared the very complete constructional article
on the four-tube model of the Grimes Inverse Duplex Receiver,
is chief engineer of the Grimes Radio Engineering Company.
The reader will notice that on page 441 appears a complete chart
of the set being described. The same terse description was
applied to the short wave transmitter in the January magazine.
It would interest us to know whether readers like this feature
well enough for us to continue it. Write us and let us know.
THE $500 prize contest for the design of a non-radiating short-
wave receiver indicates one of the most unusual steps taken
in the short-wave communication field. Amateur experimenters
have already shown that they will try hard to meet the challenge
to their ability. The four receivers shown on pages 450 and
451 follow those models of the "Radio Broadcast Universal
Receiver," so completely described in this magazine for January.
The Universal has jumped into more than immediate popularity,
not merely because RADIO BROADCAST and others say it is good —
that, by the way is certain, for it was developed in our own
laboratories — but chiefly because others have found it to be good .
Mr. Henney's article on how to use vacuum tubes on page 456,
lives up, we are certain, to all the promises made for it in this space
last month. The transmitting schedule for all stations in the
International Tests during the week of January 24th will be
found on page 463, together with all late information on the
Tests in the article which accompanies it.
ERRORS, when they occur, should be corrected and not
glossed over. In Roland F. Beers's article; "An Improved
Plate Current Supply Unit" in our December number, it was
stated on page 190 that "one lug of the single-pole double-throw
switch goes to the full secondary terminal at 1250 turns."
The phrase should read "primary" for "secondary." The
proper placement of the tap and its circuit connections are evi-
dent from the wiring layout and circuit diagram accompanying
the article.
NEXT month we expect to print details of the design of a
very interesting receiver, from the pen of a well known
radio man, whose talents entitle him to be mentioned in the
same breath as Dr. Walter Roberts. The third of the "Home
Radio Laboratory" articles, prepared by Keith Henney, will
appear in March also. This should please many constructors
who have reached the "end of their string" and who have
shown such great interest in the possibilities opened up by these
articles. Mr. J. C. Jensen, who has spent much time in research
on the subject, will have a fascinating and stimulating article on
how radio reception can be calculated from known weather con-
ditions. It is worth waiting for. — W. K. W.
DoubUday, Page S* Co.
MAGAZINES
COUNTRY LIFE
WORLD'S WORK
GARDEN & HOME BUILDER
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LE PETIT JOURNAL
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Copyright, 1926, in the United States, Newfoundland, Great Britain, Canada, and other countries by Doubleday, Page &
TERMS: $4.00 a year; single copies 35 cent*.
Doubleday. Page S" Co.
OFFICERS
F. N. DOUBLEDAY, President
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• Company. All right* reserved.
RADIO BROADCAST ADVERTISER
425
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RADIO AND THE HAMILTON RICE EXPEDITION TO BRAZIL
The country conquered by men, flying machines, and radio. The large photograph, taken in the expedition's advance airplane piloted by
Walter Hinton, was made by Captain Albert W. Stevens of the United States Army Air Service whose photographs are world renowned.
The expedition proceeded up the Rio Negro 500 miles from Manaos, Brazil. Manaos is 1500 miles from the ocean, and the base of the ex-
plorers was set up at Boa Vista. The Rio Negro at the point photographed is about three and a half miles wide and appears a veritable
archipelago of curious shaped islands. The photograph above shows the short wave transmitter and receiver used to maintain^ communica-
tion with the outside world. The natives, after they gained courage enough to wear the phones, showed little surprise at the "white man s
magic" when they heard the short wave broadcast signals from KDKA and WGY through the head set
RADIO BROADCAST
VOLUME VIII
NUMBER 4
FEBRUARY, 1926
VSI
Radios The Jutigleman^s Newspaper
Vf (^J OL. JL.
How the Rice Expedition in the Jungle Maintained Communication with the Outside World
—A Triumph of Short Waves and Low Power When Long Waves and Higher Power Failed
N
*OT so many months ago the pub-
lic was thrilled to read in its
morning newspapers an account
relating how radio amateurs all
over this and other countries had estab-
lished two-way communication with the
Rice exploration party, then in South
America. Receiving apparatus only had
been carried on the two previous expedi-
tions, which was used for reception of time
signals, necessary in accurate topographical
surveying, and of press dispatches, which
were, to the members of the expeditions,
what the London Times is to King George's
subjects. Radio's capable handling of these
assignments led Dr. A. Hamilton Rice,
vice-president of the American Geographi-
cal Society, when his third expedition
was being organized at New York, to al-
lot a more important task to the writer,
who had been radio operator on the pre-
ceding Brazilian ventures.
Where radio had been
acting the part of a listener,
a masculine part, if you
please, it was to be given a
tongue on the third expe-
dition and, now cast in a
feminine role, was, if its
abilities were not over-
estimated, to keep the ad-
vance exploration party in
touch with the base party,
and the base party, through
stations of the Brazilian
government, on speaking
terms with the rest of the
world. It must be admitted
that this mission assigned
by Doctor Rice was regarded
with a certain amount of
doubt and misgivings on the
part of the radio personnel.
The advance party, in the
Chief Radio Operator of the Expedition
first place, could only carry featherweight
apparatus and an insufficient source of
power supply, while the erection of efficient
antennas would present a big problem.
The interior of South America, experience
had taught, bred static as it did fever, while
venomous insects and rank vegetation were
not the least of their troubles.
How far radio's performance exceeded
expectations; how "it might" became "it
did," is a tale which deserves a paragraph
or two in the history of short-wave com-
munication. Called on to bridge one
hundred — two hundred miles of jungle, the
Rice Expedition's transmitters night after
night, months on end, laughed at the 3000-
odd miles of space between upper Brazil and
the United States. Naked, half-savage In-
dians were the explorers' neighbors while the
operators whispered intothe ears of amateur
radio men over half the civilized world.
LISTENING TO KDKA
From the midst of the jungle. WCY was another short-wave station
the short-wave apparatus was first tried out at Manaos, only three
heard. Two of these, curiously enough, were broadcasters, while
code station was heard
To the American amateur is due a large
share of the credit of the success of the
Rice Expedition's employment of radio
in the Amazon valley. Playing for love
of the game alone, they handled the cards
as if the stakes were gold and mountain
high. Hats off to 2 AG, 2 BR, and 2 cvs, of
New York City, i COT of Braintree, Massa-
chusetts, 3 ATE — Baltimore, 8 ES — Akron,
5 SK — Fort Worth, and the others! Radio
is a game at which one cannot play a lone
hand and Thomas S. McCaleb, former in-
spector for the Independent Wireless Tele-
graph Company, of New York, was the
writer's capable assistant and fellow burden
bearer in the tropics.
The expedition's radio history begins at
New York City where, previous to taking
ship for Para, at the mouth of the Amazon,
$6000 was expended upon a stock of radio
material which ran up and down the list
from binding posts to gener-
ators, fifty-watt tubes to bus
bar. Variable condensers
are conspicuous by their ab-
sence on the store shelves of
small Brazilian towns, and
no explorer has yet discov-
ered a jungle palm treelwhich
bears milli-voltmeters.
Once in the jungle there was
continual construction and
destruction of transmitters
and, to some extent, of re-
ceivers.
AMERICAN BROADCASTING
HEARD
INITIAL tests of the radio
I apparatus were made at
Manaos, an Amazon town
of 5000 inhabitants, 900
miles from the ocean, and
the jumping-off place for
heard. When
stations were
only a single
428
RADIO BROADCAST
FEBRUARY, 1926
these who probe the uncharted interior of
the great southern continent. Here the
expedition's 4oo-watt transmitter was set
up temporarily and put in operation on
200 kc. (1500 meters). With this set the
Para station, 850 miles distant, was "raised"
without difficulty.
Tests of short-wave receiving equipment
at Manaos did little to bolster the confi-
dence of the radio detachment. Nights of
dial-twisting and ear-straining brought in
but three short-wave stations, two of them
broadcasters. Hearing KDKA and WGY with
regularity on high frequency was, it is
true, a distinct contribution to the expe-
dition's entertainment, but reception of a
lone code station — it was 8 xi — was dis-
couraging. The road ahead appeared as
dark to the radio men at this stage as the
native tobacco they were smoking.
Radio work at Manaos was drawing to a
close when a political tidal wave engulfed
the town. Making merry in the Hotel
Grande on July 23, at a gathering to wel-
come others of the party who had just come
up the river to join their fellows, the radio
men were thrust into box seats at a South
American revolution.
Zero hour came without warning. From
the restaurant windows the explorers were
gazing idly, between drinks, at a detach-
ment of olive-skinned soldiers shuffling
down the Broadway of Manaos. Troops in
movement are so frequently encountered in
South America that the military exhibition
awakened no interest until the infantrymen
halted, took interval quickly, and sent a
steel-jacketed shower in the direction of
the governor's palace. A bullet in motion
is not a desirable neighbor, no matter who
fires it. There is small comfort in the
knowledge that marksmanship is bad when
brick dust begins to fly. There was a
great slamming and barring of doors and
windows within the Hotel Grande restau-
rant, and a scramble for safe places behind
thick walls as the government of Manaos
began to totter.
Soon a panting revolutionary wormed
the news though a crack in the hotel door
that right had triumphed. " Long live the
revolution," in its equivalent Portuguese,
came between gasps.
i Screwing up courage after a time, the
Americans filed out upon Rua 28 do Sep-
tembre to find all quiet. They stole softly
down dark thoroughfares where the arc
lights had gone on the casualty list. Care-
fully they trod to avoid slipping on the
blood which, they judged from the whole-
sale expenditure of powder, must have
showered the rough pavements. Their
guess was wrong; no blood or dead. Even
the martyred donkey, the usual accom-
paniment to tropical internecine strife, was
not encountered. Thousands of brass
cartridge shells underfoot and the white
flag flying above the governor's palace
alone lay in the wave of the revolution.
Next morning, commercial Manaos was
doing business at the same old stand.
Rebel rule imposed strict surveillance
upon foreigners, but the upheaval little
hampered the expedition's work, though it
brought an end to radio tests. The inter-
diction of ether communication at Manaos
by the de facto government was followed
by a laughable incident, the humor of
which registered even upon the officials who
called the Americans to account when it
was reported to them that antennas had
been erected by the explorers on the out-
skirts of the town.
Without much difficulty, official Manaos
was convinced that what had been described
as "radio wires " were baited fish lines set to
catch turkey buzzards, the blood of which
was being analyzed by the medical branch
of the party. When the time came to
move upriver, an old stern wheel steamer
transported the party to Vista Allegre, on
the Rio Branco, where the first semi-
permanent camp was established. Ascer-
taining that Vista Allegre was a poor radio
location, the two operators put their equip-
ment aboard a batalao (a barge towed by a
steam launch), and proceeded further up-
stream to Boa Vista, which was to be the
expedition's base during the time the ad-
vance party was in virgin territory.
During the batalao's slow ascent of the
river, the radio men slept in filthy quarters,
foggy with mosquitoes. McCaleb went
down with high fever the day of his arrival
at Boa Vista. Two weeks he lay ill at the
small mission, attended by the kindly
padres, a casualty of the never-ending
conflict between man and the insect life of
the Brazilian river country.
The anthem of the Amazon valley is the
whining, petulant song of the mosquito,
chief of a happiness-blighting clan which in-
cludes the pium, a smallish black fly with a
red-hot snout and others whose names
would carry nothing to American readers
but whose blood-sucking operations would
shame even a radio gyp dealer.
Against these barely visible foes the ex-
pedition fought. They were its unwelcome
guests at meals, its bedfellows; many a radio
message sent by LR, the portable station
set up at camps and bivouacs beyond civil-
ization's frontier, was dispatched by opera-
tors whose right hand tapped the key and»
whose left repulsed an insect onslaught.
Larger insect enemies included several
species of the ubiquitous ant, whose ac-
quaintance was made at Manaos, and
hornets encountered in the jungle. They
attacked apparatus as well as operators.
Anti-ant measures became a regular part
of radio routine after the short-wave re-
ceiver, opened one day for inspection, was
found to be full of very live radio bugs. A
blow torch, in McCaleb's hands, did for
the most of them. Those escaping crema-
tion perished under the huge feet of Chico,
native servant of the radio detachment.
Hornets, of a species which build a mud
dwelling, took possession of LR one day
upriver. The operator found that all crev-
ices in the apparatus had become hornet
home-sites. Their mud huts shorted the
grid and plate terminals of one transmitter
tube and a veritable firework display re-
sulted when the current was turned on.
ESTABLISHING THE BASE STATION
WHILE McCaleb convalesced, the
erection of a station at Boa Vista
went forward, the main trouble encoun-
tered in putting it up being inability to se-
cure timber for masts in a treeless country.
Fourdays' journey from the camp mast ma-
terial was found, cut and floated. With
the help of natives, most of them Indians,
three masts went up, eighty, seventy-five,
and forty feet high. An antenna for long-
wave work was suspended between the
two highest; a short-wave antenna was
hoisted between the shorter sticks. There
was an elaborate ground system for long-
wave work and a litzendraht cable counter-
poise for the high-frequency set.
There followed six days of calling and lis-
tening while static alone caused the head-
phone diaphragms to vibrate. Two oper-
ators were deep in the dumps, half-sick and
nearly played out when a woman's voice
floated in on the sixty-meter wave. The
song, ironically enough, was " Happy
Days." KDKA'S short-wave set did a
physician's work at Boa Vista that night.
An American amateur, 4 SA, shattered
the silence with a readable signal the next
night, but failed to respond when called
repeatedly. This was a disheartening
chapter and the events of the next few
days produced more gloom.
McCaleb, sent down the river to join
the expedition proper at Vista Alegre, took
with him the twenty-five-watt transmitter,
hoping to effect communication with the
base station wjs at Boa Vista, as the ex-
pedition moved along. The attempt failed
dismally.
The only silver lining during these days
of discouragement was that another
American amateur was heard, and wsc, an
American coastal station of the Radio Cor-
poration, boomed in. They could not be
made to hear us, however. Then things
brightened for Manaos, called in vain for
days, one morning responded with a snappy
"O. K." This was a slice of bacon where
a whole side of meat was needed.
The base party having established itself
at Boa Vista, and McCaleb in charge of wjs,
the advance party early in December set
out on the jungle trail, the twenty-five-watt
transmitter, under the wing of the writer,
accompanying it. Communication be-
tween the two parties was established with-
out difficulty after the advance party had
made some progress, and radio stock soared.
Equipment overlooked when the advance
party set out, and needed urgently by the
scientists, was ordered dispatched in pur-
suit from Boa Vista. The portable set was
demonstrating its usefulness.
At this juncture, with things going swim-
mingly, partial failure suddenly loomed
in the radio detachment's path. Short
waves and the American amateur saved the
day.
The rock on which the radio plans threa-
tened to wreck was the heavy tube mortal-
ity at wjs. The fifty-watters expired in
such numbers that not enough remained to
FEBRUARY, 1926
RADIO: THE JUNGLEMAISTS NEWSPAPER
429
ERECTING WJS S MASTS
The wood for which had to be brought from a
point four day's journey away as no suitable
trees were found at Boa Vista
pewer the long-wave base transmitter.
The Boa Vista-Manaos link broke and the
expedition's communication with the out-
side world was disrupted.
Now McCaleb's short-wave experiments
bore fruit. During the months since the
expedition's sailing, the great amateur
migration to the 40-80 meter band had
taken place. So, unable to work Manaos
which was, as radio distance is measured,
but a step away, wjs began shooting Rice
Expedition traffic almost daily to American
amateurs. First two-way communications
was effected with 2 cvs, New York City.
This success was followed by the trans-
mission of long and important messages to
dozens of other amateurs in the United
States, two in England, one at Buenos
Aires, and to sj, the United Fruit Com-
pany's efficient station at San Jose, Costa
Rica.
JUNGLE RADIO ADVENTURE
SOME of the traffic was destined to Amer-
ican points but
much of it was ad-
dressed to Manaos.
Consider what this
meant: Manaos was
400 miles from wjs but
could not be reached
direct during the tube
shortage days. A mes-
sage for Manaos went
3000 miles by ether to
the United States, 3000
miles by cable from the
United States to Para,
then by radio, a matter
of nearly 1000 miles, to
Manaos. Costly? No
end. Subject to delays?
Yes, frequently. But
the messages, many of
them of utmost im-
portance to the party,
reached those to whom
they were addressed,
and that was the ob-
ject of the game.
The advance party, with its portable set,
had now penetrated well into the dense
forests it had come to explore and map, its
canoe fleet daily engaging the rapids of the
turbulent stream, which the Indians who
live beside it have appropriately named
"The Poison River."
In a clumsy, heavy, spoon-billed craft,
more scow than canoe, radio made its fight
against the angry river, its guardians being
Weld Arnold, jovial topographer of the ex-
pedition; an Indian boatman of the region;
Antonio, in whose veins ran mixed negro
and Indian blood; and the writer.
There were many rapids up which the
canoes could be pulled by ropes, but some,
more^ waterfalls than rapids, would stop
a salmon's upstream rush. Encounter-
ing these, the canoe fleet was forced to
portage. This meant heart-breaking labor
under an unrelenting sun. It meant more
than carrying equipment and canoes on the
backs of men to navigable water above the
obstruction, because, in order that this could
be done, a trail must first be hacked with
machete* through the jungle, which came
down to the river banks. On a day when
the river seemed set to baffle the canoeists,
the party gained, with infinite labor, an
advance of one-half mile. Camp was made
that night within sight of the camp of the
night before.
Beau Brummels of the advance party
fought the river in B. V. D's and bathing
suits.
From day to day the program varied
little: During daylight a contest with the
river; in late afternoon selection and clear-
ing of a camp site, pitching of fly tents and
preparation of the evening meal, which,
if the hunters had made a kill, might include
a venison steak sweet and juicy enough to
tempt an epicure; at night, work by the
map-makers, the scientists and the radio
man, each with his specialty.
Erection of an antenna was the first
step in establishment of radio stations at
A CABOCLOS VILLAGE IN THE MIDST OF THE JUNGLE
They are a Portuguese-Indian people, and, after being presented with a few cigarettes, proved
most hospitable. The flying boat, which was piloted by Lieutenant Walter Hinton and used
to survey the country ahead of the expedition, made a forced landing at this point. The
walls of the thatched house were covered with pictures cut from various magazines, among
which were some of the 1922 New York — Rio de Janeiro flight. The natives became wildly
excited on being informed that Lieutenant Hinton was the pilot on that trip
LR S POWER SUPPLY
Which consisted of a dynamotor operated by
storage batteries. The batteries, in turn, were
charged by an auto generator belted to an
outboard motor which in turn did canoe duty
at other times. The plates of the two fifty-
watt tubes received 500 volts
the jungle camps. Trees were the masts,
and the vegetation for some distance about
the antenna trees was cleared away to give
the wires breathing space. Obtaining an
efficient ground was no problem; a length of
antenna wire thrown into the river served
well. The receiving antenna was usually a
thirty-foot length of wire, suspended one
foot off the ground. The low antenna re-
duced signal strength materially but re-
duction in static more than compensated
for this loss. In a tropical region, where
every night is a static night, LR thumbed
its nose to atmospherics.
The portable station's short-wave re-
ceiver, put together in the wilds out of camp
odds-and-ends, including two empty sugar
tins procured from Kwong, the Chinese
cook, was a thing to bring a blush of shame
to the cheek of the radio constructor who
likes to see things shipshape. That its ap-
pearance was not a measure of its sensi-
tiveness was demon-
strated when it picked
up amateur signals
from every radio dis-
trict of the United
States, and from sev-
eral foreign countries.
A simple Armstrong
circuit was used.
The transmitter, de-
signed for loo-meter
work, was revamped
upriver after its oper-
ator became convinced
that better results were
obtainable lower down
the scale. Alterations
fitted this set for eighty
and forty meter work.
The lack of a wave-
meter at the portable
station was met one
night when the opera-
tor had the good for-
tune to pick up the
standard frequency
430
RADIO BROADCAST
FEBRUARY, 1926
signals emitted by wwv, the
Bureau of Standard's sta-
tion at Washington. Util-
izing the system of har-
monics, a hastily assembled,
but accurate instrument,
was calibrated.
The portable station's
power supply was a dyna-
motor operated by storage
batteries, which were
charged by an auto genera-
tor belted to an outboard
motor, which in turn did
canoe duty at other times.
The plates of the two fifty-
watt tubes received 500
volts.
Both outboard motor and
generator threatened frequently to give up
the ghost but were nursed along to a re-
markable performance by the gas engine
experts of the party who lent a hand to the
radio operator when failure of the power
supply loomed.
Jungle days and nights were crammed
with incidents. Among them there was an
encounter with tucandera ants whose sting,
which carries a long-lived pain, the natives
dread more than that of any other insect.
The operator's carelessness in lashing one
end of his hammock to a dead tree, which
gave way in the night, made him food for
the tucanderas. Extricating himself in
the darkness from the fallen hammock he
rolled into their nest. He remained there
but a moment — there is a limit to man's
endurance — but the tucanderas which had
crawled into his clothes emerged from the
ant hill with him. Before all were routed
the radioman's skin, from head to foot,
burned with the fire to which the wicked
are headed.
More pleasant recollections are those of
the visit to one of the river camps of four
naked Guihibo Indians, shy but not un-
friendly savages of the country traversed
by the explorers. Their call on the white
men, the natives of the party learned from
them, had been made at some difficulty.
It appeared that enemy country lay be-
tween their village and the explorers' camp,
and the enemy had sought to block their
route. It had been necessary for them to
slay four hostile tribesmen.
Arrows, as long as spears,
were their main weapons; a
dugout canoe their means
of getting about.
There were few nights
spent in camp when traffic
was not exchanged between
wjs and LR and scarcely a
night when signals from
American amateur stations
were not heard on the crude
short-wave receiver. Due to
the necessity of conserving
power, the portable station's
messages destinedtothe out-
side world were habitually
shot to the base station,
which relayed them north-
THE EXPEDITION S RADIO APPARATUS
The upper picture is of the interior of the base
station at Boa Vista. It was intended that wjs
(the base station) should be employed for
communication with the station at Manaos, a
distance of about four hundred miles, but heavy
tube mortality at Boa Vista brought long-wave
medium power work with Manaos to an end.
Short-wave communication was then established
with amateur stations in the United States,
using low power and smaller tubes, the supply
of the latter being plentiful. Messages for
Manaos reached their destination by a round-
about route, often going to New York first.
The advance party's short-wave station, LR,
provided the connecting link with wjs. The
second picture shows LR'S "shack" at one of
the camps. Below: Natives listening to code
signals on the short-wave receiver
ward. This was, however,
no insult to the twenty-five-
watt set at LR for, on one
occasion, when the opera-
tor's curiosity to learn how
the low power equipment
would reach out got the
best of him, he passed with
ease a message direct to
station 4 DO, of M. M. Burns,
at Atlanta, Georgia.
Radio operations during
the final months of the ex-
pedition's workin the tropics
followed the lines established
duringthe period with which
this article deals. On Feb-
ruary 23, 1925, the writer
returned to Boa Vista by
means of an aeroplane used mainly in map-
ping from the air. His leave from the De-
partment of Commerce expired, so he came
back to the States. McCaleb took over the
portable station and capably handled his
task until early summer, when the ex-
plorers came home.
There were times when, unsuccessful in
"raising" wjs on eighty meters, a shift to
the forty-meter wave brought immediate
results. Even after nights when signals
carried poorly, when static was terrific,
there was a short period just following sun-
rise when the world could be heard. Some-
times this fruitful interval lasted two hours;
often not longer than fifteen minutes.
The amount of power used in transmission
appeared not to be a factor of much import-
ance. Many of the amateurs heard in the
forest were using sets with as little as ten
watts of power. McCaleb reported that
he was often warned that LR was about to
call, by a clearly audible sound which could
only have been occasioned by a minute
amount of radio frequency energy leaking
into the antenna when the tubes were
lighted but when the key contact points
were not actually meeting.
Elevation above sea level was important,
the ease with which traffic could be handled
apparently varying almost directly with the
elevation. During early evening the short
waves gave poor results. It was a rare
night when much work could be done be-
fore 9 o'clock.
On the whole, while trans-
mission on high frequencies
proved to a certain extent
freaky, communication was
established over such long
distances, with so little
power that the conclusion
seems unescapable that
short waves will come to be
used extensively in long
range work. We have not
yet solved many of the
mysteries of their propaga-
tion but we have opened the
gate wide enough to enable
us to see that there is much
inside the field we hardly
realized, until recently, was
ours to explore and to use.
-
I
THE MARCH OF RADIO
Past President, Institute of Radio Engineers
What Happened at the Fourth National Radio Conference
\HE radio industry is to be con-
gratulated upon the outcome of
the deliberations of the 1925 Radio
Conference, and this seems to be
the burden of the average editorial com-
ment throughout the country. The spirit
in which the various questions were ap-
proached and the remarkable display of rea-
sonableness on the part of the many con-
ferees augurs well for the healthy develop-
ment of our industry.
The radio industry can well get along
with no governmental interference or help
— that was the keynote of Secretary's
Hoover's opening address and that was the
natural conclusion to be reached from the
deliberations of the conference. Many
people are too ready to ask the government
to regulate something or other, somehow or
other, so that it is remarkable that no action
was taken along this line.
To legislate away the regenerative re-
ceiver, to subject the advertising question
to federal legislation, to pass laws closing
down the super-power stations, even before
they had started; many such questions were
in the air waiting to be settled by govern-
ment action of some kind and yet the confer-
ence actually put through no such resolution.
The one action of the conference which
The photograph above shows the towers of the beam sta-
tion at Dorchester, England, which will communicate with
New York.
stands out more than any other was the
stand taken on the number of broad-
casting stations. The opinion of the
conferees was almost unanimous in favor
of positively limiting the number of li-
censes issued. We have advocated the
limitation of the number of stations for
a long time and certainly it is gratify-
ing to hear the voice of the conference
so unanimous in settling this question.
The conference recommended that the
number of stations is not to be increased,
but is actually to be diminished. No new
licenses are to be issued and those licenses
which become forfeited because of disuse
are not to be reissued to another station un-
less there is a demand from the public.
The pleasing thing about this action is
that the question was settled with the
purpose of satisfying the radio listener
instead of the station owner. The public
is surely to be congratulated upon this
stand taken by the conference. It all
simply means that the radio listener's in-
terests are to be paramount in guiding
the future licensing of stations and matters
of similar import.
"It is a piece of hard luck, " remarks one
commentator, "for the would-be station
owner who has his station built and paid
for, to be told that no license is available
and his investment is valueless." How-
ever, unless the broadcast listeners in his
neighborhood show unmistakably their
desire for the new station it should remain
silent. No one has a right to intrude into
ether channels where he is not wanted and
those who know whether he is wanted or
not are the neighboring listeners.
Cooperation between various branches
of the radio industry, no governmental
regulation or censorship, settlement of in-
terference troubles entirely in the interests
of the broadcast listener — these three
features stand out as real accomplishments
of the Fourth National Radio Conference
so well directed by Secretary Hoover.
A Praiseworthy Bit of Radio Re-
search
IN NOVEMBER, 1925, a most remark-
able paper was presented to the Insti-
tute of Radio Engineers by a group of
three researchers of the American Tele-
phone and Telegraph Company, Messrs.
Bown, Martin, and Potter. To those of
us who look upon radio primarily as a
branch of electrical engineering rather than
simply a scheme of communication, the
paper seemed to be the best which has been
presented in years. Of all the divisions of
engineering, electrical is the most accurate
and scientific. Of the branches of elec-
432
RADIO BROADCAST
FEBRUARY, 1926
RADIO ON MOVING TRAINS
Passenger trains of the Canadian National Railways making the transcontinental run are all equipped
with broadcast receivers. The installation of a receiver to give regular service has been entirely
successful. On one trip of the "Quebec," the following stations were logged by operator N. Bonnr-
ville, who is seen in the view here: WBZ, KDKA, WFI, WGBS, WOR, WEAF, CKAC, WGR, WON, WJAS, WCAE,
CNRO, WTAM, WAAF, WGY, and WCX
trical engineering, that dealing with radio
phenomena contains the most intricate and
interesting problems. To the student who
has a keen imagination, a reasonable grasp
of mathematical relations, and an intense
desire to penetrate into the unknown, there
is today probably no more attractive field
than that in which Bown, Martin, and
Potter have been working for the past two
years and about which they reported in
their recent paper.
There are three general subdivisions in
radio engineering which offer opportunities
to the experimenter. The receiving set is
being made the subject of intensive study
by thousands of keen experimenters. The
cost of suitable laboratory facilities is com-
paratively little and the reward for a worth
while discovery is ample and sometimes
fabulous. The transmitter can be made
the subject of development work by com-
paratively few. Expensive apparatus is
required and only a small group of engineers
of the large companies can possibly work
on the improvement of transmitters.
There is another field of radio investi-
gation, however, which apparently offers
no financial return for successful endeavor,
that is the question as to how radio energy
is actually carried from the transmitter to
the receiver. Even a complete answer to
this question may bring with it no material
reward of any kind. One says "may" be-
cause there have been several cases in the
past in which an apparently useless scienti-
fic research has yielded tremendous finan-
cial returns tothose whodeveloped the idea.
We think of the work of Richardson and
other "pure scientists" who studied the
evaporation of electricity from metal,
working simply to discovering the truth,
then we consider the profits of the Radio
Corporation of America last year on tubes,
which utilized the result which these scienti-
fic workers gave to the world for nothing.
The question of how radio waves are
transmitted can be tackled only by the
best trained engineers we have today.
Not only must they be able experimenters,
but to make any reasonable progress based
on the interpretation of their results, they
must be conversant with many allied
branches of science. The electro-magnetic
theory of light (the bugaboo of many a
student of college science), must be thor-
oughly understood and the laws of reflection
and refraction of such waves be sufficiently
familiar that their occurrence is at once
recognized.
In the experiments reported to the
I. R. E., the engineers used many thous-
ands of dollars worth of the most modern
electrical apparatus; the experiments were
such that only one or two of the most pros-
perous companies could afford to finance
them. The American Telephone and Tele-
graph Company really felt the need to in-
vestigate the question because of the very
poor quality of WEAF'S signals throughout
Westchester County, only a short distance
from the transmitter. Not only was the
signal unexpectedly weak but the quality
also was poor. So began a most exhaustive
study to discover just what happened to
WEAF'S radio waves as they traveled the
fifty or more miles up Long Island Sound.
These experiments showed conclusively
that the signal received in these defective
localities is produced by waves arising from
two directions. One wave comes along the
ground and is greatly weakened as it travels
through New York's forest of steel sky-
scrapers. The other goes apparently up
in the air and is reflected after going up
perhaps one hundred miles and comes down
again to combine with the other wave which
has arrived via earth. These two waves
add their effects to give the actual signal
and, unfortunately for the dwellers in these
districts, the combined wave frequently
looks entirely different from the wave
which started out from the transmitting
station. The length of the extra path con-
tinually varies with atmospheric conditions
and thus the amount of interference of the
two waves with each other continually
changes. The result of this interference is
to make the signals so badly distorted as
to be sometimes unrecognizable. A photo-
graph of the signal current received close to
WEAF, and another photograph of the signal
current received in Westchester County,
only a few miles away, are so different that
one cannot be identified with the other.
An explanation of the extraordinary dis-
tortion which this radio current suffers,
which Bown and his co-workers offer us,
does but little at present to make the
transmission better. Their work did show,
however, that certain improvements are
possible at the transmitting station which
will make the distortion somewhat more
constant that it is at present, but that
won't help the broadcast listenerverymuch.
It appears to be a fact that certain dis-
tricts will get bad transmission from cer-
tain stations and there is at present no ap-
parent remedy for it.
Radio Control for Railroads
IT HAS been recently announced that
radio was doing much to accomplish
automatic train control, which the Inter-
state Commerce Commission has ordered
installed on all of the principal railroads.
The scheme required by the Commission
must automatically apply the brakes of a
train which runs into a danger zone so that
even if the engineer ignores the danger
signals set against him, his train will be
stopped before a wreck occurs.
Among the schemes which give promise of
success is that which uses the two rails to
carry high frequency currents. These cur-
rents, acting on a coil carried on a locomo-
tive, will apply brakes, shut off steam, or
whatever other operation is necessary.
Tuned circuits are used on the locomotive so
that different operations are carried out on
the locomotive according to the frequency
of the current in the track.
To be economically successful, it should
not be necessary to feed the high frequency
energy into the tracks at too many points,
preferably only at one point in each block.
But very high frequency currents will not
travel far along the railroad tracks, for they
waste away too rapidly. The radio
FEBRUARY, 1926
DOCTOR MILLIKAN'S NEW RAY
433
engineer trying to use this scheme must em-
ploy frequencies very low compared to
those in which the listener is ordinarily
interested. About 20,000 cycles (15,000
uieters) is as high as is generally useful in
the continuous train control scheme. The
amount of power radiated from the tracks
with such current is practically negligible.
The tracks are really acting as the two wires
of a power transmission line and there is no
real radiation of power in the scheme at all.
This "radio" system would probably oper-
ate as well or even better if there was no
radiation, so that the scheme can scarcely
be hailed as an application of radio. The
frequencies useful are those used by the
telephone engineer in carrier telephony,
they are so low that even if there was ap-
preciable radiation, no broadcast receiver,
as used by the average listener, could possi-
bly pick it up.
Detroit Has a Good Radio
Supervisor
WHEN the recent radio conference
convened there appeared on the
scene a real radio inspector prop-
erly equipped to do his job. Probably
the most pressing duty of the government
radio inspector today is to locate sources
of interference and to do this with any de-
gree of ease requires a portable receiving
set. Supervisor S. W. Edwards, of the
Detroit district saw the need some time ago
and by shrewd application of the meagre
funds furnished to the inspection service
was able to buy and equip a portable radio
laboratory. An enclosed truck was fitted
up with all kinds of receivers, frequency
measurers, and the like, so that wherever
the truck may be, measurements of fre-
quency, direction from which interfering
signals are coming, and so forth, can be
readily made.
When complaint of interference comes
into his office, Supervisor Edwards at once
dispatches his portable laboratory to the
scene and by direction finding apparatus,
wavemeters, etc., locates the source of the
trouble. He reports that in no case so far
investigated has he failed to locate the
source of interference.
Is the Loop or Antenna Receiver
More Popular?
A RECENT bit of propaganda by one
of the manufacturers of loop sets,
states that fifty-three per cent, of
the public prefer loop sets to those operated
from an antenna. Just where these figures
came from is not stated but we were sur-
prised at the conservative claims of this
loop-set manufacturer. Why not say one
hundred per cent, of us prefer loop sets-
it would not be contradicted provided the
qualifying clause were added "other things
being equal."
Naturally people prefer loop sets. They
don't have to bother with outdoor antennas
coming down in a country snowstorm or
with the obdurate city janitor when trying
to put one up. Further the loop has di-
rectional qualities (except in some steel
buildings) and this offers
the possibility of cutting
out undesired stations.
Why then don't we all
use loops? Because we
can say in general that
a set requires between
one and two extra stages
of radio frequency am-
plification to give as
strong a signal with a
loop as with an ordinary antenna. Tubes
cost money to buy and maintain. Further-
more tubes themselves give noise due to
electrical irregularities in their behavior
and when excessive amplification is used
in a multi-tube set, these noises become
quite apparent and sound much like static.
Sets having eight or more tubes at times
give a let of noise even if the input circuit is
shorted so that no static can get in. Until
very quiet tubes are available at low cost
the loop set actually works against quite a
handicap when compared to the antenna set.
A New Short Wave Ray Is Dis-
covered
A A recent meeting of the National
Academy of Sciences, Dr. R. A.
Millikan of the California Institute of
Technology reported the discovery of some
new rays of the greatest power. Doctor
Millikan's name should be known to all
radio enthusiasts because of his wonderful
work in measuring the size and charge of
the electron, the thing that evaporates from
the filament of the vacuum tube and makes
its operation possible. And when Doctor
Millikan's announces a new ray the public
may rest assured that he has one. Such
an announcement is not to be confused with
that of such exploiters as Grindell-
RADIO TRAIN CONTROL SYSTEM
Developed by Thomas Clark of Detroit who, in the early days of wireless telegraphy headed a "wireless" company of his own. The control system is really
not wireless but rather, "wired wireless," for high frequency currents are sent along the rails and used through the proper combination of apparatus to
control danger signals in the engine cab and valves which will stop the locomotive. The view at the lower left shows a close-up of the valves which
are worked by this "radio current" to stop the engine when desired. Above is shown the control device applied to the drive wheel of the locomotive.
The smaller view shows a typical locomotive on the Pere Marquette Railroad which is experimenting with the system
434
RADIO BROADCAST
FEBRUARY, 1926
Matthews, who gave to his fellow English-
men the bad attack of ague some time ago
when he announced his "death ray "which
was to be sold to the French if his country
wouldn't pay his price. This death ray,
it will be remembered, was never proved to
be at all valuable or effective.
Millikan has already received the Nobel
prize for his scientific researches which
marks at once any announcement he makes
with the stamp of reliability. The new
rays are of the nature of X-rays, he says,
but perhaps one thousand times as power-
ful. They are discovered only at great
height; he sent his measuring instruments
up in balloons and only at ten miles height
were the new rays found with intensity
great enough to be recorded.
These rays fall in with the tendency of the
times, by the way. The radio engineer
every day hears of the increasing reliability
of short waves. The shortest waves of
radiation which the scientist has known
until now are the X- or Roentgen rays.
These new rays, christened Millikan Rays
by the discoverers' fellow scientists, have
a wavelength only one thousandth that
of X-rays. Whether we shall ever be able
to produce them on earth or use them after
they are produced, is problematical, but the
probable answer to the question is "Yes."
The Ethics of Radio Advertising
SURELY when a novice looks over the
radio advertisements with the idea of
purchasing a receiving set, he must be
greatly confused and misled as to what the
different sets will do. Most extravagant
claims are made for radio apparatus of any
kind and price. Everything is the very
best and when one adviser hits upon some
extravagant word with which to brand his
goods all of its synonyms are sure to ap-
pear in the next issue of the periodical.
Now, no matter what the manufacturer
may say, we cannot believe that a forty
dollar set is as sensitive, selective and as
good in quality of reproduction as the
hundred and fifty dollar set — yet the ad-
vertisements all say so.
Mr. E. H. Jewett, recently commented on
the situation in the following way.
It (the radio advertising competition) has
reached the stage where it is practically inter-
changeable, really almost cancellable. The
race in superlative claims is so intense that most
advertisements almost duplicate one another.
One could interchange the corporate names and
hardly destroy the purpose of the advertise-
ment. . . .
The majority of radio manufacturers are much
concerned about the good name of their industry.
It is essential to their purposes that when Mr.
Ultimate Consumer shoves his money across the
counter he gets value received. So the old
admonition about letting the buyer beware is
very apropos nowadays. Every radio purchase
deserves personal investigation. Personal in-
quiry is the best checkup on too effusive ad-
vertising.
The Month In Radio
LA!
Courtesy New York Etfning World
'HOW IS YOUR RADIO RECEPTION HERE?"
AST month saw the passing of two
of our most promising radio engi-
neers. Returning from the Fourth
Radio Conference, G. Y. Allen, technical
assistant to the manager of the radio de-
partment of the Westinghouse Company,
was killed in a train wreck near New Bruns-
wick on November twelfth. He was a
graduate of Stevens
Institute, a member
of several technical
societies and was
highly appraised by
his company. "Mr.
Allen's death means a
great loss to the West-
inghouse Company,"
said E.B.Mallory, his
superior in the West-
inghouse organiza-
tion. "Brilliant as an
engineer, indetiga-
ble as a worker, and
of charming person-
ality, it will be impos-
sible to replace him."
1 1 Hi Dr. H.W.Nichols,
jl f^ lR) research engineer of
the Bell Telephone
Laboratories, died at
his home recently
after a brief illness.
After getting his
Ph.D. degree at the
University of Chi-
cago, Dr. Nichols
joined the research
staff of the Bell
Laboratory and was
CAPTAIN E. P. ECKERSLEY
London
Chief Engineer, British Broadcasting Com-
pany; in a statement especially written for
RADIO BROADCAST
"Based on our previous experience, the In-
ternational Radio Broadcast Tests in January,
1926, should mark a distinct advance. It
should be possible to secure with the assist-
ance of the International Bureau de Radio-
phonie, more definite and accurate data on
the programs of the broadcast stations on our
side of the water than ever before. It is espe-
cially important to communicate to all listeners
to the programs in these tests that there is five
hours' difference in time, for example,
between New York and London. The
tests will start Sunday, January 24 at to
p. M., Eastern Standard, or New York Time:
that will be J A. M. Monday, January 25th,
London time. The stations on our side of
the water will begin their test programs at 4
A. M. London time, or n p. M. the night be-
fore, New York time. Our European sche-
dule of transmissions is being settled at a
conference in Brussels. We believe radio
intelligently developed in the public interest
is destined to become a potent auxiliary to
international cooperation in bringing closer
together broadcast listeners and wireless en-
thusiasts all over the world. Radio should
perform invaluable work in establishing com-
mon points of interest and in consolidating
conscious world citizenship without which
there can be no assurance of permanent peace
between nations.
largely responsible for the radiophone devel-
opment carried on in this laboratory during
the past few years. He was a member of
several scientific societies, on the Board of
Direction of the Institute of Radio Engineers
and had been nominated for President of
the Institute at the time of his death.
THE Western Union Telegraph Com-
pany is not suffering much from the
air mail and radio competition, as had been
predicted; radio, the air mail, and the tele-
phone, it has been claimed, constitute a
real menace to the telegraph companies,
but Newcomb Carleton, President of the
Western Union, says they are allies of the
FEBRUARY, 1926
WHAT PEOPLE SAY ABOUT RADIO
435
telegraph rather than competitors. The
business of his company was three times as
great last year as in 1914 and the profits
have so increased that a three million
dollar salary increase is to be granted to the
employees and a fifty per cent, stock divi-
dend probably declared.
IN A previous paragraph we spoke of the
effusiveness of the radio advertiser and
how slightly his claims are influenced by
the truth. A recent advertisement of the
Radio Corporation of America, under the
attractive caption "How important is
vacuum?" claimed for its engineers that
they have succeeded in reaching a vacuum
"ten million times greater than the vacuum
of the high exhaust incandescent lamp";
the rest of the copy suggests that all of the
RCA triodes are thus exhausted.
We think that Thomas F. Logan, Inc.,
the advertising agency concerned, will find
upon inquiry that the engineers, capable as
they may be, have succeeded in doing
no such thing. The vacuum claimed is
nearly a thousand times as great as the re-
search men have succeeded in attaining un-
less some remarkable discovery, not yet
disclosed, has been recently accomplished.
A BRITISH mail plane recently en route
*»• from Croyden to Paris encountered
trouble, and anticipating a forced landing,
called to both English and French stations
for its bearings. These were promptly
given and so the plane located itself. It
had to come down on the water but was
able to send its location with sufficient
accuracy that after a few hours floating on
the Channel it was picked up by one of
the searching vessels. This is in contrast
to the radio service the PN-g No. i secured
from its own equipment and the destroy-
ers placed in the Pacific to help guide it.
THE Amsco Products, Inc. was recently
sued by the Westinghouse Company
and R C A for putting out sets which, it was
claimed, infringed the regenerative patent.
The set was supposed to be neutralized, but,
as the neutralizing condensers were ad-
justable, and instructions were given as to
how the set might be made to regenerate,
the judge decided that infringement had
been accomplished and found for the plain-
tiffs. A special master has been appointed
to assess damages.
DURING a recent talk in England, Sena-
tor Marconi stated that he and his
engineers have not only found it possible
to communicate with Argentina, from Eng-
land, with only one-fifth of a kilowatt of
power at 20,000 kilocycles (15 meters),
but that he had actually found the com-
munication more reliable in the daytime
than in the night time. This is an entirely
unexpected result as night time transmission
has always heretofore established the long
distance records.
Interesting Things
Said Interestingly
©Henry Miller News Pictures, Inc.
JOHN OCHACKI, JR. AND GEORGE SEEBER
Chief and Assistant Radio operators of the Clyde liner Lenape
which caught fire off the Delaware Capes recently and was burned
to the water's edge. Only one life was lost and passengers and
crew numbering 367 were rescued
IU (ilium
AH. MORSE (in Radio: Beam and Broadcast,
** published by D. Van Nostrand Company):
"Unquestionably there is much that Britain
and America may learn from each other in the
matter of broadcasting, and it is certain that it
would be an advantage if announcers in North
America were required to satisfy a central author-
ity as to the purity and standard quality of
their diction, as they do in Britain. This done,
there would soon be no point in the announce-
ment of the facetious German shopkeeper,
' English spoken, American understood,' and the
New York Eastsider might learn to articulate an
\A AJ. HERBERT H. FROST (Chicago;
*** president of the Radio Manufacturers
Association): "Listeners in America will never
be called upon to pay a tax of any kind to support
broadcasting, as is the case in some European
countries. This will never happen in the United
States for the reason that there are enough broad-
casting stations owned and operated by the radio
manufacturers to reach every part of the coun-
try. The manufacturer
will, if necessary, pay for
broadcasting, for his busi-
ness depends on it."
^EN. J. G. HARBORD
**•* (New York; president
of the Radio Corporation
of America): "Broadcasting
in South America is at pres-
ent chiefly confined to the
few large cities. Buenos
Aires boasts of four stations.
There are two stations in Rio
de Janeiro, two in Sao Paulo,
while smaller stations oper-
ate occasionally, one in Bahia
and one in Pernambuco.
In Chile there are two sta-
tions operating at Santiago.
These stations, while per-
haps not as powerful and
well-organized as those of
the United States, give a
very fair degree of service
in each instance though for
the most part, the sched-
CHARLES GRAY SHAW
New York
Professor of Philosophy, New York Uni-
versity, in an address "The Philosophy
of Radio," through station wjz
"Our interest in radio is as great a mystery
as radio itself. There is no real reason why
we should listen to sounds which come to us
from afar, but we have our radio sets by the
million and tune-in on anything. We listen-
in without regard to the character of what is
being broadcast. It may be an inferior soloist
or a cheap minstrel singer, a bedtime story, or
a college professor. If these artists were to
hire halls they would perform before empty
houses. But radio somehow makes it all
different.
"How we love to listen-in. A pious old
lady was found sitting enchanted listening
to the report of a prizefight, round by round.
A profane gambler boasted that on the previous
Sunday he had caught a dandy prayer.
These individuals would not have taken prife-
fighl and prayer in any way but the uncanny
one of radio. How shall we explain this
mad interest in the "air"?
ules are well interspersed with phonographic
music. In Buenos Aires excellent broadcasting
is given the people during the operatic season
when the opera is broadcast direct from the
Teatro Colon.
"It is interesting to compare the 'radio cover-
age' in the countries, Argentine, Brazil, and
Chile, with that of the United States. Here one
station serves an area of roughly 6000 square
miles, while in South America one station serves
more than 300,000 square miles. From these
figures, it is obvious that the South American
broadcasting service is wholly inadequate, even
in view of the fact that large sections are not ex-
tensively populated."
DENNO MOISEIWITSCH (London; follow-
*-* ing his recent recital from 2 LO); "Alone in
rny room, sitting at the piano without coat,
collar, or tie, with nothing whatever to distract
my thoughts, I believe I can play better than
on the platform. It was the same in the broad-
casting studio. I found when 1 arrived there
that a number of people were in the room, but,
at my request, they were asked to leave. Then
I took oflf my collar, tie and waistcoat and
abandoned myself to my task.
"I was completely happy. There was no one
near me save the operator, and the thought that,
in my own way, I was entertaining an unseen
audience of, perhaps millions, supplied me with
all the inspiration I needed.
"It is a remarkable experience."
ECENT con-
ditions in ra-
<lio broad-
casting have
resulted in new re-
quirements for the de-
sign and construction
of receiving equip-
ment. The new fre-
quency allocation of
transmitting stations,
and their increased
numbers, have created
the need for receiving
systems capable of
yielding a very high
degree of selectivity.
It is probable that the
necessity will never be
less.
Further refinements
in mechanical detail
and physical appear-
ance of receivers have
also made imperative
the most compact
internal construction.
The radio set builder,
confronted with the
problem of selecting
suitable elements for a
receiver to meet the
above requirements,
has encountered many
difficulties. Parts
available for purchase
have not been designed
to overcome the handi-
caps to reception
brought into being by these new conditions.
Radio inductances for commercial broad-
cast work have undergone only slight im-
provements in recent years and the purpose
of this paper is to point out the need for
advancement in this specialized field and to
relate some developments which are
thought to be new.
A tuned radio frequency transformer, or
"coil" as it is often referred to, is recog-
nized as being of great importance in any
receiving system. Let us consider some
of the characteristics of a radio
coil which play an important
role in the proper functioning of
a receiving system in which it is
used.
The efficiency of the coil has a
very direct and significant bear-
ing upon the receiving results
obtainable. It has been stated
many times that a coil should be
designed so as to permit sharp
tuning inherently; that is, its
resistance to the frequencies for
which it is intended should be
as low as possible. Reduction
in coil resistance is the funda-
mental design problem where
selectivity is wanted.
Various engineering texts have
defined coil efficiency in terms
of the ratio of inductance to
resistance. A coil, to be highly
Why the Conventional Inductances Do Not Meet
the Electric and Mechanical Ideal — How an Electri-
cally and Mechanically Desirable Shielded Inductance
Was Designed and a Suggestion of Its Possibilities
By W. W. HARPER
efficient, should have as much inductance
per unit of resistance as possible. There
are certain limitations to the magnitude
of this ratio, but it is reasonable to say that
a radio coil for broadcast reception should
be designed so as to permit an inductance
of 25 or more microhenries per ohm.
NECESSITY OF F1ELDLESS CHARACTERISTICS
THE need for efficient coils has been rec-
ognized for many years, but it is only
recently that we have been forced to con-
RELATTVTE MERIT OF RADIO COOS
EXPRESSED IN MICROHENRIES PER OHM
/s\ Unspaced Solenoids
^ And Basket Weaves
Coils
Coils with Fancy
(gj'Crisscross Windings
Poorly Constructed
Toroidats
15 20 25
MICROHENRIES PER OHM
FIG. I
One of the requisites of a good coil is that it have a large value of inductance
per ohm. From this chart, showing graphically the results of tests
conducted by Mr. Harper, it will be seen that some types of coil have
distinct advantages in this respect over others. This chart should help
to answer the question, "What is a good coil?"
sider carefully other
factors.
It is known quite
well throughout the
radio industry that or-
dinary coils within a
receiver may act as
miniature antennas.
Some of us have even
disconnected the an-
tenna and ground and
used the coils them-
selves in this capacity
in order to demon-
strate the so-called
merit of the receiver.
If we had sufficient
influence upon radio
wave energy so that
we could make it be-
have and enter the
first coil only of a re-
ceiving system, then
such a demonstration
as mentioned would
have a real value. It
happens, however, that
in a very unavoidable
manner the radio
energy impresses itself
with tremendous speed
upon all the coils in
the receiver. Some of
these coils may be in
circuits which tune
sharply, while •thers
may be in circuits which
are intentionally or un-
intentionally very
broad in their tuning. At any rate, under
conditions such as described, the receiver
will appear to be just as broad as the bread-
est circuit. A non-regenerative detector in-
put circuit in the ordinary tuned radio fre-
quency amplifier system is an example of a
broad circuit. It is possible, in many cases,
to have other circuits equally broad, how-
ever.
So we see why it is necessary to design a
coil which will not function as a "collector"
or antenna. The logical solution of the
problem seemingly resolves itself
into a matter of confining the
magnetic and electric fields of
the coil. It is through these
agents that this "pick-up" ac-
tion occurs. The effect of un-
confined fields is also detrimen-
tal from other standpoints.
Very compact construction of
receivers many times necessitates
the placing of other instruments
in close proximity to the coil.
Penetration of these bodies by
electrical fields of the coil is usu-
ally accompanied by resistance
increases within the coil. This
is equivalent to saying that these
adjacent objects have caused en-
ergy to be absorbed from the coil.
This disadvantage will be elim-
inated if effective confinement
of the coil fields is attained.
FEBRUARY, 1926
DESIGN OF RADIO INDUCTANCES
Silk Ins
Inter-stage coupling phenomena has also
been a drawback with the old type coils
when attempts were made to construct re-
ceivers of small size. Effects of this kind
also have their source in the electrical fields
surrounding the coils.
The mechanical characteristics are also
worthy of consideration. They should be
of such nature that the inductance, re-
sistance, and other electrical characteris-
tics will be invariable whatever the minor
mechanical stresses the coil is subjected to.
This feature is doubly important in tandem
control receivers where it is almost imper-
ative to match successive coils so as to get
identical characteristics in each circuit.
The usual method of coil building where
the insulation on the wire is relied upon for
spacing of turns, is an example of construc-
tional methods which must be discarded.
Variations in the thickness of insulation
produces similar variations in pitch of
winding. This results in unfortunate vari-
ations in inductance and other electrical
properties.
STANDARDS OF COIL DESIGN
IT SEEMS possible from the foregoing
1 generalized considerations to set down
definitely certain axioms of efficient radio
receiving coil design. These may be stated
as follows:
(1) Low resistance over the broadcast
frequency spectrum combined with as high a
value of inductance as is permissible under the
circuit conditions.
(2) Effective confinement of the electro-
magnetic field.
(3) Effective confinement of the electrostatic
field.
(4) Consistent mechanical and electrical
characteristics.
(5) Small physical dimensions so as to permit
compact construction. (Points 3 and 4 also
assist in this connection, for with the coil fields
confined it is obvious that they may be mounted
in closer proximity without harmful coupling.)
The first consideration is that of coil
efficiency in terms of low resistance com-
bined with maximum inductance. It is
necessary to select the most desirable type
of coil in this respect before any attempts
at solution of the remaining factors are
COMPARATIVE MAGNITUDE OF COIL LOSSES
DETERMINATIONS BASED ON SMALL SOLENOID COILS
Expressed in terms of Percentage increase in Total
Coil loss Averaged over Broadcast Spectrum
Note:-Irregularity (a)
<b>
/T\ Fabric Insulation
w(Turns Touching)
® Solid Frame
(Phenol Fibre)
v Skeleton Frame
(Phenol Fibre)
®
Solid Frame
(Hard Rubber)
. Impregnating
Solutions
Maximum effect
with poor Solutions
678
PER CENT
FIG. 2
From this chart it can be seen what effect the various factors entering
into the winding of a coil have upon the finished product insofar as in-
troducing losses in the coil and in the circuit in which it is used are con-
cerned
FIG. 3
The separation afforded between turns of a coil
by silk insulation is apparently uniform, but when
examined under a magnifying glass, its irregular-
ities manifest themselves. In comparison, note
the uniformity of spacing when a coil is wound
by the aid of a machine which places each turn
in position correctly. Uniformity of spacing
of turns insures accurate calibration of coils on
a quantity basis. Furthermore, by eliminating
the silk or cotton insulation from the wires and
employing a grooved cylinder, there is not the
possibility of adding to the total of losses due to
hygroscopic effects
made. Satisfactory results in any receiving
system may only be anticipated when this
requirement of maximum inductance per
unit of resistance is reached.
In Fig. i is shown a statistical chart
compiled from numerous tests conducted
on various types of coils commercially
available. The reader should not in-
correctly interpret the significance of this
data. It is well known that solenoid type
coils can be so constructed that they offer
greater values of microhenries per ohm
than given on this chart. The same ap-
plies to all the types mentioned. The im-
pressive point relative to the chart in
question resides in the fact that the figures
given are the results of averages made on
measured observations of the characteris-
tics of coils picked at random from the
commercial market. The outstanding
merit of the solenoid type coil is clearly ap-
parent. This data in combination with
other published works by various investi-
gators seems to indicate emphatically the
superiority of the solenoid inductance.
The fulfillment of the first requirement
is therefore gained by the adoption of the
solenoid type of coil, and if this were all,
our problem would be a comparatively sim-
ple one. The further requirements, as listed,
however, prevent such an easy solution.
The second and third points stated above
require that the two
field components be
confined in order to
eliminate or reduce
"pick-up" effects and
eddy current losses
arising from too com-
pact construction, as
well as serious and
unuseful coupling
phenomena. It is
therefore necessary
to cast aside the usual
solenoid and attempt
to devise something
more effective.
1 1 is known that con-
finement of the elec-
tromagnetic field may
be satisfactorily ac-
\ _ / Usually immeasurable
' V wi
I with good solutions
9 10 11 12 13 14 IS
complished by the use of a toroidal winding.
A step in this direction appears to be dis-
tinctly undesirable, however, for it is seen
from the first chart that toroidal type coils
inherently are less efficient than some other
types. 1 1 would therefore seem that the sat-
isfactory solution of one requirement which
imposed a very noticeable loss upon another
equally important one could hardly be con-
sidered the totally best solution.
It is also evident that the toroidals are
incapable of meeting the entire problem of
field confinement, since this form of winding
has little or no effect upon the electrostatic
field. The toroidal coil, is difficult to con-
struct with the aim of satisfying the fourth
requirement of electro-mechanical con-
sistency.
NEW CONSTRUCTIONAL METHODS
HP HE desirability of the space-wound
1 solenoid in respect to efficiency and
the possibility of shielding it metallically
suggested a much more satisfactory method
of fulfilling the requirements we desire to
attain.
It was reasonably safe to assume that a
metal container could be used as both
housing and shield for an efficiently de-
signed solenoid. This belief, having been
verified by experiment, led to the design of
an inductance which is called the Metaloid.
Preliminary attempts to "screen," elec-
trically, solenoid coils by metallic cans met
with many misfortunes. A solenoid which
had a very low resistance unshielded, would
Can-.^J —
40
50
60
o
<3
<3
O
Primary
Secondary
-Oi
-02
-03
(a)
FIG. 4
The connections of the Harper coil unit.
Below, the finished coil with "can" removed.
The dimensions:
Primary: Form: if" diameter, 34" long. Turns: 22,
No. 28 D S C wire. Winding: Started 18" from top of
form. Tap at 14th turn. Secondary: Form: 2" diameter,
34" long. Turns: 115, No. 28 Enamel covered wire in
grooves separated by thickness of wire. Winding: Started
?," fromj top of form. Can: Size: 3" x 3" x 5". Cubic
Volume: 45" cubic (inches. Material: 12 oz. copper.
General: Secondary-32o microhenries. Average resistance-
g.jfohms. Approximate inductance per ohm: 33 microhenries
Coil Form: Hard Rubber.
438
RADIO BROADCAST
FEBRUARY, 1926
undergo tremendous resistance increase
when "canned."
There are two obvious reasons for these
failures. It was almost a radio legend
that good solenoids could not be efficient
if they were made smaller than, say, three
inches in diameter. And true, when the
diameter was reduced to two inches, the re-
sistance increased at an enormous rate.
The larger coils, however, could not be
easily encased by a metal can. When the
can was made of convenient size, the coil
characteristics were harmed and by making
the can of correct size to avoid this diffi-
culty, it became of tremendous dimensions.
The second reason was due to lack of
knowledge regarding the shielding charac-
teristics of various metals.
Elimination of the first difficulty led to a
careful analysis of the various sources of
losses in small solenoid coils. The results of
this investigation are depicted in the chart
of Fig. 2, compiled after numerous measure-
ments of various coil losses had been made.
The magnitude of losses introduced by
insulation averaged as high as 1 5 per cent,
and in some instances ran as high as 20 per
cent. The loss effect in the framework
and impregnating solutions, which have
been thought to be of vital importance,
dwindle to inconspicuous factors in view of
insulation losses.
Insulation losses, of course, are reduced to
a very low value by space winding so that
an air-gap exists between successive turns.
The experiments leading to this discovery
yielded the data necessary to proceed with
the design of a small solenoid without the
customary resistance increase. Eliminat-
ing the insulation immediately suggested
the use of bare or enameled wire wound on
a threaded hard rubber tube. Following in
a fortunate sequence came the elimination
of impregnating solutions, which are un-
desirable from both the standpoint of man-
ufacturing and electrical efficiency.
It was also apparent that the framework
tubing could be machine threaded with
great accuracy, thereby attaining electrical
and mechanical constancy in every coil.
The Metaloid secondary is constructed
along the lines mentioned above. It is
approximately two inches long and two
inches in diameter, space wound with bare
or enameled wire in a machined groove.
The inductance is approximately 320 micro-
henries and the average resistance is 9.5
ohms. This gives approximately 33 micro-
henries per ohm. These figures are based
upon measurements made on the secondary
coil encased in the metal can, which will be
described later.
In Fig. 3 is shown a magnified comparison
between coils in which the insulation is de-
pended upon to give spacing and those in
which the wire is space wound by means of
an accurately machined groove in the sup-
porting framework. Fig. 3A indicates the
variations which arise because of variations
in the thickness of fabric insulation. Fig.
36 shows the remarkable accuracy possible
where the wire is spaced by a machine cut
groove.
The second difficulty, that of selecting
the proper metal as well as the determina-
tions of the optimum dimensions for the
can, was found to be more involved than
one might anticipate, and a detailed re-
sume of the work done is not possible within
the limits of this article.
It was found, however, that with the
small solenoid previously mentioned, a four-
sided metallic can approximately three
inches square and five inches high, of
ordinary 12-ounce copper sheet was satis-
factory in all respects.
This arrangement apparently affords
very effective confinement of both field com-
ponents. Direct signal "pick-up" is very
materially reduced as compared to other
coils. It is understood, of course, that, due
to pick up by other elements, this difficulty
cannot be totally eliminated, unless the
receiver is completely screened.
Audio-frequency transformers, sockets,
and any metallic objects may be mounted
directly against the can and no measurable
eddy current losses occur.
Grounding the individual cans to the low
potential secondary terminals of their re-
spective coils entirely obliterates electro-
static potential gradients between successive
coils. The four-sided can is also effective in
nullifying inter-stage electromagnetic coup-
ling.
The cubic volume of the can is approxi-
mately 45 inches. It should be remem-
bered that this space houses the coil as
well as its associated fields. While the
actual physical size of the Metaloid is
larger than average coils, it really takes up
less space electrically, and may therefore be
mounted more compactly.
The winding, which is seen in the photo-
graph, is the secondary. The primary is
mounted concentric and inside the second-
ary framework.
Fig. 4A is a schematic drawing of the
Metaloid windings and connections. The
primary is tapped as shown at 4, 5, and 6.
This permits theuseof large and small tubes
as well as special circuit arrangements.
Contact to the can is independent of
other connections and is made at terminal
2. In this way, the shield may be used
either "grounded," or "floating," It is
customary, however, to connect this term-
inal to the low potential end of the second-
ary winding.
The secondary terminals are indicated at
i, and 3. It was stated that the secondary
inductance is approximately 320 micro-
henries. A variable air condenser having
a maximum capacity of 250 picofarads
(.00025 microfarads) will therefore be neces-
sary to tune the coil to broadcast frequencies.
A new coil of this type appears to open
up a broad field to the receiving experi-
menter, and in its correct application to re-
ceiver problems, many handicaps have al-
ready been met.
FIG. 5
This view shows the layout of apparatus used by Mr. Harper in making radio frequency resistance measurements of coils. At the extreme left is the
radio-frequency oscillator, next in line is the wavemeter used to determine the frequency of the oscillator, and next the coupling coil. The coil being
measured is the one resting on the block. It is connected to the resistance box and then to a microammeter through a thermo-couple. Note the
magnifying glass suspended above the microammeter for precision readings. Other coils which have been tested are shown on the shelf in the lower left
side of the photograph. The Harper coil is the high one to the left of the wooden box
Grimes Inverse
Constructional Details of a Four- Tube Receiver Which is Highly Selective,
Built of Standard Parts, and Which Produces Signals of Irreproachable Quality
By FLORIAN J. FOX
Eus say in the beginning that the
Inverse Duplex is not a specific
circuit — it is a system which can be
applied to any circuit in which both
radio and audio frequency amplification
are to be found.
Reflexing, which is the foundation of the
Inverse Duplex system, permits one tube to
function as both radio and audio frequency
amplifier, and where it is employed in a
D- 3
STRAIGHT REFLEX
FIG. I
Schematic diagram of a "straight reflex," circuit.
The figures above show how the several tubes
are employed to provide more than one kind of
amplification
circuit, special attention must be paid to
the function of various parts under differ-
ing conditions for instance, small conden-
sers offer very little impedance to high
frequency radio currents, but their imped-
ance to current flow at the relatively low
voice, or audio, frequencies is extremely
high. In the case of inductances (transfor-
mer windings, choke coils, etc.) exactly the
reverse is true. Circuits can therefore be so
arranged that they discriminate against low
frequencies in favor of the radio frequencies
and vice versa. These principles are used
in reflexing. Radio and audio frequency
voltages are applied simultaneously to a
tube, and since tubes work practically as
well at radio frequencies as at audio fre-
quencies, both the applied component
voltages are ampli-
fied. By means of an
appropriate circuit
arrangement of coils
and condensers, these
amplified compon-
ents are separated in
the output circuit of
the tube. In a prop-
erly designed reflex
system, the presence
of the audio system
has no harmful effect
upon the efficiency
or "sharpness" of
the radio circuit.
that the reflexed audio signals are passed
through the amplifiers in a direction op-
posite to that of the incoming radio signals.
The simple sketches, Figs, i and 2, illus-
trate this point.
The Inverse Duplex system is superior
to the straight system in several ways. It
is more stable because any radio frequency
energy which may pass the detector and
first audio transformer through capacity
coupling will only be impressed on the in-
put of the stage ahead of the detector, in-
stead of two or more stages ahead of it as
in the case of the straight reflex. In the
latter case, oscillation due to feedback
would be almost beyond control. In a
TJOR those constructors who are interested in
•*• building a receiver which is efficient and very
sensitive, which employs no regeneration, the
Grimes Inverse Duplex receiver described so com-
pletely in the accompanying article should appeal
very strongly. This set is selective, a virtue not
present in many simple reflexed receivers, and de-
livers lone quality of a high order, because the trans-
formers selected for use in the audio channel are of
excellent quality and the design makes best use of
them. The filament and plate current drain with
four storage battery tubes suggested for the circuit is
fortunately low. Every part of the circuit can be
made by the home constructor, for complete details of
the coil construction are given, an important point,
since many experimenters desire to make their re-
ceiver, as far as possible, with their own hands.
— THE EDITOR.
straight reflex receiver the first radio tube is
usually also the first audio amplifier.
Therefore if any audio frequency noises,
such as hum from power lines, are induced
in the antenna and passed on to this first
tube they may be amplified by the suc-
ceeding audio stages to loud speaker
volume. I n the case of the I nverse Duplex
system, the first radio tube is the last or
next to the last audio amplifier, hence such
noises hardly ever reach a noticeable
volume. Inverse Duplexing also tends to
equalize the loads which the various tubes
carry. This enables one to obtain a slightly
6
^
\T71- R -1
N/ 2-A.F.-.5
- 6
2-R-2
1-A.F.-4
0-3
The Grimes Inverse
Duplex is really an
inverse reflex system.
By that we mean
RADIO BROADCAST Photograph
FIG. 3
How the Inverse Duplex Model receiver looks from the outside. Three main tuning controls,
which read almost the same for each station tuned-in, take up the major portion of the panel.
On the lower portion of the panel, from left to right may be seen the output jack, series antenna
resistance for controlling volume, audio amplifier switch, and rheostat. In the accompanying
article it is explained how the series antenna resistance is eliminated from the circuit and in its
place is substituted the antenna tap-switch which is shown in other photographs
GRIMES INVERSE DUPLEX
FIG. 2
A sketch which shows schematically how the
Grimes Inverse Duplex system works. The tubes
are shown in the order in which they are em-
ployed in the set and the figures above indicate
their functions
greater output volume level before over-
loading begins. In the sketch, Fig. 2, we
have assumed that each stage has an am-
plification of one unit. The sum for any
one tube will represent the load that it
carries.
One of the greatest advantages of the
Inverse Duplex system is its economy of
tubes and battery power. This is especi-
ally apparent if the receiver is to be oper-
ated by means of dry batteries, either in
part or entirely. In the set to be described,
if 2OI-A tubes are used throughout, the
A battery drain is only i ampere. If a
9o-volt B battery is used in connection with
a 4^-volt C bias, the total B drain from
the amplifiers will be only about .009
amperes (9 milliamperes). Since the drain
on the detector bat-
tery will be less than
2 milliamperes, even
a small battery
should last about a
year at this point.
This set properly
handled will enable
the user to get results
equal to that of a six-
tube set. This should
have a strong appeal
to those fans who like
to get greater dis-
tances on less tubes
or "more miles per
ampere."
Looking into the set
in the normal manner
the tube arrangement
440
RADIO BROADCAST
FEBRUARY, 1926
BROADCAST Photograph
FIG. 4
In this bottom view of the sub-panel, the important feature to observe is the location and distribution of the three audio transformers. Three brackets
support both sub-panel and transformers. The variable resistance unit located directly below the Rauland Lyric transformer is the stabilizer
is as follows: (from left to right) i. Third
audio, or power amplifier; 2. First radio
and second audio; 3. Second radio and
First audio; 4. Detector.
The table printed with this article
contains a list of the parts used in the
construction of this model.
If a certain amount of good judgment
is used in the se-
lection of the ma-
terials, parts made
by other reliable
manufacturers may
be substituted. For
good results one
must use depend-
able parts.
Since most experi-
menters know how
to build sets, we
shall not spend too
much time in des-
Fig. 8 shows the general panel layout.
The dimensions given should be followed
rather carefully, otherwise considerable
difficulty may be experienced later when
the set is to be mounted in its cabinet.
Only the holes for the condenser shafts are
shown because the mounting holes will be
different for different makes of condensers.
RADIO BROADCAST Photograph
Fig. 10 shows the layout of the inside
sub-panel. On account of their height,
it will be necessary to remove the bases of
the Benjamin sockets. The base is then
used as a template for drilling the four
spring terminal holes. The sockets may
then be mounted on the sub-panel as
shown in Fig. 12.
As for mounting
the vernier dials,
directions are gen-
erally given by the
manufacturer of the
dial. If Hammar-
lund condensers and
National Velvet
dials are used, it
will be necessary to
remove the fric-
tion drags supplied
1 14 / m §
cribing construc-
tional details.
FIG. 5
The coil units located in front of each tuning condenser are mounted so that their axes are aligned
at right angles to each other.
On the extreme left may be seen part of the grid leak which is shielded
by the copper strip
with the conden-
sers and to cut off
a half inch or more
of the condenser
FIG. 6
A top view of the receiver which will be of further aid to the constructor in placing the parts mounted above the sub-panel. As explained elsewhere,
the antenna coil tap-switch situated between the two tuning condensers at the left is placed in the regular model directly on the main panel
FEBRUARY, 1926
HOW TO BUILD A GRIMES INVERSE DUPLEX
441
shaft. It would probably be
easier to buy National conden-
sers complete with dials. There
are, of course, other good vernier
dials on the market which the
constructor may favor. We sug-
gest that the builder consider
the purchase of a set of straight
line frequency condensers for
this circuit for they help to
spread the tuning points of the
higher frequency (short wave)
stations, found at the lower end
of the dial.
There are quite a large number
of concerns that make radio-
frequency transformers for use
in tuned radio frequency circuits.
Since it is difficult to advise the
builder how to choose between
them, we suggest that he copy
the coils that we have designed.
The diameter of these coils is
small. Tm's concentrates the
magnetic field and thus reduces
magnetic feed-back. Also, since the voltage
per turn is low, the distributed capacity is
very low. The resistance is not appreciably
increased and the result is a coil which
tunes very sharply. Let us now describe
its manufacture.
The winding form is a bakelite or formica
tube 33 inches long and if inches in dia-
meter. A |-inch space is left in the center
of the secondary winding. In this space
the primary is wound. Before winding,
drill all necessary holes for mounting-
brackets, terminals, and anchor holes for
ts About This <•
r»
NAME OF RECEIVER: Grimes Inverse
Duplex.
No.
NAME OF PART
MAKE OR KIND
OTHERS RECOMMENDED
3
.0005 mfd. Variable
Hammarlund
Any good make
1 YPE OF ' -il'i.I 1 1 . 1 WO t unt'il rSCilO 3m—
plifier stages, detector; two audio
3
3
Condensers
4" Vernier Dials
Radio Frequency
National Velvet
Home made
| Any good make
stages refiexed through the two radio
stages; and one straight audio stage.
1
Transformers
6:1 Audio Trans.
General Radio
Amertran, Karas high
FREQUENCY RANGE: 512-1330 kc. (225-
585 meters)
1
2:1 Audio Trans.
Thordarson
Jefferson 1|:1
NUMBER OF TUBES: Four.
1
Rauland Lyric
All Amer.
Amertran 31:1
KIND OF TUBES: All uv-2oiA*s.
1
1
Audio Trans.
Panel 7" x 24"
Sub-panel 7" x 22}"
Trans. Co.
Formica
Formica
Thordarson 2:1
} Any good make
FILAMENT CURRENT: i.i ampere at 5
volts.
3
Panel Mounting
Benjamin
TOTAL PLATE CURRENT: 9 mils.
1
Brackets
Open Circuit Phone
Carter Radio Co.
Any good make
APPLIED B VOLTAGE: Amp — 90 V — Del.
__ i \i
Jack
22j V.
1
Inductance Switch
J. W. Jones
Any good make
APPLIED C VOLTAGE: 4! volts.
1
1
6-ohm Rheostat
Double-pole double-
United Scientific
Laboratories
Carter
Bradleystat, or any
good make
Any good make
SELECTIVITY: Sharp.
REPRODUCTION QUALITY: First Audio
throw Jack Switch
Good; last Audio Fair, with some
3
3
.00025-mfd. Mica
Condensers
.002-mfd. Mica Cond.
Dubilier
Dubilier
> Any good make
distortion — controllable.
NUMBER OF CONTROLS: Three for tuning.
4
Standard Sockets
Benjamin
Any good make
one for filament, one for volume,
1
1
R. F. Choke Coil
1000-ohm. Non-ind.
Var. Resistance
Home made
Central Radio
Laboratories
j Any good make
one for quality.
PARTS EMPLOYED: contained in article.
1
Radio Cabinet
Jewett Parkay
To suit builder
CONSTANTS OF CIRCUIT: contained in
Wire, Screws, etc.
article.
the ends of the windings. Then make a
cut with a hack saw in the middle of the
tube, and at an angle of about 45 degrees
to the axis of the coil. Now begin the
secondary winding in such a direction that
this saw cut can be used for leading the
wire across the 5-inch space reserved for
the primary. The secondary is wound
with No. 28 d.c.c. wire. The total winding
length is 2j inches or the equivalent of 90
turns. The primary is now wound in
the same direction as the secondary and
consists of 1 5 turns of No. 32 or 34 d.c.c.
RADIO BROADCAST Photograph
FIG. 7
An external view of the commercial model of a receiver employing the Inverse Duplex
system. The dial indicators are engraved on the panel with pointers revolving over
a semi-circular scale
wire. Two such coils are made. The
remaining, or antenna coil, has a primary
of 25 turns (same size wire as the other
primaries) tapped as follows: 2 turns, 4
turns, 8 turns, 1 5 turns, 25 turns. The
beginning of this winding is connected to
ground, and the taps are connected to
points on the inductance switch. This
arrangement provides both a volume and
selectivity control. Decreasing the num-
ber of turns by means of the switch will
decrease the volume and increase the se-
lectivity of the receiver. See Figs. 6 and 9.
BUILDING THE R.F. CHOKE COIL
THE radio frequency choke coil shown
in the wiring diagram of the receiver
is absolutely necessary. Since there are
none available on the market, this piece
of equipment will have to be made. The
choke coil described is the best we have
been able to devise. It consists of about
20 separate windings all connected in
series. Spacing the windings in this man-
ner lowers the distributed capacity to such
an extent that its presence across the tuned
circuit does not affect the setting of the
tuning condenser.
If the builder has no lathe, he can have
the form made in a machine shop, or by a
hard rubber turning company. The form
is a piece of hard rubber, hard wood, or
bakelite, 3 inches long and J to | inches in
diameter. Slots -j^ of an inch wide are cut
to a depth of J-inch. The slots are spaced
-j^-inch apart. This will enable the cutting
of about 20 slots altogether. A saw cut is
now made along the form parallel to its
axis. This will be used for leading the wire
from a filled slot to the next empty one.
Fill each slot with No. 36 d.c.c., or better,
d.s.c. wire. The ends of the wire may
be later soldered to lugs that can be screwed
to the ends of the form. An easy way to
wind a choke coil is to drill into the dead
center of one end of the form for a distance
of about one inch and leave the form on
the drill. Then clamp the breastdrill in a
442
RADIO BROADCAST
FIG. 8
The layout for the main panel
vise in such a way that by turning the
crank, the wire can be easily and rapidly
wound on. Fig. 9 shows a sketch of the
winding form.
If it is impossible to obtain the above
form, some makeshifts may be devised.
A dowel could be used and the windings
spaced by means of heavy cardboard
washers. It might even be possible to get
fair results by using a long thread spool
filled with wire. Fill the spool up as the
winding advances, do not wind in layers.
No mounting brackets will be necessary
because the finished coil can easily be
supported by the wires that connect to it.
The illustrations show the inductance
switch mounted inside of the panel. This
arrangement has been changed since the
photographs were taken. The switch
may be better placed where the small knob
appears on the panel to the left of the
middle dial. The unsymmetrical arrange-
ment of the panel, as the photographs show,
was due to a fear when this model was
designed that the parts would be too
crowded when the receiver was assembled.
The fears were not well founded. However,
the following change from the photo-
graphed model is suggested: Do not mount
the rheostat under the third dial. In-
stall a Bradleystat in the extreme lower
right hand corner of the panel, in a
position corresponding with that of the
jack in the lower left hand corner. Do
not change the position of the double-
pole double-throw jack switch. The in-
creased length of the audio transformer
leads might cause the set to howl.
O
O
FIG. 9
A detail drawing showing how the coil forms
radio-frequency transformers are prepared and
Before using the sub-panel brackets,
drill holes in the sides in such a way that
an audio transformer can be mounted to
each one. Study the photographs care-
fully in order to get the correct order and
approximate position of each transformer
on the brackets. Notice that the General
Radio transformer is at the left, the
FEBRUARY, 1926
Thordarson in the center, and the Rauland
Lyric at the right of the receiver. Before
drilling the bracket holes in the sub-panel
(marked B in Fig. 10.) check the distances
between holes and between holes and panel.
DETAILS OF CONSTRUCTION
HOLES will also have to be drilled,
before wiring, in the sub-panel to
allow for the passage of the condenser and
coil leads through it. The location of the
holes is not shown. These may be drilled
where convenient. Wherever possible, use
one of the coil mounting brackets for
bringing one of the coil leads through
the sub-panel.
The brass brackets which are
used to support the coils are shown
in Fig. 1 1.
The grid leak mounting clips
used in this model were obtained
from a Daven grid leak holder.
This is perhaps an unnecessary ex-
pense, because these parts can be
easily made from a piece of spring
brass. The clips are fixed to the
top of the sub-panel in order that
the grid leak be easily accessible.
If this feature is not desired, a grid
leak and condenser may be
mounted beneath the sub-panel,
where it is out of sight.
Notice also in the photographs
that a brass bracket is made to
support the end of the binding post
strip that is not supported by the
left hand panel mounting bracket.
The C battery and its terminals
are placed at the extreme end of
the sub-panel. In the model of the
IJTJJT Inverse Duplex shown a small
*4«-k*> spring brass bracket was used to
hold the battery against the cabi-
net. The hole for this is not shown.
The looo-ohm variable stabiliz-
ing resistance, since it is not to be
considered a control, is mounted on
the sub-panel where it is accessible for
adjustment. In order that this stabilizer
for the
wound
®
--5k--
-e-
PE
Qne ,e(,uired . Two may be used.
FIG. IO
The sub-panel dimensions
Two required : One for mounting
No. 1 Coil vert,cally from sub panel. For mount No 2 Coi, horizonta||y
One for mount.ng No 3 Co.l horizon- from ,5-pBrt.
tally from No.3 Condenser.
FIG. I I
Details of the coil mounting brackets
may work properly, the primary of the
second radio frequency coil »z«s/be reversed
as shown in the wiring diagram. If this is
not done, the stabilizing resistance will
make the set oscillate badly.
The double-pole double-throw jack
switch changes the set from a six-tube to a
five-tube outfit (theoretically) by cutting
in or out one of the audio-frequency stages.
FEBRUARY, 1926
HOW TO BUILD A GRIMES INVERSE DUPLEX
443
" Soldering lug
- -1%"-- — >
FIG. 12
The assembly for the Benjamin sockets
i\ switch that has a fibre cam should be
used if possible.
If other makes of audio transformers are
chosen, insist on two low ratio transformers
for the two reflexed stages. Use a high
ratio in the last free audio stage. This
will insure good quality in this circuit.
Because of the sub-panel construction it
is not necessary to waste time in fancy
wiring. This will appeal to
a large number of home
builders. Avoid large closed
loops in the wiring of the
audio circuits. Wherever pos-
sible, twist the wire with its
return. That is, in the case of
the wires connecting an audio
transformer, twist the plate wire
with the plus B wire and the grid
wire with its minus filament wire.
This helps to reduce the tend-
ency for audio feedback which is
very great with three stages of
audio amplification. Notice also
that the third audio tube is
placed as far away from the de-
tector tube as possible.
Do not allow the output wires
from the third audio
stage to run any-
where near the de-
tector tube or its
grid leak and con-
denser. The grid
leak and condenser
should be mounted
as close to the de-
tector grid as pos-
sible. This is very
important in a set
employing this cir-
cuit. In the set de-
scribed, a grounded
metal shield has
been placed near the
grid leak and con-
denser and the de-
tector tube. This
helps considerably
in shielding these
parts which are ex-
tremely sensitive to
induction from vari-
ous sources, such as
electric light wires,
trolleys, small
motors, and so on.
It is also desirable
to ground the brackets which support the
sub-panel and the audio transformers.
For best results in Inverse Duplexing,
there is a certain definite way of poleing
the primaries of audio transformers. A
technical explanation of this statement i§
not necessary in this article. The circuit
shows the best arrangement for the trans-
formers used. If transformers of a differ-
ent make are used some experimenting
will perhaps be necessary in order to de-
termine whether the primaries are to be
connected as marked or reversed. All
transformers do not have their primaries
marked in the same way.
For local, or perhaps moderate distance
reception, it is possible to dispense with
the antenna and substitute for it a loop.
The loop is connected in the circuit in place
of the first secondary tuning coil. It can
be so arranged that by means of a double-
pole double-throw switch, the loop is con-
nected in the circuit in place of the antenna
system. By no means can it be expected
RADIO BROADCAST Photograph
FIG. 15
The three dials on this panel seem to be similar to those on any number
of sets, especially those of the two-stage tuned radio frequency receiver.
Actually this is a panel view of the new Kurz-Kasch E-Z Toon Group
Control. By means of the center dial, all three tuning condensers may
be rotated simultaneously. All three dials have verniers, permitting
each condenser to be finely adjusted independently
FIG. 14
The circuit of the Grimes Inverse Duplex. The first and last tubes are 3rd audio and
detector tubes respectively. The other two are both radio and audio amplifiers
FIG. 13
Specifications for making the choke coil forms
that the loop will prove as satisfactory as
the antenna where only distance reception
is to be considered, but the constructor will
note that with its use there will be a free-
dom from the usual collection of noises
that find their way into a receiver via the
antenna.
The circuit is quite stable in operation
when uv or ux-icjg tubes are substituted,
but when this is done, it is well to employ
a power dry-cell tube such as the ux-120
in the last audio stage to prevent over-
loading which results in distortion.
Builders often experience a certain
amount of difficulty in constructing a set
of entirely new design. We shall
outline some of the troubles that
may be experienced, and how
to locate and correct them.
HOW TO LOCATE AND REMEDY
TROUBLE
THE first indication of trouble
is usually a howl of some
kind. These can be divided into
three main classes.
i. AUDIO HOWL. This is
a steady high pitched sing which
is absolutely independent of dial
settings. It may be caused by:
(a) audio feedback due to wiring;
(b) audio feedback due to com-
mon resistance in old B bat-
teries; (c) use of a common
detector B battery.
In this set, a sepa-
rate small 22^-volt
battery must be used
for the detector tube
except when storage
B batteries are used ;
(d) long detector
grid lead; (e) the
proximity of a loud
speaker or loud
speaker cord to the
detector tube, or to
its grid leak and con-
denser; (f) improper
shielding of audio
transformers; (g)
open grid circuits.
Look the set over
carefully and check
everything except
(a) and (f). If the
howl still persists,
there are only two
things to be done;
rewire the set, or
load the secondaries
of the audio trans-
formers. Try placing
j-meg. or
i d
meg
444
RADIO BROADCAST
FEBRUARY, 1926
grid leaks across
one, two or all three
of the secondaries.
This should cer-
tainly kill the howl.
If it does not, the
author would be
glad to hear in de-
tail by letter from
constructors and we
shall try to help
you. The addition
of these leaks, while
it reduces the ampli-
fication, tends to
improve the quality.
2. RADIO HOWL.
This is usually a
very low pitched buzzing noise. It only
occurs when two or three of the dials are
set alike. Removing the antenna and
ground tends to make it even worse.
Radio Howl is caused by radio oscillation
in the receiver. Radio oscillation, in
turn, is caused by either electrostatic or
electromagnetic feed-back between the
radio-frequency stages. It may also be
due to capacity feed-back within the tube.
In any case, first make sure that the pri-
RADIO BROADCAST Photograph
FIG. l6
How the Kurz-Kasch arrangement works. By means of the rack and gears, one dial controls three con-
densers, an advisable simplification of the tuning of any set employing three condensers. This ar-
rangement can be applied without difficulty to the Inverse Duplex set, and to many other types of
receivers employing two stages of tuned r. f. amplification
mary of the second r.f. transformer has been
reversed. Next cut in some of the sta-
bilizing resistance, retune carefully, and
repeat until no oscillation can be produced,
even at the low dial settings. If the sta-
bilizing resistance has no effect, the primary
of the second radio coil probably has not
been connected according to instructions.
3. OVERLOAD HOWL. The pitch is
generally higher than that caused by Radio
Howl. It occurs only when all three dial
readings are the
same and when an-
tenna and ground
leads are connected.
The removal of
these leads stops it
at once. Overload
Howl is produced
when the set is
tuned-in to a very
powerful local sta-
tion. If the pitch
is rather low and
occurs before the
volume reaches the
overload point of the
free audio tube as
indicated by distor-
tion, the audio transformer primaries are
poled wrong. Try reversing them in vari-
ous combinations until theOverload Howl is
of rather high pitch. This is the condition
for least overload. The receiver should now
be capable of delivering volume up to the
limit of the tube in the third audio stage.
To avoid Overload Howl always cut out one
audio stage when tuning-in to local pro-
grammes. The third audio stage should
only be used when extra volume is desired.
A PRIZE CONTEST FOR THE DESIGN OF A NON-
IO GREAT has been the interest in the
RADIO BROADCAST-Eveready experiments
_ carried out at station 2 GY, and so
many inquiries have come from readers who
want to listen on the short waves, that the
contest outlined below will serve many purposes.
In the first place it will indicate that up to the
present time there is no receiver which the
Editors of RADIO BROADCAST feel that they can
recommend. It will also indicate what these
Editors, and the judges of the contest, believe
an ideal short wave receiver should be. And
finally, it will serve to awaken interest among
the thousands of amateurs toward developing
real honest-to-goodness receivers.
Perhaps a few words on the reason for the
first statement will not be amiss. It may be
remembered by many readers of RADIO BROAD-
CAST that the clearest cut and longest standing
policy of that magazine has been to frown on
radiating receivers. It has consistently refused
to publish how-to-make-it articles on receivers
that were liable to interfere with nearby re-
ceivers, and it has endeavored in many ways to
show owners of such receivers how they can
make them innocuous and more efficient.
The second important point in this connection
is the fact that there are at present about 20,000
amateur operators listening-in on the short
waves, and practically all of them use very sim-
ple two- or three-tube sets, which are of the
"blooper" variety. To encourage thousands
of broadcast listeners to go down to the short
waves with similar receivers would be contrary
to our long established policy, and would result
in a hopeless medley of meaningless parasitic
signals on the higher frequency bands.
At 2 GY, the experimental station of RADIO
BROADCAST-Eveready, a receiving tube with
180 volts on the plate has transmitted signals
to Philadelphia, 100 miles away, under favor-
able conditions. Of course no receiver regu-
larly uses 180 volts, but with 90 volts, there
has been no difficulty in communicating over
distances of ten miles and at that distance the go
volt set produced very strong signals.
What is wanted is a non-radiating short wave
receiver, preferably one that will cover all of
the amateur bands, but most certainly the so-
called 40, 80, 1 50 meter bands.
To aid possible contestants, the following
schemes are suggested. A receiver with such
loose coupling that the single oscillating tube
cannot radiate; a simple receiver of the present
type with a stage of neutralized radio frequency
ahead of the oscillating detector; a super-
regenerator with a blocking tube ahead of it;
some simple form of super-heterodyne, such as
the O'Connor frequency-changer described in
RADIO BROADCAST for June, 1925. Such a
receiver should be as efficient as present re-
ceivers, preferably it should be better. That
is, it should go down to the noise level in places
where a single oscillating tube will not do it.
The conditions of the contest are outlined
below. In order to appear in the May issue of
RADIO BROADCAST, complete specifications,
photographs etc., of the receivers will have to be
in the editorial office by the first of March,
1926, in order to be considered.
THE CONTEST
Object: The object of this contest is to aid in
the development of improved short wave receiv-
ing apparatus, so that the possibilities of high
frequencies may be more effectively studied.
Prices: First prize, 1250; Second prize, $150;
Third prize.fioo. Only one prize to a contestant.
Eligibility: Anyone interested in short wave
reception is eligible to compete, though no prizes
will be given to manufacturers making short
wave receivers or parts therefor.
Conditions: Each contestant must submit a
complete description, photographs and hook-up
of a short wave receiver which does not radiate.
The receiver should be adapted to the entire
short wave band from 35 to 1 50 meters, although
this may be accomplished by interchangeable
coils. RADIO BROADCAST shall be permitted
to request the most promising receivers sent to
its laboratories, in order that the final award
of the prize may be determined, after exhaustive
tests. In addition to the prizes, RADIO BROAD-
CAST shall be permitted to use descriptive matter,
either in whole or in part, submitted by any
contestant, at its regular rates.
Determination of Prices: The winning re-
ceiving sets will be judged on a basis »f points
as follows:
Workmanship 15
Simplicity of handling 20
Ease of Calibration
Freedom from hand capacity
Independence of tuning and regeneration
Low Cost 10
Use of standard or easily constructed parts 5
Performance 25
Overall amplification of signals
Use in relaying
Ability to use break-in
Ability to cover foreign amateur bands
Appearance 15
Method of avoiding radiation .... 10
Total 100
Board of Judges: The following constitute the
board of judges: Boyd Phelps, Prof. Louis A.
Hazeltine, Zeh Bouck, G. C. Furness, Arthur H.
Lynch, Edgar H. Felix, Dr. Lawrence Dunn,
and Dr. A. Hoyt Taylor.
The contest positively closes March i so that
prizes may be announced in the May issue, ap-
pearing April 15. All correspondence and prize
manuscripts must be addressed: Director of the
Laboratory, RADIO BROADCAST, Doubleday, Page
& Company, Garden City, New York.
Conducted by — John Wallace
What Radio Programs Chiefly Need
w;
rAS it Irvin Cobb who des-
cribed in whimsical fashion
the dire results of his attempt
to reduce, by taking alternate
steaming hot and icy cold baths? Whoever
it was, he attests that it resulted in his de-
veloping a set of highly trained, trick pores,
capable of opening or closing at the slighest
provocation, or at no provocation at all.
This double action, hair-trigger arrange-
ment, he further averred, was no unmiti-
gated joy, inasmuch as said pores used
absolutely no discretion as to the proper
time to do their stuff, being prone, nay
even fain, to open wide on a brisk, six-
below zero morning, or shut up, like of-
fended clams, in a stuffy telephone booth.
Another disease, similar in causation,
threatens at any moment to sweep across
the continent, sparing Mr. Cobb perhaps,
but reducing to mild insanity a large army
of listeners-in. This scourge we dub Radio-
Emotionalis — or perhaps better Radio-
Super-Emotionalis (medical term for an
insidious neurotic condition).
The hapless victim of the epidemic may
be readily recognized. He will greet you
right cheerily enough, perhaps laughing
boisterously the while. But a second later
he will be weeping copiously on your
shoulder only to relapse quickly into the
belligerent, defiant attitude of one resolved
to crush out the little white menace. This
may, like as not, be followed by a period
of calm, whilst the victim, with gently
heaving chest, gazes off into space, a where-
have-you-been-all-my-life look in his eye.
Then he will cackle hideously and start
tuning-in the buttons on your coat, where-
upon you will take to your heels, unless,
as is probable, you have by that time
caught the disease, in which case you will
make it a cackling duet accompanied
by Miss Blaughk on the mighty Baldwin.
Which is reason enough for the Govern-
ment to establish a colony on some isolated
island and confine thereon, as menaces to
the public health, sixty per cent, of all ex-
isting radio program directors.
The "bigger and better" radio stations
have, in response to the nowise concealed
wishes of the listeners, largely got away
from the kaleidoscopic type of program.
But a large majority of the jerk-water
stations, keeping abreast, as is their wont,
with the times now three years passed,
still persist in this nerve-wracking offense.
An extra-horrible example of the kaleido-
scope program runs something as follows:
8:00 P.M. Announcement. Name of station.
Its street address and telephone
number. List of pickle manu-
facturers and dance halls it repre-
sents. Name of announcer. Color
of his eyes. Call letters of station.
Slogan of station. Bright remark.
8:03 Valse Triste Sibelius
8:07 (Same as 8:00 P.M.)
8:10 Itchy Foot Rag Joe Goose
8:13 (Same as 8:00 P.M.)
8:16 Elegy Massenet
8:20 (Same as 8:00 P.M. and repeated
hereafter as frequently as possible)
8:23 Reading: "The Shooting of Dan
McGrew"
8:29 Quartette: "Oh Lord Where Art
Thou?" Larch
8:36 Quartette: "Where's My Sweetie
Hiding?" Ed Ock
8:41 Solo: "Fly With Me" Verdi
8:46 Address: "Swat the Fly" by Aid.
Skink
8:51 And so forth.
BROADCASTING A CARILLON AT WJZ
On Sunday nights at 7 p. M., Eastern Standard Time, the carillon recently installed in the Park Avenue Baptist Church, through the generosity of John
D. Rockefeller, Jr., is broadcast. The chimes sound much better on the air than they do to listeners nearby. There are many high buildings near the
balfry and unfortunate sound reverberations occur. The view at the left shows engineers of wjz experimenting with the location of the microphone.
Anton Brees, formerly assistant carilloneur of the famous Antwerp Cathedral, and now in charge of the New York chimes, is shown at the manual
in the center view. The photograph at the right shows H. B. Glover, of wjz, installing the microphone above the bells
446
RADIO BROADCAST
FEBRUARY, 1926
Well, yes, we'll admit that this is a
slightly exaggerated example, but the
inconsistent program, even in its mildest
form, is very annoying. Unity is a quality
inseparable from anything that is well
constructed, whether it is a watch or play
or a sermon or a railway station. We don't
always consciously note the force that
unifies an otherwise heterogeneous col-
lection of miscellany but we quickly
and instinctively sense its absence.
Of course even a che-ild (that hypo-
thetical youngster who, as shown in num-
berless illustrated advertisements, spends
its infant years at pushing pianola ped-
als, running vacuum cleaners, operating
Blum Bros. Cross Index Files, and
cranking Tripco Trucks) could tell you
that the above program was decidedly
lacking in unity. But with the less
flagrant offenders, the problem becomes a
less evident one and its solution rests
finally on the taste and sense of the fitness-
of-things of the program director. If he
already lacks this sense the chances are he
won't acquire it, and it would be better
for the station to throw him out and get
someone else.
Appreciation of Sibelius' liaise Triste
requires that we be in a certain frame of
mind. Likewise thorough enjoyment of
The Shooting of Dan McGrew presupposes
our being in a certain frame of mind.
And the two frames are as dissimilar as
passe-partout and carved ebony. The
desirability of an audience being in re-
ceptive mood is so evident that it hardly
needs to be stated. The overture that
commonly precedes an opera constitutes
a recognition of this truism. Containing
as it does inklings of all that is to happen,
it prepares the auditor for the three or four
acts to follow and effectively bridges the
gulf that exists between listening to music
and the previous occupation of the listener,
be it clipping coupons, or punching a type-
writer.
Even the movies take cognizance of this
device. If, in one of the larger palaces, the
feature film "Why Shoot Your Husband?"
is shown, it will inevitably be preceded
by an "opulent stage presentation" show-
ing a chorus of bored wives engaged in
target practice.
If the l/alse Triste and Itchy Foot Rag
are put on the same program, one or the
other, or both, is going to suffer from the
juxtaposition. The difference in mood
between the two is greater than we can
be reasonably expected to bridge.
But giving unity to a radio program does
not, by any means, imply making it
monotonous. Variety and unity are not
necessarily antagonistic. Shakespeare, who
was no ham at play construction, and
who was a stickler for unity, didn't hesitate
IN THE STUDIO OF WRNY, NEW YORK
What probably is called a motley crew, peering through the plate glass window of the studio, inspecting Jerome Lama playing on
the musical saw, an ' ' instrument " capable of curious and unearthly melodies — as many radio listeners know from their own experience
FEBRUARY, 1926
KIND WORDS FOR THE DX FAN
447
DR. EDMUND A. WALSH
Vice President and Regent of the School of Foreign Service at George-
town University who inaugurated the first radio school of international
relations at station WRC, Washington. Conferences in this school are
broadcast weekly by WRC, and test periods have been arranged for ex-
amination of listeners who enroll for the course
to introduce variety into his tragedies.
He occasionally made use of the most
sudden and violent contrasts. For in-
stance the execrable pun pulled by Othello
as he blows out the candle preparatory to
smothering his wife, which, in 1926 version
amounts to: " I'll douse this glim, and then,
douse that one!"
If it's a joke it's a rather dismal one, and
quite in keeping with the tragic mood.
Thus Jarnefelt's Praeludium could be
sandwiched in along side of the afore-
mentioned I/alse Triste with no discon-
certing effects. For, though the one is
riotously funny and the other mournfully
sad, they are united by a common bond:
both are music.
Mixing in a lot of fundamentally dif-
ferent things in the same hour's broadcast
simply means that the edge is going to be
taken off all of them. We can only give
such a program the most superficial sort
of attention and consequently derive a most
superficial sort of enjoyment. If we were
to try to get the most out of it by changing
our mood as fast as the program director's
whims we would expose ourselves merci-
lessly to the dread disease described above
— Radio- Emotionalis.
The mixed program is doubtless the
program director's honest effort to reach
and entertain the maximum number of
people of widely varying tastes. But in
his attempt to please everybody he pleases
nobody. Moreover, in considering it his
duty to please everybody, he is flattering
himself as to his indispensability; forget-
ting he is only one of the ten or twenty,
or more, stations at the listener's command.
He performs no valuable service in
offering variety, since it is the simplest
thing in the world for the listener to get
the variety himself, if he wants it, by
tuning from one station to another. But
if the listener, on the other hand, wants
a uniform program, with no jarring
inconsistencies, his only recourse is to
tune-in on those few progressive stations
on which he can count to deliver such a
program.
And that is exactly
what the listener does.
Which is well. For
in the long run it will
mean that the hodge-
podge program sta-
tion will either come
around to some sort
of an organized pre-
sentation or simply
waste its vaudevillian
offerings on the thin
air — which would not
be economically ad-
vantageous.
So we would seem
to have been tilting
with a wind mill for
the last several hun-
dred words since all
will right itself in
time. But the sooner
the better. The ideal
state of affairs will have arrived when
each station adheres to one type of offering
for at least sixty minutes on end. Then,
but not till then, we will be able to regard
the faint snatch of something or other
we hear flickering across our dials, as a
fair sample of what that station is offering.
Under present conditions, we have more
than once been fooled into patiently
tuning-in a station because we heard a bit
of a Brahms symphony (which, now that it
is no longer the fashion to do so, we will
admit we crave inordinately) and have
been rewarded by the clear and perfect
reception of Palpitatin' Mamma.
In Defence of the DX Fishers
T1
1 :
kHE Chicago district is, at present
writing, engaged in a fearsome
battle on the question of silent
nights. One station has lingered on
through months of warfare and refused
to shut down on the specified night. Hence
the fracas. While the recalcitrant station
frequently asserts, with an air of injured
righteousness, "We are considering the
interests of the thousands of fans who, if
no local station were in the air, would be
HOW WGY IS REBROADCAST AT WCAD, CANTON NEW YORK
Left to right: Harold K. Dergman, radio operator in charge at WCAD; Ellis L. Manning, announcer
at WCAD, and instructor in physics at St. Lawrence University; S. E. Barber; Charles Geyh.contro!
room assistant, and Prof. Ward C. Priest, chief announcer. The WCAD station is maintained by the
students and faculty of St. Lawrence University and broadcasts on Wednesday evenings between 8
and 1 1 p. M., Eastern Standard Time, on a frequency of 1 140 kc. (263 meters). The main features
of the WCAD programs are rebroadcast from WGY at Schenectady, 175 miles away. The illustration
shows the staff at the receiving station, picking up the WGY signals on their lQ2.2-kc. ( 1 56o-meter) wave
448
RADIO BROADCAST
FEBRUARY, 1926
entirely deprived of radio on Monday
nights, and the multitude of owners of large
sets who can get outside stations, but who
prefer to tune-in on local programs" it is
transparent enough that it is playing the
martyr for publicity purposes.
And, of publicity, it has received plenty
in the controversy in the newspapers.
One of the most amusing communications
to the press was that of a lady who said
"Indeed we do not want silent nights.
We want to listen to the good programs in
Chicago."
Any one familiar with the general run
of Chicago programs should get a large
ha-ha out of that!
But while we have not been inflamed by
the controversy to the point of contributing
to the symposium of nasty letters, it seems
to us that were we questioned we'd advo-
cate a silent night. Why not?
The thousands of fans who "would be
entirely deprived of radio on Monday
nights" could doubtless find something
else to do. They didn't sit around thumb
twiddling in the Before-Radio age.
We can't see why there should be any
gnashing of teeth over the fact that the
capital tied up in a station lies idle on
silent night. There's many a large factory,
representing an investment equivalent to a
gross of broadcasting stations, that grinds
forth no goods of a Sunday.
Moreover, why isn't the station's force
entitled to a bit of a vacation at least once
a week? Perhaps for some stations a two-,
or even three-day vacation might be de-
sirable. Who knows but that the program
director, freed for the nonce from his
duty of filling up the programs, might,
during the enforced idleness, give birth
to an original thought concerning said
programs
DX fishing has been pooh-poohed quite
a bit by those who claim that it is a hold-
over from radio's infant days. Its chief
thrill they protest is merely (powerful
word that "merely") the satisfaction
gained in conquering vast distance. This,
they go on to say, is silly; a perversion of
radio's purpose, which is not to furnish
geographical gymnastics, but to entertain.
Granting the fact that the largest use to
which radio is put is to furnish entertain-
ment in the home, and granting likewise
that this will doubtless continue to be its
chief attraction, we still maintain that
its faculty of entertaining is not radio's
greatest attribute. Its greatest poten-
tiality is the conquering of distance.
Entertainment in the home is no new
thing. We have always had Cards and
Conversation. Pianos abound. Then
there is always Charades or Post Office,
to say nothing of Photograph Albums.
Add to all these boons the Talking Machine
and what more could you ask! Surely if
radio's claim to admission to the Hall of
Fame is on the ground that it has brought
entertainment into the home, its argument
is a feeble one. Cross Word Puzzle books
could with as much right demand a
pedestal. The unique feature of radio is
not that it entertains, but, that it conquers
distance. Every seeker after glory must
pursue that chimera in his own line — not
in the other fellow's. Hence it is in the
conquering of distance that radio must
achieve its laurels.
When we get a string quartette from
Omaha we are getting nothing that we
couldn't get out of a talking machine.
But when we get an opportunity to sit in,
by radio, on a national political convention,
in session perhaps halfway across the
continent, we are getting something we
DOC HOWARD S WKRC BROADCASTERS
Who are heard every Monday night from station WKRC at Cincinnati as a part of the " Kodel Mid-
night Frolic." The entertainment includes this jazz orchestra, a male quartet, a whistler, and
character monologuists
never got before and couldn't get any other
way. When (if ever) we are able to listen
to some important history making event
in a distant country, we are experiencing
something undreamed of a generation ago.
It is in service such as this that radio
achieves its greatest purpose.
So to us the most potent argument for
a silent night is that it encourages DX
fishing. And by stimulating DX fishing it
is stimulating designers and manufacturers
to greater efforts toward perfecting long
distance receivers. In short it is a step
toward the development of radio's greatest
and most valuable potentiality.
Readings in Foreign Languages
A1ONG the very few things that
radio is actually capable of doing
in the educational line is to assist
in the teaching of foreign languages.
Time and again we hear someone moaning
" If I could only get someone to talk to me
in French I could learn the language, but
you know you can't get it all out of a book.
You've got to hear it spoken."
We seem to remember that some years
ago the broadcasting of lectures and
readings in foreign languages enjoyed a
brief vogue. But of late we have combed
our dials assiduously and discovered a
paltry few such offerings, generally in the
form of lessons. In New York, WEAF
broadcasts a twenty minute French con-
versational lesson on Tuesday evenings
conducted by Dr. Thatcher Clark of
Columbia University and WNYC gives
an hour on Monday, Wednesday and
Friday evenings to elementary lessons
by V. Harrison Berlitz in German, Spanish,
and French. In Denver KOA contributes
forty-five minutes a week to a conver-
sational Spanish lesson on Mondays at
8 P. M. There are doubtless several
other stations we have overlooked, but
in all there is very little attention paid
this excellent educational possibility.
There may be some question in the minds
of program directors as to how widespread
an appeal such an offering would have.
Certainly it is true that'there is no universal
desire in this country to become bi-lingual.
What if the most disreputable little news-
boy in Rome can hawk his wares in three
languages? He needs to. We don't.
But with the constantly increasing ease
and decreasing cost of transportation to
foreign strands, we, of America, are
gradually going to find it more convenient
to know other tongues. Moreover, the
time is not centuries off when communi-
cation, via broadcasting, with foreign
countries will be an everyday occurrence.
Besides there are already a goodly
number of persons who would be interested
in having an opportunity to listen-in on
French or Italian or Spanish from time to
time — persons who have struggled through
Mr. Woman's or Otto-Onion's estimable
grammars in their school days and have
a foundation of knowledge which needs only
exercise to become useful.
FEBRUARY, 1926 NOTEWORTHY ADDITIONS TO BROADCAST PROGRAMS
449
Such an educational program might take
the form of a lecture on some current
topic, given perhaps by an attache" of
a consulate or by some first rate pedagogue.
Or perhaps better it might consist in
readings from some of the standard classics
in the foreign tongues. Then the radio
scholar would be able to sit with the book
in hand and supplement with his eyes what
he could not get with his ears.
The desirability of such readings or
lectures being given by someone to whom
the tongue is native, and who is possessed
of the most perfect enunciation, is evident.
Announcers as Automatons
SEVERAL readers have taken the
trouble to inform us, and in no
uncertain terms, that we are all
wrong in advocating that the radio an-
nouncer be an automaton. We were
assured that "no one wants to hear the plot
of the opera to be broadcast read in the
same monotonous voice that is used for
stock market quotations." And -we make
haste to agree heartily.
When we urged that the announcer be an
automaton rather than a personality-plus
salesman of the radio station's wares,
we had reference only to the announcer en-
gaged in the routine business of labeling the
next number and citing the name of the
performer. We still think he should sink
unobtrusively into the background.
The individual whose duty it is to
comment at length upon the program
(where absolutely necessary), to explain
the music (where absolutely necessary),
or to prepare us with some historical
background (where absolutely necessary),
is not, in the strict sense of the word,
an "announcer." Call him a public
speaker, if you will, or an "artist."
Of course he should have free rein to do
his job in the best possible manner; though,
unless he is the author, he should see
fit to read the interpolations with only the
inflection necessary to make them clear,
spritely, and pleasant, and with no attempt
to put his own personality forward.
But if, on the other hand, his obser-
vations are his own, he has a perfect right
to put them across any way he pleases —
just as he would do in ordinary conver-
sation.
Broadcast Miscellany
A CALL has been sent out by KFI
to its receptionists to send in lists
of old music dating from the Civil
War period up to 1900. Plans are on foot
in the Los Angeles station to review
American music in a thorough and pains-
taking manner. Request is also made
for copies of the old songs, songs such as
"Climbing Up the Golden Stairs, "I'll
Meet Her When the Sun Goes Down,"
or "We'll Paint the White House Green."
And, WKRC at Cincinnati performed
a similar service in ferreting out folk songs
that have been preserved in the mountain
fastness of Kentucky and are still played
and sung in the cabins that are found
in the clearings atop the mountains. This
station arranged with the Cincinnati Post
and the Rudolph Wurlitzer Company
to send a musician on a trip through the
hills to listen to, and record, the tunes —
most of them unpublished. Among the
songs, many of them two hundred years
old, that were gathered together to form
a broadcast program were: Brother Green,
Frog Went A-Courting, Lady and the Glove,
Smirwood Mountain, and the Hangman's
Song.
H. V. Kaltenborn, associate editor of
the Brooklyn Daily Eagle is on the
air again Monday evenings from eight
to eight-thirty through station WOR.
His Current Events talks have been a
popular feature of radio programs for the
past three seasons. Mr. Kaltenborn in-
terrupted the series last spring to make
an extensive journey through Europe and
the Near East in search of new material.
WITH the addition to its program of
a new feature entitled "Things
Talked About," which is presented every
Friday afternoon by Mrs. Nina Reed,
station WRC at Washington is now covering
the weekly trend of current events for
both its masculine and feminine audiences.
Mrs. Reed's new series of weekly talks
takes up the important events of the
world that are of particular interest to
women, and reviews those questions that
are not covered by Frederic William Wile
in his excellent weekly discussions of the
political situation in Washington every
Tuesday evening.
THE Uncle Charlies and other bed-time
boys who persist in calling their
juvenile listeners "kiddies" are, we suspect,
some kin of the coy word-coiners who
attempted to label the American soldiery
in the late fracas "Sammies."
WHAT ho! we thought, there is much
talk of how Music is insinuating
itself into the Radio World. Let us see,
vice-versa, how much of a ripple Radio
is creating in the Musical World.
So we hied ourself to the public library
and surrounded ourself with seven of
the current musical publications. This,
thought we, should be a fair enough index
of the interest aroused among bonafide
musicians by radio. Well, we shall
chronicle the result of our research without
comment: nowhere in the music trade
journals did we find the word "radio" as
much as mentioned. Which may or may
not prove anything.
AN INTERESTING variation of the
traditional ritual of announcing is
that employed by WEBH, Chicago. For
some time this station has been announcing
only the "next number," omitting reference
to the preceding one. Recently this
system was reversed and the practice
now followed is to announce only the
number just completed, after whick the
next number starts without any intro-
duction. Either practice is commendable
since it results in cutting the announcer's
timeonthe air in half — and announcements,
like subtitles in the movies, are best when
brief.
Of the two methods, the one finally
adopted by WEBH as a permanent practice
has the most to commend it; for frequently
a listener tunes-in during a number and is
perhaps curious to know what he has heard.
This rule of omitting introductions is
subject to exception. Where the import-
ance of the artist, or the novelty of the
offering, warrants it the announcement
is made both before and after — for routine
studio offerings the "back announcement"
alone suffices.
SOME attention-caller, amateur or
professional, ought to take it upon
himself to inform these enthusiastic and
breezy announcer-persons that g-e-n-u-i-n-e
is not pronounced genuine. Concerts
"broadcast direct" from some place or
other, also leaves us exceeding cold. The
logic of this last statement is positively
astounding. Everyone is of course familiar
with indirect concerts, and knows that the
direct brand are vastly to be preferred.
THE editor of this department is pleased
to hear from readers who agree or dis-
pute his opinion. Those who write should
address their letters to "John Wallace,
Conductor, Listeners' Point of View, RADIO
BROADCAST Magazine, Garden City, New
York," and sign their communications.
IN TAKING stock of recent noteworthy
additions to the broadcast listener's
fare, we discover that the Radio Cor-
poration of America stations have been
responsible for at least two of the out-
standing features on the winter's programs.
First in importance was the series of
recitals from Steinway Hall, sponsored
by Steinway and Sons. Such important
musicians as Josef Hofmann, Guy Maier
and Lee Pattison, pianists; Walter
Damrosch and William Mengelberg, con-
ductors; and Paul Kochanski, violinist,
were heard in this series of one and one-
half hour concerts broadcast through, wjz,
WRC, WGY, and WBZ.
Also of interest to many have been the
Lewisohn Free Chamber Music Concerts
broadcast from Hunter College, New York,
every Wednesday night. The Chamber
Music Series was founded by Dr. Henry
Fleck and is still under his direction. They
comprise the first course in musical appre-
ciation offered to the public. In arrang-
ing the concerts, Doctor Fleck devoted
the first part of the program to the classical
school of writers, presenting them in
chronological order. The second part has
been reserved for modern works, however
radical. Several excellent quartettes and
trios have been heard in this series.
Each of Wkich Were Experimented With In Developing the
"Radio Broadcast Universal" — SHou> ing How Variations in
Panel and Sub-Panel Arrangement Can Be Used to Advantage
DUE to space limitations, it was not
possible to show the readers of RADIO
BROADCAST all the models of the popular
RADIO BROADCAST "Universal" Re-
ceiver completely described in this maga-
zine for January, 1926. A great many of
these models were constructed while we
were experimenting with the circuit in
search for the final receiver. Several
of the models which were not illustrated
in our January number are shown here
and it is possible for the reader to ascertain
for himself the wide scope of application
of this circuit to other designs. Other
coil units, different panel and base layouts
may be employed. On these two pages
are shown several views and a circuit
diagram of an excellent receiver which has
points in common with the "Universal."
We believe that many of our readers are
RADIO BROADCAST Photograph
FIG. 1
Rear view of the Phonograph model. Note the compactness of the unit which is
made possible by using the Clarotuner coils and Hanscom single control unit
RADIO BROADCAST Photograph
FIG. 2
Bottom view of RADIO BROADCAST'S Universal made to fit in a
phonograph cabinet. This design is due to the engineers of the
American Mechanical Laboratories and employs several de-
partures from our original model to good advantage, including the
Bruno Brackets which make for great rigidity in a compact receiver
of this kind
FIG. 3
RADIO BROADCAST Photograph
Top view of the same receiver illustrating the ease of assembly and wiring as
well as the particularly neat appearance this form of assembly makes possible
FIG. 5
RADIO BROADCAST Photograph
Cabling the wiring — when it is done intelligently — is advisable. Here
is the base of the Samson and is a very good example of how it is done
RADIO BROADCAST Photograph
FIG. 4
A front view of the Sampson T C Receiver which
has been developed by the Sampson Electric Com-
pany of Canton, Massachusetts, after a design of
J. K. Clapp of M. I. T. This set is a very good
example of the design adaptations possible in the
Universal Receiver. The changes in the circuit
employed are briefly covered in an accompanying
illustration
undoubtedly familiar with this receiver,
the Sampson T C, and for those who are
not, it is shown here by illustration and
circuit diagram.
The circuit diagram for the "Univer-
sal" Receiver is found on page 331 and
the six pages following of RADIO BROAD-
CAST for January, 1926.
FEBRUARY, 1926
FOUR RECEIVERS
RADIO BROADCAST Photograph
FIG. 6
One of the early models of the Universal which was abandoned because of wiring and electrical feedback difficulties
FIG. 7
A very symmetrical panel may be had by bringing
the volume control resistor to the center as shown
here
RADIO BROADCAST Photograph
FIG. 8
Looking down on the Sampson T C Receiver. So
much equipment in so small a space is in itself an
accomplishment. This layout is a little difficult to
approximate, but when you have it finished it is a
real receiver. The tests run on it in our Laboratory
revealed it to be one of the best we have ever had
submitted for test. It is compact, easy to handle,
economical to use, and the tone quality is far above
the average. On the second stage audio it performs
very well with a cone speaker which is saying much
for a transformer-coupled audio receiver
RADIO BROADCAST Photograph
FIG. 9
The circuit used in the Samson receiver is our old
stand-by-the stage of neutralized, tuned radio
frequency amplification, a regenerative detector and
two stages of high quality transformer coupled
audio amplification. The neutralizing system is
particularly simple to handle and but few improve-
ments in the circuit could be made. Some reduc-
tion in plate current consumption may be had by
placing a 3 to 4? negative bias on the first tube and
better performance may be had from the audio,
without complicating either the building or oper-
ation, if the R. F. stage rheostat is confined to
that tube and ballasts are used in the filament circuits
of the first and second audio tubes. If a 201-A
type tube is used in the first stage, a j-ampere
ballast may be used and where the new 112 type
tube is used, a J-ampere ballast will serve very well.
In this last case, raising the plate voltage on the
last tube to 135 volts and increasing the grid bias
to minus 9 volts will be found worth while
:How Long Will My B Batteries Last?"
New Thoughts on an Old Question — How to Choose the Proper Unit
for the Proper Use — The Economic Importance and Use of the C Battery
By GEORGE C. FURNESS
Manager, '•Radio Division, National Carbon Company
IHE question "How Long Will My
B Battery Last?" was old when
radio broadcasting began, and from
then until now, the answers have
rarely been satisfactory. If the question
were asked of a radio battery expert, the
answer would consist of a cross-examination
of the user as to the kind and size of battery,
number of tubes, the B battery voltage, the
C-battery bias and so on, world without
end, until the inquisitive child appears
dumb in comparison. If the question
were asked of an unreliable clerk in the
radio store, who had become an expert
over night and who, knowing little, feared
less, the answer would be whatever figure
the clerk thought would most please the
questioner.
Both types of answers are equally un-
satisfactory to the radio user. In the one
case, he is not generally interested in a dis-
cussion of the many factors which affect
the life of his battery, and in the second
case, he does not want an incorrect answer.
Although the laws of physics and chemis-
try continue to operate as formerly, thus
bringing in just as many factors as of old in
affecting the life of a B battery, conditions
have become sufficiently standardized with
respect to broadcast receivers so that we
can now fix many of what formerly were
variable factors. Common practice thus
enables us to simplify a complex subject
and give results which are in close approxi-
mation to actual performance.
This article is written by a student of
radio batteries who still finds it impossible
entirely to get over the old habit of severe
cross-examination and discussion of every
factor. We are therefore unable to come
to the consideration of battery life under
simplified conditions without first explain-
ing the basis on which simplification is
accomplished.
Here then are the assumptions on which
the simplified story is built:
1. That the battery is of reliable, high grade
manufacture.
2. That 90 volts of B battery is used on both
radio and audio frequency amplifier tubes.
3. That 45 volts is used on the detector tube.
4. The battery is considered as discharged
when each 22j-volt section drops to 17 volts.
This is the conventional "cut-off" voltage.
Experience has shown that many users
continue to obtain satisfactory results and
do not discard their B batteries until long
after they have passed this 17- volt point.
5. That the grid bias on all radio frequency
tubes is zero.
6. That the grid bias on the audio amplifier
tubes is either zero (no C battery) or is
43 volts negative when a C battery is used.
FIG. I
The cylindrical cells which go to make up two
types of B battery. That at the left is for light
duty batteries, that at the right for heavy duty
batteries. A zinc cylinder encloses a compound
in which is located centrally, the carbon rod.
The carbon is the positive pole of the battery
cell, the zinc can the negative
7. That the tubes are burned at normal fila-
ment brilliancy.
8. That the receiving sets employ tubes which
have the electrical characteristics of the
uv-i<)9 or uv-2oiA.
HOW MUCH IS THE AVERAGE RECEIVER USED?
\ A/HEN a user asks "How long will my
* ' B battery last?" he wants to know
how long it will be before he will have to
buy another battery. He does not want
to be told how many hours of operation he
will get from his battery because he does
not know how much he is going to use his
receiver, and therefore he cannot tell how
soon he will have to renew his batteries.
The other horn of this dilemma is that the
life of a B battery, in terms of elapsed time,
rises and falls with the extent to which it
is used. Therefore, a satisfactory answer
forces us to a consideration of the average
hours of use of a radio receiver. This is a
fertile subject for discussion among radio
fans and, in general, one man's opinion has
been as good as another's because they have
all been opinions rather than facts drawn
from extensive investigation. We are for-
tunate in having available a considerable
amount of data which warrants the con-
clusion that average year-around use is in
the close neighborhood of two hours daily.
We have, therefore, based all of our battery
life figures on a two-hour daily use. Any
reader who feels that his use is more or less
than two hours per day, should decrease
or increase the figures given, accordingly.
In those rare instances where the average
use exceeds three hours daily, the battery
life should be somewhat more than pro-
portionately decreased. Similarly, if the
average use is less than one and one-half
hours' use daily, the battery life should not
be increased in full proportion.
Experience has shown that the drain on
FEBRUARY, 1926
"HOW LONG WILL MY B BATTERIES LAST?"
453
FIG. 3
This is a heavy duty battery designed for use
with receivers where the current drain is 14
milliamperes or over
storage battery tubes at 90 volts and -with-
out bias is 6 milliamperes per tube, and
when using the proper C battery, this figure
is reduced to 2 milliamperes. The drain
on this tube when used as a detector is also
2 milliamperes.
The difference between the B battery
current drain of dry cell and storage battery
tubes is not great enough to warrant sepa-
rate figures or calculations for dry cell tube
sets.
We have been clearing out underbrush
all this time, so that we can see one of the
two things which we must always know to
determine how long a B battery will last
that is, the current drain on the battery.
This is now merely a matter of arithmetic,
knowing the number of tubes and how they
are used. For example: here is a three
tube set without a C battery. Its drain is
twice 6 for the two audio tubes, plus 2 for
the detector, a total of 14 milliamperes.
A C battery would change the story to
twice 2 plus 2, or 6 milliamperes. (We
never work out one of these examples of the
B battery drain with and without a C
battery, that we don't marvel afresh at the
saving involved.)
Once we know the current drain of a bat-
tery, all that we have to do to determine its
life is to put it on test at that drain and see
how long it lasts. It doesn't suffice, how-
16
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MONTHS LIFE
LIGHT DUTY
"B" BATTERIES
Based on an average a»
of two hours per day
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MILLJ-AMPERE CURRENT DRAIN
*< One to Three Tubei— ^ ThrM or Mom Tube* '
FIG. 4
All the curves shown on these pages are based on the results obtained from a test
conducted to determine the average number of hours of use of a receiving set.
The unbroken part of the curve indicates the life of a battery when used with a
receiver employing one to three tubes where the total milliampere drain does not
exceed 14 milliamperes. Where more tubes are used the drain is greater and
the battery correspondingly lasts over a shorter period
ever, to test a battery at one drain and then
calculate the life at other drains, for the
electrical capacity varies somewhat with
the drain. If a battery lasts 1000 hours at
one drain, it probably will not last a full
500 hours at twice the drain. Therefore,
the only way to determine how long a bat-
tery will last at different loads is to test it at
those loads. This has been done.
The drains chosen were 4, 8, 16, 24, and
32 milliamperes, which covers the entire
range of load ordinarily encountered.
Several tests were made for each drain at
different periods and each test represents
the performance of several batteries.
The entire series of tests were made on
two sizes of batteries, designated as the
Light Duty and the Heavy Duty. The
illustrations in Fig. i show the size of the
FIG. 2
Several types of B batteries, varying both in voltage and size. All are for light duty
cells used in the Light Duty and in the
Heavy Duty battery. The illustrations
in Fig. 2 show the three common forms of
the Light Duty battery — the 22^-volt
unit which is sometimes referred to as the
"5-pound battery" and the vertical and
horizontal forms of the 45-volt unit.
The size of the cells in a battery deter-
mines its electrical capacity, not the num-
ber of cells and the voltage. The 22^-volt
and 45-volt units shown in Fig. 2 are all
Light Duty batteries, even though one is
twice the weight and dimensions of the
other.
Fig. 3 shows the Heavy Duty battery
which is generally made only in a 45-volt
unit.
One of the results of the elaborate series
of tests on the two sizes of batteries has
been to enable us to determine the field,
i.e., the drain, where each is best suited.
The answer is this: — Use the Light Duty
on all drains below 14 milliamperes and the
Heavy Duty on all drains above 14 milli-
amperes. An approximate rule, in terms
of the number of tubes, is: — The Light
Duty battery should be used on sets of one
to three tubes; the Heavy Duty size on sets
of four or more tubes. Let it be noted with
all possible emphasis that the rule makes
no mention whatever of the smaller size
batteries. This is because the Light Duty
size is more economical than any of the
smaller size batteries however low the drain.
The justification for the smaller size bat-
teries lies entirely in their portability, never
in their economy.
When we tell how to fit the right size
battery to a receiver in terms of the milli-
ampere drain of that receiver there are
practically no exceptions, for we are deal-
ing with a fixed electrical unit: the mil-
liampere; when, however, we talk in terms
of number of tubes, a simple unit, under-
454
RADIO BROADCAST
FEBRUARY, 1926
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MONTHS LIFE
HEAVY DUTY
"B" BATTERIES
OF
:YLINDRICAL CELLS
iased on an average us*
of two hours per day
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MILLI -AMPERE CURRENT DRAIN I
V Orw.Two or \ More than Three Tubes
FIG.
Where the ordinary heavy duty battery is employed for receivers having more
than three tubes, the period of life is greater as can be seen by the above curve,
than if light duty batteries were employed
standable to all, we obtain a simple rule,
but, like most simple rules, there are ex-
ceptions.
"One to three tubes" covers most sets
below 14 milliamperes, and "four or more
tubes" covers the great majority of sets
whose drain is above 14 milliamperes. One
exception is that of one model of the
Radiola super-heterodyne, which is so
designed that, although it employs six
tubes, the drain is only 12 to 13 milli-
amperes. Another exception is the four-
and five-tube receivers, recently described
in RADIO BROADCAST, which are so con-
structed that their drain is much less than
14 milliamperes. There are, therefore,
certain exceptional cases where the Light
Duty battery is the proper size for sets of
four or more tubes.
Practically no one uses the Heavy Duty
battery when the Light Duty battery should
be used. A recent survey has indicated,
however, that a large proportion of the
radio users are making the rather serious
mistake of using the Light Duty when they
should be using the Heavy Duty battery.
The use of the Heavy Duty battery on sets
of four or more tubes is not only much more
economical, but also raises still further
the high convenience factor of dry cell B
batteries.
At last we have come to the point where
we can discuss B battery life, for we know
now the two essential factors, the current
drain, and the correct size of battery to
use for that particular drain. The rest is
clear sailing.
THE LIGHT DUTY BATTERY ON ONE- TO
THREE-TUBE SETS
THE curve in Fig. 4 is derived from the
data furnished by the tests on the
Light Duty battery. To "work" the
curve is easy. Take the three-tube set
about which we have already spoken. The
drain without a C battery was 14 milli-
amperes. Reference to the curve shows
that at this load, the life is 6.4 months.
With the set pulling only 6 milliamperes
when a C battery is used, the life is just
fifteen months. "Too long," you say.
You don't believe it? Very well, we won't
quarrel. You and I both know that
Niagara Falls is very, very high, but neither
cares whether it is actually 250 or 400 feet
from top to bottom. Let's say "more than
a year" for the life of the battery and let it
go at that.
The curve does not show battery life
for drains of less than 6 milliamperes be-
cause there is little interest in a life of over
fifteen months, and also because we do not
wish to overtax the reader's credulity.
We have said that the Light Duty bat-
tery should not be used on drains in excess
of 14 milliamperes but we have extended
the curve in a dotted line up to 27 milli-
amperes. This makes it possible to deter-
mine the life of the Light Duty battery
even when wrongfully used on excessive
drains.
Another way of expressing the same data
given by the curve in Fig. 4 and of avoid-
ing the necessity of even thinking milli-
amperes, is shown in the following table:
LIFE OF LIGHT DUTY B BATTERY
(Based on average use of two hours per day)
NUMBER WITHOUT C
OF TUBES BATTERY
1 More than a year
2 1 1 months
3 6 months
WITH c
BATTERY
More than a year
More than a year
The shortest life in the table is six
months, i.e., two renewals a year. The
Light Duty story then comes down to this:
When properly used, this battery will not
require more than two renewals per year
for two hours' use per day.
THE HEAVY DUTY BATTERY ON SETS OF FOUR
OR MORE TUBES
THE life of the Heavy Duty battery
under various drains is shown in Fig.
5. In this case the curve is dotted below
14 milliamperes — the field of lower drains
where the Light Duty battery is better
suited, as previously discussed.
The life of this battery on a five-tube
neutrodyne with a C battery on the audio
stages is worked out thus: Two radio fre-
quency stages at 6 milliamperes each is 12;
the detector at 2 and each audio stage also
at 2 — totals 1 8 milliamperes. The curve
shows the life to be 8 months.
A substitute for the curve is given in the
following table:
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MONTHS LIFE
NEW TYPE FLAT CELL
HEAVY DUTY
"B"BATTERIES
Based on an average us
of two hours per day
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2 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
MILLI-AMPERE CURRENT DRAIN
FIG. 6
This curve of a newer type of heavy duty B battery shows conclusively that
where high drain is to be experienced and where long life is to be expected, the
flat type cell unit approximates, more than the other types, the ideal condition
FEBRUARY, 1926
"HOW LONG WILL MY B BATTERIES LAST?1
455
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A- Light Duty B Batter
B- Heavy Duty B Bat^
(Cylindrical C«lb>
C- Heavy Duty B Batte
(New Type Flat Cells)
BaseH on use of two noun
per day
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MILLIAMPERE CURRENT DRAIN
FIG. 7
This composite curve illustration shows very definitely the com-
paritive longivity for three types of batteries, where the current
drain is the same in each case
LIFE OF HEAVY DUTY B BATTERY
(Based on average use of two hours per day)
NUMBER OF
TUBES
4
5
6
WITHOUT C
BATTERY
*6
WITH C
BATTERY
Over a year
8 mos.
6 mos.
This figure is slightly higher than is shown
by the curve when using the calculated current
drain. Experience has shown, however, that
six months' life is generally obtained. This
longer life results from operating the receiver at
lower drains in order to avoid the distortion
which accompanies high volume in the absence
of a C battery.
The space for the battery life on a six-
tube set without a C battery is left blank
for we are not familiar with any six-tube,
factory-made set now being produced which
does not use a C battery.
Here again it will be noted that the
minimum life to be expected from the
Heavy Duty battery is six months, or two
renewals per year, based on 2 hours' use
per day.
The new type of dry cell battery, con-
sisting of flat cells piled on each other layer
by layer, instead of the conventional cylin-
drical cells soldered together, is a special
case under Our discussion of the Heavy
Duty size battery. The external dimen-
sions and general characteristics of this
new type of battery are the same as those
of the Heavy Duty battery. The differ-
ence lies in the higher capacity and longer
life of the new battery. The flat construc-
tion results in the use of more of the active
chemical ingredients per unit of volume
because it avoids the wasteof space between
the cells in the cylindrical type of battery.
The curve in Fig. 6 shows the life of this
flat cell, Heavy Duty battery at various
drains.
POWER TUBES
\A/E MUST also consider the effect of
' ' the new, highly important power
tubes, ux-i 12, ux-120, and others on B bat-
tery life. The situation is a bit complicated
technically, but is most simple from the
standpoint of results, particularly when we
confine our attention to those cases where
practically all the power
tubes will be used, i.e., in sets
of four or more tubes.
The new power tubes must
be used with a C battery.
Therefore it is necessary to
provide C battery connections
in order to use either of these
tubes in sets which were for-
merly without a C battery.
The net result of the change
will be a decrease in B bat-
tery drain, and hence longer
battery life.
The drain of these power
tubes when properly biased
averages around 5 or 6 milli-
amperes. This is 3 or 4 milli-
amperes more than that of
the biased tube which it replaces. The
use of either of these power tubes on a
set already equipped with a C battery
will therefore increase the total drain about
twenty per cent.
In selecting the proper size batteries for
multi-tube sets employing either of the new
power tubes, one point should be kept in
mind. The Heavy Duty size will, of course
be chosen to supply the original 90 volts,
but the battery which furnishes the "top
45 volts" to supply 135 volts to the power
tube should be of the Light Duty, not the
Heavy Duty, size. This "top" 45 volt
battery carries the 5 or 6 milliampere drain
of the power tube only, and will therefore
last "more than a year."
Articles on " How to Build a Radio Re-
ceiver, How to Erect your Antenna," in
fact all the "How to" articles on radio
generally have a paragraph near the end
on "How to look for trouble," as though it
were necessary to search for it. But the
precedent is too strong to break. We shall
therefore include the customary para-
graph of warning and advice.
Thefigures on the B battery life are based
on proper radio equipment and normal
operating conditions. They will not apply
under such conditions as:
(1) Leaving the set turned on for a week and
then forgetting that you did so.
(2) Use of tubes which have an abnormally
high B battery drain (an occasional misfor-
tune.)
(3) A faulty by-pass condenser or any form of
short circuit which continuously drains
the B battery.
(4) Chronic over-burning of the filaments.
(5) When using old exhausted tubes which
need renewing or re-activating.
(6) Failure to renew an exhausted C battery.
(7) Leaving the shears resting on the battery
terminals over night.
The next time any one asks us how long
his B battery will last we shall not ask a
single question, but immediately reply,
"Six months at least, generally eight
months and often a year or more." Then
if the combination of a New England
conscience and an engineering training gets
in its deadly work, we will be forced to add
"Of course you understand that this an-
swer is based on your using batteries of
proper size and of a reliable make and also
on an average use of your receiver of two
hours per day."
We might also go on to explain that there
would be occasional, rare cases where the
battery life would be only four or five
months but that for every such case there
would be literally thousands of instances,
even with multi-tube sets, where the bat-
tery life would be in the nine- to twelve-
month range.
FIG. 8
It is usual in depicting the circuit diagram of the Browning-Drake receiver described in the De-
cember, 1924, issue of Radio Broadcast, to represent the batteries employed, symbolically. Here
is the diagram showing actual illustrations of batteries connected in the circuit. The reader, how-
ever, will do well to become accustomed to the symbolical representation of batteries and other
parts of radio circuits
How to Use Vacuum Tubes
A Clear Explanation of How and Why Tubes are Rated as to Amplification Constant, Mutual
Conductance, Plate Impedance, Etc. — How to Make and Use a "Characteristic Curve" — Answers
and Explanations for the Most Commonly Asked Questions About the Use of Receiving Tubes
By KEITH HENNEY
F ALL the various instruments that go
to make a radio receiver, there are
none that approach the vacuum tube
in importance. In the majority of
receivers to-day the tube is the most essential
accessory, and upon its proper operation depend
all of the qualities of which the owner of the re-
ceiver brags. The sensitivity of the receiver,
the volume and quality of reproduction, the
economy of operation, all rest upon the tubes
that are used and the manner in which they are
operated.
Therefore, it behooves the owner or builder
of a radio receiver to become as well acquainted
as possible with the various functions which
his tubes perform, and to know what happens
when he does this or that to those small bits of
glass and metal.
In the December RADIO BROADCAST, the use
of new semi-power tubes was discussed and the
connection between undistorted audio output
and the operating conditions of tubes was out-
lined. Data on the amount of power necessary
to operate a loud speaker properly and the
power obtainable from various tubes were given.
It was pointed out that the purchase of high
quality audio transformers, or cone type loud
speakers was futile unless one used a tube with
an output of about .06 watts to operate the loud
speaker; that sufficient power was not obtainable
from a single dry-cell tube to operate a cone
type speaker without distortion; and that the
"scratching" in cone speakers was due, in the
vast majority of cases, not to the speaker but
to the amplifier which was overloaded.
In this article some of the other important
3 -
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f
Ep-SO I
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199
I
I
Ep
•90
/
/
FIG. I
These curves show the relation between the filament vol-
tage and the plate current, giving plain evidence that it
is useless to run filaments above their rated voltage.
Attention is called to the plate and grid voltage conditions
under which these curves were made
Director, Radio Broadcast Laboratory
< / JLHIS is a most unusual article in many ways.
'>••' For one thing, it contains the most up-to-date
presentation of information on the use of commer-
cially available vacuum tubes which has so far been
presented. The curves and tables in this article are
the result of tests on more than 250 tubes and show
the amount of worl( which has gone on recently in the
Laboratory. The data given here shows, for example,
what C battery potential to use with a given B battery
voltage, and what the effect of varying either or both
is. The curves show also, the proper filament poten-
tial which should be applied to many types of tubes
for greatest efficiency. All in all, this is in reality a
semi-technical guide boo}{ to radio tubeland. The
first article in this group appeared in this magazine
for December, and another will be published in an
early number which will conclude this series, prepared
by Mr. Henney, director of the RADIO BROADCAST
Laboratory. — THE EDITOR
aspects of vacuum tube operation will be dis-
cussed, and an attempt will be made to clear up
some misunderstanding with regard to what is
generally considered as complex tube terminol-
ogy.
For example, nearly everyone will say that a
tube should have a high value of mutual con-
ductance. But what does nearly everybody
understand by this high sounding phrase? And
what is a characteristic curve, how is it made,
and after one has it, of what use is
it? What of amplification
constant, "high mu,"
plate impedance, etc. What
do these terms mean?
It must be understood,
first of all, that a tube is a
complex creation, that its
actions are always con-
trolled by certain boundary
conditions which surround
it, and that everything that
it does is a product of not
only one external cause,
but of several. It will be
possible to treat of but few
of the important aspects
of vacuum tube theory
and practice in this article,
or to more than scratch
the surface of those few.
Readers are referred to
Professor Morecroft's excel-
lent book, Principles of
Radio Communication,
which has nearly half of its
1000 pages devoted to
vacuum tubes, and to the
standard jSj-page text of
Van der Bijl, Thermionic
Vacuum Tubes.
SOME FACTS ABOUT THE FILAMENT
A TUBE consists of a glass container into
^* which are sealed three metallic elements,
after which the air and gas sealed into the tube
are pumped out. The most important of these
elements is the filament. It is the thing that
lights up when the A battery is placed across its
ends; and which blows up when the B bat-
tery is accidentally connected to the terminals.
When the filament is dead the tube might as
well be buried. And when the filament wire is
poor, the tube is poor. And that's that.
In general there are three types of filament
now being sealed into glass containers for radio
use, the tungsten filament, the thoriated filament
and the oxide filament. The tungsten is repre-
sented in the detector tube, uv-2oo, thoriated
filaments are in the newer types, the 2OI-A,
the 199, the 120, and similar tubes, and oxide
filaments are used in Western Electric tubes as
well as the wo-12, and the ux-i 12.
The pure tungsten filament and the oxide
coated filaments are the oldest of the present
types. Pure tungsten must be heated to a
much higher temperature than either the thori-
ated or the oxide filament before it emits suffi-
cient electrons for ordinary operation. In
other words it is not so efficient, for more
electrical "filament power" must be expended
to get a given number of electrons. The data in
Table i represents the filament efficiency of
several tubes under average operating conditions
and shows the plate current in milliamperes
per watt expended in heating the filament.
Many questions are asked the Grid department of this
magazine concerning the proper method of connecting
A, B, and C batteries together. These diagrams give three
possible connections, giving in each case the resultant
filament, grid, and plate voltages. It has become standard
practice to connect negative A, negative B, and positive
C together
FEBRUARY, 1926
1
1
r
•199
60 80
PLATE VOLTS
FIG. 3
The effect of increasing the plate voltage on var-
ious standard tubes is shown in this Figure.
Data for these curves was made at rated filament
voltage and at zero grid voltage.
Oxide filaments are made by a complicated
process of baking on to the surface of a platinum,
or other metallic wire the oxides of strontium,
barium, and calcium, which emit electrons at a
low temperature. In Europe such tubes are
known as "dull emitters" since they
are operated at a dull red heat and
never as bright as the tungsten or
the thoriated wire. Thoriated fila-
ments are the result of a fortunate
accident in the laboratories of the
General Electric Company. A cer-
tain run of tubes was found to be
very efficient, much more so than
usual. It was found that the fila-
ment wire had come from a con-
tainer in which thorium had been
treated. The tungsten had com-
bined with some of the thorium
which like the oxides of the ele-
ments mentioned above emits elec-
trons at a low temperature.
The result of this important dis-
covery, that thorium mixed with
the filament wire would increase
the filament efficiency, was the pro-
duction of the tubes with which
everyone is now familiar. Instead
of a tube filament that needed one
ampere at <j volts to get the proper
number of electrons, present day
tubes require but one fourth of this
current. Four of the thorium tubes
can be run at the same expense as
one of the old ones. It may be in-
teresting to those who stilfuse the
soft detector tube, uv-2oo, to know
that it requires more current than
three of the 201 -A type.
The charts in Fig. i show the plate
current in milliamperes of several
important tubes for various filament
voltages. They show the futility of
burning tubes beyond their rated
voltage, for above that point
there is slight increase in plate
current. Furthermore, pushing up
HOW TO USE VACUUM TUBES
the filament voltage is one of the most certain
methods of decreasing the life of the tube.
For this reason a filament voltmeter is an im-
portant and economic addition to any existing
receiver.
THE PART PLAYED BY THE GRID AND PLATE
PHE other elements in the orthodox tube
play important parts in the operation of this
remarkable device. The plate has been men-
tioned already. It is maintained at a positive
voltage with respect to one end of the filament
by means of the B battery. The electrons
coming from the heated filament are attracted
toward the plate, because they are negative
quantities of electricity. Each electron that
arrives at the plate represents a certain flow of
electric current, and the sum total of this elec-
tronic flow makes up the plate current. The
plate battery supplies the energy for this transfer
of electrons as shown in Fig. 2.
The number of electrons that flow to the plate
depends upon at least two factors, the filament
temperature, and the plate voltage. Under
ordinary conditions the filament is heated to the
point where further increase in temperature has
no effect on the plate current. In other words
the tube is operated under the condition of
"filament saturation."
Under this condition the plate current is a
function of the plate voltage, and Fig. 3 shows
the effect of varying the B battery voltage while
a constant A voltage is applied to the filament
and a constant voltage is on the grid.
The grid is a mesh of wires placed between the
filament and the plate. It, too, has control
over the flow of electrons toward the plate for
when negative it repels the negative electrons;
when it is positive it draws more electrons out
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GRID VOLTAGE
6
8
10
FIG. 4A
FIG. 40
Characteristic curves, plate current vs. grid
voltage, are shown here. Increasing the plate
voltage on amplifier tubes makes it possible to
use much greater C voltages, with the result
that greater input voltage may be used without
distortion due to "overloading." The lower
curve of the 2O1-A tube at 45 plate volts is an
indication of an excellent detector. The long
straight portions of the 201 -A curves are the
parts that are useful for amplification
into the space between the elements, and the
plate current increases— provided the filament
temperature is up to the required point.
It is a matter of great importance that the
-voltage of the grid has more effect on controlling
the plate current than has the plate voltage.
It is for this reason that the tube amplifies, and
carries out its other multitudinous functions.
If the grid has ten times the effect that the plate
voltage has upon the plate current the amplifica-
tion factor of the tube is said to be ten, and so on.
The manner in which the grid controls the
plate current may be seen in Fig. 4A which is a
"characteristic curve" of an average ;-volt
receiving tube of the 201 -A type. There are
several curves on this plot, each one representing
the effect of the grid voltage and each taken at a
different value of plate voltage.
There are, then, three factors which control
the plate current of a vaccum tube, the filament
voltage, the plate voltage and the grid voltage.
458
RADIO BROADCAST
FEBRUARY, 1926
TABLE 1
TUBE
MILS PLATE
CURRENT
FIL. WATTS
MILS PER
WATT
MILS PER
WATT PER
DOLLAR
199
3.2
.18
17.8
7.10
201
7.6
5.00
1.52
201-A
7.6
1.25
6.1
2.44
120
7.0
.375
18.7
7.45
112
14.4
2.5
5.75
.89
12
3.6
.275
13.10
5.24
As stated before, tubes are usually operated
under the condition of filament saturation, that
is, the conditions are stable with regard to the
filament voltage. This leaves only two factors
which control the plate current, and since a tube
is usually operated with a fixed value of plate
voltage, it is only the fluctuating grid voltage
that varies the plate current.
WHAT CHARACTERISTIC CURVES MEAN
XTOW let us see how these characteristic
' curves are made, and what they mean.
Suppose that in our home laboratory we have a
double range voltmeter, such as the one made
by Weston Electric Instrument Company, or the
Jewell Model 55, or Hoyt type 17. Such a
meter will read from zero to about 10 volts
and from zero to about 100 volts. Thus it will
measure the voltage across the filament and on
FIG.
A simple arrangement of apparatus by means of
which characteristic curves of Fig. 4 may be
taken. With proper switches, two meters will
suffice for this experiment, a milliammeter and
a double-range voltmeter
Value of steady
D.C. plate Current
the plate or grid of an average
tube. Let us connect it first
across the filament of a 2OI-A
type tube, regulate the rheostat,
as shown in Fig. 5 until we have
the required 5 volts on the fila-
ment. Then the meter should be
placed across the B battery. Now
we know that the tube is oper-
ating under the proper condi-
tions and all we need to make
a characteristic curve is a plate
ammeter such as a zero to 5 or 10 milliam-
meter, Weston or Jewell, which is placed in
the circuit between the plate of the tube and
the plate battery as shown in Fig. 5. A poten-
tiometer placed across a C battery will give us
variations in grid voltage which may be meas-
ured as in Fig. 5 and placed on the grid of the
tube. As a matter of rough measurement, the
potentiometer is not necessary, and indeed our
C battery will last considerably longer if the
potentiometer is not used.
The low range part of the voltmeter is now
placed across the grid and filament to show what
voltage is being placed on the grid. The grid
voltage is then varied and each change in plate
current noted as shown in the data for Fig. 4A.
It will be found that for large negative values
of grid voltage the plate current
will be small, and that for less
negative grid voltage the current
increases. This is one reason why
a C battery on a modern five-tube
receiver is quite essential. It re-
duces the plate current of a single
tube from about 7 milliamperes to
about 3. After zero grid volts is
reached, the C battery must be re-
versed in order that positive volt-
ages may be supplied. Care must
be taken in this process, or the mil-
liammeter will be injured, since a
positive grid permits a large plate
current to flow.
For this reason a tuned radio
frequency receiver which uses a po-
tentiometer to stabilize the radio-
frequency amplifier is an expensive
proposition. In order to keep the
amplifiers from oscillating, the grids
must be kept positive by a certain
amount. This means that two am-
plifier tubes will draw considerable
current from the B battery
Now that we have collected
this data on the relation between
grid voltage and plate current,
12
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11.8300
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1 20 40 GO 80 100 120 U
PLATE VOLTS
FIG. 7
A method of obtaining the plate impedance of a
tube. Only the straight part of the curve is to
be used, and the proper values of plate current
and plate voltage may beobtained from the curve.
To simplify the calculation, the straight part
of the curve is prolonged to the zero current line.
In mathematical language, the plate impedance
is the slope of the plate current-plate voltage line
TABLE 2. 201-A TYPE TUBES
TUBE
NO.
TESTED
PLATE
CURRENT
AMP.
CNST.
PLATE
IMPEDANCE
MUTUAL
CONDUCT-
ANCE
Arion
4
1.9
9.2
14,400
638
Kismet
3
2.60
7.75
13,250
590
Ureco
8
2.62
8.15
12.300
660
Gold Seal
6
2.43
8.13
13,000
630
Duotron
9
1.83
10.00
16,000
615
Van Home
12
2.64
8.63
12,800
677
Sylfan
6
3.00
6.90
12,800
542
Sylvania
6
2.63
8.29
11,350
735
Sturdy
2
2.90
8.20
12.500
678
Magnatron
6
2.75
8.00
12,250
652
Goode
3
2.50
7.90
12,000
658
Empire-
Tron
2
1.80
9.50
16,500
581
CeCo
9
2.2
8.48
14,300
592
R. C. A.
6
3.40
7.53
10,100
745
Marathon
2
2.60
8.20
11,500
712
Supertron
3
2.00
9.50
14,600
680
Sea Gull
12
3.60
6.70
10,600
640
Boehm
4
3.62
7.10
9,740
734
Speed
5
3.82
7.35
9,950
734
Ken Rad
5
2.78
8.24
12,400
677
Cleartron
6
4.2
6.75
9,450
715
Ferryman
6
3.98
6.53
9,750
670
AVERAGE
125
2.59
8.2
12,700
660
CONDITIONS
FILAMENT VOLTS GRID VOLTS PLATE VOLTS
5 —4.5 90
¥\
A.C.plate
current
bias voltage
Input voltage wave
FIG.
Three curves showing the effect of proper and improper C bias are shown in this illustration.
It will be noted that when the grid goes negative, the plate current decreases. In (a) the
correct C voltage is used so that the plate current is a perfect reproduction of the incoming
wave. When the C bias is too negative, the lower parts of the plate current curve are cut
off. In other words the plate current is actually brought to zero at times. On the other
hand in (c) when there is not enough C battery used, the grid goes positive at times, and the
tops of the curves are cut off. Both of these latter cases produce distortion of the worst type,
most easily detected by watching a milliammeter in the plate circuit. If the needle jumps
about, one of the two latter cases is in effect
we may try another value of B battery and re-
peat the experiment. In this manner data for the
three curves shown in Fig. 4A, B and C were taken .
The only thing that remains is to plot the data
in a curve which gives a complete picture of
what happens to the plate current under varia-
tions of the grid and plate voltages. They
are called "static" characteristics because they
were made under static conditions, that is not
under the exact operating conditions, for in
actual practice there is a load of some kind, in
the plate circuit, such as a pair of receivers,
a transformer primary, or a large resistance,
whose characteristic, when alternating voltages
are applied, differs from its direct current
characteristic.
Now to see what these curves tell us, let us
look at them rather closely. It will be seen that
increasing the plate voltage increases the plate
current. For instance let us look at the curves
in Fig. 4A at the exact center of the picture at
zero grid volts. With 45 volts on the plate, the
FEBRUARY, 1926
HOW TO USE VACUUM TUBES
459
32.000
30,000
28,000
\
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
\
\
v
Eg
-0
24.000
22.000
g 20.000
J 18.000
g iwoo
I
.1 14,000
E 12.000
•10.000
8.000
6,000
4X100
2X»0
1
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A
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1 10 20 30 40 50 60 70 80 90 100 110 120 130 140
PLATE VOLTAGE
FIG. 8
The three important tube factors, plate impedance,
amplification constant, and mutual conductance all
vary with plate voltage and with grid voltage. This
curve shows how these factors vary with plate voltage
plate current of the 2O1-A is 2.2, with 90 volts,
the current is 7.6, and with 135 the current is 13.
Also it will be noted that increasing the grid
voltage increases the plate current. For ex-
ample let us take the go-volt curve. At nega-
tive 2 grid volts, the plate current is 5.6 milli-
amperes and at positive 2 the plate current is
9.7. It will be seen at once that the grid voltage
has greater effect than has the plate voltage.
The ratio of these effects is known as the ampli-
fication constant of the tube. For example it
FIG. 9
A diagram of the bridge used in RADIO BROAD-
CAST Laboratory for determining tube character-
istics. The resistances Ri and R2 may be a
simple slide wire bridge or they may be decade
resistance boxes. To measure amplification
constant, open switch No. i, throw No. 2 to the
left, close No. 3. Then when silence is obtained
in the phones, M = R2/Ri. To measure plate
impedance, close No. i, throw No. 2 to the right,
Ri x 10,000
open No. 3. Then Rp
The
R,.
tentiometer across the input with the variable
arm grounded is useful in obtaining a balance
will be found from this
data that it requires only
5.5 volts change in grid
potential to produce the
same change in plate cur-
rent that 45 plate volts
change produced. Inother
words the amplification
factor is -£§• or 8.2.
This may be stated as
follows:
Amplification factor
^change in plate volts
change in grid volts
to produce the same change in
plate current.
PROPER USE OF THE C
BATTERY
I TNDER actual operat-
^ ing conditions, the
plate is maintained at some
definite value, say 90 volts, and the grid
is biased negative by a definite value,
say 4$ volts. The incoming signals
which are impressed on the grid are
alternating in value, and they cause the
actual voltage on the grid to vary from
42 as a mean value. For instance, let
us suppose that the tube is the second
audio amplifier tube and that fluctuat-
ing voltages of a maximum, or peak,
value of one volt are coming from the previous
audio stage. When the impressed alternating
voltage is positive the actual negative grid
voltage is 45 minus i volt or 35 and when this
a.c. voltage is negative, the negative bias on the
grid has been increased to 55 volts. In other
words the voltage actually on the grid varies
from 35 to 55 volts.
We may see how the plate current varies with
these changes in grid voltage by noting the
proper values from the characteristic curve.
Fig. 6 gives a picture of the process showing
that small changes in grid voltage produce large
changes in plate current.
Now for distortionless amplification, only the
straight part of the curve may be used, and the
grid must never be permitted to become positive.
This limits the input grid voltages to certain
definite values. The characteristic curves shown
above indicate the proper value of C battery
that is to be applied to an amplifier tube with a
given value of B voltage. For example it will
be seen that if the grid of the tube shown in Fig.
4A at 90 volts B battery goes negative by 4 volts
it will be approaching the lower bend in the curve
while if it goes beyond 45 volts positive, the grid
will actually be positive with respect to the
filament and distortion is inevitable.
To find from the curve the proper C voltage
it is only necessary to measure the length of the
straight part of the curve. For example at 90
volts the length in volts is about 9 volts. Then
the C bias is about half this or 45.
At 135 volts B, about 9 volts C
battery may be used.
In an article by Mr. George Crom
in RADIO BROADCAST for October
the effect of impi oper C and B bat-
teries was discussed. A considera-
tion of the chaiacteristic curves
shows what actually happens when
incorrect values are used. For ex-
ample, when ths grid is forced
too negative by input voltages,
the curved part of the character-
istic will be used with the re-
sult that harmonics are added to
the original sounds coming from
the broadcasting microphone. If
TABLE 3. 199 TYPE TUBES
NO.
PLATE
AMP.
PLATE
MUTUAL
TESTED
CURRENT
CNST.
IMPEDANCE
COND.
Arion
5
2.00
6.8
19,650
346
CeCo
3
2.33
6.1
16,900
361
Jove
6
1.87
6.0
22,800
268
Gold Seal
3
1.50
6.3
35,400
207
Sylvania
6
1.87
6.0
19,600
305
Ferryman
2
1.80
6.35
21,475
296
Van Home
5
2.66
7.35
24,500
305
Magnatron
6
2.60
6.5
18,500
350
Empire-
Tron
2
1.70
7.1
23,400
303
Speed
3
2.2
6.0
19,500
310
Ken Rad
5
2.0
6.76
22,800
300
R. C. A.
5
2.5
6.3
18,600
332
TOTAL
51
2.00
6.5
22,400
304
CONDITIONS
FILAMENT VOLTS GRID VOLTS PLATE VOLTS
3 —4.5 90
still greater negative values are impressed on
the grid, or if the grid is biased too negatively,
the lower parts of the waves will be cut off as
shown in Fig. 6 resulting in still greater distor-
tion. As mentioned in Mr. Crom's article, a
milliammeter in the plate circuit of such a
tube will show an upward deflection under such
conditions. The remedy lies in increasing the
plate voltage to the values he specified.
Fig. 6 also shows the effect of too little C
battery. In this case a strong signal will force
the grid positive at times which again results in
distortion, though of a slightly different nature.
In this case the plate current will decrease as Mr.
Crom pointed out. Increasing the C battery
negative potential will eliminate this difficulty.
An amplifier that is working properly, with
correct B and C batteries will turn out a dis-
tortionless output — as far as the tubes are con-
cerned— only when a milliammeter in the plate
circuit remains steady. This is the best method
of investigating the conditions under which an
amplifier works. In a great many cases the C
battery value is much too low to take care of
loud signals. Increasing the C battery, however,
without making corresponding changes in the B
voltage is fatal, as Fig. 6 indicates.
Fig. 4 shows the effect of increasing the B
battery voltage. The straight part of the char-
acteristic is much longer, a fact that has import-
tant consequences. Greater values of C bias
may be used, greater input voltages may be
applied without distortion, and the tube will
have a lower plate impedance. This latter fact
is explained later in the present article, and the
value of a low plate impedance was mentioned
in the article on tubes in the December RADIO
BROADCAST.
The curves in Fig. 4, known as the static
characteristics of the tubes in question, reveal
many interesting facts. For instance the
method of calculating the amplification factor
TABLE 4. SEMI-POWER TUBES
TUBE
PLATE
CUR-
RENT
AMPLIFI-
CATION
CONST.
PLATE
IMPED-
ANCE
MUTUAL
COND.
POWER
OUTPUT
Daven
Mu-6
Cleartron
CeCo
Ureco
UX-112
216-A
Van Home
8.7
6.0
5.8
8.0
5.8
7.4
4.7
6.35
6.35
7.0
6.8
7.9
6.0
8.65
5,350
5,340
6,700
5,570
6,000
6,000
8,050
1,190
1,190
1,050
1,235
1,315
1,000
1,075
.076
.076
.060
.084
.105
.060
.0936
CONDITIONS
FILAMENT VOLTS GRID VOLTS PLATE VOLTS
AS RATED — 9 135
460
RADIO BROADCAST
FEBRUARY, 1926
of the tube has been mentioned. It is only
necessary to measure along the zero grid line
the number of milliamperes change in plate
current produced by varying the plate voltage
from 45 to go, and to take any of the three curves
and find out how many grid volts change are
required to produce the same change in plate
current.
THE MEANING OF " PLATE IMPEDANCE" AND
"MUTUAL CONDUCTANCE"
^OW there are two other important tube
* factors, known as the plate impedance,
and the mutual conductance. The plate im-
pedance is defined as the change in plate current
a given change in plate voltage produces. This
may be expressed as below
plate voltage change
Plate impedance = p,ate curfent change
and using the values ascertained for calculating
the amplification constant, the plate impedance
of the tube under question is
ohms
This value may be obtained directly from the
plate current — plate voltage curve, Fig. 3.
Fig. 7 shows how this may be done. This
second method is more accurate, since the plate
impedance varies with each change in plate or
grid voltage. For that reason it should be
calculated for small changes and only over the
straight part of the characteristic.
The mutual conductance of the tube is an im-
portant factor, since it is an expression for the
value of the grid voltage in controlling the plate
current. It is defined as
change in plate current
mutual conductance = cllinge in ^rid volts
For example from Fig. 4A we see that a change
of ten volts on the grid, from plus 6 to minus 4
of the 135-volt 201 -A curve produced a change
of 6.9 milliamperes. Therefore
mutual conductance = . 0069 amperes = .00069 mhos.
10
or expressed in the usual units of micromhos
the mutual conductance of the tube under
question is 690.
This may also be obtained from the interesting
relation between amplification constant and plate
impedance,
mutual conductance = amplification constant, or Gm = (X
plate impedance Rp
showing that the best tube is one with
a high amplification constant and a low
plate impedance — but in popular lan-
guage "try and find one."
All three of the tube factors, (i, Rp,
and Gm vary with grid voltage and
plate voltage as the curves in Fig. 8
show. For purposes of power amplifi-
cation a low plate impedance is of im-
portance, and the effect of increasing
the plate voltage to produce this low-
ered impedance is clearly indicated.
For voltage amplification, a high am-
plification constant is important.
The effect of tube impedance on the
characteristics of an audio-frequency
amplifier was shown in Curve 2 in
the article by Kendall Clough in the
January RADIO BROADCAST.
Anyone can verify the improvement
in signal quality with the use of low
plate impedance tubes by noting the
difference when substituting a high im-
pedance tube, say a 199, or a tube
designed for resistance-coupled ampli-
fiers for the final tube in a transformer-
coupled set. The low notes of the viols
and horns will be lost in the latter case
but will suddenly reappear when the low
impedance tubes are again replaced.
Characteristics of these tubes were dis-
cussed in the December RADIO BROAD-
CAST, page 163, and were found to be
an extremely important advance from
the standpoint of quality.
The methods outlined above for
obtaining the important tube charac-
teristics required only two meters, a
milliammeter and a double range
voltmeter. The method is not so accurate as
that employed in well equipped laboratories,
but is sufficient for all practical purposes pro-
vided small changes of plate and grid voltage
are used.
In the RADIO BROADCAST Laboratory a special
bridge is used which places an a.c. voltage on the
grid and measures the factors of the tube under
conditions that are closer to actual operating
conditions. A diagram of connections is given
in Fig. 9 and by the proper use of switches, only
two meters are necessary. The source of a.c.
tone may be obtained from a buzzer or from a
4000
FIG. I 1
The effect of grid voltage is clearly shown in this figure.
Plate current, plate impedance and amplification con-
stant all vary with changes in grid voltage. Mutual
conductance may be obtained by dividing the amplifica-
tion constant by the plate impedance. These curves
were made from 201 -A type tube
modulated oscillator as described
BROADCAST for September.
in RADIO
FIG. 10
A laboratory set-up for making characteristic curves of tubes. The group of instruments is a Jewell
test set and is made up of plate, grid, and filament voltmeters, and plate and filament ammeters
HOW TUBE VALUES ARE FOUND
IN PRACTICE the tube is lighted at its rated
*• voltage, the switches are thrown as indicated,
and at silence in the phones, the values are as
shown in the Figure. The accuracy of the
method is such that one can repeat measurements
to within a few per cent, depending upon the
accuracy with which the meters can be read and
readjusted to proper value. All of the data in
Table 3 were taken by means of such a bridge.
Several machines are on the radio
market which are useful in measuring the
tube constants, but attention must be
paid to the methods in which they are
used. For instance, one meter submitted
to the Laboratory measured the plate
impedance by an Ohm's law method.
It was argued that from Ohm's law,
voltage voltage
current = impedance or ""pedance = ^^
and from the data used above, impe-
dance=:5o76="840
while the actual impedance as measured
on a bridge = 7600 ohms.
The error in using such a meter is ex-
plained on page 424 of Prof. Morecroft's
Principles of Radio Communication.
In connection with tube constants
and their measurements, the question
naturally arises, at what values of grid
and plate voltage should tubes be meas-
ured and rated. At the present time
there are several points of view, to
judge from the printed matter sent out
by tube manufacturers. All tubes rated
in the Laboratory are measured under
the conditions under which they are
usually operated. For example an
FEBRUARY, 1926
HOW TO USE VACUUM TUBES
461
amplifier is usually
operated at 90 volts
on the plate and
negative 4.5 volts
on the grid. The
plate current, the
amplification con-
stant, the mutual
conductance, and
the plate impe-
dance will all be dif-
ferent under these
conditions than at
zero grid voltage.
For this reason
Laboratory meas-
urements are made
under these condi-
tions, notwith-
standing that the
fact that many tube
testers now on the
market, and in the hands of tube dealers, have
no provision for adding C batteries.
It is to be noted in this connection that the
circulars recently sent out by the Radio Cor-
poration give values for these important con-
stants under standard conditions, namely 90
volts plate and negative 4.5 volts grid. To
state tube constants at zero grid is to give no
indication of what these tubes will do under
actual conditions, and for this reason the table
of tube data included in this article gives values
at the proper C bias.
The reader who is interested in tubes and the
proper conditions under which they should work
would do well to study the booklet published
by the Radio Corporation which gives tube
constants for all of the well known detectors and
amplifiers. The reader should see that tubes
that he buys measure up to these standards,
M
FIG. 12
The main elements of a standard UV-ZOIA tube
and should not let dealers give him tubes that
the dealer has used in his own receiver — for sad to
relate, reports come frequently of this nefarious
practice.
And the data in the table of tube constants
must be considered with the proper respect for
what the ear actually hears. For instance a
tube with a mutal conductance of 650 will differ
but little — as far as the ear is concerned — from
one with a conductance of 675 or even greater.
It is probable that any of the tubes in this table
will give identical results as is pointed out in an
interesting manner by a recent booklet on tubes
published by the Radiofax Company. The
point to be noted is that the average of all those
tubes listed is about 650 and that tubes that one
buys should be of this order, and not of only 400
or so. Having a tube with a high plate current is
no disadvantage, for this current may be reduced
by the use of a C
battery. In fact the
best tubes obtaina-
ble give large plate
currents— they are
Jj equipped with
r 1|K Ji good. long lived
filaments.
From all availa-
ble data the reader
may rest assured
that reputable tube
manufacturers are
doing their best,
and that they will
be glad to replace a
defective tube, pro-
vided that it lights.
Dry cell tubes are
suitable for radio-
frequency amplifi-
ers, detectors, and
first audio amplifiers, but that for operating a loud
speaker without overloading larger tubes must be
used with greater values of B and C voltages. 1 1 is
here that the 1 12 type tubes of the R.C.A., Clear-
Iron, Sea Gull, Golden Tone, the Daven Mu6, the
2i6-A, and others are most useful. The reader
is referred to the table in the November RADIO
BROADCAST which gives the output of these tubes
in undistorted power.
For resistance and impedance-coupled ampli-
fiers, there are several tubes with higher am-
plification constants that are useful and curves
will be found of these tubes in this number.
Such tubes are Daven, Cleartron, Golden Tone,
and there are doubtless others which have not
yet been submitted to the Laboratory.
Tubes are the important items in present day re-
ceivers, they make the wheels go 'round — but they
must be operated intelligently, and with care.
T
.
NOTE
VHE data in
Table 4 repre
sents the aver-
age of at least four
tubes of each manu-
facturer. It will be
noted that it differs
in some respects from
similar data pub-
lished in December
RADIO BROADCAST.
This is due to the
fact that some man-
ufacturers, at least,
have not decided
definitely upon the
desired characteris-
tics. It is probable
that another month
will see other
changes and addi-
tions to this table.
When this article
was written (De-
cember) this data
was the best obtainable from existing tubes.
Throughout this article and in other texts
which deal with the subject of vacuum tubes,
their characteristic curves, etc., reference is made
for convenience's sake to letters and signs inten-
ded to represent some constant or value. The
y y
-199 UV-ZOh* UV-2O3
UV-90O UV-2O2
FIG. 13
The Radiotron family from the little 199 to the big water cooled
fellow that is being used at the new wjz and other stations
derivation of these symbols is originally from
Ohm's Law where volts is represented by E,
amperes by I and resistance by R. The ele-
ments of a vacuum tube, the filament, grid and
plate are represented by the letters F, G, and
P respectively. Now by combining these and
Ef . . Filament Volts
Ep. . Plate Volts
Eg. .Grid Volts
Rp. .Plate Impedance
the letters of Ohm's
Law, we can denote
a value such as plate
voltage by writing
Ep. Filament cur-
rent or amperes
would be IF and so
on.
The symbols des-
ignating amplifica-
tion constant was
borrowed from the
Greek alphabet and
is represented as /*•
Mutual conductance
is usually repre-
sented by Cm since
G is a symbol for a
"conductance," and
the term "mutual
conductance",m,was
coined by Prof. Ha-
zeltine.
Following is a list
of letter symbols
most commonly
used, with their
meaning.
Jp. . Plate Current
If. . Filament Current
fi. .Amplification Con-
stant
Gm. . Mutual Conduc-
tance
What Radio Listeners Everywhere May Expect in the Most Comprehensive
International Tests Ever Arranged — The Final Transmitting Schedules
By WILLIS *C WING
held,"
ASEDon previous experience, the
January International Radio
Broadcast Tests should mark a
distinct advance over the others
says Captain Eckersley, chief engi-
neer of the British Broadcasting Company,
in a radiogram just received by RADIO
BROADCAST. "It should be possible," he
continues, "with the cooperation and assis-
tance of the International Bureau de Radio-
phonie recently organized at Geneva, to
secure more definite and accurate data on
the test broadcasting of all the European
stations than in the Tests of November
1924. All listeners should remember the
differences in time, in order to avoid con-
fusion and disappointment. Our council
meeting at Brussels during the second
week of December, at which representatives
of all English and Continental broadcasters
took part showed a most commendable
spirit of cooperation on the part of all con-
cerned.
"We believe that radio, intelligently de-
veloped in the public interest is destined to
become a potent auxiliary of international
cooperation in bringing closer together
broadcast listeners and wireless enthusiasts
all over the world. Radio should perform
valuable work in establishing common
points of interest and in consolidating con-
scious world citizenship without which
there can be no assurance of permanent
peace between nations," concludes Captain
Eckersley.
The idea of the International Tests orig-
inated with Mr. F. N. Doubleday, president
of Doubleday, Page & Company, on his
return from a trip to England in 1923,
during which time he had made a detailed
study of radio broadcasting there. Mr.
Doubleday felt that it would be extremely
interesting and stimulating both to the pro-
gress of radio and to international friend-
ship were it possible for RADIO BROADCAST
to arrange a program of broadcasting from
this country to England. So it was ar-
ranged that a two-way test should be held.
And during the last week in November,
1923, the first International Tests took
place, between the broadcasters of England
and America. The plans were not ex-
tensive, but the success of listeners on both
sides of the water, in logging broadcasters
at great distances was really extraordinary.
And the second series of tests, during the
last week of November, 1924, more ambi-
tious than the first, since Continental
broadcasters were invited to participate,
boasted a huge total of listeners in the
United States and in England who received
stations foreign to them. This is all the
more remarkable because in both years,
atmospheric conditions were certainly not
all that could be desired. In addition to
the mere DX features of the first two
Tests, there was the side, perhaps not so
evident, but really none the less important,
that radio enthusiasts on both sides of the
water were bending their thoughts toward
a kind of international radio unity. To the
American listeners, the English and Conti-
nental peoples seemed closer, as indeed
they were, than ever before. And the
same may be said of the English listeners.
EUROPEAN PARTICIPATION GREATER
THE 1924 Tests inaugurated the broad-
casting of European stations, and the
Tests of 1926 will see the European and
the British stations in fuller cooperation
"FOR SERVICES RENDERED"
In arranging the International Test. Presented
to the editor of this magazine at the recent New
York Radio Show
than ever before. This increased coopera-
tion is due to the recent organization of the
International Bureau de Radiophonie, with
headquarters in Brussels, headed by Arthur
Burrows, formerly chief program director
for the British Broadcasting Company.
The European broadcasters have realized
that broadcasting is not a sectional or
national matter, and that they must at-
range their affairs so that all listeners may
benefit, and the international bureau,
which attempts to settle wavelength allot-
ments and allied problems, is the logical
result.
The success of the International Tests
depends entirely on the cooperation of all
the broadcasters, because silent hours,
allowing for the uninterrupted reception
of stations outside national boundaries is
essential. And in this respect, the Amer-
ican and Canadian stations have definitely
demonstrated their feeling that the Tests
meant enough to radio for them to make
special sacrifices. These sacrifices have
been greater for the American and Cana-
dian stations than they have for those of
the other nationals, because these Tests
have come on this side of the water during
the regular evening hours of broadcasting,
while the difference of time between the
American continent and Europe has called
the foreign broadcasters from their more or
less downy couch at three o'clock in the
morning, and no paraphrase of a once
popular song meant.
But what is going to happen this year?
The editors of RADIO BROADCAST felt that
the International Tests had grown too big
for any one organization in this country
to assume entire charge. So the matter of
the Tests was put up to many organiza-
tions, including the Radio Manufacturers
Association and the National Radio Trade
Association who felt that so important an
event to the radio world should not con-
tinue without their active support. The
result has been that about eighteen organ-
izations devoted to furthering the interests
of radio have aligned themselves with this
movement. So in the United States this
year, the International Radio Broadcast
Tests are not supported and supervised by
RADIO BROADCAST alone, but by all the
influential organizations in radio. And
in Europe, the aid of the three most power-
ful radio groups has been enlisted, the
British Broadcasting Company, the Inter-
national Bureau de Radiophonie, and
FEBRUARY, 1926 THE 1926 INTERNATIONAL RADIO BROADCASTING TESTS
463
DAY
RECEIVING FOREIGN STATIONS
During the International Tests of 1924, at Mitchel Field, New York.
This Army radio truck was driven to the center of the field, and a super-
heterodyne set up and many stations were heard. Light was furnished
by lanterns and flashlights
Radio Press, the latter controlling a circu-
lation of radio readers in England totalling
more than a million. Mr. Scott-Taggart,
the editor-in-chief of all the Radio Press
publications has been appointed, jointly
with Captain Eckersley, chief engineer of
the British Broadcasting Company, as
heads of the European broadcasting pro-
gram during these Tests.
In the United States and Canada, the
broadcasters, at a considerable sacrifice,
have arranged their programs so that silent
hours are provided. The activities during
this test week also involve Mexican and
Cuban and South American stations.
Among the South American stations par-
ticipating is OAX, at Lima, Peru, owned by
the Peruvian Telephone Company, operat-
ing on a wavelength of 380 meters ( 789
kc.). The Cuban broadcasters are directed
by Frank H. Jones, owner of the famous
Cuban station 6 KW. Canadian broad-
casters are operating under the direction
of Jacques Cartier, director of station
CKAC, La Presse, Montreal.
UNUSUALLY INTERESTING PROGRAMS
A GREAT number of American sta-
tions are arranging special programs
for the American test period, which is from
10 to ii p. M., Eastern Standard time.
Mr. A. Atwater Kent, whose excellent radio
programs through the WEAK chain of sta-
tions are so popular, expects to present a
program of more than usual interest to
listeners on both sides of the water. This
program will be broadcast the first night
of the Test Week, Sunday, January 24,
1926. Those in charge of WOR at Newark
admit that their program for the Test
week will offer some genuine surprises.
This station was heard abroad in both the
previous tests. Station wwj, the Detroit
News, is planning features of unusual in
terest during their transmitting period for
over-seas listeners. This is true of practi-
cally every broadcast-
ingstationon thisside
of the water, and to
list all the special
plans of all the broad-
casters would take far
more space than can
be spared in RADIO
BROADCAST. Every
individual and organ-
ization in any way
connected with Inter-
national Radio Week
realizes that this year
there is an opportun-
ity to share in an in-
ternational party of
huge proportions.
The Tests were
scheduled this time
for the last week in
January, instead of
the last week in No-
vember, because re-
ceiving conditions are
much better in Janu-
ary than in November. This was found to
be true by the experience gained in the first
two Tests and we firmly believe that receiv-
ing conditions will give a greater number .of
listeners a better chance to hear foreign
stations. Tests recently conducted by the
Bureau of Standards on the transmissions
of KDKA at Pittsburgh, seemed to show that
the worst atmospherics were found in June,
and the least in February, with the next
best months in the following order: March,
January, November, December, May,
October, April, August, July, and Septem-
ber. The worst fading was encountered in
October and the least in February. Fad-
ing increased in the months in the following
order: April, July, March, June, January,
May, November, December, August, and
September. These results, while not con-
clusive, certainly point to the last week
in January as a very favorable time to
schedule the Tests.
The final schedules and latest informa-
tion about the Tests will of course appear
in the daily newspapers. This is written
some weeks before the Test Week and
while the main features of the schedules
are settled, there are many details which
cannot be announced until a few days
before the first night of the Tests.
Wavelengths and call signals of the
European stations have been subject to
many changes since the organization of the
I nternationak. Bureau de Radiophonie and
Schedule of Transmissions International Radio Broadcast
Tests 0/1926
All the Times in This Table are Eastern Standard
Sunday, 24th January
Sunday, 24th January
Monday, 25th January
Monday, 25th January
Tuesday, 26th January
Tuesday, 26th January
Wednesday, 27th January
Wednesday, 27th January
Thursday, 28th January
Thursday, 28th January
Friday, 29th January
Saturday, 30th January
TIME
10—11 P. M.
11—12 p. M.
10—11 p. M.
11—12 p. M.
10—11 p. M.
11—12 P. M.
10—11 p. M.
11—12 P. M.
10—11 P. M.
11—12 P. M.
11— 11:15 P.M.
11:15— 11:30 P.M.
11:30— 11:45 P.M.
11:45— 12P.M.
11— 11:15 P.M.
11:15— 11:30 P.M.
11:30— 11:45 P.M.
11:45— 12 P. M.
STATIONS PARTICIPATING
Canadian, United States, Mexican, Porto
Rican, Cuban
Foreign (British, French, German, Dutch
Spanish, Italian, Austrian, Czech,
Polish and South American stations)
American Continent (as shown above)
Foreign (as shown above)
American
Foreign
American
Foreign
American
Foreign
American Eastern Standard Time Zone
stations
American Central Standard Time Zone
stations
American Mountain Time Zone stations
American Pacific Time Zone stations
All Canadian stations
Northern half United States stations
Southern half United States stations
All stations south of the United States
It will be noted that this schedule will not only give American listeners a chance to hear
stations in this country never heard before because of the station operating on a frequency
used by some near-by station, but this arrangement will also give the overseas listeners a
chance to pick up some American stations that are more distant from them than the sta-
tions almost on the edge of the Eastern seaboard. The arrangement of the American tests
so that on the first night (Friday, American time) the stations will progressively transmit
from east to west, and on the second night of those tests (Saturday, American time) trans-
mit north and south, will give American listeners a chance to experiment with DX recep-
tion such as they have never before had.
The Continental and British stations, if they follow the same plan for their territory,
on the last two nights of the test, will be on the air just one hour earlier than the American
stations. This will keep the air clear for the American transmissions which follow. The
British and Continental broadcasters will undoubtedly appreciate this arrangement, for
it will give them a chance to get a bit more rest. Since the transmissions from abroad
come at from four to five o'clock in the morning, London time, the physical strain on the
various station staffs is bound to be quite heavy by the end of the test week.
464
RADIO BROADCAST
FEBRUARY, 1926
ii HT'
Wlft II I YNfJ
CUP PRESENTED TO ARTHUR H. LYNCH
At the recent Chicago Radio Exposition for or-
ganizing and arranging the International Tests
so most of the listed frequencies of those
stations are not now accurate. On pages
465-6 of this magazine appears as complete
and accurate a list of English and Conti-
nental broadcasters as is possible to secure.
The main outline of the entire transmit-
ting schedule for all the stations is printed
elsewhere in this article and it would be
well for listeners to clip that schedule out
for reference during the Test Week. As
Captain Eckersley suggests in his radio-
gram quoted above, all listeners should
remember that there is a great difference in
time. For the convenience of listeners in
the United States and Canada, the schedule
is made out entirely in Eastern Standard
Time. Conversion to the time of the
other zones in this country is not difficult.
Five British stations including 5 xx, the
high power station of the B. B. C., will be
on the air for three nights of the test Al-
though no list is at present available of the
European stations participating, the leading
continentals will be on the air.
Without any major exception, all the
broadcasters in the United States, Canada,
Mexico, Cuba, and Porto Rico will be on
the air during their alloted periods.
And, a matter of great interest, at least
one station on the west coast of South
America will be heard, OAX 789 kc. (380
meters) at Lima, Peru. A number of
the broadcasters on the east coast of
South America are also expected to join
in the test broadcasting.
Copies of the Radio Week programs
of all the American stations which
take part are being forwarded to Mr.
Scott-Taggert of Radio Press in Lon-
don. Radio Press will undertake to
verify American programs heard by
English and European listeners during
the week. And in the United States
andj Canada, the verification of foreign
programs heard will be in charge of
the official International Radio Week
newspaper in each city. The official
programs will be printed the day after
they are sent so that all listeners can
themselves check their reception.
It is pr^able that there will be many
listeners who will not see the printed
newspaper programs and who prefer a
verification direct from RADIO BROAD-
CAST. Listeners who want a verification
direct may address their telegrams,
letters, and long distance calls to Inter-
national Radio Broadcast Test Com-
mittee, RADIO BROADCAST magazine,
Garden City, New York. Our long
distance telephone number is Garden City
800. Those who wish to address the
Committee by amateur radio may do so
by filing a message with some amateur
operator in their locality and asking him
"BIG BEN"
The famous clock atop the Houses of Parliament
whose chimes are frequently broadcast from 2 LO
and other stations in the British Broadcasting Com-
pany chain. If the English plans work out, listeners
on this side of the water may have an opportunity to
hear the deep bells of these chimes over their own
sets during the January 1926 Tests
to forward it to the above address. The
call letters of our amateur radio station
are 2 GY, and the station is tuned to 7496
kc. (40 meters).
Good going to you all during the Tests!
THOSE IN CHARGE OF CANADIAN COOPERATION
The staff of station CKAC, La Presse at Montreal. J. N. Cartier, the director of the station, fourth
from the left in the illustration, has had charge of the arrangements with all Canadian broad-
casters for their part in the Tests. In the back row, from left to right are Arthur Dupont, assistant
announcer; Adrien Arcand, radio editor of the paper; Leonard Spencer, technician; J. N. Cartier;
A. Lebeau, master of ceremonies; front row: J. P. Calligan, "Father Radio"; Mary Brotman and
Nora O'Donnel, stenographers
FEBRUARY, 1926
RADIO BROADCAST
465
Distance Computation Chart
MILES
TO FROM — >
4
BERLIN
LONDON
MADRID
k
>
i
!
PARIS
I
SAN FRANCISCO
Aberdeen
Amsterdam
700
400
400
220
1180
940
1514
1350
3280
3300
600
260
1220
820
5880
5900
Barcelona
Berlin
Bilbao
950
990
720
580
600
300
1560
200
1900
1020
1980
3200
3700
3050
540
540
480
520
740
770
5800
6300
5650
Bremen . . .
210
400
1060
1170
3580
400
800
6180
190
720
1230
900
3850
650
680
6450
280
740
1150
1000
3800
630
540
6400
500
200
830
1420
3240
160
730
5840
Buda Pesth
430
880
1200
1000
4000
750
500
6600
Cadiz
1460
1110
310
2420
2900
970
1050
5500
Cardiff
700
140
780
1680
3000
300
1020
5600
4400
3900
3800
5400
750
3800
4700
1820
Cleveland
4000
3550
3500
5100
400
3500
4400
2140
Copenhagen
Daventry
Dresden
Dublin ...
280
600
100
820
600
80
590
300
1310
850
1110
930
1000
1780
1050
1760
3700
3200
3650
3000
640
290
520
500
950
1190
640
1170
6300
SHOO
6250
5600
Geneva .
700
460
630
1500
3300
250
430
59CO
Glascow
760
4500
340
3580
1100
3250
1650
5000
3150
1350
580
3700
1230
3900
5750
3950
Helsingfors .........
700
520
1160
460
1860
660
570
1460
4300
3550
1210
260
1390
430
6900
6150
1810
1020
303
2450
2800
940
1140
5400
580
800
1580
3200
220
880
5850
Los Angeles
6300
610
5700
460
5600
580
7280
1560
2560
3200
6000
250
6300
460
5160
5800
1560
800
2130
3100
670
830
5500
Mexico City
Milan ....
6000
530
4300
530
4100
730
5900
1430
2200
3800
4400
390
4400
300
1270
6400
1020
1580
2130
4600
1540
1490
7300
Newcastle
640
260
1040
1540
3400
460
1110
6000
New York
3700
3200
3100
4600
3350
3700
2600
Oslo
540
720
151C
1060
3900
850
1260
6500
Paris
540
220
670
1540
3350
680
6000
180
620
1100
1040
3700
530
580
6300
Reval
660
1130
1840
550
4300
1160
1330
6900
740
880
830
1490
3700
680
6400
San Francisco
6300
5850
5500
7300
2600
6000
6400
Toulouse
830
570
330
1790
3150
380
560
5750
Vienna
330
750
1140
1060
3900
620
480
6500
Warsaw
320
890
1410
720
4000
850
830
6600
Eight
RADIO BROADCASTS
Booklet of
European
South American
Mexican
and
Cuban
Broadcasting Stations
January 15th, 1926
Compiled by
LAWRENCE W. CORBETT
Oslo
Lima
Warsaw
Warsaw
San Juan
Lisbon .
Lisbon .
Montesanto .
Moscow
Moscow .
Moscow .
Moscow .
Nijni-Novgorod
Barcelona .
Barcelona .
Bilbao . .
Bilbao . .
Bilbao . .
Cadiz
Cadiz
Madrid .
Madrid .
Madrid .
Madrid .
Madrid .
San Sebastian
Seville . .
Valencia .
Boden . .
Goteborg
Joenkoeping
CALL FREQUENCY
SIGNAL IN KC.
NORWAY
OSLO 785
PERU
OAX 789
POLAND
779
779
PORTO RICO
WKAQ 882
PORTUGAL
P1AA
937
750
122
RUSSIA
821
666
297
207
2998
SPAIN
EAJ1
EAJ13
EAJ9
EAJ11
EAJ3
EAJ10
EAJ2
EAJ4
EAJ6
EAJ7
EAJ15
EAJ8
EAJS
EAJ14
923
652
999
923
723
833
909
967
983
765
735
612
867
857
750
SWEDEN
SASE 219
SASB 769
SMZD 1131
Six
WAVELENGTH
IN METERS
382
380
385
385
340
320
400
2450
365
450
1010
1450
100
325
460
300
325
415
360
330
310
305
392
408
490
346
350
400
1370
390
265
POWER
IN WATTS
1000
1500
1000
300
500
1500
1500
1000
1000
1000
12,000
1000
1000
1000
1000
1000
1000
1000
1000
3000
1000
3000
6000
1000
3000
1000
1000
1500
500
1000
CALL FREQUENCY
SIGNAL IN KC.
CUBA—Continuea
Habana .
Habana .
Habana .
Habaaa .
Habana .
Habana .
Habana .
Habana .
Habana . .
Habana . .
Habana .
Habana . .
Habana .
Habana .
Habana .
Habana .
Habana .
Habana .
Matanzas .
Nueva Gerona
Puerto del Rio .
Sagua la Grande
2 HP
2JP
2 XX
2CX
2AB
PWX
2JL
2EP
2CG
2BB
2MG
2 OK
20L
2RY
2TW
2UF
2RK
2PK
5EV
8JQ
1AZ
6HS
Santiago 8FU
Santiago 8 BY
Santiago 8 HS
Santiago 8 IR
Santiago 8 JQ
1016
1110
1999
937
1276
7496
1090
845
857
1176
1071
833
999
1764
1304
1131
967
1538
833
1333
1090
1499
1333
1199
1499
1578
2306
CZECHO SLOVAKIA
Brunn
Prague-Strasnice
OKB 167
OKP 584
DENMARK
Copenhagen
Hjorring (relay)
Lyngby . . .
Lyngby . . .
Odense (relay) .
Ryvang
OXE
Reval
Helsingfors .
Skatudden .
Tammerfors
973
240
387
125
316
261
ESTHON1A
— 857
FINLAND
3NB
810
714
999
WAVELENGTH
IN METERS
295
270
150
320
235
400
275
355
350
255
280
360
300
170
230
265
310
195
360
225
275
200
225
250
200
190
130
1800
513
308
1250
775
2400
950
1150
350
370
420
300
POWER
IN WATTS
100
20
5
10
10
500
5
400
15
15
20
100
100
5
20
10
20
10
10
20
5
10
15
100
20
20
20
1000
5000
1000
500
2500
1000
1000
1000
250
Three
466
RADIO BROADCAST
FEBRUARY, 1926
LOCATION
CALL FREQUENCY
SIGNAL IN KC.
ARGENTINE
LOR 750
WAVELENGTH
IN METERS
400
350
327
375
325
425
380
404
530
265
350
312
370
350
381
310
380
312
400
400 (approx.)
385
350
360
430
400
250
225
350
340
275
200
235
275
300
POWER
IN WATTS
500
500
500
500
500
1000
500
500
2000
2500
500~
500
500
80
300
500
500
100
10
350
30
1200
50
50
10
500
100
100
20
20
10
100
LOCATION CALL FREQUENCY WAVELENGTH I
SIGNAL IN KC. IN METERS IN
SWEDEN— Continued
Norrkoeping SMW 1153 260 ]
>OWER
WATTS
000
000
000
000
000
500
1500
500
500
)
LOV 857
Malmo SASC 1110 270 ]
Stockholm SASA 702 427 ]
Buenos Aires ....
LOW 917
LOX 800
Stockholm 681 440
Sundswall SASD 550 545 ]
SWITZERLAND
Berne 993 302
LOY 923
Buenos Aires ....
Mendoza City ....
Graz
705
. LOU 790
AUSTRIA
742
Geneva . HB 1 273 1100 ]
Lausanne . HB2 353 850
ORV 566
Zurich RGZ 582 515
BELGIUM
Radio
URUGUAY
Montevideo .... 857 350
Bahia
Belgique 1131
BRAZIL
. 857
VENEZUELA
Caracas 750 400 (Approx.
Bahia
Bello Horizonte
Bello Horizonte
Pernambuco ....
Porto Alegre ....
Recife ....
SPH 961
. 857
. RSR 787
967
<7£O ASSEMBLE this eight-page booklet of
^-/ foreign broadcasting stations, first cut the
sheet on which the call signals are printed, from
the magazine. It is best to employ a razor blade
for this operation. Then trim the sheet along the
outside border line. Do not cut down the cen-
ter vertical lines. These are used as a folding
guide only. The sheet is next cut in two, across
the center horizontal line. The two pieces (each
consists of four booklet pages, of course) are then
folded down their vertical centers and inserted
into each other so that the numbered booklet pages
run concurrently.
The distances given in the chart on page eight
of the booklet are only approximately correct, but
are sufficiently accurate to serve a useful purpose.
SPE 790
SPE 961
SQE 750
750
857
CHILE
CRC 779
RC 857
. 833
ORC 697
ACB 750
CUBA
6EV 1200
7AZ 1333
7 SR 857
Central Tuinicu
Central Tuinicu
. 6KW 882
. 6JK 1090
6 YR 882
7 BY 1280
6JQ 1090
Cienfuegos
. 6BY 999
Two
Seven
LOCATION
CALL FREOUENCY
SIGNAL IN KC.
FRANCE
943
WAVELENGTH
IN METERS
318
840
276
475
350
1780
345
458
1780
2650
274
315
2500
505
576
279
418
255
288
283
292
280
249
470
251
395
296
463
1300
452
485
410
340
443
495
440
479
386
310
346
353
1600
331
328
422
POWER
IN WATTS
250
150
300
300
300
4000
500
500
100
4000
2000
250
500
4500
2000
1000
1500
1500
1500
500
1000
1000
500
1500
1500
1500
1000
1500
5000
1500
1000
1500
1000
1500
1500
1500
1500
1500
200
200
1500
20,000
200
200
1500
LOCATION CALL FREQUENCY WAVELENGTH
SIGNAL IN KC. IN METERS IN
GREAT BRITAIN— Continued
Hull 6KH 895 335
=OWER
WATTS
200
200
3000
1500
L500
1500
200
200
200
200
1000
400
1000
5000
2500 up
2000
2000
1500
500
1500
500
250
250
100
500
500
100
500
100
500
500
100
100
357
Liverpool 6 LV 952 315
1086
London 2 LO 821 365
YN 631
Manchester 2 ZY 793 378
857
Newcastle 5 NO 742 404
Paris
SFR 168
Nottingham 5 NG 920 326
Paris
5 NG 869
Plymouth 5 PY 887 338
Paris
FPTT 655
Sheffield 6FL 996 301
Paris
8AJ 168
Stoke on Trent 6 ST 980 306
Paris (Eiffel Tower) . .
FL 113
109
Swansea 5 SX 622 482
HOLLAND
Amsterdam PCFF 154 1950
Amsterdam PX9 280 1070
Amsterdam 140 2125
Bloemendaal 869 345
HUversum HDO 286 1050 !
MRD 952
Tours
YG 120
Berlin
GERMANY
594
Berlin
520
Utrecht 273 1100
Bremen (relay).
1075
717
HUNGARY
Buda Pesth 5491 546
1176
Cassel (relay) ....
1041
1059
IRISH FREE STATE
Dublin 2 RN 769 390
Dresden (relay)
. 1027
1071
Elberfeld
1204
Frankfort
638
ITALY
Milan SITI 550 545
Gleiwitz '
1195
759
Hanover (relay)
Konigsberg . ...
Konigswusterhausen .
1013
. 648
. 231
663
Rome IRO 705 425
Rome 167 1800
MEXICO
Chihuahua City . . . CZF 923 325
Mazatlan CYR 631 475
618
731
Nuremberg (relay)
Stuttgart
. 882
677
GREAT BRITAIN
2BD 606
Merida . CYY 546 549
Mexico City CYA 999 300
Mexico City CYB 1090 275
Mexico City CYH 800 375
Belfast
2 BE 681
Mexico City CYL 750 400
Birmingham ....
5 IT 626
Mexico City CYO 705 425
Bournemouth ....
6 BM 777
Mexico City CYX 923 325
Bradford )
, , _ 967
Mexico City CZE 857 350
Leeds }
. 2LS 867
Mexico City CZI 1 666 450
Cardiff
5 WA 849
Puebla City CYU 961 312
Daventry
5 XX 187
Tampico CYE 833 360
Dundee
2DE 906
Tampico CYQ 931 322
Edinburgh
2 EH 914
Vera Cruz CYC 999 300
Glasgow
SSC 711
Vera Cruz CYD 1199 250
Four
Fife
AS THE BROADCASTER SEES IT
/&»
Drawings by Fran\lyn F. Stratford
What the Institute of Radio Engineers Does for Radio
\HE Institute of Radio Engineers is a
learned society devoted to the advance-
ment of radio communication in all
its aspects, theoretical and practical.
The term "radio communication," it
must be understood, includes a great deal besides
broadcasting. To old radio telegraph engineers,
broadcasting is only the frothy comedy of radio.
What does it matter, they ask, whether the
ether is burdened with all these pretty tunes
and smart talks; no one is going to die if they
fail to reach the receivers waiting for them.
An sos call on the high seas is another matter.
So they stick to their dots and dashes.
The Institute, however, keeps pace impartially
with the developments in radio telegraphy and
telephony. As a matter of fact, the two arts
rest on the same principles and most of the
articles appearing in the Proceedings, published
six times a year by the society, are of equal
interest to specialists in both fields. If an
engineer makes some experiments on field inten-
sity of a transmitter at various points, the pres-
ence of shadows, dead spots, etc., the results
are equally applicable to telegraph transmitters
and broadcasting stations in or near the fre-
quency bands covered. The differences between
wireless telegraphy and telephony, important as
they are, are much fewer than the similarities.
Practically every technical radio man of
prominence in the United States, and many in
other countries, are members of the Institute
of Radio Engineers. But membership is not
confined to these eminent figures. The total
membership is in the neighborhood of 3000,
divided into four grades according to experience
and professional standing. At the head are
about 100 Fellows, followed by some 500 full
Members. These are very largely professional
radio engineers and administrators. The 2400
Associate Members comprise the body of the
membership. There are also approximately 150
juniors under 21 years of age.
It is not generally known that any responsible
person who is seriously interested in radio, in
either an amateur or professional capacity, is
welcomed to associate membership in the
Institute, as long as he or she can pay the dues
of f6.oo per year assessed in this grade. As
a matter of fact, the Associate gets as much for
his $6.00 as the Fellow for his annual payment
of $15.00. He may attend meetings. He may
contribute to the Proceedings if he has something
worth while to say. He can't be President,
but his vote counts as much as any one else's.
If he makes a great invention he is just as eligible
for the gold medal or the Liebmann Memorial
Prize of $500, both awarded yearly. Above all,
he gets his six copies of the Proceedings every
year. In 1924 the volume ran to 864 pages of
reading matter, printed in admirable format with
full illustrations and charts, making a thick book
of information absolutely indispensable to any-
one whose interest in radio is above the twelve-
year-old level. How the Institute does it I
don't know, although the fact that a number of
$2o,ooo-a-year men give a portion of their time
to running it, free, gratis, for nothing, as they say
in the backwoods, must have something to do
with it. Anyway, there's the book. The
subscription price to non-members is $9.00, and
it is worth that.
Members of the Institute in any grade must
be passed on and elected by the Board of Direc-
tion. Application blanks may be secured from
the Secretary, at 37 West 39th St., New York,
New York. If the application is for one of the
two top grades it must be accompanied by the
recommendation of five members in that grade,
and the Board goes over it very exactingly.
There are rigid constitutional requirements
which must be met. A Fellow must be not less
than thirty years of age; he must have been in
the active practice of his profession for at least
seven years, including three years of responsible
charge of important radio work — and "import-
ant" does not mean running a peanut roaster
broadcasting station or designing still another
receiver which is called a uni-control because you
have to move six knobs, one big and five small,
in order to tune it. A Member-applicant's record
is also subject to critical scrutiny; but the
section of the constitution referring to Associ-
ates states merely that "An Associate shall
be not less than twenty-one years of age and
shall be: (a) a radio engineer by profession;
(b) A teacher of radio subjects; (c) A person
who is interested in and connected with the
study or application of radio science or the radio
arts." That lets in everyone who wants to join
and who pays his debts and does not throw
bombs at the constituted authorities, invent
perpetual motion machines, or sell pill-box
static eliminators. Through affiliation with the
Institute, one is definitely known as a person
active in the development of radio communica-
tion, and, aside from the tangible advantages
realized, it is about the most practicable means
of testifying to a genuine interest in the art.
Not without reason, some employers in technical
radio pursuits consider membership in the
Institute of Radio Engineers as one evidence
of serious devotion to the problems of advancing
and establishing radio communication.
The principal section, of the Institute is in
New York City, where the attendance at meet-
ings is such that it is necessary to hold them in
the large Engineering Societies Building audi-
torium. However, good-sized sections have
also been organized in Washington, District of
Columbia, Boston, Massachusetts, Seattle,
Washington, San Francisco, California, Philadel-
phia, Pennsylvania, Chicago, Illinois, and
Toronto, Canada. These bodies hold meetings,
usually each month, in their respective towns.
Important engineering papers are presented and
discussed at these gatherings. It is no exaggera-
tion to say that no important radio achievement
of a technical nature has appeared without being
introduced to the engineering fraternity in this
way. Foreign engineers, as well as Americans,
contribute to the material presented at these
meetings and later published in the Proceedings,
thus giving the papers and discussions an in-
ternational flavor in keeping with the nature of
an art which knows no national boundaries or
artificial limits in its mechanism.
The Institute maintains various committees
which systematize forms and procedure in their
various fields. For example, there is a Stan-
dardization Committee which has the job of
keeping technical nomenclature and terminology
abreast of the times, so that everyone interested
may know the correct and accurate use of the
various terms. This committee and its sub-
committees issue detailed standardization re-
ports every few years.
The officers of the Institute of Radio Engineers
for 1926 are Donald McNicol (President); Ralph
Bown (Vice-President); Alfred N. Goldsmith
(Secretary and Editor of Publications); Warren
F. Hubley (Treasurer); Edward Bennett, Lloyd
Espenschied, Louis A. Hazeltine, John V. L.
Hogan, John H. Morecroft, A. H. Grebe, Mel-
ville Eastham, and A. E. Reoch (Managers).
The Past Presidents are R. H. Marriott, G. W.
Pickard, L. W. Austin, John Stone Stone, A. E.
Kennelly, M. I. Pupin, G. W. Pierce, J. V. L.
Hogan, E. F. W. Alexanderson, Fulton Cutting,
Irving Langmuir, J. H. Morecroft, and J. H.
Dellinger. Doctor Kennelly is also a Past Presi-
dent of the American Institute of Electrical
468
RADIO BROADCAST
FEBRUARY, 1926
Engineers, with which the Institute of Radio
Engineers maintains close and cordial relations;
and Doctor Pupin, the President of the A. I.E.
E. at this time, is the second engineer to hold
these two important offices during his career.
I do not go in much for exhorting the populace
or inflicting advice on my fellow citizens, but
I will say to any technical broadcasters who
happen to read this, as well as any one seriously
interested in radio work, amateur or professional,
that they are very definitely getting off on the
wrong foot if they have neglected to affiliate
themselves with the Institute of Radio Engineers.
Personally, I have never joined any fraternities,
lodges, churches, sodalities, temperance societies,
police reserve organizations, turn vereine, unions,
or pacifist brotherhoods. I declare, with several
thumps on my chest, that 1 am as little inclined
toward joinery, in the large, as an Anatole
France or a Remy de Gourmont. But I have
belonged to the I. R. E. since considerably before
the time when I became eligible to vote, and
intend to remain in it until I become too weak
to earn $10.00 a year. The sixty or seventy
dollars which I have paid it in dues during that
decade have been among the best investments
I have ever made, and if you are a radio engineer,
operator, amateur or experimenter still on the
outside, permit me to give you this tip and to
urge you to send for the application blank, as
the correspondence schools say, NOW.
Technical Routine in Broadcasting
Stations. II. Control Work
THIS is the sixth of a series of practical
articles for professional broadcasters.
Articles previously published are three on
microphone placing (September, and October,
1925; and January, 1926); one on personnel
and organization in a typical large station
(November, 1925); and one relating to wire
lines as employed in broadcasting (December,
1925). This last-named paper was the first of a
number under the general heading of Technical
Routine in Broadcasting Stations, and this dis-
cussion will now be continued with a considera-
tion of the functions and problems of broadcast
control work.
Essentially the control room is a small tele-
phone exchange. We have a radio telephone
transmitter to which various places — studios
and a variety of field points — are to be connected
in a pre-arranged order and for more or less
definite periods. The control room makes these
connections. It (meaning the men in the control
room) also "lines up" the various field points,
making sure that each will be ready to broadcast
when the program is handed over to it. The
control room supervises the output, and adjusts
the over-all amplification of the station to
appropriate levels, as required by changing
inputs and the characteristics of the equipment.
And when the station in question is connected
to other stations, hundreds or thousands of
miles away, "feeding" them a portion of its own
animating energy, the work of the control men
is further increased. These operators, therefore,
are highly trained technicians, not, like wire
telephone operators, automatons mechanically
doing the bidding of the people who use the
telephone facilities. The work of local telephone
operators can be done, and is being done better
by machine switching equipment than human
beings can do it. When it comes to long lines
and toll telephony, the procedures become some-
what too intricate for successful mechanization.
The control room of a broadcasting station
contains most of the complications of long dis-
tance wire telephony, plus complexities of its
own. If we are to see the day when machinery
takes the place of the control operators, we shall
have to get a good deal older.
One of the essential elements in good control
work, nevertheless, is an almost machine-like
uniformity in procedure. In putting the station
on the air, in changing from the studio to the
field or vice-versa, in interrupting a field event
when necessary, a definite routine should always
be followed, to be varied only when it is obviously
advantageous for some special reason. Mis-
takes are less apt to be made when the various
steps are always taken in the same order. For
example, when the control operator changes
over from the studio to an outside point it is
generally necessary for him to light a separate
amplifier to the input of which the line is con-
nected at the proper time. Unless there is some
fixed rule on the subject, there will be occasions
when the amplifier is not lighted when the
change-over is made. The result is that the
opening announcement from the remote point
is lost while the control operator rushes madly
around tracing the signal and finds he has no
voltage on his filament. If, however, it is a
regular procedure to light this tube at the begin-
ning of the last studio number, this sort of thing
is less apt to occur.
Such instances may be multiplied. It is
found that some specific formula must be used
in putting a field event on the air. The control
operator should say to the field man: "You're
on the air," and wait for the word "Right!"
before closing the switch. If various phrases
are used the station will inevitably get into
trouble. There will be a misunderstanding
and some wire talk will go out on the air. Such
mishaps occur in most complicated ways. Re-
cently I heard of one which came about through
a curious combination of circumstances. A
chorus was being broadcast from an opera house,
with no audience present. It was a first-class
aggregation of sixty trained voices, achieving
unusual and very beautiful symphonic effects.
After starting the concert the field operator
decided he was not getting quite enough bass,
and as he was set up near that section of the
chorus he ran out his own microphone, which
he had been using for communication with the
studio before the wire was turned over to the
air, some twelve feet, adding it to the two or
three concert microphones already set up. Half-
way through the program the control operator
had occasion to give a brief message to the
announcer, something about signing off one of
the stations on the chain, and, no extra pair
being available, he opened the broadcasting
line at what seemed like an opportune moment
and called, "Hello." The field operator heard
him and made a dash for his microphone. In
order to get it he had to take off his phones,
which were on the usual six foot cord. It took
him a few seconds to get back with the micro-
phone, and in this interval the control operator
gave him the message, which the field man
missed, of course. Then the control operator
said, "You're on the air," just as the field man
was putting on the phones in more or less con-
fusion and excitement. The control man waited
for a reply, and heard some noise which he inter-
preted as "Dit-Dit" — the Continental code for
"I," frequently used as an acknowledgment
by this particular field man, who had been a ship
operator in his day. So the control put the
opera house back on the air. An instant later
the field man cried, "What d'you sayr" and
this went out to Canada and Mexico while the
engineers and program managers listening on the
outside tore their hair and smashed mirrors
without being able to bring it back. The line
was immediately opened again and the mess
straightened out, but the damage was done. A
single slip like that, coming after a majestic
oratorio, dispels the dramatic illusion like a half
'IMPORTANT PAPERS ARE PRESENTED AND DISCUSSED AT THE i. R. E."
FEBRUARY, 1926
DRAMA IN RADIO CONTROL ROOMS
469
ton of gun cotton exploded in a haystack. Yet
the four or five individual mistakes made by
the technical men might occur singly without
causing a break. In this case the fates bunched
them in such a way that all hands made a show
of themselves on the air. A better organized
routine procedure would have saved all this.
In most stations, even of the half and one-
kilowatt size, all the technical equipment —
switchboards, amplifiers, and transmitting set,
is found in one room. This is fundamentally
wrong. The only advantage is in enabling the
station to be run with a small staff, since one or
two men are enough to watch the oscillators and
modulators, regulate the gain, take care of
necessary switching, and keep a 6oo-meter log.
It also means that these men have too much to
do, especially when the station gets into trouble,
and I have yet to see one which is exempt. At
the very least the line switchboard, amplifica-
tion controls, and first few stages of amplifica-
tion, should be in one room (the control room)
with the heavy machinery elsewhere. The
tendency now is to subdivide even further.
Thus, there may be a line control room where
the various local and out-of-town wires terminate
in suitable switchboards. Here the appropriate
connections are made and telegraphing over
simplex circuits is handled. The noise involved
in these operations is in this way kept away
from the second control room, where the am-
plification is adjusted and the output of the
station monitored in relative peace and quiet.
The men in this division are not responsible for
switching; their responsibility is to take what
the preceding technicians send them and pass
it on to the transmitter with the best possible
acoustic quality. The men in the first division
take care of the switching and corrollary ad-
justments. The steps then become:
1. Field operators at remote pick-up points;
2. Control operators (switching);
3. Control operators (Amplification and radio
quality);
4. Power operators.
The 6oo-meter watch is best kept, in the
majority of cases, by the men in the power plant.
It should be kept out of the control room when-
ever possible; if it must be handled there, a
separate operator listening with headphones
should be assigned for this purpose. If this job
is taken care of in the transmitter plant, a
loud speaker may be used and no additional
staff is required for this important detail.
The Memoirs of a Radio Engineer.
IX
1WENT to the College of the City of New
York for two reasons; one was that I had
none too much money, and the tuition at
the College was free. This, however, was not
a major factor; it would not have been an
insurmountable difficulty to raise the money
for a course at one of the other institutions of
learning around town. The principal force
which drew me to the City College was the
presence in the faculty of physics of a famous
radio engineer, Dr. Alfred N. Goldsmith, now
Chief Broadcast Engineer of the Radio Corpora-
tion of America. As early as 1910 or 1911 the
Doctor's renown had spread to the far corner
of the Bronx in which I struggled with insensitive
pieces of galena, hard visaged janitors who
were as ready to cut down an antenna as to step
on a cockroach, ten-cent store tools, my own
ignorance — all the animate and inanimate
obstacles in the path of the young wireless
experimenter of that benighted time. Of these
handicaps my lack of knowledge was the great-
est, and I hoped to sit at the feet of this pre-
ceptor and learn from him the theory and
practice of the wireless art.
A prominent college president, in a recent
commencement address, advised graduate stu-
dents not to attend a professional school at
random, but to select one at which some out-
standing scholar taught the subject in which
they were interested, for contact with such a
figure would be of incalculable value to aspirants
in his specialty. At the mediaeval universities,
also, a celebrated professor attracted students,
sometimes in enormous numbers; some of the
universities, in fact, grew up around such figures.
Thus my course in picking a college had ample
historical precedent, a fact of which I was prob-
ably unaware; all I knew was that I wanted to
learn radio, and Doctor Goldsmith could teach
me if he desired. In this hope I was not dis-
appointed. If 1 did not learn radio, the fault
was not in my training.
During his teaching years. Doctor Goldsmith
instructed, inspired, and in most cases got jobs
for some thirty radio engineers, among whom
may be named Julius Weinberger, William
Priess, Joseph D. R. Freed, Lester Jones, and
numerous others. He gave what was probably
the first regulation radio engineering course in
this country, and certainly one of the best
anywhere. His students were picked men,
senior students specializing in physics or en-
gineering, who showed special qualifications
for an advanced course in radio technique and
theory. The classes ran from three to six men
in number, an ideal condition in which a "course"
ceases to be what is usually meant by the term —
something to be "taken" and forgotten. The
first class was in 1913, the last in 1918, when
the pressure of other responsibilities became too
great, and the Doctor was no longer able to
devote a considerable portion of his time to a
handful of men in this one course. It was not
until the end of 1924, however, that he gave up
active teaching entirely. He was then an
Associate Professor, in charge of the Department
of Electrical Engineering at the College of the
City of New York.
While teaching physics, electrical engineering,
and radio at the College, Doctor Goldsmith
was editor of the Proceedings of the Institute
of Radio Engineers, a position which he still
holds, and has held since the Institute was
founded in 1912. Since 1918 he has also been
Secretary of the Institute. He is, accordingly,
one of the charter members and founders of the
Institute, and a Fellow from the beginning, with
activities dating back to the Society of Wireless
Telegraph Engineers and the Wireless Institute,
whose combination formed the Institute of
Radio Engineers.
Readers who are unfamiliar with these primor-
dial days of organized radio, and its outstanding
figures then and now, will probably imagine
Doctor Goldsmith as a man of at least sixty.
He is in fact thirty-eight years old. In 1913,
when I first met him, he was in his twenty-sixth
year, already a Ph.D. of Columbia University,
and an instructor in physics at the City College.
And while he was engaged in all the activities
enumerated above, he was also, from 1914 on,
Consulting Engineer, and later Director of
Research, for various commercial radio com-
panies.
The course in radio engineering was neither my
first nor last contact with Doctor Goldsmith.
Long before I was qualified for this study, I was
one of his students in physics, and a member of
the City College Radio Club, founded in 1914,
of which the Doctor was the Faculty Advisor,
and which he supported liberally, not only with
advice, but also with donations of valuable
apparatus, so that shortly it became one of the
most affluent amateur radio clubs of the city.
At the meetings he would frequently appear and
lecture for a half hour on some interesting phase
of radio to the fifteen or twenty members pres-
ent. In this way, by virtue of the fact that the
Doctor was Chairman of the I.R.E. Committee
on Papers, and Editor of the Proceedings, the
students frequently received summaries and
elucidations of important engineering literature
soon after presentation. This early contact
with first-rate engineering exposition was of
course inestimably valuable to the young men
in the club.
>
THE PROGRAM MANAGERS AND ENGINEERS LIS-
TENING ON THE OUTSIDE TORE THEIR HAIR"
470
RADIO BROADCAST
FEBRUARY, 1926
In 1913 I was in the graduating class of
Townsend Harris Hall, the preparatory school
of the College, across the campus from the other
college buildings. It was the custom to give
these "subfreshmen," during the last semester
of their preparatory course, College instructors,
space in the Main Building, and other facilities
of the university. Accordingly my class in
what was known as Physics 2, an elementary
course in light, heat, magnetism, and electricity,
received its tuition from Doctor Goldsmith.
I had seen pictures of him, and recognized him
as soon as he came into the room. He was
smooth shaven, and it became clear to me im-
mediately that a man could look very much the
scientist without the pointed beard which in-
variably characterizes the profession in the
movies. His manner was brisk and businesslike,
not at all hurried, but giving the effect of getting
to the objective without any delay or vacillation.
He knew just what he was doing, and my class-
mates, who were not above indulging in various
monkeyshines if they thought the instructor
would let them get away with it, realized,
appraising a firm chin and executive-looking
eyes, that they would get kindly treatment,
but that it would not do to throw chalk, roll
dice under the seats, or bring pet fauna into the
recitation room. With sinking hearts they re-
signed themselves to the thought of work.
I got along well enough in this course, having
gone over the electricity and magnetism part
in my private studies, and in the other branches
I studied diligently in order to impress the
instructor with my serious intentions. So did a
number of the other lads, who also had their
eyes on the radio field, although not obsessed
by it to the extent I was. We knew of the radio
engineering course, P 17, which was that year
being given for the first time, and from the lowly
position of P 2 we gazed up at the heights with
vast curiosity and longing. The radio labora-
tory, a large room on the ground floor, was
always kept locked. One made application to
get in after ringing a bell. On a certain day,
as three of us were passing the room, the Doctor
came by, nodded to us as we touched our hats
in accordance with the punctilio of the College,
'JACK PICKERILL WOULD BE COMING TO
PATCHOGUE WITH AN ELEPHANT RIFLE*'
and went in. Walking nervously up and down
the hall, we began to debate as to whether he
might show us the laboratory if we could get
up courage enough to ask him. Finally one of
us pumped up resolution and pressed the push-
button for about a quarter of a second. When
the door opened we almost turned on our heels
and ran, but it was not Doctor Goldsmith.
We explained to the College senior who appeared
that we were preparatory school students of the
Doctor's, and suppliants for a view of the labora-
tory. In a moment Doctor Goldsmith appeared,
received us cordially, and invited us in. This
was the first time that I had ever seen com-
mercial radio telegraph equipment and precision
radio measurement apparatus, and 1 was dazzled.
The neat ebonite bases, shiny brass fittings, the
carefully spaced turns of helical inductances,
and all the other marks of good design and
workmanship, were fascinating to one used to
wooden bases and cheap construction. Of
especial interest was a 3 kw. Poulsen arc,
presented to the College by Mr. Gano Dunn.
It was a laboratory afternoon for the radio
engineering students and they were engaged
on the various experiments assigned to them.
One squad was measuring the voltage of a
quarter kilowatt transformer with an electro-
static voltmeter; another was working with
wavemeters; another was taking antenna char-
acteristics, and so on. It would all seem fairly
commonplace to me to-day — I mean, I like
radio as much as ever, but the magic is no longer
there; it is the difference between having a crush
on a girl and marrying her. Radio to me to-day
is a matter of hiring men, o k'ing bills, arguing
with orchestra leaders, worrying about wire
lines, maintenance, costs, and technical bugs;
and so on. But on that day, when Doctor
Goldsmith showed us around his laboratory,
it was pure glamour.
Having introduced Professor Goldsmith into
my narrative at this point, I shall have many
more occasions to refer to his influence and good
will, which were so great an aid to these young
men eager to enter the radio field. They were
fortunate that for some years before executive
functions took over all the Doctor's time, he
was able to devote a part of his
plentiful energy toward giving
them a start. As for me, I feel
the obligation to acknowledge my
indebtedness to Doctor Goldsmith
at this point in my autobiographi-
cal sketches. Perhaps this is in bad
taste. Perhaps, with the reserve or
inarticulateness considered proper
in a country of Anglo-Saxon tradi-
tions, I should wait until the object
of my acknowledgments is dead.
But he shows no signs of disintegra-
tion, on the contrary, he is in vig-
orous health, and it might well turn
out that when he is dead I shall be
in the same state, which would in-
terfere seriously with my eulogizing.
So 1 speak my piece now.
Resurrection
A1ONG the oral and written
comments which we have
received on points of an-
cient history taken up in the
"Memoirs of a Radio Engineer"
series, is one from Mr. James M.
Baskerville of Patchogue, Long
Island. He deposes and says:
I installed and operated the
Plaza Hotel station, call letters
FS (not P) after Mr. Fred Sterry,
Manager. Harry Shoemaker designed the "Ice
Box" for the spark gap, to reduce the com-
plaint of patrons who desired to sleep nights.
Some day I'd like to tell you how I fought it
out with the Lusitania (incoming) and Sea
Gate, from FS, before there were any laws
governing good wireless conduct. No doubt
the Plaza station, aggressively manned, was the
air boss around New York, though frequently
the Waldorf Astoria (WA) station disputed
this fact with FS.
It is a good thing that Mr. Baskerville added
that last qualifying statement, or Jack Pickerill
would be coming out to Patchogue with an
elephant rifle. The boys have never got over
those days. There were no church services on
the air in 1908.
The Lingo of Radio
Artificial Terms and Trade Names
ANEW thing requires a new name, and when
a good word does not happen to be at hand,
an attempt is sometimes made to build one out
of Greek or Latin roots. "Heterodyne" is an
example. "Hetero" is from a Greek prefix
meaning "other" or "different," as in "het-
erodox," "heterogeneous." "Dyne" means
"force"; in physics the "dyne" is in fact the
unit of force. The name was applied to the re-
ception of a radio oscillation by causing it to beat
with a local oscillation of somewhat different
frequency — the local oscillation being the
"other" or "different" force. Similarly with
such terms as "homodyne," "autodyne," etc.
With the exception of "heterodyne" and a few
others, such terms do not usually attain a great
vogue; their artificiality appears to be against
them. For example, "diode" for a two-elec-
trode tube, and "triode" for a three-electrode
bulb, have not come into very wide use, logically
constructed as they are.
Trade names are sometimes built up in the
same way and frequently gain currency. For
example, "Audion," "Pliotron," " Kenotron,"
"Radiotron," "Radiola." Sometimes words with
this origin push out of use the more general
names of academic origin. "Graphophone"
and "gramophone" are correct synonyms for
"phonograph," but they are certainly less widely
known and used than "victrola," although "vic-
trola" has no dictionary standing at all. With
a generous advertiser behind it, a word may go
a long way.
Misnomers: Inappropriate Terms, Etc.
"Static" is an ambiguous term as generally
used. Its derivation is from "static electricity"
in the sense of a bound charge on some insulated
object, as distinguished from the electricity in
motion of an electric current. The charge on a
piece of sealing wax or a Leyden jar or a metal
ball on an insulating stand was called "static"
appropriately enough. In radio the word came
to be used indiscriminately to denote the various
disturbances picked up by receivers affected by
lightning storms. These are highly dynamic
effects, and it is glaringly inappropriate to speak
of them as "static." The 1922 report of the
Committee on Standardization of the Institute
of Radio Engineers limits "static" to "conduc-
tion or charging current in the antenna system
resulting from physical contact between the
antenna and charged bodies or masses of gas."
The term "strays" is applied to irregular
electromagnetic waves or impulses originating
from lightning or other sudden electrical changes,
whether natural or artificial.
One word that has fallen into deserved disre-
pute is "undamped" for "continuous wave."
We might as well speak of a girl as "unplain"
when we want to say she is pretty.
(To be continued)
How the Term "Wavelength in Meters" First Came Into Being and Why It Should
Be Discarded — Why Broadcasting Stations Are Given a Definite Frequency Separation
| VER since the old broadcasting
channels of 360 and 400 meters
discarded nearly three years ago,
the use of the expression "fre-
quency in kilocycles," rather than "wave-
length in meters," has been constantly
advocated. The reason for this is that
the broadcasting stations are now spaced
according to frequency instead of wave-
length. But, like a bad habit, the use of
the term wavelength is proving a difficult
one to drop.
Now light, radio, heat, and sound forms
of energy, are similar in one respect; they
all are transmitted by wave motion. When
the quiet surface of a pond is disturbed
by dropping a stone into it, waves are
formed which spread out in ever-widening
circles. This is a classical example of
wave motion. These waves travel out-
ward with a definite velocity, and contain
energy sufficient to set in motion any small
floating objects that they might pass.
In applying this analogy to radio waves,
consider the stone as replaced by a radio
transmitting station, the floating objects
by radio receivers, the water by the ether,
and an idea may be had of the transmission
of radio energy, except that radio waves
travel forward at a much greater velocity
than water waves.
Every wave has a length, which is con-
veniently defined as the distance from the
crest of one wave to the next. This is
easily observed in the case of water waves,
but the alternate crests and troughs,
though present, are invisible in radio and
light forms, and must be measured in-
directly. Each wave travels with a definite
velocity, defined as the distance it moves
in one second. The number of times per
second that a new crest passes a fixed point
is called the frequency. The relation be-
tween these three properties of length, vel-
ocity, and frequency, is that the velocity, or
distance one wave travels per second, when
divided by the length of each wave, gives the
frequency, or number of waves per second.
The early scientists who experimented
with radio phenomena, were able to demon-
strate that radio waves are transmitted
with the same velocity as light waves, and
that the two are the same kind of waves,
differing in frequency. They travel with
the enormous velocity of more than
186,000 miles per second, or 300,000,000
meters (the meter being a little longer than
the yard) per second. As the frequencies
By HOMER S. DAVIS
of light waves are almost too great to
comprehend, that of yellow light being six
hundred trillion per second, it was found
more convenient to classify them by their
wavelengths. In view of their similarity,
the same practice was adopted for radio
waves, and proved entirely satisfactory in
those early years, long before broadcasting
stations, not to mention interference be-
tween them, were even dreamed of.
But when the old 360 and 400 meter
channels became jammed, and the problem
of spacing the stations over a wide range of
wavelengths presented itself, it became evi-
dent, for two chief reasons, that they must
be spaced on a frequency basis rather than
of wavelength. The first reason was that
the energy radiated by a broadcasting sta-
tion consists of not only the principal, or
"carrier" frequency, but other, or "side"
frequencies, differing from the carrier by
amounts equal to the audio frequencies.
Since the useful audio frequencies range up
to about 5000 or more cycles per second, the
energy radiated by the station is distributed
from at least 5000 cycles below to 5000
cycles above the carrier frequency, a band of
10,000 cycles. To prevent overlapping, it
is evident that adjacent stations should
not use frequencies closer together than
10,000 cycles per second. The second
reason was that if two stations use fre-
quencies very close together, an audible
"beat note" or whistle will be produced,
its pitch being equal to the difference in
the frequencies of the two stations. As
this difference is increased, the pitch of the
whistle increases until it can no longer be
heard by the human ear; this occurs at a
minimum of about 10,000 cycles per second.
Thus broadcasting stations are now
allotted frequencies differing by 10 kilo-
cycles (or 10,000 cycles, "kilo" meaning
thousand), and although many stations
use the same frequency in common, they
are located in sufficiently remote parts of
the country as to cause a minimum of
interference.
HOW TO USE THE CHART
THE present time marks a period of
transition from the old custom of
speaking of wavelengths to the new one of
frequencies. It is a rather trying period,
for the old custom has not yet been fully
abandoned, and both are in general use,
resulting in a great deal of confusion. To
assist the reader in converting meters into
kilocycles, until the time when the term
wavelength is put back on the shelf of the
scientific library whence it was first bor-
rowed, the chart on the next page has been
prepared for reference use. On the right
is a scale of wavelengths from 10 to 10,000
meters, placed alongside a scale of corres-
ponding frequencies in kilocycles. To use,
merely read the desired frequency opposite
the wavelength in question. For example
200 meters corresponds to 1 500 kilocycl s,
300 meters to 1000 kilocycles, 1000 meters
to 300 kilocycles, 5000 meters to 60 kilo-
cycles, and so on. It may be seen frora the
chart that the frequencies are closer to-
gether at the shorter wavelengths than at
the longer ones; to take a specific case, the
hundred meters between 100 and 200
correspond to a frequency range of 1500
kilocycles, or 1 50 station channels, whereas
the hundred meters between 500 and 600
comprise a range of only 100 kilocycles,
or only 10 channels. Everyone who has
used the old style circular plate condenser
is familiar with this crowding of stations at
the shorter wavelengths.
On the left is a pair of similar scales
covering a more limited range; namely,
the broadcast band. It is used in the same
manner as the other pair of scales; for
example, station KDKA uses a wavelength
of 309.1 meters, which is seen from the
chart to equal a frequency of 970 kilocycles.
Here the frequency scale has been spaced
uniformly, suggesting the spacing of dial
readings when a straight line frequency
condenser is used. This clearly shows how
a properly designed condenser of this type
spreads out the short wavelength, or high
frequency, stations, relieving the critical
tuning formerly required at the low read-
ings. (This function should not be mis-
taken for selectivity.)
That the adoption of this custom of
speaking of frequencies is fully justified
may be seen by summing up its advantages;
it is in keeping with the station assign-
ments made by the United States Depart-
ment of Commerce; it replaces clumsy
wavelength numbers, such as 483.6 meters,
with useful frequency values, such as 620
kilocycles; it gives a direct indication of
the possibility of interference between
stations; it is especially convenient when
straight line frequency tuning condensers
are used; and its general use aids the move-
ment toward simplifying our every-day
terminology.
472
RADIO BROADCAST
FEBRUARY, 1926
200
210- -
220-
230-
240
260 -I_
270
280
300
350-^-
450-
550^1
1,
1,400
WAVELENGTH
FREQUENCY
CONVERSION CHART
1,300
1,200
1,100 8
1,000
900
£
O-
|3
5
o
ui
ce
800
700
10
20
30
40
50 -
100
• 5,000
— 4,000
— 3,000
200
300
400 —
500 -
1,000
3,000
5,000
10,000
30,000
10,000
1,000
o
c_>
ui
co
Q±
CO
o
O
- 500
-400
-300
-200
100
50
-40
30
RADIO BROADCAST ADVERTISER
481
Tested and approved by the manufacturers of the Raytheon tube
for use in the Raytheon "B" Eliminator
The Only Condensers specially
designed for the Ray theoriTS' Eliminator
Complete in two groups —Tested 1000 Volts D. C. t
The two Potter Condenser Groups shown
above constitute a complete condenser
equipment for building the Raytheon "B"
Eliminator. They are the only condensers
specially designed in groups for this use.
They are specially developed to stand up
under the high voltages used with the Ray-
theon tube.
Each unit in these groups has been thor-
oughly tested to a break-down voltage of not
less than 1000 Volts D. C. They are of full
capacity. They remove every vestige of A. C.
impulses. They eliminate all hum. Being far
more highly insulated than ordinary con-
densers, they will give continuous discharge
service without leakage. They insure highest
possible resistance and longest life under con-
tinuous use.
The larger of the two groups shown is the
Filter Unit, tapped for 8, 2, 2, and .5 Mfds.
This unit is also made with smaller capacities
as listed below. The smaller unit shown is the
Transformer Condenser Unit, used across
the secondary of the transformer. Both units
have strong metal jackets. They occupy min-
imum space and make for quick assembly.
These two units provide a complete and
ideal condenser equipment for the Raytheon
"B" Eliminator, yet cost practically no more
than would the cheapest condensers if bought
separately. Ask for them at your dealer's to-
day. If he cannot supply you write direct to us.
No. 350 Raytheon Filter Unit— Tested 1000 Volts D. C.— Tapped 8 Mfds.,
2Mfds.,2Mfds.and.5Mfd $12.00
No. 375 Same as 350, but tapped 6 Mfds., 2 Mfds., 2 Mfds. and.SMfd. . 11.00
No. 385 Transformer Condenser Unit— Tested 1000 Volts D. C. .... 1.50
FILTER
(An American -Made Product)
POTTER MANUFACTURING COMPANY • NORTH CHICAGO, ILLINOIS
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Tested and approved by RADIO BROADCAST
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RADIO BROADCAST ADVERTISER
TONE
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DISTANCE
Lends added enjoyment
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Ask your dealer for a demonstra-
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CHICAGO
THE GRID
A Department Devoted to Solv-
ing the Problems of our Readers
QUERIES ANSWERED
1. WHAT is MEANT BY "TUNING"?
F. B. F. — Topeka, Kansas.
2. THE CONTROL OF REGENERATION IN MY RE-
CEIVER IS NOT SATISFACTORY. WHAT CAN
I DO TO IMPROVE IT?
E. W. P. — Chicago, Illinois.
AN EXPLANATION OF TUNING
IN A circuit consisting of inductance and
capacity (coil and condenser), it is possible
to alter the value in meters of this circuit
by variations in value of either the inductance or
capacity.
If a generator of an alternating current is
connected with a coil and a variable condenser,
Generator
Condenser
A.C.MeJer
3. Is THE USE OF AN OUTPUT TRANSFORMER,
FOR A LOUD SPEAKER, OF ANY BENEFIT IN
OBTAINING GOOD QUALITY SIGNALS?
A. C. B.- — Gloucester, Massachusetts.
4. HOW IS A C BATTERY USED IN A DETECTOR
CIRCUIT TO OBTAIN RECTIFICATION?
T. C. — Newark, New Jersey.
change over to another station transmitting at a
different frequency (wavelength) it is only
necessary to re-adjust the receiving condenser
C.2 until the circuit is in resonance with the new
signal.
As was previously stated, variation in value
of a circuit may also be obtained by varying
the inductance value of the coil. This may be
done by a switch tap arrangement as in Fig.
3 A, or by the variometer method in B. The
switch-taps allow the use of more or less of the
coil turns which, at its best is only a rough
control. In the variometer arrangement, the
total inductance value is governed by the
Coil coupling of the fields of the two parts of the
coil. They are wound so that when at right
angles to each other the fields oppose each other
and the inductance value is low. When parallel,
FIG. I
then by varying this condenser it is possible, by
noting the maximum deflection of a meter
which is in the circuit, as in Fig. i, to arrive at a
setting of the condenser where the coil-condenser
part of the circuit will be resonant with the
frequency of the current set up by the generator.
We now have a new term "resonant" or
"resonance," and as defined by Hogan this
means "Agreement or harmony in frequency:
the condition under which the natural frequency
of an oscillating circuit equals the frequency of
an applied alternating electromotive force."
In the circuit A, Fig. 2, we have a frequency
generator whose frequency can be varied by the
variable condenser Ci.
Now, to bring the circuit B in "resonance,"
or "tuned" to A, it is necessary to rotate the con-
denser Ca until maximum deflection is noted on
the meter. Any change in the adjustment of
the frequency of the generator will necessitate an
adjustment for the circuit B.
Now suppose, instead of the generator circuit
A, a signal from a broadcasting station is sub-
stituted. Since broadcasting stations are as-
Variometei
\ Fixed
Condenser (Air)
the fields aid
value is high.
B
FIG. 3
each other and the inductance
Frequency
Generator Circuit
A
HOW TO OBTAIN BETTER REGENERATION
W
t
i
FIG. 2
signed to a definite frequency (wavelength), then
it is possible to adjust the circuit B, or "tune it,"
by means of the condenser C2, until it is in
resonance with the transmitted wave. To
f Tested and approved by RADIO BROADCAST ~4r
HEN a receiver of the regenerative
type goes into oscillation with a "plop"
instead of gradually doing so, as the
tickler coupling is increased, it is impossible to
tune-in distant stations satisfactorily and steps
should be taken to rectify this condition.
Often smoother oscillation can be obtained by
decreasing the B battery voltage applied to the
detector tube plate, but when this does not alter
conditions, it is then necessary to employ other
means for obtaining the desired results.
If the tickler coil produces regeneration, then
by reducing the number of turns on this coil,
one at a time, a point may be reached where,
upon advancing the tickler, there is an even,
smooth, production of oscillation.
RADIO BROADCAST ADVERTISER
483
INDUSTRIALIST
Tioneer
o ^Builder
At a time when products of his manufacturing genius
were already known to millions, Powell Crosley, Jr.,
boldly diverted his energies to the development of
radio reception, then scarcely known beyond the
laboratory walls.
Pioneering both in engineering trends and manu-
facturing practices, Mr. Crosley has been a vital
factor in making radio and broadcasting as much a
part of American life as motion pictures and the
motor car.
There is scarcely a milestone in the development of
popular radio on which his shadow has not been the
first to fall. And his announcement of December
26th concerned a milestone that dwarfed all others
in its importance — four entirely new radio receiving
sets:
The Crosley 4-29 (4-tube) . . . $29.00
The Crosley 5-38 (5-tube) . . . 38.00
The Crosley R. F. L.-60 (5-tube) . 60.00
The Crosley R. F. L.-75 (5-tube) . 75.00
These are now being demonstrated by Crosley
dealers and will be completely described in a
forthcoming issue.
*
•jf Tested and approved by RADIO BROADCAST
484
RADIO BROADCAST ADVERTISER
I35-C is furnished with leads and
phone tips for plugging into Ra-
diola Models 20, 25, ^^ _
26 and 28 $10.00
I35-A has prods for plugging in-
to Radiola Models 25 A —
and 28 $7.50
$12.50
107 Junior Tube-Checker makes
the testing of tubes in the home
easy.
NEW
Write for copies of Circulars 735
and 739 describing these three
new Jewell Radio Instruments
for Set owners.
f ORDER FROM DEALER
JEWELL ELECTRICAL
INSTRUMENT CO.
1650 WALNUT ST.
CHICAGO
26 years making Good Instruments
Variometers which are employed to produce
regeneration, should be so placed that no per-
manent coupling effects between them and other
coils used in the receiver are obtained.
Replacing the small by-pass condenser which
shunts the primary of an audio frequency trans-
former, will often improve matters. A too high
value of grid leak sometime causes this inefficient
condition while even the grid condenser's value
may be improved upon.
PROTECTING THE LOUD SPEAKER
WHEN a power amplifier is used in a re-
ceiver, it is well to consider just what is
taking place in the loud speaker. Un-
less the action is visualized and understood, the
user cannot hope to obtain maximum efficiency
from his apparatus.
Most of the loud speakers on the market are
merely elaborations of head phones, so con-
structed that a large diaphragm is actuated by
the impulses surging through the magnet wind-
ings of the loud speaker reproducer unit. Also
the majority employ a type of mechanism where
the armature, pin, or diaphragm, is pulled toward
the pole pieces of the magnet by the strong
magnetic field set up by the permanent magnet.
Now, when signals
in Fig. 4. Three wires, instead of the conven-
tional two from the loud speaker, lead to the set.
The lower side of the speaker connects to the
minus side of the filament, while the impedance
Itol Ratio Output
Transformer
are received and
passed along
through the vac-
uum tubes in the
form of impulses,
the diaphragm is
alternately released
and gripped as the
impulses first neu-
tralize then aid in
the gripping of the
diaphragm. While
such a system is
satisfactory, where
normal B battery
voltageis em-
ployed, it is not at
all to be desired in
cases where high B
potential is applied
to the plate of the
last audio tube.
The reason here
is that the heavy
current coursing through the windings of the
loud speaker tends to paralyze the diaphragm,
thereby causing imperfect reproduction.
Now, if some arrangement could allow the
diaphragm more freedom of action, then the ob-
jection to the use of high B battery potential
would automatically become void.
Such a device is simple to construct and effi-
cient in operation.
It consists of a large fixed condenser, of i mfd.
capacity, and an iron-core coil with high im-
pedance and low resistance. One having an in-
ductance value of 350 henries is highly satisfac-
tory.
The parts are connected in the circuit as shown
,5 to 1 mfd.
Characteristic Curve -i
1C
FIG.
coil connects one side to the plate of the last tube,
the other side to the high voltage terminal of
the B batteries. The upper side of the loud
speaker connects to the large fixed condenser, the
other side of which
terminates at the
plate lead of the
impedance coil.
A glance at the
circuit will show
that now the heavy
B battery potential
is circuited through
the choke coil in-
stead of through
the loud speaker
windings. The va-
riations in the
electro-magn et ic
field set up in the
choke coil, cause a
charging of the
large condenser
which in turn pro-
duces an a.c. signal
in the loud speaker.
FIG. 6
FIG. 4
Tested and approved by RADIO BROADCAST
Another type
of unit which
will do much the
same thing is an output transformer. It will be
recalled that such a transformer is employed in
push-pull amplifiers, with the exception that the
primary has a middle tap. Where the output
transformer is used in a single stage power am-
plifier, the primary and secondary each have
two terminals. The ratio of the windings is
i :i. A circuit diagram is shown in Fig. 5.
C BATTERIES IN THE DETECTOR CIRCUIT
ATELY the C battery has come in for its
bit of attention because of its use as a
satisfactory substitute for the usual grid
leak and condenser in obtaining rectification in
a tube detector circuit .
The use of a C battery as a grid bias in am-
plifiers, has been an accepted practice for years,
but little has been generally known about its
function in a rectifying circuit.
The Model 1926 receiver, described by
McMurdo Silver in the November, 1925, RADIO
BROADCAST, employed this system of detection
very successfully.
Those who have had the opportunity to com-
pare this and the old grid leak and condenser
system have, no doubt, noticed that while the
former produces a healthier signal, the latter is
more to be desired where sensitivity and selectiv-
ity are the prime considerations.
In this system the tube is acting as a distorting
amplifier, and the C battery is the agent which
produces the distortion because it shifts the
RADIO BROADCAST ADVERTISER
485
Eveready Hour
*
LIKE the fabled ship in which
Jason brought home the en-
chanted fleece of gold, the
Eveready Hour brings a rich
treasure of entertainment to
charm the harbor-homes of its
hearers.
Inaugurated two years ago,
the Eveready Hour was an
adventure in broadcasting —
an hour of connected enter-
tainment, uninterrupted by the
frequent injection of the name
of the broadcaster.
Many of these programs
have become famous. Thou-
sands of letters voice the ap-
preciation of our audience and
ask for repetition of favorites.
We make no requests for these
letters, but they mean much to
our artists and to us, and are
of great value in helping us in
our efforts to arrange programs
of a distinctive nature and
pleasing to the vast audience.
Radio has already become
a highly specialized art worthy
of the most scrupulous code of
ethics, and the Eveready Hour
represents a sincere effort to
pioneer in providing the" most
acceptable form of radio
entertainment.
Tuesday night means Eveready Hour
— 9 p.m., Eastern Standard Time,
through the following stations —
WEAF-JVew York WSAI— Cincinnati
VfJAR-Providence viv/j-Detroit
WEEi-Barton Vioc-Davenport
VfTAG-Worcester VftAR-Cleveiand
Vin-Pltiladelphia j Minneapolis
viGS-Bufalo ™ccc>\St. Paul
VfCAE-PtttsburgJi WGN-CAicofO
KSD-St. Louis
EVEREADY
Radio Batteries
-they last longer
Eveready programs cover a
wide range of entertainment
and human interest, transport-
ing us to periods of wholesome
simplicity; to barren islands
where marooned sailors meet
adventure, starvation and
death ; to battle-scarred France
with singing doughboys; to
emotional heights by telling
with music the stories of the
seasons; and to memories of
yesteryear aroused by old
ballad and musical comedy
favorites.
Eveready Hour begins at
9 p. m. each Tuesday night,
Eastern Standard Time.
NATIONAL CARBON CO., INC.
New York San Francisco
Canadian National Carbon Co., Limited
Toronto, Ontario
•4r Tested and aooroved bv RADIO BROADCAST
486
RADIO BROADCAST ADVERTISER
He was amazed
he had been sure
it was static —
MANY fans are blaming static for
noises which are not static at all.
Theyarenoises which can be eliminated.
For example, unless you keep your contacts
between tube and sockets clean at all times,
corrosion is going to cause disturbing noises
which you may lay to static.
It is easy to keep these contacts clean with the
Na-Ald No. 400 De Luxe Socket. Just a turn
or two of the tube in the socket cuts away all
corrosion from tube terminals and clears up the
voice of your radio instantly. No need to take
the tube out and sandpaper each terminal with
this socket. When the tube is turned in the
socket, Mie exclusive side-scraping duo-con-
tacts scrai« away all corrosion and the term-
inals come to rest on the scraped portions.
The Na-Ald No. 400 De Luxe Socket is the
only socket that eliminates noises due to cor-
rosion. Meter cescs nave proved this action
sure and positive.
And our No. 400-S socket (the regular No.
400 on spring mount) also eliminates micro-
phonic noises due to vibrations.
Both the No. 400 and the 400-S sockets are
made of Alden-processed Bakelite which con-
serves all the current energy. Laboratory
tests proved Na-Ald Sockets most efficient in
low loss and low capacity. Na-Ald Socket No.
400 was selected by ten famous radio engineers
as best for the famous Hammarlund-Roberts
set. It is part No. 6. List piices: No. 400
and No. 400-S, 7Sc.
The New focktt that
takes all the new tubes
THE new Na-Ald Socket No. 481-X takes all
the new tubes without adapters. Sure, Posi-
tive Contact. Alden Processed Bakelite for
lowest losses. List price, 481-X, 35c.
* Write for full information on the complete line
of Na-Ald Sockets, Dials and Adatttrs.
ALDEN MANUFACTURING
COMPANY
Dept. H-15 Springfield, Mass
Alden Processed
Sockets and Dials
operating point on the characteristic curve of the
tube to the curved portion. See Fig. 6. Here
one half cycle of the incoming signal is repro-
duced, greater in proportion to its other half.
This is because that section of the curve below
In A, practically the same circuit is shown
as that in B, but the C battery is shunted
with a potentiometer of 200 or 400 ohms. By
means of this potentiometer, it is possible to
apply a readily regulated C voltage ranging from
200 or 400 Ohm
Potentiometer -
FIG.
Showing the position for a C battery in a detector tube circuit. In A, the grid battery is shunted
with a potentiometer to control the voltage bias. A potentiometer is not essential, as B shows
the mid horizontal line of the distorted wave
form, flattens out more than the part above
it.
In Fig. 76, the C battery is shown connected
in a detector circuit, replacing the more standard
grid leak and condenser. Note the polarity of
the C and A battery leads.
o to 45 volts, or whatever the full value of the
C battery may be. Such an arrangement aids
in shifting the working point of the tube to that
position where most satisfactory distortion-
detection is to be obtained. With only the C
battery, as in B, the variation is mainly in steps
of 15 volts.
DON T ADDRESS YOUR GRID DEPARTMENT LETTERS LIKE THIS
Originating in Manitoba, Canada, this letter was forwarded by the postal authori-
ties to St. Paul, Minnesota, and there was re-addressed to Garden City as shown
GRID INQUIRY BLANK
Editor, The Grid
RADIO BROADCAST
Garden City, Tvfcw "far\
DEAR SIR:
O I am a subscriber to RADIO BROADCAST
and therefore will receive answers to my
queries free of charge.
LJ I am not a subscriber and enclose
$1
to cover cost of answers.
NAME
ADDRESS
G. F.
WHEN WRITING TO THE GRID—
A TYPEWRITTEN letter, written on one
•"* side of the paper only, is to be preferred, as it
aids in the quick formation of a satisfactory reply.
Don't fail to send a stamped addressed envel-
ope with your inquiry.
Don't send a second inquiry about the first.
Don't include questions on subscription orders
or inquiries for other departments of Doubleday,
Page & Company.
In asking questions give us all the information
that will aid in advising you. If the question
relates to apparatus described in RADIO BROAD-
CAST, give the issue, page number, and figure
number of the circuit diagram, etc.
Be explicit yet brief.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
487
F^HSfElL -|
Balkite
T{adioPower Units
Entirety Noiseless
"Permanent
_ ^^^^MH|^^^.^
Convert your present receiver into
A LIGHT SOCKET SET
with
Balkite Radio Power Units
-
c-Askyour Tfydw Dealer
Manufactured by FANSTEEL PRODUCTS COMPANY, Inc., North Chicago, Illinois
Sole Licensee] in the United Kingdom:
Messrs Radio Acceiorie> Ltd., 9-13 Hythe Rd., Welloden, London, N.W. 10
*
-4r Tested and approved bv RADIO BROADCAST
488
RADIO BROADCAST ADVERTISER
TONE
Full, sweet, mellow and
natural, without the
slightest indication of
distortion, is another
achievement that is mak-
ing the APEX SUPER
FIVE the most popular
of all receiving sets.
VOLUME
That supplies dance mu-
sic or entertainment
without any loss, is a fea-
ture for which the APEX
SUPER FIVE is world
famed.
DISTANCE
Lends added enjoyment
to radio with an inde-
scribable fascination of
tuning-in far away sta-
tions, which is always
possible with the APEX
SUPER FIVE.
Ask your dealer for a demonstra-
tion. Your eyes and your ears will
tell you that APEX stands at the
high point of perfection in both
performance and appearance. $80
without accessories.
SUPERS
APEX ELECTRIC
MFG. CO.
1410 W. 59th Street
Dept. 204
CHICAGO
:Now, I HAVE FOUND
A Department for the Exchange of Ideas and Sugges-
tions of Value to the Radio Constructor and Operator
CONTRIBUTIONS to this department are welcome and those used will be
paid for at the usual rates, that is, from two to ten dollars each. A prife
of twenty-five dollars is given for the best idea used during each three-month
period. The prizewinner for the last period is Mr. J. T. Carver, of Hunting-
ton, Tennessee, whose description of a home-made loud speaker appeared in the
last (January) RADIO BROADCAST. Manuscripts should not exceed about
three hundred words in length, and should be typewritten. Little consider-
ation can be given to manuscripts not typewritten. Envelopes should be
addressed to this department, RADIO BROADCAST, Garden City, New York.
USING A VOLTMETER AS A
MILL1AMMETER
IN LOOKING for trouble in a receiving
set, it is often convenient to connect a
milliammeter in the negative B battery
lead. Thus, as each tube is plugged in or
turned on, the change in plate current, and
thus the current drawn by this tube, may
be readily observed. A tube that is worn
out will draw very little plate current. If
there is an open
plate circuit
(caused by a
burned-out trans-
former, loud
speaker or defec-
tive jack, etc.) it
will be readily de-
tected as there will
be no increase in
the milliammeter
reading when the
tube with the open
plate circuit is
turned-on.
If a milliamme-
ter is not available
for this use, a volt-
meter may be em-
ployed as a sub-
stitute. The
deflection of a
good voltmeter is
directly propor-
tional to the
current passing
through it. The
currerft required
for full-scale de-
flection may gen-
erally be obtained
from the manu-
facturer of the
meter.
For example, a Weston 301 eight-volt
meter has a full scale deflection of 16.12
milliamperes, and there are 40 divisions on
the scale. As the reading is in proportion
to current, the reading in scale divisions
multiplied by 16. 12 and the quotient divided
by 40, gives exactly the current passing
through the meter in milliamperes. For this
particular meter it figures number of divi-
sions times .4 approximately. Thus a read-
ing of six scale divisions would indicate
6 x .4, or 2.4 milliamperes plate current.
CLAUDE SCHUDER,
Sumner, Illinois
COIL DESIGN DATA
IT HAS been generally acknowledged in
radio circles that d.c.c. wire is very satis-
factory for radio purposes, and most
designers, accordingly, specify this type of
wire in the construction of their coils.
k Tested and approved bv RADIO BROADCAST -
A PRIZE-WINNING IDEA
The home made loud speaker described by Mr.
J. T. Carver in this department of the January
RADIO BROADCAST, was awarded the quarterly
$25 prize offered by this magazine for the best
contribution published in the "Now, I Have
Found . . ." Section. Complete construe-
tional data on the construction of the speaker ap-
peared in the January number. The winner of
the next prize, that offered for the February,
March, and April period, will be announced in
the May RADIO BROADCAST. Al! manuscripts
for this department should be prepared and sent
according to the conditions given at the top of this
page. Special consideration is given to typewritten
manuscript.
The main reason for this preference seems
to lie in the fact that the comparative thick-
ness of double cotton insulation is instru-
mental in producing low distributed capac-
ity, which is, as is well known, a very desir-
able quality.
The majority of the present day variable
condensers with air dielectric, possess ex-
ceedingly high maximum to minimum ca-
pacity ratios, and naturally, very low min-
imum capacity values. Such condensers,
coupled with really
efficient radio coils
of low distributed
capacity, tend to
extend the lower
limit of our wave-
length range, thus
permitting us to
tune-in more of
the low power, high
frequency, Class
A, broadcasting
stations.
Unfortunately, a
coil madeof double
cotton covered
wire is quite in-
efficient in moist
weather because
cotton is highly
hygroscopic, which
means that it will
absorb moisture
from the air. Not
only is the effi-
ciency of such a
coil variable, but
it is often variable
to such an extent
as to make long
distance reception
in moist weather
practically impos-
sible.
To eliminate the undesirable hygroscopic
characteristic of d.c.c. coils, it has been
suggested that such coils be painted with a
light coat of thin shellac. True enough;
such precautions protect the coil from
moisture without adding greatly to its dis-
tributed capacity . However, even this in-
crease in distributed capacity, when added
to other losses inherent in construction of
the coil, causes diminished efficiency and
a shorter radius of reception.
It is for this reason the writer suggests
that celluloid cement be substituted for
shellac in coating d.c.c. coils. Celluloid
cement will: — •
1. Add less than shellac to the distrib-
uted capacity of the coil.
2. Decrease dielectric losses by making
the coils self supporting, as the winding form
may be removed when the cement dries.
Note: When such a coil is removed from
RADIO BROADCAST ADVERTISER
489
FER KENT
Fifteen acres of radio
does it mean to you?
*
Radio Speaker
Model H, $22
Model 20 Compact,
Prices slightly higher
from the Rockies west,
and in Canada.
Every Sunday Evening
The Atwater Kent Radio
Hour brings you tbe stars of
opera and concert, in Radio's
finest program. Hear it at
9:15 Eastern Time, 8:15
Central Time, through :
WEAF • New York
WJAU Providence
WEEI Boston
WCAP Washington
WSAI Cincinnati
WCCO Minn.-St. Paul
. . Philadelphia
alternating
\VCAE Pittsburgh
WGR Buffalo
WOC Davenport
WTAG Worcester
KSD St. Louis
WWJ Detroit
WEAR Cleveland
WLIB Chicago
VF. >
voo )
T OOK at this building. It is the
-«— ' factory where Atwater Kent
Receiving Sets and Radio Speakers
are made.
To every dealer this picture tells
a story of Stability.
Already the largest radio factory
in the world, our plant is still grow-
ing. The demand for Atwater Kent
Radio has proved that we didn't
have room enough.
By May, a three -and -one -half
acre addition will be completed. The
main building will then cover nearly
fifteen acres.
If this isn't enough, we shall go
on building, for we have the ground.
Think of it! Fifteen acres of radio
— and every part of every Receiving
Set and Radio Speaker made from
our own designs by our workers in
our own way. And every set and
speaker constructed with as much
care as if this were the smallest fac-
tory in the world and we had a repu-
tation yet to win.
Thus we prove our confidence in
Radio now and in Radio five, ten,
twenty years from now- indefinitely.
Look at this picture again and let
it remind you that
1. A sound product, rightly designed,
carefully manufactured, and sold at
a sensible price made possible by
large production and modern meth-
ods, has become so popular that it
takes a fifteen acre plant to meet
today's demand.
2. The Atwater Kent Manufacturing
Company has invested its money
in this plant because it is in the
radio business to stay.
Is not this something to think about?
Write for illustrated booklet telling the
tomflete ttorj of Atwater Kent Radio
ATWATER KENT MFG. CO.
j4. Atwater Kent, President
4726WISSAHICKON AVE. PHILADELPHIA
Tested and aooroved bv RADIO BROAHCAST
490
RADIO BROADCAST ADVERTISER
You can't tell the KODEL MICROPHONE
LOUD SPEAKER from the microphone the
broadcasting stations use — they are exactly
alike in size and appearance.
The efficient Kodel Sound Unit, with an in-
genious new snail-shell horn, mounted inside
the microphone case, produces a remark-
ably clear, full -toned volume. Non-vibrating
tone chamber absolutely eliminates dis-
tortion.
$15 model incorpo-
rates Kodel, Jr. unit
equipped with large
Kodel unit $20
Radio dealers
where have
them.
THE KODEL RADIO CORP.
505 E. Pearl St. Cincinnati, O.
RECEIVERS :: SPEAKERS
HOMCHARGERS
Owners of Kodel Broadcasting
Station WKRC. Send for program
Books by Telegraph
between
New York
Cleveland
Kansas City
Springfield
Toledo
St. Louis
Doubleday , Page Book Shop
the winding form, it is necessary to paint the
inside of the coil in order to render it abso-
lutely non-hygroscopic.
Now a few words about the preparation
of the celluloid cement. Obtain a wide-
mouthed bottle of acetone and small pieces
of celluloid, the quantity to be determined
by experiment. The latter does not have
to be purchased, as old photographic films
can be used after the emulsion has been re-
moved in hot water.
Into the acetone throw a quantity of cel-
luloid, taking care that the pieces are small.
Leave the bottle overnight and in the morn-
ing it will be found that the celluloid has
been dissolved. The consistency of the
solution should be that of a thin syrup.
By adding to the solution, either more ace-
tone or celluloid, you will obtain the right
consistency.
Apply the cement with a brush, and keep
the bottle well stoppered at all times, as
the acetone has a tendency to evaporate
and leave the cement too thick.
BORIS S. NAIMARK,
New York City.
A SIMPLE LONG-WAVE RECEIVER
THE radio fan who has not built him-
self an ultra audion set to play with
when his regular equipment fails to
function, just doesn't know how much fun
he is missing.
The expense of a set of this sort is quite
modest and its performance is certainly
wonderful. The transoceanic code stations
come booming in on almost any frequency
band from 300 down to 20 kilocycles (1000 to
1 5,000 meters) — and on even longer waves.
The big fellows give excellent code practice
for nearly all of them send very slowly, and
repeat each word.
I wish I could radiate some of the pleas-
ure and enthusiasm I get from the little
FIG. I
The completed ultra audion receiver. Not the
slotted strip of bakelite which permits variable
coupling between the two coils
ultra audion set pictured above. There
must be thousands of others, who, like
myself, want to get a little vacation from
the broadcasting territory on those occa-
sions when the programs just don't seem
to fit one's mood. There are all sorts
of strange and mysterious territories to
explore where whistling treasures may be
picked up. The big European stations
talk with the Americans, and Panama
sends up tones from the tropics.
I have built a number of ultra auaion
circuits, and all functioned very nicely.
f Tested and approved by RADIO BROADCAST i
But there are drawbacks; the annoying
instability of the circuit for example, and
the squeals and howls from body capacity.
Many times I have found it essential to sit
perfectly still to hold a very distant station.
Finally 1 made a discovery. By connecting
the metal case of the head phones with the
ground, the set immediately settles down to
steady work. I have a six-foot piece of
silk-covered tinsel cord with a test clip on
each end. 1 clip one end to the headband
adjustment and the other to the ground
post. It is not well to twine the cord
around the phone cord but permit it to
hang loosely.
Strange as it may seem, another improve-
ment that has been decidedly satisfactory
is the addition of a tickler. The illus-
tration, Fig. i, shows how a coil mounting
12
I
B •=
J
FIG. 2
The circuit diagram of the ultra audion. A tick-
ler coil arrangement can be included as shown
is attached to a sliding strip of bakelite,
and held in place with a thumb nut. This
coil is inserted between the positive B
binding post and the plate connection on
the socket. The condenser has a capacity
of .0005 mfd. Any tube may be used but
1 seem to get best results with a standard
UV-2OO or 0-300 with about 22 volts on the
plate. For an antenna for the transoceanic
stations, with a coil of 1000 to 1500 turns,
I have a stretch of about 125 feet of single
copper wire, thirty feet high. The tickler
for the very large coils should increase in
size in proportion. For instance, with
1500 turns I seem to get best results with
a 500-, or 75O-turn tickler.
Other than adding the tickler and the
grounding of the phone caps, the hookup is
exactly the same as shown in the DeForest
catalogues of seven or ten years ago. The
circuit is shown in Fig. 2.
H. H. BUCKWALTER
Denver, Colorado.
A GOOD AUDIO AMPLIFIER
BEING convinced that the cone type
of speaker does not do itself justice
on the standard two-stage audio
amplifier, I am giving the wiring diagram
of an amplifier which in my opinion will
really give the volume and true repro-
duction which we all strive for. See Fig. 3.
Used with a three-circuit tuner and tube
detector, it will furnish the most perfect
quality I have yet heard.
The parts may be assembled to suit the
fancy of the constructor, remembering only
the standard precautions about short grid
leads, transformers mounted at right angles
and non-parallel leads. Although there
are three stages of audio, the amplifier
RADIO BROADCAST ADVERTISER
491
Sixteen newspaper and radio publications have saved you
the work of trying out various B battery eliminators —
They have put their official okay
on the
TIMMONS
Patented May IS. 1923
We would like to tell you something about the
tests to which these publications subject the
B-Liminators. For this purpose we have pre-
pared a folder which we will send. All of these
tests were more severe than conditions the B-
Liminator will ever meet on your set.
In this folder you will also find quoted in the
exact words of publications just what the tests
showed.
B-Liminators operate on 110 volts, 60 cycle alternating
house current and completely eliminate all B batteries
The Timmons Laboratories, which produced the B-Liminator, have now developed the
Timmons Cone Talker
Price, $25.00
14-inch Cone
There are years of experience in acoustics behind
this new Timmons Cone Talker. However, as
most of the adjectives have been exhausted in
describing other loud speakers, we'll just ask you
to hear the new Timmons Cone. If you wish,
we'll first send you a folder telling you all about
it. Your dealer handles both the Timmons
B-Liminator and Timmons Cone Talker — or
we'll tell you one who does.
Timmons Radio Products Corporation
Germantown, Philadelphia, Pa.
TIMMON S Radio Products
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
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will not howl or distort, and there is no neces-
sity for grounding the transformer frames.
If the amplifier is to be used in connection
with a radio frequency set, it is advisable
to use either two tubes in parallel in each
half of the push pull, making four tubes in
the last stage, or use two power tubes, as
the volume to be handled will overload two
of the 2OI-A type tubes.
A list of material is given below, and
although it is not necessary to adhere
strictly to the list of manufactured parts
given, it is essential to use good trans-
formers.
2 Amertran transformers, ratio 5:1.
1 set of Western Electric or Como push-pull
transformers.
2 Bradleystats.
i single-circuit jack.
4 General Radio sockets.
i "Turn-It" grid leaks.
1 2-mfd. fixed condenser.
2 .oo2-mfd. fixed condensers.
2 .ooi-mfd. fixed condensers.
Only one jack is used, as I find that better
tone quality is obtained by using all the
tubes and controlling the volume by the
besides. How to eliminate them, and not
reduce the volume to the two-tube level
was at first a problem.
Connecting a resistance across the secon-
dary of the additional transformer effici-
ently eliminated the squeals and the volume
also. It was found that varying direct
and reversed grid biases had much the
same effect.
While disconnecting one of the various
unsuccessful arrangements, the dulcet tones
of a local station suddenly half deafened
the operator ! Upon said operator's spring-
ing back in surprise, the old familiar med-
ley of horrible sounds came back in full
force. In short, placing the hand of a
human ground on the grid terminal of the
second transformer accomplished what
nothing else had done. The trail now being
clearly blazed, a variable resistance of
25,000-100,000 ohms was connected be-
tween this point and the ground.
Using this arrangement, a signal which
is audible on a cone speaker with two tubes,
when the ear is placed very close to the
instrument, is magnified sufficiently to fill
comfortably quite a large sized room.
Signals from WBZ at a distance of about one
FIG. 3
The connections for the quality audio amplifier from the output of the detector tube are
shown in this diagram. There are three stages of audio but four tubes are employed
regenerator, or if the set is non-regenerative,
by the detector and first amplifier rheostat.
Due to the high amplification obtained,
it will often be found that unless ex-
ceptional volume is desired, the tubes may
be operated at four volts, thus lengthening
their life and compensating for the ad-
ditional tubes used. For those who do
not use a voltmeter, I would suggest that
the tubes be turned up to normal brilliancy
while tuning-in, and then turned down as far
as possible without destroying the tone
quality.
EDWARD T. WERDEN
Mount Vernon, New York.
IMPROVING THE VOLUME OF THE
TWO-TUBE ROBERTS CIRCUIT
DESIRING more volume than that
obtained from the usual Knock-
out two-tube set, and not want-
ing to change the whole arrangement of
the apparatus, I added one step of or-
thodox transformer-coupled audio ampli-
fication. Using a G. R. Type 285 audio
transformer gave enormous volume — and a
thousand raucous squeals, noises, and howls
hundred miles are rather too loud for
comfort in a large room.
As an important afterthought, I should
like to emphasize the fact that the quality
obtained — both transformers being of the
type mentioned — is good enough to have
caused surprised comment from a large
number of people.
J. W. TEALE,
Boston, Massachusetts.
WINDING SPIDER WEB COILS
I HAVE found that two empty thread
spools, together with a bolt of sufficient
length, a nut, and washer, are of much
help in quickly and accurately winding
spider web coils.
The bolt is passed through one spool,
then through the hole in the center of the
coil form, and then through the other
spool, after which the washer and nut are
placed on the bolt and the nut tightened.
This gives a firm and convenient handle
for holding the form during winding, greatly
facilitating that process.
H. EDWARD KNIES,
White Haven, Pennsylvania.
RADIO BROADCAST ADVERTISER
493
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these I NATIONAL RADIO INSTITUTE
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Washington, D. C.
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Dept. BUS, Washington, D. C.
g^SSp^pjj^
ORIOINATORS OF RADIO HOME-STUDY TRAINING
Without obligating me in any way, send me your free book, "Rich
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RADIO BROADCAST ADVERTISER
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money— simply pay the expressman cost on delivery. Or write for
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B. Hawley Smith, 312 Washington Ave.. Danbury, Conn.
What Constitutes a Radio Patent?
By LEO T. PARKER
Patent Attorney
ANY radio experimenters overlook
opportunities of obtaining the pro-
tection afforded by the patent laws,
simply because they are unfamiliar with the rules
by which to determine the kinds of radio in-
ventions that present patentable possibilities.
Others of these inventors and experimenters do
not understand the essential requirements of an
invention in order that a good patent may be
obtained on it.
There are at least two very important things
about which all experimenters should be fa-
miliar. One is what the word "invention"
really means when it is construed in relation
to radio circuits. The other is how the United
States Courts have dealt with important radio
patents in the past.
In the first place, the word "invention" really
means any newly discovered thing or method
which, when put to a practical test, will produce
useful results. It makes no difference if the
various parts or elements of which the invention
consists are old and well known. The important
requirement is that these old elements co-act
to accomplish new and beneficial results. So,
therefore, merely changing a wire in a radio cir-
cuit may effect an entirely new and patentable
circuit, because the signals are received with
improved tone quality, or the volume of the
incoming signals is increased, or greater selectiv-
ity is effected, or any other of the many desirable
results is attained.
Many individuals believe Marconi was the
first person to discover wireless telegraphy.
But he was not. Others had accomplished this
result many years before him.
Going back to 1905, we find the first United
States adjudicated radio patent was that of
Marconi's reissue No. 11,913. The validity of
this patent, after lengthy litigation, was upheld.
His original patent was dated July 13, 1897,
and related to apparatus used in transmitting
electrical impulses and signals, particularly re-
lated to spark telegraphy. This original patent,
however, did not protect the invention as he
thought it should, so he cancelled it and had
ano'her patent issued in its stead.
During the legal controversy, various patents
and experiments were brought to the attention
of the court in an attempt to have Marconi's
patent declared invalid, and considerable money
was spent toward this end. Nevertheless,
Marconi was declared to be the first inventor
of wireless telegraphy.
One of the first methods to be utilized for the
purpose of sending wireless messages was the
Dolbear System. A conductive principle was
employed on the banks of a body of water, and
comprised primary and secondary circuits
suitably positioned on the opposite banks,
while wires were stretched along both banks
and connected with the ground. By means of
this improvised arrangement together with the
assistance of batteries, galvanometers, and
either telephone or telegraph instruments, the
currents of electricity in the primary, generated
by the batteries, were passed across the body of
water to the terminal of the secondary circuit,
thereby making and breaking the connections
of the receiving apparatus, corresponding to the
intermittent changes of the current set up in the
primary circuit. However, the greatest distance
covered by the Dolbear System was about two
miles.
Another method of transmitting wireless
messages had been used, consisting of the
•if Tested and approved by RADIO BROADCAST •*•
principle of induction, and based upon the theory
of an arrangement of primary and secondary cir-
cuits. A battery was connected with the primary
which was positioned parallel with the secondary.
By actual test it was found that a current
made or broken in the primary circuit induces
a transient current in the secondary circuit.
This wireless system was successfully demon-
strated prior to 1887, with the utilization of
elevated conductors, vertical wires, and ground
conductors, and messages were sent through
the air for short distances. Also, in 1865,
Professor Maxwell discovered that electricity,
made manifest in the form of a spark, will
spread out in waves or undulations similar to
sound waves and he produced the effect by
means of a special radiator.
However, the important difference between
Marconi's invention and the prior ones was that
Marconi realized his messages were sent through
the ether by means of high frequency currents
of electricity and, therefore, he was enabled to
devise suitable instruments with which to in-
crease the distances over which he could com-
municate, thus rendering the invention highly
useful, and not a mere experiment.
In the patent specification Marconi referred
to his invention as "Electrical signals, actions
or manifestations, which are transmitted through
air, earth, or water, by means of oscilliations of
high frequency."
Marconi, therefore, has been said to be the
discoverer of the fact that high frequency cur-
rents are essential in the successful sending of
wireless messages. He also invented instru-
ments particularly adapted to send and receive
this type of current. Although other persons
before him had accomplished similar results
through accident, they did not know why the
phenomenon took place. In one sense of the
word, all Marconi did was to adopt, improve,
and elaborate upon existing theories, and put
the various principles on a substantial work-
ing basis.
It should be remembered that, irrespective
of how old or well known the elements of a new
radio circuit or other invention may be, if by.
means of this new combination or arrangement
the old elements are caused to co-act to perform
new and different results, such an arrangement is
a patentable invention. It does not matter how
old or common the various parts or elements are,
the important thing is whether, when acting
together, they effect a new and unitary result or
function.
THE HETERODYNE PATENT
A LMOST every inventor knows that a basic
** patent is construed broadly in favor of the
patentee, but many persons do not know that
an invention need not relate to an entirely new
science to be basic. It may relate merely to a
new application of a well known thing, as is
verified by a very recent United States Court
decision on the validity of the heterodyne patent,
which was declared to also cover the super-
heterodyne principle.
Two patents were obtained by Mr. Fessenden
on his invention of the heterodyne; one for the
method of accomplishing the results and the
other for the apparatus itself. The numbers of
these patents are, respectively, 1,050,441 and
1,050,728, and any person desiring to examine
the patents may secure them (and any others
for that matter) merely by addressing The
Commissioner of Patents, Washington, District
RADIO BROADCAST ADVERTISER
501
flRBORPHONE
What You Expect
of Your Set
'"pHERE are several thou-
•*• sand men and women,
owners of Arborphone Receiv-
ers, who will tell you — •
"You cannot equal my Arborphone
— It's all you could ask of a radio."
Anyone can tune in enough
stations to satisfy the most
ambitious air-adventurer.
From stations near or far there
is a delightful ease of tuning
and purity of tone quality un-
surpassed in radio.
Arborphone gives you perma-
nent radio. Like any good
musical instrument your pleas-
ure in Arborphone will be
measured in years.
Housed in a really beautiful
cabinet Arborphone lends "a
new charm to your prettiest
room.
You cannot buy better radio —
at any price. Ask any Arbor-
phone owner or dealer.
Most interesting radio facts —
written for everyone to under-
stand— are described and illus-
trated in Arborphone Catalog.
A copy sent free at your re-
quest.
$60.00 in Rocky Mi. and
Pacific Coast States.
MACHINE SPECIALTY COMPANY
ANN ARBOR, MICHIGAN
This is a good time to subscribe for
RADIO BROADCAST
Through your dealer or direct, by the year only $4.00
DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORK
ealers
If you are the type of dealer who hustles after business, who
isn't content to wait for trade to come in but who takes sets out
to demonstrate, can talk and eell quality merchandise, and
knows Radio values, we have a big proposition for you. Are
you that dealer?
5O% Discount to Dealers
_ We manufacture a complete line of high
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discount. We are distributors for more than
•225 Nationally advertised lines.
FREE Write ted*y for amazing offers, new
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AMERICAN RADIO MFG. CO.
426 MoGee St., Kaunas City, Mo.
BUY ALL YOUR FUTURE
B- CURRENT NOW!
RADIO PEP
B-BATTERY ELIMINATOR
is unique in that it stops ALL the hum by using
EIGHT perfected electrolytic cells and NO
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Plugged into the standard AC house lighting
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ECONOMY! No more drain of buying new
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Send for particulars and the address of the near-
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* PEP MFG. CO., Inc.
33 West 42nd Street
New York
Tested and approved by RADIO BROADCAST
502
RADIO BROADCAST ADVERTISER
What You COULD
Get From Your Set
IT isn't what you're getting now. It's
how much more you could get from
your present set.
Your set may be one of the finest in
the world but it can be no better than
its dials.
The human hand cannot tune ordinary
dials sufficiently accurate to bring in all
the stations within scope of your set.
That's where Science has stepped in
with the two dials shown above.
MYDAR Recording Dial shown at the
left above, offers a degree of tuning
efficiency not usually associated with
this price. Ample space for call letters
insures permanent logging of all stations.
Genuine Bakelite, handsomely embel-
lished—12 to 1 Ratio. Price $1.75.
The A. J. (Vernier) shown at the right
above, geared at 150 to 1, brings tones
into sharp focus like a fine camera lens.
Beautiful, dignified. Genuine Bakelite.
A master product of master craftsmen.
—Price $2.25.
Accuratune (not shown) geared 80 to 1
is admirably suited to every type of
tuning requirements.
No panel drilling necessary to substitute
any one of these dials.
MYDAR Radio Company
3 CAMPBELL STREET
NEWARK, N.J.
Tested and approved by RADIO BROADCAST
of Columbia, and enclosing ten cents for each
copy specified by the numbers.
Heterodyne, as applied to radio, is a method
by which signals are produced by beats, whose
frequency is equal to the difference between
that of a transmitted frequency and that of
locally produced oscillations. This accomplish-
ment was the important consideration for which
Mr. Fessenden was granted patents.
Broadly speaking, the method of generating
local oscillations, as performed by Mr. Fessen-
den, was a beat system, old and well known in
acoustics. The same results have been produced
many times by means of various musical in-
struments, such as tuning forks, pianos, etc.
In other words, he simply applied a well known
scientific principle to a different purpose whereby
new and beneficial results were accomplished —
an absolutely safe foundation upon which a
highly valuable and valid patent may be
obtained.
The courts regard the heterodyne invention
as one of the highest order and entitled to a very
broad scope, because it was the first application
of the old beat system in radio apparatus.
Another important thing to remember is that
Mr. Fessenden's patents do not infer or suggest
that his invention is intended for voice or
concert reception. Notwithstanding this, the
court refused to limit the patent and sustained
it as a basic patent which covers any kind of
beat system of radio reception, including the
super-heterodyne receiving set.
At a later date a Mr. Vreeland applied for
certain super-heterodyne patents but the courts
decided that although his patents Nos. 1,239,852
and 1,245,166 on the super-heterodyne circuit
doubtless improved Mr. Fessenden's invention,
he could not build his circuit without infringing.
This decision brings out another important point,
namely, that an improver of a valid patented
radio circuit cannot proceed to build his improve-
ment, in which is incorporated the original
circuit, without paying a royalty to the original
patentee.
Mr. Vreeland contended that, while his
patent may infringe Mr. Fessenden's patent,
it goes beyond it and makes a substantial
contribution to the original patent. In spite
of obvious differences between the heterodyne
and super-heterodyne circuits, the heterodyne
patents are broadly construed, in favor of the
inventor, to cover the super-heterodyne principle
of receiving incoming signals, even though the
beat system is old in acoustics, and Mr. Vree-
land's claim could not be sustained.
IMPORT DUTY ON RADIO
GOODS FOR AUSTRALIA
A CONSIDERABLE amount of American
and British radio apparatus is now on the
market in Australia, and there is keen competi-
tion between these two importing countries.
Contrary to general opinion, even Britain is
charged duty on her imports, but the percentage
is not so high as it is for American apparatus.
Radio sets imported into Australia from this
country are chargeable at the rate of 55 per cent,
ad valorem, while British set manufacturers are
required to pay a duty of only 35 per cent.,
according to the Broadcaster and Wireless Re-
tailer of London. An intermediate figure of
50 per cent., is applicable to certain countries.
British tubes were allowed into Australia duty
free until January ist of this year, but a 275
per cent, duty is now levied. American tubes
are taxed at the rate of 40 per cent, ad valorem.
The general tariff on tubes was only 1 5 per cent,
until recently. There is an intermediate tariff
of 35 per cent, on tubes from certain countries.
A general revision of duties on radio apparatus
came into force on January ist.
RADIO BROADCAST ADVERTISER
503
0
The Ideal
Receiver !
A DVANCED engineering and
/-\ years of production expe-
rience by one of the oldest
radio manufacturers in the coun-
try produced the new Chelsea
Super-Five— a Receiver with
performing features and refine-
ments found in much higher
priced sets.
Fine mahogany finish cabinet
with graceful sloping panel and
large dials for easy tuning. Con-
venient cord leads (no unsightly
binding?posts). Foolproof, dust-
proof inside panel to protect del-
icate parts. Rugged bus-wiring,
hand-soldered connections and
other refinements. This Set de-
livers wonderful tone quality and
volume and is one of the most
selective sets on the market.
Choote Chelsea and save the
difference
Write us to-day for New
Descriptive Folder
CHELSEA RADIO CO.
Chelsea, Mass. ,JL,
RADIO FANS, a one-year's subscription to Radio Broadcast will cost
you four dollars, two years six dollars. Consider this expenditure
as hoinu a necessary investment on your part for the future develop-
ment of your own knowledge of Radio.
rMOONTFORD:
• PLUNGER TYPE VARIABLE
GRID LEAK
Perfect graduation, obtains all
fractions of a megohm from ^ J
to 20 inclusive. Increases selec-
-ivity and sensitivity. UnaiFect-
. -. ed by heat or cold. Maintains
ff accuracy of range and consistency
of resistance. At your dealers or A
postpaid upon receipt of price.
W* also manufacture the Mountford Resist-
ance Coupled Kit, Prift postpaid tS.SO
C. E. MOUNTFORD
469 Greenwich St.
New York City
The New
SUPER
UNIT
t
This Speaker
Has the NEW VOICE!
t • ^»HE small diaphragm commonly used reproduces the
^ middle and upper notes of the musical scale well
enough, but it leaves much to be desired from the
middle down. Verify this yourself. Listen to almost any
speaker and you will be amazed at the muffled sound of the
middle and lower registers of voice and instrument.
The Bristol Speaker is equipped with that latest discovery
in tone reproduction, the SUPER-UNIT. This unit con-
tains an unusually large diaphragm which brings in the
full range of tones from deep bass to high treble.
The rumble of the tympani, the roll of the snare drum, the
low tones of the viols, tuba, organ, saxophone and voice —
notes you've never before heard in radio — notes which are
even more vital in reproduced music than in an actual con-
cert— are clearly and naturally audible.
The cabinet is highly polished mahogany, 17 x 10 x 10 j
inches in size, with long, freely vibrating sound chamber.
The price is $30. Ask your dealer for a demonstration and
at the same time.
Send for FREE BOOKLET
*- - 1
entitled, "How to Select Your Loud Speaker."
It tells how to look for and find tone quality
in a speaker.
BRISTOL SPEAKER
(AUDIOPHONE)
The Bristol Company Radio Div. AH, Waterbury, Conn.
For 36 years makers of the highly sensitive and accurate Bristol's Recording Instruments
Tested and approved by RADIO BROADCAST
504
RADIO BROADCAST ADVERTISER
This 4-inch dial, calibrated on
entire circumference, is built in
as part of the condenser.
"Spreads" Stations All Over the Dial
OTATIONS won't overlap one another
O when you use the Wade Condenser
Tuning Unit. This unique condenser is
geared to a dial that is graduated all the
way around — from 2gro to 360 degrees.
This means twice as much space between
stations for close tuning adjustment; even
wider separation of stations than the
rotor plate types of straightline frequency
condensers using standard 180 degree
dials. If you are one who is tuning now
with only "half a dial" you are in for a
pleasant surprise when you try Wade
Condenser Tuning Unit. It covers the
whole broadcast range and down below
200 meters.
No Body Capacity Effects
A separately grounded frame, insulated
from both sets of plates, shields the con-
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important feature, exclusively in Wade
Condensers.
Wade Tuning Unit
Including
Condenser and Dial
The Wade Condenser
Tuning Unit consists
of a Wade Condenser
geared to a four-inch
360 degree vernier dial
of 16 to 1 ratio. Prices
are for the complete
unit.
Capacity
.000125 mfd. #6.00
Capacity
.00025 mfd. #6.25
Capacity
.00035 mfd. #6.35
Capacity
.0005 mfd. #6.50
Dealers
Dealers and jobbers,
as well as the radio
public, will be inter-
ested to note the addi-
tion of a .00035 mfd.
capacity model to our
regular line. We have
had many calls for this
capacity and it will be-
yond doubt meet with
popular favor.
The Viking Tool and Machine Co. Inc. 745-A 65th Street, Brooklyn, N. Y.
_Q
Why not subscribe to Radio Broadcast? By the year
only $4.00; or two years, $6.00, saving $2.40. Send direct to
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Why pay more? Eldredge meters are accurate and long-lived.
// dealer can't supply you, write us direct
Dept. B
Eldredge Electrical Corporation -^
Springfield
Mass.
Established 1892
A KEY TO RECENT
RADIO ARTICLES
By E. G. SHAULKHAUSER
THIS is the fourth installment of references to
articles which have appeared recently in var-
ious radio periodicals. Each separate reference
should be cut out and pasted on cards for filing,
or they may be pasted in a scrap book either
alphabetically or numerically. A brief outline
of the Dewey Decimal System (employed here)
appeared in November and January RADIO
BROADCAST.
R8oo(535.3) PHOTOELECTRIC PHENOMENA. PHOTOELECTRIC
Radio News. Oct. 1925, pp. 436ff. CELL.
"The Luminptron," T. H. Nakken.
The description of a new type of photoelectric cell, and
its application to many unsolved problems, is outlined by
the inventor in this article. The cell is of the potassium
plate type. Its fundamental working principles, and some
of the results obtained with the tube, make this cell very
reliable.
. BROADCASTING. BROADCAST RANGE,
Radio News. Oct. 1925, pp. 446^. Covering the.
"Extending the Broadcast Range," S. Harris.
A possible expansion of the present broadcast band
will necessitate changes in most radio receivers to cover the
entire range. The difficulties encountered and the best
solutions are presented in an excellent discussion by the
author, who comes to the conclusion that tapped coils will
most likely be necessary.
R343- ELECTRON TUBE RECEIVING SETS. RECEIVER,
Radio News. Oct. 1925, pp. 448-449. 2000-600 kc.
(i5o-6oom).
"Another Three-Range Receiver."
Anticipating an expansion in the broadcast band of wave-
lengths, the receiver here described and illustrated uses a
novel scheme in covering the range. Sets of coils of three
sizes are built, and mounted to fit into an ordinary tube
socket. The receiver is of the regular two-stage radio
frequency type, using three tuning dials.
Rii3-8 ECLIPSES. ECLIPSE, SOLAR.
Proceedings I.R.E. Oct. 1925, pp. 539-569.
"The Effect of the Solar Eclipse of Jan. 24, 1925, on
Radio Reception," G. Pickard.
A complete resume of the observations made under the
direction of the author, is presented, with diagrams and
illustrations. The data collected lead to certain conclusions
and put us several steps ahead in our search for information
concerning the behavior of ether waves in space.
R-33I. CONSTRUCTION OF VACUUM TUBES. VACUUM TUBES.
X-L filament.
Proceedings I. R. E. Oct. 1925, pp. 580-609.
"The Application of the X-L Filament to Power Tubes,"
I. C. Warner and O. W. Pike.
The properties of the X-L or thoriated tungsten filament,
are discussed, with particular reference to the suitability
of this material for use in power tubes and its advantages
over other materials. Comparisons are given between pure
tungsten and thoriated tungsten filaments in electron
emission characteristics and effect on tube design, and
Eerformance. Several power tubes containing X-L
laments are described in detail. The improvements due
to the use of the X-L filament are illustrated by comparison
of these tubes with older types of tubes containing pure
tungsten filaments.
R375. DETECTORS AND RECTIFIERS. RECTIFIER,
QST. Nov. 1925, pp. 38-40. Raytheon.
"The Raytheon Rectifier," M. Penny-backer.
A theoretical discussion of a new rectifier tube, the
Raytheon, is given by one of the manufacturer's engineers.
The tube is a full-wave rectifier, and has many new features
which make it exceptionally well adapted to B battery
eliminator operation, according to the author. The curve in
Fig. 5 shows the relation or output voltage to output current.
A completed rectifier unit is shown in a photograph.
R35O. GENERATING APPARATUS; TRANSMITTER,
TRANSMITTING SETS. Crystal-Control.
QST. Nov. 1925, pp. 41-44.
"Navy Developments in Crystal Controlled Trans-
mitters."
A detailed account of the developments of crystal con-
trolled transmitters at the Naval Research Laboratory,
Bellevue, District of Columbia, is given, beginning with the
first experiments, May ist, 1925. Most of the research
has been done on short waves, according to the account
given. Various types of sets tested, results obtained on
different frequencies, and power input, are described, and
photographs shown for the benefit of the experimenter
who desires this information. The data presented is all
of an experimental nature.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVER,
Radio. Nov. 1925, pp. 25-26. Loop.
"An Improved Loop Receiver," R. L. Rockett.
A five-tube loop receiver, employing three stages of radio
frequency amplification, is presented, with data on con-
struction and assembly. One audio stage is reflexed.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVER,
Radio. Nov. 1925, pp. 27ff. Short-Wave.
" Building for the Future," H. A. Nickerson.
Many stations can be heard broadcasting programs
on very high frequencies (wavelengths below 100 meters)
with a receiver designed for that purpose. Such a receiver
is described in this article. It is a simple regenerative
arrangement.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
505
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on all sets designed for loop reception. Priced at $12.50.
and for sale by all good dealers. Full particulars sent for
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KORACH RADIO CO. *
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Dealers and Jobbers: Write today for attractive proposition.
The Korach Junior
A modification of
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EBY
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/ A three point wiping contact that insures a
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Its ingenious design permits the tube to
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duces microphonic noises to a minimum and
prevents tube damage.
JAll the advantages of inter changeability of
the new UX, CX, and UV tubes for 6oc.
Don't take chances on twenty loose connections
in a five-tube set. Use the new EBY positive
contact sockets for better reception.
H. H.
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write to us sending his name.
EBY MANUFACTURING CO.
4710 Stenton Ave., Philadelphia
This is the EBY Binding Post that is standard equipment on
eight out of ten of the radio receivers made in America—
your dealer has all of the 27 different markings.
Tested and approved by RADIO BROADCAST
506
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TRANSFORMERS,
[-452. Radio.
formers,"
R8oo(535.3) PHOTOELECTRIC PHENOMENA. PHOTOKI.KCTRIC
Popular Radio. Nov. 1925, pp. 397-404. CELLS.
"The Photoelectric Cell," E. E. Free.
The development of photoelectric cells is an outgrowth
of radio progress. This cell is used to convert light beams
into a stream of electrons. There efficiency, at present, is
very low, and the most modern cells still use as active metal
either potassium, sodium, lithium, caesium, or rubidium.
The action taking place within the tube is vividly described.
R375. DETECTORS AND RECTIFIERS. RECTIFIER,
Popular Radio. Nov. 1925, pp. 405-414. Raytheon.
"Raytheon Plate Supply Unit," L. M. Cockaday.
This article describes the new B battery eliminator unit
using the Raytheon tube. Cost of parts is given at about
$45.00. The tube has no filament and will last practically
indefinitely. A detailed description covering the operation
of the unit, and method of constructing, wiring, and testing,
is given.
R8oo(62i.3i4.3) TRANSFORMERS
Popular Radio. Nov. 1925, pp. 444
"Practical Pointers About Transfc
F. E. Nimmcke.
This article gives practical information concerning the
design, construction, and operation of small transformers,
as used in radio engineering. Mathematical equations and
reference examples serve to help the radio engineer in com-
prehending the problems in question.
Ruo RADIO WAVES. RADIO WAVE
Popular Radio. Nov. 1925, pp. 461-464. THEORY.
"Alexanderson's Theory of Twisting Waves."
The theory of twisting waves, as proposed by E. F. W.
Alexanderson, is illustrated by diagram, and discussed.
The phenomenon of polarization, and the effect of the
magnetic field of the earth on such polarized waves, is taken
as a probable explanation of fading signals, and so called
"dead-spots."
R333- THREE-ELECTRODE VACUUM TUBES.
VACUUM TUBES,
RADIO BROADCAST. Dec. 1925, pp. 163-166. | New types.
"Tubes: Their Uses and Abuses, Keith Henney.
The condition under which present-day vacuum tubes
must be operated to get best results, are related. A brief
but very practical discussion on theory and operation of
the detector tube, regeneration in the detector circuit,
audio and radio amplification where voltage as well as
power amplification must be considered, importance of
matching output impedance of last tube with loud speaker
impedance, transformer ratios, resistance-coupled audio
amplifiers, are questions receiving attention. The author
gives considerable information concerning the new power
amplifier tubes, ux-i2O, ux-H2, Daven MU-6, Cleartron
112, WE-2i6-A, and others.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVER,
RADIO BROADCAST. Dec. 1925, pp. 172-176.
Browning-Drake.
"A Five-Tube Receiver of Dual Efficiency," G. H. Brown-
ing.
The receiver described is an improvement of the one pre-
viously described in RADIO BROADCAST (December, 1924.}.
Three stages of impedance coupling are used in the audio
circuit. The construction of the tuned radio frequency
stages is very important. From the curve it appears that
when frequency is plotted against voltage amplification,
the Daven MU-2oand MU-6 tubes, with impedance coupling,
will give greatest amplification without distortion when
compared to other methods of amplification. Parts listed,
and diagrams covering constructional details, enable the
builder to follow instructions without difficulty. The
author lays stress on the careful construction of the Regeno-
former, and gives a very simple method of balancing the
r. f. stage, using a small disc of metal brought near the coil
winding.
R545. AMATEUR RADIO. SHORT WAVES
RADIO BROADCAST. Dec. 1925, pp. 182-184. FOR
AMATEURS
"Short Waves— A New Paradise for the DX Fan," E. H.
Felix.
The great interest manifested in high frequency tele-
graph transmission by the so-called radio amateur, is de-
picted in this article. Short-wave stations communicate
by code generally using small power transmitters (s watts
being a common output). Such apparatus can be con-
structed for sums of $20.00 and up. The receivers are
very simple and rarely use more than two tubes. The
thousands of dyed-in-the-wool "hams" are at their game
day and night and their work constitutes a most important
link in the progress of radio.
R375. DETECTORS AND RECTIFIERS. RECTIFIER,
RADIO BROADCAST. Dec. 1925, pp. 186-100. Raytheon.
"An Improved Plate-Current Supply Unit," R. F. Beers.
The operation of the Raytheon rectifier tube in B bat-
tery eliminator circuits, is discussed. The tube is rated
at 60 milliamps. at 150 volts d. c. output; is very quiet in
operation, and has good characteristics as shown by the
curve. Back currents are not detectable in the tube, and
consequently all filtering problems are simplified. There is
no filament in the Raytheon tube. Data is given enabling
the constructor to build his own transformer and choke coils.
Rii3.6 REFLECTION; REFRACTION;
DIFFRACTION REFLECTOR,
Radio. Nov. 1925, pp. i 3ff. Parabolic.
"Short Wave Reflectors," R. C. Hunter.
Method of constructing a parabolic reflector for the range
from 400,000 kc. to 401,000 kc. (-74Q6-.7477 meters) is
given. This information can be used for building larger
reflectors to operate on lower frequencies. The size here
described can be placed in a small space in a laboratory,
dimensions being about 66 x 30 x 1 8 inches. Diagrams and il-
lustrations supplement the article.
R 342.7 AUDIO-FREQUENCY AMPLIFIERS. AMPLIFIERS,
Radio. Nov. 1925, pp. 16-18. Audio-Frequency
"An Ideal Audio-Frequency Amplifier," E. W. Pfaff.
A three stage impedance-coupled amplifier, for which
unusual amplification quality is claimed, is described. The
theory of the circuit, and the construction of the set, includ-
ing list of parts, are presented in detail.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
507
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514 PAGES
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RADIO
HANDBOOK.
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Compiled by
HARRY F. DART, E.E.
Formerly with the Western Elec-
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edited by F. H. Doane.
THE I. C. S. Radio Hand-
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Electrical terms and circuits, antennas, batteries, genera-
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For tubes with thoriated filaments.
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Boston, Mass.
ACME WIRE RADIO PRODUCTS
Celatsite Battery Cable
For connecting A and B Batteries (or current supply)
to radio set. Silk braid covering 5 flexible Celatsite wires
— 5 feet long — a different color for
each terminal. Prevents messy wiring
and "blown" tubes. Adds greatly to
the appearance of your set.
Stranded Enameled Antenna
The best outdoor antenna you can put up. 7 strands
of enameled copper wire; maximum surface for recep-
tion. Enameling prevents corrosion and consequent
weak signals. 100, 150 or 200 foot coils, boxed.
Loop Antenna Wire
You can make a good loop with Acme wire made of 65 strands of fine copper
wire, green silk covered. Flexible; non-stretching, neat.
The Original Celatsite Wire
Celatsite is a tinned copper bus bar wire with a non-inflammable
" spaghetti " insulation in five colors. Supplied in 30 inch
lengths.
Flexible Varnished "Spaghetti"
A perfect insulation tube for all danger points in set wiring.
Costs little more and is worth a lot more than the cheaper sub-
stitutes offered. Black, yellow, red, green, brown, for wires No.
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Flexible Celatsite Wire
Flexible stranded wire for "point to point" and
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one for each circuit. 25 ft. coils.
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THE ACME WIRE CO., Dept. B
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Make your set a Super -Het
THE circuit described in Radio Broadcast for June and August will change any set
into a super-heterodyne. It is particularly applicable to five-tube neutrodyne and
tuned RF sets. It changes these two circuits into super-heterodynes as good as most,
and considerably better in some respects than any super-heterodyne circuit ever devised.
Stations come in at but one point on the oscillator dial. There is mathematically no
possibility of harmonics. Full scale blue prints with reprint of article $1.00.
Eastern Coil antenna coupler $6.00
O'Connor oscillator coupler 4.75
Special fixed condenser 60
Complete parts including panel, drilled and engraved, special formica
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* A. O'CONNOR & COMPANY
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RADIO BROADCAST ADVERTISER
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THE KODEL RADIO CORPORATION
505 EAST PEARL ST. CINCINNATI, OHIO
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DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORK
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R38o. PARTS OF CIRCUITS; INSTRUMRNTS. METERS,
RADIO BROADCAST, Dec. 1925, pp. 198-200.
Use in Receivers,
"How to Use Meters in Your Receiver/' James Millen.
A voltmeter for the filament circuit, and one for the B
batteries, is recommended. A plate milliameter gives the
plate current drain and shows when audio amplifiers are
properly "modulating." Method of connecting meters,
and the various uses to which they can be put otherwise,
is given; several "meter circuits" are shown.
R344- ELECTRON TUBE GENERATORS. OSCILLATORS,
RADIO BROADCAST. Dec. 1925, pp. 201-204. Modulated
"New Fields for the Home Constructor," Keith Henney.
For those who have accumulated radio apparatus and
tools, and really want to know more about radio science
and what is going on in the laboratory, this second article
of a series is given. A method of testing open circuits in
audio transformers by means of looo-cycle oscillator, and
obtaining transformer characteristics with the same oscil-
lator, is described. Other uses of the oscillator are sug-
gested, and taken up in some detail. The previous article
in this series appeared in the September, 1925, RADIO
BROADCAST.
Rii5. DIRECTIONAL PROPERTIES. BEAM
Radio. Nov. 1925, pp. ioff. TRANSMISSION
"Marconi Radio Beams," H. de A. Donjsthorpe.
The advent of beam transmission will relieve ether
congestion, and make obsolete existing high-power lonp
range stations of to-day, according to the writer. Beam
transmission will give minimum interference, due to marked
directional effects. Early experimental work is discussed,
and modern improvements made, due to the invention
of vacuum tubes, are described. The size and method
of constructing reflecting surfaces have given rise to new
theories of wave transmission. Parabolic and flat reflectors
have been used, the latter with marked results. A flat
network of wires set horizontally, serves as an antenna,
while another similar network, placed J-wavelength back-
serves as the reflector. This system will concentrate
energy within 10°, making possible thirty-six times the
transmitted energy otherwise obtained at a point.
R342.6 RADIO-FREQUENCY AMPLIFIERS. AMPLIFIERS.
Radio. Nov. 1925, pp 14-15. Radio-Frequency
"A Universal Radio-Frequency Amplifier," A. J. Haynes
A radio-frequency amplifier, which can be used ahead
of any receiving set, is described. Careful construction is
emphasized. The circuit employs an effective mean*
of controlling oscillations. This is done through the use
of a tuned choke coil, as is evident from a study of the circuit
diagram. Sufficient data is presented to enable the ex-
perimenter to construct this set. Unusual sensitivity and
volume are supposed to be the prime features incorporated
in this amplifier.
BIOGRAPHY.
M. Latour.
Rooy. BIOGRAPHICAL.
Radio. Nov. 1925, pp. igfT.
"Marius Latour," W. Emmett.
A sfeort biographical sketch of M. Latour, the French
scientist and philosopher, is presented. Mr. Latour is not
only known as a student of science, but his writings in the
field of sociology and psychology are widely read. He has
many patents to his credit, some of which are discussed
in this article.
R 145-3 INDUCTANCE. INDUCTANCE
Radio. Nov. 1925, pp. 24ff. COILS.
"Comparative Efficiencies of Coils," J. E. Anderson.
The L/I ratio of inductance coils is regarded as a measure-
ment of the efficiency of coils at low as well as high fre-
quencies. From this standpoint, the author makes a
comparison of various forms and types of coils, including
two and three layer banked coils, single layer coils of various
shapes, Lorenz coils, spiderweb coils, toroidal coils, etc.
The conclusions arrived at are summed up at the end of the
discussion.
Ri33. GENERATING ACTION. ELECTRON Ti BE
Radio. Nov. 1925, pp. 29ff. GENERATORS.
"The Vacuum Tube as a Generator," Lieut. J. B. Dow.
A theoretical as well as practical analysis of the funda-
mental principles of vacuum tubes, is presented, for the
benefit of the amateur building his own transmitter. In-
formation is given of the effect of gas in the tube, on the
grid, the internal resistance, the amplification factor, the
dynamic characteristics, the mutual conductance, the
generator action, etc. Schematic circuit diagrams illustrate
the discussion,
R375. DETECTORS AND RECTIFIERS. RECTIFIER,
Radio, Nov. 1925, pp. 35-36. Raylbetm.
"The Helium Tube Rectifier," E. E. Turner.
The Raytheon tube rectifier and its use in B battery
eliminators, is discussed. Complete description on building
a practical eliminator, including list of parts required and
diagram, is given. No hum of any kind is heard in the loud
speaker, even when the outfit is delivering 37 railliamp^s. on
a ten-tube super-heterodyne set, according to the writer.
R35O. GENERATING APPARATUS,
TRANSMITTING SETS. TRANSMITTERS,
QST. Nov. 1925, pp. 15-19- Stip.
"KFUH," Ralph M. Heintz.
The transmitter aboard the ship Kaimiloa, call KFUH,
consisting of two 25O-watters, is discussed in detail. Cir-
cuit diagrams and photographs give a clear idea of the set,
and how it has been constructed. The results obtained
have been very gratifying.
RR342.6. RADIO-FREQUENCY AMPLIFIERS AMPLIFIERS,
QST. Nov. 1925, pp 21-24. Radio-Frequency.
"The One-Stage Radio-Frequency Amplifier," P. L,
Pepdleton.
While designing a one stage radio-frequency amplifier,
results of a nature different to the conventional, were
obtained. They pertained to the control of oscillations
in the radio frequency circuit over the broadcast band
of frequencies. With the layout of Fig. i (circuit diagram
Fig. 2), and the array of coils shown in Fig. 3, considerable
information was gathered on the actual operation of such
a setup. The final arrangement adopted as giving the
best results, is shown in Fig. 4.
RADIO BROADCAST ADVERTISER
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Broadcast ? By the year
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$6.00, saving $2.40. Send
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"SUPER"
CONTROL
METER
FOR PRECISION CONTROL
of RaiUola Superheterodynes Nns. 'JO, 25 and 28
Instantly attached without any change in wiring
to jacks already installed for this purpose. Per-
mits settins rheostat for exact filament voltaee
for best reception and longest tube life.
A HOYT moving-coil voltmeter, type 17, with
bronze rim, wood case to match set, non-scratch
base and cord.
Price $8-50 *
BURTON-ROGERS CO.
26 Brighton Ave., Boston, Mass.
'The enchantment of distance,
the joy of clearness, with
fROST-fONES
New! Better!
Two useful new items of fROST- RADIO now ready
A new fROST-RADIO
socket that fits all new
type tubes
This new socket takes ALL tubes with
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full length with self -cleaning, sliding con-
tact. We believe this socket to have the
most satisfactory contacts of any socket
made. All terminals plainly marked. It
is equipped with soldering lugs. Genu-
ine black Bakelite in high lustre finish.
Order from your dealer today.
fROST-RADW
No
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FROST RADIO
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Convert your present stand-
ard sockets to UX199— CX
299, or UX120—CX220
with this adapter
With this handy, inexpensive adapter you
can instantly fit the new CX299 or UX199,
and the CX220 or the UX120, into your
present standard base sockets.
No need to rebuild your set to take the
new tubes. Genuine black Bakelite — high
lustre finish. Ask your dealer to supply you.
HERBERT H. FROST, Inc.
314-324 WEST SUPERIOR STREET, CHICAGO
NEW YORK CITY CLEVELAND KANSAS CITY LOS ANGELES
Export Office: 314 West Superior Street, Chicago
TF you like this magazine
with its coated paper and
enlarged size — then why
not subscribe and get it re-
gularly— by the year, $4.00,
Six months, $2.00.
Doubleday, Page & Co.
Garden City New York
Tested and approved bv RADIO BROADCAST
RADIO FANS, a one-year's subscription to Radio Broadcast
will cost you four dollars, two years six dollars. Consider thi»
expenditure as being a necessary investment on your part for
the future development of your own knowledge of Radio.
102-109 S. Canal St., Chicago
510
RADIO BROADCAST ADVERTISER
>C^v^c^c^cy^Kr^l>^^f^^f^^^'^^*^>-^*^<
Eastern Pickle Bottle Coils
may also be had for the following pop-
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EASTERN CLASSIC COILS (Type
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EASTERN CLASSIC COILS (Type
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BROWNING-DRAKE (Type B-D)
$8.00
THREE CIRCUIT (Type 3 C) $6.00
M. B. SLEEPER RX-1 $6.00
DX SUPERDYNE (Type S) $8.00
At your dealers or direct postpaid
KNOCKOUT COILS
(TYPE R)
for the EASTERN KNOCKOUT CIRCUIT (The
original unreflexed ROBERTS.)
Designed in strict accordance with latest Radio
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Circuits.
Minimum of capacity between N. P. winding and
secondary;mid-tap on single-layer wound N. P. coil
— simplifies neutra'ization and tuning, and brings in
the lower wave length stations with a heretofore un-
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Price, $8.50 per set.
EASTERN Pickie Bottle COILS
TRADE MARK
Ever Increasing in Popularity
No matter what the circuit, they guarantee the
best possible results from it because they incorporate
every feature essential to low loss coil design, in con-
formity with every known radio engineering principle.
Highest inductance, combined with lowest distrib-
uted capacity and dielectric losses, least insulating
material in the field, wires free of any injurious sub-
stance — no celluloid or collodion binders used.
These are some of the advantages of this extremely
efficient pickle bottle form of winding.
Elimination of losses keeps the high frequency re-
sistance at the minimum, insuring increased selec-
tivity, volume, and natural tone quality.
EASTERN COIL CORPORATION *
22 Warren Street Dept. R. B. New York
This is a good lime to subscribe for
RADIO BROADCAST
Through your dealer or direct, by the year only t4.00
DOUBLEDAY, PAGE & CO. GARDEN CITY, NEW YORK
AGENTS
WANTED
You Can Now Earn a
Tube Demonstrator FREE!
In addition to $25 to $100 a week, part or full time. Everyone
a prospect. Complete line standard sets and accessories, $5 to
$90. Write today for illustrated catalog and eiclusive selling
plan for live dealers and community agents. 20TH CENTURY
RADIO CO.. 1045 Coca Cola Bldg., Kansas City, Mo.
If Your Set Won't
Percolate
write us about it. RADIO
BROADCAST is establishing a
special repair department to assist
set builders in getting the best
out of the receivers they build
from plans published in the mag-
azine. Write for complete infor-
mation about this new depart-
ment established for your benefit.
R386. FILTERS. FILTERS.
QST. Nov. 1925, pp. 31-32. Key-Tbump.
" Key-Thump Filters,"
Practical suggestions on where to and where not to
connect a key in a transmitter to avoid key-thumps, are
presented. Six possible locations for a key are shown in Fig.
7. Only one of these locations is good. The cure for
key-thumps is found in a proper filter circuit. Analysis of
various filters brings the author to the best possible arrange-
ment of parts, shown diagramatically in Ftg. 5.
R350. GENERATING APPARATUS. TRANSMITTING SETS.
KLUTH SYSTEM.
Radio News. Nov. 1925, pp. 60 iff.
"Plastic Radio by the Kluth System," Dr. A. Graden-
witz.
A method used for producing stereophonic effects at the
receiving station is described. By means of a special high
inductance variometer, two circuits are so arranged that the
telephone current of one is slightly out of phase with that
of the other, thus producing different acoustic effects,
and giving a perfect plastic impression. Circuit diagrams
are shown and described.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVERS.
RADIO BROADCAST. Nov. 1925, pp. 36-40.
"A Model 1926 Broadcast Receiver," M. Silver.
The receiver described by Mr. Silver has, for its funda-
mental requirement, wavelength flexibility. By using
interchangeable coils a much larger frequency band can
be covered. The matter of condenser size, regeneration,
amplification, assembly, and testing, is covered in great
detail. A list of parts required to construct the set is given.
The receiver has three control dials, although, as explained,
single control is possible by betting condensers together.
R6io. EQUIPMENT; STATION DESCRIPTIONS. STATIONS.
RADIO BROADCAST. Nov. 1925, pp. 41-44-
" Radio Central-Conqueror of Time and Distance," F.J.
Turner.
A graphic description of "Radio Central," the largest
telegraph transmitting station in the world, is given. This
station is located on Long Island, was built in 1920, and is
owned by the Radio Corporation of America. It carries
on transmission with all foreign countries, handling com-
mercial messages throughout the year, twenty-four hours
per day. Photographs show the immense towers and the
station proper, interior and exterior.
R54O. PRIVATE STATIONS. STATIONS.
Private
RADIO BROADCAST. Nov. 1925, pp. 54-56.
"What Do We Know About Short Waves? " K. Henney.
The experimental short-wave station operated by RADIO
BROADCAST, call letters 2 GY, is conducting experimental
work to determine the results of short waves versus distance,
using different values of power input. The station desires
to cooperate with other experimenters in its efforts to arrive
at some conclusion regarding some of these high frequency
wave problems.
R343.7. ALTERNATING CURRENT SUPPLY. A.C. RECEIVER
AND AMPLIFIER.
RADIO BROADCAST. Nov. 1925, pp. 57-62.
"An A. C. Receiver and Power Amplifier," J. Millen.
The design and assembly of a four-tube receiver using
a.c. power supply, is given. A new high efficiency power
amplifier is developed for use in the audio stages. Care
in choosing parts for this set, especially for the power
amplifier, is considered important. The construction of a
power unit to supply B current from a 60 cycle source is
detailed, giving circuit diagram and a list of parts. Con-
siderable valuable information concerning the use of tubes
in a.c. circuits is found in this article.
R570. DISTANT CONTROL BY RADIO.
AUTOMOBILE.
Radio News. Nov. 1925, pp. 592 ff. Radio-Controlled
"Radio-Controlled Automobile," H. Green.
By means of two lo-watt transmitters, an automobile was
controlled up Fifth Avenue, New York City, the operator
following some few hundred feet in another car. The
controlling mechanism operated everything necessary
in starting and running a car. Two frequencies were
used, one to set the selector switch, the other to close
the relays for the battery current. The wiring diagram
shows the method used, photographs of the cars ana the
transmitters are also shown.
R545. AMATEUR RADIO. AMATEUR
REC. & TRANS.
Radio News. Nov. 1925, pp. 6o5ff.
"A Crack 40-80 Meter Set," E. W. Thatcher.
The construction and operation of a simple but efficient
transmitter and receiver, to operate round about 7500 kc.
.
(37-43 meters) and 3750 kc. (75-86 meters), ij described.
According to the diagram, one 5O-watt tube is connected
in the Meissner circuit for transmission purposes. Both
receiver and transmitter are considered in detail for the
benefit of those who have had very little experience in the
construction of radio sets. A table, showing the relative
merits of the various wave-bands assigned to the amateurs.
is given.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVER.
Radio News. Nov. 1925, pp. 610-61 1. Two-Range.
"A New Two-Range Receiver," S. Harris.
A receiver is described, using tapped inductances, capable
of covering a range from 500 to 2000 kc. (600 to 1 50 meters).
A single lever changes the inductances of each coil through
a switch arrangement. This is a five tube set; two radio-
frequency amplifiers, detector, and two audio frequency
stages. Three tuning controls are required. Photographs
are shown, giving constructional details.
R375 DETECTORS AND RECTIFIERS. RECTIFIER.
Radio News. Nov. 1925, pp. 6l3ff. Raytheon.
"The Raytheon Rectifier," J. Riley.
The theory and characteristics of a new rectifier tube used
in B battery eliminators is presented. Helium gas is used
in this rectifier. It differs from other rectifier tubes mainly
in the means taken to reduce the effective anode area, and
in the selection of design f9r insuring steadiness of action.
Two anodes are contained in the tube, the circuit diagram
showing how this rectifier is connected to rectify both halves
of the wave.
•jr. Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
511
every
ood set
Less wiring —
Fewer losses
Full, clear, rich tone depends on more
than on just good apparatus. It depends,
first of all, upon careful, compact wiring.
AMPER1TE eliminates complicated wir-
ing, avoiding leaks and losses. Requires
no attention. Controls the filament per-
fectly, bringing the utmost out of each
individual tube. Permits use of any tubes
or combination of tubes. Used in all pop-
ular construction sets. Price, $1.10.
There i* an AMPERITE for every tube
Write for free hook-ups +
(Bvtnpany
SO Franklin St., N. Y. City
RADIO PANELS
OF GENUINE BAKRLITE
Cut, drilled and engraved to order. Send rough sketch
for estimate. Our New Catalog on Panels, Tubes and
Rods — all of genuine Bakelite— mailed on request.
STARRETT MFG. CO. if
521 S. Green Street Chicago, 111.
RADIO BROADCAST
For March
will be a better magazine than thii. Make sure of it by
telling your newsdealer to hold one for you — or better
still, subscribe through him or direct.
RADIO BROADCAST
Garden City New York
N
Complete Separation of
Low Wave Stations
Perfectly accomplished with Tune-Rite,
the straight line frequency dial. A
marvel in scientific construction, it in-
stantly converts any set to straight line
frequency. Bring your present set up-
to-date by replacing your old dials
with Tune-Rite. Beautiful in appear-
ance. Easily mounted without drilling.
Price, $3.50 .
Write for instructions ^^
Dept. T.R.B.-l, 50 Franklin St., N. Y.
TUNE-RITE
The Straight Line Frequency Dial
M«Je by tl.e m.Wr. of Amperitc. the Sclf-AJju*tinf Rheoitat
«
"Now We Can Enjoy Radio"
NEVER knew what joy and entertainment
radio could bring into the home until we bought
our Mu-Rad. Now, with a slight movement of the
Single Dial we can tune in any station that is broad-
casting, so clear that it seems the music and artists are
right here in our home. It is a comfort to me during
the day and a relaxation to you after a busy day at the
office."
ONE DIAL CONTROL -
Transcontinental "Receiver
can bring joy and entertainment into YOUR home.
Ask your nearest dealer for a demonstration of this
wonderful Radio — in your home.
Write lor Booklet E-6
MU-RAD RADIO CORPORATION
Asbury Park, N. J.
This is a good time to subscribe for
RADIO BROADCAST
Through your dealer or direct, by the year only $4.00
Dc.nM. ,!;i\ . Page & Company Garden City, New York
RADIO WIRES
We manufacture all types.
Round braided antenna wires
Flat braided antenna wires
TRADE MARK REG. Round stranded antenna wires
Above types in copper — tinned copper' — enameled copper — tinned bronze.
Loop wires in silk or cotton covered. Antenna supporting springs.
Litz wires. Cotton and silk covered wires for set
Enameled wires. wiring. ^i
Write as for descriptive catalogue. ^\
ROSS WIRE COMPANY 69 Bath St., Providence, R. I.
512
RADIO BROADCAST ADVERTISER
itsinthcTube
A receiving set is no better than its tubes.
With other parts and connections right a set may be
as good as its tubes — no set can be better.
That's why you want CECO Tubes. They stand up
and deliver. With them your set works at its maxi-
mum. Clarity of tone, rich volume, long life — CECO
has them all to a superlative degree.
Our charted tests (results confirmed by laboratories
of national reputation) PROVE CECO TUBE SU-
PERIORITY— whether used as detectors, audio or
radio frequency amplifiers.
CECO Tubes make a Good Receiver BETTER. Try
them and you'll BUY them always — for results.
Now Ready! CECO Tubes with new type Long
PRONG BASES. Also, Power Amplifier Tubes, E
(Dry Cell Type), F (Storage Battery), for last stage
of Audio Frequency.
Dealers write giving jobber's name.
C. E. Mfg. Co., Inc.
702 Eddy Street, Providence, R. I.
Why not subscribe to Radio
Broadcast? By the year only
$4.00; or two years, $6.00,
saving $2.40. Send direct to
Doubleday, Page & Company,
Garden City, New York.
RADIO RENCH
If Your Set Won't
Percolate
write us about it. RADIO
BROADCAST is establishing a
special repair department to assist
set builders in getting the best
out of the receivers they build
from plans published in the mag-
azine. Write for complete infor-
mation about this new depart-
ment established for your benefit.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVERS.
RADIO BROADCAST. Nov. 1925, pp. 28-31.
"The RADIO BROADCAST 'Aristocrat,' " A. H. Lynch.
The author describes in detail the construction and
operation of a five-tube receiver having one stage of radio
frequency amplification, regenerative detection, and three
stages of resistance coupling. The circuit diagram, with
list of parts, is reviewed to cover many kinds of radio parts
now available. According to the author care should
be exercised in mounting resistances for amplifier to
prevent leakages. Photographs of several five-tube re-
ceivers, including the RADIO BROADCAST "Aristocrat,"
are shown.
R62o.o65. REGULATION AND CONTROL. CRYSTAL
QST. Nov. 1925, pp. 8-13. CONTROL.
"Crystal Control for Amateur Transmitters," John M.
Clayton.
Rochelle crystals, when placed between two charged metal
plates, change in shape. The fact, however, that they
absorb moisture readily makes their use impracticable for
the purpose here designated. Quartz crystal are far more
satisfactory. Because of their electrical properties, crystals
will oscillate when placed between two metal plates which
are charged. A discussion concerning the axes of crystals
and method of cutting and grinding them, follows. Ready
cut crystals may be purchased from optical companies.
Their use in practical circuits, precautions to observe,
and results that can be obtained, are outlined in detail.
R35o.
GENERATING APPARATUS;
TRANSMITTING SETS. TRANSMITTER.
QST. Nov. 1925, pp. 26-30. Standard Frequency
"The Pacific Coast Standard-Frequency Station, H. H
Henline.
A complete description of the two standard-frequency
stations located at Stanford University, California, 6xBM,
is given. A circuit diagram of the 125-1 500 kc. set, with a
detailed list of parts and construction data of coils, etc.,
make possible the duplication of such a transmitter by
experimenters. The 1 500-6000 kc. set is simpler in con-
struction, as indicated in the accompanying figure. A list
of parts is also given.
R8oo. (533.85) VACUUM APPARATUS. TUBES,
Radio News. Nov. 1925, pp. 604 ff. Gas Filled.
" Hot Cathode Metal Vapor Tubes," Dr. C. B. Bazzoni.
It is desired to obtain a detector tube with a sensitivity
so high that regeneration, with its complications, will not be
necessary For this purpose, tubes employing ionization
are considered as being much better than pure electron
discharge tubes. The use of metal vapors is therefore tried
and found superior to gas vapors for this purpose. The
author describes how tubes are filled, and what results one
can expect when connecting such a vapor filled tube into a
receiving circuit.
R8oo (534) SOUND RECORDING. SOUND
PHOTOGRAPHS
Radio News. Nov. 1925, pp. 614 ff.
"Sound Photographs and Their Reproduction," T. H.
Nakken.
A method of recording and reproducing sound waves
on a film, by means of a special tube called the Gehrke tube,
is described. Two types of records may be made, one called
by the writer the qualitative (step-ladder) type, the other
the quantitative (saw-tooth) type. The latter is considered
to be the better from several standpoints. Different types
of microphones used to convert sound wa_ves to electric
energy are also mentioned in the discussion. A circuit
diagram of a special amplifier for the weak currents is shown
and explained.
R343- ELECTRON TUBE RECEIVING SETS. RECEIVER,
Radio News. Nov. 1925, pp. 616-617. Counterpbase.
"The Counterphase Circuit," J. T. Carlton.
The much discussed "Counterphase" circuit, having
three stages of radio frequency amplification but only two
controls, has many advantages over ordinary radio frequency
sets, says the writer. First, the causes of oscillation in
sets is taken up, then the principle embodied in this circuit
is explained. Of particular interest seems to be the fact
that no kind of losses are introduced in the grid circuit,
which remains at a low resistance. Circuit diagrams and
photographs are shown.
R342.7. AUDIO-FREQUENCY AMPLIFIERS. AMPLIFIERS,
Radio News. Nov. 1925, pp. 620-623. Audio-Frequency
"The Four Types of Audio Amplifiers," S. Harris.
In receiving sets of today four types of audio amplifiers
are in common use, namely transformer, impedance,
resistance, and push-pull. Diagrams of these four types,
with detailed discussion concerning use, characteristics,
and advantages, are given. A breadboard layout of each
type is also shown. Comparison by the author shows some
interesting results concerning the particular type of ampli-
fication method to be used, especially in the many kinds of
receiving sets now being constructed. Each amplifier
arrangement has its specific advantages.
First International Meeting of
Radio Engineers
FOR the first time in the history of radio,
the scientists and engineers who made radio
telegraphy and radio broadcasting a reality
j will convene in an International Meeting and
Convention in New York City, January i8th and
igth. Notices have been sent by the Institute of
Radio Engineers, under whose auspices the meet-
ings are being held, to its members both here
and abroad. Included in its membership roll
are such illustrious names as Guglielmo Marconi,
Edwin H. Armstrong, Louis A. Hazeltine,
E. F. W. Alexanderson, George O. Squier, Lee de
Forest, Thomas A. Edison, Michael Pupin,
Irving Langmuir, Reginald Fessenden, John
Stone, David Sarnoff, and John V. L. Hogan.
RADIO BROADCAST ADVERTISER
513
'Even the organ
crescendo
was perfect'
VETERAN set-build-
. er recently remarked
about the purity of tone at
tremendous volumes that he
got through the Super-size
Precise No. 480 Audio Trans-
former. In particular was he
impressed with a recent organ
recital which he had received.
"Why," he said, "even the
organ crescendo was perfect."
The big Precise No. 480
(shown below) is truly a
master transformer, designed
for radio reception in a con-
cert hall if necessary. It
brings forth the deep rich
tones or the high clear tones
with magnificent volume.
The ratio of voltage ampli-
fication to frequency is prac-
tically a straight line, assuring
uniform amplification over
the entire range of useful
audio frequencies.
Made in two ratios, 2J to 1 and
5tol.
Price, $730 either ratio.
Ask your nearest radio dealer to
show you the complete Precise
Line.
PRECISE MANUFACTURING
CORPORATION
Rochester, N. Y.
Branch Offices:
126 Liberty Street
New Tork City
205 W. Harrison Street
Chicago. Illinois
821 Market Street
San Francisco, Cal.
1127 Pine Street
SI. Loms, Me.
701 «. 0. U. W. Bide.
Little Reck, Ark.
454 Buildrr'l Exeh.
Minneapolis, Minn.
Canadian Distributer. :
Perkins Electric. Ltd.
Toronto, Winnepeo. Montreal
Improved S. L. F. Condenser $2.75
A scientific instrument house of international reputation offers for the first
time direct to the radio fan an improved S.L.F. Variable Air Dielectric Condenser.
Due to over production on orders from prominent set manufacturers whom we
have been supplying for years!
Type offered has a maximum capacity of 315 M. M. F. with a minimum of 8
M. M. F. especially adapted to Neutrodyne, Tuned Radio Frequency, and
Radio Broadcast Hook-Ups for home construction.
Made of the best materials obtainable, of highest grade aluminum and brass; workmanship that of
precision instrument makfrl
Ordinary "Straight line frequency" cal-
ibration gives too rapid a capacity
variation near maximum capacity to
permit convenient tuning for the
longer wave lengths. Radio Engineers
will appreciate the nicely balanced
compromise we have obtained in equal
spacing broadcasting stations and
equal facilities of tuning over the en-
tire frequency band. Compact; no nar-
row pointed rotor plates of small area
to crowd the other parts of the set, but
eccentric semi-circular plates of ade-
quate area.
The low minimum capacity (7 to 8
micro-microfarads) reaching down to
200 meters, necessary for new De-
partment of Commerce allocations.
Losses are negligible.
The bearings are individually reamed to fit, with no side or
end play and are mechanically correct with dissimilar met-
als on all rubbing surfaces.
Good electrical bonding between plates, due to our highly
developed crimping process. Good centering of plates, re-
sulting from high standards in assembly and adjustment
and rigid inspection and test.
General sturdiness of construction and cleanness of workman-
ship.
Due to our large production for set manufacturers, we are
enabled to offer extremely reasonable prices on these high
grade condensers.
Sold only on a cash with order basis, money returned if you
are not more than satisfied that they are exactly what you
want and none equalled electrically or mechanically.
Price $2.75 each. Set of three, $8.00
Sent by paid parcel post anywhere in U. S. A.
THOMPSON-LEVERING COMPANY
353-357
North 57th Street
RADIO DIVISION
Trad, Hark Reyatervd
Philadelphia, Pa.,
U. S. A.
A |- T ocf-T oA Real Panel Engraving Machine
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L
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Being designed particularly for panel engraving, it is
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Price of machine with full equipment including master
letters and characters, $135.00.
f. o. b., Forestdale, R. I.
Wire or write
BRANCH TOOL CO., Dept. G
Forestdale, .'. /. Rhode
514
RADIO BROADCAST ADVERTISER
Centralab Radiohm
for oscillation control
The Centralab Radiohm gives you perfect
oscillation control — enables you to get full
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By controlling oscillation with this little
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The Radiohm provides smooth variation of resistance
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Centralab Modulator
for volume control
This improved type of potentiometer takes the
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It provides noiseless control of tone volume
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vice versa — without de-tuning.
Used in the "Silver Six" set! also in audio
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CENTRAL RADIO LABORATORIES
22 Keefe Avenue Milwaukee, Wis.
Mail the coupon
CENTRAL RADIO LABORATORIES 22 Keefe Ave., Milwaukee, Wls.
( ) Send me literature describing Centralab controls. Enclosed find
$ for which please send me the following:
( ) Centralab Modulator, at $2.00 each. ( ) Centralab Radiohm,
at $2.00 each.
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BOOK REVIEW
The Economic Background
of Radio
ECONOMICS OF THE RADIO INDUSTRY.
By Hiram L. Jome, Ph. D. Published by
A.W. Shaw Company, New York, Chicago,
and London. ))2 pages. $5.
THIS work by the Professor of Economics
at Denison University is said by the
publishers to be the pioneer book on the
subject. It is a good beginning, and marks a
transition from the state of affairs which was
epitomized, about six years ago, by a prominent
electrical manufacturing executive called on to
manufacture radio telegraph equipment.
"Radio isn't a business!" cried this gentleman
in a moment of conferential anguish, "It's a
disease!" What is more, at the time he said
this he was right, as he was also when he de-
clared vacuum tube manufacture to be "a nice
toy for the lamp works." But times change.
In 1924 the tube business alone, according to
Mr. Babson, amounted to about $50,000,000,
which is a good-sized toy for anyone. In fact,
it was able to swallow a few dozen lamp works
as an entree.
Economics of the Radio Industry is written
in four parts, with an appendix. Part I,
concerned with " Development and Extent of
the Radio Service," is largely a technical and
financial history of the whole wireless art, both
telegraphy and telephony, from the days when
the coherer was a great and indispensable
invention, down to this era of super-heterodyne
and balanced radio frequency receivers cali-
brated in kilocycles, receiving antennas nine
miles long, transmitters which put one thousand-
plus amperes into antenna systems which in
themselves constitute engineering feats, and
radio technicians who are engineers, telephone
experts, publicists, musicians, and diplomats,
all in one. The four chapter headings in this
part of the book give some idea of the range
covered: "Beginnings of Wireless"; "Early
Organization for Service"; "The Radio Corpo-
ration of America"; "The Radio Industry of
To-Day. "
Part II, under the somewhat vague heading of
" Bringing Radio Service to the People," is
principally a discussion of marketing, retailing,
and financing problems in receiving set manu-
facture, but at the end there is a chapter on
"Handling of Traffic", which includes an
elementary discussion of oscillation and vacuum
tube theory, preliminary to an analysis of
traffic conditions in long distance radio teleg-
raphy.
In Part III, "Problems of Efficiency in Radio
Service," the growing pains of broadcasting,
copyright and patents as property problems in
the radio field, and the extent to which sound
public policy requires federal and international
control of the various services, receive about
seventy-five pages of discussion. This is
followed by Part IV, "The Future of Radio," in
which the author cautiously ventures into the
domain of prophecy, having in mind the rash
remark (which he quotes) of Mr. Marconi's
youth: "As soon as my wireless system succeeds,
the vast network of cables and wires will become
useless, and the money invested in the old
system will be simply thrown away," a forecast
which has turned out to be so incorrect that
it should evermore serve as a warning to even
the greatest inventors, sales "engineers", and
promotors. The wireless system has succeeded,
and there are more wires and cables than ever.
But Dr. Jome plays safe, and in gazing into
Tested and aooroved bv RADIO BROADCAST -ir
RADIO BROADCAST ADVERTISER
515
REMEMBER!
WHEN
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THE ROBERTS'
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Antiques
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Country Life
A Douhlcday, Page Magazine
Limited Supply at Newsstands
SOCKET
THE BEST TEST
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Boston Representative:
Martin, Hartley & Dewitt Sales Co., 99 Bedford St.
Chicago Representative:
William A. Welty & Co., 36 So. State St.
LEARN THE CODE AT HOME with the OMNIGRAPH
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THE OMNIGRAPH is not an experiment. For more than 15 years, it has been sold all over the world
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OMMGRAPH has been successfully adopted by the leading Universities, Colleges and Radio Schools.
Send for FREE Catalogue describing: three modeU. DO IT TO-DAY.
THE OMNIGRAPH MFG. CO.. 1 3K Hudson St. New York City
If you own a Radio Phone set and don't know the code — uou are missing most of the fun
Order your copy of Radio Broadcast from your
news dea'er or radio store. Make sure that he
reserves a copy for you each month. If your
favorite radio store does not stock the magazine
write us giving name of radio dealer and address.
CUMP Blackburn Ground Clamps
Telephone companies using
MILLIONS. Adjustable — fits
any size pipe. Requires no pipe
cleaning — screw bores through
rust and scale. Send 12 cents
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Blackburn Specialty Company
I960 E. 66th St. Cleveland, O.
Gosilco Super Aerials
Heavy burnished silver plate on 14 copper
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Gosilco show 35% increase volume, range. K N X
lab. test. Approved Popular Radio, Radio News
All American Radio Corp. 4}c per ft., round bus
wire 12c per length, po tpaid. C. O. D.
American Luminous Products Co. If
fatenl Applied for
Huntington Park California
516
RADIO BROADCAST ADVERTISER
62
ou must
cTprotect the
circuit against
leaks and losses
HADIOM
71 ic Supreme Insulation
does it!
RADION offers the utmost possible
protection against leaks and losses.
Designed exclusively for radio purposes,
it is the most efficient insulation as in-
dicated by authoritative, impartial tests.
Radion Panels reduce surface leakage to
a minimum. Their beautiful surface fin-
ish adds to the attractiveness of any set.
Radion Dials match their beauty of fin-
ish and help to get close tuning. Radion
Sockets eliminate capacity effects; they
are made both for new UX tubes exclu-
sively and with collar adapters for old-
type tubes.
Radion dealers have the complete line of
Radion low-loss parts. Manufacturers will
find it to their interest to write us for
prices on moulded parts. Send for catalog.
FREE Booklet, "Building Your Ovn Set" mailed on request
AMERICAN HARD RUBBER COMPANY
Dept. C 14, 11 Mercer Street, New York City. Chicago Office: Conway Building
Pacific Coast Agent: — Goodyear Rubber Company, San Francisco— Portland
STUDY AT HOME
R*dla, the wonder of all •(*•,
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radio tx»«rt — turn bli-
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Y(M: EARN WHILE YOU LEARN
Our homo-
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Write for fr«. bonhl*!. ••Mllllnna UBIC
F«rK TWIN If rou •nroii now. 8«nd letter or poatal to
BADID HKT I. J. M.nrt.l.-lr.rn how to m.ke mi ML
AMERICAN RADIO RNGINERRS,
' -- c. a. A.
DURHAM^
Variable Leaks
And Tube Makers Data
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Standard Type / 5C
Instruction sheets say that you should try dif-
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New Panel Mount
Short lead
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hole.
There's a DURHAM for every need
No. 100—1,000 to 100,000 ohms (audio)
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DUKHAM6CCUhc.
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NO MORE LOOSE CONNECTIONS
X-L PUSH POST
A Binding Poet that really does excel, looks,
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No screwing or danger of shearing off wires.
Furnished attractively plated with soldering
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if Price Each, 15 Cent,
X-L RADIO LABORATORIES
2424 Lincoln Ave. CHICAGO
RADIO FANS, a one-year's subscription to
Radio Broadcast will cost you four dollars,
two years six dollars. Consider this expen-
diture as being a necessary investment on
your part for the future development of your
own knowledge of Radio.
FOR CLEAR, QUIET "B" POWER
RADIO
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exp cB^mrjn after examining batteries. 6 percent discount ror cash
with order. Mail your order now!
WORLD BATTERY COMPANY
1219 So. Wabash Ave., Dept. 24 Chicago. Ill*
Makers of the Famous World Radio" A" Storage Batten
Prices: 6-volt.lOOAmj>. $11.S5: 12OAmp.SI.9.£5:UOAmp.'*
i with Solid Rubber COM.
Alt equipped «
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STORAGE BATTERIES
Set your Radio Dial. »t 210
meters for the Dew Id
watt World Storage Battery
Station. WSHC. Chicago.
Watch for announcements.
•ft Tested and approved by RADIO BROADCAST
the future he does not relinquish the sober
and unpyrotechnical style with which he writes
of the past. As to the future of broadcasting,
he apparently favors a modification of the
British system, combining the order and sym-
metry of the latter with some of the advantages
of the American laissez-faire structure, which
admittedly begins to lean at an alarming angle.
In preparation for writing this book Dr. Jome
has very obviously talked to a great many
people and consulted a raft of documents and
authorities. There is scarcely a page without
one or more footnote references. The author
has done a thorough job at an opportune time,
and his book deserves wide reading among
people to whom radio is more than a song and
dance. Leaving aside the advent of broad-
casting, which brought up the gross sales of the
Radio Corporation of America, for example,
from $1,468,920, or 35 per cent, of the total
business, in 1921, to $50,747, 202, or 92.5 per
cent of the whole, in 1924, practically swamp-
ing, as far as magnitude goes, the communica-
tion activities of the company — even omit-
ting consideration of this shift, the changes
have been remarkable. In transoceanic com-
munication, not much over ten years ago the
practice was to build a line of 4OO-foot masts for
reception — vacuum-tube amplifiers were not
yet taken seriously — and large stone hotels were
erected for the occupancy of operating staffs of
sixty men or so off on the seashore somewhere.
These men copied the messages and re-trans-
mitted them over wire lines to the metropolis,
adding another link to the chain with that much
more chance of errors creeping in. A few years
later this whole system was changed. None
of the engineers of 1914 — and they were good
engineers — were able to foresee this development.
In a business which turns such somersaults,
there is certainly room for an economic treatise
like that which Professor Jome has given us.
A few errors and omissions may be pointed out.
On page 86 we encounter the statement that
"Consumers now looked for apparatus which
would enable them to tune-out a larger number
of stations, thus eliminating interference and eli-
minating static." Doctor Carson has proved that
sharp tuning will not eliminate or reduce static
in any way, shape, or manner. The footnote
on page 166, discussing the question of the
pioneer broadcasting station, does not mention
the later work of De Forest (in 1916) at High-
bridge, New York. On page 167, Doctor Jome
trustingly states it as his opinion that a large
number of broadcasters "have begun the
broadcasting game for no ulterior motive at all."
So they say. Possibly Munchausen wasn't a liar
either. Page 170: "The act of reception itself
does not weaken radio signals, just as the human
voice, carried by means of sound waves, can be
heard by all within range without loss of
strength." This is not true in the case of a
number of receiving antennas close to each other
and tuned to the same signal, and there is reason
to believe that the field strength of a trans-
mitter may be pulled down somewhat in urban
reception by a great number of outdoor an-
tennas tuned to it. On page 203, discussing
the motives of Heinrich Hertz, the author of
Economics of the Radio Industry fails to mention
the most probable reason why Hertz omitted
to take out a patent, to wit: that he wasn't
interested in making money. And some of the
aviators may be amused at the statement on
page 235 about what damage an aviator flying
far up above New York could do. If he
went that high he would probably have all he
could do to take care of himself. The high
estimate of beam transmission (Page 269) is
possibly somewhat too sweeping. And Professor
R. A. Fessenden's name is not found in the index
Such little points can be corrected in later
editions.
RADIO BROADCAST ADVERTISER
517
New Roberts'
Higher Amplification with
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P. P. C. O. D. if desired
7
Mail postcard for details ^w
PERFECTION RADIO MFG. CO.
24th & Race Streets Philadelphia, Pa.
> LAV! VE
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As transmitting Grid leaks, they are made in
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Crescent Radio Supply Co. 1-3 Liberty St., J.maici, N. T.
RUDYARD
KIPLING
C( Who is able to
reach you, talk to
you in your own
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pathos or power
. . . like Kipling?
Buy his books.
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The Best in the World
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The Amateur or Experimenter
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It is significant that unsolicited testimonials are
constantly being received from even the far corners
of the earth, where Norden-Hauck Engineers
have furnished the finest radio apparatus known
to the art today.
Quotations gladly furnished on radio parts and
apparatus having non-infringing uses.
Writ* for Literature ^
NORDEN-HAUCK, Inc.
Engineers
1617 Chestnut Street, Philadelphia, Pa.
Why not subscribe to Radio Broadcast? By the year only $4.00; or two
years, $6.00, saving $2.40. Send direct to Doubleday, Page & Company,
Garden City, New York.
Radio Battery Chargers
Best by Test *
$O50 . , j,
— minus bulb
east of Rockies
Your dealer can get it for you
THE ACME ELECTRIC & MFG. CO.
1410 Hamilton Avenue
Cleveland, O.
Tr Tested and approved bv RADIO BROADCAST
518
RADIO BROADCAST ADVERTISER
Make Your Own
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Why pay $35 for a cone loud speaker when you can easily assenv
hie a splendid super-sensitive one at home with the complete parts we
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254 West 34th Street, Dep't 22
New York City
SCIENTIFIC RADIO LABORATORIES
ALMOST TOO GOOD TO BE TRUE
X-L VARIO DENSERS
INSTALL THEM IN YOUR SET AND LEAVE
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Endorsed and Died by the Foremost Radio Engineer!
MODEL N — Capacity range 1.8 to 20- micro-micro-
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MODEL O — For the Cockaday circuit, filter and in-
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positive grid bias in all sets.
G-l — .00002 to .0001 Mf. G-10 — .0003 to .001 Mf.
G-5 — .0001 to .0005 Mf.
Price eich »ilh Grid Leik Clips SI. 50
It RADIO L«BOB»IORIIS
1424 Lincoln Jvtmie, CHICAGO
Battery Prices
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TREE BLUE PRINTS"
To Set Builders
TO PROVE THE SELECTIVE AND SENSITIVE
COMBINATIONS OBTAINABLE WITH
Werner Transformers
(Radio Frequency Type)
which cover the entire broadcasting wave range and
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MADE IN TWO TYPES
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Werner Loop Antenna
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Send for free circuit diagrams and descriptive literature.
Book of Up-to-date, practical R. F. circuit dia- f
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Ask Your Radio Dealer
WERNER MFG. CO.
| 204 Ninth St. Brooklyn, N. Y.
Tested and approved by RADIO BROADCAST
Chain Broadcasting an Economy
DUE to the fact that we go to press a
number of weeks before publication and
to heavy demandsiipon our space, we have
not been able to print this interesting letter
which came to our desk some time before
the last Washington Radio Conference.
Those would-be broadcasters whose hopes
were cast to the ground by the statement
that very few more stations would be
licensed, should consider the possibilities
of the use of the chain system as an alter-
native to erecting their own stations. The
following letter is representative of several
we have received on this subject.
Editor, RADIO BROADCAST
Doubleday, Page & Company,
Garden City, New York.
SIR:
Permit me to call to your attention a field
which your magazine might cover with advan-
tage to the radio public. It is a campaign to edu-
cate the prospective broadcasting station builder
into a realization of the fact that his yearnings
for fame and publicity may be attained by means
other than supplying the radio audiences with a
quantity of programs such as are now available
to all.
We have been discussing the question of who
pays for broadcasting. That, of course, is easily
answered, as easily as the question of who pays
for the full pages of advertising in the Saturday
Evening Post and our daily newspapers. Does
broadcasting pay well? That question also is
easily answered, for take note of the fact that we
are to have about forty new Class B stations and
that many of the older Class B stations are
scrambling to double and triple their present
power output.
Now the thing that puzzles me is why we, the
radio listeners, need these 40 new stations when
the air is so congested now that one can generally
hear two programs on one wave channel to the
accompaniment of a beautiful heterodyne whistle.
To which wave channels will these new stations
be assigned without increasing this annoying
interference?
My suggestion is this. Educate the prospec-
tive broadcasting station builder into spending
his money on good programs put on the air once
or twice a week through a chain of stations such
as are now connected with the American Tele-
phone & Telegraph system. The simultaneous
broadcasting from several stations of exception-
ally fine programs is far better advertising and
creates more good will than the continuous
broadcasting of mediocre or poor programs such
as we now have from many stations. More
people would be reached and at the same time
the cost of such fine programs, although expen-
sive, would not equal the cost of equipping and
maintaining a broadcasting station.
I firmly believe in interlinking broadcasting
stations for indirect advertising by means of
superfine programs of education and music.
Such a system will force the other stations to pro-
duce equally fine programs or lose the good will
of the radio public. Two very fine examples of
indirect advertising by the system of chain
broadcasting are the programs of the National
Carbon Company and the Victor Talking Ma-
chine Company. Let us have more programs
like these with fewer Class B stations using
more power.
Yours very truly,
F. L. W.,
Philadelphia, Pennsylvania.
RADIO BROADCAST ADVERTISER
537
KESTER
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RADIO BROADCAST
ARTHUR H. LTHCH, Editor
WILLIS K. WING, Associate Editor
JOHN B. BRENNAN, Technical Editor
MARCH, 1926
Vol. VIII, No. 5
Cover Design - From a Painting by Fred J. Edgars
Frontispiece ' ' A Majestic English Radio Tower
A Man and His Hobby - - - - E. E. Horine
The March of Radio - - J. H. Morecroft
Can We Forecast Radio Reception from the Weather?
J. C. Jensen
What Multiple Regeneration Can Do For Your Tuned
R. F. Amplifier - - - - V. D. Landon
As the Broadcaster Sees It Carl Dreher
Drawings by F. F. Stratford
Standards for the Home Laboratory - Keith Henney
The Listeners' Point of View - - John Wallace
An All-Purpose Coil Winder - Edward Thatcher
The First Report on the International Tests
Willis K. Wing
SupeixHeterodyne Construction - Harold C. Weber
The Grid — Questions and Answers -**«•**
Variable Voltage from a "B" Substitute
A Loop R. F. Receiver
Making Grid Leaks
Operating Characteristic* of the New Tube*
Charging Storage Batteries from D. C.
"Now, I Have Found"
How to Make Balloon Coils
An Audio Bypass Method
Improved Loud Speaker Reproduction
ALow Loss Coil
One Use for a Bypass Condenser
A New Way to Make Money in Radio
D. C. Wilfcrson
A Key to Recent Radio Articles E. G. Shalkhauser
What Our Readers Write
546
547
552
558
563
568
573
577
582
588
589
594
600
606
608
618
BEHIND EDITORIAL SCENES
THE present number of RADIO BROADCAST was prepared, and
edited during the week of the International Radio Broadcast
Tests, but in spite of the disorganization of office personnel and
the conventional magazine routine, we feel that a very interesting
lot of radio material has been assembled. E. E. Horine, who
wrote, "A Man and His Hobby" which is the leading article, is
known to many radio men as assistant radio manager of the
National Carbon Company. Professor Morecroft, in his com-
ments about the Naval Radio Service, has stirred up considerable
discussion, with rather vocal partisans on each side. In attempt-
ing to take a neutral position, we have been accused of attempting
to accomplish all sorts of dire ends. But as Professor Morecroft
has stated, the only purpose has been to indicate what seemed to
us to be the facts and to try to discover how conditions may be
remedied.
RADIO'S relation to weather conditions has been discussed
ever since the coherer days of the art, but we doubt if any
more.important or complete information has been presented than
Mr. Jensen gives in his article, "Can We Forecast Radio Re-
ception from the Weather?" By carefully studying the maps
and curves in the article, experimentally inclined radio folk have
opened to them a most interesting field for investigation. And
Mr. Landon's article on multiple regeneration is also a frankly
experimenta presentation of a subject which has very large
possibilities and we expect many interesting reports frbm home
constructors who put some of Mr. Landon's suggestions to
practical tests. The long-awaited third article in the series for
the home constructor who wants to go further in radio than set
building appears on page 573, and if the letters addressed to Mr.
Henney, the author of the series and director of our Laboratory
are any indication, those to follow are also eagerly awaited.
That interest is not hard to explain, for the series is packed full
of material of the utmost help to the radio-ambitious.
"PROM our correspondence from the increasing number of ex-
JT perimenters interested in short wave transmitting and reedy
ing.it would appear that RADIO BROADCAST'S $500 prize contest for
the design of an efficient short wave receiver was attracting a great
deal of interest. Our amateur contemporary, §ST, devoted a
page to announcing the contest in its February issue. For those
who have not seen particulars of the contest, full information may
be had by writing to the Director of the Laboratory, RADIO
BROADCAST, or on page 444 of this magazine for February.
TN THE April RADIO BROADCAST, we can promise another one
JL of Keith Henney's absorbing and informative articles on tubes.
There will also be a distinctly helpful article on various means of
filament control, prepared by John B. Brennan, Technical Editor
of this magazine. There will be a review of the International
Radio Broadcast Tests which will be of interest to nearly every
radio listener who has a receiver more elaborate than a crystal
set.— W. K. W.
Doubleday, Page Sr Co.
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WHERE ENGLISH MESSAGES LEAVE FOR THE UNITED STATES
One of the majestic towers of one of the new beam stations of the British Marconi Company. The station
is located in Dorchester, Dorsetshire and was chiefly erected to communicate with stations on the east
coast of the United States. Tests with the new equipment have been progressing for some time
RADIO BROADCAST
VOLUME VIII
NUMBER 5
MARCH, 1926
JSV
A Man and His Hobby
The Story of One Man's Experiences With Short Wave Code Transmitters onLow
Power — The Philosophy of the Radio Amateur — How; Australia Was Reached
From British Columbia With Batteries and a Receiving Tube as a Transmitter
ANEW and thrilling experience is
in store for the dyed-in-the-wool
broadcast listener when he first
tunes-in on the shorter wave-
lengths set aside for the use of the ama-
teur. Around about 7500 kc. (40 me-
ters), the air is literally full of signals of all
kinds, day and night, summer and winter.
It's all code down there. No grand opera
stars singing in heavenly voices; no promi-
nent speakers wagging the silver tongue; no
jazz. Only a succession of queer sounding
dots and dashes, in all manner of tones and
pitches, from low gutteral growls to high-
pitched, clear, chirping notes. Some of
them sound as if they might
have originated next door,
while others create the im-
pression of having come
across thousands of miles
of ocean and land; and the
chances are they have, for it
is an everyday occurrence
for amateurs of different
nations, on opposite sides
of the world, to converse
with each other. The field
of amateur radio is the DX
fan's paradise, and therein
lies a part of the fascination
of the game.
Listening-in on the ama-
teur bands stirs the imagin-
ation and arouses the curi-
osity. There seem to be
thousands of these amateurs
at work, bombarding the
ether with their messages,
clamoring away, trying to
engage some one's attention
perhaps thousands of miles
distant. Who are these
amateurs? What kind of
By E. E. HORINE
folk are they? What do they talk about?
What keeps them so everlastingly at it?
The best way to answer these perfectly
natural questions is to recount the story
of what one amateur has done. Clair
Foster, or to give him his correct entitle-
ments, Colonel Clair Foster, 6 HM, Carmel,
California, is more or less a newcomer to
the ranks of amateur radio. He calls
himself a greenhorn, but there are those
who will take emphatic issue with him
on this score. Two years ago, he knew
nothing about amateur radio. He had
constructed a few broadcast receivers and
was beginning to yearn for new worlds to
conquer, when he met John Reinartz. And
that meeting was the beginning of a new
life for Colonel Foster.
His first and natural objection was he
couldn't read code, but this was pooh-
poohed, laughed at, ridiculed. Anybody
can learn the code; a little study, a little
practice, and you are ready to stand the ex-
r.mination for a transmitting license. Age
is no barrier, nor is sex, for there are many
girl amateurs, YL'S in "ham" language
Foster says the small time and study he
devoted to learning the code was the best
investment he ever made. It has been the
means of opening up for him a new field
of activity; it has brought
him a host of new friends,
many of them on the other
side of the world, with whom
he is on terms of closest in-
timacy, yet whom he has
never seen, and probably
never will see. It has drawn
him into an international
fraternity guided by a self-
imposed code of ethics that
comes closer to being a lit-
eral application of the golden
rule than anything else on
this earth. It has afforded
him the most pleasant hours
of his life, and turned him
into a youth again, bubbling
over with enthusiasm.
HATS
OFF TO THE
WAITERS
FIVE
LOOKING TOWARD AUSTRALIA
From the little shack of Col. Clair Foster's radio cabin near Port Alberni, B. C.
The mountain is called Mount Arrowsmith, and did not seem to block the modest
radio signals from the battery-operated, j-watt, short wave transmitter installed
here by Colonel Foster and operated under the call CQCK. The story tells how a
simple transmitter was built and communication established all the way across the
Pacific with amateur radio men in Australia
HIS station at Carmel,
California, 6HM, uses
a 250-watt tube, and with
it he has "worked" fellow
amateurs in the Philippines,
Japan, Australia, and other
548
RADIO BROADCAST
MARCH, 1926
countries. But he feels that reaching out
to great distances with high power isn't so
remarkable. It's the fellow who does it
with low power that deserves credit for real
achievement, and this "most miles per
gallon" idea is now coming in for a great
deal of attention on the part of the amateur.
Commenting on this phase of radio trans-
mission, Foster says,
After working a number of distant stations
that were using very low power, my hat came off
to the chaps who could put out such clear and
steady signals with 5 waiters — and even 201 -A
receiving tubes. Every one 1 bumped into
I boned for his dope, and I have collected
through their courtesy quite a bunch of it. I
see no especial credit coming to the fellow who
busts out with the big tubes. Of course it is
satisfying to have a wallop so that when you
answer a CQ (general call) you are the fellow the
other chap almost surely hears; but the big field
for the practical use of radio can't be opened
up with the use of big, expensive equipment.
Only a small proportion of those who will be-
come interested in transmission can afford the
heavy outlay.
The big tubes themselves are expensive,
and they require a rather costly array of
auxiliary apparatus for their operation — a
high voltage motor generator, or a system
of rectifiers and filters to convert the com-
mercial alternating current into as close
an approximation of the pure direct current
of batteries as possible. But with the
small tubes, the installation cost of a com-
plete transmitter becomes ridiculously low.
The transmitter itself can be built for much
less than the cost of a good broadcast
THE TRANSMITTER THAT TALKED TO SOUTH AUSTRALIA
The photograph was taken before the coils were changed. The most notable feature of the outfit
is the careful placement of the parts which certainly had much to do with the extraordinary results
produced by the arrangement
receiver, and it can be operated successfully
and reliably from B batteries.
Foster's low power transmitter, 9 CK,
was designed and built in California, but
was operated all summer at a point on
Vancouver Island, about 125 miles north
of Victoria. The outstanding character-
istic of this transmitter is the careful and
painstaking workmanship expended on its
THE COMPLETE OUTFIT AT CQCK
The transmitter, receiver, "power plant," and operator — Colonel Clair
Foster himself. Note the wavemeter on the right top of the table
construction. There is nothing ragged or
loose about it. Every part fits perfectly
in its appointed position, and the coils, as
can be seen, are made of heavy copper
strips, with nothing touching the turns.
They are supported by their own rigidity,
and the whole transmitter is just about as
low loss as it is possible to build such a set.
This careful attention to small details is
largely responsible for the fine work done
by this transmitter.
The shack was located on the shore of a
lake surrounded by snow capped mountains
over which or through which the signals
from the little transmitter had to pass to
get anywhere. It is a wild, rugged coun-
try, remote from civilization, and naturally
no electric power available for any purpose.
There is only one way to get power in that
country, and that is to carry it along in the
form of batteries.
But that wasn't the real, fundamental
reason for deciding to run his low power
transmitter with B batteries. If the weak
signals put out by such apparatus are to
get anywhere, it is essential for the note
emitted to have a high, penetrating sound,
otherwise it can't be read at considerable
distances, and batteries are ideally suited
to impart to the transmitter a tone that is
not only penetrating, but steady and free
from swinging.
In connection with the use of B batteries
for power supply for transmitters, Colonel
Foster said, in one of his earlier letters
written before leaving Carmel for Van-
couver Island,
Along this line, most of us on 15,000 kc.
(20 meters) have been using 25O-watt tubes.
But 9 DFH has the steadiest signals I hear, and
he is using a lonely 5-watter (about the size of
an ordinary receiving tube) with less than 20
watts input. And recently, I worked 4 BL, in
Lakeland, Florida, who was coming in here fine
through heavy static disturbance, using a 201 -A
MARCH, 1926
A MAN AND HIS HOBBY
549
Audibility
RECEIV
receiving tube for transmitting!
It wasn't a freak transmission,
for 4 BL has worked some of
Canada, all United States Dis-
tricts, and Porto Rico on 7500
kc. (40 meters) with this tube.
At present, the big drawback to
the use of 1 5,000 kc. (20 meters) is
that it is so responsive to slightest
variation in current that the sig-
nals keep swinging into and out
of tune. I think batteries for
plate and filament ought to help
a lot.
HIS "A. C." BATTERIES
WH EN the little transmit-
ter first went on the air,
reports received indicated that
its note was rough and ragged,
as if produced by rectified a.c.
which Foster couldn't under-
stand, on account of the bat-
tery supply. Many a time he
was kidded over the air by
facetious hams about his "a.c.
batteries," but he finally
solved the puzzle. The flat
copper-strip coils were thrown
into slight mechanical vibra-
tion by the thumping of the relay, and it
was this vibration that caused the rough
quality of the note. New coils, made of
j-inch copper tubing, were substituted
for the original ones, after which reports
began to come in saying "Pure d.c. OM
VFB" — pure direct current, old man, very
fine business."
Your radio amateur is an optimistic
individual. Everything that happens is
encouraging. Witness this, written a few
days after the transmitter was set up.
The little j-watter, signing itself c 9 CK, here
among the mountains of Vancouver Island, seems
to be getting out a bit, on 7900 kc. (38 meters.)
Have had encouraging reports from two stations
in southern California.
Southern California! And he calls it
encouraging! In view of what he had
20 GURNET ROAD, DIJLWICH, S.A.
D J- MM ^L received .
Radio C 7/./y ur *»*«; . . _,. . j licit Oft.
.1923'
>rked
at
S.A.M.T
QRM &L. QRN /M. QSS*</_
QRK. 5 BG? P$e QSL.
C.U L. 73's (rm.
....Operator.
THE VERIFICATION CARD FROM A 5 BG
The call letters of H. R. Kauper, the amateur operator in Dulwich,
South Australia, who maintained a faithful schedule with CO.CK, to learn
how reliable communication with a 5-watt, battery-operated transmitter
could be. The back of the card lists details of their schedule: "Aug.
27 — 10 watts; 28th, QSA (strong signals); 29th QSA; 2oth, 2OIA tube,
ii watts; 3ist, QSA; Sept. ist, OK, but QRZ (weak signals); 2nd, my
transmitter out of action; 3rd, QSA; 4th, QRZ, but OK; 4th, later, QSA;
5th, QSA; 6th, vy. QSA (very strong); 7th, vy. QSA
accomplished before the summer was over,
Southern California was just around the
corner. Colonel Foster's ambition was to
work an Australian, but results along this
line were not so encouraging at first.
Saturday night I hollered my head off at the
Antipodes until 2 A.M. I imagined batteries
would show some drain after all that use. But
at the end of that time the eleven in use still
tested exactly as when I began, 485 volts.
He continued to "holler his head off"
at the Antipodes night after night without
result, until the ordinary individual would
have given up and dumped the apparatus,
batteries and all, in the lake. But your
radio amateur is not an ordinary individual.
For nearly two months he kept at it, never
losing hope, never giving up. And then,
on the morning of August nth, he made
the grade! You can imagine
the pride and enthusiasm with
which he dashed off this tele-
gram.
Port Alberni, British Columbia,
August nth, 1925.
E. E. HORINE,
Radio Division,
National Carbon Company,
New York.
Using only one 201 -A receiving
tube with input just ten watts
from Eveready Batteries worked
satisfactorily this morning five
forty to six forty-five A.M. Pacific
Standard Time Australian 3YX on
thirty nine meters. Report on
other work follows soon.
CLAIR FOSTER c 9 CK.
Some telegram! And some
message! For over an hour,
he had conversed with this
Australian amateur, and at a
time of year when broadcast
listeners have ceased to fish
for distance on account of
summer static. And look at
the time of day it all hap-
pened! 5:40 A.M.! Appar-
ently amateurs never sleep.
Once the ice was broken, things began
to break rapidly in the direction of Aus-
tralia. On August 1 3th, the performance
was repeated, this time communication
being established with Australian 2TM.
And on August 27th began what constitutes
one of the outstanding performances of
amateur radio. On that morning, Colonel
Foster reported in a telegram:
To-day again the receiving tube stop this
time forty-five minutes perfect communication
with 5 BG near Adelaide South Australia stop
these signals had to travel thousand miles or
more over land after passing the other three
stations already worked with this tube stop input
thirteen watts wavelength thirty eight and
seven tenths stop more than quarter of distance
full daylight.
The mere fact of establishing contact
"MEELAAN," MISSOURI AVENUE, GARDEN YALE (Vic., Australia)
To
'""- _>T.
jlatl"
" CARMEN™ 13 ERITH ST., MOSMAN, SYDNEY. AUSTRAL«L
TO!
QRK.2AT) PSE. QSL.
"BUSINESS CARDS OF TWO AUSTRALIAN AMATEURS
Sent to Colonel Foster after his station cgcK was heard in Australia. The initial "A" before the call signs means that the station concerned is
in Australia, just as the "C" used with Colonel Foster's call means that his station is in Canada. United States amateurs use "U" as identification.
The practise is necessary because the air is full of signals from amateurs all over the world. Note that A2TM says "I think that that's lowest power
record across the Pacific. Your signals were fading a lot, but did not drop off much when you changed tubes. 1 hope to test again with you soon.
Will try reducing power myself next time"
550
RADIO BROADCAST
MARCH, 1926
with an Australian station from Vancouver
Island, using a 2OI-A receiving tube, is a
notable achievement, but not a record.
Other amateurs have surpassed this per-
formance, and while naturally elated at
his success, Colonel Foster was conscious
that there was danger of his lapsing into
the role of the joyous ham experiencing a
major thrill instead of maintaining the
attitude of a cold-blooded observer; for
after all this might prove to be freak
transmission. To settle this point, he and
5 BG arranged a daily schedule, the idea
being, that if they could repeat the per-
formance day after day, it would establish
beyond any doubt that there was nothing
freakish about it. The maintaining of that
schedule is one of the outstanding points
of amateur radio history, for they kept it
up for fourteen days without a break,
through all kinds of interference from other
stations and static, under conditions not
considered favorable for transmission and
reception. And the daily schedule was
finally discontinued, not because communi-
cation became impossible, but because
they had demonstrated conclusively that
reliable two-way communication could be
established and maintained with extremely
small power.
THE AMATEUR: CURIOUS MIXTURE
AMATEUR call letters consist of a num-
eral followed by two or more letters.
This was all very well for a while, but of late,
international communication has become
such an everday occurrence, that it has
become necessary to adopt some means
of separating the nations of the earth!
It is customary to precede the regular call
letters with an initial, designating the
country in which the station is located.
For example: u 6 HM is station 6 HM in the
United States, c 9 CK is in Canada; A
stands for Australia, z for New Zealand,
etc. This old earth of ours is rapidly
getting too small to hold the amateur!
The fourteen day schedule with Kauper
reveals the many-sided nature of the ham.
He is interested in his work, and takes it
seriously, but not too seriously. He is
human, just like the
rest of us, and en-
joys a joke as well
as anybody. In fact,
the amateurs have
coined a word which
is used to indicate
the appreciation of a
joke, or to call at-
tention to what is
considered a joke.
Like most of the
words in ham lan-
guage, it is short,
for it must be re-
membered that all
communications are
spelled out, letter
by letter, and short
words are at a pre-
mium. This particu-
lar word is "Hi."
Freely translated, it means, "That's a hot
one! Consider me laughing. Ha! Ha!" Or,
in case the sender interjects a "Hi" into a
sentence, it means, "That's a joke — you
are supposed to laugh now."
They have a lot of fun, these hams, in
the pursuit of their labors. There is no
formality about them. Everybody is OM
— old man. Log sheets of amateur stations
fairly bristle with OM'S and other abbrevia-
tions which are as useful and effective as
they are curious. Here is the way it goes.
This is A2TM talking to cgCK at 6:15
A.M. August 13.
Only last part OM — missed QRA (your location)
again OM — say OM, send V's after call till I get
you best then QRA please — think about record
for low power OM — congratulations OM, very
fine business — want get your QRA OM please
try again.
Six "old mans" in one short message!
That's ham language.
The intimate side of the relations be-
tween amateurs is revealed in this message
from Foster, commenting on his intercourse
with Kauper, A 5 BG.
Our times are, of course, widely apart. Kauper
takes in an evening movie show, then goes to his
"shack" as every ham fondly terms his little
sanctum, the privacy of which must never be
invaded by the uninitiated without special
invitation — to listen for c 9 CK. Day before
yesterday he asked "Just what is your time
now," and added "Ours is 11:25 p-M-> August
27th". I replied, "5:55 A.M., August 28th."
Next time he came back he said "Thanks for
time. Hi."
Such conversations flashed back and
forth across the vast expanse of the Pacific
bring out many intimate touches like that.
The daily habit of going to the movies;
the fact that Kauper is married and that his
wife sometimes objects to his sitting at the
key so late at night; and many others.
And all this with a man more than nine
thousand miles away, but who, thanks to
radio, is also your next door neighbor.
That's the kind of associations formed by
amateurs. No wonder the ranks are filling
up with newcomers.
THE SHORT WAVE RECEIVER
Which is not much larger than a B battery. A receiving 201 A tube, used as
a. transmitter is on the table, near a "peanut" tube used in the receiver
One of the first things Colonel Foster
told Kauper was that his little transmitter
was being run by B batteries, such as are
used for reception, because that was one of
the unusual features of the installation.
Kauper appreciated the significance of the
use of batteries, and made frequent com-
ments on it. Several times, when the
going got too hard for him he said "Can
read, but can't you stick a few more B
batteries on her?" One day, when the
signals arriving in South Australia were
exceptionally loud and clear, Kauper said
"Say OM, you must own a couple of B
battery companies, Hi."
This kind of thing kept up for two solid
weeks. The original plan was to keep the
schedule for only one week, but the going
was so good that they hung on for another
week. Colonel Foster is convinced they
could have kept it up indefinitely. Even
after the schedule was completed, he and
Kauper chatted back and forth every now
and then, apparently enjoying the freedom
from their self-imposed task.
TRANSMITTER COST VERY LOW
IT IS hard to realize that this vast dis-
tance was bridged with a little trans-
mitter that any one with a little knowledge
of the subject can build at a total outlay
of not to exceed $50.00. That's the won-
derful part of it. This low power, long
distance transmitting is not a rich man's
game — it is within the practical reach of
all. And in the amateur ranks, there is
room for all. They welcome the new
comer with open arms, and go to unbe-
lievable lengths to help him get started
right.
Colonel Foster, like all hams, has his
facetious moments. Commenting on the
performance of the aoi-A tube in his trans-
mitter, he said:
In all fairness 1 should make the confession
that this particular 2OI-A tube is not an ordin-
ary 2OI-A. It was especially prepared for this
job. It spent eighteen months as an oscillator
in a broadcast super; then it worked for a while
as a detector in a receiver built solely for very
short waves. In this way it gained a lot of
experience as an oscil-
lator so of course it
knew its business when
it entered the trans-
mitting field.
Colonel Foster is
thoroughly con-
vinced of the value
of using B batteries
with low power
transmitters. In his
enthusiasm over
this form of power
supply, he is doing
all he can to get
other amateurs to
duplicate his ap-
paratus, batteries
and all, for he is
convinced that with
any other kind of
power supply he
MARCH, 1926
A MAN AND HIS HOBBY
551
would never have made the fine
record of keeping a two weeks
daily schedule with Kauper,
away down yonder on the un-
der side of the world.
Writing about his plans for
the winter at Carmel, he said:
"I'm going to keep on using
dry cell B batteries for this work
even if I have to give up a hun-
dred dollars apiece for them "
That was written after five
months grilling had only par-
tially exhausted the B batteries
he took with him to Vancouver.
They are now reposing in a ware-
house in Port Alberni, waiting
for next summer's work.
He takes none of the credit of
his accomplishment to himself
but distributes it impartially between the
batteries and the amateurs who helped him
out — typical of the generous spirit of
hamdom. His letters are full of praise
for Kauper and the way he hung on
through the schedule. He goes on to say
of his Australian friend:
"Am simply lost in admiration of that
chap. Just think of the courage displayed
in asking for a report that of necessity
must be more or less complicated, and
knowing that it must come back to him in
a thin, high, bird-like note that must take
a mighty fine pair of ears to hear
at that distance. Only one thing
in his favor — Cg CK'S note is abso-
lutely steady. It has been so re-
ported all over the map. This is
due partly to the set and the way it
is adjusted, but more to the fact
that both filament and plate sup-
ply are from batteries."
And again:
Kauper is a wonderful chap.
It is obvious that he is keenly alive
to the fact that in keeping this daily
schedule under actual working con-
ditions Australian amateur station
5 BG and Canadian amateur station
9 CK are helping to make radio
history.
Once, after recounting in detail
all the messages flashed back and
forth across the Pacific in one of
their scheduled communications,
Colonel Foster burst out with :
"There's a game boy for you!
That's the kind of stuff that has
sent the amateurs ahead so fast in
this new and marvelous short-wave
field that the commercial interests,
professionals, and high-brows can
only plod along behind in the dust
and pick up what the amateurs let
drop."
And that's a typical amateur
attitude too. But pardonable.
Enthusiastic as he is over past
amateur performances, Colonel
Foster is even more enthusiastic
over the future possibilities. And
the more amateurs there are testing
BREAKING CAMP AT QCK
As Harry Lyman started away from the radio shack, he remarked,
"Well, here goes GQCK'S famous QSB", Which meant cgcK's high, pene-
trating, flute-like note
away and experimenting with new things,
the sooner his dream will come true. It
isn't an expensive game — quite the reverse,
especially in the short-wave, low power
field. And in the opinion of many, that
is the field where the greatest radio progress
is to be made in the next few years. The
ease with which one can embark on this
fascinating, thrilling enterprise of radio
transmission will doubtless be responsible
for hosts of new recruits into the amateur
fraternity.
Colonel Foster's comments on the future
A 5OO-WATT AMATEUR STATION
Owned by La T. S. F. Moderne, a French radio magazine. This might
almost be dubbed a superpower station when compared to the
"midget" transmitter used so successfully by Colonel Foster
of amateur radio are timely and
pertinent.
" I feel that in these experi-
ences of mine there is really a big
story. You know me well enough
to know that I don't mean big
because I did it. It is big because
the infant art of radio did it, and
is continuing to do it. jt is big
because of the far-reaching pos-
sibilities it discloses for the hu-
man good. Not theorizing as to
the probability of long distance
communication with extremely
low power, but proving the prac-
ticability of it by doing it day
after day. Unlike the automo-
bile, heralded as the greatest
promoter of human progress,
radio can never be used to the
great advancement of the bank
robber, gunman, and bootlegger.
And just look at the future possibilities,
certainties of this inexpensive low power
stuff as a promotor of peace among the
peoples of the earth. Why, with all the
warm friendships that are being born every
day among the radio amateurs of one
country with those of another, it will soon
be all a politician's life is worth to say,
"Let's start something." Just fancy some
big stuffed shirt's telling me to go out
and fight young Kauper!
And that, mind you, was written by a
reserve officer.
Since the completion of the
summer's adventure on Vancouver
Island and the termination of cor-
respondence regarding it, Colonel
Foster has paid us a visit here in the
East. He is as sunny, as breezy, as
enthusiastic in person as one would
imagine him to be from his letters.
A most pleasant, human and com-
panionable man.
He has retired from active par-
ticipation in all business and is pur-
suing the radio transmission game
as a hobby. Unlike many hobbies,
his is useful, not only to himself,
but to others. And he is not a one-
sided man, as are many hobby
riders. He can discourse enter-
tainingly on any subject pro-
posed, for he has led an active
life, full of many and varied ex-
periences. He has a wealth of good
stories, and he tells them with a
merry twinkle in his eye that belies
his years.
He has worked hard, borne
heavy responsibilities, achieved
much; and now, after a useful
and successful business career he
is really enjoying life — thanks to
radio. Colonel Foster represents
just one type of man to whom
amateur radio has appealed and
lifted to a higher plane of en-
joyment of life, and what it has
done for him, it will do for any
one, young or old, who seriously
takes up this new and fascinating
game.
THE MARCH
I
Past President, Institute of Radio Engineers
Additional Opinions About the Naval Radio Service
UR comments regarding the
Naval Radio Service in the
December RADIO BROADCAST
brought forth some letters from
our readers which deserve presentation
with at least as much emphasis as that
used in giving our own ideas. Elsewhere
in this issue there is printed a communica-
tion from Mr. H. A. Halcomb, who was in
the radio service at the time when our
destroyer squadron went aground on the
California coast. He enjoys the distinction
of "knowing" that radio was not at fault
in this accident, as his log was used in the
investigation. Evidently then Mr. Halcomb
knows that the radip bearings received by
the fleet were correct — and still the fleet
ran aground! Does this mean that the
radio bearings were considered of so little
importance by the navigating officer that
he preferred to cruise by dead reckoning?
Had the radio compass service proved of so
little reliability in the past that a navigator
at that time preferred to depend upon his
judgment of the effects of currents, winds,
etc., rather than plot his position on a chart
in accordance with the radio signal? If
so (and we can see no other way to recon-
The photograph in the heading above shows one view of
the 2o-kw. vacuum tube transmitter at the Naval station,
NAA, at Arlington Virginia. Note the water-cooled tube.
(© Harris & Ewing)
cile the event with Mr. Halcomb's state-
ments), hadn't radio failed to function prop-
erly, to lead up to such a catastrophe?
The spirit in which our comments were
made was a friendly one, and not one of
cynical criticism. We were attempting to
answer the question — is radio doing as
much for our Navy as it is capable? If
not, conditions should be changed either
by increasing the reliability and utility
of the radio service or in educating the per-
sonnel properly to appreciate its worth.
Another letter taking us to task for the
article comes from Mr. C. J. Pannill, vice-
president of the Independent Wireless
Telegraph Company. Mr. Pannill says:
An article of this kind may do the Naval
Communication Service considerable harm, and
it is only fair to ask that Professor Morecroft
get in touch with the proper authorities in the
Navy Department and set the public right
through the publication in RADIO BROADCAST
of a correction to his article mentioned. My
idea in taking this matter up with you is due to
my particular interest in the Naval Communica-
cation Service, since I had a good deal to do
with laying the foundations of the service during
the time I served in the Navy.
Now it is just possible that pointing out
the way in which radio has not proved it-
self may do the Naval Communication
Service more good than could be accom-
plished by the method suggested by Mr.
Pannill. If misstatements were made, we
shall be the first to apologize and retract
them, but in spite of some of Mr. Pannill's
remarks, it is not evident that our criti-
cisms were in error. The circumstance
which brought forth our comments was the
dismal failure of radio communication in
the PN-g No. i near-disaster. Referring
to the U. S. S. Honda affair and the PN-Q
No. i failures, Mr. Pannill says that "they
are not chargeable to any one branch of the
Navy or its organization. These failures
may have been the -fault of the Navy but
the reasons assigned were not sound and
were evidently written without adequate
knowledge of the facts."
It so happens that as Mr. Pannill's letter
came to hand, we were reading further evi-
dence on the PN-g No. i inquiry and found
that "Lt. Byron J. Connell, pilot of
the PN-gNo. i said that he was satisfied the
PN-g No. i failed to locate the Aroostook,
the last of the station boats on the Hawaiian
flight, because the radio bearings received
were in error. The plane followed the
bearings given and landed in the sea to re-
main there for nine days." In the same
hearing, Commander Rodgers said that the
MARCH, 1926
OUTSTANDING RADIO EVENTS IN 1925
553
failure to reach the Aroostook was "due to
confusion of radio bearings and possibly an
error in navigation."
In contradistinction to the two letters
mentioned above, attempting to "soft
pedal" radio's performance in the two in-
stances named, the Navy itself sent us a
most courteous inqury for suggestions as to
what constructive criticism we could offer.
As Mr. Halcomb says, it is easy to sit
back and criticize what others have done
but how to do better? Well, in the interest
of radio progress, we insist again that the
PN-g No. i should have had an emergency
radio outfit. Too much weight? Then
leave one of the men at home and make the
rest of the crew work a little harder. Bet-
ter have eight overworked men arrive at
their destination than nine men somewhat
less fatigued drifting helplessly toward
Japan.
Unless one has looked at a map of the
Pacific in the vicinity of this near-disaster
he cannot realize how closely this crew
came to perishing. It is almost an acci-
dent that they happened to drift into an
island. Had the direction of wind changed
a little they would probably have drifted
clear into the Pacific — forever.
Shouldn't there have been some radio
outfit aboard which would keep them in
touch with their supply ship when they
were forced down? It is doubtful if any
sensible man to-day would differ with us.
If such a flight as that to Hawaii is so
close to the impossible that even the added
weight of an emergency radio outfit would
spell failure then it should not be attempted.
The Navy is not supplied with so many
capable airmen that it can afford to take
again chances as it took in that flight.
Those responsible for such projects as was
attempted by the PN-Q No. i will never be
told by their junior officers that the chances
of success are too slim to make the scheme
worth while — our officers are not of that
mind. It remains, therefore, for some rank
outsider, such as ourselves, to venture the
statement that possibly things should have
been done differently.
The Progress of Radio in 1925
PROBABLY the one event standing
out more than any other during the
year 1925 in so far as the interests of
the general listener are concerned, was the
spirit in which the questions arising at the
National Radio Conference were settled.
While the conference could not give Secre-
tary Hoover any power to act, it brought to
him so strongly the sentiment of the coun-
try on certain of radio's problems that he
has been able to act since then with the as-
surance that the radio public was behind
him. It is notable that for some weeks
now, not a single broadcast license has been
issued. It is hoped that this condition
will continue.
All questions arising in the broadcasting
realm, said the radio conferees, must be
settled in the interests of the broadcast
listeners and the establishment of this
policy for the guidance of future radio
executives will prove to be a real boon to
all of us. Any sensitive set to-day gives
heterodyne notes in many of the radio
channels which are supposed to be without
interference and this situation can be
remedied only by keeping constantly in
mind the policy that the interest of the
listener, rather than that of the broad-
caster, must prevail. Many of our present
stations must soon be eliminated, and this
event was certainly predicted by the spirit
of the radio conference.
The great attempt being made to furnish
the public with a satisfactory battery elim-
inator is perhaps the next outstanding fea-
ture of the radio season just passed. Not
yet successful enough to call the problem
solved, yet near enough to make us believe
that the real solution is at hand, the work
of those radio engineers engaged on this
problem is probably of more present signi-
ficance to the broadcast listeners than any
other. Of course, as the battery interests
maintain, there are many places where 1 10
volts a. c. cannot furnish power for the
radio outfit because there are many houses
which do not have it. The number of
such homes is rapidly diminishing so that
it may truthfully be said that the battery
eliminator (for both A and B supplies) is
awaited to-day by millions of listeners.
The remarkable popularity of the straight
line frequency condenser shows that there
was a real demand for such a piece of ap-
paratus. First introduced about two years
ago, it has, during the past year, shown it-
self so valuable that the old semi-circular
plate condenser has today a limited sale.
The innovation of this specially formed con-
denser, spreading out the stations on the
lower part of the dial, was a decided help
to the broadcast listeners.
The use of the piezo-electric crystal as a
frequency stabilizer will soon be looked
back upon as one of the milestones in the
improvement of radio transmission. With
the present spacing of stations on the fre-
quency scale, some standardization scheme
is absolutely necessary and the curiously
acting bits of quartz crystal which serve to
make a small tube oscillate at an exact and
constant frequency, are accomplishing this
purpose admirably. Rochelle salt is about
one hundred times as active a crystal as is
quartz and would probably serve the pur-
pose even better if it were not so fragile,
and soluble in water. Piezo-electrically
a wonderful material, it is mechanically
so inferior to the durable and constant
quartz, that the latter will undoubtedly
soon be fixing the frequency of all our im-
portant broadcasting stations.
Picture transmission by radio secured a
large amount of attention during the past
year, but so far has become commercially
important over only one or two channels.
It is sure to develop into a service of im-
mense importance (with the possibility of
doing away altogether with our dash and
dot communication system) but much
development work remains to be done be-
fore that is accomplished.
The quality of reception in the average
receiving set was much improved during
the past year. Great improvements were
made in the characteristics of tubes to
operate with loud speakers, by the research
engineers of the General Electric Company,
and several fundamental and important
A CORNER IN THE RADIO CABIN OF A NEW ITALIAN LINER
The Conte Biancamano, which is said to be the largest liner flying the Italian flag. The installation
is quite modern. A soo-watt tube transmitter for telegraphy can be seen in the right hand corner.
Note the position of the transmitting key, just a few inches from the edge of the operating table.
This position would be almost an impossible one for an American operator, as practically all of the
operators trained here use a sending motion which rests the entire arm on the table
554
RADIO BROADCAST
MARCH, 1926
ONE OF THE RADIO DEVELOPMENTS OF 1925
A beautifully compact vacuum tube commercial transmitter
with a power of two hundred watts. This outfit has a wave-
length range of 600 to 900 meters and is especially designed for
radio telegraphy aboard ships
studies of the characteristics of loud speak-
ers themselves were reported to our engin-
eering societies. To some extent keeping
pace with the improved quality of reception
of the average receiving set, the programs
themselves may in general be considered as
somewhat better than last year. Most
notable among the year's accomplishments
in this direction is the series of Atwater-
Kent Musical Hours. Not less pleasing,
even if less important, are several series of
concerts by certain of our well-known
trios and ensembles. The " Dinner-Hour"
music is a real treat for the average subur-
banite, who gets the benefit of good music
with his meals without the disadvantage of
a cover charge. As one turns from station
to station, however, at about eleven o'clock
in the evening, he is impressed with the
concentration of jazz. It is hard to believe
that there really is a demand for the con-
coctions the average dance orchestra sends
out over the midnight radio channels.
With the advent of two 5O-kilowatt sta-
tions, WGY and wjz, the era of international
broadcasting seems ready to start. The re-
broadcasts which have occurred to date,
of programs flung across the Atlantic,
haven't been worth while except as a
"stunt." But by raising the signal strength
ten times or more, the static disturbance
may become comparatively
unimportant. In general, these
high powers have not caused as
much disturbance as had been
anticipated; those close by
(within a few miles) have no
doubt been well deluged with
the energy of these powerful
stations, but by using proper
traps to bypass most of their
signals, much of the present
trouble will disappear. A
proper policy for a super-
power station to adopt would
be to start operation on very
low power and gradually to in-
crease the radiation, taking
perhaps three months to grow
to their normal rated strength.
This method of procedure
would do away with much of
the complaint as the near-by
listeners would gradually be-
come accustomed to methods
and apparatus for eliminating
these powerful signals.
The feeling against the re-
generative receiver has steadily
grown until the listener is
almost ashamed today to
acknowledge the ownership
of such a set. The man
known to operate such a
receiver is at once blamed
by his neighbors for all the
howls they hear and the con-
tinued cultivation of this
attitude, by those owning
non-radiating receivers, will
do much to hasten the dem-
ise of this undesired member
of the receiver familv.
A most remarkable study of wave inter-
ference and signal distortion was reported
during the past winter and it seemed to the
writer that Bown, Martin, and Potter, the
research engineers responsible for this work,
were laying out for themselves a unique
problem on which they will probably work
alone. It is likely that these engineers will
do this work so well that the field becomes
theirs and we shall look entirely to them for
explanations of transmission phenomena.
In the patent situation, the granting of
the high vacuum invention to Langmuir
stands out as the one event of the year.
Continued and expensive litigation along
other lines points out the entire inadequacy
of our present patent scheme. It seems
nowadays that the granting of a patent
has scarcely more significance than a license
to sue others. The overworked staff of
our Patent Office is so loaded up that fre-
quently five years or more are required for
a patent to be issued. Secretary Hoover
may be able to arrange some new method of
procedure so that much of the wrangling,
which now takes place before a court after
the patent is issued, might be heard before
the patent is granted, so that the patent is
really of some value to the inventor; at
present it is worth practically nothing un-
less he is backed by some powerful cor-
poration.
The year has seen a growing appreciation
of the value of scientific research — not the
research having as its goal a new receiving
set, or more economical triode, but research
in the realm of pure science, the kind under-
taken to determine the truths of an unsolved
problem. Not only has the work of the
pure scientist received increasing recogni-
tion, but from the highest sources, words of
appreciation have been showered upon him.
I
THE CONTROL PANEL OF A FORTY-KW. TUBE TRANSMITTER
Built by the General Electric Company for use in the station at Kahuku, Hawaii. This transmitter
when installed will continue the radio link now in force between Hawaii and California. Another
similar radio station competes with the cables to Japan and links Hawaii with Tokio
MARCH, 1926
HOW BROADCAST LISTENERS SERVE EACH OTHER
555
LEGEND
BiOOO WATTS OQ MOOfl
500 WATTS OO MOOE
BUT LESS THAN &OOO WATTS
LESS THAN 5OO WATTS
THE DISTRIBUTION OF BROADCASTING STATIONS IN THE UNITED STATES
On the first of November, 1925. This chart was officially compiled for the Department of Commerce.
Note how comparatively few stations there are operating with a power of more than 5 kilowatts.
Since the Fourth National Radio Conference, the number of stations has not increased. There
are now 536 broadcast stations to supply aerial provender for the estimated four and a half million
radio receivers
In a recent talk before the Society of Me-
chanical Engineers, Secretary Hoover ex-
pressed the opinion that Michael Faraday's
discoveries were of such value as to "per-
form for us in one day more service than the
whole banking community does in a year."
Yet Faraday never received more than five
hundred dollars a year, whereas the bank
executive to-day never feels himself over-
paid with a $50,000 salary. Yet even now
so little do we appreciate men with the Far-
aday point of view, that we spend for re-
search and pure science only one tenth of
what we spend for cosmetics. For every
dollar the scientist spends to discover the
truth, the women of the land spend ten to
conceal it. But when such men as Mr.
Hoover bring their influence to back up re-
search in pure science then we are well
started to fill the position in the world's
scientific progress which our country is evi-
dently destined to occupy.
A Note on the Langmuir Patent
A SHORT time ago we made a comment
*» on the "high vacuum patent"
which was issued to Langmuir, expressing
our idea- that Langmuir had not invented
anything and that the issuance of the pat-
ent was a mistake on the part of the Patent
Office. We are in receipt of a letter from
Mr. F. S. McCullough, who has been as-
sociated with vacuum tube manufacture
for many years, in which he agrees heartily
with the ideas we expressed. This tube
engineer has some old DeForest audions in
his possession, he says, which show a higher
vacuum than do the present Radio Corpo-
ration tubes. As long as facts such as these
can be certified to by reputable engineers it
is incomprehensible that the Court should
sustain the Langmuir patent.
More Millions for Radio
¥ T SEEMS that some ambitious attorneys
have persuaded R. A. Fessenden (well-
known for his submarine signalling ap-
paratus and patents on the radio hetero-
dyne principle) that he has been grossly
r
swindled by some sort of monopolistic
control in the radio industry and that by
due legal process he might collect as dam-
ages $60,000,000. It is very interesting
to a college professor, with his rather
modest income, to see how some of these
radio inventors do juggle with millions.
Their smallest unit of money seems to be
about $100,000, and to judge from the
rumors extant, some of them have collected
many units.
Fessenden really has been a very prolific
worker in the radio field, one of his ideas,
for example, being covered by the hetero-
dyne patent. To hear a high-frequency
current it must be combined with another
current of nearly the same frequency, to
produce beats. The first alternator of the
type now credited to Alexanderson was
built by Fessenden. He
now claims that eight of
the principal concerns deal-
ing in radio have conspired
to do him out of his just
rewards and have not offered
him a fair value for his in-
vention. The attorneys'
claims sound rather flimsy
to us, but possibly the men
who drew them up feel that
there is some chance of
collecting a little money for
their client.
Who Invented the
New Photo- Electric
Cell?
IN THE same mail that
brought criticism of our
naval radio article came
a letter from Mr. T. H.
Nakken, criticizing our
comments on the photo-
electric cell which ac-
complished such remark-
able effects at the recent
electrical show. The new
type of photo-electric
cell was shown by Mr.
Zworykin, of the research staff of the West-
inghouse Company That company claimed
the invention was theirs. Mr. Nakken
informs us, however, that he patented this
device several years ago and that full publi-
cation was made in England and France
three years ago. "This," according to Mr.
Nakken, "made it comparatively easy for
the Westinghouse Company to invent the
device."
So, with the aim of being fair, we cannot
do less than publish Mr. Nakken's claim
to this novel piece of apparatus. His pat-
ent in the United States was issued about
a year ago, but was filed over five years ago.
It may be that Mr. Zworykin has added
something to Nakken's ideas, but on such
a controversial point we can hardly enter
in these columns.
Broadcast Listeners Organize
IN THE Middle West, the broadcast
listeners have found it to their advan-
tage to organize in order to improve the
conditions under which they receive their
programs. One such organization, the
Broadcast Listeners Association of Indian-
apolis, reports an extensive program with
the purpose of eliminating interference of all
sorts. After only a short existence, the
membership list has expanded to twelve
hundred and the activities become quite
diversified. The small membership fee
proves sufficient to carry on what paid
work appears necessary; certain trouble
locating apparatus has been purchased and
is regularly used by some of the members in
finding out the reasons for poor reception.
According to a report recently released,
meetings are held regularly, at which radio
engineers generally give talks on interfer-
RADIO PRINCIPLES AT WORK IN THE POWER HOUSE
The so-called "storm detector" used in the power house of the
Brooklyn Edison Company at Gold Street. The principle of
the device is merely a simple application of the detection of
static charges, which is ingeniously employed to ring a bell.
With a warning of approaching storms, the power companies
can prepare for the increased load that the darkness will cause
556
RADIO BROADCAST
MARCH, 1926
ence causes and their prevention; from three
hundred to five hundred people have
attended these meetings. A campaign
against the single-circuit regenerative re-
ceiver is being constantly waged, while
for those who still prefer to use this type of
receiver, an educational series of talks on
the proper and legitimate use of regenera-
tion has been carried out.
A remarkable degree of cooperation has
been secured from the public utility com-
panies in Indianapolis and vicinity. A
typical letter, from the superintendent of
the Indianapolis Street Railway Company
says: "This company stands ready to co-
operate with the Broadcast Listeners As-
sociation at all times and will remedy any
condition of its tracks or cars that might
interfere with radio reception. We have
already cleared up several bad spots that
have been complained of by radio users."
The telephone company and the electric
power companies have similarly expressed
their desire to remedy conditions which are
pointed out by the Listeners Association
as being detrimental to good radio reception.
This association, it appears, is accomplish-
ing a really valuable work for the listeners
in Indiana.
The Month In Radio
THE annual report of the Chief
Signal Officer brings to light the
fact that the army is now regularly
using radio channels to carry on its routine
business. A net of radio stations all over
the country has been built up, the network
comprising twelve major stations and sixty
auxiliary ones. About eight hundred mes-
sages are handled each day over this network.
In requesting more appropriation for devel-
opment, General Saltzman states that if the
communication which was effected through
his radio chain had been handled by com-
mercial channels it would have cost the
government $156,000. It is just possible
that it actually cost the government more
than that if the proper charges were made,
but even so the radio chain is a valuable
asset to our country, one that the Army
should have available for emergencies in
any case, even though it could show no
saving at all.
FEW of us know enough about automo-
biles to care thoroughly for them our-
selves; we depend largely upon the service
man for inspection or repairs. Without
the country-wide service of this character
it is sure the automobile industry would
not have grown as it has.
Now, in a lesser degree probably, the radio
receiving sets of our country need the serv-
ice man. But few of the listeners know
the functions of the different parts of a set,
but they would like to know that they are
functioning properly. The "radio service
man" is due to arrive. A group of repair
and maintenance men, thoroughly familiar
with all ordinary types of receivers, could
build up quite a clientele in almost any
sizable town, we imagine. They must
know the different sets and what they are
capable of and how to remedy faults. It
seems as though quite a lucrative business
might be built up along this line and we
expect to see someone do it.
As is frequently mentioned, the way of
the inventor is long and tedious and he
never knows whether his idea is safely his
own or not. A case in point has to do with
the modulation of the output of a vacuum
tube oscillator. This scheme is used in
every broadcasting station today. In spite
of its universal application, no patent has
yet been granted. White, of the General
Electric Company, Hartley of the Bell
Laboratories, and De Forest have been in a
three-cornered argument for about eight
years. After going through the normal
Patent Office routine, the case went to the
Examiner of Interferences, who gave De
Forest priority. The Board of Examiners
in Chief was then appealed to by White and
Hartley and this board reversed the inter-
ference examiners' verdict and gave the idea
to Hartley. Then De Forest and White
appealed the case to the United States
Court of Appeals and only now have the
arguments before this court just been com-
pleted.
Even an older matter apparently still
has to be settled. The Court of Appeals
of the District of Columbia has just re-
versed a ruling of the Patent Office on
LeVy vs. Armstrong, so that now LeVy is
permitted to go ahead with interference
proceedings against Armstrong, to whom
the regenerative patent has already been
issued. And in this same line it still remains
to be settled, apparently, whether Arm-
strong or De Forest is entitled to the oscil-
lating audion patent.
EACH year the work of the Bureau of
Standards is inspected and reported
upon by a Visiting Committee, made up of
men not connected in any way with the
Bureau but all of whom are closely in touch
with the needs of our country as regards
development and research. After com-
menting upon the great value to our coun-
try shown by the results of the Bureau
workers (the report states that the auto-
mobile industry is saving $155,000,000 a
year as a result of Bureau studies) the com-
mittee emphasizes the great value of basic
research — the kind that has no immediate
apparent application.
It is the opinion of the committee that
the Bureau work should tend in this direc-
tion more than it has done in the past. It
is pointed out that private research labora-
tories are generally forced to work on cer-
tain questions having to do with special
problems of the industry maintaining them
and that these laboratories are not generally
free to publish their researches. The Bu-
reau of Standards, on the other hand, is
maintained by the government for the good
of all industries and so can most suitably
attack those apparently unremunerative
A. ATWATER KENT
Philadelphia; Radio Manufacturer
" Improved programs, I believe, will feature
11)26 broadcasting to an even greater extent
than was true in 1925. As a result oj the
Sunday night programs by world famous
artists, that I was fortunate enough to arrange,
I have found that the American public likes
good music. They will get more of it during
the coming year. Perhaps the two greatest
fields for the development of radio in 1926,
however, are its use on the farm and in
education. Steps recently taken by Secretary
Jardine to further radio service to farmers
will prove of far reaching importance. The
lime will come when every schoolroom — city
and country alike — will have a radio receiving
set to supplement the work of the teacher in
the class room. The new year will bring a
big advance toward that condition."
problems out of the results of which in-
dustry generally reaps rich rewards.
THE past year's report of the Commis-
sioner of Lighthouses, just received,
indicates the gradually increasing impor-
tance of radio signalling to the protection
of ships approaching our shores. The very
first paragraph, which is a long one, deals
only with the new radio installations.
There are now thirteen radio fog signal
stations under his direction, one of them,
installed on Lake Huron during the past
year, being the first of its kind to be tried
out on the Great Lakes. Equipment for
fifteen additional stations (all outfits of the
vacuum tube type) is ordered, six for the
Great Lakes, one for the Maine coast, and
the rest for the Pacific. We note that one
of these is for Point Arguello, the scene of
the Naval destroyer catastrophe. Cer-
tain improvements in synchronizing the
signals from adjacent stations have been
carried out and the fog signal station on
Nantucket Light has been operated during
the past year for fifteen minutes out of
every hour to test the efficiency of the sta-
tion in giving long-distance bearings for
the incoming ships. No comments are
made as to whether this service has been
of appreciable value.
Important as we may think the radio fog
signalling to be, it is actually a very small
MARCH, 1926
RECENT REMARKS ABOUT RADIO
557
GEN. CHARLES MCK. SALTZMAN
Washington; Chief Signal Officer
United States Army
" While the technical advance in radio broad-
casting apparatus for transmission and
reception during the year 1925 has been
confined largely to improvement in programs
and wider dissemination of those programs
as a result of the use of greater power and
linked up stations, there has been much
development in other fields of the art, prin-
cipally in long distance telegraphic communi-
cation. The most outstanding advance in
this branch of radio communication has
been in the development of the short wave
bands, where it has been demonstrated that on
certain frequencies, with an insignificant
amount of power and at small cost, communi-
cation has been conducted over greater dis-
tances that had hitherto been considered
only possible of accomplishment with the
extremely high power, long wave stations.
I predict that in the coming year we shall see
many improvements and novelties in the
broadcasting activities. In the commercial
field and as a result of the short wave develop-
ments, we may look for some revolutionary
advances in radio communication and
correspondingly increased use of radio for
international correspondence."
part of the total activity of this govern-
ment department. For 1926 out of a total
appropriation of $9,700,000, only $16,000
is allowed for radio fog signals. Of a total
of 1207 fog signals, fog horns, submarine
bells, whistling buoys, bell buoys, etc.,
only thirteen of them are radio stations.
The fog signal on the Ambrose Channel
Lightship is a tube transmitter which has
been operated close to the metropolitan dis-
trict since April, 1924; the report comments
on the fact that nocomplaintof interference
has ever been lodged against this station.
Had a spark transmitter been used, the
government would have heard from a great
many broadcast listeners, no doubt.
WE GENERALLY like to print rea-
sonably accurate statements in these
columns, but it seems that one slipped in a
few issues back which hasn't the stamp of
dependability. Mr. William Dubilier, who
makes a rather good living from mica con-
densers, was quoted as saying that in
America the radio industry has grown so
rapidly that it is now equal to the automo-
bile industry.
Mr. Sarnoff estimates the past year's
radio business as $350,000,000, and he
would not be inclined to understate the
matter. Motor Magazine tells us that
there was an increase in car registration in
our country of 2,132,758 last year. So
by combining Mr. Dubilier's statement and
Mr. Sarnoffs estimate with the above
figure we find that the average price of the
new automobiles purchased last year was
$164.30! We must conclude that Mr.
Dubilier's statement was open to question.
A PUBLICATION of the Bureau of the
**• Census, dealing with the Farm Census
of New Hampshire, gives the total farms
reported as 19,895, of which only 2,366 had
radio outfits. Evidently there is still plenty
of market for good receiving sets.
Interesting Things
Said Interestingly
A LMA CLUCK (New York; former opera
**• singer and still well known on the concert
stage): "Since the time a single record netted
me sufficient to buy a private house on Park
Avenue, receipts from royalties have fallen off
precipitously, and all because of radio. The
radio is a nuisance. They are perfectly darn
foolish things to have around, and, besides the
squawks, most of what one hears over the radio
is terrible."
HUGH S. Pocock (London, England; editor
of Wireless World):
"Wireless is still a new industry, and the
design of apparatus associated with broadcast
reception is passing through a stage of evolution.
The steady development which is going on is not
entirely the outcome of invention, but is more
probably due to the stabilizing of an industry
and the establishment
of an improved manu-
facturing organization.
It may be said that the
manufacturer and the
wireless enthusiast have
rivalled each other in an
endeavor to construct
equipments possessing
good selectivity, an ex-
tensive receiving range,
with easy manipulation
and the elimination of
distortion. It must be
admitted that a peculiar
position has existed
where prospective pur-
chasers would exercise
caution and seek advice
before selecting a receiv-
ing set, and exhibit a
hesitancy that would
indicate a lack of con-
fidence in the manu-
facturer. The exhibi-
tion this year indicates
that a change has come about and that the
wireless trade is now taking a lead. It is now
possible to select a broadcast receiving set built
to a design that will not be rapidly superseded
and with which the user will remain satisfied
in spite of his technical interest in receiver
design."
J. J. WALSH (Dublin, Ireland; Minister of
Posts and Telegraphs) :
"The science and practice of agriculture and
horticulture will hold a prominent place in
the items compromising the programs of our
broadcasting stations, and it will be sedulously
seen to that everything that wireless broadcast-
ing can do will be done to inform and instruct
the farming classes and to keep them in touch
with current agricultural research.
Market reports, seasonable lectures, weather
forecasts, etc., will be regular features of the
programs.
Our news service we propose to make second to
none, and how much this will be appreciated by
our country people will be understood when it is
remembered that they are insatiable gluttons
for news. Their salutations are invariably
followed by 'Bhfu.il aon sceul agat't' ('Have
you any news?')"
REV. DR. S. EDWARD YOUNG
(New York; in a sermon delivered at the
Bedford Presbyterian Church, Brooklyn):
"We should encourage broadcasting stations
and broadcasters to refrain, as far as possible,
from conflicting with the usual hours of church
worship. Since nothing can really take the
place of the assembling of God's people in God's
house, the time of their assemblage ought to be
protected from needless rivalry or distraction.
To be commended is a great broadcasting station
for not starting its tremendous entertainment
at night until after the sanctuaries have closed.
DR. JOHN J. T1GERT (Washington;
United States Commissioner of Education) :
"The benefits of hearing the best music are so
great that I have always favored making it
available to the greatest number of persons pos-
sible. Arrangement of programs such as the
Atwater Kent series marks the attainment of
an important milestone in this direction, because
it will make a vastly greater number of Ameri-
cans acquainted with the best music and the
best musicians.
IN THE MANUFACTURE OF FIXED CONDENSERS
The mica must be accurate in thickness. One degree on the large-scale
micrometer in the photograph equals one one-thousandth of an inch
Can We Forecast Radio Reception From
The Results of Many Experiments Seem to Show That Weather Conditions
Influence Radio Reception — Some Rules for the Amateur Radio- Weather Forecaster
By J. C. JENSEN
Nebraska Westeyan University
M
ARK TWAIN is
credited with the
remark that al-
though everyone
talks about the weather, no
one does anything about it.
Thirty years ago when bicycle
riding was all the rage .among
the young people, many a joy
ride of twenty miles over coun-
try roads was suddenly turned
into a weary tramp through
the mud when an unfriendly
thunderstorm got into action
in mid-afternoon. Not long
ago the newspapers carried
of automobile tour-
were marooned on
of Pike's Peak by
snowstorm, and of
our famous dirigible, the
an Ohio windstorm. It
accounts
ists who
the top
an early
)AN I forecast radio reception as the weather is forecast?" Since the
publication of Professor Van Cleef's "Do Weather Conditions Influence
Radio?" we have received many inquiries worded like that sentence. Many
amateurs who now have radio receivers are anxious to extend their hobby, but still
to maintain a distinct radio tinge to their experiments. The investigation of how
radio conditions are influenced by the weather can be done with no other equip-
ment than a good radio set and the United States Weather Bureau daily weather
map. The map is printed by most newspapers or one can be put on the mailing
list of the nearest Weather Bureau office for a small sum. Neither Mr. Van
Cleef, or Mr. Jensen would care to say that radio conditions, that is, the strength
of signals, amount of static, and the probabilities of fading can definitely be
forecast. Mr. Jensen in this highly interesting article does say, however, that,
knowing national weather conditions, it is possible to tell pretty definitely and
accurately what conditions will be. The author will of course be glad to hear from
readers who find interesting facts about thevagaries of the weather, and Mr. F. M.
Herrick of the Taylor Instrument Companies, Rochester, New York, would
similarly like to hear from experimenters. — THE EDITOR.
of
the loss
Shenandoab, in
would be un-
reasonable to expect that radio, the latest
"indoor sport," should be an exception
and escape without any handicaps resulting
from weather conditions. Radio reception
has the advantage, however, that when
J. Pluvius makes its use impracticable,
the operator suffers no further incon-
venience than the necessity of turning to
the trusty phonograph or the piano for his
entertainment.
The variations in radio reception may be
grouped under three heads:
1. Irregularities in signal strength which per-
sist for hours or even days at a time, re-
sulting in clear reception from a given
station on one evening and faint or inaudi-
ble response on the next. Such fluctua-
tions are spoken of as changes in audibility.
2. Sharp, noisy, crackling sounds are called
"Static."
3. A short period variation in signal intensity,
the usual interval from one point of high
audibility to the next being from three to
five minutes. This is called "fading."
While we may not be able to "do any-
thing about it," our purpose in what follows
is to connect these three phenomena up with
weather conditions.
10 15
DECEMBER 1921
10 15
DECEMBER 1921
FIG. I
Measurements of signal intensity variations of station NAA, the Naval station at Arlington, Virginia.
Curve B shows the variations from night to night, during the first twenty one days of December in
1921. Note that, in B, on December 3rd, NAA'S signals were 120 turns audible, while they were only
four times audible on the gth. Curve A indicates the static audibility for the same nights
RESULTS OBTAINED BY OTHER
EXPERIMENTERS
ATTEMPTS to explain the
variations in radio re-
ceiving conditions have been
made constantly since the very
beginnings of wireless trans-
mission, but the tremendous
increase in the number of per-
sons owning receiving appara-
tus since the advent of broad-
casting has resulted in a much
more general interest in all
problems affecting clearness
and regularity of reception.
Space will permit the mention
— ^— He* of only a few of the most im-
portant of these experiments.
Dr. L. W. Austin of the United States
Bureau of Standards has been engaged for
several years in recording the signal
strength of high-power, long-wave com-
mercial stations such as Nauen in Germany
and LaFayette in France. His reports
show that transmitting conditions are more
favorable at night than in the daytime and
in winter than in summer. The amount
of static disturbance varies greatly from
day to day and is worst in the summer
months. During the years 1920 and 1921,
the American Radio Relay League in
cooperation with the Bureau of Standards
conducted an extensive series of investiga-
tions in which amateurs used their receiving
sets to determine the audibility of signals
under various weather conditions. They
found that stronger signals were obtained
when the radio waves from transmitter to
receiver pass parallel to the isobars than
when they move at right angles to them.
[An isobar is an imaginary line connecting
or marking places on the earth's surface
where the barometric height, reduced to
the sea level, is the same at a given time
for a certain period.] It was found that
stormy weather at the transmitting station
does not affect the range or strength of the
signals and that an area of clear weather
connecting both stations results in less
fading. Cloudy weather at the receiving
station resulted in much more static than
did clear weather. Our British cousins
have recently completed a similar investi-
gation and report conclusions in general
agreement with those already given. They
also found that the nature of the earth's
MARCH, 1926
RADIO FORECASTING FROM THE WEATHER
559
FIG. 2
Signal intensity variations of NAA (operating on 113.1 kc., 2650
meters) for the month of April, 1922. Curve A shows the static
audibility and B the signal variations. The maximum signal au-
dibility for this month, as compared with December referred to
in Fig. i is thirty. In December, the maximum was more than
300, while the static peak record here is 750 (Curve A), more
than twice the December maximum. Curve A is static intensity.
Curve B is audibility. In Curve B, Fig. 2, maximum audibility
{530 while in Fig. i Curve B, the maximum audibility is 120.
Curve C, here and in Figs. 2 shows the angles made with the
isobars of Fig. 3 and 4, by a ruler connecting Arlington, Virginia
and Lincoln, Nebraska, on the map. Curves D (Figs, i and 2)
give the number of isobars cut by the radio waves in passing
between transmitter and receiver
15 20
APRIL 1922
:*»
30.1
WEATHER MAP
Dec. 6, 1921 7 P. M.: '.'
FIG. 3
The United States Weather Bureau map for one of the days covered by the curves in Fig. i. Mr.
Jensen explains the coincidence and relation of reception conditions with weather conditions in the
article
surface in a given region influenced the
strength of signals, water and mineral
deposits being more favorable to good re-
ception than sandy soil and rock. They
further maintain that some signal varia-
tions attributed to fading are in reality
caused by the antenna swinging in the
wind and throwing the receiver out of tune.
Early in 1924, Dr. G. W. Pickard
published an article on signal fading which
presented the first satisfactory method
by which the actual signal strength of
radio carrier waves may be recorded.
The curves obtained with his apparatus
show rapid fluctuations in the carrier wave,
the time between peaks and the amount of
change varying from night to night. The
same type of apparatus was used by Doctor
Pickard and others in obtaining data
concerning the effects of the eclipse of
last January on radio signals. The results
show a sharp rise in signal strength as the
moon's shadow passed over the observer,
conditions quickly returning to those
normal for daylight work after the eclipse
had passed. Further records made at
sunset by a considerable number of ob-
servers during the summer of 1925, by the
use of Pickard's method, showrapid fluctua-
tions in the signal strength just after sun-
set, conditions becoming steadier and the
signals reaching night intensities about
thirty minutes later.
One of the most interesting and widely
discussed articles dealing with radio and
the weather was that of Professor Van
Cleef in RADIO BROADCAST for May, 1925.
This writer combined the observations of
the lay observer of radio programmes
with the technical training in weather lore
of the climatologist and claims to have
found a number of specific relationships
between radio reception and weather
conditions. The most important of these
are that strong signals occur when trans-
mission is at right- angles to the isobars,
or lines joining points of equal barometric
pressure; signals are weaker, and fading is
worse, when radio waves pass parallel to
the isobars, and reception is weaker when
transmission crosses from one pressure
area to another. Before discussing these
points in detail, let us turn to some recent
experiments in the writer's laboratory.
RESULTS OF ACTUAL RADIO MEASUREMENTS
A MONG the most accurate and ex-
*» tensive records of signal strengths yet
made are those by Mr. M. P. Brunig, a
graduate student in the radio laboratory
at Nebraska Wesleyan University, three
years ago. The audibility of the time
signals from NAA, together with that of
static, was measured daily over a period
of several months. A local oscillator gave
a standard tone whose intensity could be
measured by means of a thermocouple
and a galvanometer. This tone was then
used to measure the sensitivity of the ear
!'••'• : • • .•'. :•'.'.•; .- .WEATHER MAP
'.'• ;."•'. •':'•':•' April. 6, 1922 7 P.M.
FIG. 4
Another Weather Map for the period covered in the curves of Fig. 2
560
RADIO BROADCAST
MARCH, 1926
FIG. <-,
The apparatus used to make the observations detailed in this article. The signals are received on a
six-tube super-heterodyne. In the plate circuit of the second detector is inserted a fifth intermediate-
frequency transformer. A head set is shunted across a .oo2-mfd. fixed condenser in series with the
primary of this transformer. Shunted around this condenser is a sensitive wall-galvanometer (seen
on the right side of the wall). In series with the secondary are a crystal detector and another .002-
mfd. condenser. The field strength of broadcasters is accurately recorded with the galvanometer.
The battery and resistance box in the foreground are used in neutralizing the small plate current of
the uv-199 tube which has more recently replaced the crystal as a detector. To the right of the
resistance box is a recording rain gauge and on the wall to the left of the galvanometer is a Compton
electrometer, both of which are used for meteorological research
of the observer and to standardize the
adjustments of the receiving set. A simple
vacuum tube receiver with the necessary
voltmeters and ammeters to check on
batteries and filament current, and an
audibility meter, completed the outfit.
The original report on this research was
published in the Monthly Weather Review
for December, 1922, but since the appear-
ance of Professor Van Cleef's article we
have gone over all the original observations
together with the corresponding weather
maps in order to study the relations of the
weather conditions between transmitter
10.15AM.
46
HME SCALE WHTJULY30. 1925
J020 1025
and receiver, and the observed signal
strength. Curve B of Fig. i shows the
remarkable variation in signal intensity
from night to night, the data covering the
first twenty-one days of December, 1921.
Signals from NAA were 120 times audible
on December 3rd, 6th, and 2Oth, while
they were only four times audible on the
gth and eight times on the I4th. Curve A
indicates the static audibility for the same
nights and it is very evident that heavy
static does not necessarily accompany
weak signals, for on the evening of Decem-
ber 3rd, static was 260 times audible yet
the signals were very loud. Ordinarily,
however, strong and frequent crashes of
static coincided with weak signals. Curves
A and B of Fig. 2 give similar data for
April, 1922. The maximum signal audibil-
ity for that month was thirty as compared
with 1 20 for December, while the static
peak record was 750, or more than twice
the December maximum.
Many newspapers at present reproduce
the daily weather map, so that if there is
any simple relation between the directions
of the isobars and radio receiving condi-
tions, a few moments' study of the map
should be sufficient for determining the
radio probabilities for the evening. In
Figs. 3 and 4 are shown two typical weather
maps, chosen from the periods covered by
the curves of Figs, i and 2. On December
6th, 1921, clear, fair weather prevailed all
the way from the high barometer area in
Colorado to the Atlantic coast. The
entire distance from eastern Nebraska
to Arlington, Virginia, lies between the two
isobars marked 30.1 inches. Conditions
on April 6th, 1922, were entirely different,
with a storm area over Nebraska and Iowa
and a high barometer region in the eastern
states. A radio signal from Arlington to
TIME SCALE KOA AUG.7,-1525
12:08 12:13
TIME SCALE WHO AUG. 8. 1925
12:18
FIG. 6
Several representative curves on different stations, taken from a great many made by Mr. Jensen. Audibility is plotted on the left
MARCH, 1926
RADIO FORECASTING FROM THE WEATHER
University Place, Nebraska, must cross six isobars, pressures
dropping from 30.3 to 29.7 inches. Curves C of Figs, i and 2
show the angles made with the isobars by a ruler connecting
Arlington, Virginia, and Lincoln, Nebraska, on the map. On
December 6th, this angle was o° while on April 6th it was about
seventy-five degrees. Curves D give the number of isobars cut
by the radio waves in passing between transmitter and receiver,
distances above the zero line indicating that the pressure was
higher at the receiving end so that the waves must travel
"uphill." From these studies, our data shows that the highest
audibilities are obtained when a ridge of high pressure extends from
the sending station to the receiver. Good results may also be
expected when the waves travel at right angles to the isobars,
provided they do not need to pass over an intervening low and
up again. Poorest signals result from passing diagonally across
the isobars or through a storm area. While these general rules
apply to a majority of our records, it must be clearly understood
that they are not infallible, and other controlling forces doubtless
should be taken into account.
MEASUREMENTS OF STATIC
THE current in a lightning discharge is of the order of 5000
to 10,000 amperes, hence it is not surprising to find that
electric waves produced by these crashes may travel for hun-
dreds of miles. Measurements made in our laboratory show that
an antenna or other insulated conductor may become charged
to potentials of more than 5000 volts when a stormcloud is
overhead and our sensitive apparatus records the smaller charges
even before the thunderstorm itself is visible on the western
horizon. In the northern hemisphere, thunderstorms are most
common in the southeast part of a low area. These conditions
prevailed in eastern Nebraska in the map of Fig. 4, and atten-
tion has already been called to the very high static audibility
for that day. In high winds, and especially with drifting snow,
the air often becomes electrified by wind friction, causing an
antenna wire to take on a charge sufficient to cause sparks to
jump across a lightning arrester to ground. Under such condi-
tions the writer has known charges to accumulate of sufficient
magnitude to be heard all over a large room as they jumped
across an antenna condenser. The worst thing about these and
other forms of static discharges is that the waves produced by
them are scattered over a large number of wavelengths so that
they are not easily tuned-out.
WHEN SIGNALS FADE
XA/HILE almost everyone who has used a radio receiver to
" * any extent has noted the gradual variations in the loud-
ness of program, special apparatus is required to measure
12:33
TIME SCALE WDAF AUG. 8. 1925
12:38
12:43
561
12:48
11:54
TIME SCALE WDAT AUG. 7, 1925
11:64
10:08 P.M.
10:13
10:18
TIME SCALE WHT AUG.?. 1925
10:23
1028
• • 29.8'
•;:•.-.••'•. ...WEATHER MAP .'•;.•:
'':•• '-'.•'.•.••.: ':':.'•'• ••'.'• .'•.';'.'. -;.'.;: Aug. 7, 19257P.M. ':'•••'•
FIG. 8
FIG. 7
Time scale plotted against audibility on several stations on the night of
August 7, 1925. The Weather Map below, (Fig. 8 ), shows the general
conditions prevailing at 7 p. M. the same day
the actual changes in signal strength.
The ear is not a reliable measuring in-
strument and tone impressions cannot
readily be kept in mind for several min-
utes for comparison. Another difficulty
lies in the fact that different parts of a
musical program may vary considerably
in loudness because of the character of
the selections themselves, a change which
has no relation whatever to true fading.
The apparatus in use for making signal
fading records in the radio laboratory of
Nebraska Wesleyan University consists
of a six-tube super-heterodyne receiver
with vernier dials for tuning, and ammeters
in the filament circuits. In the plate-
circuit of the second detector is placed a
fifth intermediate frequency transformer.
A telephone head-set is shunted across a
.oo2-mfd. condenser in series with the
primary of this transformer, for use as a
pilot in tuning and in following programs
which are being recorded. In series with
the secondary are a crystal detector and an-
other .oo2-mfd. condenser. Shunted around
this condenser is a sensitive wall galvano-
562
RADIO BROADCAST
MARCH, 1926
meter as shown in Fig. 5. More recently
we have replaced the crystal detector
with a uv-i99 tube and have also built
up an automatic recording device some-
what similar to the Shaw Recorder used
in Doctor Pickard's experiments. With
this equipment, galvanometer deflections
are proportional to the strength of the
carrier wave and are not at all affected
by the music or voice modulations heard
by the radio listener.
In Figs. 6, 7, and 8, are shown a few
typical records, chosen from the large
number now on file. Three of the four
curves in Fig. 6 are daylight graphs and
give conclusive evidence that transmission
is much more steady in the daytime than
at night. The weather map for May 16
shows a marked storm area in the region
of Lake Erie, with clear and settled weather
over the great central plains. This ac-
counts for the remarkably regular curve
from WDAF at Kansas City. From wcco
at Minneapolis, on the other hand, some
effects of the storm to the east are notice-
able. The night record for wcx at Detroit
is unusually regular, being obtained with a
"high" in northern Minnesota, a "low"
in Tennessee, and the intervening isobars
running almost exactly parallel between
University Place and Detroit.
Reference to the time scales on Figs. 7
and 8 will show that these records were all
made on the evening of August 7, with the
exception of that for WHT on July 3Oth.
The midnight curve for WDAF contains the
most rapid and violent changes of our en-
tire series to date. While the period be-
tween peaks is commonly from four to six
minutes, these are only ninety seconds
apart, and continue the cadence with great
regularity. This becomes all the more
noticeable when contrasted with the records
of WDAT at Chicago and WHO at Des Moines
taken just a few minutes before. The
graphs for WHT at Chicago and
KOA at Denver, taken earlier in
the evening, are typical mid-
summer curves. The meteoro-
logical map for the evening of
August 7th is reproduced in Fig.
9. The weather was hot and
sultry, with no well-defined
storm area in the plains region, a
condition classed as "unsettled"
by the meteorologist.
CONCLUSIONS
A DISCUSSION of the appli-
cation of the data presented
above to the Heaviside theory
of radio transmission would be
beyond the scope of this ar-
ticle. So far as it is possible
to formulate an opinion based
on actual observations, the
Eccles-Larmor theory which requires a
refracting upper layer rather than an
ionized, reflecting surface, agrees more
nearly with the facts. There is strong
evidence for definite relationships .between
weather conditions and radio reception
although other factors, such as the earth's
magnetic field, probably also play a part.
The general conclusions supported by the
data presented may be summarized as
follows:
1. Signal strength will be greatest with set-
tled weather conditions and transmission
parallel with the isobars. (Fig. 3).
2. Good reception may also occur at right
angles to the isobars unless a storm center
intervenes between sending and receiving
stations.
3. Static is most noticeable as a storm area
approaches, the crashing noises being
audible for several hundred miles; and the
hissing noises prevailing only in the im-
mediate vicinity of a "low."
4. Fading is much less troublesome in day-
light than at night.
5. Fading is much more noticeable in un-
settled weather than when transmission is
parallel with the isobars along the ridge of
a "high."
With these rules as a general guide, a
radio forecast has been sent out daily at
4:30 p. M. from station WCAJ, since October
ist, 1925, While encouraging reports have
been received, the project is yet in the ex-
perimental stage.
EDITOR'S NOTE
HpHE conclusions reached by Mr. Van
* Cleef, in his article, " Do Weather Con-
ditions Influence Radio?" in the May,
1925, RADIO BROADCAST are reprinted
below, so that experimenters can compare
the findings of the two investigators.
Mr. Van Cleef reached his conclusions
from his observations without a great deal
TIME SCALEWDAF MAY16.1925
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of study of the radio theories advanced
for variation in radio receiving conditions.
Mr. Jensen has proceeded from the point
of view of the radio investigator. Mr.
Van Cleef's first point is in direct opposition
to that of Mr. Jensen as he claims strongest
transmission at right angles to the isobars.
Mr. Jensen has found that loudest signals
are to be heard in territories parallel with
the isobars, along the ridge of a "high",
with no difference in pressure between
transmitting and receiving stations. This
conclusion is also opposed to Mr. Van
Cleef's second rule. With respect to fading,
Mr. Jensen thinks that the worst fading is
found with a "flat" barometer or large "low"
area, while the third rule of Mr. Van Cleef
assumes most fading on a ridge or parallel
with the isobars.
1. If a line connecting the receiving station
with the broadcasting station crosses the
intervening isobars at right angles, re-
ception is at its best.
2. The steeper the isobaric gradient (that is,
the closer the isobars to each other) the
stronger the reception.
3. The more nearly the transmitted waves ap-
proach parallelism with the isobars, the
weaker the reception. Under these con-
ditions, fading occurs.
4. Reception in a Low pressure area tends to
be somewhat weaker than in a High of cor-
responding intensity.
5. Reception is weaker when the transmitted
waves cross from one pressure area into
another than when they travel only within
one area.
6. The strength of reception for any station is
a factor of both its location within a pres-
sure area and its position with respect to
the broadcasting station.
7. "Bad weather" does not affect reception.
excepting as it may be the index of an un-
favorable pressure distribution.
8. Reception can be as good in "bad weather"
as in good weather if the pressure distri-
bution is right.
9. Temperature does not influence
reception, excepting as it may be
the index of pressure distribution
as follows:
(a) Reception is better in winter
than in summer because the
cyclones and anticycylones
are more intense in the win-
ter period.
(b) Reception is better when tem-
peratures are low than when
high, because low tempera-
tures usually indicate inten-
sive High pressure areas, that
is, areas with steep isobaric
gradients.
(c) rLow temperatures accom-
panying poorly defined High
pressure areas make recep-
tion poor.
10. Shallow or flat pressure areas
result in much static-noise in the
receiver.
TIME SCALE WCCO MAY 16,1925
FIG. 9
Some remarkable records of daylight re-
ception during the spring of last year
R Amplifier
Suggestions for Experimenting with and Applying Multiple Regener-
ation to a Qreat Variety of Circuits with a Consequent Large Qain
in Sensitivity — Details of the Circuit and Operating Suggestions
By V, D. LANDON
Radio Engineering Department, Westinghouse Electric and Manufacturing Company
A
GREAT deal of ex-
periment has been
•tsv
adjustment of the tickler or the
balancing condenser or of either
EXPERIMENTERS in radio' have tried for a long time to secure the un- Dalani
spent in an effort to O doubted advantages in sensitivity that multiple regeneration would give, tuning condenser, upsets the
but always there have been very serious practical obstacles in the way. This
article, by Mr. Landon, who is an experimental engineer with the Westingrjou.se
Electric &* Manufacturing Company, at present attached to their offices in
Springfield, Massachusetts, is in no sense a construction article. The basic
principles of the system are o utlined by the author, and they can be applied by
the constructor to the particular receiver which he may have. The number of
receivers employing tuned radio frequency a plifiers now in use in this country
must he much more than five hundred thousand and the Landon method is
applicable to all of them — it will add considerably to their sensitivity. The
importance of the experimental field opened up by this article can scarcely be
overestimated. — THE EDITOR.
obtain the full am-
plification of regeneration
twice or more times in the same
amplifier. The average ex-
perimenter does not obtain the
desired result, though the rea-
son for failure is somewhat
puzzling unless considerable
study is made of the subject.
Take for example the well
known Roberts Knockout Re-
ceiver. This circuit (with one
stage of audio added) is shown
in Fig. 5. If a station fifty to one hundred
miles distant is tuned-in with this receiver,
using zero tickler adjustment, a compara-
tively weak signal results while a 500- to
looo-mile station is usually inaudibly weak.
Nevertheless when the tickler is advanced
to the critical point, the gain in signal is
sufficient to bring in stations well over one
thousand miles dis-
tant and with full
loud speaker vol-
ume. Only on poor
nights or on very
weak stations is
difficulty found in
obtaining sufficient
volume for satis-
factory reception.
On such occasions,
however, im a g i n e
the thrill of having
another tickler con-
trol capable of
boosting the signal
again by the same
ratio! It was with
this in mind that a
great many experi-
menters tried the
effect of unbalanc-
ing the neutralizing
condenser in an
effort to regenerate
the antenna as well
as the detector cir-
cuit. Also many
have tried various
schemes of feeding
energy from the de-
tector back into the antenna circuit by in-
ductive coupling. One such scheme was
suggested by the technical staff in the
April, 1925, RADIO BROADCAST.
Many of those who experimented along
these lines thought they had achieved the
desired result when they tried the set
because it becomes very critical. An
FIG. I
By employing the Bremer-Tully three-coil unit, all
the windings for the dual regenerator system are very
simply provided. The rotor coil, pointed out in this
illustration, is used as the radio frequency tickler
coil while the adjustable coil and fixed coil are used
as antenna and secondary windings respectively.
The receiver pictured here was hastily assembled to
conform with the principles of construction laid down
by Mr. Landon in his article. It consisted of three
tubes, namely, regenerator, radio-frequency amplifier,
and detector. The coil unit shown at the left consti-
tutes the detector secondary, tickler and r.f. plate
circuit coil. The former and latter are both wound on
the vertical coil form while the tickler is variable and
is shown in a diagonal position
adjustment of one or more of
the other three controls. How-
ever, a more critical receiver
does not mean a more sensi-
tive one. If a comparison is
made between two sets using
the circuit of Fig. 5, one of
which is well balanced while
the other has a variable neu-
tralizing condenser, it will be
found that there is very little
difference in the sensitivity of
the two sets. This is found to
be the case in any circuit in which an
attempt is made to regenerate the antenna
circuit by means of some form of coupling
to a regenerated detector. Briefly the
reason is this:
When energy is fed back through the
tube capacity so as partly to regenerate
the antenna, the tickler setting for critical
regeneration is re-
duced, offsetting the
gain in the antenna.
In other words, if
the two circuits are
somewhat coupled,
both may be partly
regenerated, but
both may not be
completely regener-
ated, since the
system as a whole
starts oscillating be-
fore this point is
reached.
Before attempting
the true solution of
the problem, let us
reduce the Roberts
circuit of Fig. 5 to
the equivalent four-
tube circuit. This
is shown in Fig. 2,
Theoretically, the
only difference be-
tween Fig. 5 and
Fig 2 is that in Fig. 5
the first tube does
the work of the first
and third tubes of
Fig. 2. In practice,
BROADCAST Photograph
564
RADIO BROADCAST
MARCH, 1926
the circuit of Fig. 5
can be made equal
to that of Fig. 2 only
after considerable
experiment. In pre-
senting the multiple
regeneration cir-
cuits, the circuit of
Fig. 2 is used as a
starting point be-
cause it is not sub-
ject to certain
troubles which a re-
flex set may develop.
THE BEST WAY TO
ATTAIN INCREASED
SENSITIVITY
0-A-B*C
0.90
1 mfd.
FIG. 3
The Browning- Drake with regeneration added to the radio-frequency amplifier circuit
THE solution of the problem is in
regenerating each tuned circuit, all
the while keeping the coupling between
them to zero. Such a circuit is shown in
Fig. 3. It will be found with this receiver
that the advantage gained by using two
ticklers instead of one depends a great deal
on the completeness of neutralization.
The more exact the neutralization the
greater ;he gain in signal.
REGENERATOR
TUBE
Notice that the change from the circuit
of Fig. 2 is very slight. Another tube,
and a small coil were added. A means of
varying the coupling of the coil to the an-
tenna circuit must be provided. The grid
circuit of the new tube is the same as that
of the first tube, that is, the two grids are
tied together. However the plate circuit
of the new tube is separate. It consists
of the new coil which is used as a tickler.
Another method of control-
ling antenna regeneration is to
use a fixed tickler with a vari-
able resistor in series. A
bypass condenser must be pro-
vided to bypass r.f. currents
around the resistor. When the
resistance is all "in", the volt-
age applied to the plate of the
tube is insufficient for oscilla-
tion to occur. When the re-
sistance is gradually
cut out, the point of
critical regeneration
is approached until
finally oscillation
occurs. When the
set is properly con-
structed it should
be possible to start
or stop oscillation
at any wavelength
with this resistor.
There are several
good resistors for
this purpose on the
market, which have
a range of 10,000 to
100,000 ohms such
as the Royalty, Bradley, Centralab, and
Clarostat.
It is also possible to control the antenna
tickler by any of the commonly used
methods. A coil having the same value as
the secondary coil may be substituted for
the variable resistor and a variable con-
denser shunted around this coil for tickler
control. Or the tickler lead may go
directly to the B battery terminal with
a separate (vernier) rheostat on the first
tube for regeneration control. In this
latter case the tube filament brilliancy is
turned down to the point just below the
point of oscillation. This is a very simple
and effective system.
For ordinary reception, the first tube
may be left out of the socket, the set being
used like the standard Roberts Circuit.
However, when a signal is found which
cannot be brought up to the desired volume,
FIG. 4
Here are shown the important parts of the usual radio fre-
quency circuit to which has been added the extra tube whose
grid is paralleled with that of thefirst tube and whose plate return
is made through a coil coupled inductively to the first secon-
dary and thence back to the B battery. Notice that in all
the circuit diagrams accompanying this article a i-mfd.
condenser connects from the plus B to the minus A lines
FIG. 2
This is the Browning-Drake circuit, familiar to readers of
RADIO BROADCAST as one having excellent tuning qualities
-*-»•«
FIG. 5
The regular three-tube Roberts receiver consisting of one stage of tuned,
neutralized, radio frequency amplification, a regenerative detector whose
output is reflexed back to the first tube and thence followed by a straight
audio stage
FIG. 6
The Landon system of r.f. regeneration added to the reflexed Roberts
circuit. In the article, this is used as a basis for a discussion of the
merits of dual regeneration
MARCH, 1926 MULTIPLE REGENERATION IN TUNED R. F. AMPLIFIERS
a great gain in sig-
nal is to be had by
inserting the tube
and adjusting the
antenna tickler to
the critical point
which is just be-
low the oscillating
point.
It is also very
easy to provide a
filament switch to
cut in the tube
when it is needed,
but for those who
are not so particu-
lar about the fila-
ment current used, it is perfectly prac-
tical to leave all five tubes lighted
whenever the set is in operation. The
extra tube will have no effect on the cir-
cuit as long as the antenna tickler is set at
lero, and of course, this control should not
be used until necessary, since the receiver
•will radiate when the antenna circuit is
caused to oscillate. There is no point in
Facts About the Circuit System
Material required for regenerator Stage:
One socket, one tube, one tickler coil, a rheostat and filament switch.
Values of parts employed in tine Circuit:
No definite values are stipulated as it is desirable for the builder to select for himself the size of tuning coil and condenser he
wishes to cover the frequency range in which he is interested. The bypass condenser across the primary of the first audio
stage should be .001 mfd. For the tuning coils, the ratio of primary to secondary should be 1 to 4 for the antenna circuit
and 1 to 3 for the detector. The tickler coil should have j the number of turns of the secondary coil to which it is coupled.
Operation:
When first tuning for a station, keep the regenerator tube unlighted. When the distant station is tuned-in and it is desired
to increase sensitivity, turn on the filament switch of the regenerator tube and slowly advance the coupling between the
regenerator tickler and the antenna secondary coil. Do not attempt to regenerate up to or beyond the oscillation point
which manifests itself by a raucous squeal. Always employ the regenerator as a reserve of sensitivity and power.
Important points to remember:
A large bypass condenser, such as a 1-mfd. should connect from the B battery terminal of the new tickler coil direct to the
minus A; the secondary coils for r. f. stage and detector should be placed at exact right angles to each other.
advancing the antenna tickler to the oscilla-
ting point since it makes the receiver inopera-
tive as far as the reception of ungarbled, un-
distorted reception is concerned and, further-
more, interference is caused with neighboring
receivers which should be avoided at all costs.
The extra control simply provides the
operator with a reserve of power in case of
need. With this type of set it is possible to
565
get down to the
much discussed
static level except
on unusually quiet
nights. In other
words, those
broadcasting sta-
tions whose signal
intensity is higher,
or stronger than
the static inten-
sity— otherwise
termed static level,
have a very fair
chance of being
tuned-in with the
aid of the extra
control. Those below the static level have
not this possibility. Briefly, a receiver em-
ploying this regeneration system has all
the sensitivity for which there is any use.
0F,
THIS SYSTEM HAS WIDE APPLICATION
COURSE the main idea of Fig.
3
can be applied to practically all
circuits employing tuned radio frequency
N p
NP
P Placementof coils when aligning
rotor shafts parallel with top
and bottom of panel
B
•c-
FIG. 7
To obtain satisfactory neutralization of the radio frequency amplifier, it is first necessary to de-couple the tuning coil units to prevent any
undesirable feedback or inter-coupling effects which are not helpful. Here are shown several ways of placing the coils to obtain the desired effect.
In A, the secondary coil axes are at right angles to each other; in B the condition prevails excepting that the two coil units have been shifted so
that the rotor coil mounting holes in the panel are on a straight line parallel with the top and bottom edge of the panel. This is only where uniformity
and symmetry of panel layout is desired. In C the angle of coil placement, 54° — 57' made prominent by incorporation in most neutrodynes is shown.
Here it is desirable to have the coil centers; placed not less than 6 inches apart
RADIO BROADCAST Photograph,
FIG. 8
The rear view of a receiver employing dual regeneration constructed solely for experimenting. Note that the secondary coils of each tuning unit
have their axes at right angles to each other. This is an absolute necessity where a positive neutralization of the radio-frequency amplifier is to be
obtained
566
RADIO BROADCAST
MARCH, 1926
amplification. For the lovers of reflex,
Fig. 6 is given. Notice that the first two
tubes act in parallel at both radio and audio
frequency. This circuit could easily be
made from the Roberts Circuit as the only
changes necessary are the addition of a
tube and the tickler coil. Then there are
the thousands of neutrodyne receivers to
which this system is admirably adapted.
Fig. 9 shows a two-stage tuned r.f.
amplifier in which regeneration can be
obtained in two places. The neutraliza-
tion of the first stage is variable so that the
antenna can be regenerated by capacity
feedback. The detector circuit is regen-
erated by means of a tickler as usual.
There is coupling between the first two
circuits, but the coupling between the
detector and the other two circuits must
be kept as near zero as possible.
Fig. 1 1 shows a two-stage amplifier in
which regeneration occurs in three places.
In view of the foregoing, the diagram is self
explanatory.
In practice, the circuit of Fig. 1 1 would be
extremely hard to balance accurately
enough to operate satisfactorily. By using
separate batteries on each stage and by
separating them by several feet, it could
probably be done, though the sensitivity
would be greater than is ever necessary,
except perhaps for long distance daylight
reception. Probably, the most practical
circuit employing multiple regeneration
is that of Fig. 3.
It is not the purpose of this article to
give exact constructional details for this
set. Individual constructors will have
their own ideas as to what the panel layout
should be, since each will incorporate
different varieties of apparatus. However,
it will be necessary to keep in mind certain
points, if the set is to work properly.
The coils must be low loss for good re-
sults. The lower the resistance the greater
FIG. 9
The standard neutrodyne circuit employini
may be added the radio-frequency amplil
the sensitivity, even when full regeneration
is employed. The effect of resistance in
the grid circuit of a regenerated system is
thoroughly discussed in December, 1925,
Proceedings of the I. R. E. "An Analysis
of Regenerative Amplification" by the
writer and K. W. Jarvis.
The two grid coils may be any of the
well known low loss designs, so long as the
broadcast range can be covered with the
variable condensers used. The following
may help in choosing the type of wind-
ing.
CHARACTERISTICS OF THE BEST COILS
THE Lorenz or basket weave coil has
fallen into disrepute among the ex-
ponents of low loss lately. Nevertheless
it is about as good a coil as can be made in
a given small volume. In general, however,
coils wound on tubing are better because
they are larger. The chief losses in the
Lorenz type of winding are due to eddy
currents in the wire itself caused by the
magnetic flux from adjacent turns. This
loss is reduced to a minimum by using
large diameter coils and a spaced winding.
The larger the volume which is to be oc-
RADIO BROADCAST Photograph
FIG. IO
The pencil points to an adjustable antenna coil which aids greatly in obtaining the correct coupling
between antenna primary and secondary circuit of the radio-frequency amplifier. The additional
tube, which functions in the dual regenerator part of the circuit, is located directly ^behind the Bremer-
Tully coil unit
a regenerative detector. To this circuit
ler regeneration system shown in Fig. 4
cupied by a coil the larger the wire that
may be used with advantage. Number 24
wire (B & S Gauge) is about right for a coil
three inches in diameter. No. 16 wire is
better if the coil diameter is in the neighbor-
hood of six inches.
The effect of the average type of tubing
in the field of the coil is negligible in dry
weather or immediately after a coil is
thoroughly baked. However, the resistance
of a coil may be multiplied by three or four
in wet weather if proper precautions are
not taken to keep the moisture out. The
coil may be made moisture proof by treat-
ing it with a good coil varnish such as
Sterling Copal varnish. The coil should
be baked dry, then dipped in the varnish
and baked again. Painting the outside of
the coil with varnish is not sufficient, since
moisture will be absorbed by the inner
surface of the tubing. Of course collodion
will do the trick but it is rather expensive.
Celluloid sheets dissolved in acetone to a
consistency of shellac or varnish also is
effective as a coil binder.
All coils, such as primary windings and
ticklers, which are not a part of the tuned
circuit, should be wound with very fine
wire such as No. 35 d.c.c. The resistance
of these coils in themselves is not important,
but if large wire is used in them the resist-
ance of the tuned circuit to which they are
coupled is increased, and this causes a
reduction in efficiency.
It is well to remember that this article
does not deal specifically with the construc-
tion of a receiver but rather explains the
application of a regeneration control system
to existing receivers.
The ratio of primary to secondary wind-
ing should be about i to 4 in the antenna
circuit and about i to 3 in the detector
circuit. Each tickler coil should have
about | the number of turns of the grid
coils. Remember that it is necessary to
neutralize the coupling between the tuned
circuits almost perfectly if any gain is to be
noticed from multiple regeneration. This
means extreme care to place the coils at
right angles or as shown in Fig. 7 in
order to prevent inductive coupling. It
will be noticed also that any metal in
the field of either coil may distort the
field so as to cause coupling even when
the coils are at right angles. Adjustment
of the capacity balance (neutralization^
MARCH, 1926 MULTIPLE REGENERATION IN TUNED R. F. AMPLIFIERS
567
FIG. I I
Three ticklers for two r. f. stages and the detector. An hypothetical case of applying the Landon regeneration system to the neutrodyne receiver.
It is unlikely that in this instance much will be gained by its use because of the extremely critical tuning which will result. Two ticklers, one for the
second r. f. stage, and one for the detector, would be the more practial application of the Landon regeneration system.
should need no explanation. Let it suffice
to say that the adjustment should be made
as accurately as possible.
But for those who are incorporating
this system in a new construction, it is as-
sumed that neutralization has not been
obtained, therefore the following memo-
randum on neutralization will be helpful.
Maintaining zero coupling between the
first secondary and the radio frequency
tickler coil, the detector tickler is ad-
vanced to cause regeneration in that cir-
cuit. Previous to this, the receiver should
be tuned to some station which responds
at the half-way point on the tuning dials.
The squeal produced should not be made
too loud. Rotate the antenna-secondary
tuning condenser over a small arc. If the
pitch of the squeal varies, then the set is
not properly neutralized. The capacity
of the neutralizing condenser employed in
the circuit should be varied a little at a
time until the pitch of the squeal does not
vary. Then the receiver may be consid-
ered neutralized. The constructor should
not confuse squeal intensity with squeal
pitch.
BEST APPLICATION OF THESE EXPERIMENTAL
SUGGESTIONS
A NOTICEABLE gain in selectivity
will be obtained if no part of the set
is grounded except one end of the antenna
coil as shown in all the circuits printed with
this article. This is especially effective
if all battery leads are kept short.
Of course all the usual precautions
should be taken. To avoid apparatus of
poor design, buy only well known makes
of apparatus when purchasing such items
as sockets, rheostats, grid leak, variable
condensers, transformers, tubes, etc.
To aid in neutralization, keep all grid
and plate connectors as short as possible.
Run the leads to the neutralizing condenser
in as short a line as possible. Do not
omit any of the bypass condensers shown.
Those shunted across the primary of an
audio transformer should have a capacity
of about .001 mfds. The condenser across
the B battery should be about i mfd.
To avoid bad joints and leakage losses,
use rosin core or soft wire solder in wiring
the set. All battery leads should be cabled
if they are close together for a considerable
distance in a set. This will avoid closed
loops.
It should be kept in mind that all the
multiple regeneration circuits shown in this
article are capable of oscillating into the
antenna. This is true of any r.f. circuit
employing a means for neutralization and
where the neutralization is not perfect.
Care should be taken not to cause such
oscillation at any time, since interference
to neighboring receivers is the inevitable
result. This is readily accomplished if
the receiver is tuned as follows, which is
the easiest and most natural method.
Leave the antenna tickler at zero or
nearly so, and operate the set in exactly
the same way that a Roberts Knockout
Receiver is operated. Occasionally a sig-
nal will be found which is too weak to be
brought to the required volume by this
method. The antenna tickler should then
be brought up to the critical point, after
the other controls are properly adjusted.
If oscillation should occur, it will be
immediately apparent to the operator who
should back off the control at once.
The circuit of Fig. 3 is especially recom-
mended to home builders as it is the sim-
plest and most practical of the circuits
shown. It is believed that any one who
completes it will be well pleased as it is a
wonderful performer.
RADIO BROADCAST Photograph
FIG. 12
Adjustment of the neutralizing condenser is an important procedure in the correct operation of
this receiver. John B. Brennan, Technical Editor of RADIO BROADCAST, is shown here making this
adjustment in RADIO BROADCAST Laboratory
Drawings by Fran/^fyn F. Stratford
Putting the Listener Under the Microscope
JOME years ago, in a moment of despair,
I proposed the establishment of a broad-
casting station to be operated for the plea-
sure of the engineers alone, in vacuum, so
to speak. In this way the cares of the program
directors, engineers, announcers, artists and other
functionaries would be marvellously reduced.
They would be kinder to their wives and chil-
dren, and suicides and murders would be less a-
mong them. The ceaseless tension of the broad-
casting business would be relieved, and profes-
sional broadcasters would become as carefree as
shepherds on pleasant summer afternoons. I
can see them going around playing joyfully on
little pipes, the operators fraternizing with the
announcers, all hands looking ten years younger,
gaining weight, and enjoying life. And all
through the elimination of the listeners. The
method 1 suggested was to run the station with-
out an antenna. Thus no one would have to
worry about what went out, nor how it sounded,
because no one would listen to it but the station
staff, and they wouldn't give a continental.
This is a dream with which I please myself
once in a while. For, in the hard world of real-
ity, the listeners crack the whip over me and
all my colleagues in the various divisions of the
broadcasting business. They make and break
us. Please them we must, or we don't eat — -
unless we give it up altogether and become
garbage collectors and hosiery salesmen once
more. One should give prolonged consideration
to fauna of such importance to one's welfare.
Therefore we shall devote a portion of this de-
partment, without further delay, to a discussion
of the listener, testing his reactions to various
acids and alkalies, purifying and educating him,
and giving him praise where due, but nowhere else.
In the course of business I recently had occa-
sion to make a journey with a United States
Supervisor of Radio, a gentleman who is a
philosopher as well as an administrator. During
our talk he commented on the remarkable
contrast between the perfectly supine reaction
of many citizens to the avoidable evils of exis-
tence, and the fearful how-dy-do immediately
raised when something goes wrong on the radio.
An automobilist will sit almost motionless at the
ferry landing for four hours, on Labor Day or
some other holiday, waiting his turn to get
on the boat, with scarcely a murmur. If he
lives in a big city, he will submit himself and his
womenfolk to the most inordinate crowding in
their daily journeys about the town, without
batting an eyelash. He allows himself to be
robbed by hatcheck boys, abused by the traffic
cop when his car slides two inches over the line,
and to be told by conventional imbeciles that
he must not wear his straw hat after September
1 5th. None of these injuries is inevitable.
Wharves, bridges, and subways may be built to
accommodate peak loads, a posse of public-
spirited citizens could lynch a hatcheck boy and
duck one of the over-eloquent traffic directors,
and the bitter-enders among the straw hat
wearers could free themselves by marching to
the Polo Grounds in a body on September 25th
and shooting down the first hoodlum who threw
a pop bottle at them. My remedies are a
trifle radical, and all the readers of this law-
abiding periodical will not agree with them, but
there can be no debate about the underlying
thesis. In all these situations, and a multitude
more, the people stand for anything. But not
in radio! Just let some foreign freighter open
up on 450 meters during a concert, and twenty
irate listeners sit down and write a letter to
Secretary Hoover. The more moderate ones
get after the Supervisor, but there are always
some for whom nothing less than the Secretary
will do. The Secretary must suppress the
amateurs, brush the cobwebs off an ill-managed
station's carrier, stop XXX from air advertising,
and torpedo the Jugo-Slovakian merchant
marine. He must do these things right away,
or Richard Roe and John Doe will rise agin
the government.
Here is an actual instance. A large broad-
casting station was set up at a point 30 miles
from New York, the location having been deter-
mined by careful tests and calculations. New
York has a lot of suburbs, and inevitably some
of them were and are (for neither the towns nor
the station have been moved) much nearer the
transmitter than that. When the station
started testing, after only a day one gentleman,
a lawyer, sat down and wrote a long petition to
Secretary Hoover. He is quite a prominent
lawyer and writing 1200 words must have cost
him a neat sum in time and energy. It seems he
had an eleven-tube neutrodyne, which, as he
was a lawyer and had made it himself, was
absolutely perfect, and with the near-by station
going he could not hear one in Chicago which
he had to hear, or die, so there was nothing
left but to write the Secretary. As a matter of
fact, in about half the time he spent in dictating
that epistle he could have rigged up a wave trap
which would have solved his problem. The
company which put up the station knew that a
wave trap would take it out in all the near-by
towns when it wasn't wanted.
1 do not mean that all the listeners are chronic
kickers. Most of them are amiable and appreci-
ative souls, or else the martyrs at the broadcast-
ing end of the circuits would all have eaten rat
poison by this time. For instance, in the case
mentioned above, after a brief period of testing,
some 1500 letters were received, of which thirty-
eight were protests — some of them justified by
special circumstances — while the remainder
were favorable and most of them full of en-
thusiastic praise.
Listeners who desire to help the broadcasting
stations to which they write should keep in
mind the necessity for being definite in their
statements and, if the matter is a technical one,
critical in their observations. Some listeners
are too prone to imagine things. A while ago
one of the stations for whose operation I am
responsible technically developed hiccoughs a
few hours before an exceedingly important
program was scheduled to go on. The cause
was obscure, and, supported by the other heroes
on the technical staff, I started to wrestle with
the thingamajigs and doodaddles. With the
kind permission of the local Federal official, we
put the carrier on during a two-hour blank period
and let an orchestra rehearsal go out. Every-
thing— power, radiation, modulation — remained
as usual in the past year and a half, and the only
irregularity was an intermittent growl down in
the bass. While we were sweating and swearing
and tearing things apart, a listener called on the
telephone. " 1 wish to report on your test,"
he announced excitedly. I didn't want any
report, but as the most polite and speedy way of
getting rid of him I asked what he had found.
"Your station sounds just as usual," he declared
after some irrelevancies, "but the wave is
terribly broad!" Restraining an impulse to re-
ply, "So's your old man!" I thanked our
informant and got away, having lost several
minutes when I needed them as a squirrel needs
acorns during a severe February.
On the other hand, several of our listening
customers render us occasional valuable aid
with all the precision of observation and ex-
pression of trained engineers, although one of
them is a physician and others are in similarly
detached professions. Out of a spirit of pure
helpfulness, they write extensive reports full of
valuable technical data. The same thing is
true on the program end. Every program
manager has a circle of listening friends whose
judgment and criticism are important factors in
determining the nature of the material he uses.
"Applause mail" is necessarily one of the guide-
MARCH, 1926
WHERE JAZZ CAN BE FOUND, ON ORDER
569
posts in program work. Letters from people
who know definitely what they want and don't
want, and why, are always carefully read. It is
not always possible to answer them individually;
if the volume of mail is great, a system of form
answers is the only way to avoid running into
prohibitive expense, although even then some of
the letters must receive special attention.
The more pretentious the writer, the less the
value of his letter, as a general rule. Recently
I received a report on signal strength from one
well-wisher who printed "Radiotrician" under
his name. There was not the slightest sign of
an address on the letter, and all it told me was
that someone in the United States heard us
satisfactorily. And in the letter he asked for
an answer, and he is probably riled because he
failed to get one!
The listeners have their foibles, just as the
broadcasters have theirs. And it is hard to
please all the people all the time. In fact, as I
have had occasion to argue in this place before,
to attempt to do so leads directly to stultification.
And some members of the audience will always
prove unreasonable. All that is true, but in the
last analysis the progress of broadcasting is
accelerated by the pressure exerted by unsatis-
fied patrons. The power level is being raised
because people object to getting their music
mixed with the electrical racket of the vicinity.
The programs are improving because people
will no longer listen to feeble stuff, and because
they want entertainment as good as that of the
best theatres and concerts. Not everybody
can keep up with the procession. Well, if
some of the stations fall by the wayside, the
event is proof, in each case, that there is no
place for that station. So let the tomahawks
fly, and the devil take the hindmost; the time
may yet come when Mr. Hoover will be able to
separate stations by so many kilocycles that the
"dyne" squeals will be lost in the upper reaches
of audibility, and for that and other blessings
we shall have to thank, in part, the listener-
die-hards.
A Jazz Lover Lifts His Voice
C
SIR:
OMMUNICATION from a defender of
jazz harmony, Mr. Bernard Kelly of
Pueblo, Colorado:
You are about to solve a great problem for me.
I am one of "Those things" that like their jazz
straight, and in these times when radio broad-
casters are simply drenching the nation with the
polluted stuff, 1 can't seem to bag it. 1 thought
that I might be trying to operate my set without
aerial and ground, but this does not seem
reasonable, as 1 can get any number of salon
orchestras, coloratura sopranos, and players of
Bach and Wagner. Perhaps atmospheric con-
ditions here are so educated as to shut out the
barbaric jazz and give asylum to the classics
which nobody else can find. Need I add that
I was desolated until I read your December
ai tide.
Apropos of your statement: "If you want
Jazz issuing from your loud speaker, there are
certain wavelengths in every locality where you
can get it at any time." I am enclosing here-
with a little blank of my own arrangement,
together with a stamped, addressed envelope,
whereon you, being a good sport, will inscribe
these various stations. I use a Roberts Knock-
out set Let this guide you in your choice,
and remember, I'm very choosy about my jazz.
I would have been satisfied to get it on the head-
phones, but your added promise of loud speaker
volume greatly pleases me, and in return for this
favor, I'll give you a tip. KOA of Denver is one
of those stations where they specialize in uplift.
They have there some very palatable violinists
and pianists, together with an array of songsters
who have never heard of Irving Berlin. More-
over, they have just begun to give Spanish
lessons. Here indeed is a safe refuge from Jazz.
I await your reply most impatiently.
The blank to which Mr. Kelly refers is pre-
pared with, as can be seen, diabolical ingenuity
and thoroughness; its general lay-out will appear
from the sample which I am magnanimous enough
to print above:
I WHERE TO GET JAZZ WHEN YOU — ,
WANT IT
Compiled by Carl Dreber
HOURS
Mountain Time
Day 7 P.M. 8 P.M. 9 P.M. 10 P.M. 1 1 P.M. 12 P.M.
SUNDAY
MONDAY
If Mr. Kelly was "desolated" before the ap-
pearance of my article "In Defence of Broad-
casting" in the December number, by the
dearth of jazz on the Colorado steppes, he was in
no worse case than I am at this moment. I am
not merely desolated, but prostrated, and there
is nothing more terrible than to be desolated
and prostrated at the same time. In fact, the
coincidence of these two acute malaises is so rare
and dangerous that I may be able to make some
money by exhibiting myself before the annual
meeting of the American Medical Association (if
they have one), or by travelling with an old-
fashioned medicine show (if any still exist).
The last time I was so sad was twelve years ago,
when my first audion bulb gave up the ghost
after two hours of use, leaving me bankrupt and
heartbroken. My present grief flows from two
sources: first, from hearing Mr. Kelly cry "Jazz!
Jazz!" when there is no jazz, and secondly,
because I am unable to make good on the sen-
tence which Mr. Kelly has plucked out of my
article. It appears that there is a neighbor-
hood where jazz is not always on tap for those
who crave its charms. Well, that's certainly too
bad. Mr. Kelly might try some suasion on Mr.
Talbot, the program man at KOA. If all else
fails, he can move to New York, a town which
spouts hot jazz as Old Faithful spouts hot water.
Above 360 meters one gets it now and then;
below 360 meters jazz runs riot. Incidentally, in
common with the Hon. Gilbert Seldes, I have no
objection to the stuff in limited quantities and
THEN TWENTY IRATE LISTENERS WRITE A LETTER TO SECRETARY HOOVER."
570
RADIO BROADCAST
MARCH, 1926
when it is well done. I would rather listen to a
good jazz band than a rotten soloist; there are
even times when I'd rather listen to a good jazz
band in preference to a good soloist or classical
orchestra, depending on my mood. For ex-
ample, when I write out my income tax check,
once a year, I like to listen to jazz; it cheers me
up. The only reason I took Mr. Nathan up on
this question is that he seemed to think that
radio music is practically all jazz, a conclusion
with which my battered ears did not agree.
And now along comes Mr. Kelly, roasting me by
implication, because there isn't enough jazz! I
give it up!
Technical Routine in Broadcasting
Stations
3. Monitoring
THE word "monitor" is one of the con-
tributions of wire telephone practice to
broadcasting. Its technical meaning is to
listen to what is going over a circuit for the pur-
pose of making indicated adjustments. The
principal one of these adjustments, in broad-
casting, is the regulation of the^ amplification,
or "gain," as the telephone people call it.
Skillful broadcast monitoring is an art in itself.
The necessity for it arises through the fact that
radio transmitters cannot be built, at the present
stage, to accommodate the extreme ratios in
volume of many musical performances. The
energy emitted by a symphony orchestra, going
full blast, with the conductor sweating like a
stevedore and all hands sawing, thumping, and
blowing to the maximum capacity of their in-
struments, is in the ratio of about 100,000:1 to a
few of the pieces playing pianissimo. This does
HE CRIES "JAZZ, JAZZ," WHEN THERE IS NO JAZZ
not faze musicians a bit, but it gives an engineer
the willies. The power ratio of machines — the
ratio of the maximum power which the machine
can handle effectively, to the minimum, is as
a rule quite low, probably not more than 10.
One cannot build a machine which will have the
power of a locomotive, when that is required,
and which in the next second can be used to
crack nuts efficiently. If it is a good nut cracker,
it will not be an adequate locomotive, and if it
is a good locomotive it will be lamentably waste-
ful as a nut cracker. This is from the standpoint
of the engineer as a manipulator of energy — raw
horsepower. But a broadcast transmitter is not
a mere engine. It is a combination of musical
instrument and machine. So a compromise
becomes necessary. The energy ratio remains
large, say of the order 1,000:1, but even so it is
only one tenth of one per cent, of the original.
The reproduction is not perfectly natural, but
it sounds better than it would if the 1,000,000:1
ratio were the basis of operation. In that case
the low portions would drop below the noise
level, with the result that portions of the per-
formance would be lost altogether. By ironing
out the peaks and faint passages to this extent
the ultimate quality of reproduction is at its
best.
This 1000:1 reduction in ratio is accomplished
manually. Of course, in many types of music
the actual original ratio is much lower than a
million to one, and in that case the reduction
should be correspondingly modified, the object
of the competent control engineer always being
to leave the original alone just as far as the load
characteristics and noise level of the broadcast-
ing medium will permit. There are, in general,
two types of incompetent control operators.
The first is careless; he "lets it ride." Some-
• times he lets the level drop so
that no one on the outside hears
it, and at other times he allows
overloading and distortion to mar
the performance. The announce-
ments are too high or too low
with respect to the music. They
should be slightly above the aver-
age value of the music, say 60
per cent, amplitude. The second
type of undesirable control opera-
tion is the over-cautious method,
whereby the modulation is ironed
out to such a degree that most
of the contrast is lost. This fel-
low constantly pulls down the
gain when the music is loud, for
fear that it will overload, and
brings up the pianissimo passages
so that the listeners will be sure
to hear them. He can't do much
to a jazz band, but heaven help
the station which lets him loose
on a symphony orchestra. A
good gain regulator is like a good
fighter; he always has something
in reserve. He is unlike a fighter
in this: he seldom moves fast.
Jerky manipulation of the am-
plification handle is out of order.
The movement should be smooth;
the only abrupt changes in the
music should be those which the
composer wrote into it. Of
course the whole thing can be
gauged better by one who knows
the piece being played. He can
look ahead and give a more
finished performance than the
man who has no idea of what is
coming next. The gain control
should not be moved except when
C,
FIG. I
A "Gain" control in a field control set
necessary, and then its movement should never
be neglected; the competent control operator
knows which is when.
On field events, the control should be in the
hands of the field technician, he being on the
ground and in a better position to judge than
the man at the station end of the line. The
station engineer sets his gain control once and
for all, theoretically, moving it after that only
to correct errors on the part of the field man. On
studio events the job devolves on the station
control operator, necessarily. As a rule, less
monitoring is required in the studio, for very
large orchestras, organs, choruses, etc., are en-
countered more in the field.
The usual form of gain control is a potentio-
meter arrangement carrying only audio fre-
| — /wwww1-
Zero Gam
FIG. 2
quency and isolated by means of condensers
from any d.c. circuits whose variation would
give rise to noise. Fig. l shows such an arrange-
ment between stages of a resistance-coupled
amplifier. Rp is the resistance in the plate of
the first tube, C, a condenser of the order of 0.5
mfd. separating the gain control and following
tube from this plate circuit, G is the gain control,
which is so arranged that as one resistance Ri
is cut in, the other resistance, R2, is correspond-
ingly reduced, Q is the second isolating con-
denser, of the same magnitude as d, RL is the
grid leak of the following tube. Fig. 2 illus-
trates how, with the contact in one extreme
position, C2 has one side short-circuited to the
filament of the second tube, while the resistance
R: is in series between the tubes, practically
blocking the transfer of audio voltages. In
Fig. 3, the reverse condition obtains, R, being
all out, while the total drop of Rl is available
to pass on audio fluctuations to the second triode.
This gain control is noiseless, unless the sliding
contacts are so bad that they open momentarily,
Maximum Gain
FIG. 3
MARCH, 1926 "WIRELESS" TELEPHONY CREATED AN IMPRESSION IN 1912
571
breaking the connection between the tubes be-
tween which the gain control functions.
The crude gain control which is sometimes
seen in small stations — a means of cutting down
filament voltage on one of the audio amplifiers,
is bad because as the emission of the tube drops
the impedance rises, resulting in the loss of low
frequencies in most cases, as well as other ano-
malies.
Memoirs of a Radio Engineer
X
IN THE January issue it was related how the
Federal legislation of 1912 started to bring
order out of chaos in the radio world. The
job was not a small one, and now, thirteen years
later, it is not yet completed. For as fast as one
patch of chaos was ironed out in one place,
another, such as broadcasting, bobbed up some-
where else, to keep the authorities busy. That
the law was provided with teeth was demon-
strated very shortly. A young man who, after
the passage of the act providing for station and
operator's licenses, had continued to transmit
without either, on a wavelength that happened
to suit him, was haled to court and fined. This
was in 1913, and the incident received consider-
able publicity. The law had gone into effect
December 23, 1912, and by that date about
five hundred of the twelve hundred amateurs
in New York City had applied for their papers.
Those who continued to operate were warned by
W. D. Terrell, now Chief Supervisor of Radio,
with headquarters in Washington, but then in
charge of the New York district. "These ama-
teurs," said Mr. Terrell, "who make it a practice
to interfere with business communication, are
nearly all known to us. There may be a very
few whose whereabouts we have not yet found
out, but in a short time, thanks to the efforts of
commercial stations and of the vast majority
of amateurs, who realize that the delinquencies
of these few may call for laws still more strict.
we will run them all down." And indeed, after
a half year or so, the only unlicensed amateurs
left were little fellows with spark coils of limited
range; practically all the big fellows had sub-
mitted.
I had no transmitting station worth the name,
but by this time I was fairly adept at copying
and was filling my log book with such entries
as the following:
Sept. 10, 1912. 2.27?. Ward liner Havana,
WH, talking to NY. Distance, 251 miles.
Jan. ii, 1913. S.ooP. MAA, White Star
Carmania, working MSB.
Jan. 20, 1913. 2.23?. SS Moltke, DDM,
working MSB. Good sig.
Mar. i, 1913. 5-I5P- KKX, SS El Occidents,
calling MSE. Comes in well with low tone.
Wanted to know if MSE knew where SS
Comus was.
MSE was the Seagate land station, later WSE,
a famous transmitter in its day. It had a 3-kw
transmitter with rotary gap.
My log book also contains numerous messages
copied from ships and the few land stations
around town. Besides WSE, the principal
transmitters in the New York district at this
time were FNK, the Bush Terminal station of
the National Flectric Signalling Co., and TWT,
operated by the Atlantic Communication
Company at 1 1 1 Broadway. The latter two
had beautiful notes around 1000 cycles, which
they maintained with remarkable purity of tone
for weeks at a time. Their flute-like whistles
enraptured all the amateurs, half of whom
would cheerfully have killed a man for a 500-
cycle alternator and a quenched gap.
"Wireless telephony" was not unknown, but
it was as yet no more than a curiosity. The
principal hope of its proponents was that it
might supplant wireless telegraphy; its applica-
tion in broadcasting apparently occurred to no
one, as yet. The following report in the New
York Times shows how radio telephony was
regarded toward the end of 1912:
VOICES HEARD
BY WIRELESS
Marconi Operator Picks Up Conversa-
tion 150 Miles Away
SAN FRANCISCO, Dec. 18.— A demon-
stration that wireless methods may be
used for transmission of the human voice
was made on the recent trip of the Pacific
Mail liner Son Jose, which reached here
to-day from Panama. Last Monday,
while off the Lower California coast, C. H.
Kessler, the ship's Marconi operator,
distinctly heard conversation while he was
taking a wireless message. The conversa-
tion was a test of wireless telephones be-
tween Catalina Island and the mainland
of California, and was carried on 150 miles
from Kessler.
At noon, when R. H. Shimek relieved
Kessler, he also heard scraps of conversa-
tion, as well as music from a phonograph.
As several passengers were around the
wireless room he gave them individual
receivers, and they heard ragtime music
distinctly, and even danced around the
deck to the tunes. The Captain was
called in and heard the music.
This experience was said to be the first
of the kind ever recorded, and it suggests
that the wireless at sea may yet be handled
like the telephone, which would be a great
economy in time of transmission, especially
in the case of vessels in port.
Antique stuff! Even the words — "wireless,"
" ragtime," are out of date. And the speculation
in the last paragraph was on the wrong track.
By far the best way to communicate with vessels
in port is by the simple expedient of hauling a
telephone cable aboard and hooking up the
ship to the nearest exchange. The big ocean
liners all have telephone switchboards, and when
THE ENERGY EMITTED BY AN ORCHESTRA GOING FULL BLAST.
572
RADIO BROADCAST
MARCH, 1926
they are at their piers you call up the various
extensions just as you call up the local delicates-
sen dealer or the town dog-catcher. And when
they are at sea, the radio telegraph provides a
faster and more reliable service than telephony
can give. The code cuts through static and
interference where telephony would only yield
a jumble. Even now only a few ships carry
radio telephone transmitters, and they are
considered a luxury, although presumably the
time will come when the great liners will carry
extremely powerful radio telephone sets provid-
ing a ship-to-shore service linked up with the
land telephone. But the wireless phone did not
have to await this development before it could
come into its kingdom. Broadcasting supplied
that.
Broad Waves and Sharp
ONCE an error has taken firm root the
only thing to do is to wait a few centuries
until it is forgotten, for you will cer-
tainly not get rid of it in any quicker way.
Thus, probably a majority of the population
still believe that blondes are treacherous, that no
one with brown eyes can ever become a great
man, that touching a toad will cause warts,
and that Aaron Burr was a villain while Alex-
ander Hamilton was an angel. There is no
law against believing what one pleases, even
though it is wrong. This is likewise true of the
almost universal belief among radio listeners
and newspaper critics that in some mysterious
way the engineers of a broadcast station can
sharpen its wave, as if it were a pencil which can
be whittled down with a jack knife. Everybody
believes it, although it isn't so. It is true of a
spark station emitting a decadent wave train,
and that is no doubt the origin of this radio
superstition. But given a broadcasting station
of P meter-amperes modulating a continuous
wave of a certain radio frequency Y, modulated
at audio frequency X with per cent, modulation
Z, the only factors influencing the broadness of
tuning in reception are (i) The signal strength at
the point in question, and (2) The kilocycles
admittance of the receiving set at the said
frequency Y. In other words, when people
talk of a broadcasting station as having a
"broad" or "sharp" wave in the abstract
they are emitting nonsense. It be-
comes sense only when a particular
receiving location with known signal
strength from the station in question,
and the tuning characteristics of the
receiving set, are definitely specified.
When a listener declares that a certain
broadcasting station has a "broad"
wave, it usually means that he gets
a very strong signal from that sta-
tion, or that he has a badly designed
receiving set, or both. If he says that
the wave is "sharp" the conclusion is
that the signal is relatively weak, or
that the receiver tunes sharply, or
both. Assuming the power of the
station as fixed, it, has no control
over either condition.
The Lingo of Radio
Onomatopoeia
THIS disagreeable looking Greek
word is applied to those terms
which through their sound imi-
tate the thing described. There are
a few such words in radio, most of
them not of radio origin, however.
" Buzzer," for example, and " howl-
ing," "squealing," for uncontrolled
audio frequency oscillation, as of an amplifier.
The older telephone term for this phenomenon,
"singing," has not broken into radio to any
extent.
The only original radio names which exhibit
the tendency toward sound imitation in word
formation appear to be the words describing
certain kinds of strays: "Clicks," "crashes," and
"grinders." "Clicks" are the short sharp im-
pulses, "crashes" are somewhat longer and
more bothersome; "grinders" are still longer
and may consist of a succession of shorter
impulses.
Imported Words: Foreign Influences.
Except from the English, American radio is
indebted very little to foreign languages for its
radio terminology. The only instance I can
recall offhand of a word borrowed outright is the
German "litzendraht" for stranded high fre-
quency conductor, and this has been modified
into "litz."
It is interesting, however, to note how widely
British and American radio terminology differ.
The divergence, of course, is by no means con-
fined to radio. Again, a Britisher talks of "or-
dinary" and "preference" stock, where an
American says "common" and "preferred."
The following is a comparison of a few British
and American radio terms:
High frequency (h.f.)
Terminal
Telegraphist
Radio frequency (r.f.)
Binding post
Operator
BRITISH
Anode, plate
Ebonite
Gear
Components
Maker
Factor
Earth
Basket coils
Pile winding
Valve
Reaction
X's, atmospherics
Note magnifier
Accumulator
Frame aerial
Jigger
Anode (of a tube)
Low frequency (l.f.)
AMERICAN
Plate
Hard rubber
Apparatus
Parts
Manufacturer
Jobber
Ground
Spiderweb coils
Bank winding
Bulb, tube
Regeneration
Static
Audio amplifier
Storage battery
Loop
Oscillation
transformer spiral
helix
Plate
Audio frequency (a. f.)
"A YOUNG MAN WAS HALED TO COURT
The curious term "listen-in," incidentally,
appears to be of English origin. Why the "in"
was added is as much of a mystery as the appear-
ance of the same preposition in the British slang
phrase, " do him in " — " kill him." Whatever its
origin, it has led to some horrible compounds,
like "listeners-in," which is about as far as one
could go if one sat down to invent the most awk-
ward phrase possible.
Why do we speak of an air-core transformer?
The case is really one of the absence of a core,
and we might better call it a "coreless trans-
former" or an "air transformer." Of course air
is something — witness the trouble we take to
get it out of our electron tubes, but is it solid
enough for a core? However, we all talk of it
in that way.
Why "variometer" to denote a continuously
variable inductance? The instrument does not
measure anything, so the "meter" part of the
name is out of place, and the "vario" is too vague
to mean anything. In a less aggravated form,
"potentiometer" has the same or similar faults.
The only thing that can be said in favor of the
terms "A," "B," and "C," batteries, for plate
filament, and grid bias, respectively, is that they
are brief. Such arbitrary designations are
very puzzling to beginners. These terms, in-
cidentally, date back to the invention of the
three-electrode tube.
Of late years, some effort has been made to
achieve uniformity in the use of suffixes in
speaking of the common electrical properties.
On this basis it is not correct to speak of "resis-
ance" coupling in an amplifier; one should say
"resistive" coupling. An "inductor" is the
physical object or coil possessing the property
of "inductance"; its effect is "inductive."
Likewise "resistor," "resistance," and "resis-
tive"; "capacity," "capacitance," and "capaci-
tive." However, no one will be arrested for us-
ing the wrong suffix.
Proper Names
HpHE Alexanderson alternator, the Poulsen
1 arc, the Heaviside layer, are instances
where the name of a man of original ideas has
become attached to a machine or the-
ory. The common electrical units,
also commemorate the names of great
scientists, as the farad (M ichael
Faraday), the ampere (after Andre
Marie Ampere), the volt from (Count
Alessandro Volta), and the henry
(Joseph Henry — an American physi-
cist, incidentally). Then there is poor
Pierre Vernier, who died in 1637 after
inventing an attachment for indicat-
ing accurately parts of divisions in
linear measurements, and never con-
ceived of a radio set — and his name
is applied to the fine adjustment of
variable condensers three centuries
later!
Radio terms derived from the va-
rious older engineering arts are too
numerous to mention. Such words as
"decrement," "eddy currents,"
"secondary," "primary," etc., are of
old standing in electrical science.
The various prefixes which denote
magnitude, such as "meg" (one
million); "kilo" (one thousand);
"milli" (one-thousandth); "micro"
(one millionth); and their combina-
tions, are all in general scientific
use and not peculiar to radio.
Standards for the Home
How the Home Experimenter Can Build and Use the Necessary Standards
of Inductance, Capacity, and Resistance — Essential Tools for All Kinds of
Experiments — More Suggestion for the Ambitious Home Experimenter
By KEITH HENNEY
'Director, Radio "Broadcast Laboratory
THERE are two stages in the life of any
experimenter whether he be inclined
toward chemical, mechanical, or elec-
trical pursuits. The first stage may be
represented by the desire to do something of an
experimental nature, it matters little what, as
long as something happens. The second may
be marked by the experimenter's desire to know
what has happened, if anything, and how much
of it has happened. Any one can hook a con-
denser across the antenna and
ground of a receiver and note 6<a^—.,^—
what happens. Any one can at-
tach a coil across that condenser
and have a wave trap. But after
a few preliminary bouts with a
tricky device of this nature, the
experimenter will probably plot a
curve of the thing, showing what
happens to certain frequencies
when the condenser is varied.
This business of wanting to
know what happens, and how
much, when the condenser is
tuned, signalizes the entrance of
the radio experimenter into the
second stage of his career. Lord
Kelvin, one of the world's greatest
experimental and mathematical
scientists, is credited with saying j^
that any research enters upon a
scientific basis when actual figures
are put down on paper, when the experimenter
knows how much, and when, and begins to get
some idea of "why."
Just as building radio receiving sets palls on
most any one after the dozenth is completed, so
radio research, and the essential apparatus will
be described from time to time. The first article
of this series, in the September RADIO BROAD-
CAST, described a simple vacuum tube oscillator
for the home experimenter that in the Labora-
tory has proved to be of endless service. It con-
sists of a radio-frequency oscillator, a miniature
broadcast station in fact, which is modulated
with an audible tone. The uses of this oscillator
were described in the December magazine. The
C~F\/TORE than one satiated home constructor has written us that this series
" "* of articles hy Mr. Henney, the director of our Laboratory, has caused
them to renew their subscription to RADIO BROADCAST and to take a new interest
in the technical side of radio. Dust that has collected on soldering iron and
pliers is shaken off, and unused parts in the miscellaneous pile of odds and
ends owned hy every constructor worthy of the name are assuming a new value.
There are many among the amateur radio folk who have the feeling that if they
could just learn a bit more about what could be called the laboratory fundamentals
of radio, they would be able to make considerable progress in the art, and perhaps
even make a discovery of some importance. We believe that these articles, of
which this is the third, will be of great value to these inquisitive souls. Those
two valuable Government radio hooks, Bulletin No. 74 of the Bureau of Stand-
ards, and Principles Underlying Radio Communication, published by the
Army Signal Corps are used as bases in the present article. Every radio en-
thusiast who really wants to learn more about the art should own these volumes,
which can be had from the Government Printing Office. — THE EDITOR.
present article will deal more with the uses of this
device and mention a few lines of experiment
along which the home constructor should work.
WHAT ARE THE ELEMENTS OF RADIO?
will endless and aimless experimenting get to be HP HE apparatus used in radio consists largely
stale sport unless there is something to look ^ of two simole elements, inductance and ca-
forward to.
The staff of RADIO BROADCAST Laboratory
has prepared a number of experiments for those
who are interested in the more serious side of
of two simple elements, inductance and ca-
pacity, that is, coils and condensers. Each of
these components of oscillating circuits has re-
sistance, so the experimenter has to deal with
three important electrical quantities, inductance,
capacity, and resistance, and for practically all
of his work he uses these quantities in varying
proportions and in various relations to each
other. He winds a coil and finds that it will tune
to a certain frequency band with a .oooj-mfd.
condenser. He may feel that tuning is broad.
He knows then that there is resistance in the coil,
too much resistance perhaps. But he wants to
know how much, how to reduce it, and what is
the practical limit of reducing resistance.
In other words, he wants to
— ^^-jgvs know "how much?"
To do exact or even approxi-
mate work, the research engineer
and the home experimenter alike
must know to a certain degree of
precision the constants of the ap-
paratus with which he works. To
know that one's apparatus is cor-
rect to within a certain per cent,
is to know that one's results will
be valuable to that extent. Ac-
curately designed equipment, care-
fully calibrated, inspires a degree
of confidence in the worker that
will be one of his best assets.
In any well equipped Labora-
tory, the question "how much?"
is answered in one of several ways.
The simplest method and the
one most often employed is a
comparison of the apparatus under
test with some high grade standard. For in-
stancs, one builds a coil. He wishes to know its
inductance and perhaps its resistance. By a
complicated series of experiments he may arrive
at both of these values, but by a simple compari-
son with a coil already measured he may arrive
at the answer in a short time.
Among the first acquisitions to a home labor-
atory, then, are standards of inductance, capac-
ity, and resistance with which all unknown coils,
condensers, and resistances may be compared.
RADIO BROADCAST Photograph
FIG. I
Some of RADIO BROADCAST Laboratory's standard apparatus. Note the peculiar construction of the "inner works" of the resistance box. The
other apparatus is a standard variable condenser and a variometer which is used as a standard of inductance. An idea of the size of the equipment
may be judged from the ever-useful slide rule which is just 10 inches long
574
RADIO BROADCAST
MARCH, 1926
Power- (1)2 > R
FIG. 2
This represents a source of direct current energy
feeding a load which is in the box. If the
ammeter is not accurate, the amount of power
used cannot be correctly computed
These standards must be carefully made and
accurately measured. Fortunately, the con-
struction of a coil is sufficiently simple that any-
one can do it, and thanks to the work of the
Bureau of Standards physicists, the home worker
can calculate its inductance with sufficient accur-
acy for all ordinary work. Fortunately, too, he
may construct a standard of capacity, or at small
outlay he may purchase a variable condenser
equipped with a dial calibrated in micro-micro-
farads, such as the General Radio No. 247.
The importance of knowing the accuracy of
one's equipment may be illustrated by the follow-
ing experiment. Fig. 2 represents a source of
direct current feeding a certain "load" which is
in the box. We desire to know how much power
in watts it required. Knowing the resistance of
the box and having an ammeter in the circuit, it
is a simple matter to compute the power for
power = (current)2 X resistance
where power will be in watts provided the current
is in amperes and the resistance is in ohms. If
the resistance is one ohm and our ammeter says
that ten amperes are flowing, we get from our
formula (io)2 X i = 100 watts. Butifouram-
meter reads ten per cent, too low, in other words
it is only go per cent, correct, 1 1 amperes will
actually be flowing and the power will be 121
watts, an error of twenty one per cent.
Or suppose that we want to design an induc-
tance that will tune to 1000 kilocycles (300
meters) with a condenser of .0002 5 mfd. capacity.
At this frequency, the product of the capacity in
microfarads and the inductance in microhenries
is .025331, so that the inductance value must be
101.32 microhenries. If we design such a coil
and our measurements show that it has
this value when it is actually ten per
cent, greater, that is, 1 1 1 .45 microhenries,
the frequency will be about 950 kilocycles
(3 1 5 meters). These values come from the
relation between frequency, inductance,
and capactity.
F = rk,\/LC
Such errors are discouraging to any
worker, and to one who wishes to make
accurate experiments or apparatus, they
are hopeless.
Examples of some of RADIO BROAD-
CAST'S standards of inductance, capacity,
and resistance are shown in Fig. i . They
are made by the General Radio Com-
pany. Similar apparatus may be ob-
tained from Leeds and Northrup, the
Cambridge Instrument Company, and
others. The list numbers and prices for
the General Radio Equipment are given
below:
A standard fixed capacity is a good addition to
any laboratory and may be constructed of metal
plates with air dielectric. Neglecting minor
corrections, the capacity of such a condenser
may be calculated by the following formulae
Cmmf= .08858 Where S is the area of one plate in sq. cms.
— y~~ Where T is the distance apart of the plates
in cm.
Cmmf = .2258 Where S is as above in square-inches
~^f Where T is as above in inches
If some other insulator than air separates the
plates, such as mica, or glass, the formula will
not hold, and the home constructor is not advised
to stray from the use of air in his standard con-
denser. It has the advantage that it is of con-
stant "dielectric" value. Its use makes it
possible to calculate the capacity fairly accur-
ately, and like all apparatus supplied by nature,
it is free. As an example, two square plates
io cm. on a side, separated by one mm. of dry air
will have a capacity of 88.5 mmf. as shown below
Cmmf = .0885 X 10 XIQ
.1
Cmmf= 88.5
A good variable condenser may be any of the
commercial types. The General Radio Type
247 is specially valuable if provided with a cali-
brated dial. The standard should have a ca-
pacity of about .0005 to .001 microfarad, should
not be equipped with a stop so that the plates
may be rotated through a full revolution without
bringing up against a metal pillar with a thud
sufficient to move the plates on the shaft. This
would invariably spoil the calibration of the in-
strument. It should be of the old fashioned
straight line capacity variety since the curve of
such a condenser will be a straight line as is
shown in Fig. 3 which is the calibration of the
Laboratory's standard.
The ordinary small bypass condensers are not
at all suited for laboratory standards. They
have been known to depart as much as 50 per
cent, from their rated capacity and are not in-
dependent of external conditionssuch as moisture
and temperature. Sangamo fixed condensers,
however, have been found to be within io per
cent, of their rated capacity and are usually
within 5 per cent. It is probable that manufac-
turers of similar condensers will furnish ones of
measured capacities at slightly increased cost.
Variables with calibration curves may also be
N
DATA-
15
.4 cm
D= 1.1 cm
a - diam. of tubing
*d = 12.2
b<ND-15«ll-16.5
2a _ diarn. . 24.4 - , ..
b " length " T55 * *8
K for 148 = 0.598
L = 48 microhenries
100
Type 239 E
nable Air Condense
Calibration Curve
/
/
yo
Va
/
^
80
>
/
/u
60
1
1
i50
1
40
30
20
10
0
>
/
.
/
/
'
/
U)IO
BROA
DC AS
F LA!
iORAl
ORY
/
RJ
3 100 200 300 400 500 600 700 800 900 1000 1100 12
MICROMICROFARADS
FIG. 4
Essential dimensions for a coil whose (inductance
will be 48 microhenries. The dimensions are
those that are to be fitted into the formula
given in the text
obtained from well-known manufacturers, or
they may be sent to RADIO BROADCAST'S Labor-
atory where they will be calibrated at a nominal
cost.
INDUCTANCE STANDARDS MADE AT HOME
THE construction of an inductance standard
should present no difficulties to the experi-
enced home constructor. He should procure a
coil form, bakelite, hard rubber, glass, cardboard
soaked in paraffine, or some other insulating ma-
terial, wind it full of No. 18 d.c.c. wire, attach
the ends of the wire to small binding posts at the
ends of the tubing, and calculate the resultant
inductance. Fig. 4 shows the essential dimen-
sions of an inductance in centimeters and gives
the values to fit into the inductance formula be-
low, which may be found in the Bureau of Stand-
ards Circular No. 74, and the Signal Corps Book,
Principles Underlying Radio Communication
.Q395AaN * K
C
The method of applying the data to the for-
mula is shown below. The constants are taken
from Fig. 4.
_ .0395 X (I2.2PX (HEX .598 = g microhenries
16.5
These values may be found on Page 386 of the
Signal Corps Book already mentioned and a
drawing of such a coil is shown there too. As
another example a single layer coil on a five-inch
1 1 inches long and having a total of l 50
turns will have an inductance of a little
over one millihenry. This is too large for
ordinary radio measurements over the
broadcast band of frequencies, since the
coils ordinarily used have an inductance
of from .1 to .5 millihenries, or 100 to
500 microhenries.
The factor K in the above formula
varies as shown below. The inductance
may be more accurately calculated if the
coil is somewhat longer than its diameter.
Attention is also called to the coil induc-
tance chart published in RADIO BROAD-
CAST, May, 1925, Page 46.
DIAMETER K DIAMETER K DIAMETER K
L in microhenries = -
form
-959
.902
.818
-735
LENGTH
1.25
1.50
1-75
2.00
2.50
.638
• 595
.558
.526
.472
LENGTH
3.00
3-50
4.00
5.00
6.00
8.00
.429
.394
.365
.320
.285
.237
Resistance Box, Type IO2-K .1-, i-, io-,
loo-ohm units . . £47.00
Capacity Type 239-8 .001 mfd. . 19.00
Type 247-E .0005 mfd. . 5.50
Inductance Type 107-6 100 to 6000
microhenries. . . 24.00
FIG. 3
A calibration curve of the standard condenser shown in
Fig. i. It is of the "straight line capacity" type and is
an excellent standard
After the coil is wound it should be
given a coat of collodion, a performance
that will cause many eyebrows to lift. Col-
lodion, so it is said, increases both capac-
ity and resistance of a coil. This is true,
but for a standard of inductance one must
have a coil that once calibrated will not
MARCH, 1926
STANDARDS FOR THE HOME LABORATORY
575
130,000
I
iMyOOO
i
frj
fA
Wave Length- 1.884 VTC"
WaveLengthAs.SSLC
(Wave Length)2
L" 3.55 c
130,000 - 40,000
/
/
f
3.55
= 2
(1%
12/ih
-38)
/
/
i/
/
'
/
/
Y
/
1
/
1
_a
i
/
-
2
i
Mali
=18,51
iralfl
0-U
ravel
36Me
«ngtl
tere)2
•?•
400
300!
200
100
100
CONDENSER CAPACITYjyUf
200
FIG. 5
An interesting experiment that any one with a calibrated
condenser and a source of radio frequency voltage — an os-
cillator, or signals from broadcasting stations — can per-
form. This curve was made from data on a rather poor
coil, poor in that its distributed capacity is higher than is
desirable
vary. A coil whose wire is firmly held together
and to the form and made moisture proof will
have fairly fixed constants. The fact that its
resistance and capacity are somewhat greater
than desirable for a tuning coil need not bother
us at all since it is only to be used as a means of
comparing inductances.
INDUCTANCE-CAPACITY EXPERIMENTS
HERE is an interesting experiment that any
one can perform provided he has a cali-
brated condenser, a coil, a source of oscillations
variable over a certain range of frequencies, and
a simple receiver. The source of oscillations
may be broadcasting stations whose frequencies
are known, or the radio part of the modulated
oscillator; the receiver can be anything that
oscillates, from a single-circuit blooper to the
detector circuit of a Roberts, a Browning-Drake,
or any similar receiver.
The coil is shunted by the condenser and tuned
to various frequencies. To tell when it is tuned,
the inductance should be brought near the tun-
ing coil of the receiver. When the coil-condenser
unit is accurately tuned to the in-
coming frequency to which the re-
ceiver is already in resonance, a sharp
click will be heard in the telephones
indicating that enough energy has
been substracted from the oscillat-
ing detector by the tuned circuit
actually to stop oscillations. A
different frequency is then chosen
and a new point determined. After
several of these points have been
found, a curve is made, plotting the
wavelength squared against the
shunt capacity as shown in Fig. 5.
This should result in a straight
line which is really a
picture of the formula,
(wavelength)1 =
(L X C) X 3-55
The chart in Fig. 5
shows the method of
ascertaining the induc-
tance of the coil, its
natural wavelength, and
its distributed capacity.
This experiment does
not give accurate re-
sults, but it will give the
home constructor sev-
eral hours of enjoyment.
He will find that some
coils will have large
distributed capacity —
which is bad — and that
when this capacity is
The simplest method is by the use of a slide wire
bridge as shown in Fig. 6. It consists of a
straight piece of wire of uniform thickness, pre-
ferably of one of the high resistance alloys such
as manganin, advance, nichrome, or similar wires
and about two feet of No. 24 will make a very
good bridge.
The exact resistance is immaterial, although it
should be as high as is consistent with mechanical
strength. Too fine a wire will not last, and too
large a wire will not have sufficient resistance.
No. 24 seems to be a fair compromise. A scale
divided in some convenient manner is fixed below
the wire so that the ratio between A and B may
be easily read.
--Slide Wire.^
large that the coil will not tune to
the higher frequencies (lower wave-
lengths). He will be able to com-
pare the value of inductance deter-
mined in this manner with that
calculated from the formula already
given. He will begin to see how
coils and condensers perform when they are in
a receiver.
The data for Fig. 5 is as follows-
AC
FIG. 7
The principle of the slide wire bridge. When no sound is
heard in the telephones, there is a simple ratio which exists
between the various "arms" of the bridge so that the
unknown may be calculated
Cmmf
75
'25
190
250
325
380
FREQUENCY WAVELENGTH
1,224 «C. 245
985 305
845 355
736 407
674 452
605 495
L from curve = 232 mh.
" as measured on bridge = 210 mh.
(WAVELENGTH)2
6O,OOO
93,000
126,000
166,000
205,000
245,000
Now that descriptions of both capacity and
inductance standards have been given, and it is
assumed that the home constructor has added
such apparatus to his laboratory, it is necessary
to have some method by which they can be used
to measure other unknown coils and condensers.
Binding posts are provided so that telephones,
the a. c. voltage, and the standard and unknown
inductances, or other apparatus, may be at-
tached. Extra binding posts should be provided
so that fixed known resistances may be added to
the two arms of the bridge to increase its useful-
ness as indicated later.
The principle of the bridge is shown in Fig. 7.
Here are four arms, A, B, X, and S. These arms
may be resistances, capacities, or inductances, or
they may be combinations of these three variable
quantities. Usually, and as in this case, A and
B are pure resistances with a variable tap X
represents the unknown being measured, S is the
standard.
An alternating voltage is placed across the
bridge as shown in Fig. 7 and a pair of telephones
O AC. Q--
1 2
(Slider Contact
Sl,d.r Support Rod — — -
ice Wire
5 r Scale l>_\ ~) 6
. . , i , , , . i , . , i , , . . i . . , , i , , , , i . , , 1 1 , , , , i . , i , i , , , . i , , , , c/\ i , , i , i , , , , i , , , , i , , i , i i , i , i , , , i i , , , , i , , , ,
5 10 15 20 25 30 35 40 45 50 55O\6P 65 70 75 80 85 90 95 1
Flexible
ConnectiorT
•-O
8
FIG. 6
A simple slide wire bridge by means of which comparisons may be made between unknown capacities, resistances
or inductances and laboratory standards. In a home or commercial laboratory such a device is extremely useful
576
RADIO BROADCAST
MARCH, 1926
are used to indicate a balance. The a c. voltage
may be supplied by a buzzer, or better by a
vacuum tube oscillator, such as the audio part
of the modulated oscillator already mentioned.
In practice, the unknown is placed at X, the
standard at S, and the variable slider moved
along the slide wire until the sound in the phones
is balanced out. At this point the voltages at
the points C and D are equal (no voltage differ-
ence across the receivers) and the following rela-
tions hold:
(i)hA - I«X
(2) 1, B = 1 *S
(3) Divide (i) by (a)
A X
B = <T
The result is that the same ratio between X
and S exists that holds for A and B, and this
latter may be easily read from the graduated
scale below the slider. For resistance and in-
ductance it means that X may be found by sub-
stituting in the above equation and for capacity
the inverse relation is the true one. That is, for
capacity:
For example let us suppose that we have
placed our standard inductance at S and an un-
known at X and that when no sound is heard in
the phones, or a minimum sound, the slider lies
at 40. Then A = 40, B = 6o and
40 X . .
— = — = 334 microhenries
60 500
provided the standard is known to be 500 micro-
henries. If we were measuring capacity and the
standard S was equal to .001 when the slider
read 40 and 60 for the arms A and B the ratio
would be
-OO1 . , ,
~^- = .001 5 microfarads
MAKING RESISTANCE STANDARDS
HP HE construction of high frequency resistance
* standards presents a more difficult problem to
the average constructor. Such resistances should
have neither capacity nor inductance, and that's
the trouble. They should also be independent
of the current passing through them; in other
words their resistance should not vary as they
warm up.
For high frequencies there is no resistance unit
that will be better than a single straight wire as
short as possible. It has negligible inductance
at ordinary frequencies. Until the construction
of such units are described in RADIO BROADCAST
the reader is referred to the Bureau of Standards
Circular No. 74, sixty cents, or to an article by
John M. Clayton in the October, 1925, QST.
Mr. Clayton uses maganin wire, B & S
gauge No. 38 to 44, and for resistances from .1
to 30 ohms, the wire will be one quarter to 25
inches long. The ends are soldered, with a
minimum of solder, to heavy copper wires and
the resistance part of the unit sealed into small
glass tubing so that it will be protected. After
these units are constructed, they must be meas-
ured on some sort of bridge and that is where the
average home constructor will have the greatest
difficulty — for he must have a standard resistance
to begin with.
The process of making such a set of resistance
units will be described soon, and at the same time
the proper procedure to have them measured
will be outlined.
With the modulated oscillator, inductance
and capacity standards, and the simple slide wire
bridge the home experimenter can do many inter-
esting things. He may investigate the distri-
buted capacity of coils, he may neutralize his
receiver which may be built from coils whose
constants are known and whose tuning range
may be calculated in advance. He may measure
the inductance and capacity of home made or
manufactured material. When he buys a by-
pass condenser he may actually find out what its
capacity is, and many will be his surprises.
Throughout his investigations, the home ex-
perimenter should keep a careful notebook.
Everything should be put down that seems to
have any significance at all. The worker can
never tell when his data may be useful in the
future. It may save him considerable time to
be able to turn to page so-and-so in his note
book and find an exact calibration of this con-
denser, or variable inductance, or the frequencies
a certain combination of coil and condenser will
tune, or the capacities of certain fixed condensers
that are about the laboratory. And if unexplic-
able happenings take place, let the experimenter
put down as nearly as possible what he believes is
taking place, circuit diagrams, the constants of
all apparatus — perhaps at some future time such
data may be useful in patent cases. One can
never tell in these busy days of radio invention.
A WELL EQUIPPED RADIO LABORATORY
A view in the electrical engineering laboratory of Rennsselaer Polytechnic Institute at Troy, New York. The home experimenter can never hope to
attain an expensively equipped laboratory with all the various instruments lound in such laboratories as Marcellus Hartley at Columbia and Cruft at
Harvard and in other Universities. But much of the equipment can be made, and not very expensively at that, by the constructor in his own labora-
tory. As much constructional material of that sort as possible has been and will be described in this series of articles
-'^sgBigglMggj ju^CTjjym -frc-i •»»•• irmrym f/
Listeners' "Point of View
Conducted by John Wallace
Wanted: A Radio Shakespeare!
ROM Mr. Edgar H. Felix of New
York City we have received the
following pregnant theme, upon
which he has invited us to im-
provise variations:
"One of the problems which vex radio
program managers is the discovery of
suitable text for dramatic recitations. More
frequently than not, the broadcast listener
finds the efforts of would-be dramatic
artists a program of confusion because so
much that is essential is either missing or
requires the bolstering of tedious announce-
ment. One outstanding exception is found
in the prolific works of Shakespeare, which
offer a repertoire to meet the needs of every
conceivable kind of dramatic talent.
"Shakespeare contended with the very
problems which make broadcasting per-
formances fail. He, too, was practically
limited to the sense of hearing in his presen-
tations, because stage lighting and scenery
were not developed in his day. A few
uncertain candles, which hardly served to
guide the almost unseen actors to their
position on the stage, were the only sources
of illumination. There was no scenery;
colored drapes indicated the surroundings-
green a field, blue a sea,
and so forth.
"Appreciating these
handicaps, Shakespeare
always worked into the
actor's lines all the es-
sential information
which makes an aural
rendition both under-
standable and enjoyable.
There is a wealth of de-
scription which performs
the function now served
by stage setting, scenery,
and illumination, and
which permits of com-
plete appreciation
through the medium of
the microphone."
By way of checking up
on Mr. Felix's very inter-
esting point, we picked
up a volume of Shake-
speare— it happened to
be Hamlet— and found
in the first ten lines examined a demonstra-
tion of the truth of Mr. Felix's suggestion:
"Shakespeare always worked into the
actor's lines all essential information."
HAMLET
ACT ONE SCENE ONE
A Platform before the Castle
Ehinore.
Francisco at his post.
Enter to him Bernardo.
Bernardo. Who's there?
Francisco. Nay, answer me: stand and unfold
yourself.
Bernardo. Long live the king!
Francisco. Bernardo?
Bernardo. He.
Francisco. You come most carefully upon your
hour.
Bernardo. Tis now struck twelve; get thee to
bed, Francisco.
Francisco. For this relief much thanks: 'tis
bitter cold, and I am sick at heart.
Bernardo. Have you had a quiet guard?
Francisco. Not a mouse stirring.
This play was probably first presented in
broad daylight, in a circular, roofless
building (as this sort of theater preceded
the walled in, candle-lit type). Doubtless
Gentle reader is not the culinary staff of WGY broadcasting recipes for home brew but
the Players of sa.d station putting over a one-act play cabled "Dange?" and
to do with lovers buried in a coal mine
a hot noon-day sun was beating down on
the actors while they recited their lines.
Probably there was no scenery. Yet alf
necessary information was conveyed to the
audience of London citizenry, and not in
an obvious and uncomfortable manner.
First they were told the names of the
characters. Secondly they were informed
that it was twelve o'clock at night. Thirdly
they learned that it was bitter -cold. And
fourthly, that the death-like silence of
midnight prevailed (though probably the
theatre was echoing with the noise of
boisterous late comers).
Mr. Felix's immediate point, and a well
taken one, is that Shakespeare be drawn
on more frequently for dramatic recitations.
As a matter of record this has occasionally
been done. We have happened on a couple
of instances. The "To be or not to be"
soliloquy was recited by Basil Sydney, the
star of Hamlet— In Modern Dress over WOR
some time ago. This station also pre-
sented a group of readings, by whom we've
forgotten, from The Taming of ihe Shrew
and Macbeth. Station KOA had a program
in which one John Connery portrayed the
various characters in the grave-digger
scene from Hamlet.
However, even at best,
it seems unlikely that
recitations will ever
make an astounding suc-
cess with radio audi-
ences. The most potent
idea suggested by the
above letter, we think, is
that all aspiring radio-
playwrights be required
to read and assimilate in
their entirety each and
every one of Shake-
speare's dramas.
For the radio play has,
to date, proved to be an
utter and complete wash-
out. Of the many we
have heard we know of
no one we would call a
complete success. Sev-
eral were fair. The large
majority were terrible.
Once we thought we had
578
RADIO BROADCAST
MARCH, 1926
a good one: it had held us breathless, spell-
bound, and so forth, for fully ten minutes
— but just then a shooting occurred and
we spent the rest of the play trying to
figure out who in thunder had been killed.
Now if recollection immediately rushes
to your mind of some radio play which you
heard and thought was a wow, we plead
guilty to an occasional absence from the
loud speaker and protest that that must
have been one we slipped up on. Dwelling
upon those we have heard, we are unable
to decide whether, as an average, the plays
or the actors were worse. We're inclined
to hand the palm to the latter.
But in fairness to the radio Thespians
it should be observed that theirs is a more
difficult task than that of their brethren
on the visible boards. The stage actor is
assisted by props, costume, action, gesture,
and makeup. If all these accessories are
of high standard, his cerebral and vocal
deficiencies may be partly overlooked, or
at least not seem quite so glaring.
Not so of the radio actor. His ability
to 'put over his part is exclusively depen-
dent upon his ability correctly to under-
stand and interpret his lines and upon his
natural vocal endowment. We advance
fhis point, not because we think it to be
an obscure one, in the ferreting out of
which we have exhibited great acumen,
but beca'use, obvious as it is, it does not
seem to have occurred to radio play pro-
ducers. Their radio players are made up,
1 for the most part, of second rate hams
' who would in no wise add to the glory of a
third-rate stock company.
\' As a matter of fact, nothing short of an
'-' all-star cast culled from the headliners of
the legitimate stage would be able to put
across a flawless radio play, so difficult is
the chore. Such a cast we may not ex-
pect; but at least we may ask the station
directors to come a little closer to it. High
school dramatics may be endured while we
are waiting for little Oswald to go up for
his diploma, but they are likely to be
tuned-out when they
come via radio.
When, occasionally, we
have heard a genuinely
competent and experi-
enced troupe of players
perform, they have al-
most invariably been
weighted down by some
impossible stage piece
that defied their most
valiant efforts to trans-
mogrify it into a radio-
piece.
Drama is one of the
most difficult of all forms
of writing, and, per-
versely, of all forms of
writing the most easy to
criticize. Easy to criticize
because we need rely on
no objective standards or
canons of judgment; our
personal reaction is the
final criterion. We may
know nothing at all of the craft of acting,
yet we are justly entitled to pass on act-
ing. If the actor succeeds in creating the
illusion of reality (or of unreality, as the
case may be) we declare him to be a good
actor. If he creates no illusion but simply
remains an "actor" we call him a bad actor.
Simple!
So we feel encouraged to state dogmatic-
ally that we have never heard a radio play
worth two bent pins and war tax. For
we don't recall having ever been com-
pletely absorbed in, or carried away by
one. We have never experienced any
difficulty in getting "back to earth" after
listening to a radio play; to us at least,
every radio play has remained just a "radio
play" from start to finish. The reason for
their unsuccess has been stated so often it
has become banal: "Radio is an entirely
new medium and requires an entirely new
and distinct type of play." Yet, in spite
of the frequent reiteration little has been
done about it.
Now comes news of a new radio play
contest, and our hope perks up. Perhaps
something may come of it. Station WLS, of
Chicago, and the Drama League of America
are its joint sponsors. It is press agented
as the first radio play contest in the world,
which is not entirely correct. The
General Electric Company opened a
similar contest in 1923 which continued
about six months, closing on December
31 of that year. In this contest a $500.
prize was offered for the best play, and ten
additional prizes were given for manuscripts
thought to be satisfactory for radio pres-
entation. WGBS, New York, conducted
one last year, and several others of purely
local import have been held. But at any
rate the WLS contest is a pretentious under-
taking and should bring interesting results.
The prizes are sizable if not munificent;
first award is $500. And the judges are
George Arliss, Augustus Thomas, and
James O'Donnell Bennett. Doubtless by
the time this appears in print, the prizes
will have been long awarded and the plays
will have been aerially presented. But
the rules governing the contest may be still
of interest and we quote some of them, as
outlined by George Junkin, field secretary
of the Drama League:
Radio will not allow any sly stage business.
Glances, asides and business with props cannot
be put over, to the radio audience. Entrances
and exits must in some way be told in the action
of the play. Just as the movies brought about
the new drama and a new way of presenting it,
so will radio. Sounds will be the principal
vehicle. Bells of all sorts, church, dinner,
telephone, house and others can be used to ad-
vantage. Rain, storms, musical backgrounds,
horse, airplanes, automobiles, all have sounds
which can be duplicated and will lend life to the
words and action of the radio play.
Any play submitted must be original and not
have been printed.
Original one-act plays, eighteen to twenty-five
minutes in length.
Few characters — maximum, five principals.
Accompany action with appropriate sounds.
Farce, comedy, drama, melodrama, tragedy
and mystery plays.
Plays must be clean, wholesome material.
Plays should not have material which would be
objectionable to any sect or nationality.
Write plays as though they were to be pro-
duced for the blind.
Everything necessary in the action must be
made plain.
With due appreciation of Mr. Junkin's
suggestions, we hope that too many con-
testants will not go in for the clanging bells,
galloping hoofs, and wailing wind effects.
Little gain can come from such-like trickery.
In the final analysis it's the words, words,
words that count. Just as the radio actor
has to have a better command of his voice
and inflection than the legitimate actor, so
the radio playwright has to have a better
command of the President's English. With
neither scenery nor action to fill in his gaps
of thought he is up against a problem even
harder than Shakespeare had to face. So
it would seem that the radio playwright
who would do his job in
the best possible manner
will need to possess
slightly more ability than
Shakespeare. Here's hop-
ing such a man comes to
light!
Dinner Orchestras:
Excellent Radio
Features
o
CYRIL MAUDE
The famous English stage star, familiar to many theatregoers who saw him in " Are'n't We
All?" and "These Charming People," shown here listening to an American radio receiver
in use in his apartment in New York. Mr. Maude has, so far, ventured no authoritative
opinions on a comparison of English and American broadcasting
, NE of the pleas-
anter features of
radio is the dinner
orchestra. As radio
standards go, the dinner
orchestras occupy a lofty
position on their respec-
tive programs. This is
particularly true of some
of the smaller stations.
Located, as they often
are, in towns where there
is a decided dearth of
MARCH, 1926
THE DINNER ORCHESTRA IS DESERVEDLY POPULAR
579
FREDERICK STOCK
Conductor of the Chicago Symphony Orchestra,
which was heard some time ago through WMAQ
of that city
available talent (and where there should
never have been a radio station) the best
broadcast material available is often the
orchestra at the local hospice. In larger
cities the membership of these bands often
includes recruits from first rate symphony
orchestras.
It is safe to guess that some hundred
thousands of our citizenry dine nightly to
radio music. And if a careful job of tuning
has been done, and a mild pianissimo
applied, these radio strains wafting in from
the front parlor, add considerably to the
relish of home cooked victuals — to say
nothing of the delightful possibility of an
occasional healthy obligatto of static, under
cover of which one may really enjoy one's
soup or celery.
Among the dinner bands we have listened
to, we give the KDKA Little Symphony
Orchestra a class A position. This is one
of the few stations that, itself, supplies
the orchestra. Next comes to mind the
Commodore Hotel concerts from wjz and
the Waldorf Astoria Rose Room orchestra
heard through WEAF. Close to the top of
the list come the Drake Concert Ensemble
and the Blackstone String Quintette heard
through WLIB (or WON). These two orches-
tras are picked up so as to alternate num-
bers.
The Brown Palace String Orchestra at
Denver, offered by KOA is very good. KGO
relays the dinner music of a caravansary
called Roberts-at-the-Beach, which comes
in a bit later than our customary dining
hour. From Detroit comes Jules Klein's
Hotel Statler Orchestra, via wwj. WSM,
at Nashville, offers Francis Craig's Her-
mitage Hotel orchestra on alternate nights
and KGW at Portland, Oregon, presents a
first rate trio from six to seven.
Will Broadcast Stations Ever
Specialize?
ONE of the planks in the platform of
this polite if not pertinent purveyor
of program piffle is that radio
stations be constrained to specialize.
Specialization will eventually overtake the
radio industry just as surely as it has the
magazine business, and every other enter-
tainment dispensary. At some future
date we shall rant on at great length in
these pages in an attempt to prove this
point, which, since it is transparently
obvious, should not be too much of a chore.
For the present we shall be content to
record joyfully the advent of two stations
whose announced policy is to specialize.
WBAL at Baltimore, operated by the
Consolidated Gas Electric Light and Power
company of that city, broadcast the follow-
ing manifesto on its opening night:
In its desire to be known as the radio station
of good music rather than merely "another
station of the air," WBAL hopes to attain an
enviable distinction. If this station gives
Baltimore a reputation for broadcasting good
music, well performed, in a distinctive manner,
it will serve the city better than if it tried to
compete with the general run of stations by
doing exactly what they do.
WBAL has a definite weekly program
schedule: Sunday night, Twilight music
(whatever that is!) Monday, Concert night;
Tuesday, Ensemble night; Wednesday,
silent; Thursday, Concert night; Friday,
Novelty night; and Saturday, silent.
A slightly different policy is that an-
nounced by WHAP, New York:
The intention of the founders has been
to establish an institution through which high
ideals and standards can be expressed in the
fields of education, musical art, and good citizen-
ship. In matters of current opinion and in
civic and social questions, WHAP will depart
from the neutral and passive attitude generally
maintained by broadcasting stations, as it
has definite convictions, which will be expressed
on the air.
Believing that those who favor jazz music
and vaudeville songs are already receiving an
ample volume of this material from other
stations, WHAP will not broadcast any music
of this type. Without making its musical
programs at all heavy or academic, WHAP
plans to arrange radio concerts that will have
artistic merit, as well as entertainment value.
Education is also to have a prominent place on
the program, and several courses of half-hour
talks are to be given by noted university lec-
turers. American history, English literature,
and other subjects will be treated.
Of course we don't want all stations to
specialize thusly, in highbrow manner —
let it be in any manner they chose, as long
as it is specialization. For this reason we
are inclined to regret the passing of WTAS
at Elgin, Illinois.
WTAS, catering to "Willie, Tommie,
Annie, and Sammy"was frankly a lowbrow
station — and proud of it. WTAS had
thousands of devoted and enslaved listen-
ers. If you didn't particularly snap for
its offerings (nor did we) you doubtless
carefully memorized its dial markings and
learned to trip lightly past them. Mean-
while, your next door neighbor sought
them out and enjoyed his fill of peppy
pieces and flip announcing. So no harm
was done.
MADAME TAMAKf MIURA
Japanese Soprano and well-known and praised
interpreter of "Butterfly" who was heard in
recital recently from WEBH, Chicago. We can't
say who the evil genius who butted into the
picture, is, but of one thing we are moderately
certain. He is not an announcer
Consistency in Programs
ODEAR! O DEAR! The way of the
reformer is hard ! Possibly a couple
of our gentle readers will recall
that we towered to heights of what we
considered to be righteous wrath in these
columns last month in a diatribe against
the "hodge-podge" program that jumps
from one offering to another quicker than a
nervous flee in a litter of pups.
And what was our reward? No sooner
had we laid down our flaming pen than we
were slapped in the face by the following
notice in a local (Chicago), journal:
Symbolic of the variety which has
marked the daily broadcasts of WBCN
since its inception, the twenty-four-
hour program which will mark the
first anniversary of the station will
include a creditable representation of
practically every kind of talent on the
air to-day. Everything from a whis-
tler to a brass band will be offered.
There is great variety, as among the
acts booked are a brass band, two dance
orchestras, pipe organist, male vocal
octet, male vocal quartet, mixed vocal
quartet, male vocal and instrumental
quartet, three female vocal duos, two
male vocal duos, a saxophone trio, a
banjo trio, violin duo, harmonica duo,
guitar duo, mandolin-guitar duo, four
violin soloists, a cellist, a bagpiper,
pianologist, musical reader, monologist,
two dramatic readers, four speakers, an
operatic soprano, an operatic tenor, three
classical piano soloists, a blind tenor,
three jazz piano soloists a trombonist, one
harmonica soloist, three piano-accor-
dionists, two mandolin soloists, one "song
and patter" duo, a Scotch harmony duo, a
mixed harmony duo, a Scotch soloist, a
French barytone, an English soprano,
seven other sopranos, a Swedish tenor,
fourteen other tenors, a dialect singer, a
negro barytone, two blues singers, a
children's entertainer, two whistlers, two
xylophone soloists, a basso, three classical
barytones, two contraltos, one popular
barytone, a girl barytone, harmonica-
guitar player, eleven song writers, a barn
dance fiddler and a tipple-player.
580
RADIO BROADCAST
MARCH, 1926
Stories By Air
COSMO HAMILTON, the scriviner,
read a specially composed radio
novel over wjz recently, and since,
regularly at 8 P.M. each Saturday evening,
accompanied by sundry and droll remarks
on the possibilities of the new medium.
On the first night, he said in part:
My radio novel idea, which is not the con-
densation of an already written full-length novel,
but of one written newly for the radio, which
must take no longer than fifteen minutes to
read, anticipates the time when, very shortly,
the few people who still buy novels — and they
are very few — will have joined the vast majority
who look and listen but are physically and
mentally unable to stop.
But equally entertaining was F. P. A's
comment the following morning in "The
Conning Tower" of the New York World
which we cannot refrain from quoting:
Mr. Cosmo Hamilton, having said that the
radio would put the spoken drama out of busi-
ness, advances a parasang and predicts that the
radio will make unnecessary the written novel.
Novels, Mr. Hamilton forecasts, will be broad-
cast. And a jolly idea, too. Perhaps in a day
or two we shall revise, for radio audiences, some
novel or other. It would have been a glorious
thing to do in the old days. There is a scene in
Ivanboe, for example, that goes something like
this:
"My grandsire drew a good bow at Hastings."
" The foul fiend on thy grandsire and all bis
generation! In the clout! In the chut! A Hubert
forever!"
The radio audience would listen in on this:
" Hello, folks! This is Walt Scott, from WEAF,
broadcasting. Well, bere we are in Sberwood
Forest. The boys are having a contest in archery.
There they are, folks, all lined up. Now, let's see.
Well, Sir Reginald steps up and starts boasting.
"'My grandpa was a curly wolf at this game,' he
says. 'He won a cup at Hastings Field.'
"' So's your old man!" cried they all.
"And now, folks, while they're shooting, Miss
Elsie O'Brien, who takes the part of Rebecca in
the novel, will sing, 'I've an Eye for Ivanboe.'
If you like this little lady, folks, send a postal to
her in care of the Waverley Length Radio Corpora-
tion, Newark, New Jersey. The Waiierley
Length Radio Corporation, Newark, New Jersey."
w
A Leader Explodes
E ARE in receipt of the following
letter addressed to our worthy
predecessor in this department:
PUEBLO, COLORADO
MR. KINGSLEY WELLES,
Editor, "Listeners' Point of View"
SIR:
The only thing that avoided a conflagration
in the local post office last night was the fact
that I had the mental and moral strength to
contain my wrath over a period of hours before
putting it on paper.
It's all about Jazz. It seems to me that you
and most of your fraternity of critics are wearing
yourselves down to mere shadows over an evil
which does not exist. Much as it may astound
you to know it, there are those of us who prefer
jazz to the more profound type of program, and
oddly enough, our radio sets cost just as much to
run as do those of the listeners who like the
classics. Yet where is all this Jazz coming from?
Out here in the great open spaces, I twirled
the dials of our Roberts Knockout one night
last week (it was not Sunday) and brought in
fifteen stations without a single Jazz orchestra
among them. I got sermons and speeches;
sopranos and bassos; cornetists, pianists, and
violinists; organs, bands, long-winded announ-
cers, and a pain in the neck. Conditions must
be a lot different in New York.
It has come to the point where a person who
wishes to listen to a jazz concert must wait
around until ten or eleven o'clock before his wish
can be fulfilled, and even then he may be dis-
appointed. In fact, you mention a station in
New York which forbids dance orchestras the
air until ten-thirty. Fine! And now, let us
close the air to sopranos of the coloratura variety,
and to Hungarian Rhapsodies from ten-thirty
on. Apropos of this discussion, 1 have sent a
stamped, addressed envelope to Carl Dreher,
who says in part: " If you want jazz issuing from
your loud speaker, there are certain wavelengths
in every locality where you can get it at any
time." 1 confidently expect Mr. Dreher to solve
my problem for me, with the added assurance
of loud speaker volume.
For your information, may I state that KOA
of Denver seems to fulfill your ideal of a broad-
casting station? Twice a week for short periods
they have genteel dance orchestras on the air.
I pass them by rather hurriedly for the " Packard
Six" of KFI which is unashamedly a dance orches-
tra. Incidentally, I always set my dials for
KFI on Sunday night and turn on the juice
afterward. They always have a program of
lighter numbers for those who do not wish to
go to sleep with their headphones on.
Very truly yours,
BERNARD KELLY.
If we may be permitted to rally to the
defense of Mr. Welles (and incidentally
to our own, as one of the "fraternity of
critics" indicated above) we will hazard
the guess that Mr. Welles never desired to
bring conditions to such a sorry pass as Mr.
Kelly seems to have found them.
On our own behalf, we sympathize
entirely with Mr. Kelly's point of view
the while rejoicing that he has found jazz
so difficult to find. Rather too little jazz
than the vast too much that prevailed
until recently. With the demand for jazz
bands and artists slightly greater than the
supply the quality was bound to suffer.
When jazz is good it is very, very good;
but when it is bad it is horrid.
'Broadcast ^Miscellany
JULES KLEIN'S HOTEL STATLER ORCHESTRA
Which plays dinner and noon-day music from wwj in Detroit. Left to right, standing: Eric Ernst,
Raymond Epstein, Erick Wyle, Benjamin Gulp; seated: Jules Klein, and Frank Hancock
THE broadcasting of the autumn's
football games was, by all odds, the
best piece of work done by radio
during the last half year. The broadcast-
ing of basketball, hockey, and such-like
games, that has been prevalent during the
last few months has proved to be an un-
mitigated fizzle. The success of a sporting
event broadcast is dependent on the list-
eners' ability to visualize the progress of
the contest. If it is a tax on one's optics
intelligently to follow the plays of a fast
hockey match, it is a considerably greater
strain on the mind's eye to turn the same
trick. Football is fundamentally adapted
to broadcasting: the game is essentially a
spectacle — a series of clear cut and well
defined pictures. Basketball is far from
picturesque. It is all action. And the
MARCH, 1926
THE BEST RADIO FEATURE OF THE MONTH
581
action is too rapid to be delineated by the
radio reporter with any degree of interest.
We are no better able to picture the prog-
ress of the game than we are when we
read a newspaper report of it.
NOT a bad idea, WOR'S, of celebrating
a writer's birthday with a.program of
his brain children. On Rudyard Kipling's
birth anniversary, December 30, this
station broadcast a program made up of
readings of his best known verse with
•orchestral accompaniment, and several solo
renditions of poems which have been set to
music. There was also a speech by Mr.
Russell Doubleday, one of the members of
the firm which is his American publisher.
The excellent Eveready Hour over the WEAF
chain, on the following Tuesday, prepared
as usual by Mr. Paul Stacey also reminded
listeners throughout the eastern United
States of Kipling's greatness.
KSD, at St. Louis, has a Thursday
afternoon feature that may or may
not be of interest to club women. Not
being one we can't say. At any rate, the
Wednesday (!) Club of St. Louis, throws
its meetings open to the ladies at large
every Thursday from 4 to 5 o'clock (P.M).
The program is known as the "Women's
Hour." Among the subjects so far treated
at its sessions are: "The Newest Things in
Dramatics" and "Home Hygiene and
Public Health."
THE Atwater-Kent concert programs
through WEAF and its r.hain of some
fifteen stations continue to be about the
best thing on the radio bill of fare. Not the
least factor in their success is the fact that
the series has continued so long now, and
so regularly, that ninety per cent, of all
listeners know its day and hour by memory
and can thus plan their Sunday evenings to
listen-in if they desire. The occasional al-
most equally excellent program from many
another station is all too often lost in the
shuffle.
TOURING the period from January i
*—' to November 30 (1925), WEAF was
on the air almost 2800 hours; the Plant
Department or technical delays caused
by unavoidable equipment trouble in this
time totalling slightly in excess of five
hours; the studio delays or time lost be-
tween program presentations, 12 hours
and the delays occasioned by sos calls
from vessels in distress 17 hours.
WE DON'T want to boast about the
receptive qualities of our receiver,
but we are here to state that we have
listened to broadcasts of the New York
Philharmonic Orchestra, from wjz, out here
in the wilds of Illinois, from which we have
derived almost as much pleasure as from
our seat in Orchestra Hall, which, to us,
seems savini? nnitp a hit fnr raHin AnH it ho are heard nl8htly from station KGW of the Portland Oregontan. The personnel
t tor radio. And it ati0n reading from left to right: Gladys Johnson, 'cellist; Julius Walter, pianist;
OLIVER M. SAYLER'S "Footlight
and Lamplight" talks over WGBS
are worth attention. Mr. Sayler relates
current gossip of the stage, and reviews,
in a brief and entertaining manner, recent
books. The talks are on Thursday even-
ings at 8:30 P.M. Eastern time.
IT WAS WHAS (Louisville) we think —
though we tuned-out so fast we might
have got its letters wrong — that jangled
our nerves like bells out of tune the
other night by stating that it was "radio-
casting."
/^"HICAGO programs are evincing a
^— •* slight improvement. WJAZ has an
excellent program of music Thursday
nights from 10 to 12. Efforts to make
some arrangement whereby the productions
of the Chicago Civic Opera company could
be broadcast have so far been unsuccessful.
The broadcasting of opera involves a
myriad complications. To mention only
two of them: many artist's contracts
prohibit broadcasting and some opera's
copyrights prohibit broadcasting.
THE Cincinnati Symphony Orchestra
is on the air once a month during a
series of twenty community radio concerts
being broadcast in the name of the com-
munity of Cincinnati through WSAI. Fritz
Reiner is conductor of this orchestra.
Its engagement was in response to a popu-
lar demand among listeners throughout
the country, nearly 3000 letters having been
received after its first concert urging
repititions.
NOT an habitual peruser of the comic
sections, and likewise by no means a
faithful listener-in on the "kiddie" (Ouch!)
programs, we found ourself, nevertheless,
completely absorbed in Uncle Walt's (WGN)
broadcast of the comics on a recent Sunday
morning. Stumbling accidentally on this
program, we picked up the funny paper, as
instructed by the speaker, sat ourself
down, and didn't get up until he had
finished reading all eight pages!
BUT, withal, from Chicago comes the
high-spot in programs since last
writing. The Chicago Symphony Or-
chestra, which has never before con-
sented to broadcast its concerts at last
agreed to furnish a two-hour program,
which was picked up by WMAQ for the
opening program of its new looo-watt
apparatus.
The concert was one of a regular series
conducted by Frederick Stock. As a
musical offering it was the equal of any-
thing that has yet been tendered us by
radio. Of course there was the inevitable
muffling of some of the instruments,
especially during loud passages — but on
the whole a good job for non-studio broad-
casting. To date no promise has been
made of further concerts.
THIS year of grace 1926 was ushered in
by the ringing of Liberty Bell at the
stroke of midnight on New Year's eve.
Station WIP broadcast the historic gong
at the conclusion of an official ceremony
inaugurating Philadelphia's Sesquicenten-
nial year.
THE KGW DINNER CONCERT TRIO
needs kind words!
1 and instrument-
. Abe Bercovitz,
violinist. They are presented through the courtesy of Olds, Wortman & King, of Portland
An All
Hou> to Make and Use a Simple Coil Winder for Solenoid and
Lorenz Type Coils Together With Useful Inductance Tables
RADIO BROADCAST Photograph
By EDWARD THATCHER
A S LONG as radio constructors assemble sets,
•/*• there will be those who want to make the
coils they use in the set with their own hands.
There are, of course, plenty who have no desire to
wind their own coils any more than they care to
make an audio transformer or wind a set of bobbins
for head telephones. So many of our readers write in
for information on how to wind this or that sort oj
coil that the information contained here should be
of wide interest. Practically every common type of
coil can be made with this simple device, from the
simple solenoid to the more complex diamond and
basketweave types. The inclusion of an ingenious
turn-counter makes the device of great practical
value. Many examples of Mr. Thatcher's work
in other, non-radio, lines, have appeared in The
Ladies' Home Journal and other publications.
He is especially known for his excellent amateur
ship models. — THE EDITOR.
old discarded auto speedometer, which
may be purchased for about a dollar at
most auto junk yards. Perhaps a search
of the home garage may result in finding
one. A bicycle cyclometer may also be
used, if a few slight alterations are made.
Fig. 2 shows such a cyclometer mounted.
This one cost 85 cents at a mail order house.
The various forms used with the simple
machine are shown in Figs. 4, 5, 6, 7,
8, and in the top illustration on this page.
These will be described in detail later on.
It might be well to mention here that these
same forms may be found very convenient
for hand winding if you do not care to make
the machine.
In Fig. 3 may be seen the coil winder
and counter unassembled. The hook J, is
exactly similar to the one used to make
the handle I.
It should be understood that the dimen-
sions given for the coil winder and counter
may be made to suit individual needs,
those given being found convenient for
most of the coils which have come to the
writer's attention.
The frame is made from soft pine wood
taken from a packing box. A saw, plane,
drills, and a hammer, are the only tools
necessary for this part of the work. All
the parts should be very carefully marked
out and squared up before cutting them out.
M
'OST of us who tinker with radio
know the bother of keeping
count of the turns of wire on
a coil as it is being wound, or
of counting the turns after the coil is fin-
ished, particularly with such coils as the
basketweave type or other coils of a similar
nature.
With the simple coil winder and counter
shown in Fig. i, and some simple forms
which are easy to make, you may wind
practically any type of continuously
wound coil very easily, and enjoy a smoke
at the same time if you care to. You
may stop winding to light your pipe and
resume operations sure that the turns will
be counted correctly, and if you should
accidentally wind on too many turns,
you may easily unwind them. The counter
will always show the number of turns on
the coil.
This coil winder and counter is in the
form of a very simple lathe, the counter
being nothing more than part of an
RADIO BROADCAST Photograph
FIG. I
The inexpensive, easily made coil winder and counter is illustrated "in action" here. With the aid
of this device high grade coils are within the reach of all home-constructors and experimenters
MARCH, 1926
AN ALL PURPOSE COIL WINDER
583
RADIO BROADCAST Photograph
FIG. 2
A cyclometer type of turn-counter which may be
satisfactorily used. Your local hardware or
bicycle store can supply you with a similar one
In Fig. 3, A is the baseboard or bed of
the winder. This is f inch thick, 2f inches
wide, and 18 inches long. B-B are two
pieces which are used to support the coun-
ter. Each piece is -jV mcn thick (f or J
inch will do as well),
^ inches high, and
6 inches long. These
pieces are glued,
nailed, or screwed to
one end of the base-
board.
C is the base of
the sliding tailstock,
and is | inch thick,
2^ inches wide,
and jj inches long.
A slot G i inch wide
and 3! inches long
is centered in this
base. The screw F
passes through the
slot G into the base-
board A, and is
tightened up to
hold the tailstock in
position. The two
pieces E-E are made
of wood T\ or § inch
thick, and each piece is 51 inches long.
Each of these pieces is sawn out to make
room for turning the handle I, a coping or
compass saw being used for this purpose.
These two pieces, E-E, are glued and either
nailed or screwed to pieces D and C, the end
of piece D resting on top of piece C.
Piece D is | inch thick, 2^ inches wide,
and 4j inches high. In this piece is drilled
the hole H, into which the handle may
be pushed and allowed to turn easily.
The position for this hole is best found by
sliding the tailstock along the bed until the
end of the stovebolt used to make the
counter shaft, rests against D, when the
counter is mounted in position between the
pieces. B-B.
The handle I is made of a common
screwhook. This is 4 inches in length
and made of stock about \ inch in dia-
meter, a common size obtainable at most
hardware and lo-cent stores. To trans-
form the screwhook into a screw handle,
place it upright in the vise jaws, the
hook end uppermost, with the bend just
above the top of the jaws. Use a monkey-
wrench to grasp the hook and bend it out
roughly into the shape of a handle.
The handle is then removed from the vise
and straightened up a bit by hammering
on some sort of an anvil, such as the bottom
of an old flat iron, taking care not to injure
the screw thread.
The screw end of the hook will be found
rather blunt. This may be much improved
for our purposes if the threads are filed
down so that they barely show at the point,
tapering up gradually to the full thread at
the end, next to the handle, so that the
thread is much like the threaded end of a
polishing spindle. A tapered screw of this
kind will enter the wood more easily, and
the further it is screwed in the tighter it
will hold.
THE COUNTER DEVICE
It
NOW for the counting head M. It is
quite easy to remove the counting
device from
common
I
RADIO BROADCAST Photograph
FIG. 3
The coil winder partly assembled. Box wood, screw hooks, screws and a turn-counter are the re-
quirements for the construction of this handy laboratory apparatus. The lettered parts are for
identification with the Material List and refer directly to the description of the preparation of the
material in the text
Pry off the glass cover and you will usually
find that the counter may be removed
by taking out a screw or two, when it
may be lifted out and separated from the
speed indicator. The counter probably
registers a number of miles and these may
be set back on the "trip" by the device
found in most indicators. The total mile-
age however, must be turned backward
if you wish it to register oooo. Unless yoii
wish to wind coils of
more than 99 turns,
the total mileage in-
dicator may be dis-
regarded. However,
it may be turned
back after the counter
is mounted in its
frame by attaching a
hand drill to it and
turning it backward,
or fastening the
counter shaft to the
chuck of a lathe
head and running
it backward this way. Then you will have
a counter which will register up to 9999,
quite enough for most experimenters,
The trip and season counters are usually
connected by a simple cjutch arrangement,
which may be thrown in or out as you like.
In the counter shown in Fig. 10, the set
device is not made use^of, it being a simple
matter to turn the counter backward to ooo
after the coil is round and before the form
is removed.
The counter M, Fig. 10, is supported by
a simple wooden frame which is made as
follows. There are two pieces like K,
each piece being £ inch thick, \ inch wide,
and 6 inches long. These two pieces are
fastened together at the head end by a
block of wood N, i^ inches thick or high,
if inches wide, and i| inches long. The
block is glued and nailed, or screwed, to
the side pieces. Through this block is
drilled a hole to accommodate the stove
bolt L, which should turn easily in this
hole, the head of the stovebolt connecting
with the end of the
counter shaft, as
will be described
later. The exact
position of this hole
may best be found
by experimenting
with the counter
resting in position,
so that the hole
through N is exactly
in line with the
center of the shaft
of the counter.
The piece O is J
inch thick, if inches
wide, and i\ inches
long. It should be
understood that the
dimensions of all the
pieces may be
changed to accom-
modate any partic-
ular type of speedo-
If a cyclometer is
meter you may have,
used follow Fig. 2.
Now look at Fig. 1 1 . The stovebolt
L is i inch in diameter and 3 inches long.
This should be provided with two nuts
and one or more washers. The end of the
counter shaft P, on the counter M, is
filed to a flat shape like the end of a screw
driver, care being taken to have the wedge-
like end exactly in the center of the counter
RADIO BROADCAST Photograph
FIG. 4
Here are the cylindrical and pickle-bottle coil forms with a very good
example of coil binding utilizing gummed paper. Note that just
below the center hole in the end piece of each coil form is situated the
pin which engages in the nut on the turn-counter shaft
584
RADIO BROADCAST
MARCH, 1926
shaft, as this is to slip easily in
the slot in the head of the stove-
bolt, so that the latter may
turn the counter as it is turned
around by the coil form, which
in turn is turned by the handle.
A small hole is drilled in one
corner of the nut on the stove-
bolt as shown at Q, with a twist
drill about -fa 'ncrl m diameter.
A pin or brad driven in the end
of each coil form fits in this
hole to prevent the coil form
from turning on the shaft with-
out turning the counter, thereby causing a
wrong count.
When you have the counting head ready
to assemble, slip the stovebolt through the
hole in N, place a washer on the threaded
end, and then screw on the nut with the hole
Q in it until it is fixed very tightly on the
end of the thread, taking care, of course, that
the stovebolt turns easily without undue
play. The counter M should then be
mounted on its wooden frame and screwed
to it, so that every time the
stovebolt makes one revolution
the counter will register. Re-
member that the red figures on
the counter are tenths and the
black figures on the wheel next
to the red figures will count one
for every turn of the shaft.
ADJUSTING A CYCLOMETER
A CYCLOMETER also makes
*» a very good counter. It
will have to be tinkered with a
bit, however, before it will count
one for every turn of the
shaft. The cyclometer shown in
Fig. 2 was treated as follows.
The disk-like end opposite
the star wheel was removed by placing
the points of a small pair of round nosed
pliers in the two holes found in this end,
and unscrewing it. Inside this disk were
•several washers which were removed and
left out. On the end of the star wheel
shaft thus exposed, will be found a small
t>rass disk. To this disk is attached a
small pinion which engages a ring or inter-
nal gear attached to the first row of figures.
The pinion should be soldered fast to the
disk which is on the end of the star wheel
shaft. It will then be locked in the ring
gear turning this with the star wheel
shaft, one turn, one count. Care must be
taken with this soldering, and only a small
-amount of flux and solder are necessary.
Two small holes about -^ inch in diameter
are then drilled about £ inch apart and
•equidistant from the star wheel shaft,
these holes being drilled in the disk attached
to the end of the shaft, to which the pinion
was soldered.
A "U" shaped piece was then bent out
of a piece of thin steel wire taken from a
paper fastener, the points of the " U " being
J inch apart. The U shaped piece is then
soldered in the center of the slot in the head
of the stovebolt L, Fig. 2. The ends of
this soldered piece of wire engage the two
RADIO BROADCAST Photograph
FIG.
End pieces, coil form, and screws are all that is required to make up the
cylindrical form for the sample of solenoid coil shown at the right.
The wood strip indicated at A is employed as a backbone for the coil form
radio or electrical work as it is
very corrosive for such work.
It is well to coat the solder
which you are using with this
flux. The flux will be found
excellent for steel, iron, copper,
brass, etc., when these metals
are not used for carrying electric
currents. The cyclometer is
held to its frame by screwing
the lug attached to it to the
block R, Fig. 2.
COLLAPSIBLE COIL FORMS
holes drilled in the disk at the end of the
star wheel shaft. The whole should be a
rather loose fit to prevent binding.
To solder steel to steel you may find that
your regular soldering flux used for bus
bar work will not work very well. "Killed"
acid is best for this purpose. This is made
of muriatic acid in which as much pure
zinc as possible is dissolved. To make this
flux pour a small quantity of muriatic acid
in an old cup. Set this cup in a pan of
RADIO 13ROADCA9T Photograph
FIG. 6
Here are the parts for the pickle-bottle coil form. Low loss coils of this
type of winding may easily and speedily be wound for use in the many
Roberts and other circuits described in past issues of RADIO BROADCAST
water to keep it cool, taking care that
no water gets in the acid. Cut up a
number of pieces of pure zinc (the zinc
covers of old B or A battery dry cells are
excellent), and put a small quantity of
the zinc clippings in at a time and add to
them from time to time until no more zinc
will dissolve. Allow the acid to stand for a
time, strain through muslin, and it is ready
to use. The parts to be soldered are
painted with it. Never use this flux for
RADIO BROADCAST Photograph
FIG. 7
The Lorenz or basketweave coil is more difficult
to wind, but when finished, is one that any ex-
perimenter would be proud to use in his receiver.
Substantial, well-wound coils do much to insure
proper operation of one's receiver. The spool
of thread also shown above is for binding the coil
turns together
*• and counter in use, starting to make
a low loss self-supporting solenoid coil.
The spool of wire is held by a large nail
which is placed between the vise jaws,
the head of the nail being tapped with a
hammer until the coil of wire may be
turned with just the right amount of ten-
sion.
The form used to make a solenoid coil of
low loss design is shown in Fig. 5. This
particular coil is of 50 turns
wound over a 3-inch form. The
form is partially collapsed to
remove the coil when it is fin-
ished. The form may be reas-
sembled and used over again as
many times as it is desired.
The outer or cylindrical part of
the form shown is made out of a
section cut from an ice cream
container which was originally
3j inches in diameter. The two
wooden disks used as the ends
of the form are cut to such a
diameter so that when the
cardboard covering is put in
place over these wooden disks,
the outer diameter of the
whole form is 3 inches. As the thickness
of the cardboard is fa inch, it will
readily be seen that the diameter of the
wooden ends is 2^f inches.
The section cut from the ice cream con-
tainer is planned so that when it is screwed
to the wooden ends there will be a space
of from ^ to j inch left open between the
ends, on the side, as shown in Fig. 4.
Directly underneath the edges are glued
narrow strips of wood about j inch square,
as at A, Fig. 6. These strips of wood sup-
port the pasteboard which might otherwise
be drawn in by the tension of the wire
when winding a coil. These two strips
should be placed in such a manner that
the edges of the form may be easily pushed
inward when the coil is wound and the
wooden ends removed, to allow for the
removal of the finished coil.
Forms for coils of practically any diame-
ter may be made up in this manner, using
such cylindrical forms as oatmeal Boxes,
mailing tubes, and the like.
Figs. 4 and 6 show the form used to make
the pickle-bottle type of coil. Like the
cylindrical form the pickle-bottle form may
be used any number of times. The paste-
board used to make this form was ap-
proximately | inch thick (strawboard
MARCH, 1926
AN ALL PURPOSE COIL WINDER
585
taken from the sides of a packing carton).
The wooden ends are then 2 inches in
•diameter across the flats. A pattern
.should first be made for these wooden ends,
which are cut from soft pine about f inch
thick. The outside of the form is made in
•one piece divided into eight equal parts,
•each dividing line being scored on the out-
^
RADIO BROADCAST Photograph
FIG. 8
When this double-wedge rectangular form is
mounted in the coil winder, it is possible to wind
a long strip of coil with a square cross-section,
so that it may be bent into a circular form, there-
by making up the much discussed toroid coil.
On page 600 of this issue, Mr. John L. Lee shows
in detail the constructional steps in making up
such a coil
side with a sharp knife to allow the paste-
board to fold down sharply over each angle
of the wooden ends to which it is screwed.
A strip about $ inch wide is cut off one
end to prevent the
edges interfering
when the form is
collapsed, and a
strip of wood A, is
glued and tacked to
one or both edges at
the end of the form
as shown in Fig. 6.
The piece (or pieces)
A are just long
enough to fit be-
tween the wooden
ends when these are
in place. The cor-
ners formed by the
angles on the outer
edges of these
wooden forms are
cut off slightly
to allow for the
bends in the paste-
board.
A j-inch hole is
drilled in one of the
wooden ends, this end being slipped over
the threaded end of the stovebolt connected
to the counter. A short brad is driven
in this end and the head of it cut off so
that it may be pushed into the hole drilled
in one corner of the nut which is screwed
on the stovebolt. By changing the diama-
ter, or rather, building a similar form of any
desired diameter, pickle-bottle coils may
be wound as called for.
When a simple solenoid coil is to be
wound, and the form is to be left inside,
circular pieces of wood are sawed out to
fit inside of each form and these are
held with screws while the coil is being
wound. Holes are of course drilled in each
disk, one hole to fit over the stovebolt and
in the second disk a suit-
able hole is drilled into
which the screw end of the
handle is inserted.
WINDING A LOW LOSS
SOLENOID COIL
THE coil forms shown in
Figs. 4 and 5 are moun-
ted in the winding machine
as shown in Fig. i. Four
strips of gummed tape are
held, gummed side up, to
the form with rubber bands.
The handle is shown firmly
screwed into one end of the
form so that it may be
turned against the tension
likely to be put on the wire, without
slipping.
Fig. i also shows how the winding is
started. A pin is pushed through the side
of the pasteboard form where it is desired
to start the winding, and the end of the
wire wrapped once or. twice around this
pin to hold it.
The gummed side of each strip of tape
is moistened with water before the winding
is started. After this, the winding may be
proceeded with, and if everything is right,
it should go very rapidly. The speed and
MATERIAL LIST FOR COIL WINDER
PART
PART
LETTER
DIMENSIONS
NUMBER
REQUIRED
Baseboard
Counter Supports
Tail Stock Base Support
Tail Stock Face
Tail Stock Sides
A
B
C
D
E
f" X 2|" X 18"
A" x 4J" x 6"
J" x 2}{" x 51"
}" x 2{J" x 4}"
A" x 51" shaped as
1
2
1
1
shown
2
Tail Stock Screw
F
1" x No. 6 Wood
Screw
1
Tail Stock Slot
G
}" x 31"
1
Handle Hole
H
1
Handle
I
i" x 4"
1
Counter Base Sides
K
i" x ;" x 6"
2
Stove Bolt
L
i" x 3"
1
Turn Counter
M
1
Counter Head Block
Counter End Block
N
O
U"xU"xli"
r x ir x u"
1
1
No dimensions are given for coil forms as the constructor must use
his own judgment in selecting the forms for the coils he wishes to wind.
FIG. 9
"Spiderweb coil forms may be mounted in the same way as the basket-weave coil form shown
here," says Mr. Thatcher. The sliding tailstock is removed when such soils are wound
accuracy with which coils may be wound
on this simple machine with an occasional
glance at the counter, will be only too
apparent.
When the required number of turns are
wound on, stick another pin through the
coil form to wrap the wire on at the end
of the winding while the paper tape is
pasted about the coil.
Moisten the ends of the gummed paper
tape which extends beyond the winding,
first removing the elastic bands and pro-
ceed to fold the ends of the moistened tape
over the winding, pressing each strip
firmly in place.
Taps may be made in coils of this kind
by lifting up a short loop of wire at the
desired turn, twisting it, and then going on
with the winding. Another winding, such
as a primary, may be wound over the first
coil, after this is wound, and the tape stuck
to it as usual, by wrapping a single layer
of Empire tape or even gummed tape,
about the first coil and then winding the
second coil on this, this second coil being
held together with strips of gummed tape as
the first one was, the form being left in
place until both coils are wound on and the
gummed tape is dry. To remove the form,
the screws are taken out, after the handle is
unscrewed, and the
coil removed from
the counter head.
Then the wooden
ends are removed,
and the pasteboard
form is pressed in at
the joint until the
coil may be easily
slipped off.
WINDING BASKET-
WEAVE AND
DIAMONDWEAVE
COILS
THE form for
winding a bas-
ketweave coil is
shown in Fig. 9
mounted on the
counter shaft. The
extra nut provided
with the stovebolt
is used to hold it in
place, a pin in the
I\ADIO BROADCAST Photograph
RADIO BROADCAST Photograph
FIG. IO
Another use for the automobile speedometer —
only here it tells you how far you've gone and
not how fast. However, with practice, the home
constructor becomes quite efficient in making the
coil turns lay side by side at an exceeding high
speed. For an explanation of the lettered parts,
the constructor should refer to the text
586
RADIO BROADCAST
MARCH, 1926
SPIDERWEB COIL
SIZE WIRE
NUMBER
OP
SPOKES
NUMBER
OF
TURNS
INSIDE
DIAMETER
FREQUENCY
RANGE
No. 24 d.s.c.
No. 20 d.c.c.
No. 24 d.c.c.
15
17
11
52
46
50
Hin.
2 in. (no form)
l}in. "
1764-500 k.c.
(170-600 meters)
2540-565 k.c.
(118-529 meters)
2630-565 k.c.
(114-529 meters)
3ASKETWEAVE
No. 18 Enamel
d.c.c.
No. 18 d.c.c.
No. 24 d.s.c.
13
14
15
58
60
64
2J" between
peg centers
4 J" between
peg centers
2J" between
peg centers
2361-500 kc.
(127-600 meters)
2290-550 kc.
(131-545 meters)
2054-495 kc.
(146-605 meters)
DIAMONDWEAVE
No. 26 d.s.c.
No. 20 d.c.c.
No. 24 d.c.c.
15
21
15
57
36
44
2J inches
2} inches
2j inches
2040-495 kc.
(147-605 meters)
2650-694 kc.
(113-432 meters)
1 764-560 kc.
(170-535 meters)
pictures to show up better,
but plain uncolored cotton
string is usually recom-
mended for this purpose.
On the right of the top il-
lustration on page 582 will
be noticed a form for wind-
ing a diamond weave coil.
Grooves are shown in the
face of the central part of
this form. After the wire
is wound on the form, the
flexible needle is used to
thread the string up
through the winding as each
peg is removed.
DATA ON SPECIMEN COILS
THE data in the
shown elswhere on
other side engaging the hole in the first
nut. Spiderweb coil forms may be mounted
in the same way, except that a common
pin may be pushed through the form, and
through the hole in the nut, before the
second nut is screwed in place.
It will be noticed that opposite every
peg in the form shown in Figs. 7 and 9
is a deep groove, the top of which extends
into the hole for the peg.
These grooves are" made by first mak-
ing a cut with a saw and then enlarging
this with a three cornered file or a sharp
knife.
The reason for these cuts is as follows:
After the winding is finished, a flexible
needle, about 3 inches long is used with
string to sew the coil together as each peg
is removed.
The flexible needle is made of a piece of
copper wire about No. 20 gauge, bare or
enamel covered, it being doubled to form a
loop at one end. The other end, or ends, are
held together by a drop of solder which is
rounded over with emery cloth to remove
any sharpness. The needle thus made,
being very soft and flexible, may be bent
to a suitable shape to be passed into the
slot in the side of the form and up through
the top of the winding, after each peg is
removed. Black thread is used in the
RADIO BROADCAST Photograph
FIG. I I
An unassembled view of the turn counter and
support frame. With care, the shaft P should
be filed so that it engages the slot in the head
f the bolt L on which the coil for m is mounted
table
this
page will serve as a guide
to those constructors
wishing to wind coils for
use in tuned circuits. In the first test
to determine the correct number of coil
turns, a .ooo5-mfd. variable condenser was
employed.
From the table it will be noted that
for each type of coil the wire size,
number of spokes, number of turns, and
coil diameter is different for each three
examples, yet the frequency spectrum
(wavelength range) does not differ
greatly.
With a .ooo35-mfd. variable condenser,
the secondary sizes for the above types of
coils will take not more '• than 80 turns.
Usually 77 is correct. The correct value
varies slightly with changes in coil diameter
and wire size. If the tuned circuit is found
to tune to frequencies below the range de-
sired, then remove a turn at a time until
the lowest frequency (longest wave) you
wish to tune to is tuned-in somewhere near
the high end of the condenser
scale, usually between 90 and
100.
The primary and tickler
coils for use with these
secondaries should have
about one third the number
of turns as the secondaries.
For a tuned radio-frequency
amplifier circuit, employing
no neutralization system, it
will be well to reduce the
primary turns to from six
to ten, otherwise oscillation
in each stage will be un-
controllable.
It will be observed that
the number of turns for a
coil, tuned with a .ooo5-mfd.
condenser, is approximately
60, and conforms to a cer-
tain degree with the Induc-
tance chart prepared by Mr.
Homer Davis on page 587.
With this coil winder it is
also very easy to make up
such coils as are shown in
Fig. 12, which represents the
RADIO BROADCAST Photograph
FIG. 12
For the experimenter who desires the last word
in low loss, Mr. Thatcher offers this space wound
coil, which he wound on his indispensable coil
winder. A thread is wound with the wire,
separating turn from turn. When the coil is
completed and fastened together, the thread is
removed
latest design in space wound solenoids.
An ordinary cylindrical form can be used,
such as is shown in Fig. 5. A piece of
heavy thread is wound in parallel with
the wire so that all the turns are sepa-
rated, and when the coil is finally completed,
the thread separator is removed leaving
a space wound solenoid very well adapted
for use in tuned radio frequency circuits.
Adhesive tape is employed to keep the coil
together. By referring to Fig. 12 it will
be clearly seen how the tape is arranged.
In order to obtain the same inductance,
a coil of this type will require a few more
turns than are necessary for a solenoid
that is not space wound. Because of its low
loss features and low distributed capacity,
due to the spacing between turns, the wave-
length range of this coil is, in general, some-
what greater than that obtained with an
unspaced winding.
KIND OF INSULATION
ENAMEL
B. & S.
Dec
sec
DSC
ssc
ENAMEL
AND
AND
GAUGE
sec
SSC
14
13 7
14.6
14 7
15 0
15 2
14 2
14 7
15
16
15 0
16 7
16.2
18 0
16 4
18 2
17 0
19 0
17 0
18.7
15 8
17 6
16 5
18 4 I
17
18.5
20 0
20 0
21.2
21 4
19 5
20 5 1
18
19 6
22 3
22.3
23 6
24 0
21 7
22 9 I
19
22 5
25 0
25 2
27 0
27 2
24 2
25 8 1
20
24 5
27 5
27 5
29 5
30 1
26 5
28 4 I
21
27 5
30 8
30 8
32 8
33 6
29 6
31 5 1
22
30 0
34 0
34 0
36 6
37 7
32 7
35 0 1
23
32 7
37 5
37 5
40 7
42 3
36 1
39 0 1
24
35 5
41 5
41 5
45 3
47 2
39 7
43 I !
25
38 5
45 7
45 7
50 3
52.9
43 7
47 9 I
26
41 8
50 2
50 2
55 7
59 0
47 8
52 8 !
27
45 0
55 0
55 0
61 7
65 8
52 1
58 I !
28
48 5
60 0
60.0
68 3'
73 9
57 0
64 4 t
29
52 0
65 5
65 5
75 4
82.2
61 9
706 j
30
55 5
71 3
71 3
83 1
92 3
67 4
77.9 I
31
60 0
77 3
77 3
91 6
103 0
72 8
85 3 !
32
62 7
83 7
83 7
101 0
116 0
79 1
93 9 I
33
66 3
90 3
90 3
110 0
130.0
85 6
103 0 1
34
70 0
97 0
97 0
120 0
145 0
91 7
112 0 |
35
73.4
104 0
104 0
131 0
164 0
98 8
123 0 \
36
77 0
111 0
111 0 '
143 0
182 0
105.0
133 0 |
37
80.3
126 0
126 0
155 0
206 0
113 0
146 0 1
38
83.5
133 0
133 0
168 0
235 0
120 0
157 0 1
39
89 7
140 0
140 0
181 0
261 0
128 0
172 0 1
i
1
FIG 13
This table, giving the number of turns per inch of various
kinds of wire, is to be used in conjunction with the capacity-
inductance data table printed on the following page
MARCH, 1926
AN ALL PURPOSE COIL WINDER
587
d n Index Line 1 L
A C
12-
10-
-20
r. 00001
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JO
10-
9-
30
-40
•
8-
40
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-.00002
15-
~ %
-60
-
50
6-
:
' 60
-80
- .00003
5-
20-
*\
:»
-80
-100
- .00004
',
X.
CO
: 100
-.00005
4-
25J
^-x
X ""^
- i |
-150
- .00006
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£ 30-
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5-
UJ
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• 150
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200 £
' <
- .00008
3-
I :
Q.
CO
r~ !
Z
r 200^
-250 "***• N
|
2
Ql
-300 |
-.0001
-
a 40-
|
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X
-400
2-
i-
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"N^ LL.
x^
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- .0002
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CO
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UJ
§
-600
1
^800 >^ |
- .0003
Hr
60-
z
4 G
a
r 800
- 1000 ^ \
-.0004
-
70-
5 ^
1000
; \,
-.0005
- 6
- 1500
»-
80-
90-
n JL
W
- 7
- 8
- 1500 K^
o i — .
-2000
-.0006
-.0008
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100-
d^^^ ^*"**^ i
r 9
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»i-l 150 J
V vV_
J
CHART II
CHART I
Connect three known values as per key. and read fourth at point
of intersection.
Example: If L-170 mh., A-3" and n=196, then 1-3"
Connect two known values and read third at point
of intersection.
Example: If A - 550 m. and C-.0005 mfd then L 170 mh
COIL DATA CHART
With the aid of this chart, a ruler, and pencil, the experimenter can very simply determine the approximate specifications for a solenoid coil to cover a
definite frequency spectrum (wavelength range) with any condenser on hand. Full information for its use was contained in an article by Mr. Homer
Davis, on page 46 of the May, 1925, issue of RADIO BROADCAST.
Briefly, the chart is used in the following manner:
Suppose the constructor has a .ooo5-mfd. variable condenser and he wishes to cover a tuning range whose extremes are 545 kc. and 1500 kc. (550 to 200
meters). Therefore, he must wind a coil so that, with the condenser plates entirely meshed, the tuned circuit, comprising coil and condenser, will
respond to 545 kc. (550 meters). The problem is to first determine the inductance value in microhenries. By connecting together with a ruler and pencil
the values of capacity (.0005 mfd.) on column C and the wavelength extreme (550 meters) on column X (wavelength), and continuing this line so that it
intersects column L, a value of L (inductance) is denoted.
Now, knowing the size of wire he is to use. the constructor looks for the number of turns to the inch for that particular size of wire as indicated on the
wire table, Fig. 13, and then spots this position on column "n" above. If No. iSd.c.c. is to be used, the number of turns per inch will be 19.6. Then he,
knowing the diameter of the coil he is to wind, draws a line from the diameter figure point on column "d" to the inductance value in microhenries on column
L, determined previously. This latter line between d and L intersects the index line. Now from the spotting on column n (19.6 if 18 d.c.c. be em-
ployed), a line is drawn to pass through the point of intersection on the index line continuing on to the column L, thereby indicating the approximate
length in inches of the coil to be wound. Knowing this value, then L times n equals the number of turns for the complete coil.
THE ASSEMBLED WINDER
Clamped to the bench and ready
for work. By comparing this pic-
ture with the illustration Fig. i,
which shows the winder in opera-
tion, it will be plainly understood
how the solenoid form — and other
forms too for that matter — are
fixed to the winder
Tests
By WILLIS K, WING
[EVERAL days before the Third International Radio
Broadcast Tests are completed, it is a difficult matter
to prepare anything more than what the newspapers
refer to as a "bulletin" on the general success or failure
of the most elaborate of the inter-nation broadcasting efforts
which have yet taken place. A story on the results of the Tests
will appear in RADIO BROADCAST for April, after sufficient time
has elapsed for
the thousands
and thousands
of reports to be
sifted and veri-
fied. Now, with
a desk loaded
with telegrams
and detailed re-
ports of recep-
tion of foreign
stations con-
tained in letters,
covering recep-
tion for the first
few nights of the
Tests, it is not
possible to pre-
sent all the facts.
Most of the
news of immedi-
ate interest to
radio listeners
has been furn-
ished them al
ready through
their news-
papers and in
that field a
monthly maga-
zine cannot hope
to compete.
But at Inter-
national Test headquarters here in Garden City we have the
reports of eager listeners who carefully tuned to the foreign
"wavelengths, and praises be to their radio souls, lots of them
heard the coveted distant stations!
In brief, the first three nights of the Tests were very poor for
receiving, at least on the East coast of the United States and in
the Middle West. On the first two nights, reception was
moderately good north and south and indifferently good east
.and west — the most important directions to the great body of
American listeners. There were few indeed who reported
reception of the English stations on Sunday, January 24th and
of the Continentals on Monday, the day following. And, to
top it off, and not to make excuses, but rather to state a sad fact,
the oscillating receiver reared its electrical head and made
reception well-nigh impossible for many listeners whose receiv-
ing equipment was efficient and sensitive enough to have a good
chance of hearing the foreign broadcasts. If ever the genuine
menace of the radiating receiver was demonstrated, it was
demonstrated during these Tests.
On Tuesday night, the 26th, American listeners were more
successful, and Cardiff and Aberdeen were reported in a con-
siderable number of localities. Mail from the Middle and far
West has not yet reached Garden City, so it is not possible to
-say at this time how successful listeners in those parts of the
United States were in hearing English and Continental broad-
casts on that night.
But on Wednesday night, the 2?th, in the Eastern part of
the United States, weather conditions had greatly improved and
reception from the Middle European stations seemed to be much
better, many verified reports being received on Hamburg and
Prague, as well as on Madrid. The South American stations,
too, seemed to come in better than before and the three Buenos
Aires stations and the faithful OAX at Lima, Peru succeeded in
reaching a con-
siderable num-
ber of listeners.
During the
first three nights
of the interna-
tional experi-
ment, there were
storms at sea, as
a number of sos
calls gave evi-
dence that ships
on the Atlantic
were having
their own troub-
les— far more
serious than the
uncertain recep-
tion American
listeners had to
face. The con-
firmation pro-
grams from many
cf the Continen-
tal broadcasters
which were for-
warded to Gar-
den City by
D wigh t K .
Tripp, the rep-
resentativeof
RADIO BROAD-
CAST in Paris, by
courier on the S. S. Leviathan were held up two days by a delay
of that length in the arrival of the ship, due to the heavy
weather on the Atlantic.
Of dramatic happenings, there were many, and it is hoped
they can be chronicled in the April number of this magazine.
There is the story of the experiences of those of the staff who
took a broadcast receiver out to a thinly populated corner of
Long Island, far from telephone or telegraph and connected
with headquarters only by a battery-operated short wave
transmitter and receiver, but that will have to wait.
In England, early cablegrams from Percy W. Harris, editorial
manager of Radio Press, the English organization appointed by
RADIO BROADCAST in charge of the Tests there, indicate that
our fellow British enthusiasts were not highly successful in
receiving American broadcasts during the first two days of the
transmissions. There has not so far been time for reports
more complete than that. Receiving conditions in England
seemed to be exceptionally poor during the early part of the
Test week.
Reports of reception of the foreign broadcasts, which are
coming in to the offices of RADIO BROADCAST by mail and tele-
graph are being answered as promptly and completely as
possible and an official card of verification is being sent to those
fortunate enough to have heard any or all of the foreign stations.
Those who have not yet sent in their report are urged to mail
it in and to make it as complete, but as brief, as possible.
© Rand, McNally
Super-Heterodyne Construction
In Which the Various Sections of a Super-Heterodyne Are Described
in Turn — Timely Hints and Constructional Data are Qiven for the
Benefit of Those Contemplating the Construction of Such a Receiver
By HAROLD C. WEBER
A GREAT DEALof misunderstand-
ing seems to exist at present in re-
gard to just what advantage the
super-heterodyne type of receiver
has over other circuits. In the opinion of
the writer a Roberts receiver properly con-
structed gives all the selectivity, and by
the addition of two stages of audio fre-
quency amplification, all the volume one
could desire. It is remarkably free from
distortion, and if one lives in a locality
where a good outdoor antenna can be
erected, there is some doubt in the author's
mind as to whether the super-heterodyne
will produce results any more satisfactory
than those obtainable by the more simple
Roberts circuit. The big advantage ob-
tained by the use
of the super-
heterodyne circuit
is its ability to
work on a small
loop and, in so
doing, produce
just as good re-
sults as can be
obtained by other
sets with the aid of
an outdoor an-
tenna. From this
it can be seen that
the super-hetero-
dyne finds its
greatest use in
thickly populated
sections where it is
difficult to erect a
satisfactory out-
door antenna. The
builder of a super-
heterodyne may
expect to obtain
the same results
on an eighteen-or
twenty-inch loop
with his super-
heterodyne that
he has been obtaining in the same location
with an outdoor antenna on either a good
neutrodyne, for example, or a Roberts set.
If he lives on the Atlantic Coast, and has
been unable to receive Pacific Coast sta-
tions with his Roberts or neutrodyne set,
it is doubtful whether he will be able to do
any better with a super-heterodyne working
on a loop. Attempts to make the super
work on a large outdoor antenna are for the
most part unsatisfactory, due to its great
sensitivity. The weakest winter static
noises resembled in volumea heavy thunder-
storm, after passing through the set. Of
course, working the super-heterodyne on an
outdoor antenna has the further disadvan-
tage that considerable annoyance will be
caused to one's neighbors unless a buffer
or blocking tube is used in front of the
first detector.
The discussion will now be turned to the
various component parts of the super-
heterodyne, and as each section is discussed,
various experimental results which have
been obtained will be pointed out.
THE FIRST DETECTOR
THE first detector circuit of the beat
type receiver is really little different
from any other detector circuit, and it is
CIRCUIT DIAGRAM OF THE AUTHOR'S RECEIVER
A nine-tube super-heterodyne. The only controls appearing on the panel are the two condenser dials,
three rheostat knobs, a potentiometer control, and a single jack for headphone use. The loud speaker
is put in operation by merely pulling out the phone plug and turning on the audio rheostat
imperative that if one wishes to obtain satis-
factory results the same care be exercised in
building this part of the set as would be ex-
ercised in the construction of any good low
loss one-tube receiver. This means that
the condenser used for tuning the loop must
be a good one. Its capacity should not be
more than .ooo5-mfd., and it should be
equipped with a smooth-acting vernier dial.
Considerable discussion has been raised as
to whether this first detector circuit should
be operated with a grid leak and a grid
condenser or with a C battery. The author
has tried both schemes and believes that
there is nothing to be gained by the
use of the bias battery. In all of the
sets he has constructed results obtained
with the grid leak and the grid con-
denser fully equal those obtained with a C
battery. The use of regeneration on the
first detector tube will be found helpful.
This is most easily accomplished by the
use of a. split loop, as pointed out in Mr.
Silver's article in the July, 1925, RADIO
BROADCAST. It is not necessary to use the
midget variable condenser as he suggested.
One may wind the loop with bare copper
wire, and then place the center tap on that
point of the loop where the first detector
just refuses to oscillate. In place of the
midget condenser
a.ooo25-mfd. fixed
condenser may
then be used. If
the loop contains
about fourteen
turns of wire, it
will be found that
the best point for
the mid tap is ap-
proximately four
turns away from
that end of the
loop which is con-
nected to the grid
return, or ten
turns away from
that side of the
loop connected to
the grid.
One point seems
to have been over-
looked in this first
detector circuit
by a great many
constructors; that
is, the necessity
for providing a
low resistance
path for the high-
frequency oscillations in the plate circuit
of the first detector. No one would think
of constructing a single-tube regenerative
set without the use of a proper phone by-
pass condenser, and yet a great many super-
heterodyne constructors neglect to use a
bypass condenser at the same point in
their super. This bypass condenser need
not be larger than about .00015 to .00025
mfd. and, in fact, if the split-loop method
is used, the condenser which must be in-
cluded in the circuit will serve the double
purpose of providing regenerative feed-
590
RADIO BROADCAST
MARCH, 1926
back and a low-resistance path for the high-
frequency currents. The detector circuit
must be coupled to the oscillator in some
manner, and this can be done by coupling
on to the plate circuit of the detector or
to the grid circuit. Personally, the author
feels that slightly better results are obtained
by grid-circuit coupling than by plate-
circuit coupling. The pickup coil may be
placed either on the grid side of the loop or
on the grid return side. The most satis-
factory place for this coil seems to be be-
tween the grid return and that point where
the tuning condenser connects to the
loop. The coupling coil is shown con-
nected in this position in Fig. i.
Here again authors seem to differ as to
the proper number of turns to be used
for coupling. Anything from one turn
to six turns seems to work satisfactorily
on the broadcast wavelengths. Re-
sults obtained using from about six
to thirty-five turns seem to be some-
what less satisfactory. Satisfactory
operation is again obtained by the use
of anywhere from thirty-five to fifty
turns on the coupling coil. This may mean
that the detector circuit can be coupled to
the oscillator circuit either capacitively or
inductively. Evidently, the transfer of
energy is mostly by induction with the low
number of turns in the coupling coil, and
perhaps mostly by capacity when a large
number of turns is used. It does seem,
however, that there is a range from ap-
proximately six to twenty-five or thirty
turns where results are inferior to those
obtained either above or below this figure.
Incidentally, there appears to be little
actual advantage gained in making the
coupling coil movable.
THE OSCILLATOR
THE oscillator is an extremely impor-
tant part of any super-heterodyne.
The author has found the Hartley oscillator
circuit to be the most satisfactory. If a
3o-kc. (io,ooo-meter) wave is used on the
intermediate amplifie-, a suitable construc-
tion for the coils in this circuit is two twenty-
seven turn coils wound with No. 22 or 24
double silk-covered wire on a thin bakelite
or cardboard tube, approximately 2j inches
in diameter. Both coils are wound in the
same direction. The proper method of
connecting these coils in the oscillator cir-
cuit is shown in Fig. 2, and the coupling
coil in the first detector circuit should be
placed at the grid coil end of the oscillator
coil unit rather than at the plate coil end.
, FIG. I
Serious difficulty will no doubt be experi-
enced with harmonics if oneattempts to use
more than twenty-five or thirty volts on
the oscillator tube. Perfectly satisfactory
results can be obtained with ten or twelve
volts on the oscillator tube using 2OI-A
type tubes. If the coupling coil of the
first detector is coupled too closely to the
oscillator circuit, some difficulty may occur,
due to the fact that the oscillator will stop
functioning whenever the first detector
circuit is tuned to approximately the same
wavelength as the oscillator. This diffi-
culty is easily overcome by loosening the
coupling betweenthe detector and oscillator
circuits.
Too much care cannot be exercised in the
selection of a suitable tube for use in the
oscillator. This is one of the most critical
tubes in the whole set, and several should
be tried in this position until one is found
that functions satisfactorily. No station
should be heard at more than two points on
the oscillator dial in a properly constructed
super-heterodyne. Most stations, even
powerful locals four or five miles away, can
be completely tuned out by a movement of
less than one degree on the oscillator dial if
the set is working properly. The same
sharpness of tuning holds for the first de-
tector circuit, if proper care is used in its
construction, and low-loss parts are used
throughout.
INTERMEDIATE FREQUENCY AMPLIFIER
SO MUCH has been said about inter-
mediate-frequency amplifiers in vari-
ous articles that the author really hesitates
to add anything. A long discussion has
been waged as to the relative merits of the
air-core transformer versus the iron-core.
It is usually admitted that it is much easier
to amplify at a frequency of thirty kilo-
cycles than at the higher frequencies to
which most air-core transformers are
tuned. Most iron-core transformers have
their peak at about thirty kilocycles (10,000
meters), whereas the air-core transformers
work at a very much higher frequency
(shorter wavelength). This means among
other things that, in general, more grid bias
can be applied to an intermediate-frequency
amplifier, using iron-core transformers,
than to one using air-core transformers. Of
course, increasing the grid bias decreases the
B battery consumption, and when one is
using anywhere from six to nine tubes, B
battery current becomes an item of major
importance. Offsetting this gain obtained
by the use of iron-core transformers rather
than air-core ones is the fact that unless the
iron-core instrument is carefully designed,
there is a great tendency for it to amplify at
audio frequency, and therefore to be very
noisy. If one uses the higher grade types
of iron-core transformers now available, no
difficulty will be experienced with noises
from the intermediate-frequency amplifier.
RADIO BROADCAST Photograph
A SEVEN-TUBE SUPER-HETERODYNE
Note the copper shield between the first and second tube units (at the right)
MARCH, 1926
SUPER-HETERODYNE CONSTRUCTION
591
Shielding will
formers, etc.,
If the set is properly constructed, the in-
termediate-frequency amplifier often can
be run with the potentiometer arm com-
pletely over to the negative side, and it
will be found that often a few volts of C
battery can be added to this circuit.
It is claimed that, unless the set is very
thoroughly shielded,
ten thousand meter
transformers will be
likely to oick up long-
wave code signals.
It is felt that most of
the trouble experi-
enced by the users of
ten-thousand meter
transformers in this
respect is due to the
fact that their leads
have been made too
long. The best plan
at the present time
seems to be to mount
the long wave trans-
formers, if they are
of the iron core type,
directly under the
tubes to which they
are to be connected,
and then, if trouble is
still experienced, to
try grounding the
metal casings with
which most long-wave
transformers are now
protected. In fact, grounding the casings
of these transformers is usually found
advantageous in any case.
Jhe question of tuned input versus tuned
output for the intermediate-frequency am-
plifier has long been a debated point. It
has been argued that tuned output does
offer some advantage in that a sharply
tuned transformer will not pass any audio
frequency which may be picked up by the
first transformer in the train. This tends
to cut out noise in the set. The author has
tried both tuned input and output on the
same set, and has come to the conclusion
that, with the better makes of long-wave,
iron-cored radio-frequency transformers
now on the market, little trouble will be ex-
perienced from transformer noises in any
case. There is one advantage that the
tuned input circuit does have over the out-
put circuit. It will be remembered that
reference was made to the bypass con-
denser which is quite necessary across the
primary circuit terminals of the first long-
wave transformer in the first detector cir-
cuit. Placing a bypass condenser at this
point is not'Very helpful to the amplifying
action of the transformer, providing it is
an iron-core instrument; but if a tuned
air-core transformer is used at this point,
the fixed condenser necessary across its
primary terminals serves the purpose of a
bypass for the high-frequency oscillations
as well as serving as a means of tuning for
the transformer. From this point of view
it might be argued that tuned input does
have some advantage over tuned output.
Of course, if one is using a split-loop method
for obtaining regeneration this advantage
does not appear, and under these considera-
tions it is doubtful whether either a tuned
input or a tuned output offers any advan-
tages. Surely any good iron-core trans-
former, when used in a properly constructed
super-heterodyne, will give all the selec-
fixed condenser across the primary of this
instrument, and approximately a .00025
mfd. fixed condenser across the secondary.
Inasmuch as many small fixed condensers
vary somewhat, it may be necessary to try
several before satisfactory results are ob-
tained. If access can be had to a wave-
meter tuning as high
as 30 kc. (10,000
meters) of course one
can design his trans-
former so that it will
exactly match the
peak on the iron-core
transformers which
are to work with it.
A good intermediate-
frequency amplifier •
will usually give all
the amplification ne-
cessary with two
stages, and it K very
doubtful whether one
should ever use more
than three stages.
THE SECOND DETEC-
TOR AND AUDIO
AMPLIFIER
RADIO BROADCAST Photograph
A COPPER LINED CABINET
prevent body capacity effect* and also prevent the coils, trans-
picking up the transmitted waves thus impairing the efficiency
tivity in tuning that could be desired,
especially if the first detector is made regen-
erative. For those who are interested in
experimenting with tuned input and output
circuits, the following specifications will be
found useful in constructing an air-core
transformer having a peak at about 31 kc.
(9600 meters); primary, 750 turns No. 30
d. s. c. wire, random wound on a form
having a central opening £ of an inch in
diameter and ^ of an inch wide. Secon-
dary, two 8oo-turn coils connected in series
and wound with d. s. c. wire on the same
THE second detec-
t
FIG. 2
form as the primary was wound on. The
two secondary coils are to be placed one on
either side of the primary coil. If these
coils are wound on a suitable collapsible
form, they can be lightly doped with collo-
dion and made self-supporting, thus doing
away with any supporting form. In this
way some slight increase in efficiency can
be had over coils wound on solid forms.
It will be necessary to shunt a .001 mfd.
tor usually gives
very little trouble in
any set. Rather a low
value grid leak seems
to work best in this
circuit, usually about two to four megohms
and, of course, the phone bypass condenser
should not be omitted. Here again experi-
ment will show the best value for this con-
denser. Usually a condenser with a ca-
pacity of from .001 mfd. to .006 mfd. will
be found most suitable, preference being
given to the low values.
A good super-heterodyne will give all the
volume that one could desire for headphone
use without any audio amplifier, even when
receiving distant stations on the loop. For
loud-speaker operation one, and possibly
two stages of audio frequency amplification
may be added. Here again the use of good
transformers cannot be over emphasized.
If the constructor is willing to pay a high
price for one of the new type high ratio
audio-frequency transformers now on the
market, all well and good; otherwise he will
probably obtain the most satisfactory re-
sults by not attempting to use a transformer
having a ratio of more than 3 or 35 to i.
Some of the newer transformers mentioned
above will amplify in a very satisfactory
manner even though they do have ratios of
5 or 6 to i. Such a transformer cannot,
however, be constructed cheaply due to the
fact that it requires a heavy core and an
exceedingly large number of turns on its
secondary. Unless the set is to be used in
a large room or hall, one good stage of audio-
frequency amplification will usually give
enough volume for satisfactory loud-
speaker operation. If a second stage is
desired, it had best be either of the power
type using some such tube as the uv-2O2 or
the Western Electric 2i6-A, or perhaps.
592
the push-pull construction which has
been quite popular during the last year
or two.
The second stage of audio-frequency
amplification handles exceedingly heavy
currents, especially on local signals, and
any ordinary receiving tube will become so
overloaded that bad distortion will occur.
Some discussion has been raised as to the
necessity for a filter before the audio-
frequency amplifier to keep the inter-
mediate-frequency currents from entering
it. It is doubtful whether such a filter will
be found necessary if careful construction
work is done. The use of large bypass
condensers (.5 to i.o mfd.) across both the
amplifier and detector sections of the B
battery, will aid in keeping these currents
out of the audio circuits.
GENERAL CONSIDERATIONS
IF ONE is going to the expense of building
a super-heterodyne, the author would
by all means advise the use of storage bat-
tery tubes, except in those cases where a
portable set is desired, or where the charg-
ing of storage batteries is a great inconveni-
ence. The B battery current drawn by
a super-heterodyne, although it is large,
need not be excessive. The author's own
set, using nine ov-2 tubes, draws but eight
to ten milliamperes of B battery current and
from i£ to if amperes on the A battery
side, by actual measurement. If more than
twenty milliamperes are drawn in the B bat-
tery circuit by a super-heterodyne using
RADIO BROADCAST
Considerable care must be exercised
in the selection of tubes for the in-
termediate-frequency amplifier, and it
may be necessary to try several dif-
ferent arrangements of tubes in the
set before a really satisfactory ar-
rangement is found. The operation
of the whole set may be ruined by one
faulty tube anywhere before the second
detector.
A great many times it will be found
that the loop does not have much
directional effect and that it can very
often be built inside a cabinet housing
the set with practically no loss in
signal strength. This is true with the
author's own set, and such a construc-
tion does much toward improving the
appearance of the set and protecting
the loop and its connections from dirt
and injury.
A comparison of the results obtained
by the author using his set, with
those results obtained using other sets
in exactly the same location, may be
of interest. The set is located in one
of the suburbs of Boston. Several
years ago a three-tube set, employ-
ing the three-circuit tuner, was used
in the same place with a three-wire indoor
antenna about thirty-five feet long and
twenty-five feet high. New York stations
could be heard on the loud speaker regularly,
and Chicago stations occasionally. About
two years ago a five-tube neutrodyne set
was installed. This employed three stages
MARCH, 1926
Primary and Secondary
Tuning Condenser
Dubilier No. 601
op V Hard Rubber
^Supporting Leg
'^"RubberRod
Hard Wood Dowel
• Carrying Wooden
Discs Supporting Coil;
Secondary Coil
Primary Coil Secondary Coil
1st Del
ut RE
2 nd R.F.
3rd R.F. Tuned Output 2nd Del,
Transformer
1st Audio
2nd Audio
Audio
Output
Transf.
LAYOUT DIAGRAM
Of the essential parts of a nine-tube superheterodyne using two stages of audio, the second stage being
push-pull. Note the position of the oscillator tube, coils, and condenser, as far away from the first detector
as possible. The long wave transformers are mounted under the three radio frequency tubes feeding
into them, and are not shown in this sketch
FIG. 3
A sketch of the author's 96oo-meter tuned out-
put transformer drawn approximately to scale
push-pull, gives consistent loud speaker
operation on Chicago stations and fairly
consistent loud speaker operation on Cuba
and the Texas stations. London's 2 LO was
heard on the loop twice during last year's
transatlantic tests, once on the loud speaker.
The author does not feel, however, that
the present super-heterodyne, working on
its built-in loop, is any more effective as a
distance getter than was the previous neu-
trodyne set working on the thirty-five
foot indoor antenna. Of course there
is the advantage that the present
set has but two tuning controls.
Whether or not the super-hetero-
dyne is enough better than the
other good circuits known to-day to
justify the extra expense demanded
in its construction and operation,
is still a debatable question.
In conclusion let it be repeated that
it is impossible to overestimate the
undesirability of operating the super-
heterodyne on an outside antenna.
Even when a loop is employed it is
possible to interefere with other re-
ceivers in the same building. For
successful operation the type of re-
ceiver depends on the fact that it is
a miniature transmitter, and as such,
will cause considerable interference
if coupled to an outside antenna.
iron-core transformers, it is probable that
there is something wrong somewhere in the
set.
Any voltage from 45 to 90 is suitable
for use on the intermediate-frequency
tubes. For best results, one should not
use more than 20 to 30 volts on the de-
tectors.
In order to use as few rheostats as possi-
ble, the two detectors may be operated from
one rheostat, the three intermediate ampli-
fiers from a second, the oscillator perhaps
from a third, while the audio amplifiers
may well be run through fixed resistance
units rather than from a rheostat.
of neutralized radio-frequency amplifi-
cation and two stages of audio-
frequency amplification, one of the
latter being reflexed through one of
the radio tubes. Loud speaker opera-
tion on the Chicago stations was pos-
sible, using the same antenna as
outlined above; fairly consistent loud-
speaker signals on stations as far
south as Cuba and Texas were ob-
tained. The present set, a nine-tube
super-heterodyne, using three stages of
intermediate-frequency 3O-kc. amplifi-
cation and two stages of audio-frequency
amplification, the second stage being
)
i-
i
^Dr
«S!
/ =
.00025
— 0
&II
™ C i^
mfd.
^^^
sss
^>
£«2
Mil.
r
- B +
THE C BATTERY CONNECTIONS
On the first detector tube to obtain grid bias.
The potentiometer used here must be a high
resistance one of about 1800 ohms. The high
frequency bypass condenser may be seen directly
across the first transformer primary. This is the
method of connecting the condenser when re-
generation is not used on the first detector
RADIO BROADCAST ADVERTISER
£93
The Newest
Achievements of
LEY
Industrialist — Pioneer Radio Builder — Master of Mass Production
Four Entirely New 4- and 5-tube
Radio Sets— Also the Crescendon
Never before has Crosley engineering and man-
ufacturing genius been so brilliantly demon-
strated as in this group of new Crosley sets.
Here, at prices so low as to be literally revolu-
tionary, are three 5-tube sets and one 4-tube set
—entirely new in principle, design, circuit,
and appearance — entirely unique in the results
they give on distant and local stations — en-
tirely unprecedented in the values they now
introduce.
On two of these sets is offered the Crescendon,
a new and exclusive Crosley feature — an extra
volume control by which average incoming
signals can be built up or modified in a manner
nothing short of amazing. Introduced on the
new 4-29 and 5-38, the Crescendon principle
makes its first appearance in the low price field,
its use having hitherto been restricted to one set
costing several times as much.
Particular emphasis is directed to the new
Crosley RFL receiving sets that utilize an en-
tirely new and patented circuit which provides
true cascade amplification and closely ap-
proaches the theoretical maximum of efficiency
per tube. Non-oscillating at any frequency and
absolutely non-radiating, the RFL Crosleys are
specifically recommended for use in congested
areas and for satisfactory performance in the
hands of inexperienced operators.
In addition to their truly marvelous selectivity,
sensitivity, and purity of tone, these new Cros-
leys have been given a new order of beauty that
cannot help but win the highest admiration.
We do more than urge you to go to the nearest
Crosley dealer for a demonstration ! We ask
you to go prepared for the most startling reve-
lation in radio ever announced in the entire his-
tory of th« industry — and predict that your ex-
pectations will be more than satisfied!
Croslfy manufactures radio receiving sets which are licensed under Armstrong U. S. ^^
Patent No. 1,113,149, or under patent applications of Radio Frequency Laboratories, Inc.
THE CROSLEY RADIO CORPORATION, CINCINNATI, OHIO
Owning and Operating WLW first remote control super-power broadcasting station in America
The Crosley 4-
in which the Crescendon is
equivalent to one or more
additional tubes of tuned
radio frequency
amplification . .
The Crosley 5- tube— 5-38
All the volume, selectivity,
sensitivity and purity of
tone available in the best
5-tube set — plus
the Crescendon
The Crosley S>tube—RFL-M
A set so marvelous in per-
formance that its appearance
on the market is bound to
create a new stand-
ard of comparison
The Crosley S- tube— RFL-7S
For simplicity and speed in tuning,
fidelity of tone, and decorative
beauty — it stands unchal-
lenged at twice the price
West of the Rocky Mountains all prices as published are 10% higher
BETTER- COSTS
•jf Tested and approved by RADIO BROADCAST
LESS
594
RADIO BROADCAST ADVERTISER
ASK - . ANY . . RADIO . . ENGINEER
An every-night
adventure of Burgess
Radio Batteries
ONE of the reasons why
you should always buy
Burgess Radio Batteries is
that the batteries used by air'
mail pilots — battleships — ex'
plorers— and the majority of
recognized radio engineers—
are evolved in the Burgess
Laboratories and manufac'
tured in the Burgess factory.
These batteries are identi-
cal with the batteries sold
by your dealer and thousands
of other good dealers every
where.
BURGESS BATTERY COMPANY
GENERAL SALES OFFICE: CHICAGO
Canadian Factories and Offices:
Niagara Falls and Winnipeg
BURGESS
RADIO
BATTERIES
A Department Devoted to Solv-
ing the Problems of our Readers
QUERIES ANSWERED
1. HOW MAY I OBTAIN A VARIABLE VOLTAGE
SUPPLY FROM MY B BATTERY ELIMINATOR
FOR THE PLATES OF MY RADIO FREQUENCY
AMPLIFIER TUBES?
R. A. W.— New York City.
2. WILL YOU PUBLISH A SIMPLE CIRCUIT DIA-
GRAM FOR A LOOP R. F. RECEIVER?
F. M. — Cape May, New Jersey.
3. WHAT is THE BEST WAY OF MAKING MY
OWN GRID LEAKS FOR EXPERIMENTAL PUR-
POSES?
M. L. H. — Bay Shore, Long Island.
4. WHAT ARE THE OPERATING CHARACTERIS-
TICS OF THE NEW TUBES?
C. A. B.— Little Rock, Arkansas.
5. I HAVE D. C. IN MY HOME. HOW MAY I
CHARGE MY STORAGE BATTERY?
L. P.— New York City.
SEPARATE R. F. TUBE VOLTAGE FROM B BATTERY
ELIMINATORS
M'
OST B battery eliminators are so con-
structed that only two distinct voltage
values are obtainable, a variable one
for the detector tube and a fixed figure for the
audio amplifier. When a receiver employing
radio frequency amplification is used, it is
therefore necessary to apply the same potential
to the r.f. tubes as is applied to either the
detector or audio plates. It is often advisable
to use an intermediate value for the r.f. tubes,
however, and this may be accomplished by the
addition of a suitable resistance in series with
a second lead from the positive high voltage
tap of the instrument.
It is a very simple matter to make this addi-
tion to the circuit, and it is possible to obtain
the variable resistance on the market. In most
instances one having an approximately correct
IRON CORE
R.F.TRANSFORMERS
-- 200 550 Meters -
obtain the desired voltage regulation. As an
instance; if it is desired to regulate the voltage
on the r.f. tubes from 65 to 100 volts, then the
maximum resistance value is obtained by apply-
ing the formula:
E-E,
R =
I
Here EI = 65, E = 100, and I = current in
amperes per r.f. tube. If no C battery is used
in the radio-frequency amplifier then the plate
current per tube will be about 5 milliamperes,
so where the receiver consists of two r.f. stages
the. total is 10 milliamperes or .01 amperes.
Substituting values for the formula we get-:
100-65
R =
or
R = - - = 3500 ohms
.01
Where a C battery is employed, the current is
A B
FIG. 2
range will have to be selected. For instance,
if it is found that one having a maximum of
4000 ohms is necessary, one rated at 5000 ohms
will be just as satisfactory.
The user can very simply determine for him-
self the value of the resistance necessary to
Additional resistance for obtaining
Voltage lower than 100 volte
frS.OOO Ohms
(Variable)
o
B
O
•100
r^wvw\
| -, Td An/iirt frfvjuorvy
amplifier-100 volts
Bstl«y
Eliminator
o
»45
> To detector 0 to 45 volts
•&
-0
— f-B-
OelMO,
FIG. I
Tested and approved by RADIO BROADCAST -jr
reduced by a third or a half, and if the experi-
menter has a milliammeter he can determine in
an instant the actual drain per tube by inserting
the meter in each tube's plate circuit.
The connections of this additional resistance
in the B supply circuit are shown in Fig. i.
ONE DIAL LOOP RECEIVER
A VERY simply constructed one dial
receiver, employing two stages of un-
tuned radio frequency amplification, a
crystal detector, and two stages of audio fre-
quency amplification, is shown in Fig. 2.
To prevent the radio frequency stages from
oscillating continuously, a potentiometer of
200 to 400 ohms is shunted across the A battery
RADIO BROADCAST ADVERTISER
595
Unfailing
radio power
from the
LIGHT SOCKET
Balkite Radio Power Units
Balkite Radio Power Units give unfailing, uniform current for both
circuits from the light socket One very popular Balkite installation,
especially for heavy duty sets where reserve "A" power is required is
with the Balkite Battery Charger and Balkite "B." Here the noiseless,
high-rate Balkite Battery Charger is ideal If your battery should be low,
you merely turn on the charger and operate the set. Balkite"B" eliminates
"B" batteries entirely and supplies plate current from the light socket.
light socket equipment
Another very popular Balkite installation is with the Balkite Trickle
Charger and Balkite "B." The Balkite Trickle Charger converts your
"A" battery into an automatic "A" power unit that provides "A"
current from the light socket, so that both circuits operate from the
lighting circuit. This installation enables you to convert your present
receiver into a light socket set.
Noiseless — No bulbs — Permanent
All Balkite Radio Power Units are permanent pieces of equipment,
entirely noiseless, have no bulbs, nothing to break, replace or get out of
order. Their current consumption is very low. All operate from 110-
120 volt AC current, with models for 50, 60 and other cycles. All are
tested and listed as standard by the Undenimters' Laboratories.
The Balkite Railway Signal Rectifier is now standard equip-
ment on over 50 leading American and Canadian Railroads
*
MANUFACTURED BY FANSTEEL PRODUCTS COMPANY, INC., NORTH CHICAGO, ILLINOIS
Balkite Trickle Charger
Converts any 6-volt "A" battery of
30 ampere hours capacity or more
into an automatic "A" power unit
that furnishes "A" current from
the light socket. With 4-volt and
smaller 6-volt batteries may be used
either as an intermittent charger
or a trickle charger. $10. West of
Rockies, $10.50. In Canada, $15.
Balkite Battery Charger
The popularrapid charger for 6 volt
"A" batteries. Noiseless. Can be
used during operation. Special
model for 25-40 cycles. $19.50. West
of Rockies, $20. In Canada, $27.50.
Balkite "B"
Eliminates "B" batteries and sup-
plies plate current from the light
socket. For sets of 6 tubes and less.
$35. In Canada, $49.50.
Balkite "B" II
Supplies plate current from the
light socket. Will serve any stand-
ard set. Especially adapted to sets of
6tubesormore.$55.InCanada,$75.
SOLE LICENSEES IN THE UNITED KINGDOM : MESSRS. RADIO
ACCESSORIES LTD. 9-13 HYTHE RD., WELLESDEN, LONDON, N. W. 10
596
RADIO BROADCAST ADVERTISER
• ... _
Greater
Station Spread
With 360° Dial
JVTEW Wade vernier dial, finished
-L ' in beautiful black lacquer is a
vital factor in the Wade tuning effi-
ciency— Spread stations over the en-
tire 360° circun.ference and gives
twice the space between stations for
close tuning as rotor plate types of
straight line frequency condensers
using 180° dials. No more bunching
of stations, none of the annoyance
of overlapping stations.
By actual test the Wade condense.-
gives the lowest minimum capacity and
wider tuning range. Covers the whole
broadcast range and down below 200
meters.
No Body Capacity Effects
A separately grounded frame insulated
from both sets of plates shields the
condenser from afl body capacity
effects — an important feature, exclu-
sively in Wade Condensers.
WADE TUNING UNIT
Including Condenser and Dial
The Wade Tuning Unit consists of a
Wade Condenser geared to a four-inch
360 degree vernier dial of 16 to 1 ratio.
Finest possible control with no back-
lash. Prices below are for the complete
unit.
Capacity .000125 mfd $6.00
Capacity .00023 mfd 6.25
Capacity .00035 mfd 6.35
Capacity .0005 mfd 6.50
At your dealers, otherwise send pur-
chase price and you will be supplied
postpaid.
Jobbers and dealers write for further
information and opportunities in your
locality.
The Viking Tool and Machine
•jr Company, Inc.
745-A 65th Street Brooklyn, N. Y
leads. The return side of the secondary of the
first r.f. amplifying transformer and the lower
side of the loop are connected to the central
arm of this potentiometer. It is recommended
that a power tube, such as the ux-i 12, be em-
ployed in the last audio stage. This will insure
quality reproduction providing a C battery of
the proper value is employed, to bias its grid.
The use of a C battery in the first audio stage
will be found helpful also, and should be in-
cluded, although its value will not be as high as
for the second stage.
Any type of loop capable of being tuned to
the broadcast band of frequencies is suitable
tion is being centered upon the production of
units designed to be employed in receiver in-
stallations where quality is the goal.
A
FILAMENT
B
NORMAL
BATTERY
TERMINAL
BATTERY
GRID
PLATE
SUPPLY
VOLTS
(AMPLIFIER)
CURRENT
FOR THE UX-I 12 THE REQUIREMENTS ARE:
6
5
157.0
10.5
6
5
135.0
g.o
6
5
112.5
7-5
2.5
6
5
go o
6.0
2.4
FOR THE U
X-I2O THE REQUIREMENTS ARE :
4-i
3
135
22. 5
6.5
To Fot
Secondary
oflndAF,
Transformer
-9;,
To Fof
Secondary
of IstAF,
Transformer
-9
+C to -A
i ,
FIG. 3
but for those who wish to make their own, it is
suggested that a box frame, three feet square
and ten inches wide, and having 16 turns of
No. 18 bell wire wound thereon, separated 5
inch apart, be employed.
Values for the various parts are indicated in
Fig. 2 while Fig. 3 shows how two 4|-volt C
batteries, connected in series, may be used to
furnish grid bias for both audio amplifier stages.
MAKING YOUR OWN GRID LEAKS
THE true experimenter always desires to
make as much of his own apparatus as is
possible. Grid leaks are important in
maintaining the proper standard of reception
and not always is it possible for the experimenter
to secure a grid leak of the value which will pro-
duce these results.
With the aid of drawing ink and a business
FIG. 4
calling card, it is possible to make grid leaks of
various values.
One side of the card is completely covered with
the ink and then by cutting into the sides with
a pair of scissors as shown in Fig 4, it is possible
to vary the value of leak by removing the sec-
tions cut into.
Grid leaks of this type should be thoroughly
dried before using, as the value of the leak will
vary with different degrees of temperature and
moisture.
Paper clips make satisfactory connections to
the ends of the inked paper.
NEW TUBES AND THEIR CHARACTERISTICS
ONLY recently the new line of radio
tubes has been added to the fast-growing
accumulation of apparatus from which
the constructor may make his choice in building
high quality receivers. More and more atten-
Tested and approved by RADIO BROADCAST i
The new tubes offer to the constructor the
means for operating his receiver at the efficiency
at which it should be operated. However, there
are certain requirements that must be observed
in the use of these tubes.
Those that interest the constructor most are
the power tubes, ux-i 12 for 6-volt source, and
the ux-i2o for 42-volt source. Each must be
supplied with its correct grid and plate voltage
or else there is no advantage in their use. The
requirements are shown in the accompanying
table which appears at the top of this column.
HOW TO CHARGE STORAGE BATTERIES FROM D. C
THE charging of storage batteries which
serve to supply the energy for the fila-
ments of radio tubes is a problem which
has engaged the attention of many engineers
who are seeking to make this work easy for the
man at home.
In many places only alternating current is
obtainable for charging purposes and, where this
is the case, some rectifying devices must be
employed to change the current in the lighting
mains from alternating to direct current. Where
a simple rectifier is used the resultant rectified
current is not purely a constant direct current
but is more correctly termed a pulsating direct
current.
A glance at A in Fig. 5 shows how this occurs.
The alternation or cycle of current in an alter-
nating current line assumes a definite form start-
ing at a zero or neutral line. It then rises to a
positive value afterward decreasing to the
neutral again. This constitutes a half cycle.
Now it continues below the neutral line toward
the negative in the same fashion ?.s it went
positive. Therefore, it is observed that the
cycle consists of two wave forms, one positive,
the other negative in potential.
The rectifier is so designed and operated as
to exclude the negative half of the alternation,
permitting only the positive half to pass. This
results in a series of pulsations of a positive
nature which, if visible, would look like those
shown in B. It is these periodic raps or pulsa-
tions which enter the battery on charge, causing
a chemical change in the nature of the plates of
which the battery is composed, so that it resumes
its original charged state.
X — N
/ \
i ^
i
E
\ /
•>t_ ^
FIG. 5
This chemical change within the battery must
be accomplished slowly, that is, at a low ampere-
hour rate, otherwise the compound pressed into
the plates of the battery will disintegrate and
fall to the bottom of the cell, thus causing short-
circuits from plate to plate.
Where the charging current is direct current a
different procedure must be employed. Here
RADIO BROADCAST ADVERTISER
597
Perhaps you, too, can cut your
"B" battery costs in half. Just
follow the chart. It gives you
the secret of "B" battery economy.
THOUSANDS of people have
made the discovery that Ever-
eady "B" Batteries, when used
in the proper size and with a
"C" battery*, are the most eco-
nomical, reliable and satisfac-
tory source of radio current.
On sets of one to three tubes,
Eveready "B" Battery No. 772,
used with a "C" battery, will
last a year or longer, usually
longer. On sets of four and five
tubes either of the larger Heavy
Duty Eveready Batteries No.
770 or No. 486, used with a
"C" battery*, will last eight
months or more.
These figures are based on
the average use of receivers,
which a country-wide survey
has shown to be two hours daily
throughout the year. If you
listen longer, of course, your
batteries will have a somewhat
*NOTE: In addition to the increased
life which an Eveready "C" Battery gives
to your "B" batteries, it will add a quality
of reception unobtainable without it.
shorter life, and if you listen
less, they will last just that much
longer.
Here is the secret of "B" bat-
tery satisfaction and economy:
With sets of from 1 to 3
tubes, use Eveready No.
772.
With sets of 4 or more
tubes, use either of the
Heavy Duty Batteries, No.
770, or the even longer-
lived Eveready Layerbilt
No. 486.
Use a "C" battery on all
but single tube sets.
Evereadys give you their re-
markable service to the full
when they are correctly matched
in capacity to the demands made
upon them by your receiver. It
is wasteful to buy batteries that
are too small. Follow the chart.
In addition to the batteries
EVEREADY
Radio Batteries
-they last longer
illustrated, which fit practically
all of the receivers in use, we
also make a number of other
types for special purposes.
There is an Eveready Radio
Battery for every radio use. To
learn more about the entire
Eveready line, write for the
booklet, "Choosing and Using
the Right Radio Batteries,"
which we will be glad to send
you on request. This booklet
also tells about the proper bat-
tery equipment for use with the
new power tubes. There is an
Eveready dealer nearby.
Manufactured and guaranteed by
NATIONAL CARBON CO., INC.
New York San Francisco
Canadian National Carbon Co., Limited
Toronto, Ontario
Tuesday night means Eveready Hour
— 9 P. M., Eastern Standard Time,
through the following stations:
WEAF-A'no York
-vijKR-Providence
wine-Worcester
viTi-Philadelphia
VfGS-Buffato
View-Pittsburgh
vism-Cincinnati
WEKR-Cleveland
vtvtj-Detroit
wen-Chicago
-woe-Davenport
wcro J Minneapolis
\St.Paul
KSD-St. Louis
KGO-San Francisco, 8 P. M. Pacific Coast Time
Tested and approved by RADIO BROADCAST
598
RADIO BROADCAST ADVERTISER
A UX Power Tube
will increase volume and clarity
in YOUR set, too!
REWIRING UNNECESSARY
NOTE: The UX-120 tube has been designed to
increase volume and clarity in all dry battery sets.
The UX-112 tube has been designed to increase
volume and clarity in storage battery sets. To make
it easy for you to secure the great benefits of the
UX tubes without rewiring your set, a complete
line of Na-Ald Adapters and Connectoralds have
been manufactured.
Months of service have
proved their efficiency.
Below are given three
very efficient and eas-
ily made applications
of the new power tubes.
For complete details
covering all possible
applications of the new
tubes mail coupon at
bottom of ad.
How to improve sets equipped with UV-199 lakes
To increase volume and clarity in sets using UV-
199 tubes, use the UX-120 tube in the last stage.
Easily fitted to the UV-199 socket with a Na-Ald
No. 920 Connectorald which also provides cables
for attaching necessary extra 45 volts B battery
and 22J volts C battery required for the UX tube.
Price, $1.25.
How to switch to dry batteries without
sacrificing volume or quality
The combination of a UX-120 tube for the last
stage with UX-199 tubes in the other sockets pro-
vides, with dry cells, results previously obtained
only with storage bat-
teries. Fit UX-120 tube
to the UV-201A Socket
with Na-Ald Connector-
aid No. 120. Cables
provided for attaching
extra B and C batteries.
Fit UX-199 tubes in all
other sockets with Na-
Ald No. 419-X Adapters.
PH'ce, No. 120 Connect-
orald, $1.25; No. 419-X
Adupter, 35c.
How to improve storage
battery sets
Volume and clarity can
be increised in storage
battery sets by using the
UX-112 tube in the last
stage. Easily fitted to
the UV-201A socket by
means of the Na-Ald No.
112 Connectorald which
provides cables for
attaching necessary
extra B and C batteries.
Price, $1.25. Mail
coupon below for com-
plete adapter informa-
tion cpvering use of
new tubes in all sets.
ALDEN MANUFACTURING COMPANY
Dept. B 16 Springfield, Mass.
All Na-Ald Sockets, Dials and Adapters are
protected by patents. Many patents Pending
No. 419-X
Adapter
ALDEN MFG. CO..
Dept. B16. Springfield, Mass.
Please send me complete information on how to
increase volume and clarity in any set by the
use of the new tubes.
Name
Address
City ...State...
the current is already di-
rect so there is no need to
rectify. However, it us-
ually is higher in voltage
than is desirable, and if a
battery were connected to
it directly, the low resis-
tance of the battery would
cause high current to be
passed through it. This
is equivalent to a rapid
high charge which, as ex-
plained previously, causes
disintegration of the plates
of which the battery is
composed. Therefore,
when employing d.c., it
behooves us to regulate
t he current flowing
through the battery on
charge so that this break-
ing up does not occur.
If the resistance of the
battery could be increased, then less current
would flow in the circuit. Of course, it's not
possible to increase the battery resistance, but
an external resistance can be added to the circuit
which will accomplish the desired result.
By the use of a simple formula, it is possible
to calculate the resistance necessary to charge
the battery at a predetermined rate. In this
formula, W= I x E, the E represents the d.c. line
voltage, usually no volts, and I represents the
220 Watts
Resistance
55 Ohms
I = TT
I XR
R - 4-
I -
w
T
Charging Current
2 Amperes
FIG. 7
rate of charge in amperes at which we wish to
charge the battery. Let us suppose that we
wish this rate to be 2 amperes. Then I = 2, and
W represents watts, the unknown. If we could
determine this value of W, then we could make
use of the many home electric appliances, such
as electric light bulbs, toasters, irons, heaters,
etc., to charge the battery. Usually the manu-
facturers of such devices have a nameplate
fastened to the apparatus which, among other
things, tells its line voltage and watts value.
By applying the formula we find that W=
2 x 1 10 = 220 watts. From this we see that, if in
the charging circuit we employ a device rated at
220 watts, the battery will be charged at the
rate of 2 amperes. Batteries are rated in
capacity, that is, their ampere-hour capacity.
Theoretically, if a 100 ampere-hour battery be
discharged at the rate of 2 amperes, it will last
for 50 hours of use. In recharging this battery
to its former state of usefulness, it is necessary
to charge it for 50 hours at 2 amperes or 25
hours at 4 amperes or 100 hours at I ampere,
etc.
Coming back to the use of formulas, if we
wished to determine the actual resistance of the
device necessary to charge the battery at 2
amperes, the formula R=-j would be employed.
By substituting values we see that R = ^=55
ohms. To check back our first formula, W=
I x E, there is another one, W= I2xR, which will
prove that the resistance of a 220 watt device
is 55 ohms when used on a 1 10 volt d.c. line.
Tested and approved bv RADIO BROADCAST -
- 2 Amperes
Charging Current
6
FIG.
= 22X5J, or W =
* 55
Substituting values,
= 220 watts.
Often the experimenter will know his line
voltage and the wattage of a piece of electric
apparatus. By using the formulas above and
transposing symbols, it is possible to determine
the rate of charge of a battery circuit when that
apparatus is included in the circuit as part of
the charging medium. The variations or trans-
positions of the first formula \V=I x E are,
E= - and 1= g. It is the last one that we can
apply in the last case described, I=^g or l = "o
= 2 amperes. If W = 6oo, then I = 7,^=5-45
amperes. These explanations will become more
apparent from an observation of the circuits in
Figs. 6. and 7.
In a great many homes there is employed a
local lighting system, such as the farm lighting
affairs. They consist mainly of a bank of
storage batteries totalling 32 volts, with a direct
current generator, the latter being used to charge
them. Often it is not practicable to move the
radio storage battery to the location of the gen-
erator and batteries, and it is more convenient
to charge the battery from a light outlet. By
insert:ng a resistance in series with the 32-volt
line, the 6-volt battery may easily be charged.
Applying the above formula to determine the
resistance necessary to charge at the rate of
2 amperes R = -(- or, R='|= 16 ohms. Where
the value of a resistance is known, say 8 ohms,
and it is desired to determine the rate of charge
when using that resistance, then I=j^, or 1=^? =
4 amperes.
GRID INQUIRY BLANK
Editor, The Grid
RADIO BROADCAST
Garden City, 'N.ew Tor\
DEAR SIR:
Please give me the fullest information
on the attached questions. I enclose a
stamped envelope.
CH I am a subscriber to RADIO BROADCAST
and therefore will receive answers to my
queries free of charge.
I am not a subscriber and enclose SI
to cover cost of answers.
NAME . . .
ADDRESS .
G. M.
RADIO BROADCAST ADVERTISER
599
Model R Receiver:
R au land -Lyric -
equipped. Price
$90 (East of the
Rocky Mountains)
All that you -want in a radio
natural tone, sharp selectivity,
straight-line-frequency tun-
ing (360°) unaffected by posi-
tion of the fingers, extreme
sensitiveness, permanence.
Beauty and Permanence
Listeners Marvel —
at the wealth of enjoyment awaiting but a touch of the
fingers.
Women Are Delighted —
with the tasteful stateliness of the Model R cabinet, as much
as with the neatness of its battery accommodations.
Engineers Voice Approval —
of the rigid spot'welded steel chassis, protecting from damage
every part of a set that stands as a notable example of the
completely manufactured rather than the merely assembled
radio receiver.
Service Men Commend —
the thoroughness with which every part has been made proof
against the interruption of its service, so far as human
ingenuity can devise.
Dealers Are Enthusiastic —
over the excitement created everywhere by this unique
receiver and the uniform satisfaction felt by its users.
Buy "Solid Value" in Your Radio
The leading wholesaler of radio apparatus in your community
has probably been, for years, an ALL-AMERICAN Authorized
Distributor. ALL-AMERICAN Guaranteed Radio Products
are being shown everywhere by responsible and reliable dealers.
ALL-AMERICAN RADIO CORPORATION, E. N. Rauland, Pres., 4213 Belmont Ave., Chicago, U. S. A.
^Bt ITWt^iT^fcA J9^ OWNING AND OPERATING STATION WENR — 266 METERS
ALL-AMERICAN
Pioneers in the Radio Industry
Tested and approved by RADIO BROADCAST if
600
RADIO BROADCAST ADVERTISER
•
°
A Shortage
of Trained
Radio Men!
We can't supply trained
radio operators to the
shipping companies fast
enough! Atlantic, Paci-
fic— Gulf and Lakes- —
our graduates are sought
everywhere.
You can't get better ra-
dio training than that
offered by Radio Institute
of America. Courses
planned and supervised
by RCA secure you your
1st Class Commercial Ra-
dio Operator's License.
And an immediate posi-
tion awaits every graduate.
Moreover you can study
at home in spare time.
Thecoupon will bring you
complete in/ormation.
RADIO INSTITUTE
OF AMERICA
Formerly Marconi Institute
Established in 1909
328 Broadway, New York City
A Department for the Exchange of Ideas and Sugges-
tions of Value to the Radio Constructor and Operator
/CONTRIBUTIONS to this department are welcome and those used will be
\^, paid for at the usual rales, that is, from two to ten dollars each. A pri^e
of twenty-five dollars is given for the best idea used during each three-month
period. The prizewinner for the last period was announced in the February
RADIO BROADCAST. Manuscripts intended for this department should not ex-
ceed about three hundred words in length, and should be typewritten. Little con-
sideration can be given to manuscripts not typewritten. Envelopes should he
addressed to this department, RADIO BROADCAST, Garden City, New York.
HOW TO MAKE BALLOON COILS
BALLOON coils are often seen in
many of the latest circuits, but no
instructions are given for making
them, thus depriving the experimenter of
most of the real pleasure of building his
own set.
They can be easily made, however.
First of all secure a round stick about an
inch in diameter and ten inches long, for
a winding form. When using one coil
within a larger coil (primary and second-
ary), one form will
need to be larger by -wire
about a quarter inch,
or more, in diameter.
Saw a slot about
seven inches long in
the form and make
a wedge as shown in
A, Fig. i , to hold it
open while winding
the coil. Wrap this
form with paper to
prevent the insula-
tion of the wire sticking
to it when the cement
is applied. A tack is
employed to hold the
paper and is left pro-
truding from the wood
so that the beginning
of the wire may be
fastened to it when the
next procedure, that of
winding the coil, is
started. A second tack
is used to hold the
other end of the coil
when the latter has
been completely
wound. The size of
wire and number of
turns can be taken
from a manufactured
coil, or found by trial.
To hold the wires to-
gether while bending
the coil around the
core, the use of col-
lodion, or better still, a
solution of acetone
and celluloid, is recommended. When
thoroughly dry, the coil can be taken off by
removing the wedge and closing the slot.
A round piece of wood will do for a core
for a small coil, or a piece of bakelite tubing
for a larger one. Make the core any con-
venient length. The diameter of the core
may be found by cutting a strip of paper the
length of the winding and making the core
of such size that the paper will not quite
meet. Remove the paper from outside of
coil and place on the core as shown in B , Fig.
i . A waxed thread should be run through to
secure the coil to the core; then carefully
bend the coil around the core and secure
with the thread. Space the free coils as
evenly as the job requires. A thread
around the core on the outside of the coil as
shown in C, will help to hold the individual
turns steady. When these coils are to be
used one inside the other, secure the larger
coil to the core but do not space the wire*
at the joint. The small coil can be slipped
in the larger one. A narrow strip of paper
is used to space the coils as shown in sec-
tion in C. Now secure the smaller coil
with thread and space the coils as desired.
JOHN L. LEE,
/Paper
Washington, D. C.
GOOD AUDIO
BYPASS
METHOD
Fl
i
Inner Coil- -
Thread-. -
SECTION X-X
FIG. I
ROM a con-
structor's point
of view may I
register a point in con-
nection with Mr. Mil-
len's power amplifier
as published in the
November, 1925,
RADIO BROADCAST. I
have reference to the
use of a resistance as
a means of securing the
negative grid bias, as
is best illustrated in
his Fig. 9.
Let us suppose that
a milliammeter in the
plate circuit of the
power tube registers 10
milliamperes, and let us
suppose that the audio
frequency fluctuations
range from 5 milliam-
peres to 15 milliam-
peres. The voltage
drop across R3 is pro-
portional to the value
of the plate current,
since the entire plate
current must pass
through R3 in order
to reach the filament.
The voltage drop,
therefore, not only varies in the ratio of
i :3 during the audio frequency cycle but
unfortunately this variation is — as one
might say — "180 degrees out of phase"
with the grid current fluctuations. When
the grid has reached its most positive
potential, the negative grid bias is then at a
maximum, because the plate current is at
a maximum, and when the grid has reached
its most negative potential, the negative
grid bias is then at a minimum because
the plate current is at a minimum. The
effect, therefore, is to reduce the amplitude
of the grid circuit fluctuations, and con-
— - Paper
RADIO BROADCAST ADVERTISER
601
Type BD1-A
NATIONAL
TUNING UNIT
Embodying the genuine
Browning-Drake Induct-
ance Coil and the NA-
TIONAL Condenser
The New NATIONAL
EQUICYCLE Condenser
The latest development in straight line frequency con-
trol as applied to NATIONAL Condenser design.
Increases range of rotation from 180° to 270°, permit-
ting more precise adjustment and sharper separation
of stations, and accomplishes this WITHOUT
GEARS, CAMS, OR LEVERS.
It changes
a mob
into an
orderly
procession
INALlg^iEQUICYCLE"
Type BD2-A
NATIONAL
TUNING UNIT
Embodying the genuine
Browning - Drake Trans-
former and the NATION-
AL Condenser
and
lengthens
the line
of
march!
(Patented February 10, 1925)
Tests Conducted at Harvard University, by Prof. Field, give characteristics of the new
Equicycle Condenser as indicated by the following graph:
— The novel shape
of the plates spaces
the station groups at
equal intervals of 10
kilocycles (as speci-
fied by the U. S. De-
partment of Com-
merce) in a true
straight frequency
line.
Type B
NATIONAL VELVET
VERNIER DIAL
(J> <i O,
o o c
Frequency in O Kilocycles O O
"V
X
Ort
1
X
"•1
%
^
S
X
f
X
^v
«4
S
X
•
X
.
^
^
X
s
>
X
__ Tuning P<ange of Standard 180° Condenser
S
Tuninq'RanQe of /Vatic
?7d^ Equici/cie Condenser
v
V °~
C.Ct
L.Ct
T. Ti
M
tndense
3i7 =3/5 /
tie lit
ea.sv.ren
>erating
r=2J
1.H.
*OM
M.F-
|_
- If
c.\
L
IT:
:
III
witti pltte I
tent Made V
Conditions.
Oda
nde
ed.
r
Oj-
SO. Dial Setting 100.
/SO.
-The same electric-
al efficiency and me-
chanical ruggedness
that have always
characterized NA-
TIONAL DX Con-
densers have been
embodied in the new
NATIONAL
EQUICYCLE
Condenser.
Get the Genuine. Insist upon NATIONAL COMPANY'S
RADIO Products. Your dealer appreciates your
patronage and will gladly get them for you.
Write for Bulletin m-RB
NATIONAL COMPANY, Inc.
\V. A. READY, PRESIDENT
110 Brookline St. Cambridge, Mass.
•jf Tested and approved by RADIO BROADCAST -fa
NATIONAL
TRANSMITTING
CONDENSER
602
RADIO BROADCAST ADVERTISER
against leaks
and losses
THE UTMOST possible
protection against leaks
and losses in the circuit is
afforded by Radion — The
Supreme Insulation.
Radion Panels reduce sur-
face leakage and dielectric
absorption to a minimum.
Their beautiful surface fin-
ish adds to the attractive-
ness of any set. Radion
Dials match their beauty of
finish and help to get close
tuning. Radion Sockets
reduce capacity effects.
Radio dealers have the
complete line of Radion
low-loss parts. Manufac-
turers will find it to their
interest to write us for
prices on moulded parts.
Send for catalog.
FREE Booklet, "Building Your
Own Set" mailed on request.
AMERICAN
HARD RUBBER
COMPANY
Dept. G-1S
11 Mercer St.
New York City
Chicago Office:
Conway Building
Pacific Coast Agent:
Goodyear Rubber Co.
San Francisco
Portland
No. 2 Radion Socket for
new UX tubes, with collar
adapter for old type tubes.
No. 4 same as No. 2,
without collar adapter, for
new UX tubes exclusively
^flic Supreme Insulation
Made to order exclusively for radio purposes
UV-202
FIG. 2
sequently the amplification. It amounts
in fact to a reversed feedback.
The audio frequency bypass condenser,
Cj, of his Fig. 4, if transferred to Fig. 9
for simplicity of illustration, would appear
as in accompanying Fig. 2. In this posi-
tion C5 does not overcome the objections
noted as the entire plate current (both d.c.
and a.c. components) must still pass
through R3.
I wish to suggest that Cj be placed as in
Fig. 3 shown herewith. It is evident that
in this position only the average plate
current (i.e. the d.c. component) will pass
through R3, and a fairly constant grid bias
will be obtained throughout the entire
audio frequency cycle which will neither
add to, nor substract from, the grid current
fluctuations. The a.c. component of the
telephone type diaphragm and an electro-
magnet. On these speakers the magnetic
stress placed upon the diaphragm by the
non-modulated component of the plate
current is the cause of a certain drag or
excessive inertia that is productive of
distortion.
On electro-dynamic loud speakers, dis-
tortion is partially due to the great load
that the low impedance moving coils place
upon the tube with the output of which
they are connected in series.
Any overloaded loud speaker will produce
distorted reproduction.
To improve the quality of reproduction
by improving the operation of the loud
speaker used in conjunction with a set,
To Plate of
last audio
tube
To B +
Amplifier
To -A
For loud speakei
FIG. 4
-B +B
FIG. 3
plate current is now supplied by Cj, or
"bypassed" if one wishes to think of it in
that way.
With the change in position of Cj, if
now a 2O-henry 25-milliamperechoke is in-
troduced at X, the combination becomes as
good as a dry cell C battery.
JEROME KIDDER, M.D.
Salina, Kansas.
HOW TO OBTAIN IMPROVED
LOUD SPEAKER REPRODUCTION
THE ideal radio set of to-day is, no
doubt, the one constructed with a
view of securing the highest pos-
sible acoustic perfection of reproduction.
Sources of distortion in a multi-tube set
are galore, and it takes expert knowledge
to build one that can be depended upon to
bring in the favorite broadcast programs
day after day with an unfailing quality of
reproduction.
Every component that goes to make up
your receiver installation may in a way, be
considered as a distortion device. Let us
consider the present day loud speakers,
ignoring entirely for the moment all dis-
tortion that may be due to resonance and
similar phenomena. Those built along
electro-magnetic lines employ the ordinary
- Tested and approved by RADIO BROADCAST i
it is generally recommended to employ
some sort of a shunt plate feed for the
loud speaker in such a manner that only
the modulated component of the plate
current be permitted to flow through the
loud speaker coil windings.
Fig. 4 shows the conventional arrange-
ment of such a plate shunt feed, where I is
usually the secondary of an audio trans-
former or an impedance of similar charac-
teristics, C a i-to 4- mfd. blocking conden-
ser, and J an open circuit output jack.
The writer has found that practically
identical acoustical improvement can be
had by an arrangement as shown in Fig. 5,
where R is a grid leak of approximately
50,000 ohms, C a i- to 2-mfd. condenser,
and J the output jack.
For loud speaker
To Plate of
II ,
tube L
R >
50,000 Ohms->-S
To B + < ]
II 1
Amplifier
FIG. 5
This arrangement was found quite as
effective in reducing loud speaker distortion
as is the one shown in Fig. 4. It has a
tendency to stabilize the audio amplifying
system which is especially apparent when
high plate voltages are employed.
It can be built into any set as it takes
up very little space, and it does not cost
nearly as much as the impedance shunt-
plate feed that is the more commonly used.
BORIS S. NAIMARK,
New York City.
A LOW LOSS COIL
THE following method describes the
making of a low loss solenoid coil
which is quite rigid and can be
removed with ease from the coil form.
RADIO BROADCAST ADVERTISER
60.'$
I C K L E S
Aristocrat
F. W. Sickles Co. felt strongly that a receiver so advanced in design as the
"Aristocrat" deserved coils just as advanced in order to give to the home
constructor the inherent benefits of this receiver.
As a consequence Mr. Sickles, who is the developer of the proved "Diamond Weave"
principle in coils and who is chief engineer of the F. W. Sickles Co., set to work.
The result of his engineering ability backed by thorough-going and practical
research, is being enthusiastically welcomed by laboratories everywhere in America.
The "Aristocrat" Coil by Sickles is based upon scientific facts, not wishes nor
fancies. And these facts were determined by an exhaustive and conclusive series of
tests upon highly sensitive and calibrated electrical instruments.
The "Aristocrat" Coil is unquestionably the best coil ever produced by Sickles.
Write for Radio Broadcast's Five Foot Diagrams.
THE F. W. SICKLES C
132 Union Street, Springfield, Mass.
Tested and approved bv RADIO BROADCAST
604
RADIO BROADCAST ADVERTISER
The AmerTran
DeLuxeis made in
two types, a first
and second stage,
Price, either type,
$10.00.
jl flew Standardof Excellence
in AudioAmplification
The realism of this new audio trans-
former is outstanding. Realism of
this kind results from the uniform
amplification of the fundamental
tones of the lower register. The
AmerTran DeLuxe makes possible
the natural reproduction of not only
the Overtones, but all of the trans-
mitted Fundamental tones.
The AmerChoke
type 854 is a choke
coil or impedance
of general utility.
Price $6.00.
A Qood Audio Amplifier
Requires enough plate and grid bias
voltage on its tubes to prevent them
from being overloaded by the signal
voltage.
The AmerTran PF-45 or PF-52 with
the half wave high voltage rectifying
tubes now available and suitable
condensers and resistances— together
with three AmerChokes Type 854
will furnish these proper voltages.
This combination will give real
quality loudspeaker volume. Amer-
Tran Power Transformers also sup-
ply A. C. filament current for the
last audio tube. A
^^
AmerTran Audio
Transformers type
AF6 (turn Ratio 5)
and AF7 (turn ratio
3^2) are the leaders
in their class. Price,
either type, $5.00.
Write for booklet describing these and other
AmerTranProducto — with recommendations
on their use. It's free on request. All prices
are F. O. B. Newark, N. J.
AMERICAN TRANSFORMER CO.
178 Emmet Street, Newark, N. J.
"Transformrr builders for over twenty-fire yean"
Sold Only at Authorized AmerTran Dealers.
To make the coil form, a wooden block
is turned down to a hollow cylinder 2\
inches in diameter and 4.5 inches long.
See Fig. 6. Then two plugs and two rings
are made, one ring and plug for each end
of the tube. The diagram shows the con-
structional data for these. Now two
grooves are cut lengthwise on opposite
sides of the tube, and a saw cut is made
halfway between the grooves on one side.
This completes the coil form.
The four bakelite strips, shown in the
illustration, are heated until they can be
slightly curved, as shown in Fig. 7, and
are then allowed to cool. By curving the
strips the middle turns of the coil are
ONE USE FOR A BYPASS
CONDENSER
IT IS noticeable that in a large number
of radio receivers, commercial or home
made, the quality of tone is not as
good as it should be. In some receivers
there is a distinct hiss or a high shrill
whistle which comes in continuously with
the music or speech. This whistle or hiss
is caused by some slight feedback between
the tubes, and seems to indicate that there
is some oscillation in the audio frequency
end which should not be there. To the
critical listener this is very objectionable.
It may often be effectively stopped, without
a-B,
\ rMfSCf/Kfs m of
ef/vff aaenety -*fr ne z. .
FIG. 6
held fast. The strips are, of course,
equal in width to the grooves mentioned
above.
Before starting to wind the coil, the two
copper-wire rings are put on the form ends
and the plugs inserted. Then two of the
bakelite strips, with their screws, are
placed in the grooves and the curve taken
out by binding with string at the middle.
The beginning of the wire is bent around
one of the screws, which are used for termi-
nal posts, and the winding proceeded with
in the usual manner, care being taken to
keep the bakelite pieces straight. When
finished, bend the wire around the other
screw and then fasten down the other two
bakelite strips on top of the wire. A little
binder can be used to cement the wire
to the strips.
affecting the volume of the receiver, by
placing a small mica type bypass condenser
in the proper place. The condenser should
be placed across the plate and plus filament
of the last, or in other words, the output
tube. Its value should not be iess than
.005 mfd. but it may be found on trial that
-Fil.
Bottom view
of socket
Grid
Small Brass Strips-
FIG. 8
FIG. 7
To slip the coil off, remove plugs and
rings and compress the tube.
The experimenter can, by lengthening
the bakelite strips and using the same size
wire, wind a primary coil at one end of
the tube. If smaller wire is used, the
outside strips will have to be in two pieces.
Also a fixed or movable tickler could be
mounted at the other end of the coil.
EVERETT FREELAND,
Dowagiac, Michigan.
this should be increased to .01 mfd. A con-
venient way of mounting the condenser is
given in the sketch Fig. 8, which shows the
underneath part of the socket and contact
springs. A small brass strip about one
inch long, with a hole near each end, can
be bolted direct to the condenser and to the
bolt holding the socket spring. This idea
was tried out on a manufactured set of
the lower priced kind, and the results were
so much improved that such a condenser
is being placed on every set of this type
that is sold. Placing a condenser across
the speaker posts of the receiver was not
found to produce the same results as the
volume was reduced to some extent, and
the tone changed.
K. B. HUMPHREY,
Brooklyn, New York.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
G05
CARDWELL
CONDENSER
The Allen D. Cardwell Mfg. Corp.
81 Prospect Street Brooklyn, N. Y.
ARTHUR H. LTNCH ap-
proved the new Type E taper plate
Cardwell as the ideal for use in the
"Aristocrat" and other receivers as soon
as he saw and tested it.
(Dhe new taper plate Type E Cardwell
is the logical answer to the demand for a
straight frequency tuning curve. Semi'
circular plates, far heavier than ever
used before, assure permanent calibra'
tion, and it will mount entirely behind a
four'inch dial. Its depth bac\ of the
panel is less than three inches.
(Dhe price for the .0005 mfd. size is
$5.00. Other sizes are priced propor*
tionately.
Write for illustrated catalogue
If your dealer can't supply you, order
direct from us
"THE STANDARD OF COMPARISON"
Tested and approved by RADIO BROADCAST
606
RADIO BROADCAST ADVERTISER
flRBORPHONE
A New Conception
of Good Radio
NO MATTER what experience you
have had with radio you've a new
thrill coming when you listen to Arbor-
phone performance the first time.
Clear reception — even on D X work —
is the outstanding quality that endears
Arborphone to thousands of owners all
over this country. Your Arborphone
makes a radio concert something to en-
joy with unmarred enthusiasm.
Mother, sister or any member of the
family can get plenty of stations on the
Arborphone. An expert isn't required
to operate this remarkably simplified re-
ceiver. Another point — this artistic set
is incased in a gracefully designed cab-
inet, a masterpiece of the woodworker's
art.
By all means buy no set before trying
out the Arborphone at your dealer's.
No value in radio to equal it. Let us
send you a copy of our new and interest-
ing radio book.
Dealers
The sales plan back of this
wonderful set assures you a
splendid year 'round business.
Ask for details — by mail or
^ wire.
£60.00 in Rocky Mt. and
Pacific Coast States.
MACHINE SPECIALTY CO.
321 S. Main St. Ann Arbor, Michigan
"Alt you could Ask of a Radio"
fe
RADIO FANS, a one-year's subscription to Radio Broadcast
will cost you four dollars, two years six dollars. Consider this
expenditure as being a necessary investment on your part for
the future development of your own knowledge of Radio.
PARTS,
HOOK-UPS:
SET
KITS
1O2-1O9 S. Canal St.. Chicaeo
111
As Long as New Apartment Houses Are Being Erected,
There Will Be Plenty of Opportunity for the Qo- Ahead Man
By D. C. WILKERSON
AS WITH the swing of the pendulum, the
first impressions which labeled radio
with the yellow-golden streak as a
bonanza for quick wealth, seem to have changed
of late.
Hundreds of fly-by-night radio enterprises
are going permanently out of business, and
perhaps their disgusted proprietors have spread
the story that "radio is a lemon." At any
rate, although many attractions are offered to
young men to take up radio and kindred sub-
jects by the large corporations, most of whom
spend real mor?y to train these neophytes,
the 1925 crop of college graduates has not
leaped into the arms of these welcoming
agencies.
Regardless of false impressions blabbed about
IN EACH ROOM
r
Set "
•K- ;
!
— i
Power
Amplifier
1
CENTRAL DISTRIBUTION PLAN
A series of jacks, one in each hotel room or apartment living
room, may be connected in parallel to the output of a central
receiver kept in tune by the telephone operator. A separate
ground for each jack is often advisable, it being as near to the
jack as possible
hither, thither, and yon, by those who may be
soured on radio, the radio art is yet a sound and
promising field for men, young or middle-aged,
or even old. Its possibilities are so tremendous
that one can scarcely grasp them. A field for
radio not generally realized will be discussed
here.
Have you ever stopped to
consider how radio in real
estate is a genuine asset?
Only last month one realty
firm of note advertised that
their new subdivision of
houses was in an excellent
location for radio, in other
words, out of the dead spot
zones.
Now then, how many new
houses are being built by
companies of large operating
facilities in your neighbor-
hood? Perhaps ten, fifty, a
hundred, or maybe a thou-
sand, depending upon where
you live.
Would these houses sell
more readily if they were
equipped with antenna and
ground, and convenient con-
nections inside? You can bet your new loud
speaker they would.
Now then, who has enough initiative to
organize and broach the proposition of making
such installations for the building operations
company? It would not require much invest-
ment in the way of tools and equipment, while
copper wire, insulators, screws, spreaders, masts,
and the like, can be obtained anywhere. You
could make a deal with your local hardware
store to supply you at a discount.
Armed with a ladder, some roof "stickers,"
and some gumption, a couple of bright active
fellows could "clean up" in the home town on
a job like this. Old clothes, a flock of screw
drivers, and a smile or two, would make valuable
adjuncts.
Why not try it some of you fans
who want to capitalize your hard-
earned knowledge of radio?
Again, another market for your
knowledge presents itself. It is be-
coming quite the thing for multiple
installations to be rigged up for
hotels and apartment houses. Here
is a field.
Some jack plates for wall plugs,
wiring connecting to a central dis-
tribution point where the elevator
operator, or telephone girl, keeps
tuned-in to some program or
other, is not a difficult job.
Inexpensive loud speakers, with
plug in each suite, complete the
panorama. Some of the finest
hotels and apartment houses
in the country are being built
with these radio conveniences in-
stalled.
The work must be done by some-
body, and it might as well be you.
STURDY ERECTION A PRIME FACTOR
AND here is another stunt. How about
'* these tanglefoot rooftops which entrap the
wary burglar or zealous fireman with equal
facility? More rigid fire regulations will surely
Antenna N(U
A NEAT MULTIPLE ANTENNA ARRANGEMENT
By the use of iron piping supports, several antennas may
be supported without fear of disaster during heavy storms
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
607
Sentt for this
Mew 7/ookup
No choicer group of radio
products has ever been em-
bodied in a single radio re-
ceiver. Not only are these
manufacturers nationally
known and accepted as the
leaders in radio design and
construction, but they have de-
veloped for the S-C receiver
many new features which
will create a new standard in
reception throughout the
radio world.
Represented Manufacturers:
Belden Mfg. Co.
S-C Wiring Harness
Central Radio Laboratories
Ccntralab Resistance
Polymet Mfg. Corporation
Fixed Condensers, Leak
and Leak Clips
Silver-Marshall, Inc.
Variable Condensers,Coil Sockets,
Coils, Tube Sockets, Vernier Dial,
Mounting Brackets
Thordarson Electric Mfg. Co.
Equiformer Audio
Transformers
Poster & Co.
Drilled and Processed Front Panel
and Drilled Sub-Panel
Yaxley Mfg. Co.
Four Tube Receiver
Here is the outstanding radio receiver development of the season, in which
is combined thegenius of two of the most successful and distinguished radio
engineers, assisted by the engineering and laboratory staffs of seven prom-
inent radio manufacturers. Here is a receiver for the home builder that will
represent for several seasons to come a far greater value than any other
design available. Send for the book. Read how to obtain the following
Startling New Features
SINGLE CONTROL — But one tuning or station selector control.
SELECTIVITY — In a residential district of New York City, within a few hundred
yards of powerful stations, thirty-five stations were heard between 9 and 10 p. m.
on the loud-speaker. KFI, in Los Angeles, was heard with ample volume to fill |
two rooms. Tests in Chicago brought in either coast with ample speaker volume,
and indicated that a consistent range of 1,000 to 2,500 miles might be expected.
QUALITY — Two new-type Thordarson power amplifying transformers possess-
ing a substantially flat frequency characteristic over the range of 40 to 6,000 cycles,
give a quality of reproduction so perfect that com-
parison by the best trained human ear with other
types ofamplifiers will not reveal any superior type.
VOLUME — In all cases the volume will exceed that
obtainable from other four-tube receivers, and in
practically all cases equal or exceed that obtainable
from standard five and six-tube receivers.
UNLIMITED WAVE LENGTH RANGE— Through the use
of interchangeable coils, the wave-length tange is practically
unlimited.
WIRING AND ASSEMBLY— All wiring is carried in a spe-
cial harness. Since each wire is exactly the right length, and
has a special color, it is impossible to go wrong in wiring.
No soldering is needed unless preferred By the builder. Only
a screwdriver and a pair of pliers necessary to assemble this
set in less than two hours.
Over-all design, rugged and solid. Adapted to practically any
standard cabinet, any standard tube.any battery or eliminator
source of supply, outdoor antenna or loop. While the parts
are the best that the leading laboratories of the country
afford, the set can be built at an extremely low cost. Full de-
scription of the receiver will be published in the March
issue of Popular Radio.
Get the hand book at your nearest Radio Dealer or clip the
coupon and send with 25 cents TO-DAY. Address
The S-C Merchandising
Committee
106 S. Wabash Ave. ^ ^ ^
Chicago ^ ^
^ ^
1 — ^* Name
The S-C
Merchandising
0 ^ - 706 S. Wabash <zAvenue • Chicago
& •-
Gentlemen: Please find enclosed 25c, for which
send me hand book of the new S-C Receiver.
Address
608
RADIO BROADCAST ADVERTISER
itsinthcTube
A receiving set is no better than its tubes.
With other parts and connections right a set may be
as good as its tubes — no set can be better.
That's why you want CECO Tubes. They stand up
and deliver. With them your set works at its maxi-
mum. Clarity of tone, rich volume, long life — CECO
has them all to a superlative degree.
Our charted tests (results confirmed by laboratories
of national reputation) PROVE CECO TUBE SU-
PERIORITY— whether used as detectors, audio or
radio frequency amplifiers.
CECO Tubes make a Good Receiver BETTER. Try
them and you'll BUY them always — for results.
Now Ready! CECO Tubes with new type Long
PRONG BASES. Also, Power Amplifier Tubes, E
(Dry Cell Type), F (Storage Battery), for last stage
of Audio Frequency.
Dealers write giving jobber's name.
C E. Mfg. Co., Inc.
702 Eddy Street, Providence, R. I.
REMEMBER!
WHEN BUILDING
THE ROBERTS',
KNOCK-OUT AND ARISTOCRAT
receivers that CLAROTUNERS are easier to mount, easier to
hook-up, and that a more even approach to the point of
MAXIMUM r AMPLIFICATION is effected with CLARO-
TUNERS.
DO YOU KNOW
thai CLAROSTAT is the perfect variable resistor, having a greater range and a greater
carrying capacity than any other, and that it is the only logical resistor
for the UNIVERSAL receiver?
I Send Stamp for Hook-ups
^ American Mechanical Labs., Inc.
285 North Sixth Street Brooklyn, New York
A KEY TO RECENT
RADIO ARTICLES
By E. G. SHALKHAUSER
THIS is the fifth installment of references to
articles which have appeared recently in var-
ious radio periodicals. Each separate reference
should be cut out and pasted on cards for filing,
or pasted in a scrap book either alphabetically
or numerically. An outline of the Dewey
Decimal System (employed here) appeared in
the November and January RADIO BROADCAST,
and u'ill be reprinted iti an early number.
NDUCTORS
.
QST. Dec. 1925, pp. <} 12
"oroids," F. J. Marco.
.
"To
COILS.
Toroids.
, . . .
Through the increased use of radio frequency amplifica-
tion, coils have been designed which are said to give greater
selectivity than is the case with common solenoid coils
The toroid coil is an outgrowth of some of these newer
developments. It has practically no external field. Con-
siderable theoretical and practical data accumulated by the
author, is presented. The advantage of this new coil lies in
the lessening of interstage magnetic coupling. !t does not
nullify interstage oscillations in r. f. amplification.
R$82. TRANSMISSION OF PHOTOGRAPHS. PHOTOGRAPH
QST. Dec. 1925, pp. 12-17. TRANSMISSION.
"Practical Picture Transmission," T. P. Dewhirst.
The Jenkins Laboratories have two picture transmission
machines available for amateur use, the "Midget" and the
"Junior." Both of these instruments are pictured and des-
cribed in detail. Certain facts regarding the use of the ap-
paratus and method of operating it are considered. Cir-
cuit diagrams are shown and explained.
R}86. FILTERS. FILTERS.
QST. Dec. 1925, pp. 24-26.
"Amateur Filter Problems," F. S. Dellenbaugh.
A summary of problems pertaining, to low-pass filters
from 25 cycles a. c. to commutator ripples in generators, is
given. A full page of design data covering construction of
induction coils with carrying capacity of .05-. 5 amperes, is
included. The "brute force" and "intelligence" method of
filtering are discussed, and diagrams shown. Tests of filter
action using telephone induction coil and headphones are
diagrammatically included.
R357. FREQUENCY CHANGERS. FREQUENCY
QST. Dec. 1925, pp. 29-30. Doubling
"Frequency Doubling in Vacuum Tubes," T. T. Green-
wood.
A method whereby the ordinary three-electrode tube may
be used to double the output frequency in a circuit, is des-
cribed. Use is made of the decrease of grid current for
either increase or decrease of plate potential. Diagrams il-
lustrate the points under consideration.
R-374. DETECTORS, CRYSTAL. CRYSTAL,
QST. Dec. 1925. pp. 31-32. Carborundum.
"The New Carborundum Detector," M. L. Hartmann
and J. R. Meagher.
A fixed crystal detector for broadcast receivers is de-
scribed. Carborundum is used since this crystal is superior
to any others, considering electrical stability and perman-
ence. It has been developed to a point, according to the
author, where its use may be an asset to modern receiving
sets. The commercial product is shown and circuit diagram
given.
R4O2. SHORT WAVES. SHORT-WAVE
Proc. I. R. E. Dec. 1925, pp. 677-683. TRANSMISSION.
"An Investigation of Transmission on the Higher Radio
Frequencies," A. Hoyt Taylor.
A preliminary range chart has been constructed for tele-
graphic communication, 5 kw. in the antenna, at various fre-
quencies. The conclusions upon which the range chart is
based are derived from experiments made by the Naval
Research Laboratory, from experiments made by amateurs,
and from such data as the Laboratory has had access to
from commerical and Government sources at home and
abroad.
An attempt has been made to indicate in a general way
the advantages and disadvantages of high frequency tele-
graphic transmission. Various critical regions are pointed
out where new phenomena make their appearance; (i)
region between 2000 and 3000 kcs. (2) region around 6000
kcs. (3) developments at higher frequencies of uncertain
ranges.
The development of a missing region to extensive areas
is shown to take place with a frequency rise to 20,000 kcs.
The chart also attempts to indicate, in a general way, the
region of uncertain communication and the regions where
further exploration is urgently needed. It is quite evident
that the range data is far from complete and that many in-
dividual cases will be found in contradiction to the chart, but
it does represent a general average of the situation as it
presents itself to the engineers in the Naval Service.
Ri is. DIRECTIONAL PROPERTIES. DIRECTION A i
Proc. I. R. E. Dec. 1925, pp. 685-707. RECEIVERS
"A New Directional Receiving System," H. T. Friis.
The paper discusses methods of combining the signal
currents from the different antennas in a directional receiv-
ing system, and a detailed description is given of a system
by which all phase and amplitude adjustments are per-
formed upon the beating current inputs of a double detection
receiver. The theoretically derived shape of the directional
characteristic of a two-loop system has been verified by ex-
periments, and data on reduction of static for such a system
are given. Photographs and diagrams are shown of all the
apparatus used.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
(509
INWORKTHATIS
ALMOST ROMANil
Jff,
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Dept. CU5, Washington, D. C.
^
ORIGINATORS OF RADIO HOME -STUDY TRAINING
Instruments
Given with Course
All instruments ' shown here
and many others given to
students for practice work
while learning. Receiving
sets, from simplest kind
to thousand mile receiv-
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NATIONAL RADIO INSTITUTE
Dept. CUB
Washington, D. C.
Without obligating me in an
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Name Age.
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610
RADIO BROADCAST ADVERTISER
JVfeuTAM S CO Products
AMSCO
SIAMESE
CONDENSERS
Used by William H.
Preiss in his "Straight
8" Receiver, R. E.
Lacault in his '"Ultra-
dyne," L. M. Coclcaday
in his "L. C. 26" Re-
ceiver, and specified by
Lester L. Jones for single
control receivers.
It Clicks into Contact
AMSCO
UNIVERSAL
SOCKET
All standard UX
and C X radio
tubes snap in with
a click that assures
positive contact.
Patented Amsco
construction fully
enclosed in genu-
ine Bakelite. One
hole mounting.
They save space
DE LUXE MODEL.
AMSCO VERNIER DIALS
Nowfinishedin gold, silver,
and jet. Free acting-forward
or backward, fast or slow,
without momentum or back-
lash. (Jives finesse to fingers.
FOR STRAIGHT-LINE
AMPLIFICATION
AMSCO
RESISTANCE
COUPLERS
The perfected instru-
ments for straight-line
amplification. All fre-
quencies within the
voice and music ranges,
from the highest treble
to the lowest bass, are
augmented equally, giv-
ing true tone reproduc-
tion without distortion.
Investigate Amsco Re-
sistance Couplers, Grid
Gates and Resistors.
AMSCO PRODUCTS, INC.
Broome & Lafayette Sts., New York
Make your set a Super -Het
THE circuit described in Radio Broadcast for June and August will change any set
into a super-heterodyne. It is particularly applicable to five-tube neutrodyne and
tuned RF sets. It changes these two circuits into super-heterodynes as good as most,
and considerably better in some respects than any super-heterodyne circuit ever devised.
Stations come in at but one point on the oscillator dial. There is mathematically no
possibility of harmonics. Full scale blue prints with reprint of article $1.00.
Eastern Coil antenna coupler $6.00
O'Connor oscillator coupler 4.75
Special fixed condenser 60
Complete parts including panel, drilled and engraved, special formica
bushings, screws, and wire, blue prints and reprint 37.50
* A. O'CONNOR & COMPANY
Super-Heterodyne Headquarters Since 1923
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R 1 40. CIRCUITS. CIRCUITS,
Radio. Dec. 1925, pp. 26 ff. Transmitting.
"How to Indentify the Transmitting Circuits," Lieut. J.
B. Dow, U. S. N.
An oscillating tube circuit is used for transmitting pur-
poses. Six basic circuits, the Meissner, Coupled plate, Coupled
grid, Hartley, Modified Hartley, and Colpitts, are listed by
the author, together with diagrams and a general discussion.
Other circuits, such as the grid condenser and leak system,
are considered modifications of the fundamental ones.
Some of the modifications are taken up and diagrams shown.
R343. ELECTRON TUBE RECEIVING SET. RECEIVER,
Popular Radio. Dec. 1925, pp. 495-511. LC-26.
"LC-26 Receiver," L. M. Cockaday.
A receiver considered by the author as the best one yet
constructed, and available in parts for the radio experi-
menter, is described. It is a five-tube resistance-coupled
set. Front, rear, and side views, including wiring diagram
and list of parts, are shown. All details pertaining to the
set are carefully presented.
R38i. CONDENSERS CONDENSER
Popular Radio. Dec. 1925, pp. 521-525. LOSSES
"Condensers," S. Harris.
The question of losses in condensers is a difficult problem
in radio engineering, but one should have some idea about
high frequency resistances in condensers. The radio experi-
menter will have no difficulty in understanding some of the
effects due to eddy currents, dielectric losses, etc., the author
believes. A simple method of measuring such losses in con-
densers is presented by the writer.
R55Q. BROADCASTING. INSTRUMENTS,
Popular Radio. Dec. 1925, pp. 526-532. Placing oj
''The Oboe in 4-D," T. L Bayard. t
"The location of each instrument in group radio trans-
mission, orchestra or band, before the studio microphone,
is a problem which has been studied at some length and
solved to some extent by engineers of station KDKA at Pitts-
burgh. Charts and explanations furnish the reader with
considerable detailed information.
R582. TRANSMISSION OF PHOTOGRAPHS PHOTOGRAPHIC
Popular Radio. Dec. 1925, pp. 540-544. TRANSMISSION.
"Pictures by Telephone or Radio," E. H. Hansen.
A new method of transmitting pictures by radio, called the
"Phono-Photo" method, is described. Fundamental data
on present types of systems developed, are reviewed and
compared with the system presented by the author. A
photo-electric cell is required, actual pictures being trans-
mitted over the ordinary telephone lines in a remarkable
short time.
R26i. ELECTRON TUBE VOLTMETERS. VOLTMETERS,
Popular Radio. Dec. 1925, pp. 552-555. Vacuum Tube.
"A Vacuum Tube as a Voltmeter," L. M. Cockaday.
A three-electrode vacuum tube is used as a voltmeter to
cover a considerably greater range than the voltmeter in com-
mon use, since it can be applied to either d. c. or a. c., from a
fraction of a volt to several hundred volts. An explanation
of its uses, and the method of applying it, is given in detail.
Circuit diagram and apparatus assembled, is shown.
Rj82. INDUCTORS. INDUCTANCE
Popular Radio. Dec. 1925, pp. 559-561. VALUES.
"The Relative Merit of Some Types of Inductance," B.
B. Minnium.
The author presents a careful analysis of several types of
inductance coils, mainly pertaining to the method of wind-
ing them, and makes a comparison of their relative L-R
values. Some conspicuous results are obtained, which
should be considered carefully before deciding which coils
are the best. A graph shows the L-R ratio and the wave-
length plotted for six types of windings. The torus coil
appears to be far the poorest coil investigated.
CRYSTAL DETECTORS. CRYSTALS.
Popular Radio. Dec. 1925, pp. 575-576.
"Do Impurities Improve Crystal Detectors?,"
Doctor Wherry, of the Bureau of Chemistry, presents one
of the most complete lists of crystal detector minerals and
their composition, which has ever been published. It ap-
pears that crystals with some impurities are better for high
frequency detecting purposes than the pure minerals, al-
though there are some exceptions.
R342.7. AUDIO-FREQUENCY AMPLIFIERS. AMPLICATION
RADIO BROADCAST. Jan. 1926, pp. 313-316. Audio-
Frequency
"Additional Notes on the Mode! 1926 Receiver," E. R.
Pfaif.
The author describes an improved audio amplifying unit
to be used with the McMurdo Silver receiver (described in
Nov., 1925, RADIO BROADCAST) using transformer, resistance,
or choke-coil coupled amplifiers. In using increased plate
voltages for power tubes, it is frequently necessary to use a
shunt method of horn connection for good results. Resist-
ance coupling, with its advantages and precautions to be
observed, is reviewed at length.
R402. SHORT WAVES. SHORT-WAVE
RADIO BROADCAST. Jan. 1926, TRANSMITTER.
pp. 321-325.
"A Universal Short-Wave Transmitter," N. Hagemann.
The construction of a high frequency telegraph transmit-
ter, using receiving parts, is described. The circuit shown
is capable of steady oscillations even when plate or filament
current should vary somewhat. Complete instructions,
wiring diagrams, and photographs are given.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVER,
RADIO BROADCAST. Jan. 1926, pp. 331-336. Universal.
"Radio Broadcast's Universal Receiver.", A. H. Lynch.
The article starts with a general review of the radio parts
situation at the present time and proceeds to give a detailed
account of several good receivers which may be built by
the home constructor, The "Universal," an exceptionally
efficient four-tube receiver, using one r. f. stage, tuned
and neutralized, a regenerative detector, and good audio
stages, is described, photographs serving to illustrate t*ie
general layout of instruments.
Tested and approved hy RADIO BROADCAST
RADIO BROADCAST ADVERTISER
611
Every Radio Fan
should have this book
JUST OUT — 514 PAGES
I.C.S.
RADIO
HANDBOOK
Compiled by
HARRY F. DART, E.E.
Formerly with the Weitira
Electric Co., and U. S. Army
Instructor of Radio.
Technically edited by
F. H. Doane
VTO MORE need you turn
IN from book to book,
hoping to find what you
want. It is all here, in
514 pages crammed full
1 of every possible radio de-
1 tail. Written in plain
language, by engineers for
laymen. 100.000 sold.
IT EXPLAINS : Electrical terms and circuits, antennas,
batteries, generators and motors, electron (vacuum) tubes,
many receiving hook-ups, radio and audio frequency am-
plification, broadcast and commercial transmitters and
receivers, super-regeneration, codes, etc.
Send $1 today and get thit 514-page I. C. S. Radio
Handbook- — the biggest value in radio today.
""T
International. Correspondence School!
Box 8299-E, Seranton, Penna.
I enclose One Dollar. Please send me — post-paid —
the 514-page I. C. S. Radio Handbook. It Is
understood that if I am not entirely satisfied I may
return this book within five dajs and you will
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Costs little more and is worth a lot more than the cheaper sub-
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Celatsite Battery Cable
For connecting A and B Batteries (or current supply)
to radio set. Silk braid covering 5 flexible Celatsite wires
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and "blown" tubes. Adds greatly to
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Enameled Antenna Stranded
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You can make a good loop with Acme wire made of 65 strands of fine copper
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KS?O. BROADCASTING, STATION.
Radio News. Dec. 1925, pp. 798 ff. Broadcasting.
"What Happens In the Broadcast Station," A. P. Peck.
A fundamental description of the operation of a modern
broadcasting station, including the principles of sound vibra-
tions, the purpose of the microphone, the operation of tht-
transmitting tubes, the method of modulating high fre-
quency currents, and the equipment of the rooms housing
the broadcasting station.
Ri42.3. INDUCTIVE COUPLING. COUPLING.
Radio News, Dec. 1925, pp. 800 ff.
'.'Coupling— Tight or Loose?", S. Harris.
In this article, the first of a series, is presented a mathe-
matical treatise on the question of coupling between coils.
Actual measurements, made with different coils, are shown
graphically, with constants of the coils given. Only con-
centric coils are considered, variations being made in dia-
meter of coils, number of turns, and position of primary with
respect to secondary (whether in center or to one end).
The effect of the antenna constants, when considered with
coil coupling, is another important factor.
R402. SHORT WAVES. TRANSMITTER,
Radio News. Dec. 1925, pp. 803 ff. Short-Wave.
"The Baby Transmitter," W. B. Schulte.
A complete description of a low power transmitter using
UV-IQQ tube, and operating at high frequencies (7500 kc.).
is given. The modified Colpitts oscillator used, was devel-
oped at the Burgess Laboratories. Ordinary dry batterie>
furnish the plate and filament supply. The circuitjdiagrams
show clearly how this set can bt constructed.
R334- FOUR-KLECTRODE TUBES. ELECTRON TUBES,
Radio News. Dec. 1925, pp. 804 ff. Four-electrode.
" Multiple Grid Vacuum Tubes and Their Advantages "
f . H. Nakken.
The author presents an analysis and working principle of
a two-grid tube, giving its advantages and theory of opera-
tion. One grid is connected directly to part of the B bat-
tery voltage in order totneutralize the space charge within
the tube. The other grid performs its regular functions as
in three-electrode tubes. It is said that capacity effects
between grid and plate may be prevented by this unique ar-
rangement of grids. As a power tube, this device has many
possibilities.
!<402. SHORT WAVES. TRANSMITTER,
Radio News. Dec. 192^, pp. 807 ff. Five-Meter.
"Five-Meter Transmission," R. E. Kolo.
The construction of a transmitter and receiver operating
on =10,000 kc. (3 meters) and the arrangement of Lecher wires
to measure these high frequency currents, is given. The
I niverMty of Illinois experimental station worked out the
apparatus design. Data on construction and operation is
given in detail.
R}8i. CONDENSERS. CONDENSERS.
Radio News. Dec. 1925, pp. 8o8f. EUitrolylii.
"Electrolytic Condensers,' I". A. Smith and J. Millen.
"A description of the much talked of electrolytic con-
densers, is presented. Tables give relation of capacity to
voltage formation values and the critical voltages for alu-
minum anodes with various electrolytes. Construction of
such condensers for transmitting and receiving purposes,
and proper sized choke coils to be used for good results,
is part of the information given to enable the constructor
to build his own.
1<375. DK i KCIOKS; RECIIFIERS;
MISCELLANEOUS. ELIMINATORS,
Radio. Dec. 1925, pp. 15 ff. A, B, and C B alter v.
"The ABC Battery Eliminator," G. M. Best.
The construction of an eliminator to replace the A, B, and
C batteries, thus operating the radio receiver from the regu-
lar 1 10 volt a. c. power circuit, is described. Any set using
up to and including eight tubes, may connect to this elimin-
ator. Some changes in wiring are necessary in the set. A
list of complete parts are given and diagrams shown. The
construction of the eliminator is not difficult, and is con-
sidered quiet in operation. Rewiring diagrams for the
Browning-Drake and also an eight-tube super-heterodyne,
are given.
Ro73- TRAINING OF OPERATORS. EXAMINATIONS,
Radio. Dec. 1925, pp. 22 ff. Government
"Passing Your Next Radio Examination," C. W. Rados.
Complete information is presented concerning the license
examinations for amateur and commercial operators. These
examinations are conducted by the Department of Com-
merce and may be taken at any one of the district offices.
A code test comes first, followed by an examination in theors
and laws of radio communication. A sample code test i>
also included in this very complete article.
Rj43. ELECTRON TUBE RECEIVING SET. RECEIVER.
Radio. Dec. 1925, pp. 25 ff. Browning-Drabs
Single Control
"The Single Control Browning-Drake Receiver," H. A.
Nickerson.
A method of converting the Browning-Drake circuit to
single control is described, using two condensers mounted on
one shaft. This circuit is well adapted to such an arrange-
ment, writes the author. The principle of operation, with
the change suggested, is considered at some length. Other
changes to be made are also given consideration.
DAMPING.
R242. REACTANCE-VARIATION METHOD.
COIL
Radio. Dec. i gas, pp. 31. MEASUREMENTS
"A Standard of Coil Comparison," G. F. Lampkin.
The author makes a plea for expressing in some standard
way the meaning of coil efficiency. He suggests that the
ratio of L-R be used, and gives his reasons, explaining this
ratio of reactance to resistance at some length.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
613
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RADIO BROADCAST
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prevents tube damage.
JAll the advantages of inter changeability of
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Don't take chances on twenty loose connections
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This is the EBY Binding Post that is standard equipment on
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Tested and approved by RADIO BROADCAST if
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RADIO BROADCAST ADVERTISER
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Loop wires in silk or cotton covered. Antenna supporting springs.
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wiring. . A .
Write us for descriptive catalogue. ^
ROSS WIRE COMPANY
69 Bath St., Providence, R. I.
R 134.4. RECENERAIIVE ACTION. REGENERATIVE
Proc. 1. R. E. Dec. 1925. pp. 709-753. AMPLIFICATION
"An Analysis of Regenerative Amplification," V. D.
Landon and K. W. Jarvis.
This paper shows some of the defects of present theories
regarding regeneration, and presents a new method of
analysis based on the idea of a power balance. It is shown
that a signal voltage does not supply power to a regenerated
circuit, but merely prevents certain losses from occurring.
This upsets the balance between power input from the tickler
and power lost in the circuit, so thai oscillation occurs. The
amplification obtainable -in this way has a definite limit, the
limit being caused by variations in the plate and grid im-
pedances of the vacuum tube, as the amplitude of the grid
voltage increases. The rate of variation of these impedances
as the grid voltage increases, depends on the tube and on
the direct voltage used.
The use of a grid leak and condenser decreases the voltage
amplification, by increasing the rate of change of the plate-
filament impedance. In general, however, increased detect-
ing efficiency more than makes up for the difference when
audio frequency output is considered. The effect of resist-
ance in the grid circuit is to decrease the amplification by
increasing the effect of the impedance variations.
The best turn ratio to use in a regenerated transformer is
the same ratio that should be used in a non-regenerated
transformer. The amplification obtainable increases
rapidly as the strength of an applied signal is decreased.
Although the inductance-capacity ratio does not affect tne
amplification obtained on an a. c. wave train, this ratio does
affect the amplitude of the audio output when a modulated
signal is being amplified. If a low L-C ratio is used, high
notes will be lost when a weak signal is being received with
full regeneration.
Regenerative amplification also occurs'when'a tube is in a
condition of self-oscillation, providing the strength of the
local oscillation is weak. A regenerated circuit amplifies
non-resonant frequencies to a certain extent, the amount
depending on the value of the reactance that would be
needed to tune the circuit to the non-resonant frequency.
R382.5. OSCILLATION TRANSFORMERS. INDUCTANCES,
Proc. I. R. E. Dec. 1925, pp. 755-766. Air-Core.
" Designs and Efficiencies of Large Air-Core Inductances,"
W. W. Brown and J. E. Love.
Representative designs of large air-core antenna tuning
inductances suitable for outdoor and indoor service, are
described. The latest improved designs are described in
greater detail and compared with earlier designs on a basis
of efficiency and kilovolt-ampere capacity. Formulas are
given for calculating the ohmic and eddy current conductor
power factor of coils using finely stranded, separately
insulated, strands. In graphical form are shown the varia-
tions of ohmic and eddy current power factor with frequency,
with four different conductors wound in a given arrangement
to given dimensions. Also the variation of the sum of ohmic
and eddy current power factors, with frequencies for a rep-
resentative conductor on various diameters, are given.
These values were calculated by the formulas given, and in-
dicate very high efficiencies for the latest types of coils.
R342.6. RADIO-FREQUENCY AMPLIFIERS. TRANSFORMERS,
Proc. 1. R. E, Dec. 192$, pp. 767-779. Radio-Frequency
"An Efficient Tuned Radio-Frequency Transformer,"
F. H. Drake and G. H. Browning.
A mathematical discussion of a new type of r. f. amplifying
transformer is given, which, it is claimed, is capable of giving
greater amplification per stage than other transformers now
used. Circuit diagrams and charts are shown verifying the
theoretical work done.
R6io. EQUIPMENT; STATION DESCRIPTION. STATION,
Radio News . Dec . 1925, pp. 770 ff . H roadca sting.
"Britain's New Superpower Broadcasting Station," A.
Dinsdale.
Great Britain's largest broadcasting station, located at
Daventry, is described. Several photographs show imerior
and exterior arrangements. The present rated power out-
put is 25 kw., although up to 60 kw. can be used in the future.
The circuit design, oscillator, amplifier, modulator, and sob-
modulator, are discussed separately. The tubes are water-
cooled, the system employed being taken up in detail. The
station frequency is 187 kc. (1600 meters), call letters 5 xx.
Ri 13.1 FADING. FADING.
Radio News. Dec. 1925, pp. 772 ff.
"The Nature, Cause, and Reduction of Fading," G. W.
Pickard.
Mr. Pickard discusses the inconstancy of the space circuit,
giving a very exhaustive and complete study of the probable
causes o.' f?ding. His explanations are supplemented by
charts and data taken over long periods of time. From his
observations it appears that the Kennedy-Heaviside layer
theory does not explain day and night and seasonal varia-
tions, but the cause must be found elsewhere. A system of
multipoint antennas for receiver, transmitter, or both, is pro-
posed to improve conditions.
Ri3o. ELECTRON TUBES.
TUBES,
laiho
Tubes," C. B.
Radio News. Dec. 1925, pp. 786 ff. Cold-Catbode.
"Cold-Cathode Gas-Filled Discharge
Bazzoni.
Some fundamental principles pertaining to electron dis-
charges through vacua, are presented. The Crookes dark
space and the Faraday dark space in partially exhausted
tubes, are two of the interesting phenomena explained at
some length.
R35O. GENERATING APPARATUS;
TRANSMITTING SETS. TRANSMITTERS,
Radio News. Dec. 1925, pp. 790 ff. Radio Telephone.
"Transatlantic Radio Telephony," G. C. B. Rowe.
According to information in this article, the Western
Electric Cpmpany will announce transatlantic radio tele-
phone service on a commercial basis shortly. A new system
of transmission, known as the single side-band eliminated
carrier, is used. This system is described and illustrated.
A special system of reception is necessary, a local oscillator
being employed in order to properly detect the signals.
The advantages of this new system are discussed at some
length.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
615
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Consequently, in B Battery Eliminators, where
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If your dealer cannot supply you, write direct 7^
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Special types for "A" and "B" Battery Eliminators available for Manufacturers.
Mica Condensers
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is immense.
Now you can get Sangamo Mica Con-
densers in capacities in between the
usual stock sizes, so you can build with
greater accuracy than ever before. They
are guaranteed to be accurate and they
always stay accurate, being solidly
molded in bakelite. Neither heat, cold,
moisture, pressure nor acid fumes will
affect their capacity, because bakelite
seals the delicate parts against all out-
side influences.
Capacities in microfarads and prices
0.00004
0.00005
0.00006
0.00007
0.00008
O.OOOI
0.00012
0.00015
0.000175
O.OOO2
0.00025
0.0003
0.00035
0.0004
0.0005
0.0006
0.0007
0.0008
4oc.
O.OOI
O.OOI2
0.0015
0.00175
O.OO2
0.0025
0.003
0.0035
0.004
0.005
0.006
0.007
0.0075
0.008
0.01
O.OI2
0.015
50c.
6oc.
7oc.
8Sc.
900.
950.
$1.00
i-iS
1. 20
1.25
With Resistor clips, loc. extra
Also Sangamo By-Pass Condensers -JL-
i/io mfd. 8oc. 1/2 mfd. goc.
1/4 mfd. 8oc. i mfd. $1.25
Sangamo Electric Company
6332-1 Springfield, Illinois
RADIO DIVISION, 50 Church Street, Netv York
SALES OFFICES— PRINCIPAL CITIES
For Canada — Sangamo Electric Co. of Canada, Ltd. Toronto.
For Europe — British Sangamo Co., Ponders End, Middlesex, Eng.
For Far East — Ashida Engineering Co., Osaka, Japan.
Tested and approved by RADIO BROADCAST
616
RADIO BROADCAST ADVERTISER
The Best in the World
No Batteries
are required even
to operate the
most powerfial
10- tube receiver
pictured above, if
you use the new
laboratory type
Model A
Power Unit
One Customer Telegraphs:
"Receiver assembled, per-
forming like a thorobred."
The Amateur or Experimenter
with his ultra-modern high-
powered receiver is years ahead
of Commercial Radio.
It is significant that unsolicited testimonials are
constantly being received from even the far corners
of the earth, where Norden-Hauck Engineers
have furnished the finest radio apparatus known
to the art today.
Quotations gladly furnished on radio parts and
apparatus having non-infringing uses.
Write for Literature ^
NORDEN-HAUCK, Inc.
Engineers
1617 Chestnut Street, Philadelphia, Pa.
Why not subscribe to Radio Broadcast? By the year only $4.00; or two years, $6.00, saving
$2.40. Send direct to Doubleday, Page & Company Garden City, New York.
Speaker with Concert Unit
The Heart of the Speaker
Large size and scientific construction of the Concert Unit
gives the remarkable tone values which
combined with the special amplifying prop-
erties of the BURNS horn produce re-
markable results.
Manufacturers
Burns horn is of distinctive design with
pyralin flare in several handsome finishes.
jtfmericaa&ectricQrnptuiy
State and 64th Streets, Chicago, U. S. A.
demand a changing of this bad condition. Who
is going to be the bright fellow to straighten it
out at a profit to himself?
A survey of most apartment-house roofs in
the country will show what has to be done.
Far beyond the unsightliness of these trap-
maze, antenna-ridden roofs, it is not pleasant to
have to duck and dodge such affairs when bent
on getting a breath of fresh air.
. There are two ways to get this thing ironed
out. Dr. A. Hoyt Taylor has invented a
multiple-tap antenna from which as many as a
hundred sets can be connected. Why not apply
this principle to rigging up apartment house
roofs in a more workmanlike manner?
On larger txjildingt
intermediate supports with 1 joints —
Space for Antennas t
Iron Pipe Supports
A STOUT ANTENNA SYSTEM
In which the possibility of a tangled mass of
collapsed antennas is greatly mitigated. Nowa-
days the average apartment house rooftop is
"enhanced" by a multiplicity of awkwardly
arranged antennas in all stages of confusion
Or again, the use of a solid spreader at either
end of a roof made of iron pipe and joints,
properly braced, and carrying a whole gang of
antennas at a safe height above the roof, is easy
to set up.
Who is going to get this business? It. is
there, waiting for somebody. Big or little; a
crowd of young men interested in radio should
have no trouble in making their knowledge pay
them big dividends.
Here are some sketches to show you just how
to solve such problems. It is essential that
radio encourage young men, all men, in fact,
to get into the game and use their knowledge for
the advancement of the craft. There is always
a scarcity of men who know their business,
especially in radio.
There are more men versed in the bread-and-
butter knowledge of radio, of a type fitted to
perform the work outlined here, than in almost
every other industry. You men who read this
publication must know quite a bit about radio
Put your knowledge to work. It means
money to you; it means experience, and new
minds, and more willing hands to do the work
that radio needs to have done.
DEMAND FOR RADIOS IN-
CREASES IN CZECHO-
SLOVAKIA
pOLLOWING a severe depression in the radio
1 business during the summer months in
Czechoslovakia, things are now beginning to
look up again, and the last few winter months
have seen quite a strong demand for radio equip-
ment. It is extremely difficult to obtain ac-
curate figures of the total number of receiving
sets now in use, but two reliable sources estimate
this figure to approximate 20,000, of which 8000
are located in the city of Prague, where is a 5000
watt broadcasting station. At present there an.
forty-nine manufacturers of radio equipment in
Czechoslovakia, but they do little business, most
of the apparatus there being of foreign manu-
facture.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
617
NEW PROFITS
for RADIO DEALERS
The II & U 5 Battery Charger will Charge
.1 Radio "A" batteries at once. Built for
110 volts, no power line needed. PluK it in
on any lamp socket and set it to work. It
pays for itself in two to three months.
Price, $60 with bulb.
Send for cur Charger booklet.
BURTON & ROGERS MFG. CO.
755 Boyleston St. Boston, Mass.
LATEST "COAST TO COAST" FULLY GUARANTEED
RADIO* -mwa
SAVE'/rro'A
Users everywhere report Miraco Radios get
program B coast to coaat on loud speaker;
outperform sets three times as costly.
Many hear foreign countries. Radio a
most amazing values in unconditionally
Euaranteed, factory -built long distance
Bets-let testimony of users convince you.
. PowerfulNewMulti-
ttube Miraco gets
llong distance on
• loud speaker. Set*
I ONLY
RADIO
GETS'EM
COAST *>
- COAST
""• improved 1 to 5 tuho mod-
els, new low prices, testimony of
users and SPECIAL OFFER. Write:
MIDWEST RADIO CORP'N
Pioneer Builders of Sri*
40G-W E. 8th St. Cincinnati, O.
Blackburn Ground Clamps
Telephone companies using
MILLIONS. Adjustable — fits
any size pipe. Requires no pipe
cleaning— screw bores through
rust and scale. Send 12 cents
for sample and postage.
Blackburn Specialty Compan;
1960 E. 66th St. Clerela
npany
ml. O.
Better Condenser'\
The TOBE DEUTSCHMANN High-Voltage Bi-
Pass Condenser in its silvered, shielded metal case is
designed for all usual by-pass work in radio receiving-
sets, and for construction of "B" eliminators of the
Raytheon and other types.
0.10 Mfd.. .$0.60c. 0.5 Mfd.. .$0.75
0.25 Mfd.. .$0.70c. 1.0 Mfd.. .$0.90
2.0 Mfd.. .$1.75
We announce a new TOBE High-Voltage Filter
Condenser for strictly filter uses, for power ampli'
fiers and other high-tension work up to 750 volts.
Each of these is individually tested and stamped with
date of test. Accuracy is guaranteed to within 5%
of rating. Put up in heavy metal cases and recom*
mended for precision work. Prices are the same as
our former list on filter condensers.
The new TOBE "B" BLOCK is out, for "B" elim-
inator construction, with one 8 M/d., two 2 Mfd., and
two 1 Mfd. condensers in one case. Saves $2.50 over
cost of separate units, — saves space, — saves wiring.
Send for free eliminator diagrams ^Lr
TOBE DEUTSCHMANN CO.
Cornhill, Boston, Mass. f
NXI
VARIABLE-RATIO
A UDIO-TRANSFORMER
4 to 1 - 6 to 1 - 8 to 1
all in one transformer
With this new Como Variable Ratio Transformer the set
builder may secure for each stage of audio amplification
the exact ratio best suited to the purpose. He may
match more closely the primary impedance of the trans-
former with the plate impedance of his tubes, with a
choice of 6 different values.
Built by a pioneer in radio manufacturing, this new Como
product will reproduce music and speech with lifelike
faithfulness.
In the familiar Como round-top, shielded metal case, at
your dealers.
PRICE, $/*00
^^
Send for descriptive pamphlet K
COMO APPARATUS COMPANY, INC.
Kelley Street Manchester, N. H.
This is a good time to subscribe for
RADIO BROADCAST
Through your dealer or direct, by the year only $4.00
DOUBLEDAY, PAGE & CO.
GARDEN CITY, NEW YORK
ARE You THE MAN
to be first in your town to sell and demonstrate POWEROLA, the famous 5-tube, no battery
ELECTRIC LIGHT SOCKET RADIO RECEIVER (not an attachment), universal for D. C.
or A C (100-115 v. 40-60 cycle,) three now sold and demonstrated by THE NEW YORK EDISON
CO., public utility companies and radio, electric and music dealers everywhere. Absolutely de-
pendable, fully guaranteed, powerful, practical, perfect in performance. Tested and indorsed by
Popular Radio, Radio Broadcast, Radio News, all leading authorities and engineers of your local
electric light company.
Are You the Man Who Sees Opportunities Ahead for Real Money Making?
YOU. TOO. CAN MAKE POWEROLA
Send $1.00 for wiring diagrams showing parts used and how to make any set or circuit (1 to 8 tubes) operate
satisfactorily without A, B or C batteries, from A. C. or D. C. This is the newest and greatest proposition
Write for literature, terms and prices at once
THE POWEROLA RADIO CORP.. 1845 BROADWAY. NEW YORK CITY
•ft Tested and approved by RADIO BROADCAST
618
RADIO BROADCAST ADVERTISER
Product of
38 Years'
Experience
eproduction
"I have listened to many loud
speakers, but never to any
music which can compare
with that reproduced by the
Amplion. The sound is clear,
sweet and well modulated. It
brings in clearly instruments
in bands and orchestras that
were lost in other speakers.
Through my Amplion I enjoy
my radio to a degree I had
never thought possible."
You will be as appreciative as this gen-
tleman, once you hear your set through
an Amplion. Creation of the origina-
tors and oldest makers of loud speaking
devices — Alfred Graham&Co.,London,
England — The Amplion leads in pop-
ularity throughout the world.
Enjoy an Amplion demonstration at
your dealer's. Six models, including
phonograph units, equipped with cords
and panel plugs, $12 up. Write for the
-jL. "Amplion Pedigree."
THE AMPLION CORPORATION
OF AMERICA
Suite L, 280 Madison Atie., New York City
Chicago B
Used in SO big broadcasting stations. 14,000,
48,000, 50,000 and 100,000 ohms. For distortion-
less amplification. Order a Crescent today at $1 .50.
Special sizes made to order. Discounts to dealers.
Crescent Radio Supply Co. ,1-3 Liberty St., Jamaica, N. Y.
RADIO RENCH
Kiagara Melil Slampinq Corp
Dent. 502, Niagara Fills, K.I.
Naval Radio
DROFESSOR MORECROFT'S com-
* ments on the Naval Radio Service in
the December RADIO BROADCAST created
quite a considerable amount of interest.
This especially interesting letter from a
gentleman apparently in an excellent
position to criticize, should be read in con-
junction with Professor Morecroft's re-
marks elsewhere in this number.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
After a long month of waiting for your Decem-
ber issue to reach the Coast, 1 was successful in
obtaining a copy today.
After reading Prof. J. H. Morecroft's article
about the Naval Radio Service I decided that an
answer to a few of his statements and questions
was in order.
Just a year ago on the 22nd of this month, I
was discharged from the Naval Radio Service.
At the time of the Honda disaster I was on the
U. S. S. Sumner, No. 333, 12th Squadron of the
Pacific Destroyer Force. My log was used at
the hearing which was held at North Island and
1 know it was through no fault of radio that the
disaster occurred. If Mr. Morecroft had looked
this matter up more carefully before his writing,
he would not have made such a statement.
As for the California-Hawaii flight Mr. More-
croft states: "According to the planes com-
mander, a perfect landing on the ocean was made
and nothing happened to interfere with the radio
apparatus performing as it was intended to do.
\Vhy didn't it perform?" The generators for
the radio are wind driven therefore a plane must
do her working before landing. Also the trans-
mitting antenna is reeled in before landing. It
is a known fact that these planes could not carry
the extra weight necessary to transmit while on
the water. Of course we all have some ideas of
'How it should have been done' but put yourself
in their position and you will see it different.
All possible space was needed for fuel, etc., and
fuel is heavy — so are batteries, or other equip-
ment necessary for transmission while a plane is
down.
Very truly yours,
H. A. HALCOMB.
San Diego, California.
Standardisation of Radio Parts
HPHE need for universal standardization
1 of radio parts is still very general,
but much progress in this matter has
been made since the inception of broadcast-
ing. The subject was revived in a recent
letter to this office, and we would like the
comment of our readers on this matter.
ASSOCIATED MANUFACTURERS OF ELECTRI-
CAL SUPPLIES, CHICAGO, ILLINOIS
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
Every one in the radio industry realizes that
standardization of radio parts and sets is neces-
sary to bring about a more stabilized condition.
The A. M. E. S., which has brought about the
•jr Tested and approved by RADIO BROADCAST -
••.-.r^^
FREE!
12-Cell-24-VoIt
Storage'B'Battery
Positively given free with each
purchase of a WORLD "A"
Storage Battery. You must
scml this ad with your order.
WORLD Batteries are famous
for their guaranteed quality
and service. Backed by years
of successful manufacture and
thousands of satisfied users
Equipped with Solid Rubber Cane.
an insurance apninst acid and lenk-
age. YouraveSOpercentandgeta
2-Year Guarantee
Bond in Writing
•
Solid Rubber Case Radio Batteries
6-Volt, lOO-Amperea ..... ill 25
- -
12-Volt. 7-'lst«
we will ship day order iu
press C. O. D., subject to
received, by Ex-
-- -+t, your examination
l. FKtt U Battery included.
Extra Offer: 5 per cent discount for caab
in full with order. Buy now ami gftaeuar-'
anteed batter/ at 60 per cent navin* to y"u.
WORLD BATTERY COMPANY
1219 So. Wabash Ave., Dept. 24 CHICAGO. ILL.
Science
tute of Stand-
ards. Popular
Radio Labors-
torfee, Kadio
Broadcast Lab-
oratories, Radio
In the Home,
andL«fax. Inc.
World
STORAGE BATTERIES
8. t your Radio Diala at 210
metera tor the new 1000
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AGENTS
WANTED
You Can Now Knrn a
5 Tube Demonstrator FREE!
In addition to $25 to $100 a week, part or full time. Everyone
a prospect. Complete line standard sets and accessories, $5 to
$90. Write today for illustrated catalog and exclusive selling
plan for live dealers and community agents. 20TH CENTURY
RADIO CO.. 1045 Coca Cola Bldg.. Kansas City. Mo.
Wonderful
Volume with Clearness
AMPL-TONE
Phonograph makers have spent years perfecting the
acoustic properties of their phonographs. Use an AMPL-
TONE Unit and make a real Loud Speaker in an instant or
use it in your horn and get better results.
After all. speakers are as good as their unit. We make a
real unit at a real price. Money gladly returned if you are
not entirely satisfied.
The UNION FABRIC CO.
DERBY, CONN.
Makers of the Excellent French AMPL-TONE Headset
Please send me an AMPL-TONE Unit for which I en-
close $3.00.
Name
Address
State. . .
RADIO BROADCAST ADVERTISER
619
THE ARISTOCRAT
HEATH RESISTANCE COUPLED
AMPLIFIER
Used in Radio Broadcast's Latest Set
Resistance Coupled Amplification has improved radio
reception and simplified set construction. For these
reasons Radio Broadcast used resistance coupling in the
design of their new Aristocrat Receiver. In this won-
der set Radio Broadcast recommends the use of Heath's
3'Stage Resistance Coupled Amplifier. The well known
quality and performance of Heath's compact, 3-stage
unit makes it particularly suitable for any set where full
volume and unusual quality are desired.
Write for Literature J^
Heath Radio and Electric Mfg. Co.
206-210 First Street Newark, N. J.
BUS BAR WIRE
VJOOKS'
We make a superior wire
of pure copper
Every piece of Cook Bus Bar Wire is now plainly
stamped "COOK'S" — your protection against
substitutes.
It is finished square or round, properly tinned and
correctly tempered for radio use.
Furnished in standard lengths of 2 feet.
EDWARD N. COOK
PLATE CO.
70 Ship Street Providence, R. I.
^Representatives
A. ALLEN SMITH MR. W. I. OTIS
304 E. Fourth St., Lo« Angela, Gal. Rialto Building, San Francisco, Cal.
WOOD if LANE CO.
915 Olive Street, St. Loui«, Mo.
HARRY J. CAFFREY
51 East 42nd St., New York, N. Y.
Complete list of
GUARANTEED PARTS FOR
Cilvcr - Marshall
l—J Model IwJL 1926
"MODERN BROADCAST
6-TUBE RECEIVER"
When building this receiver be sure you use only the parts
specified and you will have the satisfaction of possessing the finest
receiver yet developed.
3— S-M 311 .00035 S. L. F. Condensers
3 — 4 in. Kurz Krasch Moulded Dials
3— S-M 515 Coil Sockets
2 — S-M 112A Inductances
1 — S-M 110A Inductance-
6— S-M 510 Sockets
2 — Carter 6-ohm imp. Rheostats
1 — Central Laboratory 500,000 ohm Modulator
3 — Daven Resistance couplers complete
1— Carter 101 Jack
1— Carter 102A Jack
1 — Carter On-off Switch
1 — .002 M. F. Condenser
2 — Dubilier .5 M. F. By-pass Condensers
1 — 7 x 24 Drilled, Sanded and Engraved Bakelite Panel
1 — 7 x 23 Oak Base Board, Bus-bar. Screws, Lugs, etc.
1 — Belden 5-lead color cable
Complete Parts $4Q.50
as Specified, Only . . T^«X
Wired and Ready to Use $8. Extra
EXTRAS
Daven MU-20 Tubes
Daven MU-6 Power Tube ».-»»•••••
Western Electric 540-A.W. Cone Speaker - - -
All parts carried for Every
SILVER-MARSHALL CIRCUIT
$ 4.00
5.00
27.50
WE ALSO CARRY ALL THE PARTS FOR THE
R HAMMARLUND
OBERTS-RECEIVER
Endorsed by Ten Leading Radio Engine?!*
Engineers of the leading manufacturers who make these parts endorse
the operation of the Hammarlund-Roberts Receiver only when it is con-
structed with these specified units which the designers have found to co-
ordinate most efficiently with one another.
Order from this list and we guarantee you prompt delivery.
Unit No. 1. 2 Rauland-Lyric Transformers at $9.00 $18.00
Unit No. 3. 2 Hammarlund .0005 mfd. Model "C" or
S. L. F. Condensers at 5.00 10.00
Unit No. 2. 1 Hammarlund "Midget" Condenser 5
plate. 16 mmfd at 1.80
Unit No. 4. 1 Set Hammarlund-Roberts Coils at 7.50
Unit No. 5. 2 Na-ald "Super DeLuxe" 4 in. Bakelite at .75
Unit No. 6. 5 Na-ald "DeLuxe" Sockets at .75
Unit No. 7. 1 Na-ald K3S44 — 1J4 in. Dial at .20
Unit No. 10. 1 Carter 25-ohm "Imp" Rheostat at 1.00
Unit No. 11. Carter Single Circuit No. 101 "Hold-
Tite" Jack at .70
Unit No. 12. Carter "Imp" Battery Switch at .65
Unit No. 16. Durham Metallized Resistor at .40
Unit No. 8. 4Ampwites No. 1-A at 1.10
Unit No. 13. Dubilier Type 640-G .00025 mfd. Grid
Condenser at .50
Unit No. 14. Dubilier Type 640 .002 mfd. Fixed Con-
denser at .45
Unit No. 15. 1 Dubilier Type 640 .006 mfd. Fixed Con-
denser ..at .80
Unit No. 9. 5 Prs. Union Phone Tip Jacks, per pair at .25
Unit No. 17. 1 Hammarlund-Roberts Foundation Unit
(contains engraved bakelite-Westing-
house Micarta panel, drilled bakelite
sub-panel metal brackets and wire ..at 7.90
1.80
7.50
1.50
3.75
.20
1.00
.70
.65
.40
4.40
.50
.45
.80
1.25
7.90
Complete Parts as specified $57'50
Hammarlund De Luxe Cabinet $12.
Wired and Ready to Use $10. Extra
General Radio
UNIVERSAL RECEIVER
This is the simplified 4-tube circuit described in detail in the Jan-
uary issue of this magazine. Diagrams and complete instructions
furnished with each complete set of parts.
Complete Parts
Tested and approved by RADIO BROADCAST
Mail order* thipped fame day received
HEINS & BOLET
40 PARK PLACE. NEW YORK
$33.50
620
RADIO BROADCAST ADVERTISER
for
radio
aerials
—COPPER
wire
-MM-
COPPER combines
the essential
qualities of —
resistance to cor-
rosion,
tensile strength,
high conductivity.
COPPER & BRASS
RESEARCH ASSOCIATION
25 Broadway, New York
Order your copy of Radio Broadcast from your
news dealer or radio store. Make sure that he
reserves a copy for you each month. If your
favorite radio store does nof'stock the magazine
write us giving name of radio dealer and address.
LOW LOSS
Tuners and Coils for all circuits
3 Circuit Amateur and Broadcast tuners $7-oo
Radio Frequency Transformers (each) $2.00
Coils to order. Write for literature.
Davenport Radio Laboratories -fr
1711 W. Locust Street Davenport, Iowa
standards in the electric light and power field,
have created a Radio Section to standardize
radio sets and parts.
The Radio Section so far has made wonderful
progress in radio standards, but before going
further, it is considered advisable to get as much
information as possible as to what should be
standardized. Some of the things we have in
mind that should be standardized at once are as
follows:
1. Should Rheostats, Condensers, etc., be of
the one-hole mounting type, or mounted by
means of screws?
2. Should Dials and Condensers be so designed
that when the dial is turned to the right the
numbers on the dial increase, or should the num-
bers increase when the dial is turned to the left?
It seems to us that inasmuch as rheostats turn
from left to right, that the other controls should
turn in the same direction. There are many sets
and condensers on the market on which the dials
turn from right to left. It would seem that if
this could be standardized it would be a step in
the right direction.
3. Should all Dials and Knobs have the same
size Holes, and if so, what size do you recom-
mend?
4. How far should Condenser Shafts project
through the panel?
There seems to be no standard length of con-
denser shaft, which results in much annoyance,
due to the fact that dials do not fit properly.
The Radio Section has already standardized
such items as Cords, Cord-tips, Plugs, Jacks,
Rheostat Shafts, Standard Color Code for wiring
sets, etc.
What other specifications, in your opinion,
should be standardized?
Your recommendations will be beneficial and
we will greatly appreciate any assistance or sug-
gestions you care to give.
Very truly yours,
A. J. CARTER.
Chairman, Parts Committee Radio Section.
A Letter from Chicago's
Radio"
'Miss
BEFORE the commencement of the
recently concluded International
Tests, RADIO BROADCAST appointed listen-
ing posts all over the country so that
the fullest possible data could be collected
on this subject after the Tests were com-
pleted. One of our letters was sent to
Chicago's" Miss Radio," and here is her
reply.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
Sir:
I would like very much to be appointed as an
official listening post for the International Radio
Broadcast Tests. I have a certificate of reception
awarded to me last year for the successful
reception of programs as broadcast from 2 to and
FPTT, Paris.
1 am using an Atwater Kent-io, an Atwater
Kent-2o, and an Apex Super-Five. 1 have three
different antennas; (i) 140 feet long, south to
north; (2) 100 feet long, east to west; (3) 50 feet
long, north to south. 1 have logged 264 different
broadcasting stations, and am still going strong.
The Atwater Kent-io was my first set, and was
bought in March, 1924.
I was awarded second prize in the "Radio
Diana" contest conducted by the Radio World's
Fair in New York City, and was awarded
first prize in the "Miss Radio" contest at the
Chicago Radio Show. I hope to have a five-
watt short-wave transmitter going soon.
Very truly yours,
FLOSSIE E. ERICKSON,
Bloomington, Illinois.
T Tested and approved by RADIO BROADCAST -
NEW MODEL T CABINET
Si:es in stock. Have pi.ino hinge, and are full 8" and
10" deep inside.
Siz.
7x18-8
7x21-8
7x24-S
7x26-8
7x28-8
7x30-8
Mahnenny Mahogany
$8.55
9.30
10.10
10.70
11.80
12.75
$9.50
11.50
12.60
15.35
14.70
15.85
Mahogany Mahogany
Finish or
Walnut
7xlv-10
7x21-10
7x24-10
7x26-10
7x28-10
7x30-10
$10.20
10.90
11.70
12.65
13.00
13.30
$11.55
13.25
14.65
15.80
16.20
16.65
HAMMARLUND ROBERTS CABINET
With piano hinge, sloping panel, and fancy line grooves.
Mahogany or Walnut $14.00
Mahogany Finish 1 1 .50
BROADCAST UNIVERSAL AND
ARISTOCRAT CABINETS
Model T design, with slots and drilling to specifications
Mahogany or Walnut $11.00
Mahogany Finish 9-00
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"CORBETTS CABINETS" have been preferred for
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Tested and approved by RADIO BROADCAST
RADIO BROADCAST
ARTHUR H. LYNCH. Editor
WILLIS K. WING, Managing Editor
JOHN B. BRENNAN, Technical Editor
APRIL, 1926
Vol. VIII, No. 6
Cover Design ' - From a Painting by Fred J. Edgars
Frontispiece - - Listening-in at Petyn 642
How Radio Grew Up Robert H. Marriott 643
What Happened During the 1926 International Tests
Willis K. Wing 647
The March of Radio -J. H. Morecroft 652
The $500 Short' Wave Receiver Contest < 657
The Tube and Its Best Uses Keith Henney 658
The "Aristocrat" Receiver - 664
Radio Sets for Light Keepers - - - 666
The Listeners' Point of View - - John Wallace 667
As the Broadcaster Sees It - Carl Dreher 672
Drawings by F. F. Stratford
How a Portable B Battery Transmitter Works
By the Laboratory Staff 678
The Use of the Filament Resistance John B. Brennan 682
Cutting out the Locals - - - - H. E. Rhodes 686
The Grid — Questions and Answers
Coil Dimensions for the "Universal" Receiver
Eliminating the Reflex in the Roberts Circuit
How to Calculate Capacity in Series or Parallel
A Three-Tube R. F. Circuit with Impedance Amplification
"Now, I Have Found" - - - -
Improving Reproduction in Cone Speakers
How to Provide a Counterpoise System
The Silver "Model 1926 Receiver4'
A Coil Winder for Diamondweave Coils
A Battery Throw-over Switch
Economical Sub'panel Brackets
Short Wave Stations of the World
A Key to Recent Radio Articles E. G. Shaltyiauser
What Our Readers Write Us
696
702
708
710
716
1
EDITORIAL SCENES
ROBERT H. MARRIOTT is one of the "old men of
radio" in the United States and his articles about "How
Radio Grew Up" seem to please both old and new radio folk.
The first article in the series he is writing for RADIO BROADCAST
appeared in December, 1925. However much we may marvel
now at the accomplishments of the amateur in throwing a faint
short-wave signal half way around the world with his simple
apparatus, there is still much of the remarkable in the accom-
plishments of the early radio workers, and there is no one better
able to tell about it than Mr. Marriott. There are other arti-
cles to follow by him.
A LTHOUGH the International Tests are considerably be-
•/!. hind us in this rapidly moving radio world, the corres-
pondence from radio listeners all over the United States and
from foreign countries still continues to bombard the office.
For those who listened in vain for a peep on a foreign wave-
length, the review of the results of the Tests on page 647 of
this issue should attract attention. A letter just received from
a woman in Iowa is especially interesting. "To settle an ar-
gument with my husband," she writes, "will you please tell me
whether or not the following program came from any foreign
station?" The program in question came from Bournemouth,
and since that station was added to the list at the last minute,
she, among many listeners, did not know they were on. We
settled the argument.
THE third in the series of Keith Henney's valuable articles
on tubes appears in this number. The previous two ap-
peared in the December and February issues of RADIO BROAD-
CAST. "The Tube and Its Best Uses" is specially designed to
answer all sorts of questions on the practical use of the tube in
radio circuits, and it was written in a large measure to answer
definite inquiries which came to our office.
/DOMING numbers of RADIO BROADCAST will have much of
\—J interest to every sort of reader. One wishes that space
limitations did not prevent us from including in this issue some
of these articles which have been omitted for that reason. In an
early number, there will be another of the home laboratory arti-
cles, describing a very useful wavemeter wit,, complete instruc-
tions on how to use this valuable device in the home laboratory.
Then there is another article by H. E. Rhodes on wavetraps, de-
scribing a number of valuable types, which will be a great help
to those who are having their own difficulties with a receiver
which is not selective enough. There will be more informa-
tion on short-wave transmitters — that subject which has
proved widely popular with our readers. Edgar H. Felix has
written a very helpful article on how to learn the code which
many a mystified struggler with the Continental dots and
dashes will find of great value. The article by J. C. Jensen
in the April number, "Can We Forecast Radio Reception from
the Weather?" has stirred up no end of interest and discussion.
Shortly after the magazine appeared, the Associated Press car-
ried a story about Mr. Jensen's conclusions. Mr. Jensen's
article has inspired other investigators in the same field to tell
us of their work and we hope soon to print the conclusions of
some of these men.
MANUSCRIPTS on the $500 short-wave receiver contest
are piling into the office, and those who have not yet
become actively interested in the problem should turn at once
to page 657 and set their brains to work. — W. K. W.
0*=
Doubleday, Page & Co.
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LISTENING-IN AT PEKIN
©American Museum of Natural History and Asia
Although radio broadcasting has already made its debut in some Chinese centers, most of the natives listening-in here were doing so for
the first time. The sets are those of the scientific expedition headed by Roy Chapman Andrews, which was sent to Mongolia through the
cooperative efforts of the American Museum of Natural History, and Asia magazine. The upper picture shows one of the expedition
mystified by the voice in the box, while the other retainers are shown listening to a program from Tientsin in the lower picture
RADIO BROADCAST
VOLUME VIII
NUMBER 6
APRIL, 1926
The Period 1872 to 1897— Hughes, Dolbear, Hertz, Branley, Lodge, Tesla,
Popoff — Marconi's Early Life — Wireless is First Put on a Commercial Basis
By ROBERT H. MARRIOTT
IN CHAPTER I of "How Radio Grew
Up" we rapidly traced the growth of
radio science from its earliest stages —
from the time when Luigi Galvani con-
ducted his researches in 1790, probably
knowing little about what he was actually
doing, through the researches of De Salva,
of Morse, and of Maxwell. The electro-
magnetic induction experiments of Faraday
were also described, and the story concluded
with one Loomis, who, in 1872, took out a
patent for a special apparatus designed to
utilize electricity collected from the atmos-
phere for transmitting purposes. Taking
up our story at this point (where it was
dropped in the December, 1925, RADIO
BROADCAST,) the first new name in
the series is that of Professor D. E.
Hughes, who, in 1872, managed to
transmit and receive intelligible
signals over a distance of a quarter
of a mile, using, for receiving pur-
poses, both coherers and microphonic
detectors.
He described his devices before the
Royal Society on May 8, 1878.
During his experiments, he walked
up and down Great Portland Street
in London with his microphonic de-
tector and telephone receiver, and
it was at this time that he got signals
up to a quarter of a mile or more
from his transmitter. Had he per-
sisted with his apparatus, and if it
had been possible to employ at that
time a present day publicity agent,
radio might have gone into public
service many years earlier than it
did, for some of the accounts in-
dicate that his apparatus was every
bit as efficient as apparatus used
seventeen years later. In this coun-
try we quickly abandoned the later
First President, Institute of Radio Engineers
coherer method of reception and went back
to the telephone and detector method.
Hughes made his demonstrations to
fellow scientists who appeared to be bent
on discouraging him, and years later he
said, " I was so discouraged at being unable
to convince them of the truth of these
aerial electric waves that I actually re-
fused to write a paper on the subject — — ."
In 1882, Professor A. E. Dolbear, of
Tufts College, built a transmitter and a
receiver, with antenna and ground, that
apparently must have operated according
to the electro-magnetic theory. On Oc-
tober 5, 1886, he was granted United States
patent number 350,299. He described
EDOUARD BRANLY
French scientist who made a very valuable contribution
wireless telegraphy in designing a detector known as a
coherer. It was later improved by Sir Oliver Lodge
his invention as a mode of electric com-
munication, and said in the description,
"Communication may thus be established
between points certainly more than half
a mile apart; but how much farther I cannot
now say."
It looks now as though both Hughes's and
Dolbear's devices were pretty fair radio
devices for that time; but apparently those
equipments were not deliberately designed
and operated on the basis of the now
accepted electro-magnetic wave theory of
Maxwell.
Following Hughes and Dolbear, we next
come to the exponents of the earlier Max-
well theory. The first of these is Henrich
Hertz, a German scientist, who, in
1886, proceeding on Maxwell's
theory, built and used a carefully
tuned radio transmitter and receiver.
However, it could not be heard
enough to do much more than serve
as proof of the Maxwell theory, be-
cause the detector was insensitive.
Sir William Crookes, in discussing
Hertz's apparatus, said, quoting from
the Fortnightly Review, London, Feb-
ruary, 1892, "Here, then, is revealed
the bewildering possibility of tele-
graph without wires, posts, cables, or
any of our present costly appliances."
HERTZ THE FATHER OF RADIO ?
SOME scientists and other folk
who have studied the history of
radio and who are not biased by
nationality or by some company's
pay roll, are inclined to say that radio
is a product of evolution; while
others prefer to say that radio was
invented. As a rule, those unbiased
ones who prefer to say it was in-
vented, give the credit to Hertz.
644
RADIO BROADCAST
APRIL, 1926
NIKOLA TESLA
Was born in Austria-Hungary in 1857, Serbian
by race. It was originally intended that he
should be trained for the clergy, but he developed
scientific tendencies instead. He came to
America in 1884 and immediately entered the
Edison works, afterward starting out on his
own. In 1893 he invented methods of wireless
transmission
In 1891, Edouard Branly, a French
scientist, made a more sensitive detector
than that used by Hertz, intended for use
in the latter's receiver. This detector was
called the Branly coherer. It consisted of
particles of metal that would stick together
when affected by radio currents, and would
then pass a battery current. Sir Oliver
Lodge used the Hertz-Branly combination,
but added a tapper that automatically de-
cohered the coherer after a signal.
In 1893, Nicola Tesla proposed that high
antennas and a
ground connection
be used at the sending
and receiving instru-
ments to get the great-
est possible distance.
In 1895 Vladimir
Popoff, a Russian,
added antenna and
ground to the Hertz-
Branly - Lodge com-
bination, and gave
demonstrations to
students and scien-
tific people. The dis-
tances covered grew
with these successive
steps.
By 1894, wireless,
that is the induction
system like that Fara-
day had used, and the
conduction system
which Morse had
demonstrated, had
been successfully and
repeatedly used to
telegraph over dis-
tances up to three
miles or more. The
Hertz-Branly- Lodge-
Tesla- Popoff combi-
nation apparently
worked best. It was
the product of German, French, English,
American, and Russian scientists, arrived
at by sticking to the Scotchman's (Max-
well's) theory.
MARCONI'S EARLY LIFE
WHILE this radio development was
going on in the scientific circles of
the world, young Marconi had been taking
a course under science teachers at Leghorn
and Bologna, and became interested in
radio in 1895, when about twenty-one
years old. He had means and influential
connections in both Italy and Great Britain.
He came from Italian ancestry on his
father's side, and Irish ancestry on his
mother's side.
In 1896, Marconi went to England and
filed a patent in which he described the
Hertz-Branly-Lodge-Tesla- Popoff devices
and a special form of spark gap that had
been designed by the Italian scientist
Righi, which gap was not necessary but
could be used as a substitute for the one
used by Hertz. Then he commenced
demonstrating what was actually known
about radio up to that time, to government
representatives and to business men, to
newspaper and magazine writers. His
demonstrating extended radio from college
environment to political, military, and
mercenary circles. By the middle of 1897,
business men had become sufficiently inter-
ested to form a £100,000 company for
exploiting radio.
Marconi played the part of a salesman,
and, as is still often the case where scientists
and salesmen are involved, the salesman
got money out of it while the scientists
THE CATALINA SENDING STATION
Located at Avalon, about twenty-five miles from the California Coast station. Until Mr. Marriott
erected this station there was no means of communication with the mainland except by means of
the boat service which was not at all reliable, especially in bad weather. One of the first uses to
which this wireless was put was to receive the result of a big fight which took place in San Francisco.
Skeptics doubted the authenticity of the wireless reports and even after they were confirmed, various
theories as to how the messages were actually received were advanced. Some said that carrier
pigeons were used. Others said they saw a man in a small boat land on the Island with the news.
Another theory was that signals by means of powerful lights were sent from the mainland to Catalina
GUGLIELMO MARCONI
Whom Mr. Marriott describes as a sales engineer.
He studied and conducted his early experiments
at the University of Bologna in Italy. In 1899
he succeeded in communicating across the
English Channel for the first time, and in 1901,
across the Atlantic Ocean. He was awarded
the Nobel Prize for Physics in 1909
didn't. Also, as part of the promotion
scheme for getting money, Marconi was
advertised as deserving the honor for what
the scientists had done, making him appear
as a profound scientist and almost super-
natural inventor.
The scheme was to make it appear that
Marconi had invented radio and thereby
get a world wide radio patent monopoly.
That was the beginning of many dupli-
cated attempts to advertise inventions and
inventors for the purpose of getting a
monopoly of radio, or to sell stock. It has
been tried more or
less right up to this
very minute. In the
United States, how-
ever, the patents were
shown up for what
they were worth, or
avoided by making
other devices that
would serve the same
purpose.
The virtue of the
Marconi Company's
advertising was in the
publicity it gave to
radio and not in the
claims they made for
themselves. That
publicity started
quite active develop-
ment of radio in sev-
eral countries. It put
more money and peo-
ple into the develop-
ing of this so-called
new science.
The advertising
brought radio to the
attention of people in
all walks of life, in-
cluding numerous un-
attached young
would - be scientists
and engineers, who,
APRIL, 1926
HOW RADIO GREW UP
645
like Marconi, as yet
had no scientific or
engineering reputa-
tions to lose, and
therefore, could take
a chance in this new
field.
It became obvious
to many that radio
could be useful if
properly applied.
Its apparent possi-
bilities made it an
easy thing for stock
jobbers to sell stock
in radio companies.
They were inclined
to depart very
widely from the kind
of rules laid down in
Christian Sunday
schools in disposing
of their stocks, how-
ever. Radio was an
obviously fertile
field, but without
immediate returns
in it. It contained
some more or less
AN EARLY DETECTOR
Is shown in this photographic reproduction of the sketch and description of those made by Mr.
Swenson (Mr. Marriott's able assistant) to Mr. Marriott's specifications. These were used in the
California-Catalina Island circuit for several years. They consisted of converted spherometers
dangerous Indians.
Scientists, with reli-
able incomes and
reputations that
might get sunk na-
turally were afraid
to go into radio.
However, there
were quite a num-
ber of young men
who had been given
scientific training,
and who had not
made any scientific
or engineering repu-
tations that could
be lost. Some of
them were adven-
turous enough to go
into radio then, and
a few still survive.
The writer is one of
these young men.
After 1897, the
works and workers
became so increas-
ingly numerous that
only some of the es-
sence of them can be
C. S. KEMP, AN EARLY ASSISTANT OF SENATOR MARCONI
Photographed in England with the apparatus used by Mr. Marconi in his experiments at Bologna, Italy, in 1895. The copper plate at the top is the
antenna used for short distances, while for greater distances, kite balloons ten feet in diameter with a copper antenna wire attached, were employed.
The telegraph key is at the right, the large induction coil shown in the center operating from batteries, furnished the high-frequency energy
646
RADIO BROADCAST
APRIL, 1926
given here. Radio stations began to bob
up in various parts of the world like mush-
rooms, and like mushrooms, they did not
last long in any one place; as a rule because
they didn't pay expenses, and also because
a great many of them were temporary
stations erected purely for demonstration
purposes, devoted to showing the possibili-
ties at that place, or to sell stock. In
1902, the writer succeeded in establishing a
radio circuit between Catalina Island and
the mainland of California, the first in the
United States that stayed put, although
several circuits had been tried before that.
That circuit continued for twenty-one
years, becoming a radio telephone circuit
in its later days. The use of telephony
killed it, for too many uninvited folks were
able to listen-in.
The steamship companies were slow to
install radio on their ships. The directors
of the companies had too many other
places where they wanted to put their
money. The captains likewise did not
want it because, without it, they were
kings between docks, but with it, the
owners might play king and give them
orders. A la<-ge proportion of the first ship
radio stations were established on board free
of charge to the steamship companies.
The United States law which compelled
ships to be equipped with radio, took effect
in 1912, and caused a large increase in
radio on vessels, and also resulted in some
of the old captains recalling for service all
the cuss words they had mentally vo-
cabularized during, perhaps, forty years at
sea. The writer had intimate contact with
this aspect of radio, because, when the law
went into effect, he helped enforce it at
New York as United States Radio In-
A 1902 COMMERCIAL RADIO CIRCUIT
The wireless telegraph installation at Catalina Island, made by Mr. Marriott and his
assistants. The switchboard at the right controlled the dynamo circuits for light and
transmitter power. The switchboard in the back carried two remote control switch
arms which switched the antenna from "send" to "receive". The box bearing the
spark rods is a large induction coil capable of giving a 2O-inch spark but actually de-
livering a f-inch spark when connected to the antenna. The piece of paper covers a
mechanical interrupter, which, at the time the picture was taken, was a secret
spector. After a captain's big noisy kick
was divested of its profane trimmings,
about all it amounted to was a statement
to the effect that he had sailed the seas
ever since the time when vessels were
pushed along by the wind, and that he had
THE RECEIVING EQUIPMENT
Of the last Santa Catalina public service station, which was closed in July, 1923, as its traffic was listened-in to
by many outsiders. The receiving loop may be detected in the background. A submarine cable was substituted
for the radio link
gotten along without wireless up to date
so why shouldn't he and everybody else
continue to get along without it. All the
radio inspector had to say was, "Maybe
so, but if your radio isn't in proper working
order before you leave port I will have to
report it, and you will be liable to
a fine of five thousand dollars."
Not many words, but they were
effective.
The value of radio as a protec-
tion against the loss of life and
property, and the failure of steam-
ship companies to avail themselves
of it, made the law necessary. Had
there been a radio monopoly, this
law would probably have been all
the more necessary because the
monopoly would have undoubt-
edly held up the prices, and steam-
ship owners would have fought
harder against its enforcement.
The United States took the lead
in the production of the best de-
tectors and receivers; Germany
took the lead in the production of
the best transmitters. Receivers
and detectors were inexpensive to
build, as compared with trans-
mitters. This was what probably
caused the various workers in the
United States to advance rapidly
in making the best detectors and
receivers. By the time the Euro-
pean War started in 1914, however,
the United States was catching
up with Germany in making first
class transmitters.
A Complete Report of the Plans, Their Progress and Success — What Stations Were Qenerally Heard
— How Bloopers Spoiled Reception — The Qreat Popularity of the Regional Broadcasting Experiment
By WILLIS K. WING
•ANY old wives' tales are common
knowledge about events which occur
in the dark of the moon. And by
the same token, things which happen
during the full moon must take their chances of
success. The third of the International Radio
Broadcast Tests took place during the fullest
of full moons, we remind the superstitious, and
if that be any comfort to those who failed to
hear signals from the foreign broadcasters, all of
that gentry are free to make the most of that celes-
tial condition. For to review the Tests briefly,
a comparatively small number of American and
Canadian listeners heard broadcasting stations
on the other side of the Atlantic. If that is the
only measure of failure, the Tests were a failure.
However, the Tests this year, lasting for an
hour for seven days, included but five days of
transmission from transatlantic stations. The
other two days, as everyone knows, were devoted
to distance receiving trials on the North and
South American continents. And in those two
days, the average listener probably heard more
stations on this continent than he had ever
heard before. The genuinely new feature of
the Tests proved a great success.
The plans for the Tests were published so
completely in newspapers in this country and
in Canada, that there is no point in completely
reviewing them here, for no monthly magazine
can hope to compete with a newspaper. But
the 1926 Tests were the third to be held. The
first Test was held in November, 1923, and
involved only the stations of the British Broad-
casting Company, abroad. The sec-
ond occurred in November, 1924. In
that, the British stations and broad-
casters in Spain, Italy, France, and
Belgium took part. The third an-
nual Test was to have been held in
November, 1925, but was postponed
to January, 1926 in order to take
advantage of what was fondly sup-
posed to be better weather condi-
tions.
There is always plenty of enthu-
siasm for international broadcasting
from this side of the Atlantic, but
the desire for a special Test of this
sort is not so great on the other side
of the water, and especially in Eng-
land, where there are probably more
active listeners than in any of the
Continental countries. Owing to
the difference in time, it is possi-
ble for any European listener to sit
up a bit after twelve at night, and if
he has a sensitive receiver, tune-in
an occasional American station.
So that when the special Interna-
tional Tests are arranged, with
listening periods for American sta-
tions at from three to four o'clock
in the morning, European time, the
desire on the part of foreign fans for
special long distance tests is apt to be less
ardent than here, where the listening period has
never been later than midnight, Eastern time.
LARGE NUMBER OF STATIONS INVOLVED
DUT in spite of these handicaps, the foreign
^ arrangements for the Tests went forward
with great completeness and more foreign sta-
tions were listed in the schedules this year than
have ever taken part before. John Scott-
Taggart, editor of the British Radio Press
publications was appointed foreign director of
the Tests, and through his good offices and those
of his able assistant, Percy W. Harris, editorial
manager for those publications, the work went
forward. On the Continent, the arrangements
were in charge of Dwight K. Tripp, a former
member of the editorial staff of RADIO BROAD-
CAST, who is now residing in Paris. Mr. Tripp
worked in close cooperation with Arthur Bur-
rows, head of the newly formed Bureau Inter-
national de Radiophonie at Geneva.
Although the engineers of all the Continental
broadcasting stations have, for the past few
months, been conducting some special late
broadcasting tests of their own, in the effort to
solve the problem in international heterodyning
between stations which is now very serious, they
entered into the spirit of the plan and assumed
the additional burden of broadcasting for an
hour several nights of the Test at the unpleas-
antly early hour of four o'clock in the morning,
their time. It was chiefly through the fortunate
official influence of Mr. Burrows that the Con-
THE SHORT-WAVE OUTFIT IN USE AT 2 GY
During the International Tests, a 40- and an 8o-meter transmitter were
used constantly in checking receiving conditions with amateur operators
in this country and in Europe. Many reports of reception were handled
by this short-wave link
tinental cooperation was as general and complete
as it was. And Mr. Tripp was untiring in his
efforts to make the many complicated arrange-
ments necessary.
On this side of the Atlantic, the greatest
number of broadcasting stations ever to take
part in a concerted plan of this sort were on
the schedule. There were the 37 Canadian
broadcasting stations, some 550 American broad-
casters, 1 6 Mexican stations, 36 Cuban broad-
casters, one station in Porto Rico, one in Lima,
Peru, and three in Argentina taking part.
The cooperation of the Cuban stations was
secured by Mr. Frank H. Jones, owner of sta-
tion 6Kw at Tuinicu. The cooperation of the
American broadcasting stations was practically
complete with the exception of several of the
California stations, notably KNX at Hollywood
and KFI at Los Angeles. The operators of KFI
it was announced, felt that their individuality
would be greatly limited by participation in the
Tests and confidently undertook to analyze
the desires of all the radio listeners within range
of their five kilowatts, and decided, to the tune
of wide publicity, that they would remain on the
air during the silent periods. They stated that
the chances of California listeners for hearing
foreign broadcasting was very slim, and to that
confident assertion was added the confession
that theirs was in part a commercial station,
devoted to selling time on the air, and that they
saw no reason for making any financial sacrifice.
Our records show that a number of listeners
in Oregon and Washington did hear fragments
of the foreign programs, a remark-
•^^ able receiving record. A very large
number, comparatively speaking,
heard OAX at Lima, Peru and sev-
eral of the Buenos Aires stations.
The sentiment quoted from the let-
ter printed below is similar to that
contained in a great many letters
and telegrams which came into the
office of RADIO BROADCAST both
during and after the Tests.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR,
1 am a radio dealer and a fan as
well. May we not in some way en-
ter protest against California sta-
tions remaining on the air during
the quiet hour Sunday night (Janu-
ary'24th) during the Tests? I think
I picked them all up. 1 like Cali-
fornia, but I like them to shut up
at least once a year and I am sure
I speak the sentiments of many
more of your readers and fans in
this locality.
Very truly yours,
W. M. CURTRIGHT,
Flat River, Missouri.
No purpose would be served in
648
RADIO BROADCAST
APRIL, 1926
embroidering this controversy, except to add, in
fairness to the Pacific Radio Trade Association,
who failed to cooperate positively in the national
United States arrangements, that they finally
agreed to recommend silence for the West coast
stations even though they were in highly active
opposition to the plan. And during the first
few nights of the Tests, some of the Pacific coast
stations did not keep silence, but in the main,
their insurgent tactics caused no national radio
calamity. Our judgment that radio listeners
there, and elsewhere, wanted the Tests to go
through as planned, whether or not the in-
dividual felt he had a chance of hearing Europe,
has certainly been vindicated if our heavy
correspondence is any criterion.
HOW THE TESTS WERE ADMINISTERED
THE Tests were managed this year by a
representative organization, drawn from
all branches of the radio industry. A committee
was chosen from the National Radio Trade
Association, with Powel Crosley, Jr., as chair-
main and L. A. Nixon executive secretary.
There were other cooperating committees from
the National Association of Broadcasters and
the Radio Manufacturers' Association. The
editors of RADIO BROADCAST felt in planning
the test this year, that the interest caused by the
first two Tests, which were almost entirely
managed from this office, had made the affair
so important that the entire radio industry
should be represented in its management.
The Test Committee at its headquarters in
New York managed the American side of the
affair and furnished the newspapers and press
associations with daily and hourly bulletins.
Certain newspapers in representative cities were
furnished with the official programs as received
from the foreign representatives of RADIO
BROADCAST. This made the task of checking
foreign reception vastly easier and far more ac-
curate than in the previous two Tests. Busy
long distance wires, and piles of telegrams at
the New York office made the scene there dur-
ing the Test Week one of the most active we
have ever witnessed, and we have been in more
than one metropolitan newspaper office at World
Series time, or on the occasion of a big disaster.
A large number of official listening posts were
appointed by RADIO BROADCAST and their
reports, sent in by mail, telegraph, and by the
short wave amateur radio link with our experi-
mental station 2 GY was of constant help in
determining how receiving conditions were in
all parts of the country. Many radio manu-
facturers had special receiving stations. The
National Association of Broadcasters appointed
a listening committee, headed by Paul F.
Godley, of Upper Montclair, New Jersey. Mr.
Godley, it will be recalled, about five years ago
was successful in hearing American amateur
transmissions, the first across the Atlantic, from
a special receiver he established at Androssan,
Scotland. The Boston Herald-Traveller estab-
lished a listening station at Baker's Island near
Boston, manned by several operators, and a
meteorologist. F. R. Hoyt, of Stamford, Con-
necticut set up his interesting radio recording
apparatus at Shippan Point, Connecticut, and
reported that he succeeded in making partial
records of foreign programs. R. P. Worden,
radio editor of the Cleveland News sent especially
complete reports of receiving conditions and
success in the Cleveland area which were very
helpful.
In addition, RADIO BROADCAST had several
receivers in operation at Garden City, and two
operators were constantly on watch at station
2 CY using the 40- and 8o-meter transmitting
bands simultaneously. During the Test periods,
2 GY received frequent reports from all parts of
the United States on receiving conditions, and
on several occasions, communicated directly
with Europe to discover weather and receiving
conditions at the time. An article on another
page of this number describes in part some of
those arrangements with short wave communica-
tion. Receiving conditions are never especially
favorable at Garden City for extreme long dis-
NEWS HEADQUARTERS FOR THE TESTS IN NEW YORK CITY
With L. A. Nixon, Secretary of the International Radio Week Committee, wearing the telephone
receiver. During the Test Week, an office was set up in the Hotel McAlpin, New York, where
official programs were given to the Official Radio Week newspapers; the United Press, and the Asso-
ciated Press were given hourly bulletins as to the progress of events. This left the wires freer at
Garden City for communications from our official listening stations
tance work, so several members of the staff
took sensitive receivers to Riverhead, Long
Island, where it was thought that the air would
be free from radiating receivers and their havoc.
Even there, miles from the nearest house, the
bloopers got in their furious work.
THE BUSINESS OF VERIFICATION
REPORTS from listeners in this country
went chiefly to the local newspapers, to
the broadcasting stations, and to radio manu-
facturers. Many newspapers furnished verifica-
tion cards to successful listeners. Telegrams
sent to RADIO BROADCAST for verification of
reports were answered the same day they were
received, which was no small chore, considering
their number. Letters with details of reception
have come in to our office by thousands and
are being checked and verified as rapidly as
possible. An official verification card is being
mailed to all listeners who write to RADIO
BROADCAST whose report can be verified.
This task of verification is not easy, but its
onus is frequently broken by conscious or un-
conscious humor. " While listening last night,"
reads a sample letter, " I picked up a lady singing
on 360 meters, but she soon faded out. Can
you tell me who it was?" This achievement,
if it is a radio affair at all, is worthy of note, and
a curiously large number of letters read just like
that. Verification from such meagre informa-
tion is out of the question and there are prob-
ably many disappointed listeners whose letters
were equally bare of facts who still wonder why
"the coveted pasteboard" was not sent them.
Still others sent in confident letters announcing
that they heard 2 LO, or Madrid, or whatnot,
"very clearly," but failed utterly to specify
their success in detail. Reports like that were
not considered. But many others mailed reports
that were more than complete and very accurate,
making our task almost easy.
The question that everyone wants to have
answered is: What success did listeners have
generally, and what foreign stations were heard?
There is not space enough at our disposal to
list the listeners whose reports have been veri-
fied, but it is possible to tell what stations were
most generally heard. Station OAX at Lima,
Peru.was heard by more listeners than any other,
and that is no mean accomplishment, from the
point of view of distance and can be pointed
to with as much pride as the electrical bagging
of a European broadcaster. Reports on English
stations were few and far between, but all of the
English stations participating were heard in var-
ious parts of the United States. Almost no Cana-
dian listeners heard British broadcasters. The
Madrid and Barcelona stations got through to
the United States very well also. Prague, M unich,
Berlin, Hamburg, Brussels, and Munster were
also widely reported during their transmission
times. Hamburg signed off in code with the
letters "h a" and one faithful reporter although
he did not know the Continental code, related
that he heard the name of the city and the code
sign, four dots, dot dash.
NO RECEIVING LOCATION PERFECT
Hp HERE were spots of fair reception, although
» in no locality did any of the transmitting
stations come in with any laudable volume. In
parts of New England there were a number of
successful listeners who heard both Europe and
South America. There were a few, similarly
fortunate, in eastern Pennsylvania, New Jersey,
and New York. A listener in Bermuda heard
Madrid and he reported that many other Ber-
mudians heard LOX, and numbers of European
stations. Moving farther west, there were a
considerable number of listeners in southern
APRIL, 1926
THE 1926 INTERNATIONAL TESTS
649
Ohio and Kentucky who heard fragments from
the Continent and more than that from the
South American stations. Missouri seemed to
be fortunate in having more favorable receiving
conditions than some of her neighbor states.
Reports from the Middle and Far West were
scattering, but in these localities, OAX at Lima,
and the Buenos Aires stations seemed to get
through quite consistently.
The unfortunate atmospheric conditions
affected reception on the other side of the ocean
and only four American stations were reported
heard by our foreign aides. Mr. Tripp, in
Paris, reported that KDKA was heard there and
Mr. Harris, in London radioed that WGY, WJAZ,
and WLW had been heard 'in England. Other
reports may yet come through by mail. It
was reported by the Associated Press that WEAF
and wjz had been heard in Moscow and in
Germany, but no further verification could be
obtained.
Mr. Paul Godley, whose reputation as a radio
authority is of long standing, reported some very
interesting conclusions from his listening post
at Barnegat, New Jersey. He had a special
antenna and about eight sensitive receiving
sets under his direction. On every evening of
the Tests, it was his experience that receiving
was much better in a north and south direction
than east and west. This condition, he avers,
has always held good in the United States, but
was particularly noticeable during the Test week.
As an example, on one evening, he was able to
hold the entire program of OAX at Lima, with
fair volume, while not even a carrier wave could
be heard on any of the European frequencies.
Other careful observers noted the same condi-
tion and it is unfortunate that there is not room
to quote from their reports.
It is interesting to note that practically all of
those who listened during this Test and during
the two which preceded it, accepted the challenge
of the thing in the sporting spirit in which it was
conceived. All realized that there was no
absolute certainty of hearing any of the foreign
stations, but made their best receiving efforts
and took their chances of success. Even a
casual glance over the mass of mail which has
been sent to Garden City about the Tests from
radio enthusiasts in every section of the country,
shows that no listener is childish enough to
think that because his receiver failed to bring in a
foreign program on the loud speaker that there-
fore radio is all wrong, overestimated, and a
failure.
PRINTABLE REMARKS ABOUT BLOOPERS
'"pHERE is something to be said about radiat-
1 ing receivers, although indications are that
a wide variety of remarks, mostly unprintable,
have already been made about the subject
during the Tests. "International radio week,"
says the Hamilton, Ontario, Spectator editorially,
"is proving to be just a howl, instead of the
howling success it was hoped it would be." And
with this terse opinion about oscillating receivers
everyone seems to agree. Says the Kansas
City Star:
Whatever conclusion may be drawn by the
committee in charge of the International Tests
as to the success of transoceanic broadcasting,
it can be definitely stated that the Tests demon-
strated to radio listeners the menace of the
radiating receiver and the ignorance of many
persons in the operation of such sets.
The silent hour for the hundred of licensed
broadcasting stations was only the signal for
thousands of unlicensed bloopers to fill the air
with such howling, squealing, and sputtering as
to make it a miracle indeed that any listeners
were able to pick up foreign broadcasting. . . .
Such a situation is a hangover from the early
days of radio when
no thought was
given to the matter
of radiation: when
single circuits and
regeneration were
the vogue with
builders whose
chief object was
distance. I n t h e
last two .years,
these circuits have
been gradually
junked in favor of
the more advanced
sets. . . . Reports
of foreign reception
have been fre-
quent, yet not at
all in proportion to
the number of re-
ceivers capable of
the distance jump
to Europe. Those
that were not pre-
vented by interfer-
ence, probably gave
up where the repul-
sion against squeals
was stronger than
the lure of DX.
January 24, 1926
January 30, 1926
INTERNATIONAL
RADIO BROADCAST TEST
Under the Auspices of RADIO BROADCAST Magazine
<@fcf
ri
"it-
Located at 1 1^« mftt^ **nf*Vi<7<r**- n, r- ••
Has assisted and participated in the International Radio7 Test, and that information
received and checked at Radio Broadcast Laboratory (Headquarters of the Test) indi-
cates successful reception of test programs from cooperating European Stations.
lynch
national Tests
THE VERIFICATION CERTIFICATE
The successful listeners who heard European or South American stations re-
ceived an official verification card from RADIO BROADCAST similar to this
one issued to Mr. Charles Ellis of Clark Island, Maine
The Star's radio writer has well put the case
for the whole country. There is not a commun-
ity in the United States where the blooping
receiver did not make distance reception nearly
impossible. Those who were successful in
getting through were either fortunate in their
neighbors, or fortunate in an especially good
location, or both. One imaginative listener, in
describing his experience to us said, " It was like
trying to pick out the buzz of one bee through
the sound made by an entire hive, when I tried
for Europe through the barrage of squeals."
Our correspondents have been eloquent on the
subject of the radiating receiver and it is hard to
refrain from quoting indefinitely. Mr. Charles
Temple of Waltham, Massachusetts, wrote:
For three nights now, my wife and I have sat
for one hour with the head phones on, taking
the punishment that is meted out to us by the
thousands on thousands of bloopers. It is
absolutely past description the noise that we
get from these radiating sets, and I want to
say in capital letters that man has never made
a set that will distinguish even a local station,
to say nothing of foreign ones, through the
din that they set up.
It is our suggestion and the suggestion of all
other radio lovers who get pleasure from the
air and who are interested in the future of radio
that you spend the next season in efforts for
legislation against these bloopers who are a
hindrance to the whole future of radio. I am
not a chronic kicker, either, but I'm only one
of thousands who have been standing by and
watching this nuisance increase rather than
diminish for the past two years. I am not in
the radio business, but am simply an ordinary
citizen who likes to stay at home nights and
get some pleasure out of the air without listen-
ing to the sound of fire sirens ripping up the
atmosphere.
Mr. Temple adds another word, which, al-
THE STUDIO OF STATION SBR AT BRUSSELS
SBR was one of the European stations very generally heard in this country and suc-
ceeded also in pushing its signals to the United States during the Tests in 1924
650
RADIO BROADCAST
© Barratt's
WHEN *, XX WAS UNDER CONSTRUCTION
The Daventry station of the British Broadcasting Company, using 25 kilowatts
input now furnishes good program service to a very large number of British and
Continental listeners. But during the Tests, the signals of 5 xx were not reli-
ably reported in this country, despite the fact that a 1601 -meter wavelength
was used, a frequency which WGY has reported to be most satisfactory for
general relay work
though perhaps not applying directly to the
subject in hand, is a graceful bit of praise:
I want to thank you (RADIO BROADCAST and
the International Test Committee) and let you
know that I certainly appreciate the time, money,
and effort that you have spent in the months
past in an endeavor to give American radio
listeners an interesting week, and perhaps the
thrill that comes once a year in hearing music
from across the Atlantic.
RADIO BROADCAST has been working for the
better part of its magazine career against the
radiating re-
ceiver, has never
described a re-
ceiver that will
radiate, and fre-
quently, at a se-
vere financial
disadvantage, has
refused to publish
advertisements
featuring radiat-
ing sets. But the
fight is apparent-
ly a losing one,
and our own
weapons not
strong enough to
combat a menace
of this size.
RECEIVING CON-
DITIONS
THE weather
conditions
were even less
favorable than
they were during
the Tests of 1924.
Here is what
Captain A. G. D.
West, assistant
chief engineer of
the British
B roadcastin g
Company, wrote
in an article in
the Radio Times
(London) of the 1924 Tests:
The second International Radio Week was
held in November, 1924, and although agree-
ments had been made with all the American
broadcasting stations to "keep off the air"
during the periods of the European transmissions
so as not to interfere with these transmissions,
the results were not, on the whole, very satis-
factory, as atmospheric conditions during the
week of the tests were remarkably unfavorable.
It was just a matter of bad luck that this was
so, because reception during the week before
and during the week after was very good.
THE "RADIO BROADCAST" EXPEDITION ON LONG ISLAND
Setting up the short wave transmitter and receiver near Riverhead, Long Island. The short wave
link connected the listeners with headquarters at Garden City. What with blooping receivers and
unfavorable receiving conditions nothing more definite than strong carrier waves could be heard at
that location. In the photograph, left to right: Arthur H. Lynch, editor of this magazine; Keith
Henney, director of the Laboratory; John B. Brennan, technical editor
APRIL, 1926
Very few of the reports of reception could be
verified.
Reports from all over this continent showed
that reception was bad, not only on the foreign
programs, but also on American stations.
" KFI and KCO are, under average radio weather
conditions, easily picked up in this locality,"
writes W. W. Mulr, of Lockport, New York,
"and under extremely favorable conditions, are
heard with great volume and clarity. For the
last four or five nights, it has been impossible
to pick up even the carrier wave from either
of these stations with a very sensitive receiving
set." And Wilfred Taylor, at Thompson,
Connecticut says: "Atmospheric conditions,
with the possible exception of those in evidence
on Wednesday (January 27), were unspeakably
bad. Western United States stations were en-
tirely blank, and none but the large Eastern
stations could be heard. On Wednesday, I
got through to KGO with fair speaker volume,
and on that night code and bloopers were heard
all over the lot."
And from far off North Dakota, Professor
E. W. Bellinger, of the University of North
Dakota, at Grand Forks writes:
The failure to receive foreign stations was
undoubtedly due to the extremely poor weather
conditions, it being impossible to receive United
States stations with sufficient volume, and in
some instances, it has been impossible to receive
a single station. This condition has prevailed
during the larger part of the winter and is per-
haps the poorest reception we have ever ex-
perienced.
Receiving conditions can not be guaranteed
in advance, and in choosing January, we thought
that a great improvement would be noticed.
Receiving conditions in the first year of the
Tests were rather good, and as Captain West
of the British Broadcasting Company writes:
The first Test Week gave rise to a great in-
terest in transatlantic broadcasting, in fact, this
can be referred to as the beginning of interest by
the general public in receiving and transmit-
ting broadcast programs across the Atlantic.
Conditions during this week were, on the whole,
fairly good and a very large number of amateurs
in Great Britain were able for the first time to
hear on their own sets some of the broadcasting
stations of the United States. Also, the reports
of reception of British stations by amateurs
in America were very many, of which some
thousands were verified.
THE POPULAR REGIONAL TESTS
ASIDE from the correspondence and invec-
tive by the bloopers' performance during
the Tests, the innovations of the North and
South and East and West test of the last two
nights of the Tests appeared to create the most
interest during the period. It suggested to
many listeners that here was a national arrange-
ment which might be well continued in the future.
Listeners on the Pacific coast rarely hear Eastern
United States stations, owing to the difference in
time. And stations in Mexico and South America
are infrequently heard because stations here
operate simultaneously on similar frequencies.
During the silent period for American stations,
the sonorous call of CZE of Mexico City was
heard all over the United States, and the an-
nouncer at that station made many friends by
his thoughtfulness in frequent announcements.
"I think it would meet with the approbation
of thousands of radio fans," writes Henry
B. Newhall of New York, "if perhaps not this
winter, but possibly during next season, regional
broadcasting, preferably during two hour periods
similar to those of the last two nights of the
Tests, could be arranged to take place every
APRIL, 1926
THE 1926 INTERNATIONAL TESTS
651
MANY LISTENERS MADE SPECIAL PREPARATIONS FOR
THE TESTS
The photograph shows a special antenna being put up at a good
receiving location on Long Island. Practically every listener
overhauled his set, steamed up his batteries, and tightened con-
nections, all to hear the foreign signals. The overhauling is not
such a bad idea regardless of the Tests. It is a good plan to go
over a set at least every six months
A SPECIAL LISTENING STATION IN MASSACHUSETTS
Samuel Curtis, Jr., and Leslie Barnard of the Boston American at their
receiving station at Pembroke, Massachusetts. In all parts of the coun-
try, deeply interested listeners took an assortment of receivers to the
best location near by they knew of and did their best to pull in the foreign
signals. Mr. J. L. Snyder, of Patton, Pennsylvania, for example, set up
a receiver on the side of a mountain and reported very successful reception
two weeks or every four weeks. I should think
it would not seriously interfere with the pro-
grams of the regular broadcasters if the tests
were arranged for the mid-week so that they
would not break in on Saturday and Sunday
programs. Such an arrangement is really about
the only chance now we have to give our sets
tests for distance. The only other way I can
get California, for instance, is to rise up out of
my warm bed at two o'clock in the morning.
My bed has usually looked
better than California."
question of silent nights. It might be wise,
for instance, instead of silencing all the stations
in one city, so that listeners could hear programs
from other cities, to arrange for silent periods
for all stations in one time belt to be silent,
either for several hours, or for an evening. We
suggest this, knowing full well that it will start
a storm of protest in some quarters. Our own
feeling in the matter is quite neutral; after all
the matter is for the majority of listeners to
decide. We believe pretty firmly in the sov-
reignty of the local station. It should be able
pretty generally to meet the wishes of the major-
ity of its listeners in most instances. If it fail,
then the listeners ought to become vocal and
state their feelings.
And so we write "Finis" on the 1926 Tests
Better luck next time!
There is a great deal
of interest in the question
of regional broadcasting,
with silent periods for
the other groups, and it
may be that this may
point to a solution
of that always debated
A CORNER OF THE
EXPERIMENTAL LAB-
ORATORY AT WGY
With a monitoring opera-
tor at the desk. This is a
part of the short wave,
high power transmitter
installation. During the
Tests, WGY used its usual
power, although on the
intersectional transmitting
periods the last two days
of the Tests, 50 kw. was
employed. The station
was heard in England and
OP the Continent
I
THE MARCH OF RADIO
Past President, Institute of Radio Engineers
A Legal Test Case For Our Radio Laws
|HE government, it appears, is en-
gaged in testing the legality of the
present regulations of radio broad-
casting stations and the outcome of
this test case will be followed with profound
interest by all of those operating broadcast-
ing stations and by many of us who merely
listen.
Station WJAZ in Chicago has questioned
the authority of the Department of Com-
merce to regulate its broadcasting assign-
ments. This station is owned by the Zenith
Radio Corporation and the issue is created
by Mr. E. F. McDonald, Jr., who has
much to say about "the freedom of the
air." Well, we hasten to comment that
there is no such thing as freedom of the
air in the sense that Mr. McDonald uses it.
The tactics he has pursued in forcing legal
action on the part of the Department of
Commerce are unfortunate.
Some time ago, apparently at Mr.
McDonald's request, his station was as-
signed to operate on the same frequency
with KOA, the General Electric station at
Denver, Only two hours a week were free,
so WJAZ was given these two, a small share
of the time, we do admit. Not being con-
tent with this allotment, the Chicago sta-
The photograph which forms the heading for this month
shows H. I. Rothrock, Jr., of the radio laboratory. Bureau of
Standards, Washington, testing the high vacuum pump
used for exhausting tubes. (© Harris & Ewing).
tion searched for another channel and found
a neighboring one frequently free.
This new frequency selected by this
active philosophy of force had been re-
served, by mutual agreement, for the Ca-
nadian stations. Of the ninety-five avail-
able frequencies in the present broadcast
band, we have appropriated eighty-nine
and left only six for Canada. Now a
"freedom of the air" exponent finds it nec-
essary to step into one of these six Canad-
ian channels. This presents not only a
national, but an international radio prob-
lem of serious proportions.
Mr. McDonald has given a statement of
his case to the press and we can easily see
his reasons for feeling aggrieved. He has
invested a deal of money in his station and
now finds it practically valueless. He feels
that he has been discriminated against —
that he has as much right on the air as
any other broadcaster. After having spent
several weeks in Washington trying to get
an assignment from the Department of
Commerce and not having achieved the
success he expected, he evidently felt that
he was entitled to go back home and try
other means. Perhaps the course was jus-
tified, but why bring Canada into the fray?
Certainly her meagre share of the ether
could be left alone.
Why didn't Mr. McDonald start to
operate on KOA'S time? He felt, according
to his statement, that stations such as KOA
had been assigned a disproportionately large
part of the total time — -166 hours a week
to two for WJAZ. Of course the General
Electric Company could reply that they
had been using the channel regularly
and possession being nine-tenths of the
law, they are entitled to keep the chan-
nel.
The question of division of time between
the stations operated by the Radio Cor-
poration group and "independent" stations
is suggested in Mr. McDonald's press state-
ment and we think it brings up a very im-
portant point. Someone should compare
the R. C. A. group "channel-hours" to the
independent "channel-hours" and let us
see where we stand on this question. We
have twice legislated that the ether is in-
alienably the property of the citizens of the
United States so we had better take inven-
tory and see whether it is or not.
Even if the combine controls 75 per cent,
of our broadcasting time we are not at once
ready to denounce it. Are the people more
pleased to listen to the combine stations or
the independent stations? — that is the thing
that really counts. The people of the
country are the ones who have "the free-
dom of the air" and not the r wner of any
special broadcasting station.
APRIL, 1926
FIRST NATIONAL GATHERING OF RADIO ENGINEERS
653
The Institute of Radio
Engineers Convention
THE first national convention
of the Institute of Radio En-
gineers recently closed and
even the most modest commentator
must declare it was an unexpected
success. Not only did the attend-
ance justify the opinion that there
is a host of capable engineers work-
ing in the radio field to-day, but the
fact that so many of them should
come long distances at considerable
expense speaks well for the past
year's prosperity in the radio busi-
ness. Enthusiastic as radio workers
may be, without a materially pros-
perous business behind them backing
up their plans and ambitions, the
engineers could not have turned out
the numbers they did.
RADIO BROADCAST announces with
regret that Mr. Arthur H. Lynch, who
has edited the magazine from its third number to
the present one has decided to leave editorial
work and go into manufacturing.
The managing editor, Mr. Willis K. Wing,
will succeed him, and the rest of the staff will
remain the same, with Mr. John B. Brennan as
technical editor, and Mr. Keith Henney as di'
rector of the Laboratory. The policy of the
magazine will continue along the lines set during
Mr. Lynch's editorship. Professor Morecroft
will continue to write "The March of Radio"
and the other departments will be continued
by the same writers.
DOUBLEDAY, PAGE fi COMPANY.
be the finest in the world is worth
having.
When did we concede audibly that
British broadcasting was better than
ours?
And further — a Sidney trader,
after a trip to the United States, said:
The Institute is not yet fifteen years old
but the membership already totals about
three thousand. Probably in no other
national engineering society is there such a
preponderance of young men, and it is the
presence of young men in an association of
this kind that promises much for its future.
The older societies with their venerable and
bemedalled members of the engineering
profession may well point with pride to the
accomplishments of these well-known fig-
ures, but their work is in general in the
past. It is in the hands of the younger
and almost unrecognized members that
the future of the profession lies.
It was with some doubt that the
Board of Direction of the Institute
started their plans for this first con-
vention but the out-come well justi-
fies their judgment that it would be
worth while. Such a call a decade ago
would not have gathered more than a
dozen men, but so great has been the
recent demand and the resulting sup-
ply for technical radio men that sev-
eral hundred attended this meeting.
The convention did not attempt the
ambitious programs carried through
by some of the other engineering
bodies, yet there were some valuable
papers presented and interesting and
profitable trips were planned to the
Bell Telephone Laboratories, to the
high-powered station wjz at Bound
Brook and to the factory of the
A. H. Grebe Company operating sta-
tion WAHG. The session closed with
a most successful banquet and we
must admit that never before had we
believed that so many radio workers
could attend a five-dollar dinner, but
there were hundreds of them there to
testify to radio's prosperity. Jewett,
Nally, Alexanderson, Langmuir, Fes-
•senden, and other noted workers in
the radio field gave brief talks, all of
them bringing out the tremendous
strides radio is sure to make in the
coming decade. (The modest writer
of these editorials was also among
the speakers. — Editor.)
in What the Australians Think
Their Broadcasting
of
N'
[O POSITIVE methods of comparing
foreign broadcasting with that in the
United States exist, but it is always
to note what outsiders say. A. W. Watt,
editor of Wireless Weekly (New South
Wales), writes:
The broadcasting in Australia is excellent.
This is the well-considered opinion of an official
of one of the largest British wireless concerns.
This opinion coming from one who has, if only
from a business point of view, intensively studied
the quality of British broadcasting which is
conceded even by our cousins in America to
I went over there to admire American
broadcasting but I came back with the
full conviction that taken all around our
Australian broadcasting was better.
More boost has been put into American
broadcasting than into any other thing
and it becomes natural for us to associate
everything that is good in broadcasting
with the country whence that boost
emanates. . . . We blink at the
fact that America ... is now up
against a serious problem of extricating
the broadcasting situation from the
chaotic condition under which it labors. . . .
And then to make sure that we are down
for the count of ten — " if we must pattern
ourselves after somebody else let it be after
the British system which, built up on a solid
foundation, stands out as preeminent."
This is criticism indeed, from one of our most
respected neighbors. Are we really as good
as we have been telling ourselves we are?
'An Official Indiscretion"
NDER this caption, the editorial
writer of the Wireless World takes
to task that admirable British en-
gineer, Captain Eckersley, Assistant Con-
u
SOME OF THE LEADING MEMBERS OF THE INSTITUTE OF RADIO ENGINEERS
Photographed during the recent convention of that organization in New York. In the front row, reading
left to right: Frank Conrad, assistant chief engineer of the Westinghouse Company, who received the 1925
?500 award of the Institute for his work in short wave broadcasting; Donald McNichol, president of the
Institute; Dr. J. H. Dellinger, director of the radio laboratory, Bureau of Standards, and retiring president;
Dr. A. N. Goldsmith, chief broadcast engineer, Radio Corporation of America; R. H. Marriott, first presi-
dent of the Institute; second row, left to right: W. H. Hubley; John V. L. Hogan; C. W. Home, manager
of radio for the Westinghouse Company; Lloyd Espenschied; A. H. Grebe; Professor J. H. Morecroft of
Columbia University and member of the staff of RADIO BROADCAST; Melville Eastham, president of the
General Radio Company; Dr. G. W. Pickard, research engineer, Wireless Specialty Apparatus Company;
L. E. Whittemore, and Dr. E. F. W. Alexanderson of the General Electric Company
654
RADIO BROADCAST
APRIL, 1926
trailer and Chief Engineer of the British
Broadcasting Company.
In an interview entitled "A Talk to
Homemakers" he saw fit rather severely to
criticize the enthusiast who buys parts and
assembles them into the well-known home-
made set. Not only did he tell the radio
"tinker" that he was generally wasting his
time and money but further intimated that
the home builder was actually doing an
unethical thing: that he was using ideas
which had cost the manufacturer thousands
of pounds to develop and for which the
manufacturer was entitled to believe that
the radio listener would buy his sets and
thus help pay for the cost of research. " If
home making simply means copying what
some one else has taken pains to design,
may I suggest that mental indigestion may
result, and more, might I point out that a
new and great industry is being ham-
pered"?
The home builder is one of the important
vitamines of the radio industry. He really
learns a lot about radio, he spends much
money for parts; he spends his time at
home, contented and enthusiastic about
his task, he occasionally lets his family
actually listen to a whole selection from
some distant station before he tunes to
another, and in many instances he also
buys a manufactured set. So actually in-
stead of cheating the set manufacturer
from his legitimate profit he generally does
contribute his bit and in addition creates a
healthy demand for "parts."
The Recent International Radio
Broadcast Tests
THIS year's international tests ran
into difficulties with a vengeance.
It seems as though nature, as well as
the bloopers, were making all efforts to
keep America for Americans. It probably
pleased many of our short-sighted senators
to think that circumstances were doing so
well to keep us from being contaminated
by touch, even over an ether channel, with
our transatlantic fellow men. Rapidly
changing weather conditions, which always
bring plenty of static, resulted in violent
Atlantic storms, and as soon as the static
had partially abated, the transocean chan-
nels were required for more important ser-
vice than that of friendly intercourse. Radio
was being used to locate the men who were
fighting against death in the ocean storms,
and no one of us has ever begrudged giving
up his radio hours for such a cause.
The law of compensation played its part
in the ocean tragedy, however; one of the
benefits of these International Tests which
some of us had continually urged is that
arising from the better understanding be-
tween nations. This must result from our
repeated attempts, always more successful,
to get in radio touch with those in Europe
and South America. When peoples are in
MARINE RADIO DIRECTION FINDERS
Three nations have recently joined to honor the Captain and crew of the S. S. President Roosevelt on their rescue of the crew of the British steamer
Antinoe. It was radio which brought the rescue ship and the radio compass which guided the Roosevelt to the drifting Anlinoe after the American ship
had drifted more than 100 miles out of her course during the night. The large illustration on the right is the Kolster radio compass installed on the bridge
of the S. S. President Harding, a sister ship of the Roosevelt. The wheel operates a loop above, which leads to the receiver at the right of the operator.
The view at the left is the antenna of the British Bellini-Tosi direction finder, installed on the bridge of an English merchant ship. Its principle of
operation is somewhat different from the Kolster system used on American vessels
APRIL, 1926
THE INTERNATIONAL TESTS
655
close communication with each other, many
sources of friction and causes of discord will
disappear. Now the time used for the
sos calls during the International Test
schedule resulted in American crews and
German crews risking their lives for British
crews, certainly an international episode of
as much importance as the exchange of the
"Star-Spangled Banner" for the strains of
"God Save the King."
This year's Tests further emphasized the
undesirable character of the regenerative
receiver in the hands of unskilled or careless
users. Much of the time when the air was
otherwise clear and the chances of having
European and South American radio chan-
nels end in our homes, was rendered useless
to us by the howling receivers. As soon as
we located one of the transatlantic channels
and were endeavoring to copy the program,
a flock of howling receivers would start to
work around, trying to locate the same
station. It is high time that common de-
cency to our neighbors prohibit the use of
such equipment and especially on such an
occasion as the long-distance tests.
How They Run Radio in Canada
IN CANADA the radio activities of the
government are carried out in the De-
partment of Marine and Fisheries, a
logical place for it when we remember that
radio served the marine service long before
it was used for broadcasting entertainment.
We have commented before on what seemed
to us the very reasonable and sane course
the Canadian officials take in developing
radio — in fact, we have also previously ex-
pressed the opinion that the work was done
in a manner somewhat superior to that
which our officials display in attacking
radio questions. It is good to find the
quality of directness of attack for which
the Canadians won a reputation during the
war, shown in the annual report of the
Canadian radio service.
The totai number of stations coming
under government supervision is 93,049,
apparently a prodigious number, but we
hasten to recall that all receiving sets are
classed there as receiving stations and come
under government supervision. There are
92,000 of these receiving stations in the
dominion which pay to the government
$1.00 a year for their operation. After re-
viewing the compass service and the twice
daily weather report to shipping, the prob-
able development of radiophone service to
certain classes of shipping is discussed.
The ordinary weather and compass reports
are of course sent out in code and the re-
ceiving ship must have a trained operator
on board. But it is thought that harbor
shipping might use radiophone channels
and thus get the benefit of radio without
the expense of a specially trained man.
A frequency of 1 500 kc. is to be used so as
not to interfere with broadcast channels.
It seems to us that such a scheme is only
practical when the shipping is not dense.
Around New York harbor, such an attempt
would be unwise indeed.
Strange as it may seem to those in con-
trol of our governmental attitude, the
Canadian government has a definite policy
by which broadcasting licenses are issued.
"One wavelength is issued to each city or
area and three stations are licensed to use
it, one station at a time. In case the li-
censees are unable to arrive amicably at a
division of time, the department itself di-
vides the time on an equitable basis." This
is different from the Cincinnati row we had
when the Department of Commerce officials
said it was none of their business and left
the stations to fight it out. In the larger
Canadian cities, a second wavelength is
assigned but the station operating on the
second wave must be at least ten miles
out from the city!
For the past two years, licenses issued
by the Department have permitted indirect
advertising without restriction and direct
advertising before 6 P. M. In spite of the
permission, practically all direct advertis-
ing has been abandoned, the stations ap-
parently having reached the same con-
clusion that direct advertising fell on
"deaf" receiving sets.
In 1923 the United States assigned to its
numerous licensees all of the broadcast
bands available for this continent, a not
very neighborly action. Ninety-five chan-
nels to be properly proportioned between
Canada and ourselves so we use all of them !
"As a result, the transmission of practically
every one of our stations was subject to
severe interference." The United States
Department of Commerce finally agreed to
regard six of the ninety-five channels as
exclusively Canadian and also to use cer-
tain of the other channels for our southern
stations only, that is, these channels might
also be used by our northern neighbor.
Taking into account the unlikelihood of
West Coast stations interfering with her
eastern stations, Canada counts on 19
available channels.
Continues the report:
Every Canadian station is checked each night
by some specified inspector and offending sta-
tions are at once ordered back to their specified
wavelength. Should the offending station be
under the jurisdiction of the United States, the
Supervisor of Radio for the area in which the
offending station is located is advised by tele-
graph and in all cases promptly and effectively
attends to the complaint.
The report speaks of the surrender of the
1000- and 66o-kc. channels by the shipping
approaching our shores. They are not
used by ships of Great Britain, United
States, Belgium, Denmark, and Sweden
when within 250 miles of our shore. "Un-
fortunately France has not seen her way
to accede to our request and we still have
a prolific source of interference in the
coast station operated by that government
at St. Pierre Island, south of Newfound-
land." Under the caption " Regenerative
Whistles" we learn that "We have as a
matter of fact, considered getting all the
Canadian radio manufacturers together
with a view to having them mutually agree
to stop the manufacture of the regenerative
type of apparatus. But as there is no
legislation available to compel any manu-
facturer to abide by the same, etc. "
With comparatively few broadcasting
stations (only nineteen channels), Canada
has thirty-eight inspectors. "Generally
speaking," the Commissioner modestly
concludes, "the Canadian broadcast lis-
tener would appear to receive at least as
much, if not more, service than the lis-
teners in any other part of the world,
whether licensed or not, and we have not
as yet really got into our stride!"
RADIO HEADQUARTERS OF THE SIGNAL CORPS
At Washington, all the official business of the Signal Corps of the Army which is transacted by radio
through the network of Army stations is received at this central office. General Saltzman, Chief
Signal Officer, reported recently that radio was the means of saving a large sum over the usual tele-
graph tolls paid by the Army for official communication. This radio central is located twenty feet
below large receiving loops on the roof of the building
656
RADIO BROADCAST
APRIL, 1926
The Month In Radio
REGINALD A. FESSENDEN
Chestnut Hill, Massachusetts
at the Institute of Radio Engineers
Dinner, New York
" There are in existence to-day, fully de-
veloped and tested, wireless methods for
operating substantially without disturbance
from static or interference, and these means
have been tested with large capacity high
antennas between Boston and Panama, in
summer.
" There are also in existence to-day, fully
developed and tested in all essential details,
•wireless methods for operating direct, without
exchanges, by setting direct to the subscribers'
numbers, between bodies of subscribers as
large as those comprising the New York ex-
changes.
" The wireless pheroscope has been de-
veloped from the first crude apparatus of
1906 to a device capable of putting wireless
vision into every house in the United States,
and was tendered to the United States Navy
under guarantee in 1921, and to others.
Its success depends upon tu.o inventions — •
the multiple valued function method, as it is
called, and the shutter which has been opera-
ted by independent engineers at a frequency
of 400,000 per second and is capable of
more. I have pleasure in showing you the
shutter, a photograph showing its general
arrangement in action, and a sample of the
wire used, of which it takes goo twisted to-
gether to make the si^e of a single hair; and
of presenting these historical exhibits to the
archives of the Radio Engineers."
THE large station at Rocky Point (Radio
Central) has for some time been able to send
telephone messages across the Atlantic to Eng-
land where a receiving station has been set up
at Chedzoy; this, it is expected, will be the Eng-
lish receiving station for the transatlantic radio-
phone channel. The British have been at work
on a transmitting station for their end of the
channel and a cable to the New York Times says
that the station is now complete and has been
taken oxer by the British Postoffice, which will
operate the communication scheme.
The English news puts the price of a three-
minute talk to America at five dollars. This
seems like an unreasonably low price for the
service and certainly cannot be based on the
idea of earning a reasonable return on the in-
vestment.
NOTHING more indicative of the emancipa-
tion which Turkish women have experi-
enced in the last decade has occurred than the
broadcasting of a speech by the wife of the
Curator of the Evkaf Museum in Constanti-
nople. Only a few years ago the face of the
Turkish women could be seen by her master
only, and never could she talk to other men.
Now she not only shows her face as other women
do but addresses an audience numbered in the
hundreds of thousands by the most modern of
our scientific achievements. Mme. Aly ad-
dressed the British radio audience on "The
Turkish lady of Yesterday and To-day." The
topic certainly seems to offer opportunities for
some striking contrasts.
FROM wov, the radio audience had a chance
to listen recently to a most striking ex-
periment. Professor Wold of Union College,
gave a series of talks on the electron and its
activities and during one of his lectures he let his
listeners actually hear an electron as it splashed
its way through a cloud of gas particles. Some
substances, said to be radio-active, are con-
tinually shooting off positive and negative
electrons, and as these, traveling at high speed,
bump their way through a small air chamber and
so affect the air particles they bump that the
air becomes partially conducting. This change
in the conductivity of the air is made to affect
a vacuum tube amplifier and thus modulate
the carrier wave of the broadcast station.
The noise is scarcely more pleasing than static
noise, but it will be certainly more interesting
when one realizes that each noise represents the
collisions caused by one electron, the smallest
thing in the universe of which the scientist
knows to-day.
Interesting Things
Said Interestingly
j. c. HARBORD (New York;
-* president Radio Corporation of America):
"The world leadership of the United States in the
development of the radio art and industry has
won for our manufacturers and engineers a
dominant position in the radio affairs of South
America, where to-day the greater percentage
of the total business is carried on by Americans.
In spite of foreign competition, our products
and methods remain the most acceptable to
South Americans. Our four years of experience
in the development and production of broad-
casting devices both for transmission and re-
ception, has stood us in good stead in Latin
America. Americans are contributing a full
measure of this experience toward the develop-
ment of radio in South America and we have the
hearty cooperation of local South American
radio interests."
E. F. W. ALEXANDERSON (Schenectady;
Chief Consulting Engineer, Radio Corpora-
tion of America): "The great problems in radio
are static, interference and fading. The trend
of the radio art in the past has been determined
by improvements that have been made in over-
coming these difficulties. The practical solu-
tions of these problems to-day are; directive re-
ception for reduction of static; continuous waves
CAPT. A. G. D. WEST
London; Assistant Chief Engineer •,
British Broadcasting Company; in an
interview before the recent
International Tests
" The tests will not give such a unique
opportunity to European listeners because
they can listen on any night to American
stations withmit fear of interruption from
broadcasting stations on this side of the
Atlantic. American stations usually take
very great care with regard to maintaining
their wavelengths and their power constant
over long periods of time, so that amateurs on
this side who want to do serious experimental
work on long distance reception on various
wavelengths, can do so throughout the winter
season, but there are not many experimenters
who would have time and opportunity and
also inclination to listen in the early hours
night after night for American stations to
obtain data that will be valuable from a
scientific point of view, and it is during
Radio Week that a more useful opportunity
is given to those who want to try occasional
American reception.
" Even now it is not advisable for listeners
with sets containing less than two valves to
attempt to pick up these (American) pro-
grams, and it is certainly most important
to make sure that the sets do not oscillate and
cause local interference. Even just a few
oscillators playing around the wavelength of
a distant station can completely spoil the
reception of that station by listeners situated
many miles around."
to minimize interference; and the use of long
waves to minimize fading. The future answer
to these problems may be different. At least
we have reason to think that the new knowledge
which we have gained regarding wave propaga-
tion will furnish us additional methods of dis-
criminating between signals and disturbances.
Wave polarization will undoubtedly be one of
the important factors in this new development."
PROF. A. M. LOW (London; from an article
in John Bull) : " Before many years are
passed we are sure to have the radio serial story,
and we are sure to have plays acted by radio with
various incidents leading up to exciting passages
which are always 'to be continued in our next.'"
News of the $500 Short- Wave Receiver
Prize Contest
Entries May Be Made Up to April 1, 1926, Instead of March 1 — Conditions
and Further In/ormation of a Contest to Interest Amateurs Everywhere
THE short-wave receiving set con-
test, announcement of which was
made in the February issue of
RADIO BROADCAST, has won the
enthusiastic response of numerous experi-
menters in the short-wave field, judging
from the correspondence which has come in
since the announcement was made. So
many complaints were received that there
was not sufficient time for some of the ex-
perimenters to finish their sets for sub-
mission before the contest closes, that it
has been decided to extend the time limit
from March i st to April i st, 1926. A
request by the New York representative of
Popular Wireless, London, that the receivers
of entrants shipped from Europe not later
than April ist should be considered, has
been granted. It is probable that the ex-
tension date will also enable Australian
short-wave enthusiasts to compete.
One of the interesting things which the
contest has brought forward is the fact
that up to this time there has been little
or no novelty in the design and construc-
tion of short-wave receivers. The con-
ventional types have given satisfactory
results and consequently, prior to this
contest, the stimulation to designing better
receivers has been lacking.
According to present indications, among
the contenders for the prize money will be
super-heterodynes, regenerative neutro-
dynes and even the much neglected super-
regenerative receiver. Certainly some-
thing worth while should be brought
forward. In practice, however, Reinartz
receivers are being used almost to the
exclusion of other types. Attention is
called again to the basis of points upon
which the prize is to be awarded. Con-
testants should observe that a paramount
requirement is that the receiver shall be
adapted by its design and construction to
practical amateur relaying. The only
circuit limitation imposed is that radiation
be reduced to a minimum. Otherwise, any
type of receiver which will function with
the utmost sensitiveness, stability, and
reliability, is eligible for consideration.
The extension of the contest, which has
been widely announced, will give contes-
tants opportunity to do additional work,
which should not be overlooked.
The basis of points is as follows:
Workmanship 15
Simplicity of handling 20
Ease of Calibration
Freedom from hand capacity
Independence of tuning and regeneration
Low Cost 10
Use of standard or easily constructed parts 5
Performance 25
Overall amplification of signals
Use in relaying
Ability to use break-in
Ability to cover foreign amateur bands
Appearance 15
Method of avoiding radiation .... 10
Total .... 100
Much comment has resulted from our in-
sistence on the non-radiating feature. Cer-
tainly we are aware that there are differ-
ences between continuous wave reception
and broadcast reception. The enjoyment
of a broadcast entertainment can be com-
pletely ruined by a near-by radiating receiver
but continuous wave reception is not neces-
sarily impossible within range of a radiat-
ing receiver. Continuous wave reception
is not the only thing to consider, however.
Short waves are also used for rebroadcast-
ing purposes and for supplying programs
to broadcasting stations from remote
points. A few hundred radiating receivers
on short wavelengths, used for rebroadcast-
ing purposes, would be sufficient to make
these short wave radio telephone links
practically inoperative. In anticipation of
this problem, RADIO BROADCAST adheres to
its fixed policy to discourage the use of radi-
ating receivers on any and all wavelengths.
We have been invited to exhibit receivers
entered in the short-wave contest at the
Sixth Annual Radio Show and Convention
held at New York under the management of
the Executive Radio Council of the Second
District. If a sufficiently interesting ex-
hibit can be assembled so early in the con-
test, there will be an opportunity to see
some of the latest designs in the short-wave
art.
We have sought to make the board
of judges a composite one, which will be
thoroughly capable in considering all of
the qualities of a receiver. You will
observe that it includes practical ama-
teurs, who have extensive experience in
short wave relay work; scientists and
mathematicians, who know how to meas-
ure and appraise in impersonal quantitative
terms, and writers and commercial engi-
neers who are able to judge the simplicity of
workmanship and ease of construction from
the point of view of the average home
constructor. There are many names which
we would have liked to include in the
Board who were perforce omitted, lest it
become too large to be efficient in its work,
but we are sure that each member has a
specific and definite contribution to make
which should result in a fair decision from
every standpoint.
That public interest and attention is
turning toward short waves is no longer a
debatable question. The announcement
of this contest, the RADIO BROADCAST-
Eveready short-wave experiments con-
ducted with the cooperation of the National
Carbon Company, the long-distance records
of 2 GY have, individually and collectively,
aroused so much attention that we are in-
clined to predict that the number of enthusi-
asts in short-wave transmission and re-
ception will continue to increase with the
marked rapidity of the last few months for
some time yet. After all, your receiver
may respond to signals coming in for
distances of thousands of miles, but until
you, yourself, have mastered the ether by
making it subservient to the will of your
own transmitter, your conquest is not
complete. It is our hope that through
the disclosure of a better short-wave re-
ceiver, RADIO BROADCAST may be the
means of introducing you to a new phase of
radio entertainment — the mastery of the
ether through the use of the short waves.
THE CONTEST
OBJECT: The object of this contest is to
aid in the development of improved short-
wave receiving apparatus, so that the
possibilities of high frequencies may be
more effectively studied.
PRIZES: First prize, $250; Second prize,
$150; Third prize, $100. Only one prize
to a contestant.
ELIGIBILITY: Anyone interested in short-
wave reception is eligible to compete,
though no prizes will be given to manu-
facturers making short-wave receivers or
parts therefor.
CONDITIONS: Each contestant must sub-
mit a complete description, photographs,
and hook-up of a short- wave receiver which
does not radiate. The receiver should be
adapted to the entire short-wave band
from 8566 to 1999 kc, although this may
be accomplished by interchangeable coils.
RADIO BROADCAST is permitted to request
that the most promising receivers be sent
to its laboratories, in order that the final
award of the prize may be determined,
after exhaustive tests. In addition to
the prizes, RADIO BROADCAST is to be per-
mitted to use descriptive matter, either in
whole or in part, submitted by any con-
testant, at its regular rates.
BOARD OF JUDGES: The following consti-
tute the board of judges: Boyd Phelps,
Prof. Louis A. Hazeltine, Zeh Bouck, G. C.
Furness, Arthur H. Lynch, Edgar H. Felix,
Dr. Lawrence Dunn, and Dr. A. Hoyt
Taylor.
The Tube and Its Best Uses
Explanations of Some Qeneral Instructions on How Best to Use Tubes
— How Characteristics are Measured and Their Importance — Relative
Merits of Amplifier Connections — The Facts About Tube Rejuvenation
By KEITH HENNEY
ADIO receivers arrive in American
homes at the present time in one of
two ways, either the home buys a
completed receiver or someone in the
home builds it, assembling material that some
manufacturer has designed and constructed.
In either case, the receiver is a static thing
until the listener buys the tubes and turns on
the A battery. From the moment that this
final act is completed, the receiver ceases to be
a mere assembly of electrical apparatus and
becomes, for the time being at least, a stage upon
which many interesting things happen.
Few builders, or purchasers, of radio receivers
seem to realize that the tube is about the only
part of the complete installation over which they
have any control. The purchased set comes
"without tubes" and the final contribution to
the home made receiver must be tubes. These
tubes must be chosen with considerable discre-
tion and operated with care.
It is sufficient for the average listener if his
set works, and under this happy condition a
tube is a tube, an ingenius device that fits into a
socket. Yet let something happen, a mix-up
in A and B battery leads, a broken connection, a
dropped tube, and the user realizes without de-
lay that the tube is the vital thing, and that
upon its proper functioning depends the success
of the receiver.
For this reason this article, with those pub-
lished in the December and February RADIO
BROADCAST, endeavors to explain some tube in-
formation and some tube idiosyncrasies. Such
information, in the words of a certain college
professor "is in all the books" but many that
should have noted it, have not. To judge from
the enthusiastic reception given the first two
tube articles, this field is a profitable one for
study.
Among other things about tubes that are fre-
quently mentioned in radio magazines and news-
paper radio sections is the fact that an amplifier
grid should never be allowed to go positive, and
this seems a logical point of attack for the present
article.
It is also stated that the characteristics of tubes
as ordinarily measured are "static" and have
little to do with the tube under actual operating
conditions. At least one manufacturer of tube
testers claims that his device measures the
"dynamic" characteristics of tubes giving the
lie to others whose products measure tubes
statically. This particularly efficient instru-
ment, so the manufacturer says, measures tubes
dynamically because it uses a source of alternat-
ing current for the measurements, and everyone
knows that tubes are alternating current ampli-
fiers. And there you are!
Naturally, what the average listener wants is
information that will aid him in operating his
tubes intelligently; it matters little to him by
what name you call tube characteristics, or how
they are measured. He wants the "cold dope."
And the experimenter — how many there are who
'•Director, Radio ''Broadcast Laboratory
have requested tube data from RADIO BROAD-
CAST Laboratory — wants to know how to meas-
ure tubes in the most approved fashion. The
present article may be of interest to both of
these types of readers.
With regard to static and dynamic character-
istics, there is this to be said — a difference does
exist between them; both are important; neither
is difficult to measure. And it is doubtful if the
dynamic tube tester mentioned before has any-
thing to do with the so-called dynamic character-
istics of vacuum tubes.
WHAT IS NEEDED TO TELL TUBE CHARACTERISTICS
ASIDE from the tube and its accessory bat-
teries, all that is necessary to measure static
characteristics of tubes, which show in the form
of curves the relations between grid, plate, and
filament voltages and the corresponding cur-
rents, is a good voltmeter of double range, o-io
and o-ioo volts, and a good milliammeter, and
any one in his home laboratory can have many
hours of enjoyment studying tubes by means of
these instruments. With such apparatus dia-
grammatically represented in Fig. I, let us carry
out the following procedure:
a. Measure the B battery voltage.
b. Set the filament at proper voltage.
c. Vary C voltage in convenient steps, meas-
uring with voltmeter.
d. Note plate current at each different C
voltage.
e. Plot the results similar to Fig. 2.
For 199 and 2OI-A tubes, the normal plate
voltages are 45, 90, and 135. The C voltage may
be varied in steps of 2 volts from minus 10 to
plus 10. Semi-power tubes normally use 135
volts on the plate but as many as 180 may be
safely used. On some tubes of this type — not of
L Efc.Ep-.->|
EP=EB
FIG. I
Apparatus required for measuring static charac-
teristics of tubes. A double-range voltmeter
can be used to measure A, B, and C battery
voltages
the oxide coated filament type — plate voltages
up to 400 have been used in the Laboratory with
complete success. The C voltage on these tubes
of the 1 12 type may be varied in steps of 5 volts
from minus 35 to plus 5.
Now it is a common statement in published
tube information that only the straight — com-
paratively speaking — part of this grid-voltage-
plate-current-curve should be used for distor-
tionless amplification. Any one can see that the
curve is not straight at the bottom, and on page
458 of the February RADIO BROADCAST, the effect
of using this part of the curve is shown. But
any one can see that the curve continues to be
straight beyond the zero grid line. In other
words, there seems to be no reason why the
grid should not be allowed to go positive. There
must be a catch somewhere.
The catch lies in the fact that the method of
discovering the relation between Ip and Eg
(plate current and grid voltage) illustrated above
does not tell us exactly what the tube will do
under actual amplifying conditions. For in-
stance, an amplifier tube always works into a
load of some kind; as the telephone engineers
say, the tube "looks" into a transformer, a re-
sistance, or 'a pair of telephones, and the grid
circuit, in the same language "looks back into"
a transformer secondary, a resistance, or some
combination of resistance, inductance and ca-
pacity.
Therefore, if we insert into the grid and plate
circuits of the tube under test, a resistance ap-
proximating the impedance into which the tube
normally looks we shall have the conditions of
test more nearly like those occurring in practice.
Fig. 3 contrasted with Fig. i shows these addi-
tions, and Fig. 4 the method of calculating the
input and output resistance. The tube normally
looks back into the output impedance of a similar
tube which is "stepped up" by the square of the
turn ratio of the connecting transformer. Fig. 5
shows how two differing impedances may be
coupled together by means of a transformer. In
this case Zi may be the output impedance of a
semi-power tube and 7.t the impedance of a loud
speaker. If the turn ratio of the transformer
obeys the formula
or
the maximum amount of power will be trans-
ferred; in other words, quality reproduction will
result.
In connection with this formula it is well to
remember that the voltages appearing on prim-
ary and secondary of transformers vary di-
rectly as the turn ratio, while the impedances
which the transformer connects vary as the
square of the turn ratio.
In the case of a first stage amplifier working
from a detector tube — whose impedance will be
APRIL, 1926
TUBES AND THEIR
USES
659
about 30,000 ohms — and coupled to it by means
of a 3:1 ratio transformer, the tube looks back
into approximately 30,000 x (3)" or 30,000 x o, =
270,000 ohms. If the tube is the second of a
two- or three-stage resistance amplifier employ-
ing high-mu tubes, the tube looks back into three
impedances in parallel as shown in Fig. 4. In
the case of the last tube in a set which works into
the loud speaker, its output impedance will be
approximately matched by the impedance of the
plate voltage is less than the B
battery voltage by the drop in
the load impedance. The plate
current will be less naturally.
When the grid goes positive it
begins to draw current so that
variations in grid voltage are no
longer as effective in changing
plate current; then these varia-
tions only produce more or less
grid current.
To Preceeding
Tube
, To Following
Tube
In a poten-
tiometer-con-
trolled radio
frequency
a m p 1 i fi e r ,
very heavy-
plate currents
are drawn
when the grid
is forced posi-
tive by stabi-
lizing adjust-
ments. This is due to
TABLE 1
TUBE
V-
Rp
Gm
V?
RP
1*
l/Rp
CONDI-
TIONS
199
201-A
12
120
112
210
Mu20
6.5
8.2
5.6
3.3
7.0
7.65
20.00
22,400
12.700
14.0CO
(MM
6150
5100
33,000
304
660
400
500
1140
1500
600
19.8 x 10-*
55.3
15.0
12.8
80.0
107.0
121.0
4.45 x 10-'
7.37
3.87
3.58
8.95
10.35
11.00
a
a
a
b
c
d
e
CONDITIONS
Eg
Ep
a — 4.5
b 22.1,
c — 9.0
d —27.0
e 0.0
90
135
135
350
90
u - amplification constant
Rp = Plate impedance in ohms
Gm = mutual conductance in micromhos
Eg-Ec-Ig Rj
Ep-EB-IpRL
k~—
FIG. 3
To obtain the curves shown in Fig. 2 it is necessary to add resist-
ances in the input and output circuit of an amplifier tube. These
resistances simulate the impedances of the preceding and following
tubes together with accessory coupling apparatus
speaker, but in intermediate stages, the primary
impedance of the coupling transformer should be
at least three times the output impedance of the
tube at the lowest audio frequency which it is
required to amplify. This means that the prim-
ary of the transformer must have 50 henries in-
ductance at 100 cycles when working from a
2oi-A tube with an output impedance of 10,000
ohms. If the transformer has a "flat" charac-
teristic at loo cycles, the higher frequencies will
be taken care of by a complicated combination of
capacity and core loss in the transformer.
In other words in the first amplifier the factor
RL will be about 30,000 ohms, while in the last
amplifier this factor will be about 10,000 for a
20 1 -A and 5000 for a 112 tube.
In Fig. 3 RL and RI represent the combined
impedance of the tube and the connecting ap-
paratus looking away from the tube under test.
Under these conditions, shown in Fig. 3, some-
what different curves result when one plots plate
current against change in grid volts. In this
case the plate voltage is not the B battery voltage
but is less by the drop in the load resistance, and
the voltage actually applied to the grid is not
the same as the C battery but is less by the drop
in the input resistance — when the grid goes
positive.
As soon as the grid goes positive, current flows
in the grid circuit, depressing the input voltage,
and the plate current curve flattens out or act-
ually drops. Distortion is inevitable because the
plate current no longer is an exact replica of the
applied voltage. The tops of the waves are com-
pletely obliterated and the plate current jumps
about when incoming signals force the grid posi-
tive. What comes from the loud speaker differs
widely from what leaves the transmitting station.
Curves which show this flattening are in Fig. 2
in which the load impedance is 12,000 ohms,
and many excellent curves of this nature may be
found in a recent article in Popular Radio by
Hugh S. Knowles.
What actually happens is the following: the
fact that there is very little
resistance in the plate circuit
of these amplifier tubes which
operate under "static" con-
ditions. At the same time
another effect begins to be
noticed. When an amplifier
grid is negative and drawing
no current, the tube input
impedance is extremely high.
In other words, it puts no
load on the input device, say
a tuning inductance and condenser. When the
grid takes current, however, power is required,
the input impedance becomes very low, effec-
tively shunting the tuning circuit and making
tuning broad.
As a matter of fact, the above experiment has
not as yet measured
what vacuum tube ex-
perts know as "a. c.
dynamic characteris-
tics" which show the
relation between alter-
nating plate current
values as related to
alternating grid volts.
Some excellent curves of
this type may be found
in the December, 1925,
Proceedings of the Insti-
tute of Radio Engineers.
What we have meas-
ured are known as "d.c.
dynamic" characteris-
tics. Since we have
used pure resistance
loads, the curves for
d.c. and a.c. will be the
same. This would not
be true had we used an
inductance in the plate
circuit. But the fact
has been clearly demon-
strated that amplifier
grids should not be per-
mitted to go positive —
they should not be over-
loaded. The remedy,
naturally, is increased C
battery and this in turn
necessitates greater B
battery.
It seems to be a
psychological fact that
the wants louder and louder signals — he becomes
radio deaf. For example the first stage in the
average listener's radio life is that of a single
tube which delivers its output to the listener
through head phones. After a time he wants
a loud speaker and he adds one or two stages
of audio amplification to his one-tube set.
He is satisfied with 90 volts on the plate and
negative 4.5 on the grid. Then he finds that
signals do not seem as loud as they did at first.
So he uses 135 volts on the plate and negative 9
on the grid and installs a semi-power tube.
Then he finds after a time that signals might be
louder. So he goes to 180 volts on the plate and
negative 1 5 on the grid, or to two tubes in paral-
lel or push-pull, or to the final stage where he
uses a power tube with 350 volts on the plate
and about negative 25 on the grid. The more
the listener gets, the more he wants. In another
12
10
8
6
4
2
0
i
UV
201-
= *
A
/
RI
|
.n.
/
/
/]
f F
*L=<
B=90
)
-Ep
f
y
/
/
/
RL
= 12,000
• = 136 -
--1
f
•
«
f
^-
EB
~~~-
,/
^
RI
F
foo
,000
/,
•
- m •
Hi]
p— •" * *
— • " "
/
/
*
f
^
S
/
/
/.
S*
^>
S
*'
^
16 14 12 10 8 6 4 2 - 0 + Z 4 6 8
C BATJ£/?Y WiTS- EC
the average listener
FIG. 2
What one gets by measuring tube characteristics with and without a
load in the plate circuit. Note how the curve of plate current flattens
out when a load is included. This is due to the fact that the effective
voltage on the plate has been reduced. It shows why people get into
trouble when they use resistance amplifiers with low mu tubes and with
low plate voltages
660
RADIO BROADCAST
APRIL, 1926
©RESISTANCE AMPLIFIER
Rp(Hi-mu) = 60,000 Ohms
0 DETECTOR
Rp (Detector) = 30,000 Ohms
Ri - 32xRp =270.000 "
® AMPLIFIER
Rp (Amplifier) = 15,000 Ohms
Ri=42 x 15,000 = 240.000 Ohms
FIG. 4
Methods of calculating Ri and Rp for three general amplifier cases
direction there is an analogy — rouge blindness!
The more rouge, the more . . . but per-
haps we had better not go into that.
So much for distortion owing to positive grids.
Too much C battery, however, will force signals
to use too much of the lower part of the charac-
teristics and will cause distortion. A load in the
plate circuit, however, has the tendency to
straighten out the Ip-Eg (plate current-grid
voltage) curve, so that the bottom of the curve
is not so bad as it looks from the static character-
istics.
Consideration of the curves in Fig. <> and those
in Popular Radio already mentioned show that
the greater the impedance in the plate circuit
the straighter will be the characteristic. Some
loud speakers have very little impedance at low
frequencies so that the curve worked over is not
straight but curved and a peculiar distortion re-
sults when bass viols, or kettle drums are played.
The remedy lies in a lower impedance tube, say
one of 4000 ohms, and some tube manufacturers
are making preparations to supply such tubes.
They will necessarily have a low amplification
factor and will draw considerable plate current
but will be capable of delivering considerable
power. Output transformers useful in overcom-
ing this type of distortion are manufactured by
the General Radio Company, and are designed
to couple low imp.-dance speakers of the cone
type to 20 1 -A tubes and to low impedance
power tubes.
Among other things that are often discussed
by those interested in tubes is the importance of
producing and using tubes with a high value of
mutual conductance. In preceding articles of
this series, methods of measuring this impor-
tant tube constant have been shown. Tables
Were given showing the value of mutual
conductance of tubes recently tested in the
Laboratory.
Let us examine this term and see what it
means in relation to proper tube operation.
Tubes are most frequently called upon to per-
form one of two functions, voltage and power
amplification. It is important then to know
how useful a given tube will be when used as a
Np
Ns
0-
Np=Primary Turns
Ns-Secondary Turns
FIG. <j
How a transformer may be used to couple two
impedances. As a matter of fact, such trans-
formers in the telephone industry are called
"repeating coils" since they repeat into a
second circuit what goes on in a first circuit
which may be of widely differing impedance
characteristics
voltage or power multiplier. It is also impor-
tant to know the power in watts that a given
tube will deliver to a loud speaker.
It can be shown by mathematics that voltage
and power amplification, and power output are
related to the mutual conductance, usually
abbreviated to read Cm and defined as the
amplification constant divided by the plate
impedance.
The same mathematics, however, shows that
these functions are related in the following
manner:
Voltage Amplification = j \/Ri X , -t
V Rp
Power Amplification = — ' X 73
2 Kp
Eif* u.2
Power Output = -p X £•
Kp
ti.
Mutual Conductance = 77-
RP
The mutual conductance, then, is a measure
of a tube considered without regard to the circuit
in which it works, while the other facts outlined
above depend upon these external conditions.
F'or example, the values in Table
are for £
Kp
and , — and knowing the input impedance as
y RP
figured in Fig. 4 and the voltage that is being
placed on the grid of an amplifier, it is a simple
matter to compute the power and voltage am-
plification and the actual power output in watts
delivered to a loud speaker. It has already been
mentioned that a reasonable amount of power to
require from an amplifier is .06 watts which will
give a good comfortable signal from an average
loud speaker of the cone type without overload-
ing distortion.
When one is interested in oscillators and mod-
ulators, for example, in a transmitting circuit,
the mutual conductance of a tube is a valuable
measure, but it is believed that in amplifier prac-
tice some other factor such as £• is a better
Kp
figure of merit by which to rate tubes. In
England such a factor has been used for some
time.
M- 5
® SINGLE TUBE
© PARALLEL TUBES
FIG. 6
PUSH PULL
Methods of calculating the important factors of three commonly used amplifier connections. One point worth noting is the fact that the push-pull input
coil divides the voltage so that the effective step-up to each grid is only one half the total turn ratio of the transformer. In the push-pull circuit, the
two tube irrpedances are in series: in the parallel case they are cut in half
APRIL, 1926
TUBES AND THEIR BEST USES
661
THE MERITS OF VARIOUS AMPLIFIER CONNECTIONS
NOW with these facts in mind let us settle a
few arguments about the relative merits of
a single tube compared with a push-pull amplifier
or with two tubes in parallel, each working into
a loud speaker designed to match approximately
the output impedance of the amplifier. In Fig.
6 these three amplifiers are shown and the values
„!
of rr, voltage amplification, and power output
given. The factor j which is included in the
above expressions for voltage and power ampli-
fication has not been used in these computations
since in these cases a high impedance open cir-
cuit secondary is used.
It will be noted that the push-pull and parallel
tube amplifier will deliver twice as much power
to a loud speaker as a single tube with the same
input voltage, but that the push-pull amplifier
is behind the others when it comes to voltage
amplification. Now, in any amplifier,
the tubes, with the exception of the
last one, are primarily acting as volt-
age amplifiers, boosting the voltage as
much as possible without distortion so
that the last tube whose power output
is expressed as (input v°'tage " *>*
oKp
gets as much voltage input as pos-
sible. The push-pull amplifier should
be used to feed power into the loud
speaker, and practically any tube can
be used up to that point, that is a
199, 12, or2oi-A. These preliminary
tubes are not required to handle much
power since they are functioning
primarily as voltage multipliers.
The Electrical "Shorthand" Terms Used in
This Article
Ep
= Plate Voltage
Eb
= B Battery Voltage
Eg
= Grid Voltage
EC
= C Battery Voltage
Ef
= Filament Voltage
Ip
= Plate Current
Ig
= Grid Current
I*
= Amplification Constant
Rp
= Plate Impedance
Gm
= Mutual Conductance
There is one other consideration when investi-
gating the merits of the three amplifiers men-
tioned above. Owing to the electrical symmetry
of the push-pull amplifier, each tube has supplied
to its grid only one-half of the total input volt-
TABLE 2
V?
Rp
POWER OUTPUT
= WO
VOLTAGE
AMPLIFICATION=N
Single
tube
V _ 00-
I-' x .0025
o
= .01125 watts
l/14400x32x V • 0025
= 18 times =25.1 T. U.
10,000
Push-
pull
(2 x 6)i
I/ 14400 x 3" x V -00125
= 12.7 times =22.1 T. U.
20,000 •°01"5
= .0225 watts
Parallel
tubes
5«
f*.005
= .0225 watts
V 144000 x y x i/. 005
=24.5 times =28.1 T. U.
5,000 -00-
age. In other words, one can apply greater in-
put voltages to a push-pull amplifier than to a
single or parallel tube arrangement. Owing to
this same symmetry, certain harmonics, due to
curvature of the characteristic, are balanced out
so that about 25 per cent, more overloading can
be tolerated.
The parallel tube arrangement has the only
advantage that its output impedance is lower
than the single tube, due to the two plate im-
pedances connected in parallel, and for this
reason greater power can be delivered to a loud
speaker of low impedance. Practically all loud
speakers now on the market are comparatively
high in impedance so the advantage in the paral-
lel tube arrangement is not usually realized.
Since the output impedance of the push-pull
amplifier is the sum of the tube impedance, a
high impedance speaker must be used. If a low
impedance speaker is used such as the Western
Electric 54O-AW, an output trans-
former should be used. The push-
pull amplifier has both advantages
and disadvantages, and at the present
time it is impossible to get input
transformers that compare in quality
with the best of the single-tube trans-
formers. With power tubes of low
impedance and capable of delivering
relatively large amounts of power, the
usefulness of the push-pull amplifier
is not so great as it has been.
THE EAR AS A MEASURING INSTRUMENT
AND while we are speaking of im-
** pedance matching and voltage
amplification, one should not lose
MEASURING THE TUBE S HEARTBEATS
Apparatus necessary for laboratory tests of tubes is shown here.
The diagram of connections controlling this set-up of apparatus
was given on page 459 of February Radio Broadcast, and in-
volves the use of accurate resistance standards, a source of a.c.
voltage, accessory batteries and switches, and several meters
662
RADIO BROADCAST
APRIL, 1926
sight of the fact that the ear is a de-
ceptive measuring instrument. It hears
according to a logarithmic scale, that is, a
signal with one hundred times the power
of another signal will sound only twice
as loud. For that reason, the difference
between a 3:1 and a 4:1 transformer in
an audio amplifier is scarcely noticeable.
For example, the parallel tube amplifier
compared to a single tube has 1.4 times
the voltage amplification and twice the
power output. This difference in logarithmic
"transmission" units is only three units, and
it takes a trained ear to detect such small
differences.
For the same reason the fact that it is not
possible to "match" a loud speaker to a
tube at every frequency in the useful audio
range should not worry a listener too much.
Any one can tell the difference between a
terrible loud speaker of ante-quality days
and a fine one, or with the latter the differ-
ence between running it from a 199 tube
and a 1 12, but in general any one should be
satisfied with an amplifier that uses two of
the modern high grade transformers, or a
resistance or impedance amplifier properly
constructed and operated, with a semi-power
tube in the last stage and] proper B and C
batteries, especially if this amplifier delivers its
output to a cone type speaker that is properly
made.
At this point it seems fair to point out that a
speaker that merely uses a paper cone is not
necessarily better than a speaker of the horn
type. Much depends upon the element that
drives the cone and upon the methods of con-
struction and mounting. The only test is to
listen to it compared with other speakers in
which the listener is interested. Comparisons
should be made both as regards fidelity (quality)
and efficiency (volume with a given input).
Some cones are remarkably inefficient.
HOW NOT TO CONTROL VOLUME
IT IS weli too, to point out the fallacy of con-
trolling volume by regulating the filament
voltage of audio frequency amplifiers. As soon
as the voltage is reduced to the point where
volume is reduced, the impedance of the tube
is increased, resulting in the dropping out of the
low notes. If the low notes seem to have been
lost, or the amplifier has a tendency to howl,
charge the battery. Much distortion can be
laid to a detector or amplifier filament that is run
at too low a voltage. Reduced emission due to
too low filament voltage results in distortion due
to the inability of the plate current to follow the
peak input voltages. Low B battery voltages
also result in poor quality due to increased plate
impedances.
TABLE 3
REJUVENATED TUBES
201-A 199
PLATE PLATE
CURRENT CURRENT
@ 90 Ep, 0 EJ <g» 90 Ep, 0 Eg
Before
After Before
After
3.0
3.0 0.0
4.0
.5
5.0 0.0
3.0
1.0
9.0 0.3
4.0
0.0
6.5 0.2
3.4
0.0
2.0 0.4
4.0
0.0
1.0 2.0
3.8
3.5
2.0 0.2
0.9
4.0
1.3 0.1
3.2
2.0
5.8 1.0
4.2
0.5
5.0 0.5
3.0
0.4
4.8 2.4
4.0
39
4.8 2.4
dead
1.8
5.0 2.2
4.2
32
56
4.9
4.7
3.6
2.0
2.6
4.8
Number of 201-A tubes 24
5.0 •• •• 199 •• 13
1.0
2.8
1.2
0.2
Average increase in 201-A Ip 2.4 mils,
dead 199 Ip 2.2 "
Average Ip of new 201-A 6.5 '
d««d • 199 3.5 '
1.5
Some question has been raised regarding the
proper method of coupling a good loud speaker
to a high quality amplifier. In Fig. 7 are shown
three common systems. In any case there are
two primary considerations; will the d.c. plate
current of the power tube harm the loud speaker,
and will the impedance of the speaker match the
tube? If one uses a power amplifier as was de-
scribed by James Millen in the November RADIO
BROADCAST in which the plate current is of the
order of 30 milliamperes, the speaker should cer-
tainly be protected.
When the loud speaker is directly in the plate
circuit it looks directly into the tube impedance.
This is also the case with the condenser-choke
mfd.
IN THE PLATE CIRCUIT
Rp= ZL
CONDENSER CHOKE
Rp= ZL
FIG. 7
Methods of coupling a loud speaker to a power
tube. When the impedances of speaker and
tube are approximately the same, either "a,"
or "b" may be used. When they differ, an
adjusting coil should be used — commonly called
an output transformer. Its turn ratio as
controlled by the impedances is given by the
above formula
system since the choke and condenser are so
large that they have no effect upon the audio
frequency output, and in both of these cases the
loud speaker and tube impedances should be of
the same order. In case of the output trans-
former, the impedances can be anything, pro-
vided the primary of the transformer
matches the tube and the secondary matches
the speaker. Either the condenser-choke or
the output transformer will keep the direct
plate current out of the speaker.
THE MEANING OF THE "SQUARE LAW"
DETECTOR
IT HAS been stated that distortion in radio
reception arises from the use of detectors
which function according to a "square law."
In other words the output current varies
as the square of the input voltage. This
statement may be discussed in the follow-
ing manner. If the detector acted accord-
ing to a linear law, i. e., output current
directly proportional to input voltage, there
would be no detection — only amplification.
In other words our detector, which is in-
herently a distortion device, would amplify.
At the transmitting station a modulator
is used which functions according to a com-
plicated law, approximating a square law.
This is distortion at the very start of the
whole radio circuit. At the receiving sta-
tion a detector is employed as a "demodu-
lator" which brings the distorted signals
back to their original form. The detector is
l|||pH|||±J
© OUTPUT TRANSFORMER
NS ZL
Rp= Plate Impedance
ZL= Loud Speaker Impedance
Rp not equal to ZL
the reverse of the modulator and may be said to
introduce approximately complementary dis-
tortion. Neither would work at all unless there
were a bend in the characteristic curve. As a
matter of fact a crystal detector does not follow a
linear law but approximates a square law. Fig.
8 shows the curve of a crystal detector and its
similarity to a three-element tube curve is ap-
parent at once. Detection takes place on the
bend of the curve. If an amplifier is operated
on the bend of its characteristic it acts as a de-
tector (distorts). Recent research on detectors
by F. M. Colebrook in England, shows that tube
detectors are more efficient at low frequencies
than at high, say 100 cycles compared with
5000, and some distortion results. The extent
of this distortion may be considerable.
USE OF "HICH-MU" TUBES
UESTICNS are frequently asked regarding
e use of tubes with a high amplification
constant. These tubes are primarily designed
for use in resistance and impedance amplifiers.
As a matter of fact a low mu tube will not " load
up" a power amplifier unless coupled to it by
means of a transformer. For example, the aver-
age amplifier to deliver .06 watts power requires
APRIL, 1926
TUBES AND THEIR BEST USES
663
at least 9 volts variation on its
grid. A tube with a mu of 8
coupled by means of resistance or
impedance to the amplifier can-
not produce a variation of vol-
tage greater than 8 volts and
probably not over 6, so that the
amplifier will not deliver its rated
quota of power. On the other
hand a tube with a mu of 20, or a
tube with a mu of 5 coupled by
means of a 2:1 transformer, can
easily produce the desired change
in input voltage. High mu tubes
can be used as detectors and hence
are useful in vacuum tube volt-
meters. Their use in resistance
and impedance amplifiers makes
the latter practical without in-
creasing the B battery voltage
beyond reason. It must be said
here that the mu of such tubes is
not the only important constant.
The plate impedance must be con-
sidered and, like all other tubes,
the usefulness of high-mu tubes
increases as their impedance de-
creases.
REJUVENATING TUBES
80
70
o
ci
Q
V)
U
cc
o
CC.
o
60
50
40
30
g 20
10
10
20
PERIKON
CRYSTAL
.1
.2
THERE are many rejuvenat-
ing devices on the market at
the present time. These cannot
be used with any tubes except
those which have thoriated fila-
ments. They will be of no ser-
vice with the old tungsten filament
201 or 200 type tubes, or with the new ux-i 12, or
with Western Electric tubes. On the other hand
they are very efficient when worked with thor-
iated filaments of the 199, 2OI-A, 120, 210 and
certain 1 12 type tubes. The data in Table 3
gives the result of recent rejuvenating in the
Laboratory showing the plate current in milli-
amperes at 90 volts on the plate and zero grid
-0 + .1
(Ej) A.C. VOLTS
FIG. 8
This curve shows that the crystal detector follows a complicated
curve — not a straight line — differing but little from the grid
voltage-plate current or grid voltage-grid current curve of a
vacuum tube. The apparent increase in quality when using a
crystal detector is probably due to lack of tube noise introduced
by a grid condenser-grid leak detector
before and after the process. Fig. 9 shows sev-
eral tube flashers that have been tested in the
Laboratory. It will be seen that some tubes
went dead in the flashing process while many
gave increased plate current. At any rate the
user has everything to gain, nothing to lose in
the process. If his vacuum tube is no good be-
fore, it cannot be worse after the rejuvenating
process. Tubes can often be re-
vived by burning the filament for
several hours without the B battery.
WHAT "IMPEDANCE" MEANS
FOR the many readers to whom
the term "impedance" is some-
thing of a mystery, the following
explanation may be of aid — it is
not intended for engineers. In
direct current circuits — vacuum
tube filament circuits, for exam-
ple— the resistance controls the
flow of current. In alternating
current circuits, for example, the
plate circuit of a tube in which
there is an inductance coil, an
additional factor comes into play.
There is resistance and induc-
tance, both of which tend to limit
the flow of current. These two
factors may be combined into a
single term called impedance. If
there is no inductance or capacity
in an a.c. circuit, the impedance
is the same as the resistance; if
these other factors appear in the
circuit, the resistance must be
combined with them to calculate
the impedance.
The impedance between the
filament and plate of a vacuum
tube is practically pure resistance,
and its d.c. plate circuit resistance
may be figured knowing the plate
voltage and the plate current.
As an example: If the plate
voltage is 90 and the plate current 6 milliam-
peres, the d.c. resistance is 1 5,000 ohms. The
impedance of the tube, however, as measured on
an alternating current meter differs from this
value, and since tubes are used in alternating
current circuits it is not correct to use the above
figure when calculating the amplification, etc., as
has been done in this article.
.3
FIG. 9
A few of the tube rejuvenators now on the market. Those illustrated here are the Jefferson, the Sterling, the Burton and Rogers and the "Socket" tube
reviver. The device with two meters is to measure the plate current of a tube so that one can tell if the reviving process had any effect. Another re-
juvenator which is not shown here but which has been used in the Laboratory is the Hemco
RADIO BROADCAST Photograph
WHERE TWO CONDENSERS ARE EMPLOYED
To tune the RADIO BROADCAST "Aristocrat," a very symmetrical layout may
be had. In the receiver illustrated here, Silver straight line frequency condensers
have been used. The panel size is 7 x 18 inches
The "ARISTOCRAT"
Some Variations of this Popular Quality
Circuit which Originally Was Described
in the November, 1925, "Radio Broadcast"
—the Application of Dual-Control Tuning
RADIO BROADCAST Photograph
UNDER THE SUB-BASE
Showing most of the wiring and the method of mounting of Daven resisto-couplers and Amperite filament control. Moulded
hard rubber brackets have been used to hold the panel and sub-panel together, and to act as rests for the completed receiver.
This receiver and other models of the "Aristocrat" were designed by Arthur Lynch
A TOP VIEW OF THE TWO-CONTROL "ARISTOCRAT"
The layout, on an ordinary baseboard, and simplicity of wiring, make for compactness without stray capacities or the necessity of shielding. In this receiver the
single General Radio 20-ohm rheostat is in the filament circuit of the r.f. tube. Daven j-ampere ballasts are used in all the other filament circuits save the extreme
right, where the size of ballast depends on the output tube used. The plate voltage arrangement found best with this receiver was 90 on the r.f. and a 4.5
negative bias; 45 on the detector, and 135 on all three audio stages with 4.5 bias on the first two and between 9 and 11 volts on the last. The parts employed
in this model are Formica panel, Kurz-Kasch dials, Silver SLF condensers and Knockout coils, Daven ballasts, fixed resistors, and resisto-couplers, Silver ux tube
sockets, Tobe-Deutschmann bypass condenser X-L neutralizing condenser, Eby binding posts, Sangamo condensers, Carter switch, and Pacent jacks
ANOTHER TWIN-CONTROL
"ARISTOCRAT"
In this model the layout is altered somewhat by the
use of a sub-base. This receiver is identical to the
original RADIO BROADCAST "Aristocrat" for which
working drawings in blueprint form are available.
Amsco vernier dials, whether black, silver, or gold,
show up nicely on the Insuline panel. The other
knobs, left to right, are Carter antenna switch,
Royalty r.f. rheostat, Hammarlund neutralizing con-
denser, and Eastern tickler control
RADIO BROADCAST Photograph
A REAR VIEW OF THE SUB-BASE RECEIVER
Furnishing a general idea of the complete assembly. The tubes, left to right, are Cleartron cx-201-A Detector; two Cleartron Hi-Constron CT-101-A high-mu
amplifier tubes; ux-112 Radiotron power tube; and ux-201-A radio-frequency amplifier. In this layout the resisto-couplers are hung below the sub-base rather
than mounted on it as shown in some of the original models
A BEHIND-THE-PANEL VIEW
RADIO BROADCAST Photograph
Of the set shown above, the layout above the sub-base, and the freedom from visible wiring this form of construction makes possible, is distinctly shown.
The use of the Cardwell SLF condensers and Eastern Coils, resulted in both dials reading the same for any given station throughout the broadcast rar.ge..
Benjamin cushioned sockets for ux-base tubes were found very satisfactory. In this receiver Dubilier fixed condensers were used
I EGRET ARY of Commerce, Herbert Hoover's letter, reproduced on this page, is
quite self-explanatory. There are without question, many radio receivers in
working condition which are idle, and which would be of inestimable service
to the lighthouse keepers at their lonely posts. We believe that readers of RADIO
BROADCAST, if they know the service they can render by the donation of good receiv-
ing sets, will not be slow in rendering the aid they can so easily offer.
Readers of this magazine who have multi-tube sets which they are willing to donate
to the lighthouse keepers, should pack them carefully and ship them to the Commis-
sioner of Lighthouses, Washington, D. C., together with an explanatory letter to that
official, who will see that the set is delivered to a keeper who could best use it. It is
well to keep in mind the fact that the set should be capable of long distance reception,
for as every marine traveler
knows, lighthouses are neces-
sarily located at lonely and
COMMERCE \y i out-of-the-way spots, often far
from any broadcasting station.
There are few more worthy
causes than this, which RADIO
January s?. l \ BROADCAST is glad to present,
and we are sure that our read-
ers, who best know the pleas-
ure that a broadcast receiver
can bring, will not be slow in
Garden ci* j • - j showing their generosity.
to
Dear
H^^^lCfeSlT^f;;:™1-
toysj^^g ^SSHo^tW* *°ffitnPtht °ut °£ the *»7
Tlien too » {j«civ© ®^ £®° . fovsA*
^uBMally ® -t ^ff'h.tliO1-LS ® ^ nets
g^l^^HS^^f;^;,
i / "**\f 4
»5£*
^S^Bfc^
LEAVING A LIGHTHOUSE
Heavy weather often makes relief for the keeper
uncertain and infrequent. There are many
lonely marine outposts such as this where radio
would bring much comfort and pleasure. The
gift of a sensitive radio receiver would be a
welcome one indeed
HB-»«
Conducted by — John Wallace
Radio and the Taste of the Nation
Comes now radio, stalking in like the prover-
bial last straw, to put on the complete kibosh the
few straggling remnants of good taste that have
managed to linger on in this Land of the Cretin
and Home of the Depraved.
— words taken from the utterances of any one
of several of God's private secretaries, expressed
editorially in any one of several pastel colored
periodicals on the occasion of that sage's dis-
covery of the existence of radio.
THE text of most of this pious pessimism is
that the taste of the American nation is
lower than that of any other similar body
of men on this sphere, and that, among the
agents engaged in undermining it, radio promises
to be one of the most effective.
Nor is the custom of unfavorably comparing
the kuliur of America to that of any other
nation confined to the so-called intelligentsia.
The habit is so widespread as to constitute
almost a Dulcyism. That America, in respect
to its appreciation of the "higher things" is an
infant among nations is, in fact, one of the
cardinal planks in the American credo. It
finds place in our code of national convictions
along side of such sacred
tenets as "We must avoid all
entangling alliances," "The
French do not know how to
make coffee," "Success is
always the reward of effort,"
"Newspaper men are con-
scienceless scoundrels."
"Abraham Lincoln was the
incarnation of all virtue," and
"The Japs are a dangerous
little people."
It seems unfathomable on
the face of it that this nation
of 100 per cent, boosters
should be so clamorously in-
sistent upon deprecating the
aesthetic consciousness of its
citizenry. But it needs no
Freud or Jung to explain this
seeming paradox.
Try saying aloud; "Why,
my dear, you know our people
have simply no taste at all.
Why any French workman, or
Italian ditch digger, or Ger-
man peasant, or heathen
Chinee, has ten times as much
appreciation of good art and
good music as the average
American. They seem to
take naturally to the bettah
things."
There now, doesn't that give you a delightful
glow; doesn't that tickle your superiority com-
plex; doesn't that neatly, though not too
obviously, set you aside as one of the chosen few
who appreciate the bettah things; doesn't it
give you a cosmopolitan and world traveled air?
That at any rate is our explanation of the
national delusion that the taste of the average
American is inferior to the taste of the average
Anything-else.
At risk of appearing to make ourself out to be
very widely traveled, we assert that this theory
is pure and undiluted bunk. The "man in the
street" in Naples or Shanghai or Buenos Aires
or Berlin or Paris is every bit as much of a dumb-
bell as "the man in the street" in Janesville,
Wisconsin. In fact if any difference in their
stupidity exists we should be inclined to give
the American an edge more of appreciation.
Paris — the cultural capital of the world!
There is more inferior and ridiculous statuary
lining the boulevards of Paris for the delectation
of the Parisian "man in the street" than could
ever be found in a thousand miles of our Main
Streets.
"Ah, but the Italians," the self abasing Amer-
CECILIA HANSEN AND DR. WALTER DAMROSCH
Two artists recently heard on Sunday evening Atwater-Kent radio hours. Miss
Hansen presented a violin program splendidly played, although the program numbers
were hackneyed. Doctor Damrosch led his New York Symphony orchestra in a
special program for the International Tests, which was unfortunately cut short on
some of the stations of the "chain" by an sos call in mid-Atlantic
icano cries out, "see how they appreciate mu-
sic. It is born in them. It is part of them!"
We are urged to ascend to the garlic saturated
heights of the galleries of our local opera houses,
and find there the Latins, the true appreciators of
operatic music. And we find them there. But
when? When the silly melodramas of Guiseppe
Verdi or Donezetti are being yawped forth from
the stage beneath.
The tired business man of Milan goes out in
the evening to have his spirit refreshed by some
cafe or street corner band doling out dolorous
and sentimental tunes garnered from the jam
pots of the "classics." The tired business man
in Pittsburgh takes his musical stimulus in the
form of a program of jazz. And we are inclined
to attribute a superior discrimination to the
Pittsburgher. His taste savours less of the
maudlin and more of the virile and lusty.
We are told that the European instinctively
knows a good picture when he sees it, and at the
same time we find on the walls of his home, even
as we do in Texas, color prints of "Aurora" or of
one of Carlo Dolci's sickly saints.
But it is the man in the streets of ancient
Athens who is most frequently held up to our
gaze as the supreme example
of the artistic cultivation of
the masses. And without
pausing to examine any of the
numerous reference books on
the golden age of Greece, we
venture to guess that though
civic art at that time reached
a perfection never to be ap-
proached it was no doing of
hoi polloi. The politicians of
the time happened to be
gentlemen of artistic leanings,
so they put up public build-
ings that seemed to them
good — and they were good.
The bourgeois Athenian ac-
cepted these exquisite edifices
because they were there, no
whit realizing that they were
supreme examples of architec-
ture. Doubtless he admired
the Parthenon, but not so
much for its purity of form as
for the gaudy colors with
which it was then daubed.
In brief, we hold that there
is no evidence to support the
contention that the American
taste is on a lower level
than that of other countries
(speaking always of the
"average man's" taste.)
668
RADIO BROADCAST
APRIL, 1926
But let not our impassioned defense of the
aesthetic discrimination of our fellow citizen
lead you to suspect that we consider his taste
worth a row of pins. Our argument is entirely
relative; we simply believe he is no worse off
than any foreigner of the same intellectual strata.
For the taste of the American nation is
incontrovertibly low. It could adorn itself
with a parasol and still walk under a dachshund
to the small discomfiture of the beast. Our
newsstands are loaded with printed rubbish, our
theaters are decadent and demented, our
music is punk in proportion to its popularity, and
our movies . . . ah, there is exhibit A ...
fifteen years of almost unrelieved drivel.
However picture us not as sitting here gnash-
ing our hair or tearing our teeth over the fact.
On the contrary it disturbs us not a bit. If the
magazines on the stands and the movies at the
theaters actually represent what the great mass
of the people want, so be it, and well and
good. One book read for enjoyment is worth
three books read for uplift.
Yet our peace of mind is occasionally dis-
turbed by the suspicion that perhaps this
nefarious fare doesn't exactly reflect the desires
of the masses. Perhaps they, or some of them,
could be getting a bit more entertainment out
of something a little better. If so it would
seem an economic waste for them to be content
with inferior substitution. Which brings us back
to the subject on hand — the influence of radio on
the taste of the nation.
Radio, we conclude after some pondering, will
have no vast and far reaching effect on the
nation's taste. But far from lowering it, as has
been prognosticated by the pious pessimists, it
will, if it reacts upon it at all, more likely im-
prove it. And for several good reasons.
Taste in art, like taste in anything else, is the
index of our ability to enjoy the more highly
civilized forms of entertainment or stimuli.
Our friend Mr. Mulligan gets an immense kick
out of a prize fight. Our friend Mr. Van Peyster
gets an immense kick out of a George Bellow's
picture of a prize fight. And though we are
inclined to suspect that Mr. Van Peyster's en-
joyment is a bit more acute, there is no way to
prove it. More power to both of them in their
varied pursuits!
But perhaps Mr. Mulligan might likewise get
a kick out of Bellow's prize fight paintings if he
were ever exposed to one. And then what a
desirable state of affairs would have been
reached: Mr. Mulligan could spend his days
enjoying fisticuffs and his evenings enjoying
pictures of fisticuffs and thus be assured of six-
teen hours a day of happiness.
But all fooling aside, it is in just this way that
radio is likely to prove of service. It is exposing
the American nation nightly to better things
in music than it has been accustomed to hear.
Among the millions thus exposed to good music
are certainly some few who were not vaccinated
against it at birth, and they will, as they have
been doing, "catch" it.
To say that good music is not heard by radio —
as has been said by some critics — is simply to
confess an utter ignorance of what is being
broadcast. For good music is being broadcast,
indifferently performed in many instances no
doubt, but nevertheless good music.
The man in the street, like the man in the
jungle, has a tremendous fear of the Unknown.
Offer him an artichoke and he will bristle at the
brow and foam at the mouth. Conduct a nation-
wide advertising campaign with the slogan,
ARTICHOKES FOR HEARTY FOLKS
and he will deposit his pennies in the Piggly
Wiggly for dozens of them.
Such names as Beethoven, or Moussorgski
or Debussy formerly filled our lowbrow with
wide eyed fright, gave him the blind staggers,
lashed him into a frenzy of terror. And now he
has found that his fears were groundless; that
even the baby can listen to these names as
they come in via the family receiving set, perhaps
even to the tunes themselves, without dying
of some mysterious blight.
His curiosity is piqued. Who were these
men? Did they ever run for alderman? Could
they stand a show against Irving Berlin? And
lo and behold! if he has not been too thoroughly
inoculated against them by heredity, he finds
himself actually enjoying them. Voila ! The
deed is done! Our lowbrow has found a new
source of amusement. He has not been "up-
lifted." He has not been "cultivated." He
has simply stumbled upon something as effective
in another way as a bag of peanuts, or a game of
pinochle, in assuaging the griefs of this world.
And radio will be a tremendous boon to those
who imagine they are already possessed of a
polite and enviable taste for music. More often
than not, an imagined appreciation of music is at
bottom simply an appreciation of all the frip-
peries and gew-gaws that deck it. The cut of
the soprano's gown, the twirl of the violinist's
moustache, the presence of the "400", and so
forth, are of greater interest to a large pro-
portion of concert goers than the music itself.
Attention to the concert is frittered away
through the eye. What with attending to the
gymnastics of the conductor, the foot work of the
tympanist, and the amazing alertness of the
piccolo player, small part of the cerebral hemi-
spheres is available for following the music.
The remedy, in the case of concert halls, is to
darken the auditorium. But this, few impre-
sarios have the temerity to attempt. Their
business is to fill the seats, and plenty of light
wherewith to peruse the programs is the demand
of their clientele. Individuals feeling more
rabid on the subject than we have gone so far
as to protest that "no executive artist should
ever be visible to the audience." We vaguely
recollect that a concert hall in London made the
experiment one time of screening the stage.
Radio is, of course, the complete answer to this
problem. The listener, of necessity, does
naught but listen. So we can not help but
believe that in the long run this training in
listening exclusively will have a demonstrable
effect on the mass of musically inclined people.
The WGBS Prize Play
COMES to our desk a copy of Sue 'Em,
the radio play which won first prize in
the contest recently conducted by WGBS
and which was acted over the air for the first
time some months ago by members of the
Provincetown players.
The title page makes known that the author
is Nancy Bancroft Brosius, that it is published
by Brentano's, and is the first radio play printed
in America.
Unfortunately (or fortunately?) we didn't
hear the play presented, but we have just read
it through two times — the second trip being
attributable only to our burning desire to dis-
cover, if possible, why it won the prize. That
discovery we have yet to make. We dismiss the
most ready answer — that it was the best one
submitted — as a rather too unkind reflection on
the other contestants.
The characters are four: Mrs. Dorn, "middle
aged and of settled disposition " her henpecked
husband, the "flapper" daughter Effie, and the
son Bill. The family is sitting around waiting
to go to the movies when pa finally puts in a
belated appearance. Ma gives pa a good
bawling out and is not at all appeased by his
explanation that he was delayed by a cop who
wanted to arrest him for jay walking. Pa, it
seems, tried to walk into a truck which brushed
by his leg.
But suddenly it is suggested to ma that the
truck drivers might be sued ! Then pa is quickly
shifted from the role of doddering jay walker to
that of martyr.
In a few moments he is quite dead and buried,
the suit is set at $2000 and the receipts budgeted
out and all but spent. Pa is now a wounded
hero and the truck driver indicted as a criminal
menace to the safety of honest citizens. The
dialogue working up to this right-about-face
on the part of Mrs. Dorn is well written and
humorous in a broad fashion.
Then the twist is introduced: Bill, the son,
enters the room, disheveled of appearance and
terror stricken of mien. He announces that he
has been out driving in the family Ford; that a
man walked right in front of his car, that he
struck him, and probably killed him! The
consternation of the family is augmented when
Bill says they will probably be sued by the man's
widow and four orphans. Ma then executes
another right-about-face and discourses at
length about the carelessness of pedestrians and
the injustice of the widow's presuming to sue
her innocent little Bill.
An amusing situation, we grant, but how
was it arrived at: Bill, after witnessing his
family's absurd shift of ground, breaks into
merry laughter and announces that it's all a joke,
he never hit anyone. This announcement,
which is supposed to constitute a climax, is,
as a matter of fact, a silly let down, and takes
away whatever merit the play hitherto had.
It is irritating as it discloses the author as trying
to put one over on the audience. In other
words the situation is not developed but forced.
It is like killing off the husband in the third act
to solve the unsolvable triangle problem.
A Plea for More Novelties on First
Class Programs
CECILIA HANSEN, violinist, sharing a
program with Florence Austral, soprano,
was heard in the third of this year's
Atwater Kent concerts. Miss Hansen's contri-
bution to the concert was as follows:
a Poent . , .
Fibich
b. false Blueite. . .
a. Meditation. "Thais"
b. Caprice Viennois
Drigo-Auer
Massenet
Kriesler
Arensky
a. Humoresque .
b. Ave Maria .
Dvorak
Schubert- Wilhelmj
Now suppose you, gentle reader (if such there
be!), help us finish this article. Turn to your
nearest neighbor and ask him to "name five
solos for the violin that have been massacred
more often than any others by radio performers."
Done? Well now we'll just bet you our Hyper-
whichomodyne against your thirteenth tube
that your five numbers are included in the above
program.
Who was responsible for Miss Hansen's dish-
ing out such an assortment of trite tunes we
don't know, but we are willing to be quoted as
saying it was a stupid move. Cecilia Hansen is
in the first rank of her profession. Her skill
as a violinist is not even exceeded by her good
looks (a considerable tribute that). So why,
APRIL, 1926
WHAT LISTENERS THINK OF BROADCASTING
669
WILLIAM DIEFENDORF
A well known performer on the musical saw who
was heard during the recent International
Tests from WHAZ, at Troy
oh why, couldn't we have heard something a
little less threadbare from her?
Dvorak's Humoresque, Massenet's Meditation,
and the rest of the above pieces have become
hackneyed for the very good reason that they
are beautiful tunes. So charming in themselves
that they defy the efforts of the vilest cat gut
scratcher to completely disguise their beauty.
Ever assured of an enthusiastic reception, they
have become fixtures on the repertoires of every
fourth rate vaudeville or radio fiddler.
But hackneyed they nevertheless are. Of
course any alert musical theorist can furnish
proof beyond contradiction that a great compo-
sition can never get old, no matter how often it
is heard. But, aside from theory, the facts of
the case are we do get tired of hearing the same
thing over and over again.
And for this reason we regretted that an artist
of Miss Hansen's ability allowed these musical
banalities not merely to encroach on, but to
completely monopolize her program. On the
strength of her skillful interpretation she could
have made just as enjoyable a program of less
familiar, though equally worthy, selections — and
thus enriched our musical acquaintanceship,
leaving these sure-fire-hits to her weaker sisters.
We ramble on at such length not
because this concert alone would
seem to warrant it, but because it is
typical of many other offenses in
kind. The John McCormack con-
cert, for instance, was made up
largely of the ditties that you, as do
we, sing so effectively in the bath
tub. And we are not entirely con-
vinced that John sang them a bit
better than we have ourselves under
the stimulus of fragrant soap suds.
Doubtless there are some more diffi-
cult tenor airs that Mr. McCormack
could do more justice to than we,
but they were, in the main, lopped
off his program. Which seems to us
somewhat of a waste — rather like
using a nice shiny silver cock-
tail shaker to mix up the baby's
barley water.
have been "played to death" on the radio, the
eight directors of the concert orchestras whose
programs are featured weekly by station WRC, at
Washington, will for one week include in their
programs only those new-old compositions
which are seldom, if ever, heard on the concert
stage or on the air.
Working in cooperation with Ralph Edmunds,
Program Manager of station WRC, the eight
directors will search their libraries for musical
compositions whose melodies lie half-forgotten
on their shelves, and will eliminate from their
programs any numbers that they themselves
have played in radio concerts in the past year or
any which they may have heard played by some
other orchestra. This innovation was decided
upon following numerous requests from listeners
for "new" music, instead of the almost continual
repetition of selections which in many cases have
become prevalent during the past six months.
So far, a list of more than a hundred such
compositions has been compiled by Mr. Ed-
munds and submitted to the directors for their
consideration. Included in the programs for the
"music revival" week will also be a number of
original compositions which are being written
by the directors and members of their orchestras.
A second list of more than one hundred and fifty
selections has been made, all of which are placed
definitely under the radio ban for the week.
Is It too Early for the Burlesque
Program?
1 OME time ago it occurred to us that radio
had attained of sufficient age and
accumulated enough foibles in the ageing
for some intrepid station to undertake a bur-
lesque program, poking fun at the broadcasting
game and possibly effecting some reform through
the medium of mild satire. As we rotated the
idea in our mind we were struck by the limitless
number of opportunities for screamingly funny
burlesque that are offered. In fact we had al-
most reached the point of writing to some station
director and imploring him to hazard such a
program when we ran across the following article
in the New York Times, whereupon we decided
'twere better not.
LONDON, Jan. 17. — Great excitement and fear were
caused here and in all parts of Great Britain and Ireland
last evening when radio listeners-in, by a comedy of
errors, heard on the air the announcement that a revolu-
tion had broken out in London.
Among other things they were told that the National
Gallery had been laid in ruins by an army of unem-
ployed; that the Savoy Hotel had been blown sky high,
S(
FRED SMITH
Formerly program director of WLW at Cincinnati,
and lately the guiding spirit behind the splendid
and entirely unique civic music programs
sponsored by the Cincinnati Chamber of Com-
merce and broadcast through WSAI. Business
men of that city have subscribed more than
$15,000 to support twenty monthly programs
which have featured such artists as Fritz Reiner,
and the Cincinnati Symphony Orchestra,
Marguerite Lizsniewska, Mieczyslaw Munz,
Francis McMillan, and Paul Althouse. Edward
J. Hoff, of the Chamber of Commerce, is Chair-
man of the Broadcasting Committee
that the interior of the House of Commons had been
bombed, and that there had been a massacre of people
in St. James's Park. A realistic touch was given to
the terrifying details by sounds as though of distant
explosions, the tumult of terror-stricken crowds and
the crash of falling buildings.
The listeners-in spread the news and soon the news-
paper offices everywhere were bombarded with tele-
phone calls from people anxious to get further details.
These offices were kept busy all day today reassuring
frightened inquirers, for the rumors were still circulating
in country towns and villages, and the fact that bad
weather delayed the arrival of the morning papers was
taken by many persons as confirmation that the worst
had happened.
It was learned later that Father Ronald Knox had
been broadcasting from the Edinburgh wireless station
a series of burlesque "news items" and it seems that
many in the radio audjence had failed to tune-in scon
enough to hear a preliminary announcement warning
that the stories should not be taken seriously.
But the British Broadcasting Company is being se-
verely criticized for what is described as a bad joke and
has found it necessary to issue an explanation to the
public. It regrets that any listeners should have been
" perturbed by this purely fantastic picture," but points
out that preliminary warning was given that the enter-
tainment was not to be taken seriously.
Father Knox's burlesque news bulletin
was given with so many touches of humor
that it seems incredible that what he said
could have been taken literally, yet at
least one woman fainted when she heard it.
The Listeners Speak
Themselves
for
T*
A arn
After writing the above the in-
formation below came to our atten-
tion. The novelty week referred to
was inaugurated last January.
Banning all musical selections that
THE CAST OF THE WGBS PRIZE PLAY, SUE EM
Recently presented at the New York station. Last year, a contest was
conducted by the station and the prize for the best manuscript for the
group was given to Miss N. B. Brosius, of Cleveland. In the photograph,
left to right: John Huston, Eugene Lincoln, Marion Berry, and Jeanie
Begg. All are members of the Provincetown Players of New York
following statistics should
of interest. They were
arrived at by a canvass of
2800 radio fans scattered through
48 states. The poll was undertaken
by A. Atwater Kent of Philadelphia
and its result catalogued by Carl
H. Butman of Washington.
Practically all listeners agreed
that there are far too many small
broadcasting stations operating in
the lower wave band, and that there
is too little high-class entertainment,
although many believe that the
chain broadcasters are giving ex-
cellent service.
Lack of variety in programs
and poor announcing from many
stations, are given as constructive
670
RADIO BROADCAST
APRIL, 1926
criticisms by radio denizens of over five hundred
cities and towns. "No, there is not too much
classical music," 2400 reports out of 2600 state.
On the other hand, there is too much jazz,
according to 1420 replies out of a total of 2534
answers. Short talks and timely speeches also
appear to hold fan interest, the survey shows.
Interference from various sources is noted by
more than half the correspondents; only about
nine per cent. of the writers claim they have no in-
terference. Static is blamed by more than seventy
per cent, of those having reception difficulties,
and seventy-five per cent, of them admit that
their local or near-by stations come in the best.
This is believed partly due to the static handi-
cap. Code reception still causes some inter-
ference; about a third of the fans reporting
interference, say this form bothers them.
A large number insist most of the interference
is due chiefly to the fact that so many stations
are crowded into the wavelengths between 300
and 200 meters. A Pennsylvania listener
wished three-fourths of them would sign off for
good. Some say they never try to tune-in below
the wavelength of KDKA. The use of a selective
set and careful tuning seems to bring in lots of
little fellows pretty well, and some of them offer
unique programs. This fact is pointed out by
another fan, who asserts he likes some of the
smaller, independent stations better than the
high-powered broadcasters due to their individu-
alitys and unusual features.
One correspondent, an old time listener from
Cleveland, states boldly that, although some of
the larger stations which frequently hook up on
national programs with WEAF or wjz are fine, he
believes ninety per cent, of all the programs are
not worth while. The ideal conditionswill only be
realized, he declares, when there is but one local
in a city or town, and one or two good conti-
nental chains. More broadcasting of inter-
national events, conventions and really good
speakers will make for greater understanding and
contentment in radio land, he adds. Many of
the smaller stations, he points out, put on artists
from cheap vaudeville shows, whose acts and
lines of patter are often offensive and sometimes
obscene. His statement that the programs
handled by linked stations are usually good, is
borne out by approximately eighty-five per
cent, of the replies filed, which endorse this type
of entertainment.
A pertinent suggestion is offered by a fan who
says he can't see why these chain hook-ups
always work one way, that is out of New York;
He would like something from Detroit, Chicago,
Philadelphia and other cities broadcast over a
series of stations for a change, believing there is
also good talent available in those cities.
A feminine fan is willing to listen to dance
music and jazz when there is some semblance of
melody to be heard, but objects to tuneless
selections which sound as if they were written
for noise alone. She also makes a plea for
variety, pointing out that a whole evening of
classical music is boresome while a solid program
of jazz is worse.
The ears of careless operators of regenerative
sets would certainly burn if they could read
some of the caustic complaints regarding oscillat-
ing receivers. This type of set should not be
manufactured, one letter protests, while another
listener claims all should cooperate to suppress
them or teach the owners how to handle them.
Semi-technical talks on operation would help
remedy this condition, he believes.
Just after Christmas for about three months,
one writer says he never tries to listen-in, be-
cause the kids trying to operate their cheap
"radiators" make the nights hideous until they
run their batteries down or break up their sets
Another fan expresses disappointment that
Secretary Hoover hasn't put a stop to the use of
oscillating sets, adding that it now looks as if
radio was doomed to failure in this country
where it should be the best in the world. An
Ohio listener says he quits in disgust every night
about eight when the howlers and squealers
begin. "I would gladly pay a national tax on
my antenna or set," this man declares, "if we
could be guaranteed from the interference of
these nuisances." This man seems to ha\e
spoken for a large number of listeners.
Some of the suggestions for improving the
programs call for humorous talks sprinkled in
with miscellaneous matter, touching on the
general request for novelties and variety, which
of course make it harder than ever for the over-
worked station managers. One man wonders
why practically all stations open up at almost
the same hour and suggests that some start
earlier, say at dinner time and carry on through
THE FLONZALEY QUARTET
Heard in a recent Victor Hour, broadcast over wjz, WCY, WRC, KDKA, and WBZ. This group of musicians is
internationally conceded to be one of the most perfectly balanced chamber music organizations on the concert stage
APRIL, 1926
THE BEST CURRENT BROADCAST FEATURES
671
the early evening, while others come on a little
later. Perhaps they would interfere less if they
operated on staggered schedules. A train
dispatcher is evidently needed if they all want us
to ride with them. After all, we can't ride on
more than one train or listen-in on more than a
single wave at a time satisfactorily.
Thoughtful members of the listeners' clan,
point out that more instruction on reception is
necessary; that dealers should be particular to
sell correct accessories and, particularly, suitable
length antennas, designating the proper instal-
lation of antennas and grounds for new comers.
Incorrectly erected and poorly insulated an-
tennas are the cause of a great amount of poor
reception, several correspondents hold. Faith
in fairly long outside antennas is evidently still
strong, as 83 per cent, of the fans listed use them,
nearly half of them being between 75 and 100
feet in length.
A few listeners admit they would prefer one or
two good programs a week rather than a con-
tinuous nightly performance by mediocre talent
or even fair entertainment. Many offer to pay
for better broadcast programs if it is necessary,
so as to eliminate the amateur and inferior
stations.
The calls for silent nights were not missing,
but most of the fans reporting seem able to get
at least a few outside stations when they want
to do so. This is perhaps because a large
percentage of those writing in own three-, four-,
or five-tube sets. Out of 2660 fans replying to
the question, 40 per cent, operate five-tube sets,
while 22 per cent, own three-tube receivers, and
13 four-tube sets. Very few boast of more tubes
and even less seem content with single tubes or
crystals. This would indicate that listeners are
slightly better equipped that a year ago. Most
of them get loud speaker volume on some station
as 85 per cent, of their sets are equipped with
loud speakers. Of these, horns seem still most
prevalent, although the more modern types are
coming into use gradually.
These folk who wrote in about their sets,
appear to prefer wet A batteries, but dry B
batteries, although a few have installed elimi-
nators.
Complaints against barefaced advertising and
sales talks were also registered, while protests
against the conduct of announcers would make
a story in itself.
'Broadcast ^Miscellany
A NOTABLE contribution to recent radio
offerings was the series of Free Chamber
Music Concerts by the Lenox String
Quartette broadcast through wjz from the
Music Library in New York City.
These concerts were made possible through the
courtesy of Mrs. Elizabeth S. Coolidge, who has
taken a great interest in the development of
musical appreciation in the American people
and has spent large sums of money in the ad-
vancement of the education of the people along
these lines. She is the founder of the Coolidge
Chamber Music Festival, which is an annual
event of three or four days duration in Washing-
ton each Autumn. It is Mrs. Coolidge's aim
to institute free music concerts in every city in
the United States and make the public libraries
the seat of musical as well as literary education.
It was she who paid for these concerts and her
only stipulation was that the works of at least
one American composer be played at each con-
cert.
The Lenox String Quartette is composed of
HENRY FORD'S OLD FASHIONED DANCE ORCHESTRA
Composed of cymbalom, sousaphone, "fiddle," and dulcimer, which recently broadcast an interesting
program of old time dance music over WEAF, WJAR, WEEI, woo, WCAP, WCAE, WTAG, WGR, wwj,
woe, WEAR, wcco, WON, and KSD
Wolfe Wolfmsohn, first violin; Edwin Ideler,
second violin; Herbert Borodkin, viola; and
Emmeran Stoeber, violoncello.
A WELCOME addition to the Chicago
*» district's dinner music programs is the
offering of the KDKA Little Symphony concert
through KYW. This is effected through KDKA'S
short wave relay system which connects that
station also with WBZ and KFKX.
A MONO the novelties recently introduced
*> was the Henry Ford Old Fashioned Dance
Orchestra broadcast through WEAF and Associ-
ates. Besides the still up-to-date violin this
quartette boasts of a cymbalom, sousaphone,
and dulcimer.
/^\NE of the best of the permanent features on
^-^ KGO'S program, is the concert by the
station's Little Symphony Orchestra every
Sunday afternoon at 3:30. The orchestra is
conducted by Carl Rhodehamel. Explanatory
remarks are made by Arthur S. Garbett.
STIMULATE a greater interest in the
*• operations of governmental machinery and
national problems, the Minneapolis League of
Women Voters has arranged a series of 20
weekly talks from wcco. These are to be given
at 2:00 p. M. every Tuesday. Each week the
speaker will devote five minutes to answering
questions which the listeners have sent in. The
subjects to be discussed are: "Is Woman
Suffrage a Failure?"; Why Vote?" "How Can
Women Help in Bringing Universal Peace?";
"How Does My Vote Affect the Home?";
"City Government?"; "State Government?";
"National Government?"; "Women in Indus-
try?"; "Women in Professional Life?"; "The
Child at Play."; "The Child at School."
f~\f THE stations we receive regularly on our
^-' set, we know of none that flaunts its call
letters and location more frequently and per-
sistently than WJAX at Jacksonville, Florida.
Since it is a municipal station, the explanation
lies, probably, in its desire to impress the name
of the village on the world at large. Personally,
we're over-impressed.
"THE custom in Europe, we are told, is to
*• announce the name of the station at the
commencement of the program, and then to
make no subsequent reference to it. The only
exceptions are Toulouse, Oslo, Rome, and
Munster, where the announcers state the
station's name with every single announcement
throughout the program.
DROBABLY the most irritating mode of
announcing in present use is that em-
ployed by WBBM, Chicago. An oh so cheery,
oh so democratic voice greets the listener before
each number with a "Yes sir! Yesma'm! This
is the so-and-so Company station!!!"
IN NOTING the recent high spots in radio
1 programs we first take occasion to welcome
again the Victor Hour. The series started out
auspiciously with John McCormack and Lu-
cretia Bori, on whose heels quickly followed
Titta Ruffo and the Flonzaley Quartette.
DUT what we consider the best news since
L* last writing is the winning over of the
Boston Symphony Orchestra to broadcasting.
For the first time in its history it has undertaken
to broadcast its regular winter series of twelve
concerts Saturday evenings through WEEI.
The fact that season ticket holders have com-
pletely filled Symphony Hall for the last two
seasons, to the exclusion of the general public,
was a determining factor in causing the trustees
to authorize the broadcast.
Communications
Mr. John Wallace,
RADIO BROADCAST,
Garden City, New York
SIR:
I have been hoping that someone would take
a crack at those announcers who urge us to
"write in." Why always "in?" Can't they
say "out" or even "round about" once in a
while?
Also something about the announcers who only-
have "little" songs, "little" compositions, etc.
Why not have something of a fair size or perhaps
even large now and then?
I grow somewhat tired, too, of the announcers
who are so sure we are enjoying their programs.
BEECHER OGDEN.
Pleasantville, New York.
AS THE BROADCASTER SEES IT
Drawings by Fran^lyn F. Stratford
How Radio Has Progressed
W!
"E ARE so constantly bom-
barded with the idea of
'progress," nowadays, that
we are apt to conclude that
it is a notion of universal validity, which
has always existed. This is an error.
Progress, as a matter of fact, was first
boomed in earnest by the late Victorians.
No doubt it existed before, but it was taken
for granted, and no one got excited over
it. Presumably a civilized Greek of the
EC's realized that he was housed and fed
better, and more comfortably situated in
general, than his remote ancestors, but he
did not feel the urge to deliver lectures on
the subject. As for the mediaeval mind,
the idea of progress was as remote from it
as oil circuit breakers.
The reason for this deplorable lack must
lie in the fact that these people were not
blessed and burdened with machinery.
Their main concern, after the primal com-
forts had been taken care of, was with
the things of the spirit. Hence they did
not believe in progress, probably never even
thought of it. For it can hardly be denied
that as far as spiritual comfort is concerned,
one age is no better off than another. If
we assume that happiness is the aim of
life — an assumption which holds good for
me, and you are free to accept it or to
make your own assumption, as you please —
then certainly a man of this age has made
no progress over a man of the age of Pericles
or even Rameses. Or, if you like, go back
further. These men were as free to learn, and
to make love, and more free to get drunk,
than we are, and they had less to worry
about. I doubt if 1 am happier than they
were, all the way back to Pithecanthropus
Erectus. So much for progress in that
sense.
But when it comes to machinery, we
face a different situation. As soon as
machinery enters the door, progress breaks
in at the window and sits down in the best
chair. There are no perfect machines,
and few good ones. Some, however, are
better than others. As soon as you start
in on that line, you must follow it to the
grave. If you build one machine, you
must shortly build another and better one,
or some one else will. And so Progress has
you by the neck. Progress, therefore, is a
specialized and narrow thing, valid only in
certain applications. To us it seems uni-
versal, because we are interested only in
the things to which the concept of progress
is applicable.
Of these things radio is one. Here is a
field, taken by itself, in which the advances
are evident to any one who has not been
traveling in Tibet for the past five years.
(The qualification may not be an apt one;
by the time this gets into print, radio may
have invaded Tibet.)
Let us go back those five years. That,
of course, is an arbitrary figure. As we
have often emphasized in this place, radio
was very much alive before 1921; even
radio telephony was not a novelty to those
"in on the know," and there had been
stations properly describable as broadcast-
ing stations before that time. But it was
toward the end of 1921 that radio became
a subject for public participation, rather
than the esoteric preoccupation of a few
engineers, operators, and amateurs. And,
entirely aside from the "1 did it first"
claimants, that is when broadcasting as we
know it had its beginning.
Toward the end of 1921 I was living up
on Cape Cod in Massachusetts, not far
from the beach where, in his day, Henry
Thoreau paced the sands and declaimed
Homer to the ocean waves; but my occupa-
tions were more prosaic. I was engaged
in my trade of wireless telegraphy, to-
gether with about forty other men at a
transoceanic-and-marine station. Some
of the operators, at their homes in the
evening, listened to broadcasting from
Newark, New Jersey, and spoke to me
about it. I was not much impressed,
having often heard wireless telephone
transmission before. The trouble with it,
they said, was the interference; various
ship and shore stations broke in continually
while the children were listening to the
bedtime story, and set them to yowling
instead of putting them to sleep, and
hashed up the phonograph music, which
was otherwise grand. Reception, of course,
was on headphones. The sets were one-
and two-tube affairs, inductively coupled,
with tickler regeneration. These sets
were decidedly better than the average,
having been built by professional operators
with all the controls necessary to achieve
the best results, and perhaps a few in
addition. They were not selective enough,
however, to achieve freedom from inter-
ference, aggravated by the distance of the
broadcasting station (some 200 miles),
and the relative nearness of the spark
transmitters of ships rounding the Cape
and sending on 300 and 450 meters.
At this time a majority of the listeners
were probably still in the skilled class
mentioned above — commercial or amateur
wireless telegraph operators having a little
fun with telephone reception. Their num-
ber was limited, while the number of
potential unskilled listeners was enormous.
The latter were rapidly catching up and
passed the first group very early in 1922.
The receivers offered for sale to the lay
public at this stage were very crude.
Most of them were built for only one wave-
length (360 meters), and the only variable
element was to enable reception of signals
of this frequency with various sizes of
antennas. The best known of them was r
single-circuit crystal receiver in a small
box, with switch taps for varying the in-
ductance of a single-layer solenoid. The
tuning was so broad that with a large an-
tenna— and everyone tried to get as large
an antenna as possible — it did not matter
much where the switch was set; everything
from 175 to 500 meters came through,
more or less. Then there were some better
sets, also of the single-circuit type, but with
a variometer adjustment and a more
scientific connection of the detector circuit
to the antenna inductance (through a
suitable tap arrangement on the latter)
APRIL, 1926 HOW BROADCASTING TO-DAY COMPARES WITH THAT IN 1921
673
so that the tuning was as good as one could
expect of such a simple arrangement. Of
course the more complicated three-circuit,
four-control tube receivers favored by the
amateurs were available, but bold indeed
was the novice who essayed to operate one
right off the bat. A three- or four-control
receiver nowadays usually has most or all
of the dials lined up so that for a given
setting of one, the others should be ad-
justed to about the same numbers on the
scales. Besides, in the meantime the
public has been educated by radio periodi-
cals, trade catalogs, and comparison of
notes on the 8:13 into town. But in
1921-22 the more complicated receivers
were still operated by intuition rather than
figuring, and if you lacked the intuition
you had to fall back on the crystal re-
ceivers, which were therefore in the vast
majority. The typical radio fan was a
slightly deranged but harmless fellow who
sat all evening with a pair of headphones
on his ears, tinkering with a wire which he
called a "catwhisker" wherewith he gently
prodded a "crystal," muttering at inter-
vals, "Maybe 1 can find a better spot on
this d — d piece of galena." So much for
the technical equipment.
And what did he hear? Mainly phono-
graph music riding on top of great splashes
of telegraph code. Although, for a time,
very respectable artists broadcast for the
sheer novelty of the thing, and a ride to
Newark in a Packard with a lively party
at the Robert Treat following. Then,
when the cute little fish began to grow up
and threatened to attain the dimensions
of a whale, they found it better to stay
away from its aquarium. Also the music
composers, and the custodians of their
copyrights, began to oil their six-shooters
and to sharpen the tips of their harpoons.
There followed some lean years, judged
by the artistic standard, but the marvel of
getting voices, and a species of music, out
of the air, kept the new art, not only going,
but growing.
As for the broadcasting stations them-
selves, they were good for their day, even
though they would give a modern broad-
cast engineer, i.e., one practicing four
years later, convulsions and suicidal im-
pulses. Their audio frequency bands were
too narrow and had a great number of
humps and dips, most of the tubes over-
loaded, the microphones had joyfully
responsive resonance peaks and were
addicted to blasting; the wire lines carried
almost as much sixty cycle hum and tele-
graph clicking as modulating energy for
the broadcasters who leased them. It was
a grand old time, and I myself grow senti-
mental over it after a few drinks of ginger
ale — but let us thank God that we do not
have to listen to its effusions again, with
our sensitized and critical ears. (We
prodigies who did not know, five years ago,
whether a 373-W "mike" had one button,
or two, or as many as a vest.)
Let us now regard the present. We have
receiving sets so selective that they clip
the side-bands off the transmitted wave,
if we are not careful, and they operate on
one or two tuning controls. They are a
thousand times as sensitive as they need
to be for anything but extreme long dis-
tance reception, and are used most of the
time with the volume control near its
minimum position. The output can be
made as loud as the original performance
in the studio or concert hall, without
noticeable distortion. The users of such
sets need not be cautioned to hold down
the volume in order to keep the quality
decent; they can get all the output the
window panes can stand, without hashing
up anything. As for headphones, most
radio listeners no longer associate them
with radio sets at all. Modern loud
speakers transmit all the frequencies from
70 to 7000 per second, and if they have
serrations they are not as high as a cathe-
dral door, nor as close as saw teeth, so
that the human ear, which is no precision
instrument itself, takes little note of them.
These sets not only work well, but they
look well. The programs, in large part,
are on the same level. More and more
they are being supported by professional
musicians, and, among the greatest artists
and aggregations of artists, there are now
more who have broadcast, and are going
to do it again, than those who still fight
shy of the microphone. Scarcely an event
of public importance is run off without that
little instrument in the foreground, and
half of them are planned as much for the
"invisible audience" as for the people
physically present. As for the broad-
casting stations, it is not fitting for a
professional broadcaster to point publicly
to their many excellencies. Nor is it
prudent, because whenever he gets that
way all the modulators immediately go
soft, the cat gets tangled up with the ten
thousand five hundred, and the breakers
go out and won't go back while Lucrecia
Bori takes a top note. Still, it may be
said that there are ten or twenty stations
in the States which are pretty good, con-
sidering that their whiskers are not yet
beginning to sprout. They are connected
by quiet and well equalized lines, their
frequency characteristics are satisfactory,
their power is fairly adequate, their staffs
know something about music and practical
acoustics. All in all, the look backward
is flattering, and the prospect encouraging.
What with static, forced sales, copyright
disputes, and lack of wavelengths, we are
certainly not out of the woods, but one
does not have to be a member of the Ki-
wanis sodality to recognize the fact that
we are on intimate terms with the goddess
Progress.
Among the Broadcasters
WBAL
THIS new 5 kw. transmitter at
Baltimore, Maryland, uses the
"mixing panel" idea in solving
its studio pick-up problems. Instead of
employing one microphone, which must be
moved to the proper position for proper
balance on vocal solos with instrumental
accompaniment, orchestras, and the like,
WBAL utilizes three microphones with
separate controls which are under the hand
of the supervising operator. The electrical
energy fed to the set from each of these
microphones may be increased or decreased
at will, without noise or other complica-
tions, so that one microphone may be
cut out altogether, and another cut in,
during a musical number. In other words,
microphones may be changed at any time,
without disturbance, the only precaution
necessary being that the cutting out and
swinging in must be accomplished in in-
verse proportion, so that the over-all
volume resulting remains about constant.
IN IQ2I, THE SPARK INTERFERENCE ON 360 METERS MADE THE CHILDREN HOWL
674
RADIO BROADCAST
APRIL, 1926
Or, the pick-up of the three microphones,
or any two of them, may be "mixed" to
produce a musical balance better than can
be secured on one (assuming no physical
movement of the microphones). I insert
this last qualifying clause because it is my
opinion that in a studio of moderate size
with experience and reasonable control
in placing of musicians, one can do as good
a job with one microphone as with a dozen.
One microphone, properly placed, will give
as satisfactory results on small ensembles,
as any combination. The advantage of
the multiple pick-up arrangements is the
flexibility in adjustment secured when it is
found during the first number of a per-
formance that no one microphone is
properly placed. If there is only one
microphone, the choice is between entering
the studio during the number and moving
the transmitter, which always disturbs
the artists and may cause a noise on the
air, and letting it ride for that number,
i.e. doing a bad job for five or ten minutes,
and fixing things up during the first in-
terval. In other words, the broadcaster
has to choose between the electrical devil
and the deep sea. But if he has a number
of microphones independently mounted
and controlled, his life is made a little
easier. Suppose he encounters a soprano
of unknown potentialities, with the usual
piano accompaniment. If she sings very
loud, it may be well to place her five feet
from the microphone, say, while the piano
THE MIXING PANEL AT WBAL
Part of the standard sooowatt equipment at that station. The mixing
panel for various studio microphones is that av the extreme right of the
illustration
is two feet to one side.
(See Fig. i, position A).
But if she sings softly,
the piano will predom-
inate with this set-up.
Well, all you have to do
is place your microphone
B say three feet from
the lady. As soon as she
starts you will know
which transmitter to use,
and as you have control
of both it is the work of
only an instant to swing
in the right one. Or, it
may be convenient to
combine the outputs of
the two microphones.
This, in brief, is the sys-
tem used at WBAL. With
it there is much less
excuse for poor musical
balances, blasting, etc.,
than when only a single pick-up unit is
available.
The WBAL announcement which has
reached us merely explains the purpose of
the system described, without giving the
technical modus operandi. One way of
doing it would be to use separate amplifier
systems with individual gain controls of
the type described in this department in
the March issue ("Technical Routine in
Broadcasting Stations: Monitoring"), the
outputs being combined after two stages of
low power amplifica-
tion. This has the ad-
vantage of including
a number of parallel
chains: microphone
plus amplification up
to the five watt level,
say; and if anything
happens to one of the
amplifiers or micro-
phones, that particu-
lar system is cut out
as a unit, leaving one
or two others still
functioning. It has
the disadvantage
of complexity. A
method of using a
multiplicity of micro-
phones, individually
controlled, "input-
ting," as Zeh Bouck
says, to a single am-
plifier, is shown below
under "Technical
Operation of Broad-
casting Stations:
Multiple Pick-Up."
KOA
FROM KOA, the big
fellow in Denver,
comes the news that
the technical staff at
that station are util-
izing a "magic rug
remedy" to keep
public speakers
X) Accompanist
T Microphone
"A"
•*• Microphone
"6"L
X Soprano
Soloist
FIG.
within range of the microphone. The
stunt is to place a small rug at the best
pick-up location. Afte.- ten months' trial
Alfred Thomas, the resident engineer in
charge at KOA, has this to say about his
device:
Not once has our magic device failed to turn
the trick. Most any type of rug fills the bill if
it is soft and of contrasting color with the floor.
It should, however, be of small dimensions, say
three or four feet. It is placed a few feet from
the microphone, the distance depending wholly
upon the voice of the person to be heard.
Unconsciously, the speaker assumes a position
on this rug before the microphone and there
remains until his remarks are concluded. Sub-
consciously he regards this piece of floor-covering
with its imaginary boundaries, as an island of
safety, and he is disinclined to venture elsewhere
about the stage. As a result, broadcast listeners
are enabled to hear the talk in full. Otherwise,
some of the speaker's comments would be lost to
the invisible audience.
Ministers, it is further stated, are the
best behaved subjects before the micro-
phone, while political speakers are the
worst. How about the Rev. Billy Sunday?
I have my doubts about the rug remedy
if that acrobat-evangelist should be per-
suaded to broadcast.
Dr. D. E. Phillips, a psychologist of the
University of Denver, makes the remark
that "KOA'S plan to prevent a speaker from
taking gymnastic exercises on the lecture
platform is indeed novel." With a heavy
heart I must take issue with the eminent
scholar of the U. of D. The stunt is a
good one, but it is neither novel nor orig-
inal. Public address operators in vari-
ous parts of the country have been using
it for years. In fact, if I am not mistaken,
and I'm not, it was mentioned in the paper
on public address systems by Green and
Maxfield in the journal of the A.l.E.E.
for April, 1923.
THE sketch shows the layout of the
new Chicago studio of WJJD, with
transmitter at Mooseheart, Illinois. The
new quarters consist of eight rooms — the
APRIL, 1926
DETAILS OF SOME BROADCASTING STATIONS
675
"Radio Suite" — on the twenty-fourth
floor of the Palmer House, which, when the
second section is completed, is expected
to be the largest hotel in the world. The
director of WJJD is Jack Nelson, one of the
pioneer broadcasters of the Middle West.
The new studio arrangement was not
thrown together haphazardly, but was
carefully planned by Mr. Nelson and the
architects of the building. Under these
conditions, the people in charge had a
relatively free hand in arranging things as
past experience indicated they should be.
No doubt in the future many new buildings
will include broadcasting facilities in the
plans; Mr. Rothaphel's New York theatre,
now in process of construction, is an
example of this evolution.
At WJJD there are two studios, to facili-
tate rehearsals and avoid delays in running
off the programs. No one who has not
tried to get a thirty-piece band out of a
moderate sized room, with the air blank
or desperately "plugged" until they could
be got out and the next number set up,
can appreciate what a help an auxiliary
studio is to the program and operating
staffs of a station. By means of buzzer
and light signals the operator in the room
between the studios keeps control of the
proceedings. The artists in the studio are
directed by means of electric signs reading,
"Get Ready," "Broadcast" (in red), and
others like "Too Loud," "Too Soft,"
"Too Much Piano," etc.
A motion picture booth is provided for
taking pictures of celebrities who broad-
cast. Here the necessary cameras and
lights are stored, ready for use and out of
the way, and cables leading direct from
the main power switchboard of the hotel
furnish the currents necessary.
Microphone stands are considered passe
at WJJD. Instead, the transmitters are
suspended from eight-foot decorative
wrought iron arms adjustable to any height
and position. This eliminates microphone
wires trailing around the floor, with the
possibility of people tripping over them.
Loud speakers placed in the Studio
Parlor, each of the rest rooms, the Direc-
tor's office, and the Control Room, permit
the program to be followed at all of these
points. The reception parlor is furnished
on the style of a well furnished living room,
with chairs and lounges for waiting artists
and guests. The windows between the
studios and the reception room are so
draped that the guests can see into the
studios, but the artists, while on the air,
cannot be disconcerted by a view in the
opposite direction. This arrangement gets
around the difficulty encountered when the
studio is glass enclosed on one side, of
causing the artists to feel as if they were
in an aquarium.
A twenty-pair cable connects the control
room of the WJJD suite to the public address
control room of the hotel, so that public
address service can be provided in any
portion of the hotel on radio programs, and,
conversely, the station can pick up broad-
cast material from any of the ballrooms,
dining rooms, and
other points
reached by the
public address
system. For ex-
ample, any one of
the five orches-
tras which will
play regularly in
the Palmer House
will be available
in this way.
One important
item that is
frequently neg-
lected in broad-
casting studios
has not been
overlooked in this
instance. This
is the matter of
ventilation. It is stated that more than
$10,000 was spent for ventilation in the
new quarters of WJJD.
WFBG
WFBG is a loo-watt outfit at Altoona,
Pennsylvania, owned and operated
by the William F. Gable Company and
the Times-Tribune Company of that city.
Walter S. Greevy is the director; the chief
operator is William K. Aughenbaugh.
WFBG broadcasts regularly from eighteen
remote control studios, over leased wires,
and about once a week they pick up a
special program, using portable equip-
ment. The shortest loop is 3000 feet and
the longest about 4 miles, not counting
central office wiring. A. T. & T. circuits
are used In the main.
The transmitter is a Western Electric
2 A, with 100 watts output, fed by a 24^
speech input amplifier and equipped with
the 36 receiver and KS22J3 power panel.
There is also a set of storage batteries
for plate and filament supply. The set
reaches out 600 miles on evening programs.
In making some pleasant remarks about
this department in its relation to broad-
casters, Mr. Aughenbaugh comments on
the lack of books about land line broad-
STUDIO PARLOR
STUDIO No.l
THE CHICAGO STUDIO OF WJJD
It is located in the New Palmer House and especially designed for the station
cast transmission and broadcasting in
general. There is certainly a paucity of
such works. However, many valuable
papers have appeared in the Journal of tbe
A.I.E.E. and the Proceedings of the I.R.E.
A list of the more conspicuous ones was
given in this department in the April
1925 RADIO BROADCAST. Every broadcast
engineer and operator should read the
articles therein named, if nothing else.
However, a complete file of the journals
mentioned for 1923, 1924, and 1925 would
be a good investment. There are also
valuable papers in the Bell System Technical
Journal, G. E. Review, and other technical
periodicals. We are thinking of summariz-
ing one such article each month, in its
practical aspects, for technical broadcasters
who are so situated that the originals are
inaccessible to them. But we can do that
only if we have reason to believe there is a
decided demand for such material among
our readers. How do you feel about it?
You can have what you like, but you must
let us know what it is.
WLS
IN A town with an ancient and Mediter-
ranean name, Crete, Illinois, there is
situated the new jooo-watt transmitter of
THE ARTISTS FEEL AS IF THEY WERE IN AN AQUARIUM
676
RADIO BROADCAST
APRIL, 1926
jL__ ">
Ml E2Z3— O-WW\^—
M2E 3 O — ,/WW —
lajE 23— — O^WW I I ||
6V B.
window is a miniature theatre
which is to be open to the pub-
lic. It seats about 50 people,
who hear the program through
loud speakers while watching
the broadcasting. The usual
reception room, offices, operat-
ing and battery rooms are of
course included.
Broadcast Transmitters
and Tuning
c
FIG. 2
WLS, with studio in the Hotel Sherman
Annex in Chicago. This well-known sta-
tion is maintained by the Sears-Roebuck
Agricultural Foundation. Curtis D. Peck
is the chief operator.
The power plant is located on a two-
and-a-half acre plot on the Dixie Highway,
just south of Crete. The site is landscaped,
with ample drives and parking space for
visitors. The lawns cover some fifteen
miles of ground wire, plowed in during
the period of construction of the station.
The building contains a large operating
room, an office, a reception room for visi-
tors, generator and battery rooms, switch
closets, and an entrance hall. The con-
struction is up to date in every respect,
including factors affecting radio transmis-
sion. The layout and joining of metal
lath, for example, is such as to minimize
radio frequency losses. An elaborate water
cooling system for the tubes, with provision
against freezing during the winter, has
been provided. The towers, measuring
forty feet at the base, and two hundred
feet high, are visible from the Indiana state
line.
The transmitting set is a product of the
Western Electric Company. The wave-
length is 344.6 meters, corresponding to
870 kilocycles. The Army experimental
call letters are A z 3.
The studio on the sixth floor of the Hotel
Sherman Annex was fixed up by a well-
known interior decorator with the aim of
expressing the radio motif (on the nature
of which there may riot be perfect agree-
ment). According to an announcement,
" Every piece of equipment and furniture,
the walls, ceiling and lighting fixtures
. . . emanate the speed, intensity, and
universality of the mysterious forces of
the air." Black, red, and silver are the
colors, with representations of sound waves
on the walls and ceilings, giving the visitor
the impression that "he has stepped inside
of Einstein's brain." Well, at last some-
one understands Einstein.
There are two studios. One is 55 feet
long and 20 feet wide, for orchestras,
bands, and dramatic productions; a smaller
studio accommodates soloists. Separated
from the larger studio by a plate glass
OMMENTING orally
on the substance of
my remarks on " Broad
Waves and Sharp," in the
March issue, in which I let
loose a few growls at the broad-
cast listeners and operators
who labor under the delusion that a c.w.
telephone station can "sharpen" its wave
in some recondite manner, Mr. John
V. L. Hogan, the well-known consult-
ing engineer and Past President of the
Institute of Radio Engineers, points out
that there is one case in which a broad-
casting station may contribute to broad
tuning at the receiving end. That is when
the carrier frequency fluctuates with modu-
lation. This malady is probably a rare
one among broadcasting stations worth
listening to, but it may occur among some
of the loose and flapping small time agita-
tors of the ether, so let it be included for
the sake of completeness. Mr. Hogan
discussed this complaint in the September
and October, 1924 numbers of Popular
Radio. If the fluctuations are rapid
enough, such a carrier will not only tune
broadly, but it will be noisy. I think even
in this case we should not apply the terms
"sharp" and "broad" to the carrier, but
should refer to its "steady" or "fluctuat-
ing" nature, as the case may be. The
term "broad" should be reserved for the
tuning of receivers, and the radiation of
spark transmitters, with their adjustable
decrement.
For that matter, the broadness of tuning
of every c.w. transmitter varies with
modulation. The carrier, the carrier plus
the modulating frequency, and the carrier
minus me modulating frequency, are the
three frequencies radiated. Hence when
emitting a note of high musical pitch a
station should tune somewhat broader
than when its carrier is modulated down
in the bass. Whatever broadness of tun-
ing is introduced in that way is a conse-
quence of the fundamental function of the
station. Again, there is a practicable
form of radiation, called "single side band
transmission," in which the carrier and
one side frequency are suppressed at the
transmitter. A substitute carrier is in-
troduced at the receiver, and the modula-
tion reproduced by the use of the single
side frequency which is radiated. This
method is very economical in that it re-
quires a much narrower frequency band
per station, and consequently allows more
channels to be crowded between given
frequency limits. It has not yet been
introduced into broadcasting, so this is
as far as we shall let it worry us for the
present.
Radio Lingo, Past and Present
Miscellaneous Influences: The Novice
BEGINNERS in the radio art, and
the public in general, say, "My
radio" where initiates refer to
"my receiver," or "my receiving set"
or, more loosely, "my radio set." The
broadcast listener is interested only in
receivers, so a receiver is a "radio" to
him.
The same slackness is evident in the
"23-plate" nomenclature for condensers.
The beginner is not interested in capaci-
tance, which is a concept and takes some
experience and thought to grasp, but he
can see and count, and so condensers are
sold by the number of plates rather than
by the essential factor of capacity. We
may expect a widening gap between the
engineering and selling terminology of
radio, for the engineering interests will
certainly not give up their ways of cal-
culating and designating, and the public
cannot be expected to take up the engineers'
way of looking at things.
Among other influences that have
formed radio terminology is that of the
sea. We have all heard the announcer
say, " Please stand by for the next feature
on our program." Now, "stand by"
is a general term meaning "to be near,'
"to be present." As a nautical term it
means "get ready," as "Stand by to launch
the boats." This phrase entered radio
apparently by the nautical route, but had
to undergo a change in meaning to "Wait a
minute; I'll be with you shortly." When
two ship stations called a coast station, the
land operator would tell one of them to
"stand by." The early tuners had a
"stand-by circuit" — a broadly tuned cir-
cuit, picking up any signal within a
wide range of wavelengths. Many an
old operator remembers the musical swing
of Cape Race's "std bi" in the dim ro-
mantic spark days. And now the broad-
cast announcers have it. An honorable
and manly phrase of deep salt water, it
has become a prefix to jazz orchestra-
tions.
Past, Present, and Future
SO RADIO has passed from the
backyard-spark coil-coherer stage to
the universal communication level, and
ways of speech have changed with it. In
the early telegraph days the note or tone
of the signals was anything. The object
was just to get a sound through. The
Marconi spark coils, with their gastric
growling, were supplanted by the sixty
cycle spark, because sixty cycles happened
to be handy. Gradually aspirations for a
musical note took form and the question
arose, "How's his note?" when one was
speaking of a station. A decade later the
question is, "How is their quality?"
APRIL, 1926
SIMULTANEOUS USE OF SEVERAL MICROPHONES
677
when people discuss the merits of a broad-
casting station — quality being the effect
of a great complexity of notes and their
faithful reproduction. Behind the change
in phrase there is an evolution from the
relatively simple to the relatively com-
plex.
And the end is not yet. If radio movies
become a reality, will radio fans be asking,
"How's the visibility?" a decade or two
hence?
Technical Operation of Broad-
casting Stations
4. Multiple Pick-Up
FIGURE 2 shows the layout of what
is commonly known as a "mixing
panel" for combining the outputs
of several microphones. The transmitters
M,, Ms, -M3, are of the carbon type,
and they are fed in multiple from a
single battery B, each having its own
resistance R,, R2, or R3, in series, to limit
the d.c. through the microphone to the
proper value. Each microphone feeds its
audio output into a repeating coil, which is
simply a 1:1 transformer, usually with a
torodial winding on an iron core, much
used in wire telephone practice. This
repeating coil is marked RC, with the
appropriate numerical suffix. Also, the
secondary of each repeating coil is paral-
leled by a potentiometer, P,, etc. The
variable terminals of these potentiometers
are connected in series, as shown in Fig.
2. One extreme terminal goes to one
terminal of the low side of the input
transformer IT ahead of the first tube;
the other extreme terminal of the potentio-
meter chain goes to the other side of the
input transformer primary. The secon-
dary winding of the transformer goes to
the tube. In the output of this tube there
may be an over-all gain control, as de-
scribed in the March issue, supplementing
the individual gains afforded by the
potentiometers.
The value of the impedances will now be
given roughly. For a 6-volt battery, R
will be of the order of 200 ohms, which with
the 100 ohms impedance offered by each
button of the microphone limits the d.c.
per button to the appropriate value of 20
milliamperes. Since, for audio frequencies,
the buttons are in series, a normal carbon
microphone has an output impedance of
about 200 ohms. This matches such a
repeating coil as the Western Electric
yy-A. The impedance does not change in
the repeating coil (the windings being
alike) hence the potentiometer across each
secondary may also be of the order of
several hundred ohms total resistance.
The primary of the input transformer has
an impedance at low frequencies of 500
ohms, stepped up to about 50,000 ohms
in the secondary to match the input im-
pedance of the vacuum tube. This trans-
former has, it will be seen, an impedance
ratio of 100:1, corresponding to a turns
ratio of loii.^the impedance varying as the
square of the number of turns.
It is important that the potentiometers
should be smoothly variable, to avoid
abrupt changes in the output of the indivi-
dual microphones, and that a true zero be
obtainable, so that any microphone on the
panel may be cut out completely if desired.
Usually telephone keys are provided, so
that after the gain on a transmitter has
been set at zero, its circuit may be opened
entirely by means of a key or switch.
The diagram shows the operation of this
system with carbon microphones, but a
condenser type may be used equally well
provided that its associated amplifier has
a step-down transformer whose output
matches a carbon microphone approxi-
mately (200-500 ohms.) This output is
then connected to the two outside posts of
one of the sets of three, the middle post,
to which the frame or diaphragm terminal
of a carbon microphone goes, being left
unconnected. The output of the condenser
may then be mixed with a carbon micro-
phone output, if desired. In fact, there
is no reason why the outputs of several
transmitters of differing frequency charac-
teristics may not be mixed in this way, for
the purpose of securing an over-all output
superior to any of the component pick-
ups. Or, in the more usual situation,
several more or less identical microphones
have their outputs mixed, combining pick-
ups which differ owing to the physical
positions of the respective microphones
with reference to the source of sound.
Finally, any microphones may be swung
in or taken out at will, to suit changing
conditions during a concert. All these
operations are noiseless, inasmuch as the
variation is carried out in a circuit carrying
nothing but audio frequency currents.
RADIO GRIPPED THE FAN AS EARLY AS
Works
Details of Actual Operation of a Forty- and
Eighty-Meter Transmitter Using B Batteries
for Plate Supply — How the Record of Twenty-
Six Thousand Miles Per Watt Was Attained
By THE LABORATORY STAFF
STATION 9ECC AT MINNEAPOLIS
Note the chemical rectifier on the floor and
the businesslike transmitter arrangement
W!
*ITH the approach of the
International Tests and re-
ceiving conditions in Garden
City nothing to brag about,
it became necessary to make arrangements
for an expedition to the wilds of some
" blooperless " land. The problem of
communication with Headquarters was a
serious one indeed, for there was no telling
where the expedition might lead. There
seemed but one solution — amateur radio.
What the Test committee needed was a
light, easily portable transmitter and
receiver that could be transported with its
power to points unknown with the assur-
ance that pressing the key in the wilds
would awake activity in Garden City.
For some time the Experimental Station
2 GY operated by RADIO BROADCAST Labor-
atory and the National Carbon Company
had been the scene of much activity on
short waves and low power. A circuit
described in the January magazine by
Niklaus Hageman had proved quite
successful but secured a perfectly steady
note at the expense of greater plate cur-
rents, and for hauling a transmitter to
distant points, a foolproof, and especially
a very economical circuit was essential.
The transmitter shown in Fig. i is the
result. The circuit is the simplest possible,
the Hartley, and is shown at Fig. 2. In
construction or operation there is nothing
easier. A coil made of No. 8 soft copper
wound on a dry cell tube and allowed to
expand until the required diameter of four
inches is reached constitutes the closed
circuit inductance the ends of which are
attached to the grid and plate of the
oscillator tube. For the 40- and 8o-meter
bands, 10 turns are required when a
.ooo25-mfd. condenser is used for tuning.
Another coil of four turns of the same con-
struction couples the antenna to this
circuit.
So much for
the construction
for the present.
Let's imagine for
a few minutes
that you are sit-
ting out in the
radio shack at 2 GY with the operators, about
to try the new transmitter. It is to get its
power from batteries; storage battery to
light the filament of the tube, B batteries for
plate supply, for it is obviously impossible
to carry generators to the country and who
can predict the kind of power available
from the lighting mains of Podunk?
It is 8:00 p. m. on the night of December
nth and Operator Mann (Mn) is at the
key with Bob Blanchard standing by to
throw switches and be generally helpful.
The air is filled with 4O-meter stations and
among them is 9 DDE, John Wilcox, Chicago
whom we call without result. Then at
8:15 we send out a "CQ" which is answered
by 9 ECC, Floyd E. Wilkins, at Minneapolis.
At that time the transmitter tube, a
ux-2io, was drawing 22 milliamperes at
400 volts. For an hour 2 GY conversed
with 9 ECC, reducing the power with the
following results:
22
16
6
3.8
400
300
130
90
WATTS
8.8
4.8
.78
.342
SIGNAL
STRENGTH
R4
R3.5
R3.3
R1-R3
Not bad for a start ! 1000 miles on .342
watts — less power than is taken by the
average receiving set.
On the i jth at 9:32 p. m. E. S. T., the
same stunt is repeated. 2 GY connects
with 8 BZK, Paul Roth, Cleveland, using
40 mils, at 500 volts and power is reduced
as follows:
RADIO BROADCAST Photograph
FIG.
Transmitter receiver and B battery compartment complete. Space is provided for ten standard
receiving B batteries totalling 450 volts. The throw-over switch is unnecessary if an additional
antpnn:i is nroviHpH for receiving. The same batteries can be used on both transmitter and
antenna is provided for receiving. The same batteries can
receiver if proper precautions are taken
APRIL, 1926
A PORTABLE B BATTERY TRANSMITTER
679
Antenna Current
I
Antenna Series Condenser
F lament Volhmeter
Plate Current Meter
Closed Circuit Condenser
RADIO BROADCAST Photograph
FIG. 2
A rear view of the transmitter showing location of component parts. The induc-
tance coils are strapped to two dowel rods and kept away from metallic objects
40
30
15
8
500
400
320
130
WATTS
20
12
4.8
1.4
SIGNAL
STRENGTH
R6
R6
R4
R3
At this point, local interference pre-
vented going lower in power, but the
meters on the transmitter could not read
much lower anyway!
On December i6th at 8:18 p. m., 2 GY
connected with 9 DCG, Frederick G. Braig,
Rockford, 111., and with an input of 1.8
watts (10 mils, at 180 volts) he said signals
were audible all over the room.
At 10:05 P- m- on the night of December
1 7th, communication was established with
9 CCQ, Vere Davis, at Braymer, Missouri
and the first of a long series of tests was
carried out. That night 2 GY was using
a Sea Gull 201 -A tube as follows:
19
13
7
4
1
290
200
120
75
40
5.5
2.6
.84
.3
.04
SIGNAL
STRENGTH
R3
R3
R2
R2
Rl
A message was given to 9 CCQ at .3 watts
which he received perfectly. Arrange-
ments were made by wire to communicate
nightly on low power. He was using
three 201 -A tubes with 250 volts of B
batteries, no meters or any other means of
indicating resonance in the antenna.
Beginning December 21, a nightly sche-
dule was maintained with 9 CCQ except
when weather conditions prevented, until
January 5th when it was necessary to test
the transmitter in the field. During this
time communication was held many times
with other stations with a maximum input
at 2 GY of 20 watts. Schedules with 9 CM,
Edward N. Fridgen, L'Anse, Michigan
and 9 ECC proved conclusively that battery
operated sets could be depended upon for
consistent work.
INSTALLING THE PORTABLE TRANSMITTER
AT PATCHOGUE, Long Island, 40
miles from Garden City, the trans-
mitter was installed in a hotel room with
the antenna against a metal building
and parallel with a metal roof not more than
20 feet from the ground. Strong signals
were received at 2 GY in the daytime and
at night until 1 0:00 p. m. when interference
and the skip distance made further com-
munication impossible on 40 meters. At
80 meters, however, communication was
easily accomplished. During the Inter-
national Tests, the receiver and trans-
mitter, set up in a farmhouse miles from
anywhere, provided the only means of
communication with Test Headquarters.
Now all of this low power work was done
without special arrangements. After com-
munication had been established, the power
could be reduced, and often 2 GY got into
communication directly on low power.
The antenna system was amusing — a
single wire poorly insulated, neither vertical
nor horizontal and only about 35 feet long.
The single wire counterpoise ran in a
direction opposite to the antenna and like-
wise was not insulated. Antenna currents
were never over .3 amperes.
All of which shows that on 40 meters,
Grid Leak
#8 Soft Copper Y/ire ^Antenna Coil
I
Grid Co nd. \ClosedCircuit \ Yf Dowel Rod
Counterpoise
RADIO BROADCAST Photograph
FIG. 3
Another view behind the front panel giving an idea of how simple the whole transmitter is
680
RADIO BROADCAST
APRIL, 1926
there is no reason why any one can-
not be in communication with any
one else without a lot of expensive
apparatus. Witness the fact that
with 9 CCQ, a power input of .04
watts was successful in maintaining
communication over a distance
which represents a record of 26,500
miles per watt. It required less
power to transmit the messages
than it did to receive them.
The photographs of the trans-
mitter should give all the construc-
tional details that are necessary
and the simplicity of the antenna
throwover switch is shown in Fig. 3.
The plate batteries are contained in the
lower compartment as shown in Fig. 4
and the whole outfit can be set up for
operation in less than five minutes. All
that is necessary is to remove the front
board which has on it the key, plug in the
A and B battery cables, throw a wire over
a tree and spread on the ground the
counterpoise — or use the automobile as a
counterpoise — tune the antenna and closed
circuits by means of the proper condensers
until maximum current is obtained on the
wavelength desired. The current on in-
puts up to 20 watts should not be high, at
least not over one half ampere.
DATE
TIME
STATION
DISTANCE
WATT
INPUT
MILES PER
WATT
11/13
9:35 P.M.
4 DO
745
14.4
51.6
11/13
11:55 P.M.
9 DZN
970
6.7
145.0
11/14
12:35 A.M.
9 AJI
750
6.7
112.0
11/23
9:45 P.M.
9 DSL
860
10.8
800
11/23
10:00 P.M.
9TJ
1080
10.8
100.0
11/23
10:10 P.M.
9 DXX
860
108
80.0
11/24
1:10 A.M.
9 ECL
1080
10.8
100.0
12/11
8:15 P.M.
9 ECC
1030
.342
3000.0
12/15
9:32 P M.
8 BZK
600
1.04
580.0
12/16
8:20 P.M.
9DCG
740
1.80
4100
12/17
8:40 P.M.
9 CBZ
700
.21
35000
12/17
10:00 P.M.
9 CCQ
1060
.04
26500.0
12 21
9:00 P.M.
9 CCQ
1060
.11
9650.0
12/29
8:40 P.M.
9 DIB
860
17.0
50.5
12/29
9:40 P.M.
9 BAL
860
17.0
50.5
If the current is higher than .5 amperes,
more wire should be added to the antenna
to increase the radiation resistance. Quite
often it is impossible to raise any one on
.5 amperes, but adding ten feet to the
antenna will decrease the current to .2
with the result that good distance can be
worked.
Sangamo condensers will stand voltages
up to 1000 volts, provided of course that
the currents are not high. Ordinary
receiving condensers will serve as tuning
capacities. Practically any tube will do.
At 2 GY excellent results have been ob-
tained with the standard 2OI-A tube of
various manufacturers. A Ureco 1 12 tube
is practically the equal of the uv-
210 tube which requires more fila-
ment current.
The center tap to the closed cir-
cuit inductance which completes
the Hartley circuit is variable and
should be near the grid end of the
coil for maximum efficiency. Mov-
ing it toward the plate end will in-
crease the power taken by the tube
without much increase in the power
taken by the tube and with little
increase in antenna current. Only
two meters are essential and one of
these can be avoided if a small flash-
light bulb is used to indicate antenna res-
onance. This was explained in the January
article in RADIO BROADCAST by Nicklaus
Hageman. If a 2OI-A or 1 12 tube is used,
the filament voltage should be only high
enough to insure that the maximum
efficiency is being obtained. This can be
obtained by watching plate or antenna
current meters and varying the filament
rheostat. If a 210 tube is used, it may
be run on 6 volts without a rheostat — and
naturally no filament voltmeter is neces-
sary.
Regardless of the fact that no especial
insulation has been used at 2 GY, the
antenna-counterpoise system should be as
FIG. 4
A photograph of 9 CCQ at Braymer, Missouri. The three 201 -A tubes with their elements in parallel, the calibrated short wave receiver,
and the compendium of amateur information— QS T — are worthy of notice. We suspect the big box at the left is a broadcast receiver
APRIL, 1926
A PORTABLE B BATTERY TRANSMITTER
681
BACK VIEW
SIDE VIEW
— Flexible Connection-..^
END VIEW OF CAM
Rubber
Handle
TABLE OF AUDIBILITY SIGNS
Rl — Faint signals, just audible
R2 — Weak signals, barely readable
R3 — Weak signals, but readable
R4 — Fair signals, easily readable
R5 — Moderately strong signals
R6 — Strong signals
R7 — Good strong signals. Would be
readable through heavy QRN
and QRM
R8 — Very strong signals. "Several
feet-from-phones signals"
R9 — Extremely strong signals
Right Angle
Bracket
Switch^
Jaw
R.H.Screw.-'
.F.H.Screw
-t-Panel
4
^-~ R.H. Wood Screws --'
FIG. 6
Details of the throw-over switch which changes the
antenna and batteries from sending to receiving
NEW INSULATORS
Now being installed
at 2 GY
DETAIL OF SWITCH JAW
well insulated as possible,
and an accompanying photo-
graph shows some Pyrex in-
sulators made by the Corning Glass Works
which are now being installed at 2 GY.
Coupling to the antenna should be loose
enough so that the tube continues to
oscillate under all conditions. If coupling
is too close, the wavelength will jump about
and no listening operator can read what
you are trying to send.
On 40 meters, reception is erratic, fading
is bad, but phenomenal distances can be
attained with low powers. On 80 meters
transmitting distances are not so great,
but steady signals, good traffic handling,
and the possibility of phone transmission
make it a very interesting band in which to
work.
A few words about g CCQ may not be
amiss to show that the work done between
that station and 2 GY is not due to unusual
conditions but rather to the great carrying
power of transmissions on 40 meters
with pure d. c. plate supply. Station 9 CCQ
is operated by Mr. Vere Davis at Braymer,
Missouri, about 1080 miles from Garden
City. Braymer is 60 miles East of Kansas
City and 20 miles southwest of Chillicothe
in rolling country which is still blessed with
considerable timber.
Mr. Davis says he "became interested in
broadcast radio about three years ago and
it's just a case of drifting from bad to worse,
I guess. Have had an amateur's license
now about four or five months and have
been active about two and one-half. I
became interested in amateur radio just
about the same way most anybody of my
age and interests does. I've always read
radio magazines when I got the chance
RADIO BROADCAST Photograph
and of course couldn't help seeing short
wave circuits and the marvelous things
they were supposed to do. I made my
first successful short wave receiver last
spring, a little less than a year ago, with
the intention first of listening to the short
wave broadcasts and was very disappointed
when KDKA came in strong but with bad fad-
ing and distortion. So another fan, now
9 CJD, and I began practicingthe code, and
to our surprise passed the amateurs' exam-
ination. My first communication was with
9 WQ at Elmhurst, Illinois (40 meters),
at about 4 o'clock p. m. November ist.
Next was 9 BV at Council Bluffs, Iowa,
and the third was 8 CJM, Elyria, Ohio,
but I found trouble raising stations. I
could get a large current in the antenna
but it wasn't effective. In a month
or so I got time to improve the system
and although I don't get the current I
did, reports are better now. Have been
reported at 5 AQI, Meridian, Mississippi,
R 6 at about noon. Plate voltage 220,
mils., 33."
Since the International Tests, this
simple transmitter has been in opera-
tion at 2 GY with complete success, re-
ports indicating that the pure d.c. note
penetrates much better than our "high
powered" outfit, for distances up to 1000
miles. The operators at 2 GY welcome
reports of reception and will be glad to
advise any of RADIO BROADCAST'S readers
who are interested in low power, short
wavelength amateur work.
.-2 .002 mfd
** in series
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.002 mfd.
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f A Bat. switch
l/yvw
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, 4
Grid Leak . >-^
0
FIG. 5
O The complete Hartley circuit
+
— used in the transmitter
ANT. GNO
I
The Use of the
What the Filament Rheostat
Different Type of Tube — Use
GL
Filament Resistance
Can be, How to Decide the Proper Size for Each
and Desirability of the Fixed Filament Resistance
JOHN B. BRENNAN
THE vacuum tube, that indispensable
unit of the radio receiver, which trans-
forms unintelligible radio signals into
sounds that we can hear has been dealt
with at length admirably by Keith Henney in
the Decembsr, 1925, and February, 1926, issues
of RADIO BROADCAST. In these articles, Mr.
Henney dwelt upon the selection, use, and func-
tion of the vacuum tube in radio circuits and
described in detail the parts played by the three
elements of the tube, the plate, grid, and fila-
ment.
It is the last named, which is taken as the
subject for this article. We shall try to show
how this filament performs its task efficiently
by the use of suitable control devices which
adjust or regulate the current and voltage ap-
plied to it.
The filament is the thing that lights up when
the A battery is applied to its terminals and
emits electrons at a given rate. The grid
is the regulator or shutter which stops or lets
flow the electronic stream to the plate, the third
element. In this way, feeble radio impulses
impressed on the grid releass a stronger impulse
in the plate and its attendant circuits.
Manufacturers of the early tubes found it
necessary to employ a control in the filament
circuit of the tube so that the tube might be
adjusted to its most efficient point of operation.
Naturally they could not use a six-volt filament
energized by a six-volt battery because the
regulation so necessary would not be obtained.
The five-volt filament, energized by the six
volt storage battery, allowed for an adjustment
FIG. I
Ammeterto \ simple circuit compris-
read current • r i^
ing a source of voltage
(battery) a resistance (R)
and a means for reading
the current flowing
This arrangement is com-
parable to a tube circuit where the resistance R
is represented by the tube filament and the ex-
ternal control device
Or if all r values are the same
R=r' x N
Where N= Number of resistance units
Battery
through the circuit.
R -«-
FIG. 3
Resistances in series retard to a greater extent
the flow of current in a circuit than where only
one resistance unit is used. The total resistance
of a series-resistance circuit is equal to the sum
of all the resistances employed. In a circuit of
this kind it is possible to employ two 3-volt
tubes energized from a 6-volt source
presumably from zero to six volts by means of a
variable resistance. Soft tubes, as they were
known not so long ago, required critical filament
adjustment and to obtain this end, a rheostat
had to be used. Sometimes the best operating
voltage was found to be five but most times not.
Each tube had its own peculiarities.
Now, the manufacturers have advanced the
design and manufacture of the tubes to such a
point that the filament adjustment is not
critical.
Keith Henney has pointed out in RADIO
BROADCAST that with the present tubes, a
decrease in filament voltage below five is usually
accompanied by a falling off in signal tone
quality. Also, a slight increase above the
rated filament voltage always causes a surprising
decrease in filament life. To prevent this it is
obvious that the old six-volt storage battery,
borrowed from the automobile days, must still
be retained so that a regulation of one volt in
the rheostat may be had to maintain the filament
at five volts.
When the battery is newly charged, more
resistance of the rheostat will be in the circuit
to maintain it at five volts. However, when the
battery voltage drops off then this resistance is
cut out of the circuit to compensate for the drop
in voltage at the battery terminals. Theoretic-
ally this is true but in actual practise, the battery
maintains its full charge over the major portion
of a single charge life. Toward the end it
does drop in voltage but its energy has been
expended to the point where the rheostat is
useful, in maintaining the tube voltage at 5
only for a few hours. Then the battery may
be considered in need of recharging.
Some tubes require l.i volts, others 3 volts
and still others 5 volts. Therefore, it is essential
that we adjust each of these filaments economic-
ally and efficiently. To make this clearer, it would
not be strict economy or efficiency to control
a i.i-volt tube filament with a 6o-ohm rheostat
where only i .6 ohms are required, only unless the
battery voltage was much higher than i j. Even
this is an unusual case.
SELECTING THE PROPER RESISTANCE
pOR the radio set constructor then, there
arises a problem in selecting the proper
size of rheostat for the tube or tubes he is going
to use. To understand what is happening
in a circuit where voltage, resistance, and
current are present, it is necessary to review the
law governing the use and application of re-
sistances in a circuit. Ohm's Law says that
where a pressure of one volt is exerted in a
circuit whose resistance is one ohm, then one
ampere of current will flow. Now if the re-
sistance is reduced to one half, the voltage
FIG. 2
When several resis-
tances, such as tube fila-
ments are connected in
parallel as is the case in
the majority of receivers,
the total resistance of the
circuit offered to the flow
of current is less than
were only one resistance
unit used in the circuit
because several paths
are provided for the flow of current
R = J-
APRIL, 1926
THE USE OF THE FILAMENT RESISTANCE
683
r i- r z r
Or,where the resistance of r1 is the same
as, r2orr3 then
Where N = Numberof resistance units
FIG. 4
A series-parallel circuit. The total resistance of
the circuit is determined by first calculating the
parallel circuit resistance of r1, r2, and r3 and
adding that total to r4
remaining constant, then double the current
will flow. This gives rise to the equation
I =^ where I is the current in amperes, E is the
pressure in volts and R the resistance in ohms.
From this equation it is possible by transposing,
to find any one value where the other two are
known. That is to say E = IxR and R = -•
A circuit comprising these three factors is
shown in Fig. i.
If a resistance is paralleled by another of the
same value, then two paths are provided for the
flow of current so the total resistance to this
flow is cut in half. If the resistances are added
to each other, that is, connected in series, then
the current flow is retarded because the total
circuit resistance has been increased. To
•determine the total resistance of a circuit where
resistances are in parallel the formula R =
J _i_ -L -L- — ls employed, as shown in Fig. 2.
R~.~r Rz T R3
Where the resistances are in series, the total
resistance is equal to the sum of all the resistances
or where the resistance per unit is the same, then
the total is equal to the value of one unit multi-
plied by the number of units employed. Ex-
pressed algebraically R = rt + r2 + r3,
etc. or R = rzXN where R = total resistance
r = resistance per unit and N = number of
units. This is illustrated in Fig. 3.
It is possible to combine resistances in a
circuit so that a series-parallel arrangement
is produced. This is the case where it is desired
to know the total resistance of a circuit com-
prising several tubes in parallel with a single
rheostat in series with the tubes and battery.
To calculate this total resistance, it is first
necessary to find the resistance of all the tubes
in parallel. Then when this value is known it
is added to the value of the resistance of the
rheostat. This is illustrated in Fig. 4.
In the matter of determining the resistance
of the tube filament Ohm's Law is employed
first and then where it is desired to know the
total resistance of a circuit, where such an ar-
rangement exists as in Fig. 4 then the formula
for resistances in series is employed.
Take, for example, a five-volt tube. Its
filament should be energized by the battery
so that .25 ampere of current flows in the
circuit when the voltage at the tube terminals
is 5. With these two known factors it is possible
to determine the resistance of the circuit. Since
the resistance of the battery and wire for the cir-
cuit is negligible, therefore the resistance com-
puted will be purely tube resistance. Applying
the tube, E = rated voltage of tube, I = rated
filament current in amperes. Then R = — = 20
ohms.
WHY RESISTANCES ARE NEEDED
"MOW if six volts is applied to a filament,
" the current will be correspondingly greater
than with five volts. In order to keep the current
at that point stipulated by the tube manufac-
turer, it is necessary to decrease this voltage by
adding resistance to the circuit.
Until a short while ago the one means for
regulating the current flow and voltage in a
filament circuit was by means of the rheostat
but lately there has been placed on the market
the filament ballast, otherwise termed filament
regulator. That is, they automatically decrease
the battery voltage to the correct point for
application to the filament terminals.
It is a known fact that the battery voltage
remains quite constant over the major portion
of its discharge life but at the end takes a decided
and sudden drop. A curve illustrating this is
shown in Fig. 5. It is because of this voltage
life-retaining property of the battery that
filament ballasts have proved satisfactory for
use as filament controls. For those who desire
simplicity of control, the filament ballast will
commend itself.
Writers of radio articles have differed widely
for years concerning the correct value of rheostat
to be used in a filament circuit. The best
possible advice, and the easiest to follow is that
our old friend Ohm's Law be used. Where two
factors or values of this equation are known, the
third can be determined by the application of
the formula.
Let's look over a typical filament circuit
consisting of tube, rheostat and battery, such
as that in Fig. 6 B. The filament Rof the tube
is considered as a resistance and, therefore, its
value may be rated in ohms. The battery E
is the source of the energy which lights the fil-
ament and has a certain voltage, usually six. The
rheostat r, has a variable external resistance
whose total resistance we do not know, but wish
to ascertain. If there were no rheostat r, in the
circuit and the voltage of the battery were 5,
then the total resistance of the circuit would
be 20 ohms. If the battery voltage were
raised to 6 then .3 amperes of current would flow
in the circuit instead of the rated .25 amperes.
Now by introducing a resistance in the form
of the rheostat r, not only is the current reduced
but the voltage at the filament terminals is
accordingly diminished. By applying the
formula R = j then R = — = 24 ohms which
is the total resistance of the circuit. How much
B
Where r = Rheostat resistance
E = Battery voltage
EI= Filament terminal voltage
I = Filament amperes
Example :
' =(!)-(!) -*
FIG. 6
Determining the resistance value of the unit 'r'
in the circuit above involves the use of the
formula as shown. The battery voltage, the
tube resistance and the current are usually known ;
from these values it is possible to calculate the
unknown
resistance is necessary in the rheostat? The
answer may be found by subtracting the circuit
resistance at 5 volts from the circuit resistance at
6 volts i. e. 24—20 = 4 ohms as shown in Fig.6A.
From this we see that with 4 ohms in the circuit
where a fully charged 6-voIt storage battery
is employed, .25 amperes of current will flow.
Theoretically, as the charge in the battery de-
creases, the voltage decreases; therefore, to keep
the circuit characteristics at their rated level, it
is necessary to cut out part of the external
resistance to compensate for the corresponding
drop in battery voltage.
Now the main rub comes in the advocacy of
rheostats larger than 4 ohms where only one
tube is to be controlled by it. Of course, if one
rheostat controls more than one tube, the proper
resistance value may be calculated since usually
the tube filaments are in parallel and as such the
total resistance of these filaments is figured from
the formula R = ~^+~j^+~^31 etc.
To use a rheostat of 4 ohms means that when
the movable arm touches the first turn of the wire
BATTERY LIFE & VOLTAGE DROP
10
15
20
25 30 35 40 45 50 55
DISCHARGE LIFE IN AMPERE-HOURS
60
65 70
75
Ohm's Law R = - where R
resistance of
FIG. 5
When a fully charged battery is first used, its voltage is slightly above six volts. The major portion
of its life, however, is at a fairly constant voltage level, the gradual drop being from 6 to 5.7 volts.
When this low point has been reached, the battery is considered discharged and is in need of recharge.
As the 5.7 point is reached the rheostat in a filament circuit is of greatest use because as the rheostat
arm is advanced the voltage at the tube terminals is maintained at its highest point
684
RADIO BROADCAST
APRIL, 1926
Table I
Various Types of Tubes and Their Respective
Rheostats
uv-200
UX-112
NUMBER
OF
TUBES
IN PARALLEL
MAXIMUM
RESISTANCE
OF RHEOSTAT
IN OHMS
NUMBER
OF
TUBES
IN PARALLEL
MAXIMUM
RESISTANCE
OF RHEOSTAT
IN OHMS
1
1.0
1
2
.5
1.0
uv-201
TYPE 199
1
2
3
4
1.0
.5
.33
.25
1
2
3
4
25.0
12.5
8.33
6.25
TYPE 201 A
TYPE 120
3
4
4.0
2.0
1.33
1.0
1
2
12.0
6.0
WD-12
NUMEER
MAXIMUM
OF
RESISTANCE
TUBES
OF RHEOSTAT
IN PARALLEL
IN OHMS
1
1.6
2
.8
3
.53
4
.4
i
on the rheostat, the required amount of resistance
is immediately introduced in the circuit. Then
as the battery voltage drops, off toward the
end of its ampere hour capacity this arm can be
advanced over the entire periphery of the
rheostat surface to keep the filament voltage
constant. Where a 2o-ohm rheostat is em-
ployed, four-fifths of the rheostat is unused as
only the last 4 ohms is required in the circuit.
Then as the battery voltage drops, the regulation
is over only one fifth the surface as compared
to the entire surface of the 4-ohm rheostat.
Various diameters and textures of resistance
wires have different current carrying properties.
In the case just cited, assuming that the 4-ohm,
and 2o-ohm rheostats are of the same physical
dimensions, then the space in which the resist-
ance unit is placed is the same for each. Now
if on one, there is to be wound resistance wire
totaling 20 ohms, while on the other there is to
be only 4 ohms, then the both must be wound
with such a diameter of wire as will fill up the
whole space. The ao-ohm rheostat will be
wound with thinner wire so that
the full 20 ohms are accommodated
on the same size form. The thinner
wire is used because per inch it has
more resistance than that used on
the 4-ohm rheostat. Less current
can be carried by small wires than
by larger wires. So, by forcing too
great a current through a small
wire, heat is produced, and in its
dissipation sometimes warps or
otherwise injures the forms of the
rheostat wound with small wire.
This is especially true in the case
of 2o-ohm rheostats where it is in-
tended to use only 4 ohms. This
means that one-fifth of the entire
wire is used where if a 4-, or 6-
ohm rheostat were used in the first
place, it would be safer because the
wire would be larger, insuring am-
ple current carrying capacity and
also any desired variation in cur-
rent would be finer since the change
in resistance produced by a move-
ment of the contact arm would be
less per unit of change than if the
same movement were made on the
2o-ohm rheostat.
THE FILAMENT BALLAST
THE only point that may be
raised in objection to the use of
filament ballasts is that they do
not permit of detector filament regulation for
regeneration control as the rheostat does. How-
ever, now as ticklers, feedback condensers and
variable plate circuit resistors are generally used
for oscillation control, that objection is not
serious.
Examine the curve in Fig. 5, showing the
voltage of a battery over a period of discharge
hours. The battery practically maintains its
voltage until very near the end of its charged
life, then rapidly falls. The use of the rheostat
or filament ballast is helpful only up to the point
where the sudden drop occurs. When past this
point the battery must be recharged and rheo-
Input
FIG. 9
By tapping on
to part of the
_ . rheostat, it is
EG = Grid bias possible to ob-
tain a voltage
drop through
the resistance
which can be
A effectively used
for biasing the grid of a tube with the same result
as a C battery. However, this practice is not to
be recommended as the difficulties of soldering
and unsoldering the lead necessary to obtain the
correct grid bias for a tube is great compared to
the ease and simplicity of providing a C battery
for this purpose
stats and filament ballast will not assist for long
in maintaining the tube voltage at 5.
Look at the curve for a filament ballast in
Fig. 7. From 6 volts, the charged state of the
battery, to 5.7 volts when the battery is con-
sidered discharged, there is only a change of .006
amperes from the rated .25 amperes of filament
current, surely not enough to be seriously
considered as affecting the proper and efficient
operation of the tube in a radio circuit.
In the case of dry cell tubes, there is not this
constancy of voltage in dry cell batteries as com-
pared with the storage battery unless many bat-
teries are connected in parallel so, therefore, it is
essential that a variable resistor be used to main-
tain the tube filament voltage at a constant level
even though the battery does drop in voltage
from 4.5 to 3 volts as is the case where 199 type
tubes are employed. When the battery voltage
falls below 3 then tone quality will probably
suffer and it is wise to replace with new batteries.
FILAMENT BALLAST CURRENT REGULATION CURVE
Discharged :
. Drop in volts from charged to discharged state
causes ,006 amperes change in current
FIG. 8
Four types of filament ballasts
that were tested are shown here.
From left to right they are the
Elkay manufactured by the Lang-
bien Kaufman Radio Co., the
Brach-stat (L. S.Brach Mfg. Co.,)
the Amperite (Radiall Co.,) and
the Daven ballast, (Daven Radio
Corporation.) Several instruments
used in the collection and calcula-
tion of figures presented in this
article are also shown
-
RADIO BROADCAST Photograph
5.8
BATTERY VOLTS
FIG. 7
Filament ballasts are used to regulate the flow of current in a tube
circuit. Their purpose is to maintain this current value at a con-
stant point as the battery becomes discharged. From the above it
will be seen how successfully this purpose is accomplished. As the
battery fell off in voltage, the filament ballast caused a change in the
current in the tube circuit from .25 amperes to .244 amperes — .006
amperes, not enough to be seriously considered as affecting the
proper operation of the tube at its rated filament characteristic
Table II
Tube Operating Characteristics
TYPE OF
TUBE
FILAMENT
CURRENT
IN AMPERES
FILAMENT
VOLTS
BATTERY
VOLTS
FILAMENT
RESISTANCE
201A
199
120
1 112
12
I UV-200
| UV-201
.25
.06
.125
.5
.25
1.0
1.0
5
3
3
5
1.1
5
5
6.
4.5
4.5
6.
1.5
6
6
20
50
24
10
4.4
5
5
1
APRIL, 1926
THE USE OF THE FILAMENT RESISTANCE
685
FIG.
The C battery is
shown in its proper
place here. This _
is by far the better
way to obtain grid bias for receiving tubes since
if it is desired to vary the grid bias voltage,
more or less C battery may be placed in the
circuit
Rheostats are variable resistances with
which an accurate control of the filament
voltage and current is obtained. The selection
of a rheostat for one tube has already been
explained and the radio experimenter should
not become confused where more than one tube
is controlled by a single rheostat. As it has
been said, in a radio circuit it is usual to connect
several tubes in parallel, the path for the flow
of current will become greater hence there will be
less resistance to the flow of this current. In
tube circuits it is customary to employ tubes all
of one nature, that is, all 5- or all 3-voIt tubes.
The total resistance then, of a circuit, is equal
to the resistance of one tube divided by the
number of tubes in the parallel arrangement.
See Fig. 4. For instance, 2oi-A's have a
resistance of 20 ohms. Where four are con-
nected in parallel the total circuit resistance
is 5 ohms. Therefore, to cut down the battery
voltage so that five volts are applied to the
filament terminals, i ohm of external resistance
must be added to the circuit. Before, the
method by which the rheostat value was ascer-
tained was to subtract the circuit resistance at
5 volts from the circuit resistance at 6 volts.
Another method, also very good, is to employ
the formula R = — — ' where R = resistance
of rheostat, Ej= filament voltage, E = battery
voltage and 1 = total current of circuit. This
last factor, total current, is obtained by multi-
plying the current rate of one tube by the
number of tubes to be controlled by the rheostat.
Again, using four tubes, the total current would
be 4 x .25 amperes = i ampere. Then, applying
the formula R = — — = i ohm.
WHERE SHOULD THE RESIS-
TANCE GO?
INDEPENDENT tube
' manufacturers as well as
the pioneers in tube produc-
tion advocate the use of the
rheostat in the negative side
of the A battery lead. The
writer became convinced
that this procedure was
proper only where the rheo-
stat was to be employed to
provide a grid bias of a few
volts. This usually was
supplied by tapping on to a
portion of the rheostat so
that a voltage drop through
that portion of the resis-
tance employed would pro-
vide the necessary few volts
for grid biasing.
In Fig. 9 the circuit shows
how this tap is arranged.
This manner of obtaining
grid bias is unusual inasmuch as it entails first, a
calculation as to the necessary amount of resis-
tance wire to be included in the tap-off circuit so
as to supply the necessary grid voltage. Secondly,
it is sometimes desirable to vary the grid bias and
when the connection is soldered to the rheostat a
change in voltage is impossible unless the tap-off
be unsoldered.
The use of a C battery provides the more
convenient and simpler way to obtain grid bias
and with this change it is possible to place the
rheostat in the positive side of the A supply lead
so that all the negative leads are at ground
potential as in Fig. 9. The use of the rheostat
in the positive side instead of the negative side
of the A battery supply makes for more accurate
wiring, clearer understanding of circuit diagrams,
and the surety that one part of the complete
wiring circuit will be at ground potential insuring
shorter leads from other units in the circuit which
of necessity must be connected to the ground line.
Among the rheostats tested because of the
difference in design and principle was the
Bradleystat, and the Filkostat. Both these
devices insure a continuous, even increase
in voltage differing from the wire-wound
rheostat which provided the increase in steps
as more turns of wire was cut out of the circuit.
Voltage regulation is secured by the change in
resistance of the device as carbon discs are
compressed by means of a thumb screw.
Table III
Filament Ballasts for Various Tubes
TUBE
ELKAY
RADIALL
DAVEN
BRACH
EQUAL1ZOR
AMPERITE
BALLAST
BRACHSTAT
1 type 199
No. 50 for 6
No. 6V 199
1 C for 4 volt
volt source
for 6 volt
source
source No. 4
1 D for 6 volt
V 199 for 4
source
or 4.5 volt
source
2 type 199's
No. 25
No. 120
2 C
1 type 120
No. 25
No. 120
2 C
1 type 201-A
No. 4
No. 1-A
No. 1
1 B
2 type 201 -A's
No. 2
No. 112
No. 2
2 B
1 type 112
No. 2
No. 112
Use No. 3 for
2 B
3 type-201
A's and No
4 for 4 type
201A's
MU20
No. O
MU6
No. O
WD 11
WD 12
WX 12
C 11
D 11
1 A
C 12
CX 12
^^^ ana,,,,,,, IMIIIIItll(l u UUUIIUII1III1 1JIIUII , w((tl uu , imm
If you intend to build a super-heterodyne and
control eight tubes with one rheostat then that
rheostat should be of the power variety capable
of carrying from 2 to 3 amperes of current.
This is especially necessary where the new power
tubes are to be employed in the audio end since
they take more current than the ordinary 201 -A
type of tube. Fortunately, filament ballast
makers have kept up with the development of
the power tubes and today it is possible to
purchase special ballasts designed solely for use
with these new tubes.
The total watts consumed in a filament is
1.5, of this, .25 watts is dissipated in the rheostat
or other filament resistance. This means that
there is a 16 f per cent, loss of power in the
filament resistor and only 83 % per cent, of the
power being utilized in the filament directly.
Outstanding are these several not-to-be
ignored facts:
A 4-ohm rheostat is satisfactory for controlling
a single 2oiA.
A variable resistance may be used for detector
filament regulation but for other tubes fixed
resistances are satisfactory.
Filament ballasts may be used successfully
in all tube filament circuits except detectors.
Dry cell tubes need variable filament control.
Where grid biasing is desired, use a C battery.
Tone quality suffers when the filament or
plate voltage is reduced.
PACENT
Ammeter-
Battery
FIG. I I
Voltmeters and ammeters indicate the amount
RRAnir
BKADLErSTAT
FIG. 12
FIIKOSTAT NULEY
RADIO BROADCAST Photograph
of voltage and current in a circuit. This is the Only a few of the many rheostats that were tested are shown here. The Kellog type of resistance
circuit of the test set actually employed in check- unit has its circular form, with the resistance wire thereon as the rotating unit. The same is true of
ing the regulation properties of rheostats and the Cutler-Hammer rheostat. Two carbon-pile type of resistance units are represented in the Filko-
filament ballasts described in this article stat and Bradleystat
Cmttine Out the Locals
Simple and Efficient Wave Traps to Eliminate Interfering Near-by Stations
By HOWARD E. RHODES
CT"HE trend in broadcasting for some time has
•*• been toward the use of higher powers, where-
ever that is possible, and this, combined with the
concentration of many stations in large centers, has
made the problem of selectivity a serious one for
many listeners. It is easy to remedy most of the
trouble encountered in the average receiver by
simply adding a wave trap of good design, and the
accompanying article reviews the subject in a very
helpful fashion. The present article is concerned
with types which can be made very easily, and a
second article, to be printed soon, will describe a
radio-frequency amplifier and detail how it func-
tions as a wave trap. — THE EDITOR.
WITH the increase in power of a
great many of our broadcasting
stations, listeners find need of some
efficient method whereby un-
desired signals may be eliminated. These
signals sometimes are caused by direct pick-up
by the coils of the set so that its natural selec-
tivity is of no avail in eliminating them. This
occurs when the set is being operated in prox-
imity to a broadcasting station with the result
that the field strength in the vicinity is great
enough to induce currents directly in the various
coils of the receiver. Under these conditions
it will be found possible to hear the program
with the antenna disconnected.
The only practical methods to be used in
eliminating this type of interference are either
shielding of the receiver or using some form of
close field coil, such as a toroid. If the set is to
be shielded, it is necessary to line the entire
FIG. 2
One method
of connecting
a wave trap
in circuit
C2
cc
o
inside of the cabinet, including the cover and
the panel, with thin copper. Any joints in the
copper sheet are soldered together and connec-
tion is finally made between the shield and the
minus A terminal which should, in this case, be
connected to ground. This puts the entire shield
at ground potential, thereby excluding from the
coils any external electrical fields. It should
also be pointed out that this shielding will also
eliminate any interference caused by power
lines, motors, etc., provided they are causing
trouble by setting up currents directly in the
coils. However, if this interference is reaching
FREQUENCY
FIG. I
The impedance curve of a well-made wave trap
the set by way of the antenna system, shielding
will be of no aid.
A second and rather recently developed
method of eliminating this type of interference
is by the use of toroid coils. This type of coil
is now being widely employed in instances where
there is need of an inductor that is unaffected by
external fields. The reason why toroids are not
sensible to magnetic fields is easy to understand.
Suppose such a coil is placed in a magnetic field.
Then a voltage is induced in practically every
turn of the coil. However, the voltage induced
in one half of the coil is exactly equal and op-
posite to the voltage produced in the other half
of the coil. These two voltages react against
each other and the resultant effective voltage is
therefore zero. This type of winding can be
placed in comparatively strong magnetic fields
without having any appreciable voltage pro-
duced in it. Toroids are, therefore, very useful
in eliminating that type of interference caused by
some form of direct pick-up by the coil units of
a receiver. These two methods which have just
been outlined, first, shielding of the set, and
secondly, using Toroid coils, are practically
the only methods of eliminating this type of
interference.
There is a second type of interfering signal
that also causes considerable trouble, and against
this type the two methods so far described are
useless. If the signals being induced in the
antenna are sufficiently strong, it is possible
that a receiver may not have a selectivity sharp
enough to eliminate them completely, although
its selectivity under ordinary conditions may be
perfectly satisfactory. Take, for example, the
curve of Fig. 10 which represents the resonance
curves of a fairly good receiver. For ordinary
reception this degree of selectivity is satisfactory,
but under some unusual condition, even greater
selectivity might be required. For instance,
the receiver might be operated at a location
quite close to a powerful broadcasting station
so that the signal strength from this station, in
comparison with the strength of the signals that
it is desired to receive, is so great as to produce
considerable interference, even though the
receiver is considerably detuned from the
interfering signal. It is apparent then that in
some way this powerful signal must be impeded
so as to decrease its strength.
THE SIMPLICITY OF A WAVE TRAP
THE most common piece of apparatus for use
in this connection is the so-called wave
trap which is actually a filter circuit tuned to
absorb the interfering signals. These wave
traps are very easily constructed, and cost little.
They consist merely of an ordinary coil and a
condenser. The traps are connected in the
antenna circuit and are adjusted so that at the
frequency of the interfering signal they have a
very high impedance, the exact value depend-
ing on whether the unit is connected in series or
parallel with the antenna. This high impedance
prevents the signal from passing down through
the primary of the antenna coupling and so into
FIG. 3
Another meth-
od of connect-
ing the trap to
your receiver,
by the induc-
tive method.
This very often
produces satis-
factory results
without materi-
ally changing
the tuning of
the antenna
circuit
APRIL, 1926
CUTTING OUT THE LOCALS
687
the receiver. At the same time, these wave
traps offer a very low impedance to all
other frequencies. In Fig. i there has
been plotted the change in impedance of a
wave trap as the frequency is varied, and
this gives a good idea how a wave trap
functions. At the frequency marked / on
the diagram, the impedance as read on the
ordinate of the curve is very high and
since this circuit would be connected in the
antenna system of a receiver, it is evident
that at this frequency the impedance of
the antenna system to this particular
frequency would be very high, and for
that reason practically no energy could be re-
ceived at this frequency. At the same time
the impedance of the trap to any other fre-
SETTING OF CONDENSER Cz
FIG. 5
A curve showing the decrease in interfer-
ence obtained by the use of a wave trap
quencies, either above or below the frequency
/, is very low. The efficiency with which the
trap operates depends upon the steepness of the
sides of the curve, and in order to obtain satis-
factory operation, it is essential that a sharp
resonance curve be obtained.
This idea of high impedance at resonance may
1.
Tc,
FIG. 6
The small arrows indicate the circulating cur-
rent set up in the wave trap by the interfering
signal
require some explanation since we are accus-
tomed to think of resonant circuits as having a
low impedance. At resonance, a circuit con-
sisting of a coil and a condenser has a low im-
pedance to the flow of current around the path
FIG. 4
The circuit diagram of the test apparatus used
to obtain some of the data given in this article
indicated in Fig. 6, by the small arrows. This
is important current with regard to the various
tuned circuits of a receiver. In a wave trap,
however, we wish to impede the flow of current
in the circuit AGCa, and at resonance, the trap
circuit offers high impedance to the flow of
current in this circuit.
There are several methods of connecting
these traps. Fig. 2 shows the most common
method. In this drawing L, C, constitutes
the trap circuit, and Lj, C, the antenna coupler
and tuning condenser of the receiving set.
It is seen that the trap is connected between
the antenna post of the receiver and the
antenna lead-in. Fig. 3 represents a
slightly different method of connecting
the trap in the circuit. In this latter
method, the wave trap is inductively
coupled to the antenna. This inductive
coupling is obtained by winding a few
turns of wire about one end of the coil L,.
One end of this new winding connects to
the antenna and the other to the antenna
post of the receiver. This circuit is prac- _
tically equivalent to that of Fig. 2 with the differ-
ence that somewhat sharper tuning is obtained.
WHY THE CIRCUIT PREVENTS INTERFERENCE
IN ORDER to give an idea of the effective-
ness of these traps, a series of experiments
were carried out in the RADIO BROADCAST Labo-
ratory to illustrate how interfering signals are
eliminated by the use of such a filter. The circuit
illustrated in Fig. 4 was excited by means of an
oscillator. The output of the oscillator was
fed into the coil L^ which was inductively
coupled to coil L4. This coupling was very
loose so that variation in the test circuit caused
no change in the oscillator output. L, d is
the trap circuit and L^ C2 represents the
input circuit of the receiver. As shown in
the diagram, a vacuum tube voltmeter was
placed across the L, C2 circuit so as to measure
the voltage induced across this circuit. This
would be the voltage that would ordinarily be
applied to the grid of the first tube of a receiving
set and the extent to which
this voltage is reduced by the
wave trap is a measure of the
trap's efficiency.
With the trap circuit Lt C,
detuned from the incoming
frequency produced by the
oscillator, the condenser G* was
adjusted until maximum volt-
age was read on the vacuum
tube voltmeter. This indicated
that this circuit was adjusted
to resonance. The frequency
of the oscillator was then
changed by 10,060 cycles but
no change was made in La C2.
This circuit was, therefore, tuned to a wave
10,000 cycles (10 kc.) different in frequency
from that being supplied by the oscillator.
However, a certain amount of voltage was still
to be measured on the vacuum tube voltmeter
I
but since the circuit was not tuned to the
oscillator frequency, the voltage which was
measurable represented an interfering
signal. This voltage read on the vacuum
tube voltmeter under these conditions is
represented as Et in Fig. 5, The trap was
then adjusted and as condenser Ci was
varied, the voltage across L, Ca was re-
corded and a curve Fig. 5, plotted, showing
the variation of voltage as the trap con-
denser Ci was changed. This curve shows
a large decrease in voltage as the trap
circuit is brought into resonance with
the incoming frequency. With the trap in
resonance the voltage decreased to about 15
per cent, of its former value.
This whole test was analogous to the case of a
RADIO BROADCAST Photograph
FIG. 7
Space-wound solenoid coils can be used
to construct a very efficient wave trap
receiver tuned to a particular station and at the
same time receiving a certain amount of energy
from another station differing in frequency by
10 kilocycles (10,000 cycles). Under such
conditions, the use of a trap would have caused
a decrease of about 85 per cent, in the strength
of the interfering signal. Let us take a numeri-
7
FIG. 8
A simplified diagram of a receiver employing three stages of
radio frequency amplification, really successive wave traps
cal example of such a case. Suppose it is desired
to receive a signal having a frequency of 500
kilocycles and to eliminate the interference from
another station operating on 510 kilocycles.
The antenna circuit of the receiver would be
688
FIG. 9
This is the equivalent circuit of Fig. 9. It
was used in obtaining the curves in Fig. 10
RADIO BROADCAST
best results with the induc-
tively coupled circuit. Every
effort should be made to have
as good a ground and antenna
as possible, but if it is necessary
to use a long ground lead to a
rather poor ground system, the
direct coupled
wave trap will
probably give
most satisfactory
operation.
When using
the latter method
of direct coupling
as illustrated in
Fig. 2, some small change
APRIL, 1926
In order to aid the home constructor in build-
ing up his own wave traps, the accompanying
table has been compiled.
For those wishing to duplicate the model
constructed in the Laboratory, the following
material should be secured: one 36-turn Hammar-
lund Roberts 3-inch coil, one Cardwell .ooi-mfd.
TYPE OF
SIZE
NO. OF
DIAMETER
NO. OF
COIL
WIRE
TURNS
OF COIL
PEGS
Spiderweb
20
40
2t"
13
3 Diamondweave
20
30
2"
17
Solenoid
20 28
3}"
tuned to 500 kilocycles and then the wave trap
would be tuned to 510 kilocycles with the result
that the interfering signal of 5 10 kilocycles would
be decreased to 85 per cent, of the value it would
be without the trap. Under some conditions,
it will be found that the type of connection used
1,000
900
CYCLES DIFFERENT FROM RESONANCE
FIG. IO
Here's a curve that shows the effect of us-
ing several stages of tuned radio frequency
in the test suppresses too much of the main
signal and it will be best to change over to the
hook-up shown in Fig 3. With the trap
inductively coupled to the antenna circuit, the
tuning is usually very much sharper but at the
same time it is generally found that the interfer-
ence is not as completely suppressed. Since the
operating characteristics of the trap depend to
some extent on the conditions at which the
receiver is being operated, it is best to try both
types of connection and determine which
method gives the most satisfactory results.
Sometimes the frequency separation between
the signals it is desired to receive and the signals
it is desired to suppress is very much greater
than 10 kilocycles, and under such conditions
the trap will operate even more efficiently.
w:
WHICH CONNECTION TO USE
'HETHER the trap circuit of Fig. 2
or that of Fig. 3 is used depends to a
considerable extent upon the characteristics of
the antenna system. A well insulated antenna
with a short lead-in and a short ground wire to a
good ground, such as the cold water mains, gives
BASE BOARD
the tuning of the antenna con-
denser will be noticed whereas
with inductive coupling practically no change in
tuning takes place. This represents a slight
advantage in favor of inductive coupling, since
it will be possible to continue to use the same old
dial readings after the trap has been installed.
In designing a trap circuit, the difficulty arises
in making one that will do its work well when
the frequency separation is only 10 kilocycles.
If the trap is poorly made it may elimi-
nate the interfering signals but will also de-
crease the strength of those signals we desire
to receive. The most common cause of poor
results with wave traps is due to the use of high
resistance coils and low
grade condensers.
It is therefore essen-
tial that the trap oper-
ate efficiently, and in
order to obtain such
operation, it is generally
best to use a fairly small
coil and a large conden-
ser. With a large coil
the elimination is usu-
ally more complete but
the neutralized band is
larger so that the trap
interferes with reception
on wavelengths adjacent
to that wave on which
the interfering station is
operating. Most satis-
factory results are ob-
tained when low loss
coils are used.
Any type of multiple-
stage tuned radio fre-
quency receiver is actu-
ally a series of traps or
filters coupled together. The circuit shown
in Fig. 8 is really equivalent to the circuit of
Fig. 9. The tubes function as amplifiers and
do not alter the resonance curves to any con-
siderable extent. Fig. 10 shows a set of reso-
nance curves obtained from a circuit connected
as in Fig. 9. In a one-stage r. f. amplifier a
resonance curve like i would be obtained.
Adding two and then three stages give us
curves 2 and 3 respectively.
In order to obtain maximum benefit from such
an r. f. amplifier, it is essential that the various
tuning units be constructed as efficiently as
possible and if this is done it will not be neces-
sary, under ordinary circumstances, to use a
wave trap in conjunction with this type of
receiver. Nevertheless, under some conditions,
for instance when a set is being operated very
close to a broadcasting station, the currents
induced in the antenna might be strong
enough to override the selectivity of such a
receiver, and it will be necessary to use a wave
trap.
variable condenser, one 3-inch dial, one panel
7x8 inches, and necessary binding posts, screws,
etc. The apparatus layout is shown in Fig. 1 1.
It is obvious that similar capacities and induc-
tances, of any make, or home made, will be
just as satisfactory.
Th2 antenna winding consistsof 10 turnsof No.
20 wire wound directly over the Hammarlund
Roberts coil and fastened with a small amount
of collodion. If the trap is to be connected as
in Fig. 2, the antenna goes to binding post
No. i and the antenna terminal of the receiver to
terminal No. 2 on the wave trap. For inductive
coupling as in Fig. 3, the antenna connects to
No. 3 and terminal No. 4 goes to the antenna
binding post on the receiver.
O000
PANEL '
FIG. I I
The layout of apparatus for a wave trap.
Note how simple the construction is
FIG. 12
Circuit diagram of the wave trap shown in Fig. 1 1 .
The notation on the binding posts in Fig. 12 cor-
respond to the numbers on this diagram
RADIO BROADCAST ADVERTISER
695
The Crosley 4-tube— 4-29
in which the Crescendon is equal
to one or more additional tubes
of tuned radio fre-
quency amplification
(Ul KfVM
$29
The
Crescendon
— an amazing
new volume con-
trol exclusive to
Crosley sets.
Hear it!
The Crosley 5-tube— 5-38
All the volume, selectivity and
purity of tone available in the
best 5-tube set — plus
the Crescendon .
m i'i i"c
$38
Widespread Popularity Marks
Another Great Success
Spectacular as has been each stride in
radio achieved by Powel Crosley, Jr., never
before has a Crosley success received such
prompt and widespread recognition. Here
in the radio plant which has made more
radios than any other factory in all the
world, every man and machine is going at
top speed, every hour is a crowded hour,
every night a working day, as the result of
orders for the four new Crosley sets.
Even the sweeping success of the Crosley
Musicone did not match this merciless
demand upon an organization tuned to
mass production. With the first demonstra-
tions by Crosley dealers, public approval
was expressed in orders that have increased
in volume day by day and show no inclina-
tion to relax.
This popularity is distributed quite evenly
between the four new 4- and 5-tube sets.
Thousands who had formerly believed that
worth while reception was exclusive to high
priced sets, have found in Crosley 4-29 and
5-38 all that they could ask of radio. The
accurate selectivity and pure tone of these
instruments would be enough. That mag-
nificent volume achieved through the
Crescendon is the final touch.
And in Crosley "RFL" types there is a
revelation for all. For here true cascade
amplification makes its first appearance.
Here what was considered impossible in
expert opinion has been achieved by ampli-
fication closely approaching theoretical
maximum efficiency per tube !
What a joy to find, and in a low priced set,
rare beauty, rich tone, volume subject only
to your desire, and no howling at any pitch
by any mishandling under any conditions.
Each instrument delights the ear, fires the
enthusiam of the lay technician, converts
the staunchest skeptic to love of radio.
See the new Crosley receiving sets at your dealer's or write Dept.20 for descriptive catalog
Crosley manufactures radio receiving sets which are licensed under Armstrong U. S.
Patent No. i, 1 1 3, 149, or under patent applications of Radio Frequency Laboratories, Inc.
THE CROSLEY RADIO CORPORATION, CINCINNATI, OHIO
Powel Crosley, Jr., President
Owning and Operating WLW, 6rst remote control super-power broadcasting station in America
*
The Crosley 5-tube— RFL-60
A set of marvelous performance
and beautified by the
artistic decorative Hk/^O
panel
The Crosley 5-tube— RFL- 75
Simplicity and speed in tuning,
fidelity of tone and decorative
beauty, enhanced by the
art panel
Add 10% to all prices west of the Rockies
BETTER— COSTS LESS
FOR THE ENTERTAINMENT CORNER
\\ir "P ATlin "
696
RADIO BROADCAST ADVERTISER
andnov
more stations
come in
distinctly
A UX Power Tube
will increase the clarity and vol-
ume of YOUR set
REWIRING UNNECESSARY
NOTE: The UX-120 tube for dry battery sets and
the UX-112 for storage battery sets reproduce more
perfectly the excellent broadcasting of to-day.
These tubes handle the powerful signals of nearby
stations so that the quality of the tone is preserved
without distortion. You can easily obtain this in-
crease in clarity without rewiring your set. A com-
plete line of Na-Ald Adapters and Connectoralds
have been made to
meet this purpose.
Their scientific design
insures a nicety of op-
eration. Below are
given three efficient
and easily made appli-
cations of the new
power tubes. For com-
plete details covering
No. 920 these and other appli-
Connectorald cations of the new tube
mail the coupon below.
How la improve storafe battery sets
Clarity and volume can be increased in storage
battery sets by using the UX-112 tube in the last
stage. Easily fitted to the UV-201A socket by
means of the Na-Ald No. 112 Connectorald which
provide* cables for attaching necessary extra B
and C batteries. Price $1.25. Mail coupon below
for complete adapter information covering use of
new tubes in all sets.
Haw to improve sets equipped with UV-199 lutes
To increase volume and clarity in sets using UV-
199 tubes, use the UX-120 tube in the last stage.
Easily fitted to the UV-199 socket with a Na-Ald
No. 920 Connectorald which also provides cables
for attaching necessary extra 45 volts B battery
and 22J volts C battery required for the UX tube.
Price, $1.25.
How to switch to dry bat-
teries without sacrificial
volume or quality
The combination of a
UX-120 tube for the last
stage with UX-199 tubes
in the other sockets pro-
vides, with dry cells, re-
sults previously obtained
only with storage bat-
teries. Fit UX-120 tube
to the UV-201A Socket
with Na-Ald Connector-
aid No. 120. Cables
provided for attaching
extra B and C batteries.
Fit UX-199 tubes in all
other sockets with Na-
Ald No. 419-X Adapters.
Price, No. 120 Connect-
orald, $1.25; No. 419-X
Adapter, 35c.
No. 120
Connectorald
ALDEN MANUFACTURING COMPANY
Dept. B 17 Springfield, Mass.
All Na-Ald Sockets, Dials and Adapters are
protected by patents. Many patents Pending
ALDEN MFG. CO.,
Dept. B17. Springfield. Mass.
Please send me complete information on how to
increase volume and clarity in any set by the
use of the new tubes.
Name
Address
City State
THE
A Department Devoted to Solv-
ing the Problems of our Readers
QUERIES ANSWERED
1. WHAT ARE THE DIMENSIONS AND NUMBER OF
TURNS FOR THE COILS USED IN THE "UNI-
VERSAL" RECEIVER RECENTLY DESCRIBED IN
RADIO BROADCAST?
L. T. — Flushing, New York.
2. HOW MAY I ELIMINATE THE REFLEX PART OF
THE ROBERTS CIRCUIT?
G. C. — Altoona, Pennsylvania.
"UNIVERSAL" RECEIVER COILS
THE coil units employed in the "Universal"
receiver may very easily be made by
winding on a 2j inch diameter cylindrical
form, 59 turns of No. 24 d.s.c. wire in the manner
shown in Fig. i.
L 2%"
No 24 D.S.C. Wire
FIG. I
The first winding put on the coil form is the
secondary, and over it, at one end of the form, is
wrapped a piece of insulating material, such as
ANTENNA COUPLER
>. To Grid
1 Mid-tap
Ant
Prim.
Gnd.
FIG. 2
paper, cambric cloth, etc. The width of this
piece is about TSJ inch, and over it is wound 15
turns of the same wire for a primary. For the
interstage coupler, located between the radio
frequency and detector tubes, the coil unit has
J. WHAT ARE THE SIMPLE LAWS GOVERNING
THE CALCULATION OF CAPACITY IN SERIES
OR PARALLEL?
J. C. — Chicago, Illinois.
4. PLEASE PUBLISH A GOOD THREE TUBE R. F.
CIRCUIT FOR A RECEIVER EMPLOYING ONE
STAGE OF IMPEDANCE-COUPLED AUDIO FRE-
QUENCY AMPLIFICATION.
H. H. McC.— Dayton, Ohio.
a tap at the aoth turn from the grid end of the sec-
ondary. The antenna coil unit has its second-
ary tapped at the center turn. The circuit
connections are shown in Figs. 2 and 3
ELIMINATING THE REFLEX IN THE ROBERTS
CIRCUIT
THE RADIO BROADCAST Knockout four-
tube receiver has enjoyed widespread
popularity for more than a year, and is
still going strong. For many it has proven
to be the "par excellence" circuit.
In such a highly specialized circuit where each
branch has its own important role to play, there
is bound to be trouble when constructors dis-
regard the simple fundamental rules of receiver
design, or where cheap parts are substituted
for those recommended.
R.F.& DETECTOR
COUPLER
To Isolating
Condenser
To Plate
of
R.F Tube
V.
to Primary
of
Audio Transformer
To Plate of
"Detector Tube
->- ToNeutCond.
FIG. 3
Reflex, at its best, is a system of dual ampli-
fication that must be handled with utmost
consideration and, when installed properly in a
receiver, offers advantages, economically and
electrically, that cannot be seriously disregarded.
However, there are those who, in attempting
to rid their receiver of the troubles caused by an
inefficient reflex system, desire to eliminate the
reflex feature entirely and substitute for it a
stage of straight audio frequency amplification.
The circuit-changes necessary to make-over a
four-tube receiver are few, and are shown in
Figs. 4 and 5. In Fig. 4 the regular four-tube
circuit is shown. Fig. 5 shows the new circuit.
RADIO BROADCAST ADVERTISER
007
Type BD1-A
NATIONAL
TUNING UNIT
Embodying the genuine
Browning-Drake Induct-
ance Coil and the NA-
TIONAL Condenser
The New NATIONAL
EQUICYCLE Condenser
The latest development in straight line frequency con-
trol as applied to NATIONAL Condenser design.
Increases range of rotation from 180° to 270°, permit-
ting more precise adjustment and sharper separation
of stations, and accomplishes this WITHOUT
GEARS, CAMS, OR LEVERS.
It changes
a mob
into an
orderly
procession
Type BD2-A
NATIONAL
TUNING UNIT
Embodying the genuine
Browning - Drake Trans-
former and the NATION-
AL Condenser
and
lengthens
the line
of
march!
(Patented February 10, 1925)
Tests Conducted at Harvard University, by Prof. Field, give characteristics of the new
Equicycle Condenser as indicated by the following graph:
— The novel shape
of the plates spaces
the station groups at
equal intervals of 10
kilocycles (as speci-
fied by the U. S. De-
partment of Com-
merce) in a true
straight frequency
line.
Type B
NATIONAL VELVET
VERNIER DIAL
o, § C;
o o o
Frequency in O Kilocycles O O
*S
S
_— 2,
Y)
1
"X
^
1
^
S
^
i
\
X
*v
n-4
•—
S
X
i
N
^
^
^
N
s
^>
[N
_ Tuning P&nge of Standard 180° Condenser^
N
Tuninq'R&nQe of Natic
nal
£quici/cle Condenser
~
"^
^?
tl
c.c
L.C
T. T
M
->ndt
Jli =
jbe
eas
•>era
>nse
3/5/
lit
*rer*
>ing
r~2't
1.H.
TOM
/f./=
\
I?
-<*(
L
Hi
witri plate i
tent Made 1}
Conditions.
OciC
nde
ed.
S
Of
— The same electric-
al efficiency and me-
chanical ruggedness
that have always
characterized NA-
TIONAL DX Con-
densers have been
embodied in the new
NATIONAL
EQUICYCLE
Condenser.
SO. Dial Setting 100.
150.
Get the Genuine. Insist upon NATIONAL COMPANY'S
RADIO Products. Your dealer appreciates your
patronage and will gladly get them for you.
Write for Bulletin m-RB
NATIONAL COMPANY, Inc.
W. A. READY, PRESIDENT
110 Brookline St. Cambridge, Mass.
if Tested and approved by RADIO BROADCAST if
NATIONAL
TRANSMITTING
CONDENSER
RADIO BROADCAST ADVERTISER
A BETTER
LEAD-IN
Then this
picture will
tell you why
you should re-
fuse anything
but an Electrad
Certified Lead'In.
Saves marring your window or
door frames. Fits under locked
windows. Bends to any de-
sired shape. Imitations do that
too, but they stop there. Notice
what else you obtain in this Electrad
Lead'In. Insulation, 10 inches long,
waterproofed and protected entire
length. Riveted and soldered Fahne'
stock clips.
Sold at all good radio stores and
counters. Price 40c. Canada 60c.
Ask for it by name. For safety's sake
refuse imitations.
For
Clearer
Purer
Reception
Do This
Place an Electrad Audiohm across the second-
ary of your audio-transformer. Then you
will enjoy your radio. Kills distortion, elim-
inates squeals and howls. Fits all audio trans-
formers. Easy to attach. For sale at good radio
stores and counters. $1.50. Canada $2.10.
Jill
ELECTRAD
INC.
428 Broadway New York
Makers of Certified Radio 'Essentials and Accessories:
Grid Leaks, Fixed Condensers. By-Pass Condensers,
Variohms, Resistances, Rheostats and Potentiometers,
Jacks, Switches, etc. Write for catalog.
FIG. 4
the dotted lines indicating that part of the
former circuit which was reflexed.
It may be observed from these two circuit
sketches that the audio transformer employed
as the reflex agent is merely eliminated from its
position and re-located as the transformer for
the first straight audio amplifier. The primary
but has not the correct size, as recommended, on
hand.
It is quite a simple matter to get over this,
however, by the combination of a variable and a
fixed condenser.
For example, suppose a condenser of .001 mfd.
is desired. By shunting the usually handy
.0005 variable condenser with a fixed .0005.
mfd. condenser, the desired capacity is obtained.
FIG. 5
C2
\\
of the push-pull input transformer, instead of
being in the plate circuit of the radio frequency
tube, is in the plate circuit of the new audio
stage.
With the new circuit, where ux-i 12 tubes are
used in the push-pull amplifier, well-nigh perfect
reproduction will result, With the use of this
type of tube, it is es-
sential that 9 volts C
battery be employed
as a grid bias for the
push-pull amplifier,
with 135 volts plate
potential.
CONDENSERS IN SERIES
AND PARALLEL
IT IS often the case
that the radio man
will require a con-
denser of a certain
specified capacity when
experimentally hook-
ing up a new circuit
Max. .0005 mfd
Min. .000025 -
If, with this same variable condenser, it is desired
to lower the total capacity in a circuit to which
it is applied, then a condenser in series with it
will produce the desired result.
In the first case — the fixed condenser in parallel1
arrangement— the minimum capacity that can.
be obtained with the plates of the variable
condenser completely
unmeshed will be
greater than when only
the variable condenser
alone is used, by a ca-
i Q- pacity equal to that of
the fixed condenser
used. If the minimum
capacity of the varia-
ble condenser is.oooo2^
mfd., the total mini-
mum capacity of the
two condensers is
.0005
mfd.
C -
------- C -----
FIG. 6
.000025 plus .0005
mfd. See Fig. 6. If
the condensers are ar-
ranged in series, as in
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
699
*
radio is always top notch.
What do you do to keep it so full
of pep?"
KEEPING your "B" batteries full of pep, without
frequent renewals, is simply a matter of using the
right size Evereadys for your particular set with
a "C" battery*.
The rule which determines the right size "B"
batteries to use is so simple no one can make a mis-
take, and once learned it definitely settles the ques-
tion of "B" battery service and economy.
On 1 to 3 tubes — Use Eveready No. 772.
On 4 or more tubes — Use the Heavy Duty
"B" Batteries, either No. 770, or the even
longer-lived Eveready
Layerbilt No. 486.
On all but single tube sets
— Use a "C" battery.
When following these
rules, No. 772, on 1 to 3
tube sets, will last for a year
or more, and Heavy Duties
on sets of 4 or more tubes,
for 8 months or longer.
These life figures are
based on the established fact
that the average year-round
use of a set is 2 hours a day.
A pair of Eveready No.
772's for a 5-tube set
instead of 2 Eveready No. 770's or 2 Eveready
Layerbilts No. 486 — looks at first glance like an
economy because of lower first cost. But in a few
months the 772's will be exhausted and have to be
replaced. After the same length of time the Ever-
eady No. 770's or the Eveready Layerbilts No. 486
will still be good for many more months of service.
We have prepared for your individual use a new
booklet, "Choosing and Using the Right Radio
Batteries," which we will be glad to send you upon
request. This booklet also tells about the proper
battery equipment for use
with the new power tubes.
•NOTE : In addition to the increased
life which an Eveready "C" Bat-
tery gives to your "B" batteries, it
will add a quality of reception
unobtainable without it.
Manufactured and guaranteed by
NATIONAL CARBON Co., Inc.
New York San Francisco
Canadian National Carbon Co., Limited
Toronto, Ontario
LEFT-JVo. 486,
jor 4, 5 of more
tubes. $5.50.
RIGHT- Ever-
eady Dry Cell
Radio "A" Bat-
tery, \V, volts.
Radio Batteries
~they last longer
Tuesday night means Eveready Hour — 9
P. M., Eastern Standard Time, through the
following stations:
WEKT -New York
WJAR— Providence
WKB-AofM
vrsAi-Cincinnati
WEAR— Cleveland
Vfv/j-Detroit
wen-Chicago
Viac-Davmtort
Turrn i Minneapolis
'" \ St. Paul
Louis
Pacific Coast, Eveready Program,
uco-San Francisco. & to1) P. M.
v,'Vi-Philadelphia
V!GK-Bufalo
WCKZ-Pittsburgh
Tested and approved by RADIO BROADCAST
700
RADIO BROADCAST ADVERTISER
The AmerTran
DeLuxcis made in
two types, a first
and second stage,
Price, either type,
$10.00.
^A Hew Standard of Excellence
in A udioAmplif (cation
The realism of this new audio trans-
former is outstanding. Realism of
this kind results from the uniform
amplification of the fundamental
tones of the lower register. The
AmerTran DeLuxe makes possible
the natural reproduction of not only
the Overtones, but all of the trans'
mitted Fundamental tones.
The AmerChoke
type 854 is a choke
coil or impedance
of general utility.
Price $6.00.
A Good Audio Amplifier
Requires enough plate and grid bias
voltage on its tubes to prevent them
from being overloaded by the signal
voltage.
The AmerTran PF-45 or PF-52 with
the half wave high voltage rectifying
tubes now available and suitable
condensers and resistances— together
with three AmerChokes Type 854
will furnish these proper voltages.
This combination will give real
quality loudspeaker volume. Amer'
Tran Power Transformers also sup-
ply A. C. filament current for the
last audio tube. A
AmerTran Audio
Transformers type
AF6 (turn Ratio 5)
and AF7 (turn ratio
3H) are the leaders
in their class. Price,
either type, $5.00.
Write for booklet describing these and other
AmerTranProducta — with recommendations
on their use. It's free on request. All prices
are F. O. B. Newark, N. J.
AMERICAN TRANSFORMER CO.
178 Emmet Street, Newark, N. J.
"Transformer builders for over twenty-fire years"
Sold Only at Authorized AmerTran Dealers.
Fig. 7, then the minimum capacity of the cir-
cuit is calculated by the following formula:
where Q equals the minimum capacity of the
variable condenser (.000025 mfd.) and Ct equals
Min. .000025 mfd.
Max .0005
.0005 mfd.
C2
C-T
FIG 7.
the capacity of the fixed condenser,
stitution in this formula, we get:
— -f —
Ci T Cz
By sub-
= .000024 mfd.
i
.000025 .0005
.0005
The same formula may be applied for finding
the maximum capacity of the arrangement,
the maximum capacity of the variable condenser
being substituted for d.
AN IMPEDANCE-COUPLED AUDIO AMPLIFIER
FOR a means of amplifying audio fre-
quencies, the impedance method is
commendable because of its simplicity of
connection, and also because use can be made of
discarded transformers or other coils. From
the circuit in Fig. 8 it will be seen that all that
is necessary for a coupling agent between the re-
generative detector tube and the first audio tube,
is a coil having an iron core. Of course, this
coil unit should have certain definite dimensions
for most efficient functioning, but it has been
found that such coil units as the secondary of a
transformer which has been rendered useless by
a burned-out primary, or the wire-wound bobbins
of discarded head phones, are satisfactory make-
shifts for an amplifier unit. The connections
for an entire receiving circuit, showing the
application of an impedance or choke coil to it,
are clearly indicated in the accompanying
circuit diagram.
The two tuning units in this circuit are stand-
ard coupler units. In the antenna unit, the
secondary coil is tapped at the mid-turn for the
filament return connection. Rice neutralization
is employed. The neutralizing condenser is con-
nected between the plate of the radio frequency
tube and the lower end of the first coil-unit
secondary. These connections are clearly shown
in the diagram. The value of the neutralizing
condenser is .000016 mfd. The tuning con-
densers are both about .0005 mfd.
The similarity between impedance and resis-
tance audio amplification is apparent from a
glance at the circuit diagram. In resistance am-
plification a resistor of approximately 100,000
ohms is substituted for the impedance coil, and
there is a B battery voltage drop across the
plate resistance. Any variation in voltage causes
a corresponding voltage variation in the resistor,
and these voltage variations are applied to the
grid of the succeding tube, and magnified by the
latter's action. For an impedance amplifier, the
general action is much the same, with the ex-
ception that, instead of utilizing the voltage drop
across a resistance, the variation in voltage
across an inductance is used. It is essential that
the isolating condenser C, should be of the
highest quality, one of mica dielectric being rec-
ommended.
'CHOKE OR IMPEDANCE
AUDIO AMPLIFIER
FIG. 8
GRID INQUIRY BLANK
Editor, The Grid
RADIO BROADCAST
Garden City, J^eu> Yorlf
DEAR SIR,
Please give me the fullest information on the attached questions. I enclose a stamped
envelope.
CH I am a subscriber to RADIO BROADCAST and therefore will receive this information free
of charge.
D I am not a subscriber and enclose $1 to cover cost of answers.
NAME
ADDRESS .
G. A.
Tested and approved by RADIO BROADCAST
RADIO BROADCAST ADVERTISER
701
R
H"amm ar Ivmdl )
•hinoton, D. C,
Testimonials on the
Hamtnarlund-Roberts
Receiver
i
Qrandview, Washinoton
Last night I received PWX
at Havana, Cuba on the
loud speaker. Other sta-
tions that I get regularly
are : WFGB at Atlanta,
Georgia; WSM, Nashville,
Tenn. ; WGY. Schenectady,
N. Y.; WSMB, New Or-
leans. Louisiana ; C'/K,
Mexico City, Mexico.
Ready to back your set
against any other of the
same size. Logged over
100 stations the first weelr
R. F.
2
Butte, Montana
During tests the Hammai-
lund-Roberts was installed
in the Butte Radio Club
Headquarters and dials set
Tor 2LO. Immediately we
were able to get through
for a few moments, long
enough to hear announce-
ments made in English,
German, and Spanish. This
was followed by both in-
strumental and vocal music.
M. R. C.
Wheeling, W. Va.
On January 25th, 1926, I
picked up 7EAJ of Madrid,
Spain. Reception was so
loud and clear from the
cone speaker. It was de-
sirable to cut the volume
considerably.
I have received CZE of
Mexico City and PWX of
Havana. Cuba ; both of
these stations I have re-
ceived before these tests
however.
I have logged over 90 sta-
tions and more are coming
In all the time. N. B.C.
l/iousands Have ftufltlt!
SIMPLICITY of assembly is an outstanding feature of the Hammarlund-Roberts
receiver. Thousands of amateur builders in all parts of the country testify en-
thusiastically to the ease of assembling this circuit and express their delight at the
results secured by their own handiwork.
The secret of their success lies in the flawless technique of every part entering
into the assembling of this set. The Hammarlund-Roberts receiver represents the
composite achievement of ten leading engineers, backed by ten of the best known man-
ufacturers of radio parts. Every part is the work of a specialist and has been chosen
because it meshes easily and yet efficiently with every other related part in the set.
After you have assembled this receiver you will want your friends to call around
and judge for themselves your ability as a radio engineer. And your pride will be
justified. The Hammarlund-Roberts receiver combines remarkable volume and
sensitivity with an unusual degree of selectivity and tone quality. As for distance —
you have on either side enthusiastic testimony by users of the Hammarlund-Roberts
in all sections of the country. A perusal of these comments will revolutionize all
your previous ideas of five-tube performance. Should you desire to verify any of
these reports we will be glad to furnish you with full name and address on request.
ilng during the
>gged in no less
dozen stations,
regenerative sets
ruined reception.
le to make out
some station in
rlca operating at
s. From results
I am sure that
und-Roberts is cap-
Trans-Atlantic Re-
I feel that Ham-
Roberts is one of
buys in radio to-
G. J. A.
Electrical Engineer
Williamsport, Pa.
We have tested the Ham-
marlund-Roberts and find it
to be exactly as you rec-
ommended. Surprising vol-
ume and very clear and
deep tune, exceedingly se-
lective, H. B. S.
10
Lansing, Mich.
On the first night of the
Trans-Atlantic Tests, I had
PWX, Havana, Cuba, on
the loud speaker, so loud
that it could be heard at
times all over s six-room
house.
Have not heard of anyone
beating this record. I have
ten witnesses to this recep-
tion. J. i ;.
13
Morristown, Tennessee
I assembled the Hammar-
lund-Roberts Receiver in
one day's time. The set is
highly efficient and up to
all claims made by you.
I have owned many factory
built sets and will say that
the Hammarlund-Roberts is
superior to them all. This
set is capable of building
up tremendous volume with-
out distortion and behaves
like a thoroughbred.
I get New York, Atlantic
City, Jacksonville, San
Francisco, Montreal, Havana,
Cuba, and Mexico City.
4iamma
Hammarlund-Roberts 1182-A Broadway, New York City
This famous instru-
ment and other parts
shown here are some
of the quality units
in the Hammarlund-
Roberts.
DURHAM
RESISTORS
RHEOSTATS
UNION
PHONE TIP
JACKS
DIALS and SOCKETS
SEND FOR THIS
BOOK
Contains step-by-step In-
structions on the assem-
bly, wiring and operation.
of the Hammarlund-Rob-
erts. Fully illustrated ;
most complete "How to
Build It" radio book ever
published. 25c.
Tested and approved by RADIO BROADCAST
702
RADIO BROADCAST ADVERTISER
Sent/ for this
The outstanding receiver develop-
ment of the season, in which is
combined the genius of two of the
most distinguished radio engineers.
A receiver for the home builder
that will represent for several
seasons to come a far
greater value than any
other design available.
Several outstanding fea-
tures place the design in
a position far in advance
of anything available or
contemplated. Unlimited wavelength range,
with interchangeable antenna and detector
coils; marvelously improved audio trans-
formers; a special self-contained wiring
harness; but one tuning or station selector
control, are special features.
Over-all design is rugged and solid. Adapt-
ed to practically any standard cabinet, any
standard tube, any battery or eliminator
source of supply, outdoor antenna or loop.
Only a screw driver and pair of pliers nec-
essary. The set can be built at an ex-
tremely low cost and parts are readily
available at all radio dealers.
'Represented Manufacturers:
Belden Mfg. Co.—S-C Wiring Harness
Central Radio Laboratories — Centralab
Resistance
Polymet Mfg. Corporation — Fixed Con-
densers, Leak, and Leak Clips
Poster & Co. — Drilled and Processed
Front Panel and Drilled Sub-Panel
Silver-Marshall, Inc. — Variable Con-
densers, Coil Sockets, Coils, Tube
Sockets, Vernier Dial, Mounting
Brackets
Thordarson Elec. Mfg. Co.— £200
Power Transformers
Yaxley Mfg. Co. — Rheostat, Jacks,
Switch
Get the hand-book at your radio dealer's,
or clip the coupon and send 25 cents to
S-C MERCHANDISING
COMPANY
65 E. Jackson Blvd. Chicago
S-C Merchandising Company
65 E. Jackson Blvd., Chicago
Herewith please find 25 cents for which
send me the hand-book of the new S-C
Four-Tube Receiver
Name . .
Address
:Now, I HAVE FOUND * . <
A Department for the Exchange of Ideas and Sugges-
tions of Value to the Radio Constructor and Operator
(CONTRIBUTIONS to this department are welcome and those used will be
^ paid for at the usual rates, that is, from two to ten dollars each. A pri{e
of twenty-five dollars is given for the best idea used during each three-month
period. The prizewinner for the last period was announced in the February
RADIO BROADCAST. Manuscripts intended for this department should not ex-
ceed about three hundred words in length, and should be typewritten. Little con-
sideration can be given to manuscripts not typewritten. Envelopes should be
addressed to this department, RADIO BROADCAST, Garden City, New York.
BETTER REPRODUCTION IN CONE
SPEAKERS
Al EASY way to eliminate the jingle
in the high notes and reproduce
the bass notes more faithfully in a
cone loud speaker, taking as an example
the Western Electric No. 540 AW, is as
follows:
Loosen the set screw in front which holds
the pin, then remove the screws in the back
thus allowing the metal ring, fibre ring, and
screen to be removed.
This exposes the telephone unit held to
the frame by three screws. First, mark
the frame where the unit is held to it so
that it can be put back in the same place,
and then remove the screws and carefully
lift out the unit.
Remove the screw holding the pin to
its support and insert a piece of electric tape
between these two members, first making
a hole through the tape for the screw to
go through. Replace the screw.
Then slip over the pin a rubber tube 5
inch or more in thickness reaching from
the base of the pin to just short of the parch-
ment, and having its bore slightly smaller
than that of the pin, so as to grip it tightly.
With the use of this system, the possibility
of bending or otherwise injuring the pin by
loading it with rubber tape is avoided.
See Fig. i.
Cone
/Angle
Rubber covering
-Tape Cushion
FIG. I
Re-assemble, taking care to have the pin
straight and to put the telephone unit
back in the same place on the frame as
marked. Tighten the screw in front to
the pin.
Before replacing the screen, tune in on
some good station and test out the speaker.
If there is any jingle leave the set screw in
front secured to the pin, loosen up the
screws holding the telephone unit to the
frame, and move the unit until the jingle
disappears and the best reproduction is
obtained. Then tighten up the screws.
Replace the screen and rings, thoroughly
tightening up all screws.
WILLIAM C. MORRILL, E. E.
New York.
it Tested and aonroved bv RADIO BROADCAST -A
HOW TO PROVIDE A COUN-
TERPOISE SYSTEM
THOSE who use the Roberts or
Browning-Drake circuits and are
troubled with broad tuning antenna
couplers, might well use the single induct-
ance with a conductively coupled antenna,
placing the antenna tap about one third up
from the filament end of the inductance,
and grounding the negative A battery line.
For those who have the space or who live
in shingled houses, the substitution of a
counterpoise for a ground (entirely elimi-
nating the ground will materially sharpen
the tuning and in my case was found to
produce much clearer signals, with greater
intensity, than with the ground. The
lower edge of the shingles generally stops
about 3 feet from the ground and overhangs
the foundation wall by several inches.
Small insulated screw eyes placed under
the shingle-overhang all the way around
the house will hold a good counterpoise.
If the shingles go all the way to the ground,
a row of screw eyes about the height of the
doorways will work almost as good. See
Fig. 2.
My antenna combination is now an 80-
foot antenna and a loo-foot counterpoise.
J. B. GREENMAN,
Montclair, New Jersey.
SOME NOTES ON SILVER'S MODEL
1926 RECEIVER WITH CHOKE
AMPLIFICATION
VARIATIONS on the theme of
McMurdo Silver's "Model 1926
Broadcast Receiver," introduced
to its readers in the November, 1925,
number of RADIO BROADCAST, were pre-
sented by E. R. Pfaff in the January,
1926, number. Before the appearance of
the latter article, the writer had con-
structed a receiver of this type using
Thordarson Autoformer audio amplifica-
tion. As the set was constructed for
experimental purposes, and this circuit is
peculiarly adapted to this end, one or two
wrinkles used may be of interest.
As described, the set has no binding
RADIO BROADCAST ADVERTISER
703
aradofi
ECTROSTA1IC CONDENSERS
19 YEARS OF SPECIALIZATION
IN THE RADIO FIELD
TYPE I TERMINALS
For Soldered Connections in Any
Portion of Circuit
TYPE II TERMINALS
Holds Standard Cartridge Grid Leak-
Also Takes Soldered Connections
TYPE III TERMINALS
For Transformer or Other Binding
Post Mounting
Also Takes Soldered Connections
are behind each Condenser Trade Marked
*
In Radio Receiving Sets
The Biggest Little Things Are
The FIXED CONDENSERS
The MODEL T FARADON is furnished in all usual
sizes to meet the requirements of Quality Performance.
Quotations covering quantity requirements furnished
to
SET MANUFACTURERS
promptly upon request.
Some Important FARADON Users:
U. S. Army General Electric Co.
U. S. Navy Radio Corp. of America
U. S. Signal Corps Western Electric Company
U. S. Bureau of Standards Tropical Radio Tel. Co.
Westinghouse Electric 85 Mfg. Co.
WIRELESS SPECIALTY APPARATUS COMPANY
JAMAICA PLAIN — BOSTON, MASS.
if Tested and approved by RADIO BROADCAST Vk"
704
RADIO BROADCAST ADVERTISER
Seven Years of Superiority
KNOWN as the original HI-MU tubes
before the days of BCL;
Preferred by amateurs and experts be'
fore the first popular receiving set was sold;
Progressively improved in construction
and performance;
Made in the newest and best equipped
plant in America.
Get the World on Your Dial
With Myers Tubes
Low impedance, high amplification constant, high
mutual conductance. Best results in any circuit
—impedance, resistance or transformer coupled.
cAt Your 'Dealer's
Myers Radio Tube Corporation
Cleveland, Ohio
Attractive, compact, correct
inside and out, no clumsy
materials. Made by pioneer
designers and builders of
Radio Tubes.
PUT
Marvelous
Clarity and
Distance
Use Myers Tubes
in any set and get
better results in vol-
ume, tone, range
and ease of control.
Made with stand-
ard four prong base,
or double - end, in
types Myers 01 A,
Myers 01 X, My-
ers 99, Myers 99 X.
List Price
Type 01 $2.00
Type 99 2.25
At Your Dealers
SEND FOR
New No. 739 Circular describing special
voltmeters for Radiola, Victor
and Brunswick sets
Jewell
Order from Dealer j^
Electrical Instrument Co.
1650 Walnut St. - Chicago
"26 Years Making Good Instruments"
posts, the ends of a Belden battery cord
being attached directly to various terminals,
transformer, switch, etc., in the set. For
experimental purposes, it is handier to use
binding posts, however. Choke amplifica-
tion may be used with either 90 or 120-135
volts of B battery. In case 90 volts of B
battery is used, the 90 volts go to both r.f.
and a.f. amplifiers, while the detector re-
ceives 45 volts. If, however, it is desired
To coils & To
Condensers Switch
To
Rheostat
TO TOA.F.
A.F. Resistances
FIG. 3
to employ 120-135 volts of B battery
on the last audio stage, then the r.f. am-
plifier and the first two stages of audio
receive 90 volts. There are three separate
units to be provided for, the r.f., ist and
2nd a.f. amplifiers, the detector, and the
last a.f. amplifier stage. If three B plus
binding posts are used, one for each unit,
the a.f., r.f., or the detector may be quickly
connected at the binding posts to facilitate
the use of various values of B potential
without tearing the set apart.
The December, 1926, RADIO BROADCAST
contained two very interesting articles
on the use of high-mu tubes, one by Keith
Henney and the other by Glenn H. Brown-
ing. The latter describes the use of Daven
wood Mandrel with ISspokes
Bushings with
/ set screws >
-- 2 -
.' HDia. Rod
VM
pr-ea
tHi ;,
Wood disc
' ' with nails
(or counte
Spike o
rod 2i
x
r brass
l*«Vii
/Dasher-
, WOOd ;
/Support! /
-C---1S4--*
i
f- Crank
T — — ^
//H
Small finishing
nails % :l'lon(
Baseboard
FIG. 4
high-mu tubes in conjunction with Na-
tional chokes, using 90 volts of B battery.
When two Daven MU-2O and one Daven
MU-6 (in the last stage) are used in the
"Model 1926 Receiver" with Thordarson
chokes on 90 volts, an appreciable gain in
volume is experienced. When, however,
120-135 volts of B battery are used in the
a.f. circuit, as suggested by Mr. Henney, the
receiver talks right out. Furthermore,
quality is not sacrificed.
When Daven tubes are used, the rheostat
lead to these tubes may be disconnected
from the rheostat and connected directly to
the current supply, as these tubes operate
TesteH and approved by RADIO BROADCAST -f
directly from a 6-volt battery. A switch
of the midget type mounted inside the set
makes this change simple.
To care for added C battery (6 to ~j\
volts) to the a.f. circuit, an extra pair of C
binding posts may be used to advantage, as
indicated in Fig. 3.
DAVENPORT HOOKER,
Pittsburgh, Pennsylvania.
A HOME-MADE COIL WINDER FOR
DIAMONDWEAVE COILS
THOSE preferring to "roll their own"
will find in the accompanying sketches,
Figs. 4, 5, and 6, sufficient instruc-
tions to build an efficient coil winder for
diamondweave coils. It consists of a
wood mandrel and metal spokes for a
coil form, mounted on a shaft; also a
counter and a wire guide made of small
thread spools, and a small screw eye to
give correct tension to the wire.
Brassor
Wood Bushing
, Wood Spool
ft '•* 4
r
a ,,,,73,
ft
P 1~
Brass strip
%" wide "-.4
%2 Threaded ,
— - f
a
"*
y^ "
f\ ^3
Rod ~'*H
dE"
•
t-i
-*>-, Y Y
J=- f 1 - I "^
FIG. 5
Care must be taken in marking and bor-
ing to the correct size, the holes in the
mandrel to take the spokes. Place the
spool or wire guide in an upright position,
and far enough away from the winder
proper to allow easy handling of the wire
with the hand (about five inches from the
shaft support). To wind, run the wire
through the eye and under first spool, then
between the two and over the top spool;
set counter and begin winding. With a
little practice one can soon learn the
"swing" of "over two, under two," done
with the left hand.
After winding, remove the mandrel
from the shaft, pull the spokes just out of
the wood, but leave them engaged in the
wire until sewn. About twenty nails in
Wood Mandrel of
diameterdesired
, 2% *3/iJ Spike
or Brass Rod
FIG. 6
RADIO BROADCAST ADVERTISER
705
This is Station 2-L.O. London,— 12 Midnight
WHEN listeners-in on this side of the At-
lantic first heard the voice of the British
announcer, and then a program of music from the
famous Savoy in London, they experienced one of
the real thrills of radio.
To get everything that is on the air — the faint sig-
nals as well as the strong ones — effective insulation
of all radio parts is a prime essential. The best
way to make sure that a radio set or parts are well
insulated, is to buy those in which Bakelite is used.
Bakelite is used by 95% of radio set and parts
manufacturers. It is the standard material for
front and base panels, dials, knobs, tube sockets
and bases, fixed and variable condensers, rheostats,
plugs and other radio accessories and parts. Write
us for a copy of Booklet No. 29, "Bakelite in Radio"
— it's a helpful guide in buying radio equipment.
BAKELITE CORPORATION
247 Park Avenue, New York, N. Y.
Chicago Office: 636 West 22nd St.
BAKELITE CORPORATION of CANADA, Ltd.
163 Dufferin Street, Toronto, Ontario, Canada.
BAKE LIT
REGISTERED j f^ \ U_._S. PAT. OFF.
THE MATERIAL OF
A THOUSAND USES
"The registered Trade Mark and Symbol shown above may be used only on products made from materials
manufactured by Bakelite Corporation. Under the capital "B" is the numerical sign for infinity, or unlimited,
quantity It symbolizes the infinite number of present and future uses of Bakelite Corporation's products."
^ Tested and approved bv RADIO BROADCAST ^
706
RADIO BROADCAST ADVERTISER
screw machine
products
— brass
For plugs, jacks, clips,
condenser and trans-
former parts, etc.,
BRASS assures econo-
my in quantity pro-
duction. It also gives
the right electrical
conductivity and the
mechanical accuracy
essential to proper op-
eration of radio sets
and parts.
COPPERS BRASS
RESEARCH ASSOCIATION
25 Broadway, New York
STATIC ;
Without Loss of Volume
ELIMINATE STATIC
Enjoy perfect reception regardless of weather
conditions. The Static Eliminator — the newest
and most startling thins in Radio — cuts out
practically all static without loss of volume!
And in addition it will help increase selec-
tivity, tune out local stations, sharpen signals,
remove noises, lessen interference, and prevent
re -radiation !
Use It with any receiving set — simply hook
up according to our simple instructions and en-
joy perfect reception
unmarred by static.
Satisfaction abso-
lutely guaranteed — •
- ^*KI Money back if Elim-
«^j7 inator is returned
_ ^Jl within 5 days.
Miil your order Today.
627
! : L Ml*. I!/:
United Bank BldiCincinnati.O.
the counter disk is correct for a two-inch
disk. By means of the screw on the crank,
and the counter, each turn of the crank
registers one complete turn of the coil.
It is easier to use two rings of heavy card-
board tubing of given diameter and half
an inch in width, clamped on each side of
the spokes with two pieces of heavy sheet
metal, than to make various size wood
mandrels. In this way, one mandrel
serves for all diameter coils. Take care to
center these properly on the form before
winding. An excellent coil can be wound
in this way. These coils give fine results
in a RADIO BROADCAST "Knockout"
receiver.
MATERIAL REQUIRED
i — 45-inch x j-inch metal rod for shaft
(60 penny spike will do),
i — Piece of hard wood f-inch wide and of
diameter desired,
i — Piece of hard wood 5 inches x i j inches
(support for shaft),
i — Piece of heavy sheet metal 3 inches x
f inches for crank.
15 — 21-inch x A-inch spikes for spokes
(with heads cut off).
2 — Pieces of brass bushing, j-inch inside
diameter, j-inch wide, with set
screws.
i — Baseboard about 15 x 8 x f inches.
i — Small wood disk about 2 inches
diameter j-inch thick for counter,
with some small fishing nails to go
around periphery.
2 — Wood spools of same size (thread
spools.)
2 — Pieces of A threaded rod 2 inches long.
2 — Pieces of brass or wood tubing (pipe
stems) | inch longer than spools.
2 — Pieces of metal strip 4 x f inches wide
to hold spools.
R. S. HART,
Pisgah, Kentucky.
A HANDY BATTERY THROW-OVER
SWITCH
WHEN a vibrating magnetic recti-
fier, such as the " Homcharger, "
is employed to charge the storage
battery, it is necessary to observe the fol-
lowing procedure:
To charge:
1. Disconnect battery from receiver.
2. Connect charger to line supply
(no volts a.c., 60 cycles).
3. Connect battery to charger.
To discharge:
1. Disconnect battery from charger.
2. Disconnect charger from mains.
3. Connect battery to receiver.
To eliminate the clumsy connection and
removal of clips, the author has devised
a simple arrangement whereby the com-
plete process of connection necessary to
the proper charge and discharge of the
baitery is controlled merely by the move-
ment of a double-throw switch.
The switching device is illustrated in the
accompanying diagram, Fig. 7. The di-
mensions of the switch itself are unim-
portant, so long as the extra contact which
connects the charger to the line supply is
made large enough so that the switch
blades connected to the battery are en-
tirely clear of their contacts before the
line supply is cut off.
BERNARD SALZBERG,
New York City.
ECONOMICAL SUB-PANEL
BRACKETS
BEING suddenly faced with the neces-
sity of making a pair of brackets
for a sub-panel, I tried the following:
Get from a good hardware or plumbing
supply store, a piece of i*s-inch channel
brass, |-inch wide. This will be shaped as
shown in i, Fig. 8.
Measure how far the bracket must pro-
ject back from the front panel and add
about two inches for support to fasten
on to the front panel. At the point where
you wish to bend the strip make a cut,
perpendicular and square across, with a
hack saw, merely cutting through the side
walls as illustrated in 2, Fig. 8.
Then, with a three-cornered file, widen
the saw cut to a "V" shaped notch, as in
FIG. 7
Tested and approved by RADIO BROADCAST
FIG. 8
3. Be sure the angle at the bottom of
the notch is one of 90° and that it is pretty
accurately placed 45° on each side of the
perpendicular. The bracket is now bent,
as shown in 4. If your angle is correct,
the top piece will project from the panel
exactly square, and the weight on the sub-
panel will be supported nicely by the side
walls of the notch as they come together.
Of course, by regulating the angle of the
filed notch, you may make a bracket that
projects from the panel at any angle of
more or less than 90° as you wish. This
idea could be used in making sets with a
sloping panel.
To finish the bracket, fill the corner
where the brass was bent, with solder.
This prevents the bracket from bending
back under pressure from beneath, such
as is exerted when the foot on the sub-
panel rests on a table or the bottom of the
cabinet.
R. L. DOUGLAS,
Huntington Park, California.
RADIO BROADCAST ADVERTISER
707
ATWATE R KENT
RAD I
Are you running a store
or a museum?"
THAT'S what the caustic stranger
said to the radio merchant.
The merchant started to flare up,
but thought better of it. Instead, when
the visitor departed he spent a profit-
able half-hour with his own thoughts.
Had he taken on too many lines?
Had he selected them indiscrimi-
nately? Didn't unsalable reminders
clutter his shelves? Obsolete models,
discontinued by the manufacturer in
the middle of the year? Orphan sets
— maker gone out of business?
Those job lots he had bought to
"move quickly" — weren't they still
hanging around? Yes, and good sets,
but without the necessary advertising
to make people want them? And sets
that looked good but ate their heads
offin service calls? Sets t^at had come
in with drums beating — and stayed
while the parade passed on?
"It is a museum," said the merchant.
"I only thought it was a store." Where-
upon he cleared out the relics as best
he could, concentrated on two lines
his customers really wanted, and lived
happily ever after.
* * *
Has the Radio you handle commer-
cial value ? Is it a good product, nation-
ally advertised, and fairly priced? Has
it a record of consistent sales and as-
surance of permanence? Does it sell
easily — and stay sold, enabling you to
turnyour capital often with a minimum
of overhead? In short, is '^.profitable
— over a period of time?
If April is your month for mental
stock taking — for figuring what you
have been doing, where you stand and
whither you are bound — isn't this a
good time to look around, see what the
Atwater Kent Radio merchants have
done and what they think of the radio
business?
Perhaps you would fit into the pic-
ture, too.
EVERY SUNDAY EVENING
The Atwater Kent Radio Hour brings you the stars
of opera and concert, in Radio's finest program. Hear
it at 9:15 Eastern Time, 8:15 Central Time, through:
WEAF New York
WJAR Providence
WEEI Boston
WSAI Cincinnati
WCAP Washington
wcco . . . Minn.-Sl. Paul
WEAR Cleveland
WLIB Chicago
WFI 1. ... Philadelphia
woo / alternating
WCAE Pittsburgh
WGR Bu/alo
woe Davenport
WTAG Worcester
KSD St. Louis
wwj Detroit
Write for illustrated bookjet of Ativater Kent Radio.
ATWATER KENT MANUFACTURING CO.
A. At-wattr Kent, President
4726 WISSAHICKON AVENUE, PHILADELPHIA, PA.
*
Tested and approved by RADIO BROADCAST if
708
RADIO BROADCAST ADVERTISER
FROST-RADIO
No. 530 Socket
for all new type tubes
The new No. 530 FROST-RADIO Socket
takes ALL of the new type tubes. It
is made from black polished Bakelite,
and has sturdy contact springs which
hold the tube prongs for almost their
entire length. Price 40c at your near-
est dealers.
The No. 630 is a rich-looking socket because it is
made from real Bakelite. Takes all the new typ«
tubes. Price »0o
Note the spring construction as revealed by this
cut-away view. These sturdy springs are held be-
tween cast bosses, and stay put.
When the tube is inserted each prong is gripped
the full length on two sides and held in a vice-
like grip. Dirt cannot remain on the springs or
prongs here.
HERBERT H. FROST, Inc.
314-324 WEST SUPERIOR ST., CHICAGO
New York City Cleveland Kansas City
Los Angeles
Export Office: 314 W. Superior St., Chicago
Blackburn Ground Clamps
Telephone companies using
MILLIONS. Adjustable — fits
any size pipe. Requires no pipe
cleaning — screw bores through
rust and scale. Send 12 cents
for sample and postage.
Blackburn Specialty Company
1960 E. 66th St. Cleveland, O.
OTtXS
PERFECT REPRODUCER
Loud, Pleasing tone. Handsome
material. Distinctive design.
Horns, $22.50 to $30.00
Units, 10.00 to 12.00
American fflectric
State & 04th Sts.
COMPANV
Clih-aeo
Short- Wave Stations of the World
'"THIS list, containing more than a hundred short-wave stations situated throughout the world, is
* about the most completely accurate one yet to be printed. The Traffic Department of the Radio
Corporation of America cooperated in its compilation. Included in this list are stations known to be
operating on the wavelengths given, stations licensed for operation, and stations which have been in
operation to any considerable extent during the past year, and which are not definitely discontinued.
CALL
SIGNAL
POP
2XS
2XAW
2BR
POP
NKF
2BR
POP
2XAD
KFVM
POP
NAL
NEPQ
NKF
WIK
2 YT
POY
FW
NKF
AGA
PCMM
POW
2X1
NAL
2YT
ANE
NAJ
WQO
PCMM
PCUU
KFVM
NAS
NAJ
NPG
NRRL
NOW
2XAC
NKF
2XAF
5XH
FW
WIZ
WQO
KZA
KZB
PCLL
WHO
NPM
2XAD
SAJ
WQN
NPU
NBA
NKF
WQN
KFKX
ANF
1 XAO
WQN
KDKA
KDC
2YT
KDKA
8XS
NPO
WRB
WRP
2 XAO
POX
NPO
Nauen, Germany ....
Rocky Point, New York . . .
Schenectady, New York .
Chelmsford, England
Nauen, Germany
Anacostia, District of Columbia
Chelmsford, England
Nauen, Germany ....
Schenectady, New York .
SS Iilalia
Nauen, Germany ....
Washington, District of Columbia
USS Relief ....
Anacostia, District of Columbia .
New Brunswick, New Jersey .
Poldhu, England
Nauen, Germany ....
Sainte Assise, France
Anacostia, District of Columbia .
Nauen, Germany
Kootwijck, Holland ....
Nauen, Germany ....
Schenectady, New York .
Washington, District of Columbia
Poldhu, England
Malabar, Java
Great Lakes, Illinois ....
Rocky Point, New York . . .
Kootwjjck, Holland ....
Kootwijck, Holland ....
SS Idalia
Pensacola, Florida ....
Great Lakes, Illinois ....
San Francisco, California . . .
USS Seattle
USS New Mexico
Schenectady, New York .
Anacostia, District of Columbia .
WG Y— Schenectady ....
New Orleans, Louisiana. .
Sainte Assise, France
New Brunswick, New Jersey.
Rocky Point, New York .
Los Angeles, California .
Los Angeles, California .
Kootwijck, Holland ....
Sharon, Pennsylvania
Honolulu, Territory of Hawaii
Schenectady, New, York .
Karlsborg, Sweden ....
Rocky Point, New York .
Tutuila, Samoa
Balboa, Canal Zone ....
Anacostia, District of Columbia.
Rocky Point, New York .
Hastings, Nebraska ....
Malabar, Java
Belfast, Maine
Rocky Point, New York . . .
East Pittsburg, Pennsylvania
Casper, Wyoming ....
Poldhu, England
East Pittsburgh, Pennsylvania .
East Pittsburgh, Pennsylvania .
Cavite, Philippine Islands
Miami, Florida
Miami, Florida
Belfast, Maine
Nauen, Germany ....
Cavite, Philippine Islands
FREQUENCY
IN KC.
22209
20082
19988
19988
IST.'iS
18738
NERM USS Los Angeles
San Diego, California . . . .
Anacostia, District of Columbia.
San Diego, California
New Brunswick, New Jersey.
Paris, France
USS Pope
USS Canopus
Great Lakes, Illinois .
Quantico, Virginia
Iwatsuki, Japan
SSJdalia
Lakehurst, New Jersey
Schenectady, New York .
San Francisco, California
Anacostia, District of Columbia .
Moscow, Russia ...
Anacostia, District of Columbia.
Paris, France
San Diego. California
Kahuku, Territory Hawaii
Poldhu, England
Bolinas. California . . . .
East Pittsburgh, Pennsylvania .
Nauen, Germany
Norfolk, Virginia
Tuckerton, New Jersey .
SS Big Bill
Schenectady, New York .
SS Eloise
SS Facile
SS Gallavant
Belfast. Maine
Paris, France
SS Nirvana
SS Bridget
NQG
NKF
NPL
WIR
SFR
NUQB
NIRX
NAJ
NFV
J1AA
KFVM
NEL
2XK
NPG
NKF!
ROW
NKF
SFR
NQG
KIO
2 YT
KEL
8XS
POX
NAM
WGH
WHU
2XK
KFVT
KFHV
KFWJ
1 XAO
FL
KFWK
KFVB
• Tested and approved by RADIO BROADCAST
16657
14991
14991
14991
14991
14991
14414
13628
11993
11993
11993
11758
11532
10903
10708
9994
9798
9369
9369
8630
8560
8328
7890
7496
7496
7496
7496
7496
7496
7496
7260
7160
7139
7139
6970
6814
6814
68!4
6518
6119
6119
5996
5996
5822
5657
5552
5511
5501
5354
5354
5354
5260
5100
5082
4997
4759
4475
4409
4383
4383
4283
4283
4283
(4283
(3548
4253
4205
4182
4052
3998
3998
3998
3945
3874
3795
3748
3748
3748
3701
3679
3612
3569
3527
3486
3331
3190
3156
3123
2998
2998
2911
2855
2751
2726
2726
2726
2677
2607
2607
2600
WAVELENGTH
METERS
13.5
14.93
15
15
16
16
17
18
20
20
20
20
20
20.8
22
25
25
25
25.5
26
27.5
28
30
30.6
32
32
34
35.03
36
38
40
40
40
40
40
40
40
41.3
41.88
42
42
43.02
44
44
44
46
49
49
50
50
51.5
53
54
54.4
54.5
56
56
56
57
58.79
59
60
63
67
68
68.4
68.4
70
70
70
(70 to
184.5
70.5
71.3
71.7
74
75
75
75
76
77.4
79
80
80
80
81
81.5
83
84
85
86
90
94
95
96
100
100
103
105
109
110
110
110
112
115
115
115.3
RADIO BROADCAST ADVERTISER
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Cardwell Taper Plate Type"E" condensers
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They are priced the same — the .0005 mfd.
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HAMMARLUND MANUFACTURING CO.
424-438 West 33rd Street New York City
A KEY TO RECENT
RADIO ARTICLES
By E. G. SHAULKHAUSER
THIS is the sixth installment of references to
articles which have appeared recently in var-
ious radio periodicals. Each separate reference
should be cut out and pasted on cards for filing,
or pasted in a scrap book either alphabetically
or numerically. An outline of the Dewey
Decimal System (employed here) appeared in
the November and January RADIO BROADCAST,
and will be reprinted in an early number.
Rii3.4. IONI7AT10N; HEAVISIDE LAYER HEAVISIDE
Popular Radio. Jan. 1926, pp. 61-63. LAYER.
"Up and Down Movement of the Heaviside Layer."
Dr E.E. Free.
A short outline covering the research in high frequencies
carried on at the Naval Research Laboratory by Dr. A. H.
Taylor and Dr. E. O. Hulburt, is reported. Most of the
phenomena observed are explained on the basis of the Heavi-
side Layer movements. Skipped distances and fading appar-
ently depend upon the height of this Jayer and its position
during day and night.
R38z. INDUCTORS. INDUCTION
Popular Radio. Jan. 1926, pp. 80 83. COILS.
"Some Methods for Determining the Distributed Capacity
of Coils," H. S. Knowles.
A discussion covering several methods which may be used
in measuring the distributed capacity of coils, is presented.
Mathematics and graphs are used in giving the information.
R38z. INDUCTORS. INDUCTION
RADIO BROADCAST. Feb. 1926, pp. 436-438 COILS.
"Design of Radio Inductances," W. W. Harper.
Inductances, whose efficiency is high, must be designed to
have a low high frequency resistance compared to inductance,
twenty-five or more microhenries per ohm being considered a
good coil in the opinion of the writer. Such a coil results
in sharp tuning when combined with good condensers, al-
though pick-up action of coils and crowding of apparatus
in sets may make tuning broad. The standards of coil
design are given as follows: (i) Low resistance over the
broadcast frequency spectrum combined with as high a value
of inductance as is permissible under the circuit conditions:
(2) Effective confinement of electrostatic and electromagnetic
field: (3) Consistent mechanical and electrical characteristics:
(4) Small physical dimensions so as to permit compact con-
struction. Experiments and tests have shown that space-
wound solenoids are best for radio frequency purposes. With
proper copper shielding and grooved space winding, the new
so-called Metaloid coil was designed and built. Its L/R value
(5320/9.5, equal to 33, as given in the data.
R343. ELECTRON TUBE RECEIVING SETS. RECEIVERS,
RADIO BROADCAST. Feb. 1926, pp. 430-444 Crimes Reflex
"How to Build a Grimes Inverse Duplex," F. J. Fox.
Constructional details of a four-tube Grimes Inverse Duplex
receiver are given. The set is considered very sensitive
and selective, and is easily built by the home constructor.
Photographs, circuit diagrams, details of coil construction,
panel layout, and method of locating audio, radio, or
overload howl, which might be found in the completed re-
ceiver, give the necessary information desired when building
such a receiver.
R8oo (621.353) BATTERIES, PRIMARY. BATTERIES,
RADIO BROADCAST. Feb. 1926, pp. 452-455. Life of B.
"How Long Will My B Batteries Last?", G. C. Furness.
A discussion on the life of B batteries in all sets from one
to eight tubes or more, leads the author to the conclusion
that the life of B batteries depends entirely upon current
drain and size of cells in the battery. Charts and figures are
presented, verified experimentally, showing how a definite
time limit of six, eight, or twelve months can be set on the
average life of B batteries when these are chosen properly
for the receiver in question.
Rl3l. Characteristic Curves; General Properties. VACUUM
TUBES.
RADIO BROADCAST. Feb. 1926, pp. 456-461. Characteristics.
" How to Use Vacuum Tubes," Keith Henney.
In this article, the elementary principles of vacuum tubes
and their characteristics are discussed, a clear meaning of such
terms as amplification constant, mutual conductance, plate
impedance, of tube characteristics in general, etc; being
included. Data covering a great many makes and varieties
of tubes are presented. Circuit diagrams show how this
information was obtained. The proper use of C batteries and
correct amount of fi'ament current, are essential in good
tube operation, according to the author.
R62o.o68. TESTING. TESTS OF
RADIO BROADCAST. Feb. 1926, pp. 462-464 BROADCASTING
"The 1926 International Radio Broadcasting Tests, "
W. K. Wing.
An outline of the plans and the transmitting schedule for the
1926 International Radio Broadcasting Tests are given.
Many foreign stations |ent their full cooperation and support
to the success of this undertaking sponsored by RADIO
BROADCAST.
Raio. FREQUENCY; WAVELENGTH. FREQUENCY TO
RADIO BROADCAST. Feb 1926, pp 471-472 WAVELENGTH.
"Taking the Complexity Out of Wavelength-Frequency
Conversion," H. S. Davis.
A simple full-page frequency-wavelength conversion chart
is presented together with information on how to use it. The
author emphasizes the fact that the term frequency and not
wavelength is the proper term to use, and gives definite
reasons.
Tested and approved by RADIO BROADCAST
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A receiving set is no better than its tubes.
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R343. ELECTRON TUBE RECEIVING SETS. KKHVERS.
QST. Jan. 1926, pp. 17-20. Reflex.
"A New Reflex Circuit", L. W. Hairy.
A reflex circuit using good high primary-impedance audio
transformers and proper bypass condensers, is described.
Distortion is prevented also by reflexing through a radio
frequency tube with a shunt rather than a series audio fre-
quency connection. The method and circuit arrangement
in a two- and three-tube set are discussed in some detail.
R344-3 TRANSMITTING SETS. TRANSMITTERS.
QST. Jan. 1926, pp. 21-25. Crystal Controlled
" Practical Crystal Controlled Transmitters' .
A description of crystal controlled transmitters operating
from a d.c. as well as a. c. source of supply is submitted
Complete constructional details of the crystal controlling
station at 4 XE are given. It operates from a d.c. sourceusingan
ux-2io and three 2O4-A tubes. The a. c. crystal controlled
set described operates, with two ux- 210 and two 2O3-A tubes.
Method of mounting the crystals and certain precaution^
are necessary in handling them, according to the author.
R402. SHORT WAVES SHORT-WAVE
QST, Jan. 1926, p. 28. TRANSMITTERS.
"Getting |")own Below Five Meters", H. Lyman.
Several circuit diagrams with constants of transmitters
suitable for the very high frequency bands used by amateurs,
are given.
Rooy. REGULATIONS CONFERENCE,
QST. Jan. 1926, pp. 33-16. Fourth National.
"The Fourth National Radio Conference", K. B. Warner.
A survey of the transactions and recommendations made by
the various committees at the Fourth National Radio Con-
ference, is given. Several changes in the allocation of fre-
quencies were proposed, including amateur phone operation
on the 3500-3600 kc band (8^.7-83.3 meters). Broadcasting
conditions are to be placed on a higher plane than heretofore,
through elimination of some of the stations and adoption of
new regulations govering their operation. The new frequency
assignments from 550 kilocycles up (545 meters down) are also
published in this summary.
R6io. EQUIPMENT; STATION DESCRIPTION. STATIONS,
Radio. Jan 1926, pp. 10-1 i. Portable.
"The Radio Detective".
A car, completely equipped with necessary transmitter and
receivers for use in connection with the radio supervisor's work
in the 8th district, is described and illustrated. A Kolster
direction finder, short- and long-wave receivers of various
types, a 50-watt transmitter, and equipment for giving
license examinations anywhere, make this portable radio
station a modern radio supervisor's office on wheels. The
diagram of the field strength measuring set is shown, and
constants of the circuit given.
R343- ELECTRON TUBE RECEIVING SETS. RECEIVER.
Radio. Jan. 1926, pp. i2ff. LC Modified
"An Exceptional Four-Tube Receiver", E. E. Turner.
A four tube receiver, r. f. stage, regenerative detector, and
two stages of audio amplification, is described. The wiring
diagram shows several unique features, which are also taken
up in the general discussion. Among these is the method of
controlling oscillations in the regenerative circuit. Data
on coil construction and panel layout, serve as a guide to
building the set. An ABC eliminator may be used with the set.
the wiring diagram of the complete circuit being shown.
This set is a modification of the LC circuit described in the
October, 1025, issue of Radio.
R53I.2. STATION CALL LETTERS STATIONS,
Radio. Jan. 1926, p. 22. Short-wave.
"Short-Wave Stations".
A complete list of short-wave stations both, limited com-
mercial and general public, operating in the United States,
is given. There are forty-six in all. The inclusion of class,
frequency, wavelength, owner, power, and call, makes this
table a most complete reference guide.
R3y6.3 LOUD SPEAKING REPRODUCERS. LOUD SPEAKERS,
Radio. Jan. 1926, pp. 24ff. Hornless.
"Hornless Types of Loud Speakers", Dr. J. P. Minton.
The author enters into a detailed discussion concerning
the general types of loud speakers now used. The new
cone type speakers make use of large vibrating surfaces. Flat
surfaces may be used to obtain good sound vibrations over
a large frequency range, but shaping such surfaces into the
form of a cone gives greater rigidity and less natural resonance,
at the same time rendering also better acoustic radiation.
Three types of driving units jhave been employed in the
commercial cone speakers; electro-dynamic, balanced arma-
ture, and bipolar unit. These are discussed in detail.
R383. RESISTORS.
Radio. Jan. 1926, pp. ijft.
"Vacuum Tube Resistors",
RESISTORS,
Vacuum Tube.
, G. F. Lampkin.
Vacuum tubes, in addition to being used as detectors,
amplifiers, and oscillators, may be used as variable resistors
to very good advantage. As such they have several advan-
tages not found in grid leaks or regular resistances. They
are especially good as a grid leaks in an oscillator to control
keying and phone transmission. Data on actual tests made
with 201-A and 202 tubes, and information concerning their
uses as grid leak resisters, are given.
Ri48. MODULATION. MODULATION,
Radio. Jan. 1926, pp. 31-32. Methods.
"Speech Modulation Methods", Lieut. J. B. Dow.
Three methods of speech modulation, the variable ab-
sorption method, grid voltage variation method, and the
plate power variation method, are taken up. Several circuits,
including the Meissner and a combination Heissing and
Colpitts, are shown, and an account of their performances
discussed in some detail.
R.343- ELECTRON TUBE RECEIVING SETS RECEIVERS,
Radio. Jan. 1926, p. 33. Sbort-tt'ai-c.
"A Good Short-Wave Receiver", F. C. Jones/1
For use on the very high frequency stations, a receiver
must be capable of sharp yet not too sensitive tuning. Herein
is described a two-tube receiver operating on the capacity
feedback principle, the tube capacity being large enough for
this purpose, Oscillations are controlled by means of a tuned-
plate circuit. Constructions! data and circuit diagram are
given.
RADIO BROADCAST ADVERTISER
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R343- ELECTRON TUBE RECEIVING SETS. RECEIVERS,
Radio, Jan. 1926, pp. 2gff. Reflex.
" Proper Reflex Circuit Assembly, '* L. W. Hatry.
Some very good points on the construction of a three-tube
reflex receiver are contained in this article. The use of con-
densers and choke coils, and valuable suggestions pertaining
to the circuit layout, accompany the article.
Rs53. METEOROLOGICAL SIGNALS. EARTHQUAKE
Radio. Jan. 1926, pp. 35ff. t RECORDING.
" Radio as an Aid in Recording Earthquakes," G. M. Best
An account is given of a method of recording earthquake
tremors automatically and accurately. Both the horizontal
and vertical components of such tremors can be recorded, the
exact time of such tremors being received from some naval
time-signalling station and recorded on the same chart. A
circuit diagram of the apparatus is shown.
R8oo (533). SOUND. PHONOGRAPH
Popular Radio. Ian. 1926, pp 3-0. REPRODUCTION.
"The New Wave-Transmission Phonograph," H. C.
Harrison.
Principles developed in the mechanical reproduction of
sound by Bell Telephone engineers, have been applied to
the phonograph, with the result that now five and one-half
octaves are faithfully reproduced instead of three, as was the
case in the old type of phonograph, according to the article.
The construction of the new reproducer is described and
shown in a diagram. Comparison is made between electrical
and mechanical constants, the similarity being very evident.
R343. ELECTRON TUBE RECEIVING SETS RECEIVER,
Popular Radio. Jan. 1926, pp. 10-23. LC-26
"How to Get the Most out of Your LC-26 Set," S. G.
Taylor and L. M. Cockaday.
Information is given concerning the theory and operation
of the LC-26 receiver described in the December issue of
Popular Radio. Details pertaining to antenna and ground con-
nection, tubes and batteries to be used, installation, equipment,
and operation of the receiver, are given. A shunt-plate feed
unit, which keeps the d. c. out of the loud speaker, is a feature
of this circuit.
R8oo (530) PHYSICS. ATOM.
Popular Radio. Jan. 1926, pp. 24-29
"The Atom," Sir William Bragg.
The place that the separate atoms take in forming crystals,
is outlined. Most substances crystallize in very orderly and
regular fashion. X-Rays are used in analyzing transparent
solids of crystaline structure to determine their arrangement.
Examples and illustrations are given to show how atoms may
arrange themselves and how X-Rays detect this arrangement.
R382. INDUCTORS. INDUCTION
Popular Radio, Jan. 1926, pp. 30-39. COILS.
" Some New and Useful Facts about Coils, " D. R. Demons.
A discussion pertaining to distributed capacity of induction
coils, employing various types of windings and materials
for mountings, is given. The distribution and strength
of The fields of magnetic and electrostatic forces, depending
upon the kind of insulation used about the wire, is illustrated
by means of graphs and diagrams, A lot of experimental
data is given.
R38i . CONDENSERS. CONDENSERS
Popular Radio. Jan. 1926, pp. 48-55. F9R TUNING.
"The Part That Your Condenser Plays in Tuning,"
H. J. Harries.
Condensers of the circular plate, the square-law plate,
and the straight line frequency plate, are compared. The
effect each one of these condensers has on sharpness or broad-
ness of tuning covering the present broadcast band, is shown
by curves, data, and discussion. A low minimum condenser
is really not what is desired in the opinion of the writer, but
rather a condenser having a low resistance path at high
frequencies.
R38o. PARTS OF CIRCUITS; INSTRUMENTS. TONE METER.
QST. Jan. 1926, pp. 37-39-
-The tone Meter," L. j. Wolf.
A device indicating the condition of the plate supply current
of vacuum tube transmitters, is described. Any source other
than a high voltage storage battery will give a more or less
fluctuating power supply which necessitates filtering. An
a.c. voltmeter is used in series with a condenser, the condenser
preventing the d. c. from getting through the meter and acting
also as a multiplier. The multiplying factor depends on the fre-
quency, the capacity of the condenser, and the resistance of the
voltmeter. Its value can be determined, as described. The
entire arrangement is called a Tone Meter.
R375- DETECTORS AND RECTIFIERS. RECTIFIER,
QST. Jan. 1926, pp. 4iff. Epom.
"The Epom Rectifier and Filter," R. S. Kruse.
The new Epom rectifier tube uses no filament but operates
on the principle of ionization of a gas at low pressures within
the tube. Argon gas is used for several reasons. The
construction of the tube, and the circuit diagram are described .
The tube may be used as a d. c. source of plate supply in
transmitting tubes if properly loaded.
R28i.7i. QUARTZ. QUARTZ CRYSTAL
Radio News. Jan. 1926, pp. 9^2 ff. CONTROL.
"Quartz Crystals Control Wavelengths of Broadcasting
Stations," S. R. Winters and I. F. Byrnes.
The use of quartz crystals in the control of frequencies in
broadcasting stations is growing, as is evidenced by the de-
cision of the Westinghouse Company, and the General Electric
Company, i. e., to equip all of their stations with this piezo-
electric mineral, according to the authors. Its properties,
operation in circuits, the use of harmonics produced by such an
oscillating crystal, methods of mounting, and results obtained
by the Navy and others, indicate that the quartz crystal will
be in general use among transmitting stations before long.
HIGH FREQUENCY
SYSTEMS.
," Dr. A. Hoyt
R4O2. SHORT-WAVE SYSTEMS.
Radio News. Jan. 1926. pp. 9S4ff.
"Navy Investigates Ultra Frequ
Taylor.
The investigation carried on by the Naval Research
laboratory with ultra frequencies is presented in graphic
and systematic form. Night and day range, comparison of
phenomena at various frequencies, and directional effects,
show that certain bands of frequencies should be chosen for
definite transmission schedules depending upon time, distance,
and season.
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Rii3. TRANSMISSION PHENOMENA. FADING AND
Radio News. Jan. 1926, pp. 956 ff. DISTORTION.
"Unraveling a Broadcast Enigma"., A. Van A. Summers.
Many data on fading and distortion of signals from
broadcasting stations, which were accumulated by the Amer-
ican T.& T Company are presented. Conclusions arrived at
indicate that the ether is not a perfect carrier of electro-
magnetic waves, especially when these waves are near large
masses of iron and steel. Refraction and absorption are
probably the causes for most of the distortion observed.
The author discusses at some length the conclusions arrived at
through these experiments.
Rii4. STRAYS. AURORA BOREALIS.
Radio News. Jan. 1926, pp. 064 ff.
"New Facts About the Aurora Borealis", C. L. Davis.
An experiment relating the effect of the Aurora Borealis on
a telephone line, and the subsequent conclusions drawn from
this phenomenon, are described. A frequency of one cycle for
fifteen minutes was noted on a voltmeter.
Rno. RADIO WAVES
Radio News. Jan. 1026, pp. 066 ff.
Are Radio V
INDUCTION
COILS
RADIO WAVES.
.. io Waves? ", I . Riley.
An elementary explanation of the nature of radio waves, is
given. Stress and strain, displacement of f elds, electrostatic
and electro-magnetic fields of force, questions on radiation,
current and voltage relations in antennae, are some of the
subject? d:scussed.
R 1 34.45. SUPER REGENERATIVE ACTION.
SUPER-REGENERATIVE
Radio News. Jan. 1926, pp. 976 ff. ACTION
"Super Regenerat:on and the Future", A. K. Laing.
The original Armstrong super regenerative circuit, modified
somewhat, is presented, with points on construction and
operation given. These, it is claimed, will make this type of
amplification as popular as the super-heterodyne. The
drawbacks of _the circuit are enumerated and taken up in
detail. The circuit is said to give much more amplification
on the higher frequencies than on the low ones.
RH4.75. SUPER-HETERODYNE. SUPER-HETERODYNE.
Radio News. Jan. 1926, pp. 082 ff.
"An Improved Laboratory Super-Heterodyne"
F. R. Pfaff.
A seven-tube super-heterodyne covering the frequencies
from 5 5pkc. to ;oookc. (5 50 to 50 meters) using plug-in coils,
is described. The oscillator is connected ahead of the first
detector in this circuit. Complete constructional data are
given.
RjSz. INDUCTORS.
Radio News. Jan. 1926, pp. 086 ff.
"Which Type of Coil is Best?",
An exhaustive study of various types of coils, dealing with
their overall efficiency, is presented. Circuits used in the
measurement of resistance at high frequencies, graphs showing
the efficiency and distributed capacity of coils and the result
obtained through experimental hookups, are discussed. The
best all around coil, according to the writer, consists of
ordinary bell wire wound on a bakelite tube in the regular
fashion.
R2OI.7 USE OF HIGH-FREQUENCY OSCILLOGRAPH. TUBES,
OSCILLOGRAPH
Radio News. Jan. 1926, pp. o88ff. W.E.
"The Cathode Ray Oscillograph In Radio Work",
Dr. C. B. Bazzom.
The author reviews the elementary principles concerning
electric waves and their forms, referring to pitch and quality
of sound as an analogy. To study these wave forms, the
cathode ray tube, illustrated, is of great importance in high
frequency circuits. The tube used here was developed bv
the Western Electric Company. Electric and magnetic
deflections of the electron stream through plates and coils
near these electrons, picture the resulting wave forms for
closer analysis. Lissajou figures produced, enable the
experimenter to synchronize circuits or adjust them to manv
different ratios of oscillations.
R343 ELECTRON TUBE RECEIVING SETS, RECEIVERS,
Radio Progress. Dec. 15, 1925.00. !3ff. Deresnadyne.
"Revamping a Popular Radio", H. J. Marx.
An analysis of the five-tube Deresnadyne receiver is given,
showing the wiring diagram and method of operation. This
receiver is equipped with a B-eliminator, and trickle charger for
the A battery; the speaker is built in the cover, thus making
this set complete. Oscillations are prevented in the tuned
radio frequency stages by controlling the plate voltage
on the tubes through a series resistance. The coil angle may
also be varied, depending upon the type and characteristic
of the tubes used. Other details of operation are mentioned.
R342.7. AUDIO-FREQUENCY AMPLIFIERS. AMPLIFICATION.
RADIO BROADCAST. Jan. 1926, pp. 308-312. Audio Fre-
quency.
"The Requirements for Better Audio Amplification,"
K. Clongh.
An analysis of the various instruments used in sound pro-
duction show that a good amplifying device should respond
equally well to frequencies from 32 to 8192 cycles or more.
A full logarithmic scale is considered best in plotting charac-
teristics of amplifying units. Of considerable importance
are the characteristics of the tubes used in audio amplifiers,
and good results are obtained only when the entire amplify-
ing unit is tested as one device. It is stated that in the
present type of resistance-coupled units, the lower notes are
somewhat suppressed. Transformers having a cruciform
core construction seem to give best results. Reference is
made to Mr. Crom's article on audio amplification in the
Oct., 1925, RADIO BROADCAST.
R342.6. RADIO-FREQUENCY AMPLIFIERS. R. F. AMPLIFIERS,
RADIO BROADCAST. Oscillations in.
Jan. 1926. pp. 3wff.
" Methods for Controlling Oscillation in R. F. Circuits."
J. Bernard.
Many methods are used in r. f. amplifiers to prevent tubes
from oscillating or to control oscillations. Some of these
are discussed briefly by the author. A somewhat novel
method is employed in the "Counterphase" circuit, diagram-
med and described here. This scheme makes use of a com-
bined resistance and capacity control, and is considered very
effective over the entire range of frequencies to which the re-
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The International Tests
AS MIGHT be expected, we were
**• simply inundated with letters from
all quarters of the country and abroad,
after the recently concluded International
Tests. Space limitations permit the publi-
cation of only three or four here, but these
convey the sentiment expressed in the
letters of many other correspondents.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
I hear over KCO'S news items that California
was silent during the test period. I wish to
refute this statement for I distinctly heard KNX,
Hollywood, on two different occasions while
trying for British stations. ... I think
KNJ was on the air too, for 1 heard a station at a
setting on my dials where this station usually
comes in, but I could not be positive about this.
There is nothing too small for California to do.
Very truly yours,
F. W. DALLEY.
Lyons, Colorado.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
Just a line in appreciation of last week's
silence tests, especially those of Friday and
Saturday evenings. Is it possible to have an
arrangement for regular zonal silence periods,
thus allowing uninterrupted sectional exchanges
of programs? Here is one unsolicited vote in
favor of such a scheme.
Very truly yours,
R. M. BOULDEN,
Los Angeles, California.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
Organize an anti-bloop club with a big turn-
out at first meeting. What are the other cities
doing along this line?
Very truly yours,
E. M. RAY,
Rochester, Minnesota.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
I am a regular reader of your excellent maga-
zine, and am also a confirmed radio fan, being
interested in the reception of both broadcast
matter and code. I was greatly interested in the
International Tests, although they were a failure
as far as I am concerned. In 1924, I received
British stations with a modified three-tube
Reinartz set. This year, nothing but interfer-
ence, static, bloopers, and almost everything
injurious to satisfactory radio reception. One
thing that has come to my attention is that dur-
ing the period from half-moon until the moon
begins to wane, radio reception is not what it
should be — it is noisy. At other periods, when
there is no moon, reception is much better, I
have found. During Test Week, the moon was
pretty well full. I have been watching this
phenomenon since last July. I wonder if any
one else has noticed it. Wishing you continued
RADIO BROADCAST ADVERTISER
717
For 'Better <Rjidio Reproduction
Hear this
World-Wide
Favorite
Creation of Alfred Graham & Co., Eng-
land, 38 years experienced in producing
loud speaking devices, Amplions lead
in sales throughout the world. Hear an
Amplion— in comparison! Six models.includ-
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plugs, $12 up. Write for Amplion
Pedigree."
THE AMPLION CORPORATION;
OF AMERICA
Suite L, 280 Madison Avenue, New York
Chicago Branch: 27-29 No. Morgan St.
Burndept of Canada. Ltd. , Toronto
Radio's Newest
'on need thil big FREE book. I
BARAWIKCO.
102-109 S. Canal St., Chicago I
Pocket Meters
Hoyt
Type 51
Pocket Meter
The indispensable pocket instrument for Dealers
and Radio-Owners for checking the condition of A
s up 1
and'a
peres. All scales are hand -co. libra led, resistance of
meter is unusually high for this type, accuracy
does not vary in extreme heat or cold.
Finished in polished nickel, of small size, con-
venient for handling. .^fc
Price, complete with lead #3.00 ^^
BURTON-ROGERS CO.
26 Brighton Ave. Boston, Mass.
National Distributors
HOYT makes a complete line of Radio Meters.
Send for booklet "HOTT Meters for Radio"
and
Volume Control
ESSENTIAL to thoroughly enjoy present
day broadcasting. New high-priced sets
feature tone control as their greatest im-
provement. You can have this new feature
in your old set by attaching a Centralab
Modulator Plug in place of the old phone
plug. Takes a moment — no tools required.
Gives any degree of tone volume from a
whisper to maximum by simply turning
the small knob on plug. Static interference
is reduced and programs come in clear and
true with just the volume you most enjoy.
Order from your dealer, or mailed
direct on receipt of the price $2.50,
CENTRAL RADIO LABORATORIES
22 Keefe Ave. Milwaukee, Wisconsin
Centralab Radiohms or Modulators
are standard controls on sixty 'Six
well-known sets.
Gentmlab
DIAMOND-WEAVE
(TRADE-MARK REGISTERED Aug. 4, 1925)
SICKLES
COILS
Sickles Coil Set No ISA for Roberts
Circuit, containing our new center-
tapped N-P Coil. Price $8.00.
Sickles Coils for the "Aristocrat"
Circuit, designed upon new scientific
discoveries, set highest standards of
efficiency.
COIL PRICES
No. ISA Roberts Circuit $ 8.00 set
No. 24 Browning-Drake 7.50 set
Craig Circuit 4.50 set
Acme Reflex 4.50 set
Knockout Reflex 4.00 set
Hoyt Circuit 10.00 set
"Aristocrat" Circuit 8.00 set
No. 20
No. 19
No. 8
No. 21
No. 25
For the "Aristocrat,"
Browning-Drake, Roberts,
Craig, and Hoyt Circuits
(Patented Aug. 21, 1923)
Our Coil Set No. 25 is specifically de-
signed for the new "Aristocrat" Circuit,
already very popular.
Compactness of form, rigidity of con-
struction, and the supremely efficient
Diamond-Weave method of winding are
well-known characteristics of Sickles
Coils.
These refinements of design and con-
struction result in low distributed ca-
pacity, low dielectric losses and large
range of frequency with small variable
capacity.
There are Sickles Diamond Weave
Coils for all leading circuits.
Send for descriptive catalog
The F. W. Sickles Co.
132 Union Street
SPRINGFIELD, MASS.
Tested and approved by RADIO BROADCAST
718
RADIO BROADCAST ADVERTISER
12-Cell-24-Volt
Storage'B'Battery
Positively given free with each
purchase of a WORLD "A"
Storage Battery. You must
send this ad with your order.
WORLD Batteries are famous
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and service. Backed by years
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Equipped with Solid Rukbtr Case.
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age. YoupaveoOpercentaodBeta
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"tell their friends." That 'a our bent Proof
of performance, bend your order in today.
Solid Rubber Case Radio Batteries
6-Volt. 100-Amperea 511.25
6-Volt. 120-Amperes. ..... 13.25
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Solid Rubber Case Auto Batteries
6-Volt, ll-Plate $11.25
6-Volt. 13-' late .
12-Volt, 7-.'Iate . 16.OO
Send No Money fc'
• 17 order la I
subject to S
ill ehiDday order is rec
press C. O D., subject to your examination
on arrival. FREE "B" Battery included.
Approved
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torlea, Popular
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WORLD BATTERY COMPANY
1219SO. WabasliAve., Dept. 24 CHICAGO, ILL.
World
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S. t your Radio Dials mt 210
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tation. WSBC. Chicago.
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A real guide. Shows fac* I
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BARAWIKCO.
102-109 S. Canal St. Chicago
" It gets
that
last
mile"
IRGAP
SOCKET
Will rid your set of those squawks,
howls and frying noises. They pre-
vent closed circuit absorption of cur-
rent, inter-coupling of circuits,
feedback and undesirable capacity.
THEY MAKE ANY CIRCUIT more
stable and sharpen tuning, resulting
in purer and clearer tones with more
volume particularly on distant
stations.
At all dealers 75c each
Sent direct if your dealer cannot
supply you.
AIRGAP PRODUCTS CO. MFR. <\.
188 N. J. R. Rd. Ave., „
Newark, N. J. e^Y~ .,
success, and next year — or whenever you decide
to have another week of international tests —
let's hope that there will not be so many bloopers
If they all make sets described in RADIO BROAD-
CAST, there certainly will not be.
Very truly yours,
G. JOHNSON.
Bloomington, Illinois.
A Setback to the Florida Boom
IN MANY districts code interference has
been materially reduced through a gen-
eral cooperative campaign of the news-
papers and magazines which circulate
in those areas, in which pressure was
brought to bear on the offenders. There
are still too many districts, however, where
broadly tuned transmitters are a source of
constant annoyance to listeners of both
local and distant broadcasting stations.
The Florida peninsula, it would appear,
from this letter suffers badly from coast to
shore interference.
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
Sir:
Ship to shore transmission is responsible
in this locality for the worst form of interference
encountered. "Sparks" will sit on the key
at just about the time the broadcast program is
at its best, and often it seems as if he had held
up his work to fill the air between then and
twelve o'clock. The wonderful New Year's
treat from wjz was perfect as regards volume
and modulation, but all through the stellar offer-
ing of McCormack and Bori there was only one
brief song not ruined by code.
Very truly yours,
FREDERIC B. HYDE,
Miami, Florida.
A Letter from the Philippines
^TAKING Horace Greeley's "Go West"
1 thoroughly to heart, apparently irre-
spective of any human element, one copy
of RADIO BROADCAST has monthly wended
its weary way right out to the Philippines,
there, we presume from that so enthusi-
astic letter following, to be eagerly read by
at least one "satisfied customer." The
letter:
Editor, RADIO BROADCAST,
Doubleday, Page & Company,
Garden City, New York.
SIR:
I have already received the new size November
and December numbers of the RADIO BROAD-
CAST. I want to congratulate you on the
progress and success your magazine is making.
It is the best magazine of its kind that I have
ever yet seen and so cheap that anybody can
afford to subscribe. Its articles are very inter-
esting and highly instructive. Its hook-ups are
all "knockouts."
Before I subscribed to this magazine ! hadn't
an inkling of radio; now I am proud to say that
I am the first home-constructor in this province.
The department "For the Radio Beginner"
should be continued as it is always very instruc-
tive to the novices and fans.
Wishing you a prosperous year for RADIO
BROADCAST.
Very truly yours,
JUAN CARBALLO.
La Carlota, Philippines.
f Tested and approved by RADIO BROADCAST -
Convert your present
radio receiver into a
light socket set with a
Balkite Trickle Charger
and Balkite "B"
FANSTEEL PRODUCTS CO., Inc.
North Chicago, Illinois
Thorola Receivers
and Speakers *
Must Outperform
Reichmann Company, 1725-39 W. 74th St., Chicago
fbe Distortionless Jfmp/ifi
Insure distortionless amplifications and a clarity
of tone not obtained through any other resistance.
All capacities 12,000 ohms and up. List price $1.50.
Special sizes to order. Write for full information.
Crescent Radio Supply Co. 1-3 Liberty St., Jamaica. N. Y.
$6.50
APOLLO
Parlor Model
Stands 22 inches high,
has a ten inch bell, gives
faithful reproduction
and may be varied from
a whisper to a torrent
of sound by the adjust-
able unit control with-
out the least loss of the
sweet mellow. clear tones
that are found in the
Apollo Speakers. Mail
orders promptly filled.
Send no money, just
pay the poitman.
HARD RUBBER PANELS
Size
10..
12..
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18.
21. .
24. .
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Rix Radio Supply House, Inc.
5505 Fourth Ave. Dept. 45 Brooklyn, N. Y.
THE Dependable B-POWER
'"i.
Replaces Your "B" Batteries Permanently
A PER installing the All 'American "Constant-!?"
you need only snap the electric switch to have
permanent and constant plate power for your radio,
direct from the light socket. With it there is no ruin-
ous acid, no hum — nothing but the pure, full tone that
is only possible when the "B" voltage is constantly
up to standard. Write for descriptive folder showing
how to use "Constant'B" with any set.
Price $45
COMPLETE WITH
RAYTHEON TUBE
ALL-AMERICAN RADIO CORPORATION
Pioneers in the Radio Industry
4213 BELMONT AVENUE, CHICAGO, U. S. A.
Complete instructions for building a similar
"Permanent Plate Supply Unit" may be had
free upon request. Specify Bulletin B-82.
*j( Tested and approved by RADIO BROADCAST
^Another
Model
?cNew and Improved/
FRESHMAN
SASTERPIECB
The World's Greatest
Radio Receiving Set
Freshman's latest sensation has a real ap-
peal to the women of the home. It is built
of five-ply genuine mahogany; a handsome
piece of furniture that fits in any corner of
the room. It is compact and comparatively
small, giving it preference over clumsy con-
soles. Contains an especially large tone
chamber.
With Built-in Loud Speaker of
Great Volume and Superb Tone
When not used as a radio it can be entirely
closed. The top is stationary and provides
an attractive resting place for vases and
other ornaments. Spacious compartments
afford ample room for all batteries, etc.—
not a single wire being visible.
THE RADIO RECEIVER WOMEN
HAVE BEEN WAITING FOR-
Prices slightly highfr Denver and West and Canada
Sold on Convenient Terms by Authorized Freshman
Dealers Who Also Install and Service Them
CHAS. FRESHMAN CO., Inc.
2626 W.
, New York
Blvd., Chicago
Tested and approved by RADIO BROADCAST
THE COUNTRY LIFE PRESS, GARDEN CITY, NEW YORK
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