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iKattaaa  (Ettij 
lubltr  library 


From  the  collection  of  the 


Prejinger 
v    ijibrary 


San  Francisco,  California 
2007 


33CENTS 


How  to  Build  a  Two-Stage  Radio-Frequency  Amplifier 

THE  MARCH  OF  RADIO* ub^nLs^c^ 
.  New  Method  of  Transmitting  Pictures  by  Wire  or  Radio 


N 


OUBLEDAY,  PAGE  &  COMPANY 


GARDEN  CITY,  NEW  YORK 


Two  Strikes 
Three  Balls! 

The    pitcher    has   com- 
pleted that  slow,  leisure- 
ly, tantalizing  wind-up. 
That  long,  lithe,  million 
dollar   arm   has  flashed 
back.       A   moment  .  .  . 
and  the  ball,  a  white,  hissing 
streak,  is  catapulting  toward 
the  catcher's  waiting  mitt. 
And  the  winning  or  losing  of 
a   World    Series   depends   on 
whether  or  not  the  batter  has 
his  eye  on  the  ball. 


A  Cunningham  Tube  always  has 
its  eye  on  the  ball.  It  stands  ready 
to  transmute  an  electrical  impulse, 
traveling  at  a  speed  which  would 
make  the  speed  of  a  baseball  seem 
a  snail's  pace,  into  music,  a  Pres- 
ident's message— what  you  will. 


Since  1915- 

Standard  for  All  Sets 


Types  C-301A:  C-299:  C-300:  C-ll:  C-12,  In  the  orange  and 
blue  carton. 

Price  $3.00  each 


RADIO  /y  TUBES 


Patent  Notice:  Cunningham  tubes  are  covered  by  patents  dated  2-18-08.  2-18-12.  12-30-13.  10-23-17.  10-23-17  and  others  issued  and  pending 


^  Tested  and  approved  by  RADIO  BROADCAST  if 

Bound  OEC     1    1921 


RADIO  BROADCAST 


VOLUME  VII 

MAY,  1925,  to  OCTOBER,  1925 


BETTER  RADIO 


GARDEN  CITY  NEW  YORK 

DOUBLEDAY,  PAGE   &  COMPANY 

1925 


Copyright,  1925,  by 
DOUBLEDAY,  PAGE  &  COMPANY 


RADIO 
BROADCAST 


Vol.  7,  No.  i 


May, 


A  New  Method  of  Transmitting 
Pictures  by  JVire  or  Radio 


A  Review  of  Existing  Methods  of  Sending  Photographs — Details 
of  the  Cooley  System  Never  Before  Published — An  Efficient  and  Very 
Fast  Transmitter  Whose  Applications  are  Many  and  Important 

By   CHARLES   C.   HENRY 


I 


MAGINE,  a  hundred  messengers  deliver- 
ing photographic  reproductions  of  busi- 
ness letters,  photographs,  printed  matter, 
legal  papers,  social  correspondence,  and 
nnumerable  forms  of  communication  received 
from  distant  points  by  a  single  instrument. 
The  instrument  that  will  accomplish  this 
is  already  known  to  many  as  a  phototelegra- 
phic  receiver.  Few  even  of  those  who  have 
followed  the  recent  developments  in  photo- 
"elegraphy  appreciate  the  huge  commercial 

d  economic  importance  it  will  have  in  the 
ujar  future. 

.  Most  of  us  read  with  interest  the  accounts 
of  the  transmitting  of  photographs  across  the 
Atlantic  and  admired  the  engineering  achieve- 
ment of  reproducing  them  with  such  fidelity 
here  in  America.  In  hundreds  of  magazines 
and  papers,  copies  of  the  received  pictures  of 
President  Coolidge,  Secretary  Hughes,  the 
Prince  of  Wales,  and  others  were  prominently 
displayed. 

The  whole  world  has  heard  about  the  trans- 
mission of  the  1924  Republican  Presidential 
Convention  pictures  by  the  American  Tele- 
phone and  Telegraph  Company.  The  quality 


of  the  pictures  received  in  New  York  from 
Cleveland  compare  favorably  with  the  aver- 
age newspaper  picture. 

The  Chicago  Tribune,  the  New  York  Daily 
News,  and  the  Los  Angeles  Times  have  been 
tied  together  for  several  months  with  the  Mar- 
vin Ferree  system  of  phototelegraphy  operat- 
ing over  leased  telegraph  lines.  Pictures 
are  exchanged  daily  between  these  prominent 
newspapers  and  appear  in  their  columns  beside 
other  news  pictures.  There  is  no  noticeable 
difference  in  quality  between  the  two.  The 
trade  name  "Telepix"  is  attached  to  all  of 
these  telegraphed  photos. 

Not  long  ago,  C.  Francis  Jenkins,  of  Wash- 
ington, D.  C.,  conducted  radio  phototrans- 
mission  experiments  between  Anacostia, 
Maryland,  and  Medford  Hillside,  Massa- 
chusetts. His  received  pictures  were  badly 
mutilated  by  commercial  radio  telegraph 
traffic  because  of  the  particular  wavelength 
used;  but  with  better  radio  facilities  at  his  com- 
mand, it  is  likely  that  his  test  pictures  would 
have  been  quite  successful. 

Edouard  Belin  is  at  present  in  New  York  en- 
gaged in  the  intensely  interesting  experiment 


20 


Radio  Broadcast 


of  attempting  to  re- 
ceive radio  photo- 
grams  from  a  Paris 
station.  The  St. 
Louis  Post-Dispatch 
and  the  New  York 
World  have  closely 
followed  and  sup- 
ported his  work  for 
many  years.  Using 
his  system,  these  two 
newspapers  trans- 
mitted pictures  with 
great  success  last  De- 
cember between  St. 
Louis  and  New  York 
City. 

Those  engaged  in 
this  work  of  photo- 
telegraphy are  racing 
with  each  other  in 
their  attempts  to 
build  up  the  first 
strong  commercial 
foundation.  It  seems 
evident  that  the  com- 
mercial field  will  be 
limited  to  one  or  two 
systems.  It  is  quite 
possible  that  the 
ultimate  system  will 
be  made  up  of 
contributions  by  the 
many  scientists  now  engaged  in  the  work. 

Millions  of  dollars  have  been  spent  for  the 
development  of  phototelegraphy  by  those 
who  appreciate  its  adaptability  to  handling 
communications  of  all  kinds,  whether  it  be 
photographs,  drawings,  script,  or  printed 


Thirty-Seven  Seconds  for  a 
Picture 

The Cooley  system, described  in  Mr.  Henry's 
article,  is  capable  of  transmitting  a  five-by- 
seven-inch  half-tone  photograph  or  a  line 
drawing  over  a  perfect  wire  line  in  thirty- 
seven  seconds.  There  are  other  methods  in 
present  use  which  send  photographs  by  radio 
and  by  wire,  but  the  time  consumed  is  from 
four  to  fifteen  minutes.  Speeding  up  the 
transmission  involves  very  great  technical 
problems.  Notable  among  these  are  the 
systems  of  the  Radio  Corporation,  the 
American  Telephone  and  Telegraph  Com- 
pany, Marvin  Ferree,  Edouard  Belin,  and 
C.  Francis  Jenkins.  RADIO  BROADCAST  is 
proud  to  present  this  story  of  Mr.  Cooley's 
achievements,  particularly  because  much  of 
the  development  work  was  done  in  its  own 
Laboratory. 

Every  sign  points  toward  the  early  per- 
fection of  a  commercially  practicable  system 
of  phototelegraphy  whose  aid  and  influence 
in  industry  will  be  incalculable.  RADIO 
BROADCAST  believes  the  technical  attain- 
ments of  Mr.  Cooley's  system  are  of  the  great- 
est importance.  Every  reader  who  is  inter- 
ested in  general  scientific  progress  and  all 
those  engaged  in  developing  radio  and  wire 
communication  will  read  of  what  has  been  done 
with  the  deepest  interest. — THE  EDITOR 


matter.  The  speed  at 
which  typewritten 
messages  may  be 
transmitted  over  such 
a  system  is  so  great 
that  one  set  of  ap- 
paratus could  handle 
all  the  messages  go- 
ing between  New 
York  and  Boston, 
which  are  now  being 
tV  a  n  s  m  i  1 1  e  d  over 
thirteen  lines  of  au- 
tomatic printing  tele- 
graph. The  adapta- 
tion of  phototelegra- 
phy to  transoceanic 
radio  communication 
will  not  only  speed 
up  the  service  but 
will  tend  greatly  to  re- 
duce the  unfortunate 
effect  that  static  now 
has.  In  the  present 
system,  letters  form- 
ing the  words  are 
coded  into  dots  and 
dashes  and  sent  very 
rapidly.  A  bad  crash 
of  static  will  com- 
pletely destroy  one  or 
more  words.  Such 
a  crash  of  static 

would  only  mar  portions  of  letters  from 
different  words  if  the  message  were  trans- 
mitted by  phototelegraphy.  To  meet  the 
keen  competition  of  the  cables,  transoceanic 
radio  companies  must  adapt  some  system 
that  will  insure  reliability  and  at  the  same 


MOUNT    RAINIER,    IN   WASHINGTON 

Transmitted  by  the  Cooley  system.     Much  of  the  recent  development  work  on  this  system  which  was  started 
in  Cambridge,  Massachusetts,  in  1922,  was  done  in  the  Laboratory  of  RADIO  BROADCAST  at  Garden  City 


A  New  Method  of  Transmitting  Pictures  by  Wire  or  Radio          21 


time  increase  the  capacities  of  their  present 
stations. 

HOW    PICTURES    SOUND 

IF  YOU  should  ever  listen  to  radio  signals 
that  are  serving  to  transmit  photographs, 
you  will  hear  a  buzz  of  constant  pitch  but  of 
varying  intensity.  The  variations  in  in- 
tensity seem  to  repeat  every  second,  or 
probably  oftener,  but  each  repetition  will  be 
slightly  different  from  the  previous  buzz. 
Each  impulse,  that  goes  to  make  up  the  buzz, 
represents  the  light  coming  from  a  tiny  area 
on  the  picture  being  transmitted.  Every  one 
knows  that  newspaper  prints  are  made  up  of 
thousands  of  tiny  dots.  In  light  places  on  the 
pictures,  these  dots  are  very  small.  The 
dark  portions  are  made  up  of  dots  so  large 
they  form  together  to  make  a  solid  black  mass. 
When  transmitting  any  photograph,  a  dot  is 
sent  with  each  electrical  impulse,  but  these 
impulses  occur  so  rapidly  that  they  appear 
as  a  buzz  when  one  hears  them  on  the  radio. 
Rows  of  dots  are  sent  in  rapid  succession;  this 
explains  the  repetition  of  the  signal  intensities 
at  short  intervals.  It  is  not  necessary  to  split 
the  photograph  up  into  tiny  dots  before  trans- 
mitting, for  this  is  automatically  done  by  the 


electrical  apparatus  in  the  photograph  trans- 
mitter. 

At  the  receiving  station,  the  electrical  im- 
pulses are  transferred  on  a  suitable  paper  back 
into  dots  and  these  dots  are  arranged  exactly 
as  they  are  on  the  original  picture.  To  do 
this,  both  transmitting  and  receiving  appara- 
tus must  operate  at  exactly  the  same  speed, 
that  is  to  say,  they  must  be  synchronized. 
The  technical  problems  involved  in  syn- 
chronizing have  been  some  of  the  most  impor- 
tant of  the  many  difficult  ones  in  developing 
the  transmitting  apparatus. 

A  picture  that  is  to  be  transmitted  across 
the  Atlantic  by  the  Radio  Corporation  of 
America's  system,  or  from  one  city  to  another 
over  the  Bell  System  lines,  is  first  printed  on  a 
transparent  film.  This  process  is  rather 
simple  and  does  not  require  much  time. 
Nevertheless,  such  a  procedure  would  involve 
undesirable  complications  for  constant  and 
regular  commercial  service.  Both  the  Tele- 
pix  and  Belin  systems  call  for  especial  types 
of  negatives  peculiar  to  the  transmitting 
methods  employed.  The  making  of  such  neg- 
atives requires  a  little  more  time  than  do  the 
prints  used  on  the  Radio  Corporation  and 
American  Telephone  and  Telegraph  Company 


RADIO  BROADCAST  Photograph 
THE    RADIO    BROADCAST    LABORATORY 

Showing  the  antenna  and  counterpoise  system.     Two  masts  eighty-five  feet  high  support  the  two  cage 

antennas.     The  longer  antenna  has  a  spread  of  154  feet.     The  laboratory  where  Mr.  Cooley  did  much  of 

the  development  work  on  his  photograph  transmission  system  is  located  in  the  white  cabin  between  the 

two  masts.     The  buildings  of  Doubleday,  Page  &  Company  are  in  the  background 


22 


Radio  Broadcast 


BEFORE — AND    AFTER 

The  original  and  a  radio  transmitted  version  of  a  photograph  sent  during  the  early  experiments  of  the 
Cooley-Hainsworth  system.     The  picture  on  the  right  was  sent  with  fifty  dots  to  the  inch.     Average  news- 
paper halftones  have  sixty-five  dots  to  the  inch  (this  magazine's  halftones  have  1 10  dots  to  the  inch) 


HON;R.B<HOWELL,  OCTC8ER    1,1324-. 

UASHIKGTOH.D.C. 

OEAR  SENATOR  HOWELL:-   MAY   I   CALL  YO'JR   ATTENTION  TO   A   RE* 

VETHO'D  OF  cc^miicATios,  THE  RADIO  PHOTO  LETTER.     IT  RE- 
TAIKS  THE  AUTH£r<nC  CHARACTER  OF  AN  AUTOGRAPH  LETTER  *HIU 
DELIVERING  IT  AT  T8£  SPEED  OF  RADIO.     IT  IS  THE  BEGINNING  OF 
THE  PRACTICAL  APPLICATION  OF  *Y  TEW.  YSARS  DEVELOPMENT  OF  A 
frAJMO  SERVICE  TO  7KE  HYE,  WHERE  HERETOFORE.  RAO  10.  HAS  BEEN 
DEVELOPED  ONLY  AS  A  SERVICE  TO  THE  EA-?.      ISN'T  IT  ABOUT 
TIKE  "THE  GOVSiWsOT  BEGAN  COtJSIQEHIHG  A  MORE  RAPID  COMM- 
5UCAT13N  SERVICE  TO  BUSINESS?    PHOTO  COP l£3  OF  LETTERS  ARE 
IN  COURT.    PHOTO  COPi£$  OF  BUSINESS  LETTERS  J)E-v 
ev  SADIC"  CAT  THE  SPEED  OF  LIGHT)  WOULD  BE  JUST- AS 

HTSC    A!*0   BINDING  WHfL.C    SPEEDING    UP   CQ.V.V-ERCE   EMORVOUSL Y 
ftiE    L!K£    A?<   ARJJY,    C*«   GO  FORWARD   NO   FASTER   THAN    ITS 
OF  COaMUK'ICATIO^.      A   «0r?£   RAPID  MEA^S   OF    INTERCOURSE 
S  A  Stsr  TOOL  FOR  .SPEEDING    UP   BUSINESS. 

L   VfEAtTH. 


A    REAL    RADIO    LETTER 

Sent  by  the  inventor  of  the  system,  C.  Francis  Jenkins,  from  Anacostia, 
Maryland,  to  Washington  by  radio  last  October.  The  Jenkins  system 
has  some  points  in  common  with  the  development  of  Mr.  Cooley,  but 
in  essence,  the  Cooley  system  operates  along  other  and  entirely  new  lines. 
The  radio  photoletter  may  in  a  few  years  be  an  accepted  part  of  our 
industrial  svstem 


systems.  A  good  com- 
mercial system  of  photo- 
telegraphy should  be  able 
to  transmit,  without 
further  preparation,  any 
photograph  or  message 
printed  on  ordinary  pho- 
tograph paper. 

THE  MECHANICS  OF  PHOTO- 
GRAPH   SENDING 

SOME  systems  transmit 
the  signals  in  dots  and 
dashes  instead  of  dots  of 
intensity  corresponding  to 
the  portion  of  the  picture 
being  transmitted.  The 
dashes  represent  dark 
places  in  the  pictures  and 
the  dots  make  up  the 
light  areas.  This  system 
is  readily  adapted  to  oper- 
ation on  telegraph  circuits 
or  radio  telegraph  sta- 
tions. The  cost  of  these 


A  New  Method  of  Transmitting  Pictures  by  Wire  or  Radio         23 


CHARLES    EVANS    HUGHES 

Former  Secretary  of  State,  whose  photograph  was 
sent  across  the  Atlantic  by  the  Ranger-Radio 
Corporation  of  America  "  photoradiogram  "  system. 
The  Ranger  method,  while  used  in  this  instance  on 
a  high  power,  long  wavelength  radio  circuit,  can  be 
used  on  a  wire  line  equally  well 


communication  channels  is  much  lower  than 
the  ones  required  for  the  dot  system  as  used 
by  the  American  Telephone  and  Telegraph 
Company,  Jenkins,  Belin,  and  others.  The 
Radio  Corporation  sent  pictures  across  the 
Atlantic  in  twenty  minutes  by  the  dot-dash 
method.  An  hour  or  more  is  required  to 
transmit  a  Telepix  picture  over  a  telegraph 
wire,  but  these  pictures  are  larger  and  contain 
more  detail  than  those  handled  by  the  Radio 
Corporation.  The  American  Telephone  and 
Telegraph  Company  have  transmitted  pictures 
of  considerable  detail  in  four  or  five  minutes, 
but  special  wires  were  required.  The  cost 
of  the  communication  channels  used  is  an 
important  factor  that  will  determine  the 
commercial  value  of  any  system.  In  some 
cases  the  high  cost  may  be  offset  by  the  great 
capacity  of  the  apparatus  operating  over  the 
channel. 

When  a  system  of  phototelegraphy  goes 
into  commercial  use,  there  will  probably  be 
separate  rates  for  printed  matter  and  photo- 


graphs. This  is  because  the  adjustments  of 
the  apparatus  can  remain  fixed  when  handling 
black  and  white  subjects  while  the  transmit- 
ting of  a  photograph  would  require  special 
attention  so  that  the  tones  and  shades 
ma^v  be  properly  reproduced  at  the  receiving 
station.  A  picture  having  little  contrast  and 
printed  on  sepia  paper  would  require  adjust- 
ments of  the  apparatus  entirely  different  from 
one  having  contrast  and  printed  on  a  glossy 
paper. 

THE    STORY    OF    THE    COOLEY    SYSTEM 

E  Cooley  system,  which  has  never  been 
made  public,  incorporates  more  contribu- 
tions to  the  art  than  does  that  of  any  other  in- 
ventor. This  development  is  an  outgrowth  of 


VERITABLE       RADIO    WRITING 

A  sample  of  writing  of  Doctor  Hainsworth,  one  of 
the  inventors  of  the  Cooley-Hainsworth  phototele- 
graph    transmitting    system.     This    was    sent    ex- 
perimentally  in   Cambridge   in    1922 


Radio  Broadcast 


work  begun  by  Dr.  William  R.  Hainsworth 
at  the  Massachusetts  Institute  of  Technology, 
Cambridge,  Massachusetts,  in  November, 
1921.  From  that  time  until  March,  1923,  the 
investigation  centered  on  the  use  of  methods 
paralleling  very  closely  those  made  public  by 
the  American  Telepho.ne  and  Telegraph  Com- 
pany last  summer.  Austin  G.  Coolev,  then 
a  student  at  the  Massachusetts  Institute  of 
Technology,  joined  Dr.  Hainsworth  in  the  fall 
of  1922  for  the  purpose  of  assisting  in  the  ap- 
plication of  radio  to  the  equipment  which  was 
being  operated  satisfactorily  in  the  laboratory. 
Having  become  convinced  that  this  system 
was  too  unreliable,  that  it  was  definitely 
limited  in  speed,  and  that  it  was  encumbered 


with  so  many  obstacles  in  the  way  of  its  future 
acceptance  as  anything  but  an  elaborate 
laboratory  toy,  in  the  spring  of  1923  they 
decided  to  abandon  their  ideas  and  to  start 
out  along  entirely  different  lines  of  research. 

C.  E.  Tucker,  a  well  known  authority  on 
electrical  communication;  Prof.  F.  S.  Dellen- 
baugh,  a  prominent  electrical  engineer;  Dr.  F. 
G.  Keys,  director  of  the  Physical  Chemistry 
Department  at  the  Institute;  Captain  Clayton 
and  Sergeant  Truax,  both  of  the  United  States 
Army  Signal  Corps,  were  a  few  of  the  members 
of  the  faculty  of  the  Massachusetts  Institute 
of  Technology  who  took  an  active  interest  in 
the  Cooley-Hainsworth  development  work 
and  furnished  valuable  assistance  in  securing 


RECEIVING    APPARATUS    OF    THE    RANGER    SYSTEM 

Used  by  the  Radio  Corporation  of  America.  The  picture  is  printed  on  the  small  revolving  drum  in  the 
foreground  which  is  driven  by  the  motor  directly  behind  it.  Exact  synchronism  between  the  motor  of  the 
transmitting  and  receiving  apparatus  is  an  essential  of  all  photographic  sending  systems.  The  first  public 
demonstration  of  this  system  took  place  during  the  week  of  December  i,  1924,  between  New  York  and 

London 


A  New  Method  of  Transmitting  Pictures  by  Wire  or  Radio         25 


A    TELEPIX    PHOTOGRAPH 

Which  was  sent  between  New  York  and  Chicago.     The  photograph  was  retouched  after  it  was  received. 
A  comparison  between  this  and  the  original  below  shows  that  considerable  detail  was  lost  in  the  transmit- 
ting process.     A  picture  of  this  type  is  one  of  the  most  difficult  to  transmit 


the  necessary  apparatus  and  instruments. 
Dr.  Jacob  Kunz  of  the  University  of  Illinois 
had  contributed  materially  to  the  work  by 


placing  at  their  disposal  his  newly  developed 
photoelectric  cell. 

Many  of  the  radio  fans  in  the  vicinity  of 


AN    ORIGINAL    PHOTOGRAPH 
The  telegraph  version  is  shown  above 


26 


Radio  Broadcast 


Boston  will  recall  hearing  mysterious  buzzes 
accompanied  by  clicks  occurring  at  intervals  of 
a  little  more  than  a  second  apart  on  a  200 
meter  radio  wave  during  the  month  of  Decem- 
ber, 1922.  Many  inquiries  were  answered  by 
explaining  that  "special  tests  on  radio  control 
were  being  conducted."  Probably  no  one  had 
the  slightest  conception  that  pictures  were 
being  sent  over  the  air.  It  was  from  the  ex- 
perimental radio  station  IXM,  located  at  the 
Institute,  that  the  pictures  were  transmitted. 
They  Were  received  in  Dr.  Hainsworth's 
laboratory,  not  far  distant.  The  quality  of 
the  received  pictures  was  poor,  but  the  work 
must  be  given  considerable  credit,  for  it  was 
probably  the  first  time  that  the  synchronizing 
of  the  receiver  with  the  transmitter  was  ac- 
complished by  radio. 

The  development  work  on  the  phototele- 
graphic  system  was  conducted  in  Dr.  Hains- 
worth's laboratory  and  radio  station  IXM 
where  Mr.  Cooley  spent  most  of  his  time.  In 
the  summer  of  1923,  the  first  tests  on  the  new 
system  designed  by  Mr.  Cooley  were  made  in 
this  radio  "shack."  It  is  seldom  that  appara- 
tus of  new  and  unusual  design  meets  its 
builder's  expectations.  Mr.  Cooley  was  pre- 
pared to  be  disappointed.  But  on  the  con- 
trary, unusual  and  encouraging  results  were 
obtained. 

With  the  aid  of  a  colleague,  Mr.  R.  A. 
Cunningham,  Mr.  Cooley  rushed  along  the 
construction  work  on  a  complete  set  of  appara- 
tus to  be  used  for  demonstration  purposes. 
Dr.  Hainsworth  left  Boston  during  the  summer 
of  1923  to  take  up  some  other  work  in  Seattle. 
Since  that  time  he  has  not  been  able  to  take 
an  active  part  in  the  development  of  the 
phototelegraphy  system  for  which  he  is  respon- 
sible. 

AT  THE  RADIO  BROADCAST  LABORATORY 

WHEN  Arthur  H.  Lynch,  editor  of  this 
magazine,  was  asked  to  assist  in  obtain- 
ing laboratory  space  for  the  development 
of  the  Cooley  phototelegraphic  work,  he 
was  quick  to  realize  its  possibilities.  Without 
the  slightest  hesitation  he  freely  offered 
the  facilities  of  the  RADIO  BROADCAST  Lab- 
oratory for  the  test  of  Cooley's  ideas. 
Accordingly,  night  and  day,  and  with  this 
precious  equipment  constantly  under  the  eyes 
of  watchmen,  Cooley  pursued  his  tests  of 
a  high  speed  phototransmission  device  for 
reproducing  at  distant  points  photographs 
having  all  the  shades  necessary  to  make  up  a 
perfect  picture. 

It   was   not   until   after  the   International 


Radio  Broadcast  Tests  in  December,  1924, 
that  the  various  units  of  the  new  Cooley 
phototelegraphic  system  had  been  properly 
coordinated  and  it  was  possible  to  send  pic- 
tures of  satisfactory  quality  in  the  RADIO 
BROADCAST  Laboratory.  Arrangements  were 
made  to  loop  the  picture  signals  through  two 
local  telephone  exchanges  and  to  return  them 
to  the  Laboratory,  where  both  transmission 
and  reception  might  be  watched  by  the  opera- 
tors. The  transmitter  was  connected  to  a 
telegraph  line  which  terminated  at  the  RADIO 
BROADCAST  office.  At  this  point,  the  signals 
were  acoustically  transferred  to  a  telephone 
which  was  connected  to  the  private  branch 
exchange  of  Doubleday,  Page  &  Company. 
This  private  branch  exchange  was  in  turn 
connected  to  the  Garden  City  telephone  ex- 
change, where  the  usual  telephone  connections 
were  set  up  for  the  wire  which  serves  the 
Laboratory  telephone. 

SUCCESS    ON    THE    FIRST    TEST 

IN  THIRTY  minutes  ten  pictures  were 
transmitted.  The  apparatus  was  readily 
synchronized  within  ten  seconds  before  the 
reception  of  each  picture  began.  The  pictures 
transmitted  were  taken  from  magazines  and 
rotogravure  sections  of  newspapers.  In  the 
receiving  apparatus,  the  pictures  were  printed 
out  on  an  inexpensive  photographic  paper 
that  required  developing  and  fixing  before 
the  image  could  be  seen.  The  thirty  minutes 
mentioned  included  the  time  required  for  this 
work.  The  quality  of  the  received  pictures 
was  fair,  in  spite  of  a  defective  device  in  the 
transmitter.  This  device  was  the  photo- 
electric cell,  a  necessary  part  of  the  equipment. 
Air  had  leaked  into  it  and  caused  its  action  to 
be  sluggish.  A  new  one  is  now  being  built  by 
Dr.  Kunz,  especially  designed  to  meet  the  high 
speed  requirements  in  this  system  of  photo- 
telegraphy. 

The  limitations  of  the  Cooley  system  are 
unknown.  It  is  probable  that  a  commercial 
type  model,  which  can  handle  four  hundred 
messages  an  hour,  will  be  constructed  within 
the  next  year.  Compare  this  with  the  present 
machine-printing  telegraph,  which  averages 
about  fifty  messages  an  hour. 

Using  the  Cooley  design,  the  transmitter  or 
receiver  is  neither  bulky  nor  expensive  to  con- 
struct. In  a  commercial  embodiment  planned 
for  an  early  date,  a  portable  transmitter  will 
be  built  for  the  use  of  newspaper  photogra- 
phers. It  will  be  necessary  only  to  connect  the 
machine  to  the  electric  light  socket,  get  the 
newspaper  office  by  telephone,  and  place 


A  New  Method  of  Transmitting  Pictures  by   Wire  or  Radio         27 


the  negative,  still  wet  from  the  developing 
solution  (if  utmost  speed  is  desired)  in  the  ma- 
chine, and,  in  the  course  of  a  minute  or  two, 
transmit  it  to  the  photographer's  headquar- 
ters. And,  wonderful  though  it  may  seem,  the 
photographer  may  send  it  to  be  received  as 
either  a  negative  or  a  positive.  He  may  also 
send  a  print  or  even  a  clipping  from  a  magazine 
or  newspaper  and  have  the  replica  in  the  hands 
of  the  editor  within  a  few  minutes  after  com- 
pleting his  telephone  connection.  Since  this 
work  may  be  done  acoustically,  there  is  no 
need  of  any  electrical  connection  between  the 
photo-transmitter  and  the  telephone. 

ONE    PICTURE — EVERY    HALF    MINUTE 

MR.  COOLEY  has  not  lost  sight  of  the 
fact  that  1200  impulses  per  second  is 
about  the  maximum  number  that  can  be  trans- 
mitted over  a  commercial  telephone  line. 
This  limits  the  speed  of  transmission  to  about 
seventeen  square  inches  per  minute  if  the  pic- 
ture is  to  be  printed  out  with  sixty-five  dots 
per  inch,  this  being  standard  for  newspaper 
prints.  The  speed  might  be  increased  through 
the  use  of  high  quality  transmission  lines  such 
as  are  used  for  carrying  programs  from  a  studio 


to  a  broadcast  station.  In  such  lines  the 
circuits  are  so  arranged  that  frequencies  up  to 
4000  cycles  per  second  are  passed.  At  the  4000 
impulse  rate,  only  thirty-seven  seconds  would 
be  required  to  send  a  five-by-seven-inch  picture. 

Before  this  copy  of  RADIO  BROADCAST  reaches 
the  reader,  it  is  confidentially  expected  that 
the  necessary  alterations  in  the  present  model 
will  be  made,  so  that  the  most  detailed  photo- 
graph with  all  its  half-tone  shadings  can  be 
transmitted  over  any  telephone  or  radio  circuit 
that  is  capable  of  transmitting  intelligible 
speech.  There  is  every  hope  for  the  early  de- 
tailed announcement  of  this  phototelegraphic 
system  that  is  fundamentally  new  and  novel  in 
its  transmission  and  receiving  methods. 

The  quality  of  the  photographs  transmit- 
ted by  this  system  can  be  made  especially 
good  for  magazine  use.  By  increasing  the 
speed  of  transmission,  photographs  can  be  sent 
at  a  greater  speed,  for  use  in  newspapers.  I  n  its 
final  form,  the  apparatus  will  be  extremely  sim- 
ple, relatively  inexpensive,  and  equally  adapt- 
able for  line  or  radio  transmission. 

In  connection  with  this  work,  a  very  im- 
portant new  use  of  the  vacuum  tube  has  been 
discovered  and  a  very  plausible  theory  has 


THE  ORIGINAL — AND  THE  TELEGRAPHED  PHOTOGRAPH 

Sent  from  New  York  to  Chicago  by  the  "Telepix"  system  now  in  use  by  the  Chicago  Tribune  and  the 
New  York  Daily  News.  The  cut  on  the  right  is  a  print  of  the  wired  picture  after  it  had  been  slightly  re- 
touched. At  present,  wired  photography  is  decidedly  expensive  and  too  slow  for  general  commercial  use 


28 


Radio  Broadcast 


been  formulated  for  its  operation.  Still  an- 
other use  of  the  vacuum  tube  has  been  de- 
veloped to  an  extent  which  shows  excellent 


promise.  It  is  now  thought  that  it  can  be 
included  in  the  design  of  a  new  and  novel  re- 
ceiving circuit  which  will  be  a  great  improve- 
ment in  the  sensitivity  as  compared  to  present- 
day  receivers.  Many  patents  are  now  pending 
for  the  various  inventions  which  have  been 
made  in  connection  with  the  Cooley  system. 
As  rapidly  as  the  patent  work  permits, 
RADIO  BROADCAST  will  disclose  the  technical 
developments  that  are  made  as  the  work 
progresses. 

There  has  been  much  discussion  in  recent 
years  about  the  theories  of  the  German  scien- 
tist Einstein  and  his  theory  of  the  relativity 
of  time  and  space.  In  a  very  definite  and 
striking  way,  the  radio  transmission  of  photo- 
graphs illustrates  the  contentions  of  that 
famous  scientist,  although  certainly  not  in  the 
way  he  intended. 

This  new  art  has  reached  the  stage  where 
commercial  telephone,  telegraph,  and  radio 
companies  must  recognize  it  as  an  ally  or  pre- 
pare to  meet  its  competition.  The  constant 
barrier  of  distance  is  again  about  to  be  dealt  a 
blow  as  deadly  as  that  delivered  by  the  general 
utilization  of  the  locomotive,  automobile, 
airplane,  the  telegraph,  and  radio.  Since 
time  is  the  only  important  measure  of  geo- 
graphical space,  phototelegraphy  bids  fair 
appreciably  to  shrink  the  magnitude  of  our 
world. 


CALVIN    COOL1DGE 

President  of  the  United  States.     This  photograph 

was  also  sent  across  the  Atlantic  by  the  Ranger 

system.     The  dots  and  lines  which  go  to  make  the 

picture  can  be  clearly  seen. 


COMPLETE  instructions  on  how  to  build  the  Roberts  four-tube  Knockout  re- 
^  ceiver  so  that  it  can  be  fitted  into  any  phonograph  cabinet  will  appear  in  an 
early  number  of  RADIO  BROADCAST.  It  is  now  possible  to  buy  manufactured 
sets  which  can  be  used  in  a  phonograph  cabinet,  but  thus  far,  no  information  has 
yet  appeared  which  is  of  any  help  to  the  home  builder.  The  mechanical  details 
of  the  receiver  are  especially  well  worked  out  and  the  panel  can  be  used  with 
any  type  of  cabinet  phonograph  now  on  the  market. 


How  the  Government  Is  Regulat- 
ing Radio  Broadcasting 

The  "Interest  of  the  Listener"  Is  the  Final  Test  of  Regulation 
—The  Present  Situation  and  Future  Possibilities — An  Inter- 
view with  Judge  Davis  of  the  Department  of  Commerce 


BY  R.  S.  McBRIDE 


INCREASING  service  to  the  listener,"  is 
the  only  proper  basis  for  radio  regulation 
and  development  in  the  opinion  of  Her- 
bert Hoover,  Secretary  of  Commerce. 
But  it  is  a  long  way  from  this  generalization 
to  the  practical  working  out  of  a  Government 
policy.  So  RADIO  BROADCAST  has  undertaken 
to  study  the  depart- 
mental policy  as  to  the 
control  of  broadcast- 
ing to  see  just  what 
this  statement  really 
means.  For  this  pur- 
pose, an  interview 
was  secured  with 
Judge  Stephen  B. 
Davis,  Solicitor  of  the 
Department  of  Com- 
merce, with  results 
that  are  most  grati- 
fying from  the  point 
of  view  of  the  listener. 
There  is  no  doubt 
that  the  radio  audi- 
ence is  assured  of 
every  protection  and 
aid  which  the  skilled 
agents  of  the  Govern- 
ment can  offer  and 
that  fair  and  helpful 
service  will  be  given 
to  any  broadcasting 
development  that  has 
real  merit. 

GARDENING   FOR  JACK 
OF    THE     BEAN     STALK 

E  can  well  im- 

agine  the  troubles  which  a  gardener 
would  have  had  caring  for  the  yard  of  Jack 
of  bean-stalk  fame.  But  such  a  gardener 
would  have  had  no  more  trouble  in  pruning 
the  bean  stalk  to  shapely  form  than  does  the 
Department  of  Commerce  in  directing  the 


The  Wavelength's  the  Thing 

Everyone  who  knows  the  pleasant  pressure 
of  head  phones  or  who  is  often  attentive  to  a 
loud  speaker  has  discovered  that  the  ether 
paths  are  becoming  more  crowded  every  day. 
The  average  radio  listener — if  there  is  such  a 
person — has  probably  wondered  how  the 
Government  is  dealing  with  the  serious  prob- 
lem of  distributing  the  broadcast  wave- 
lengths, which,  when  one  considers  the  num- 
ber of  applicants  for  the  comparatively  few 
available,  are  few  enough.  There  has  been  a 
deal  of  excited  speculation  on  what  would 
happen  if  a  number  of  so-called  super-power 
stations  were  licensed — speculation,  it  may 
be  said,  with  only  an  indifferent  knowledge 
of  the  facts.  Mr.  McBride  has  gone  to  head- 
quarters for  his  information  and  we  think  he 
has  presented  very  well  the  attitude  of  the 
Department  of  Commerce.  The  Depart- 
ment is  charged  with  administering  the  Radio 
Act  under  the  very  difficult  changing  condi- 
tions of  radio.  That  radio  progress  has  not 
been  greatly  hindered  by  hasty  and  ill- 
considered  legislation  is  due  to  the  many  good 
and  capable  friends  of  radio  who  have  used 
their  influence  honestly  and  well  in  Wash- 
ington.— THE  EDITOR 


growth  of  the  radio  broadcasting  business.  In 
this,  as  in  the  fairy  tale,  not  even  the  sky  is 
the  limit,  so  it  seemsj 

Four  years  ago — or  August,  1921,  to  be 
exact — the  first  broadcasting  was  begun. 
To-day  the  Department  lists  nearly  600  broad- 
casting stations  in  operation  or  under  con- 
struction. These 
must  be  guided  and 
safeguarded  if  the 
real  interest  of  the 
industry,  which 
means  the  wishes  of 
the  general  public  of 
listeners,  is  to  be 
adequately  protected. 
And  with  ether  space 
so  much  at  a  prem- 
ium to-day,  the  task 
is  not  an  easy  one. 

In  view  of  the  con- 
tinued rapid  growth 
of  broadcasting,  many 
have  foreseen  a  con- 
stantly increasing 
confusion  in  the  air, 
which  would  be  help- 
ful to  no  one  and 
harmful  to  all.  An- 
ticipating this  situ- 
ation the  Department 
was  asked,  "How 
much  worse  must 
things  get  before  they 
can  begin  to  improve 
again?"  Or  put- 
ting it  another  way, 
"How  much  more 

broadcasting  interference  must  the  public 
tolerate  before  it  will  rise  up  and  demand  rigid 
regulation  and  complete  elimination  of  the 
interfering  stations?" 

These  questions  were  addressed  to  Judge 
Davis,  who  is  really  acting  as  first  officer  of 


Radio  Broadcast 


the  good  ship  Radio.  The  answer  which  he 
makes  is  most  encouraging.  He  says,  "Con- 
ditions will  not  be  allowed  to  get  any  worse. 
They  are  far  too  bad  already."  Pressed  fur- 
ther on  this  matter,  Judge  Davis  stated  that 
there  are  no  more  wavelengths  available  for 
broadcasting  in  the  Class  B  wavelength  area. 
Practically,  this  is  an  announcement  to  all 
newcomers  in  the  broadcasting  field  that  they 
will  not  be  permitted  to  crowd  in  and  add 
confusion  between  280  and  550  meters.  And 
to  the  broadcast  listeners,  as  to  all  other  well 
wishers  of  radio,  this  is  the  most  welcome  news 
of  many  months  past. 

FIXED  CONDITIONS  TO-DAY  CHANGE  TO-MORROW 

BUT  in  stating  this  conclusion,  Judge 
Davis  repeatedly  emphasized  that  no 
plan  of  the  Department  can  be  regarded  as 
permanently  fixed.  Radio  itself  is  changing; 
the  Department's  plans  must  keep  pace  or 
become  a  handicap.  It  is  clearly  the  purpose 
of  the  Department  to  prevent  any  such  un- 
fortunate result.  For  to-day,  however,  it  is 
safe  to  conclude  that  the  Department  intends 
to  protect  the  listener's  interest  by  limiting  the 
number  of  stations  which  can  work  within  the 
so-called  Class  B  range.  To-morrow  some 
new  scheme  may  develop  which  will  permit 
granting  of  more  Class  B  licenses  on  these 
wavelengths,  but  radio  science  to-day  does  not 
apparently  hold  forth  this  possibility. 

Already  in  this  Class  B  range,  the  average 
broadcast  listener  has  a  choice  of  several  pro- 
grams at  ordinary  broadcasting  hours.  But 
the  Department  is  not  content  with  this,  for 
it  seems  to  be  well  demonstrated  that  with  a 
gradual  advance  in  power  at  the  stations  in 
different  parts  of  the  country,  the  number  of 
unquestionably  good  programs  from  which  the 
great  body  of  radio  listeners  may  choose  can 
be  increased  up  to  eight  or  ten.  If  so,  many 
different  stations  can  be  made  regularly 
available  to  each  of  us.  There  will  then 
be  ample  opportunity  for  choice  between 
grand  opera,  jazz,  oratory,  and  educational 
productions.  The  Department  is  working 
toward  this  goal,  cautiously,  to  be  sure, 
but  with  every  confidence  that  it  is  entirely 
practicable. 

SAFE-GUARDING   SMALL   STATIONS 

CLASS  B  stations  with  power  of  from  500 
to  2000  watts  now  afford  the  most  relia- 
ble broadcasting  service  over  a  considerable 
area.  But  the  Department  still  regards  the 
small  local  stations  of  great  importance  to 
the  communities  that  they  serve.  Secretary 


Hoover,  commenting  on  this  situation  at  the 
recent  radio  conference,  said: 

1  know  the  importance  of  these  smaller  stations 
to  the  communities  they  serve.  1  know  that  there 
are  millions  of  crystal  sets  and  small  tube  sets  whose 
owners  are  practically  compelled  to-day  to  rely 
upon  the  stations  at  their  doors  and  are  getting  good 
service  from  them.  These  are  the  people  I  have  in 
mind  and  the  ones  1  primarily  want  to  serve,  for  the 
owner  of  the  multi-tube  set,  reaching  out  for  an  in- 
definite number  of  miles,  is  pretty  well  able  to  look 
out  for  himself.  1  want  to  see  the  little  fellow  get 
something  more  than  he  has  now. 

From  this  statement  it  is  evident  that  any 
plan  for  improving  the  service  from  the  power- 
ful Class  B  group  is  not  going  to  involve  serious 
hazards  for  local  use  of  low-power  stations  that 
fit  properly  into  the  general  scheme  of  things. 

The  Department,  Judge  Davis  emphasizes, 
still  regards  the  small  set,  even  the  crystal  set, 
as  the  most  important  unit  for  consideration 
in  planning  broadcast  regulations. 

THE    SUPER-POWER    BUG-A-BOO 

THE  recent  suggestion  of  Mr.  David  Sar- 
noff  that  one  or  two  very  powerful  stations 
using  perhaps  50,000  watts  should  be  erected 
to  serve  the  entire  country  aroused  a  storm  of 
protest.  Much  of  the  objection  came  from 
misunderstanding.  Some  came  from  propa- 
ganda spread  abroad  by  small-station  broad- 
casters who  feared  the  results  of  such  a 
development.  The  Department  was  quick  to 
answer  these  objections  with  the  announce- 
ment that  no  alarming  or  radical  changes  are 
being  contemplated. 

Thus  far,  Judge  Davis  explains,  only  two 
stations  have  advanced  as  far  as  2000  watts 
and  only  eight  or  ten  are  using  as  much  as 
1 500  watts.  This  advance  has  been  made  in 
steps  of  500  watts  and  each  forward  step  is 
closely  watched  by  the  Department. 

The  object  of  these  advances  is  two-fold: 
First,  an  increase  in  the  dependability  of  radio, 
from  the  listener's  point  of  view,  over  the 
ordinary  range  of  regular  reception.  Second, 
an  extension  of  the  effective  range  so  that  the 
rural  districts  of  the  country  will  be  adequately 
served  and  afforded  some  choice  of  program 
wherever  that  is  possible.  The  first  of  these 
advantages  means  regular  loud  speaker  service 
from  stations  that  now  are  simply  passable 
contributors  to  the  family  enjoyment  when 
head  phones  are  used.  The  second  advantage 
means  widening  of  the  possible  field  of  service 
without  creation  of  any  new  stations,  new 
interference,  or  new  expenses. 

The  useful  range  of  a  broadcasting  station, 


How  the  Government  is  Regulating  Radio  Broadcasting 


the  Department  emphasizes,  is  the  area  within 
which  signal  strength  is  sufficiently  greater 
than  static  or  other  interference  that  the  pro- 
gram is  regularly  audible  at  all  times  dur- 
ing broadcasting  periods.  Broadcast  stations 
with  inadequate  power  are  about  as  useful  as 
an  ordinary  telephone  beside  a  pneumatic 
riveter.  We  know  the  message  desired  is 
coming  through  the  instrument,  but  it  does 
us  no  good.  Until  we  find  out  how  to  quiet 


In  the  early  days  the  Department  decided 
that  a  spacing  between  stations  of  ten  kilo- 
cycles was  as  close  as  could  properly  be  used 
without  interference.  In  other  words,  they 
permitted  each  station  to  take  a  seat  ten 
kilocycles  wide.  Now  all  the  seats  are  taken 
and  each  man  must  hold  his  overcoat  on  his 
lap  and  put  his  hat  under  his  own  seat.  Nat- 
urally it  seems  a  bit  more  crowded;  but,  as 
the  Department  officials  clearly  explained,  it 


HERBERT    HOOVER    AND   JUDGE    STEPHEN    B.    DAVIS 

Captains  of  the  good  ship  Radio.  As  Secretary  of  Commerce,  Mr.  Hoover  for  the  last  four  years  has  had  to 
face  some  very  difficult  administrative  problems,  for  radio  communication  has  greatly  altered  during  that 
time.  Broadcasting  was  merely  a  commercial  experiment  in  1921.  Compare  the  radio  situation  when 
Mr.  Hoover  took  office,  with  conditions  on  the  fourth  of  March,  1925,  when  the  whole  country  was  "hooked 
up"  by  wire  and  radio  and  enabled  to  hear  the  inaugural  ceremonies  in  Washington.  Judge  Davis,  as  the 
solicitor  for  the  Department,  has  been  in  direct  touch  with  radio  affairs  and  it  is  known  that  his  opinions  are 

very  similar  to  those  of  Mr.  Hoover's 


the  riveter  of  static  we  have  no  choice  but  to 
increase  the  power  of  the  station  so  that  we 
can  hear  it  despite  this  interference. 

IS    BROADCAST    CROWDING    ONLY    APPARENT? 

IF  WE  go  to  the  movies  in  the  early  afternoon 
there  is  usually  plenty  of  room  so  that  we 
can  put  our  hat  and  overcoat  in  a  vacant  seat 
beside  us  and  sit  with  comfort  any  place  in 
the  theater  that. we  may  choose.  So  it  was  in 
radio  broadcasting  a  few  years  ago.  All  of  the 
newcomers  found  plenty  of  room.  They 
were  given  wavelengths  that  allowed  all  the 
freedom  for  careless  operation  that  the  crudi- 
ties of  early  apparatus  made  inevitable.  But 
to-day  the  broadcast  territory  is  as  badly 
crowded  as  the  movies  when  the  town's  favor- 
ite star  is  showing  in  her  newest  film. 


is  simply  that  all  the  assignments  possible  are 
now  made,  not  that  there  is  any  closer  assign- 
ment authorized  to-day  than  heretofore. 

The  Department  undertook  a  series  of  ex- 
periments during  the  middle  of  the  winter  to 
see  whether  a  closer  spacing  was  not  feasible. 
In  other  words,  they  tried  to  make  each  radio 
seat  a  few  inches  narrower.  On  attempting 
a  seven-kilocycle  spacing  in  this  experiment, 
came  the  answer  very  clearly.  The  De- 
partment admitted  that  the  answer  was  very 
definitely  "No!" 

Secretary  Hoover  has  announced  this  find- 
ing in  unmistakable  language.  He  says,  "The 
recent  experiment  of  the  Department  in  at- 
tempting to  increase  the  number  of  wave- 
lengths by  decreasing  the  difference  to  seven 
kilocycles  proved  unsuccessful  with  the  present 


Radio  Broadcast 


development  of  instruments."  And,  further 
on  in  a  recent  official  statement,  the  Secretary 
stated  that  "it  is  absolutely  necessary  to  main- 
tain a  wide  kilocycle  separation  between 
stations  so  close  together  (geographically). 
Otherwise  they  will  destroy  each  other."  And 
as  the  Department  well  recognizes,  they  will 
destroy  the  listener's  patience  and  interest 
even  more  promptly. 

THE    SURVIVAL   OF   THE    FITTEST 

EVOLUTIONISTS  explain  that  the  ad- 
vance from  animal  to  man  occurred  by 
the  survival  and  development  of  the  fittest 
form  of  life.  In  radio,  a  similar  evolution  to 
the  high-class  station  which  all  can  anticipate 
for  the  future  is  now  in  progress.  When  one 
station  makes  great  improvements,  the  neigh- 
boring stations  have  three  choices: 


DAVID    SARNOFF 

Vice-president  and  general  manager  of  the  Radio 
Corporation  of  America.  At  the  third  annual  radio 
conference  in  Washington  which  met  at  the  call  of 
Secretary  of  Commerce  Hoover  in  October,  1924, 
Mr.  Sarnoff  suggested  that  the  way  to  solve  some  of 
the  broadcasting  problems  would  be  to  license 
several  very  high-powered  stations  of  the  order  of 
fifty  kilowatts  which,  located  in  various  parts  of  the 
nation,  would  give  dependable  broadcast  service 
over  a  large  area.  A  high-powered  broadcast  sta- 
tion has  recently  been  erected  by  the  British  Broad- 
casting Company  in  England 


1.  They  may  keep  up  by  making  similar  im- 
provement. 

2.  They  may  confess  inferiority  by  continuing  on 
the  old  superseded  basis. 

3.  They  may  go  out  of  business. 

The  history  of  radio  indicates  that  alterna- 
tives i  and  3  are  about  the  only  possible  ones. 
Judge  Davis  made  this  point  very  clear  by  a 
large  radio  map  which  hangs  on  his  office  wall. 
On  that  map  blue  pins  show  the  Class  B 
stations,  green  pins  the  Class  A,  and  black 
pins  the  stations  that  have  been,  but  are  no 
more.  At  almost  every  point  where  blue  pins 
appear  they  are  surrounded  by  the  black 
markers  of  discontinued  stations,  stations 
which  could  not  stand  the  pace  and  there- 
fore quit  rather  than  confess  permanent 
inferiority. 

The  Department  is  wondering  whether  this 
is  not  a  necessary  and  logical  course  to  be  fol- 
lowed. That  station  which  is  most  progressive 
and  gives  the  best  service,  judged  always  from 
the  standpoint  of  the  listener,  will  succeed. 
The  neighboring  stations  which  cannot  do 'so 
well  are  not  long  in  learning  that  their  effort 
and  expenditure  is  producing  no  advantageous 
result.  It  is  well  from  all  points  of  view,  even 
their  own,  that  they  should  go  out  of  business; 
fortunately  they  do. 

CONCENTRATION    WITHOUT   MONOPOLY 

THE  Class  B  stations,  which  now  afford  the 
widest  and  most  dependable  class  of  serv- 
ice, offer  the  most  serious  problem  in  inter- 
ference. Any  DX  fan  in  the  center  of  the 
country  can  safely  boast  that  his  set  will  reach 
from  Orono,  Maine,  to  Los  Angeles,  and  from 
Winnipeg  to  Cuba,  but  his  boast  is  true  only 
when  he  speaks  of  Class  B  stations,  for  those 
of  Class  A  rarely  have  sufficient  power  to  be 
heard  more  than  occasionally  beyond  a  hun- 
dred miles. 

In  the  Class  B  range  there  are  built  or  build- 
ing more  than  100  stations,  with  only  forty- 
seven  wavelengths  to  be  distributed  among 
them.  So  now,  on  the  average,  there  is  less 
than  one  wavelength  for  each  two  stations, 
which  means  that  many  Class  B  stations  must 
divide  their  time  of  operation.  This  division 
of  time  has  led  to  much  difficulty;  but  the 
Department,  for  the  present  at  least,  is  allow- 
ing the  problem  to  solve  itself. 

UNCLE  SAM:  HOTEL  CLERK 

THE  Department  in  radio  takes  much  the 
same    attitude   as   the  room   clerk  at   a 
popular  hotel.    As  evening  approaches  all  of 
the  rooms  are  engaged,  yet  there  are  numerous 


How  the  Government  is  Regulating  Radio  Broadcasting 


33 


DR.    J.    H.    DELLINGER    AND    D.    B.    CARSON 

Dr.  Bellinger  .is.  head  of  the  radio  laboratory  of  the  Bureau  of  Standards,  which,  being  a  division  of  the 
Department.^  Commerce,  works  closely  with  the  Radio  Service.     D.  B.  Carson  is  Commissioner  of  Naviga- 
tion and  is  the  general  supervisory  head  of  the  Radio  Service 


demands  for  accommodations  still  to  be  met. 
In  the  radio  Class  B  hotel,  it  is  sun-down  and 
all  of  the  wavelengths  are  assigned.  What 
does  Uncle  Sam,  the'  radio  room  clerk,  do? 
Just  what  the  hotel  clerk  would  do  under  the 
same  circumstances. 

The  newcomer  arrives  and  wishes  accommo- 
dations. If  he  has  a  friend  who  will  share 
with  him  his  room,  or  Class  B  wavelength, 
the  clerk  welcomes  him  and  makes  this  room 
assignment.  He  is  glad  to  have  each  double 
bed  filled  with  two  paying  guests.  If  a  third 
friend  arrives  and  the  first  two  are  willing  to 
have  a  cot  placed  in  the  room,  all  are  happy 
and  are  all  accommodated.  But  if  the  late- 
comer does  not  find  such  a  friend  to  accommo- 
date him,  obviously  the  clerk  will  not  turn  out 
one  of  his  regular  patrons  to  make  room  for  the 
newcomer,  nor  will  he  insist  that  the  earlier 
arrival  share  his  bed,  or  wavelength. 

Uncle  Sam,  in  planning  wavelength  assign- 
ments in  the  Class  B  wavelength  range,  takes 
the  same  stand.  As  the  Secretary  of  Com- 
merce puts  it,  "The  Department  cannot  give 
what  it  has  not  got."  And  it  is  perfectly  clear 
that  there  are  no  Class  B  wavelengths  left. 
Hence  one  can  properly  read  between  the  lines 
of  the  Department's  recent  statement  that 
there  will  be  no  further  assignment  of  Class  B 
wavelengths  for  the  present  or  the  near  future. 
Nor  will  the  Department  willingly  destroy  the 
value  of  present  wavelength  assignments  by 


demanding  that  they  be  shared  with  late- 
comers. 

"S.    R.    O."    AT   THE    BOX    OFFICE 

I  ET  us  go  back  again  to  the  theater  for 
L»  comparison  with  the  radio  station.  The 
early-comers,  or  those  who  bought  tickets  in 
advance,  fill  all  the  seats,  yet  there  is  a  long 
line  at  the  box  office  despite  the  sign  "Standing 
Room  Only."  Uncle  Sam,  with  no  radio 
seats  in  the  Class  B  orchestra,  has  hung  out 
his  "S.  R.  O."  sign,  too.  But  he  will,  in  fact 
under  the  law  he  must,  grant  licenses  and 
assign  wavelengths.  He  does  this  by  a  ticket 
of  admission  which  entitles  the  new  broad- 
caster to  work  only  in  the  Class  A  range,  205 
to  280  meters.  In  this  range  he  is  not  com- 
fortably seated  as  a  member  of  the  radio 
broadcasting  party.  He  finds  himself  stand- 
ing behind  the  back  seats,  jostled  by  other 
late-comers,  and  seeing  the  performance  at 
great  disadvantage.  But  he  is  simply  paying 
the  penalty  as  a  late-comer. 

If  some  of  the  present  Class  B  stations  dis- 
continue service  or  cease  to  give  service  ade- 
quate from  the  public  point  of  view,  their  li- 
censes, which  are  renewable  every  90  days, 
will  doubtless  not  be  renewed  for  comfortable 
third-row  aisle  seats.  In  fact,  Uncle  Sam, 
just  as  the  theater  management,  reserves  the 
right  to  withdraw  the  admission  ticket  at  any 
time.  Hence  a  disorderly  station,  like  a  dis- 


-34 


Radio  Broadcast 


orderly  spectator,  will  promptly  find  himself 
outside.  As  one  leaves,  another  may  be 
seated.  The  place  he  gets  depends  upon  the 
appropriateness  of  location,  service  proposed, 
and  wavelength  thus  made  available. 

THE    CINCINNATI    "  ROW " 

RECENTLY,  a  controversy  over  division 
of  broadcasting  time  in  Cincinnati  was 
not  promptly  settled  by  the  local  Class  B  sta- 
tions, two  of  which  for  several  nights  broadcast 
simultaneously  on  the  same  wavelength.  The 
Department  officials  were  asked  in  this  and 
in  one  other  similar  case,  "What  are  you  going 
to  do  about  it?"  The  answer  was  very  simple, 
"Nothing." 

If  two  stations  insits  on  killing  themselves 
and  each  other,  the  Department  is  perfectly 
willing  that  they  should  do  so  but  it  will  not 
allow  this  situation  to  interfere  with  public 
service.  Two  such  disorderly  patrons  of  the 
radio  hotel  will  be  permitted  to  settle  their 


controversy  outside.  The  wavelength  which 
they  should  have  agreed  to  share  peaceably 
will  very  promptly  be  given  to  someone  else 
who  will  use  it  in  the  public  interest. 

Only  one  or  two  such  examples  will  be 
ample  to  demonstrate  to  broadcasters  that 
the  public  interest  must  be  served.  On  no 
other  basis  can  the  radio  broadcaster  exist. 
On  no  other  basis  will  he  be  permitted  to  re- 
tain his  Class  B  license. 

POLICING    IS    NOT   CENSORSHIP 

THE  Department  properly  is  insisting  that 
each  station  maintain  a  certain  technical 
standard  of  service  and  that  it  stay  properly 
on  its  own  wavelength.  But  the  Depart- 
ment is  equally  emphatic  that  this  is  policing, 
not  censorship. 

Judge  Davis  explains  that  neither  he  nor 
any  one  else  in  the  Department  is  willing  to 
assume  that  they  know  enough  to  determine 
on  behalf  of  the  public  what  may  and  what 


WHERE    AMERICAN    RADIO    ACTIVITIES    ARE    CONTROLLED 

The  Department  of  Commerce  building  in  Washington.  Here,  in  the  Bureau  of  Navigation,  Radio  Service 
offices,  the  administrative  lines  run  to  the  entire  nation.  The  Department  controls  every  amateur  operator 
with  a  transmitting  station  and  every  commercial  ship  and  shore  station,  as  well  as  the  very  host  of  broad- 
casters. The  radio  inspection  staff  and  the  appropriation  supplied  them  has  never  been  large  enough  so  that 
the  inspection  duties  could  be  adequately  done 


How  the  Government  is  Regulating  Radio  Broadcasting 


35 


may  not  be  broadcast.  Whether  such  a 
station  provides  jazz  or  education,  whether  it 
runs  from  six  o'clock  to  midnight,  or  from 
midnight  to  noon,  is  not  defined  or  regulated 
in  any  way.  The  public  is  the  judge,  and  the 
public  makes  its  wishes  known  in  no  uncertain 
manner  to  the  broadcast  station  which  does 
or  does  not  serve  its  needs  or  whims. 

But  providing  all  this  power  over  the 
stations  for  the  listener  is  not  an  easy  mat- 
ter, and  at  times  the  Department  does  not 
get  undivided  encouragement  and  support 
from  the  public.  One  difficulty  which  has 
been  raised  by  the  effort  to  protect  the  Class 
B  wavelengths  against  undue  crowding  is  the 
vigorous  protest  of  some  listeners  that  they 
cannot  separate  accurately  all  of  the  stations 
in  the  Class  A  group,  the  band  from  205  to 
280  meters.  Naturally  they  cannot;  and  as 
crowding  in  that  band  becomes  worse,  the 
difficulty  will  be  greater.  But  this  crowding 
is  in  the  public  interest.  It  means  that 
nine  tenths  of  the  useful  wavelength  area  is 
reasonably  safeguarded  by  suitable  spacing 
between  wavelengths  and  only  one  tenth  is 
crowded.  As  the  listener  understands  the 
great  advantage  of  this,  the  Department 
hopes  that  it  may  gain  even  greater  support 
for  this  idea.  Certainly  from  the  point  of 


view  of  the  public,  nine-tenths  of  the  radio 
loaf  is  better  than  none. 


A  LMOST  since  1912  when  the  Department  of 
*»•  Commerce  was  charged  with  the  enforce- 
ment of  the  radio  laws,  and  certainly  since  the 
advent  of  broadcasting,  they  have  struggled 
along  as  best  they  could,  making  Herculean 
efforts  to  accomplish  their  tasks  with  the  piti- 
fully small  staff  and  Congressional  appropria- 
tion granted  them.  The  radio  affairs  of  the 
country  are  supervised  from  nine  district 
offices.  If  each  radio  inspector  had  an 
equal  territory,  that  would  give  each  one 
five  and  one  third  states  to  look  after.  And 
in  some  district  offices,  an  inspector  and 
one  or  two  assistants  are  expected  to  do  all 
the  work. 

The  recommendations  of  the  radio  con- 
ference, called  in  October,  1924,  by  Secretary  of 
Commerce  Hoover,  were  the  consensus  of  the 
"best  minds"  of  radio  who  were  gathered 
there.  It  is  generally  agreed  that  the  reason 
the  changes  suggested  were  not  put  in  force 
was  because  the  Department  was  so  crippled 
in  available  funds  and  in  personnel  that  any 
additional  undertakings  on  their  part  were 
absolutely  out  of  the  question. — THE  EDITOR. 


T  T  E  WAS  a  distance  fiend, 
JL  JL  A  leather  of  anything  near. 

Though  WOOF  had  a  singer  of  opera  fame, 
And  wow  a  soprano  of  national  name, 
He  passed  them  both  up  for  a  Kansas  quartet 
A  thousand  miles  off  and  hence  "  harder  to  get." 

New  York  was  too  easy  to  hear. 
He  was  a  distance  fiend. 


He  was  a  distance  fiend, 

His  radio  ruling  his  life. 
When  he  and  his  family  went  to  the  play, 
He'd  take  them  to  Yonkers  instead  of  Broadway. 
The  show  being  over,  he'd  blow  to  a  bite 
In  far  Staten  Island,  that  very  same  night. 

God  pities  his  daughter  and  wife, 
He  was  a  distance  fiend. 


He  was  a  distance  fiend. 

Alas,  but  he  died  one  day. 
Saint  Peter  obligingly  asked  would  he  tell 
His  choice  of  a  residence — Heaven  or  Hell? 
He  replied,  with  a  show  of  consistency  fine: 
"Good  sir,  you  have  hit  on  a  hobby  of  mine. 

Which  place  is  the  farthest  away  ?" 
He  was  a  distance  fiend. 

— A.  H.  FOLWELL,  in  The  New  Yorker 


RADIO    IN    A    VIRGINIA    CAVE 

Endless  Caverns  at  Newmarket,  Virginia.     Experiments  with  radio  reception  have  been  tried  in  many  un- 
usual locations  from  coal  mines  to  bank  vaults,  but  it  is  doubtful  if  any  radio  equipment  has  been  located  in 

more  picturesque  surroundings 


THE  MARCH  OF  RADIO 


B- 


Past  President,  Institute  of  Radio  Engineers 


What  Does  the  New  Allocation  of  Broadcast  Wavelengths 

Mean? 


JUST  why  the   Department  of  Commerce 
reallocated  many   broadcast   wavelengths 
is    not    evident.     "The    Department    of 
Commerce  has    been    engaged    for    some 
time    in    an    attempt    to    divide    the    ether 
more  efficiently  than  has  been  the  case  hither- 
to," was  the  announcement  from  Washington. 
Here  are  some  examples  of  the  new  assign- 
ments: WEAF  491.5   meters,  instead  of  492, 
WGBS  315.6  instead  of  316,  wjy  405.2  instead 


of  405,  WHN  361.2  instead  of  360,  etc.  These 
changes  are  so  insignificant  that  just  what  is 
gained  is  not  at  all  evident.  Certainly  no  new 
channels  have  been  created  by  such  diminutive 
shifts  from  former  wavelengths.  The  changes 
are  so  small  that  unless  very  careful  observa- 
tion was  made  before  and  after  the  change, 
the  average  listener  would  not  realize  that  any 
change  had  been  made.  If  for  example, 
WJY  tuned  at  30  on  a  condenser  dial  before, 


The  March  of  Radio 


37 


it  will  now  tune  at  30.03,  but  such  a  shift  is 
much  less  than  the  width  of  one  of  the  division 
marks  on  the  dial.  Most  of  the  changes  in  the 
other  well  known  stations  are  of  equal  insigni- 
ficance insofar  as  the  average  listener  is  con- 
cerned. 

The  First  Presidential  Radio  Inaugural 

GREATER  and  greater  become  the 
radio  audiences  which  are  invited  to 
attend  the  country's  important  events. 
When  President  Coolidge  took  the  oath  of 
office  on  March  4,  the  whole  country  was  en- 
abled to  listen-in,  and  we  must  add,  his 
speeches  generally  make  very  good  listening. 
At  least  21  stations  participated  in  the  broad- 
casting network,  extending  from  Boston  to 
San  Francisco,  and  from  St.  Paul  to  Atlanta. 
This  was  the  Telephone  Company  group  and 
in  addition,  WRC,  wjz,  and  WGY  of  the  Radio 
Corporation  were  tied  in  by  their  own  wires. 

It  must  give  President  Coolidge  increased 
courage  (if  such  were  necessary)  to  reaffirm  his 
stand  for  safeguarding  the  country's  funds — 
this  idea  of  realizing  that  he  can  talk  directly 
to  probably  15,000,000  of  his  countrymen. 

We  hope  that  soon  Congress  will  be 
forced  to  broadcast  its  activities.  Verbose 
senators  may  have  their  activities  some- 
what rationalized  and  sobered  if  they 
realize  that  secret  chamber  procedure  is  no 
longer  available  to  them.  Not  very  many 


of  them  would  care  to  vote  in  the  affirmative 
to  increase  their  own  salaries  immediately 
after  the  president  had  outlined  his  economy 
program — that  is,  they  wouldn't  care  to  if 
they  knew  that  a  few  million  of  their  constitu- 
ents were  listening  carefully  to  their  words. 

What  Membership  in  the  Institute  of 
Radio  Engineers  Means 

FREQUENTLY    we  get    inquiries  about 
the  status   of  some   radio   writer   who 
signs     himself     "radio     engineer"     or 
some  such  title,  or  declares  his  status  by  giving 
membership   in  this  or  that   society.    It   is 
perhaps  pertinent  to  explain  the  significance 
of  membership  in  the  Institute  of  Radio  Engi- 
neers.    Insofar  as  we  know,  this  is  the  onJl-y 
bona  fide  association   of   radio  engineers   in 
existence. 

In  its  membership  of  about  2500,  three 
grades  are  recognized,  and  the  ranking  of  a 
member  in  one  or  the  other  of  these  grades 
gives  a  very  trustworthy  estimate  of  the  man's 
standing  in  the  radio  profession. 

Anyone  of  mature  age  who  is  actively  in- 
terested in  radio  may  become  an  Associate 
member  of  the  Institute.  The  applicant  has 
certain  formalities  to  go  through,  such  as 
filling  out  a  regular  membership  blank  giving 
his  training,  business,  references, "  etc.,  but 
no  difficult  conditions  are  imposed  to  hinder 
him  from  becoming  an  associate  memiber. 


THE    FIRST    RADIO    INAUGURATION 

President  Calvin  Coolidge,  taking  the  oath  of  office  from  Chief  Justice  William  Howard  Taft,  of  the  United 
States  Supreme  Court      March  4,  1925,  was  the  first  time  in  American  history  that  an  ex-^presidenit  ad- 
ministered the  oath  of  office  to  an  incoming  president.     The  twenty-four  stations  which  broadcast  the 
ceremonies  practically  linked  up  the  entire  nation 


Radio  Broadcast 


ENGAGING  A  HOTEL  ROOM  AND  RADIO 

Is  now  possible  at  the  Drake  Hotel  in  Chicago,  the  Roosevelt  in 
New  York,  and  the  Benjamin  Franklin  in  Philadelphia.  A  portable 
set  is  installed  in  the  room  of  the  guest  ordering  it.  Having  an  in- 
dividual receiver  allows  the  guest  to  select  his  own  radio  entertain- 
ment. In  some  large  apartment  houses,  hotels,  and  hospitals  a 
central  receiver  has  been  installed  and  the  output  is  then  wired  to  the 
various  rooms.  The  disadvantage  is  that  but  one  program  can  be 
heard  at  a  time  and  little  or  no  selection  is  offered  the  guest 


apartment  houses  in  New  York, 
the  management  of  the  Roosevelt 
has  decided  that  the  guests  could 
be  better  served  by  putting  ac- 
tual radio  sets  in  the  rooms.  To 
start  the  experiment,  a  dozen 
portable  receivers  with  self- 
contained  loop  antennas  have 
been  purchased  and  are  at  the 
call  of  any  guest.  Presumably 
the  management  will  see  that 
the  sets  are  maintained  in  good 
condition,  and  the  guest  has 
merely  to  ask  for  radio  service, 
and  a  receiving  set  will  be  dis- 
patched to  his  room  at  once  and 
he  may  tune-in  on  any  station 
he  desires. 

Broadcast  Licenses  Should 

Be  Granted  Only  on 

Petition 


The  rank  as  Associate  I.  R.  E.  does  not  carry 
with  it  any  certification  by  the  Institute  that  the 
member  is  or  is  not  a  capable  radio  engineer. 

To  become  a  member  of  the  Institute 
(Member,  I.  R.  E.)  a  man  must  submit  to  the 
Board  of  Direction  a  record  of  his  radio 
achievements.  This  record  is  carefully  scru- 
tinized by  men  who  know  the  radio  field  well. 
Membership  is  given  only  if  the  man's  record 
shows  him  to  be  a  capable  engineer  of  sufficient 
ability  to  carry  out  any  ordinary  radio  project. 
Possibly  one  quarter  of  the  total  membership 
of  the  Institute  have  the  rank  of  member  and 
in  this  group  will  be  found  practically  all  those 
engineers  who  are  responsible  for  modern 
radio  development. 

The  Institute  has  for  its  highest  grade  of 
membership  that  of  Fellow.  This  rank  is  be- 
stowed only  upon  those  few  engineers  who 
have  proved  themselves  leaders  in  the  radio 
field.  Probably  less  than  one  twentieth  of 
the  total  membership  has  been  given  this 
highest  rank. 

Radio  a  la  Carte 

THE  Hotel  Roosevelt,  New  York  among 
others  has  installed  a  novel  radio  service. 
Instead  of  putting   a  receiving   station 
on  the  roof  and  installing  wires  to  the  guest's 
room  as  has  been  done  in  some  of  the  larger 


A i  CHURCHES, hotels,  Elks, 
Klansmen.'and  apparently 
everyone  else,  scramble  for 
broadcasting  licenses,  and  get 
them,  the  question  must  occur 
to  any  one  with  common  sense,  where  is  it  all 
leading  to  and  why  should  the  practice  be 
kept  up?  What  policy  controls  the  Depart- 
ment of  Commerce  in  issuing  licenses?  Or 
has  it  no  policy?  Is  the  real  situation  the 
same  as  the  apparent  one — that  any  one  can 
get  a  broadcasting  license  who  applies  for  it? 

Apparently  feeling  that  he  owed  the  public 
some  comment  on  the  rapidly  congesting  con- 
dition of  the  radio  channels,  whirh  is  accumu- 
lating under  his  direct  supervision,  Mr.  Hoover 
recently  issued  a  long  statement  on  the  radio 
situation  parts  of  which  we  quote: 

There  are  at  present  563  broadcasting  stations  in 
operation,  or  under  construction.  The  most  diffi- 
cult problem  in  radio  regulation  and  development 
is  the  distribution  of  wavelengths  in  such  a  way  as 
to  prevent  interference  between  stations.  There 
are  in  all  86  different  wavelengths  available,  if  we 
keep  the  stations  10  kilocycles  apart  and  stagger  the 
assignment  of  wavelengths  geographically  so  as 
to  prevent  overlap  in  the  area  of  effective  reception. 

The  recent  experiment  of  the  Department  in  at- 
tempting to  increase  the  number  of  channels  by  de- 
creasing the  difference  to  7  kilocycles  proved  un- 
successful with  the  present  development  of  radio 
receiving  apparatus. 

All  through  the  lengthy  document  we 
searched  to  see  if  Mr.  Hoover  did  not  expect 
some  time  to  lessen  his  license-issuing  activi- 
ties. There  is  no  mention  of  it.  It  looks  as 


The  March  of  Radio* 


39 


though  the  Secretary  thought  he  had  no  dis- 
cretionary power  in  withholding  permission 
from  the  new  stations,  or  else  that  he  greatly 
feared  to  use  it,  but  that  conclusion  scarcely 
seems  justified  in  view  of  the  personality  of 
the  present  Secretary. 

According  to  one  of  the  writers  in  the  New 
York  Times: 

There  is  difficulty  in  seeing  just  what  excuse  there 
is  for  granting  the  broadcasting  privilege  to  one 
applicant  and  denying  it  to  others  equally  reputable. 
Nevertheless  a  justification  for  drawing  the  line 
somewhere  on  mere  numbers  of  grantees  must  be 
found  if  radio  is  to  progress  toward  the  realization 
of  its  possibilities,  or  if  it  even  is  to  retain  those 
which  it  now  demonstrates. 

Some  time  soon  Mr.  Hoover  will  have  to  say 
"No,  I  cannot  see  that  the  interests  of  the 
radio  listener  will  be  served  by  granting  you  a 
license,  so  I  must  decline  to  issue  one  to  your 
anticipated  station."  It  scorns  as  though 
someone  is  missing  the  real  idea  of  radio's 
possible  progress.  The  issuance  of  a  license 
should  not  depend  upon  either  precedent, 
favor,  standing  of  the  applicant,  fear  of  em- 
barrassment, or  any  other  item  of  this  nature. 
As  many  of  our  correspondents  continually 
point  out,  the  question  Mr.  Hoover  has  to 
ask  himself  is,  Do 
the  listeners  want 
this  proposed  sta- 
tion? If  they  don't 
want  the  station 
then  the  license 
should  not  be 
granted. 

We  venture  to 
suggest  that  a 
new  applicant  be 
obliged  to  accom- 
pany his  request 
for  a  license  by  a 
petition,  signed  by 
at  least  100,000 
people  who  live 
within,  say  50  miles 
of  the  site  of  the 
proposed  station. 
The  number  of  re- 
quired petitioners 
should  depend 
upon  the  locality 
— around  Chicago 
and  New  York  it 
might  well  be 
1,000,000,  and  in 
sparsely  settled 
country,  possibly 


50,000  or  less.  •  This  procedure  would  decide 
the  question  just  as  it  should  be  decided — in 
the  interest  of  the  radio  listener. 

Will    the    British    Receiver    License 
System  Fail? 

WE  HAVE  mentioned  onceor  twice  that 
if  this  government  should  ever  decide 
to  take  over  radio  broadcasting  and 
should  attempt  to  maintain  the  service  by 
collecting  revenue  from  the  listeners  in  the 
form  of  a  tax  or  license,  it  would  require  a 
tremendous  force  of  collectors  with  hundreds 
of  thousands  of  warrants,  to  make  the  collec- 
tions good.  We  think  that  the  broadcast 
listener  does  not  want  to  be  licensed,  and  if  the 
good  American  public  does  not  want  to  pay  a 
license  fee,  it  probably  won't.  The  nation  has 
been  told  to  stop  drinking  intoxicating  liquor 
for  some  years  now,  but  hasn't  yet  agreed  to 
submit  to  a  ban  on  what  is  still  regarded  by 
many  as  a  "legitimate,"  even  though  unconsti- 
tutional, privilege. 

There  are  several  countries  where  license 
fees  from  the  listeners  are  depended  upon  for 
maintaining  broadcast  service,  among  them, 
England.  We  can  safely  say  that  the  Eng- 


ROY    A.    WEAGANT 

Chief  Engineer  of  the  De  Forest  Radio  Company,  at  work  on  a  receiver  circuit  in  bis 

laboratory 


Radio  Broadcast 


lishman  is  a  more  law-abiding  citizen  than 
we  are.  The  Post  Office  authorities,  who 
have  the  task  of  supervising  British  radio, 
estimate,  says  a  news  dispatch,  that  there  are 
2,500,000  pirates,  who  have  listening  sets  but 
who  have  not  paid  the  government  fee.  A 
bill  is  urged  to  permit  drastic  punishment  for 
these  ether  robbers.  Twelve  months'  im- 
prisonment or  $500  fine  has  been  suggested. 
Even  should  such  a  measure  be  enacted, 
trouble  would  still  be  encountered  because 
before  entering  a  man's  house  a  warrant  is  re- 
quired, and  the  promiscuous  issuance  of  search 
warrants  would  certainly  arouse  a  tremendous 
antagonism  in  a  land  where  every  man's  cottage 
is  supposedly  still  regarded  as  his  castle. 

If  there  really  are  2,500,000  radio  pirates  in 
England,  it  doesn't  augur  well  for  the  license 
system  of  control.  If  these  reports  are  accur- 
ate, it  looks  as  if  the  license  system  in  England 
is  doomed  to  fail  in  the  very  near  future. 

Radio  Quality  Will  Count 

yi  S  WE  glance  through  the  radio  adver- 

f-\    tisements  each  month,   it   is  only  too 

plain .  that    many    radio    firms,    like 

Kipling's  ships,  "pass  in  the  night."     Many  a 

man  who  knew  nothing  whatever  of  the  radio 


game,  was  persuaded  by  some  overenthusiastic 
adviser  that  "mints  of  money"  were  to  be 
gleaned  from  the  radio  public.  All  one  had 
to  do  was  to  get  something  which  sounded  like 
radio  and  then  spend  lots  of  money  on  adver- 
tising. After  that  it  was  to  be  nothing  but  a 
matter  of  counting  profits.  These  inexper- 
ienced radio  adventurers  are  the  ones  who 
come  and  go— but  few  of  them  last  to  enjoy 
the  confidence  of  the  radio  public. 

As  these  bargain-apparatus  firms  start  up 
with  apparently  a  tremendous  price  slash  over 
the  older  and  more  conservative  firms  dealing 
in  the  same  line  of  goods,  it  must  frequently 
seem  to  these  manufacturers  that  their  sales 
are  due  for  a  slump.  But  they  don't  slump 
and  if  the  quality  is  maintained  high,  they 
won't.  New  as  radio  is,  people  already  realize 
that  the  apparatus  with  a  name  behind  it  is 
probably  worth  more  than  the  nameless  waifs 
with  which  the  irresponsible  -store  has  its 
shelves  loaded.  A  reliable  firm  name  means 
much  in  the  paint,  steel,  or  tool  business. 
.Conservative  radio  firms,  whether  they  manu- 
facture panels,  binding  posts,  condensers,  or 
what  not,  will  soon  start  to  reap  the  benefit 
of  their  reputation.  It  probably  won't  be 
very  long  before  the  radio  public  learns  to  buy 
"by  the  name"  rather  than  "by  the  price." 


THE    WRITING    ON    THE    WALL 

During  the  presentation  of  a  radio  play  in  an  English  broadcasting  studio.     The  typewritten  pages  of  the 

manuscript  were  projected  on  a  screen  on  the  studio  wall  where  all  could  see  it.     The  microphone,  English 

style,  is  enclosed  in  the  rectangular  box  in  the  center 


The  March  of  Radio 


Vacuum  Tubes 

in    Another 

Legal  Tangle 

JUST  before  the 
De  Forest  au- 
dion  patent 
expired,  the  attor- 
neys for  his  com- 
pany brought 
about  an  action 
which  had  a  start- 
ling effect  upon 
the  Radio  Corpo- 
ration subsidiaries. 
In  the  United 
States  District 
Court  at  Wilming- 
ton, Delaware, 
Judge  Hugh  M. 
.  Morris,  granted  an 
injunction  which 
stopped  the  Radio 
Corporation's  sale 
of  tubes  manufac- 
tured by  the  West- 
inghouse  Lamp 
Works.  The  case 
involved  nothing 
of  direct  interest 
to  the  radio  lis- 
tener. It  seemed  merely  to  be  a  legal  squab- 
ble. 

When  one  stops  to  think  of  it,  the  legal  pro- 
fession seems  to  be  the  most  inbred  union 
in  existence.  You  have  to  be  a  lawyer  to 
make  a  law,  and  you  have  to  be  a  lawyer  to 
prove  that  someone  else  is  breaking  a  law. 
Furthermore,  one  can't  become  a  lawyer  un- 
less the  rest  of  the  union  wants  him,  because 
the  lawyers  write  the  entrance  examination 
for  the  union.  One  set  of  lawyers  draws  up 
a  legal  document  to  permit  a  lamp  company 
to  manufacture  vacuum  tubes  and  another 
lawyer  hails  them  into  court  to  show  that 
their  law  was  bad.  It  appears  that  the  De 
Forest  agreement  which  would  permit  the 
Wcstinghouse  Electric  and  Manufacturing 
Company  to  manufacture  tubes  would  not 
permit  the  Westinghouse  Lamps  Works  to 
do  so,  even  though  it  is  acknowledged  by  all 
that  the  Lamp  Company  is  simply  that  part 
of  the  Westinghouse  Company  which  had  the 
facilities  for  making  tubes:  The  Manufac- 
turing Company  is  equipped  for  making 
motors  and  all  kinds  of  electrical  machinery, 
but  not  for  turning  out  delicate  lamps  and 
vacuum  tubes,  and  so  naturally  turned  its 


ABOARD    THE    S.S.    "GEORGE    WASHINGTON" 

Captain  Cunningham  has  a  broadcast  receiver  which  he  uses  in  the  time  he  can 

spare  from  his  nautical  duties.     Captain  Cunningham  was  navigator  of  the  U.  S.  A. 

T.  Leviathan  during  the  War.     From  left  to  right,  Captain  Cunningham,  W.  J. 

Roche,  and  T.  H.  Rossbottom 


tube  activities  over  to  the  lamp  division. 
Judge  Morris  ruled  that  even  though  the 
parent  company  had  the  right  to  manufacture 
tubes,  the  Lamp  Company  had  no  sQch  right 
and  all  the  tubes  it  had  wrongfully  manufac- 
tured must  be  confiscated  and  held. 

So  the  lawyers  go,  one  getting  a  company 
into  trouble,  so  that  another  can  get  it  out. 
It  looks  as  though  in  this  case  the  attorneys 
for  the  De  Forest  Company  have  been  a  little 
bit  shrewder  than  those  of  the  Radio  Corpor- 
ation. 

Radio  Dispute  in  Cincinnati 

THE  ever   increasing  number  of  broad- 
casting licenses  issued   by  the  Depart- 
ment of  Commerce  is  practically  certain 
to  bring  trouble  in  a  short  time,  in  ever  increas- 
ing   amounts.     Some    method    of    equitably 
limiting  the  number  of  stations  must  be  found 
by  the  Department.     It  is  their  job  and  they 
might  just  as  well  tackle  it  now. 

A  strange  instance  of  the  Department's  in- 
activity took  place  in  Cincinnati.  Two 
stations  in  that  city  had  been  granted  licenses 
to  operate  on  the  same  wavelength.  After 
much  squabbling  as  to  the  proper  division  of 


Radio  Broadcast 


time,  they  finally  did  operate  on  the  same 
wavelength — at  the  same  time!  It  was  re- 
ported from  Washington  that  the  Department 
of  Commerce  had  been  repeatedly  asked  to 
step  in  and  settle  this  impossible  situation  but 
had  declined  on  the  ground  that  to  set  such 
a  precedent  would  get  the  Department  hope- 
lessly enmeshed  in  a  maze  of  disagreements 
between  stations. 

One  might  well  ask  the  Department  how  it 
did  expect  such  disputes  to  be  settled.  It  is  a 
strange  idea  of  privilege  and  duty  which  con- 
sents to  the  issuance  of  broadcasting  licenses 
to  any  who  want  them  and  then  when  trouble 
comes  to  the  listening  public  as  a  result  of  the 
excessive  number  of  stations,  to  turn  one's 
back  and  let  someone  else  settle  the  trouble — 
trouble  directly  due  to  the  Department's 
freedom  with  its  licenses.  Who,  we  may 
well  ask,  does  Mr.  Hoover  think  will  step  in 
to  straighten  out  such  troubles  between  the 
various  stations,  if  his  department  thinks  the 
task  too  onerous? 

Making  Radio  Transmission  Surer 

IN  A  recent  talk  before  the  American  Insti- 
tute of  ElectricarEngineers,jMr.  Alexander- 
son,    chief    consulting    engineer    of    the 
Radio  Corporation,  gave  a  general  description 
of  their  network  of  channels  which  is  being 


LAYING    A    ROGERS    UNDERGROUND    ANTENNA 
At  Hyattsville,  Maryland.     Dr.  J.  Harris  Rogers  is  nearest  the  camera. 
The  Rogers  system  has  been  developing  experimentally  for  some  time  and 
has  been  watched  by  officials  of  the  War  and  Navy  Departments 


rapidly  extended  over  the  earth.  After  out- 
lining general  troubles  and  difficulties  which 
an  engineering  audience  could  well  appreciate, 
the  speaker  went  more  into  detail  to  show  how 
the  Radio  Corporation  was  continually  work- 
ing to  increase  the  certainty  of  communication 
over  their  radio  links.  He  spoke  of  the  re- 
markable wave  antennas  used  at  Riverhead, 
over  which  signals  from  all  the  stations  in 
Europe  are  received.  Although  static  has 
not  been  annihilated  by  the  R.  C.  A.  engineers, 
this  reception  scheme  of  theirs  ensures  com- 
munication unless  there  is  a  severe  local  thun- 
derstorm. To  obviate  the  possibility  of  such 
a  storm  interferingwith  transatlantic  channels, 
another  receiving  antenna  has  been  fitted  up 
in  Maine,  so  that  either  can  now  be  used,  de- 
pending upon  where  the  atmospheric  disturb- 
ance is  least. 

He  spoke  of  new  features  in  short  wave 
transmission,  a  so-called  high-angle  beam. 
If  one  could  rely  upon  his  rather  scanty  de- 
scription, it  appears  that  he  thinks  it  may  be 
possible  to  send  short  wave  energy  from  one 
place  to  another  by  some  kind  of  beam  system 
which  is  directed  high  up  in  the  air.  to  come 
down  at  a  desired  spot  by  reflecting  from  the 
earth's  upper  conducting  atmosphere.  This 
story  reads  more  like  a  poet's  dream  than 
like  an  engineer's  narrative,  so  don't  give  it  too 
much  credence  as  yet. 

It  may  be  possible  to  send 
beams  of  energy  high  up  in 
to  the  sky  and  so  around  the 
Heaviside  layer,  but  it  is 
more  likely  that  such  an 
etfect  will  be  found  in  Eng- 
land than  here.  America  has 
done  practically  nothing 
with  directed  beam  trans- 
mission, but  Marconi  and 
Round  seem  to  be  progress- 
ing continually  along  just 
these  lines. 

If  directed  beams  sent 
high  into  the  air  actually 
get  much  farther  than  those 
sent  along  the  earth's  sur- 
face they  would  probably 
have  found  out  and  reported 
it  to  us  long  ago. 

The  Day  of  Good  Music 

'ERV  recently  a  most 
welcome  announce- 
ment   was  made    by 
Mr.  John   A.    Holman, 
broadcasting     manager    of 


V 


The  March  of  Radio 


43 


station  WEAK.  The 
public's  demand 
for  jazz  has  greatly 
decreased,  he  as- 
serts, as  evidenced 
by  the  letters  re- 
ceived from  the 
station's  listeners. 
Of  the  many  thou- 
sands of  listeners 
who  now  write  in, 
by  far  the  most 
want  good  music, 
he  says;  and 
thanks  be,  say  we, 
that  the  managers 
are  waking  up  to 
the  fact  that  the 
whining,  croaking, 
saxophone  with  its 
associated  agony- 
producing  pieces 
of  barbarism,  are 
due  for  the  dis- 
icard,  as  far  as 
the  radio  listener 
is  concerned. 

Mr.    Holman 

evidently  thinks  there  has  been  a  change 
of  appreciation  on  the  part  of  the  listen- 
ers, but  we  doubt  this  very  much.  The  let- 
ters no  doubt  indicate  such  to  be  the  fact, 
but  it  seems  more  likely  that  the  admirer 
of  jazz  would  write  enthusiastic  letters  to 
the  broadcaster  more  often  than  a  lover  of 
Chopin  and  Mozart.  The  appreciator  of  jazz 
is  the  one  who  makes  the  most  noise,  just  as 
a  dozen  wild  American- Irish  would  make 
enough  noise  against  such  a  speaker  as  Mr. 
Lloyd  George  to  drown  out  the  approbation 
of  the  remaining  2000  in  the  audience.  This 
has  probably  been  the  case  with  the  radio 
audience — those  who  wanted  good  music  are 
the  quiet  type  who  suffered  much  and  long 
before  remonstrating  against  the  finally  un- 
bearable monotonies  of  much  of  the  modern 
jazz. 

What  the  Radio  Corporation  Did  in 
1924 

SEVERAL  points  in  the  annual  report  of 
President    Harbord  of  the   Radio   Cor- 
poration   for    the    year     1924    demand 
comment.     We  think  it  is  only  fair  to  give  the 
Radio  Corporation  credit  for  being  the  first 
to   inaugurate   broadcast    concerts    by   well- 
known    phonograph    recording    artists.     The 
idea,  which  was  later  taken  up  by  the  American 


CHARTING    THE    DEPTH    OF   THE    PACIFIC   OCEAN 

With  the  sonic  depth  finder,  a  new  application  of  well-known  radio  principles.  The 
apparatus  projects  a  vibration  which  follows  through  the  water  to  the  ocean  bed;  it 
is  then  reflected  back.  The  elapsed  time  is  measured  from  which  the  depth  of 
water  can  be  calculated.  Lieut.  Clore  of  the  U.  S.  S.  Pioneer  is  shown  in  the  radio 
cabin  of  his  vessel  operating  the  depth  finder 


Telephone  and  Telegraph  Company  with 
much  success,  originated  in  an  agreement  be- 
tween the  Radio  Corporation  and  the  Bruns- 
wick-Balke-Collender  Company.  This  inno- 
vation in  broadcasting  programs  was  an 
inspiration,  and  it  is  a  pleasure  to  record  our 
appreciation  of  its  inception. 

In  speaking  of  the  value  of  the  radio  busi- 
ness, General  Harbord  made  the  interesting 
statement  that  for  every  dollar  spent  on 
musical  instruments  of  all  kinds,  phonographs, 
pianos,  and  organs,  seventy-five  cents  was 
spent  on  radio.  Radio  business  was  about 
three-quarters  that  of  the  entire  jewelry 
business  of  the  United  States. 

In  transoceanic  traffic,  radio  carried  be- 
tween twenty  and  thirty  per  cent,  of  European 
traffic,  and  fifty  per  cent,  of  the  trans-pacific 
messages.  Apparently  the  proportion  of  radio 
to  cable  messages  is  not  changing  very  rapidly, 
as  it  is  our  recollection  that  about  the  same 
proportion  existed  during  the  previous  year. 

Radio  Raises  Cable  Earnings 

INSTEAD  of  taking  business  away  from  the 
transoceanic  cables,   the  development  of 
radio  appears  actually  to  have  put  money 
into  the  coffers  of  the  cable  companies,  accord- 
ing to  a  statement  of  Clarence  H.  Mackay. 
Mr.  Mackay  says  that  the  Commercial  Cable 


44 


Radio  Broadcast 


E.    F.    W.    ALEXANDERSON 

Schenectady;  Chief  Consulting  Engineer, 

Radio  Corporation  of  America 
"  There  is  a  large  and  growing  group  of  amateurs 
who  pursue  radio  for  the  love  of  the  art.  The  art 
to  them  is  not  the  performance  in  the  studio  hut 
the  technical  art  of  radio  itself.  Radio  has  en- 
joyed a  greater  following  of  amateurs  than  any 
other  branch  of  engineering,  and  it  is  the  thought 
of  these  amateurs  that  moulds  the  future.  They 
are  one  step  closer  to  reality  than  the  imaginative 
•writers,  like  Kipling  and  Jules  Verne,  who  give 
us  glimpses  of  the  future  long  before  they  can  be 
realised.  The  amateur  likes  to  anticipate  what 
advances  in  the  art  may  reasonably  be  expected 
within  the  next  decade" 


Company  had  handled  more  business  over  its 
cables  in  1924  than  during  any  previous  year 
of  the  company's  existence. 

The  changing  economic  situation  in  Europe 
was  reflected  in  a  growing  demand  for  cable 
service,  and  as  for  radio's  encroachment  on  the 
cable's  territory,  Mr.  Mackay  says  "on  the 
contrary,  the  radio  has  actually  stimulated  the 
use  of  electrical  communication  between  the 
continents,  and  of  the  new  business  so  created, 
the  cables  are  really  getting  more  than  their 
proportionate  share." 

Mr.  Sarnoff  As  An  Optimist 

SEVERAL  times  during  the  last  decade 
the  press  has  chronicled  that   someone 
had    laid   low   Demon  Static  and  that 
hereafter,  by  the  application  of  some  heaven- 
born  device,  radio  was  to  be  freed  of  trouble- 
some   atmospheric    disturbances.    Too    well 
now,  we  know  that  these  were  all  illusions. 
But  now  Mr.  Sarnoff,  General  Manager  of 


the  R.  C.  A.,  strikes  an  entirely  different  note 
when  mentioning  static.  At  a  recent  dinner 
he  ventures  the  opinion  that  static,  after  all, 
is  not  an  unmixed  evil. 

I  often  wonder,  whether  the  same  minds  saw  the 
limitations  of  radio  telephony  because  of  the  lack 
of  secrecy,  and  now  see  a  limitation  of  radio  because 
of  static,  might  not  be  disappointed  to  wake  up  some 
morning  in  the  future  to  find  that  the  static,  which 
is  all-pervading,  represents  a  great  and  free  gift  of 
nature  to  man,  who  may  yet  learn  to  harness  that 
energy,  get  it  from  the  air,  and  make  it  do  a  great 
work  for  man. 

Not  seeing  through  the  same  rosy-hued 
glasses  as  does  the  speaker  on  this  occasion, 
we  venture  that  the  man  who  gets  static  out 
of  the  air,  no  matter  what  he  does  with  it 
after  he  removed  it  from  the  radio  realm,  will 
already  have  done  a  great  work  for  man. 

Incidentally,  Franklin  with  his  kite  did 
show  us  exactly  how  to  do  this  thing  quite 
some  vears  ago,  didn't  he? 


Interesting  Things 
Said 


Interestingly 


P\R  WILLIS  R.  WHITNEY  (Schenectady;  di- 
*-^  rector  of  research  for  the  General  Electric 
Company):  "We  are  building  a  $150,000  laboratory 
to  be  devoted  to  research  in  the  field  of  directional 
radio  and  short  wavelengths.  Our  experimenters 
have  obtained  results  on  wavelengths  on  less  than 
fifty  meters.  We  can't  yet  explain  why  such  waves 
travel  as  far  as  they  do,  with  relatively  weak  im- 
pulses behind  them,  or  why  they  should  have  passed, 
unaffected,  through  the  belt  of  darkness  produced 
by  the  eclipse,  while  the  longer  wavelengths  were 
either  accelerated  or  deflected.  .  .  . 

We  can  look  for  the  transmission  of  power  by  radio 
if  we  are  satisfied  to  use  99  per  cent,  of  our  power  in 
transmitting  the  other  one  per  cent.  It  is  a  matter 
of  cost.  So  long  as  it  is  cheaper  to  send  power  over 
wires,  there  is  no  incentive  to  send  it  over  the  air. 
The  ordinary  radio  transmitter  sends  power  through 
the  air,  though  in  relatively  small  quantities  It 
may  be  more  economical  to  send  power  through  the 
air  for  operating  a  powerhouse  switch  than  to  send 
a  man  to  do  it." 

'THE  REV.  FATHER  JOHN  HANDLY  (So- 
*  ciety  of  the  Paulist  Fathers.  New  York):  "The 
thing  that  impressed  me  along  the  lines  of  my  daily 
work  in  collecting  money  for  the  new  Paulist  League 
broadcasting  station  was  the  fact  that  our  Divine 
Lord  was  describing  a  scene  very  familiar  to  me  in 
the  parable  of  the  Sower  and  the  Seed,  because  I  was 
reared  on  a  stony  briar-choked  farm  down  in  Ten- 
nessee. .  .  .  There  are  many  who  are  doubtful 
about  the  value  of  radio  as  a.  means  of  teaching  relt- 


The  March  of  Radio 


45 


gion.  I  want  to  call  their  attention  to  this  point — 
that  our  Lord  thought  it  worth  while  to  broadcast 
the  Word  of  God  in  spite  of  the  fact  that  some  of 
the  seed  fell  by  the  wayside.  ...  He  thought 
it  worth  while  because  he  hoped  some  would  fall  on 
good  ground  and  bring  forth  fruit." 

\A7ILLIAM  A.  FISCHER  (Boston;  in  a  recent 
"  *  paper  read  before  the  Music  Teachers'  Na- 
tional Association  in  St.  Louis):  "Radio  listeners  in 
this  country  are  tax  free  and  have  been  trained  to 
expect  a  startling  variety  of  entertainment  for 
nothing,  while  broadcasters  have  been,  and  still  are, 
placing  their  dependence  on  performers  and  speakers 
who  give  their  services  without  pay  in  their  eager- 
ness for  publicity.  Thus  a  vicious  circle  has  been 
started.  Until  artists  worth  paying  for  are  regularly 
engaged,  radio  concerts,  with  exceptions,  will  con- 
tinue to  be  merely  a  source  of  advertising  to  imma- 
ture performers  who,  instead  of  helping  the  public  to 
enjoy  good  music,  often  cast  opprobrium  on  it  by 
their  inadequate  and  inarticulate  performances." 

D  OBERT  L.  COX  (New  York;  second  vice- 
*^-  president,  Metropolitan  Life  Insurance  Com- 
pany, speaking  of  the  Company's  plans  for  broad- 
casting setting-up  exercises  through  WEAF,  WJAR, 
and  WEEI):  "While  -radio  itself  is  no  experiment, 
the  use  of  it  for  teaching  health  is  still  in  the  develop- 
mental stage.  We  are  going  to  give  the  radio  audi- 
ence what  they  want  in  this  respect,  but  we  don't 
propose  stopping  with  the  letters.  We  have  other 
means  of  finding  out  what  people  want.  .  .  . 
Through  our  agents,  we  shall  be  able  to  make  a 
house-to-house  canvass  and  learn  what  the  radio 
fans  think,  not  only  of  our  health  messages  and 
exercises,  but  of  radio  programs  in  general." 

D  OBERT  H.  RANGER  (New  York;  engineer, 
^  Radio  Corporation  of  America;  in  charge  of 
development  work  of  the  Radio  Corporation  system 
of  transmission  of  photographs  by  radio):  "For 
eighty  years  a  thousand  or  more  investigators  and 
certainly  millions  of  dollars  have  been  concerned  in 
the  attempt  to  transmit  pictures  successfully  at  a 
distance.  Economics  enters  into  the  problem  as 
much  as  mechanical  and  electrical  design.  In  the 
photoradiograms  transmitted  across  the  Atlantic 
in  December,  we  narrowed  them  down  to  a  kind  of 
sketchy,  shorthand  form,  because  of  the  economic 
factors  of  time,  power,  and  cost,  all  of  which  are 
highly  important  in  picture  transmission.  .  .  . 
The  response  accorded  photoradiograms,  which  was 
far  greater  than  those  of  us  who  have  been  concen- 
trating on  prosaic  long-distance  wireless  telegraph 
communication  ever  expected,  has  greatly  encour- 
aged us  in  our  efforts  to  refine  and  improve  the 
transmitted  picture." 

D  UDOLPH  H.  WURLITZER  (New  York;  man- 
F^-  ufacturer  of  musical  instruments):  "Our 
company  believes  that  radio  will  develop  the  musical 
taste  of  the  people  of  the  United  States  more 
rapidly  than  if  radio  had  not  existed.  We  regard 
our  sales,  totalling  $14,782,576  during  a  nine- 


MARTIN    P.    RICE 


Schenectady;  Director  of  Broadcasting, 

General  Electric  Company 
"  The  Department  of  Commerce  is  now  embar- 
rassed by  the  number  of  broadcasting  stations 
desired  in  comparison  to  the  number  of  wave- 
lengths available.  A  reallotmenl  of  wavelengths 
is  now  in  progress  in  the  hope  of  improving  con- 
ditions for  the  radio  listener.  It  would  be  highly 
desirable  to  provide  an  exclusive  wavelength  for 
each  station  operating  with  sufficient  power  to 
reach  across  the  continent  and  having  programs 
of  national  interest.  Such  a  plan  would  increase 
materially  the  reliability  of  long  distance  broad- 
cast reception  and  the  increased  range  would 
stimulate  the  large  stations  to  strive  for  the  best 
in  programs.  Progress  along  these  lines  would 
not  restrict  the  development  of  the  strictly  local 
stations  designed  to  reflect  the  community  life  of 
their  own  districts.  Such  stations,  operating 
on  another  band  of  wavelengths,  have  their  own 
function  and  they  may,  on  occasion,  be  tied  into 
the  general  or  national  group  by  means  of  wire 
lines  or  radio  rebroadcasting" 


months'  period  when  radio  was  mounting  in  popu- 
larity, as  compared  with  $13,653,809  during  the 
same  period  in  1923,  as  significant.  It  is  estimated 
that  more  than  thirty  million  people  in  this  country 
play  some  musical  instrument.  When  such  a  large 
population  of  players  have  their  natural  human  in- 
terest in  music  stimulated  by  the  radio  programs, 
an  increased  demand  for  musical  instruments  is  not 
at  all  surprising." 

"THIS  ADVERTISEMENT   is  a   "tabloid    His- 
*  tory   of  American  Civilization;   a   capsule  cri- 
tique of  the  Higher  Learner  in  these  U.  S/A.;  it  ap- 
peared in  the  Shreveport  Journal,"  comments  F.P.A. 
in  the  New  York  World.     The  advertisement: 
ONE  SET  HARVARD  CLASSICS,   51    Books, 
new,    for    Radio    Receiving    Set.     Box    634, 
Journal. 


How  to  Design  Radio  Coils 

A  Simple  Non-Mathematical  Method- Which 
Can  Be  Applied  by  Any  Radio  Constructor 


BY    HOMER  S.   DAVIS 


ONE  of  the  most  frequent  problems 
confronting    the    amateur    radio 
builder  is  the  design  of  the  induc- 
tance   coils    of    a    new    receiver. 
Often  the  size  of  tubing  or  kind  of  wire  speci- 
fied by  the  designer  is  unobtainable,  or  one 
may  prefer  to  re-design  a  coil  to  conform  to  the 
principles  of  low-loss  design.     "Cut  and  try" 
methods  are  crude  at  best,  and  if  the  amateur 
has  some  means  of  easily  computing  the  in- 
ductance of  a  coil,  he  can  save  both  time  and 
expense  by  its  use. 

The  solenoid,  or  single-layer  winding,  is  a 
common  form  of  coil,  and  it  is  rather  generally 
agreed  to  be  the  most  efficient  for  a  given  value 
of  inductance.  But  although  the  simplest 
to  design,  the  formula  for  a  solenoid  is  rather 
difficult  to  use  unless  one  is  quite  familiar  with 
mathematics.  Fortunately,  there  are  several 
methods  of  representing  formulas  graphically, 
and  of  these,  the  alignment  chart  is  probably 
the  easiest  to  use,  and  therefore  offers  the  best 
solution  to  our  diffi- 
culties. A  pencil  and 
a  ruler  are  all  that  are 
required  to  use  these 
charts. 

A  discussion  of  the 
manner  in  which  they 
were  worked  out  is 
given  below  for  the 
benefit  of  any  who 
may  care  to  follow  it 
through,  although  it 
is  not  in  any  way 
essential  to  the  use 
of  the  charts.  The 
reader  may  skip  en- 
tirely over  this  discus- 
sion if  he  so  desires. 

The  formula  for 
the  inductance  of  a 
single -layer  solenoid 


crohenries,  d  the  diameter  in  inches,  n  the 
number  of  turns  per  inch,  I  the  length  of  the 
solenoid  in  inches,  and  K  the  shape  factor. 
The  latter  depends  upon  the  ratio  of  the  diam- 
eter to  the  length,  and  its  value  may  be  ob- 
tained from  tables  in  the  Bureau  of  Standards 
Bulletin  No.  74  and  elsewhere.  Thus  it  is 
not  especially  difficult  to  solve  for  the  induc- 
tance of  a  coil  when  d,  n,  and  1  are  known. 
But  the  factor  K  causes  no  end  of  trouble  when 
we  try  to  use  the  formula  in  the  reverse  di- 
rection, solving  for  1,  since  K  is  then  an  un- 
known also.  Cut  and  try  methods  must  be 
resorted  to.  We  can  express  K  in  a  for- 
mula in  terms  of  d  and  1,  but  the  relationship 
is  not  simple.  However,  in  most  cases,  the 

value  of  the  ratio  -  lies  between  £  and  2,  and 

between  these  limits  we  may  express  K  as 
approximately:  K=o6?4  /d\  -*» 


(r) 


where    L    represents 
the  inductance  in  mi- 


A  Coil  Calculator 

Is  what  the  chart  which  accompanies  this 
article  of  Mr.  Davis's,  really  is.  Any  number 
of  constructors  who  tried  to  build  a  radio 
set  from  directions  have  been  stopped  short 
by  their  inability  to  secure  a  certain  size 
coil  and  had  no  way  of  calculating  its  size, 
except  by  mathematics.  And  mathematics, 
to  many  of  the  radio  constructing  gentry,  is 
not  a  desirable  part  of  the  picture.  Many 
of  the  advanced  radio  calculations  lead  one 
directly  into  the  calculus.  Those  who  wish 
nothing  more  than  a  good  rule-of-thumb  will 
find  the  chart  will  allow  them  to  build 
coils  to  the  specifications  of  the  various  con- 
struction articles,  will  allow  them  to  build  a 
coil  to  attain  a  certain  wavelength  range  with 
a  condenser  of  given  size,  and  by  reversing 
the  process,  it  is  possible  to  find  out  what 
size  condenser  should  be  used  with  a  given 
coil  to  attain  a  known  wavelength.  The 
chart  and  the  wire  table  should  be  of  great 
help  to  the  builder  of  sets. — THE  EDITOR 


Substituting  this  in 
the  first  formula,  we 
have: 

L  =  .oi69n->dI-7tt7l1-29:J 
and  K  has  been  eli- 
minated. It  is  now 
possible  to  solve  for 
any  one  value  when 
the  three  others  are 
known.  It  is  still  a 
formidable  looking 
equation,  but  it  may 
be  charted  with  ease. 
It  is  hardly  necessary 
to  explain  here  how 
the  charts  are  con- 
structed, but  suffice 
it  to  say  that  they 
are  based  upon  the 
same  theory  as  the 
slide  rule,  which  was 
described  in  the  "R.. 
B.  Lab."  department 
of  the  January  192^ 
number  of  RADIO 
BROADCAST. 


How  to  Design  Radio  Coils 


47 


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15 

Radio  Broadcast 


The  formula  from  which  Chart  i  was  con- 
structed is 


where  X  represents  the  wavelength  in  meters, 
L  the  inductance  in  microhenries,  and  C  the 
capacity  of  the  tuning  condenser  in  micro- 
farads. 

Referring  to  Fig.  i,  it  is  seen  that  the  two 
charts  have  been  placed  side  by  side,  with  the 
L-scale  in  common.  As  an  example  of  the 
use  of  these  charts,  let  us  say  that  we  wish  our 
tuned  circuit  to  reach  a  maximum  wavelength 
of  550  meters,  and  that  we  plan  to  use  a  .0005 
mfd.  variable  condenser  tubing  three  inches  in 
diameter,  and  No.  18  d.  c.  c.  wire.  With  a 
pencil  and  ruler  we  draw  a  line  from  .0005 
on  the  C-scale  through  550  on  the  X-scale, 
until  it  intersects  the  L-scale,  reading  170 
mh.,  as  the  required  inductance  of  our  coil. 
Another  line  is  drawn  from  L=  170  to  d  =  3. 


Referring  to  the  copper  wire  table,  Fig.  2,  we 
find  that  No.  18  d.  c.  c.  wire  can  be  wound  \g.6 
turns  to  the  inch,  so  we  draw  a  third  line 
from  this  value  on  the  n-scale,  through  the 
intersection  of  the  second  line  and  the  index 
line,  until  it  intersects  the  I-scale.  This 
shows  us  that  the  coil  should  be  wound  to 
a  length  of  three  inches,  and  the  product  of 
n  and  1  gives  59  as  the  number  of  turns  re- 
quired. 

The  chart  may  be  worked  in  the  reverse 
direction  in  exactly  the  same  manner,  always 
making  sure  that  the  correct  pairs  of  scales  are 
connected  together. 

The  amateur  builder  will  find  many  uses 
for  these  charts.  In  addition  to  their  value 
in  designing  inductances  for  a  new  receiver, 
they  may  be  used  to  redesign  a  coil  for  dif- 
ferent sizes  of  tubing,  wire,  or  tuning  con- 
denser than  originally  specified. 


KIND  OF  INSULATION 

B.  &  S. 

DCC 

sec 

DSC 

ssc 

ENAMEL 

ENA 
AND 

MEL 
AND 

GAUGE 

sec 

SSC 

14 

13.7 

14.6 

14.7 

15.0 

15.2 

14.2 

14.7 

15 

15.0 

16.2 

16.4 

17.0 

17.0 

15.8 

16.5 

16 

16.7 

18.0 

18.2 

19.0 

18.7 

17.6 

18.4 

17 

18.5 

20.0 

20.0 

21.2 

21  A 

19.5 

20.5 

18 

19.6 

22.3 

22.3 

23.6 

24.0 

21.7 

22.9 

19 

22.5 

25.0 

25.2 

27.0 

27.2 

24.2 

25.8 

20 

24.5 

27.5 

27.5 

29.5 

30.1 

26.5 

28.4 

21 

27.5 

30.8 

30.8 

32.8 

33.6 

29.6 

31.5 

22 

30.0 

34.0 

34.0 

36.6 

37.7 

32.7 

35  0 

23 

32.7 

37.5 

37.5 

40.7 

42.3 

36.1 

39.0 

24 

35.5 

41.5 

41.5 

45.3 

47.2 

39.7 

43.1 

25 

38.5 

45.7 

45.7 

50.3 

52.9 

43.7 

47.9 

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 

58.1 

28 

48.5 

60.0 

60.0 

68.3 

73.9 

57.0 

64.4 

29 

52.0 

65.5 

65.5 

75.4 

82.2 

61.9 

70.6 

30 

55.5 

71.3 

71.3 

83.1 

92.3 

67.4 

77.9 

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 

33 

66.3 

90.3 

90.3 

110.0 

130.0 

85.6 

103.0 

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 

38 

83.5 

133.0 

133.0 

168.0 

235.0 

120.0 

157.0 

39 

89.7 

140.0 

140.0 

181.0 

261.0 

128  0 

172  0 

FIG.    2 
Wire  turns  per  linear  inch 


OVER   THE    TOP 


RADIO  BROADCAST  Photograph 


A  layout  view  showing  the  actual  scarcity  of  wiring.     The 
angle    of    placement    of    the    coils    is    clearly    indicated 


How  to  Build  a  Two-Stage  Radio 
Frequency  Amplifier 


BY  JOHN  B.   BRENNAN 


1~*HE  amplifier  described  in  this  article  incorporates  some  new  and  desirable  ideas 
in  construction.  Leads  have  been  reduced  to  the  shortest  possible  length, 
the  famous  Roberts  system  of  double-wound  coils  has  been  used  for  the  neutral- 
ization of  each  stage,  and  the  especially  efficient  diamond  weave  coils  employed  for 
the  transformers.  This  unit  is  simply  a  radio-frequency  amplifier  which  can  be 
connected  to  any  detector.  A  later  article  will  describe  a  detector  and  audio- 
frequency amplifier  which  may  be  used  with  it.  In  these  days  of  high  power  broad- 
cast stations,  the  selectivity  gained  by  the  use  of  radio  frequency  amplification  is 
especially  desirable.  By  completely  neutralizing  both  stages  of  this  amplifier, 
the  full  gain  from  each  tube  is  secured.  The  simplicity  of  design  and  the  ease  of 
construction  of  this  unit,  in  addition  to  its  important  feature  of  non-radiation, 
should  appeal  to  every  constructor. — THE  EDITOR 


EFORE  dealing  with  the  construction 
of  a  radio-frequency   amplifier  it   is 
well  to  understand  just  what  radio 
frequency  energy  is  and  how  it  may 
be  amplified. 

The  signal  radiated  by  a  broadcast  station  is 
composed  of  many  electromagnetic  vibrations 
or  alternations.  Due  to  many  causes,  such 
as  the  power  of  the  transmitting  station, 
absorption  losses,  location  of  the  receiver,  etc., 
these  impulses  which  are  collected  by  the 
receiving  antenna  may  be  too  feeble  to  actuate 
the  detector  tube.  When  this  is  the  case, 


little  or  no  rectification  in  the  detector  tube 
takes  place,  making  it  impossible  for  the  signal 
to  be  heard.  To  state  the  case  simply,  the 
detector  tube  performs  the  function  of  rectify- 
ing and  making  audible  the  very  high  or  radio 
frequencies  which  cannot  be  sensed  by  the  ear. 
This  tube,  so  to  speak,  transforms  or  lowers  the 
radio-frequency  currents  to  an  audible  or 
audio-frequency  current. 

The  vacuum  tube  can  function  as  an  am- 
plifier (or  repeater,)  and  it  is  possible  to 
strengthen  the  amplitude  of  the  very  feeble 
received  signal  from  the  antenna,  by  means  cf 


Radio  Broadcast 


a  radio-frequency  amplifier,  before  it  reaches 
ihe  detector. 

Contrary  to  the  general  belief,  the  original 
signal  potential  is  not  passed  along  and  ampli- 
fied in  these  successive  stages  of  radio- 
frequency  amplification.  The  action  in  these 
units  is  more  on  the  order  of  a  trigger  releasing 
device.  To  understand  this,  the  action  of  an 
amplifier  must  be  observed. 

THE  TRIGGER  ACTION  OF  THE  TUBE 

WHEN  a  signal  is  applied  to  the  grid 
of  an  amplifying  tube,  the  electronic 
emission  from  the  filament  is  interrupted  in  its 
path  to  the  plate  because  the  grid  acts  as  a 
shutter  or  trigger  device.  By  means  of  a 
local  source  of  potential  (the  B  battery),  the 
variation  in  signal  frequency  is  faithfully 
reproduced  in  the  plate  circuit  of  the  tube  in 
the  form  of  a  varying,  direct  current  potential 
many  times  greater  in  strength  than  the 
original  signal  applied  to  the  grid  of  the  tube. 

In  other  words,  the  vacuum  tube  has  re- 
peated and  amplified  the  incoming  signal  with- 
out changing  any  of  its  characteristics. 

We  have  so  far  traced  the  action  in  this 
circuit  to  the  plate  circuit  of  the  first  tube. 

A  typical  two-stage  radio-frequency  ampli- 
fier with  detector  and  one-stage  audio  ampli- 
fier is  shown  in  Fig.  i . 

Now  in  this  plate  circuit  is  contained  the 
primary  coil  Pa  of  the  radio-frequency  coup- 
ling unit.  This  unit,  consisting  of  the  primary 
and  a  secondary  which  is  connected  to  the 
input  of  the  next  tube,  performs  the  function 
of  inductively  coupling  one  tube  circuit  to 
the  next  so  that  the  signal  received  by  the 
antenna  may  be  repeated  at  a  greater  ampli- 


Mu,  OR  AMPLIFICATION  FACTOR 
OF  TUBE 


-Incoming  Signal 

(continuous  wave* 

which  is  impressed 

on  Grid  of  Tube 


FIG.    2 

How  a  tube  amplifies,  graphically  shown.     This  only 

takes  into  consideration  the  amplification  factor  of 

the  tube.     Actually,  the  amplification  is  greater,  due 

to  the  step-up  value  of  the  r.  f.  coupler  unit 

tude  in  each  successive  stage.  In  this  instance, 
the  unit  is  a  radio-frequency  transformer. 
When  the  variation  of  current  takes  place 
in  the  first  plate  circuit,  coinciding  with  the 
variation  of  frequency  of  the  received  signal, 
an  electro-magnetic  field  is  set  up  in  and  about 
the  plate  coil,  the  intensity  of  which  varies 
with  the  variation  of  the  plate  energy.  This 
varying  magnetic  field  induces  in  the  secon- 
dary of'the  transformer,  which  is  the  grid  coil 
of  the  next  tube,  a  magnified  voltage  corre- 
sponding exactly  to  that  to  be  found  in  the 
preceeding  plate  circuit.  (The  direction  in 
which  the  current  flows  in  the  two  coils  is 


AUDIO 
AMPLIFIER 


no.  i 

A  typical  radie-frequency  amplifier  circuit.     Oscillation  control  is  obtained  by  the  potentiometer 


How  to  Build  a  Two-Stage  Radio-Frequency  Amplifier 


opposite,  but,  for  our  present  study,  that  fact 
makes  no  difference.) 

Then,  of  course,  the  magnified  signal  is 
applied  to  the  grid  of  this  second  tube  and 
the  entire  tube  action  is  repeated  again,  and 
so  on  for  each  successive  stage.  See  Figs. 
2  and  3. 

The  variable  condensers  €1-2-3  shunted 
across  the  various  secondaries  are  employed 
to  tune  the  circuits  to  the  wavelength  of  the 
received  signal.  For  this  reason  the  unit  ?2, 
82  and  €2  in  combination,  is  called  a  tuned 
radio-frequency  transformer.  We  may  sum 
up  then  by  saying  that  in  action,  a  radio- 
frequency  amplifier  will  magnify  the  feeble 
antenna  vibrations  which  ordinarily  would 
not  be  strong  enough  to  actuate  the  detector 
tube. 

While  radio-frequency  amplifiers  do,  to  a 
certain  degree,  increase  the  volume  of  a  re- 
ceiver, their  main  function  is  to  amplify  feeble 
radio  energy  which  comes  from  great  distances. 
This  is  the  way  in  which  a  radio-frequency 
amplifier  will  increase  the  receiving  range  of  a 
radio  receiver.  Such  an  amplifier  will  not, 
as  a  rule,  increase  the  volume  of  signals  which 
are  already  strong  enough  to  be  heard  well. 

THE    DESIGN    OF    AN    AMPLIFIER 

""pO  PASS  the  action  of  amplification  from 
*  one  tube    to    another,    called    cascading, 
some  coupling  means,  which  was  previously 
explained,  must    be    employed. 

Several  methods  for  coupling  have  been 
devised,  such  as  untuned  transformer-coupled, 
tuned  impedance-coupled,  and  tuned  trans- 
former coupled.  The  names  indicate  the 
method  employed  to  induce  energy  from 
the  plate  circuit  of  one  tube  to  the  grid  of  the 
next.  Amplifiers  employing  tuned  radio- 


frequency  transformers  have  been  generally 
accepted  as  the  most  satisfactory  and  they  are 
embodied  in  the  amplifier  to  be  described  here. 
The  satisfactory  operation  of  the  set  depends 
to  a  great  extent  upon  the  correct  design  of  the 
radio-frequency  coupling-unit. 

The  ratio  of  transformation  is  important. 
In  some  cases  a  i  to  i  ratio  is  employed,  but  in 
the  majority  of  cases  the  radio-frequency 
coupler  has  a  step-up  ratio  of  its  own.  For 
instance  the  primary  or  plate  coil  will  be 
wound  with  ten  turns  of  wire  while  the  secon- 
dary coil  will  have  sixty  turns.  This  is  a  6 
to  i  ratio  between  secondary  and  primary 
respectively.  The  shape  and  size  of  the  coils 
also  have  their  good  and  bad  effects  on  the 
successful  operation  of  the  receiver.  The 
meaning  of  this  ratio  must  not  be  misunder- 
stood. Actually,  when  the  number  of  turns 
on  the  primary  nearly  equal  one  half  of  the 
secondary,  the  voltage  step-up  is  greatest  but 
the  neutralization  becomes  increasingly  diffi- 
cult with  the  increase  in  size  of  the  primary 
winding. 

When  the  amplifier  employs  coupling  units 
of  large  physical  dimensions  there  is  danger  of 
a  feedback  action  between  these  several  coup- 
ling units.  This  undesirable  feedback  is  due 
to  the  magnetic  fields  of  the  coils  becoming 
interlinked  and  interfering  with  each  other. 
This  danger  is  also  present  even  when  small 
coils  are  used,  if  they  are  placed  too  close 
together.  The  difficulty  is  overcome  by  turn- 
ing the  coils  at  such  angles  to  each  other  that 
the  coupling  effects  between  the  coils  of  the 
transformers  themselves  are  minimized. 

There  are  other  methods  of  bringing  this 
result  about.  In  some  amplifiers  we  find 
metal  shielding  which  prevents  feedback. 
Changing  the  angle  of  the  coils  is  a  simple 


RADIO  BROADCAST  Photograph 


BEHIND   THE    WORKS 

A  general  vie\v  of  the  distribution  of  the  parts.     The  Bradleystats  are  situated  behind  the  tube  sockets 


Radio  Broadcast 


OAA, 


u 


SHOWING  GRAPHICALLY, 
THE  AMPLIFICATION  IN  SUCCESSIVE   STAGES 

FIG.    3 

A    graph    showing    the    successive 
amplification  in  a  cascade  amplifier 

effective  method.  It  is  necessary  to  wind  the 
several  transformers  as  nearly  alike  as  possible 
so  that  when  the  secondaries  are  shunted  by 
condensers  of  a  like  capacity  the  wavelength 
range  will  be  the  same  for  each  stage.  The 
dials  will  then  read  the  same. 

OSCILLATION;   FEED-BACK  NEUTRALIZATION 

VACUUM  tubes,  when  connected  to  the 
usual  grid  and  plate  coils  may  be  made  to 
generate  an  oscillation  whose  frequency  de- 
pends largely  upon  the  inductance  of  the  grid 
coil  and  capacity  of  the  condenser  shunting  it. 
See  Fig.  4. 

It  is  a  well-known  fact  that,  if  a  circuit  em- 
bodying these  characteristics  were  utilized,  a 
miniature  radio  transmitter  would  result. 
This  would  be  not  only  uncomfortable  for  the 
user  himself  because  of  the  many-toned  squeals 
set  up,  but  an  amplifier  of  this  sort  would  also 
seriously  affect  neighboring  receiving  installa- 
tions because  it  would  act  as  a  transmitter, 
producing  squeals  in  every  receiver  within 
range.  This  property  is  usually  termed  the 
radiation  characteristic  of  an  amplifier. 

Some  means  of  balancing  out  these  squeals 
must  be  provided.  Lossers,  compensators, 
traps,  and  reverse  feed-back  are  sometimes 
employed  but  they  are,  as  a  rule,  not  as  stable 
as  the  arrangement  proposed  here.  A  very 
fine  form  of  this  neutralizing  system  has  been 
brought  out  by  Hazeltine  and  Roberts.  In 
their  system,  any  tendency  to  oscillate  is  com- 
pletely neutralized  or  balanced  out  by  the 
neutralizing  condenser  and  the  proper  placing 
of  the  coils,  all  exerting  a  force  on  the  grid  of 
the  tube  equal  and  opposite  to  that  set  up  by 
the  action  of  the  inter-capacity  coupling  of 
the  tube  as  well  as  the  inter-coil  coupling  of 
the  radio-frequency  transformers.  An  expla- 
nation in  detail  of  this  theory  by  Mr.  W.  Van 
B.  Roberts,  appeared  in  the  April,  1924,  and 


was  repeated  in  the  January,  1925,  RADIO 
BROADCAST. 

Wiring  also  presents  a  problem  to  be  solved 
by  a  careful  and  well  planned  procedure. 
Grid  and  plate  leads  should  be  as  short  as 
possible  and  should  not  be  parallel  to  each 
other.  There  should  not  be  any  inductive 
loops  in  the  filament  circuit.  In  fact,  the 
filament  circuit  should  be  finished  first.  Then 
the  other  connections  to  it  may  be  made  as 
short  as  possible. 

Soldering  is  an  important  consideration 
and  should  not  be  overlooked.  Too  much 
solder  is  just  as  bad  as  too  little.  Keep  your 
iron  evenly  hot  and  clean  all  the  time.  Don't 
use  a  great  quantity  of  soldering  paste  and  use 
a  good  grade  of  solder.  While  it  seems  strange 
that  such  mechanical  considerations  should 
enter  into  a  discussion  of  the  design  of  radio- 
frequency  amplifiers,  its  worth  may  be  real- 
ized when  it  is  considered  that  a  poor  soldering 
job  will  completely  offset  the  finest  design  and 
assembly,  and  render  the  amplifier  practically 
inoperative. 

HOW   MANY    STAGES? 

NOW  the  number  of  stages  of  radio- 
frequency  amplification  that  may  be 
successfully  employed  is  limited  by  the  human 
element.  Two  stages  of  radio-frequency 
amplification  have  become  accepted  as  the 
maximum  number  that  may  be  advantage- 
ously operated.  More  than  this  usually  lowers 
the  operating  efficiency  of  the  receiver.  Multi- 
stage radio-frequency  amplifiers  have  made 
their  appearance  on  the  radio-market.  These 
types  are  usually  controlled  by  a  gear  arrange- 
ment actuating  the  several  condensers,  but  due 
to  electrical  and  mechanical  difficulties,  have 
not  become  very  popular. 


Inter-Coupling  between 

the  Grid  and  Plate  Coil 

is  afforded  by  the  capacity 

action  of  the  tube 


,    /  Represents  Tube 
*  Capacity 


II 1 

II  i 


FIG.    4 

A  circuit  capable  of  oscillating — thereby  becoming 
a  miniature  transmitter  when  coupled  to  an  antenna 


How  to  Build  a  Two-Stage  Radio-Frequency  Amplifier 


53 


RADIO-FREQUENCY    TRANSFORMER    DESIGN 

'"THE  style  of  winding  of  a  radio-frequency 
*  coupler  offers  an  interesting  field  for 
study.  Spiderweb  and  diamond  weave  styles 
have  lately  come  to  the  forefront  of  radio 
design  because  of  the  mechanical  and  electrical 
advantage  they  present  and  the  ease  with 
which  they  may  be  made  and  mounted.  The 
same  value  of  inductance  can  be  provided  in 
a  concentrated  spiderweb  or  diamond  weave 
form  which,  if  constructed  as  an  ordinary 
single-layer  coil  would  require  a  much  larger 
space.  Also,  with  these  new  inductances, 
the  distributed  capacity  of  the  coil  has  been 
materially  lowered  which  increases  the  overall 
efficiency  of  the  unit.  When  the  winding  is 
concentrated,  the  magnetic  field  set  up  by  the 
currents  travelling  through  the  coil  is  similarly 
concentrated  and  does  not  feed  over  into 
adjacent  coil  units. 

Engineers  have  made  electrostatic  coupling 
a  special  study.  Full  reports  of  their  findings 
are  not  yet  available.  However,  the  few  bare 
facts  such  as  separation  of  parts,  concentration 
of  coil  winding,  and  simplicity  of  wiring  serve 
to  guide  us  toward  correct  constructional 
design.  The  circuit  of  the  radio-frequency 
amplifier  described  here  is  shown  in  Fig.  5. 
This  amplifier  may  be  used  with  any  type  of 
detector  and  audio-frequency  amplifier  now 
available.  In  a  future  number  of  RADIO 
BROADCAST  we  shall  describe  a  detector  and 


amplifier  unit  especially  designed  for  use  with 
this  radio-frequency  amplifier. 

This  circuit  consists  of  three  tuned  circuits. 
The  output  of  the  last  circuit  connects  to  the 
input  of  the  detector  tube  to  be  used.  The 
antenna  and  ground  are  connected  to  the 
primary  of  the  first  circuit. 

As  may  be  seen  by  the  several  photographs 
accompanying  this  article,  all  the  parts  are 
mounted  upon  the  panel  and  a  baseboard  is 
eliminated.  As  far  as  possible,  the  ideas 
brought  out  in  this  discussion  have  been 
incorporated  in  the  amplifier  unit  described 
here. 

CONSTRUCTION    OF   THE    UNIT 

MAKE  the  amplifier  in  accordance  with 
these  instructions,  it  is  well  to  procure  the 
parts  as  listed.  Other  parts  of  similar  design 
and  quality  may  be  used  with  equally  good  re- 
sults. The  use  of  uv-2oi-A  or  ov-2  tubes  is  re- 
commended but  others  such  as  i£  and  3  volt 
tubes  may  be  satisfactorily  employed. 

The  coils  used  were  made  up  by  the  F.  W. 
Sickles  Co.  of  Springfield,  Mass.,  from  specifi- 
cations supplied.  For  those  who  wish  to  wind 
their  own,  the  coil  data  is  included  in  the 
following  pages. 

THE    PANEL 

TN  LOCATING  the  holes  to  be  drilled  in  the 
*  panel,  it  is  well  to  lay  off  the  dimensions 
on  the  rear  of  the  panel.  Otherwise  the 


r 


DETECTOR  CIRCUIT 
3-5Megs 


6V.  A 


45  V.  B 


45  V.  B 


FIG.    5 


The  schematic  circuit  diagram  of  the  amplifier  whose  construction  is  de- 
scribed.   The  heavy  line  indicates  the  brass  bus  bar  strip  connections 


54 


Radio  Broadcast 


r 


CM 
I 


X 
=  (O 


•-I 


0 


*-<£- 


^^^_y  ^___ 

>k- -Jfr-— -H 


^o  «  as 

v.  .5 

S^g 

"•    S^ 


How  to  Build  a  Two-Stage  Radio-Frequency  Amplifier 


55 


scriber  lines,  if  marked  on 
the  front,  would  be  visible 
and  unsightly  unless  re- 
moved by  a  graining  pro- 
cess. Some  builders  will 
wish  to  provide  a  grained 
surface  on  the  front  of  the 
panel.  Graining  may  be 
accomplished  by  rubbing 
the  panel  along  its  length, 
with  a  straight  motion, 
with  No.  o  emery  cloth. 
This  is  continued  until  all 
the  glossy  marks  on  the 
panel  have  been  removed. 
The  graining  process  usually  takes  place  after 
all  the  holes  are  drilled.  The  panel  is  then 
polished  with  an  oiled  cloth. 

In  drilling  the  holes  it  is  well  to  drill  all  of 
them  first,  with  a  No.  28  drill  and  then  enlarge 
to  the  required  size  with  the  correct  size  drill. 
This  procedure  affords  a  more  accurately 
drilled  panel  than  if  all  the  holes  were  directly 
drilled  with  the  required  size  drills  in  the  begin- 
ning. By  referring  to  the  panel  layout  in  Fig. 
6A  it  will  be  observed  which  holes  are  to  be 
countersunk.  This  layout  should  be  thor- 
oughly understood  before  actual  construction 
is  begun. 

In  a  similar  manner  of  layout,  the  binding 
post  strips  and  brass  mounting  bus-bar  strip 
are  prepared  and  drilled.  See  Fig.  6  C,  D, 
-E,  and  F. 

WINDING   THE   COILS 

THE  type  of  coil  used  here  is  termed  the 
diamond    weave.     To    wind    these    coils 
it  is  necessary  to  have  a  cylindrical  wooden 
form  (a  rolling  pin  of  the  required  size  will  do) 
2!  inches  in  diameter.     Around  the  circum- 


-B- 


RADIO  BROADCAST  Photograph 
A    SYMMETRICAL    PANEL   ARRANGEMENT 

The  jack  in  the  lovrer  left  is  for  plugging-in  a  loop. 
Vernier  dials  may  be  substituted  for  those  shown 


ference  of  this  cylinder,  at  approximately  £  inch 
intervals  are  driven  brass  or  wooden  pins  T8ff 
inch  in  diameter  i|  inches  long.  The  coil 
winding  form  is  illustrated  in  the  sketch  Fig. 
A.  No.  22  d.c.c.  wire  is  used  throughout  the 
windings. 

The  antenna  coupler  has  only  a  primary  and 
secondary.     The  other  two  coil  units  have  a 


Parts  required:  „         f 
I  cylinder  2^dia.  1   wide 
35  spokes  il,£'long  %'4'di 


SHOWING  FIRST  THREE 
TURNS  ON  FORM 


FIG.    7 

A.  is  a  coil  form  for  winding  the  diamond  weaves. 

B.  How  the  weave  is  produced.     Under  two,  then 

over  two,  is  the  rule 


-B      2 no  TURN 


FIG.    8 

Shows  the  first  three  turns  in  their  relative  positions 
to  the  spokes  in  producing  a  successive  overlap  re- 
sulting in  the  diamond  weave  coil 

double-wound  primary,  constituting  the  N-P 
coils,  and  a  secondary  (S),  as  illustrated  in  Fig-5. 

The  weave  of  the  coil  is  produced  as  out- 
lined in  Figs.  78  and  8A-B-C.  The  first 
three  turn  positions  are  illustrated  and  will 
serve  to  indicate  the  progressive  overlap  of 
each  additional  layer  of  the  winding.  Suc- 
cess in  this  winding  is  all  in  the  start.  The 
beginning  of  the  wire,  allowing  for  a  six  inch 
lead,  is  fastened  at  the  pin  i.  From  there  it 
is  brought  diagonally  to  2.  From  around 
the  outside  of  2  and  3  it  diagonally  crosses  to  4. 
Here  it  again  goes  around  the  outside  of  4,  and 
5,  and  so  on.  It  will  be  observed  from  this 
that  the  winding  style  is  continued  over  two 
and  under  two  spokes. 

Due  to  the  odd  number  of  spokes,  the  suc- 
cessive layers  progress  or  stagger  themselves. 
This  permits  a  winding  which  makes  the 
position  of  each  layer  wound  different  from 


Radio  Broadcast 


adjacent  layers.  So  the  diamond  weave  is 
produced. 

For  the  second  and  third  radio-frequency 
couplers,  the  primaries  must  be  double-wound 
to  provide  the  neutralizing  winding  which  is 
connected  to  the  grid  of  the  tube  through  the 
neutralizing  condenser.  In  winding  the  double 
primary  it  is  well  to  have  two  spools  of  wire, 
one  preferably  colored  so  as  to  facilitate 
identity  of  connections. 

Six  and  one  half  turns  of  the  pair  of  wires 
are  wound  for  the  primaries  of  the  second  and 
third  couplers.  This  ratio  was  selected  after 
tests  were  conducted  where  12  and  18  turn 
primaries  were  employed. 

The  antenna  primary  consists  of  a  single 
wire  wound  for  six  and  a  half  turns. 

After  the  primaries  are  wound,  the  secon- 
daries are  wound  directly  over  them  for  forty- 
five  turns  in  the  same  fashion  and  in  the  same 
direction  as  the  primary.  The  inside  lead  or 
beginning  of  the  secondary  is  started  several 
spokes  away  from  the  end  of  the  primary  so 
that  the  leads  are  not  too  close  together  in  the 
finished  coil. 

The  coil  may  be  painted  with  a  solution 
as  a  binder  which  has  been  prepared  by  dis- 
solving celluloid  in  acetone,  or  other  "dope" 
of  this  nature.  The  best  coils  are  made  with- 
out dope  and  their  turns  are  held  in  place 
by  lacing  made  of  ordinary  grocer's  white 
cord. 

To  remove  the  coil  from  the  form,  withdraw 
all  the  spokes  and  then  slide  the  coil  off,  taking 
care  to  prevent  it  from  coming  loose.  Fig.  9 
shows  how  to  insert  the  mounting  screw  so  that 
the  coil  may  be  fastened  to  the  brass  bus  bar 
running  the  entire  length  of  the  receiver. 

The  outside  turn  of  the  secondary  connects 
to  this  screw.  The  brass  bus  bar  constitutes 


Coil 


,Coil 


Inside  "S" 
Terminal 


Insulation 
Mounting  Screw 


Shows  position  of 
Insulating  Sleeve 

—  —  COIL  FORM 
(Fibre,  Celluloid  or 
Hard  Rubber 
1/2  wide) 

-  -  Diamond  Weave  Coil 


IJspss  ^Insulating  Sleeve 

^---Threaded  Suppbrt  Bushing 

(to  which  is  connected  Outside  S  lead) 


Brass  Bus  Bar 


FIG.   9 

How  the  coil  is  mounted  on  the  brass  bus  bar  strip 


Brass  Bus  Bar' 


METHOD  OF  ASSEMBLY  OF  CONDENSER, 
ANGLE  BRACKET,  COIL  AND   TERMINAL  BOARD 

FIG.     IO 

All  the  parts  are  sustained  by  means 
of   the    panel    and    angle    brackets 


the  negative  or  grounded  line  of  the  entire 
circuit. 

As  may  be  seen  from  this  sketch,  the  -^ 
mounting  screw  is  securely  fastened  to  the  coil 
by  means  of  washers  and  nuts.  If  it  is  obtain- 
able, a  piece  of  bakelite  or  fibre  tubing  -fa  inch 
in  diameter  may  be  slipped  over  the  mounting 
screw  to  insulate  it  from  the  coil  winding.  The 
narrow  strip  of  hard  rubber  or  celluloid  used 
as  a  coil  form  and  inserted  after  it  is  wound 
is  also  fastened  underneath  the  head  of  the 
screw  and  washer. 

The  coil  support  may  be  a  larger-diametered 
piece  of  tubing  or  a  brass  rod  may  be  turned 
down  if  the  machinery  is  available.  But  as 
little  metal  as  possible  should  be  used  in  the 
direct  field  of  the  coils. 

ASSEMBLY 

\A7ITH  the  panel  drilled,  the  coils  wound, 
*  »  and  all  the  other  material  on  hand,  the 
job  of  assembly  may  now  be  started. 

First  the  sockets,  then  the  rheostats  and 
finally  the  condensers  are  mounted  on  the 
panel.  It  is  well  to  state  here  that  the 
assembly  directions  as  outlined  only  hold  good 
for  the  material  as  listed.  When  other  parts 
are  used,  the  builder  must  employ  his  own 
ingenuity  in  producing  an  arrangement  as 
nearly  like  that  described  as  possible. 

Looking  at  the  back  of  the  panel,  the  lower 
right  screw  of  the  right  and  center  condensers 
holding  the  end  plate  of  the  condensers  to  its 
frame  is  removed.  Also  the  lower  screw  of 
the  left  condenser  is  removed. 

Brass  angle  brackets  3J|  x  i^  inches  x  £ 
inch  are  fastened,  as  shown  in  Fig.  10,  to  the 
condensers  at  the  places  where  these  screws 
have  just  been  removed,  by  replacing  the 
screws  securing  the  brackets  at  the  same  time. 
It  is  absolutely  essential  that  these  screws  be 


How  to  Build  a  Two-Stage  Radio-Frequency  Amplifier 


57 


RADIO  BROADCAST  Photograph 

A    VIEW    OF    THE    ANGLE    BRACKET 
FROM    THE    RIGHT    SIDE 

exceptionally  tight,  but  not  tight  enough  to 
turn  off  the  heads,  so  that  a  positive  electrical 
connection  between  the  condenser  and  plate, 
angle  bracket,  and  bus-bar  strip  is  assured. 

Fig.  10  also  shows  how  the  binding  post 
terminal  strip  is  mounted  on  the  bracket. 
Connections  to  the  binding  posts  are  made  on 
the  under  side,  and  the  wires  are  soldered  to 
lugs  fastened  to  the  posts. 

Fig.  13  shows  the  angle  at  which  the  coils 
are  placed  when  mounted  upon  the  bus  bar 
strip. 

WIRING 

E  to  the  placement  of  the  parts,  the  grid 
and  plate  leads  are  comparatively  short 
and  well  separated.  In  fact  the  only  long 
leads  in  the  circuit  are  the  filament  supply 
connections. 

All  connections  should  be  soldered.  Lugs 
may  be  used  at  socket  and  condenser  terminals 
to  facilitate  the  soldering  job  and  this  also 
permits  the  terminal  nuts  to  be  tightly  fastened 
down  on  the  lugs  before  the  soldering  is 
begun.  Suitable  wrenches  for  this  work  are 
now  on  the  market.  The  wiring  plan  is  shown 
in  Fig.  n.  The  schematic  circuit  diagram 
is  Fig.  5. 

The  jack  shown  in  the  lower  left  hand  corner 
of  the  panel  photograph  is  used  for  plugging-in 
the  loop  to  the  first  tube  circuit.  This  jack 
performs  the  function  of  automatically  dis- 
connecting the  first  secondary  coil  from  the 
tuning  condenser  and  replacing  it  with  the 
loop.  See  Fig.  14. 

The  inside  lead  to  this  secondary  connects 
to  the  blade  of  the  jack  marked  No.  2.  The 


outside  lead  connects  to  the  brass  bus  bar 
negative  line  through  the  metal  screw  and 
support  bushing.  The  third  and  fourth 
blades  of  the  jack  also  connect  to  the  negative 
bus  bar.  Blade  No.  i  connects  to  the  stator 
plates  of  the  condenser.  These  points  are 
made  clear  in  Fig.  14. 

The  connections  to  the  coils  are  as  follows: 

The  antenna  connects  to  the  inside  of  the 
primary,  the  outside  to  the  ground.  The 
inside  of  the  secondaries  connect  to  their  re- 
spective grid  socket  terminals,  the  outside 
leads  being  connected  to  the  negative  side  of 
the  filament  line.  The  mounting  screw  is 
utilized  and  another  scfew  terminal  provided 
as  shown  in  Fig.  9  for  the  secondary  leads. 
The  primary  leads  merely  project  out  of  the 
coil. 

For  the  double-wound  primaries,  the  inside 
lead  of  one  of  the  pair  of  wires  connects  to  the 
plate  of  the  preceding  tube.  The  outside  end 
of  the  other  coil  connects  to  the 'grid  through 
the  neutralizing  condenser.  The  remaining 
two  leads  are  connected  together  and  are 
brought  to  the  positive  B  battery  terminal. 

A  .002  mfd.  fixed  condenser  is.  connected 
from  the  B  terminal  to  the  minus  A  terminal. 
A  detector  circuit  (to  which,  of  course,  may  be 
added  several  stages  of  audio-frequency 
amplification)  is  connected  to  the  r.  f.  ampli- 
fier as  shown  in  Fig.  5.  for  test  purposes. 

OPERATING    THE    AMPLIFIER 

ASSUMING    that     uv-2oi-A's     are    used 
throughout  (although  any  standard  type 
of  tube  may  be  substituted)  the  6  volt  filament 


RADIO  BROADCAST  Photograph 


LEFT    SIDE    OF   THE    AMPLIFIER 

The  bracket  supporting  the  bus  bar,  coil,  and  binding 

post  terminal  board  is  clearly  shown,  and  the  jack 

mounting  as  well 


Radio  Broadcast 


How  to  Build  a  Two-Stage  Radio-Frequency  Amplifier 


59 


RADIO  BROADCAST  Photograph 
LOOKING    UP    FROM    UNDER 

The  function  of  the  bus  bar  as  part  of  the  circuit  and  as  a  support- 
ing member  is  clear.     The  sockets  are  of  the  panel  mounting  type 


battery  is  connected  to  the  battery  posts 
on  the  terminal  board  at  the  left  of  the 
amplifier  (looking  at  the  rear).  From  right 
to  left,  these  posts  are  designated  as  fol- 
lows:— negative  filament,  positive  filament, 
positive  B  battery,  grid  output,  negative 
filament  output. 

The  posts  on  the  right  terminal  strip  are: — 
antenna  and  ground,  from  right  to  left.  The  B 
battery  post  is  connected  to  the  90  volt  termi- 
nal of  the  B  battery.  The  other  connections 
are  made  as  shown  in  Fig.  5. 

With  the  aid  of  the  wavelength  curve  shown 
in  Fig.  1 2,  the  approximate  position  of  the  dials 
may  be  ascertained  for  a  desired  wavelength 


setting.  Due  to  differences  in  winding  the 
coils  and  wiring,  this  curve  will  not  be  accurate 
for  every  amplifier  of  this  type  which  may  be 
constructed. 

It  will  be  observed  that  the  antenna  coupler 
condenser  will  tune  rather  broadly  in  compari- 
son to  the  other  two. 

The  method  of  tuning  the  amplifier  would  be 
to  set  the  antenna  condenser  dial  at  the  desired 
setting,  referring  to  the  curve  and  then  slowly 
rotate  the  other  two  simultaneously  through  a 
small  arc  at  approximately  the  same  setting. 
When  the  sharpest  point  has  been  obtained, 
retune  the  antenna  condenser  dial  for  a  final 
setting. 


LIST    OF    PARTS    USED 


i  Panel  7  x  14  x  T\  inches @$i.oo 


3  Hammarlund  Variable  Condensers  .00037  mfd. 
2  Federal  Panel  Mounting  Sockets 

2  Bradleystats 

3  Sickles  Coil  units       .... 

2  X-L  Vario-densers     .... 

3  Na-ald  Super  De-Luxe  Dials 

Brass  strip 

Mounting  screws — wire,  etc. 

i   Double-circuit  Carter  Jack 


@ 
@ 


@ 


4-75 
i  .20 
i  .85 

i  .00 
i  .00 


When  the  coils  are  home-made  the  supplies  necessary  for  their  winding  are  as  follows  :- 
^  Ib.  No.  22  d.c.c.  wire 
Bakelite  or  metal  bushing  supports 
Washers 

Insulation  strip,  fibre,  celluloid,  etc. 
Screws  and  nuts 


>  i  .00 

14.25 

2.40 

3.70 

2.OO 

3-OO 

.50 

.50 

I  .OO 

'28.35 


6o 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 
A    DETAILED    VIEW    OF    THE    NEUTRALIZE!* 

Part  of  this  condenser  is  cut  away.    The  turning 
of  the  screw,  top  center,  varies  the  capacity 


NEUTRALIZING    THE    AMPLIFIER 

ON  THE  lower  wavelengths  it  will  be  ob- 
served that  the  amplifier  will  go  into 
oscillation  more  easily  than  on  the  higher 
wavelengths. 

Now,  by  turning  the  adjusting  screw  of  the 
neutralizing  condenser,  up  and  down,  a  point 
may  be  reached  where  the  self  oscillation  is 
entirely  eliminated  or  perhaps  only  feebly 
present.  This  oscillation  is  recognized  in  the 
form  of  a  squeal  whose  pitch  varies.  The  de- 
tailed method  of  neutralization  was  fully 
described  in  "Notes  on  the  Robert  Circuit," 
in  the  January,  1925,  RADIO  BROADCAST. 

It  is  well  to  apply  the  neutralization  process 
at  several  wavelengths,  noting  the  position 
of  the  tubing  for  each  change,  so  that  an  aver- 
age may  be  struck.  If  the  amplifier  works 
properly,  no  great  difference  in  the  several 
neutralizer  settings  will  be  noted. 

Since  this  circuit,  is  not  reflected  it  is 
quite  satisfactory  to  employ  the  standard 
neutrodyne  method  of  neutralization.  Briefly 
explained,  that  is  as  follows:  A  station  is 
tuned-in,  preferably  a  distant  one,  so  that  the 
signal  is  not  as  loud  as  a  local.  Then  the 
first  tube  is  removed  from  the  socket,  and  one 
filament  prong  is  covered  with  a  slip  of  paper 
or  spaghetti  tubing,  so  as  to  insulate  it  when 
replaced  in  the  socket.  Now  after  inserting 
in  the  socket  (the  filament  will  not  light) 
the  station  previously  tuned-in  may  be  heard 
faintly.  Carefully  retune  for  maximum  signal 
strength,  which  will  not  be  as  loud  as  when  the 


tube  was  lighted.  Then  adjust  the  neutraliz- 
ing condenser  until  the  signal  almost,  or  per- 
haps actually  disappears.  This  tube  is  then 
completely  neutralized  and  the  same  process 
may  be  applied  to  the  next  tube.  As  each 
tube  is  neutralized,  the  filament  prong  insu- 
lation is  removed. 

With  the  condensers  and  coils  used,  as 
described,  the  amplifier  will  cover  a  wave- 
length range  varying  from  230  to  600  meters 
for  the  entire  broadcast  band. 

WHAT   TO    EXPECT    FROM    THE    AMPLIFIER 

THE  author  does  not  attempt  to  set  a 
distance  limit  on  reception  of  a  set  using 
this  amplifier  when  connected  to  a  detector 
circuit.  The  radio  public  has  educated  itself 
to  the  point  where  it  takes  with  a  grain  of 
salt  the  highly  imaginative  claims  of  some- 
times over-enthusiastic  set  designers  about  the 
distance  range  of  their  receivers. 

It  is  not  our  desire  to  put  a  limit  on  the 
reception  qualities  of  this  amplifier.  Rather 
let  us  say  that  it  will  equal  any  two  stage 
radio-frequency  amplifier  we  have  ever  tested 


625 
600 
575 
550 
525 
500 

475 

I 

I  450 

9 

uj425 
5  400 
375 
350 

325 
300 

275 
250 
•>">* 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

j 

T 

/ 

/ 

/ 

/ 

/ 

f 

/ 

/ 

f 

"0      10     20     30     40     50     60     70     80     90    100 
Cz  CONDENSER  SCALE 

FIG.     12 

A  wavelength  chart  which  may  be 
used  as  an  aid  in  locating  stations 


How  to  Build  a  Two-Stage  Radio-Frequency  Amplifier 


61 


Condenser 


Approx.  g 


FIG.    13 

To  obtain  complete  neutralization,  the  coils  should 
be  turned  at  an  angle  to  the  bus  bar  as  shown  here. 
The   value   is   approximate.     Actual   test   will   de- 
termine the  correct  placement 


— and  we've  surely  tested  more  than  a  few. 

This  radio  frequency  amplifier  is  especially 
adaptable  for  use  with  a  loop. 

In  a  future  article  the  construction  of  a 
detector  amplifier  unit  will  be  described 
which,  while"  it  may  be  used  with  any  tuner, 
is  especially  intended  for  use  with  the  radio- 
frequency  amplifier  described  here. 


General  Additional  Notes 


'"TpHE  use  of  a  loop  with  this  amplifier  wil' 
*•  naturally  reduce  the  strength  of  received 
signals  and  therefore  not  a  great  deal  of  dis- 
tance work  will  be  accomplished  when  the 
loop  is  used. 

However,  for  sharpness  of  tuning,  and 
quality  of  reception,  the  results  when  a  frame 
antenna  is  used  are  difficult  to  equal  where 
local  stations  are  being  received.  Loop  re- 
ception on  locals  is  desirable  where  tone 
quality  and  clarity  are  prime  factors.  The 
placement  of  the  loop  near  the  antenna-ground 
wires  (which  may  be  connected  .together) 


loosely  couple  it  to  the  antenna  circuit  which 
increases  the  volume  but  may  effect  the 
quality  of  reception  because  this  connection 
will  cause  some  static  to  be  received  when 
any  is  receivable. 

The  tuning  of  the  first  condenser  when  a 
loop  is  used  will  depend  largely  upon  the  num- 
ber of  turns  of  wire  wound  on  the  loop. 

For  all  practical  purposes,  a  standard  pan- 
cake loop  30  inches  square,  wound  with  16 
turns  of  wire  spaced  f  of  an  inch  apart  will 
suffice  covering  the  entire  broadcast  wave- 
length band. 

If  variable  plate  neutralizing  condensers  are 
used,  some  other  means  for  mounting  them  on 
the  brass  bus  bar  strip  must  be  arranged.  It 
is  not  advisable  to  mount  them  on  the  panel 
unless  such  an  arrangement  permits  of  the 
use  of  very  short  leads.  The  adjustment  of 
this  neutralizer  is  very  rarely  changed,  so  that 
for  all  practical  purposes,  the  back-of-panel 
mounting  will  prove  quite  satisfactory. 


Double  Circuit  Jack 
LOOP  JACK  DETAILS 


Rear  of  Jack 


FIG.    14 

When  a  jack  is  incorporated  for  the  use  of  a  loop, 

the  circuit   must   be  altered   so  that  the  antenna 

coupler  may  be  automatically  thrown  in  the  circuit 

when  the  loop  is  not  being  used 


rHE  material  appearing  in  this  magazine  is  fully  protected  by  copy- 
right, and  editors  of  periodicals  are  advised  that  unauthorized  publi- 
cation of  circuit  diagrams,  technical  descriptions,  and  parts  or  the  whole  of 
articles,  without  due  permission  and  credit,  is  an  infraction  of  the  law. 
Those  who  wish  to  reprint  material  appearing  in  these  pages  are  asfed  to 
communicate  with  the  editor. 


he  .listeners'  -^  JPoint  of  View 


Good  National  Radio  Programs  Prove 
"What  the  Public  Wants" 


THE  linking  of  a  sufficient  number  of 
stations  to  carry  to  uncounted  lis- 
teners the  WEAF  programs  of  out- 
standing musical  quality  will  do  more 
to  bring  about  a  reform  in  the  general  charac- 
ter of  all  radio  music 
than  any  other  attempt 
that  has  yet  been  made 
with  such  an  end  in 
view.  Not  that  the 
powers  that  rule  WEAF 
had  this  in  mind  when 
establishing  this  wide 
connection  through  the 
country.  Quite  the 
contrary.  With  those 
officials  it  is  wholly  a 
matter  of  business,  as 
all  who  are  familiar 
with  the  firms  who  are 
putting  these  programs 
on  the  air  through 
WEAF  well  know.  But 
one  could  scarcely  ask 
the  American  Tele- 
phone and  Telegraph 


JOSEPH    KNECHT 


Lovers  of  good  music  now  glory  in  the  op- 
portunity to  hear  it  through  their  receiving 
sets  on  those  nights  when  such  music  is  spe- 
cially featured.  And  we  are  confident  that 
hundreds  of  thousands  who  have  until  now 
always  referred  to  such 
people  as  "highbrows" 
or  "  poseurs,"  are  going 
to  go  over  to  these  very 
ranks  when  they  find 
through  experience  that 
love  of  good  music  is  no 
more  a  pose  than  is  the 
preference  of  living  in  a 
neighborhood  where 
the  surroundings  are 
beautiful  to  the  eye 
rather  than  in  one 
where  ash  and  garbage 
cans  predominate. 

It  might  seem,  after 
all,  as  if  the  best  way  to 
cure  the  public  of  a  de- 
sire for  the  undesirable 
is  to  surfeit  it  with  the 
undesirable.  After 
having  heard  an- 


Company  to  give  this    Without  whom  the  Waldorf  Astoria  would  almost 

well-nigh   priceless  op-    have  to  go  out  of  business,  or  so  it  seems     He  has   nounced,  "The  brches- 
long  been  conductor  of  this  hotel  s  Concert  Orches- 

Their  Sunday  evening  programs,  broadcast  by    *ra    W1" 


tra. 


portunity  to  the  public 
for  nothing.  So,  as  the 
intricate  question 
"Who  is  to  Pay  for  Broadcasting?"  apparently 
remains  as  far  from  being  answered  as  ever,  we 
may  well  be  thankful  that  we  have  this  present 
development  which  makes  possible  the  hearing 
of  real  artists  at  stated  times,  instead  of,  as  be- 
fore, being  almost  always  nationally  swamped 
by  mediocrity  or  worse. 


wjz,  are  prime  favorites  with  radio  listeners 


play, 

'Dirty    Face,' "   about 
one  hundred  thousand 

times,  they  may  welcome  hearing  that  the 
Victor  Talking  Machine  Company  orchestra 
will  play  the  "Ballet  Music  from  'Faust'." 
Especially  will  they  welcome  the  announce- 
ment after  they  hear  this  music  a  sufficient 
number  of  times  to  become  familiar  with  it. 
You  see,  we  are  taking  it  for  granted  that 


The  Listener's  Point  of  View 


63 


ANNA    PINTO 

The  youthful  harpist  who  has  been  heard  frequently 
during  the  season  from  wjz,  is  now  "off  the  air" 
until  fall,  having  gone  on  a  well-deserved  vacation 


64 


Radio  Broadcast 


those  who  have  been  reveling  in  "  Dirty 
Face"  over  the  radio  lack  acquaintance  with 
this  ballet  music  which  is  probably  as  well 
known  as  any  music  of  its  kind  ever  written. 

The  much-discussed  question  of  having  a 
few  very  high-powered  stations  in  this  country 
that  would  ultimately  control  all  the  broad- 
casting has  met  with  violent  opposition  from 
the  hundreds  of  stations  conducted  for  the 
purpose  of  ad- 
vertising the 
products  of 
the  business 
firms  operat- 
ing them.  The 
majority  of 
these  stations 
are  far  below 
any  com- 
mendable 
standard  so 
far  as  their 
programs  and 
the  manner  in 
which  they 
are  presented 
are concerned. 
Will  this  new 
d  e  v  elopment 
in  radio,which 
is  bringing  the 
best  in  radio 
music  to  far 
distantpoints, 
in  time  put 
these  stations 
out  of  busi- 
ness? There 
wo  u 1 d  be 
nothing  lost 
and  a  good 
deal  gained 
for  the  public 
were  this  to 
come  to  pass. 

Does  it  not  look  as  if  this  linking  of  stations 
is  but  another  way  of  having  the  broadcasting 
within  the  power  of  the  few?  Be  this  as  it 
may,  developments  along  the  right  line  are 
coming  so  rapidly  that  all  who  have  deplored 
the  quality  of  radio  programs  in  this  country 
are  beginning  to  grow  optimistic.  Whether 
the  methods  used  to  bring  about  this  change 
will  be  permanent,  no  one  can  say.  But  of 
one  thing  we  may  be  absolutely  assured. 
Radio  music  having  had  this  upward  trend, 
can  never  again  sink  to  the  low  level  that  has 
so  widely  obtained. 


PROFESSOR    MARSHALL    S.    BROWN 

Dean  of  the  faculties  of  New  York  University,  who  has  delivered  interest- 
ing weekly  lectures  on  American  history  from  station  wjz,  New  York 


Of  great  interest  are  the  statistics  given 
by  John  A.  Holman,  broadcasting  manager  of 
the  American  Telephone  and  Telegraph  Com- 
pany relative  to  his  opinions  of  the  change  in 
the  musical  taste  of  radio  listeners  during  the 
past  two  years.  In  January,  1923,  approxi- 
mately seventy-five  per  cent,  of  radio  fans 
favored  jazz.  In  the  same  month  of  1924 
this  percentage  fell  to  thirty  five  and  in 

January  of 
this  year  to 
five  per  cent. 
These  figures 
tell  their  own 
story. 

Among  the 
fine  programs 
regularly  fea- 
tured through 
w  E  A  F  are 
those  given  by 
the  Atwater 
Kent  Com- 
pany. Have 
you  noticed 
that  the  sing- 
ers  of  the 
quartet  heard 
in  these  pro- 
grams are 
never  an- 
nounced by 
name?  That 
should  be 
qualified  b  y 
saying  that 
we  have  never 
heard  them  so 
announced. 
"The  tenor  of 
the  Atwater 
Kent  Quartet 
will  now  be 
heard  in  the 
solo,  "On- 

away,  Awake,  Beloved!"  And  when  you  hear 
him  sing  you  know  that  he  is  not  an  amateur 
looking  for  publicity  through  the  microphone; 
indeed  if  he  were,  he  would  insist  on  having  his 
name  announced,  "before  and  after."  We  are 
quite  willing  to  hazard  the  guess  that  this 
quartet  is  made  up  of  paid  professionals — and 
admirable  ones  at  that — who  do  not  want  their 
names  sent  out  as  "radio  artists,"  a  position 
that  can  be  understood  considering  the  present 
chaotic  conditions  prevailing  in  broadcasting. 
If  this  guess  is  a  wrong  one,  we  stand  ready  to 
be  corrected. 


The  Listeners'  Point  of  View 


Are  not  the  phonograph  companies,  as  long 
as  they  broadcast  programs  made  up  from 
titles  almost  entirely  taken  from  the  titles  of 
records  made  by  each  artist  presented,  in 
danger  of  a  repetition  that  will  be  tiresome? 
Here  is  a  tip  for  the  Victor  authorities.  Have 
all  your  baritones  avoid  "La  Paloma"  for  a 
time! 

Great  Artists  Are  Coming  to  Radio 

UNDER   no  circumstances  will    I   ever 
permit   an   artist   under   my   manage- 
ment   to    be    heard    by   radio.     Were 
such  a  thing  to  happen  without  my  consent, 
I  would  consider  it  ground  for  cancellation  of 
contract  and  take  immediate  steps  to  bring 
that  about." 

Many  managers  of  musical  artists  have  said 
this  to  the  present  writer.  And  one  and  all 
are  now  permitting,  evidently  gladly,  the 
most  famous  people  under  their  management 
to  be  heard  over  the  microphone.  Nor  are 
these  hearings  con- 
fined to  the  pro- 
grams of  the  phon- 
ograph companies, 
but  go  so  far  as  to 
include  appear- 
ances at  public 
concerts.  We  do 
not  know  that,  to 
date,  any  complete 
public  recital  by 
any  artist  has  been 
broadcast,  but 
where  the  program 
is  a  mixed  one, 
various  artists  ap- 
pearing, a  portion 
at  least  of  each 
artist's  contribu- 
tion to  the  whole  is 
given  to  the  radio 
public.  It  all  but 
goes  to  prove  that 
we  must  either 
keep  up  with  the 
procession  or  drop 
out  of  it  altogether. 


offers  of  hearing  and  seeing  these  same  artists 
in  concert?  We  are  of  the  belief  that,  with 
the  majority  of  people,  hearing  an  artist  in  a 
few  numbers  would  arouse  the  desire  to  hear 
him  in  an  entire  concert  if  possible. 

What  Happened  at  WTAM 

IN  TH  E  March  number  of  this  magazine,  the 
statement  was  made  in  "The  Listeners' 
Point  of  View"  that  on  Christmas  Eve, 
"Silent  Night,  Holy  Night,"  was  jazzed  from 
station-  WTAM,    Cleveland.     The    statement 
carried  the  explanation  that  the  present  writer 
did  not  hear  this  sacrilege  and  hotly  denied  it 
when  first  given   the   information,   but   that 
this  information  came  from  a  sufficient  num- 
ber of  sources  to  seem  to  prove  it  true.     It  ap- 
peared at  the  time  all  the  more  inexcusable 
considering  the  standard  maintained  by  WTAM 
which  is  conducted  by  the  Willard  Storage 
Battery  Company. 
It    is    with    pleasure,    therefore,    that    we 


DOES  hearing 
the  phono- 
graph programs 
stimulate  your  de- 
sire to  take  advan- 
tage of  the  oppor- 
tunity  when  it 


ROSELINE    GREENE 

Leading  woman  of  the  WGY  Players,  who  is  but  eighteen  years  old,  and  a  junior  in 

the  New  York  State  College  for  Teachers,  where  she  is  taking  the  classical  course. 

Her  entire  professional  dramatic  experience  has  been  gained  under  Edward  H. 

Smith,  the  director  of  the  WGY  Players 


66 


Radio  Broadcast 


publish  a  denial  of  this  statement  received  in  a 
letter  from  Mr.  S.  E.  Baldwin,  in  charge  of 
broadcasting  at  WTAM: 

So  far  as  we  know,  the  only  time  this  particular 
piece  of  music  has  been  sung  or  played  over  station 
WTAM  was  on  the  night  of  December  24,  1924 — 
Christmas  Eve.  On  that  particular  program  it  was 
played  or  sung  some  five  times,  being  first  sung  by 
the  Cleveland  Music  School  Settlement,  under  the 
leadership  of  Alice  Shaw  Duggan. 

The  second  time  it  was  sung  by  the  Old  Stone 
Church  Quartet,  composed  of  Mrs.  Robert  J.  Kelly, 
Alice  Shaw  Dug- 
gan,  Harold 
Branch,  and  Fred 
S.  True.  This 
quartet  is  prob- 
ably the  best 
known  church 
quartet  in  thecity 
of  Cleveland. 

It  was  then 
sung  by  Miss 
Marie  Similink, 
one  of  the  leading 
contraltos  of 
Cleveland.  Later 
in  the  evening  it 
was  again  sung 
by  Doris  Stadden 
Kaser,  and  at 
midnight  played 
by  trumpeters  of 
the  Cleveland 
Concert  Band  in 
conjunction  with 
chimes  from  th? 
Old  Stone 
Church. 

The  writer  was 
either  present  or 
listened  by  radio 
to  the  entire  con- 
cert; he  is  per- 
fectly familiar 
with  the  music, 
and  to  the  best  of 

his  knowledge,  nothing  of  the  kind  of  which  you 
accuse  us  occurred  on  the  night  of  December  24th. 

Isn't  it  rather  unjust  to  publish  statements  of  this 
kind  without  first  taking  them  up  with  the  supposed 
offender?  There  is  a  possibility  that  sometime  you 
may  be  wrong. 

Frankly  acknowledged.  Probably  a  number 
of  people  heard  more  than  one  station  at  once 
at  that  hour,  the  leading  fault  of  radio  at  pres- 
ent. At  any  rate,  there  is  a  moral  in  this. 
Never  say  it  was  so  unless  you  heard  it  yourself. 


MAGDELINE    BRARD 

A  very  artistic  French  pianist,  who,  although  scarcely  out  of  her 
'teens,  commands  the  admiration  of  connoisseurs  in  both  this  and 
her  native  country.  She  was  recently  heard  through  station  WEAF 


ABE  MARTIN  says:     "So  far  I  ain't  no- 
ticed that  any  romances  hev  cum  from 
th'  publishing  of  radio  photographs." 


Shall  Broadcast  Music  Be  Explained? 

IT  WOULD  be  well  if  all  the  musical  explana- 
tions now  preceding  the  numbers  presented 
on  the  Victor  and  Atwater  Kent  programs 
were  completely  done  away  with  until  they 
can  be  presented  as  they  should.     Some  of  us 
even  go  so  far  as  to  believe  they  should  never 
be  attempted  under  any  circumstances.     As 
matters  now  stand,  they  are  compiled  evi- 
dently from  the  studio  dictionary  by  someone 
who  knows  nothingof  the  subject.  They  are  put 

into  type  and 
then  read  by 
the  announcer. 
When  Toti 
Del  Monte 
sang  "Caro 
Nome"  from 
"Rigoletto," 
the  attempt  to 
explain  what 
the  song  meant 
was  wholly  fu- 
tile. For  that 
matter,  you  can 
go  to  any  of 
these  early 
Verdi  operas 
and  never  com- 
pletely  know 
what  the  story 
is  about.  How, 
then,  can 
Gilda's  infatu- 
ation for  the 
dissolute  Duke 
be  explained? 

Then  there 
was  De  Luca's 
singing  of 
"Largo  al  fac- 
totum" from 

Rossini's  "Barber  of  Seville."  We  defy  any- 
one who  has  been  to  see  this  opera  one  hun- 
dred times  to  tell  the  plot  offhand.  There 
was  no  attempt  to  tell  the  plot  when  De  Luca 
gave  his  superlative  rendition  of  this  number, 
but  there  were  some  jumbled  comments  about 
his  fame  in  the  role  of  "Rigoletto,"  and  then 
something  about  the  role  of  the  barber, 
"Figaro,"  in  the  Rossini  opera. 

If  something  must  have  been  said,  why  not 
let  it  go  with  saying  that  "Largo  al  factotum" 
is  one  of  the  most  famous  comic  songs  in  all 
operatic  literature,  and  that  De  Luca  is  un- 
excelled among  living  baritones  in  its  interpre- 
tation? 


The  Listeners'  Point  of  View 


LOLA    SUMMERS 

Ingenue  of  the  WGY   Players.     She  has  been  as- 
sociated with  this  radio  dramatic  company  since 
their  first  production 

HowClassical  Music  Should  Be  Played 

WE  ARE  much  interested  in  learning 
the  outcome  of  the  suit  for  $10,000 
damages  filed  by  Francis  E.  Wood- 
ward, a  music  teacher  of  Spokane,  against  the 
leader  of  an  orchestra  in  that  city,  the  alleg- 
ation being  that  the  rendition  by  the  orchestra 
of  the  classical  compositions  of  the  old  masters 
is  such. that,  "the  public  has  received  a  per- 
verted idea  of  classical  music,  insofar  that 
children  may  no  longer  desire  a  musical  edu- 
cation." 

The  jazzing  of  the  classics  is  the  greatest 
outrage  perpetrated  by  jazz  orchestras.  Mr. 
Woodward  assuredly  had  the  courage  of  his 
convictions  in  entering  this  suit.  A  pity  he 
could  not  have  filed  it  against  the  city  instead 
of  an  individual.  Where  the  classics  are 
seldom  heard  in  their  original  form  in  public 
performance,  the  influence  of  these  mutila- 
tions would  be  much  more  far-reaching  than 
in  Chicago  or  New  York,  let  us  say.  Would 
that  Mr.  Woodward  might  win  ten  times  ten 
thousand  dollars! 

The  Fame  of  Georges  Bizet 

IF  GEORGES   BIZET,  composer  of  "Car- 
men," and  of  the  "  L'Arlesienne  Suite"  so 
frequently  heard  over  the  radio  from   the 
better   class   stations    could    know   that    his 
name,  through  the  means  of  broadcasting,  is 
now  familiar  to  practically  the  entire  Ameri- 
can public,  well,  imagination  fails  to  measure 
his  astonishment.     After  meeting  with  little 
but  failure  throughout  his  short  life,  he  died 


at  the  age  of  thirty-nine,  a  few  days  after  his 
"Carmen",  now  judged  by  many  as  the  one 
perfect  opera  ever  written,  was  first  produced. 
Three  years  before  this  he  had  been  com- 
missioned to  write  incidental  music  to  Al- 
phonse  Daudet's  three-act  play,  "L'Arle- 
sienne." The  play  was  withdrawn  after 
fifteen  performances.  Of  the  twenty-seven 
musical  numbers  written  for  this  drama,  Bizet 
chose  various  ones  and  from  them  made'a  suite 
for  concert  use,  and  this  was  successful.  The 
music,  as  all  who  have  heard  it  know,  is  ex- 
quisite. It  has  all  the  elegance  and  finesse 
of  the  French  school,  and  in  the  "Adagietto" 
carries  the  theme  of  sadness  with  such  art 
that  it  becomes  beauty  rather  than  sorrow. 

But  Bizet  did  not  confine  himself  to  the 
French  school  by  any  means  when  he  wrote 
"Carmen."  Here  is  a  Spanish  story  trans- 
lated by  a  Frenchman  into  Spanish  atmos- 
phere with  music  that,  while  although  it  is  not 
of  Spanish  origin,  sounds  as  if  it  were.  But 
it  speaks  of  admiration  of  Wagner,  even  more. 

June  3,  1925,  will  mark  the  fiftieth  anni- 
versary of  Bizet's  death.  After  all,  that  is 
not  so  very  long  to  have  become  established  as 
world  famous,  when,  in  dying,  success,  to  say 
nothing  of  fame,  seemed  a  myth. 


JOHN    A.    HOLMAN 

Director  of  Broadcasting  for  the  American  Tele- 
phone and  Telegraph  Company.  He  has  made  a 
careful  study  of  the  preferences  of  radio  listeners, 
judging  from  the  letters  written  to  the  various  sta- 
tions controlled  by  his  company,  and  recently 
announced  that  public  preference  was  swinging  from 

jazz  to  classical  music 


How  to  Record  Radio  Signals 


THERE  are  many  occasions  when  it  is 
desirable  to  make  records  of  wireless 
reception.     Figs,  i,  2,  and  3  illustrate 
a  system  of  recording  that  is  compar- 
atively simple  and  yet  quite  effective.     The 
apparatus  described  was  installed  as  a  check 
on  fading  phenomena  during  the  total  eclipse 
of  the  sun  on  January  24th,  1925. 

The  apparatus  consists  of  three  primary 
parts,  the  tuner  —  which  may  be  any  con- 
venient set  —  the  amplifier,  and  the  recording 
dictaphones.  Two  stages  of  amplification  are 
sufficient,  although 
three  steps  of  resis- 
tance-coupled inten- 
sification with  volume 
control  were  used  in 
this  laboratory.  It  is 
advisable  to  have 
some  volume  regula- 
tion in  order  to  lower 
the  maximum  intens- 
ity below  the  blasting 
point  of  the  recording 
diaphragms. 

Standard  office 
dictaphones  were  prepared  by  affixing  tele- 
phone receivers  to  the  throats  of  the  speaking 
tubes.  The  soft  rubber  fixtures  intended  for 
adapting  head  sets  to  horns,  are  convenient  for 
the  purpose.  Two  dictaphones  are  not  re- 
quired but  were  employed  in  the  RADIO  BROAD- 
CAST tests  to  insure  an  unbroken  record. 

The  machines  should  be  located  at  least  five 
feet  from  the  receiver  and  more  if  convenient, 
to  eliminate  motor  induction.  Grounding  the 
frames  of  the  machines  will  also  reduce  inter- 
ference from  this  source. 

It  is  generally  desirable  to  monitor  record- 
ing on  a  loud  speaker.  This  is  most  easily 


In  the  R.  B.  Lab.  This  Month 


A  Complete  Article — Radio  Recording  with  a 
variety  of  applications,  such  as  tracing  oscillat- 
ing receiver  interference,  learning  the  radio 
code,  and  others. 

Shooting  Trouble — How  we  go  about  it. 
This  article  is  the  first  of  a  series  that  will 
help  the  reader  to  solve  difficulties  in  his  receiver 
systematically  and  swiftly. 

Notes  on  Wiring  Your  Own  Lab. 


accomplished  by  connecting  the  telephone 
receivers  (clamped  to  the  recording  instru- 
ments) in  series  with  the  loud  speaker.  A 
shunt  variable  resistance,  200  to  5000  ohms, 
across  the  phones,  provides  the  recommended 
volume  adjustment,  without  greatly  affect- 
ing the  loud  speaker.  I  f  more  convenient,  any 
other  satisfactory  form  of  speaker  unit  may 
be  substituted  for  the  phones. 

In  recording  fading,  it  is  advisable  to  keep 
the  receiver  oscillating  and  record  the  beat  note 
or  squeal  of  the  distant  stations.  I  n  addition  to 
the  greater  intensity 
and  sensitivity  of  this 
arrangement,  signal 
variations  will  be 
much  more  noticeable 
due  to  the  fact  that 
the  sound  will  vary 
approximately  as  the 
square  of  the  signal 
variations. 


OTHER    USES 


ASIDE  from  the  re- 
•**  cording  of  fading 
and  swinging,  this  apparatus  may  be  put  to 
many  other  interesting  and  useful  purposes. 
It  will  immediately  suggest  itself  for  record- 
ing programs  of  special  or  historical  interest, 
such  as  the  inaugural  address  of  the  President 
of  the  United  States.  Reception  is  affected 
in  the  manner  described,  except,  of  course, 
that  no  beat  note  is  produced. 

LEARNING   CODE 

pVlCTAPHONES  have  been  used  for  some 
*~J  time  in  the  reception  of  high  speed  (80 
to  100  words  per  minute)  radio  telegraph  code 
signals.  For  transcription,  the  machine  is 


In  the  R.  B.  Lab. 


slowed  down  considerably,  and  the  messages 
typed  off  at  perhaps  twenty  words  a  minute. 
Speed  reduction  presents  an  excellent  system 
for  learning  the  code  —  an  acquisition  which 
many  broadcast  enthusiasts  are  attempting. 
It  is  merely  necessary  to  speed  the  machine 
slightly  and  record  any  six  hundred  meter 
commercial  station,  or  two  hundred  meter 
amateur  station,  and  copy  the  sending  of  the 
operator  at  the  desired  reduction.  The  machine 
is  tireless  and  will  give  you  any  number  of 
repetitions. 

TRACING    CODE    INTERFERENCE 

ALL  types  of  interference  can  be  logged  on 
*  »  the  machines  and  later  identified  by  an 
expert,  as  amateur  interference  or  commercial 
code,  arc-lights,  leaky  pole  transformers,  etc. 
It  is  only  when  the  type  of  interference  has  been 
determined  that  it  is  possible  for  the  radio  in- 
spector to  take  steps  to  eliminate  it. 

Systematic   logging  of  all    kinds  of  inter- 
ference for  later  identification  by  an  expert 
radio  telegraph  code  operator  would  go  far 
toward  clearing  up  the  air. 
An  identified  "blooper"  made  to  listen  to 


his  own  mush,  recorded  on  a  neighboring 
receiver,  may  be  thoroughly  impressed  with 
the  iniquity  of  his  action. 

REPRODUCING 

PHERE  are  two  convenient  ways  of  re- 
1  producing  the  radio  records.  The  first, 
and  perhaps  more  satisfactory  method,  is  to 
employ  the  standard  dictaphone  transcribing 
machine,  listening  in  the  customary  manner 
through  the  rubber  tubing.  The  second,  and 
more  spectacular  system,  is  to  reproduce 
electrically,  amplifying  the  sound  and  out- 
putting  it  to  a  loud  speaker.  This  method  is 
illustrated  in  Figs.  2  and  3. 

The  arrangement  as  suggested  in  the  dia- 
gram consists  of  three  parts,  the  microphone 
for  picking  up  the  sound,  the  amplifier,  and  the 
talker.  This  apparatus  may  readily  be  a 
simple  re-arrangement  of  the  equipment  em- 
ployed for  recording.  The  microphone  (of  the 
magnetic  type)  is  conveniently  the  telephone 
receiver  or  loud  speaker  unit  clamped  to  the 
throat  of  the  dictaphone  adjusted  for  repro- 
ducing, but  connected  to  the  input  instead  of 
the  output  of  the  amplifier.  The  loud  speaker 


FIG. 


Making  fading  records  in  The  R.  B.  Lab.     Beat-note  fluctuations  are  mon- 
itored on  the  loud  speaker  and  permanently  recorded  on  the  dictaphones 


Radio  Broadcast 


remains  in  the  plate  circuit  of     Telephone 
the  last  tube. 

When  recording  and  then  re- 
producing in  this  fashion,  it  is 
most  important  that  the  ampli- 
fier, which  is  really  used  twice,  be 
free  from  audible  distortion. 
With  the  interposition  of  the 
several  mediums,  it  is  inevitable 
that  quality  will  be  lost,  and 
every  effort  must  be  made  to  re- 
produce faithfully.  Unless  the 
experimenter  is  very  sure  of  the 
results  produced  by  his  amplifier, 
resistance  coupling  is  recom- 
mended. In  the  photographs, 
a  three-stage  resistance-coupled  amplifier  was 
employed  for  recording,  and  a  two-stage 
transformer-coupled  amplifier  for  reproduc- 
ing. 

The  reproducing  system  can  be  readily 
applied  to  any  phonograph  arrangement 
where  great  volume  or  electrical  transmission 
is  desired.  It  is  only  necessary  to  place  the 
microphone  where  it  will  intercept  the  sound 
waves  at  a  point  of  fair  concentration.  A 
magnetic  microphone  of  the  type  described 
is  preferable  to  the  ordinary  carbon  grain 
variety. 


Output 


6  V. 


FIG.    3 

The  circuit  diagram  for  the  amplified   reproduction  of  audio 

records.     This  system  may  be  employed  for  the  amplification 

and  transmission  of  phonograph  music 


SHOOTING     TROUBLE 

EVERY  laboratory,  and  every  radio 
experimenter  for  that  matter,  must  be 
prepared  for  the  innumerable  diffi- 
culties that  beset  the  way  of  radio  experiment. 
This  laboratory  has  its  full  share  of  them;  in 
fact  it  is  part  of  its  business.  Shooting  trouble 
may  be  simplified  and  thereby  made  more 
swift  and  efficient,  by  following  a  certain  logi- 
cal procedure.  A  doctor  does  not  treat  his 
patients  in  a  haphazard  manner.  He  does  not 
tap  them  on  the  chest  when  they  have  a  tooth- 


FIG.    2 


The  amplifying  arrangement  for  reproducing  the  records  on  the  loud  speaker.     The  telephone  re- 
ceivers or  loud  speakers  employed  for  recording  may  be  used  as  pick-up  microphones  in  reproducing 


In  the  R.  B.   Lab. 


ache,  but  rather  he  observes  the  symptoms  and 
through  a  sequence  of  thought  and  experiment 
establishes  just  what  and  where  the  trouble  is. 
Likewise  in  radio  a  few  consistent  observations, 
even  by  the  most  unexpert  member  of  the 
family,  will  often  solve  the  difficulty  without 
calling  in  an  expert. 

There  are  three  types  of  radio  difficulties: 

Absolute  Inoperation 
Poor  Operation 

Noises 

These  are  general  headings  and  they  cover  a 
multitude  of  the  conventional  radio  sins.  In 
this  article  we  shall  begin  to  treat  the  first 
group,  not  because  it  is  the  most  prevalent 
(which  is  doubtful)  but  because  its  treatment 
is  the  more  definite  and  simple. 

THE    SET   WON'T   WORK 

OERHAPS  the  receiver  is  turned  on  in  the 
*  usual  manner  but  nothing  happens.  The 
receivers  or  loud  speaker  is  dead,  and  the 
twisting  of  dials  futile.  The  first  thing  to  be 
done  is  to  locate  the  trouble.  The  second 


task  — to  be  treated  next  month  —  is  to  apply 
the  remedy  associated  with  that  particular 
trouble. 

Test  No.  i — Turn  off  the  bulbs,  listening  for 
a  click  in  the  phones  or  speaker.  No  click  in- 
dicates a  break  somewhere  in  some  battery 
circuit.  When  there  is  no  click,  we  proceed  to 

Test  No.  2 — Inspect  the  bulbs.  If  they 
light,  the  filament  circuit  is  O.  K.  A  very  dim, 
partial  light  (which  however,  should  give  a 
faint  click  in  Test  No.  i)  suggests  a  low  A 
battery.  One  or  more  bulbs  may  be  "  blown  ". 
If  the  bulbs  do  not  light  we  try 

Test  No.  3 — Make  a  momentary  "short"  of 
the  binding  posts  on  the  set  generally  marked 
A-pIus  and  A-minus,  with  a  pair  of  scissors  or 
any  other  metal  object  that  is  convenient.  A 
spark  indicates  trouble  in  the  set  itself — fila- 
ment wiring,  burnt-out  rheostats,  loose  socket 
prongs,  filament  control  jack,  or  an  inoper- 
ative switch.  No  spark  shows  that  the  trouble 
is  on  the  battery  side  —  in  the  leads  to  the 
battery,  in  the  battery  terminals,  or  a  dead 
battery. 

If  Test   No.   2   finds   the   bulbs   normally 


FIG.  4 

"There  is  no  spark,  Harry, You  'd  better  take  a  look  at  those  battery  leads".     There  are  many  simple  tests 

that  almost  any  one  can  make  which  will  show  up  the  more  common  radio  ailments,  and  suggest  a  way  to 

remedy  the  difficulty  without  calling  in  an  expert 


Radio  Broadcast 


FIG.  5 

If  the  bulbs  light,  pull  the  plug  out,  listening  for  a  click  in  the  loud  speaker  or  phones.     When  these  simple 
tests  do  not  actually  show  you  the  way  out  of  your  difficulty,  a  description  of  the  results  will  be  of  very 
great  benefit  to  the  Grid  Department,  or  to  your  local  expert  in  helping  you  out 


lighted,  the  plate  circuit  in  the  last  tube  is, 
probably  open.  This  may  be  additionally 
ascertained  by 

Test  No.  4. — Pull  the  phone  plug  in  and  out, 
listening  for  a  click.  Change  from  phones  to 
loud  speaker  and  repeat  the  test.  This  will 
place  the  difficulty  in  either  the  output  instru- 
ment or  within  the  set.  If  one  pair  of  tele- 
phones give  a  click  in  response,  it  is  evident 
that  the  difficulty  lies  in  the  other.  If  the 
trouble  is  in  the  receiver  proper,  and  neither 
phones  or  speaker  work,  try 

Test  No.  5 — Place  another  tube  in  the  last 
socket  and  repeat  Test  No.  4.  No  response 
absolves  the  tube,  placing  the  blame  on  an 
open  B  battery  circuit,  with  the  probability 
that  the  phones  and  speaker  are  in  good  con- 
(dition. 

Test  No.  6 — This  should  be  in  the  form  of  a 
momentary  short,  or,  better,  a  voltmeter  test 
across  the  B  battery  posts  on  the  set.  If 
current  is  indicated,  this  shows  the  trouble  is 
within  the  set;  the  current  from  the  battery 
has  succeeded  in  traveling  as  far  as  the  binding 
posts.  No  deflection  on  the  voltmeter  or  spark, 
if  the  voltmeter  is  not  used,  locates  the  diffi- 
culty on  the  battery  side. 


If  tests  No.  i  or  No.  4  show  that  there  is  a 
plate  circuit,  that  the  batteries  are  O.  K.,  the 
next  test  on  non-regenerative  sets  (neutrodynes 
and  stabilized  radio  frequency)  is 

Test  No.  7 — It  is  then  possible  that  there  are 
no  receivable  stations  on,  which  means  that 
they  are  off  schedule  or  shut  down  by  an  sos. 
More  than  one  fan  has  decimated  his  set  dur- 
ing the  enforced  silence  accompanying  a  dis- 
tress call  at  sea.  Have  someone  ring  your 
doorbell,  or  turn  on  and  off  your  electric  light, 
respectively  while  you  listen  for  a  rough  buzz 
or  clicks  in  the  receivers  or  loud  speaker. 
These  will  indicate  that  in  all  probability 
everything  is  O.  K.,  or  that  the  trouble  is  in  the 
antenna  or  ground  connections.  No  results 
or  results  below  normal,  suggest  the  radio 
frequency  circuit  is  the  source  of  difficulty. 

Test  No.  8 — With  regenerative  receivers, 
those  employing  detector  feed-back  and  po- 
tentiometer or  similarly  controlled  radio  fre- 
quency circuits,  this  test  will  probably  precede 
test  No.  7.  Turn  up  the  regenerative  or 
"volume"  control.  The  usual  oscillations, 
"  plops  ","or  squeal,  show  that  the  regenerative 
detector  and  audio  frequency  tubes  are  O.  K. 
The  operator  will  then  proceed  to  Test  No. 


In  the  R.  B.  Lab 


73 


7.  Negative  results  from  Test  No.  8  show  a 
fault  in  the  regenerative  tube  or  tubes  or  in 
any  of  the  audio  stages  except  the  last,  which 
Tests  i  and  4  proved  O.  K. 

Test  No.  g — Tap  the  bulbs  with  a  pencil, 
moving  progressively  toward  the  antenna 
connection.  This  generally  means  from  right 
to  left:  second  audio,  first  audio,  detector, 
etc.  No  ring  will  be  heard  in  the  loud  speaker 
when  the  faulty  tube  or  stage  is  reached. 

Test  No.  10 — Changing  tubes  will  almost 
always  eliminate  or  define  the  bulbs  as  the 
source  of  difficulty. 

Try  all  these  tests  when  your  set  is  working, 
immediately  when  the  trouble  is  discovered  if 
possible,  in  order  to  acquaint  yourself  with  the 
response  you  may  expect  from  a  working  re- 
ceiver. 

BUILDING  YOUR  OWN  LAB 

WIRE  your  lab.  with  an  eye  for  con- 
venience   in    testing    and    operating 
more  than  one  receiver  in  different 
parts  of  the  laboratory.     The  arrangement  de- 
veloped in  the  R.  B.  LAB  can  be  enlarged  or 
reduced  to  suit  individual  convenience. 


Filament  and  plate  batteries  are  centrally 
located  with  charging  apparatus,  and  are 
wired  to  the  benches  using  colored  wire,  often 
called  "code  wire." 

Six  outlets  are  desirable,  which  provide  for 
the  connections  to  as  many  receivers  or  test 
apparatus.  Seven  wires  are  used.  Two  differ- 
ently colored  heavy  stranded  wires  carry  the 
A  battery  current.  Four  No.  18  annunciator 
wires  of  variegated  hues,  provide  plus  B 
battery  from  22\  to  140  volts.  The  negative 
B  is  connected  to  positive  A  on  the  battery 
table..  The  seventh  wire  connects  to  an  out- 
side antenna  which  may  be  disconnected  by  a 
switch  at  each  of  the  six  outlets. 

One  hundred  and  ten  volt  lines  are  run  in 
metal  moulding  along  the  edges  of  the  benches 
with  similar  outlets.  The  moulding  itself 
affords  the  ground.  The  moulding  should  be 
installed  according  to  underwriter's  require- 
ments, who,  however,  have  no  jurisdiction 
over  the  other  wiring. 

If  desired,  fuses,  switches,  and  meters  (volt, 
ampere  and  milli-ampere),  can  be  installed  at 
the  battery  table.  Several  photographs 
taken  in  the  Lab.  depict  the  utility  of  this 
arrangement. 


FIG.  6 

Tap  the  bulbs  and  listen  for  the  usual  ring.     A  ring  from  any  of 
the  r.  f.  or  detector  tubes  shows  that  the  audio  amplifier  is  O.  K. 


ike  troc|c[cc|ster  sees  xi 


Drawings  by  Franklyn  F.  Stratford 


How  Much  Power  is  "Super-Power"? 


HOW  big  must  a  broadcasting  station 
be  to  claim  attention  as  a  "super- 
power" outfit?  Estimates  appear 
to  vary.  The  owners  and  publicity 
representatives  of  the  j-kw  transmitters  now 
being  put  into  operation  in  various  sections  of 
the  country  like  to  refer  to  them  as  super- 
power equipment.  But  if  5  kw  is  super- 
power, what  would  50  kw  be?  We  had  better 
be  careful,  or  we  shall  run  out  of  awe-inspiring 
prefixes.  It  is  certain  that  Mr.  David  Sarnoff, 
who  is  responsible  for  the  idea  and  for  the 
spreading  abroad  of  the  term,  had  a  consider- 
ably greater  magnitude  in  mind  than  5  kw. 
However  that  may  be,  it  is  a  fact  that 
the  power  rating  of  present-day  broadcasting 
stations  is  trifling  compared  to  that  of  the 
great  transoceanic  and  transcontinental  radio 
telegraph  installations.  One  of  these  immense 
transmitters  is  described  in  a  paper  by  Dr. 
Cornelius  J.  DeGroot  in  the  December,  1924, 
number  of  the  Proceedings  of  the  Institute  of 
Radio  Engineers,  "The  High-Power  Station 
at  Malabar,  Java."  This  station  connects 
the  Dutch  East  Indies  directly  with  Holland, 
arc  transmitters  being  used  in  the  main.  At 
the  present  time  2,400  kw  is  the  power  supply 
to  the  arcs,  whereby  1,200  kw  are  fed  to  the 
antenna,  as  compared  to  0.5  kw  in  the  antenna 
of  a  standard  Class  B  broadcasting  station. 
1,200  kilowatts!  Ten  years  ago  all  the  man- 
made  radio  frequency  energy  in  the  world 
probably  did  not  amount  to  1,200  kw.  Dr. 
DeGroot  is  not  satisfied,  however.  He  assures 
us  that  when  he  gets  another  motor  generator 
from  the  General  Electric  Company  he  will 
be  able  to  supply  3,200  kw  to  his  arcs,  obtain- 
ing about  i, 600  kw  in  the  antenna.  This  will 


put  the  station  on  a  2o-hour-a-day  basis  of 
communication  over  its  7,5oo-mile  circuit, 
which  is  in  excess  of  the  traffic  requirements. 

But,  simply  regarded  as  power,  1,200  or 
i, 600  kw  are  not  figures  to  arouse  respect 
among  power  engineers.  In  a  good-sized 
power  plant,  such  as  one  of  those  which  supply 
energy  for  the  subways  of  New  York  City,  the 
wattmeter  reads  in  the  neighborhood  of 
100,000  kilowatts  on  normal  load,  and  this 
load  fluctuates  5,000  up  and  down.  The 
mere  variation  in  the  load  carried  by  such  a 
plant  is  far  greater  than  the  maximum  output 
of  the  largest  radio  station  in  existence. 

The  comparison  is  instructive,  and  chasten- 
ing to  the  pride  of  the  radio  engineer,  but  at 
bottom  it  really  does  not  mean  much,  for  the 
commodities  are  not  in  the  same  class.  Raw 
electric  energy  is  one  thing,  and  modulated 
radio  energy — especially  that  voice  or  musi- 
cally modulated — is  quite  another.  Moreover, 
this  difference  between  simplicity  and  com- 
plexity is  only  the  first  of  a  number  of  unlike- 
nesses.  There  is  a  difference  in  reception,  for 
one  thing.  The  subway  train  or  the  electric 
toaster  takes  power  from  the  line  and  uses  it 
up.  Radio  receiving  sets,  in  general,  amplify, 
sometimes  very  greatly,  the  quantity  of  energy 
which  they  pick  up.  A  super-heterodyne  in 
robust  form  may  possess  a  voltage-amplifying 
capacity  of  from  5,000  to  ro.ooo  times,  accord- 
ing to  Mr.  Armstrong  (from  25  to  100  million 
times  energy  amplification),  and  no  doubt 
many  receivers  of  more  plebeian  types  have  an 
energy  amplification  of  millions  of  times 
(energy  amplification  is  the  square  of  voltage 
or  current  amplification).  It  should  be  noted 
that  this  development  of  receiving  amplifiers 


As  the  Broadcaster  Sees  It 


75 


has  been  necessitated  by  the  great  attenu- 
ation involved  in  radio  transmission,  the 
losses  in  the  intervening  medium  being  far 
greater  than  those  of  an  electric  power  trans- 
mission network. 

But  the  principal  distinction  lies  in  the 
extraordinarily  small  amount  of  energy  re- 
quired to  satisfy  the  human  ear.  "The  speech 
energy  output  of  the  normal  voice  has  been 
found  to  be  at  the  rate  of  about  125  ergs  per 
second.  If  we  could  have  a  million  persons 
talking  steadily  and  convert  the  energy  of  the 
voice  vibrations  into  heat,  they  would  have  to 
talk  for  an  hour  and  a  half  to  produce  enough 
heat  to  make  a  cup  of  tea.  This  merely  serves 
to  illustrate  that  in  terms  of  power  or  energy 
human  speech  is  exceedingly  weak.  Further- 
more, most  of  this  energy  is  carried  by  the 
vowel  sounds.  At  the  upper  and  lower  limits 
of  audition  it  takes  about  a  hundred  million 
times  as  much  energy  to  enable  one  to  hear  as 
it  does  in  the  range  of  1,000  to  5,000  cycles, 
where  the  ear  is  most  sensitive.  At  all  frequen- 
cies, the  energy  required  is  small,  and  in  the 
most  favorable  region  the  minimum  audible 
tone  corresponds  to  a  pressure  change  per 
square  centimeter  of  about  o.ooi  of  a  dyne. 
This  pressure  is  roughly  equivalent  to  the 
weight  of  a  section  of  a  human  hair  about  one 
thousandth  of  an  inch  long  (about  one  third 
as  long  as  its  diameter)."  (R.  L.  Jones: 
"The  Nature  of  Language."  Journal 
A.  I.  E.  E.,  April,  1924.) 

Thus  a  public  address  system  or  a  moderate- 
powered  broadcasting  transmitter  may,  as 
has  been  pointed  out,  contain  more  speech 
energy  than  all  the  inhabitants  of  the  globe 
yelling  with  all  their  might  and  main  at  the 
same  instant — if  they  could  be  persuaded  to 
cooperate  to  this  extent,  which  I  doubt.  It 
is  for  this  reason,  basically,  that  wireless 
stations  are 
not,  relatively 
speaking, 
powerful. 
They  need  not 
be  as  powerful 
as  agencies 
which  light 
homes  or 
transport 
freight  or 
press  trousers, 
because  these 
actions  re- 
quire  i  n  fi  - 
nitely  more 
energy  than 


speech  and  hearing,  and  it  is  in  hearing 
that  radio  communication  usually  terminates. 
That  is  why  super-power  in  electrical  en- 
gineering— the  section-wide  coordination  and 
integration  of  power  generating  facilities — 
deals  with  magnitudes  enormously  greater 
than  the  super-power  projects  of  radio  broad- 
casting. The  latter,  however,  assume  impos- 
ing proportions  as  soon  as  we  compare  them 
with  the  energy  levels  of  unaided  speech  or 
the  general  run  of  sounds  found  in  nature. 


SUPER-SEX 

A 

SUPER 
DRAMA 


Since  writing  the  above  I  have  come  across 
two  newspaper  articles  bearing  on  this  sub- 
ject. One  of  them  is  a  publicity  release  by 
Mr.  J.  D.  R.  Freed,  also  pointing  out  that 
"super-power"  is  a  term  too  loosely  and 
inflatedly  used  in  radio  at  the  present  time. 
Mr.  Freed  compares  the  power  of  a  large 
broadcasting  station  like  WEAF,  with  2  kilo- 
watts in  the  antenna,  with  the  665  kilowatts 
consumed  by  a  ten-car  subway  train  (presum- 
ably this  is  starting  energy).  An  electric 
sign  on  Broadway  consumes  263  kilowatts. 
The  average  broadcasting  station  of  to-day 
puts  into  the  antenna  only  about  as  much 
power  as  one  needs  to  light  a  six-room  flat. 
Mr.  Freed's  idea  of  super-power  is  from  1000 
to  10,000  kw  for  an  international  program  dis- 
tribution. In  other  words,  he  would  go  up; 
to  and  above  the  level  of  the  Malabar  trans- 
mitter of  Dr.  DeGroot.  The  only  question 
we  raise  at  this  point  is :  Who  is  going  to  put  up 
the  money?  Also,  in  his  comparison  of  power 
magnitudes,  Mr.  Freed  does  not  discuss  the 
bearing  of  the  relatively  minute  energy  re- 
quired by  electro-acoustic  devices,  on  the 
problem  of  radio  power. 

However,  Mr.  Freed  is  an  engineer  and 
what  he  says  is  sound  and  pertinent.  At  the 
opposite  extreme  is  a  publicity  release  by  a 

radio  and 
phonograph 
company 
which  is  about 
to  enter  the 
broadcasting 
field  with  a 
"station  of 
tremendous 
power.  It  is 
said  that  it 
will  have  a 
range  of  from 
15,000  to 
20,000  miles." 
And  what  is 
going  to  be 


super"  mean? 


76 


Radio  Broadcast 


the  power  of  this  colossus?  Answer^  kw. 
You  may  breathe  again. 

Moreover,  the  engineer  of  the  company  in- 
forms the  world  that  this  new  station  will  "in- 
fluence profoundly  broadcasting  in  daylight." 
This  gives  the  impression,  to  the  lay  reader, 
that  the  daylight  range  of  a  5  kw  transmitter 
must  be  somewhat  comparable  with  the  night 
range  of  the  present  order  of  figure  o  .5  kw 
sets.  This  belief  is  entirely  erroneous. 

Messrs.  H.  W.  Nichols  and  Lloyd  Espen- 
schied,  two  prominent  radio  and  telephone 
engineers,  investigated  this  subject  some 
years  ago,  in  the  course  of  a  larger  work  which 
occupied  them  at  that  time,  and  reported 
their  results  in  a  scientific  paper.  (Nichols 
and  Espenschied:  "Radio  Extension  of  the 
Telephone  System  to  Ships  at  Sea,"  Proc. 
I.  R.  E.,  Vol.  XI,  No.  3,  June,  1923.)  They 
made  actual  measurements.  It  was  found 
that  in  order  to  equal  during  daylight  the  freak 
ranges  secured  by  radio  telephone  stations  on 
broadcasting  wavelengths  (then  360  and  400 
meters)  during  the  most  favorable  times  at 
night,  about  10,000  times  as  much  power 
would  be  required.  A  0.5  kilowatt  station 
would  have  to  raise  its  power  to  5000  kilo- 
watts! 

But  what's  a  little  multiplier  like  1000  to  a 
publicity  representative  and  radio  engineer, 
model  1925?  Less  than  nothing,  for  these 
gentry  never  heard  of  Nichols  and  Espenschied 
and  Alexanderson  and  Wien  and  Braun  and 
Armstrong  and  Latour  and  DeForest  and  the 
few  hundred  other  earnest  engineers  whose 
exclusive  creation  radio  broadcasting  is.  And, 
if  they  have  heard  of  them,  they  care  no 


•vVe  iveecL  drtistic  micropKoives 


more  for  scientifically  derived  data  than  the 
Long  Island  fanatics  who  recently  awaited 
the  end  of  the  world. 

Artistic   Stands   for  the   Microphone 

THE  design  of  microphone  stands,  at 
the  present  time,  is  far  too  con- 
ventional. They  are  tame,  unimagi- 
native things  wrought  of  bronze  pipes  or  one- 
time respectable  parlor  lamps.  This  has 
a  depressing  effect  on  the  whole  broadcasting 
art,  for  the  general  public  gets  its  ideas  of 
radio  largely  from  the  myriads  of  pictures 
showing  the  great,  and  the  aspirants  to  great- 
ness, posed  before  a  microphone  stand  in  the 
attitude  of  talking  to  10,000,000  fellow 
citizens — even  when  the  station  power  is  about 
10  watts.  What  an  opportunity  is  neglected 
here!  The  future  belongs  to  the  genius  who 
will  express  himself  through  radio  microphone 
stands,  fitting  them  to  special  situations, 
somewhat  as  follows: 

A  ravishing  silver-plated  girl  in  attractive 
deshabille  for  lecturers  on  literary  censorship, 
denouncers  of  the  younger  generation  and  pet- 
ting parties,  etc. 

For  Mayor  John  F.  Hylan  of  New  York 
City,  a  bust  of  Gen.  John  F.  O'Ryan,  his 
opponent  in  the  local  traction  controversy. 
General  O'Ryan  could  hold  the  microphone  in 
his  teeth. 

A  foaming  stein  or  champagne  bottle  for 
prohibitionists. 

At  woe,  the  learned  chiropractors  might 
talk  to  a  mound  of  issues  of  the  Journal  of  the 
American  Medical  Association,  the  microphone 
surmounting  the  same. 

For  Messrs.  Arthur  Lynch,  Willis  K. 
Wing,  and  Zeh  Bouck,  the  desperate  crusaders 
for  a  squealless  ether,  what  could  be  more 
appropriate  than  a  giganticdiagram  of  a  single- 
circuit  regenerator,  rampant,  with  the  micro- 
phone suspended  from  the  oscillations? 

The  ramifications  of  the  idea  are  obvious. 
Its  inspirational  properties  are  unlimited. 
We  leave  its  execution  to  philanthropists  and 
artists. 

Note  on  Announcing 

A  COMMITTEE  has  recently  been  occu- 
pied, in  New  York  City,  with  the  task 
of  raising  the  standards  of  announc- 
ing.   Various  conclusions  as  to  rate,  pitch, 
inflections,    and    other    characteristics    were 
reached  and  duly  published. 

A  most  praiseworthy  work.  But  the  com- 
mittee omitted  consideration  of  one  funda- 


As  the  Broadcaster  Sees  It 


77 


mental  fault  with  which  nine  announcers  out 
of  ten  are  afflicted:  they  talk  too  much. 

How  and  Why  Stations  Heterodyne 
One  Another 

THE  problem  of  heterodyne  interference 
between  broadcasting  stations  has  the 
same  origin  as  the  rush  hour  jam  in  a 
large  city:  too  many  people  are  in  the  same 
place  at  the  same  time. 

Class  B  stations  are  supposed  to  be 
spaced  ten  kilocycles  apart,  with  an  effort 
being  made  to  reduce  the  separation  to  7^ 
cycles,  in  order  to  create  additional  chan- 
nels for  new  stations.  These  are  theoretical 
separations,  conditioned  on  all  the  stations 
keeping  their  exact  assigned  frequency.  Un- 
fortunately, they  vary.  When  they  get  a  few 
thousand  cycles  apart,  all  the  listeners  within 
range  of  both  hear  a  beat-note,  a  continuous 
melancholy  whistle,  varying  slightly  in  pitch 
from  minute  to  minute,  and  well  calculated 
to  drive  sensitive  persons  crazy — although, 
through  the  psychological  phenomenon  of 
auditory  fatigue,  some  people  get  used  to  the 
beat  and  hardly  hear  it  after  a  time,  unless  it 
is  very  loud. 

As  a  matter  of  fact,  any  two — or  any  number 
of  stations,  for  that  matter — have  a  beat  note 
in  any  receiver  capable  of  picking  up  their 
waves.  If  they  are  10  kilocycles  apart,  they 
have  a  beat  note  of  10  kilocycles,  or  10,000 
cycles,  which  is  over  twice  as  high  as  the 
highest  note  on  a  piano.  This  pitch  is  too 
high  to  pass  effectively  through  the  audio- 
amplifying  circuits  of  a  receiver,  and  what 
little  does  get  through  is  suppressed  by  the 
loud  speaker  and  the  human  ear,  neither  of 
which  is  designed  to  respond  ardently  to  such 
an  acute  note.  In  short,  nothing  is  heard. 
But  as  the  two  stations,  through  the  deviation 
of  one  or  the  other,  or  both,  from  its  or  their 
assigned  frequency,  approach  each  other,  the 
beat  note  between  them  passes  into  the  band 
of  audible  and  essential  frequencies  to  which 
the  acoustic  apparatus  of  the  receiver  and 
listener  responds.  The  resulting  interference 
may  be  anything  from  a  very  shrill  whistle 
up  around  4000  cycles,  scarcely  audible  to 
one  not  listening  for  it,  down  to  an  angry 
recurrent  growl  on  either  side  of  zero-beats,  if 
the  two  stations  happen  to  be  right  on  the 
same  wavelength.  Or,  it  may  be  a  loud,  con- 
tinuous whistle  of  medium  musical  pitch. 
Loudness  depends  on  the  strength  of  the 
electric  fields  of  the  two  interfering  stations  at 
the  heterodyning  location;  pitch  depends  on 


clowiv  staiioiv.  xnierJference 


their  respective  frequencies  and  the  variations 
therein.  The  ultimate  result  is  telephone  and 
telegraph  calls  from  irate  listeners. 

Unfortunately,  a  station  which  is  too  weak 
to  produce  a  workable  signal  in  a  given 
neighborhood,  is  perfectly  capable  of  giving 
rise  to  heterodyne  interference  with  stations 
supplying  a  powerful  signal  to  the  locality 
on  which  it  depends  for  program  service. 
This  is  one  of  the  inherent  traits  of  heterodyne 
amplification,  the  same  which  enables  an 
oscillating  receiver  to  hold  a  very  audible  beat- 
note  with  a  distant  station,  while,  in  the  non- 
oscillating  condition,  the  modulation  of  the 
station  in  question  is  inaudible  —  a  character- 
istic which  is  therefore  responsible  for  the 
reprehensible  use  of  beat  reception  by  users 
of  radiating  receivers.  Great  is  heterodyne 
amplification,  and,  like  many  other  great 
things,  it  is  also  capable  of  causing  a  deal  of 
mischief. 

The  result  is  that  in,  say,  New  York  City, 
you  may  be  listening  to  one  of  the  local 
stations  five  or  ten  miles  distant,  employing 
enough  amplification  to  get  a  comfortable 
signal;  and  although  in  that  condition  your 
set  could  not  possibly  hear  a  Chicago  broad- 
caster of  the  same  power,  when  that  Chicago 
station  climbs  on  to  your  New  York  station's 
wavelength,  you  get  a  beat-note  of  perhaps  a 
quarter  the  intensity  of  the  local  station's 
signal.  (Living  in  New  York,  and  being 
responsible  for  the  technical  operation  of  two 
of  the  local  broadcasters,  I  naturally  assume, 
and  stand  ready  to  prove  it  with  wavemeters 
and  firearms,  that  the  Chicago  station  is  at 


Radio  Broadcast 


fault.)  But  if  the  New  York  broadcaster 
then  takes  his  carrier  off  the  air,  and  you  let 
your  receiver  alone,  there  is  silence.  You 
have  to  bring  up  your  amplification  in  order 
to  hear  Chicago. 

This  has  an  important  bearing  on  the  prob- 
lem of  running  down  heterodyne  interference 
when  it  does  occur.  The  only  receiver  which 
can  be  safely  used  in  such  work  is  one  which 
has  a  volume  control  independent  of  the 
frequency  adjustments.  If  the  tuning  and 
intensity  controls  are  electrically  interlinked, 
I  should  say  that  the  receiver  is  worthless 
for  detective  equipment. 

If  you  are  near  one  of  the  heterodyning 
transmitters,  you  are  not  likely  to  be  able  to 
identify  the  more  distant  one  unless  Number 
i  takes  his  carrier  off  the  air.  If  the  inter- 
ference is  serious,  and  the  transmission  of  the 
station  is  properly  monitored  from  a  point 
outside  the  studio,  this  is  likely  to  be  done. 
The  engineers  are  waking  up  to  the  fact  that 
they  can  best  solve  their  station-interference 
problems  by  direct  action,  by  exchange  of 
telegrams  between  the  broadcasters  involved, 
as  soon  as  the  trouble  starts.  The  telegraph 
companies  are  generally  willing  to  give  priority 
to  such  messages.  It  is  preferable  to  take  the 
carrier  off  the  air  for  a  few  minutes,  for  the 
purpose  of  identifying  the  interfering  station, 
and  to  send  him  a  telegram  explaining  the 
situation,  rather  than  to  suffer  the  con- 
dition to  continue  and  to  allow  the  program 
to  be  hashed  up,  in  greater  or  less  degree,  for 
the  entire  evening. 

It  is  customary,  when  shutting  down  for 
this  purpose,  to  take  the  listeners  into  one's 
confidence  and  to  solicit  their  aid,  for,  with 
the  great  natural  variations  in  receiving  con- 
ditions, quite  possibly  some  outsider  will  be 
able  to  do  the  job  better  than  the  one  or  two 
members  of  the  station  personnel  engaged  in 
chasing  down  the  trouble.  The  purpose  of  this 
article  is  to  give  listeners  some  data  which  will 
make  their  testimony  reliable  in  this  regard. 

The  rules  of  the  game  may  be  summarized 
as  follows: 

1.  When  the  announcement  goes  out,  tune  your 
set  precisely  to  the  wavelength  of  the  local  broad- 
caster who  complains  of  the  interference.     This  can 
usually  be  done  in  the  few  remaining  seconds  of 
transmission. 

2.  If  you  are  receiving  on  a  loud  speaker,  change 
to  head  telephones;  your  chances  with  the  phones 
are  obviously  better. 

3.  When  the  carrier  goes  off  the  air,  bring  up 
your  volume  control  till  the  interfering  station  is 
readable.     Don't  touch  the  frequency  controls. 

4.  If  you  are  able,  under  these  conditions,  to 


make  a  positive  identification,  and  you  feel  inclined 
to  do  that  much  for  the  cause,  dispatch  a  telegram 
to  the  party  of  the  first  part  who  has  gone  off  the  air. 
The  next  best  thing  is  to  write  a  letter. 

5.  If  the  intensity  and  wavelength  (frequency) 
controls  of  your  set  are  not  perfectly  free  from  inter- 
action, or  if  you  are  not  confident  that  your  set 
tunes  very  sharply,  you  can  be  of  greatest  service  by 
staying  out  of  the  controversy.  Your  testimony 
will  only  confuse  the  issue. 

Of  course,  if  you  have  a  set  accurately 
calibrated  in  kilocycles,  it  may  be  permissible 
to  try  to  determine  the  actual  frequencies  of 
the  stations  involved,  but  with  ordinary 
equipment  one  is  not  justified  in  testifying  that 
Station  Number  2  was  actually  on  the  wave- 
length of  Station  Number  i  unless  the  fre- 
quency-determining elements  of  the  receiver 
remained  unchanged.  Even  this,  of  course, 
is  only  a  beginning,  for  Station  Number  i 
may  have  been  off  his  wave.  Once  it  has  been 
established,  however,  which  stations  have 
been  involved,  it  is  usually  possible  to  clear  up 
the  situation  for  the  time  being,  and  the  accu- 
rate calibration  of  their  frequency  indicators 
must  be  left  to  the  Federal  radio  supervisors. 

The  necessity  of  instructing  the  l:sieners  in 
the  above  procedure,  if  they  are  to  be  of  service 
in  these  situations,  was  brought  home  to  me  by 
a  recent  incident.  I  was  listening  at  my 
home  when  one  of  the  stations  in  which  I  am 
interested  developed  heterodyne  interference 
early  in  the  evening.  Program  complications 
made  it  inadvisable  to  interrupt  the  service 
later,  so  I  telephoned  immediately  and  had 
the  carrier  taken  off  the  air  for  four  minutes. 
Before  these  instructions  could  be  carried  out 
the  interfering  station  shifted  his  wavelength, 
and  the  beat-note  ceased.  It  was  too  late  to 
cancel  the  order,  and  the  carrier  went  off.  I 
listened  on  the  chance  that  the  distant  station 
might  come  in  again  during  the  four-minute 
period  of  observation,  but  heard  nothing 
except  two  extremely  distant  transmitters 
heterodyning  each  other,  and  a  spark  station 
in  the  English  Channel.  As  soon  as  the 
carrier  went  back  on  the  air,  Dr.  Alfred  N. 
Goldsmith  telephoned  me  to  say  that  he  also 
had  heard  nothing  to  indicate  that  any  one 
was  on  our  wavelength,  and  that  on  his 
specially  calibrated  super-heterodyne  both  of 
the  out-of-town  stations  which  occasionally 
clash  with  us  were  on  their  assigned  frequen- 
cies. Dr.  Goldsmith  is  the  chief  broadcast 
engineer  of  the  largest  radio  company  in 
the  world,  and  has  been  making  precision 
measurements  in  radio  for  about  fifteen  years, 
so  that  what  he  says  must  be  accepted  as  ex 


As  the  Broadcaster  Sees  It 


79 


cathedra.  But  a  considerable  number  of 
listeners  notified  the  station  that  X  and  Y, 
the  two  transmitters  with  which  we  some- 
times have  difficulty,  were  on  our  wavelength. 
We  know  that  at  this  particular  time  X  and  Y 
were  innocent.  Clearly  our  well-meaning 
informants  were  wrong  in  their  conclusions. 
As  long  as  only  two  stations  heterodyne  each 
other,  there  is  hope,  but  in  the  not  infrequent 
case  where  three  transmitters  are  involved, 
one  can  do  little  but  sit  back  and  stand  the 
gaff.  Generally,  when  one  carrier  is  taken  off 
the  air,  the  remaining  two  beat  with  each 
other  to  such  a  degree  that  the  announcements 
of  neither  can  be  understood.  The  only  thing 
that  a  broadcaster  in  this  situation  could  do 
would  be  to  shift  his  own  wavelength  and  get 
clear  of  them  both.  But  that  is  reprehensible, 
for  if  individuals  start  taking  the  law  or  the 
wavelength  into  their  own  hands  in  this  way, 
the  present  difficulties  of  ether  congestion  will 
become  aggravated  to  the  point  of  chaos. 
Such  a  remedy  is  worse,  in  the  long  run,  than 
the  disease.  Communication  and  cooperation 
between  broadcasters  should  all  be  in  the 
direction  of  keeping  every  one  on  his  assigned 
frequency.  If  the  stations  will  only  stay  put, 
we  shall  be  able  to  say,  as  far  as  beat  interfer- 
ence is  concerned,  "The  rest  is  silence." 

Who  is  Which  in  Radio- 
Colonel  Combust 

ON  OUR  recent  trip  abroad  we  carried 
letters  of  introduction  to  Colonel 
Combust,  the  Chief  Signal  Officer  of 
the  unmatched  Euphratean  army.  We  had 
considerable  difficulty  catching  up  with 
Colonel  Combust,  for  the  Euphratean  forces 
were  just  then  retreating  before  the  matchless 
Kustanian  army,  a  war  having  sprung  up 
between  the  two  monarchies  over  a  chorus 
girl.  Finally  the  officer  was  located,  standing 
up  to  his  mustache  in  a  river,  and  waving  his 
sword  to  encourage  the  brave  Euphrateans 
who  were  swimming  around  him.  Delivering 
our  letters  through  an  orderly,  we  hove  to  in 
our  rowboat,  waiting  for  a  statement. 

"We  shall  deceive  the  enemy,"  cried  the 
gallant  colonel,  "for  the  code  our  signal  corps 
operators  send  is  absolutely  unrecognizable, 
even  by  ourselves.  Therefore  the  cursed 
Kustanians  will  be  unable  to  discover  our 
designs,  our  arms  will  triumph,  and  the  lovely 
chorus  girl  Tina  will  be  restored  to  the  Eu- 
phratean "Follies,"  from  which  she  was  want- 
only kidnapped  by  the  King  of  Kustania,  that 
insolent  pig!" 


As  the  valiant  colonel  swung  his  sword  close 
to  our  nose  during  this  denunciation,  we 
rowed  several  boat-lengths  upstream  before 
asking: 

"Has  the  King  of  Kustania  no  chorus  girls 
in  his  own  dominions?" 

"He  has,"  explained  the  colonel,  "but  his 
taste  in  that  line  is  exotic,  like  that  of  a  DX 
hunter,  who  praises  the  stations  of  every 
country  but  his  own." 

"Are  you,  then,  afflicted  with  broadcasting 
stations,  sir?"  we  inquired. 

"Yes,  indeed,"  answered  Colonel  Combust, 
"and  1  predict  with  confidence  that,  after  we 
have  defeated  the  enemy  in  this  present  war 
over  Tina,  the  next  war  between  Euphratea 
and  Kustania  will  be  brought  about  by  the 
broadcasting  stations." 

"What!"  we  cried.  "We  understood  that 
broadcasting  was  to  lead  to  universal  peace, 
the  hearts  of  the  Mongolians,  Californians, 
and  Esthonians  being  softened  by  mutual 
listening  to  bedtime  stories,  lectures  on  the 
dog-collar  industry,  and  reports  on  measure- 
ments of  the  losses  in  No-Loss  variable 
condensers.  Nay,  more,  we  had  worked  out  a 
plan  whereby  all  international  disputes  were 
to  be  settled,  not  by  citizens  shedding  each 
other's  blood,  but  by  the  announcers  of  the 
several  countries  being  allowed  and  incited 
to  talk  each  other  to  death.  Thus  an  orderly 
and  beneficial  process  would  be  substituted 
for  barbarous  warfare.  What  could  be  sweeter 
than  to  have  the  announcers  die  for  their 
countries,  while  other  citizens  continue  to  hug 
their  girls — 

"Whose  girls — the  announcers'?"  inter- 
rupted the  colonel  with  great  interest. 

"Announcers  have  no  girls,"  we  exclaimed 
impatiently.  "The  conjugal  tie  cannot  long 
unite  two  such  verbose  entities  as  a  woman 
and  an  announcer,  and  girls,  realizing  this 


ike  Lo<jt  osciUdtetl  like  <l  Hooper 


8o 


Radio  Broadcast 


fact,  do  not  waste  their  time  on  the  gentlemen 
of  this  trade." 

"Nature  is  wonderful,"  agreed  the  doughty 
officer. 

"As  we  were  saying,"  we  continued,  "the 
announcers  will  perish,  but  respectable  real- 
tors, cheese-brokers,  and  clothing  dealers  will 
continue  to  drink  chocolate  sodas  and  to  roll 
the  bones.  No  longer  will  war  ravage  and 
impoverish  countries.  Such,  at  least,  was  my 
plan  and  expectation.  And  now  you,  Colonel, 
tell  me  that  the  great  nations  of  Euphratea 
and  Kustania  are  on  the  brink  of  another 
war — when  they  finish  the  present  one — over 
a  question  of  broadcasting  stations!  Oh, 
Colonel — 

Such  was  our  agitation  that  we  stood  up  in 
the  rowboat. 

"Sit  down,"  called  the  officer.  "You  are 
rocking  the  boat." 

Indeed,  the  boat  was  oscillating  like  the 
single-circuit  receiver  owned  by  the  janitor's 
little  boy.  We  sat  down. 

"Nothing  could  be  more  natural,"  Colonel 
Combust  asserted.  "The  Euphratean  engi- 
neers having  erected  a  3-kilowatt  station, 
immediately  the  greasy  Kustanians  proceeded 
to  put  up  one  of  10  kilowatts.  Is  not  that  a 
casus  belli  ?  Shall  we  hesitate  to  defend 
our  national  honor?" 

"But,  sir,"  we  assured  him,  "does  any  one 
doubt  that  three  Euphratian  kilowatts  are 
worth  ten  Kustanian  kilowatts?" 

"Absolutely,"  cried  the  Colonel.  "But 
you  should  hear  the  modulation.  It  is  an 
atrocity,  The  whole  world  should  make  war 
on  a  country  which  permits  such  distortions 
in  the  ether." 

"Don't  say  that,  Colonel!  On  that  basis, 
will  not  the  League  of  Nations  attack  Newark, 
New  Jersey,  and  stab  it  in  the  lower  wave- 
lengths?" 


committees  are  iu 


ciimouiicers 


"Why  not?"  inquired  Colonel  Combust,  un- 
disturbed, as  ever,  at  the  prospect  of  another 
war.  "The  surrounding  marshes  will  be 
eternally  grateful  to  any  power  which  delivers 
them  from  some  of  those  Class  A  coffee- 
grinder  broadcasters." 

"  Besides,"  he  continued,  reverting  to  his 
favorite  subject  of  the  disputes  between 
Euphratea  and  its  hostile  neighbor,  "why 
should  Kustania  have  a  broadcasting  station 
at  all?  The  miserable  Kustanian  goatherds 
have  no  more  valid  use  for  such  an  apparatus 
than  a  football  player  has  for  a  brassiere." 

"Are  they  deaf  and  dumb,  then?"  we  asked. 

"No,"  answered  our  informant,  "although 
it  would  be  a  blessing  if  they  were.  You 
should  hear  their  so-called  broadcasting. 
What  uncouth  speech!  What  asinine  argu- 
ments! What  unadulterated  drivel!  Music 
such  as  little  children  make  on  their  drums 
and  fish-horns  on  Christmas!  It  is  indescrib- 
able. One  must  hear  it.  But,  as  you  seem  a 
well-meaning  and  moral  young  man,  I  pray 
that  you  may  be  preserved  from  such  an 
ordeal." 

"Colonel,  you  speak  exactly  like  one  broad- 
caster about  another  in  the  same  town — in  my 
country.  They  refer  to  each  other,  recipro- 
cally, in  such  sweet  terms.  But  this  is  a 
conflict  which  we  cannot  resolve  at  the  present 
time.  So  tell  me,  Colonel,  would  it  not  be 
possible  for  you  to  issue  forth  from  this  river 
and  have  dinner  with  me  in  that  town  I  see  on 
the  horizon?" 

"It  would  be  bad  tactics,"  answered  the 
immersed  officer,  regretfully.  "We  have 
strategically  placed  our  superb  army  in  this 
river  because  the  despicable  Kustanians  have 
60,000  more  men  .than  we.  But,  such  is  their 
fear  of  being  washed,  that  they  will  not  ven- 
ture near  a  body  of  water  of  this  size.  Thus 
by  remaining  in  the  river  we  are  carrying  the 
war  to  a  glorious  conclusion." 

"The  sensation  of  hunger,"  writes  the 
physiologist  Cannon,  ".  .  .  may  take 
imperious  control  of  human  actions."  A 
journalist  is  human.  Hunger  forced  us  to 
take  leave  of  the  heroic  Colonel  Combust 
and  the  other  brave  Euphrateans.  When  we 
had  rowed  about  fifty  feet  towards  the  shore 
the  Colonel  hailed  us. 

"Sir,  will  you  grant  me  a  great  favor?"  he 
called.  "  Bring  me  back  a  ham  sandwich  and 
a  water-proof  radio  receiver." 

"Why  the  radio  receiver?"  we  asked. 
"Would  you  not  rather  have  two  ham  sand- 
wiches?" 

"No,"  answered  the  valiant  soldier  pile- 


As  the  Broadcaster  Sees  It 


81 


ously,  "my  feet  are  cold,  and  1  would  warm 
them  by  listening  to  the  strains  of  'Red  Hot 
Mamma'  broadcast  nightly  by  500  American 
stations." 

Unfortunately,  when  we  returned  the  river 
had  frozen  over  from  shore  to  shore,  and  no 
sign  remained  of  the  great-hearted  colonel  and 
his  army.  Furthermore,  the  Kustanians  beat 
us  up  to  within  an  inch  of  our  lives  for  afford- 
ing assistance  to  the  enemy.  We  are  proud, 
therefore,  to  present  to  our  readers  this  last 
interview  with  Colonel  Combust.  Requiescat 
in  pace — which,  translated,  means,  May  he 
freeze  in  peace. 

Why  Should   Radio  Appeal  Only  to 
the  Auditory  Sense? 

THE  quotation   with  which  we  are  now 
about  to  grace  this  crude  and  material- 
istic department  is  ladled  out  from  the 
daily  sugarwater  offering  of  a  metropolitan 
radio  critic: 

Deferring  to  the  guest  of  honor's  habitual  aversion 
to  radio,  broadcasting  forces  had  tactfully  concealed 
the  microphone  among  masses  of  flowers.  Their 
sweet  odor  was  infused  into  the  words  of  the  speak- 
ers, which  transmitted  with  unusual  clarity  in  spite 
of  the  blossomy  screen. 

A  sweet  odor  was  infused  into  the  words  of 
the  speakers,  ladies  and  gentlemen.  Observe 
that  honeyed  figure  of  speech. 

However,  this  is  not  the  time  to  make  my 
confessions  in  full.  What  I  started  out  to 
develop  was  a  speculation  on  the  relation  of 
radio  to  the  various  senses  of  a  human  being, 
as  suggested  by  the  above  quotation.  Is  it 
conceivable  that  odors  will  ever  actually  be 
transmitted  by  radio?  It  certainly  is.  In 
radio  telephony  we  start  with  a  microphone, 
which  changes  sound  waves  to  electrical 
impulses;  the  rest  is  easy.  In  the  photo- 
radiogram  processes  which  have  recently  been 
demonstrated,  we  allow  light  to  impinge  on  a 
photoelectric  cell,  the  light  waves  are  trans- 
formed into  electrical  fluctuations,  and  photo- 
graphs are  sent  over  the  ocean.  Anything 
that  can  be  translated  into  electrical  energy 
can  be  transmitted  by  radio.  Hence  why  not 
smells?  The  sense  of  smell  involves  the 
chemical  action  of  vapors,  essences,  gases,  or 
finely  divided  particles  brought  into  contact 
with  special  organs  of  sense,  the  olfactory 
nerves.  All  we  have  to  do  is  to  invent  an 
olfactory-electric  cell,  containing  suitable 
chemical  reagents,  which  will  generate  pro- 
portionate and  appropriate  electrical  impulses 


smelling*  a  civet  cat  across  tteworW 


when  exposed  to  vapors,  essences,  gases,  or 
finely  divided  particles  suspended  in  air;  and 
the  rest  is  a  cinch.  When  that  dingus  is 
invented — and  anything  can  be  developed  if 
the  Board  of  Directors  will  appropriate  enough 
money — we  shall  be  able  to  smell  a  civet  cat  or 
a  piece  of  frontage  de  brie  across  the  world. 
Oh,  but  that  will  be  a  glad  day! 

When  will  it  dawn?  No  one  who  has  given 
due  heed  to  the  human  mania  for  invention  can 
doubt  that  it  will  arrive.  But  when?  Not 
immediately.  For  those  who  insist  on  figures, 
I  am  glad  to  estimate  that  its  chances  of 
arriving  within  the  present  century  are  only 
314  in  1,000,000,000,000,000,000,000,000,000. 
Our  readers  will  recognize  this  proportion 
immediately  as  being  of  about  the  same  order 
of  magnitude  as  the  probability  of  M.  Leon 
Trotzky  voyaging  to  the  United  States  to 
address  Congress  and  to  become  a  master  of 
boy  scouts. 

The  second  portion  of  this  learned  treatise 
occurred  to  me  while  I  was  engaged  in  some 
research  work  of  a  medical  nature.  It  appears 
that  when  a  man  dies  the  senses  usually  fail 
in  the  following  order:  smell  and  taste,  sight, 
touch,  and  hearing.  The  significance  of  this 
to  broadcast  listeners  is  obvious,  In  the 
physiological  turmoil  of  dissolution,,  when  the 
individual  is  no  longer  responsive  to  odors, 
tastes,  spectacles,  and  contacts,  he  can  still 
harken  to  his  favorite  broadcasting  station. 
He  can  hear  that,  more  or  less,  until  he  blows 
up  entirely.  There  is  an  assurance  which 
should  destroy  the  fear  of  death!  If  any 
patron  of  broadcasting  wishes,  in  gratitude, 
to  send  me  a  check  for  $10,000,  my  address 
may  be  obtained  from  the  Editors. 


ON 


"BIRTHDAY 


WITH    this    number,     RADIO 
BROADCAST  is  three  years  old 
and  we  are  going  to  take  this 
opportunity  of  climbing  to  the 
house  top  and  shouting  about  ourselves. 
During  the  remainder  of  the  year,  we  will 
be   modest  and  hide  our   light   under  a 
bushel,  but  on  our  birthday  we   should 
have  a  bit  more  latitude. 

We  feel  that  we  are  doing  the  job  that 
we  set  out  to  do  pretty  well.  If  this  pre- 
sumption is  unwarranted,  we  invite  you  to 
tell  us  wherein  we  have  failed  in  order 
that  we  may  not  appear  to  fail  again.  Our 
job  is  not  an  easy  one  and  we're  human 
just  like  you,  and  we  not  only  can,  but 
sometimes  do  make  mistakes.  As  a  rule 
our  mistakes  are  brought  home  to  us  in 
no  uncertain  terms,  but  there  may  be  a 
few  we've  made  that  you  haven't  told  us 
about. 

DURING  the  last  three  years  we  have 
been  plugging  along  with  ideals, 
which,  for  a  while,  seemed  like  the  pot  of 
gold  at  the  rainbow's  end.  These  ideals 
are  approaching  nearer  to  actuality  all 
the  time.  Our  first  and  perhaps  most 
important  ideal  from  your  point  of  view  is 
a  desire  to  present  to  our  readers  the  best 
technical  information  that.research  makes 
available.  It  is  with  considerable  pride 
that  we  recall  having  published  the  first 
article  on  a  transformer-coupled  super- 
heterodyne, and  another  article  describing 
various  important  experiments  with  the 
"super."  It  is  significant  to  note  that 
literally  hundreds  of  "supers"  have  been 
described  by  other  publications  and  that 
we  find  our  first  set  for  home  construction 
is  just  about  as  good  as  any  of  the  newer 
types — with  the  single  exception  of  the 
Hanscom  super-heterodyne,  and  that  re- 
ceiver saw  the  light  of  day  in  our  own  pages. 
There  are  other  circuits  we  have  des- 
cribed in  the  magazine  during  our  short 
three  years  of  publication.  The  Knockout 
series  of  receivers  have  been  tremendously 
well  received  by  readers  of  the  magazine 
in  practically  every  part  of  the  world,  and 
if  the  letters  which  you,  the  reader,  write 
us,  can  be  accepted  as  any  indication,  that 
series  is  becoming  increasingly  popu- 
lar. And  these  receivers  are  popular,  fX 
we  feel,  because  they  fill  a  very  definite  V 


want  among  radio  constructors.  Our  cri- 
terion is  "  Such  a  receiver  and  circuit  must 
be  reliable  and  technically  sound.  It  must 
be  helpful  and  useful  to  the  radio  construc- 
tor." These  requirements,  we  feel,  our 
construction  articles  have  fulfilled. 

And  while  we're  on  the  subject  of  cir- 
cuits, it  is  in  order  to  say  a  word  about 
our  attitude  toward  "trick  circuits." 
We  never  have  and  never  will  publish  any 
construction  articles  on  trick  circuits. 
Our  ideal  is  the  publication  of  one  ex- 
tremely good  "how  to  make  it"  article  a 
month.  If  it  employs  a  new,  but  good 
circuit — such  as  the  two-tube  super- 
heterodyne we  have  up  our  sleeves  for 
next  month — so  much  the  better.  If  on 
the  other  hand,  no  really  new  circuit  is 
found,  a  more  satisfactory  arrangement 
of  an  old  but  good  one  is,  as  a  rule,  of  real 
value.  In  March  of  last  year  we  published 
an  article  entitled  "The  Truth  About 
Trick  Circuits."  One  gentleman  whose 
circuit  was  rather  severely  criticized  in  the 
article  brought  suit  against  us  in  court 
for  $100,000  damages.  Fortunately  for 
you  and  for  us,  the  jury  decided  in  our 
favor.  We  shall  continue  our  policy  of 
telling  the  truth,  even  when  it  hurts. 

AS  A  parting  shot,  we  cannot  resist 
mentioning  the  International  Radio 
Broadcast  Tests  which  were  conducted 
by  us  for  the  second  time  last  November. 
To  you  we  owe  a  vote  of  thanks  for  your 
cooperation  in  making  them  a  success. 
And  they  were  more  successful  than  any- 
thing of  the  kind  ever  attempted.  From 
last  year's  experience  we  have  learned 
much  which  will  make  our  work  of  prep- 
aration for  next  fall  much  more  effective. 
Everything  considered,  we  have  had  a 
fairly  good  and  profitable  time  together 
during  our  short  friendship,  and  our  plans 
for  the  immediate  future  will,  we  trust, 
meet  with  your  entire  approval.  As  an 
example  of  some  of  our  plans,  we  are  glad 
to  announce  that  we  are  going  to  add  eight 
pages  of  text  beginning  with  the  June 
magazine.  We  greatly  appreciate  your 
friendly  support  and  trust  that  our  efforts 
in  the  future  will  warrant  its  continuance. 


New  Fashions  in  Radio  Programs 

How  the  Present  Trend  of  Radio  Advertising  Is  Improving  the  Quality  of 
Broadcast  Programs — A  New  and  More  Intelligent  Role  for  the  Announcer 
—What  the  "Balanced  Performance"  Means  to  the  Radio  Listener 

BY  JAMES  C.   YOUNG 


AY  BODY  who  has  listened-in  on   the 
radio  knows  that  weary  feeling  which 
sometimes  steals  upon  the  heart  when 
the  announcer  reaches  the  next  num- 
ber.    As  for  the  announcer,  he  is  a  man  wor- 
thy of  kindly  thoughts.     He  must  go  through 
365  nights  in  the  year,  announcing  anything 
up   to   a  dozen   numbers  every  night.     And 
he  must  endeavor  to  introduce  each  one  in 
an  original  way. 

Some  announcers  are  businesslike  and  crisp. 
They  stick  to  their  subject.  Others  affect 
the  grand  manner  and  cultivate  theatrical 
inflections  of  the  voice.  Some  others — alas! 
— turn  to  humor.  That  is  the  most  painful 
method  in  the  end.  But  whatever  the  method, 
the  announcer  has  one 
of  the  hardest  jobs  in 
the  radio  business. 
He  strives  to  make 
himself  interesting 
every  evening,  and  he 
must  attempt  the 
thing  with  the  same 
old  tools.  We  know 
in  advance,  every 
trick  that  he  can  play 
yet  we  must  listen 
and  hope  for  the  best. 
Only  a  brave  man 
would  apply  for  the 
job.  There  should  be 
a  certain  award  in 
paradise  for  every 
announcer. 

Of  all  the  announc- 
ers known  to  the  ra- 
dio public,  the  noted 
"Roxie"  has  gained 
the  surest  hold  on 
popular  favor.  His 
methods  .are  dis- 
tinctly personal  and 
highly  successful.  He 
is  the  leading  man 
of  his  own  program 
and  probably  known 


So  This  Is  Advertising! 

For  some  time,  radio  listeners  in  the  east- 
ern and  central  parts  of  the  United  States 
have  listened  faithfully  every  Tuesday  night 
at  nine  to  the  entertainment  given  during 
what  was  called  the  Eveready  Hour.  These 
programs  have  differed  from  the  usual  run 
of  radio  entertainment,  for  they  have  been 
presented  as  a  complete  unit.  And  they 
have  been  well  done.  The  idea  of  making  a 
radio  program  follow  one  plan  or  idea  for 
several  hours  at  a  time  is  not  new — WGY  and 
others  have  used  it  in  the  radio  play,  and 
wjz  made  some  sporadic  efforts  along  this 
line  with  their  "Spanish  Night"  and  others. 
Radio  broadcasting  is  nothing  more  or  less 
than  good  showmanship,  and  as  Mr.  Young 
points  out,  we  cannot  expect  the  announcer 
to  do  constant  marvels  with  an  old  bag  of 
tricks.  The  step  in  broadcast  programs 
which  the  author  describes  so  interestingly 
is  a  real  forward  and  important  one,  we  be- 
lieve. One  frequently  hears  the  fear  ex- 
pressed that  broadcast  programs  will  even- 
tually turn  into  nothing  but  constant  and 
very  insidious  advertising,  but  it  is  our  opin- 
ion that  the  natural  adjustment  of  things 
will  prevent  the  overloading  of  the  air  with 
advertising  that  is  objectionable. — THE 
EDITOR 


to  a  larger  number  of  followers  than  any  other 
personality  associated  with  radio. 

Interesting  things  happened  when  the  men 
higher  up  at  WEAF  undertook  to  edit  "  Roxie's" 
little  monologues.  For  some  time  WEAF  has 
believed  that  the  endless  repetition  of  announce- 
ments was  trying  on  radio  nerves.  And  WEAF 
suspected  that  "Roxie's"  monologues  were 
somewhat  trying  as  well.  Therefore  the  blue 
pencil  went  into  his  talk  about  the  old  folk 
back  home  and  the  condition  of  Aunt  Ma- 
tilda's health. 

On  one  eventful  Sunday  night  several 
months  ago  "Roxie"  out-did  the  most  stilted 
introduction  known  to  radio.  A  host  of  fol- 
lowers listened  and  wondered  and  became 
amazed.  What  was 
the  matter  with 
"Roxie"?  Next  day 
the  papers  told  them. 
He  had  been  edited. 
Immediately  an  al- 
most unanimous  pro- 
test poured  in  upon 
WEAF,  the  greatest 
expression  of  opinion 
ever  drawn  from  a  ra- 
dio audience.  There 
was  plenty  of  static 
in  that  protest.  It 
spluttered  a  good 
deal,  demanding  that 
the  editorial  frown 
be  removed  from 
"Roxie's"  copy.  And 
WEAF  relented,  with- 
out even  putting  an 
ear  to  the  ground. 
Such  is  the  public 
estimate  of  one  an- 
nouncer who  has 
caught  the  popular 
favor.  But  he  is  al- 
most alone  among  a 
multitude.  For  some 
time  it  has  been  evi- 
dent that  radio  must 


84 


Radio  Broadcast 


evolve  a  better  method  of  presentation  for  its 
programs. 

It  was  this  kind  of  reasoning  that  led  to  one 
of  the  distinct  innovations  in  radio,  a  dramatic 
program  presenting  music  and  theme  in  a  form 
of  continuity  which  holds  many  possibilities. 
When  radio  was  new  somebody  perceived  the 
need  of  a  cue  to  what  the  programs  meant, 
and  that  brought  in  the  announcer,  of  whom 
great  things  were  required.  He  .has  met 
the  task  well,  but  the  continuous  program, 
built  in  dramatic  sequence,  will  make  his 
work  considerably  easier  for  himself  and  the 
listener. 

Instead  of  bobbing  up  every  ten  minutes, 
like  those  in  a  class,  he  can  make  one  an- 
nouncement in  an  hour  and  try  to  do  it  in 
a  humanly  interesting  fashion.  No  tricks  are 
required,  just  a  plain  statement  of  what 
should  be  a  few  pertinent  facts.  Then  the 
continuing  theme  must  keep  alive  the  interest 
created,  constantly  reminding  the  listener  of 
the  general  trend,  but  steadily  developing  the 
performance  as  it  is  done  in  the  theater,  on 
the  screen — everywhere  the  drama  has  an  in- 
fluence. This,  in  fact,  is  the  true  radio  drama 
and  not  a  hybrid  adaptation  such  as  the  read- 
ing of  a  play.  Radio  has  developed  every 
means  of  expression  peculiar  to  itself  and  it  is 
thoroughly  reasonable  to  suppose  that  its  own 
kind  of  drama  will  be  the  next  step  in  evolu- 
tion. 

That  stage  is  now  opening  before  us,  if  we% 
may  believe  the  evidence  furnished  by  one 
successful  broadcaster,  responsible  for  .  the 
performance  known  to  a  national  radio  aud- 
ience as  the  Eveready  Hour.  Promptly  at 
nine  o'clock  each  Tuesday  night  the  enter- 
tainers in  this  group  take  over  the  air  as  con- 
trolled by  WEAF  in  New  York.  For  the  next 
hour,  some  millions  of  Americans  are  enter- 
tained in  a  way  distinctly  new  to  radio. 
WEAF  transmits  the  program  to  ten  other 
stations,  WFI,  WCAE,  WGR,  WEEI,  WEAR,  wcco, 
wwj,  woe,  WSAI,  and  WJAR.  And  for  sixty 
intensive  minutes  an  invisible  audience  equal 
to  the  population  of  many  nations  may  enjoy 
a  real  radio  drama. 

SOMETHING    GOOD    DOING    EVERY    MINUTE 

HOW  is  the  thing  done?  The  answer  to 
that  question  goes  back  a  little  way. 
The  first  attempt  grew  from  an  acute  sense  of 
the  elements  lacking  in  a  typical  program, 
which  too  often  has  reached  the  point  where 
the  old  minstrel  show  wound  up.  No  matter 
how  clever  Mr.  Bones  might  be,  it  was  not 
possible  for  him  to  continue  longer  than  he  did. 


And  the  announcer  in  a  large  measure  corres- 
ponds to  Mr.  Bones.  He  is  supposed  to  say 
something  clever  whenever  the  show  lags. 

The  Armistice  Day  program  of  last  year  for 
the  Eveready  Hour  was  a  notable  example  of 
what  can  be  done  to  brighten  a  radio  perform- 
ance. The  announcer  made  known  in  an 
easy,  conversational  way  that  his  listeners 
were  to  think  of  themselves  as  the  men  inside 
"a  sleeping  stretch  of  tents,  thousands  of  men 
at  their  rest.  The  sun  has  just  risen;  the 
guard  has  raised  the  flag  and  our  slumbers  are 
broken  by  reveille,  'Oh,  How  1  Hate  to  Get 
Up  in  the  Morning.'" 

Here  was  a  bit  of  rapid  fire  psychology  at 
its  quickest.  The  listener  instinctively 
handed  over  his  imagination  to  the  entertainers 
and  let  them  do  with  it  just  about  as  they 
pleased.  This  quality  of  imagination  ac- 
counts for  a  fair  half  of  the  success  which 
attends  any  program.  And  this  is  the  way 
the  entertainers  proceeded,  a  quick  succession 
of  voices : 

Sergeant:  "Fall  in!  'Ten-shun!  Right 
Dress!  Front — Count  off." 

Then  the  other  voices  came  into  play  in  a 
way  familiar  to  a  large  number  of  listeners: 

"1—2—3—4 1—2—3—4", 

.  .  .  Sir,  the  company  is  formed." 

Any  man  ever  in  the  army,  or  whoever  had 
a  friend  in  the  ranks,  or  who  even  knew  any- 
thing about  the  war,  must  be  beguiled  by  that 
kind  of  introduction.  -Then  the  Captain 
speaks: 

"Sergeant,  after  mess  march  the  company 
to  the  Y  hut.  There  will  not  be  any  drill  this 
morning.  The  Eveready  entertainers  have 
come  to  camp  and  they  will  put  on  a  show 
this  morning.  That's  all,  sergeant." 

This  was  getting  over  the  difficult  business 
of  introduction  in  a  way  to  please  and  charm 
and  not  once  to  jar  the  senses.  Next  came  the 
assembled  voices  in  the  supposed  Y  hut,  evok- 
ing memories  of  1917,  when  the  world  seemed 
as  if  it  might  be  going  to  pot.  After  a  period  of 
singing,  the  announcer  speaks  again,  but  he 
has  become  a  monologist  by  this  time  and  we 
feel  friendly  toward  him  instead  of  wishing 
that  he  would  get  through  once  and  for  all  and 
keep  quiet.  This  is  what  he  says: 

"We've  come  to  the  day  when  tin  hats  have 
been  issued  and  the  boys  are  laying  bets 
that  they  will  sail  soon.  They  win.  We're 
on  the  transport.  There  isn't  much  noise 
permitted  as  the  big  hulk  creeps  out  of  Ho- 
boken  in  the  blackness  of  early  morning,  but 
many  of  the  uniformed  passengers  feel  like 
singing."  And  they  do  sing,  just  about  what- 


New  Fashions  in  Radio  Programs 


ever    they    like- — "Good    Bye,    Broadway," 
"Over  There,"  and  "'Till  We  Meet  Again." 

If  a  listener  could  resist  a  tug  at  the  heart 
when  that  last  song  died  out  he  would  be  a 
strange  sort  of  American.  But  it  has  not  been 
recorded  that  anybody  failed  to  keep  spiritual 
company  with  the  transport  on  its  eventful 
way.  Then  comes  France:  danger,  war,  and 
death.  At  the  end,  "Flanders  Fields"  is 
declaimed  to  music,  and  taps  sounded. 

UNITY  AND  INTEREST  FOR  THE  PERFORMANCE 

THAT  is  an  excellent  example  of  the  con- 
tinuous dramatic  performance  by  radio. 
It  is  the  same  kind  of  vehicle  that  once  was 
used  to  carry  along  the  old  variety  show  when 
it  began  to  emerge  from  a  number  of  disjointed 
acts,  which  afterward  became  vaudeville. 
Although  vaudeville  is  a  reversion,  in  a  meas- 
ure, it  is  a  performance  requiring  no  interpre- 
tation by  announcement.  Even  the  boy  who 
used  to  come  out  and  change  the  signs  has 
disappeared,  and  now  an  electrical  device 
supplies  the  information  that  the  next  act 
will  be  the  performing  seals. 

Although  radio  has  not  offered  us  the  seals 
as  yet — at  least,  not  under  that  description — 
there  is  a  wide  field  of  development  possible 
by  the  adoption  of  the  continuous  theme. 
The  idea  was  not  wholly  original  with  the 
group  of  entertainers  who  have  scored  so 


successfully  by  this  means,  but  they  at  least 
have  utilized  it  with  more  definitely  successful 
results  than  any  other  group.  Therefore  they 
must  receive  recognition  for  their  efforts, 
along  with  the  men  in  charge. 

There  is  virtually  no  limitation  on  what  may 
be  done  with  the  dramatic  theme  by  radio. 
Another  of  the  Eveready  Hours  was  devoted 
to  a  performance  described  as  the  Age  of  Man 
program.  This  choice  arose  from  the  wish  to 
present  a  program  of  old  songs  in  a  new  way, 
attempting  to  escape  from  the  boresome  device 
of  an  announcer  with  trembling  voice  who 
talked  about  the  days  down  on  the  farm. 
That  sort  of  introduction  is  particularly  bad 
when  the  announcer  speaks  about  a  farm  with 
all  the  intimate  acquaintance  of  a  native  New 
Yorker.  In  this  case  the  introduction  was 
managed  to  the  accompaniment  of  a  piano  and 
violin  playing  a  lullaby,  which  swiftly  devel- 
oped into  "  Rock-a-Bye,  Baby." 

CLEVER   THEATRICAL    MECHANICS 

IT  IS  not  an  easy  matter  to  prepare  the  mind 
of  a  radio  audience  in  something  like  two 
minutes  for  such  a  song  as  "Rock-a-Bye, 
Baby."  Everybody  in  America  has  heard 
that  lullaby  so  often  at  all  stages  of  life,  that 
it  must  be  particularly  well  rendered  to  hold 
the  attention.  It  cannot  be  literally  thrown 
at  an  audience,  as  so  many  songs  are  tossed 


MEMBERS    OF   THE    RADIO    ENTERTAINERS 

Grouped  during  a  typical  Eveready  Hour.  They  are:  Left  to  right,  seated:  Charles  Harrison,  tenor;  Beulah 
Young,  soprano;  Rose  Bryant,  contralto;  Wilfred  Glenn,  baritone;  all  of  the  Eveready  Mixed  Quartet;  stand- 
ing beside  Mr.  Harrison,  Graham  McNamee,  announcer;  standing  behind  Mr.  Harrison,  A.  J.  Klein,  noted 
African  hunter;  standing  to  Mr.  Glenn's  right  Edward  Berge,  pianist;  Alex  Hackel,  violinist,  and  Jacque  de 
Pool,  cellist,  of  the  Eveready  Trio.  Others  are  chorus  singers  selected  from  the  New  York  Oratorio  Society 

and  extra  orchestral  players 


86 


Radio  Broadcast 


through  the  ether.  "Rock-a-Bye,  Baby"  re- 
quires gentle  treatment  and  a  sympathetic 
mood. 

Well,  this  particular  evening  of  old  songs 
was  pronounced  one  of  the  biggest  things 
done  in  radio  entertaining  for  months.  A  re- 
sponse from  far  and  near  showed  that  the 
program  landed  in  the  psychological  center 
of  the  public  favor.  This  program  progressed 
from  its  opening  number  with  such  music  as 
Brahm's  "Cra- 
dle Song,"  grad- 
ually advancing 
through  the 
songs  of  boy- 
hood, youth, 
and  the  court- 
ing age.  Then 
the  songs  went 
on  to  the  suc- 
ceeding stages 
of  life  and  what 
obviously  must 
be  the  last — 
Home,  Sweet 
Home. 

Still  another 
successful  pro- 
gram was  made 
up  of  sea  songs, 
a  class  of  musi- 
cal composi- 
tion especially 
suited  for  radio 
because  of  the 
long  lilt  to  the 
melodies,  which 
seem  to  slip 
onto  the  ethe- 
real waves  with 
a  genius  all  their 
own.  A  depar- 
ture still  further 

afield  brought  before  the  microphone  one  Mar- 
tin Christiansen,  able  seaman  turned  taxi  driver. 
And  the  announcer  made  known  that  Christian- 
sen literally  was  going  to  tell  "the  story  of  his 
life."  Of  course,  he  did  not  express  the  matter 
just  that  way.  Instead,  he  explained  that  some 
time  before/ Christiansen  was  sitting  on  the 
box  of  his  cab  in  New  York,  reading  a  morning 
paper,  when  he  chanced  to  see  in  the  news 
that  William  Beebe  was  homeward  bound 
from  the  Galapagos  Islands,  one  of  the  lost 
places  of  the  Pacific. 

Christiansen  read  that  item  and  rushed 
down  to  the  dock  so  that  he  might  greet  the 
only  man  he  had  ever  heard  about  who  knew 


RED   CHRISTIANSEN 

The  "sea-going"  taxi  driver  of  New  York  whose  adventures  in  the 
lost  islands  of  the  Pacific  were  seized  upon  as  material  for  one  pre- 
sentation of  a  new  type  of  radio  program 


those  islands.  Christiansen  was  on  the  dock 
when  the  explorer  arrived  and  the  story  he 
told  Beebe  afterward  constituted  a  rattling 
good  chapter  in  the  explorer's  book  about 
those  islands.  All  of  that  explanation  was 
packed  into  a  few  sentences  by  the  announcer, 
who  then  turned  over  the  air  to  Christiansen, 
and  let  him  speak  for  himself.  He  was  the 
sort  of  man  fully  capable  of  that  effort  and 
proceeded  along  this  line: 

SOMETHING   DE- 
CIDEDLY  NEW 

WELL>  l 

suppose 
the  story  begins 
when  I  signed 
up  with  the 
bark  Alexander, 
down  on  the 
other  side  of  the 
world.  That 
was  at  New- 
castle, New 
South  Wales,  in 
Australia.  The 
Alexander  was 
loaded  with  a 
cargo  of  coal 
bound  east- 
ward across  the 
Pacific  for  Pa- 
nama. She  car- 
ried a  captain, 
mate,  cook, 
and  sixteen  of 
us  men." 

Now  almost 
every  boy  in 
the  world  has 
wanted  to  be  a 
sailor  and  prac- 
tically every  girl 

has  feared  that  her  first  sweetheart  would  run 
away,  as  he  threatened,  because  she  refused  his 
manly  hand.  The  appeal  of  the  sea  is  universal. 
It  is  probable  that  no  other  class  of  fiction  ever 
written  is  read  by  so  many  people.  If  Chris- 
tiansen's introduction  of  his  story  had  ap- 
peared upon  the  printed  page,  instinctively  we 
would  have  moved  a  little  closer  to  the  light 
and  have  settled  down  for  an  evening's  joy. 

That  is  what  happened  with  the  radio 
audience.  Who  can  imagine  a  man  telling  us 
about  sailing  on  a  trip  like  that,  without  every 
poor  landlubber  lending  eager  ear?  Chris- 
tiansen was  better  than  a  passable  story  teller. 
He  went  on  in  this  strain: 


SCENES    IN    THE    GALAPAGOS    ISLANDS 

Often  called  the  lost  islands  of  the  Pacific,  which  \\illiam  Beebe,  the  noted  explorer  and  scientist, 
investigated  some  years  ago.  A  taxi  driver  in  New  York,  who  had  been  a  sailor  shipwrecked  on  the  islands 
appeared  on  a  radio  program  and  described  his  experiences  there.  Broadcasting  programs  of  a  high  order  are 
tending  toward  better  unity  and  the  "  Explorer's  Night  Program"  in  which  Mr.  Christiansen  took  part  from 
WEAF  and  connected  stations  was  one  of  this  new  type.  The  center  cut  shows  a  giant  marine  lizard  which 
exists  only  in  the  Galapagos  Islands.  It  lives  in  the  sea  and  is  about  five  feet  long.  The  upper  left  picture 
shows  specimens  from  the  sea  being  gathered  from  the  yard-arm  of  the  exploring  ship.  The  upper  right 
photograph  shows  a  huge  boa  constrictor  caught  near  the  Islands.  The  lower  left  picture  is  of  a  giant 
marine  lizard  feeding  in  the  surf.  The  lower  right  shows  a  Hoatzin  fledgling,  the  missing  link  between  the 

lizard  and  the  bird 


Radio  Broadcast 


"  I  had  been  living  in  a  sailor's  boarding 
house,  run  by  Nellie  Simonds.  The  day  we 
shipped,  Nellie  rowed  out  in  the  bay  and 
brought  some  refreshments  along  as  a  parting 
gift.  I  don't  mind  telling  you  that  her  brand 
of  refreshments  made  a  bigger  hit  with  us  than 
the  stuff  we  had  to  drink  before  we  got  through 
that  voyage.  As  the  tug  took  hold  and  started 
off,  we  sang  to  her  and  she  sang  back.  It  was 
a  happy  send-off." 

That  immediately  opened  the  way  for  the 
quartette  to  sing  one  of  those  good-bye  songs, 
and  the  quartette  performed  in  fine  fettle. 
Then  Christiansen  went  on  again.  Before  he 
stopped  talking,  there  was  hardly  a  radio  ear 
in  some  thousands  of  miles  that  was  not 
aquiver  with  his  story  about  those  forsaken 
islands  and  the  things  that  happened  there. 
It  was  such  a  yarn  as  Stevenson  would  have 


liked  to  spin.  A  listener  could  experience  for 
himself  all  the  heartache,  thirst,  and  peril  that 
went  into  the  sailor's  adventures.  In  the  end, 
it  was  pleasant  to  know  that  he  had  adopted 
the  comparitively  easy  and  safe  pursuit  of  driv- 
ing a  New  York  taxicab,  although  many  men 
of  a  less  eventful  past  might  call  that  high 
adventure. 

The  Christiansen  story  was  a  new  endeavor 
in  many  ways,  and  received  wide  recognition 
from  the  press. 

THIS    IS    ADVERTISING 

WHO  would  ever  undertake,  let  us  say, 
to  link  the  yarn  of  a  sailor's  adventures 
with  advertising?  And  the  Eveready  Hour 
entertainers,  of  course,  represent  the  idea  of 
selling  by  publicity.  Here  is  a  development 
so  broad  that  the  possibilities  cannot  be  even 


EXCELLENT   CLASSICAL   MUSIC 

Is  given  during  the  Eveready  Hour  by  the  Mixed  Quartette,  which  consists  of  Wilfred  Glenn  (left),  baritone; 
Rose  Bryant,  contralto;  Beulah  Young,  soprano;  Charles  Harrison,  tenor,  Tom  Grisselle.  During  the 
specially  arranged  hour  of  entertainment,  given  each  week  by  this  organization,  each  is  a  complete  entity. 
The  program  by  this  group  and  others  of  the  organization  is  part  of  a  completely  balanced  program  which  has 

been  well  received  by  the  listeners 


New  Fashions  in  Radio  Programs 


89 


estimated.  We  may  conceive  of  a  new  expe- 
dition to  the  pole  so  that  the  explorer  shall 
describe  to  us  how  comfortable  he  was  in  some 
particular  brand  of  knit  underwear,  while  he 
drank  a  special  blend  of  tea  and  munched  upon 
a  soda  cracker  of  national  reputation. 

Whatever  are  the  developments  in  store 
for  us,  the  established  fact  is  that  a  sailor's 
tale  of  perilous  deeds  in  far  places  makes 
mighty  interesting  material  for  a  radio  pro- 
gram. This  is  a  far  step  from  the  day  not 
long  past  when  the  only  kind  of  discourse 
known  to  radio  was  the  sort  which  dealt  with 
the  advisability  of  accumulating  enough  for 
old  age  by  smoking  one  cigar  less  every  day. 
Nobody  will  fall  out  with  the  wisdom  of  that 
discourse,  but  it  hardly  was  entertainment. 
There  has  been  no  perceptible  diminution  in 
the  consumption  of  cigars  nor  any  appreciable 
gain  in  the  total  of  savings  from  the  thousands  of 
such  lectures  forced  upon  the  ear  of  the  nation. 

But  if  we  know  the  human  heart  at  all,  we 
cannot  doubt  that  Christiansen's  yarn  will  be 
talked  about  around  uncounted  firesides  for 
many  months.  It  was  the  kind  of  tale  to 
make  everybody  huddle  closer  to  the  hickory 
log— or  even  the  radiator — and  bless  their 
stars  that  those  islands  with  the  terrible  name 
are  so  far  away.  By  association,  those  who 
heard  the  story  at  first  hand  will  long  think  of 
it  as  a  part  of  the  Eveready  Hour  program. 
And  the  programs  just  as  inevitably  are  asso- 
ciated with  national 'advertising  of  the  wares 
behind  them. 

Such  considerations  lead  naturally  to  the 
oft  discussed  problem  of  where  advertising 
legitimately  stops— or  begins — in  radio  broad- 
casting. Whatever  the  ethics  of  the  case, 
it  is  beyond  dispute  that  radio  advertising  has 
increased  greatly  within  recent  months.  It 
is  in  a  fair  way  to  equal  the  power  of  the 
accepted  advertising  in  newspapers  and  mag- 
azines. So  far  it  usually  has  taken  the  in- 
direct form.  But  the  appeal  is  none  the  less 
direct,  we  may  be  assured  by  the  large  number 
of  concerns  turning  to  this  method. 


At  a  moment  when  the  country  is  enjoying 
a  broad  prosperity,  radio  advertising  would 
seem  to  have  entered  upon  a  period  of  develop- 
ment that  will  surpass  anything  ever  known. 
The  experiences  of  the  automobile  industry 
and  the  movies  are  being  repeated  anew.  All 
of  these  considerations  may  or  may  not  in- 
terest the  radio  user.  What  he  seems  to  care 
about  principally  is  the  quality  of  entertain- 
ment offered  for  his  amusement.  Certainly 
that  quality  grows  better  every  day  and  the 
element  of  originality  introduced  by  the  enter- 
tainers '  in  question,  under  the  immediate 
direction  of  Paul  F.  Stacy,  suggests  a  means 
of  enlivening  the  radio  program  for  the  benefit 
of  everybody. 

The  day  evidently  is  not  far  removed  when 
the  typical  radio  program  will  cease  being  its 
present  jumble  of  odds  and,  ends  put  together 
on  the  general  pattern  of  Joseph's  coat.  We 
may  expect  a  balanced  performance,  to  use  a 
theatrical  term,  and  it  is  not  improbable  that 
an  entire  evening's  entertainment  will  be  pre- 
sented by  the  medium  outlined.  It  should  be 
possible  to  arrange  such  a  program  so  as  to 
encompass  a  wide  variety  and  still  preserve 
the  theme  of  continuity.  .  A  theatrical  setting 
of  the  kind  suggested  on  the  transport  and  the 
canteen  would  be  easily  adaptable  to  lengthy 
performances.  One  of  the  first  dramatic 
principles  holds  that  the  continuity  of  time, 
place,  and  action  best  assures  command  of 
attention. 

Whether  this  development  be  great  or  small, 
the  radio  audience  of  America  at  least  may  be 
thankful  to  the  Everyeady  Hour  entertainers 
for  introducing  a  device  to  help  out  the  hard 
working  announcer.  Poor  fellow,  he  has 
labored  nobly,  turning  phrases  around,  trying 
to  be  humorous  and  grave,  and  otherwise 
experimenting  with  the  tools  in  his  kit.:  Al- 
though there  may  be  nothing  distinctly  new 
beneath  the  sun,  it  is  certain  that  the  con- 
tinuous dramatic  theme  for  radio  programs  is 
a  decidedly  fresh  and  pleasant  departure  "on 
the  air." 


:..-  •  ...... 

GUGLIELMO  M ARGON  I  has  written  an  artic-le  for  RADIO  BROADCAST 
which  will  appear  in  an  early  number.     He  writes,  of  his : recent  experi-'^' 
ments,  in  England,  at  sea,  and  aboard  his  yacht,  with  radio  transmission  by  His 
famous  "beam  system".    Signor  Marconi  firmly  believes  that  beam  transmission 
of  radio  energy  on  very  short  wavelengths  is  a  general  development  that  is  now 
upon  us.     This  article  is  the  first  that  Signor  Marconi  has  published  in  America 
describing  what  he  believes  is  a  revolution  in  radio  transmission. 


Do  Weather  Conditions  Influence 

Radio? 

A  New  Theory,  Advanced  by  a  Climatologist,  Tending 
to  Prove  That  Atmospheric  "Highs"  and  "Lows"  and 
Other  Weather  Phenomena  Affect  Receiving  Conditions 

BY  EUGENE  VAN  CLEEF 


Ohio  State  University 


IT  IS  certainly  not  uncommon  to  hear  radio 
enthusiasts  say,  "  I  couldn't  get  much  last 
night,  too  much  static,"  or  "Bad  night 
last  night,  couldn't  get  a  thing  from  the 
west  and  just  a  few  eastern  stations,"  or  again, 
"Can't  expect  results  to-night,  too  rainy." 
Correct  as  the  reports 
may  be  as  far  as  ac- 
tual poor  reception  is 
concerned,  the  diag- 
noses are  not  always 
true.  This  is  because 
the  average  person  is 
unacquainted  with 
the  mechanics  of  the 
circulation  of  the 
atmosphere.  He 
knows  that  the 
weather  changes,  but 
does  not  appreciate 
fully  the  direction  of 
these  changes  and  the 
part  which  atmos- 
pheric pressure  plays 
in  our  daily  weather. 

Weather,  of  course, 
is  local  at  any  given 
time.  One  could  well 
say  that  weather 
travels,  and  the 
weather  which  a  given 
city  west  of  us  has 
to-day,  may  be  the 
kind  of  weather  we 
shall  have  within  the 
next  twenty-four  to 
thirty-six  hours.  This 
suggests  that  a  certain 

brand  of  weather  is  not  universal  at  a  given 
time  of  day  or  night,  but  that  there  may  be 
a  radical  difference  in  the  state  of  the  weather 
at  the  broadcasting  station  and  that  where  the 
receiving  instrument  is  located. 

The  weather  in  the  United  States  changes 


Talk — Minus  Facts 

T"*HQSE  interested  in  radio  have  for  years 
*  tried  to  find  out  the  factors  which  in- 
fluence the  radiation  and  reception  of  radio 
waves.  There  have  been  a  number  of  theories 
adduced  to  explain  the  sometimes  peculiar 
variation  of  the  signals.  Probably  best 
known  of  such  theories  is  the  Heaviside  layer 
theory,  which,  very  briefly,  assumes  that  the 
various  ionized  layers  of  the  upper  atmos- 
phere refract,  absorb,  or  aid  the  waves  in  their 
passage.  RADIOBROADCAST  does  not  assume 
responsibility  for  Mr.  Van  Cleef's  conclusions 
that  weather  conditions  definitely  affect  radio 
conditions,  but  we  should  like  to  observe  that 
his  findings  seem  to  fit  in  very  well  with  what 
actually  is  the  case.  It  is  quite  possible  that 
atmospheric  conditions  have  a  definite  and 
yet  unexplained  relation  to  the  variations  in 
the  Heaviside  layer.  It  may  be,  too,  that 
the  findings  of  this  experimenter  can  be  put 
with  the  conclusions  of  other  experimenters 
and  relations  between  phenomena  as  yet  un- 
known may  be  seen.  At  least,  the  author 
has  done  a  genuinely  good  piece  of  work. 
Those  who  have  similar  access  to  national 
weather  information  should  be  very  much 
interested  in  continuing  and  checking  these 
conclusions.— THE  EDITOR 


because  of  the  influence  of  shifting  atmospheric 
pressure  areas  known  technically  as  Cyclones 
and  Anti-Cyclones.  In  the  cyclone,  the  air  in 
general  blows  spirally  inward,  upward,  and 
in  counter-clockwise  fashion.  In  the  anti- 
cyclone, the  air  blows  spirally  downward, 
outward,  and  in  a 
clockwise  direction. 
In  neither  pressure 
area  is  the  movement 
violent.  The  dia- 
meters of  the  storms 
may  be  anywhere 
from  400  to  i  500 
miles.  These  pressure 
areas  are  not  always 
symmetrical  in  form 
and  consequently 
their  diameters  may 
vary  along  a  dozen 
different  radii. 

These  storms  travel 
across  the  United 
States  in  a  general 
easterly  direction,  en- 
tering the  United 
States  either  from  the 
southwest,  west,  or 
northwest  and  leav- 
ing by  way  of  the 
Atlantic  coast,  but 
most  often  by  the  St. 
Lawrence  river  val- 
ley. In  the  autumn 
months,  September 
to  November,  hurri- 
canes and  violent 
cyclones,  may  enter 

the  United  States  from  the  southeast  in  the 
vicinity  of  Florida,  penetrate  at  times'  as  far 
as  the  Galveston  coast  of  the  Gulf  of  Mexico, 
and  then  following  the  customary  paths 
across  the  eastern  half  of  the  country.  The 
hurricane  is  the  exception  and  not  the  rule. 


Do  Weather  Conditions  Influence  Radio? 


CYCLONES  and  anti-cyclones  pass  across 
V-*  the  country  approximately  every  three 
to  four  days,  varying  in  frequency  with  the 
season  of  the  year.  They  always  occur  alter- 
nately. Two  high  pressure  areas  (anti- 
cyclones) or  two  low  pressure  areas  (cyclones) 
never  succeed  each  other.  "Lows"  and 
"Highs,"  as  they  are  named  on  the  weather 
map,  always  alternate.  Meteorologists  have 
studied  the  variety  of  weather  associated  with 
these  pressure  centers,  and  through  the  agency 
of  the  United  States  Weather  Bureau,  the 
forecasting  of  the  passing  weather  has  attained 
a  fair  degree  of  accuracy. 

In  general,  it  may  be  said,  that  cloudy, 
rainy,  or  snowy  weather  and  moderate  to  high 
temperatures  are  the  accompaniment  of  Lows, 
while  clear  and  cool  to  very  cold  weather 
accompanies  Highs.  There  are  exceptions  to 
both  of  these  assertions,  but  they  are  not 
many.  Now,  a  striking  feature  of  these 
pressure  areas  lies  in  the  variation  of  their 
respective  intensities  as  revealed  by  the 
arrangement  of  their  Isobars.  An  isobar  is  a 


line  which  passes  through  all  points  having  the 
same  atmospheric  pressure,  i.e.,  through  all 
points  where  the  barometer  reads  the  same. 
The  isobars  tend  toward  a  concentric  arrange- 
ment. In  an  ideal  pressure  center  they  would 
be  absolutely  concentric.  Irregularities  in 
their  course  may  be  due  to  many  reasons,  such 
as  temperature  differences,  variations  in  mois- 
ture content  of  the  air,  topography,  and  so  on. 

DO    WEATHER    CONDITIONS     INFLUENCE     RADIO 
RECEPTION? 

IT  OCCURRED  to  the  writer  when  he 
1  heard  statements  referring  to  the  weather 
and  radio  reception,  such  as  are  quoted  at  the 
beginning  of  this  discussion,  that  their  logic 
was  frequently  faulty.  It  seemed  that  with 
broadcasting  and  receiving  stations  often- 
times 500  to  1000  miles  apart,  the  local 
weather  conditions  at  the  receiving  station 
could  not  have  much  influence  on  reception, 
unless  the  same  conditions  prevailed  over  all 
the  country  between  the  two  stations.  Such 
uniformity  in  weather  is  not  common.  There- 
fore, to  ascribe  poor  receptivity  to  the  local 
weather  could  not  be  an  accurate  analysis. 
Furthermore,  it  was  true  that  occasionally 


ment  of  Agriculture 
DAILY  WEATHER 


OTES 

,  76th  meridian  time. 
Air  pressure  reduced  to  vea  level 
ISOBARS,  (continuous  lines)  paas  through  points  of 

ERMS  (dotted  lines)  pass  through  point*  of 

equal  temperature;  drawn  for  every  10* 
Symbols  indicate  state  of  weather    O  clear  9  partly  cloudy 
•cloudy   ©rain    ©snow    ®  report  missing 
Arrows  fly  with  the  wind. 
SHADED  AREA  shows  precipitation  of  0.01  inchor 

more  during  last  24  hours 
Wind  Velocities  of  less  than   10  miles  an  hour,  and  amounu 

of  precipitation  of  less  than  0.01  inch,  are  not  published 


A    TYPICAL    WEATHER   MAP   OF   THE    UNITED    STATES 

Which  shows  clearly  the  alternating  "Highs"  and  "Lows."     According  to  the  theory  advanced  by  the 
author,  radio  reception  in  a  low  pressure  area  tends  to  be  somewhat  weaker  than  in  a  high  pressure  zone  of 

corresponding  intensity 


Radio  Broadcast 


when  the  weather  was  "bad,"  reception  was 
good,  although  the  association  of  the  two  facts 
at  such  times  was  entirely  overlooked.  It 
seems  to  be  a  common  trait  among  most  of  us 
to  analyze  and  criticise  rather  thoroughly 
when  things  go  wrong  but  to  take  matters  for 
granted  when  we  are  enjoying  results  which 
seem  to  us  to  be  wholly  normal. 

The  situation  just  noted  led  to  an  investi- 
gation, which  has  thus  far  revealed  some  strik- 
ing conclusions.  ;lt  seems  that  since  broad- 
casting involves  the  transmission  of  electro- 
magnetic waves,  a  wave  motion  transverse 
in  ;type,  there  might  be  a  definite  relation 
between  such  transmission  and  the  circulation 
of  air  in  High  and  Low  pressures.  Obser- 
vations were  made  to  determine  whether  any 
su^h  relationship  might  exist,  or  whether  there 
could  be  a  relation  between  the  strength  and 
clarity  of  reception,  and  the  arrangement  of 
isobars. 

NEW   THEORIES    FOR    RADIO   CONDITIONS 

AFlVE-tube  neutrodyne  set  was  used,  with 
an  outside  antenna  about  125  feet  long, 
and  about  30  feet. from   the   ground.     The 


direction  of  the  antenna  was  almost  exact- 
ly northeast-southwest.  The  observations 
follow: — 

1.  If  a  line  connecting  the  receiving  station  with 
the  broadcasting  station  crosses  the  interven- 
ing isobars  at  right  angles,  reception  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  conditions,  fading 
occurs. 

4.  Reception  in  a  Low  pressure  area  tends  to  be 
somewhat  weaker  than  in  a  High  of  correspond- 
ing 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  pressure  area 
and  its  position  with  respect  to  the  broadcast- 
ing station. 

7.  "Bad  weather"  does  not  affect  reception,  ex- 
cepting as  it  may  be  the  index  of  an  unfavor- 
able pressure  distribution. 


AN    IDEAL   WEATHER    MAP 

Drawn  to  show  the  relation  of  the  strength  and  clarity  of  reception  to  the  angle  between  the  direction  of 

transmission  and  the  isobars.     An  isobar  is  a  line  which  passes  through  all  points  whose  barometric  pressure 

is  the  same.    The  arrows  on  the  map  indicate  the  direction  from  which  broadcast  signals  were  received  during 

one  of  the  tests  made  at  the  author's  station  in  Columbus,  Ohio 


Do  Weather  Conditions  Influence  Radio? 


93 


8.  Reception  can  be  as  good  in  "bad  weather" 
as  in  good  weather  if  the  pressure  distribution 
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  anti- 
cyclones are  more  intense  in  the  winter 
period. 

(b)  Reception  is  better  when  temperatures 
are  low  than  when   high,   because  low 
temperatures  usually  indicate  intensive 
High  pressure  areas,  that  is,  areas  with 
steep  isobaric  gradients. 

(c)  Low  temperatures  accompanying  poorly 
defined   High   pressure  areas   make   re- 
ception poor. 

10.     Shallow  or  flat  pressure  areas  result  in  much 
static-noise  in  the  receiver. 

HOW    CONDITIONS    CAN    BE    FORECAST 

WITH  the  above  observations  well  de- 
fined, the  question  which  quite  natur- 
ally arises  is,  Can  the  strength  and  clarity  of 
reception  be  forecast?  The  answer  is,  "Yes!" 
It  can  be  forecast  with  the  same  degree  of 
accuracy  as  the  weather,  but  hardly  with  any 
greater  degree.  Forecasting  the  weather  de- 
pends upon  a  knowledge  of  the  movements  of 
cyclones  and  anti-cyclones  and  their  peculiari- 
ties in  various  seasons  of  the  year.  Forecast- 
ing radio  reception,  assuming  no  interference 


©  Underwood  &  Underwood 
WEATHER    FORECASTING    APPARATUS 


According  to  the  results  of  the  experiments  of  the  author,  when  weather 
conditions  are  accurately  known  and  compared  with  radio  transmission 
and  reception  phenomena,  it  is  probable  that  much  may  be  discovered 
about  the  mysteries  of  freak  radio  signals.  The  device  shown  in  the 
photograph  records  the  direction  and  velocity  of  the  wind 


©  Underwood  &  Underwood 
THE    NETHOSCOPE 

Used  by  the  Weather  Bureau  to  aid  in  predicting  the 

weather.     Simplified,    the    apparatus    is    a    black 

mirror  and  is  used  to  determine  the  direction  and 

velocity  of  clouds 


by  regenerative  sets  or  the  like,  is  dependent 
likewise  upon  a  knowledge  of  the  movements 
of  the  same  pressure  areas.  However  it  in- 
volves not  the  forecast- 
ing of  the  probable  state 
of  the  weather  at  the 
station  concerned,  but 
only  the  prognostication 
of  the  arrangement  of 
the  isobars  between  the 
respective  receiving  and 
broadcasting  stations,  and 
the  probable  steepness  of 
the  isobaric  gradients. 

By  such  forecasts,  much 
may  be  saved  to  the 
people.  One  may  know 
the  futility  of  trying  to 
get  certain  stations  on 
given  nights  and  save 
power,  time  and  nervous 
energy.  Sets  may  not  be 
blamed  for  poor  service 
when  pressure  conditions 
are  the  cause;  and  broad- 
casters  may  not  be 
criticised  for  failure  to 
speak  plainly  or  loudly 
enough,  or  in  general  be- 
cause of  lack  of  efficiency, 


94 


Radio  Broadcast 


when  as  a  matter  of  fact  they  are  performing 
properly  and  well. 

Another  phase  to  this  problem,  not  yet 
worked  out,  involves  the  relation  between  the 
power  required  to  send  the  waves  and  a 
possible  adjustment  with  respect  to  the 
atmospheric  pressure.  We  know  there  is 
some  relation  to  sunshine,  for  during  the 


daytime  one  can  not  receive  over  great  dis- 
tances, unless  the  sky  is  clouded  the  entire 
distance.  So  there  may  be  a  correspondence 
between  the  wave  motion  itself  and  the  air 
pressure,  which  if  learned,  would  reduce  the 
amount  of  power  required  for  wave  trans- 
mission and  perhaps  in  still  other  ways  wholly 
revolutionize  broadcasting. 


how  DO 

vou 

KNOW  I        o 
CALIFORM/A, 


OBSERVATIONS   ON   THE    RADIO    LIFE.'   NO.    2 

California  on  the  loud  speaker 


PRIMARILY   the  star  of  approval,   which  appears  in   RADIO 
BROADCAST  advertising,  means  "Approved  by  Radio  Broadcast 
Laboratory."     Although  this  certification  means  a  great  deal 
to  those  advertisers  whose  copy  bears  this  mark  of  approval,  it 
does  not  necessarily  discriminate  against  the  copy  not  so  marked. 

In  placing  this  sign  of  approval  in  our  advertising  pages,  several 
issues  are  considered.  It  is  far  from  humanly  possible  for  us  to  test 
each  item  advertised  by  every  manufacturer  and  still  do  the  great 
amount  of  development  work  which  has  proved  so  valuable  to  our  read- 
ers. Where  we  have  sufficient  knowledge  of  a  manufacturer's  products 
and  his  business  standing,  we  place  our  Star  on  his  copy  with  the  assur- 
ance that,  if  the  customer  is  not  satisfied,  the  manufacturer  will  refund 
his  money.  In  case  a  manufacturer  develops  a  questionable  device  we 
always  request  that  samples  be  submitted  for  our  inspection.  Adver- 
tisers with  whose  products  we  are  not  thoroughly  familiar  are  required 
to  submit  samples  before  receiving  the  Star. 

The  meaning  of  the  Star  however,  is  not  thus  limited,  for,  added  to 
the  approval,  which  is  advantageous  to  the  manufacturers,  we  are  not 
overlooking  the  prospective  customers.  A  reader  seeing  the  Star  should 
not  necessarily  draw  the  inference  that  here  is  a  product  better  than  any 
other.  It  does,  however,  mean  to  the  reader  that  he  will  either  get 
satisfaction  or  his  money  back.  In  placing  .the  Star  in  advertising,  we 
are  assuring  the  reader  of  our  confidence  in  these  manufacturers.  The 
omission  of  the  Star  indicates  that  we  have  not  had  the  opportunity 
to  become  thoroughly  familiar  with  the  products  advertised.  The  fact 
that  advertising  appears  in  our  pages  at  all  indicates  that  we  consider 
it  reliable. 

In  placing  our  approval  on  apparatus  submitted  for  test  we  have  no 
intention  of  causing  friction  by  unfair  discrimination.  Our  approval 
does  not  in  any  way  indicate  that  we  assume  that  the  products  of  those 
advertisers  are  perfect.  What  it  does  mean  is  that  the  manufacturer  has 
satisfactorily  met  the  claims  he  is  making  for  such  apparatus  and  that 
he  supports  his  claims  with  a  "money-back"  guarantee.  In  passing 
on  the  apparatus  in  this  manner,  we  must  necessarily  take  its  selling 
price  into  consideration  and  so  the  Star  is  an  assurance  that  one  will  get 
full  value  on  his  investment. 

"Approved  by  Radio  Broadcast  Laboratory"  gives  the  purchaser 
assurance  that  he  is  buying  the  product  of  a  reliable  manufacturer  and 
that  he  can  in  this  way  feel  certain  of  getting  reasonably  satisfactory 
results.  Its  purpose  is  to  boost  the  legitimate  and  honest  manufacturer. 
It  is  our  intention  to  extend  our  present  plans  to  the  point  where  RADIO 
BROADCAST  will  carry  no  advertising  where  the  apparatus  has  not  ac- 
tually been  tested  in  our  laboratory. 


How  to  Solder 


BY  WILLIAM  F.  CROSBY 


TO  THE  uninitiated,  the  art  of  solder- 
ing appears  to  be  something  which 
only  the  most  expert  workman  can  do. 
It  appears  to  be  a  talent  which  the 
novice  can  hope  to  acquire  only  with  years  of 
practise.  It  may  be  an  art,  but  it  is  an  easy 
art,  and  one  which  even  some  of  the  most  in- 
expert of  our  radio  builders  have  conquered, 
to  the  great  improvement  of  the  sets  they 
build. 

There  is  just  one  fundamental  rule  in  suc- 
cessful soldering,  and  that  is  cleanliness.  This 
does  not  necessarily  mean  that  the  man  doing 
the  work  must  have  on  a  clean  collar  and  his 
hands  must  be  manicured;  but  it  does  mean 
that  he  must  see  that  the  soldering  iron  has  a 
clean  collar  of  solder  and  that  the  surfaces  to 
be  soldered  are  manicured. 

Seriously,  though,  soldering  is  easy,  once  the 
importance  of  having  everything  clean  is 
realized.  Solder  will  positively  not  stick  to  a 
surface  which  is  oily  or  corroded.  If  one 
part  is  clean  and  the  other  dirty,  the  solder 
will  stick  to  the  clean  surface  but  not  to  the 
dirty.  If  you  do  not  believe  this  just  try  it 
and  see.  Fully  half  of  those  who  have 
trouble  with  soldering  because  the  surfaces 
will  not  stick,  or  the  solder  drops  off,  have  not 
realized  that  a  clean  surface  is  the  first  essential. 


RADIO  BROADCAST  Photograph 
FIG.    I 

The  soldering  iron  should  always  be  shinily  clean. 
The  burned  coating  which  collects  on  the  working 
surface  of  a  gas  iron  can  be  removed  with  a  flat  file 
as  shown  in  the  photograph.  When  using  the  file, 
the  solderer  should  push  it  away  from  him  and  lift 
the  file  from  the  surface  on  the  return  motion 


The  next  step  is  the  consideration  of  the 
soldering  iron  itself.  Many  constructors  are 
using  gas  heated  irons  with  varying  degrees 
of  success,  but  once  let  a  man  use  an  electric 
soldering  iron  and  he  will  never  make  further 
use  of  the  gas  range.  These  irons  may  be 
secured  in  many  sizes  and  shapes  and  some  of 
them  have  interchangeable  points.  With  this 
type  of  iron  it  is  possible  to  secure  a  fine  point 
for  small  work,  a  curved  point  for  the  inac- 
cessible places  or  a  blunt,  heavy  point  for  the 
work  which  is  more  in  the  open.  The  writer 
is  of  the  opinion  that  the  fine  pointed  iron  is 
the  best  for  all  around  radio  work.  It  is 
satisfactory  for  coarse  soldering  and  also  for 
the  finer  work  and  if  a  little  care  is  exercised 
in  wiring  the  set,  there  is  no  reason  why  every 
connection  cannot  be  reached.  Of  course  the 
inside  wires  should  be  placed  first  and  the 
work  carried  on  so  that  the  outermost  wires 
come  last. 

"TINNING"  THE  IRON 

f~^  ENERALLY  a  new  soldering  iron  is  not 
^-*  "tinned."  In  other  words  the  surface 
is  coppery  all  over  and,  in  passing,  it  might  be 
just  as  well  to  point  out  that  soldering  "irons" 
are  not  iron  at  all  but  "copper,"  for  it  seems 
to  conduct  and  hold  the  heat  better. 

Now  suppose  we  want  to  "tin"  a  new  iron. 
The  first  thing  to  do,  of  course,  is  to  get  it  hot, 
not  red  hot,  and  not  cherry  red  either.  Usu- 
ally a  good  test  is  to  have  a  small  can  of  solder- 
ing paste  handy  and  dip  the  point  of  the  iron 
in  this  from  time  to  time.  When  the  iron  is 
sufficiently  hot,  the  paste  will  sputter  in  a 
good  lively  fashion  and  after  a  little  experience 
you  will  be  able  to  tell  at  just  what  point  the 
soldering  is  easiest. 

Assuming  that  the  iron  is  properly  heated 
the  next  step  is  to  plunge  the  end  briefly  into 
the  can  of  soldering  paste.  Before  this  is 
entirely  burned  off,  solder  should  be  applied  to 
the  end  of  the  iron  and  then  rubbed  over  the 
point  with  a  soft  rag.  It  is  surprising  to  ob- 
serve the  ease  with  which  this  is  made  to 
adhere,  provided,  of  course,  the  point  is 
clean.  The  whole  end  of  the  iron  should  be 
treated  in  this  manner  until  it  is  tinned 
completely.  Make  sure  that  the  rag  is 
doubled  back  and  forth  several  times  so  that 


How  to  Solder 


97 


KAURI  BROADCAST  1'hotograph 

FIG.   2 

Rubbing  the  working  top  of  the  iron  on  a  piece  of 
sal  ammoniac  removes  the  oxide  coating  and  pre- 
pares it  for  tinning.  The  iron  must  be  quite  hot 
and  the  surface  of  the  sal  ammoniac  must  be  clean 


\  uur  hand  will  not  come  into  contact  with  the 
hot  iron.  This  rag  should  be  kept  handy  at 
all  times  and  when  doing  extensive  soldering, 
the  point  should  be  wiped  clean  occasionally. 
It  may  also  be  necessary  to  re-tin  the  point  if 
the  iron  has  become  too  hot  at  any  time. 
When  this  is  done,  it  is  first  necessary  to  scrape 
the  point  with  a  file  so  that  the  shiny  copper 
is  again  exposed.  The  rest  of  the  procedure  is 
then  followed  as  outlined  before. 


RADIO  BROADCAST  Photograph 
FIG.    3 

Applying  the  strip  solder  to  the  cleaned  tip  of  the 

iron.     The  solder  should  quickly  take  to  the  iron 

after  it  has  been  properly  cleaned 


WHAT    SOLDER   TO    USE 

'"THERE  are  many  different  kinds  of  solder 
*  on  the  market,  but  it  is  generally  con- 
ceded among  radio  men  that  good  resin  core 
solder  is  the  best  for  all  around  work.  This  is 
excellent  if  used  with  a  small  amount  of  solder- 
ing paste  and  you  can  make  up  a  joint  which 
will  last  for  years. 

Acid  core  solder  is  completely  out  of  place 
as  far  as  radio  is  concerned.  The  acid  will 
attack  the  copper  and  cause  quick  corrosion 
with  consequent  noise  in  the  set.  Of  course 
plain  wire  solder  is  excellent,  but  it  will  be 
necessary  to  use  a  little  more  paste  with  it. 

The  paste  consists  of  a  resinous  material 
of  a  pasty  consistency  which  helps  to  make  the 
solder  stick  by  acting  as  a  cleaning  agent. 


RADIO  BROADCAST  Photograph 
FIG.    4 

A  good  soldering  outfit.     From  left  to  right:  liquid 

soldering  flux,  paste  flux,  flat  nose  pliers,  electric 

iron,  sal  ammoniac,  and  strip  solder 


There  are  many  forms  of  this  material  some 
of  which  are  liquid  in  form.  It  is  never  ad- 
visable to  use  too  much  of  any  of  these  ma- 
terials, because  all  of  them  will  cause  trouble 
if  applied  in  this  manner. 

The  customary  thing  is  to  have  a  match 
handy,  and  with  this  dip  out  just  a  tiny  bit 
of  the  paste  and  apply  it  to  both  surfaces  to  be 
soldered.  A  little  solder  is  then  applied  to  the 
end  of  the  hot  iron,  the  two  surfaces  placed  to- 
gether, and  the  solder  applied.  Make  sure  that 
the  surfaces  are  held  tightly  together  until 
the  solder  has  had  a  chance  to  cool.  This  is  a 
matter  of  seconds  only  and  before  the  joint 
becomes  entirely  cold,  wipe  it  off  with  the  rag 
used  for  cleaning  the  iron.  This  wiping  off 
will  remove  surplus  soldering  paste  or  flux  and 
prevent  possible  corrosion  of  the  joint. 

Remember  that  a  tiny  drop  of  the  solder 


98 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 


FIG.    5 

Wiping  the  iron  to  keep  it  bright.     A  clean  iron 

means  good  work.     Any  old  cloth  may  be  used  to 

wipe  the  iron 


will  do  the  work  better  than  a  big  crystal-like 
lump.  The  solder  should  be  hot  enough  to 
flow  evenly  almost  like  water.  The  surface 
of  a  correctly  soldered  joint  should  be  smooth 
with  only  enough  solder  to  hold  the  joint  to- 
gether. Wiping  it  off  as  suggested,  will  do 
much  to  improve  the  appearance. 

A   PRACTICAL  EXAMPLE  OF  A  SOLDERING  PROB- 
LEM 

LET  us  actually  solder  a  joint.  We  will 
make  a  connection  between  a  new  piece 
of  bus  bar  and  an  old  soldering  lug  on  a  vari- 
able condenser.  This  condenser  happens  to 
be  mounted  on  a  panel  in  the  usual  manner. 

The  first  thing  to  do  is  to  place  the  iron  on 
to  heat,  either  by  plugging  it  in  on  the  electric 
light  socket  or  by  placing  it  over  the  gas  flame 
in  the  kitchen.  While  the  iron  is  heating  we 
get  the  rag,  wire  solder,  and  paste  handy  and 
then  proceed  to  clean  off  the  surfaces.  The 
lug  on  the  condenser  is  badly  corroded  and  it 
will  never  hold  solder.  A  small  file  or  a  bit  of 
emery  paper  will  help  us  here  and  the  lug  is 
soon  shiny.  It  is  also  advisable  to  touch  up 
the  bus  bar  a  little  despite  the  fact  that  it  is 
new.  The  grease  on  the  hands  will  sometimes 
cause  failure  in  a  connection  of  this  kind, 
especially  if  the  wire  has  been  handled  a  lot. 
A  light  scraping  with  a  knife  is  sufficient  to 
clean  the  bus  bar. 

The  wire  is  now  bent  into  place  so  that  it 
touches  the  soldering  lug  on  the  condenser. 


If  possible,  arrange  this  in  such  a  way  that  the 
wire  rests  in  place  by  itself.  This  makes  mat- 
ters easier  and  takes  the  strain  from  the  con- 
nection. Since  solder,  like  water  will  not  run 
up  hill,  it  will  be  far  easier  to  make  this  con- 
nection if  we  tilt  the  whole  set  forward  so  that 
the  lug  on  the  condenser  is  on  top. 

When  the  soldering  iron  is  sufficiently  hot, 
it  is  dipped  for  an  instant  in  the  paste.  A 
bit  of  this  paste  is  applied  with  the  match  to 
the  bus  bar  and  the  lug.  Next  take  the  solder 
and  hold  it  so  that  a  small  drop  adheres  to 
the  surface  of  the  iron.  Apply  the  iron  to  the 
joint  then  and  allow  the  solder  to  flow  in 
smoothly  around  the  wire  and  the  lug.  It  is 
not  necessary  to  cover  the  wire  entirely  as  long 
as  it  is  held  securely.  Put  the  iron  back  to 
heat,  and  by  this  time  the  joint  should  be 
hardened  sufficiently  to  hold.  The  next  step 
is  to  wipe  it  off  with  the  rag.  An  excellent 
joint  results. 

GENERAL    ADVICE    TO   THE    SOLDERER 

D  EMEMBER  that  the  solder  is  in  a  liquid 
1^-  form  and  if  you  handle  the  iron  too 
quickly  it  will  drop  off  and  possibly  burn  you 
or  your  clothing.  Remember  also  that  copper 
and  brass  are  good  conductors  of  heat  and  if 
you  handle  the  parts  just  soldered  too  soon, 
you  may  get  a  bad  burn.  Brass  binding  posts 
particularly,  have  a  way  of  staying  hot  for  a 
long  time  and  some  of  the  fixed  condensers  are 
veritable  furnaces  for  holding  the  heat.  In 
fact  due  to  this  alone,  it  is  far  better  to  make  a 
connection  through  a  fixed  condenser  with  a 
small  machine  screw  rather  than  soldering  the 


RADIO  BROADCAST  Photograph 
FIG.    6 

Re-tinning  the  iron.  A  small  can  cover  containing 
a  portion  of  melted  solder  and  paste  flux  may  be 
employed  for  periodically  re-tinning  the  iron.  The 
flux  cleans  the  soldering  iron  surface  so  that  the 
solder  in  the  can  cover  will  adhere  to  it 


RADIO  BROADCAST  Photograph 
FIG.    7 

How  to  prepare  a  joint  for  soldering.  A  bit  of  flux 
is  applied,  with  the  aid  of  a  stick  or  scrap  piece  of  bus 
bar,  to  the  joint  to  be  soldered.  This  flux  cleanses 
both  wires  so  that  the  solder  will  stick  to  them 


wire  to  it.  Many  fixed  condensers  have  actu- 
ally been  short  circuited  by  the  soldering  pro- 
cess. 

Do  not  think  that  because  every  joint  is 
soldered,  the  set  cannot  have  a  loose  connec- 
tion, because  this  happens  far  too  often. 
Sometimes  too  much  paste  applied  to  a  joint 
will  cause  a  layer  of  this  material  to  harden 
in  between  the  two  surfaces.  Naturally  such 
a  condition  will  make  the  set  very  noisy.  In 
another  case  the  writer  found  a  set  in  which  a 
soldered  connection  had  completely  parted  due 


to  the  fact  that  the  wires  had  been  under  too 
much  tension  when  soldered.  This  joint  had 
pulled  apart  during  the  set  owner's  absence, 
and  it  was  only  after  several  evenings  of  frantic 
effort  that  the  trouble  was  finally  located  in 
one  of  the  most  inaccessible  parts  of  the  set. 

To  sum  up  the  whole  art  of  soldering,  the 
"artist"  must  remember  just  two  things. 
Keep  the  soldering  iron  clean  and  the  surfaces 
clean.  This  is  the  whole  secret  of  the  thing. 


RADIO  BROADCAST  Photograph 
FIG.    8 

The  iron  should  be  held  firmly  on  the  joint  to  be 
soldered,  touching  both  pieces  so  that  when  they 
become  heated,  the  solder  on  the  tip  of  the  iron  will 
flow  evenly  over  the  point.  Additional  solder  may 
be  fed  from  the  strip  solder  wire  or  it  may  be  "  picked 
up"  from  the  can  cover 


Latest  Alterations  in  Broadcasting  Wavelengths 


/COMPLETING  the  list  of  Class  B  broad- 
\**_  casting  stations  whose  wavelengths 
have  been  realloted  by  the  Radio  Service, 
Department  of  Commerce,  the  following 
Pacific  Coast  stations  received  new  wave- 
length assignments: 

KNX  "  Los  Angeles,  Calif.  336.9  meters 

KFAE  Pullman,  Wash.  348.6 

KGO  Oakland,  Calif.  361.2 

KFOA  Seattle,  Wash.  384.4 

KHJ  Los  Angeles,  Calif.  405.2 

KPO  San  Francisco,  Calif.  420.3 

KFI  Los  Angeles,  Calif.  468.5 

KGW  Portland,  Ore.  491.5 

KIX  Oakland,  Calif.  508.2 


Wavelengths  assigned  to  points  where 
broadcasting  stations  are  to  be  erected  were: 

Corvallis,  Ore.,  280.2  meters,  Los  Angeles,  293.9, 
Phoenix,  Ariz.,  299.8,  Seattle,  Wash.,  305.9,  Pasa- 
dena, Cal.,  315.6;  Salt  Lake  City,  333.1;  Missoula, 
Mont.,  394.5,  and  Seattle,  454.3. 

It  was  recently  announced  in  a  news  dis- 
patch from  Washington  that  the  Radio  Ser- 
vice was  considering  readjusting  the  entire 
wavelength  assignments  now  in  force  with 
Class  B  stations.  This  would  be  done  in  order 
to  give  each  station  a  separation  of  fifteen 
kilocycles  instead  of  ten,  as  is  now  the  case. 
It  is  not  now  known  when  that  reassignment 
will  take  place. 


The  Revelations  of  Enoch 

The  Short- Wave  Doodlebug— Pocket  Humor  and  Radio 
Philosophy  Uttered  by  a  New  Electro-Optical  Discovery 

BY  W.   R.   BRADFORD 


IN  THE  baseboard  that  runs  around  the 
floor  of  my  studio,   and  radio  lab.  is  a 
hole  made  by  a  mouse  at  some  earlier 
time.     The  hole  at  present  is  occupied  by 
a  Doodlebug,  who  holds  forth  there,  in  bache- 
lor quarters.     I  had  gone  to  quite  some  pains 
in  making  friends  with  this  little  fellow,  and  at 
last  succeeded  to  the  point  where  he  would 
poke  his  head  from  the  hole  and  look  me  over 
carefully  with  his  beady,  black  little  eyes. 

As  we  became  better  acquainted,  I  began 
to  take  liberties.  One  day  I  held  forth  a 
finger  for  his  inspection,  and  the  little  cuss 
mounted  my  finger,  whereupon,  I  lifted  him 
to  my  desk,  where  reposed  a  Knockout  « 
Roberts  set.  The  Doodlebug  gazed  at  the 
set  and  began  to  show  interest. 

1  made  a  little  ladder  and  placed  it  against 
the  panel.  The  Doodlebug  climbed  the 
ladder!  After  a  careful  inspection  of  the 
set,  he  turned  and  waved  his  antenna  in  a 
peculiar,  jerky  manner.  Getting  no  response, 
he  repeated  this  several  times.  Suddenly  I 
discovered  he  was  wigwagging  me,  in  the  In- 
ternational code! 

"Make  a  short  wave  set,"  said  the  Doodle- 
bug: "  I  want  to  talk  to  you!" 

"What  wavelength  shall  1  make  it?"  I  wig- 
wagged back. 

"  Make  it  one  half  of  one  per  cent."  said  the 
Doodlebug. 


Alas!  My  lab  contained  no  equipment  to 
comply  with  this  Volsteadian  requirement: 
"Talk  with  me  in  wigwag,"  I  signalled: 
"Later  on  I  shall  make  a  set." 

The  Doodlebug  pulled  down  his  vest,  meta- 
phorically speaking,  and  wigwagged  the  follow- 
ing: 

NEW    RADIO    PHILOSOPHY 

RADIO  is  nothing  new  to  me.     I  was  born 
with  it,  as  all  of  the  insect  family  are. 
Few  of  the  insects  have  vocal  cords,  so  we  de- 


"THE    LITTLE    CUSS   MOUNTED   MY 
FINGER 


ENOCH   TESTING    A    GRID    CONDENSER 

And  putting  the  hall  mark  of  approval  on  it 

pend  on  radio  for  our  communication.  No, 
we  have  no  understanding  of  the  sign  language, 
such  as  your  mutes  use,  though  our  different 
postures  and  actions  indicate  our  feelings  and 
desires,  in  a  more  or  less  crude  manner.  But 
our  main  means  of  communication  is  by  radio. 
Our  waves  are  similar  to  those  you  use,  but 
very  much  shorter.  Man  may  some  day  be 
able  to  communicate  with  us  when  he  under- 
stands our  units  of  measurement,  which  are 
minute,  compared  to  your  methods. 

"We  do  not  receive  and  send  by  your 
methods.  What  you  would  call  nerves,  are 
all  arranged  for,  in  our  antenna,  our  segmented 
organs  of  sensation.  You  depend  on  sound. 
We  feel  vibrations.  Though  these  vibrations 
are  minute,  we  can  receive  and  send  them  a 
considerable  distance — as  much  as  two  hun- 
dred feet.  No,  we  are  not  bothered  with 


The  Revelations  of  Enoch 


101 


IT  S    A    WISE    BUG 

That  knows  its  own  receiver.     Enoch,  the  confiden- 
tial radio  bug,  is  photographed  in  a  moment  of  his 
marked  preference  for  the  Roberts  Knockout  set 


static,  or  extraneous  interference.  We  have  no 
'squeal  hounds'  to  make  our  radio  a  thing 
to  swear  at.  There  is  no  'best  circuit'  with 
us.  Each  one  of  us  is  his  own  super-hetero- 
dyne, so  to  speak.  Thus,  much  valuable  time 
is  saved,  which  would  otherwise  be  wasted  in 
endless  wrangling  over  'low  loss  apparatus,' 
and  such  flubdub!" 

(Did  you  ever  hear  the  likes  of  that?  The 
very  kernel  of  good,  sound  radio  sense!) 

The  Doodlebug  continued:  "Maybe  you 
doubt  me?  Well,  the  ignorant  ever  condem 
that  which  they  do  not  understand." 

(Get  that?  That  little  jasper  has  read 
Rochefoucauld's  Maxims,  I  betchuh!) 

The  Doodlebug  waved  on:  "An  ant  finds 
an  open  sugar  bowl.  He  is  not  like  a  human 
— greedy,  and  wanting  all  for  himself.  No. 
He  is  one  of  God's  creatures  who  share  with 
others — at  least,  with  their  own  kind.  Does  he 
waste  valuable  time  running  wildly  around, 
shouting:  'Oi,  yoi,  yoi!  Come  and  get  a 
mouthful  of  sugar'?  No.  He  broadcasts  the 
news  with  his  own  little  station — his  nerves, 
and  his  antenna.  Each  ant's  sensory  appara- 
tus, his  antenna,  is  tuned  to  the  same  wave- 
length, which  never  varies.  All  the  ants 


within  range  of  his  broadcast  come  and  tune 
into  the  feast — until  one  of  you  humans  turn 
loose  with  a  howitzer  loaded  with  insect 
powder." 

(So  that  was  the  way  ants  learned  of  sugar 
banquets!  Come  to  think  of  it,  it  must  be  so. 
One  time  an  ant  crawled  down  my  back — •  and 
took  his  broadcasting  station  with  him.  In- 
side of  two  minutes,  a  string  of  ants  had  begun 
to  crawl  up  my  trouser  leg!  I'll  wager  the 
explorer  ant  got  lonesome,  and  broadcast  for 
company !) 

Just  then  Mrs.  Betterhalf  called:  "The  fur- 
nace needs  attention!"  Quick  as  a  flash  the 
Doodlebug  ran  down  the  ladder  and  made  for 
his  hole  in  the  baseboard. 

Bachelor  Doodlebug?  Such  actions  denote 
fear  of  the  feminine,  and  indicate  that  this  lit- 
tle rascal  at  some  time  had  some  unpleasant 
matrimonial  melange.  (I  fear  the  plot  is 
going  to  thicken  somewhere.) 

His  actions  brought  to  mind  those  of  a  comic 
character  of  mine,  so  I  named  him  Enoch. 
Enoch,  you  remember  was  afraid  of  his  wife. 

I  shall  make  a  short-wave  set.  The  shorter 
the  better,  evidently.  Then  in  our  next  inter- 
view we  may  learn  more  about  short-wave 
radio — and  other  things.  We  shall  see. 

(As  Enoch  hurried  to  his  hole,  I  pot-shotted 
him  with  my  faithful  camera.  Doesn't  it 
make  a  nice  little  tail  piece,  for  a  story  finish? 
Thanks.  I  thought  you'd  like  it.) 


2iiiiiiimiiiiiiiiiimiiiiiiiimiimiiiiiiiiiiiiiimiimiiiiiiiimiiiiiiiiiiiiimiiiii iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiMiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiniitiiiiiiiiiiiiiiiiMiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiu 

["NO\X/  I  HAVE  FOUND.    ...     .     " 

A  Department  Where  Readers  Can  Exchange  Ideas 
and  Suqaestions  of  Value  to  the  Radio  Constructor  andOperator  I 

3  r 


ALTERNATING  CURRENT  AS  A 
SOURCE  OF  FILAMENT  SUPPLY 

RECENTLY  I  have  been  experimenting 
with  alternating  current  as  a  means 
of  heating  the  filaments  of  vacuum 
tubes.  The  idea  is,  of  course,  an  old  one, 
but  for  some  reason  has  never  been  put  into 
practice  to  any  great  extent.  Alternating 
current  cannot  be  used  satisfactorily  to  heat  a 
detector  tube  filament.  This  article  will  be 
confined  to  a  discussion  of  the  use  of  alternating 
current  in  amplifiers. 

With  the  advent  of  the  dry  cell  tube  our 
troubles  concerning  filament  supply  would 
seem  to  be  ended.  However,  these  small 
tubes  are  so  designed  that  they  are  unable  to 
handle  much  power  and  hence  are  not  very 
satisfactory  as  audio-frequency  amplifiers,  es- 
pecially in  the  second  stage.  For  tubes  re- 
quiring more  than  .25  ampere  filament  cur- 
rent, dry  cells  are  uneconomical. 

The  difficulty  to  be  overcome  when  alter- 
nating current  is  used,  is  the  hum  which  is 
produced  in  two  ways: 

1.  If  the  grid  return  be  connected  to  either  end 
of  the  filament,  then  the  grid  potential  becomes  al- 
ternately positive  and  negative  with  respect  to  the 
midpoint  of  the  filament.     If  it  were  possible  to 
connect  the  grid  return  to  the  midpoint  of  the  fila- 
ment, then,  of  course,  its  potential  would  not  change. 
This  cannot  be  done  but  a  trick  may  be  employed 
which  by  means  of  a  potentiometer,  as  shown  in  Fig. 
i,  the  same  results  may  be  produced.     Here  we  see 
that  the  midpoint  of  the  potentiometer  remains  at 
constant  potential,  namely,  the  same  potential  as 
the  filament   midpoint.     Hence,   by  adjusting  the 
potentiometer  we  can  make  the  grid  return  remain 
at  this  same  potential.     This  simple  adjustment  is 
easily  made  and  the  hum  reduced  to  a  very  small 
quantity. 

2.  The  temperature  of  the  filaments  does  not  re- 
main constant,  but  changes  continually  from  a  max- 
imum value  to  a  minimum  value  as  the  current 
through  the  filament  passes  through  its  cycle. — zero, 
positive  maximum,  zero,  negative  maximum,  zero. 
See  Fig.  2. 

For  the  usual  house  lighting  supply,  the 
frequency  is  60  cycles  per  second.  The  fila- 
ment temperature,  therefore,  reaches  its  max- 


imum and  minimum  temperatures  120  times 
per  second.  This  produces  an  audible  hum 
in  the  phones  at  a  frequency  of  120  vibrations 
per  second.  It  is  interesting  to  check  this 
value  against  the  tone  of  B  below  middle  on  a 
properly  tuned  piano.  If  middle  C  is  256 
vibrations  per  second,  then  B,  an  octave  below, 
is  about  123  vibrations  per  second.  By  listen- 
ing to  the  hum  produced  in  the  phones  when 
the  potentiometer  arm  is  properly  adjusted 
for  constant  grid  potential,  and  comparing  this 
hum  to  B  below  middle  C,  we  cannot  detect 
the  three  cycles  difference. 

If  the  potentiofneter  arm  be  moved  so  that 
the  grid  return  is  connected  to  one  end  of  the 
filament,  instead  of  midway  between  its  two 
ends,  then  the  grid  potential  varies  with  re- 
spect to  the  filament  at  the  rate  of  60  cycles 
per  second.  This,  of  course,  causes  a  60  cycle 
hum  in  the  phones  in  the  plate  circuit.  If  we 
actually  move  the  potentiometer  arm  away 
from  its  mid  position  and  at  the  same  time 
listen  in  the  phones,  we  hear  the  120  cycle 
hum  gradually  become  lost  in  the  60  cycle 
hum,  as  the  latter  increases  in  amplitude  the 
further  we  move  the  potentiometer  arm  from 
its  midpoint. 

Well,  all  this  theory  sounds  very  fine,  but 
what  good  is  it?  In  answer  to  this  I  shall 
describe  briefly  a  single-stage  audio-frequency 
amplifier  which  I  have  constructed  employing 
the  potentiometer  feature  as  outlined,  and  find 
entirely  satisfactory  from  every  standpoint. 
The  quality  of  reproduction  is  good,  the  vol- 
ume is  ample,  and  there  is  no  noticeable  a.  c. 
hum.  The  loud  speaker  which  I  am  using  is 
merely  a  fibre  megaphone  about  2  feet  long 
with  a  wye  victrola  headset  connector  soldered 
to  it,  and  a  pair  of  Western  Electric  phones. 
The  quality  of  reproduction  is  better  than 
many  loud  speakers  now  on  the  market. 

Now  for  the  amplifier  itself.  The  apparatus 
required: 

An  audio-frequency  amplifying  transformer. 
Rheostat,  tubes,  socket. 
Potentiometer  (200  ohms  or  more). 

The  apparatus  is  assembled  in  a  manner 
similar  to  the  usual  audio-frequency  amplifier. 
The  rheostat  must  be  placed  between  the 


"Now,  I  Have  Found 


103 


potentiometer  and  the  a.  c.  supply  as  shown. 
See  Fig.  3. 

I  am  using  this  amplifier  in  conjunction  with 
a  one-tube  reflex  set.  This  tube  is  a  uv-igg, 
and  its  filament  supply  consists  of  three  dry 
cells  in  series.  The  proper  negative  grid  bias 
for  the  audio  amplifier  tube  may  be  obtained 
either  from  a  separate  C  battery,  or,  by  con- 
necting the  A  battery  of  the  first  tube  so  that 
it  acts  as  C  battery  for  the  second.  This  is 
shown  in  Fig.  3. 

The  value  of  C  battery  which  will  give  un- 
distorted  amplification  depends  upon  the  type 
of  tube  used  and  also  upon  the  plate  voltage. 
For  200  and  300  tubes,  use  about  1.5  volts. 
For  20 1 -A  and  301 -A  tubes  use  1.5  volts  for  a 
plate  voltage  of  40  volts,  and  4.5  volts  for  a 
plate  voltage  of  90  volts. 

The  a.  c.  supply  for  filament  must  of  course 
be  transformed  from  1 10  volts  to  a  lower  value. 
This  is  most  economically  done  by  means  of  a 
toy  transformer  which  can  be  purchased  for 
a  couple  of  dollars.  The  secondary  voltage 
may  be  from  5  to  10  volts.  Most  storage 
battery  tubes  are  designed  to  operate  at  a 
filament  voltage  of  5  volts.  I  am  using  a 
uv-200  tube,  consuming  a  filament  current 
of  i  ampere.  The  secondary  of  my  trans- 
former gives  me  5  volts.  The  type  of  rheo- 
stat used  depends  upon  the  tube.  In  this 
circuit,  a  6  ohm  rheostat  is  used. 

In  order  to  find  out  the  resistance  of  the 
rheostat  necessary,  first  determine  the  normal 
filament  voltage  and  current  of  your  tube  and 
the  secondary  voltage  of  your  transformer. 
Subtract  the  filament  voltage  from  the  trans- 
former voltage  and  divide  by  the  current. 
This  gives  the  value  of  normal  resistance  in 
series  with  filament.  The  rheostat  should, 
to  allow  for  discrepancies,  have  a  somewhat 
higher  resistance  than  this  computed  value, 
say  25  per  cent.  For  example: 

Given 

Filament  voltage — 5  volts. 
Filament  current — j  ampere. 


Transformer  secondary  voltage — 8  volts. 
8 — 5  volts  =  3  volts. 
3  -i-  j  =   12  ohms. 

Adding  25  per  cent,  we  get  15  ohms  as  the 
resistance  of  the  rheostat.  It  can  be  seen 
from  the  above  that  any  value  of  transformer 
voltage  may  be  used  provided  the  rheostat 
resistance  is  properly  computed. 

I  use  only  one  stage  of  amplification  on  my 
set  because  the  resulting  volume  of  signal  is 
quite  sufficient.  However,  there  is  no  reason 
why  two  stages  cannot  be  used,  employing  a 
common  potentiometer  and  filament  rheostat. 
The  rheostat  as  determined  for  one  stage  may 
also  be  used  for  two  stages. 

Of  course,  the  filament  transformer  may  be 
constructed  without  much  trouble,  but  its 
specifications  will  not  be  given  here. 

The  audio  amplifier  using  a  storage  battery 
may  readily  be  converted  to  use  a.  c.  merely 
by  the  addition  of  the  potentiometer.  The 
total  initial  cost  of  the  a.  c.  amplifier  is  less 
than  the  usual  method  and  its  upkeep  is  less. 
Another  point  of  some  importance  is  the  fact 
that  tube  filaments  have  a  longer  life  when 
heated  with  a.  c.  than  when  d.  c.  is  used. — -J. 
B.  CLOTHIER,  JR.,  Lansdowne,  Pennsylvania. 

A  SCREW  STARTER 

WHEN  constructing  radio  sets  it  is  often 
difficult  to  hold  the  screws  so  that 
they  may  be  put  in  some  nearly  in- 
accessible place.  An  efficient  device  may  be 
made  by  slotting  a  piece  of  quarter-inch  brass 
rod  about  six  inches  long,  with  a  hack  saw,  for 
about  a  half  inch.  In  this  slot  two  phosphor 
bronze  strips  about  an  inch  and  a  quarter  long 
are  inserted  and  soldered  in.  The  tips  are  then 
filed  so  that  they  will  be  thin  enough  to  insert 
in  the  slots  of  small  screws.  They  are  then 
sprung  so  that  their  natural  position  is  with 
the  ends  about  an  eighth  of  an  inch  apart. 
When  these  tips  are  pressed  together  and 
placed  in  the  slot  in  the  screw,  and  then  re- 


A.F.T. 


To  phones  or 
2nd  amplifier 


Rheostat 

A  A.C.  6 


One  complete  cycle 
for  60  cycle  current 


FIGS.    I,    2,    AND   3 


To 

stepped-down 
A.C.  supply 


104 


Radio  Broadcast 


-Shape  as  desired 


Phosphor  Bronze  Spring 
/  strips  soldered  in 
/  saw  slot 


I/A  Brass  rod 
/  6"  long 


FIG.    4 

leased,  they  will  hold  the  screw  securely  until 
it  has  been  started,  and  then  it  can  be  released 
by  simply  pulling.  The  sketch,  Fig.  4,  shows 
the  details. 

A  CONVENIENT  MOUNTING  STRIP 

A  VERY  practical  method  of  installing 
a  receiver  is  to  bring  all  battery 
leads  up  through  the  top  of  the  op- 
erating table,  to  binding  posts  mounted  on  a 
strip  of  bakelite  which  is  fastened  to  the  table 
top.  Fig.  5  shows  the  details.  This  not  only 
provides  an  exceptionally  neat  installation 
by  keeping  all  wires  and  batteries  out  of  the 
way,  but  will  be  found  very  advantageous 
whenever  it  is  necessary  to  change  from  one 
receiver  to  another,  or  to  test  out  any  receiving 
set.  The  A  battery  and  B  battery  posts  are 
not  connected  in  any  way,  due  to  the  indi- 
vidual requirements  of  the  various  circuits, 
but  these  connections  can  be  bridged  across 
from  one  post  to  another,  if  such  connections 
are  not  taken  care  of  in  the  wiring  of  the  re- 
ceiver itself. 

Short  pieces  of  wire  are  run  from  the  posts 
on  the  mounting  strip,  to  the  posts  at  the  rear 
of  the  receiver,  and  when  taking  off  one  receiv- 
ing set  to  try  another,  it  is  merely  necessary  to 
loosen  the  binding  posts  on  the  table,  allowing 
the  connecting  wires  to  remain  attached  to  the 
receiving  set,  and  they  will  then  be  in  proper 
position  for  re-connecting. 

This  method  of  bringing  antenna,  ground, 
and  battery  leads  to  a  receiving  set  will  im- 
mediately find  favor  v/ith  all  experimenters 
who  ever  have  occasion  to  disconnect  one 
receiver  to  test  out  another  circuit. — HARRY 
W.  GILLIAM,  Big  Stone  Gap,  Virginia. 

(Bakelite  strip   14 V  1 1/2' « 3/is    


Mounting' 
Screw 


'Binding  Posts  . 


Bakelite 
binding  post 
TV      strip 


Hole  through  s 
Table  Tc?. 


Table  Top 


A  GOOD  FILTER  CONDENSER 

NO   DOUBT    many    readers   were   very 
much  interested  in  the  B  battery  from 
the  lamp  socket,  as  described  by  Mr. 
Le  Bel  in  the  September,  1924,  RADIO  BROAD- 
CAST.    Perhaps  they  may  also  be  interested  in 
the  following  description  of  an   electrolytic 
condenser  for  use  in  such  an  outfit. 

The  condensers  built  by  the  writer  and 
used  in  this  outfit  were  made  as  described  be- 
low and  as  illustrated  by  the  sketch,  Fig.  6. 
Each  condenser  required  one  large  mouthed 
glass  jar,  a  hard  rubber  or  wooden  top,  an 
aluminum  sheet,  a  quarter  inch  diameter 
steel  rod  and  an  electrolyte  of  ammonium 
phosphate  in  pure  water.  The  aluminum 
sheets  used  were  four  inches  wide  by  five  feet 
long  and  one  sixty-fourth  inch  thick.  A 
small  tab  or  ear  was  left  on  each  for  making  a 
connection.  The  sheets  were  rolled  into  a 
spiral  as  shown.  The  steel  rod  is  for  making 
contact  with  the  solution. 
-  After  the  parts  are  assembled  and  the  so- 
lution poured  into  the  glass  jars,  the  plates 
must  be  formed  by  passing  a  current  through 
the  condensers.  This  may  be  done  by  con- 
necting a  100  watt  lamp  in  series  with  them 
and  plugging  the  circuit  into  a  lamp  socket.. 
It  takes  a  long  time  to  form  the  plates  but  it 
can  be  done  with  a  little  patience.  When  the 


Aluminum  Sheet 
coiled  into  Form 


%dia.  Steel  Rod<N 


Glass  Jar- . 


35 

il           rT 

Hard  Rubber 

HIM.  •  • 

•  i  i  1    ll 

mill! 

k                  Cjl  1 

1 

1- 

-J    ^vl 

ij 

' 
1 

'I, 

II.         1 

' 

H 

ji 

,  -Aluminum 
Sheet 

"    ! 

1                ' 

||                  L.J 

ll 
Jl 

FIG.    5 


FIG.    6 


"Now,   I   Have  Found 


IQ5 


forming  is  advanced  far  enough  a  good  spark 
should  occur  when  the  condenser  is  short 
circuited  after  a  charge. 

A  pair  of  these  is  now  working  very  well  in  a 
lamp  socket  B  battery  outfit.  The  residual 
hum  is  small  enough  to  be  negligible  and  it 
seems  to  become  less  with  use.  This  outfit 
is  supplying  the  plate  potential  for  a  Roberts 
Knockout  circuit  in  very  satisfactory  fashion. 
— C.  E.  SEIFERT,  Cincinnati,  Ohio. 

MAKING  YOUR  OWN  CABINET 

THE  average  amateur  makes  a  very  poor 
job  of  his  cabinet,  which  spoils  the  ap- 
pearance of  an  otherwise  good  receiver. 
The  following  is  a  description  of  how  to  make 
it  look  like  a  factory  job  with  a  piano  finish, 
without  the  use  of  a  lot  of  clamps. 

It  is  possible  even  to  use  an  old  walnut  sew- 
ing machine  top  for  the  wood.  The  general 
specifications  are  outlined  in  Fig.  7. 

The  joint  at  "a"  is  glued,  but  clamps  are  not 
required- to- hold  it.-  It  is  sawed  .as  in  "b." 
First  use  a  marking  gauge,  place  a  back  on  the 
line  to  keep  the  saw  straight,  or  use  a  mitre 


box  if  one  is  available.  Next  use  a  chisel  on 
the  end  to  cut  it  out. 

Then  bore  three  holes  in  each  side  piece  for 
round  headed  brass  screws  as  at  "a,"  place  the 
back  of  the  case  in  a  check  and  mark  the  holes 
through;  but  when  drilling  allow  a  little 
draught  to  draw  pieces  up  tight,  as  in  C. 

This  will  bring  the  pieces  up  tight  when 
glue  and  screws  are  applied  so  that  the  joint 
will  not  show.  The  bottom  moulding  is  in 
two  pieces.  The  top  bead  is  a  strip  \  x  ij 
inches  with  outside  edge  rounded  and  corner 
mitred'  shown  at  "b." 

The  base  "c"  is  moulded  with  two  chisels: 
one  is  a  core  box  gouge,  and  the  other  a  plain 
flat  chisel.  This  is  quite  easy  to  do.  When 
finished,  scrape  and  sandpaper.  The  top 
bead  "b"  is  then  glued  to  the  base  "c." 

After  the  case  is  together,  get  a  bottle  of 
white  shellac  and  a  small  sponge.  Apply  three 
coats  with  the  sponge,  one  right  after  the  other 
as  soon  as  dry.  Allow  about  twenty  minutes 
between  coats.  Then  have  a  small  piece  of 
cotton  batting  tied  up  in  a  piece  of  woolen  rag, 
wet  this  in  alcohol  and  rub  all  over  the  case 
well.  Now  go  all  over  the  case  with  a  piece 


Saw, 


..Block  to 
'  guide  saw 


-E 


e 


b 

strip 


1® 


O) 


S   \y* 


-JlftV- 


nc.  7 


io6 


Radio  Broadcast 


of  tallow,  then  dust  on  rotten  stone  from  a 
woolen  bag  and  rub  well  with  the  heel  of  the 
hand  and  a  clean  rag.  The  more  you  rub 
the  better  the  finish.  Try  it  and  see;  the  fin- 
ish will  look  like  a  piano,  provided  the  wood 
is  smooth  when  you  start. — WELSFORD  A. 
WEST,  Hopewell,  Nova  Scotia. 

A  TICKLER  KINK  FOR  THE  ROBERTS 

AFTER  trying  every  conceivable  way  of 
working   the    tickler   for  my    Roberts 
set,  I  have  devised  the  scheme  shown 
in  Fig.  8.     I  have  found  it  more  satisfactory 
mechanically  and  electrically  than  the  factory- 
made  apparatus. 

This  arrangement  cost  me  thirty  cents  (not 
including  coils).  It  is  made  from  the  hard- 
ware of  a  1 80°  coupler  bought  at  a  five  and  ten 
cent  store. 

As  will  be  seen,  the  tickler  coil  is  brought 


P&N 


*2 


P&N-x 


i1      iii  i'3fa  Minimi 
IjU,        /  Coupli 


T 

Minimum 
Coupling 


^////^/////////////////W 


Panel—' 


FIG.   8 


into  the  field  of  the  S3  coil  very  gradually  by 
turning  the  dial. 

Another  feature  is  the  small  amount  of 
space  required  behind  the  panel;  it  is  about 
25  inches. 

The  coils  are  wound  on  standard  forms,  the 
T  coil  being  cut  smaller  than  the  others. — 
J.  BELL,  Ottawa,  Canada. 

WHEN  WORKING  BAKELITE 

TO  SQUARE  up  the  edges  of  bakelite,  a 
common  wood  plane  may  be  used  if  it 
is  set  rather  finely. 

An  excellent  and  rather  Unusual  finish  may 
be  given  bakelite  by  inserting  in  the  chuck  of 
a  drill  press,  a  piece  of  wood  about  f  inch  in 
diameter,  and  bringing  this  down  on  the  sur- 
face of  the  bakelite  so  that  the  circles  produced 
will  overlap  slightly.  The  finish  is  similar  to 
that  given  the  armor  plate  of  safes,  and  when 
done  evenly,  gives  a  very  pretty  effect.  It 
is  best  to  practice  on  the  wrong  side  of  the 
piece  or  on  a  scrap  piece  until  the  knack  is 
acquired. — CARL  PENTHER,  Oakland,  Cali- 
fornia. 

DULL  FINISH  FOR  PANELS 

THE  instructions  usually  given  for  remov- 
ing the  gloss  finish  from  bakelite,  formica, 
or  condensite  panels,  are  to  rub  them 
down  with  No.  o  sandpaper  and  oil.  How- 
ever, in  practice  I  have  found  that  a  very 
smooth  yet  dull  finish,  with  no  scratches,  is 
more  easily  obtained  by  rubbing  the  panel 
down  with  No.  oo  steel  wool,  dry.  Oil  may 
be  used  with  the  steel  wool,  or  applied  after- 
ward, but  is  not  at  all  necessary.  The  di- 
rection of  rubbing  should  be  back  and  forth, 
lengthwise  with  the  panel.  After  the  panel  is 
rubbed  down  in  this  way,  it  is  very  easy  to 
mark  locations  on  it  with  a  sharp  lead  pencil, 
when  laying  it  off  preparatory  to  drilling. 
— HARRY  W.  GILLIAM,  Big  Stone  Gap,  Vir- 
ginia. 


FOR  a  long  time,  RADIO  BROADCAST  has  felt  the  need  of  an  outlet  for  the  many  excellent  ideas  dealing 
with  various  features  of  radio  construction  which  reach  our  office.  If  you  have  an  idea  about  a  valuable 
and  useful  new  circuit,  some  new  device,  a  construction  or  operating  suggestion,  we  should  like  to  have  it. 
Payment  of  from  two  to  ten  dollars  will  be  made  for  every  idea  accepted.  The  description  should  be 
limited  to  three  hundred  words  and  typewritten.  Accompanying  sketches,  drawings,  and  circuit  diagrams 
should  be  as  plain  as  possible.  We  do  not  want  simple,  obvious  suggestions.  Material  to  be  acceptable 
for  this  department  must  offer  something  of  definite  value  to  the  constructor.  Mere  novelty  is  not 
desired.  Address  your  manuscripts  to  this  department.  RADIO  BROADCAST.  Garden  City,  New  York. 


QUESTIONS  AND  AN$W£Rc/° 

\J3 


See  Important  Special  Announcement  on  Page  112 

QUERIES  ANSWERED 


HOW  MAY  I  USE  A  VOLTMETER  AND  MILLIAMMETER 
IN  A   RADIOLA  SUPER-HETERODYNE  CIRCUIT? 

C.  J.  M. — Pittsburgh,  Pennsylvania. 

I  WISH  TO  ADD  A  STAGE  OF  R.  F.  AMPLIFICATION  TO 
MY  REGENERATIVE  RECEIVER.       HOW  SHALL  I  DO  IT? 

W.  D.  M. — Worcester,  Massachusetts. 

•  WHERE  MAY  i   OBTAIN   A   COLLEGE   CORRESPON- 
DENCE COURSE  IN  RADIO? 

L.  G.  B. — Wilkes-Barre,  Pennsylvania. 

WlLL  YOU    PUBLISH  A    CIRCUIT   DIAGRAM    SHOWING 


HOW  TO  USE  STRAIGHT  AUDIO,  PUSH-PULL,  OR  RE- 
SISTANCE-COUPLED AMPLIFICATION  WITH  THE  TWO- 
TUBE  ROBERTS  CIRCUIT? 

K.  H. —  Burlington,  Vermont. 

I  HAVE  BECOME  CONFUSED  WITH  THE  MARKINGS 
ON  AUDIO-FREQUENCY  TRANSFORMERS.  WILL  YOU 
EXPLAIN  THE  PROPER  MARKINGS  AND  CONNECTIONS? 

.  -  B.  W.  E. — Roanoke,  Virginia. 

HAVE  YOU  ANY  OTHER  ADDITIONAL  NOTES  ON  THE 
ROBERTS  CIRCUIT? 

C.  T.  S. — El  Paso,  Texas. 


METERS    AND    B    BATTERIES 

HERE  again  we  discuss  the  specific  problem  of 
the  use  and  aid  of  meters  in  the  B  battery 
circuit  of  a  Radiola  super-heterodyne  to 
determine  the  state  of  life  of  these  batteries. 

A  milliammeter  (o — 100  milliampere  scale)  when 
placed  in  the  circuits  as  shown  in  Fig.  i,  A-B-C  and 
D  registers  the  drain  upon  the  B  batteries  in  milli- 
amperes.  This  meter  itself  does  not  consume  any 
of  the  energy  as  it  is  of  low  resistance.  It  may  be 
permanently  included  in  the  circuit. 

The  full  B  battery  drain  will  be  indicated  when 
the  meter  is  connected  in  the  terminal  as  in  D,  be- 
cause this  is  the  common  return  lead  of  the  battery 
for  both  45  and  90  volt  terminals.  In  C  only  the 
45  volt  drain  would  be  indicated,  and  in  B  only  the 
amplifier  drain  would  be  manifest. 

The  voltmeter  (with  a  scale  reading  from  o  to  i  50 
volts)  is  used  to  indicate  the  state  of  voltage  of  the 
B  battery.  When  voltage  tests  are  made,  the 
terminal  leads  of  the  meter  should  only  be  momen- 
tarily touched  to  the  B  battery. 

The  resistance  of  a  voltmeter  is  such  that  a  leak- 
age path  would  be  provided  for  the  B  battery  cur- 
rent, and  would  soon  discharge  the  battery,  making 
it  inoperative.  Therefore  it  is  not  well  to  connect 
the  voltmeter  permanently  across  the  B  battery 
terminals.  A  switch  may  be  provided  which  will 
connect  it  in  the  circuit  for  momentary  readings. 

The  milliammeter  and  voltmeter  afford  all  definite 
check  on  the  life  and  condition  of  the  B  batteries 
and  should  be  included  in  all  installations,  especially 
where  many  tubes  are  employed. 


ADDING      R.      F.      AMPLIFICATION     TO     REGENERATIVE 
RECEIVERS 

A  METHOD  for  adding  radio  frequency  ampli- 
fication to  a  regenerative  receiver  was  dis- 
cussed in  the  March,  and  May,  1924,  RADIO 
BROADCAST,  but  as  these  issues  are  out  of  stock  at 
Doubleday,  Page  &  Co.,  the  subject  will  be  briefly 
treated  here. 

The  problem  to  be  considered  in  an  addition  of 
this  kind  is  to  construct  an  amplifier  which  will  not 
radiate  of  itself  into  the  antenna  or  pass  along  the 
oscillations  of  the  regenerating  detector. 

The  coupler  T-i ,  in  Fig.  2,  is  of  the  standard  type, 
a  primary  with  a  secondary  of  about  50  turns 
shunted  by  a  .0005  mfd.  variable  condenser.  The 
primary  may  be  variably  coupled  to  the  secondary. 
A  tube  socket,  rheostat,  .002  mfd.  fixed  condenser  and 
200  ohm  resistance  is  all  that  is  otherwise  necessary. 

The  primary  of  the  regenerative  receiver  serves 
as  the  plate  coil  of  the  amplifier.  Radiation  is 
prevented  by  the  use  of  the  200  ohm  resistance, 
which  may  be  termed  a  losser,  in  series  with  the  high 
voltage  lead  of  the  B  battery  supply. 

Fig.  3  shows  the  Roberts  form  of  amplifier  which 
is  highly  recommended.  Here,  the  plate  coil  of 
the  amplifier  must  be  specially  wound  with  a  pair  of 
wires.  The  inside  lead  of  one  coil  connects  to  the 
grid  of  the  tube  through  a  neutralizing  condenser, 
and  the  outside  lead  of  the  other  coil  connects  to  the 
plate.  The  remaining  two  leads  are  connected  to- 
gether and  thence  connected  to  the  high  voltage  B 
battery  lead.  The  antenna  coupler  is  of  the  stand- 
ard type. 


io8  Radio  Broadcast 

To  Interior  of  Receiver 


\-       To  -8  Battery 
Terminal 


Position  of  Meter 

when  used  in 

this  circuit 


-B- 


/To  Interior  of  Receiver  „ 


B- 


mi  i  nun 


8- 


-A- 


t  ----  To  Interior 
of  Receiver 


-C- 


B- 


WILUAMPERE  READING 
FOR45V."B"TAP 


90  VOLT  8  AMPLIFIER  DRAIN 


To  Interior  of  Receiver, _ 


B  +  45 


11,11 

FULL  DRAIN  READING 


B  +  90 


COLLEGE    RADIO    CORRESPONDENCE    COURSES 

INTENDING  in  no  way  to  discriminate,  this 
department  can  advise  that  for  those  wishing  to 
further  their  radio  studies  the  course  as  outlined 
by  the  prospectus  of  the  Department  of  Engineering 
of  the  Pennsylvania  State  College,  State  College, 
Pennsylvania,  is  especially  interesting. 

Two  courses  are  provided,  one,  elementary,  cover- 
ing the  principles  of  radio  electricity — how  tele- 
phone, crystal,  and  vacuum  tube  sets  work — 
amplification,  etc. — working  drawings  for  eight 
typical  receivers — discussions  on  topics  such  as 
static,  directional  effects,  radio-photography,  test 
methods,  etc.  This  course  is  of  ten  assignments 
and  costs  f  10.00. 

The  advanced  course  is  also  in  ten  assignments 
and  the  price  is  $i  5.00.  It  applies  to  technical  men 
and  amateurs,  desiring  the  mathematical  treatment 
of  the  subject,  together  with  the  electrical  theory 
involved.  It  covers  elementary  electricity,  radio 
circuits,  electromagnetic  waves,  damped  wave 
transmission,  the  electron  tube,  apparatus  for  recep- 
tion, the  tube  as  a  generator,  radio  telephony,  etc. 


,     REGENERATIVE  DETECTOR 


AUDIO      AMPLIFIER 


CIRCUITS       FOR 
RECEIVER 


THE       ROBERTS 


IT  IS  to  be' remembered  that  the  original  two- 
tube  Roberts  circuit  already  contains  one  stage 
of  audio-frequency  amplification  in  the  reflexed 
first  tube.     Now,  in  the  addition  of  amplifiers  the 
following  has  been  determined: 

i.     The  standard  straight  stage  of  audio  usually 


REGENERATIVE   DETECTOR 


A  -       -  B»«5 


FIG.    2 


FIG.    3 

overloads  and  causes  distortion  unless  the  trans- 
former secondary  is  shunted  by  a  variable  resistance 
of  a  value  of  10,000  to  100,000  ohms.  The  full 
amplification  factor  of  the  stage  is  not  realized  be- 
cause of  the  inclusion  of  this  "losser" . 

2.  The  push-pull  amplifier  is  admirably  suited 
for  controlling  the  output  of  the  two-tube  receiver 
and  will  furnish  plenty  of  volume.     However,  as  is 
the  case  with  all  audio-frequency  transformers,  the 
quality  of  reproduction  is  slightly  affected  because 
the  amplification  characteristic  of  the  transformer 
favors  some  band  of  frequencies  over  others. 

3.  The  resistance-coupled  amplifier  will  not  pro- 


RADIO  BROADCAST  ADVERTISER 


109 


•  »V«  ^fZ*  ^fmm 

BCIS !  not  Fancier 


Do  you.  hnow 

Where  Condenser  losses 

Come  -from? 

RESISTANCE  LOSSES   are 

,  the  losses  which  most  serious- 
ly affect  the  efficiency  of  aconden- 
ser  when  at  working  radio  fre- 
quencies. They  arise  from  poor 
contacts  between  plates  and  from 
poor  bearing  contacts.  Soldered 
plates  and  positive  contact  spring 
bearings  reduce  these  losses  to  a 
minimum, 

Eddy  current  losses  occur  in 
metal  end  plates  and  the  conden- 
ser plates  themselves.  While  not 
so  serious  as  resistance  losses, 
they  increase  with  the  frequency, 
and  therefore  should  be  kept  as 
low  as  possible. 

Dielectric  losses  are  due  to  ab- 
sorption of  energy  by  the  insulat- 
ing material.  Inasmuch  as  they 
vary  inversely  as  the  frequency, 
they  have  less  effect  upon  the 
efficiency  of  a  condenser  at  radio 
frequencies  than  any  other  set  of 
losses.  The  use  of  metal  end 
plates  in  short-wave  reception  to 
eliminate  dielectric  losses  is  never 
justified,  because  they  introduce 
greater  losses  than  well-designed 
end  plates  of  good  dielectric. 


The  design  of  General  Radio  Condensers 
is  based  on  scientific  facts  and  principles, 
not  on  style  and  fancies. 

Specially  shaped  plates  always  in  perfect 
alignment  give  the  uniform  wave-length 
variation  which,  permits  extremely  sharp 
tuning. 

Rotor  plates  are  counterbalanced  to  make 
possible  accurate  dial  settings. 

In  1915  the  General  Radio  Company  in- 
troduced to  this  country  the  first  Low  Loss 
Condenser,  and  ever  since  has  been  the 
leader  in  condenser  design. 

Lower  Losses  and  Lower  Prices  make 
General  Radio  Condensers  the  outstanding 
values  of  condenser  design. 

Licensed  for  multiple  tuning  under  Hogan 
Patent  No.  1,014,002 


$CJOO 


Type  247-H,  with  geared  Vernier 
Capacity,  500  MMF.     Price 

Type  ;247*F,  without    Vernier 
Capacity,  500  MMF.    Price 


GENERAL  RADIO  CO. 

CAMBRIDGE,  MASS. 


Quality  Parts 


Tested  and  approved  by  RADIO  BROADCAST 


no 


Radio  Broadcast 


duce  as  much  volume  as  the  push-pull  amplifier  hut 
will  be  faultless  in  quality  when  properly  adjusted. 
In  all  three  types  of  amplifiers,  the  input  connects 
to  the  two  central  blades  of  the  double  circuit  jack. 
The  diagram,  Fig.  4,  is  self-explanatory. 

AUDIO   TRANSFORMER    MARKINGS 

THE  designations  of  binding  post  markings  on 
audio-frequency   transformers    have    become 
standardized  to  a  great  extent,  but  there  are 
still  some  that  do  not  follow  general  practice. 

In  Fig.  5,  the  binding  post  marks  coincide  with 

2  TUBE  ROBERT5CIRCUIT 


1  STAGE 
STRAIGHT  AUDIO  AMPLIFICATION 


-  A  -     B-  B 

45V  90V 

FIG.    4 

the  markings  as  applied  to  circuit  diagrams.  Fig. 
6  shows  how  the  marks  appear  when  the  primary 
posts  are  turned  the  other  way  around.  The  out- 
side lead  of  the  secondary  is  the  point  of  high  po- 
tential in  the  secondary  circuit  and  usually  connects 
to  the  grid.  Standard  practice  has  it  that  the  out- 
side of  the  primary  should  then  go  to  the  plate. 
However,  be  sure  to  have  the  grid  connected  to  its 
proper  post,  then  if  results  are  not  as  expected  it  is 
well  to  try  reversing  the  leads  to  the  primary  of  the 
transformer.  This  is  especially  important  in  reflex 
circuits  such  as  the  Roberts. 

NOTES   ON   THE    ROBERTS   CIRCUIT 

THOSE  who  used  Sickles  coils  in  the  Roberts 
circuit  may  have  found  that  it  was  not  pos- 
sible to  tune  to  the  lower  wavelengths.    This 
is  especially  true  of  the  first  lot  of  Sickles  coils 
manufactured.     The  condition  may  be  remedied  in 
two  ways: 

1 .  Change  the  connection  of  the  return  side  of 
the  secondary  to  the  negative  side  of  the  A  battery 
line  instead  of  the  positive,  as  is  commonly  shown 
in  the  circuit  diagrams. 

2.  Remove  five  or  six  turns  from  the  NP  and 
tickler  coils. 

When  removing  turns  from  the  tickler  coil  simply 
unwind  them  from  the  outside  of  the  coil.  When 
removing  turns  from  the  NP  coils,  unsolder  the 
outside  ends  of  both  the  green  and  white  wires,  and 
unwind  both  of  them  together  until  you  have  taken 


-I- 


-A 


PUSH-PULL 
AUDIO  AMPLIFICATION 


I 

—  rtVi. 

\ 

1                ' 

O 

o 

0 

o 

0 

r 

1 

+  90-120V 


2  STAGES 

RESISTANCE  COUPLED  AMPLIFICATION 
i006mfd.  i|.006mfd. 


Top  view  of 

Audio  Frequency 

Transformer 

/Secondary, 


FIG.    5 


-  Primary" 

Top  view  of 

Audio  Frequency 

Transformer 


FIG.    6  ] 


off  six  turns,  then  connect  the  green  and  white  wire 
exactly  as  they  were  connected  before. 

This  will  make  your  set  operate  perfectly  down  to 


I?ADIO  BROADCAST  ADVERTISER 


111 


Lacault  Scores  A&ain/ 


'528 

005  m.f.d.  Capacity 


i  The  new  Ultra-Lowloss  con- 
dfenser  is  the  latest  radio  improved 
device  designed  by  R.  E.  Lacault. 
formerly  Associate  Editor  of 
Radio  News,  the  originator  of 
Llltradyne  Receivers  and  now  Chief 
Engineer  of  Phenix  Radio  Corpor- 
ation. 


CONDENSER 


:Simpliflcs  radio  timing.  IVncil- 
record  a  station  on  the  d'al  — 
thereafter,  simply  turn  the  tlnd-r 
to  your  pencil  mark  to  get  that 
station  instantly.  Easy — quick 
to  mount.  Eliminates  fumblinc, 
guessing.  Furnished  clockwise  or 
anti-clockwise  in  gold  or  silver 
finish.  Gear  ratio  20  to  1 
Silver  J2.50  Cold  $3.50 


/T  IKE  every  Lacault  development,  this  new  Ultra-Lowloss  Con- 
J-'  denser  represents  the  pinnacle  of  ultra  efficiency — overcomes 
losses  usually  experienced  in  other  condensers. 

Special  design  and  cut  of  stator  plates  produces  a  straight  line 
frequency  curve,  separates  the  stations  of  various  wave  lengths  evenly 
over  the  dial  range,  making  close  tuning  positive  and  easy. 

With  one  station  of  known  frequency  located  on  the  dial,  other 
stations  separated  by  the  same  number  of  kilocycles  are  the  same 
number  of  degrees  apart  on  the  dial. 

In  the  Lacault  Ultra-Lowloss  Condenser  losses  are  reduced  to  a 
minimum  by  use  of  only  one  small  strip  of  insulation,  by  the  small 
amount  of  high  resistance  metal  in  the  field  and  frame,  and  by  a 
special  monoblock  mounting  of  fixed  and  movable  plates. 

At  your  dealer's,  otherwise  send  purchase  price  and  you  will  be 
supplied  postpaid. 


Design  of  lowloss  coils  furnished  free  with  each  condenser  for  amateur  and 
broadcast  frequencies  showing  which  will  function  most  efficiently  with  the 
condenser. 


This  seal  on  a  radio  product  is 
your  assurance  of  satisfaction  and 
guarantee  of  Lacault  design. 


To  Manufacturers  Who  Wish  to  Improve  Their  Sets 

The  Ultra-Lowloss  Condenser  offers  manufacturers  the  opportunity 
to  greatly  improve  the  present  operation  of  their  receiving  sets. 

Mr.  Lacault  will  gladly  consult  with  any  manufacturer  regarding 
the  application  of  this  condenser  to  his  circuit  for  obtaining  efficiency. 


PHENIX  RADIO    CORPORATION,    116-C   East  25th  St.,  New  York 


Tested  and  approved  by  RADIO  BROADCAST 


I  12 


Radio  Broadcast 


one  hundred  and  eighty  meters  and  will  not  in  any 
way  weaken  the  received  strength  of  the  long  wave- 
length stations.  If  for  any  reason  you  cannot  get 
regeneration  at  five  hundred  and  fifty  meters  in- 
crease the  detector  plate  voltage. 

When  mounting  the  Sickles  coils  in  the  four-tube 
Roberts  layout,  the  planes  of  the  coils  are  practically 
opposite  to  that  arrangement  employing  the  Nazeley 
spiderwebs.  The  builder  must  exercise  his  own 
ingenuity  in  the  proper  placement  of  his  coils  so  that 
they  will  not  hinder  the  action  of  the  variable  con- 
densers and  he  must  make  sure  that  the  action  of  the 
tickler  coil  be  not  restricted. 

The  antenna  coupler  may  be  mounted  directly  on 
the  panel  slightly  below  the  switch  blade.  This 
brings  the  tap  leads  quite  close  to  the  switch  points. 
It  also  allows  ready  adjustment  of  the  coupling 
between  the  primary  and  secondary. 


Antenna  Coupler  Unit 

mounted  directly 
behind  and  below 
switch  points 


The  arrangement  is  as  shown  in  Fig.  7  and  permits 
of  short  leads  to  both  switch  points  and  variable 
condenser.  A  binding  post  strip  may  be  mounted 
directly  behind  the  tickler  coil  to  accommodate  the 
flexible  leads  from  the  tickler  and  the  bus  bar 
connections  to  it. 


PHOUSANDS  of  you  are  writing  the  Grid  for  technical  advice  every  month.  The  expense 
JL  of  framing  a  complete  and  exhaustive  reply  to  each  letter  is  very  high.  The  editors  have 
decided  that  the  benefit  of  the  questions  and  answers  service  will  continue  to  be  extended  to 
regular  subscribers,  but  that  non-subscribers,  from  April  15  on,  will  be  charged  a  fee  of  $1  for 
each  letter  of  inquiry  which  they  send  to  our  technical  department.  Very  frequently,  our 
technical  information  service  proves  of  definite  money  value  to  you  who  write  us,  for  we  are 
often  able  by  a  sentence  or  two  of  explanation,  to  put  you  on  the  right  path  before  you  have  made 
a  perhaps  expensive  mistake. 

The  occasional  reader  of  RADIO  BROADCAST  will  be  charged  a  fee  of  $1  for  complete  reply 
to  his  questions,  and  the  regular  subscriber  can  continue  to  take  advantage  of  the  service  as  before. 
In  that  way,  the  non-subscriber  will  help  share  the  cost  of  the  technical  staff  whose  service  he 
gets.  Every  letter  receives  the  benefit  of  the  experience  of  the  editor  and  the  technical  staff 
and  every  correspondent  may  be  sure  that  his  questions  will  receive  careful  consideration  and 
reply. 

When  writing  to  the  Grid,  please  use  the  blank  printed  below. 


GRID  INQUIRY  BLANK 
!    Editor,  The  Grid, 

|  RADIO  BROADCAST, 

!    Garden  City,  New  Yor\. 
\    Dear  Sir, 

Attached  please  find  a  sheet  containing  questions  upon  which  kindly  give  me  fullest  possible 
!    information.     I  enclose  stamped  return  envelope, 

(ChecJ^  the  proper  square) 
!    [U    /  am  a  subscriber  to  RADIO  BROADCAST.     Information  is  to  be  supplied  to  me  free  of 

charge. 
EH    /  am  not  a  subscriber.     I  enclose  $1  to  cover  costs  of  a  letter  answering  my  questions. 


I    My  name  is 


I    My  address  is- 


RADIO  BROADCAST  ADVERTISER 


113 


The  two  outstanding 

parts  in  radio! 


Give  low  losses  and  amplification 
without    distortion    to    any   set 


QUALITY  and  distance  are 
what  a  radio  set  must  give. 
To  insure  Quality,  amplification 
without  distortion  is  essential. 
And  to  insure  Distance,  low  losses 
are  essential.  That  is  radio  in  a 
nutshell. 

People  in  whose  sets  Acme 
Transformers  are  used,  are  sure 
of  hearing  concerts  "loud  and 
clear"  so  a  whole  roomful  of 
people  can  enjoy  them. 

The  Acme  A-2  Audio  Amplify- 
ing Transformer  is  the  part  that 
gives  quality.  It  is  the  result  of 
5  years  of  research  and  experi- 
menting. It  gives  amplification 
without  distortion  to  any  set. 
Whether  you  have  a  neutrodyne, 
super-heterodyne,  regenerative 
or  reflex,  the  addition  of  the  Acme 
A-2  will  make  it  better. 


To  get  the  thrill  of  hearing  dis- 
tant stations  loud  and  clear,  your 
set  must  have  low  losses,  for  it  is 
low  losses  that  give  sharp  tuning 
to  cut  through  the  locals,  and  it 
is  low  losses  that  allow  the  little 
energy  in  your  antenna  to  come 
to  the  amplifier  undiminished. 
That's  what  the  Acme  condenser 
will  do  for  any  set.  And  it  will  do  it 
for  years  because  the  ends  can't 
warp,  the  bearings  can't  stick  and 
the  dust  can't  get  in  and  drive  up 
thelosses  several  hundred  per  cent. 

The  Acme  Reflex  (trade  mark) 
owes  its  success  and  its  continued 
popularity  to  these  two  outstand- 
ing parts  in  the  radio  industry, 
for  low  losses  and  amplification 
go  hand  in  hand. 

Use  these  two  parts  in  the  set 
you  build.  Insist  on  them  in  the 


set  you  buy. 
Send  10  cents  for  40-page  book, 

** Amplification  "without  Distortion1 


Acme  A-2  Audio  Frequency 
Amplifying  Transformer 


WE  HAVE  prepared  a  40-page 
book  called  "Amplification 
without  Distortion."  It  contains 
19  valuable  wiring  diagrams.  In 
clear  non-technical  language  it 
discusses  such  subjects  as,  Radio 
Essentials  and  Set-building.  How 
to  make  a  loop;  Audio  frequency 
amplifying  apparatus  and  cir- 
cuits; Instructions  for  construct- 
ing and  operating  Reflex  ampli- 


ACME T 


fiers;  How  to  operate  Reflex 
receivers;  Antenna  tuning  cir- 
cuits for  Reflex  sets;  "D"  Coil 
added  to  Acme  four  tube  reflex; 
"D"  coil  tuned  R.  F.  and  Reflex 
diagrams;  and  several  more  be- 
sides. It  will  help  you  build  a  set 
or  make  your  present  set  better. 
Send  us  10  cents  with  coupon 
below  and  we  will  mail  you  a 
copy  at  once. 


ACME  APPARATUS  COMPANY 

Transformer  and  Radio  Engineers  and  Manufacturers 
Dept.  F4,  Cambridge,  Mass. 

SEND  THIS  COUPON 


ACME  APPARATUS  COMPANY 
Dept.  F4,  Cambridge,  Mass. 
Gentlemen : — 

I  am  enclosing  10  cents  (U.  S.  stamps  or  coin) 
for  a  copy  of  your  book  "Amplification  with- 
out distortion." 

Name 


Street. 


City. State 


amplification 


Tested  and  approved  by  RADIO  BROADCAST 


New  Equipment 


THE    ANDREWS 
PADDLEWHEEL      COIL 

A  well  made  inductance 
designed  to  give  a  higher 
ratio  of  inductance  to  re- 
sistance. The  several  groups 
of  spiral  windings  are  space 
insulated  from  each  other 
without  the  use  of  any  ad- 
hesives  or  dope.  Tuned  with 
a  .00025  mfd.  condenser,  this 
R.  F.  transformer  inductance 
has  a  range  from  200  to  600 
meters.  Made  by  Radio 
Units  Inc.,  Maywood,  Illi- 
nois. Price  $3.00 


TOGGLE  BATTERY  SWITCH 

A  new  battery  switch  designed  for 
use  in  the  radio  receiver.  It  is 
neat  in  appearance  with  a  pol- 
ished nickel  finish  and  has  large 
make-and-break  contact  surfaces. 
The  wide  spacing  of  the  terminals 
permits  ease  in  making  connections. 
It  is  easily  mounted  on  the  panel 
with  only  one  hole  required.  Made 
by  The  Cutler-Hammer  Mfg.  Co., 
Milwaukee,  Wisconsin 


KELLOGG    CONDENSER 

A  low  loss  variable  condenser  with  a 
heavy  brass  frame  containing  a  minimum 
amount  of  metal.  Direct  three-point 
contact  with  the  rotor  assures  positive 
connection.  A  special  Kellogg  dial  in 
conjunction  with  the  vernier  attachment 
makes  for  very  fine  tuning  adjustment. 
Made  by  the  Kellogg  Switchboard  and 
Supply  Co.,  Adams  and  Aberdeen  Sts., 
Chicago,  Illinois 


BALLGRIP       SOCKET 

A  molded  bakelite  socket  of  unusual  design.  Contact  with 
the  tube  prongs  is  obtained  through  a  ball  socket  arrange- 
ment molded  into  the  base  of  the  unit.  The  construction 
is  such  as  to  eliminate  the  possibility  of  internal  short 
circuiting.  Made  by  Quality  Molded  Products,  Inc., 
1  Exchange  Place,  Jersey  City,  New  Jersey.  Price  $1.25 


AMPLION    LOUD    SPEAKER 

This  speaker  is  designed  to  give  great 
sensitivity  and  naturalness  of  tone.  The 
Amplion  "Floating  Diaphragm,"  kept 
from  contact  with  metal  by  rubber  gas- 
kets, rests  on  a  narrow  ledge  in  the  case, 
lightly  held  there  by  a  spring  ring  with 
enough  pressure  to  prevent  "chatter" 
when  extreme  volume  is  desired.  Another 
feature  of  the  Amplion  is  the  use  of  rubber 
insulation  between  the  several  sections 
of  the  horn  to  eliminate  any  ring  or 
resonance.  Made  by  The  Amplion 
Corporation  of  America,  280  Madison 
Ave.,  New  York  City 


RADIO 
BROADCAST 


Vol.  7,  No.  2 


June,   1925 


The  Story  of  Broadcasting  in 

England 

The  Growth  of  the  Radio  Giant  in  Great  Britain  Compared 
With  that  in  America — How  John  Bull  Regulates  Broadcast- 
ing— The  New  Radio  Import  and  Licensing  Regulations 


By  F.  J.  BROWN 

Late  Assistant  Secretary  of  the  British  Post  Office 


BROADCASTING    in    Great    Britain 
began  in  a  very  small  way  by  a  half- 
hour's    transmission    of    a    musical 
program  once  a  week  from  a  station 
belonging  to  the  Marconi  Company  at  Writtle, 
in  Essex.     This  was  authorized  as  a  concession 
to  the  two  or  three  thousand  amateurs  who  at 
that  time  had  received  experimental  licenses 
from  the  Post  Office,  and  who  wished  to  test 
the  efficiency  of  their  apparatus  by  picking  up 
Writtle's  signals.     They  were  mainly  gramo- 
phone records,  but  occasionally  more  ambi- 
tious programs  were  introduced. 

This  was  the  limit  of  development  in  the 
winter  of  1921-2,  when  I  visited  Washington 
as  Expert  Adviser  on  Communications  to  the 
British  Delegation  at  the  Arms  Conference. 
At  that  time,  the  broadcasting  boom  in 
America  had  just  begun.  Fortunately,  I  was 
in  a  position  to  receive  full  information  as  to 
its  progress  from  my  friends  General  Squier, 
Doctor  Austin  and  Doctor  Cohen;  and  through 
their  courtesy  I  was  present  at  some  of  the 
meetings  of  Mr.  Hoover's  first  Radio  Confer- 
ence, where  I  met  other  world-famous  Ameri- 


can radio  authorities.  An  extract  from  a  letter 
which  I  wrote  to  one  of  my  colleagues  in  Lon- 
don on  the  subject  in  February,  1922,  may  be 
of  some  historical  interest : 

The  thing  which  has  made  the  most  remarkable 
progress  here  recently  is  broadcasting.  The  num- 
ber of  receiving  sets  which  are  being  used  is  marvel- 
ous. The  Westinghouse  people  gave  it  a  great 
impetus.  They  have  put  up  several  broadcasting 
stations,  and  are  stated  to  be  selling  receiving  sets 
(varying  in  price  from  $30  to  $150)  at  the  rate  of 
25,000  a  month,  and  are  then  quite  unable  to  meet 
the  demand.  Other  people  are  following  suit,  and 
it  is  likely  that  there  are  now  between  200,000  and 
300,000  receiving  sets  in  use,  though  the  number 
can't  be  stated  exactly,  as  licenses  are  not  issued  for 
reception.  The  sending  stations  broadcast  on  360 
meters.  They  probably  interfere  to  some  extent 
with  ship-and-shore  work,  and  they  certainly  tend 
to  interfere  with  one  another.  1  heard  a  program 
from  one  of  them  last  Sunday  afternoon  at  Dr. 
Frank  B.  Jewett's  home,  by  means  of  his  boy's  re- 
ceiving set.  Both  speech  and  music  were  quite 
clear.  The  opinion  is  growing  here  that  broadcast- 
ing is  the  main  sphere  of  wireless  in  the  future. 

On  my  return  to  London  in  March,  1922,  I 


Radio  Broadcast 


found  that  applications  were  being  made  to 
the  Post  Office  by  certain  wireless  manufactur- 
ing firms  for  permission  to  broadcast  pro- 
grams of  music,  etc.,  for  the  purpose  of 
promoting  the  sale  of  their  apparatus. 

ENGLAND  REFUSED  TO  GRANT  A   BROADCASTING 
MONOPOLY 

IT  SOON  became  evident  that,  within  the 
circumscribed  area  of  Great  Britain,  it 
would  be  impossible  to 
permit  the  establish- 
ment of  broadcasting 
stations  with  any- 
thing like  the  freedom 
which  was  being 
granted  in  America. 
It  was  equally  con- 
trary to  the  policy  of 
the  British  Govern- 
ment to  grant  a  mo- 
nopoly of  broadcast- 
ing to  one,  or  even  to 
two  or  three,  manu- 
facturing firms,  as  this 
would  place  them  in 
a  superior  position  to 
their  competitors  for 
pushing  the  sale  of 
their  goods. 

In  these  circum- 
stances, the  whole 
question  was  referred 
to  the  Imperial  Com- 
munications Commit- 
tee. This  committee 
is  composed  of  repre- 
sentatives  of  the 
Army,  Navy,  Air 
Force,  Post  Office, 
and  other  British  gov- 
ernment departments 
which  are  interested  in 

wireless.  It  is  presided  over  by  a  member  of 
the  Cabinet,  and  considers  all  important 
questions  of  imperial  policy  with  regard  to 
wireless  and  cables.  To  this  committee  I 
explained  the  position  which  had  arisen  in 
America,  and  the  difficulties  which  were 
presenting  themselves  in  England. 

The  Committee  recommended  that  an  en- 
deavor should  be  made  to  induce  the  various 
manufacturing  firms  to  cooperate  in  the 
establishment  of  a  single  Broadcasting  Com- 
pany, which,  it  was  thought,  might  be  al- 
lowed to  establish  stations  of  moderate  power 
(say  from  i|  to  3  kilowatts)  in  eight  areas, 
centering  on  London,  Birmingham,  Cardiff, 


Facts    From    Headquarters 

/COMPARISONS,  if  not  exactly  odious, 
^  are  frequently  too  easily  and  carelessly 
made.  One  hears  it  said  that  in  England 
the  radio  people  do  it  this  way,  or  that, 
which  is  better  or  worse  than  our  method, 
as  the  case  may  be.  This  story  of  affairs 
radio  in  England  is  authoritative  and  ex- 
tremely interesting  to  any  one  who  has 
wondered  how  England  has  handled  her 
radio  problems.  Mr.  Brown,  the  author,  was, 
until  last  January,  the  Assistant  Secretary 
of  the  British  Post  Office  and  in  administra- 
tive control  of  broadcasting  and  other  wire- 
less activities  for  the  Government.  He  tells 
in  interesting  fashion  just  what  happened 
in  England  to  the  licensing  system  which  was 
inaugurated  when  broadcasting  got  its  real 
start  there  in  November,  1922 — exactly  one 
year  after  regular  broadcasting  service  began 
in  this  country.  It  was  the  home  construc- 
tor who  spoiled  the  scheme  and  the  revised 
schedule  under  which  receiving  licenses  are 
now  granted  takes  him  into  consideration. 
This  article  by  Mr.  Brown  and  "How  the 
Government  Is  Regulating  Radio  Broadcast- 
ing" by  R.  S.  McBride  in  RADIO  BROADCAST 
for  May,  are  of  especial  interest  because  they 
show  how  the  two  governments  are  trying 
to  solve  their  administrative  problems. — THE 
EDITOR 


Plymouth,  Manchester,  Newcastle,  Edinburgh 
(or  Glasgow)  and  Aberdeen.  These  stations 
would  roughly  cover  the  whole  of  the  country. 
The  Committee  further  recommended  that  a 
band  of  wavelengths  from  350  to  425  meters 
should  be  assigned  to  the  stations.  They 
considered  that  the  Broadcasting  Company 
should  not  be  allowed  to  broadcast  advertis- 
ing matter,  or  to  receive  payment  for  matter 
broadcast.  They  also  considered  that,  as 
the  new  organization 
would  be  placed  in  a 
privileged  position  (in 
that  no  competitor 
would  be  allowed)  it 
was  only  fair  to  the 
press  and  the  news 
agencies  that  its  oper- 
ations as  a  distributor 
of  news  should  be 
rather  severely  re- 
stricted. They  pro- 
posed that  its  rev- 
enue should  be 
provided  mainly  by 
a  share  of  one-half 
of  the  license-fee  of 
ten  shillings  (about 
$2.50)  collected  by 
the  Post  Office  on 
the  issue  of  each  re- 
ceiving license. 

In  this  connection, 
it  should  be  men- 
tioned that,  in  Great 
Britain  (unlike  the 
United  States),  a  li- 
cense from  a  gov- 
ernmental authority 
has  always  been 
held  to  be  necessary 
for  each  receiving 
set,  as  well  as  for 
transmitting  apparatus. 

ENGLISH    BROADCASTING   BEGAN   IN  NOVEMBER, 
1922 

MR.  KELLAWAY,  who  was  Postmaster 
General  at  the  time  (he  has  since 
become  Managing  Director  of  the  Marconi 
Company),  threw  himself  into  the  scheme 
with  much  avidity;  and  on  May  4th,  1922,  he 
announced  in  the  House  of  Commons  that  he 
had  decided  to  allow  the  establishment  of  a 
limited  number  of  broadcasting  stations,  and 
was  calling  a  conference  of  the  firms  who  had 
applied  for  licenses  to  open  them.  This  con- 
ference was  held  a  fortnight  later  and  was  at- 


The  Story  of  Broadcasting  in  England 


177 


tended  by  representatives  of  twenty-four  firms. 
A  committee  of  manufacturers  was  subse- 
quently appointed  by  these  firms,  in  conjunc- 
tion with  all  other  firms  who  were  known  to  be 
engaged  in  the  manufacture  of  wireless  appara- 
tus. Prolonged  negotiations  took  place. 

At  one  stage,  the  negotiations  almost  broke 
down.  It  seemed  to  be  impossible  for  the 
manufacturers  to  agree  on  the  formation  of  a 
single  broadcasting  organization:  there  was  a 
marked  tendency  toward  a  division  into  two 
groups,  which  would  have  involved  the  crea- 
tion of  two  broadcasting  companies,  each 
representing  one  of  the 
groups.  But  finally  all  dif- 
ficulties were  surmounted 
and  a  single  broadcasting 
organization  was  formed — 
although  it  was  not  until 
January  i8th,  1923,  that  a 
license  was  actually  issued 
to  that  organization.  In 
the  meantime  (on  Novem- 
ber i5th),  a  daily  broad- 
casting service  had  been 
started  at  the  London  sta- 
tion, and  later  at  Birming- 
ham and  Manchester.  The 
issue  of  broadcast  receiving 
licenses  by  the  Post  Office 
began  November  i,  1922. 

HOW    ENGLAND    PLANNED 
BROADCASTING 

THE  scheme  as  embod- 
ied in  the  license  to 
the  broadcasting  organiza- 
tion was  recognized  from 
the  start  as  being  neces- 
sarily of  a  provisional  na- 
ture; and  the  term  of  the 
license  was  accordingly 
limited  to  two  years.  The 
principal  features  of  the 
scheme  have  been  officially 
summarized  as  follows: — 

(a)  A  Company  (called  the 
British  Broadcasting  Com- 
pany) to  be  formed  among 
British  manufacturers  of  wire- 
less apparatus.  Any  such 
manufacturer  to  be  entitled  to 
join  the  Company  upon  his 
subscribing  for  one  or  more 
£i  shares,  and  entering  into  an 
agreement  in  the  form  approved 
by  the  Postmaster  General. 

(b  The  Company  to  es- 
tablish eight  broadcasting 


stations  and  to  provide  a  regular  service  to  the 
reasonable  satisfaction  of  the  Postmaster  General. 
The  Company  to  pay  a  royalty  of  £50  per  annum  in 
respect  of  each  station. 

(c)  The  Post  Office  to  issue  broadcast  receiving 
licenses  at  a  fee  of  los.  a  year,  containing  a  condition 
that  the  sets  used,  and  certain  parts  (viz.,  valves, 
valve  amplifiers,  head  telephones,  and  loud  speakers), 
must   bear  a   standard   mark — "  B.    B.   C. — Type 
approved  by  Postmaster  General." 

(d)  The  Post  Office  to  pay  the  Company  a  sum 
equal  to  one  half  of  the  license  fees  received  in 
respect   of   broadcast    and    experimental    receiving 
licenses. 


RADIO    LISTENERS    IN    GERMANY 

Broadcasting  in  the  German  Republic  has  not  attained  as  great  popular- 
ity as  in  either  England  or  the  United  States.  England  is  very  com- 
pletely served  by  a  system  of  master  stations  and  small  local  relay  sta- 
tions. The  master  stations  in  the  larger  centers  originate  programs  of 
their  own  and  relay  programs  from  the  London  studio  of  the  Broadcasting 
Company.  This  system,  perfectly  suited  to  England,  could  hardly  be 
applied  to  American  conditions.  American  stations  have  been  "tied" 
together  for  programs  from  WEAF,  New  York,  but  the  "tie-up"  has  been 
usually  with  stations  only  as  far  west  as  the  Mississippi  because  of  the 
difference  in  time  between  New  York  and  the  Central  and  Far  West. 
The  German  enthusiasts  here  are  using  a  receiver  which  is  incorporated  in 
a  table  lamp.  The  loop  is  covered 


1 78 


Radio  Broadcast 


(e)  The  sets  sold  by  members  of  the  Company, 
as  a  condition  of  bearing  the  "  B.  B.  C."  mark,  to 
be  British  made,  to  carry  a  payment  to  the  Company 
in  accordance  with  a  tariff  approved  by  the  Post- 
master  General,    and    to    require    the    Postmaster 
General's  approval  of  the  type  of  set,  such  approval 
being  confined  to  securing  that  the  apparatus  would 
not  be  likely  to  cause  radiation  from  the  receiving 
antenna. 

(f)  No  advertising  or  paid  matter  to  be  broad- 
cast, and  only  such  news  as  is  obtained  from  news 
agencies  approved  by  the  Postmaster  General. 

(g)  The  Company  not  to  pay  dividends  at  a 
higher  rate  than  75  per  cent,  per  annum. 

(h)  An  understanding  to  be  given  that  the  re- 
quisite capital  would  be  subscribed,  that  the  service 
would  be  continued  throughout  the  period  of  the 
license,  and  that  any  deficit  should  be  met.  Six 
firms  undertook  these  responsibilities  and  were 
given  the  right  each  to  nominate  a  director,  two 
additional  directors  being  nominated  by  the  remain- 
ing firms  who  might  take  up  shares,  and  an  indepen- 
dent chairman  being  appointed  by  the  six  firms. 

THE    RADIO   CHILD   GROWS 

THE  scheme  excited  much  public  interest 
and  was,  on  the  whole,  well  received.  In 
the  winter  months  following  the  first  issue  of 
broadcast  receiving  licenses  by  the  Post  Office 
(on  November  i,  1922),  a  considerable  number 
of  these  licenses  were  sold.  By  the  end  of 
March,  1923,  the  total  was  about  150,000  and 
the  income  of  the  Company  from  all  licenses 
was  about  £60,000  (about  $1,270,000).  How- 
ever, at  that  time  difficulties  began  to  be 
encountered.  As  already  explained,  the  broad- 
cast receiving  license  was  applicable  only  to 
sets  bearing  the  "B.  B.  C."  mark.  But  in 
explaining  the  scheme  to  the  House  of  Com- 
mons in  July,  1922,  Mr.  Kellaway  had  given  an 
assurance  that  "provision  would  be  made 
under  which  amateurs  who  constructed  their 
own  receiving  sets  would  be  allowed  to  use 
them."  The  view  then  taken  by  the  Post 
Office  was  that,  if  a  person  were  sufficiently 
skilled  to  make  his  own  apparatus,  he  would 
have  sufficient  knowledge  of  the  subject  to  be 
described  as  an  experimenter,  and  to  be  en- 
titled to  hold  the  experimental  license  which 
the  Post  Office,  in  its  arrangements  with  the 
Company,  had  reserved  the  right  to  issue  in- 
dependently of  the  broadcast  receiving  license. 
I  will  say  that  the  Post  Office  at  that  time  had 
no  adequate  conception  of  the  extent  to  which 
members  of  the  public  would  make  their  own 
apparatus.  Moreover,  on  the  strength  of 
Mr.  Kellaway's  assurance,  firms  began  to 
place  on  the  market  ready-made  parts  which 
any  intelligent  person  could  build  up  into  an 
effective  receiving  set  by  the  aid  of  a  diagram 


and  a  screw-driver.  Such  persons  could 
obviously  not  properly  be  regarded  as  "experi- 
menters, and  it  would  not  have  been  fair  to 
the  Broadcasting  Company,  and  especially  to 
the  manufacturing  firms  who  constituted  that 
Company,  to  issue  experimental  licenses  to 
such  persons,  seeing  that  their  apparatus 
carried  no  royalty  payment  to  the  Broadcast- 
ing Company  and  provided  no  revenue  to  the 
manufacturer. 

THEN  CAME  THE  HOME  CONSTRUCTOR 

THE  Post  Office  had,  indeed,  no  license  to 
fit  the  case  of  these  persons.  The  ex- 
perimental license  was  not  applicable,  and 
they  were  not  entitled  to  the  broadcast  re- 
ceiving license,  inasmuch  as  it  covered  appara- 
tus bearing  the  B.  B.  C.  mark  only.  A  dead- 
lock had,  in  fact,  arisen.  Many  thousands 
of  "home  constructors"  were  applying  for 
licenses  and  their  demand  could  not  be  met. 
What  was  to  be  done?  Suggestions  were 
made  from  various  sources  that  a  new  type  of 
"constructor's  license"  should  be  issued;  but, 
although  the  Broadcasting  Company  agreed 
in  principle  to  the  issue  of  such  a  license, 
notwithstanding  the  fact  that  they  need  not 
have  done  so  under  the  terms  of  their  operat- 
ing license,  it  proved  impossible  for  the  Post 
Office  and  the  Company  to  arrive  at  an  agree- 
ment as  to  the  precise  conditions  upon  which 
such  licenses  should  be  issued.  A  situation 
intolerable  alike  to  the  Post  Office,  to  the 
Company  and  to  the  general  community  hav- 
ing thus  arisen,  Sir  William  Joynson-Hicks, 
who  was  then  Postmaster  General,  referred 
the  question  to  a  committee  known  as  the 
Broadcasting  Committee.  The  Committee 
comprised  representatives  of  the  Post  Office, 
of  the  Broadcasting  Company,  of  the  House 
of  Commons,  of  the  radio  amateurs  and  of 
the  general  public.  It  held  several  meetings, 
and  gave  the  most  careful  attention  to  the 
whole  subject.  Finally  it  recommended  sev- 
eral important  modifications  of  the  original 
scheme — although  it  recognized  that,  as  the 
original  proposal  had  been  embodied  in  a 
legal  agreement  between  the  Post  Office  and 
the  Broadcasting  Company,  these  modifica- 
tions could  not  be  carried  out  without  the 
consent  of  the  Company  until  that  agreement 
had  expired  at  the  end  of  1924.  The  sub- 
stance of  these  modifications  was  as  follows: 

(i)  A  uniform  and  simple  type  of  receiving  license 
at  i  os.  ($2.50)  to  be  issued  and  placed  on  sale  at 
Post  Offices  without  any  formalities — the  restric- 
tion against  the  use  of  apparatus  not  bearing  the 
"B.  B.  C."  mark  being  abolished. 


The  Story  of  Broadcasting  in  England 


179 


(2)  The    Broadcasting    Company    to    receive    a 
maximum  of  75.6^.  instead  of  55.— out  of  the  license 
fee,  subject  to  the  operation  of  a  sliding  scale  under 
which  the  payment  per  license  would  decrease  as 
the  number  of  licenses  increased. 

(3)  The  method  of  deriving  revenue  on  royalties  on 
the  sale  of  "  B.  B.  C."  apparatus  to  be  discontinued. 

(4)  Effective   measures   to   be   taken    to   prevent 
evasion  of  the  license,  and  certain  additional  statu- 
tory powers  to  be  obtained  to  strengthen  the  Post- 
master General's  hands. 

(5)  The  gradual  extension  of  the  broadcasting  of 
news  to  be  allowed  under  proper  safeguards. 

(6)  The  broadcast  band  of  wavelengths  (hitherto 
from  350  to  425  meters)  to  be  increased  so  as  to 
include  wavelengths  between  300  and   500  meters 
(except  those  from  440  to  460  meters  which  are  used 
for  maritime  purposes. 

(7)  The    Broadcasting   Company's   license   to   be 
extended  from  the  end  of  1924  to  the  end  of  1926, 
but  the  Government  to  keep  its  hands  free  to  grant 
additional  licenses  if  considered  desirable. 

The  Committee  paid  a  well  deserved  tribute 
to  the  excellent  service  provided  by  the  Broad- 
casting Company — a  tribute  which,  when  the 
Report  was  published,  was  generally  echoed 
by  the  press. 

SOLVING    A    DIFFICULT    PROBLEM 

WHEN  the  then  Postmaster  General,  Sir 
Laming  Worthington-Evans,  received 
the  Report  in  August,  1923,  he  immediately 
initiated  further  negotiations  with  the  Broad- 
casting Company.  He  found  the  Company, 
as  might  have  been  expected,  unwilling  to 
accept  the  Report  as  it  stood,  in  view  of  their 
strong  legal  position.  They  met  him,  how- 
ever, in  a  very  reasonable  spirit  and  a  com- 
promise was  arranged  without  serious  diffi- 
culty. This  compromise  had  been  tentatively 
suggested  while  the  Committee  was  sitting, 
and  both  parties,  as  well  as  the  public,  were 
well  satisfied  with  it.  Under  this  compromise, 
which  was  announced  about  the  beginning  of 
October,  1923,  it  was  agreed  that  up  to  the  end 
of  that  month  a  special  form  of  license,  known 
as  the  "interim  license,"  should  be  issued 
in  order  to  "whitewash"  the  many  unlicensed 
receiving  sets  which,  it  was  believed,  had  come 
into  existence  during  the  period  of  the  dead- 
lock. The  fee  for  this  "interim  license"  was 
to  be  155.  a  year,  out  of  which  the  Broad- 
casting Company  was  to  receive  \2s.6d.  In 
addition  to  this  form  of  license,  the  broad- 
cast receiving  license  at  ios.,  applicable  only 
to  apparatus  bearing  the  B.  B.  C.  mark,  was 
continue  to  be  issued;  and  a  constructor's 
license  at  155.  was  to  be  introduced,  applicable 
to  apparatus  made  or  put  together  by  or  on 
behalf  of  the  licensee  himself.  The  only 


special  condition  of  this  license  was  to  be  an 
undertaking  by  the  licensee  not  intentionally 
to  use,  in  the  construction  of  his  set,  material 
or  parts  made  elsewhere  than  in  Great  Britain. 

ONE    MILLION    TWO    HUNDRED    THOUSAND    RE- 
CEIVER   LICENSES    IN    ENGLAND 

THERE  was  immediately  a  very  large 
demand  for  the  "interim  license,"  and 
some  200,000  of  these  were  issued  up  to  the 
end  of  October.  The  constructor's  license 
also  proved  popular,  being  issued  in  the  pro- 
portion of  about  two  to  one  B.  B.  C.  license. 
The  total  number  of  licenses  continued  to 
grow  at  a  rapid  rate,  and  by  the  end  of  the 
year  it  had  reached  about  500,000.  Each 
month  of  the  new  year  also  saw  a  rapid  growth, 


THE  MASTS  OF  THE  NEW  BRITISH  STATION 
Which  will  soon  be  opened  at  Daventry.  This 
station  will  use  1600  meters  and  about  25  kilowatts 
and  will  originate  programs  of  its  own  as  well  as 
broadcasting  programs  from  the  main  London  studio 
of  the  British  Broadcasting  Company.  The  site 
of  the  station  is  600  feet  above  sea  level  and  the 
ground  itself  is  about  300  feet  above  the  surrounding 
territory.  The  two  masts  are  500  feet  high  and  800 
feet  apart 


i8o 


Radio  Broadcast 


although  there  was  some  falling  off  during  the 
summer  months.  By  October,  1924,  the  total 
had  practically  reached  1,000,000  and  at  the 
time  of  writing  (February,  1925,)  it  is  1,200,000. 
In  the  new  arrangements  with  the  Broad- 
casting Company,  the  Postmaster  General 
had  reserved  the  right  to  issue  on  January  ist, 
1925,  the  simple  and  uniform  license  (at  los.) 
which  had  been  recommended  by  the  Broad- 
casting Committee.  In  view  of  the  fact  that 


;  THE    CHELMSFORD    MAST 

Of  the  experimental  station  jxx  of  the  British  Broadcasting  Company.  The  usual 
broadcast  wavelengths  of  the  various  English  stations  are  much  the  same  as  in  this 
country,  but  jxx  uses  a  1600  meter  wavelength  and  a  power  of  about  25  kilowatts. 
The  Broadcasting  Company  engineers  were  testing  with  this  station  the  possibilities 
of  using  a  high  powered  station,  located  at  a  central  point,  broadcasting  programs 
to  be  picked  up  anywhere  in  England  with  a  crystal  receiver 


this  further  reform  was  drawing  near,  and 
that  there  would  be  difficulty  in  inducing  the 
public  to  pay  15$.  for  the  constructor's 
license  in  the  autumn  of  1924  instead  of  wait- 
ing until  the  beginning  of  1925  to  secure  a 
license  for  ios.,  the  Broadcasting  Company 
agreed  to  introduce  this  further  reform  at  an 
earlier  date.  The  growth  in  the  number  of 
licenses,  and  consequently  in  their  revenue, 
had  put  them  in  a  good  financial  position; 

and  they  accord- 
ingly agreed  that 
the  ios.  license 
should  be  issued 
as  from  July  ist, 
1924.  The  condi- 
tion about  British 
manufacture  was 
to  be  retained  until 
the  end  of  the  year. 
This  reduction  in 
the  license  fee  no 
doubt  assisted  in 
the  growth  in  the 
number  of  licenses 
above  referred  to. 
On  and  from  Jan- 
uary ist,  1925,  a 
simple  form  of 
license  (at  ios.), 
without  any  re- 
striction as  to  the 
country  of  origin 
of  the  licensed  ap- 
paratus, has  been 
in  existence. 

Meanwhile,  with 
the  increase  in  rev- 
enue, the  Broad- 
casting Company 
had  been  able  to 
maintain  a  very 
efficient  service  at 
their  original  sta- 
tions, and  they  also 
had  been  able  to 
erect  a  number  of 
additional  stations. 
These,  for  the  most 
part,  have  been  so- 
c ailed  relay  sta- 
tions, with  a  power 
of  from  100  to  200 
watts.  A  more  in- 
teresting develop- 
ment, however,  has 
been  the  use,  ex- 
perimentally, of 


The  Story  of  Broadcasting  in  England 


181 


a  much  higher-powered  station.  For  this 
experimental  work  a  2O-kilowatt  station  of 
the  Marconi  Company  at  Chelmsford  has 
been  used,  and  the  effect  of  its  use  upon  other 
services  has  been  closely  watched  by  the . 
government  experts,  in  order  to  see  whether 
undue  interference  was  likely  to  be  caused. 
On  the  whole  the  results  were  satisfactory; 
and  the  Company  was  accordingly  given  per- 
mission to  erect  a  permanent  station  at 
Daventry  (near  the  center  of  England). 
This  station  is  now  nearing  completion.  It 
will  use  a  wavelength  of  1600  meters  and  will 
broadcast  an  independent  program,  which 
will  be  transmitted  from  London  by  means  of 
the  ordinary  telephone  circuits  and  then  re- 
layed. This  station  will,  it  is  expected, 
enable  programs  to  be  received  by  a  simple 
crystal  set  within  a  radius  of  about  100  miles, 
as  compared  with  the  crystal  radius  of  about 
ten  or  fifteen  miles  which  is  covered  by  the  ex- 
isting main  stations  of  the  Company,  and  the 
crystal  radius  of  four  or  five  miles  which  is 
covered  by  the  relay  stations.  It  is  possible 
that  the  Company  may  wish  to  erect  similar 
high-powered  stations  in  other  parts  of  the 


country,  with  the  object  of  bringing  practi- 
cally the  whole  population  within  crystal 
radius. 

THE    BRITISH    LICENSING    SCHEME    IS    WORKING 

SINCE  the  revised  scheme  of  licensing 
was  brought  into  operation  in  October, 
1923,  the  arrangements  have  worked  with 
remarkable  smoothness  and  success.  Those 
who  have  been  concerned  with  them  flatter 
themselves  that  the  arrangements  have  re- 
sulted in  what  is  probably,  on  the  whole,  the 
most  satisfactory  and  efficient  broadcasting 
service  in  the  world.  It  is,  of  course,  ex- 
tremely doubtful  whether  the  same  arrange- 
ments could  have  been  adopted  in  the  United 
States,  where  no  attempt  has  ever  been  made 
to  introduce  a  licensing  system  for  receiving 
sets.  Where  the  public  have  once  got  into  the 
habit  of  installing  receiving  sets  without  let 
or  hindrance  it  would  be  a  very  difficult  mat- 
ter to  induce  them  to  accept  licenses  and  to 
pay  a  licensing  fee.  Hence,  I  do  not  for  a 
moment  suggest  that  the  system  which  has 
been  applied  in  Great  Britain  would  be  suit- 
able for  the  United  States.  But  here,  where 


APPARATUS    AT   THE    GLASGOW    STATION 

Of  the  British  Broadcasting  Company.     Many  of  the  switches  in  the 
foreground  are  for  controlling  the  wire  lines  between  the  various  stations 


1 82 


Radio  Broadcast 


the  licensing  habit  is  already  in  existence,  it 
has  proved  a  very  simple  and  efficient  method 
of  collecting  funds  for  the  purpose  of  the 
broadcasting  service — a  matter  which,  1 
understand,  is  likely  eventually  to  result  in  a 
rather  difficult  problem  in  America.  No 
doubt  there  is  some  amount  of  evasion  in 
Great  Britain;  how  much  evasion,  there  is 
no  means  of  saying:  but  that  the  evasion  runs 
to  the  lengths  which  some  suggest  is  quite 
improbable.  The  figures,  in  fact,  speak  for 
themselves.  There  are  1,200,000  licenses  in 
existence  at  the  present  moment.  The  same 
ratio  of  licenses  to  population  would  give  a 
total  of  nearly  4,000,000  licenses  if  the  popula- 
tion of  Great  Britain  were  as  large  as  that  of 
the  United  States.  Of  course,  no  one  knows 
how  many  households  have  receiving  sets  in 
the  United  States;  but  I  think  the  most  au- 
thoritative estimates  place  the  number  at 
between  5,000,000  and  6,000,000.  Bearing 
in  mind  the  greater  prevalence  of  the  telephone 
habit  in  the  United  States  than  in  Great 
Britain,  one  may  reasonably  assume  that  the 
habit  of  broadcast  reception  is  also  more 
widely  spread  in  the  States  than  here.  And 
taking  these  factors  into  account,  one  may 
safely  conclude  that  the  great  majority  of 
listeners  in  Great  Britain  and  Ireland  have 
taken  out  licenses. 

But  of  late  a  source  of  difficulty  has  arisen. 
Hypercritical  persons  have  been  examining  the 
Wireless  Telegraphy  Act  of  1904,  upon  which 
the  whole  system  of  licensing  is  based,  and 


have  raised  the  question  whether  it  really 
applies  to  receiving  sets  at  all,  as  distinct  from 
sending  sets.  I  am  not  a  lawyer,  but  1  know 
the  opinion  of  lawyers  who  are  well  qualified 
to  judge;  and,  personally,  1  have  no  doubt  in 
the  matter  at  all.  The  question,  however, 
has  never  been  referred  to  a  Court  of  Law,  so 
that  there  is  no  authoritative  decision  on  the 
subject;  and  the  Postmaster  General,  rather 
than  risk  an  adverse  decision,  has  decided 
that  no  proceedings  shall  be  taken  against  any 
person  who  fails  to  take  out  a  license  for  a 
receiving  set,  until  the  point  has  been  placed 
beyond  the  shadow  of  doubt  by  means  of  new 
legislation  which  he  has  recently  introduced  in 
the  House  of  Commons.  This  decision  has 
no  doubt  resulted  in  some  decrease  in  the 
number  of  licenses  taken  out;  but  one  is  in- 
clined to  believe  that  the  great  majority  of 
the  public  are  disposed  to  play  fair  in  this 
matter  and,  irrespective  of  the  Postmaster 
General's  decision,  to  contribute  their  quota 
to  the  expenses  of  the  broadcast  programs  to 
which  they  listen.  The  new  Bill,  besides 
setting  this  point  at  rest,  imposes  a  number  of 
new  provisions  in  regard  to  licensing  which  do 
not  in  particular  apply  to  broadcasting:  and, 
as  I  write,  it  is  arousing  a  good  deal  of  criticism 
in  Parliament  and  the  press.  What  will  be 
its  fate  does  not  yet  appear;  but  the  system 
of  licensing  in  connection  with  the  broadcast- 
ing arrangements  has  proved  so  convenient 
and  popular  that  one  cannot  imagine  that 
Parliament  will  scrap  it. 


ENGLISH    BROADCASTING    APPARATUS 

Is  not  very  different  from  that  used  by  most  American  stations.     One  of  the 
British  stations,  indeed,  uses  apparatus  manufactured  by  an  American  company 


THE    U.    S.    S.        SHENANDOAH 

During  the  recent  transcontinental  trip  of  the  Shenandoah,  the  Naval  radio  operators  aboard  the  ship  were 
in  constant  communication  through  their  short  wave  transmission  with  radio  amateurs  in  all  parts  of  the 
country,  as  well  as  with  the  Naval  Laboratory  at  Belleview,  near  Washington.  A  wavelength  of  80  meters 
was  used.  The  cooperation  extended  by  the  amateurs  in  this  instance  was  one  of  many  examples  of  a 

similar  sort 


New  Paths  for  the  Short  Waves 

Details  of  the  Great  Contributions  Made  by  the  American  Radio 
Amateur  to  Radio  Transmitting  Knowledge — How  the  Amateurs  Are 
Cooperating  With  the  Navy— A  New  Theory  for  Radio  Transmission 

BY  KENNETH  BOLLES 


THE  first  congress  of  the  International 
Amateur  Radio  Union  which  was  held 
in  Paris,  April  14  to  19,  with  many 
delegates   present  speaking   a    great 
variety  of  languages,  is  really  the  first  practi- 
cal indication  that  amateur  radio  is  destined 
to  become  an  efficient  and  orderly  world  force. 
It  has  taken  hardly  two  years  for  amateur 
radio  to  grow  from  a  localized  activity,  chiefly 
confined  to  the  United  States,  to  an  inter- 
national relay  system  with  far  reaching  in- 
fluence.    It   must   have  its  regulations   and 
understandings  in  order  that  equal  freedom 
and  fair  play  may  be  given  to  those  who  de- 
sire   to    participate    in    its    activities.     The 


congress  is  the  first  official  step  in  making  such 
provisions. 

Amateur  radio,  under  the  guidance  of  the 
American  Radio  Relay  League,  has  trained 
some  20,000  young  men  in  the  principles  of 
radio  science  and  in  a  knowledge  of  the  code. 
Those  who  refer  to  it  as  purely  a  sport  reckon 
without  a  true  appreciation  of  its  influence 
in  the  development  of  commercial  radio  and 
broadcasting.  Hiram  Percy  Maxim,  and  Ken- 
neth B.  Warner,  president,  and  secretary  of 
the  A.  R.  R.  L.,  respectively,  and  delegates 
to  the  I.  A.  R.  U.,  said  upon  leaving,  that  they 
believed  international  friendships  by  radio 
would  be  a  factor  in  bringing  world  peace. 


1 84 


Radio  Broadcast 


They  said  that  in  all  countries,  where  ama- 
teurs are  found,  hope  may  be  held  for  swift 
progress  in  all  lines  of  radio  science. 

The  progress  of  amateur  radio  is  already 
being  realized  by  governments  of  various 
countries  where  amateurs  are  active.  The 
1.  A.  R.  U.  may  crystalize  the  opinion  of 
amateurs  all  over  the  world  for  the  benefit  of 
those  countries  which 
desire  technical  guid- 
ance in  drawing  up 
regulations  governing 
private  international 
communication.  The 
desire  of  amateurs  to 
gain  the  utmost  free- 
dom is  no  stronger 
than  their  wish  to 
turn  over  to  the  radio 
public  the  results  of 
their  deductions  and 
experiments. 

What  have  the  am- 
ateurs done  to  war- 
rant any  sort  of  world- 
wide recognition? 
What  practical  thing 
have  they  accom- 
plished that  would 
justify  giving  them 
greater  freedom? 
Almost  everyone  is 
familiar  with  their 
message  handling 
during  emergencies, 
their  cooperation 
with  the  American 
Railway  Association, 
their  assistance  to  the 
Navy  Department 
during  the  transcon- 
tinental trip  of  the 
Shenandoab ,  but 
these  are  outside  of 
their  established  rou- 
tine and  are  not  as 

convincing  as  those  things  which  are  a  last- 
ing and  permanent  benefit  to  radio  develop- 
ment. 

WHAT    HAVE    THE    AMATEURS    DONE? 

THE  one  great  outstanding  contribution  of 
amateurs  to  .the  radio  art  is  their  de- 
velopment of  the  short  waves.  They  have 
gone  farther  in  this  field  than  any  other  group. 
They  have  proved  short  waves  are  of  unsus- 
pected importance.  The  various  radio  groups 
have  become  interested  in  these  bands  be- 


A  Record  of  Accomplishment 

HpHE  American  Radio  Relay  League  is 
*  one  of  the  unique  organizations  in  Amer- 
ica— a  land  of  many  organizations.  It  was 
founded  a  little  over  ten  years  ago  to  band 
together  amateur  radio  telegraph  experimen- 
ters whose  activities  were  largely  concerned 
with  exchanging  private  messages  with  one 
another  over  comparatively  short  distances. 
Now,  more  than  15,000  experimenters  are 
members  and  the  exchange  of  messages  is  but 
a  small  part  of  their  activities.  Perhaps  the 
field  in  which  they  have  aroused  most  interest 
is  in  their  experiments  with  very  short  radio 
waves.  Every  reader  of  newspapers  knows 
that  the  only  link  that  Donald  MacMillan  had 
with  the  outside  world  when  he  made  the 
recent  trip  of  exploration  in  the  Arctic  was 
that  forged  by  amateur  radio  communication. 
The  Department  of  Commerce  recently  re- 
cognized the  excellent  development  work  the 
radio  amateurs  were  doing  with  short  waves 
by  granting  them  a  band  of  waves  between 
.7496  and  .7477  meter.  The  present  article 
describes  some  of  the  activities  of  the  Amer- 
ican Radio  Relay  League  and  tells  particu- 
larly of  the  work  of  two  of  their  most  prom- 
inent members,  John  L.  Reinartz,  and  F.  H. 
Schnell.  The  work  of  these  earnest  amateurs 
is  reflected  in  their  excellent  and  authorita- 
tive publication,  Q  S  T,  and  the  Navy  De- 
partment has  shown  its  confidence  in  their 
earnestness  by  arranging  to  have  Mr.  Schnell, 
Traffic  Manager  of  the  League,  accompany 
the  Pacific  fleet  on  its  manoeuvres  this  sum- 
mer.— THE  EDITOR 


cause  of  the  pioneer  work  that  has  been  done 
by  amateurs. 

With  these  short  bands  given  over  to  their 
exclusive  use,  amateurs  in  this  country  have 
demonstrated  they  can  send  their  signals 
to  any  part  of  the  world  where  there  are  radio 
fans  and  radio  receivers  to  pick  them  up.  It 
has  become  practically  impossible  to  name 
any  country  in  the 
world  where  local 
amateurs  are  at  all 
active  that  has  not 
heardAmerican  ama- 
teurs calling. 

The  signals  of  oper- 
ators on  the  west 
coast  of  this  country 
are  being  heard  regu- 
larly in  South  Amer- 
ica and  over  sim- 
ilar distances, 
almost  with  as  much 
ease  as  European  and 
American  amateurs 
could  communicate 
with  one  another  a 
year  ago.  English 
and  New  Zealand 
"brasspounders" 
demonstrate  their 
superior  skill  by  com- 
municating with  the 
Antipodes.  Barthol- 
omew Molinariof  San 
Francisco,  winner  of 
the  Hoover  amateur 
efficiency  cup  for 
1924,  reports  that  his 
signals  ha've  been 
heard  in  the  following 
lands  and  islands: 
France,  England, 
Italy,  Chile,  Argen- 
tina, Cuba,  Panama, 
Tahiti,  Tonga,  Sa- 
moa, Pribiloff  Is- 
lands, Tasmania,  Korea,  China,  British  India, 
South  Africa,  Philippine  Islands,  Malay 
Straits  Settlements,  on  ships  off  Cape  Horn 
and  off  the  coasts  of  Borneo,  Guatemala, 
Honduras,  Nicaragua  and  Costa  Rica,  and 
the  Republic  of  Salvador. 

The  assumption  upon  reading  this  and  many 
other  similar  records,  is  that  short  waves  and 
low  power  are  as  capable  of  covering  as  great 
distances  as  long  waves  and  high  power  at  aj 
cost  that  is  astonishingly  less. 

That  the  development  of  short  waves  has  < 


New  Paths  for  the  Short  Waves 


by  no  means  been  exhausted  was  demon- 
strated recently  by  two  important  events, 
one  of  these  being  the  decision  of  the  Navy 
Department  to  seek  the  cooperation  of  Ameri- 
can Radio  Relay  League  amateurs  in  an 
investigation  of  short  waves  during  manoeu- 
vers  of  the  Pacific  Fleet  this  summer;  the 
other,  the  announcement  of  John  L.  Reinartz's 
theory  of  daylight  transmission. 

WHAT   THE    AMATEURS    ARE    DOING 

IN  ORDER  to  carry  out  the  navy  experi- 
ments successfully,  F.  H.  Schnell,  traffic 
manager  of  the  American  Radio  Relay  League 
who  has  been  given  a  seven  months'  leave  of 
absence  by  the  League,  will  conduct  tests  with 
amateurs  in  many  countries.  His  work  will 
serve  as  one  more  important  link  between 
American  amateurs  and  transmitting  opera- 
tors in  other  parts  of  the  world,  and  he  will,  at 
the  same  time,  demonstrate  under  official 
supervision  what  short  waves  can  do.  His 
experience  as  traffic  manager  of  the  A.  R.  R.  L. 
has  given  him  a  wide  acquaintance  among  am- 
ateurs which  the  Navy  believed  would  be  of 
great  service  in  the  short  wave  tests  and  so  it 
called  him  in  active  service  in  the  Depart- 
ment with  the  rank  of  lieutenant. 

It  is  significant  that  following  closely  upon 
the  first  international  amateur  congress,  the 


U.  S.  S.  Seattle  is  now  steaming  in  Pacific 
waters  equipped,  among  other  apparatus,  with 
a  typical  amateur  radio  transmitter  and  re- 
ceiver. This  first  amateur  type  station  to 
be  installed  on  a  Navy  ship  will  have  the  call 
NRRL.  One  may  imagine  the  interest  and 
enthusiasm  in  which  amateurs  in  Australasia, 
the  Philippine  Islands,  China,  Japan,  South 
America,  and  probably  Europe  and  Africa 
will  listen  for  this  special  Navy  station,  pleased 
with  the  thought  that  the  communication 
they  have  helped  to  build  has  been  recognized 
by  the  United  States  Navy. 

THE  y.  s.  s.  "SEATTLE"  EXPERIMENTS 

THE  amateurs  who  intend  to  listen  for 
NRRL,  no  matter  whether  they  are  located 
in  this  or  foreign  countries,  must  be  prepared 
to  tune-in  on  a  number  of  different  wave- 
lengths, for  the  tests  are  to  cover  several  bands 
of  short  waves.  At  night,  the  main  set  at 
NRRL  will  transmit  on  54.4  meters  while  in 
daylight  it  will  shift  to  27.2  meters.  There 
will  also  be  transmitters  functioning  on  20, 
40,  and  80  meters. 

If  it  is  found  that  the  low  power  amateur 
stations  employing  less  than  one  kilowatt  are 
just  as  efficient  as  regards  the  distance  cov- 
ered and  dependability  of  operation,  it  may 
be  seen  very  readily  that  their  use  would  mean 


JOHN    L.    REINARTZ 

Of  South  Manchester,  Connecticut.     Mr.   Reinartz,  using  a  wavelength  of  21  meters  and  low  power 

recently  established  communication  with  an  amateur  on  the  Pacific  coast  at  noon.    This  remarkable  feat 

showed  strikingly  the  possibilities  of  short  wave  radio  work 


1 86 


Radio  Broadcast 


LIEUTENANT  F.  H.  SCHNELL 

Traffic  manager  of  the  American  Radio  Relay 
League.  Mr.  Schnell  has  been  commissioned  a 
Lieutenant  in  the  Navy,  assigned  to  the  fleet  on  its 
Pacific  cruise  this  summer.  He  will  experiment 
with  short  radio  waves  and  communicate  with 
transmitting  amateurs  all  over  the  world.  The 
American  Radio  Relay  League  has  about  20,000 
members,  excellently  organized  for  intercommunica- 
tion by  radio.  Members  of  the  organization  have 
communicated  great  distances  using  short  wave- 
lengths and  very  low  power 

a  tremendous  saving  in  the  cost  of  the  initial 
radio  installation.  The  average  amateur 
transmitter  can  be  put  together  for  about 
$250.  while  the  high  power  navy  set  may 
average  somewhere  around  $6000.  It  is 
even  possible  that  if  the  tests  made  by  NRRL 


are  quite  successful,  we  may  see  the  Navy 
changing  to  low  wave  sets  in  preference  to 
the  longer  wave,  high  power  transmitters 
they  are  now  using. 

The  reader  should  not  interpret  from  this 
that  the  Navy  is  just  now  beginning  to  show 
an  interest  in  the  short  waves,  for  it  has  been 
working  hand  in  hand  with  amateurs  for  some 
time.  Some  of  the  most  important  experi- 
ments ever  made  in  connection  with  low  power 
transmission  have  been  undertaken  through 
correct  cooperation  between  the  Navy  and 
amateur  operators.  The  Navy  has  been  us- 
ing short  wave  transmitters  on  certain  ships 
for  many  months  and  as  long  as  two  years 
ago,  the  short  wave  station  of  the  U.  S.  S. 
Oloio  was  heard  on  the  west  coast. 

The  theory  of  daylight  transmission  pre- 
viously mentioned  in  this  article  was  a  direct 
result  of  tests  conducted  by  John  L.  Reinartz 
at  South  Manchester,  Connecticut,  and  Dr. 
A.  H.  Taylor  of  the  Naval  Research  Labora- 
tory at  Bellevue,  Washington,  D.  C.  The 
experiments  which  they  started  a  year  ago 
are  still  in  progress.  As  a  result  Reinartz 
has  demonstrated  repeatedly  that  with  a 
low  powered  transmitter  using  2 1  meters,  great 
distances  can  be  covered  in  daylight.  While 
transmitting  from  his  station  at  South  Man- 
chester, Connecticut,  about  noon,  Eastern 
Standard  Time,  his  signals  have  been  heard 
by  amateurs  on  the  west  coast,  in  Florida, 
and  in  England,  and  he  has  several  times  con- 
ducted two-way  communication  direct  with 
the  Pacific  coast  at  noon. 

This  gave  definite  proof  that  the  very 
short  waves  travel  farther  in  the  daytime 
than  they  do  at  night,  which  is  the  reverse  of 
what  has  already  been  known,  that  the  long 


THE    2OO   WATT   TUBE   TRANSMITTER 

For  use  on  very  short  waves  which  Mr.  Schnell  will  use  for  experimental  communi- 
cation while   he   accompanies   the   Navy  fleet  on  its  Pacific  cruise  this  summer 


i87 


THE    U.    S.    S.        SEATTLE 

Where  Mr.  Schnell  will  make  his  headquarters  during  his  short  wave  tests.  The  Navy  has  shown  great 
interest  in  the  possibilities  of  short  wave  communication  and  is  cooperating  with  the  American  radio  ama- 
teurs who  have  contributed  a  great  deal  to  the  development  of  this  transmission.  At  present,  Naval  com- 
munication is  carried  on  chiefly  by  long  wave  high  power  radio  transmitters,  which  are  not  only  expensive, 
but  subject  to  the  familiar  effects  of  daylight  fading 


waves  could  cover  great  distances  at  night,  but 
were  unable  to  travel  very  far  under  daylight 
conditions.  Until  then,  it  was  thought  the  ion- 
ization  of  the  atmosphere  caused  by  the  sun's 
rays  had  practically  the  same  unfortunate  ef- 
fect on  all  waves  and  that  daylight  might  be 
always  a  big  hindrance  to  radio  transmission. 

THE    EFFICIENCY    OF    SHORT    WAVES 

IN  ADDITION  to  making  the  bare  discovery, 
Mr.  Reinartz  developed  a  theory  which  ap- 
pears to  explain  the  phenomenon  satisfactorily. 
It  is  based  on  the  well  known  fact  that  radio 
waves  are  reflected  by  the  atmosphere  in  the 
same  manner  that  light  rays  are  reflected 
with  the  aid  of  a  polished  surface.  The  dis- 
tance that  radio  waves  will  travel  in  daylight 
is  determined  by  the  length  of  the  wave,  for 
it  appears  it  is  this  factor  which  controls  the 
height  at  which  the  reflection  takes  place. 

There  is  a  definite  relationship  which  con- 
nects the  position  and  effect  of  the  sun  with 
the  length  of  the  radio  wave  and  the  distance 
that  it  will  be  reflected.  The  depth  of  the 
reflecting  layer  varies  with  the  time  of  day 
and  season.  The  shorter  waves  seemingly 
have  the  peculiar  faculty  of  penetrating 
farther  into  the  ionization  layer  and  they  are 
therefore  capable  of  being  reflected  to  a  much 
greater  distance. 


"The  fact  that  the  shorter  wave  penetrates 
the  ionization  layer  to  a  greater  height," 
declares  Mr.  Reinartz,  "causes  the  reflection  to 
take  place  at  a  higher  altitude  than  would  be 
the  case  for  the  longer;  therefore,  the  diameter 
of  the  circle  at  which  the  short  wave  again 
appears  on  the  earth's  surface  is  larger. 
Inside  of  this  circle  there  is  no  evidence  of 
the  radio  wave  until  one  gets  very  close  to  the 
transmitting  station.  The  reason  for  this 
is  that  the  waves  which  travel  along  the 
earth's  surface  have  been  subjected  to  all  the 
absorbing  influence  which  that  surface  car- 
ries, while  those  which  went  up  to  the  ionized 
layer  and  were  reflected  back  have  traveled 
through  a  considerable  space  and  very  little 
energy  has  been  lost.  This  makes  it  possible 
to  cover  tremendous  distances  with  but  a 
fraction  of  the  energy  needed  for  some  of  the 
longer  waves. 

"It  is  possible  to  use  this  information  in 
such  a  way  as  to  obtain  reliable  daylight 
ranges  considerably  in  excess  of  reliable  night 
ranges  obtainable  with  the  same  power." 

Mr.  Reinartz  makes  the  prediction  that  this 
year  will  see  communication  established  be- 
tween amateurs  of  the  United  States  and  Aus- 
tralasia on  a  wavelength  of  about  20  meters 
in  broad  daylight.  Mr.  Reinartz  will  have  an 
intensely  interesting  opportunity  to  test  his 


1 88 


Radio  Broadcast 


theory  when  he  leaves  as  operator  on  Donald 
MacMillan's  Bowdoin  on  June  i5th  of  this 
year.  Extensive  experiments  are  to  be  carried 
on  with  daylight  transmission  on  20  meters 
while  the  ship  is  in  polar  waters.  Mr.  Rein- 
artz  as  operator,  has  been  appointed  to  the 
place  held  by  Donald  Mix  aboard  this  ship 
on  the  previous  voyage.  Mr.  Mix  is  also 
a  member  of  the  American  Radio  Relay 
League. 

Both  those  appointments  show  beyond 
question  the  value  placed  on  amateur  talents. 

For  a  number  of  years  American  amateurs 
worked  with  all  of  their  might  to  send  their 
signals  across  the  Atlantic  ocean.  Their  final 
success  marked  the  real  beginning  of  inter- 
national amateur  communication  for  it  was 
not  until  that  time  that  the  future  possibilities 
of  low  power  and  short  waves  were  fully  real- 
ized. Their  next  task  was  so  to  perfect  their 
instruments  and  method  of  operation  that 


they  could  exchange  messages  at  will  with 
private  individuals  in  various  foreign  coun- 
tries. 

Immediately  that  two-way  communication 
was  established  between  amateurs  on  oppo- 
site sides  of  the  ocean,  interest  of  operators 
in  this  country  reached  a  high  state  of  en- 
thusiasm and  amateurs  began  to  spring  up 
here  and  there  in  countries  where  they  had 
never  been  heard  of  before,  until  now  they 
may  be  found  dotting  almost  every  part  of 
the  world.  Three  or  four  years  ago  American 
amateurs  kept  before  them  constantly  a  wall 
map  of  the  United  States,  while  now  in  these 
same  radio  shacks  may  be  found  world  maps 
and  globes. 

With  one  kilowatt  of  power  and  a  barrel 
of  enthusiasm,  amateurs  threaten  to  conquer 
the  three  obstacles  to  radio  communication, 
time,  space,  and  daylight,  using  short  waves 
that  once  nobody  thought  were  of  value. 


THE  WINNER  OF  THE  HOOVER  CUP  FOR  1924 

Bartholomew  Molinari,  owner  of  amateur  radio  station  6  AWT,  San  Francisco.     The  transmitter  is  one  250- 

watt  tube,  shown  on  the  panel  in  the  lower  left.     Note  the  wall  map  of  the  world,  dotted  with  colored  pins, 

showing  the  various  parts  of  the  world  in  which  6  AWT  has  been  heard.     Ten  years  ago,  distance  records 

such  as  these  would  have  been  considered  an  absolute  impossibility 


Making  Radio  Receivers  More 

Selective 

Practical  Instructions  on  How  to  Improve  the  Selectivity  of  Various  Popular 
Circuits  in  Use — A  Clear  Explanation  of  the  Theory  Involved  in  the  Changes 


BY  KEITH   HENNEY 


THE  problem  that  has  been  bothering  many  radio  listeners  recently,  is  one  of 
the  selectivity  of  their  receivers.  Mr.  Henney,  in  this  article,  has  discussed 
the  whole  question  of  selectivity.  There  is  such  a  variety  of  circuits  and  sets  to 
be  considered  when  one  tries  to  solve  the  problem  of  increasing  the  sharpness  of 
tuning  that  a  general  consideration  such  as  this,  we  think  is  the  best  way  to  help 
the  individual.  This  is  distinctly  not  a  how-to-make-it  article,  but  the  reader  will 
find  all  the  necessary  constructional  information  given.  The  individual  can  apply 
this  information  to  suit  his  own  problem.  The  suggestions  here  given  are  more  in 
the  nature  of  a  remedy  than  a  cure.  The  real  cure  for  the  situation  lies  in  a  re- 
adjustment of  the  broadcast  transmitting  situation.  We  believe  that  Mr.  Henney's 
discussion  of  the  theory  involved  here  will  prove  very  helpful  to  the  radio  con- 
structor.— THE  EDITOR 


ACCORDING    to    the    average    radio 
listener,   the   flaws   in  the  present 
scheme  of  broadcasting  are  two:  the 
multiplicity  of  stations  and  the  ap- 
proach of  "super-power."     And  in  his  pecu- 
liar dilemma  of  wanting  to  be  in  touch  with 
all  that  goes  on  in  the  ether  and  yet  to  be 
exclusive,  the  listener  must  turn  in  but  one 
direction,  to  increased  selectivity. 

Whether  the  problem  is  to  doctor  a  receiver 
now  in  operation  or  to  build  a  set  that  will  be 
sufficiently  selective,  the  questions  that  face 
the  radio  listener  are  the  same: 
What  is  selectivity? 
How  may  it  be  obtained? 
How  much  is  necessary,  or  desirable? 

WHAT    IS    SELECTIVITY? 

CELECTIV1TY  is  a  relative  term,  and 
^  signifies  the  ability  of  a  receiver  to  dis- 
tinguish between  several  transmitting  stations 
operating  on  frequencies  that  do  not  differ 
much  from  one  another.  To  take  an  analogy 
from  the  phonograph  field,  let  us  suppose 
that  the  mechanism  for  recording  music  would 
respond  only  to  those  tones  that  lie  between 
middle  C  and  one  octave  above.  Then  no 
matter  how  many  notes  a  pianist  might  play, 
the  mechanism  would  record  only  those  be- 
tween the  proper  limits.  In  other  words,  the 


recording  apparatus  would  be  selective,  and 
other  tones  would  not  bother  it. 

Broadcasting  stations  in  Class  B  are  now 
stationed  10,000  cycles  apart.  A  receiver 
sufficiently  selective  will,  respond  to  only  one 
station  at  a  time.  Frequencies  10,000  cycles 
different  from  that  to  which  the  receiver  is 
tuned  will  not  be  heard  to  any  marked  degree. 


799  800  801      KILOCYCLES 


799  800  801 
FREQUENCY  IN   KILOCYCLES 

FIG.     I 

The  current  in  a  receiving  circuit  increases  as  the 
resonance  point  is  reached,  as  shown  in  this  Figure. 
This  receiver  would  be  too  sharp  since  it  will  respond 
to  a  band  of  frequencies  only  two  kilocycles  wide 
and  would  lose  the  higher  musical  notes  entirely. 
A  good  receiver  should  have  a  resonance  curve  10 
kilocycles  wide  in  order  to  get  all  of  the  notes  broad- 
cast from  the  transmitter 


190 


Radio  Broadcast 


FIG.  2 

This  is  the  typical  "blooper"  circuit  in  which  the 
antenna  is  closely  coupled.  This  close  coupling 
brings  in  the  signals,  but  when  the  tube  oscillates, 
it  sends  out  signals  as  well — much  to  the  discomfort 
of  all  near-by  listeners 


Fig.  i  is  a  resonance  curve  of  a  receiving 
set  that  will  respond  to  a  band  10,000  cycles 
wide. 

Such  is  the  ideally  selective  receiver. 

How  may  it  be  obtained? 

There  is  but  one  cause  of  poor  selectivity — 


resistance,  and  the  remedy  is  obvious:  eli- 
minate that  resistance.  This  task,  however, 
of  separating  the  various  resistances  from  a 
receiver  reminds  one  of  the  adage  of  cutting 
off  one's  nose  to  spite  one's  face,  for  to  remove 
all  of  the  resistance  would  be  to  remove  the 
receiver  itself. 

For  the  listener  who  builds  his  own  receiv- 
ing set,  resistance  is  added  through  the  use  of 
long  connections,  poor  coils  and  condensers, 
by  placing  coils  too  near  large  masses  of 
metal,  poor  contacts,  or  by  closely  coupling  a 
low  resistance  circuit  to  one  in  which  consider- 
able resistance  exists. 

The  listener  who  owns  a  manufactured  set 
must  place  his  faith  in  the  engineer  who  de- 
signed it  and  the  factory  that  made  it.  There 
is  little  that  can  be  done  to  the  inner  "works" 
that  will  better  its  tuning  qualities.  That 
little  will  be  described  in  this  article  as  well 
as  the  tricks  that  can  be  performed  external 
to  the  receiver  itself. 

TO    IMPROVE    SELECTIVITY 

THERE  are  two  general  methods  of  im- 
proving selectivity.  The  first  strikes  at 
the  cause,  resistance.  The  second  relies  upon 
tricks  such  as  placing  obstacles  in  the  path  of 
unwanted  signals,  or  of  filtering  out  those 
that  are  desired  and  letting  the  others  go 
where  they  will.  In  the  latter  method  lie 


RADIO  BROADCAST  Photograph 


FIG.    3 

A  photograph  of  a  single-circuit  receiver  in  which  the  antenna  is  not  actually  connected  to  the  detector  but 

through  another  coil  closely  coupled  to  it.     One  stage  of  audio  frequency  amplification  has  been  added. 

This  is  the  nucleus  of  a  good  receiver  such  as  shown  in  the  photograph  in  Fig.  4 


Making  Radio  Receivers  More  Selective 


191 


RADIO  BROADCAST  Photograph 


FIG.   4 


Here  is  a  complete  receiver  built  around  the  single-circuit  blooper.  The  coil  and  condenser  to  the  left  com- 
pose the  essentials  of  a  radio-frequency  amplifier,  the  second  coil  is  the  detector  secondary  and  the  amplifier 
plate  coil  coupled  to  it.  The  third  condenser  is  for  introducing  regeneration  in  the  detector.  There  are  five 
tubes,  three  producing  audio  frequency  amplification.  The  Pyrex  socket  is  a  good  one  for  radio  amplifiers 

due  to  its  low  losses 


the  wave   traps  and  radio-frequency  ampli- 
fier circuits. 

In  other  words,  we  may  eliminate  the  cause 
of  poor  selectivity — and  there  is  a  certain 
limit  beyond  which  we  cannot  go  in  this  di- 
rection— or  we  may  force  signals  to  go  through 
a  kind  of  maze  through  which  those  that  are 
desired  will  emerge  and  in  which  the  others 
will  be  lost. 

IMPROVING     THE     SINGLE     CIRCUIT     RECEIVER 

IT  IS  in  the  realm  of  the  simple  receivers, 
the  bloopers  and  any  set  that  employs  no 
radio  frequency  amplification  that  the  most 
can  be  done  to  sharpen  the  tuning.  In  Fig.  2 
is  the  typical  blooper  circuit  with  its  antenna 
closely  coupled  to  the  remainder  of  the  cir- 
cuit— a  condition  that  broadens  the  tuning, 
and  sends  out  into  the  ether  the  parasitic 
signals  that  condemn  this  type  of  receiver. 
Fig.  3  shows  how  simply  such  a  receiver  may 
be  made  and  provided  with  one  stage  of  audio 
frequency  amplification. 

The  use  of  regeneration  is  a  method  of  re- 
ducing an  already  existent  resistance,  and  the 
ability  of  this  simple  receiver  to  go  out  and 
get  distance  lies  in  this  resistance  reduction 
— the  same  phenomenon  that  makes  it  a  nui- 
sance to  all  near-by  listeners.  An  oscillating 
receiver  is  without  doubt  the  most  sensitive 
and  selective,  but  its  very  sensitivity  makes  it 


unhandy.  Small  changes  in  the  antenna  sys- 
tem cause  the  oscillating  frequency  to  vary 
with  accompanying  distortion. 

The  best  possible  addition  to  make  to  a 
blooper  is  a  single  stage  of  radio  frequency 
amplification,  an  addition  that  increases  its 
range,  its  volume,  and  its  selectivity  as  well 
as  eliminating  its  liability  toward  radiation. 
Fig.  4  represents  such  a  circuit,  together  with 
appropriate  audio  amplifiers.  The  coils 
should  be  far  apart  and  at  right  angles  to 
each  other,  so  that  proper  neutralization  may 
take  place.  The  photograph  shows  how 
simply  such  an  amplifier  can  be  made  and 
clearly  illustrates  the  proper  placing  of  coils. 

The  amplifier  plate  coil  may  be  made  by 
winding  ten  or  fifteen  turns  around  the  middle 
of  the  blooper  secondary  that  is  now  used, 
forming  the  connection  between  the  amplifier 
and  the  detector.  The  coupling  between  the 
antenna  and  secondary  of  the  radio-frequency 
amplifier  should  be  as  loose  as  is  consistent 
with  good  signal  strength,  and  the  same  may 
be  said  of  the  coupling  existing  between  the 
plate  coil  and  the  detector  secondary.  In  Fig.  5 
is  shown  the  effect  of  close  coupling,  which 
is  one  of  the  best  methods  of  adding  resis- 
tance to  a  circuit  and  ruining  its  selectivity. 

The  effect  of  retaining  regeneration  in  the 
detector  is  shown  in  Fig.  6  where  the  re- 
sonance curve  becomes  sharper  and  sharper 


192 


Radio  Broadcast 


**-Uow  Resistance   Circuits'' 
RADIO  FREQUENCY  AMPLIFIER 

FIG.    5 

Whenever  a  circuit  of  low  resistance  is  closely 
coupled  to  a  circuit  of  high  resistance,  it  tunes 
broadly.  In  other  words  some  of  the  high  resis- 
tance has  been  "reflected"  into  the  low  resistance. 
The  solution  to  this  trouble  lies  in  separating  the 
two  coils  as  far  as  is  consistent  with  signal  strength 


10 


<->  i 

Ul      * 

ce 
0 


_-J  10,000 


,-'5000 


1000 


INCREASING    TICKLER    COUPLING 


FIG.    6 

According  to  most  authorities,  regeneration  is  a  means  of  reducing  the 
resistance  in  a  circuit.  It  is  accompanied  by  sharp  tuning,  and  the 
more  regeneration  that  is  used,  the  narrower  is  the  frequency  band  taken 
in  by  the  circuit.  Near  the  oscillation  point,  the  circuit  may  become 
so  sharp  that  "side  bands"  are  chopped  off  and  poor  quality  results 


FIG.     7 

A  coil  and  a  condenser  are  the  requisites  of  an  obstacle  to  put  in  the 
path  of  a  radio  frequency  current.  Such  a  device,  if  properly  used, 
may  sharpen  the  tuning  because  it  must  be  accurately  tuned  before  any 
energy  can  get  through.  Two  or  more  increase  the  selectivity  because 
nothing  gets  through  until  each  obstacle  is  tuned  correctly 


with  the  result  that  near  the  oscillation  point, 
the  quality  goes  bad. 

With  the  addition  of  such  an  amplifier  to 
a  blooper,  the  listener  now  has  the  advantage 
of  decreased  resistance  due  to  regeneration 
but  the  added  feature  of  a  wave  trap  in  the 
antenna  circuit.  All  signals  must  pass  the 
tuned  circuit  consisting  of  a  coil  and  a  con- 
denser before  they  can  get  to  the  detector, 
and  before  that  happens  they  must  also  pass 
through  the  vacuum  tube  which  boosts  their 
voltage  by  at  least  six  times.  The  wave  trap 
sharpens  the  tuning  and  additional  tuned 
circuits  may  increase  still  further  the  nar- 
rowness of  the  received  frequency  band, 
but  the  trap  itself  does  not  add  voltage; 
this  is  the  function  of  the  tube.  These  facts 
are  shown  in  Figs.  7  and  8. 

WAVE    TRAPS 


TF  THE  listener  does  not 
*  care  to  add  anothertube, 
or  if  he  already  possesses  a 
stage  or  two  of  radio  fre- 
quency  amplification,  he 
may  use  the  coil  and  con- 
denser of  Fig.  3  as  a  "wave 
trap,"  and  provided  that 
they  be  of  low  resistance, 
he  will  be  able  to  cut  his 
path  through  interference 
with  greater  ease. 

Wave  traps,  in  general, 
are  of  two  kinds:  those  that 
are  shunted  across  the  an- 
tenna and  ground  and 
called  "acceptors,"  and 
those  that  are  in  series  with 
the  antenna  and  ground 
which  are  called  "rejec- 
tors." A  rejector  prevents 
one  frequency  from  getting 
into  the  receiver,  but  lets 
all  others  pass;  in  other 
words,  it  cuts  a  slice  out  of 
the  stations  that  are  on 
the  air.  An  acceptor  pro- 
vides a  convenient  by-pass 
for  all  frequencies  but  the 
one  that  the  listener  de- 
sires to  hear. 

The  wave  trap  is  simply 
a  good  coil  and  a  good 
condenser  connected  and 
placed  in  some  part  of  the 
antenna  -  ground  system. 
The  trap  used  in  RADIO 
BROADCAST  Laboratory 


Making  Radio  Receivers  More  Selective 


\7 


1st  Stage 
Radio  ;• 


2nd  Stage 
Radio   • 


Detector, 


1=0=0=: 


8 

A  radio-frequency  amplifier  not  only  acts  as  a 
trap  for  unwanted  signals  but  boosts  the  voltage  of 
the  one  signal  desired.  In  this  Figure,  the  effects 
of  adding  several  stages  of  tuned  amplification  are 
illustrated.  Each  additional  stage  cuts  down  the 
width  of  the  frequency  band  that  is  passed  and  in- 
creases the  voltage 

and  shown  in  Fig.  9  consists  of  a  General 
Radio  .0005  mfd.  condenser,  across  the  ter- 
minals of  which  is  shunted  a  low-loss  in- 
ductance coil.  Around  the  coil  were  wound 
several  turns  of  wire,  and  it  is  these  turns  that 
are  inserted  in  the  antenna-ground  system. 
Any  good  coil  and  condenser  that  will  cover 
the  frequency  range  may  be  used.  The  re- 
ceiver shown  in  Fig.  9,  then,  consists  of  a 
single  circuit  blooper  with  a  wave  trap  to 
sharpen  the  tuning  and  cut  down  interfer- 
ence and  a  Samson  3-1  transformer  to  provide 
additional  volume.  Fig.  10  shows  in  a  sche- 
matic manner  the  connections  of  a  wave  trap. 
Various  methods  of  connecting  the  trap  to 
a  receiver  now  in  use  are  shown  in  Fig.  1 1 . 
When  in  series  with  the  antenna,  as  in  A  or  C, 
they  may  be  set  at  the  wavelength  of  some  in- 
terfering station.  That  station  will  not  in- 


terrupt until  the  tuning  of  the  trap  has  been 
changed.  When  across  the  input  to  the 
receiver,  as  in  B  or  D,  a  trap  will  let  into  the 
set  only  the  signal  that  is  desired,  and  make 
tuning  somewhat  more  complicated.  On  the 
other  hand,  once  the  listener  becomes  accus- 
tomed to  the  tuning,  he  will  find  this  type  of 
considerable  value. 

Two  traps  may  be  used,  one  tuned  to  some 
particular  station  and  thereby  eliminating  its 
signals,  and  the  other  adjusted  along  with 
the  tuning  of  the  receiver  itself,  as  is  illus- 
trated in  E,  Fig.  1 1. 

A  wave  trap  will  not  increase  signal  strength; 
it  will  work  well  only  with  a  receiver  in  which 
the  antenna  circuit  is  completely  or  partially 
tuned;  it  will  perform  its  duties  only  if  low 


O  Q  Q  Q  Q  Q  Q 


FIG.    IO 

The  connections  of  the  wave  trap  shown  in  Fig.  9 

The  coils  and  condensers  in  such  a  device  should 

be  of  low  resistance  to  make  the  tuning  sharp 


graph 


FIG.    9 

A  simple  wave  trap  consisting  of  a  coil  shunted  by  a  condenser  is  inserted  in  the  antenna  circuit  by  means  of 
several  turns  of  wire  wound  around  the  coil.     This  is  then  a  "rejector"  since  it  rejects  one  frequency  that 

is  unwanted 


194 


Radio  Broadcast 


resistance  parts  are  used;  and  will  not  be  of 
value  to  the  more  complicated  receivers  of 
the  radio-frequency  amplifier  type. 

On  the  other  hand,  a  wave  trap  will  be 
a  boon  to  the  blooper,  to  the  two-,  the 
three-,  and  the  four-circuit  receivers;  for 
it  will  cut  a  slice  out  of  the  ether  where 
there  is  some  interfering  station,  and  it  will 
stiffen  up  the  tuning  of  the  antenna  circuit 
considerably. 

The  coil  and  condenser  shown  in  Fig.  9  may 
be  calibrated  in  wavelengths  or  frequencies 
and  used  as  a  measure  of  incoming  waves,  and 
it  need  only  be  placed  near  one  of  the  coils  of  a 
receiver,  be  it  a  blooper  or  a  five-tube  affair, 
to  indicate  the  frequency  of  incoming  signals. 
When  the  condenser  is  tuned,  a  marked  de- 
crease in  signals  will  be  noted,  and  if  it  is 
used  with  an  oscillating  receiver,  a  sharp  click 
will  be  noted  in  the  phones  when  passing  the 
frequency  of  the  signal. 

For  this  purpose,  the  additional  winding  is 
not  necessary  and  the  unit  then  consists  of 
simply  a  coil  and  a  condenser,  which  may  be 


RADIO   FREQUENCY    AMPLIFIER 


o 
•o 

o 


FIG.     12 

A  simple  method  of  increasing  selectivity  is  illus- 
trated in  this  Figure.     The  condenser  may  be  var- 
iable, but  after  the  correct  place  to  tap  the  coil  is 
found  there  is  no  need  for  further  adjustment 


calibrated  either  in  wavelengths  or  frequencies 
by  noting  where  several  well  known  broad- 
casting stations  are  tuned.  A  curve  may  then 
be  plotted  showing  the  relation  between  con- 
denser setting  and  wavelengths  or  frequencies. 


c- 


-D- 


FIG.     1  I 

Wave  traps  are  really  simple  devices,  consisting  of  a  coil  shunted  by  a  condenser.  But  to  be  effective,  both 
of  these  component  parts  must  be  of  low  resistance.  In  this  Figure  are  shown  several  methods  of  connect- 
ing such  a  trap  to  the  antenna  circuit  of  a  receiver.  They  are  useful  only  if  the  antenna  is  partially  or  com- 
pletely tuned,  and  will  not  do  much  good  when  used  with  a  complicated  receiver.  With  the  simple  circuits, 
however,  they  will  enable  the  listener  to  cut  out  unwanted  stations,  and  to  sharpen  the  tuning  of  his  receiver 


Making  Radio  Receivers  More  Selective 


195 


RADIO     FREQUENCY    AMPLIFIER-REGENERATIVE 
DETECTOR    RECEIVERS 

I N  RECEIVERS  such  as  the  Roberts  Knock- 
*  out,  the  Browning-Drake,  the  Teledyne, 
and  others  of  similar  nature  using  a  regenera- 
tive detector  with  one  or  more  stages  of  radio 
frequency  amplification,  there  are  several 
things  that  may  be  done  to  improve  the  over- 
all selectivity. 

The  series  condenser  in  Fig.  12  is  a  potent 
device  for  sharpening  tuning,  especially  since 


T 


0 
0 

o 

i 
•*— 

-A- 

o 

A 

o 

TV 

9 

B 

o 

/ 

^  g   LJ^ 

i 

1 

o 

I 

iiriii 

—  < 

o 

o            9 

^ 

4=^ 

*"">                       ' 

o 

> 

-?     e 

-B- 


FIG.    13 

Adding  an  inductance  coil  to  the  antenna  circuit  and 
partially  tuning  it  by  taps  or  completely  tuning  the 
circuit  by  a  variable  condenser  will  add  to  the  abil- 
ity of  the  receiver  to  select  the  signals  a  listener 
wants.  The  coupling  to  the  receiver  may  be  de- 
cidedly loose  if  the  antenna  is  carefully  tuned  by 
means  of  the  variable  condenser 

regeneration  in  the  detector  makes  up  for 
any  loss  in  signal  strength  resulting  from  the 
insertion  of  this  condenser. 

Another  method  was  described  in  RADIO 
BROADCAST  for  April  in  the  article  on  experi- 
ment with  the  Roberts  circuit.  This  is  the 
addition  of  inductance  in  series  with  the  an- 
tenna and  partial  tuning  by  means  of  taps,  or 
complete  tuning  by  means  of  a  variable  con- 
denser. Fig.  13  illustrates  both  methods. 

Loose  coupling  between  the  antenna  coil 
and  the  secondary  of  the  amplifier  and  the  two 
coils  connecting  the  amplifier  and  detector  is 
necessary  for  the  sharpest  tuning,  as  shown 


FIRST  RADIO   AMPLIFIER 


NEUTRODYNE   CIRCUIT 


COOP 


FIG.     14 

The  use  of  a  loop  in  place  of  the  first  coil  of  a  neutro- 
dyne  presents  few  difficulties,  especially  when  it  is 
to  be  used  on  local  stations.  The  loop  should  have 
the  correct  dimensions  so  that  it  will  take  the  place 
of  the  neutrodyne  coil  that  is  removed.  The  loop 
will  provide  a  decided  increase  in  selectivity  due  to 
its  directional  effect,  but  of  course  will  cut  down 
signal  strength 

in  Fig.  j.     This  feature  is  embodied  in  several 
coils  now  made  for  the  Roberts  receivers. 

THE    NEUTRODYNE 

THE  two  stages  of  radio  frequency  ampli- 
fication of  the  neutrodyne  are  simply  so 
many  wave  traps,  each  making  the  band  of 


RADIO  BROADCAST  Photograph 
FIG.     I> 

The  "inner  works"  of  a  wave  trap  used  in  RADIO 

BROADCAST'S   Laboratory.     The  conventional  coil 

and  condenser  are  well  illustrated  as  well  as  a  method 

of  mounting  them 


196 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 
FIG.     l6 

The  outward  appearance  of  the  wave  trap  illustrated 

in  Fig.  15.     This  makes  a  neat-appearing  addition 

to  any  broadcast  listener's  equipment 

frequencies  that  is  finally  passed  into  the  de- 
tector, sharper.  For  this  reason  a  neutrodyne 
should  be  very  selective.  There  is  the  addi- 
tional advantage  in  the  tuned  radio  fre- 
quency circuits  that  each  vacuum  tube  adds 
a  certain  amount  of  amplification,  so  that 
there  is  a  gain  in  volume  as  well  as  in  select 
ivity,  as  shown  in  Fig.  8. 

The  use  of  a  small  antenna  is  advisable  if 
interference  is  to  be  cut  to  a  minimum.  If 
space  is  available,  two  antennas  may  be 
erected  at  right  angles  to  each  other  and  their 
directional  properties  used  in  cutting  out  un- 
wanted stations. 

Proper  neutralization  is  highly  important 
in  those  receivers  using  the  Hazeltine  scheme 
of  stabilization,  and  in  the  potentiometer- 
stabilized  sets,  this  instrument  should  be 
used  as  far  as  possible  toward  the  negative 
end  of  its  scale. 

Often  the  addition  of  slight  regeneration  in 
the  detector  circuit  is  helpful,  but  a  receiver 
with  two  stages  of  high-frequency  amplifica- 
tion is  a  bad  place  to  add  a  tickler.  The 
whole  system  is  liable  to  howl. 

Much  will  be  gained  by  the  use  of  a  loop 
instead  of  an  antenna,  or  even  in  place  of  the 


first  coil  of  a  neutrodyne.  This  is  especially 
true  when  there  are  powerful  near-by  broad- 
casting stations.  Fig.  14  shows  how  the  an- 
tenna loop  may  be  substituted  for  the  antenna 
coil  and  secondary  of  the  first  amplifier. 

The  scheme  illustrated  in  Fig.  1 1,  in  which 
a  small  condenser,  say  about  .0001  mfd.,  is 
placed  in  series  with  the  antenna,  may  be  ap- 
plied to  the  neutrodyne.  This  tends  to 
loosen  the  coupling  with  the  antenna  and  to 
prevent  its  high  resistance  from  getting  into 
the  amplifier.  It  has  the  disadvantage  that 
it  may  cause  somewhat  weaker  signals  and 
change  the  readings  on  the  first  condenser. 

IMPROVING    THE    SUPER-HETERODYNE 

THERE  is  no  receiver  available  to-day 
that  has  the  potential  sharpness  of  tuning 
of  the  super-heterodyne.  Here  is  an  oscillat- 
ting  circuit,  in  itself  a  maximum  of  selectivity; 
here  are  two  or  more  intermediate  circuits 
through  which  the  signals  must  pass  before, 
being  heard;  here  is  a  low-resistance  energy 
collector,  a  loop. 

There  is  little  that  can  be  done  with  a 
"super"  that  is  already  in  operation.  Meth- 
ods of  adding  regeneration  to  a  loop  have 
been  described  in  RADIO  BROADCAST.  If  an 
external  loop  is  used,  the  listener  should  make 
sure  that  it  is  of  low  resistance,  not  placed 
near  any  metallic  objects,  such  as  a  radiator, 
or  wall  of  a  steel-lathed  room  or  a  steel  build- 
ing. I  f  there  are  taps,  they  should  make  good 
contact. 

A  good  loop  is  directional,  that  is,  it  re- 
ceives better  when  pointed  in  the  direction  of 
the  transmitting  station.  Full  advantage 
should  be  taken  of  this  tuning  aid  by  the 
proper  use  of  a  compass  fixed  to  the  base  of 
the  loop. 

HOW    MUCH    SELECTIVITY? 

THE  question  finally  faces  the  listener  of 
how  much  selectivity  is  necessary  or  de- 
sirable. Broadcasting  stations  transmit  into 
the  ether  a  band  of  frequencies  about  ten 
thousand  cycles  wide,  these  frequencies  being 
distributed  on  either  side  of  a  single  sharp 
"carrier  wave."  Theoretically,  all  that  is 
required  for  clear  reception,  is  the  carrier 
wave  and  one  of  the  two  "side  bands,"  which 
would  require  a  receiver  with  a  resonance  curve 
only  five  thousand  cycles  wide.  Practically, 
it  is  difficult  to  make  coils  with  low  enough 
resistance  that  the  resonance  peak  will  be 
less  than  ten  thousand  cycles  wide,  and  if 
this  sharpness  is  secured  the  listener  will 
have  no  difficulty  in  separating  Class  B  sta- 


Making  Radio  Receivers  More  Selective 


197 


tions — provided  that  they  stay  on  their  al- 
lotted frequencies. 

Regeneration  decreases  the  width  of  the 
resonance  curve,  and  when  it  is  pushed  too 
far  the  higher  audio  notes  begin  to  drop  out, 
producing  considerable  distortion. 

There  is  a  scheme  that  might  be  tried  on 
super-heterodynes  that  will  bring  in  any  sta- 
tion that  happens  to  be  transmitting  with 
quality  sufficient  so  that  the  announcer  may 
be  understood — but  music  will  be  pretty 
badly  distorted.  This  scheme  consists  in 
placing  a  band  filter  in  the  receiver  passing 
only  frequencies  between  1,000  and  2,000 
cycles.  This  will  make  tuning  so  sharp  that 
little  interference  will  be  experienced  and 
many  of  the  low-frequency  spurts  of  static 
and  noises  will  be  eliminated. 


Since  the  voice  frequencies  that  carry  in- 
telligibility lie  above  1000  cycles,  such  a  filter 
would  let  through  speech  that  could  be  under- 
stood, although  entirely  unnatural. 

The  band  filter  is  really  two  wave  traps  in 
series,  one  cutting  off  all  low  frequencies 
and  the  other  cutting  off  the  high  ones.  If 
their  cut-off  frequencies  are  close  enough 
together  they  will  let  pass  a  narrow  band  of 
frequencies,  and  this  band  of  frequencies 
can  be  made  as  wide  or  as  narrow  as  is  neces- 
sary to  get  the  required  selectivity.  Since 
the  frequencies  dealt  with  in  this  double  wave 
trap  are  audio  frequencies,  large  coils  and 
condensers  are  required,  and  the  proper  de- 
sign of  these  coils  depends  on  measurements 
which  cannot  be  made  by  the  average  radio 
constructor. 


nderwood   &  Underwood 


A  WAVE   TRAP    IN    A   CABINET 

Interior  view  of  a  wave  trap  using  a  Heath  radiant  condenser  and  a  coil,  which  can  be  wound  by  the  con- 
structor.    The  simplicity  of  construction  is  obvious.     The  overall  size  of  this  cabinet  is  8  x  7  x  5  inches 


HOW  TO  MAKE  A  DETECTOR  AND  TWO-STAGE  AMPLIFIER  UNIT 

REMARKABLY  efficient  radio-frequency  amplifier  unit  was  described 
by  John  B.  Brennan  in  the  May  RADIO  BROADCAST  which  has  made  a  great 
appeal  to  many  constructors  who  wanted  to  build  such  a  unit  using  the  most  ad- 
vanced ideas  of  construction.  In  an  early  number  of  RADIO  BROADCAST,  Mr. 
Brennan  will  describe  the  construction  of  a  detector  and  two-stage  audio  amplifier. 
The  unit  is  quite  as  compact  as  the  radio-frequency  one.  The  general  experimenter 
will  find  the  detector-amplifier  unit  of  excellent  service  in  testing  out  intermediate 
amplifier,  tuned  radio  frequency,  and  other  circuits.  This  unit  is  easy  to  build,  it 
is  well  made  and  substantial  and  incorporates  some  excellent  constructional  features. 


THE  u.  s.  s  "ARKANSAS" 

With  her  battery  of  big  guns  and  radio  antennas.     At  least  seven  separate  antennas  can  be  seen  in  tht 
picture.     All  the  Naval  radio  communication  is  carried  on  in  the  longer  wavelengths  with  cipher  codes 
The  larger  ships  have  complete  radio  telephone  equipment,  which  is  chiefly  used  for  communication  be- 
tween ships  over  short  distances 


THE  MARCH  OF  RADIO 


B 


Past  President,  Institute  of  Radio  Engineers 


Why  Does  Congress  Refuse  to  Broadcast  Its  Proceedings? 


WE  ARE  wont  to  give  ourselves 
credit  for  being  the  most  modern 
and  progressive  of  people,  and 
in  the  same  breath  affirm  that 
the  English  are  the  most  conservative,  and 
that  their  excessive  caution  not  to  upset  the 
accepted  customs  and  methods  of  procedure 
effectually  prevents  progress.     And  of  all  the 
conservative  bodies  of  statesmen  in  the  world 
we  have  readily  granted  that  Parliament  was 
the  most  striking  example. 


Imagine  then,  introducing  a  new  and  novel 
instrumentality  such  as  radio  into  the  Houses 
of  Parliament.  Yet  Prime  Minister  Stanley 
Baldwin  announced  recently  that  he  contem- 
plated creating  a  committee  of  members  of 
both  Houses  to  consider  the  question  of  broad- 
casting the  proceedings  of  that  ancient  and 
honorable  body. 

Are  we  going  to  let  our  conservative  friends 
show  us  the  way? — or  shall  we  introduce 
radio  broadcasting  as  a  part  of  Congressional 


The  March  of  Radio 


199 


procedure  at  once,  before  Parliament  gets  the 
"air"?  It  would  appear  from  past  news  stories 
that  many  congressmen  seriously  object  to 
having  their  oral  activities  spread  out  over 
the  countryside  where  their  constituents  might 
be  listening  to  their  speeches.  Can  we  sup- 
pose that  the  filibustering  tactics,  which  have 
successfully  blocked  constructive  legislation  in 
the  past  as  a  result  of  petty  partisan  politics, 
could  be  carried  out  if  several  million  healthy 
Americans  were  listening-in?  Probably  not. 
It  would  take  more  nerve  than  the  average 
senator  has,  to  get  on  his  feet  and  read  for 
hours  senseless  nothings  for  the  Congressional 
Record  with  the  idea  of  blocking  some  measure 
which  millions  of  his  listeners  might  want.  He 
would  get  much  worse  than  "Helen  Marias" 
in  his  morning's  mail,  we  imagine,  and  it  would 
probably  be  unnecessary  for  Vice  President 
Dawes  to  advocate  changes  in  senatorial  pro- 
cedure. 

We  broadcast  political  conventions  because, 


we  now  know,  the  people  are  intensely  inter- 
ested in  the  methods  of  governmental  proced- 
ure, as  well  as  in  the  men  chosen  to  run  for 
office.     But  we  might  well  ask:     What  is  more 
important,  to  know  who  is  chosen  to  run  for 
office  or  to  know  what  he  does  after  he  gets  in? 
Assuredly  the  activities  of  Congress  are  of 
more  importance  to  the  average  citizen  than 
are  the  proceedings  of  the  national  conven- 
tions.    Let  us  then  broadcast  the  proceedings 
of  our  congressmen,  whether  they  will  or  no. 
The  nation  has  certainly  the  right  to  demand 
the  privilege  of  hearing  its  elected  representa- 
tives perform  in  office.     Fewer  words  would 
be  used  and  much  more  government  business 
would  be  transacted,  we  venture  to  prophesy. 
As  the  most  probable  man  to  act,  we  appeal 
to  General   Dawes  to  father  the  movement. 
Were  this  sponsoring  to  occur  we  are  sure  he 
would  be  no  longer  concerned  with  senatorial 
procedure  and  that  incomprehensible  political 
cross-word  puzzle  would  soon  solve  itself. 


RADIO  EQUIPMENT  FOR  THE  HOTEL 

Among  the  many  hotels  in  the  country  to  install  radio  service  for  guests  is  the  Biltmore,  in  New  York. 

ividual  receivers  are  used  with  A  and  B  supply  and  loud  speaker  all  contained  in  one  cabinet      An 

:  is  tuning  the  receiver  for  Marion  Benda  (left)  and  Mary  Mulhern,  musical  comedy  actresses 


200 


Radio  Broadcast 


When  Radio  Aided  Politics 

THE  service  of  radio  to  the  public  has 
been  frequently  analyzed  and  generally 
much  over-estimated.     The  number  of 
radio  listeners  is  generally  given  as   several 
million  more  than  it  is,  with  the  idea  of  lending 
color   to   the   news.     Without   exaggeration, 
however,  it  may  now  be  stated  that  radio  has 
really  helped  millions  in  at  least  one  state. 
This  help  was  not  only  in  culture  and  enter- 


tainment, bat  it  can  be  measured  in  real  dollars 
and  cents. 

Governor  Smith  of  New  York  State  was  ac- 
tively working  for  the  passage  of  an  income  tax 
reduction  of  25  per  cent.,  but  the  majority  of 
his  legislators,  being  of  different  political  faith, 
were  doing  their  best  to  thwart  his  plans. 
Probably  had  they  thought  at  all  (which  is 
questionable)  they  would  have  been  in  favor 
of  tax  reduction  themselves,  if  the  reduction 
could  have  been  pointed  out  as  a  Republican 
measure.  But  never  must 
a  Democrat  be  allowed  to 
get  credit  for  such  a  uni- 
versally desired  piece  of 
legislation.  So  the  tax 
measure  seemed  well  on  the 
way  to  be  defeated  by  petty 
politics.  From  the  Republi- 
can point  of  view  this 
probably  seemed  a  happy 
idea,  for  since  they  were 
in  the  majority,  they  could 
control  the  distribution  of 


THE    S.    Y.       ARA 

Owned  by  William  K.  Vanderbilt.  The  ship  is  lying  in  the  Hudson  River,  off  Riverside  Drive  with  some 
apartment  buildings  of  upper  New  York  in  the  background.  The  radio  equipment  of  the  Ara  is  very  com- 
plete and  equals  that  of  the  largest  of  express  liners.  The  interior  of  the  radio  cabin  is  shown  in  the  insert. 
On  the  left  is  the  \\  kilowatt  c.  w.  transmitter,  next  is  the  radio  compass  equipment  and  then  the  receivers 
for  long  and  short  waves.  A  \\  kilowatt  quenched  spark  damped  wave  transmitter  and  a  %  kilowatt  emer- 
gency set  complete  the  elaborate  equipment  of  station  KFBO.  The  operator  is  using  a  double  speed  key, 

known  among  operators  as  a  "side-wheeler" 


The  March  of  Radio 


20 1 


norrv  m  ri-^ 

USED  \ N I92O 

aused  much      :          TODA 

N 


EXHIBIT       A       FROM   THE    RADIO    AMATEUR 

A  display  that  speaks  for  itself  which  was  one  of  the  exhibits  at  the  re- 
cent radio  show  held  by  the  amateurs  of  the  Second  United  States  District 


the  vast  sums  which  the  unneeded  taxes  would 
bring  in. 

The  upstate  press  which  is  largely  Republi- 
can, carried  very  little,  if  any,  material  which 
might  make  their  readers  think  well  of  the 
Democratic  governor,  and  probably  most  of 
the  voters  who  read  those  papers  thought  him 
an  impractical  visionary,  but  he  wasn't  one, 
and  the  petty  Republican  politicians  soon 
discovered  that  even  with  their  influenced 
press  the  truth  could  not  be  kept  from  their 
constituents.  Governor  Smith  decided  to 
talk  over  the  radio  directly  to  the  taxpayer, 
be  he  Democrat  or  Republican.  "Al"  Smith 
did  talk  and,  so  effectively  did  he  place  his 
arguments  before  the  people  of  New  York 
State  that  the  Republican  majority  were 
forced  to  accede  to  him  and  pass  this  legisla- 
tion which  the  people  wanted.  That  is  a  real 
service  which  helps  to  weed  out  the  petty, 
self-seeking  politician  and  expose  his  actions  to 
the  sight  of  millions  of  those  he  is  supposed  to 
represent.  Then  indeed  has  radio  the  right 
to  be  counted  as  one  of  the  important  factors 
of  our  economic  life. 

The  Tangled  Broadcast  Situation 


T! 


kHE  press   recently  featured  interviews 
with    such    well-known    radio    men    as 
Professor    M.    I.    Pupin    of    Columbia 
University  and  Arthur  Batcheller,  the  Super- 


visor of  Radio  for  the  Second  District. 
The  subject  of  the  interviews  was  the  ever 
increasing  number  of  stations  coming  on  the 
air.  "We  are  at  the  end  of  the  rope," 
says  Mr.  Batcheller.  "The  ether  has  reached 
the  saturation  point  for  broadcasters."  Now 
if  any  one  really  knows  about  the  situation  it 
probably  is  Mr.  Batcheller.  He  is  the  Govern- 
ment's representative  in  the  most  congested 
radio  district  in  the  world,  and  from  morning 
to  night  he  has  to  listen  to  radio  troubles.  In 
the  opinion  of  Professor  Pupin,  "licenses  were 
granted  in  the  beginning  without  any  discrim- 
ination,"— and  we  would  add  that  such  a 
policy  still  seems  to  control  the  issuance  of 
licenses. 

A  strange  instance  of  the  attitude  of  the 
Department  of  Commerce  on  this  jamming  of 
the  ether  was  recently  reported  from  Cincin- 
nati. Two  stations  in  that  city  had  been 
granted  licenses  to  operate  on  the  same  wave- 
length, and  after  much  squabbling  as  to  a  di- 
vision of  time  they  finally  did  operate  on  the 
same  wavelength  and  at  the  same  time!  It 
was  reported  from  Washington  that  the  De- 
partment of  Commerce  had  been  repeatedly 
asked  to  step  in  and  settle  this  impossible  sit- 
uation, but  had  declined  on  the  ground  that 
"to  set  such  a  precedent  would  get  the  Depart- 
ment hopelessly  enmeshed  in  a  maze  of  dis- 
agreements between  stations."  One  might 
well  ask  the  Department  how  it  did  expect 


2O2 


Radio  Broadcast 


such  disputes  to  be  settled?  It  is  a  strange  idea 
of  privilege  and  duty  which  consents  to  the 
issuance  of  broadcasting  licenses  to  any  who 
want  them  and  then  when  trouble  comes  to  the 
listening  public  as  a  result  of  the  excessive 
number  of  stations,  to  turn  one's  back  and  let 
someone  else  settle  the  trouble  when  that 
trouble  was  directly  due  to  the  Department's 
freedom  with  licenses.  Who,  we  also  again 
ask,  does  Mr.  Hoover  think  will  step  in  to 
straighten  out  trouble  between  various  sta- 
tions if  his  department  thinks  the  task  too 
onerous? 

Let  us  venture  again  the  proposition  that 
licenses  be  refused  to  a  new  station  unless  the 
request  is  accompanied  by  a  petition  signed 
by  a  reasonable  number  of  prospective  lis- 
teners. The  more  we  consider  this  idea  the 
more  it  appeals  to  us  as  a  sensible  method  of 
controlling  the  number  of  broadcasting  sta- 
tions in  the  interest  t>f  the  listening  public. 

The  Navy   Establishes   an   Amateur 
Radio  Reserve 

CAPTAIN  RIDLEY  McLEAN,  Direc- 
tor of  Naval  Communications,  has 
conceived  the  idea  of  increasing  the 
effectiveness  of  the  Naval  Reserve  Force  by 
enlisting  in  its  personnel  the  radio  amateurs 
of  the  country.  During  the  World  War,  much 
time  and  effort  were  spent  in  training  a  staff  of 
radio  operators  and  technicians;  several 
schools  had  to  specialize  in  such  work  because, 
at  that  time,  there  was  a  great  demand  for 
radio  communication,  both  on  sea  and  ashore. 
Hiram  Percy  Maxim,  President  of  the  Amer- 
ican Radio  Relay  League,  has  sent  out  a  call  to 
all  members  of  his  organization  to  file  certifi- 
cates of  willingness  to  join  the  Naval  Reserve. 
Such  enrolled  amateurs  will  receive  instruction 
in  the  use  of  Naval  radio  equipment,  so  that 
in  any  emergency  the  active  radio  personnel 
of  the  military  organizations  can  be  at  once 
increased  to  its  proper  complement.  It  is  ex- 
pected that  possibly  6000  amateurs  will  re- 
spond to  this  call.  We  regard  this  move  as 
an  exceptionally  desirable  one  on  the  part  of 
the  Navy.  There  is  much  talent  among 
American  amateurs  which  can  be  used  to  good 
advantage  by  the  Navy. 

The  Month  in  Radio 

EVERY  month  brings  with  it  some  pa- 
tent decision  in  the  radio  field.     There 
are  so  many  suits  being  waged  to-day 
that  it  would  be  strange  if  the  month  did  not 


record  some  decision  or  other.  As  to  who  was 
the  real  inventor  of  the  regenerative  circuit, 
generally  credited  to  Armstrong,  seems  yet  to 
be  a  mooted  question.  The  fortunes  of  legal 
war  pass  back  and  forth,  and  it  appears  that  a 
recent  decision  of  Judge  Learned  Hand,  having 
to  do  with  the  possibility  of  a  suit  against  the 
De  Forest  Radio  Company,  shows  the  tide  of 
battle  turning  in  favor  of  the  De  Forest  Com- 
pany. However,  we  cannot  pretend  to  under- 
stand all  the  legal  complexities  and  ramifica- 
tions in  these  patent  suits,  but  we  note,  in 
passing,  that  neither  litigant  seems  to  have 
received  a  knock-out  blow  up  to  this  writing. 
They  are  both  still  in  the  commercial  running. 

IN  SOME  preliminary  tests  having  to  do  with 
equipping  army  planes  for  summer  maneu- 
vers, it  was  found  feasible  for  pilots  in  different 
machines  to  converse  with  each  other  when 
they  were  in  full  flight,  and  as  far  as  five 
miles  apart.  This  seems  like  a  very  short 
distance  to  us  who  nightly  hear  concerts  a 
thousand  miles  away,  but  it  is  to  be  remem- 
bered that  the  power  output  of  the  airplane 
transmitter  is  necessarily  low  and  the  difficulty 
of  receiving  is  enormous  because  of  the  exces- 
sive noise  caused  by  the  powerful  motors  ex- 
hausting almost  in  one's  ear  and  the  hurricane- 
rush  of  the  wind  as  the  plane  speeds  through 
the  air  faster  than  two  miles  a  minute. 

IS  THE  radio  market  saturated?  Every  time 
a  temporary  falling  off  of  sales  occurs,  this 
question  is  brought  up.  It  seems  that  con- 
servative estimates  place  the  number  of  re- 
ceiving sets  in  the  United  States  at  about 
3,000,000  and  on  this  basis  we  surely  can  guar- 
antee the  radio  manufacturer  a  fruitful  market 
for  some  time  to  come.  Certainly  as  many- 
people  should  own  radio  sets  as  at  present 
own  automobiles  and  phonographs  and  each 
of  these  numbers  close  to  1 5,000,000.  Because 
of  the  lower  cost  of  radio  sets  it  would  not  be 
unreasonable  to  estimate  the  saturation  point 
for  radio  receivers  considerably  higher  than 
that  for  automobiles  and  phonographs.  Our 
belief  is  that  the  market  will  keep  on  absorb- 
ing radio  sets  until  there  are  about  20,000,000 
in  use. 

WHEN  Donald  B.  MacMillan  departs 
again  for  the  polar  regions  the  latter 
part  of  this  year  his  radio  outfit  will  be  pri- 
marily designed  to  use  short  waves.  His 
experiences  with  radio  during  his  last  expedi- 
tion, as  well  as  his  recent  conferences  with 
radio  experts  here,  have  convinced  him  that 


The  March  of  Radio 


203 


the  short  wave  channels  will  prove  more  re- 
liable than  the  longer  wavelengths  used  by 
broadcasting  and  commercial  stations.  So, 
if  you  want  to  hear  news  from  the  North  Pole 
next  winter,  have  one  of  your  amateur  friends 
build  you  a  receiver  for  tuning  to  waves  as  low 
as  20  meters  and  then  listen  for  MacMillan. 

THE  Turk  has  decided  to  modernize  him- 
self as  far  as  radio  is  concerned,  and  the 
Radio  Corporation  of  America  seems  likely 
to  get  a  contract  to  build  a  huge  station  at 
Angora.  The  former  station  there  was  of 
German  construction  and,  according  to  the 
press  dispatches,  it  is  not  suitable  for  trans- 
oceanic traffic.  It  will  probably  be  repaired  and 
modernized  sufficiently  to  carry  on  whatever 
European  traffic  may  originate  at  this  point. 

HPHE  Navy  has  put  the  airplane  and  radio 
1  to  a  new  service  in  which  they  prove  to  be 
valuable  aids  in  naval  maneuvers.  The  mod- 
ern gun  has  such  a  range  that  the  target  may 
be  out  of  sight,  or  at  least  so  far  away  as  to 
make  visual  observation  extremely  unreliable. 
By  having  an  observer  equipped  with  a  radio 
telephone  in  an  airplane  hovering  over  the 
target,  the  fire  control  officer  on  board  the  war- 
ship is  at  once  notified  of  the  accuracy  of  his 
fire.  This  method  of  control,  using  two-way 


communication,  is  so  rapid  and  accurate  that 
proper  corrections  can  easily  be  applied  to 
successive  broadsides  without  interfering  at 
all  with  the  rapidity  of  fire. 

FROM  the  radio  research  laboratory  of  the 
Soviet  Government  at  Nijni  Novgorod 
comes  news  that  the  workers  there  are  perfect- 
ing a  water-cooled  triode.tube.  Apparently 
the  scientific  workers,  or  their  press  representa- 
tives, are  going  along  the  same  independent 
lines  of  endeavor  as  are  their  experimenters  in 
the  fields  of  economics  and  sociology.  Could 
they  but  profit  by  the  experience  of  others  they 
would  find  that  the  triode  being  "developed" 
there  had  already  been  developed  successfully 
here  quite  some  time  ago. 

THE  Senate  has  just  authorized  the  con- 
tinuance for  two  more  years  of  the  private 
use  of  Pacific  Naval  Radio  stations.  The  De- 
partment of  Commerce  recommends  this  use 
of  the  Government's  stations,  for  it  is  their 
opinion  that  the  pri- 
vate stations  on  the 
west  coast  are  not 
now  in  a  position  to 
undertake  efficiently 
the  transmittal  of 
all  the  commercial 


THE  EXPERIMENTAL  SHORT  WAVE  ANTENNA  OF  KDKA 

At  East  Pittsburgh.  The  high  wooden  poles  to  which  the  fan  antenna  is  attached  forms  the  experimental  309 
meter  antenna  from  which  regular  programs  are  radiated.  The  shorter  vertical  pole  above  the  roof  of  the 
building  is  the  short  wave  antenna.  The  oval  at  the  right  shows  a  close-up  of  the  short  wave  transmitting 
antenna.  Note  how  short  the  actual  antenna  is  and  that  the  conductor  itself  is  rigid.  Rigidity  of  the  antenna 
conductor  is  absolutely  essential  where  very  short  waves  are  being  transmitted.  Signals  from  this  short  wave 
station  have  been  recently  heard  in  Australia,  a  distance  of  about  1 1,000  miles  from  Pittsburgh 


2O4 


Radio  Broadcast 


JOSEPH  C.  SMYTH E  AND  ANTHONY  GERHARD 
iBoth  of  New  York  City  who  won  the  awards  of  the  Executive 
Radio  Council  of  the  Second  Radio  District  for  commercial  radio 
code  speed  proficiency.  Mr.  Gerhard  copied  56^  words  a  minute 
without  an  error.  It  is  almost  impossible  to  send  the  Continental 
code  by  hand  at  such  a  speed  and  the  achievement  of  such  a  record 
is  remarkable 


112  meter  wave  and  picked  up 
by  the  Radio  Corporation's  ex- 
perimental laboratory  on  the 
outskirts  of  New  York.  From 
that  point  the  signals  went  by 
wire  to  control  station  wjz. 

So  the  movement  for  trans- 
atlantic broadcasting,  started  by 
RADIO  BROADCAST  in  November, 
1923,  has  gone  on.  First  by  KDKA 
sending  its  signals  to  control  2to 
in  London  and  now  we  have  our 
stations  controlled  by  signals 
emanating  from  London.  To  be 
sure  the  reception  of  the  Lon- 
don program  here  was  so  poor 
that  the  encounter  must  be 
recorded  as  a  victory  for  Static, 
but  it  is  a  beginning  and  we  can 
expect  to  hear  the  chimes  of  Big 
Ben  with  ever  increasing  dis- 
tinctness and  faithfulness  of 
reproduction. 

Transatlantic    Telephony 
Is  Not  Yet 


and  private  messages  which  are  being  sent 
to-day.  "Continuation  of  the  service  by  the 
Navy  is  necessary,"  says  Senator  Jones  (Rep., 
Washington),  "because  the  private  agencies 
have  been  unable  so  far  to  complete  construc- 
tion of  facilities  and  handle  all  the  messages. 

The  Progress  of  International 
Broadcasting 

FREQUENTLY  the  press  tells  us  that  the 
programs  of  KDKA  and  other  American 
stations  have  served  for  operating  the 
English  stations,  thus  giving  our  English 
friends  the  same  programs  as  we  were  listening 
to.  Never  has  this  been  accomplished,  how- 
ever, in  the  reverse  direction.  It  seems  more 
difficult  for  us  to  receive  a  European  station 
than  for  them  to  hear  ours.  A  short  time  ago, 
however,  a  start  was  made  which  at  least  shows 
us  the  difficulties  encountered. 

The  Radio  Corporation  station,  wjz,  has 
on  several  occasions  lately  been  actuated  by 
signals  received  from  5xx  Chelmsford,  Eng- 
land. The  transatlantic  signals  were  sent 
across  the  water  on  a  1600  meter  wave  to  Bel- 
fast, Maine,  and  from  there  rebroadcast  on  a 


N  HIS  recent  annual  report, 
H.  B.  Thayer,  Chairman  of 
A    the    Board  of    Directors  of 
the    American    Telephone   and 
Telegraph  Company,  reviewed  his  company's 
attitude  toward  radio  development. 

"In  view  of  the  great  public  interest  in  wire- 
less telephony,  it  seems  proper  to  mention  the 
continued  preparation  of  the  British  Post 
Office  for  transmission  from  Great  Britain. 
When  that  is  completed  it  is  expected  that  the 
experiments  referred  to  in  the  annual  report  of 
1922,  will  be  resumed,  and  that  experimental 
conversations  with  this  country  will  follow. 
It  is  impossible  at  present  to  predict  the  date 
of  telephone  conversation  with  Great  Britain 
or  even  to  predict,  on  the  basis  of  present  con- 
ditions, that  it  will  be  a  practical  and  commer- 
cial possibility,  taking  into  consideration  other 
difficulties.  Any  other  applications  of  wire- 
less telephony  to  telephone  service,  except 
in  minor  instances  where  wire  connection  is 
impossible,  appear  even  more  remote." 

When  Trains  Are  Run  by  Radio 


W: 


HEN  an  engineer  is  giving  a  technical 
talk  to  laymen  not  well  acquainted 
with  the  field  being  analyzed,  he  is 
very  likely  to  make  statements  that  will  appeal 
to  the  imagination  of  his  listeners.  With  the 


The  March  of  Radio 


205 


idea  of  gaining  their  attention  and  interest,  he 
is  likely  to  venture  much  farther  than  he 
would  if  talking  to  a  number  of  fellow  engin- 
eers. We  therefore  take  with  a  grain  of  salt 
a  prediction  of  Mr.  G.  Y.  Allen,  of  the  Radio 
Department  of  the  Westinghouse  Company, 
given  in  a  talk  before  the  New  York  Railroad 
Club.  After  telling  of  the  possibility  of  guided 
radio  waves,  that  is,  high-frequency  current 
over  wires,  Mr.  Allen  went  on  to  tell  of  the 
uses  to  which  such  currents  could  be  put  in 
railroad  operation.  "It  is  entirely  feasible," 
said  he,  "through  a  combination  of  electric 
controls,  and  radio  supervisory  control,  to 
start  a  train  without  a  crew  from  a  station, 
run  it  at  full  speed  over  clear  tracks,  and  to 
slow  down  and  stop  it  automatically  in  accord- 
ance with  automatic  block  signals,  giving  to  a 
central  despatcher  at  the  same  time  complete 
supervisory  control  of  all  of  the  movements  of 
trains  on  a  system." 

Certainly  all  these  things  are  possible,  for  it 
was  only  a  short  time  ago  that  a  warship  was 
completely  controlled  in  its  course  by  suitable 
relays  actuated  by  means  of  radio  signals. 
But  just  as  our  warships  still  require  crews  of 
more  than  a  thousand  men  to  handle  them,  so 
our  trains  will,  for  quite  some  time  to  come, 
require  the  crews  to  which  we  are  accustomed. 
For  the  time  being,  we  prefer  to  have  a  train 
controlled  by  an  experienced  engineer  rather 
than  by  a  fraction  of  a  watt  of  high-frequency 
power  which,  as  we  all  know,  may  have  all  of 
its  good  intentions  seriously  interfered  with, 
and  possibly  thwarted  al- 
together, by  static  and 
other  disturbances. 

More  Facts  About 
Radio  Transmission 


EVER  since  Marconi's 
first  transatlantic  ex- 
periment, attempts 
have  been  made  to  explain 
the  difference  between  night 
and  daylight  transmission, 
the  effect  of  wavelength  on 
the  distance  a  signal  could 
travel,  the  reason  for  the 
difference  in  receiving  be- 
tween summer  and  winter, 
and  many  other  observed 
facts.  With  the  ever  in- 
creasing use  of  short 
waves,  we  are  more  than 
ever  convinced  that  much 
of  our  supposed  knowledge 


of  how  radio  waves  are  propagated  is  not 
based  on  fact.  Waves  100  meters  long  should 
theoretically  travel  but  a  short  distance  before 
being  dissipated,  but  in  spite  of  this,  they,  at 
times,  reach  half  way  around  the  world. 

Two  of  the  engineers  of  the  Bell  Telephone 
Laboratories,  W.  H.  Nichols,  and  J.  C.  Shell- 
ing, recently  published  a  preliminary  note  on 
some  theoretical  work  they  are  carrying  out. 
This  note  states  that,  due  to  the  combined 
effects  of  the  ionized  (electrified)  upper  atmos- 
phere and  the  earth's  magnetic  field,  peculiar 
effects  on  radio  wave  propagation  may  be 
expected.  The  theory,  logically  based  on  the 
known  behavior  of  electric  charges  moving  in 
magnetic  fields,  seems  capable  of  explaining 
the  remarkable  fading  and  bending  to  which 
we  well  know  the  average  radio  wave  is  sub- 
jected. Possibly  even  the  peculiar  effects 
noted  during  the  January,  1925,  eclipse  would 
prove  explicable  in  the  light  of  this  new  analy- 
sis. Dr.  G.  W.  Pickard  has  just  presented  an 
interesting  paper  before  the  Institute  of  Radio 
Engineers,  giving  his  findings  on  radio  trans- 
mission during  the  recent  sun's  eclipse. 

Wireless  Vision  Achieved 

SUCH    an    announcement    recently    ap- 
peared in  the  London  press!    Strange 
and  unbelievable  as  this  concept  of  tele- 
vision might  have  seemed  ten  years  ago,  it 
now  seems  almost  sure  to  materialize  at  some 
time  not  far  distant.     The  idea  of  seeing  what 


PACHYDERM  AND  MICROPHONE 

Station  wjz,  New  York,  recently  broadcast  the  sounds  and  scenes  of  the 

circus.     '"Dolly,"  a  two-year-old  elephant,  is  doing  the  right  thing  by  the 

radio  audience 


2O6 


Radio  Broadcast 


GEORGE    BERNARD    SHAW 
London;  Author  and  Playwright 

"  //  /  could  see  and  hear  a  play  from  my  fireside, 
I  would  never  enter  a  theatre  again.  I  shall 
not  prophesy,  but  I  remind  our  managers  that 
theatre-going  is  eery  dear,  very  inconvenient,  and 
horribly  stuffy  and  promiscuous.  Unless  they 
can  overcome  those  disadvantages  by  the  over- 
powering fascination  of  good  plays,  good  acting, 
and  theatres  that  are  like  enchanted  palaces  in- 
stead of  hotel  smoking  rooms,  broadcasting  will 
knock  them  out." 


is  taking  place  a  thousand  miles  away  would 
have  been  classed  as  the  working  of  an  un- 
balanced mind  a  decade  or  so  ago,  but  now, 
after  millions  of  us  have  heard,  with  perfect 
intonation,  voices  of  speakers  thousands  of 
miles  away,  why  should  we  be  surprised  at 
seeing  things  from  the  same  distance?  It  is, 
as  a  matter  of  fact,  as  difficult  a  concept  to 
picture  radio  carrying  on  voice  communica- 
tion- as  it  would  be  to  have  it  carry  picture 
messages  to  our  eyes.  In  voice  communica- 
tion, sound  has  to  be  changed  to  electro- 
magnetic waves  to  transmit  the  suitable 
energy  impulses  and  then  these  have  to  be 
changed  back  to  sound  for  the  benefit  of  the 
listener.  The  eye  requires  electromagnetic 
waves  for  its  activation,  and  this  is  exactly  the 
form  of  energy  used  in  radio  communication. 
The  transmission  of  pictures  by  radio  has 
already  been  accomplished  and  many  examples 
of  these  pictures  have  been  printed  in  the  daily 
papers.  By  most  of  the  present  methods  it 
takes  about  twenty  minutes  to  transmit  a 


five-by-seven-inch  picture.  This  process  is 
really  television.  If  the  distant  scene  remains 
fixed  for  some  minutes,  it  can  evidently  be 
sent  by  radio  to  the  distant  onlooker.  Instead 
of  gazing  into  the  fabled  crystal  sphere,  how- 
ever, he  would  look  at  some  kind  of  a  chart, 
ink  marked  or  photographic,  upon  which  the 
distant  scene  would  be  slowly  reproduced. 

Now,  if  we  imagine  that  such  pictures  could 
be  reproduced  in  one  tenth  of  a  second  instead 
of  twenty  minutes,  wireless  vision  would  be 
achieved.  Thus  the  speed  must  be  increased 
some  thousands  of  times  over  its  present 
value,  but  this  is  not  at  all  unlikely.  Many 
of  us  have  seen  the  oscillograms  by  which 
the  telephone  engineer  analyzes  his  sounds 
and  the  power  engineer  discovers  what  pe- 
culiarities exist  in  his  transmission  lines. 
Such  pictures  of  electric  current  are  reasonably 
accurate  if  the  wave  to  be  photographed  does 
not  reverse  more  rapidly  than  about  one  thou- 
sand times  a  second.  To  get  pictures  of  fre- 
quencies higher  than  this  has  not  seemed 
feasible  in  the  past,  yet  recently  it  has  been 
found  possible  to  photograph  electric  cur- 
rents which  are  reversing  as  rapidly  as  twenty 
million  times  a  second.  Here  is  an  increase 
of  speed  of  about  ten  thousand  times,  accom- 
plished by  an  ingenious  change  in  the  method 
of  photography  employed.  Instead  of  using 
light  waves  to  affect  the  photographic  plate, 
the  electrons  themselves,  by  the  activities  of 
which  ordinary  light  waves  are  set  up,  are 
used  to  bombard  the  sensitized  gelatine.  This 
revolutionary  step  has  increased  the  speed  of 
oscillography  thousands  of  times.  By  a 
similar  application  of  the  electron's  activities 
to  the  problem  of  radio  vision,  the  solution 
does  not  seem  improbable. 

We  Need    More    Delicacy  in    Radio 
Advertising 

THE  American  Telephone  and  Telegraph 
Company,  as  has  been  frequently  stated, 
is  experimenting  with  the  commercial 
possibilities  of  broadcasting.  Their  station, 
WEAF,  is  admittedly  an  advertising  venture. 
To  be  sure,  much  excellent  material  is  sent 
out  over  this  channel  which  brings  the  owners 
of  the  station  no  financial  return,  but  in  the 
course  of  a  week  many  hundreds  of  dollars 
find  their  way  into  its  coffers  through  the  ap- 
pearance of  the  Gold  Dust  Twins  and  other 
organizations  of  a  like  character.  The  price 
of  the  station  for  broadcast  purposes  is  high, 
but  not  so  high,  we  imagine,  that  the  annual 
balance  does  not  have  to  be  written  in  red 


The  March  of  Radio 


207 


figures.  Certainly  its  income  from  adver- 
tising is  much  greater  than  that  of  any  other 
station.  The  entire  radio  field  looks  to  it  as  a 
trail  blazer  in  the  realm  of  radio  broadcasting. 
In  the  interest,  then,  of  radio  advertising,  we 
suggest  that  altogether  too  much  time  and  too 
many  words  are  spent  in  telling  us  who  is  pay- 
ing for  the  next  hour's  operation  of  the  station. 
A  mere  statement  that  the  Happiness  Candy 
Stores  are  going  to  give  the  next  hour's  enter- 
tainment does  not  harm  the  listeners  or  the 
candy  business,  but  to  listen  to  a  stiff,  stereo- 
typed eulogy  of  this  special  brand  of  candy  is 
irritating,  to  say  the  least.  Probably  the 
candy  firm,  in  common  with  others  "using  the 


PROFESSOR  MAR1US  C.  A.  LATOUR 
The  French  radio  inventor,  whose  patent  claims 
on  many  important  radio  devices  and  circuits  have 
been  recognized  by  the  American  Telephone  & 
Telegraph  Company,  the  Radio  Corporation  of 
America,  and  others.  The  Hazeltine  group  of 
manufacturers  purchased  the  American  license  for 
the  Latour  patents  and  the  A.  T.  &.  T.  Company, 
and  the  Radio  Corporation  have  non-exclusive  li- 
licenses  from  Prof.  Latour  whose  patents  are  such 
as  to  involve,  so  he  claims,  every  radio  receiver  made 

facilities"  of  this  station,  specifies  how  much 
propaganda  must  be  poured  into  their  radio 
channel.  If  this  be  so,  we  suggest  that  a  bit 
more  music  and  a  correspondingly  decreased 
period  of  self-approbation  would  be  more  con- 
ductive to  candy  buying.  It  takes  but  little 
propaganda  to  give  to  radio  advertising  a  dis- 
tinctly negative  value  and  that  negative  value 
has  been  reached  several  times  by  the  clients 
of  WEAF. 

Electrical  Exports  Are  Increasing 

THE   Department  of  Commerce  reports 
that  during  1924,  the  total  of  our  electri- 
cal  exports    approximates   $85,000,000, 
a  $12,000,000  increase  over   1923.     Most  of 
this  money  is  spent  for  machinery  and  trans- 
mission line  equipment,  but  radio  and  its  ac- 


cessories are  showing  an  ever-increasing  share 
of  the  export  business.  The  total  for  radio  is 
estimated  by  the  department  to  be  $5,000,000. 
Dry  batteries  alone  show  an  export  value  of 
nearly  $800,000  during  the  past  year. 

South  America,  which  last  year  was  one  of 
our  principal  foreign  customers,  has  dropped 
from  third  to  fourth  place,  probably  due  to  the 
activity  of  German  merchants,  especially  in 
such  countries  as  Argentina  where  German 
sympathizers  are  very  active. 

Although  the  total  of  our  electrical  ex- 
ports shows  a  very  considerable  figure,  this 
pales  into  insignificance  when  our  own  ex- 
penditure for  engineering  projects  is  con- 
sidered. Electrical  power  plants,  dams,  water 
and  sewage  systems,  for  1924  mounted  to  the 
enormous  total  of  $2,002,533,000.  It's  no 
wonder  our  engineering  schools  find  great 
demand  for  their  graduates  when  such  techni- 
cal activity  prevails  throughout  the  country. 


Interesting  Things    Interestingly 
Said 


F\AVID  SARNOFF  (New  York;  vice  president 
*-*  and  general  manager  of  the  Radio  Corporation 
of  America):  "In  whatever  direction  radib  may 
develop,  it  will  be,  I  believe,  toward  supplementa- 
tion, not  substitution.  The  truth  is,  printer's  ink 
achieves  something  that  radio  cannot  achieve; 
conversely,  the  security  of  radio  lies  in  the  fact  that 
it  provides  a  different  service  than  the  printed  word 
ever  rendered  or  ever  could  render." 

LJUGH  S.  POCOCK  (London;  Editor  of  the 
•  Wireless  florid):  "To-day  a  number  of  broad- 
casting stations  in  different  parts  of  the  world  are 
making  use  of  Esperanto  as  a  means  of  linking  up 
with  other  countries. 

".  .  .  The  employment  of  short  waves  for 
long-distance  transmission  using  low  power,  the  im- 
portance of  which  was  first  demonstrated  by  the 
amateur  worker,  has  provided  those  who  conduct 
experimental  work  with  a  means  of  linking  up  with 
their  fellow  workers  all  over  the  world,  however  dis- 
tant. Demonstration  has,  in  fact,  already  been 
given  that  there  is  no  point  on  the  globe  so  remote 
that  it  cannot  be  reached  on  short  waves  by  ama- 
teurs, even  when  using  very  limited  power.  As  the 
range  over  which  amateurs  communicate  has  been 
gradually  extended,  so  the  necessity  for  some  com- 
mon language  has  arisen. 

".  .  .  To-day  it  is  not  by  any  means  an  un- 
usual occurrence  when  overhearing  short-wave  inter- 
communication to  come  upon  the  exchange  of  com- 
ment in  Esperanto  between  amateurs  of  two  differ- 


208 


Radio  Broadcast 


ent  countries  whilst  experimental  work  is  being 
carried  out,  each  understanding  the  other  without 
difficulty,  although  their  native  languages  may  be 
entirely  unintelligible  to  either." 

CRANK  T.  ST ANTON  (New  York;  president 
Frank  T.  Stanton  and  Company):  "I  am  not 
at  all  in  sympathy  with  statements  I  have  heard 
that  the  radio  industry  has  been  overfmanced.  In 
fact,  I  still  maintain  that  the  radio  industry  is  under- 
financed. There  is  hardly  a  question  that  if  the 
tremendous  sums  that  have  been  paid  for  radio  se- 
curities during  the  past  six  months  had  all  found 
their  way  into  the  treasuries  of  the  companies 
rather  than  into  the  pockets  of  the  original  organ- 
izers, a  vastly  different  story  could  now  be  written 
regarding  the  market  for  securities  representing 
manufacturing  enterprises." 

CRANK  J.  McENIRY  (Denver,  Colorado; 
General  Electric  Company,  station  KOA): 
"Never  did  Marconi,  Armstrong,  Hazeltine,  Alex- 
anderson  and  other  famous  experimenters  dream 
that  some  day,  the  results  of  their  efforts — radio — 
would  be  employed  to  capture  murderers  and  ban- 
dits, put  across  community  chest  drives,  detect 
human  ills,  recover  lost  dogs,  and  bring  together 
parents  and  wandering  or  kidnapped'  children. 
What  radio  will  accomplish  and  what  is  predicted 
for  it  are  two  entirely  different  things,  according 
to  experts  in  this  field.  On  the  face  of  it,  however, 
radio  is  confronted  with  the  peculiar  problem  of 
living  up  to  everything  that  is  expected  of  it." 

(~*.  C.  FOSTER  (New  York;  President  of  the 
^^  American  Piano  Company):  "The  question  as 
to  the  effect  of  radio  on  the  piano  business  is  fre- 
quently asked.  We  believe  that  radio  is  decidedly 
helpful.  It  is  increasing  the  knowledge  and  appre- 
ciation of  music,  and  it  is  awakening  an  interest  in 
many  to  whom  it  has  hitherto  been  a  matter  of  in- 
difference. It  is  increasing  the  desire  to  hear  better 
music,  especially  in  the  home.  The  enjoyment  that 
the  radio  brings  has  unquestionably  pointed  a  way 
to  even  greater  enjoyment  through  the  actual  pos- 
session of  a  means  of  making  music,  which  leads 
directly  to  the  thought  of  a  piano." 

r\R.  E.  F.  W.  ALEX  ANDERSON  (New  York; 
*-*  Chief  Consulting  Engineer,  Radio  Corpora- 
tion of  America):  "The  shortest  element  of  the 
telegraphic  signal  is  the  dot.  The  higher  the  sig- 
naling speed  the  shorter  is  the  dot.  Thus,  while 
the  wave  amplitude  is  kept  constant  the  total 
energy  contained  in  the  dot  sign  is  inversely  propor- 
tional to  the  speed  of  signaling.  When  the  strong- 
est single  atmospheric  impulse  prevalent  at  any 
time  contains  as  much  energy  as  the  dot  in  the 
telegraphic  code  it  may  be  mistaken  for  a  dot,  or 
it  may  break  up  a  dash  into  two  dots,  thus  causing 
false  telegraphic  signals.  It  is  therefore  necessary 
to  maintain  a  speed  of  signaling  in  which  the  total 
energy  of  the  dot  is  somewhat  greater  than  the 
maximum  energy  of  a  single  atmospheric  impulse. 
Thus,  if  a  wave  amplitude  is  doubled,  the  length 
of  the  dot  may  be  shortened  to  one-half.  This  ex- 


©  Underwood  &  Underwood 
G.    Y.    ALLEN 

New  York;  Radio  Department,  Westinghouse — 

Electric  &  Manufacturing. Company 

"  Tbroitgb  the  use  of  modern  developments  in 
radio,  it  is  entirely  possible  to  operate  electric 
trains  from  a  central  control  office.  I  do  not 
wish  to  be  understood  as  advocating  the  elimina- 
tion of  the  molorman,  conductor,  and  crew.  No 
mechanical  device,  however  perfect,  can  take  tbe 
place  of  human  intelligence,  but  it  is  interesting 
to  note  some  of  tbe  possibilities  of  radio  control. 

"It  is  now  entirely  feasible,  through  a  combina- 
tion of  automatic  control  and  radio  supervisory 
control,  to  start  a  train  without  a  crew  from  a 
station,  rim  it  at  full  speed  over  clear  tracks,  slow 
it  down  or  stop  it,  in  accordance  with  the  signals 
of  an  automatic  block  signaling  system,  start  it 
up  again  when  the  signals  clear,  stop  it  at  its 
next  station  stop,  and  open  its  doors." 


plains  why  in  practice  the  telegraphic  amplitude  is 
double  the  length  of  the  wave  amplitude  and  also 
why  it  is  inversely  proportional  to  the  atmospheric 
disturbance." 

A  LBERT  E.  HAASE:  (New  York;  in  an  article 
**  in  Printers'  Ink):  "There  is  no  doubt  in  the 
minds  of  many  who  are  getting  their  livelihood  from 
radio  that  if  this  mad  rush  to  get  the  advertisers' 
dollar  for  the  support  of  radio  continues,  radio  itself 
will  suffer.  And  that  would  mean  public  resent- 
ment against  advertising — all  forms  of  advertising, 
for  the  public  does  not  distinguish  between  adver- 
tising mediums.  It  is  this  point  that  makes  it 
imperative  for  all  thoughtful  manufacturers  to 
watch  and  study  the  attempts  that  are  being  made 
to  turn  radio  broadcasting  into  an  advertising 
medium." 


THE  s.  s.  "ARCTURUS" 

The  marine  headquarters  of  William  Beebe,  the  scientist  and  explorer.  The  Arcturus  is  the  most 
perfectly  equipped  ship  for  scientific  exploration  in  existence.  A  3!  kilowatt  continuous  wave 
radio  transmitter  aboard  keeps  the  expedition  in  constant  touch  with  the  mainland.  Exclusive  news 
dispatches  from  Doctor  Beebe  appear  in  the  New  York  Times,  telling  of  the  findings  of  the  party 


Radio's  Part  in  the  Sargasso  Sea 

Exploration 

Dr.  William  Beebe's  Scientific  Expedition  to  the  Unfamiliar  Reaches  of 
the  Atlantic  Ocean  is  Constantly  in  Touch  with  the  World  by  Radio 


BY  ALFRED  M.   CADDELL 


WHAT   did   you   write   on    that 
paper  that  you  put  in  a  bottle 
and  cast  from  the  ship  on  your 
last    sea    voyage?     Have    you 
heard  from  some  romantic  young  lady,  or  from 
some    ne'er-do-well    beachcomber    who    has 
found   your   bottled   message   buried   in   the 
sands  of  some  distant  resort?     If  not,  then  the 
possibilities  are  that  your  bottle  has  followed 
;in  the  wake  of  a  derelict  on  its  way  to  the 
Sargasso  Sea.    Situated  between  two  legend- 
ary points  on  the  compass,  somewhere  between 
Africa  and  the  Continent  on  the  west,  lies  the 
Sargasso  Sea — that  mysterious  part  of  the  At- 
lantic Ocean  which,  it  is  thought,  marks  the 


grave  of  the  fabled  continent  Atlantis,  and 
which  has  now  become  the  graveyard  of  dere- 
licts floating  wreckage  of  all  sorts. 

Curiously  enough,  human  nature  likes  to 
build  fables  and  yarns  upon  which  to  feed  the 
imagination,  and  there  are  many  weird  stories 
told  of  this  great  waste  of  seaweed  and  drift- 
wood. And  out  of  these  stories  there  has 
grown  the  belief  that,  perhaps,  after  all,  there 
may  be  a  Sargasso  Sea.  Once  that  is  admitted 
it  is  logical  to  conclude  that  there  is  a  sunken 
continent  under  that  grayish  expanse  of  slug- 
gish water  and  that  on  the  continent,  if  explor- 
ation were  possible,  there  might  be  found 
treasures  in  gold  and  ornaments  and  in  his- 


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Radio  Broadcast 


torical  value,  equal  to  those  uncovered  when 
Tut-ankh-Amen's  tomb  was  first  opened. 

And  so,  not  so  much  in  the  hope  of  discover- 
ing lost  treasure,  but  rather  in  the  hope  of 
obtaining  valuable  research  data,  an  expedi- 
tion has  started  for  the  Sargasso  Sea.  The  ex- 
pedition under  the  direction  of  Dr.  William 
Beebe,  has  been  fortunate  in  obtaining  a  party 
of  noted  scientists,  among  whom  is  Dr.  William 
K.  Gregory  of  Columbia  University  and  the 
American  Museum  of  Natural  History. 


The  Ardurus,  for  so  the  vessel  that  has  been 
chosen  for  this  important  work  has  been 
named,  is  the  largest  ship  that  has  ever  been 
employed  in  explorations  of  this  character. 
She  is  280  feet  long  and  has  a  46-foot  beam. 
She  is  equipped  with  every  facility  required  to 
probe  into  the  mysterious  Sargasso's  secrets. 
Her  laboratory,  which  is  undoubtedly  the  fin- 
est afloat,  is  provided  with  every  scientific 
instrument  which  can  possibly  be  of  service  in 
making  observations  of  whatever  forms  of  life 
the  dredge  of  the  ship  may  bring  to  the  surface. 
The  Ardurus  is  equipped  with  a  drum  on 
which  is  wound  seven  miles  of  cable,  so  that  the 
ocean  may  be  dredged  at  any  known  depth. 
The  cable  is  lowered  with  trawls  which  auto- 
matically close  at  prescribed  depths,  so  that  if 
any  deep  sea  monsters  become  enmeshed  in 
the  trawls,  the  depth  at  which  they  live  will 
be  known.  This  will  assist  the  scientists 
in  tracing,  step  by  step,  the  evolution  from 
surface  fish  forms  to  the  extraordinary 


PLUMBING   THE    MARINE    DEPTHS 

From  the  bow  of  the  Ardurus.     A  specially  arranged  bridge  from  the  bow  of  the  ship  has  been  rigged  so 
that  the  members  of  the  party  can  work  directly  over  the  sea  instead  of  having  to  drop  a  line  over  the  side. 

The  insert  shows  Doctor  Beebe 


Radio's  Part  in  the  Sargasso  Sea  Exploration 


211 


marine  life  which  inhabits  the  lower  regions 
of  the  sea. 

THE    SEARCH    FOR    UNDERWATER    TREASURES 

DEEP  sea  monsters  provide  treasure  for 
almost  inexhaustible  thought.  Many 
fish  with  remarkable  lighting  systems  have 
been  caught.  Some  of  them  are  said  to  be 
aflame  with  light,  so  that  they  look  more  like 
a  Hudson  river  night  boat  than  fish,  while 
others  carry  green,  red,  yellow,  and  pink 
lights.  Some  have  peculiar  shaped  lanterns 
at  the  ends  of  long  feelers,  while  the  bodies  of 
others  of  this  peculiar  species  of  fish  are 
studded  with  blazing  search  lights.  Some 
have  eyes  from  which  radiance  streams,  and 
others  are  continuously  lighted.  It  is  believed 
that  only  a  small  portion  of  the  various  species 
of  lighted  fish  have  been  caught,  so  that  they 
will  be  subjected  to  very  careful  study  on  this 
expedition. 

Another  interesting  phase  of  deep-sea  life 
will  also  engage  the  attention  of  the  scientists. 
Deep  sea  fish,  it 
is  known,  fill 
their  tissues  with 
compressed  gases 
to  resist  the  pres- 
sure of  the  water 
at  great  depths, 
so  that  when 
they  are  hoisted 
to  the  surface, 
the  diminishing 
pressure  no 
longer  neutra- 
lizes the  pressure 
of  gas  from  with- 
in, causing  them, 
sometimes,  to  ex- 
pand or  burst 
like  popcorn. 
Other  fish  are 
able  to  live  at 
various  levels  by 
means  of  mus- 
c  u  1  a  r  valves 
which  release  the 
compressed  gases 
from  their  tissues 
as  they  rise,  and 
replenish  their 
chambers  again 
when  they  de- 
scend. Needless 
to  say,  special 
study  will  be 
given  to  the  com- 


pressor and  decompressor  systems  possessed 
by  these  monsters. 

Then  on  the  Ardurus  there  are  many  tanks 
and  one  great  aquarium  in  which  many 
things  of  interest  will  be  brought  back  to  New 
York  when  the  explorers  return  from  that  re- 
gion of  the  South  Atlantic  where  the  Sargasso 
is  supposed  to  be. 

But  best  of  all,  one  of  mankind's  recently 
developed  wonders  is  playing  an  import- 
ant part  in  this  expedition.  We  will  let 
Charles  J.  Pannill,  General  Manager  of  the 
Independent  Wireless  Telegraph  Company, 
tell  us  about  the  radio  installation  on  board 
the  Ardurus. 

"  If  you  are  able  to  tune-in  on  a  2400  meter 
wavelength,"  said  Mr.  Pannill,  "y°u  will  be 
able  to  listen-in  on  some  mighty  interesting 
press  despatches,  if  you  can  read  code.  Here- 
tofore, expeditions  have  seldom  been  heard 
from  until  they  returned  to  their  point  of  de- 
parture, so  that  when  to-day  we  are  able  to 
follow  explorers,  step  by  step,  through  their 


THE  RADIO  CABIN  OF  THE  "ARCTURUS" 

The  radio  equipment  is  controlled  by  the  Independent  Wireless  Telegraph  Com- 
pany. The  ^returns  is  a  wooden  ship  built  by  the  Shipping  Board  during  the  war  for 
the  Alaskan  trade.  It  was  owned  by  the  Union  Sulphur  Company  and  was  donated  by 
Henry  D.  Whiton  to  the  New  York  Zoological  Society  for  this  voyage  of  exploration 


212 


Radio  Broadcast 


tribulations  and  hardships,  it  only  goes  to 
show  to  what  extent  radio  has  become  a  daily 
adjunct  in  our  lives.  And,  too,  it  is  interest- 
ing to  note  that  the  progressive  newspaper 
realizes  the  value  of  radio  from  the  point  of 
view  of  press  despatches.  The  following  ex- 
cerpt from  an  article  in  the  New  York  Times, 
takes  the  reader  right  to  the  spot  and  almost 
enables  him  to  participate  in  the  exploration: 

"We  are  now  at  the  site  of  the  fabled  At- 
lantis on  Atlantic  Ridge,  midway  between 
America  and  Africa,  with  2300  fathoms  of  sea 
below  us,  and  this  morning  our  radio  receiving 
set  brought  to  us  the  lively  music  of  a  Pitts- 
burgh orchestra  playing  'Hands  Across  the 
Sea' — Souza's  march. 

' '  Even  with  continued  heavy  seas  we  have 
brought  our  heavy  dredging  apparatus  into 
play,  and  yesterday  our  first  bottom  dredge 
brought  up  glass  sponges  and  volcanic  rock 
from  a  sea  abyss  three  and  one-half  miles 
below  us. 

"The  Arciurus  has  on  board  a  radio  instal- 
lation furnished  by  the  Independent  Wireless 
Telegraph  Company,  and  consisting  of  a 
3^  kw.  arc  transmitter  with  daylight  range 
of  approximately  1 500  miles,  and  also  a  one- 
half  kw.  spark  transmitter  for  emergency 
short  range  work.  Doctor  Beebe  has  arranged 
with  the  New  York  Times  to  report  an  account 
of  their  operations,  which  dispatches  are  han- 
dled through  the  East  Moriches,  Long  Island, 
station.  Thus  the  public  and  the  philanthrop- 
ists who  contributed  toward  this  expedition 
are  enabled  to  read  the  despatches  the  day 
after  they  are  sent.  What  an  advance  over 
the  communication  systems  of  other  expedi- 
tions and  other  days!" 

The  Ardurus  left  the  Sargasso  Sea  some- 
time during  the  last  week  in  March,  and  on  the 
29th  of  March,  Captain  J.  S.  Howes  reported 
by  wireless  that  all  was  well  with  the  Ardurus 
and  her  crew,  and  gave  her  position  as  200 
miles  south  of  Balboa,  Panama,  in  the  Pacific 
Ocean.  The  Ardurus  had  left  Balboa,  Canal 
Zone,  on  the  28th  of  March  and  had  headed 
directly  for  the  Galapagos  Islands,  where  Doc- 
tor Beebe  and  his  party  of  scientists  intended 
to  continue  their  researches,  and  also,  it  is  be- 
lieved, to  study  the  Humboldt  Current,  of 
which  little  is  known.  But  there  was  a 
period  of  two  weeks  after  the  Ardurus  sailed 
for  the  Galapagos,  where  nothing  was  heard 
from  her — nothing  further  at  least,  than  the 
Captain's  report  on  the  29th  of  March.  It 


was  then  that  grave  fears  for  her  safety  be- 
gan to  be  expressed,  and  there  was  much  ex- 
cited comment  as  to  her  fate. 

The  waters  of  the  Pacific  Ocean  in  the 
vicinity  of  the  Galapagos,  and  following  the 
waters  of  the  Humboldt  Current  along  the 
Peruvian  coast,  are  far  from  truculent.  In 
fact,  so  calm  is  it  in  this  immediate  vicinity 
that  it  has  become  noted  for  this  alone. 

Recently,  Dr.  Robert  Cushman  Murphy, 
Assistant  Director  of  the  American  Museum  of 
Natural  History,  returning  from  a  study  of  the 
vicinity,  with  new  data  on  unfamiliar  cur- 
rents, told  of  the  unprecedented  weather  in  the 
vicinity  of  the  Humboldt  Current,  and  he  ex- 
pressed the  opinion  that  some  trouble  might 
have  been  experienced  with  the  wireless  outfit 
on  board  the  Arciurus.  But  there  was  little 
ground  for  this  belief,  for  as  previously  stated 
in  this  article,  the  Ardurus  is  fully  equipped 
and  ready  for  any  possible  emergency  to  her 
radio  or  to  any  other  part  of  her  scientific 
equipment. 

Members  of  the  New  York  Zoological 
Society  were  unable  to  explain  the  Ardurus' s 
silence,  for  the  vessel  had  previously  com- 
municated directly  with  East  Moriches,  Long 
Island,  sending  her  position  to  the  radio  station 
there  every  day.  President  Henry  Fairfield 
Osborn  of  the  Museum  of  Natural  History, 
sailed  from  Miami  on  the  steamship  George 
Washington  recently.  The  George  Washing- 
ton has  the  same  equipment  as  that  in- 
stalled on  the  Ardurus,  but  though  the 
operator  on  this  vessel  attempted  persist- 
ently to  get  into  communication  with  the 
expedition,  he  was  unsuccessful.  Then  it  was 
that  all  vessels  south  of  the  canal  zone  were 
asked  to  call  the  Ardurus,  and  the  Naval  radio 
station  at  Darien,  Canal  Zone,  was  instructed 
to  send  out  her  call. 

What  then,  had  happened  to  the  Ardurus? 
Had  her  officers  and  men  found  another 
Sargasso  Sea,  never  to  return  and  tell  us  about 
it?  Or,  was  it  merely  that  old  complaint 
"static"  about  which  we  hear  so  much  now-a- 
days?  Perhaps,  even  then,  they  were  ap- 
proaching the  land  of  the  tortoise,  the 
Galapagos,  the  mysterious  and  romantic  Gala- 
pagos of  the  i6th  century  Spanish  buccaneers. 
And,  indeed,  this  proved  to  be  so,  for  on  April 
i  ith,  it  was  learned  through  the  Navy  Depart- 
ment, that  once  again  the  Ardurus  had  been 
heard  from  and  that  all  was  well  with  those  on 
board. 


'CHe  Listeners'  Point  of" 

6y          eJ^ennie  Irene 


Has  Radio  Any  Relation  to  tke  Supernatural? 


IT  WAS  in  1906  that  Dr.  Thomas  Troward 
put  forth  the  statement  in  his  Edinburgh 
Lectures  on  Mental  Science  that  there  is 
no  such  thing  as  time  or  space:  that,  as 
the  smallest  portion  of  the  ether  contains  all 
the  elements  of  the  whole,  then  every  portion 
of  the  whole  is  within  this  smallest  portion. 
Therefore,  the  entire  universe  is  in  one  place 
and  every  place  at  one 
and   the   same   time. 
Thus,  neither  time 
nor  space  exists. 

This  was,  of  course, 
long  before  the  days 
of  broadcasting,  and 
the  lectures  aroused, 
except  among  those 
who  had  themselves 
gone  deeply  into  the 
subject,  the  ridicule 
with  which  all  new 
ideas  are  received. 
People  thinking  only 
on  the  surface  in- 
terpreted Doctor 
Troward  as  saying 
that  you  did  not  have 
to  cover  any  ground 
whatever  to  get  from 
New  York  to  China 
because  there  wasn't 
any  ground.  And  so 
they  went  on. 

The  simple  fact  was  that  Doctor  Troward 
was  anticipating  radio.  Had  you  asked  him, 
"What  is  the  difference  in  time  between 
London  and  New  York?"  he  would  have  re- 
plied, "There  is  no  difference,  nor  between 
any  other  two  points  in  the  world,  no  matter 
how  far  they  are  separated  according  to  the 
estimate  of  the  geographers." 

We  know  now  that  this  is  true,  and  has  been 


VLADIMIR    RASSOUCHINE 

Pianist,  who  was  heard  recently  at   KGO 

and  gained  favor  with  a  large  number  of 

listeners 


true  since  ever  the  earth  was  formed.  The 
fact  that  while  it  may  be  daylight  in  this  coun- 
try it  is  night  in  China  has  nothing  to  do  with 
the  matter  as  set  forth  by  Doctor  Troward. 
He  deals  with  those  elements  outside  of  the 
material  that  control  our  lives,  and  over 
which  we  have  practically  no  control,  and, 
therefore,  foolishly  grope  our  way  blindly 
among  all  the  other 
blind. 

Years  ago — for  it 
must  have  been  quite 
a  time  before  these 
Troward  lectures  were 
brought  before  the 
public,  F.  Marion 
Crawford  wrote  a 
novel  called  Mr. 
Isaacs,  in  which  the 
scenes  are  largely  laid 
in  India,  and  the 
psychic  powers  of  the 
Hindoos,  figure  in  the 
story.  One  of  the 
characters  remarks 
quite  casually  to 
another  that  he  saw  a 
mutual  friend  of  theirs 
in  a  town  some  one 
hundred  miles  distant 
from  his  home  al- 
though he  knew 
perfectly  well  that 
the  friend  was  in  his  home. 

Marion  Crawford  states  that  long  after 
this  book  was  published,  a  woman  asked  him: 
"Why  did  you  put  such  an  absurd  incident 
into  a  novel  that,  in  the  main,  is  plausible?" 
Mr.  Crawford  replied  that  while  he  was  in 
India  he  heard  many  such  statements,  and 
others  that  seemed  even  more  impossible  of 
belief.  He  asked  the  man  who  had  seen  his 


214 


Radio  Broadcast 


THE    EVEREAD^ 


Whose  artistic  playing  is  frequently  heard  during  the  programs  of  the  Eveready  Hour,  broadcast  each 
Tuesday  from  nine  to  ten.     From  left  to  right  they  are,  Alex  Hackel,  violinist,  Edward  Berge,  pianist, 

Jacque  de  Pool,  'cellist 


friend  one  hundred  miles  distant  from  where 
he  was  in  the  body,  just  what  he  meant.  The 
Hindoo  said,  "But  that  is  not  unusual.  By 
controlling  vibrations  one  can  project  his  per- 
sonality through  the  ether  to  distant  points." 

Radio  is  projecting  personalities  in  the  form 
of  photographs  to  distant  points,  by  a  man- 
made  machine.  Perhaps  the  Hindoo  was 
right  and  one's  personality  can  be  projected 
by  a  God-made  machine,  the  mind. 

Impossible?  Who  can  say  that  anything 
is  impossible? 

According  to  Edward  Jewett  of  Detroit,  who 
talked  in  an  interview  on  what  the  boys  have 
done  for  radio,  they  do  not  know  the  word 
"Impossible."  He  said: 

"The  boy  mind  grasps  the  theory  of  radio 
better  than  can  the  man  mind  because  to  the 
boy  mind  there  are  no  inhibitions  and  im- 
possibilities. Men,  as  they  become  men,  learn 
that  so  many  things,  'cannot  be  done.'  The 
boy  doesn't  know  that.  So  he  goes  ahead 
and  does  it.  ...  I  asked  one  youngster 
what  he  did  when  he  discovered  that  a  thing 
could  not  be  done.  'Find  out  how  to  do  it,' 
was  his  prompt  reply." 

(Perhaps  by  using  this  boy's  method  we  may 


learn  how  to  control  vibrations  with  the  mind  so 
that  we  may  be  benefited  by  such  control!) 

To  revert  to  Mr.  Jewett: 

"The  youth  grasps  at  the  intangible  far 
better  than  the  grown  person.  He  can  see 
a  thing  that  isn't  there,  and  the  minute  that 
he  sees  it,  then  it  is  there.  His  imagination  is 
neither  tired  nor  spoiled.  Boys  think  and  say 
uncanny  things.  One  remarked  to  me  once, 
'  It's  curious  to  know  that  every  voice  in  all  the 
world  is  here,  now,  in  this  very  room,  isn't  it?' 

"You  mean,"  I  countered  with  the  old 
man  wisdom  we  are  so  likely  to  effect,  "that 
it's  here  if  we  bring  it  here." 

"'No,'  said  he,  'it's  here  now  if  we  will 
give  it  a  fair  chance  to  reproduce  itself. 
If  we  don't  hear  it,  that's  our  fault." 

And  yet  you  may  be  sure  that  youth  had 
not  read  Troward  although  he  was  stating 
the  basic  principle  of  his  Edinburgh  lectures. 

How  Archaeology  "Came  Over"  on 
the  Radio 

IF    YOU    missed    hearing   Joseph    Emerson 
Smith  give  a  talk  last  month  through  sta- 
tion KOA,  Denver,  then  you  are  unfortunate. 


The  Listeners'  Point  of  View 


215 


Mr.  Smith  was  a  member  of  the  expedition 
sent  by  the  Colorado  State  Museum  to  the 
recently  discovered  prehistoric  city  of  pit- 
houses  extending  along  the  tops  of  a  straggling 
series  of  mesas  in  southwestern  Colorado,  and 
that  swing  from  a  point  near  the  Colorado- 
Utah  border  in  the  Paradox  Valley  to  Pagosa 
Springs,  Colorado,  and  then  south,  well  into 
New  Mexico. 

This  is  the  largest  lost  city  yet  discovered 
on  the  American  continent.     Its  civilization 


goes  back  to  a  period  previous  to  that  hitherto 
believed  to  be  the  oldest  that  ever  existed  on 
this  continent,  antedating  the  cliff  dwellers 
by  at  least  one  thousand  years.  It  is  com- 
posed of  scores  of  separate  and  distinct  units, 
which,  for  the  sake  of  defense  advantages, 
were  confined  to  the  tops  of  mesas  or  table- 
lands, high  above  the  valleys.  Five  hundred 
pithouses  in  one  group  alone  have  just  been 
mapped  in  what  is  known  as  Chimney  Rock. 
There  are  tens  of  thousands  of  these  pit- 


AN    ANCIENT    WATCH    TOWER 

And  skeleton  of  a  prehistoric  woman  which  were  uncovered  in  the  nearby  pithouse,  inhabited  twenty-two 

centuries  ago  in  what  is  now  Colorado.     A  lecture  on  these  archaeological  discoveries  was  given  at  station 

KOA,  Denver,  and  is  commented  upon  elsewhere  in  this  department 


2l6 


Radio  Broadcast 


houses,  large  and  small,  dotting  the  tops  of 
the  mesas.  Archaelogical  surveys  indicate 
that  they  were  excavated  by  the  original 
builders  to  a  depth  of  from  three  to  five  feet, 
and  were  surrounded  by  sleeping  chambers 
and  granaries.  Entrance  to  these  homes  was 
through  a  steep  decline  or  tunnel,  accommo- 
dating only  one  body  at  a  time.  Fires  were 
apparently  built  in  the  exact  center  of  the 
large  or  main  room,  and  an  opening  at  the 
roof  was  skillfully  fashioned  to  let  out  the 
smoke. 

So  far  as  investigation  has  at  present  gone 
it  has  been  discovered  that  these  people  had 
a  crude  knowledge  of  astronomy,  and  carried 
on  truck  gardening  and  irrigation.  Their  prin- 
cipal crops  were  gourds,  tubers,  corn,  melons, 
yucca  and  greens.  Figurines  have  been  dis- 
covered, of  rare  design  and  finish,  and  pot- 
tery that  might  well  be  used  for  decorative 
purposes  to-day. 


LUKE    HILL 

No,  the  small  boy,  who  is  all  of  seven,  isn't  impersonating  Oliver  Twist  and  asking 
for  "more."  As  a  singer  he  was  the  "hit"  of  the  radio  show  given  recently  for 
the  benefit  of  "The  City  of  Childhood,"  maintained  by  the  Loyal  Order  of  Moose 
for  the  dependent  children  of  their  deceased  brothers.  It  was  presented  through 

WJJD 


The  photograph  reproduced  on  page  215 
shows  the  remains  of  an  old  watch  tower, 
and  also  the  perfectly  preserved  skeleton  of 
a  woman  about  35  or  40  years  of  age,  who 
was  about  five  feet  ten  inches  in  height.  It 
will  be  seen  that  the  right  cheek  was  resting 
on  the  right  hand,  and  the  left  arm  was  placed 
across  the  breast.  The  knees  were  flexed.  Be- 
side the  skeleton  was  an  unusual  elaborate  gray 
bowl  decorated  with  a  conventionalized  de- 
sign of  butterflies.  Near  by  was  a  complete 
pottery  face,  that  of  a  doll  which  originally 
was  supported  by  a  corncob. 

Mr.  Smith  has  been  quoted  indirectly,  be- 
cause to  attempt  quoting  him  verbatim  would 
be  an  injustice  to  the  exceptional  interest  with 
which  every  moment  of  this  talk  was  filled. 
Station  KOA  has  put  on  many  fine  features 
during  its  short  existence,  but  probably 
nothing  of  greater  interest  to  a  certain 
class  of  listeners-in  than  this  one. 


American    Mu- 
sic   Is    Inferior 
to  None 

IN  THE  course 
of  a  very  inter- 
esting article 
comparing  British 
and  American  radio 
receivers,  the  au- 
thor says,  in  the 
Wireless  World  and 
Radio  Review  (Lon- 
don): "It  may  be 
said  definitely  that, 
taken  as  a  whole, 
British  wireless  sets 
and  components 
are  superior  to 
those  manufac- 
tured in  the  United 
St ates,  both  in 
quality  of  work- 
manship, and  in 
quality  of  repro- 
duction. This  is 
not  so  much  due  to 
the  fact  that  Amer- 
ican manufacturers 
are  lacking  in  skill 
in  the  design  of 
good  transformers, 
etc.,  as  it  is  due  to 
the  mentality  of  the 
American  people. 
Anybody  who  is 


The  Listeners'  Point  of  View 


217 


intimately  ac- 
quainted with 
modern  American 
music,  or  has  had 
the  opportunity  of 
comparing  the  per- 
formances of  the 
average  quality 
orchestras  in  thea- 
tres and  restau- 
rants in  the  two 
countries,  will 
readily  understand 
why  the  quality  of 
reproduction  in  the 
British  sets  is  so 
greatly  superior  to 
that  in  those  which 
emanate  from  the 
U.  S.  A.  Indeed, 
the  performance  of 
an  orchestra  which 
would  be  consid- 
ered mediocre  in 
England,  is  usually 
termed,  '  High- 
brow'on  the  other 
side  of  the  water." 

Taking  restau- 
rant music  by  and 
large  in  England, 
this  is  no  doubt 
true.  Also,  all  who 
have  taken  the 

trouble  to  inform  themselves  regarding  radio 
programs  in  that  country  as  compared  with 
American  programs,  know  that  England  gives, 
on  the  average,  music  far  superior  to  ours. 

But  the  writer  of  this  article,  M.  P.  Vincer- 
Minter  seems  unconsciously,  to  carry  the 
impression  that  all  music  produced  in  Eng- 
land, whether  by  radio  or  through  the  usual 
public  channels,  is  superior  to  American  mu- 
sic. In  truth,  the  opposite  is  exactly  the  case. 
Except  for  her  great  choruses  which  give 
yearly  festivals,  English  music  as  heard  in 
concert  halls  and  opera  houses  cannot  for 
a  moment  stand  comparison  with  the  great 
attractions  in  these  same  lines  available  in 
this  country  every  season.  England  has  been 
called,  "The  Ballad  Country,"  for  the  reason 
that  her  people  have  never  risen,  as  have  the 
American  people,  to  a  point  of  appreciation  of 
the  lovely  and  masterly  songs  of  such  com- 
posers as  Schubert,  Schumann,  and  Brahms. 

Also,  where  this  country  has  well  nigh  a 
dozen  orchestras  of  the  highest  rank,  England 
has  one  and  that  is  the  London  Phil'  ar  loric. 


THE    CAMERON    SISTERS 

Fair  charmers  with  the  flute  and  harp  who 
broadcast  an  attractive  program  from   KGO 


Covent  Garden  Opera  has  been  discontinued 
since  the  war,  while  here  the  Metropolitan 
and  Chicago  forces  are  still  carrying  on.  All 
these  points  are  cited,  not  to  correct  the  writer 
in  the  Wireless  World,  but  because  to  some 
he  may  unconsciously  give  the  impression  that 
he  is  talking  about  American  music  in  general. 


When  an  Announcer  Confides 


M 


R.  H.  W.  ARLIN,  of  station  KDKA, 
who  made  his  debut  as  one  of  the 
world's  pioneer  radio  announcers  in 
1921,  assures  the  public  that,  "Although  I 
have  been  continually  on  the  job  ever  since 
then,  it  has  never  grown  stale.  This,  for  the 
reason  that  there  are  always  certain  indi- 
viduals who  furnish  diversion.  Such  as,  for 
instance,  the  woman  who  telephones:  'I  have 
just  left  a  package  of  pajamas  on  the  street 
car,  and  would  like  to  have  the  service  of 
your  station  in  recovering  them.'" 

"Or,  'I  have  just  arrived  at  the  Pennsyl- 
vania station  and  have  some  relatives  living 


218 


Radio  Broadcast 


in  the  city,  but  do  not  know  where  they  live. 
Will  you  please  announce  over  the  radio  that 
I  am  here  and  waiting  for  them  to  get  in 
touch  with  me?" 

Or,  when  Christine  Miller  Clemson,  for 
many  years  one  of  the  leading  concert  con- 
traltos of  the  country,  was  requested  to  sing, 
"Red  Hot  Mama!" 

What  the  Flonzaley  Quartet  Think  of 
Radio 

A)OLPH    BETT1,    first    violin    and    di- 
rector  of   the    Flonzaley   Quartet,    in 
speaking  to  the  present  writer  of  the 
first  broadcasting  experience  of  this  organiza- 
tion when  they  were  heard  on  a  Victor  program 
through  WEAF,  said: 

"It  is  incredible,  radio.  It  is  the  greatest 
influence  in  the  world  to-day!  It  will  trans- 
form, perhaps,  musical  conditions  and  the 
transition  stages  may  make  confusion.  But 
it  will  lead  to  glorious  results.  It  is  still 


impossible  for  me  to  realize  that  we  were 
really  heard  by  outside  listeners  as  we  played 
in  that  studio.  We  sat  there,  and  played  with 
the  same  ease  and  comfort  as  if  in  the  parlor 
of  friends.  When  the  telephone  calls  began 
to  come  in  telling  how  clearly  we  were  heard 
even  at  a  great  distance,  I  could  only  exclaim: 
'But  did  they  really  hear  us?'  I  still  cannot 
comprehend.  I  only  know  it  is  marvellous 
and  that  I  am  deeply  interested.'" 

This  from  one  of  the  very  greatest  of  living 
musicians. 

The    Battleground   of   Jazz   Opinion 

DR.    R.    S.    M1NERD    raised    quite    a 
breeze  among  the  proponents  of  jazz 
through    his  letter   published   against 
cheap   jazz    last    month,    judging   from   the 
letters    received    by   the    conductor   of   this 
department    calling    him    down.     He    raised 
quite  a  breeze  among  the  anti-jazzites,  too. 
All  the  letters  that  have  ever  been  received 


"DO   A    GOOD   TURN    DAILY 

Picked  members  from  a  number  of  crack  Scout  Troops  assembled  around  a  radio  set  to  receive  instructions 
in  hooking  up  and  operating  the  one-dial  Mohawk  set  which  is  to  be  distributed  through  the  Chicago 
Tribune  to  the  blind  of  that  city.  The  boys  are  installing  the  sets  and  instructing  the  sightless  owners  how 

to  use  them 


The  Listeners'  Point  of  View 


219 


by  the  editor  of  this  department  upholding 
jazz,  condemn  what  they  call  "the  classics" 
being  devoid  of  melody.  Yet  at  least  ninety 
per  cent,  of  jazz  is  written  from  melodies 
drawn  from  the  great  composers,  distorted 
for  jazz  purposes. 

Probably,  "Yes,  We  Have  no  Bananas,"  is 
not  jazz,  but  the  song  is  taken  literally  from 
the  "Hallelujah"  chorus  of  Handel's  "Mes- 
siah." 

IT  IS  little  short  of  wonderful  the  way  station 
KGO,  operated  by  the  General  Electric 
Company,  keeps  up  the  high  standard  of  its 
programs.  Congratulations  are  well  in  order, 
not  only  for  this  station  but  KOA  at  Denver, 
operated  by  the  same  company.  Both  of 
them  have  fortunately  managed  to  avoid  many 
of  the  pitfalls  into  which  new  stations  stumble 
through  ignorance. 

The  Stage  and  Radio  Are  Not  Op- 
posed 

COSMO   HAMILTON,   the  playwright, 
is    among  those  who  are  pessimistic 
regarding  the  effect   of  radio  on   the 
theatre.     People  simply  will  not  go  to  plays. 
They  will  stay  at  home  and  listen  to  them  by 
radio. 

Can  any  one  imagine  an  intelligent  person 
preferring  to  listen-in  this  way  to  Bernard 
Shaw's  "Saint  Joan"  rather  than  to  attend 
the  performance  in  person?  We  may  be  sure 
that  the  theatre  will  not  be  seriously  affected 
by  radio  until  sight  and  sound  are  absolutely 
synchronized  and  equally  successful  in  pro- 
duction. And  we  doubt  if  even  then  the  pub- 
lic will  accept  this  sort  of  production  as  a 
substitute  for  the  real  thing. 

WE  ARE,  indeed,  making  progress  in 
radio  music  but  only  because  a  few  (very 
few)  stations  have  progressive  program  direc- 
tors. In  featuring  a  series  of  concerts  and 
lectures  given  during  February  and  March  at 
the  Detroit  Athletic  Club,  station  wwj  of  that 
city  made  it  possible  for  their  listeners  to 
hear,  in  the  musical  line,  William  Backaus, 
pianist  of  international  fame,  Reinald  Werren- 
rath,  and  Margaret  Matzenauer.  One  could 
not  ask  for  more  than  this. 

A  NY  day  or  evening  you  can  tune-in  and 
•*»•  hear  from  one  station  or  another  some 
of  the  latest  books  discussed.  It  may  in- 
terest the  broadcast  directors  to  know  that 
many  people  enjoy  this  feature  who  are  not 


FLORENCE    STERN 

The  youthful  violinist  who  has 
been  heard  through  station  WEAF 


among  those  inclined  to  write  letters  express- 
ing their  commendation. 

THE  young  woman  who,  each  evening  at 
7.05,  from  station  WBZ,  Springfield,  talks 
to  the  kiddies  is  one  of  the  star  radio  enter- 
tainers along  this  line.  She  gives  the  children 
such  worthwhile  stories  that  they  are  also 
enjoyed  by  grown-ups,  which  is  the  test  that 
all  stories  for  children  must  meet  before  they 
can  be  called  literature. 

MISTAKES  in  program  printing  are  not 
infrequent.     A   short   time  ago  a  pro- 
gram  contained  the  announcement,   "Valet 
Music  from  Rosamund  Suite  by  Schubert." 

THERE  must  be  good  piano  teachers  in 
Iowa  and  Nebraska  judging  from  some 
of  the  pupils  heard  through  the  radio  stations 
in  those  states. 

ALL  communications  addressed  to  this  de- 
partment should  be  signed  with  the  full 
name  and  the  address  of  the  writer.  Letters 
are  sometimes  received  that  contain  valuable 
comments  or  suggestions,  but  signed  with  a 
fictitious  name.  It  is  contrary  to  the  policy  of 
this  department  either  to  quote  from  or  other- 
wise to  acknowledge  any  anonymous  com- 
munication. 


How  to  Make  a  Chemical  Plate 

Supply  Unit 

A  Double- Wave  Rectifier  Without  Any  of  the  Faults  of  the  Usual  Type— It  Is 
Very  Simple  and  Inexpensive  to  Make  and  the  Parts  Can  Easily  Be  Secured 


BY  JAMES  MILLEN 


THIS  article  of  Mr.  Millen's  is  a  careful  presentation  of  a  new  suggestion  for  a  chem- 
ical rectifier  to  furnish  plate  potential.  The  average  person  is  inclined  to  think  that 
a  chemical  rectifier  is  necessarily  sloppy  and  unreliable.  This  is  not  precisely  true.  A 
well-made  chemical  rectifier  is,  all  things  taken  into  consideration,  highly  satisfactory  for 
use  as  a  plate  supply.  This  unit  will  furnish  plate  potential  up  to  120  volts  and  current 
enough  for  any  receiver.  On  tests  made  on  one  of  these  units  connected  to  a  receiver  in 
our  laboratory  it  was  noted  that  no  hum  at  all  was  present  in  the  loud  speaker  or  telephones. 
It  will  be  seen  that  the  whole  unit  can  be  put  together  for  less  than  $20,  and  for  those  who 
are  anxious  to  build  a  plate  supply  unit,  we  can  recommend  this  highly.  Service  tests  of 
several  hundred  hours'  duration  made  simultaneously  with  three  complete  units  failed  to 
show  any  noticeable  sign  of  deterioration  in  any  of  the  units.  The  Bureau  of  Standards 
Technologic  paper  No.  265,  "Theory  and  Performance  of  Rectifiers"  by  H.  D.  Holler 
and  J.  P.  Schrodt  may  be  found  very  interesting  to  those  readers  who  wish  to  go  deeper 
into  the  theoretical  side  of  this  subject  than  Mr.  Millen  has. — THE  EDITOR 


THERE  have  been  many  articles  pub- 
lished on  B  eliminators  employing 
thermionic  tubes,  mean  free  path  gas 
tubes,  and  even  miniature  dynamotors 
and  motor  generators.  Very  little  has  as 
yet  appeared  about  a  system  which  is  in 
many  ways  superior  to  any  of  the  others.  No 
doubt  this  evasion  of  the  chemical  rectifier  is 
due  to  a  considerable  extent  to  the  existing 
opinion  in  the  minds  of  many  that  this  type 
of  rectifier  is  sloppy,  inefficient,  and  requires 
considerable  attention.  This,  unfortunately, 
is  true  of  the  majority  of  borax  rectifiers  used 
in  many  amateur  transmitting  stations.  Sev- 
eral years  ago  when  chemical  rectifiers  were 
first  used  for  that  purpose  someone  suggested 
a  solution  of  borax  as  an  electrolyte  and  as  a 


result  borax  has  been  almost  exclusively  used 
for  this  purpose  ever  since.  Of  all  the  differ- 
ent solutions  available,  borax  is  in  my  opinion 
by  far  the  poorest.  I  n  fact  one  is  almost  justi- 
fied in  condemning  the  chemical  rectifier  if  his 
experience  has  been  restricted  to  the  use  of 
borax  as  an  electrolyte. 

Fortunately,  however,  there  are  several  ex- 
ceedingly fine  solutions  for  use  in  lead-alumi- 
num rectifiers,  and  a  properly  made  cell,  such 
as  is  described  in  this  paper,  is  compact,  clean, 
inexpensive,,  and  efficient.  Furthermore,  it 
will  seldom  require  any  attention.  The  relia- 
bility of  the  chemical  rectifier  when  properly 
made  is  most  strongly  emphasized  by  its  use 
by  one  of  the  largest  public  utility  corporations 
in  the  world. 


TRANSFORMER 

+  90 

RADIO   \ 
SET 

RECTIFIER 

FILTER 

+  22 

•  B 

u* 

110  V. 
A.C.  _ 

FIG.    I 

From  lamp  socket  to  radio  receiver.    The  illustration  shows  the  entire  system   as  used   to  change  the 
1 10  volt  alternating  current  to  a  variable  d.  c.  voltage  for  supplying  plate  potential   to   any   radio  set 


How  to  Make  a  Chemical  Plate  Supply  Unit 


221 


Primary 


Pilot  Lamp 
Secondary 


High  Voltage 
Secondary 


FIG.   3 

A  sketch  of  the  transformer  which  steps  up  the 
voltage  to  compensate  for  the  drop  in  voltage 
through  the  rectifier.  This  transformer  is  easily 
reconstructed  from  a  toy  transformer.  An  addi- 
tional winding  of  a  few  turns  provides  for  the  pilot 
light  current  supply 


As  the  chemical  rectifier  unit  is  very  much 
cheaper  than  a  tube  rectifier,  it  is  possible, 
without  greatly  increasing  the  cost  of  the  com- 
plete B  supply  unit,  to  rectify  both  halves  of 
the  alternating  current  cycle.  This  complete 
rectification  makes  possible  the  use  of  a  much 
smaller  filter  system.  Still  another  reason  for 
the  much  greater  ease  with  which  the  output 
of  a  chemical  rectifier  may  be  filtered  is  the 
high  inherent  electrostatic  capacity  of  the 
unit.  The  capacity  of  the  single  unit  des- 
scribed  in  this  paper  is  approximately  i  mfd. 
as  compared  with  the  negligible  capacity  of 
thermionic  tubes. 

Each  cell  (when  used  with  the  solution  men- 
tioned below)  will  stand  well  over  100  volts, 
which  makes  it  possible  to  obtain  between  80 
and  1 20  volts  at  the  set,  depending  upon  the 
transformer  voltage.  This  is  ample  when  used 
with  the  average  broadcast  receiver.  Where 
it  is  necessary  to  rectify  higher  voltages,  then 
several  cells  must  be  used  in  series. 

CONNECTIONS    OF    CHEMICAL    RECTIFIERS 

THERE   are  two  methods  of  connecting 
chemical  rectifiers.     In  the  first  or  bridge 
method,  Fig.  4,  four  small  cells  are  required. 
In  the  second  method,  Fig.  8,  only  one  cell 


(slightly  larger)  is  required,  but  a  double 
transformer  secondary  is  needed  to  feed  it. 
Thus  the  saving  in  rectifier  cells  in  the  one  case 
is  more  than  offset  by  the  additional  trans- 
former secondary  required  in  the  other. 

The  jar  is  a  three  ounce  "salt  mouth" 
bottle  fitted  with  a  rubber  stopper  having 
three  holes,  as  shown  in  Fig.  2.  The  elec- 
trodes are  TVmcn  rods.  The  aluminum  rods 
must  be  chemically  pure.  Commercial  alum- 
inum will  positively  prove  unsatisfactory. 
Lead  rods,  chemically  pure  aluminum  rods, 
and  "salt  mouth"  bottles  are  carried  by  the 
large  chemical  supply  houses.  Eimer  and 
Amend,  i8th  St.  and  2nd  Ave.,  New  York 
City  can  furnish  these  supplies.  In  drilling, 
tapping,  and  cutting  the  aluminum,  extreme 
care  should  be  exercised  not  to  lay  the  rod  in 
any  metal  filings  which  may  be  on  the  work 
bench,  or  to  fasten  it  in  the  metal  jaws  of  a  vise 
unless  protected  by  wood,  cloth,  or  paper.  If 
any  small  metallic  filings  become  imbedded  in 
the  surface  of  the  aluminum,  then  the  film  of 
aluminum  oxide  which  forms  and  breaks  down 
again  with  every  reversal  of  the  current  when 
the  rectifier  is  in  operation,  will  not  be  com- 
plete at  that  point.  In  operation,  this  failure 


Pb 

Cathode) 


Al 

--\ Anode) 


, ^  Seal  with 

parafin 


Collodion  coating 
- 1/4"  above  and 
below  surface  of 
liquid 


FIG.    2 

The  rectifying  jar.  Several  of  these  cells  go  to  make 
up  the  complete  rectifying  unit.  The  anode, 
cathode,  and  vent  are  supported  in  a  cork  top 


222 


Radio  Broadcast 


•110  V. 


FIG.    4 

The  circuit  of  the  chemical  rectifier.     Four  jars  are 
arranged  in  series-parallel   to  obtain    the  double- 
wave  rectification  which  is  properly  smoothed  out 
in  the  filter  resulting  in  a  direct  current 

of  the  oxide  film  completely  to  insulate 'the 
aluminum  electrode  from  the  electrolyte  will 
be  indicated  by  tiny  sparks  appearing  at  the 
impurity.  This  type  of  sparking  should  not 
be  confused  with  the  general  scintillating 
sparking  caused  by  using  too  high  a  voltage 
across  the  rectifiers.  Such  sparking  is  due  to 


the  electrical  breakdown  of  the  insulating 
film  of  aluminum  oxide  and  will  begin  to  take 
place  when  the  impressed  a.  c.  voltage  is 
over  1 60  volts.  The  aluminum  electrode  in  a 
properly  operating  cell  will  glow  with  a  pale 
yellowish-green  light  and  there  will  be  no 
sparking.  A  slight  sparking  does  not,  of 
course,  make  a  cell  inoperative.  In  order  to 
prevent  sparking  and  consequent  consumption 
of  aluminum  at  the  surface  of  the  electrolyte 
where  a  protective  film  is  not  formed,  the 
upper  part  of  the  electrode  is  coated  with 
collodion,  as  shown  in  the  illustrations.  A 
short  length  of  glass  tubing  is  inserted  in  the 
vent  hole  in  order  to  prevent  its  closing  when 
the  stopper  is  squeezed  into  the  bottle. 

Although  there  are  several  good  solutions, 
I  have  found  the  two  given  below  to  be  con- 
siderably superior  to  any  others  that  1  have 
tried. 

Though  not  very  generally  known,  they 
were  among  the  original  electrolytes  used  by 
Professor  Nodon  in  developing  his  "Nodon" 
Valve.  (See  list  of  references  at  the  end  of 
this  article.) 

WHAT    SOLUTION    TO   USE 

THOUGH  not  the  better  of  the  two,  the  sol- 
ution most  easily  obtainable  is  a  saturated 
solution  of  ammonium  borate.  It  is  most 
easily  prepared  by  the  layman  by  adding  sev- 
eral tablespoon fuls  of  ordinary  boracic  (or 
boric)  acid,  such  as  is  to  be  found  in  the  med- 
icine chest  of  every  home,  to  a  half  quart  of 
distilled  water  in  a  glass  or  china  container. 
Add  four  tablespoonfuls  of  ordinary  household 


FIG.    5 

The  complete  circuit  diagram  of  the  chemical  plate  supply  from  input  to  output.      The  dotted  lines  indicate 

the  various  subdivisions  of  the  device,  as  follows:   pilot  filament,  step-up  transformer,  chemical  rectifier, 

filter.     Usual  engineering  practise  is  used  in  this  diagram  referring  to  condenser  capacities 


How  to  Make  a  Chemical  Plate  Supply  Unit 


223 


liov. 


FIG.    7 

The  three  posts  on  the  right  are  the  output.  An 
external  resistance  (variable)  is  connected  between 
the  +90  and  +45  posts  to  obtain  the  detector  voltage 

ammonia  (the  clear  kind — not  the  kind  con- 
taining soap  or  borax).  Shake  well  and  let 
stand  for  several  hours.  The  excess  salt  will 
precipitate  on  the  bottom  and  the  clear  solu- 
tion is  to  be  used  in  the  rectifiers. 

The  other,  and  better,  electrolyte  is  a  satur- 
ated solution  of  primary  ammonium  phos- 
phate. (NH4H2PO4).  It  is  prepared  by  ad- 
ding enough  crystals  of  primary  ammonium 
phosphate  to  one-half  quart  of  distilled  water 
so  that  no  more  will  dissolve  and  then  using 
the  clear  solution  after  the  excess  crystals 
have  settled  to  the  bottom. 

The  practice  of  adding  sodium  or  potassium 
salts  to  the  electrolyte  in  order  to  reduce  its 
resistivity  is  not  to  be  recommended,  for  it  will 
pit  and  corrode  the  anode  (Al).  The  pre- 
sence of  sodium  salts  in  any  quantity  will  also 
cause  the  rectifier  to  give  off  an  unpleasant 
odor  after  it  has  been  in  use  for  some  time. 

Never  add  anything  but  distilled  water  to 
take  care  of  the  loss  of  electrolyte  due  to  elec- 
trolysis and  evaporation.  Addition  of  dis- 
tilled water  for  every  400  hours  of  use  will 
generally  be  sufficient  unless  an  unusually 
large  vent  is  incorporated  in  the  cell. 

In  order  to  prevent  a  short  circuit  when  the 
negative  B  terminal  of  the  set  is  grounded, 
which  is  generally  essential  in  order  to  en- 
tirely eliminate  all  a.  c.  hum,  and  also  to  raise 
the  a.  c.  voltage,  it  is  necessary  to  provide  a 
transformer  in  the  1 10  volt  a.  c.  line.  The 
standard  75  watt  amateur  c.  w.  type  trans- 
former may  be  used  for  this  purpose  by  run- 
ning it  with  a  resistance  in  the  primary  circuit 
or  by  feeding  the  1 10  volt  winding  with  a  lower 


voltage  obtained  from  a  toy  step-down  trans- 
former, in  order  to  reduce  the  out-put  voltage 
to  a  usable  value.  Such  an  arrangement  is, 
however,  both  needlessly  expensive  and  in- 
efficient. A  bell-ringing  transformer  may  be 
worked  backwards  from  a  toy  step-down 
transformer.  Another  bell  transformer  can 
not,  however,  be  substituted  for  the  toy  trans- 
former. Very  satisfactory  results  were  ob- 
tained by  using  an  Acme  i|-henry  double 
choke  as  a  transformer.  One  winding  serves 
as  a  primary  and  the  other  as  a  secondary. 
The  air-gap  must  be  tightly  closed.  (Some 
choke  coils  have  no  air-gap.)  This  will,  of 
course,  be  merely  a  "one-to-one"  transformer, 
and  due  to  the  design,  the  voltage  regulation 
is  poor. 

HOW   TO    MAKE    THE    TRANSFORMER 

FOR  best  results,  a  transformer  should  be 
made  which  will  meet  the  exact  require- 
ments. As  the  cutting  and  rolling  of  silicon 
steel  for  transformer  cores  is  a  task  which  the 
average  person  will  not  care  to  tackle,  the  use 
of  the  core  from  a  toy  step-down  transformer 
is  recommended.  These  cores  are  well  made, 
of  the  shell  type,  and  of  the  right  size.  The 
only  thing  to  be  discarded  is  the  low  voltage 
secondary.  Moreover,  they  may  be  pur- 
chased at  very  reasonable  prices,  the  list  for 
the  one  best  suited  for  this  purpose  being  but 
$3.75.  A  transformer  should  be  selected 
which  has  a  no-load  power  consumption  of  not 
more  than  ten  watts.  The  transformer  re- 
ferred to  above  and  used  in  the  current  tap 
shown  in  the  photographs  meets  all  these  re- 
quirements. It  is  the  new  model  40  watt 

K- 110  V.-- - 


Pb 


DC 

FIG.    8 

The  single  cell  method  of  rectifying.   A  double  trans- 
former secondary  is  necessary  as  the  circuit  shows 


224 


Radio  Broadcast 


Condensers 


Pilot  Lamp, 


45V. 


FIG.    6 

The  wiring  layout.  This  drawing  should  be  compared  with  the  circuit  diagram  in  Fig.  5  to  identify 
the  several  parts  and  also  the  internal  circuits  of  the  choke  coil  and  the  transformer.  The  voltage  regu- 
lation will  be  from  120  to  90  and  45  1024,  depending  upon  the  internal  characteristics  of  the  transformer 


Lionel  toy  transformer.  The  task  of  removing 
the  core  will  be  greatly  simplified  if  some  al- 
cohol is  first  applied  in  order  to  dissolve  the 
shellac  which  binds  the  core  together.  Re- 
move the  low  voltage  winding  and  in  its  place 
substitute  a  secondary  wound  with  No.  28  or 
No.  30  enameled  copper  wire.  Insulate  each 
layer  with  thin  tough  paper.  Protect  the  new 
winding  from  the  core  and  case  with  Empire 
cloth  or  other  suitable  insulation.  The  proper 
number  of  turns  will  be  1 125  for  use  with  am- 
monium borate  electrolyte  and  1030  for  use 
with  the  primary  ammonium  phosphate  elec- 
trolyte. In  either  case,  the  final  filtered  d.  c. 


voltage  will  be  approximately  1 10  volts.     For 
lower  voltages  use  fewer  turns. 

The  fact  that  turning  off  the  A  battery 
switch  on  the  set  does  not  shut  off  the  input 
to  the  power  unit,  makes  it  desirable  to  em- 
ploy a  pilot  lamp  in  order  to  remind  one  of 
the  second  switch.  This  lamp  should  be  so 
connected  as  to  burn  whenever  the  power  unit 
is  turned  on.  A  small-flash  light  bulb,  or  even 
an  automobile  type  bulb  may  be  used  for  this 
purpose.  In  order  that  its  life  may  be  long, 
it  should  be  burned  at  less  than  rated  voltage. 
It  is  to  be  fed  from  a  separate  transformer 
winding  of  a  few  turns  of  No.  20,  No.  22,  or 


PARTS  REQUIRED 


2  Lionel  transformers,  40  watts       .      .  $7.50 

4  W.  E.  2  mfd.  condensers    .      .      .      .  3.60 

i   pound  No.  30  enameled  copper  wire  .  .88 

i    Bradleyohm  No.  10 2.00 

i    Flashlight  bulb  and  socket       ...  .20 

Steel  box,  panel,  binding  posts,  etc.   . 

4  3-02.  "salt-mouth"  bottles       ...  .20 

4  No.  6  rubber  stoppers .20 

i  2-ft.   length   chemically   pure    alum- 
inum rod  f56  inch  diam.  .20 


i  2-ft.  length  lead  rod  iVinch  diam. 
i  6-inch  length  jV  outside  diameter 

glass  tubing 

i  oz.  NH4  H2  PO4  at  6oc  8  oz.      . 


.20 

.05 

•  15 


Total  between  $  15.00  and  $16.00 

The  lead  and  aluminum  rods  come  in  2-foot 
lengths.  This  is  more  than  required,  but  frac- 
tional parts  of  a  bar  are  not  sold. 


How  to  Make  a  Chemical  Plate  Supply  Unit 


225 


No.  24  wire.  The  winding  must  be  well  insu- 
lated from  the  other  windings.  Ten  turns 
will  be  right  for  a  3-volt  flashlight  bulb. 

If  the  output  of  the  rectifier  were  to  be  fed 
directly  into  the  radio  set,  a  disagreeable  hum 
would  be  heard  in  the  loud  speaker.  The  first 
step  to  be  taken  in  the  elimination  of  this  hum 
is  to  pass  the  current  through  a  filter  before 
it  reaches  the  set.  The  purpose  of  the  filter 
is  to  "smooth  out"  the  pulsations  in  the  recti- 
fied current  in  much  the  same  manner  as  the 


air  dome  on  a  reciprocating  water  pump 
"  smooths  out "  the  flow  of  the  water.  Where 
very  large  capacity  condensers  are  employed  in 
the  filter  circuit  (such  as  described  by  Mr.  C.  J. 
Lebel  in  the  September,  1924,  RADIO  BROAD- 
CAST) then  a  more  nearly  correct  hydraulic 
analog  would  be  a  pump  feeding  a  reservoir 
from  Which  a  steady  stream  of  water  might  be 
drawn.  Filters  of  the  reservoir  type,  while 
exceedingly  effective,  are  needlessly  expensive 
and  cumbersome,  so  that  the  use  of  a  filter  of: 


RADIO  BROADCAST  Photograph 
FIG.    9 

The  top  is  removed  from  the  unit  to  show  the  construction.      Either  the  transformer  or  choke  coil  should 

be  shielded.      In  this  model,  the  choke  coil  is  shielded.      This  shield  is  grounded  to  the  metal  box  which  in 

turn  is  connected  to  the  negative  side  of  the  output  supply 


226 


Radio  Broadcast 


the  "smoothing"  type,  such  as  was  described 
in  RADIO  BROADCAST  for  December,  1924,  by 
Mr.  R.  F.  Beers,  is  to  be  recommended  for  use 
with  this  B  supply  unit.  (When  an  S  tube  is 
employed  as  the  rectifying  device,  then  it  be- 
comes imperative  to  use  the  larger  filter).  The 
filter  details  are  given  in  Fig.  5.  The  choke 
coil  should  have  an  inductance  of  about  twenty 
henries  and  must  be  of  fairly  low  resistance. 
The  choke  referred  to  in  the  December,  1924, 
RADIO  BROADCAST  meets  these  requirements. 

MAKING   THE    CHOKE    COIL 

AN  EXCEEDINGLY  fine  choke  for  use 
with  this  outfit  consists  of  one  pound  of 
No.  30  enameled  copper  wire  wound  on  the 
same  type  of  core  as  recommended  for  the 
transformer.  If  No.  30  wire  is  used  for  the 
transformer  secondary,  then  one  pound  of 
wire  will  be  sufficient  for  both  purposes,  as  the 


transformer  will  require  only  about  an  ounce 
of  wire.  The  d.  c.  resistance  of  such  a  choke 
is  but  320  ohms.  Thus  the  voltage  drop  across 
the  choke  will  be  negligible.  The  use  of  audio 
frequency  transformer  secondaries  as  chokes  is 
not  to  be  recommended,  because  of  their  ex- 
tremely high  d.  c.  resistance.  (About  2500 
ohms  for  the  average  transformer  secondary.) 
There  have  been  many  complaints  about 
B  substitutes  whose  output  voltage  varies 
considerably  with  different  loads.  Thus  such 
devices  might  supply  90  volts  to  the  plates  of 
the  amplifiers  in  a  small  two-  or  three-tube 
set  equipped  with  proper  C  batteries,  whereas 
they  would  not  deliver  more  than  forty  or  fifty 
volts  when  connected  to  a  big  "super,"  es- 
pecially if  no  C  batteries  are  employed.  Such 
difficulties  will  never  be  encountered  with  the 
current-tap  described  in  this  paper,  owing  to 
the  extremely  low  relative  resistance  of  the 


RADIO  BROADCAST  Photograph 


FIG.     IO 


A  metal  pan  for  the  jars  keeps  them  in  place  and  prevents  spilling  ot  the  electrolyte  and  the  breaking  of 
jars.     A  wooden  sub-base  allows  the  unit  to  be  assembled  first  and  then  placed  in  the  metal  cabinet 


How  to  Make  a  Chemical  Plate  Supply  Unit 


227 


choke  and  valves  as  well  as  the  excellent  vol- 
tage regulation  of  the  shell-core  transformer 
employed. 

DETAILS    OF    CONSTRUCTION 

'"IP  HE  next  and  almost  equally  important 

*•  step  to  be  taken  in  the  hum  elimination  is 
the  grounding  of  the  negative  B  lead  from  the 
B  eliminator.  This  is  very  important!  Be- 
fore doing  it,  however,  examine  the  regular 
ground  connection  to  your  set  and  see  whether  or 
not  it  is  on  the  opposite  side  of  the  A  battery 
from  the  negative  B.  If  it  is,  then  a  large  fixed 
condenser  must  be  connected  in  series  with 
the  regular  ground  lead  or  else  it  must  be  re- 
moved altogether.  (We  mean  the  ground  to 
the  set,  not  the  ground  to  the  power  supply.) 
If  both  sides  of  the  A  battery  were  to  be  di- 
rectly grounded,  the  A  battery  would  be  short 
circuited. 

The  third  step  is  to  insert  C  batteries  in 
your  set  so  as  to  reduce  the  tube  space  current 
to  a  minimum  consistent  with  good  quality. 

The  fourth  step  is  to  shield  the  choke  coil 
from  the  power  transformer.  I  f  they  are  both 
in  the  same  metal  box,  then  merely  placing 
their  cores  at  right  angles  to  each  other  may  be 
all  that  will  be  required,  although  quite  fre- 
quently, it  is  necessary  to  place  a  grounded 
iron  or  steel  partition  between  them,  or  even 
to  place  one  of  them  in  a  separate  metal  box. 
The  entire  unit  should  be  located  at  least 
three  feet  from  the  set.  This 
is  not  always  essential,  espe- 
cially where  the  unit  is  thor- 
oughly shielded,  but  never- 
theless it  is  a  good  rule  to 
follow. 

The  fifth  and  last  of  the 
precautions  to  be  taken  is  to 
remove  as  far  as  practicable 
from  the  set  any  lamp  cords 
carrying  house  current.  Oc- 
casionally when  one  fails 
completely  to  eliminate  all 
the  a.  c.  hum  in  a  receiver 
using  this  B  supply  it  may 
be  due  to  ungrounded  BX 
cables  and  conduits  which  are  used  in  the 
house  wiring. 

It  might  also  be  well  to  add  that  in  regen- 
erative sets  a  large  fixed  condenser  (^  to  i 
m'fd.)  must  be  connected  directly  from  the 
plus  detector  B  binding  post  on  the  set  to  the 
negative  B  binding  post.  This  condenser 
must  be  located  at  the  set  and  not  several 
feet  away  at  the  unit  itself.  The  small  con- 
denser  connected  across  the  primary  of  the 


FIG.    12 

A  dummy  jar  element 
unit  showing  how  Fahne- 
stock  clip  binding  posts 
of  a  special  type  can  be 
used  to  connect  to  the 
elements.  The  support 
stopper  is  of  rubber. 
The  clips  are  so  designed 
that  they  will  slip  easily 
over  the  anode  and 
cathode  tops 


RADIO  BROADCAST  Photograph 


first  audio  transformer  in  many  such  sets  will 
not  act  as  a  substitute  for  the  larger  condenser 
connected  as  .explained  above.  All  regular 
neutrodynes  have  a  small  condenser  con- 
nected directly  from  the  detector  plate  to  the 
negative  B  which  is  sufficient  in  such  cases. 
Don't,  however,  try  such  an  arrangement  on 
a  regenerative  set  or  it  will  cease  regenerating. 
The  small  pocket  voltmeters  sold  for  testing 
B  batteries  are  worthless  for  determining  the 


RADIO  BROADCAST  Photograph 
FIG.     I  I 
It  is  neat  in  appearance  and 


The  finished  product.  It  is  neat  in  appearance  and 
very  convenient.  The  unit  may  be  placed  on  a 
lower  compartment  of  the  same  table  as  the  radio 
receiver,  unlike  many  unsightly  home  made  plate 
current  supply  devices 


228 


Radio  Broadcast 


voltage  supplied  to  the  set  by  a  B  substitute. 
If  a  milliammeter  and  some  B  batteries  are 
available,  then  a  fair  method  is  to  read  the 
plate  current  when  the  power  supply  is  being 
used,  and  then  switch  over  to  the  B  batteries 
and  by  varying  the  number  in  use,  obtain  the 
same  plate  current  as  with  the  power  supply. 
The  voltage  of  the  B  substitute  is  then  roughly 


that  of  the  B  batteries,  producing  the  same 
plate  current. 

The  cost  of  operating  a  power  unit  drawing 
approximately  ten  watts  from  the  house  cur- 
rent is  $0.0009  per  hour,  Thus  it  costs  but 
about  ninety  cents  for  one  thousand  hours  of 
B  supply  and  there  is  no  shelf  life  deterioration 
when  the  set  is  not  in  use. 


GENERAL    REFERENCES 


For  the  benefit  of  those  who  may  desire  to 
obtain  further  information  on  the  interesting 
subject  of  electrolytic  rectifiers,  the  following 
references  are  given: 


Vol.  i 


Vol.  i 


Transactions    of    the    International 
Electric    Congress    of    1904     "The 
Nodon  Valve,"  by  Prof.  Nodon. 
Transactions     of     The     American 


trolytic   Rectifiers,"   by   Prof.  Bur 
gess. 

QST:  June,  1922,  "Electrolytic  Rectifiers 
for  Amateur  Transmitting  Work," 
by  S.  Kruse. 

These  references  are  mainly  of  a  scientific 
nature  and  contain  little  constructional  infor- 
mation which  would  help  the  builder  of  a  plate 


Electro-chemical  Society,  1902:  "Elec-      supply  unit  such  as  described  in  this  paper. 


WILLIAM    H.    ECCLES 

Demonstrating  at  a  lecture  at  the  Imperial  College  of  Science  in  London  a  circuit  on  which  he  has  spent 
much  time,  which  is  to  bring  about  a  new  method  of  wireless  communication.  The  sending  apparatus 
produces  easily  recognizable  musical  chords  at  the  receiving  station.  The  most  common  chords  would  be 
assigned  to  the  vowel  sounds.  Dr.  Eccles  is  Professor  of  Applied  Physics  and  Electrical  Engineering  at 
the  London  Technical  College  and  a  well-known  authority  on  radio 


Jby  Carl  Dreher 

Drawings  by  Franklyn  F.  Stratford 


Computing  How  Far  a  Radio  Station  Can  Be  Heard 


M 


R.  HARRY  L.  BEACH  of  Bristol, 
Connecticut,  referring  to  our  article 
on  the  sos  in  RADIO  BROADCAST  for 
March,    raises    a    pertinent    issue. 
He  writes  as  follows: 


While  listening  to  the  various  stations  each  night, 
if  I  get  KGO  I  am  highly  elated,  having  accomplished 
an  extraordinary  feat.  On  the  other  hand,  if  I  get 
some  little  station  in  New  Jersey,  I  never  know 
whether  to  be  elated  or  scornful.  You  have  pro- 
posed an  empirical  formula  for  the  interference 
caused  by  any  station  to  a  6oo-meter  signal.  Can 
you  produce  an  equally  simple  formula  expressing 
some  convenient  unit  of  power  or  relative  power 
available  to  me  from  a  broadcast  station,  given  its 
distance  watts  and  frequency?  Local  conditions 
and  'the  efficiency  of  my  receiver  make  it  impossible 
for  me  to  compare  directly  with  any  other  receiver, 
but  if  I  knew  I  was  doing  as  well  to  receive  XYZ  at 
200  miles  as  KGO  across  the  continent  I  would  have 
that  "Grand  and  Glorious  Feeling"  more  often  and 
would  worry  less. 

A  formula  along  these  lines  already  exists, 
fourteen  years  old.  It  is  the  Austin-Cohen 
transmission  formula,  first  reported  in  "Some 
Quantitative  Experiments  in  Long  Distance 
Radio  Telegraphy,"  by  L.  W.  Austin,  in  the 
Bulletin  of  the  Bureau  of  Standards,  Vol.  7,  No. 
3,  Page  315,  arid  reprinted  in  numerous  places 
since.  This  formula  gives  the  received  cur- 
rent in  terms  of  the  current  in  the  transmit- 
ting antenna,  the  effective  or  electrical  height 
(which  is  only  a  fraction  of  the  physical  height) 
of  both  antennas,  the  wavelength,  the  dis- 
tance, and  some  exponential  factors.  The 


exponential  factors  may  be  neglected — not 
because  they  are  small,  for  as  a  matter  of  fact 
they  are  exceedingly  great,  but  for  the  reason 
that  distance  reception  is  accomplished  at 
those  times  when  the  absorption  is  slight,  and 
the  loss  in  signal  is  only  that  imposed  by  the 
simple  inverse-wit  h-distance  law.  In  'other 
words,  the  only  time  that  a  listener  has  a 
chance  to  make  a  distance  record  is  when 
atmospheric  conditions  are  such  that  the 
exponential  factor  approaches  unity  and  does 
not  figure  in  the  problem. 

It  follows  that  the  ability  of  a  station  to 
reach  out  is  expressed  by  its  meter-amperes 
product,  obtained  by  multiplying  the  effective 
height  of  its  antenna  by  the  amperes  flowing 
in  the  ground  lead  thereof.  Suppose 'we' have 
a  typical  5OO-watt  station  with  an  antenna 
whose  physical  height  above  ground  is  1 50 
feet  (roughly  50  meters).  The  effective  or 
electrical  height  might  be  half  of  that,  or  25 
meters.  The  antenna  current  will  be  around 
8  amperes.:  Hence  the  meter-amperes  prod- 
uct is  around  200.  .Some. "mosquito"  broad- 
caster might  have  an  ampere  in  the  antenna 
and  a  height  of  ten.  meters  electrically:  he 
would  rate  only  10  in  this  scale.  High  power 
trans-  and  in.ter-contiriental  radio  telegraph 
stations  range  from  20,000  to  300,000  meter- 
amperes. 

The  sporting  factor  sought  by  Mr.  Beach 
might  be  very  simply  expressed  as 

Distance  in  Kilometers 

DX  Index  = — 

Meter-Amperes 


230 


Radio  Broadcast 


The  only  trouble  is  that  the  Department  of 
Commerce  does  not  publish  the  meter-amperes 
product  of  broadcasting  stations,  although  it 
asks  for  them  in  the  license  application. 
Worse,  this  product  is  seldom  accurately 
known,  because  a  rather  intricate  procedure 
is  required  to  determine  the  electrical  height. 
So,  for  practical  purposes,  we  are  more  or  less 
out  of  luck.  A  rough  approximation  would 
be  simply  to  divide  the  distance  in  miles  by 
the  power  in  watts.  The  Department  does 
print  the  ostensible  power  of  the  stations  in 
occasional  issues  of  the  Radio  Service  Bulletin, 
a  monthly  publication  obtainable  from  the 
Superintendent  of  Documents  at  twenty-five 
cents  a  year.  On 
this  basis,  KGO  with, 
say,  2,000  watts  in 
the  antenna,  heard 
over  a  distance  of 
3,000  miles,  would 
have  a  constant  of 
1.5.  KMO,  with  10 
watts,  would  have 
the  same  constant 
only  15  miles  away. 
This  looks  as  if  there 
should  be  some 
weighting  in  favor  of 
the  higher  powers, 
cutting  them  down  a 
little.  However,  with 
the  meter  -  amperes 
product  unavailable 
the  problem  really 
passes  out  of  the 
realm  of  engineering 
speculation.  It  re- 
minds me  of  a  remark 
of  Professor  N.  S. 


THE   TIPPED    MICROPHONE 


Giuseppe  de   Luca,  baritone   of  the  Metroplitan 
Opera  Company,  toying  with  a  broadcasting  micro- 
phone.    When  the  microphone  is   placed   in  this 
position,  it  becomes  practically  inoperative 


stations  will  put  a  crimp  in  DX  motives.  But 
as  long  as  little  stations  exist,  they  will  have 
the  function,  not  only  of  affording  expres- 
sion to  local  talent  and  taste,  but  also  of  keep- 
ing the  DX  spirit  alive,  by  giving  its  devotees 
an  almost  inaudible  signal,  smothered  in  noise 
nine  tenths  of  the  time,  to  shoot  at. 

Signor  De  Luca  Tips  the  "Mike" 

OUR  illustration  shows  what  happens 
when  you  let  the  artists  run  a  station, 
or  rather  what  would  happen  if  they 
were  allowed  to  run  one.  Here  is  Signor 
Giuseppe  de  Luca,  one  of  the  most  talented 
of  baritones,  publicly 
tipping  a  carbon  mic- 
rophone. Naughty, 
naughty!  For,  when 
a  carbon  transmitter 
is  tipped  at  such  an 
angle,  it  ceases  to  be 
a  microphone.  The 
carbon  falls  away 
from  the  diaphragm, 
and  can  no  longer 
transform  into  elec- 
trical impulses  the 
agitations  produced 
in  the  latter  by  sound 
waves.  Microphones 
of  this  type  must  be 
kept  in  the  vertical 
plane  if  one  intends 
to  allow  it  to  be  acted 
upon  by  voice  or 
music.  But  in  a 


Shaler  regarding  the  scientific  value  of  spiri- 
tualistic manifestations,  that  it  is  like  trying 
to  make  a  topographic  survey  of  the  land  of 
dreams.  Besides,  we  have  steered  entirely 
clear  of  such  factors  as  frequency. 

Nevertheless,  the  fact  remains  that  our 
correspondent's  idea  is  a  logical  one.  The 
fault  is  in  the  rating  of  stations  by  power  alone, 
neglecting  consideration  of  the  actual  radiat- 
ing element,  the  antenna.  If  DX  fishing  is 
anything  at  all,  it  should  follow  that  the 
smaller  the  fish,  other  things  being  equal,  the 
greater  the  glory.  It  is  therefore  a  unique 
sort  of  fishing,  for  all  the  followers  of  Izaak 
Walton  boast  of  the  great  size  of  their 
catches;  they  love  to  stretch  wide  their  arms 
and  mouths  when  recounting  their  piscatorial 
exploits.  The  advent  of  real  super-power 


photograph  any  mic- 
rophone   one  can 
find,  is  just  as  good 
lying  down  as  standing  up. 

Looking  at  the  picture  again,  we  derive  an 
obscure  but  definite,  anarchistic  pleasure 
from  it.  We  are  so  tired  of  upright  micro- 
phones! They  stand  for  good  transmission 
or  the  devil  to  pay,  for  correct  placing,  proper 
vocal-orchestral  balance,  criticism,  watchful- 
ness— all  the  tribulations  and  strains  of  the 
job  of  broadcasting.  But  a  slanting  micro- 
phone— there  is  freedom,  a  simian  carelessness 
for  consequences,  a  flinging  of  heels  to  the  sky! 
It  affects  us  like  the  spectacle  of  an  orthodox, 
stout,  and  reputable  citizen,  reeling,  in 
evening  dress  and  hopelessly  drunk,  down 
Fifth  Avenue  on  Sunday  morning  while  the 
church-bells  ring  for  all  those  who  can  hear 
them.  Bravo  for  Signor  de  Luca  and  the 
publicity  representatives! 


As  the  Broadcaster  Sees  It 


231 


The  "Layer  of  Lines"  Confesses 

IN    THE    New    York    Herald-Tribune    for 
February    27th,    "Pioneer,"    one    of   the 
bright    constellations    of   radio   criticism, 
writes: 

The  lines  from  Schenectady  to  New  York  were 
blown  down  by  high  winds  last  night.  That  is  why 
the  comedy  by  the  WGY  players  did  not  come  as 
scheduled  to  the  listeners  at  WJY.  We  wonder  if 
this  was  not  due  in  some  measure  to  careless  laying 
of  the  lines. 

"Pioneer"  is  a  charming,  conscientious,  but 
non-technical  lady;  she  has  never  straddled  a 
cross-arm  forty  feet  above  ground  in  a  howl- 
ing gale;  the  pole  covered  with  ice,  perhaps, 
and  maybe  a  30,000  volt  transmission  line  in 
close  proximity.  In  other  words,  she  has 
never  had  the  job  of  keeping  an  open  wire 
circuit  during  bad  weather. 

It  happens  that  1  am  very  intimately  con- 
nected with  WJY,  in  fact,  I  "lay"  the  lines. 
Whenever  WGY  and  WJY  are  hooked  up,  I 
start  out  from  Aeolian  Hall  in  the  afternoon, 
a  reel  of  twisted  pair  twelve  feet  in  diameter 
under  my  left  arm,  my  mouth  filled  with  car- 
pet tacks,  and  a  sledge  hammer  in  my  right 
fin.  Loping  along  at  the  pace  of  Mr.  Nurmi, 
I  pay  out  the  line  with  inconceivable  rapidity, 
dodging  trains,  automobiles,  and  dangerous 
animals,  and  here  and  there  fastening  the  pair 
to  a  handy  telegraph  pole  with  a  carpet  tack 
and  a  blow  of  the  hammer.  I  cross  creeks, 
rivers,  ridges,  valleys,  and  mountains,  keeping 
as  straight  a  course  as  possible  up  the  Hudson 
Valley.  At  about  the  same  time  a  represen- 
tative of  WGY  starts  south  with  the  same 
paraphernalia  and  good  intentions.  We  meet 
at  Poughkeepsie,  splice  the  wires,  drink  each 
other's  health  in  a  bucket  of  Hudson  River 
water,  and  return  to  our  respective  stations. 

On  the  afternoon  of  February  26th,  ob- 
serving the  nasty  weather,  I  fortified  myself 
with  three  or  four  dozen  drinks,  prescribed 
by  my  physician,  before  starting  out  on  my 
course.  Something  was  wrong  with  those 
drinks,  or  else  I  did  not  have  enough,  for  no 
sooner  had  I  started  than  I  perceived  that  I 
was  not  in  my  best  form.  I  veered  from  one 
side  to  the  other  of  Manhattan  Island,  missed 
the  telegraph  pole  at  Columbus  Circle,  strik- 
ing a  traffic  officer  instead,  and  mashed  my 
thumb  instead  of  the  carpet  tacks  in  several 
instances.  Nevertheless,  after  the  fashion  of 
heroic  radio  men,  I  persisted  and  made  fair 
progress  until  the  Harlem  River  was  reached. 
I  generally  cross  this  by  way  of  the  Spuyten 


Duyvil  bridge,  because  a  pretty  girl  lives 
near  the  Bronx  end  of  the  viaduct  and 
waves  to  me  as  I  pass.  Besides  the  girl,  I 
always  pay  the  tribute  of  a  thought  to  the 
intrepid  Dutch  courier  who  perished  here 
when  he  plunged  into  the  flood,  crying  that 
he  would  cross  "in  spite  of  the  Devil!"  to 
warn  the  burghers  of  New  Amsterdam  of  an 
Indian  rising  to  the  north — from  which  episode 
the  strait  derived  its  name.  All  I  can  say  is 
that  I  headed  directly  for  the  bridge.  I 
missed  it  by  fifteen  yards,  equivalent  to  about 
a  foot  for  each  drink.  Maladetto  diavalo,  but 
the  water  was  cold!  And  I  had  never  drunk 
the  Harlem  water  before.  The  mammoth  reel 
of  wire  and  the  sledge  hammer  weighted  me 
down.  I  thought  I  would  meet  the  fate  of  the 
Dutch  rider,  and  the  channel  would  have  to 
be  renamed  WJZ-WJY.  How  I  struggled  and 
yelled,  churning  up  the  waters  of  the  Harlem 
like  a  steamboat,  and  bouncing  my  voice 
against  the  side  of  Inwood  Hill.  Suddenly 
something  snapped.  I  thought  it  was  my 
suspenders,  but  now  I  know  it  must  have 
been  the  twisted  pair.  After  epic  exertion, 
I  emerged  on  the  north  side  of  the  river,  and 
raced  on  to  make  up  lost  time.  I  flew  past  Yon- 
kers,  Tarrytown,  Ossining,  where  I  glimpsed 
the  warm  and  well-fed  convicts  at  their  eve- 
ning movie  show,  and  Peekskill.  Wet,  frozen, 
and  bedraggled,  I  staggered  into  Poughkeep- 
sie at  7  o'clock.  My  WGY  colleague  sat  at  the 
amplifier. 

"You're  drunk  and  late,"  he  said. 

"Yes,"  I  wept  hysterically,  "but  here  are 
the  pair!" 

We  spliced  the  wires  in  silence,  and  began 
calling  New  York.  More  silence.  New  York 
did  not  answer.  Then  I  realized  that  the 


I  start  out  A*itli  a  reel  of  twisted  poii 


232 


Radio  Broadcast 


line  was  broken,  grounded  and  crossed  at 
Spuyten  Duyvil.  All  was  lost,  including 
honor!  And  the  next  day  "Pioneer"  razzed 
us  in  her  column.  (A  new  critic  has  just  been 
appointed  and  now  rules  in  Pioneer's  place.) 

The   Memoirs  of  a   Radio   Engineer 

RADIO  is  different  from  all  the  engineer- 
ing arts,  and  has  moved  faster  than 
any  of  the  others  in  the  last  two  dec- 
ades. That  is  my  first  excuse  for  printing 
these  memories  now,  instead  of  waiting  until 
I  am  seventy  years  old.  In  the  second  place, 
to  wait  until  one  is  old,  before  writing  anything 
of  an  autobiographical  nature,  is  a  disparage- 
ment of  youth.  If  the  experiences  of  youth 
are  worth  anything — and  they  appear  singu- 
larly precious  to  all  but  the  most  desiccated  of 
men — surely  they  are  worth  setting  down  at  a 
time  when  they  are  still  comparatively  fresh 
in  one's  memory,  when  some  vestige  of  feeling 
still  clings  to  them.  It  is  logical,  therefore, 
to  write  one's  memoirs  in  two  sections,  one 
at  the  age  of  about  thirty,  the  other  after  one 
has  passed  sixty.  The  writing  of  this  first 
section  is  what  I  now  undertake,  in  somewhat 
the  same  spirit  as  that  which  impelled  Max 
Beerbohm  to  issue  his  "complete  works"  at 
the  age  of  twenty-four. 

Two  objections  remain  to  be  disposed  of. 
The  writing  of  memoirs  is,  for  presumably 
sound  reasons,  a  prerogative  of  famous  per- 
sons, and,  indisputably,  I  am  not  famous.  The 
answer  to  this  is  that  such  personages  will 
appear  in  the  narrative:  I  can  be  Boswell,  if 
not  Johnson.  Furthermore,  only  the  radio 
aspects  of  my  career  will  be  illuminated.  The 
last  suspicion  of  impropriety,  that  involved  in 
the  writing  of  such  a  history  by  a  man  still  in 
the  full  tide  of  events,  may  be  met  by  ter- 


^tfempi:  012  £)£her « 


minating  the  story  at  a  point  sufficiently  far 
back  to  allay  the  apprehensions  of  the  in- 
dividuals and  groups  with  whom  I  have 
fought  so  recently  that  they  still  remember  it. 

These  apologies  and  reassurances  completed, 
the  epic  begins. 

In  1907,  when  I  was  about  eleven  years  old, 
one  of  the  elementary  school  teachers  under 
whom  I  was  incarcerated  delivered  to  his  class 
a  lecture  on  magnetism,  using  for  illustra- 
tion one  of  those  small,  flat,  red-enameled 
horseshoe  magnets  which  at  that  time  sold  for 
a  penny  in  the  stationery  stores.  At  the  same 
time  he  told  the  boys  a  cock-and-bull  story 
about  Mohammed's  coffin,  which,  he  alleged, 
was  suspended  between  heaven  and  earth, 
without  visible  support,  through  the  agency 
of  magnetism.  This  instruction  was  not  a 
part  of  the  work  of  that  class,  I  might  mention; 
the  teacher  was  endeavoring  to  amuse  us, 
during  an  interlude,  in  reward  for  good  be- 
havior. At  any  rate,  the  next  day  I  bought 
one  of  these  little  steel  magnets  instead  of  gum 
drops,  and  amused  myself  magnetizing  my 
mother's  knitting  needles.  I  also  made  an 
attempt  on  my  father's  watch,  and,  while  I  did 
not  succeed  in  imparting  to  it  any  appreciable 
polarization,  my  efforts  were  not  entirely  in 
vain,  for  the  watch  stopped  the  same  day. 
In  my  endeavors  to  suspend  a  miniature  Mo- 
hammed's coffin  between  the  magnet  and  the 
table  I  failed  utterly.  The  armature  either 
jumped  to  the  magnet  or  fell  to  the  table. 
After  a  time  I  gave  it  up  and  shot  one  of  my 
playmates  with  an  air-rifle. 

Shortly  afterward  I  became  interested  in 
electricity.  As  yet  I  did  not  suspect  that 
magnetism  and  electricity  had  any  connec- 
tion. The  first  attracted  iron;  the  second 
rang  bells.  I  crawled  around  in  a  dark  and 
dusty  compartment  under  the  stairs  of  my 
home,  where  the  electric  battery  which  rang 
the  bells  was  located.  This  battery  consisted 
of  sal-ammoniac  cells,  each  with  a  ponderous 
carbon  cylinder  and  a  zinc  rod  in  a  solution  of 
ammonium  chloride.  Three  such  cells  rang 
the  bells  of  the  house.  Dry  cells  were  very 
well  known  by  this  time,  but  their  quality 
was  not  then  good  enough  to  push  wet  cells 
entirely  out  of  the  market.  For  the  same 
reason,  partly,  the  popular  use  of  electric 
flashlights  was  practically  unknown.  The 
electrical  industry  has  changed  remarkably, 
even  in  these  eighteen  years.  There  were  as 
yet  no  tungsten  or  other  metallic  filament 
bulbs,  and  most  store  windows  in  New  York 
City  were  still  lighted  by  Welsbach  gas 
mantles.  However,  I  was  not  yet  interested 


As  the  Broadcaster  Sees  It 


233 


in  the  state  of  the  electric  industry.  The 
Leclanche  cells  in  the  cellar  represented,  to 
me,  a  kind  of  magic.  I  did  not  know  them  by 
their  correct  name,  of  course,  and  in  some  way 
I  got  the  idea  that  they  were  storage  batteries. 
In  due  time  I  went  to  my  parents  and  asked 
for  a  battery  for  Christmas.  I  had  no  clear 
idea  of  what  I  wanted  to  do  with  it,  but  I  be- 
lieved that  with  a  battery  one  might  sustain 
and  impart  electric  shocks  and  perform  mis- 
cellaneous wonders. 

My  father,  then  as  now,  was  a  business  man; 
he  knew  nothing  about  batteries  and  cared 
less.  However,  apparently  he  realized  that  a 
battery  alone  would  not  serve  my  purpose. 
He  bought  me  a  small  electromagnetic  en- 
gine, a  little  wire,  and  three  dry  cells.  This 
engine  could  be  belted,  with  a  rubber  band  or 
a  piece  of  string,  to  a  toy  buzz  saw  which,  on 
days  when  it  was  feeling  good,  could  cut  a 
matchstick  in  two.  I  operated  this  machine 
for  hours  every  day,  and  soon  ran  down  the 
dry  cells.  At  this  time  I  became  acquainted 
with  the  odor  of  ozone,  for  the  remarkable 
engine  functioned  with  a  make-and-break 
contact  at  which  a  fascinating  blue  spark 
flashed.  All  the  boys  in  the  neighborhood 
came  to  see  the  spark,  to  smell  the  ozone,  and 
to  have  matchsticks  cut  in  two.  I  received 
many  flattering  trading  propositions  in  con-; 
nection  "with  "this  possession — a  cannon  eight 
inches  long,  a  dog  which  the  owner  swore 
was  capable  of  speaking  several  intelligible 
words,  and  a  wagon  with  a  soap-box  body  and 
iron  baby-carriage  wheels,  being  among  the 
offers.  All  were  declined. 

But,  among  children,  as  with  their  elders, 
the  tendency  is  to  grow  tired  of  even  the  most 
precious  possessions.  After  a  few  weeks,  the 
excitement  over  the  electric  engine  had  died 
down,  and  it  became  necessary  to  seek  new 
diversions.  The  engine  had  brought  with  it 
the  catalogue  of  an  electrical  supply  firm,  and 
we  began  to  study  this.  Such  books  are  not 
only  informing  in  themselves,  but,  to  a  boy, 
they  bring  up  questions  the  answers  to  which 
he  must  seek  elsewhere.  What  was  a  make- 
and-break  spark  coil,  or  a  polar  relay,  and 
how  did  a  burglar  alarm  work?  Four  or 
five  of  us  began  to  inquire  about  these  mat- 
ters, more  or  less  urgently.  We  were  lucky 
because  an  electrician  lived  in  the  neighbor- 
hood who  had  a  much  greater  theoretical  in- 
terest in  his  craft  than  is  common;  he  did  not 
consider  us  merely  as  nuisances,  which  we  un- 
doubtedly were,  but  good-naturedly  tried  to 
answer  our  questions.  But  he  was  not  our 
only  source  of  information.  In  the  public 


small  Lqys  carae  io  smell  "the  ozone 


D 


library  we  found  perhaps  a  half-dozen  books  of 
the  "boy-electrician"  type,  written  expressly 
for  aspiring  juvenile  experimenters  like  our- 
selves. They  contained  directions  for  build- 
ing voltaic  batteries  out  of  tin  cans,  tele- 
graph sounders  constructed  of  wood  and  the 
vital  parts  of  discarded  electric  bells,  and  even 
induction  coils  which  could  throw  one-quarter- 
inch  sparks.  We  devoured  these  volumes 
and  pooled  our  money  to  buy  wire  and  10- 
cent-store  tools.  At  the  same  time  we  were 
perfectly  normal  and  primitive,  we  had  fist 
fights,  pursued  the  neighborhood  cats  with 
bean-shooters,  and  played  baseball  on  the 
vacant  lots.  If  any  one  had  urged  us  to  study 
electricity  we  should  probably  have  resisted 
instruction  violently.  But,  as  no  one  cared 
one  way  or  the  other,  we  made  fairly  rapid 
progress.  The  main  obstacle  in  our  experi- 
ments was  a  well-known  ailment  of  the  human 
race:  lack  of  money. 

Most  of  our  energy,  on  this  account,  was 
taken  up  in  finding  substitutes  for  expensive 
materials.  For  instance,  when  I  was  twelve 
years  old  I  built  an  electrophorus.  This  is 
an  induction  device  for  collecting  posi- 
tive charges  on  a  metal  plate,  usually  of 
polished  brass,  held  by  an  insulating  handle. 
In  its  classical  form  it  consists  of  an  ebonite 
disc  about  a  foot  in  diameter.  This  is  elec- 
trified negatively  by  beating  or  rubbing  with 
a  piece  of  cat's  fur.  A  metal  plate  of  about  the 
same  size  is  set  on  top  of  the  charged  ebonite. 
The  experimenter  touches  the  top  of  the  metal 
piece.  This  draws  off  the  negative  charge 
of  the  same,  while  the  positive  charge  induced 
by  the  ebonite  remains  bound.  The  metal 
electrode  is  then  lifted  by  the  insulating 
handle.  Now  let  the  knuckle  be  presented 
to  the  edge  of  the  metal  disc,  and  a  spark 
about  an  eighth  of  an  inch  long  will  leap  to  it 
with  a  slight  stinging  sensation.  To  me,  this 


234 


Radio  Broadcast 


workman  prefers  radio  iowLisLey 


was  an  indescribably  dramatic  occurrence. 
Furthermore,  by  repeating  the  touch-and-lift 
procedure,  one  could  draw  sparks  for  hours, 
on  a  dry  day,  without  the  necessity  of  rubbing 
the  non-conductor  again.  This  puzzled  me. 
It  was  not  until  years  later  that  I  understood 
that  1  had  to  work  for  each  spark  by  over- 
coming the  electrostatic  attraction  between 
the  charged  non-conductor  and  the  metal 
plate. 

My  electrophorus  was  not  as  aristocrati- 
cally constructed  as  the  one  described  above. 
Instead  of  ebonite,  I  used  beeswax  and  rosin 
in  various  proportions.  I  spent  at  least  two 
months  melting  and  remelting  these  ingredi- 
ents over  the  gas  stove  in  my  mother's  kitchen, 
in  one  of  her  pie  plates  donated  to  the  cause 
of  science,  in  the  hope  of  getting  a  spark 
a  sixteenth  of  an  inch  longer  than  in  some 
previous  attempt.  When  the  composition 
had  cooled,  I  would  flagellate  it  with  a  piece 
of  flannel,  and  set  on  top  of  it  a  wooden  disc 
coated  with  tin-foil,  which  had  originally 
sheltered  a  piece  of  Liederkranz  cheese.  The 
handle  was  a  stick  of  sealing  wax.  Nature, 
however,  is  impartial.  With  blind  equity,  she 
bestowed  her  electrostatic  sparks  alike  on  me 
and  on  the  learned  professors  at  Princeton 
and  Johns  Hopkins. 

(To  be  Continued) 

Blame  It  on  Radio.  II 

THE  custodians  of  the  art  and  industry 
of  the  theater,  which,  according  to  the 
eloquent   Mr.   Brady,   is  in   process  of 
ruin  through  the  intrusion  of  radio  broadcast- 
ing, may  find  comfort  in  the  similar  sad  plight 
of  other  altruists.    Other  hearts  are  breaking. 
The  British  rum  shops  are  emptied  of  custom- 
ers, the  libraries  are  full  of  books  which  no 
one  reads,  the  once  lovely  maids  and  matrons 
of  Germany  become  the  despair  of  beauty 


specialists.  We  reprint  the  evidence  so  that 
our  readers  may  join  in  the  universal  lamenta- 
tion: 

PREFER   RADIO   TO    WHISKY 

British  Workers  are  more  Sober,  Salvation 
Army  Finds 


LONDON,  Feb.  26.— The  British  workman  of  to- 
day prefers  wireless  to  whisky  and  Bunyan  to 
Barleycorn,  Captain  Charles  Nicholson  of  the  Salva- 
tion Army  told  the  Finsbury  justices  at  their  meet- 
ing to  consider  liquor  license  renewals. 

"  Drunkenness  has  been  reduced  by  one  half  during 
the  last  few  years,"  said  the  Captain,  "and  many 
public  drinking  houses  are  often  empty  on  Sundaj 
evenings." 

— New  York  Times,  Feb.  27,  1925 

RADIO  REDUCES  DEMAND 
FOR  LIBRARY  BOOKS 


It  has  been  said  that  the  new  and  increasing  in. 
terest  in  radio  work  has  caused  a  falling  off  of  interest 
in  the  libraries  of  England.  The  Middlesex  Li- 
brary Committee  reports  that  for  November  of  last 
year  there  were  over  five  thousand  fewer  books  taken 
from  the  library  than  during  the  corresponding 
month  of  the  year  before.  Even  the  work  of  the 
conference  library  was  lessened  by  20  per  cent,  dur- 
ing the  same  time. 

— New  York  Sun,  Jan.  16,  1925 

"RADIO   WRINKLES"    MAR  FAIR 
LISTENERS'   FACES 


By  the  Associated  Press 


BERLIN 


Radio  wrinkles  are  the  latest  bugaboo  of  German 
women,  who  see  their  faces  marred  by  folds  and 
creases  brought  on  by  the  strain  of  listening  to  wire- 
less programs.  Beauty  specialists  affect  to  find  that 
the  faces  of  female  radio  fans  acquire  a  strained  ex- 
pression from  listening  night  after  night  to  the  radio. 

Their  brows  become  knitted,  their  lips  firmly 
pressed  together  and  their  whole  expression  har- 
dened and  less  womanlike,  say  the  beauty  experts. 
The  consequence  is  what  is  called  the  "radio  face," 
of  which  the  chief  characteristics  are  radio  wrinkles. 
— New  York  Herald-Tribune,  January  4,  1925. 

As  a  professional  broadcaster,  practicing 
his  art  and  mystery  in  the  United  States,  I  de- 
rive a  certain  comfort  from  the  last  item, 
which  may  be  set  against  my  grief  at  seeing 
the  sum  total  of  female  pulchritude  in  the 
world  diminished.  May  one  not  infer  from 
this  despatch  that  the  German  broadcast 
programs  are  even  worse  than  the  worst 
American  efforts? 


As  the  Broadcaster  Sees  It 


235 


Oliver  Heaviside 

HOW  many  people  who  own  radio  sets 
heard  of,  much  less  heeded,  the  recent 
death  of  Oliver  Heaviside,  referred  to 
in  the  current  issue  of  the  Journal  of  tie  A.  I. 
E.  E.  as  "an  illustrious  successor  to  Wheat- 
stone,  Maxwell,  and  Kelvin."  Probably  not 
as  many  as  would  regret  the  passing  of  some 
self-styled  radio  expert  who  never  did  any- 
thing better  than  write  meaningless  letters 
after  his  name,  revamp  in  disguised  form  the 
inventions  of  better  men,  turn  out  a  few 
trashy  magazine  articles,  and  plug  himself  in 
the  Saturday  radio  supplements.  That  is  the 
way  of  the  world. 

For  Heaviside  never  tried,  in  the  phrase 
of  the  day,  to  "sell"  himself,  to  be  popular 
and  recognized.  He  was  of  the  stature  of 
the  greatest  figures  of  mathematical  physics, 
and  what  he  wrote  was  not  adapted  to  the 
needs  of  the  kindergarten  or  of  the  consumers 
of  predigested  mental  foods.  No  editor  of  a 
tabloid  newspaper  ever  printed  his  photo- 
graph beside  that  of  some  distinguished  movie 
actress  who  had  just  shot  her  latest  lover,  not 
only  because  no  tabloid  newspaper  editor 
ever  heard  of  him,  but  also  because  few  photo- 
graphs of  Heaviside  existed.  In  his  reluctance 
to  be  photographed  he  resembled  a  great 
American,  Henry  Adams,  a  man  of  somewhat 
less  originality  but  not  dissimilar  tempera- 
ment. 

Heaviside  was  an  Englishman.  He  wrote 
occasional  articles  for  the  Philosophical  Maga- 
\ine,  the  London  Electrician,  and  other  learned 
journals.  He  applied  his  mathematics,  in 
which  he  was  not  much  less  adept  than 
Newton  or  Leibnitz,  to  such  problems  as  the 
propagation  of  electrical  waves  along  wires, 
the  distributed  constants  of  telephone  lines, 
and  the  development  of  the  electromagnetic 
theory  generally.  His  papers  are  inordinately 
hard  to  read.  This  being  called  to  his  atten- 
tion on  one  occasion,  he  answered  sardonically 
that  they  were  even  harder  to  write. 

His  work  had  very  practical  consequences. 
The  fact  is  that  the  Armstrongs,  the  Poulsens, 
the  He'isings,  the  De  Forests,  stand  on  the 
shoulders  of  the  Maxwells,  the  Hertzs,  the  Ray- 
leighs,  the  Websters,  and  all  the  other  dreamy 
investigators  who  live  in  a  shadowy  mathe- 
matical universe  and  write  incomprehensible 
articles  instead  of  selling  real  estate  and  trying 
to  make  enough  money  to  buy  a  Packard. 
The  engineers  and  inventors  deserve  all  the 
credit  they  get,  but  it  should  not  be  forgotten 
that  they  owe  their  eminence  and  high  visi- 


bility to  the  pure  physicists  who  bear  them  up. 
In  the  case  of  Heaviside,  it  is  a  matter  of 
common  knowledge  that  Dr.  Pupin's  work  in 
the  loading  of  telephone  lines  was  largely  the 
conversion  into  physical  facts  of  the  British 
investigator's  abstruse  generalizations.  The 
result  was  a  clarification  of  speech  and  ex- 
tension '  of  range  on  telephone  circuits,  re- 
puted, at  the  time,  to  be  worth  a  few  million 
dollars  to  the  telephone  companies,  and 
probably  second  only  to  the  development  of 
modern  equalizers  and  electronic  repeaters  in 
the  expansion  of  the  telephone  art — which 
includes  radio  broadcasting  and  the  tying  up 
of  broadcasting  stations  by  wire  lines — this  last 
for  the  benefit  of  those  radio  listeners  who 
don't  see  what  Heaviside  has  to  do  with 
them.  Pupin  himself  is  a  rare  combination; 
he  is  equally  at  home  as  a  mathematical 
physicist  and  as  an  engineer  and  inventor. 
He  did  not  complain  that  Heaviside's  articles 
required  hard  work  on  the  part  of  those  who 
read  them;  he  did  the  work  and  collected  his 
royalties.  Personally,  I  am  frank  to  say 
that  I  never  had  the  brains  to  read  Heaviside, 
but  I  have  the  sense  to  raise  my  hat. 

Heaviside  was  deaf  all  his  life,  and  because 
of  that  and  no  doubt  other  causes  he  was  as 
shy  and  seclusive  as  Darwin,  who  could  not 
take  an  ordinary  railroad  journey  without 
the  most  profound  agitation.  He  lived  alone 
in  a  small  cottage  in  Torquay,  which  is  in 
Devonshire  on  the  English  Channel.  He  was 
extremely  poor,  and  in  his  last  years  subsisted 
on  a  pension  of  £  200  a  year.  Nevertheless, 
he  was  seventy-seven  when  he  died.  There 
is  nothing  to  show  that  he  cared  one  way 
or  the  other  about  either  circumstance. 
What  could  such  ephemeralities  mean  to  a 
Heaviside? 


stretch  tieir  arras  and  toasi 


SIMULTANEOUS  OR  TANDEM  TUNING 


AMN  something  new  that  is  not  new 
has  come  up  in  radio.  In  Septem- 
ber, 1910,  John  V.  L.  Hogan  filed  a 
patent  application  for  the  "tuning 
of  circuits."  .The  application  stated  that  the 
primary  object  of  the  methods  described  was 
to  render  the  manipulation  of  the  tuning 
elements  more  easy  and  accurate.  Mr. 
Hogan  goes  on  to  state  the  specific  case  of  two 
or  more  tuned  circuits  having  the  same  values 
of  inductance  (elec^ 
trically  identical  coils 
and  wiring),  shunted 
by  the  same  capacities 
in  variable  condens- 
ers, which  can  be 
maintained  in  reson- 
ance (tuned  to  a  com- 
mon wave),  through- 
out the  entire  range 
of  the  circuits  by 
varying  the  capaci- 
ties "similarly  and 
simultaneously." 
Mr.  Hogan  suggests, 
"The  component 

parts  of  capacities  €2  and  Cj  (the  two  con- 
densers) can  be  mounted  on  the  same  movable 
support."  This  patent  was  granted  twenty- 
eight  months  later.  Twelve  years  afterward, 
several  companies  appreciating  the  possibili- 
ties of  simultaneous  tuning,  built  condensers 
with  two  or  more  sets  of  stator  plates,  and 
with  the  rotating  plates  mounted  on  a  single 
shaft — "the  same  movable  support."  These 
manufacturers  were  somewhat  surprised  to  find 
themselves  antedated  by  a  decade  and  more. 
The  experimenter  who  is  seriously  interested 
in  this  excellent  arrangement  will  find  in- 


Tbe  Lab  Offers  You  This  Month 

ARTICLES  ON 

— Simultaneous  tuning  of  two  or  more  circuits 
with  tandem  condensers — Pointers  that  may 
save  you  months  of  experiment. 
— The  second  step  in  the  Lab  system  of  remedy- 
ing radio  troubles. 

• — How  to  build  an  efficient  and  simple  loop. 
— A  modification  of  the  Knockout  Amplifier. 
— A  safer  and  better  way  of  connecting  most 
loud  speakers. 


valuable  the  theoretical  considerations  treated 
in  Mr.  Hogan's  patent  No.  1,014,002,  and  is 
strongly  advised  to  study  it.  The  enthusi- 
ast who  does  so  will  be  less  prone  to  fall  for 
the  incorrect  arguments  that  prevail  to-day 
among  the  advocates  of  simultaneous  tuning. 
One  of  the  principal  misconceptions  among 
these  is  the  idea  that  any  lack  of  matching  in 
the  coils  can  be  compensated  for  by  the  use 
of  verniers  across  the  condensers.  This  is 
not  the  case,  for  if 
this  is  done,  a  balance 
is  achieved  only  for 
one  setting  of  the 
main  condensers,  and 
it  is  lost  with  the  next 
variation  of  the  tun- 
ing control.  Sets 
employing  such  ver- 
niers take  advantage 
of  the  simultaneous 
tuning  effect  only 
approximately,  and 
the  verniers  in  many 
cases  are  really  sepa- 
rate controls. 

To  achieve  simultaneous  tuning  of  two  or 
more  circuits  the  inductance  values  must  be 
the  same.  Also,  the  capacity  values  must  be 
the  same  and  varied  similarly.  This  last 
provision  is  not  so  difficult.  Any  condenser 
carefully  constructed  will  have  identical 
capacities  (or  sufficiently  near  to  them)  at  the 
same  degree  of  turn.  The  circuit-inductance 
discrepancies  are  more  difficult  to  balance, 
and  experiments  in  the  R.  B.  LAB  show  them 
to  be  the  real  problem  associated  with  simul- 
taneous tuning.  These  inductive  differences 
are  caused  by  the  difficulty  of  winding  r.  f. 


In  the  R.  B.  Lab. 


237 


transformers  to  exactly  similar  inductance 
values,  and  the  unequal  effects  of  wiring  which 
even  the  most  scrupulous  care  will  not  always 
eliminate. 

Fig.  i  shows  the  conventional  two-stage 
tuned  r.  f.  circuit,  with  potentiometer  con- 
trol, adapted  to  simultaneous  tuning.  It 
will  be  observed  that  the  tandem  condenser  is 
used  on  the  last  two  tubes,  one  stator  to  the 
second  r.  f.  stage,  the  other  to  the  detector 
secondary,  and  the  common  rotor  shaft  to  the 
negative  A  battery  terminal.  A  single  con- 
denser tunes  the  first  stage,  r.  f.  Due  to  the 
presence  of  the  antenna  primary  coil,  which  is 
generally  closely  coupled  to  the  secondary  of 
the  first  stage,  the  inductive  discrepancies 
which  we  are  endeavoring  to  avoid  are  gener- 
ally introduced  in  this  coil.  For  this  reason  a 
single  control  (one  shaft  and  three  rotors)  is 
not  advised  in  a  first  attempt  at  tandem  tun- 
ing. '  Also,  in  the  author's  mind,  a  two  con- 
trol set  is  the  more  logical  and  desirable  ar- 
rangement. 

The  grid  leak  is  returned  to  positive  side  of 
the  filament  to  provide  the  desirable  detecting 
bias. 

The  circuit  should,  it  is  needless  to  empha- 
size, be  wired  with  care  to  maintain  r.  f.  leads 
at  similar  inductive  values,  i.  e.,  the  same 
lengths  and  spacing  from  metallic  parts.  If 
the  experimenter  is  successful  in  this,  and  the 
condenser  and  coils  are  matched,  no  further 
adjustments  will  be  necessary,  and  Fig.  i  repre- 
sents the  most  simple  and  ideal  arrangement. 


A  neutrodyne  stabilizing  condenser,  C2  is  conveni- 
ent for  correctly  balancing  the  capacities  of  the  two 
circuits 

Should  the  inductances,  however,  not  be 
balanced  as  will  probably  be  the  case,  they 
must  be  matched  by  additional  adjustments. 
The  simplest  method  is  to  apply  copper  shield- 
ing to  the  coil  with  the  highest  wave,  a  fact 
that  can  be  located  experimentally.  This  will 
lower  the  wavelength  of  that  coil.  Shielding 
is  easily  applied  by  rotating  a  disk  (cut  from 
^j-inch  copper  sheet)  slightly  smaller  than 
the  diameter  of  the  coil,  in  the  field  of  the 
coil  as  you  would  a  tickler.  Or,  strips  of  the 
metal  cut  into  semi-circles,  can  be  clamped  on 
the  outside  of  the  secondary,  the  width  of 
which  will  determine  the  amount  of  inductive 
variation. 

If  these  experiments  fail  to  result  in  satis- 
factory resonance  throughout  the  entire 
tuning  range,  it  is  probable  that  the  capacities 
are  slightly  off  balance  due  to  wiring,  etc. 
This  can  generally  be  remedied  by  connecting 
a  condenser  designed  for  neutralizing  circuits 


GO 


-8   +22.5    +90 


FIG.    I 

Simultaneous  tuning  of  the  conventional  r.  f.  cir- 
cuit. Note  the  grid  condenser-grid  leak  connections 


238 


Radio  Broadcast 


FIG.  3 

Type  of  "tandem  circuit"  sets  experimented  with  in  the  R.  B.  Lab.     Three  circuits 
and  one  dial  is  considerably  more  difficult   than   the   two  control  arrangement 


as  suggested  in  Fig.  2.  A  condenser  of  this 
type  consists  of  two  separated  metal  rods, 
covered  by  a  glass  tube,  over  which  is  clamped 
a  movable  metal  clamp.  Moving  the  clamp 


or  slide  will  throw  the  extra  capacity  to  the 
correct  circuit. 

Simultaneous   tuning  may  be  adapted  to 
any  form  of  circuit.     Even  three  or  four  cir- 


RADIO  BROADCAST  Photograph 


FIG.    4 

Coils,  transformers,  and  condensers  are  easily  tested  in  respect 
to  "opens"  or  break  down  with  a  small  battery  and  ear  phones 


In  the  R.  B.  Lab. 


239 


cuits  can  be  controlled  with  one  dial,  if  the 
arrangement  is  effected  with  expert  nicety. 
With  more  than  two  stators,  shielding  is 
generally  necessary  between  and  around  the 
stators  to  reduce  undesirable  capacity  effects. 
Elementary  shielding  is  illustrated  in  the 
single  control  set  in  Fig.  3. 

SHOOTING  TROUBLE 
PART  II 

WE  DISCUSSED  last  month  a  logical 
and  efficient  system  for  locating  the 
"trouble  area,"  in  the  various  cases  of  a  re- 
ceiver becoming  inoperative.  When  the 
difficulty  has  been  located,  the  remedy  is  gen- 
erally obvious  and  simple.  Running  in  the 
same  order  as  the  tests,  the  following  are  the 
logical  curative  processes: 

A    BATTERY 

IF  THE  battery  is  found  to  be  low,  recharge 
it.  Replace  broken  leads  with  new  wire. 
Corroded  terminals  should  be  scraped,  sand- 
papered, and  coated  with  vaseline.  Should 
hydrometer  readings  show  a  repeatedly  low 
drop  and  short  life  in  one  cell,  the  battery 
should  be  taken  to  a  dealer  for  examination. 
Rheostats  can  usually  be  repaired. 

B    BATTERY 

Replace  or  short  out  low  cells  or  batteries. 


Last  Amp  Tube 


111  Mfd 


0 

+  90-150  V 

FIG.    6 

A  better  way  of  connecting  your  loud   speaker, 
without  decreasing  volume.     This  diagram  offers 

several  advantages 


AUDIO    FREQUENCY    AMPLIFIER 

JACK  prongs  and  sockets  bear  the  first 
inspection.  Pressing  up  or  down  with  a 
pencil  or  a  strip  of  wood  will  locate  a 
faulty  spring,  which  may  be  permanently 
bent  into  place. 

The  cure  for  broken  connections  in  any  part 
of  the  set  is  obvious.  Knocking  about  the 
bus-bar  with  a  pencil  will  often  locate  a  break 
(generally  at  a  soldered  joint)  which  has  be- 
fore eluded  a  painstaking  search. 

Opens  or  breaks  occasionally  occur  in  the 
flexible  leads  to  audio  frequency  transformers. 
Transformers  and  coils  are  easily  tested  for 
opens,  with  a  small  battery  and  a  pair  of  re- 


OA- 
3 

OB  + 
135-150 

FIG.    5 

The  improved   Knockout  amplifier  circuit.     Volume  control  by  the  elimination  of  the  transformer  is 
effected  by  the  rotary  switch,  and  the  extra  A  battery  post  facilitates  the  use  of  an  8-volt  power  tube 

in  the  last  stage 


240 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 
FIG.    7 
The  completed  loop  from  the  rear 


ceivers.  (Fig.  4).  One  phone  -cord  runs  to 
the  battery,  and  the  other  to  the  winding  under 
test.  The  remaining  connection  is  from  the 
winding  to  the  battery.  A  loud  click  on  break- 
ing the  circuit  indicates  a  perfect  coil.  Trans- 
formers can  be  tested  while  in  the  set. 

Terminal  breaks  can  be  soldered,  but  in- 
terior breaks  in  the  transformer  winding  can- 
not be  easily  repaired.  In  a  case  like  this  it 
is  much  better  to  buy  a  new  transformer. 

Impedances  and  resistances  can  be  tested  in 
the  same  manner,  and  should  be  replaced  if 
defective. 

RADIO    FREQUENCY    AMPLIFIER    AND    DETECTOR 

OPEN   circuit   in   wiring   or   windings    in 
radio  frequency  transformers,  can  almost 
always  be  soldered  with  comparative    ease. 
Potentiometers  may  be  repaired  or  replaced 
according  to  the  ability  of  the  experimenter. 


Broken  down  bypass  con- 
densers should  be  replaced 
with  new  ones. 

TUBES 

A  BAD  tube  is  generally 
incurable.  Once  in  a 
blue  moon  a  hard  knock 
with  a  pencil  will  help 
matters,  but  a  replacement 
is  generally  the  only  re- 
course. 

PHONES  AND  LOUD  SPEAKER 

I  EADS  are  simply  replaced 
•-»  and  terminal  breaks 
can  be  resoldered  with  res- 
in core  solder.  Breaks  in 
the  windings  are  best  re- 
ferred to  the  manufacturer 
for  repair. 

ANTENNA    AND    GROUND 

IF  THE  trouble  is  traced 
to   the    antenna    or  the 
ground,   most  of  the  rem- 
edies are  obvious.     If  the 
antenna  is  down,  there  is 
but  one  thing  to  do.     If  the 
lead-in  is  short-circuiting 
against  part  of  the  building, 
the  leads  should  be  read- 
justed so  that    the  proper 
tension    is    preserved.      If 
there    is    a    break    in    the 
ground  lead    soldering  the 
broken  connection  or  replacing  the  damaged 
wire  will  solve  this  problem. 

In  the  July  RADIO  BROADCAST,  we  will  dis- 
cuss remedies  for  the  receiver  when  it  works 
poorly. 


F 


AN  IMPROVED  KNOCK-OUT 
AMPLIFIER 

IGURE  5  shows  a  modification  of  the 
Knockout  amplifier  described  in  the 
December  RADIO  BROADCAST.  The 
essential  variation  of  this  diagram  from  the 
original  circuit  is  switch  "S,"  of  the  two-blade 
rotary  type  permitting  the  elimination  of 
the  transformer.  This  provides  a  desirable 
volume  control  in  the  many  instances  when 
the  intensity  delivered  by  the  full  complement 
of  tubes  is  excessive.  With  the  transformer 
out,  the  amplifier  functions  as  two  stages  of 
straight  resistance  coupling.  Because  of 


In  the  R.  B.  Lab. 


this,  best  results  will  probably  be  secured  by 
using  a  loo.ooo-ohm  resistor  as  a  coupling 
resistance  in  the  first  resistance-coupled  stage 
rather  than  the  25o,ooo-ohm  unit  recom- 
mended in  the  original  article.  The  sug- 
gested values  hold  for  the  remainder  of  the 
circuit. 

In  Fig.  5  a  further  modification  will  be 
noted  in  the  provision  of  a  separate  binding 
post  for  the  positive  filament  terminal  of  the 
output  tube.  This  provides  for  the  use  of  a 
uv-2O2  or  similar  power  tube  in  the  last  stage. 
This  tube  requires  a  lighting  potential  of 
eight  volts  for  most  efficient  operation. 
When  so  used  the  six-volt  leads  run  to  posts  2 
and  3,  while  the  eight-volt  lead  or  tap  is  con- 
nected to  post  No.  i.  When  six-volt  tubes 
are  employed  throughout,  posts  i  and  2  are 
birdged  over. 

This  amplifier  may  be  added  to  any  receiv- 
ing set,  immediately  following  the  detector  or 
reflex  tube.  For  additional  details,  the  in- 
terested reader  is  referred  to 
December,  1924,  RADIO 
BROADCAST. 

A  BETTER  LOUD 
SPEAKER  CONNECTION 

IN  MANY  cases,  from  the 
standpoint  of  general  re- 
sults, it  is  incorrect  prac- 
tice to  connect  the  loud  speaker 
directly  in  the  plate  circuit  of 
the  last  or  output  tube  of  the 
amplifier.  Such  a  connection 
is  usually  recommended  by  the 
manufacturer  because  of  its 
simplicity.  The  improvement 
suggested  in  Fig.  6  is  offered 
to  the  fan  who  has  been  grad- 
uated from  his  first  book  of 
instruction. 

The  diagram  represents  the 
last  stage  of  any  amplifying 
system :  resistance,  impedance, 
or  transformer  coupling,  and 
its  output,  the  loud  speaker. 
The  additional  parts  required 
are  the  choke,  "X",  and  the 
one  -  microfarad  condenser  C. 
Reactance  "X"  can  conveni- 
ently be  the  secondary  of  an 
ordinary  amplifying  trans- 
former. It  will  be  observed, 
and  herein  lies  the  variation 
from  the  conventional,  that 
the  loud  speaker  is  not  in  the 


plate  circuit  proper,  but  its  place  is  taken  by 
the  choke  coil.  The  audio  results  are  of  the 
same  intensity  as  those  outputted  by  the  more 
usual  arrangement,  with  the  following  ad- 
vantages: 

Only  alternating  current,  the  sound- 
producing  variations,  passes  through  the 
speaker  windings.  This  removes  the  stress 
of  a  strong  magnetic  attraction  on  the  dia- 
phragm, a  strain  that  often  results  in  a 
rattle  when  strong  signals  are  coursing 
through  the  windings.  The  loud  speaker 
windings  are  also  safeguarded  from  induced 
surges  when  the  plate  circuit  is  suddenly 
opened,  or  the  stress  resulting  from  short- 
circuited  tube. 

There  are,  however,  a  few  loud  speakers, 
especially  designed  for  inclusion  in  the  direct 
plate  circuit,  and  which  work  better  in  that 
position.  These  instruments  generally  place 
importance  on  the  polarity  of  connections. 
In  Fig.  6,  no  consideration  is  given  to  polarity. 


FIG.    8 


RADIO  BROADCAST  Photograph 


The  center  construction  of  the  loop.     Any  convenient 
wire  below  No.  20  can  be  substituted  for  the  braid 


242 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 
FIG.   9 
An  attractive  and  efficient  coil  antenna 


A  UNIQUE  LOOP 

MANY  descriptions  of  receiving  sets 
take  the  loop  a  little  too  much  for 
granted,  merely  specifying  it  as  the 
correct  antenna,  and  leaving  the  details  to  the 
imagination  of  an  often  inexperienced  radio 
constructor.  The  loop  pictured  in  Figs.  7,  8, 
and  9,  will  function  very  satisfactorily  on  all 
loop  receivers  and  will  cover  the  broadcast 
band  when  shunted  by  a  .00035  mfd.  variable 
condenser.  Its  form  is  somewhat  unique  and 
its  qualities  excellent.  The  following  parts 
were  used  in  making  this  loop: 

6  pieces  of  Formica,  or  hardwood,  12  inches  long, 

f  inch  wide  and  j>6  inch  thick. 
i  piece  of  Formica  cut  in  the  shape  of  a  hexagon, 

4§  inch  from  face  to  face  and  -fg  inch  thick. 
I  piece  of  brass  tubing  or  rod  20  inches  long  and  f 

inch  in  diameter. 


100  feet  of  Springfield    i6-strand   braided  copper, 

made  at  Springfield,  Mass. 
121  brass  round  head  machine  screws,  /.>  or  £f,  and 

\  inch  long. 
10  brass   round    head    machine   screws   -^   and   f 

inch  long. 
2  brass  round  head  machine  screws  ^  inch  and 

1 1  inch  long. 
2  brass  washers  about  f  inch  thick  and  with  a  hole 

in    them    large    enough    for   the  -fc  machine 

screws  to  go  through. 

Any  convenient  wire  can  be  substituted  for 
the  braid.  No.  18  annunciator  wire  will 
probably  give  quite  as  good  results,  though  ap- 
pearances may  suffer  slightly. 

The  bottom  spoke  of  the  loop  should  have  2 1 
holes  threaded  in  it  with  an  -fa  or  -^  tap, 
beginning  one  half  inch  from  the  outside  end 
and  spacing  the  holes  one  half  inch  toward  the 
inside  end.  The  remaining  five  spokes  have 
only  20  holes  beginning  one  half  inch  from 
the  outside  end.  From  the  inside  end  of  all 
six  spokes  tap  two  holes,  the  first  f  of  an 
inch  from  the  end  and  the  second  if  inch  on  a 
line  through  the  center. 

The  rest  of  the  story  is  told  in  the  photo- 
graphs. Fig.  7  details  the  control 
construction  and  the  manner  of 
winding.  Fig.  8  is  a  rear  view  of 
the  complete  loop,  which  Fig.  9 
shows  in  operation. 

COLDERING  has  been  a  problem 
^  of  the  radio  fan  for  some  time. 
The  acid  fluxes  and  pastes  that 
facilitate  a  creditable  joint  in  the 
more  strenuous  trades  are  taboo  in 
radio  construction.  Acid  corrodes 
the  delicate  wires,  and,  like  the  con- 
ventional pastes,  works  its  way  into 
places  where  it  introduces  leaks 
with  accompanying  noises.  The  R.  B.  LAB 
has  had  great  success  with  an  excellent  non- 
acid  soldering  fluid  manufactured  and  sold 
by  John  Firth  and  Company,  New  York 
City. 

THERE  are  four  or  five  different  sizes  of 
B  batteries  available  to  the  radio  experi- 
menter, and  it  is  often  a  puzzling  question  as  to 
which  size  is  the  most  economical  in  the  long 
run.  The  ultimate  economy  is  determined  by 
the  number  of  tubes,  and  where  the  batteries 
are  to  be  used  (r.  f.,  a.  f.,  etc.),  B  battery  volt- 
age, C  battery,  and  the  amount  of  usage  and 
the  individual  characteristics  of  the  tubes 
themselves. 

If  you  replace  your  B  batteries  more  often 
than  every  three  months,  it  will  be  profitable 
for  vou  to  change  to  a  larger  size. 


Some  Facts  About  Sound  Waves 

How  They  Are  Produced  and  How  They  Are  Analyzed 
— The    Laws   That    Govern   the    Action    of    Sound 


BY  B.  F.  MIESSNER 


COUND,  as  radio  experimenters  who  have  had  a  hand  in  developing  communi- 
*•*  cation  by  radio  telephony  have  discovered,  is  a  subject  deserving  of  much 
study  and  experiment.  Broadcasting,  after  all,  is  merely  the  transference  of  sound 
from  a  broadcasting  studio  to  the  listener.  We  are  using  radio  means  to  accomplish 
this,  and  many  devious  electrical  paths  does  the  sound  follow  before  it  emerges  from 
the  loud  speaker  of  the  radio  listener.  A  good  broadcast  engineer  has  to  devote  almost 
as  much  of  his  attention  to  sound  as  he  does  to  the  actual  radio  mechanics  of  its 
transmission.  Mr.  Miessner  in  these  articles  is  attempting  to  tell  the  important 
physical  facts  about  sound.  In  his  first  article  (RADIO  BROADCAST,  for  January, 
1925),  he  told  of  the  importance  of  sound  in  the  cosmic  system  and  its  particular 
relation  to  radio.  His  second  article  in  the  April  RADIO  BROADCAST  was  a  dis- 
cussion of  the  basic  physical  facts  about  sound.  This  article  continues  the  dis- 
cussion and  includes  some  excellent  photographs  and  diagrams  of  sound  waves. 
This  discussion  of  Mr.  Miessner's,  while  somewhat  technical,  has  a  direct  and  im- 
portant bearing  on  radio  broadcasting. — THE  EDITOR 


THE  sound  waves  we  hear  are  produced 
by  minute  variations  in  the  normal 
pressure    of    the    atmosphere.     The 
crests  of  these  waves  are  called  con- 
densations, because  in  them  the  air  is  con- 
densed or  compressed.    In  a  graphical  analysis 
they  are  shown  as  the  positive  halves  of  the 
wave  graph.     The  hollows  of 
the  waves  are  called  rarefac- 
tions, because  in  them  the  air 
pressure  is  lessened  or  rarefied; 
these  in  graphical  analysis  are 
shown  as  the  negative  halves 
of  the  wave  graph. 

The  actual  variation  in  pres- 
sure constituting  sound  waves 
is  very  small  indeed  compared 
with  normal  pressure.  While 
measurements  of  these  varia- 
tions are  very  difficult  to  make 
because  of  their  extreme  min- 
uteness and  fleeting  nature,  the 
most  reliable  results  thus  far 
indicate  that  the  ear  can  hear 
a  sound  having  an  amplitude  or 
pressure  variation  of  only  one 
one  thousandth  of  a  dyne  per 
square  centimeter.  The  actual 
pressure  variation  of  the  weak- 
est audible  sound  is  about  one 
part  in  ten  billion — in  terms  of 


the  normal  atmospheric  pressure  of  nearly 
fifteen  pounds  per  square  inch.  A  pressure 
variation  of  one  thousand  dynes  per  square 
centimeter,  which  is  one  million  times  the  min- 
imum audible  variation,  is  painfully  loud  and 
represents  the  high  intensity  extreme  ordinarily 
encountered.  Extremely  loud  sounds  then, 


FIG.    I 


A  photograph  showing  the  reflection  of  a  circular  water 
wave  by  a  plane  surface,  such  as  a  straight  sea  wall 


244 


Radio  Broadcast 


FIG.  2 

The  photograph  shows  the  reflection  of  a  circular 
water  wave  by  a  curved  surface  as  a  curved  sea  wall 

are  produced  by  pressure  variations  of  only  one 
ten  thousandth  part  of  the  normal  atmos- 
pheric pressure,  or,  in  actual  pressure,  about 
.0015  pounds  per  square  inch.  There  is  no 
pressure  gauge  which  will  measure  such  small 
variations  of  pressure.  Some  indication  of 
the  delicacy  and  sensitivity  of  the  human  ear 
may  be  gained  by  these  facts. 

SOUND   WAVE    PICTURES 

DHYSICISTS  have  long  used  a  kind  of 
*  topographic  map  to  indicate  the  sound 
waves  in  a  given  locality.  As  the 
civil  engineer  shows  high  lands 
by  closely  spaced  lines  and  low 
lands  by  widely  spaced  lines,  and 
connects  all  points  of  equal  eleva- 
tion by  these  lines,  so  the  phys- 
icist has  used  such  lines  to  indi- 
cate the  regions  of  high  and  low 
pressure  forming  the  condensa- 
tions and  rarefactions  of  sound 
waves.  The  actual  photographs 
of  spark  waves  published  in  a 
previous  article  of  this  series 
(RADIO  BROADCAST  for  April), 
show  these  same  effects  very 
clearly  and  beautifully.  Refrac- 
tion shadows  of  water  waves  also 
show  them  very  clearly. 

As  the  result  of  much  experi- 
ment, the  writer  has  succeeded  in 
developing  an  exceedingly  simple 
method  of  producing  and  photo- 
graphing water  waves,  which  illus- 


trate perfectly  the  effects  of  sound  waves 
and  the  laws  determining  their  behavior. 
Several  of  these  photographs  are  repro- 
duced herewith,  and  numerous  others  will 
be  used  in  succeeding  articles. 

While  these  representations  of  sound 
waves  are  valuable  in  aiding  the  under- 
standing of  acoustic  phenomena,  and  par- 
ticularly in  tracing  qualitatively  the  effects 
of  reflection,  refraction,  absorption,  diffrac- 
tion, and  other  important  characteristics, 
a  more  accurate  method  is  necessary  for 
quantitative  representation  and  analysis. 
If  we  take  an  instantaneous  cross  section 
of  a  simple  water  wave,  we  may  get  a  pic- 
ture like  that  shown  in  our  illustration. 
Such  views  of  waves  may  be  obtained  in 
aquariums,  where  a  plate  glass  window 
constitutes  one  side  of  the  tank,  and  per- 
mits observation  of  the  fishes  inside.  The 
wave  is  seen  here  as  variations  of  height 
from  point  to  point  above  and  below  the 
normal  water  level. 

If  we  place  a  pressure  measuring  device  at  P 
and  measure  the  pressure  of  the  water  at  that 
point  at  equal  time  intervals  as  the  wave 
passes  overhead,  we  may  construct  a  curve  or 
graph  with  rectangular  coordinates,  which 
will  show  the  variations  of  pressure  with  time, 
as  the  illustration  shows.  If  the  point  P 
moves  downwards,  thus  increasing  the  normal 
or  steady  pressure  of  the  water,  the  axis  of  the 
curve  will  move  upwards,  and  vice  versa,  but 
the  wave  itself  will  remain  unchanged,  being 
shifted  up  or  down  accordingly.  The  vertical 


FIG.  3 

How  a  circular  water  wave  is  absorbed  without  reflec- 
tion   by  an  inclined  surface  such  as  a  sandy  beach 


Some  Facts  About  Sound  Waves 


245 


lines  or  ordinates  represent  pressure,  the  hori- 
zontal lines  or  abscissae,  represent  time.  Such 
representations  of  waves,  or  in  fact  any  kind 
of  variation,  are  quite  common  and  serve  a 
very  useful  purpose  in  study  and  analysis. 

THE   PHYSICAL  CHARACTERISTICS  OF  SOUND 

COUND  waves,  like  alternating  currents, 
^  are  classified  and  described  physically 
according  to  amplitude,  frequency,  length, 
and  form. 

Amplitude.  The  amplitude  of  a  sound  wave 
refers  physically  to  the  actual  increase  above 
or  decrease  below  the  normal  atmospheric 
pressure  at  the  crest  or  hollow  respectively. 
It  is  usually  expressed  in  terms  of  dynes  per 
square  centimeter  although  for  convenience, 
any  other  units  of  force  and  area  may  be  used. 
The  amplitude  is  related  to  the  volume  or 
loudness  of  a  sound.  But  while  the  loudness 
increases  with  the  amplitude,  the  relation 
between  them  is  not  simple  or  linear.  The 
loudness  is  more  closely  related  to  what  the 
physicist  calls  the  energy  of  the  vibration. 
The  physical  energy  of  a  simple  vibration  is 
proportional  to  the  square  of  the  amplitude. 
This  expresses  a  general  law  true  for  all  kinds 
of  vibratory  energy.  To  illustrate:  If  several 
similar  waves  have  amplitudes  of  one,  two, 
and  three,  their  respective  energies  will  be 
in  the  ratio  of  one,  four,  and  nine. 

While  the  physicist  must  use  such  interpre- 
tation in  his  study  of  the  physics  of  sound,  the 
psychologist  knows  that  the  ear  does  not  re- 
spond with  a  loudness  sensation  strictly 
proportional  to  the  physical  energy  of  the  im- 
pressed sound.  There  is  a  general  law  familiar 


-   Water p 


FIG.    5 

Waves  of  similar  frequency,  but  of  differing  ampli- 
tudes.    This  drawing  shows  that  the  energy  of  a 
simple  wave  is  proportional  to  the  square  of  the 
amplitude,  the  frequency  remaining  constant 

to  the  psychologist  as  Weber's  law,  which  has 
been  verified  approximately  for  most  of  the 
senses,  and  which  states  that  the  sensation 
produced  by  a  sense  stimulus  is  proportional  to 
the  logarithm  of  the  physical  energy  of  that 
stimulus.  That  is  to  say,  if  the  loudness  of  a 
given  sound  be  increased  from  i,  to  5,  to  10, 
the  actual  energy  would  be  increased  ac- 
cordingly from  i,  to  150,  to  22,500.  The 
corresponding  physical  amplitudes  would  be 
the  square  roots  of  these  latter  values,  or,  i, 
12,  and  150. 

This  law,  while  not  accurately  true,  and 
varying  considerably  for 
different  ears,  is  neverthe- 
less important  and  must 
constantly  be  borne  in  mind 
in  radio.  For  example,  if  a 
loud  speaker  must  be  made 
to  give  five  times  as  much 
sound  intensity  or  volume, 
it  must  be  provided  with 
about  1 50  times  as  much 
energy  in  its  actuating  cur- 
rent! 


Screen ; 


FIG.    4 

A  sketch  of  a  water  wave  as  seen  through  the  glass  side  of  a  tank, 
showing  the  wave  in  cross  section.  If  one  view  the  wave  on  one 
side  through  a  cross  section  screen  as  indicated,  with  its  lower  left 
hand  corner  on  P,  the  wave  appears  as  a  graph  on  the  rectangular 
coordinates.  Moving  P  and  the  screen  up  and  down  merely  moves 
the  curve  oppositely  on  the  chart  without  changing  the  wave  form 


SOUND   WAVE     FREQUENCY 

THE  frequency  of  a 
sound  wave,  like  the 
frequency  of  any  other 
wave,  may  be  stated  as  the 
number  of  similar  waves 
passing  a  given  point  in  a 
second.  The  term  wave  de- 


246 


Radio  Broadcast 


notes  a  compression  and  a  rarefaction.  Fre- 
quency in  general  terms  refers  to  the  pitch  of  a 
sound.  Grave  or  low-pitched  sounds  are  low 
in  frequency;  shrill  or  high-pitched  sounds 
are  high  in  frequency. 

The  lowest  sound  on  a  piano  tuned  to  inter- 
national pitch  is  27  vibrations  per  second; 
middle  C  is  259,  and  the  frequency  of  the 
highest  sound  is  4138  cycles,  or  double  vi- 
brations, per  second.  Fig.  6  shows  a  piano 
keyboard  tuned  to  international  pitch  and  the 
corresponding  sound  pitch  and  wavelength  of 
each  key.  The  piano  is  thus  an  extremely 
valuable  frequency  standard  for  use  in  deter- 
mining by  comparison  the  frequency  of  any 
musical  sound.  While  not  so  accurate  and 
unchanging  as  a  set  of  tuning  forks,  it  is  never- 
theless a  very  convenient  and  fairly  accurate 
standard  which  is  available  in  almost  every 
home.  The  piano  strings,  of  course,  sound 
many  overtones,  so  that  each  key  actually 
produces  a  number  of  sounds  besides  the 
lowest  or  fundamental  vibration.  These  are 
exact  multiples  of  the  fundamental.  I  nasmuch 
as  the  fundamental  tone  characterizes  the 
pitch  as  we  hear  it,  we  need  not  concern  our- 
selves with  the  overtones  in  such  pitch 
comparisons  for  determining  the  vibration 
frequency  of  some  other  sound  source. 

The  normal  human  ear  will  detect  sounds  of 
frequencies  as  low  as  16  and  as  high  as  20,000 
cycles  per  second.  The  actual  limiting  fre- 
quencies depend  largely  on  the  intensity  of  the 
sounds  themselves,  the  limits  extending  with 
the  loudness  of  the  test  sounds;  for  example, 


with  very  weak  sounds  the  limits  might  be  20 
to  15,000  cycles — for  very  strong  sounds  12  to 
25,000  cycles. 

SOUND    WAVELENGTH 

THE  length  of  a  sound  wave  is  the  distance 
between  successive  waves  measured  from 
corresponding  points.  If  the  frequency  be 
known,  the  wavelength  may  be  computed  by 
dividing  the  frequency  into  the  velocity  of 
propagation.  Thus,  a  sound  having  a  fre- 
quency of  100  double  vibrations  (cycles)  per 
second  has  a  length  of  1090  divided  by  100, 
or  10.9  feet. 

In  general,  these  relations  are  represented 
by  the  equation  V  =  NL,  where  V  is  the 
velocity,  and  L  the  length  of  the  wave.  By 
using  V  =  300,000,000,  the  velocity  of  radio 
waves  in  meters  per  second,  N  in  cycles  per 
second,  and  L  in  meters,  the  wavelength  or 
frequency  of  any  radio  broadcast  wave  may 
be  computed  similarly,  providing  one  of  these 
factors  be  known. 

The  loudness  sensation  of  sounds  having 
the  same  physical  amplitude  but  differing  in 
frequency  (i.e.,  wavelength),  is  not  the  same. 
It  requires  a  much  greater  amplitude  in  low 
than  in  high  tones  to  produce  a  given  loudness 
sensation.  This  curious  fact  may  easily  be 
observed  in  a  piano.  The  large,  low-toned 
strings  move  visibly  and  strangely  with  a  circu- 
lar kind  of  motion,  the  higher  strings  vibrate 
less  visibly,  and  the  very  highest  cannot  be  seen 
to  vibrate  at  all.  And  yet  all  of  the  strings 
emit  sounds  of  about  the  same  loudness. 


I! 


00  (ji 


O  tO  M  *>  CT>  ~vl  VO 

us  in  ro  co  -u  -si 


_ .  to  ro  {*  oo  co  oo 

10  o  cr>  01  oo  01  oo 


00171  ID  ~j-vj 


roro 
oooto 
coaiO 


orv> 
vooo 
010 


N>N> 
£t 

IDCTi 


rou> 

VON) 

toco 


FIG.    6 

The  frequencies  and  corresponding  wavelengths  of  the  sounds  produced  by  the  keys  on  a  piano 


Some  Facts  About  Sound  Waves 


247 


The  physical  law,  true  for  all  vibratory 
energy,  states  that  the  energy  of  the  vibration 
is  proportional  to  the  square  of  the  frequency, 
the  amplitude  remaining  constant.  To  illus- 
trate: Three  sounds  having  equal  amplitudes 
but  unequal  frequencies  such  as  100,  200,  and 
300,  would  have  physical  energies  in  the  re- 
lation of  i,  4,  and  9.  The  actual  perceived 
loudness,  however  does  not  follow  this  physical 
law  closely.  While  a  detailed  analysis  of  the 
perception  of  sound  is  not  properly  a  part 
of  a  physical  discussion,  and  will  be  reserved 
for  a  later  article,  it  may  be  stated  in  passing, 
that,  for  equal  energies  the  ear  hears  very  high 
pitched  sounds  louder  than  very  low  ones, 
and  mid-range  sounds  louder  than  either  high 
or  low.  We  can  hear  sounds  of  wavelengths 
between  about  68  feet  (i.e.,  16  cycles)  and 
0.65  inch  (i.e.,  20,000  cycles).  When  both 
the  amplitude  and  frequency  vary,  the  energy 
is  proportioned  to  the  product  of  amplitude 
squared  and  frequency  squared. 

THE    WAVE    FORM    OF    SOUND 

THE  only  form  of  wave  thus  far  discussed 
is  that  of  the  simplest  possible  type  which 
is  known  as  the  curve  of  sines,  or  more  gener- 
ally as  a  sine  wave.  Its  mathematical 
derivation  need  not  be  introduced  here.  This 
type  of  wave  in  sound,  while  valuable  as  a 
basis  for  analysis,  is  really  an  extremely  rare 
phenomena. 

The  sine-wave  sound  is  called  a  pure  sound 
or  tone,  meaning  that  it  consists  of  but  one 
vibration  frequency;  it  has  no  overtones. 
The  purity  of  a  tone  refers  to  its  freedom  from 
overtones,  and  not  to  any  aesthetic  quality 
which  this  expression  is  sometimes  meant  to 
convey.  A  pure  tone  is  extremely  uninterest- 
ing musically. 

The  sounds  of  nature,  of  music  and  of 
speech,  are  always  relatively  complex  in  this 
sense.  Your  voice  in  speaking  or  in  singing 
what  you  think  is  a  single  tone  may  consist 
of  twenty-five  or  more  component  simple 
tones,  extending  upwards  in  frequency  from 
the  fundamental  or  lowest  frequency  vibration 
to  the  highest  overtone  detectable  by  the 
human  ear.  A  few  musical  instruments,  such 
as  the  flute,  the  French  horn,  and  certain  types 
of  organ  pipes,  can  be  made  to  produce  nearly 
pure  sounds,  in  which  most  of  the  emitted 
energy  is  concentrated  in  one  frequency, 
but  a  few  weak  overtones  are  always  present. 

Complex  sounds  consisting  of  many  com- 
ponent partial  tones,  do  not  have  the  simple 
wave  form  of  the  pure  sound.  Instead,  the 
wave  form,  like  the  sound  itself,  is  very  com- 


FIG.    7 

Waves  of  the  same  amplitude,  but  of  differing  fre- 
quency.    The  energy  is  shown  here  as  proportional 
to  the  square  of  the  frequency  when  the  amplitude 
is  the  same 

plex.  Fig.  9  shows  such  a  wave  form  repre- 
senting the  complex  sound  of  a  single  organ 
pipe.  The  frequencies,  amplitudes,  and  ener- 
gies of  all  the  partial  simple  tones  in  this  sound, 
as  tabulated,  completely  describe  the  sound 
itself,  except  for  what  is  known  as  the  phase 
relations  of  the  components,  which  is  a  matter 
of  secondary  and  even  doubtful  importance. 
The  energy  column  is  calculated  from  the 
other  two.  The  sum  of  the  energies  of  the 
separate  component  partial  tones  is  the  total 
energy  of  the  whole  sound. 

FINDING   THE    WAVE    FORM   OF    SOUNDS 

THE  wave  forms  of  various  sounds  can  be 
photographically  recorded  by  an  instru- 
ment known  as  the  oscillograph.  The  electri- 
cal oscillograph  when  used  in  conjunction  with 
special  microphones  and  amplifiers  such  as 
are  now  used  in  high-quality  broadcasting, 
will  produce  a  visual  moving  picture  or  a 
photographic  record  of  the  wave  form  of  any 
sound  impressed  on  the  microphone. 

Professor  Dayton  C.  Miller,  of  the  Case 
School  of  Applied  Science,  about  ten  years 
ago  devised  a  remarkable  type  of  sound 
oscillograph  which  he  calls  the  "Phonodeik." 
This  ingenious  instrument  permitted  him  to 
record  the  wave  forms  of  many  different  types 
of  sound  and  to  analyze  their  records  at 
leisure.  By  his  skillful  mathematical  calcula- 
tions, the  slight  distortion  of  the  instruments 
could  be  corrected  and  the  true  wave  form  of 
the  recorded  sound  developed. 


248 


Radio  Broadcast 


frequencies  and  amplitudes  of  all  the  com- 
ponent partials.  This  may  be  done  by  a 
rather  laborious  mathematical  calculation 
using  the  Fourrier  equations,  or  an  instrument 


FIG.    8 

Waves  whose  frequency  and  amplitude  are  both 

different.     The  energy  is  here  shown  as  proportional 

to  the  product  of  the  amplitude  squared  and  the 

frequency  squared 


Once  the  wave  form  is  obtained,  it  is  possible 
for  sounds  with  only  harmonic  components 
(tha,t  is  exact  multiples  of  the  fundamental 
frequency)  to  analyze  the  wave  and  to  de- 
termine exactly  what  simple  waves  it  contains; 
it  is  further  possible  to  determine  the  relative 


FREQ. 

AMP. 

ENERGY-N^ 

Fundamental  =lst  Partial 

100 

32.0 

104.0 

2nd      " 

200 

22.0 

194.0 

3rd      " 

300 

13.0 

152.0 

4th       " 

400 

7.0 

78.5 

5th       " 

500 

3.5 

30.6 

6th       " 

600 

3.0 

32.4 

7th       " 

700 

2.0 

19.5 

8th       " 

800 

4.0 

102.0 

9th       " 

900 

2.0 

32.0 

10th      " 

1000 

1.5 

22.5 

llth      " 

1100. 

1.0 

12.1 

12th      " 

1200 

1.0 

14.4 

FIG.    9 

The  complex  sound  wave  produced  by  a  single  organ 
pipe.  Its  harmonic  analysis  gave  the  table  of 
simple  tones  which  provides  an  accurate  physical 
description  of  the  sound  itself.  The  wave  was  ob- 
tained by  Professor  Dayton  C.  Miller  of  Case  School 
of  Applied  Science,  Cleveland,  with  his  "Phonodeik" 


FIG.    10 
Professor  Miller's  "Phonodeik"  which  records  the  wave  form  of  sounds 


known  as  the  Harmonic  Analyzer  may  be 
used  (based  on  the  same  mathematical  laws) 
which  traces  the  curves  of  all  the  partial 
tones  directly. 


FIG.    A 

Through  an  error,  the  spark  wave  photographs  pub- 
lished on  page  1061  in  Mr.  Miessner's  article,  "The 
Physics  of  Sound"  in  RADIO  BROADCAST  for  April 
were  printed  so  as  not  to  show  the  actual  waves 
themselves.  Figs.  A,  B  and  C,  are  reproductions 
showing  the  circular  shadows  of  the  spherical  waves 
of  condensation  (dark),  and  rarefaction  (light)  pro- 
duced by  an  electric  spark  behind  the  central  black 
disc.  This,  Fig.  A,  shows  a  curved  wave  striking  a 
soft  felt  pad  without  reflection.  Here  the  wave  in 
the  felt  is  being  absorbed  and  converted  into  heat 


FIG.    B 

Here  the  large  circle  is  the  shadow  of  an  expanding 
spherical  wave.  These  photographs  are  presented 
through  the  courtesy  of  the  Riverbank  Laboratories, 
Geneva,  Illinois 


249 

By  means  of  such  a  process  of  recording  and 
analysis,  the  mixture  of  simple  tones  in  musi- 
cal sounds  can  be  determined  just  as  the 
optician  can  determine  with  the  spectroscope 
the  various  light  frequencies  present  in  any 
particular  light  emitted  by  a  given  light  source. 

Not  only  this,  but  even  more  remarkable 
things  can  be  accomplished.  With  such  an 
analysis  of  any  given  sound  as  is  shown  in  Fig. 
9,  the  physicist,  like  the  artist  who  mixes 
numerous  colors  to  produce  the  particular 
shade  he  desires,  can  synthetically  produce  the 
same  kind  of  sound.  To  do  this  he  produces 
simultaneously  the  component  pure  tones  of 
correct  frequency  and  amplitude,  as  deter- 
mined by  the  analysis,  using  electrically 
vibrated  tuning  forks  or  stopped  organ  pipes. 
Almost  any  kind  of  musical  sound  can  thus  be 
imitated  with  practically  perfect  completeness. 


FIG.    C 

The  wave  here  shown  is  being  reflected  with  reversed 
curvature  from  a  hard,  flat  surface.  It  shows  the 
reflection  or  "echoing"  of  a  spark  sound  at  the 
surface  of  a  hard  body.  These  photographs  are 
very  unusual  ones,  even  though  from  a  photographic 
point  of  view  they  may  appear  to  be  slightly  hazy. 
The  poor  appearance  of  the  negatives  is  due  in  no 
part  to  poor  photographic  technique,  but  it  is  wholly 
the  result  of  the  extreme  difficulty  of  the  subject 

The  modern  pipe  organ  is  one  of  the  finest 
examples  in  which  these  principles  are  used. 
Dozens  of  different  musical  qualities  or  tone 
colors  can  be  produced  by  control  of  the  tone 
mixing  stops  on  the  manual.  The  "Telhar- 
monium"  and  the  "Choralcello,"  in  which 
similar  effects  are  produced  by  electrically 
vibrated  sounding  bodies,  have  wonderful 
possibilities  in  this  direction,  but  have  never 
attained  commercial  development. 


The  Better  Receiver  Contest 

Additional  Information  About  Our  Search  for  an  Improved  Receiver 
for  Home  Construction— A  Prize  of  $200  for  the  Design  of  a  Better  Set 


A  EX  PLAINED  in  the  April  maga- 
zine, RADIO  BROADCAST,  since  its 
inception,  has  been  endeavoring  to 
present  to  its  readers  an  abundance 
of  up-to-the-minute  radio  information  with 
special  attention  to  exceptional  receivers  for 
home  construction.  Not  content,  however, 
with  news  alone,  it  has  always  been  a  policy 
that  nothing  be  printed  that  was  not  an  im- 
provement over  that  which  had  gone  before. 
So  it  was  that  eventually  the  Roberts 
Knockout  receiver  was  first  presented  to  the 
radio  field,  and  we  have  failed  since  that  time 
to  find  a  better  circuit  combining  the  various 
and  singular  attributes  of  this  unusual  set, 
although  much  effort  and  considerable  money 
have  been  spent  in  this  direction  by  the 
RADIO  BROADCAST  Laboratory.  Members  of 
our  technical  staff,  combining  a  wealth  of 
technical  knowledge  and  experience,  have  been 
experimenting  for  the  past  eight  months,  but 
they  confess  that  they  are  unable  to  improve 
the  basic  features  of  this  receiver. 

Now  what  we  should  like  to  know  is,  Where 
can  a  better  receiver  be  found?  We  confess 
we  are  beaten,  and  we  are  ready  to  pass  the 
buck.  The  responsibility  naturally  devolves 
upon  those  to  whom  the  radio  field,  in  the 
final  analysis,  owes  most,  to  those  experi- 
menters and  amateurs,  engineers  and  what 
not,  who  have  contributed  development  upon 
development,  discovery  upon  discovery  to  the 
art  of  radio  telegraphy  and  telephony. 

WHERE    CAN    A    BETTER    RECEIVER    BE    FOUND? 

DO  YOU  know  of  a  better  receiver?  If 
you  do  write  to  us  and  tell  us  about  it, 
or,  better  still,  send  us  a  set  all  hooked-up 
and  we  will  test  it  in  our  Laboratory.  If  it 
is  better  than  the  Roberts  we  are  willing  to 
pay  generously  for  an  article  completely  de- 
scribing it  and  if  it  meets  with  the  approval 
of  those  selected  to  serve  as  judges  in  this 
contest,  we  will  mail  you  a  check,  not  for  $100 
as  indicated  in  our  April  announcement,  but 
for  $200  which  amount  we  consider  more  in 
keeping  with  the  magnitude  of  the  task  which 
we  have  set  before  you. 

We  remain  unconvinced.  We  don't  be- 
lieve that  you  can  do  it.  Do  you  think  you 
can?  Then  write  to  us  and  prove  it ! 


The  following  specifications  must  be  in- 
corporated in  the  desired  receiver: 

1 .  The  receiver  must  not  radiate. 

2.  It  may  employ  four  tubes  (or  less  if  you 
think  four  are  unnecessary). 

3.  It  must  be  extremely  selective. 

4.  It  must  be  constructed  to  occupy  a  reason- 

ably small  amount  of  space. 

5.  It  must  be  capable  of  operation  with  dry  cell 

and  storage  battery  tubes. 

6.  It  must  be  capable  of  operation  with  tubes 

operated  at  their  normal  filament  voltage. 

7.  It  must  be  built  to  permit  the  transfer  of 

tubes  from  one  socket  to  another  without 
materially  changing  the  results  obtained. 

8.  It  must  produce  good  quality,  without  blast- 

ing or  rattling  on  a  cone-type  loud  speaker. 

9.  It  must  be  capable  of  satisfactory  perfor- 

mance with  several  makes  of  parts  designed 
for  similar  use. 

10.  It  must  not  require  critical  grid  condenser 

or  grid-leak  adjustment. 

11.  It  must  be  simple  to  control. 

12.  It  must  permit  the  use  of  voltage  up  to  120 
on  the  audio  amplifier  tubes  (though  less  may 
be  used  if  desired). 

13.  The  plate  current  consumption  of  the  four 
tubes  (measured  at  normal  filament  voltage) 
must  not  exceed  10  milliamperes  when  stor- 
age battery  tubes  are  used. 

14.  It   must   be   capable   of  exceptional   long- 
distance reception,  with  volume  sufficient  to 
fill  a  good-sized  living  room. 

15.  It  must  be  simple  to  operate. 

16.  It  must  be  free  from  hand  capacity. 

17.  Shielding  must  not  be  used. 

1 8.  It  must  be  capable  of  loud  speaker  opera- 
tion on  two  tubes. 

It  will  be  noticed  by  comparing  the  above 
specifications  with  those  contained  in  the  April 
announcement  that  a  few  changes  have  been 
made.  These  changes  have  been  considered 
necessary  in  view  of  the  extreme  difficulty  of 
the  task  we  have  set  before  you,  and  they 
make  the  goal,  on  the  whole,  perhaps  easier 
of  attainment. 

Three  judges  have  been  appointed  to  de- 
cide impartially  which  is  the  better  receiver — 
yours  or  the  Roberts.  You  will  get  a  square 
deal  at  their  hands. 

The  conditions  of  the  tests  which  we  will 
give  your  apparatus  remain  as  indicated  in  the 
original  announcement. 

This  offer  is  made,  we  repeat,  only  to  those 


The  Better  Receiver  Contest 


251 


who  are  interested  in  designing  receivers  for 
home  construction.  Later,  if  manufacturers 
of  complete  sets  wish  to  employ  a  similar 
method  of  proving  the  excellence  of  their 
apparatus,  we  will  have  no  objection,  but  in 
this  particular  contest  only  home  built  sets 
are  concerned. 

Most  of  the  letters  received  thus  far  present- 
ing us  with  descriptions  of  apparatus  to  be 
entered  in  this  contest,  have  failed  to  comply 
with  the  conditions  set  forth  above.  We 
caution  future  participants  that  unless  the 
rules  governing  this  contest  are  adhered  to, 


their  communications  will  not  receive  our 
consideration.  Many  of  our  correspondents 
about  this  contest  have  failed  to  adhere  to 
some  one  or  more  of  the  rules.  The  receiver 
to  be  entered  must  fit  the  specifications 
printed  above.  When  you  write  us  about 
your  receiver,  please  condense  your  informa- 
tion as  much  as  possible  and  take  great  care 
with  the  circuit  diagrams. 

Now  we  ask  again,  Have  you  a  better  re- 
ceiver than  we  have  discovered?  We  doubt 
it,  but  if  you  are  sure  you  have,  submit  it  to 
us  and  we  will  test  it  out. 


FITTING   THE    RADIO   TO   THE    RADIATOR 

This  photograph  shows  a  receiver  placed  on  a  metal  cabinet  which  fits  over  the  radiator.  Ordinarily,  the  ra- 
diator, especially  in  small  homes  and  apartments  is  somewhat  uneconomical,  because  the  space  it  occu- 
pies cannot  be  used  for  anything  else.  The  cabinet  contains  a  humidor  which  moistens  the  air  and  the 
shelf  is  insulated  which  keeps  it  from  absorbing  heat.  With  this  cabinet,  made  by  the  Dixie  Metal  Pro- 
ducts Company  at  Birmingham,  Alabama,  the  radiator  is  made  to  do  double  duty.  The  new  Farrand- 
Godley  loud  speaker  and  Carter  self-supporting  loop  are  also  shown 


HTHE  photograph  in  the  lower  left  shows 
the  receiver  with  the  Lynch  Lead  ready  to 
put  in  the  automobile.  The  circle  in  the  upper 
left  shows  how  a  potato  can  be  used  to  de- 
termine the  polarity  of  the  battery  leads. 
When  the  current  is  on  and  the  bare  wires 
applied  to  the  potato,  a  green  deposit  forms 
around  the  negative  wire  which  is  then  con- 
nected to  the  negative  terminal  of  your  receiver 


Take  Your  Radio  Set  to  the 

\\  THEN  your  radio  receiver  goes  on  summer  motor  and  camping 
W  ent  to  take  along  storage  batteries  to  supply  the  filament  vol 
of  the  automobile  furnishes  six  volts  which  is  the  proper  potential 
of  the  tubes.  The  photographs  on  these  pages  show  how  the  Lynch 
H.  Lynch,  editor  of  this  magazine,  can  be  used  for  connecting  the 
to  the  radio  receiver.  The  Radiola  super-heterodyne  is  supplied 
the  illustrations  show  how  Brightson  True  Blue  Power  Plus  tubes 
tery  filament  and  a  small  base  can  be  substituted  in  the  "super." 

In  the  Radiola  super-heterodyne,  the  dry  cells  which  furnish 
considerably  to  the  weight  of  the  receiver.  If  the  Lynch  Lead  is 
tomobile  storage  battery  for  the  dry  cells  the  "decreased  weight  of 
more  portable — an  important  consideration  for  summer  radio. 

Any  radio  receiver,  including  all  those  described  in  this  magazine, 
can  be  operated  in  this  way  from  the  automobile  battery.  The 
shows  Mr.  Lynch  operating  superheterodyne  in- his  automobile, 
loud  speaker  in  use. 


upper  cut  shows  John  B.  Brennan,  Technical   Editor 
of  RADIO   BROADCAST,  substituting   Brightson  True    Blue 
Tubes    in  the   Radiola    super-heterodyne    so  that   it   may  be 
operated  from  the   automobile  storage  battery.     The  center 
photograph  shows  the  space  left  in  the  battery  compartment  of 
the  "super"  when  the  dry  cell  A  batteries  are  removed 


Country ! 

trips,  it  is  often  inconveni' 
tage.  The  storage  battery 
for  supplying  the  filaments 
Lead,  developed  by  Arthur 
automobile  storage  battery 
with  three-volt  tubes  and 
which  have  a  storage  bat' 

the  filament  potential  add 
used,  substituting  the  au- 
the  receiver  makes  it  far 

with  the  use  of  this  cord, 
photograph  at  the  right 
Note  the  small  Amplion 


A  Simple  and  Inexpensive  Unit  Which  the  Home  Constructor 
Can  Easily  Build— It  Can  Be  Applied  to  Any  Type  of  Receiver 

BY  A.   O'CONNOR 


ANY  number  of  radio  users  have  tried  for  a  long  time  to  find  a  simple  method  of 
converting  their  present  receivers  to  super-heterodynes.  Nothing  short  of 
complete  rebuilding  has  been  the  solution  in  the  past.  Up  to  now,  there  has  really 
been  no  satisfactory  method.  The  frequency-changer  circuit  described  by  Mr. 
O'Connor  in  this  article  is  really  a  "canned"  super-heterodyne  which  can  be  applied 
to  any  kind  of  a  receiver  except  a  super-heterodyne  itself. 

Obviously  there  are  two  main  avenues  of  endeavor  which  lead  to  the  discoveries 
of  real  improvements  in  radio:  those  undertaken  by  commercial  interests,  and  those 
in  which  the  home  experimenter  plays  the  leading  r61e.  RADIO  BROADCAST  believes 
that  it  should  present  the  best  and  most  helpful  material  which  may  be  developed 
by  both  types  of  radio  investigators.  We  judge  the  material  which  is  considered 
fortheeditorialpagesof  the  magazine  by  one  measure:  Will  it  help  the  reader?  The 
fact  that  Mr.  O'Connor  falls  into  the  commercial  rather  than  the  private  investi- 
gator class  has  not  influenced  our  policy  in  publishing  this  interesting  and  helpful 
article. — THE  EDITOR 


A^UPER-HFTERpDYNE  of  two  tubes 
is  not  only  possible  but  practical;  any 
receiver  now  in  operation   may  be 
made  into  a  sensitive,  selective  super- 
heterodyne.    With    these    two    thoughts    in 
mind,  the  writer  began  experiments  over  a 
year  ago  that  brought  the  results  outlined  in 
this  article  describing  a  simple  one-tube  unit 
that  will  make  a  "super"  out  of  any  good  re- 
ceiver, be  it  simple  or  complicated. 

Briefly,  this  unit  changes  incoming  signals 
to  a  given  frequency,  just  like  the  best  of 
super-heterodynes,  and  the  receiver  that  the 
listener  now  possesses  acts  as  the  "intermedi- 
ate frequency  amplifier"  that  is  such  an  im- 
portant part  of  present  super-heterodynes. 
This  unit  is  not  difficult  to  construct,  requires 
but  little  room,  and  uses  standard  parts  that 
may  be  obtained  generally. 

Such  a  unit  will  allow  hundreds  of  thousands 
of  listeners  to  have  the  benefits  of  the  "super" 
at  small  cost  and  without  discarding  their 
present  receivers. 

WHAT   THE    "SUPER"    REALLY    IS 

TO    UNDERSTAND    just    how    such    a 
simple    super-heterodyne    may    be    con- 
structed it  is  necessary  to  delve  a  bit  into  the 
theory  underlying  this  selective  circuit.     The 
"super"  is  really  a  frequency-changer,    and 


this  unit,  described  in  RADIO  BROADCAST  for 
the  first  time  is,  simply,  a  frequency  changer. 
In  super-heterodyne  receivers  incoming  fre- 
quencies are  changed  to  some  lower  frequency, 
after  which  they  are  amplified  by  "inter- 
mediate-frequency" amplifiers  and  then  de- 


FIG.   1 

The  broadcasting  band  of  frequencies  is  820,000 
cycles  wide  and  is  represented  here  by  taking  a 
point  on  the  circumference  of  a  wheel  and  marking 
out  its  path  as  it  rolls  along  the  frequency  line.  At 
the  end  of  one  complete  revolution  the  point  has 
traversed  820,000  cycles.  The  smaller  wheel 
representing  the  oscillator  dial  traces  a  similar  path 
but  in  one  revolution  it  traverses  only  30,000  cycles. 
There  are  two  points  60,000  cycles  apart  that  a  given 
station  may  be  heard 

tected  in  the  usual  fashion.  The  lower  fre- 
quency varies  with  different  super-heterodynes, 
but  usually  is  about  30,000  cycles  (10,000 
meters).  There  are  reasons  why  this  frequency 


Making  Your  Receiver  a  Super-Heterodyne 


255 


may  not  be  much  lower,  but  few  why  it  cannot 
be  higher,  and  that  is  what  is  done  in  this  unit 
where  an  intermediate  frequency  of  about 
500,000  cycles  (600  meters)  is  used. 

These  lower  frequencies  are  generated  by  a 
phenomenon  called  "beats"  and  are  the  result 
of  compounding  two  waves  of  different  fre- 
quency. As  a  concrete  example,  let  us  suppose 
the  intermediate  amplifiers  are  tuned  to  30,000 
cycles  and  an  incoming  signal  has  a  frequency 
of  750,000  cycles  (400  meters.)  Within  the 
receiver  is  a  frequency  generator  which  we  may 
vary  until  the  difference  between  its  frequency 
and  that  of  the  incoming  wave  is  30,000  cycles. 
At  this  point  the  intermediate  amplifiers  work 


r 50o,ooo~ 

K- 820,000~- 

* i.ooo.ooo 

FIG.    2 

By  making  the  smaller  wheel  much  larger,  the  path 
a  given  point  on  its  circumference  would  trace  out 
is  longer.  Before  it  completes  two  revolutions  how- 
ever, it  is  outside  the  broadcasting  band,  and  for  this 
reason  there  will  be  only  one  point  on  the  oscillator 
dial  where  a  given  station  will  be  heard 

best  and  the  signal  will  be  passed  along  to  the 
detector. 

This  lower  frequency  may  be  obtained,  in 
general,  at  two  adjustments  of  the  oscillator 
dial,  namely,  at  the  750,000  plus  30,000  or 


780,000  cycles  and  750,000  minus  30,000  or 
720,000  cycles.  These  two  points  correspond 
to  417  and  385  meters. 

Thirty  thousand  cycles  is  such  a  small  per- 
centage of  the  broadcasting  frequencies  that 
the  two  points  on  the  oscillator  dial  are  always 
close  to  the  value  of  the  incoming  frequency, 
although  on  the  longer  waves  the  two  points 
are  farther  apart  on  the  dial  than  at  the  low 
wavelength  end  of  the  dial. 

These  two  points  are  60,000  cycles  apart, 
and  the  action  of  tuning  a  given  station  at  two 
points  within  the  broadcasting  band  is  some- 
thing like  a  small  wheel  revolving  within  a 
large  one  as  shown  in  Fig.  i .  The  small  wheel 
may  begin  to  rotate  at  any  point,  but  at  the 
end  of  two  complete  revolutions  the  same 
broadcasting  station  may  be  heard  again. 
And  since  the  present  broadcasting  band 
covers  820,000  cycles,  it  is  apparent  that  there 
will  always  be  two  points  on  the  oscillator  dial 
for  each  incoming  frequency — if  the  inter- 
mediate amplifiers  are  tuned  to  30,000  cycles. 

Suppose,  however,  that  the  intermediate 
amplifiers  are  tuned  to  500,000  cycles.  In  this 
case,  the  same  station  will  be  found  at  two 
points  1,000,000  cycles  apart,  and  since  the 
broadcasting  band  is  only  820,000  cycles  wide, 
we  may  plan  our  coils  and  condensers  so  that 
the  incoming  frequency  will  be  heterodyned  at 
only  one  point  on  the  oscillator  dial. 

All  we  have  to  do  now  is  to  design  an  oscilla- 
tor that  will  beat  at  frequencies  500,000  cycles 
different  from  incoming  frequencies.  At  the 
lower  end  of  the  broadcast  wavelength  band, 
220  meters  equals  1,363,636  cycles  and  at  the 


JONNOR  FREQUENCY-CHANC 


RADIO  BROADCAST  Photograph 
FIG.    3 

Fhe  panel  view  of  the  frequency  changer.     Simplicity  and  symmetry  are  the  keynotes  of  construction  and 
ayout.     Due  to  the  engraved  indicators,  the  functions  of  the  various  control  dials  are  self  explanatory 


256 


Radio  Broadcast 


other  end  of  the  broadcasting  band,  550  meters 
corresponds  to  545,454  cycles.  To  find  the 
frequency  of  the  oscillator  to  give  us  the 
required  5OO,ooo-cycle  beat  note,  we  must 
add  to  or  subtract  500,000  cycles  from  these 
two  extreme  frequencies.  Thus, 
220  meters  =  1,363,636  cycles  plus  500,000  cycles  = 

1,863,636 
220  meters  =  1,363,636  cycles  minus  500,000  cycles 

=  863,363 
550  meters  =  545,454  cycles  plus  500,000  cycles  = 

1,045,454 
550  meters  =   545,454  cycles  minus  500,000  cycles 

=  45.454 

Therefore  an  oscillator  of  the  range 
1,863,636  to  1,045,454  or  an  oscillator  of  the 
range  of  863,363  to  45,454  cycles  would  give 
the  required  beat  frequency.  These  two  os- 
cillators would  cover  wavelengths  from  161  to 
287  meters  or  348  to  6600  meters.  Obviously 
the  first  one  is  the  proper  one  to  use. 

In  this  case  there  will  be  only  one  point  in 


ing  with  the  attendant  howls  and  moans. 
Sometimes  the  upper  point  of  station  No.  i 
interferes  with  the  lower  point  of  station  No. 
3  which  is  on  a  longer  wavelength;  again  we 
have  heterodyning  with  the  resultant  dis- 
cordance, and  we  find  that  we  are  unable  to 
get  station  No.  i  clearly  on  either  of  its  two 
points.  Such  a  condition  is  impossible  with 
500,000  cycle  beat  frequencies,  as  it  is  im- 
possible to  get  a  station  at  more  than  one 
point  on  the  oscillator  dial. 

With  most  "supers,"  the  oscillator  is  con- 
tinually making  an  audible  heterodyne  with 
the  incoming  station  as  the  dial  is  turned 
between  the  two  points  for  the  incoming 
station.  This  is  because  of  the  fact  that 
half  way  between  the  two  points  it  is  actually 
on  the  exact  frequency  of  the  incoming  sta- 
tion. With  a  5OO,ooo-cycle  beat  frequency 
this  is  impossible  as  the  oscillator  always 
beats  500,000  cycles  away  from  the  incoming 
station. 


7 

c 

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0 
0 
O 

Output 
d  -^—  .*-^-^-.  .—  _^ 

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e^OOOOOpv     .                          1     II     Jk 

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VvUUvwl                                                                                                UD-H 

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II       I                            ^iim    J 

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o 

K~~> 

HE                                                    f        1)      -=- 

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X      •; 

•••                                                                             \l      ^  //        ^~« 

i. 

S     *~ 

7*"                                     Al                                                                                              P8  »«a*r                  "~~ 

c 

i 
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J-l  1'                                                        n  Y"^                                 •-  —  g_ 

2 

a 

b 

SCHEMATIC    DIAGRAM                          -H|ljlf+ 
A  Battery 

a  -Primary  of  pickle  bottle  coil                 g-.  00013  Fixed  cond.  * 
b-  Secondary                                                 h-  nnn^t;  rAn/Honcor  o/ivt  <nQC> 

c- Tickler 

d-  Oscillator  plate  coil 

e-  Oscillator  grid  coil 

f -.0005  Condenser  247  F(Tuner) 


k  -.00025  grid  condenser 

m-  1  Meg.Leak 

n-  30  Ohm  rheostat 


FIG.    4 

The  schematic  diagram  of  the  frequency  changer  showing  the  Arm- 
strong system  of  securing  local  oscillations  in  the  first  detector  tube 


the  oscillator  dial  where  a  given  station  may 
be  found  as  shown  in  Fig.  2. 

There  is  still  another  advantage  in  heter- 
odyning to  500,000  cycles.  When  heter- 
odyning to  30,000  cycles,  it  is  quite  often  the 
case  that  the  lower  one  of  the  two  points  for 
station  No.  i  is  in  exactly  the  same  spot  as  the 
upper  point  of  station  No.  2  which  is  on  a 
snorter  wavelength.  This  causes  heterodyn- 


HOW    YOUR    PRESENT    RECEIVER    IS    USED 

NOW  that  we  have  the  5oo,ooo-cycle 
beat  note  generated  in  our  frequency- 
changer,  it  remains  to  provide  an  intermedi- 
ate amplifier  tuned  to  this  frequency,  and 
here  is  where  our  receiver  now  in  operation 
comes  in.  All  that  is  necessary  is  to  tune  it 
to  600  meters  (500,000  cycles)  and  to  place 


Making  Your  Receiver  a  Super-Heterodyne 


257 


FIG.    5 


RADIO  BROADCAST  Photograph 


Looking  down  on  the  layout  one  clearly  sees  the  general  disposition  of  parts  and  the  wiring 
scheme.     The  frequency-changer  is  really  a  very  simple  unit  as  this  photograph  shows 


Back 


Loop     Ant.  Gnd.  A-    A+   B+  Output 
Q    Q     Q     Q    Q     Q    O 


FIG.    6 

The  wiring  diagram  of  the  one  tube  super-heterodyne  showing  the  connections  of  the  various  units 


l-s 


M  O 

.513 


.        ,y 

H-o 


Making  Your  Receiver  a  Super-Heterodyne 


259 


its  antenna  and  ground  connection  to  the 
output  of  the  frequency-changer,  and  we 
have  a  super-heterodyne. 

Fig.  4  shows  the  schematic  diagram  of  the 
circuit  and  Fig.  6  shows  the  connection 
hookup.  In  Fig.  6,  coils  A,  B,  and  C  are  the 


V- 

:                i' 

tX) 

t               V 

III 

J                              ^ 

*£; 

r 

<—  -     IB—    --> 

CONDENSER  COUPLING   UNIT 

FIG.   8 

To  shield  the  condenser  from  body  capacity  effects 

it  should  be  placed  some  distance  from  the  panel  and 

this  coupling  member  enables  the  proper  spacing  to 

be  carried  out 

three  windings  of  a  three-circuit  tuner,  the 
primary  (A)  being  untuned.  Incoming  sta- 
tions are  tuned  by  the  condenser  F  across 
the  primary  coil  B.  Their  frequencies  are 
heterodyned  to  500,000  cycles  by  oscillator 
coils  D  and  E,  the  latter  coil  being  tuned  by 
condenser  G  and  H.  Condenser  G  is  placed 
in  the  circuit  to  increase  the  spread  of  the 
stations  on  the  oscillator  dial.  The  plate 
circuit,  before  it  is  introduced  into  the  next 
tuning  circuit,  is  brought  into  inductive  rela- 


tion with  the  secondary  tuning  coil  B,  thus 
causing  regeneration  and  increasing  both 
volume  and  selectivity.  The  plate  circuit 
now  contains,  among  other  frequencies,  the 
desired  frequency  of  500,000  cycles,  and  is 
introduced  into  the  receiving  system,  where 
it  is  tuned  and  rectified  in  the  same  way  that 
a  6oo-meter  station  can  be  tuned  in. 

You  will  note  that  in  this  arrangement, 
one  tube  receives  and  heterodynes  at  the 
same  time.  Up  until  a  year  ago  this  was  not 
considered  feasible,  because  tuning  the  oscil- 
lator circuit  would  detune  the  antenna  cir- 
cuit, due  to  the  two  frequencies  being  so 
close  together.  Major  Armstrong  showed 
that  it  is  possible,  if  the  frequencies  are  quite 
a  distance  apart,  and  exhibited  an  ingenious 
scheme  for  using  one  tube  while  maintaining 
a  low  frequency  intermediate  wave.  In  the 
frequency-changer  which  we  are  describing, 
the  two  circuits  are  always  500,000  cycles 
apart  and  tuning  one  circuit  has  no  effect  on 
the  other.  In  constructing  the  frequency- 
changer,  the  idea  of  low  loss  has  been  kept 
constantly  in  mind,  and,  by  direct  compari- 
son, low  loss  parts  gave  the  best  results.  Dis- 
tributed capacity  in  coils  was  hunted  down, 
and  condensers  of  the  highest  type  were  used, 
the  oscillator  condenser  being  insulated  from 
the  hand  by  means  of  a  good  dielectric.  The 
parts  used  are  listed  below,  but  of  course 
equivalent  parts  can  be  used,  always  provid- 
ing that  the  constants  are  correct. 


RADIO  BROADCAST  Photograph 
FIG.   9 

This  rear  view  shows  clearly  the  disposition  of  the  coils  and  other  apparatus.     Note  how  the  oscillator 
coils  are  clamped  between  the  two  bakelite  strips  which  are  fastened  to  the  oscillator  condenser 


260 


Radio  Broadcast 


ITEM 

/ 

2 


14 


75 
16 


18 


1  Formica  panel  7  x  14  x  T\  inches 

\  Baseboard  12  f  x  7  x  \  inches  Poplar 

2  National  Velvet  Vernier  4-inch  Dials 

i  General  Radio  Switch  Lever  f-inch  with  two 

Contact  Points  and  two  stops 
i  General  Radio  No.  301  Knob  and  Pointer;  for 

use  on  the  tickler  coil. 
i  General  Radio  No.  301  Rheostat  3o-ohm. 
i  General  Radio  No.  247  F  Condenser  .00025 

mfd.  logarithmic  plates. 

3  f-inch    Lengths    Formica  Tubing   &    inch 
o.  d.  T8s  inch  i.  d.  to  space  Item  7  from  panel 

i  Formica  Coupling  Member  for  Item  7  (Fig.  6) 
i  General  Radio  247F  Condenser  .0005  mfd. 

logarithmic  plates 
35  inch  Lengths  Formica  Tube  fg  inch  o.  d. 

•fs  inch  i.  d. 
i  Eastern  Coil  Corporation  Coupler,  Broadcast 

Wavelength,  (15  turns  on  tickler,  with  middle 

tap  on  primary) 

i  King  Socket  R730  for  uv-20  1  -A  Tube 
i   Dubilier  Grid  Condenser  .00025  mfd.  Type 

60  1  -G. 

i   Daven  Grid  Leak  .!  megohm 
i   Binding  Post  Panel  complete  with  9  binding 

posts 
i  Oscillator  Coupler  as  per  Fig.  7;  coupler  in- 

cludes two  coils  as  per  description  later  in 

this  article. 
Screws,  wire,  spaghetti,  terminal  lugs,  etc. 


Total  cost  of  the  above  parts  should  be  between 
$35.00  and  $40.00. 

Fig.  7  shows  the  actual  drilling  template 
for  the  panel,  but  of  course  changes  must  be 
made  if  other  material  is  used. 

Fig.  8  shows  a  coupling  member  for  the 


.ooo25-mfd.  variable  condenser.  This  in- 
sulates the  condenser  from  body  capacity. 
Item  No.  3  in  the  list  above  covers  three 
Formica  tubes  which  are  used  to  set  the 
oscillator  condenser  back  from  the  panel,  and 
to  line  it  up  with  the  other  condenser.  Item 
1 1  covers  spacers  for  the  .0005  mfd.  conden- 
ser. These  are  necessary  because  the  design 
of  the  Velvet  Vernier  dial  requires  that  the 
condenser  be  set  back  from  the  panel. 

The  Eastern  Coil  Corporation  coupler  is 
known  as  a  pickle-bottle  coil,  and  has  fewer 
turns  than  normal  due  to  the  fact  that  it  is  in 
circuit  with  the  plate  coil  of  the  oscillator 
coupler. 

THE    UNUSUAL   OSCILLATOR   COUPLER 

FIG.  10  shows  the  details  of  the  oscillator 
coupler.  This  coupler  is  not  the  con- 
ventional type  at  all.  In  the  usual  coupler, 
the  coupling  between  the  plate  and  grid  coils 
is  fixed,  and  the  coils  are  so  large  that  their 
external  fields  exert  an  influence  on  all  parts 
within  a  range  of  several  inches.  An  at- 
tempt was  made  in  this  frequency-changer  to 
design  an  oscillator  which  would  have  no 
effect  on  other  parts,  and  this  result  was 
finally  achieved.  The  coils  shown  have  an 
exceptionally  small  external  field,  and  the 
grid  coil  is  placed  1 1  inches  back  of  the  oscil- 
lator variable  .condenser,  a  position  in  which 
it  has  no  effect  on  the  condenser.  The  coils 
are  known  as  "cross-wound,"  and  have  about 
as  little  distributed  capacity  as  any  coil 
known.  The  coils  are  wound  on  a  f-inch 
core,  are  |  inch  thick,  and  each  has  49  turns 


No.27Drill      Drill  and  tap  6-32         No.27Drill 


COIL  MOUNTING  PART  No.l 
3/i6  Formica  Stock 


Drill  and  tap 


COIL  MOUNTING  PART  No.2 
3^6  Formica  Stock 


Part  No.2 


Coils  clamped  between 
bakelite  strips 

Part  No.l 


-  6-32  Screws 


Brass  Stock 


Solder  lugs 

Part  No.3- 

i 

COIL  MOUNTING  ASSEMBLY 


COIL  MOUNTING  PART  No.3 
FIG.     10 


The  details  of  the  oscillator  coupler  are  shown  in  this  Figure.     Small  coils  placed  at  some  distance  from  their 
tuning  condensers  decrease  the  external  field  and  the  resultant  coupling  effects  to  other  parts  of  the  circuit 


Making  Your  Receiver  a  Super-Heterodyne 


of  No.  24  double  cotton  covered  wire.  Ex- 
perimenters who  desire  to  wind  their  oscilla- 
tor coils,  and  are  unable  to  make  cross-wound 
coils,  can  use  Lorenz  (basket-weave)  such 
as  made  by  the  Perfection  Coil  Co.  or  Sickles 
(diamond-weave)  coils,  and  attain  the  same 
results,  although  the  coils  should  be  set  back 
some  distance  from  the  oscillator  variable 
condenser.  By  a  cut-and-try  method,  the 
right  number  of  turns  can  be  ascertained, 
the  calibration  being  determined  by  changing 
the  old  receiving  set  to  600  meters  (or  as  high 
as  possible),  and  adjusting  turns  on  the  oscil- 
lator grid  coil  until  545  meters  comes  in  at 
approximately  95  on  the  oscillator  dial,  and 
220  meters  at  5  on  the  dial.  Without  fixed 


of  coupling  that  is  good  for  some  frequencies 
and  poor  for  others. 

The  best  value  of  coupling  for  a  given 
frequency  is  minimum  coupling;  in  other 
words,  the  coupling  should  be  decreased  until 
the  point  is  reached  where  the  tube  is  just 
ready  to  stop  oscillating.  By  finding  this 
coupling  distance  for  all  frequencies,  a  point 
can  be  determined  that  will  give  the  best 
average  coupling  for  all  frequencies.  In  the 


RADIO  BROADCAST  Photograph 


FIG.     I  I 


End  view  showing  the  method  of  placing  the  condenser  some  distance  behind  the  panel  to 
lessen  body  capacity  effects.     The  separation  of  the  coupling  coils  is  clearly  shown  here 


condenser  G  of  Fig.  4  it  would  be  impossible 
to  obtain  this  spread  on  the  dial  and  the 
capacity  of  this  condenser  will  have  to  be 
determined  by  trial.  The  value  used  in  the 
frequency-changer  shown  in  the  photograph 
was  .00013  mfd. 

As  mentioned  above,  in  the  usual  oscillator 
coupler  the  coupling  between  plate  and  grid 
coils  is  fixed.  Yet  the  best  value  of  coupling 
varies  with  the  frequency,  and  experiments 
have  shown  that  most  couplers  have  a  value 


coupler  shown  in  Fig.  10  this  point  is  deter- 
mined by  test,  and  the  coil  locked  in  place. 

HOW    TO    PUT   THE    "  SUPER*'    TOGETHER 

MOUNT  all  apparatus  on  panel  and  base- 
board, assemble  the  oscillator  coupler 
on  rear  of  .00025  m^.  condenser,  or  some 
distance  back  of  the  condenser  if  other  than 
cross-wound  coils  are  used.  Connect  the 
parts  as  per  connection  diagram  Fig.  10, 
soldering  wires  to  the  terminal  lugs  instead  of 


262 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 


FIG.    12 


A  perspective  of  the  completed  frequency  changer.     The  grid  leak 
and  condenser  are  supported  by  the  tube  socket  and  the  wiring  to  it 


wrapping  them  around  screws.  Connections 
to  Si  and  82  on  the  pickle-bottle  coil  should 
preferably  be  of  flexible  wire,  as  these  two  wires 
must  be  disconnected  if  a  loop  is  to  be  used. 
A  loop  can  be  used  when  this  unit  is  to  be  at- 
tached to  a  multi-tube  set  such  as  a  neu- 
trodyne,  or  tuned  radio  frequency  set.  If 
the  unit  is  to  be  used  with  a  single-circuit  or 
three-circuit  regenerative  set,  a  loop  can  be 
used  if  maximum  selectivity  and  a  range  of 
100  to  200  miles  is  all  that  is  desired. 

After  all  internal  connections  are  made, 
connect  the  battery  terminals  to  the  same 
battery  terminals  on  your  present  set,  making 
sure  that  positive  B  on  the  frequency-changer 
has  a  value  of  at  least  45  volts.  You  will 
notice  that  there  is  no  minus  B  on  the 
frequency-changer.  This  is  because  this 
connection  is  taken  care  of  in  your  present 
set.  Connect  the  antenna  and  ground  to 
the  frequency-changer  instead  of  to  your 
present  set.  If  you  have  a  five-  or  six-tube 
radio  frequency  set,  you  may  use  a  loop  in- 
stead of  the  antenna  and  ground  by  dis- 
connecting Si  and  S2  of  Fig.  2  from  the 
secondary  windingof  the  pickle-bottle  coupler. 
Now  tune  your  receiving  set  to  600  meters, 
get  maximum  regeneration,  and  leave  your 
dials  set.  All  tuning  is  now  taken  care  of  by 


the  two  dials  on  the  frequency-changer  panel 
and  regeneration  can  be  obtained  by  rotating 
the  pickle  bottle  tickler. 

CARE    MUST    BE    USED    IN    CONNECTIONS 

BE  VERY  careful  to  examine  the  circuit 
in  your  set  to  which  the  output  circuit 
of  the  frequency-changer  is  connected.  This 
circuit  must  not  be  connected  to  the  A  battery 
circuit,  or  else  there  will  be  a  short-circuit 
across  45  volts  of  the  B  battery.  In  some 
regenerative  sets,  and  in  neutrodynes,  the  A 
battery  is  grounded  and  this  connection 
must  be  broken. 

In  an  article  to  follow  we  will  show  a  num- 
ber of  single-tube  regenerative  circuits  and 
discuss  the  connections  to,  and  operation  of, 
the  frequency-changer.  We  will  also  show 
how  it  is  possible  to  "tune-in  by  the  squeal" 
without  annoying  your  neighbors.  We  will 
show  the  frequency-changer  connected  to 
a  neutrodyne  circuit  and  illustrate  how  to 
operate  it  on  an  antenna  or  on  a  loop.  Best  of 
all  will  be  a  method  of  connecting  a 
frequency-changer  to  a  crystal  set,  giving  the 
long  distance  range  of  a  single  tube  set  with 
the  selectivity  equal  to  the  finest  super- 
heterodyne circuit.  This  makes  a  one  tube 
circuit  with  the  finest  selectivity  known. 


Phonograph 
Receiver 


Radio 


Broadcast  s 


An  Entirely  New  Method  of  Building  the 
Four-Tube  Knock-out  Receiver  to  Fit  in 
Any  Phonograph — A  Design  Which  Sets 
A  New  Mark  for  Home-Built  Receivers 


By  ARTHUR  H.  LYNCH 


THE  most  popular  phonograph  to-day 
is  the  phonograph  in  which  radio  is  an 
integral  part.     It  is  possible  to  double 
the    use    and    value    of    the    many 
thousands    of   phonographs    in    this    country 
to  make  them  better  instruments  for  the  home 
by  using  some  sort  of  radio  receiver  in  connec- 
tion with  them.     For  some  months,  it  has  been 
possible  to  buy  factory-made  radio  receivers 
which  could  be  fitted  into  a  compartment  of 
the  phonograph.     But  the  home  constructor 
has  had  to  worry  along  as  best  he  could. 

RADIO  BROADCAST  has  determined  to  ex- 
periment with  the  idea  of  furnishing  the  best 
design  possible  for  home  constructed  receivers 
in  the  phonograph.  We  are  gambling  on 
our  conviction  that  the  home  constructor,  that 
everyone,  in  fact,  is  interested  in  making  the 
phonograph  a  more  valuable  bit  of  domestic 
equipment.  To  that  end,  we  have  spent  a 
great  deal  of  time  and  money  in  canvassing  the 
entire  situation  and  we  shall  bring  to  you  every 
month,  for  some  time  to  come,  the  results  of 
our  findings.  Those  findings,  we  think,  involve 
some  distinctly  new  ideas  in  radio  construction. 
We  shall  offer  you  an  opportunity  to  build 


various  models  of  one  of  the  most  compact  and 
efficient  radio  receivers  for  home  construction 
that  we  have  ever  seen. 

The  phonograph  is  a  very  satisfactory  means 
of  entertainment,  and  we  feel  sure  that  by 
the  proper  design  of  a  receiver  for  incorpora- 
tion in  practically  any  model  of  phonograph 
we  are  going  to  present  something  of  great 
use  to  a  large  number  of  people.  Many  a 
perfectly  good  phonograph  has  been  done  out 
of  a  home  by  the  radio  set.  Many  more  have 
been  pushed  aside,  and  their  sole  present  use 
is  to  hold  a  beautiful  lamp  or  a  flower  pot. 

HOW   TO    GET   THE    MOST    RADIO    IN    THE    LEAST 
SPACE 

RADIO  has  brought  a  new  problem  into  the 
home.  Space  in  many  modern  homes  is 
often  scarce.  When  the  piano,  the  books,  the 
library  table,  and  the  phonograph  are  prop- 
erly placed,  where  to  put  the  radio  receiver 
has  caused  many  brows  to  wrinkle.  If 
a  phonograph  is  part  of  the  household  equip- 
ment, it  is  often  necessary  to  relegate  it  to  an 
inconspicuous  corner.  And,  if  our  observa- 
tion counts  for  anything,  there  are  entirely 


264 


Radio  Broadcast 


too  many  phonographs  that  are  now  gathering 
whatever  dust  the  housewife  will  permit  it  to 
collect.  Too  many  phonographs  are  not  used 


from  one  end  of  the  year  to  the  other.  This 
has  been  the  case  in  the  homes  of  a  number  of 
our  staff  and  in  the  homes  of  many  people 
with  whom  we  come  in  contact.  We  hope 
to  show  the  home  constructor  how  he  may  very 
desirably  combine  the  beauty  of  his  phono- 
graph with  the  efficiency  and  compactness  of  a 
home  constructed  four-tube  receiver. 

Home  constructors,  ever  since  they  began 
their  researches  with  blue  print  and  pliers 
have  naturally  turned  more  of  their  attention 
to  the  electrical  side  of  their  receiver  than 
they  have  to  what  might  be  called  the  aesthe- 


RADIO  BROADCAST 

Photograph 

FIG.    I.      A    SIDE    VIEW   OF    MODEL   NO.    I 

The  principal  points  shown  in  this  illustration  are  the  extreme  rigidity  of 
assembly  and  indication  of  the  compactness  of  the  unit.  In  this  case  a  panel 
fourteen  inches  high  has  been  used  to  fit  the  console  requiring  a  vertical  as- 
sembly. In  an  assembly  of  this  kind  it  is  entirely  practical  to  fit  it  into  a 
wooden  carrying  case  for  camping  purposes.  Dry  cells  and  the  necessary  B 
batteries  may  have  plenty  of  room  below  the  receiver  assembly.  Though 
dry  cell  tubes  may  be  used  in  this  way  better  results  are  obtained  from  stan- 
dard tubes  and  the  use  of  the  Lynch  lead  is  very  useful  for  camping  purposes 
as  illustrated  on  pages  252-3.  The  use  of  a  small  switch  mounted  in  the  an- 
tenna coupler  to  permit  regulation  of  the  left  hand  tuning  dial  for  antennas 
of  different  lengths  makes  the  panel  assembly  more  presentable  Since  this 
switch  need  only  be  adjusted  once  for  a  given  antenna  and  then  remains  a 
fixture  there  is  no  need  for  having  it  on  the  panel.  Manufacturers  assure 
us  that  they  will  soon  market  switches  and  fittings  for  this  purpose.  This 
idea  was  suggested  to  us  by  P.  R.  Morrison  of  Freeport,  Long  Island 


Radio  Broadcast's  Phonograph  Receiver 


265 


FIG.    2. 


RADIO  BROADCAST  Photograph 
TOP    VIEW    OF    THE    PHONOGRAPH    UNIT 


Particular  attention  is  called  to  the  assembly  of  the  sub-panel  as  well  as  the  position  of  the  tube  sockets.  In 
order  to  permit  the  complete  unit  to  be  used  in  either  a  vertical  or  horizontal  position  without  requiring  a 
single  change  in  construction  and  to  offset  the  possibility  of  the  tube  filaments  sagging  and  touching  the  grids, 
the  correct  placing  of  the  sockets  is  important.  Manufacturers  who  are  to  market  a  four-tube  sub-base  of 
this  type  at  our  suggestion  have  agreed  to  see  that  tneir  products  incorporate  this  attractive  and  important 
feature.  Even  though  this  receiver  is  very  compact  it  will  be  observed  that  there  is  no  crowding 


REAR    VIEW    OF    RADIO    BROADCAST  S 
COMBINATION    CONSOLE 


By  placing  the  receiver  assembly  well  toward  the  top  of  the  panel 
plenty  of  room  is  found  for  locating  all  the  batteries  below  and  be- 
hind the  radio  panel.     The  back  of  the  phonograph  has  been  re- 
moved to  show  the  location  of  the  various  units 


266 


Radio  Broadcast 


FIG.  4 

A    loud     speaker    and     phonograph 
tone-arm  now  available  commercially 


tic  side.  If  the  set  was  put  together  and  it 
worked,  the  cabinet  in  which  the  set  was  con- 
tained was  often  a  secondary  consideration. 

RADIO  BROADCAST'S  Phonograph  Receivers 
will  allow  the  constructor  to  utilize  the  hand- 
some qualities  of  his  phonograph  cabinet,  and 
the  excellent  sound  chamber  of  that  instru- 
ment. For  these  two  reasons  alone,  we  be- 
lieve that  many,  many  phonographs  are  going 
to  come  out  of  the  shadow,  not  only  to  be 
seen  but  to  be  used  again. 


FIG.   6.       FROM   THE    REAR 
This  is  how  the  unit  appears 


RADIO  BROADCAST  Photograph 


Radio  Broadcast's  Phonograph  Receiver 


267 


FIG.    6A.    AN- 
OTHER    REAR 

VIEW 

Showing  how  other 
coils  and  condensers 
may  be  employed 
without  any  change 
in  layout 


RADIO  BROADCAST  Photograph 


RADIO  BROADCAST  Photograph 
FIG.    7.       FROM    THE    BOTTOM 

We  get  some  idea  of  the  wiring.  In  this  unit  we  have  used  audio  transformers  of  rather  large  physical 
dimensions  in  order  to  be  sure  that  practically  any  transformers  may  be  used  without  undue  crowding. 
Amperites  are  used  in  the  filament  circuits  of  the  push-pull  tubes  to  reduce  the  number  of  manual  controls 
as  in  Fig.  12.  In  receivers  designed  for  use  with  UV-IQQ  or  similar  tubes  for  operation  from  flashlight  or  dry 
batteries  it  is  sometimes  advisable  to  use  a  single  rheostat  for  the  two  tubes  as  shown  diagrammatically 

in  Fig.  1 1 


268 


Radio  Broadcast 


FIG.   8.      ANOTHER   SAMPLE 


RADIO  BROADCAST  Photograph 


In  this  arrangement  another  group  of  audio  transformers  are  used  and  the  spring  sockets  have  been  replaced 
by  the  rigid  type.  In  order  to  cushion  the  tubes  two  strips  of  sponge  rubber  are  placed  between  the  sub- 
panel  and  its  supporting  brackets.  In  this  receiver,  flexible  wiring  is  used  and  a  series  of  wires  with  special 
colored  covering  as  described  in  the  article  on  standardization  in  the  April  RADIO  BROADCAST  is  suggested. 
It  is  not  a  difficult  matter  to  arrange  color  combinations  within  the  receiver  just  as  standards  have  been 
suggested  for  the  wiring  outside  the  receiver.  It  is  not  unlikely  that  design  of  this  nature  will  soon  find  its 
way  into  receivers  other  than  those  for  home  construction.  Wire  manufacturers  assure  us  they  will  soon  be 
ready  to  supply  such  wire.  It  is  well  to  compare  this  unit  with  Fig.  6.  There  was  no  noticeable  difference 
in  performance.  Convenience  for  your  particular  assembly  problem  is  the  factor  to  decide  upon  between 

the  two 


If  you  use  this  combined  radio-phonograph 
unit,  there  is  no  reason  why  you  should  ever 
be  deprived  of  the  very  best  in  the  world's 
entertainment.  When  the  radio  programs 
do  not  suit  your  mood,  there  is  certain  to  be  a 
record  among  your  collection  which  will  suit 
the  occasion.  The  radio  receiver  and  the 
phonograph  have  taken  a  tremendously  im- 
portant place  in  the  home,  and  RADIO  BROAD- 
CAST believes  that  both  should  be  used  to  their 
fullest  capabilities. 

A  radio  receiver  for  a  phonograph  has  to 
be  designed  so  that  it  will  fit  the  various  cabi- 
nets in  which  it  might  be  installed.  The 
RADIO  BROADCAST  Phonograph  Receiver  con- 
sists of  an  extremely  compact  unit  employing 
the  excellent  circuit  developed  for  us  by  Walter 
Van  Braam  Roberts  of  Princeton  University. 
The  unit  itself  is  so  designed  that  it  can  be 


adapted  to  a  panel  of  any  size.  The  dimen- 
sions of  the  panel  conform  to  the  size  of  the 
phonograph  cabinet  into  which  the  receiver  is 
to  be  put. 

THE  MAIN  FEATURES  OF  THE  PHONOGRAPH 
RECEIVER 

COLLOWING  articles  will  show  just  how 
*  to  build  this  receiver,  down  to  the 
very  last  binding  post  and  drop  of  solder. 
The  photographs  which  are  reproduced  with 
this  story  show  just  what  we  have  been  able 
to  do  with  the  Phonograph  Receiver  and 
several  representative  types  of  phonograph 
cabinets.  For  the  experienced  radio  construc- 
tor, the  photographs  are  self  explanatory,  but 
for  the  builder  who  sets  great  store  by  com- 
plete constructional  details  and  diagrams,  the 
later  articles  will  show  exactly  how  it  is  done. 


Radio  Broadcast's  Phonograph  Receiver 


269 


The  main  feature  of  the  Phonograph  Re- 
ceiver is  its  wonderful  compactness.  The  panel 
layout,  as  you  will  observe,  is  extremely  sym- 


FIG.    9.       A    SIMPLE    METHOD   OF    CONVERT- 
ING THE  TONE  CHAMBER  OF  A  PHONOGRAPH 
INTO   A    LOUD    SPEAKER 


metrical.  The  assembly  of  the  parts  is  not 
particularly  difficult  and  the  results  which 
we  have  obtained  with  several  models  with 
which  we  have  been  experimenting  have  been 
highly  satisfactory.  This  Phonograph  Re- 
ceiver combines  all  the  good  features  of 
the  Four-Tube  Knockout,  plus  some  very 
significant  mechanical  and  electrical  improve- 
ments.' By  referring  to  the  announcement 
of  the  Better  Receiver  Contest,  which  appears 
on  another  page  of  this  magazine,  you  will 
find  listed  the  qualifications  which  the  Roberts 
Knockout  receiver  possesses.  We  believe 
that  tube  for  tube,  dollar  for  dollar,  and  result 
for  result,  this  is  by  far  the  best  receiver  ever 
designed  for  home  construction. 

After  we  had  satisfied  ourselves  that  we 
had  the  best  possible  receiver  for  the  purpose, 
the  next  most  important  point  was  the  actual 
mechanical  layout  of  the  parts.  In  this,  we 
feel,  we  have  been  highly  successful. 


RADIO  BROADCAST  Photograph 
FIG.    IO.      THE    UNIT  ON    A    SMALLER    PANEL 

This  model  was  made  to  illustrate  the  points  outlined  in  Fig.  8  and  shows  a  very  symmetrical  panel  design. 
The  application  of  a  unit  like  this  to  any  phonograph  is  a  very  simple  matter.  It  is  merely  necessary  to  pro- 
cure a  piece  of  five  ply  veneer  large  enough  to  fill  the  desired  space,  cut  a  hole  in  wherever  the  unit  will  fit 
most  satisfactorily  and  set  it  in  place.  If,  to  conserve  space,  it  is  necessary  to  install  the  receiver  in  a  side- 
wise  position,  the  precaution  concerning  the  position  of  the  tube  sockets  to  prevent  sagging  filaments  touch- 
ing the  grids  must  be  taken  into  consideration  and  the  mounting  of  the  sockets  changed  accordingly.  The  en- 
graving may  then  be  put  on  the  proper  part  of  the  panel  to  make  reading  the  dials  from  the  side  unnecessary 


270 


Radio  Broadcast 


,OU1S1DE  LtfcO 

I    7 

<i-      ^ 

2 

'•PIKTES 

IV.  •= 

iiCj  T*      »T 

~IH   "s"oKJ±- 


FIGS.    11-12.      THE    SIMPLEST   WIRING    ARRANGEMENT 

Is  shown  in  Fig.  1 1 .  It  differs  from  Fig.  12,  (below),  in  several  minor  details.  Simple  jacks  are  used  instead  of 
those  incorporating  the  filament  control  feature.  A  rheostat  controls  the  filaments  in  the  push-pull  tubes  in- 
stead of  the  Amperites.  This  circuit  is  a  much  simpler  wiring  job  but  where  the  receiver  is  to  be  used  by  the 
entire  family  the  additional  wiring  necessitated  by  Fig.  12  will  be  found  very  much  worth  while.  The  dotted 
lines  in  both  these  diagrams  illustrate  simple  and  effective  methods  for  overcoming  any  difficulties  which 
may  arise  in  the  audio  amplifiers  such  as  a  continual  whistle  which  was  observed  when  certain  transformer 

combinations  were  used 


FIG.     12 


The  possibilities  of  this  Phonograph  Re- 
ceiver are  best  shown  by  an  examination  of 
the  accompanying  illustrations. 

A  great  many  Victor  phonographs  of  the 
upright  type  are  in  use  to-day.  In  these,  the 
record  cabinet  is  of  two  kinds.  Some  have 
two  sets  of  shelves;  the  upper  holding  books 
for  ten-inch  records  and  the  lower  holding 
books  for  twelve-inch  records.  In  order 
to  fit  the  Phonograph  Receiver  in  such  a 
cabinet,  it  is  merely  necessary  to  remove  the 
upper  shelf  and  find  some  other  convenient 
place  for  them.  An  unused  corner  of  a  book- 
case does  very  well.  A  panel  of  wood  or  some 
composition  is  then  made  to  fit  the  space 
previously  occupied  by  the  record-books  and 
the  receiver-unit  is  then  fitted  directly  to  this 
panel,  or  to  a  sub-panel  mounted  on  the 
panel  which  is  substituted  for  the  record- 
book  shelf. 

The  illustrations  show  that  this  radio- 
phonograph  combination  will  save  a  great 
deal  of  space,  and  since  the  storage  battery  and 
the  B  batteries  may  be  included  in  the  phono- 
graph itself  they  are  permanently  placed  out  of 
sight.  This  is,  of  course,  impossible  when  the 
radio  set  is  used  on  some  sort  of  table 


In  another  upright  Victor  model,  there  are  a 
series  of  four  to  six  shelves  used  to  hold  the 
phonograph  records,  with  books  to  contain 
them.  In  placing  the  Phonograph  Receiver 
in  such  a  cabinet,  it  is  only  necessary  to 
measure  about  twelve  inches  down  from  the 
upper  end  of  the  record  space,  remove  the 
shelves  and  have  a  panel  of  wood  or  composi- 
tion made  to  fit  this  space. 

There  are  a  great  many  receiver  devices 
now  on  the  market  which  enable  one  to  use  a 
so-called  loud  speaker  attachment  with  the 
phonograph.  These  devices  are  connected  to 
the  audio  output  of  the  receiver  and  the  unit 
itself  mechanically  coupled  to  the  tone-arm  of 
the  phonograph.  The  sound  compartment  of 
the  phonograph  is  used  as  the  loud  speaker. 
This  operation  is  very  simple,  as  can  be  seen 
from  one  of  the  illustrations.  The  character 
of  the  signal  resulting  from  the  use  of  a  good 
loud  speaker  attachment  and  the  phonograph 
itself  as  the  "loud  speaker"  is  extremely  good. 
There  are  also  some  new  types  of  tone-arms 
which  combine  both  the  tone  arm  for  the 
phonograph  and  an  attachment  for  employing 
the  loud  speaker  unit.  In  such  a  combination, 
the  phonograph  or  loud  speaker  attachment 


Radio  Broadcast's  Phonograph  Receiver 


271 


FIG.    13.      ANOTHER    SUB-PANEL    (BOTTOM   VIEW) 

All  the  wiring  shown  in  this  illustration  may  be  done  before  the  sub-panel  and  main 

panel  are  permanently  joined.     In  order  to  conserve  space  the  strip  carrying  the  binding 

posts  is  held  away  from  the  outer  end  of  the  brackets  by  two  bushings  and  long  machine 

screws.     The  space  saved  in  this  way  is  nearly  f  of  an  inch.     Units  like  this  completely  wired  are  soon  to  be 

placed  on  the  market.      The  Radio  Research  Laboratories,  New  York  City,  are  the  originators  of  this  unit 

idea.      It  would  be  well  to  compare  this  illustration  with  Fig.  7  to  note  the  changes 


may  be  used  at  will  without  taking  the  sound 
box  from  the  tone  arm.  A  tone-arm  of  the 
sort  described  has  been  used  in  our  laboratory 
and  has  produced  very  satisfactory  results. 
In  our  experiments  with  this  new  design,  we 
have  used  a  great  number  of  different  radio 
parts  designed  for  the  same  purpose.  In  prac- 
tically every  case,  the  overall  efficiency  of  the 
resulting  models  has  been  substantially  the 
same.  For  example,  we  have  used  a  number 
of  different  types  of  transformers.  We  have 
used  various  kinds  of  coils,  various  makes  of 
rheostats,  and  vacuum  tube  sockets.  We 
have  not  as  yet  been  able  to  use  standard 
jacks  in  this  receiver,  although  we  are  working 
on  that  problem  now.  It  may,  perhaps,  be 
difficult  for  some  of  our  readers  to  secure  cir- 
cular jacks  as  used  in  these  Phonograph  Re- 
ceivers in  their  locality,  but  these  may  be 


obtained  by  mail  order  in  a  few  days  from  al- 
most any  part  of  the  country. 

What  we  are  trying  to  do  is  to  present  a 
design,  which  in  the  final  analysis  will  give 
satisfaction,  even  in  the  hands  of  an  inex- 
perienced person.  We  are  trying  to  make  it 
possible  for  the  home  constructor  to  obtain 
the  necessary  parts  without  putting  himself  to 
a  great  deal  of  trouble.  By  incorporating 
as  we  have,  well  known,  standard  parts,  we 
have  made  it  possible  for  the  radio  dealer  to 
supply  all  the  necessary  units  for  this  receiver 
with  a  minimum  of  trouble. 

All  those  who  have  seen  the  first  models  of 
the  RADIO  BROADCAST  Phonograph  Receiver 
are  unanimous  in  agreeing  with  us  that  it  fills 
a  distinct  need  of  the  home  constructor.  The 
next  article  will  describe  the  building  of  this 
receiver. 


MARCONI  HIMSELF 


I I  AS  written  about  his  most  recent  experiments.     During  late  years, 

^  Senator  Marconi  has  centered  his  energies  on  perfecting  a  method 

for  transmitting  guided  radio  waves  and  he  believes  that  one  of  the  great 

developments  is  in  radio  "beam"  transmitting.     Senator  Marconi's  article 

will  appear  exclusively  in  RADIO  BROADCAST  for  July.     It  contains  many 

interesting  photographs  never  before  published  in  this  country. 


QUESTIONS  AND  ANSWERS 
\j? 


See  Important  Special  Announcement  on  Page  278 
QUERIES  ANSWERED 


WHAT   is  THE   FUNCTION   OF   A   DETECTOR  TUBE? 
A.  G.  N.— Atlanta,  Ga. 

WlLL     YOU     PUBLISH     A     CIRCUIT    ON     IMPEDANCE — 
COUPLED   AUDIO-FREQUENCY   AMPLIFICATION? 

L.  P. — San  Antonio,  Tex. 


WHAT  is  THE  CIRCUIT  DIAGRAM  FOR  INCLUDING  A 

I  IO-VOLT    LAMP     IN     A    B    BATTERY    CIRCUIT    FOR 
PROTECTING  THE  TUBE  FILAMENT? 

P.  V.  O. — Grand  Rapids,  Michigan. 


WHAT  is  THE  PROPER  WAY  TO  STAIN  AND  POLISH 

A  HOME-MADE  CABINET? 

N.  D. — Nashville,  Tennessee. 

EXPLAIN  IN  DETAIL  THE  USE  OF  THE  COIL  WINDING 
CHART  FOR  DETERMINING  CONDENSER  CAPACITY, 
J.  H.  W— St.  Louis,  Mo. 

WERE  THE  DIMENSIONS  USED  FOR  THE  PANEL  IN 
THE  CONSTRUCTION  OF  THE  TWO-STAGE  RADIO- 
FREQUENCY  AMPLIFIER  IN  THE  MAY,  1925,  ISSUE  OF 
R/.DIO  BROADCAST  CORRECT? 

L.  G.— Chicago,  111. 


HOW  A  DETECTOR  TUBE   DETECTS 

THE  term  detect  is  somewhat  erroneous  when 
used  in  describing  the  function  of  a  vacuum 
tube  detector.     If  our  ear  mechanisms  were 
able  to  respond  to  radio  signals  as  they  are  trans- 
mitted, there  would  be  no  need  for  detector  tubes. 

However,  the  frequency,  or  in  other  words,  the 
rapidity  with  which  the  radio  vibrations  are  pro- 
duced, is  too  great  for  us  to  hear,  so  that  some  means 
of  reducing  the  number  of  vibrations  must  be  em- 
ployed. The  action  is  one  of  rectification  rather 


Filament 


FIG.     I 


FIG.    2 


than  one  of  detection.  For  instance,  the  maximum 
number  of  vibrations  that  can  be  heard  by  the 
human  ear  is  about  20,000  cycles,  while  the  mini- 
mum number  that  can  be  heard  is  but  16  cycles. 


RADIO  BROADCAST  ADVERTISER 


273 


Do  you  know 

where  Condenser  losses 

Come,  -from? 

TDESISTANCE  LOSSES   are 

the  losses  which  most  serious- 
ly affect  the  efficiency  of  aconden- 
ser  when  at  working  "radio  ^  fre- 
quencies. They  arise  from  poor 
contacts  between  plates  and  from 
poor  bearing  contacts..  Soldered 
plates  and  positive  contact  spring 
bearings  reduce  these  losses  to  .a 
minimum.N 

Eddy  current  fosses  occur 'in 
metal  end  plates  and  the  conden- 
ser plates  themselves.  While  not 
so  serious  as  resistance  losses, 
they  increase  with  the  frequency, 
and  therefore  should  be  kept  as 
low  as  possible. 

Dielectric  losses  are  due  to  ab- 
sorption of  energy  by  the  insulat- 
ing material.  Inasmuch  as  they 
vary  inversely  as  the  frequency, 
they  have  less  effect  upon  the 
efficiency  of  a  condenser  at  radio 
frequencies  than  any  other  set  of 
losses.  The  use  of  metal  end 
plates  in  short-wave  reception  to 
eliminate  dielectric  losses  is  never 
justified,  because  they  introduce 
greater  losses  than  well-designed 
end  plates  of  good  dielectric. 


The  design  of  General  Radio  Condensers 
is  based  on  scientific  facts  and  principles, 
not  on  style  and  fancies. 

Specially  shaped  plates  always  in  perfect 
alignment  give  the  uniform  wave-length 
variation  which,  permits  extremely  sharp 
tuning.? 

Rotor  plates  are  counterbalanced  to  make 
possible  accurate  dial  settings. 

In  1915  the  General  Radio  Company  in- 
troduced to  this  country  the  first  Low  Loss 
Condenser,  and .  ever .  since  has  beenjthe 
leader  in  condenser  design. 

Lower  Losses  and^Lower  Prices  make 
General  Radio  Condenserslthe  outstanding 
values  of  condenser  design. 

Licensed  for  multiple  tuning  under  Hogan 
Patent  No.  It014,002 

Type  247-H,  with  geared  Vernier 
Capacity,  500  MMF.     Price 

Type   247-F,  without    Vernier     </> 
Capacity,  500  MMF.    Price       ^J 

GENERAL  RADIO  CO, 

.  A  CAMBRIDGE,  MASS. 


Quality  Parts 


Tested  and  approved  by  RADIO  BROADCAST 


274 


Radio  Broadcast 


Now  waves  of  greater  or  lesser  frequencies  than  this 
must  be  either  increased  or  reduced  before  they  can 
be  heard.  To  accomplish  this  purpose,  a  detector, 
or  rectifier,  is  used,  which  breaks  up  the  frequency 
of  the  oscillations  into  groups  and  makes  it  possible 
to  hear  the  vibrations  as  they  are  recorded  on  the 
telephone  diaphragm. 

The  elements  of  which  the  tube  consists  are  (A) 
a  filament  which  is  energized  by  a  source  of  direct 
current  (storage  A  battery.)  Around  this  filament 
is  (B)  a  wire  mesh  or  grid.  Then  outside  and  around 
the  grid  is  (C)  a  metallic  member  termed  the  plate. 
These  elements  are  supported  by  wire  rods  imbedded 
in  a  glass  tube  from  which  the  air  has  been  evacu- 
ated. Convenient  contacts  are  provided  by  prongs 
protruding  through  the  base. 

Diagrammatically,  the  vacuum  tube  is  repre- 
sented as  in  Fig.  i  while  Fig.  2  shows  a  vacuum  tube 
connected  in  an  ordinary  receiving  circuit. 

The  action  of  the  circuit  and  the  function  of  the 
tube  are  as  follows: 

The  antenna  circuit  consisting  of  the  antenna,  pri- 
mary, the  variable  condenser  and  the  ground,  have 
been  adjusted  to  the  wavelength  of  a  transmitting 
station. 

The  secondary  circuit,  S-C2,  to  which  is  connected 
the  vacuum  tube,  its  batteries  and  phones,  is  tuned 
in  resonance  with  the  primary. 

This  makes  it  possible  to  receive  energy  in  the 
antenna  circuit  so  as  to  set  up  an  electro-magnetic 


CONSTANT  AMPLITUDE  ALTERNATIONS 


FIG.    3 


Rl 

na 


field,  which  induces  a  voltage  in  the  secondary  cir- 
cuit. 

Now,  by  referring  to  Fig.  2,  it  will  be  seen  that 
there  are,  primarily,  three  parts  to  the  circuit. 

When  the  filament  is  lighted  to  incandescence  it 
emits  electrons  which  flow  to  the  plate,  so  that  when 
a  signal  is  received,  it  sets  up  in  the  antenna  circuit 
an  electro-magnetic  field,  due  to  the  variations  in 
amplitude  of  the  received  signal.  See  Fig. 
3A  and  B.  This  field  induces  in  the  secon- 
dary, or  grid  circuit,  a  voltage  which 
charges  the  grid  condenser. 

Doctor  Van  der  Bijl  explains  the  suc- 
ceeding rectifying  action  as  follows: 

"When  the  grid  potential  becomes 
positive,  electrons  are  attracted  to 
the  grid  and  during  the  next  half  cycle 
when  the  grid  potential  becomes 
negative,  the  electrons  cannot  escape 
from  the  grid,  because  they  are 
trapped  on  the  insulated  part  of  the 
circuit  comprising  the  grid  and  the  one 
plate  of  the  condenser  C3-  During  the 
next  positive  loop  of  the  incoming 


wave  the  grid  attracts  more  electrons,  which 
are  also  trapped  so  that  they  cannot  escape 
from  the  grid  during  the  succeeding  negative 
loop.  In  this  way,  the  grid  builds  up  a  nega- 
tive potential,  and  the  high  frequency  poten- 
tial variations  on  the  grid,  vary  around  a  mean 
value  of  the  grid  potential,  which  becomes  more 
and  more  negative  as  the  strength  of  the  in- 
coming oscillations  increase.  This  reduces  the 


Grid  potential 


Audio  current 
in  telephone 


FIG.    4 

plate  current,  and  if  the  condenser  C3,  and  the 
insulation  of  the  part  of  the  circuit  comprising 
C3  and  the  grid  were  perfect  the  plate  current 
would  be  permanently  reduced  and  this  would 
make  the  tube  inoperative.  To  prevent  this, 
a  high  resistance  leak,  R2,  is  shunted  across 
the  condenser,  its  value  being  so  proportioned 
that  the  electrons  cannot  leak  off  this  resis- 
tance to  any  appreciable  extent  in  a  time  com- 
parable with  the  period  of  the  high  frequency 
oscillations.  But  the  electrons  do  leak  off  in 
the  time  of  the  order  of  magnitude  of  the  low 
frequency  variations  of  the  amplitude  of  the 
high  frequency  oscillations.  The  result  is, 
that  the  potential  of  the  grid  takes  such  values 
as  are  represented  by  the  curve  in  Fig.  4A. 
The  high  frequency  variations  in  the  plate 
circuit  pass  through  the  condenser  C4  inserted 
in  the  output  circuit,  and  the  current  in  the 
telephone  receiver  takes  the  shape  shown  by 
the  curve  in  Fig.  48." 

The  current   passing   through  the   phones  ener- 
gizes  the   electromagnets   and    conforms   with    its 

Isolating  condensers 

2mfd./         1st  Audio         '•.2T.fd-  2nd  Audio 

Amplifier 


9   A 


FIG. 


RADIO  BROADCAST  ADVERTISER 


275 


positive  as  BjgBen 


SET  Big  Ben  at  seven  and  at  seven  o'clock  you're  bound  to 
get  the  alarm. 

Just  so,  the  Ultra-Lowloss  condenser  can  be  set  at  any  wave- 
length —  the  corresponding  station  will  come  in  clear  and  sharp. 
You  know  instantly  where  to  turn,  once  a  station  of  known 
wavelength  is  located.  Makes  tuning  easy  —  direct  —  positive. 
Special  Cutlass  Stator  Plates  spread  wavelengths  evenly  over 
a  100  degree  scale  dial  so  that  each  degree  represents  approxi- 
mately 3J  meters. 

Ultra-Lowloss  condensers  are  designed  by  R.  E.  Lacault, 
originator  of  the  famous  Ultradyne  Receivers,  and  built  upon 
scientific  principles  which  overcome  losses  usually  experienced 
in  other  condensers. 

At  your  dealers,  otherwise  send  purchase  price  and  you  will  be 
supplied  postpaid. 

Design  of  lowloss  coils  furnished  free  with  each  condenser  for 
amateur  and  broadcast  wavelengths  showing  which  will  function 
most  efficiently  with  the  condenser. 

J.Q  Manufacturer8  who  Wish  To    Improve  Their  Sets 

Mr.  Lacault  will  gladly  consult  with  any  manufacturer  regarding  the  appli- 
cation  of  this  condenser  to  his  circuit  for  obtaining  best  possible  efficiency. 


TUN.NS    CONTROL 

Simplifies  radio  tuning.  Pencil- 
record  a  station  on  the  dial  —  there- 
after,  simply  turn  the  finder  to  your 
pencil  mark  to  get  that  station  in- 
stantly.  Easy-quick  to  mount. 
Eliminates  fumbling,  guessing.  Fur- 
mshed  clockwise  or  anti-clockwise 
in  gold  or  silver  finish.  Gear  ratio 
20  to  1. 

Silver,  $2.50  Gold,  $3.50 

PHENIX   RADIO   CORPORATION     -     116-C  East  25th  Street     -     New  York 


—  .  l 


CON   DENSER 


Tested  and  approved  by  RADIO  BROADCAST 


276 


The  Grid 


strength,  actuating  the  diaphragm  which  produces 
sound  vibrations  which  are  audible  to  the  ear. 

IMPEDANCE-COUPLED    AUDIO    AMPLIFICATION 

FOR  those  who  wish  to  experiment  with  choke 
coil  audio  amplification,  the  circuit  in  Fig.  5 
is  especially  interesting. 

A  detector  and  two-stage  amplifier  is  shown. 

In  the  plate  circuit  of  the  detector  and  first  stage 
amplifier,  the  variations  in  voltage  drop  take  place 
in  the  choke  coils.  These  variations  are  impressed 
on  the  grid  of  the  succeeding  tube  through  the  large 
isolating  condenser.  In  the  amplifiers  the  grid 
leaks  connected  from  the  grids  to  the  negative  side 
of  the  filament  (through  a  small  C  battery)  furnish 
a  path  for  excessive  negative  voltages,  which  are 
accumulated  on  the  grid,  to  leak  off. 

The  choke  coil  may  be  the  secondary  of  an  audio 
transformer.  Usually  transformers  having  burned 
out  primaries  may  be  found  in  the  junk  box  of  the 
radio  laboratory  which  will  fit  in  nicely  here. 

The  small  C  battery  applies  a  negative  bias  on  the 
grids  which  permits  the  amplifier  tubes  to  operate 
on  the  proper  point  on  their  characteristic  curve. 

The  value  of  an  isolating  condenser  is  such  that  a 
minimum  of  voltage  loss  is  effected  by  its  use. 

Besides  being  a  coupling  agent  between  the  plate 
and  grid  of  adjacent  tubes,  this  condenser  isolates 
the  high  B  voltage  from  the  grid  of  the  tube. 

The  values  of  the  parts  are  Ci  .00025  rnfd.,  C.2 
2  mfd.;  C3  2  mfd.;  C^  .001  mfd:  Ri  3  megohms; 
R2  and  R3  ^  to  2  megohms. 


THE  LAMP  AS  APPLIED  TO  A  STANDARD  CIRCUIT 

m 


J&. 

R 


-       B 


Safety  Lamp  • 


25  or  50  Watt  Tungsten 
Filament  Lamp  inserted  in 
/  the-B  lead 


I  I  I  I  I  I  I  I 

B  Battery 
FIG.    6 


A    TUBE    PROTECTOR 

VERY  often  radio  tubes  are  consigned  to  the 
junk   heap   because   some   too   enthusiastic 
experimenter  was  not  careful  enough  to  keep 
his  high  voltage  B  battery  leads  away  from  the 
filament  circuit  of  his  receiver. 

By  the  simple  addition  of  a  25  or  50  watt  lamp 
inserted  in  the  negative  B  battery  lead  (Fig.  6), 


tubes  may  forever  be  protected  from  blow-outs. 
Ordinarily  the  negative  side  of  the  B  battery  con- 
nects to  either  the  plus  or  minus  of  the  A  battery. 

Assuming  that  the  connection  is  made  to  the  plus 
A,  if  the  plus  B  should  happen  to  come  in  contact 
with  the  minus  A,  then  45  or  90  volts  (as  the  case 
may  be)  would  be  applied  to  6  volt  filaments. 
Result:  blown  out  tubes. 

Now,  by  placing  the  lamp  in  the  negative  side  of 
the  B  battery,  the  full  voltage  of  the  battery  is 
applied  to  its  filament  thereby  choking  off  the  B  cur- 
rent and  so  protecting  the  tube  filaments  due  to  the 
relatively  high  resistance  of  the  lamp  being  inserted 
in  series  in  the  circuit.  The  tungsten  type  of  lamp 
seems  to  give  better  results  than  the  carbon  filament 
type.  Ordinarily  if  the  plus  B  lead  should  touch  the 
plus  A  lead  then  the  B  battery  would  become  short- 
circuited,  but  if  the  lamp  is  in  the  circuit  it  will 
indicate  the  connection  by  lighting  brilliantly. 

STAINING    AND    POLISHING    CABINETS 

THE  true  constructor  must  know  a  bit  about 
the  carpentry   that  enters  into  the  make-up 
of  a  receiver.     The  art  of  carpentry  is  closely 
allied  with  the  radio  art  as  is  manifest  in  the  elabo- 
rate cabinet  designs  now  so  plentiful  in  the  radio 
market. 

For  the  home-constructor,  a  few  pointers  on 
staining  and  polishing  will  not  be  amiss.  There 
are  several  kinds  of  stains,  namely,  the,  alcohol 
stain,  the  penetrating  stain,  and  the  oil  stain.  The 
first  two  named  seem  to  act  better  for  quality 
work,  although  no  doubt  good  work  may  be  accom- 
plished with  oil  stain.  This  discussion  will  apply 
only  to  the  penetrating  and  alcohol  stains. 
The  equipment  needed  is  as  follows: 

1.  A  small  supply  of  alcohol — one  pint. 

2.  Stain. 

3.  Cheesecloth  pad  made  with  cotton  waste. 

4.  Steel  wool. 

5.  Rotten  stone. 

6.  Wax  (in  powdered  or  grease  form). 

7.  Shellac — one-half  pint  jar. 

The  cabinet  is  first  coated  evenly  with  the  stain 
until  the  desired  shade  is  obtained.  Shellac  is 
applied  with  the  cloth  pad  so  that  the  entire  surface 
is  covered.  Then  with  the  alcohol,  the  surface  is 
lightly  washed,  which  removes  much  of  the  surplus 
shellac.  After  this  coat  is  allowed  to  dry  for  about 
twenty  minutes,  another  coating  of  shellac  is  applied 
which  is  again  washed  down  with  the  alcohol.  This 
is  repeated  until  the  desired  surface  effect  is  ob- 
tained. Then,  with  rotten  stone  the  surface  is  fully 
cleaned,  after  which  it  is  rubbed  down  by  the  steel 
wool.  Finishing  touches  consist  of  polishing  with  a 
waxed  cloth. 

THE     COIL    WINDING    CHART     FOR     CALCULATING     CA- 
PACITY 

IN  LAST  months'  RADIO  BROADCAST,  a  chart 
for  the  computation  of  coil  sizes  was  described 
on  page  46,  which  would  aid  the  experimenter 
in  determining  the  proper  size  coil  required  where 


RADIO  BROADCAST  ADVERTISER 


277 


EVEREADY    HOUR 
EVERY   TUESDAY  AT  8   P.  M. 

Eastern  Standard  Time 

For   real   radio   enjoyment,   tune  in   the 
"Eyeready  Group."    Broadcast  through 
stations  — 
WEAF  New  York 
WJAR  Providence 
WEEI    Boston 


WFI       Philadelphia 
WGR     Buffalo 
WCAE  Pittsburgh 


WEAR  Cleveland 
WSAI    Cincinnati 
Detroit 

f  Minneapolis 
gt  Pauj 

WOC     Davenport 


WWJ 


Eveready 

Columbia 

Jsfttor 

Battery 

The  proven 

dry  cell 

lor  all 

radio 
dry  cell 

tubes 
\l/2  volts 


No.  766 
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'    Evereadys  have 
long-lasting  power 

THE  long-lasting  power  of  Evereadys 
more  than  justifies  their  price.  It  is 
false  economy  to  buy  batteries  that  may 
be  cheaper  in  first  cost,  but  which  are 
much  shorter  lived.  Considering  price 
and  size,  Evereadys  are  the  most 
economical  batteries  there  are,  and  in 
addition  they  are  most  satisfactory. 
Buy  Eveready  "B"  Batteries.  To  light 
the  filaments  of  all  radio  dry  cell  tubes, 
use  the  famous  Eveready  Columbia 
Ignitor. 

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 


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ts&m 


No.  772 
45-volt 
Large 
Vertical 
Price 
$3.75 


Tested  and  approved  by  RADIO  BROADCAST 


2jS  Radio  Broadcast 

a  certain  sized  condenser  was  designated  to  tune  is  indicated  by  where  this  last  line  touches  the  in- 

:i  circuit  to  a  predetermined  wavelength  range.  ductance   scale,    and    by    knowing   the    maximum 

In  the  article  it  was  mentioned  that  the  chart  wavelength  range  desired,  we  draw  a  line  between 

might  be  used  in  the  reverse  manner,  where  the-coil  these  two  points  and  continue  the  line  on  to  the 

size  and  wavelength  range  desired  were  known,  to  capacity  scale.     This  intersection  at  the  capacity 

determine  the  value  of  variable  condenser  needed  to  scale  gives  us  the  maximum  capacity  of  the  variable 

accomplish  this  end.  condenser  necessary  for  tuning  the  coil  in  question 

In  detail  this  reverse  operation  is  described  as  to  the  maximum  wavelength  indicated, 
follows: 

Count  the  number  of  turns  per  inch  on  the  coil  CORRECTED  DIMENSIONS 
and    measure   its   length.     On   the   chart   connect 

these  two  points  by  a  pencil  line.     Then  determine  A  I  ^HE  dimensions  for  the  panel  used  in  the  con- 

the  diameter  of  the  coil  and  at  that  value  on  the  struction   of   the    two-stage   radio-frequency 

chart  and  draw  a  line  to  intersect  with  the  one  1     amplifier  described  in  the  May,  1925,  issue  of 

previously  drawn,  at  the  index  line  and  at  the  indue-  Radio  Broadcast  Magazine  should  read  as  follows: 

tance  scale.  Panel  7  inches  wide,   18  inches  long,  and  f\  inch 

Then  by  knowing  the  inductance  value,  since  it  thick. 


Before  Ton  Write  to  the  Grid 

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RADIO  BROADCAST, 

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Dear  Sir: 

Attached  please  find  a  sheet  containing  questions  upon  which  \indly  give  me  fullest 
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RADIO  BROADCAST  ADVERTISER 


279 


By-Pass 


noises  and 


Y-PASS  Condensers  do  a  double 
job.  They  filter  the  fluctuating 
"B"  battery  current.  They  provide  a 
free  path  for  the  radio  frequency  cur- 
rents around  the  high  internal  resis- 
tance "B"  battery. 

The  first  function  tends  to  remove 
disturbing  noises — the  second  increases 
efficiency  by  reducing  losses  and  prop- 
erly routing  the  available  energy. 

The  tone  quality  of  every  set  will  be 
greater  in  strength — purer — smoother 
—with  a  By-Pass  Condenser. 


External  connections  for  the  By- 
Pass  Condenser  may  be  made  by 
connecting  it  from  the  minus  "B" 
terminal  to  the  plus  "B". 


Dubilicr 

CONDENSER    AND   RADIO    CORPORATION 


Tested  and  approved  by  RADIO  BROADCAST 


New  Equipment 


SEE-ESS    WINDER 

The  winding  of  numerous  inductances  for  ex- 
perimental work  is  made  easy  with  the  above 
apparatus.  The  result  is  a  self-supporting 
diamond  weave  coil  of  any  desired  inductance. 
A  desirable  addition  to  the  constructor's  labor- 
atory. Distributed  by  the  Wireless  Electric 
Co.,  204-206  Stanwix  St.,  Pittsburgh,  Pennsyl- 
vania. Price,  $10.00 


KELLOGG   REPRODUCER 

The  unit  of  this  speaker  is  of  special 
construction,  having  a  magnetically 
modulated  diaphragm.  Coupled 
with  this  is  the  horn  which  was  de- 
veloped to  be  as  nearly  correct 
acoustically,  both  as  to  shape  and 
material,  as  possible.  This  repro- 
ducer covers  practically  the  entire 
auditory  range  of  sound  waves  very 
successfully.  Made  by  the  Kellogg 
Switchboard  &  Supply  Co.,  Adams 
&  Aberdeen  Sts.,  Chicago,  Illinois. 
Price,  $20.00 


BALLGRIP 

BINDING 

POST 

These  interesting 
binding  posts  re- 
present a  new 
idea  in  this  field. 
Connections  may 
be  made  instantly 
and  the  opening 
in  the  post  is 
large  enough  for 
receiver  cord  tips. 
Springs  force  the 
ball  to  make  good 
electrical  contact 
when  a  wire  is 
placed  in  position. 
The  fact  that 
there  is  no  head 
to  loosen  and  be 
lost  is  a  decided 
point  in  its  favor. 
Made  by  the 
Quality  Moulded 
Products  Inc., 
Jersey  City,  New 
Jersey 


BELDEN    LOOP   WIRE 

A  wire  composed  of  60  strands  of  bare  copper 
twisted  with  5  strands  of  half  hard  phosphor 
bronze  wire.  This  twist  is  then  covered  with 
cotton  and  finally  with  a  good  looking  brown 
covering  to  match  the  better  grades  of  loop 
frames.  Made  by  the  well  known  makers  of 
wire,  the  Belden  Manufacturing  Company, 
Chicago,  Illinois 


VELVET   VERNIER   DIAL 

An  all-vernier  dial  with  a  ratio  of  approximately 
four  to  one  and  is  entirely  free  from  back -lash. 
With  this  dial  you  not  only  enhance  the  appear- 
ance of  your  receiver  but  also  make  tuning  very 
easy.  Made  by  the  National  Company,  Inc., 
110  Brookline  St.,  Cambridge,  Massachusetts 


RADIO  BROADCAST  ADVERTISER 


321 


WD-11 

WD-12 
UV-199 

UV-200 
UV-201-a 

Radiotrons  with  these  model 
numbers  are  only  genuine  when 
they  bear  the  name  Radiotron 
and  the  RCA  mark. 


* 


in  Names 


Do  you  buy  things  by  name  because  the  name 
tells  the  quality?  Do  you  ask  for  a  RADIOTRON, 
instead  of  just  a  "vacuum  tube"—  demand  the 
standard  by  the  name  that  marks  it  as  genuine? 

The  most  important  part  of  a  radio  set  is  the  tube, 
and  you  can't  get  the  best  out  of  any  set  without 
putting  the  best  tubes  into  it.  There's  a  Radio- 
tron for  every  use,  in  every  kind  of  set.  Look 
for  the  name  —  and  the  RCA  mark  —  and  be  sure 
it  is  genuine. 

Radio  Corporation  of  America 

Sales  Offices:  Suite  37 

233  Broadway,  New  York  10  So.  La  Salle  St.,  Chicago,  11L 

28  Geary  Street.  San  Francisco,  Cal. 


Radiotr 


REG. U.S.  PAT.  OFF.  — 


PRODUCED    ONLY    BY     RCA 


Tested  and  approved  by  RADIO  BROADCAST  -jr 


SUMMER-TIME    RADIO 


The  super-autodyne  described  in  this  issue  is  made  portable  by  use  of  the  Lynch  Lead  which  connects 
the  filaments  to  the  automobile  battery.  The  Crosley  "  Musicone  "  is  connected  by  a  long  cord  so  that 
the  receiver  may  be  left  in  the  car  and  the  speaker  taken  to  any  convenient  spot  nearby.  It  is  grow- 
ing more  and  more  fashionable  to  make  a  portable  set  a  part  of  motoring  and  camping  equipment 


BROADCAST 


Vol.  7,  No.  3 


July,  1925 


"  Stations  Revolutionize 
Radio? 


Senator  Marconi's  Own  Story  of  His  Experiments  with  Short  Waves  —  Increased  Effici- 
ency and  Greater  Sending  Speed  Made  Possible  by  Focussed  High-Power  Short  Waves 

By  GUGLIELMO   MARCONI 


THE  art  of  radio  communication  might 
well  adopt  as  its  motto,  paralleling  a 
well-known     Roman    saying     about 
Africa,     "Ex    radio    semper    aliquid 
novi,"  or,  to  put  it  in  the  vernacular,  "Out- 
of  radio   we   are   always   getting   something 
new."  , 

For  many  years,  all  the  important  radio 
communication  enterprises  of  the  world  have 
been  engaged  in  building  larger  and  more 
powerful  stations,  employing  many  hundreds  of 
kilowatts  in  order  to  be  able  to  send  forth  into 
the  ether  more  powerful  and  longer  electric 
waves,  which  have,  in  some  cases,  reached  a 
length  of  about  15  miles.  But  had  a  little 
more  time  been  devoted  to  a  systematic  in- 
vestigation of  short  waves,  produced  by  a 
power  equal  to  only  a  fraction  of  that  used  in 
all  of  the  big  stations  in  the  world,  the  dis- 
covery might  have  been  made  that  a  modest 
loo-foot  wave,  utilizing  only  some  15  kilo- 
watts or  20  horse  power,  could  successfuly 
travel  from  England  to  Australia  and  South 
America,  even  during  daylight,  and  there  re- 
produce easily  decipherable  telegraphic  sig- 
nals. 


But  most  experts,  relying  on  theories  which 
had  not  been  thoroughly  tested  or  on  insuffi- 
cient experimental  data,  had  made  up  their 
minds  as  to  what  short  electric  waves  could  or 
could  not  do.  It  was  reserved  for  the  years 
1923  and  1924  to  show  conclusively  that  such 
short  waves  could,  and  did,  perform  efficiently 
and  reliably  most  of  the  things  which  the 
experts  had  considered  until  then  either  im- 
possible or  impracticable. 

I  think  I  am  justified  in  saying,  as  a  result 
of  the  experiments  which  I  have  carried  on  for 
a  number  of  years  and  which  culminated  in 
1923  and  1924,  that  a  combination  of  short 
electric  waves  with  what  is  known  as  the  Beam 
System,  is  likely  to  bring  about  what  amounts 
to  nothing  less  than  a  revolution  in  the  meth- 
ods of  commercial  long-distance  radio  com- 
munication. 

SHORT  WIRELESS   WAVES    ARE    HISTORICAL 

THE  use  of  short  electric  waves  is  as  old  as 
the  discovery  of  the  waves   themselves. 
Hertz  made  use  of  them  in  his  first  classical 
experiments,  and  he  proved  that  they  obeyed 
the  same  laws  as  the  infinitely  shorter  light 


324 


Radio  Broadcast 


waves  in  regard  to  the  speed  of  propagation, 
reflection,  refraction,  and  diffraction.  Some 
twenty-nine  years  ago  in  my  own  first  experi- 
ments, in  Italy,  and  shortly  afterward  in  Eng- 
land, 1  used  short  waves  in  combination  with 
metallic  reflectors  and,  curiously  enough,  I 
was  then  able  to  transmit  signals  with  them 
over  a  distance  of  a  mile  and  three  quarters, 
while  with  the  elevated  antenna  and  much 
longer  waves,  i.  e.,  using  the  same  system  that 
is  used  to-day  in  all  the  high-power  stations  of 
the  world,  1  could  only 
manage  to  communi- 
cate over  a  distance 
of  half  a  mile. 

It  is  perhaps  regret- 
table that  the  subse- 
quent rapid  develop- 
ment of  the  long-wave 
system,  which  in  three 
or  four  years  achieved 
such  spectacular  re- 
sults, drew  away  the 
attention  of  most  of 
us  not  only  from  the 
possibilities  of  the 
short  waves,  but  also 
from  the  use  of  suit- 
able reflectors  to  con- 
centrate them  into  a 
beam  in  a  definite 
direction,  which  is 
possible  only  with 
short  waves.  I  never 
quite  abandoned  the 
idea,  however,  of  uti- 
lizing the  latter  and, 
in  addition,  1  always 
realized  the  import- 
ance of  evolving  a 
practical  directive 
system  of  radio  com- 
munication. 

I  believe  it  is  gen- 
erally admitted  now 
that  electric  waves 

are  far  too  valuable  to  be  always  allowed 
to  spread  out  in  every  direction  when  it  is 
desired  to  communicate  with  only  one  par- 
ticular place.  If  a  station  in  Great  Britain 
wishes  to  communicate  with  one  in  the  United 
States,  for  example,  there  seems  to  be  no 
good  reason  why,  if  it  can  be  helped,  what 
it  has  to  say  should  be  heard  in  Siberia,  and 
Egypt,  as  well  as  in  Nicaragua  and  India. 
Naturally,  non-directional  stations,  which 
scatter  their  waves  in  every  direction,  are  of 
great  utility  for  many  naval  and  war  purposes, 


What  Senator  Marconi  Is 


HIS  last  trip  to  the  United  States, 
Senator  Marconi  presented  a  paper  be- 
fore the  Institute  of  Radio  Engineers  de- 
scribing various  radio  experiments  bein& 
conducted  under  his  direction.  That  paper 
was  read  June  30,  1922,  and  dealt  to  a  lar&e 
extent  with  experiments  with  short  radio 
waves. 

It  should  not  be  thought  that  short  wave 
radio  transmission  is  new,  simply  because 
experiment  in  this  field  has  lately  received 
a  &ood  deal  of  attention  from  amateur  and 
commercial  engineer  alike.  Senator  Mar- 
coni's earliest  experiments  with  wireless 
waves  in  1895  and  1896  used  waves  not 
more  than  a  few  inches  loh&.  A-nd'noWj- 
after  radio  stations  have  been  built  to  use 
waves  as  lon&  as  20,000  meters,  the  cycle  of 
radio  investigation  swings  back  to  something 
very  similar  to  that  of  the  first  radio  experi- 
ments. But  in  these  experiments,  the  aim  is 
to  do  away  with  the  fading  and  absorption  of 
signals,  interference  by  natural  electric 
•waves,  and  to  make  transmission  directional. 
In  this  article,  Senator  Marconi  himself  tells 
of  •what  he  and  his  engineers  have  lately  done 
to  revolutionize  radio.  —  THE  EDITOR 


and  of  course  for  broadcasting,  where  the  very 
soul  of  the  process  lies  in  the  fact  that  the 
waves  are  scattered  all  around  to  be  picked  up 
by  any  one  with  a  suitable  receiving  set. 
But  it  has  always  seemed  to  me  that,  if  possi- 
ble, the  right  thing  to  do  would  be  to  concen- 
trate the  whole  of  the  radiated  energy  into  a 
beam  directed  toward  the  locality  with 
which  it  is  desired  to  communicate,  just  as  the 
beam  of  light  waves  from  a  searchlight  is  thrown 
in  one  direction  by  means  of  reflectors. 

Such  a  result  is 
greatly  to  be  desired 
on  many  grounds, 
such  as  the  low  cost 
of  installation  and 
economy  of  upkeep 
entailed  by  the  much 
lower  amount  of  en- 
ergy required,  the  re- 
duction of  interfer- 
ence with  other 
stations,  and  the  com- 
parative  secrecy 
which  can  be  ob- 
tained. 

Economy  of  energy 
is  a  matter  which  is 
instantly  translatable 
into  pounds,  shillings, 
and  pence.  I  f  we  con- 
sider a  high  -  power 
station  similar  to  the 
one  recently  built  in 
•the  Argentine  for 
communication  with 
Europe  over  a  dis- 
tance of  about  6000 
miles,  every  time  the 
operator  depresses  the 
key  and  sends  a  signal 
flashing  through  the 
ether,  some  800  kilo- 
watts (about  i 100  h. 
p.)  is  expended,  al- 
though in  the  case  of 

these  long  waves,  only  a  small  fraction  of  the 
power  is  radiated  from  the  antenna,  which,  in 
this  case,  is  supported  by  ten  steel  towers  each 
690  feet  high.  It  is  evident  that  if  a  signal 
as  easily  readable  can  be  sent  with  30  or  40 
kilowatts  (about  50  h.  p.)  and  by  means  of  an 
antenna  supported  by  much  lower  and  fewer 
masts,  there  will  be  not  only  a  greatly  de- 
creased cost  of  installation  of  the  station,  but 
also  a  great  reduction  in  the  cost  of  maintain- 
ing the  station. 
With  regard  to  the  question  of  interference 


Will  "Beam"  Stations  Revolutionize  Radio? 


325 


with  other  stations,  it  should  be  remembered 
that  the  number  of  available  wavelengths  is, 
after  all,  far  from  being  unlimited,  and  if 
Brazil  wishes  to  let  New  York  know  the  prices 
of  coffee  and  rubber  on  a  certain  wavelength, 
it  would  seem  useless  and,  in  certain  cases,  per- 
haps, undesirable,  to  broadcast  the  same  in- 
formation over  Africa,  Europe,  the  Pacific 
Ocean  and  probably  a  large  part  of  Asia. 

BEAM    RADIO    TRANSMISSION     IS    MORE     SECRET 

AS  REGARDS  secrecy,  the  beam  system 
possesses  a  considerable  advantage  be- 
cause only  places  situated  within  a  certain 
angle  or  sector  of  the  beam  are  able 
to  receive  a  signal  sent  out  by  this 
method.  This  comparative  secrecy 
or  privacy,  which  cannot  be  obtained 
with  any  other  system  of  radio  com- 
munication, might  prove  of  the  great- 
est possible  value  in  war  time  and, 
moreover,  as  has  already  been  said, 
by  reducing  mutual  interference,  it 
will  increase  the  number  of  stations 
that  can  be  operated  within  a  cer- 
tain area. 

During  the  early  stages  of  the  War, 
1  became  convinced  that  we  had  per- 


mitted ourselves  to  get  into  a  rut  by  allowing 
our  attention  to  be  monpolized  almost  exclu- 
sively by  long  waves,  and  1  decided  to  take  up 
the  systematic  study  of  short  waves  in  com- 
bination with  arrangements  for  directing  them 
in  any  given  direction.  My  first  experiments 
along  these  lines  in  Genoa  and  later  in  Livorno 
in  191 6;  showed  me  that  good  directional  work- 
ing could  always  be  obtained  with  properly 
constructed  reflectors,  and  with  the  apparatus 
then  available  a  range  of  six  miles  was  at- 
tained. 

Further  experiments,   carried  out  by  my 
assistant,  Mr.  C.  S.  Franklin,  between  Carn- 


©  Kadel  &  Herbert 

THE  "  ELETTRA" 

Senator  Marconi's  floating  radio  laboratory  and  pleasure  yacht.     Much  of  this  great  investigator's,  most 

important  work  has  been  done  aboard  his  yacht.     Some  of  the  experiments  described  in  this  article  were 

made  on  the  Eleitra  while  she  was  in  the  Mediterranean,  communicating  with  the  station  at  Inchkeith,  shown 

in  the  cut  on  page  327.    The  insert  shows  Senator  Marconi  in  his  radio  cabin 


326 


Radio  Broadcast 


arvon,  in  Wales,  and  Ireland,  and  subse- 
quently between  Hendon,  near  London,  and 
Birmingham,  increased  this  range  to  nearly  a 
hundred  miles  and  strong  radio-telephonic 
speech  was  received  with  the  use  of  a  power  of 
only  700  watts  (less  than  i  h.  p.)-  One  very 
important  experiment  led  to  the  knowledge 
that,  when  suitable  reflectors  were  used  at 
both  ends,  that  is,  one  reflector  to  concentrate 
and  project  the  waves  in  a  beam  and  the  other 
to  focus  them  at  the  receiving  end  on  the  re- 
ceiving antenna,  the  received  energy  was  some 
200  times  greater  than  when  no  reflectors 
were  used. 

The  success  of  these  experiments  led  me  to 
carry  out  a  series  of  tests  between  a  small 
experimental  transmitting  station  at  Poldhu 
in  Cornwall,  and  a  receiver  installed  on  my 
yacht,  the  Elettra,  which  would  enable  me  to 
vary  the  distance  between  the  transmitting 
and  receiving  ends  at  will.  Until  then,  most 
technicians  were  under  the  general  impression 
that  the  range  of  short  waves  during  daytime 
was  variable  and  short,  and  that  though  their 
night  range  was,  as  a  rule,  much  greater,  it 
was  far  too  unreliable  to  be  of  any  use  for 
practical  commercial  work.  In  addition  it 
was  thought  that  any  considerable  mass  of 
land,  especially  if  it  were  of  a  mountainous 
nature,  would  very  materially  reduce  the 
working  range  with  them.  My  experiments, 
which  were  carried  out  chiefly  with  waves  of 
about  100  meters  in  length,  and  with  about 
12  kilowatts  (about  16  h.  p.),  served  to  dis- 
prove a  considerable  portion  of  these  beliefs 
and  theories. 

I  knew,  of  course,  like  every  other  experi- 
menter, that  short  waves,  or  at  any  rate 
short  waves  of  the  length  I  was  then  using, 
had  much  shorter  ranges  during  daytime  than 
at  night.  This  fact  was  first  observed  by  me 
in  February,  1902,  and  my  subsequent  dis- 
covery that  waves  of  the  order  of  several 
thousand  meters  would,  on  the  average, 
work  as  well  by  day  as  by  night,  was  one  of 
the  main  contributory  causes  to  the  develop- 
ment of  the  use  of  long  waves  for  long-distance 
communication. 

In  the  1923  experiments  with  the  Elettra, 
"however,  I  found  that  the  day  ranges  were 
reliable  and  of  a  quite  respectable  magnitude, 
that  the  night  ranges  were  much  greater 
than  any  one,  including  myself,  had  expected, 
and  that  intervening  land  and  large  portions 
of  continents,  mountainous  or  other  wise,  did 
not  prove  any  serious  obstacle  to  the  propaga- 
tion of  short  waves.  I  found  also,  which  was 
extremely  interesting  and  important,  that 


"day-range"  is  not  an  accurate  term  as  the 
strength  of  the  signals  received  varies  def- 
initely and  regularly  in  proportion  to  the 
mean  altitude  of  the  sun  over  the  space  be- 
tween the  two  communicating  stations.  That 
is  to  say,  the  "day-range"  depends  on  the 
particular  time  of  day. 

A    TEST    AT    SEA    WITH    SHORT    WAVES 

WE  STARTED  off  from  Falmouth,  and 
even  when  we  reached  Seville  and  were 
anchored  in  the  Gudalquivir  River,  a  very  un- 
favorable position  for  reception,  as  the  banks 
of  the  river  were  high  and  covered  with  trees 
and  buildings,  we  found  that  the  night  signals 
were  almost  as  strong  as  they  had  been  in  Fal- 
mouth Harbour,  12  miles  from  Poldhu,  al- 
though at  Seville,  the  whole  of  Spain,  consist- 
ting  of  over  300  miles  of  high  and  mountainous 
land  intervened  between  the  sending  and  re- 
ceiving stations. 

When  we  reached  the  Moroccan  coast  at 
Casablanca,  I  gave  instructions  that  the  re- 
flectors at  Poldhu  should  be  set  up  and  we 
then  proceeded  to  the  Island  of  Madeira,  and 
finally  to  St.  Vincent,  in  the  Cape  Verde 
Islands  where,  at  a  distance  of  2230  nautical 
miles,  we  continued  to  receive  the  night  signals 
with  such  strength  that  it  was  nearly  always 
possible  to  do  without  an  amplifier  or  to  dis- 
connect the  antenna  or  put  it  out  of  tune.  In 
fact  the  signals  were  so  extraordinarily  strong 
that  we  never  .experienced  the  slightest  trouble 
in  consequence  of  static.  The  power  then 
being  used  at  Poldhu  was  about  1 2  kilowatts, 
and  the  reflector  so  concentrated  the  energy 
in  the  direction  of  the  Cape  Verde  Islands 
that  the  strength  of  the  signals  was  such  that 
it  would  have  required  1 20  kilowatts  at  Poldhu 
without  the  use  of  reflectors. 

Because  I  was  obliged  to  return  to  England 
without  going  any  farther,  I  gave  instructions 
to  diminish  this  power  gradually  and  found 
that  with  only  i  kilowatt  (about  i|  h.  p.),  the 
signals  were  still  stronger  than  would  have 
been  required  to  carry  on  commercial  work 
at  night  at  that  distance.  It  is  interesting  to 
note  that  these  night  signals,  received  at 
St.  Vincent,  even  when  Poldhu  was  using  only 
i  kilowatt,  were  much  stronger  than  those 
which  could  be  received  from  the  high-power 
station  at  Carnarvon  or  the  British  Govern- 
ment station  at  Leafield  (using  200  to  300 
kilowatts)  or  from  any  of  the  other  European 
or  American  high-power  stations. 

In  view  of  these  rather  encouraging  results, 
further  tests  were  made  early  in  1924  between 
Poldhu,  using  some  17  kilowatts  of  power  and 


Will  "Beam"  Stations  Revolutionize  Radio? 


327 


©  Underwood  &  Underwood  and  Marconi's  Wireless  Telegraph  Company 
A    REVOLVING    BEAM   TRANSMITTER    AT    INCHKEITH,    ENGLAND 

One  of  the  experimental  transmitters  of  directed  radio  energy  used  by  Senator  Marconi  in  his  experiments 
between  his  yacht  Elettra  and  England  is  shown  in  the  photograph  below.  The  main  rigging  on  the  towers 
is  used  as  the  reflector,  while  the  transmitting  antenna  is  very  short  and  can  be  seen  just  above  the  two 
blocks  at  the  outside  of  the  circle  at  the  base  of  the  mast.  This  reflector  can  be  moved  so  as  to  "mirror" 
signals  in  any  desired  direction.  The  photograph  above  shows  a  model  of  the  beam  transmitter  used  by 
Senator  Marconi  when  he  read  a  paper  before  the  Institute  of  Radio  Engineers  at  New  York  several  years 
ago,  explaining  his  beam  experiments.  The  transmitting  antenna  is  the  short  vertical  wire  at  the  center 

of  the  wire  "mirror" 


328 


Radio  Broadcast 


TRANSRADIO 

The  imposing  towers  of  the  new  international  station  at  Monte  Grande,  Argentina.  The  power  house  and 
masts  are  the  center  of  the  largest  international  radio  telegraph  station  ever  erected  in  South  America.  The 
towers  are  about  690  feet  high.  The  smaller  towers  in  the  left  foreground  form  an  anchorage  for  the  down- 
leads from  the  antenna.  This  station  is  for  communication  on  long  wavelengths  and  high  power.  The 
beam  method  of  transmitting  has  not  been  applied  to  this  station 


waves  of  92  meters  and  a  special  receiver  in- 
stalled on  the  White  Star  Liner  Cedric.  The 
result  showed  that  during  the  daytime  signals 
could  be  received  up  to  1400  nautical  miles 
and  confirmation  was  obtained  that  their 
intensity  was  dependent  on  the  mean  altitude 
of  the  sun  at  all  times. 

Advantage  was  taken  of  these  tests  to  ask 
engineers  of  our  associated  companies  in 
Australia,  Canada,  and  the  United  States  to 
attempt  to  listen  to  these  transmissions  from 
Poldhu  and,  rather  to  my  surprise,  it  was  re- 
ported to  us  from  Australia,  that  they  could 
be  heard  distinctly  every  day  in  Sydney, 
from  5  to  9  p.  m.  (Greenwich  time)  and  again 
from  6.30  to  8.30  a.  m.,  and  this  with  what 
might  be  called  an  improvised  receiver.  If 
we  consider  the  position  and  the  altitude  of 
the  sun,  the  preference  of  short  waves  for 
traveling  over  regions  not  illuminated  by  the 
sun  was  made  manifest,  for  it  appeared  quite 
obvious,  that  during  the  morning  period,  the 


waves  traveled  over  12,000  miles  between 
England  and  Australia  in  a  westerly  direction 
across  the  Atlantic,  America,  and  the  Pacific, 
while  during  the  evening  period  they  must 
have  traveled  in  an  easterly  direction  across 
Europe  and  Asia,  over  the  shortest  distance, 
which  is  about  9380  nautical  miles. 

I  was,  however,  by  no  means  satisfied,  for 
one  of  the  essentials  of  a  good  telegraph  sys- 
tem, whether  it  be  with  or  without  wires,  is 
to  be  able  to  transmit  the  messages  as  soon 
as  they  are  handed  in  and,  therefore,  the 
limitation  of  the  period  of  working  to  practi- 
cally the  night  hours  constituted  an  un- 
doubted disadvantage.  That  this  was  so, 
admitted  of  no  doubt,  so  far  as  1  had  gone. 
For  example,  although  the  signals  sent  from 
Poldhu  were  received  with  great  strength 
at  New  York,  Rio,  and  Buenos.  Aires  when 
darkness  existed  over  the  whole  or  the  greater 
part  of  the  track  followed  by  the  waves,  no 
signals  at  all  were  received  when  the  same 


Will  "Beam"  Stations  Revolutionize  Radio? 


329 


track  or  the  greater  part  of  it  was  exposed  to 
the  light  of  the  sun.  Even  an  increase  of 
power  or  the  use  of  reflectors  augmented  the 
working  hours  very  slightly.  I  had  the  im- 
pression of  being  faced  with  conditions  ana- 
logous to  those  produced  by  a  fog  on  the  trans- 
mission of  light.  If  the  fog  be  thick  enough, 
no  matter  how  much  the  luminous  intensity 
is  increased,  the  light  waves  fail  to  penetrate 
it  for  any  considerable  distance. 

DISCOVERIES  ABOUT  SHORT  WAVES  IN  DAYLIGHT 

I  THEREFORE  resolved  to  make  further 
1  experiments  between  Poldhu  and  the  Elec- 
tra,  to  see  if  some  means  could  not  be  found 


to  overcome  the  limitation  of  working  hours 
imposed  by  daylight.  I  tried  the  effect  of 
still  further  decreasing  the  wavelength,  reduc- 
ing it  to  60,  47,  and,  finally,  to  32  meters  and 
I  found  that  the  opaqueness  of  space  in  the 
daytime  diminished  rapidly  as  the  wavelength 
decreased.  During  these  tests,  which  were 
conducted  in  August  and  September  of  last 
year,  the  92-meter  wave  could  not  be  heard  for 
many  hours  in  Madeira — a  distance  of  1 100 
miles  entirely  over  the  sea.  At  Beyruth,  in 
the  Mediterranean,  the  32-meter  waves  were 
regularly  received  all  day,  although  the  dis- 
tance was  2100  miles,  practically  all  over 
mountainous  land. 


THE    POWER    HOUSE    AT   TRANSRADIO 

The  most  interesting  thing  in  this  photograph  is  the  antenna  radiation  meter  which  registers  up  to  1200 

amperes.     Energy  from  large  radio  telegraph  stations  such  as  this  is  radiated  in  every  direction  and  much  of 

it  serves  no  useful  purpose.     Senator  Marconi  believes  that  beam  transmission  of  radio  signals  on  short 

waves  will  do  much  to  alter  the  whole  course  of  long  distance  radio  communication 


330 


Radio  Broadcast 


©  Marconi's  Wireless  Telegraph  Company 
A    CANADIAN    MARCONI    TRANSMITTING 

ANTENNA 

Note  the  high  towers  in  process  of  erection.  Present 
international  stations  use  wavelengths  of  from  six  to 
seven  miles,  while  the  beam  transmitting  stations 
will  use  wavelengths  of  about  120  feet.  POZ  at 
Nauen,  Germany  is  carrying  on  long  distance  com- 
munication on  high  power  on  a  wavelength  of  about 
40  meters,  while  the  stations  of  the  Radio  Corpora- 
\\on  of  America  are  being  equipped  to  use  short 
waves  as  an  auxiliary  to  their  regular  long  wave 
equipment.  Short  wave  transmitters  do  not  require 
nearly  the  elaborate  antenna  installation  that  the 
present  long  wave  stations  do.  Senator  Marconi 
contends  that  reflected  short  waves  are  much  less 
subject  to  unfortunate  fading  effects  than  are  the 
long  waves 

This  discovery  was  so  interesting  and  satis- 
factory that  I  thought  it  wise  to  confirm  it 
over  longer  distances  and,  in  October  and 
December  of  last  year,  with  only  12  kilowatts 
of  power,  it  was  immediately  found  possible 
to  transmit  signals  and  messages  from  Poldhu 
to  New  York,  Rio  de  Janeiro,  and  Buenos 
Aires  when  the  whole  of  the  track  separating 
these  places  from  Poldhu  was  exposed  to 
daylight.  Poldhu  was  also  able  to  communi- 
cate with  Sydney,  in  Australia,  for  a  period 
of  23!  hours  out  of  24. 

To  sum  up  my  impressions  of  all  these  ex- 
periments, 1  can  say  that  I  am  now  firmly 
convinced  that  the  day  is  fast  approaching 
when  beam  stations,  using  short  waves,  and 
employing  only  a  fraction  of  the  power  util- 
ized in  the  present  high-power  stations,  and 
with  much  lower  and  fewer  masts,  will  be  able 
to  carry  on  communication  at  practically  any 
time  between  any  two  points  of  the  earth's 
surface  and  at  much  higher  speeds  than  are 


now  possible.  It  should  be  mentioned  here 
that  very  high  speeds  appear  to  be  possible 
only  with  short  waves  and,  therefore,  even  if 
only  a  portion  of  the  24  hours  were  utilized, 
a  much  greater  number  of  words  could  be 
transmitted  than  would  be  possible  with  a 
slow-speed,  long-wave  service,  even  should  it 
be  found  capable  of  working  during  the  whole 
of  the  24  hours.  It  should  also  be  borne  in 
mind  that,  although  communication  at  great 
distances  has  been  obtained  without  the  use  of 
reflectors,  still  1  am  of  the  opinion  that  these 
will  be  found  to  be  essential  for  the  carrying 
on  of  commercial,  high-speed  services,  be- 
cause, apart  from  their  directive  effects,  they 
enormously  increase  the  effective  strength  of 
the  signals,  thus  minimizing  the  effects  of 
what  is  known  as  "fading."  Reflectors,  1 
find,  also  increase  the  margin  of  readability 
of  the  signals. 

WE  DON'T  KNOW  MUCH  ABOUT  THE  LAWS  OF 
SHORT  WAVES 

NATURALLY  a  good  deal  remains  to  be 
done  in  connection  with  a  further  and 
still  more  systematic  study  of  these  short 
waves  and  the  conditions  and  laws  which 
regulate  their  propagation  through  space. 
For  some  time,  the  practical  technical  side 
of  radio  has  been  far  in  advance  of  the  theory 
of  the  subject.  We  have  known  a  great  deal 
about  the  methods  of  producing  electric 
waves  and  about  the  various  methods  of 
receiving  such  waves,  but  our  knowledge 
of  the  conditions  that  govern  their  propaga- 
tion through  space  is  far  from  exact.  Other^ 
wise,  as  I  have  said,  we  might  have  known 
long  ago  that  it  was  possible  to  send  messages 
to  Australia  throughout  the  24  hours  on  a 
3O-meter  wave  with  only  10  or  12  h.  p.  of 
energy  in  the  antenna. 

However,  now  that  this  has  been  ascertained 
and  confirmed  by  numerous  experiments,  I 
have  no  doubt  that  the  development  of  short- 
wave beam  stations  will  be  more  rapid  than 
that  of  the  old  super-power  stations,  and  it  is 
my  firm  personal  opinion  that  these  latter 
will,  sooner  or  later,  be  found  to  be  uneconomi- 
cal and  comparatively  inefficient  so  far  as 
long-distance  commercial  communication  is 
concerned. 

One  final  point  remains  to  be  mentioned  in 
connection  with  these  newly  discovered  prop- 
erties of  short  electric  waves.  We  may  be 
on  the  threshold  of  a  day  when  broadcasting, 
that  application  of  radio  which  interests  the 
whole  of  the  civilized  world,  will  have  its 
range  enormously  increased.  Within  a  year 


Will  "Beam"  Stations  Revolutionize  Radio? 


331 


or  two,  the  voice  of  the  King  of 
England,  for  example,  may  be 
easily  and  clearly  heard  by  mil- 
lions of  his  subjects  in  places  as 
far  apart  as  India,  Australia, 
Canada,  and  South  Africa.  A 
service  in  Westminster  Abbey, 
with  its  sermon,  choral  and  organ 
music,  may  be  clearly  heard  in 
Capetown.  It  may  become  as 
easy  to  listen-in  for  the  Philhar- 
monic Orchestra  in  London,  as 
it  would  be  now  in  Philadelphia. 
Perhaps  the  voice  of  the  short 
wave  will  be  able  to  accomplish 
for  human  brotherhood  and  our 
common  civilization  what  has  not 
yet  been  done  by  the  better- 
known  long  wave,  although  radio 
is  already  one  of  the  most  power- 
ful agents  in  the  linking  of  man- 
kind into  one  great  whole. 


MASTS    AT   THE    CARNARVON, 
WALES    STATION 

Of  Marconi's  Wireless  Telegraph  Com- 
pany. These  tall  masts  help  to  con- 
duct the  high  power  long  wave  radio 
telegraph  signals  into  the  ether.  Com- 
pare the  size  of  the  power  pole  with 

that  of  the  radio  masts.   This  transmitter  spreads  its  energy  in  practically  every  direction  while  the  beam 
station,  illustrated  below,  directs  its  energy  in  a  beam 


©  Marconi's  Wireless  Telegraph  Company 

HOW   THE    POLDHU    BEAM    STATION    WILL    LOOK 

High  towers  support  the  reflecting  antenna  while  the  very  short  sending  antenna  is  in  the  exact  center  of  the 
whole  structure.  The  English  Marconi  Company  recently  announced  that  it  planned  to  erect  beam  trans- 
mitting stations  which  will  link  England  with  all  her  colonies.  The  English  Company  expects  to  establish 
surer  and  more  efficient  communication,  using  the  methods  developed  by  Senator  Marconi,  which  may, 
perhaps,  replace  the  extensive  installations  now  necessary  for  radio  telegraph  communication  over  very  long 

distances 


INSIDE    THE    CRATER   OF    MT.    VESUVIUS 

Professor  Rogotti  of  Milan,  with  two  assistants,  transported  a  radio  receiver  inside  the  crater  of  this  famous 
old  volcano  to  test  the  radio  receiving  qualities  of  this  somewhat  sparcely  populated  area.  The  tests  seem 
to  prove  that  there  was  no  radio  reception  near  the  eruptive  cone  of  the  volcano,  while  at  a  distance  of  300 
feet  from  the  cone,  reception  was  rather  poor.  The  experimenters,  as  the  photograph  shows,  wore  masks 
as  a  protection  against  the  stifling  gases  from  the  erupting  cone 


Past  President,  Institute  of  Radio  Engineers 


How  the  Propagandists  Work  in  Radio 


UNDOUBTEDLY  there  are  millions 
of  people  in  the  United  States  to-day 
who  have  a  real  interest  in  radio 
broadcasting.     Discounting     many 
times  (as  any  sensible  person  unconsciously 
does)  the  figures  given  out  by  over-enthusiastic 


broadcasting  managers,  we  still  must  place  the 
number  of  these  radio  folk  at  some  millions. 

The  purchasing  power  of  such  a  number  of 
people  is  tremendous,  and  is  measured,  of 
course,  in  the  hundreds  of  millions  of  dollars. 
It  is  natural  that  some  of  the  radio  manufac- 


How  Radio  Propagandists  Work 


333 


turers  have  reached  the  conclusion  that  the 
employment  of  professional  propagandists — 
"public  relations  counsel"  is  a  kinder  phrase — 
would  be  greatly  to  their  advantage.  These 
gentlemen,  honorable,  no  doubt,  draw  their 
pay  for  creating  in  the  minds  of  the  public  a 
favorable  impression  for  the  man  or  product 
they  write  about.  Stories  at  regular  intervals 
come  from  these  rather  undesirable  publicists 
in  which  their  employers  are  favorably 
featured.  These  stories  frequently  find  their 
way  into  the  daily  press  and  so  appear  as 
unbiased  news  to  the  casual  reader. 

By  sheer  repetition,  one  is  frequently  con- 
vinced that  the  repeated  statement  is  fact, 
even  though  no  proof  has  been  given.  This  is 
illustrated  by  the  current  belief  that  four  people 
out  of  five  -  have 
a  certain  malady, 
whereas  the  pre- 
valence of  this 
trouble  is  un- 
doubtedly greatly 
exaggerated  in  the 
well  known  adver- 
tisements. If  one 
reads  enough  sto- 
ries, each  begin- 
ning with,  Mr.  A. 
B.  C,  the  well- 
known  radio  engi- 
neer and  inventor, 
one  is  quite  likely 
to  think  that  the 
man  in  question 
is  a  radio  engineer 
and  inventor,  when 
that  may  not  be 
the  case  at  all. 
Then  if  the  story 
gives  Mr.  A.  B. 
C.'s  ideas  on  a 
certain  radio  sub- 
ject one  is  likely 
to  think  that  an 
authoritative,  un- 
biased opinion  is 
being  presented, 
when  as  a  matter 
of  fact,  the  gen- 
tleman in  question 
is  simply  succeed- 
ing in  a  bit  of  in- 
direct advertising. 

So  prolific  are 
the  writers  of  this 
type  that  the  ra- 
dio editors  of  our 


newspapers  never  lack  material  with  which 
to  fill  their  daily  columns.  One  of  our  friends 
recently  offered  to  write  for  a  certain  paper 
a  series  of  popular  articles  dealing  with  the 
relative  merits  of  different  receivers  on  the 
market,  showing  how  they  worked,  why  one 
was  more  selective  than  the  other,  another 
good  only  for  local  reception  and  still  another 
preferable  for  distant  stations,  etc.  He  was 
told  by  the  radio  editor,  however,  that  in- 
stead of  paying  for  radio  articles,  he  had  quite 
a  task  in  selecting  his  stories  from  material 
which  was  sent  in  voluntarily. 

To  the  best  of  our  knowledge,  there  are  very 
few  men  writing  stories  (even  radio  ones) 
to-day  for  the  mere  love  of  writing.  We 
should  like  to  suggest  that  when  next  you  read 


\ 


A    WIRELESS-EQUIPPED    LIFEBOAT 

Aboard  the  S.  S.  Orbita.  The  British  Board  of  Trade  has  ruled  that  to  every  ten 
lifeboats  aboard  large  passenger  ships,  there  shall  be  one  lifeboat  with  radio  trans- 
mitting and  receiving  equipment.  The  operator  has  a  small  cabin  'way  up  fo'ard. 
The  transmitter  has  a  range  of  about  100  miles.  A  small  two-wire  antenna  is  used. 
In  the  bow  of  the  boat  is  the  rectangular  loop  used  in  the  direction-finder  equipment 


334 


Radio  Broadcast 


8616- 


JLJL 


ARCHITECT  S    DRAWING    OF    A    PROPOSED 

BUFFALO  STATION 

Which  incorporates  some  new  ideas  in  station  design.  The  towers 
rise  60  feet  above  their  pyramidal  pedestals,  whose  design  was 
suggested  by  a  pyramid  built  in  Guatemala  many  thousands  of  years 
old.  The  broadcasting  station  has  been  designed  especially  for 
the  new  Liberty  National  Bank  building  at  Buffalo.  Alfred  C. 
Bossom,  of  New  York  is  the  architect 


one  of  those  interesting  interviews  with  "Mr. 
A.  B.  C.  the  well-known  radio  engineer  and 
inventor,"  you  ask  yourself  first  whether  he 
really  is  such  a  well-known  engineer  and  next 
why  he  said  that  a  crystal  was  better  for  a 
detector  than  a  tube,  etc.  Just  possibly  his 
revenues  will  be  increased  if  you  direct  your 
purchases  along  the  line  he  suggests. 

Super  Power  Is  Almost  Here 

A  MOST  as  soon  as  this  magazine  appears, 
the  new  broadcasting  venture  of  the 
Radio  Corporation  will   be   launched. 
At    Bound    Brook,    New    Jersey,    the    Cor- 
poration  has   erected   its  first  high-powered 


broadcasting  station,  and  we  un- 
derstand that,  opening  some  time 
in  June  with  a  moderate  power 
output,  this  station  will  gradu- 
ally increase  its  power  until  its 
full  output  of  forty  to  fifty  kilo- 
watts is  reached.  Familiar  wjz, 
which  was  first  berthed  in  New- 
ark, New  Jersey  and  was  later 
transferred  to  the  heart  of  New 
York  City,  is  now  to  migrate  to 
Bound  Brook,  the  while  with 
greatly  increased  output. 

It  is  our  belief  that  the  op- 
eration of  high-powered  stations 
such  as  this,  is  one  of  the  real 
solutions  for  static.  This  ever- 
present  disturbance  does  not 
greatly  bother  those  of  us  who 
are  within  perhaps  twenty-five 
miles  of  a  low-powered  station, 
but  for  those  more  than  a  hun- 
dred miles  away  from  one  of  our 
present  5OO-watt  stations,  the 
pulses  of  static  are  at  least  as 
strong  as  the  signal  during  parts 
of  the  year.  During  a  few  of 
the  summer  months,  the  static 
noises  are  so  loud  that  they 
make  a  program  from  the  dis- 
tant station  unsatisfactory. 

As  the  various  static  elimina- 
tors   come    forward    and    then 
quietly    retire    from    the    radio 
stage,  we  can  find  no  evidence 
of  defeat  or  even  fatigue  in  our 
atmospheric  disturbances.    The 
only  evident  remedy  to  circum- 
vent nature  in  her  pernicious  in- 
terference is  to  greatly  increase 
the  strength  of  the  radio  signals, 
to  drown  out  static.     That  will 
require  a  great  many  kilowatts 
of  power,  as  wjz  anticipates  using.     We  shall 
all  watch  with  great  interest  the  public's  reac- 
tion to  the  new  venture. 

Again  it  is  to  be  pointed  out  that  those  radio 
listeners  near  the  high-powered  station  will 
naturally  have  some  difficulty  in  tuning  it  out 
sufficiently  well  to  hear  distant  stations  of 
nearly  the  same  wavelength.  This  tuning 
difficulty  will  be  true  of  the  average  set  as  used 
to-day.  It  will  be  possible,  however,  to  build 
special  rejector  circuits  which  will  greatly 
cut  down  the  wjz  signals  even  for  those  in 
its  immediate  vicinity.  Undoubtedly  a  re- 
jector circuit  for  a  reasonable  price  will  be 
put  on  the  market. 


What  is  a  "Bootleg"  Tube? 


335 


m- 


1  he  Crime  of  a  Radio  Manufacturer 

JUST  as  we  had  thought  the  single-circuit 
regenerative  receiver  was  beginning  to  dis- 
appear from  the  market  we  learn  from  a 
most  reliable  source  that  an  order  for  about 
one  hundred  thousand  of  these  receivers  is 
being  put  through  the  shops  of  one  of  the  larg- 
est radio  manufacturers.    One  hundred  thou- 
sand more  potential  squealers  from  one  manu- 
facturer is  a  frightful  stop  to  radio  progress. 
This  is  no  step  forward  in  the  march  of  radio. 
It  looks  as  though  this  manufacturer  was  more 
interested  in  dividends  than  in  the  advance- 
ment of  the  art. 

What  Is  a  "Bootleg"  Tube? 

A  ONE  after  another  of  the  vacuum 
tube  patents  expire,  it  becomes 
creasingly  diffi- 
cult to  say  just  what  is 
a  bootleg  tube  and 
what  isn't.  While 
Fleming's  valve  patent 
and  De  Forest's  three- 
electrode  patent  were 
still  running  their 
seventeen-year  life,  it 
was  an  easy  matter  to 
distinguish  between 
genuine  and  counter- 
feit tubes.  But  now 
with  the  fundamental 
three-electrode  idea 
thrown  open  to  all, 
(the  patent  expired  in 
February)  one  has  to 
look  more  carefully  to 
see  if  a  tube  is  infring- 
ing those  design  patents 
and  others  which  still 
have  some  time  to  run. 
Before  a  manufac- 
turer invests  much 
money  in  the  business 
of  tube  making,  he 
would  do  well  to  con- 
sult some  patent  at- 
torney who  is  closely 
in  touch  with  this  par- 
ticular field.  There  are 
many  patents  on  the 
details  of  construction 
which  may  still  be  in- 


probably  not  possible  for  any  manufacturer  but 
the  Radio  Corporation  to  make  tubes  whose 
filaments  are  made  electronically  active  by 
the  addition  of  thorium.  There  may  be  other 
ways  of  making  even  better  tungsten.  It 
seems  quite  possible  that  European  tubes  are 
made  sensitive  by  some  other  process,  and  if 
so,  such  a  process  may  become  available  to 
independent  manufacturers  here.  Schemes 
used  for  attaining  this  high  vacuum  are  fully 
patented.  The  difficulties  of  properly  exhaust- 
ing tubes  frequently  are  so  great  as  to  cause  the 
downfall  of  the  inexperienced  manufacturer. 
There  is  one  very  interesting  phase  of  the  tube 
situation  which  has  still  to  be  settled.  Years 
ago,  the  American  Telephone  and  Telegraph 
Company  and  the  General  Electric  Company 
were  involved  in  a  very  seriously  contested 
suit  having  to  do  with  the  question  of  degree 


fringed.  The  sensitized 
tungsten  which  is  used 
in  the  modern  tube  is  a 
patented  product.  It  is 


LIEUTENANTS    McCORMICK    AND    FLOOD 
United  States  Army,  looking  over  their  receiving  apparatus  which  was  of  con- 
siderable aid  during  the  recent  national  balloon  elimination  race.     The  race 
was  won  by  Ward  T.  VanOrman.     Broadcasting  stations  near  the  air  course 
broadcast  special  weather  instructions  and  metereological  information  to  the 

racers 


336 


Radio  Broadcast 


of  vacuum  used  in  triodes.  Doctor  De  Forest, 
several  times,  apparently,  had  admitted  the 
advantage  of  some  gas  in  his  audions  so  that 
the  question  of  a  tube  having  very  high  va- 
cuum was  still  unsettled.  Doctors  Langmuir, 
of  the  General  Electric  Company,  and  Arnold, 
of  the  Western  Electric  Company,  both  had 
patent  applications  for  high  vacuum  tubes 
whose  vacuum  was  so  high  that  whatever  gas 
was  present  played  no  important  role  in  the 
functioning  of  the  tube,  as  it  generally  did  in 
the  De  Forest  audion.  Most  extensive  testi- 
mony was  taken  and  intricate  experiments 
were  performed  before  the  court  to  illustrate 
the  effect  of  small  amounts  of  various  gases  in 
vacuum  tubes. 

On  a  case  like  this,  a  judge  has  a  hard  time 
in  reaching  a  reasonable  decision,  and  in  this 
case  no  decision  at  all  has  yet  been  reached. 
The  court  has  first  to  determine  whether  a  high 
vacuum  of  this  sort  is  patentable,  and  then  if 
it  is,  to  whom  the  patent  should  issue.  And 
this  question  of  high  vacuum  is  not  as  easy  as 
one  might  think.  The  "gas"  tube,  for  ex- 


ample, might  be  claimed  as  high  vacuum  be- 
cause there  is  only  about  one  hundred  mil- 
lionth of  the  original  amount  of  gas  left  in  the 
tube.  But  the  high  vacuum  expert  comes 
along  and  tells  the  judge  that  although  only 
one  hundred  millionth  of  the  original  gas  is 
left  in  the  tube  there  are  still  ten  thousand 
million  gas  molecules  per  cubic  centimeter 
left  in  the  tube!  In  such  a  dilemma,  what  was 
the  judge  to  conclude? 

This  high  vacuum  patent,  if  it  should  ever 
be  granted,  would  most  seriously  affect  the  in- 
dependent manufacturer.  In  fact,  should  the 
court  decide  to  grant  a  patent  of  this  kind 
for  seventeen  more  years,  the  Radio  Corpora- 
tion or  the  American  Telephone  and  Telegraph 
Company  would  completely  control  the  tube 
situation.  We  regard  that  control  as  lament- 
able because  we  still  remember  the  $6  we 
used  to  give  for  Radio  Corporation  tubes  until 
the  De  Forest  patent  was  about  to  expire 
when  bootleg  tubes  appeared  more  plentifully 
with  the  resultant  cut  in  selfing  price  of  3 
to  i. 


AT   WELLESLEY    COLLEGE 

Wellesley,  Massachusetts,  some  of  the  advanced  students  in  the  Physics  Department  are  learning  something 
about  radio.  Left  to  right:  Miss  Lucy  Begeman  and  Miss  Louise  McDowell,  instructors  of  radio  in  the 
Physics  department  of  the  College;  Miss  Truko  Nakamura,  Tokyo,  Japan;  Miss  Jane  Whigham,  Pittsburgh; 
and  Miss  Ruth  Lovejoy,  Boston.  The  essentials  of  a  fifty-watt  continuous  wave  transmitter  are  being 

assembled 


Extravagant  Radio  Claims  Are  Not  Legal 


337 


K.    INUKAI 
Japanese  Minister  of  Communications,  listening  to  a  Tokio  radio  program  with  members  of  his  family 


Radio  Sets   Must   Meet  the  Claims 
Made  for  Them 

A  MOST  commendable  decision   was  re- 
cently handed  down  by  Judge  Woester 
in  the  Municipal  Court  of  Cincinnati. 
A  radio  supply  house  had  sold  a  five-tube  set 
with  the  guarantee  that  it  would  "get"  all 
the  stations  from  coast  to  coast.    The  user 
claimed  that  the  set  did  not  bring  in  every 
broadcaster  and  he  refused  to  pay  for  it  and 
was  subsequently  sued. 

The  Judge  ruled  that  if  the  set  was  guaran- 
teed to  do  certain  things  it  must  live  up  to 
its  guarantee.  If  the  claims  were  not  met, 
the  purchaser  was  not  obliged  to  pay  the 
price  specified.  It  was  argued  that  the  pur- 
chaser didn't  have  a  good  ground  or  antenna; 
the  plaintiff  evaded  the  obvious  confession, 
that  his  claims  for  the  operation  of  the  set 
were  extravagant.  It  would  be  a  good  thing 
to  have  a  few  more  decisions  of  this  nature  on 
record.  We  think  that  then  dealers  and  sales- 
men might  be  more  careful  about  their  en- 
thusiasms. It  may  be  that  the  ruling  of  the 
Municipal  judge  will  be  reversed  when  the 
case  is  carried  to  the  higher  courts,  but  we 
hope  not.  Absurd  and  extravagant  claims  of 
radio  salesmen  have  far  too  often  resulted  in 
the  disappointment  of  the  purchaser. 


The  Associated  Press  Recognizes 
Broadcasting 

DURING  the  recent  annual  meeting  of 
the  Associated  Press  in  New  York  this 
conservative  organization  yielded  to 
the  pressure  of  the  modernists  within  its  ranks 
and  decided  to  make  radio  broadcasting  one  of 
its  many  allies.  The  great  national  interest 
in  the  broadcasting  of  the  last  presidential 
election  was  the  lever  used  to  upset  the  con- 
servatives. By  a  vote  of  130  to  10,  the  As- 
sociation decided  to  permit  its  dispatches  to 
be  used  over  radio  channels  when  the  items 
can  be  regarded  as  of  "transcendent  import- 
ance." 

The  resolution  which  admits  radio  as  a 
friendly  arm  of  the  Association  was  as  follows: 

Whereas,  the  tremendous  and  continuing  growth 
of  radio  broadcasting  is  presenting  many  new  prob- 
lems not  contemplated  when  the  existing  by-laws 
and  rules  of  The  Associated  Press  were  adopted;  and 

Whereas,  the  great  public  interest  in  the  result  of 
Presidential  elections  and  other  events  of  nation- 
wide importance  has  repeatedly  raised  the  question 
of  the  advisability  and  wisdom  of  permitting  the 
limited  and  restricted  use  of  Associated  Press  matter 
in  the  broadcasting  of  such  special  and  outstanding 
events;  therefore  be  it 

Resolved,  That  the  Board  of  Directors  be  author- 
ized to  adopt  the  necessary  rules  and  regulations 


338 


Radio  Broadcast 


which  shall  permit  the  broadcast  of  such  news  of  the 
Association  as  it  shall  deem  of  transcendent  national 
and  international  importance  and  which  cannot  by 
its  very  nature  be  exclusive,  provide  adequate  safe- 
guards, and  require  that  proper  credit  in  each  and 
every  instance  be  accorded  the  Associated  Press. 

The  great  activity  of  the  Associated  Press, 
with  its  1 195  newspaper  members,  is  indicated 
by  the  treasurer's  report  which  showed  an 
income  during  the  past  year  of  more  than  seven 
million  dollars. 

At  about  the  time  that  the  "A.  P."  was  tak- 
ing this  action  on  radio,  the  American  News 
paper  Publishers'  Association  was  also  taking 
cognizance  of  this  newest  method  of  communi- 
cation, endeavoring  to  eliminate  propaganda 
and  direct  advertising  from  the  radio  channels 
conducted  by  the  newspapers.  The  resolution 
passed  by  the  publishers  was  as  follows: 


SCIENCE    INVADES   THE    CHURCH 

The  microphone  an  excellent  symbol  of  modern  progress  suspended  over 
the  famous  carved  pulpit  of  Notre  Dame  de  Paris.  The  pulpit  was 
designed  by  ViolIet-le-Duc.  The  microphone  is  not  for  broadcasting  but 
for  the  public  address  system  which  has  just  been  installed  in  this  famous 
old  cathedral 


Whereas,  direct  advertising  by  radio  is  likely  to 
destroy  the  entertainment  and  educational  value  of 
broadcasting  and  result  in  the  loss  of  the  good-will 
of  the  public,  therefore  be  it 

Resolved,  that  members  of  the  A.  N.  P.  A.  refuse 
to  publish  free  publicity  in  their  news  columns  con- 
cerning programs  consisting  of  direct  advertising; 
also  that  they  eliminate  from  program  announce- 
ments the  name  of  trade-marked  merchandise  or 
known  products  obviously  used  for  advertising,  and 
that  newspaper  broadcasters  eliminate  all  talks 
which  are  broadcast  for  direct  advertising  purpose. 

The  Victor  Company  Joins  the  Radio 
Ranks 

THE  phonograph  companies  have,  one 
by  one,  yielded  to  radio.  The  recent 
annual  report  of  Eldridge  P.  Johnson, 
president  of  the  Victor  Talking  Machine 
Company,  announces  the 
future  radio  activities  of 
this  company.  "Plans  care- 
fully and  deliberately  de- 
veloped toward  meeting  the 
conditions  confronting  the 
industry  are  rapidly  nearing 
maturity,  and  are  antici- 
pated to  maintain  your 
company  in  its  position  in 
the  van  of  the  entertain- 
ment field."  These  "condi- 
tions" of  course,  are  the 
effects  of  the  popularity  of 
radio  receivers  on  the  sales 
of  talking  machines.  We 
may  expect  the  Victor  or- 
ganization to  make  an  ex- 
cellent impression  on  the 
public  when  they  do  enter 
the  radio  field.  The  won- 
derful entertainment  their 
artists  gave  us  last  winter 
through  WEAF,  and  other 
stations,  would  permit 
nothing  else. 

There  is  a  fine  opportu- 
nity for  the  marketing  of  an 
artistic  high  quality  loud 
speaker.  Rumor  has  it  that 
the  Victor  Company  has 
secured  the  patent  rights  to 
a  loud  speaker  developed 
and  patented  in  France. 
Some  European  engineers 
have  spoken  of  this  talker 
as  better  than  anything 
we  have  in  America,  and 
if  this  is  true,  we  certainly 


The  World  Conference  of  Amateurs 


339 


would    like   to   see   it    put    on    the   market 
here. 

We  sincerely  hope  that  the  new  policy  of  the 
company  will  not  interfere  with  continued 
concerts  by  their  artists,  as  it  is  impossible  at 
this  time  to  imagine  a  better  combination 
than  the  artistic  talent  of  the  Victor  perform- 
ers and  the  technical  excellence  of  the  broad- 
casting apparatus  of  the  American  Telephone 
and  Telegraph  Company  engineers. 

There  Are  So  Few  American  Radio 
Tubes 

IN  A  recent  issue  of  the  Wireless  World 
(London),  editorial  dissatisfaction  is  ex- 
pressed with  the  number  of  tubes  now  on 
the  English  market.  So  many  experimental 
and  war  type  tubes  as  well  as  more  standard 
recent  ones  are  available  to  the  radio  experi- 
menter, that  many  times  he  buys  tubes  en- 
tirely unsuitable  for  his  work.  Improvement 
would  be  brought  about,  according  to  Hugh  S. 
Pocock,  the  editor,  if  most  of  the  types  were 
withdrawn  from  the  market,  leaving  only  two 
or  three  standard  types. 

If  we  in  America  have  any  difficulty  of  this 
sort,  it  is  rather  on  the  opposite  side.  We 
really  have  only  two  types  of  tubes  for  re- 
ceivers on  the  market;  the  quarter-ampere 
5-volt  filament,  and  the  sixteenth-ampere 
3-volt  filament.  The  latter  is  hardly  to  be 
regarded  as  a  success  because  of  its  fragility 
and  short  life.  In  Holland,  a  Dutch  engineer 
recently  told  us,  the  Phillips  Lamp  Works  is 
putting  on  the  market  a  tube  which  he  regards 
as  the  equal,  if  not  the  superior,  to  any  of  our 
tubes.  The  Dutch  tube  uses  in  its  filament 
circuit  a  sixteenth  of  an  ampere  at  one  volt, 
that  is,  just  one  third  the  power  which  ours 
uses.  We  would  welcome  this  Dutch  tube  to 
our  present  small  assortment.  The  tube 
which  uses  alternating  current  in  its  filament 
and  operates  from  a  light  socket,  is  surely  on 
its  way.  The  so-called  McCullough  A  C  tube 
built  on  this  principle,  has  recently  been  an- 
nounced and  just  as  sure  as  the  public  takes 
to  this  tube,  the  Radio  Corporation  will  put 
out  one  to  equal  or  possibly  surpass  it. 

We  sincerely  hope  that  the  McCullough 
tube  has  been  so  carefully  built  that  it  will  not 
fail,  and  thus  give  this  desirable  type  of  tube 
a  bad  reputation  before  it  has  been  even  well 
tried  out.  In  a  new  development  of  this  kind 
it  is  very  easy  to  make  technical  and  manufac- 
turing errors,  and  so  give  a  product  a  bad  name 
when  more  care  and  study  would  have  made 
it  a  complete  success.  We  certainly  extend 


©Harris  &  Ewing 
W.    E.    DOWNEY 

Technical  radio  expert  of  the  Bureau  of  Navigation, 
Department  of  Commerce.  On  Mr.  Downey's 
shoulders  fall  much  of  the  technical  advisory  work 
which  is  a  constant  necessity  in  the  administrative 
branch  of  government  radio  control 


to  this  first  alternating  current  tube  our  very 
best  wishes. 


The  World  Conference  of  Amateurs 

THE  first  world  conference  of  amateurs 
has  just  come  to  a  close.     And  thinking 
of  this  world  union,  the  amateurs  may 
well  feel  that  progress  is  being  made.     Ten 
years  ago,  the  American  Radio  Relay  League 
was  just  starting;  now  its  members  are  num- 
bered in  many  thousands  and  they  assume  a 
commanding  role  in  any  international  question 
having  to  do  with  radio  amateurs. 

The  conference  recommended  wavelength 
assignments  for  the  amateur  channels  as  fol- 
lows: United  States,  85  to  70  meters  and  41 .50 
to  37.50;  Canada  and  Newfoundland,  120  to 
1 15  and  43  to  41.50;  Europe,  1 15  to  95,  75  to 
70,  and  57  to  43;  other  countries,  95  to  85  and 
37.50  to  35.  These  short  wave  channels,  of 
course,  must  be  approved  by  the  respective 
governments  concerned  before  becoming  the 
official  domain  of  the  amateurs. 

It  is  interesting  to  note  how  important  the 
short  wave  channels  are  becoming.  American 
British,  and  German  commercial  companies 
are  all  carrying  on  intensive  experimentation 
in  the  development  of  transmitters  and  re- 
ceivers for  these  nearly  ten  million-cycle 
currents.  The  German  station  POZ,  for  exam- 
ple, is  working  to  Argentine  with  a  4i-meter 
channel,  and  it  won't  be  long  before  the  five- 


340 


Radio  Broadcast 


or  ten-turn  coil,  a  couple  of  inches  in  diameter, 
becomes  recognized  as  a  regular  tuning  coil. 

We  cannot  urge  too  strongly  that  the  ama- 
teurs get  busy  with  their  short  wave  receivers. 
As  this  issue  goes  to  press,  Donald  MacMillan 
is  leaving  the  country  for  his  next  polar  trip. 
In  view  of  the  fine  showing  made  by  short 
wave  communication  on  his  last  trip,  Mr.  Mac- 
Millan has  decided  that  his  outfit  this  time 
will  be  short  wave  equipment  altogether,  and 
he  has  indeed  chosen  a  short  wave  expert  to 
accompany  him,  in  John  L.  Reinartz  of  South 
Manchester,  Connecticut. 

Plans  for  the  expedition  include  the  trans- 
mission of  a  daily  resume  of  their  activities  and 
findings,  sent  out  at  noon  on  a  2O-meter  wave. 
Recent  successful  daylight  transmission  with 
these  extremely  high  frequency  currents  lead 
to  the  belief  that  the  signals  will  be  picked  up 
at  Washington  where  the  government  services 
will  be  listening,  and  thus  permit  a  rebroad- 
cast  on  ordinary  wavelengths. 


Work  for  Hoover's  Third  Radio 
Conference 


s 


ECRETARY    HOOVER    is    again    con- 
templating calling  in  the  best  radio  minds 
in  the  country  for  a  third  annual  confer- 
ence. 

The  possibility  of  such  a  call  was  considered 
by  the  conference  of  the  Radio  Committee  of 
the  League  of  Nations  which  has  been  in  ses- 
sion in  Geneva.  It  was  anticipated  in  Geneva 
that  the  Washington  call  would  not  come  until 
the  spring  of  1926  at  the  earliest.  This  com- 
mittee decided  to  call  to  the  attention  of  the 
Washington  conference  the  necessity  of  elab- 
orating the  international  regulation  of  radio 
communication  concerning  security  at  sea 
and  the  protection  of  navigation.  It  has  not 
been  apparent  that  commercial  radio  has  se- 
riously interfered  with  the  channels  reserved 
for  navigation  and  distress  messages,  but  it 
may  be  that  the  problem  in  European  waters 
is  more  serious.  If  this  is  so,  the  Washington 
Conference  would  do  well  to  consider  it. 


The  Month  in  Radio 


N  GERMANY  it  is  a  crime  to  listen-in  on 
broadcast  programs  unless  the  government 
fee  has  been  paid,  and  according  to  a  press 
dispatch,  there  are  more  than  550,000  obedient 
citizens  who  pay  the  Post  Office  Department 


about  fifty  cents  a  month  for  their  radio  en- 
tertainment. At  present  the  government  re- 
ceives more  than  three  million  dollars  annually 
from  the  radio  enthusiasts. 

MORE  than  three  years  ago,  in  fact  in  our 
very  first  editorial,  we  suggested  that  phil- 
anthropists should  leave  money  for  equipping 
and  endowing  high  class  broadcasting  stations. 
This  movement  had  its  inception  at  the  Uni- 
versity of  Notre  Dame  and  the  University  of 
Illinois,  both  of  which  are  to  be  given  modern 
stations  as  memorials  to  Roger  C.  Sullivan, 
a  well-known  Democratic  leader  of  Illinois 
who  died  five  years  ago.  The  stations  are 
gifts  from  his  son,  B.  H.  Sullivan.  This  is  a 
fine  beginning  of  a  worth-while  enterprise. 

THE  Radio  Corporation's  quarterly  report 
shows  its  gross  earnings  for  the  quar- 
ter ending  March  315!  to  be  more  than 
$15,000,000.  This  indicates  a  total  for  the 
present  year  at  the  same  rate  of  $61,000,000 
or  about  $6,000,000  in  excess  of  last  year's 
business. 

I  AST  month  saw  the  exportation  of  some  of 
kf  America's  good  radio  capital.  Dr.  Ma- 
rius  Latour,  a  French  scientist,  owns  many 
patents  on  details  of  radio  receivers,  some 
of  which  have  been  used  promiscuously  by 
American  radio  concerns,  who  were  appar- 
ently all  oblivious  of  his  patents.  In  a  suit 
which  he  brought  against  the  Hazeltine  Cor- 
poration, Latour  was  successful  in  sustaining 
his  claims,  so  this  radio  company,  and  several 
others  decided  to  capitulate  and  buy  him  out. 
One  of  his  patents  covers  the  use  of  iron  cores 
in  radio  transformers.  No  sensible  engineer 
ever  thought  of  using  anything  but  iron  cores 
insofar  as  we  know,  yet  Latour  was  able  to  get 
a  patent  on  the  idea.  Most  of  his  other  patents 
are  of  similar  import,  but,  lacking  as  they  may 
be  in  scientific  merit,  they  were  sufficiently 
important  to  cause  our  American  companies 
to  part  with  several  hundred  thousand  dollars. 

A  CCORDING  to  newspaper  stories,  the 
•*»•  General  Electric  Company  recently  dem- 
onstrated the  operation  of  a  loud  speaker 
from  a  crystal  set.  From  the  layman-writer's 
description  it  appears  that  the  instrument  is  a 
cross  between  the  large  paper  cone  speaker 
and  a  French  type  using  a  small,  flexibly  sup- 
ported, rigid  cone.  Needless  to  say  a  crystal 
set  must  be  very  close  to  a  transmitting  station 
if  a  loud  speaker  is  to  be  operated  by  it,  be- 
cause at  any  appreciable  distance,  the  receiv- 


What  People  Say  About  Radio 


ing  antenna  cannot  pick  up  enough  power  to 
give  audible  sounds  in  any  loud  speaker. 
With  tube  sets,  the  local  B  battery  gives  the 
energy  to  operate  the  loud  speaker.  The  re- 
ceived signal  merely  serves  to  control  this 
energy. 

SOME  interesting  figures  on  the  income  of 
broadcasting  stations  were  given  out  re- 
cently by  the  Radio  Artists'  Association.  Ac- 
cording to  their  report,  some  stations  are  ac- 
tually making  money.  WHN  of  New  York, 
for  example,  has  a  reputed  income  of  $300,000 
a  year  and  expenditures  of  not  more  than 
$50,000  a  year.  WFBH  in  the  same  city,  has 
contracts  which  bring  in  $90,000  a  year  with 
an  annual  expenditure  of  $35,000,  it  is  reported. 
The  stations  in  present  Telephone  Com- 
pany network  charge  as  follows: 

WEAF  $500  per  hour,  $195.35  per  quarter  hour; 
WEEI,  WJAR,  and  wcco  $250  each  per  hour;  woo, 
WFI,  WCAE,  WGR,  wsAi,  and  wwj  $200  each  per 
hour;  WCAP,  WEAR,  and  woe  $150  each  per  hour. 
For  the  "facilities"  of  all  these  stations,  the  gross 
charge  is  $2600  per  hour.  To  give  a  ten  minute 
talk  over  this  wire-radio  network  would  cost  $1300, 
or  about  a  dollar  per  word. 

The  manager  of  WHN,  when  shown  the  re- 
port characterized  it  as  a  gross  misstatement, 
and  similarly,  WFBH'S  manager  claimed  that 
his  income  was  only  just  sufficient  to  meet 
expenses. 


Interesting  Things  Interestingly 
Said 


DAVID  SARNOFF  (New  York;  vice-president 
and  general  manager  of  the  Radio  Corporation 
of  America):  "At  present  it  cannot  be  said  that  ad- 
vertising over  the  radio  is  parallel  in  effectiveness 
with  advertising  in  periodicals  and  newspapers. 
The  standards  of  periodical  and  newspaper  adver- 
tising should  also  apply  to  the  standards  of  the  air 
and  no  advertisement  should  be  broadcast  without 
the  plain  advertising  label." 

HARRY  M.  WARNER  (New  York;  president, 
Warner  Brothers,  a  motion  picture  company): 
"My  attention  has  long  been  directed  to  a  general 
tendency  to  fight  radio  within  the  amusement  field. 
The  identical  arguments  used  only  a  few  years  ago 
in  an  effort  to  minimize  the  popularity  of  motion 
pictures  are  being  dragged  out  and  pointed  at  an 
entertainment  which  now,  roughly,  has  20,000,000 
supporters  in  the  United  States.  .  .  .  The  cry 
of  'the  pictures  will  ruin  the  theatre,'  is  within  easy 
memory.  But  they  didn't,  although  there  is  no 
doubt  that  the  pictures  inflicted  considerable  dam- 


POWEL   CROSLEY,    JR. 

-Cincinnati;  Radio  Manufacturer- 


"/  am  looking  forward  to  the  day  when  first  class 
broadcasting  stations  will  use  from  50  to  too 
kilowatts.  I  believe  that  this  is  as  essential  as 
it  was  for  the  commercial  companies  figuratively 
to  boost  the  power  of  the  original  f  kilowatt 
used  by  Marconi  when  he  sent  the  famous  letter 
"s"  across  the  Atlantic  Ocean  to  50  kilowatt; 
and  later,  to  200  kilowatts,  for  satisfactory  trans- 
oceanic communication.  The  high  power  broad- 
casting stations  of  the  future  must  be  located 
away  from  large  centers  of  population  so  as  not 
to  cause  undue  local  interference. 

"  The  quality  of  service  rendered  by  the  higher 
powered  stations  should  be  recognised  by  the 
Department  of  Commerce  in  assignment  of  wave- 
lengths, and  this  recognition  should  necessarily 
have  coupled  with  it,  certain  requirements  as  to 
quality  of  service.  .  .  .  There  must  be  more 
recognition  of  quality  of  service  and  priority 
than  there  has  been  heretofore.  First  class  sta- 
tions should  not  be  asked  to  divide  time  with  third 
class  ones.  .  .  .  Though  still  untried,  I  be- 
lieve more  strongly  than  ever  in  super-power" 


age  to  the  cheaper  theatrical  attractions.  .  .  . 
To  this  has  been  added  the  alarm,  'the  radio  will 
ruin  the  theatre  and  pictures.'  It  will  not,  provided 
it  is  used  intelligently.  .  .  .  The  radio  is  here 
to  stay  just  as  the  theatres  and  pictures  are  here  to 
stay.  They  all  have  their  followers,  and  just  as  the 
picture  audience  is  a  theatre  audience,  so  is  the  radio 
audience  largely  a  picture  audience.  ...  To 
my  mind,  any  effort  to  fight  an  entertainment  that 


342 


Radio  Broadcast 


©  Underwood  &  Underwood 
CAPTAIN    A.    W.    STEVENS 


New  York;  Aerial  Photographer  with 

the  Rice  Expedition  in  Brazil 

"Although  we  worked  with  portable  radio  appar- 
atus in  the  heart  of  the  world's  greatest  forest,  we 
established  a  record  in  short-wave  communication 
with  England.  Long-wave  communication  was 
carried  on  between  the  expedition  and  Manaos 
and  short-wave  communication  to  many  parts  of 
the  world,  including  New  York,  San  Francisco, 
London,  Rio  de  Janeiro,  and  New  Zealand.  The 
signals  were  reported  as  very  strong,  both  in  New 
York  and  London.  Part  of  the  apparatus  was 
designed  and  assembled  on  the  fob  by  the  opera- 
tors, John  W.  Swanson  and  Thomas  M .  Mc- 
Caleb. 

"  The  antenna  system  was  often  erected  by  saw- 
ing down  a  number  of  large  trees  in  the  forest 
and  stringing  the  wires  between  other  tall  trees 
on  the  edges  of  the  roughly  cleared  space.  A  wire 
was  usually  strung  from  the  folding  table  that 
held  the  instruments  to  a  ground  loop." 


has  the  backing  of  20,000,000  people  is  sadly  mis- 
directed and  will  react  harmfully  on  the  entire  in- 
dustry. If  radio  has  had  an  effect  on  motion  pic- 
tures— as  those  exhibitors  who  should  know  what 
they  are  talking  about  claim — my  idea  is  not  to 
wage  a  useless  fight  against  it,  but  to  use  radio  to 
the  best  possible  advantage." 

N.  P.    VINCER-MINTER    (London,    England; 
in  an  article  in  the  Wireless  World}:    "From  a 
point  of  view  of  artistic  appearance,  American-made 
radio  sets  show  a  marked  superiority  over  those 


made  in  England.  In  this  respect  we  are  not  re- 
ferring to  the  hundred-guinea  type  of  cabinet  set, 
whose  artistry  cannot,  of  course,  be  denied,  but  to 
the  ordinary  type  of  good  quality  set  which  sells  at 
prices  ranging  from  £20  to  £40  or  thereabouts. 
.  .  .  One  has  only  to  glance  through  the  adver- 
tisement pages  of  any  of  the  American  radio  journals 
to  note  the  large  number  of  really  efficient  and 
attractive-looking  sets  at  not  unreasonable  prices, 
to  be  acutely  aware  of  how  much  greater  is  the  range 
of  choice  accorded  to  American  purchasers.  Al- 
though, of  course,  some  of  the  claims  made  in  these 
advertisements  are  typically  American,  it  must  be 
admitted  that  on  the  whole  the  sets  are  highly 
efficient." 

BRUCE  J.  A.  M.  ELDER  (Sydney,  Australia; 
Commissioner  for  Australia  in  the  United 
States):  "Production  costs  have  increased  enor- 
mously, until  now  wages  in  the  tailoring  trade  are 
300  per  cent,  above  the  pre-war  level.  Factory  ex- 
penses have  also  doubled.  .  .  .  But  there  are 
other  factors  equally  important.  In  the  United 
States,  there  are  more  than  17,000,000  motor  cars, 
which  exceeds  the  number  of  telephones.  These 
cars  are  bought  on  time  payment  as  are  also  the 
majority  of  wireless  sets  in  the  country.  I  am  of 
the  opinion  that  the  purchasers  of  cars  and  radio 
sets  meet  obligations  by  saving  on  clothing  for 
themselves,  their  wives  and  families.  Radio  causes 
people  to  stay  in  their  homes,  thus  lessening  the 
demand  for  clothing.  American  bankers  go  further 
and  say  that  people  do  not  wear  good  clothes  in 
motor  cars  and  consequently  purchase  new  clothes 
less  frequently." 

COWARD  H.  JEWETT  (Detroit,  Michigan; 
*->  president  of  the  Jewett  Radio  and  Phonograph 
Company):  "Time  was  when  open  cars  were  all  the 
rage  and  most  autoists  stored  their  cars  during  the 
winter.  .  .  .  Radio  has  developed  similarly. 
From  a  purely  winter  instrument  it  has  been 
brought  to  the  point  in  development — thanks  to  the 
fine  engineering  talent  in  the  radio  industry — where 
it  affords  the  radio  enthusiast  a  full  year's  pleasure 
and  utility.  .  .  .  Mighty  few  vacationists  will 
be  without  their  radio  this  summer.  Modern  port- 
able sets  are  as  easily  taken  along  on  a  summer 
journey  as  the  ordinary  suitcase.  The  summer 
camper  may  pick  the  wildest,  loneliest  spot  for  his 
vacation  and  yet  be  in  touch  with  the  world  through 
his  radio." 

S.  H.  MAPES  (Chicago,  Illinois;  vice-president 
and  general  sales  manager,  Joseph  W.  Jones 
Radio  Manufacturing  Company) :  "  Is  the  possibility 
of  extensive  improvements  in  radio  sets  affecting 
sales?  The  answer  is  an  emphatic  no.  For  the 
improvements  that  will  come  will  be  those  of  'evo- 
lution rather  than  revolution.'  .  .  .  Radical 
changes  will  not  be  made,  but  refinements  will  con- 
tinue to  appear  as  they  have  in  the  automobile  and 
other  industries.  The  more  noticeable  changes  will 
be  made  in  transmitting  and  not  in  receiving  sets." 


'CHe  Listeners'  Point 


JENNIE   IRENE   MIX,  who  has  written 
"The    Listeners'    Point    of   View"    since 
April,   1924,  died  suddenly  after  a  short 
illness  at  her  home  in  Toledo,  Ohio  on  April 
26th. 

When  "The  Listeners'  Point  of  View" 
started  it  was  the  first  attempt  to  present 
sound  radio  program  criticism  in  any  maga- 
zine. Miss  Mix  was  probably  better  qualified 
than  any  other  writer  who  could  have  been 
selected  for  the  task.  For  many  years  she  had 
been  writing  music,  thinking  music,  and  almost 
living  it.  She  was  well  known  in  the  musical 
life  of  Pittsburgh.  From  1904  to  1918  she 
was  music  critic  of  the  Pittsburgh  Post. 
During  many  music  seasons  she  covered  impor- 
tant musical  events  in  Boston,  Philadelphia, 
Cincinnati,  Cleveland,  Ann  Arbor,  and 
Chicago. 

Miss  Mix  spent  some  time  abroad,  where  she 
furnished  music  correspondence  to  a  number  of 
prominent  American  newspapers  from  such 
centers  as  Paris.jBerlin, 

Munich,  Dresden,  and  •••^•^^•^^•^^ 
Bayreuth.  In  1920, 
Henry  Holt  and  Com- 
pany published  a  novel 
from  her  pen,  At  Fame's 
Gateway,  which  deals 
with  the  life  of  a  young 
music  student  in  New 
York.  Comment  on 
this  book  was  very 
favorable  and  very 
widespread.  Several 
years  before,  Miss  Mix 
had  turned  her  talents 
in  another  way  and 
Mighty  Animals,  pub- 
lished by  the  American 
Book  Company,  pre- 
sented in  an  entirely 
new  fashion  the  story 
of  prehistoric  animals. 
The  preface  to  this 


Jennie  HJrene 

26,  1925 


volume  was  written  by  Dr.  Frederick  A. 
Lucas,  director  of  the  American  Museum 
of  Natural  History.  The  book  is  used  as  a 
supplementary  reader  in  public  and  private 
schools. 

A  woman  of  striking  personality,  Miss  Mix 
had  a  peculiar  talent  for  transferring  her 
personal  charm  to  her  work,  which  was  one 
reason  for  her  great  popularity  with  the  readers 
of  RADIO  BROADCAST.  It  is  interesting  to 
note,  also  that,  in  the  newspapers,  her  writings 
were  almost  as  widely  quoted  as  those  of 
Professor  Morecroft  in  "the  March  of  Radio." 
Miss  Mix  felt  that,  since  the  greater  part 
of  radio  broadcasting  was  music,  helpful  cri- 
ticism and  comment  about  radio  music  would 
be  welcomed  by  interested  radio  readers 
everywhere.  She  had  a  wide  acquaintance 
among  musicians  throughout  the  country,  and 
she  spent  many  a  musical  season  in  New 
York  covering  the  events  for  newspapers  in 
various  parts  of  the  country.  In  "The  Lis- 
teners' Point  of  View," 

i^"^^^^™«"^^"  she  was  singularly  suc- 
cessful in  presenting 
comments  about  radio 
broadcasting  programs 
which  could  be  found 
nowhere  else.  Her  re- 
marks on  programs  and 
personalities,  her  news 
and  comment  on  the 
new  world  of  radio, 
made  for  her  and  for 
RADIO  BROADCAST 
many  firm  friends. 

The  Listener's  Point 
of  View  will  be  con- 
tinued in  the  magazine 
as  before,  and  the  new 
conductor  of  thedepart- 
ment  will  take  up  Miss 
Mix's  duties  in  the 
August  number  of  RA- 
DIO BROADCAST. 


in  Interesting  Answer  to  the  Question,  "How  Can  I  Leanr 
lore  About  Radio?" — What  the  Colleges  Offer— The  Place 
Value  of  the  Commercial  Radio  School — Some  Help  and 
Suggestion  for  the  Earnest  Student  Who  Works  at  Home 

BY  KEITH  HENNEY 


OF  ALL  the  many  questions  that 
come  to  RADIO  BROADCAST  there 
is  one  that  causes  the  Editors 
more  than  usual  thought.  The 
query  of  "How  can  1  become  a  radio  en- 
gineer?" seems  to  worry  a  great  variety  of 
people.  High  school  students  contemplating 
their  college  courses,  mature  engineers,  me- 
chanical, electrical,  civil,  chemical  or  mining, 
and  professional  electricians;  all  want  to 
know  how  to  fit  themselves  to  enter  the  radio 
engineering  field.  And  aside  from  those  who 
actively  plan  a  dash  into  the  land  of  radio  there 
are  many  who  would  like  to  know  more  about 
this  fascinating  subject  than  most  of  the 
present  day  radio  books  tell  them.  They  are 
doctors,  lawyers,  ministers,  and  the  great 
army  of  tradespeople  who  are  interested  in 
radio,  and  who  are  interested,  incidentally, 
in  the  whole  vast  field  of  science,  for  its  own 
sake. 

And  while  it  is  not  the  purpose  of  the  writer 
to  argue  the  point  here  of  whether  there  is  or 
is  not  a  future  for  a  man  fitting  himself  to  be  a 
radio  engineer,  it  is  well  to  call  attention  to  two 
conflicting  statements  appearing  in  the  press 
within  the  last  year. 

According  to  Colonel   Percy   E.   Barbour, 


Editor  of  Mining  and  Metallurgy,  the  engineer- 
ing field  is  already  overcrowded,  and  he  takes 
exception  to  the  press  report  that  colleges 
and  universities  are  falling  behind  in  their  out- 
put of  capable  engineers. 

The  other  statement  may  be  found  in  some 
radio  school  advertisements  wherein  the  mar- 
vellous salary  of  $10,000  a  year  appears  in 
large  type,  and  one  gets  the  idea  that  such  a 
munificent  sum  may  be  commanded  within 
a  few  months  after  completing  some  particular 
course  which  the  school  offers. 

It  is  very  difficult  to  judge  the  truth  of  the 
first  statement,  but  it  is  certainly  true  that 
any  capable  wide-awake  engineer  may  find  a 
position  if  he  has  the  qualifications  mentioned 
later  in  this  article.  The.  engineering  pro- 
fession, like  all  other  walks  of  life,  needs  big 
men,  and  this  means  those  who  have  fitted 
themselves  with  all  of  the  modern  educational 
equipment. 

As  for  the  $10,000  year  salary,  it  is  again 
largely  a  question  of  the  man.  No  student 
who  follows  any  radio  course,  whether  in 
college  or  by  correspondence  can  hope  to  at- 
tain this  sum  unless  he  has  the  most  extensive 
experience  behind  him.  And  that  entails 
work,  several  years  of  it  at  least. 


What  Are  the  Royal  Roads  to  Radio? 


345 


WHAT    IS    A    RADIO    ENGINEER? 

IN  THE  first  place,  as  Professor  Morecroft 
pointed  out  in  RADIO  BROADCAST  in  July, 
1924: 

"To  the  best  of  our  knowledge,  none  of  the 
good  technical  schools  of  this  country  confer 
the  degree  of  'radio  engineer.'  " 

The  nearest  approach  is  that  given  by  Har- 
vard University  and  other  large  institutions 
which  have  a  number  of  courses  grouped  under 
the  title  of  "communication  engineering"  but 
here,  as  in  other  branches  of  electrical  en- 
gineering, the  first  degree  given  after  four 
years  of  study  is  "bachelor  of  science  in 
engineering." 

The  degree  of  electrical  engineering  "  E.  E." 
is  usually  won  only  after  the  bachelor's  degree 
has  been  taken  and  after  at  least  two  years  of 
commercial  experience. 

A  real  radio  engineer- will  probably  be  proud 
of  the  fact  that  he  has  had  a  technical  training, 
but  he  will  hesitate  to  admit  that  he  is  a  radio 
engineer,  so  thickly  populated  has  the  radio 
profession  become  with  self-labelled  authori- 
ties without  training 
or  experience  beyond 
that  of  any  boy  who 
has  assembled  radio 


apparatus. 

The  field  of  radio 
engineering  is  simply 
a  branch  of  electrical 
engineering.  A  power 
engineer,  a  telephone, 
or  a  telegraph  en- 
gineer must  first  of  all 
be  an  electrical  en- 
gineer, and  a  good 
one  too.  In  nearly 
every  case,  one  must 
have  a  general  en- 
gineering training  be- 
fore he  can  specialize 
in  any  of  its  many 
branches. 

THE    STRAIGHT  AND 
NARROW    PATH 

THE  young  man 
who  is  anxious  to 
fit  himself  best  for  the 
radio  world,  should 
learn  all  he  can  from 
elementary  books 
which  he  can  secure 
in  the  public  library, 
and  from  actual  ex- 


There  Isn't  Any  Formula— 


FOR  success  in  any  line  of  activity. 
Not  very  long  ago,  someone  set  down 
three  rules  for  mental  progress.  They  are: 
"i.  Sit  down  in  front  of  a  blank  wall. 
2.  Ask  yourself  difficult  questions.  3.  An- 
swer them."  And  so  with  radio.  The  best 
way  to  learn  more  about  radio  is  to  learn  it. 
However,  there  are  so  many  who  really  want 
helpful  and  definite  suggestions  about  how 
they  may  improve  their  radio  knowledge, 
where  good  college  courses  in  radio  are  to  be 
had,  and  what  books  to  read,  that  it  seemed 
that  a  helpful  discussion  of  the  entire  subject 
would  be  read  with  great  interest.  Boys 
in  high  school,  preparing  for  college,  want  to 
know  what  subjects  to  study  so  they  may 
progress  as  fast  as  possible;  older  men,  out 
in  the  whirl  of  daily  existence  are  eager  to 
know  what  books  will  help  them  to  get  a 
good  technical  foundation  in  radio  theory; 
and  radio  salesmen  want  to  learn  the  tech- 
nical facts  about  the  merchandise  they  are 
selling.  This  article  does  not  pretend  to 
present  complete  instructions  for  success 
for  any  of  these  interested  persons.  But 
there  is  information  here  which  should  be  of 
genuine  aid.  Mr.  Henney,  who  is  director 
of  the  RADIO  BROADCAST  Laboratory,  is  a 
graduate  of  Western  Reserve,  and  of  Harvard 
University  which  granted  him  the  degree  of 
Master  of  Science.  — THE  EDITOR 


perience  with  radio  apparatus.  This  experi- 
ence should  include  both  transmitting  and  re- 
ceiving apparatus,  and  here  is  where  the 
"amateur"  has  the  advantage  over  his  brothers 
who  casually  decide  to  enter  the  radio  world. 
It  is  probable  that  the  greatest  number  of 
our  future  radio  authorities  will  come  from 
the  ranks  of  these  so-called  amateurs,  youths 
who  construct  and  operate  apparatus  that 
enables  them  to  converse  with  other  amateurs 
across  unbelievable  distances. 

It  is  surprising  what  an  advantage  these 
amateurs  have  when  they  go  to  college  for 
their  further  training.  They  have  the  "feel" 
of  radio  equipment,  they  are  already  familiar 
with  laboratory  apparatus,  and  they  have 
acquired  first-hand  knowledge  that  gives  them 
a  great  advantage  over  their  classmates. 
These  relatively  inexperienced  men  who  are 
not  so  fortunate  require  some  considerable 
time  to  gain  equal  familiarity. 

The  student  should  pay  as  much  attention 
to  his  mathematics  and  physics  as  possible 
during  high  school,  for  all  that  is  learned  here 
will  save  time  in  college.  If  he  has  time  for 
French  in  high  school, 
several  years  of  that 
language  will  be  a 
great  help.  Or  French 
and  German  may  be 
learned  in  college,  and 
if  the  student  has  a 
fair  reading  knowl- 
edge before  his  arrival 
there  he  will  find  it  a 
distinct  advantage. 
These  two  languages 
have  become  impor- 
tant adjuncts  to  an 
engineer's  training, 
for  so  much  good 
work  is  being  done  on 
the  Continent  that  a 
well  posted  expert 
must  keep  in  touch 
with  what  goes  on 
there.  One  ought  to 
follow  the  work  of  for- 
eign investigators  in 
their  own  language. 

After  arrival  in  col- 
lege, the  student  may 
approach  radio  from 
one  of  two  angles, 
either  through  the 
conventional  elec- 
trical engineering  de- 
partment or  through 


346 


Radio  Broadcast 


the  physics  department.  For  the  first  year 
the  courses  studied  will  be  much  the  same 
Whether  the  student  is  in  engineering  school 
or  in  the  "arts"  college  where  he  will  elect 
scientific  subjects. 

A  continuation  of  his  higher  algebra,  trig- 
onometry, analytical  geometry  and  an  in- 
troduction to  the  calculus  will  complete  his 
mathematical  background  for  the  more  serious 
work  to  follow.  He  will  go  through  the  usual 
Freshman  English  which  is  aimed  to  give  him 
practice  in  writing.  He  will  continue  his 
foreign  languages,  and  probably  learn  some- 
thing of  history,  sociology,  or  economics. 

In  the  second  college  year,  the  student  en- 
gineers continue  to  study  more  mathematics 
and  they  begin  to  branch  out  and  to  concen- 
trate in  their  various  fields.  Both  the  engin- 
eers and  the  physics  students  learn  something 
of  the  several  branches  of  physics.  Electricity 
appeals  to  the  embryo  radio  expert,  but  he 
should  not  forget  that  acoustics  has  become  a 
very  important  part  of  radio  engineering,  and 
his  course  on  sound  will  prove  valuable  in  his 
future  work. 

The  third  and  fourth  years  are  given  to 
more  specialized  courses.  The  study  of 
vacuum  tubes,  and  their  properties  of  amplify- 
ing, detecting,  and  oscillating,  will  be  begun, 
and  for  the  radio  enthusiast,  this  course  will 
prove  to  be  more  than  interesting  as  will  the 
study  of  oscillations  and  electric  waves. 

Should  all  this  time  and  work  seem  un- 
necessary to  the  budding  engineer,  he  should 
remember  that  he  will  be  forced  to  compete 
with  other  engineers,  and  that  the  better 
trained  will  have  the  better  chance  of  success. 
The  attendance  at  colleges  and  technical 
schools  increases  each  year,  and  it  seems  that 
the  youth  who  passes  up  a  college  training 
without  good  cause  will  find  himself  somewhat 
handicapped. 

THE    WIDE    SWEEP   OF    RADIO 

RADIO  is  perhaps  the  broadest  of  the 
various  related  fields  of  electricity,  for 
it  requires  knowledge  and  practise  derived 
from  engineering,  from  physics,  from  chemis- 
try, and  from  mathematics.  For  this  reason, 
the  radio  man  who  is  being  trained  for  radio, 
should  have  as  broad  a  scientific  education 
as  he  has  time  to  accumulate. 

The  radio  engineer  must  know  the  funda- 
mentals of  electricity,  and  there  is  no  royal 
road  to  this  knowledge.  He  must  understand 
the  principles  of  the  various  branches  of 
physics,  such  as  light,  heat,  electricity,  me- 
chanics, and  sound.  He  must  be  able  to 


design  apparatus  that  can  be  made  by  ordin- 
ary machine  practices,  for  a  device  that  cannot 
be  manufactured  might  as  well  not  be  in- 
vented, from  a  practical  point  of  view. 

All  of  these  subjects  require  a  knowledge  of 
mathematics,  and  the  more  a  man  is  at  home 
with  his  algebra,  and  his  trigonometry  and 
his  calculus,  the  better  is  he  able  to  visualize 
the  electrical  and  mechanical  problems  that 
come  to  him. 

At  the  present  time,  there  are  surprisingly 
few  really  outstanding  radio  experts  in  this 
country.  Among  them  are  college  professors 
whose  training  and  experience  has  been  so 
extensive — not  necessarily  in  engineering — 
that  they  can  speak  authoritatively  on  radio 
theory  and  radio  practises.  There  are  others 
whose  training  has  not  had  the  formality  of 
any  college  at  all,  but  they  have  learned  their 
profession  in  the  more  arduous  one  of  experi- 
ence. It  is  probable  that  none  of  these  men 
hangs  out  his  shingle  as  a  "radio  engineer." 
It  is  probable  that  few  of  them  can  copy 
"twenty  words  a  minute"  of  Continental 
Morse  code. 

A  real  engineer  then,  is  one  who  understands 
electricity,  who  can  design  apparatus,  not 
merely  building  it  by  the  cut-and-try  method, 
and  who  by  the  aid  of  his  mathematics  can 
arrive  at  preliminary  solutions  to  important 
problems  without  the  necessity  of  long  labora- 
tory experiment. 

"COMMUNICATION"  COURSES 

SOME  technical  schools  are  recognizing 
that  the  field  of  communication  is  a  dis- 
tinct entity  within  the  larger  one  of  electrical 
engineering.  As  a  result,  their  communica- 
tion courses  include  more  about  vacuum  tubes, 
for  example,  than  about  power  machinery. 
Included  in  such  courses  is  work  on  telephone 
lines  and  their  associated  apparatus,  the 
methods  of  signalling  under  water,  telegraph, 
and,  naturally,  radio. 

"MAN  SPECIFICATIONS" 

AN  INTERESTING  statement  was  made 
some  time  ago  by  John  Mills,  a  promin- 
ent educator  and  engineer  who  hires  the 
technical  men  for  the  Western  Electric  Com- 
pany and  indirectly  men  for  the  American 
Telephone  and  Telegraph  Company.  In  this 
statement  he  said: 

I  look  for  six  characteristics,  without  regard  to 
the  engineering  course  in  which  the  student  has  been 
trained;  and  I  accept  for  the  same  opportunity  men 
who  as  arts  college  students  have  had  no  engineering 
courses  whatever. 


What  Are  the  Royal  Roads  to  Radio? 


In  the  first  place  I  look  for  "intellectual  curiosity." 
Unquenched  and  unquenchable  intellectual  curiosity 
is  to  my  mind  the  first  requisite  for  growth  in  our 
rapidly  progressing  age.  The  second  requisite  is  the 
ability  to  study.  It  is  perhaps  the  one  real  aim  in 
education.  The  percentage  of  population  which 
has  the  ability  to  study  is  much  less  than  the  per- 
centage of  degrees  and  other  evidence  of  learning 
would  indicate.  Learning  looks  to  the  past,  while 
study  looks  to  the  future. 

The  third  requirement  is  the  habit  of  study. 

The  three  remaining  requirements  have  nothing 
to  do  with  the  content  of  engineering  courses,  but 
they  have  a  great  deal  to  do  with  the  natural 


water,  but  he  was  curious  to  know  how,  and 
to-day  his  intellectual  curiosity  has  got  him 
much  farther  than  his  fellows  who  were  not 
particularly  thrilled  by  the  fact  that"HaO" 
was  the  chemist's  shorthand  symbol  for  one  of 
nature's  grandest  explosions. 

WHAT    TRAINING    IS    VALUABLE 

TT  IS  surprising  when  one  looks  over  the 
I  names  of  those  who  appear  in  the  Who's 
Wlno  in  Engineering  to  see  the  great  number  of 
prominent  men  who  have  had  general  college 
training  and  who  are,  technically  speaking,  not 
engineers  at  all.  On  the  other  hand  one 
should  not  forget  that  President  Emeritus 
Charles  W.  Eliot  of  Harvard  University  was  a 


—Ha 


rdCV 


CRUFT    HIGH    TENSION    LABORATORY 

At  Harvard  University.     This  building  is  one  of  the  few  university 
buildings  in  the  country  devoted  exclusively  to  radio  work.     The 
oval  shows  students  at  work  in  one  of  the  laboratories.     Dr.  E.  L. 
Chaffee  is  standing  at  the  extreme  left.     Most  of  the  students 
who  are  taking  work  in  this  building  are  graudate  students,  many 
of  them  from  other  universities  than  Harvard.     Professors  George  W.  Pierce,  A.  E.  Kennelly,  and  Dr.  E. 
L.  Chaffee  give  courses  and  supervise  radio  research  at  the  Laboratory 


characteristics  of  the  student  and  his  general 
training;  they  are:  first,  the  ability  to  learn  from 
men;  second,  the  ability  to  cooperate  with  men; 
third,  a  promise  of  the  ability  to  lead  men. 

In  connection  with  the  first  requirement, 
intellectual  curiosity,  the  writer  remembers 
distinctly  a  fellow  student  in  freshman  chemis- 
try. A  young  instructor  was  lecturing  at 
some  length  upon  the  simple  fact  that  two 
molecules  of  hydrogen  and  one  of  oxygen 
combine  to  form  the  well  known  "HaO",  and 
this  chap  wanted  to  know  "how."  Such  a 
heretical  question  apparently  astonished  the 
instructor,  for  he  struck  up  the  usual  attitude 
of  a  young  teacher  who  finds  himself  in  deep 
water. 

But  that  freshman  who  was  not  satisfied  by 
knowing  that  hydrogen  and  oxygen  did  form 


professor  of  chemistry,  or  that  Herbert 
Hoover  is  a  graduate  mining  engineer. 

It  seems  that  aside  from  the  intrinsic  value 
of  a  technical  education,  there  is  much  to  be 
said  in  favor  of  general  training.  It  is  prob- 
able that  the  best-known  doctors,  lawyers, 
and  educators  are  those  who  have  studied 
many  subjects  not  directly  related  to  their 
particular  interest. 

Here  again  it  is  "intellectual  curiosity"  and 
the  ability  to  study  that  counts,  for  a  man 
trained  in  one  field  may  find  himself  thrust  into 
another.  It  is  probable  that  the  executive 
engineers  who  become  presidents  of  corpora- 
tions are  those  who  have  had  the  widest 
possible  training  outside  of  their  narrow 
technical  study. 

Benjamin    Franklin    was    "craftsman    and 


348 


Radio  Broadcast 


tradesman,  philosopher  and  publicist,  states- 
man, patriot,  and  diplomat."  Yet,  too,  he 
was  a  scientist. 

Good  radio  courses  are  given  by  many  state 
universities,  and  the  work  that  is  done  at 
Harvard  University  under  Professors  Pierce 
and  Chaffee,  at  Columbia  by  Professor  More- 
croft,  and  by  Professor  Hazeltine  at  Stevens  is 
well  known.  There  are  a  number  of  technical 
schools  like  Rensselaer  or  Massachusetts  In- 
stitute of  Technology  that  give  highly  special- 
ized work  in  radio  subjects  in  connection  with 
their  departments  of  electrical  engineering. 

The  student  who  cannot  go  to  one  of  these 
large  institutions  should  not  feel  discouraged, 
for  any  well  taught  engineering  course  will 
give  him  the  background  for  research  or  gradu- 
ate work  in  radio  subjects.  It  must  be  remem- 
bered that  a  radio  engineer  may  be  a  physi- 
cist, and  there  are  few  colleges  that  do  not  have 
physics  departments.  The  principal  thing 
for  the  student  to  remember  is  to  get  the 
fundamentals  of  electricity  and  mathematics 
well  in  hand;  the  value  of  the  superstructure 
of  one's  training  depends  entirely  upon  how 
well  the  ground  work  has  been  laid. 

COMMERCIAL    RADIO    SCHOOLS 

THOSE  who  are  interested  in  radio  and  who 
cannot  go  to  college  can  learn  a  great  deal 
about  radio.  It  is  probable  that  the  greater 
number  of  workers  in  this  fascinating  study 
fall  into  this  class,  for  they  are  those  who  are 
now  working  with  radio  equipment  and  have 
neither  the  time  nor  the  inclination  to  go 
through  the  somewhat  lengthy  process  of  be- 
coming thoroughly  trained. 

The  point  is  that  any  one  can  be  well  posted 
on  radio,  and  can  become  well  acquainted 
with  radio  phenomena  at  home,  or  by  attend- 
ing some  radio  school.  Before  the  day  of 
broadcasting  such  schools  confined  their  ac- 
tivities to  preparing  men  for  the  government 
commercial  license  examinations.  To-day  the 
picture  has  changed  and  presents  a  much 
broader  aspect.  Experts  are  needed  for  sales- 
men, for  operators,  Tor  broadcasting  duties,  for 
inspectors  in  manufacturing  plants,  and  for 
designers  of  radio  apparatus.  Each  of  these 
particular  positions  requires  somewhat  different 
training,  but  the  fundamentals  of  radio  should 
be  understood  by  all.  And  it  is  these  funda- 
mentals that  can  be  learned  at  home,  or  in  day 
or  night  school,  or  by  correspondence. 

The  Department  of  Engineering  Extension 
of  Pennsylvania  State  College  gives  two 
courses  by  correspondence.  One  of  these  is 
an  elementary  course  for  those  who  know  little 


about  radio;  the  other  is  more  technical  and 
complete  in  its  scope  and  uses  as  its  text,  the 
book  Principles  Underlying  Radio  Communi- 
cation prepared  by  the  Bureau  of  Standards. 
These  schools  draw  their  students  from  all 
walks  of  life,  there  are  few  professions  that  are 
not  enrolled.  A  statement  from  one  of  the 
large  radio  schools  is  significant: 

An  analysis  of  last  year's  enrollment  showed 
that  134  distinct  and  separate  professions  were  rep- 
resented in  our  student  body,  and  among  them 
were  doctors,  lawyers,  electrical,  mechanical,  and 
civil  engineers,  postmasters,  building  contractors, 
dentists  and  men  of  similar  occupations. 

CHOOSING    A    RADIO    SCHOOL 

THE  task  of  choosing  a  radio  school  is  no 
simpler  than  that  of  choosing  a  college; 
there  are  the  same  questions  to  be  answered. 
One  should  decide  what  one  is  to  expect  from 
such  a  school  and  to  find  out  whether  it  offers 
the  course  that  is  wanted.  Some  schools  are 
offering  courses  in  radio  research  for  the  ad- 
vanced student,  but  there  is  no  reason  why  the 
enthusiast  cannot  perform  the  experiments 
included  in  such  a  course  at  home — provided 
he  has  the  apparatus. 

It  is  surprising  how  many  of  the  funda- 
mental facts  of  radio  may  be  discovered  by 
reading  and  by  simple  measurements  that 
any  radio  hobbyist  may  do.  In  future  issues 
of  RADIO  BROADCAST  will  be  found  descriptions 
of  apparatus  and  experiments  that  will  teach 
much  about  the  characteristics  of  tubes  used 
as  amplifiers,  detectors,  and  generators;  of  the 
theories  of  resonance  and  tuning;  of  the  effects 
of  resistance  in  circuits,  and  of  similar  work 
in  high  frequency  alternating  current  cir- 
cuits. 

Those  who  have  had  technical  training 
should  get  acquainted  with  their  mathematics 
again,  specially  the  major  operations  in  alge- 
bra, trigonometry  and  calculus.  They  should 
master  alternating  current  theory,  especially 
the  effect  of  inductance  and  capacity  in  tun- 
ing. Technical  articles  appearing  in  the  radio 
publications,  especially  in  the  Proceedings  of 
the  Institute  of  Radio  Engineers  may  be  read 
with  much  profit.  Here  are  descriptions  of 
modern  radio  stations,  amateur,  ship,  broad- 
casting, and  high  power,  complete  with  techni- 
cal data  and  methods  of  operation.  Here,  too, 
are  descriptions  of  new  applications  of  existing 
apparatus. 

The  correspondence  and  day  or  night  schools 
have  much  to  offer  for  those  who  want  to  know 
more  about  radio,  and  the  good  that  can  be 
done  in  this  direction  is  incalculable.  Radio 


What  Are  the  Royal  Roads  to  Radio? 


349 


is  suffering  from  a  lack 
of  first  hand  informa- 
tion. 

The  stores  that  are 
doing  the  largest  busi- 
ness are  those  that  em- 
ploy trained  radio 
salesmen,  and  it  seems 
reasonable  to  suppose 
that  those  that  will 
continue  to  exist  in 
these  days  of  compe- 
tition will  be  those  that 
are  best  posted  on  radio 
facts.  The  buying  pub- 
lic likes  to  feel  that  the 
salesmen  know  what 
they  are  talking  about. 

RADIO    BOOKS 

MANY  books  have 
appeared  on  radio 
since  the  advent  of 
broadcasting.  Some  of 
these  ^appeal  to  some 
people,  but  seem 
sketchy  and  stupid  to 
others.  It  is  impossi- 
ble to  recommend  a 
book  unless  one  knows 
the  background  of  the 
reader.  A  book  that  is 
too  technical  for  some 
is  too  simple  for  others; 
and  there  you  are. 

Books  are  a  reservoir 
of  knowledge  and  those 
that  are  listed  below 
are  not  all  that  have 
been  printed  by  any 
means.  Two  that  may 
be  obtained  from  the 
Superintendent  of  Doc- 
uments,  Washington, 
D.  C.,  should  be  part 

of  every  radio  man's  library.  They  are  the 
Principles  Underlying  Radio  Communication, 
which  costs  one  dollar,  and  the  Bureau  of 
Standards  Bulletin  No.  74,  which  costs  sixty 
cents. 

Books  written  for  the  laymen  are  Radio 
Communication  by  E.  W.  Stone,  An  Outline  of 
Radio  by  John  V.  L.  Hogan,  and  Dunlap's 
Radio  Manual  by  Orrin  E.  Dunlap,  Jr.  John 
Mills'  book  Letters  of  a  Radio  Engineer  to  his 
Son  presents  the  fundamentals  of  radio  science 
in  an  unusual  and  interesting  manner. 

Among  the  more  technical  books,  there  are 


A    MARINE    RADIO   OPERATOR    AT   WORK 

Senior  operator  J.  T.  Williams,  and  Captain  John  Roberts  of  the  S.  S.  Homeric. 
Part  of  the  tube  transmitter  is  visible.  Those  who  want  tjo  gain  as  much  radio 
experience  as  possible  often  spend  several  years  or  more  as  a  marine  radio 
operator.  Operators,  when  they  are  granted  their  government  licenses,  are 
thoroughly  examined  on  their  knowledge  of  radio  theory  and  practise.  Prac- 
tical experience  aboard  ship  is  very  valuable  to  the  man  who  wants  to  have  a 
thorough  knowledge  of  radio.  Great  numbers  of  prominent  radio  men  have 
graduated  from  the  marine  operator  class  to  positions  of  considerable  radio 
success.  The  amateur  radio  operator  learns  much  about  the  fundamentals  of 
radio  without  leaving  his  own  home.  He  can  gain  much  from  a  study  of  good 
radio  text  books  and  magazines,  and  more  by  practical  experiments  with 
radio.  The  study  of  radio  at  home,  as  the  author  points  out  in  this  arti- 
cle, although  it  cannot  substitute  for  study  at  a  technical  school  or  college,  can 
do  much  toward  building  a  radio  groundwork 


none  that  are  as  complete  and  as  useful  as 
Professor  Morecroft's  Principles  of  Radio 
Communication.  Thermionic  Halves,  by  Van 
der  Bijl  is  useful  to  the  vacuum  tube  student, 
but  this  book  is  highly  technical  and  was 
written  from  the  point  of  view  of  the  telephone 
engineer.  The  mathematically  inclined  reader 
and  those  who  crave  exact  proofs  of  state- 
ments will  enjoy  Professor  Pierce's  Electrical 
Waves  and  Electrical  Oscillations — which,  by  the 
way,  contains  some  excellent  material  on  elec- 
tric lines  and  filters,  a  subject  that  is  treated 
very  sketchily  in  other  publications. 


4$  ike  krocldcaster  sees  xi 

Toy  CxcVzl  LlxeKear 


Drawings  by  Franklyn  F.  Stratford 


High  Power  and  Elimination  of  Strays 


THE  only  reason  that  static  is  bother- 
some, even  occasionally,  in  radio  re- 
ception, is  that  the  amount  of  energy 
normally  picked  up  from  a  distant  sta- 
tion is  almost  incredibly  minute.  Dr.  W.  R. 
Whitney  of  the  General  Electric  Company, 
is  reported  to  have  calculated  recently,  that 
the  energy  expended  by  a  house  fly  in  climbing 
one  inch  up  a  wall,  is  equal  to  the  total  energy 
which  would  be  picked  up  by  a  one-foot  loop 
at  Schenectady,  New  York,  from  a  normal 
broadcasting  station  in  San  Francisco,  over  a 
continuous  period  of  35  years.  Yet  we  know 
that,  given  a  suitable  receiver,  reception  of 
KGO  on  a  one-foot  loop  at  Schenectady  is  not 
an  extraordinary  feat.  It  is  the  amplification 
required — and  available  in  a  good  set — which 
is  extraordinary. 

When  amplification  is  raised  to  this  level,  it 
is  to  be  expected  that  any  natural  or  artificial 
electrical  forces  which  may  happen  to  be  hang- 
ing about  will  also  make  themselves  heard  in 
the  loud  speaker.  Leaving  aside  the  relatively 
rare  periods  of  local  lightning,  static  interfer- 
ence is  not  caused  by  the  strength  of  the  static, 
but  by  the  weakness  of  the  signal.  The  static 
is  not  particularly  vicious,  but  we  stick  our 
hands  into  its  cage,  in  DX  reception,  and  in- 
vite it  to  bite  us.  Or,  to  change  the  metaphor, 
we  look  for  needles  in  a  haystack,  and  then 
complain  of  the  hay.  Archimedes  said  that 
given  a  long  enough  lever,  and  a  place  at  the 
fulcrum  to  rest  it  on,  he  could  move  the  earth. 
The  modern  radio  engineer  can  paraphrase 
Archimedes  with  the  declaration  that,  given 
enough  stages  of  r.  f.  and  a.  f.  amplification, 
he  can  sit  in  California  and  hear  all  the  x-ray 
machines  in  Maine;  or,  since  we  are  talking 


about  static,  he  may  hear  all  the  lightning 
flashes  in  Korea  and  all  the  meteorites  hitting 
the  Heaviside  layer,  assuming  that  this  cosmic 
bombardment  gives  rise  to  certain  varieties  of 
static,  as  has  been  alleged  by  some  specialists 
in  the  subject. 

In  discussing  static  interference  in  radio  it 
is  necessary  to  differentiate  between  interfer- 
ence with  program  service  and  interference 
with  distance  reception.  Static  frequently  in- 
terferes with  distance  reception,  particularly 
in  the  summer,  because  the  received  signal  re- 
quires great  amplification.  Interference  with 
program  service  is  relatively  rare.  When  the 
signal  from  a  given  station  in  a  given  locality 
is  strong  enough  to  ride  over  the  usual  disturb- 
ances, this  ability  being  taken  as  the  criterion 
of  program  service,  it  will  be  found  that  pe- 
riods of  abnormal  disturbance  are  not  as 
unusual  as  railroad  wrecks  or  tornadoes,  but 
neither  are  they  more  common  than  "rotten" 
pictures  at  the  movies,  or  automobile  tire 
punctures,  or  arguments  with  one's  wife.  In 
other  words,  as  regards  static,  radio  is  in  the 
position  of  other  public  utilities  and  domestic 
conveniences  with  reference  to  their  peculiar 
difficulties;  it  is  imperfect,  but  good,  and  not 
to  be  appreciated  until  one  has  to  do  without 
it. 

While  we  are  thus  attempting  to  view  the 
problem  in  its  true  proportions,  it  is  not  to  be 
denied  that  a  compact,  cheap,  simple  static 
eliminator  would  be  of  great  utility,  especially 
to  people  who  live  several  hundred  miles  from 
the  nearest  broadcasting  station,  and  of  even 
more  value  to  listeners  in  the  tropics, 
where  static  is  at  its  worst.  A  nice  little  tube, 
to  be  connected  in  the  antenna  lead,  which 


Higher  Power  Will  Mean   Better  Broadcasting  Service 


351 


would  stop  the  static  and  let  the  signals  go  on 
down,  would  be  just  the  thing.  1  would  go 
to  the  five  -and  ten-cent  store  myself  to  buy 
one.  Unfortunately,  while  many  good  men 
have  attempted  to  invent  some  such  device, 
and  have  brought  great  ingenuity  and  assid- 
uity to  bear,  the  job  remains  to  be  done. 
Very  successful  means  of  static  reduction 
have  been  devised,  but  all  are  complicated 
and  costly.  They  are  used  only  in  long  dis- 
tance radio  telegraph  circuits,  where  the  plant 
investment  is  in  any  event  great  and  where 
profits  are  more  or  less  proportional  to  ability 
to  ride  over  static  disturbances.  Most  of 
these  successful  methods  operate  on  the  di- 
rectional principle.  The  signal  comes  from 
only  one  direction,  and  the  static  may  come 
from  a  different  direction.  If  you  can  confine 
your  reception  within  as  narrow  an  angle  as 
possible,  pointing  in  the  direction  of  the  ap- 
proaching waves  of  the  desired  station,  you 
may  be  able  to  shut  out  an  appreciable  propor- 
tion of  the  static.  This  is  the  principle  of  the 
barrage  receivers  of  Alexanderson,  the  loop-, 
vertical  combinations  of  Pickard,  some  of 
Weagant's  devices,  and  the  "wave  antenna" 
of  Beverage,  Rice,  and  Kellogg.  The  latter 
employs  antennas  nine  miles  long  for  trans- 
oceanic reception.  The  antenna  is  supposed 
to  be  about  a  wavelength  long,  so  even  for 
broadcast  reception  one  needs  about  a  quarter 
of  a  mile.  As  yet  no  one  has  put  up  a  wave 
antenna  on  Riverside  Drive  or  Michigan 
Boulevard!  In  any  case,  for  broadcast  recep- 
tion, the  direction  of  all  such  telescopic 
receivers  must  be  variable,  since  one  will  gener- 
ally want  to  listen  to  stations  in  any  direction. 
Many  aspiring  anti-static  gladiators  come 
forward  periodically  with  vest-pocket  elimina- 
tors which  do  not  work,  but  which  add  to  the 
gayety  of  the  indus- 
try; Recently  the 
ancient  device  of  two 
circuits,  one  tuned  to 
the  wavelength  of  the 
desired  station,  the 
other  to  some  other 
frequency,  followed 
by  rectification  in 
each  branch,  and  an 
a.  f.  balance  in  a 
differential  trans- 
former, was  once 
more  revealed.  This 
method  was  in  its  first 
flush  of  youth  in 
about  1916;  it  was  de- 


aooui  1910:11  was  ae-      .-.       -,       .c  ,1  n    T.     .  .    ,-.    -i 

scribed  in  a  paper  by     "^V  hunt  lor  needles  and  object  to  the  hajr 


Dr.  Cornelis  J.  DeGroot,  "On  the  Nature  and 
Elimination  of  Strays,"  (Proc.  Institute  of 
Radio  Engineers,  Vol.  5,  No.  2,  April,  1917.) 
Whosoever  is  interested  can  also  discover,  in 
the  printed  discussion  following  the  article, 
some  of  the  reasons  why  this  plausible  method 
will  not  work. 

Another  exhibit  is  found  in  an  issue,  early 
this  year,  of  a  trade  paper  advertising  one  of 
those  five  tube  stabilized  radio  frequency  sets, 
with  three  big  knobs  and  two  or  three  little 
ones,  which  is  an  imitation  of  an  imitation  of 
a  five  tube  stabilized  radio  frequency  set,  but 
no  doubt  just  as  good.  There  is  the  usual  cut, 
with  captions  on  either  side  detailing  the  vir- 
tues of  the  set,  and  heading  all  the  other  claims 
is  the  bald  statement,  "It  Eliminates  Static." 
Of  course  it  doesn't. 

However,  although  the  ordinary  broadcast- 
ing receiver  is  not  a  static  eliminator,  it  is 
important  to  note  that  when  improperly  used 
it  may  show  a  much  less  favorable  signal-to- 
static  ratio  than  when  properly  handled.  The 
output  of  a  vacuum  tube  is  of  course  a  limited 
quantity.  If  it  is  pushed  too  hard,  a  point  is 
reached  at  which  the  signal  volume  can  no 
longer  be  increased,  while  minor  disturbances 
are  still  swinging  the  grids  over  the  steep  por- 
tion of  the  curve.  This  results  in  bringing  up 
static  or  inductive  interference  or  whatnot,  to 
the  disadvantage  of  the  desired  modulation, 
which  is  incidentally  distorted.  Not  infre- 
quently one  sees  receivers  which  are  capable 
of  delivering  a  clear,  relatively  disturbance- 
free  output  of  moderate  volume,  pushed  to  a 
point  where  a  mushy  signal,  full  of  squeaks, 
crashes,  and  hisses,  but  loud  enough  to  be  heard 
in  the  next  county,  is  duly  brought  forth.  A 
radio  receiver  of  the  usual  design  cannot  be 
expected  to  do  the  work  of  a  public  address 
system,  any  more 
than  a  billy-goat  can 
drag  a  five-ton  load. 
If  more  people  would 
form  the  habit  of 
holding  down  the  am- 
plification to  a  com- 
fortable level,  com- 
plaints of  radio  noise 
interference  would  be 
greatly  reduced. 

Finally,  freedom 
from  static  and 
other  extraneous 
sounds  is  a  matter  of 
transmitting  power. 
Given  the  power, 
we  can  ride  over 


352 


Radio  Broadcast 


anything  within  reason.  With  inadequate 
power,  one  is  in  the  position  of  a  man  talking 
in  a  whisper  in  any  crowded  place.  Radio 
communication  is  inherently  a  problem  in  am- 
plification. In  the  studio  one  starts  with 
energy  of  the  order  of  microwatts — millionths 
of  a  watt.  This  is  enormously  magnified — to 
the  level  of  say  500  watts  in  the  transmitting 
antenna,  but  the  method  of  distribution  is  such 
that  the  receiver  gets  only  a  few  microwatts  to 
work  with.  Once  more  this  is  amplified,  until 
it  is  strong  enough  to  actuate  a  loud  speaker 
reproducing  the  original  sounds.  But  here  is 
the  rub:  where  amplification  at  the  transmitter 
brings  up  only  the  desired  sounds,  as 
amplification  at  the  receiver  magnifies  these 
and  all  other  impulses  that  happen  to  be  flying 
around.  The  former  is  selective  amplification ; 
the  latter  is  general,  undiscriminating  amplifi- 
cation, except  in  the  one  particular  of  fre- 
quency selection. 

Thus  even  the  engineer  who  is  skeptical 
about  static  elimination  at  the  receiver,  sees 
no  reason  why  static  cannot  be  substantially 
eliminated  by  perfectly  feasible  increases  of 
power  at  the  transmitter.  Largely,  in  fact, 
this  has  already  been  accomplished.  People 
who  live  within  a  few  miles  of  a  powerful  sta- 
tion hardly  know  that  static  exists.  Farther 
out,  they  hear  it  occasionally,  but  it  is  hardly 
as  annoying  as  the  coughing  at  a  symphony 
concert — a  form  of  disturbance  which,  inciden- 
tally, is  effectively  eliminated  for  radio  lis- 
teners by  close  microphone  placing.  With  the 
constant  increase  in  power  of  broadcasting 
stations,  the  area  of  practically  interference- 


JK)  more  can  a  tilly^odt  pull  A  5  ton  load 


free  reception  increases  in  proportion.  The 
time  is  not  so  far  off  when  the  area  subject, 
more  or  less,  to  radio  disturbances,  will  dis- 
appear entirely,  just  as  the  frontier  of  the 
United  States  disappeared,  through  the  in- 
crease and  distribution  of  the  population, 
toward  the  end  of  the  last  century. 

Among  the  Broadcasters — Howard  E. 
Campbell 

MR.  CAMPBELL  was  a  radio  man  in  the 
days  when   "broadcasting"   was    not 
yet  in  a  radio  man's  vocabulary.      He 
is  now  chief  radio  engineer  and  director  of 
broadcasting  for  the  Jewett  Radio  &  Phono- 
graph Company  of  Detroit,  which  is  about  to 
put  into  operation  a  5-k.  w.  station  at  Pontiac, 
near  that  city. 

Leaving  the  University  of  Indiana  in  1909, 
Mr.  Campbell  enrolled  in  the  Naval  Electrical 
School  at  Brooklyn,  New  York,  where  trem- 
bling amateurs  and  professional  aspirants,  a 
few  years  later,  were  summoned  for  their  oper- 
ator's license  examinations,  before  the  Depart- 
ment of  Commerce  took  over  that  function. 
But  that  examination  Mr.  Campbell  did  not 
take  until  in  1912,  after  spending  most  of  the 
intervening  period  as  a  Naval  Radio  Electri- 
cian in  Atlantic  waters,  for  the  simple  reason 
that  until  1912  there  was  no  examination  to 
take.  With  his  first  grade  ticket  he  made  one 
trip  as  a  marine  operator  in  the  coastwise 
service,  before  being  transferred  to  the  Mar- 
coni Company's  installation  force  early  in 
1913.  Ultimately  he  became  chief  radio  in- 
spector at  the  port  of  New  York  for  the  Mar- 
coni Company,  and  no  doubt  held  down  many 
a  key  while  squeezing  the  last  milliampere  out 
of  the  old  quenched  spark  set.  He  also  in- 
stalled sets  on  sealing  vessels  in  Newfound- 
land. 

By  this  time,  apparently,  Mr.  Campbell  felt 
that  he  had  graduated  from  marine  radio,  for, 
following  a  brief  period  as  technical  assistant 
at  the  Aldene,  New  Jersey,  plant,  he  is  next 
discovered  as  engineer-in-charge  of  the  300- 
k.  w.  New  Brunswick,  New  Jersey,  transatlan- 
tic station,  which  was  a  timed-spark  outfit  of 
the  type  still  being  used  at  Stavanger,  Norway 
(LCM),  for  communication  with  the  United 
States.  New  Brunswick  was  under  test  at 
this  time,  and  soon  after  that  job  was  in  a 
stage  of  completion  Mr.  Campbell  went  out 
to  Bolinas,  California,  to  assist  in  the  installa- 
tion of  a  similar  outfit  for  communication  with 
Hawaii  and  Japan.  All  this,  of  course,  was 


Strong  Radio  Signals  for  Every  Farmer's  Front  Yard  353 


in  the  dot-aml-dash  business;  radio  telephony 
was  still  in  the  incubator. 

In  February,  1917,  Mr.  Campbell  was 
engineer-in-charge  at  Bolinas,  and  then  the 
war  came  along.  The  day  after  the  United 
States  declared  war  against  Germany,  the 
station  and  all  of  its  personnel  were  taken  over 
by  the  Navy,  Mr.  Campbell  remaining  in 
charge  with  the  rank  of  Radio  Gunner.  When 
the  armistice  was  signed  he  was  officer-in- 
charge  of  the  Naval  Radio  Training  School 
at  Marshall,  California,  following  which  he 
went  back  to  Bolinas, 
as  Chief  Radio  Gunner, 
to  recondition  the  sta- 
tion before  it  was 
turned  back  to  the 
Marconi  Company  by 
the  Navy.  In  May, 
1919,  Mr.  Campbell 
was  detailed  as  Radio 
Communication  officer 
on  the  staff  of  the 
Pacific  Coast  Commu- 
nications Superinten- 
dent, and  this  turned 
out  to  be  his  last 
assignment  in  the  ser- 
vice, for  in  September 
he  received  his  dis- 
charge and  returned 
to  his  home  in  New 
York  City,  in  plenty 
of  time  to  participate 

in  the  broadcasting  boom   which  started   in 
the  East  in  September,  1921. 

As  soon  as  Mr.  Campbell  reached  New  York 
he  made  a  connection  with  the  Western  Elec- 
tric Company  as  radio  designing  engineer,  and 
in  that  capacity  he  had  much  to  do  with  the 
design  of  the  first  5OO-watt  radio  telegraph  and 
telephone  transmitter,  from  which  the  present 
standard  5Oowatt  broadcasting  outfit  was  de- 
veloped with  comparatively  unimportant  mod- 
ifications. Having  been  in  intimate  touch 
with  the  design,  Mr.  Campbell  was  ready  to 
operate  this  equipment  when  he  became  chief 
engineer  of  station  wwj  in  Detroit  early  in 
1922,  and  his  success  may  be  judged  by  the 
fact  that  this  station  was  shortly  cited  by  the 
Bureau  of  Standards  as  one  of  the  few  standard 
frequency  stations  of  the  country,  varying 
from  its  assigned  frequency  less  than  one-tenth 
of  one  per  cent,  over  a  period  of  seventeen 
months.  From  wwj,  Mr.  Campbell  passed 
over  to  his  present  connection. 

Mr.  Campbell  has  been  a  full  member  of  the 
Institute  of  Radio  Engineers  since  1914. 


HOWARD    E.    CAMPBELL 


Radio  Is  Too  Urban 

FROM    Miami,  Arizona,  comes    a    com- 
ment by  Mr.  W.  H.   Mayfield  relative 
to  the  discussion  of  DX  vs.  Programs 
in  our  April  issue.     Mr.  Mayfield  points  out, 
pertinently  enough,  that  some  listeners  are  DX 
hunters    through    necessity.     "The    closest 
station  of  any  size,"  he  writes,  "is  450  miles, 
air  line,    whereas   a   45omile   circle   drawn 
around  Mr.  Dreher's  listening  post  would  un- 
doubtedly include  a  hundred  stations.    We 
necessarily  have  to  be 
'DX  hounds'  here,   if 
we  are  to  get  anything, 
and  to  listen  to  stations 
for  selection  after  selec- 
tion without  announce- 
ment,   and   when    the 
announcement  is  made 
to  have  it  entirely  un- 
intelligible,   or    'down 
in  the  trough,'   as  he 
puts  it,  is  discouraging, 
to  say  the  least." 

Mr.  Mayfield  sug- 
gests that  the  an- 
nouncer have  a  key 
and  buzzer  handy,  and 
give  the  call  signal  in 
Continental  Morse. 
There  are  numerous 
objections  to  this 
method.  Here  in 

New  York  only  one  of  the  announcers  in  my 
acquaintance  knows  the  code  well  enough  to 
learn  to  send  even  a  simple  combination  of 
letters.  Announcers  are  not  chosen  for  tele- 
graphic ability,  but  for  a  ready  tongue,  a 
pleasant  voice,  knowledge  of  music  and  show- 
manship, good  manners  and  a  measure  of 
good  looks.  (The  last  to  put  female  artists 
into  a  pleasant  frame  of  mind,  so  far  as  possi- 
ble). In  the  second  place,  nine-tenths  of  the 
listeners  know  as  little  code  as  the  announcers. 
Thirdly,  code  signals,  almost  as  much  as  key 
words  like  Watch  George  Yoke,  would  be  out 
of  atmosphere.  At  one  station  in  the  East 
there  was  a  device  for  chopper-modulation  of 
the  carrier  whenever  the  microphone  was  off, 
giving  a  characteristic  monotonous  note 
of  musical  pitch  for  listeners  to  tune  to.  It 
sounded  pretty  nasty  on  test,  and  was  never 
put  on  the  air. 

The  answer  to  the  problem  is  twofold: 

(i)  Frequent  announcing  with  modulation  not 
below  the  mean  level  of  the  music.  We  shall  be 
glad  to  hear  from  listeners  about  stations  which 


354 


Radio  Broadcast 


neglect  to  give  their  call  letters  at  reasonably  fre- 
quent intervals,  it  being  borne  in  mind,  however, 
that  on  some  types  of  programs,  such  as  church  ser- 
vices and  theatrical  features,  frequent  cut-in  an- 
nouncements may  not  be  feasible. 

(2)  Adequate  power  to  reach  the  backwoods. 
Radio  is  at  present  too  much  an  urban  proposition. 
The  people  out  on  the  plains  and  up  in  the  hills  need 
it  as  much,  and  more,  and  they  will  buy  the  sets 
when  the  service  is  offered  them.  One  of  the  kings 
of  France — Henry  was  his  name,  but  I  don't  recol- 
lect his  number  offhand — who  had  a  great  zeal  for 
the  welfare  of  his  subjects,  declared  his  ambition 
was  that  every  French  peasant  should  have  a  fowl 
in  his  kitchen  pot  on  Sunday.  Well,  every  Amer- 
ican farmer  must  have  a  radio  signal  field  strength 
of  I  .o  millivolt  per  meter  in  his  front  yard  on  Sunday 
and  every  other  day.  When  all  announcements 
made  are  certain  to  reach  the  listeners,  then  the 
determination  of  the  proper  frequency  of  call-letter 
repetitions  will  be  a  trifling  problem  indeed. 

Is  Government  Action  Needed  on  the 
SOS  Question? 

ON  MARCH  2ist  there  was  another  east 
coast  sos,  and  Mr.  John  S.  Dunham, 
of  Larchmont,  New  York,  kept  a  log 
of  the  proceedings,  sending  a  copy  to  Mr. 
Arthur  Batcheller,  United  States  Supervisor 
of  Radio  in  the  second  district,  and  one  to  us. 
The  record  is  very  complete  and  covers  from 
7.46?,  when  the  alarm  was  first  given,  to  8.27, 
when  NAH  (Brooklyn  Navy  Yard)  sent  out  the 
"Resume  traffic"  message. 

WEAF  apparently  got  the  original  sos,  or  an 
immediate  relay,  for  it  is  in  this  instance  in 
the  honorable  position  of  going  off  the  air 
first,  at  7.46.  wjz,  WNYC,  WOR,  WGBS,  KDKA, 
and  others  kept  right  on  broadcasting.  At 
7.57,  NAH,  the  naval  control  station  in  this  dis- 
trict, sent  out  a  QRT  (Stop  Sending).  There- 
upon wjz  took  off  its  carrier,  followed  within 
a  few"minutes  by  WNYC,  WGBS,  and  WOR  (8.01). 
The  inland  broadcasters  continued  their  pro- 
grams, and  WIP,  Philadelphia,  508.2  meters, 
likewise  failed  to  break  its  carrier,  until  8.22, 
when  Mr.  Dunham's  log  states,  "WIP  at  last 
off." 

Mr.  Batcheller,  in  a  communication  to  Mr. 
Dunham,  commented  as  follows: 

"Class  B  stations  only,  which  are  on  the 
coast  and  capable  of  interfering  on  600  meters 
are  required  to  cease  transmission  during  the 
transmission  of  an  sos  and  signals  relating 
thereto.  Inland  Class  B  stations  and  all'-Class 
A  stations  are  not  required  to  cease"  trans- 
mission." 

That  puts  the  sos  situation  substantially  on 
the  basis  we  advocated  in  our  first  article  on 


the  subject  in  RADIO  BROADCAST.  (We  do 
not  mean  to  imply  that  that  brought  about  the 
readjustment,  which  had  probably  been  in 
contemplation  for  some  time.) 

However,  Mr.  Dunham  feels  that  all  sta- 
tions above  300  meters  should  cease  broad- 
casting when  an  sos  goes  out,  on  the  ground 
that  damage  to  antenna  or  apparatus  might 
necessitate  the  use  of  a  lower  wavelength  than 
600  meters,  the  standard  distress  call  wave- 
length. He  calls  attention,  also,  to  the  case  of 
WIP,  which  is  Class  B,  near  the  coast,  and  not 
so  far  from  600  meters.  There  may  be  a 
difference  of  opinion  on  the  first  question,  and 
evidently  the  Department  of  Commerce,  hav- 
ing liberalized  the  rules,  considers  the  low- 
wave  distress  call  contingency  remote.  But, 
whichever  way  you  look  at  it,  there  is  little 
to  be  said  in  favor  of  WIF  if  Mr.  Dunham's  log 
is  correct. 

Dr.  Frank  W.  Elliott,  Manager  at  woe,  also 
contributes  to  this  discussion,  pointing  out 
that  the  Department  of  Commerce  has  never 
seen  fit  to  enforce  the  regulations  as  regards 
inland  broadcasters,  and  that  it  would  be 
difficult  to  pick  up  sos  calls  on  either  coast  at 
points  in  the  Central  states.  He  writes  fur- 
ther: 

"If  some  way  could  be  developed  to  give 
information  to  the  stations  inland  by  telephone 
or  telegraph  I  am  sure  that  all  would  be  willing 
to  cooperate.  I  know  that  we  would." 

It  was  not  our  intention  to  criticise  the  in- 
land broadcasters  in  this  regard.  We  were 
calling  attention  to  a  general  condition,  using 
particular  stations  merely  for  illustration. 
The  fact  remains  that  some  of  the  sos  calls 
which  take  the  coast  broadcasters  off  the  air 
originate  several  thousand  miles  out  at  sea. 
A  powerful  inland  station  on  one  of  the  higher 
wavelengths  might  conceivably  interfere  with 
the  traffic  following  such  a  call.  The  argu- 
ment in  the  March  issue  was  for  a  formula  or 
some  equivalent  means  of  differentiating  dan- 
gerous stations  from  the  others.  This  still 
seems  a  rational  procedure.  It  is  merely  one 
of  a  number  of  radio  problems  which  could 
stand  scientific  investigation  as  a  basis  for 
appropriate  action. 

Receiving  equipment  exists  which  could 
give  an  adequate  sos  service  to  those  broad- 
casters, however,  far  from  the  coast,  who 
might  be  designated  to  stand  an  sos  watch. 
Or,  as  Doctor  Elliott  points  out,  a  wire  service 
might  be  organized. 

We  are  glad  to  hear  from  woe,  not  only  for 
their  specific  addition  to  what  has  been  said 
on  the  sos  question,  but  because  the  exchang- 


The  Progress  of  a  Young  Electrician 


355 


ing  and  debating  of  different  points  of  view 
among  the  broadcasters  is  exactly  what  this 
department  is  here  for. 

The  Memoirs  of  a  Radio  Engineer. 
II 

BESIDES  constructing  an  electrophorus, 
from  which,  when  the  weather  was  not 
too  wet,  sparks  could  be  drawn,  my 
companions  and  I  built  several  detecting  de- 
vices, or  electroscopes.  These  were  of  two 
general  types,  which  used  metal  foil  and  pith 
balls,  respectively.  The  latter  form  consists 
very  simply  of  two  small  sheets  of  gold-leaf  or 
other  very  thin  metal  foil,  suspended  from  a 
metal  rod  so  that  they  will  separate  on  the 
approach  of  an  electric  charge,  owing  to  the 
repulsion  effect  between  two  similarly  charged 
bodies.  In  our  case,  we  stuck  a  fairly  heavy 
copper  wire  through  the  cork  of  a  pickle  bottle, 
or  any  bottle  of  diameter  uniform  over  the 
entire  length,  bent  it  over  at  the  lower  end, 
and  hung  pieces  of  aluminum  foil  over  the 
horizontal  part  of  the  wire.  The  object  of  the 
bottle  was  to  shield  the  apparatus  from  air  cur- 
rents. The  proud  operator  of  the  electroscope 
would  demonstrate  it,  before  a  gaping  congre- 
gation of  children,  by  running  an  ebonite 
comb,  very  likely  stolen,  through  his  hair, 
and  bringing  it  close  to  the  upper  end  of  the 
metal  rod  or  wire.  Promptly  the  leaves  would 
separate,  standing  stiffly  apart  at  an  angle  of 
about  forty-five  degrees.  For  a  small  consid- 
eration, the  spectators  were  permitted  to  rub 
the  comb,  each  in  his  own  hair,  and  by  per- 
forming the  experiment  personally  to  satisfy 
themselves  that  there  was  no  fraud.  Many 
of  them  believed  that  the  electricity  was 
drawn  out  of  the  head,  that  some  individuals 
had  more  than  others,  and  that  there  was  a 
peculiar  virtue  in  having  a  great  deal;  argu- 
ments arose  as  to  who  had  the  most,  and  in 
the  more  acute  cases  led  to  fist-fights  and 
neighborhood  feuds.  One  boy  in  particular 
vaunted  himself  on  his  remarkable  virility, 
for  he  was  able  to  make  the  pieces  of  foil  leap 
apart  so  violently  that  they  reached  the  sides 
of  the  bottle  and  clung  there.  His  enemies 
maintained,  probably  not  without  truth,  that 
he  was  able  to  do  this  because  his  mother  never 
made  him  wash  his  head.  They  caught  one 
of  the  stray  cats  of  the  neighbourhood,  rubbed 
its  back  with  the  comb,  and  proved  that  it 
yielded  an  even  more  striking  effect  on  the 
electroscope  than  the  hair  of  the  champion, 
who  stood  near  by,  surrounded  by  his  adher- 
ents, sneering.  Finally  one  of  them  threw  a 


rock,  smashing  the  electroscope;  the  cat  es- 
caped, all  the  contestants,  abandoning  science, 
rushed  to  arms,  and  in  the  ensuing  melee 
I  received  a  bloody  nose,  neither  the  first 
nor  last  injury  of  that  nature  which  I 
sustained. 

The  other  type  of  electroscope  worked  on 
the  same  principle,  but  utilized  pith  balls 
suspended  by  threads.  The  pith  we  obtained 
by  hunting  for  the  dried  stalks  of  weeds,  which 
abounded  in  the  vacant  lots  of  the  Bronx. 
Pith  ball  electroscopes  were  cheaper,  and  hence 
more  common.  One  could  be  bought  from  the 
manufacturers,  if  I  recollect,  for  about  five 
marbles  of  the  type  known  as  "immies,"  while 
the  aluminum  foil  product  sold  only  for  cash. 
As  much  as  ten  cents  changed  hands  in  some 
transactions. 

These  experiments  were  successful  and 
profitable,  but  many  other  adventures  in  static 
electricity  failed.  For  example,  we  were  never 
able  to  build  a  static  machine,  or  generator  of 
static  electricity  with  moving  parts.  Our 
greatest  ambition  was  to  own  what  is  known  as 
a  Wimshurst  machine,  which  consists  of  two 
glass  disks  revolving  in  opposite  directions, 
with  brushes  and  combs  for  drawing  off  a 
continuous  charge.  This  was  beyond  our  con- 
structional ability,  and  we  had  no  more  chance 
of  buying  one,  with  the  money  derived  from 
snow  shovelling,  running  errands,  and  begging 
from  our  parents,  than  we  had  of  buying  a  rail- 
road or  an  automobile.  Yet  we  yearned  for 
one,  hopelessly  and  yet  pleasurably,  as  a  farm- 
hand longs  for  a  Follies  girl  or  a  case  of  Scotch. 
Always  there  is  something  beyond  one's  reach, 
and  one  must  accept  substitutes.  We  tried  to 
build  a  simpler  electric  machine,  using  a  re- 
volving glass  cylinder  rubbing  against  a  silk 
pad,  and  we  did  succeed  in  mounting  a  bottle 


roved,  "fliat  {here  was  no  fraud 


356 


Radio  Broadcast 


on  a  shaft  turned  by  a  crank,  but  no  amount  of 
turning  and  sweating  got  us  an  appreciable 
static  charge,  presumably  because  the  glass 
was  not  the  right  kind.  We  fell  back  on  the 
electrophorus  as  a  generator. 

Another  great  diversion  was  collecting  or 
accumulating  charges  in  condensers,  which 
were  known  to  us  only  in  the  form  of  Leyden 
jars.  These  we  manufactured  out  of  glass 
test  tubes,  coated  on  the  outside  with  tinfoil, 
and  filled  with  salt  water  for  the  inside  elec- 
trode. By  imparting  about  fifty  charges  from 
the  electroscope  to  the  ball  of  the  Leyden  jar, 
one  could  get  a  fairly  severe  shock  on 
discharging  the  jar.  This  was  far  more  enter- 
taining than  the  comparatively  feeble,  pain- 
less, and  less  noisy  sparks  of  the  electrophorus. 
The  spark  of  the  Leyden  jar  was  blue  and  loud, 
and  by  combining  a  number  of  test  tubes  one 
could  get  it  to  jump  as  much  as  a  quarter  of 
an  inch.  We  persuaded  one  innocent  youth 
to  hold  such  a  battery  in  his  hand,  and  to 
present  his  tongue  to  the  brass  ball  which  was 
connected  to  the  inner  coating;  the  shock 
knocked  him  down,  and  in  falling  he  broke  the 
four  condensers  of  the  battery.  Thus  we  were 
justly  punished  for  our  cruelty. 

This  incident  marked  the  limit  of  our  prog- 
ress in  electrostatics.  We  now  turned  to 
experiments  with  electric  currents,  as  distin- 
guished from  static  charges,  and  numerous 
galvanoscopes  and  galvanometers — devices  for 
detecting  and  measuring  electric  currents — 
were  built  and  torn  apart.  Our  raw  material 
was  mainly  in  the  form  of  old  electric  bells, 
which  we  bought  from  the  neighborhood 
electricians  for  ten  cents  apiece.  Some  of 
them  had  been  incapacitated  by  a  coat  of 
kitchen  paint,  others  concealed  a  dead  cock- 
roach in  their  vitals,  many  had  simply  failed 
from  old  age,  but  they  were  all  precious  to  us 
for  the  two  electromagnets  which  they  con- 
tained. Some  of  these  we  unwound  from  the 
core  and  rewound  on  cardboard  forms,  within 
which  a  magnetized  sewing  needle,  suitably 
suspended,  twitched  violently  when  a  dry 
battery  was  connected  to  the  terminals  of  the 
coil.  We  attached  scales  to  these  instruments, 
but  we  had  nd  means  of  calibrating  them  and 
so  they  never  really  measured  anything. 
However,  1  do  recollect  building  a  tangent 
galvanometer,  on  which  I  worked  for  some 
months,  the  frame  consisted  of  one  of  those 
small  wooden  hoops  which  are  used  in  em- 
broidering, which  I  got  from  my  sister,  by 
either  force  or  stealth.  The  scale  was  cor- 
rectly laid  out,  and  probably  the  instrument 
was  capable  of  fairly  accurate  measurements, 


but  at  the  time  I  built  it  I  did  not  know  what 
a  tangent  was  nor  what  part  it  played  in  the 
operation  of  the  galvanometer. 

Our  great  problem  was  a  source  of  current 
supply,  for  when  our  dry  cells  ran  down  we 
frequently  had  no  money  with  which  to  buy 
new  ones.  A  dry  cell  cost  a  quarter,  equiva- 
lent to  five  strawberry  frappes  or  the  same 
number  of  visits  to  the  nickelodeon,  as  the  then 
primitive  movie  theatres  were  called.  Some- 
times we  were  able  to  get  more  or  less  ex- 
hausted cells,  from  garages  or  electricians,  at 
a  much  reduced  rate,  and  various  householders 
in  the  neighborhood,  sympathizing  with  our 
endeavors,  gave  us  their  warn-out  batteries. 
These  we  attempted  to  rejuvenate  with  in- 
jections of  vinegar,  salt  water,  and  on  one 
occasion  I  was  inspired  to  try  beer  (5  per  cent, 
alcohol  in  1909)  but  the  improvement  was 
not  worth  the  beer. 

And  now,  at  the  age  of  about  thirteen,  we 
became  telegraphers.  Our  communication 
was  neither  by  radio  nor  over  a  wire,  for  at 
first  we  had  only  one  instrument,  which  was 
communally  owned  and  operated.  The  key 
and  sounder  were  separate,  and  constructed 
mainly  of  wood,  with  a  few  screws  and  wires 
for  the  current-carrying  and  sounding  parts. 
For  example,  the  lever  and  the  anvil  of  the 
sounder  were  both  of  wood,  whittled  from  a 
cigar  box,  but  screws  were  provided  at  the 
proper  points  in  order  to  obtain  the  proper 
clicking  sound.  The  sounder  magnets  were 
taken  from  a  bell,  of  course,  and  likewise  the 
armature.  The  difficulty  of  learning  the 
Morse  code  dampened  the  ardor  of  all  except 
some  four  of  the  group  of  urchins  who  had 
originally  started  out  to  become  electricians. 
There  was  no  drama  in  sitting  in  a  cellar  and 
making  stupid  clicking  noises  for  hour  on  hour. 
We  were  considered  to  be  obsessed  by  a  dull 
and  malignant  spirit,  and  in  fact  we  did  go 
around  telegraphing  to  each  other  by  mouth 
signals  of  the  dah-dit-dah  variety,  and  many 
people  took  us  for  idiots  incapable  of  intelligi- 
ble speech.  Even  in  school  we  practised  in 
solitude  by  clicking  pencils  between  our  teeth 
or  portions  of  the  desks.  Occasionally  we 
would  go  down  to  a  near-by  railroad  station 
and  hang  around  the  ticket  office,  listening  to 
the  sounders  of  the  railroad  telegraph,  but  the 
speed  was  much  too  great  for  us  and  we  only 
caught  a  letter  now  and  then.  We  looked  with 
envy  at  the  station  master  and  wondered  if 
we  should  ever  own  a  real  telegraph  sounder 
of  shiny  brass,  mounted  in  a  mahogany  reson- 
ator, with  a  tin  tobacco  can  jammed  between 
the  anvil  and  the  wood  to  give  each  sounder  a 


When  "th"  Gets  on  the  Air 


357 


characteristic  tone.     As  yet  all  we  were  able 
to  get  was  the  tobacco  can. 

It  was  not  long  before  we  were  able  to  secure 
a  few  hundred  feet  of  annunciator  wire,  and  to 
build  additional  wooden  keys  and  sounders, 
enabling  us  to  connect  our  several  homes  and 
to  spend  our  evenings  telegraphing  instead  of 
doing  our  lessons.  By  that  time  we  were  good 
for  about  12  words  a  minute  in  American 
Morse,  with  its  spaced  characters.  Conti- 
nental Morse,  save  perhaps  in  cable  traffic, 
was  not  yet  recognized  in  the  United  States. 
Even  radio,  in  this  country,  started  in  Amer- 
ican Morse  and  continued  so  for  several  years. 
As  yet  we  were  not  interested  in  radio.  We 
were  aware  that  such  a  thing  existed — 
"wireless,"  it  was  called,  but  no  one  knew 
anything  definite  about  it.  It  was  unknown, 
remote,  nebulous,  no  doubt  costly;  we  regarded 
it  somewhat  as  a  grocer  thinks  of  celestial 
mechanics — not  very  pertinent  to  the  practical 
business  in  hand. 

(To  Be  Continued) 

I I 

|    Microphone  Miscellany  j 


"Irate  Listener" 


ON  MARCH  i4th,  early  in  the  evening, 
wj'z  in  New  York  was  rebroadcasting 
a  concert  from  2LO,  London,  the  stuff 
going  from  the  Savoy  to  5\x,  Chelmsford,  by 
wire  line,  thence  over  the  Atlantic  on  1,600 
meters,  to  be  picked  up  at  the  Radio  Corpora- 
tion experimental  station  at  Belfast,  Maine, 
retransmitted  on  112  meters,  picked  up  again 
at  the  laboratories  adjacent  to  Van  Cortlandt 
Park,  New  York,  amplified,  and  sent  down  to 
/Eolian  Hall  on  42nd  Street  by  wire  line, 
where  finally  it  modulated  its  last  carrier  and 
could  be  heard  by  any  one  within  range  of 
wjz. 

While  the  congratulatory  telegrams  were 
pouring  in,  a  listener  called  up  on  the  tele- 
phone, gave  his  name,  and  with  unrestrained 
indignation  spoke  his  mind,  as  follows: 

"I  listen  to  your  station  often  and  enjoy 
your  programs  .  .  .  but  your  quality 
seems  different.  It  isn't  my  set,  other  stations 
sound  all  right.  There  must  be  something  the 
matter  with  your  microphone.  Why  don't 
your  engineers  get  on  the  job?  Don't  they 
know  what  they're  sending  out?" 

Finally  the  studio  attendant  who  had  an- 
swered the  telephone  managed  to  get  in  a 
word,  a  great  light  burst  on  the  complaining 


BCL,  and  with  a  single  Oh!  he  hung  up  the 
receiver. 

THINGS   I   AM  TIRED  OF  ON   THE   RADIO 

WIOLET  ray  machines. 
»         Hearing  middle  aged  sopranos  coyly 
singing  "The  Lilac  Tree,"  and,  worse,  seeing 
them  do  it. 

Publicity  stunts  in  which  some  self-styled 
musical  genius  broadcasts  on  200  watts  to  his 
loving  wife  and  children  seated  at  the  receiver 
in  Tibet,  8,000  miles  away. 

Radio  critics  who  turn  out  stuff  like  this: 

Nature,  in  a  mjelting  mood  last  night,  was  not 
generous  to  radio.  Languorous  air  made  thick  the 
voices  of  soprano  and  barytone  and  injected  squeaks 


We 


Around.  iKe  ieledrapli  office 


into  the  tender  violin.  Though  they  brightened  as 
the  night  waxed  cooler,  the  effects  were  most  lugu- 
brious early  in  the  evening. 

THOSE    ELUSIVE   TH's 

THE  best  broadcasting  station  in  the 
world,  and  the  finest  receiving  set  and 
loudspeaker,  can't  as  yet  reproduce  the  conso- 
nant combination  tb  to  perfection.  Thus 
when  the  announcer  of  a  New  York  station, 
broadcasting  from  the  annual  radio  show  and 
convention  at  the  Hotel  Pennsylvania,  told 
the  radio  audience,  "The  grand  ballroom  is  all 
filled  with  booths,  that  innocent  word  came  out 
on  the  air  as  boo^e,  an  altogether  unintended 
indictment  or  compliment. 

EVERYBODY    BELIEVES    IT,    BUT    IT'S   NOT    SO 

COMEBODY— probably  Artemus  Ward— 
**?  said  that  it  isn't  the  things  we  don't 
know  that  hurt  us,  but  the  things  we  know 
that  aren't  so.  A  few  examples  in  the  radio 
art: 

That  a  coupled  circuit  receiver  cannot  radiate. 


358 


Radio  Broadcast 


at  tteir  detut  all  ariists  are  panicky 

That  broadcasting  stations  have  a  decrement. 

That  generators  in  a  broadcast  transmitter  always 
result  in  a  noisy  carrier  and  that  the  only  remedy  is 
to  buy  a  bank  of  storage  batteries. 

That  artists  appearing  before  the  microphone  for 
the  first  time  are  all  in  a  very  panicky  state  and 
about  ready  to  faint  with  fright. 

COMFORT    FOR   THE    ANNOUNCERS 

CVERYBODY,  including  myself,  takes 
J— '  pleasure  in  harassing  the  announcers  for 
their  lapses,  mistakes  in  diction,  and  whatnot, 
in  spite  of  the  knowledge  that  they  have  to 
make  up  what  they  say  as  they  go  along, 
admittedly  no  easy  task.  One  would  think, 
sometimes,  that  only  announcers  make  mis- 
takes. To  disprove  that  theory,  may  we  not 
present  the  first  sentence  of  an  announcement 
sent  out  by  the  wealthy  and  influential  New 
York  section  of  a  national  electrical  organi- 
zation 

"There  has  been  procured  for  our  next  meet- 
ing two  speakers  of  prominence  in  the  en- 
gineering and  business  world,  who  will 
talk.  .  .  ." 

Have  the  stenographer  of  the  honorable 
secretary  of  the  section  no  knowledge  of  Eng- 


lish   grammar?     Have   she   no   proof-reader? 
Have    .     .     ." 

What  About  a  Broadcasters' 
Association? 

IN  THE  United  States  and  Canada  there 
are  about  600  broadcasting  stations,  with 
staffs  numbering  from  one  person  up  to 
sixty.  Probably  the  average  personnel  is 
around  four.  That  would  make  a  total  of 
about  2400  professional  broadcasters. 

There  were  not  that  many  radio  engineers  in 
the  world  when  the  Institute  of  Radio  Engi- 
neers was  founded  in  1912,  and  that  was 
antedated  by  five  years  by  the  venerable  So- 
ciety of  Wireless  Telegraph  Engineers.  The 
technicians  among  the  broadcasters  are  largely 
affiliated — and  those  who  are  not,  should  be — 
with  the  Institute  of  Radio  Engineers.  But 
broadcasting,  after  all,  is  a  special  occupation, 
and  it  is  probable  that  before  long  the  broad- 
casters, both  program  officials  and  technical 
men,  will  feel  the  need  for  some  form  of 
association  of  their  own.  In  two  or  three  or 
five  years  broadcasting  will  have  got  over  its 
growing  pains,  and  the  energy  for  founding 
such  a  body  will  become  available.  Some  of 
the  owners  of  broadcasting  stations  already 
have  an  organization,  but  what  we  are  think- 
ing of  is  an  association  of  the  men  who  actually 
book  the  programs,  make  the  announcements, 
and  turn  the  knobs,  and  whoever  may  be  in- 
terested in  their  work. 

In  the  meantime,  our  hope  is  that  this 
department  of  RADIO  BROADCAST  will  serve  as  a 
broadcasters'  forum,  where  all  the  practition- 
ers and  friends  of  the  art  will  have  a  chance, 
not  only  to  watch  the  general  flux  of  projects 
and  ideas,  but  also  to  express  thoughts,  contri- 
bute opinions,  and  to  vent  feelings  which,  in  the 
present  adolescence  of  the  industry,  frequently 
require  such  relief. 


AN  EFFICIENT  RECEIVER  FOR  SHORT  WAVES 


of  the  best  known  experimenters  in  the  country,  George  j.  Eltz,  jr., 
is  developing  a  receiver  for  use  on  very  short  waves.  The  circuit  errr 
ploys  super-regeneration — a  highly  efficient"  receiving  method  on  the  very 
high  frequencies.  Broadcast  listeners  who  want  to  hear  the  short  wave 
broadcasting  now  taking  place  at  several  large  American  stations,  and  trans- 
mitting  amateurs  will  find  Mr.  Eltz'  receiver  an  excellent  addition  to  their 
equipment.  It  will  be  described  in  an  early  number 


How  to  Be  a  Good  Radio 
Neighbor 

PART  ONE:   WHY  YOUR  RECEIVER  SQUEALS 

Helpful  and  Informative  Discussion  by  Two  Radio  Authorities  on  the 
Menace  of  Squealing  Receivers — How  to  Tell  What  Receivers  Oscillate  into 
the  Antenna  and  How  to  Prevent  that  Oscillation — Practical  Instruction  on 
How  to  Operate  Your  Receiver  Without  Annoying  Your  Radio  Neighbors 

BY  JOHN  V.  L.  HOGAN 

Consulting  Radio  Engineer 


GENERALLY  speaking,  there  are 
two  types  of  whistling  interference 
heard  in  radio  receivers.  One 
type  is  the  result  of  two  broad- 
casting stations  sending  simultaneously  at 
wave  frequencies  (wavelengths)  that  are  too 
close  together.  Their  waves  react  on  each 
other  and  produce  a  more  or  less  uniform 
whistling  note,  often  of  very  high  pitch,  in  all 
the  radio  receivers  within  range.  This  sort 
of  interference  is  somewhat  bothersome  when 
listening-in  on  the  present  thickly  populated 
broadcast  wave  bands  It  is  daily  growing  of 
less  importance,  and  for  the  moment  we  need 
not  consider  it  further,  although  it  will  be  dis- 
cussed in  a  future  article  of  this  series. 

The  second  type  of  whistling  interference  is 
caused  by  radiating  receivers,  or,  in  other 
words,  by  receiving  stations  that  are  so 
designed  and  so  operated  that  they  act  as 
small  radio  transmitters.  This  kind  of  inter- 
ference is  exceedingly  troublesome  and  breaks 


FIG.    I 

The  old   time    single-circuit   regenerative  receiver 
which  is  the  worst  offender  where  radiation  is  con- 
cerned.    When    in    an    oscillating    condition    this 
circuit  is  a  very  effective  transmitter 


up  a  great  deal  of  broadcast  reception.  It  is 
particularly  a  nuisance  in  localities  where  there 
are  many  radio  receivers  close  together,  as  in 
the  cities;  but  even  in  the  country  this  squeal- 
ing and  whistling  interference  often  prevents 
satisfactory  receiving. 

It  is  safe  to  say  that  nearly  every  broadcast 
listener  has  heard  the  chirp  or  whistle  of  rapidly 
varying  pitch  that  is  the  mark  of  this  kind  of 


FIG.    2 

The  variocoupler-variometer  circuit  also  is  a  gener- 
ator of  squeals.  When  in  an  extremely  sensitive 
oscillating  condition  it  possesses  the  ability  to  pass 
energy  into  the  antenna  circuit  which  creates  in- 
terference in  neighboring  receivers 


interference.  Many  listeners,  however,  do  not 
know  what  causes  the  troublesome  whistles 
and  many  do  not  know  that  their  own  receivers 
may  be  adding  somewhat  to  the  nightly  din 
of  squawks  and  squeals. 

WHY   WHISTLES   OCCUR 

THE  reason  for  these  chirps  and  whistles  is 
not   known    to  many  radio  listeners,  al- 
though the  scientific  basis  of  the  action  is  not 
complicated.     It    is    merely    another    mani- 


360 


Radio  Broadcast 


^\AA  — 

i      t  ~^~     ^ 

•H-    jf. 


THE    INCORRECT   WAY 

Of  connecting  a  variocoupler.     Here  the  coupler  is  connected  to  a  detector  circuit  with  the  rotor  coil 
used  as  a  tickler  to  produce  regeneration.     While  this  circuit  is  more  sensitive  than  the  one  illustrated  be- 
low, it  is  quite  broad  in  tuning  and  is  an  excellent  transmitter  of  squeals 


festation  of  the  common  phenomenon  of 
"beats"  that  is  frequently  noted  in  acoustics. 
You  may  have  observed  that  when  two  musical 
tones  of  neighboring  pitch  are  sounded  simul- 
taneously, the  combined  tone  flutters  in  in- 
tensity. This  happens  because  the  two  sound- 
waves interact  or  "beat"  together,  and  the 


rapidity,  of  the  flutter  is  always  equal  to  the 
difference  in  frequency  of  the  two  sounds. 
Thus,  if  two  organ  pipes  of  32  and  36  vibrations 
per  second,  respectively,  are  blown  at  the  same 
time,  the  sound  heard  will  grow  strong  and 
weak  (or  flutter  in  strength)  four  times  per 
second. 


THE    CORRECT    WAY 

A  standard  variocoupler  consisting  of  a  primary  and  secondary  winding  connected  to  the  other  essentials 
of  the  circuit  in  a  way  that  will  not  cause  the  outlawed  radiation.     Tuning  is  accomplished  by  the  vari- 
able condenser  and  the  switch  making  contact  with  the  switch  points  indicated 


How  to  Be  a  Good  Radio  Neighbor 


361 


FIG.    3 

The  threc'circuit  tuner  consists  of  primary,  second- 
ary, and  tickler  coils.  Radiation  may  be  somewhat 
diminished  by  employing  a  primary  coil  having 
only  a  few  turns,  loosely  coupled  to  the  secondary 


In  the  same  way,  if  two  radio  waves  or  two 
radio  frequency  currents  of  somewhat  different 
frequencies  are  allowed  to  interact  upon  each 
other  they  will  produce  beats.  Thus  a  carrier 
wave  from  station  WEAF,  at  the  frequency  of 
610,000  cycles  per  second,  might  interact  with 
the  carrier  wave  from  another  transmitter 
at  611,000  cycles  per  second  to  produce  1000 
beats  per  second.  When  picked  up  and  recti- 
fied, such  beating  waves  would  produce,  in  the 
listening  telephones  or  loud  speaker,  a  note  of 
1000  per  second  pitch,  corresponding  approxi- 
mately to  the  second  C  above  middle  C  on  the 
musical  scale.  Any  change  in  frequency  of 
either  beating  wave  would  produce  a  change  in 
the  pitch  of  the  beat  note,  since  this  must  al- 
ways equal  the  difference  in  the  two  wave 
frequencies. 

In  the  same  way,  a  carrier  wave  from  any 
broadcasting  station  will  beat  with  waves  or 
currents  produced  by  any  self-oscillating  re- 
ceiving set.  The  frequency  of  the  oscillations 


in  the  receiver,  and  of  the  waves  that  those 
oscillations  will  send  out  if  they  are  allowed 
to  get  into  the  receiving  antenna,  depends 
upon  the  tuning  adjustments  of  the  receiving 
set.  As  the  tuning  knobs  are  turned,  the 
frequency  changes.  Consequently  the  pitch 
of  the  beat-note  produced  also  changes,  and 
this  is  what  gives  rise  to  the  bird-like  chirps 
and  whistles  that  are  so  often  heard. 

If  you  have  a  radio  receiver  of  any  of  the 
types  that  can  be  made  to  cause  oscillations 
in  the  antenna  circuit,  your  set  is  one  that  may 
interfere  with  your  radio  neighbor's  reception. 
The  receivers  that  can  be  made  to  generate 
antenna  circuit  oscillations,  and  thus  to  inter- 
fere with  receiving  throughout  the  neighbor- 
hood, are  probably  made  and  used  in  larger 


FIG.    4 

A  blocking  tube  circuit  which  was  fully  described  in 
the  March  and  May,  1924,  issues  of  RADIO  BROADCAST 


FIG.    5 

Is  the  recent  circuit  contribution  to  radio  by  Roy  A. 
Weagant.  A  description  of  the  additional  ap- 
paratus and  its  method  of  use  is  contained  in  the  text 


numbers  than   the   non-radiating  and   hence 
non-interfering  sets. 

TYPES    OF    RADIATING    RECEIVERS 

NEARLY,  if  not  absolutely,  all  of  the  inter- 
ference-producing receivers  'are  of  the 
simple  regenerative  type,  though  more  com- 
plicated outfits  such  as  the  super-heterodyne, 
when  used  with  an  antenna,  may  cause  this 
trouble.  They  may  be  of  single-circuit 
double  circuit,  triple-circuit  or  of  any  other 
design;  the  offending  set  may  be  of  the  unneu- 
tralized  radio-frequency  amplifier  or  reflex 
type.  Many  of  these  will  generate  oscillations 
in  the  antenna  circuit  and  produce  interfer- 
ence if  not  specifically  designed  otherwise, 
particularly  when  they  are  not  correctly 
handled  by  the  user. 

There  are  only  two  ways  to  stop  the  whist- 
ling interference  produced  by  oscillating  re- 
ceivers. The  first  and  simplest  way  is  simply 


362 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 
A   THREE-CIRCUIT  TUNER 

Which  illustrates  very  well  the  method  of  obtaining  very  loose  coupling  between  primary  and  secondary 
to  reduce  the  possibilities  of  radiation.    The  parts  are  labelled  respectively  T,  tickler,  S,  secondary,  and 

P,  primary 


to  tune  and  manipulate  your  own  receiver 
properly,  and  to  teach  your  radio  friends  to 
do  the  same  with  theirs.  A  little  work  among 
your  near-by  radio  listeners  will  produce 
wonderful  results,  for  no  one  wants  to  trouble 
his  friends.  Ordinarily,  by  a  little  coopera- 
tion, a  neighborhood  can  be  relieved  of 
the  strongest  receiver-produced  whistles  quite 
easily.  The  second  and  more  difficult  method 
is  to  arrange  your  receiver  so  that  it  cannot 
produce  oscillations,  or  so  that  when  it  does 
oscillate,  the  currents  will  not  reach  the  an- 
tenna. By  preventing  the  generation  of 
oscillations  in  your  antenna  you  prevent  the 
radiation  of  interfering  waves. 

IS    MY    RECEIVER   OSCILLATING? 

MANY  of  you  are  perhaps  wondering  how 
you  can  tell  whether  or  not  your  own 
receiver  is  ever  a  source  of  neighborhood  inter- 
ference. There  is  one  simple  rule  that  answers 
this  question:  //,  when  turning  your  wavelength 
or  tuning  control  knob,  you  hear  a  whistling  note 
in  your  telephone  or  loud  speaker  and  if,  also, 
you  can  change  the  pitch  of  that  note  by  turning 
the  tuning  knob,  you  are  making  interference  for 
all  the  listeners  who  live  near  you,  unless  your 


receiver  is  so  designed  that  it  will  keep  the  oscilla- 
tions out  of  the  antenna  circuit.  Whistles 
whose  pitch  you  cannot  control  do  not  come 
from  your  set,  and  you  need  not  blame  your- 
self for  causing  them.  On  the  other  hand,  if 
you  have  no  blocking  tube  in  your  set,  when- 
ever you,  hear  a  whistle  and  find  that  you  can 
vary  its  pitch  by  moving  your  tuning  control, 
you  may  be  sure  that  all  your  neighbors  who 
are  listening  to  the  same  station  are  hearing 
the  same  whistle.  Thus  you  are  not  only 
spoiling  your  own  reception  but  also  theirs. 

Unless  you  use  a  blocking  tube,  the  wise  and 
considerate  thing  to  do  is  to  keep  your  receiver 
adjusted  so  that  it  is  not  in  an  oscillating  con- 
dition. Whenever  you  hear  a  whistle  of  this 
kind,  stop  your  set  from  oscillating.  If  you 
will  follow  that  rule  and  will  impress  its  im- 
portance upon  your  radio  friends,  you  will 
find  that  great  reductions  in  the  amount  of 
whistling  interference  can  be  made. 

The  article  which  follows,  by  Dr.  A.  N.  Gold- 
smith, gives  a  detailed  description  of  how  to  tune 
without  permitting  your  receiver  to  radiate 
and  so  show  you  how  to  protect  your  neigh- 
bors from  interference  caused  by  the  oscilla- 
tions of  your  set. 


How  to  Be  a  Good  Radio  Neighbor 

PART   TWO 
Operating  Your  Radiating  Receiver  Without  Squeals 

BY  DR.  ALFRED   N.   GOLDSMITH 

Chief  Broadcast  Engineer,  Radio  Corporation  of  America 


363 


EVERY  time  your  receiver  produces  a 
squeal  in  your  own  telephones  or  loud 
speaker,  or  every  time  it  is  in  what  is 
called  the  "oscillating  condition,"  you  are 
spoiling  your  neighbor's  enjoyment  of  his  con- 
cert and  annoying  people  who  have  done  you 
no  harm.  (There  is  but  one  exception  to  this 
rule,  and  that  is  the  new  non-radiating  regener- 
ative and  non-radiating  super-heterodyne  re- 
ceiver, which  is  specially  built  at  the  factory 
so  that  it  will  not  radiate  appreciably  when 
used  in  accordance  with  the  manufacturer's 
instructions.  The  definite  "non-radiating 
guarantee"  of  a  reputable  manufacturer  re- 
lieves the  user  of  worry  relative  to  this  point). 
May  I  make  an  earnest  plea  to  you,  to  apply 
the  best  possible  rule  of  conduct,  and  to  do 
to  other  broadcast  listeners  only  what  you 
would  like  them  to  do  to  you?  Would  you 
like  to  be  interrupted  by  a  loud  noise  while 
you  were  listening  to  a  beautiful  selection  on 
the  fine  receiver  which  you  bought  or  built 


recently,  and  which  represents  toil  and  ex- 
pense? Would  you  want  an  evening's  party 
ruined,  after  your  guests  had  assembled  to 
hear  a  particular  concert  which  they  were  en- 
joying, by  some  inconsiderate  outsider  who, 
instead  of  being  a  good  neighbor,  is  really  a 
neighborhood  nuisance?  Surely  you  would 
not  want  either  of  these  things.  Then  re- 
member that  it  is  up  to  you  to  consider  other 
people. 

HOW  TO  TUNE   YOUR   RECEIVER 

BUT,"  you  may   rightly  ask,  "how  am  I 
to  avoid  bothering  my  neighbor?    What 
must  I  do?    No  one  has  yet  given  me  definite 


RADIO  BROADCAST  Photograph 
THE    INCORRECT   WAY   OF   TUNING 

A  regenerative  receiver.     Rotating  the  tickler  or  regenerative  dial  causes  bird-like  tweets  to  be  radiated 
from  your  antenna.     The  effect  on  the  neighbors  is  well  known 


364 


Radio  Broadcast 


instructions."  And  it  is  to  give  you  a  partial 
answer  to  your  proper  and  reasonable  ques- 
tions that  this  article  is  written.  In  it,  a  few 
simple  rules  are  set  forth,  which,  if  consistently 
followed,  will  make  your  neighborhood  cleaner 
and  quieter  in  the  radio  sense,  and  enable  you 
and  everyone  else  to  be  reasonably  sure  of  an 
evening's  entertainment  whenever  you  want 
it  by  radio.  Of  course,  the  best  and  simplest 
way  is  to  use  a  guaranteed  non-radiating  re- 
ceiver. The  following  rules  apply,  however, 
to  receivers  which  can  radiate. 

1.  Find  out  what  adjustment,  or  adjust- 
ments, on  your  set  make  it  oscillate.     By  this 
I  mean,  turn  the  knobs  of  your  set  experi- 
mentally until  you  find  that  knob  (or  those 
knobs)  which,  as  you  turn  them  past  a  cer- 
tain point,  cause  the  well  known  squeal  or 
tweeting  birdlike  sound  in  your  telephones  or 
loud   speaker.     Usually  this  knob  is  labeled 
Tickler,  or  Amplification,  or  Volume  Control, 
or  Loud-Soft  or  some  such  term.     In  some  sets 
it  is  even  marked  Potentiometer.     In  other 
sets,  there  will  be  several  knobs  which  cause 
the  trouble  of  squeals,  including  the  filament 
current  control  knob. 

In  all  this,  I  assume  that  you  are  not  using 
an  ordinary  super-heterodyne  or  super-regener- 
ative set  on  an  antenna.  If  you  are,  all  I  can 
say  is,  please  don't.  Put  that  set  on  a  loop 
right  away.  If  it  does  not  work  on  a  loop,  it 
is  so  badly  designed  and  built  that  it  had  best 
be  replaced  by  some  other  set.  Any  one  who 
deliberately  uses  a  set  which  is  continually 
oscillating — like  the'ordinary  super-heterodyne 
or  super-regenerative  sets — on  an  antenna,  is 
either  ignorant  of  what  he  is  doing  or  devoid 
of  consideration  for  his  neighbor.  In  the 
radio  sense,  he  is  a  public  nuisance. 

Assuming,  then,  that  you  have  found  the 
knobs  which  cause  your  set  to  squeal,  try  to 
carry  out  the  next  suggestion. 

2.  a)  Get  a  clear  idea  of  the  settings  of  each 
of  these  knobs  where  the  squealing  begins,  for 
the  stations  to  which  you  generally  listen. 

b)  Then  mark  with  a  pencil  the  point  on 
the  scale  of  each  knob  where  the  trouble  be- 


c)  To  make  it  still  clearer,  a  small  piece  of 
white  paper  may  be  pasted  next  to  the  scale 
with  its  left  hand  edge  at  the  point  marked  by 
the  pencil. 

d)  The  pencil  or  paper  mark  on  the  scale 
then  represents  the  danger  mark.     Whenever 
you  approach  it,  you  are  coming  nearer  and 
nearer  to  making  trouble  for  others,  and  you 
should  proceed  with  the  utmost  caution  in  so 
doing.     (There  are  some  sets  for  which  this 


plan  will  not  work  because  the  settings  of  the 
knobs  are  too  complicated  and  too  variable. 
But  it  will  work  particularly  well  for  many 
of  the  simpler  sets.) 

3.  In  using  your  receiver,  develop  the  habit 
of  slowing  up  the  knob-turning  process  as  you 
get  near  the  danger  mark.     There  are  people 
who  twist  the  Tickler  knob  around  until  they 
are  sure  that  the  set  will  produce  squeals,  and 
then  they  throw  the  wavelength  control  knobs 
for  selecting  a  station,  back  and  forth  rapidly, 
thus  producing  a  multitude  of  howls  in  other 
people's  receivers.     This  is  a  vicious  way  of 
picking  up  a  station.     If  such  people  knew 
what  their  neighbors  thought  of  them,  they 
would  be  astonished.     Why  store  up  ill  will 
and  discourage  other  people  in  their  attempts 
to  listen?     Don't  do  it,  but  give  them  a  chance 
by  picking  up  only  such  stations  as  you  can 
get  WITHOUT  HAVING  THE  KNOBS  IN 
THE  POSITION  WHERE  SQUEALS  CAN 
BE  PRODUCED.     I  know  that  this  means 
very  careful  work  in  handling  the  set  at  times, 
particularly  for  receiving  other  than  local  sta- 
tions, but  it  is  truly  worth  while.     Get  into 
the  habit,  and  you  will  be  astonished  how  easy 
it  will  soon  become. 

4.  If  you  have  the  kind  of  a  set  which  pro- 
duces squeals  (and  too  many  people  have), 
be  content  with  a  little  less  distance  rather 
than  making  so  much  trouble  in  the  air.     If 
getting  a  very  remote  station  means  a  great 
deal  of  fussing  and  adjustment  and  a  lot  of 
squeals,  you  had  better  let  it  go,  and  listen  to 
nearer  stations.     You  will  be  a  neighborhood 
blessing  if  you  do. 

INSTRUCTIONS    FOR   NEIGHBORLY    RADIO 

TO  PUT  it  differently,  don't  overwork  your 
set.  Keep  away  from  burning  the  fila- 
ments of  the  tubes  too  brightly  or  increasing  the 
plate  battery  voltage  or  altering  the  set  con- 
struction as  received  from  the  factory,  or  doing 
any  of  the  other  things  which  may  possibly 
give  a  little  more  distance,  but,  on  the  other 
hand,  make  you  a  pest.  If  you  have  a  re- 
ceiver which  does  not  radiate  (and  there 
are  some  excellent  varieties  now  on  the 
market),  leave  its  construction  severely  alone. 
It  left  the  factory  in  proper  shape  and  if  you 
meddle  with  it,  you  are  bound  sooner  or  later 
to  put  it  out  of  order. 

It  is  hoped  that  there  is  not  too  much  of  the 
sermon  in  this  article.  But  it  is  so  simple  a 
matter  to  avoid  producing  squeals  that  refus- 
ing to  take  the  slight  trouble  necessary  to 
avoid  them  is.likethrowing  banana  peels  on  the 
sidewalk.  It  may  be  a  natural  and  thoughtless 


How  to  Be  a  Good  Radio  Neighbor 


365 


act,  but  the  man  whose  leg  is  broken  when  he 
slips  and  falls,  knows  that  you  have  been 
guilty  of  criminal  carelessness.  The  person 
who  produces  radio  interference  deliberately 
is  not  only  violating  the  law  of  the  land  but  is 
also  devoid  of  the  spirit  of  community  help- 
fulness. Broadcast  listeners  of  the  United 
States,  give  an  extra  minute  and  a  little 
thought  to  your  neighbors  when  tuning  your 
set,  and  urge  them  to  do  the  same  for  you. 


THE  WEAGANT  RADIATION   ELIMINATOR 

Early  this  year  Roy  A.  Weagant,  Chief 
Engineer  of  the  Deforest  Radio  Company,  re- 
leased to  the  public  the  circuit  diagram 
showing  the  use  of  a  small  choke  coil  and  con- 
denser in  regenerative  receivers  for  eliminating 
radiation.  The  circuit  is  that  of  Fig  5.  The 
heavy  lines  show  where  these  two  pieces  of 
apparatus  are  inserted  in  such  a  circuit.  The 
usual  antenna  circuit  consisting  of  the  antenna, 
primary  coil,  and  ground  is  not  employed,  the 
antenna  coil  being  eliminated  with  the  antenna 
connected  to  the  grid  of  the  audio-frequency 
tube  and  the  ground  connected  to  the  negative 
side  of  the  A  battery. 


The  theory  of  operation  as  explained  by  the 
Deforest  Company  is  as  follows: 

It  will  be  seen  from  the  circuit  that  the  in- 
coming signal  is  impressed  upon  the  grid  of 
the  audio-frequency  tube  instead  of  the  grid 
of  the  detector  tube.  This  audio-frequency 
stage  acts  as  a  radio-frequency  amplifier  re- 
sulting in  radio-frequency  variations  in  its 
plate  circuit.  The  insertion  of  the  choke  coil 
L2  produces  a  radio-frequency  potential  which 
is  passed  to  the  grid  of  the  detector  tube 
through  the  condenser  C.  Inasmuch  as  this 
condenser  has  a  small  value  of  capacity  and 
the  grid  and  plate  capacity  of  an  audio- 
frequency is  very  small,  any  oscillation  of  the 
detector  tube  causes  only  a  negligible  amount 
of  radio-frequency  current  to  be  passed  into 
the  antenna.  The  capacity  of  condenser  C 
is  .000025  mfds.  and  the  choke  coil  has  a  very 
high  inductance.  It  is  composed  of  many 
small  coils  connected  in  series.  Each  coil 
has  a  natural  wavelength  some  place  in  the 
broadcast  wavelength. — THE  EDITOR 


RADIO  BROADCAST  Photograph 
THE    CORRECT   WAY    OF    TUNING 

A  regenerative  receiver.  Here,  the  tickler  dial  is  turned  nearly  to  zero.  The  tuning  is  mainly  accom- 
plished with  the  condenser  dial,  the  first  one  on  the  left.  Once  a  station  has  been  received,  the  regenera- 
tive dial  may  be  advanced,  but  not  beyond  the  point  where  squeals  are  produced.  In  some  receivers,  the 
left  dial  is  the  tickler  and  the  right  the  antenna  tuning  dial.  A  glance  inside  the  cabinet  will  usually 

make  this  point  clear 


liiiiiiiiiiiiiimiiiiiiiiiiiiiinii 


For  the  Radio  Beginner 

How  to  Make  a  Radio  Receiver  for  $1.82 


IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIH 


E  WHO  have  played  and  worked  at  radio  for  many  years  are  perhaps 
prone  to  neglect  the  thousands  that  every  month  approach  their  first 
radio  experiments.  Beginners  are  apt  to  be  discouraged  by  the  complexities 
which  are  life  and  nourishment  to  the  average  fan,  and  to  which,  as  a  popular 
radio  magazine,  we  have  given  the  most  attention.  We  have,  however,  pub- 
lished an  occasional  article  for  the  less  advanced  enthusiast,  and  the  reception 
which  has  been  tendered  them,  has  encouraged  us  to  inaugurate  a  department, 
devoted  to  the  education  and  interest  of  the  radio  beginner.  He  will  find  here 
articles  on  the  construction  of  simple  apparatus  built  from  inexpensive  -ma- 
terial. Particular  attention  will  be  paid  to  the  possibilities  of  five-and- 
ten-cent  store  parts. 

The  editor  will  he  pleased  to  hear  from  readers  to  whom  this  department 
is  dedicated,  telling  him  what  they  would  like  to  see  in  it,  the  problems  they 
would  like  discussed,  and  the  sets  they  wish  to  build.  We  shall  gladly  con- 
sider manuscripts  and  short  notes  dealing  with  the  design  and  construction 
of  simple  apparatus  and  shall  pay  for  acceptable  material  at  our  usual  rates. 

— THE  EDITOR. 


RADIO  to-day  is  neither  an  expensive 
nor  a  complicated  proposition,  unless 
the  enthusiast  himself  desires  to  make 
it  so.  The  advent  of  the  five-and-ten- 
cent  store  into  the  radio  field  has  cut  the  cost 
of  almost  all  parts,  and  these,  arranged  into 
simple  circuits,  present  the  logical  start  for 
the  radio  beginner's  first  experiment. 

The  crystal  receiver  we  are  describing  was 
constructed  entirely  of  such  items.  They 
can  be  duplicated  in  almost  any  of  the  five- 
and-ten-cent  stores  scattered  throughout  the 
United  States  and  Canada,  for  one  dollar  and 
eighty-two  cents. 

THE    PARTS   FOR  THE    CRYSTAL    RECEIVER 

'IPHE  parts  used  in  the  construction  of  this 
*  receiver  are  photographed  before  assem- 
bly in  Fig.  i. 

No.    i     Eleven   plate   variable   condenser,  * 

built  up  of  parts;  totalling       :     .  $0.77 

No.    2     Dial .10 

No.    3     Crystal  detector  stand 10 

No.    4     Fixed  condenser,  .001  mfd.  capacity  .10 
No.    5     Crystal    for    detector    (shown    in 

detector  stand) .25 

No.    6    Lightning  arrester .10 

No.    7     Switch  lever  with  knob  and  bushing  .10 

No.    8     Four  binding  posts .10 


No.    9    Winding  form  cut  from  pasteboard 
No.  10    Spool  of  No.  24  enameled  wire      .         .10 
No.  ii     Switch  taps  (3  for  jc.)  ....         .10 
Cigar  Box      

Total       .     .     .     .     $1.82 

The  lettering  beside  some  of  the  parts, 
indicates  the  abbreviation  by  which  they  are 
designated  on  the  diagram  Fig.  2. 

Extra  equipment,  if  not  on  hand,  may  be 
added  to  the  above  list  as  follows: 

Antenna  Wire 

Insulators . 

Telephone  receivers 

This  brings  the  grand  total  for  complete  re- 
ceiving equipment  to  $5.52. 

If  it  is  desired,  a  panel  and  cabinet  can  be 
substituted  for  the  cigar  box.  This  adds 
considerably  to  the  cost.  The  writer  preferred 
the  box  arrangement  because  it  simplified  con- 
struction, both  in  the  drilling  or  working  of  the 
panel  material  and  in  the  elimination  of  more 
or  less  elaborate  fittings.-  The  cigar  box  can 
be  stained  if  desired,  but  when  merely  cleaned 
and  sand-papered,  it  presents  a  not  unpleasing 
appearance. 

Following  the  accumulation  of  the  parts, 
it  is  weir  to  make  sure  that  the  necessary  tools 


P  -40 

.30 

3.00 


How  to  Make  a  Radio  Receiver  for  $1.82 


367 


are  on  hand.    While  this  simple  set  can  be 
constructed  with  no  other  implements  than 

A  pair  of  scissors, 
A  jack-knife, 
A  screw-driver,  and 
A  gimlet 

a  neater  and  quicker  job  can  be  made  if  these 
elementary  tools  are  supplemented  by 

A  brace, 

A  J"  drill, 

Countersink, 

No.  18  drill, 

No.  27  drill, 

Hand-drill, 

Reamer, 

A  pair  of  wire-cutting  pliers  and 

A  compass  or  dividers 

THE    PANEL 

THE  cigar  box  should  be  of  average  size — 
about  eight  or  nine  inches  long,  five  inches 
high  and  two  and  one  half  inches  deep.  The 
paper  can  be  removed  by  soaking  in  hot  water 
for  one  half  hour.  It  should  be  sand-papered, 
dried,  and  sand-papered  again.  The  hinged 


top  of  the  box  is  discarded,  unless  it  is  attached 
with  metal  hinges. 

Fig.  3  shows  how  the  "panel"  or  bottom 
of  the  box  is  drilled  to  receive  the  mounted 
parts.  A  horizontal  pencil  line  is  drawn  across 
the  box  half  way  between  top  and  bottom  of 
the  panel.  On  the  left  hand  side,  a  vertical 
line  -is  drawn  2^  inches  in.  This  line  will 
cross  the  horizontal  line  at  A,  at  which  point 
a  quarter-inch  hole  is  bored  to  pass  the  variable 
condenser  shaft.  The  screw  holes  for  the 
condenser  are  drilled  according  to  the  pattern 
or  "template"  furnished  with  the  condenser, 
and  are  countersunk. 

Two  and  one  quarter  inches  from  the  other 
end  of  the  panel,  a  second  perpendicular  line 
is  drawn.  Holes  for  the  detector,  the  exact 
placing  of  which  will  vary  with  different 
obtainable  detectors,  are  drilled  on  the  upper 
part  of  this  line.  The  switch  lever  and  tap 
holes  are  located  on  the  lower  portion  of  this 
line  as  shown.  The  tap  holes  are  drilled 
with  the  No.  27  drill,  and  the  lever  hole,  B, 
with  the  quarter-inch  size  and  thus  reamed 
to  fit  the  bushing.  The  radius  of  the  taps 


LA 


FIG.    I 

These  parts,  which  altogether  cost  $1.82,  can  be  built  into  a  simple  but  efficient  receiver. 
All  parts,  excepting  the  lightning  arrester,  item  6,  are  included  in  the  receiver  proper 


368 


Radio  Broadcast 


N 

y  Antenna 

Detector 
•      .                                          1% 

r  ! 

0 

—  #*- 

00  ,_ 

O.L 

II 

O 

^-.,25  Turns 

O                         — 

y 

0                       / 

O15  Turns 

^^1  in  Tnrnc        *- 

Phones 


Ground 

FIG.    2 

How  the  different  parts  of  the  receiver  are  con- 
nected.    The  heavy  wire  in  the  antenna   circuit 
should  not  be  smaller  than  No.  14 

will  be  determined  by  the  length  of  the  switch 
arm. 

Each  end  of  the  box  is  drilled  according  to 
the  right  hand  sketch  in  Fig.  3.  These  holes 
are  for  the  binding  posts. 

Care  should  be  exercised  in  drilling  the  box 
in  order  to  avoid  splitting.  The  metal  drills 
are  much  preferred  to  the  gimlet.  The  drills 
should  be  sharp  and  turned  rapidly  but  with 
little  pressure.  This  procedure  will  result  in 
clean,  unchipped  holes. 

After  the  required  holes  are  drilled,  the 
pencil  lines  should  be  erased  by  sandpapering 


and  a  coat  or  two  of  stain  can  be  applied  if 
desired. 

THE   COIL 

WHILE  the  stain  is  drying — or  perhaps 
while  the  paper  is  being  soaked  from  the 
box — the  coil  can  be  wound.  If  the  builder 
prefers,  the  winding  form  can  be  bought  for  a 
few  pennies  from  the  same  ten-cent  store  that 
supplied  the  rest  of  the  parts.  But  it  is  easily 
cut  from  stiff  card-board  in  exact  duplication 
of  the  drawing  in  Fig.  4.  It  is  wound  with  45 
turns  of  wire,  over  three,  under  three,  with  taps 
taken  with  yth,  i4th,  and  2ist  turns.  Over 
three  under  three  means  over  three  spokes  of 
the  spider-web  form,  and  under  three  spokes,  as 
illustrated  in  Fig.  5.  The  turns  are  wound 
tightly.  After  seven  turns  are  wound,  a  loop 
about  three  inches  long  is  twisted  forming  a 
double  lead.  This  constitutes  the  first  tap. 
The  winding  is  continued,  additional  taps 
being  made,  as  directed,  at  the  I4th,  and  2ist 
turns. 

In  connecting  the  set,  looking  at  the  panel 
from  the  rear,  the  start  or  lower  terminal  of 
the  coil  leads  to  the  first  switch  point  (from 
left  to  right),  the  ist  tap  to  the  second  switch 
point,  the  and  tap  to  the  third  switch  point 
and  the  3rd  tap  to  the  four  or  right  hand  point. 
The  outer  end  of  the  coil  leads  to  the  antenna 
post.  Loops  are  made  in  the  tap  leads,  and 
the  enamel  scraped  off,  so  that  contact  will  be 
made  with  the  nuts  on  the  switch  points  under 
which  they  are  placed. 

Fig.  6  shows  how  the  taps  are  twisted  and 
connected  to  the  switch  points. 


r 


^ 


Holes  For 
Condenser 


_4. 


Holes'For 
Binding  Posts 


BOTTOM  OF  BOX 


EACH  END  OF  BOX 


FIG.    3 

How  the  holes  should  be  drilled.     The  condenser  and  switch  point  holeJ  are  most  easily 
Two  binding-post  holes  are  'drilled  in  each  -end  of  the  box 


"  Panel  layout." 

placed  with  a  pair  of  dividers  or  a  compass. 


Wiring  the  Set 


369 


<- Wire 


FIG.  5 

The   meaning  of 

winding    "over 

three,      under 

three" 


MOUNTING 

A  FTER  the  eleven  plate 
"^  •**•    condenser     has     been 

assembled  (in  many  cases 
it  can  be  bought  complete 
for  the  total  cost  of  its 
parts),  it  is  mounted  on  the 
L  panel  by  the  three  screws 

i  provided  for  this  purpose. 

If  the  holes   in  the  panel 
'  are  not  quite  properly 

0  spaced,  they  can  be  reamed 

slightly  to  compensate  for 
any  discrepancy.     The  dial 
!  is  adjusted  so  that  zero  is 

J  at  the  top  of  the  panel  (at 

L  which  point   an   indicating 

line  may  be  inked  in)  when 
-_  Snokes       the  rotary  plates  are   en- 
tirely out. 

The  bushing  for  the 
switch  lever  and  the  four 
switch  points  are  secured 
in  their  proper  places.  The 
crystal  detector 
stand  is  mounted 
with  a  single 
screw  through 
the  center,  two  small 
holes  on  the  right  hand 
side  being  provided  for 
the  leads. 

The  remaining  parts 
of  the  receiver,  the  fixed 
condenser  and  the  coil, 
are  supported  by  the 
wiring  in  back  of  the 
panel. 

WIRING   THE    SET 

THE  internal  connec- 
tions of  the  set  are 
shown  in  the  diagram 
Fig.  2.  Small  "a"  is 
the  antenna  post  (upper 
left  from  the  front)  run- 
ning to  the  top  of  coil  L, 
to  one  side  of  the  con- 
denser, and  to  the  crys- 
tal detector.  The  lower 
terminal  and  taps  of  the 
coil  are  connected  as  de- 
scribed. The  bushing 
of  the  switch  lever  is 
wired  to  the  ground  post 
-"b"  (lower  left)  and  to 
the  variable  condenser 


and  telephone  receiver  post  (lower  right)  "d". 
The  upper  telephone  post  runs  to  the  crystal 
detector.  The  fixed  condenser,  C2,  is  con- 
nected across  the  phone  binding  posts,  "c" 
and  "d."  Figs.  7  and  8  are  rear  and  front 
views  of  the  completed  receiver.  The  connec- 
tions within  the  set  may  be  made  with  what 
wire  is  left  over  after  winding  the  coil.  The 
writer,  however,  had  some  No.  18  bell  or 
annunciator  wire,  which,  being  larger  and 
stiffer,  was  a  bit  better  for  this  purpose. 
Using  the  parts  photographed  and  described, 
no  soldering  was  necessary. 

THE  telephone  receivers  are  connected  to 
the  posts  provided  for  them.  The 
antenna  is  connected  to  "a"  and  the  ground 
to  "b."  The  lightning  arrester,  LA,  is  con- 
nected between  antenna  and  ground  as  shown. 
The  lightning  arrester  is  conveniently  mounted 
on  the  windowsill.  The  antenna  wire  should 
not  be  smaller  than  No.  14  B  &  S  gauge,  or  its 
equivalent  in  stranded  wire,  and  this  same 
large  wire  should  be  used  for  the  heavy  leads 
shown  in  Fig.  2. 


3  ^"Overall  Diam. 


FIG. 

A  pattern  for  the  coil  form. 


. .  r This  may  be  cut  out  and 

pasted  on  cardboard  so  that  it  can  be  duplicated  exactly 


370 


Radio  Broadcast 


FIG.  6 

Showing    the    twisted    leads   or 

"  taps,"  and  the  manner  in  which 

they  are  connected  to  the  switch 

points 


WHAT   ANTENNA   TO   USE 


THE  crystal   receiver  will  operate  on  an 
indoor  antenna,  but  will  give  much  more 
satisfactory   results   on   an   outdoor   system. 


RADIO  BROADCAST  Photograph 


For  an  indoor  antenna,  it  is  advisable  to 
run  a  single  stretch  of  wire  through  rooms 
and  hall  as  far  as  possible  without  doubling 
back  upon  itself.  No  particular  precautions 
need  be  taken  for  insulation,  nor  is  a 


RADIO  BROADCAST  Photograph 
FIG.    7 
Rear  view  of  the  crystal  set.     No  soldering  has  been  necessary  in  connecting  the  different  parts 


The  Lead-in,  Antenna,  and  The  Ground 


37* 


lightning  arrester  necessary  with  an  indoor 
antenna. 

A  horizontal  length  of  about  seventy-five 
feet  is  best  with  an  outdoor  system.  A 
longer  antenna,  while  increasing  volume  and 
distance,  generally  boosts  up  interference  in 
the  same  proportion.  The  antenna  should  be 
swung  as  high  and  clear  as  is  conveniently 
possible.  Low  antennas  and  antennas  sur- 
rounded by  houses  and  trees  will  work,  but 
efficiency  will  increase  almost  in  proportion 
with  the  height  and  the  absence  of  near-by 
dumbwaiter  shafts,  tin  roofs,  trees,  and  other 
absorbing  obstructions. 

The  antenna  should  be  insulated  at  each 
end,  and,  if  possible,  the  horizontal  and 
vertical  (which  means  the  lead-in)  parts 
should  be  one  long  piece  of  wire,  as  suggested 
in  Fig.  9.  It  two  lengths  of  wire  are  used, 
they  should  be  soldered  at  the  joint.  As  a 
rule  more  than  one  wire  for  receiving  is  un- 
necessary. 

The  lead-in  should  be  guyed  away  from 
walls  if  necessary,  and  should  be  heavily 
taped  or  otherwise  insulated  wherever  it  comes 
in  contact  with  fire  escapes,  windows,  etc. 
Remember,  the  crystal  receiver  depends 
altogether  upon  the  energy  the  antenna 
system  picks  up,  and  it  must  be  conserved 
by  every  practical  care.  There  is  no  radio 


«gnB»    i' 

' 


FIG.    9 

A   simple   but   efficient   antenna   system.     If  con- 
veniently possible,  the  stretch  A,  B,  C  should  be  a 
single  length  of  wire 

frequency  amplification,  or  local  batteries, 
and  the  telephone  receivers  are  actuated  by 
the  minute  currents  induced  by  the  radio 
wave. 

The  lead-in  may  be  brought  through  the 
top  of  the  window  with  the  usual  precaution 
of  taping.  Or,  any  of  the  several  lead-in 
devices  may  be  employed  if  the  experimenter 
so  desires. 


FIG.  8 


RADIO  BROADCAST  Photograph 


The  complete  receiver,   connected   to  antenna  and   ground,   and 
ready  for  action.     No  batteries  of  any  kind  are  necessary  or  desirable 


372 


Radio  Broadcast 


Bind 


FIG.     IO 


The  layout  of  the  studs  or  nails,  and  the 
method  of  winding  the  simple  low  loss  coils 


THE    GROUND 

THE  water-pipe  or  radiator  make  equally 
satisfactory  grounds.  The  wire  need  only 
be  wrapped  tightly  around  a  scraped  portion  of 
the  pipe  and  taped.  Such  a  ground,  however, 
should  be  renewed  every  six  months  or  so.  A 
more  permanent  ground  is  secured  by  soldering 
or  by  using  the  common  ground  clamp.  A 
ground  wire  can  often  be  clamped  under  a 
valve  nut  on  the  radiator,  forming  a  lasting 
and  satisfactory  connection. 

HOW  TO  OPERATE  THE   RECEIVER 

THE  operation  of  even  a  simple  receiver  is 
a  matter  best  taught  by  individual  ex- 
perience. A  good  starting  point  on  our 
crystal  receiver  is  to  set  the  switch  on  the 
second  tap,  and  tune  for  stations  with  the 
condenser  while  the  detector  is  being  adjusted. 


The  process  of  adjusting  the  detector  consists 
of  moving  the  catwhisker  lightly  over  the 
surface  until  a  sensitive  spot  is  found.  It  is  a 
simple  matter  on  most  crystals  obtainable 
to-day  where  the  entire  surface  is  compara- 
tively sensitive.  An  occasionally  difficult 
adjustment  can  be  expedited  by  having  some- 
one ring  the  doorbell  while  the  catwhisker 
is  being  moved.  A  rough  buzz  will  be  heard 
in  the  'phones  when  a  sensitive  spot  is  dis- 
covered. 

The  highest  waves  will  be  tuned-in  with  the 
switch  lever  set  on  the  right,  the  lowest  waves 
on  the  left  and  the  intermediate  lengths  in 
between. 

HOW     FAR     CAN     I     HEAR    ON     A     CRYSTAL? 

THE  probable  range  of  broadcast  receiving 
apparatus  is  little  more  than  a  matter  of 
guess.  It  depends  too  much  on  individual 
conditions.  Crystal  sets  have  received  dis- 
tances over  a  thousand  miles  on  many  occa- 
sions. Using  a  short  indoor  antenna,  stations 
fifteen  miles  away  have  been  enjoyably  re- 
ceived in  our  New  York  laboratory.  Using 
an  average  outside  antenna,  the  crystal  set 
as  we  have  described  it  should  not  be  de- 
pended on  for  consistent  reception  of  pleasur- 
able loudness  over  distances  in  excess  of  25 
miles. 

HOW  TO  MAKE  A  SIMPLE  LOW-LOSS 
COIL 

THE  trouble  with   most  low-loss   coils, 
from   the  amateur's   point  of  view,  is 
the  difficulty  in  executing  the  generally 
eccentric  windings.     The  Lorenz,  or  basket- 
weave  coil  is  an  exception  to  the  rule,  and  it  is 
probably  more  easy  to  wind  than  the  straight 
solenoid.     Like  most  low-loss  coils  at  broad- 
cast frequencies,   losses  are  lowered,   not  so 
much  by  the  type  of  winding  itself  but  by  the 


RADIO  BROADCAST  Photograph 


FIG.     I  I 

The  winding  form   and   three   Lorenz   type  coils.     The   left 
hand  coil  has  been  mounted  on  a  standard  honeycomb  base 


How  to  Make  Low- Loss  Coils 


373 


fact  that  the  inductance  (coil)  is  self-support- 
ing. This  eliminates  much  of  the  metal  and 
insulating  supports  with  their  attendant  in- 
efficiencies and  mechanical  problems.  Com- 
bined with  the  simplicity  of  construction, 
this  added  desirability  recommends  the 
Lorenz  coil  to  the  inexperienced  experi- 
menter. 

A  piece  of  scrap  board  and  a  handful  of  two 
or  three  inch  nails  represent  the  winding  equip- 
ment. The  heads  should  be  cut  from  the 
nails.  A  circle  the  size  of  the  desired  coil  is 
circumscribed  on  the  board,  and  an  odd  number 
of  nails  driven  into  equally  spaced  points  on 
the  circumference.  The  arrangement  of  the 
points  is  best  laid  out  with  a  protractor  and 
dividers.  Fifteen  nails  were  used  by  the 
writer,  which  represents  a  spacing  of  24 
degrees  of  arc.  Twenty  four  degrees  are 
measured  from  the  diameter  with  the  protrac- 
tor, and  the  same  distance  (A,  B,  in  Fig.  10) 
is  marked  off  on  the  circumference  with  divi- 
ders or  compass. 

The  length  of  the  nails  is  governed  by  the 
height  of  the  contemplated  coil  and  they 
should  be  driven  firmly  into  the  board. 

The  manner  of  winding  is  illustrated  by  the 
sketch,  Fig.  10.  Two  turns  are  placed  around 
the  starting  nail,  and  the  winding  commenced 
over  one  under  one.  The  desired  number  of 
turns  is  wound  and  the  coil  completed  by 
winding  the  wire  twice  about  the  finishing  pin, 
which  is  one  nail  farther  on  than  the  starting 
pin.  The  coil  is  laced  or  bound  before  it  is 
lifted  from  the  nails.  Thread  is  generally  used 
for  this  purpose,  tying  in  four  places  beginning 
with  the  crossing  between  the  start  and  finish 
pins.  The  coil  can  be  pried  up  with  a  knife 
or  screw-driver  sufficiently  to  pass  the  binding 
thread  under  the  inductance.  The  black 
thread  binding  can  be  discerned  on  the  left 
hand  coil  in  Fig.  n,  in  which  is  shown  the 
simple  winding  machinery  and  three  of  its 
products. 

The  Lorenz  coils  can  be  mounted  in  a 
variety  of  simple  ways.  The  left  hand  coil 
in  Fig.  1 1  has  been  soldered  to  the  terminals 
of  the  standard  honeycomb  coil  base.  A  more 
general  form  of  mounting  is  to  clamp  the  coils 
between  strips  of  wood  or  bakelite  as  suggested 
in  Fig.  12. 


RADIO  BROADCAST  Photograph 
FIG.    12 

A  simple  way  of  mounting  Lorenz  coils  is  to  clamp 
them   between    two   strips   of   wood    or   bakelite 

Primary  and  secondary  coils  can  be  wound 
alongside  of  each  other  as  is  occasionally 
done  in  the  case  of  solenoids.  It  is  a  good 
idea,  however,  to  overlap  two  turns  in  order 
to  insure  strength  in  the  unit.  The  secondary 
should  be  started  two  turns  before  the  com- 
pletion of  the  primary.  After  one  turn  of  the 
secondary,  the  next  to  the  last  turn  of  the 
primary  is  wound  over  the  secondary  turn. 
The  second  turn  of  the  secondary  is  next  made 
over  the  primary  turn  and  the  last  turn  of  the 
the  primary  over  the  second  turn  of  the  secon- 
dary. The  secondary  is  then  continued  by 
itself.  The  two  coils  are  so  interlocked  that 
their  self-supporting  quality  is  not  weakened, 
However,  little  is  ever  gained  electrically 
by  the  winding  of  primaries  in  low-loss  fashion. 

Low-loss  secondaries  for  broadcast  wave- 
lengths can  be  wound,  of  course,  on  various 
diameters.  On  a  three-inch  diameter,  fifty 
turns  should  be  wound  and  on  a  four-inch 
diameter,  thirty  turns.  Shunted  by  a  .0025 
mfd.  variable  condenser,  such  coils  will  cover 
the  broadcast  band.  If  the  reader  desires, 
the  inductance  for  the  simple  receiver  com- 
pletely desscribed  on  another  page  of  this 
Department  can  be  wound  Lorenz  fashion  in 
preference  to  the  spider-web.  Either  of  the 
two  coils  just  suggested  can  be  wound,  and 
taps  taken  at  f ,  %,  and  \  the  total  number  of 
turns. 


,  HAT  Oui 
Readei 
Write  Us 


Line  Voltages  Supplied  by  Power 
Companies 

THE  following  letter  was  received  the 
other  day  from  the  Brooklyn  Edison 
Company,  Incorporated,  taking  issue  with  a 
statement,  in  an  article  by  Phil  Fay,  "Select- 
ing a  B-Battery  Eliminator,"  which  appeared 
in  the  March  issue  of  this  magazine. 

Editor,  RADIO  BROADCAST, 

Doubleday,  Page  &  Company, 

Garden  City,  New  York. 
SIR, 

The  first  paragraph  at  the  top  of  page  858  of  your 
March  1925  issue,  states  that  there  are  wide  varia- 
tions in  voltage  at  different  hours  of  the  day  and 
night  on  power  circuits  ranging  between  100  and  120 
volts.  We  believe  this  statement,  as  a  definite 
statement,  as  made  in  your  magazine,  is  incorrect 
and  does  electric  supply  companies  an  injustice. 

While  it  is  true  that  in  some  cases  such  a  variation 
as  you  mention  may  take  place  on  lines  of  some 
companies  occasionally,  it  is  not  the  usual  practice 
and  we  believe  that  the  statement  would  have  been 
more  correct  if  it  had  been  stated  that  a  variation 
in  the  amount  of  the  proportions  given  may  oc- 
casionally occur.  The  practice  of  this  company  is 
to  permit  a  voltage  variation  of  4  volts  either  above 
or  below  the  normal  voltage  of  120  volts  which  we 
supply.  In  other  words,  the  range  in  voltage  we 
undertake  to  supply  is  from  1 16  to  124  volts. 

I  hope  that  you  will  be  able  to  make  some  correc- 
tion of  the  statement  referred  to  above  in  your 
magazine. 

Very  truly  yours, 

R.  A.  Paine,  Jr. 
Outside  Plant  Engineer 

E  — 

The  paragraph    referred    to    above    is 
i  follows: 

"There  are  many  differences  between  one  power 
circuit  and  another.  First,  there  are  wide  variations 
in  voltage  at  different  hours  of  the  day  and  night, 
ranging  between  100  and  120  volts.  These  are  not 
noticeable  in  the  brilliancy  of  electric  lights  or  in 
the  operation  of  ordinary  household  equipment, 
largely  because  this  apparatus,  unlike  radio  equip- 
ment, is  not  especially  sensitive  to  voltage  varia- 
tions of  this  amount.  In  a  current  tap  supplying 
a  set  line,  voltage  differences  are  of  the  utmost  im- 
portance." 


What  Do  the  Roberts  Knockout  Users 
Think? 

THE  list  of  radio  constructors  all  over  the 
United  States,  Canada,  and  foreign 
countries  who  have  written  enthusiastic  let- 
ters about  their  experience  with  the  Roberts 
Knockout  Receiver  would  fill  many  lines  of 
type  indeed.  There  have  been  a  number  of 
these  correspondents  who  wanted  to  get  in 
touch  with  others  in  their  own  vicinity  to  talk 
about  their  mutual  experiences  with  the  cir- 
cuit and  to  discuss  their  various  experiments 
with  it.  Keith  Henney's  article  "Progressive 
Experiment  With  the  Roberts  Circuit"  which 
appeared  in  RADIO  BROADCAST  for  April,  1925, 
in  especial  excited  a  great  deal  of  interest. 
"Can't  you  put  me  in  touch  with  other  radio 
fans  in  my  city  who  have  been  experimenting 
with  this  remarkable  circuit?"  was  the  ques- 
tion we  received  in  more  than  one  letter  after 
that  article  appeared.  As  a  matter  of  fact, 
similar  requests,  differently  phrased,  have 
come  in  the  offices  ever  since  the  publication 
of  the  original  article  about  this  circuit  by  Doc- 
tor Roberts  in  the  April,  1924,  RADIO  BROAD- 
CAST. The  suggestion  in  the  letter  printed 
below  is  therefore  not  new,  but  it  expresses 
very  concisely  what  a  lot  of  correspondents 
have  been  suggesting.  RADIO  BROADCAST 
will  publish  a  list  by  cities  and  states  of 
the  names  and  addresses  of  Roberts  Knockout 
users  providing  those  users  who  are  interested 
in  taking  up  the  suggestion  outlined  below  will 
send  us  their  names  and  addresses. 

Editor,  RADIO  BROADCAST, 

Doubleday,  Page  &  Company, 

Garden  City,  New  York. 
SIR, 

About  a  month  ago  1  wrote  a  letter  to  Mr.  Zeh 
Bouck,  partly  personal  and  partly  asking  some  ad- 
vice regarding  some  trouble  I  was  having  with 
a  Roberts  Four-tube  set  I  had  built.  I  had 
hardly  mailed  my  letter  when  the  April  num- 
ber of  the  magazine  came  and  informed  me  that 
Mr.  Bouck  was  away  on  a  vacation.  The  purpose  of 


What  Our  Readers  Write  Us 


375 


this  note  is  to  have  you,  if  you  please,  tell  Mr. 
Bouck  when  he  returns  that  I  have  since  been  able 
to  settle  my  difficulties  quite  satisfactorily  by  chang- 
ing the  tubes.  I  wonder  if  this  suggestion  is  any 
good?  Let  RADIO  BROADCAST  offer  to  print  the 
names  of  some  fans  in  each  of  the  large  cities  who 
have  built  say  two  or  three  Roberts  outfits  and  are 
willing  to  share  their  experiences  with  others. 
The  Roberts  circuit  is  so  good  that  unless  you  treat 
it  right  in  construction,  you'll  have  trouble.  A  few 
dont's  from  one  who  has  done  only  to  his  sorrow,  may 
save  perplexities  later  on.  This  is  offered  for  what 
you  think  it  worth. 

Very  sincerely  yours, 
(Rev.)  Robert  E.  Holland,  S.  J. 

What  Doctor  Pickard  Thinks  About 
Fading 

THERE  have  been  many  interesting  argu- 
ments presented  of  late  upon  the  effect  of 
weather  conditions  upon  radio  transmission. 
Doctor  Pickard,  Consulting  Engineer  of  the 
Wireless  Apparatus  Company  of  Boston,  has 
made  an  intensive  study  of  fading  in  trans- 
mission extending  over  a  period  of  several 
years  and  which  has  brought  out  much  valu- 
able information.  His  most  important  work 
probably  has  been  his  study  of  the  eclipse  of 
the  sun  in  January,  1925.  His  observations 
during  the  period  of  the  eclipse  were  reviewed 
in  a  paper  which  was  read  before  the  Insti- 
tute of  Radio  Engineers  in  April,  and  dealt 
rather  conclusively  with  this  very  interesting 
subject. 

Doctor  Pickard's  reaction  to  Professor 
Van  Cleef's  article,  which  appeared  in  RADIO 
BROADCAST  for  May,  is  therefore,  of  especial 
interest.  Mr.  Van  Cleef  reviewed  in  his 
article  the  factors  which  influenced  the  trans- 
mission and  reception  of  radio  waves.  There 
have  been  many  theories  put  forth  to  explain 
the  peculiar  condition  of  fading.  The  most 
popular  theory  is,  perhaps,  that  of  the  Heavi- 
side  Layer,  which,  in  part,  assumes  that  the 
various  ionized  layers  of  the  upper  atmosphere 
refract,  absorb,  or  aid  the  waves  in  their 
passage.  Doctor  Pickard's  letter  follows: 

Editor,  RADIO  BROADCAST, 

Doubleday,  Page  &  Company, 

Garden  City,  New  York. 
SIR, 

I  am  indeed  indebted  to  you  for  the  galley-proof 
of  Professor  Van  Cleef's  interesting  article.  We 
certainly  need  the  aid  of  the  meteorologist  in  the 
correlation  of  weather  and  radio  transmission. 

Few  radio  engineers  who  have  specialized  on 
transmission  phenomena  still  retain  the  original  or 
reflecting  Heaviside  Layer  hypothesis.  Not  only 
did  this  hypothesis  involve  a  grotesque  amount 


and  arrangement  of  atmospheric  ionization,  but 
to-day  we  realize  that  to  act  upon  waves  by  con- 
ductivity would  damp  them  out  more  rapidly  than 
it  would  bend  them.  It  is  therefore  refreshing 
to  find  a  writer  who  pays  no  attention  to  the 
Heaviside  Layer. 

For  nearly  a  quarter  of  a  century  it  has  been 
recognized  that  those  happenings  below  the  isother- 
mal layer,  which  we  call  weather,  were  related  to 
radio  transmission.  Some  five  or  six  years  ago  a 
Frenchman,  whose  name  has  temporarily  escaped 
me,  made  a  very  similar  analysis  to  that  of  Professor 
Van  Cleef,  although  he  came  to  somewhat  different 
conclusions. 

However,  I  do  not  share  the  author's  assurance 
that  reception  conditions  can  be  forecast  with  the 
same  degree  of  accuracy  as  the  weather,  because  I 
know  several  other  factors  profoundly  affect  trans- 
mission. But  there  is  little  that  I  can  criticize  in 
Professor  Van  Cleef's  article. 

The  principal  factor  in  radio  reception  is  not  the 
electric  field  at  the  receiving  point,  because  this  can 
be  discounted  by  increased  amplification.  The 
principal  factor,  is,  however,  the  height  of  the  dis- 
turbance level  or  noise  background.  The  fact  that 
winter  reception  is  better  than  summer  reception 
is  really  due  to  two  things.  First,  there  is  less 
static  or  noise  background,  and  second,  there  is 
less  sunlight,  and  therefore  less  ionization  of  the 
lower  levels  of  the  atmosphere. 

Sincerely  yours, 
GREENLEAF  PICKARD. 

On  Our  Anniversary 

IT  IS  a  pleasure  to  receive  letters  of  the  sort 
reproduced  below.  Such  expressions  make 
us  feel  that  our  earnest  endeavors  to  present 
to  the  radio  public  a  magazine  of  the  highest 
grade  have  not  been  wasted.  But  our  efforts 
for  the  last  three  years  have  not  been  confined 
to  the  dissemination  of  the  best  in  radio  alone. 
In  November,  1923,  RADIO  BROADCAST  in- 
augurated the  first  International  Broadcast 
tests.  The  tests  were  repeated  in  1924  as  they 
will  be  in  1925,  and  the  data  obtained  from 
these  tests  as  well  as  in  many  other  and  differ- 
ent researches  conducted  by  RADIO  BROAD- 
CAST has  been  invaluable  to  the  radio  field. 
Mr.  Rice  is  Manager  of  Broadcasting  for  the 
General  Electric  Company. 

GENERAL  ELECTRIC  COMPANY 

Editor,  RADIO  BROADCAST, 

Doubleday,  Page  &  Company, 

Garden  City,  New  York. 
SIR, 

In  looking  over  the  May  issue  of  RADIO  BROAD- 
CAST I  find  that  it  is  an  anniversary  number.  I 
congratulate  you  on  the  high  grade  and  interesting 
magazine  which  you  have  edited  for  the  past  three 
years. 

Very  truly  yours, 

MARTIN  P.  RICE. 
Manager  of  Broadcasting. 


Front  view  of  the  super-autodyne  receiver,  assembled  on  a  standard  7  x  18  x  j-inch  bakelite  panel.     The 

knob  at  the  lower  left  is  the  wavelength  change  switch  which  controls  the  loop.     The  designation  letters  in 

this  Figure  coincide  with  those  in  the  list  of  parts,  and  in  the  remainder  of  the  illustrations 

The  Super- Autodyne 

Complete  Data  for  Building  an  Improved  Type  of  "Super- 
Autodyne"  Using  But  Six  Tubes  for  Portable  or  Home  Use 

BY  McMURDO  SILVER 


THE  super-heterodyne  described  in  this  article  has  a  number  of  features  which 
commend  it  to  the  radio  constructor.  In  the  first  place,  it  uses  six  tubes, 
with  a  total  plate  current  consumption  of  12  milliamperes.  As  for  actual  mechani- 
cal arrangement  and  layout,  we  feel  that  the  author  has  done  a  very  good  bit  of  de- 
sign, for  the  set  is  exceptionally  easy  to  wire,  and  if  the  constructional  outline  is 
carefully  followed  there  should  be  no  difficulties  from  this  source.  The  entire  re- 
ceiver has  been  concentrated  in  a  7  x  i8-inch  panel,  a  vastly  more  compact  arrange- 
ment than  one  finds  with  most  super-heterodynes.  No  reflexing  is  used.  The  quality 
of  tone  we  believe  excellent.  It  is  somewhat  difficult  to  tune  this  receiver,  as  the  dial 
functions  differ  from  those  in  the  common  types  of  super-heterodyne.  The  in- 
terested constructor  will,  however,  find  that  this  is  not  merely  "another  super- 
heterodyne." Many  radio  enthusiasts,  old  and  new,  are  looking  for  a  portable  loop 
receiver  to  use  in  vacation  trips  this  summer;  this  receiver  should  satisfy  their  summer 
requirements  as  well  as  giving  them  a  set  for  all-around  home  use. — THE  EDITOR 


THAT  it  possess  features  which  defi- 
nitely lift  it  above  the  class  of  the  best 
receivers  heretofore  developed — is  the 
first  requirement  of  any  new  receiving 
system  in  order  that  it  may,  in  a  measure, 
justify  that  age-old  human  cry  of  "something 
new  under  the  sun."     And  if  for  purposes  of 
differentiation  it  is  elected  to  call  this  new  re- 
ceiver by  a  name  which  includes  the  word 


"dyne,"  then  there  must  certainly  be  some- 
thing to  recommend  it  other  than  that  its 
designer  has  managed  to  unearth  some  new 
prefix  or  suffix  for  that  word.  The  receiver  to 
be  described  in  this  paper  has  but  two  basic 
claims  to  thefirst  of  these  requirements  and  one 
to  the  second — it  uses  but  six  tubes,  and  its  name 
is  as  logical  as  that  of  the  super-heterodyne. 
Essentially,  the  receiver  is  a  super- 


The  Super-Autodyne 


377 


heterodyne,  employing  an  autodyne  detector- 
oscillator,  and  what  the  writer  believes  to  be 
an  exceptionally  efficient  intermediate  am- 
plifier. Because  of  the  use  of  the  autodyne 
frequency-changer,  the  circuit  has  been  called 
a  "super-autodyne,"  which  seems  to  be  a 
more  logical  name  than  "super-heterodyne." 
It  might  be  argued  that  the  usual  interpreta- 
tion of  the  word  "heterodyne"  implies  the 
use  of  a  separate  detector  and  oscillator  to 
produce  a  beat  note,  whereas  in  this  system 
but  one  tube  is  used  (autodyne).  The  name 
at  least  serves  to  distinguish  this  system  from 
the  conventional  ones. 

THEORY    OF    THE    AUTODYNE    CIRCUIT 

/T"*HE  autodyne  circuit,  which  is  the  most 
1  interesting  feature,  is  worthy  of  explana- 
tion. The  difficulty  which  has  heretofore 
prevented  the  use  of  one  tube  for  both  detector 
and  oscillator  has  been  that  of  isolating  the 
loop  or  pickup  circuit  from  the  local  oscillator 
circuit.  It  has  been  impossible  to  couple  a 
tuned  pickup  circuit  to  a  tuned  oscillator 
when  the  two  are  to  operate  but  fifty  or  sixty 
kilocycles  apart  throughout  the  broadcast 
wavelength  range,  and  not  have  the  tuning  of 
one  section  react  on  that  of  the  other.  Arm- 
strong and  Houck  developed  the  second  har- 
monic system,  whereby  the  oscillator,  working 
at  double  the  desired  wave,  did  not  react 
greatly  upon  the  loop  circuit.  Then,  a 
harmonic  of  the  oscillator  was  used  for  hetero- 


dyning.  This  meant  two  waves  of  sufficient 
power  to  cause  radiation  were  being  produced 
by  the  oscillator,  which  necessitated  the  use  of 
a  muffler  tube  ahead  of  the  detector-oscillator 
to  prevent  radiation.  Thus,  two  tubes  were 
still  used,  though  the  gain  in  signal  strength 
was  equal  to  or  slightly  better  than  that  ob- 
tained with  a  good  regenerative  detector  and 
oscillator.  At  best,  this  system  is  not  entirely 
satisfactory  for  home  assembly. 

Then  came  the  development  of  the  balanced 
autodyne  circuit,  by  J.  H.  Pressley,  a  Signal 
Corps  engineer,  which  performs  the  required 
function  with  one  tube. 

The  actual  first  tube  circuit  is  shown  in 
Fig.  9.  The  coils  L2,  Lj  ace  theoretically 
equal,  as  are  the  condensers  CX,  CX.  Actually 
they  cannot  be  made  fixed  and  equal,  so  CX, 
CX  are  made  adjustable,  to  obtain  substan- 
tially a  condition  of  equality.  These  units 
make  up  a  bridge  circuit,  shown  by  the  heavy 
lines.  Since  L2  equals  L^,  the  potential 
across  them  is  equal,  so  that  it  is  also  equal 
between  points  3,  and  4,  and  5  and  6.  Like- 
wise, the  potential  across  CX  and  CX  is  equal. 
Since  the  potential  across  3  and  6  is  the  same 
for  both  inductance  and  capacity,  then  point 
4,  5  and  the  connection  between  CX,  CX  are 
at  equal  potential,  and  are  also  theoretically 
at  zero  potential,  since  these  points  are  neutral 
with  respect  to  3  and  6.  Then,  circuit  Bi, 
C2,  82,  may  be  connected  at  these  neutral 
points  with  substantially  no  reaction  on  the 

V2,  VI 


c- 


FIG.    2 


RADIO  BROADCAST  Photograph 


The  completed  receiver  from  the  rear.     Note  how  the  color  cable  runs  into  the  assembly,  and  how  two  of  its 

leads  terminate  on  the  rear  left  posts  of  transformers  Ti  and  T2.     Condensers  €9,  and  Cio  should  be 

fastened  to  the  under  side  of  the  sub-panel,  using  holes  provided  in  this  socket-panel 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 
FIG.    3 

Details  of  the  finished  receiver  from  above.     Note  how  the  five  leads  of  the  color  cable  separate:  one  to  tV, 

rheostat  R3,  one  to  the  switch  Si,  two  to  Ti,  and  one  to  T2.     The  gang-socket  used  in  this  particular  model 

of  the  set  is  a  home-assembly,  and  the  springs  are  held  by  screws.     In  the  factory  product,  the  springs  at. 

held  by  hollow  rivets  which  permit  connections  to  be  made  from  either  above  or  below  quite  simply 


frequency  of  the  bridge  circuit.  Further, 
as  these  points  are  neutral  with  respect  to  3 
and  6,  no  energy  in  the  bridge  circuit  can  get 
into  Bi,  €2,  62,  since  there  is  no  potential 
difference  across  these"  points  of  the  bridge. 
Therefore,  the  frequency  adjustment  of  the 
bridge  circuit  cannot  react  upon  that  of  the 
Bi,  C2,  62,  circuit,  and  vice  versa. 


LoctateCondenserspO     Here 

/    _»    .    ^**/^*    ,    \ 


Since  the  signal  is  fed  from  the  loop  and  its 
tuning  condenser  to  the  oscillator,  it  will 
divide  equally  across  the  bridge  arms.  If  a 
tube  detector  is  connected  across  one  capacity 
CX,  the  drop  in  potential  may  be  used  to 
cause  rectification.  The  coil  Li,  coupled  to 
L.2,  I_3,  causes  the  bridge  circuit  to  oscillate 
at  a  frequency  determined  by  these  coils, 


c- 


R5 


RADIO  BROADCAST  Photograph 


FIG.   4 

Bottom  view.  Condensers  C6,  Cg,  and  Cio  should  be  fastened  to  the  sub-panel  at  the  points  shown 
similarly  to  €3,  04  and  €5.  The  proper  hole  locations  are  given  in  Fig.  7.  Connections  from  C3  and  G* 
to  the  socket  grid  terminals  are  by  means  of  lugs,  just  visible  between  the  condensers  and  the  nuts  to  the  real 
This  view  shows  quite  clearly  how  the  bypass  condensers  are  held  by  the  same  screws  holding  th< 

mounting  brackets 


left. 


The  Super-Autodyne 


379 


CX,  CX,  and  Ci  which  Is  made  variable  for 
the  purpose  of  tuning  the  oscillator  circuit. 
As  previously  explained,  this  energy  cannot 
get  into  the  loop  circuit,  so  radiation  is  con- 
fined to  what  may  be  experienced  from  the 
oscillator  coil  system  itself — a  negligible 
amount. 

It  is  desirable  that  the  losses  in  these  cir- 
cuits be  kept  low,  particularly  in  Ci,  C2,  CX 
and  CX.  Further,  CX  and  CX  should  be 
quite  small  so  as  not  to  lessen  the  tuning  range 
of  the  circuits,  and  in  order  that  maximum 
voltage  may  be  impressed  upon  the  detector 
terminals.  In  some  cases,  it  has  been  found 
possible  to  use  the  tube  capacity  for  one  con- 
denser CX,  while  a  very  small  variable  was 
used  for  the  other  capacity. 

INTERMEDIATE    AMPLIFIER 

THE    intermediate    amplifier    is    the   only 
other    unusual    feature    of  the   receiver. 
It  employs  but  two  stages  and  is  on  the  order 


ot  those  described  by  the  writer  in  RADIO 
BROADCAST  for  October  1924,  and  January, 
1925.  It  differs,  however,  in  that  it  employs 
transformers  which  are  a  compromise  between 
the  extreme  selectivity  of  properly  designed 
air-core  coils,  and  the  great  stability  and  am- 
plification of  good  iron  core  transformers. 
But  two  core  laminations  are  used  in  each 
transformer,  of  y-mil  silicon  steel,  one  in  the 
shape  of  an-'"F"  and  one  an  "L". 

CONSTRUCTION    OF   THE    SET 

THE  material  required  to  build  this  re- 
ceiver is  listed  below,  with  the  designation 
letters  used  in  the  diagrams  and  cuts  following 
the  quantity  of  each  item  required.  It  is 
entirely  permissible  to  substitute  any  other 
standard  parts  for  those  listed.  The  actual 
space  available  is  such  that  if  in  some  instances 
parts  of  larger  or  different  dimensions  are 
substituted,  considerable  difficulty  will  be 
encountered  in  making  the  units  fit  in  the 


RADIO  BROADCAST  Photograph 


FIG.    5 

The  receiver  in  an  automobile.  The  A  battery  supply  comes  from  the  automobile  by  using  the  Lynch 
Lead.  The  rather  dilapidated  bag  in  the  rear  holds  the  B  and  audio  amplifier  C  batteries.  The  Am- 
plion  loud  speaker  and  the  folding  loop  also  go  in  this  bag  when  not  in  use.  Blanket-roll  straps  provide  a 

convenient  means  for  carrying  the  set  itself 


380 


Radio  Broadcast 


up 

a. 

in 

an 

fj| 

space   provided.     In    the   case  of   the  r.  f. 
transformers,  it  would  be  inadvisable  to  sub- 
^       stitute,  since  the  results  of  the  receiver  depend 
.?!,..     in  a  large  measure  upon  the  use  of  the  types 

//        H  + 

\^P~ 

re 

2  ( 

:ommended. 

Zi,  C2     S-M    30I-A     (or  3O5-A  S.  L.  F.)  Con- 
densers 
4"  Moulded  dials,  vernier  type  pref- 
erably 
r^  +"S      i  R4                U.  S.  L.  6  ohm 

JiMM> 

Wffi^ 

^% 

2 

^^m 

r—  ^ 

*  * 

Y^TT 

<M               o       ^^«o=                            rheostat 

«^«  Oil  "1                l  R3                 U'    ^'    L'    24° 
i00    ^     o  «u                           ohm    potentio- 

JlflJ&fl?/- 

O^m                           meter 
Q!^  o                    3  Bi.  62.  B^  Insulated     top 

i           i 
^ 

"^         „,  c                            binding  posts 

TftOOO^ 

DC 

(i-spring) 
i  J  i               Carter      IO2-A 
jack  (,3-spring) 
iC-5,  211       S-M    211    filter  with   matched 
tuning  capacity 
2  210,  210       S-M   210  charted  intermediate 
transformers 
i  Li,  L2,  L3  S-M  loi-B  coupling  unit 
i                      S-M  or  Benjamin  6  gang  socket 
shelf  (536-20IA,  No.  537-199) 
2  Ti,  T2         Thordarson  3^:1   or  2:1   trans- 
formers 
2  C?,  C8         S-M  or  Dubilier   .5  mfd.  Con- 
densers 

£s 

CVJoL 

ro 

C\I 

p|: 

CO 

lf^-—  ^  \+ 

JlQM£y- 

0 

OOOOOf- 

2  C3-C4          Muter    .00025   mfd.  condensers 
with  2  clips 
2  Cg,  Cio       Muter  .002  mfd.  condensers 
i  C6                Muter  .0075  mfd.  condenser 
2  CX,  CX       Continental    .000025   mW.   con- 
densers 
i  Ri                S-M  or  Muter  .5  Meg.  leak 
i  R2                S-M  or  Muter  2  meg.  leak 
i  Si                 Carter  No.  3  jack  switch  (s.  p. 
d.t.) 
i  S2                 Benjamin    8630    switch    (s.    p. 
s.t.) 
i                      S-M    No.    701    color  cable    (5 
leads) 
i  pair              Benjamin  No.  8629  shelf  brack- 
ets 
i     Bakelite  Panel,  7  x  18  x  | 
O  rt               inches 

t^Ljlr- 

'•*  S=5 

0  0  0  0  0'  '  - 

5 

f«l 

"o 

(ft)000+) 
II 

u 
<^^ 

-o    ' 

M  U 

tr 

E 

ro 

=|p^yr 

PI 

su 

x 

Mv 

II       

i     Small  parts:  29  -fa  R.H. 
^  o,              N.    P.   machine  screws  f 

<s_ 

^B 

__^r 

±0 

~WCD              inch 
2  6-  R.H.  N.  P.  machine 

CX 

•J      •* 

JKKKKKL 

,fj 

WM              screws  if  in. 

31  A  nuts 
i  spaghetti 
10  strips  bus-bar 

2?  luffS 

11 

F1G.    6 

Complete  wiring  diagram  of  the  super-autodyne    receiver.     If   this 

diagram  is  used  in  connection  with  the  picture  layout  diagram,  an 

error  in  connections  is  impossible 


Tools  required:  i  hand-drill 
with  drills  and  countersink, 
i  soldering  iron  with  rosin- 


The  Super-Autodyne 


381 


core  solder  and  non-corrosive  paste,  i  side-cutting 
pliers,  i  screw-driver,  hammer,  and  centerpunch. 

THE    OSCILLATOR   COUPLER   AND    GENERAL 
ASSEMBLY 

THE  oscillator  coupler  may  be  made  by 
winding  two  sections  separated  TVinch 
apart  on  a  2|-inch  bakelite  or  condensite 
tube;  each  section  containing  twenty-eight 
turns  of  No.  28  d.s.c.  wire.  The  rotor  coil 
also  consists  of  twenty-eight  turns  of  the  same 
size  wire  on  a  i|-inch  tube  rotatable  within 
the  stator  tube. 

As  soon  as  the  materials  have  been  procured, 
each  item  should  be  carefully  examined  to 
see  that  all  screws  and  nuts  are  tight,  and  lugs 
placed  as  shown  in  the  photographs,  so  that 
those  on  the  various  instruments  will  point  in 
the  best  directions  for  short  leads.  Socket 
springs  should  be  bent  up  to  make  good  con- 
tact with  tube  pins.  Condenser  bearings 
should  be  adjusted  to  give  the  desired  tension. 

If  the  builder  already  has  Benjamin  sockets, 
the  socket-shelf  may  be  made  up  by  drilling 
a  piece  of  bakelite  17!  x  4!  x  \  inch  in  accor- 
dance with  Fig.  7.  The  bases  should  be 
removed  from  the  Benjamin  sockets  so  that 
they  may  be  fastened  directly  to  the  sub-base 
with  their  original  screws.  On  each  terminal 
will  be  found  a  round  knurled  nut,  a  hex- 
agonal nut,  and  a  round-headed  screw.  The 
screw  should  be  put  through  the  hole  in  the 
spring,  pointing  downward.  The  knurled 
nut  is  turned  up  on  the  screw  under  the  spring, 
the  screw  pushed  through  its  hole  in  the  shelf, 
a  lug  placed  over  it  if  necessary,  and  the  "hex" 
nut  tightened  up  on  the  under  side  of  the 
shelf.  Care  should  be  taken  to  prevent  the 
spring  from  twisting  as  the  nut  is  tightened, 
due  to  rotation  of  the  screw.  If  this  occurs, 
the  socket  will  not  ride  evenly  on  its  spring. 
Details  of  these  operations  may  be  obtained 
from  Figs.  2,  3,  and  4.  Either  uv-i9Q  or 
standard  uv-2oiA  sockets  may  be  used.  They 
should  be  arranged  so  that  their  grid  terminals 
come  out  at  the  left  rear,  as  in  Fig.  3. 

The  front  panel  may  be  laid  out  in  accor- 
dance with  Fig.  8,  using  a  rule  and  scriber 
after  which  the  hole  locations  should  be 
punched  with  a  center-punch  or  nail,  and  a 
hammer.  After  drilling  the  holes,  the  panel 
may  be  grained  with  fine  sand-paper  and  oil, 
rubbing  in  one  direction  until  the  original 
polished  finish  has  disappeared.  After  wiping 
the  panel  off  with  alcohol,  indicating  marks 
for  the  dials  may  be  scratched  as  in  Fig.  i, 
and  filled  with  Chinese  white.  The  sub  panel 
should  not  be  grained. 


FIG.    7 
Drilling  dimensions  for  the  sub-panel 


Radio  Broadcast 


FIG.    8 

Panel  drilling  dimensions.     If  a  meter  is  used  with  this  set,  which 
is  strongly  advised,  the  holes  indicated  should  be  drilled.     The 


ASSEMBLY   OF    PARTS 

BEFORE  starting  with  the  as- 
sembly, the  photographs 
should  be  very  carefully  studied, 
to  see  just  how  each  part  is  put 
on,  and  just  where  each  of  the 
different  parts  go.  If  the  S-M  or 
Benjamin  shelf  is  used,  it  will  be 
unnecessary  to  drill  any  additional 
holes,  as  these  shelves  are  supplied 
completely  drilled  for  the  parts  re- 
commended. 

Figs,  i,  3,  and  4  should  be  ex- 
amined to  see  how  the  parts  are 
arranged  on  the  panel.  The  con- 
densers Ci  and  Ca,  the  Carter 
jacks  and  jack-switch  and  the  Ben- 
jamin switch  should  be  put  on  the 
panel,  followed  by  the  rheostat  and 
potentiometer.  The  posts  of  these 
latter  instruments  should  be  on  the 
bottom,  and  their  contact  arms 
should  point  upward  when  their 
indicating  arrows  do  likewise. 

All  parts  should  be  put  on  the 
sub-panel  as  shown  in  the  various 
photographs.  In  these  C6,  Cg 
and  C 10  are  shown  inconveniently 
located.  They  should  be  placed  in 
the  positions  indicated  in  Fig.  4,  on 
the  under  side  of  the  shelf.  They 
are  held  to  the  sub-panel  by  ma- 
chine screws  and  nuts.  Lugs  placed 
between  these  condensers  and  the 
sub-panel  may  be  soldered  directly 
to  the  socket  terminals  in  the  case 
of  CQ  and  Cio,  since  they  run  to 
plate  and  F  of  sockets  ¥5  and  V6. 
Condensers  C3  and  C4  may  have 
one  of  their  contacts  connected  to 
the  grid  terminals  of  sockets  Vi 
and  V4  respectively  in  the  same 
manner.  Lugs  for  C$  should  be 
placed  on  the  upper  side  of  the 
shelf,  as  well  as  on  one  terminal 
each  of  C3  and  C4,  since  some  of 
the  condenser  connections  will  be 
made  from  above. 

WIRING  THE   RECEIVER 

TN  WIRING  the  receiver,  a  well- 
1  tinned  iron  should  be  employed 
in  conjunction  with  rosin-core  sol- 
der. A  small  amount  of  paste  may 
be  used  on  each  connection  if  de- 
sired; but  not  on  any  of  the  fixed 


o^  .  .    .  .  j  3llc      .    UUl     IH-ii    wii    «ny    *-*•    m^   it^-^^» 

Weston  double  range  voltrneter  type  301,  which  may  be  used  on  V  ronnections 

the  panel  requires  the  additional  switch  hole  indicated  condensers.     Here,   cor 


The  Super-Autodyne 


383 


may  be  soldered  to  lugs,  or  to  the  condensers 
directly. 

Only  two  connections  can  be  put  on  the 
panel  alone.  These  are  a  connection  between 
the  rheostat  and  potentiometer,  and  one  be- 
tween the  potentiometer  and  Si.  (See  Figs. 
3  and  4.)  Bus-bar  should  be  used,  straight- 
ened, carefully  cut,  and  bent  to  proper  length 
before  any  attempt  is  made  to  solder  it  in 
place.  A  long  piece  of  bus-bar  should  not 
be  soldered  to  a  lug,  and  then  bent  and  twisted 
until  it  reaches  the  other  lug  to  which  it  is  to 
be  soldered.  Each  piece  should  be  bent  to 
fit  properly,  cut  to  size  and  then  soldered 
in  place. 

ASSEMBLING  ON   THE    SUB-PANEL 

CTARTING  on  the  sub-panel,  all  the 
^  wiring  visible  on  it  in  Fig.  3  should  be 
put  on,  the  shelf  then  turned  over,  and  the 
wiring  necessary  on  the  bottom  put  in  place. 
All  of  the  r.f.  and  a.f.  transformer  cases  are 
connected  together,  and  in  turn  connected 
to  the  negative  filament  line,  which  joins  the 
minus  lugs  of  all  sockets,  just  as  the  positive 
line  joins  all  the  plus  terminals  of  the  six 
sockets. 
The  Benjamin  brackets  should  be  fastened 


Li^fc1 


FIG.    9 

to  the  sub  base,  and  in  turn  loosely  fastened 
of  the  panel.  The  lugs  of  the  bypass  conden- 
sers Cy  and  C8  are  bent  at  right  angles,  and 
slipped  in  between  the  brackets  and  fastening 
nuts,  as  in  Fig.  4.  This  makes  a  solid  mount-? 
ing  for  these  condensers,  after  the  screws  are 
tightened,  as  well  as  for  the  shelf-brackets. 
The  balance  of  the  wiring  is  then  put  in, 
running  between  the  parts  on  the  sub-shelf 
and  those  on  the  panel.  This  will  not  be 
found  difficult,  particularly  if  spaghetti  is 
used  only  where  there  is  danger  of  two  wires 
shorting,  or  a  wire  shorting  on  an  instrument. 


/ 


- 1- 

Ll 


Pivots 
Here 


V 


2  1 

ROTOR 

All  Coils 
No.  28  DSC  Wire 


Rotor 
Li 


Spring  Brass 
,  Bent  To  Shape  > 

||f~ 

1          '                \~ 

f  :  i 

/ 

; 

1: 

1 

V" 

1     ! 

OSCILLATOR  COUPLER 
CONSTRUaiON   DETAILS 

Upper  Coil 
L2 


Lower  Coil 


23  45 

DIRECTION  OF  WINDING 


DETAILS   OF    CONSTRUCTION    OF   THE    OSCILLATOR   COUPLER 


384 


Radio  Broadcast 


FIG.  I  I 

A  picture  wiring  diagram  of  the  super-autodyne.     The  location  of  every  wire 

in  the  circuit  is  shown.   This  should  be  used  in  connection  with  Fig.  6 

A  C  battery  is  used  on  the  r.f.  amplifier,  point,   the  wire  is  broken,   and   a  ten-inch 

It  connects  to  the  two  flexible  leads  marked  lead  of  lamp  cord  soldered  to  the  potentio- 

C  minus   and   C  plus   in   the  photographs,  meter  arm  for  the  C  plus  lead  and  another 

No  provision  is  shown  for  it  in  the  diagram,  similar  wire  soldered   to  the  joint  between 

except  the  point  marked  "Note."    At  this  Cj  and  the  A  minus  lugs  of  the  211  filter  and 


The  Super-Autodyne 


385 


its  adjacent  210  transformer.  This  C  bat- 
tery is  3  volts,  and  may  be  placed  in  the 
cabinet  under  the  sub-shelf,  since  its  leads 
should  be  short.  It  had  best  be  wrapped 
in  paper  to  prevent  shorting  on  any  of  the 
wiring.  For  UV-2OIA  tubes,  these  leads  may 
be  shorted  and  the  battery  eliminated  en- 
tirely if  the  amplifier  will  oscillate  without  it. 
The  remaining  battery  leads  are  brought  out 
through  a  color  cable,  which  should  be  coded 
in  accordance  with  the  data  presented  on 
page  1034  of  the  April  RADIO  BROADCAST. 
Unfortunately,  there  are  a  few  manufacturers 
who  have  not  yet  adopted  this  coding  for  their 
cables.  In  Fig.  6,  the  colors  of  the  various 
wires  in  the  cable  used  for  different  voltages 
are  given.  This  was  for  one  particular  make 
of  cord,  used  on  an  experimental  set.  It  will 
be  noticed  that  the  black  lead  with  red  tracer 
is  used  for  three  connections,  which  are  made 
between  the  batteries  themselves  by  means 
of  other  wires. 

ACCESSORIES   AND   TESTING 

ASSUMING    the    receiver    to    have  been 
wired,  it   is  ready  for  test.     The  addi- 
tional material  required  is  as  follows: 

6  Radiotron  tubes,  uv-2OiA,  or  uv-icjg.  ov-3 
De  Forest  tubes  may  be  substituted  for  199*5,  but 
will  require  a  standard-base  socket  shelf. 

i  A-battery.  This  may  be  a  storage  battery,  6 
volts,  90  ampere  hours  for  uv-2oiA*s,  or  it  may 
be  the  battery  used  in  an  auto,  tapped  by  means 
of  Lynch  Leads.  For  dry  cell  tubes,  three  dry 
cells  may  be  used,  or,  better  yet,  for  home  in- 
stallation six  in  series-parallel. 

1  B-battery.     For     permanent     installation     90 
volts,  of  large  size  22,  or  45  volt  batteries  should 
be  used.     For  portable  work,  6y|  volts  will  be 
sufficient,    of   medium   or   small-size    batteries, 
since  the  current  drain  is  but   12  milliamperes 
for  20 1  A   tubes,   and   9   milliamperes  for    1995. 
(90  volts  will  give  only  slightly  more  volume 
than  (f]\,  so  it  is  hardly  worth  while  to  carry 
around  the  extra  22-volt  battery. 

2  C-batteries.    One  3-voIt  battery  required  in  the 
set  box  for  the  r.f.  amplifier,  and  one  4^-volt 
battery  for  the  a.f.  amplifier. 

i  Loop  with  center  tap.  Any  good  tapped  loop 
may  be  used,  or  one  may  be  made  by  winding 
16  turns  spirally  on  a  form  about  24  inches 
square,  tapped  at  the  center,  with  j  inches 
between  turns.  This  loop  with  eighteen  turns, 
T\  inches  apart,  may  be  wound  on  the  back 
of  a  cabinet  large  enough  to  hold  the  set,  with 
the  batteries  beneath  if  desired. 


i  Loud  speaker.  The  small  Amplion  is  recom- 
mended for  portable  work  as  it  is  a  most  excellent 
speaker,  and  delivers  very  good  volume  and 
quality.  For  home  use,  the  Western  Electric 
cone  speaker  is  best,  with  its  leads  shunted  by  a 
.0075  mfd.  condenser. 

i     Phone  plug. 

I  Set  Lynch  Leads  if  the  set  is  to  be  operated  in  a 
car,'  using  the  starting  and  lighting  battery. 
The  Lynch  Lead  may  be  made  up  from  any 
double  conductor  wire.  Several  types  of  wire 
can  be  used,  but  the  flexible,  rubber  covered  lead 
is  recommended.  The  wires,  which  should  be 
colored  for  ease  in  identification,  should  be 
scraped  on  one  end,  for  connection  to  the  fila- 
ment posts  on  the  receiver.  The  other  end  of 
the  lead  should  be  connected  to  a  plug  which 
will  fit  into  the  dashboard  connection  to  the 
automobile  storage  battery. 

i     7  inch  x  18  inch  x  7  inch  mahogany  cabinet. 


200        250        30Q        350        400        450        500        550       600 
WAVELENGTH  IN  METEKS 

FIG.    12 

Typical  tuning  chart  of  a  super-autodyne.  The 
curve  marked  "Loop  S"  is  for  the  loop  condenser 
with  the  switch  in  the  "L"  position.  Only  one 
curve  is  shown  for  the  oscillator.  The  curve  em- 
bracing the  upper  heterodyne  points  would  parallel 
the  one  given,  starting  about  four  degrees  higher  at 
250  meters  and  ending  about  thirty  degrees  higher 
at  530  or  540  meters 

CONNECTIONS 

THE  A  battery  should  be  connected  to 
its  leads,  one  tube  inserted  in  a  socket, 
switch  S2  closed,  and  rheostat  R4  just  turned 
on.  If  the  tube  lights,  it  should  be  moved 
from  socket  to  socket  to  see  that  all  A  connec- 
tions are  correct.  The  positive  battery  lead 
should  then  be  connected  to  the  845  and  B 
90  posts.  If  the  tube  lights,  the  wiring  or 
assembly  is  faulty  and  should  be  checked. 
The  tube  should  only  light  when  the  A  battery 
is  connected  to  the  A  leads. 

The  remaining  batteries  may  be  connected, 
and  the  loop  leads  run  to  posts  B  i,  62,  and  83. 
If  the  loop  is  spiral,  Bi  goes  to  the  outside 


386 


Radio  Broadcast 


lead,  82  to  the  center  and  83  to  the  inside. 
When  switch  Si  is  to  the  left,  or  short  position, 
only  half  the  loop  is  used.  When  it  is  to  the 
right,  the  whole  loop  is  used.  This  means 
all  low  wave  stations  up  to  380  meters  will 
come  in  on  dial  C2  from  o  to  100  degrees. 
Stations  from  350  meters  up  will  come  in  on 
C2  with  switch  Si  thrown  to  the  right,  or  long 
position.  This  means  that  in  the  long  posi- 
tion, C2  will  read  about  20  for  345  meter 
stations,  and  about  70  for  536  meter  stations. 
On  the  short  position,  C2  will  read  about  85 
for  345  meter  stations,  and  about  45  for  270 
meter  stations.  These  figures  are  approxi- 
mate, but  show  that  to  cover  the  entire  wave- 
length range,  C2  must  be  varied  from  o  to  100 
degrees  to  go  up  to  370  meters  with  Si  to  the 
left,  then  Si  turned  to  the  right  and  the  re- 
maining wavelength  range  secured  by  varying 
€2  again  from  o  to  100,  allowing,  of  course, 
for  over-lapping.  Ci,  the  oscillator,  starts 
around  18  for  270  meters,  and  brings  in  the 
lower  heterodyne  point  for  536  meters  at  about 
70.  Two  points  can.be  found  for  each  station 
on  this  dial,  which  will  help  in  tuning,  as 
when  interference  is  experienced  on  one  point, 
the  other  may  be  used. 

TUNING     AND    TESTING    THE     COMPLETED    RECEIVER 

THE  first  test  should  be  to  check  tube  Vi  for 
oscillation.  Insert  only  tube  Vi,  set  R4  just 
on  and  connect  the  phones  in  series  with  the  845 
lead.  Then  touch  lugs  3,  or  6  of  the  coupler.  If 
a  plucking  sound  is  heard,  this  tube  is  oscillating. 
If  not,  adjusting  the  rotor  coil  will  cause  it  to 
oscillate.  When  this  rotor  winding  is  in  the  same 
plane  as  the  stator  windings,  turning  it  180  degrees 
around  will  either  start  or  stop  oscillation.  When 
once  set  to  produce  oscillation,  this  coil  should  never 
be  touched.  If  the  tube  squeals  at  low  settings  of 
Ci,  reduce  Ri  to  .25-megohms,  or  try  another 


.5  megohm  leak.  Use  the  highest  value  of  leak 
possible — (up  to  i  meg).  The  receiver  will  prob- 
ably squeal  below  10  degress  on  Ci  in  any  case. 
R2  is  not  critical  and  may  vary  from  i  to  3  megohms. 
With  tube  Vi  oscillating  constantly,  insert  the 
remaining  tubes  in  the  set,  turn  the  rheostat  seven- 
eights  on  for  20 1  A  tubes,  or  on  one-third  for  190/5, 
and  rotate  the  potentiometer  from  positive  to  nega- 
tive. If  both  Ci  and  C2  are  set  at  100  degrees,  a 
plunk  will  be  heard  at  some  point  as  R3  is  adjusted, 
indicating  amplifier  oscillation.  If  Ci  is  adjusted, 
squeals  will  be  heard.  R3  should  be  set  with  its 
arm  just  positive  of  the  point  where  squeals  can 
be  heard,  and  either  left  set  at  this  point,  or  used  to 
control  volume.  Now,  with  Si  to  the  right,  and 
Ci  set  at  50,  rotate  C2  over  its  entire  range.  A 
click  will  be  heard  near  the  center  of  its  scale.  The 
condenser  CX  connected  between  terminals  3  and 
4  of  the  coupling  unit  should  now  be  slowly  turned 
out  in  small  steps  until  rotating  C2  fails  to  produce 
a  click.  The  receiver  is  now  balanced  and  CX,  CX 
should  never  be  touched  unless  tube  Vi  is  changed. 

In  tuning,  C2  will  appear  rather  broad,  which  is 
correct,  while  Ci  will  be  extremely  sharp.  This 
permits  of  extremely  easy  logging,  since  C2  need 
only  be  set  approximately  correct,  and  Ci  rotated 
in  order  to  find  a  station.  The  chart  printed  on 
page  385  will  help  in  preliminary  tuning.  The 
set  will  log  definitely,  and  a  station  once  heard  may 
be  brought  in  again  at  the  same  settings  of  Si,  Ci 
and  C2,  providing  CX,  CX  have  not  been  tampered 
with. 

Due  to  the  sensitivity  of  the  circuit,  a  small 
amount  of  hand  capacity  may  be  noticeable  on  Ci. 
This  may  be  overcome  by  grounding  the  negative 
filament  line  to  a  piping  system,  or  it  may  be  com- 
pensated for  by  tuning-in  a  station,  increasing  Ci 
slightly  until  the  volume  begins  to  decrease,  and 
removing  the  hands  from  the  set.  The  signal  will 
then  return  to  full  intensity.  It  will  be  evident  in 
those  few  cases  where  it  may  be  encountered,  only 
on  weak,  low  wave  stations,  and  is  seldom  bother- 


An  Explanation 

THE  similarity  in  name  of  Dr.  Walter  Van  Braam  Roberts  and  J.  E.  Roberts  has  led  to  some  confusion  among 
the  readers  of  RADIO  BROADCAST.     Doctor  Roberts,  of  Princeton  University,  is  responsible  for  the  inception 
and  the  design  of  the  Roberts  Knockout  receiver.     Doctor  Roberts  wrote  two  articles  describing  this  receiver 
which  appeared  in  the  April  and  May,  1924,  RADIO  BROADCAST. 

Immediately  after  the  publication  of  these  two  articles,  a  great  deal  of  interest  was  shown  by  radio  con' 
structors  all  over  the  country  in  the  design  and  operation  of  the  set.  Many  investigators  started  building  the 
receiver,  making  additions  and  alterations  according  to  their  own  ideas.  One  of  these  enthusiasts  was  J.  E. 
Roberts,  of  Cleveland,  Ohio,  who  prepared  an  article  describing  how  to  build  the  original  two'tube  circuit  in  a 
cabinet  with  an  additional  stage  of  audio  amplification,  making  three  tubes. 

We  have  received  many  letters  from  residents  of  Cleveland  and  vicinity  who  have  taken  issue  with  what 
they  regarded  as  an  unfortunate  use  of  the  similarity  of  last  names  of  these  two  men.  The  situation  which 
drew  the  protest  was  in  Cleveland  and  other  cities.  And  in  especial,  a  number  of  our  correspondents  did 
not  like  printed  matter  which  was  distributed  by  a  Cleveland  radio  shop. 

Mr.  J.  E.  Roberts  has  no  connection  with  RADIO  BROADCAST  other  than  that  of  a  former  contributor  to  its 
pages.  The  only  approved  models  of  the  Roberts  Knockout  circuit  have  been  described  in  the  magazine.  We 
can  take  no  responsibility  for  any  printed  matter  or  representations  of  individuals  relative  to  this  circuit  released 
by  other  sources  than  this  magazine  except  that  of  approved  manufacturers  of  parts  which  may  be  used  in  the 
Roberts  circuit. 


A  New  Method  of  Radio 
Frequency  Amplification 

The  Theory  of  Various  Arrangements  for  Neutralizing  Tube  Capacity  in 
Radio-Frequency  Amplifier  Circuits  and  a  Discussion  of  a  New  Method — An 
Arrangement  for  the  Measurement  of  Amplification  Constant  and  Impedance 

BY  C.  L.  FARRAND 


'T'HIS  paper  of  Mr.  Farrand's  was  presented  More  a  meeting  of  the  Radio 
•*•  Club  of  America,  in  New  York,  and  involves  an  interesting  history 
and  discussion  of  neutralising  methods  in  radio  frequency  amplification. 
Toward  the  end  of  the  paper,  the  author  also  describes  a  method  for  connecting 
and  using  a  vacuum  tube  voltmeter  which  should  be  particularly  interesting  to 
many  readers.  In  a  later  number  we  shall  print  another  article  by  the  same 
author,  dealing  with  his  later  investigations.  The  papers  presented  before  the 
Radio  Club  appear  from  time  to  time  in  this  magazine.  The  editor  assumes 
no  responsibility  for  statements  made  by  the  authors  of  the  papers,  but  is  very 
glad  indeed  to  present  them  to  the  readers  of  RADIO  BROADCAST. — THE  EDITOR 


IT  IS  the  purpose  of  this  paper  to  present 
a  new  method  of  radio  frequency  ampli- 
fication, together  with  the  necessary  data 
for  the  design  and  construction  of  the  circuits. 
Tuned  radio  frequency  amplification  is  not 
new.  See  Schloemilch  and  Von  Bronk,  United 
States  Patent  No.  1,087,982.  This  method 
has  been  used  with  considerable  success, 
more  difficulty  being  experienced  as  the 
number  of  stages  were  increased.  These 
difficulties  were  due  to  incipient  couplings 
in  the  amplifier  circuits,  either  between  the 
input  and  output  circuits  of  a  single  tube  or 
between  the  input  and  output  circuits  of 
more  than  one  tube.  These  couplings  are 
either  electro-magnetic  or  electro-static,  as  in 
a  good  design,  resistance  couplings  are  elimi- 
nated. The  magnetic  couplings  can  best  be 
taken  care  of  by  disposing  the  transformer 
windings  so  that  their  axes  are  at  right  angles, 
and  on  the  same  center  line,  with  reasonable 
distance  between  windings. 

Static  couplings  between  the  input  and  out- 
put circuits  of  the  tubes  can  be  eliminated  by 
shielding  in  all  cases  excepting  the  inherent 
capacity  coupling  of  the  tube  itself.  From 
general  considerations  it  is  apparent,  having 
been  brought  out  before,  that  there  are  three 
capacities  in  a  three-electrode  vacuum  tube, 
two  of  which  act  in  shunt  to  the  input  and  out- 
put circuits  respectively,  and  the  third  which 
is  the  grid  to  plate  capacity,  acts  as  a  coupling 
between  the  input  and  output  circuits.  See 


Fig.  i.  To  eliminate  this  coupling,  it  is 
necessary  to  resort  to  balancing  arrangements 
or  to  additonal  circuits  which  will  nullify 
the  influence  of  the  coupling  current  flowing 
through  this  capacity.  The  coupling  in- 
creases with  frequency,  and,  it  is  in  the  broad- 
casting range  and  shorter  waves  that  the 
most  difficulty  is  experienced. 

Various  methods  have  been  suggested  for 
neutralizing  or  balancing  the  tube  coupling. 
Hartley  (R.  V.  L.  Hartley,  United  States 
Patent  No.  1,183,875)  has  suggested  a  mag- 
netic balance,  which  is  the  equivalent  to  a 
reverse  tickler  coil.  See  Fig.  2. 

By  this  method,  the  coupling  effect  of  the 
grid-to-plate  capacity  of  the  tube  is  balanced 
by  an  equal  and  opposite  magnetic  coupling 
between  the  input  and  output  circuits.  This 
condition  holds  for  only  one  wavelength. 
In  the  Figure  shown,  the  static  tube-coupling 
increases  with  frequency,  while  the  magnetic 
coupling  remains  constant. 

THE    RICE    METHOD 

RICE  (C.  W.  Rice,  United  States  Patent 
No.   1,334,118)  has  suggested  a  capacity 
balance  which  is  in  effect   Fig.   3.     By  this 
method,  the  coupling  effect  of  the  grid-to-plate 
capacity  is  balanced  by  a  capacity  of  equal 
value  connected  between  the  plate  and  an  in- 
put coil  being  opposite  potential  to  the  grid. 
Hazeltine  (L.  A.  Hazeltine,  United  States 
Patent     No.    1,450,080)     has     suggested     a 


388 


Radio  Broadcast 


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FIG.    I 

capacity  balance  wherein  the  effect  of  the 
grid  to  plate  capacity  of  the  tube  is  balanced 
by  means  of  an  output  transformer.  Fig.  4. 
Here  the  coupling  effect  of  the  grid-to- 
plate  capacity  is  balanced  by  a  capacity  con- 
nected between  the  grid  and  an  output  coil 
having  a  potential  opposite  to  the  plate. 


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FIG.    2 

The  output  coil  is  the  secondary  of  the  trans- 
former supplying  the  next  tube  and  has  a 
ratio  of  turns  greater  than  unity  to  satisfy 
the  impedance  relation,  so  that  it  is  necessary 
that  the  value  of  the  balancing  capacity  be 
chosen  to  equal  the  grid-to-plate  capacity 
divided  by  the  voltage  ratio  of  the  output 
transformer. 


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FIG.  3 

The  disadvantages  of  the  above  methods 
are  that,  particularly  on  short  wavelengths, 
it  is  very  difficult  to  maintain  a  balance 
when  more  than  one  stage  of  radio  frequency 
amplification  is  used.  This  is  due  to  stray 
capacities,  which  tend  to  upset  the  balance 
of  the  circuit.  Oscillations  then  result.  Dif- 
ficulty of  this  sort  is  also  brought  about  by 
the  variation  of  grid-to-plate  capacity  of 
commercial  tubes,  which  vary  so  much  that 


a  balance  obtained  for  one  tube  may  not  hold 
for  another. 

A    NEW    NEUTRALIZING    SCHEME 

THE  method  of  nullifying  the  effect  of  the 
grid-to-plate  capacity  of  three-electrode 
vacuum  tubes  described  in  this  paper  does 
not  depend  upon  a  capacity  balance  and  is 
free  from  the  disturbing  effects  described 
above.  The  method  involves  a  resistance 
connected  between  the  grid  and  plate  of  the 
tube  as  in  Fig.  5. 

The  effect  of  this  arrangement  is  to  change 
the  phase  of  the  coupling  current  flowing 
between;  the  input  and  output  circuits,  thereby 
reducing  the  energy  transfer  or  feed-back 
between  these  circuits  and  causes  the  remaining 
energy  to  be  absorbed  as  quickly  as  it  is  trans- 
ferred or  fed  back.  The  value  of  resistance 
necessary  to  nullify  the  grid-to-plate  coupling 
is  dependent  upon  the  design  of  the  tube,  as 


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FIG.    4 

well  as  the  circuits.  This  resistance  value 
is  not  critical.  For  the  storage  battery  tubes 
now  in  commercial  production,  a  resistance 
ranging  between  twenty-five  and  thirty-five 
thousand  ohms  gives  satisfactory  performance 
for  multistage  operation.  The  value  for  mul- 
tistage operation  is  slightly  lower  as  it  is 
possible  to  take  care  of  the  stray  overall 
coupling  by  a  slight  reduction  of  resistance. 
One  hundred  thousand  ohms  is  a  satisfactory 
value  for  the  present  dry  cell  tubes  and 
may  vary  between  ninety  and  one  hundred 
and  twenty  thousand  ohms. 

The  resistance  should  preferably  be  non- 
inductive  and  of  low  capacity.  Present  forms 
of  conducting  coated-paper  resistances,  and 


A  New  Neutralizing  Scheme 


389 


carbon  filament  wound  lavite  resistances  are 
satisfactory. 

The  circuit  for  a  two-stage  amplifier  is 
shown  in  Fig.  6. 

It  will  be  noted  that  a  condenser  is  inserted 
in  series  with  the  resistance  between  grid 
and  plate  to  prevent  the  plate  battery  from 
flowing  through  it  to  filament.  The  con- 


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i  7 

c 
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0 

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FIG.    5 

denser  is  purely  a  blocking  condenser  and 
may  range  in  value  between  one  microfarad 
and  one  one-thousandth  of  a  microfarad,  and 
is  only  needed  to  permit  the  amplifier  tubes 
to  be  operated  from  a  common  plate  battery. 
The  transformer  windings  should  preferably 
be  tightly  coupled,  although  this  is  not 
necessary  as  long  as  a  suitable  voltage  ratio 
is  maintained  between  primary  and  secondary. 
A  suitable  design  consists  of  one  hundred 
turns  of  No.  26  B  &  S  gauge  wire  on  a  cylin- 
drical tube,  two  inches  in  diameter  and  about 
two  and  three  quarter  inches  in  length. 
This  is  the  secondary  winding.  The  primary 
should  be  wound  with  about  twenty-five  turns 
of  the  same  size  wire  on  a  concentric  cylindri- 
cal tube  of  about  one  and  three  quarter  inches 
in  diameter.  It  is  preferable  to  have  the 
primary  winding  the  same  length  as  the  sec- 
ondary winding  is  when  enclosed  by  the  secon- 
ary  winding.  This  arrangement  gives  the 
tightest  coupling,  although  the  same  result 
may  be  secured  by  using  more  primary  turns 
and  less  coupling.  This  will  be  discussed 
more  in  detail  later.  The  primary  is,  in 
practice,  wound  opposite  to  the  secondary. 
That  is  to  say,  if  the  secondary  is  wound 
clockwise,  the  primary  is  wound  counter- 
clockwise, or  vice  versa.  The  end  of  the 
primary  winding  directly  under  the  grid  end 
of  the  secondary  should  be  connected  to  the 
plate  battery.  The  other  terminals  follow 
as  usual.  The  secondary  tuning  condenser 
should  have  a  capacity  of  approximately  two 
hundred  and  fifty  micro-microfarads.  The 
increase  in  intensity  produced  by  each  stage 
of  radio  frequency  amplification  as  outlined 
above  is  nearly  as  much  as  that  produced  by 
each  stage  of  audio  frequency  amplification. 
This  is  a  very  general  statement  but  holds 


fairly  closely  for  radio  stages  up  to  three  or 
four  before  the  detector  when  compared  one 
stage  at  a  time  with  one  and  two  stage  of 
audio  after  the  detector,  although  the  voltage 
amplification  of  the  radio  stages  were  only 
about  twelve  each  while  the  audio  amplifiers 
gave  approximately  twenty  per  stage. 

This  indicates  that  while  the  detector  char- 
acteristic is  not  linear  it  is  far  from  a  square 
law. 

REGENERATIVE  AMPLIFICATION  IN  THIS  CIRCUIT 

IN  ADDITION  to  the  radio  frequency  ampli- 
*  fication  of  each  stage,  it  is  possible  to  obtain 
a  regenerative  amplification  which  is  equiva- 
lent in  increased  volume  to  the  addition  of 
two  audio  stages  on  a  signal  of  average  in- 
tensity. Fig.  7  shows  the  circuit  of  a  receiver 
consisting  of  three  stages  of  radio  frequency 
amplification,  a  detector  and  two  audio  stages. 
The  regeneration  here  shown  is  provided 
for  by  omitting  the  nullifying  resistance  of 
the  third  radio  stage,  and  controlling  the 
feed-back  due  to  the  tube  coupling  by  means 
of  a  potentiometer  on  the  grid  of  this  same 


FIG.  6 

tube.  This  gives  very  satisfactory  operation. 
Equally  satisfactory  operation  may  be  had 
by  the  use  of  a  variometer  in  the  plate  of  the 
detector  tube  in  the  usual  manner.  In  this 
case  the  nullifying  resistance  must  be  used 
across  the  grid  and  plate  of  the  third  tube  as 
well  as  across  the  first  and  second.  In  the  use 
of  three  stages  of  radio  frequency  amplifica- 
tion without  regeneration  it  is  not  necessary 
to  take  any  particular  precautions  except  to 
dispose  the  transformer  windings  at  right 
angles  and  to  use  care  to  provide  for  short 
grid  leads,  and  that  the  grid  lead  of  one  tube 
does  not  run  close  to  the  grid  lead  of  another 
tube.  If  such  precautions  are  not  taken,  the 
amplifier  may  regenerate  and  oscillate  at  the 
lower  wavelengths.  It  will  be  found  that 
when  the  regenerative  feature  is  added  to  the 
amplifier  or  detector,  better  control  of  the 
regeneration  will  be  obtained  if  the  receiver 


3QO 


Radio  Broadcast 


has  first  operated  satisfactorily  without  re- 
generation. This  means  that  the  interstage 
coupling  has  been  reduced  to  a  minimum  and 
that  this  provides  for  the  localization  and 
better  control  of  the  regeneration.  In  the 
operation  of  a  receiver  as  outlined  above  using 
two  or  three  stages  of  radio  frequency  ampli- 
fication in  addition  to  regeneration,  the  local 
oscillations  produced  during  the  adjustment 
of  the  regenerative  amplifier  or  detector  tube 
do  not  radiate  from  the  antenna  in  any 
noticeable  degree  sufficient  to  cause  inter- 
ference with  near-by  receivers.  As  a  typical 
example  of  this,  a  receiver  has  been  operated 
on  an  outdoor  antenna  approximately  forty  feet 
from  an  adjacent  antenna  which  is  paralleled 
for  approximately  twenty  feet.  Both  anten- 
nas were  approximately  forty  feet  high  and  had 
a  total  length  of  about  one  hundred  and 
twenty  five  feet.  The  beat  produced  by  the 
receiver  was  noticeable  on  the  receiver  of  the 
adjacent  antenna  only  on  reception  from  sta- 
tions nearly  one  thousand  miles  distant  and 
then  was  not  particularly  objectionable. 

Due  to  the  low  input  impedance  of  the 
present  commercially  produced  tubes  and  the 
consequently  large  damping  effect  produced 
thereby,  the  tuning  of  transformers  is  broader 
than  would  be  anticipated.  While  objec- 
tionable in  single-stage  operation,  the  tuning 
sharpens  considerably  with  the  addition  of 
several  stages  until  very  reasonable  selectivity 
is  obtained.  It  is  also  possible  and  extremely 


practicable  to  tune  the  transformers  by  means 
of  condensers  on  a  common  shaft  as  suggested 
by  Hogan.  (J.  V.  L.  Hogan,  United  States 
Patent  No.  1,014,002).  This  has  been 
done  very  successfully  with  three  stages  of 
radio  frequency  amplification  using  an  aperi- 
odic antenna  input  by  means  of  four  conden- 
sers on  a  common  shaft  and  with  six  stages  of 
radio  frequency  amplification  by  means  of 
eight  condensers  on  a  common  shaft.  In  the 
latter  case  one  condenser  was  used  to  tune 
the  antenna  separately  which  was  loosely 
coupled  to  the  amplifier  input  circuit.  The 
condensers  were  electro-statically  shielded 
from  each  other,  and  the  tube  coupling  capaci- 
ties were  nullified  by  means  of  the  resistances 
of  values  given  above. 

Additional  improvements  in  selectivity  have 
been  made,  which,  unfortunately  cannot  be 
disclosed  at  the  present  time  and  will  have  to 
form  the  subject  of  a  later  paper.  It  might 
be  mentioned  that  by  these  means,  reception 
without  regeneration  of  five  hundred  and  nine- 
meter  stations  in  Philadelphia,  through  a 
local  four  hundred  and  ninety  two-meter 
station,  is  entirely  practicable. 

MEASUREMENTS    OF    AMPLIFICATION    CONSTANT 
AND    IMPEDANCE 

A  METHOD  of  measuring  the  voltage 
**  amplification  of  radio-frequency  ampli- 
fiers during  the  writer's  experiments  became 
very  desirable.  After  various  methods  were 


MR.  FARRAND  DEMONSTRATING  HIS  RECEIVER 

Before  a  meeting  of  the  Radio  Club  of  America  in  New  York.     The  entire  back  of  the  panel  is  shielded,  as 
can  be  seen  from  the  photograph.     The  condensers  are  all  tuned  by  one  knob  which  controls  a  gear  arrange- 
ment.    Nine  tubes  are  used  in  this  model 


Measurement  of  Amplification  Constant 


391 


FIG.    7 


considered  and  used,  the  peak  volt-meter  was 
selected  as  giving  most  promise.  This 
method  consisted  in  determining  the  actual 
voltages  of  the  grids  under  working  condi- 
tions by  use  of  a  three-electrode  vacuum 
tube.  The  use  of  three-electrode  tubes  as 
volt  meters  is  well  known  and  has  been  des- 
cribed before. 

The  voltmeter  was  calibrated  as  follows: 
A  uv-2oiA  tube  was  used  with  approximately 
67  volts  on  the  plate  and  about  12  volts  nega- 
tive on  the  grid.  The  plate  current  was  then 
normally  about  10  micro-amperes.  A  known 
radio  frequency  voltage  was  applied  to  the 
grid  and  the  grid  negative  voltage  was  in- 
creased until  the  plate  current  reached  a 
known  value  which  was  the  10  micro-amperes. 
The  increment  of  negative  grid  voltage  was 
recorded.  It  was  found  that  the  tube  would 
always  reproduce  these  conditions  with  the 
same  voltages.  In  this  manner  the  voltmeter 
was  calibrated  in  terms  of  increments  of  nega- 
tive grid  voltages  vs.  applied  root  mean  square 
values.  To  save  interpolation  the  measure- 
ments of  impedance  and  voltage  amplifica- 
tion were  made  with  the  same  r.m.s.  value  of 
voltage  applied  to  the  voltmeter.  This  value 
was  set  at  .5  volts  and  the  input  voltage  of 
the  preceding  tube  changed  until  this  value 
was  produced. 

The  following  is  a  diagram  of  the  voltmeter 
and  circuit  used  for  these  measurements: 

The  capacity  of  the  voltmeter  is  very  small, 
since  it  is  only  the  grid-to-filament  capacity 
of  the  tube  plus  small  lead  capacity  which 
would  approximate  10  to  20  micro-micro- 
farads. This  capacity  is  connected  in  parallel 
to  the  tuning  condenser  and  therefore  does 
not  affect  the  result.  The  impedance  of  the 
voltmeter  can  be  considered  as  purely  resis- 
tance in  nature  and  very  high,  probably  sev- 
eral, megohms,  as  the  grid  has  in  excess  of  10 
volts  negative  applied. 


MEASUREMENTS      WITH      THE      VACUUM      TUBE 
VOLTMETER 

THE  voltage  amplification  per  stage  is  the 
voltage  of  the  grid  of  the  second  tube 
divided  by  the  voltage  of  the  first  tube.  It 
was  necessary  to  determine  that  the  imped- 
ance of  the  plate  circuit  of  the  second  tube 
would  not  affect  the  impedance  of  its  grid, 
as  in  multistage  operation  the  plate  circuit  of 
the  second  tube  would  be  tuned  by  a  trans- 
former to  supply  the  grid  of  the  succeeding 
tube,  and  if  this  high  impedance  caused  by 
the  plate  tuning  of  the  second  tube  affected 
its  grid  to  filament  impedance,  the  measure- 
ment as  outlined  would  not  hold.  Non- 
inductive  resistances  of  10,000  ohms  were 
inserted  in  the  plate  circuit  and  the  plate 
voltage  was  maintained  constant  by  adding 
sufficient  battery  to  take  care  of  the  resistance 
drop,  and  at  radio  frequencies  this  was  found 
to  affect  the  input  impedance  of  the  grid  very 
considerably.  This  corresponded  somewhat 
to  the  results  obtained  by  Weinberger. 
(J.  Weinberger,  Proc.  I.  R.  E.,  page  584,  sec. 
1919.)  It  was  thought  that  this  change  of 
impedance  might  be  due  solely  to  capacity 
coupling  of  the  tube  causing  feed-back  action, 
therefore  the  applied  frequency  was  reduced 
to  1000  cycles  and  it  was  found  that  at  this 
frequency,  the  grid-to-filament  impedance 
was  independent  of  the  plate  load  impedance. 
It  followed,  therefore,  that  any  influence  of 
the  plate  load  on  the  grid  impedance  was  due 
to  regeneration  and  would  disappear  when  the 
regeneration  was  nullified. 

The  measurements  of  voltage  ratio  by  this 
method  would  hold  and  give. the  true  radio 
frequency  amplification  without  feed-back  as 
long  as  the  amplifier  was  non-regenerative. 

The  voltage  ratio  was  determined  for.  a 
tuned  radio-frequency  transformer  as  shown 
in  the  Figure  and  the  radio  frequency  ampli- 


392 


Radio  Broadcast 


FIG 


fication  factor  per 
stage  obtained.  A 
similar  transformer 
was  then  connected 
to  the  plate  of  the 
second  tube  and  ar- 
ranged to  supply  the 
grid -to -filament  cir- 
cuit of  a  third  tube 

which  was  connected  as  the  second  tube  had 
been  in  the  first  case.  The  voltage  on  the  grid 
of  the  second  tube  was  found  to  be  decidedly 
higher  due  to  feed-back  action.  A  nullifying 
resistance  was  then  connected  from  grid  to 
plate  of  the  second  tube  and  adjusted  until 
the  voltage  of  its  grid  equalled  the  original 
voltage  as  given  when  the  output  of  the  plate 
was  shorted  by  switch  "S."  The  resistance 
had  then  nullified  the  feed-back  action  due 
to  the  natural  capacity  between  the  grid  and 
plate  of  the  tube  and  the  voltage  amplification 
obtained  was  the  original  non-regenerative 
radio  frequency  amplification.  The  value  of 
nullifying  resistance  thus  obtained  was  found 
to  be  between  30,000  and  50,000  ohms  for 
uv-2oiA  tubes  and  between  80,000  and 
120,000  ohms  for  uv-igg  and  WD-II  tubes 
The  values  of  resistance  approximate  the  ca- 
pacity coupling  reactance  of  the  tubes,  i.  e., 
the  grid  to  plate  capacity  in  ohms  at  the 
operating  frequency. 

IMPEDANCE  VALUES  OF  COMMERCIAL  TUBES 

v>~pHE   maximum   voltage   amplification  de- 

*  termined  and  the  turn  ratios  for  maximum 

amplification  lead  to  the  conclusion  that  the 


grid  to  filament  im- 
pedance was  much, 
lower  than  antici- 
pated, when  the  grid 
was  connected  to  neg- 
ative filament.  Since 
the  grid  to-filament 
impedance  was  al- 
ways shunted  with  a 

secondary  tuning  condenser,  it  could  be  consid- 
ered as  purely  resistance  in  nature.  It  was  de- 
cided to  determine  this  impedance  value  for 
commercial  tubes.  The  peak  voltmeter  method 
was  very  well  suited  to  this  measurement  as  it 
was  only  necessary  to  substitute  a  known  non- 
inductive  resistance  for  the  tube,  retune  to 
compensate  for  the  reduction  of  capacity  of  the 
grid-to-filament  and  adjust  the  resistance  until 
the  voltage  of  the  grid  of  the  second  tube  was  at 
its  original  value.  The  resistance  thus  deter- 
mined was  then  equal  to  the  resistance  of  the 
grid-to-filament  path  of  the  tube.  These 
values  for  uv-2oiA  tubes  with  grid  connected 
to  negative  filament  were  found  to  be  between 
120,000  and  150,000  ohms  with  130,000  ohms 
as  a  fair  average.  This  accounted  for  the 
broadness  of  tuning  of  non-regenerative  radio- 
frequency  amplifiers,  as  with  a  circuit  using  a 
condenser  of  250  micro-microfarads  maximum, 
for  the  broadcasting  range,  the  condenser 
reactance  at  400  meters  is  approximately 
1800  ohms  and  the  effect  of  130,000  ohms  in 
shunt  to  such  a  circuit  is  the  same  as  if  ap- 
proximately 25  ohms  had  been  inserted  in 
series  with  the  condenser  and  inductance,  and 
consequently  produces  very  large  damping. 


How  to  Build  Radio  Broadcast's 
Phonograph  Receiver 


BY  ARTHUR  H.  LYNCH 


IN  THE  June  RADIO  BROADCAST  we  de- 
scribed  a   receiver  which   has   been   de- 
signed to  fit  in  any  phonograph.     This 
article,  the  second  of  the  series  describing 
this  receiver,  deals  with  the  actual  construc- 
tion of  the  apparatus  and  indicates  by  illus- 
trations what  has  been  done  in  RADIO  BROAD- 
CAST'S  Laboratory  to  apply  this  unit  to  a 
number  of  phonographs. 

It  may  be  seen  from  the  illustrations  accom- 
panying this  article,  that  it  is  not  necessary 
to  use  one  specified  unit  in  building  this  re- 
ceiver. For  example,  any  good  audio  trans- 
former will  function  satisfactorily  in  the  re- 
flex stage,  and  any  good  push-pull  transformer 
will  work  in  the  amplifier  arrangement.  In 
the  diagrams  shown  in  Figures  23-A  and  B,  the 
panel  and  sub-base  arrangements  have  been 
designed  to  accommodate  practically  any 
.0005  mfd.  condenser,  and  almost  any  tube 
sockets  and  other  units  which  make  up  the 
assemblage. 

RADIO  BROADCAST'S  Phonograph  Receiver 
has  not  been  designed  to  satisfy  the  demand 
for  the  ultimate  in  radio  reception.  It  will, 
however,  bring  in  excellent  quality  with  very 
good  volume  and  at  the  same  time  cover  a 


very  reasonable  wavelength  range.  With 
a  similar  set  operated  here  on  Long  Island 
during  the  month  of  April,  and  using  but  two 
tubes,  the  following  log  was  made  in  one  hour 
and  twenty  minutes: 


DIAL    SETTINGS 

12-12 

15-15 

19*19 

21-21 

22-22 

28-28 

31-31 

32-32 

34-34 
39-39 
41-41 
42-42 

45-45 
46-46 

49-49 
52-52 

57-57 
60-60 
62-62 
64-64 
69-69 
80-80 


CALL   LETTERS 
WC  AD 
WEAN 
WTAS,   WPG 
KDKA 
WGBS 
WLS 
CFCA 
WHN 
WGN 
WTAM 
WLIT 
WOR 
CHYC 
PWX 
WLW 
WOS 
WJZ 
WCAE 
WCAP 
WEEI 
WEAF 
WNYC 


When  this  log  was  made,  the  set  was  tuned 
with   but   two   controls.    The   rheostat   and 


RADIO  BROADCAST  Photograph 


FIG.    I.       SUB-PANEL    ASSEMBLY 

The  photograph  illustrates  how  the  rheostat  panel  and  tube  sockets  are  mounted  upon  the  brackets.    AH  con- 
necting leads  to  the. main  panel  are  temporarily  coiled  and  labeled  until  this  assembly  is  ready  for  further  use 
This  is  the  "Robert-Unit"  made  by  the  Radio  Research  Laboratories 


394 


Radio  Broadcast 


tickler  controls  were  not  used.  It  will  be 
noted  that  the  positions  of  the  two  dials 
throughout  this  log  coincide  over  the  entire 
broadcast  range. 

HOW  TO  ASSEMBLE   AND  WIRE  THE   SUB-PANEL 

BEFORE  drilling   holes    in    the   sub-panel 
for  mounting  the  various  units  it   must 
hold,  it  is  advisable  to  place  the  sub-panel  it- 
self upon  the  brackets  which  are  going  to 
support  it  on  the  main  panel.     Then  place 


the  tube  sockets  in  their  proper  places  and  if 
necessary,  secure  them  with  a  few  pieces  of 
string.  Then  turn  the  sub-panel  upside  down 
and  mark  off  the  positions  to  be  occupied  by 
the  transformers,  but  make  certain  that  there 
is  plenty  of  space  surrounding  each  unit  to 
permit  the  wiring  to  be  done  easily. 

It  is  good  practise  to  do  as  much  wiring 
on  the  sub-panel  as  possible  before  perma- 
nently attaching  it  to  the  panel  as  shown  in 
Fig.  i. 


FIG.    2.      A    TEMPLATE    FOR   THE    SPIDER   WEB    COILS 

Exact  size.  The  windings  for  these  coils,  as  used  in  various  parts  of  the  Roberts  circuit  and  indicated 
by  the  letters  are  as  follows:  A  (antenna  coil):  40  turns  No.  22  DCC  wire  tapped  1-2-5-10-20-30-40;  Si : 
44  turns  No.  22  DCC  wire;  N:  20  turns  No.  26  DCC  wire;  P:  20  turns  No.  26  DCC  wire  (two  wires  of  N 
and  P  are  wound  parallel  as  a  pair);  82:  44  turns  No.  22  DCC  wire;  T:  18  turns  No.  22  DCC  wire.  Coils  A, 
Si,  82  and  T  are  each  individually  wound  under  two  and  over  two  spokes  of  the  form.  The  NP  coil  is 

wound  under  one  and  over  one  spoke 


How  to  Build  Radio  Broadcast's  Phonograph  Receiver 


395 


RADIO  BROADCAST  Photograph 
FIG.    3A-B.      A   HOME   MADE   COIL   UNIT 

Constructed  from  odds  and  ends  around  the  laboratory.  The 
binding  posts  to  which  flexible  leads  from  the  coils  are  attached 
are  mounted  on  bakelite  supports.  Coupling  between  the  pri- 
mary and  secondary  is  obtained  by  loosening  the  hexagon  nuts 
and  shifting  the  position  of  the  primary  coil 


THE    PANEL 

IN  ARRANGING  the  units  on  the  panel  the 
layouts  in  Figs.  21 -A  and  B  will  be  found 
very  helpful.  Then,  too,  it  is  good  practise  to 
wire  as  much  of  the  panel  as  possible  before  the 
sub-panel  is  attached.  If  this  plan  is  followed 
the  balance  of  the  wiring  will  be  brought  to 


a  minimum  and  the  attendant  work  will  be 
much  simplified. 

HOME-MADE    COILS 

E  of  the  simplest  forms  of  coil  for  home 
construction  and  which  may  be  used 
in  this  receiver  is  the  spider-web  coil.  The 
form  dimensions  are  given  in  Fig.  2.  The 
various  wire  sizes,  and  the  number  of  turns 
to  be  wound  on  each  coil  are  indicated  in  the 
caption  of  Fig.  2  on  page  394. 

A  simple  and  good  method  of  mounting  and 
coupling  home  made  coils  has  been  designed 
by  John  B.  Brennan,  Technical  Editor  of 
RADIO  BROADCAST.  This  system  is  illus- 
trated in  Fig.  3A-B. 

ANTENNA   SWITCH 

IN  ORDER  to  compensate  for  the  use  of 
antennas  of  various   lengths,  a  switch   is 
placed   in   the   antenna   circuit   to   alter  the 


RADIO  BROADCAST  Photograph 
FIG.    4.      THE    TAP    SWITCH 
The  antenna  coil  sections  may  be  included  in  the 
primary  circuit  by  means  of  this  switch  which  is 
mounted  upon  a  piece  of  bakelite  supported  within 
the  coil  unit  as  shown  above.     This  is  a  control 
which  need  not  be  varied  once  the  correct  adjust- 
ment has  been  obtained.     Therefore,  it  is  not  neces- 
sary to  mount  the  switch  upon  the  panel  proper 


IADIO  BROADCAST  Photograph 

FIG.    5.      THE    BRACKETS 

For  supporting  the  sub-panel  upon  which  is  mounted 

the   transformer,  etc.      The   arrows    indicate   the 

points  at  which  the  projected  parts  of  the  brackets 

are  removed 


396 


Radio  Broadcast 


number  of  turns  in  the  primary  of  the  antenna 
coupler.  By  the  proper  adjustment  of  this 
switch,  the  two  main  control  dials,  the  an- 
tenna and  the  radio-frequency  tuning  dials, 
will  be  found  to  read  approximately  the  same 
for  given  stations  within  the  tuning  range. 
This  feature  is  particularly  valuable  when  the 
receiver  is  used  by  an  inexperienced  person. 
In  order  to  make  the  layout  of  our  phonograph 
model  more  symmetrical  we  have  placed  this 
switch  behind  the  panel  as  shown  in  Fig.  4. 
When  the  receiver  has  been  completed  it 
should  be  tested  before  it  is  placed  in  its  cabi- 
net and  the  proper  setting  for  the  antenna 
switch  should  be  determined. 

RUBBER    BUSHINGS 

WHERE  cushion   sockets  are  not  used, 
sponge  rubber,  which  may  be  procured 
from  many  dealers,  or  from  several  radio  mail 
order  houses  or  rubber  companies,  is  ideal  for 

FIG.    6.      THE    BUSHINGS 

Note  that  the  sub-panel  is  raised  up  from  the 
brackets  by  means  of  the  knurled  nuts  taken  from 
the  socket  terminals  and  which  are  used  as  bushings. 
This  is  necessary  so  that  the  bottom  of  the  audio 
reflex  transformer — mounted  out  of 
sight  in  this  photograph  at  the  far  end 
of  the  sub-panel — does  not  project 
beyond  the  bottom  of  the  panel 


RADIO  BROADCAST  Photograph 


RADIO  BROADCAST  Photograph 


FIG.    7.      THE    BATTERIES 

Are   here   shown   stacked    up   to  fit 
underneath  the  sub-panel.     This  re- 
ceiver may  be  used  as  a  portable  outfit, 
i^-volt  dry  cell  tubes  are  used 


cushioning  the  tubes  to  prevent 
microphonic  noises  which  are 
sometimes  noticed  where  rigid 
construction  is  used.  Flexible 
wiring  is  employed  between  the 
main  and  the  sub-panels.  This 
is  necessary  to  insure  the  suc- 
cess of  the  cushioning.  An  ideal 
system  for  applying  bushings  of 
this  kind  is  shown  in  Fig.  6. 

TUBE    IRREGULARITIES 

TUBES,  particularly  those 
which  have  been  in  use  for 
some  time,  are  often  found  to 
be  anything  but  uniform  in  per- 
formance. A  tube  which  may 
do  very  well  as  a  radio  or  audio 
amplifier  may  not  function  prop- 
erly as  a  detector  and  vice  versa. 
Therefore,  the  tubes  must  be 
tried  in  various  positions  until 
the  best  combination  is  found. 


How  to  Build  Radio  Broadcast's  Phonograph  Receiver 


397 


-8     45       90     US 


FIG.    8.      THE    WIRING   ARRANGEMENT 


From  this  circuit  it  will  be  seen  that  the  push-pull  amplifier  circuit  differs  from  the  original  four-tube  hook-up. 

The  balance  of  the  circuit,  however,  remains  the  same.     In  this  illustration  Amperites  have  been  substituted 

for  the  rheostat  controlling  the  two  push-pull  tubes.     Also  a  condenser  Cy  has  been  added  in  the  circuit. 

This  condenser  will  effectively  prevent  the  amplifying  transformer  from  singing 


ABOUT    PLATE    AND   GRID    VOLTAGES 

THE  plate  voltage  on  the  radio  and  audio- 
amplifier  tubes  is  not  critical  and  for  prac- 
tical purposes  in  the  home  we  have  found  90 
volts  to  be  ideal.     It  is  unnecessary,  unless 
great  volume  is  required,  to  use  more  than  90 

-BINDING  POST  STRIP 


volts  in  any  part  of  the  circuit,  and  it  has  been 
found  that  a  jumper  between  the  two  last 
terminals  on  the  binding  post  strip,  as  indi- 
cated by  the  dotted  line  in  Fig.  IO-A,  serves  to 


Variable  Connection  For 

Proper  Detector  Plate  Voltage 

-AB 


B  45 


'v  6  Volt 
Storage  Battery 


45\CBat' 

'B45 

Remove  Dotted  Line 

Connection  When  Using 

Only  90  Volts  On  Both 

Amplifier  Posts. 


Symbolical 
Representation  ^ 


Amp. 
B+13& 


FIG.  IOA-B  THE  JUMPER  CONNECTION 
When  it  is  desired  to  use  but  90  volts  upon  the  am- 
plifier tubes  the  connections  to  the  B  batteries  must 
be  changed  as  shown  in  Fig.  IO-A.  The  connection 
represented  by  the  dotted  line  is  removed  and  a 
jumper  connection  is  fastened  between  the  amplifier 
B  plus  binding  posts.  Fig.  IO-B  shows  the  con- 
nections when  the  full  135  volts  are  used 

.  BINDING  POST  STRIP 


FIG.  9.  TESTING  PLATE  VOLTAGE 
For  some  detector  tubes  it  is  necessary  to  employ  a 
definite  plate  voltage  which  must  be  ascertained  by 
actual  test.  The  pointed  lead  attached  to  the  B 
plus  binding  post  may  be  touched  upon  the  several 
taps  of  the  first  45  volt  B  Battery  until  the  desired 
value  of  plate  voltage  is  obtained 


-  6  Volt 
Storage  Battery 


45      Shows  Connections 
When  Full  135  Volts  is 
Used 


FIG.    II.      ANTENNA    SUBSTITUTE 

For  an  outside  antenna  called  the  Antennaphone.  1 1 
is  only  necessary  to  place  a  metal  disc  under  a  desk 
telephone  to  obtain  an  antenna  installation.  The 
disc  is  then  connected  to  the  antenna  binding  post 
on  the  receiver.  Wire  is  supplied  for  this  purpose 


>98 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 

FIG.    12.      ANOTHER   ANTENNA    SUBSTITUTE 
This  unit  is  r.ierely  plugged  in  to  any  electric  light  lamp 
socket.     Several  methods  of  use  are  shown  in  Fig.  13 


bring  this  voltage  into  play  on  all  tubes  but  the 
detector. 

Caution:  When  using  the  jumper  between 
the  terminals  in  the  diagrams  marked  minus 
90  and  minus  135,  as  indicated  by  the  dotted 
lines,  make  sure  that  the  135-volt  connection 
to  the  B  battery  is  taken  off.  Otherwise  the 


FIG.    13 

The  several  ways  in  which  the  Ducon  lamp-socket 
antenna  may  be  connected  to  the  receiver 


FIG.    14.    AN    ELABORATE    PIECE   OF    RADIO 
FURNITURE 

A  Jewett  Highboy  loud  speaker-radio  cabinet  in 
which  has  been  combined  a  loud  speaker,  a  battery 
cabinet  and  receiver  housing.  The  sliding  doors 
have  been  so  arranged  that  any  standard-sized  re- 
ceiver may  be  fitted  within  the  housing.  There  is 
still  ample  room  for  the  installation  of  a  home-made 
or  portable  phonograph 


last   section   of  the  battery  will   be  ruined. 
This  is  also  shown  in  Fig.  IO-A. 

The  regeneration  of  volume  of  this  receiver 
must  be  controlled  smoothly,  and  we  have 
found  that  much  depends  on  the  type  of  de- 
tector tube  used.  The  45  volts  indicated  in  the 
diagrams  is  a  very  flexible  standard,  and  various 
voltages  from  8  to  90  h#ve  been  employed 
successfully  with  various  tubes.  The  detector 
connection  in  Fig.  9  is  therefore  variable. 

CENTER   HOLES    ONLY 

TEMPLATES  for  drilling  accompany  all 
modern  parts,  and  to  avoid  giving  the  im- 
pression that  particular  units  must  be  em- 
ployed, we  have  merely  indicated  the  center 
holes  for  condensers,  coils,  rheostats,  jacks, 
and  the  filament  switch  mounting  in  the 
panel-layouts. 

MAKING  A  PORTABLE  OF  THE  RADIO  BROADCAST 
PHONOGRAPH    RECEIVER 

IN  FIG.  7,  we  illustrate  a  receiver  which  was 
made  to  fit  in  a  console  phonograph.     By 
removing  the  entire  unit   from  the  console 


How  to  Build  Radio  Broadcast's  Phonograph  Receiver 


399 


FIG.    l6 

The  rear  view  of  the  Sonora  cabinet  illustrating 
the  ample  space  which  has  been  provided  for  the 
installation  of  even  larger  types  of  storage  B 
battery.  The  removable  back-panel  is  shown  at 
the  right  of  the  main  cabinet 


FIG.    15.    A  STANDARD  FORM  OF  RADIO- 
PHONOGRAPH 

In  this  cabinet,  manufactured  by  the  Sonora 
Phonograph  Company,  has  been  built  a 
Roberts  four-tube  receiver.  The  compart- 
ment underneath  the  receiver  contains  all  the 
necessary  batteries  for  its  operation 

and  placing  it  in  a  wooden  carrying  case,  or 
other  container,  and  using  dry  cell  tubes  we 
have  an  ideal  portable  for  use  on  automobile 
trips,  boat  rides,  and  other  summer  activities. 


RADIO  BROADCAST  Photograph 


For  use  of  this  sort  we  have  found  that 
wo-12  tubes  are  very  satisfactory  and  that 
either  three  or  four  standard  dry  cells  con- 
nected in  parallel  work  very  nicely.  If  the 
receiver  is  not  to  be  used  as  a  portable  for 
more  than  a  few  weeks,  three  dry  cells  will 
suffice,  but  for 'periods  longer  than  a  month 


RADIO  BROADCAST  Photograph 

FIG.     17.       FLEXIBLE    WIRING 

A  receiver  employing  the  new  type  of  Como  push-pull  amplifying  transformers.     It  will  be  seen 
from  the  photograph  that  direct  wiring  has  been  employed  to  connect  the  various  units 


4<x> 


Radio  Broadcast 


1 8. 


RADIO  BROADCAST  Photograph 


FIG.    18.      THE    SUB-PANEL 

Another  view  of  the  bottom  of  the  sub-panel  illustrat- 
ing the  use  of  Jefferson  push-pull  transformers.     The 
same  make  of  audio  transformer  has  been  employed 
for  the  audio-reflex  stage 

we  recommend  the  use  of  four  cells.  The  con- 
nections are  shown  in  Fig.  10-8.  The  plate 
current  drain  with  dry  cell  tubes  is  very  low 
and  for  this  reason  the  very  small  B  batteries 
may  be  used.  When  operating  the  receiver 
about  two  hours  a  day,  these  batteries  will 
last  a  month  or  more.  There  is  room  enough 
for  the  sky-scraper  type,  however,  and  they 
will  last  much  longer  and  are  more  worth- 
while where  weight  is  not  the  primary  con- 
sideration. 

THE    SUMMER   TIME    ANTENNA 

THERE  are  many  methods  for  the  provi- 
sion of  antenna  for  use  with  this  receiver 
in  the  open.  No  doubt  there  is  a  good  market 
for  an  antenna  made  in  the  form  of  a  reel, 
similar  to  a  fishing  reel.  Several  antenna 
reels  have  been  brought  to  us  in  an  unfinished 
condition,  but  we  know  of  none  now  on  the 
market.  This  type  of  radio  specialty  offers 
a  very  attractive  field,  and  we  believe  that  the 

FIG.  19.  IN  PLACE  OF  RECORDS 
Here  is  illustrated  a  method  of  mounting  the  RADIO 
BROADCAST  Phonograph  receiver  unit  in  that  part  of 
a  Victrola  cabinet  ordinarily  used  for  the  storage  of 
phonograph  records.  Several  shelves  have  been  re- 
moved to  make  room  for  the  unit  and  some  shelves 
for  records  still  remain.  A  loud  speaker  unit  has  been 
mounted  on  the  tone  arm  thereby  making  use  of  the 
Victrola  sound  box  mounted  within  the  cabinet 


How  to  Build  Radio  Broadcast's  Phonograph  Receiver 


401 


RADIO  BROADCAST  Photograph 
FIG.    2O.      THE    CUSHION    SOCKETS 

The  photograph  illustrates  how  the  Benjamin  spring  cushion  sockets  may  be  mounted  directly  on  the  sub- 
panel.      A  manufactured  unit  of  this  type  is  being  marketed  by  the  Benjamin  Company 


BRf 
H 

1- 

kCKET   MOUNTING 

)LE   *27  DRILL 
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BRACKET  MOUNTING 
HOLE  *ll  DRILL*. 

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•_t 
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16          4  ~    *~~8~"                           HOLES  *27  DRILL 
in'" 

8             8" 

I 

-5" 

FIG.    21.      THE    BAKELITE    BINDING    POST   LAYOUT 


COIL  MOUNTING                                            SOCKETS  ON                                                     2  BRACKETS  MOUNTING 

HOLE  *Z7  DRILL                                 ^,-  TOP  OF  BASE-^                                                 HOLES    «Z7  DRILL'. 

t 

/'            /                                                                               ^.                                          -^                                                                            .'              1 

Ml 

00 

-( 

>\.l 

/ 

X 

X 

f1 

T 

TJ 

RADIO   FRECcUENCY                   DETECTOR 

PUSH  PULL 

PUSH  PULL 

• 
Ml 
f 

t> 

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if 

SOCKET                            SOCKET 

SOCKET 

SOCKET 

.1 

roi«o 

•— 

P                             6JLP                             G 

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P                           6 

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>• 

""5  NEUTRALIZING                       1    GRID  CONDENSER 
!__    _    *TCOND.ONTOP         [.  !^J~"  UNDER  BASE 

ir 

r                                       j 

f~ 

1 

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4 

"^4 

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yt  BRACKET,' 
MOUNTING  HOLES 
*Z7  DRILL 

^^TRANSFORMER                       ,NpuT  WSH  wu 
UNDER.  BASE                                  TRANSFORMER. 

OUTPUT  PUSH  PULL 
TRANSFORMER 

UNDER,  BASE. 

UNDER  BASE 

-.  ...                                                     mL" 

FIG.    22.      THE    SUB-PANEL    LAYOUT 
Showing  how  the  parts,  are  placed  underneath  the  base 


4O2 


Radio  Broadcast 


FIG.    23A-B.    THE- MAIN    PANEL 

And  sub-base  with  most  of  the  wiring  completed.  A  circuit  diagram  is  shown  in  Fig.  8.  The  numbered 
leads  are  connected  to  the  following  terminals;  they  may  be  traced  directly  to  the  apparatus  in  the  Figure 
above.  No.  i  goes  to  the  single  circuit  inside  jack.  No.  2  connects  to  the  outside  filament  circuit  and  double 
circuit  jack.  No.  3  goes  to  the  ground  lead  and  the  switch  arm.  No.  4  leads  to  the  antenna  coil  T-I. 
No.  5  connects  to  the  inside  secondary  T-2  and  to  the  rotary  c-i.  Nos.  6  and  7  go  to  the  output  jack, 
single  circuit.  No.  8  goes  to  the  inside  jack,  double  circuit.  No.  9  to  the  outside  jack,  double  circuit.  No.  10 
goes  to  stationary  plate  02  inside  T-2  secondary.  No.  1 1  goes  to  the  N-P  coil  neutralizing  condenser.  No.  12 
connects  to  the  tickler  coil  detector  plate.  No.  13  goes  to  stationary  plate  c-i  and  outside  secondary  T-I. 
No.  14  is  connected  directly  to  the  tickler.  No.  15,  to  the  center  tap  N-P  and  No.  16  to  N-P  coil  plate 

2  34 


16 


How  to  Build  Radio  Broadcast's  Phonograph  Receiver  403 


FIG.    24.      THE    MAIN    PANEL    LAYOUT 

Showing  drill  sizes  and  dimensions.     No  condenser  mounting  holes 
are  indicated  because  this  depends  upon  the  type  of  condenser  used 


404 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 
FIG.    25 

Shows  a  very  fine  addition  to  any  radio  and  phono- 
graph combination.  The  use  of  th  ephonograph 
horn  for  either  radio  or  phonograph  purposes  may 
be  had  by  turning  the  knob  shown  in  the  direct  cen- 
ter of  the  illustration.  The  loud  speaker  unit  is 
mounted  upon  the  cap  of  the  Selectron  unit.  The 
tone  arm  fits  on  the  right  side  and  the  speaker  unit 
on  the  left 

concern  that  will  manufacture  such  an  antenna 
will  have  no  trouble  in  marketing  this  product. 

There  are  several  other  antenna  devices 
for  use  in  connection  with  electric  light  cir- 
cuits and  telephone  lines  which  make  a  regu- 
lar antenna  unnecessary.  Where  there  is  a 
portable  receiver  and  a  small  loud  speaker 
at  hand  that  may  be  put  in  the  car,  it  is 
becoming  increasingly  popular  for  the  radio 
enthusiast  to  take  his  "music  box"  with  him 
when  visiting  friends.  This  makes  com- 
parison of  results  obtained  in  various  loca- 
tions with  different  types  of  receivers  possible 
and  frequently  makes  an  otherwise  boresome 
visit  a  really  pleasant  one. 

The  antennaphone,  which  is  illustrated  in 
Fig.  n,  is  a  very  simple  device  and  is  in  no 
way  connected  to  the  telephone.  It  is  laid 
on  a  table  or  other  convenient  place  and  the 
telephone  is  set  down  on  it.  This  makes  the 
use  of  a  regular  antenna  unnecessary. 

The  antenna  attachments  for  use  with  the 
light  sockets  are  illustrated  in  Fig.  12  and  the 
various  methods  for  employing  them  are  il- 
lustrated in  Fig.  13.  It  is  impossible  to 
tell  in  advance  just  which  connection  will  be 
best.  Each  should  be  tried.  Devices  of  this 
kind  have  been  found  of  little  value  in  some 
places  but  better  than  a  regular  antenna  in 
others.  Radio  products  of  reliable  manu- 
facture are  sold  on  a  money-back-guarantee 
basis.  They  are  well  worth  trying  for  those 
whose  problem  of  antenna  erection  is  difficult 
and  often  impossible. 


ANY  STANDARD  PARTS  MAY  BE  USED 

THERE  is  little  necessity  for  reviewing  the 
havoc  caused  by  the  new  and  novel  fea- 
tures which  have  attracted  the  buying  public 
from  time  to  time.  Buyers  have  spent  large 
sums  of  money  in  the  purchase  of  new  equip- 
ment, spuriously  advertised,  only  to  find  that 
their  money  had  been  grossly  misspent  and 
that  their  purchases  were  neither  new  nor 
revolutionary.  Quite  probably  many  in- 
dividuals have  grown  to  think  that  the  manu- 
facturers desired  only  to  sell  parts  regardless 
of  the  satisfaction  that  they  might  otherwise 
give. 

After  all,  there  is  but  one  basis  upon  which  a 
parts  business  can  exist  and  that  is  to  give  the 
home  builder  at  least  some  value  for  the 
money  he  has  expended. 

For  example,  there  once  was  heralded  a 
revolutionary  super-heterodyne  which  em- 
ployed nine  tubes.  As  a  result  of  the  pub- 
licity it  received  many  of  the  parts  specified 
for  use  in  it  were  sold  to  jobbers  and  dealers 
in  comparatively  large  quantities.  But  it  did 
not  last  long;  it  was  too  unreliable  for  that. 
As  an  example  of  its  "efficiency"  it  consumed 
73  milliamperes  in  the  plate  circuit — a  good 
super-heterodyne  should  not  use  more  than 
20,  and  many  require  much  less— the  Hanscom 
six-tube  receiver  described  in  RADIO  BROAD- 
CAST for  June,  1924,  for  instance.  Now,  73 
milliamperes  means  that  dry  cells  are  out  of 
the  question  and  even  battery  eliminators 
can  not  be  used.  There  is  then  nothing  left 
but  storage  B  battery  operation.  When 
equally  satisfactory  results  may  be  obtained — 
and  this  is  stating  the  case  conservatively 
— from  one  of  the  receivers  employing  the 
Roberts  circuit  and  four  tubes  drawing  less 
than  10  milliamperes,  it  is  not  difficult  to 
understand  what  we  are  talking  about  when 
we  say  we  are  trying  to  show  how  good  radio 
parts  can  be  bought  by  the  interested  con- 
structor, and  real  service  be  secured  from  their 
use. 

RADIO  BROADCAST'S  Phonograph  Receiver 
may  be  constructed  by  the  use  of  any  good 
standard  parts,  but  we  strongly  oppose  the 
use  of  parts  which  have  not  become  stand- 
ard. 

After  all,  it  is  the  consumer  who  eventually 
pays  the  piper  and  we  can  but  hope  that  he, 
in  making  his  purchase,  will  choose  only  those 
products  which  he  knows  to  be  sound.  Even- 
tually this  practice  will  lead  to  a  market 
unencumbered  by  the  "gyp"  parasites  which 
at  times  even  now  defile  it. 


How  to  Build  Radio  Broadcast's  Phonograph  Receiver  405 


FIG.    I, 


FIG.  2 


FIG.    3 


FIG.   4 


A  CONNECTION    CORD   FOR   OUTSIDE    LEADS 

In  the  Phonograph  receiver.  Figs.  1  to  4  show  the  processes  in  preparing  the  wires  for  attaching  at  both  ends. 
The  cable,  composed  of  two  No.  16  and  three  No.  20  conductors  is  used  to  connect  the  batteries  to  the  set. 
The  conductors  are  each  rubber  insulated  and  each  of  a  different  color.  First  shirr  the  outer  braid  back  about 
six  or  eight  inches,  or  as  far  back  as  is  necessary  to  make  connections.  Next  fold  the  loose  ends  back  over  the 
cable  and  finish  off  neatly  by  wrapping  a  piece  of  half 'inch  adhesive  tape  around  the  cable  as  shown  in  Fig.  2. 

With  scissors,  trim  off  the  frayed  edges  as  shown  in  Fig.  3.  In  pre- 
paring  the  individual  conductors,  skce  the  insulation  at  three  or 
four  points  around  the  wire  about  one  inch  back,  permitting  the  in- 
sulation to  be  removed  very  easily.  The  finished  ends  my  be  wrapped 
with  a  quarter-inch  strip  of  adhesive  tape  for  neatness.  If  some 
shellac  is  available,  the  ends  might  be  dipped  in  it  and  dried  before 
the  insulation  is  removed.  The  copper  wire  should  be  scraped 
brightly  and  twisted  tightly  to  prevent  the  wires  from  spreading. 
Fig.  5  shows  one  end  of  the  completed  lead.  In  the  Phonograph 
Receiver,  the  top  lead  is  plus  B  120  volts,  the  next  to  the  left  is  plus 
B  90  volts,  the  third  plus  B  45  volts,  the  next  plus  A,  and  the  last 
minus  A  and  B.  This  does  not  provide  for  C  battery  connections, 
which  should  be  made  with  separate  leads.  The  C  battery  itself 
can  well  be  included  inside  the  set.  Considerable  importance 
attaches  to  proper  C  battery  potential  in  this  receiver.  This  cord  is 
available  on  the  market  as  R-1360  and  made  by  the  Belden  Manu' 
facturing  Company. 


FIG.    5 


llllim iniMiniMnillllMIMIIinMinlllllMIIIIIMIIIMIIIIMIIMIIIIIUIIIIIIIIIIIIIMIIIMIMIinilinilMIIIIIIMIIIMMIMIIIIIinNIMMIMIMIIIMIIlllllllllMMIIIIIIIMIIIIIIIIIIMIIIMIIIIIIMIMIIIIIIlnilllllinn 


i  « » 

i 


NO\X/  I  HAVE  FOUND  ...     ...     I 

A  Department  Where  Readers  Can  Exchange  Ideas 
and  Suggestions  of  Value  to  the  Radio  Construcfor  andOperator  I 

3 


FIG.    I 


A  FOUR  TUBE  ROBERTS  RECEIVER 

THE  outfit  shown  in  the  photograph, 
Fig.  i.  represents  one  of  the  highest 
types  of  receivers  embodying  the 
Roberts  circuit.  Of  several  hundred  various 
Roberts  sets  made  by  the  writer  and  Mr.  S. 
Schneider,  it  was  selected  as  the  best  of  the 
lot  as  far  as  tone  quality  and  ease  of  volume 
control  were  concerned. 

The  feature  of  the  set  is  its  employment  of 
a  brace  of  Western  Electric  push-pull  trans- 
formers removed  from  a  y-A  amplifier  unit. 
The  tapped  input  transformer  is  connected  in 
the  circuit  as  the  reflex  transformer,  feeding 
the  audio  component  of  the  detector  plate 
current  back  into  the  grid  circuit  of  the  first 
tube.  The  secondary  winding  is  the  tapped 
one,  there  being  five  taps  in  all.  The  switch 
arm  is  connected  to  the  positive  side  of  the 
C  battery,  and  the  negative  pole  of  the  latter 
is  then  carried  to  the  lower  side  of  the  antenna 
coupler  secondary. 

The  actual  switch  and  contact  points  are 
mounted  on  the  panel  at  the  extreme  left. 
They  are  not  visible  in  the  photograph  because 
they  are  covered  by  the  antenna  coupler  coils. 
This  switch  directly  controls  the  volume  ob- 
tainable from  the  receiver. 

The  push-pull  transformers  are  wired  to  a 
pair  of 'tube  sockets  in  the  standard  arrange- 


ment. These  parts  occupy  the  section  of  the 
baseboard  to  the  right  of  the  detector  tube 
socket. 

Two  automatic  filament  control  jacks  allow 
the  use  of  either  two  or  four  tubes.  Individual 
rheostats  are  provided  on  the  panel  for  the 
r.  f.  and  detector  tubes,  while  another  rheostat, 
screwed  to  the  baseboard  near  the  second 
phone  jack,  regulates  the  less  critical  audio 
bulbs.  This  thiid  rheostat  is  turned  to  the 
best  position  for  amplifier  operation,  and  can 
then  be  entirely  neglected.  The  filament 
jacks  take  care  of  all  switching. 

The  unusual  transformer  system  does  not 
alter  the  operating  characteristics  of  the  cir- 
cuit in  the  slightest.  The  set  tunes  exactly 
like  other  Roberts  sets. 

In  active  service  this  receiver  is  truly  a 
"knockout."  It  is  being  used  by  a  resident 
of  Washington  Heights,  New  York  City,  and 
under  the  adverse  local  conditions  has  brought 
in  Pacific  Coast  stations  on  only  two  tubes. 
The  reproduction,  thanks  to  the  excellent 
transformers,  is  as  perfect  as  the  modulation 
of  the  broadcasting  stations  permits.  The 
volume  with  uv-2oiA  tubes,  or  others  of 
similar  constants,  is  more  than  sufficient  for 
the  large  apartment  in  which  the  set  is  used. 
And  the  appearance,  it  might  be  stated,  is 
quite  commensurate  with  the  electrical  effi- 
ciency.— H.  Q.  HORNEIJ,  New  York  City. 


How  to  Make  a  Low  Melting  Point  Solder 


407 


FIG.    2B 


A  SIMPLE   variable    mounting  for  the 
antenna    inductance    of    the    Roberts 
receiver  may  be  a  practical  suggestion 
which    will    interest    the   readers    of   RADIO 
BROADCAST. 

The  several  Figures  are  as  follows :  Fig.  2  A — 
the  assembled  coils,  cross  section  view;  Fig.  2  B 
front  view  of  secondary,  unassembled;  Fig.  2  C 
— cross  section  view  of  antenna  coil,  unassem- 
bled. 

The  blocks  of  wood  which  hold  the  coils  are 
^  inch  thick.  The  constructor  may  use  his 
own  judgment  as  to  the  width  but  i^  by  i| 
by  ^  inches  has  been  found  satisfactory  for  the 
secondary  mounting  and  i  by  i^  by  \  inch 
for  the  antenna  mounting. 


Coils  -.„ 


The  base  which  supports  the  sliding  second- 
ary and  the  stationary  antenna  coil  is  \  inch 
thick,  i  \  inches  wide  and  4  inches  long. 

This  base  may  be  set  back  a  distance  from 
the  panel,  and  the  control  rod  cut  to  the 
proper  length  accordingly. 

The  antenna  coil  is  fastened  to  the  block  by 
small  'screws.  This  block  is  permanently 
fastened  to  the  base.  It  has  a  hole  drilled  in 
it  to  allow  the  shaft  which  moves  the  second- 
ary to  pass  back  and  forth  through  it. 

With  this  arrangement,  very  fine  variable 
coupling  between  the  primary  and  secondary 
coils  may  be  obtained. 

The  sketches  show  very  clearly  the  mechan- 
ical features  involved  in  the  construction  of 
these  mountings.— H.  BATCHELDER,  Yakima, 
Washington. 


FIG.    2C 


HOW  TO  MAKE  A  LOW  MELTING 
POINT  SOLDER 


w: 


FIG.    2A 


•  HAT  radio  fan  has  not  found,  when 
soldering,  that  some  of  the  work  got 
so  hot  that  either  the  appearance  or 
utility  of  the  soldered  part  was  affected? 

While  in  many  cases  it  may  be  true  that 
sufficient  experience  would  have  allowed  the 
constructor  to  avoid  the  trouble,  still  any 
method  of  soldering  with  less  heat  would  be 
greatly  appreciated  by  many  of  us.  The 
answer  is  simple.  Use  solder  that  melts  at  a 


Radio  Broadcast 


lower  temperature  than  that  ordinarily  sold 
on  the  market. 

Solder  is  made  of  a  mixture  of  lead  and  tin. 
Since  tin  is  much  more  expensive  than  lead, 
the  manufacturer  is  inclined  to  put  in  more 
lead  and  less  tin.  Probably  no  solder  avail- 
able to  the  radio  fan  is  more  than  half  tin, 
in  spite  of  the  fact  that  the  melting  point  of 
solder  becomes  lower  and  lower  with  the 
increase  of  tin  until  a  combination  of  about 
three  fourths  tin  is  reached.  Such  solder, 
with  a  low  melting  point,  is  known  as  "soft 
solder." 

Soft  solder  may  easily  be  made  in  the  home 
by  adding  tin  to  ordinary  solder.  Small 
quantities  of  tin  are  available  in  every  home 
in  the  form  of  ordinary  tin-foil.  One  must 
notice  that  not  all  of  the  "tin-foil"  is  really 
made  of  tin.  The  genuine  article  may  be 
recognized  by  its  softness  and  bright  finish. 
Tin-foil  which  comes  around  eatables  will 
really  be  made  of  tin  if  it  comes  into  direct 
contact  with  them.  One  may  be  certain  that 
foil  which  is  separated  from  the  eatable  by 
waxed  paper  is  not  pure  tin  and  can  not  be 
used  for  this  purpose. 

To  get  the  tin  into  usable  shape,  put  the 
foil  into  a  metal  cover,  such  as  a  baking  powder 
can  cover,  and  add  to  it  about  as  much  rosin, 
by  bulk,  as  you  have  foil,  and  then  heat  over 
a  gas  stove  or  other  fire.  Stir  with  the  end 
of  a  match  stick.  Presently  the  tin  will  ap- 
pear as  a  bright  puddle  with  a  lot  of  black 
dirt  over  it. 

Now,  to  make  the  extra  soft  solder,  add  to 
this  tin,  ordinary  solder  about  equal  in  amount 
to  the  tin  recovered  from  the  foil  and  heat 
until  the  two  melt  together. 

The  resulting  compound  may  be  left  in  the 
cover  to  be  picked  up  by  the  soldering  iron, 
or  it  may  be  made  into  "wire"  solder  either 
by  pouring  into  a  groove  gouged  out  of  a  piece 
of  wood  or  by  pouring  into  a  soda  straw  with 
the  lower  end  pinched  shut. 

By  using  a  soldering  iron  just  hot  enough 


to  cause  the  solder  to  flow  freely  when  using 
this  soft  solder,  work  may  be  done  with  ap- 
preciably less  heating  than  usual. 

This  solder  is  not  quite  as  strong  as  the 
ordinary  solder,  but,  in  radio  work,  joints  are 
soldered  for  good  electrical  contact  rather 
than  for  mechanical  strength. — G.  D.  ROBIN- 
SON, Annapolis,  Maryland. 


7" 


o 
o 
o 
o 
o 
o 


FIG.  4 


B+ 
FIG.    3 

THE   OSCILLATOR    IN    YOUR   SUPER- 
HETERODYNE 

IT  IS  not  the  purpose  of  this  article  to  extol 
the  super-heterodyne  but  to  show  you 
how  to  make  yours  more  efficient.  By 
efficiency  I  mean  output  divided  by  input.  It 
is  obvious  that  with  a  given  input  we  can  in- 
crease the  efficiency  of  a  set  by  increasing  the 
output.  Or  if  with  a  smaller  input  the  output 
is  the  same  in  both  cases  then  we  have  in- 
creased the  efficiency.  The  average  radio  lis- 
tener is  more  or  less  familiar  with  the  action 
of  a  vacuum  tube  as  an  amplifier.  He  proba- 
bly has  less  understanding  of  the  tube's  action 
as  a  detector  and  unless  he  is  a  transmitting 
amateur  he  has  practically  no  knowledge  of  an 
oscillator. 

There  are  several  oscillating  systems  in 
popular  favor  with  the  amateur  for  transmit- 
ting purposes,  but  of  these  only  one,  the 
Hartley,  is  satisfactory  as  an  oscillator  in  a 
super-heterodyne.  There  are  three  forms  of 
the  Hartley.  The  one  shown  in,  Fig.  3  is  used 
almost  universally,  and  this  is  the  one  we  are 
about  to  consider. 


How  to  Test  Headphones 


409 


As  a  generator  of  alternating  current  this 
form  of  oscillator  is  above  reproach.  In  fact 
it  does  that  too  well,  for  it  generates  a  lot  more 
current  than  we  can  possibly  use,  and  in  the 
matter  of  squeals  it  is  almost  as  great  an  of- 
fender as  those  receivers  we  know  as  bloopers. 
This  is  perhaps  the  most  serious  charge  that 
can  be  brought  against  it.  Used  in  its  present 
form  it  is  not  as  efficient  as  it  might  be. 

Such  an  oscillator,  with  5  volts  filament 
supply  and  90  volts  plate  supply,  will  draw 
about  .025  amperes  (25  milliamperes.)  If  we 
stop  the  tube  from  oscillating  by  short  circuit- 
ing the  grid  coil,  the  plate  current  drops  to 
6  or  7  milliamperes. 

If  we  cut  the  plate  voltage  down  to  20  volts, 
the  tube,  oscillating,  will  draw  about  5  milli- 
amperes. But 'this  is  not  good  enough. 

There  is  no  advantage  in  using  a  201  A  tube 
as  an  oscillator.  A  uv-igg  is  suitable  for  all  of 
our  purposes.  By  using  a  uv-igg  in  the  cir- 
cuit in  Fig.  3,  with  20  volts  on  the  plate,  the 
B  battery  drain  will  be  but  3  milliamperes. 
This  is  better  since  we  have  also  reduced  our 
A  battery  current.  A  uv-igg  can  be  used  in 
the  same  set  with  uv-2oiA  tubes  by  using  a 
separate  rheostat,  or  better  an  amperite. 

Fig.  4  is  a  form  of  Hartley  oscillator  in  com- 
mon use  among  amateurs  for  transmftting 
purposes  but  there  is  nothing  in  particular  to 
be  gained  by  its  use. 

A  third  form  of  Hartley  oscillator  is  shown 
in  Fig.  5.  This  is  the  ideal  form  for  our  pur- 
poses. The  plate  current  for  a  uv-igg  oscilla- 
tor with  the  constants  shown,  will  be  from 
.0001  to  .00015  amperes  (100  to  150  micro- 
amperes). If  you  are  using  45  volts  on  the 
detector  plate  and  do  not  want  to  provide  a 
separate  B  battery  connection  for  the  oscilla- 
tor, you  will  have  to  use  a  somewhat  lower  re- 
sistance grid  leak.  This  oscillator  will  give 
you  all  the  output  that  you  can  use  to  advan- 
tage. However,  it  is  not  strong  enough  to 
radiate  seriously  and  it  will  oscillate  smoothly 


and  evenly  over  the  entire  broadcasting  wave- 
length range. 

A  tube  will  often  oscillate  in  this  circuit 
when  it  will  not  in  the  first  one  shown  here, 
because  the  filament  emission  is  not  great 
enough  to  sustain  oscillations  in  the  former. 

If  the  tube  is  stopped  from  oscillating  in  the 
circuit 'shown  in  Fig.  5  the  plate  current  rises 
to  about  .4  milliamperes.  If  the  filament  emis- 
sion is  great  enough  to  supply  a  plate  current 
of  0.2  milliamperes,  it  will  oscillate  in  this 
circuit. 

The  insertion  of  a  grid  leak  and  condenser 
at  the  point  marked  X  in  Fig.  3  will  result  in  a 
greatly  improved  oscillator — almost  as  good  as 
that  shown  in  Fig.  5.  However,  for  those  who 
already  have  a  "super,"  it  offers  less  changing 
in  wiring  and  will  do  very  nicely. 

There  are  several  schemes  for  using  the  so- 
called  first  detector  as  an  oscillator.  Exam- 
ples of  this  are  the  second  harmonic  oscillating 
system  and  the  Pressley  method.  I  do  not 
recommend  any  of  these  because  the  added 
impedence  in  the  grid  circuit  of  this  first  tube 
more  than  offsets  any  advantage  gained  by 
using  this  tube — especially  when  a  really  good 
oscillator  consumes  only  60  milliamperes  of 
A  battery,  and  1 5  microamperes  of  B  battery, 
current. — F.  W.  HUTTON,  Woodhaven,  New 
York. 


North 


1-Current  'On*  Connections  wrong 

2-  -       Off" 

3-  «      "On" Connections  OK 


Phone  Phone 

FIGS.    6    AND    7 


B+20 


FIG.    5 


A  PHONE  CIRCUIT  TEST 

IT  IS  quite  commonly  known  that  to  insure 
long  life   to  the   permanent   magnets  of 
phones,  the  field  produced  by  the  plate 
current  flowing  through  the  phone  windings 
should  assist  and  not  buck  that  set  up  by  the 
permanent  magnets.     Relatively  few  experi- 
menters know  how  to  determine  which  con- 
dition exists. 

The  object  of  this  article  is  to  give  an  ex- 
perimental method  for  such  determination 
involving  no  more  elaborate  apparatus  than 


410 


Radio  Broadcast 


a  pocket-compass,  which  should,  however,  be 
fairly  sensitive.  No  knowledge  of  electricity 
is  needed,  although  of  course  it  would  help  the 
operator  understand  the  "why  "of  the  method. 

First  unscrew  the  cap  from  the  receiver  and 
remove  the  diaphragm  (unless  the  receiver  be 
of  the  Baldwin  type  which  has  a  mica  dia- 
phragm). The  phones  and  compass  should 
then  be  placed  in  the  relative  positions  shown 
in  Fig.  6,  paying  attention  to  the  fact  that  the 
compass  should  be  north  of  the  receiver.  The 
north-seeking  pole  should  point  toward  the 
phone  when  brought  near  it.  If  such  is  not 
the  case,  the  receiver  should  be  revolved  about 
the  axis  a-a^  bringing  the  other  pole  nearest 
the  compass. 

The  compass,  which  may  be  placed  on  a 
safety  match  box  or  anything  not  having  iron 
or  steel  in  its  construction  to  facilitate  move- 
ment, is  then  shifted  to  a  position  approx- 
imately as  shown  in  Fig.  7.  The  exact  spot 
is  determined  by  finding  where  the  needle 
starts  to  swing  to  its  normal  north-seeking 
position.  Just  before  it  has  left  the  influence 
of  the  phone  magnet,  which  is  when  further 
slight  movement  causes  the  needle  to  swing 
abruptly  toward  the  north,  the  plate  current 
should  be  allowed  to  flow  through  the  phones, 
preferably  when  a  strong  signal  is  coming 
through.  If  the  needle  swings  toward  the 
phones,  the  fields  are  mutual  and  the  con- 
nections correct.  If  the  needle  swings  to  the 
north,  the  phone  connections  to  the  plug 
or ,  the  binding  posts,  whichever  are  used, 
should  be  reversed.  The  deflection  will  be 
slight  but  unmistakable. — L.  T.  PHELAN, 
Washington,  District  of  Columbia. 

TO- DAY, there  is  small  necessity  for  "match- 
ing tubes".  The  fact  is,  for  most  pur- 
poses tubes  are  so  similar  in  their  character- 
istics that  they  may  be  considered  as  being 
matched.  The  notable  exception  is  in  the 
super-heterodyne,  where  juggling  tubes  around 
in  the  intermediate  stages  is  usually  neces- 
sary to  secure  satisfactory  reception.  Howl- 
ing, instability  (uncontrollable  oscillations 
with  beat  whistles)  at  normal  plate  voltages 
are  evidence  of  poor  or  improperly  balanced 
tubes  in  the  intermediate  amplifier. 


Potato 


ndicates 
Positive  pole  • 


THERE  are  devices  on  the  market  for 
finding  the  polarity  of  an  electric  bat- 
tery. That  is,  to  find  out  which  is  the 
negative  pole  and  which  is  the  positive  pole. 
This  is  always  necessary  when  connecting  up 
an  automobile  or  a  radio  battery  or  in  making 
electrical  experiments.  But  did  you  know 
that  all  this  could  be  done  with  the  aid  of  a 
common  white  potato? 

Choose  a  potato  with  nice  white  meat  and 
shave  off  a  section  of  skin  about  the  size  of  a 
half  dollar  so  that  the  inside  is  exposed.  Then 
turn  on  the  current  from  your  source  of  elec- 
tricity and  grasp  one  of  the  wires  with  bared 
ends  in  each  hand.  Touch  the  wire  ends  to 
the  potato  about  |  inch  apart  and  watch  the 
result.  In  a  few  seconds  the  potato  under  one 
of  the  wires  will  be  found  to  turn  a  shade  of 
green.  The  section  of  the  potato  which  the 
other  wire  touches  will  remain  clear  and  white. 
See  Fig.  8. 

The  wire  causing  the  greenish  hue  on  the 
potato  is  connected  to  the  positive  pole  of  the 
battery.  Therefore  the  other  wire  must  be 
connected  to  the  negative  pole.  This  exper- 
iment will  not  work  on  alternating  current  of 
the  house  lighting  circuit.  It  is  a  good  test, 
however  for  storage  or  dry  batteries  or  small, 
direct  current  generators  such  as  are  found  in 
cars  and  power  boats. — L.  B.  ROBBINS,  Har- 
wich, Massachusetts. 


THE  "  Now  I  Have  Found    .    .    ."  department  in  this  magazine  is  planned  to  furnish  an  outlet  for 
the  many  excellent  ideas  dealing  with  various  features  of  radio  construction  and  operation  which 
reach  our  office.     If  you  have  an  idea  about  a  valuable  and  useful  new  circuit,  some  new  device,  or  a 
construction  or  operating  suggestion,  we  should  like  to  have  it.     We  do  not  want  simple  or  obvious 
suggestions,  and  material  to  be  acceptable  for  this  department  must  offer  something  of  definite  value 
to  the  constructor;  mere  novelty  is  not  desired.     Payment  from  two  to  ten  dollars  will  be  made  for 
every  idea  accepted.    Manuscript  should  not  be  longer  than  300  words  and  typewritten.    An  award 
of  twenty-five  dollars  will  be  paid  for  the  best  article  published  in  every  three'month's  period. 
Address  your  manuscript  to  this  department,  RADIO  BROADCAST,  Garden  City,  New  York 


QUESTION*/  AND 


See  the  Announcement  on  Page  418 

QUERIES  ANSWERED 


CAN    A    LOOP    BE    USED   WITH    ONE-TUBE    SETS? 

P.  B—  Canton,  N.  Y. 

WlLL      YOU      EXPLAIN      THE      MEANING      OF      WAVE- 
LENGTH? 

F.  C. — Lansing,  Mich. 

HOW    DOES    THE    HIGH-MU    RECEIVER    DIFFER    FROM 
THE    ROBERTS? 

E.  L.  J.— Berkeley,  Calif. 

HOW    SHALL    I     BE    GUIDED    IN     THE     SELECTION     OF 
A    STORAGE    BATTERY? 

A.  M. — Brooklyn,  N.  Y. 

Is   THE    FOUR-TUBE    CRYSTAL     REFLEX     CIRCUIT     IN 


THE  JUNE,   1924,  ISSUE   OF   RADIO   BROADCAST 

CORRECT?  • 

J.  N.  T. — San  Antonio,  Texas. 

WlLL  YOU  PUBLISH  A  CIRCUIT  SHOWING  A  NEU- 
TRODYNE  RECEIVER  EMPLOYING  PUSH-PULL  AUDIO 
FREQUENCY  AMPLIFICATION  FOR  THE  LAST  STAGE? 

L.  J.  T.   Portland,  Me. 

WHAT  TOOLS  ARE  NECESSARY  FOR  GOOD  RADIO 
CONSTRUCTION? 

K.  W.  J.— Marion,  Ohio. 

How      MAY     I      PROCURE     THE      L.YNCH     LEAD      DE- 
SCRIBED IN  THE  JUNE,  1925,   RADIO   BROADCAST 
R.   B.— Albany,  N.  Y. 


THE  energy  transmitted  by  a  broadcasting 
station  must  be  collected  or  absorbed  by 
some  collective  or  absorbing  agency  so  that 
a  receiver  may  be  actuated  to  produce  results. 
Upon  the  size  of  this  agency  depends  the  efficiency 
at  which  the  receiver  operates,  all  other  things 
being  equal.  However,  this  agency,  which  is  the 
antenna,  also  is  affected  by  other  electrical  disturb- 
ances in  the  ether,  i.  e.,  atmospherics,  artificial 
static  like  motor  commutator  sparking,  sparking 
trolley  lines,  defective  power  lines,  and  similar 
disturbances. 

On  one-,  two-,  and  three-tube  sets,  an  outside 
antenna  is  connected  to  the  detector  tube  through  a 
coupler  unit.  A  loop  will  not  be  satisfactory  for 
such  a  receiver  because  the  feeble  impulses  which 
it  receives  will  not  actuate  the  detector  tube  suf- 
ficiently to  produce  energy  which  may  be  trans- 
formed into  an  audible  signal. 

A  loop  can  only  be  used  on  receivers  employing 
one  or  more  stages  of  radio  frequency  amplification 
or  in  super-heterodynes  which  tend  to  magnify 
these  feebly  received  impulses  so  that  they  are 
strong  enough  to  be  heard  after  being  rectified  to 
an  audible  signal  in  the  detector  tube. 

While  an  antenna  has  directional  effects,  it  is 
not  practicable  to  move  it  about  so  that  signals  from 
all  directions  may  be  received  with  comparatively 
equal  strength. 


A  loop  can  be  rotated  without  much  effort,  for 
directional  effects.  The  larger,  physically,  a  loop  is 
the  greater  its  energy  pickup  will  be.  However,  for 
most  practical  purposes  its  size  is  limited  by  indi- 
vidual requirements, 
then  we  have  the  equation 

WHAT  WAVELENGTH   MEANS 

RADIO   waves  travel    through    space  at  the 
same  velocity  as  light,  roughly  186,000  miles 
per   second.     Rather,    the   wave   motion   is 
propagated  at  that  velocity,  which,  when  spoken 
of  in  meters  equals  300,000,000  meters  per  second. 
That  is  a  fixed  value.     Now  if  we  vary  the  length  of 
one  wave,  the  frequency  or  number  of  times  it  will 
repeat  itself,  will  vary.   As  represented  in  a  formula 

186,000    miles    (300,000,000   meters) 

Frequency  =  — 

length  of  wave 

If  N  equals  the  frequency  or  number  of  oscillations 
occurring,  V  (300,000,000)  indicates  velocity  of 
waves  in  meters,  and  L  equals  length  of  wave  form 
then  we  have  the  equation. 

V 

v  =  — 

L 

L,  the  length  of  one  wave  depends  upon  the  ad- 
justments of  the  tuning  elements  to  produce  an 
oscillation  which  repeats  itself  in  a  propagated  wave 


412 


Radio  Broadcast 


form  at  a  certain  frequency.  We  can  term  this  the 
number  of  oscillations  produced  by  an  adjustment 
which  gives  each  oscillation  a  definite  length  in 
meters. 

Reduced  the  formula  is 


To  deal  with  round  numbers  let  us  suppose  we  start 
with  a  wave  i  meter  long.  Then  the  number  oi 
oscillations  (waves  or  cycles)  occurring  during  the 
one  second  it  takes  to  travel  186,000  miles  (or 
300,000,000  meters)  is  exactly  300,000,000. 

Supposing  we  wish  to  determine  the  frequency 
(N)  of  a  wave  600  meters  in  length  then 


N  = 


300,000,000 

=  500,000  oscillations 

600 


If  it  is  a  wave  300  meters  long  then 

300,000,000 

N  = =  1,000,000  oscillations 

300 

If  it  is  a  wave  150  meters  long  then 

300,000,000 

N  = •  =  2,000,000  oscillations 

150 

Therefore  from  this  we  can  judge  that  while  the 
speed  at  which  the  wave  travels  remains  constant, 
any  change  in  wavelength  will  alter  the  number  of 
oscillations  (waves)  occurring  over  that  distance  of 
186,000  miles.  This  is  explained  in  Fig.  i  A,  B.andC. 


1*600*  - 
one  cycle 


600  METERS 
500,000  cycles  per  second 


300  METERS 
1,000,000  cycles  per  sec 


150  METERS 
2,000,000  cycles  per  sec 


186,000  miles 
one  second  of  time 

FIG.    I 


Since  the  space  covered  by  the  wave  forms  is 
186,000  miles  then  for  each  one  there  occurs  a  dif- 
ferent number  of  waves  in  that  space. 

Assuming  that  the  same  power  is  used  in  all  three 
cases  to  produce  the  same  amplitude  then  in  A 
(600  meters)  there  will  be  500,000  oscillations  or 
cycles  each  600  meters  long  from  start  to  finish. 
In  B  there  will  be  1,000,000  and  in  C  there  will  be 
2,600,000, 


Summing  up  we  can  say  that  the  length  of  one 
cycle  determines  the  number  of  cycles  occurring 
during  one  second  of  time  or  covering  186,000 
miles. 

In  broadcasting,  a  station  transmits  a  wave  called 
the  carrier  wave,  which  has  a  constant  amplitude. 
This  wave,  occurring  at  a  frequency  to  which  the 
transmitter  has  been  adjusted,  is  inaudible  to  the 
ear.  Now  by  super-imposing  an  audio  frequency 
wave  on  it,  it  is  modulated  into  varying  amplitudes 
but  still  inaudible  until  rectified  by  the  detector 
tube. 


FIG.    2 


Fig.  2  shows  how  the  modulated  wave,  to  conform 
to  the  voice  and  music  variations,  is  produced.  At 
A  we  have  the  constant  amplitude  of  the  carrier 
wave  but  between  A  and  C  (B)  the  wave  is  of  a  con- 
tinually varying  amplitude.  This  is  due  to  the 
audio  wave  being  super-imposed  on  the  carrier 
wave. 


THE    HIGH    MU    AND   THE    ROBERTS 

THE  question  arises  "how  does  the  High-Mu 
Browning-Drake  receiver  differ  from  the 
Roberts  Knockout?"  Well  fundamentally 
both  circuits  are  similar,  each  employing  a  stage  of 
radio  frequency  amplification  before  a  regenerative 
detector  circuit.  However,  in  the  Roberts  Knock- 
out, the  first  tube  circuit  contains  a  reflex  audio 
transformer  providing  an  additional  stage  of  audio 
amplification.  Also,  the  neutralization  methods 
are  not  alike.  The  novel  Roberts  system  is  quite 
different  in  principle  to  that  employed  in  the  High- 
Mu  receiver  which  is  similar  to  the  standard 
Hazeltine  neutralizing  scheme. 

The  High-Mu  receiver  was  designed  for  use  with 
uv-i99  tubes  but  uv-2oiA*s  may  be  employed 
without  any  changes  other  than  supplying  the 
correct  filament  and  plate  voltages.  This  is  borne 
out  in  the  description  of  the  "Good  Fpiir  Tube 
Receiver"  in  this  magazine  for  March,  1925,  which 
is  very  similar  to  both  the  Roberts  and  High-Mu 
sets. 


HOW  TO  SELECT  A  STORAGE  BATTERY 

WHEN   selecting  a  storage  battery,  every 
owner  of  a  receiving  set  desires  one  of  suffi- 
cient capacity  to  make  frequent  recharging 
unnecessary,  yet  small  enough  to  reduce  the  first 
cost  to  a  minimum.     The  owner's  ideas  about  what 


RADIO  BROADCAST  ADVERTISER 


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Master's  amplifying  bell  are  all  of  wood — because  wood  pro- 
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Heavy  cast  aluminum  eliminates  over-vibration,  develops  sound 
without  distortion  and  imparts  a  unique  tonal  brilliance. 
This  balance  of  resonant  wood  and  non-resonant  metal  preserves, 
reproduces  and  re-creates  the  natural  qualities  of  instrument  and 
voice — and  makes 

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414 


Radio  Broadcast 


to  specify,  in  order 
to  obtain  this  high- 
ly desirable  com- 
bination maybe 
somewhat  hazy, 
but  he  is  never  in 
doubt  as  to  the 
result  he  seeks. 

Various  types  of 
storage  battery 
selection  charts 
have  been  de- 
veloped in  the 
past,  which  were 
intended  to  assist 
the  owner  of  a  re- 
ceiving set  in  mak- 
ing  a  proper 
selection.  Gener- 
ally speaking,  these 
charts  recom- 
mended certain 
types  and  capaci- 
ties of  batteries 
for  certain  tubes. 
The  Prest-O-Lite 
Storage  Battery 
Laboratories  have 
just  developed  a 
chart  which  takes 
into  consideration 
the  numbers,  types, 
and  combinations 
of  tubes  in  a  way 
that  makes  the 
selection  of  a  satisfactory  battery  a  simple  matter. 

Voltage  of  tubes,  number  of  tubes,  type  of  tubes, 
the  rated  ampere  drain  and  the  recharging  interval 
are  treated  in  the  chart  in  such  a  way  that  the  receiv- 
ing set  owner  has  a  choice  of  two  recharging  periods. 
For  instance,  for  a  set  using  one  uv-2oo  and  three 
uv-aoiA  tubes, with  a  rated  ampere  drain  of  if,  and 
an  A  battery  of  115  amperes  (at  a  one  ampere 


Voltage 
of 

Tubes 

No. 

Tubes 
In  Set 

Type 
of 

Tubes 
(see  foot-note) 

Total 
Rated 
Ampere 
Drain 

Storage  "A"  Battery 
Size 
Recommended 

Amp.  Hours 
at  1  Amp. 
Drain 

Days 
between 
Charging* 

5-Volt 
Tubes 

C-300  and  UV-200 
are  interchange- 
able 

C-301A,  DV-2and 
UV-201A  are  in- 
terchangeable 

Copyright,  1925 
The  Prest-O-Lite  Co..Inc 

1 

UV-200 

1 

65 

22 

47 

16 

2 

UV-201A 

J-2 

47 

33 

2 

1  UV-200 
1  UV-20IA 

IK 

80 

22 

65 

17 

3 

UV-201A 

K 

65 

29 

47 

22 

3 

1  UV-200 
2UV-20IA 

IK 

95 

21 

65 

14 

4 

UV-201A 

1 

65 

22 

47 

16 

4 

1  UV-200 
3  UV-20IA 

Wi 

115 

22 

80 

15 

5 

UV-201A 

IX 

SO 
65 

22 

17 

S 

I  UV-200 
4UV-201A 

2 

115 

19 

80 

13 

6 

UV-201A 

IK 

95 

21 

65 

14 

8 

UV-20IA 

2 

125 

21 

95 

15 

For  sets  using  cur- 
rent at  a  rate  higher 
than  2  amperes. 

2K 

140 
95 

22 

13 

2K 

140 

19 

125 

16 

For  combinations  of  tubes  not  listed:  Use  the  same  battery  combinations  recommended 
for  tubes  having  voltage  and  current  requirements  similar  to  the  tubes  ydu  have. 

NOTE:  If  you  use  a  loud  speaker  operated  from  your  "A"  Battery,  add  Yt  ampere  to 
the  total  rated  current  drain  of  your  tubes  and  then  select  a  battery  giving  this  total 
current  consumption. 

drain)  will  give  22 
days  of  service 
without  recharging 
when  used  daily 
for  an  average  of 
three  hours;  while 
with  the  same  tube 
combination,  a 
battery  of  80  am- 
peres will  have  a 
recharging  interval 
of  1 5  days.  Simi- 
larly, for  a  set  hav- 
ing three  uv-2oiA 
tubes  at  a  f -ampere 
drain,  a  battery  of 
65  amperes  insures 
29  days  of  service 
while  the  smaller 
47-ampere  battery 
gives  22  days  of 
service  between 
rechargings. 

By  recalling  at- 
tention to  the  types 
of  tubes  that  are 
interchangeable,  it 
will  be  noted  that 
the  accompanying 
chart,  Fig.  3,  gives 
practically  every 
combination  of  5- 
volt  tubes  in  gen- 
eral use. 


CORRECTIONS    IN    THE    FOUR-TUBE    CRYSTAL    REFLEX 
RECEIVER 

IN  QUESTIONING  the  accuracy  of  the  four- 
tube  Knockout  crystal  reflex  circuit  appearing 
in  Fig.  3   page   103  of  the  June,  1924,  issue  of 
RADIO  BROADCAST  and  also  in  Fig.  3  page  41  of  our 
Knockout  Series  Booklet,  it  has  been  brought  to  our 


4r  ? 

-o  +o — o-  04-  o+  120 


"A'  "B"90 


FIG.    4 


RADIO  BROADCAST  ADVERTISER 


415 


Stations 
Don't  Bunch 
On  the  Dials 


CONDENSERS 


The  location  of  the  -| 
same  stations  on  the 
same  dial  using  Ultra- 
LowLoss  Condensers  — 
"  spread  ",  simplifying 
tuning. 


0 


0 


.0005  mfd 


PATENT  PENDING 


0 


0 


tlLTR^-VSRHISR 

TUNING     CONTROL 

Simplifies  radio  tuning.  Pen- 
cil record  a  station  on  the 
dial — thereafter,  simply  turn 
the  finder  to  your  pencil 
mark  and  you  get  that  station 
instantly.  Easy  —  quick  to 
mount.  Eliminates  fumbling, 
guessing.  A  single  vernier 
control,  gear  ratio  20  to  1. 
Furnished  clockwise  or  anti- 
clockwise in  gold  or  silver 
finish. 

Silver  $2.50 
Gold  $3.50 


Tuning  Simplified Novt  f 

The  day  of  tedious  fumbling  about  for  your  stations  is  past — 
science  has  been  brought  into  play.  Now,  with  the  Ultra- 
LowLoss  Condenser  you  can  instantly  tune  in  on  any  station 
as  easy  as  turning  the  hands  of  a  clock  to  the  hour. 

With  one  station  of  known  wavelength  located  on  the  dial,  all  others 
can  be  found  instantly.  Each  degree  on  a  100  degree  dial  represents 
approximately  3%  meters  difference  in  wave  length.  This  applies  to 
both  high  and  low  wavelengths.  Other  than  100  degree  dials  vary  ac- 
cordingly, l 
This  simplification  of  tuning  is  made  possible  by  the  new  Gutless  Stator 
Plates  to  be  found  only  in  the  Ultra-LowLoss  Condensers.  Every  fea- 
ture of  the  Ultra-LowLoss  Condenser  was  developed  with  one  predomi- 
nating purpose — to  overcome  losses  common  in  other  condensers.  De- 
signed by  R.  E.  Lacault,  originator  of  the  famous  Ultradyne  Receivers 
and  Ultra- Vernier  Tuning  Controls. 

At  your  dealers,  otherwise  send  purchase  price  and  you  will  be  supplied  postpaid. 
Design  of  lowloss  coils  furnished  with  each  condenser  for  amateur  and 
broadcast  wavelengths  showing  which  will  function  most  efficiently  with 
the  condenser. 

TO  MANUFACTURERS  WHO  WISH  TO  IMPROVE  THEIR  SETS 
Mr.    Lacault  will  gladly   consult  with  any  manufacturer  regarding  the  application 
of  this  condenser  to  his  circuit  for  obtaining  best  possible  efficiency. 


CONDENSER 

PHENIX  RADIO  CORPORATION  116-C  East  25th  Street,  New  York  City 


Tested  and  approved  bv  RADIO  BROADCAST 


416 


Radio  Broadcast 


1ST.R.F.  STAGE 


2ND.R.F.  STAGE  DETECTOR 

,C9 


1ST  AF.  STAGE  2NDAF.  STAGE 

(Push-Pull  Amplification) 


FIG.    5 


attention  that  in  its  present  form  the  A  battery 
would  short-circuit  itself  through  the  rheostat  Ry 
when  that  rheostat  is  turned  on.  The  defect  in  the 
circuit  diagram  is  in  making  the  connection  of  the 
lower  side  of  Ra  tokthat  lead  of  the  filament  circuit 
connecting  to  the  upper  end  of  the  rheostat  Ry. 

The  correct  connection  should  be  made  to  the 
line  just  below  where  the  connection  is  now  made, 
or  in  other  words,  to  that  lead  running  from  the  left 
hand  side  of  each  of  the  filaments  of  the  first  two 
tubes. 

The  corrected  circuit  diagram  appears  in  Fig.  4. 

A   NEUTRODYNE   CIRCUIT 

MR.  D.  C.  asks  for  a  neutrodyne  circuit  em- 
ploying a  push-pull  amplifier  as  the  second 
audio  stage.  The  complete  circuit  is  shown 
in  Fig.  5. 

The  values  of  the  various  parts  are: — 

Ri,  RJ,  R3,  R6,  and  Rj — ao-ohm  Rheostats 

R4 — 3-megohm  grid  leak. 

Rj — Variable  resistance  25,000  to  100,000  ohms. 

Cb — C  Battery  45  to  9  volts. 

Ci,  C2,.  €3 — Variable  condensers — .00035  mfds. 

C4 — Grid  condenser — .00025  mfds. 

C5 — Stabilizing  condenser — .0005  mfds. 

C6,  Cy — Bypass  condensers — .006  mfds. 

C8,  €9 — Neutralizing  condensers. 

The  several  radio  frequency  coil  units  consist  of 
primary  and  secondary  coils  wound  on  35  inch  bake- 
lite  or  cardboard  tubing.  The  secondaries  are 
wound  with  60  turns  of  No.  22  DCC  wire  and  the 
primaries,  situated  at  the  lower  end  of  the  coil,  that 
is,  the  end  which  connects  to  the  negative  side  of  the 
filament,  consist  of  about  6  to  10  turns  of  the  same 
wire. 

Any  standard  neutralizing  condenser  may  be  em- 
ployed. 

Information  relative  to  the  proper  neutralization 
and  to  the  operation  of  push-pull  amplifiers  has  ap- 
peared in  past  issues  of  RADIO  BROADCAST. 

RADIO  TOOLS 

THE  need  for  good  tools  in  radio  construction 
is  paramount  where  one  wants  good  work  to 
result.     The    ordinary    tools    usually    to  be 
found  around  the  house  are  not  of  very  much  use. 


The  well-planned  radio  kit  should  contain: 
2  screw  drivers  one  with  \  inch  and  another  with 
T\  inch  blade, 
pair  of  wire  cutting  pliers. 
"    "  side 
"    "  duck  bill 

round  nose 
centerpunch 
ball  peen  hammer 
scriber 

adjustable  square 
6-inch  scale 
pair  dividers 
set  of  socket  wrenches 
soldering  iron 
hand  drill  and  set  of  drills 
Countersink 
Brace  and  wood  bits 

The  scale,  square,  scriber,  centerpunch,  hammer, 
etc.,  all  aid  in  the  laying  out  and  marking  of  panels, 
brass  and  other  work,  while  the  hand  drill,  drills, 
countersink,  etc.,  are  used  to  do  the  actual  work  in 
the  drilling  of  these  materials.  Round  nose  pliers 
are  indispensable  for  bus  wire  bending  and  duckbill 
pliers  may  be  handy  for  loosening  and  tightening 
nuts,  bolts,  etc.  Side  cutting  pliers  are  usually 
employed  for  cutting  wire  and  stripping  off  insula- 
tion. 

In  the  use  of  drills  special  care  should  be  used 
when  large  holes  are  drilled.  It  is  much  easier  to 
drill  a  |-inch  hole  by  first  using  a  No.  28  drill  in  a 
hand  drill  and  then  enlarging  it  by  redrilling  with  a 
^-inch  drill  inserted  in  the  chuck  of  a  brace,  than 
to  drill  with  a  |-inch  drill  at  the  very  beginning. 
Furthermore,  this  practice  tends  toward  accurate 
drilling  because  the  point  of  a  larger  drill  becomes 
displaced  from  the  centermark  easier  than  a  small 
drill. 

A  set  of  socket  wrenches  or  ordinary  S  wrenches 
helps  the  constructor  greatly  in  insuring  secure 
assembly  work.  It  is  well  to  remember  that  not 
too  much  strain  should  be  placed  upon  nuts  and 
bolts  because,  due  to  their  soft  brass  composition, 
it  is  easy  to  strip  the  threads. 

Every  constructor  ought  to  have  an  ample  supply 
of  bus  wire,  lugs,  nuts,  bolts,  washers,  and  wood 
screws. 


RADIO  BROADCAST  ADVERTISER 


EVEREADY  HOUR 

EVERY  TUESDAY 

AT  8  P.  M. 

(Eastern  Standard  Time) 
For  real  radio  enjoyment 
tune  in  the  "Eveready 
Group."  Broadcast  through 
stations 

New  York 
Providence 
Boston 
Philadelphia 
Buffalo 
Pittsburgh 
Cleveland 
Cincinnati 
.Detroit 
I  Minneapolis 
\  st.  Paul 
WOC         Davenport 


WEAF 

WJAR 

WE  El 

WFI 

WGR 

WCAE 

WEAR 

WSAI 

WWJ 


Eveready 
Columbia 

Ignitor 
the  proven 
Dry  Cell 

for  all 

Radio 
Dry  Cell 

Tubes 
\ya  volts 


a  good  _ set  - 
and  Evereadys 

To  ENJOY  radio  for  the  rest  of  your  life,  get  the  best 
set  you  can  afford.  There  are  receivers  at  all  prices, 
made  by  reputable  manufacturers;  it  isn't  necessary 
for  anyone  to  get  'round-the-corner,  unproved,  un- 
reliable merchandise  at  any  price.  That  applies 
to  batteries  too.  Eveready  Radio  Batteries  are  made 
in  so  many  sizes  and  prices  that  there  is  a  correct, 
long-lasting  Eveready  for  every  receiver  and  for 
every  radio  home,  ship  or  commercial  station.  Specify 
Evereadys  for  your  new  radio  set.  It  is  false  economy 
to  buy  nondescript  batteries  at  any  time.  In  the  long 
run  you'll  find  it  most  economical  to  buy  either  the 
large  or  extra  large  Evereadys.  Always  buy  Ever- 
eadys and  enjoy  the  knowledge  that  no  one  can  get 
any  more  in  batteries  for  the  money  than  you.  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 

EVEREADY 

Radio  Batteries 

"they  last  longer 


No.  772 

4S-volt 

Large 

Vertical 

Price 

$3.75 


No.  766 
22y,-volt 

Large 

Horizontal 

Price 

$2.00 


No.  771 
41/2-volt 

"C" 
Battery 
improves 
quality, 

saves 

"B" 
Batteries 

Price 
60c 


Tested  and  approved  by  RADIO  BROADCAST 


4i8 


Radio  Broadcast 


The  following  is  a  suggested  list  of  what  the  supply 
should  be: 


Bolts  —  Round  SIZE 

and  Flat  Head    No.  A 
(Brass)  No.  A 

Nuts  —  (Hexa-     No.  A  &  A 
gon  Brass) 

Wood   Screws —    No.  3 

Round — Flat 
&  Oval  Head 

(Brass      or 
Nickel  Plated)No.  5  |"-i 

Washers  — size  to  fit  screws 


//  _    3H  // 


tn  \n  atf 
"2      "4 


LONG    CORDS 

INQUIRIES  have  been  received  asking  where  the 
1  Lynch  Lead  may  be  procured.  This  lead,  des- 
cribed in  the  June  1925  issue  of  RADIO  BROADCAST 
and  illustrated  in  the  frontispiece  of  this  issue  of 
RADIO  BROADCAST,  making  possible  the  use  of  an 
automobile  storage  battery  by  plugging  in  to  the 
lamp  socket  on  the  dashboard  of  a  car  is  manu- 
factured by  the  Belden  Manufacturing  Company, 
Chicago,  Illinois,  and  the  Crescent  Braid  Com- 
pany, Providence,  Rhode  Island. 

The  extra  length  loudspeaker  cord  also  illustrated 
in  the  frontispiece  of  this  issue  may  be  obtained 
from  the  Alden  Manufacturing  Company,  Spring- 
field, Massachusetts. 


Before  You  Write  to  the  Grid 

THOUSANDS  of  you  are  writing  the  Grid  for  technical  advice  every  month.  The 
expense  of  framing  a  complete  and  exhaustive  reply  to  each  letter  is  very  high.  The  edi' 
tors  have  decided  that  the  benefit  of  the  questions  and  answers  service  will  continue  to  be 
extended  to  regular  subscribers,  but  that  non'subscribers,  from  April  15,  on,  will  be  charged 
a  fee  of  $1  for  each  letter  of  inquiry  which  they  send  to  our  technical  department.  Very 
frequently,  our  technical  information  service  proves  of  definite  money  value  to  you  who 
write  us,  for  we  are  often  able  by  a  sentence  or  two  of  explanation,  to  put  you  on  the  right 
path  before  you  have  made  a  perhaps  expensive  mistake. 

The  occasional  reader  of  RADIO  BROADCAST  will  be  charged  a  fee  of  $1  for  complete 
reply  to  his  questions,  and  the  regular  subscriber  can  continue  to  take  advantage  of  the 
service  as  before.  In  that  way  the  non'subscriber  will  help  share  the  cost  of  the  technical 
staff  whose  service  he  gets.  Every  letter  receives  the  benefit  of  the  experience  of  the  editor 
and  the  technical  staff  and  every  correspondent  may  be  sure  that  his  questions  will  receive 
careful  consideration  and  reply. 

When  writing  to  the  Grid,  please  use  the  blank  printed  below. 


GRID  INQUIRY  BLANK 
Editor,  The  Grid, 

RADIO  BROADCAST, 

Garden  City,  }^ew  Tor\. 
Dear  Sir: 

Attached  please  find  a  sheet  containing  questions  upon  which  \indly  give  me  fullest 
possible  information.     I  enclose  a  stamped  return  envelope. 

(Chec\  the  proper  square} 

O  I  am  a  subscriber  to  RADIO  BROADCAST.     Information  is  to  be  supplied  to  me  free 
of  charge. 

EH  I  am  not  a  subscriber.    I  enclose  $1  to  cover  costs  of  a  letter  answering  my  questions. 

My  name  is 

My  address  is. : 


>\ 


The  $1.50  Ducon 


and  no  antenna! 


A  small  Ducon  screwed  into  a  light  socket— 
or  a  cumbersome,  unsightly  aerial?  Surely 
the  Ducon!  It's  so  inexpensive — so  easy  to 
use — so  sure  in  its  results. 

Take  home  a  Ducon  to-day — and  hear  to- 
night's best  programs! 

The  Ducon  is  sold  by  all  reliable  dealers.  Try  one 
for  five  days.  If  it  is  not  thoroughly  satisfactory, 
your  money  will  be  refunded. 


Dubilier 

CONDENSER    AND    RADIO    CORPORATION 


Tested  and  approved  by  RADIO  BROADCAST 


New  Equipment 


ERLA   RHEOSTAT 

Designed  to  require  a  min- 
imum of  room  behind  the 
panel  and  yet  it  does  not 
sacrifice  the  good  qualities 
of  larger  rheostats.  The 
split  contact  arm  facilitates 
its  operation  over  the  re- 
sistance winding.  It  is 
secured  to  the  panel  by  a 
one-hole  mounting,  a  con- 
structional feature  now  This  battery  charger  is  one  of  those  units  employing  a  Tungar  rectifying  tube.  It  does  its 
becoming  quite  popular,  work  very  well,  whether  it  is  charging  A  batteries  or  high  voltage  B  batteries.  The  unit  is  corn- 
Made  by  the  Electrical  posed  of  the  necessary  transformer  and  connections  so  that  it  may  be  connected  directly  to  the 
Research  Laboratorties,  power  mains.  Made  by  the  Acme  Electric  and  Manufacturing  Company,  Cleveland,  Ohio 
2505  Cottage  Grove  Ave., 
Chicago,  Illinois 


ACME    BATTERY   CHARGER 


BRADLEYDENSER 

This  interesting  condenser 
is  manufactured  by  the 
makers  of  the  well-known 
Bradleystats.  It  is  equipped 
with  a  brass  shield  designed 
to  keep  dust  from  the  plates. 
Dust  particles  that  become 
damp  or  electrically  charged 
are  responsible  for  much  of 
the  "swishing"  noise  that 
takes  place  when  receivers 
are  tuned.  The  condenser 
has  a  minimum  of  dielectric, 
low  resistance  plates  and  a 
smooth  action 


HERCULES   AERIAL   MAST 

The  above  illustration  shows  how  an  efficient  and 
good  looking  mast  may  be  erected  for  your  antenna. 
S.  W.  Hull  and  Company,  2048  East  79th  St. 
Cleveland,  Ohio,  make  these  masts  in  three  standard 
lengths— 20ft.,  40  ft.,  and  60ft.,  all  steel  construction. 
They  are  of  a  special  angle  construction  that  gives 
great  strength  and  light  weight,  each  of  which  is  a 
decided  advantage.  When  erected  these  masts 
will  stand  a  five  hundred-pound  pull  at  the  top 


SANGAMO    FIXED 
CONDENSERS 

These  condensers,  made  by 
the  Sangamo  Electric  Com- 
pany of  Springfield,  Illinois, 
makers  of  the  well  known 
Sangamo  meters,  are  a  distinct 
addition  to  the  condenser 
market.  They  may  be 

thrown  on  a  cement  floor 
without  breaking,  heated 
with  a  soldering  iron  without 
changing  their  capacity,  and 
soaked  in  water  without  ab- 
sorbing moisture.  Their 
capacity  is  indeed  "fixed" 


RADIO  BROADCAST  ADVERTISER 


44£ 


Vital  to  every  radio  fan 

In  a  radio  set,  it  is  the  tube  that  detects  the 
sound — that  amplifies  the  sound — that  deter- 
mines in  large  part  the  quality  and  volume  of 
the  sound.  Therefore  the  tube — intricate  of 
mechanism  and  delicate  to  make — is  the  vital 
spot  in  every  set  And  it  always  pays  to  be 
sure  you  use  genuine  Radiotrons — made  with 
experienced  precision. 

Build  any  circuit — simple  or  complex.  Buy 
any  set,  plain  or  fancy,  simply  boxed  or  elab- 
orately cabineted.  But  give  it  every  chance 
to  achieve  its  best — with  genuine  Radiotrons. 
Be  just  as  careful  when  you  replace  tubes,  too. 
Ahuays  see  for  yourself  that  each  one  bears  the 
identifying  marks  of  a  Radiotron:  The  word 
Radiotron  and  the  RCA  mark. 


Radio  Corporation  of  America 


Chicago 


New  York 


San  Francisco 


Radiotr 


PRODUCED    ONLY    BY     RCA 


Tested  and  approved  by  RADIO  BROADCAST 


"i  noiinii  nmini  ginn  i inimin  Hiiniii«iiiiiii>ni  mm  m  in man :;.!i itraii  mi 


THE    SOCIAL    SIDE    OF    RADIO 

Mrs.  Dr.  Elliott  Norton,  center,  Frances  Peralta,  soprano  of  the  Metropolitan  Opera 
Company,  right,  and  Mrs.  Alberta  N.  Burton,  at  a  radio  set  during  the  tea-hour.  Women 
throughout  the  country  are  finding  that  they  may  hear  delightful  tea  and  dinner  music 
during  the  late  afternoon  and  evening,  and  a  radio  concert,  given  by  a  good 
orchestra,  often  adds  to  the  pleasure  of  a  cup  of  tea 


,  :r  ,'T     Illllini!!  tllllllllll    III  II IIIIIIIIIIIIIIIIIHIIIIIIIIIIII 


iiiiiiiiiiiiiiiiniiiiiiiiiiiniiini 


RADIO 
BROADCAST 


Vol.  7,  No.  4 


August,   1925 


/ 


From  Figures  to  Fame 

• ; 

Professor  Louis  Alan  Hazeltine  Finds  that  the  Algebraic  Un- 
known Quantity,  X,  Equals  Fame,  Fortune,  and  the  Neutrodyne 


BY  MYRA  MAY 

ELDOM,  if  ever,  would  any  one  select  sytricate  problems  of  the  higher  branch.    And 
algebra   as   a   sure    road   to  fortune,      so  the  unknown  quantity,  X,  may,  after  all, 

be  the  Fame  and 
Fortune  of  your 
dreams  as  well  as 
the  solution  to  your 
involved  algebraic 
equation, 
dom  that 


c 

jl  While  plumb- 
S*^  ing,  banking, 
advertising,  physics 
and  every  kind  of 
concentration  are 
glaringly  depicted  as 
a  part  of  the  curricu- 
lum of  most  corres- 
pondence school 
courses,  it  is  exceed- 
ingly unlikely  that 
these  confident  ad- 
vertisers would  in- 
dicate algebra  as  the 
one  path  through 
which  one  might  at- 
tain to  Fame  and 
Fortune— that  vision- 
ary goal  of  one's 
dreams.  But  it  has 
been  demonstrated 
that  algebra  and 
Fame  and  Fortune 
are  somewhat  synon- 
ymous and  that  one 
gains  experience  from 
the  one  branch  of 
mathematics  that 
helps  to  solve  the  in- 


PROFESSOR  LOUIS  ALAN   HAZELTINE 

Inventor  of  the  neutrodyne  circuit,  embodied  in 
thousands  of  receivers  used  all  over  this  country  and 
abroad.  Mr.  Hazeltine  is  head  of  the  Department 
of  Electrical  Engineering  at  Stevens  Institute  of 
Technology  at  Hoboken,  New  Jersey,  and  is  here 
shown  using  a  wavemeter  in  his  laboratory 


It  is  sel- 
one  gains 
Fame  and  Fortune 
through  the  direct 
application  of  mathe- 
matics, however,  and, 
student  or  scholar,  he 
is  fortunate,  indeed, 
who,  having  solved 
his  algebraic  problem, 
finds  that  the  X,  lit- 
erally spells  Fortune 
itself.  Such  was  the 
case  with  Louis  Alan 
Hazeltine,  inventor 
of  the  "neutrodyne" 
circuit. 

If  someone  were  to 
ask  you  why  radio 
interested  you,  you 
might  reply  that  you 
liked  to  try  for  dis- 
tance, or  that  you 
enjoyed  the  enter- 


452 


Radio  Broadcast 


tainment  that  a  full  program  affords,  or 
you  might,  like  Professor  Hazeltine,  answer 
that  it  is  the  science  of  radio  which  interests 
you.  Professor  Hazeltine  explains  that  it 
was  the  opportunity  to  work  out  mathematical 
problems  that  first  led  him  to  experiment 
with  radio.  He  has  never  been  especially 
interested  in  either  the  programs  of  broad- 
casting stations  or  in  attempts  to  receive  long 
distances.  He  has  been  concerned  with  little 
but  the  scientific  side  of  wireless.  It  is  char- 
acteristic of  the  man  that  he  did  not  have  a 
neutrodyne  set  himself  until  several  years 
after  he  had  worked  out  the  fundamental 
theory  mathematically  and  had  made  appli- 
cation for  his  patents. 

PROFESSOR     HAZELTINE      LIKES      MATHEMATICS 

MATHEMATICS  has  always  been  a  fa- 
vorite of  mine,"  he  says.  "At  school 
I  once  received  a  prize  for  my  good  work 
and  my  highest  grades  were  always  in  mathe- 
matics. By  chance,  I  graduated  first  in  my 
class,  but  that  was  only  by  chance,  for  I  had 
consistently  held  second  place  until  the 
leader  went  to  live  in  ahpther  city.  From  a 
high  school  in  New  London,  Connecticut,  I 
transferred  to  Stevens  Institut&-of  Technology 
where  in  1906  I  graduated  with  the  degree 
of  Mechanical  Engineer." 

Professor  Hazeltine  is  too  modest  .to  tell 
that  he  finished  his  school  and  college  course 
in  twelve  years  instead  of  the  sixteen  most 
of  us  give  to  it.  He  prefers  to  let  people  find 
that  out  for  themselves. 

"I  remember,"  he  reminisces,  "when  I  was 
a  little  boy  I  saw  my  uncle  working  out  some 
algebraic  calculations:  he  explained  that  he 
made  those  queer  hieroglyphics  just  for 
amusement.  1  marvelled  at  such  a  pastime 
when  there  were  such  sports  as  baseball  and 
swimming  to  claim  spare  hours.  I  had  no 
premonition  that  some  day  I,  too,  would 
devote  my  leisure  to  the  same  queer  hiero- 
glyphics. 

"When  I  entered  Stevens  Institute  I  did 
not  know  what  branch  of  engineering  I 
wanted  to  take  up,  but  I  did  know  that  I  had 
a  prejudice  against  electrical  engineering. 
Nevertheless,  near  the  end  of  my  course  I 
began  to  feel  that  the  performance  of  elec- 
trical apparatus  could  be  predetermined 
more  accurately  than  that  of  mechanical.  It 
was  this  feeling  that  led  me  to  change  my 
field  to  electrical  engineering  in  spite  of 
my  former  prejudices,  and  later,  it  was  this 
same  feeling  that  led  me  to  specialize  in  radio." 

After  graduating   from   Stevens    Institute, 


Professor  Hazeltine  entered  the  testing  de- 
partment of  the  General  Electric  Company 
in  Schenectady  where  he  received  a  practical 
training.  This  was  his  only  venture  along 
the  highroad  of  business,  for  the  following 
year  he  was  offered  a  position  as  assistant  in 
the  Department  of  Electrical  Engineering 
at  Stevens  Institute  and  he  has  remained 
at  that  college  ever  since. 

WHY    HAZELTINE    SPECIALIZED    IN    RADIO 

1WAS  fortunate  in  my  surroundings  at 
Stevens,"  says  Professor  Hazeltine,  "for 
my  work  covered  all  branches  of  electrical 
engineering  and  the  head  of  the  department, 
Professor  Albert  F.  Ganz,  was  always  aiding 
and  inspiring  my  further  progress.  During 
this  period  I  specialized  in  one  branch  of 
electrical  engineering  after  another,  and  pre- 
pared much  of  the  material  for  presentation 
to  my  classes.  It  was  in  this  manner  that 
I  gradually  developed  a  text  on  electrical 
engineering,  which  has  but  recently  been  pub- 
lished. 

"Professor  Ganz  was  the  foremost  author- 
ity in  this  country  on  the  subject  of  electro- 
lytic corrosion  of  underground  structures  by 
stray  electric  current,  particularly  from  elec- 
tric railways.  At  times  I  assisted  him  in 
this  work  and  for  several  years  after  his  death 
I  was  associated  with  the  firm  of  Albert  F. 
Ganz,  Incorporated,  which  .continued  ^  his 
professional  work  in  electrolysis.". 

During  the  winter  of  1914-1915,  the  well- 
known  radio  experimenter,  E.  H.  Armstrong, 
wrote  a  paper,  presented  before  the  Institute 
of  Radio  Engineers,  on  the  fundamentals  of 
the  three-electrode  vacuum  tube  and  then  in  a 
subsequent  paper  described  in  detail  the  tube's 
capabilities  for  oscillating  which  he  had  dis- 
covered. The  young  instructor  at  Stevens, 
who  had  always  been  partial  to  any  branch  of 
mathematical  science,  found  a  new  and  delight- 
ful field  before  him.  Here  at  last  was  a  real 
opportunity  to  apply  mathematical  analysis. 

THEORY    PRECEDES    PRACTISE 

LONG  before  Professor  Hazeltine  had  one 
of  the  desired  vacuum  tubes  he  began  a 
theoretical  study  of  its  operation,  and  it  was 
in  this  manner  that  he  worked  out  the  theoret- 
ical requisite  for  the  production  of  oscilla- 
tions. Not  until  then  did  he  obtain  a  vacuum 
tube  (then  known  as  an  audion)  to  trace  its 
characteristic  curve.  On  the  basis  of  that 
information  he  designed  his  circuit,  wired  it, 
and  immediately  obtained  the  anticipated 
result. 


From  Figures  to  Fame 


45? 


TWO    RECEIVERS 

Designed  by  Professor  Hazeltine.  The  one  in  the  insert  was  designed  for  the  Navy  Department  during 
the  war  and  is  known  officially  as  the  SE  1420.  It  was  while  he  was  developing  this  .receiver  that  the  idea 
for  the  neutrodyne  circuit  was  partially  evolved.  The  larger  photograph  shows  Mr.  Hazeltine  and  one  of 

his  models  of  the  neutrodyne 


In  spite  of  this  remarkable  performance, 
Professor  Hazeltine  continued  his  theoretical 
studies  coupled  with  experimental  verifica- 
tions for  the  next  two  years,  and  it  was  not 
until  1917  that  he  felt  that  his  work  was  in 
sufficiently  perfect  form  to  give  it  to  the 
world.  His  paper  on  "Oscillating  Audion 
Circuits"  which  gave  the  results  of  his  in- 
vestigations was  read  before  the  Institute  of 
Radio  Engineers.  This  was  the  first  time  that 
a  general  and  yet  a  simple  mathematical 
method  for  the  treatment  of  oscillating  au- 
dion  circuits  had  been  given.  It  was  in  this 
paper  that  Professor  Hazeltine  used  the  ex- 
pression "mutual  conductance,"  a  term  that 
has  since  become  as  much  a  part  of  radio 
language  as  have  antennas  and  batteries. 
Professor  Hazeltine  asserts  that  all  of  his 
subsequent  radio  work  and  whatever  success 


he  has  achieved  may  be  traced  to  that  pa- 
per. 

Wireless  was  claiming  more  and  more  of 
Professor  Hazeltine's  time.  The  following 
summer  he  devoted  to  experimental  work  in 
radio  telegraphy  and  telephony  in  conjunc- 
tion with  Mr.  Paul  Ware.  Later  Mr.  Ware 
joined  the  Signal  Corps  of  the  United  States 
Army  where  he  continued  his  research  and 
produced  a  valuable  portable  set  that  has 
since  been  adopted  as  a  standard  equipment 
by  the  Signal  Corps. 

Meanwhile  Professor  Hazeltine  was  also 
conducting  a  radio  and  buzzer  class  to  train 
operators  for  the  Signal  Corps.  And  then 
when  Professor  Ganz  died,  Professor  Hazel- 
tine  was  appointed  in  his  place  to  serve  as 
head  of  the  Department  of  Electrical  En- 
gineering. 


454 


Radio  Broadcast 


From  Figures  to  Fame 


455 


THE    SE    1420 

DURING  the  following  year  I  was  asked  to 
join  the  technical  staff  of  the  radio 
laboratory  at  the  Navy  Yard  at  Washington," 
he  narrates.  "  1  spent  the  summer  in  Wash- 
ington doing  miscellaneous  development  work 
and  in  the  early  fall  1  designed  a  radio  re- 
ceiver which  was  standardized  by  the  Navy 
Department  and  has  been  in  wide  use  ever 
since.  To  Naval  operators  it  is  known  as 
SE  1420.  This  receiver  contained  several 
novel  features,  and  its  design  was  of  particular 
interest  to  me  because  it  was  based  on  the 
theoretical  formulae  which  I  myself  had 
evolved  and  which  were  incorporated  in  my 
paper  on  'Oscillating  Audion  Circuits. '  These 
methods  were  borne  out  so  well  by  experiment 
that  only  a  single  shop  model  was  constructed 
on  which  a  few  minor  adjustments  had  to  be 
made  before  the  final  drawings  and  specifi- 
cations were  prepared  for  the  submission  of 
bids. 

"In  the  midst  of  my  work  I  was  stricken 
with  an  attack  of  influenza  which  kept  me 
away  from  the  laboratory  for  a  few  weeks. 
On  my  return  I  found  that  another  member 
of  the  technical  staff  had  practically  com- 


pleted the  development  of  a  receiver  similar 
to  my  own.  The  officer  in  charge  of  the  work, 
Lieutenant  W.  A.  Eaton,  suggested  that  I 
abandon  my  development  on  the  ground  that 
time  was  pressing  and  that  the  other  receiver 
was  nearly  ready.  Had  he  given  me  definite 
instructions  I  would,  of  course,  have  obeyed 
him'.  But  inasmuch  as  he  merely  expressed 
a  wish  that  I  do  so  and  because  I  had  great 
confidence  in  my  own  design,  I  felt  justified 
in  continuing  with  my  work.  The  result 
was  that  when  these  receivers  were  tested 
mine  was  shown  to  be  distinctly  superior  to 
the  other  and  it  was  eventually  adopted. 
Although  it  is  strictly  against  the  copy-book 
traditions  I  feel  that  a  subordinate  is  justified 
in  going  against  the  wishes  of  his  superior  if 
he  is  confident  that  he  is  right  and  if  he  is  not 
disobeying  positive  instructions. 

ELIMINATING    CAPACITY    COUPLING 

IN  THE  design  of  this  Navy  "receiver  I  was 
particularly  interested  in  trying  to  eli- 
minate capacity  coupling  between  the  pri- 
mary and  the  secondary  circuits,  for  experi- 
ence had  shown  me  that  this  was  a  source  of 
much  interference  in  reception.  By  suitable 
shielding  I  was  able  to  eliminate  all  capacity 


THE    STAFF    OF   THE    ELECTRICAL    ENGINEERING    DEPARTMENT 

Of  Stevens  Institute  of  Technology.      Professor  Hazeltine,  head  of  the  Department,   is  seated  in  the  first 

row,  center.      Front  row,  left  to  right,  Professor  F.  C.  Stockwell,  Professor  L.  A.  Hazeltine,  W.  P.  Powers. 

Back  row,  H.  L.  Paulding,  V.  C.  McNabb,  Samuel  Slingerland,  and  H.  C.  Roters 


456 


Radio  Broadcast 


coupling  in  the  primary  and  secondary  cir- 
cuits except  between  two  coils,  one  of  which 
was  necessarily  in  the  field  of  the  other. 
Then  it  occurred  to  me  that  I  could  minimize 
this  coupling  by  partially  shielding  one  of 
these  coils  through  an  auxiliary  coil  wound 
over  it.  I  realized  that  this  coil  would  pick 
up  some  current,  and  1  quickly  saw  that  this 
current  might  be  employed  to  neutralize 
whatever  capacity  coupling  remained.  This 
was  the  first  thought  of  capacity  neutraliza- 
tion that  I  had,  and  I  did  not  realize  at  the 
time  that  it  was  destined  to  be  what  one  might 
call  the  keystone  of  the  neutrodyne.  The 
neutralization  was  actually  incorporated  in 
therNavy  receiver  although  it  was  of  the  na- 
ture'of  a  refinement  rather  than  of  a  necessity. 
"Later  I  attempted  the  design  of  an  audio- 
frequency amplifier  which  would  give  a  par- 
ticularly high  amplification,  but  after  a  time 
I  came  to  the  conclusion  that  such  an  amplifier 
would  oscillate  persistently  on  account  of 
the  capacity  coupling  between  the  plate  and 
the  grid  of  the  vacuum  tube,  in  its  circuit,  for 
the  plate  and  the  grid  circuits  would  be  con- 
nected to  similar  transformers  and  would 
therefore  be  in  resonance — a  condition  par- 
ticularly conducive  to  oscillation.  Almost  at 
once  I  saw  the  solution — the  deleterious  ca- 
pacity coupling.  I  suppose  that  my  experi- 
ence with  the  Navy  receiver  helped  me  to 
reason  out  the  method  which  I  thus  evolved. 
My  experience  seems  to  me  to  be  an  illustra- 
tion of  the  adage  that  the  realization  of  a 
problem  is  frequently  more  important  and 
more  difficult  than  its  solution.  This  neu- 
tralization of  capacity  coupling  in  vacuum 
tubes  was  the  basis  of  the  neutrodyne  circuit, 
the  practical  development  of  which  came 
several  years  later. 

THE  WAY  TO  SOLVE  PROBLEMS SOLVE  THEM 

IN  1919  I  started  to  devote  my  time  to  a 
study  of  the  application  of  three-electrode 
vacuum  tubes  to  the  various  problems  of  power 
conversion,  with  efficiency  the  primary  ob- 
ject. This  work  was  to  some  extent  a  con- 
tinuation of  my  earlier  work  on  oscillating 
circuits,  for  the  form  of  conversion  which  I 
first  investigated  was  from  direct  current  to 
high-frequency  current  as  used  [for  radio 
transmission.  The  work  was  carried  on  much 
further,  however,  in  order  that  it  might 
include  conversion  of  alternating  current 
power  into  direct  current  power,  of  one  fre- 
quency into  another  frequency,  of  direct 
current  into  alternating  current  of  controllable 
frequency,  and  so  forth.  This  new  subject 


was  a  valuable  background  for  my  other 
work  and  made  me  realize  that  although  two 
problems  might  not  be  closely  related,  they 
might,  nevertheless,  have  a  common  ground 
in  their  respective  solutions. 

"In  my  college  work  I  constantly  see  many 
boys  who  seem  quicker  than  1  in  absorbing 
mathematical  theories,  but  they  have  not  the 
fondness  for  work  that  leads  to  original  inves- 
tigations. I  have  long  believed  that  the 
prime  requisite  for  success  along  mathematical 
lines — and  this  applies  to  all  scientific  prog- 
ress— is  not  so  much  a  natural  ability,  as  it 
is  a  certain  fondness  for  the  subject.  The 
only  way  to  learn  to  solve  problems  is  to  solve 
them. 

"I  was  engaged  in  the  development  of 
radio  receivers  during  the  fall  of  1922  when 
my  attention  was  directed  to  the  immense 
possibilities  of  a  receiver  employing  tuned 
radio  frequency  amplification.  I  knew  that 
the  great  limitation  of  this  type  of  receiver, 
which  had  thus  far  prevented  its  successful 
introduction,  was  in  its  strong  tendency  to 
oscillate  because  of  the  feed-back  of  the 
capacity  coupling  of  the  vacuum  tube.  This 
feed-back  was  accentuated  by  the  tuned  input 
and  output  circuits.  I  realized  that  my  earlier 
work  on  the  neutralization  of  this  capacity 
coupling  was  directly  applicable.  A  model  re- 
ceiver was  constructed  to  incorporate  these 
ideas  and  it  was  christened  the  neutrodyne. 

"  During  this  period,  several  manufacturers 
were  eager  to  obtain  a  receiver  of  this  sort, 
and  Mr.  I.  P.  Rodman,  an  officer  of  the 
present  Garod  Corporation  who  had  become 
convinced  of  the  great  value  of  a  tuned  radio- 
frequency  amplifier,  had  much  to  do  with  its 
development.  The  neutrodyne  was  first 
brought  before  the  public  at  a  meeting  of  the 
Radio  Club  of  America  in  March,  1923. 

HOW    INVENTIONS    ARE    MADE. 

THERE  is  much  curiosity  as  to  how  in- 
ventions are  made.  In  the  earlier  devel- 
opment of  an  art,  most  inventions  are  the  re- 
sults of  experimental  discoveries,  and  this  is 
often  the  case  even  in  their  subsequent 
growth.  For  example,  Armstrong's  inventions 
of  regeneration  and  super-regeneration  come 
under  this  category.  My  inventions,  on  the 
other  hand,  have  all  been  the  result  of  theor- 
etical studies,  verified  and  modified  by  later 
experimental  work.  Again  some  inventions 
are  the  result  of  mathematical  analysis  as, 
for  example,  Pupin's  and  Campbell's  loading 
coils  on  electrical  filters  in  telephone  lines. 
Although  I  have  used  mathematical  analysis 


From  Figures  to  Fame 


457 


PROFESSOR    HAZELTINE    AND   A    CLASS 

At  work  in  a  laboratory  in  the  Department  of  Electrical 
Engineering  at  Stevens  Institute  at  Hoboken,  New  Jersey 


quite  freely  in  my  studies,  it  so  happens  that 
my  inventions  have  been  based  on  elementary 
technical  considerations  and  can  be  fully 
described  either  with  or  without  the  most 
elementary  sort  of  mathematics. 

"Some  inventions  are  made  deliberately; 
that  is,  the  inventor  has  a  problem  before 
him  which  he  attacks  in  every  way  that  he 
can  think  of  until  he  solves  it.  It  was  in  this 
manner  that  I  made  my  invention  of  capacity 
coupling  neutralization  as  applied  to  vacuum 
tubes  and  my  high  efficiency  arrangements 
for  power  conversion  with  vacuum  tubes. 

"It  is  interesting  to  compare  the  problems 
which  confronted  the  engineers  of  a  few  years 
ago  with  those  which  puzzle  them  to-day. 
In  the  days  immediately  following  Arm- 
strong's regenerative  work,  the  great  problem 
was  to  get  vacuum  tubes  to  oscillate,  and  I 
have  spent  many  hours  in  trying  to  produce 
oscillations  in  circuits  where  the  conditions 
were  essentially  unfavorable.  In  the  Navy 


receivers  which  preceded  mine,  the  idea  of 
obtaining  oscillations  under  all  conditions  of 
coupling  and  wavelength  had  been  definitely 
abandoned  and  it  required  all  of  the  refine- 
ment of  calculation  of  which  I  was  capable  to 
produce  controllable  oscillation  in  my  own 
receiver. 

"The  problem  of  tuned  radio  frequency 
amplification,  however,  has  been  solved  by 
the  elimination  of  oscillations  and  I  have  spent 
as  many  hours  getting  rid  of  stray  coupling 
and  thereby  stopping  all  tendency  to  oscillate 
as  I  have  previously  devoted  to  the  encourage- 
ment of  oscillation.  So  radio  progresses." 

It  may  be  that  Professor  Hazeltine  has  used 
the  same  method  of  progress  for  himself.  In 
any  event,  he  has  come  up  by  almost  pure 
mathematical  processes  to  vindicate  the  stu- 
dent. He  has  made  inventions  that  others 
have  repeatedly  failed  to  approximate,  and 
he  has  placed  himself  in  the  foreground  of  im- 
portant figures  in  the  technical  world  to-day. 


RADIO  BROADCAST  Photograph 


FIG.     I 


A  parts  picture.     With  the  exception  of  the  fixed  condenser,  all  the  parts  entering  in  the  construction 
of  the  detector  amplifier  are  shown  here.       The  numbers  correspond  with  those   of   the  parts  list 


How  to  Build  a  Two-Stage 
Detector-Amplifier  Unit 


BY  JOHN  B.  BRENNAN 


BELIEVE  that  radio  constructors  are  becoming  more  and  more  interested 
in  building  receivers  thai  will  produce  signals  of  excellent  quality.  As  Mr. 
Brennan,  technical  editor  of  this  magazine,  brings  out  in  this  article,  it  is  not  now 
so  important  fust  how  much  noise  a  receiver  will  deliver,  or  bow  far  it  can  be  beard, 
but  tbe  quality  of  the  program  it  produces.  .  This  unit,  which  is  designed  to  fit  with 
the  two-stage  radio-frequency  amplifier  unit  described  by  tbe  same  author  in  this 
magazine  for  May,  192$,  has  been  especially  designed  to  give  the  best  possible 
quality.  The  cost  of  parts  is  not  high,  and  the  constructor  will  find  that  assem- 
bly and  wiring  is  quite  easy. — THE  EDITOR 


SLOWLY  but  surely  the  trend  in  radio 
is  swinging  toward  quality.     We  are 
learning  that  it  is  not  how  much,  but 
how  good  that  counts  in  radio. 
There  was  a  time  when  the  radio  store  which 
had  the  largest   horn  sticking  out  its  front 
window  with   a   power   amplifier  behind   it, 
assumed  a  kind  of  local  radio  supremacy  due 
entirely    to   the   pure   force   of   the   racket. 
Times  have  fortunately  changed,  and  to-day 
we  see  many  dignified  if  modest  radio  estab- 
lishments equipped  with  individual  listening-in 
booths  where  receivers   are  on  display   and 
demonstration. 

So,  too,  the  change  has  been  felt  in  the  design 
of  radio  apparatus.  Parts  and  complete 
sets  have  been  materially  improved.  Good 
voice  and  music  quality  and  perfectness  of 


loud  speaker  reproduction  have  assumed  their 
rightful  importance  in  design  and  construction. 
That  old  term  "tremendous  loud  speaker 
volume"  is  slowly  slipping  into  the  discard. 
It  is  being  helped  along  by  an  occasional 
shove  in  the  form  of  an  amplifier  which 
produces  loud  speaker  signals  with  clarity 
and  fidelity. 
This  paper  describes  such  an  amplifier. 

WHAT    DO    WE    WANT    IN     AN     AMPLIFIER? 

TO  BE  efficient,  a  detector  and   amplifier 
must  have  the  qualifications  of  sensitivity, 
honesty  of  reproduction,  ease  of  control,  and 
must  produce  loud  speaker  volume  sufficient 
for  dancing.    Its  construction  must  be  simple. 
The  sensitivity  largely  depends  upon  the 
type  of  tuner  employed  to  tune  the  incoming 


How  to  Build  a  Two-Stage  Detector-Amplifier  Unit 


459 


signal  before  it  reaches  the  detector  tube. 
However,  the  detector  tube  must  also  be 
possessed  of  qualities  which  will  make  of  it  a 
sensitive  rectifier  of  these  signals. 

Honesty  of  reproduction,  or  in  other  words, 
the  property  of  the  amplifier  to  repeat 
faithfully  the  sounds  as  transmitted,  is  a 
function  governed  by  the  selection  of  a 
suitable  audio-frequency  transformer,  plus  the 
intelligent  use  of  A,  B,  and  C  batteries. 

All  detector-amplifier  circuits  are  pretty 
much  alike.  Their  differences  are  mainly 
in  the  design  which  affects  the  control  of  the 
various  parts  entering  into  the  construction  of 
a  completed  unit.  Undoubtedly  a  unit  may  be 
produced  in  which  everything  possible  is  varia- 
ble: C  battery  adjustment  to  the  amplifiers, 
grid  leak,  grid  condenser,  tapped  transformer 
primaries  and  secondaries,  and  B  battery 
voltages.  It  is  hardly  necessary  to  state 
that  the  tubes  would  be  individually  controlled 
by  separate  rheostats.  However,  a  unit  such 
as  this  would  soon  loose  its  value  if  it  were 
to  be  used  in  a  permanent  installation  where 
there  would  be  no  need  for  all  these  controls 
once  a  satisfactory  adjustment  has  been  ob- 
tained. Such  a  completely  variable  unit 
would  rather  be  suitable  for  the  laboratory. 

The  volume  produced  by  an  audio  amplifier 


depends  upon  the  number  of  stages  of  ampli- 
fication which  may  safely  be  used  without 
overloading  the  amplifier  tubes.  Volume 
also  depends  upon  the  sensitivity  of  the  de- 
tector and  the  ability  of  the  amplifier  to  take 
whatever  is  produced  in  the  detector  and 
amplify  it  without  altering  the  signal  charac- 
teristics. Briefly  explained,  this  means  that 
some  amplifying  transformers  have  the  ten- 
dency to  favor  some  voice  and  music  notes 
over  others,  depending  upon  the  electrical 
and  mechanical  makeup  of  the  transformer. 
The  distributed  capacity  in  transformer  wind- 
ings causes  a  favoring  of  the  lower  fre- 
quencies over  the  higher  frequencies.  Also, 
when  little  iron  is  used  in  the  core  construc- 
tion, it  becomes  over-saturated  by  the  forceful 
variations  of  electromagnetic  flux  and  prevents 
the  transformer  from  functioning  successfully. 

GOOD   QUALITY    AND    SUFFICIENT    VOLUME 

THE  detector  and  two-stage  audio- 
frequency amplifier  described  here  is  the 
result  of  experimentation  along  the  lines  as 
explained  above.  It  has  been  reduced  to  a 
practicable  working  unit  producing  a  very 
high  quality  of  signal  with  plenty  of  volume. 

This  detector-amplifier  may  be  used  with 
any  tuner  now  available,  but  has  been  especi- 


©  DETECTOR 


FIRST  STAGE 
A.F.  AUDIO 

TRANSFORMER     AMPLIFIER 


A.F. 

TRANSFORMER 


SECOND  STAGE 

AUDIO 
AMPLIFIER 


-  O  A  O  -O 


FIG.    2 

The  circuit  of  the  detector-amplifier.      The  numbered  units  refer  to  those  panel  controls  as  marked  on  the 
panel  illustration  Fig.  3.      In  wiring  it  is  well  to  make  frequent  use  of  this  circuit  and  the  schematic  wiring 

diagram,  Fig.  7 


460 


Radio  Broadcast 


I 

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5"  —                         -» 

Screw  Holes 
All  Na27 

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Working  .^ 
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FIGS.    3    AND   4 

This  front  view  of  the  panel  indicates  the  symmetrical  layout  which  has  not  caused  any  sacrificing  in  effi- 
ciency for  the  sake  of  appearance.  Ample  room  on  the  upper  side  allows  for  the  mounting  of  a  filament 
voltmeter  and  plate  milliammeter  or  plate  voltmeter.  The  working  drawing  above  shows  the  panel  layout 


RADIO  BROADCAST  Photograph 


How  to  Build  a  Two-Stage  Detector-Amplifier  Unit 


6V 


SUPPORT  BRACKETS 
(Material:  V  B 


FIG.    6 
The  angle  bracket  details.     Two  are  required 

ally  designed  as  the  audio  unit  for  the  two 
stage  radio-frequency  amplifier  described  in 
the  May,  1925,  RADIO  BROADCAST. 

The  circuit  comprises  a  vacuum  tube  de- 
tector with  variable  grid  leak  and  independent 
filament  rheostat  and  a  two-stage  audio 
amplifier  with  filament  controlled  by  one 
rheostat.  Large  core  audio-frequency  trans- 
formers of  a  ratio  of  approximately  3  to  i, 
and  a  C  battery  bias  upon  the  grids  of  the 
amplifying  tubes  are  important  items  entering 
into  the  construction.  None  of  the  adjust- 
ments is  exceedingly  critical  but  are  found 
to  be  of  actual  necessity  when  maximum 
service  is  desired. 

All  thebindingposts  for  theconnection  of  the 
tuner,  batteries  and  loud  speaker  are  mounted 
upon  the  rear  of  a  bakelite  shelf  which  also 
supports  the  audio  transformers. 

A  filament  switch,  the  grid  leak  and  con- 
denser, rheostats,  sockets  and  jacks  are 
mounted  upon  the  panel.  The  bakelite 
sub-base  is  mounted  upon  the  brass  angle 
brackets  which  are  fastened  to  the  back  of  the 
panel. 


WHAT    PARTS    TO.  USE    IN    THIS    UNIT 

CATISFACTORY  results  with  this  design 
*-}  depend  entirely  upon  the  selection  of 
many  of  the  same  parts  as  employed  in  our 
construction.  This  is  quite  logical.  It  is 
probable  that  another  type  of  amplifier  can 
be  designed  using  other  parts — but  that's 
another  story. 

The  parts  employed  in  the  construction  of 
this  unit  are  listed  as  follows: 

1.  3  Federal  sockets — panel  mounting 

2.  2  Bradleystats 

3.  i  Bradleyleak,  with  .00025  mfd.  condenser 

4.  2    Carter    Jacks,    i    open    single-circuit,    I 

closed  single-circuit 

5.  2  Rauland  Lyric  audio-frequency  transform- 

ers ratio  3.95  to  i 

6.  i  Carter  filament  switch 

7.  i  Panel  7  x  10  x  T\  inches 

8.  i  Panel  3^  x  9T35  x  T8ff  inches 

9.  10  Eby  binding  posts 

10.  Brass  strip  20  x  \  x  \  inches 

11.  Bus  wire — lugs 

12.  14  \  inch  x  gej  Round  head  machine  screws 

with  hex  nuts. 

13.  6  \  inch   x  -fa   Flat   head   machine   screws 

with  hex  nuts 

14.  i  -  .0005  mfd.  fixed  condenser 

The  reader  will  probably  ask,  "can  other 
transformers  be  used  instead  of  those  shown?" 
Of  course,  yes,  but  so  can  other  parts  be  used 
-throughout  the  construction.  If  this  variation 
is  allowed  in  parts  selected,  the  individual 
constructor  would  have  to  lay  out  his  own  job. 
He  would,  of  necessity,  have  to  rearrange  the 


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All  Holes  Na  27  Drill 
O 


<j>  (j)  <j> 


SUB  PANEL 


t 


Q  3/  '' 

9^6  - 


FIG.       5 

In  the  layout  of  the  sub-base,  the  dimensions  are  marked  starting  from  the  center  line.     By 
actually   placing   the   audio   transformers   in    place,    their   mounting   holes    may    be   scribed 


462 


Radio  Broadcast 
SUB  BASE 


FIG.    7 

Is  a  schematic  wiring  diagram  of  the  completed  receiver.     For  the  sake  of 
clearness,  the  panel  is  represented  as  being  on  the  same  plane  as  the  sub-base 


various  mounting  holes  on  the  panel  and  also  scheme  of  construction  and  that  is  hardly  new. 

the  sub-panel  holes  would  be  changed.  Therefore  for  those  who  wish  to  benefit  by  the 

If  the  parts  were  not  thoughtfully  selected  experience  gained  in  the  test  of  several  types 

there  would  be  nothing  left  but  the  idea  and  of  apparatus,  it  is  suggested  that  they  con- 


How  to  Build  a  Two-Stage  Detector-Amplifier  Unit 


463 


form  to  the  selection  of  parts  as  closely  as 
possible  to  the  list  as  shown. 

The  heart  of  the  unit  is  the  two  audio- 
frequency transformers.  They  have  been 
selected  because  of  the  large  cores  upon  which 
are  wound  plenty  of  wire.  These  two  features 


RADIO  BROADCAST  Photograph 

In  laying  out  the  panel,  place  it  face  down 
on  a  table  with  its  length  running  right  and 
left.  Now  divide  the  length  into  two  sections 
evenly,  both  of  five  inches  each.  The  dividing 
line  is  the  working  center  line.  Working  up, 
three  quarters  of  an  inch  from  the  bottom 


TWO  STAGE 
RADIO  FREQUENCY  AMPLIFIER 


DETECTOR 
TWO  STAGE  AMPLIFIER 


-A-     B+90 


FIG.    8 


How  the  detector  two-stage  amplifier  would  be  connected  to  the  two-stage  radio-frequency  amplifier 
described  in  the  May,   1925,  RADIO   BROADCAST.     The  cut  above  shows  the  two  units  connected 


alone  prevent  over-saturation  and  insure 
against  overloading. 

Those  used  in  this  amplifier  are  of  a  low 
ratio  and  are  capable  of  taking  a  very  strong 
signal  and  amplifying  it  without  changing  its 
characteristics.  The  circuit  employed  is  that 
of  Fig.  2. 

The  numbered  symbols  in  Fig.  2  are  those 
with  variable  controls  that  are  mounted  on 
the  panel.  They  may  be  identified  in  the 
panel  illustration  Fig.  3. 

ASSEMBLY    IS    EASY    USING   THE    NUMBERS 

THE  construction  of  the  detector-amplifier 
is  almost  entirely  a  matter  of  assembly, 
and  wiring.  We  suggest  proceeding  as 
follows: — After  the  parts  have  been  obtained, 
the  panels  are  prepared  by  drilling  all  the  holes 
and  graining  the  surface  by  rubbing  with 
fine  emery  paper. 


scribe  a  line  (i)  across  the  length  of  the  panel. 
On  it  will  be  located  the  two  jacks.  Then 
one  half  inch  above  it  scribe  another  line 
(2)  all  the  way  across.  This  is  for  the  socket 
mounting  holes.  Another  line  (3)  is  scribed 


SUB  BASE 

Output       B ^A  —    ^C—       Input 

®      Q      Q      ®      Q     O      O      ' 


To  Tuner 


FIG.    9 

Here  is  how  the  batteries,  A,  B,  and  C  are  con- 
nected to  the  binding  posts  on  the  sub-base 


464 


Radio  Broadcast 


Plate  Variometer 
Inserted  in  Plate 
Circuit  of 
Detector  Tube 


7 

4 

0005   H 
mfd 

-6  A  0  + 


B-t-90 


if  inches  above  the  last  one  for  the  grid 
leak  and  two  rheostats.  The  filament  switch 
hole  intersection  line  (4)  is  marked  directly 
on  the  center  line  2§  inches  above  the 
line  No.  3. 

Working  out  from  the  center  line  on  line  No. 
i,  the  two  jack  holes  are  located  \\  inches 
away.  The  mounting  holes  for  the  brass 
brackets  are  located  on  this  line  f  of  an  inch 
from  the  sides  of  the  panel. 

Now  jump  up  to  line  No.  3  for  the  rheostats 
and  grid  leak,  etc.  One  is  centrally  located 
on  the  center  line  and  the  other  is  3  inches 
to  the  side  as  is  the  grid  leak  hole.  After 
locating  these  three  points,  continue  the  scriber 
lines  down  so  as  to  interesect  line  No.  2.  Then 
coming  back  to  line  No.  2  the  socket  mount- 
ing holes  are  located  f  of  an  inch  either 
side  of  the  point  of  intersection  of  the  rheostat 
hole  lines.  The  complete  layout  is  shown 
in  Fig.  4. 


Attaches  To 

Plate  of  Detector 

Tube 


Several  tuner  and  radio-frequency  amplifier 
circuits  which  may  be  used;  with  this  de- 
tector amplifier,  i.  is  a  standard  tuner 
with  primary  and  secondary,  the  latter 
shunted  by  a  .0005  mfd.  condenser;  2.  is 
the  old  standby,  the  varipmeter-vario- 
coupler  tuner;  3.  is  the  variometer  antenna 
tuner;  4.  a  non-radiating  radio-frequency  amplifier 
and  tuner;  5.  the  Reinartz  tuner;  and  6.  a  loop 
and  r.  f.  circuit.  In  the  detector  circuit,  the  return 
of  the  grid  circuit  is  made  to  the  negative  side  of 
the  A  battery  line.  If  results  are  not  satisfactory, 
try  making  this  connection  on  the  positive  side 
of  the  A  supply 


This  completes  the  panel.  The  sub-base 
dimensions  may  be  laid  off  in  a  similar  manner 
and  are  shown  in  Fig.  5. 

The  binding  posts  are  situated  three  quar- 
ters of  an  inch  from  each  other  beginning  at 
the  center  line.  The  holes  for  screws  holding 
the  sub-base  to  the  brass  brackets  are  located 
on  each  end  j  of  an  inch  in  from  the  edge. 
The  transformer  holes  are  given  but  are  not 
accurate  for  all  transformers  of  the  same  man- 
ufacture. Therefore,  in  laying  out  these 
holes  it  is  well  to  place  the  transformers  on 
the  base  so  that  the  holes  on  one  side  are  -^ 
of  an  inch  from  the  front  edge.  Then  holding 


How  to  Build  a  Two-Stage  Detector-Amplifier  Unit 


465 


FIG.     I  I    AND  FIG.     12 

The  top  side  with  all  parts  excepting  the  bypass  condenser  in  view.  Note 
how  the  two  audio  transformers  are  mounted  with  their  cores  at  right  angles 
to  each  other.  Much  of  the  wiring  is  on  the  under  side  of  the  sub-base 


466 


Radio  Broadcast 


the  transformer  in  place,  mark  the  holes  with 
a  scriber. 

The  brass  brackets  are  bent  and  drilled 
in  accordance  with  the  layout  shown  in 
Fig.  6. 

With  this  preliminary  preparation  ac- 
counted for,  the  work  of  assembly  is  next  in 
line.  The  several  parts  are  mounted  in  order 
named,  from  the  top  of  the  panel  down;  first 
filament  switch,  then  rheostats,  and  grid 
leak,  next  sockets  and  finally  jacks. 

For  the  sub-base,  first  mount  all  the  binding 
posts  having  the  lugs  on  the  under  side  of'the 
panel  and  pointing  in  toward  its  middle. 
Next  mount  the  panel  upon  the  brackets  and 
after  this  is  done,  secure  the  two  transformers 
firmly  with  |-inch  x  -j%  round  head  machine 
screws.  The  cores  are  placed  at  right  angles 
to  each  other  as  may  be  seen  from  the  sche- 
matic wiring  diagram  Fig.  7  and  the  illustra- 
tions. 

The  completed  sub-base  unit  is  fastened 
to  the  panel  by  two  round  head  brass  or  nickel 
plated  machine  screws  ^  inch  long. 


THE    UNIT 

IN  AN  assembly  job  as  compact  as  this,  it 
is  absolutely  essential  that  insulated  wire 
be  used,  at  least  where  there  is  danger  of  short 
circuits.  In  the  unit  described,  insulated 
wire  has  been  used  throughout.  Contrary 
to  what  one  might  think,  the  wiring  job  is 
simplicity  itself.  It  is  only  to  be  remembered 
that  the  wires  should  run  direct  from  one  part 
to  the  other  without  unduly  twisting  or  bend- 
ing them.  The  schematic  wiring  diagram  in 
Fig.  7  will  be  of  aid  here. 

Wherever  possible,  lugs  have  been  clamped 
down  under  terminal  nuts  to  provide  an 
easily  accessible  point  of  soldering. 

As  a  standard  detector-tv/o-stage  audio 
amplifier,  this  unit  is  admirable  for  use  around 
the  laboratory  where  the  experimenter  is  fre- 
quently trying  new  tuner  circuits  and  requires 
a  means  for  detecting  and  amplifying  his  re- 
ceived signal.  Its  primary  purpose  is  for  use 
with  the  two-stage  radio-frequency  amplifier 
described  in  the  May,  1925,  RADIO  BROADCAST. 


FIG.     13 
Looking  at  the  amplifier  from  the  right  side 


How  to  Build  a  Two-Stage  Detector- Amplifier  Unit 


FIG.  14 

The  left  side  view 


The  circuit  diagram,  Fig.  8,  shows  how  these 
two  units  may  be  connected  together. 

Plate  voltages  of  from  90  to  120  may  be 
used  on  the  two  audio  stages  while  for  the 
detector  45  to  90  volts  will  be  suitable.  '  No 
definite  voltage  requirements  are  specified 
as  this  depends  entirely  upon  the  tubes  and 
transformers  used.  Six-volt  tubes  will  prob- 
ably give  greater  satisfaction  in  this  unit, 
although  it  is  of  course  entirely  possible  to 
use  one  and  one  half  and  three-  volt  tubes. 

The  loud  speaker  may  either  be  plugged 
into  the  last  jack  or  the  cord  tips  fastened  in 
the  output  binding  posts.  The  jack  for  the 
first  stage  is  not  of  the  conventional  double- 
circuit  type  but  is  a  single  closed-circuit  jack 
which  includes  the  phones  or  loud  speaker  in 
series  with  the  primary  of  the  first  transformer 
when  the  plug  is  inserted. 

OPERATION    OF   THE    AMPLIFIER 


the   unit    has   been    adjusted   for 
one   particular    time,    for    instance,    an 
evening  enjoyment  of  a  radio  program,  there 


is  nothing  that  need  be  touched  with  the 
possible  exception  of  the  grid  leak.  Tubes 
should  be  burned  only  as  brightly  as  is  con- 
sistent with  clear  and  sufficient  volume. 
To  go  beyond  this  point  usually  results  in 
decidedly  decreasing  the  life  of  the  tube. 

The  batteries  are  connected  to  the  binding 
posts  of  the  amplifier  as  shown  in  Fig.  9. 
The  C  battery  voltage  will  vary  conversely 
with  the  B  battery  voltage  applied  and  may 
conform  with  this  table: 

C  Volts 
3.0  to   4.5 
4. 5  to    6.0 
6.0  to    9.0 
9.0  to  12.0 

The  tuner  unit  output  is  connected  to  the 
detector-amplifier  input  at  its  input  binding 
posts.  Amplifier  output  posts  are  provided 
which  allows  the  use  of  a  loud  speaker  without 
plugging  into  the  jack.  Several  tuner  and 
radio  frequency  circuits  with  which  this  unit 
might  be  used  are  shown  in  Fig.  10. 


468 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 
FIG.     15 

Simplicity  in  wiring  is  clearly  indicated  in  this  bottom  view.     It  also  shows  the  need  for  accuracy 
in  layout,  as  there  is  not  much  room  to  spare  for  the  sockets  between  the  two  brass  brackets 


If  there  is  the  slightest  trace  of  a  high- 
pitched  singing  noise,  it  is  well  to  ground  the 
negative  side  of  the  A  battery  and  the  cores 
of  both  audio-frequency  transformers. 

Where  trouble  is  apt  to  be  encountered,  it  is 
suggested  that  the  constructor  proceed  first 
by  re-checking  the  entire  circuit  diagram  with 
the  wired  circuit  of  the  unit.  Sometimes  it  is 
possible  that  transformer  windings  are  open- 
circuited  or  bypass  condensers  short-circuited. 
Be  sure  also  that  positive  contact  is  made 
between  the  several  blades  of  the  jacks  and 
that  the  filament  switch  is  working  correctly. 
Tube  prongs  may  also  be  bent  down  too  far, 


preventing  the  tube  from  making  contact 
with  the  socket  blades. 

From  the  several  assembly  and  wiring 
photographs  it  will  be  seen  that  some  leads 
have  been  passed  through  holes  drilled  for  the 
purpose  in  the  sub-base.  Many  of  the  leads 
running  from  the  sub-base  assembly  to  the 
panel  pass  through  the  narrow  space  between 
the  sub-base  and  the  rear  of  the  sockets. 

When  enclosed  in  a  suitable  cabinet,  this 
detector-amplifier  in  appearance  will  grace 
any  installation  and  is  admirably  adapted 
for  the  special  requirements  of  the  experi- 
menter. 


The  material  appearing  in  this  magazine  is  fully  protected  by  copyright,  and 
editors  of  periodicals  are  advised  that  unauthorized  publication  of  circuit 
diagrams,  technical  descriptions,  and  parts  or  the  whole  of  articles,  without  due 
permission  and  credit,  is  an  infraction  of  the  law.  Those  who  wish  to  reprint 
material  appearing  in  these  pages  are  asked  to  communicate  with  the  editor. 


"  Point   of^ 

by  Koines  leg 


Summer  Radio  Programs  Are  Attractive 


WE  IMAGINE  that  the  broad- 
cast program  directors,  har- 
assed fellows  that  they  are, 
breathe  a  sigh  of  relief  when  the 
summer  season  comes  around.  A  glance  at 
the  daily  radio  programs  in  the  newspapers, 
bought  these  steamy  summer  days,  shows  that 
there  is  plenty  of  interesting  entertainment 
which  can  be  led  into  the  willing  maw  of  the 
domestic  loud 
speaker.  At  the 
risk  of  incurring 
the  wrath  of 
those  who  make 
what  is  flip- 
pantly called  a 
livelihood  from 
the  business  of 
transportation, 
we  should  like  to 
suggest  that  the 
faithful  radio  set 
can  provide  en- 
tertainment and 
amusement  in 
the  coolness  of 
one's  home  which 
make  a  trip  to 
the  scene  of  the 
festivities  entire- 
ly unnecessary. 

Although  the 
concert  season 
has  closed,  and 
the  members  of 
orchestras  which 
have  been  heard 
from  many  sta- 
tions during  the 
winter  and  spring 
with  so  much 


FRITZ    REINER 

The  famous  conductor  of  the  Cincinnati  Symphony  Orchestra 
which  has  been  heard  over  station  WLW,  of  Cincinnati.  Mr. 
Reiner,  who  is  quoted  elsewhere  in  this  department,  thinks 
that  radio  can  do  much  to  elevate  American  musical  taste. 
His  own  activities  through  WLW  have  done  a  great  deal  toward 
giving  broadcast  listeners  music  of  unequalled  quality 


pleasure  have  scattered,  there  are  still  many  ex- 
cellent bands  which  will  be  on  the  air  from  vari- 
ous stations  during  the  summer.  The  United 
States  Marine  Band  is  probably  the  best  known 
of  musical  organizations  of  this  sort  that  can 
be  heard  during  warm  weather.  Every  Wed- 
nesday evening  from  five  to  six  thirty,  East- 
ern Standard  Time,  this  band  can  be  heard 
through  stations  WRC  of  Washington  and  wjz 

of  New  York. 
These  late  after- 
noon concerts 
will  supplement 
the  regular 
weekly  concerts 
played  in  the 
Sylvan  Theatre 
at  Washington 
which  are  broad- 
cast every  Thurs- 
day night  from' 
seven  thirty  to 
nine,  Eastern 
standard  time. 
WEAF  and  eight 
others  are  broad- 
casting several 
concerts  weekly 
of  the  Goldman 
band  from  the 
bandstand  on  the 
campus  of  New 
York  University, 
beginning  318:30 
and  concluding 
at  10:15  Eastern 
daylight  saving 
time  on  the  eve- 
nings concerned, 
wjz,  WGY,  and 
WRC  will  broad- 


470 


Radio  Broadcast 


cast  three  times  weekly  concerts  of  the  New 
York  Philharmonic  Society.  The  orchestra 
plays  in  the  Lewisohn  Stadium,  New  York. 

Listeners  to  wwj,  of  Detroit,  remember 
with  much  pleasure  the  concerts  of  Schme- 
man's  Band  which  have  been  broadcast  from 
Belle  Isle  park  in  that  city.  Alert  program 
managers  in  many  other  cities  promise  bands 
of  high  grade. 

And  sporting  events  seem  to  get  on  the  air 
more  regularly  during  the  warmer  months, 
which  is  probably  most  simply  explained  by 
the  fact  that  there  is  more  activity  of  this  sort 
at  this  time  of  year.  The  famous  Indianapolis 
automobile  races  were  broadcast  from  WGN 
at  Chicago  on  Memorial  Day  with  great  suc- 
cess. College  baseball  games  were  on  the  air 
in  many  sections  of  the  country  in  the  weeks 
before  academic  doors  closed  for  the  summer 
holiday,  wjz  handled  particularly  well  the 
job  of  reporting  a  recent  game  between  Yale 


GOVERNOR    NELLIE    TAYLOE    ROSS 

Of  Wyoming  and  Governor  Clarence  J.  Morley  of  Colorado,  before  the  micro- 
phone of  KOA,   at    Denver.     Governor   Ross  shares  national   honors  with 
Governor  "  Ma"  Ferguson,  of  Texas  as  the  first  members  of  their  sex  to  guide 
the  political  destinies  of  an  American  state 


and   Princeton   to  say  nothing  of  the   Yale 
Commencement  exercises  in  June. 

Station  WJAZ,  of  Chicago,  is  making  plans  to 
broadcast  the  classic  Lake  Michigan  sailing 
yacht  races  between  Chicago  and  Mackinac 
Island.  A  small  short  wave  transmitter  will 
be  set  up  on  a  power  boat  which  will  follow 
the  yachts  as  they  speed  up  the  lake. 

It  is  unfortunate  that  one  or  more  of  the 
enterprising  Eastern  broadcasters  do  not 
arrange  to  broadcast  more  of  the  college  crew 
races,  wjz  made  a  brave  stab  at  it  not  long 
ago  when  they  put  a  short  wave  transmitter 
aboard  the  yacht  Elco  in  the  Harlem  with 
the  capable  Major  J.  Andrew  White  at  the 
microphone  and  broadcast  the  Childs'  Cup 
race  between  the  eights  of  Columbia,  Penn- 
sylvania, and  Syracuse.  The  Poughkeepsie 
races  in  June  afforded  a  tremendously  exciting 
event  to  listeners  interested  in  sports.  Major 
White  at  the  traveling  wjz  microphone 
brought  his  listeners 
along  with  him  by  the 
color  and  imagination 
of  his  picturesque  de- 
scriptions. 

In  the  main,  out-of- 
door  broadcasting  is 
more  successful  than 
might  be  thought. 
Reverberations  present 
in  a  large  hall  make 
the  problem  of  properly 
broadcasting  an  or- 
chestra or  band  most 
difficult.  As  Mr.  Carl 
Dreher  suggests  this 
month  in  "As  the 
Broadcaster  Sees  It" 
open  air  broadcasting 
is  usually  quiet  and  free 
from  the  unpleasant 
effects  of  sound,  bounc- 
ing about  where  it 
should  not  go.  And, 
barring  the  barking  of 
disturbed  and  inquisi- 
tive dogs,  and  the  squal- 
ling of  tired  children, 
the  broadcaster  who 
sets  up  microphone  and 
speech  amplifier  in  the 
open  air  is  usually  quite 
successful. 

However,  a  few  weeks 
ago,  wjz  was  broad- 
casting the  ceremonies 
incident  to  the  unveil- 


Open-Air  Broadcasting 


471 


MARION    DAVIES 
Who  was  heard  at  a  "Motion  Picture  and  Vaudeville  Star's  Radio  Party"  from  station  WIP,  in  Philadelphia 


ing  of  a  tablet  to  Thomas  A.  Edison,  from 
Menlo  Park,  New  Jersey.  The  speeches  were 
in  the  open  air  and  came  through  in  excellent 
fashion.  But  the  scene  of  the  affair  was  close 
to  the  main  line  of  a  railroad,  and  at  times 
during  the  broadcasting,  the  hasty  puff  of  the 
engines  came  through  the  microphone  with 
such  force  as  to  interrupt  the  words  of  the 
speakers.  Governor  Silzer,  of  New  Jersey, 
who  made  one  of  the  principal  addresses, 


remarked  that  the  occasion  was  probably  the 
first  time  that  the  State  of  New  Jersey  was  in 
direct  competition  with  the  railroads. 

Many  of  us  have  felt,  during  the  broad- 
casting of  a  prize  fight,  to  choose  a  happy 
example,  that  the  miscellaneous  noises — the 
cheering  of  the  crowd,  the  gongs  and  bellow 
of  the  announcer  in  the  ring — are  a  decidedly 
necessary  and  desirable  part  of  the  affair. 
The  commercial  noises  of  a  railroad,  however, 


472 


Radio  Broadcast 


THE    SANDMAN    OF    STATION    KHJ 

At  Los  Angeles.     Those  who  have  that  unusual  ability  to  talk  to 

children  instead  of  down  to  them  are  heard  from  many  broadcasting 

stations,  and  the  "Sandman"  of  KHJ  is  one  of  the  most  able  and 

most  popular  of  the  broadcasters  of  this  sort 


After  that,  it  seemed  as  if  news- 
paper and  magazine  radio  critics 
increased  even  as  the  beasts  of 
the  field. 

There  are  now  probably 
anywhere  from  three  to  five 
million  radio  receivers  in  this 
country,  if  one  accept  the  most 
credible  estimates  of  those 
arithmetical  persons  who  inter- 
minably compile  statistics  on 
the  number  of  radio  listeners. 
That  chip  falling  where  it  may, 
however,  it  is  our  hope  that 
some  of  the  owners  of  the  five 
million  receivers  may  find  some- 
thing interesting  in  these  pages 
each  month.  That  object  being 
attained,  as  J.  Caesar  would  say, 
we  hope  to  read  your  letters  of 
opinion  and  comment  on  broad- 
casting— our  mutual  concern. 

What  Makes  a  Broadcast- 
ing Station  Popular 


are  not  much  of  an  addition  to  most  outdoor 
pick-ups. 

A  Statement  of  Policy 

IT  IS  no  easy  task  to  take  up  "The  Listener's 
Point  of  View"  where  Miss  Mix  left  it. 
In  the  fourteen  months  that  she  wrote  this 
department,  she  succeeded  in  building  up  a 
following  of  readers  in  all  parts  of  the  country 
which  any  writer  might  envy.  This  was 
natural  indeed,  for  her  comments  and  criticism 
combined  in  delightful  fashion,  great  breadth 
of  knowledge  of  matters  musical  and  a  charm- 
ing style  of  presentation. 

The  present  writer,  readers  willing,  will 
attempt  to  carry  on.  His  design  involves  news 
and  comment  of  broadcasting  stations,  artists, 
and  broadcast  programs,  and  all  else  which  is 
of  the  ether  etherial. 

It  was  in  February,  1924,  that  the  editors 
of  RADIO  BROADCAST  planned  this  department, 
and  in  the  April,  1924,  magazine  that  Miss 
Mix's  first  department  appeared.  A  few  days 
before  the  April  number  appeared  on  the  news 
stands,  the  New  York  Herald  Tribune  began 
their  daily  broadcastingcritique"  Last  Night  on 
the  Radio"  written  by  the  caustic  Mr.  Raymond 
Francis  Yates,  who  used  the  name  "Pioneer." 


IN  THE  first  exciting  days  of 
broadcasting,  the  very  act 
of  receiving  the  sounds  of 
tinny  phonograph  records  and  the  noisome 
regularities  of  a  mechanical  piano  was  re- 
garded by  the  wondering  public  as  a  stunt, 
a  kind  of  theatrical  laboratory  experiment. 
And  many  of  our  broadcast  directors  have 
never  allowed  that  feeling  to  weaken  in  the 
minds  of  what  they  are  pleased  to  call  their 
clientele.  While  listeners  are  able  to  depend 
on  this  station  and  that  for  regular  features  of 
one  sort  or  another,  they  look  to  others  to 
supply  them  with  something  new,  curious, 
outre. 

Witness  the  Philadelphia  broadcaster  who 
sent  a  studio  favorite  in  a  diving  suit  to  the 
bottom  of  the  ocean  near  Atlantic  City,  where 
for  some  fifteen  minutes  he  regaled  his  listeners 
with  sub-aqueous,  non-scientific  platitudes. 
A  year  ago,  much  journalistic  to-do  was  ex- 
cited over  the  broadcasting  of  the  sounds  of 
the  circus.  And  so  we  have  had  various  at- 
tempts at  broadcasting  from  an  airplane,  none 
of  them  especially  successful. 

The  learned  Secretary  Wilbur  arranged  with 
his  Naval  radio  and  publicity  experts  to 
install  a  low  powered  broadcasting  set  on  the 
Los  Angeles  when  she  made  a  recent  all-day 
voyage  over  Philadelphia,  laden  with  a  cargo 
of  merchants.  Gar  Wood's  "race"  "between 
one  of  his  speed  boats  and  the  Twentieth 


Are  Broadcasting  "Stunts"  Desirable? 


473 


Century  Limited  was  reported  by  radio  from 
an  airplane  flying  over  the  racers  on  their  two 
hour  trip  down  the  Hudson  from  Albany  to 
New  York.  One  hesitates  to  conjecture  what 
the  next  stunt  will  be.  In  some  respects  our 
English  friends  are  not  far  behind;  was  not 
the  song  of  the  nightingale  broadcast  from 
2LO  to  the  tune  of  newspaper  space,  measur- 
able only  in  feet? 

The  directors  of  broadcasting  stations  will 
admit,  almost  to  a  man,  that  they  are,  after 
four  years,  still  experimenting.  They  are  not 
yet  reaHy  certain  what  the  public  wants.  But 
we  are  certain  that  the  public  is  primarily 
interested  in  the  best.  If  a  broadcasting 
station  has  gained  a  reputation  for  excellent 
classical  music  or  for  jazz  music  of  good 
quality,  or  for  good  lectures  and  speeches,  or 
whatnot,  that  station  can  be  best  kept  in  the 


favor  of  the  public  by  a  continuance  of  the 
policy.  We  doubt  very  much  that  temporary 
bursts  of  publicity,  gained  from  the  studio 
presence  of  movie  stars  who  tell  radio  listeners 
of  their  innermost  thoughts,  or  by  the  broad- 
casting of  a  jazz  melange  from  a  steamship 
at  dock  can  do  much  permanently  to  gain 
public  favor.  The  station  which  daily  meets 
the  real  wishes  of  its  listeners  is  the  one  whose 
popularity  will  last. 

An     Orchestra     Conductor     Speaks 
About  Radio 

THE  greatest  hope  for  radio  -is  that  it 
may  bring  good  music  to  all  parts  of 
this  vast  country,  and  awaken  in  the 

soul  of  America  a  thirst  for  the  best  in  music. 

Radio  should  teach  the  people  to  learn  to  love 
good  music.  There  can 
be  no  cultural  progress 
so  long  as  people  are 
given  only  what  they 
already  enjoy.  Let  us 
teach  the  people  to 
want  something  which 
has  not  yet  been  given 
them. 

"For  the  most  part, 
radio  is  considered  by 
everyone  as  merely  a 
medium  of  entertain- 
ment. And  this  en- 
tertainment is  almost 
entirely  music.  This  is 
a  desecration.  Music 


MAY    SINGHI    BREEN    AND    PETER    DE    ROSE 

Who  have  been  heard  from  station  WEAF  and  others  in  banjo  and  piano  duets.  Miss  Breen  is  a  banjo  player 
of  striking  talent  and  is  well  known  to  radio  audiences.  The  insert  shows  the  head  of  a  banjo  she  has 
used  in  many  radio  studios  with  its  signatures  of  radio  favorites,  including  Jack  Yellen,  Doctor  "Billy" 

Axt,  and  George  Gershwin 


474 


Radio  Broadcast 


should  be  a  divine  service  to  humanity.  It 
is  a  pleasant  thing  when  enjoyed  as  a  mere 
pastime.  But  with  every  mental  uplift,  there 
must  be  a  consequent  struggle,  and  in  order 
to  comprehend  the  divine  beauty  of  music, 
one  must  be  willing  to  make  the  sacrifice  of 
laboring  to  understand. 

"One  of  the  beautiful  possibilities  of  radio, 
as  I  see  it,"  continues  Mr.  Fritz  Reiner, 
conductor  of  the  Cincinnati  Symphony 
Orchestra,  "is  to  teach  the  fundamentals  of 
music  to  the  people.  Americans  have  plenty 
of  sentiment;  they  are  not  cold  blooded. 
Their  only  drawback  is  that  they  do  not  know 
how  to  express  themselves.  Teach  them  the 
fundamentals  of  music  and  the  genuis  of  the 
nation  will  assert  itself.  When  the  whole 
nation  loves  good  music  it  will  pay  for  good 
music  and  thus  afford  an  incentive  to  its  youth 
of  talent  and  intelligence." 

Mr.  Fred  Smith,  director  of  station  WLW 
gathered  these  interesting  ideas  from  Mr. 
Reiner,  who  is  accepted  as  one  of  the  outstand- 
ing symphony  conductors  now  in  America. 
WLW  has  done  much  in  furnishing  good  music 
to  its  listeners.  When  the  new  long  range 
station  of  WLW  was  opened,  Mr.  Reiner  had 
charge  of  the  dedication  program,  when  he 
conducted  a  special  concert  with  an  orchestra 
of  fifty  picked  men  from  the  Cincinnati  Or- 
chestra, At  other  times,  his  Orchestra  has 
been  heard  from  WLW. 

Other  stations  are  known  for  the  good  music 
on  their  programs.  Station  KSD  of  St.  Louis 
has  the  record  of  broadcasting  every  sym- 
phony concert  of  the  St.  Louis  Symphony 
during  the  past  season.  The  Detroit  News 
orchestra,  a  permanent  part  of  the  studio  staff 
of  station  wwj,  is  composed  of  members  of  the 
talented  Detroit  Symphony  Orchestra.  Sta- 
tion WEAF,  of  New  York  has  broadcast  regu- 
larly the  concerts  of  the  New  York  Philhar- 
monic Orchestra.  The  good  music  that  Mr. 
Reiner  hopes  American  listeners  can  hear  is 
being  sent  out  from  various  parts  of  the 
country,  though  it  has  to  force  its  way  through 
a  blanket  of  jazz.  It  is  the  contention  of  many 
that  enough  good  radio  music  is  being  played 
now  so  that  the  taste  of  American  listeners  is 
slowly  being  raised.  More  will  be  said  of 
this  later,  however. 

Broadcasting,  Canadian  Style 

IT  IS  bad  enough,"  someone  remarked,  with 
what    was    probably     a    vocal     twinkle, 
"when  one    listens  to  a    Floridan  or  a 
Californian  sing  the  praises  of  his  climate  to  a 


small  group,  but  when  they  buy  radio  stations 
and,  in  a  manner  of  speaking,  tell  the  world 
about  it,  the  situation  becomes  serious." 
Good  residents  of  Florida  and  good  residents 
of  California  have  bought  broadcasting  stations, 
but  it  must  be  recorded  that  they  are  reason- 
ably restrained  about  the  climatic  merits  of 
their  communities. 

But  now  are  the  Canadians  fallen  from 
virtue.  CKAC,  the  excellent  station  of  La 
Presse  at  Montreal,  cannot  withold  the 
attractions  of  the  Province  from  a  listening 
world.  On  their  program  for  the  two  weeks 
beginning  May  3Oth,  appeared  the  following 
legends. 

June  2:  8:30  P.  M.  Talk  on  Attractions  of  Province 
of  Quebec 

June  6:  8:30  P.  M.  Road  reports;  talk  on  the  at- 
tractions of  the  Province  of  Quebec 

June  9:  8:30  P.  M.  Talks  on  the  attractions  of  the 
Province  of  Quebec.  Road  conditions  reports 

June  13:  8:30  P.  M.  Studio  program;  talk  on 
Quebec  attraction. 

Sir  Robert  Falconer,  President  of  the  Uni- 
versity of  Toronto,  has  been  giving  a  series  of 
lectures  before  English  Universities  on  the 
general  subject  of  Canadian  and  American 
relations.  One  of  the  interesting  points  that 
he  made  was  that  Canada  and  the  United 
States  were  closer  in  some  respects  than 
England  and  Canada.  This  is  due,  Sir  Robert 
thinks,  to  the  fact  that  Canadians  read 
American  magazines  and  hear  American 
broadcast  programs,  both  prepared  for  purely 
American  consumption.  A  Rotary  Club  speech 
from  some  Middle  West  city  is  heard  by  a 
group  of  far-off  ranchers  in  distant  Canada. 
So,  thinks  Sir  Robert,  do  American  ideas 
penetrate  Canada. 

But  now  the  American  leaven  is  working, 
and  listeners  on  this  side  of  the  border  are 
getting  some  of  their  own  medicine.  A  new 
and  amusing  form  of  reciprocity! 

General  Dawes  as  a  Musician 

SINCE  Charles  G.  Dawes,  Chicago 
banker,  attained  world  wide,  and 
later  national  fame  through  his  feats 
of  statesmanship  and  politics,  broadcast 
directors  have  discovered  that  this  picturesque 
and  extraordinary  person  is  a  composer  of 
parts.  Several  of  his  compositions  including 
his  "Melody  in  A  Major"  have  been  heard 
by  radio  listeners.  Which  calls  to  mind  the 
Washington  experience  of  Mr.  Heywood 
Broun,  the  genial  columnist  of  the  New 
York  World  who  inquired  of  a  politically  in- 


The  Demand  for  Old  Fashioned  Music 


475 


clined  woman  of  his  acquaintance  how  the 
General  ranked  among  composers. 

"Does  he  write  good  music?"  asked  Mr. 
Broun. 

"That  all  depends,"  the  lady  answered, 
"on  whether  you  are  for  or  against  changing 
the  rules  of  the  Senate." 

When    Central   Americans   Overhear 
the  United  States 

A/1ER1CAN  broadcasting  stations  are 
picked  up 
throughout  all 
the  Central  American 
republics,  and  pro- 
grams are  enjoyed  as 
a  rule,  though  there 
has  been  some  com- 
plaint regarding  the 
quality  of  music,"  re- 
ports R.  A.  Lund- 
quist,  chief  of  the 
electrical  equipment 
division  of  the  Bureau 
of  Foreign  and  Do- 
mestic Commerce  at 
Washington,  after  a 
recent  trip  through 
that  territory. 

"O n  the  other 
hand,  in  several  cases, 
radio  fans  who  had 
instruments  of  suffi- 
cient selectivity  and 
range  to  choose  be- 
tween American  sta- 
tions, commented 
favorably  on  this 
point,  saying  that 
they  were  surprised 
to  note  the  quality 
of  music  received 
from  small  towns 
where  the  programs 
were  given  by  local 

talent.  This  was  especially  true  of  the 
Middle  Western  states  which  are  apparently 
in  some  sections  picked  up  more  readily  than 
are  those  in  the  East  or  far  West." 

Those  who  use  care  in  tuning  and  pick  up 
some  of  the  smaller  mid-West  stations  will 
hear  good  music,  well  played.  In  these  locali- 
ties, there  are  numberless  amateurs  of  the  voice, 
piano,  and  violin,  whose  names  never  appear  on 
great  concert  programs,  who  are  heard  over  the 
radio  from  stations  the  length  and  breadth  of 
the  country. 


TEN    EYCK   CLAY 

The  new  director  of  the  WGY  Players.     Station  WGY 

was  the  pioneer  in  securing  and  presenting  radio 

plays  and  has  found  that  radio  listeners  favor  short 

plays,  prepared  especially  for  broadcasting 


"We  have  used  the  home  type  of  music  and 
program  at  our  station,"  said  Mr.  Henry 
Field,  of  Shenandoah  Iowa,  owner  of  station 
KFNF,  "partly  because  it  was  the  easiest  thing 
for  us  to  do,  and  partly  because  I  had  the 
definite  opinion  that  people  were  hungry  for 
the  home  type  of  music.  We  feel  that  there  is 
a  big  demand,  which  many  people  do  not  sus- 
pect, for  simple,  wholesome,  old-fashioned 
music.  I  find  that  a  surprisingly  large  num- 
ber of  listeners  of  all  classes  are  very  tired  of 
cabaret  music  and  would  like  to  have  more^of 
the  old  home-town 
stuff."  Mr.  Field  was 
addressing  one  of  the 
committees  at  Secre- 
tary Hoover's  annual 
radio  conference  at 
Washington,  last  Oc- 
tober. He  continued, 
"I  have  a  letter  in 
my  pocket  from  a 
prominent  man  here 
in  Washington  who 
listens-in  regularly. 
Both  he  and  his  wife 
are  small  town  peo- 
ple. It  would  be  in- 
teresting to  hear  their 
comments  on  the 
cabaret  type  of  music 
which  they  get  from 
so  many  stations,  and 
how  "it  seemed  like 
a  breath  of  air  from 
the  prairies"  to  hear 
Gospel  hymns  over 
the  radio." 

Fewer  jazz  orches- 
tras and  a  bit  more 
of  what  may  be 
called  standard  music 
from  broadcast  sta- 
tions would  meet 
with  great  favor 
from  the  public,  if 
signs  may  be  taken  as  any  crite- 


existmg 
rion. 


Broadcast  Miscellany 


o 


NE  of  the  two  women  governors  in  the 
United  States  was  heard  over  the 
radio  from  station  KOA,  Denver,  some 
weeks  ago.  She  spoke  on  "Cheyenne  Frontier 
Days  and  Wyoming  of  To-day."  Listeners 
were  much  interested  in  her  description  of  the 
change. in  her  native  state. 


Radio  Broadcast 


SIGNING  off,"  that  phrase  heard  from 
every  broadcaster  at  least  once  during 
the  day's  program,  is  to  be  abolished  at 
station  WLW.  Some  "appropriate  quotation" 
will  be  given  instead,  and  finality  achieved  by 
"Good  night."  The  news  bureau  of  WLW 
offers  as  a  sample  quotation:  "Great  thoughts, 
like  little  deeds  need  no  trumpet;  good  night." 
"Signing  off"  is  a  hold-over  phrase  from  the 
telegraph  side  of  radio,  and,  like  the  use  of  call 
letters  to  designate  stations,  has  little  to  do 
with  broadcasting.  We  think  this  is  a  step 
in  the  right  direction,  but  why  complicate  the 
closing  with  a  sententious  quotation?  Isn't 
a  simple  "Good  night"  enough? 

LISTENERS  are  constantly  on  the  search 
for  an   up-to-date  list    of    broadcasting 
stations,  their  wavelengths,  power,  and  call 
signals.     One  of  the  best  of  the  many  books 


we  have  seen  is  Dunlap's  Radio  Call  Book. 
In  addition  to  listing  all  the  radio  broadcasting 
stations  of  the  world,  the  book  contains  their 
slogans,  and  is  kept  up  to  date  by  a  monthly 
supplement  containing  changes  and  cor- 
rections. It  may  be  secured  for  $i  from  Dun- 
lap's  Radio  Call  Book  Service,  Box  88, 
Flushing,  New  York. 

CORRESPONDENCE  from  controversial- 
^>  minded  readers  of  this  department  is 
invited.  We  are  anxious  to  present  the 
opinions  of  readers  on  broadcasting  and  its 
problems,  and  it  is  our  hope  that  this  depart- 
ment will  be  considered  a  forum,  open  to  any 
one  who  has  something  to  say  and  says  it  with 
clarity  and  intelligence.  Correspondents  are 
asked  to  do  us  the  courtesy  of  signing  their  full 
name  and  address,  which  will  not  be  used  if 
if  they  so  request. 


THE    MECHANICS   OF    A    RADIO    PLAY 

In  operation  at  WGY,  when  the  WGY  Players  put  on  "Rip  Van  Winkle."     Ten  Eyck  Clay,  director  and  lead- 
ing man  of  the  Players  is  at  the  microphone  as  Rip.     Frank  Oliver  [is  'pouring  water  through  a  sieve  to  give 
the  effect  of  rain.    In  the  background  are  the  thunder  sheet  and  the  wind  machine.   The  radio  Players  seem 
to  be  enjoying  their  share  of  the  performance  as  much  as  the  listeners,  which  is  putting  it  mildly 


The  Revolution  in  the  Art  of 

Teaching 

The  Long  Arm  of  Radio  Is  Bringing  the  Best  from  the  College  to  the  Re- 
motest Districts — What  the  Public  Wants  and  How  Their  Wants  Are  Being  Met 


BY  FREDERICK  P.  MAYER 


THE  long  trips  on  cold  trains  in  win- 
ter, the  meals  in  poor  restaurants,  the 
leaving  of  work  and  papers  to  do  what 
seemed  of  doubtful  permanency  are 
things  that  only  the  professor  who  used  to 
give  lectures  to  small  groups  in  various  com- 
munities can  understand. 

The  university  extension  course  was  given 
in  the  high  school  auditorium  of  some  small 
town  where  there  were  enough  high  school 
and  grade  school  teachers  and  enough  inter- 
ested club  women  to  make  an  audience  of 
perhaps  a  hundred.  To  this  small  group,  the 
university  sent  out,  at 
a  heavy  financial  out- 
lay,  a  part-time 
"extra-mural"  teach- 
er who  traveled  to  the 
small  town  from  his 
school,  delivered  his 
lecture  to  the  one 
hundred  teachers,  and 
went  home  again — 
with  little  done  for 
the  outer  world  of 
popular  education 
and  little  done  for 
himself  and  his  school. 
But  radio  is  chang- 
ing all  this.  The  pro- 
fessor of  to-day  pre- 
pares his  lecture  for 
his  radio  class  with 
greater  care  than  he 
gives  to  the  class  lec- 
ture on  the  campus. 
His  audience  may  in- 
clude professors  in  his 
own  field  who  are 
eager  to  check  the 
work  his  school  is  do- 
ing; he  knows  that 
business  men  and  high 
school  boys,  men  in 
barber  shops  and 
clubs  are  his  class. 


Giving  the  Teacher  the  Air 

IS  ANOTHER  experiment  with  the  possi- 
*•  bilities  of  radio.  Mr.  Mayer  does  not 
attempt  to  tell  what  every  university  and 
college  in  the  country  has  tried  to  do  with 
broadcasting,  but  he  does  tell  what  has  been 
in  progress  at  Pittsburgh.  Columbia,  Renn- 
selear  Polytechnic,  New  York  University, 
Kansas  State  Agricultural  College,  and  many 
others  for  some  time  have  been  broadcasting 
subjects  gathered  from  their  class  rooms. 
And  many  broadcasters  have  presented  talks 
given  by  members  of  various  college  facul- 
ties. There  are  many  who  feel  that  radio 
can  never  lend  the  personal  contact  that  the 
University  has  always  felt  to  be  a  necessity 
for  instruction.  But  there  are  others  who 
are  quite  willing  to  let  radio  do  what  it  can 
to  broaden  the  scope  of  higher  education, 
and  some  of  the  experiments  seem  to  prove 
that  radio  has  indeed  a  field  here.  It  is 
maintained  by  some  that  broadcasting  is 
more  a  medium  for  entertainment  than  in- 
struction, but  those  who  are  in  charge  of  the 
various  "air  courses'*  undoubtedly  have 
something  to  say  about  that.  In  an  early 
number,  RADIO  BROADCAST  will  publish  an 
article  by  Major  J.  Andrew  White,  the  famous 
descriptive  broadcaster,  which  humorously 
shows  that  radio  education  is — well,  not  as 
effective  as  it  might  be. — THE  EDITOR 


Having  prepared  his  lecture,  he  goes  to  the 
broadcasting  studio,  that  curious  muffled 
room  where  his  voice  frightens  him  by  meet- 
ing him  as  he  walks  in.  The  room  is  draped 
with  gray  cloth,  and  there  are  wicker  chairs, 
a  desk,  and  floor  lamps.  And  reasonably  in- 
conspicuous, are  the  ever-faithful  microphones, 
from  which  you  hear  the  lecture  on  "Why 
Read  Fiction?"  or  "Political  Parties  from 
Washington  to  Jackson,"  listeners-in  from 
Florida  to  Washington,  and  throughout 
Canada  eagerly  tune-in. 

The  light  flashes;  the  man  at  the  announc- 
er's desk  calls  "all 
right"  to  his  friends 
at  the  broadcasting 
station ;  they  return 
the  signal;  he  flashes 
the  "Silence"  sign  at 
the  desk,  and  opens 
the  line.  The  air  is 
ready.  The  instruc- 
tor begins  after  the 
University  announcer 
says,  "Good  evening! 
This  is  the  University 
of  Pittsburgh  studio 
of  station  KDKA,  East 
Pittsburgh,  Pennsyl- 
vania. This  evening, 
Professor  Smith,  of 
the  English  Depart- 
ment is  going  to  talk 
to  you  about  'The 
Contemporary 
Novel."'  Then  a 
slight  pause,  and  the 
Professor  begins  his 
talk.  This  is  what 
has  been  occurring 
regularly  at  KDKA  in 
cooperation  with  the 
University  of  Pitts- 
burgh, and  is  true  of 
other  broadcasting 
stations  in  many  parts 


478 


Radio  Broadcast 


of  the  nation.  Some  universities  have  erected 
their  own  broadcasting  stations  to  give  "air 
college  courses."  Notable  among  the  colleges 
to  try  this  experiment  in  education  is  the 
Kansas  State  Agricultural  College  whose  call, 
KSAC  is  known  to  many. 

At  Pittsburgh,  extensive  plans  have  been 
made  for  bringing  the  learning  of  the  college 
class  room  to  the  radio  listener.  A  year,  or 
more  ago,  the  University  of  Pittsburgh, 
through  its  committee  on  radio  extension, 
discussed  ways  and  means  of  beginning  radio 
extension  through  its 
own  studio.  Confer- 
ences resulted  in  an 
agreement  of  mutual 
responsibility  for  the 
new  venture.  The 
University  agreed  to 
furnish  the  studio  and 
to  appoint  a  full  time 
radio  manager  whose 
business  it  would  be 
to  arrange  programs 
of  consistently  high 
merit.  The  Broad- 
caster installed  trans- 
mitting apparatus 
which  cost  several 
thousand  dollars. 

The  opening  night 
was  an  important 
event  for  the  radio 
world.  There  had,  of 
course,  been  univers- 
ity studios  in  opera- 
tion before  KDKA  and 
"Pitt"  began,  but 
none  had  consis- 
tently pledged  them- 
selves to  serious  ex- 
tension work.  Uni- 
versity and  commercial  studios  had,  before 
this,  differed  little  in  aims. 

The  program  opened  with  University  songs 
by  a  University  quartet.  Then  Mr!  H.  P. 
Davis,  vice  president  of  the  Westinghouse 
Company,  delivered  the  first  address,  and 
turned  the  studio  over  to  the  University  for 
its  use  as  an  added  means  of  bringing  knowl- 
edge and  new  ideas  to  the  people  it  hoped  to 
serve.  Dr.  John  G.  Bowman,  Chancellor  of 
the  University,  followed  Mr.  Davis  with  a 
brief  talk  of  acceptance,  and  outlined  the 
plans  and  aims  of  the  program  of  popular  edu- 
cation. Mr.  Marcus  Aaron,  President  of  the 
Board  of  Education  of  Pittsburgh,  then  told 
how  the  people  in  Pittsburgh  had  a  new  means 


The  Future  of  Radio  Education 

\  A /HEN  radio  has  settled  down  to  a  con- 
^  "  structive  basis,  instead  of  being,  as  now, 
chiefly  a  medium  for  light  entertainment, 
educational  courses  will  take  on  a  more  im- 
portant aspect.  No  doubt,  broadcast  direc- 
tors would  hesitate  to  put  on  a  musical  lec- 
ture that  lasted  more  than  an  hour.  They 
would  see,  in  their  imagination,  thousands 
of  impatient  listeners,  tuning-out  to  a  more 
congenial  attraction.  Yet,  they  might  use 
their  imaginations  to  realize  that  those  who 
interest  themselves  in  these  education  courses 
would  be  more  numerous  if  they  thought  that 
the  paying  of  a  fee  of  one  dollar,  for  example, 
for  literature  and  examination  papers  would 
include  an  hour's  instruction  weekly. 

Perhaps,  in  time,  we  shall  have  certain 
broadcasting  stations  given  over  wholly  to 
educational  programs.  If  this  day  comes — 
and  such  a  thing  is  not  unlikely — a  course  in 
musical  appreciation,  in  literature,  or  any  of 
the  other  educational  subjects  now  put  on  the 
air  will  be  more  thorough  than  is  at  present 
possible." — JENNIE  IRENE  Mix,  in  "The 
Listener's  Point  of  View,"  RADIO  BROADCAST 
for  February,  7925. 


of  education  advancement  put  into  their 
hands.  At  the  close  of  the  evening,  the 
University  was  launched  upon  its  experiment, 
with  Miss  Helen  J.  Ostrander,  manager,  in 
charge  of  programs  and  speakers. 

THE    FIRST   YEAR 

THAT  year  was  a  busy  one  for  the  new 
studio.     Two   ten-week  courses,   one  on 
literature,  by  members  of  the  English   De- 
partment, and  one  on  party  government,  by 
members  of  the  History,   and  the  Political 
Science  Departments, 
were    broadcast    on 
successive     Mondays 
and  Tuesdays.     Dur- 
ing the  first  month  of 
lectures    a    very  en- 
couraging number  of 
appreciative  letters 
were  received  by  the 
University,  and  so  the 
University  added  ex- 
tra lectures  by  mem- 
bers of  its  staff. 

There  were  talks 
about  trees  and  wild 
flowers,  weeds,  birds, 
fish,  and  the  stars.  It 
was  amazing  to  see 
how  great  a  demand 
for  nature  talks  there 
was  in  the  indus- 
trial radius  of  Pitts- 
burgh, a  section  that1 
is  normally  listed  as 
interested  only  i  n! 
steel  affairs  and  the 
making  of  rails.  Not 
only  boy  scouts,  but 
also  men  and  women 
wanted  to  know  more 

about  plant  and  animal  life  and  the  wider 
world  round  about.  Broadcasting  educa- 
tional talks,  the  University  believes,  is  one 
form  of  radio  work  that  can  be  made  to  have 
genuine  value  as  a  means  of  getting  popular 
education  to  more  people.  The  days  of  the 
educational  phonograph  record,  the  corres- 
pondence courses,  and  the  extension  courses 
are  threatened  by  the  new  method  of  giving 
course  instruction  to  thousands  who  want  it 
and  find  it  hard  to  get.  The  demand  for 
outside  readings  and  questions  for  study  and 
printed  forms  of  the  lectures  made  it  neces- 
sary to  print  radio  publications  which  were 
distributed  at  small  cost  to  listeners  all  over 
the  country,  who  gave  some  of  their  winter 


The  Revolution  in  the  Art  of  Teaching 


479 


nights  to  pleasant  reading  under  the  direction 
of  a  university  faculty  hundreds  of  miles 
away. 

THE    POSSIBLE    AND   THE    IMPOSSIBLE 

PHE  universities  which  are  experimenting 
*  with  radio  as  a  means  of  instruction  do 
so  with  no  illusions.  The  standard  of  the 
work  done,  the  knowledge  of  the  student's 
abilities,  the  supervision  of  study  that  a 
campus  course  or  an  old  extension  course  can 
give  is  indispensable  for  serious  study  of  a 
high  academic  rate.  It  is  manifestly  impos- 


sible to  give  university  credit  for  radio  study. 
As  yet,  no  means  has  been  found  to  check  up 
on  work  done  by  radio  students.  A  radio 
course  can  never  take  the-  place  of  a  college 
year  spent  on  the  campus. 

Universities  that  are  giving  radio  courses 
seem  to  believe  that  they  can  give  the  means 
for  individual  self  culture  to  people  who  are 
interested  in  having  new  ideas,  no  matter 
where  they  live.  There  are  men  and  women 
so  far  from  the  contact  of  intellectual  forces 
and  the  opportunities  of  libraries  and  lectures, 
that  new  facts,  new  thoughts  about  their 
world  and  the  things  that  are  going 
on  in  politics,  and  letters  and  science, 
cannot  help  but  be  a  means  towards 
happier  living  in  an  isolated  area. 
The  radio  can  inspire  the  same  in- 
terest in  social  and  political  progress 
that  a  good  magazine,  clearly  written, 
can  give.  Indeed,  the  radio  can  do 
more.  It  gives  the  same  material  as 
the  magazine  does,  but  it  gives  it  in  a 
more  immediate  form.  It  is  easier  to 
listen  to  a  man. speaking  than  to  go 


BROADCASTING    HEADQUARTERS    OF    THE    UNIVERSITY 
And  Miss  Mary  F.  Philput,  radio  manager  for  the  University  of  Pittsburgh 


Radio  Broadcast 


to  his  book,  provided  that  he  speaks  clearly, 
slowly,  and  with  a  sense  of  real  interest  in  his 
subject.  That  is  what  the  men  at  the  Uni- 
versity have  had  to  discover.  They  must 
talk  with  more  energy  to  a  class  that  they 
cannot  see  than  to  one  that  is  in  the  room  with 
them,  because  the  voice  is  their  only  chance  of 
appeal.  What  applause  is  to  a  vaudeville 
rope  climber,  the  presence  of  a  flesh  and  blood 
class  is  to  the  teacher.  He  needs  applause, 
and  he  has  to  fight  the  blankness  of  the  micro- 
phone while  he  delivers  his  radio  lecture.  It 
is  amusing  to  see  a  teacher  stand  before  a 
tnicrophone  and  wave  his  arms  with  his  usual 
class-room  gestures  and  find  that  they  mean 
nothing  to  the  silent  microphone  or  to  the 
man  on  the  North  Dakota  farm  who  is 
wondering  "why  doesn't  that  chap  talk  so  I 
can  hear." 

Is  radio  instruction  reaching  an  audience 
that  wants  such  help?  As  an  answer  to  this 
important  question,  the  University  could 
look  only  to  whatever  letters  came  in.  But 
would  anybody  care  enough  about  political 
parties  and  the  contemporary  novel  to  write 
even  a  post-card!  And  if  they  heard  the 
talks,  would  they  like  them?  The  answer 
came  almost  immediately.  The  files  of  the 
t*adio  room  are  stuffed  with  letters  from  listen- 
ers from  Canada  and  thirty  states,  including 
Nebraska  in  the  West,  Minnesota  in  the 
North,  Louisiana  in  the  South,  and  every 
state  on  the  Atlantic  coast.  Among  the 
writers  are  lawyers,  dentists,  physicians, 
bankers,  business  men  and  women,  high  school 
students,  farm  men  and  women,  teachers, 
housewives,  college  students,  club-women,  and 
grade  school  children. 

i  Of  course,  there  were  complaints.  The 
University  expected  them,  more  than  came  in. 
But  not  one  letter  of  objection  to  the  idea  as  a 
whole  appeared.  All  the  writers  liked  to  lis- 
ten to  the  talks,  but  they  objected  to  big  and 
little  things  in  the  way  the  talks  were  given — 
and  mostly  with  justification.  One  man  ob- 
jected to  the  pronunciation  of  the  word  "vau- 
deville," and  he  was  right.  One  man  said  the 
speaker  talked  too  fast;  he  had  sat  by  his 
typewriter  and  tried  to  take  down  the  names 
of  books  to  read,  and  the  speaker  rushed 
through  them  without  a  chance  for  a  note. 
The  lecturer  of  that  night,  who  was  accus- 
tomed to  dumping  masses  of  material  on  col- 
lege classes  who  could  go  to  a  library  later, 
spoke  more  slowly  on  the  following  nights. 
Another  writer  asked  if  we  wanted  any  one  to 
hear  what  we  were  saying.  If  we  did,  would 
we  talk  louder?  And  we  did.  Several  wo- 


men who  were  normal  school  graduates  and 
wanted  college  work  insisted  on  getting  credit 
for  "the  lectures;  they  asked  for  examinations 
and  papers  to  be  graded.  That  request, 
much  as  the  University  wished  to  help,  was 
refused. 

WHAT  THE    PEOPLE    SAID 

A  PPRECIATION  for  the  new  thing  came 
*"»  in  all  forms,  from  the  serious  to  the 
funny.  The  people  who  wrote  ranged  from 
men  and  women  with  college  degrees  to  farm- 
ers who  had  little  advanced  schooling,  and  yet 
thought  it  was  worth  their  while  to  say  that 
they  liked  the  programs.  Stationery  ran 
from  beautiful  sheets  of  embossed  personal 
writing  paper  and  bond  sheets  of  discreet 
banking  houses  to  the  printed  splash  of  an 
Iowa  seed  store,  and  the  pencilled  scratchings 
of  an  old  man  who  found  the  "  radio  was  some- 
thing to  look  forward  to  once  a  week." 

A  letter  came  from  a  friend  of  a  young  man 
sick  with  tuberculosis.  He  asked  for  a  read- 
ing list  that  might  "be  of  some  benefit."  The 
boy  wanted  "in  that  way  to  educate  himself 
as -much  as  possible  from  this  source."  Need- 
less to  say,  the  English  department  got  busy. 
A  group  of  students  from  Wittenberg  College 
were  gracious  enough  to  want  the  lecturer 
to  know  that  they  were  taking  a  course  in  the 
novel  with  him.  A  club  woman  from  South 
Carolina  found  that  the  lectures  helped  her  in 
preparing  a  program  on  the  contemporary 
novel.  A  woman  on  a  New  Hampshire  farm, 
who  had  taken  a  course  in  the  novel  with 
Katherine  Lee  Bates  in  her  college  days,  said 
"  I  now  live  on  a  remote  farm,  and  I  am  es- 
pecially pleased  with  your  proposed  course, 
What  that  means  in  terms  of  days  on  a  farm, 
no  mere  city  reader  can  quite  understand." 

A  mother  wrote  for  the  novel  bibliography. 
"We  are  desirous  of  putting  the  best  of  reading 
matter  before  our  four  children." 

A  man  from  Philadelphia  wrote  to  the  Uni- 
versity and  asked  for  an  outline  of  the  lecture, 
because  he  missed  part  when  his  daughter  ran  a 
splinter  into  her  finger,  and  he  had  to  leave  the 
phones  and  help.  Unfortunately  he  did  not 
give  his  address.  A  directory  searcher  gave  us 
his  address,  and  the  following  letter  is  the 
result  of  this  correspondence. 

Did  I  hear  the  announcer  say  to  send  10  cents  for 
the  program?  My  daughter  run  a  splinter  in  her 
finger  so  Dad  missed  part  of  the  broadcasting.  I 
had  to  get  that  splinter  out.  Well  1  am  one  of 
KDKA  listeners  in  and  must  say  I  am  very  much 
interested  in  education  and  if  nothing  prevents  me 
1  will  be  a  regular  listener.  In  Phila.  we  have  a  lot 


The  Revolution  in  the  Art  of  Teaching 


481 


of  single  circuits  so  we  who  are  anxious  to  learn  will 
have  to  make  the  best  of  it.  Well  Mr.  Manager  it 
is  well  worth  trying  for.  When  you  go  fishing-some 
get  little  ones  others  get  big  ones  so  1  hope  I  will  be 
be  able  to  get  all  that  is  possible  out  of  your  generos- 
ity. 

That  is  the  sort  of  friendship  the  University 
of  Pittsburgh  feels  glad  to  have  made;  it  is 
worth  much  to  the  people  who  are  wondering 
whether  or  not  radio  pays. 

A  gentleman  from  Pittsburgh  wrote, 

1  am  an  invalid  who  is  getting  -well.  \  have  had 
a  wonderful  sense  of  help  by  radio  in  listening  to 
the  good  sermons,  prayers,  and  lectures.  I  have 
been  ill  many  years  and  have  spent  many  years  in 
bed  with  too  much  weak- 
ness to  even  listen-in. 
Radio  opens  a  glorious 
avenue  to  me.  I  love 
the  fairy  stories  for 
children  and  the  bed 
time  talks.  .  .  . 
Now  I  see  that  light  and 
health  are  coming.  This 
beautiful  spring  day — 
all  Nature  simply  sing- 
ing— I  had  to  write  you 
this  personal  side  of 
things,  it  seemed.  Par- 
don me,  but  you  will  be 
glad  to  know  it.  You 
asked  so  kindly  what 
we  would  enjoy.  I 
would  enjoy  bird  lore 
and  nature  talks,  woods 
and  out-doors.  It  is  so 
lovely  to  hear  word  pic- 
tures over  the  radio.  I 
imagine  I  am  living  it. 
One  enters  with  much 
more  intimacy  into  the 
mind  of  the  speaker  when 
there  is  nothing  to  di- 
vert. I  enjoy  the  litera- 
ture professors.  .  .  . 
I  enjoy  your  voice  so 
much. 


DR.    JOHN    G.    BOWMAN 

Chancellor,  the  University  of  Pittsburgh.     Radio 

college  courses  have  been  tried  under  his  direction 

and  are  meeting  with  a  favorable  reception  according 

to   statements   of   the    University   authorities 


And  this  is  another  of  the  letters  the  uni- 
versity studio  is  happy  to  have  on  file." 

WHAT   THE    PEOPLE    WANT 

AMONG  the  courses  asked  for  by  listeners 
were  lectures  on  ancient  and  medieval 
and  modern  history,  biology,  banking,  adver- 
tising, and  salesmanship,  musical  apprecia- 
tion, and  history.  Radio  teaching  will  mean 
a  busy  life  for  the  University  if  it  tries  to  meet 
suggested  demands. 

An  alumna  in  New  York  felt  that  she  was 
back  on  the  campus  again  when  she  heard  the 
English  lectures,  and  asked  for  a  series  on  Child 


Psychology.  "Of  course,  I  realize  that  any 
work  of  this  kind  must,  of  necessity,  be  very 
superficial  but  it  certainly  has  some  value 
dependent  largely  upon  the  amount  of  sup- 
plementary work  that  is  done  in  connection 
with  it." 

So  the  letters  came  in.  Each  mail  brought 
new-  acquaintances  from  new  places.  The 
first  year  of  University  Extension  by  radio 
was  a  successful  experiment.  It  is,  as  yet, 
only  an  experiment.  What  science  can  do  to 
make  radio  reception  easier  and  more  certain, 
what  the  University  can  do  to  give  more  and 
better  lectures,  what  the  listener-in  can  do  in 
the  way  of  preparation  for  what  he  reads,  make 
the  trio  of  factors 
upon  which  success  in 
popular  education  de- 
pends. 

Some  people — as 
the  hundreds  of  let- 
ters show — are  get- 
ting pleasure  and 
profit  from  the  work. 
But  can  it  hold  its 
own  place,  this  educa- 
tional program,  in  the 
face  of  dance  music 
and  comedians?  Or 
is  the  percentage  of 
fans  who  do  not  want 
this,  large  enough  to 
make  the  radiobroad- 
casting companies  re- 
ject educational  fea- 
tures because  they  are 
unpopular  with  a  ma- 
jority? Only  time 
will  tell. 

The  best  letter  of 
appreciation  for  se- 
rious programs  came 
to  the  broadcasters 
from  the  pastor  of  the 

Point  Breeze  Church,  to  whom  the  following 
letter  of  thanks  was  addressed. 

Monday 

To  the  Minister  of  the  POINT  FREE  PRESBYTERIAN 
CHURCH 

PITTSBURGH,  PA. 
DEAR  SIR: 

Last  night  while  making  for  port  off  the  Montauk 
Point  Light,  I  was  listening  in  on  my  radio  which  I 
installed  on  the  last  trip  to  the  States,  and  the  first 
which  came  in  was  the  music  and  then  the  rest  of 
the  service  at  your  church.  I  write  this  to  you  for 
the  purpose  of  calling  your  attention  to  what  I  call 
a  study  mixed  mentality.  When  I  got  the  music 


482 


Radio  Broadcast 


the  deck  hands  as  well  as  the  dog  watch  was  in  the 
Cabin  all 'hoping  that  the  "  Darnation  thing  would 
work"  and  when  1  said  1  had  a  church  service  on  the 
air  they  all  gave  a  great  guffaw  and  laughed  heartily. 
After  a, time  the  grins,  and  horse  jokes  laid  off,  and 
the  faces  of  the  swabs  all  took  on  a  serious  look  and 
aftef  a  time,  I  said  well  1  guess  thats  enough  of 
that  stuff,  and  much  to  my  surprise,  every  damn  one 
of  them  roared  out,  No  leave  it  alone  and  lets  hear 
what  that  stuff  is  all  about.  1  held  the  service  all 
the  way  to  the  finish  and  the  trouth  is  that  they  all 
was  pleased  when  they  had  the  whole  of  it  as  they 
said  it  was  the  first  time  they  ever  had  anything  of 
that  kind  served  to  them,  except  when  1  read  the 
service  for  the  dead  at  sea,  and  they  all  admit  1  aint 
great  shakes  at  that.  Had  two  to  slide  over  the  side 
on  the  last  trip.  The  mast  hands  told  me  to  get  in 
on  it  next  Sunday,  but  since  we  clear  for  South 
Africa  Friday,  1  am  afraid  we  will  be  out  of  range, 
but  at  that  we  will  be  listening  in  and  if  you  are  on 
the  air  we  will  get  it  from  Hell  to  Breakefast.  The 
funny  thing  and  the  thing  that  struck  me  as  so  queer 
is  that  most  of  the  square  heads  that  I  have  aboard 
hasnt  been  inside  a  church  since  they  was  born,  and 


now  damned  if  they  aint  talking  about  the  church 
they  heard  on  the  radio  while  they  are  unloading 
cargo,  and  I  can  hear  'em  through  the  port.  Next 
Sunday  talk  strong,  and  slip  over  something  about 
sailors,  and  1  believe  you  will  be  making  church 
goers  of  a  lot  of  swabs  that  aint  much  good  and 
never  will  be.  Muck  oblidged  for  your  music  and 
preackin  Sunday,  and  say  1  want  to  tell  you  you 
have  some  singers,  and  especially  the  first  saprano 
who  was  nearest  the  speaking  makine  her  voice 
come  over  like  a  bell.  Heres  hoping  we  can  get  you 
all  the  way  cross,  and  more  power  to  you  for  your 
favor.  Excuse  me  taking  the  liberty  of  shooting  all 
this  off  to  you  but  I  thought  as  how  you  might  like 
to  know  what  kind  of  a  lot  know  nothings  at  least 
some  of  them  you  have  for  your  services. 
Yours  truly 
(Signed)  JOHN  CLAPMAN 

Master 

Barkentine  Plymouth 
Registered  Lloyds 
London 

p.  s.     Your  preaching  is  good     Its  the  first  I  heard 
in  eighteen  years  and  1  enjoyed  it. 


AIRPLANE    VIEW    OF    THE    CAMPUS,    UNIVERSITY    OF    PITTSBURGH 

The  large  open  square  with  the  tennis  courts,  lower  right,  is  the  fourteen-acre  plot  which  is  the  site  of  the  new 

University  of  Pittsburgh  "Cathedral  of  Learning,"  a  fifty-two  story  Gothic  building.     Plans  are  already 

under  way  for  this  structure.     The  radio  studio  of  the  University  is  located  in  a  room  in  one  of  the  smaller 

buildings  near  the  center  of  the  campus.     It  is  connected  by   wire  to  the  broadcasting  station 


STAMPING   OUT   THE    STEEL    LAMINATIONS 

For  audiofrequency  transformers.     Transformers,  like  all  other  radio  parts,  are  made 
in  very  large  quantities  and  special  machines  have  been  built  for  their  manufacture 


THE  MARCH  OF  RADIO 


BY 


Past  President,  Institute  of  Radio  Engineers 


Why  the  Radio  Industry  Will  Not  Be  Revolutionized 


ONE  of  the  prominent  radio  manu- 
facturers   recently    expressed    his 
opinion  of  the  phrase,  "  revolution- 
izing the  radio  industry,  "coined 
by  some  business  man  with  the  idea,  of  pre- 
paring the  public  to  buy  the  set  he  had  in  pro- 
cess of  manufacture.     The  term  has  been  used 
by  many  radio  publicity  writers.     They  un- 
doubtedly  think   that   their  use  of  the   ex- 
pression   would    make   their  task   easier  by 
giving  to  the  buying  public  the  idea  that 
everything  so  far  accomplished  in  radio  de- 


velopment was  to  be  scrapped  in  favor  of 
some  wonderful  device  which  they  alone  could 
produce. 

"The  well  meaning  chap  who  coined  that 
infernal  expression"  says  Edward  Jewett, 
of  Detroit,  "did  radio  an  ill  turn.  It  has 
raised  false  expectations  and  has  cut  the  radio 
season  short  by  about  three  months.  Two  years 
ago  the  peak  of  the  radio  season  was  in  April, 
a  year  ago  it  was  in  February,  and  this  last 
year  it  came  around  the  Christmas  holidays." 

In    Mr.   Jewett's   opinion,    "the   principal 


484 


Radio  Broadcast 


INSTALLING  A  NEW  ANTENNA  FOR  STATION  WCG 
The  New  York  coastal  radio  telegraph  station  of  the  Independent  Wire- 
less Telegraph  Company.  Many  ships  in  the  transatlantic  and  coastwise 
service  communicate  with  this  station,  sending  and  receiving  weather  in- 
formation and  commercial  messages.  This  station  has  a  power  of  3^  kw. 
and  will  use  wavelengths  of  600,  706,  and  2100  to  2400  meters 


contributing  cause  was  the  wide  circulation  of 
the  expression  'revolutionizing  the  radio  in- 
dustry.' When  people  heard  it  they  imme- 
diately hesitated,  as  much  as  if  to  say  '  If  such 
wonderful  things  are  going  to  happen,  we'd 
better  wait  a  while.'  Most  of  them  are  still 
waiting  and  if  they  are  going  to  wait  until  the 
industry  is  revolutionized,  they  will  be  waiting 
forever." 

This  opinion  is  a  sound  one  and  unques- 
tionably founded  on  fact.  A  great  many 
people  actually  have  the  idea  that  to-morrow 
a  new  set  is  to  be  put  out  which  will  eclipse 
anything  at  present  on  the  market,  and  that 
the  purchase  of  radio  equipment  obtainable 
to-day  is  a  waste  of  money.  So  undoubtedly 
the  apt  phrase  has  boomeranged  on  the  in- 
dustry and  made  inactive  a  large  part  of  the 


prospective    purchasers    of 
radio  equipment. 

To  one  who  has  even 
casually  looked  over  the 
development  of  radio  dur- 
ing the  past  twenty-five 
years  the  idea  of  a  revolu- 
tionary step  is  hard  to 
grasp.  There  has  never 
been  any  such  step  in  so 
far  as  the  technical  pro- 
gress is  concerned.  The 
Fleming  valve,  De  Forest 
audion,  and  the  concept  of 
amplification  and  regenera- 
tion were  all  old  in  the  art 
before  the  present  radio 
public  existed.  And  each 
of  these  came  into  being 
rather  quietly;  wonderful 
as  they  were,  they  inspired 
only  moderate  enthusiasm 
because  those  who  appreci- 
ated their  significance  and 
value  were  so  few.  The 
super-heterodyne,  con- 
ceived by  Armstrong  while 
working  for  the  Govern- 
ment on  radio  development, 
and  the  neutralized  ampli- 
fying receiver,  first  thought 
out  by  Hazeltine,  Rice,  and 
others,  were  both  finished 
before  the  era  of  broadcast- 
ing even  began. 

If  we  look  then  for  an 
epoch-making  radio  de- 
velopment during  the  past 
five  years,  the  life  of  radio 
broadcasting,  we  really  find 
none.  Improvements  there  certainly  have 
been,  both  in  parts  and  sets,  but  nothing  which 
has  "revolutionized"  the  industry.  The 
thoriated  vacuum  tube  filament  was  a  great 
advance  over  the  pure  tungsten  filaments, 
which  had  been  generally  used  in  radio  tubes, 
but  even  thoriated  tungsten  is  not  really  a 
revolutionary  step  over  the  oxide-coated  fila- 
ment, itself  older  than  the  radio  industry. 

Probably  the  greatest  recent  advance  in 
radio  has  been  in  the  loud  speaker  and  we 
all  know  that  this  development  has  been 
gradual  enough;  it  has  been  evolution  rather 
than  revolution.  A  few  scientists  have,  on 
occasion,  been  willing  to  announce  to  the 
press  that  they  had  conquered  static,  but  even 
these  venturesome  ones  are  gradually  retiring 
from  the  stage  and  by  their  silence  rather 


Quality  of  the  Received  Signal  Growing  More  Important          485 


conceding  that  even  static  is  to  be  conquered 
by  diligence  and  well  conceived  steps  rather 
than  by  any  spectacular  invention. 

If  one  wants  a  radio  set  he  should  go  and 


FEKfifrORY  OF  HAW 


PHOTOS  SENT 
§Y  RIO  HERE 

TOM 


Radio  Corporation  and 
Army  Send  Pictures  Over 
LamL  Sea*  SjjQCfissMK 

Greatest  Pittance  Ever 
Soanned:  First  Achieve- 
ment o*  its  Kind 


buy  one  now.    The  heralded  revolution  in  the 
radio  industry  probably  will  not  materialize. 

What  is  the  Radio  Receiver  of 
To-morrow? 


N' 


'O  GREAT  single  step  in  radio  progress 
is  likely  to  be  made  in  the  near  future. 
But  to  counteract  the  impression  that 
radio  is  stagnant,  let  us  look  at  to-morrow's 
radio  receiver  to  see  what  we  shall  be  buying 
a  year  from  now. 

The  one  respect  in  which  the  set  of  the 
future  will  outrank  that  of  to-day  is  in  quality 
of  reproduction.  At  the  transmitting  sta- 
tions, hundreds  of  thousands  of  dollars  are 
being  spent  in  improving  the  quality  of  the 
radio  signal  emitted.  Scores  of  the  very  best 
radio  engineers  in  the  world  are  analyzing 
each  minute  step  from  the  voice  to  the  an- 
tenna, taking  pictures  of  the  currents  in  the 
various  circuits  and  comparing  them  with 
theoretically  correct  forms.  Exact  knowledge 
is  possible  in  this  end  of  the  radio  channel 
because  of  the  money  and  talent  at  work  on 
the  problems. 

Has  the  reproduction  of  sound  in  the  home, 
from  the  radio  signal  sent  out  by  these  high 


STANDARD  HIGH  POWER 
TRANSMITTING  APPARATUS 
AT  KAHUK.U»» 


LAND  LINES 
MARSHALL  TO  BOLIHAS 

19  MILES 
LAND  LINES 

KOKO  HEAD  TO  HONOLULU - 
'10  MILES 


RADIO  PHOTOGRAPHIC --' 
TRANSMITTING  APPARATUS 
Al  HONOLULU 


RECEIVING  STATION 
AT    KOKO  HEAD 
CONFIRMING   MESSAGES 
FROM   NEW  YORK 


PHOTOGRAPHS     BY     RADIO      FROM 
HAWAII    TO   NEW    YORK 

The  map  shows  the  number  of  electrical 
transfers  the  original  photograph  sent 
from  the  Radio  Corporation  high  power 
telegraph  transmitter  at  Kahuku,  Hawaii 
had  to  undergo  before  it  reached  New 
York.  The  insert  above  shows  how  a 
photograph  of  a  section  of  an  Hawaian 
newspaper  looked  after  being  flashed 
through  the  ether  to  New  York.  The 
lower  insert  is  a  radio-transmitted  photo- 
graph of  soldiers  on  Hawaiian  duty  at 
mess.  At  the  time  this  experiment  occurred,  May  7,  1925,  the  Army-Navy  "war  game"  was  in  progress,  and 
an  excellent  opportunity  was  afforded  for  showing  the  value  of  that  unusual  kind  of  radio  communication 


Radio  Broadcast 


WHEN    WJZ    WAS    PORTABLE 

The  short  wave  transmitter  aboard  the  yacht  Elco  which  was  used  as  floating  broadcasting  headquarters  to 
report  the  Childs  cup  rowing  races  between  Columbia,  Princeton,  and  the  University  of  Pennsylvania.  A 
similar  arrangement  was  used  to  broadcast  the  rowing  races  at  the  Poughkeepsie  Regatta,  late  in  June. 
A  receiver  on  shore  picked  up  the  short  wave  signals  of  the  station,  announced  by  Major  J.  Andrew  White 
(at  the  microphone  in  this  photograph)  and  thence  they  were  relayed  by  wire  to  the  main  wjz  station 


priced  transmitters,  kept  pace  with  their  de- 
velopment? Certainly  not,  and  here  is  the 
place  where  progress,  is  to  be  expected.  Ask 
any  one  with  a  musical  ear  if  a  radio  orchestral 
rendition  is  as  pleasing  as  the  original  and  the 
answer  must  now  be  in  the  negative.  The 
response  of  the  average  loud  speaker  and 
amplifying  set  is  woefully  lacking  in  faith- 
fulness of  reproduction.  Few  radio  listeners 
turn  around  in  surprise  to  find  that  their 
friend,  who  is  talking  over  the  radio,  is  not 
in  the  room  with  them — that  a  loud  speaker 
is  sending  out  (or  trying  to  send  out)  the  well 
known  voice.  And  until  such  surprises  exist 
we  can  surely  say  that  here  radio  is  to  be 
improved.  We  do  feel  that  great  progress 
has  been  made,  but  still  more  remains  to  be 
accomplished. 

In  spite  of  the  slowness  of  its  appearance  we 
believe  that  the  completely  batteryless  set  is 
sure  to  appear.  It  is  reasonably  close  to 
accomplishment  for  all  except  the  "distance 
hound,"  who  may  be  bothered  by  the  slight 
hum  which  may  exist  sometimes  in  these  sets. 


Improvement  in  quality  of  reproduction, 
besides  keeping  the  loud-speaker  manufacturer 
busy,  entails  on  the  set  manufacturer  a  burden 
which  he  has  not  so  far  assumed.  To  get 
good  quality,  we  must  use  in  our  sets  at  least 
one  tube  of  much  greater  output  capacity 
than  the  present  receiver  tubes  possess.  A 
small-power  tube  of  from  five  to  ten  watts  rat- 
ing, must  be  put  into  the  set  to  operate  the  loud 
speaker  if  the  great  variation  in  power  of  the 
voice  or  orchestra  is  to  be  truthfully  followed. 
To  operate  such  a  power  tube,  several  watts 
will  be  required  for  the  filament,  and  the 
plate  supply  must  be  of  a  much  higher  volt- 
age than  can  be  efficiently  obtained  from  bat- 
teries. This  development,  sure  to  come,  will 
hasten  the  time  when  the  lighting  company's 
power  is  used  completely  for  the  receiving  set. 

For  some  time  there  will  be  many  cases, 
of  course,  where  batteries  must  continue  to 
be  of  service;  there  are  millions  of  homes  in 
America  which  are  not  electrically  equipped. 
This  radio  change  from  battery  to  house  wires 
will  also  be  gradual,  not  revolutionary. 


Coming  Developments  in  Radio  Receivers 


487 


The  day  of  the  nine-dial  set  (of  which  one 
of  our  friends  boasted  some  time  ago)  is  as- 
suredly doomed.  Much  has  been  written 
about  the  one-dial  set.  Possibly  with  re- 
finement in  mechanical  design  and  manufac- 
ture, it  will  be  made  sufficiently  efficient  to 
create  a  market  for  itself.  It  is  much  easier 
however,  to  make  a  two-dial  set  operate  ef- 
ficiently than  a  one-dial  and  as  we  have  two 
hands  which  permit  simultaneous  adjustment 
of  two  dials,  two  controls  seems  reasonable 
and  justified.  The  average  listener  probably 
prefers  two  dials  to  one.  With  two  dials, 
the  adjustment  is  easy  enough,  and  with  one 
the  three-year-old  child  could  adjust  the 
radio  outfit  as  well  as  Father.  Such  a  situa- 
tion will  probably  not  be  encouraged  by  the 
older  member  of  the  family — he  would  lose 
too  much  prestige. 

The  purchaser,  who  acquires  to-morrow's 
set  will  probably  acquire  an  outfit  with  this 
•gradually  improved  quality  of  reproduction, 


greater  freedom  from  battery  trouble  and 
easier  adjustment.  Improvements  in  the 
set's  appearance,  necessarily  costly,  will  come 
as  the  buying  public  shows  its  preference  for 
the  art  type  of  receiver. 

The  Radio  Receiver  of  the  Victor 
Company 


T 


HE  Victor  Talking  Machine  Company 
has  finally  entered  the  radio  field. 
Said  a  representative  of  the  company: 


We  have  been  urged  by  every  known  means  to 
manufacture  a  set  of  our  own.  There  are  many 
reasons  why  we  should  not  do  so.  First,  the  men 
and  women  who  work  in  our  factory  are  skilled  in 
the  delicate  assembling  required  in  the  manufacture 
of  talking  machines.  It  would  take  a  long  time  for 
them  to  develop  similar  efficiency  in  the  assembling 
of  radio  equipment,  a  process  which  would  be 
profitable  neither  to  us  nor  to  the  public. 


THE    RADIO    ROOM    ON    A    GREAT    LAKES    PASSENGER    SHIP 

Radio  is  being  modernized  on  the  Great  Lakes  and  tube  transmitters  and  receivers  installed.  This  is  a 
corner  of  the  radio  cabin  on  the  S.  S.  Greater  Detroit  which  sails  nightly  between  Buffalo  and  Detroit.  This 
new  liner  of  the  inland  sea  is  more  than  500  feet  long  and  has  a  passenger  capacity  of  more  than  1500. 
Traffic  on  the  Great  Lakes  is  growing  heavier  each  year,  both  as  regards  number  of  ships  and  radio  com- 
munication . 


Radio  Broadcast 


The  Victor  Company  has  completed  an 
arrangement  with  the  Radio  Corporation  of 
America  to  have  super-heterodyne  sets  built 
for  their  talking  machines.  The  engineers 
of  the  Victor  Company  decided  to  use  this 
set,  it  was  announced,  after  trying  all  the 
other  sets  on  the  market.  A  design  of  loud 
speaker  new  to  this  country  is  to  be  incor- 
porated and  it  seems  that  this  set,  to  appear 
in  the  fall,  should  prove  most  acceptable  to 
the  buying  public. 

Having  thus  allied  itself  to  a  certain  extent 
with  the  Radio  Corporation,  the  thought 
naturally  arises:  Will  Victor  artists  broadcast 
next  winter  through  Radio  Corporation  sta- 
tions or  through  American  Telephone  and 
Telegraph  Company  stations?  The  concerts 
by  the  Victor  artists  were  the  bright  spots 
in  last  winter's  radio  programs  and  everyone 
wants  them  continued,  on  the  old  lines  if 
possible.  When  questioned  regarding  next 
winter's  broadcasting  the  company's  repre- 
sentative said: 

Yes,  the  Victor  Company  expects  to  broadcast. 
It  is  neither  our  intention  nor  our  wish  to  withhold 
great  voices  or  great  artists  from  the  air.  This 
phase  of  the  situation,  though,  is  not  without  its 
difficulties.  A  first  requisite  is  that  the  artists  be 
willing  to  cooperate  and  to  cooperate  at  such  com- 
pensation as  may  be  commercially  practicable.  An 
offset  to  this  condition  is  our  own  obligation  to  se- 
cure for  them  such  reception  as  shall  be  worthy  of 
their  talents.  But  our  plans  are  not  yet  worked 
out,  nor  can  they  be  until  a  later  date. 


It  will  be  remembered  that  the  Brunswick- 
Balke-Collender  Company  has  been  for  some 
time  selling  talking  machines,  with  built-in 
Radio  Corporation  sets.  Both  talking  ma- 
chine companies  will  now  put  out  RCA. 
receivers.  Mr.  B.  E.  Bensinger,  president  of 
the  Brunswick  Company,  states  that  the  same 
special  receivers  furnished  to  the  Victor  Com- 
pany will  continue  to  be  furnished  to  his 
company.  He  made  the  graceful  gesture  of 
complimenting  the  Victor  Company  on  hav- 
ing followed  out  the  same  procedure  as  did 
his  company  the  year  previous. 

When  Great  Men  Speak  of  Radio 

THE  "electrical   wizard"  as  Thomas  A. 
Edison  is   frequently   called,    said  in  a 
recent   interview:  "Static  can  never  be 
eliminated." 

Perhaps  this  is  so,  but  Mr.  Edison's  saying 
that  it  is  so  doesn't  make  it  necessarily  true. 
Many  great  men  have  been  free  in  expressing 
their  opinions  on  subjects  they  didn't  under- 
stand. The  American  public  apparently 
wants  to  believe  that  a  man  who  has  accom- 
plished such  great  things  as  has  Mr.  Edison 
can  give  a  reasonable  opinion  on  many  other 
things.  So  in  considering  Mr.  Edison's 
views  on  radio,  let  us  remember  Mr.  Ford's 
peace  ship  which  was  "to  get  the  boys  out  of 
the  trenches  before  Christmas."  Mr.  Ford 
didn't  understand  the  war  situation  and 


AN    ENGLISH    RADIO    CONSTRUCTOR 
Master  J.  H.  Facer,  aged  16,  with  his  entries  in  a  recent  radio  exhibition  held  in  London 


What  Edison  Thinks  of  Radio 


489 


possibly  Mr.  Edison  does  not  understand  all 
the  intricacies  of  radio. 

Does  Radio  Need  a  High 
Commissioner? 

THE  idea  of  a  unified  control  of  baseball 
by  Judge  Landis,  voluntarily  vesting 
in  him  autocratic  power  in  regulating 
all  disputes  which  may  arise,  is  a  good  ex- 
ample of  an  ingenious  American  plan  to 
regulate  and  control  a  very  difficult  situation. 
The  movie  industry  voluntarily  put  itself 
under  the  same  kind  of  control.  But  of  all 
the  things  requiring  control  of  this  kind,  radio 
certainly  stands  foremost.  In  no  field  that 
we  can  think  of  is  there  more  cause  for 
disputes  which  will  react  to  the  detriment  of 
the  listener.  To  be  sure,  Herbert  Hoover 
has  shown  great  tact  and  diplomatic  skill  in 
arranging  the  past  three  international  radio 
conferences,  successfully  bringing  into  line 
various  conflicting  opinions,  both  national 
and  international,  but  his  authority  is  by 
no  means  as  powerful  as  that  of  the  baseball 
Commissioner. 

But  our  high  commissioner  idea  has  been 
so  well  thought  of  in  Europe  that  radio  there 
has  just  adopted  it  and  all  radio  conflicts 
hereafter  will  be  settled  by  one  man  who 
holds  his  position  at  the  request  of  the  various 
radio  interests.  Sitting  in  Geneva,  where 
so  many  international  movements  seem  to 
centralize,  Mr.  Arthur  Burrows,  an  English- 
man, will  adjudicate  all  radio  conflicts  which 
originate  in  Europe. 

This  new  international  radio  bureau,  which 
Mr.  Burrows  heads,  aims  "to  establish  an 
effective  link  between  the  various  European 
broadcasting  stations,  keeping  in  view  the 
possibility  of  activities  being  extended  to 
other  continents;  to  defend  all  policies  and 
measures  affecting  stations'  interests;  to  cen- 
tralize the  study  of  all  questions  arising  from 
the  rapid  development  of  wireless  telephony 
and  to  initiate  and  further  all  efforts  towards 
the  improvement  of  broadcasting  generally 
for  the  benefit  of  all  nations  both  individually 
and  collectively."  From  this  statement  it 
will  be  seen  that  head  of  the  bureau  auto- 
matically becomes  the  Landis  of  radio. 

The  bureau  intends  at  once  to  interest  it- 
self in  the  question  of  radio  relaying,  a  prob- 
lem of  ever  increasing  importance.  More 
and  more,  as  we  see  it,  the  tendency  will  be 
to  do  away  with  the  talent  of  Main  Street. 
We  shall  send  out  instead  the  most  artistic 
performances  obtainable.  This  accomplish- 


ROBERT    M.    FOSTER 

Of  Montreal,  Canada,  the  radio  operator  aboard  the 
Canadian  Coast  Guard  ship  Arctic  which  sailed  for 
Etah,  Greenland  the  latter  part  of  June.  He  will 
experiment  on  20,  40,  and  80  meters,  using  the  call 
VDM.  Short  wave  experiments  with  Canadian  and 
American  amateurs  and  KDKA,  East  Pittsburgh 
were  very  successful  during  the  1924  expedition  and 
more  extensive  tests  are  planned  this  year.  The 
two  ships  of  Donald  MacMillan's  Arctic  expedition 
will  also  be  in  the  same  waters  at  about  the  same 
time.  The  MacMillan  vessels  are  equipped  with 
short  wave  telegraph  transmitters  also 

ment  of  course  is  possible  only  by  some 
scheme  of  relaying.  The  European  bureau 
intends  to  be  itself  a  direct  channel  for  the 
interchange  of  programs,  ideas,  and  regulation 
of  all  matters  directly  affecting  radio  broad- 
casting. 

Radio  Broadcast's  Phonograph 
Receiver 

THE  two  great  centers  of  home  enter- 
tainment are  without  question  the 
radio  and  the  phonograph.  For  the 
past  four  years,  the  radio  set  has  probably 
usurped  the  domestic  center  of  attention  and 
the  phonograph  has  had  to  take  second 
place.  But  now  that  radio  constructors  are 
a  little  less  eager  to  build  every  new  circuit 
— being  attracted  to  it  simply  because  it  is 
"new" — the  attention  of  every  radio  user  has 
naturally  centered  on  the  appearance  of  his 
receiver.  It  is  assumed  that  he  has  found  a 
type  of  set  which  satisfies  his  daily  radio 
wants. 

It  has  been  the  aim  of  RADIO  BROADCAST 
to  produce  a  radio  receiver  for  home  construe- 


490 


Radio  Broadcast 


J.    C.    GILBERT 

Washington;  Chief,  Radio  Market  Service, ' 

Department  of  Agriculture 

"  Progress  in  the  field  of  radio  broadcasting  must 
include  a  systematic  organisation  of  weather, 
crop,  and  market  reports  and  helpful  agricultural 
information.  There  must  be  greater  cooperation 
between  all  agencies  concerned.  I  should  like  to 
see  some  general  instruction  broadcast  to  farmers 
about  their  radio  sets,  and  bow  they  should  be 
installed  and  operated.  The  surveys  which  the 
United  States  Department  of  Agriculture  made 
in  1923  and  1924  showed  that  the  use  of  radio  on 
farms  is  increasing  rapidly.  570,000  radio  sets 
on  farms  were  estimated  for  1924  as  compared 
with  145,000  in  1923.  About  fifty  per  cent,  of 
farmer-owned  radio  sets  are  home  assembled. 
This  is  not  extraordinary,  for  people  on  farms 
have  much  experience  in  making  their  own  tools 
and  equipment.  There  is  no  group  or  class  of 
people  in  this  country  to  whom  radio  means  so 
much  as  to  the  farmers." 


tion  which  will  satisfy  the  obvious  require- 
ments for  practically  every  radio  use:  one 
that  will  deliver  faithful  service  and  one 
that  readily  can  be  built  from  standard  and 
available  parts.  Further,  we  have  tried  to 
design  this  set  so  that  it  is  easily  made  port- 
able, if  that  be  the  desire,  but  chiefly  to  make 
it  easy  to  install  in  the  various  types  of  phono- 
graphs found  in  American  homes.  These 
aims  we  are  convinced  we  have  attained  in 
the  Phonograph  Receiver. 

If  the  constructor  has  a  phonograph  of 
any  one  of  the  standard  types  which  have 
been  sold  in  such  enormous  quantities,  the 
Phonograph  Receiver  can  be  built  and  in- 
stalled with  ease,  and  the  phonograph  will  not 
be  marred  or  made  less  useful  in  any  way. 


In  fact,  we  feel  that  we  have  shown  the 
way  to  make  the  phonograph  doubly  useful. 
To  combine  in  one  instrument  the  amazing 
breadth  of  entertainment  the  phonograph 
affords  and  the  instant  and  vital  daily  enter- 
tainment that  is  the  charm  of  radio  is  an 
accomplishment  which  should  interest  every 
one  who  sets  store  by  his  home  and  all  that 
therein  is.  Our  correspondence  shows  that 
our  solemnizing  the  marriage  of  the  phono- 
graph and  the  radio  has  met  with  very  wide- 
spread approval. 

Reform  Is  Needed  in  Radio 
Advertising 

THERE  is  no  doubt  at  all  that  radio 
has  a  rather  unsavory  reputation  with 
much  of  the  buying  public.  We  are 
continually  asked  about  "what  set  to  buy," 
and  find  that  the  intelligent  public  believe 
little  that  is  written  about  the  merits  of  this 
set  or  that  one.  The  reason  for  this  disgust 
is  at  once  evident  to  one  who  picks  up  an 
average  radio  magazine  or  newspaper  and 
looks  over  the  radio  advertisements.  There 
is  apparently  no  set  that  isn't  the  best,  no 
condenser  that  hasn't  the  lowest  loss,  no  coil 
that  isn't  the  most  efficient.  Obviously  they 
can't  all  be  the  best.  The  reader  naturally 
distrusts  all  of  them. 

The  average  radio  advertisement  is  not  an 
honest  attempt  to  tell  just  what  the  appara- 
tus will  do,  but  rather  a  claim  that  it  is  better 
than  that  of  any  other  advertiser.  The  "low 
loss"  advertisements  which  have  filled  the 
magazine  pages  for  months  past  are  enough 
to  demoralize  any  prospective  purchaser. 
Each  condenser  has  such  low  losses  that  this 
or  the  other  laboratory  found  it  impossible 
to  measure  them.  Even  if  it  were  so,  the  fact 
remains  that  the  purchaser  could  not  tell  the 
difference  between  perhaps  twenty  different 
makes,  in  so  far  as  condenser  loss  is  concerned. 
The  losses  in  the  coils  (which  always  must 
be  used  with  condensers)  are  so  much  greater 
than  those  of  the  condenser  that  any  one  of 
twenty  good  condensers  will  act  practically 
the  same  in  so  far  as  strength  of  signals  is 
concerned. 

When  it  comes  to  complete  sets,  the  situa- 
tion is  much  worse.  Were  one  to  believe  the 
extravagant  claims  made  by  dozens  of  manu- 
facturers he  could  take  a  set  home  and  after 
about  ten  minutes  time  spent  in  installation, 
hear  practically  any  station  he  wanted  to 
from  one  coast  to  another.  But  this  isn't  the 
truth  and  many  a  purchaser  has  been  grossly 


What  People  Say  About  Radio 


491 


deceived   by  advertisements  interested  only 
in  immediate  profit. 

Isn't  it  about  time  that  radio  advertising 
settled  down  to  a  more  reasonable  basis? 
Extravagant  and  foolish  claims  will  eventually 
only  hurt  a  product  and  undoubtedly  those 
advertisers  who  state  sanely  and  reasonably 
what  their  apparatus  is  designed  to  do,  and 
under  what  conditions,  will  in  the  end  gain 
the  confidence  of  the  buying  public. 


Interesting  Things  Interestingly 
Said 


CIR  ROBERT  FALCONER  (Toronto;  Presi- 
*••'  dent,  University  of  Toronto;  in  an  address 
at  Edinburgh  University):  "It  is  the  theatre,  the 
moving  picture  show,  and  the  radio  which  are 
exercising  the  most  penetrating  and  subtle  influence 
upon  the  social  standards  of  Canadians.  .  .  . 
Every  night  thousands  of  young  Canadians  listen  to 
addresses  and  talks  directed  to  the  people  who  live 
in  the  central  cities  of  the  United  States.  As  immi- 
grants from  Europe  have  precisely  the  same  charac- 
ter and  outlook  as  those  who  have  made  their  way 
into  the  United  States  pour  into  Canada,  they  will, 
through  the  constant  repetition  of  similar  ideas  in 
picture,  play,  illustrated  paper,  and  radio,  soon  be  a 
type  that  will  no  longer  be  Canadian.  .  .  ." 

LJUGH  S.  POCOCK  (London;  editor  Wireless 
*  World}:  "The  strongest  ties  exist  between 
the  radio  amateur  of  this  country  and  America. 
The  first  long  distance  communication  employing 
short  waves  was  achieved  between  Europe  and  the 
United  States  by  amateurs,  and  although  France 
succeeded  in  reaching  America  first,  British  ama- 
teurs quickly  followed,  and  since  that  day,  two-way 
direct  communication  has  been  permanently  es- 
tablished with  many  friends  on  the  other  side.  .  .  . 
It  is  impossible  to  overestimate  the  importance  of 
the  American  section  of  the  amateur  fraternity. 
Their  organization,  the  American  Radio  Relay 
League,  is  without  parallel  in  the  world.  In  no 
other  country  is  such  freedom  extended  to  amateur 
activity  or  such  use  made  of  the  facilities  so 
granted." 

Y\R.  ARTHUR  H.  HAMMERSCHLAG  (New 
*-^  York;  president,  The  Research  Corporation): 
"The  greatest  scientific  advance  in  1924  was  in  the 
field  of  communication — in  radio  and  in  radio 
photography." 

/^AMILLE  FLAMMARION  (the  late  French 
^•**  astronomer):  "We  might  communicate  with 
Mars  by  some  other  means  than  light  and  optics. 
Who  can  predict  the  future  progress  of  science? 
Can  we  say  that  the  Martians  have  not  already 
tried  by  means  of  radio-telegraphic  waves?  Whence 
come  certain  unexplained  disturbances  of  wireless 


Harris  &  Ewing 

D.  B.  CARSON 


Commissioner  of  Navigation, 

Department  of  Commerce 

"  The  public  probably  will  continue  to  contribute 
to  broadcasting  liberally  through  the  cost  of 
equipment  purchased.  At  present,  there  does 
not  appear  to  be  a  more  equitable  way  of  dis- 
tributing the  cost  while,  on  the  other  hand,  such 
stations  must  have  considerable  advertising  value, 
justifying  the  expense  of  operation  where  the 
owners  of  the  stations  gain  their  support  through 
the  sales  of  radio  apparatus." 


telegraphy?  Perhaps  from  the  sun,  the  effects 
of  whose  electric  storms  extend  as  far  as  the  earth. 
Yet,  for  all  we  know,  they  may  come  from  another 
source." 

IORD  DAWSON,  OF  PENN  (London;  persona, 
*-*  physician  to  King  George;  in  an  address  to 
visiting  American  physicians):  "The  central  reason 
for  the  stress  of  modern  life  is  our  material  progress. 
-The  movement  has  been  so  rapid  that  it  has  out- 
stripped our  rate  of  adaptation.  The  internal  com- 
bustion engine,  the  telephone,  and  the  wireless  have 
so  tuned  up  the  modern  man's  mind  that  he  remains 
in  the  same  key  when  he  is  at  work  and  when  he 
takes  his  so-called  play." 

A  ATWATER  KENT  (Philadelphia;  radio 
**  manufacturer,  who  broadcast  from  the  Los 
Angeles  on  her  recent  flight  over  Philadelphia):  "I 
hope  there  will  be  more  broadcasting  from  airships. 
The  people  will,  one  may  be  sure,  listen  eagerly  to 
brisk  narratives  of  flight  while  the  flight  is  actually 
taking  place.  Certainly  those  who  were  permitted 
to  speak  into  the  microphone  on  this  first  broadcast- 
ing voyage  cf  the  Los  Angeles  were  thrilled." 


ninimninuiiiiiiiiiiiiiiiiiiiii 


For  the  Radio  Beginner 


Adding  a  Bulb  to  the  Beginner's  Crystal  Set 


A  CRYSTAL  receiver  does  not  survive 
very  long  in  these  days  of  inexpensive 
vacuum-tube     apparatus.     But     its 
short  existence  serves  a  purpose  by 
initiating   the    beginner    into    an    intelligent 
appreciation  of  radio  elements  and  stimulates 
a  desire  for  something  better. 

The  crystal  receiver  described  in  this  de- 
partment last  month,  having  served  this 
creditable  purpose,  can  be  converted  into  a 
bulb  set  at  an  expense  little  in  excess  of  its 
original  low  cost.  The  converted  receiver 
will  be  more  selective  than  before.  This  is 
because  the  resistance  imposed  by  the  crystal 
is  eliminated.  Resistance  added  to  any  tuned 
or  resonant  circuit 
broadens  the  tuning 
of  the  circuit.  Also 
the  receiver  will  be 
more  sensitive  and 
the  signals  more  loud 
due  to  the  superior 
efficiency  of  the  bulb 
as  a  detector. 


No.  3  uvi99  Tube 

No.  4  Grid  condenser,  capacity  .00025  mfd. 

No.  5  Grid  leak  mounting 

No.  6  2-megohm  grid  leak 

No.  7  Burgess  small  22. 5  volt  B  battery 

No.  8  3  dry  cells  at  3JC.  each 

No.  9  4  Binding  posts 


3.00 

.  10 

.  10 

.  10 

1.22 

1.05 

.  10 

66.12 


THE    PARTS    WE    NEED 

THE  necessary 
parts  for  the 
conversion  of  the  Be- 
ginner's Crystal  Re- 
ceiver described  in 
this  department  for 
July,  1925  into  a  one- 
bulb  set,  are  photo- 
graphed in  Fig.  i.  The 
lettering  is  that  con- 
ventionally employed 
in  diagramming  the 
various  parts.  The 
items  and  their  prices 


10 


•  25 


No.  i     Socket 

(receptacle) 
No.  i     Socket 

(screws    and 

springs) 
No.  2     One  30- 

ohm  rheostat 


A  Course  for  the  Radio  Beginner 


With  the  exception  of  the  tube  and  batteries, 
all  parts  were  purchased  in  the  5,  10,  and  25- 
cent  stores.  The  cost  of  the  crystal  receiver 
described  last  month  with  the  addition  of  a 
good  pair  of  phones  and  antenna  equipment 
was  $5.52.  Thus  the  expense  of  the  com- 
bination crystal — 
bulb  set,  including 
all  equipment,  is  less 
than  $12.00. 


^f  On  page  366  of  RADIO  BROADCAST  for 
July,  a  simple  crystal  receiver  was  described 
which  could  be  built  from  parts  bought  at 
the  five-and-ten-cent  store,  at  a  total  cost 
of  f  1.82.  The  set  will  receive  good  broad- 
cast signals  from  near-by  stations.  This 
month,  a  vacuum  tube  which  will  increase 
the  receiving  range  of  the  set  is  added  to  that 
assembly. 

If  In  this  department  also  is  begun  a  series 
of  simple  explanation  of  some  of  the  simplest 
radio  phenomena.  What  "detection"  means 
is  the  subject  of  explanation  this  month. 
If  Additional  help  for  the  beginner  is  found 
in  "The  Radio  Lexicon"  which  simply 
defines  all  the  radio  terms  used  in  this  article. 
"The  Radio  Library"  recommends  chapter 
and  verse  in  good  radio  text  books  which 
cover  more  fully  the  same  ground  as  this 
department. 

If  Zeh  Bouck,  one  of  the  ablest  radio  writers 
in  the  country,  is  preparing  this  department. 
Mr.  Bouck  is  an  amateur  himself  of  long 
experience  and  sympathetic  mind  and  has 
passed  through  the  stages  of  trial  and  error, 
of  seeking  and  finding  which  all  radio  en- 
thusiasts experience.  •  He  is  known  on  the  air 
and  to  readers  of  the  New  York  Sun  AS  2  PL, 
author  of  the  column  "What  Are  the  Air 
Waves  Saying?"  and  to  readers  of  Boy's  Life 
as  editor  of  its  radio  department. 

— THE  EDITOR 


THE   CIRCUIT 

FIGURE  2  shows 
how  these  simple 
parts  are  connected 
together  and  how 
they  are  wired  to  the 
crystal  set  described 
in  this  department 
last  month,  or  to  any 
similar  receiver.  The 
heavy  lines  on  the 
right  hand  side  indi- 
cate the  connections 
between  the  new  ap- 
paratus. One  side  of 
the  grid  condenser  (C) 
is  connected  to  the 
grid  (G)  post  on  the 
socket,  and  the  grid 
leak  mounting  is  con- 
nected across  the 
condenser.  The  grid 
leak  (R2)  is  clipped 
into  the  mounting. 
The  plate  (P)  bind- 
ing post  on  the 
socket  is  run  to  a 
binding  post  (D), 
which,  with  post  C 


A  Tube  Set  for  Radio  Beginners 


493 


affords  the  B  battery  posts  (D  and  C)  for  the 
set. 

The  rheostat  (Ri)  is  connected  to  one  of  the 
filament  (F)  posts  on  the  socket.  The  re- 
maining filament  post  and  rheostat  post  are 
run  to  set  binding-posts  respectively  for 
plus  and  minus  A  battery  connections  (A 
and  B). 

The  bulb  apparatus  can  be  connected  to 
almost  any  crystal  receiver  in  the  following 
manner,  and  in  accordance  with  the  dotted 
lines  in  Fig.  i. 

The  minus  B  battery  post  (C)  is  led  to 
that  side  of  the  crystal  detector  nearest  to  the 
telephone  receivers  ("X"  in  the  case  of  The 


Radio  Broadcast  Beginner's  Set).  The  free 
terminal  of  the  grid  condenser  leads  to  the 
other  side  of  the  crystal  detector  ("Y"  on 
the  Beginner's  Set).  The  plus  filament  lead 
is  connected  to  that  side  of  the  telephone 
receivers  farther  from  the  crystal  detector, 
or  ("Z"  in  the  Beginner's  Receiver). 

CONSTRUCTION  OF  THE  TUBE  RECEIVER 

IF  IT.  is  desired  to  add  the  bulb  to  any 
crystal  receiver  other  than  that  described 
on  page  366  in  RADIO  BROADCAST  last  month, 
the  mechanics  of  the  arrangement  will  be  left 
to  individual  invention.  The  parts  may  be 
mounted  into  a  separate  unit  if  desired,  or 


R 


FIG.    I 

Complete  equipment  for  changing  any  crystal  receiver  into  a  single-bulb  set.     The  apparatus 
photographed   here  costs  $6.12.     The  dry  cells  are  wired  in  series,  forming  the  A  battery 


494 


Radio  Broadcast 


The'Beginner's 

Crystal  Reciever*          l_ I 


FIG.    2 

The  connections.      The   heavy   line   indicates   the 

wiring  of  the  new  apparatus,  and  the  dotted  lines 

show  how  it  is  connected  to  the  RADIO  BROADCAST 

Beginner's  Set 


perhaps  room  can  be  found  for  them  in  the 
set  proper  as  is  the  case  with  specific  crystal 
set  to  which  we  have  already  referred. 

The  photographs,  Figs.  3,  and  4,  clearly 
indicate  how  the  single  tube  was  combined 
with  the  crystal  receiver.  The  combination 
can  be  effected  with  the  same  tools  suggested 
for  the  original  construction  of  the  tuner. 

The  socket  and  rheostat  are  mounted  on  the 
top  of  the  cigar-box  cabinet  and  the  extra 
binding  posts  two  on  each  side.  The  re- 
mainder of  the  parts — the  grid  leak,  its  mount- 
ing, and  the  grid  condenser — are  placed  inside 
the  cabinet. 

The  socket  and  rheostat  are  mounted  on  the 
center  line  of  the  top  of  the  box,  with  centers 
two  and  one  quarter  inches  in  from  the  ends. 
The  socket  is  mounted  with  two  wood  screws, 
and  the  rheostat  with  the  screws  provided 
for  that  purpose.  Rather  than  bring  the 
wires  through  the  "cabinet "  top  to  the  outside 
posts  of  the  socket,  four  small  holes  were 
drilled  underneath  the  socket  prongs  through 
which  the  connections  were  made.  The 
wires  were  secured  under  the  heads  of  the 
screws  that  project  through  the  base  of  the 
socket  as  binding  posts.  The  battery  binding 
posts  are  mounted  directly  behind  the  antenna, 
ground,  and  phone  terminals  on  the  original 
set — about  f  inch  in  from  the  rear  edge. 
The  A  battery  posts  are  behind  the  antenna 
and  ground  posts.  These  arrangements  are 
clearly  suggested  in  Fig.  3. 

The  grid  condenser  and  grid  leak  mounting 
have  the  same  spacing  between  mounting 
holes,  so  they  were  combined  into  a  single 
unit  as  shown  in  Fig.  4.  The  condenser  and 
mounting  are  held  firmly  in  place  by  the  con- 
necting wires.  A  few  feet  of  No.  18  belt  wire 
were  used  in  making  connections. 


No  solder  need  be  used  in  making  this  set 
an  electrically  efficient  job. 

NOTES  ON  OPERATION  OF  THE  SET 

THE  finished  receiver  is  a  combination  set. 
It  can  be  operated  with  either  crystal  or 
bulb  detector.  When  the  crystal  is  adjusted 
and  the  rheostat  turned  off,  the  set  will  receive 
as  well  as  ever  on  the  crystal.  When  the  tube 
is  used,  the  rheostat  is  turned  on  and  the 
catwhisker  must  be  lifted  away  from  the  crystal. 
With  this  latter  arrangement,  the  receiver 
functions  as  a  single-tube  wow-regenerative  set. 
Single-tube  regenerative  sets  are  radiators  of 
interfering  oscillations,  particularly  when 
operated  by  inexperienced  listeners.  For 
this  reason,  no  slight  alterations  should  be 
attempted  in  order  to  make  the  receiver  re- 
generate. 

The  three  dry  cells  forming  the  A  battery 
are  connected  in  series — i.e.  the  negative  post 
of  one  cell  to  positive  post  of  the  next,  as 
suggested  in  Fig.  i.  The  negative  terminal 
is  the  zinc,  and  the  positive  terminal  is  the 
center  or  carbon.  The  A  and  B  batteries 
are  connected  to  their  respective  posts. 

With  new  or  fully  charged  batteries  it  will 
be  necessary  only  to  turn  the  rheostat  "just 
on."  As  the  A  battery  is  discharged — in  the 
course  of  a  month  or  two — the  rheostat  must 
be  turned  farther  and  farther  up.  The  opera- 
tion of  the  set  as  a  bulb  receiver  in  respect  to 
tuning  is  identical  with  that  of  the  crystal  set. 

The  tube  should  be  turned  off  by  means  of 
the  rheostat  when  the  set  is  not  being  used. 

-jiniimmiiimnmmiimmmimiiiimiiimimmii iiiimiiiiiiiimiiiiiiiiiiimiiiiiiiiimiiiiij. 

THE    RADIO   PRIMER 


What  "Detection"  Means 

'lllMIIIIIIIIIIIIIIIIIIIIIIIIIMIIIIIIIIIIIIMIIIIIIIIIIIIIIMNIIIIIIIIIIIIIIIIIIIIIIIIIIIIIMIIIIIIIIIIIIIIIIIIIIIln 

IT  IS  impossible  to  start  at  the  very  begin- 
ning of  things.     To  all  adult  arguments 
and  explanations,  some  premises  must  be 
granted.     Before    beginning   to    explain    the 
necessity  for  a  form  of  detector  such  as  the 
crystal,  certain  conditions  under  which  the 
detector   operates    must    be    admitted    even 
when,  by  some,  they  may  not  be  thoroughly 
understood. 

In  every  receiving  set,  and  therefore  in  a 
crystal  receiver,  a  high  frequency  alternating 
current  flows  through  the  tuning  circuits 
whenever  a  transmitting  station  is  being  re- 
ceived. This  high  frequency  current  is  iden- 
tical in  every  respect  except  in  strength  with 
that  surging  in  the  transmitter  many  miles 


The  Phenomenon  of  "Detection" 


495 


distant,  and  is  set  up  in  the  receiver  through  the 
action  of  the  radio  wave.  When  the  current 
grows  more  powerful  in  the  transmitter,  it 
grows  similarly  more  powerful  in  the  receiver. 
Every  variation  of  the  transmitting  current  is 
duplicated,  at  practically  the  same  time,  in  all 
receiving  sets  tuned  to  this  transmitter. 

Now  these  variations  are  caused  by  differ- 
ent tones  and  notes  impinging  on  the  micro- 
phone in  the  studio  of  the  transmitting  station. 
With  one  note,  the  transmitting  current  will 
grow  stronger,  while  on  another  it  will  be 
weakened.  Thus,  in  the  receiving  set,  we 
shall  have  an  alternating  current,  the  strength 
of  which  will  vary  with  the  spoken  words  or 
music  picked  up  by  the  small  round  micro- 
phone in  a  broadcasting  station  perhaps  a 
thousand  miles  away.  This  alternating  cur- 
rent is  conserved  and  brought  to  its  maximum 
stength  in  the  receiver  by  the  process  of  tun- 
ing. When  you  twist  the  dials  of  your  re- 
ceiving set,  you  are  merely  adjusting  local 
conditions  so  that  the  most  can  be  made  of  the 
infinitesimal  energy  which  you  pick  up  many 
miles  from  its  starting  point. 

MAKING     ALTERNATING     CURRENT     "AUDIBLE" 

HAVING  picked  up,  conserved,  and,  per- 
haps, strengthened  this  weak  alternating 
current,  it  now  remains  to  make  it  audible — 


to  conjure  it  forth  from  the  loud  speaker  or 
telephone  receivers  as  enjoyable  sound.  This 
process  is  well  named  "detection,"  and  it  is 
here  that  the  "detector"  (a  crystal  in  this 
case)  comes  into  its  all-important  action. 

A  high  frequency  alternating  current  will 
not  actuate  the  diaphragms  of  a  loud  speaker  or 
telephone  receivers.  Both  of  these  instruments 
severally  consist  of  a  permanent  magnet  over 
which  are  wound  several  thousand  turns  of 
wire.  When  electricity  passes  through  these 
turns  there  exists  the  combination  effect  of  a 
permanent  magnet,  such  as  the  familiar  horse- 
shoe magnet  and  an  electromagnet,  such  as 
the  bobbins  that  actuate  the  armature  of  an 
electric  bell. 

All  magnets  have  two  poles,  and  the  lines 
of  magnetic  force  are  imagined  as  leaving  one 
pole  and  entering  into  the  other.  Thus  the 
magnetic  lines  of  force  may  be  said  to  be 
characterized  by  direction,  running,  as  it 
happens,  from  the  north  pole  of  a  magnet  to 


FIG.  3 

Front  view  of  the  be- 
ginner's combination 
crystal-bulb  set,  showing 
the  mounting  of  the 
socket,  rheostat  and  right 
hand  binding-posts 


496 


Radio  Broadcast 


the  south  pole.  The  directions  of  the  lines 
of  force  in  an  electromagnet  are  determined 
by  the  direction  of  the  current  flowing  through 
the  winding.  When  the  direction  of  the  cur- 
rent is  reversed,  the  magnetic  field  is  reversed. 

An  alternating  current,  as  most  of  us  ap- 
preciate, is  a  current  that  reverses  its  direction 
of  flow  many  times  a  second.  For  a  fraction 
of  a  second  it  courses  through  the  wire  or 
conductor  in  one  direction.  Then  it  weakens 
to  zero  strength,  and  turns  about,  growing 
stronger  in  the  opposite  direction.  Its  action 
is  comparable  to  the  motion  of  a  piston  actuat- 
ing a  revolving  flywheel.  The  piston  is  con- 
stantly reversing  its  direction  of  motion  (one 
reversal  for  every  revolution  of  the  wheel)  and 
yet  it  continuously  exerts  a  power  or  force 
that  is  useful.  The  number  of  times  this 
reversal  takes  place  is  known  as  its  frequency. 

Therefore,  if  we  pass  an  alternating  current 
through  the  coils  of  an  electromagnet,  the 
direction  of  the  lines  of  force,  comprising  the 
flux  or  magnetic  field,  will  reverse  with  the 
alternations  of  the  current.  The  action  of  this 
field  is  suggested  in  the  drawings  Fig.  5. 

The  field  of  a  permanent  magnet  is,  as  its 
name  suggests,  permanent.  It  exerts  a 
magnetic  attraction  without  the  assistance  of 
electric  current,  and,  excepting  under  very 
powerful  electrical  stresses,  the  polarity,  or 
direction  of  the  lines  of  force,  is  never  reversed. 

THE    "WORKS"    OF   THE    LOUD   SPEAKER 

WE  HAVE  said  that  the  diaphragm  of  a 
loud  speaker  or  telephone  receiver  is 
actuated  by  a  combination  of  permanent 
and  electromagnets.  Let  us  investigate 
what  would  happen  if  we  pass  a  high  frequency 
alternating  current  through  the  winding  of 
such  a  reproducer.  I  n  one  direction  of  current 
flow,  the  electromagnetic  field  will  assist  the 
permanent  magnetic  field,  and  the  diaphragm 
will  be  drawn  farther  down  toward  the  magnet. 
However,  with  the  reversal  of  the  current  (and 
accompanying  reversal  of  the  electromagnetic 
field)  the  electromagnetic  field  will  oppose 
the  permanent  field.  This  will  result  in  the 
weakening  of  the  permanent  field,  and  the 
diaphragm  will  spring  away  from  the  magnet 
even  beyond  the  point  of  normal  equilibrium 
(when  there  is  no  current  flowing  through  the 
winding).  Thus  with  every  cycle  or  complete 
alternation  of  the  current,  the  diaphragm  will 
move  toward  and  from  the  magnet.  But  in 
high  frequency  radio  currents  used  in  broad- 
cast transmission,  these  alternations  take 
place  anywhere  from  300,000  to  6,000,000 
times  per  second!  Due  to  inertia,  it  is  im- 


possible for  so  heavy  an  object  as  a  diaphragm 
to  reverse  its  motion  this  many  times  a  second, 
and  even  were  it  possible  for  the  metal  disk 
to  vibrate  so  rapidly,  the  frequency  is  far 
above  the  upper  limits  which  the  ear  can 
detect  as  sound. 

It  is  therefore  necessary  to  rectify  the  high 
frequency  alternating  current,  to  change  it  into 
direct  current,  i.e.,  a  current  that  flows  only 
in  one  direction.  Such  a  current  will  con- 
tinuously oppose  or  assist  (the  more  efficient 
arrangement)  the  permanent  magnetic  field, 
either  releasing  the  diaphragm  or  pulling  it 
more  powerfully,  respectively,  as  long  as  the 
current  flows.  It  is  only  with  a  variation  of 
the  current,  which  it  will  be  remembered 
changes  with  the  sound  impulses  picked  up  by 
the  microphone  in  the  transmitting  station, 
that  the  diaphragm  will  move,  thus  reproduc- 
ing the  sounds  spoken,  sung,  or  played  in  the 
distant  studio. 

Many  crystals,  such  as  galena  or  silicon, 
possess  the  property  of  unilateral  conductivity, 
which  means  that  they  will  conduct  an  electric 
current  better  in  one  direction.  If  an  alter- 
nating current  is  applied  to  a  circuit  containing 
a  properly  connected  crystal,  the  alternations 
in  one  direction  will  be  passed  quite  readily, 
while  those  in  a  reverse  direction  will  be  weak- 
ened and  impeded.  This  is  a  sort  of  auto- 
matic valve  action,  passing  one  half  of  the 
alternating  current  cycle  and  repulsing  the 
other  half.  The  final  effect  is  that  of  rectifica- 
tion, the  changing  of  the  alternating  current 
into  a  direct  or  uni-directional  current,  which 
is  effective  in  actuating  the  telephone  receivers 
or  loud  speaker. 


THE    RADIO   LIBRARY 


THE  action  of  the  crystal   detector  has 
been    covered    from    various  points  of 
view  in  the  following  references.     The 
student  reader  can  obtain  these  books  from 
up-to-date  public  libraries,  and  will  find  the 
indicated  chapters  well  worth  the  reading. 

The  Outline  of  Radio,  by  John  V.  L.  Hogan,  pages 
147  through  161.  A  very  interesting  and  non- 
technical exposition  on  the  necessity  for  detection 
and  the  action  of  the  crystal  rectifier. 

The  I.  C.  S.  Radio  Handbook,  pages  174  through 
180.  A  less  elementary  description  of  crystal  and 
similar  detecting  actions. 

Principles  of  Radio  Communication,  ].  H.  More- 
croft,  pages  336  through  350.  A  highly  interesting 


Radio  Terms  Defined 


497 


but  mathematical  exposition  recommended  to  the 
student. 

iJIIIIIIIIIIIIIIIIIIIIMIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIMIIIIMIIIIIIIIIIIIIIIIIIIIIIII^ 

THE   RADIO   LEXICON 

^lllllllllllllllllllltlllllllllllllllllllllMIIIMIIIIIIIIIIIIIIIIIIIIIIMIIIIIIIIIIIIIIIIIIMIIIIIIIIIIIIIIIIMIItlli? 

Important  technical  terms  and  words  used 
in  this  month's  department  for  the  radio 
broadcast  beginner: 

ALTERNATION:  Specifically,  the  re- 
versal of  an  alternating  electric  current. 

CRYSTAL  DETECTOR:  A  detector  of 
radio  signals  that  functions  by  means 
of  the  rectifying  property  of  some  mineral 
such  as  galena  or  silicon. 

CYCLE:  The  complete  motion  of  an  al- 
ternating current,  from  the  beginning  of 
one  alternation  to  the  end  of  the  next. 

DETECTION:    The   process   of   making 
audible  the  radio  frequency  currents  set 
up  in  a  receiving  set  by  the  passing  radio ' 
wave. 

DETECTOR:  The  instrument  or  group 
of  parts  arranged  into  a  unit  that  performs 
the  act  of  detection. 

ELECTROMAGNET:  A  magnet  about 
which  lines  of  force  are  set  up  by  a  current 


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[i.'xr?~T~-r*^>*l 


(7R 

\ 


I 


^N 


FIG.    5 

Suggesting  the  manner  in  which  the  direction  of  the 
magnectic  lines  of  force  reverse  with  a  reversal  of 
current  in  an  electro-magnet.  The  arrows  on  the 
solid  lines  indicate  the  direction  of  current  flow  in 
the  wires,  while  the  arrows  on  the  dotted  lines  of 
force  show  the  direction  taken  by  the  field.  In  A 
the  current  flows  in  one  direction,  which  is  reversed 
in  B 


passing  through  its  winding.  The  bobbins 
of  a  door-bell  are  electromagnets. 

FREQUENCY:  Broadly,  the  number  of 
times  a  phenomenon  repeats  itself  within  a 
given  time.  In  electricity,  "frequency" 
generally  refers  to  the  number  of  cycles  per 
second  of  an  alternating  current.  In 
sound,  "frequency"  means  the  number  of 
air  vibrations  per  second. 

LINES  OF  FORCE:  More  or  less  im- 
aginary lines  of  magnetic  energy  running 
from  the  north  pole  of  a  magnet  to  the  south 


FIG.  4 

Rear  view  of  the  combination  receiver.  The  grid  condenser 
and  leak  holder,  combined  into  a  single  unit,  can  be  seen  near 
the  top  of  the  box.  No.  18  bell  wire  has  been  used  for  wiring 


498 


Radio  Broadcast 


pole,  the  sum  total  of  which  is  the  magnetic 
flux  or  field. 

PERMANENT  MAGNET:  A  magnet, 
such  as  the  common  horse-shoe  magnet 
which  is  permanently  magnetized  through 
a  peculiar  disposition  of  the  molecules  of 
steel  or  iron.  Unlike  the  electromagnet, 
no  winding,  passing  an  electric  current,  is 
required  to  provide  the  attracting  field. 

RECTIFICATION:  The  changing  of  an 
alternating  current  to  a  direct  current, 
generally  by  passing  one  half  the  cycle 
(all  motion  of  the  alternating  current  in 


one  direction),  and  impeding  the  other 
half. 

SELECTIVITY:  The  ability  of  a  circuit 
or  receiving  set  to  eliminate  undesired 
stations,  while  bringing  in  the  desired 
signal. 

SHARPNESS:  The  criticalness  of  tun- 
ing. A  set  that  tunes  sharply  will  tune  a 
station  in  or  out  with  a  degree  or  two  of 
variation  on  the  tuning  dials.  Sharpness 
does  not  mean  "selectivity,"  The  use  of 
a  large  variable  tuning  condenser  will 
sharpen  tuning  without  affecting  selectivity. 


Wavelength  or  Frequency 

Which? 


In  An  Effort  to  Clarify  Radio  Terminology,  RADIO  BROADCAST 
Will  Hereafter  Refer  to  Frequencies  Instead  of  Wavelengths 

BY  J.  H.   MORECROFT 

Past  President,  Institute  of  Radio  Engineers 


WE  ARE  all,  being  human,  natur- 
ally very  loath  to  give  up  one 
line  of  thought  for  another.     It 
has  taken  a  certain  amount  of 
effort  to  accomplish  a  method,  and  common 
sense  tells  us  not  to  discard  one  habit,  or 
scheme   of    thinking    for    another,    unless    a 
marked  advantage  is  evident. 

A  most  remarkable  illustration  of  this  men- 
tal inertia  is  our  present  system  of  units  for 
measuring,  in  the  so-called  English  system, 
and  our  hodge-podge  method  of  spelling  words. 
So  many  times,  as  the  writer  has  witnessed 
the  efforts  of  school  children  trying  to  master 
the  crazy  tables  of  measuring  units  with  which 
an  elementary  arithmetic  is  loaded,  the 
thought  has  occurred  to  him,  "  How  inefficient 
and  useless  is  this  antiquated  method  we  have 
of  measuring  things  in  everyday  life!"  Gills, 
hogsheads,  rods,  miles,  drams,  ounces,  and 
pounds,  with  their  heterogeneous  relationships, 
unnecessarily  take  up  a  tremendous  amount 
of  time  and  effort  of  the  young  student. 
Just  because  his  parents  haven't  had  the 
courage  to  break  away  from  unit  systems  be- 
queathed by  semi-civilized  ancestry  (apologies 
to  Mr.  Bryan)  the  boy  of  to-day  has  to  spend 
many  a  dreary  hour  learning  tables  of  quanti- 


ties which  had  much  better  be  replaced  by 
others.  If  the  metric  system  of  units  could 
be  universally  adopted  in  this  country,  the 
amount  of  time  spent  on  arithmetic  in  schools 
might  very  likely  be  halved.  But  the  father 
of  the  schoolboy,  having  an  expensive  set  of 
jigs,  fixtures,  machines,  bolts,  and  whatnots 
in  his  factory  all  worked  out  on  the  English 
system,  does  not  contemplate  with  equanim- 
ity changing  his  scheme  of  measurement.  It 
would  temporarily  seriously  affect  his  profits. 
And  so,  through  the  land,  millions  of  boys  and 
girls  continue  to  expend  many  of  their  precious 
hours  memorizing  useless  relationships  which 
could  readily  be  replaced  by  others  much 
simpler. 

WHEN    CHANGE    IS    DESIRABLE 

EVEN  a  lethargic  reader  can  see  that  change 
is  many  times  useful  and  desirable.  Now 
when  radio  began,  the  effort  was  made  to 
identify  electric  disturbances  with  light,  and 
naturally  this  branch  of  electric  science  took 
over  the  nomenclature  of  the  physics  of  light. 
The  various  frequencies  used  in  radio  were 
identified  by  their  wavelengths,  as  in  light. 
So  radio  folk  grew  accustomed  to  speak  of  the 
wavelength  of  an  alternating  current. 


Wavelength  or  Frequency — Which? 


499 


The  student  of  radio  to-day  finds' th'at  he  has 
to  start  with  the  elementary  laws  of  the  al- 
ternating current  circuit  and  in  these  laws  he 
finds  that  the  frequency  of  the  alternations 
plays  a  very  important  part  in  the  action  of 
the  current.  He  finds  that  commercial  al- 
ternating currents  have  frequencies  of  25  to 
60  cycles  per  second,  voice  (or  telephone) 
frequencies  from  100  to  10,000  cycles  per 
second.  He  becomes  accustomed  to  thinking 
of  these  currents  in  terms  of  their  frequencies. 
He  learns  in  telephony  that  one  frequency 
can  be  separated  from  another  by  so-called 
filters,  the  theory  and  action  of  which  is  ex- 
plained in  terms  of  frequencies.  In  carrier 
telephony,  using  frequencies  perhaps  as  high 
as  50,000  cycles  per  second,  the  engineer  still 
thinks  of  frequencies.  Instead  of  speaking  of 
50,000  cycles  he  speaks  of  50  kilocycles, 
adopting  the  metric  system  of  easy  conversion 
from  one  size  unit  to  another.  The  electrical 
engineer  long  ago  found  it  convenient  to  use 
the  kilowatt  instead  of  the  watt,  and  all  elec- 
tric bills  are  now  rendered  for  so  many  kilo- 
watt hours,  as  every  householder  knows. 

There  is  no  reason  at  all  for  speaking  of  radio 
currents  in  wavelengths.  All  the  theory  and 
apparatus  of  the  radio  engineer  is  worked  out 
on  the  idea  of  frequency.  The  Bureau  of 
Standards  early  recognized  the  needless  com- 
plexity and  the  uselessness  of  the  wavelength 
unit  and  in  all  of  its  publications  now  uses  the 
frequency  of  the  radio  current  instead  of  its 
so-called  wavelength. 

THE  DISADVANTAGES  OF  WAVELENGTH 

IT  SO  happens  that  in  broadcasting,  the  term 
wavelength  has  an  added  disadvantage,  one 
which  argues  most  strongly  for  change  to  the 
frequency  unit.  A  broadcast 'telephone  chan- 
nel requires  a  certain  width  of  the  frequency 
scale  to  transmit  the  voice  properly.  An 
ordinary  station  rated  at  500  kilocycles,  for 
example,  requires  a  frequency  band  from  490 
to  510  kilocycles  for  perfect  transmission  of 
speech.  This  width  of  frequency  band,  of  say 
20  kilocycles,  is  required  for  radio  telephony 
no  matter  what  the  frequency  of  the  station's 
current  may  be.  Thus  a  station  at  present 
rated  as  150  meters  wavelength  requires  a 
frequency  band  from  1990  kilocycles  to  2010 
kilocycles,  a  band  the  same  in  width  as  for  the 
5Oo-kilocycle  station.  If  we  continue  to  think 


of  wavelength,  however,  we  shall  find  no  easy 
way  of  telling  how  closely  two  stations  might 
be  tuned  without  interfering  with  one  an- 
other's channels.  This  separation  would  be 
20  meters,  perhaps,  in  one  part  of  the  radio 
frequency  band  and  only  2  meters  in  another. 

On  the  basis  of  2o-kilocycle  separation,  the 
Department  of  Commerce  could  assign  fre- 
quencies every  20  kilocycles  up  the  radio  fre- 
quency scale,  knowing  that  such  assignments 
would  not  interfere.  But  if  we  stick  to 
wavelength,  we  shall  find  the  wavelength  scale 
divided  in  a  most  irregular  and  apparently 
unreasonable  manner. 

Radio  receiving  sets  can  be  made  to  have 
dials  of  uniform  frequency  scale.  Dials  and 
condensers  of  this  kind  are  already  appearing 
on  the  market. 

The  Department  of  Commerce  specifies 
radio  station  assignments  in  both  kilocycles 
and  meters.  The  tendency  of  radio  engineer- 
ing practice  is  to  use  and  express  frequency  in 
kilocycles  rather  than  wavelength  in  meters. 
"Kilo"  means  a  thousand,  and  "cycle"  means 
one  complete  alternation.  The  number  of 
kilocycles  indicates  the  number  of  thousands 
of  times  that  the  rapidly  alternating  current 
in  the  antenna  repeats  its  flow  in  either  direc- 
tion in  one  second.  The  smaller  the  wave- 
length in  meters,  the  larger  is  the  frequency  in 
kilocycles.  The  numerical  relation  between 
the  two  is  very  simple.  For  approximate  cal- 
culation, to  obtain  kilocycles,  divide  300,000 
by  the  number  of  meters;  to  obtain  meters 
divide  300,000  by  the  number  of  kilocycles. 
For  example,  100  meters  equals  approximately 
3000  kilocycles,  300  m.  equals  1000  kc.  1000 
m.  equals  300  kc.,  3000  m.  equals  10.  kc. 

For  highly  accurate  conversion,  the  factor 
299,820  should  be  used  instead  of  300,000. 

From  this  number  of  RADIO  BROADCAST,  re- 
ference in  the  magazine  will  no  longer  be  made 
to  wavelength  alone.  Frequencies  will  be  the 
standard,  but  in  order  not  to  confuse  the  in- 
experienced reader,  the  corresponding  wave- 
length will  always  be  used,  in  parentheses. 

Page  no,  of  RADIO  BROADCAST  for  Novem- 
ber, 1924  contained  instructions  on  bow  to  con- 
vert wavelengths  to  frequencies  and  vice  versa. 
The  Bureau  of  Standards  has  available,  for 
limited  distribution,  a  conversion  table,  worked 
out  on  the  factor  299,820.  —THE  EDITOR. 


V  CARL  DREHER 

Drawings  by  Franklyn  F.  Stratford 


Diagnosis  of  the  Radio  Amateur 


WHAT  is  a  radio  amateur?  Great 
confusion  surrounds  the  answer, 
if  there  is  one.  To'  owners  of 
single-circuit  receivers  in  his  im- 
mediate vicinity,  the  amateur  is  a  vicious  ogre 
who  emits  strange  buzzing  noises  which  inter- 
fere with  their  broadcast  reception.  To  com- 
mercial operators,  he  is  a  talented  young  man 
who  might  even  aspire  to  become  a  commercial 
operator.  To  some  of  the  amateurs  them- 
selves, who  have  taken  their  degrees  as  feature 
writers  disseminating  the  gospel  every  Satur- 
day afternoon  in  the  radio  supplements,  the 
amateur  is  the  inventor  of  radio,  from  the 
antenna  insulators  to  the  ground,  in  the  past; 
its  generous  and  disinterested  supporter  in  the 
present;  and  its  only  hope  in  the  future.  To 
several  score  of  other  witnesses  he  is  several 
score  of  other  things. 

The  dictionary,  with  its  definition  of  an 
amateur  as  "one  who  is  attached  to  or  culti- 
vates a  particular  pursuit,  study,  or  science 
from  taste,  without  pursuing  it  profession- 
ally," helps  us  but  little.  1  venture  to  assert 
that  from  one  third  to  one  half  of  all  the 
"amateur"  radio  men  in  the  United  States 
are  making,  or  trying  to  make,  money  in  the 
radio  field,  although  not  directly  out  of  their 
activities  as  amateurs.  That  is,  they  make  no 
money  out  of  their  radio  telegraph  activities, 


but  they  keep  radio  shops  or  service  receiving 
sets  or  run  broadcasting  stations  for  pay.  Yet 
they  remain  amateurs  in  excellent  standing. 
Now  we  are  beginning  to  see  light.  An  ama- 
teur, in  radio,  is  a  person  who  experiments 
gratuitously  with  transmitting  sets — gener- 
ally radio  telegraph  transmitters — and  with 
receivers  adapted  for  communication  with 
transmitting  sets  so  tended;  but  who  is  free, 
without  prejudice  to  his  amateur  standing,  to 
make  all  the  money  he  can  out  of  radio  other- 
wise. If  he  telegraphs  around  the  country 
with  just  one  set,  and  receives  ditto,  purely 
for  the  love  of  it,  then  his  standing  as  a  radio 
amateur  is  secure,  and  he  can  collect  all  the 
cash  he  is  able  to  get  in  any  other  radio  activi- 
ties whatsoever.  It  is  a  unique  conception, 
and  as  far  as  I  know,  peculiar  to  radio.  The 
jealous  differentiation  between  amateur  and 
professional  which  prevails  in  athletics,  for 
example,  is  entirely  absent  in  radio.  The 
boys  out  in  the  wheat  belt,  nursing  along  their 
five-watters  because  they  can't  afford  replace- 
ments until  they  save  up  some  more  pocket 
money,  and  Mr.  E.  H.  Armstrong,  who  has 
realized  an  amount  said  to  run  into  six  figures 
in  royalties  from  his  radio  inventions,  both 
claim  the  title  of  amateur,  and  are  equally 
proud  of  it. 

The  fact  is  that  one  must  look  on  amateur 


The  Magic  of  Dots  and  Dashes 


501 


radio  as  a  species  of  freemasonry.  The  spirit 
of  fellowship  and  brotherly  sympathy  is  cer- 
tainly there.  If  you  don't  believe  it,  attack 
the  amateurs  singly,  or  en  masse,  and  see  what 
happens  to  you.  They  are  a  scrappy  lot, 
and  if  they  ever  fall,  they  will  fall  together. 
They  have  other  lodgecharacteristics.  They  de- 
light in  titles,  such  as  "Traffic  Manager,  Delta 
Division."  These  titles,  while  undoubtedly 
they  mean  something,  and  frequently  involve 
a  lot  of  work  in  the  way  of  staying  up  until 
4  A.  M.  relaying  messages  and  preparing  re- 
ports, do  not  carry  quite  as  much  weight  or 
responsibility  as  the  corresponding  position 
in  a  quarter  billion-dollar  corporation.  These 
dignitaries  are  somewhat  on  the  order  of  the 
Grand  Omnipotent  Ruler  of  a  lodge;  he  may 
be  grand  and  all,  but  he  isn't  really  omnipo- 
tent. And  they  write  numbers  and  letters 
after  their  names,  such  as  "Marcus  Gavotte, 
12  GHQ,"  which  astound  and  flabbergast  the 
laity,  who  imagine  that  these  mystic  designa- 
tions are  so  many  Ph.  D.'s  and  Orders  of  the 
Bath,  if  not  Congressional  Medals  of  Honor. 
(As  I  write  these  sentences  I  can  visualize 
innumerable  Division  Managers  glowering  at 
me  across  the  country  and  sitting  down  at 
their  "mills"  to  write  me  fiery  letters.  Peace, 
gentlemen!  Before  I  get  through  you  will 
hear  such  praise  of  your  fraternity  that  your 
only  impulse  will  be  to  catch  the  first  train  to 
Garden  City  for  the  purpose  of  decorating 
and  embracing  me.) 

The  telegraph  code  itself,  while  invented 
purely  for  the  purpose  of  communication  by 
symbols,  and  so  used  commercially,  becomes, 
in  the  hands  of  the  amateurs,  a  medium  with 
something  ritualistic 
about  it,  fulfilling  a  func- 
tion not  unlike  that  of 
ceremonies  and  liturgies 
in  secret  orders.  Is  the 
comparison  far-fetched? 
If  so,  why  do  the  ama- 
teurs use  their  lingo  or- 
ally and  in  writing,  at 
every  opportunity?  It 
is  impossible  for  one 
saturated  amateur  to 
write  to  another  in  Eng- 
lish; they  get  to  a  point 
where  they  must  express 
everything  in  pigeon- 
Phillips  (code)  and  Con- 
tinental abbreviations. 
I  should  not  be  sur- 
prised to  hear  of  one 


office  of  another  and  asking  him  for  a  job  in 
these  words:  "Sa  OM  QRW?  I  am  QRXing 
for  a  job.  QRU?  Nil?  Sorri  tks  j^s  c  u 
agn  gb  gb  dit  dit  dit  dah  dit  dahhh".  This 
lingo  is  not  used  merely  for  brevity  and  con- 
venience; it  is  also  a  philological  toy,  posses- 
sion of  which  sets  one  off  from  the  common 
herd.  I  am  not  immune  myself.  I  have  in 
my  office  a  key-and-buzzer  telegraph  which 
communicates  with  other  departments  of  the 
station,  and,  while  its  use  is  largely  limited  to 
acting  as  a  calling  device  for  a  telephone  line, 
I  have  noticed  that  it  excites  the  admiration 
of  lay  visitors.  No  matter  how  busy  I  am, 
I  am  rarely  able  to  resist  the  temptation  to 
exchange  reminiscences  with  an  old  operator, 
to  dwell  sentimentally  on  the  never-to-be- 
forgotten  note  of  HA,  and  to  brag  about  the 
time  when  I  could  copy  35  a  minute  in  10- 
letter  code. 

But,  aside  from  these  factors,  undeniably 
there  is  a  certain  magic  in  dots  and  dashes. 
There  is  a  rhythm  and  lilt  to  the  sending  of  a 
good  operator  which  is  capable  of  producing  a 
definite  esthetic  response  in  a  trained  listener. 
It  is  even  possible  to  put  across  rudimentary 
emotional  states  by  variations  and  shading  in 
the  style  of  transmission.  Even  a  novice  can 
tell  when  the  man  at  the  other  end  of  the  cir- 
cuit is  impatient  or  angry  or  confused.  Styles 
of  sending  are  as  numerous  as  the  shapes  of 
men's  ears,  and  as  varied  as  their  ways  of 
walking  and  talking.  Many  amateurs,  as 
well  as  professionals,  are  connoisseurs  of  the 
subtleties  of  code  work.  Many  others — 
probably  the  majority — are  and  will  always 
remain  rotten  operators,  just  as  the  majority 


5O2 


Radio  Broadcast 


of  people  who  learn  to  play  the  piano  simply 
learn  to  murder  the  instrument  and  the  music. 
There  are  always  more  dubs  than  artists. 
That  there  are  artists  among  amateur  radio 
telegraphers,  no  one  who  has  any  feeling  for 
these  matters  will  attempt  to  deny. 

Neither  would  I  deny  that  the  traffic  men  of 
the  American  Radio  Relay  League  sometimes 
try  just  as  hard  to  get  a  message  through  as 
any  commercial  operator.  But  not  one  out  of 
500  such  messages  means  anything.  When 
anybody  has  a  message  he  wants  delivered,  he 
gives  it  to  a  commercial  telegraph  company. 
The  difference  between  the  work  of  the  ama- 
teurs and  that  of  commercial  interests  is  the 
difference  between  a  sham  battle  and  a  real 
one. 

A  great  deal  has  been  written  about  the  in- 
genuity of  amateurs  and  experimenters  in 
building  their  own  sets,  transmitting  and  re- 
ceiving. It  is  true  that  some  of  them  show 
immense  skill,  but  things  should  be  called  by 
their  proper  names,  and  it  is  a  fact  that  no 
amateur,  experimenter,  or  other  isolated 
individual  is  in  a  position  to  build  even  a 
simple  radio  set.  He  can  only  assemble  one 
out  of  factory-built  parts.  What  amateur  or 
radio  fan  makes  his  own  audio  transformers, 
vacuum  tubes,  telephone  receivers,  plugs  and 
jacks,  bakelite  panels?  It  is  purely  an  as- 
sembly and  wiring  proposition.  The  creative- 
ness  of  the  amateur,  therefore,  is  at  best  a 
secondary  one. 

Liberally  mixed  with  hokum,  also,  are  the 
vast  and  all-embracing  claims  made  for  the 
inventive  genius  of  the  amateur.  To  read 
some  of  these  narratives,  one  would  think 
that  radio  had  sprung  full  grown  out  of  the 
foreheads  of  a  lot  of  sixteen-year-old  geniuses. 
What  first-rate  radio  invention  has  been  made 
by  an  amateur?  The  work  of  Armstrong  will 
immediately  be  cited.  But  at  the  time  that 
Armstrong  was  doing  his  early  work  on  re- 
generative circuits  he  was  a  student  at  Colum- 
bia University  and  had  the  run  of  the  unex- 
celled Marcellus  Hartley  electrical  laboratory 
on  Morningside  Heights.  He  did  not  yet  have 
the  degree,  but  he  was  already  a  distinguished 
electrical  engineer  in  every  other  respect. 
However,  instead  of  laboring  the  point,  let  us 
classify  Major  Armstrong's  early  work  as  an 
amateur  achievement.  What  then?  One 
swallow  does  not  make  a  summer.  What 
other  first-rate  radio  inventions  have  come 
out  of  amateur  circles?  How  many  second 
and  third-rate  innovations,  even?  I  know  of 
few,  very  few.  The  unromantic  fact  is  that 
most  of  the  inventions  that  have  brought  the 


art  to  its  present  level  have  come  out  of  well- 
equipped  physical  laboratories,  after  develop- 
ing from  the  ideas  of  trained  investigators  and 
engineers.  A  great  number  have  originated 
in  the  research  departments  of  great  industrial 
corporations,  thence  percolating  down  to  the 
amateurs.  The  business  of  invention  and 
research  has  become  highly  intricate,  and  is 
no  longer  carried  on  to  the  best  advantage  in  a 
garret. 

So  much  for  the  negative.  Now  let  us  give 
credit  where  credit  is  due.  Given  the  incep- 
tive ideas,  the  amateurs  have  again  and  again, 
with  immense  industry  and  ingenuity,  de- 
veloped fields  of  radio  scarcely  touched  by 
other  interests.  The  present  short-wave  fever 
is  an  instance.  The  value  and  specific  utility 
of  the  very  high  frequencies  is  still  only 
partly  determined,  but  at  any  rate  research 
in  this  field  will  yield  interesting  and  important 
data.  Men  like  Reinartz  and  Schnell  are 
among  the  leaders  in  this  experimenting.  If 
they  do  not  initiate  the  great  theoretical  and 
practical  advances,  the  amateurs  do  un- 
doubtedly mop  up  brilliantly  in  the  immedi- 
ate wake  of  the  pioneers.  Let  an  idea  be 
published,  and  immediately  a  few  thousand 
of  them  are  at  work  squeezing  the  juice  out  of 
it,  trying  out  all  the  variations,  and  showing 
that  it  can  be  made  out  of  tin  cans  and  empty 
tooth  paste  tubes. 

Secondly,  amateur  experience  is  an  excellent 
preparation  for  commercial  activity  in  the 
radio  field.  Look  up  copies  of  the  radio 
magazines  of  1910  to  1914,  and  you  will  dis- 
cover the  names  of  many  prominent  engineers, 
commercial  men,  and  operators  of  to-day 
signed  to  amateur  articles.  In  another  decade 
many  of  the  younger  amateurs  of  to-day  will 
be  running  the  works. 

In  time  of  emergency,  this  process  is  con- 
siderably expedited.  During  the  last  war, 
the  signal  services  of  both  the  army  and  the 
navy  drew  a  sizable  proportion  of  their  per- 
sonnel from  the  ranks  of  the  amateurs.  Some 
of  these  men  required  no  training.  Others 
needed  only  a  fraction  of  the  training  which 
would  otherwise  have  been  necessary.  The 
time  thus  gained  was  precious.  Similar 
emergency  service  may  be  rendered  by  the 
amateurs  in  time  of  earthquakes,  floods,  or 
other  disasters.  A  country  with  fifteen  or 
twenty  thousand  more  or  less  skilled  tele- 
graphers and  radio  signal  men  available  as 
reserves  behind  the  professional  operating 
staffs,  is  that  much  better  off  when  communi- 
cations get  into  a  jam. 

Thirdly,  the  amateurs  are  amusing  them- 


Day-time  and  Night-time  Reception 


503 


selves,  instead  of  paying  someone  to  amuse 
them.  They  are  playing  ball,  instead  of 
watching  someone  else  do  it  for  $20,000  a  year. 
Even  if  their  activities  were  purely  recrea- 
tional, they  could  be  amply  justified.  It  is  a 
good  thing  to  get  one's  fun  through  one's  exer- 
tions, rather  than  to  have  it  served  up,  cooked 
and  predigested,  on  a  platter.  Let  us  dust  the 
earth  with  our  hats  in  salutation  to  these 
young  men  who  reach  out  six  thousand  miles, 
across  seas  and  continents,  for  their  amuse- 
ment. 

Why  Summer  Broadcasting  is  Better 

ANOTHER  reason  for  cleaving  to  radio 
throughout  the  summer,  the  argument 
in  this  case  being  addressed  to  sym- 
phony concert  listeners: 

A  large  orchestra  sounds  better,  by  direct 
audition,  indoors  than  outdoors.  The  brilli- 
ancy of  the  strings  is  superior,  and  much 
detail  is  perfectly  clear  indoors,  where  it  is 
partially  lost  outdoors  except  to  those  mem- 
bers of  the  audience  who  have  seats  well  up 
front.  (This  is  for  the  connoisseurs  and  great 
musical  sharks;  probably  most  listeners  would 
not  make  the  distinction.)  But,  by  radio, 
a  big  outdoor  orchestra  is  usually  better  than 
the  same  orchestra  in  an  auditorium,  owing 
to  the  relative  absence  of  reverberation. 
Hence,  for  the  best  symphonic  radio  music, 
listen  during  the  summer.  You  will  get  good 
stuff  all  year  around,  but  the  summer  has,  as 
the  sporting  writers  say,  the  edge. 

Daylight  Broadcast  Reception 

MR.  ALEXANDER  L.  SHERIDAN  of 
South  Raub,  Indiana  considers  the 
night-day  ratio  of  signal  strength, 
quoted  on  page  76  of  the  May  issue,  as  too 
high.  This  figure,  it  will  be  remembered,  was 
quoted  from  the  well-known  paper  of  Nichols 
and  Espenschied,  wherein  it  appeared  that 
the  power  of  a  broadcasting  station  would 
have  to  be  multiplied  by  a  figure  of  the  order 
of  10,000,  in  order  for  it  to  supply  the  same 
signal  at  a  distant  point  during  daylight  as 
the  signal  received  at  that  point  during  the 
best  times  at  night.  With  a  standard  super- 
heterodyne receiver,  using  external  loop  and 
outside  antenna  combinations,  Mr.  Raub  is 
able  to  hear  WGY,  WCAE,  and  KDKA,  day  and 
night.  At  the  time  he  wrote  (April),  WEAF, 
800  miles  away,  was  audible,  although  not 
quite  understandable,  at  noon.  During  the 
preceding  December,  and  January,  states  Mr. 


Raub,  he  was  able  to  hear  WEAF  on  a  loud 
speaker  any  time  after  2.30  P.M.  S.  C.  T.,  and 
to  determine  the  nature  of  the  material 
broadcast.  WEAF'S  power  at  this  time  was 
1.5  or  2.0  kw.  Accordingly,  our  correspon- 
dent does  not  believe  that  the  discrepancy 
between  day  and  night  reception  is  as  high  as 
reported. 

These  observations  are  very  interesting, 
and,  certainly,  data  on  daylight  reception  is 
most  welcome,  being  rather  scarce  in  the 
broadcast  field.  However,  there  is  little  in 
the  above  data  to  discredit  the  observations 
of  Messrs.  Nichols  and  Espenschied,  and 
any  one  who  knows  these  engineers  and  their 
methods  of  procedure  would  hesitate  a  long 
time  before  challenging  any  of  their  results. 
In  our  quotation  we  were  careful  to  retain  the 
qualifying  clause  relative  to  "the  best  times 
at  night,"  those  periods,  that  is,  when  the 
signal  rises  to  a  peak  value  based  on  an 
inversely-as-the-first-power-of-the-distance  at- 
tenuation. Normally  the  received  signal 
drops  off  according  to  a  higher  power,  owing 
to  the  absorption  it  encounters  along  the  way. 
Sometimes,  at  night,  through  the  fortuitous 
and  uncontrollable  action  of  meteorological 
forces  in  the  great  open  spaces,  this  absorption 
is  wiped  out  for  a  few  seconds.  These  are  the 
crowded  moments  for  which  the  DX  hunter 
prays;  their  occurrence  is  his  glory,  their 
brief  duration  and  rareness  make  him  miser- 
able. All  that  Messrs.  Nichols  and  Espen- 
schied said  was  that  to  duplicate  that  transi- 
tory night  peak  with  a  continually  serviceable 
daylight  signal  of  the  same  strength,  over  the 
same  distance,  you  would  need  10,000  times 
as  much  power.  I  believe  you  would.  All 
that  Mr.  Raub  has  shown  is  that,  given  the 


tne.y  learn  ~ko  murder  tL.e  instrument 


504 


Radio  Broadcast 


almost  incredible  sensitivity  of  the  modern 
super-heterodyne,  one  can  hear  the  higher- 
powered  broadcasters  over  very  considerable 
ranges  in  daylight,  a  fact  which  no  one  will 
dispute. 

It  should  be  noted  that  in  this  discussion 
the  important  distinction  between  hearing  a 
signal  well  enough  to  log  it,  and  getting  it  well 
enough  to  justify  use  of  the  term  "program 
service,"  has  not  yet  been  introduced.  At  the 
risk  of  wearying  our  readers,  we  once  more 
point  out  the  necessity  of  clearly  understand- 
ing what  we  are  talking  about  in  this  respect. 
The  interest  of  this  department,  and  our 
whole  manner  of  thinking  about  radio  prob- 
lems, generally  centers  about  program  service 
rather  than  catching  on  the  fly  some  distorted 
sounds  which  are  here  now  and  gone  the  next 
minute.  This  is  not  to  say  that  one  cannot 
have  a  lot  of  fun  with  DX  signals;  a  few  mil- 
lion people  are  ready  to  testify  that  one  can. 
But  the  serious  development  of  radio  is  clearly 
in  the  direction  of  immaculate  program  service 
for  an  ever  increasing  number  of  people.  By 
such  service  we  mean  a  signal  of  about  phono- 
graph volume,  at  least  as  good  as  the  best 
phonograph  quality,  and  free  from  annoying 
disturbances,  natural  and  artificial.  Hence 
the  trend  toward  higher  powers.  Hence 
the  usefulness  of  quantitative  data  covering 
both  day  and  night  conditions  in  broadcast 
reception. 

The  Memoirs  of  a  Radio  Engineer,  1 1 1 

(Continued  from  the  July  Number) 

OCCASIONALLY  rumors  came  our 
way  of  the  wonders  and  potentialities 
of  "wireless."  A  seventeen-year-old 
cousin  of  a  friend  of  a  member  of  the  gang 
was  said  to  be  telegraphing  across  his  back- 
yard in  Yonkers,  without  the  use  of  wires  be- 
tween the  two  stations,  although  there  was 
plenty  of  wire  at  either  end.  Another  en- 
thusiast had  erected  an  antenna  on  his  roof 
and  was  engaged  in  what  he  called  transmis- 
sion, using  a  spark  coil,  until  his  mother  hap- 
pened to  come  in  contact  with  that  antenna 
while  she  was  engaged  in  hanging  out  the 
wash.  His  experiments  were  abruptly  ter- 
minated, and  the  subsequent  spanking  was 
said  to  have  been  of  volcanic  violence.  An- 
other inventor,  according  to  reports,  was  en- 
gaged in  destroying  nickels,  and  even  a  dime, 
with  a  file,  in  an  endeavor  to  construct  a 
"coherer."  We  did  not  know  what  the 
coherer  was  supposed  to  do,  but  we  were 
agreed  that  the  only  explanation  of  the  experi- 


menter's conduct  was  madness.  Would  any 
sane  boy  attack  a  dime  with  a  file? 

Nevertheless,  we  were  not  sure.  Possibly 
the  fellow  expected  to  realize  some  special 
raptures  through  his  sacrifice.  Wireless  began 
to  appeal  to  our  imaginations.  Thereupon, 
of  course,  we  were  lost.  We  had  to  have  a 
"wireless." 

We  secured  a  piece  of  glass  tubing,  two 
nails,  and  a  nickel.  Securing  some  filings 
from  the  coin,  we  placed  them  between  the 
two  nails,  and,  according  to  the  books,  we  had 
a  coherer.  An  electric  bell,  wired  for  single 
stroke  operation,  was  the  decoherer.  But  we 
had  no  relay,  and  there  was  not  the  slightest 
chance  of  acquiring  one.  Furthermore,  there 
was  no  transmitter,  and  therefore  nothing  to 
receive.  Finally,  while  it  was  possible  to  get 
clear  and  detailed  information  from  the  boy 
electrician  books  about  batteries,  sounders, 
motors,  and  the  like,  the  data  on  wireless  was 
fragmentary,  and  we  suspected  that  the  au- 
thors knew  little  more  about  it  than  we  did. 
After  a  period  of  despair,  we  were  saved  by  a 
description  of  an  "auto-coherer,"  consisting 
of  a  carbon  and  a  steel  rod  in  contact  with  a 
drop  of  mercury  within  a  glass  tube.  It  was 
said  to  have  been  invented  by  Marconi,  and 
to  be  in  use  in  the  Italian  Navy.  The  virtue 
of  this  instrument  was  that  it  was  sensitive 
and  would  operate  a  telephone  receiver.  We 
had  two  seventy-five-ohm  receivers  of  the 
"watchcase"  type;  one  of  the  boys  had  got 
them  as  a  Christmas  present,  and  we  had 
constructed  a  primitive  telephone  line  with 
them  in  the  intervals  of  our  telegraphing. 
The  materials  for  the  auto-coherer  were  ob- 
tainable. The  nail  and  glass  tube  we  had. 
With  a  hacksaw  blade  we  cut  a  carbon  rod  out 
of  an  old  dry  battery  carbon,  and  filed  it  down 
to  approximate  roundness.  The  physics 
teacher  in  the  elementary  school  gave  us  a  few 
drops  of  mercury.  To  our  delight  and  as- 
tonishment, the  detector  worked.  The  tele- 
phone receiver  being  connected  to  it,  the  dis- 
charge of  a  Leyden  jar  in  the  next  room  could 
be  heard  as  a  distinct  click.  One  could  send 
dots  with  it,  but  no  dashes.  We  arranged  a 
set  of  signals  on  this  basis.  In  order  to  send 
even  one  dot,  of  course,  it  was  necessary  to 
charge  the  Leyden  jar  with  the  electrophorus, 
which  took  several  minutes.  It  was  not  high 
speed  telegraphy,  but  it  was  "wireless,"  un- 
deniably. 

We  now  heard  of  a  still  simpler  and  even 
more  sensitive  form  of  detector  of  the  micro- 
phonic  type.  This  consisted  of  two  steel 
needles,  stuck  into  a  piece  of  wood  and  pro- 


Rocking  the  Cradle  of  Radio 


505 


vided  with  leads,  and  a  piece  of  pencil  lead 
laid  across  them.  It  worked  with  a  telephone 
and  a  local  battery.  It  was  said  that,  placed 
on  a  cigar  box,  it  would  register  the  noise  made 
by  a  fly  walking  across  the  box.  We  placed  it 
in  this  position  and  waited  patiently  for  a  fly 
ta  promenade  thereon.  But  the  flies  were 
wary.  It  was  necessary  for  us  to  catch  a 
beetle,  and,  indeed,  he  was  quite  audible  in  the 
telephone  receivers  as  he  scampered  off  the 
box.  But  this  was  not  wireless,  we  realized. 
It  was  a  digression. 

At  this  time  (early  in  1909),  there  were  al- 
ready wireless  amateurs  who  had  reached  a 
stage  much  in  advance  of  ours.  In  the  same 
year  they  founded  the  "Junior  Wireless  Club, 
Ltd,"  with  headquarters  at  the  Hotel  Ansonia, 
where  the  President,  W.  E.  D.  Stokes,  Jr.,  had 
his  home  and  antenna.  The  history  of  this 
group  was  graphically  described  by  my  friend 
George  Burghard,  now  President  of  the  Radio 
Club  of  America,  in  "Eighteen  Years  of 
Amateur  Radio,"  (RADIO  BROADCAST,  August, 
1923).  These  were  the  genuine  amateur  radio 
pioneers  in  the  East.  Some  of  these  boys  had 
started  experimenting  as  early  as  1905.  They 
were  about  four  years  ahead  of  us,  and  some 
five  years  behind  the  commercial  radio 
pioneers  of  this  country.  Our  group  in  upper 
New  York  might  therefore  be  classified  as 
part  of  the  third  pioneering  migration  with 
some  of  the  ground  already  cleared  and  the 
Indians  no  longer  on  the  offensive.  But  we 
were  on  our  own.  We  had  no  contacts  with 
the  West  Side  aristocracy  of  radio  amateurs, 
whose  resources  and  facilities  were  far  superior 
to  ours,  enabling  them  to  establish  two-way 
communication  over  distances  up  to  a  mile  at 
about  this  period. 

However,  we  heard  of  an  amateur  about  a 
third  of  a  mile  from  our  location,  who  had  a 
transmitting  set  consisting  of  an  antenna,  a 
spark  coil,  spark  gap,  key,  and  battery.  He 
was  languishing  for  someone  to  listen  to  him. 
If  we  would  put  up  an  antenna,  he  would  send 
to  us.  This  appealed  to  us  irresistibly.  We 
secured  two  poles,  one  about  fifteen  feet  long, 
which  we  placed  on  the  roof  of  the  two  story 
frame  house  in  which  I  lived,  and  a  somewhat 
longer  one  which  we  were  allowed  to  erect  on 
the  roof  of  a  barn  some  sixty  feet  distant. 
Between  these  poles  we  swung  a  4-wire  an- 
tenna of  the  flat-top  type,  not  much  different 
from  those  now  in  use.  The  wire  was  No.  18 
annunciator;  broomsticks  served  as  spreaders, 
and  the  insulators  were  porcelain  cleats.  The 
lead-in  ran  into  my  mother's  kitchen,  and  we 
obtained  a  ground  on  the  water  faucet.  One 


•  in  sudden  contact  wi£k  iKe  antenna 

afternoon  in  June  the  great  experiment  came 
to  a  climax.  Our  steel  needle-pencil  carbon 
detector  was  connected  to  the  antenna  and 
ground,  in  parallel  with  the  battery  and  tele- 
phone. The  latter  was  pressed  to  the  ear  with 
the  hand;  we  had  no  headband.  Tuning 
there  was  none.  The  combination  was  prob- 
ably aperiodic,  or  nearly  so,  and  would  respond 
to  a  wide  band  of  frequencies,  given  a  signal 
strong  enough.  It  worked  as  soon  as  it  was 
put  together.  We  had  arranged  to  use  the 
call  "YF,"  and  the  first  fellow  to  put  the  tele- 
phone to  his  ear  heard  the  tripping  Morse 
accents  of  the  transmitting  operator  up  on 
Prospect  Avenue.  A  look  of  ineffable,  joy 
overspread  the  face  of  Lamont  Whitney,  who 
was  the  first,  I  believe,  to  listen  at  our  end, 
and  we  knew  he  was  hearing  something.  (He 
is  now  chief  operator  on  the  SS.  President 
Roosevelt,  and  no  doubt  it  takes  more  than  a 
radio  signal  to  make  him  happy  now.)  With 
reluctance  he  yielded  the  telephone  receiver  to 
me,  and  I  heard  the  low-pitched,  perfectly 
clear  buzzing  of  the  spark  coil  six  blocks  away. 
We  took  turns  at  listening  all  afternoon.  In 
all,  I  believe,  there  were  four  of  us.  We  also 
listened  in  the  evening,  but  heard  nothing. 
We  left  the  apparatus  connected  and  went  to 
bed,  I  in  my  room  not  far  from  the  lead-in,  and 
the  other  boys  to  their  homes. 

The  experience  of  the  afternoon,  and  tne 
proximity  of  the  wireless  receiver,  excited  me 
so  that  for  some  hours  I  did  not  sleep.  Fin- 
ally I  drifted  off.  At  about  two  o'clock  in  the 
morning  I  awoke  with  a  sense  of  impending 
disaster.  Something  had  frightened  me.  I 
sat  up  in  bed,  my  heart  thumping.  It  was  a 
hot,  sultry  night.  Suddenly  I  knew  what  it 
was.  An  ominous  distant  growling,  followed 
by  a  crash,  broke  the  stillness  of  the  night. 
A  lightning  storm  was  approaching.  I  had  a~ 


506 


Radio  Broadcast 


vague  notion  that  radio  had  something  to  do 
with  lightning,  and  that  it  was  the  proper 
practice  to  ground  the  antenna  when  not  in 
use.  This  we  had  neglected  to  do.  Actu- 
ally, of  course,  the  risk  was  infinitesimal.  The 
antenna  might  have  been  left  ungrounded  all 
through  the  thunderstorm,  and  nothing  would 
have  happened.  I  was  not  taking  nearly  as 
much  risk  as  I  did  daily  hitching  on  the  back 
of  ice-wagons,  climbing  trees,  and  fighting. 
But  how  was  I  to  know  this?  I  visualized 
the  antenna  on  its  long  poles  sticking  up  pro- 
vocatively above  the  roof  of  the  house,  and  all 
the  time  the  storm  was  coming  nearer,  the 
lightning  lit  up  the  room  with  ghastly  blue 
flashes,  and  the  thunder  began  to  shake  the 
windows.  It  seemed  to  me  that  inevitably 
the  lightning  must  hit  that  antenna  and  the 
house,  with  my  father,  mother,  and  sister, 
would  all  be  incinerated.  My  teeth  chattered; 
I  was  sick  with  fright.  The  thing  to  do,  I 
realized,  was  to  get  up  and  ground  the  antenna 
before  the  storm  came  any  nearer,  but  I  was 
afraid  to  go  near  the  lead-in.  I  was  a  boy 
of  thirteen,  in  conflict  with  stupendous  cosmic 
forces.  I  began  to  whimper.  My  parents, 
sleeping  in  the  next  room,  had  also  been 
awakened  by  the  storm,  and  they  soon  heard 
me.  My  father  appeared  in  his  nightshirt 
and  demanded  the  cause  of  my  tears.  I  in- 
formed him,  sobbing,  that  the  house  was  about 
to  be  struck  by  lightning.  He  immediately 
understood  that  there  was  some  connection 
between  the  antenna  and  my  fear  of  lightning 
a  thing  which  had  not  occurred  to  him  before, 
or  probably  he  would  not  have  permitted  the 


erection  of  the  antenna.  The  gas  was  lit/ 
the  whole  family  was  aroused,  and  stood  about 
quaking;  my  father  was  angry  and  denounced 
me  as  a  young  fool  in  tones  which  rivaled  the 
thunder.  This  aroused  my  resolution.  I 
leaped  suddenly  out  of  bed  and  charged  across 
the  hall  to  do  or  die.  I  grasped  the  antenna 
wire  frantically — and  nothing  happened.  I 
was  not  electrocuted,  not  even  a  spark  leaped 
to  my  hand.  Tearing  the  wire  from  its  con- 
nection to  the  detector,  1  wrapped  it  around 
the  water  pipe,  just  before  my  father  collared 
me  and  dragged  me  away  from  the  set.  The 
storm  passed  over  and  faded  into  the  distance: 
with  it,  the  alarm  subsided,  and  my  family 
went  back  to  bed.  My  father  lectured  me  at 
length  the  next  day,  but  he  allowed  the  an- 
tenna to  remain  up,  having  received  assurances 
from  other  sources  that  it  was  not  dangerous. 
But  I  was  compelled  to  swing  the  lead-in  from 
the  kitchen  down  to  a  small  storage  house  in 
the  yard.  And  there,  for  reasons  to  appear, 
we  had  no  further  success  in  our  wireless  ex- 
periments. 

I  have  recounted  this  hysterical  scene,  not 
only  for  the  amusement  of  my  readers,  but  to 
show  what  a  part  unreasoning  fear  plays  in  the 
psychology  of  people  whenever  they  are  faced 
by  anything  unknown.  Since  those  days, 
millions  of  antennas  have  been  erected  and 
used  without  damage  from  lightning.  They 
are  no  more  dangerous  than  telephone  or 
electric  light  service  wires.  For  half  a  dollar 
one  gets  a  lightning  arrester  which  supplies  all 
the  protection  needed.  But  things  were 
different  in  1909.  (To  be  continued). 


I  tore  tlie  -wire  off  the  detector 


The  Power  of  Broadcasting 
Stations 

ANEW  broadcasting  station  an- 
nounces:    "While    rated    at 
looo  watts,  the  actual  power 
attained  when  voice  or  music  are  in 
the  air  will  reach  a  peak   of   2500 
watts."     And  so  the  press   releases 
speak   of   the  purchase  of  "a  new 
25OO-watt     .     .     .     transmitter." 

On  that  basis  it  would  be  just  as 
reasonable  to  rate  the  set  at  250 
watts.  For,  each  time  that  a  2500 
watt  peak  is  reached  for  y^V^  second 
or  thereabouts,  in  the  next  TTfW 
second  the  power  will  drop  to  about 
zero.  The  method  of  operation  of 
the  Heising  system  of  modulation  is 
that  the  modulating  power  is  alter- 


How  Much  Should  the  Carrier  be  Modulated? 


507 


nately  added  to  and  subtracted  from  the 
carrier  power.  Thus  the  average  or  effective 
radiating  power  is  that  of  the  unmodulated 
carrier,  and  the  carrier  power  is  the  proper 
rating  of  the  station. 

A  corollary  question  which  arises  is:  How 
much  should  the  carrier  be  modulated?  My 
own  answer  would  be:  80  per  cent,  on  the 
highest  peaks.  No  higher,  for  if  this  figure  is 
exceeded  over-modulation  will  inevitably 
result  at  times.  With  a  20  per  cent,  margin, 
one  can  reduce  accidental  over-modulation 
so  that  it  is  very  rare.  Nor  should  the  per- 
centage of  modulation  be  much  below  a 
maximum  of  80  per  cent.,  for  two  reasons. 
First,  the  loss  in  signal  strength;  secondly,  the 
fact  that  in  the  receiving  .set  the  carrier 
amplifies  any  disturbances  that  may  happen 
to  be  floating  around,  more  or  less  in  propor- 
tion to  its  amplitude,  regardless  of  the  modula- 
tion. If,  therefore,  a  station  has  a  strong 
carrier  field  at  any  point,  weakly  modulated, 
it  is  amplifying  disturbances  to  the  disad- 
vantage of  its  own  signal.  The  80  per  cent, 
figure  steers  a  course  between  the  devil  and  the 
deep  sea. 


Microphone  Miscellany 


THE    MIRACULOUS    MR.    BURROWS 

TEM  from  the  New  York  Times  of  May  8th: 

Geneva,  May  7  (A.  P.) — Broadcasting  by  private 
European  companies  will  be  regulated  from  Geneva, 
with  the  arrival  here  to-day  of  Arthur  Burrows,  an 
Englishman,  who  has  been  appointed  mediator  for 
all  broadcasting  companies. 

His  special  mission  is  to  prevent  the  clashing  of 
wavelengths  and  consequent  interference  of  aerial 
concerts  with  each  other.  Geneva  was  chosen  for 
the  base  of  operations  because  of  its  steady  growth 
as  an  international  centre  and  its  central  geographi- 
cal position. 

Burrows  expects  to  produce  order  out  of  the 
chaos  that  has  disturbed  European  listeners-in. 

This  is  delightful  indeed.  Here  we  are 
breaking  our  heads  over  this  situation,  and  a 
solution  is  ready  at  hand.  If  Mr.  Burrows 
can  perform  as  predicted,  we  propose  that  he 
be  invited  to  the  United  States  and,  the 
constitutional  inhibition  on  a  foreign-born 
president  being  waived,  he  may  be  voted  to 
that  office  by  acclamation.  He  can  then  pro- 
ceed to  iron  out  the  new  stations-no  wave- 
lengths problem  which  has  our  Department  of 
Commerce  so  worried,  and  he  will  rank  among 


I  took  ilie  child  from  "the "mike" 


Presidents    with    George    Washington    and 
Abraham  Lincoln. 

THE    EPIC   OF   THE    LITTLE    CHILD 

HASTILY  written  report  of  a  field  operator 
at  wjz  in  explanation  of  noise  interfer- 
ence at  the  beginning  of  a  hotel  music  pro- 
gram: 

At  the  beginning  of  the  first  number  a  little 
child  got  to  rattling  the  mic.  stand  and  pulling  the 
mic.  cord  and  I  not  being  able  to  see  it  I  didn't  know 
what  the  matter  was  but  was  put  on  the  air  again 
and  I  discovered  the  trouble  and  cleared  the  trouble 
by  taking  the  child  away  from  the  mic. 

Brutal  field  operator!  We  hope  the  child's 
mother  broke  a  soup  tureen  over  the  operator's 
head. 

Who  Will  Lay  It?  A  gentleman  wrote  to  a 
broadcasting  station  inquiring  whether  any  one 
had  thought  of  using  a  submarine  cable  to 
bring  broadcast  material  from  Europe  to  the 
United  States,  thence  to  be  re-broadcast  from 
American  stations.  Some  harassed  member 
of  the  technical  staff  answered  that  the  idea 
was  not  feasible,  for  the  electrical  characteris- 
tics of  existing  types  of  long  cables  were  such 
that  they  would  not  transmit  the  rapid  varia- 
tions of  speech  and  music.  Rebuttal  was  as 
follows : 

You  say  the  Atlantic  cable  cannot  be  used  to 
transmit.  Well,  let  us  lay  a  Radio  Cable  some 
concern  with  money  or  the  Government. 

Who  are  we  to  say  that  it  can't  be  done? 
Maybe  it  can.  We  will  need  $2,500,000  for 
research.  Another  $5,000,000  will  cover  the 
manufacture  and  laying  of  the  new  marvel  of 
science.  Total,  $7,500,000.  Will  some  phil- 
anthropist with  that  much  money  incommod- 
ing him  please  remit  as  soon  as  convenient? 


An  Induction  Loud 
Speaker 

The  Acoustical  and  Electrical  Characteristics  of  a  Loud  Speaker  Capable  of 
Handling  Large  Amounts  of  Energy  and  which  Produces  Sounds  of  Tremen- 
dous Volume  with  Negligible  Distortion — The  Mathematics  of  Its  Design 

BY  C.  W.  HEWLETT 

Research  Laboratory,  General_Electric  Company 

HE  loud  speaker  described  in  this  paper  cannot  be  used  for  the  purposes  of  the 
ordinary  broadcast  listener,  but  it  is  an  electrical  device  of  extraordinary  interest. 
Because  it  can  handle  such  large  quantities  of  power  and  reproduce  voice  and  music 
with  such  unusual  faithfulness,  this  device  has  attracted  a  great  deal  of  attention.  This 
paper  was  delivered  before  a  recent  meeting  of  the  Radio  Club  of  America,  in  New  York 
City  and  is  full  of  the  theory  and  mathematics  of  design,  but  it  is  an  interesting  and 
complete  presentation  of  an  excellent  piece  of  work. — THE  EDITOR 


THE  problem  of  reproducing  speech  and 
music  by  electrical  means  may  be  arbitrarily 
divided  into  four  main  parts.  The  first 
of  these  concerns  the  operation,  known 
technically  as  "pick  up."  In  this  operation,  the 
sounds  to  be  reproduced  are  allowed  to  produce 
electrical  effects  which  are  usually  quite  small. 
The  second  part  of  the  problem  concerns  the  ampli- 
fication of  the  small  electrical  effects  produced  by 
the  original  sound  waves.  The  third  part  of  the 
problem  concerns  the  transmission  of  the  electrical 
signals  from  one  place  to  another.  This  usually 
occurs  between  the  stages  of  amplification.  The 
fourth  part  of  the  problem  is  that  of  reproducing 
sound  waves  by  means  of  the  amplified  electrical 
effects.  In  case  the  transmission  is  accomplished 
by  electrical  waves  in  space,  there  is  still  another 
part  of  the  problem,  namely,  that  of  receiving  the 
signals.  This  may,  however,  be  included  in  the 
division  of  the  problem  concerning  amplification, 
because  many  of  the  considerations  involved  in  radio 
reception  are  of  a  similar  nature  to  those  involved 
in  amplification. 

This  discussion  will  concern  itself  mainly  with  the 
fourth  part  of  the  problem  as  outlined  above;  namely 
the  reproduction  of  speech  and  music  by  operating 
by  electrical  means  upon  a  particular  type  of  "loud 
speaker." 

The  loud  speaker,  which  I  shall  describe  and 
discuss,  is  known  as  the  "Induction  Loud  Speaker," 
and  has  already  been  described  in  its  essential 
features  in  previous  publications  (Phys.  Rev.  17,  p. 
257,  1921  and  19,  p.  52,  1922.  Jr.  Opt.  Soc.  Am.  4, 
p.  1059,  1922).  For  the  sake  of  completeness  I 
shall  repeat  here  a  brief  description  of  the  construc- 
tion and  principle  of  operation  of  the  instrument. 

ESSENTIALS   OF   THE    SPEAKER 

'  I  'HE  induction  loud  speaker  consists  of  two  flat 

1  circular  coils  mounted  coaxially  on  either  side 

of  a  circular  sheet  of  metal  such  as  aluminum.   Fig.  I 


shows  a  picture  of  the  parts,  and  Fig.  2  several 
models  of  the  assembled  instrument.  Each  coil  is 
made  up  of  sections  with  annular  air  spaces  between 
them.  These  sections  are  secured  to  the  wooden 
framework  by  means  of  wires  which  pass  around 
them  and  through  holes  in  the  spider.  The  sections 
are  connected  in  series  and  the  terminals  of  each 
coil  are  brought  out  to  two  binding  posts  fixed  to 
the  circular  frame.  The  circular  diaphragm  of 
aluminum  has  the  same  diameter  as  that  of  the 
circular  framework.  It  is  lightly  held  between 
the  two  frames  by  small  pieces  of  felt  placed  between 
the  diaphragm  and  each  frame  at  intervals  of  about 
3  inches  around  its  circumference.  This  method  of 
support  leaves  the  diaphragm  quite  free  to  vibrate 
through  such  amplitudes  as  are  required  of  it  and 
allows  it  to  expand  when  it  gets  hot.  It  also 
allows  a  certain  amount  of  convection  of  air  to  pass 
upward  between  the  coils  and  diaphragm  and  out  at 
the  top  between  the  frames  and  diaphragm.  The 
two  coils  shown  in  Fig.  i  are  25  inches  in  diameter, 
have  an  axial  width  of  about  ^  inch  and  contain 
about  75  pounds  of  45  mil  wire.  The  frames  and 
diaphragm  are  30  inches  in  diameter.  When 
mounted  the  coils  are  about  J  inch  from  the  alumi- 
num diaphragm,  whose  thickness  is  10  mils. 

In  operation  the  instrument  is  connected  as 
shown  in  Fig.  3. 

The  generator  sends  a  direct  current  through  the 
coils  which  are  connected  so  that  the  two  magnetic 
fields  due  to  this  current  oppose  one  another.  The 
resultant  magnetic  field  in  the  space  occupied  by  the 
diaphragm  lies  along  the  radii  of  the  diaphragm. 
The  by-pass  condensers  C  C  enable  the  voice  current 
from  the  amplifier  to  pass  through  the  two  coils  in 
multiple.  From  the  standpoint  of  the  voice  cur- 
rents, the  instrument  is  an  alternating  current 
transformer,  the  two  coils  being  the  primary  and 
the  aluminum  diaphragm  a  one-turn  secondary. 
The  alternating  current  in  the  diaphragm  distributes 


An  Induction  Loud  Speaker 


509 


itself  throughout  the  whole  diaphragm,  and  the 
flow  lines  are  circles  concentric  with  the  axis  of  the 
diaphragm,  and  consequently  are  at  right  angles  to 
the  radius  of  the  diaphragm  at  all  points.  The 
magnetic  field,  due  to  the  direct  current,  and  the 
induced  voice  currents  in  the  diaphragm,  are  there- 
fore at  right  angles  at  all  points,  and  the  diaphragm 
experiences  an  electrodynamic  force  of  the  same 
character  as  the  wave  form  of  the  voice  current. 
This  force  is  distributed  fairly  uniformly  over  the 
whole  of  the  diaphragm,  and  to  a  high  degree  of 
approximation,  the  phase  of  the  force  is  the  same  at 
all  points,  at  least  for  the  range  of  frequencies  con- 
cerned in  the  reproduction  of  speech  and  music. 

CHARACTERISTICS   OF   THE   SPEAKER 

THIS  instrument  reproduces  speech  and  music 
with  remarkable  faithfulness,  but  its  sensitive- 
ness is  much  below  that  of  the  more  usual  types  of 
sound  reproducing  devices.  On  account  of  its  size 
and  ruggedness,  however,  it  may  be  supplied  with 
large  amounts  of  power,  so  that  an  enormous  volume 
of  sound  may  be  produced.  In  fact,  the  device 
readily  lends  itself  to  the  field  of  public  address 
where  thousands  of  people  are  to  be  reached  in  large 
auditoriums,  or  even  out  of  doors. 

This  instrument  embodies  several  features  which 


are  obviously  of  great  importance  for  the  faithful 
reproduction  of  speech  and  music.  In  the  first 
place,  the  diaphragm  is  aperiodic  which,  while 
contributing  to  the  instrument's  lack  of  sensitive- 
ness, eliminates  all  distortion  due  to  resonance.  In 
the  second  place,  the  force  moving  the  diaphragm 
is  distributed  fairly  uniformly  over  its  whole  surface 
so  that  the  diaphragm  moves  as  a  whole,  there  being 
no  tendency  for  it  to  vibrate  in  segments,  which 
might  result  in  resonance  at  frequencies  correspond- 
ing to  .its  partial  vibrations.  Thirdly,  the  large 
area  of  the  diaphragm  results  in  relatively  efficient 
radiation  over  the  lower  range  of  frequencies,  with- 
out the  use  of  a  horn.  In  speech  and  many  forms 
of  music  most  of  the  sound  energy  is  carried  by  the 
lower  frequency  components,  while  the  naturalness 
of  speech  is  lost  if  these  lower  frequencies  are  not 
present  in  sufficient  quantity.  In  the  fourth  place, 
the  instrument  is  simple  and  rugged  in  construction 
and  does  not  require  any  fine  adjustments.  When 
once  put  into  operating  condition  it  will  remain  so 
indefinitely. 

OPERATION    OF    A    LARGE    DIAPHRAGM 

IN  ORDER  to  make  some  calculations  of  what  we 
•should  expect  in  the  performance  of  a  large  area 
diaphragm,  we  shall  make  certain  simplifying 


FIG.    I 


Several  of  the  Hewlitt  Induction  loud  speakers  in  a  corner  of  the 
research  laboratory  of  the  General  Electric  Company  at  Schenectady 


5io 


Radio  Broadcast 


assumptions  in  regard  to  the  boundary  conditions 
in  the  surrounding  medium,  and  in  regard  to  the 
driving  forces  acting  on  the  diaphragm. 

In  the  first  place,  we  shall  assume  that  the  dia- 
phragm moves  as  a  whole  when  vibrating.  The 
degree  to  which  this  is  realized  in  practice  depends 
upon  the  distribution  and  phases  of  the  electrody- 
namic  forces  over  the  diaphragm;  upon  the  natural 
periods  of  vibration  in  which  the  diaphragm  may 
vibrate  owing  to  its  elastic  properties;  and  upon  the 
manner  in  which  it  is  supported.  The  polarizing 
field,  which  is  radial,  is  weak  near  the  center,  but 
fairly  uniform  over  the  major  portion  of  the  dia- 
phragm. The  magnitude  of  this  component  of  the 
field  in  gauss  is  very  roughly  given  by  the  total 
ampere-turns  on  both  sides  of  the  diaphragm  di- 
vided by  the  diameter  of  the  diaphragm.  The 
induced  current  in  the  diaphragm  should  be  most 
densely  distributed  in  the  central  portion  of  the 
diaphragm  where  the  radial  field  is  the  weakest. 
Since  the  electrodynamic  force  acting  on  the  dia- 
phragm is  proportional  to  the  product  of  the  radial 
field  and  the  current  induced  in  the  diaphragm,  it 
would  seem  that  to  a  first  degree  of  approximation 
we  would  be  justified  in  assuming  that  the  force  is 
uniformly  distributed  over  the  diaphragm.  This 
assumption  neglects  whatever  phase  difference  exist 
between  the  induced  currents  in  the  different  parts 
of  the  diaphragm. 

In  regard  to  resonant  periods  the  diaphragm  is 
so  large,  and  so  loosely  held  between  the  edges  of 
the  supporting  framework,  that  the  fundamental 
period  would  be  only  a  few  cycles  per  second.  More- 
over the  restoring  force  is  so  small,  and  the  dissipa- 
tion so  great  on  account  of  the  looseness  with  which 
the  diaphragm  is  held,  that  the  partial  vibrations 
would  not  arise  with  appreciable  intensity.  The 
fact  that  the  diaphragm  is  held  around  the  edges 
should  not  affect  its  motion  very  far  from  the  edge, 
for  the  maximum  amplitudes  of  motion  under 
ordinary  conditions  of  use  would  not  exceed  i  mm. 
for  frequencies  as  low  as  30  cycles,  and  for  higher 
frequencies,  the  amplitude  falls  off  almost  as  fast  as 
the  inverse  square  of  the  frequency.  Actual  listen- 
ing tests  have  shown  that  the  quality  of  speech  or 
music  produced  by  a  large  diaphragm,  say  2  feet 
in  diameter,  suspended  by  two  strings  cannot  be 
distinguished  from  that  produced  by  one  clamped 
around  the  edges. 

INTENSITY    OF    SOUND    WAVES    FROM    A     LARGE 
DIAPHRAGM 

WE  SHALL  also  assume  that  the  diaphragm  is 
bounded  by  an  infinite  plane  which  is  at  rest, 
and  that  the  medium  extends  indefinitely  in  all 
directions  on  both  sides  of  the  plane.  In  actual 
practice,  the  instrument  is  not  bounded  by  a  large 
plane.  This  assumption  introduces  very  little  error 
into  the  calculations  we  shall  make  for  waves  short 
compared  to  the  circumference  of  the  diaphragm, 
but  when  the  length  of  the  waves  becomes  com- 
parable to  the  circumference  of  the  diaphragm, 
the  calculation  will  give  too  great  radiation,  and 
the  error  will  be  greater,  the  longer  the  waves. 
The  problem  of  calculating  the  intensity  of  the 


sound  waves  given  off  from  a  vibrating  diaphragm 
under  the  conditions  as  we  have  limited  them  has 
been  solved  by  Lord  Rayleigh.  (Theory  of  Sound, 
Vol.  II,  p.  162-169). 

The  equation  of  motion  for  a  simple  harmonic 
application  of  force  is 


maF  +  kdi 


+  n2x  =  F  cos 


where  x  is  the  displacement  of  the  diaphragm  from 
its  position  of  equilibrium,  F  is  the  maximum  value 
of  the  harmonic  force  impressed  on  the  diaphragm, 
o>  =  2T  times  the  frequency,  n2  is  the  elastic  force 
opposing  displacement  for  unit  displacement, 

m  =  mo  +  IL^  K,  (2  a  R) 

Z3          Z5  Z7 


WhemKt(i)-£lTC- 


2-32-5 


and  m0  is  the  mass  of  the  diaphragm,  p  is  the  den- 
sity of  the  air,  a  =  ?^X  is  the  wave   length  of 

the  air  vibration  set  up  by  the  diaphragm,  R  is  the 
radius  of  the  diaphragm. 


k  =  v  p 

Ji  (z)  is  the  Bessell  function  of  the  ist  order  of  z, 
and  v  is  the  velocity  of  sound. 

In  the  case  under  discussion,  the  diaphragm 
vibrates  across  a  radial  magnetic  field,  so  that  there 
is  a  magnetic  damping  force  acting  on  the  dia- 
phragm in  addition  to  that  due  to  the  emission  of 
sound  waves.  The  approximate  calculation  of 
this  effect  is  given  in  appendix  I  and  is  shown  to 
consist  of  two  force  terms,  one  multiplying  the  dis- 
placement, and  the  other  the  velocity.  Both  terms 
are  shown  to  be  negligible  compared  to  the  other 
terms  present. 

The  force  driving  the  diaphragm  arises  from  the 
interaction  of  the  radial  magnetic  field  and  the 
currents  induced  in  the  diaphragm  by  those  in  the 
coils.  In  appendix  II,  the  approximate  magnitude 
of  this  force  is  calculated  and  shown  to  be 


where  H  is  the  strength  of  the  radial  magnetic  field, 
W0  is  the  audio  power  transferred  from  the  coils  to 
the  diaphragm,  r  is  the  superficial  resistivity  of  the 
diaphragm  and  A  is  its  area.  The  square  of  the 
force  acting  on  the  diaphragm  is  thus  proportional 
to  its  area  for  definite  values  of  H,  W0>  and  r. 

Returning  to  the  equation  of  motion  of  the  dia- 
phragm we  may  calculate  the  power  expended  by 
the  driving  force  F  cos  wt. 


This  is  W= 


Estimation  of  n2  for  the  diaphragm  under  considera- 
tion shows  it  to  be  entirely  negligible  compared  to 


An  Induction  Loud  Speaker 


FIG.    2 
Various  size  models  of  the  induction  loud  speaker 


w2m  for  all  frequencies  with  which  we  are  concerned. 
The  sound  energy  radiated  each  second  then  be- 
comes 

k  P 


~  2  (K2  +  «*m») 

For  very  short  waves  this  is  radiated  almost  as  a 
beam  of  plane  waves  of  cross  section  equal  to  that 
of  the  diaphragm.  As  the  waves  get  longer,  the 
beam  spreads  out,  and  when  the  length  of  the  waves 
is  comparable  to  the  circumference  of  the  diaphragm 
the  radiation  passes  out  in  all  directions,  and  at  the 
same  time  the  above  expression  for  W  gives  too 
large  a  value  for  the  total  radiation,  because  the 
diaphragm  is  not  bounded  by  an  infinite  plane  at 
rest.  If  a  sound  measuring  device  were  placed  in 
front  of  the  vibrating  diaphragm,  and  its  indications 
taken  for  a  wide  range  of  frequencies,  these  indica- 
tions would  be  proportional  to  W,  calculated  from 
the  above  expression,  only  for  wavelengths  short 
compared  to  the  circumference  of  the  diaphragm. 
For  increasing  wavelengths  comparable  to  and 
larger  than  the  circumference,  the  indications  of 
the  measuring  instrument  would  increase  less  rapidly 
than  W  calculated  from  the  above  expression  for  two 
reasons.  First,  because  on  account  of  the  greater 
spreading  for  long  wavelengths  a  less  proportion  of 
the  energy  radiated  would  enter  the  measuring 
instrument,  and  second,  because  the  expression 
gives  too  great  a  value  for  the  radiation  at  long 
wavelengths.  This  consideration  should  be  borne 
in  mind  when  examining  the  tables  and  curves  to 


follow  showing  the  sound  energy  radiated  from  the 
diaphragms  as  a  function  of  the  frequency. 

CALCULATION    OF    SOUND    RADIATION 

''PHE  sound  radiation  will  be  calculated  for 
*  several  different  sizes  of  diaphragms.  In  order 
to  make  the  results  comparable,  we  shall  assume 
that  the  radial  magnetic  field  has  the  same  strength 
for  all  sizes  of  diaphragm.  As  is  shown  in  appendix 
III,  this  corresponds  approximately  to  dissipating 
an  amount  of  direct  current  power  proportional 
to  the  square  of  the  diameter  of  the  instrument. 
We  shall  also  assume  that  the  same  amount  of  voice- 
current  power  will  be  supplied  to  all  sizes  of  instru- 
ment, that  is,  we  shall  employ  the  full  output  of  a 
given  audio  amplifier  to  drive  all  instruments.  As 
has  been  shown,  this  means  that  the  force  actuating 
the  diaphragm  is  proportional  to  its  radius.  A 
comparison  of  the  results  so  obtained  will  favor  the 
smaller  instruments  from  the  standpoint  of  total 
sound  output,  for  the  radial  field  may  be  made 
stronger  at  a  constant  temperature  of  operation, 
and  more  audio  power  may  be  safely  supplied  to  the 
larger  than  to  the  smaller  instruments.  With  the 
same  limiting  temperature  of  operation  the  field  of 
the  largest  instrument  discussed  might  be  from  one 
to  two  times  as  great  as  that  of  the  smallest,  while 
the  audio  power  input  might  be  from  ten  to  twenty 
times  as  great,  so  that  the  total  sound  energy 
output  might  be  twenty  to  forty  times  as  great  in 
the  case  of  the  largest  instrument.  For  any  one 
instrument,  however,  these  considerations  would 


512 


Radio  Broadcast 


not  affect  the  relative  amount  of  sound  energy 
output  at  different  frequencies.  It  might  be  re- 
marked at  this  point  that  as  the  sound  energy  output 
is  proportional  to  the  product  of  the  strength  of  the 
polarizing  field,  and  the  audio  current  in  the  dia- 
phragm, and  as  the  total  power  supplied  is  limited 
by  the  allowable  temperature  rise,  the  sound  energy 
output  is  a  maximum  when  the  two  powers  are  equal 
(see  appendix  IV).  But  owing  to  the  great  disparity 
in  the  cost  of  polarizing  and  audio  power  it  is  ad- 
visable to  use  polarizing  power  to  within  a  small 
percentage  of  the  allowable  dissipation.  For  ex- 
ample, using  the  25-inch  instrument  with  800  watts 
of  polarizing  power,  and  30  watts  of  audio  power, 
the  sound  pressure  output  is  about  15  per  cent,  of 
what  it  would  be  using  415  watts  of  each  kind  of 
power. 

VALUES   OF   DIFFERENT   DIAPHRAGMS 

HpHE  calculation  has  been  carried  out  for  five 
*  different  sizes  of  diaphragm  assuming  a  uniform 
field  strength  H  =  3oo  gauss,  and  that  the  audio 
power  input  is  i  watt  in  each  case. 

The  diaphragms  are  all  of  aluminum  .025  cm. 
thick.  The  following  table  gives  the  results  of  the 
calculations  and  these  are  represented  graphically 
in  Fig.  4. 


Radius 


60 


150 


300 


w  cm.       Trcm. 
W  in  Kiloergs  per  sec. 


3° 

8.81 

16.5 

26.9 

53-4 

60 

2.85 

8.05 

16.6 

27.4 

55.0 

100 

2-55 

7.91 

16.5 

27.1 

57-1 

150 

2.46 

8.40 

16.2 

26.2 

50.6 

2OO 

2.51 

7.63 

15.1 

25.1 

31.0 

3OO 

2.48 

7.22 

'3-5 

17.2 

16.9 

4OO 

2.28 

6.23 

9.61 

8.69 

9-3 

6OO 

2.18 

4.65 

4.23 

4.69 

6.9 

750 

I  .96 

3-13 

2.83 

1000 

1.61 

1.56 

1.68 

1500 

0.80 

0.78 

2OOO 

0.39 

30OO 

0.18 

As  already  stated,  it  should  be  borne  in  mind  that 
the  actual  frequency  characteristic  as  perceived  by 
one  standing  in  front  of  the  instrument  would  not  be 
so  pronounced  as  indicated  by  the  table  and  curves, 
because  the  calculation  gives  too  great  a  value  for 
the  radiation  at  low  frequencies,  and  also  the  lower 
the  frequency  the  more  the  spreading  of  the  sound. 
Moreover  the  response  of  the  ear  mechanism  is 
proportional  to  the  sound  wave  pressure  rather  than 
to  the  energy  flux.  At  any  given  frequency  the 
sound  wave  pressure  is  proportional  to  the  square 
root  of  the  energy  flux.  Still  another  consideration 
is  the  relation  between  the  impedance  of  the  ampli- 
fier and  that  of  the  loud  speaker.  Fig.  5  shows  the 
impedance-frequency  curve  for  the  25-inch  or 

I OO 

R  =  —     cm.  instrument,  provided  with  an  aluminum 

diaphragm  .025  cm.  thick.  The  by-pass  condensers 
shown  in  Fig.  3  were  3  mfd.  each.  It  is  apparent 
that  if  the  power  amplifier  has  an  impedance  of  1000 


c: 
o 
o 
to 
o 
o 


o 
o 

OL 
O 

o 


FIG.    3 

The  circuit  diagram  of  the  Hewlitt  induction  loud 

speaker.    L  L  are  the  two  flat  coils;  D,  the  aluminum 

diaphragm;  G,  a  direct  current  generator;  and  C  C, 

by-pass  condensers 

ohms,  then  the  power  delivered  to  the  loud  speaker 
is  going  to  fall  off  rapidly  below  a  frequency  of  600 
cycles,  which  will  prevent  the  excessive  radiation 
of  low  frequencies.  In  fact,  quite  noticeable 
changes  in  the  general  pitch  level  of  the  reproduced 
speech  of  music  can  be  accomplished  by  adjusting 
the  impedance  of  the  loud  speaker  by  means  of 
transformers.  The  difference  in  the  directivity  of 
the  loud  speaker  for  short  and  long  waves  is  shown 
by  the  progressive  loss  in  articulation,  particularly 
with  the  larger  instruments,  as  the  angle  between 
the  axis  of  the  instrument  and  a  line  drawn  from  the 
instrument  to  the  observer  is  increased.  When 
using  the  larger  instruments  out  of  doors  and  in 
auditoriums  it  is  well  to  use  at  least  two  in  order  to 
so  direct  them  as  to  minimize  the  effect  just  men- 
tioned. 

QUALITY  OF   THE   SPEAKER  ON   LOW   FREQUENCIES 

IN  ORDER  to  arrive  at  some  idea  as  to  how  great 
*an  error  is  made  in  assuming  for  the  purposes  of 
calculation  that  the  diaphragm  is  bounded  by  an 
infinite  plane  at  rest,  a  large  board,  6  feet  square, 
was  prepared  with  a  circular  hole  of  variable  diame- 
ter in  the  center  into  which  various  size  instruments 
could  be  placed.  It  was  found  with  the  smallest 

instrument,  R  =  i-  cm.,  the  general  pitch  level  of 

7T 

speech  and  music  was  noticeably  lowered  when  placed 
in  the  hole  in  the  board,  while  with  the  instrument 

R  =  —  cm.  this  lowering  of  the  general  pitch  level 

7T 

was  barely  noticeable.  This  means  that,  for  the 
range  of  frequencies  with  which  we  are  ordinarily 
concerned  in  the  reproduction  of  speech  and  music, 
the  failure  of  the  expression  for  W  at  low  frequencies 
is  of  little  importance.  Of  course,  there  is  still  left 
the  effect  of  the  greater  spreading  of  the  lower 
frequencies. 

On  the  whole,  after  taking  everything  into  con- 
sideration, it  appears  that  the  instrument  ought  to 
reproduce  well  the  lower  frequencies  which  is  neces- 
sary for  naturalness  in  the  reproduction  of  the  hu- 
man voice  and  for  richness  of  quality  in  music.  It 
is  seen  that  the  smaller  diaphragms  should  give  a 
fairly  flat  frequency  characteristic  over  a  greater 


An  Induction  Loud  Speaker 


range  than  do  the  larger  ones.  That  is,  the  higher 
tones  should  be  relatively  more  important  in  the 
smaller  than  in  the  larger  instruments.  These 
conclusions  are  borne  out  by  experience. 

APPENDIX   I 

\A/E  SHALL  only  attempt  to  get  a  rough  esti- 
"  ^  mate  of  the  order  of  magnitude  of  the  magnetic 
damping  force  acting  on  the  diaphragm  owing  to 
its  vibration  across  the  radial  magnetic  field.  For 
this  purpose  let  us  suppose  that  the  metal  composing 
the  diaphragm  is  concentrated  into  a  single  circular 
turn  of  wire  of  circular  cross  section  whose  diameter 
is  one  half  that  of  the  diaphragm.  Let  this  ring 
vibrate  parallel  to  its  axis  with  displacement  x, 
velocity  v  and  amplitude  A.  Then  x  =  A  sin  wt 
and  v  =  wA  cos  wt.  The  induced  electromotive 
force  is  e  =  v  c  H,  where  c  is  the  circumference  of 
the  circular  wire  and  H  is  the  strength  of  the  radial 
magnetic  field.  Then 

e  =  w  A  c  H  cos  w  t 
=  E  cos  wt,  where  E  =  wA  c  H 

Applying  Kirchoff's  law,  letting  i  be  the  induced 
current 

i  r  +  L  -T^-  =  Ecoswt 
dt 

where  r  and  L  are  the  resistance  and  inductance  of 
the  wire.  From  this  follows 

'  =     /  2  4.  tu  i  \2  cos  (wt  ~~  e)  where  tan  6  =  — 
The  reaction  of  the  field  on  this  current  is 
f  =  i  c  H  =  ^  (C  H)2  cos  (w  t  —  9) 
where  Z  =  V2  +  (w  U2 


f  .  -A(CH)«  [r  cos 
HV    dx 


k  P 


In  order  to  take  account  of  this  force,  we  may 
assume  that  this  is  the  magnetic  drag  that  would 
act  on  the  diaphragm  represented  by  the  ring,  and 

dx 

we  may  then  add  the  above  coefficients  of  —  and  X 

dt 

to  the  corresponding  coefficients  in  the  original 
equation  of  motion.  To  carry  this  out  for  a  particu- 

lar case,  the  instrument  R  =  —  cm.  with  an  alumi- 

7T 

num  diaphragm  .025  cm.  thick  was  chosen.  It  is 
assumed  that  H  =  300  gauss;  calculation  of  the 
other  quantities  concerned  give 

r        =  3.52  x  io5  e.m.u. 
L       =  7.41  x  io2 
C  H  =  2.95  x  io4 


b 


(C  H\2 
~Z~  I 


. 
—  =  w  L 


HY 
7—  I 

Z   J 


W  = 


The  radiation  in  kiloergs  /sec.  and  the  amplitude  in 
cm.  calculated  for  this  instrument  for  an  input  of  i 
watt  of  audio  power  is  given  in  table  II. 


FREQUENCY 
CYCLES  /SEC. 

30 

60 
150 
3OO 
6OO 


TABLE  II 

W   /  A  CM. 
KILOERGS /SEC. 

16.9  1960  x  io-6 

16.9  JOO 

l6.7  85 

13.5  24 

4.2  7 


then  the  expression  for  the  sound  energy  radiated  is 


From  a  comparison  of  the  values  of  W  in  Table 
II  with  those  for  the  same  instrument  in  Table  I 
it  is  apparent  that  the  damping  of  the  magnetic 
field  has  no  appreciable  effect  on  the  frequency- 
radiation  characteristic  of  the  loud  speaker. 

APPENDIX    II 

TN  ORDER  to  get  an  approximate  idea  of  the 
•*•  periodic  force  driving  the  diaphragm,  let  us  as- 
sume that  the  audio  power  is  transferred  quantita- 
tively to  the  diaphragm,  and  is  there  dissipated  in 
heat.  The  audio  impedance  with  diaphragm  is 
only  a  few  per  cent,  of  that  without  diaphragm,  and 
it  is  seen  from  Table  I  that  with  a  field  strength  of 
300  gauss  somewhat  less  than  0.2  per  cent,  of  the 
audio  power  is  converted  into  sound  radiation. 
The  above  assumption  is,  therefore,  justified  for  a 
first  approximation.  We  shall  also  assume  that  the 
induced  current  in  the  diaphragm  is  uniformly  dis- 
tributed. Let  I  be  the  maximum  value  of  a  sine 
wave  audio  current  through  an  annulus  of  the  dia- 
phragm, i  cm.  wide,  and  let  r  be  the  superficial 
resistivity  of  the  diaphragm.  Let  A  be  the  area  of 
the  diaphragm,  and  W0  the  audio  power  supplied. 
Then  I2  r  A  =2  W0,  and  the  maximum  value  of 

the  force  on  the  diaphragm  is  H  I  A  =  H  J  2  W°  A 

where  H  is  the  strength  of  the  radial  magnetic  field. 
For  a  given  thickness  of  diaphragm  of  a  given 
material,  a  given  field  strength,  and  a  definite 
supply  of  audio  power,  the  square  of  the  force  driv- 
ing the  diaphragm  is  proportional  to  the  area  of  the 
diaphragm. 

APPENDIX    III 

HP  HE  power  dissipated  in  the  instrument  has  to 
*  be  eliminated  through  the  faces  of  the  coils,  and 
in  the  absence  of  forced  ventilation,  the  amount  of 
power  that  can  be  dissipated  from  instruments  of 
various  size  with  a  given  mean  temperature  rise  of 
the  coils  will  be  proportional  to  the  area  of  the 
coils.  The  induction  loud  speakers  have  been 
designed  to  operate  at  a  temperature  of  100°  C. 
The  power  to  be  dissipated  is  practically  the  polariz- 
ing power,  since  the  audio  power  under  actual 
conditions  of  operation  is  only  a  few  per  cent,  of  the 


Radio  Broadcast 


polarizing  power.  The  following  brief  analysis  will 
show  the  relation  between  the  polarizing  voltage, 
the  number  of  turns,  and  the  linear  dimensions 
of  the  coils: 

Let  R  =  radius  of  one  pancake  coil 
r   =  resistance  one  pancake  coil 
t   =  axial  depth  of  winding 
n    =  number  of  turns  in  one  pancake 
E  =  voltage  on  one  pancake 
S  =  space  factor  of  windings 
p  =  specific  resistance  of  the  wire. 

Let  us  assume  a  constant  space  factor  for  coil 
windings  when  using  wire  of  various  sizes,  and  for 
various  size  coils.  This  factor  may  vary  from  0.40 
to  0.50,  and  takes  account  of  the  thickness  of  in- 
sulation, the  circular  section  of  the  wire,  and  the 
space  between  sections  for  the  passage  of  sound 
waves. 

-Trrr-V-?-''.?         0) 


Let  us  suppose  this  proportional  to 


For  the  25-inch  instrument  described  in  this 
paper,  K!  has  a  value  of  1.31  x  io-6  at  20°  C  with  r 
measured  in  ohms,  and  t  in  cm.  This  is  a  good 
representative  value  for  Ki  and  corresponds  to  a 
space  factor  of  0.426  and  a  specific  resistivity  of 
1.78  x  io-8  ohms  per  cm3. 

Equation  (i)  shows  that  the  resistance  of  a  pan- 
cake can  be  expressed  in  terms  of  the  number  of 
turns  of  wire  and  the  axial  thickness  of  the  winding, 
independent  of  the  diameter  of  the  instrument. 

The   power   dissipated    in   one    pancake   coil   is 


2.8  - 

R-tf- 

-» 

1 

2.7  - 

^ 

\ 

R- 

i 

\ 

u> 

-i 

\ 

R- 

iM 

•\ 

3 

•s, 

\ 

' 

R- 

\ 

1.9  - 

J 

-~i 

- 

—— 

=* 

*s 

\ 

X 

I 

L 

i.; 

^ 

\ 

I" 

\\ 

0 

>  —  i 

R-* 

s 

B 

^»- 

—  -4 

—  * 

V 

V 

1 

> 

\ 

! 

\ 

] 

\ 

i 

\ 

\ 

\ 

s 

\ 

' 

1.4         1.6          1.8         2.0         22         24         2.6          28          3.0         32         M 
\                  I                            LOG  FREQUENCY          1                                1 
30               60          100       150  200      300  400      600  750  1000    1500  2000  300C 
CYCLES 

E2  =    E2t 
r        K;ns 

the  exposed  area  of  the  pancake  coil.     Then 

K^2  =  Kz  R2 

When  both  pancakes  are  mounted  together  as  they 
are  in  the  assembled  instrument,  it  is  found  that  a 
temperature  rise  of  80°  C  corresponds  to  a  value  of 
K2  =  0.50  when  R  is  measured  in  cm.,  and  the  power 
in  watts.  K2  R2  then  gives  the  power  dissipated  as 
heat  in  each  pancake  coil. 

Solving  the  last  equation  for  n  we  have 


!   K2 


(2) 


that  is  for  a  given  operating  voltage,  the  number  of 
,.  F  Ft* 

turns  is  proportional  to  ^5-  The  current  is  i  =  —  =  -=-; — 
K  r  ivn 

Et 

The  ampere-turns  for  one  pancake  coil  are  ni  =  ^— 

and  by  Ampere's  law,  the  strength  of  the  radial 
component  of  the  magnetic  field  contributed  by  one 

pancake  is  approximately  proportional  to  ^  =  77— '-5 

Let  us  see  what  condition  must  be  fulfilled  in  order 
that  we  may  have  the  same  strength  of  magnetic 
field  for  instruments  of  all  sizes,  that  is 


Et 


(3) 


FIG.    4 


Ktn  R 

If  E  is  expressed  in  volts,  and  the  other  quantities 
expressed  as  previously  specified,  then  K^  is  approxi- 
mately 1.6  times  the  strength  of  the  radial  compo- 
nent of  the  magnetic  field  due  to  one  pancake,  or 
0.8  times  the  total  radial  component  when  both 
pancakes  are  present,  the  strength  of  the  magnetic 
field  being  expressed  in  gauss. 

Eliminating  —  from  (2)  and  (3)  we  have  t  =  — —^ 
Kn  Kj 

or  the  axial  thickness  of  all  the  coils  must  be  the 
same.  Actually,  the  demands  on  the  instrument 
from  the  standpoint  of  an  audio  transformer  are  such 
that  the  thickness  of  the  coils  may  be  made  larger 
in  the  larger  instruments  than  in  the  smaller  ones. 
Therefore,  with  the  larger  instruments  we  may  have 
a  stronger  radial  magnetic  field  than  with  the 
smaller  ones  when  operating  at  the  same  tempera- 
ture. 

In  order  to  design  the  windings  for  an  induction 
loud  speaker,  the  following  procedure  will  be  found 
to  be  as  direct  as  any.  Suppose  the  approximate 
radius,  R,  of  the  pancake  coils  ,and  E,  half  the  polar- 
izing voltage,  are  given.  First  choose  t,  the  axial 
thickness  of  the  pancake,  which  may  be  0.5  inches 
for  coils  as  small  as  4.5  in.  radius  to  i.o  inch  for 
coils  as  large  as  18  in.  radius.  Choose  next,  a 
space  factor  between  0.40  and  0.50.  Calculate  K. 

K  Ki  t 

and  take  K2  =  0.50.     Then  H  =  — J  =  1.251'  ~u-~ 

o.o  K.I 

which  should  be  at  least  as  large  as  280  e.m.u. 
If  H  is  not  this  large,  t  or  s  should  be  adjusted 


An  Induction  Loud  Speaker 


515 


accordingly.     The  resistance  of  the  pancake  coil  is 

E2 
given  by  .    If  d  is  the  density  of  copper  ""R2t  Sd 

gives  the  mass  of  copper  in  the  pancake,  and  from 
this  and  the  resistance,  the  size  of  wire  to  be  used 
may  be  read  off  from  a  wire  table.  The  number  of 
turns  may  be  calculated  from  equation  (i).  Using 
the  above  figures  as  approximations,  the  coil  may 
now  be  accurately  designed  by  obvious  procedure. 
If  the  polarizing  voltage  is  very  low,  say  less  than 
loo  volts,  the  instrument  may  require  excessive 
current,  and  be  of  very  low  impedance,  while  if  the 
voltage  is  high,  the  reverse  conditions  may  be 
encountered.  250  to  500  volts  for  polarizing  have 
been  found  to  give  very  satisfactory  results,  both 
from  the  standpoint  of  polarizing  current  and  audio 
impedance  for  all  sizes  of  instruments  so  far  built. 

APPENDIX    IV 

LET  us  determine  the  condition  for  the  maximum 
amount  of  sound  radiation  output  for  a  given 
total  amount  of  polarizing  and  audio  power  input. 
The  force  driving  the  diaphragm  is  directly  pro- 
portional to  the  strength  of  the  radial  magnetic 
field,  which  in  turn  is  directly  proportional  to  the 
.polarizing  current  h.  The  force  is  also  proportional 
to  the  audio  current  in  the  diaphragm,  which  in 
turn  is  proportional  to  the  audio  current  in  the  coils 
i2.  The  sound  pressure  output  p  is  proportional  to 
the  force  acting  on  the  diaphragm  and,  therefore, 
we  may  write 

p  =  K!hi2  (i) 

If  TI  and  r2  are  the  d-c  and  audio  resistances,  re- 
spectively, of  the  instrument,  then  the  condition 
that  the  total  power  supplied  shall  be  independent 
of  the  relative  proportions  of  polarizing  and  audio 
powers,  is 

i,  2rx  +  i2  2r2  =  K2  (2) 

differentiating  (i)  and  (2)  with  respect  to  i],  we  have 


1200 
1100 
1000 

900 

m 

700 
^600 
500 

400 
300 
200 
100 
n 

046 

084 
0.82 
0*. 
0.78  1 
0.76.1 
0.74  °- 
0.72 
0.70 
068 
0.66 
0.64 

/ 

*\ 

\p.f. 

^  —  • 

X 

z  

"" 

s 

„  —  - 

^^^ 

^ 

^^-- 

^^^ 

\ 

s 



s 

f 

' 

FIG.    5 


:  -j    r2 
dh 


From  (4)  we  have  ^  =  —  I1 


(4) 


(5) 


dh 


dh 


(3) 


Substituting  (5)  in  (3)  and  equating  to  o,  we  have 
i2  2r2  =  i!  2r](  which  is  the  condition  that  p  shall  be  a 
maximum.  It  therefore  follows  that  the  audio  and 
polarizing  powers  should  be  equal  in  order  that  the 
maximum  sound  radiation  should  be  produced. 


ACKNOWLEDGEMENTS 

The  writer  wishes  to  gratefully  acknowledge  the 
helpful  interest  shown  by  Dr.  W .  R.  Whitney  through- 
out the  development  of  this  instrument.  His  ever 
present  encouragement  and  faith  is  largely  responsible 
for  the  successful  outcome  of  this  work.  I  wish  also 
to  take  this  opportunity  to  express  my  appreciation  of 
many  helpful  suggestions  from  my  colleagues  Messrs. 
E.  W.  Kellogg,  E.  P.  Lawsing,  and  C.  W.  Rice.  The 
instrument  described  in  this  paper  was  invented  in  1919 
while  the  writer  was  teaching  at  the  University  of 
Iowa,  Iowa  City,  Iowa.  Its  development  described  in 
this  paper  was  carried  out  in  the  Research  Laboratory 
of  The  General  Electric  Company,  Schenectady,  New 
York. 


NEUTRALIZING  AND  TUNED  RADIO  FREQUENCY 

ANOTHER  paper  presented  before  the  Radio  Club  of  America  will  appear  in 
RADIO  BROADCAST  for  September.  It  is  by  C.  L.  Farrand  and  deals  with 
his  further  findings  in  the  field  of  tuned  radio  frequency  amplification,  especially  in 
the  important  matter  of  neutrali2ation.  The  progress  of  Mr.  Farrand's  experi' 
ments  is  traced  and  diagrams  and  photographs  show  clearly  his  research  in  this 
very  important  subject. — THE  EDITOR. 


Making  a  "Super-Het"  From  Your 
Neutrodyne  or  Single-Circuit  Set 

How  to  Apply  the  Frequency-Changer  to  Two  Very  Popular  Types  of 
Receivers,  Resulting  in  Greater  Receiving  Range  and  Sharper  Tuning 


BY  A.  O'CONNOR 

'/ID  10  constructors  and  radio  operators  everywhere  have  long  been  interested 
in  some  method  which  would  permit  them  to  add  a  device  to  their  set  which 
would  make  it  into  a  super-heterodyne.  That  receiver  still  stands  as  one  of  the 
most  sensitive  and  desirable  from  many  points  of  view.  In  RADIO  BROADCAST 
for  June,  Mr.  O'Connor  described  the  details  of  construction  of  the  Frequency- 
Changer  developed  by  him,  and  in  this  article,  his  very  clear  instructions  tell  just 
how  it  may  be  applied  to  a  single-circuit  or  a  neutrodyne  receiver.  The  first 
article  aroused  a  great  deal  of  interest,  and  we  feel  sure  that  this  one  will  appeal 
to  a  great  number  of  broadcast  listeners  who  want  the  well  known  benefits  of  super- 
heterodyne reception. — THE  EDITOR 


THE  ambition  of  many  owners  of  re- 
ceiving sets  to  own  a  super-heterodyne 
has  been  deterred  for  several  reasons, 
chief  of  them  being  the  high  cost  and 
because  the  owner  of  an  already  existant  re- 
ceiver did  not  feel  like  disposing  of  it  at  a 
sacrifice.     In  RADIO  BROADCAST  for  June  the 
writer  described  a  simple  one-tube  Frequency 
Changer  that  could  be  added  to  any  receiver, 
thereby  converting  it  to  a  most  efficient  and 
inexpensive    super-heterodyne.       And    after 
constructing  such  a  unit,  the  first  thought  in 
the  builder's  mind  must  be  the  question  of 
applying  it  to  the  receiver  he  owns. 

Perhaps  the  simplest  place  to  utilize  this 
Frequency-Changer  is  in  connection  with  the 
simplest  known  receiver,  the  single-circuit 
"  blooper. "  This  type  of  receiver  being,  prob- 
ably, more  generally  owned  than  any  of  the 
others,  it  seems  logical  to  show  the  tricks  that 
must  be  performed  with  the  blooper  before 
it  is  a  "super." 

Briefly,  the  Frequency-Changer  is  a  device 
for  heterodyning  incoming  signals  and  passing 
them  on  to  the  intermediate-frequency  ampli- 
fier at  a  greatly  changed  frequency.  The  in- 
termediate amplifier  consists  of  the  present 
receiver,  and  the  changing  of  frequencies  takes 
place  in  the  unit  described  in  this  magazine 
for  June. 

As  stated  in  the  first  article  of  the  series, 
the  unit  will  increase  the  volume  of  signals, 
will  enable  any  receiver  to  reach  out  to  greater 
distances,  will  add  greatly  to  the  selectivity 
of  the  existing  receiver,  and  will  be  an  aid 


toward  preventing  radiation.  Due  to  the 
fact  that  the  beat  frequency  generated  in  this 
unit  is  very  high,  compared  to  the  usual  super- 
heterodyne, stations  will  appear  only  once 
on  the  tuning  dials,  an  advantage  that  will 
appeal  to  all  those  who  like  ease  of  tuning. 

ADVANTAGES   OF  THE   FREQUENCY-CHANGER 

A  NOTHER  advantage  of  this  addition  to 
•*»•  any  receiver  lies  in  the  fact  that  all  tuning 
is  done  on  the  Frequency-Changer,  and  none 
on  the  receiver.  This  feature  is  particularly 
important  to  users  of  neutrodynes  and  the 
more  complicated  four-  and  five-tube  receivers, 
for  with  the  addition  of  the  unit,  tuning  con- 
trols have  been  reduced  to  two.  The  dial 
numbers  will  be  essentially  alike  at  all  broad- 
casting frequencies,  and  may  be  calibrated. 

Fig.  i  is  a  schematic  diagram  of  the  Fre- 
quency-Changer, and  Fig.  2  is  a  photograph 
of  the  completed  unit,  both  illustrating  the 
simplicity  of  the  device.  Fig.  3  represents 
the  more  usual  types  of  single-circuit  receiv- 
ers, and  the  methods  of  attaching  the  Fre- 
quency-Changer unit  to  them. 

There  is  only  one  difficulty  in  connecting 
the  unit  to  such  receivers,  and  that  lies  in  the 
fact  that  it  is  possible  to  short-circuit  the  45- 
volt  B  battery  which  is  connected  in  the  out- 
put of  the  unit.  This  can  be  prevented  by 
simple  precautions.  The  grid  circuit  of  some 
types  of  this  regenerative  receiver  is  connected 
to  the  negative  B  and  since  the  Frequency- 
Changer  is  connected  to  plus  B  there  is  the 
possibility  of  short-circuiting  the  B  battery. 


Making  Your  Set  a  Super-Heterodyne 


517 


a-  Primary  of  pickle  bottle  coil 

b-  Secondary 

c- Tickler 

d-  Oscillator  plate  coil 

e-  Oscillator  grid  coil 

f  -.0005  Condenser  247  F(Tuner) 


A  Battery 

g-. 00013  Fixed  cond. 

h-  .00025  Condenser  247k  (OSC) 

k-. 00025  grid  condenser 

m-  1  Megleak 

n  -  30  Ohm  rheostat 


FIG.     I 


The  Frequency-Changer  unit  that  may  be  added  to  any  receiver  to  make  it  into  a  super-heterodyne 


This  is  illustrated  A  and  in  B  of  Fig.  3  and  the 
method  of  avoiding  trouble  is  shown.  In  A, 
the  method  consists  of  winding  a  small  coup- 
ling coil  of  6  turns  of  No.  20  double  silk  cov- 
ered wire  around  the  grid  coil  of  the  receiver 
and  insulating  the  two  windings  by  a  layer 
of  empire  cloth  or  tape.  The  antenna  and 


ground  connections  are  then  connected  to- 
gether. In  B,  the  method  is  simpler,  since.it 
is  only  necessary  to  cut  the  connecting  wire 
between  the  small  primary  coil  and  the  second- 
ary winding. 

The  matter  of  selection  of  the  type  of  tube  is 
not  highly  important,  since  any  of  the  standard 


FIG.  2 

The  disposition  of  the  parts  and  the  simplicity  of  the  wiring  may  be  seen 
from  this  photograph  which  looks  down  upon  the  Frequency-Changer. 
How  to  build  this  unit  was  described  in  RADIO  BROADCAST  for  June,  1925 


5l8 


Radio  Broadcast 


SINGLE  CIRCUIT  REGENERATIVE 


Wind  Six  Turns  Around  End  of  Coupler  Stator 


APERIODIC  OR  UNTUNED  PRIMARY 


B 


\7 


PP- 


WITH  THE  FREQUENCY  CHANGER 

i 

A 


Output  of 

Frequency 

Changer 


Break  This 
Connection 


GRID  AND  PLATE -VARIOMETER  TUNED 


WITH  THE  FREQUENCY  CHANGER 


PLATE -VARIOMETER  GRID-CONDENSER  TUNED 

Q 


WITH  THE  FREQUENCY  CHANGER 
A_ 


Output  of 
Frequency 
Changer 


A  May  be  Used 


x^  Use  About 
10  Turns  of 
Primary 


PLATE  INDUCTIVE  FEEDBACK 
Such  as  Honeycomb  Coil 


WITH  THE  FREQUENCY  CHANGER 


Output  of 
Frequency 
Changer 


'*Use  10  or  15 
Turn  Coil 


FIG.    3 

Here  is  the  whole  family  of  single-circuit  bloopers  together  with  the  methods  of  attaching  the  Frequency- 
Changer  to  them.     In  A  and  B  are  two  methods  of  avoiding  possible  short-circuiting  of  the  B  battery 


Making  Your  Set  a  Super-Heterodyne 


519 


tubes  will  work  properly.  As  a  matter  of  fact, 
the  6-volt  type  is  best,  the  3-volt  type  second, 
and  the  i^-volt  tubes  a  fair  third.  The  opera- 
tion of  the  Frequency-Changer  and  the  receiver 
to  which  it  is  attached,  is  a  simple  matter.  It 
is  only  necessary  to  tune  the  receiver  to  600 
meters  or  as  near  to  it  as  possible,  and  crank  up 
the  regeneration  to  a  point  where  considerable 
gain  is  evidenced,  but  not  so  far  that  oscilla- 
tions actually  take  place.  Once  the  tuning 
dial  is  set  at  600  meters  or  near  it,  it  will  not 
be  necessary  to  touch  it  again,  since  all  tuning 
is  done  with  the  Frequency-Changer  dials. 

Both  dials  of  the  Frequency-Changer  will 
tune  nearly  alike,  and  the  tuning  is  sharp 
enough  to  demand  a  good  vernier  dial.  Those 
on  the  Frequency-Changer  illustrated  in  the 
photographs  are  Velvet  Vernier  dials  made 
by  the  National  Company,  Inc.  of  Cambridge, 
Massachusetts. 

WHY  THE   RECEIVER   IS  TUNED  TO  6OO  METERS 

THE  object  in  using  600  meters  is  to  place 
the  intermediate -frequency  amplifiers 
above  the  broadcasting  wavelength  bands  to 
avoid  interference.  If  the  receiver  will  not 
tune  high  enough,  a  small  fixed  condenser, 
of,  say  .0001  mfd.  capacity,  may  be  placed 
across  the  tuning  condenser,  and  the  receiver 
tuned  to  some  point  well  above  the  longest 
broadcasting  wavelength.  Many  ocean  ves- 
sels use  the  6co-meter  band  for  ship  to  shore 
communication  and  one  method  of  tuning  the 
receiver  to  this  wavelength  is  by  listening  for 
code  signals.  The  exact  wavelength  is  not 
important,  as  long  as  it  is  out  of  the  broad- 
casting band. 

In  case  no  heterodyne  action  is  noted,  it 
may  be  necessary  to  reverse  the  connections 
to  one  of  the  two  coils  in  the  oscillator  coupler, 


and  for  best  operation  it  is  well  to  try  revers- 
ing the  output  connections  from  the  Fre- 
quency-Changer. 

The  tickler  of  the  pickle  bottle  coil  will 
give  regeneration  which  will  be  especially  use- 
ful on  distant  stations,  as  well  as  sharpening 
up  the  tuning.  If  the  coupling  of  the  two 
oscillator  coils  is  correct,  the  tickler  of  the 
pickle  bottle  coil  will  just  cause  oscillations 
when  KSD  or  some  other  high  wavelength 
station  is  tuned-in.  With  this  setting,  the 
tickler  will  not  have  to  be  adjusted  more  than 
three  times  when  going  down  toward  the 
lower  wavelengths.  Thus  there  are  only  two 
tuning  controls. 

In  order  to  get  maximum  selectivity,  a 
selector  switch  has  been  added  which  makes 
it  possible  to  use  three  or  six  turns  in  the 
primary  of  the  Frequency-Changer.  The 
smaller  number  of  turns  may  decrease  signal 
strength  somewhat  but  will  enable  the  opera- 
tor to  cut  his  way  through  interfering  stations 
with  greater  freedom. 

One  of  the  important  points  about  this 
device  when  added  to  a  single-circuit  blooper 
is  the  fact  that  the  blooper  may  oscillate 
without  its  radiation  getting  to  the  antenna. 
These  oscillations  are  confined  to  the  receiver 
itself,  and  do  not  pass  through  the  Frequency- 
Changer  to  get  out  on  the  antenna.  It  is 
possible  to  tune-in  stations  by  the  usual 
"squeal"  method,  without  annoying  the 
neighbors — a  most  important  point. 

GUARDING   AGAINST   RADIATION 

THE  oscillator  circuit  itself  does  not  radiate, 
and  there  is  only  one  other  adjustment 
that  is  liable  to  disturb  the  neighbors.     If  the 
tickler  of  the   Frequency-Changer  is  turned 
until  a  click  is  heard  in  the  phones,  the  Fre- 


FIG.  4 

Here  is  a  two-tube  super-heterodyne  made  by  adding  the  Frequency-Changer  to  a  single-circuit  tickler 

feedback  receiver.     The  addition   of   the   Frequency-Changer  improves  the  selectivity,  adds  distance, 

and  eliminates  all  possibility  of  the  receiver  radiating  into  the  ether 


520 


Radio  Broadcast 


R.F.  AMPLIFIER 
"  Interstage  Transformers  — ' 


FIG.    5 

This  is  the  conventional  neutrodyne  diagram  of  connections.  Without 
the  neutralizing  condensers  it  would  represent  the  connections  for  the 
first  three  tubes  of  the  usual  five-tube  tuned  radio  frequency  receiver 


quency-Changer  is  oscillating  at  the  frequency 
of  the  incoming  signals  and  will  radiate  at 
this  frequency.  But  the  minute  this  occurs, 
the  whole  system  becomes  inoperative,  no 
signals  get  through  to  the  loud  speaker  or 
head  phones,  and  the  operator  naturally 
turns  down  the  tickler.  For  this  reason,  the 
danger  of  parasitic  oscillations  going  out  into 
the  ether  is  remote,  and  at  any  rate  will  only 
last  a  second  or  two. 

When  attached  to  a  single-circuit  receiver 
as  shown  in  Fig/4,  the  two  tubes  make  phone 
reception  from  distant  stations  easily  pos- 
sible. With  the  addition  of  two  amplifier 
tubes,  loud  speaker  operation  in  Cleveland 
was  possible  from  WHAS  on  750  kilocycles  (399.8 
meters)  and  WGY  on  790  kilocycles  (379.5 
meters)  when  WEAR  or  WTAM  on  770  kilocycles, 
(389.4  meters)  were  operating,  and  without 
hearing  the  local  stations  at  all.  Equal  se- 
lectivity was  enjoyed  in  the  Laboratory  of 
RADIO  BROADCAST  although  the  "local"  sta- 
tions in  this  case  were  about  20  miles  away. 
KSD,  St.  Louis,  was  heard  in  Garden  City 
while  New  York  stations  were  operating. 
This  was  an  indication  of  the  sensitivity  of 
the  receiver  since  KSD  is  rarely  heard  in  the 


ij'ri 

ir1 


FIG.  6 

The  addition  of  the  Frequency-Changer  to  a  receiver  like  that  of  Fig.  5 
is  a  simple  matter  as  this  diagram  shows.     It  is  important  that  the  con- 
nection indicated  be  broken  to  avoid  shorting  the  B  battery 


Laboratory  under  the  best 
conditions. 

THE     FREQUENCY    CHANGER 
APPLIED     TO      NEUTRODYNE 

BY  FAR  the  greatest  ap- 
plication of  the  Fre- 
quency-Changer is  in  con- 
nection with  the  many 
neutrodyne  receivers. 
There  are  possibly  400,000 
of  these  receivers  in  the 
United  States,  and  each  of 
them  is  a  potential  super- 
heterodyne with  all  of  the 
advantages  of  this  selective 
receiver,  and  without  some  of  the  disadvan- 
tages that  both  the  neutrodyne  and  "super- 
het"  possess.  With  the  addition  of  the 
Frequency-Changer,  the  neutrodyne,  whether 
it  is  good,  bad,  or  indifferent,  lifts  its  head 
and  becomes  a  full  fledged  "super"  with  two 
stages  of  neutralized  intermediate  frequency 
amplification,  and  if  the  audio  frequency  trans- 
formers are  good,  and  provided  that  the  proper 
C  batteries  are  used,  the  six  tubes  then  in 
operation  will  provide  a  receiver  that  will  be 
hard  to  beat. 

In  Cleveland  the  average  neutrodyne  will 
not  tune  sharp  enough  to  approach  within 
50  meters  of  local  stations  without  interfer- 
ence. Although  other  stations  may  be  heard 
the  local  is  heard  also,  and  "we  don't  count 
them,  if  we  hear  the  local."  A  Frequency- 
Changer  added  to  a  four-tube  reflexed  neutro- 
dyne, such  as  the  Fada  four-tube,  or  the 
Ware,  or  others,  and  operating  on  a  long  an- 
tenna has  so  improved  selectivity  that  WGY 
and  WHAS  (whose  wavelength  is  10  meters 
from  locals)  can  be  brought  in  without  inter- 
ference from  WTAM  or  WEAR.  Attaching  the 
Frequency-Changer  to  a  five-tube  set  enables 
the  operator  to  use  a  loop,  and  under  these 
conditions,  stations  in  Phil- 
adelphia (whose  wave  is  5 
meters  wavelength  away 
from  locals)  may  be  picked 
up  without  local  disturb- 
ance. The  reflexing  feature 
seems  to  make  no  difference 
in  the  selectivity  of  the  out- 
fit, but  the  loss  in  volume 
is  clearly  noticeable. 

Tuning  is  sharper  when 
using  a  loop,  although  some 
volume  is  naturally  lost.  A 
five-tube  neutrodyne  with  a 
Frequency-Changer  at- 


Making  Your  Set  a  Super-Heterodyne 


521 


tached  to  a  collapsible  loop  has  picked  up 
California  from  Cleveland  during  the  month  of 
February,  although  this  is  to  be  regarded  as  a 
stunt,  and  not  regular  performance.  One 
thousand  mile  reception  in  favorable  weather 
is  the  usual  range  of  such  a  hook  up. 

Let  us  examine  the  neutrodyne  circuits  and 
apply  the  Frequency-Changer  to  them.  Fig. 
6  illustrates  the  essential  connections  of  a  five- 
tube  neutrodyne  set.  Fig.  7  shows  a  tuned 
radio  frequency  set  with  a  Frequency-Changer 
added  to  it.  The  output  circuit  of  the  Fre- 
quency-Changer is  connected  only  to  the 
aperiodic  primary  of  the  first  neutroformer.  In 
a  neutrodyne  set,  the  primary  is  usually  con- 
nected to  both  negative  A  and  ground,  and 
it  is  absolutely  necessary  to  disconnect  the 
negative  A  connection  as  we  did  with  the  single- 
circuit  set.  This  will  eliminate  all  danger  of 
short-circuiting  the  B  battery  which  is  con- 
nected through  the  output  circuit  of  the 
Frequency-Changer. 


VARIOUS    TYPES    OF    NEUTRODYNES 

SOME  neutrodyne  sets  have  but  one 
winding  in  the  first  transformer,  the  an- 
tenna and  ground  being  connected  to  taps 
on  this  winding  as  shown  in  Fig.  8.  This 
method  of  getting  coupling  to  the  antenna 
cannot  be  used  in  connection  with  the  Fre- 
quency-Changer due  to  the  fact  that  the  output 
of  the  .unit  carries  45  volts  of  B  battery.  A 
pair  of  phones  and  a  small  battery,  such  as  a 
C  battery,  or  a  few  volts  of  B  battery  are  all 
that  is  necessary  to  ascertain  whether  such  a 
coupling  method  is  used  or  not.  The  phones, 
battery  and  antenna  may  be  connected  in 
series,  and  the  remaining  wire  touched  to  the 
filament  of  the  first  tube,  as  shown  in  Fig". 
9.  If  a  click  results,  it  is  evident  that  the 
antenna  binding  post  is  connected  to  the  first 
coil  and  naturally  through  the  wiring  back 
to  the  B  battery. 
An  additional  winding  must  be  used  in 


FIG.  7 

With  the  addition  of  the  Frequency-Changer  to  any  of  the  well-known  neutrodynes,  or  the  radio  frequency 

receivers,  the  owner  has  an  excellent  six-tube  superheterodyne  that  may  be  operated  on  a  loop  from  medium 

distant  stations.    The  receiver  illustrated  here  is  a  well-known  five-tube  radio  frequency  set 


522 


Radio  Broadcast 


FIG.  8 

It  sometimes  happens  that  the  antenna  is  connected 
to  the  receiver  as  shown  in  A  of  this  Figure  and  the 
method  of  adding  the  Frequency-Changer  is  illus- 
trated in  B,  where  a  few  turns  of  wire  are  wound 
around  the  grid  coil  of  the  first  tube 


such  cases  and  the  method  of  connecting  it 
into  the  circuit  is  shown  in  Fig.  10  where  an 
aperiodic  winding  of  six  turns  of  No.  20  d.  s.  c. 
wire  are  wound  on  the  outside  of  the  coil  and 
separated  from  it  by  a  thin  layer  of  empire 
cloth. 


HOW   TO   TUNE 

A  GREAT  many  neutrodyne  sets  are  per- 
fectly neutralized,  and  in  this  case  the 
operation  will  be  all  that  can  be  desired.  The 
great  majority,  however,  might  be  better 
neutralized  and  the  sets  oscillate  when  being 
tuned.  If  such  a  receiver  oscillates  at  pres- 
ent (squeals  when  tuning),  we  would  advise 
adding  a  aoo-ohm  potentiometer,  as  is  illus- 
trated in  Fig.  10.  When  the  arm  on  the 
potentiometer  is  rotated  toward  the  negative  A 
binding  post,  the  set  will  operate  as  it  did 
before  the  potentiometer  was  added,  and 
will  oscillate.  By  turning  the  arm  away 
from  negative  A  a  very  short  distance,  the 
oscillations  will  cease  and  perfect  tone  will 
result. 

Tuning  is  done  in  exactly  the  same  manner 
as  with  the  single-circuit  regenerative  re- 
ceivers. If  it  is  known  that  your  set  will  tune 
up  to  600  meters,  set  all  three  dials  at  the  point 
where  6oo-meter  stations  are  tuned-in.  The 


FIG.    9 

A  pair  of  phones  and  a  battery  are  all  that  are  needed  to  determine  whether  the  receiver  is  wired  like  that  in 
Fig.  8.  One  of  the  wires  going  into  the  cabinet  is  connected  to  the  antenna  binding  post  and  the  other  to 
the  grid  coil  of  the  first  radio-frequency  amplifier  tube.  If  there  is  a  click  it  demonstrates  that  the  antenna 

is  directly  connected  to  this  first  coil 


Making  Your  Set  a  Super-Heterodyne 


523 


three  dials  of  a  neutrodyne  set  run  fairly 
close  together  and  the  change  in  wavelength 
per  dial  degree  will  enable  the  operator  to 
determine  just  where  to  tune  for  600  meters. 
For  instance,  let  us  suppose  that  two  stations 
near  the  top  of  the  condenser  dial  are  20 
meters  apart,  representing  a  change  of  4 
degrees  on  the  dial.  Then  each  degree  repre- 
sents 5  meters  change  and  it  is  a  simple  matter 
to  calculate  where  600  meters  will  be.  Now 
pick  up  stations  on  the  Frequency-Changer  and 
check  with  the  calibration  chart  in  the  next 
column.  If  stations  are  considerably  below  the 
reading  on  the  chart,  it  will  be  necessary  to 
tune  your  neutrodyne  still  higher.  A  strong 
oscillation  point  may  be  found  at  the  upper 


CALIBRATION  OF  OSCILLATOR  DIAL 


FIG.    IO 

If  the  neutrodyne  or  the  tuned  radio  frequency  set 
has  a  tendency  to  oscillate  when  in  tune,  the  addition 
of  a  potentiometer  will  aid  in  controlling  the  ampli- 
fiers. The  method  of  making  this  addition  is 
illustrated  in  this  Figure 


90 
80 
70 

5  60 
& 

350 

£*0 

0 

30 
20 
10 
n 

V 

fCX          516        88 
fEAF       492        83 
fEEI        476        78.5 
ILW        422        64 
fGY         380        50.5 
rGN         370       47.5 
WJ        353       43.5 
rBZ         333       36 
DKA       309       27 
IHK.        273        125 

V 

_  \ 

V 

U 

,x 

s 

^ 

^ 

V 

\ 

~~  K 
V 

s 

~ 

/ 

/ 

f 

/ 

,/ 

/ 

< 

/ 

300  350  400  450 

WAVE  LENGTH  IN  METERS 

FIG.     I  I 

This  chart  shows  the  relation  between  the  oscillator 
dial  numbers  and  the  wavelengths  to  be  received. 
If  the  intermediate  amplifiers  are  tuned  to  600 
meters,  the  tuner  dial  figures  will  be  very  near  those 
shown  on  this  chart 


part  of  your  oscillator  dial.  This  means  that 
the  Frequency-Changer  is  interfering  with  the 
neutrodyne  setting.  By  tuning  the  neutrodyne 
up  to  600  meters  this  oscillation  point  will  be 
eliminated.  If  the  receiver  will  not  tune 
to  600  meters,  connect  a  .0001  mfd.  fixed  mica 
condenser  across  the  three  variable  con- 
densers, which  will  effectively  increase  the 
upper  tuning  range. 


D  EADERS  of  RADIO  BROADCAST 
1^-  read  with  much  sympathetic  in- 
terest and  the  tribute  of  an  earned 
smile  the  article  by  W.  R.  Bradford. 
"Radio  Heaven  Via  the  Roberts  Cir- 
cuit," March,  1925.  His  cartoons  we 
have  used  were  popular  too.  The  car- 
toon at  the  right  was  sent  in  to  us  just 
a  short  time  ago  by  Mr.  Bradford  from 
his  Philadelphia  headquarters  at  the 
North  American.  Mr.  Bradford  was 
a  great  booster  for  the  Roberts  circuit 
with  which  he  had  great  success. 

After  a  short  illness,  Mr.  Bradford 
died  at  his  home  in  Philadelphia,  on  the 
6th  of  June.  He  had  been  for  a  num- 
ber of  years,  cartoonist  on  the  North 
American  and  within  the  past  eight 
months  had  been  radio  editor  of  the 
samepaper.  RADIO  BROADCAST  records 
the  death  of  Mr.  Bradford  with  the 
knowledge  that  newspaperdom  has  lost 
an  able  cartoonist  and  writer.  Radio 
enthusiasts  have  lost  from  their  ranks 
a  genuine  and  earnest  experimenter. 


HERE1.  HERES 
KANSAS  crrY 

T=OR_  YOU.  r'uu 
GET  vou  THE- 

COAST, 
<JOOO 


Coils  and  Condensers 

A  Discussion  of  Present  Tendencies  of  Radio  Design  as 
Evidenced  by  Tuning  Apparatus  Produced  by  Well 
Known  Radio  Manufacturers — Two  New  Receivers 

BY  THE  LABORATORY  STAFF 


rHE  RADIO  BROADCAST  Laboratory  was  founded  for  two  reasons,  to  protect  its 
advertising  pages  and  to  provide  a  fund  of  information  upon  which  our  readers 
might  draw.  The  purchaser  of  radio  equipment  has  little  chance  to  find  out  what  is 
wheat  and  what  is  chaff  among  the  material  that  is  for  sale — that  has  become  the  task  of 
the  Laboratory.  Whatever  information  it  has,  will  be  contained  in  these  pages  for  the 
benefit  of  our  readers. 

It  is  obviously  impossible  to  test  in  the  Laboratory,  or  to  illustrate,  or  even  to  mention 
all  radio  equipment  that  appears  for  sale.  Last  year  there  were  400  manufacturers 
of  condensers  alone  and  to  test  all  of  their  products  would  make  it  impossible  for  the 
Staff  to  know  about  anything  else. 

The  apparatus  illustrated  or  mentioned  in  these  pages  is  neither  all  that  is  tested  in 
the  Laboratory  nor  what  the  Laboratory  believes  to  be  the  best  on  the  market — it  is  merely 
representative  equipment.  It  is  obvious  that  nothing  in  which  the  Laboratory  does 
not  believe  will  be  described,  nor  will  advertisements  of  poor  apparatus  coming  from 
unreliable  concerns  be  included  in  the  magazine. — THE  EDITOR. 


THE  tuning  elements — coils  and  condensers — 
are,  perhaps,  as  important  as  any  apparatus 
that  goes  into  radio  receivers.  Upon  them 
depends  the  strength  of  signals  and  the  selec- 
tivity of  the  receiver.  The  quality  of  reception 
depends  upon  other  apparatus. 

Much  effort  has  been  spent  in  making  good  con- 
densers, and  it  is  probable  that  the  ultimate  has 
been  reached  in  "low  loss"  condenser  design. 
Several  important  trends  are  to  be  noted  among 
condenser  manufacturers.  The  first  is  the  attempt 
to  make  condensers  of  "low  loss,"  the  second  is  the 
tendency  toward  "straight  line"  wavelength  or 
frequency  curves,  and  the  third  is  the  advent  of 
condensers  and  dials  which  turn  through  360  degrees 
instead  of  the  orthodox  180  degree  instruments. 

Readers  interested  in  the  low  loss  business,  will 
do  well  to  read  the  results  of  work  done  by  Sylvan 
Harris  and  published  in  the  Proceedings  of  the 
Institute  of  Radio  Engineers  for  February,  1925. 
An  abstract  with  the  available  facts  has  been  placed 
in  a  small  booklet  by  the  Rathbun  Manufacturing 
Company  which  shows  that  practically  all  modern 
condensers  are  "low  loss";  in  other  words,  one  is  as 
good  as  another  as  regards  electrical  efficiency. 
The  figures  show  that  there  is  little,  if  any,  difference 
between  condensers  with  metal  or  composition  end 
plates,  although  it  may  be  significant  that  practically 
all  of  the  manufacturers  are  using  metal  end  plates 
— and  that  the  General  Radio  Company,  one  of  the 
oldest  builders  of  quality  radio  equipment,  uses 
composition  plates. 

The  tendency  toward  condensers  that  distri- 
bute the  broadcasting  stations  evenly  over  the 
entire  dial  is  much  to  be  desired. 

In  the  older  condensers,  the  capacity  varied 
directly  as  the  angle  through  which  the  plates 


turned,  so  that  the  relation  between  the  marks  on 
the  dial  and  the  capacity  of  the  instrument  could  be 
represented  by  a  straight  line.  This  condenser 
bunches  the  stations  operating  on  high  frequencies 
(low  wavelengths)  and  spreads  apart  those  on  the 
lower  frequencies,  an  obvious  disadvantage,  since 
there  are  more  stations  on  the  higher  frequencies. 

There  are  two  methods  of  avoiding  this  difficulty. 
One  is  to  make  a  condenser  which  will  distribute 
all  stations  according  to  their  wavelengths,  and  the 
other  is  to  distribute  them  according  to  their  fre- 
quencies. In  other  words  if  Class  B  stations  are  10 
kilocycles  apart  in  frequency,  they  will  be  a 
certain  number  of  condenser  degrees  apart 
whether  they  are  at  the  high  or  low  end  of  the 
frequency  gamut. 

There  is  little  difference  between  these  two 
methods  of  attaining  the  same  object,  except  that 
it  is  simpler  to  talk  frequencies  and  more  scientific—- 
when we  all  get  used  to  it. 

The  shape  of  the  plates  determines  the  capacity 
curve,  and  many  and  strange  are  the  modern 
condenser  plates.  Some  manufacturers  make  them 
strange  to  begin  with,  while  others  cut  holes  in  an 
ordinary  semi-circular  plate.  The  cutting  away  of 
an  orthodox  plate  is  the  usual  method,  and  the 
Kellogg,  the  newer  General  Radio,  or  the  Lacault 
condensers  show  this  method.  The  business  of 
carving  something  from  the  center  of  the  plate  is 
shown  on  our  photograph  by  the  New  York  Coil 
Co.  The  Rathbun  condenser  has  part  of  the 
plate  interior  cut  away,  although  the  illustration 
does  not  show  it. 

The  third  factor  in  modern  condenser  design,  the 
36o-degree  dials  is  important.  Instead  of  grouping 
the  eighty-odd  Class  B  and  innumerable  Class  A 
stations  into  half  a  dial,  or  180  degrees,  they  are 


Coils  and  Condensers 


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New  Apparatus 


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TWO   NEW    RECEIVERS 

These  receivers  mark  the  entry  of  two  well  known  manufacturers  into  the  radio  field.  The  lower  photo- 
graph is  that  of  the  Stromberg  Carlson  Neutrodyne,  a  five-tube  receiver  that  conforms  to  the  best  type  of 
home  decoration,  and  in  the  Laboratory  proved  itself  to  be  an  excellent  receiver.  The  loud  speaker  is  also 
from  Stromberg  Carlson.  The  upper  receiver  is  made  by  Stewart  Warner,  manufacturers  of  a  complete 
line  of  radio  equipment,  including  tubes.  This  receiver  is  a  five  tube,  tuned  radio  frequency  amplifier  set 

and  is  housed  in  a  beautiful  cabinet 


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distributed  around  the  circumference  of  a  complete 
circle  with  somewhat  greater  ease  of  tuning. 

WHAT     IS     A     GOOD     COIL? 

COILS  have  come  in  for  their  share  of  attention 
too,  although  it  must  be  said  that  it  is  a  much 
greater  task  to  build  an  efficient  coil  than  an  equally 
efficient  condenser. 

A  coil  has  but  one  purpose  in  a  receiver,  and  that 
is  to  furnish  inductance  to  the  circuit.  Unfortun- 
ately it  also  has  resistance  and  capacity,  neither  of 
which  is  desirable. 

A  good  coil  then,  has  a  maximum  of  inductance, 
a  minimum  of  resistance  and  a  minimum  of  capacity. 
The  first  two  determine  the  selectivity  of  the  re- 
ceiver and  the  strength  of  signals.  The  capacity 
of  the  coil  determines  the  highest  frequency  (lowest 
wavelength)  that  can  be  received  with  a  given 
condenser. 

All  coils  have  a  magnetic  field  surrounding  them. 
This  field  is  usually  useful  but  does  a  lot  of  things 
it  should  not,  and  is  difficult  to  measure.  In 
general,  the  larger  the  field,  the  more  space  the  coil 
requires,  the  greater  will  be  the  losses  in  the  coil 
when  in  a  receiver,  and  the  greater  will  be  the  danger 
of  unwanted  coupling  with  other  parts  of  the  circuit. 

When  a  coil  comes  to  the  Laboratory,  the  first 
thing  that  is  done  is  to  measure  its  inductance, 
then  its  resistance  at  various  broadcasting  fre- 
quencies is  determined,  and  then  its  relative  effi- 
ciency determined.  Unfortunately,  these  measure- 
ments are  not  the  same  when  the  coil  is  actually  in 
circuit,  but  are  a  good  measure  of  how  well  it  will 
work  in  a  receiver.  Never  yet  has  a  coil  that  was 
poor  in  Laboratory  measurements  proved  to  be 
excellent  when  in  actual  operation. 

Coils  of  all  types,  solenoid,  spiderweb,  basket 
weave,  what  not  have  been  tested.  If  they  were 
wound  with  average  sized  wire,  with  a  minimum  of 
dielectric  and  without  "stickem"  to  hold  them  to- 
gether their  losses  were  about  equal.  It  is  probable 
that  the  best  type  to-day  is  the  old  fashioned  sole- 
noid wound  on  "air",  with  the  basket  weave  made 
with  many  pegs — so  that  it  approaches  a  solenoid — 
a  close  second. 

Spacing  between  turns  is  more  important  than 
most  manufacturers  realize,  though  the  coils  made 
by  the  National  Company  and  wavemeter  coils 
made  by  the  General  Radio  Company,  reduce  losses 
made  by  this  method.  Elimination  of  dielec- 
tric is  necessary  for  a  coil  to  have  very  low  losses. 
The  use  of  large  wire  does  not  seem  to  reduce  losses 
but  it  adds  mechanical  strength,  an  important  point. 

Skeleton  forms  made  by  the  Ambassador  Sales 
Co.  Inc.,  and  the  Bruno  Radio  Corporation,  are 
now  available  and  if  the  wire  wound  on  them  is 
slightly  spaced  it  is  doubtful  if  better  coils  can  be 
made  by  the  home  constructor. 

TOROID  COILS 

VA/ITH1N  the  last  few  months  a  new  type  of  coil 
*  *  has  appeared  that  offers  much  for  radio. 
This  is  the  "toroid"  coil  and  is  designed  to  have  a 
small  external  magnetic  field.  This  small  field 
makes  it  possible  to  place  the  coil  near  metal  plates 


without  the  usual  increase  of  coil  resistance.  This 
means  that  a  receiver  may  be  made  more  compact. 

Since  the  external  field  is  small,  signifying  that 
little  gets  out  of  the  coil,  it  follows  that  little  will 
get  into  it  from  the  outside  through  unwanted 
coupling.  For  this  reason  two  coils  may  be  placed 
close  together  without  regard  to  the  angle  between 
them.  Signals  will  not  be  impressed  upon  a  part 
of  a  circuit  except  through  the  channel  provided 
for  it  to  follow. 

At  the  same  time  it  should  be  possible  to  build  a 
coil  that  will  not  fall  below  the  standards,  of  a  good 
solenoid — especially  when  placed  in  the  circuit 
where  it  is  to  be  used. 

Unfortunately  there  are  some  disadvantages  to 
the  toroid  coil,  for  they  cannot  be  tapped,  for  this 
destroys  the  toroid  effect.  It  is  difficult  to  get 
energy  into  the  coils,  except  through  the  use  of 
external  coupling  coils  which  may  introduce  both 
resistance  and  capacity — both  of  which  decrease  the 
efficiency  of  the  coil.  Regeneration  must  be  added 
to  a  circuit  through  capacity  feedback  instead  of 
the  customary  tickler.  There  is  nothing  wrong  with 
this  system  except  that  it  is  unusual  and  not  so  well 
understood  by  the  average  constructor. 

The  Laboratory  believes  that  the  toroid  coil  is  an 
important  development  in  the  proper  direction, 
and  specimens  made  by  the  Pathe  Phonograph  and 
Radio  Corporation,  The  Electrical  Research 
Laboratories,  and  the  Reichmann  Company  have 
been  interesting  and  efficient  inductances. 

A  useful  dial  recently  added  to  the  General  Radio 
line  and  the  American  Brand  worm  geared  condenser 
are  devices  that  will  make  tuning  a  simpler  problem. 

THE  COMBINATION  OF  COIL  AND  CONDENSER 

HP  HE  combination  of  a  coil  and  a  condenser  is 
*  the  fundamental  unit  about  which  the  entire 
receiver  pivots,  and  a  purchaser  of  such  tuning 
elements  should  know  that  he  is  getting  the  best. 
Condensers  have  been  developed  until  there  is 
little  more  to  be  expected  in  the  way  of  eliminating 
losses.  The  "straight  line"  vogue  is  worth  while. 
Condensers  which  have  36o-degree  tuning  dials 
and  which  are  illustrated  in  this  article  are  made  by 
Remler,  Nelson  Tool  Co.,  Wade,  and  Barrett  and 
Paden.  The  tandem  condenser  made  by  Cardwell 
and  others  is  interesting  in  connection  with  in- 
creased simplicity  of  tuning,  because  two  or  more 
units  can  be  operated  on  one  shaft. 

For  some  time  it  has  been  realized  that  coils 
could  be  improved,  and  the  newer  inductances 
wound  with  a  minimum  of  dielectric,  of  fairly  large 
wire,  with  space  between  turns,  are  steps  in  the  right 
direction.  Basket  weave  coils  made  by  the  Per- 
fection Co.,  the  General  Winding  Co.,  and  the  Globe 
Radio  Equipment  Co.,  have  very  low  losses.  The 
"  baby  "  coil  of  the  Ambassador  Sales  Co.,  is  designed 
for  the  short  waves  and  with  a  .0005  mfd.  condenser, 
tunes  from  50  to  1 50  meters.  Basket  weave  coils, 
similar  to  those  illustrated,  but  for  the  short  waves 
are  made  by  A.  C.  Lopez  &  Co.,  of  New  York  City. 
The  "Padd  lew  heel"  coil  made  by  Radio  Units  Inc., 
is  a  distinctly  different  type,  and  is  effectively  used 
in  the  Deresnadyne  receiver. 


RADIO  BROADCAST  Photograph 

USING  RADIO  BROADCAST'S  PHONOGRAPH  RECEIVER  ON  A.  c. 

In  tests  made  in  RADIO  BROADCAST'S  Laboratory  it  was  found  that  the  Balkite  B  could  be  used  in 
connection  with  the  Phonograph  Receiver  without  causing  any  hum  even  though  located  in  the  same 
compartment  as  the  receiver  itself.  The  illustration  shows  the  A,  B,  and  C  battery  arrangement  for 
use  with  dry  battery  tubes.  Where  standard  tubes  are  employed  it  will  be  found  that  a  small  storage 
battery  may  be  used  in  the  same  space  without  difficulty 


More  About  Radio  Broadcast's 
Phonograph  Receiver 

A  Few  Tips  on  Wiring,  Circuit  Juggling,  and  Operation  Which 
Should  Be    Found    Useful  for  Home  and  Portable  Models 


BY  ARTHUR  H.   LYNCH 


A  THOUGH    we  have  called  our  latest 
receiver  by  a  name  which  would  indi- 
cate at   first    thought   a   somewhat 
limited  use,  the  applications  to  which 
it  may  be  put  are  many  and  the  manner  in 
which  it  performs  has  already  made  it  the 


most  talked  of  receiver  for  home  construction 
offered  the  radio  public  for  many  moons. 
We  have  not  and  do  not  expect  to  make  any 
astounding  claims  for  ease  of  assembly  or  per- 
formance. We  do  claim  that  RADIO  BROAD- 
CAST'S Phonograph  Receiver  is  the  most  prac- 


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Radio  Broadcast 


tical  application  of  a  circuit  which  in  itself  is 
unusually  good  and  that  the  receiver  is  still 
further  one  of  the  most  practical  receivers  for 
operation  by  the  whole  family  which  has  ever 
been  devised. 

Some  of  the  interesting  points  of  excellence 
of  this  receiver  which  are  of  more  interest  to 
the  family  than  to  the  enthusiastic  circuit  fan 
are: 

Exceptional  tone  quality.  Operating  the  re- 
ceiver on  either  two  or  four  tubes  produces  real 
music  and  speech  which  makes  it  easy  to  recog- 
nize the  voice  characteristics  of  the  speaker. 

Satisfactory  volume.  On  two  tubes,  local 
stations  may  be  received  on  the  loud  speaker 
with  enough  volume  to  fill  the  average  living 
room,  and  distant  stations  may  be  heard  in  a 
similar  fashion  at  night.  On  four  tubes  the 


RADIO  BROADCAST  Photograph 
A    TYPICAL    PHONOGRAPH 
The  panel  used   is  somewhat  larger  than  that  re- 
quired for  an  upright  type  Victrola.      It  will  be  ob- 
served that  the   layout  of  the  equipment  has  not 
been  changed  in  any  way  and  that  the  assembly  al- 
lows plenty  of  room  for  records.     In  a  cabinet  of  this 
kind  there  is  plenty  of  room  for  all  of  the  batteries 


volume  may  be  made  unusually  great,  and 
with  a  good  loud  speaker  the  music  may  eas- 
ily be  made  loud  enough  to  provide  dance 
music  for  a  large  hall.  One  of  the  advantages 
of  this  receiver  is  that  the  loud  music  retains 
its  tone  because  of  the  design  of  the  tone  am- 
plifier circuit. 

Ease  of  operation.  When  the  plug  is  in- 
serted in  its  receptacle,  the  current  from  the 
batteries  is  automatically  turned  on  and  only 
the  actual  number  of  tubes  in  use  are  lighted. 
When  the  plug  is  placed  in  the  first  receptacle, 
the  receiver  operates  on  two  tubes;  in  the 
second  receptacle,  on  four  tubes.  Whether 
two  or  four  tubes  are  used,  the  finding  of  vari- 
ous stations  and  the  control  of  their  volume  re- 
mains the  same.  Once  the  receiver  has  been 
set  in  operation  and  the  preliminary  adjust- 
ments made,  it  is  but  necessary  to  employ 
only  two  dials  to  choose  the  desired  station  and 
the  dial  settings  usually  coincide  throughout 
most  of  the  tuning  range.  Then,  too,  once  a 
station  has  been  logged  it  will  be  found  again 
in  the  same  place.  The  third,  or  volume  con- 
trol, need  not  be  touched  for  ordinary  opera- 
tion but  is  put  to  work  in  building  up  the 
volume  from  distant  stations  when  they 
would  ordinarily  be  too  weak.  There  is  not  a 
critical  control  in  any  one  of  the  circuits,  which 
means  that  the  children  may  operate  the  re- 
ceiver without  any  difficulty. 

Selection  of  stations.  This  is  one  of  the  out- 
standing points  of  excellence  in  RADIO  BROAD- 
CAST'S Phonograph  Receiver,  which  has  been 
recognized  by  the  home  builders  and  other 
interested  persons  as  soon  as  they  have  seen 
one  of  the  receivers  in  operation.  Where  with 
many  other  receivers  it  is  difficult  or  impossible 
to  prevent  entertainment  from  one  station  to 
be  separated  from  another,  the  difficulty  may 
usually  be  overcome  when  our  new  receiver  is 
put  to  work.  It  will  show  up  very  well  in 
direct  competition  with  the  best  of  the  super- 
heterodynes, which  are  recognized  as  the 
standard  by  which  selectivity,  or  the  ability  to 
separate  the  desired  stations,  is  judged. 

The  cost  of  the  parts  for  this  receiver  is  not  too 
low  to  cause  any  one  to  doubt  its  practicability. 
On  the  other  hand,  it  is  not  too  high  to  cause 
alarm  to  any  one  who  is  the  owner  of  a  cabinet 
or  console  type  phonograph.  Using  high 
grade  parts,  to  be  sure  of  the  best  performance, 
will  bring  the  cost  (exclusive  of  accessories)  to 
about  fifty  dollars.  In  what  other  way  would 
it  be  possible  for  you  and  your  family  to  get 
as  much  real  enjoyment  for  anything  like  that 
figure? 

Your  phonograph  will  do  very  well  to  house 


More  About  Radio  Broadcast's  Phonograph  Receiver 


531 


this  receiver,  for  it  has  been  fitted  into  nearly 
every  type  of  upright  and  console  cabinet  in 
our  laboratory.  In  most  of  the  phonographs 
we  have  used,  there  has  been  room  for  batteries 
of  average  size  and  since  the  receiver  is  econo- 
mical in  the  drain  on  the  batteries  there  is 
no  reason  for  using  batteries  of  more  than 
average  size.  In  fact,  the  drain  is  so  small 
that  the  very  small  batteries,  such  as  are  used 
in  portable  receivers,  may  be  employed  with 
satisfaction.  It  is  a  simple  matter  to  use  the 
reproducing  part  of  your  phonograph  with  this 
receiver  for  a  loud  speaker  and  several  combin- 
ations of  this  kind  have  been  described  in  the 
two  preceeding  articles  which  appeared  in 
RADIO  BROADCAST  for  June,  and  July.  As 
the  accompanying  illustrations  will  show, 
there  is  plenty  of  space,  even  in  the  upright 
type  of  phonograph  for  filing  your  records, 
even  after  the  receiver  and  its  accessories  have 
been  installed.  For  the  small  apartment,  a 
better  combination  would  be  very  hard  to  find. 

A   FEW   WORDS    FOR  THE   CIRCUIT   FAN 

IN'DESIGNING  the  receiver  which  has  been 
described  in  the  last  three  numbers  of  RADIO 
BROADCAST,  we  have  attempted  to  keep  in 
mind  the  needs  of  the  class  of  folk  who  will 
derive  most  pleasure  from  the  use  of  this  re- 
ceiver. It  is  not  the  last  word  in  sensitive  re- 
ceivers, though  it  will  out-distance  any  re- 
ceiver we  have  seen  with  the  sole  exception  of 
RADIO  BROADCAST'S  Four-Tube  Knockout 
Receiver  and  it  compares  very  favorably  with 
that.  It  is  the  kind  of  a  receiver  you  can  turn 
over  to  the  family  for  their  enjoyment,  while 
you  go  ahead  with  your  experimenting  on  an- 
other layout.  Because  of  its  compactness, 
some  of  the  standard  types  of  coils  for  use  with 
the  Roberts  circuit  can  not  be  used  and  for 
your  work  on  this  circuit,  if  it  is  to  be  of  an 
experimental  nature,  you  may  prefer  the  design 
described  by  John  B.  Brennan,  our  Technical 
Editor,  in  RADIO  BROADCAST  for  September, 
1924. 

In  connection  with  the  phonograph  receiver, 
as  is  also  true  of  the  Four-Tube  Knockout, 
it  is  sometimes  desirable  to  vary  the  plate  vol- 
tage of  the  amplifying  circuits,  and  we  have 
found  that  it  is  possible  to  operate  the  reflex 
stage  with  but  45  volts  on  the  plate  circuit  with 
some  tubes,  if  the  C  voltage  is  reduced  to  1.5 
and  the  circuit  is  properly  neutralized.  It  is 
rarely  necessary  to  employ  more  than  22.5 
volts  on  the  detector  plate,  and  we  frequently 
use  even  less. 

With  some  transformer  combinations,  we 
have  found  that  an  audio-frequency  howl  is 


RADIO  BROADCAST  Photograph 
A    PHONOGRAPH    LOUD    SPEAKER 
By  employing  the  Dulce-Tone  made  by  the  Teagle 
Company  of  Cleveland,  Ohio  in  the  manner  indi- 
cated here,   the  tone  chamber  becomes   the   loud 
speaker  horn  and  obviates  the  use  of  an  outside 
speaker 

set  up  when  all  four  tubes  are  used  and  the 
juggling  of  the  plate  and  bias  voltages  de- 
scribed above  usually  does  away  with  that 
difficulty.  If  it  persists,  it  may  be  overcome 
by  connecting  the  cores  of  the  push-pull 
transformers  together  by  a  short  piece  of  wire. 
It  is  not  necessary,  as  a  rule,  to  ground  these 
cores,  but  it  is  sometimes  found  of  advantage. 
Another  trick  which  seems  to  work  well  in 
eliminating  any  trouble  which  may  arise  in  the 
amplifier  is  the  switching  of  the  two  grid  leads 
to  the  input  transformer  in  the  push-pull  stage. 
Some  of  the  adaptations  of  radio  devices 
which  are  now  on  the  market  to  RADIO 
BROADCAST'S  Phonograph  Receiver  are  shown 
in  some  of  the  accompanying  illustrations. 
Others  will  suggest  themselves  to  the  experi- 
enced home  constructor,  and  we  would  greatly 
appreciate  having  them  brought  to  our  atten- 
tion. We  are  attempting,  with  this  receiver 
design,  to  produce  the  most  satisfactory  results 
possible  for  the  greatest  number  of  radio  lis- 
teners, with  the  least  difficulty.  Every  unit 
which  can  be  incorporated  in  this  design  will 
make  our  plan  just  so  much  more  effective, 
because  it  will  make  it  easier  to  procure  the 
necessary  parts. 


$32 


Radio  Broadcast 


A    NEW    PHONOGRAPH    UNIT 

A  very  interesting  loud  speaker  unit  em- 
ploying the  special  design  illustrated  here 
has  been  made  by  the  Radioceve  Company. 
This  unit  can  be  had  in  various  impedances 
in  order  to  match  the  output  impedances 
of  the  tubes  used.  In  tests  made  in  RADIO 
BROADCAST'S  Laboratory  it  has  been  found 
very  satisfactory 


ADDITIONAL    MODELS 

THE  two  receivers,  submitted  to  us  by  the 
Electrical  Research  Laboratories  in 
Chicago,  indicate  very  clearly  how  the  devices 
made  by  that  company,  for  other  circuits,  may 
be  used  in  our  receiver  to  good  advantage. 
We  recommend  that  receivers  of  this  type  be 
made  with  flexible  wiring,  however,  and  in  our 
own  work  have  found  Acme  Celatsite  to  work 
out  very  well.  Number  18  bare,  soft  drawn 
copper  wire  does  very  well,  when  used  with 
spaghetti. 

The  use  of  current  tap  devices,  in  the  plate 
circuits  has  been  tried  and  found  very  useful. 
Many  of  the  tube  type  devices,  such  as  the 
Mayolian,  Mu-Rad,  etc.,  have  been  used,  but 
we  have  found  that  it  is  necessary  to  keep  these 
devices  some  little  distance  from  the  receiver 
itself  to  prevent  picking  up  the  a.  c.  hum. 
Experiments  with  Balkite  B  show  that  it  may 
be  used  right  beside  the  receiver  without 
causing  any  appreciable  disturbance. 

The  new  coils,  which  have  been  made  by  the 
F.  W.  Sickles  Company  for  use  in  our  phono- 
graph receiver  are  shown  on  another  page  of 
this  number,  and  we  have  found  them  to  be 
very  satisfactory.  They  may,  of  course,  be 
used  in  any  receiver,  employing  the  now- 


famous  Roberts  circuit.  Another  new  set  of 
coils  has  been  produced  by  the  Victor  Radio 
Company,  and  they  have  been  found  to  be 
very  satisfactory.  Other  manufacturers  as- 
sure us,  that  they  are  going  to  put  coils  for  our 
phonograph  receiver  on  the  market  and  the 
temporary  shortage,  which  is  now  apparent, 
should  soon  be  overcome. 

If  we  have  been  successful  in  presenting 
a  design  which  will  satisfy  the  demands  of 
the  average  listener,  the  average  home  con- 
structor, we  will  feel  greatly  encouraged  and 
believe  that  we  are  serving  our  readers  in 
a  satisfactory  manner.  We  constantly  strive 
to  increase  the  number  of  people  who  derive 
satisfaction  from  the  operation  of  their  re- 
ceivers. 

Next  month,  if  it  is  possible  to  carry  out 
the  plans  we  are  working  on,  we  will  illustrate 
a  new  group  of  phonographs  in  which  our  re- 
ceiver has  been  installed  and  will  illustrate 
new  devices  now  manufactured  for  use  in  con- 
nection with  it. 

Where  the  space  occupied  in  your  phono- 
graph by  our  receiver  will  not  permit  the  use 
of  the  regular  storage  battery  equipment,  it  is 
possible  to  use  dry-cell  tubes  and  the  very 
small  type  B  batteries  and  flashlight  batteries 
in  the  grid  circuits  for  biassing. 


Additional  photographs  showing  other  applications 
of  the  Phonograph  Receiver  to  various  panels  and 
equipment  are  found  on  the  two  following  pages 


More  About  Radio  Broadcast's  Phonograph  Receiver 


533 


RADIO  BROADCAST  Photograph 

RADIO  BROADCAST'S  PHONOGRAPH  RECEIVER  is  UNIVERSAL 

This  receiver  composed  entirely  of  parts  made  by  the  Electrical  Research  Laboratories  in  Chicago  illustrates 
in  a  very  comprehensive  way  the  ease  with  which  products  of  different  design  may  be  applied  to  our  Phono- 
graph Receiver.  Some  slight  changes  in  wiring  may  be  necessary  and  in  this  case  the  most  significant  one 
is  the  wiring  of  the  transformers  which  is  done  above  the  sub-panel  instead  of  below  it  after  the  manner 

illustrated  in  our  past  articles 


RADIO  BROADCAST  Photograph 


534 


Radio  Broadcast 


THE    ONLY     DIFFER- 
ENCE 

Between  the  two  re- 
ceivers illustrated  here 
is  found  in  the  antenna 
circuit.  In  the  upper 
receiver  a  Selectoformer 
has  been  used  whereas 
in  the  lower  receiver  one 
of  the  Toroid  coils  made 
by  the  Electrical  Re- 
search Laboratories  in 
Chicago  has  been  in- 
corporated in  the  circuit. 
In  building  receivers  of 
this  kind  it  is  much 
better  for  the  home  con- 
structor to  fuse  flexible 
wiring  instead  of  the  bus 
bar  illustrated  here 


RADIO  BROADCAST  Photograph 


RADIO  BROADCAST  Photograph 


^uuiiuiiiiiMiiiimnMiiimiiiiiMiHmHiMmiiiHiimiiiiimHiiiiimMiiiimiiiiuiiiMmMmmMiiimiiMmiimiHmHMMmimiNiH 


,  I  HAVE  FOUND  .    .    .     . 

A  Department  *\V here  Readers  Can  Exchange  Ideas 

and  Suqqesttons  of  Value  to  the  Radio  Construcfor  andOperator  I 

3 


rlllllllllMIMIIIIIIIIIMIIIIIIIIIIIMIIIIIIIII— -^j 


ROBERTS 


PROBABLY   the  most   satisfactory  way 
to  neutralize  a  tuned  radio  frequency 
amplifier  is  to  use  the  method  recom- 
mended  by   the   neutrodyne   manufacturers. 
This  method  may  be  applied  to  the  Roberts 
with  good  results  and  eliminates  the  uncer- 
tainty of  whether  or  not  the  amplifier  is  really 
neutralized  or  not. 

A  glance  at  the  diagram,  Fig.  i,  shows  that 
the  Roberts  consists  of  three  circuits,  tuned 
radio  frequency,  detector  with  regeneration, 
and  the  reflex  circuit.  It  is  because  of  the 
reflex  circuit  that  ordinarily  the  regular 
method  of  neutralizing  cannot  be  used,  because 
in  removing  the  first  tube,  the  audio  frequency 
circuit  is  broken. 

However,  if  the  reflex  circuit  is  eliminated, 
we  still  have  one  stage  of  tuned  radio  fre- 
quency and  detector  with  regeneration  and 
can  then  proceed  to  neutralize  in  the  regular 
manner,  as  in  any  other  tuned  radio  frequency 
amplifier. 

The  procedure  is  as  follows — remove  the 
phones  from  their  regular  position  in  the  plate 
circuit  of  the  first  tube  in  the 
circuit  (X)  and  place  them 
in  the  plate  circuit  of  the  de- 
tector  tube  (Y).    We   then 
have  a  set  consisting  of  one 
stage   of    tuned    radio    fre- 
quency amplification,  and   a 
detector    with  regeneration. 

In  the  two-tube  set,  when 
the  experimenter  removes  the 
phones  from  X,  it  leaves  the 
plate  circuit  of  the  first  tube 
open.  This  may  be  remedied 
by  short-circuiting  a  phone 
plug  and  inserting  it  in  the 
jack  or  short  circuiting  the 
phone  binding  posts,  as  the 
case  may  be. 

With  the  three-and  four- 
tube  sets  this  is  not  necessary 
as  the  jacks  will  take  care  of 
this. 


/ 

nmiiiiMiifiiimmiiiiiiiiiiiiimiiiM- 


Tune-in  on  a  semi-distant  station  to  maxi- 
mum signal  strength. 

Then  remove  the  first  tube  and  insulate  one 
of  the  filament  prongs  with  a  slip  of  paper  or 
spaghetti  and  replace  the  tube  in  the  socket. 
Retune  to  bring  the  signal  to  loudest  point 
and  then  adjust  the  neutralizing  condenser 
until  the  signal  vanishes  or  reaches  minimum 
strength.  Remove  the  insulation  from  first 
tube,  replace  phones  to  their  regular  position, 
and  as  Roxy  so  ably  puts  it,  "There  you  are." 
— M.  B.  WHITNEY,  Bethel,  Vermont. 


I 


F  YOU  are  interested  in  the  Roberts 
Circuit  here  is  an  arrangement  that  will 
prove  to  be  of  a  definite  value  to  you  in 
winding  the  necessary  coils.  A  small  block 
of  hard  wood  (maple  perhaps),  is  turned  to  a 
cylindrical  form  of  2\  inches  in  diameter  and 
2^  inches  in  length,  as  in  Fig.  2.  The  circum- 
ference of  this  form  is  divided  into  thirteen 
equal  parts.  The  easiest  way  to  accomplish 
this  is  to  lay  out  the  circle  on  a  sheet  of  paper, 
as  in  the  diagram  and  make  several  trials  at 


RADIO  FREQU£NCY 
AMPLIFIER  CIRCUIT. 


FIG. 


536 


Radio  Broadcast 


Spikes' 


^2-Drill 

1  6  o  o  o  a 

—  r 
e* 

CM 

U_ 2*T -J 


FIG.  2 

division,  and  then  when  the  result  is  satis- 
factory, transfer  it  to  the  cylinder. 

In  drilling  the  holes,  care  must  be  taken  to 
keep  them  of  the  same  depth  on  the  centers. 
The  pins  are  made  from  4-  or  5-inch  nails. 
After  the  heads  and  points  have  been  removed 
they  should  be  cut  approximately  2f  inches  in 
length,  then  cut  in  half. 

Thirteen  of  these  pins  must  be  prepared. 
They  should  be  rubbed  with  emery  cloth  until 
a  fairly  snug  fit  in  the  cylinder  is  produced. 
After  the  coil  is  wound,  a  small  dab  of  collodion 
is  applied  to  each  intersection.  The  coil  is 
quite  easily  removed  by  first  twisting  and  then 
pulling  out  each  pin  with  a  pair  of  pliers. 

And  now  for  the  coils.  Antenna  coil  P 
consists  of  40  turns  with  taps  of  3-5-7-10-40. 
Coil  S  has  44  turns.  All  coils  except  the  NP 
one  are  wound  over  two  pins  and  then  under 
two  pins  and  so  on  with  No.  22  d.c.c.  wire. 
Coil  NP  consists  of  two  wires  of  No.  26  d.c.c. 
wound  together,  over  and  under  each  pin 
twenty  times.  Try  twisting  .these  two  wires 


together  before  winding.  The  tickler  coil 
T  consists  of  18  turns  of  No.  22  d.c.c.  wire. — 
RALPH  PALMER,  London,  Ontario,  Canada. 

R.   F.  TRANSFORMERS  AND  HIGH 
PLATE  VOLTAGE 

IN  WINDING  radio-frequency  transformers 
for  an  amplifier  as  described  in  the  May 
RADIO  BROADCAST  it  is  common  practice 
to  place  the  "S"  winding  directly  on  top  of 
the  P  and  N  windings.  As  the  difference  in 
d.  c.  potential  between  the  "S"  winding  and 
either  the  P  or  N  winding  is  generally  in  the 
order  of  90  volts  or  more,  the  ordinary  cotton 
covering  of  magnet  wire  is  not  to  be  depended 
upon.  When  this  insulation  between  these 
windings  breaks  down,  the  result  depends 
largely  upon  the  condition  of  the  B  supply 
(mine  is  140  volts  of  large  size  storage  and  the 
results  were  surprisingly  complete).  Just  to 
play  safe,  in  winding  the  coils  put  six  or  eight 
turns  of  heavy  silk  fishing  line  or  other  cord  be- 
tween the  S  winding  and  the  P  and  N  windings. 
After  having  done  this,  the  next  and  equally 
essential  spot  in  which  to  place  a  safeguard  is 
the  neutralizing  condenser  circuit.  I  used 
the  commercial  type  midget  variables.  These 
were  none  too  well  built  and  one  of  them  shorted 
while  being  adjusted.  Fortunately  this  short 
occurred  on  the  proper  side  of  the  A  battery 
and  the  tubes  survived,  but  one  of  the  r.f. 
transformers  disappeared  in  a  nice  puff  of  green 
smoke.  To  avoid  a  recurrence  of  these  pyro- 
technics, I  have  put  a  .001  mfd.  fixed  mica 
condenser  in  series  with  the  leads  between  the 
N  coil  and  the  variable  neutralizing  condensers 
These  condensers  are  sufficiently  large  in 
capacity  so  as  to  have  little  effect  upon  the 
settings  of  the  neutralizing  condensers  with 
which  they  are  in  series  and  the  protection 
which  ihey  afford  well  justifies  their  cost. — 
M.  K.  T. 

HELPS  FOR  CONSTRUCTORS 

TO   START  a   screw  in  an   inaccessible 
place,  rub  some  beeswax  into  the  slot, 
push  the  point  of  the  screw  driver  into 
the  slot  and  place  it  where  desired. 

To  recover  a  screw  or  other  small  part 
which  has  been  dropped  into  an  inaccessible 
place,  put  some  beeswax  on  the  end  of  a  stick 
or  suitably  shaped  tool,  push  it  against  the 
screw  and  remove  it. 

Never  put  a  hot  soldering  iron  into  the  can 
of  acid  soldering  paste.  It  ruins  the  paste 
and  the  solder  will  not  flow  as  easily  or  adhere 
as  firmly  as  before.  Even  melting  it  down 


Solder  and  Its  Use 


537 


from  the  sides  of  the  can  injures  it.  Acid 
soldering  paste  has  no  place  in  radio  work 
anyway.  Rosin  core  solder  is  just  as  easy  to 
use  if  the  surfaces  are  clean  and  the  end  of  the 
solder  is  held  against  the  metal  in  such  a  posi- 
tion that  the  melted  rosin  flows  freely  over 
the  metal  before  the  melted  solder  flows  over 
it.  Of  course,  the  point  of  the  iron  must  be 
clean  and  tinned  to  solder  well  with  any  kind 
of  flux,  and  as  the  solder  on  the  point  becomes 
dirty  from  oxidation  it  should  be  wiped  off. 
Solder  will  not  adhere  firmly  unless  the  surface 
of  the  metal  has  been  raised  to  a  temperature 
high  enough  to  melt  the  solder. — JOHN  V. 
FREDERICK,  Los  Angeles,  California. 

WINDING  COILS  "ON  AIR" 

A  GOOD  form  on  which  to  wind  the 
efficient  "pickle  bottle"  coils,  is  made 
from  a  piece  of  bakelite  tubing  of  the 
required  diameter,  which  has  a  slot  about  f 
inch  wide  cut  through  it  lengthwise.  The 
tube  is  then  placed  in  a  winding  rig,  the  proper 
number  of  turns  of  wire  put  on  and  secured 
by  narrow  strips  of  gummed  paper,  or  other- 
wise. After  which  the  tube  may  be  taken 
from  the  rig  and  the  edges  sprung  together 
sufficiently  to  allow  the  coil  of  wire  to  drop 
off.  The  coil  may  then  be  further  strength- 
ened by  putting  narrow  strips  of  gummed 
paper  inside. 

A  SAFE  HOMEMADE  B 
SUBSTITUTE  USING  no  VOLTS  A.C. 

THIS  B  battery  substitute  uses  one  toy 
transformer  such  as  is  sold  for  small 
electric  trains,  etc.,  and  while  it  has  been 
suggested  before,  this  circuit  was  always  con- 
sidered unsafe,  due  to  the  fact  that  generally 
one  leg  of  the  alternating  current  line  in 
household  use  is  grounded.  You  can  test  this 
by  putting  a  i  lo-volt  light  globe  in  a  circuit 
in  series  with  either  of  the  i  lo-volt  wires  and 
a  ground  connection.  If  the 
globe  lights  up  then  that  wire 
is  not  grounded,  if  it  does  not 
light,  the  wire  touched  is 
grounded. 

In  the  case  of  the  radio  circuit 
the  minus  B  is  practically  always 
grounded.  In  the  case  of  this 
B  substitute,  we  must  have 
the  same  wire  grounded,  other- 
wise there  will  be  a  direct  short 
and  something  will  happen. 
Where  the  B  transformer  is  set 


in  a  stationary  place  and  permanently  wired 
in  to  the  no-volt  circuit  the  grounded  side 
can  be  determined  and  the  connections  made 
accordingly.  But  where  it  is  desired  to  merely 
screw  a  plug  into  any  light  socket  for  the  B 
current  the  hook-up  shown  in  Fig.  3  must 
be  used.  First  a  two-part  screw  plug  should  be 
used.  Second  a  iio-volt  light  globe  must  be 
wired  into  the  circuit  as  shown. 

With  the  B  substitute  connected  to  the  set 
and  the  ground  (and  it  makes  no  difference 
whether  the  ground  runs  from  the  negative 
B  on  the  set  or  from  the  B  substitute  unit,) 
screw  the  first  half  of  the  plug  into  the  socket. 
Place  the  other  half  in  place  and  if  the  bulb 
does  not  light  the  grounded  wire  is  in  circuit 
with  the  grounded  negative  B.  This  is  O.  K. 
However  if  it  does  light  it  indicates  that  the 
non-grounded  side  of  the  line  is  in  circuit 
with  the  grounded  negative  B.  This  we  do 
not  want. 

To  correct  matters,  reverse  the  plug  con- 
nection, by  pulling  it  out  and  turning  half 
around  and  insert.  The  bulb  does  not  light 
in  this  position.  The  connections  are  now 
safe  for  operation  of  the  radio  set.  This  light 
globe  also  acts  to  prevent  burning  out  of 
the  tubes  in  case  of  a  short  circuit  in  the  set. 

The  writer  has  used  a  B  substitute  on  a 
three-tube  set  with  201  A  tubes  and  also  on  a 
8-tube  super-heterodyne  using  UV-IQQ  tubes 
and  has  had  excellent  results. 

A  toy  transformer  of  75  watts  capacity  is 
used.  For  the  choke  a  small  bell-ringing 
transformer  is  used  and  two  condensers  of 
3  mfd.  each.  An  adjustable  wire  resistance 
controls  the  201  A  tube  used  as  a  rectifier  and 
I  find  it  delivers  ample  current  for  the  sets 
mentioned  above. 

The  voltage  delivered  will  range  from  90 
to  105.  The  proper  voltage  for  the  detector 
current  can  be  obtained  by  inserting  a  resis- 
tance in  the  positive  B  line  after  taking 
off  a  tap  for  the  amplifier  voltage,  which 
generally  should  be  90  volts.  This  B  supply 


60  -  75  Watt 
/  Toy  Transformer 


FIG.  3 


53* 


Radio  Broadcast 


substitute  can  be  built  for  a  cost  not  exceeding 
$12.50. 

Alternating  current  hum  will  in  no  case  be 
noticeable  using  the  loud  speaker.  In  the 
case  of  headphones,  the  a.c.  hum  is  noticed 
when  forcing  the  set  on  DX  but  not  ordinar- 
ily. More  condensers  and  chokes  will  elimi- 
nate the  balance  of  the  a.c.  hum. — JAMES  B. 
HAYS,  Boise,  Idaho. 

RHEOSTATS     AND     VERNIERS     CON- 
TROLLED WITH   HORIZONTAL  DIALS 

THE  experimenter  who  wishes  to  incor- 
porate a  refinement  and  a  novel  mode 
of  adjustment  in  his  receiver  may  fol- 
low the  suggestions  in  the  drawings,  Fig.  4. 

The  rheostat  may  be  mounted  under  the 
socket  in  a  horizontal  position  with  the 
bracket,  shelf,  bushings  and  bolts.  The  dial 
used  is  cut  from  a  piece  of  bakelite  and  the 
edge  serrated  with  a  file.  It  must  be  large 
enough  to  extend  |  inch  through  the  panel 
perforation. 

The  extra  contacts  of  a  vernier  condenser, 
in  which  a  low  value  (3  plate)  unit  is  incor- 


rd  rubber  shelf 
$   Fibre  bushings ,...7 


Brass  bushing  — -— 
Dial-5" 


^'x  h"  Threaded   shaft ' 
FIG.  4 


Dial 
7/16"'V*l%"Threaded  shaft' 


Bracket 
and  bearing\ 


Bend  ", 


Panel    perforation 
FIG.   5 


porated,  theoretically  increase  its  internal  re- 
sistance. Any  condenser,  variometer,  or 
coupler  dial  may  be  fitted  with  a  friction  ver- 
nier as  shown  in  Fig.  5. 


The  panel  is  perforated  below  and  behind 
the  dial  and  the  vertical  shaft  is  held  in  posi- 
tion by  the  bracket  bearing  which  is  cut  and 
bent  from  heavy  brass  or  copper.  The  shaft 
is  fitted  with  a  rubber  knob  at  the  top  (the 
rubber  may  be  part  of  an  old  shoe  heel)  which 
working  through  the  apperture  comes  into 
frictional  contact  with  the  back  of  the  dial. 
The  dial  at  the  other  end  of  the  shaft  extends 
through  the  panel. 

These  dials  may  be  turned  with  a  sidewise 
rubbing  movement  which  will  give  true  micro- 
meter adjustment. — J.  T.  CARVES,  Hunting- 
ton,  Tennessee. 


PORCELAIN 
^ 

LEAD-lti 


WINDOW 
J50ARD 


(JAP 


w^y 

JXVBBZR 

I  COVZK. 

TO  GROUND /^l 


RADIO  LIGHTNING  ARRESTER  MADE 
FROM  SPARK  PLUG 

A  GOOD,   serviceable   lightning  arrester 
that  will  give  ample  protection   from 
lightning  surges  to  the  set  can  be  made 
by  any  radio  fan  from  old  spark-plugs.     All 
that  is  necessary  to  insure  safety,  is  to  see  that 
the  porcelain  and  shell  are  in  good  shape  so 
that  there  are  no  leakages  of  antenna  current 
to  affect  the  reception  qualities  of  the  receiver. 


A  Lightning  Arrester  Made  from  a  Spark  Plug 


539 


The  illustration,  Fig.  6  shows  the  method  of 
installation  and  is  explained  as  follows. 

Drill  and  tap  a  small  hole  in  the  shell  as 
shown,  and  thread  in  a  short  machine  screw 
with  washer.  Lead  the  antenna  down  to  the 
terminal  of  a  spark-plug  porcelain  thrust 
through  a  window  board.  The  lead  to  the  set 
can  be  soldered  to  the  contact  wire  in  the 
other  end  of  the  porcelain  as  indicated.  That 
takes  care  of  the  connection  of  antenna  to  set 
and  insures  good  insulation  from  the  house. 

Now  hang  the  spark-plug  previously  men- 
tioned from  the  binding  post  of  the  above 
mentioned  porcelain  by  a  short  piece  of  wire. 
Then  connect  the  ground  wire  to  the  shell  by 
the  machine  screw  and  the  arrester  is  com- 
plete. By  tying  a  short  length  of  old  inner 
tube  around  the  plug,  rain  will  be  prevented 
from  short-circuiting  the  gap  between  the 
points  of  the  plug.  It  is  this  gap  that  allows 
a  surge  of  electricity  from  the  antenna  to  pass 
down  into  the  ground  wire  rather  than  allow 
it  to  pass  through  the  set.  It  is  the  same  idea 
as  employed  in  many  forms  of  commercial 
arresters  and  will  do  the  work  as  well  and  at 
less  expense.  A  separate  ground  wire  will  be 
necessary  from  the  set  to  the  ground  connec- 
tion.— L.  B.  ROBBINS,  Harwich,  Massachu- 
setts. 

MAKING  HARD  RUBBER  SPIDERWEBS 
FOR  THE  ROBERTS  SET 

WITH  the  aid  of  the  pattern  published, 
in    RADIO    BROADCAST  for  January, 
1925,  cut  a  template  from  cardboard. 
Cut  five   5   inch   squares  from  T^  inch  hard 
rubber.     Drill  each  square  at  its  center  to  pass 
a  -fy  machine  screw,  and  snip  the  corners  off  so 
as  to  approximate  a  circle. 

Make  a  jig  from  two  pieces  of  hard  wood 
about  io"x  3"  xf  ".  The  construction  is  shown 
in  the  sketch.  Clamp  the  two  pieces  together, 
and  drill  three  No.  28  holes,  one  2§  inches 
from  the  top,  the  second  3^  inches  below  that, 
and  the  third  an  inch  from  the  bottom.  Re- 
move the  pieces  from  the  vise  and  clamp  them 


FIG.  7 

together  with  -^  machine  screws  3  inches 
long.  Place  the  cardboard  template  under- 
neath the  head  of  the  top  screw;  mark  and 
cut  the  slot  and  top  as  shown. 

Using  the  cardboard  template,  scratch  the 
outline  on  the  first  rough  form  and  clamp  it 
between  the  two  halves  of  the  jig.  Spacers 
are  used  to  keep  the  halves  of  the  jig  parallel. 
Clamp  the  jig  in  a  vise;  line  up  the  scratches 
of  one  slot  and  apply  a  clamp  at  B  to  keep  the 
form  from  turning.  Make  two  cuts  with  a 
hack  saw.  Knock  off  the  waste  material  with 
a  hammer  and  screw-driver.  If  the  cut  is 
stopped  short  of  the  bottom,  the  piece  will 
break  off  above  the  danger  point.  Use  a  file 
to  finish  the  slot  and  round  the  top.  Loosen 
the  clamp,  turn  the  form  to  the  next  set  of 
scratches,  tighten  the  clamp,  saw,  chip,  file, 
and  continue  the  exercise  until  the  form  is 
finished.  The  jig  and  form  is  shown  in  Fig.  7. 

If  this  first  form  is  satisfactory,  use  it  as  a 
template  to  scratch  another,  as  the  cardboard 
form  is  probably  hors  de  combat  by  this  time. 
Then  clamp  the  remaining  four  in  the  jig,  the 
marked  form  being  nearest  you;  and,  if  you 
keep  everything  lined  up,  you  will  have  a 
good  set  of  forms  in  short  order. — WAYLAND 
S.  BAILEY,  Cambridge,  Mass. 


THE  "Now  I  Have  Found     .     .     ."  department  in  this  magazine  is  planned  to  furnish  an  outlet  for 
the  many  excellent  ideas  dealing  with  various  features  of  radio  construction  and  operation  which 
reach  our  office.     If  you  have  an  idea  about  a  valuable  and  useful  new  circuit,  some  new  device  or  a 
construction  or  operating  suggestion,  we  should  like  to  have  it.     We  do  not  want  simple  or  obvious 
suggestions,  and  material  to  be  acceptable  for  this  department  must  offer  something  of  definite  value 
to  the  constructor;  mere  novelty  is  not  desired.     Payment  from  two  to  ten  dollars  will  be  made  for 
every  idea  accepted.     Manuscript  should  not  be  longer  than  300  words  and  typewritten.     An  award 
of  twenty-five   dollars  will  be  paid  for  the  best  article  published  in  every  three-month's  period. 
Address  your  manuscript  to  this  department,  RADIO  BROADCAST,  Garden  City,  New  York. 


See  the  Announcement  on  Page  548 
QUERIES  ANSWERED 


I  WISH  YOU  WOULD  RE-DESCRIBE  THE  WINDING  OF 
THE  COILS  USED  IN  THE  ROBERTS  RECEIVER. 

H.  S. — Minneapolis,  Minnesota. 

HOW  DO  YOU  APPLY  THE  ROBERTS  NEUTRALIZATION 
TO  THE  NEUTRODYNE  CIRCUIT? 

B.  O. — Coffeyville,  Kansas. 

SHOULD  A  RHEOSTAT  BE  PLACED  IN  THE  POSITIVE 
OR  NEGATIVE  SIDE  OF  THE  FILAMENT  SUPPLY? 

A.  F. —  Baltimore,  Maryland. 

WHAT  PRECAUTION  DO  YOU  ADVISE  IN  CHARGING 
B  BATTERIES  FROM  I  I  O- VOLT  A.  C.  LINES? 

H.  W—  New  York  Citv. 


HOW   TO   MAKE    THE    ORIGINAL    ROBERTS   COILS 

MOST  of  the  recent  descriptions  of  receivers 
employing  the  Roberts  system  of  neutraliza- 
tion have  referred  to  the  coil  units  as  de- 
signed by  Mr.  W.  Van  B.  Roberts  and  described 
by  him  in  the  April,  1924,  RADIO  BROADCAST. 

Slight  modifications  were  made  in  the  design  as 
described  in  the  May,  1924,  magazine  which  are  now 
standard. 

To  make  these  coils,  the  constructor  must  have 
five  spiderweb  forms  23  inches  inside  diameter  with 


To  Plate 


Represents  .,'• 
winding  of  N.P.coil 


To  Grid 
Neutralizing  Condenser 


FIG.    I 


WHY,    IN    THE    HANSCOM   "SUPER",   DOES    THE 
RECEIVER  NOT  OSCILLATE  ON  THE  LOWER  WAVES? 
C.  J.  B. — Dover,  Delaware. 

WlLL  YOU  PUBLISH  A  CIRCUIT  OF  AN  EFFICIENT 
TRANSMITTER-RECEIVER? 

J.  A.  H. — Augusta,  Maine. 

WlLL  YOU  OUTLINE  A  SYSTEM  FOR  A  COMMON 
AND  STANDARD  PRACTISE  OF  CONNECTING  TOGETHER 
A  AND  B  BATTERIES? 

H.  E. — Lincoln,  Nebraska. 

I  WANT  TO  LEARN  THE  CODE.  CAN  YOU  TELL  ME 
A  SATISFACTORY  METHOD? 

G.  J. — Boston,  Massachusetts. 


Primary  Coupling 


S       T 


Variable 
----- coupling  nut  - — .. 


Shaft  supported  by 
bushing  in  Panel 


FIG.    2 

spokes  i  T7?  inches  long,  T8s  inches  wide  at  the  top 
and  tV  inches  wide  at  the  inside  diameter. 

The  antenna  coil  is  wound  with  forty  turns  of 
No.  22  d.  c.  c.  wire  and  tapped  at  the  1-2-5-10-20-30 
and  4Oth  turns.  The  secondaries  are  wound  each 
having  forty-four  turns  of  the  same  wire.  The  tickler 
is  wound  with  twenty  turns.  The  N-P  coil  con- 
sists of  a  pair  of  No.  26  d.  c.  c.  wires' wound  together 
for  twenty  turns.  In  these  coils,  the  beginning  of 
one  and  the  end  of  the  other  are  connected  together 
and  from  this  point  a  lead  is  brought  to  the  top 
blade  of  the  double  circuit  jack  in  the  receiver. 

The  remaining  leads  of  this  coil  connect,  one  to 
the  plate  and  the  other  to  the  grid  neutralizing  con- 
denser. See  Fig.  i.  The  antenna,  secondary, 
and  tickler  coils  are  wound  over  two  and  under  two 
spokes.  The  N-P  coil  is  wound  under  one  and  over 
one  spoke  of  the  coil  form. 

A  mounting  scheme  is  suggested  in  Fig.  2. 


RADIO  BROADCAST  ADVERTISER 


541 


*ou  may  escape 

uie  collection  ~     /^y^i^^  «  w  *  o«7^ 
but  not  the  need  vfUZARKASERVICE 


'IPHE  satisfaction  you  re- 
-L  ceive  from  your  radio 
depends  not  on  what  it  does 
once  in  a  while— but  night 
after  night  and  month  after 
month.  Whether  you  grin 
or  cuss  depends  on  the  serv- 
ice behind  your  radio. 

Ozarka  radio  instruments 
are  only  sold  by  trained  fac- 
tory representatives,  men 
who  not  only  specialize  in 
radio  but  sell  and  service 
Ozarkasonly.  3, 100  of  these 
men,  trained  directly  under 
Ozarka  engineers  consti- 
tute a  service  force,  un- 
equalled elsewhere  in  radio 
today. 

When  you  buy  a  radio  you'll  com- 
pare appearance,  tone,  volume  and 
selectivity  by  having  various  in- 
struments set  up  in  your  own  home 


but— that  isn't  enough— compare 
the  service  behind  each  one. 

Any  Ozarka  factory  representative 
will  set  up  an  Ozarka  in  your  home 
— he  will  not  even  operate  it  him- 
self, but  will  depend  for  his  sale  on 
what  you  yourself  do.  If  you,  by 
your  own  operating,  do  not  bring 
in  the  distance,  the  volume  and 
tone,  you  expect  a  radio  to  give, 
then  you  do  not  buy  the  Ozarka. 
If  you  do  buy  it,  you  can  rest  as- 
sured, no  matter  what  happens,  a 
competent  service  man  is  at  your 
call  at  all  times.  No  Ozarka  rep- 
resentative can  sell  Ozarka  Instru- 
ments without  giving  Ozarka  serv- 
ice. You  are  entitled  to  such  serv- 
ice—demand it! 

That  is  why  our  book,  "Ozarka 
Instruments  No.  200,"  describing 
all  models  of  Ozarka  should  be  of 
particular  interest  to  you.  This 
book  and  the  name  of  the  Ozarka 
representative  near  you,  will  be 
sent  immediately  at  your  request. 
Please  give  name  of  your  county. 


We  Have  Openings  for 

More  Ozarka  Factory 

Representatives 

f^ZARKA  Incorporated,  is  now  enter- 
'-'  ing  its  4th  year.  From  a  beginning 
with  one  engineer,  one  stenographer, 
one  salesman  —  our  present  president, 
the  Ozarka  organization  has  grown  to 
over  3100  people.  There  must  be  some 
good  reason  for  this  growth. 
Ozarka  instruments  have  made  good — 
they  have  more  than  met  competition. 
Ozarka  representatives  have  _  made 
good  not  only  because  Ozarka  instru- 
ments were  right,  but  because  they 
have  been  willing  to  learn  what  Ozar k a 
engineers  were  willing  and  capable  to 
teach  them — Ozarka  unusual  sales- 
manship and  Ozarka  service. 
Radio  offers  a  wonderful  opportunity 
to  men  who  are  willing  to  start  at  the 
bottom  and  build.  You  need  not  know 
salemanship,  but  will  you  learn  what 
we  will  gladly  teach  you?  You  may 
not  know  radio,  but  we  can  and  will 
teach  you  if  you  will  do  your  part. 
With  such  knowledge  and  willingness 
to  work,  it  doesn't  seem  possible  that 
you  cannot  make  good.  Sign  the  cou- 
pon below,  don't  fail  to  give  the  name 
of  your  county.  Better  still  write  a  let- 
ter, tell  us  about  yourself  and  attach 
coupon.  If  interested  in  our  salesm an 's 
plan  ask  for  "Ozarka  Plan  No.  100." 


119  Austin  and  La  Salic  Streets 
Chicago,  Illinois 

Gentlemen:     Without  obligation  send  book  "Ozarka  In- 
struments No.  200"  and  name  of  Ozarka  representative. 


Name 

Address ...  City  YOU'LL  KNOW 

THE  MAN  BY 
County State THIS  BUTTON! 


1 19  Austin  and  La  Salle  Streets 
Chicago,  Illinois 


Gentlemen:  I  am  greatly  interested  in  the  FREE  BOOK 
"The  Ozarka  Plan  '  whereby  I  can  sell  your  radio  Instru- 
ments. 

Name 

Address City 

County State ..„ 


542 


Radio  Broadcast 


DETECTOR 


2  STAGES 
AUDIO  FREQUENCY 

,  Audio  Frequency  Transformers-, 
5-1  Ratio  2-1  Ratio 


O         O 

-  A   * 

6V  22  45V.   4590V. 


FIG.    3 


AN    R.    F.    CIRCUIT    EMPLOYING    ROBERTS 
NEUTRALIZATION 

FOR  a  two-stage  radio-frequency  amplifier, 
with  detector  and  two  stages  of  audio- 
frequency amplification,  the  circuit  in  Fig.  3 
is  recommended. 

The  Roberts  system  of  neutralization  is  em- 
ployed and  is  recommended  over  the  other  forms 
of  neutralization.  In  others,  the  maximum  voltage 
gain  is  not  realized,  because  the  primaries  of  the 
usual  couplers  are  wound  with  only  six  to  ten  turns 
of  wire.  In  the  Roberts  system,  more  gain  is  ob- 
tained by  the  use  of  primaries  of  20  turns.  These 
primaries  are  double  wound  and  connected  as  shown 
in  the  circuit  diagram.  No  regeneration  is  em- 
ployed but  will  increase  the  efficiency  of  the  receiver 
when  included. 

It  may  also  be  found  that  two  stages  of  straight 
audio  frequency  amplification  will  distort  the  signals 
received  on  account  of  not  being  able  to  handle  the 
detector  output  properly.  When  this  is  the  exper- 
ience, push-pull  or  resistance-coupled  amplification 
will  usually  prove  satisfactory. 

RHEOSTAT   LOCATION 

THE   placement  of  a   rheostat   in  either  the 
negative  or  positive  side  of  the  vacuum  tube 
filament  supply  opens  up  a  question  which  is 
subject  to  much  discussion.     It  is  our  purpose  here 
simply  to  make  some  observations  which  may  aid 
the  experimenter  in  his  constructional  work. 

In  a  detector  circuit  it  is  desirable  to  have  the  re- 
turn side  of  the  secondary  coil  connect  to  the  positive 
filament  lead  so  that  a  positive  voltage  be  applied 
to  the  grid  of  the  tube.  This  is  quite  necessary  for 
rectification  purposes. 

Now  in  an  amplifier  circuit,  it  is  desired  to  have 
the  return  side  of  the  secondary  of  the  audio  trans- 
former connect  to  the  negative  side  of  the  filament 
lead  so  that  the  amplifying  action  will  take  place, 
figuratively  speaking,  on  the  straight  portion  on  the 
vacuum  tube  characteristic  curve. 

By  placing  a  rheostat  in  the  negative  line,  a 
varying  negative  potential  of  from  o  to  6  volts  may 
be  obtained,  providing  the  return  side  of  the  audio 


transformer  secondary  connects  to  a  point  on  the 
rheostat  winding.  The  value  of  this  negative  po- 
tential will  depend  upon  the  location  of  this  connec- 
tion on  the  rheostat  winding. 

Naturally  if  a  C  battery  is  used  there  is  no  need 
for  obtaining  a  negative  grid  bias  in  this  manner. 

It  is  debatable  whether  or  not  any  difference  in 
operation  can  be  noticed  when  comparisons  are 
made  with  the  rheostat  first  in  one  side  and  then 
in  the  other  side  of  the  filament  leads  where  the 
return  is  made  direct  to  the  negative  filament  socket 
terminal. 

In  the  December,  1924,  Grid  on  page  304,  Fig.  i, 
is  shown  the  use  of  a  C  battery  and  potentiometer 
to  give  a  smoothly  varying  value  of  negative  grid 
volts.  Of  course  such  a  circuit  is  practical  for  test 
and  research  purposes  but  not  for  ordinary  con- 
tinuous use.  The  shunting  of  a  400  ohm  potentio- 
meter across  a  45-volt  C  battery  would  discharge 
the  battery  at  the  rate  of  .01 1  amperes  until  it  was 
completely  run  down. 

HOW   TO   CHARGE    B    BATTERIES    FROM    A.    C. 

THE  charging  of  storage  B  batteries  presents 
a  problem  to  the  individual,  especially  where 
the  house  current  is  alternating. 
Several  months  ago  explicit  instructions  with  dia- 
grams were  contained  in  the  Grid  showing  the  charg- 
ing of   B  batteries  from   various  d.c.  line  supplies. 
This  discussion  will  take  up  the  charging  of  B 
batteries  from  a.  c. 

Usually,  in  a  radio  installation,  about  96  to  124 
volts  of  B  battery  are  used.  Now  ordinary  alter- 
nating current  lines  fluctuate  in  the  voltage  supply 
varying  approximately  from  106  to  115  volts  for 
a  1 10  volt  line.  Generally  the  drop  occurs  at 
night  when  the  lines  are  heavily  loaded  for  illu- 
mination purposes. 

Therefore,  to  be  on  the  safe  side  it  is  well  never 
to  try  to  charge  more  than  96  volts  (2  units  of  24 
volts  in  series)  at  a  time.  Because  if  the  line  volt- 
age drops  below  that  of  the  batteries  they  will  dis- 
charge back  into  the  line.  Of  course  several  banks 
of  96  volts  each  may  be  connected  in  parallel  but 
the  load  on  the  line  will  be  greater. 


RADIO  BROADCAST  ADVERTISER 


543 


Simplifies  radio  tuning. 
Pencil  record  a  station  on  the 
dial  —  thereafter,  limply  turn 
the  finder  to  your  pencil  mark 
to  get  that  station  instantly. 
Easy  —  quick  to  mount.  Elimi- 
nates fumbling,  guessing. 
Furnished  clockwise  or  anti- 
clockwise in  gold  or  silver 
finish.  Gear  ratio  20  to  1. 

Silver  $2.50. 
In  gold  finish,  $3.50. 


TUNING       CONTROL 


Unusual  Features 
IncrcascReceiving  Efficiency 

TN  LESS  than  six  months  the  Ultra-Lowloss  Condenser 
has  proved  its  right  to  leadership  by  greatly  simplified 
design,  greater  tuning  efficiency,  and  radically  different 
operating  results — not  only  in  the  eyes  of  scientific  and 
engineering  men,  but  with  the  buying  public  as  well. 

These  are  the  predominating  Ultra-Lowloss  features:  (1)  Single  insu- 
lation strip  reduces  leakage  losses  materially,  (2)  Monoblock  mounting 
with  plates  cast  into  block  reduces  series  resistance  and  assures  posi- 
tive contact,  (3)  Minimum  of  metal  of  high  resistance  material  in  the 
field  and  frame  reduces  eddy  current  losses,  (4)  Cutlass  Stator  Plates 
produce  a  straight  line  wavelength  curve — separating  stations  evenly 
over  the  dial.  Each  degree  on  a  100  degree  scale  dial  represents  ap- 
proximately 3/4  meters  over  the  broadcast  wave  length  range. 
This  even  separation  applies  to  both  high  and  low  wavelengths  1 
Simplifies  tuning  materially  ! 

The  Ultra-Lowloss  Condenser  is  a  recent  development  of  R.  E.  Lacault, 
E.  E.,  originator  of  the  famous  Ultradyne  receiver. 
Design  of  Lowloss  Coils  furnished  free  with  each  Condenser  for 
amateur  and  broadcast  wavelengths  showing  which  will  function 
most  efficiently  with  the  Condenser. 

At  your  Dealer's.     Otherwise,  send  purchase  price 
and  you  will  be  supplied  postpaid. 

ULTR^-LOTULOSS 

CONDENSER 


To  manufacturers 

who  wish  to  improve 

their  sets 

I  will  gladly  consult  with 
any  manufacturer  regarding 
the  application  of  this  con- 
denser to  his  circuit  for 
obtaining  best  possible 
efficiency. 


Write  for  Descriptive  Folder. 


PHENIX    RADIO    CORPORATION 


116C  East   25th   Street 


New  York 


Tested  and  approved  by  RADIO  BROADCAST 


544 


Radio  Broadcast 


The  charging  device  may  be  any  one  of  several 
types  such  as  the  chemical  rectifier,  vibrating  mag- 
netic rectifier  or  tungar  tube  rectifier. 

In  the  first  named,  the  drop  through  the  charger 
is  about  30  volts  so  some  means  for  stepping  up  the 
voltage  must  be  employed.  Transformers  are  on 
the  market  which  will  accomplish  this. 

The  rate  of  charge  depends  upon  the  resistance 
of  the  circuit  and  voltage  of  the  supply.  The  bat- 
tery resistance  is  negligible  so  therefore  some  ex- 
ternal resistance  must  be  employed. 

Vibrating  rectifiers  depend  upon  mechanically 
perfect  construction  and  adjustment  for  satisfac- 
tory operation  and  will  not  be  discussed  here. 

In  the  tungar  rectifier,  the  tungar  tube  by  an  elec- 
tronic rectifying  action  produces  the  desired  effects. 

As  there  is  a  voltage  drop  through  this  tube  the 
same  means  for  stepping  up  the  voltage  as  used  for 
the  chemical  rectifier  must  be  employed. 

For  circuit  diagrams  relative  to  the  various 
points  brought  out  herein  the  reader  is  referred  to 
pages  230  to  236  of  the  July,  1924,  RADIO  BROADCAST. 

WHY    THE    HANSCOM    "SUPER"    WON'T   OSCILLATE  ON 
LOW   WAVES 

IN  THE  usual  radio  circuits,  experimenters  have 
noted   that  on   tuning  to   the  lower  broadcast 
waves,  the  tendency  of  the  receiver  to  go  into  oscil- 
ation  increases  conversely  with  reduction  in  wave- 
length.    In  the  Hanscom  super-heterodyne,  just  the 
opposite  phenomena  has  been  experienced. 
Mr.  Hanscom  explains  as  follows: — 

In  regard  to  the  tendency  to  oscillate  on  the 
higher  waves,  this  is  really  a  tuned  plate  effect  of 
the  first  tube,  the  resonant  point  in  the  plate 
circuit  being  governed  by  the  inductance  of  the 
Duratran  transformer.  We  think  that  some 
of  this  difficulty  may  be  due  to  long  leads  to  the 
neutralizing  condenser  as  it  is  customary  for  the 
set  to  oscillate  at  about  400  meters  with  the 
Chelten  condenser  set  at  zero.  In  general,  the 
more  turns  on  the  loop  the  earlier  the  set  will 
oscillate.  In  order  to  prove  the  case  we  suggest 
disconnecting  the  lead  from  the  Duratran  to  the 
Chelton  condenser  after  tuning  in  a  low  wave- 
length station,  and  it  will  be  found  that  the  signal 
strength  materially  increases.  Unfortunately 
there  is  no  small  condenser  on  the  market  with  a 
sufficiently  low  minimum  capacity  although  we 
have  had  good  success  with  a  condenser  employ- 
ing three  regular  size  plates  which  were  cut 
away  so  that  the  rotor  and  stator  plates  were  a 
considerable  distance  apart  at  zero  setting. 
The  foregoing  is  an  explanation  of  the  broadness 
of  loop  tuning  because  the  loop  tuning  becomes 
sharper  as  the  oscillating  point  of  the  first  tube  is 
approached. 

A   TRANSMITTER-RECEIVER   CIRCUIT 

HEREWITH     is    described     a     transmitter- 
receiver  circuit  which  of  late   has  been  in 
demand,  especially  by  our  English  readers. 
The  description  of  this  apparatus  originally  appeared 
in  the  May  1923  RADIO  BROADCAST. 

The  circuit  comprises  the  usual  one-tube  arrange- 
ment with  the  exception  that  by  means  of  a  special 
keying  system  it  also  acts  as  a  transmitter.  It  is 


especially  desirable  as  a  portable  affair.  Its  only 
drawback  lies  in  the  maintenance  of  a  fixed  trans- 
mitting adjustment  and  at  the  same  time  allowing 
of  tuning  for  receiving.  Ordinarily  transmission 
occurs  at  only  one  of  two  or  possibly  three  pre- 
arranged wavelengths.  The  tuning  and  adjust- 
ment to  resonance  at  these  wavelengths  is  reasonably 
sharp  so  that  to  maintain  two-way  communication 
it  would  be  necessary  to  shift  wavelength  adjust- 
ments, supposing  that  the  two  stations  were  not 
working  on  the  same  wavelength.  As  an  example, 
if  one  station  (A)  works  on  1 50  meters  and  the  other 
(B)  on  1 80  meters  then  A  after  concluding  his 
transmission  must  shift  his  dials  so  as  to  listen  in  on 


180  meters  (B's  wave).  Of  course,  this  is  not  a 
serious  disadvantage,  but  unless  there  is  means 
for  accurately  retuning  the  set  for  transmission  every 
time  communication  is  maintained  it  makes  it 


,-  c 

•'"    Rotor 
36  to  40  Turns 


-M 


<— ,  A 

50  Turns 

No.18D.C-C. 

Wire 


t— -  B 

10  Turns 

No-lSD.C.C. 
Wire 


FIG.    5 


545 


EVEREADY  HOUR 

EVERY  TUESDAY 

AT  8  P.  M. 

Eastern  Standard  Time 
For   real    radio _  enjoy- 
ment,   tune   in   the 
"Eveready    Group." 
Broadcast   through 


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WFI 

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WEAR 

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WWJ 

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Eveready 
Columbia 

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"A"  Battery  \ 

The 

proven 

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for  all 

radio 

dry  cell 

tubes 

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Cleveland 
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Minneapolis 
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PREFERRED 

IT  is  no  accident  that  more  Eveready 
Radio  Batteries  are  purchased  by  the 
radio  public  than  any  other  radio  batteries. 

Such  complete  and  voluntary  endorse- 
ment can  lead  to  but  one  conclusion — for 
best  reception  and  longest  life,  Eveready 
Radio  Batteries  lead  the  field. 

You  can  prove  this  for  yourself  by 
hooking  Eveready  Radio  Batteries  to 
your  set.  You  will  find  that  they  deliver 
a  steady,  vigorous  stream  of  power  that 
lasts  longer.  It  is  Eveready  economy 
that  has  created  such  an  overwhelming 
preference  for  Evereadys.  There  is  an 
Eveready  dealer  nearby. 

Manufactured  and  guaranteed  by 

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Price 
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546 


Radio  Broadcast 


No  Common  Line 


FIG.    6 


-dlllllll 


Common  Line  System 


FIG.    7 

difficult  for  the  receiving  station  to  pick  up  the  wave 
of  the  transmitter. 

In  Fig.  4  the  coils  A,  B  and  C  comprise  a  standard 
vario-coupler  redesigned  as  to  winding  in  the  manner 
shown  in  Fig.  5.  The  coil  A  consists  of  50  turns 
of  No.  18  d.  c.  c.  wire,  B  10  turns  of  the  same  wire 
and  C  36  to  40  turns  of  any  size  wire  from  No's. 
26  to  1 8.  It  will  be  necessary  to  experiment  with 
the  exact  number  of  turns  for  C  so  that  smooth 
control  of  regeneration  is  obtained  over  the  entire 
wavelength  band.  Tuning  is  controlled  by  the 
variable  condenser  in  series  with  the  antenna.  Its 
capacity  rating  is  .001  mfd.  With  the  key  in  the 
position  shown,  the  circuit  operates  as  a  receiver 
but  when  the  key  is  depressed  it  opens  the  phone 
circuit,  closes  the  plate  circuit  and  operates  the 
apparatus  as  a  transmitter. 

Undoubtedly  with  the  advent  of  the  recent 
activity  in  short  wave  transmission  this  circuit  will 
prove  exceedingly  interesting  for  experimentation. 

NEEDED    REFORM    IN    RADIO    STANDARD    PRACTISE 

WITH  something  like  250  manufactured  sets 
gracing  the  radio  market  and  easily  a  like 
number  of  circuits  for  home  construction, 
the  need  for  standardization  of  circuit  and  connection 
methods  becomes  appallingly  imperative.    The  ques- 
tion of  A  and  B  battery  connections  is  only  one  of 
many  but  is  the  main  subject  of  this  discourse. 

Many  of  the  present  circuits  connect  the  plus  A 
and  B  negative  terminals  together.  Aside  from 


adding  a  few  more  plate  volts  potential  in  the 
plate  circuit,  there  is  no  other  reason  for  this  special 
method  of  connection.  It  is  not  an  advantage  and 
is  decidedly  a  disadvantage  for  the  following  rea- 
son. 

First,  it  is  an  electrical  common  practise  to  have  a 
power  circuit  with  part  of  it  at  ground  potential. 
At  least  there  is  a  common  lead  which  serves  as  a 
base  for  meter  reading. 

Obviously  it  is  impossible  to  make  the  positive 
leads  (for  instance  of  A  and  B  batteries)  common, 
so  the  most  natural  thing  and  advantageous  me- 
thod would  be  to  make  the  negative  sides  common. 
See  Fig.  6.  This  system  would  greatly  facilitate 
meter  reading  of  A  and  B  potentials  by  merely 
flipping  a  switch.  It  would  also  make  the  reading 
of  circuit  diagrams  easier. 

Another  desirable  point  of  standardization  lies 
in  the  placement  of  rheostats.  Tube  manufactur- 


600  Meter  Traffic L-  100  to  150  Turn  Honeycomb  Coil 

1200-2600A    »    L-300to400      ••*;;-'"• 

2600-5000A    »   L=  750  »  - 

5000-15J300A    -   L=1500  »  *  » 

FIG.    8 


Ant       Gnd. 


B 


FIG.    9 


RADIO  BROADCAST  ADVERTISER 


f  f   f  ? 


I  ou  ARE  PLANNING  to  build  a  radio  receiver  and  you  want 
to  know  what  kind  to  make.  Shall  it  be  a  one-tube  reflex, 
or  a  four-tube  ultra-sensitive  tuned  and  neutralized  radio- 
frequency  receiver  using  regeneration  and  push-pull  ampli- 
fication? The  book  which  will  satisfy  the  needs  of  every 
radio  constructor,  RADIO  BROADCAST'S  KNOCK-OUT  RE- 
CEIVERS, contains  instructions  on  how  to  build  these — in 
fact  it  tells  how  to  make  eight  separate  receivers. 

CVERY  PURSE  and  every  desire  is  satisfied  in  the  collection  of 
receivers  described  in  this  book.  Each  one  of  the  receivers  was 
developed  through  the  cooperation  of  RADIO  BROADCAST,  and 
thousands  of  radio  enthusiasts  all  over  the  country  have  built 
these  sets  with  the  greatest  of  satisfaction. 

J.  HERE  IS  NO  BETTER  group  of  receivers  from  which  to  pick  the 
type  to  build  than  those  contained  in  RADIO  BROADCAST'S  KNOCK- 
OUT RECEIVERS  because  they  have  been  designed  by  experts  to  fit  the 
need  of  the  broadcast  listener.  All  of  them  can  be  built  from  standard  parts. 

COMPLETE  INFORMATION  is  contained  in  the  book  (which  has  one  hundred 
pages),  for  building  these  receivers,  but  no  blue  prints  can  be  sold  with  it. 
Well  known  radio  authors  like  Walter  Van  B.  Roberts,  Zeh  Bouck,  Kenneth 
Harkness,  John  B.  Brennan,  and  others  have  written  the  descriptions.  This 
book  is  now  being  printed  and  deliveries  will  be  made  at  once.  It  will  be 
sent  to  any  address  on  receipt  of  $1.00. 


DOUBLEDAY,  PAGE  &  COMPANY, 
GARDEN  CITY,  NEW  YORK 

Please  find  enclosed  $1.00  for  RADIO  BROADCAST'S  KNOCK-OUT  RECEIVERS  to 
be  sent  to 


548  Radio  Broadcast 

ers  advise  placing  a  rheostat  in  the  negative  side  of  tube,  socket,  rheostat  and  batteries  (antenna  and 

the  filament  supply  so  that  a  negative  grid  bias  ground  also)  it  is  possible  to  listen  in  on  NSS,  Annap- 

may  be  obtained.  olis,  17,000  meters;  YN,  Lyons,  France,  on  15,100 

With  the  use  of  C  batteries  for  biasing  there  is  meters;  KET,  Bolinas,  California  on   13,345,  ar|d  so 

no  reason  for  not  placing  the  rheostat  in  the  posi-  on  down  the  scale. 

tive  lead  which  is  the  more  practicable.     See  Fig.  7.  Some  of  these  stations  transmit  slowly,  repeating 

each  word  so  that  after  one  becomes  proficient  here 

CODE  INSTRUCTION  he  may  jump  down  to  the  faster  lanes  of  ship  to 

FOR  learning  the  code  by  one's  self  there  is  shore  traffic, 

nothing  better  than   memorizing  the  char-  The  circuit  of  the  receiver  is  shown  in  Fig.  8  and 

acters  and   then   listening-in  on   long  wave  the  layout  of  the  parts  in  Fig.  9.     A  i-inch  board 

transmission.     And  the  surprising  thing  about  it  is  8  inches  wide  and    12  inches  long  is  suitable.     A 

that  it  can  be  done  with  a  single  tube.     The  Ameri-  panel  7  inches  high  and   12  inches  long  allows  for 

can  Radio  Relay  League's  publication,  QST,  outlines  the  mounting  of  the  condenser,  rheostat  and  jack, 

in  its  March  and  June,  1925,  issues  a  receiver  satis-  Wire  with  bus  wire  for  permanency.     For  additional 

factory  for  just  such  purposes.  information  on  this  receiver  it  is  well  to   consult 

With  a  single  honeycomb  coil,  variable  condenser,  the  issues  of  QST  mentioned  above. 


Before  You  Write  to  the  Grid 

THOUSANDS  of  you  are  writing  the  Grid  for  technical  advice  every  month.  The 
expense  of  framing  a  complete  and  exhaustive  reply  to  each  letter  is  very  high.  The  edi- 
tors have  decided  that  the  benefit  of  the  questions  and  answers  service  will  continue 
to  be  extended  to  regular  subscribers,  but  that  non'subscribers  will  be  charged  a  fee 
of  $1  for  each  letter  of  inquiry  which  they  send  to  our  technical  department.  Very 
frequently,  our  technical  information  service  proves  of  definite  money  value  to  you  who 
write  us,  for  we  are  often  able  by  a  sentence  or  two  of  explanation,  to  put  you  on  the  right 
path  before  you  have  made  a  perhaps  expensive  mistake. 

The  occasional  reader  of  RADIO  BROADCAST  will  be  charged  a  fee  of  $1  for  complete 
reply  to  his  questions,  and  the  regular  subscriber  can  continue  to  take  advantage  of  the 
service  as  before.  In  that  way  the  non-subscriber  will  help  share  the  cost  of  the  technical 
staff  whose  service  he  gets.  Every  letter  receives  the  benefit  of  the  experience  of  the  editor 
and  the  technical  staff  and  every  correspondent  may  be  sure  that  his  questions  will  receive 
careful  consideration  and  reply. 

When  writing  to  the  Grid,  please  use  the  blank  printed  below. 


GRID  INQUIRY   BLANK 
Editor,  The  Grid, 

RADIO  BROADCAST, 

Garden  City,  J^ew  Tor\. 
Dear  Sir. 

Attached  please  find  a  sheet  containing  questions  upon  which  tyndly  give  me  fullest 
possible  information.     I  enclose  a  stamped  return  envelope. 

.  (Chec}{  the  proper  square} 

EH  I  am  a  subscriber  to  RADIO  BROADCAST.     Information  is  to  be  supplied  to  me  free 
of  charge. 

EH  I  am  not  a  subscriber.    I  enclose  $1  to  cover  costs  of  a  letter  answering  my  questions. 
My  name  is : 


My  address  is. 

G.  A. 


RADIO  BROADCAST  ADVERTISER 


573 


The  familiar  names 
WD-11,  WD-12, 
UV-199,  UV-200 
and  UV-20I-A 
rightfully  belong 
to  Radiotrons 
only.  To  be  sure  of 
quality,  it  is  irn- 
portanttolookcare- 
iully  at  the  base  of 
every  tube  you  buy 
to  see  that  it  carries 
the  name  Radio- 
tron  and  the  RCA 
mark  as  proof  that 
it  is  a  genuine 
Radiotron. 


It  isn't  a 


UV-199 
unless 


ts  a 


adiotron 


Radio  Corporation  of  America 


Chicago 


New  York 


San  Francisco 


iotron 


Tested  and  approved  by  RADIO  BROADCAST 


WHERE  RADIO  IS  NOT  SIMPLY  "FURNITURE" 

A  farmer  s  home  in  central  Iowa,  where  the  radio  receiver  is  a 
"bit  al  part  of  the  home  equipment.  Farmers  have  found  market 
reports  a  direct  financial  help  to  them  during  the  daylight 
hours.  In  the  evening  the  farmers  are  some  of  the  most  inter- 
ested of  broadcast  listeners.  Radio  is  helping  to  solve  the 
problem  of  how  to  keep  the  farmers  on  the  farm 


RADIO 
BROADCAST 


Vol.  7  No.  5 


September,  1925 


Is  the  Radio  Newspaper  Next? 

Newspaper  Organizations  Have  Been  Quick  to  Seize  the 
Opportunity  of  Radio — How  the  News  is  Sent  Ashore  and 
Afloat — The  Possibilities  of  the  Tabloid  Radio  Newspaper 


BY  JAMES  C.  YOUNG. 


THE  future  of  the  press  lies  in  the  air. 
Radio  represents  the  one  channel  of 
news  expansion  not  already  developed 
to  the  full.    When  Fort  Sumter  was 
fired  on  in  1861,  the  Pony  Express  rode  full  tilt 
for  a  whole  week  to  carry  the  news  to  Cali- 
fornia.    Even  then  the  telegraph  wire,  linked 
from  pole  to  pole  between  skirmishes  with 
Indians,  was  advancing  across  the  continent. 
This  was  the  eighth  wonder  of  the  world,  sur- 
passing all  other  wonders  in  the  descent  of  man 
— a  tiny  thread  of  copper  carrying  sound  un- 
measured distances. 

Then  came  the  telephone.  Its  appearance 
was  coincidental  with  the  girdling  of  the  globe 
by  cable  lines.  But  the  last  and  greatest 
age  of  communication  did  not  begin  until  three 
decades  later,  when  crude  instruments  first 
feebly  recorded  wireless  waves.  The  last  ten 
years  have  served  to  improve  radio  to  such  an 
extent  that  man  can  instantly  transmit  his 
thoughts  around  the  sphere. 

Meanwhile  the  newspaper  has  also  de- 
veloped until  now  it  has  become  a  permanent 
record  of  modern  life.  What  is  said  and  done 
the  world  over  finds  expression  in  this  record. 
The  total  number  of  words  sent  daily  by  tele- 
phone, telegraph  and  cable,  between  news- 
papers everywhere,  would  test  the  average 
man's  imagination.  Radio,  the  newest  agent 


of  the  press,  bears  but  a  small  part  of  this 
burden.  On  busy  days,  the  word  traffic  be- 
tween Europe  and  America  will  rise  to  100,000 
words.  When  business  is  dull  this  total  falls 
off  to  50,000  or  even  less. 

But  radio  by  no  means  is  limited  to  the 
transmission  of  news  between  agents  of  the 
press.  It  is  rapidly  becoming  a  part  of  the 
press.  We  might  call  it  an  aerial  edition  and  not 
be  far  in  the  wrong.  More  than  fifty  American 
newspapers  send  out  bulletins  at  short  inter- 
vals to  the  owners  of  radio  sets  both  far  and 
near,  informing  them  of  the  latest  decision  of 
the  British  cabinet.  That  decision  may  not  be 
half  an  hour  old  when  some  sheep  herder  in 
the  backlands  of  Texas  will  learn  that  English 
labor  has  prevailed  in  its  demands  for  better 
housing  at  state  expense.  Or  the  speeding 
waves  of  radio  may  convey  word  that  Morocco 
is  engaged  in  a  new  war.  Even  the  gossip  of 
Broadway  and  the  last  quotation  on  wheat  are 
whisked  around  the  world  for  all  to  hear. 

This  aerial  edition  of  the  press,  usually 
issued  every  thirty  minutes  by  the  newspapers 
participating,  offers  possibilities  which  excel 
those  of  the  established  editions  published 
daily  by  the  great  metropolitan  plants.  The 
instant  communication  of  important  matters 
to  the  whole  body  of  mankind  is  now  possible. 
Any  great  event  that  transpires  to-day  must 


576 


Radio  Broadcast 


THE    PONY    EXPRESS 

In  the  earlier  days  of  national  development  was  the 
chief  means  of  communicating  intelligence.  The 
method  was  slow,  not  especially  certain,  and  rather 
hard  on  the  pony  expressman.  This  old  engraving 
shows  an  express  relay  station  in  the  Rocky  Moun- 
tains 

be  known  within  five  minutes  wherever  men 
have  ears. 

THE    INFLUENCE    OF    NEWS    BROADCASTING    ON 
THE    PRESS 

THIS  new  practice  of  instantaneous  news 
broadcasting  must  essentially  have  a  wide 
influence  on  the  press.  A  dozen  years  ago  the 
"extra  edition"  was  the  special  marvel  of  the 
newspaper  field.  In  some  plants  it  was  possi- 
ble to  produce  such  an  edition  within  twenty 
minutes  from  the  time  of  a  world  develop- 
ment. During  the  recent  war  these  extra 
editions  were  almost  an  hourly  event,  parti- 
cularly when  the  battle  of  the  Marne  hung  in 
suspense  and  the  Germans  beat  hard  upon  the 
door  of  Flanders. 

Peace  brought  fewer  editions  and  a  steadier 
tone  to  the  press.  In  the  few  years  since 
1918,  radio  broadcasting  has  developed  so 
extensively  and  intensively  that  extra  editions 
would  lose  much  of  their  interest  if  the  war 
were  under  way  to-day.  It  might  be  argued 
that  bulletins  in  front  of  newspaper  offices 
whet  the  public  appetite  for  news,  instead  of 
dulling  its  edge.  But  these  bulletins  are 
glimpsed  by  only  a  few  thousands  of  people. 
And  at  best  they  are  nothing  more  than  skele- 
tonized dispatches. 

This  is  not  the  case  with  radio  news  broad- 
casting. When  events  justify,  announcers 
inform  a  myriad  listeners  what  has  transpired. 
It  is  easy  to  read  dispatches  in  full.  Ordinarily 
news  of  the  first  rank  arrives  in  short,  preg- 


nant messages.  The  man  with  a  radio  set  may 
learn  in  the  evening  of  some  great  event  that 
his  particular  newspaper  will  not  convey  to 
him  until  the  next  morning.  When  an  event 
of  this  kind  is  far  distant — such  as  the  Tokio 
earthquake — it  frequently  happens  that  a  day 
or  more  will  elapse  before  details  begin  to 
come  through. 

In  view  of  all  of  these  considerations,  no 
one  may  doubt  that  radio  is  exerting  a  strong 
influence  on  the  press,  and  the  press  certainly 
will  have  an  equal  bearing  on  radio.  It  would 
seem  that  the  press  has  been  somewhat  back- 
ward in  developing  the  possibilities  of  news 
transmission  and  broadcasting.  Only  a  com- 
paratively small  group  of  American  news- 
papers are  using  the  international  stations 
and  there  are  but  two  press  receiving  stations 
in  existence. 

Publishers  of  small  newspapers  have  found 
that  radio  broadcasting  reduces  interest  in 
warmed  over  news.  It  is  an  old  axiom  of  such 
newspapers  that  the  scissors  are  mightier  than 
the  pen  and  seldom  are  the  shears  idle  when  a 
small  paper  is  in  the  making.  But  the  publica- 
tion of  matters  already  covered  by  some 
broadcasting  station  will  not  satisfy  even 
country  readers.  The  event  may  have  been 
completed,  perhaps  wholly  reversed,  by  the 
time  that  these  papers  appear. 

Therefore  small  papers  are  beginning  to 
suffer  from  radio  competition.  Even  the 
papers  in  large  cities  will  feel  the  stress  of  this 
competition  as  it  expands.  But  we  may  be 
certain  that  the  newspaper  is  a  fixed  institu- 
tion. Although  it  may  lose  some  of  its  claim 
to  freshness,  when  news  broadcasting  becomes 
general,  it  will  have  wide  opportunity  to 
amplify  and  develop  news.  In  a  measure,  the 
newspaper  is  likely  to  evolve  along  the  lines 
of  established  magazine  practice,  departing 
somewhat  from  the  breathless,  last  minute 
attitude  that  marks  such  a  large  section  of 
the  press.  If  that  evolution  ever  comes  about, 
it  will  bring  a  large  measure  of  relief  to  an 
abused  public.  We  may  conceive  of  the  day 
when  no  paper  can  print  such  headlines  as  this 
one — "Burglar  Slays  Widow;  Flees  With 
Jewels" — for  the  excellent  reason  that  it  will 
be  "old  stuff."  When  the  next  edition  comes 
out  the  burglar  may  be  in  jail,  by  the  help  of 
radio. 

THE    EFFECT   OF   THE    WAR 

AFTER  the  Armistice,  radio  development 
received   a   new  stimulus.     But   it    also 
lost  in  momentum  because  of  the  lessening  of 
concentrated   attention   bv  the  world's   best 


Is  the  Radio  Newspaper  Next  ? 


577 


©  Underwood  &  Underwood 
A    CALIFORNIA    STAGE    COACH 

Navigating  a  mountain  road.     The  article  by  Mr.  Young  draws  an  interesting  parallel  between  the  present 
almost  instant  methods  of  spreading  news,  seconds  after  it  is  news,  and  the  infinitely  slower  methods  avail- 
able to  our  great-grandfathers 


inventive  brains.  For  a  year  or  two  the  whole 
subject  was  vague  and  uncertain.  Transatlan- 
tic service  was  bad.  So  the  New  York  Times, 
always  among  the  leaders  in  news  enterprise, 
determined  to  install  its  own  station.  This 
station  first  went  into  use  in  1920,  becoming  the 
example  and  cornerstone  for  all  latter  day  de- 
velopments. In  the  beginning  it  was  largely 
an  experiment,  and  the  experimental  spirit  has 
continued  to  dominate  its  operation. 

The  New  York  Times  has  been  called  a  war 
paper,  because  much  of  its  prestige  resulted 
from  the  thoroughness  of  its  dispatches  from 
1914  to  1918.  In  the  language  of  newspaper 
men,  the  Times  "covered  the  war  like  it 
covered  Harlem."  The  coming  of  peace  left 
so  many  problems  unsettled  in  Europe  that 
prompt,  dependable  radio  service  was  a 
necessity  for  the  continuance  of  this  policy. 


The  station  has  been  equipped  for  the  widest 
range  of  transmission.  Its  daily  news  report 
averages  about  10,000  words,  and  these  mes- 
sages can  be  recorded  from  three  stations 
simultaneously,  on  wavelengths  of  50  to  25,000 
meters.  Some  of  these  dispatches  literally 
are  sent  around  the  world. 

How  such  enterprise  may  be  rewarded  was 
indicated  not  long  ago  when  the  Shenandoah, 
the  Navy's  big  dirigible,  broke  from  her  moor- 
ing mast  at  Lakehurst,  New  Jersey,  and  went 
careening  away  in  a  wild  storm.  The  Navy 
already  had  lost  two  dirigibles,  both  by  ex- 
plosions, with  heavy  loss  of  life.  Seemingly 
another  tragedy  impended.  But  word  scarcely 
had  been  flashed  from  Lakehurst  when  the 
Times  station  picked  up  the  Shenandoab's  call 
and  learned  that  all  was  well,  the  big  ship  plung- 
ing along  in  the  gale,  embarrassed  but  safe. 


578 


Radio  Broadcast 


This  event  took  place  just  about  the  hour 
that  the  Times  was  going  to  press.  The  news 
was  duly  printed  on  the  first  page,  giving  the 
paper  a  "beat"  such  as  seldom  falls  to  any 
publication  in  this  day  of  news  organization. 
The  Times  station  also  has  been  first  with  a 
number  of  sos  messages  and  it  figures  daily  in 
the  dissemination  of  world  news. 

NEWSPAPERS     INSTALL     A     JOINT     STATION 

PLAINLY  the  early  success  of  the  Times 
with  radio  dispatches  was  not  to  go  un- 
observed. The  American  Newspaper  Publish- 
ers Association,  working  through  a  special 
committee,  determined  to  experiment  with  ra- 
dio transmission.  The  Times  and  the  Chicago 
Tribune  have  been  prominent  supporters  of  the 
plan,  which  resulted  in  the  erection  of  a  sta- 
tion at  Dartmouth,  Nova  Scotia,  for  trans- 
atlantic work.  This  station  is  just  across  the 
bay  from  Halifax  and  affords  the  advantage 
of  acknowledging  radio  dispatches  by  means 
of  the  imperial  cable  ending  at  Halifax. 

In  February  of  1922,  the  station  began 
operation  and  now  is  in  direct  communication 
daily  with  four  of  the  big  plants  in  Europe, 
those  at  Leafield,  and  Northolt,  England, 
Lyons,  France,  and  Coltano,  Italy.  A  new 
station  is  now  under  construction  near  by  for 
the  retransmission  of  dispatches  which  come 


to  Dartmouth.  So  far  the  traffic  has  been 
handled  by  telegraph  and  telephone  wires, 
but  it  is  planned  to  send  the  news  direct  to 
subscribers  from  the  new  plant. 

This  Dartmouth  station  and  that  of  the 
Times  work  in  close  cooperation,  one  relieving 
the  other  when  storms  or  other  causes  render 
reception  difficult.  The  two  of  them  would 
seem  to  have  proved  that  radio  transmission 
across  the  Atlantic  is  a  thoroughly  practical 
undertaking  for  private  newspaper  organiza- 
tions. Such  plants  also  afford  some  measure 
of  protection  in  the  despatch  of  news  which 
may  have  great  value.  It  is  to  be  believed 
that  the  next  year  or  two  will  witness  further 
enterprise  in  this  direction. 

The  New  York  World,  also  interested  in  the 
Nova  Scotia  plant,  has  conducted  wide  experi- 
ments in  the  transmission  of  photographs  by 
radio.  This  subject  has  had  attention  from 
the  World  for  several  years  and  the  photo- 
graphs already  received  warrant  belief  that 
the  World  may  install  a  station  one  of  these 
days  exclusively  for  the  purpose  of  transmit- 
ting radio  photographs. 

Extensive  experiments  have  been  conducted 
by  the  International  News  Service,  one  of  the 
Hearst  organizations,  for  the  purpose  of  au- 
tomatic reception  and  elimination  of  static, 
doubtless  with  the  view  to  installing  a  trans- 


THE    TRANSATLANTIC    NEWSPAPER    RADIO    STATION 

At  Halifax,  Nova  Scotia,  as  it  looked  under  construction  in  1922.  J.  A.  Burch,  engineer,  and  F.  E.  Mein- 
holtz,  chief  operator,  New  York  Times,  are  seated,  left  to  right.  This  station  is  maintained  by  a  syndicate 
of  about  nine  of  the  largest  newspapers  in  the  United  States  purely  to  receive  press  messages  addressed  to 
it  from  foreign  countries.  The  messages  are  then  forwarded  to  the  supporting  newspapers  by  the  usual 
methods.  Little  transmitting  is  done  from  this  site  except  to  acknowledge  messages  and  to  get  correc- 
tions. A  power  of  about  ten  kw.  is  employed 


Is  the  Radio  Newspaper  Next  ? 


579 


atlantic  station  when  conditions  warrant  it. 
These  four  news  organizations  have  the  radio 
field  practically  to  themselves. 

In  the  matter  of  broadcasting,  first  honors 
fall  to  the  Chicago  Tribune,  which  introduced 
the  half  hourly  bulletin  now  sent  out  regularly 
from  WON  in  Chicago.  The  Tribune  operated 
its  own  plant  for  a  time  but  later  determined  to 
use  one  of  the  commercial  stations.  Its  bulle- 
tins are  well  known  to  a  large  section  of  the 
American  public,  furnishing  a  brief  survey  in 
terse  language  of  just  what  is  going  on  in  the 
world.  The  bulletins  sent  out  by  the  Radio 
Corporation  of  America  also  are  copied  on 
ships  in  the  seven  seas.  Some  of  the  big 
passenger  vessels,  maintaining  their  own 
printing  plants,  reproduce  these  dispatches  in 
the  form  of  miniature  newspapers  which  are 
distributed  every  day  the  traveler  is  aboard. 
On  other  ships,  lacking  this  pretentious  equip- 
ment, they  still  constitute  a  tie  with  the  world 
of  affairs  which  lies  behind  and  before. 

KYW,  also  in  Chicago,  broadcasts  the  bulle- 
tins of  the  local  Hearst  papers,  which  further 
inform  the  public  of  the  activities  of  its  neigh- 
bors whether  they  happen  to  live  in  the  next 
county  or  on  the  next  continent.  Even  secret 
treaties  and  whispered  understandings  have 
drifted  into  this  great  hopper  of  news.  Radio 
now  supplements  the  press  in  disseminating 
such  information  everywhere.  The  man  who 


runs  need  not  pause  to  read.  He  can  listen 
as  he  goes  and  take  with  him  a  concise,  photo- 
graphic mind  picture  of  how  the  world  is  con- 
ducting itself. 

MANY    PAPERS    BROADCAST  NEWS 

OTHER  papers  in  many  states  are  broad- 
casting news  by  radio,  ranging  from  such 
diverse  communities  as  Detroit  to  Fort  Worth. 
It  is  an  odd  phase  of  New  York  journalism 
that  none  of  the  country's  greatest  papers  so 
far  have  embarked  in  news  broadcasting.  But 
the  practice  is  growing  daily,  notably  in  cities 
of  the  200,000  class,  where  life  is  not  quite  so 
busy  as  in  the  big  centers,  and  people  pre- 
sumably have  more  time  to  heed  the  world's 
gossip.  It  is  even  said  that  farmers'  wives 
have  quit  listening  on  the  party  line  when 
Mrs.  Jones  calls  up  the  grocer,  preferring  to 
get  the  latest  word  from  Paris  about  this 
season's  dresses.  Radio  news  is  broadly 
diversified,  as  it  should  be.  It  is  a  noticeable 
reflection  of  the  daily  newspaper.  First  comes 
the  "leader,"  the  big  story  of  the  hour.  Then 
the  other  news  in  a  descending  scale.  Occa- 
sionally there  is  an  editorial  squib.  The  sports 
department,  ordinarily  the  last  in  rank,  fre- 
quently enjoys  a  larger  number  of  minutes 
than  all  of  the  other  departments  joined  to- 
gether. The  public  may  or  may  not  care 
about  the  British  cabinet  decision  and  the  new 


THE    RADIO    ROOM    OF    THE    NEW    YORK       TIMES 

Here,  operators  are  constantly  on  duty  receiving  press  messages  addressed  to  them  from  their  correspon- 
dents abroad.  A  watch  is  also  kept  on  the  various  commercial  wavelengths.  In  that  way,  news  is  trans- 
muted almost  instantly  from  the  air  to  the  printed  page.  The  Times  has  been  able  to  score  many  news 
"beats"  through  the  enterprise  of  their  listening  radio  operators.  F.  E.  Meinholtz,  chief  radio  operator  of 
the  Times  is  standing,  and  R.  J.  Iveson  is  seated  at  the  typewriter.  The  apparatus  on  the  long  table  is 
devoted  almost  entirely  to  receiving  from  European  stations  on  wavelengths  of  10,000  meters  and  above 


580 


Radio  Broadcast 


war  in  Morocco,  but  it  always  wants  to  know 
whether  Babe  Ruth  has  knocked  another  homer 
and  if  it  really  is  true  that  poor  old  Ty  Cobb 
has  a  "charlie  horse"  and  must  quit  the  game. 
If  the  moralist  wished  to  seek  a  lesson  from 
the  example  the  preponderance  of  sports  news 
over  other  kinds,  as  broadcasted  in  the  great 
radio  press,  he  might  find  a  number  of  in- 
teresting suggestions.  For  one  thing,  Ameri- 
cans are  a  vigorous  people,  with  a  strong  lean- 
ing to  the  dramatic.  Since  Mr.  Ruth  and  Mr. 
Cobb  are  the  very  essence  of  our  national 
drama,  the  average  radio  user  is  deeply  inter- 
ested in  their  home  runs  and  "charlie  horses." 


NEWS    FROM    AIRPLANES 

Is  being  forwarded  by  radio.  Both  means  have  been  most  successful  in 
impressing  the  present  generation  with  the  speed  with  which  news  is 
gathered  and  disseminated.  The  photograph  shows  a  radio  transmitter 
and  receiver  installed  aboard  one  of  the  latest  types  of  British  airplanes 
belonging  to  the  British  Imperial  Air-ways  and  used  in  cross-channel 
passenger  and  freight  flights.  This  is  the  first  photograph  to  reach  this 
country  of  the  interior  of  the  control  equipment  of  these  planes,  and  is 
one  of  the  few  good  photographs  in  existence  of  an  airplane  interior 


Another  thing  worth  considering  is  the  fact 
that  sports  news  was  the  first  of  any  kind  to 
be  sent  out  by  radio.  Baseball,  football,  and 
the  prize  ring  lead  where  the  serious  figures  of 
news  and  editorials  are  now  beginning  to 
follow. 

It  does  not  take  much  imagination  to  call 
up  the  day  when  we  shall  get  a  complete  news- 
paper by  radio  read  to  us  by  a  specially 
trained  voice.  Life  is  to  be  made  a  little 
simpler  for  the  man  who  works  all  day  and 
says  he  is  "too  tired  to  read  the  paper  to- 
night." Before  long  he  may  have  it  read  for 
him  by  a  man  who  knows  how,  a  man  who  will 
study  his  tastes  and  reac- 
tions with  the  skill  of  an 
actor. 

Doubtless,  our  mentor  not 
only  will  read  us  the  news 
and  the  editorials  and  all 
about  the  baseball  team,  but 
maybe  he  will  have  a  comic 
strip  of  his  own,  and  we  can 
imagine  the  funny  little  fig- 
ures while  he  reads  the  cap- 
tions. Then  we  also  may 
expect  a  column  of  wit,  writ- 
ten to  order  every  day, never 
repeating  a  joke  older  than 
that  one  about  the  Irishman 
who  carried  bricks  up  the 
ladder  while  the  man  on  top 
did  the  work. 

Such  is  to  be  the  radio 
newspaper  of  to-morrow,  or 
something  approximating 
this  brief  glimpse.  Perhaps 
it  will  have  a  fashion  col- 
umn and  the  busy  housewife 
can  note  down  the  sizes  and 
descriptions  of  new  dresses. 
Conceivably  the  cross  word 
puzzle  will  be  a  feature  if 
the  fad  lasts  much  longer. 
We  could  draw  our  own 
squares  and  spend  the  rest 
of  the  night  happily,  after 
the  announcer  gave  us  a 
few  instructions.  In  fact, 
the  radio  newspaper  may 
be  made  almost  anything 
that  the  public  wants. 
Whatever  this  evolution  is 
destined  to  be,  the  radio 
newspaper  has  become  an 
accomplished  fact.  And 
certainly  there  is  the  call  now 
for  the  latest  bit  of  news. 


An  All- Wave  Tuned  Radio 
Frequency  Receiver 

How  to  Build  an  Efficient  Receiver  With  High-Quality 
Audio  Amplification,  Designed  to  Cover  the  Frequency 
Band  from  1500  to  116  Kilocycles  (200  to  2600  Meters) 


BY  ZEH  BOUCK 


rj  ^  HIS  receiver  embodies  no  especially  new  circuit  ideas,  but  it  forms  a  very  valuable 
•*-  acquisition  to  the  receiving  equipment  of  the  experimenter  who  wishes  to  hear 
signals  on  other  waves  that  those  alloted  to  broadcasting  in  the  United  States  and  near-bv 
countries.  In  France,  England,  Australia,  and  Germany  there  are  broadcast  stations 
transmitting  way  above  the  conventional  wavelengths,  and  many  American  listeners  have 
expressed  a  lively  interest  in  hearing  signals  from  those  broadcasters.  The  use  of 
resistance-coupled  amplification  insures  excellent  quality  in  the  audio  part  of  this  cir- 
cuit. And,  too,  for  those  broadcast  listeners  who  are  beginning  to  be  curious  about  what 
is  going  on  in  radio  telegraph  channels,  this  set  will  give  them  a  good  frequency  band 
from  which  to  choose  their  signals.  They  can  hear  much  traffic  between  ships  at  sea 
and  shore  stations  and  some  amateui  communication  as  well.— THE  EDITOR 


UNLIKE  American  stations,  foreign 
broadcasters  are  not  confined  to  the 
frequency  band  between  1500  and 
520  kilocycles  (200  to  575  meters). 
On  the  contrary,  many  foreign  stations,  par- 
ticularly those  of  continental  Europe,  broad- 
cast on  frequencies  below  500  kilocycles  (above 
600  meters),  as  well  as  upon  the  wavelengths 
with  which  our  domestic  amateurs  are  fami- 
liar.    This  elasticity  of  tuning  somewhat  com- 
plicates the  situation  of  the  foreign  enthusiast, 
whose  problems  were  recently  brought  home 
to  the  writer  by  the  request  of  a  Belgian  friend 
for  a  receiver  filling  these  particular  require- 
ments. 

The  set  is  to  be  operated  at  Turnhout,  Bel- 
gium, some  three  hundred  miles  from  SBR 
Brussels,  the  nearest  broadcasting  station,  and 
about  seventy-five  miles  from  Antwerp.  As 
the  radio  entertainment  of  my  friend's  family 
will  be  divided  between  England  and  the 
continent  (and  perhaps  American  stations), 
the  receiver  must  respond  with  equal  efficiency 
over  a  comparatively  large  frequency  band — 
between  1500  and  116  kilocycles  (200  to 
2600  meters). 

It  is,  of  course,  difficult  to  design  an  efficient 
receiver  to  cover  this  band  employing  one 
permanent  set  of  inductances,  i.  e.,  using 
sufficiently  large  coils  to  attain  the  higher 
waves,  and  tapping  for  the  lower  waves.  The 
losses  and  inefficiencies  attending  such  ex- 


tensive tapping  would  seriously  impair  the 
effectiveness  of  the  receiver  on  the  higher 
frequencies  (lower  waves). 

Honeycomb  coils  suggest  themselves  in  the 
usual  three  coil,  primary,  secondary,  and  tick- 
ler arrangement,  as  an  obvious  solution. 
Unfortunately,  the  wide  separation  of  foreign 
stations  implies  the  necessity  of  at  least  one 
stage  of  radio  frequency  amplification  if  con- 
sistent reception  of  four  fifths  of  the  stations 
is  to  be  achieved.  The  efficiencies  of  the 
honeycomb  coils  in  the  conventional  long  wave 
circuits,  however,  are  quite  applicable  to  radio 
frequency  amplification,  and  the  ultimate  re- 
ceiver almost  solves  its  own  problems  in  the 
form  of  a  "five  honeycomb  coil  set." 

With  the  growing  stimulation  of  interest  in 
international  broadcasting  and  its  reception,  it 
is  probable  that  many  American  enthusiasts 
will  be  interested  in  duplicating  this  receiver. 

HONEYCOMB    INDUCTANCES    ARE    USED 

THE  circuit  is  diagrammed  in  Fig.  i.  The 
coils  L  are  all  honeycombs.  L,  is  the 
antenna  primary,  and  L2  secondary  inputting 
to  the  r.  f.  tube.  L3  functions  as  the  primary  of 
the  radio-frequency  transformer.  L4  is  the 
r.  f.  secondary  in  the  grid  circuit  of  the  de- 
tector tube,  and  L5  is  the  tickler  coil.  It  will 
be  observed  that  the  circuit  is  merely  the  con- 
ventional three-coil  arrangement  with  the 
addition  of  a  stage  of  tuned  radio  frequency 


582 


Radio  Broadcast 


amplification.  In  changing  wave  bands,  the 
coils  in  each  of  the  five  mounts  are  replaced 
by  different  sizes.  By  selecting  the  proper 
values,  any  frequencies  used  to-day  for  trans- 
mission of  radio  telephony  or  telegraphy  can 
be  received. 

Returning  to  the  circuit,  switch  St  is  the 
usual  series-parallel  switch  which  adds  con- 
siderably to  the  tuning  possibilities  of  the 
antenna  tuning-condenser  Q.  d  is  preferably 
a  forty-three  plate  variable  condenser.  C2 
and  C3  are  secondary  tuning  variable  con- 
densers each  having  a  capacity  of  .0005  mfd. 
C4  is  a  .006  mfd.  Micadon  by-pass  con- 
denser. C3  is  a  .0025  mfd.  bypass.  C6  is  the 
usual  .00025  mfd.  grid  condenser.  Cj,  C8, 
and  CQ  are  the  isolating-coupling  condensers 
of  the  resistance-coupled  amplifier,  all  being 
Micadons  of  .006  mfd.  capacity.  Cio  is  an 
output  bypass  condenser,  capacity  .006  mfd. 
which  may  or  may  not  be  necessary  in  in- 
dividual receivers. 

Rx  is  a  three  hundred-  to  four  hundred-ohm 
potentiometer  which  stabilizes  the  r.  f.  circuit. 
Ra  is  the  conventional  2-megohm  grid  leak 
across  the  grid  condenser.  R3  is  a  General 
Radio  ten-ohm  rheostat.  R4  is  a  dismantled 
twenty-ohm  rheostat  placed  in  series  with  the 
small  three-volt  pilot  lamp,  PL.  This  lamp 
is  located  behind  a  colored  glass  jewel  on  the 
panel  and  is  an  effective  and  attractive  signal 
that  the  tubes  are  burning.  It  is  not,  of 
course,  essential  to  the  operation  of  the  re- 
ceiver. R5  throughout  the  resistance-coupled 
amplifier  represents  the  coupling  resistors  of 
one  hundred  thousand  ohms  resistance.  R6, 
Rj,  and  R8  are  amplifier  grid  leaks,  having 
respective  values  of  i  megohm,  \  megohm, 
and  j  megohm. 

The  coupling  resistors,  coupling  condensers, 
and  amplifying  tube  grid  leaks  are  combined 
for  efficient  compactness  into  three  Daven 
Resisto-Couplers.  Daven  resistors  are  used 
throughout  the  amplifier.  The  initials  on 
the  diagram  represent  the  initialing  on  the 
couplers. 

JT  is  a  standard  closed  circuit  jack,  placed 
in  the  plate  circuit  of  the  first  audio  frequency 
tube.  This  is  preferable  to  plugging-in  on  the 
detector.  Jack  J2  is  an  open  circuit  jack  with 
filament  control.  Switch  S2  turns  on  all  fila- 
ments when  the  loud  speaker  plug  is  in  jack 
]„  and  the  first  three  tubes  with  the  plug  is 
in  jack  Jt. 

The  4-5-volt  C  battery  while  not  altogether 
necessary,  is  desirable.  Particular  note  should 
be  taken  of  the  amplifier  grid  leak  connec- 
tions. 


LIST   OF    PARTS 

THE  circuit  diagram,  Fig.  i,  represents  the 
following  parts  used  in  the  construction 
of  the  receiver: 

One  three  coil  Branston  Mounting 
Two  Cotocoil  mounting  brackets 
5  Na-ald  Sockets 

2  .0005  mfd.  variable  condensers 
.001  mfd.  variable  condenser 
Midget  vernier  condenser  (across  C3) 
series  parallel  switch 
Cutler-Hammer  battery  pull  switch 
General  Radio  ten-ohm  rheostat 
4Oo-ohm  General  Radio  potentiometer 
.00025  mfd.  Micadon 

5  .006  mfd.  Micadons 
i  .0025  mfd.  Micadon 

4  Daven  grid  leak  resistors,  2  meg.,  i  meg.,  ^  meg. 
and  j  meg. 

3  Daven  ioo,ooo-ohm  coupling  resistors, 
i  7-inch  x  21 -inch  bakelite  panel 

3  Daven  Resisto-Couplers 

8  Eby  binding  posts 

i  Pacent  closed  circuit  jack 

i  Pacent  open  circuit,  filament  control  jack 

These  parts  represent  an  approximate  cost  of 
thirty-five  dollars.  To  this  price  must  be  added 
the  expense  of  whatever  honeycomb  coils  are  se- 
lected for  reception  of  various  frequencies. 

CONSTRUCTION 

pHE  constructional  details  of  the  all-wave 
*  receiver  are  clearly  suggested  in  the  panel 
layout,  Fig.  3,  and  in  the  photographs  of  the 
completed  receiver,  Figs.  2,  and  4. 

Referring  to  the  back  of  panel  photograph, 
Fig.  2,  the  Cotocoil  single  honeycomb  coil 
mountings  are  screwed  to  the  baseboard  near 
the  right  hand  (rear  view)  end.  Coils  L,  and 
LB  are  plugged  into  these  receptacles.  Partly 
hidden  and  to  the  right  of  the  coils  a  resistance 
strip  from  a  rheostat  can  be  discerned,  fastened 
to  the  baseboard.  This  is  placed  in  series 
with  the  small  three-volt  pilot  lamp  as  de- 
scribed in  reference  to  the  circuit  diagram. 

The  pilot  lamp  itself  is  screwed  into  a  small 
miniature  socket  from  which  the  porcelain 
shell  has  been  removed.  It  is  placed  beneath 
the  antenna  tuning  condenser,  and  the  glass 
jewel  can  be  seen  in  the  lower  left  of  Fig.  4. 

The  large  dial  controls,  in  the  panel  photo- 
graph Fig.  4,  are,  left  to  right,  tuning  con- 
densers, C,,  C2,  and  C3.  The  lower  left  is  the 
series-parallel  switch.  The  upper  right  hand 
knob  is  the  midget  vernier  condenser  across 
the  tuning  condenser  Q.  Below  the  vernier 
is  the  potentiometer. 

In  wiring  the  receiver,  particular  care  should 


An  All-Wave  Tuned  R.  F.  Receiver 


FIG.    I 

The  circuit  diagram  for  the  all-wave  tuned  radio  frequency  receiver 


FIG.    2 

Mack  of  panel  view  of  the  all-wave  set  showing  construction  of 
the  resistance-coupled  amplifier  and  the  mounting  of  Li  and  1,2 


Radio  Broadcast 


FIG.    3 

The  panel  layout  for  the  universal  receiver.     The  numerals  near  the 
designated  holes  indicate  the  size  drills  to  be  used  in  drilling  them 


be  observed  in  making  connections  between  the 
A  battery  and  the  various  tubes,  resistances, 
and  switches,  being  careful  to  follow  every 
sequence  on  the  diagram. 

OPERATION 

TUNING  and  operation  of  the  receiver  is 
quite  the  same  as' that  of  the  conventional 
three  honeycomb  coil  arrangement  with  the 
slight  added  complication  of  an  extra  con- 
trol. 

The  following  is  a  table  of  coil  sizes  for  the 
various  domestic  and  foreign  broadcasting 
wavelengths: 

1500    TO    6OO    K1LOCYCLF.S    (200-500    METERS) 

35  50  35  50  75 

665  TO  334  KG.  (450  TO  900  METERS) 

100  100  50  100  120 

483  TO  272  KG.  (620  TO  i  loo  METERS) 

loo  150  75  150  150 

272  TO  1 1 5  KG.  (iioo  TO  2600  METERS) 

150  250  150  250  200 

Unfortunately,  the  receiver  I  am  describing 
was  not  in  my  hands  sufficiently  long  to  deter- 
mine coil  values  for  still  higher  waves.  It  is 
suggested  that  the  experimenter  guide  himself 
by  the  sizes  specified  for  the  conventional 
three-coil  long  wave  receiver. 


There  is  also  no  reason  why  the  all-wave 
receiver,  efficiently  constructed,  should  not  be 
quite  satisfactory  on  the  extremely  short 
waves — the  region  of  megacycles.  With  Lo- 
renz  coils  wound  on  a  three-inch  form,  with 
fifteen  spokes,  the  following  sizes  should  cover 
from  40  to  70  meters.  Lx  3  turns,  L2  6  turns, 
L3  5  turns,  L4  6  turns  and  L5  1 1  turns.  On 
these  extremely  high  frequencies,  it  is  recom- 
mended that  capacity  neutralization  be  sub- 
stituted for  bias  stabilization,  with  the  poten- 
tiometer. A  three-turn  neutralizing  coil 
should  be  wound  simultaneously  with  L3,  and 
connected  as  in  the  usual  Roberts  or  Browning 
Drake  arrangements.  It  is  suggested  that 
experimentation  on  wavelengths  below  two 
hundred  meters  be  left  to  the  more  advanced 
and  serious  experimenter  and  amateur.  The 
manipulation  of  the  receiver  on  these  frequen- 
cies requires  more  than  ordinary  skill,  and 
even  a  comparatively  non-radiating  receiver, 
such  as  we  have  described  is  not  innocuous 
under  inexperienced  operation. 

In  operating  the  all-wave  receiver,  the  po- 
tentiometer should  always  be  kept  sufficiently 
far  on  the  positive  side  to  stabilize  the  r.  f. 
tube. 

Selectivity  will  be  increased  as  coupling  is 
loosened  between  L3  and  L4,  as  is  usual  with 
honeycomb  receivers.  Loosening  this  coup- 
ling will  also  increase  the  effectiveness  of  the 
r.  f.  controls.  If  situated  within  a  mile  or  so 
of  a  high  powered  station,  interfering  oscilla- 
tions may  force  themselves  across  the  radio- 
frequency  circuits.  Breaking  the  connection 
close  to  the  ground  lead  at  X,  Fig.  I  will 
eliminate  such  by-passed  interference. 


An  All-Wave  Tuned  R.  F.  Receiver 


585 


•  X 


FIG.   4 

Front  view  of  the  completed  receiver.     The  two  honeycomb 
coils  to  the  left  function  as  a  tuned  radio  frequency  transformer 


HIGH-MU  TUBES  IN  THE  LAST  AUDIO  STAGE 

IT  IS  recommended  that  five-volt  vacuum 
*•  tubes  be  used  throughout  the  receiver.  They 
will  give  excellent  loud  speaker  results  on  dis- 
tant stations  with  a  good  antenna.  However, 
if  high-mu  tubes  (there  are  several  makes  on 
the  market)  are  available,  they  can  be  em- 
ployed most  effectively  in  the  first  and  second 
stages  of  the  resistance-coupled  amplifier.  A 
power  tube  (never  a  high-mu  tube)  in  the 


output  socket  will  increase  the  possible  volume 
without  distortion.  If  the  output  is  taken 
from  jack  J,  a  standard  tube  should  be  used 
in  the  first  resistance-coupled  stage. 

The  tuning  characteristics  of  the  all-wave 
receiver  are  most  satisfactory,  providing  se- 
lectivity and  distance,  while  the  resistance- 
coupled  amplifier  insures  quality  beyond  re- 
proach. 

The  following  is  a  list  of  long  wave  broad- 
casting stations: 


FOREIGN   BROADCASTING  STATIONS 


AUSTRALIA: 

2FC,  272  kc.  (uoo  meters) 
2FL,  389  kc.  (770  meters) 
3to,  174  kc.  (1720  meters) 
5M.\,  352  kc.  (850  meters) 

AUSTRIA: 

RH  500  kc.  (600  meters) 

BELGIUM: 

BAV,  272  kc.  (uoo  meters) 

CZECHOSLOVAKIA  : 

OKP,  260  kc.  (1150  meters) 
Komarov  167  kc.  (1800  meters) 
Prague,  PRO,  300  kc.    (1000  meters) 

DENMARK: 

OXE.  130  kc.  (2400  meters) 


FRANCE: 

FL,  115  kc.  (2600  meters) 

GERMANY: 

LP,  440  kc.  (680  meters) 

HOLLAND: 

PCGG,  280  kc.  (1070  meters) 
PA  5  286  kc.  (1050  meters) 
PCFF  150  kc.  (2000  meters) 

HUNGARY,  BUDA  PESTH: 
1 50  kc.  (2000  meters) 

SPAIN: 

EBX,  250  kc.  (1200  meters) 

SWITZERLAND: 

HBI,  272  kc.  (uoo  meters) 


When   Broadcast  Stations 
Interfere 

An  Explanation  of  "Heterodyne"  Interference  Produced  By 
Broadcast  Stations — What  the  Department  of  Commerce  Is 
Doing  to  Minimize  the  Difficulty — How  the  Listener  Can  Aid 

BY  C.  B.  JOLLIFFE 

Physicist,  Bureau  of  Standards 

more  ihan  a  year,  RADIO  BROADCAST  has  been  printing  informative  articles 
about  bow  various  kinds  of  interference  troublesome  to  the  broadcast  listener  may 
be  traced,  reduced,  or  altogether  conquered.  Among  the  first  of  these  was  a  series  on 
"Man-Made  Static"  by  A.  F.  Van  Dyck,  the  first  of  which  appeared  in  this  magazine  for 
April,  1924.  In  the  July  RADIO  BROADCAST,  there  were  two  articles,  one  by  John  V .  L. 
Hogan  and  the  other  by  Dr.  Alfred  N.  Goldsmith,  which  told  how  to  use  single-circuit 
receivers  without  annoyance  to  one's  neighbors.  This  article,  which  is  published  by  per- 
mission of  the  Director  of  the  Bureau  of  Standards  of  the  Department  of  Commerce,  tells 
bow  the  steady  squeals  produced  by  any  two  broadcast  stations  which  are  heterodyning 
each  other  occur,  and  the  efforts  being  made  by  the  Department  of  Commerce  to  lessen  this 
rather  unusual  form  of  interference. — THE  EDITOR 


A  TIMES,  when  tuning-in  a  broad- 
casting station,  there  is  heard  in  the 
receiving  set  a  whistling  sound  whose 
pitch  (frequency)  cannot  be  changed 
no  matter  what  is  done  to  the  controls  of  the 
set.  As  the  tuning  adjustments  are  changed, 
the  whistle  reaches  greatest  intensity  at  one 
point  on  the  dials  and  dies  away  gradually  as 
they  are  turned  from  this  tuning  point.  The 
fact  that  the  note  remains  the  same  pitch  dis- 
tinguishes it  from  the  whistle  of  varying  pitch 
("birdies")  pro- 
duced by  your 
own  or  some 
other  person's 
generating  (os- 
cillating) re- 
ceiving set. 

If  the  tuning 
con'trols  are 
turned  slowly 
while  one  lis- 
tens carefully  it 
will  usually  be 
found  that 
there  are  two 
stations  which 
can  be  heard 
very  close  to- 
gether when 
the  whistle  is 
at  its  maxi- 


HOW   BEAT   NOTES    ARE    PRODUCED 

In  No.  i  the  curve  A-A1  covers  a  range  of  from  795  to  805  kilo- 
cycles with  its  peak  at  800  kc.  Curve  B-B1  with  its  peak  at  80 1 
kc.  covers  a  band  of  796  to  806  kc.  The  beat  is  equal  to  the 
difference  of  the  two — in  this  case  1,000  cycles.  In  No.  2  we  have 
a  less  pronounced  example.  Here  the  peak  of  C-C1  is  at  820  kc. 
while  that  of  D-D1  is  at  828.  Since  the  transmitted  wave  is 
assumed  to  cover  a  band  10  kc.  wide  it  is  obvious  that  there  will 
be  an  overlapping.  The  difference  here  is  8  kc.  or  8000  cycles. 
Example  No.  3  shows  no  overlapping  and  no  beat  is  produced. 
It  is  possible  in  some  instances  where  there  is  overlapping  that 
the  difference  is  so  great  as  to  produce  a  beat  above  the  frequency 
range  which  the  human  ear  can  hear 


mum  loudness.  These  two  transmitting 
stations  are  "beating"  and  producing  the 
whistle.  Let  us  take,  for  example,  two  sta- 
tions that  are  on  frequencies  of  800  and  80 1, 
kilocycles  per  second  (wavelengths  375,  and 
374.5  meters).  Signals  from  both  of  these 
stations  enter  the  receiving  set  and  in  addition 
to  giving  up  to  the  set  the  messages  (music, 
etc.)  which  they  carry,  the  radio-frequency 
currents  produced  by  the  carrier  waves  com- 
bine and  produce  a  note  which  has  a  frequency 

equal  to  the 
difference  be- 
tween the  fre- 
quencies of  the 
two  received 
waves,  in  this 
case  i  ooo  cycles 
per  second. 
This  is  a  high- 
pitched  whistle. 
Any  two  sta- 
tions that  are 
closer  together 
than  3000  cy- 
cles will  give  a 
whistle  which 
can  be  heard 
and  which  is 
very  annoying. 
The  frequency 
of  the  whistle 


When   Broadcast  Stations   Interfere 


587 


is  always  the  difference  in  the  frequencies  of 
the  waves  of  the  two  beating  stations. 

The  assignment  of  frequencies  (wave- 
lengths) which  is  made  by  the  Department  of 
Commerce  to  the  transmitting  stations  is 
such  that  no  two  Class  B  stations  operating 
simultaneously  should  be  closer  in  frequency 
than  10,000  cycles.  Two  stations  having  a 
difference  in  their  frequencies  of  10,000  cycles 
produce  a  beat  note  which  is  too  high  to  be 
readily  audible.  So  if  all  Class  B  broadcast- 
ing stations  maintain  accurately  the  frequency 
which  they  are  legally  entitled  to  use  they 
would  produce  no  beat  interference.  These 
Class  B  stations  are  the  ones  to  which  the 
large  majority  of  the  people  listen  and  are 
assigned  frequencies  between  550  and  1000 
kilocycles  (wavelengths  545  to  300  me- 
ters) 


WHAT    THE    RADIO    SUPERVISORS    ARE    DOING 

E  radio  supervisors  are  continually 
checking  and  adjusting  the  frequencies 
of  the  stations  in  their  districts  and  making  an 
effort  to  keep  them  exactly  on  their  assigned 
frequencies.  A  transmitting  station,  however, 
requires  constant  inspection  of  its  frequency 
for  its  operators  to  be  sure  that  it  remains  con- 
stant. .  The  supervisors  are  unable  to  give 
this  much  attention  to  a  single  station  since 
there  may  be  several  hundred  stations  (broad- 
cast, amateur,  commercial,  etc.)  under  the 
jurisdiction  of  one  supervisor  and  his  two  or 
three  assistants.  It  has  been  recommended 
that  all  broadcasting  stations  require  and  use 
an  indicating  instrument  which  tells  them 


HOW    THE    BROADCAST    STATION 
CHECKS    ITS   WAVELENGTH 

With  the  wavemeter,  which  the  operator  is  adjusting  here,  it  is  possible  to  know  whether  the  broadcasting 
station  is  complying  with  government  regulations  and  transmitting  on  the  wavelength  assigned  to  it.  In 
the  photograph  at  the  right,  the  hand  is  pointing  to  chokes  in  the  radio  frequency  circuit.  Sometimes  in  an 
oscillating  circuit  there  are  harmonic  frequencies  set  up  besides  the  fundamental  frequency  on  which  the 
station  operates.  To  eliminate  harmonic  frequencies,  choke  coils  resonant  to  these  frequencies  are  em- 
ployed to  absorb  them.  Incidentally  here  is  shown  a  very  good  example  of  the  compact  and  rugged  con- 
struction of  the  transmitter  proper 


588 


Radio  Broadcast 


when  they  are  exactly  on  their  assigned  fre- 
quencies. Specifications  for  an  instrument 
for  this  purpose  have  been  prepared  by  the 
Bureau  of  Standards,  and  it  has  been  put  in 
use  in  several  broadcasting  stations  after 
being  set  at  the  Bureau.  This  device  has 
been  found  to  be  a  valuable  help  in  maintain- 
ing the  stations  on  their  proper  frequencies. 

During  the  past  year,  the  Bureau  of  Stand- 
ards has  also  been  active  in  assisting  the  super- 
visors of  radio  in  setting  the  broadcasting 
stations  to  their  assigned  frequencies  and 
keeping  them  there.  The  Bureau  of  Stand- 
ards has  occasionally  made  simultaneous 
measurements  with  various  supervisors  on 
broadcasting  stations  to  determine  the  fre- 
quency of  the  station  or  to  check  the  setting 
made  by  the  supervisors.  This  also  serves 
as  a  check  on  the  accuracy  of  the  supervisor's 
wavemeter.  Twice  each  month,  standard 
frequency  signals  are  sent  out  by  the  Bureau 
which  can  be  used  by  the  supervisors  of  radio 
as  well  as  others  to  calibrate  their  wavemeters. 

In  addition  to  the  measurements  requested 
by  the  supervisors,  the  Bureau  has  made  fre- 
quency measurements  on  many  broadcasting 
stations.  The  results  of  these  measurements 
are  furnished  to  the  supervisors  and  tell  them 
what  stations  in  their  district  are  varying 
from  their  frequency  and  producing  beats  or 
likely  to  do  so.  Some  of  the  supervisors  of 


radio  are  also  equipped  to  make  frequency 
measurements  on  distant  broadcasting  stations 
at  their  office.  These  measurements  show 
that  there  are  a  few  stations  which  have 
maintained  their  frequencies  very  accurately 
for  nearly  a  year;  in  fact,  so  constant  that  they 
have  been  announced  as  standard  frequency 
stations  suitable  for  use  for  wavemeter  cali- 
bration. These  stations  are  announced  each 
month  in  the  Radio  Service  Bulletin,  a  publica- 
tion of  the  Department  of  Commerce.  The 
price  is  25  cents  a  year  and  orders  should  be 
placed  with  the  Superintendent  of  Documents, 
Government  Printing  Office,  Washington, 
D.  C.  The  constancy  of  these  stations  dem- 
onstrates that  if  special  care  is  given  by  the 
operator,  a  transmitting  set  can  be  adjusted 
to  its  assigned  frequency  and  be  kept  there 
over  a  long  period  of  time. 

HOW    THE     RADIO     SERVICE     HELPS     ELIMINATE 
INTERFERENCE 

THE  work  of  the  supervisors  of  radio,  as- 
sisted by  the  Bureau  of  Standards,  in 
setting  and  maintaining  the  frequencies  of 
Class  B  broadcasting  stations  has  been  very 
successful.  There  are  really  very  few  whistles 
produced  by  transmitting  stations.  However, 
nearly  constant  supervision  is  necessary  to 
keep  the  stations  from  changing.  The  station 
operators  are  cooperating  in  this  work  and 


Station 

Standard  Frequency  Stations 

As- 
signed 
fre- 
quency 
(kilo- 
cycles) 

Period 
covered 
by 
measure- 
ments 
(months) 

Num- 
ber of 
times 
meas- 
ured 

Deviations  from 
assigned  fre- 
quencies noted 
in  measure- 
ments 

Owner 

Location 

Aver- 
age 

Great- 
est 
since 
Mar. 
20,  1925 

WQL 

NSS 
WCI. 

WGG 

wso 

WVA 
WEAF 

WCAP 
WRC 

WSB 
WOY 
WBZ 

KDKA 

Radio    Corporation    of 
America. 
United  States  Navy  
Radio    Corporation    of 
America. 
do 

Coram  Hill,  Long  Is- 
land, N.  Y. 
Annapolis,  Md  

17.13 

17.60 
17.95 

18.86 
25.80 
100 
610 

640 

040 

700 
790 
900 

970 

4 

20 
2 

20 
20 
1 

4 

19 
16 

19 
22 
12 

19 

31 

156 
13 

159 
122 
20 
45 

87 
69 

78 
124 
35 

158 

Per  ct. 
0.1 

.2 
.2 

.1 

.3 
.1 
.0 

.1 
,1 

.1 
.1 
.1 

.1 

Per  ct. 
0.2 

.8 
.3 

.4 
.2 
.4 
.0 

.2 
.2 

.4 
.2 
.4 

.3 

Barnegat,  N.  J    .    

Tuckerton  No.  1,  N.  J. 
Marion,  Mass 

do  

United  States  Army  
Amrrican  Telegraph  <fe 
Telephone  Co. 
Chesapeake  &  Potomac 
Telephone  Co 
Radio    Corporation    of 
America. 
Atlanta  Journal  

Annapolis,  Md 

New  York,  N.  Y 

Washington,  D.  C  
do      

Atlanta,  Ga  

General  Electric  Co  
Westinghouse  Electric  & 
Manufacturing  Co. 
do  

Schenectady,  N.  Y  
Springfield,  Mass  

East  Pittsburgh,  Pa... 

When  Broadcast  Stations  Interfere 


589 


most  of  them  are  taking  particular  care  to  keep 
the  frequency  of  their  station  where  it  should  be. 
You  can  assist  in  the  elimination  of  beat  notes 
produced  by  the  interaction  of  the  waves  of 
two  stations.  Whenever  you  hear  a  whistle 
of  constant  pitch,  that  is,  one  which  varies 
only  in  loudness  as  the  controls  of  your  re- 
ceiving set  are  adjusted,  it  usually  indicates 
that  one  or  both  of  two  transmitting  stations 
are  not  adjusted  to  their  assigned  frequencies. 
If  you  can  identify  the  two  stations  producing 
this  whistle,  notify  the  Supervisor  of  Radio 
in  whose  district  the  stations  are  located. 
A  list  of  the  radio  districts  is  given  at  the  end 
of  this  article.  It  is  necessary  that  both  sta- 
tions which  are  producing  the  whistle  be 
identified,  for  it  is  only  necessary  for  one  of 
them  to  be  off  its  assigned  frequency  to  pro- 
duce a  beat  and  without  measuring  instru- 
ments it  is  impossible  to  tell  which  one  is 
wrong.  There  is  also  a  possibility  that  one 
of  the  stations  causing  the  "beating"  is  not  a 
broadcasting  station  but  an  "oscillating" 
set  of  some  kind  whose  frequency  is  being 
maintained  constant.  However,  it  is  ex- 


ceptional for  a  receiving  set  to  be  left  adjusted 
in  such  a  condition  continuously,  and  when- 
ever the  frequency  is  changed  the  character- 
istic variable  pitch  whistle  will  be  heard. 

OSCILLATING    RECEIVER    INTERFERENCE 
MINIMIZED 

IF  THE  broadcasting  stations  will  maintain 
exactly  their  assigned  frequencies  it  will 
not  only  eliminate  the  whistles  caused  by  beats 
but  will  also  help  in  the  elimination  of  the 
other  type  of  whistle  caused  by  hunting  for 
broadcasting  stations  while  the  receiving  set 
is  in  an  oscillating  condition.  When  a  trans- 
mitting station  is  located  on  the  tuning  dials, 
a  record  can  be  made  of  the  dial  setting.  Then 
the  next  time  it  is  desired  to  find  out  if  that 
station  is  operating,  all  that  is  necessary  is  to 
set  the  controls  at  the  point  determined  be- 
fore. New  stations  can  also  be  located  with 
respect  to  the  position  of  known  stations. 

The  maintaining  of  the  exact  frequency  of 
broadcasting  stations  therefore  is  of  twofold 
importance:  (i)  the  elimination  of  the  whistles 
produced  by  the  stations  themselves,  and  (2) 


SEEING       THE    RADIO   WAVE 

At  wjz,  an  oscillograph,  or  visual  means  for  observing  the  character  of  the  transmitted  wave,  is  employed 
to  check  up  on  transmission.     With  this  instrument  the  engineer  may  see  whether  his  wave  is  within  bounds, 

during  all  broadcast  periods 


590 


Radio  Broadcast 


increase  in  the  ease  of  setting  the  dials  to  find 
stations  and  so  eliminating  some  of  the  whistles 
produced  by  hunting  for  stations  with  a  gen- 
erating (oscillating)  receiving  set. 

SUPERVISORS    OF    RADIO 

First  District  — Maine,  New  Hampshire,  Ver- 
mont, Massachusetts,  Rhode  Isl- 
and, Connecticut — U.  S.  Super- 
visor of  Radio,  Customhouse, 
Boston,  Massachusetts. 

Second  District  — New  York  City  and  vicinity, 
Southeastern  New  York — U.  S. 
Supervisor  of  Radio,  Custom- 
house, New  York,  New  York. 

Third  District  - — Eastern  Pennsylvania,  Southern 
New  Jersey,  Delaware,  Mary- 
land, Virginia,  D.  C—  U.  S. 
Supervisor  of  Radio,  Custom- 
house, Baltimore,  Maryland. 

Fourth  District  — North  Carolina,  South  Carolina, 
Georgia,  Florida, — U.  S.  Super- 
visor of  Radio,  Federal  Building, 
Atlanta,  Georgia. 


Fifth  District  — Tennessee,  Alabama,  Louisiana, 
Mississippi,  Arkansas,  Oklahoma, 
Texas,  New  Mexico — U.  S. 
Supervisor  of  Radio,  Custom- 
house, New  Orleans,  Louisiana. 

Sixth  District  — Arizona,  Utah,  Nevada,  Califor- 
nia— U.  S.  Supervisor  of  Radio, 
Customhouse,  San  Francisco, 
California. 

Seventh  District — Washington,  Oregon,  Idaho, 
Montana,  Wyoming — U.  S.  Su- 
pervisor of  Radio,  2301  L.  C. 
Smith  Bldg.,  Seattle,  Washington. 

Eighth  District  — New  York  (except  second  dis- 
trict), Western  Pennsylvania, 
West  Virginia,  Ohio,  Michigan — 
U.  S.  .Supervisor  of  Radio,  Fed- 
eral Bldg.,  Detroit,  Michigan. 

Ninth  District  — Indiana,  Illinois,  Kentucky,  Wis- 
consin, Minnesota,  Iowa,  Mis- 
souri, North  Dakota,  South 
Dakota,  Nebraska,  Kansas,  Col- 
orado— U.  S.  Supervisor  of  Radio, 
Federal  Bldg.,  Chicago,  Illinois. 


Cutting   Down   Spark   Inter- 
ference on  the   Great  Lakes 

Results  of  the  Canadian-American  Conference  at  Detroit  Which 
Will  Result  in  Better  Receiving  Conditions  for  Upper  New  York, 
Ohio,  Michigan,  Ontario,  Illinois,  Indiana,  Wisconsin,  and  Minnesota 

BY  CORLEY  W.  KIRBY 


INTERFERENCE   from  spark  transmit- 
ting stations,  which  has  regularly  marred 
broadcast  reception  in  every  city  along 
the  Great  Lakes,  will  be  eliminated  as  a 
result  of  the  conference  held  in  Detroit  May 
4th  and  5th  by  representatives  of  the  United 
States  Department  of  Commerce  and  the  Can- 
adian  Department  of  Marine  and  Fisheries. 
In  addition  to  representatives  of  the  two  gov- 
ernments,  the  conference   was   attended   by 
representatives  of  the  Canadian  and  American 
commercial  radio  companies,  steamship  com- 
panies and  others  who  were  directly  interested. 
The   recommendations   of  the   conference, 
which  will  undoubtedly  be  accepted  by  the 
respective    governments,     and    which    were 
agreed  to  by  the  commercial  representatives 
attending,  follow: 

All  Canadian  and  American  coast  and  ship  sta- 
tions on  the  Great  Lakes  open  for  general  public 


service  business  must  be  equipped  to  work  on  a 
frequency  of  420  kilocycles  (a  wavelength  of  715 
meters),  which  will  be  the  normal  frequency  of  the 
station.  All  Canadian  and  American  stations  must 
maintain  a  watch  on  this  frequency. 

The  frequency  of  342  kc.  (875  meters)  is  author- 
ized for  the  handling  of  general  public  service  cor- 
respondence. The  use  of  this  wavelength  by 
coastal  stations  is  optional. 

Communication  between  a  coastal  station  and  a 
station  on  shipboard  or  between  ship  stations  shall 
be  exchanged  on  the  part  of  both  by  means  of  the 
same  wavelength. 

For  general  public  service,  communications  be- 
tween ship  and  shore  and  ship  and  ship  when  work- 
ing with  stations  other  than  the  nearest  station 
must  be  on  a  wavelength  of  875  meters  or  higher. 
Communication  with  a  distant  station  will  not  be 
permitted  if  interference  with  the  nearby  station 
results. 

All  correspondence  transmitted  from  a  ship  or 
shore  station  will  be  in  regular  message  form  and 


Cutting  Down  Spark  Interference  on  the  Great  Lakes 


591 


TWO    LARGE    GREAT    LAKES    PASSENGER    SHIPS 

The  SS.  South  American,  which  runs  between  Chicago  and  Buffalo,  and  the  SS.  Twnesta  which  is  one  of  two 
other  passenger  ships  running  between  Buffalo  and  Duluth.  There  are  many  similar  passenger  ships  and 
many  more  cargo  vessels  whose  radio  traffic,  carried  on  with  spark  transmitters  near  the  broadcast  band  has 
caused  interference  with  broadcast  receivers  throughout  much  of  the  Middle  West.  The  North  American 
and  South  American  and  a  number  of  cargo  vessels  have  been  equipped  with  continuous  wave  transmitters 
which  does  much  to  do  away  with  broadcast  interference.  Vessels  on  the  Pacific  and  Atlantic  coasts  are 
gradually  being  changed  to  continuous  wave  equipment  also 


copies  of  these  communications  must  be  placed  on 
file. 

The  practice  of  transmitting  notes  under  the  pre- 
fix svc  or  carrying  on  unofficial  conversations  must 
be  discontinued. 

The  United  States  Government  was  repre- 
sented by  D.  B.  Carson,  Commissioner  of 
Navigation,  and  chairman  of  the  conference; 


W.  D.  Terrell,  Chief  Supervisor  of  Radio; 
Arthur  Batcheller,  Supervisor  of  Radio  at 
New  York;  E.  A.  Beane,  Supervisor  of  Radio 
at  Chicago,  and  S.  W.  Edwards,  Supervisor  of 
Radio  at  Detroit. 

The  principal  Canadian  delegates  were 
C.  P.  Edwards,  Director  of  Radio  Service  for 
the  Department  of  Marine  and  Fisheries; 


CANADIAN    AND    AMERICAN    RADIO    OFFICIALS    AT   THE    CONFERENCE 

Held  at  Detroit,  which  arrived  at  the  agreement  to  move  the  commercial  radio  communication  channels 
above  the  broadcast  range.  At  the  head  of  the  table  is  D.  B.  Carson,  Commissioner  of  Navigation,  Depart- 
ment of  Commerce.  Next  on  his  left  is  E.  A.  Beane,  Radio  Supervisor  at  Chicago,  C.  P.  Edwards,  Director 
of  the  Radio  Service  of  the  Canadian  Government,  Department  of  Marine  and  Fisheries;  next  to  Mr. 
Edwards  is  W.  D.  Terrell,  Chief  Supervisor  of  Radio,  Department  of  Commerce,  and  next,  Arthur 
Batcheller,  New  York  Radio  Supervisor.  H.  M.  Short,  Managing  Director  of  the  Canadian  Marconi 

Company  is  at  the  left  of  Mr.  Carson 


Radio  Broadcast 


THE  HARBOR  AT  DULUTH,  MINNESOTA 

With  Superior,  Wisconsin,  in  the  background.  Duluth  is  the  Northern  terminus  of  Great  Lakes  steamship 
lines,  and  many  cargo  and  passenger  ships  have  carried  on  commercial  radio  traffic  while  in  or  near  this  area 
which  has  seriously  interfered  with  broadcast  reception.  Radio  listeners  as  far  West  as  Minneapolis  have 
been  bothered  by  interference  from  ships  on  Lake  Superior.  The  new  agreement  which  goes  into  effect 
July  1 5th  lifts  the  ship-to-shore  bands  above  broadcast  channels 


W.  A.  Rush  and  S.  J.  Ellis,  Supervisors  of 
Radio  in  Canada,  and  H.  M.  Short,  Managing 
Director  of  the  Canadian  Marconi  Company. 

The  acceptance  of  the  recommendations  of 
the  conference  means  the  readjustment  of  the 
equipment  of  every  ship  and  shore  radio  sta- 
tion on  the  Great  Lakes.  Due  to  the  immense 
amount  of  work  required  to  do  this,  the  date 
when  all  of  the  changes  must  be  completed 
has  been  set  for  midnight  July  1 5.  There  are 
more  than  300  ship  and  50  shore  stations 
which  will  go  on  wavelengths  beyond  the 
range  of  the  broadcast  receivers  as  a  result  of 
the  conference. 

Since  the  advent  of  radio  broadcasting,  the 
interference  from  the  old  type  spark  trans- 
mitters used  in  handling  lake  traffic  has  been 
most  annoying  during  the  summer  months 
when  navigation  on  the  lakes  was  in  full  swing. 
This  interference  has  been  recognized  by  every 
one  connected  with  radio  as  one  of  the  greatest 
drawbacks  to  summer  radio  reception,  but  the 
expense  which  would  be  involved  in  changing 
all  of  them  to  non-interfering  transmitters  was 
considered  too  great  for  the  commercial  com- 
panies to  bear. 

THE    CANADIAN    GOVERNMENT   CALLED 
THE    CONFERENCE 

THIS  conference,  which  was  called  on  the 
initiative  of  the   Canadian   government, 
reached  an  inexpensive  and  satisfactory  solu- 
tion of  the  problem  with  very  little  difficulty. 


As  a  result  of  the  accord  arrived  at,  there  will 
probably  be  annual  conferences  of  a  like  nature 
to  discuss  problems  which  are  of  mutual  con- 
cern to  the  two  governments. 

"We  have  recognized  that  the  number  of 
broadcast  listeners  is  constantly  increasing, 
and  it  was  the  result  of  a  desire  to  bring  them 
pleasure  and  enjoyment  from  summer  radio 
that  prompted  the  calling  of  this  conference," 
said  C.  P.  Edwards,  Director  of  the  Canadian 
Radio  Service.  "Our  government  this  year  is 
spending  more  than  $50,000  in  changing  the 
Sarnia,  Toronto,  Sault  Sainte  Marie,  and  Port 
Arthur  shore  stations  from  spark  transmitters 
to  continuous  wave  sets  which  cannot  interfere 
which  broadcast  reception.  These  Canadian 
stations  were  equipped  with  5^  k.  w.  24O-cycle 
synchronous  spaik  transmitters. 

"An  effort  has  been  made  to  get  all  ships 
to  cease  using  their  radio  transmitters  while 
passing  through  the  Detroit  River  and  have 
them  report  to  their  respective  companies  by 
land  lines;  but  this  would  cause  expensive  de- 
lays, and  for  the  present  all  ships  will  continue 
to  transmit  necessary  and  important  business 
while  they  are  passing  through  the  Detroit 
River.  Finally,  when  all  spark  transmitters 
are  outlawed  by  international  agreement,  all 
possibility  of  interference  from  commercial 
sources  will  be  eliminated  for  the  broadcast 
listener.  I  expect  this  agreement  to  be 
reached  in  March,  1926,  at  the  scheduled 
International  Conference  at  Washington." 


KING    ALFONSO   OF    SPAIN 

Before  the  microphone  of  the  new  Madrid  broadcasting  station.     It  is  interesting 
to  note  the  Marconi  type  microphone,  suspended  in  a  cradle  of  sponge  rubber 


THE  MARCH  OF  RADIO 


BY 


Past  President,  Institute  of  Radio  Engineers 


The  Increasing  Use  of  Short  Waves 


IF  ONE  read  the  signs  of  the  times  aright, 
we  shall  all  have  to  acquaint  ourselves 
with  sets  designed  for  frequencies  about 
ten  times  as  high  as  those  we  use  to-day. 
The  ordinary  frequency  range  to  which  we 
are  accustomed   extends  from  545.1   to   1363 
kilocycles  (550   to   220  meters)  and  the  re- 
cent accounts  of   the  progress  of   radio  in- 
dicate that  we  must  soon  be  tuning  our  sets 
from    one    thousand   to    ten   thousand   kilo- 
cycles,   (300  to   30  meters),   ten   times   our 
present  frequency. 

We  have  often  spoken  of  the  necessity  of 
extending  our  present  broadcast  band  in  order 


to  minimize  interference  among  the  ever  in- 
creasing number  of  broadcasting  stations. 
From  the  accounts  of  short  wave  work  we  con- 
tinually see,  it  will  not  only  be  advisable;  but 
necessary  to  go  to  these  higher  frequencies. 

At  three  o'clock  in  the  morning  some  British 
amateurs  (what  enthusiastic  fellows  they  must 
be!),  working  with  a  portable  field  set,  picked 
up  American  amateurs  using  only  a  few  watts 
of  very  high  frequency  power.  With  a  fre- 
quency of  about  fifteen  thousand  kilocycles, 
(20  meters),  an  English  amateur  has  been  able 
to  communicate  with  a  fellow  Britisher  in 
Australia.  Our  navy  is  carrying  on  extensive 


594 


Radio  Broadcast 


©  Barratt's 

BRITISH    AMATEURS   ON    A    FIELD    DAY 

The  radio  societies  of  Golders  Green,  Hendon,  Hournslow,  and  Inland  Revenue  held  an  outdoor  meeting 
recently.     Their  short  wave  transmitter  is  shown  in  the  photograph.     Successful  communication  was 

obtained  in  daylight  with  American  amateurs 


tests  with  frequencies  between  five  thousand 
and  fifteen  thousand  kilocycles  (60  to  20 
meters),  and  is  reporting  unusual  success  with 
these  waves  and  very  small  power.  Argen- 
tina and  South  Africa  have  been  able  to  carry 
reliable  communications  with  small  amounts 
of  power  at  these  high  frequencies. 

Sets  designed  for  receiving  these  very  short 
waves  are  very  different  from  those  to  which 
we  are  accustomed.  Condensers  of  two  or 
three  plates  and  small  coils  of  from  five  to  ten 
turns,  depending  upon  their  diameter,  make 
up  the  tuning  circuits;  the  antenna  may  be 
from  ten  to  twenty  feet  long.  There  is  almost 
as  much  difference  in  appearance  between 
these  sets  and  those  we  are  using  to-day  as 
there  is  between  our  present  ones  and  the  re- 
ceivers used  for  commercial  transoceanic  tele- 
graphy. 

Radio  Comes  to  the  Russian 

A  CORDING    to   the    Russian    Informa- 
tion Bureau  in  Washington,  even  the 
lethargic    Russian    peasant     is    being 
rapidly  converted  to  an  appreciation  of  radio. 
Not  only  is  the  number  of  private  receiving 
sets  rapidly  increasing,  despite  the  poverty  of 


the  average  Russian  to-day,  but  a  more  in- 
teresting development  is  taking  place. 

In  the  Moscow  province  alone,  two  hundred 
additional  village  reading  rooms  were  equipped 
with  receiving  sets  and  loud  speakers  during 
the  past  season.  Thus  radio  news  becomes 
directly  available  to  the  peasant  who  could 
hardly  afford  a  set  of  his  own  and  also  attracts 
him  to  a  village  center  where  other  educating 
influences  are  at  work. 

The  use  of  private  receiving  sets  was  pro- 
hibited by  the  Soviet  Government  up  until 
last  fall,  when  a  licensing  scheme  went  into 
effect.  In  Moscow  alone  it  was  estimated 
there  were  at  least  twenty  thousand  illegal 
sets  in  use  before  governmental  permission 
for  their  maintenance  was  granted.  Within 
two  months  after  the  licensing  arrangement 
went  into  effect  there  were  more  than  fifty 
thousand  sets  in  use. 

The  State  controls  the  radio  industry  in 
the  same  way  that  it  controls  all  the 
others.  Radio  comes  under  the  control  of  the 
Commissariat  of  Posts  and  Telegraphs.  That 
bureau  has  forty-three  transmitting  stations 
and  two  hundred  and  eighty-two  receiving 
stations,  scattered  throughout  the  territory  of 
the  Soviet  union  under  its  direction.  The 


The  Amateur  Tries  Radio  Picture  Sending 


595 


M.    EDOUARD    B§LIN 


©Barratt's 


Explaining  his  system  of  transmission  of  photographs  by  wire.  It  is  understood  that  little  change  in  the 

equipment  is  necessary  for  application  to  radio  circuits.     For  sending  telegraphic  messages,  the  exact 

original  is  duplicated  at  the  receiving  end.     The  Paris  Post  Office  is  using  the  system 


manufacture  of  radio  machinery,  including 
receiving  sets  and  parts,  has  been  concen- 
trated in  a  State  manufacturing  syndicate 
which  operates  three  factories  in  Leningrad, 
one  in  Moscow,  and  one  in  Nijni-Novgorod. 
The  Russian  Information  Service  calls  the 
Moscow  factory  one  of  the  largest  and  most 
modern  of  those  in  Europe. 

The  Amateur  Can  Try  Radio  Pictures 

EVER  in  the  forefront  of  radio  develop- 
ment, the  amateur  has  now  been  in- 
vited by  Mr.  C.  Francis  Jenkins,  well 
known  for  his  radio  picture  development,  to 
share  his  experiments.  Mr.  Jenkins  has  de- 
vised apparatus  tor  radio  picture  transmission 
which  has  showed  itself  practicable  to  a  cer- 
tain extent  and  now  apparently  feels  that  the 
amateur  can  help  to  work  the  apparatus  up 
into  a  form  which  may  possibly  be  of  more 
service  than  at  present. 

The  Government  will  permit  amateurs  to 
carry  on  these  experiments,  provided  they 
stay  within  their  prescribed  frequency  limits, 
and  Mr.  Jenkins  is  ready  to  furnish  apparatus 
which  will  start  the  keen  amateur  off  on  a  new 
radio  venture.  Incidentally,  if  he  takes  up  the 


study  of  radio  picture  transmission  seriously, 
the  experiments  will  impart  to  the  embryo 
radio  engineer  a  good  deal  of  modern  science. 

What  Broadcast  Wave  Is  Best? 

MANY  problems  of  radio,  such  as  the 
amount  of  static  or  other  interference 
present,  prevalence  of  fading,  etc.,  can 
be  solved  only  by  the  statistical  method. 
If  an  engineer  wants  to  solve  a  technical 
problem  he  generally  goes  to  his  laboratory, 
sets  up  the  proper  apparatus  and  directly  gets 
the  necessary  answer.  If  an  insurance  execu- 
tive wants  to  know  how  long  you  or  I  will  live, 
so  he  can  offer  fair  insurance  rates,  he  looks  up 
vital  statistics  on  perhaps  one  hundred 
thousand  others  about  like  us  in  age  and  oc- 
cupation and  so  gets  the  answer  for  his  prob- 
lem by  the  so-called  statistical  method.  It 
seems  that  many  of  radio's  problems  must  be 
solved  in  this  fashion. 

WGY  is  now  sending  out  its  programs  simul- 
taneously on  four  frequencies  of  approxi- 
mately 180.6,  790,  1750,  and  7890  kiloy cycles 
(1600,  379.5,  171.3,  and  38  meters).  The  ordi- 
nary broadcast  receiver  will  tune  for  only  one  of 
these,  790  kilocycles,  but  with  a  little  work, 


596 


Radio  Broadcast 


a  short  wave  tuner  can  be  built  to  receive  the 
two  higher  ones,  and  the  experiment  is  well 
worth  trying.  Schenectady  is  keeping  a  rec- 
cord  of  the  amount  of  power  they  send  out  on 
the  different  antennas,  and  if  listeners  will 
send  to  the  engineers  a  record  as  to  how  well 
the  program  was  received  on  the  different 
frequencies,  whether  static  interfered  more  in 
one  channel  than  in  another,  where  fading 
was  most  noticeable,  etc.,  a  mass  of  data  will 
be  accumulated  which  will  be  useful  in  obtain- 
ing a  statistical  answer  to  the  question  as  to 
what  frequencies  are  best  for  broadcasting. 

Receiving  Is  Good  in  California 

THE  California  "booster"  has  still  an- 
other catchy  phrase  with  which  to 
advertise  his  Heaven  on  Earth.  "No 
Static"  is  the  phrase  which  measurements  re- 
cently made  by  the  Bureau  of  Standards 
Transmission  Laboratory  permit  the  Cali- 
fornian  to  add  to  the  present  long  list  of  that 
country's  attractions. 

The  scientist  talks  about  radio  signals  as  so 
many  "micro-volts  per  meter."  A  radio 
wave  carries  with  it,  or  rather  is,  an  electric 
field,  whose  intensity  determines  how  loud  the 
signal  will  be  when  properly  received.  An 
idea  of  the  extremely  weak  electric  field  as- 
sociated with  signals  from  distant  stations 
may  be  had  from  this  comparison. 

The  ordinary  dry  cell  develops  an  electro- 
motive force  of  about  1.5  volts.  In  the  air 
between  the  two  terminals  of  a  battery  there 
is  an  electric  field,  rather  weak  to  be  sure,  but 
still  strong  enough  to  be  detected  by  a  sensi- 
tive instrument.  (The  air  will  stand  an 
electric  field  of  about  twenty  thousand  volts 
per  inch  before  breaking  down,  permitting  a 
spark  to  pass).  If  now  we  attach  two  metal 
plates  to  the  terminals  of  the  battery,  hold 
them  parallel  to  one  another  and  about  fifty 
inches  apart,  the  electric  field  between  these 
two  plates  will  be  about  one  volt  per  meter. 
As  the  plates  are  moved  farther  and  farther 
apart,  the  electric  field  between  them  becomes 
correspondingly  weaker,  and  if  we  were  able  to 
get  the  plates  about  one  thousand  miles  apart, 
and  still  have  them  connected  to  the  two 
teiminals  of  the  dry  cell,  the  electric  field 
would  be  about  one  micro-volt  per  meter. 
An  electric  field  so  weak  is  far  past  the  com- 
prehension, or  even  the  imagination,  of  one 
who  has  not  continually  worked  along  scienti- 
fic lines. 

According  to  Dr.  L.  W.  Austin,  the  man  who 
has  done  more  in  this  field  than  any  other 


American  scientist,  the  signals  from  Europe 
in  the  Eastern  United  States,  are  from  twenty 
to  one  hundred  micro-volts  per  meter  in 
strength.  This  is  a  good  readable  signal  un- 
less static  is  exceptionally  bad.  This  same 
experimenter,  working  on  the  California 
coast,  finds  that  the  received  signals  from 
Java  and  the  Philippines  are  only  two  to  five 
micro-volts  per  meter  and  yet  these  weak 
signals  are  readable.  That  such  weak  electric 
fields  are  sufficient  for  successful  communica- 
tion speaks  volumes  for  the  absence  of  atmos- 
pheric disturbance  on  our  West  coast.  A  cor- 
responding signal  strength  on  the  East  coast  of 
our  country  would  be  completely  buried  in  the 
noise  produced  by  atmospheric  disturbances. 

The  Radio  Situation  in  South  America 

THE  president  of  the  Radio  Corporation 
has  just  returned  from  an  extensive 
visit  to  South  America.  "In  spite  of 
foreign  competition"  he  says,  "American 
products  and  methods  remain  the  most  ac- 
ceptable to  South  Americans."  That  must 
be  good  news  for  his  company,  which  is  ac- 
tively striving  to  gain  the  South  American 
market.  There  seems  to  be  an  increasing 
demand  both  for  transmitting  and  receiving 
apparatus. 

The  installation  of  more  transmitting  sta- 
tions seems  to  be  the  immediate  need  in  South 
America.  In  our  country  one  station  serves, 
on  the  average,  six  thousand  square  miles  of 
territory,  General  Harbord  says,  while  in 
South  America,  one  station  serves  three  hun- 
dred thousand  square  miles.  The  General 
might  also  have  added  that  in  our  country 
most  of  the  stations  try  to  serve  the  same  six 
thousand  square  miles. 

Commenting  on  the  economic  situation 
General  Harbord  remarks  that  the  bill  for 
broadcasting  is  in  most  cases  paid  for  by 
radio  advertisers  and  the  trade,  which  co- 
operate with  the  stations  to  the  extent  of 
putting  aside  a  percentage  of  their  revenues 
from  the  sales  of  receiving  sets  to  meet  the 
broadcasting  expense.  Some  stations  accept 
advertisements  from  local  merchants  and  these 
paid  advertisements  are  sandwiched  between 
the  musical  numbers  which  make  up  the  pro- 
gram. The  novelty  of  radio,  and  scarcity  of 
diversified  programs,  make  the  listeners  toler- 
ate advertising  for  the  present,  but  there  is  no 
indication,  according  to  General  Harbord's 
opinion,  that  this  method  of  payment  will  be 
the  final  solution  of  the  problem  in  South 
America. 


Who  Will  Represent  the  Radio  Listener? 


597 


Frauds  in  Manufacturing 

THOSE    acquainted    with    the    develop- 
ment   of   commercial   radio  during  the 
last  two  decades  are  well  aware  of  its 
rather  checkered  career.     Many  a  man  has 
thought  of  radio  as  the  happy  hunting  ground 
for  stock  promotion. 

A  radio  fraud  not  so  evident  as  these  has 
recently  come  to  light,  and  we  are  glad  to  say 
that  the  alleged  swindler  is  speedily  to  be 
brought  to  trial.  One  of  the  well  known 
resistor  manufacturers,  the  Daven 
Radio  Corporation,  who,  by  care 
and  engineering  talent  have  built 
up  a  reputation  for  accurate  re- 
sistors to  be  used  as  grid  leaks 
etc.,  discovered  that  the  product 
sold  to  the  public  under  his  trade- 
mark was  by  no  means  was  de- 
pendable as  the  factory  tests 
showed. 

District  Attorney  Salomon  was 
sufficiently  impressed  by  the  evi- 
dence of  illegal  traffic  that  he 
proceeded  against  the  alleged 
head  of  this  swindling  ring,  Moe 
Goldman.  It  appeared  that  the 
resistors  Goldman  was  putting 
out  were  most  unreliable.  The 
reliable  manufacturers  in  the 
radio  field  are  not  so  numerous 
that  we  can  afford  to  have  our 
faith  in  any  of  them  shaken  by 
such  methods  as  Goldman  was 
apparently  using. 


Who  Will  Protect  the  Radio 
Listener? 

PAUL  B.  KLUGH,  Executive 
Chairman  of  the  National 
Association  of  Broadcasters, 
recently  commented  on  the  pres- 
ent   crowded    condition    of    the 
ether,  due  to  the  limited  frequency 
band  available  for  class  B  stations 
and  the  ever  increasing  demand 
for  room  in  this  field  by  new  sta- 
tions. 

Apparently  having  in  mind 
some  certain  cantankerous  man- 
ager, Mr.  Klugh  said: 

Unless  a  certain  broadcasting  sta- 
tion, which  is  dissatisfied  with  its 
present  wave  allottment,  recedes  from 
the  position  it  has  taken,  the  matter 
will  probably  land  in  the  courts.  This 


would  be  unfortunate  because  under  the  present  law, 
Secretary  Hoover  is  almost  defenseless  and  is  doing 
his  best  to  preserve  harmony.  It  is  a  hard  thing  to 
dissuade  certain  citizens,  conversant  with  those 
phases  of  the  Constitution  which  guarantee  "equal- 
ity," from  demanding  that  which  they  believe  to  be 
their  rights.  The  fact  that  the  air  is  crowded  to  the 
limit  doesn't  interest  them. 

It  is  almost  certain  that  the  next  Congress 
will  pass  some  legislation  giving  to  the  Secre- 
tary of  Commerce  more  legal  hold  on  the 
broadcast  situation.  It  is  no  secret  that  he 


THE    NAVY    GIVES    INSTRUCTION 

To  interested  natives  in  Hawaii.     Since  the  lessons  are  distinctly 

personal,  it  is  evident  that  greater  success  can  be  had  with  head 

phones  than  the  more  public  loud  speaker 


598 


Radio  Broadcast 


ARTHUR    BURROWS 

The  first  manager  of  the  new  International  Broad- 
cast Bureau  at  Geneva.  It  is  Mr.  Burrows's  work  to 
attempt  an  amicable  settlement  of  disputed  points 
between  the  Continental  broadcasters.  There  are 
said  to  be  fifty-two  stations  there  for  forty-eight 
possible  wave  bands.  Mr.  Burrows  was  assistant 
controller  and  director  of  programs  for  the  British 
Broadcasting  Company 

has  practically  none  at  present.  It  might  be 
a  very  good  thing  to  have  a  court  fight  on 
record  so  that  our  congressmen  who  have  de- 
layed action  so  long  might  be  convinced  that 
some  action  is  an  immediate  necessity. 

Mr.  Klugh  speaks  for  the  broadcasters. 
But  who  speaks  for  the  listeners?  When 
one  talks  about  equality  in  this  broadcast 
tangle,  the  listener  must  come  into  the 
argument  too.  The  broadcast  channels  must 
be  assigned  and  used  in  such  a  manner  that 
the  most  good  and  enjoyment  comes  to  the 
millions  of  listeners.  With  this  idea  in  mind, 
it  is  evident  at  once  that  the  granting  of  a 
license  to  a  new  station  should  not  rest  at  all 
on  so-called  constitutional  rights.  The  desires 
of  the  listeners  who  will  be  benefited  or  be 
disturbed  by  the  new  broadcast  channel 
should  rule  the  granting  of  the  license. 

The  Radio  Service  Needs  Money 

A  WASHINGTON  dispatch  to  the  New 
York  Herald-Tribune  says  that  Secre- 
tary  Hoover  will   ask  Congress   next 
winter  for  an  appropriation  for  the  support  of 
more  adequate  radio  inspection.     There  are 
entirely  too  few  radio  inspectors  now  in  the 
Department    of    Commerce    service.     Their 


number  is  small  and  their  primary  duty  is  to 
look  out  for  marine  radio.  The  radio  inspec- 
tion service  was  organized  specifically  to  see 
that  radio  was  installed  and  used  at  land 
stations  and  on  shipboard  so  as  to  afford  a 
maximum  of  protection. 

When  the  problems  of  broadcasting  des- 
cended on  them,  a  tremendous  increase  of  work 
has  been  loaded  on  the  entirely  inadequate 
inspection  bureau.  With  the  hundreds  of 
broadcasting  stations  which  have  to  be  super- 
vised by  the  few  government  men,  and  the 
hundreds  of  thousands  of  single-circuit  re- 
generative receivers  acting  as  transmitters, 
it  is  no  wonder  that  thousands  of  complaints 
which  pour  into  the  radio  bureau  of  the  De- 
partment of  Commerce  receive  such  scant 
consideration.  They  simply  cannot  be 
handled. 

The  dispatch  referred  to  above  states  that 
$125,000  is  to  be  requested  for  extra  radio 
"cops,"  whose  function  it  will  be  to  keep  their 
eyes  on  the  broadcast  channels,  eliminating 
interference  where  possible  and  generally  act- 
ing to  keep  the  ether  traffic  moving  in  orderly 
manner.  One  hopes  the  Commerce  Bureau 
will  get  this  needed  financial  aid. 

Supply  and  Demand  in  Radio 

CERTAIN  commodities  enjoy  a  year 
round  demand.  We  need  telephone 
service,  for  example,  just  as  much  in 
the  spring  as  in  the  fall,  and  just  as  many 
groceries  in  the  summer  as.  in  the  winter. 
Not  so  with  radio  apparatus,  however;  there  is 
great  decrease  in  the  public  demand  for  radio 
material  as  the  summer  months  approach. 
In  spite  of  many  published  opinions  to  the 
contrary,  every  sensible  person  knows  that 
radio  is  not  as  much  in  demand  in  summer  as 
in  winter.  Furthermore  the  outdoor  attrac- 
tions in  summer  call  us  away  from  the  easy 
chair  and  the  radio  entertainment  and  prob- 
ably it  is  best  for  us  that  such  is  the  case. 

Radio  sales  must  be  extremely  seasonable.  A 
radio  manufacturer  may  look  for  a  healthy  de- 
mand for  his  products  possibly  eight  months  in 
the  year  and  he  must  so  organize  his  finances  and 
production  that  the  four  comparatively  "light" 
months  do  not  force  him  into  bankruptcy. 
This  past  season  has  caused  many  a  downfall 
because  these  precautions  were  not  taken. 
It  is  no  secret  that  the  great  demand  for  sets 
last  fall  caused  many  an  inexperienced  manu- 
facturer to  overload  himself  with  parts  and 
complete  sets,  so  that  when  the  slump  came 
he  found  himself  with  finished  apparatus  for 


A  Suggestion  to  Radio  Manufacturers 


599 


which  there  was  no  demand,  an  excessive  in- 
ventory of  parts,  and  a  painfully  strained 
credit. 

A  manufacturer  in  such  a  situation  must  sell 
his  output  no  matter  how  great  the  sacrifice. 
It  may  bankrupt  him  to  move  out  his  goods 
at  half  their  listed  price  but  if  they  didn't 
move  at  all  he  surely  would  be  ruined.  This 
situation  caused  a  tremendous  dumping  of 
sets  on  the  market  this  spring  and  dozens  of 
different  sets  could  be  bought  for  less  than 
half  their  original  selling  price.  In  spite  of 
this  enforced  movement  of  sacrificed  sets, 
many  smaller  firms  were  forced  to  the  wall. 
The  industry  probably  benefited  by  the 
withdrawal  of  these  poorly  organized  con- 
cerns. The  public  will  be  hesitant  about 
purchasing  sets  in  the  fall  at  say  a  hundred 
dollars  when  past  experience  leads  them  to 
believe  the  same  set  can  be  purchased  for 
forty-five  dollars  in  the  spring.  This  condi- 
tion is  unhealthy  and  is  not  conducive  to  a 
real  March  of  Radio.  Why  is  it  not  logical 
for  the  business  man,  launching  out  into  the 
radio  game,  to  emulate  the  iceman  in  a  small 
town?  Ice,  coal,  and  wood,  are  his  products, 
and  fickle  indeed  must  be  the  season  when  one 
or  the  other  of  his  wares  is  not  in  demand. 
The  radio  business  would  be  most  economi- 
cally carried  on  in  conjunction  with  some 
other  electrical  enterprise  (sufficiently  like 
radio  so  that  the  same  ma- 
chinery and  employees 
could  be  used)  which  would 
keep  the  factory  busy  at 
times  when  atmospherics 
and  the  open  air  turn  our 
desires  away  from  radio 
receivers. 

"Ethics"  In  Radio 


THERE  are  many  of 
us  who  have  sensed  a 
very  unsavory  condi- 
tion in  certain  commercial 
aspects  of  radio  and  cer- 
tainly the  recent  proceed- 
ings between  the  Radio 
Corporation  and  the  De 
Forest  Company  do  nothing 
to  weaken  the  impression 
that  some  of  the  commer- 
cial ethics  of  the  radio  are 
not  of  the  highest  type. 

The  first  inkling  the  pub- 
lic had  of  the  bad  feeling 
between  the  two  companies 


referred  to  above  was  in  newspaper  reports  to 
the  effect  that  the  Radio  Corporation  had 
planted  spies  throughout  the  plant  of  the  De 
Forest  Company.  Further,  it  was  said  that 
these  spies  were  delivering  to  the  Radio  Corpor- 
ation all  of  the  De  Forest  secrets  which  might 
be  useful  to  a  competitor  —  manufacturing 
processes  and  costs,  sources  of  supplies,  names 
of  customers,  quantities  of  apparatus  sold  and 
terms  allowed  to  jobbers.  The  reports  seemed 
to  show  that  by  this  system  of  espionage  the 
Radio  Corporation  was  well  on  its  way  to 
ferret  out  every  bit  of  information  which 
might  be  of  value  in  competitive  warfare. 

So  serious  were  these  charges  that  one  was 
inclined  to  disbelieve  them.  An  emphatic 
denial  was  awaited  from  the  Radio  Corpora- 
tion officials.  But  the  denial  did  not  come; 
instead  it  was  admitted  that  the  Radio  Cor- 
poration had  actually  established  a  system  of 
spies  in  the  De  Forest  plant  and  that  these 
spies  did  bring  their  information  to  one  of  the 
Radio  Corporation's  trusted  employes. 

In  the  preliminary  hearing,  the  Radio  Cor- 
poration was  enjoined  from  further  spying  on 
De  Forest  but  was  granted  permission  to  use, 
for  patent  infringement  purposes,  whatever 
pertinent  information  its  spy  system  had  al- 
ready brought  forth. 

Actions  of  this  kind  don't  impress  the  radio 
public  very  favorably. 


©U  nderwoodA  Underwood 
COMMANDER    A.    HOYT   TAYLOR 

Of  the  Naval  Research  laboratory  at  the  experimental  short  wave  re- 
ceiver.    Using  a  21 -meter  wave,  operators  at  the  laboratory  recently 
communicated  with  Australia,  a  distance  of  more  than   10,000  miles. 
A  power  of  less  than  one  kw.  was  used 


6oo 


Radio  Broadcast 


jJllllllimimimilllimillllllimlimillimilllllllllllllllllllMlimmimilimi Illllllllllllllllllll^ 

The  Month  in  Radio 

i  i 

nlllllllllllimmlimilllimiimilllllllllllllNINIimillimillimimiimimillllllimimmi imr 

THE  Hazeltine  Corporation  reports  that 
during   1923,   the  public  bought  95,094 
Neutrodyne  sets,     During  1924  a  total 
of   279,780,    and    during    the    present    year 
129,630  such  sets  had  been  sold  up  to  May 
first.     These    figures    show    that    more  than 
500,000   neutrodyne   sets   have   been   manu- 
factured and  sold  during  the  brief  life  of  the 
patent. 

IN  THE  annual  summary  of  telegraph  statis- 
tics, published  by  the  Berne  International 
Wireless  Telegraph  Bureau,  it  is  shown  that 
radio  has  had  an  ever  increasing  role  in  main- 
taining safety  of  life  at  sea.  At  the  end  of 
1913,  there  were  3998  ship-to-shore  stations 
in  use,  at  the  end  of  1919,  6623  such  stations, 
and  at  the  end  of  1924  there  were  16,971  sta- 
tions carrying  messages  from  land  to  sea  and 
vice  versa. 

p  ENERAL  HARBORD'S  report  that  for- 
^-^  eigners  like  our  radio  apparatus  is  well 
borne  out  by  the  figures  on  exports  for  the 
present  year.  Last  year  the  total  radio  ex- 
ports were  only  slightly  over  $6,000,000., 
but  the  present  year  makes  a  much  better 
showing.  Figures  for  corresponding  months 
of  last  year  and  this  year  show  the  following 
values  for  radio  exports. 

1924  1925 

January $    331,849.00  $-  784,619.00 

February 302,121.00  477,1591.00 

March 288,812.00  604,769.00 

April 279,903.00  853.148.00 

Total                           $1,222,6815.00  $2,720,127.00 

These  figures  indicate  a  total  export  for 
this  year  of  more  than  $8,000,000. 

JN  SEPTEMBER,  three  Navy  seaplanes  will 
•I  hop  off  from  San  Diego  for  Honolulu,  thus 
furthering  the  prestige  of  an  air  force  which 
already  has  the  Newfoundland-Azores  flight  to 
its  credit.  The  distance  to  be  covered  is  much 
greater  than  the  long  flight  of  1919,  for  twenty- 
eight  hundred  miles  separate  San  Diego  and 
Hawaii. 

Careful  preparations  are  being  carried  out  to 
insure  the  safety  of  the  venturesome  pilots, 
and  radio  is  expected  to  do  its  part.  Unlike 
Amundsen,  who  kept  us  all  on  edge  for  many 
days  wondering  where  he  was  and  how  he  was 


faring  (he  had  no  radio  apparatus  whatsoever), 
our  flyers  will  carry  the  most  modern  radio 
outfits.  The  transmitters  are  of  one  hundred 
watts  rating  and  should  be  good  for  transmit- 
ting at  least  five  hundred  miles. 

It  is  interesting  to  note  that  the  very  short 
waves  with  which  broadcast  engineers  are 
experimenting  nowadays  have  been  found  un- 
suitable for  airplanes.  The  ignition  system 
of  the  engine  is  a  prolific  source  of  highly 
damped,  high  frequency  currents  which  seri- 
ously interfere  with  the  reception  of  signals  in 
the  region  of  ten  thousand  kilocycles  (30 
meters). 

THE  Music  Master  Corporation  has  just 
concluded  a  contract  with  the  Ware  Radio 
Corporation  by  which,  hereafter,  all  the  Ware 
products  are  to  be  marketed  through  the 
Music  Master  Company.  The  output  of  these 
combined  companies  will  in  the  future  carry 
the  trade  name  "Music  Master- Ware." 

THE  annual  talk  on  the  budget  and  taxes 
by  President  Coolidge  and  General  Lord, 
was  broadcast  over  a  large  part  of  our  country 
a  short  time  ago.  These  annual  talks  by  those 
officials  responsible  for  spending  the  money  we 
pay  as  taxes  seem  an  excellent  illustration  of 
the  value  of  radio  in  government.  If  county 
and  state  officials  likewise  were  made  to  ac- 
count for  their  expenditures  so  that  the  tax- 
payers might  see  where  their  money  was  going, 
this  good  work  of  radio  would  be  extended  in 
the  right  direction  and  undoubtedly  state  and 
local  taxes  might  be  diminished  the  same  as 
the  federal  taxes  have  been. 

AT  Bound  Brook,  New  Jersey,  the  Radio 
Corporation's  engineers  are  erecting 
what  we  had  expected  to  pronounce  the  largest 
broadcast  station  in  the  world,  but  evidently 
the  Germans  are  to  outdo  us.  By  next  winter 
they  expect  to  have  on  the  air  a  station  in 
Bavaria  which  will  send  out  one  hundred 
kilowatts  of  power.  Some  trouble  may  be 
experienced  in  the  control  of  this  amount  of 
power  by  the  human  voice,  but  with  their  well 
known  technical  ability  the  German  engineers 
will  undoubtedly  accomplish  it.  A  frequency 
of  three  hundred  kilocycles  (1000  meters)  is 
to  be  used  at  this  new  Bavarian  station. 

Another  large  German  station  of  fifty 
kilowatts  rating  is  being  erected  at  Konigs- 
wusterhausen.  With  these  two  large  stations 
it  is  expected  that  all  Germans,  even  if  equip- 
ped with  crystal  sets  only,  will  be  able  to  pick 
up  broadcast  programs.  It  is  not  at  all  un- 


Current  Events  In  Radio 


601 


H.    A.    BELLOWS 

•Minneapolis;  Director,  Gold  Medal- 
Station  wcco 


"Any  one  who  would  now  undertake  to  say 
what  can  be  done  through  a  great  broadcasting 
station  would  be  simply  inviting  trouble.  An 
agency  for  the  distribution  of  ideas,  for  education, 
service,  and  entertainment,  has  been  created  so 
suddenly  that  its  possible  scope  is  still  impossible 
to  define. 

"  The  only  real  guide  to  the  direction  of  a  radio 
broadcasting  station  is  public  service.  It  is  im- 
possible to  give  everybody  everything  he  wants. 
Just  as  a  great  newspaper  combines  its  news, 
market,  editorial,  and  sports  features  with  its  en- 
tertainment and  educational  features,  so  we  are 
trying  to  make  the  service  rendered  to  the  public 
by  our  station  so  full  that  every  listener,  no  matter 
who  he  is  or  where  he  may  be,  will  feel  that  we  have 
something  of  direct  and  personal  value  to  him." 


likely  that  many  American  listeners,  at  least 
in  the  winter  time,  will  also  hear  these  German 
stations. 

AN  INTERESTING  example  of  how  much 
unwise  faith  we  place  on  our  impressions 
was  illustrated  by  the  dispatch  stating  that 
2LO,  London,  had  recently  changed  its  antenna 
arrangement  and  as  a  result  many  of  the 
listeners  had  reported  improvements  in  signal 
strength  of  twenty-five  per  cent,  and  some 
even  as  much  as  fifty  per  cent.  It  might  in- 
terest these  listeners  to  know  that  even  if  two 
signals  are  compared  on  the  same  night,  one 
right  after  the  other,  not  one  of  them  could 
tell  if  one  signal  was  twenty-five  per  cent. 


louder  than  the  other  and  if  the  signals  were  on 
successive  nights,  as  theirs  must  have  been, 
they  couldn't  possibly  have  told  if  one  signal 
was  one  hundred  per  cent,  louder.  The  ear  is 
of  little  value  as  a  measurer  of  sound  intensity, 
probably  because  it  has  never  been  used  in 
work  of  this  kind.  If  two  signals  are  compared 
on  successive  nights  it  would  require  a  differ- 
ence of  several  times  rather  than  a  few  per 
cent:  before  the  ear  would  give  a  reliable  in- 
dication of  change. 

AFTER  many  tests  to  ascertain  the  utility 
of  radio  beacons  on  the  coast  of  France, 
the  Undersecretary  of  Merchant  Marine,  M. 
Danielou,  has  become  convinced  that  his 
country  would  do  well  to  help  their  navigators 
by  putting  in  a  quite  extensive  installation. 
A  total  of  about  thirty  such  radio  searchlights 
are  to  be  put  in  as  soon  as  possible,  some  of 
them  sufficiently  powerful  to  be  of  use  to 
vessels  hundreds  of  miles  at  sea,  some  of  them 
of  low  power  for  the  guidance  of  ships  in  the 
larger  harbors,  while  most  of  them  will  have 
a  fifty-mile  range. 

A  FEW  months  ago  we  heard  a  deal  of 
talk  about  broadcast  silent  night,  the 
idea  being  that  one  night  of  the  week  should  be 
kept  free  by  local  broadcasters  so  that  DX  fans 
might  have  a  chance  to  tune-in  distant  sta- 
tions. Thus  if  New  York  stations  all  stopped 
broadcasting  at  8  p.  M.,  New  Yorkers  who  so 
desired  might  listen  to  Philadelphia  or 
Chicago,  or  other  laige  cities.  Similarly,  the 
listeners  in  these  cities  could  hear  New  York 
if  their  local  stations  kept  off  the  air  once 
every  week.  The  idea  doesn't  seem  to  be 
"taking"  at  all.  Chicago  tried  it,  but  new 
stations  going  on  the  air  in  that  city  do  not 
anticipate  falling  in  with  this  scheme. 

It  is  quite  evident  to  any  one  that  listeners 
in  New  York  City,  for  example,  cannot  hope 
to  hear  distant  stations  under  ordinary  condi- 
tions; with  a  dozen  or  more  powerful  local 
stations  going,  the  station  a  thousand  miles 
away  has  small  chance  of  coming  through  on 
the  average  radio  receiver.  We  can  well  see 
why  New  Yorkers  don't  take  up  the  silent 
night  idea  but  think  it  might  be  worth  while 
for  some  of  the  other  cities  to  do  so.  The 
best  radio  programs  obtainable  are  sent  out 
from  New  York,  so  what  is  the  use  of  depriv- 
ing the  listeners  of  this  entertainment  that  a 
few  enthusiasts  may  tell  their  fellow  workers 
on  the  morrow  that  they  heard  Cuba,  or  San 
Francisco.  Silent  night  may  be  observed  on 
Main  Street,  but  it  never  will  be  on  Broadway. 


602 


Radio  Broadcast 


SIR  JAMES   A.    M.    ELDER 

New  York;  Commissioner  for  Australia 

in  the  United  States 

"No  element  of  world  intercourse  to-day  is  so 
pregnant  with  possibility  or  so  potentially  effec- 
tive in  the  -world's  relationships  as  that  modern 
miracle — the  radio.  While  personal  visitation 
and  conversation  must  always  remain  preeminent 
in  the  world's  activities  and  work,  these  are  neces- 
sarily restricted  to  but  a  comparative  few;  radio 
reaches  millions.  Radio  has  brought  America 
and  Australia  still  closer  together  and  is  cement- 
ing the  existing  close  friendship.  The  projection 
of  the  human  voice  across  leagues  of  land  and 
ocean  opens  up  inestimable  possibilities  for  the 
future. 

"  Some  months  ago,  I  had  the  unique  privilege 
of  speaking  to  Australia  from  Pittsburgh,  a  dis- 
tance often  thousand  miles,  an  historic  and  epoch- 
making  event.  Radio  is  already  in  the  possession 
of  all  Americans.  It  is  a  daily  domestic  neces- 
sity. In  Australia,  its  use  is  rapidly  extending; 
it  is  bringing  the  life  of  the  great  world  into  the 
homes  and  lives  of  sturdy  pioneers  in  the  far  in- 
terior. Their  isolation  has  disappeared,  and 
their  leisure  hours  are  occupied  to  the  full  in  these 
personal  advantages  which  the  radio  provides. 
Radio  is  destined  to  be  as  popular  in  Australia  as 
in  America." 


Why  is  the  Radio  Conference 
Postponed  ? 

THE    League    of    Nations    has    recom- 
mended that  the  coming  international 
radio  conference  called   by  the  United 
States  to  meet   in  Washington  this  fall   be 
postponed  until   1927.     Government  officials 
in   Washington  who  have  been   interviewed 
were  apparently  inclined  to  believe  that  the 
League's  recommendation  would  be  followed. 


It  appears  that,  from  the  European  point 
of  view,  postponement  is  advisable.  A  Paris 
radio  conference  is  called  for  September  of 
this  year  and  the  actions  of  this  conference 
will  of  course  affect  the  views  of  European 
delegates  who  attend  the  United  States  con- 
ference. There  are  various  matters  which 
the  new  agencies  of  Europe  wish  to  bring  up 
for  action  and  it  seems  that  the  European 
conferees  would  do  well  to  discuss  their  prob- 
lems before  bringing  them  to  Washington. 
Our  recent  Pan-American  conference  is  re- 
garded as  pointing  the  way  for  this  prelimin- 
ary European  meeting. 

Matters  which  the  European  contingent 
of  the  conference  expect  to  bring  up  include 
the  inviolability  of  messages,  particularly 
copyrighted  press  matter,  establishment  of 
rules  concerning  multiple  address  messages 
delivered  by  the  no-answer  method,  and  cen- 
sorship of  radio  telephone  broadcasting.  It 
seems  that  among  other  items  which  we 
might  logically  bring  up  for  discussion  is  that 
of  broadcast  licenses.  The  idea  of  liberty 
has,  it  seems,  gone  to  the  limit  in  this  field; 
month  after  month  new  licenses  are  issued 
and  these  certainly  are  not,  in  the  main,  for 
the  benefit  of  the  listening  public.  It  cer- 
tainly would  do  no  harm  to  have  a  general 
open  discussion  on  this  question,  and  among 
those  contributing  to  the  discussion  should 
be  some  capable  representatives  of  the  broad- 
cast listeners. 

We  feel  that  there  are  too  many  matters 
of  great  importance  now  pending  for  this  in- 
ternational conference  to  be  postponed.  It 
should  be  held  not  later  than  the  Winter  of 
1925. 

The  Music  Publishers 
Oppose  Broadcasting 

A  THEIR  annual  convention,  the  Na- 
tional Association  of  Sheet  Music 
Dealers  passed  a  resolution  which  ex- 
pressed their  idea  of  radio's  help  to  sheet 
music  sales.  Radio  may  stimulate  their 
sales  for  a  short  time,  it  was  said,  but  in  the 
long  run  the  sales  are  decreased  if  the  song  is 
used  in  the  radio  channels.  In  the  discussion, 
it  was  admitted  that  for  music  of  a  semi- 
classical  nature  the  demand  has  increased 
after  being  broadcast  by  artists  of  ability. 
Some  of  the  convention  members  pointed  out 
that  songs  of  a  generation  past,  entirely  for- 
gotten, have  been  revived  by  using  them  in  the 
radio  programs. 

Mr.  Samuel  Fox,  one  of  the  sheet  music 


What  People  Say  About  Radio 


603 


publishers,  however,  favored  the  most  string- 
ent regulation  of  the  broadcast  performance 
of  copyrighted  music.  He  would  have  the 
publishers  tell  the  broadcast  program  director 
just  when  and  how  he  might  use  their  songs. 

Several  dealers  had  expressed  the  idea  that 
radio  had  increased  their  sheet  music  sales, 
but  Mr.  Fox  requested  that  the  minutes  of  the 
conference  be  changed  so  that  this  favorable 
comment  regarding  radio  would  be  deleted. 


Interesting  Things  Interestingly 
Said 


EH.  ANDERSON  (New  York;  Director  of  the 
'  New  York  Public  Library):  "Neither  the 
movies,  radio,  or  crossword  puzzles  have  caused 
any  decrease  in  the  use  of  books,  but  whenever  a 
decrease  does  occur  in  the  use  of  books  (jn  the  New 
York  Library)  it  is  because  of  a  shortage  of  books." 

I/ENNETH  B.WARNER  (Hartford,  Connecti- 
^  *•  cut;  Editor,  QST,  the  official  publication  of 
the  American  Radio  Relay  League,  writing  about 
international  amateur  radio  experiments  on  short 
waves):  "To  us  the  most  fascinating  angle  to  this 
international  DX  game  is  that  it  isn't  a  rich  man's 
sport  and  it  doesn't  take  an  expert.  It's  wide  open 
to  everybody.  The  lowest-powered  transmitters  in 
the  country  are  heard  as  far  as  the  big  watt-eaters, 
and  the  very  simplest  ham  tuner  pulls  in  the  signals 
from  the  other  side  of  the  earth.  We  don't  know  to 
what  it  is  leading,  but  it  surely  seems  to  be  advanc- 
ing that  dream  of  ours  of  the  day  when  large  num- 
bers of  private  citizens  all  over  the  world  will  sit 
down  at  their  personally  owned  apparatus  and 
converse  with  their  friends  in  every  clime.  Amateur 
radio  is  performing  a  powerful  service  in  the  ad- 
vancement of  world-understanding." 

\AELVILLE  E.  STONE  (New  York;  Counselor 
*"*  Associated  Press):  "1  don't  believe  that 
radio  can  ever  compete  with  the  newspaper  in 
supplying  the  public  with  news.  There  are  funda- 
mental difficulties  in  the  collection  and  transmission 
of  news  by  radio  that  could  not  meet  the  organized 
facilities  of  the  cooperative  associations  of  the  news- 
papers for  gathering  and  distributing  news." 

A  CONVERSATION  in  the  House  of  Commons 
**  quoted  in  the  New  York  Times  relating  to 
unauthorized  making  of  phonograph  records  from 
radio  programs:  Sir  B.  Chadwick,  Parliamentary 
Secretary  for  the  Board  of  Trade  said:  "There  has 
been  such  a  remarkable  growth  in  radio  that  the 
law  has  not  kept  pace  with  it.  There  is  reason  to 
believe  that  the  day  is  not  far  distant  when  an  eager 
public  may  listen  to  the  proceedings  of  Parliament. 

One  member:  "God  help  us." 

The  Deputy  Speaker:  "  I  would  point  out  that  the 
bill  refers  to  musical  and  dramatic  performances." 


/^OSMO  HAMILTON:  (New  York;  playwright 
^  and  author):  "Radio  will  profoundly  affect 
writing  in  the  next  few  years.  Novelists  will  have 
to  boil  down  their  productions  from  the  100,000 
words  of  the  present  to  5000  words,  so  that  they 
may  be  read  over  the  radio.  In  five  years,  reading 
will  be  superseded  to  a  greac  extent.  The  public 
will  listen  to  the  author's  stories  over  the  radio  and 
see  its  plays  in  the  moving  picture  theaters." 

COLONEL  ALLEN  S.  PECK  (Denver;  Dis- 
trict Forester  in  charge  of  government  timber 
lands  in  Colorado,  Wyoming,  South  Dakota,  Ne- 
braska, Michigan,  and  Minnesota):  "A  large  num- 
ber of  the  200  rangers  and  twenty-six  supervisors  on 
duty  in  our  six  states  are  equipped  with  radio  receiv- 
ing sets.  The  fire  warnings  which  are  being  broad- 
cast over  station  KOA  will  therefore  be  of  the  greatest 
practical  value.  Radio  will  also  be  of  the  greatest 
value  in  reaching  hundreds  of  cooperators  and  key- 
men  in  time  of  danger.  Fire  warnings  will  have 
the  broadcast  right-of-way  at  KOA." 

pHAUNCEY  M.  DEPEW  (New  York;  publi- 
V*  cist;  in  an  address  opening  WRNY,  New  York): 
"Many  boys  and  girls  listening  to  me  this  evening 
have  made  their  own  radio  machines.  The  boys 
and  girls  of  to-day  have  so  many  opportunities  for 
their  mental  and  spiritual  advancement,  which 
never  existed  before,  that  we  older  people  wonder 
how  we  ever  got  on  at  all.  .  .  .  Much  as  we 
admire  and  wonder  at  these  marvels,  of  which 
radio  is  one,  which  are  the  commonplace  of  our  day, 
one  may  well  wonder  if  they  are  necessary  to  great- 
ness or  great  achievements.  The  greatest  thinkers 
of  antiquity,  Plato,  Socrates,  and  Aristotle,  the 
guides  of  modern  times,  had  none  of  these  wonders. 
Washington,  Lincoln,  and  the  others  accomplished 
their  great  and  immortal  deeds  with  only  such  op- 
portunities as  their  times  afforded." 

"THE  Rev.  Dr.  James  M.  Ludlow  (Pastor 
*  Emeritus,  Munn  Avenue  Presbyterian  Church, 
East  Orange,  New  Jersey):  "Radio  is  a  scientific 
gain  to  humanity  and  a  genuine  pleasure  to  all  man- 
kind and  will  elevate  the  standards  of  sermons  of 
ministers  all  over  the  country.  Clergymen  know 
that  their  church  members  would  remain  at  home  to 
hear  a  good  sermon  being  broadcast  rather  than  go 
to  a  church  to  hear  the  usual  line  which  so  often  is 
given  out  from  the  pulpit  on  Sunday." 

IN  AN  editorial  in  the  New  York  Times:    " .     .     . 
Yet  there  is  no  setting  limits  to  the  response  of 
the  American  public  to  judicious  stimulation.     One 
may  now  go  to  London  or  Cherbourg  for  the  price 
of  a  radio  set." 

LJ.  R.  KIBLER  (Chicago;  secretary,  National 
*  *  Farm  Radio  Council):  "Radio  will  assume  a 
new  significance  to  farmers  and  their  families  when 
it  brings  them,  in  addition  to  entertainment, 
information  that  can  be  supplied  to  their  everyday 
problems.  Radio  must  serve  the  farmer  as  a 
schoolhouse  as  well  as  a  theatre." 


Fascinating  New  Fields  for  the  Enthusiastic  Radio  Constructor 
Who  Wants  to  Go  Further  in  Radio  Than  Set-Building—How  to 
Build  and  Use  Laboratory  Apparatus  Which  Will  Enable  the 
Radio  Student  to  Take  a  Real  Share  in  Radio  Testing  and  Design 

BY  KEITH  HENNEY 


'  j^HE  veritable  army  of  citizens  who  have  become  radio  addicts  since  the  coming  of  broadcast- 
-*•  ing  have  found  that  there  are  two  distinct  pleasures  in  radio.  The  first  and  foremost,  and 
certainly  the  most  lasting  joy,  comes  from  tapping  the  wealth  of  entertainment  from  the  "infinite 
reaches  of  the  air."  The  second,  hardly  less  important,  is  derived  from  the  home  assembly  of 
radio  parts  into  a  complete  whole.  There  is  the  pride  of  mechanical  accomplishment  in  that. 
But  as  Mr.  Henney  brings  out  in  this  excellent  article,  the  home  constructor  who  has  passed 
through  the  various  stages  of  construction,  finally  finds  himself  equipped  with  one  or  more  re- 
ceivers which  satisfy  him.  What  is  he  to  do  then?  It  is  of  course  true  that  radio  designers  are 
constantly  making  this  improvement  and  that,  and  are  passing  the  information  along  to  readers 
of  their  articles.  No  enthusiast  who  builds  radio  sets,  trying  first  this  one  and  that  until  he  finds 
what  to  him  is  the  ultimate,  is  wasting  his  time;  we  think  that  he  could  scarcely  have  spent  his 
time  in  better  fashion.  But  it  is  our  purpose  in  the  series  of  articles,  of  which  this  is  the  first,  to 
carry  these  constructors  on  farther,  and  to  show  them  experiments  which  will  lead  them  in  valu- 
able and  definite  directions.  —  THE  EDITOR 


THE    number    of    radio    enthusiasts 
in  this  country  who  have  learned  the 
great  amount  they  know  about  radio 
from  building  sets  must  be  consider- 
able.    In  addition  to  the  amateurs,  those  tire- 
less non-professional  investigators  of  anything 
and  everything  radio,  there  is  a  new  body  of 
American  citizens  who  have  amassed  a  great 
deal  of  radio  knowledge.     They  have  built 
this  receiver  and  that  and  they  have  found  out 
by  genuine  practical  experience  many  of  the 
great  electrical  facts  about  radio — and  found 
them  out  in  a  reasonably  painless  manner. 

Let  us  take  the  case  of  the  individual  whom 
for  want  of  a  better  name  we  shall  call  the 
"home  constructor."  He  has  found  that  some 
of  the  sets  he  has  built  do  what  was  claimed  for 
them,  while  others  fall  short.  He  is  not  sure 
whether  the  trouble  lay  in  his  own  part  of  the 
work,  or  in  the  fundamental  design.  It  is 
quite  probable  that  in  his  variously  appor- 
tioned radio  reading,  our  constructor  has 
acquired  a  pretty  good  working  knowledge  of 
radio  theory.  But  after  he  has  built  his  quota 
of  receivers,  what  is  left  for  him?  Should  he 
go  on  building  more  receivers?  If  he  is  an 
incurable  constructor,  he  probably  does. 
Somewhere  in  his  array  of  sets  he  has  found  a 
number  that  satisfy  him.  His  satisfactory 


set  gives  him  distance,  selectivity  and,  best  of 
all,  quality.  What  then? 

The  editors. of  RADIO  BROADCAST  feel  that 
there  is  more  in  radio  than  this  type  of  experi- 
menter has  found.  The  constructor  has  built 
his  receiving  sets,  and  that  is  a  necessary  stage 
in  his  progress.  He  has  had  the  real  fun  of 
making  an  intricate  electrical  unit  that  works; 
he  has  had  a  hand  in  harnessing  those  mysteri- 
ous electrical  forces  with  which  so  much  is  done 
and  about  which  so  little  is  generally  known. 

The  home  constructor  is  really  a  person 
with  considerable  mechanical  and  electrical 
talent  and  ingenuity,  but  in  the  last  analysis 
he  really  assembles  units  which  someone  else 
has  designed,  someone  better  equipped  tech- 
nically than  he. 

He  knows  that  experiments  and  measure- 
ments are  constantly  going  on  in  well-equipped 
radio  laboratories.  New  and  more  efficient 
coils  must  be  made,  the  phenomena  of  audio 
frequency  amplifiers  and  their  associated  ap- 
paratus is  being  investigated — much  is  yet  to 
be  learned  about  radio  generally. 

The  value  of  the  radio  work  of  the  Bureau 
of  Standards  is  well  known  to  our  constructor 
and  the  bulletins  describing  this  work  may  be 
had  for  the  cost  of  printing  them.  Papers 
are  read  before  the  Institute  of  Radio  En- 


What  Is  to  Become  of  the  Home  Constructor? 


605 


FIG.     I 

The  radio  frequency  circuit  is  schematically  repre- 
sented in  this  Figure.  There  is  nothing  tricky  about 
it  and  the  coils  and  condensers  may  be  of  any  standard 
make  provided  their  dimensions  are  such  that  they 
cover  the  range  of  wavelengths  desired 

gineers  which  circulate  among  a  limited  num- 
ber. Probably  an  equal  number  have  train- 
ing to  comprehend  their  contents. 

NEW     FIELDS    FOR   THE    HOME    CONSTRUCTOR 

THERE  is  a  big  gap  between  the  scientific 
papers  and  text  books  and  the  final  syn- 
thesis of  radio  apparatus  resulting  from  the 
technical  discoveries  which  antedated  them. 
These  papers  and  books  are  either  too  techni- 
cal, or  at  the  other  extreme,  popular  articles 
in  many  radio  magazines  are  too  simple. 
Many  times  the  articles  which  attempt  to 
popularize  radio  principles  are  incorrect  or 
hazy,  or  both.  Often  they  successfully  leave 
the  impression  that  the  writer  himself  was  not 
certain  about  what  he  wrote. 

There  is,  unfortunately,  no  middle  ground 
between  the  work  of  Government,  university, 
and  commercial  laboratories  and  the  home 
workshop  of  the  constructor.  It  is  to  supply 
such  a  middle  ground,  that  the  staff  of  the 
Laboratory  has  been  working  for  some  months, 
and  in  future  issues  of  RADIO  BROADCAST  they 
hope  to  present  the  result  of  their  work.  They 
hope  to  describe  the  building  and  use  of  simple 
and  not  too  expensive  apparatus  which  the 
constructor  can  assemble  at  home.  With  the 
aid  of  this  equipment,  the  home  constructor 
will  find  an  entirely  new  outlet  for  his  energies. 
He  will  no  longer  be  forced  to  make  new  re- 
ceivers, when  he  is  on  building  bent,  but  he 
can  turn  his  attention  to  the  deeper  and  more 
lasting  and  equally  interesting  field  of  radio 
phenomena. 

On  the  conviction  that  there  were  many  of 
the  radio  fraternity  who  desire  to  know  more 
about  radio,  RADIO  BROADCAST  was  en- 
couraged to  publish  in  June,  1925,  an  article 
on  the  training  required  for  a  real  radio  en- 


gineer, and  the  promise  was  made  that  future 
issues  of  this  magazine  would  contain  experi- 
ments that  the  home  worker  could  perform, 
experiments  that  may  prove  to  be  much  more 
interesting  than  the  construction  of  apparatus 
that  someone  else  has  designed.  The  response 
to  the  article  on  radio  training  has  made  it 
evident  that  there  were  many  of  the  home  con- 
structors who  were  suffering  somewhat  from 
ennui  from  the  continuous  round  of  one  re- 
ceiver after  another,  and  gave  the  Editors  the 
courage  to  go  ahead  with  their  endeavor  to 
entice  readers  of  RADIO  BROADCAST  into  the 
fascinating  field  of  radio  experiment. 

CONSTRUCTION   ARTICLES  OF  PRACTICAL  VALUE 

THESE  experiments  will  be  tied  up  prac- 
tically to  radio  equipment.  The  methods 
of  design  will  be  explained.  And  with  this 
explanation,  will  be  copious  references  to 
pamphlets  and  text  books  bearing  on  the 
subject  under  discussion.  Where  mathe- 
matics is  involved,  aid  will  be  given  in  the  use 
of  the  formulas,  and  it  is  hoped  that  it  will 
be  possible  for  the  interested  experimenter 
pleasantly  to  learn  more  about  the  use  of 
simple  radio  mathematics.  There  are  any 
number  of  people  who  are  not  content  to  be 
told  that  a  thing  is  so,  they  want  to  know  why 
it  is  so.  If  they  can  discover  the  whys  them- 
selves, and  go  further  after  that  discovery, 
they  have  an  absorbing  future  indeed  before 
them.  And  who  does  not  feel  a  peculiar 
psychological  satisfaction  at  accomplishing 
some  one  definite  object  of  value? 

This  series  of  articles  will  come  close  at 
times  to  the  field  of  general  physical  and  elec- 
trical science.  The  facts  that  are  learned 
about  radio,  will  often  apply  to  similar  pheno- 
mena in  the  realm  of  sound  and  light,  and 


Push-pulK 
Output 
Transformer 


FIG.    2 


The  audio  frequency  part  of  the  oscillator  is,  like 
the  radio  part,  a  simple  Hartley  circuit  and  a  push- 
pull  output  transformer  with  a  mid-tap  may  be 
tuned  by  a  fixed  condenser  so  that  the  tone  emitted 
will  be  approximately  1000  cycles 


6o6 


Radio  Broadcast 


1.00025  mfd 


B 
45  Volts 

w 

FIG.    3 

This  schematic  diagrams  represents  the  completed  modulated  oscillator 
with  all  of  the  accessory  apparatus.  Switches  make  it  possible  to  operate 
either  tube  independently  of  the  other,  and  in  the  audio-frequency  oscilla- 
tor is  a  jack  so  that  the  tone  may  be  taken  out  for  any  of  the  uses  de- 
scribed in  the  article 


sometimes  will  have  an  important  bearing 
on  our  appreciation  of  some  of  the  fine  arts, 
ft  is  tremendously  difficult  for  the  isolated 
experimenter  to  know  all  that  is  going  on  in 
this  feverishly  active  field  of  radio.  The  ex- 
perimenter is  often  at  a  loss  to  know  what  to 
read  and  what  to  do.  It  is  distinctly  possible 
to  translate  the  highly  interesting  activities 
of  the  radio  engineer  into  apparatus  and  into 
terms  that  the  reasonably  well-equipped  ex- 
perimenter can  use  and  understand.  It  is 
just  this  task  that  the  staff  of  RADIO  BROAD- 
CAST Laboratory  hopes  to  accomplish. 

THE    USEFUL    MODULATED   OSCILLATOR 

THE  first  instrument  that  will  be  des- 
cribed has  been  called  a  "modulated 
oscillator,"  a  name  that  perhaps  sounds 
formidable.  It  is  really  one  of  the  most  useful, 
and,  withal  one  of  the  most  simple  pieces  of 
laboratory  apparatus. 

Briefly,  it  is  a  combination  of  a  radio- 
frequency  oscillator — a  miniature  transmit- 
ter— and  an  audio-frequency  oscillator.  The 
radio  frequency  part  of  the  unit  is  so  arranged 
that  it  will  cover  all  frequencies  from  the 
lowest  broadcasting  frequency  to  the  highest 
used  by  the  transmitting  amateur — from 
6000  to  500  kilocycles  (50  to  600  meters). 
The  audio  oscillator  can  be  tuned  to  some 
definite  tone,  say  1000  cycles,  and  may  be  used 
to  "modulate"  the  high  frequency  energy,  or 
in  the  several  ways  mentioned  below. 

Either  of  the  units  comprising  this  appara- 
tus may  be  used  alone  or  both  together,  and 
if  placed  in  a  box  including  batteries,  it  is 


a  self-contained  miniature 
broadcasting  station.  The 
laboratory  instrument  was 
designed  with  this  object  in 
view.  The  entire  gear  was 
placed  in  a  box  (lof  x  7  x  6 
inches),  although  it  must  be 
admitted  that  a  larger  cabi- 
net would  have  made  the 
assembly  much  simpler! 

The  radio  frequency  part 
of  the  circuit  is  shown  in 
Fig.  i  which  is  a  simple 
Hartley  oscillator  circuit. 
The  condenser  may  be  any 
good  low  loss  instrument, 
preferably  of  the  straight 
line  frequency  or  straight 
line  wavelength  type.  That 
used  in  the  oscillator  illus- 
trated was  the  Lacault  con- 
denser with  a  straight  line 
wavelength  curve.  The  coils  may  be  of  any 
variety,  although  those  of  the  General  Radio 
Company  are  very  satisfactory  as  regards  low 
loss  and  the  simplicity  with  which  the  various 
wave  bands  may  be  covered. 

DETAILS    OF    THE    CIRCUIT 

THE  audio  frequency  part  of  the  circuit 
is  shown  in  Fig.  2  and  is  composed  of  the 
output  coil  of  a  push-pull  amplifier.  Instead 
of  the  primary  leads  going  to  the  plates  of  two 
tubes,  the  two  ends  of  the  winding  are  con- 
nected to  the  grid  and  plate  of  one  tube.  The 
other  winding  is  placed  in  the  plate  circuit  of 
the  radio  oscillator,  thereby  introducing  the 
audible  tone  into  that  circuit. 

Fig.  3  is  a  schematic  diagram  of  the  com- 
bined unit  utilizing  common  A  and  B  batteries. 
In  the  Laboratory  model  illustrated  in  Fig.  4, 
two  WD-ia  tubes  were  used  and  two  dry  cells 
were  placed  within  the  cabinet.  Two  switches 
are  included  so  that  either  tube  may  be  oper- 
ated independently  of  the  other,  and  a  closed 
circuit  jack  is  placed  in  the  audio  oscillator  so 
that  the  tone  may  be  taken  out  for  any  of  the 
purposes  suggested  below. 

Although  the  grid  condenser  and  leak  values 
are  designated  on  the  diagrams,  these  values 
are  not  at  all  critical  and  may  be  varied  within 
rather  wide  limits  before  the  tubes  refuse  to 
function.  The  size  of  the  condenser  across 
the  radio  frequency  coil  determines,  together 
with  the  inductance  of  the  coil,  the  frequency 
to  be  generated.  The  General  Radio  coils 
are  so  designed  that  with  a  .0005  mfd.  con- 
denser, the  6o-turn  coil  will  cover  the  range 


What  Is  to  Become  of  the  Home  Constructor? 


607 


FIG.  4 

This  photograph  shows  clearly  the.  panel  layout  of  the  modulated  oscillator  and  it  gives  an  idea  of 
how  the  set  of  coils  may  be  used  to  cover  the  entire  band  of  wavelengths  from  50  to  600  meters 


FIG.    5 

The  disposition  of  the  various  parts  of  the  receiver  may  be  seen  from  this  photograph  which  looks  down  upon 
the  completed  oscillator.     It  must  be  admitted  that  less  difficulty  will  be  had  in  constructing  the  unit  if 

more  space  is  provided  for  the  various  parts 


6o8 


Radio  Broadcast 


FIG.  6 

A  rear  view  of  the  oscillator  gives  a  good  idea  of  the  small  size  of  the  one  used  in  RADIO  BROADCAST  Labor- 
atory.    Both  A  and  B  batteries  are  contained  in  the  cabinet  so  that  it  is  a  veritable  portable  broadcast- 
ing station 


FIG.    7 

An  end  view  of  the  oscillator  showing  how  the  coil  is  placed  with  respect  to  the  other  equip- 
ment.    This  coil  happens  to  be  the  one  which  will  cover  the  50  to  150  meter  wavelengths 


What  Is  to  Become  of  the  Home  Constructor? 


609 


1500  to  500  kilocycles  (200  to  600  meters)  the 
30  turn  coil  3000  to  1000  kilocycles  (100  to 
300  meters)  and  the  I5~turn  coil,  6000  to  2000 
kilocycles  (50  to  150  meters). 

BUILDING   THE    OSCILLATOR    IS    EASY 

THE  actual  construction  of  the  oscillator 
is  not  complicated.  No  one  who  has  built 
a  radio  receiver  should  experience  the  slightest 
difficulty  with  this  instrument.  The  photo- 
graphs in  this  article  show  something  .of  the 
layout  used  in  the  Laboratory,  although  more 
room  is  to  be  desired.  The  radio  frequency 
leads  between  coil  and  condenser,  and  grid 
and  plate  of  the  associated  tube  should  be 
short.  Any  tubes  may  be  used;  wo-i2's  were 
chosen  in  this  case  because  it  was  possible  to 
make  the  apparatus  portable  and  self  con- 
tained. 

It  would  be  well  to  build  the  low  frequency 
part  of  the  circuit  first  since  only  a  pair  of 
telephone  receivers  is  necessary  to  ascertain 
whether  the  tube  is  oscillating  or  not.  The 
coil  used  in  the  Laboratory's  set-up  was  the 
Ail-American  push-pull  output  coil,  and  tuned 
to  about  1000  cycles  with  a  condenser  of  .003 
mfd.  across  the  secondary.  Placing  the  tele- 
phones across  the  secondary  winding,  or  in 
series  with  the  plate  of  the  tubes  will  enable 
the  constructor  to  tell  at  once  what  tone  is 
being  generated,  and  changing  the  tuning  con- 
denser will  naturally  change  this  tone.  At 
about  1000  cycles,  the  receivers  will  work  most 
efficiently,  which  can  be  told  by  the  greater 
volume  of  sound  emitted  when  the  set-up 
approaches  this  frequency. 

The  actual  frequency  of  the  audio  oscillator 
is  not  important,  since  all  condenser  and  air- 
core  coil  measurements  do  not  vary  over  the 
usual  range  of  audio  frequencies.  The  object 
of  choosing  approximately  1000  cycles  is  two- 
fold. First  of  all,  the  ear  is  most  sensitive 
to  frequencies  in  this  neighborhood,  and 
secondly,  telephone  receivers  give  the  greatest 
response  at  about  the  same  frequency. 

After  the  audio  end  of  the  oscillator  is  func- 
tioning properly,  the  radio  frequency  circuit 
may  be  wired.  It  is  only  necessary  to  bring 
the  oscillator  near  a  receiving  set  to  tell 
whether  the  combined  units  are  operating  pro- 
perly. 

HOW  TO   CALIBRATE   THE    OSCILLATOR 

'"THE  simplest  method  of  calibrating  the 
1  oscillator  is  to  use  it  in  connection  with  a 
receiver  whose  dials  are  already  calibrated 
from  the  frequencies  of  known  broadcasting 
stations.  For  instance,  KYW  or  WEAF  may 


be  tuned-in  at  the  lower  end  of  the  broadcast- 
ing frequency  band  and  then  the  modulated 
oscillator  dial  turned  until  the  looo-cycle  note 
is  heard  in  the  receiver.  At  this  point,  the 
oscillator  is  sending  out  a  signal  on  the  fre- 
quency of  the  broadcasting  station.  If  the 
radio-frequency  condenser  is  a  straight  line 
wavelength  affair,  only  two  points  are  needed 
to  make  a  wavelength  curve  of  the  oscillator, 
but  it  is  safer  to  calibrate  it  by  tuning-in 
several'  broadcasting  stations.  If  the  con- 
denser is  a  straight  line  frequency  instrument, 
a  frequency  curve  may  be  made  with  two 
points.  If  the  capacity  of  the  condenser 
follows  a  straight  line  law.  several  points  will 
be  needed  and  neither  the  condenser  degree- 
wavelength  or  frequency  curve  will  be  a 
straight  line. 

In  future  articles  of  this  series  will  be 
described  a  new  method  for  measuring  the 
resistance  of  coils  an  extremely  simple  and 
accurate  method  that  has  not  before  been 
described  in  this  country.  A  simple  alternat- 
ing current  bridge  developed  in  RADIO  BROAD- 
CAST Laboratory  will  be  described  which  will 
enable  the  home  constructor  to  measure  the 
inductance  of  coils,  the  capacity  of  condensers, 
and  the  resistance  of  various  radio  instru- 
ments. Other  instruments  and  experiments 
will  follow  from  time  to  time  and  whatever 
theory  is  necessary  will  be  explained  as  fully 
as  possible. 

The  uses  to  which  the  modulated  oscillator 
may  be  put  are  listed  below  and  specific 
directions  for  the  use  with  special  apparatus 
will  follow  in  later  articles. 

USES    OF    THE    MODULATED   OSCILLATOR 

1.  AUDIO  OSCILLATOR 

A.  Source  of  tone  for  testing  open  circuits. 

B.  Source    of    tone    for    measuring    capacity, 
inductance,  and  resistance  on  an  alternating 

current  bridge. 

C.  Measuring    audio    frequency    instruments, 
such  as  transformers,  loud  speakers,  etc. 

2.  RADIO  OSCILLATOR. 

A.  Source  of  radio  frequency  energy. 

B.  Separate   heterodyne   for   super-heterodyne 
reception  with  any  existing  receiver. 

C.  For  measuring  losses  in  radio  frequency  cir- 
cuits. 

D.  For  measuring  high  frequency  resistance  of 

coils. 

E.  Heterodyne  wavemeter. 

3.  MODULATED  OSCILLATOR. 

A.  Source  of  modulated  radio  frequency  energy 

— a  miniature  broadcasting  station. 

B.  Calibrate  receiving  sets. 

C.  To  measure  frequency  of  incoming  signals. 


as  the  LroacLc  aster  sees   it 


Jyy  Carl  DreLer 

Drawings  by  Franklyn  F.  Stratford 


How  Broadcast  Stations  Function — From  the  Inside 


OME  of  the  delicate  points  of  broad- 
casting station  organization  lies  in 
the  relation  between  the  operators 
and  announcers,  or,  in  a  broader 
sense,  between  the  program  and  operating 
staffs.  It  is  absent  only  where  the  diverse 
functions  of  operation  and  announcing  are 
united  in  one  genius,  who  cajoles  the  artists, 
pours  out  his  soul  in  expositions  and  introduc- 
tions, and  at  the  same  time  keeps  a  fearful 
eye  on  the  antenna  ammeter.  Before  these 
miracle-workers  of  the  ten-watt  class  we  can 
only  bow  in  reverence,  while  wishing  them, 
in  the  not  inappropriate  airplane  pilots' 
phrase:  "Soft  landings,  and  the  best  of  luck!" 
But  in  all  the  larger  stations  the  announcing  is 
done  by  one  squad  of  men,  and  the  operating 
by  another,  and  as  a  rule  the  two  groups  differ 
widely  in  background,  experience,  training, 
outlook,  objects,  and  traditions.  Yet,  if 
the  program  is  to  run  smoothly,  the  an- 
nouncers and  program  people  on  the  one  hand, 
the  operators  on  the  other,  must  work  to- 
gether at  all  times;  the  least  failure  in  co- 
ordination may  mean  a  break  on  the  air.  The 
necessary  degree  of  cooperation  can  generally 
be  secured  only  when  each  group,  (i)  knows 
its  own  business  thoroughly,  and  (2)  minds 
it,  while  (3)  knowing  enough  of  the  problems 
of  the  other  department  to  grease  the  ma- 
chinery where  required.  In  practice,  this  is 
not  always  as  simple  as  it  sounds  in  these 
general  terms. 
The  trouble  with  the  studio  people  is  that 


some  of  them  expect  miracles  from  the  techni- 
cians. Or  perhaps  it  would  be  more  accurate 
to  say  that  they  act  as  if  they  expected 
miracles,  while  verbally  disclaiming  any  such 
intention.  They  rarely  have  any  engineering 
background,  and  from  this  it  follows  that  they 
usually  have  a  defective  perception  of  techni- 
cal requirements.  They  do  not  realize  the 
sharp  limitations  of  electrical  equipment, 
and  the  fact  that  any  technical  enterprise  is 
certain  to  fail  unless  the  characteristics  of  the 
machinery  are  taken  into  account  at  every 
step.  In  engineering  there  are  any  number  of 
ways  of  getting  into  trouble,  and  only  a  few 
ways — frequently  only  one — of  doing  the  job 
right.  This  conclusion  is  beaten  or  burned 
into  the  hide  of  a  technical  man  in  his  im- 
pressionable years.  Any  man  who  has  sud- 
denly found  his  face  six  inches  above  a  200- 
ampere  arc  when  his  screwdriver  fell  across 
the  one-hundred-and-ten,  or  who  has  seen 
lightning  come  into  an  inadequately  protected 
power  plant  and  knock  the  switchboard  into 
the  next  county,  or  viewed  the  remains  of  a 
$75  thermo-couple  meter  after  the  leads  got 
twisted,  conceives  a  wholesome  respect  for 
inanimate  nature.  He  realizes,  not  merely  in 
words,  but  deep  down  in  his  liver,  that  one 
does  not  coerce  nature;  one  can  only  take  ad- 
vantage of  what  she  wants  to  do.  This  un- 
derstanding does  not  make  him  an  engineer, 
but  it  prepares  him  to  be  one.  He  realizes 
that  he  must  play  the  game  according  to  the 
rules  of  things  as  they  are,  if  he  wants  to  play 


The  Announcer  Is  Not  the  Radio  Alpha-Omega 


611 


at  all.  His  ingenuity,  resourcefulness,  and 
general  wonder-working  must  all  be  erected  on 
that  foundation.  Let  him  forget  it,  and 
immediately  he  comes  to  grief.  Huxley  said: 
"Nature's  discipline  is  not  even  a  word  and  a 
blow,  and  the  blow  first,  but  the  blow  without 
the  word.  It  is  left  to  you  to  find  out  why 
your  ears  are  boxed."  This  is  true  just  as 
much  in  the  practical  applications  of  science 
as  in  the  biological  situations  to  which  Huxley 
had  reference.  Nature  encompasses  the  car- 
bon granules  and  the  stretched  steel  dia- 
phragm of  a  microphone  just  as  much  as  the 
digestive  processes  of  a  lion  in  the  African 
jungle;  everything  that  happens  anywhere,  in 
the  woods  or  in  a  broadcasting  studio,  is  na- 
tural. The  only  difference  between  the 
technician  and  the  layman  is  that  the  techni- 
cian knows  better  in  his  special  field  what  he 
can't  get  away  with.  He  knows  also  that  if 
one  opening  is  left  the  thing  will  go  wrong,  just 
as  when  there  is  one  hole  in  a  kettle  the  soup 
will  leak  out,  even  if  the  rest  is  sound.  Hence, 
in  broadcasting,  when,  to  the  studio  group,  the 
men  in  charge  of  transmission  seem  most 
meticulous,  dilatory,  and  over-cautious,  the 
only  trouble  with  them  may  be  that  they  know 
their  business. 

There  is  no  specific  reason  why  announcers 
and  operators,  the  principal  representatives, 
in  point  of  numbers,  of  the  program  and 
technical  groups,  should  not  get  on  well 
together.  They  are  in  the  same  boat.  Both 
are  in  the  show  business,  in  which  it  is  im- 
possible to  confine  blunders  and 
lapses  to  an  inner  circle.  The 
operator  lives  in  constant  anx- 
iety that  something  will  happen 
to  interfere  with  transmission. 
The  announcer,  likewise,  is  al- 
ways handling  dynamite.  He 
must  always  be  ready  to  recon- 
cile diverse  elements,  to  fill  in 
awkward  gaps,  and  to  be  inter- 
esting without  offending  anyone 
in  his  highly  variegated  audience. 
He  certainly  has  no  sinecure.  As 
a  rule,  operators  and  announcers 
live  together  amicably  enough. 
When  any  ill  feeling  arises  be- 
tween them,  it  is  generally  found 
to  arise  through  the  presence  of 
inconsiderate  and  conceited  indi- 
viduals in  one  group  or  the  other. 
An  operator  may  be  intolerant 
and  arbitrary.  When  there  is 
time,  he  should  always  explain 
why  he  wants  something  done 


rather  than  take  refuge  behind  the  cloak  of 
technical  necessity,  which  covers  a  multitude 
of  botched  jobs.  The  mysteries  of  his  craft 
are  often  susceptible  of  simple  explanation  to 
persons  of  average  intelligence.  It  is  not 
hard  to  explain  to  an  announcer  why  he 
should  keep  his  head  turned  toward  the  micro- 
phone, and  he  is  more  apt  to  keep  it  that  way 
if  he  knows  definitely  what  happens  when  he 
turns  it  to  one  side. 

The  announcer,  on  his  part,  just  because  he 
is  a  much  photographed  and  advertised  young 
man,  should  not  get  the  idea  that  he  is  the 
whole  works.  .  The  technical  men  behind  the 
scenes  are  just  as  important  as  he  is.  It  was 
the  work  of  men  of  their  class,  after  all,  that 
made  radio  broadcasting,  and  got  the  an- 
nouncers jobs  in  which  they  get  more  publicity 
per  ounce  of  effort  expended,  than  in  any 
other  vocation  they  could  possibly  enter. 
It  is  greatly  to  the  credit  of  announcers  as  a 
class  that  they  rarely  let  adulation  turn  their 
heads.  Now  and  then  the  thing  happens, 
manifesting  itself  in  various  annoying  ways. 
I  recollect  one  announcer,  now  happily  de- 
parted from  the  pathways  of  the  ether,  who 
had  the  habit  of  using  forms  like,  "7  will 
now  switch  you  over  to  the  concert  micro- 
phone. .  .  ."  Actually  the  operators  did  the 
switching.  It  would  have  been  better  to  say 
"we."  A  small  matter?  Yes,  an  exceedingly 
small  matter.  But,  in  this  world  of  clashing 
egos,  it  happens  to  be  one  of  those  small  mat- 
ters which  play  an  appreciable  part  in  human 


\;\  \\\ 


v;\>.\ 


\ 


f.5. 


lie  conceives  ct  respect  for  naiure 


6l2 


Radio  Broadcast 


relations,  with  power  to  influence  enterprises 
for  good  or  bad,  according  to  the  effect  on  the 
individuals  who  conduct  them. 

Divided  responsibility  has  its  disadvantages, 
but  the  larger  broadcasting  stations  will 
probably  continue  to  be  run  by  two  more  or 
less  independent  departments,  for  the  reason 
that  it  is  rarely  possible  to  get  the  required 
qualifications  united  in  one  individual,  and 
because  the  advantages  of  specialization  out- 
weigh its  disadvantages,  on  the  whole  and  in 
the  long  run.  When  you  listen  to  a  broad- 
casting station  whose  program  runs  off 
smoothly,  keeping  up  to  schedule,  without 
gaps  on  the  air,  snappy  change-overs  between 
the  field  and  the  studio,  and  the  general 
impression  of  a  systematized,  properly 
thought-out  organization,  you  may  be  sure 
that  the  technical  and  the  studio  staffs  are 
working  together,  with  each  squad  taking  care 
of  its  assignment  and  making  it  as  easy  as 
possible  for  the  others  to  cover  theirs.  When, 
on  the  contrary,  you  listen  to  false  starts, 
wire  talk  going  out  on  the  air,  orchestras 
starting  while  the  announcer  is  still  talking, 
and  periods  filled  with  nothing  but  the  carrier 
hiss,  the  chances  are  that  the  studio  and 
operating  divisions  are  pulling  in  opposite 
directions.  That  may  not  be  the  only  trouble, 
but  it  is  probably  one  of  them. 

Microphone  Placing  in  Studios 

BEGINNING  with  this  issue,  it  is  our 
intention  to  publish  each  month  at 
least  one  article  on  some  technical 
aspect  of  the  broadcaster's  business.  These 
articles  will  be  on  such  subjects  as  micro- 
phone placing  in  studio  and  field  work,  effec- 
tive broadcast  station  organization,  main- 
tenance problems,  and  various  devices  of 
practical  aid  in  securing  first-class  transmis- 
sion. In  such  a  relatively  new  field  as  this, 
unanimity  of  opinion  is  neither  to  be  desired 
nor  expected,  and  the  views  of  other  operators 
of  broadcasting  stations  will  always  be  wel- 
come. 

One  of  the  vital  factors  influencing  the 
quality  of  a  station's  output  is  the  placing 
of  microphones  in  the  studio.  It  is  of  about 
the  same  order  of  importance  as  the  transmis- 
sion characteristics  of  the  audio  amplifier 
and  modulating  system,  which  determine  the 
treatment  of  the  various  frequencies  of  speech 
and  music.  If  either  the  frequency  charac- 
teristic or  the  microphone  placing  of  the 
station  should  be  very  far  off,  good  transmis- 
sion is  out  of  the  question.  By  "good  trans- 


mission" we  mean  reasonably  accurate  re- 
production in  receiving  sets  of  the  performance 
in  the  studio. 

The  walls  of  studios  are  generally  padded 
with  felt,  or  covered  with  curtain  material  of 
the  type  known  as  Monk's  Cloth,  or  otherwise 
deadened  to  reduce  reverberation.  The  reason 
for  this  is  that  any  echo  or  reverberation 
in  the  studio  is  exaggerated  or  added  to 
by  the  reverberation  in  the  room  in  which  the 
performance  is  ultimately  heard  through  the 
loud  speaker.  The  proper  "reverberation 
time" — the  time  required  for  a  sound  to  die 
down  to  practical  inaudibility — for  good  musi- 
cal taste,  is  somewhat  over  one  second.  A 
good  studio  will  in  general  have  a  reverbera- 
tion time  well  below  this  value.  The  rever- 
beration period  of  the  room  in  which  the  re- 
ceiver is  placed  will  then  make  up  the  differ- 
ence. 

The  most  commonly  used  microphone  is 
the  double-button  car  bontype,  because  of 
its  simplicity  and  low  impedance.  The 
latter  characteristic  permits  the  use  of  long 
leads,  whose  capacity,  while  much  too  large 
to  be  placed  in  parallel  with  a  condenser 
transmitter,  is  negligible,  when  paralleled  with 
an  impedance  of  some  200  ohms,  like  that  of  a 
carbon  microphone.  Fig.  i  shows,  schemati- 
cally, how  a  double-button  microphone  is 
built  and  connected  to  the  amplifier  system  of 
a  broadcasting  station.  The  microphone  con- 
sists of  a  diaphragm,  D,  formerly  made  of 
steel,  which  in  later  models  was  changed  to 
duralumin,  an  alloy  of  aluminum,  in  order  to 
improve  the  sensitivity  and  the  ratio  of  signal 
output  to  hiss.  (Inasmuch  as  the  operation 
of  the  device  requires  passing  a  direct  current 
through  the  carbon,  some  hiss  is  always 
present,  and  this  may  become  objectionable  if 
the  sounds  being  picked  up  are  very  faint.) 
This  diaphragm,  about  two-thousandths  of  an 
inch  thick,  is  stretched  between  clamping 
rings,  and  one  side  (the  back)  is  about  the 
same  distance  from  a  flat  metal  surface.  The 
combination  of  mechanical  tension  and  air 
damping  gives  the  necessary  characteristics 
of  very  high  natural  frequency  and  damping 
so  that  the  device  responds  uniformly  to 
sound  frequencies  between  about  30  and  6500, 
or  higher,  depending  to  some  extent  on  the 
freshness  of  the  carbon.  This  quality  of  uni- 
form response  is  of  course  essential  for  good 
quality.  If  a  microphone  has  a  natural  period 
of  1000  cycles,  say,  it  will  respond  violently 
to  notes  of  this  pitch,  giving  them  undue 
prominence;  some  low  grade  transmitters 
actually  show  this  fault.  Again,  the  low  or 


How  to  Place  the  Studio  Microphone 


6,3 


Figi 


high  frequencies  may  be  lost,  resulting  in 
"tinny"  or  "drummy"  (muffled)  output, 
respectively.  It  should  be  noted  that  the 
flat  characteristic  necessary  for  high  quality 
reproduction  is  obtained  only  at  the  expense 
of  sensitivity.  The  broadcasting  microphone 
is  about  on,3  one-thousandth  as  sensitive  as  the 
common  telephone  microphone,  but  the  latter 
does  not  get  much  over  2000  cycles,  and  has 


an    8oo-cycle   resonance   peak.     That    won't 
do  for  broadcasting  in  the  1925  style. 

The  stretched  diaphragm,  shown  at  D  in 
Fig.  i,  is  free  to  vibrate  between  two  cups  or 
buttons,  B,  and  B2,  filled  with  polished 
globular  or  egg-shaped  carbon  granules  of  a 
peculiarly  rare  and  aristocratic  variety,  the 
output  of  which  is  largely  produced  by  the 
concern  which  sends  you  your  telephone  bill 


ARTIST 


i 


MICROPHONE 

A 


MICI?OPHONE 

t 

X  ^ 

V»ov«*     , 

x  x  i2**V  PI*NO 

^owoHa^V  V.CLOJEO 

"      X^fl^ 


c^$ 

X 

6At»-i° 


J**1*^ 


614 


Radio  Broadcast 


each  month.  All  is  not  carbon  for  broad- 
casting microphones  which  is  black,  just  as 
all  which  glitters  is  not  gold.  The  two  buttons 
are  connected  to  the  primary  or  low  impedance 
winding  of  a  transformer,  IT,  the  secondary 
of  which  feeds  a  tube,  and  so  on  up  to  the 
modulators.  The  vibration  of  the  diaphragm, 
when  sound  waves  impinge  on  the  open  side, 
varies  the  resistance  of  the  two  carbon  paths 
according  to  the  push-pull  principle;  at  the 
same  time  direct  current  is  fed  to  the  buttons 
from  a  battery  B,  with  its  positive  terminal 
connected  to  a  midpoint  tap  on  the  trans- 
former primary,  while  the  negative  pole  goes 
to  the  diaphragm  through  a  variable  resistance 
R  and  milliammeter  A.  The  direct  current  is 
adjusted  to  a  value  of  15-20  milliamperes  per 
button,  or  about  40  mA.  in  all.  Better  still, 
a  milliammeter  may  be  connected  in  each  leg 
rather  than  in  the  common  lead;  then  any 
serious  difference  in  resistance  may  be  de- 
tected immediately.  The  buttons  should 
not  differ  by  more  than  50  per  cent.;  a  greater 
divergence  indicates  aging  carbon  or  some 
other  irregularity.  It  will  be  seen  that  with 
d.  c.  passing  through  the  carbon,  any  variation 
in  resistance  supplies  an  alternating  current 
to  the  input  transformer.  This  current 
varies  in  accordance  with  the  frequency  and 
amplitude  of  the  sound  waves  which  reach 
the  diaphragm.  In  other  words,  the  device 
is  a  microphone,  changing  sound  energy  to 
proportionate  electric  currents.  There  is 
also  a  "gain"  control,  G,  which  varies  the 
input  to  the  first  tube. 

The  carbon  microphone  is  subject  to  a  form 
of  distortion  called  "blasting,"  and  that  is 
one  of  the  principal  difficulties  to  be  avoided 
in  placing  them.  It  is  caused  by  excessive 
sound  energy  striking  the  diaphragm,  and 
causing  it  to  swing  through  such  an  amplitude 
that  the  carbon  leaves  the  diaphragm  momen- 
tarily, an  effect  which  manifests  itself  both 
visually  and  audibly.  The  visual  indication 
is  on  the  microphone  milliammeter,  whose 
reading  may  drop  from  40  mA.  to  perhaps  35 
while  the  soprano  holds  a  fortissimo  note  and 
takes  a  step  forward  impetuously  at  the  same 
time.  The  audible  indication  is  a  harsh, 
throttling  noise  accompanying  the  music. 
Still  another  indication  may  be  observed  on 
the  face  of  the  control  operator,  who  may  also 
give  expression  to  a  blanket  indictment  of 
sopranos  at  such  times. 

The  carbon  in  the  microphone  has  a  good 
deal  to  do  with  blasting.  If  the  carbon  is 
getting  old,  as  indicated  by  rising  resistance, 
it  will  blast  more  readily  than  when  fresh. 


And,  of  course,  it  must  be  the  right  sort  of 
carbon.  However,  the  best  microphones  will 
blast  if  the  sound  hits  them  hard  enough. 
Some  voices  blast  more  readily  than  others, 
and  some  instruments  more  than  others. 
A  cornet  or  trombone,  for  example,  blasts 
quite  readily.  The  violin  is  less  liable  to  this 
difficulty,  but  by  no  means  immune.  The 
saxophone  is  quite  free  from  it.  It  would 
seem  that  preponderance  of  certain  high  fre- 
quencies, with  a  steep  wave-form,  is  conducive 
to  blasting.  Soft  instruments  and  voices  do 
not  blast.  Moderate  volume  is  also  a  protec- 
tion, and  that  is  why,  for  broadcasting  pur- 
poses, very  powerful  voices  are  not  at  all 
desirable  as  a  general  thing. 

In  placing  microphones,  one  tries  to  avoid 
blasting,  in  the  first  place,  and  to  get  the 
correct  ratio  of  accompaniment  to  voice,  or  of 
one  instrument  to  another,  as  a  second  and 
equally  important  consideration.  In  this 
process,  something  depends  on  the  performers. 
For  example,  if  one  encounters  a  baritone  who 
persists  in  singing  with  operatic  volume  in  a 
small  studio,  he  will  probably  cause  micro- 
phone blasting.  You  try  to  reduce  the  blast- 
ing by  moving  the  "mike"  away  from  him, 
thereby  cutting  down  the  energy  of  the  sound 
reaching  the  diaphragm.  The  result  is  that 
you  run  into  a  lot  of  reflection  from  the  walls, 
the  energy  of  which  begins  to  be  comparable 
with  the  sound  reaching  the  transmitter  di- 
rectly from  the  performer,  causing  more  or  less 
distortion.  At  the  same  time,  you  lose  the 
pianissimo  portions,  for  it  is  a  fact  that  people 
who  try  to  broadcast  with  excessive  volume 
usually  sing  very  softly  in  the  intervals  be- 
tween outbursts.  The  only  solution  is  to 
arrange  with  the  studio  manager  to  avoid 
booking  soloists  of  extreme  volume  range,  and 
to  blacklist  them  when  they  get  by  the  audi- 
tion. 

Fig.  2  shows  (a)  a  good  general  set-up  for 
vocal  solos  with  piano  accompaniment;  and 
(b)  for  violin  solos.  The  arrangement  will 
vary  somewhat  with  different  studios,  but  it  is 
a  good  first  approximation.  Fig.  2c  is  a  set-up 
for  piano  solo  work. 

It  is  always  bad  practice  to  let  a  singer  use 
the  accompanist's  notes.  If  the  singer  re- 
quires notes  he  should  have  his  own  music 
sheets.  It  is  hardly  possible  to  keep  a  balance 
if  the  soloist  hovers  around  the  keyboard  of 
the  piano. 

Fig.  3  illustrates  set-ups  for  (a)  jazz  or- 
chestra; (b)  brass  band;  and  (c)  string  en- 
semble. In  the  case  of  the  jazz  orchestra,  the 
violin  is  about  three  feet  from  the  microphone, 


Are  Listeners  Content  With  5OO-Watt  Stations? 


615 


and  the  farthest  instruments  some  14  feet. 
The  violinist,  if  he  is  also  the  leader,  may  be 
angled  off  somewhat,  so  that  he  can  direct  the 
orchestra  without  being  lost  to  the  micro- 
phone. In  the  case  of  the  brass  band,  the  dis- 
tance of  the  instruments  varies  from  about  four 
to  thirty  feet;  if  the  studio  is  small,  it  may  be 
necessary  to  obviate  blasting  by  reversing  the 
microphone,  placing  it  back  to  the  orchestra 
and  with  the  bridge  facing  a  dead  surface. 
The  string  ensemble  is  shown  with  a  parlor 
organ. 

The  height  of  the  microphone  is  a  factor 
which  remains  to  be  discussed.  With  vocal 
solists  and  violinists,  it  should  normally  be 
shoulder  or  head  high.  On  piano  solos,  five 
feet  remains  about  right,  and  this  need  not 
be  changed  for  small  ensembles.  A  brass 
band  is  sometimes  better  with  microphone 
elevations  of  about  seven  feet.  However, 
there  are  some  curious  nodes  and  anti-nodes 
set  up  in  various  studios  which  require  experi- 
mentation with  microphone  elvations,  as  well 
as  horizontal  placing.  The  data  given  is  only 
a  first  approximation  in  any  case. 

Radio  Power  and  Noise  Level 

IN  A  recent  talk  before  the  Connecticut 
section  of  the  A.  I.  E.  E.,  Prof.  W.  J. 
Williams  of  Rensselaer  Polytechnic  In- 
stitute delivered  himself  of  the  opinion  that 
power  levels  of  broadcasting  stations  should  re- 
main just  where  they  are.  He  is  against  any 
increase  in  power.  The  objection,  to  be  sure, 
is  a  somewhat  academic  one,  in  view  of  the 
fact  that  almost  everyone  who  can  afford  the 
money  is  getting  a  5  kw.  set  to  replace  his 
0.5  kw.  outfit.  Not  everyone,  alas,  can 
undertake  this  expenditure.  Among  all  the 
sounds  heard  in  broadcasting  studios,  the 
jingling  of  the  cash  register  is  the  least  fre- 
quent. 

A  large  station  costs  a  pile  of  money,  and  all 
that  one  gets  for  the  disbursement,  besides  the 
ability  to  address  the  populace,  is  the  privilege 
of  spending  a  lot  more  cash  to  keep  the  thing 
going.  But  it  is  not  out  of  pity  for  the  groan- 
ing broadcasters  that  Professor  Williams  rises 
in  meeting.  Were  it  so,  we  should  wire  him 
our  congratulations  and  let  it  go  at  that.  He 
speaks,  ostensibly,  for  the  listeners.  We,  also, 
are  awash  with  altruism.  Our  heart  goes  out 
to  the  knob-turners  of  the  land,  as  does  the 
heart  of  the  learned  engineer  from  R.  P.  I., 
but  our  reasoning  is  at  variance  with  his. 
So  much  so,  that  we  must  have  at  him,  even 
if  the  magazine  is  barred  from  the  newsstands 


of  Troy,  and  our  name  is  hissed  by  all  the 
listeners  of  WHAZ. 

We  shall  be  surprised,  indeed,  if  the  members 
of  this  WHAZ  audience  do  not  send  us  loads  of 
poisoned  cigars,  live  tarantulas,  and  infernal 
machines,  for  now,  according  to  Professor 
Williams,  they  are  a  perfectly  satisfied  lot. 
"When  we  know," he  says,  "that  this  5oo-watt 
station  has  been  heard  consistently  in  cool 
weather — about  forty  weeks  a  year  for  three 
years — across  the  continent  in  one  direction 
and  in  Europe  in  the  other,  we  can  hardly  be 
criticized  for  taking  the  stand  that  a  power 
level  of  approximately  this  value  is  sufficiently 
high  to  meet  the  demands  of  the  radio  audi- 
ence." What  is  the  radio  audience,  and  what 
are  its  demands?  Possibly  those  members 
who  are  distance  hunters  pure  and  simple, 
who  are  satisfied  to  pick  out  the  mystic  letters 
W-H-A-Z  while  being  batted  in  the  ear  by 
crashes  of  static,  violet  ray  machines,  electric 
bells,  door-openers,  and  other  miscellaneous 
natural  and  artificial  noise  makers — possibly 
this  portion  of  the  clientele  is  satisfied.  In 
their  interest,  it  might  be  a  good  thing  to 
drop  WHAZ'S  power  to  50  watts  or  so.  The 
station  would  be  ten  times  as  hard  to  hear, 
and  the  more  rabid  DX  addicts  would  be 
proportionately  happier.  At  the  same  time, 
Rensselaer's  power  bills  would  be  somewhat 
reduced. 

But  what  about  the  people  who,  while  per- 
haps not  disdaining  to  take  a  little  DX  flyer 
once  in  a  while,  want  to  get  good  music  and  de- 
cently intelligible  speech  out  of  their  radio 
sets?  They  are  getting  it — from  the  locals, 


a.  blanket  mdicimeni  of  sopranos 


6i6 


Radio  Broadcast 


lie  execis    ii  "to  Le 


and,  at  greater  distances,  from  those  relatively 
few  and  enterprising  stations  which  are  in  a 
position  to  pile  on  the  kilowatts  when  they  are 
needed.  And  what  about  the  people  whose 
nearest  "locals"  are  several  hundred  miles 
away,  and  who  want  program  service,  not  a 
guessing  contest?  Does  anyone  imagine  that 
they  are  up  in  arms  about  so-and-so  tripling 
the  number  of  amperes  in  his  antenna?  Not 
at  all,  they  think  it  is  a  very  fine  thing  that 
they  are  able  to  get  their  market  reports  and 
jazz  without  samples  of  bedlam.  They  are  in 
favor  of  an  adequate  signal  for  the  farmers 
and  ranchers,  and  they  feel  that  they  are  en- 
titled to  it  just  as  much  as  the  city-dwellers. 
If  you  don't  believe  it,  go  out  into  the  country 
and  talk  to  them.  Professor  Williams,  when 
he  went  to  Hartford  to  deliver  his  paper, 
might  have  stopped  off  at  the  Berkshire  village 
of  Litchfield,  30  miles  East,  and  inquired 
whether  the  Litchfielders  get  their  program 
service  from  WHAZ,  73  miles  to  the  Northwest, 
or  WGY,  83  miles  in  the  same  direction.  The 
answers  would  have  given  him  a  few  foot-notes 
for  his  discourse. 

Having  expressed  his  undying  trust  in  500 
watts,  the  Professor  proceeds  to  discuss 
radio  noise,  which  in  part,  he  feels,  shows  a 
"healthy  development  condition,"  inasmuch 
as  radio  broadcasting  is  "the  latest  child  of 
the  physical  sciences,  and  like  every  other 
child  we  should  expect  it  to  be  noisy."  This 
metaphor  must  be  very  comforting  to  discrim- 
inating listeners  who  want  to  hear  the  "Adagio 
Lamentoso"  of  the  "Pathetique"  with  a  quiet 
background.  The  amount  of  noise  must  be 
limited,  we  are  told.  By  all  means.  Some 
good  work  is  being  done  by  public  utility 
companies  and  other  agencies  in  eliminating 
leaky  insulators,  radiating  smoke  precipita- 


tors,  and  the  like;  at  the  same  time  a  vigorous 
publicity  campaign  against  squealing  receivers 
has  greatly  reduced  one  source  of  disturbance. 
But  when  we  get  through,  considerable  noise 
will  still  remain  for  our  "supers",  with  their 
amplification  of  io,ooo-fold,  to  pick  up. 
The  only  way  to  eliminate  that  would  be  to 
move  to  Samuel  Butler's  Erehwon,  where  no 
machinery  was  to  be  permitted,  thereby 
eliminating  radio  noise,  radio  sets,  and  radio 
problems  at  a  single  stroke.  This  fact  Pro- 
fessor Williams  recognizes;  he  admits  that  it  is 
"both  theoretically  and  practically  impossi- 
ble to  reduce  the  noise  level  to  the  vanishing 
point,  as  the  cost  to  the  public  of  such  re- 
finements would  make  the  price  of  these  utili- 
ties prohibitive."  If  this  is  true  of  artificial 
disturbances,  is  it  not  even  more  pertinent 
when  it  comes  to  the  natural  disturbance  of 
static?  As  has  been  pointed  out  in  a  previous 
article  in  this  department,  no  static  reducing 
devices  applicable  to  broadcast  reception  are 
available.  The  situation,  as  regards  both 
natural  and  artificial  static,  may  therefore 
be  summed  up  as  follows  (calling  A  the  signal 
strength  and  B  the  static):  A  should  be 
greater  than  B.  B  is  too  large,  and  cannot 
be  economically  reduced  to  an  inconsequential 
level.  The  obvious  course  is  to  increase  A. 
To  this  measure  Professor  Williams  objects, 
on  the  ground  that  it  will  increase  interference. 
"It  is  necessary  to  establish  a  reasonably  low 
power  level  limit,"  he  maintains,  "as  the  ex- 
treme sensitivity  of  the  receiving  set  cannot 
be  used  without  disagreeable  interference." 

Let  us  go  to  the  bottom  of  this.  Why  are 
receiving  sets  made  so  sensitive?  Because 
people  want  to  hear  distant  stations,  and  be- 
cause those  stations  provide  only  a  very  weak 
field  at  distant  points,  a  lot  of  amplification  is 
required  to  bring  up  the  energy  to  audible 
level.  If  transmitter  powers  were  increased, 
there  would  be  no  necessity  for  using  the  full 
sensitiveness  of  the  set  at  any  reasonable  dis- 
tances. Hence  station  interference  would  not 
be  increased,  except  in  the  case  of  relatively 
primitive  receivers  located  close  to  powerful 
stations.  Nor  is  there  any  reason  why  sensi- 
tive receivers,  equipped  with  a  suitable 
volume  control,  should  not  be  capable  of  dis- 
tortionless reception  from  near-by  powerful 
stations.  At  the  same  time,  the  ability  of 
the  signal  to  ride  over  disturbances  would  be 
increased.  As  we  have  pointed  out  before 
in  discussions  on  this  topic,  radio  transmission 
is  really  the  sum  of  two  kinds  of  amplifica- 
tion, carried  out  at  the  transmitter  and  re- 
ceiver, respectively.  The  first  is  inherently 


The  Ceiling  Won't  Fall  When  "Super"  Stations  Are  Heard        617 


a  selective  and  purposeful  sort  of  amplification 
which  .brings  up  the  desired  signal  only.  The 
second  is  a  generalized  variety  of  amplification 
which  brings  up  signal  and  noise  indiscrimin- 
ately. The  latter  has  been  pushed  to  a 
length  which  is  not  altogether  healthy,  and 
the  next  rational  step  is  a  boost  in  the  cen- 
tralized amplification  of  transmitters.  A 
somewhat  analogous  situation  is  found  in  the 
electrification  of  railroads.  The  primary 
reason  for  electrification  is  that  coal  can  be 
converted  into  power  more  economically  at 
great  centralized  plants,  and  then  transmitted 
to  the  individual  electric  locomotives,  instead 
of  burning  it  at  relatively  low  efficiency  in 
a  large  number  of  steam  locomotives.  In 
radio  the  problem  is  not  merely  efficiency  in 
the  sense  of  ratio  of  output  to  input,  but  a  high 
ratio  of  signal  output  to  undesired  forms  of 
energy,  i.  e.,  noise.  In  both  fields,  however, 
there  is  a  trend  toward  centralization  and 
higher  power  as  the  most  effective  means  of 
gaining  their  respective  objectives. 

Quantitatively,  in  terms  of  amplification, 
just  what  does  increase  in  power  of  broadcast 
transmitters  amount  to?  Most  people  have 
a  greatly  exaggerated  idea  of  what  so-called 
"super-power"  really  means.  They  imagine 
receiving  tubes  within  a  hundred  miles  going 
blue,  loud  speakers  dancing  about  on  the 
table,  ceilings  tumbling  down,  and  citizens 
frying  eggs  on  electric  ovens  attached  to  their 
antennas.  No  such  wonders,  unfortunately, 
will  come  to  pass.  If  we  assume  50  kw.  as 
the  antenna  power  of  a  super-station,  it  will, 
under  the  same  conditions,  deliver  a  signal 
louder  by  one  stage  of  transformer-coupled 
plus  one  stage  of  resistance-coupled  audio 
amplification,  than  the  signal  of  a  5oo-watt 
installation.  The  signal  strength  being  pro- 
portional to  the  power,  the  50  kw.  transmitter 
will,  at  the  same  distance  and  with  all  other 
factors  held  constant,  give  a  signal  strength 
100  times  that  of  a  0.5  kw.  set.  A  single  stage 
of  audio  amplification,  assuming  a  5:1  ratio 
for  the  transformer  and  an  amplification 
constant  of  5.  in  the  tube,  which  is  about  right 
for  a  uv-igg  on  90  volts  plate,  is  good  for  a 
current  amplification  of  25.  Follow  this 
with  one  stage  of  resistance — or  impedance- 
coupled  amplification,  and  the  over-all  magni- 
fication is  already  125,  a  figure  greater  than  the 
multiplying  factor  of  the  50  kw.  station  over 
its  0.5  kw.  rival.  If  two  stages  of  transformer 
amplification,  with  ratios  of  5:1  and  3:1 
respectively,  should  be  considered,  the  over-all 
amplification  is  375,  a  figure  much  in  excess 
of  100.  What  a  "super"  transmitter  of  this 


order  amounts  to,  therefore,  is  the  presenta- 
tion of  a  stage  and  a  half  of  audio  amplifica- 
tion to  anyone  who  wants  to  listen  to  it.  But 
amplification  of  the  right  kind,  be  it  noted — 
amplification  of  the  signal  only.  In  other 
words,  if  you  want  to  know  what  super-power 
to  the  extent  of  50  kw.  would  sound  like, 
tune-in  a  distant  5OO-watt  station,  and  imagine 
its  loudness  increased  by  one  and  a  half 
stages  of  audio  amplification,  without  any 
increase  in  whatever  interference  accompanies 
the  5Oo-watt  signal.  Or,  better,  assume  the 
signal  of  the  5OO-watt  station  to  remain  con- 
stant; in  that  case  the  disturbances,  for  a 
50  kw.  outfit,  will  drop  to  one  one-hundredth 
of  the  present  level,  or  one  and  one  half  audio 
stages  "down." 

From  the  standpoint  of  the  radio  audience, 
would  it  not  be  better  to  have  such  stations, 
even  at  the  expense  of  further  loss  in  prestige 
by  some  of  the  midge  broadcasters,  instead  of  a 
crazy-quilt  of  5OO-odd  stations,  many  of  which 
are  worthless  in  quality  of  transmission  and 
program,  and  serve  no  purpose  except  to  cater- 
waul and  heterodyne  each  other.  If  Mr. 
Williams  wants  to  reduce  station  interference, 
he  should  advocate  a  reduction  in  the  number 
of  poor  transmitters  by  enforcing  decent 
standards  of  service,  instead  of  opposing  the 
sound  engineering  adjustments  of  organiza- 
tions with  the  resources  and  determination 
to  maintain  the  progress  of  the  art.  And,  if 
he  will  ponder  a  little  on  the  difference  between 
the  "  I-think-I-heard-your-station-last-night" 
range  and  the  effective  service  range  of  a 
station,  he  will  perhaps  reconsider  an  argu- 
ment which  is  reminiscent  of  the  early  days 
of  automobiling,  when  it  was  decreed  that  a 
flagman  had  to  walk  ahead  of  each  automo- 
bile to  prevent  it  from  scaring  horses. 


ike  cash  register  seldom  iinldes 


6i8 


Radio  Broadcast 


The  Memoirs  of  a  Radio 
Engineer.     IV 

THE  experiments  of  our  small  and 
youthful  group  of  radio  experimenters 
continued,  during  the  summer  of  1909, 
with  the  antenna  lead-in  swung  to  a  small 
house  in  the  backyard.  This  place  was  used 
for  storage,  and  two  buggy  horses  were  also 
kept  there,  for  the  Bronx  section  of  New  York 
City  was  still  semi-rural,  and  automobiles, 
while  already  common,  had  not  yet  driven  out 
equine  motive  power  to  the  present  extent. 
This  backyard  was  quite  spacious,  and  not 
confined  to  the  back;  it  also  extended  along 
the  sides  of  the  house,  and  contained  four 
pear  trees,  two  grapevines  and  summer- 
houses,  and  an  unused  well,  covered  with  a 
great  stone,  harking  back  to  the  days  when 
the  borough  had  not  attained  the  luxury  of  a 
municipal  water  supply.  We  had  a  miniature 
baseball  diamond,  about  20  feet  square,  in 
the  yard,  where  we  played  ball  during  the 
day,  and  at  night  we  foregathered,  immedi- 
ately after  dinner,  in  the  combined  stable  and 
storage  house,  to  listen  for  wireless  signals. 
Our  set  was  the  same:  the  four-wire  flat  top 
antenna,  the  detector  of  two  needles  with  a 
length  of  pencil  lead  lying  across  them,  the 
dry  cell,  and  the  75-ohm  watchcase  telephone 
receiver.  It  was  a  simple  set,  if  nothing  else 
can  be  said  for  it.  It  could  not  squeal  and 
disturb  the  neighbors,  it  had  no  knobs  to  turn, 
no  tubes  to  burn  out.  We  sat  around  it  on 
the  floor,  taking  turns  in  listening,  but  no 
sound  was  heard  except  the  occasional  stamp 
of  a  horse's  hoof  on  the  other  side  of  the  parti- 
tion. We  had  a  lantern,  which  we  lit  after 
dark,  although,  the  set  being  one  of  zero 
adjustments,  an  expert  could  manage  it  just 
as  well  in  the  dark.  But,  light  or  dark,  it 
brought  in  no  signals.  The  only  thing  that 
had  been  changed  was  the  ground.  When  the 
antenna  came  into  the  house  the  ground  had 
been  a  water  pipe;  now  it  consisted  of  a  length 
of  gas  pipe,  driven  into  the  ground  between 
the  planks  of  the  floor.  It  did  not  get  into 
the  earth  more  than  18  inches,  and  electri- 
cally it  was  probably  not  a  ground  at  all.  We 
had  some  suspicion  that  it  was  the  source  of 
our  difficulties,  and  we  poured  a  few  buckets- 
ful  of  water  on  it,  but  without  avail.  Proba- 
bly it  would  have  had  to  go  down  eight  or  ten 
feet,  in  that  dry  soil,  before  we  could  have 
got  any  signals  out  of  it.  We  didn't  have 
that  much  pipe.  Besides,  we  now  got  into 
trouble  in  another  way. 

In  a  house  a  few  hundred  feet  distant,  a 


telephone  went  out  of  order.  The  trouble 
man  came  around  and  fixed  it.  A  few  days 
later  it  again  developed  a  fault.  It  was  re- 
paired once  more.  In  some  way  the  sub- 
scriber got  it  into  his  head  that  the  near-by 
"wireless"  was  interfering  with  the  telephone 
service.  He  communicated  this  theory  to 
the  father  of  one  of  the  boys  in  our  crew,  and 
in  vain  we  pointed  out  that  we  had  no  trans- 
mitting set,  and  that  it  was  impossible  that 
our  antenna  could  influence  a  wire  line  in  any 
way.  People  are  always  suspicious  of  any- 
thing they  do  not  understand.  The  whole 
neighborhood  believed  that  some  nefarious 
principle  emanated  from  our  outfit.  It  was 
not  long  before  the  owner  of  the  barn  on 
which  one  of  our  antenna  supports  rested  re- 
quested that  we  hang  our  wires  somewhere 
else.  Anyway,  we  were  not  getting  any 
signals.  We  could  not  hear  the  amateur  up 
on  Prospect  Avenue,  nor  the  Waldorf  Astoria 
Hotel,  on  the  roof  of  which  a  grand  antenna 
had  been  erected.  Public  opinion  was  against 
us,  and  there  was  no  friendly  buzzing  in  the 
telephones  to  encourage  us.  It  was  Septem- 
ber, school  was  starting  again,  and  we  were 
in  a  low  frame  of  mind.  We  took  the  antenna 
down  altogether,  one  afternoon,  and  the 
career  of  our  first  radio  set  was  over. 

There  were  better  sets  than  ours,  however. 
From  the  May,  1909,  issue  of  the  primordial 
radio  magazine,  Modern  Electrics,  the  follow- 
ing description  of  one  of  them,  owned  by  Mr. 
Ernest  Carter  of  Abilene,  Texas,  is  lifted: 

Enclosed  please  find  a  picture  of  my  wireless 
station.  1  am  15  years  old  and  have  been  experi- 
menting with  wireless  six  months.  On  the  right 
are  the  sending  instruments.  I  use  a  one-inch  in- 
duction coil,  and  run  my  coil  from  the  1 10  volts 
alternating  current  here.  I  use  a  water  rheostat 
in  connection  with  same;  this  gives  very  good  re- 
sults. You  can  see  rheostat  just  back  of  coil. 

1  use  two  3-quart  Leyden  jars  for  sending  con- 
denser, one  on  each  side  of  spark  gap.  On  this  side 
of  coil  is  my  sending  helix,  which  I  made  from 
10  feet  of  No.  8  brass  wire.  The  spark  gap  is  on 
top  of  coil.  I  use  an  ordinary  strap  key  for  send- 
ing. With  these  instruments  I  can  easily  get  a 
station  5  miles  from  here.  For  receiving  I  use  3 
complete  outfits,  one  is  a  75-ohm  relay  with  a 
coherer  and  decoherer,  which  signals  me. 

Another  is  a  i,ooo-ohm  receiverwhich  I  made  from 
a  75-ohm  one,  and  an  "auto"  coherer  with  a  rheo- 
stat regulator.  The  last  one  is  a  looo-ohm  re- 
ceiver in  connection  with  an  electrolytic  detector, 
tuning  coil,  condenser,  and  a  potentiometer  made 
of  German  silver  wire.  With  the  above  instruments 
at  night  I  can  hear  the  Galveston  and  Dallas  sta- 
tions. I  use  the  "auto"  coherer  to  communicate 
with  my  friends  that  have  stations  here. 


The  "Good  Old"  Radio  Days 


Just  to  the  right  above  the  coil  is  my  d.  p.  d.  t. 
switch,  used  to  connect  the  sending  and  receiving 
with  ground  and  aerial.  My  aerial  is  suspended 
from  two  5o-foot  poles  and  is  composed  of  2  No.  14 
B.  S.  copper  wires  50  feet  long  and  2  feet  apart. 

Modern  Electrics  is  a  fine  magazine,  especially  for 
wireless  experimenters,  and  is  a  great  help  to  me. 

This  was  indeed  a  grand  set,  and  it  won  the 
first  prize  of  $3  in  the  "Wireless  Telegraph 
Contest."  The  1 5-year-old  experimenter  al- 
ready had  the  temerity  to  feed  his  spark  coil 
from  the  i  lo-volt  circuit,  curbing  it  with  a 
water  rheostat;  yet  it  was  good  for  5  miles. 
He  was  the  possessor  of  "3  complete  outfits," 
including  the  looo-ohm  receiver  made  out  of 
a  75-ohm  one — a  characteristic  touch!  Fin- 
ally, this  Sybarite  gloried  in  the  possession 
of  such  astounding  instruments  as  an  elec- 
trolytic detector,  a  tuning  coil,  a  condenser, 
and  a  potentiometer  made  of  German  silver 
wire.  All  I  can  say  is  that  he  would  not 
have  been  safe  in  our  neighborhood.  Un- 
fortunately the  picture  printed  with  the 
description  does  not  lend  itself  to  reproduc- 
tion. 

The  runner-up  in  this  "Wireless  Telegraph 
Contest"  was  Mr.  Bowden  Washington,  who 
has  since  become  a  prominent  radio  engineer, 
and  a  Fellow  of  the  Institute.  No  doubt  in 
other  issues,  numerous  names  appear  which 
were  obscure  at  that  time,  whose  owners  later 
played  great  roles  on  the  radio  stage. 

The  contrast  between  the  problems  of  the 
radio  experimenter  of  sixteen  years  ago  and 
those  of  to-day  is  rather  striking.  Broadly 
speaking,  the  problems  of  to-day  are  those  of 
congestion,  while  those  of  1909  were  questions 
arising  from  the  primitive  state  of  the  art 
and  the  limitations  of  both  quantity  and 
quality  of  personnel,  equipment,  and  informa- 
tion. To-day  our  problem  is  not  to  hear 
stations,  but,  often,  to  shut  them  out,  in  order 
that  we  may  listen  to  one  desired  signal.  At 
the  time  of  which  I  am  writing,  an  experimen- 
ter often  listened  for  hours  without  hearing  a 
signal.  There  were  not  many  stations,  and 
with  the  rudimentary  receiving  equipment 
available  only  a  few  near-by  transmitters  could 
be  heard  at  best.  Picking  up  a  signal  was  an 


you  coulct   ctkuse  tim  in  morse 


event.  "I  heard  a  station  last  night,"  the 
proud  operator  would  inform  everyone  he  met 
the  next  morning.  To-day  there  are  not 
wavelengths  enough  to  go  around.  Stations 
are  crowded  10  kilocycles  apart,  and  most 
of  them  have  to  divide  time,  or  encounter 
interference,  or  feel  some  of  the  other  effects 
of  congestion.  In  1909,  compared  to  this, 
radio  was  an  anarchist's  paradise.  If  you 
wanted  to  put  up  a  station  and  send,  you 
asked  no  one's  leave.  You  picked  any  wave- 
length you  pleased,  which  was  probably  what- 
ever wavelength  your  antenna  happened  to 
have,  in  its  natural  and  innocent  state.  The 
Government  took  no  notice  of  you.  It  did 
not  assign  you  to  704.2  kilocycles,  for  no  one 
knew  what  a  kilocycle  was.  If  anyone  inter- 
fered with  you,  you  could  abuse  him  in  Morse, 
and  the  police  power  would  not  interfere  unless 
you  followed  it  up  with  a  personal  assault. 
This  procedure,  incidentally,  was  quite  comme 
il  faut;  many  a  pair  of  commercial  operators 
met  on  West  Street,  New  York,  after  a  voy- 
age, to  have  it  out  with  their  fists  over  an  in- 
cident of  "jamming"  which  had  marred  the 
serenity  of  the  ether,  as  late  as  1914.  Good 
old  days,  bad  old  days,  as  you  please;  only 
one  thing  is  sure: — we  shall  never  see  anything 
like  them  again. 


i 


The  material  appearing  in  this  magazine  is  fully  protected  by  copyright,  and 
editors  of  periodicals  are  advised  that  unauthorized  publication  or  circuit 
diagrams,  technical  descriptions,  and  parts  or  the  whole  of  articles,  without  due 
permission  and  credit,  is  an  infraction  of  the  law.  Those  who  wish  to  reprint 
material  appearing  in  these  pages  are  asked  to  communicate  with  the  editor. 


A  Single-Control  Receiver 

Recent  Developments  in  a  Multi-Stage,  Neutral- 
ized, Tuned  Radio  Frequency  Receiver  —  Some 
Experiences  and  Data  on  Neutralizing  Methods 


BY  C.  L.  FARRAND 


ft  f  HIS  paper  is  the  second  bv  Mr.  Farrand  giving  the  constants  and  data  on  his  tuned 
J_  radio  frequency  receiver  known  as  the  super-pliodyne.  The  first  paper  was  printed 
in  the  July  RADIO  BROADCAST  and  dealt  with  the  experiments  and  developmental  work 
on  the  circuit.  This  paper  describes  further  work  on  the  neutralisation  methods  used 
in  the  receiver.  It  is  one  of  the  Radio  Club  of  America  papers  which  appear  ex- 
clusively in  Ms  magazine.  —  THE  EDITOR 


IN  A  paper  read  before  the  Radio  Club  of  America 
on    February   20,    1924,    published    in    RADIO 
BROADCAST  for  July,  1925,  a  method  of  neutral- 
izing feed-back  in  vacuum  tubes,  due  to  capa- 
city coupling  of  the  electrodes,  was  described.     The 
purpose  of  the  present  paper  is  to  describe  a  new 
method  of  neutralization  which  leads  to  greater 
selectivity  and  which  may  be  combined  with  the 
former  method  to  secure  a  desired  selectivity  and 
sensitivity. 

The  former  method  gave  what  in  the  present  day 
would  be  considered  minimum  selectivity.  The 
greatly  increased  number  of  broadcasting  stations 
has,  in  turn,  increased  the  demand  for  greater  selec- 
tivity in  sets.  It  was  in  attempting  to  satisfy 
this  demand  that  the  new  method  was  derived. 
The  selectivity  of  a  multi-stage  radio-frequency 
amplifier  increases  rapidly  with  the  number  of 
stages.  The  circuit  design  for  each  stage  may  be 
such  that  with  a  single  stage,  the  selectivity  may 
be  entirely  unsatisfactory;  yet,  with  the  chosen 
number  of  stages  in  circuit,  the  desired  selectivity 
would  be  obtained.  It  is  therefore  necessary,  de- 
pendant upon  the  number  of  stages  to  be  used,  to 
regulate  the  selectivity  of  each  circuit  to  the  desired 
value.  In  this,  it  is  assumed  that  all  the  -radio 
frequency  circuits  of  the  several  stages  are  similar. 
The  circuit  of  each  stage  of,  for  example,  a  two- 
stage  amplifier,  must  be  extremely  sharp.  This 
same  circuit  used  in  a  five-or-six-stage  amplifier 
would  have  such  selectivity  that  it  would  be  practi- 
cally impossible  to  tune  the  stations  in.  Amplifiers 

10  mmf.  II 


b 

ir 

C3 

0 

^* 

^•^ 

^>          Cj 

y                           2500   mmf. 

x       S 

^       ^ 
o      7 

—                                           = 
"50   mmf. 

^         ^~"*^ 

C2         <^ 

)0 
0> 

| 

have  been  constructed  with  a  single  control  so 
selective  that  stations  could  only  be  tuned-in  with 
extreme  difficulty.  Stations  of  substantial  volume 
in  that  case  were  passed  over  without  being  noticed. 

TUNING   THIS   SINGLE-CONTROL   RECEIVER 

IN  TH  E  manipulation  of  a  single-control  receiver  of 
this  type,  the  rotation  of  the  control  dial  from 
200  meters  to  550  meters  can  be  accomplished  by  a 
simple  half  revolution.  The  incoming  signals  of 
different  wavelengths,  as  they  are  passed  through 
rapidly,  give  rise  only  to  a  dull  thud  or  click,  sound- 
ing much  the  same  as  when  the  grid  of  an  oscillating 


10  mmf.  || 

r 

II  / 

* 

^•^. 

GJ      /  p 

<O 

1 

7 

4 

2500 

//,--,  s    v-\  25000  mmf. 

^^ 

2        § 
<=> 

0 

mmf. 

?S»w^ 

<^ 

0 

i    F 

^—•^ 

(T 

i 

j 

FIG.    I 


FIG.    2 

receiver  is  touched,  stopping  the  oscillations.  At 
times,  twenty  or  thirty  such  station  clicks  may  be 
heard  with  one  turn  of  the  control  dial.  If  the  con- 
trol is  stopped  at  one  of  the  clicking  points,  the 
modulation  will  come  through. 

It  is,  furthermore,  necessary  that  the  amplifier 
circuits  be  tuned  in  unison.  It  is  obvious  that  the 
sharper  the  tuning  of  each  circuit,  the  greater  will 
be  the  difficulty  experienced  in  maintaining  tuning 
of  each  circuit.  It  is,  however,  practical  in  com- 
mercial production,  to  secure  selectivity  at  least 
equal  to  that  obtained  by  some  super-heterodyne 
receivers,  considering  only  one  tuning  position.  The 
super-heterodyne,  at  the  best,  tunes  at  two  points 
and,  if  not  properly  designed,  at  four  and  more 
tuning  positions.  The  Super-Pliodyne  receiver, 
using  this  system,  tunes  only  at  one  point.  The 


A  Single-Control  Receiver 


621 


necessity  of  matching  individual  circuits  of  the 
receiver  has  produced  a  uniformity  of  circuits  from 
receiver  to  receiver  within  very  accurate  limits  and, 
consequently,  the  entire  receiver  becomes  practi- 
cally a  precision  wavemeter;  variation  in  calibra- 
tion of  the  receiver  varying  about  two  meters. 

COUPLING    IN    VACUUM    TUBE    CIRCUITS 

IT  IS  obvious  that  the  coupling  of  vacuum  tubes 
*  and  their  associated  circuits  caused  by  the  grid- 
to-plate  capacity  is  dependent  upon  the  proportion 
of  the  associated  capacities  due  to  the  internal 
capacity  of  the  tube.  That  is,  if  the  circuit  capacity 
is  equal  to  the  electrode,  the  capacity  of  tube  coupl- 
ing will  be  very  great.  If,  however,  the  circuit 
capacity  is  very  large  in  comparison  to  the  electrode 
capacity,  the  coupling  will  be  small. 

The  actual  coupling,  with  a  given  coupling  capa- 
city and  given  input  and  output  capacities,  is  in- 
dependent of  wavelength.  In  other  words,  the 
coupling  is  dependent  upon  the  ratio  of  electrode 
capacity  to  input  and  output  tuning  capacity  only, 
and  not  strictly  speaking  dependent  upon  wave- 
length. The  coupling,  K,  is  given  by  the  equation 

K_  C« 


C.)  (C8+C8) 
A  circuit  as  shown  in  Fig.  i  would  regenerate  and 
oscillate  vigorously  when  connected  as  vacuum  tube 
input  and  output  circuit.     However,  a  circuit  as 


FIG.    3 

shown  in  Fig.  2,  with  the  input  and  output  tuning 
capacities  increased  tenfold,  would  have  a  coupling 
coefficient  of  one  tenth  that  of  Fig.  i  and  would  be 
very  stable. 

In  other  words,  a  successful  radio-frequency 
amplifier  could  be  built  which  would  have  no  ten- 
dency to  regenerate,  using  a  capacity  of  the  order  of 
.002 5  mfd.  tuning  the  input  circuit,  and  .025  mfd. 
tuning  the  output  circuit.  It  is,  however,  im- 
practicable to  build  variable  condensers  of  such 
capacity,  particularly  if  it  is  desired  to  have  them 
agree  with  each  other 
within  close  limits. 


A  COMPLETED  RECEIVER 

Six  stages  of  radio  frequency  amplification  are  used  in  this  model.     The  set  can  be  used  with  a  very 
short  antenna  and  in  his  demonstration  before  the  Radio  Club,  Mr.  Farrand  used  a  12-foot  wire 


Radio  Broadcast 


FIG.  4 


The  same  result  can  be  secured  by  resorting  to  a 
transformer.  It  is  well  known  that  a  capacity 
connected  to  one  winding  of  a  transformer  will  be 
effective  across  the  terminals  of  the  other  winding 
inversely  as  the  square  of  the  ratio  of  turns  of  the 
transformer,  assuming  the  transformer  has  unity 
coupling.  In  practice  it  is  difficult  to  approach 
unity  coupling  and  the  relations  are  slightly  differ- 
ent, requiring,  in  general,  an  increase  in  turns  of  the 
untuned  windings. 

TUNING   CIRCUITS   OF   THIS    SET 

HpHE  present  method  involves  connecting  the 
*  tuning  condenser  of  a  chosen  size  which,  from 
practical  consideration,  should  be  approximately 
250  mmfd.  across  the  terminals  of  a  tuning  winding. 
(See  Fig.  3)  Closely  coupled  to  each  other  and  to 
this  winding  are  an  input  winding  and  an  output 
winding.  The  input  winding  and  output  winding 
are  chosen  with  a  step-up  ratio  to  satisfy  the  output 
and  input  impedances  of  a  tube.  This  ratio  should 
be  between  3  and  4^  to  i,  depending  upon  the  tubes 
used.  In  the  Figure,  a  ratio  of  \/io  or  3.16  is  used. 
The  ratio  of  turns  of  these  two  windings  to  the  tun- 
ing winding  is  chosen  so  as  to  increase  the  effective 
tuning  capacity  of  the  grid  circuit  and,  conse- 
quently, will  increase  the  effective  tuning  capacity 
of  the  plate  circuit.  In  practice,  the  ratio  to  be 
chosen  depends  upon  the  number  of  stages  to  be 
used,  as  it  is  necessary  to  use  a  more  broadly  tuned 
circuit  with  a  greater  number  of  stages. 

For  a  two-stage  amplifier,  the  ratio  of  tuning 
winding  to  grid  winding  should  be  about  2.  For  a 
five-stage  amplifier,  this  ratio  should  be  about  three. 

In  view  of  the  fact  that  the  effective  tuning  capac- 
ity of  the  grid  circuit  has  been  increased,  the  result- 
ing load  of  the  input  impedances  of  the  tube  upon 
the  tuning  circuit  has  been  decreased.  In  this  way, 
tuning  is  materially  sharpened.  In  case  the  selec- 
tivity is  too  great,  the  compromise  design  may  be 
made  with  the  method  described  in  the  previous 
paper.  The  transformer  may  be  designed  so  that 


only  a  portion  of  the  interstage  coupling  is  neu- 
tralized by  increasing  of  effective  capacity,  and  the 
remainder  of  the  capacity  is  neutralized  by  connec- 
tion of  resistance  between  the  plate  and  grid  elec- 
trode. (A  condenser  may  be  connected  in  series 
with  a  resistance  to  prevent  a  flow  of  direct  current 
from  the  common  plate  battery.)  In  this  way,  the 
over-all  selectivity  of  the  amplifier  may  be  regulated 
within  very  wide  limits. 

The  effect  of  the  input  capacity  of  the  vacuum 
tube  upon  the  tuning  is  less.  This  is  because  the 
transformer  makes  the  effective  tuning  capacity 
larger  in  proportion  to  the  input  capacity.  This  is 
advantageous  as  it  is  possible  to  increase  the  wave- 
length range  within  the  scale  of  a  condenser  of  given 
size.  In  practice,  a  range  of  200  to  555  meters 
can  be  secured  with  a  capacity  of  250  mmfd. 

The  same  effect  may  be  produced  by  auto  trans- 
former construction  but  is  less  desirable  on  account 
of  circuit  difficulties. 

It  is  desirable  to  destroy  the  natural  period  of  the 
grid  winding  of  the  transformer  by  winding  it  with 
resistance  wire.  This  has  no  effect  upon  the  opera- 
tion of  the  transformer. 

It  is  also  desirable  to  locate  the  transformer 
(input  and  output)  winding  at  the  low  potential  end 
of  the  tuning  winding.  This  tends  to  prevent 
losses  and  permit  a  larger  wavelength  range. 

Fig.  4  shows  a  two-stage  radio-frequency  ampli- 
fier circuit.  The  plate  winding  consists  of  15  turns, 
wound  left  hand;  the  grid  winding  47  turns  of  resis- 
tance wire  wound  right  hand;  the  tuning  wind- 
ing 80  turns,  wound  right  hand.  The  plate  and 
grid  windings  are  tightly  coupled  together,  of  equal 
length  and  about  one  third  the  length  of  the  tuning 
winding,  and  are  placed  at  the  filament  end.  The 
plate  winding  is  placed  between  the  grid  and  tuning 
winding;  the  end  of  the  plate  winding  opposite  the 
filament  ends  of  grid  and  tuning  winding  is  con- 
nected to  plate.  The  end  of  the  plate  winding  op- 
posite the  grid  end  of  grid  winding,  toward  the 
stator  end  of  the  tuning  winding,  is  connected  to 
positive  plate  battery. 


IIIIIIIIIIIIIIIIHIIIIIIIIIIIIIIIIII 


For  the  Radio  Beginner 


iiiiiiiiiiiiiiiniiiiiiiiiiiiiiiii'i 


How  to  Build  the  R.  B.  One-Tube  Knockout  Receiver 


HP  HERE  are  so  many  beginners  in  radio  who  want  to  know  how  to  build  a  good  but 
*  inexpensive  receiver  that  a  series  of  articles,  of  which  this  is  the  third,  have  been  pre- 
pared by  Mr.  Zeh  Bouck,  especially  for  the  inexperienced  builder.  Most  of  the  material 
for  the  first  two  receivers,  described  in  the  July  and  August  numbers  of  this  magazine, 
can  be  built  from  workable  parts  obtained  at  the  five-and-ten  cent  stores.  The  simple 
crystal  receiver,  described  in  the  July  magazine  can  be  built  for  about  $1.82,  while  the 
additional  parts  for  the  one-tube  receiver  outlined  in  the  August  number  cost  about  $6. 12. 
The  receiver  described  in  this  article  is  a  revision  of  the  One-tube  Knockout  receiver, 
made  famous  after  its  publication  in  this  magazine  in  November,  1923. 

The  "Radio  Lexicon"  and  "The  Radio  Primer"  explain  the  theory  involved  in  the 
receiver  described  and  will  be  found  very  helpful  to  the  newcomer  in  radio  who  not  only 
wants  to  build  a  receiver  that  "works"  but  who  also  wants  to  know  why  it  functions. 
Recommendation  of  collateral  reading  in  the  best  text  books  is  also  given. — THE  EDITOR 


IN  THE  last  two  issues  of  RADIO  BROAD- 
CAST we  have  described  the  construction 
of  a  crystal  and  bulb  receiver.     It  is  now 
quite  logical  that  we  combine  these  two 
receivers  into  a  reflex  set,  the  one-tube  RADIO 
BROADCAST  Knockout  Set  that  will  operate 
a    loud    speaker. 

Though  this  receiver  is  necessarily  more 
complicated  than  those  we  have  so  far  des- 
cribed in  The  Beginners'  Department,  the  in- 
experienced fan  will  not  be  over  taxed  in  its 
design  and  construction.  The  photographs 
and  drawings  illustrate  very  clearly  the  man- 
ner in  which  the  set  is  assembled,  and  we  shall 
endeavor  to  make  these  points  still  more  plain 
in  our  descriptions. 

LIST   OF    MATERIALS 

In  Figure  i  Description 

No.   i     2  Variable  condensers,  .0005  mfd.      (Ham- 

marlund,  $5.00  each) 
No.  2.     2  3-inch  dials  (5  and  10  cts  store,  at  10  cts., 

each) 
No.  3     i  Crystal  detector,  preferably  fixed  (Pyra- 

tek  with  mounting,  |i.25) 
No.  4     Rheostat,  Amperite,  or  Daven  Ballast  for 

tube  used   (Daven   Ballast  with  mount- 
ing $1.00) 
No.  5     J  pound  of  No.  22  s.  c.  c.  or  enameled  wire 

(5  and  10  cts.  store,  25  cts.) 
No.  6     Socket  for  tube  used  (5  and  10  cts.,  store 

for  uvigg,  2octs.) 
No.  7     Audio  amplifying  transformer,  ratio  about 

four  to  one,  such  as  the  Rau land-Lyric, 

Acme,     General     Radio,    or    AmerTran 

(AmerTran,  $7.00) 
No.  8     5  Fahnestock  clips  or  binding  posts  (5  and 

10  cts.  store  clips,  10  cts.) 


Cigar  box,  base-board,  sheet  of  paste- 
board, a  few  feet  of  bus  bar  and  No.  18 
annunciator  wire,  screws. 

Following  the  mention  of  the  parts,  the 
exact  make  and  price  used  in  the  receiver  we 
are  describing  is  given  in  parenthesis.  This 
represents  a  total  expenditure  of  $20.00 
which  can  be  considerably  reduced,  if  desired, 
by  the  following  substitutions  purchased  at 
the  five-and-t en-cent  stores:  Variable  con- 
densers, 22  plates,  at  $1.44  apiece;  rheostat  at 
$.25,  crystal  detector,  $.20. 

THE    PANEL 

ONCE  again  the  cigar-box,  the  mechanical 
genius  of  the  radio  beginner,  plays  the 
combination  part  of  panel  and  cabinet.  A 
rather  large  box,  about  ten  by  six  inches, 
should  be  secured.  The  hinged  cover  and 
paper  are  removed  by  soaking  in  water,  and 
the  wood  is  sandpapered  to  a  clean,  smooth 
finish.  The  bottom  of  the  box  is  marked  and 
drilled  according  to  the  panel  layout  in  Fig.  2. 
(Detailed  instructions  on  the  preparation  and 
working  of  cigar-box  wood  are  given  in  The 
Radio  Beginners'  Department  for  July.) 
The  writer  found  it  more  convenient  to  take 
the  box  apart  and  re-assemble  it  as  the  parts 
were  mounted. 

Due  to  the  number  and  size  of  the  parts 
represented  by  the  one-tube  reflex  set,  the 
depth  of  the  cigar-box  is  rarely  sufficient  to 
contain  them  all.  Therefore,  a  large  base- 
board six  inches  wide,  is  substituted  for  one 
side  of  the  cigar-box  as  suggested  in  the  draw- 
ing, Fig.  3.  After  the  panel  is  drilled,  the 


624 


Radio  Broadcast 


FIG.    I 

The  purchased  parts  that  go  into  the  construction  of  the  Begin- 
ners' Model  of  RADIO  BROADCAST'S  Knockout  One-tube  receiver 


cigar-box — or  what  is  left  of  it — is  built  up 
around  the  baseboard,  three  inches  or  so  of 
which  will  project  out  in  back  of  the  box.  The 
top  of  the  box  (originally  a  side)  is  nailed  in 
place  last,  after  the  socket  is  fastened  to  it, 
and  the  condensers  and  coils  mounted  res- 
pectively on  the  panel  and  sides. 

A  coating  of  green  stain  applied  to  this 
woodwork  will  add  considerably  to  the  ap- 
pearance of  the  completed  set. 

THE    COILS 

CPIDERWEB  coils  offer  a  simple  form  of 
^  inductance  to  the  inexperienced  builder, 
and  they  were  chosen  in  the  construction  of 
this  receiver.  The  winding  form,  drawn  to 
exact  size,  is  shown  in  Fig.  4.  This  can  be  cut 
out  and  traced  on  pasteboard,  from  which  ma- 
terial the  forms  are  cut,  or  the  dimensions  can 
be  noted  and  the  figure  re-drawn.  Two  com- 
bination coils,  therefore  two  forms,  are  re- 
quired, designated  as  Ti  and  T2  on  the  wiring 
diagram.  Two  windings  are  placed  on  each 
form,  a  primary  and  a  secondary.  A  small 
hole  is  punched  in  the  cardboard,  the  wire  in- 
serted, and  then  wound  over  and  under  the 
spokes.  This  first  winding  is  the  primary. 
The  primary  of  Ti  has  1 5  turns  of  wire, and  the 


primary  of  T2,25  turns.  At  the  finish  of  the 
primary  winding,  another  hole  is  punched  in 
the  form  and  the  free  end  of  the  wire  slipped 
through.  At  the  next  spoke,  just  above  the 
primary  winding — a  thirty-second  of  an  inch 
or  so — a  third  hole  is  punched,  and  the  secon- 
dary winding  begun.  The  secondary  is  wound 
the  same  way  as  the  primary  and  fastened  to  a 
fourth  hole  at  the  final  turn.  The  secondary 
of  Ti  has  33  turns  of  wire  and  that  of  T2,3O 
turns. 

Coil  Ti  is  mounted  on  the  left  hand  side  of 
the  box  (looking  from  the  front)  and  T2  on  the 
right  hand  side.  They  are  held  in  place  by  the 
wiring  and  by  a  tack,  through  one  spoke  on 
each  coil,  into  their  respective  sides  of  the  box. 

If  it  is  preferred,  solenoid  coils,  such  as  those 
illustrated  in  Fig.  5,  can  be  substituted  for 
the  spiderwebs.  These  are  wound  on  two  and 
a  half-inch  diameter  winding  forms.  The 
secondaries  are  wound  first  and  consist  of 
sixty  turns  of  wire  for  both  Ti  and  T2.  A 
layer  of  tape  or  empire  cloth  is  placed  over  the 
secondaries,  followed  by  the  primary  windings 
of  fifteen  turns  on  Ti  and  35  turns  on  T2. 
(There  are  several  commercial  makes  of  trans- 
formers marketed  for  use  with  the  so-called 
"Harkness  Reflex"  receiver,  originally  de- 


How  to  Wire  the  One-Tube  Receiver 


625 


I  /%  Dril1 

-%-— e- — ? 

X^  No.  27  DrilK'' 


10  Approx. 


FIG.    2 

The  layout  of  the  cigar  box  panel.     The  screw  holes  for  the  condensers 
are  placed  with  the  aid  of  the  template  furnished  with  the  condenser 


scribed  in  this  magazine  for  November,  1923, 
which  can  be  substituted  for  Ti  and  T2). 

The  socket  is  mounted  on  the  top  of  the 
cabinet  as  suggested  in  Figs.  3,  6,  7,  and  8. 
Four  small  holes  are  drilled  beneath  it  through 
which  wires  pass,  connecting  to  the  socket 
terminals.  No.  18  annunciator  wire  is  used 
for  this  purpose,  the  remainder  of  the  con- 
nections being  made  with  the  heavier  bus  bar. 

All  parts,  excepting  the  transformer,  can 
now  be  mounted.  From  left  to  right  in  Fig.  6, 
the  following  parts  are  seen:  Coil  T2,  variable 
condenser  €2.  the  fixed  crystal  detector,  the 
amplifying  transformer,  variable  condenser 
Ci,  the  Amperite  or  Daven  Ballast  resistance 
and  coil  Ti.  The  Fahnestock  clips,  from  left 
to  right  are:  i,  telephone  receivers;  2,  tele- 
phone receivers  and  plus  B  battery; 3,  minus 
B  battery  and  plus  filament  battery;  4,  minus 
filament  battery  and  ground;  5,  antenna. 

HOW   TO    DO   THE    WIRING 

PHE  connections  of  the  various  parts  are 
1  most  conveniently  made  in  the  following 
order,  with  all  parts,  excepting  the  amplifying 
transformer  T^,  permanently  mounted: 

Filament  post  on  socket  to  binding  post  or 
Fahnestock  clip  number  3;  remaining  fila- 
ment post  to  filament  resistance  (R  in  Fig.  9), 
and  from  the  filament  resistance  to  post  num- 
ber 4. 


Outside  secondary  terminal  of  Ti  to  grid  of 
tube  and  stationary  plates  of  the  Ci;  the 
inside  (or  beginning)  secondary  terminal  to 
the  rotating  plates  of  C  i :  The  outside  terminal 
of  T2  secondary  connects  to  the  stationary 
plates  of  C2  and  the  inside  terminal  to  the 
rotating  plates. 

The  inside  terminal  of  the  Ti  primary  con- 
nects to  the  antenna  post  of  Fahnestock  clip 
number  5;  the  outside  or  finish  primary  ter- 
minal leads  to  post  number  4. 

The  plate  of  the  vacuum  tube  is  wired  to  the 
beginning  of  the  T2  primary  and  end  of  the 
primary  to  Fahnestock  clip  number  i. 

The  audio-frequency  amplifying  trans- 
former, secondary  to  the  right,  is  now  mounted 
and  the  connections  completed  as  follows: 

The  rotating  plates  of  C2  to  one  side  of  the 
crystal  detector,  DET;  the  other  side  of  the 
crystal  detector  to  the  P  post  on  the  primary 
of  the  amplifying  transformer;  the  plus  prim- 
ary post  is  wired  to  the  stationary  plates  of 
C2.  The  G  post  of  the  secondary  runs  to  the 
rotating  plates  of  Ci  and  the  F  post  to  Fahne- 
stock clip  number  4. 

All  joints  should  be  soldered  cleanly,  and 
the  wires  bent  carefully  into  right  angle  bends. 
The  inexperienced  solderer  is  advised  to  read 
"How  to  Solder"  by  William  Crosby  in  RADIO 
BROADCAST  for  May,  1925,  before  wiring  the 
One-Tube  Knockout  receiver. 


626 


Radio  Broadcast 


Base  Board 


FIG.    3 

Showing  how  the  cigar  box  is 
built  up  about  the  baseboard 


FIG.   4 

Exact  size  of  the  winding 
form  used  in  making  the 
spiderweb  coils  Ti  and  T2 


TUBES    AND   BATTERIES 

THE  receiver  described  is  designed  for  use 
with  the  uv-i99  type  tube  and  an  A 
battery  of  three  dry  cells.  It  will  function, 
however,  equally  well  on  five-volt  tubes  of  the 
uv-aoiA  type,  with  the  proper  A  battery  and 
filament  resistance.  Ninety  volts  on  the 
plate  will  be  correct  for  both  tubes,  though  still 
higher  voltages  can  be  safely  applied  to  the 
larger  tube. 

HOW  TO  INSTALL  THE  RECEIVER 

A  SUITABLE  antenna,  such  as  described 
in  RADIO  BROADCAST  for  July  for  use 
with  the  Beginners'  crystal  receiver,  is  con- 
nected to  Fahnestock  clip  or  binding  post 
number  5.  The  ground  lead  is  connected  to 
post  number  4,  as  well  as  the  wire  leading  to 
the  minus  terminal  of  the  A  battery.  The 
plus  A  battery  and  the  minus  lead  of  the  B 
battery  connect  with  post  number  3.  The 


4%  DJam.- 


The  One-Tube  Set  Is  Easy  to  Operate 


627 


plus  B  battery  terminal  is  wired 
to  post  number  2.  The  tele- 
phone receivers  connect  to  posts 
2  and  i.  These  connections  are 
still  further  explained  in  the 
wiring  diagram,  Fig.  8. 

OPERATING    INSTRUCTIONS 

HP  HE  tube  is  plugged  into 
*  the  socket  and  the  rheostat 
turned  on,  or  the  Amperite  or 
Daven  Ballast  clipped  into  the 
mounting.  The  dials  should  be 
set  so  that  they  read  maximum 
when  the  rotary  plates  of  their 
respective  condensers  are  fully 
in  between  the  stationary  plates.  The  two  dials  are  now 
moved  simultaneously  over  the  tuning  range,  keeping 
them  at  approximately  the  same  settings.  When  a  sta- 
tion is  heard,  the  controls  are  carefully  adjusted  for 
maximum  response.  If  the  catwhisker  type  of  crystal 
detector  is  used,  it  will  require  the 
usual  adjustment.  Reversing  the  con- 
nections to  the  crystal  detector  will 
often  increase  signal  strength. 

Properly  constructed,  this  receiver 
should  give  loud  speaker  results  on 
local  stations. 

CARE    AND   UPKEEP 

E  filament  and   plate   batter- 
ies  should  be  kept  at  the  proper 
voltage  and  B  batteries  which  show 


FIG.    5 

The  rear  view  of  a  more  elaborate 
layout  using  solenoid  coils.  The  more 
experienced  builder  will  find  herein 
plenty  of  play  for  his  talent  and 
ingenuity 


FIG.   6 

The  finished  receiver  from 
the  rear.  The  transformer 
is  mounted  and  wired  last 


628 


Radio  Broadcast 


FIG.  7 

Looking  down  on  the  completed  set,  showing  the  arrangement  of  the  exposed  parts 


a  drop  of  more  than  25  per  cent,  should  be 
discarded. 

Inspect  all  connections  occasionally  and 
clean  wiping  contacts,  such  as  in  the  vacuum 
tube  socket,  in  order  that  there  will  be  no  loss 
due  to  contact  resistance. 

HiiiiiiiiiiiiiiiiiiiiiiiiiiuiiiiiiiiiiiiiiiiiiiiiiiiiiniiiiiiiiiiiiiiiiiiiiiitiiiniiiiiiiiiiiiiiiiiiiHiiiiiniiiiti 

THE  RADIO  PRIMER 


The  Vacuum  Tube  as  an  Amplifier 

^MmilllimmiimmillllimnimmilimiimlllllllllllllllMMIIIIIIIimmilllllllllllimillimilllllltf 

AS  USUAL  in  any  discussion,  exposi- 
tion, or  argument,  we  must  have  as  a 
background  a  common  fund  of  knowl- 
edge which  contributes  to  the  discussion  but 
does  not  need  to  be  explained  itself.  It  is  our 
starting  point  or  premise — or  perhaps  the 
tools  with  which  we  are  going  to  work.  Most 
of  our  readers  will  understand  these  primary 
facts  while  those  that  do  not  are  asked  to  ac- 
cept them  as  truths,  exactly  as  they  do  the 
assertion  that  the  earth  is  round — without  a 
personal  demonstration  of  the  undoubted  fact. 


WHAT    WE    KNOW 

IN  OUR  explanation  of  how  a  bulb  amplifier 
operates,  we  shall  assume  to  know  the  fol- 
lowing: 

1.  The  grid  of  a  vacuum  tube  is  the 
screen-like  element  situated  between  the 
filament  and  plate. 

2.  Under  normal  operating  conditions, 
a  positive  charge  placed  upon  the  grid  will 
increase  the  plate  current — the  current  sup- 
plied to  the  tube  by  the  B  battery.    The 
plate  current  flows  through  the  plate  cir- 
cuit which  includes  the  space  between  plate 
and  filament. 

3.  When  a  negative  charge  is  placed 
upon  the  grid,  the  plate  current  is  decreased. 

4.  An  alternating  current  is  a  current 
that  reverses  its  direction  of  flow  periodi- 
cally— usually    many    times    per    second. 
Another  way  of  putting  it  is  to  state  that 
any  two  points  in  an  alternating  current 
circuit  reverse  their  polarities  periodically. 

5.  A  coil  of  wire  passing  a  direct  current 
that  pulsates — grows  weaker  and  stronger 
periodically — will  induce  in  itself  and  in  a 


Theory  of  Operation  of  the  Set 


629 


near-by  circuit  or  coil,  an  alternating 
current. 

6.  In  radio  communication,  we 
have  mostly  to  deal  with  alternating 
currents — the  high  or  radio  frequency 
currents  associated  with  the  wave 
itself  before  detection  (see  The  Ra- 
dio Primer  for  August),  and  the  au- 
dio frequency  currents  that  follow 
detection. 


FIG.    8 

Front  view  of  the  fin- 
ished "works."  Not 
bad  for  a  cigar  box! 


OPERATION  OF  THE  CIRCUIT  SIMPLY   EXPLAINED 

IN  ALL  multi-tube  receivers,  and  several 
single-tube  arrangements  such  as  that 
described  in  this  department,  all  tubes  exterior 
of  the  detecting  circuit  are  amplifying  tubes. 
The  tubes  that  precede  the  detector  (generally 
a  crystal  or  a  tube)  are  radio  frequency  tubes, 
and  those  that  follow  it  are  audio  frequency 
tubes.  In  other  words,  the  tubes  before  the 
detector  amplify  or  make  stronger  the  radio 
frequency  currents  picked  up  from  the  radio 
wave,  while  those  after  the  detector  intensify 
the  sound  frequencies.  The  difference  be- 
tween these  two  frequencies  was  explained  in 
this  department  last  month. 

Both  forms  of  amplification  have  their  re- 
spective advantages  and  disadvantages.  Radio 
frequency  amplification,  amplifying  before  de- 
tection, takes  advantage  of  the  multiplying 
action  of  the  detector  tube,  and  discriminates 
against  stray  sound  frequencies.  On  the  other 
hand  it  amplifies  all  r.  f.  (radio  frequency)  dis- 
turbances, such  as  static.  Audio  frequency 


amplification  provides  the  power  required  for 
the  operation  of  loud  speakers,  but  in  addition 
to  the  desired  signal  it  amplifies  equally  well 
parasitic  tube  noises  and  so  forth.  A  judi- 
cious combination  of  the  two  systems  is  the 
closest  approach  to  an  ideal  amplifying  ar- 
rangement. 

Both  amplifying  systems  function  in  the 
same  manner — i.  e.,  through  the  repeating  and 
amplifying  action  of  the  vacuum  tube.  Re- 
ferring to  diagram  A  in  Fig.  10,  let  us  assume 
that  a  radio  frequency  current  is  flowing  in  Li. 
This  would  be  the  case  during  reception  if  this 
coil  were  the  secondary  of  a  vario-coupler  or  a 
previous  amplifying  transformer.  Thus  the 
polarity  at  the  terminals  of  the  coil,  X  and  Yf 
will  change  periodically,  depending  on  the 
frequency  of  the  station  being  received.  For 
one  fraction  of  a  second  X  will  be  plus  and  Y 
negative,  and  in  the  next  instant,  Y  will  be  plus 
or  positive  and  X  minus  or  negative. 

Terminal  X  is  connected  directly  to  the 
grid  of  the  amplifying  tube,  and  therefore  the 
polarity  existing  at  X  for  any  fraction  of  a 


630 


Radio  Broadcast 


second,  will  be  immediately  applied  to  the 
grid.  When  X  is  positive  the  plate  current 
through  \J2  will  increase.  With  the  next 
alternation,  and  the  reversal  of  polarity  at  X, 
the  plate  current  will  decrease. 

Thus  we  have  a  rising  and  falling  (or  pul- 
sating) direct  current  through  a  coil  of  wire, 
La.  Therefore,  according  to  our  fifth  premise, 
there  will  be  induced  in  La  and  in  LJ,  which  is 
another  coil  placed  close  to  La,  an  alternating 
current.  This  alternating  current  will  be 
characterized  by  the  same  frequency  as  the 
original  current  flowing  in  Li.  However,  due 
to  the  amplifying  action  of  the  vacuum  tube, 
the  alternating  current  power  in  L2  will  be  more 
powerful  than  the  alternating  current  in  Li .  The 
action  is  analagous  to  the  comparatively  weak 
pressure  of  the  finger  on  the  trigger  of  a  gun 
releasing,  or  controlling  as  it  were,  the  much 
greater  power  expressed  in  the  exploding 
cartridge.  As  little  power  will  be  lost  in  in- 
duction, the  energy  in  L3  will  similarly  be 
greater  than  that  in  Li .  This  magnified  signal 
is  now  applied  to  the  next  tube,  either  the  de- 
tector or  another  amplifier,  by  connecting  L^ 
in  the  same  manner  that  Li  is  connected  to  the 


first  tube.  Thus  amplification  may  be  carried 
on  through  as  many  stages  as  is  desired  or 
expedient. 

The  coils  La  and  L^  are  combined  into  a 
single  instrument  or  part  that  is  designated  as 
an  amplifying  transformer,  of  which  La  is  the 
primary  winding  and  L$  the  secondary  wind- 
ing. 

Transformer-coupled  audio  frequency  am- 
plification (amplification  after  the  detector) 
is  effected  in  the  same  manner,  which  is  easily 
followed  in  diagram  B  of  Fig.  10.  Audio  fre- 
quency alternating  current  is  applied  across 
the  terminals  X  and  Y  of  Li  instead  of  high  or 
radio  frequency  current,  and  a  magnified  du- 
plicate is  caused  to  flow  in  L^.  Audio  fre- 
quency transformers,  in  order  to  meet  the 
particular  conditions  under  which  they  must 
operate,  are  wound  on  iron  cores  which  are 
diagrammatically  expressed  by  the  lines  be- 
tween the  primary  and  secondary  coils. 

AN    EXPLANATION    OF    REFLEX   CIRCUITS 

IN  REFLEX  circuits,  one  or  more  tubes  are 
made  to  amplify  both  radio  and  audio  fre- 
quency  currents.     This   combined  operation 


A 

Battery 


The  wiring  diagram.  If 
a  ballast  resistance  or 
Amperite  is  used  at  R, 
the  builder  may  find  it 
convenient  to  include  a 
small  battery  switch  at 
"X" 


The  Amplifier  Action 


631 


will  be  made  quite  clear  by  tracing  the  opera- 
tion of  the  one-tube  Knockout  receiver 
described  for  the  radio  beginner  this  month. 

The  radio  frequency  current  is  impressed 
upon  the  amplifying  tube  through  the  antenna 
coupler  T  i  .  Here  the  radio  frequency  current 
is  amplified  and  applied  to  the  detecting  cir- 
cuit through  the  r.  f.  transformer  T2.  It  is 
detected  as  described  in  the  Beginners'  De- 
partment last  month.  The  resulting  audio 
frequency  energy  is  now  returned  to  the  tube 
by  the  audio-frequency  amplifying  trans- 
former T3  where  it  is  amplified,  and  finally 
outputted  to  the  telephone  receivers  or  loud 
speaker  plugged  into  the  jack. 


THE   RADIO   LEXICON 

THIIimmillllllllllimilllllllllllllllllllllllllllllllllimilimiimillllllllllimillllllimilllinmmilll? 

PLATE  CIRCUIT:  The  path  of  the  current  sup- 
plied by  the  plate  or  B  battery,  i.  e.,  through 
the  B  battery,  the  filament  of  the  tube,  across 
the  space  within  the  tube  to  the  plate,  thiough 
whatever  coils,  such  as  loud  speaker  or  tele- 
phone receiver  windings,  transformer  primary 
or  variometer,  that  may  be  included  in  the 
circuit  and  back  to  the  B  battery.  The  plate 
circuits  in  Fig.  10  have  been  drawn  with  heavy 
lines. 

PLATE  CURRENT:  The  current  that  flows 
through  the  plate  circuit.  It  is  sometimes  re- 
ferred to  as  "space  current"  due  to  the  fact 
that  it  passes  across  the  space  between  fila- 
ment and  plate  of  the  vacuum  tube. 

PERIODIC:  Reccuring  with  equal  intervals  of 
time,  such  as  the  swing  of  a  pendulum  or  the 
vibrations  of  a  radio  wave. 

TRANSFORMER:  An  electrical  instrument  hav- 
ing two  windings,  a  primary  and  secondary, 
generally  placed  close  together,  or  otherwise 
maintained  in  inductive  relation  to  each  other. 
An  alternating  current  of  the  proper  fre- 
quency flowing  in  one  winding  will  induce  a 
similar  current  in  the  other. 

AMPLIFYING  TRANSFORMER:  A  transformer 
used  for  coupling  the  output  of  one  amplifying 
tube  to  the  input  of  the  other.  The  primary 
of  the  transformer  is  connected  in  the  plate 
circuit  of  the  preceding  tube  and  the  secondary 
in  the  grid  circuit  of  the  succeeding  tube. 
Special  types  of  transformers  are  used  in  both 
radio  and  audio  frequency  amplification. 


FIG.     10 

Describing  the  action  of  an  amplifier.  The  ampli- 
fication is  due  to  the  relay  action  of  the  tube,  the 
coils  or  transformers  being  merely  used  for  the 
transference  of  energy  from  one  circuit  or  tube  to 

another 


REFLEX:  "Reflex"  refers  to  imposing  the 
double  duty  of  a  single  vacuum  tube  of  ampli- 
fying both  radio  and  audio  frequencies.  The 
audio  frequency  output  of  the  detector  is  re- 
flexed  (thrown  back)  on  the  r.  f.  tube  or  tubes. 


tlllMIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIMIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII^ 

THE   RADIO   LIBRARY 

E  = 

IMMMMMMM mmiiiiiiimimim iiiiimiiiiiiiiiimiiiimiiiiiiiiiiiiiiiiiiiiimi 

THE  action  of  the  vacuum  tube  as  an 
amplifier  will  be  made  more  clear  to  the 
enthusiast  and  student  by  reference  to 
the  following  works  and  pages: 

The  Outline  of  Radio  by  John  V.  L.  Hogan, 
Chapter  Nine.  A  non-technical  and  highly 
interesting  account  of  amplification  and 
vacuum  tubes. 

The  I.  C.  S.  Radio  Handbook.  Pages  237 
to  239.  A  little  more  technical  than  Mr. 
Hogan's  chapter,  but  still  quite  comprehensi- 
ble to  the  layman. 

Thermionic  Vacuum  Tube  by  Van  Der  Bijl. 
Chapter  Seven.  A  highly  technical  treatise 
of  the  vacuum-tube  amplifier.  This  is  rec- 
ommended to  the  student  with  a  mathema- 
tical education  as  is: 

Principles  of  Radio  Communication,  by 
J.  H.  Morecroft,  Pages  570  to  571  and  824  to 
830. 


1  Point   o:P 

by  Koindsletj      OTellcs 

WKat    Is   Wrong   WitK   Sunday   Radio 

Programs? 


M 


OST  radio  programs  that  my  set 

brings   in  on   Sunday  are  pretty 

bad,"  remarked  an  acquaintance 

of  ours  the  other  day.  "There 
are  exceptions,  I  admit,  but  the  Sunday  radio 
menu  seems  to  be  religion,  served  up  more  or 
less  tastefully  with  garnishing  some  times 
pleasant  and  more  often  not."  He  went  on  to 
explain  that  he  was  not  an  unreligious  person, 
but  that  he  did  not  care  to  have  his  loud 
speaker  blare  forth  things  religious  all  day. 

Well,  it  takes  all 
kinds  of  people  to  make 
a  radio  audience  —  to 
give  a  radio  twist  to  the 
common  platitude 
about  the  world — and 
there  is  no  question 
that  a  standardized 
Sunday  program  would 
not  please  everyone.  1 1 
is  impossible  for  any- 
one, even  a  practised 
program  director — 
who,  by  the  way,  is 
gradually  becoming 
known  as  a  radio  im- 
pressario — to  design  a 
Sabbath  program  with, 
say,  four  parts  "relig- 
ion," three  parts  class- 
ical music,  and  one  part 
dance  music,  shake  it 
well  before  using  and  GOVERNOR  ALFRED  E.  SMITH 


Sunday    programs    in    the    neatest    possible 
manner  by  simply  shutting  up  shop  for  the 
day.     Others  turn  over  their  wavelength  to 
a  church  and  broadcast  the  entire  service. 
Some  of  these  add  a  musical  program  later  on 
in  the  day.    The  truth  is,  of  course,  that  most 
of  the   directors   are   groping,    nothing  less. 
Some  of  them  go  to  absurdities,  as  witness 
WHT,  the  new  Chicago  broadcaster  who  an- 
nounces with  ill  concealed  pride  that  they 
broadcast    special    Sunday    services,    "The 
National     Radio 
Chapel"  without  stop 
for  fourteen  hours  each 
Sunday.     A   non-stop 
religious    service  for 
fourteen    hours    auto- 
matically goes    in  the 
same  class  with  six-day 
bicycle  races,  and  en- 


durance dancing  con- 
tests. 

And  on  Sunday  after- 
noon, when  we  search 
the  ether  lanes,  we  find 
them  singularly  quiet. 
An  indifferently  cap- 
able soprano  here,  an 
installment  of  Sunday- 
school  music  there,  or 
nothing.  Later  come 
vesper  services  and 
music.  In  the  evening, 
the  variety  grows.  The 


pour  the  result  on  the  Of  New  York,  at  his  desk  in  Albany  where  he  re-  Capitol  Theatre  enter- 
air,    and    know    he    is  cently  spoke  through  WGY  and  wjz  to  the  people  of  tainment,    devised    by 
right  the  State  on  the  question  of  Long  Island  parks.  tne    popular    "Roxy" 
c    '  Four  times  within  the  last  year  Governor  Smith  *~,     ^ 
Some  stations   have  has  resorted  to  radio  to  bring  his  ideas  directly  be-  reaches  the  Eastern  and 
evaded  the  problem  of                                fore  the  citizens  Middle  United   States 


More  Ambitious  Sunday  Programs 


633 


through      WEAF,     WCAP,     WJAR,     WCTS,    WEEI, 

WCAE,  and  wwj.  Ably  staged,  with  artists  of 
much  more  than  ordinary  ability,  this  program 
is  to  many  the  one  glowing  star  in  Sunday 
radio  entertainment.  The  Goldman  band 
concerts,  reaching  listeners  through  the  same 
group  of  stations,  are  worth  staying  home  for. 

Dance  music  can  be  found  on  the  air  Sun- 
day, too.  However,  most  of  the  stations  wait 
until  eight  or  nine  o'clock  in  the  evening  before 
their  jazz  musicians  put  lip  to  saxophone. 
Perhaps  we  are  a  bit  new-fashioned,  but  we 
cannot  quite  agree  with  a  correspondent  who 
wrote  us  that  "strains  of  jazz,  breaking  up 
Sunday  peace  and  quiet,  are  little  short  of  an 
outrage.  I  like  radioed  jazz  but  little  at  best; 
on  week  days  I  can  stand  it.  On  Sunday, 
however,  I  think  station  directors  might  give 
us  one  day  of  rest." 

Dance  music  on  Sunday  via  radio  is  not  a 
whit  more  wrong  than  dance  music  on  Sunday 
played  on  the  phonograph  or  the  piano.  We 
will  wager  a  shiny  new  B  battery  that  there 
are  few  homes  where  a  dance  tune  does  not 
trickle  from  a  phonograph  or  piano  at  least 
once  on  Sunday.  It  is  not  fundamentally 
wrong  to  play  light  music  on  Sunday.  True 
enough,  it  is  the  Lord's  Day,  but  aren't  our 
ideas  now  of  how  it  should  be  observed  a  bit 
different  from  those  current  in  the  Massachu- 
setts Bay  Colony  in  the  early  Eighteenth 
Century? 

Program  directors  crowd 
their  daily  programs  with 
every  kind  of  talent  known 
to  radio,  but  have  leaned 
over  backwards  when  it 
comes  to  Sunday  arrange- 
ments. 

Why  doesn't  some  enter- 
prising broadcaster  try  the 
experiment  of  broadening 
out  his  Sunday  offering? 
An  instrumental  concert 
from  one  to  two  in  the 
afternoon  would  be  very 
well  received.  The  week 
day  dinner  concerts  broad- 
cast from  a  number  of  sta- 
tions are  deservedly  popu- 
lar. The  domestic  lares  and 
penates  are  most  apt  to  be 
guarded  by  the  entire  family 
on  Sunday  and  programs 
aimed  at  the  entire  family 
would  be  most  successful 
on  that  day. 

Let   us   hear  a   traveller 


who  knows  how  to  describe  countries  and 
people  he  knows.  A  speaker  who  can  talk 
interestingly  on  books  and  plays  should  be 
well  received.  The  Sunday  papers  have  a 
following  of  readers  who  are  popularly  thought 
to  find  their  varied  contents  pleasing  Sab- 
bath reading.  If  the  broadcasters  edit  their 
programs  with  restraint  along  similar  lines, 
we  think  they  would  strike  a  very  popular 
note. 

It  is  a  mistake,  by  way  of  conclusion,  to 
broadcast  church  services  in  toto.  The  church 
service  is  designed  for  the  worshipper  who 
participates  by  his  presence.  Pick-ups  from 
churches  are  only  moderately  successful,  be- 
cause the  highest  skill  of  the  broadcast  engi- 
neer cannot  overcome  the  reverberations 
always  present  in  large  church  auditoriums. 
Resuit:  the  choir  and  the  voice  of  the  minister 
come  through  well,  but  the  responsive  reading 
and  hymns  sung  by  the  congregation  are  fear- 
fully muffled  and  usually  sound  like  nothing 
human.  The  services  run  along  at  great 
length,  without  announcements — poor  policy 
at  best.  The  broadcaster  discovered  early  that 
broadcasting  a  play  direct  from  the  stage  was 
not  satisfactory.  Then  came  the  so-called 
radio  drama,  given  in  the  studio — a  much 
more  effective  and  desirable  thing.  For  ex- 
actly the  same  reason,  the  especially  prepared 
radio  divine  service  is  vastly  more  satisfactory. 


BROADCASTING  KITCHEN  SECRETS 


Mrs.  Ida  Bailey  Allen  at  the  microphone  of  WMCA,  New  York,  telling  the 
secret  of  a  luscious  fruit  cocktail.  Mrs.  Allen  is  known  throughout  the 
country  as  the  author  of  Mrs.  Allen  on  Cooking — Menus — Service.  Chef 
Louis  Parquet  of  the  Hotel  McAlpin  is  preparing  the  dish  and  Arthur  L. 
Lee,  managing  director  of  the  hotel  looks  on 


634 


Radio  Broadcast 


The  "Loud  Speaker  Ear" 


635 


TWO    PACIFIC   COAST   ANNOUNCERS 

The  "Town  Crier,"  well  known  to  the  listeners  of  KNX  at  Hollywood,  is  represented  in  the  photograph 
at  the  left,  and  "C.  A.",  Carl  Anderson,  one  of  the  announcers  of  KGO  at  Oakland  is  the  other 


Quality,  Quality,  Who's  Got 
the  Quality? 

IT  IS  not  uncommon  to  hear  an  ardent 
broadcast  listener  say,  during  the  reception 
of  a  program,  "That  sounds  as  if  it  had 
just  gone  through  the  wringer.  Those  fellows 
at  XYZ  aren't  putting  out  very  good  quality." 
The  piano  "sounds  terrible,"  or  "that  violin 
squeaks  like  a  wheezy  wheezy  Ford."  So  go 
the  criticisms  of  these  indoor  amateur  author- 
ities. The  truth  is  that  the  quality  of  musical 
sounds  and  speech  from  the  majority  of  broad- 
casting stations  is  quite  high.  Good  programs 
of  good  quality  are  the  business  of  the  broad- 
caster, and  it  is  really  no  secret  that  he  attends 
to  it  uniformly  well. 

It  is  the  sad  truth  that  radio  receivers  in 
many  a  home  are  quite  incapable  of  perfect 
reproduction  of  sounds,  music,  and  voice.  As 
listeners,  we  have  really  been  interested  in 
how  much  volume  our  set  would  deliver,  rather 
than  in  the  quality  which  issues  from  our  loud 
speaker.  A  change  is  coming  in  radio  styles 
and  the  criterion  is  becoming  not  "how  loud?" 
but  "how  good?" 

A  listener  of  our  acquaintance  went  one 
evening  to  hear  an  orchestra  which  had  always 
been  a  radio  favorite  of  his.  He  admitted 
after  the  experience  that  the  orchestra  did  not 
sound  natural  to  him.  His  was  a  case  of 
"loud  speaker  ear,"  although  he  was  probably 
unaware  of  his  malady.  He  had  grown  so 
used  to  hearing  the  orchestra  whose  tones  and 
overtones  were  made  unreal  by  his  loud 


speaker  that  when  he  heard  the  real  tones 
they  sounded  entirely  unnatural.  His  re- 
ceiver and  its  appended  loud  speaker  were 
simply  unfaithful  electrically.  The  biblical 
injunction  to  "first  cast  the  mote  out  of  thine 
own  eye"  applies  only  too  well  in  radio.  Be- 
fore heaving  coals  of  written  or  verbal  criticism 
at  the  broadcaster,  first  see  that  there  is  no 
mote  in  your  audio  circuit. 

And  now  that  summer  is  here  it  is  popular 
to  rail  at  "static."  It  is  foolish  to  minimize 
static.  Every  radio  authority  knows  static 
exists  and  he  knows  that  at  times  it  is  apt  to 
be  heavy  in  the  summer,  but  being  philosophi- 
cal, he  knows  that  it  is  temporary.  Static  in 
radio  is  really  no  more  bothersome,  taken  by 
and  large,  than  is  coughing  in  a  theatre,  as  some 
thoughtful  soul  once  remarked.  If  static  is 
bothersome  during  the  summer,  listeners  may 
well  be  content  with  programs  near  by.  Forc- 
ing a  receiver  on  weak  signals  serves  only  to 
make  the  atmospherics  boom  in  more  strongly. 
And  in  passing,  it  is  pertinent  to  remark  that 
all  that  disturbs  the  listener  is  not  static. 
Stray  squeals  and  howls  in  a  receiver  are  us- 
ually due  not  to  the  heavenly  forces,  but  to 
some  temporary  indisposition  of  the  receiver 
such  as  discharged  B  batteries,  or  to  too  much 
regeneration. 

The  radio  listener  these  days  no  longer 
regards  his  set  as  an  electro-mechanical  won- 
der. He  wants  an  instrument  which  he  can 
install  in  his  home  without  doing  violence  to 
his  ideas  of  interior  decoration  and  which  he 
can  compare  with  his  phonograph  in  volume 


636 


Radio  Broadcast 


and  quality  of  voice  and  music.  And  now, 
Barkis  willin',  there  is  no  reason  why  he 
shouldn't  have  it. 

These  U.  S.  As  Others  Hear  'Em 

CAME,   as   the   movie  subtitles   say,   a 
letter  into  the  office  from  Costa  Rica 
the  other  day  which  phrased  in  inter- 
esting fashion,  excellent  suggestions  for  an- 
nouncers,   in    which    listeners    not    "amidst 
tropical    heat    and    evergreen    foliage"    will 
heartily  concur: 

So  far  down  as  my  country  is  from  yours,  between 
1500  and  3100  miles  of  radius,  south  and  amidst 
tropical  heat  and  evergreen  foliage,  we  can  judge 
good  music  and  good  entertainment  with  full  loud 
speaker.  Some  tiempo  perhaps  a  sonata  is  on  the 
air,  an  opera,  a  Novaes  piano,  a  Burmerster  violin, 
a  Cincinnati  bell  song,  or  a  beautiful  negro  glee 
club  from  Beaumont,  Texas — is  enjoyable,  but  the 
announcer  fails  to  give  us  clearly  the  station  or 
description,  and  that  may  be  for  the  hesitation  of 
speaking  or  from  not  toned  voice,  that  although  we 
can  hear  refined  selections,  we  can  not  judge  where 
they  exactly  come  from. 

It  was  suggested  to  Sefior  Amando  Cespedes 
of  Heredia,  Costa  Rica,  the  writer,  that  per- 
haps too  frequent  announcement  of  the  station 
call  would  be  boring  to  local  listeners,  and  that 
the  program  was  the  thing. 

"After  all,"  Senor  Cespedes  wrotejn  answer, 
"are  we  not  more  interested  in  knowing  with 
the  beautiful  program,  the  dear  old  spot  on 
the  map  from  which  it  comes?  That  is  my 
reply.  Radio  to-day  is  not  only  yours.  We 
down  here  have  bought  it  from  you,  and  we 
have  a  right  to  condense  from  the  air  the  mil- 
lions of  frequencies  that  carry  sweet  chances, 
no  matter  if  they  are  from  jazz  or  from  many 
a  bad  cowboy  political  talker." 

"Sweet  chances"  from  the  air  reach  the 
ardent  Costa  Rican  as  well  as  the  interested 
American.  Senor  Cespedes  says  that  with  his 
Roberts  four-tube  receiver  he  hears  KSD, 

WGY,  WSAI,  WTAM,  KFKX,  KFDM,  CYB,  PWX,  and 

KGO,  who  "are  always  very  good  on  the  air." 
"Davenport,  woe,  is  also  a  life  constructor," 
he  continues.  "But  last  night,  I  heard  KFRU, 
from  little  Bristow  of  Oklahoma,  doing  an  ex- 
cellent, beautiful  pass  time  that  many  a 
broadcaster  should  imitate.  We  all  do  not 
want  jazz  or  string  noise,  and  as  we  can  easily 
tune-out,  easily  too  can  be  done  by  the  broad- 
casters to  pick  out  with  good  intelligence  their 
call  letters." 

Senor  Cespedes  hopes  that  his  "tiny  Costa 
Rica  country"  may  some  day  reciprocate  with 


broadcasting.  "Some  day  we  will  send  our 
radio  waves  to  you  like  Tuinicu,  Porto  Rico, 
or  Europe  are  doing.  Then  you  will  hear 
music  from  the  tropics,  from  the  senoritas, 
from  the  monkies,  or  from  our  lovely  bird 
singers;  then  you  will  feel  my  lovely  country 
near  you,  feel  our  fresh  air,  our  hurricane  winds 
that  do  not  harm  any,  you  will  hear  our  volca- 
nos  that  stand  proud  near  cities." 

This  "Super- Power"  Nonsense 

PERHAPS  it  is  the  publicity  folk  who 
are  at  it  again,  but  it  must  be  said 
that  a  lot  of  nonsense  is  being  written — 
and  worse,  printed— about  "super-power" 
broadcasting  stations.  When  a  5oo-watt 
station  increases  it  power  to  5000  watts,  the 
publicity  men  dash  for  their  typewriters  and 
tell  the  world  that  a  new  "super-power"  sta- 
tion is  now  in  existence,  and  intimate,  if  they 
do  not  actually  say  so,  that  forthwith  any 
listener  in  Bangkok  with  a  radio  receiver  assem- 
bled from  a  rubber  boot  and  a  tin  can  will  be 
able  to  hear  the  emanations  of  their  particular 
station. 

"Super-power"  is  a  term  torn  bodily  from 
the  electric  power  jargon.  In  that  business 
the  word  means  what  it  says.  But  in  radio, 
five  kilowatts  is  not  much.  Five  hundred 
watts  is  about  as  much  current  as  an  ordinary 
domestic  electric  heater  draws.  It  is  equal 
to  the  current  demanded  by  ten  fifty-watt 
incandescent  lamps. 

When  "super-power"  was  being  debated  at 
the  last  Hoover  Radio  Conference  in  Washing- 
ton last  October,  Mr.  David  Sarnoff,  vice- 
president  of  the  Radio  Corporation,  very  sen- 
sibly suggested  that  it  would  be  more  accurate 
to  call  stations  operating  on  increased  power 
"long  range  stations."  And  so  it  would. 
Local  listeners  will  notice  but  little  increase  in 
intensity  from  a  near-by  five  kilowatt  broad- 
caster, particularly  if  the  station  be  located 
some  ten  miles  or  more  from  the  center  of  the 
city.  At  the  time  of  writing,  the  Department 
of  Commerce  has  allowed  five  broadcasters 
to  use  five  kw.  They  are  woe,  Davenport, 
WLW,  and  WSAI,  of  Cincinnati,  WCBD,  Zion, 
Illinois,  and  wcco,  Minneapolis-St.  Paul. 
WEAF,  New  York,  is  now  using  3  kw.  and 
WTAM,  Cleveland,  2^  kw,  or  2,500  watts. 
This  increase  means  better  program  service 
to  more  listeners,  as  Mr.  Carl  Dreher  suggests 
on  another  page  of  this  issue. 

As  many  listeners  know,  wjz,  New  York, 
will  soon  move  its  transmitter  to  Bound  Brook, 
New  Jersey,  where  40,000  watts  will  be  avail- 


What  the  sos   Means  to   Listeners 


637 


able,  although  it  is  probable  that  when  the  new 
station  goes  on  the  air  late  in  August,  that 
only  a  fraction  ot  that  power  will  be  used. 

If  rumored  plans  of  the  Radio  Corporation 
go  through,  radio  programs  during  the  winter 
will  have  a  strong  international  flavor.  Says 
General  J.  G.  Harbord,  president  of  that 
Corporation 

Within  one  year,  American  radio  fans  possessing 
the  ordinary  sets  will  be  able  to  receive  from  Ger- 
many direct,  through  arrangements  completed  for 
broadcasting  German  programs  through  the  plant 
of  the  Radio  Corporation. 

The  foreign  programs  will  be  picked  up  by 
a  sensitive  receiver  "somewhere  in  Maine," 
sent  to  Bound  Brook  by  wire,  and  transferred 
there  to  the  glowing  wjz  tubes.  During  the 
late  fall  of  1924,  wjz  rebroadcast  some  con- 
certs from  London,  sent  through  the  long 
range  broadcasting  station,  5XX,  of  the  British 
Broadcasting  Company  at  Chelmsford.  These 
were  only  moderately  successful,  but  there  is 
every  reason  to  believe  that  an  exchange  of 
good  programs  between  the  United  States, 
England,  and  Germany  will  be  an  accomplished 
fact  before  the  close  of  1925.  A  Manila  paper 
received  here  recently  tells  of  the  great  inter- 
est in  American  programs.  With  high  pow- 
ered broadcasters  looming  on  the  electrical 
horizon,  that  should  be  possible  in  a  year  or  so. 
So  radio  progresses. 

Broadcast  Miscellany 


IT  IS  not  unsuual  for  radio  programs  from 
stations  on  the  East  and  West  Coasts  to 
be  suddenly  interrupted— almost  in  the 
middle  of  a  bar — without  any  warning  or 
announcement.  Results  frantic  testing  of 
local  tubes,  batteries,  and  connections  to  de- 
termine some  unsuspected  flaw  in  the  radio 
machine.  The  stoppage  of  the  program  is 
almost  never  due  to  faulty  apparatus,  for  an 
sos  from  a  ship  a  thousand  miles  away  can 
cause  an  instant  curtailment  of  every  bit  of 
radio  traffic — broadcasting  and  ship-to-shore 
communication  alike — with  those  dread  code 

characters,    ... ...      Broadcasting 

stations  near  the  coast  are  required  to  listen-in 
for  distress  calls  and  stop  their  programs  when 
an  sos  is  heard. 

DROADCASTING    stations    receive    some 
'  curious  letters,  ranging  from  those  which 
request  aid  in  finding  lost  dogs  to  those  plead- 
ing for  another  playing  of  whatever  the  current 


BENNETT    B.    SCHNEIDER 

At  the  microphone  of  WBZ,  at  Springfield,  delivering 
one  of  his  Monday  evening  talks  about  books  and 
their  writers.  Mr.  Schneider,  who  is  manager  of 
the  Doubleday,  Page  bookshop  in  Springfield,  is 
presenting  books  in  a  pleasantly  different  fashion. 
Instead  of  critically  discussing  a  book  that  many  of 
his  hearers  have  not  read,  Mr.  Schneider  attempts 
to  give  the  facts  about  each  book  which  are  calcu- 
lated to  inspire  interest  in  reading  it.  His  talks  are 
on  alternate  Monday  nights  at  10:40  Eastern  Sum- 
mer time 


version  of  "Red  Hot  Mamma"  happens  to  be. 
But  the  request  which  made  the  most  serious 
problem  to  one  broadcast  station  secretary 
was  this:  "I  live  on  a  farm  a  long  distance 
from  an  electrical  store.  Will  you  please 
write  me  an  address  of  a  place  which  will  sell 
me  a  cold  storage  battery?" 

CTATION  WMCA,  New  York,  every  Tues- 
^  day  evening  puts  on  a  program  called  the 
"Chiropractic  Hour  of  Music."  We  confess 
that  we  were  consumed  by  curiosity  to  know 
what  chiropractic  music  was.  Perhaps  there 
would  be  a  saxophone  sextette  in  which  the 
virtuosi  could  show  their  technical  training  by 
manipulating  the  spine  of  each  silvered  horn. 
Perhaps  .  .  .  but  we  heard  their  program 
before  speculation  could  proceed  further. 
Rather  well  played  selections  from  well-known 
operas  there  were.  Our  main  disappointment 
came  with  the  conclusion  of  the  "  Hour"  when 
they  closed  without  the  expected  formality 
of  a  spinal  "chord"! 

WE  OFFER  our  congratulations  to  our 
contemporary,  Radio  News,  on  the  open- 
ing of  its  broadcast  station  WRNY,  atop  the  Ho- 
tel Roosevelt  in  New  York.     Mr.  HugoGerns- 


638 


Radio  Broadcast 


FRED   J.    TURNER 

Whose  "Trips  and  Adventures"  made  him  many 
friends  through  WEAF.  Mr.  Turner  is  now  broad- 
casting his  weekly  feature  through  wjz.  In  the 
course  of  his  radio  travels,  Mr.  Turner  has  "visited" 
industrial  plants  of  all  kinds  and  many  places  of 
public  interest 


back,  editor  of  the  magazine  and  supervisor 
of  the  station,  has  more  than  an  ordinary 
problem  on  his  hands,  for  having  been  assigned 
a  frequency  of  1160  kilocycles  (258.5  meters), 
WRNY  will  probably  find  it  very  difficult  to 
"get  out."  The  short  wavelength  stations 
on  Manhattan  Island  have  always  had  trouble 
working  north  and  south,  although  little  in 
the  matter  of  radiating  west.  And  the  sta- 
tion, representing  a  periodical  dealing  with 
radio  subjects,  will  be  looked  up  to  by  radio 
listeners  everywhere  to  maintain  a  high  stand- 
ard of  programs.  A  number  of  experiments 
are  being  tried  at  Mr.  Gernsback's  station,  one 
of  which  is  the  broadcasting  of  hook-ups,  in 
cooperation  with  the  New  York  Sun.  Another 
feature  is  a  musical  signal,  dubbed  the  "stac- 
catone" — a  flute-like  note  emitted  before  the 
start  of  a  program,  during  intermissions,  and 
following  the  last  number.  The  announced 
purpose  of  the  signal  is  to  make  it  more  easy 
to  recognize  the  station  when  the  words  of 
the  announcer  are  indistinct. 

INTERESTING  material  about  books  is  as 
*  rare  in  broadcast  programs  as  it  is  in  the 
average  daily  newspaper.  But  there  are  two 
features  on  the  air  in  the  East  which  listeners 
have  come  to  rate  very  highly.  Mr.  Oliver 
Sayler,  an  authority  on  the  theatre  and  a  de- 
cidedly interesting  speaker  about  books  and 
their  makers,  may  be  heard  from  WGBS,  New 
York  (948.8  kilocycles,  316  meters)  every 
Thursday  evening  at  8:30,  Eastern  summer 
time,  And  from  WBZ,  Springfield,  Mr. 


Bennett  Schneider,  manager  of  the  Doubleday, 
Page  &  Company  bookshop  in  Springfield, 
broadcasts  talks  on  books  on  alternate  Mon- 
day evenings  at  10:40,  Eastern  summer  time. 
Reports  from  WBZ  listeners  say  that  Mr. 
Schneider's  talks  are  received  with  great  favor. 

ANNOUNCERS  have  heard  so  much 
•*~\  about  clarity  of  speech  and  have  had  so 
many  complaints  about  this  and  that  and 
whatnot  that  many  of  them  are  leaning  over 
backward  in  these  matters,  if,  indeed,  one 
can  lean  verbally  backward.  Any  number  of 
these  gentry  describing  the  evening  musical 
progression  of  an  orchestra  stress  their  words, 
particularly  "orchestra."  It  is  almost  in- 
variably given  as  or-CHES-tra.  Webster  and 
other  crystallizations  of  good  verbal  usage 
demand  that  the  accent  be  placed  on  the  first 
syllable.  And  some  announcers  of  the  Radio 
Corporation  of  America  stations  insist  on  call- 
ing their  company  the  Radio  Corporation  of 
Amurrica — which  is  wholly  out  of  place  with 
the  usually  high  quality  of  their  announcing. 
And  in  passing,  it  should  be  noted  that  the 
deep-toned  announcers  of  WGY  have  not  yet 
discovered  that  the  name  of  their  company  is 
the  General  £-lectric  and  not  the  General 
y/-lectric  Company.  Small  matters,  these, 
perhaps,  but  mispronunciation  and  careless 
pronunciation  can  work  wonders  in  spoiling 
an  otherwise  perfect  program. 

I'LL  See  You  in  My  Dreams  from  WOR" 
was  the  startling  information  trickling 
through  our  critical  loud  speaker  the  other  eve- 
ning. .  .  .  and,  again,  WGBS  was  recently 
broadcasting  a  farewell  concert  from  a  White 
Star  Line  pier  in  New  York.  A  sixty-piece  or- 
chestra made  up  of  members  of  the  Musician's 
Mutual  Protective  Association  had  gathered 
to  wish  musical  godspeed  to  Mr.  Samuel  Un- 
termyer,  a  New  York  lawyer  who  has  done 
a  great  deal  for  their  membership.  As  the 
time  for  sailing  neared,  the  parting  siren  of  the 
ship  and  the  incidental  noise  of  departure 
stopped  further  musical  broadcasting.  The 
announcer  was  stalling  for  time,  so  he  resorted 
to  ex  tempore  description.  "As  the  last  siren 
has  blown,  I  see  Mr.  Untermyer  leaning  over 
the  rail  of  this  ship  .  .  .  and  now  .  .  . 
the  last  line  which  holds  this  magnificent  liar 
.  .  .  this  magnificent  liner,  to  the  pier  is 
parted."  Mr.  Untermyer,  being  a  lawyer, 
probably  has  been  called  worse  names  in  the 
heat  of  legal  controversy,  but  the  unintentional 
description  of  the  bothered  WGBS  announcer 
caused  many  a  local  chuckle. 


When  Twenty-Eight  Stations  Broadcast  at  Once 


639 


ON  JULY  4th,  at  ten  o'clock,  Eastern 
summer  time,  the  War  Department 
arranged  the  second  national  program  as  a  cli- 
max to  Defense  Test  Day.  The  entire  nation 
was  hooked  up  to  Washington  by  long  dis- 
tance telephone  lines  which  supplied  the  pro- 
gram to  twenty-eight  broadcasting  stations. 
This,  as  General  Salzman,  Chief  Signal  Officer 
of  the  Army,  and  Master  of  Ceremonies  for 
the  occasion,  announced,  was  the  largest 
number  of  broadcasting  stations  ever  to  radiate 
a  single  program.  Seventy  thousand  miles 
of  wire  were  involved  in  the  long  distance 
hook-up.  The  stations  participating  were 

WEAF,  WCAP,  WJAR,  WCTS,  WTIC,  WGY,  WGR, 
WFI,  WCAE,  WSB,  WTAM,  WSAI,  WWJ,  KYW, 
KSD,  WDAF,  WCCO,  WOC,  WFAA,  WOAW,  KOA, 

KSL,  KFI,  KPO,  KGO,  ROW,  and  KFOA.  And 
many  of  us  will  not  soon  forget  the  address 
made  by  General  Pershing  and  his  stirring 


appeal  for  adequate  preparation  for  national 
emergencies.  The  program  was  by  no  means 
as  impressive  as  that  broadcast  on  September 
1 2th  last  year  because  it  was  not  as  skillfully 
arranged.  But  even  hardened  radio  men 
were  impressed  with  the  genuine  drama  of 
the  affair.  The  success  of  this  impressive 
hour  must  be  laid  directly  at  the  door  of  the 
American  Telephone  and  Telegraph  Com- 
pany, who  donated  their  long  distance  wire 
network  for  the  program.  The  technical  ex- 
cellence of  their  obscure  engineers,  quietly 
watching  over  the  balance  of  those  long  lines, 
made  it  possible.  And  in  time  of  national 
emergency,  if  ever  again  it  comes,  the  Presi- 
dent of  the  United  States  can  address  the  en- 
tire country  from  his  study  in  Washington. 
What  would  Wilson  have  given  for  such  an 
opportunity  when  he  made  his  immortal  ad- 
dress to  Congress  in  April,  1917! 


PUTTING   THE    VILLAGE    SMITHY   ON    THE    AIR 

Winger's  Crescent  Park  Entertainers  who  are  heard  from  WGR,  Buffalo,  on  Friday  evenings,  shown  playing 

in  the  village  blacksmith  shop  at  Ridgeway,  Ontario,  near  Buffalo.     In  the  photograph,  left  to  right  are  Sam 

Anger,  Mrs.  Anger,  Hugo  Lautz,  W.  A.  Winger,  J.  G.  Willet,  Ernie  Clair,  and  Howard  Brandel.     The  emery 

wheel,  bellows,  and  forging  hammer  are  not  in  use 


How  to  Make  a  Universal 
Battery   Charger 

An  Unusually  Complete  Description  of  a  Two- Ampere  Charger 
Consuming  but  150  Watts  Which  Will  Operate  on  Any  Alter- 
nating Current  Supply  of  from  Twenty-Five  to  Seventy  Cycles 

BY  ROLAND  F.   BEERS 


TTflTHIN  the  past  year  or  so,  radio  constructors  have  shown  a  great  interest  in 
P'  building  battery  chargers.  An  inexpensive  chemical  rectifier  was  described  by 
James  Mitten  in  this  magazine  for  June  which  has  satisfied  many  readers  who  wished  to 
construct  a  unit  of  the  chemical  type.  The  unit  outlined  in  this  article  is  slightly  more 
difficult  to  construct,  hut  the  time  and  care  taken  in  construction  and  assembly  will  he  well 
repaid.  The  cost  of  parts,  it  will  he  noted,  is  only  $/  / .  The  wide  range  of  commercial 
frequencies  covered  by  this  device  will  appeal  to  many  radio  listeners  who  have  an  al- 
ternating current  supply  other  than  60  cycles.  The  current  consumption  of  this  charger 
is  quite  low — 150  watts  on  full  load — and  that  should  appeal  to  the  home  builder  very 
strongly. — THE  EDITOR 


BATTERY  chargers  may  be  classified 
into   three   general    groups:   electro- 
lytic, thermionic,  and  vibrator  types. 
When  adapted  to  charging  radio  or 
automobile  storage  batteries,  all  three  types 
possess     similar     operating     characteristics. 
Their  principal  function  is  to  convert  the  1 10- 
volt  alternating  current  obtained  from  a  light 
socket  to  direct  current  at  proper  voltages  to 
charge  storage  batteries. 

The  direct  current  output  of  battery  charg- 
ers is  not  uniform  in  magnitude  but  is  com- 
posed of  a  seriesof  individual  pulses, each  a  half 
cycle  of  rectified  alternating  current  as  shown 
in  Fig.  i.  With  the  advent  of  each  half  cycle 
or  rectified  wave,  there  occurs  a  change  in 
current  from  the  charger,  increasing  and 
decreasing  rapidly  as  shown  by  the  shape  of 
the  current  curve  at  A.  Here  is  shown  the 
introduction  of  a  positive  half  cycle  or  half 
wavelength,  of  duration  denoted  by  ^T, 
where  T  represents  the  period  of  an  entire 
cycle  or  wavelength.  During  this  first  half 
period,  energy  is  fairly  shoved  into  the  storage 
battery.  The  total  amount  of  charging  energy 
per  cycle  is  represented  by  the  area  beneath 
the  curve  A  times  the  average  voltage  for 
the  same  period.  During  the  second  half 
period,  \  T,  we  have  a  complete  cutting  off 
of  the  charging  current,  which  is  caused  by 
the  valve  or  rectifier  action  of  the  charger. 
If  the  charger  is  of  the  electrolytic  or  ther- 
mionic type,  we  may  say  in  truth  that  a 


valve  is  closed  to  the  reversed  current,  as 
shown  by  the  flat  portion  of  the  curve  at  B. 
In  the  vibrator  charger,  a  switch  automati- 
cally opens  the  battery  circuit  at  the  end  of 
the  first  half  cycle  in  order  to  prevent  a  re- 
versal of  current  through  the  battery.  At 
the  end  of  this  complete  wave  and  at  the  be- 
ginning of  a  second,  we  repeat  the  action  and 
charging  of  the  battery  is  resumed. 


FIG.     I 

A  graphic  representation  of  how  a  charger  functions. 
The  curve  labeled  "secondary  voltage"  shows  the 
sine  wave-form  of  the  6o-cycle  lighting  circuit. 
That  curve  labeled  "charging  current"  shows 
the  portion  of  the  alternating  wave  which  is  rejected 
in  the  rectifier  allowing  only  the  periodic  pulsations 
of  that  portion  of  the  curve  where  the  current  is 
"direct  current"  to  enter  the  battery 


How  to  Make  a  Universal  Battery  Charger 


641 


Solution 

or 
Electrolyte 


FIG.    2 

A  chemical  rectifier  in  its  simplest  form.  The  posi- 
tive terminal  is  the  anode  and  the  negative  electrode 
is  the  cathode.  Current  may  be  passed  from  the 
cathode  to  the  anode  but  not  vice  versa.  There- 
fore, when  the  alternating  current  is  on  the  positive 
half  of  the  cycle,  current  flows  through  the  rectifier 
into  the  battery  but  when  the  current  is  on  the 
negative  side  of  the  cycle  no  current  flows.  This 
also  produces  a  pulsating  periodic  flow  of  d.c. 


NEVER    CHARGE     BATTERIES    CONNECTED    TO    A 
RECEIVER 

A  BRIEF  study  of  the  character  of  the 
«*  current  supplied  by  battery  chargers 
as  outlined  above  will  show  why  it  is  neither 
feasible  nor  advisable  to  charge  storage 
batteries  while  they  are  connected  to  a  radio 
receiver.  The  constantly  changing  battery 
current,  when  applied  to  the  radio  antenna 
and  ground  system,  causes  untold  disturbance 
in  the  surrounding  ether  and  may  be  inter- 
preted as  a  form  of  malicious  interference 
with  radio  reception.  Fortunately,  many 
charger  manufacturers  connect  one  side  of  the 
a.  c.  line  to  the  output  of  the  charger  so  that 
a  house  fuse  is  blown  when  the  charger  is 
operated  as  it  is  connected  to  a  radio  re- 
ceiver. 

Let  us  return  to  the  consideration  of  charger 
design,  in  order  to  determine  what  are  the 
elements  with  which  we  have  to  contend. 
The  charger  of  lowest  cost,  from  the  point  of 
view  of  home  construction,  could  be  made 
of  the  electrolytic  type,  provided  pure  metals 
could  be  procured  for  the  rectifier  electrodes. 
The  rectifier  cell  illustrated  in  Fig.  2  consists 
of  two  electrodes,  A  and  C,  suitably  suspended 
in  a  water  solution  in  such  a  fashion  that  recti- 
fication occurs  without  excessive  heating  of 


the  rectifier  cell.  The  combination  usually 
employed  in  home-constructed  chargers  is  a 
lead  (negative)  and  an  aluminum  (positive) 
electrode  dipping  into  a  saturated  solution  of 
common  borax.  Other  solutions  which  have 
been  used  successfully  for  charging  B  batteries 
are  sodium  phosphate,  ammonium  phosphate, 
and  sodium  acid  tartrate.  One  form  of  this 
charger  on  the  market  consists  of  an  iron  cup 
which  contains  the  solution,  into  which  dips 
the  aluminum  rod.  Another  form  of  elec- 
trolytic rectifier  on  the  market  consists  of  a 
tantalum  electrode  dipping  into  a  solution  of 
sulphuric  acid,  whose  specific  gravity  is 
1.250.  The  area  of  the  tantalum  electrode  is 
1 5  sq.  cms.  and  the  volume  of  the  electrolyte 
must  be  great  enough  to  prevent  excessive 
temperature  rise. 

A    TWO-AMPERE    "UNIVERSAL"    CHARGER 

FIGURE  3  is  a  schematic  diagram  which 
shows  the  electrical  apparatus  and  con- 
nections necessary  to  assemble  a  battery 
charger.  Details  of  construction  are  given 
below  for  a  two-ampere  charger  which  has 
universal  frequency  characteristics.  That  is 
to  say,  this  charger,  when  built  in  accordance 
with  the  specifications,  will  operate  satis- 
factorily on  commercial  frequencies  ranging 
from  25  to  70  cycles,  inclusive.  The  design 
disclosed  below  is  not  perhaps  the  most 
economically  constructed  for  use  on  6o-cycle 
current,  but  its  cost  of  operation  is  very 
small  and  should  prove  no  objection  to  the 
experimenter  who  really  wants  to  build  his 
own  charger.  In  addition,  the  improved 
efficiency  of  operation  will  be  of  considerable 


For  Fuse  Plug 


To  Negative  Pole  on 
Storage  Battery 


FIG.    3 

The  actual  circuit  diagram  of  the  Beers  tungar 
rectifier.  This  is  different  from  that  of  the  charger 
circuit  in  Fig.  10  in  that  a  separate  charging  second- 
ary is  provided.  Alternating  current  is  induced 
into  this  secondary  while  the  circuit  in  Fig.  10  is 
that  of  an  auto-transformer  employing  the  conduc- 
tive system.  There  is  no  great  difference  between 
the  two 


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Radio  Broadcast 


FIG.  4 

How  the  made-up  charger  looks.     A  bakelite  panel,  situated  above  the  transformer  core 
supports  the  output  terminals,  tungar  tube  and  socket  and  input  socket  with  fuse  block 


How  to  Make  a  Universal  Battery  Charger 


643 


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TRANSFORMER  CORE 


symbols  Authors  Design 

Cross-Sectional  Area=axb_ 2.0  Sq.  Ins. 

Outside  Dimensions  :Length=-a  +  c _  5.5  Ins. 

Width  =a  +  d__ 4.5  Jns. 

Height=b i.4|ns. 

Width  of  Steel  Strips  -a ..1.4  Ins. 

Thickness  •       »     -t ..  .OH  ins. 

SizeofWindow  =exf 4^5  Sq.lns. 

Weightof  Core=(2c  +  2d)(axb)x.28Lbs. _    8.0  Lbs. 

Mean  Length  ofCore-2c-t-2d 144  |ns 

FIG.    5 

The  details  and  specifications  for  the  construction  of  the  core  are  outlined  here.     After  the  core-pieces  are 
cut,  it  is  absolutely  essential  that  burrs  be  removed  from  the  edges  and  that  they  be  entirely  flat.     This  is 
necessary  to  obtain  the  required  number  of  pieces  for  the  specified  height  of  the  core 


advantage  to  the  battery  owner  from  the 
standpoint  of  power  consumption.  The  no- 
load  power  of  this  charger  on  6o-cycle  supply 
was  measured  and  found  to  be  less  than  10 
watts.  The  full  load  power  consumption  was 
found  to  be  150  watts. 

Fig.  3  shows  a  transformer  with  three  wind- 
ings, which  we  will  designate  as  P,  S'  and 
S".  P  is  the  'primary  winding  and  is  connected 
to  the  i  lo-volt  alternating  current  light 
socket.  S'  is  the  filament  secondary  and 
supplies  the  power  for  heating  the  tungar 
bulb  filament.  This  winding  is  provided 
with  a  center  tap  (6-7)  which  will  be  explained 
jn  detail  later.  Winding  S"  is  the  charging 
\winding  and  supplies  the  necessary  potential 
to  operate  the  tungar  arc.  Leads  are  taken 
out  from  points  9  and  10  which  lead,  re- 
spectively, to  the  positive  and  negative  termi- 
nals of  the  storage  battery. 


HOW    A    THERMIONIC    RECTIFIER    OPERATES 

THE  operation  of  the  tungar  or  other  thermi- 
onic rectifier  is  fairly  simple  of  explanation.  It 
is  well  known  that  a  heated  filament  in  vacua 
under  the  stress  of  potential  will  emit  electrons 
which  will  flow  in  the  direction  of  the  applied  po- 
tential. In  other  words,  if  the  hot  filament  be 
made  cathode  and  the  cold  plate  the  corresponding 
anode,  a  stream  of  electrons,  hence  electricity,  will 
flow  from  cathode  (-)  to  anode  (+).  However,  no 
current  will  flow  in  the  reverse  direction,  from  plate 
to  filament,  and  in  this  fact  we  obtain  the  valve  or 
rectifier  action  of  the  tube.  Now  when  we  attempt 
to  obtain  heavy  electronic  emission  in  vacua  (i.e. 
of  the  order  of  i  ampere)  we  are  confronted  with  a 
secondary  phenomenon.  Very  soon  so  many  elec- 
trons fill  the  space  between  plate  and  filament  that 
they  neutralize  the  effect  of  the  positive  charge 
on  the  plate.  The  result  is  a  slowing  up  of  the  elec- 
tron stream,  and  a  decrease  in  the  current  output 
of  the  rectifier.  In  order  to  offset  the  effect  of 
the  space  charge,  as  it  is  called,  the  manufacturers 


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Radio  Broadcast 


of  the  tungar  tube  introduce  into  the  chamber  a 
small  amount  of  inert  gas,  called  argon.  This 
gas  is  unable  to  unite  chemically  with  the  metallic 
elements  within  the  tube,  but  is  capable  of  ioniza- 
tion  through  the  bombardment  of  the  electron 
stream.  The  constant  impact  of  the  billions  of 
electrons  passing  to  the  anode  soon  detaches  from 
the  atoms  of  argon  gas  their  positive  nuclei  and 
their  charges.  When  these  positive  charges  are 
liberated,  their  immediate  action  is  to  neutralize 
the  space  charge  of  the  tube,  as  established  by  the 
excess  electrons  in  the  space  between  filament  and 
plate.  Every  positive  charge  attaches  itself  to  a 
negative  electron  and  the  result  is  a  neutral  atom. 
The  process  of  breaking  up  and  reconstruction  con- 
tinues until  the  tungar  tube  is  shut  off,  and  the 
total  effect  of  the  ionization  is  to  produce  a  greater 
current-carrying  capacity 

It  may  be  mentioned  here  that  the  tungar 
and  similar  types  of  thermionic  tube  do  not 
perform  well  on  voltages  above  50  on  account 
of  the  irregularity  in  the  ionization  process. 
If  it  were  not  for  this  fact,  the  tube  might 
be  used  as  the  rectifier  element  in  a  form  of  B 
battery  eliminator,  as  has  been  attempted  by 
the  author. 

We  will  now  proceed  to  the  construction  of 
a  two-ampere  charger,  as  illustrated  in  the 
photograph,  Fig  4.  The  part  of  the  unit  most 
difficult  to  construct  is  the  transformer,  but  if 
the  following  instructions  are  carefully  studied, 
the  author  believes  that  the  experimenter 
will  have  very  little  trouble  in  obtaining  suc- 
cessful operation  from  his  model. 

THE    PARTS    AND   MATERIALS    REQUIRED 

HPHE  following  table  gives  the  exact  amount 
*  of  materials  required.  Deviations  from 
the  design  given  below  may  require  somewhat 
greater  amounts  of  copper  and  steel,  which 
will  have  to  be  estimated  by  the  builder. 


MATERIALS    REQUIRED 

8  Ibs.  silicon  steel,  thickness  .018"  to  .010" 
i  Ib.  No.  20  d.  c.  c.  wire 

1  j  Ib.  No.  15  d.  c.  c.  wire 

2  Ib.  No.  14  d.  c.  c.  wire 

1  porcelain  Edison  socket 

i,  2-plug  porcelain  fuse  block  .      .      .      . 

2  separable  plugs 

1  2-ampere  plug  fuse 

28  inches  i  inch  x  £  inch  angle  iron      .     -. 
4  2  x  j  inch  stove  bolts  and  nuts  . 

2  battery  clips 

i  Fahnestock  clip     .... 

6  feet  twisted  lamp  cord 

4  feet  rubber  covered  No.  14  flexible  cord 
i  2-ampere  tungar  rectifier  tube,  list  . 
i  bakelite  panel  4x7  inches    .... 

|io.65 
Prices  given  above  are  the  highest  retail  prices 


i. 60 

i  .00 

1.25 

.50 

.20 

•35 
.30 
.05 

•25 
.05 
.40 
.05 
•'5 
•25 
4.00 


experienced  by  the  author.     Most  builders  have 
access  to  materials  at  lower  cost. 

In  Fig.  5  are  given  the  complete  dimensions 
of  the  transformer  core.  In  view  of  the 
difficulty  with  which  the  average  amateur  ob- 
tains silicon  steel  sheets  such  as  are  necessary 
to  make  this  transformer,  a  few  remarks  may 
be  of  service  in  the  process  of  construction. 

The  simplest  way  to  obtain  the  steel  lami- 
nations for  the  core  is  to  go  to  your  local 
electric  light  company  office  and  ask  for  a 
junked  pole  transformer  of  from  i  to  5  k.  v.  a. 
capacity.  Such  transformers  are  often  thrown 
away  and  are  frequently  sold  for  $i  or  less. 
If  you  are  fortunate  enough  to  obtain  one  of 
these  burned  out  units,  your  problem  of  find- 
ing steel  of  the  right  quality  is  solved. 

Another  equally  good  source  of  silicon 
steel  is  from  amateur  supply  houses  who- 
make  a  specialty  of  furnishing  this  material1 
to  transmitting  amateurs.  Advertisements  of 
these  firms  are  carried  in  current  radio  periodi- 
cals. The  price  is  generally  less  than  20 
cents  per  pound  in  lo-pound  lots. 

Assuming  that  you  are  still  unable  to 
obtain  silicon  steel  of  approximately  .014 
inch  thickness  (limits  .010  inch  to  .018  inch), 
get  in  touch  with  transformer  manufacturers 
or  steel  jobbers,  from  trade  journals,  which 
are  frequently  on  file  in  public  libraries. 
Many  times  the  author  has  received  extreme 
courtesy  from  such  firms  who  are  willing  to 
accommodate  their  inquirers  with  small 
quantities  of  scrap  steel. 

As  a  last  resort  for  core  material,  go  to  your 
local  tinsmith  and  get  the  best  grade  of  soft 
sheet  iron  or  steel  he  has.  For  the  60- 
cycle  design  outlined  below,  use  exactly  the 
amount  of  soft  iron  as  is  specified  for  the 
silicon  sheet  steel.  For  the  lower  frequency 
design,  such  as  25  cycles,  use  one  half  more 
cross-sectional  area  in  the  core.  For  example, 
using  soft  iron  on  25-cycle  chargers,  we  would 
build  a  core  measuring  in  cross-section  1.8 
inches  x  1.8  inch  or  the  equivalent,  instead 
of  the  core  as  specified,  which  measures  1.4 
inches  x  1.4  inches.  For  frequencies  inter- 
mediate between  25  and  60  use  a  direct  pro- 
portion to  obtain  the  proper  amount  of  soft 
iron.  However,  the  author  strongly  recom- 
mends the  use  of  silicon  sheet  steel,  if  it  can 
possibly  be  obtained. 

MAKING  THE   CORE    FROM    POWER 
TRANSFORMER    PARTS 

T  F  YOU  have  obtained  a  junked  transformer, 
*  place  it  near  a  hot  stove  or  furnace  for  half 
a  day  in  order  to  soften  the  filling  compound. 


How  to  Make  a  Universal  Battery  Charger 


645 


Having  removed  the  cover,  attack  the  bolts 
which  hold  the  core  to  the  case.  Remove 
these,  together  with  as  much  of  the  black 
filling  compound  as  possible  and  dump  out 
the  transformer  on  to  a  pile  of  old  newspapers. 
If  the  core  can  now  be  taken  out  of  doors  and 
washed  with  kerosene,  most  of  the  black  com- 
pound can  be  cleaned  off.  With  a  heavy  block 
of  wood  or  wooden  mallet,  drive  out  the 
core  from  the  center  of  the  windings.  A  con- 
venient way  to  do  this  is  to  block  up  the 
windings  on  two  2  x  4-inch  pieces  while  you 
are  hammering  on  the  core  in  the  attempt  to 
start  it.  Once  loosened,  the  entire  core  can 
be  pushed  out  when  it  will  fall  into  bunches 
of  steel  laminations.  These  should  be  care- 
fully separated  and  cleaned  off  with  kerosene 
or  carbon  tetrachloride.  Avoid  bending  or 
breaking  any  of  the  pieces,  as  you  may  need 
them  all  during  the  construction  of  the  charger. 

Most  power  transformers  are  made  up  of 
U-shaped  pieces  and  straight  pieces,  as  shown 
in  Fig.  6.  If  you  are  fortunate  enough  to 
obtain  such  pieces  as  these,  your  core  con- 
struction will  be  very  simple.  The  dotted 
line  shown  at  c — c,  Fig.  6,  shows  how  the 
steel  laminations  can  be  cut  down  to  make 
the  proper  sized  core.  End  pieces  (shown  at 
s)  can  be  cut  from  the  waste  to  make  a  closed 
rectangle.  When  cutting  the  steel  for  the 
core,  extreme  care  should  be  taken  in  obtain- 
ing a  perfectly  tight  fit,  at  g  Fig.  6.  If  the 
cutting  is  done  by  hand,  only  very  large  shears 
should  be  used  and  each  strip  should  be 
accurately  measured  and  marked  out  before 
cutting.  Carelessness  in  assembling  this  part 
of  the  charger  may  result  in  its  failure  to 
operate.  The  best  way  to  cut  the  pieces 
for  the  core,  regardless  of  their  shape,  is  to 
take  the  entire  lot  of  steel  and  your  pattern 
to  the  local  tinsmith's  shop,  where  you  will 
find  squaring  shears  that  may  be  used  to 
great  advantage  in  obtaining  square  edges. 
Often  the  tinsmith  will  let  you  do  your  own 
cutting,  unless  he  is  cautious  in  preventing 
accidents.  In  either  event,  the  entire  lot  of 
steel  can  be  cut  out  in  this  manner  in  less 
than  an  hour. 

In  case  you  have  been  unable  to  obtain  the 
U-shaped  pieces  for  the  core,  you  may  pos- 
sibly get  enough  steel  from  the  old  transformer 
to  make  up  the  charger  core  in  other  ways. 
Fig.  7  shows  the  possibilities  that  may  occur 
with  commercial  transformers,  and  the  in- 
genuity of  the  experimenter  will  serve  him  in 
assembling  the  right  amount  of  core  material. 
Fig.  5  shows  the  dimensions  recommended  for 
an  efficient  two-ampere  charger  on  all  fre- 


quencies. On  account  of  the  variations  in 
the  sizes  of  steel  laminations  available,  it  may 
be  impossible  to  adhere  to  these  dimensions 
exactly.  For  the  benefit  of  those  who  do 
find  these  variations,  the  following  limits 
will  be  helpful: 

min.  max. 

1.  Crpss  -  sectional  area 

of  core — a   x   b     .       2.0  sq.  ins.      2.0  sq.  ins. 

may  be,  as  shown, 

1.4  ins.  x  1.4  ins. 

or  i  in.  x  2  ins. 

or  2  ins.  x  i  in. 

etc. 

2.  Mean  length  of  core 

— 2c  -j-  2d        .      .      12.0  ins.  6.0  ins. 

where  c  and  d  are 
measured  along 
center  line  of  core 

3.  Area  of  window — exf 

— (c  -j-  a)  (d  +  a)       3.8  sq.  ins.      4.6  sq.  in* 

FIRST  CORE    ASSEMBLY 

HAVING  determined  the  size  and  shape 
of  the  core  within  the  limits  specified 
above,  the  pieces  are  temporarily  assembled 
to  determine  if  enough  steel  has  been  cut  out. 
Piles  of  each  leg  or  half  core  are  stacked  up 
and  clamped  up  in  a  vise  so  that  the  actual 
core  height  (b)  can  be  measured.  When  suf- 
ficient steel  has  been  prepared,  the  outside 
measurements  and  cross-section  are  taken 
and  noted  for  future  reference. 

We  now  proceed  with  the  winding  of  the 
coils  P,  S'  and  S".  The  first  thing  to  do  is 
to  cut  from  a  block  of  wood  a  piece  shaped 
exactly  like  the  section  of  the  core  which  is 
to  contain  the  windings  (see  Fig.  8).  Di- 
mensions shown  are  for  the  design  recom- 
mended by  the  author.  Whatever  changes 
are  necessitated  by  variation  in  steel  sizes 
must  be  calculated  by  the  builder.  The 
winding  block  should  be  approximately  o.io 
inch  larger  than  the  maximum  width  and 
height  of  the  core  in  order  to  facilitate  appli- 
cation of  the  completed  windings.  Slots  0.75 
inch  wide  and  o.  10  inch  deep  are  cut  longi- 
tudinally along  each  face  of  the  block,  in 
which  strips  of  friction  tape  are  laid  before 
the  winding  is  begun.  A  hole  is  drilled 
through  the  center  of  the  block  large  enough 
to  pass  a  j-inch  stove  bolt  for  clamping  the 
block  in  a  chuck.  Two  pieces  3  inches  x 
3  inches  are  now  cut  from  j-inch  stock  to 
provide  heads  for  holding  the  winding  in 
place  as  it  is  wound.  Quarter-inch  holes  are 
also  centered  in  these  pieces  as  shown  in  Fig. 
8.  The  winding  form  and  spool  heads  are 
now  assembled  upon  the  j-inch  bolt,  and  a  nut 


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c    »/> 

•s  s. 


•o 

1-3 


1  e 

^  I 
I.-3 

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FIGS.    6    AND    7 

Several  types  of  transformer  cores  which  may  be  employed 
in  this   construction.     The  sketches  are  self-explanatory 


How  to  Make  a  Universal  Battery  Charger 


647 


WoocH-Required 


Angle  Iron 
Clamping  Strips 


r 


<r 


1" Wrought  Iron;4-Required 


o 


Assembled  Winding  Form 


FIGS.    8    AND   9 

Details  of  construction  for  the  coil  winding  form  and  iron  angle  pieces.     It  is  to  be  noted  that  many  of  the 
dimensions  are  indicated  in  decimals  and  it   is  urged   that  constructors  adhere  to  these  specifications 


clamps  the  entire  form  together  as  shown 
in  Fig.  8.  The  protruding  end  of  the  stove 
bolt  is  clamped  in  the  chuck  of  a  breast  drill, 
hand  drill,  or  carpenter's  brace  preparatory 
to  winding  the  coils.  Four  pieces  of  f-inch 
friction  tape  are  cut  approximately  6  inches 
long  and  laid  squarely  in  the  slots  provided 
for  them.  The  long  ends  of  the  tape  are 
drawn  up  over  the  edge  of  the  spool  heads 
and  stuck  together  in  one  spot  near  the 
center  of  the  spool  heads.  A  strip  of  heavy 
Manila  wrapping  paper  is  now  cut  four  feet 
long  and  as  wide  as  the  distance  between 
spool  heads.  Fig.  8  shows  this  strip,  1.7 
inches  wide.  This  strip  of  paper  is  tightly 
wrapped  over  the  winding  form  after  gluing 
the  first  end  in  place.  If  the  builder  sees 
fit,  he  may  apply  a  thin  layer  of  glue  con- 
tinuously over  each  layer  of  paper  so  that 
the  paper  shell  when  completed  will  serve 
as  a  firm  support  for  the  coils. 

WINDING   THE    COILS 

'TPHE  primary  winding  is  wound  first  and 

1  consists  of  570  turns  of  No.  20  d.  c.  c.  wire, 

wound  in  smooth  layers.     The  first  end  of  the 


primary  winding  is  brought  up  the  side  of 
the  spool  and  is  later  taped  in  place  by  means 
of  one  of  the  adjacent  strips  of  tape.  Ap- 
proximately 24  turns  per  inch  should  be 
wound  and  pains  should  be  taken  to  wind  the 
wire  as  smoothly  as  possible,  preventing  over- 
lapping of  adjacent  turns.  When  the  winding 
is  completed,  the  end  of  the  wire  is  left  about 
eight  inches  long  as  a  terminal  to  connect 
to  the  flexible  extension  cord  or  terminal 
block  as  shown  in  the  photograph.  The  long 
ends  of  tape  which  have  hitherto  been  fast- 
ened to  the  spool  ends  are  now  drawn  tightly 
over  the  winding  and  fastened  in  place.  The 
spool  heads  are  removed  and  the  entire  wind- 
ing is  now  taped  securely  with  one  layer  of 
friction  tape,  half  lapped.  The  coil  is  now 
ready  for  assembly  but  before  we  can  put  the 
laminations  in  place,  we  must  prepare  the 
second  coil  which  has  two  separate  windings, 
S'  and  S". 

Winding  S"  consists  of  150  turns  of  No. 
15  d.  c.  c.  wire  wound  in  the  same  manner 
as  P.  Terminals  are  brought  out  each  end  of 
the  coil,  each  consisting  of  about  eight  inches 
of  the  same  wire  used  to  wind  the  coils, 


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Input, 


FIG.     10 

How  the  tungar  tube  rectifies.  The  transformer 
primary  (7)  induces  into  the  filament  winding  (6) 
a  voltage  for  lighting  the  filament  of  the  tube  (5). 
When  the  battery  (3)  is  in  the  circuit  and  current 
turned  on,  an  arc  is  set  up  between  the  filament  and 
the  graphite  electrode  (4).  When  the  line  (i) 
is  positive,  current  flows  through  it  to  the  battery 
and  through  the  electrode  (4).  Then  through  the 
arc  to  the  filament  and  back  to  the  other  side  of  the 
line  (2)  completing  the  circuit.  However,  when 
the  line  (i)  is  negative,  current  tends  to  flow  into  the 
bulb  from  the  filament  to  the  graphite  electrode,  but 
as  the  resistance  offered  to  the  flow  of  current  in  this 
direction  is  very  high  no  current  will  flow  through 
it  to  the  battery.  Therefore,  periodic  pulsations  of 
current  in  the  right  direction  of  flow  is  passed  through 
the  battery  changing  the  chemical  composition  of  its 
negative  and  positive  plates  thus  restoring  them  to 
their  original  charged  condition.  This  is  a  simple 
rectifier  circuit  of  the  standard  manufactured  type  of 
tungar  rectifier.  Both  this  type  and  that  described 
by  Mr.  Beers  produce  the  same  results 

No.  15  d.  c.  c.  One  layer  of  friction  tape  is 
wrapped  securely  over  S",  and  then  winding 
S'  is  applied,  which  consists  of  1 1  turns  of 
two  parallel  No.  14  d.  c.  c.  wires  with  a  tap 
at  the  5^  turn.  For  convenience  in  winding 
this  coil,  the  half  pound  of  No.  14  d.  c.  c. 
which  the  builder  has  purchased  is  divided 
into  two  equal  lengths  which  are  wound  to- 
gether on  one  spool  preparatory  to  winding 
the  parallel  strands.  Then  as  the  spool  is 
unreeled  during  the  process  of  winding,  it 
will  be  a  simple  matter  to  maintain  the  two 
wires  parallel  at  all  times,  and  to  avoid  their 
twisting  or  crossing  each  other.  The  tap 
brought  out  at  the  5^  turn  should  be  a  loop 
taken  in  the  two  wires  at  the  same  point, 
and  should  be  in  length  about  two  inches. 
This  tap  is  later  cleaned  thoroughly  and  a 
generous  coating  of  solder  is  applied  to  form 
a  lug  of  large  current-carrying  capacity.  The 
end  terminals  of  this  winding  (S')  are  treated 
in  the  same  manner  and  are  left  of  such  a 
length  that  they  can  be  carried  directly  to 


the  screws  on  the  Edison  socket  without 
splicing.  It  is  important  that  this  circuit 
be  of  very  low  resistance  (i.  e.  less  than  one 
ohm)  so  that  it  will  carry  the  filament  current 
of  4  amperes  without  heating.  The  finished 
coil,  containing  the  windings  S'  and  S"  is 
now  removed  from  the  winding  form  and 
taped  with  one  half-lapped  layer  of  friction 
tape. 

HOW    TO    ASSEMBLE    CORE    AND    WINDINGS 

IN  FIG.  4  may  be  seen  the  appearance  of 
the  finished  coils  as  they  are  assembled  on 
the  core.  When  assembling  the  core,  the 
steel  strips  or  laminations  should  be  inserted 
from  first  one  side  and  then  from  the  other 
so  as  to  alternate  the  position  of  the  air  gap 
in  the  core  at  every  layer.  Figs.  6  and  7  show 
the  position  of  the  various  types  of  lamina- 
tions and  the  manner  in  which  they  should  be 
arranged.  Care  should  be  taken  when  as- 
sembling the  steel  core  that  the  insulation 
on  the  windings  is  not  damaged  to  such  an 
extent  that  turns  of  wire  may  become  short- 
circuited  to  one  another  or  to  the  core.  When 
nearing  the  top  of  the  core,  place  the  partly 
assembled  transformer  in  a  vise,  compressing 
the  laminations  as  much  as  possible,  and  then 
squeeze  in  a  few  more  pieces  of  steel.  It  may 
be  necessary  to  hammer  the  last  one  or  two 
pieces  in  place  in  order  to  obtain  the  necessary 
cross-sectional  area  of  the  core,  but  the 
operation  should  be  attended  with  great  care 
lest  the  coil  windings  become  damaged. 

The  completed  transformer  is  clamped  to- 
gether between  four  pieces  of  one  inch  angle 
iron  or  hard  wood  strips  as  shown  in  Fig.  9. 
One-quarter  inch  stove  bolts,  two  inches 
long  are  needed  for  the  transformer  design 
shown  in  Fig.  5;  others  may  be  supplied  by 
the  builder  to  suit  his  individual  requirements. 
The  completed  transformer  should  now  be 
given  a  coat  of  black  insulating  paint  in  order 
to  preserve  the  appearance  and  prevent  rust- 
ing of  the  iron  parts.  It  is  advisable  to  paint 
the  lead  wires  as  well,  in  order  to  improve 
the  effect  of  the  insulation  on  them.  For 
want  of  better  insulating  paint,  the  author 
used  automobile  enamel,  which  has  withstood 
the  heating  effect  of  the  charger  remarkably 
well. 

We  are  now  ready  to  assemble  the  charger 
in  whatever  manner  seems  advisable  to  the 
builder.  If  he  desires,  he  may  cut  a  base- 
board of  ^-inch  hard  wood,  measuring  7  by 
8  inches,  and  all  parts  may  be  assembled  on 
this  base  in  a  compact  manner.  A  more 
shipshape  assembly,  and  one  which  leads  to  a 


How  to  Make  a  Universal  Battery  Charger 


649 


more  commercial  appearance,  is  illustrated 
in  Fig.  4,  where  a  terminal  board  of  |-inch 
bakelite  4  by  7  inches  is  mounted  on  the  top 
of  the  transformer  and  contains  the  tungar 
tube  socket,  battery  terminals  and  fuse  block. 
The  terminal  board  is  set  by  brass  bushings 
j  inch  above  the  angle  iron  brackets  and 
holes  are  drilled  for  mounting  the  various 
equipment  and  for  passing  the  lead  wires  up 
to  the  proper  terminals.  This  method  of 


FIG.    12 

A  typical  rectifier  tube.  The 
screw-base  allows  it  to  be  in- 
serted in  a  standard  lamp 
socket  from  which  current  is 
obtained  for  the  filament. 
Connection  is  made  to  the 
graphite  disc  by  means  of  a 
Fahnestock  connector  which 
clips  on  to  the  wire  post  pro- 
jecting from  the  other  end  of 
the  tube 


FIG.    I  I 


Another  view  of  the  completed  charger.     This  is  an 

end-view  picture  and  shows  how  the  angle  pieces 

are  employed   not  only  to  hold   the  core  together 

but  as  feet  and  supports  for  the  bakelite  shelf 


assembly  and  wiring,  suggested  by  H.  F. 
Mason,  is  very  compact  and  neat,  as  may  be 
seen  from  the  photograph,  Fig.  4. 

The  porcelain  fuse  block  serves  two  pur- 
poses: as  a  fuse  holder  for  the  two-ampere 
fuse  and  as  a  terminal  block  for  the  1 10- 
volt  extension  cord.  Wiring  and  connec- 
tions are  made  in  accordance  with  Fig.  3. 
Leads  to  the  storage  battery  clips  should  be 
of  No.  14  stranded  rubber  covered  wire,  and 
if  a  twin  conductor  cable  is  used,  a  polarity 
indicator  should  be  provided.  For  want  of 
a  better  indication,  the  terminal  leading  to 
the  positive  battery  terminal  may  have  a 
knot  tied  in  it,  or  it  may  have  a  red  string 
tied  to  it.  The  i  lo-volt  extension  cord  may 
be  of  ordinary  lamp  cord. 

FINAL   INSTRUCTIONS 

WHEN  the  charger  has  been  assembled  and 
connected  to  the  battery  for  charging,  inspec- 
tion should  be  made  to  observe  the  initial  perform- 
ance. If  possible,  the  charging  rate  should  be 
measured,  if  only  by  means  of  a  Ford  dash  ammeter 
or  similar  device.  When  charging  a  6-volt  storage 
battery,  the  rate  should  be  2  amperes;  on  a  12-volt 
battery  the  rate  will  be  i  ampere.  If  the  charger 
delivers  less  current  than  the  above  amounts,  and 
still  gives  some  current  greater  than  zero,  turns 
should  be  added  to  winding  S"  until  the  proper  rate 
is  attained.  The  percentage  of  turns  it  is  necessary 
to  add  may  be  calculated  from  the  percentage  de- 
viation from  the  normal  charging  rate.  In  case 
the  charger  fails  entirely  to  operate,  first  look  for 
loose  wires  or  broken  connections.  Then  try  re- 
versing the  battery  leads  or  clips  and  observe  if 
charging  ensues.  Occasionally  it  will  require  the 
addition  of  several  turns  of  wire  to  winding  S"  in 
order  to  obtain  satisfactory  starting  of  the  tungar 
arc,  but  tfhis  should  be  necessary  only  when  the 
transformer  has  been  assembled  or  wound  care- 


650 


Radio  Broadcast 


lessly.  The  extra  turns  are  then  necessary  to  off- 
set the  excess  leakage  flux  from  the  transformer  core. 
When  the  charger  has  been  adjusted  so  that  it 
does  charge  at  the  proper  rate,  it  should  be  left 
charging  for  at  least  two  hours  under  inspection 
before  it  is  pronounced  satisfactory.  During  the 
inspection  period,  tests  should  be  made  of  the 
core  and  coil  temperatures.  They  will  normally 
run  at  such  a  temperature  that  the  hand  can  just 


be  held  upon  the  hot  parts  without  burning.  Occa- 
sionally a  charger  will  be  found  that  will  blister  the 
hand  if  left  on  more  than  i  5  seconds,  but  this  charger 
is  running  at  a  high  loss.  If  the  temperature  of 
any  of  the  parts  become  as  hot  as  this,  look  for 
short-circuited  turns,  low  quality  steel,  or  careless 
assembly  of  the  core.  Any  of  these  three  points 
will  in  itself  be  sufficient  to  warrant  rebuilding  the 
transformer. 


/NTEREST  among  radio  constructors  is  very  strong 
in  the  problems  offered  in  the  design  and  construction 
of  chemical  plate  supply  units.     James  Millen,   in  the 
June  RADIO  BROADCAST,  described  an  inexpensive  chemi- 
cal plate  supply  unit  which  has  been  built  by  a  large  num- 
ber of  experimenters.     Another  article  by  Mr.  Millen  will 
appear  in  an  early  number  of  the  magazine.     It  will  dis- 
cuss the  problems  encountered  in  his  and  other  chemical 
rectifiers,  and  answers  to  many  queries  about  variation  in 
the  use  and  design  of  this  unit. 


The  New  Transmitting  Station  of  "Radio  Broadcast" 


FOR  the  past  three  months,  the 
Laboratory  of  RADIO  BROADCAST 
has  had  a  short  wave  transmitter 
in  operation.  The  beginnings  have  been 
modest,  for  the  antenna  is  supplied  by  a 
fifty-watt  tube,  operating  on  a  plate  volt- 
age of  1 100.  A  wavelength  of  40  meters 
is  now  in  use,  although  in  the  near  fu- 
ture the  station  will  also  be  operating 
on  the  lower  waves  at  present  permitted 
in  the  amateur  communication  band.  Al- 
though various  methods  of  plate  supply 
have  been  tried,  the  transmitter  is  now 
operating  from  a  bank  of  B  batteries,  and 
a  good  deal  of  experiment  is  in  progress 
with  the  problems  involved. 

Since  the  call  letters  of  the  RADIO 
BROADCAST  station,  2GY,  were  assigned, 
a  large  number  of  cards  from  amateurs 
who  have  heard  our  signals  have  been  re- 
ceived. Since  2GY  is  listed  in  the  current 
Government  list  of  United  States  amateur 
call  letters,  practically  all  of  the  cards 
announcing  the  successful  hearing  of  2GY 
have  been  sent  to  Mr.  F.  X.  Hayes,  162 
East  82nd  Street,  New  York,  the  former 
possessor  of  that  call. 


Amateurs  who  hear  our  station  are 
asked  to  address  their  cards  to  the  Direc- 
tor of  the  Laboratory,  RADIO  BROADCAST 
Magazine,  Garden  City,  New  York. 
We  are  very  anxious  to  have  complete 
reports  from  any  listening  amateur  who 
will  be  good  enough  to  send  them  to  us. 
An  acknowledgement  will  be  sent  in  reply. 

The  transmitter  in  its  present  experi- 
mental stage,  has  a  dependable  daylight 
range  of  between  eight  hundred  and  a 
thousand  miles.  Communication  has 
been  established  with  many  radio  ama- 
teurs who  are  located  within  a  thousand- 
mile  radius  of  Garden  City. 

A  number  of  interesting  experiments  in 
short  wave  transmission  are  in  progress, 
and  in  later  numbers  of  this  magazine 
they  will  be  described.  It  need  not  be 
thought  by  the  broadcast  listener  that 
transmitting  experiments  of  this  sort  are 
uninteresting  to  him.  On  the  contrary, 
some  of  the  most  fascinating  experiments 
being  conducted  in  radio  to-day  lie  in  the 
field  of  short  waves.  Many  of  the  prob- 
lems to  be  solved  in  this  work  are  very 
similar  to  those  in  the  broadcast  field. 


RADIO  BROADCAST  Laboratory  Analyzes  Devices  Commercially  Available  to 
Help  Operate  Receivers  from  Alternating  Current  —  Helpful  New  Devices 
from  the  Manufacturers  for  the  RADIO  BROADCAST  Phonograph  Receiver 

BY  THE  LABORATORY  STAFF 

^TT     TfACH  mo-nth,  the  RADIO  BROADCAST  Laboratory  will  bring  to  its  readers  some  of  its 
^j     •*-'  findings  in  the  field  peopled  by  the  manufacturers.     The  purchaser  of  radio  equip- 
l/    ment  has  little  chance  to  find  out  what  is  wheat  and  what  is  chaff  among  the  material 
that  is  for  sale — that  has  become  one  of  the  tasks  of  the  Laboratory.     It  is  obviously 
impossible  to  test  in  the  Laboratory,  to  illustrate,  or  even  mention,  all  radio  equipment 
which  appears  for  sale.     The  apparatus  mentioned  in  these  pages  is  neither  all  that  has 
been  tested  nor  that  which  we  believe  to  be  the  best  on  the  market— it  is  merely  representa- 
tive equipment.     Nothing  in  which  the  Laboratory  does  not  believe  will  be  described,  nor 
will  advertisements  of  poor  apparatus  coming  from  unreliable  concerns  be  included  in 
this  magazine. — THE  EDITOR 


A    THE  present  time,  there  are  two  types  of 
apparatus  for  sale  to  the  radio  public  that 
operate    from    the    light   socket,    battery 
chargers  and  battery  eliminators.     Of  the 
chargers  there  are  three  kinds,  depending  upon  the 
type  of  rectifying  element  that  is  used — whether 
vacuum    tube,   chemical,   or   mechanical.     Of   the 
eliminators,  there  are  only  two,  since  a  mechanical 
rectifier  has   not,   as   yet,   put   in   its   appearance. 
These  two  types  eliminate  only  the  B  battery,  al- 
though manufacturers  promise  that  the  near  future 
will  see  devices  which  will  eliminate  the  A  battery 
as  well.     !t  is  only  a  question  of  time  until  it  will  be 
possible  to  get  A,  B,  and  C  batteries  from  a  light 
socket. 

Tube  battery-chargers  consist  essentially  of  a 
transformer  to  change  the  alternating  voltage  cur- 
rent to  the  proper  value  to  operate  the  tube  and 
deliver  the  charging  current;  a  Tungar  or  Rectigon 
two-element  tube,  which  is  the  rectifier  element, 
changing  alternating  current  to  pulsating  direct 
current;  and  certain  resistances  which  are  required 
to  reduce  the  voltage  to  the  proper  value  for  charg- 
ing A  or  B  batteries. 

The  Acme  charger,  which  is  illustrated,  was  sent 
to  the  Laboratory  for  test  and  after  performing  well 
all  winter  still  pushes  two  amperes  into  the  Labora- 
tory batteries.  Similar  chargers  are  made  by  others, 
and  those  sent  to  the  Laboratory  by  the  Westing- 
house  and  General  Electric  companies  are  examples 
of  a  very  high  grade  of  electrical  equipment. 

Chemical  chargers  have  a  transformer  and  one  or 
more  jars  of  solution  in  which  are  two  metallic 
elements.  Current  will  pass  through  the  affair  in 
one  direction  but  not  in  the  other.  The  Balkite 
charger,  now  in  the  Laboratory,  may  be  used  when 
the  receiving  set  is  in  operation — provided  the 
battery  is  not  too  low  in  charge, 


Mechanical  chargers  have  vibrating  contacts 
which  permit  current  to  flow  into  the  battery  in  the 
proper  direction  at  the  proper  time.  They  make  a 
a  humming  noise  in  operation,  and  like  all  other  A 
battery  chargers,  their  efficiency  is  about  25  per 
cent,  when  in  actual  use.  In  other  words,  75  per 
cent,  of  the  power  put  into  the  charger  disappears 
there  and  only  one  fourth  gets  into  the  battery. 

The  Full-Wave  Charger  made  by  the  Liberty 
Electric  Corporation  of  New  York  City  has  been  in 
use  in  the  Laboratory  and  is  a  fast  worker.  The 
Ward-Leonard  variable  resistance  in  the  photo- 
graph is  used  to  lower  the  output  voltage  so  that  B 
batteries  may  be  charged  at  various  rates  not  to 
exceed  one  third  of  an  ampere.  A  lamp  may  be 
used  in  place  of  the  resistance,  the  size  depending 
upon  the  voltage  of  the  battery  to  be  charged  as 
well  as  the  rate  desired. 

BATTERY    ELIMINATORS 

HP  HERE  is  great  interest  in   battery  "elimina- 
*  tors"  at  the  present  time.     The  more  important 
questions  to  be  asked  by  a  prospective  purchaser 
are: 

1.  Is   the    eliminator   effective? 

2.  Is  it  economical? 

3.  How  long  will  it  last? 

4.  Is  it  quiet  in  operation? 

All  eliminators  consist  of  a  transformer,  a  rectify- 
ing device,  and  a  filter.  The  transformer  boosts  the 
no  volts  a.  c.  to  whatever  voltage  is  required  so 
that  the  output  is  about  90  volts  after  accounting 
for  the  voltage  drops  in  the  rectifier  and  the  filter. 

Tube  eliminators  employ  standard  s-volt,  three- 
element  receiving  tubes,  or  special  two-element 
rectifier  tubes,  and  are  high  resistance  devices.  In 
Other  words,  the  more  current  that  is  drawn  from 


652 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 

Substitutes  for  B  batteries  are  of  two  kinds,  and  here  are  examples  of  both  of  them.     The  Balkite  device 

uses  a  chemical  rectifier  and  is  made  by  the  Fansteel  Products  Co.      The  Super-Ducon  uses  a  vacuum 

tube  as  the  rectifier  and  is  made  by  the  Dubilier  condenser  people.     The  photo  btlow  shows  the  Acme 

charger  with  a  Philco  A  battery.     All  have  been  in  use  in  the  Laboratory. 


RADIO  BROADCAST  Photograph 


Shall  !   Run  My  Set  from  the  Lamp  Socket 


653 


The  Apco  B  substi- 
tute using  two  recti- 
fier tubes,  and  a 
convenient  layout  of 
accessory  apparatus 


RADIO  BROADCAST  Photograph 


The  transformers  below  for  transforming  1 10  volts  a.  c.  to  the 

voltage  required  for  other  purposes  are  made  by  the  Dongan 

Electric  Mfg.  Co.,  and  the  Radio  Foundation 


RADIO  BROADCAST  Photograph 


RADIO  BROADCAST  Photograph 


Two    electrical    instruments    from  well  known   manufacturers.     The  Eveready  A 
battery  and  the  Westinghouse  A  battery  charger  —  which  will  also  charge  B  batteries 


654 


Radio  Broadcast 


The  A.  C.  tube  to- 
gether with  several 
rectifier  tubes 
which  serve  the 
various  purposes 
outlined  in  the  text 


RADIO  BROADCAST  Photograph 


A  B  battery  substitute  that  anybody  may  build  up  from  Moliiformer 
parts.     Here  are  chemical  rectifier  jars,  filters  and  a  transformer. 


The  Full  Wave  charger  with  a  resistance  such  as  the  Ward 
Leonard  shown  will  charge  B  batteries  at  the  proper  rate 


Shall  I   Run  My  Set  from  the  Lamp  Socket 


655 


RADIO  BROADCAST  Photograph 

Several  interesting  devices  that  have  been  sent  to  the  Laboratory.     They  are  variable  high  resistances, 
a  pilot  lamp,  a  lock  filament  switch  and  a  ballast  resistance  designed  to  eliminate  the  need  of  rheostats 


RADIO  BROADCAST  Photograph 

Two  views  of  a  tube  socket  panel,  the  lower  made  by  Burton  &  Rogers  of  Boston,  the  upper  one  by  The 
Alden  Mfg.  Co.,  of  Springfield,  Mass.     Both  are  designed  for  RADIO  BROADCAST'S  Phonograph  Receiver 


RADIO  BROADCAST  Photograph 


656 


Radio  Broadcast 


them  the  lower  will  be  the  output  voltage.  That  is  a 
disadvantage  and  is  due  to  the  high  resistance  in  the 
tube  itself  and  in  the  filter.  If  a  sufficiently  high 
voltage  is  used  at  the  start  and  if  control  resistances 
are  included,  this  disadvantage  may  be  partially 
overcome.  There  is  one  advantage  in  the  high  re- 
sistance feature  since  it  is  impossible  to  draw  enough 
current  from  the  device  to  blow  up  tubes,  during 
accidental  mix-ups  in  A  and  B  battery  leads. 

Chemical  B  battery  suppliers  are  generally  low 
resistance  affairs,  and  the  output  voltage  is  more 
independent  of  the  output  current  load.  The 
Balkite  eliminator  is  an  excellent  example  of  this 
type  of  supply  unit. 

THE    LIFE    OF    A    TUBE    TYPE    ELIMINATOR 

'"THE  useful   life  of  a   tube  operated  eliminator 

*  depends  entirely  upon  the  life  of  the  tube. 
In  practice,  the  tube  is  used  as  a  two-element  recti- 
fier and  receiving  tubes  do  not  have  sufficient  elec- 
tron emission  to  stand  up  under  this  kind  of  treat- 
ment. In  the  Laboratory,  an  average  life  of  200 
hours  has  been  obtained  with  receiving  tubes  with  a 
five-tube  set  drawing  about  25  mils.  Some  tubes 
lasted  about  50  hours,  others  as  long  as  400  hours, 
but  the  average  is  too  low.  Special  two-element 
tubes  are  now  on  the  market  for  this  service 
and  samples  have  been  sent  to  the  Laboratory 
from  Kellogg,  Dubilier,  Sea  Gull,  and  Timmons. 
An  average  life  of  600  hours  may  be  expected  from 
this  newer  type  of  tube. 

Eliminators  employing  two  tubes  will  last  longer 
and  deliver  a  better  form  of  current — theoretically, 
at  least.  The  component  parts  of  such  a  set  are 
well  shown  in  the  photograph  of  the  Apco  layout, 
and  the  "works"  of  a  chemical  supply  unit  may  be 
seen  in  the  Molliformer  kit  photograph. 

Tube  B  battery  substitutes  have  been  sent  to  the 
Laboratory  by  the  following  manufacturers,  Tim- 
mons, Kellogg,  Mayo,  Rhamstine,  Dubilier,  Apco, 
and  Mu-Rad. 

Several  interesting  tubes  are  shown  in  the  ac- 
companying photographs.  They  are  the  Rectron 
of  Dubilier  (used  in  the  Super-Ducon)  for  B  battery 
eliminator  service,  a  Tungar  for  charging  batteries, 
the  McCuIlough  tube  whose  filament  runs  from 
a.  c.,  the  S  tube  of  the  Amrad  Corporation  and  the 
Neon  Tube  of  the  Neon  Products  Corporation. 
The  latter  two  do  not  have  filaments  and  operate 
upon  the  gaseous  conduction  principle.  They  may 
be  used  in  either  receiving  or  transmitting  rectifiers, 
since  100  milliamperes  may  be  taken  from  them 
safely. 

The  filters  used  in  these  various  types  of  B  battery 
suppliers  are  required  to  iron  out  the  remaining  hum 
which  is  due  to  the  alternating  current.  If  the 
filter  has  high  enough  inductance  and  enough  con- 
densers, the  hum  will  not  be  noticeable  on  either 
loud  speaker  or  head  phones,  and  is  a  vital  part  of 
the  instrument. 

A  step-down  transformer  is  necessary  for  theMc-  ' 
Cullough  tube,  and  two  are  illustrated  in  this  article. 


One  is  made  by  Dongan  and  the  other  by  the  Radio 
Foundation.  A  special  transformer  which  supplies 
low  voltage  for  amplifier  filaments  and  350  volts  for 
power  amplifier  plate  is  also  illustrated. 

In  deciding  to  purchase  a  battery  eliminator,  the 
prospective  owner  should  discover  whether  it  will 
cost  him  more  to  run  than  batteries,  if  it  will  be  more 
convenient,  and  if  more  convenient  and  more  ex- 
pensive whether  it  is  worth  it.  An  average  five- 
tube  set  worked  three  or  four  hours  a  day  will 
cost  about  $15  a  year  in  B  batteries,  and  an 
average  B  battery  eliminator  can  be  run  ten  hours 
for  one  cent,  payable  to  the  lighting  company. 
Special  tubes  or  the  old  type  201  tungsten  filament 
tube  should  last  at  least  500  hours — and  there  you 
are. 

PHONOGRAPH    RECEIVER    APPARATUS 

A  NUMBER  of  interesting  gadgets  have  come  to 
•**  the  Laboratory  which  have  an  application  to 
the  Phonograph  Receiver.  One  of  these  is  an  A 
battery  protector  which  automatically  breaks  that 
circuit  when  too  much  current  is  drawn.  It  is 
made  by  the  Precise  Corporation  of  Rochester  who 
made  circuit  breakers  for  power  companies  before 
radio  was  literally  on  earth.  It  will  protect  a  bat- 
tery from  accidental  short  circuit,  or,  when  charging 
batteries  from  current  surges. 

Four-tube  base  panels  are  made  by  Benjamin 
Electric  Company  of  Chicago,  Alden  of  Springfield, 
and  Burton  &  Rogers  of  Boston.  The  latter  has 
the  sockets  set  somewhat  below  the  panel  so  that 
considerable  space  is  saved.  Views  of  these  panels 
are  shown. 

Pilot  lamps  to  tell  one  when  tubes  are  lighted  are 
made  by  Yaxley,  and  Carter  of  Chicago.  These 
small  lamps  are  set  behind  the  panel  with  a  glass 
window  through  which  they  may  be  seen.  They 
take  about  .1  ampere  at  five  volts,  and  make  an  at- 
tractive and  useful  addition  to  any  receiver. 

Ballast  resistances  which  will  take  the  place  of 
rheostats  in  filament  control  have  been  sent  to  the 
Laboratory  by  Daven  and  Amperite. 

A  useful  and  interesting  lock  switch  I-.as  recently 
come  to  the  Laboratory  from  Carter.  This  switch 
turns  on  or  off  the  filaments  and  requires  a  key 
similar  to  that  used  in  automobile  locks. 

Two  volume  controls  have  presented  themselves, 
one  known  as  a  Clarostat  and  the  other  a  graphite 
resistance  of  several  ranges  sold  by  Electrad,  Inc. 
Both  of  these  may  be  used  as  volume  controls — as 
may  the  Bradleyohm — by  placing  them  across 
audio-frequency  transformers;  for  B  battery  elimina- 
tors and  for  any  other  purpose  where  a  high  variable 
resistance  is  needed. 

A  very  useful  place  for  such  variable  resistance  is 
across  a  fixed  tickler,  to  control  regeneration  in  a 
detector  circuit  as  in  the  Roberts  circuit.  The  ease 
of  control  appeals  to  the  operator  of  the  receiver, 
and  the  fact  that  amplifier  plate  voltages  may  be 
placed  on  the  detector  eliminates  the  business  of 
tapping  a  B.  battery. 


Shall  I   Run  My  Set  from  the  Lamp  Socket 


657 


Two  receivers  and  a  loud  speaker  are  illustrated  in  these  photographs.  The  receivers  are 
the  Clearfield  and  the  Richardson  "5"  Th  .y  are  both  of  the  tuned  radio  frequency  type. 
The  Superspeaker  Console  speaker  comes  /ro.,i  the  Jewett  Radio  and  Phonograph  Co! 


aiiiiiimmminiiiimiiiimimmiiiMiiiii  ......  iiMMiMiiiiiiinMiiinniiuiiiiMiiMMniiiiiiiiiiiiiiiiiiiiiMiMiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiHiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiMiiliiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiniiniiiiiiJ 

' 


I  HAv/E  FOUND.    .    .     . 

A  Department  ^here  Readers  Can  Exchange  Ideas 
and  Suggestions  of  Value  to  the  Radio  Cons  trucfor  and  Operator 

33  r 


A  FIFTEEN  DOLLAR  CW  "LOW 
LOSSER" 

MANY  fans  wish  to  know  something 
about  the  shorter  wave  work,  which  is 
both  c.  w.  (continuous  wave)  and 
phone.  It  is  very  much  worth  while  to  build 
a  "low  losser"  for  such  work  because  the 
results  obtained  are  noticeably  superior. 

Low-loss,  when  stripped  of  all  technicalities, 
simply  means  high  efficiency.  The  big 
bugaboo  of  radio  is  resistance.  So,  any  set 
which  is  built  with  the  idea  of  reducing  this 
will  be  a  low-loss  one  and  therefore  of  so  much 
higher  working  efficiency.  That  being  the 
case,  make  up  your  mind  that  the  best  is  the 
cheapest  in  the  long  run  and  you  will  not  spoil 
what  otherwise  is  an  excellent  set.  The  total 
cost  will  not  be  over  fifteen  dollars,  exclusive 
of  tubes,  batteries,  and  the  head  telephones. 

The  three  circuits  A,  B,  and  C  shown  in 
Fig.  3,  are  all  suitable  for  our  purpose,  but 
A  has  the  disadvantage  of  being  coupled  too 


FIG.   I 

Looking  at  the 

receiver   from 

the  rear 


closely  to  the  antenna  and  we  may  therefore 
disregard  it.  B  and  C  are  not  open  to  this 
objection,  as  the  antenna  circuit  is  coupled 
inductively  to  the  secondary  and  entirely 
separate  from  the  rest  of  the  set.  The  choice 
between  these  two  lies  only  in  the  method  of 
securing  the  feedback  control.  In  B  it  is 
secured  by  the  tickler  coil  method  so  well 
known  to  the  exponents  of  the  so-called  "three 
coil  tuner."  In  C  it  is  obtained  by  a  variable 
condenser.  Take  your  choice. 

Coil  P  need  consist  of  but  three  turns  of  No. 
1 8  "bell  wire"  3^  inches  in  diameter  and 
bound  or  taped  into  circular  form.  Then 
mount  it  in  any  fashion  so  as  to  have  it 
"stood  up"  a  few  inches  from  the  grid  lead  of 
coil  S.  An  easy  way  to  do  this  is  to  support 
the  free  ends  in  two  binding  posts. 

Coil  S  is  constructed  as  follows:  obtain  two 
pieces  of  bakelite  tubing  each  3^  inches  in 
diameter  and  one  half  inch  long.  Obtain 
also  six  strips  of  bakelite  each  J  inch  thick, 
I  inch  wide  and  3  inches  long.  Mark  the 


A  Low-Loss  Short-Wave  Receiver 


659 


FIG.    2 
A  front,  panel  view  of  the  receiver 


periphery  of  each  bakelite  tube  into  six 
equally  divided  segments  and  drill  a  hole  to 
take  a  6-32  brass  bolt  at  each  point.  Drill 
the  ends  of  the  strips  with  similar  holes  and 
you  then  have  a  nearly  cylindrical  form  for 
winding,  the  ends  of  which  are  the  two 
bakelite  tube  pieces  and  the  sides  of  which 
are  the  strips.  In  case  bakelite  is  not  avail- 
able dry  wood  may  be  used  and  the  strips 
mounted  with  the  aid  of  small  wood  screws. 
Be  sure  to  have  all  wood  thoroughly  dry  and 
to  treat  it  with  a  light  coat  of  melted  paraffin 
to  prevent  moisture  absorption. 

Various  methods  of  mounting  this  coil  may 
be  devised.  The  writer  attached  an  old 
Paramount  coil  mount  by  means  of  two 
machine  screws  and  used  an  ordinary  Remler 
honeycomb  coil  mount  as  receiver  for  it.  Two 
Remlers  will  do  the  same  thing  and  such  an 
idea  enables  coils  to  be  easily  shifted  for 
different  wavelength  ranges.  For  the  longer 
amateur  waves,  fifteen  turns  of  No.  18  bell 
wire  are  used  and  ten  turns  for  lower  waves. 

For  the  tickler  coil  "ball  assemblies"  may 
be  made  or  purchased  and  first  treated  with  a 
paraffin  bath.  Be  sure  to  place  your  tickler 
at  the  filament  lead  of  S  to  reduce  its  effect  on 
tuning  and  remember  to  reverse  its  leads  if 
regeneration  is  not  first  obtained.  A  small 
fickler  of  more  turns  has  less  disturbing  effect 


on  tuning  than  a  larger  one  of  fewer  turns. 
The  number  of  turns  varies  in  different  sets, 
but  ten  turns  may  serve  as  a  trial. 

A  small  radio  frequency  choke  may  be 
needed  at  Ch  in  C. 

In  using  condenser  feedback,  merely  wind 
coil  S  and  continue  the  winding,  adding  about 
ten  turns  to  comprise  the  feedback  winding, 
having  provided  a  twist  tap  for  filament. 
The  feedback  condenser,  here,  may  be  of 
.00025  mfd. 

A  well  made  variable  condenser  is  a  positive 
necessity.  It  should  have  a  small  amount  of 
insulation  present,  it  should  be  mechanically 
rigid,  and  good  electrical  connection  must  be 
had  between  members.  The  capacity  should 
be  .00025  mfd.  maximum. 

A  good  socket  and  variable  grid  leak  are  to 
be  included.  Finally,  be  sure  you  have  a  real 
antenna  and  ground.  A  single  wire  is  suffici- 
ent. No  panel  layout  is  given  here  because 
so  many  experimenters  will  wish  to  work  out 
their  own. 

In  operating  the  set,  note  that  the  distance 
of  the  coil  P  may  be  varied  from  S  as  an  ad- 
vantageous feature  because  smooth  tuning 
may  not  be  had  otherwise  due  to  a  reson- 
ance effect  in  the  antenna,  causing  a  "blank" 
in  the  tuning  dial. 

Several  novel  features  to  be  noted  in  this  set: 


66o 


Radio  Broadcast 


1 .  Ease  of  coil  changes. 

2.  Filament  connections  by  plug  and  jack,  allow- 
ing ease  of  change  to  another  set. 

3.  Use  of  Fahnestock  clips  as  the  set  is  primarily 
an   experimental   one   and   changes   may   be 
easily  made. 

4.  A  low-loss  coil  that  is  mechanically  strong 
and  electrically  efficient. 

5.  A  set  which  is  simple,  efficient,  and  easy  to 
operate. 

6.  A  set  which  is  very  low  in  cost. 

— C.  S.  MUNDT,  San  Francisco,  California. 
TWO  SHOP  TRICKS 

HERE'S  an  idea  for  a  simple  home  made 
rig  for  cutting  spiderweb  coil  forms,  bezel 
holes  in  panels,  or  holes  for  the  Ballan- 
tine  vario-transformers.  First  drill  a  center 
hole  with  about  a  f -inch  twist  drill  in  the  panel, 
then  drill  a  hole  in  a  piece  of  hard  wood  about 
|  x  j  x  6  inches  long.  Remove  the  drill  from 
the  brace  or  hand  drill  and  leave  the  drill  in 
the  piece  of  wood.  Next  take  a  small  file  and 
grind  the  end  down  as  shown  in  the  sketch, 
Fig.  4,  and  clamp  the  file  to  the  piece  of  wood 
with  two  five-and-ten-cent-store  clamps.  Fit 
the  drill  in  the  center  hole  in  the  panel  and  go 
round  and  round  and  back  and  forth,  holding 
the  drill  in  the  left  hand  and  the  stick  in  the 
right.  A  stick  6  inches  long  will  give  you 
plenty  of  leverage.  Cut  from  both  sides  and 
the  result  is  a  clean  cut  hole  and,  best  of  all,  it 
is  round.  I  can  cut  spiderweb  forms  with 
this  which  have  one  tooth  longer  than  the 
others  for  support  and  all  are  the  same  size 
and  look  like  factory  goods. 

This  is  a  suggestion  for  a  three-plate  vernier 
condenser  built  for  about  tweny  cents,  and 
looks  well  from  the  front  of  the  panel.  First 
get  a  panel  switch  with  bushing  and  about  five 
cents  worth  of  common  sheet  zinc  (same  as 
used  for  flashing).  Cut  out  a  piece  the  size 
shown  and  solder  it  to  the  end  of  the  switch 


Made  From  an  Old  File.-, 


.00025  mfd. 


Center  Hole 


PANEL - 


FIG.  4 


FIG.  3 


shaft.  After  cutting  out  the  other  piece  to 
the  shape  shown  fasten  it  to  the  panel  with 
screws  and  nuts  or  you  can  use  switch  points 
if  you  have  them  on  hand.  Connect  this  in 
parallel  with  the  main  variable  condenser 
and  you  will  get  the  surprise  of  your  life. 
The  rotor  should  be  grounded.  I  made  one 
of  these  the  other  day  and  found  it  better  than 
the  ordinary  vernier  condenser.  See  Fig.  5. 
Only  the  switch  knob  shows  on  the  panel 
with  the  lever  cut  off. — WELSFORD  A.  WEST, 
Hopewell,  Nova  Scotia. 


A  Glass  Drill 


66 1 


AN  AUTOMATIC  POTENTIOMETER 
CUT-OUT 

NOW  that  multitube  radio  sets  are  being 
used  so  extensively  we  have  frequent 
recourse  to  potentiometers  to  stabilize 
the  radio  frequency  circuits.  In  the  usual 
hook-up  for  a  potentiometer,  Fig.  6  it  is 
hooked  up  directly  across  the  A  battery 
terminals.  This,  of  course,  slowly  uses  up 
current  and  as  sets  employing  r.  f.  consume 
plenty  of  current  without  the  help  of  a  con- 
tinual leak,  we  frequently  resort  to  some  form 
of  cut-out  switch. 

The  usual  ratings  of  potentiometers  are  200 
and  400  ohms.  The  loss  across  a  2oo-ohm  one 
amounts  to  about  0.03  amperes  day  and  night 
or  nearly  one  half  the  current  consumption 
of  a  uv-199  vacuum  tube.  The  4OO-ohm  size 
has  a  current  flow  of  0.015  amperes,  which  in 
three  or  four  weeks  would  run  down  a  storage 
battery  without  the  set  being  used  at  all. 

The  setting  of  a  potentiometer  does  not  af- 
fect this  loss,  as  the  entire  resistance  is  con- 
nected across  the  battery  and  turning  the  dial 
to  zero  does  not  open  the  circuit,  contrary  to 
the  belief  of  many  people. 


FIGS.  6  AND  7 

Fig.  7  shows  a  hook-up  that  automatically 
cuts  out  the  potentiometer  when  the  filament 
rheostat  of  the  first  r.  f.  tube  is  turned  off. 
The  ohmage  of  the  rheostat  is  added  to  that 
of  the  potentiometer,  but  that  does  not  detract 
from  its  efficiency. — K.  W.  ROOT,  Boston, 
Massachusetts. 

A  TOOL  TO  DRILL  HOLES  IN  GLASS 

TAKE    an    old   three-cornered   file    and 
on  an  emery  wheel,   smooth  down  the 
face  of  all  three  sides,  so  that  the  edges 
are  knife-like. 

Then  break  off  the  point  of  the  file,  say 
about  one  inch  from  the  bottom,  and  with 
the  emery  wheel  bring  all  the  sides  to  a  point 
as  in  Fig.  8. 

To  drill  holes  in  glass,  mark  your  holes  the 
same  as  on  a  bakelite  panel  but  use  a  glass 
cutter  to  make  the  center  mark.  Make  a 


LOOK 
PANEL  F 

f" 

*!* 

ING  ATT 
*OM  THE 

^ 

|  i 

IE 

HE 
REAR 

1       "I- 

c^\    7  * 

O/           TT 

[           ¥     * 

k-I^.^ 

"^iBend  Line 

J-- 

o! 

^"Radius 
on  Rotor 

-<  Determined  by  the  Length  >j 
of  Switch  on  Shaft 

THE.  WAY  TO 
BEND  THE  STATOR 


FIG.    5 

small  cross  where  you  want  the  hole,  then  take 
the  tool  and  put  it  in  a  brace.  Put  some 
turpentine  in  a  small  oil  can  and  apply  a  little 
on  the  tool.  Do  not  try  to  drill  too  fast  as  you 
are  apt  to  break  the  glass,  also  do  not  press  too 
hard  on  the  drill.  When  almost  through  the 
glass,  that  is,  when  the  point  comes  through 
the  other  side,  turn  the  glass  over  and  drill 
from  that  side.  Do  not  cut  too  fast  or  chip- 
ping will  occur. 

Be  sure  to  apply  plenty  of  turpentine  to  the 
tool  or  it  will  not  work  satisfactorily.  If  it 
is  desired  to  make  the  hole  larger,  use  a  file  of 
greater  size  and  ream  out  as  with  bakelite 
panels.  Be  sure  the  glass  is  on  a  level  founda- 
tion.— C.  J.  EISEN,  Watertown,  South  Dakota. 

Sharpened 
.'  Point  "• 


"Ground  File 
FIG.  8 

SEVEN  CONSTRUCTION  IDEAS 

TO  START  a  screw  in  an  inaccessible 
spot,  an  electrician  sticks  a  bit  of  tape 
over  the  end  of  his  screw  driver,  just 
thick  enough  to  make  a  snug  fit  in  the-screw 
slot.  In  this  way  he  can  start  the  screw  down 
a  hole  as  deep  as  the  screw  driver  itself. 

The  clock  maker  and  watch  maker  use 
wooden  screw  drivers  to  handle  their  small 
screws.  That  is  they  sharpen  a  toothpick  or 
wooden  skewer  to  make  a  snug  fit  in  the  screw 
slot.  You  can  start  a  nut  in  a  hard  place  by 
lightly  forcing  it  on  the  end  of  a  hardwood 
stick,  leaving  one  or  two  threads  free. 

Another  trick  is  to  wind  a  wire  around  the 
screw,  to  hold  the  screw  where  you  want  Co 


662 


Radio  Broadcast 


start  it.  The  wooden-screw  driver  or  the 
electrician's  tape  trick — paper  will  do  in  place 
of  the  tape — meet  most  emergencies,  however. 

Clockmakers,  when  they  break  off  a  steel 
screw  in  a  brass  plate,  boil  the  plate  in  alum 
water.  The  alum  attacks  the  steel,  but  not 
the  brass. 

Rubber  panels,  with  all  their  advantages, 
have  one  defect  which  must  be  watched. 
Under  constant  pressure,  rubber  gives;  and  a 
nut,  driven  home  tight,  will  gradually  loosen. 
Go  over  your  panel  after  a  few  weeks,  and  give 
all  nuts  an  added  turn  with  the  socket  wrench. 

Wind  the  NP  coil,  of  the  Roberts  set,  on  the 
same  frame  as  its  secondary,  using  No.  36,  or 
finer,  wire.  Wind  the  NP  on  first,  then  the 
secondary  on  top  of  it.  I  think  that  the 
diamond-weave  is  best,  giving  a  broader  wave 
band  and  sharper  tuning.  Remove  spokes  of 
the  winding  form,  and  sew  coil  together  with 
dental  silk.  Then  a  half-inch  strip  of  bakelite, 
•fa  inch  thick,  slipped  through  the  coil  makes 
a  firm  support  and  provides  space  for  ter- 
minals. 

This  use  of  fine  wire  primary  is  in  line  with 
recent  developments,  to  cut  down  capacity 
between  primary  and  secondary.  Grebe 
used  No.  40  wire  in  the  Synchrophase;  and 
Browning-Drake  concentrates  a  fine  winding 
in  a  narrow  slot  at  one  end  of  the  secondary. 

Wind  a  few  turns  too  many  on  the  second- 
ary; then  remove  the  excess,  turn  by  turn, 
until  the  right  hand  dial  tunes  exactly  like  the 
left  hand  dial. 

Space  the  tickler  coil  fully  an  inch  from  the 
face  of  the  secondary.  The  better  your  set  is 
designed,  the  fewer  tickler  turns  will  suffice. 
Start  with  15,  and  remove  them  turn  by  turn, 
until  it  just  spills  over  when  fully  advanced, 
on  the  high  wave.  In  a  lively  set,  with  a  de- 
tector tube  that  oscillates  easily,  12  turns 
should  be  enough.  Choose  a  good  oscillator 
for  your  detector  tube,  and  burn  it  as  low  as 
possible. 

Why  not  adopt  and  familiarize  the  prefix 
"pico"  for  micromikes?  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. 
Thus  our  standard  ratings  would  be  in  1000, 
500,  350,  and  250  picos,  for  tuning  condensers; 
and  we  would  specify  balancing  condensers 
as  from  5  to  10  to  50  picos.  Also,  to  say  a 
tuning  condenser  has  a  minimum  of  15  picos 
would  be  much  simpler  to  the  average  mind 


than  to  follow  the  present  practise  of  saying 
.000015  nifd. — F.  I.  ANDERSON,  New  York. 

MAKING  A  NEUTRALIZING  CON- 
DENSER 

A    NEUTRALIZING    condenser    can    be 

/-\  made  at  home  very  easily  and  at  the  same 

time  very  cheaply.     Get  a  piece  of  good 

dielectric  about  3  inches  long  and  drill  a  hole 

about  ^  inch  from  each  end.     Bend  two  pieces 

of  sheet  copper  or  brass  as  shown  in  Fig.  9. 

Fasten  them  to  the  base  by  means  of  binding 

posts.     Obtain  a  threaded  brass  rod  2^  inches 

long  that  will  fit  a  nut  taken  from  a  dry  cell. 


FIG.    9 

Solder  the  nut  to  one  of  the  bent  pieces  of 
copper  or  brass.  Get  a  piece  of  copper  about 
the  size  of  a  nickel  and  solder  it  to  the  brass 
rod,  screw  the  rod  into  the  nut  and  mount  a 
small  knob  on  the  other  end.  You  may 
neutralize  your  tubes  by  turning  the  knob 
back  and  forth,  varying  the  space  between  the 
disc  and  the  other  copper  angle. — CARL 
ROBERSON,  Laurel,  Montana. 


:~Panel 


FIG.   IO 


A  Substitute  Detector 


663 


A  GOOD  SINGLE  BEARING  FOR  ROTOR 
COILS 

THE  bearing  described  here  was  first 
made  for  use  with  the  self  supporting 
low-loss  coils  recommended  by  Mr. 
Silver  for  his  "Good  Four-Tube  Set." 

The  cross-section  sketch,  Fig.  10,  shows 
pretty  clearly  just  how  the  bearing  mounts 
and  works.  A  piece  of  regular  i-inch  brass  rod 
is  turned  down  on  one  end  and  threaded  to  the 
size  of  a  6-32  machine  screw.  Usually  this 
end  will  be  about  f-inch  long.  The  uncut  end 
of  the  rod  from  the  collar  out  is  left  standard 
length,  about  i  inch  long,  to  take  a  dial  or 
pointer. 

The  two  strips  in  the  drawing  are  cut  from 
some  scrap  3-16  inch  bakelite  or  similar 
material.  The  piece  B  may  be  about  3  by 
4  inches  instead  of  just  a  strip,  as  this  will 
give  the  stator  a  more  solid  rest.  It  will  also 
leave  plenty  of  room  for  mounting  binding 
posts  where  the  various  coil  connections  are 
made.  The  stator  is  firmly  clamped  between 
A  and  B  by  tapping  holes  and  fastening  with 
machine  screws  as  shown  at  C-C,  countersunk. 
This  whole  unit  which  now  holds  the  stator 
coil  is  clamped  to  the  back  of  the  panel  by  the 
two  machine  screws  at  D-D. 

Drill  the  panel  to  just  clear  the  j-inch  shaft. 
The  collar  will  rest  against  the  strip  B  just 
behind  the  panel.  Now  drill  the  strips  A  and 
B  to  just  clear  the  turned  parts  of  the  shaft, 
the  6-32  end. 

Place  a  brass  washer  over  th'e  shaft  and 
rest  against  inside  face  of  A.  A  small  spring 
is  placed  over  the  shaft  and  held  against  the 
washer  by  a  6-32  hexagon  brass  nut.  Place 
the  rotor  on  the  shaft  and  clamp  in  place  with 
the  second  nut. 

Tension  on  the  bearing  is  adjusted  by  tigh- 
tening or  loosening  the  two  brass  nuts.  This 
should  be  just  enough  to  allow  your  rotor  to 
stay  where  last  turned  without  any  undue 
binding.  I  find  this  a  real  economical  bearing 
which  solves  low  loss  coil  mounting  troubles 
and  is  easily  made  from  parts  in  your  "scrap 
box." — GERALD  GRAY,  West  New  York,  New 
Jersey. 

A  HANDY  CRYSTAL  DETECTOR 

A  BURN  ED   out    tube  can    be  used    in 
making    a    crystal    detector    that    is 
easily  substituted  for  the  detector  tube 
in  single  or  multiple  tube  sets. 

An  old  tube  is  held  in  a  gas  flame  until  the 
cement  holding  it  loosens  sufficiently  to  allow 


O<--  Use  No.17  Drill  ~ 

,-*°          °X 
/  No.17  O         \ 
\  ,-*o  o^  \ 

'Use  No.48  Drill*' 

O—  Use  Nc.17  Drill  - 


the  bulb  to  be  drawn  out  of  the  base.  A  small 
piece  of  brass  is  soldered  across  the  inside 
of  the  tube  base,  about  i  -32  of  an  inch  from  the 
top.  This  is  drilled  and  tapped  for  an  5-32 
screw  as  in  Fig.  1 1  A. 

Cut  a  piece  of  bakelite  or  hard  rubber  about 
two  inches  square  and  drill  as  shown  in  B. 

Solder  four  pieces  of  No.  18  bare  copper  wire 
3  inches  long  in  the  prongs  on  the  base,  allow- 
ing them  to  project  slightly.  Slide  the  bakelite 
over  the  wires  on  top  and  put  in  the  5-32  screw 
in  center.  The  wire  is  looped  around  machine 
screws  in  each  corner.  The  crystal  detector 
(which  can,  of  course,  be  a  fixed  one)  is  con- 
nected from  grid  to  plate,  which  is  the  same 
side  as  the  pin  is  on.  The  other  screws  which 
connect  to  plus  and  minus  filament  have  bind- 
ing posts.  See  C  in  Fig.  1 1. 

To  use  this  device,  remove  the  detector 
tube  from  its  socket,  short  circuit  the  grid 
condenser,  remove  the  detector  plus  B  wire 
from  the  battery  and  connect  it  on  the  binding 
post  of  the  crystal  detector,  but  be  sure  to  use 
the  one  which  leads  to  your  grid  return  as  in 
D. — FRANK  MEISTER,  Jersey  City,  New 
Jersey. 


QUESTIONS  AND 

^^3 


QUERIES  ANSWERED 


MAY    I    HAVE    A    CIRCUIT    AND    EXPLANATION     FOR 
THE   TESTING   OF   VACUUM   TUBES? 

E.   F.  McC. — Chicago,  Illinois. 

HOW  CAN   I   MAKE  A  TEST  FOR  A  GOOD  GROUND? 

N.  P.  L.— Brooklyn,  New  York. 

Is  THERE  SOME  SIMPLE  WAY  FOR  COMPARING  LOUD 
SPEAKERS? 

A.  S. — Newark,  New  Jersey. 

WlLL     YOU     PUBLISH     A     CIRCUIT     FOR     A     SIMPLE 
CRYSTAL    RECEIVER? 

M.  O. — Patterson,  New  Jersey. 


WHAT  is  MEANT  BY  "MATCHING  TUBES?" 

S.  T.  A. — Montreal,  Canada. 

CAN     THE      ROBERTS      RECEIVER      BE     USED     WITH 
A    LOOP? 

L.  A.- — San  Juan,  Porto  Rico. 

WHAT  COIL    COMBINATION    WILL    REPLACE    THE 
UV-I7l6  TRANSFORMER  IN  SUPER-HETERODYNES? 
V.  St.  M. — Baltimore,  Maryland. 

HOW     MAY     TOROin    COILS     BE     USED    IN    NEUTRO- 
DYNES? 

R.  M.  T. — Detroit,  Michigan. 


HOW  TO  TELL  THE  CONDITION  OF  VACUUM  TUBES 

HOW    efficient    are    your    vacuum   tubes?  A 
vacuum   tube,  to  be   satisfactory   must   be 
able  to  operate  over  a  long  period  of  time  at 
maximum  efficiency. 

Merely  inserting  a  tube  in  a  socket  and  noting 
whether  it  lights  does  not  constitute  a  practical 
test  of  the  tube's  efficiency.  Above  it  was  said 
that  a  tube  should  be  at  its  maximum  point  of 
efficiency  for  a  long  period  of  time  to  be  satisfactory 
but  this  is  the  only  figuratively  speaking.  Under 
actual  operating  conditions  the 
efficiency  of  a  tube  will  fall  off 
as  its  hours  of  use  increase. 

To  determine  the  condition 
of  a  tube  it  is  necessary  to  know 
several  things  such  as  input 
voltage,  its  filament  voltage 
and  amperage,  plate  voltage, 
and  the  current  in  milliamperes 
which  is  being  consumed  in  the 
plate  circuit.  To  know  these 
facts  a  test  circuit  having  me- 
ters for  testing  the  various  volt- 
ages and  currents  must  be  em- 
ployed. Such  a  circuit  is  sh6wn 
in  Fig.  i. 

Storage  battery  tubes  are 
usually  operated  at  5  volts  and 
at  this  potential  the  current 
consumption  should  not  be  over 
|  of  an  ampere  for  the  201 -A 
type.  Dry  cell  tubes  are  either 
of  3-volt  or  i^-volt  operating 
potential  and  draw  not  over 
.06  amperes  for  the  former  and 
.25  ampere  is  for  the  latter. 

When    tubes    are   new,    the 


electronic  emission  which  is  indicated  in  plate  mil- 
liamperes is  naturally  high  when  a  normal  plate 
voltage  is  applied,  say  90  volts.  As  the  tube  grows 
older  or  if  the  filament  is  burned  too  brilliantly  the 
plate  mils  decrease  quite  rapidly,  materially  affect- 
ing the  property  of  the  tube  to  function  correctly 
and  efficiently. 

With  the  meter  circuit  described  here  it  is  pos- 
sible to  make  graphs  of  the  function  of  a  tube  at 
various  grid  or  input  voltages.  By  means  of  the 
variable  resistance  Ri,  the  grid  voltage  may  be 
varied  from  10  volts  negative  to  10  volts  positive. 


Rj  -  400  Ohms 

R2  "     60  Ohms 

PM  -  Plate  Milliammeter 

PV  -  Plate  Voltmeter 


0-10 
0-120 


O-     A      +O 
6  Volts 


FA— Filament  Ammeter    0-1.5 
FV  -  Filament  Voltmeter    0-6 
G  V  -  Grid  Voltmeter        10-0-10 


FIG.     I 


RADIO  BROADCAST  ADVERTISER 


665 


A  N  attractive  cabinet  can  never  make  an 
**•  Ozarka  out  of  any  other  radio.  Far  too 
many  radio  buyers  pay  more  attention  to 
the  outer  appearance  and  not  enough  to 


When  your  automobile  runs  as 
the  manufacturer  intended  it 
should  it  is  a  real  pleasure  to 
drive  it.  But  what  do  you  do 
when  something  goes  wrong? 
Do  you  immediately  condemn 
the  car? — no.  Do  you  call  in  some 
handy  man  who  can  fix  any- 
thing?— no. 

You  send  for  a  service  man 
who  is  trained  in  repairing  your 
make  of  car.  To  correct  the 
fault  is  easy  for  him  because  he 
knows.  Some  other  mechanic 
might  have  to  tear  the  car  apart 
to  locate  the  trouble. 

The  same  is  true  of  radio,  no 
matter  what  price  you  pay — 
you  will  sometimes  need  the 
service  of  a  service  man.  If  he 
is  factory  trained  and  experi- 
enced he  can  and  will  deliver 
the  kind  of  service  you  know 
you  ought  to  have. 

Ozarka  instruments  are  only 
sold  by  direct  factory  repre- 
sentatives who  are  required  to 


122  Austin  Avenue  B 
Chicago,  Illinois 


Gentlemen:  Without  obligation  send  book  "Ozarka  In- 
struments No.  200"  and  name  of  Ozarka  representative. 


take  a  complete  course  of  in- 
structions in  Ozarka  service  di- 
rectly under  Ozarka  engineers. 
By  so  doing  we  are  assured  that 
every  purchaser  of  an  Ozarka 
will  have  an  experienced  service 
man  within  reach  at  all  times. 
3100  such  men  today  comprise 
the  Ozarka  service  organization 
— more  are  being  added  daily. 
Ozarka  service  does  not  add  a 
single  cent  to  the  price  you  pay 
for  your  radio — then  why  not 
benefit  by  it. 

Ozarka  instruments  are  sold 
only  in  competition  side  by  side 
with  others — do  your  own  tun- 
ing and  therefore  decide  for 
yourself  just  what  Ozarka  will 
do  for  selectivity,  distance,  vol- 
ume and  above  all,  tone. 

Send  for  the  book  Ozarka  In- 
struments No.  200;  please  give 
name  of  your  county  and  we'll 
gladly  have  our  Ozarka  repre- 
sentative arrange  a  demonstra- 
tion in  your  own  home. 


if  I  had 

]our  FurlWouldrtt 
e  a  Rabbit " 

the  inside.  The  service  behind  the  radio 
you  buy  is  even  more  important  than  the 
inside  or  outside,  your  satisfaction  depends 
on  it.  Let  us  see  just  what  radio  service  is. 

We  Need  a  Few  More 
OZARKA  Representatives 


RADIO  offers  a  wonderful  opportunity  to 
men  who  wish  to  get  into  business  for 
themselves.  It  is  work  that  can  be  done, 
at  the  start,  in  the  evenings  and  your  spare 
time.  You  can  hold  your  present  positon  and 
learn  radio  under  our  plan.  Ozarka  instru- 
ments have  been  on  the  market  for  four  years 
—they  have  successfully  met  all  competition. 
Ozarka  representatives  have  made  good,  not 
only  because  Ozarka  Instruments  are  right 
but  because  our  training  in  both  selling  and 
service  is  the  most  complete  possible. 
All  we  ask  is  that  you  are  willing  to  purchase 
your  demonstrating  instrument  and  willing  to 
learn  what  we  are  willing  to  teach  you. 
We  have  proven  with  3100  men  that  with  this 
training  you  can  make  good  in  radio.  The 
Ozarka  sales  course  consists  of  twelve  lessons 
— a  real  course  in  salesmanship  that  costs  you 
nothing  —  our  training  in  service  is  so  com- 
plete that  you  will  know  Ozarka  Instruments 
in  every  detail. 

Send  Coupon  for  Free  Book 

To  such  a  man,  who  will  freely  tell  us  some- 
thing about  himself  we  will  gladly  send  a  copy 
of  the  Ozarka  Plan  No..  100,  a  rather  unusual 
book.  You'll  find  it  interesting  because  it 
proves  why  some  men  are  millionaires  and 
now  others  made  them  so — why  some  men 
get  to  the  top  while  others  don't — best  of  all  it  will 
show  you  how  you  can  make  more  money  and  become 
really  independent.  Send  for  it  today,  but  please 
mention  the  name  of  your  county. 


Name.  .. 
Address. 


122  Austin  Avenue,  B 
Chicago,  Illinois 


City YOU'LL  KNOW 

THE  MAN  BY 
County State THIS  BUTTON! 


Gentlemen  :  I  am  greatly  interested  in  the  FREE  BOOK 
"The  Ozarka  Plan"  whereby  I  can  sell  your  instruments. 

Name  ........................................... 

Address  ........................  City  ........... 

County  ......................  State  ............... 


666 


Radio  Broadcast 


At  each  value  of  grid  volts  a  reading  of  plate  cur- 
rent (in  milliamperes)  is  obtained.  Only  the  grid 
volts  reading  is  varied.  The  plate  voltage  is  fixed 
at  a  definite  setting  such  as  90  volts.  The  filament 
circuit  is  adjusted  to  the  correct  filament  voltage 
and  amperage.  Thereafter  it  is  not  varied  for  that 
particular  tube. 

With  cross-section  paper  it  is  possible  to  make 
a  curve  of  the  operating  characteristics  of  the  tube. 
Along  the  left  hand  vertical  edge  of  the  paper  may 
be  indicated  the  plate  milliampere  readings,  and  the 
grid  volts  may  be  indicated  along  the  bottom  hori- 
zontal edge  of  the  paper. 

Starting  at  10  volts  negative  grid,  a  reading  of 
the  plate  current  is  taken  and  repeated  for  every 
two  volts  of  grid  input.  This  results  in  a  series  of 
points  which  gradually,  then  rapidly  and  then  again 
gradually  rise  diagonally  across  the  paper.  After 
the  readings  are  complete,  the  points  may  be 
joined  together  with  a  pencil  or  ink  line  producing 
a  characteristic  curve  of  the  tube.  See  Fig.  2. 

The  more  compact  and  vertical  the  curve  is  the 
better  the  tube  functions  as  an  amplifier.  When  the 


Detector 
Curve 


FIG.    2 

lower  or  upper  portion  of  the  curve  is  spread  out, 
the  tube  will  operate  very  successfully  as  a  de- 
tector. By  means  of  this  calibration  method  tubes 
may  be  compared  and  also  selected  for  their  vari- 
ous uses  in  a  radio  receiver. 

A    GOOD   GROUND 

THE  problem  of  securing  as  near  a  perfect 
ground  system  for  a  receiver  is  one  that 
should  receive  as  much  attention  as  the 
business  of  erecting  a  ship-shape  antenna. 

Cold  water  and  radiator  pipes  are  the  usual 
grounding  systems  employed,  but  where  the  BX 
covering  of  light  lines  or  in  some  instances  the 
neutral  line  of  a  3-wire  light  system  is  utilized  it 
is  well  to  make  sure  that  they  are  actually  grounded. 
To  do  this  screw  a  iio-volt  lamp  into  a  socket  to 
which  has  been  attached  two  leads  about  two  feet 
long.  Use  this  arrangement  as  a  test  circuit  by 
touching  one  of  the  leads  on  an  object  which  pre- 
viously has  been  quite  definitely  grounded.  Now 
with  the  other  free  lead  touch  its  end  to  first  one 
side  of  the  line,  then  the  other  and  finally  touch 
the  middle  line. 

A  circuit  should  occur  on  the  two  outside  lines 
indicating  that  they  are  not  grounded.  However, 
for  the  middle  line  there  will  be  no  circuit  inasmuch 
as  it  is  the  assumed  grounded  side  of  the  3-wire 
line.  Under  no  circumstances  should  the  lamp  be 
shunted  across  both  outside  lines  as  the  voltage 
there  would  be  about  220  volts;  blowing  out  the 
lamp. 

Needless  to  say  these  tests  should  be  made  at 
the  meter  box  where  the  3-line  system  enters  the 
house.  Now  while  this  test  will  indicate  that  the 
center  line  is  not  of  a  high  potential  in  respect  to 
the  ground  it  is  not  a  definite  indication  that  it  is 


2?      1  Assumed  Grounded  Line ^ 


FIG.    3 


Phones 


Ground 


grounded.  Therefore,  a  circuit  test  should  be  made 
as  shown  in  Fig.  3.  A  pair  of  phones  and  a  B  battery 
are  all  that  is  required.  If  a  click  occurs,  the 
middle  line  is  grounded. 

HOW    TO   COMPARE    LOUD    SPEAKERS 

RADIO  dealers,  experimenters  and  broadcast 
listeners  are  always  interested  to  know 
whether  or  not  their  loud  speaker  is  func- 
tioning satisfactorily. 

Considering  that  a  true  test  of  a  loud  speaker 
would  necessitate  an  elaborate  outlay  of  precision 
test  instruments  it  would  seem  that  for  those  who 
wish  to  know  how  their  own  type  of  reproducer 
operates  there  is  no  suitable  elementary  method  of 
attaining  such  ends.  This  is  not  entirely  true  where 
a  comparison  test  will  suffice. 

Such  a  method  is  outlined  and  best  understood 
by  the  circuit  diagram  in  Fig.  4.  A  microphone 
button  is  attached  to  the  pin  lever  of  a  phono- 
graph tone  arm.  The  primary  of  an  audio  fre- 
quency transformer  is  connected  to  the  terminals 
of  the  button  and  the  circuit  is  energized  by  a 
45-volt  battery.  By  means  of  a  two-point  switch 
which  is  connected  to  the  secondary  circuit  of  the 
transformer  as  shown,  it  is  possible,  when  loud 
speakers  are  attached  to  the  binding  posts,  to  flip 
over  from  one  to  the  other  making  comparisons  on 
volume  output,  the  quality,  resonance  points,  etc. 

The  music  or  other  audio  signal  is  obtained  by 
having  a  record  revolving  on  a  phonograph  turn- 
table. 

A  good  audio-frequency  transformer  is  an  ab- 
solute requisite  in  this  construction.  One  having 
plenty  of  iron  in  its  core  (which  is  of  large  size), 
large  windings  and  also  important  one  of  low  ratio 

Loud 
Speakers 


Microphone   Placed  on  Tone  Arm 
',  of  Phone grcph 


667 


TUNING       CONTROL 

Simplifies  radio  tuning.  Pencil  record 
a  station  on  the  dial — thereafter,  simply 
turn  the  tinder  to  your  pencil  mark 
and  you  Ret  that  station  instantly. 
Easy — quick  to  mount.  Eliminates 
fumbling,  guessing.  A  single  vernier 
control,  gear  ratio  20  to  1.  Furnished 
clockwise  or  anti-clockwise  in  gold  or 
silver  finish. 
Stiver,  $8.50  Gold,  $8.50 


, positive  funinq 


O  PEED— ability  to  turn  directly  to  any  station,  to 
k3  tune-in  instantly  and  get  your  station  without  inter- 
ference from  broadcasting  on  similar  wavelengths — is  the 
outstanding  feature  of  the  Ultra-Lowloss  Condenser. 

With  one  station  of  known  wavelength  located  on  the  dial,  all 
others  can  be  found  instantly.  Special  design  of  Cutlass  stator 
plates  distributes  stations  evenly  over  the  dial — each  degree  on 
a  100  degree  dial  represents  approximately  3^  meters  differ- 
ence in  wavelength. 

In  addition,  losses  common  in  other  condensers  are  reduced  in 
the  Ultra-Lowloss  to  a  minimum  by  use  of  only  one  small  strip 
of  insulation,  by  the  small  amount  of  high  resistance  metal  in 
the  field  and  frame,  and  by  a  special  monoblock  mounting  of 
fixed  and  movable  plates.  Designed  by  R.  E.  Lacault,  E.E., 
originator  of  the  famous  Ultradyne  receiver  and  Ultra-Vernier 
tuning  controls. 

At  your  dealer's;  otherwise  send  purchase  price  and  you,  ivill 
be  supplied  postpaid 


PHENIX  RADIO  CORPORATION          116-C  E.  25th  St.  New  York 


Tested  and  approved  by  RADIO  BROADCAST 


668 


Radio  Broadcast 


is  desired.  The  Rauland-Lyric  and  the  General 
Radio  285  and  28$A.  transformers  are  satisfactory 
for  such  purposes. 

Such  an  arrangement  offers  an  exceptional  field 
for  test  and  experiment  not  only  of  loud  speakers 
but  of  microphone  buttons  and  audio  transformers 
which  may  or  may  not  be  suitable  for  such  work. 

A    GOOD    CRYSTAL    RECEIVER 

FOR   a   good  crystal    receiver   circuit   we   are 
pleased  to  offer  that  indicated  in  Fig.  5. 
The  arrangement  is  simplicity  itself.     The 
parts  cost  is  very  low  and  such  items  as  the  coil  and 
detector  may  be  home-made.     Winding  A  consists  of 
415  turns  of  No.  22  d.  c.  c.  wire  wound  on  a  3^  inch 
cardboard    or    bakelite    tube.     The    ends    of    this 
winding  are  connected   to  the  variable  condenser 
terminals.     This  part  of  the  circuit  acts  as  a  se- 
lector trap. 

The  winding  B  is  wound  for  10  turns  directly  on 
top  of  winding  A.  It  is  insulated  from  winding  A 
by  a  strip  of  paper  or  cambric  cloth.  For  purposes 
of  experiment  it  may  be  advisable  to  have  winding 
B  wound  with  20  turns  of  wire  tapped  every  5  turns. 

A     THREE-TUBE     DOUBLE     REFLEXED     RECEIVER 

MANY  inquirers  want  data  and  a  circuit  dia- 
gram for  a  Roberts  receiver  which  could  be 
used  with  a  loop. 

In  RADIO  BROADCAST'S  Laboratory  it  has  been 
found  possible  to  operate  an  orthodox  four-tube 
Roberts  receiver  on  the  antenna  coil  secondary  with- 
out the  aid  of  an  antenna  or  ground.  Naturally, 
too,  a  loop  was  successfully  employed — but  only  for 
local  stations.  The  first  secondary  coil  was  merely 
replaced  by  a  loop  as  shown  in  Fig.  8. 

If  the  reflex  feature  is  taken  out  and  a  stage  of 
straight  audio  substituted,  much  better  quality  of 
signals  and  sharpness  of  tuning  will  be  observed. 

For  those  experimentally  inclined,  the  circuit  dia- 
gram Fig.  6.  should  prove  of  unending  interest. 
Here  is  shown  a  three-tube  double  reflexed  receiver 
equal,  in  theory,  to  a  standard  five-tube  set.  Ex- 


Antenna 


Crystal 
Detector 


=r  Grourid 


FIG.    5 


periments  have  been  conducted  at  RADIO  BROAD- 
CAST'S Laboratory  and  the  set  worked  very  well. 
But  from  a  "how-to-make-it"  standpoint  it  was 
felt  to  be  of  such  little  practical  value  that  it  was 
never  especially  described  in  the  magazine. 

Care  should  be  taken  in  placing  the  coil  units  so 
that  they  are  on  the  same  plane  and  at  right  angles 
to  each  other.  Bypass  condensers  are  also  impor- 
tant. For  best  results,  the  experimenter  should  try 
various  values.  Low  ratio  audio  transformers  have 
been  found  best  for  reflex  work  and  especially  so  in 
all  audio  amplifiers  where  tone  quality  of  the  highest 
degree  obtainable  is  desired.  This  data  is  advanced 
to  our  readers  for  what  it's  worth.  It  is  not  possible 
for  us  to  furnish  additional  constructional  notes  for 
a  completed  layout.  This  data  merely  is  to  be  re- 
garded as  of  an  experimental  nature. 

MAKING  TRANSFORMERS  FOR  THE  SUPER-HET 

FOR  about  a  year  after  the  UV-iyiG  long  wave 
radio-frequency   transformers    were    put   on 
the  market,  they  acted  as  dust  collectors  and 
paper    weights     in     many     retail     establishments 
throughout  this  country.     Many  of  the  radio  job- 
bers found  it  difficult  to  explain  to  these  dealers  why 


+  B  -*- 


RADIO  BROADCAST  ADVERTISER 


669 


Only 

specialists 

can  make 

good  fixed  condensers 

THE  small  fixed  condensers  in  your  radio  set  are 
there  to  help  you  get  clear  reception.  If  these 
little  condensers  are  not  made  most  accurately  the 
quality  of  reception  you  get  —  even  though  your  set 
may  be  excellent  in  all  other  respects*  —  will  be 
greatly  impaired. 

You  will  find  that  nearly  all  sets  made  —  in  fact  over 
90%  of  them  —  are  equipped  with  Dubilier  Micadons. 
This  is  the  name  by  which  all  Dubilier  fixed  con- 
densers are  known. 

Be  sure  your  set  —  whether  you  buy  it  or  build  it  — 
is  equipped  with  Micadons.  They  are  made  by 
specialists. 


CONDENSER    AND   RADIO    CORPORATION 


II 


Tested  and  approved  by  RADIO  BROADCAST 


6yo 


Radio  Broadcast 


.0002.? 


urns 


FIG..  7 

so  many  of  these  transformers  had  been  unloaded  on 
them  by  glib  salesmen.  "Who,"  they  would  ask, 
"wants  to  use  five  thousand  meter  transformers 
when  all  the  broadcasting  is  being  done  on  less  than 
six  hundred  meters?" 

George  J.  Eltz,  Jr.,  who  is  manager  of  the  Radio 
Department  for  the  Manhattan  Electrical  Supply 
Company,  found  this  question  extremely  embarras- 
sing. By  developing  a  super- 
heterodyne in  which  these 
transformers  would  be  used,  he 
helped  unload  the  shelves  of 
every  retail  store  in  the  country. 

Today  there  are  many  types, 
shapes  and  sizes  of  intermediate 
transformers,  but  for  those  who 
wish  to  make  their  own,  the 
data  presented  here  will  be  of 
interest  and  value. 

One  of  the  simplest  substi- 
tutes for  this  transformer, 
when  used  at  its  most  efficient 
point — about  47,000  cycles — 
may  be  made  as  follows: 

Procure  a  DL-2  50  coil  and  a 
piece  of  mailing  tube  just  large 
enough  to  pass  through  it  read- 
ily. On  the  mailing  tube  wind 
72  turns  of  No.  32  double  cotton- 
covered  wire.  These  72  turns 
form  the  primary.  The  DL-2 50 
coil  is  shunted  by  a  ,00025  mfd. 


variable  condenser.  See  Fig.  7.  The  current  in 
the  primary  from  the  plate  should  flow  in  the  re- 
verse of  that  entering  the  secondary  from  the  grid. 

In  the  development  of  the  super-heterodyne, 
several  designers  deemed  it  expedient  to  get  away 
from  the  long  wave  transformers  designed  to  cover 
a  wide  band  of  frequencies  in  favor  of  another  type 
for  which  certain  advantages  are  claimed.  This 
latter  type  requires  no  iron  in  its  core  nor  does  it 
require  tuning.  Its  fundamental  frequency  is  com- 
paratively high,  and  it  will  not  permit  audio- 
frequency disturbances  to  pass  through  the  radio 
stages. 

A  wooden  spool  2\  inches  in  diameter  with  two 
slots  3-16  inch  wide  separated  by  f  inch  and  with  a 
base  diameter  of  f  inch  is  the  winding  form  used  for 
the  windings.  In  the  interstage  transformers  the 
primaries  are  wound  with  800  turns  of  No.  32  d.s.  c. 
wire,  and  the  secondaries  with  1000  turns  of  the  same 
wire.  The  input  transformer  differs  only  in  having 
its  primary  winding  reduced  to  300  turns  so  that 
with  the  .0005  mfd.  condenser  across  this  winding 
it  resonates  at  approximately  99.9  K.  c.  (3000 
meters). 

The  outside  primary  lead  is  run  to  the  plate,  the 
outside  secondary  to  the  grid.  The  inside  primary 
goes  to  the  B  battery  and  the  inside  secondary  to  the 
stabilizer  arm.  The  input  transformer  is  used  to 
feed  from  the  first  detector  into  the  first  r.  f.  tube. 

TOROIDS    FOR    NEUTRODYNES 

ONE  of   the   latest   improvements  in   radio 
apparatus,  the  low  loss  toroid  coil,  can  be 
used  in  any  of  the  neutrodyne  and  tuned 
radio  frequency  receivers  to  increase  selectivity  in 
tuning  through  local  stations,  and  to  stabilize  the 
circuit.     Its  use  in  place  of  the  customary  aperiodic 
coupler  used  for  tuning  the  first  stage  will  improve 
the  average  receiver. 
The  interference,  noise,  and  general  tuning  quali- 


FIG.    8 


RADIO  BROADCAST  ADVERTISER 


671 


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NOW  anyone  can  build  the  finest  of  receivers  in 
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But  most  amazing  is  the  new  inductance  princi- 
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the  Erla  Circloid  principle  of  amplification. 

Four  vital  improvements  result  from  this  great 
discovery,  which  are  not  found  in  ordinary  sets. 

1.  Greater    Distance:    Erla   *Balloon   *Circloids 
have  no  external  field,  consequently  do  not  affect 
adjacent  coils  or  wiring  circuits.    This  enables  con- 
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2.  More  Volume:  Increased  radio  frequency  am- 
plification made  possible  by  Erla  Balloon  Circloids 
gives  concert  volume  to  distant  signals  inaudible 
with  receivers  of  conventional  type. 

3.  Increased  Selectivity:    Erla  Balloon   Circloids 
have  no  pick-up  quality  of  their  own.    Hence  only 
signals  flowing  in  the  antenna  circuit  are  amplified. 
Static  is  greatly  reduced  for  this  reason. 


4.  Improved  Tone  Quality:  The  self-inclosed 
field  of  Erla  Balloon  Circloids  eliminates  stray  feed- 
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City 


.State. 


Tested  and  approved  by  RADIO  BROADCAST 


Radio  Broadcast 


ties  of  the  first  stage  are  amplified  and  eventually 
become  the  output  of  the  receiver.  If  the  first  stage 
is  broad  in  tuning,  the  receiver  will  very  likely  lack 
selectivity.  The  action  of  the  first  stage  has  a  great 
deal  to  do  with  the  ultimate  performance  of  the 
receiver. 

The  usual  type  of  transformer  used  has  a  single 
layer-wound  coil  on  a  tube,  with  a  tap  taken  off  for 
the  antenna  connection.  The  field  of  the  magnetic 
lines  of  force  around  the  ends  of  the  coil,  created  by 
the  flow  of  current  through  the  wire,  spreads  out  and 
sprays  near-by  pieces  of  apparatus,  causing  distor- 
tion and  making  the  receiver  unstable  in  operation. 

The  toroid  type  of  coil,  on  the  other  hand,  has  an 
entirely  self  contained  field  that  prevents  magnetic 
spraying  effects.  The  low  loss  feature  of  one  of  the 
manufactured  type  of  coil  now  obtainable  is  due  to 
the  fact  that  the  wires  are  indented  at  every  other 
face  around  the  coil,  thereby  lowering  the  distri- 
buted capacity  and  resistance  losses  below  that  of 
ordinary  coils  to  a  noticeable  degree. 

To  incorporate  the  coil  in  a  regular  neutrodyne  or 
tuned  radio  frequency  receiver,  all  that  is  necessary 
is  to  remove  the  present  coil  used  for  tuning  the 
antenna  circuit  and  replace  it  with  a  toroid  coupler. 
The  same  condenser  can  be  used  to  tune  the  re- 
ceiver providing  it  is  of  .0005  mfd.  capacity. 

To  construct  the  complete  receiver  as  shown  in  the 
diagram  Fig.  9,  the  following  list  of  apparatus  will 
be  needed: 

i — toroid  coupler. 

2 — radio  frequency  transformers,  tuned  type. 
(Radio  Frequency  transformers  of  the  toroid 
type  may  be  used  here  with  excellent  results). 

3 — .0005  mfd.  variable  condensers,  preferably 
straight-line  frequency  low  loss  condensers  so 
that  the  lower  wavelength  stations  will  be 
separated  far  apart  enough  to  make  tuning 
easy. 

5 — standard  vacuum  tube  sockets  and  five  rheo- 


stats, 25-ohm  for  the  6-volt  and  4o-ohm  for 

the  3-volt  type  tubes. 
2 — low  ratio  audio  frequency  transformers,  3  to  i 

ratio, 
i — .00025  mfd.  fixed  grid  condenser;  2-megohm 

grid  leak;  single  circuit  phone  jack,  binding 

posts,  wire,  a  7  x  24  or  26-inch  panel,  and  a 
7  x  23-inch  baseboard  will  complete  the  list  of 

apparatus  necessary. 

Follow  out  the  wiring  diagram  Fig.  9  in  building 
the  receiver,  spacing  the  regular  tuned  radio  fre- 
quency transformers  at  least  six  and  one  half  inches 
apart.  If  toroid  transformers  are  used,  as  well  as 
the  coupler,  then  the  spacing  can  suit  the  arrange- 
ment of  the  rest  of  the  apparatus  in  your  set,  without 
fear  of  interstage  coupling. 

ON    MATCHING    AND    UNMATCHING    TUBES 

WITH  the  general  consistency  of  the 
better  vacuum  tubes  being  sold  to-day 
there  is  small  necessity  for  "matching 
tubes."  The  fact  is,  for  most  purposes  tubes  are  so 
similar  in  their  characteristics  that  they  may  be  con- 
sidered as  being  matched.  The  notable  exception  is 
in  the  super-heterodyne,  where  juggling  tubes 
around  in  the  intermediate  stages  is  usually  neces- 
sary to  secure  satisfactory  reception.  But  contrary 
to  the  general  idea,  this  changing  of  tubes  does  not 
necessarily  constitute  matching.  It  is  often  a  proc- 
ess of  deliberate  unmatching,  which  in  many  cases 
stabilizes  the  action  of  the  amplifier. 

Satisfactory  reception  on  the  "super"  can  seldom 
be  achieved  other  than  by  use  of  the  highest  grade 
tubes.  Some  bulbs,  which  function  in  other  re- 
ceivers in  this  laboratory  show  up  their  defects  in 
"super"  operation.  Howling,  instability  (uncon- 
trollable oscillations  with  beat  whistles)  at  normal 
plate  voltages  are  evidence  of  poor  or  improperly 
balanced  tubes  in  the  intermediate  amplifier. 


^  Gnd. 


-A        +A         -B       +  45V    B90V  + 


FIG.   9 


RADIO  BROADCAST  ADVERTISER 


17 


Its  ^genuine  UV-2Q1-A 
only  when  it  bears 
the  name  Radiotron 
and  the  RCA  mark 


WD-ll,  WD-12,  UV-199,  UV-200,  and 
UV-201-A  are  the  type  names  of  Radio- 
trons.  They  belong  to  Radiotrons  only. 
To  be  sure  you  are  buying  the  genuine, 
look  for  the  name  Radiotron  and  the 
RCA  mark  on  the  base.  Then  you  are 
sure  of  quality. 


Radio  Corporation  of  America 


Chicago 


New  York 


San  Francisco 


* 


adiotroit 


R EC. as.. -PAT.  ore 


AN    RCA    PRODUCT 


Tested  and  approved  by  RADIO  BROADCAST 


as-        Peary.  April  6.  19O9        as- 


THE  MACMILLANARCTICEXPEDITION_ 

UNDER  THE    AUSPICES  OF 

THE  NATIONAL  GEOGRAPHIC  SOCIETY 


Route  of  Ships 
•  •••••    Route  of  Planes  to  Estatdish  Airplane  Base 

oooooo  Proposed. Routes  of  Exploration  Flights 

100      400        500 


Drtwn  in  Map  Dtp>.  of  The  National  Geographic  Society 


THE    ROUTE    OF   THE    MACMILLAN 
ARCTIC    EXPEDITION 

At  present  in  Arctic  waters.  The  map  shows  the  route  of  the  two  ships.the  Peary  and  the  Bowdoin.  The  cut 
at  the  upper  left  shows  the  command  of  the  expedition  in  the  pilot  house  of  the  Peary.  At  the  left  is  Lieut. 
Commander  E.  F.  McDonald,  Jr.  (U.  S.  N.  R.  F.),  in  command  of  the  Peary,  next  is  Captain  George  Steele 
of  the  Peary,  and  at  the  right  is  Commander  Donald  Macmillan,  in  charge  of  the  expedition.  The  insert  at 
the  right  shows  John  L.  Reinartz,  radio  operator  in  his  cabin  aboard  the  Bowdoin.  Radio  communication 
with  the  40-  and  ao-meter  transmitters  aboard  both  ships  has  been  established  with  amateur  operators  in  the 
United  States,  Canada,  and  England  from  the  Greenland  base.  Short  waves  are  used  because  they  are 
less  subject  to  attenuation  in  daylight.  The  expedition  during  its  entire  time  in  northern  latitudes  will  be 
in  constant  daylight.  2  GY,  the  short  wave  station  maintained  by  RADIO  BROADCAST  has  been  in  com- 
munication with  the  Peary,  WAP,  using  a  wavelength  of  40  meters  at  her  Etah,  Greenland  base 


RADIO 
BROADCAST 


Vol.  7  No.  6 


October,  1923 


And  Now — The  Radio  Lighthouse 


I 


The  Navy  and  the  Lighthouse  Service  Have  Joined  Hands  to 
Make  Going  Down  to  the  Sea  in  Ships  Increasingly  Safer — 
How  Ships  Make  Port,  Guided  by  Invisible  Radio  Stations 

BY  JAMES  C.  YOUNG 

N  ALL  the  drama  of  radio,  nothing  equals  mains  on  the  high  seas  without  its  protection, 
that  stirring  call  for  help  which  some-  From  the  moment  that  a  ship  leaves  Europe 
times  comes  from  the  sea.  Since  the  first  until  she  ties  up  at  her  pier  in  New  York,  the 


sos  flashed  word  of 
peril  afloat,  the  imagina- 
tion of  mankind  has  re- 
sponded. Many  a  fol- 
lower of  the  nightly 
programs,  seated  quietly 
at  home  beside  his  own 
comfortable  hearth,  has 
heard  this  sudden,  vivid 
call,  when  the  voice  of 
every  station  is  hushed 
as  a  tense  audience 
awaits  word  of  what  goes 
on  upon  the  far  reaches 
of  the  deep.  Surely  no 
other  experience  quite 
compares  with  this  wait- 
ing for  the  next  message 
from  a  stricken  ship,  the 
message  that  may  report 
her  sinking  with  all 
hands,  or  convey  the 
cheering  news  that  an- 
othership  is  standingby. 
Radio  has  developed 
rapidly,  and  now  hardly 
a  passenger  vessel  re- 


AMBROSE    CHANNEL    LIGHTSHIP 

Stationed  outside  New  York  harbor.  With- 
in the  past  year,  radio  equipment  has  been 
added  to  the  other  devices  aboard  this  ship, 
which  mark  another  step  in  the  constant 
march  of  progress  in  making  life  safer  at 
sea.  The  light  at  the  masthead,  the  out- 
side and  the  submarine  bells,  and  the  radio, 
all  do  their  share  to  make  the  task  of 
the  navigator  an  easy  one.  During  thick 
weather,  day  and  night,  a  radio  transmitter 
aboard  this  vessel  sends  out  radio  beacon 
signals  on  299  kc.  ( 1000  meters).  The  Gov- 
ernment has  installed  similar  transmitters  on 
many  important  lightships  on  the  Atlantic 
and  Pacific  coasts  and  on  the  Great  Lakes 


long  arm  of  radio  guards 
the  passengers  aboard. 
Throughout  the  voyage 
it  makes  possible  accu- 
rate reports  on  weather 
conditions,  the  move- 
ment of  icebergs  and 
ships,  and  any  'chance 
developments  that  for- 
tune may  bring. 

In  the  open  sea  there 
is  relatively  little  danger 
to  a  ship,  unless  she  en- 
counters weather  of  the 
worst  sort,  but  on  ap- 
proaching the  coast  her 
safety  diminishes.  There 
are  other  ships  on  all 
sides,  reefs  ahead,  and  a 
thousand  possibilities 
bound  up  in  fog  and 
storm.  This  is  the  point 
where  the  lighthouse 
service  of  the  United 
States  takes  charge  of 
the  ship's  destiny. 

This    service,     estab- 


720 


Radio  Broadcast 


ROBERT    GRAEME 

Radio  operator  aboard  the  Ambrose.  The  radio 
equipment  of  this  important  light  vessel  serves 
probably  a  greater  number  of  ships,  totalling  a  larger 
tonnage,  than  similar  equipment  near  any  port  in 
the  world 

lished  in  Colonial  times,  is  the  oldest  branch 
of  the  Federal  Government,  antedating  even 
the  army  and  navy.  And  no  government 
service  has  a  finer  record  of  brave  deeds  and 
high  loyalty.  During  two  hundred  years  of 
operation  it  has  lighted  the  way  of  countless 
men  and  ships  through  dark  waters.  Boston 
Light,  the  oldest  in  the  country,  was  destroyed 
by  Indians  when  first  built,  and  the  Sandy 
Hook  lighthouse,  erected  in  1764,  was  con- 
sidered a  particularly  dangerous  point.  Red- 
skins were  all  around  and  they  showed  small 
friendliness  for  lighthouses. 

These  ancient  beacons  of  the  sea  have 
served  to  guide  all  kinds  of  ships.  First 
came  the  high-prowed  English  frigates  with  or- 
namented forecastles,  and  brass  cannon  gleam- 
ing in  the  sun;  stately  Spanish  galleons,  prowl- 
ing down  the  coast  ready  to  seize  any  un- 
protected settlement;  and  graceful  French 
corvettes,  sails  billowed  in  the  wind.  Then 
came  our  clipper  ships  to  hang  up  records 
in  the  seven  seas,  the  fastest  things  afloat. 

The  steadfast  lights  also  guided  the  whal- 
ing ships,  now  almost  a  lost  race  of  the  sea, 
that  brought  home  wealth  in  oil  and  bone  for 
their  New  England  skippers.  They  pointed 
the  way  for  slave  ships,  the  scourge  of  the 
seas.  And  who  knows  but  Captain  Charles 
Gibbs,  the  dread  pirate  who  roamed  the  Long 
Island  shore,  set  his  compass  by  the  Sandy 
Hook  light? 

But  gone  now  are  the  frigates  and  the  gal- 


leons; slave  ships  and  pirates  have  fled  the 
seas,  and  in  their  stead  we  have  ocean  liners 
and  submarines.  And  though  the  lighthouse 
service  still  goes  on,  time  has  wrought  great 
changes  in  it. 

A  new  feature  of  the  service  is  the  light- 
ships, which  lie  along  the  coast  year  in  and 
year  out  in  positions  which  ships  can  deter- 
mine within  a  few  feet.  Every  ship  from 
Europe  lays  a  direct  course  for  Ambrose  Light- 
ship, anchored  fifteen  miles  off  the  port  of 
New  York,  and  thus  acting  as  the  outpost  of 
the  harbor. 

RADIO    SIGNPOSTS    FOR   NAVIGATORS 

IF  THE  weather  is  bad  on  nearing  the  coast 
the  master  of  an  incoming  vessel  is  anxious 
to  know  if  he  is  steering  a  correct  course.  He 
may  also  have  doubt  about  his  position  at  sea. 
Of  course,  every  ship  keeps  a  daily  log  of 
speed  and  progress,  by  means  of  which  her 
navigator  can,  theoretically,  determine  his 
position  at  any  time.  But  navigators,  log 
books,  and  theories  have  a  way  of  working  at 
variance.  Therefore,  if  the  weather  is  thick 
and  the  coast  not  many  miles  away,  the  cap- 
tain will  look  to  the  lighthouse  service  for 
help.  Now,  it  might  seem  to  any  one  not 
versed  in  nautical  matters  that  the  captain 
should  be  able  to  learn  with  little  trouble  just 
where  his  ship  rides  through  the  night  and  fog. 
But  it  is  really  a  complicated  problem.  The 
captain  will  listen  by  radio  for  an  automatic 


CAPTAIN  AUGUST  LANCE 
Of  the  Lightship  Ambrose,  a  familiar  "watermark" 
to  all  marine  travelers  in  and  out  of  New  York  har- 
bor. Captain  Lange  says  that  broadcast  programs 
do  yeoman  service  in  breaking  the  solitude  of  months 
of  sea  duty 


And  Now — the  Radio  Lighthouse 


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signal  sent  out  from  several  points  off  the 
Atlantic  coast.  These  signals  are  transmit- 
ted as  a  part  of  the  radio  compass  service, 
which  joins  vessels  at  sea  with  the  lightships 
anchored  near  to  shore.  In  the  case  of  the 
Ambrose  Lightship,  her  transmitter  sends 
forth  an  automatic  signal  which  continues  for 
sixty-five  seconds  and  is  then  silent  twenty- 
five  seconds,  a  sequence  maintained  as  long 
as  the  weather  continues  bad.  A  similar 
signal  also  will  be  sent  out  from  Fire  Island 
lightship  and  another  from  the  ship  at  Five 
Fathoms,  near  Cape  May,  New  Jersey. 

The  captain  who  is  trying  to  get  his  bear- 
ings has  on  board  a  receiving  apparatus  which 
makes  these  signals  audible.  This  apparatus 
is  operated  by  means  of  a  dial  placed  in  the 
center  of  a  circle  on  which  appear  the  360 
numbered  degrees  of  the  compass.  In  order 
to  take  the  position  of  the  Fire  Island  light- 
ship the  operator  on  the  incoming  vessel 
turns  the  dial  of  his  radio  compass  to  the 
point  where  the  Fire  Island  signal  becomes 
the  faintest.  If  we  assume  that  this  point  is 
on  the  right  hand,  or  landward  side  of  the 
ship,  the  master  then  knows  that  he  has 
Fire  Island  at  just  about  the  point  desired. 
But  this  signal  a.one  will  not  provide  him 
with  an  accurate  bearing.  In  order  definitely 
to  determine  his  position,  he  must  take  what 
is  known  as  a  three-point  bearing.  And  the 
lighthouse  service  once  more  is  the  means  of 
assistance.  Again  turning  the  compass  dial, 


another  point  is  found  where  the  Ambrose 
signal  sounds  the  faintest.  This  should  be 
somewhere  directly  ahead.  Then  the  opera- 
tor endeavors  to  locate  the  ship  at  Five 
Fathoms,  once  more  turning  his  dial  until  the 
automatic  signal  from  that  point  is  fainter 
than  anywhere  else  on  the  compass.  In  a 
general  way  the  Fire  Island  signal  represents 
East,  the  Ambrose  signal  stands  for  West  and 
that  of  Five  Fathoms  for  South.  When  the 
three  lightships  are  thus  linked  with  the  in- 
coming vessel  her  captain  draws  a  line  on  his 
chart  from  each  one  to  a  point  of  latitude  and 
longitude  where  the  three  lines  meet.  That 
point  represents  the  position  of  his  ship. 
This  is  a  highly  scientific  and  extremely 
accurate  method  of  navigation,  so  that  the 
master  can  be  sure  he  is  on  the  right  course, 
and  where  his  ship  speeds  through  the  night. 

"FINDING"  SHIPS  AT  SEA 

IN  BAD  weather  the  radio  compass  service 
would  be  put  into  operation  without  re- 
quest, but  it  is  also  possible  for  the  master 
of  a  ship  nearing  New  York — and  this  is 
true  in  many  other  American  ports  where  the 
Navy  has  installed  compass  stations — to  get 
his  bearings  in  another  way,  namely,  by  mak- 
ing use  of  station  NAH.  This  is  the  navy 
plant  on  Fire  Island  and  has  no  connection 
with  the  lightship  at  sea.  A  master  using 
this  second  method  would  flash  a  message  of 
inquiry  to  NAH  (probably  the  international 


A    TYPICAL    DERELICT 

Awash  and  abandoned.     Government  radio  services  are  doing  much,  through  the  radio  beacons  and  radio 

compass  service  furnished  at  many  important  United  States  ports,  to  prevent  wrecks.     In  addition,  warnings 

of  these  menaces  to  navigation  are  broadcast  to  ships  through  the  agency  of  the  Coast  Guard.     Last  year, 

notice  of  75  such  partially  submerged  wrecks  was  broadcast  by  radio  telegraphy 


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Radio  Broadcast 


signal  QTE,  "What  is  my  bearing?")  to  which 
the  navy  station  would  answer,  QRX  "Stand 
by."  Then  the  radio  operator  at  sea  would 
begin  sending  a  conventional  signal,  usually 
the  letter  "m,"  repeated  many  times,  fol- 
lowed by  his  own  call.  While  this  message 
was  in  the  air,  NAH  would  call  the  lighthouse 
shore  stations  at  Sandy  Hook  and  Manas- 
quan,  New  Jersey,  by  land  lines,  asking  them 
to  take  the  call  of  the  ship  and  send  back  the 
results.  NAH  could  then  figure  a  three-point 
bearing  for  the  vessel  by  a  reverse  of  the 
process  used  by  the  master  when  determining 
his  bearings  by  means  of  the  lightship.  Once 
determined,  this  bearing  would  be  flashed  to 
the  vessel  and  she  could  lay  her  course  ac- 
cordingly. 

The  radio  compass  represents  the  greatest 
advance  in  navigation  since  man  first  invented 
the  compass  itself.  Before  the  introduction 
of  this  new  aid  to  navigation  some  few  years 
ago,  ships  were  steered  in  much  the  same 
manner  as  they  had  been  centuries  ago.  From 
the  beginning  of  man's  adventure  upon  the 
water,  he  depended  in  large  measure  upon  the 
old  and  honored  lead  for  his  enlightenment 
about  shoals  and  his  general  position.  Within 
the  last  century  almost  every  coast  in  the 
world  has  been  extensively  charted.  Each 
navigator  has  a  map  which  shows  the  ap- 
proximate depth  of  water  along  any  coast  that 
he  may  be  sailing.  By  means  of  the  lead 
line,  thrown  overboard  at  frequent  intervals. 
it  is  possible  to  keep  a  check  on  the  progress  of 
the  ship  and  determine  whether  or  not  she  is 
getting  into  dangerous  water.  But  a  lead 
line  at  night,  in  a  fog  or  heavy  weather  is 
sometimes  deceptive  and  difficult  to  operate. 
Yet  it  was  the  only  indicator  approaching 
reliability  that  could  be  used  by  navigators  of 
large  and  small  steamships  alike  until  the 
advent  of  the  radio  compass  made  it  possible 
to  obtain  land  bearings  even  when  still  at  sea 
or  in  bad  weather.  The  benefit  of  this  in- 
vention to  shipping  the  world  around  sur- 
passes all  estimates.  It  has  brought  a  new 
measure  of  science  into  the  always  hazardous 
enterprise  of  steering  a  ship  safely  into  port. 

The  Ambrose  lightship  is  a  dangerous 
station.  Captain  August  Lange,  her  master, 
remembers  more  than  one  vessel  which 
loomed  up  out  of  the  night  and  fog  and  almost 
ran  her  down.  At  least  one  of  these  trouble- 
some visitors  struck  the  lightship  head  on, 
because  the  man  at  her  wheel  was  headed 
directly  for  the  exact  spot  where  the  lightship 
rides  at  her  chain.  But  such  incidents  are 
fortunately  not  common,  owing  to  various 


devices  used  by  the  lightship  for  self-protec- 
tion. One  of  these  is  a  submarine  bell, 
dangling  over  her  side,  which  sends  out 
warnings  at  intervals.  This  bell  has  a  deep, 
ominous  tone.  Each  clang  of  its  brazen 
tongue  resounds  underneath  the  surface  of  the 
water  and  is  caught  up  by  means  of  a  receiving 
instrument  on  the  bow  of  the  approaching 
ship.  Before  the  coming  of  the  radio  com- 
pass, the  submarine  bell  was  looked  upon  as  a 
great  advance  in  the  science  of  navigation. 
Although  the  bell  has  a  distinct  value,  it  by 
no  means  compares  with  the  method  of  com- 
munication from  ship  to  shore. 

Another  means  of  warning  the  advancing 
vessel  is  the  dependable  steam  whistle 
mounted  alongside  her  single  stack.  In  foggy 
weather  this  whistle  blows  loud  and  long,  a 
mournful,  warning  blast,  that  can  be  heard 
miles  away.  The  whistle  is  also  regulated 
automatically  and  experienced  mariners  lend 
sharp  ear  on  approaching  the  coast  for  this 
sturdy  friend. 

The  last  defense  of  the  lightship,  for  her 
own  protection  and  for  that  of  all  who  travel 
the  sea,  is  the  two  winking  lights  at  her  mast- 
heads, burning  brightly  all  the  year  round. 
In  clear  weather  they  can  be  seen  for  miles, 
the  first  signal  of  home  that  greets  the  return- 
ing sojourner  from  foreign  lands.  They  have 
been  the  object  of  anxious  regard  for  many  an 
eye  long  denied  the  sight  of  home.  Every 
soldier  who  went  to  France  looked  back  to  the 
Ambrose  lightship  as  the  goal  of  his  hopes. 

Once  past  this  first  beacon  of  the  harbor, 
the  navigator  will  usually  turn  his  ship  toward 
shore  and  steer  for  the  sea  buoy,  three  miles 
nearer  land.  This  buoy  has  a  winking  gas 
light  of  its  own,  a  whistle  operated  by  the 
motion  of  the  sea,  and  a  submarine  bell. 
From  the  buoy  it  is  two  and  a  quarter  miles  to 
the  entrance  of  Ambrose  channel,  the  highway 
of  New  York  harbor,  through  which  must 
pass  the  greatest  volume  of  shipping  known  to 
any  port. 

Ambrose  Channel  has  a  spread  of  2000  feet. 
It  takes  a  nice  eye  to  strike  the  middle  of  that 
channel  at  night,  but  many  ships  pass  in  and 
out,  under  the  hand  of  pilots  picked  up  from 
the  pilot  boat  at  the  mouth  of  the  channel. 
Along  both  sides  of  the  way  a  string  of  buoys 
keeps  guard  over  the  course.  Those  upon  the 
right  are  called  nuns  of  the  sea  because  of  their 
red  cones,  like  the  headdress  of  religious  wo- 
men in  the  Middle  Ages.  The  buoys  upon 
the  left  are  black  cans  with  white  lights. 
The  Channel  runs  at  an  angle  toward  the 
coast  of  Staten  Island  and  the  man  at  the 


And  Now — the  Radio  Lighthouse 


wheel  is  guided  by  the  West  Bank  Light,  with 
the  Staten  Island  Light  further  off.  These 
are  known  as  ranges,  and  by  keeping  his  ship's 
head  directly  on  the  ranges,  a  pilot  reaches  the 
point  in  the  Channel  where  he  must  put  over 
his  wheel  and  turn  in  toward  the  Narrows. 
If  it  is  night  he  drops  anchor  at  Quarantine 
and  waits  for  the  doctors  to  come  aboard  the 
next  morning.  Some  hours  later  he  will  carry 
his  charge  up  the  bay,  under  the  glory  of  the 
morning  sun,  to  her  dock.  And  thus  with  the 
aid  of  the  lighthouse  service  ships  come  safely 
in  from  the  sea. 

HOW   THE   COASTS   ARE    GUARDED 

A  LTHOUGH  this  service  is  the  most 
•*»•  important  and,  perhaps,  the  most  drama- 
tic rendered  by  the  men  of  the  lighthouses 
and  their  fellows  afloat,  it  by  no  means  com- 
prehends the  entire  operation  of  their  depart- 


ment. The  United  States  has  a  larger  number 
of  lighthouses  and  a  coast  better  protected  by 
sea  buoys  than  almost  any  other  country. 
There  are  also  many  inland  waters,  such  as  the 
Great  Lakes,  that  require  protection. 

Throughout  the  service,  a  high  degree  of 
skill  is  needed,  and  the  men  who  follow  this 
trade  have  the  loneliest  vocation  in  the  world. 
They  spend  twenty-one  days  on  duty  in  the 
lighthouse  or  lightship  with  nine  days  shore- 
leave.  On  such  posts  as  the  Diamond  Shoals 
lightship,  off  Cape  Hatteras,  it  requires  stout 
hearts  to  resist  melancholy.  This  ship  is 
anchored  about  300  miles  from  shore  and  has 
virtually  no  communication  with  the  world  out- 
side or  passing  craft.  Shore  leave  from  a  post 
like  that  is  a  matter  of  first  importance  and  it 
is  almost  the  only  thing  that  breaks  the  mono- 
tony of  existence.  However,  during  the  war, 
men  serving  on  the  Diamond  Shoals  light- 


PROTECTION    AT   SEA 

On  the  left  is  a  lonely  beacon  of  the  sea,  familiar  and  important  to  ship  masters.  It  is  interesting  to  note 
that  radio,  which  has  been  turned  so  successfully  to  the  aid  of  the  navigator,  through  the  sending  of  radio 
beacon  signals  from  important  marine  outposts  such  as  this,  has  also  been  applied  to  the  good  service  of  de- 
creasing the  loneliness  of  the  crew  at  these  outposts.  Broadcast  programs  bring  the  life  of  the  outside  world 
to  the  crews  at  these  stations.  At  the  right-  the  sea  buoy  at  the  entrance  to  Ambrose  Channel.  Above: 
dropping  a  four-ton  "toy"  buoy  at  its  station 


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Radio  Broadcast 


A    COAST    GUARD    SURFBOAT 


©Charles  A.  Harbaugh 


Bucking  a  heavy  sea  to  aid  a  distressed  vessel.     The  dangers  of  navigation  are  con- 
stantly being  lessened  through  the  good  offices  of  radio,  now  compulsory  on  most  ships 


ship  had  enough  excitement  to  make  up  for 
days  of  dullness,  when  the  ship  was  sunk  by  a 
German  submarine.  But  all  hands  got  safely 
to  shore. 

Most  radio  operators  on  the  lightships  have 
an  interesting  and  often  eventful  life.  They 
are  expert  men  whose  duties  require  a  technical 
skill  and  a  measure  of  intelligence  of  the  first 
order.  Robert  Graeme,  relief  operator  on  the 
lightship  at  Fire  Island  and  Ambrose  Channel, 
is  only  twenty-three  years  old,  but  is  looked 
upon  as  one  of  the  ablest  operators  in  the 
service.  He  has  had  six  years  of  experience 
with  radio  operation,  having  learned  his 
vocation  in  one  of  the  navy  schools,  and  he 
has  conducted  a  number  of  experiments  with 
radio  transmission.  "  It's  a  great  job,"  he  told 
the  writer,  "and  I  get  a  lot  of  fun  out  of  it." 
Mr.  Graeme  serves  a  month  on  each  ship  and 
then  has  a  month  ashore. 

RADIO    BREAKS    SOLITUDE    AT    SEA 

pHE  Ambrose  Lightship  is  manned  by  a 

*  crew  of  old  sailors,  men  who  served  before 

the  mast  in  the  days  of  the  square-riggers  when 

those  with  the  hardest  heads  lived  to  be  the 


oldest.  That  was  long  before  radio  helped  to 
brighten  the  tedium  of  voyages  around  the 
Horn  and  through  the  far  seas.  But,  as 
Captain  Lange  said,  "The  sea  was  the  sea 
then.  We  had  wooden  ships  and  iron  men. 
Nowadays  they  are  mostly  iron  ships  and 
wooden  men.  .  .  .  You  know,"  he  con- 
tinued reminiscently,  "when  1  listen  to  radio 
programs  I  imagine  myself  ashore  at  the 
theater  or  a  concert.  And  Sunday  after- 
noons at  three-thirty  there  is  a  program 
that  reminds  me  of  the  days  when  I  was  a 
boy  and  used  to  sit  in  the  village  church, 
long  before  I  ran  away  to  become  a  cabin 
boy  and  finally  an  old  sailor.  But  some  of 
us  have  got  to  stay  out  here  and  keep  the 
lights  going.  I  have  been  forty-six  years 
out  of  port  and  I  suppose  I  would  be  lost 
at  a  land  station.  The  sea  is  a  hard  master, 
but  it's  not  easy  to  quit  the  sea  once  a  man 
has  sailed  it." 

He  looked  off  to  port  with  a  wave  of  his 
hand  over  the  stretches  of  heaving  water, 
gray  as  a  tern's  wing.  Just  then  the  fog 
settled  down  and  the  mournful  steam  whistle 
broke  into  its  sad  refrain. 


New  Developments  and  Experi- 
ments   with    Receiving    Circuits 


BY  KEITH  HENNEY 


/N  tins  article,  Mr.  Henney  has  some  interesting  things  to  say  about  reflexing  and 
discusses  the  design  of  a  fire-tube  receiver  without  the  reflex.  The  analysis  of  radio 
and  audio  amplification,  and  in  especial  the  recommendation  of  the  use  of  power  tubes  in 
the  last  audio  stage,  will  be  found  of  great  interest.  Innumerable  radio  constructors 
have  built  the  Roberts  set,  in  the  two-,  three-,  or  four-tube  layouts,  and  it  is  not  break- 
ing any  confidences  to  say  that  the  Roberts  Knockout  receiver  is  the  most  -popular  ever 
designed  for  home  construction.  In  April,  1925,  Mr.  Henney' s  article,  "Progressive 
Experiment  With  the  Roberts  Circuit,"  told  of  his  experiments  in  our  Laboratory  on 
improvements  and  alterations  in  certain  individual  parts  of  the  set.  This  entire 
article  is,  we  think,  a  distinct  contribution  to  the  best  current  thought  on  radio  design. 
The  author  is  interested  in  hearing  from  readers  who  follow  his  recommendations,  or 
who  feel  they  have  made  helpful  discoveries  during  the  course  of  their  work. — THE 
EDITOR 


FOR  the  dyed-in-the-wool  experimenter, 
there  are  few  radio  circuits  that  offer 
him  more  possibilities  than  the  type  of 
which  the  RADIO  BROADCAST  Knock- 
out is  a  well  known  example.     Here  is  a  radio- 
frequency  amplifier,  a  regenerative  detector,  a 
reflex,  and  an  audio  amplifier.     Each  of  these 
component  parts  needs  development,  and  offers 
fields  of  experiment  for  those  so  inclined. 

In  the  April  RADIO  BROADCAST,  a  number  of 
experiments  were  cited  which  were  designed  to 
improve  the  selectivity  of  the  receiver  as  well 
as  several  features  upon  which  the  home  con- 
structor might  work.  Letters  from  readers 


have  suggested  other  experiments,  and  the 
present  article  deals  with  what  is  going  on  in 
the  Laboratory  on  this  famous  circuit  and 
suggests  other  arrangements  of  apparatus  upon 
which  readers  can  experiment. 

The  business  of  making  coils  for  this  receiver 
has  occupied  the  attention  of  many,  and  judg- 
ing from  the  questions  that  have  arisen  on  this 
point,  it  is  a  fertile  field  of  work.  Contrary 
to  general  opinion,  there  is  no  reason  why  the 
old  fashioned  solenoid  coil  cannot  be  used  in 
this  circuit.  In  fact  it  is  quite  probable  that 
if  the  coils  are  well  made,  with  a  thought  to- 
ward "low-loss",  better  over-all  results  will  be 


FIG.     I 

Two  types  of  coils  that  may  be  used  in  the  Knockout  receivers.  The  solenoid  coils  are  wound  on  a  form  and 
the  winding  bound  with  passe-partout.  The  basket-weave  coil  form  has  an  uneven  number  of  pegs — and 
the  more  pegs  the  nearer  the  coil  approaches  a  solenoid.  The  number  of  turns  is  four  times  the  number 
that  can  be  counted  on  a  side.  The  coil  illustrated  has  64  turns  and  the  mean  diameter  is  three  inches 


726 


Radio  Broadcast 


/  Jack  For  Phone  Reception 


Oto  10,000 
Ohms  Resistance 
Volume  Control 


FIG.    2 

A  power  amplifier  to  be  added  to  a  radio-frequency  amplifier  and  a  de- 
tector. The  last  tube  is  one  that  will  handle  at  least  300  volts  on  the 
plate,  and  whose  filament  may  be  operated  by  alternating  current  by 
means  of  a  step-down  transformer.  The  quality  of  music  transmitted 
by  such  an  amplifier  is  a  function  of  the  transformers  only  since  high 
enough  C  battery  voltage  may  be  applied  to  prevent  overloading.  The  out- 
put transformer  referred  to  in  the  diagram  as  an  "output  coil"  is  impor- 
tant since  it  keeps  the  heavy  plate  current  from  the  loud  speaker  windings 


obtained  than  by  the  use  of  other  forms  of  in- 
ductances. Typical  solenoid  coils  are  shown  in 
Fig.  i.  and  have  the  following  dimensions  to 
work  with  condensers  of  .0005  mfd.  capacity. 

Antenna  coil,   50  turns  No.  22  d.c.c.,  2  inches  in 

diameter,  2^  inches  long. 
Detector  coil,  45  turns  No.  22  d.c.c.,  3j  inches  in 

diameter,  2  inches  long. 

If  other  sizes  of  wire  and  tubing  are  used,  the 
constructor  should  consult  the  inductance- 
capacity  chart  given  in  the  May  RADIO  BROAD- 
CAST, page  46. 

In  winding  low-loss  coils,  the  points  to  be 
remembered  are  these;  use 
fairly  large  wire  say  No.  22 
to  No.  18;  use  as  little 
dielectric  as  possible;  space 
the  wire  about  the  diameter 
of  the  copper;  and  use  solder 
sparingly. 

Basket  weave  coils  are 
illustrated  in  Fig.  i  together 
with  a  home  made  form  upon 
which  they  may  be  wound. 
It  pays  to  use  rather  large, 
well  insulated  wire  here. 
The  coils  are  stronger  me- 
chanically if  the  larger  wire 
is  used. 


,u.v.  202  orw.E.E Tube  where  this  additional  tube 
may  be  used,  either  as  a 
stage  of  radio  frequency 
amplification,  or  in  the  form 
of  a  separate  audio  ampli- 
fier by  eliminating  the  reflex 
part  of  the  original  circuit. 
The  first  arrangement  re- 
quires an  additional  coil  and 
condenser  but  it  is  some- 
what of  a  trick  to  attain 
successful  operation  due  to 
the  numerous  feed-backs 
which  result  when  two 
"high-powered"  radio  am- 
plifiers are  hooked  together. 
This  use  of  an  extra  tube  is 
explained  in  the  March 
RADIO  BROADCAST,  page 

939- 

By  eliminating  the  reflex, 
the  constructor  gains  several  worthy  points. 
The  radio  amplifier  is  free  to  give  its  maximum 
output,  which  is  considerable  if  that  amplifier 
is  correctly  designed;  there  is  greater  selectiv- 
ity; the  quality  is  somewhat  improved — though 
the  average  loud  speaker  and  the  average  un- 
trained ear  will  not  detect  the  difference — and 
the  rumbling  noises  peculiar  to  reflex  receivers 
disappear.  The  receiver  will  then  consist  of  a 
straight  radio  amplifier,  a  detector  with  re- 
generation, and  as  much  audio  amplification 
as  the  builder  desires  to  use. 

On  the  other  hand  the  receiver  on  two  tubes 
will  not  operate  a  loud  speaker,  which  is  one 


A    FIVE-TUBE     KNOCKOUT 

MANY  readers  have  re- 
quested    information 
regarding  the  addition  of  an 
extra  tube  to  the  four-tube 
set.    There  are  two  places 


FIG.    3 

The  original  and  to  date  most  popular  reflexed  radio  amplifier.  The  by- 
pass condenser  from  tuning  coil  to  filament  tends  to  eliminate  the  higher 
musical  tones,  and  the  iron  cored  inductances  in  both  grid  and  plate 
circuits  of  the  first  tube  make  an  excellent  audio  oscillator  at  certain  ad- 
justments of  tuning  condensers 


New  Developments  and  Experiments  with  Receivers 


727 


of  the  greatest  advantages  of  Dr.  Roberts's 
original  design.  The  elimination  of  the  reflex 
involves  the  additional  cost  in  upkeep. 

The  English  expert,  Scott-Taggart,  for  many 
years  the  champion  of  reflex  circuits,  has 
changed  his  opinion  recently  on  this  subject. 
Quoting  from  Wireless  Weekly  for  Feb.  25, 
1925,  one  of  Scott-Taggart 's  papers: 

I  can  forsee  a  fairly  .  .  .  distinct  tendency 
to  depart  from  reflex  circuits  altogether.  1  think 
the  reduction  in  price  of  valves  and  the  development 
of  the  dull  emitter  will  do  more  than  anything  else 
to  oust  the  reflex  circuit  from  popular  favor.  The 
reflex  is  popular  simply  because  the  great  demand 
is  for  signal  strength  with  a  minimum  number  of 
valves.  Economy  ...  is  the  one  and  only  reason 
for  the  use  of  a  reflex  arrangement,  and  if  we  have 
the  advantage  of  improving  the  selectivity  and  the 
range  and  generally  making  the  set  more  effective, 
then  an  extra  valve  will  probably  be  cheerfully 
added.  A  straight  circuit  will  give  better  results  in 
nine  cases  out  of  ten,  than  the  same  circuit  con- 
densed so  as  to  use  one  less  valve,  the  reflex  princi- 
ple being  introduced. 

In  the  opinion  of  the  writer,  the  future  set 
will  require  but  four  tubes,  the  last  of  which 
will  be  a  power  or  semi-power  tube  whose  fila- 
ment will  be  lighted  from  alternating  current 
and  which  will  deliver  enough  output  to  oper- 
ate the  best  loud  speaker  without  overloading. 
Such  tubes  and  the  devices  for  operating  them 
will  be  on  the  market  as  soon  as  home  con- 
structors have  created  a  demand  for  them. 

At  the  present  time  input  push-pull  coils 
are  not  so  good  as  our  best  types  of  audio  fre- 
quency transformers.  A  four-tube  set  would 
get  around  this  difficulty.  We  would  then  no 
longer  be  troubled  with  much  of  the  distortion 
now  present  in  two-stage 
amplifiers  and  noticeable 
when  low  impedance  cone 
type  loud  speakers  are  used. 

An  amplifier  of  this  type 
is  shown  in  Fig.  2. 

It  is  a  simple  matter  to 
eliminate  the  reflex  in  the 
Roberts  receiver  and  Figs.  3 
and  4  show  the  differences 
between  the  reflexed  and 
the  straight  radio  amplifier. 
The  correct  connections  are 
indicated. 

The  increase  in  gain  of 
the  radio  amplifier  is  quite 
noticeable  and  maybe  cause 
for  trouble  unless  certain 
precautions  are  taken  to 
prevent  feed  -  backs.  The 


coils,  especially  if  low-loss,  must  be  on  the  same 
plane  and  at  right  angles  to  each  other.  A 
good  radio-frequency  amplifier  will  oscillate  if 
the  grid  and  plate  coils  are  an  inch  out  of  line. 
This  is,  in  fact,  a  good  test  to  see  whether  one 
has  an  amplifier  that  is  giving  full  gain  or  not. 

The  gain  in  quality  over  the  reflexed  ar- 
rangement is  due  to  the  fact  that  the  reflexed 
transf9rmer  secondary  must  be  shunted  with  a 
rather  large  condenser  which  causes  this 
secondary  coil  to  resonate  at  lower  frequency 
and  naturally  to  lose  those  audio  notes  above 
about  3000  cycles. 

The  increase  in  selectivity  is  due  to  the  de- 
creased losses  in  the  radio  amplifier  circuit 
which  are  large  when  an  iron  core  coil  is  placed 
nearby,  as  in  the  reflex. 

It  is  probable  that  the  average  voltage  gain 
of  the  first  tube  with  its  accessory  apparatus 
in  a  radio  amplifier  circuit  will  be  about  seven 
or  eight,  while  the  average  neutrodyne  has  a 
gain  of  about  three — which  explains  why  these 
receivers  have  two  stages  of  radio!  If  an  am- 
plifier is  well  constructed  with  plenty  of  plate 
inductance  and  is  properly  neutralized,  it  is  pos- 
sible to  have  a  voltage  gain  of  more  than  ten. 

In  the  RADIO  BROADCAST  Laboratory,  a 
five-tube  receiver,  without  antenna  or  ground, 
gave  comfortably  loud  signals  on  New  York 
City  stations  20  miles  away,  and  on  a  short 
antenna  equalled  any  receiver  that  was  com- 
pared with  it.  A  laboratory  model  is  shown 
in  Fig.  5  . 

NEUTRALIZING   THE    ROBERTS 

OERHAPS  the  most  distinctive  feature  of 

the  original  Roberts  circuit  is  the  method 

of  neutralization,  namely,  the  double  wound 


FIG.  4 

The  non-reflexed  Knock-out  circuit.  The  radio  amplifier  is  now  freed 
from  audio  frequency  currents  which  occasionally  modulate  the  incoming 
highfrequencies  with  considerable  distortion  as  a  result.  The  gain  of  this 
tube  is  increased  over  the  reflexed  arrangement — but  one  more  tube  is 

required 


728 


Radio  Broadcast 


FIG.  5 

A  Laboratory  model  of  a  five-tube  Knockout  receiver 


NP  coil,  or  as  it  is  used  now,  the  mid-tap  coil. 
If  the  audio  frequency  currents  are  removed 
from  the  first  tube,  as  in  the  unreflexed  set, 
neutralization  becomes  increasingly  important, 
and  experimenters  will  do  well  to  investigate 
the  various  methods  of  capacity  balancing 
illustrated  in  Fig.  6. 

The  double  wound  NP  coil  has  one  serious 
fault,  especially  when  collodion  is  used  as  a 
binder.  These  two  parallel  wires  have  a  large 
capacity  which  tunes  with  the  inductance  to 
give  the  coil  a  natural  wavelength  somewhere 
in  the  broadcasting  band.  The  effect  is  im- 
mediate and  obvious — the  receiver  refuses  to 
tune  to  the  lower  wavelengths,  it  tunes 
broadly,  and  makes  peculiar  and  irritating 
noises  at  certain  positions  of  the  two  tuning 
condensers.  One  coil,  whose  high-frequency 
resistance  was  found  in  the  Laboratory  to  be 
300  ohms  at  300  meters,  was  quite  worthless, 
but  became  a  highly  efficient  inductance  when 
the  midtapped  arrangement  was  used.  The 
resistance  then  dropped  to  less  than  30  ohms, 
which  is  about  average,  The  most  satisfactory 
commercial  coil  sets  now  made  for  the  Roberts 
receiver  are  equipped  with  mid-tap  coils. 

NEUTRODYNE    NEUTRALIZATION 

THERE  is  one  advantage  in  the  neutrodyne 
method  of  balancing  out  grid-plate  capac- 
ity in  that  it  eliminates  the  double  sized  NP 


coil.  The  presence  of  the  large  primary  tends 
to  broaden  the  detector  tuning,  due  to  capacity 
coupling  and  the  mass  of  the  metal  in  the  coil 
being  near  the  detector  inductance.  The  neu- 
trodyne method  will  not  give  any  measurable 
gain  over  the  Roberts.  The  tap  on  the  detector 
coil  should  be  near  the  filament  end  of  the  coil, 
and  the  neutralization  will  not  be  independent 
of  frequency — contrary  to  general  opinion. 

THE    RICE    METHOD 

THE  Rice  method  as  well  as  the  Roberts  sys- 
tem, possesses  a  distinct  advantage  over 
the  neutrodyne  method  of  neutralization  in 
that  all  of  the  balancing  apparatus,  the  in- 
ductance and  neutralizing  condenser,  are  kept 
within  the  amplifier  circuit  itself  and  are  not 
carried  on  to  the  detector.  The  Rice  method 
has  another  advantage  because  the  neutraliz- 
ing condenser  is  not  attached  to  the  grid  but 
to  the  less  critical  plate,  and  if  the  exact  center 
of  the  input  coil  is  found,  neutralization  will 
be  independent  of  frequency.  The  antenna- 
ground  connections  must  be  placed  symme- 
trically with  respect  to  the  mid-tap  if  correct 
neutralization  is  to  be  maintained. 

REGENERATION    IN    THE    AMPLIFIER 

AN   INTERESTING   point  was  discussed 
about  a  year  ago  in  radio  technical  com- 
ment, regarding  the  policy  of  completely  neu- 


New  Developments  and  Experiments  with  Receivers 


729 


tralizing  a  radio  amplifier  It  was  argued  by 
some  writers  that  a  little  regeneration  in  the 
amplifier  was  advantageous.  Dr.  L.  M.  Hull 
published  an  article  on  this  subject  in  Q.  S.  T . 
January,  1924,  which  the  experimenter  should 
read  and  digest. 

Dr.  Paul  Ginnings,  of  Greensboro  College, 
North  Carolina,  has  sent  a  useful  device  to  the 


ROBERTS  METHOD 


RICE  METHOD 
FIG.    6 

Methods  of  neutralizing  the  radio-frequency  ampli- 
fier of  the  Roberts  receiver.  The  original  N-P 
arrangement  of  Roberts  is  contrasted  with  the 
Hazeltine  and  Rice  methods.  The  advantages  of 
:  these  three  systems  are  outlined  in  the  text 

Laboratory  which  is  designed  to  introduce  a 
given  amount  of  regeneration  into  the  first 
tube  of  the  Roberts  set.  A  diagram  of  the 
connections  is  shown  in  Fig.  7  and  a  photo- 
graph in  Fig.  8.  What  Dr.  Ginnings  con- 
denser does,  is  to  add  a  constantly  increasing 
amount  of  regeneration  to  the  amplifier  so 
that  the  longer  wave  stations  will  be  received 
with  greater  strength  than  ordinarily.  In 
practice,  the  device  consists  of  an  additional 


FIG.    7 

Dr.  Ginnings's  method  of  introducing  regeneration 
into  the  radio  amplifier  of  the  Roberts  receiver. 
The  reception  of  the  longer  wavelength  stations  is 
improved  by  this  method.  The  double  condenser 
shown  is  the  tuning  capacity  to  which  is  attached  a 
single  plate  which  is  connected  to  the  plate  circuit. 
The  tap  is  placed  so  that  the  ratio  of  turns  is  about 
6  to  i 

plate  attached  to  the  amplifier  tuning  con- 
denser which  is  so  adjusted  that  oscillations 
are  just  prevented  at  the  lowest  wavelength 
to  be  received.  Then  as  the  tuning  condenser 
is  adjusted  to  the  longer  waves,  more  and  more 
unbalance  is  attained  through  the  extra  con- 
denser. 

DETECTOR    REGENERATION 

CEVERAL  interesting  methods  of  introduc- 
^  ing  and  controlling  regeneration  in  the 
detector  circuit  have  been  used  recently  in 


FIG.  8 

A    photograph    of    Dr.    Ginnings's    device.     The 

method    of   attaching   the   feedback   condenser   is 

shown 


730 


Radio  Broadcast 


Fixed 
Tickler 


y  Variable 
'If  Resistance 


FIG.    9 

Methods  of  introducing  regeneration  into  the  de- 
tector. The  familiar  tickler  is  contrasted  with  two 
methods  of  avoiding  the  mechanical  difficulties  inci- 
dent to  a  variable  inductive  feedback.  A  Bradley- 
ohm,  a  Clarostat,  or  any  resistance  variable  from  a 
few  ohms  to  a  few  thousand  may  be  placed  across 
a  fixed  tickler  and  affords  a  smooth  control 


the  Laboratory.  Fig.  9  shows 
the  conventional  tickler  feed- 
back and  two  systems  for 
avoiding  the  variable  coupling 
between  tickler  and  detector 
coite. 

In  practice,  the  tickler  is 
fixed  in  position  so  that  oscil- 
lations will  occur  on  the  longest 
wave  to  be  received  without 
resistance  control.  Then,  by 
adjusting  the  resistance,  either 
shunt  or  series,  oscillations 
may  be  secured  on  other  wave- 


CAPACITY  FEED-BACK 

FIG.     IO 

A  condenser  may  be  used  to  introduce  regeneration 
in  connection  with  a  fixed  tickler  coil.  Here  again 
the  control  is  more  even  than  with  the  conventional 

"floppy"  tickler 

lengths.  This  regeneration  is  fairly  indepen- 
dent of  frequency — which  is  not  true  of  the 
usual  "flopping"  tickler  system — and  should 
not  affect  the  tuning  of  the  detector  circuit. 
In  the  five-tube  receiver,  this  is  particularly 
valuable  since  there  is  less  danger  of  un- 
wanted coupling  back  to  the  amplifier  than 
with  the  moving  tickler  coil. 

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  de- 
tector secondary  and  coupling  to  the  plate 
is  effected  by  means  of  a  series  condenser. 
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.  10  and 
a  drawing  of  a  choke  in  Fig.  1 1 .  There  should 
be  no  condenser  across  the  output  in  this 

Hard  Rubber 
or  Bakelite 


FIG.     I  I 

A  drawing  of  a  choke  coil  to  be  used  in  connection  with  condenser 
feed  back.  Fine  wire  may  be  used  and  up  to  100  turns  may  be  placed 
in  each  slot.  The  number  is  unimportant,  and  the  choke  itself  may 
be  eliminated  if  oscillations  occur  without  it.  Possibly  the  radio 
frequency  currents  will  be  kept  in  the  feedback  circuit  by  the  imped- 
ance of  the  telephones  or  audio  transformer  in  which  case  the  choke 
is  unnecessary 


New  Developments  and  Experiments  with  Receivers 


73i 


arrangement.  This  method  of  adding  regener- 
ation is  particularly  smooth  in  operation,  and 
it  avoids  the  movable  tickler  with  its  varying 
field. 

TUNED    PLATE    FEEDBACK 

ANOTHER  effective  method  of  adding  re- 
generation is  shown  in  Fig.  12.  This  is  the 
tuned  plate  scheme  popular  with  amateurs 
for  many  years.  The  coil  and  condenser  may 
be  of  the  same  dimensions  as  the  detector  tun- 
ing elements,  and  if  this  is  the  case,  the  dial 
readings  will  be  about  the  same  at  various  fre- 
quencies. 

This  system  is  particularly  effective  when 
using  toroid  coils  since  it  obviates  the  neces- 
sity of  tapping  the  inductances — which  would 
destrov  the  toroid  effect. 


TUNED   PLATE 


FIG.    12 

The  old  method  of  tuning  the  plate  circuit  to  the 
same  frequency  as  the  grid  circuit.  Oscillations 
will  occur,  and  if  this  plate  circuit  has  somewhat 
higher  resistance  than  ordinary,  oscillations  will  be 
controlled  very  easily.  It  is  possible  with  this 
arrangement  to  have  the  tickler  dial  read  like  the 
tuning  dials 


WIRELESS    COMES   TO   THE    LIGHTSHIP 

The  English  lightship  No.  67  at  Haisbro  is  one  of  many  in  the  British  and  other  services  to  be  equipped 
with  radio  receivers  to  entertain  the  crews  while  they  are  anchored  at  their  lonely  stations.  Many  of  these 
ships  are  equipped  with  automatic  radio  transmitters  which  transmit  radio  fog  signals  on  299  kc 
(1000  meters).  The  United  States  has  particularly  led  in  this  respect,  and  many  lightships  on  the  Atlantic 
and  Pacific  coasts  and  the  Great  Lakes  have  "radiophares"  or  directional  wireless  signals  for  ships 


so  THIS  is  VENICE! 

The  directorate  of  the  Venetian  "Rapid  Transit  Company"  is  equipping  all  of  its  conveyances  with  radio 
receivers.     Patrons   will   in   future   be  provided  with    timely  entertainment  in  the  event   of   a   tie-up 


THE  MARCH  OF  RADIO 


BY 


Past  President,  Institute  of  Radio  Engineers 


The  Horizontally  Polarized  Wave — Another  Radio  Bombshell 


WE    HAVE    all   become  familiar 
with  the  vagaries  of  energy  trans- 
portation  by   radio  waves  and 
have   practically   schooled  our- 
selves into  the  idea  that  fluctuation  and  fading 
of  signals  is  one  of  their  characteristics  and 
thus  not  to  be  remedied  or  be  done  away  with. 
But  also  we  have  learned  that  scientific  attack 
on  many  of  radio's  problems  has  frequently 
yielded  valuable  results  in  the  past,  so  when 
a  recognized  authority  puts  forth  a  new  idea  or 
radio  theory  we  are  ready  to  accept  it,  strange 
and  odd  as  it  may  sound  at  first. 

As  an  illustration  of  how  our  radio  ideas 
have  been  upset,  we  have  only  to  think  of  the 


directions  in  which  radio  waves  are  supposed 
to  travel.  Textbooks  tell  us  that  these 
waves  travel  out  from  a  station  in  a  straight 
line,  becoming  less  intense  with  increasing 
distance.  But  many  features  are  now  known 
to  affect  this.  Measurements  of  signals  from 
WEAF,  for  example,  in  the  vicinity  of  New 
York  City  show  that  at  many  places  the 
signals  come  from  directions  at  right  angles 
to  the  expected  one  and  further,  that  signals 
may  increase  in  intensity  with  increasing 
distance  instead  of  diminishing  as  they  should. 
So  we  have  to  be  ready  to  accept  other  odd 
ideas  if  they  are  based  on  experimental  fact. 
Engineers  of  the  General  Electric  Company 


Radio  Makes  the  North  Pole  "Next  Door" 


733 


and  the  Bell  Telephone  Laboratories  have  re- 
cently been  carrying  on  some  most  fascinating 
work  to  determine  exactly  what  happens  to 
radio  waves  as  they  travel  along.  We  can 
see  a  water  wave  as  it  goes  over  the  ocean 
surface,  see  it  twist  and  turn  around  a  pro- 
jecting pier  or  rear  itself  and  fall  over  on  a 
sand  bar,  but  to  find  what  happens  to  radio 
waves,  our  eyes  are  not  very  helpful.  Delicate 
vacuum  tube  apparatus  and  wonderful  oscillo- 
graphs are  necessary  to  show  photographically 
the  electric  currents  which  tell  us  definitely  of 
the  action  of  the  radio  waves. 

Interpreting  the  pictures  they  have  ob- 
tained, the  research  engineers  now  tell  us 
that  the  radio  waves  twist  and  turn  as  they 
travel  outward  from  the  station — that  in  some 
places  a  vertical  antenna  will  pick  up  more 
power  than  the  usual  horizontal  kind.  Fur- 
thermore, at  some  instance  the  horizontal  an- 
tenna may  be  better  than  the  vertical  one  and 
then,  as  the  amount  of  twisting  of  the  waves 
changes,  the  reverse  may  be  true. 

According  to  E.  F.  W.  Alexanderson,  con- 
sulting engineer  of  the  Radio  Corporation, 
this  haphazard  twisting  accounts  for  much  of 
the  rapid  fading  to  which  some  signals  are 
subject  and  he  suggests  a  possible  remedy. 
To  use  two  transmitting  antennas  is  appar- 


ently his  idea,  one  of  them  to  be  a  horizontal 
one  and  the  other  a  vertical  one.  Then  as 
these  two  waves  travel  out  from  the  broad- 
casting station,  their  total  effect  on  the  re- 
ceiving antenna  will  be  about  the  same  no 
matter  how  much  twisting  the  wave  has  suf- 
fered. In  his  opinion,  a  scheme  of  this  kind 
will  do  much  to  lessen  fading.  At  the  same 
time,  it  should  increase  the  ratio  of  signal 
strength  to  static;  which  is  the  same  as  though 
static' had  been  to  some  extent  eliminated. 

Mr.  Alexanderson  refers  to  this  second,  and 
aiding  radio  wave  as  horizontally  polarized. 
It  is  interesting  to  note,  in  this  connection,  an 
article  by  Walter  Van  B.  Roberts,  "Can 
Static  Interference  Be  Eliminated?"  in  RADIO 
BROADCAST  for  December,  1924.  Mr.  Ro- 
berts, in  that  article,  reviewed  methods  for  the 
elimination  of  static  interference  and  sug- 
gested, among  other  things,  that  horizontally 
polarized  waves  might  offer  a  solution  to  the 
difficulty. 

Radio,  the  Handmaiden  of  Explorers 

CERTAINLY   no  explorer  ever  started 
on  a  polar   expedition   with   the  as- 
surance reasonably   assumed  by   Mr. 
Donald  MacMillan  on  his  latest  venture  into 


E.    F.    W.    ALEXANDERSON  S    ANTENNA 

With  which  he  is  carrying  on  extensive  experiments  in  his  laboratory  at  Schenectady  in  radiating  horizontal 
polarized  waves.     It  is  possible  that  his  and  others'  experiments  will  result  in  the  diminution  of  static  and 

fading,  two  of  the  listeners'  deadliest  foes 


734 


Radio  Broadcast 


the  unknown  seas  around  the  North  Pole. 
A  few  years  ago  he  would  have  left  civiliza- 
tion with  the  reasonable  certainty  that  he 
would  not  hear  white  men  again  for  perhaps 
two  years;  all  that  time  his  triumphs  and  dis- 
asters would  be  known  to  him  alone,  those  at 
home  blindly  trusting  to  his  ability  to  return 
when  his  self  imposed  task  was  finished.  If 
he  was  not  heard  from  after  a  year  or  two  a 
relief  expedition  might  start  out  with  the 
slim  hope  of  picking  up  his  trail  and  giving 
what  aid  they  might. 

On  the  present  expedition,  radio  is  keeping 
the  explorer's  friends  constantly  advised  of 
his  progress;  both  ships  of  the  expedition  are 
well  equipped  with  apparatus  designed  specifi- 
cally to  best  maintain  the  polar  radio  channels 
open.  The  experience  with  radio  gained  by 
iMacMillan  and  his  operator,  Donald  Mix,  on 
the  previous  expedition  was  such  that  short 
waves  are  to  be  largely  depended  on  during 
the  present  trip.  Frequencies  from  about 


2000  kilocycles  up  will  be  used,  the  highest 
being  15,000  kilocycles  (150-20  meters). 
Only  specially  designed  receiving  sets  will 
pick  up  such  high  frequency  signals,  for  even 
the  lowest  of  these  frequencies  is  very  far 
beyond  the  highest  useful  frequency  of  broad- 
cast receivers. 

Already  the  peculiar  conditions  discovered 
on  the  last  trip  have  been  re-encountered. 
As  this  is  written,  the  Bowdoin  and  the  Peary 
are  in  the  Greenland  ice  fields,  not  isolated  as 
previous  explorers  have  been,  but  in  easy 
communication  with  those  at  home.  Instead 
of  reaching  the  eastern  coast  of  the  United 
States,  however,  the  radio  messages  are  al- 
ready veering  west,  and  again  the  operators  in 
Washington,  British  Columbia,  and  Iowa,  are 
the  ones  who  have  to  relay  MacMillan's  mes- 
sages to  us.  His  compass  pointed  due  west — 
a  fact  that  makes  us  well  appreciate  how 
far  from  usual  are  the  experiences  through 
which  these  northern  explorers  pass. 


Harris  &  Ewing. 


L.    A.    CORRIDON 

Of  the  Department  of  Commerce  who  is  responsible  for  the  selection  of  all  new  call  letters  for  broadcasting 
and  telegraphy  stations.     The  fact  that  he  is  tied  down  to  the  initial  letters,  N,  K  and  W,  makes  this  no 

simple  matter 


Broadcast  Interference  in  Europe 


735 


How   the    League   of    Nations    Aids 
Radio 

IN  SPITE  of  the  assertions  of  many  of  our 
politicians  that  the  League  of  Nations  is 
dead,  it  seems  to  be  gradually  working 
out  problems  which,  without  the  international 
cooperation  the  League  guarantees,  might  be 
the  cause  of  much  bad  feeling.  Of  especial 
interest  to  us  is  the  attack  being  made  on  the 
radio  broadcast  problem.  With  our  561 
broadcasting  stations,  the  interference  prob- 
lem is  by  no  means  as  important  and  difficult 
question  as  it  is  in  Europe  with  its  fifty  odd 
stations. 

With  the  possible  exception  of  a  small  part 
of  our  northern  border,  the  interference  be- 
tween various  stations  in  America  is  na- 
tional rather  than  international.  Hard 
feelings,  if  any  are  really  engendered,  are 
not  of  international  significance  and  can 
lead  to  no  serious  trouble.  In  Europe, 
however,  the  fifty  odd  stations  may  cause 
a  tremendous  amount  of  international  dis- 
sention.  The  countries  are  so  small,  and 
so  close  together,  that  a  station  of  any 


one  country  is  very  apt  to  reach  out  into 
all  the  others.  The  band  of  frequencies 
available  for  broadcasting  in  Europe  permits 
of  only  forty-two  channels,  so  that  with  the 
fifty-seven  stations  operating,  some  inter- 
ference is  almost  sure  to  occur. 

The  technical  committee  of  the  Interna- 
tional Radiophone  Union  acting  under  the 
auspices  of  the  Communication  Section  of  the 
League  of  Nations,  has  just  met  to  discuss  and 
act  upon  the  European  broadcast  situation. 
Taking  up  the  interference  question  in  a 
reasonable  and  amicable  manner,  the  com- 


THE    JOHANNESBURG    BROADCASTING    STATION 

Showing  the  antenna  atop  Stuttafords  Buildings  in  Pritchard  Street.  Transmissions  from  KDKA  at  Pitts- 
burgh are  often  re-radiated  from  this  antenna  after  being  picked  up  at  a  distance  of  about  three  miles  from 
the  studio  and  then  carried  by  land  line  to  the  transmitter.  The  smaller  picture  shows  Miss  Peggy  Cook 
giving  a  recital  from  the  station,  JB.  The  floor  of  the  studio,  it  will  be  noticed,  is  squared  off  to  enable  the 
director  to  place  the  artists  to  best  advantage 


736 


Radio  Broadcast 


mittee  decided  that  with  the  amount  of 
information  avilable,  a  proper  solution  of  the 
problem  was  not  possible.  It  was  decided  that 
during  the  next  two  months,  extensive  testing 
would  be  taken  up,  on  regular  schedules  after 
the  broadcasting  hours,  to  accumulate  the 
necessary  data  on  the  interference  effects. 
Two  months  experimenting  are  necessary  in 
the  committee's  opinion  and  so  the  session 
was  adjourned  for  about  this  length  of  time, 
after  which  another  meeting  will  be  called  to 
further  analyze  the  question.  We  are  glad  to 
see  that,  to  all  appearances,  European  inter- 
ference will  be  settled  in  a  friendly  manner  in 
spite  of  the  international,  and  therefore  vexa- 
tious, questions  involved. 

The    News    Value    of    Broadcasting 

PROBABLY     never     before     has     radio 
performed  such  a  countrywide  service 
as  when  the  news  about  Mr.   Bryan's 
death  was  broadcast.     Whether  for  or  against 
him  there  was  none  of  us  who  could  help 
being  interested  in  the  passing  of  this  noted 
American.     His  death  came  so  suddenly  and 


WHAT   ARE    THEY    LISTENING   TO? 

Or  are  they  merely  resting  between  "paddles"?  The  photographer  tells 
us  that  the  two  youngsters  are  enjoying  the  music  provided  by  their 
radio,  but  we  fail  to  detect  any  antenna  and  we  hardly  suspect  that  an 
enclosed  loop  would  give  satisfactory  results  with  a  neutrodyne  receiver 


unexpectedly  that  it  made  the  service  of  radio 
seem  even  more  striking  than  it  has  been  on 
other  occasions,  when  a  previously  announced 
event  has  been  spread  over  the  country. 

On  Sunday  evening,  the  radio  audience  is 
probably  larger  than  at  any  other  time  and, 
as  every  important  broadcasting  station  was 
at  once  notified  by  telephone,  telegraph  or 
radio  of  Mr.  Bryan's  death  in  the  obscure 
Tennessee  village,  it  seems  not  at  all  unlikely 
that  within  a  few  hours  of  its  happening,  from 
five  to  ten  millions  of  his  countrymen  had  been 
notified  of  the  sad  event. 

"Weeding  Out"  in  the  Radio  Trade 

A  RECENT  summary  of  the  midsummer 
conditions  of  the  radio  industry  shows 
that    although    many    of   the   smaller 
companies  must  succumb  as  a  result  of  over 
production,    and    consequent    cut    price   dis- 
position of  their  stock,  many  of  the  companies, 
by  pooling  patents  and  credits,  consolidation 
of  manufacturing  facilities,  etc.,  are  putting 
themselves  on  a  reliable  and  trustworthy  basis 
for  the  resumption  of  trade  in  the  fall. 

When  we  consider  the  ex- 
traordinarily rapid  growth 
of  the  radio  business,  it 
seems  remarkable  that 
even  more  business  failures 
have  not  occurred.  In  1920, 
the  radio  business  was  esti- 
mated at  two  million,  in 
1921  five  million,  1922  sixty 
million,  1923  one  hundred 
and  twenty  million,  and  in 
1924  three  hundred  million 
dollars.  The  estimates  for 
the  radio  business  for  the 
present  year  go  as  high  as 
four  hundred  and  fifty  mil- 
lion. 

A  short  time  ago  the 
stock  exchange  saw  a  new 
radio  stock  practicaMy 
every  day,  and  during  this 
year  about  five  million 
shares  of  radio  stock  were 
sold  to  the  public.  The  ad- 
vertisements of  this  stock 
were  generally  worded  to 
indicate  that  reliable  busi- 
ness regarded  them  as  a 
gamble,  but  the  public  was 
willing  to  take  a  chance, 
and  did  so.  Comparison  of 
the  original  selling  price  of 


Great  Radio  Activity  Abroad 


737 


TWO    PROMINENT    BRITISHERS 

On  the  left  is  J.  C.  Reith,  who  is  the  managing  director  of  the  British  Broadcasting  Com- 
pany and  a  popular  figure  among  the  British  listening  public.  The  Right  Hon.  F.  G. 
Kellaway  is  shown  in  the  second  photograph.  He  succeeded  Godfrey  Isaacs  as  manag- 
ing director  of  the  Marconi  Wireless  Telegraph  Co.  Ltd.  and  the  Marconi  International 

Communication  Co.  Ltd. 


the  stock  with  the  present  quotations  show  that 
the  trusting  public  has  already  suffered  a  paper 
loss  of  more  than  $  \  00,000,000.  Probably  this 
loss  will  be  a  real  one  and  of  even  greater 
magnitude  before  the  radio  business  is  com- 
pletely stabilized. 

Present  estimates — all  of  them  founded  on 
no  especially  reliable  facts — place  the  number 
of  radio  sets  in  the  hands  of  the  public  at 
2,500,000,  and  as  we  have  about  9,000,000 
phonographs  in  our  homes,  and  12,000,000 
automobiles,  it  is  evident  that  for  those 
companies  which  make  reliable  apparatus  and 
which  are  properly  financed  to  stand  the 
periods  of  depression,  there  is  still  plenty  of 
market  left  to  absorb  their  products. 

Radio  in  Foreign  Countries 

FROM  the  Department  of  Commerce 
comes  a  summary  of  the  radio  situa- 
tion in  foreign  countries,  compiled  for 
the  benefit  of  American  manufacturers  who 
are  seeking  to  do  export  business. 

In  Austria,  where  broadcasting  began  a 
year  ago,  much  interest  is  displayed,  and  it  is 
estimated  there  are  at  present  fifty  thousand 
receivers  in  use;  most  of  which  are  of  home 
manufacture  due  to  the  high  tax  imposed  on 
imported  sets.  The  broadcast  listener  must 
obtain  a  license  before  using  a  receiving  set. 
The  license  costs  at  the  present  rate  of  ex- 
change about  fifty  cents  a  year. 

In  Czecho-Slovakia,  a  broadcast  station  of 


five  kilowatts  capacity  is  about  to  be  erected 
in  Prague.  If  receivers  of  the  type  common 
in  America  are  used,  this  station  should  reach 
over  most  of  the  country. 

In  Spain  there  is  a  considerable  demand  for 
radio  apparatus,  due  largely  to  the  operation 
of  two  broadcasting  stations  in  Madrid. 
Although  most  of  the  receiving  apparatus  is  of 
British  and  French  origin,  the  American 
manufacturer  can  well  afford  to  go  after  this 
market.  In  the  first  quarter  of  1925  more  than 
$100,000,  worth  of  American  apparatus  was 
imported. 

In  South  America,  Argentina  continues  to 
lead,  possibly  because  the  government  has  not 
as  yet  put  any  restriction  on  the  use  of  radio 
receivers.  It  is  claimed  that  practically  all 
the  radio  apparatus  used  there  is  of  American 
manufacture. 

New  Zealand  has  just  put  in  several  broad- 
casting stations  and  the  number  of  radio  re- 
ceivers is  rapidly  on  the  increase.  It  seems 
that  most  of  this  apparatus  must  be  of  home 
manufacture  or  else  of  British  origin  as  the 
imports  from  America  for  the  first  quarter  of 
1925  totaled  only  $23,700. 

Our  commercial  attache  in  London  reports 
that  although  but  little  American  apparatus  is 
as  yet  used  in  England  he  believes  that  there 
will  be  a  considerable  market  for  highly  sensi- 
tive sets  which  will  be  sought  only  by  the 
"distance  hound"  because  those  who  listen 
only  to  local  stations  do  not  require  multi-tube 
receivers.  There  are  twenty-two  stations  on 


738 


Radio  Broadcast 


the  mainland,  only  as  large  as  New  York  and 
Pennsylvania  combined,  so  that  no  listener  is 
very  far  from  his  closest  station. 

Is    Canada    Showing    Us   the   Way? 

WE  ARE  glad  to  notice  that  someofour 
Canadian  friends  have  earnestly  taken 
up   the   fight   against   radiating  re- 
ceivers.    The  position  of  this   magazine  on 
the  question  has  been  stated  repeatedly  and 
we  are  glad  to  commend  our  northern  neigh- 
bors for  the  attack  they  have  started. 

The  Victoria  Radio  Club  of  Victoria, 
British  Columbia,  have  sent  their  views  on 
the  question  to  the  Dominion  government  in 
the  following  letter: 

Honorable,  the  Minister  of  Marine  and  Fisheries, 

Dominion  Government, 

Ottawa. 

SIR: 

Whereas  in  the  opinion  of  the  members  of  the 
Victoria  Radio  Club,  the  use  of  radiating  sets  has 
become  a  public  nuisance,  it  is  the  opinion  of  this 
club  that  some  government  action  must  be  taken. 

We  believe  that  the  manufacture  and  sale  of 
radiating  sets  in  Canada  should  at  once  be  stopped 
by  law,  that  on  all  licenses  the  type  of  receiving  set 
used  should  be  specified,  and,  in  reasonable  time, 
the  use  of  all  radiating  sets  absolutely  prohibited 
by  law.  Also  that  all  radio  inspectors  be  given  full 
power  to  act  at  once  in  case  of  persistent  interfer- 
ence. 

Yours  truly, 
Victoria  Radio  Club. 


The  Month  in  Radio 


niiiiiiiimiliiimiiiiiiiiiiiiiimmilliHimillimmiimililiimiimiiiimiiiiiiiiiii  .......  iiiinimmin 

THE  Bureau  of  Foreign  Commerce  in 
Washington  reports  the  successful 
transmission  of  energy  by  radio,  the 
feat  having  been  accomplished  by  an 
Italian  inventor.  The  radio  waves  he  used 
were  so  short  that  the  kilocycle  becomes  an 
inconveniently  small  unit  for  expressing  their 
frequency.  In  wavelength,  so  the  dispatch 
states,  the  radio  wave  resembles  a  light  wave 
rather  than  a  radio  wave,  the  length  being 
only  about  one  hundred  millionth  of  a  meter. 
Remembering  the  "achievement"  of  another 
Italian  inventor,  who,  during  the  war,  was  to 
explode  submerged  bombs  from  great  distances 
by  the  use  of  a  ray  much  the  same  as  this,  we 
would  not  even  mention  the  present  dispatch 
if  it  had  not  come  to  us  in  a  Department  of 
Commerce  communication.  It  is  onlv  a 


short  time  ago  that  the  inventor  of  a 
wonderful  "death  ray"  had  headlines  in  all 
of  our  newspapers  but  to  the  best  of  our 
knowledge  he  never  showed  a  single  experi- 
ment to  back  up  these  claims. 

/CONGRESSMAN  SOL  BLOOM  of  New 
^-^  York  has  just  announced  that  he  is 
about  to  lead  a  battle  to  purify  the  ether  from 
the  taint  of  radio  advertising.  At  the  next 
session  of  Congress  he  will  introduce  a  bill 
abolishing  all  advertising  through  the  broad- 
cast channels.  He  denounced  the  exploita- 
tion of  the  radio  public  by  advertisers  in  no 
uncertain  terms.  We  hasten  to  point  out  to 
him  that  he  would  be  wise  to  proceed  slowly. 
The  public  will  never  get  something  for 
nothing  and  so  if  they  are  to  get  a  good  musi- 
cal program  without  paying  a  cent  for  the 
artists,  it  will  probably  be  necessary  to  listen 
to  the  name  of  the  donor  of  the  hour's  enter- 
tainment. This  indirect  advertising,  if  well 
done,  is  not  at  all  disagreeable.  If  Mr.  Bloom 
is  successful,  he  will  legislate  away  our  best 
radio  entertainments. 

JUST  why  the  police  should  permit  a 
demonstration  of  a  radio  controlled  car 
on  crowded  New  York  streets  is  a  mystery,  yet 
just  that  did  happen.  On  one  of  New  York's 
busiest  thoroughfares  an  automobile,  con- 
trolled by  radio  from  another  car  a  few  yards 
away  from  it,  was  allowed  to  careen  its  way 
against  traffic,  making  other  cars  climb  up  on 
the  sidewalks  to  avoid  collisions,  narrowly 
missing  a  fire  engine,  and  finally  plunging  into 
a  photographer's  car. 

There  is  nothing  remarkable  about  such  a 
demonstration  except  the  foolishness  of  the 
police  in  permitting  it.  The  remote  control  of 
vehicles,  boats,  and  even  aeroplanes  has  been 
accomplished  many  times  before,  but  never 
before  on  a  crowded  city  street. 

HpHE  Navy  Department,  which  is  tem- 
*  porarily  carrying  on  commercial  radio 
business  across  the  Pacific,  announces  that 
traffic  to  Tahiti  is  now  possible.  From  our 
west  coast  to  Hawaii,  then  to  the  Samoan 
Islands,  and  so  to  Tahiti,  the  radio  reaches 
over  the  expanse  of  the  Pacific. 

AT  THIS  year's  commencement  of  Union 
College,  the  Bailey  prize,  given  each 
year  to  that  senior  who  contributes  most  to 
the  college,  went  to  Edward  B.  Redington, 
who  had  carried  on  experiments  in  the  genera- 
tion of  very  high  frequency  oscillations  by 


Current  Events  in  Radio 


739 


vacuum  tubes.  By  using  very  short  connec- 
tions for  inductances  and  in  place  of  an 
ordinary  condenser  utilizing  the  capacity 
between  the  grid  and  plate  of  the  tube,  he 
was  able  to  obtain  frequencies  as  high  as 
80,000  kilocycles  (3.8  meters)  using  fifty-watt 
tubes.  Those  who  have  tried  to  make  large 
tubes  oscillate  at  very  high  frequencies 
realize  the  difficulties  which  the  young  re- 
searcher encountered  and  feel  that  he  well 
deserved  the  prize. 

TN  LONDON,  a  bill  has  just  passed  Parlia- 
*  ment  which  makes  it  illegal  to  make  phono- 
graph records  from  radio  signals.  It  is  said 
that  many  well  known  artists  have  refused  to 
sing  over  the  radio  because  of  the  possibility 
of  records  being  made  in  this  way,  and  quite 
naturally  the  artists  are  not 
anxious  to  "stand  for"  the 
indifferent  quality  the  aver- 
age radio  set  gives. 


THE  city  of  Philadelphia 
has  just  awarded  Wil- 
liam G.  Housekeeper  of  the 
Bell  Telephone  Laborato- 
ries, the  John  Scott  medal 
for  his  contribution  to  tech- 
nical progress.  The  award 
carries  with  it  a  $1000  prize. 
By  this  public  award,  Mr. 
Housekeeper  is  recognized 
as  the  one  responsible  for 
the  development  of  the 
metal-glass  seal  which  was 
the  one  step  required  to 
increase  the  capacity  of 
triodes  from  one  kilowatt 
to  one  hundred  kilowatts 
or  more.  As  previously 
explained  in  these  columns, 
to  seal  successfully  a  large 
copper  thimble  to  a  large 
glass  tube  was  impossible 
until  Mr.  Housekeeper  dis- 
covered that  if  the  edge  of 
the  copper  tube  was  made 
very  thin  where  it  met  the 
glass,  the  joint  would  not 
crack,  as  was  always  the 
case  when  this  simple  expe- 
dient was  not  resorted  to. 
Copper  and  glass  contract 
to  different  degrees  on  cool- 
ing so  that  the  joint  has 
always  cracked  as  the  glass 
cooled  down,  thus  spoiling 


the  vacuum  tube.  If,  however,  the  copper  tube 
is  drawn  to  a  thin  edge  where  it  meets  the  glass 
it  becomes  sufficiently  elastic  that  as  the  cooling 
glass  tries  to  pull  away  from  it  the  copper  yields 
and  thus  permits  the  joint  to  stay  air-tight. 

The  Misuse  of  a  Municipal  Broadcast 
Station 

ABOUT  a  year  ago,  when  the  mayor  of 
New    York    City   was    contemplating 
the  installation  of  a  municipal  broad- 
casting  station,    we   pointed   out    the   very 
likely  misuse  to  which  such  a  station  could  be 
put  by  unscrupulous  politicians.     We  don't 
yet   appreciate   either   the   importance  of   a 
broadcasting  station  of  this  stripe  nor  yet  its 
proper  economic  classification. 


PREMIER    STANLEY    BALDWIN 

Delivering  an  address  which  was  simultaneously  broadcast  from  every 
one  of  the  British  broadcasting  stations.  The  occasion  was  the  recent 
rally  of  more  than  100,000  persons  at  Welbeck  Abbey,  celebrating  the 
signal  victory  of  conservatism  under  Premier  Baldwin.  Note  the  two 
microphones  which  are  enclosed  within  the  boxes  in  front  of  him 


740 


Radio  Broadcast 


GOVERNOR    ALFRED    E.    SMITH 


-Of  New  York  State- 


"  The  American  democracy  covers  so  vast  a 
territory  that  we  must  heartily  welcome  an  art 
that  brings  its  executives  and  legislators  into  the 
most  immediate  contact  with  the  public  they  have 
been  elected  to  serve.  The  advantage  is  double. 
Radio  expedites  the  sending  of  an  intimate  mes- 
sage to  the  whole  body  of  citizens  and  it  secures  to 
the  speaker  a  more  prompt  and  frank  expression 
of  personal  opinion  than  he  could  obtain  in  any 
other  way.  Thus  there  is  preserved  a  mutual 
relationship  thai  is  of  especially  high  value  as  new 
problems  arise  which  can  best  be  solved  by  a 
renewed  meeting  of  minds. 

"Recent  experiences  in  broadcasting  matters  of 
public  moment  through  the  medium  of  WGY  have 
given  me  a  new  sense  of  close  fellowship  with  my 
fellow  citizens;  their  many  replies  have  been  an 
inspiration  in  seeking  a  solution  to  the  questions 
which  an  executive  can  conscientiously  answer 
only  in  the  full  light  of  the  common  thought." 


Is  it  a  proper  use  of  public  funds  to  es- 
tablish such  a  publicity  medium,  which  can 
so  easily  be  used  to  wage  warfare  on  those 
who  incur  the  disfavor  of  the  temporary  muni- 
cipal rulers?  This  question  has  been  brought 
up  in  the  case  of  WNYC,  New  York.  A 
citizen  claimed  that  the  establishment  and 
maintenance  of  the  station  was  a  misuse  of  the 
city's  funds.  In  the  suit  against  the  city 
authorities,  the  plaintiff's  attorney  states 
that: 

the  City  of  New  York,  and  the  defendants  are  with- 
out authority  to  expend  or  use  the  funds  of  the  City 
of  New  York  for  the  purchase,  construction,  or  opera- 
tion of  the  station.  That  there  is  no  authority  in 
law  for  broadcasting  official  reports  by  radio,  the 
publication  of  such  reports  being  otherwise  provided 


for.  That  there  is  no  authority  for  the  use  or  ex- 
penditure of  city  funds  for  the  broadcasting  of  po- 
litical propaganda  on  behalf  of  the  defendant  or 
any  other  person  or  persons. 

That  unless  restrained  the  illegal  acts  of  the  de- 
fendants will  continue.  .  .  . 

More  than  a  year  ago,  Mr.  Grover  Whelan, 
then  Commissioner  of  Plants  and  Structures, 
through  whom  the  Mayor's  orders  regarding 
the  station  were  carried  out,  made  a  public 
statement  of  what  the  station's  activities  were 
to  be.  Said  he,  when  the  station  was  being 
installed, 

editorial  writers  are  now  concerning  themselves 
with  the  possible  misuse  of  the  municipal  station. 
Let  me  assure  these  gentlemen  that  no  administra- 
tion would  be  foolhardy  enough  to  invade  the 
sacred  precincts  of  the  homes  of  its  people  with  any 
political  propaganda.  .  .  . 

The  complaint  states  that  "the  purpose  and 
use  of  this  broadcasting  station  have  been 
utterly  different  from  what  was  indicated  in 
the  above  statement  and  it  has  been  used  re- 
peatedly and  continuously  for  grossly  im- 
proper political  propaganda." 

The  city  officials  have  given  out  reports 
which  are  supposed  to  show  that  the  material 
sent  out  over  the  broadcast  channel  was  en- 
tirely non-partisan.  Any  listener  who  has 
heard  the  political  "news"  broadcast  from 
station  WNYC  knows  the  facts  to  be  otherwise. 
Fulsome  praise  of  the  city's  mayor  has  always 
been  a  dominant  note  of  the  so-called  "news 
of  the  day"  and  violent  attacks  on  any  who 
dared  question  his  actions  have  always  been 
used  to  accentuate  his  wisdom  and  his 
thoughtfulness  for  the  city's  dwellers. 

The  actual  situation  is  readily  made  clear 
when  one  recalls  that  any  talk  to  be  sent  out 
over  WNYC'S  channel  has  to  be  written  out 
beforehand — as  is  true  of  almost  every  first- 
class  station — and  submitted  to  the  mayor 
or  his  hirelings  for  criticism  and  correction 
before  being  delivered.  The  Mayor  or  his 
commissioners  are  quite  free  to  say  what  they 
want  to  on  any  subject  uppermost  in  their 
minds. 

Supreme  Court  Justice  Churchill  denied  the 
injunction  asked  by  the  Citizen's  Union,  the 
body  behind  the  movement,  to  confine  the 
use  of  the  station  to  proper  activities.  In  his 
decision,  he  states  that  "it  was  within  the  dis- 
cretion of  the  legislative  bodies  (of  the  city) 
either  to  confine  the  use  of  the  station  to  the 
administrative  work  of  the  city's  officials  or 
to  permit  a  wider  use."  The  court  also  as- 
serted that  it  was  "a  question  which  no  court 


The  City  Broadcast  Station  of  New  York— A  Failure 


has  a  right  to  consider."  So  that  evidently 
the  taxpayer  in  New  York  has  no  redress;  if 
he  doesn't  want  to  hear  what  a  wonderful 
mayor  the  city  has  had  for  the  last  seven  years 
and  reasons  for  putting  him  back  in  office,  his 
only  recourse  is  to  tune-in  on  other  channels. 
The  course  of  events  following  the  opening 
of  this  municipal  station  is  exactly  as  we 
predicted  it  would  be  when  discussing  its  in- 
stallation; while  ostensibly  of  service  to  the 
police  and  other  departments  its  most  im- 
portant function  may  be  to  spread  political 
propaganda  for  those  in  office. 

The  Radio  Corporation  Announces  a 
Deficit 

FOR  the  first  time  in  its  history,  the 
Radio  Corporation  of  America  has 
reported  a  deficit.  Its  expenses  for 
the  second  quarter  of  the  year  exceeded  its 
income  by  nearly  $400,000.  This  is  the  first 
check  in  a  remarkable  growth,  and  one  almost 
without  parallel  in  financial  circles. 

Up  to  1921,  the  Radio  Corporation  retained 
its  original  character.  Founded  during  the 
war  to  improve  the  overseas  communication 
channels  for  the  government,  for  several  years 
it  was  essentially  a  transoceanic  communica- 
tion company  with  a  comparatively  small  busi- 
ness. Even  the  total  transoceanic  communi- 
cation business  is  not  very  large  and  of  course 
the  radio  channels  got  only  a  resonable  frac- 
tion of  the  total.  In  1921,  when  radio  broad- 
casting began,  the  total  business  of  the 
Corporation  was  less  than  $1,500,000.  Last 
year,  its  business  totalled  $50,000,000.  Such 
a  rapid  growth  has  seldom  been  seen  in  the 
industrial  world. 

During  the  first  quarter  of  this  year,  the 
earnings  of  the  company  were  $15,229,923, 
which,  with  expenses  of  $13,301,594,  left  a 
comfortable  surplus  for  dividends.  But  the 
second  quarter  showed  earnings  somewhat 
less  than  $4,600,000,  and  the  expenses  were 
nearly  $5,000,000,  leaving  a  deficit  for  the 
quarter  of  $391,053.  This  report  shows  the 
high  seasonal  character  of  the  radio  business 
and  serves  to  emphasize  the  fact  that  a  com- 
pany must  have  a  good  deal  of  financial 
reserve  or  else  carry  on  at  the  same  time  some 
other  business  which  fills  in  the  slack  periods 
of  the  radio  season. 

It  is  quite  evident  that  the  Radio  Corpora- 
tion is  feeling  the  pressure  of  competition  and 
the  tremendous  unloading  of  sacrificed  stock 
which  many  of  the  smaller  companies  were 
forced  to  carry  out  this  summer.  Unlike  the 


EDWARD    H.    JEWETT 

Detroit;   President  Jewett   Phonograph 

and  Radio  Company 

"  There  is  no  question  about  the  public  s  baring 
purchased  a  terrible  lot  of  junk  in  the  past  years, 
believing,  of  course,  that  they  were  buying  reliable 
radio  apparatus.  It  has  not  given  them  any 
satisfaction  and  it  certainly  has  done  the  radio 
industry  harm. 

"Re  sure  to  go  to  a  dealer  in  whom  you  hare 
confidence  and  then  add  the  caution  of  compari- 
son. Gear  your  actions  to  what  you  hear 
demonstrated,  not  to  what  you  arc  promised.  I 
am  sure  that  if  any  one  of  you  "were  out  to  pur- 
chase a  trotting  horse,  for  example,  and  the  seller 
said  the  horse  could  make  a  mile  in  two  minutes 
flat,  you  would  not  make  the  purchase  on  such 
hearsay.  More  likely  you  would  say,  'Is  that 
so?  Let's  see  the  bound  do  it.' 

"Approach  your  radio  purchases  the  same  way. 
Remember  that  you  are  buying  something  you  will 
want  for  a  long  time  and  apply  that  thought  to  the 
measure  of  what  you  spend.  The  difference  be- 
tween cheapness  and  economy  is  almost  the  same 
as  the  difference  between  disgust  and  satisfac- 
tion." 


smaller  companies,  however,  this  great  cor- 
poration has  sufficient  reserve  power  to  stand 
several  such  temporary  setbacks. 

Where  is  'the  Channel  Cable? 

NOT    long    ago   we    enthusiastically    re- 
ported  the  success   of  an   experiment 
which,  although  not  belonging  strictly 
in  the  radio  realm,  was  sufficiently  close  to  it 
to  be  classed  by  many  as  a  new  conquest  for 
radio  signalling. 
On  manv  occasions  the  traffic  in  our  im- 


742 


Radio  Broadcast 


portant  harbors  is  held  up  for  hours  and  some- 
times days,  by  heavy  fogs.  Where  the 
channels  are  narrow  and  winding,  the  cautious 
pilot  generally  holds  up  his  ship  until  he  can 
see  the  familiar  landmarks.  These  delays  of 
course  are  very  cos"tly  to  steamship  companies 
and  aggravating  to  homecoming  passengers  so 
that  the  public  hailed  with  delight  some 
months  ago  the  announcement  of  a  new 
scheme  for  piloting  ships  into  harbors  in  spite 
of  fog. 

An  insulated  electric  cable  laid  on  the 
bottom  of  the  channel,  carrying  alternating 
current  of  about  500  cycles  frequency,  was  to 
act  as  a  guide  to  the  fog-bound  ship;  large  coils 
carried  on  the  ship's  sides  were  to  be  used  to 
pick  up  the  alternating  magnetic  field  surround- 
ing the  cable  and  by  suitable  setting  of  these 
coils,  as  the  received  signal  was  heard  in  a  pair 
of  head  phones,  the  ship  could  be  held  on  a 
course  right  over  the  top  of  the  submerged 
cable.  As  this  was  laid  in  the  center  of  the 
channel,  the  scheme  (at  least  on  paper)  seemed 
sure  to  permit  the  pilot  to  bring  his  vessel  up 
the  harbor  no  matter  what  the  weather  condi- 
tions might  be. 

After  the  successful  experiments  were  re- 
ported, it  seemed  certain  that  the  scheme 
would  be  put  into  operation.  The  cable 
installation  could  not  be  very  expensive  and 
the  apparatus  required  on  board  ship  was  so 
cheap  and  simple  that  its  immediate  applica- 
tion in  important  harbors  seemed  almost 
certain.  But  either  the  reporter  responsible 
for  the  story  of  the  successful  tryout  was  too 
optimistic  or  else  the  pilots  refused  to  accept 
newfangled  ideas,  otherwise  we  should  not 
read  in  a  current  paper  that  "fifteen  steamers, 
including  eight  passenger  liners,  lie  off  Am- 
brose Light  waiting  for  the  fog  to  lift."  The 
Ambrose  channel  is  exactly  the  place  where 
the  successful  cable  tests  were  carried  out. 


Interesting  Things  Interestingly 
Said 


CULTAN  CHINEY  (Bombay;  interviewed 
*~  during  his  recent  visit  to  this  country): 
"At  present  there  is  no  commercial  wireless  in  India 
but  we  have  recently  started  the  India  Radio  Tele- 
graph Company,  Ltd.,  and  obtained  all  the  rights 
of  the  Marconi  Wireless  Telegraph  Company  with 
their  affiliations  in  America,  Germany,  and  France, 


and  are  putting  up  beam  stations  to  connect  in  the 
first  instance  with  England  and  then  America  and 
gradually  with  the  rest  of  the  world.  The  Gover- 
ment  of  India  is  going  to  give  a  single  license  to  one 
company,  such  as  the  British  Broadcasting  Com- 
pany has  received  for  England.  Interest  in  radio 
has  become  tremendous  in  India  and  there  are 
many  radio  sets  in  use,  some  of  them  of  American 
origin.  But  we  have  a  large  population  and  one 
difficulty  that  confronts  us  is  that  if  we  wish  to  make 
everybody  understand  what  we  are  broadcasting, 
we  shall  have  to  use  about  nineteen  languages.  I 
rather  think  we  shall  have  to  concentrate  on  two — 
the  Hindu  and  English. 

p\R.  J.  H.  DELLINGER  (Washington,  D.  C.; 
*-~^  Chief,  Radio  Laboratory,  Bureau  of  Stan- 
dards): "There  has  been  considerable  discussion  over 
the  question  of  regulating  the  character  of  programs 
sent  out  by  broadcasting  stations.  The  Govern- 
ment has  consistently  opposed  censorship,  and  the 
result  is  that  the  stations  are  entirely  free  in  their 
choice  of  material.  The  radio  broadcasting  system 
of  the  United  States  can  be  characterized  as  one  of 
extreme  freedom.  Any  one  is  free  to  erect  a  broad- 
casting station  and  no  license  or  regulation  other 
than  patent  right  is  imposed  upon  the  sale,  purchase 
and  use  of  receiving  apparatus.  This  accounts  in 
large  measure  for  the  remarkable  growth  of  radio 
broadcasting.  It  is  also  responsible  for  the  principal 
difficulty  in  which  broadcasting  finds  itself  at 
present,  the  existance  of  too  many  broadcasting 
stations." 

DISHOP  JAMES  E.  FREEMAN  (Washington; 
*-*  National  Cathedral):  "More  and  more  am  I 
coming  to  the  conviction  that,  through  the  me- 
dium of  radio,  we  are  to  bring  about,  among  all 
types  and  classes  of  our  people,  not  only  a  better 
understanding,  but  a  finer  spirit  of  unity  and 
comradeship.  In  the  course  of  a  ministry  covering 
thirty-one  years  I  have  never  had  a  greater  evidence 
of  the  widespread  interest  in  religion — and  that 
from  all  types  of  people — than  during  the  year  and 
a  half  in  which  we  have  been  broadcasting  our 
services  from  the  National  Cathedral  in  Washing- 
ton." 

\AARTIN  P.  RICE  (Schenectady;  manager  of 
^*  broadcasting  for  the  General  Electric  Com- 
pany): "Radio  programs  are  slowly  but  surely  im- 
proving. The  listening  public  is  becoming  more  dis- 
criminating and  exacting.  The  advertising  program 
is  being  weighed  in  the  balance  of  public  favor  and 
it  is  doubtful  if  it  will  be  accepted.  More  skill,  art 
and  talent  are  needed  to  make  advertising  by  radio 
successful.  Good  music  is  appreciated  every- 
where, and  the  stations  broadcasting  it  are  always 
popular.  Jazz  still  has  a  place  on  programs 
especially  for  dancing,  but  it  is  not  so  noisy  as  it 
used  to  be  and  it  is  more  melodious." 


Guiding  the  Good  Ship  Radio 

An  Interview  with  W.  D.  Terrell,  Chief  Supervisor  of  Radio,  Department 
of  Commerce — The  Radio  Inspector's  Relation  to  Broadcasting — The 
Amateur's  Service  to  Radio — Elimination  of  Interference  by  Cooperation 


BY  DWIGHT  K.   TRIPP 


MANY  people  think  that  the  amateur 
is  a  boy  playing  with  a  toy,  and 
that  he  serves  no  useful  purpose," 
says  W.  D.  Terrell,  Chief  Super- 
visor of  Radio,  Department  of  Commerce. 
"This  is  a  mistaken  idea.  The  licensed 
amateurs  of  this  country  number  in  their 
ranks  doctors,  lawyers,  business  men,  engi- 
neers, and,  in  fact,  men 
and  boys  of  all  ages 
and  of  all  walks  of  life. 
Many  of  our  amateurs 
are  men  who  are  ser- 
iously interested  in  the 
development  of  radio, 
and  the  boys,  through 
their  amateur  training, 
develop  into  the  most 
successful  commercial 
operators.  As  ama- 
teurs these  boys  learn 
to  adjust  their  sets 
properly,  make  repairs, 
receive  messages  under 
the  most  difficult  con- 
ditions, and  become 
generally  self-reliant. 
They  proved  their 
value  to  this  country  as 
a  reserve  force  during 

the  late  war.  As  a  rule,  they  are  law-abiding, 
unselfish,  and  anxious  to  cooperate  with  our 
branch  of  the  government  service  to  the  fullest 
possible  extent.  This  country  has  long 
appreciated  their  worth  and  it  has  extended  to 
them  privileges  not  enjoyed  by  the  amateur 
of  any  other  country.  Recently,  I  am  glad 
to  say,  other  countries  have  begun  to  take  a 
more  liberal  view  of  their  activities." 

Through  the  energies  of  the  radio  amateur, 
many  new  and  wonderful  discoveries  have 
been  made,  among  the  most  important  of 
which  was  the  discovery  a  short  time  ago  that 
short  wavelengths  are  more  efficient  than  the 
longer  ones.  Through  the  use  of  wavelengths 
as  low  as  three-quarters  of  a  meter,  amateurs 
have  recently  conducted  two-way  conver- 
sations over  hitherto  unheard  of  distances. 


"The  radio  inspection  service,"  says  Mr. 
Terrell,  "has  done  much  for  the  amateur,  by 
explaining  that  much  of  the  interference  at- 
tributed to  the  amateur  by  the  broadcast  listen- 
er, is,  in  fact,  caused  in  some  other  way.  Last 
winter,  many  complaints  of  amateur  interfer- 
ence through  the  Middle  West  and  in  the  Great 
Lakes  region  were  received.  Investigation  by 
the  inspection  service 
disclosed  the  fact  that 
nearly  all  of  this  inter- 
ference was  caused  by 
commercial  ship  sta- 
tions operating  in  the 
Atlantic  Ocean  and  in 
the  Gulf  of  Mexico.  At 
that  time,  ship  stations 
were  permitted  to  use 
666  kilocycles  (450 
meters)  well  within  the 
broadcasting  band. 
The  situation  was  se- 
rious, and  when  it  was 
brought  to  the  atten- 
tion of  the  Secretary  of 
Commerce,  a  regula- 
tion was  issued  pro- 
hibiting the  use  of  that 
wavelength  by  ships, 
assigning  to  them  in- 
stead a  wavelength  of  706  meters  (425  kc.)." 
The  first  radio  regulation  was  inaugurated 
in  June,  1910,  for  the  purpose  of  enforcing  the 
installation  of  wireless  equipment  on  certain 
passenger-carrying  vessels.  Since  that  time 
the  Radio  Inspection  Service  has  developed 
into  one  of  the  most  important  branches  of 
the  Department  of  Commerce.  Under  the 
Act  of  1910,  the  Secretary  of  Commerce  and 
Labor  organized  on  July  11,  1911,  the  Radio 
Service  of  the  Bureau  of  Navigation.  A 
subsequent  Act,  approved  in  1912,  stipulated 
that  all  vessels  navigating  the  ocean  or  the 
Great  Lakes  and  carrying  fifty  or  more 
persons,  including  passengers  and  crew,  be 
equipped  with  radio.  An  Act  to  Regulate 
Radio  Communication  was  approved  in 
August,  1912.  Under  this  Act,  transmitting 


Harris  &  Ewing 
W.    D.    TERRELL 


744 


Radio  Broadcast 


stations  and  radio  operators  are  licensed  by 
the  Department  of  Commerce. 

THE    RADIO    POLICE 

JUST  as  Ariel,  in  the  fables  of  the  Middle 
Ages,  was  a  spirit  guardian  of  the  air,  so  in 
this  day  of  wireless,  the  Radio  Inspector,  a 
modern  Ariel,  stands  a  silent  watch  over  the 
ether.  But  though  he  may  be  silent  and, 
indeed,  an  angel,  he  is  far  from  a  fable,  as  those 
who  attempt  to  dispute  his  wavemeter  soon 
find  out.  For  the  Radio  Inspector,  ready  at 
all  times  to  be  of  assistance  to  those  who  need 
him,  is  essentially  a  traffic  officer  of  the  air, 
and  to  him  falls  the  tedious  duty  of  directing 
the  myriad  of  amateur,  commercial,  experi- 
mental, and  broadcasting  stations  under  his 
jurisdiction. 

"The  Radio  Inspector's  work,"  Mr.  Terrell 
continues,  "enables  the  broadcast  listener  to 
receive  programs  without  unnecessary  inter- 
ference. This  is  accomplished  in  part  by  the 
careful  adjustment  of  broadcast  transmitters 
to  their  assigned  frequencies  and  to  a  con- 
stant inspection  of  these  transmitters  to  insure 
their  remaining  so  adjusted. 

"The  careful  adjustment  of  commercial 
and  amateur  transmitters  accomplishes  the 
same  results.  Readjustments  are  necessary 
whenever  it  is  found  that  one  station  is 
heterodyning  another  because  of  a  slight 
change  in  the  adjustment  of  the  transmitter. 

"Investigations    of    complaints    of    inter- 


ference caused  by  electrical  devices  other  than 
radio  transmitters,  such  as,  for  instance,  leaky 
power  lines,  magnetos  on  telephone  lines,  x-ray 
and  violet-fay  machines,  electrical  precipi- 
tation plants,  and  so  forth,  are  not  controlled 
by  the  present  radio  law,  but  many  of  such 
sources  of  interference  are  eliminated  through 
cooperation. 

"Radio  Inspectors  frequently  give  short 
talks  to  audiences  in  the  cities  which  they 
visit  concerning  the  problems  which  they 
encounter  in  their  work,  as  well  as  the  problems 
of  the  listeners-in. 

AND   WHAT    ABOUT   THE    FUTURE? 

THE  Radio  Inspection  Service  has  helped 
the  commercial  operator  to  maintain  a 
high  standard  of  excellence  by  providing 
examinations  for  commercial  operators  which 
only  well  qualified  men  have  been  able  to  pass. 
The  results  have  been  gratifying,  for  in  the 
many  cases  of  disaster  to  ships  at  sea,  not  one 
case  has  been  reported  where  the  commercial 
operator  has  failed  to  observe  the  orders  of  the 
master  of  the  vessel,  has  failed  to  show  the 
highest  courage,  or  has  failed  to  remain  at 
his  post  until  his  duties  have  been  fully  per- 
formed." 

No,  the  task  of  the  Radio  Inspector  is  not 
an  easy  one  nor  does  it  promise  to  be  easier 
in  the  future.  But  as  for  the  radio  future, 
we  can  safely  say  that  it  will  take  care  of  it- 
self, for  it  is  in  exceedingly  competent  hands. 


RADIO    INSPECTION    DISTRICTS   OF   THE    UNITED    STATES 


Some  Remarks  on  Audio 
Amplification 

If  You  Aim  at  High  Quality  in  Radio  Reception,  Here  Are  Some  Suggestions 
on  Improvement  Through  the  Use  of  High  Plate  Voltage  and  a  Special  Use 
of  By-Pass  Condensers— A  Discussion  of  What  Occurs  in  the  Audio  Circuit 

BY  GEORGE  C.  CROM,   JR. 

^TT    rj^HE  search  for  high  quality  in  the  audio  circuit  of  the  radio  receiver  is  growing  more 
^|     -*    general  and  more  popular  every  month.     In  the  August ,  1925,  RADIO  BROADCAST 
I/   an  article  by  John  B.  Brennan  appeared  describing  the  construction  of  a  two-stage  audio 
amplifier  of  very  high  quality.     This  article  by  Mr.  Crom,  while  in  no  sense  a  con- 
struction article,  contains  some  interesting  ideas  on  methods  for  securing  better  quality. 
These  suggestions,  as  far  as  we  know,  have  not  been  formulated  by  any  other  writer. 
The  Crom  amplifier  demands  a  high  plate  voltage,  which  is  best  supplied  from  alternating 
current  and  Mr.  James  Millen  will  describe  an  amplifier  unit,  practically  embodying 
Mr.  Crom  s  suggestions,  in  an  early  number  of  this  magazine. — THE  EDITOR 


OME  of  the  most  common  of  all  radio 
devices  is  the  two-stage  amplifier, 
which,  common  though  it  may  be, 
is  often  not  constructed  or  operated 
in  the  most  satisfactory  manner.  Insufficient 
thought  is  given  to  each  of  the  components 
and  their  relation  to  each  other  and  this  re- 
sults in  the  production  of  sound  in  the  loud 
speaker  utterly  different  from  that  imposed 
on  the  input  circuit  of  the  audio  amplifying 
arrangement.  The  faults  of  design  are  made 
very  evident  when  the  audio  amplifier  output 
circuit  is  fed  to  a  good  loud  speaker  of  the  cone 
type.  In  some  instances,  poor  reproduction 
has  been  blamed  on  the  speaker  instead  of  on 
the  audio  amplifier,  where  it  actually  belongs. 

THE  PROBLEM  OF  GOOD  AMPLIFIER  DESIGN 

AN  AUDIO  amplifier  must  be  capable  of 
raising  a  weak  audio   signal   of  rapidly 
varying  frequency  to  the  required  strength 
without  materially  changing  the  relative  value 
of  each  frequency. 

It  should,  if  it  is  to  be  an  ideal  amplifier,  be 
easy  to  build  and  operate  and  should  be  low 
in  first,  and  upkeep  cost.  The  latter  require- 
ments, if  the  others  are  not  to  be  sacrificed, 
are  very  difficult  to  realize. 

In  order  to  visualize  the  problem  more 
completely,  let  us  consider  the  functions  of 
each  part  in  the  amplifier  circuit,  assuming 
that  the  tone  quality  being  received  on  the 
detector  is  sufficiently  good  for  most  purposes. 
The  small  currents  in  the  detector  circuit 
must  be  fed  into  the  primary  of  the  trans- 


former and  converted  by  the  transformer  into 
a  voltage  variation  on  the  grid  of  the  first  am- 
plifying tube. 

Although,  perhaps,  this  process  does  not  seem 
to  be  particularly  difficult,  it  is  well  to  remem- 
ber that  these  small  currents  are  composed  of 
three  entirely  distinct  forms.  We  have  a 
direct  current  which  is  supplied  by  the  detector 
B  battery,  a  radio  frequency  current  derived 
from  the  carrier  wave  of  the  broadcasting 
station,  and  the  audio  frequency  current  re- 
sulting from  the  rectifying  action  of  the  de- 
tector tube.  It  is  this  last  current  which  we 
wish  to  amplify. 

Fig.  i  shows  the  paths  of  the  various  cur- 
rents in  the  detector  circuit.  The  radio  fre- 
quency or  carrier  current  is  by-passed  directly 
to  ground  by  the  condenser  placed  between  the 
plate  and  the  negative  filament  terminal. 
The  usefulness  of  this  path  is  directly  propor- 
tional to  the  size  of  the  condenser,  and  if  this 
part  of  the  circuit  were  considered  alone,  a 
very  large  condenser  would  give  best  results. 
But  a  practical  difficulty  arises  in  that  a  large 
by-pass  condenser  here  will  also  by-pass  some 
of  the  audio  frequencies  which  we  wish  to 
amplify,  that  is,  the  upper  audio  frequencies, 
approaching  the  lower  radio  frequencies.  So 
in  practice,  the  size  of  this  condenser  is  limited 
by  the  necessity  of  conserving  the  audio  fre- 
quency voltages  present  in  the  plate  circuit, 
and  sizes  between  .001  and  .006  mfd.  are 
generally  used.  The  exact  sizes  that  give  best 
results  for  a  particular  layout  are  found  by 
experiment. 


746 


Radio  Broadcast 


The  effect  of  the  direct  current  in  the  plate 
circuit  does  not  pass  beyond  the  transformer 
itself,  as  only  fluctuating  current  or  voltage 
will  pass  through  a  transformer. 

The  audio  frequency  current  passes  through 
the  primary,  and  through  the  large  by-pass 
condenser  (i  or  2  mfd.)  back  to  the  filament 
of  the  detector  tube.  This  large  by-pass  con- 
denser is  a  necessity  for  quality  reproduction, 
as  it  prevents  this  audio  current  from  flowing 
through  the  leads  to  the  B  battery  and  the 
B  battery  itself,  and  conducts  it  through  a 
short  path  to  the  filament.  The  B  battery 
and  its  leads  have  resistance  and  inductance. 
If  the  audio  currents  flowed  through  these 
leads,  it  would  couple  the  circuit  of  the  de- 
tector path  to  the  plate  circuits  of  the  other 
tubes  using  the  same  B  batteries  and  leads,  by 
means  of  this  common  resistance  and  induc- 
tance. The  majority  of  squeals  and  audio 
howls  in  an  amplifier  are  caused  by  common 
circuits  and  by  capacity  couplings. 

The  audio  current,  in  passing  through  the 
primary  of  the  transformer,  induces  a  voltage 
in  the  secondary  by  means  of  the  magnetic 
flux  induced  in  the  iron  core  of  the  transformer, 
and  this  voltage  is  impressed  between  the  grid 
and  filament  of  the  first  audio  tube.  The 
plate  current  of  the  audio  tube  is  controlled  by 
this  voltage,  and  variations  exactly  similar  in 
form  to  those  of  the  grid  voltage  will  follow 


in  the  plate  current  if  the  operating  conditions 
of  the  tube  are  correct. 

GOOD  QUALITY  OF  RECEPTION  MEANS  GOOD 
TRANSFORMERS 

IN  CHAPTER  VII  of  The  Thermionic  Va- 
*  cuum  Tube,  by  Van  der  Bijl,  a  complete  dis- 
cussion of  the  action  of  the  vacuum  tube  when 
used  as  an  amplifier  is  given,  and  the  reader 
is  referred  to  this  book  for  complete  informa- 
tion, some  of  which  is  too  involved  or  too 
technical  for  presentation  in  this  article. 
Proof  of  most  of  the  statements  made  in  this 
article  can  be  found  by  the  careful  reader  in 
this  book. 

Before  discussing  operating  conditions  of 
amplifier  tubes  it  is  necessary  to  make  one 
further  statement  about  transformers.  Good 
quality  of  radio  reproduction — to  which  more 
attention  is  constantly  being  given — can  not  be 
obtained  with  cheap,  poorly  designed  trans- 
formers. In  order  to  obtain  amplification  of 
the  lower  audio  frequencies,  such  as  those  of 
a  drum  or  bass  viol,  it  is  necessary  that  the 
impedance  of  the  primary  winding  of  the  audio 
transformers  shall  be,  at  that  particular  low 
frequency,  at  least  two  and  one  half  times  the 
impedance  of  the  tube  connected  to  the  prim- 
ary of  the  transformer.  Transformers  made 
by  most  of  the  reliable  manufacturers  have 
this  necessary  primary  impedance. 


o 
-  c 


o 

-    A 


•«-->•  Radio  Frequency  Paths 
•* — »•  Audio         ••  • 

•     >  Direct  Current         • 

FIG.    I 


The  paths  which  must  be  followed  by  the  different  currents  in  a  good  audio 
frequency  amplifier.     The  author  tells  how  to  keep  them  on  the  right  path 


Some  Remarks  on  Audio  Amplification 


747 


DISTORTIONLESS    AMPLIFIER    OPERATION 

THE  conditions  for  distortionless  amplifi- 
fication  in  the  amplifier  tube  itself  are  as 
follows: 

ist — The  filament  must  be  operated  at  a  tempera- 
ture high  enough  to  supply  all  the  electrons  result- 
ing from  the  sum  of  the  direct  plate  current  and  its 
audio  frequency  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. 

2nd — The  plate  circuit  should  have  sufficiently 
high  impedance.  This  high  impedance  straightens 
out  the  curve  which  is  usually  referred  to  as  the 
operating  characteristic,  and  is  explained  in  Para- 
graph 60  of  Van  Der  Bijl's  book.  This  is  too  in- 
volved a  discussion  for  this  article. 

3rd — The  grid  must  be  maintained  negative  with 
respect  to  the  filament  so  that  at  the  positive  peaks 
of  the  signal-voltage  wave,  appreciable  current  does 
not  flow  to  the  grid.  If  current  does  flow  to  the 
grid,  it  pulls  down  the  plate  current  and  causes  a 
bend  in  the  operating  characteristic  curve,  that  is, 
the  positive  peaks  of  the  plate  current  waves  are  cut 
off.  As  current  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 
necessarily  depends  upon  the  structure  of  the  tube 


used  and  upon  the  signal  voltage.  Most  tubes  can 
be  operated  one  or  two  volts  positive  at  the  peak 
signal  voltage.  This  is  not  necessarily  true,  for 
individual  tubes  vary  widely. 

4th — The  plate  voltage  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  apparatus  in 
the  plate  circuit  and  still  apply  enough  voltage  to 
the  tube,  so  that  at  the  maximum  negative  signal 
voltage  on  the  grid  some  plate  current  will  still  be 
flowing.  In  other  words,  the  negative  peaks  of  the 
plate  current  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  A  battery 
charged.  The  second  is:  Use  good  trans- 
formers. The  third  and  fourth  are:  Use  the 
proper  value  of  C  battery  for  the  signal  voltage 
at  the  grid  of  each  tube,  and  the  plate  voltage 
Which  corresponds  to  this  C  voltage. 

One  way  to  check  up  on  these  last  two  con- 
ditions, is  to  measure  the  signal  voltage  at  the 
grid  of  each  tube  with  a  vacuum  tube  volt- 
meter, which  measures  peak  voltages,  and  use 
the  value  of  the  voltage  measured  as  the 
amount  of  the  C  battery  voltage,  and  increase 
the  plate  voltage  to  the  value  given  by  the 
tube  manufacturers  for  this  C  voltage.  This  is 


DETECTOR 


SECOND  AUDIO 


Amp.  Transformer 
P    G 


Output  Transformer 
G      P       P       G 


Cabled  Leads  May  be  of 
Any  Length.  All  Others 
Should  be  Short  and  Straight 


B     F 


~-  Cable  These  Leads       / 
<—  Keep  Battery  Leads  -' 
to  Each  Tube  Together 


-   A  +       -  B 

Batteries  or  Power  Supply 


n 


Highest  B  Voltage 


FIG.    2 

The  circuit  diagram  of  a  high  quality  audio  frequency  amplifier.     Note  in 
particular  the  output  transformer,  by-pass  condensers,  and  cabled  leads 


748 


Radio  Broadcast 


AN    EARLY   TYPE   OF    HIGH   QUALITY    PUSH    PULL  AMPLIFIER 
A  front  and  rear  view  of  one  of  the  first  high  quality  amplifiers  to  be  put  on  the 
market.     It  is  of  the  push-pull  type,  and  made  by  the  Western  Electric  Company 


Some  Remarks  on  Audio  Amplification 


749 


beyond  the  usual  fan,  because  vacuum  tube 
voltmeters  are  expensive  and  scarce. 

The  most  satisfactory  method,  and  also  the 
easiest,  of  determining  these  last  two  condi- 
tions is  to  put  a  milliammeter  (d.  c.  of,  say, 
o-i  5  milliamperes)  in  the  plate  of  the  amplifier 
tube  under  investigation  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  prevent 
the  grid  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.  In- 
creasing the  plate  voltage  will  remove  this 
difficulty. 

Both  of  these  effects  may  be,  and  often  are, 
present  at  the  same  time  so  the  needle  of  the 
milliammeter  may  fluctuate  violently. 

For  quality  amplification,  the  plate  cur- 
rent should  not  vary,  so  it  is  necessary  to 


increase  the  C  battery  and  the  plate  battery, 
until  there  is  no  appreciable  variation  of  the 
plate  current  of  each  tube  on  the  strongest 
signal  that  will  be  received.  Most  of  the 
better  grade  filament  voltmeters  now  on  the 
market  can  be  used  as  milliammeters  as  they 
usually  have  a  full  scale  deflection  for  about 
1 5  mA.  The  milliammeter  (or  filament  volt- 
meter) can  be  best  put  in  the  lead  to  the  B 
battery  near  the  battery  where  its  capacity 
will  have  no  effect  on  the  operation  of  the 
amplifier. 

CHECKING   THE    CIRCUIT   FOR   QUALITY 

AFTER  the  first  stage  amplifier  is  checked 
up  in  this  manner,  the  same  method  may 
be  applied  to  the  second  stage.  It  is  easily 
seen  that  the  signal  voltage  on  the  grid  of  the 
second  stage  will  be  higher  than  that  on  the 
first,  so  it  is  necessary  that  the  C  battery 
voltage  applied  to  the  second  amplifier  should 
be  higher  than  on  the  first  and  its  plate  voltage 
should  be  correspondingly  higher.  The  mil- 
liammeter test  will  show  by  its  fluctuations  if 
these  voltages  are  not  right. 

The  signal  voltage  on  the  grid  of  each  am- 


IMPROVING   QUALITY    IN    A   TWO-STAGE    AMPLIFIER 
How  by-pass  condensers  whose  value  is  suggested  in  this  article,  may  be  added  to 
the  Quality  Amplifier  described  by  Mr.  Brennan  in  the  August  RADIO  BROADCAST 


750 


Radio  Broadcast 


plifier  tube  determines  the  amount  of  C  battery 
to  be  used.  The  signal  voltage  and  the  C 
battery  voltage  fix  the  plate  voltage  required. 
The  C  battery  voltage  and  B  battery  voltage 
can  be  higher  than  necessary  but  cannot  be 
lower,  without  overloading  the  grid  of  the 
tube  and  causing  distortion  in  the  tube  itself. 

The  average  receiving  set,  regenerative  or 
neutrodyne,  or  other  circuits  of  equal  merit, 
require  much  higher  C  and  B  voltages  on  the 
first  and  especially  on  the  second  stage,  than 
are  usually  supplied. 

A  large  number  of  tests  have  shown  that 
these  voltages  should  be,  depending  on  signal 
voltage,  tubes,  and  transformers: 

ist-Stage     €-4.5-9  Volts      6-90-120  Volts 
2nd-  "        C-I2-30  Volts     6-200-450  Volts 

Where  plate  voltages  such  as  these  last 
values  are  not  available  or  are  not  desired  for 
economic  reasons,  even  though  the  second 
audio  tube  is  overloaded,  the  signal  voltage 
can  be  decreased  by  using  a  low  ratio  trans- 
former, or  by  putting  a  grid  leak  of  less  than 
one  tenth  of  a  megohm  across  the  secondary. 
A  push-pull  amplifier  allows  appreciable  dis- 
tortion in  each  half  of  the  circuit,  but  as  the 
two  audio  currents  are  180  degrees  out  of 
phase,  the  distortion  cancels  out;  so  the  push- 
pull  amplifier  can  be  used  with  a  limited  plate 
voltage  to  give  amplification  without  distor- 
tion. 

Perhaps  the  best  way  to  obtain  good  quality 
is  to  obtain  the  required  B  voltage  from  a 
plate  supply  system  operated  from  the  a.  c. 
electric  light  socket.  Such  a  system  permits 
using  a  5-watt  tube  in  the  last  stage,  as  its 
filament  may  be  operated  from  the  same  trans- 
former that  supplies  the  plate  power.  But 
that  is  another  story. 

A    SUGGESTED    HIGH-QUAl.il  V    AMPLIFIER 

IN  FIG.  2,  a  diagram  of  a  two-stage  amplifier 
is  shown.     Attention  is  called  to  the  way 
in    which    by-pass    condensers    are    used    to 


shorten  the  audio  frequency  paths,  and  to  keep 
these  frequencies  in  their  separate  circuits. 
Also  note  the  way  in  which  aH  the  battery  leads 
are  grouped  closely  together  in  a  cable,  thus 
avoiding  closed  loops,  which  might  cause 
coupling  between  stages.  Grid  and  plate 
leads  should  be  kept  short  and  straight.  The 
leads  to  the  by-pass  condenser  should  also 
be  kept  short  as  they  are  part  of  the  audio 
circuit. 

More  than  two  audio  stages  are  unnecessary 
except  where  more  than  one  loud  speaker  is 
to  be  operated.  Two  well  built  audio  stages, 
with  proper  grid  and  plate  voltages,  will  oper- 
ate two  cone  type  loud-speakers  so  that  they 
may  be  heard  for  several  blocks  without  dis- 
tortion. 

The  general  purpose  five-volt  tubes  will 
hold  up  under  continuous  operation  at  plate 
voltages  of  250  to  300  with  a  C  battery  of  16  to 
22  volts.  Sometimes,  however,  it  is  necessary 
to  pick  out  of  several  tubes,  the  one  which  will 
stand  up  best  under  this  load.  Several  of 
one  make  of  five-volt  tubes  were  operated 
for  six  months  with  350  volts  on  the  plate 
and  were  still  going  strong  v/hen  the  test  was 
ended. 

In  using  such  high  plate  voltages  on  the  last 
stage  it  is  essential  that  the  direct  plate  current 
be  kept  out  of  the  loud  speaker.  This  can  be 
done  either  by  using  an  output  transformer, 
or  by  using  a  choke  coil  of  75  to  100  henries, 
in  the  plate  circuit  with  a  condenser  of  two  to 
six  mfd.  between  the  loud  speaker  and  the 
plate.  The  audio  current  will  pass  through 
the  condenser  to  the  loud  speaker  and  then 
return  to  the  filament,  while  the  d.  c.  passes 
through  the  choke  coil  to  the  battery. 

Now  that  good  loud  speakers  (such  as  the 
cone  type)  are  available,  and  broadcasting 
stations  are  transmitting  signals  of  high  qual- 
ity, distortion  of  the  signal  in  radio  receivers 
is  absolutely  unnecessary,  and  can  and  should 
be  prevented. 


The  material  appearing  in  this  magazine  is  fully  protected  by  copyright,  and 
editors  of  periodicals  are  advised  that  unauthorized  publication  of  circuit 
diagrams,  technical  descriptions,  and  parts  or  the  whole  of  articles,  without  due 
permission  and  credit;  is  an  infraction  of  the  law.  Those  who  wish  to  reprint 
material  appearing  in  these  pages  are  asked  to  communicate  with  the  editor. 


^"  Point   o:P 

f  onducTted    by  Koindsley 


Do  We  Meed   "Silent  Nights"   for   Radio 

Stations? 


THOSE  two  letters  "  DX  "  have  caused 
as  much  radio  joy  and  sorrow  as  any 
others  known  in  the  vast  and  mystic 
terminology  of  the  science.  To  radio 
widows,  the  term  is  anathema;  to  radio  fans, 
it  represents  a  high  form  of  enjoyment.  To 
build  or  buy  a  set  which  will  bring  in  the  call 
letters  of  some  broadcaster  two  or  three 
thousand  miles  removed  is  better  than  being 
elected  to  Tammany  Hall,  or  fathering  the 
prize  baby  in  the  annual  exhibition  at  Atlantic 
City.  Those  captious  souls  who  sneer  at  radio 
like  to  say  that  broad- 
cast listeners  have 
installed  their  radio 
merely  to  indulge  this 
passion  for  distance. 
Well,  that  portion 
of  the  radio  audience 
whose  religion  is  DX 
come  by  that  hon- 
estly. The  very  terms 
comes  from  the  vo- 
cabulary of  the  intent 
amateur  whose  con- 
stant lust  has  been 
to  project  signals 
from  his  own  little 
transmitter  to  some 
listener  equally  intent 
a  great  distance  away. 
In  the  prehistoric 
wireless  times  of 
about  1909,  his  cup 
of  joy  fairly  bubbled 
if  reports  of  recep- 
tion came  from  a 
paltry  twenty  miles. 


OLIVER    SAYLER 

Who  presents,  through  WGBS,  New  York,  one  of  the 
most  interesting  features  given  by  any  broad- 
casting station  in  his  talk  every  Thursday  evening 
at  8:30  called  "Footlight  and  Lamplight."  Mr. 
Sayler  never  fails  to  bring  his  listeners  something 
worth  hearing 


Now  your  amateur  speaks  calmly  of  com- 
munication with  Australia.  The  alluring 
possibility  of  being  able  to  send  signals  six  or 
seven  thousand  miles  is  the  chief  force  which 
makes  the  experimenter  an  "amateur"  and 
keeps  him  up  indecently  late  o'  nights. 

And  a  very  large  body  of  radio  broadcast 
listeners,  who  differ  very  little  essentially  from 
the  "transmitting  amateurs,"  gain  their  chief 
pleasures  from  searching  out  the  elusive  carrier 
wave  of  a  broadcaster  terrifically  far  away. 
The  publicity  writer  for  station  KFI,  Los  An- 
geles, has  put  the  lure 
well: 


For  the  Atlantic  Coast 
to  hear  the  Pacific  Coast 
or  vice  versa  is  to  jour- 
ney into  the  unknown 
and  come  back  with  a 
new  lease  on  life.  DX  is 
the  home  run,  the  hole- 
in-one,  the  six-pound 
trout,  the  twelve-point 
buck,  the  royal  flush  of 
the  radio  game,  and 
those  who  seek  to  dis- 
courage it  are  striking 
at  the  very  well-springs 
of  the  go-getting  na- 
tional spirit.  Earle  C. 
Anthony  says,  "Let  the 
DX'er  take  for  his 
motto,  'We  will  fight  it 
out  along  these  lines  if 
it  takes  all  summer', 
and  continue  to  burn  the 
midnight  tubes.  After 
all,  who  wants  to  tune-in 
when  you  can  see  the 
whites  of  their  eyes?" 


752 


Radio  Broadcast 


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Do  Poor  Local  Programs  Inspire  the  Desire  for  "Silent  Nights?"     753 


CONDUCTORS   OF   THE   NEW   YORK    PHILHARMONIC  ORCHESTRA 

Whose  programs  have  been  beautifully  transmitted  by  wjz,  WGY,  and  WRC.  At  the  left  is  Rudolph  Ganz, 
conductor  of  the  St.  Louis  Symphony  Orchestra.  In  the  upper  center  circle  is  Nikolai  Sokoloff,  conductor 
of  the  Cleveland  Symphony  Orchestra.  Fritz  Reiner  (right)  is  the  conductor  of  the  Cincinnati  Symphony 
Orchestra.  In  the  lower  circle,  center,  is  Willem  Van  Hoogstraten,  conductor  of  the  New  York  Philharmonic 
Orchestra.  Mr.  Ganz,  Mr.  Sokoloff,  and  Mr.  Reiner  were  invited  to  act  as  guest  conductors  of  the  Orchestra 


This  ether  fishing  is  no  chore  for  the  listener 
located  at  a  moderate  distance  from  stations  of 
large  power.  But  for  the  unfortunates  in  large 
cities  where  broadcasters  keep  their  tubes 
glowing  from  the  setting-up  exercises  in  the 
morning  until  the  last  dance  orchestra  has 
folded  up  its  drums  and  silently  stolen  away, 
the  job  is  not  so  easy.  No  matter  how  selec- 
tive a  receiver  is,  it  is  hard  to  get  through  the 
strong  waves  of  the  locals  and  to  hear  the  elu- 
sive DX  broadcaster. 

By  a  kind  of  gentleman's  agreement  during 
the  past  year,  Chicago  broadcasters  have  kept 
off  the  air  on  Monday  nights  to  allow  the 
natives  to  indulge  their  urge  for  distance. 
Lately,  the  news  has  quietly  leaked  out 
through  the  medium  of  the  Associated  Press 
that  there  is  dissention  among  the  broadcast- 
ers in  the  Chicago  area  and  the  listeners  in 
same.  Those  broadcasters  who  have  studios 
in  Chicago  and  transmitters  in  the  suburbs 
feel,  it  seems^  that  since  they  are  not  local  in 
a  very  strict  interpretation  of  the  word,  there 
is  no  reason  why  they  should  keep  to  the  si- 
lence agreement.  So  the  local  stations  have 
been  silent  on  Monday  nights  and  the  subur- 


ban transmitters  have  been  whacking  away 
at  the  ether. 

Mr.  Frank  H.  McDonald,  president  of  the 
Broadcast  Listener's  Association,  has  an- 
nounced that  a  canvass  of  radio  listeners  in 
Chicago  shows  that  98  per  cent,  of  the  can- 
vassed listeners  are  in  favor  of  a  silent  night. 
He  further  says  his  Association  is  planning  to 
have  a  bill  submitted  to  the  next  Congress 
which  would  divide  the  country  into  six  radio 
areas  and  assign  a  different  quiet  night  to 
each.  Sunday,  according  to  this  proposal, 
would  be  open  night. 

Mr.  McDonald's  Chicago  broadcast  listen- 
ers are  doing  well  to  organize  in  order  to  ex- 
press their  opinions,  but  the  mere  fact  that  a 
large  and  powerful  Chicago  group  want  to 
indulge  in  DX  fishing  is  no  reason  for  making 
national  silent  nights  legally  compulsory  on 
the  entire  country.  We  have  no  quarrel  with 
DX  hunting,  or  with  the  silent  night  idea, 
but  the  matter  is  manifestly  one  for  local  op- 
tion. 

One  cannot  help  but  suspect  that,  when 
there  is  so  strong  a  demand  from  listeners  to 
hear  programs  from  other  localities,  there  are 


Radio  Broadcast 


serious  lacks  in  the  local  programs.  There  has 
never  been,  in  the  New  York  area,  for  example, 
any  similar  widespread  desire  for  a  silent  night. 
If  one  judge  the  signs  in  that  territory  aright, 
in  the  main,  the  local  programs  have  proved 
quite  satisfactory  for  every  taste.  And  since 
WEAF  has  linked  itself  through  the  long  lines 
of  the  Bell  system  regularly  to  representative 
stations  in  the  East  and  Middle  West,  pro- 
grams of  the  highest  quality  and  of  great  var- 
iety of  appeal  have  been  made  available  to  a 
larger  number  of  listeners  than  ever  before. 

We  might  as  well  call  things  by  their  right 
names.  If  radio  is  really  entertainment,  then 
the  program  is  the  important  thing.  If  that 
is  true,  the  source  matters  less  than,  in  a  man- 
ner of  speaking,  the  bone  and  sinew  of  the 
program  itself.  But,  on  the  other  hand,  if 
radio  reception  is  a  kind  of  elaborate  animated 
geography  lesson,  then  every  effort  ought  to 
be  bent  to  give  those  devotees  the  chance  to 
hear  distant  names  whisked  through  the 
microphone. 

Brooms  for  Symphonies 

YOU  excellent  folk  who  live  in  civiliza- 
tion don't  know  and  can't  realize  what 
a  wonder  first-rate  broadcasting  is  to 
those  who  live  in  distant  places.     Oh  yes,  we 
are  civilized — we  have  in  some  homes  modern 


COUNT   ALEXANDER    SKRZNSKI 

Foreign  Minister  who  spoke  recently  over  WEAF 
and  a  chain  of  eight  others.  His  address  came  at 
the  end  of  an  excellent  hour  of  Polish  music.  When 
the  WEAF  announcer  described  the  program,  he 
made  the  startling  statement  that  Count  Skrznski 
would  be  "accompanied  by  a  Polish  orchestra" 


plumbing,  and  electric  lights  in  most,  and 
that's  more  than  Bach  ever  had  or  dreamed  of. 
We  have  stations  of  our  own  which  do  their 
best  .  .  .  with  nth  rate  singers  (why  will 
they  sing?).  But  perhaps  it  is  unkind  to  look 
at  gift  horses. 

"Last  night,"  continues  IVlr.  P.  H.  Russell, 
of  Red  Deer,  Alberta,  from  whose  recent  letter 
we  have  taken  the  liberty  to  quote,  "  I  turned 
the  switch  on  my  home-made  Haynes  super- 
heterodyne, and  was  more  than  thrilled  to  hear 
faintly  through  the  midsummer  heat — you'd 
not  guess  unless  you  heard  it — Bach's  double 
sonata!" 

This  is  a  small  place.  There  are  2400  people  of 
all  ages,  sizes,  conditions,  and  sorts.  There  is  one 
pianist  who  is  such,  and  is  a  sort  of  prodigy.  He  is 
good,  too.  There  are  also  one  or  two  others  who 
don't  know  anything  about  music  but  who  know 
what  they  like.  So  you  will  gather  that  the  stan- 
dard is  high  for  a  town  in  the  wilds.  Sitting  with 
me  were  the  top  local  fraulein  and  a  friend,  ap- 
pointed masculine  associate  for  the  nonce,  smoking 
cigarettes  with  me. 

My  office  has  a  forgery  of  George  Clausen  on  the 
wall,  and  a  Raeburn  copy,  and  a  print  of  Praxiteles' 
"  Hypnos."  My  walls  are  covered  with  books 
ranging  from  Gibbon's  Decline  and  Fall  to  detective 
stories.  There  are  a  few  law  books,  of  course. 
So  I  can  smoke  cigarettes  with  the  stenographer 
freely  (when  no  Methodists  infest  with  their  ac- 
customed severity.) 

"  Believe  me,"  continues  Mr.  Russell,  "when 
that  music  came  winding  in,  a  wonderful, 
faint  thread  of  beauty,  then  a  latter-day  (and 
really  rather  charming)  flapper  and  her  youth, 
a  railway  fireman,  ceased  from  talking  and 
listened.  They  didn't  say  so,  but  I  knew,  for 
they  looked  it — they  had  never  heard  anything 
like  it  before.  Then  the  thread  faded  into 
mutterings  of  static  and  I  never  heard  whence 
it  came.  But  it  sounded  like  the  music  of  the 
spheres." 

Those  stranded  souls  who  live  in  the  terri- 
tory rather  vulgarly  called  the  sticks  depend 
much  on  what  the  broadcasters  offer,  and  how 
much  more  worth  while  radio  must  make  life! 
Fortunate  are  those  rural  inhabitants  who  like 
jazz  and  non-musical  programs  of  like  level. 
For  radio  stations  are  really  making  the  ether 
one  huge  vaudeville  performance,  with  the  em- 
phasis on  ultra-popular  music,  quite  in  the 
manner  of  the  variety  theatre.  All  stations, 
with  the  exception  of  those  operated  by  relig- 
ious organizations,  are  trying  to  be  all  things 
to  all  men.  Here  a  child  prodigy  on  the  violin, 
there  a  famous  boxer,  giving  his  opinions  on 
how  to  become  a  famous  boxer;  a  politician 
casting  pearls  of  partisan  wisdom;  an  actress 


The  Poorly  Designed  Radio*  Menu 


755 


whispering  secrets  of  temporary  beauty;  a  re- 
turned traveler  confiding  the  curious  customs 
of  the  Senegambians;  and  jazz  orchestras,  jazz 
orchestras,  and  jazz  orchestras. 

The  impression  of  many  listeners  that  radio 
programs  are  too  much  devoted  to  jazz  is 
heightened  by  the  fact  that  of  necessity,  all 
distance  reception  is  carried  on  at  night  and 
everybody  knows  that  the  later  evening  slices 
of  programs  are  invariably  devoted  to  the 
local  currently  popular  jazz  orchestra. 

Not  even  the  most  rabid  demanders  and  de- 
fenders of  jazz  hardly  insist  on  a  steady  radio 
diet  of  it.  And  those  listeners  who  are  in  range 
of  the  Bell  System  wire  tie-up  who  can  hear 
the  "pop"  concerts,  the  Eveready  Hour,  the 
Goldman  Band,  and  the  WEAF  opera  company, 
have  the  opportunity  to  hear  good  music, 
played  as  it  should  be  played.  These  are  some 
breaks  in  what  some  months  ago  appeared  to 
be  an  endless  evening  radio  barrage  of  jazz. 
Considering  this  purview  to  beonly  moderately 


accurate,  one  can  sympathize  with  Mr.  Russell's 
concluding  plea:  "Tell  the  broadcaster,  to  feed 
us  provincials  Bach,  Beethoven,  and  Brahms, 
then  Mozart  and — but  you  know  them  all  as 
well  as  I  used  to  when  I  lived  in  London. 
That  seems  ninety  years  ago.  Won't  you  give 
me  a  job  sweeping  your  office,  so  that  I  can 
hear  a  symphony  concert  now  and  then?" 

The  Popular  Dinner  Concert 

THE  dinner  concert  has  come  to  be  one 
of  the  most  popular  of  radio  features. 
The  term  is  rather  inclusive,  for  while 
many  of  the  concerts  are  produced  by  musical 
organizations  innocent  of  any  saxophone  and 
associated  evils,  not  a  few  are  out  and  out 
dance  orchestras.  The  best  dinner  music  on 
the  radio  is  that  furnished  through  WEAF  by 
Joseph  Knecht's  Waldorf  Astoria  Rose  Room 
orchestra  and  the  Commodore  Hotel  concerts 
from  wjz.  The  Benjamin  Franklin  Hotel 


THE   HOOT  OWLS   OF  KGW,  AT  PORTLAND  OREGON 

A  popular  organization  heard  frequently  from  the  Portland  Oregonian  station.  The  members  are  business 
and  professional  men  of  the  vicinity  and  their  breezy  entertainment  is  eagerly  tuned-for,  out  where  the  West 
is.  Left  to  right,  Ashley  C.  Dixon,  himself  a  broadcaster  (KFJR);  Allen  Greeb;  R.  G.  Calvert,  Grand  Skidoo; 
Charles  F.  Berg,  Grand  Screech;  Henry  W.  Metzger,  Grand  Slam;  Barnett  Goldstein,  Grand  Schmoos; 
Tige  Reynolds  (cartoonist  of  the  Oregonian),  Grand  Sketch;  Frank  J.  Sardam,  Grand  Scream;  and  William 

R.  Boon,  Grand  Skipano,  at  the  piano 


756 


Radio  Broadcast 


Concert  orchestra,  heard  through  WIP,  Phila- 
delphia is  also  deservedly  popular.  KHJ,  Los 
Angeles,  occasionally  sends  out  the  excellent 
concert  orchestra  of  Art  Hickman,  playing  at 
the  Biltmore  Hotel.  The  dinner  organ  reci- 
tals, played  by  Phyllis  Griswold  at  the  Rialto 
Theatre  and  broadcast  through  WOAW,  Omaha 
are  worth  hearing,  as  well. 

In  Cleveland,  WTAM  frequently  offers  the 
popular  music  played  by  the  Golden  Pheasant 
orchestra.  At  wwj,  in  Detroit,  they  have  the 
curious  custom  of  alternating  selections  played 
by  a  dance  orchestra  with  classical  music  by 
an  instrumental  trio.  The  effect  is  highly  dis- 
concerting when  one  hears  an  old  classical 
favorite  immediately  followed  by  "Collegiate," 
or  "Don't  Bring  Lulu."  That  wwj  dinner 
program  assures  one  that  the  wise  individual 
who,  in  the  dim  rhetorical  past,  asserted  that 
it  was  impossible  to  be  both  flesh  and  good 
red  herring,  had  a  great  weight  of  truth  on  his 
side.  There  is  something  radically  wrong 
with  the  microphone  placing  at  wwj's  pick-up 
at  the  Hotel  Statler,  because  the  harp  in  the 
instrumental  trio  comes  through  like  the  fabled 
falling  bricks,  while  the  piano  and  violin  do 
their  best  to  form  a  melodic  background. 

The  dinner  programs  from  WTAM,  Cleveland, 
wcx,  and  wwj,  Detroit  are  also  distinguished 


by  a  glaring,  and  what  should  be  an  unneces- 
sary fault  in  broadcasting — that  of  long  pauses 
between  individual  numbers.  One  can  almost 
progress  from  the  soup  to  the  salad  course  dur- 
ing some  of  the  Detroit  program  hiatuses. 

Station  KSD'S  Fine  Record 

STATION  KSD,  of  the  St.  Louis  Posl- 
Dispatcb  has  long  held  its  place  among 
the  best  of  our  broadcasters.  On  June 
26,  1925,  the  station  celebrated  its  third  anni- 
versary, and  a  review  of  its  activities  show  that 
its  programs  entitle  it  to  the  high  esteem  it  has 
gained.  During  the  three  years,  1434  pro- 
grams have  been  arranged,  and  1383  individ- 
uals took  part.  The  artists  represented  fifteen 
different  nationalities,  twenty-five  states  of  the 
Union,  and  115  cities  of  the  United  States. 
During  the  three-year  period,  379  pianists  and 
310  vocalists  appeared  on  their  programs. 
There  were  also  71  children  who  appeared  be- 
fore the  microphone,  and  a  distressing  total  of 
41  readers.  The  large  number  of  the  latter 
strikes  us  as  curious,  because  radio  listeners 
seem  to  be  united  in  their  dislike  of  readers. 
The  address  of  the  late  President  Warren 
Harding  was  broadcast  when  he  spoke  at  the 
St.  Louis  Coliseum  on  June  21,  1923.  This  was 
the  first  time  that  the  voice  of  a 
President  of  the  United  States 
had  been  broadcast.  KSD  has 
broadcast  practically  all  of  the 
important  national  radio  politi- 
cal and  non-political  addresses 
which  have  been  sent  out  over 
the  long  lines  of  the  A.  T.  &  T. 
Company. 

During  the  first  International 
radio  broadcast  tests,  KSD  was 
reported  by  a  representative 
number  of  listeners  in  England. 
The  station  is  under  the  capable 
direction  of  Miss  V.  A.  L.  Jones. 
One  wishes  the  station,  in  that 
good  old  fashion  of  speaking,  a 
long  life  and  a  merry. 

Reading    of     Applause 
Telegrams  is  Unnecessary 


JOE    NOVAK 

Giving  one  of  his  weekly  lessons  on  golf  from  KGO,  Oakland,  Cali- 
fornia.    Mr.  Novak  is  a  professional  golfer  and  instructor  and  goes 
on  the  air  at  KGO,  at  7:15,  Pacific  Coast  Time  every  Thursday 
evening 


BY  THE  time  this  number 
of  the  magazine   is  pub- 
lished, station  WJR  of  the 
Jewett    Phonograph  and  Radio 
Company  at  Pontiac,  Michigan, 
will   be  on   the  air  with    1500 
watts,    transmitting    at    a    fre- 


"Applause"  Telegrams  Should  Be  Seen— Not  Heard 


757 


quency  of  579.9  kilocycles 
(517  [meters).  Corley  W. 
Kirby,  formerly  director  of 
station  wwj,  of  Detroit,  is 
the  director  of  the  new  sta- 
tion, and  if  he  succeeds  as 
well  with  his  new  charge  as 
he  did  with  the  old,  station 
WJR  will  leap  into  immediate 
favor,  wwj  was  licensed 
in  September,  1921,  which 
makes  it  the  first  American 
broadcaster.  Mr.-  Kirby 
was  associated  with  the 
station  during  its  pioneering 
days. 

Telegrams  and  greetings 
directed  to  WJR  will  not  be 
read  or  acknowledged  over 
the  air  during  the  inaugural 
program  or  later  on,  Mr. 
Edward  H.  Jewett,  presi- 
dent of  the  operating  com- 
pany announces.  He  goes 
on,  to  say  very  sensibly: 
"Telegrams  and  greetings 
do  not  entertain  those  who 
are  listening.  They  please 
only  those  persons  who  are 
mentioned  in  them.  We 
want  WJR  to  please  the 
public,  not  ourselves." 

The  number  of  first-class 
stations  who  read  tele- 
grams, whether  they  be 
from  listeners  in  the  next 
block  or  half  way  across 
the  continent,  is  pleasantly 
small.  No  listener  should 
from  sending  his 


A  RADIO  APARTMENT  IN  SEATTLE 

A  picture  of  the  roof  of  the  Biltmore  Apartments  in  that  city.  Provision 
has  been  made  for  twenty-four  antennas — one  for  each  apartment.  The 
owner  and  architect,  Mr.  Stephen  Berg,  is  an  enthusiastic  radio  devotee 
himself.  The  local  KFOA  supplies  the  tenants  with  much  of  their  radio 
enjoyment,  but  distant  stations  are  heard  as  well 


be  discouraged 
telegrams  of  appreciation 
to  a  station  whose  offerings  please  him.  But 
it  is  hard  to  find  an  excuse  for  reading 
them  over  the  air.  And,  we  might  add,  the 
listener  who  feels  a  deep  throb  at  hearing  these 
telegrams  read  is  probably  the  same  person, 
who,  in  the  cruder  electrical  days,  spent  much 
time  in  listening-in  on  party  lines. 

The   WGBS    Prize    Play   Contest 

NANCY     BANCROFT     BROSIUS     of 
Cleveland,  Ohio,  won  the  $75  prize  in 
the  radio  play  contest  conducted   by 
station  WGBS,  New  York  in  conjunction  with 
WIP,    Philadelphia    and    WGY,    Schenectady. 
Hers  was  a  one-act  play  entitled  Sue   'Em. 
The  play  will  be  produced  on  the  air  through 
the  three  stations  bv  the  well  known  Province- 


town  Players  of  New  York.  Mr.  Oliver 
Sayler,  in  making  the  announcement  from 
WGBS  during  his  charming  "  Footlight  and 
Lamplight"  period  on  a  recent  Thursday  even- 
ing, said: 

The  most  frequent  fault  which  the  judges  found 
among  the  manuscripts  was  a  failure  to  remember 
that  radio  drama,  unlike  good  little  children,  is  heard 
but  not  seen.  A  number  of  plays  .were  submitted 
which  might  interest  a  Little  Theatre,  but  the  de- 
pendence on  the  eye  was  too  great.  Still  another 
fault  which  was  frequently  encountered  was  the 
choice  of  a  subject  so  fantastic  that  all  the  methods 
by. which  illusion  is  gained  in  an  actual  theatre 
would  be  necessary  to  make  the  play  convincing. 

Good  plays  are  becoming  more  frequent  over 
the  air.  Station  WGY  has  produced  a  number 
of  Mr.  Cosmo  Hamilton's  plays  which  have 
rightly  met  with  enthusiastic  approval.  KOA 
and  KGO  have  also  been  active  with  plays  dur- 


758 


Radio  Broadcast 


ing  the  summer  months.  Elliott  Nugent's 
Kempy  was  recently  produced  by  Kcowith 
great  success. 


L 


Broadcast  Miscellany 


THE  Sunday  evening  programs  of  wjz 
and  WGY  are  of  unusually  high  standard 
The  Lakewood  Farm  Inn  Ensemble,  a 
Joseph  Knecht  group,  led  by  Mr.  Jan  Weber, 
furnishes  the  first  part  of  the  program — from 
7:45  to  9,  Eastern  Summer  Time — and  the 
delightful  solo  work  of  Godfrey  Ludlow,  violin- 
ist, the  second  half,  which  continues  from  9 
until  10.  The  Lakewood  Farm  Inn  Ensemble 
never  fails  to  present  a  program  of  varied  in- 
terest, and  their  work  shows  that  good  music 
need  not  necessarily  be  boring  or  "high  brow" 
— frightful  term.  Godfrey  Ludlow,  the  staff 
violinist  of  wjz,  is  an  artist  of  very  much  more 
than  ordinary  talent  and  those  in  reach  of  the 
radio  emanations  of  WGY  and  wjz  are  missing 
a  delightful  feature  if  they  do  not  hear  his 
recitals.  The  accompanying  verbal  program 
notes  of  Mr.  Milton  J.  Cross,  the  veteran  an- 
nouncer of  wjz  are  well  presented,  informative, 
and  in  excellent  taste. 

AND  now  to  chronicle  the  temporary  pass- 
ing of  "  Roxy,"  the  impressario  of  the 
Capitol  Theatre,  New  York,  whose  Sunday 
evening  programs  are  heard  over  WEAF,  WEEI, 
WJAR,  WCAP,  WCTS,  WCAE,  and  wwj.  Mr. 
Rothafel  will  have  a  theatre  of  his  own  in  New 
York  and  has  severed  connections  with  the 
Capitol,  but  the  Capitol  programs  will  con- 
tinue as  before  with  Major  Edward  Bowes, 
managing  director  of  the  Theatre,  in  charge. 
The  "Gang"  — excellent  group  of  musicians 
that  they  are — are  maintaining  the  standard  of 
their  programs  quite  as  before.  The  musical 
quality  of  this  very  popular  feature  we  have 
never  questioned,  but  it  must  be  admitted 
that  the  drooling  sentimentality  of  the  pres- 
entation spoils  what  would  otherwise  be  an 
almost  perfect  program  of  its  type.  Mr. 
Rothafel  deserves  much  credit  for  devising  a 
genuinely  new  type  of  radio  presentation,  but 
why  that  presentation  had  to  be  constantly 
weighted  with  expressions  of  almost  tearful 
sentiment  and  side  remarks  which  somehow 
are  invariably  weightily  saccharine — we  could 
never  understand. 


C TAN LEY  W.  BARNETT,  known  to  woe 
^  listeners  as  "BWS"  has  resigned  his  post 
as  chief  announcer  at  that  station  to  assume 
similar  duties  at  a  new  station  now  under 
construction  at  Baltimore,  Maryland.  His 
place  at  woe  will  'be  taken  by  L.  E.  Wass,  a 
native  of  Davenport,  Iowa. 

OVER  at  wjz,  New  York,  they  have  started 
a  feature  which  is  great  delight  to  a  large 
number  of  invalids  and  those  afflicted  with 
blindness.  At  4:10  p.  M.,  Eastern  Summer 
Time,  J.  B.  Daniel,  a  staff  announcer,  reads 
short  stories,  novels,  works  of  history,  and 
general  selections  from  good  literature.  It  is 
dangerously  near  a  bromide  to  say  that  radio 
has  taken  an  almost  irreplaceable  part  in  the 
lives  of  those  who  are  shut  in.  Radio  stations 
receive  more  mail  from  persons  who  can  not 
actively  join  in  the  life  of  the  world  than  from 
any  others.  This  feature  could  well  be  adopted 
by  many  other  stations  who  desire  to  expand 
their  field  of  service. 

ON  AUGUST  first,  there  were  561  broad- 
casting stations  in  the  United  States,  ten 
less  than  on  July  first,  1925.  WEAF,  New 
York,  is  now  using  5000  watts,  and  WORD, 
Batavia,  Illinois  is  now  operating  on  5000 
watts.  Among  the  long  range  stations,  WGY 
has  been  testing  recently  with  50,000  watts, 
chiefly  after  midnight,  wjz  expects  to  have 
40,000  watts  "in  the  air"  about  the  time  this 
magazine  appears,  although  unexpected  delays 
may  retard  this  date  a  week  or  so  more. 
KGO,  Oakland,  California  is  now  using  3000 
watts,  WBBM,  Chiacgo,  and  WTAS,  Elgin,  Illi- 
nois are  using  1500  watts.  In  England,  the 
Daventry  station  of  the  British  Broadcasting 
Company  (5xx)  is  now  transmitting  on  a 
frequency  of  187.4  kilocycles  (1600  meters), 
using  15,000  watts  (7500  watts,  American 
rating),  which  brings  the  total  of  British  sta- 
tions to  22,  of  which  eight  are  relay  stations. 
5 xx  should  be  heard  in  this  country  by  listen- 
ers whose  receivers  can  tune  to  that  frequency. 
.  .  .  Among  those  broadcasters  gracefully 
retiring  from  the  field  are  WDM,  Church  of  the 
Covenant,  Washington,  D.  C.;  WWAO,  Michi- 
gan College  of  Mines,  at  Houghton;  WVAY, 
The  Milwaukee  Civic  Broadcasting  Station, 
Milwaukee,  Wisconsin,  and  WRAA,  The  Rice 
Institute,  Houston,  Texas. 


In  Which  Some  Discrepancies  Are 

Cleared  Up 


Some  Interesting  Correspondence  Relating  to  an  Article  by  E.  T. 
Flewelling  in  Our  Friendly  Contemporary,  Radio  in  the  Home 


W 


E  WERE  surprised  to  find  in  the  July 
number  of  our  contemporary  Radio  in 
the  Home,  for  which  we  have  had  a  lot 
of  respect,  an  article  by  E.T.  Flewelling, 
one  of  the  Associate  Editors,  in  which  a  very  severe 
criticism  of  a  circuit  appearing  in  RADIO  BROADCAST 
for  June  was  made.  The  attack  was  made  on  the 
Frequency-Changer  or  Super-Heterodyne  Conver- 
ter described  by  Mr.  A.  O'Connor  of  Cleveland, 
Ohio. 

The  various  letters  passing  between  Mr.  O'Connor 
and  the  Editor  of  Radio  in  the  Home,  as  well  as  our 
own  office,  point  out  quite  clearly  that  we  were 
perfectly  justified  in  bringing  the  Frequency- 
Changer  to  the  attention  of  our  readers. 

It  did  violence  to  some  of  our  ideals  of  profes- 
sional ethics  to  find  that  the  Associate  Editors  of 
Radio  in  the  Home  find  it  advisable  to  criticise  the 
technical  articles  appearing  in  RADIO  BROADCAST. 
Some  of  our  old  readers  will  remember  that  Kenneth 
Harkness'  first  claim  to  fame  came  as  a  result  of 
the  publicity  he  received  in  connection  with  the 
single-tube  reflex  receiver  described  in  RADIO 
BROADCAST  in  November,  1923.  Following  his 
connection  with  Radio  in  the  Home,  Mr.  Harkness 
maintained,  in  an  article  appearing  in  that  maga- 
zine, that  resistance-coupled  amplification  was  of 
no  practical  value.  He  seemed  to  forget  that  one 
of  the  principal  objections  to  resistance-coupling 
had  been  overcome  when  the  dry  cell  tube  and  the 
quarter-ampere  storage  battery  tube  had  been 
developed.  If  there  are  any  among  our  readers  who 
have  a  notion  that  resistance-coupling  is  not  worth 
while,  we  shall  be  delighted  to  demonstrate  a  re- 
sistance-coupled receiver  for  their  benefit  at  any 
time  they  would  like  to  visit  our  laboratory. 

The  situation  with  regard  to  the  O'Connor  Fre- 
quency-Changer may  well  be  understood  by  reading 
the  letters  which  follows: 

June,     2.6     1925. 
Mr.  Henry  M.  Neely, 
%  Henry  M.  Neely  Pub.  Co., 
608  Chestnut  St., 
Philadelphia,   Pa. 

DEAR  SIR: 

The  writer  has  just  read  with  a  great  deal  of 
interest  the  article  entitled  "Why  Not  a  Super- 
Het  Converter"  in  July  issue  of  Radio  in  tbe  Home. 
Your  "word  of  explanation"  was  particularly  in- 
teresting. 

I  am  glad  to  see  that  Mr.  Flewelling  was  finally 
clever  enough  to  "tackle  it  right"  and  got  the 
circuit  working.  He  may  be  interested  in  knowing 


that  numerous  BCL's  have  had  wonderful  success 
with  the  circuit  in  June  RADIO  BROADCAST,  (to 
which  he  referred.) 

The  writer  has  read  your  magazine  from  the 
beginning  with  a  great  deal  of  interest  and  while 
not  always  agreeing  with  you,  has  admired  you  for 
having  the  courage  of  your  convictions.  I  am, 
however,  very  much  surprised  in  this  issue  to  notice 
that  your  magazine  allows  a  direct  slam  at  such  a 
high  class  magazine  as  RADIO  BROADCAST.  Mr. 
Flewelling  by  this  time  should  know  that  RADIO 
BROADCAST  will  not  publish  a  circuit  until  they  are 
absolutely  sure  that  it  is  correct.  I  don't  think 
that  Mr.  Arthur  Lynch  is  going  to  like  Mr.  Flew- 
elling's  remarks  in  your  "word  of  explanation." 
Very  truly  yours, 

A.  O'CONNOR. 


June     30,     1925. 
Mr.  A.  O'Connor, 
9702  Euclid  Ave., 
Cleveland,  Ohio. 

DEAR  MR.  O'CONNOR: 

It  was  with  something  like  a  shock  that  I  learned 
from  your  letter  of  June  26th  that  the  magazine  to 
which  Mr.  Flewelling  made  unfavorable  reference 
was  RADIO  BROADCAST.  I  thought  at  the  time  of 
publication  that  the  magazine  was  .  .  .  and 
that  is  why  I  let  the  Flewelling  remarks  go  as  they 
were.  If  I  had  known  that  they  referred  to  RADIO 
BROADCAST,  I  should  not  have  printed  them  be- 
cause I  can  assure  you  that  no  one  in  the  whole 
radio  field  has  a  higher  respect  for  RADIO  BROADCAST 
nor  a  greater  personal  liking  for  Arthur  Lynch, 
Editor,  than  I  have. 

Yours  very  truly, 

HENRY  M.  NEELY. 


July    7,     1925. 
Mr.  H.  M.  Neely,  Editor, 
Radio  in  the  Home, 
608    Chestnut    St., 
Philadelphia,  Pa. 

DEAR  FRIEND  NEELY: 

A  few  months  ago  you  took  RADIO  BROADCAST 
for  a  rather  severe  ride  concerning  resistance- 
coupled  amplification,  and  Kenneth  Harkness,  one 
of  your  Associate  Editors,  said  that  resistance- 
coupling  should  never  have  been  taken  from  the 
grave  in  which  it  was  peacefully  reposing,  or  words 
to  that  effect.  I  cannot  refrain  from  putting  you 
on  the  pan  this  morning  for  a  little  roasting  and 
trust  that  you  will  take  what  I  have  to  say  in  good 
part,  as  I  know  you  will. 

On  page  14  of  the  July,  1925,  number  of  Radio 
in  the  Home  we  find  a  rather  interesting  disserta- 


760 


Radio  Broadcast 


tion  by  Flewelling  on  "Why  Not  a  Super-Het 
Converter?"  Among  other  things  Mr.  Flewell- 
ing says:  "In  discussing  the  subject  with  H.  M. 
N.,  I  started  a  line  of  thought  that  appealed  some- 
what to  both  of  us  as  one  that  should  prove  of  very 
great  value  to  the  public  as  a  whole  so  far  as  its 
selectivity  problems  are  concerned.  The  thought  is 
not  entirely  new,  because  more  than  one  engineer 
has  probably  given  time  to  it,  but,  so  far  as  we 
know,  it  has  never  been  given  to  the  public." 

In  the  editorial  box  accompanying  this  article 
we  find  the  following  statement  also  credited  to 
Mr.  Flewelling:  "The  Super-Het  converter  is 
working  great.  I  see  that  another  magazine  hit  at 
it  in  their  June  issue.  The  thing  doesn't  work, 
however.  I  know  several  good  men  who  have  tried 
it  and  found  it  a  dud." 

With  regard  to  the  first  statement  that  the  super- 
het  converter  is  not  entirely  new,  Mr.  Flewelling  is 
entirely  right.  A  similar  idea  was  described  by 
George  J.  Eltz,  Jr.,  in  RADIO  BROADCAST  for  De- 
cember, 1923,  and  another  arrangement  of  the  same 
general  character  was  described  by  Zeh  Bouck  in 
RADIO  BROADCAST  Lab  Department  for  January, 
1924.  A  wave-changer  described  by  Mr.  A. 
O'Connor  employing  the  same  principle  was  pub- 
lished in  RADIO  BROADCAST  for  June,  1925,  and  it 
is  evident  from  what  Mr.  Flewelling  has  said  that 
it  is  our  frequency-changer  which  has  been  char- 
acterized by  him  as  a  dud  since  we  have  not  been  able 
to  discover  an  article  on  the  frequency  changer  in 
any  of  the  other  periodicals  in  their  June  number. 

Mr.  Flewelling  is  wrong,  impossible  as  that  may 
seem.  The  O'Connor  wave-changer  is  anything 
but  a  dud.  We  have  used  it  in  our  laboratory  for 
months  and  have  tried  it  in  connection  with  all 
kinds  of  receivers.  It  works  in  an  extremely  satis- 
factory fashion  and  we  know  definitely  that  a 
great  many  readers  of  RADIO  BROADCAST  have  built 
this  Frequency-Changer  and  are  finding  that  it 
works  as  well  for  them  as  it  does  for  us. 

Now,  we  don't  mind  having  somebody  grab  off 
our  ideas,  and  put  a  new  face  on  them  and  call 
them  new,  but  we  do  hate  to  have  our  com- 
petitors publish  statements  which  in  themselves 
are  untrue — and  the  statement  that  our  frequency- 
changer  is  a  dud  is  untrue — and  if  you  don't 
think  so,  come  over  to  Garden  City  and  I  will 


be  delighted  to  show  you  how  well  it  works.  In 
fact,  I  will  go  further  than  that  if  you  think  it  is 
necessary,  and  drop  in  at  your  own  laboratory  with 
the  Frequency-Changer  under  my  arm. 

We,  as  you  know,  are  trying  to  do  a  good  job  on 
RADIO  BROADCAST  and  we  feel  sure  that  you  are 
attempting  the  same  thing  in  your  field.  We  feel 
that  the  attack  on  our  technical  accuracy  is  entirely 
uncalled  for,  and  in  this  instance,  entirely  unjust. 
We  believe  that  in  fairness  to  us,  a  statement  from 
you  and  one  from  Mr.  Flewelling  appearing  in  your 
paper  concerning  the  O'Connor  Frequency-Changer 
described  by  us  should  be  made. 

I  have  not  overlooked  your  magnaminity  in 
proclaiming  RADIO  BROADCAST'S  Roberts  Knock- 
out the  most  popular  circuit  of  the  season.  And 
for  this  statement  I  am  duly  grateful. 

Cordially  yours, 
ARTHUR  H.  LYNCH,  Editor, 
RADIO  BROADCAST 


July  29,  1925. 

Mr.  Arthur  H.  Lynch,  Editor 
RADIO  BROADCAST, 
Doubleday,   Page  &  Company, 
Garden  City,  N.  Y. 

DEAR  ARTHUR: 

As  1  told  you  during  the  chat  we  had  at  Atlantic 
City,  I  am  extremely  sorry  that  the  attack  made 
by  Flewelling  on  your  Frequency-Changer  should 
ever  have  been  made,  and  I  am  equally  to  blame 
for  having  published  it  without  having  made  a 
thorough  investigation. 

It  was  an  error,  and  you  may  be  sure  we  will 
make  every  effort  to  cooperate  with  vou  in  repairing 
any  damage  it  may  have  done. 

Cordially  yours, 
HENRY  M.  NEELY,  Editor, 
Radio  in  the  Home. 

The  letter  above  is  characteristically  a  Neely 
letter.  Mr.  Neely  is  broad-minded  enough  and 
honest  enough  to  admit  a  mistake  and  make  every 
effort  to  try  to  rectify  it.  Which  should  close  the 
subject. 


A   COMPLETE  receiver  has  been  designed  by  RADIO  BROADCAST  with  two 
aims  in  view — high  quality  in  the  audio  side  of  the  circuit,  and  opera- 
tion  of  the  audio  amplifier  tube,  and  the  plate  supply  of  the  radio,  detector, 
and  first  audio  tube  directly  from  the  alternating  current  house  supply.     The 
receiver  circuit  is  a  tried  and  true  design.      Overloading — that  general  fault 
in  audio  circuits  is  avoided  by  the  use  of  a  power  tube,  entirely  operated 
from  a.  c.     This  receiver  for  home  construction  will  arouse  a  great  deal  of 
interest  because  it  takes  the  lead  in  current  receiver  design- — a  sensitive  cir* 
cuit,  used  with  an  audio  amplifier  whose  quality  is  irreproachable.    An  arti- 
cle fully  describing  this  receiver  will  appear  in  an  early  number. 


ty  CARL  DPEHER 

Drawings  by  Franklyn  F.  Stratford 


A  Debate:  Resolved,  That  500- Watt  Stations  Are  Not 
Sufficient  for  Program  Service 

Affirmative:  Mr.  Dreher  Negative:  Professor  Williams,  WHAZ 


IN  ANSWER  to  your 
article     on    "  Radio 
Power  and   Noise 
Level"  in  your  Sep- 
tember issue,  which  I  have 
read  with  great  interest," 
writes  Professor  Williams 
of  Rensselaer  Polytechnic 
Institute,  "I  must  confess 
surprise     at    finding    an 
article  in  your  magazine 
written    on  such   a   high 
noise  and  such  a  low  power 
level. 

"As  stated  in  your 
article,  I  do  object  to 
raising  the  power  level  of 
broadcasting  stations  for 
the  same  reason  that  I 
object  to  increasing  the 
time  assignments  of  exist- 
ing broadcasting  stations, 
and  the  addition  of  new 
broadcasting  stations.  All 
these  changes  increase  the 
amount  of  interference 


~DEGULAR  readers  of  this  department 
•*•  •-  -will  recall  that  Mr.  Dreber  took  excep- 
tion to  statements  made  by  Professor  Wil- 
liams of  Rensselaer  Polytechnic  Institute 
in  a  recent  address  at  Hartford.  Professor 
Williams  contended,  in  brief,  that  the  pro- 
posal to  permit  the  operation  of  long  range 
broadcasting  stations  was  technically  un- 
necessary and  that  the  familiar  ^oo-watt 
broadcaster  produced  a  satisfactory  signal 
under  most  conditions.  Mr.  Dreher  parti- 
cularly took  exceptions  to  Professor  Wil- 
liams' remarks  about  power  level.  Professor 
Williams  has  been  good  enough  to  amplify 
his  ideas  and  they,  together  with  Mr. 
Dreher' s  reply,  are  printed  below.  The  sub- 
ject is  important,  for  it  concerns  every  broad- 
caster and  every  broadcast  listener.  Intelli- 
gent discussion  of  the  subject  can  do  a  great 
deal  to  clarify  opinion  on  this  much-dis- 
cussed question  of  "super-power"  and  we 
believe  that  the  remarks  printed  belaw  do 
precisely  that. — THE  EDITOR. 


experienced  by  radio 
listeners.  It  is  strange, 
but  true,  that  while  the 
electric  light  and  power 
companies,  the  telephone 
companies,  the  radio  ama- 
teurs, and,  in  fact,  all 
users  of  electrical  energy 
who  have  been  causing 
radio  interference,  have 
done  everything  within 
reason  to  eliminate  inter- 
ference, the  broadcasters 
have  done  everything 
possible  to  increase  inter- 
ference. They  act  as  if 
they  want  to  make  con- 
ditions so  bad  that  the 
Government  will  have  to 
step  in  with  drastic  gov- 
ernmental regulation. 
No  doubt  some  of  the 
more  influential  broad- 
casters might  gain  a  ma- 
terial advantage  through 
such  a  procedure,  but  the 


762 


Radio  Broadcast 


great  majority  of  broadcasters  would  find  themselves 
in  a  position  much  worse  than  that  which  they 
previously  enjoyed. 

"In  order  to  make  my  position  on  the  question 
of  power  level  perfectly  clear  to  your  readers,  I  will 
quote  exactly  what  1  said  on  this  subject  in  my  talk 
on  interference  at  Hartford,  Connecticut.  'The 
other  limitation,  which  is  the  more  important,  that 
must  be  imposed  upon  radio  broadcasting  is  that  of 
intensity  or  power  level.  If  we  allow  a  large  varia- 
tion in  power  level,  we  make  it  extremely  difficult 
to  design  and  construct  receiving  equipment  which 
can  be  operated  by  the  average  radio  listener  with 
equally  good  results  over  the  whole  intensity  range. 
We  in  Troy  have  experienced  more  trouble  from 
this  source  than  from  any  other  in  the  whole  field 
of  radio  broadcasting.  Radio  listeners  have  con- 
structed for  themselves  or  bought  so-called  super- 
sensitive  sets  with  which  they  hope  to  hear  the 
Pacific  Coast  and  European  stations;  also  the  Troy 
and  Schenectady  stations.  It  has  been  our  experi- 
ence that  it  is  impossible  for  the  majority  of  these 
people  to  receive  satisfactorily  either  the  distant 
or  the  near-by  stations.  The  near-by  stations  have 
an  intensity  which  is  too  high  to  be  received  without 
distortion.  The  distant  stations  have  a  power 
level  which  is  so  low  that  they  cannot  be  received 
in  many  locations  without  sufficient  noise  to  make 
the  reception  unpleasant.  You  may  think  that  this 
condition  is  the  fault  of  the  radio  listener,  and  that 
he  can  be  educated  to  use  his  set  in  such  a  way  that 
these  difficulties  will  be  overcome.  This  is  un- 
doubtedly true  in  most  instances  regarding  the 
reception  from  near-by  stations,  but  it  is  not  true 
regarding  the  distant  stations.  There  is  no  place — 
at  least  I  have  been  unable  to  find  a  place — where 
there  is  a  zero  noise  level.  The  noise  level  does  vary 
greatly  at  different  locations,  and  a  sensitive  set 
which  may  function  satisfactorily  at  one  location 
will  prove  to  be  entirely  unsatisfactory  at  another 
location.  It  is  therefore  evident,  that  at  each 
location,  there  is  a  minimum  signal  strength  which 
can  be  satisfactorily  received  on  the  most  sensitive 
receiving  set  and  if  we  attempt,  at  this  location,  to 
receive  a  program  from  a  station  which  has  a  signal 
strength  below  this  minimum,  we  receive  so  much 
noise  along  with  the  program  that  for  all  practical 
purposes  the  program  is  ruined.  At  first  sight,  it 
would  appear  that  we  could  lower  this  minimum 
signal  strength  to  any  desired  value  by  eliminating, 
in  the  territory  considered,  the  various  sources  of 
noise.  Theoretically  this  is  possible,  but  practically 
and  economically  it  is  impossible.  If  the  radio 
listeners  require  the  Public  Service  Corporations 
operating  in  their  territory  to  reduce  the  noise 
level  produced  by  them,  they  would  require  these 
corporations  to  spend  vast  sums  of  money  in  chang- 
ing equipment,  improving  insulation,  etc.  Eventu- 
ally the  public,  which  includes  the  broadcast  lis- 
teners, would  have  to  pay  for  these  improvements. 
This  would  mean  that  the  cost  to  the  consumer  of 
the  services  he  receives  from  these  corporations 
would  increase  proportionately.  If  the  broadcast 
listeners  carried  their  demand  to  the  limit  of  no,  or 


nearly  no  noise,  it  would  mean  that  the  public 
could  not  afford  to  pay  for  the  service  rendered  by 
our  public  utilities,  and  the  broadcast  listeners 
would  be,  in  fact,  sacrificing  the  benefits  they  now 
receive  from  these  corporations  for  the  sake  of 
improving  and  extending  the  range  of  their  broad- 
cast reception.  As  stated  earlier  in  this  talk,  no 
one,  when  he  realized  what  he  was  doing,  would  be 
willing  to  make  this  sacrifice.  It  is,  therefore, 
necessary  to  establish  a  reasonable  lower  power 
level  limit.  Then  if  any  particular  broadcast 
listener  wishes  to  construct  or  buy  a  sensitive  re- 
ceiver, which  will  receive  programs  below  this 
power  level,  he  should  do  it  with  the  knowledge  that, 
in  general,  he  will  not  be  able  to  use  the  extreme 
sensitivity  of  his  set  without  experiencing  disagree- 
able interference.  If  he  is  made  to  understand 
that  what  he  is  doing  is,  in  every  way,  equivalent  to 
placing  a  symphony  orchestra  in  a  boiler  shop,  very 
few  will  be  foolish  enough  to  do  it,  and  our  troubles 
from  interference  will  be  very  materially  reduced. 

'  'With  regard  to  the  upper  power  limit,  there  is 
room  for  considerable  difference  of  opinion.  Our 
experience  in  Troy  has  convinced  us  that  there  is  no 
necessity  for  these  superpower  broadcasting  sta- 
tions. When  we  know  that  a  5oo-watt  station  can 
be  consistently  heard  throughout  the  cool  weather 
all  the  way  across  this  continent  in  one  direction, 
and  in  Europe  in  the  other  direction,  we  can  hardly 
be  criticized  for  taking  the  stand  that  a  power  level 
of  approximately  this  value  is  sufficiently  high  to 
meet  the  needs  of  the  radio  audience.  When  it  is 
necessary  to  lift  the  power  level  all  over  the  coun- 
try, when  something  of  national  importance  is  being 
broadcast,  it  can  be  done  very  satisfactorily  by 
linking  by  wires  several  broadcasting  stations, 
chosen  on  account  of  their  location.' 

"Comparing  the  above  with  your  remarks  in  the 
September  RADIO  BROADCAST,  it  is  evident  that  we 
are  in  substantial  agreement  with  regard  to  the 
necessity  for  a  low  power  level  limit.  If  this  level 
is  established  sufficiently  high  so  that  'static' 
interference  is  not  disagreeable,  we  can  unquestion- 
ably keep  man-made  interference  at  the  same  level 
as  'static'  interference,  and  thus  also  avoid  this 
form  of  interference. 

SUPER-POWER  VERSUS  SUPER-BROADCASTING 

"\  A /ITH  reference  to  the  upper  power  level,  we 
*  *  agree  that  this  should  be  maintained  as  high 
as  practicable,  and  differ  only  in  our  methods  of 
obtaining  this  high  power  level  over  large  areas. 
Your  method  is  to  use  a  super-power  broadcasting 
station;  my  method  is  to  use  a  super-broadcasting 
system,  by  which  I  mean,  as  stated  above,  several 
broadcasting  stations  of  approximately  500  watts 
connected  by  wires.  With  your  system  you  would 
have  an  excessively  high  power  level  in  the  neighbor- 
hood of  your  super-power  station,  and  this  power 
level  would  fall  off  rapidly  with  distance  from  your 
station.  With  my  method  you  would  not  have  an 
excessively  power  level  at  any  point,  and  you 
would  have  a  more  uniform  power  level  over  the 


The  Case  for  Low  Power  Broadcasters 


763 


area  to  be  covered  by  the  program.  By  my 
method  an  average  power  level  could  be  main- 
tained at  a  higher  value  than  by  the  one  you  sug- 
gest. 

"  You  use  the  electrification  of  our  railways  as  an 
illustration  of  the  centralization  of  power  produc- 
tion, which  you  think  should  be  followed  in  the 
case  of  radio  broadcasting.  Do  you  propose  a 
super-generating  station  at  the  central  points  of  our 
transcontinental  railway  systems  to  feed  energy 
over  the  entire  line?  Do  you  not  know  that  it  is 
the  intention  of  those  who  are  considering  the 
electrification  of  our  railway  systems  to  take  the 
power  required  from  our  super-power  systems? 
And  what  is  a  superpower  or  giant  power  system  in 
the  minds  of  those  who  are  forming  them?  It  isn't 
a  super-power  plant,  but  a  relatively  large  number 
of  generating  stations  connected  by  transmission 
lines.  In  such  a  system,  the  electrical  energy  con- 
sumed in  a  given  locality  is,  under  ordinary  operat- 
ing conditions,  produced  at  the  power  plants  origin- 
ally designed  and  constructed  for  supplying  the 
energy  to  that  part  of  the  system  serving  the  given 
locality.  This  system  is  interconnected  by  trans- 
mission lines  with  its  neighboring  systems  so  that, 
when  necessary,  there  can  be  an  interchange  of 
energy  between  the  distributing  systems  by  means 
of  the  connecting  transmission  lines.  The  general 
opinion  of  power  engineers  on  this  subject  is  stated, 
as  follows,  on  page  438  of  the  July  1925,  National 
Electric  Light  Association  Bulletin: 

During  the  past  decade,  the  rapid  growth  of  the 
industry  has  required  the  greatest  amount  of  atten- 
tion to  a  development  which  was  marked  at  every 
step  by  notable  increases  in  size  and  capacity  of  the 
individual  components  of  our  physical  plants.  In 
studying  the  trend  of  growth  for  the  future,  it  is 
quite  likely  that  the  necessity  for  a  continuing  in- 
crease in  capacity  of  equipment  will  be  far  less  than 
we  have  been  forced  to  meet  during  the  past  dec- 
ade. Further  increases  will  be  largely  determined 
by  the  economics  of  the  situation,  and  while  esti- 
mates of  future  growth  indicate  that  the  total 
energy  demand  will  treble  during  the  next  ten 
years,  there  is  little  likelihood  that  unit  capacities  of 
equipment  for  generation  and  distribution  will 
increase  in  anywhere  near  the  same  ratio. 

I  have  been  intimately  associated  with  the  electric 
light  and  power  industry  for  the  past  twenty  years, 
and  am  not  aware  of  any  tendency  in  the  direction 
of  super-power  plants,  but  am  entirely  in  sympathy 
with  the  trend  toward  the  consolidation  of  trans- 
mission systems,  and  the  ultimate  establishment  of 
the  so-called  super-power  systems. 

LINKING  A  DEVELOPMENT  IN  THE  POWER  AND  COMMU- 
NICATION FIELDS 

"IN  THE  communication  field  we  have  a  similar 
*  development.  The  local  telephone  exchange 
gives  the  community,  which  it  serves  local  telephone 
service.  The  American  Telephone  and  Telegraph 
Company,  with  its  long  distance  lines  intercon- 
nects these  local  telephone  exchanges  into  a  super- 
telephone  system,  which  gives  national  telephone 


service.  The  writer  has  studied  the  development 
of  the  telephone  industry  in  this  country  for  the 
past  fifteen  years  and  is  unaware  of  any  tendency 
toward  the  development  of  a  super-telephone  office, 
but  is  aware  of  the  fact  that  the  interconnection  of 
these  offices  by  telephone  transmission  lines  has 
produced  the  super-telephone  system. 

"In  your  article  you  endeavor  to  show  by  com- 
putation, the  advantages  of  a  50  kw.  broadcasting 
station-  from  the  point  of  view  of  economy.  Let  us 
carry  your  argument  a  little  further,  and  see  what 
conclusions  we  arrive  at.  On  Page  117  of  the 
November,  1922,  Bell  System  Technical  Journal  we 
find  the  following: 

Economy  of  transmission  requires  the  handling 
of  messages  at  as  low  an  energy  level  as  possible  and, 
as  the  author  points  out,  wire  transmission  satisfies 
this  requirement  much  better  than  radio.  Refer- 
ring to  the  transcontinental  line  with  radio  ex- 
tensions, which  was  used  recently  to  talk  from 
Catalina  Island  in  the  Pacific  Ocean  to  a  ship  in  the 
Atlantic  Ocean,  it  is  stated  that,  had  all  of  the 
necessary  energy  been  introduced  at  one  end  of  the 
circuit,  there  being  no  intermediate  amplification, 
the  total  power  required  would  have  been  1.8 
x  io88  kilowatts,  an  amount  unavailable  in  the 
world.  In  the  actual  system,  distributing  the 
amplification  along  the  transmission  line,  the  power 
required  sums  up  to  something  less  than  i  kilowatt. 

This  statement  needs  no  amplification  by  me.  I 
have  used  it  for  the  reason  that  the  data  have  been 
taken  from  an  actual  transmission  problem  and  is, 
therefore,  not  academic.  If  your  readers  will  write 
down  1 8  with  twenty-eight  zeros  after  it  before  they 
come  to  .the  decimal  point,  they  will  have  some 
idea  of  what  will  be  required  in  the  way  of  a  super- 
power station  if  you  wish  all  the  amplification  to 
be  transferred  from  the  receiving  set  to  the  trans- 
mitting set,  which  is  the  development  suggested  in 
your  article. 

"The  super-broadcasting  system,  suggested  in  my 
article,  operates  on  exactly  the  same  principle  as 
that  used  on  this  transcontinental  line.  It  would 
be  operated  between  perfectly  definite  power  level 
limits  and  for  the  same  reason  that  the  transcon- 
tinental telephone  line  is  operated  between  per- 
fectly definite  power  level  limits.  In  telephone 
transmission,  the  power  level  must  be  maintained 
above  the  noise  level  so  that  the  noise  does  not  in- 
terfere with  articulation.  The  upper  power  level  is 
maintained  as  low  as  practicable  so  as  to  reduce  the 
interference  between  the  various  telephone  cir- 
cuits. The  electric  light  and  power  engineers 
in  this  country  are  very  anxious  to  have  the  com- 
munication systems  increase  their  power  level,  as  it 
would  reduce  very  materially  the  interference  pro- 
duced by  the  light  and  power  systems  in  the  com- 
munication systems.  The  telephone  engineers  ob- 
ject to  raising  their  upper  power  level  because  they 
know,  from  experience,  that  increasing  this  upper 
power  level  increases  the  interference  from  one 
telephone  circuit  into  another.  Increasing  the 
upper  power  level  for  broadcasting  by  the  use  of 
super-power  stations  produces  practically  the  same 


764 


Radio  Broadcast 


kind  of  interference  between  stations  in  the  receiv- 
ing sets,  and  when  broadcasters  have  had  a  little 
more  experience  they  will  be  no  more  anxious  to 
increase  their  upper  power  levels  than  are  the  tele- 
phone engineers. 

LOCAL  BROADCASTERS  AS  OPPOSED  TO  " SUPER"  ONES 

"/CONTRARY  to  the  statements  made  in  your 
S-*  article,  if  we  wish  to  take  advantage  of  the 
past  experience  of  power  and  telephone  engineers 
and  develop  broadcasting  along  similar  lines,  we 
must  have  local  broadcasting  stations  for  local 
service,  which  may  be  interconnected,  thus  forming 
super-broadcasting  systems  when  we  wish  important 
programs  to  cover  large  areas  efficiently,  economi- 
cally and  with  minimum  interference. 

"We  are  at  a  loss  to  understand  why  your  maga- 
zine has  completely  reversed  its  opinion  with  re- 
ference to  500-watt  stations.  Two  years  ago  this 
winter  you  asked  WHAZ  to  cooperate  with  you 
in  your  transatlantic  tests.  At  that  time  we 
were  using  a  little  less  than  500  watts  in  our 
antenna  and  yet,  according  to  your  own  report, 
we  made  a  very  creditable  showing  in  spite  of  the 
fact  that  a  larger  powered  station  operating  on  the 
same  wavelength,  occupied  approximately  one  half 
of  our  broadcasting  period,  leaving  approximately 
only  eight  minutes  for  the  broadcast  listeners  on  the 
other  side  of  the  Atlantic  to  tune-in  station  WHAZ. 
These  and  other  long  distance  listeners  were  not,  as 
you  say,  'batted  in  the  ear  by  crashes  of  static, 
violet  ray  machines,  electric  bells,  door-openers,  and 
other  miscellaneous  natural  and  artificial  noise 
makers.'  If  you  will  procure  and  read  a  copy  of  the 
National  Electric  Light  Association's  serial  report 
of  the  inductive  coordination  committee,  technical 
national  section,  Radio  Interference  published 
July,  1925,  you  will  find  that  arrangements  have 
been  completed  for  making  the  noises  you  refer  to 
part  of  radio's  ancient  history.  Why  resurrect  this 
corpse  and  use  it  for  an  argument  in  favor  of 
super-power  stations? 

WHY   WHAZ    ISN'T   HEARD   OFTENER 

'""THE  real  reason  why  fewer  long  distance  listen- 
*  ers  are  unable  to  pick  out 'the  mystic  letters 
WHAZ'  is  because  they  are  "batted  in  the  ear'  by 
their  so-called  local  superpower  and  the  squealing 
produced  by  the  heterodyning  of  carrier  waves  from 
too  many  stations  broadcasting  simultaneously. 

"You  say  that  'a  large  station  costs  a  pile  of 
money  and  all  that  one  gets  from  the  disbursement, 
besides  the  ability  to  address  the  populace,  is  the 
privilege  of  spending  a  lot  more  cash  to  keep  the 
thing  going.'  This  statement  would  lead  one  to 
believe  that  the  scramble  one  witnesses  at  a  radio 
conference  for  more  time,  more  stations,  and  more 
power  is  due  to  the  anxiety  of  the  broadcasters  to 
spend  their  money  for  nothing.  This  is  absolutely 
false.  The  reason  why  our  present  broadcasters 
are  asking  for  more  time  and  more  power,  and  new 
broadcasters  wish  to  enter  the  field,  is  because  they 
know  'it  pays  to  advertise.'  What  sense  is 
there  in  telling  the  public  that  radio  broadcasting 


stations  are  philanthropic  organizations,  when  any- 
one who  has  sense  enough  to  read  knows  it  isn't  so? 
Can  any  one  imagine  the  stockholders  of  a  radio 
manufacturing  concern  voting  large  sums  of  money 
to  be  spent  for  entertaining  the  public  without 
any  money  return  to  the  corporation?  The  groan- 
ing broadcasters  referred  to  in  your  article  are  as 
hard  to  find  as  the  missing  link  which  would  have 
been  of  so  much  value  recently  at  Dayton,  Ten- 
nessee. 

"You  say  that  'among  all  the  sounds  heard  in 
broadcasting  studios,  the  jingling  of  the  cash  regis- 
ter is  the  least  frequent.'  Do  you  not  know  that 
no  one  expects  to  find  cash  registers  in  the  advertis- 
ing department  of  any  business,  and  that  they 
are  found  in  the  sales  department?  Any  one 
who  has  purchased  radio  apparatus  has  heard  the 
cash  register  jingle  more  than  once.  The  stores 
that  operate  broadcasting  stations  have  their  cash 
registers  behind  the  counter  or  in  the  cashier's 
cage.  The  hotels  that  operate  broadcasting  sta- 
tions have  their  cash  registers  in  the  cashier's  cage, 
etc.  If  the  cash  register  manufacturers  are  losing 
business  through  broadcasting,  the  writer  doesn't 
know  it. 

"  In  your  enthusiasm  for  those  who  have  money 
to  spend  on  super-power  stations  you  say  'If  Mr. 
Williams  wants  to  reduce  station  interference,  he 
should  advocate  a  reduction  in  the  number  of  poor 
transmitters  by  enforcing  decent  standards  of 
service,  instead  of  opposing  the  sound  engineering 
adjustments  of  organizations  with  the  resources 
and  determination  to  maintain  the  progress  of  the 
art.  And,  if  he  will  ponder  a  little  on  the  difference 
between  the  '  I-think-I-heard-your-station-last- 
night'  range,  and  the  effective  service  range  of  a 
station,  he  will  perhaps  reconsider  an  argument 
which  is  reminiscent  of  the  early  days  of  automobil- 
ing,  when  it  was  decreed  that  a  flagman  had  to 
walk  ahead  of  each  automobile  to  prevent  it  from 
scaring  horses.'  Let  us  look  into  this  matter  and 
see  if  it  is  as  foolish  as  it  sounds.  Bringing  the 
idea  of  your  flagman  up  to  date,  are  you  not  aware 
of  the  fact  that  the  1925  flagman  is  represented  by 
our  various  State  Motor  Vehicle  laws,  with  the  re- 
quired personnel  for  enforcement?  And  why  is  the 
1925  model  flagman  necessary?  It  is  because  auto- 
mobilists,  with  resources  in  the  form  of  automobiles 
and  determination  in  the  form  of  a  well  filled  gas 
tank,  have  attempted  to  use  our  public  highways 
without  due  appreciation  of  the  rights  of  others  to 
use  these  same  highways  unmolested.  Are  you 
asking  me  to  advocate  the  construction  and  opera- 
tion of  super-power  stations  by  those  organizations 
which  have  the  necessary  financial  resources  and 
influence,  to  mislead  them  into  believing  that  they 
may  ride  rough-shod  through  our  ether  highways, 
without  any  regard  for  the  rights  of  those  localities 
that  wish  to  operate  lower  powered  broadcasting 
stations,  and  use  the  same  ether  highways  uiv 
molested?  We  agree  that  there  are  too  many  500- 
watt  stations  operated  simultaneously  at  the 
present  time.  We  also  know  that  conditions  will 
be  worse  than  they  are  now,  if  all  these  stations 


Long  Range  Broadcasters  Represent  Progress 


765 


increase  their  power.  This  is  why  I  refuse  to  ad- 
vocate the  use  of  super-power.  I  know  that  each 
section  of  these  United  States  has  as  much  right 
to  the  use  of  the  ether  as  any  other  section,  and  I 
do  not  believe  the  American  people  will  ever  stand 
for  a  monopoly  in  broadcasting,  either  by  one  sec- 
tion of  the  country  or  by  one  corporation. 

LIMITATION    OF    POWER   NECESSARY 

"C  INGE  each  section  of  the  country  has  an  equal 
^  right  with  every  other  section  to  broadcast, 
we  must  expect  to  have  a  relatively  large  number  of 
broadcasting  stations,  and  the  only  possible  way  of 
operating  them  simultaneously,  without  annoying 
interference,  is  to  limit  their  power.  The  separate 
stations  can  then  operate  independently  for  local 
service  and  can  be  linked  together  by  land  wires  for 
national  service.  If  this  method  were  followed, 
there  would  be  less  necessity  for  a  flagman  of  the 
ether  and  I  am  of  the  opinion  that  the  fewer  laws 
required  to  regulate  broadasting  the  better  for 
everyone.  This  is  a  question,  however,  which  must 
be  eventually  settled  by  the  radio  audience,  so  let  us 
see  who  they  are. 

"  In  your  article  you  ask  'What  is  the  radio  audi- 
ence and  what  are  its  demands?'  You  indicate 
your  answer  as  follows:  'We  shall  be  surprised,  in- 
deed, if  the  members  of  this  WHAZ  audience  do  not 
send  us  loads  of  poisoned  cigars,  live  tarantulas,  and 
infernal  machines.'  We  will  have  to  part  company 
with  you  on  this  subject  also,  as  we  have  found  the 
radio  audience  intellectually  on  a  par  with  the 
broadcasters  and  we  are  very  grateful  to  them  for  the 
manner  in  which  they  have  shown  us  their  apprecia- 
tion of  our  endeavors  in  the  broadcasting  field. 
They  believe  in  free  broadcasting  as  thoroughly  as 
they  believe  in  free  speech.  They  have  indicated 
in  the  past  that  they  can  recognize  a  monopoly  in  the 
forming  and  that  they  have  no  intention  of  standing 
for  a  radio  monopoly.  We  believe  that  the  radio 
audience  are  intelligent  and  that  if  they  decide  to 
have  a  radio  broadcasting  station  of  any  size  in  a 
certain  locality  and  are  told  that  the  cost  will  be 
prohibitive,  they  have  back-bone  enough  to  start 
an  investigation  to  determine  why  powerful  radio 
broadcasting  equipment  is  so  expensive,vand  deter- 
mination enough  to  carry  the  investigation  through 
to  a  conclusion,  and  thus  put  the  skids  under  that 
argument. 

RADIO   AT  WHAZ 

NOW  I  wish  to  say  a  few  words  regarding  the 
broadcasting  activities  of  this  Institution. 
The  Rensselaer  Polytechnic  Institute  has  had 
broadcasting  equipment  since  the  winter  of  1909- 
10.  It  was  procured  at  that  time  because  we 
believed  it  had  a  great  future,  although  it  was 
known  then  by  the  unpretentious  name  of  a  wire- 
less telephone.  We  believe  that,  in  the  future, 
innumerable  practical  applications  will  be  found 
for  high  frequency  electrical  energy  and  for  that 
reason  we  are,  at  this  time,  designing  and  construct- 
ing an  addition  to  our  radio  laboratory,  which  will 
give  us  approximately  3000  square  feet  of  addi- 


i  wonlc&rt  Lave  those  moons 


tional  floor  space.  Educational  institutions  are  not 
made  of  money  but  some  of  them  have  an  uncanny 
way  of  looking  into  the  future.  This  Institution 
intends  to  use  this  additional  laboratory  space  for 
laying  the  foundation  for  our  part  in  this  future 
development.  As  soon  as  we  find  it  necessary  for 
our  purpose  to  have  a  5  kw.  or  a  50  kw.  transmit- 
ter, we  will  have  it.  You  may  rest  assured  on  that 
point.  We  have  been  drawn  into  this  broadcasting 
controversy  because  we  had  the  audacity  to  use  our 
laboratory  equipment  for  part  of  one  evening  each 
week  for  broadcasting.  Practical  engineers,  to 
say  nothing  of  academic  ones,  never  start  anything 
they  can't  finish,  so  you  are  quite  likely  to  find  this 
station  interested  in  this  controversy  until  a  solu- 
tion is  found  which  meets  the  needs  of  the  American 
public. 

"In  closing,  I  wish  to  restate  what  everyone 
knows,  who  has  anything  to  think  with  and  uses 
that  God-given  power: 

(1)  The  American  people  are  worthy  of,  and  will 
have,   the  best   local,   national   and   international 
broadcasting,  and  they  will  have  this  service  with  a 
minimum  amount  of  interference. 

(2)  In  order  to  reduce  interference,  upper  and 
lower  broadcasting  power  levels  must  be  established. 

(3)  There  are  too  many  Class  B  Stations  operating 
simultaneously,  and   to  allow  these   stations  still 
further  to  increase  their  power  can  only  result  in 
making  conditions  worse. 

(4)  The  most  economical,  efficient  and  satisfac- 
tory system  will  limit  the  power  used  by  stations  for 
localibroadcasting,  and  will  unite  these  local  stations 
into  a  super-broadcasting  system  for  national  ser- 
vice. 

(5)  There  can  be  no  private  broadcasting  mono- 
poly, either  by  a  section  of  this  country  or  by  a 
corporation. 

(6)  It  pays  to  advertise — broadcasting  at  present 
is  advertising,  therefore,  broadcasting  pays. 

(7)  The  radio  public  pays  for  broadcasting  and 
what  they  pay  for  they  will  control." 


y66 


Radio  Broadcast 


Mr.  Dreher's  Reply 


AONG  in  the  very  early  part  of  the  seven- 
teenth century,  Galileo,  having  devised  a 
sufficiently  effective  telescope,  was  able 
to  view  the  four  moons  of  Jupiter.  When  he  an- 
nounced his  discovery,  all  the  Aristotelian  astronom- 
ers of  the  day,  who  had  their  jobs  and  were  satisfied 
with  the  heavens  as  they  knew  them,  rose  in  horror. 
One  Sizzi,  a  learned  star-gazer  of  Florence,  de- 
clared that  as  there  were  only  seven  apertures  in  the 
head:  two  eyes,  two  ears,  two  nostrils,  and  one 
mouth;  and  as  there  were  only  seven  metals  (he 
was  sure  of  that),  and  seven  days  in  the  week,  so 
there  could  be  only  seven  planets.  Being  persuaded 
that  the  four  satellites  were  actually  visible  in  the 
telescope,  the  scholarly  Sizzi  shifted  his  position  a 
trifle.  He  now  argued  that  as  the  circumjovian 
planets  were  invisible  to  the  naked  eye,  they  could 
exercise  no  influence  on  human  beings,  they  were 
useless;  finally,  therefore,  they  did  not  exist.  In 
short,  Sizzi  just  wouldn't  have  those  moons,  and 
that  was  all  there  was  to  it. 

With  apologies,  I  must  confess  that  ProfessorW.  J. 
Williams'  remarks  regarding  my  article  on  "Radio 
Power  and  Noise  Level"  in  the  September  RADIO 
BROADCAST  affect  me  much  like  the  arguments  of 
the  staunch  conservative  Sizzi  in  his  day.  It  is  true 
that  I  have  not  invented  a  telescope,  nor  made  any 
celestial  discoveries.  With  touching  modesty,  I 
confess  that  I  see  no  resemblance  between  Galileo 
and  myself,  but  1  do  feel  that  a  comparison  between 
Professor  Sizzi  and  Professor  Williams  is  not  too  far 
fetched.  As  Sizzi  clung  desperately  to  the  mystic 
number  seven,  so  Mr.  Williams  will  never  abandon 
five  hundred.  Five  hundred  watts,  that's  the  power 
for  a  good  honest  broadcasting  station!  It  was 
good  enough  in  1922,  and  why  shouldn't  it  serve 
now?  In  youth  it  sheltered  me,  and  I'll  protect  it  now! 
as  we  used  to  declaim  in  the  high  school  elocution 
classes.  As  for  any  higher  power,  Professor 
Williams  simply  won't  see  it. 

At  no  point  in  his  argument  is  Professor  Williams 
courageous  enough  to  discuss,  simply  and  without 
obfuscations  my  contention  that  the  addition  of  a 
stage  or  two  of  audio  amplification  to  the  listener's 


-wear  telts   or  suspenders? 


signal,  without  a  proportionate  rise  in  the  noise  level, 
would  improve  broadcasting  as  a  public  service, 
stabilize  the  industry,  free  it  to  a  great  extent  from 
seasonal  variations,  and  benefit  everyone  con- 
cerned except,  perhaps,  the  owners  of  a  few  anti- 
quated and  unprogressive  broadcasting  stations. 
Instead,  he  begins  with  a  restatement  of  his  dicta 
on  noise  level.  He  has  apparently  never  heard  of  an 
effective  volume  control  on  a  receiving  set,  for  he 
repeats  his  entirely  erroneous  notion  that  it  is  not 
feasible  to  design  receiving  equipment  capable  of 
distortionless  reception  from  powerful  near-by 
stations  as  well  as  distance  work.  Such  a  sensitivity 
control  costs  about  twenty  cents,  and  there  are  al- 
most as  many  ways  of  doing  the  thing.  His  attitude 
toward  radio  noise  is  apparently  quite  fatalistic,  as 
in  his  Hartford  address,  where  he  declared  that 
the  radio  art,  being  in  its  infancy,  must  be  expected 
to  be  noisy!  This  is  like  saying  that  there  is  no 
reason  why  men  should  wear  belts  or  suspenders,  for 
they  can  hold  up  their  trousers  with  their  hands. 
He  compares  distance  reception  to  placing  a  sym- 
phony orchestra  in  a  boiler  shop,  and  says  that  it  is 
a  very  foolish  thing  to  do.  There  we  agree.  But 
it  is  not  half  so  foolish  as  continuing  to  suffer  noisy 
reception  when  one  can  overcome  these  disturbances. 
I'  do  not  understand  Mr.  Williams's  supine  and  com- 
placent attitude  with  regard  to  this  problem.  An 
engineer  is  not  expected  to  turn  his  back  on  difficul- 
ties; he  is  supposed  to  be  trained  to  overcome  them. 
By  increasing  transmitter  power,  we  can  propor- 
tionately reduce  amplification  at  the  receiver, 
thereby  riding  over  disturbances  without  any  in- 
crease in  station  interference  whatsoever.  Pro- 
fessor Williams,  who  is  not  a  radio  engineer,  and 
whose  talk,  to  which  I  took  exception,  was  not 
delivered  before  an  audience  of  radio  engineers, 
persists  in  dragging  all  sorts  of  bogeys  into  the 
field  which  it  has  pleased  him  to  invade  at  this  late 
date.  Finally,  when  he  does  come  down  to  figures, 
he  quotes  the  computations  of  a  telephone  engineer, 
which  I  used  myself  in  an  article  for  Radio  two  years 
ago,  to  the  effect  that,  if  one  tried  to  get  as  much 
voice  power  at  the  receiving  end  of  a  line,  without 
repeaters,  as  one  can  get  with  them,  the  required  in- 
put to  the  line  would  be  i.8X  io29  kilowatts.  This 
is  glorious,  but  what  is  its  relevancy?  This  is  what 
Professor  Williams  calls  carrying  my  argument  for 
a  50  kw.  station  "a  little  further."  By  what 
right?  I  gave  my  figure,  and  I  knew  what  I  wanted 
to  say  If  I  want  to  ride  from  Boston  to  Provi- 
dence, must  I  go  on  to  Washington,  because  the 
conductor  of  the  train  goes  that  far? 

Apparently  Mr.  Williams  sees  some  antithesis  be- 
tween wire  line  transfer  of  programs  and  super- 
power. He  devotes  several  hundred  words  to  argu- 
ments in  favor  of  linking  up  stations  by  wire  lines. 
Every  radio  engineer  will  agree  with  him  heartily. 
We  know  the  advantages  and  disadvantages  of  wire 
lines,  and  use  them  whenever  it  is  expedient  and  we 
have  the  money  to  pay  for  the  lease.  But  if  all  the 
500-watt  stations  in  the  country — to  name  the 
power  which  has  become  Professor  Williams's  fetish 
— were  to  be  linked  up  by  wire  lines,  there  would  still 


There  Is  No  Monopoly  In  Broadcasting 


767 


be  vast  areas  unprovided  with  program  service, 
and  every  time  a  lightning  storm  came  up  (static 
has  remarkably  little  respect  for  500  watts  in  the 
antenna)  all  the  listeners  who  lived  more  than  a 
mile  from  one  of  those  stations  would  encounter  a 
certain  amount  of  unnecessary  interference.  By  all 
means,  when  we  have  stations  of  adequate  power,  let 
them  get  their  modulation  as  best  they  can — by 
bringing  their  artists  to  the  studio  in  airplanes,  or 
by  the  use  of  wire  lines  umpty  thousand  miles  long, 
or  in  any  other  way  that  works. 

CONTINUOUS    PROGRESS    IS   NEEDED   IN    RADIO 

DROFESSOR  WILLIAMS'  complete  insensi- 
•  bility  to  the  need  for  continuous  progress  in  a 
field  like  radio  broadcasting  amazes  me.  I  should 
like  to  know,  for  example,  what  he  would  do  about 
transoceanic  or  international  broadcasting.  Would 
he  permit  the  erection  of  a  super-power  station  or 
two  for  that  purpose,  or  would  he  forbid  that  also, 
on  the  ground  that  it  might  interfere  with  reception 
in  the  rural  location  in  which  it  would  naturally  be 
placed,  or  that  it  might  encourage  the  growth  of, 
the  nefarious  monopoly  which  agitates  Professor 
Williams's  imagination  so  violently?  Would  he 
try  to  send  a  program  over  to  France  for  re-broad- 
casting there,  or  get  one  from  England,  with  his  all- 
encompassing  ^  kw.?  His  predilection  for  that 
power  reminds  me  of  nothing  so  much  as  the  sacred 
decretals  of  the  pious  Bishop  Homenas  in  Rabelais, 
with  which  he  hoped  to  redeem  mankind,  and  to 
accomplish  all  things  good.  It  is  not  at  all  certain 
that  the  Professor  would  not  attempt  this,  for  he 
says  flatly,  in  his  reply  to  my  article,  that  the 
European  listeners  to  WHAZ  in  the  transatlantics 


two  years  ago  "were  not,  as  you  say,  'batted  in  the 
ear  by  crashes  of  static,  violet  ray  machines,  electric 
bells,  door-openers,  and  other  miscellaneous  natural 
and  artificial  noise  makers.'"  Heaven,  then,  inter- 
vened with  a  miracle,  and  the  European  listeners 
heard  WHAZ  against  a  quiet  background.  Has  the 
man  ever  listened  to  DX  at  all,  or  is  he  only  writing 
about  it?  Luckily  for  the  radio  business,  a  lot  of 
radio  listeners  are  situated  so  close  to  broadcasting 
stations  that  they  are  able  to  get  quiet  reception, 
by  virtue  of  the  powerful  fields  that  Professor 
Williams  can't  abide,  even  in  prospect;  but  before 
we  get  through  there  is  no  reason  why  everyone 
who  wants  to  buy  a  radio  set,  should  not  be  able  to 
enjoy  freedom  from  disturbances  practically  all  of 
the  time. 

Professor  Williams  is  an  optimist.  He  says 
artificial  inductive  noises  have  been  eliminated. 
He  quotes  a  report.  Well,  then  it  must  be  so. 
Only,  someone  should  inform  the  noises  that  they 
have  been  eliminated.  With  all  due  credit  and 
encouragement  to  the  men  working  on  this  problem, 
I  am  bound  to  say  that  considerable  noise  is  still 
getting  by  them.  Besides,  Professor  Williams  him- 
self points  out  that  there  is  a  limit  below  which  it  is 
not  practicable  to  go  in  electrical  noise  suppression. 
The  remedy  lies  only  partly  in  attacking  artificial 
noise  at  the  source;  the  signals  of  broadcasting  sta- 
tions should  be  brought  up  to  a  level  where  every 
cat  rubbing  his  back  against  a  fence  will  not  in- 
terfere with  reception. 

In  the  matter  of  the  electrification  of  railroads, 
and  giant  power,  I  will  yield  the  field  to  my  oppon- 
ent. There  I  freely  acknowledge  that  he  knows 
more  than  I  do,  and  it  is  therefore  proper  that 


ARCHITECT'S  DRAWING  OF  THE  NEW  WJAZ  STUDIO  AT  CHICAGO 


768 


Radio  Broadcast 


j^Microphone 
Director 


-e 


CO 

o> 
G 


£ 

s 


CO 


/Jl       j 

Tubas 


Altos 


Troinbones 


JL $ 


Ti 


FIG.     I 

An  effective  studio  set-up  for  a  brass  band  in  a  small  broadcasting  studio, 

twenty-five  by  nineteen  feet.     In  this  particular  case,  a  typewriter  cover 

was  placed  over  the  microphone  to  lessen  volume 

I  should  defer  to  him.  I  used  this  process  as  an 
illustration.  If  it  was  not  an  apt  illustration,  I  am 
glad  to  be  corrected. 

Professor  Williams'  treatise  on  the  location  of 
cash  registers  is  really  too  absurd.  All  I  have  to 
say  is  that  the  editors  and  readers  of  this  magazine 
do  not  encourage  dull  writing  in  their  contributors. 
They  understand  a  bit  of  sarcasm  and  do  not  write  a 
homily  about  it.  Of  course  the  broadcasters  are  not 
altruists.  They  are  working  for  the  same  two  ends 
that  Professor  Williams  strives  to  attain:  to  earn 
a  living,  or  better;  and  to  be  useful  in  the  world,  if 
possible. 

THERE    IS   NO   MONOPOLY    IN    BROADCASTING 

MONOPOLY!  Already  about  twenty  stations  in 
*  *  *  this  country  are  going  up  in  leaps  and  bounds 
to  the  5  kw.  level,  including  department  stores; 
electrical,  radio,  and  phonograph  manufacturers, 
schools  of  chiropractic,  newspapers,  churches,  and 
communication  companies.  Where  is  the  monop- 
oly? And  the  50  kw.  and  too  kw.  broadcasting 
stations  built  or  building  in  England  and  Germany, 
are  they  a  part  of  the  world-girdling  octopus?  Stuff 
and  nonsense!  Everybody  is  increasing  power 
who  has  the  money,  because  it  is  the  next  sound 
technical  step.  Professor  Williams  tries  to  put 
me  in  the  position  of  traducing  the  radio  audience. 
Why  should  I?  I  earn  my  living  through  it.  I 
refuse,  however,  to  flatter  the  listeners  by  attrib- 
uting to  them  technical  knowledge  which  both  they 


and  I  know  they  do  not  possess' 
This  sort  of  playing  to  the  gal- 
leries is  deplorable  in  a  teacher 
of  science  and  technology.  We 
want  engineering  data,  not 
rhetoric.  We  can  get  the  latter 
on  any  street  corner  around 
election  time. 

Professor  Williams  seems,  to 
think  it  necessary  to  defend 
WHAZ.  I  have  no  doubt  that 
WHAZ  is  a  good  station.  I  wish 
I  could  hear  it  on  those  Mon- 
day evenings  when  I  am  told 
it  is  on  the  air.  I  can't,  with 
any  degree  of  pleasure,  although 
I'm  not  150  miles  away.  If 
R.  P.  I .  intends  to  get  the  5  kw. 
or  50  kw.  station  that  the 
Professor  hints  at,  all  I  have 
to  say  is:  "Congratulations! 
Welcome  to  our  city!  But  in 
the  meantime,  gentlemen,  don't 
obstruct  traffic.  You  may  join 
the  parade  when  you  are 
ready." 

By  the   time   this  gets  into 
print,    genuine     super -power 
stations  will,  I  hope,  be  audible 
on   the  air.     I    believe  it  will 
not  take  many  months  of  use 
of   these  transmitters  to  con- 
vince Mr.  Williams  that  he  was 
wrong  in  his  views,  honestly 
mistaken,  no  doubt,  but   mistaken.     After  all,  he 
and  I  can  talk  ourselves   dry  and   in  the  end  the 
issue  will  be  decided  by  performance.     So  I  am  con- 
tent to  leave  the  ultimate  decision  to  the  future. 


WJAZ's  New  Studio 


kH  E  photograph  on  page  767  shows  one  view  of 
the  new  Zenith  broadcasting  studio  located  on 
the  twenty-third  floor  of  the  Straus  Building 
in  Chicago.    The  call  letters  of  the  transmitter  are 
WJAZ,  the  same  that  were  used  by  the  earlier  station 
of  the  same  company   at   the   Edgewater    Beach 
Hotel. 

The  new  broadcasting  parlor  does  away  with 
drapes  and  Monk's  Cloth  for  purposes  of  keeping 
down  reverberation,  but  accomplishes  the  same 
object  by  suitable  acoustic  treatment  of  the  walls 
and  ceiling,  an  expedient  which  is  not  novel  in  this 
field,  but  seldom  employed  because  of  the  increased 
expense.  However,  it  looks  much  better  and  is 
worth  the  expenditure. 

There  is  a  large  reception  room  with  tapestry 
and  rugs  and  period  furniture,  and  from  this  an 
artistic  archway  leads  one  into  the  studio,  laid  out 
to  suggest  a  garden,  with  stone  seats,  statues,  and  a 
real  fountain  in  which  Japanese  goldfish  are  permit- 
ted to  listen  to  the  broadcasting.  The  floors  are 
tiled;  potted  plants  and  an  awning  may  also  be  seen. 
The  only  way  you  can  tell  that  it's  a  studio  is  by 
the  piano. 


Microphone  Placement  for  Two  Famous  Broadcasts 


769 


According  to  reports,  lighting  effects  are  to  be 
introduced  for  the  inspiration  of  the  artists.  Some 
of  the  dear  things  need  inspiration,  heaven  knows. 
For  instance,  let  one  of  them  sing  of  love,  and  the 
garden  will  be  bathed  in  moonlight,  etc.  Quite  an 
idea.  We  have  been  advocating  the  use  of  symbolic 
microphone  stands  ourselves,  be  it  remembered. 
But  what  will  happen  to  the  operator  of  the  lights 
at  \VJAZ  when  he  gives  some  nervous  soprano  a  spot 
which  doesn't  suit  her  complexion! 

More  About  How  to  Place  the 
Microphone 

CONTINUING  with  our  technical  series  for 
broadcasters,  we  show  in  Fig.  i  a  very 
successful  studio  set-up  for  brass  band, 
due  to  Mr.  F.  D.  Leslie.  This  was  a  Naval  band 
playing  with  great  energy  to  a  carbon  microphone  in 
a  25  by  19  studio,  so  that  it  had  a  decided  tendency 
to  blast.  The  microphone  was  turned  back  to  the 
orchestra,  with  its  sensitive  side  toward  a  fairly 
dead  surface,  and  a  typewriter  cover  was  slung 
over  it.  The  typewriter  cover  was  a  rather  bar- 
barous expedient,  but  if  it  took  out  the  higher  fre- 
quencies, as  theoretically  it  might  be  expected  to 
do,  the  difference  was  not  noticeable  on  the  air,  and 
there  was  certainly  no  blasting.  This  set-up  should 
be  compared  with  the  arrangement  for  brass  band 
shown  in  Fig.  3-8  last  month.  The  principal 
difference,  aside  from  the  reversing  of  the  micro- 
phone, is  in  the  position  of  the  cornets,  which  in  the 
present  case  are  ranged  on  one  side  of  the  room  on  a 
line  perpendicular  to  the  plane  of  the  microphone. 


Fig.  2  illustrates  the  outdoor  pick-up  of  the  New 
York  Philharmonic  Orchestra  of  1 10  men,  conducted 
by  Willem  van  Hoogstraten,  at  the  Lewisohn  Stadium 
in  New  York  City.  This  is  full  stature  symphonic 
material,  all  *he  Brahms  symphonies  being  played 
during  the  season  of  about  two  months,  most  of  the 
Tchaikowskys  and  Beethovens,  and  others  by 
Schubert,  Mozart,  Schumann,  Dvorak,  Rachmani- 
noff, Respigh1'.  and  Rimski-Korsakoff.  The  popu- 
lar overtures  rnd  light  classics  find  no  place.  The 
management  i:  rather  proud  of  the  fact  that  in  the 
last  few  years  he  programs  have  been  built  "with- 
out concession:."  Nevertheless,  audiences  as  high 
as  11,000  a  nig  it  attend  these  open-air  concerts. 

The  orchestra  plays  on  a  stand  surmounted  by 
a  huge  reflector,  and  flanked  by  sounding  boards. 
The  spread  of  the  orchestra  over  a  front  of  about 
sixty  feet  makes  the  pick-up  somewhat  complicated. 
Using  carbon  microphones,  a  combination  of  close 
and  overhead  pick-up  is  found  suitable.  It  is  clear 
from  Fig.  2  that  the  two  overhead  microphones, 
receiving  sound  directly  from  the  orchestra  as  well 
as  from  the  reflector,  may  be  made  to  do  the  bulk 
of  the  work.  They  are  far  enough  away  to  ob- 
viate blasting,  and  near  enough  to  handle  loud 
and  medium  passages.  At  a  pinch  they  will  also 
do  for  pianissimo  portions,  single  instruments,  etc., 
but  the  gain  must  be  brought  up  to  a  point  where 
the  hiss  is  objectionable  and  such  disturbances  as 
automobile  horns  on  nearby  streets  come  in  faintly. 
For  first-class  pick-up,  therefore,  a  third  microphone 
is  placed  on  a  stand  two  or  three  feet  from  the 
conductor  and  concert  master.  This  microphone 
has  its  individual  gain  control  and  it  is  kept  throttled 


Side  Eleva.ti.on 


I 


' 


TXoo  suspended 
microphones 

Concert 
master 
microphone 


-15M 


Plan 


Percussion. 

Wind 

<0 

-2 

~w 
U 

V> 

"Wood.  Winds 

Violas 

Violins 

Cellos 
.  Conductor 

tl     Concert  master  microphone 
if* 

l*"^-* 

Suspended  microphones 
Audience- 


FIG.  2 

The  Lewisohn  Stadium  at  New  York,  where  the  New  York  Philharmonic  Orchestra  presents  its  famous 
Stadium  Concerts.     This  concert,  in  common  with  many  others  of  its  type,  presents  some  genuine  problems. 
Mr.  Dreher  discusses  in  the  accompanying  article  the  way  in  which  they  are  solved 


770 


Radio  Broadcast 


down  much  of  the  time,  for  it  is  so  close  to  the 
players  that  full  orchestra  will  cause  it  to  blast. 
During  low  passages,  however,  it  is  swung  in 
noiselessly  and  it  will  pick  up  single  instruments 
with  great  detail  and  no  hiss  to  speak  of.  This 
requires  some  finesse,  of  course,  on  the  part  of  the 
man  operating  the  amplifier. 

The  job  might  be  done  with  only  a  single  micro- 
phone suspended  about  fifteen  feet  in  front  of 
the  orchestra  stand  and  twenty-five  feet  high, 
together  with  the  concert  master's  microphone 
for  the  low  portions,  but  two  suspended  trans- 
mitters give  somewhat  better  reproduction  over 
the  wide  front  of  the  orchestra  seating.  As 
Philharmonic  audiences  are  perfectly  quiet  dur- 
ing the  performance,  there  is  no  need  to  watch 
out  for  crowd  noise,  and  the  fact  that  part  of 
the  audience  sits  under  the  suspended  microphones 
is  of  no  consequence,  except  that  the  suspension 
must  be  made  as  safe  as  possible.  The  cables  are 
good  for  800  pounds  (^-inch  galvanized  steel  rope); 
and  as  two  carbon  microphones  weigh  five  pounds,  it 
is  unlikely  that  accidents  will  occur.  This  is  a  rather 
important  factor  in  field  broadcasting;  one  must 
look  out  for  the  artistic  features,  of  course,  but  care 
should  be  taken  not  to  jeopardize  the  audience. 
A  two-and-a-half-pound  lump  of  steel  does  not  have 
to  fall  very  far  to  crack  a  man's  skull. 

Fig.  3  is  a  photograph  of  the  general  lay-out  at 
the  Lewisohn  Stadium,  showing  the  microphone 
suspension  and  the  orchestra  stand.  The  broad- 
casting of  the  Philharmonic  Concerts  is  by  wjz,  WGY, 
and  WRC  being  connected  to  it  by  land  lines. 

A  very  similar  job,  technically,  is  the  transmission 
of  the  Goldman  Band,  which  plays  on  the  campus 
of  New  York  University.  Fig.  4  shows  the  dis- 
position of  the  microphones.  This  orchestra  is 
strong  in  brass,  with  the  addition  of  a  string  section, 
and  the  number  of  players  is  considerably  less. 
The  selections  are  largely  marches  and  popular 
classics.  The  broadcasting  company  in  this  case 
erected  a  frame  of  two-inch  iron  pipe  for  the  over- 
head suspension,  and  did  not  find  it  necessary  to 
spread  the  two  microphones;  they  are  angled  off 
somewhat,  however,  to  face  the  two  halves  of  the 
band.  There  is  also  a  microphone  near  the  con- 
ductor for  the  close  work.  The  pick-up  in  this  case 
is  done  by  WEAF  and  the  modulation  is  sent  on  to  a 
long  chain  of  stations. 

The  radio  critic  of  the  New  York  Herald-Tribune, 
"Pioneer",  says  of  these  two  summer  features: 

There  are  two  downright  perfect  examples  of 
microphone  placement  and  balanced  pick-up  of 
large  orchestras  which  this  summer  has  produced. 
WEAF'S  pick-up  of  the  Goldman  Band  and  wjz's 
ditto  of  the  PhilharmonicOrchestra,  achieve  effective 
reproductions  of  the  entire  orchestras,  which  have 
never  before  (to  our  ears,  at  least)  been  equalled 
and  between  which  there  is  little  to  choose. 

Well,  perfect  is  an  elastic  word,  and  what  is  per- 
fect this  year  will  be  in  the  garbage  can  next  sum- 
mer, for  electrical  reproduction  of  music  has  this 
characteristic — anything  at  all  good  sounds  fine 
.  .  .  until  you  have  something  better  to  compare 


it  with.  Only  then  do  its  faults  stand  out.  How- 
ever, on  a  good  flat  receiving  set  and  loud  speaker, 
these  two  jobs  really  appear  to  get  quite  close  to 
the  actual  performance  of  their  respective  orches- 
tras. The  details  of  the  simple  pick-up  used  may 
be  of  interest  to  other  broadcasters  at  this  time. 

The  Memoirs  of  a  Radio  Engineer.  V 

1  RELATED,  in  the  preceding  issue,  the  mel- 
ancholy story  of  how  wireless  urchins  were 
persecuted  in  1909,  resulting,  in  our  case,  in 
the  loss  of  our  four-wire  flat  top  antenna.  We 
continued  our  experiments  without  an  antenna. 
By  some  means  we  secured  a  small  induction  coil 
of  the  type  used  for  home  "medical"  treatment  of 
rheumatism,  a  "shocking  coil"  with  electrodes 
gripped  in  the  hands  which  would  impart  quite  a  "wal- 
lop" when  the  apparatus  was  adjusted  to  give  maxi- 
mum voltage.  By  using  excessive  primary  voltage 
on  this  coil  we  were  able,  at  times,  to  draw  a  sV-inch 
spark  between  needle  points  across  the  secondary. 
We  made  a  spark  gap  out  of  tin  cracker  cans,  the 
electrodes  being  cut  to  very  sharp  points.  This 
was  a  sort  of  radio  transmitter,  capable  of  producing 
a  buzzing  sound  in  the  telephone  of  the  steel-carbon 
detector,  at  distances  of  six  or  eight  feet,  when  the 
vibrator  was  not  sticking,  and  the  spark  gap  not  in 
excess  of  the  -fa  inch  which  was  its  absolute  limit. 
Near  the  end  of  1909  1  made  an  inventory  of  our 
possessions  in  a  small  memorandum  book,  which 
I  still  possess.  Some  of  the  items  are  as  follows: 

Alarm,  burglar,  made  home,  good. 

Battery,  about  run  out. 

Buzzer,  made  home. 

Bottles,  numerous. 

Catalogues,  useful. 

Carbon,  powdered,  from  dry  battery,  also  in 
chunks. 

Foil,  tin. 

Galvanoscope,  small,  very  sensitive  to  week  cur- 
rents. 

Junk,  of  every  kind  and  description. 

Jar,  Leyden,  unbreakable. 

Magneto,  Etheric  Co.,  good. 

Magnet,  large,  powerful.  Increased  power  of  the 
magneto. 

Mercury,  very  little. 

Motor,  Gem,  power  and  speed.     Runs  fine. 

Press,  printing,  for  printing  laboratory  literature. 

Resonator  for  the  telegraph,  small. 

Saw  mill,  toy. 

Shaft,  counter. 

Wood,  under  closet. 

The  printing  press,  it  should  be  stated,  was 
merely  one  of  those  small  wooden  forms  in  which 
rubber  type  could  be  inserted  to  print  more  or  less 
legible  sentences  in  red  ink.  With  it  we  printed 
the  following  report,  dated  December,  1909. 

Red  Seal  batteries  have  been  pronownced  run  out 
and  have  had  binding  posts  removed.  The  ever 
ready s  are  of  no  more  use.  Have  bought  an  X 
ray,  very  good.  Motor  and  Mesco  Engine  run 
fine.  Have  built  during  the  past  month  a  winding 
gear  for  the  motor,  and  a  key  for  the  telegraph,  also 


772 


Radio  Broadcast 


a  buzzer.     Good  quantity  of  wood  in  stock.     Have 
made  this  new  index  book.     Now  for  1910. 

The  X  Ray,  bought  after  the  batteries  had  been 
pronownced  run  out  and  subjected  to  removal  of 
binding  posts  and  no  doubt  evisceration  for  the 
salvaging  of  the  powdered  carbon,  was  also,  a  dry 
cell,  not,  as  the  report  might  be  taken  to  mean,  a 
Roentgen  outfit  or  anything  else  so  elaborate.  It 
will  be  noted,  also,  that  1  had  not  reached  the  stage 
of  quantitative  exactness.  There  was  the  gal- 
vanoscope,  "very  sensitive  to  week  currents," 
— but  no  one  knew  just  how  "week"  those  cur- 
rents were,  and  the  magnet,  "large,  powerful," 
which  increased  the  power  of  the  "good"  magneto. 
A  similar  uncertainty  manifests  itself  in  the  spell- 
ing. In  fact,  the  book  exhibits  two  individualistic 
spellings  of  "catalogue," — "catalouge"  and  "cat- 
alougle";  and  I  was  in  some  uncertainty  as  to 
whether  an  engine  ran  "fine"  or  "finely."  But 
these  were  small  matters.  In  the  words  of  a  popular 
play,  we  knew  what  we  wanted. 

What  was  the  status  of  commercial  radio  in  1909, 
is  a  question  that  may  occur  to  some  readers  while 
I  devote  so  much  space  to  the  infantile  flounderings 
of  our  group  of  boy  radio  wonders.  As  I  have  stated 
previously  in  these  articles,  there  were  many 
amateurs  ahead  of  us,  and  the  commercial  interests 
were  leading  the  amateurs  by  a  very  comfortable 
margin,  such  investigators  as  Stone,  Fessenden, 
De  Forest,  Massie,  Pickard,  Shoemaker,  and 
numerous  others  having  been  at  work  in  this  coun- 
try for  some  time.  In  1901,  Marconi  had  suc- 
ceeded in  transmitting  the  letter  "S"  across  the 
Atlantic  from  Poldhu,  Cornwall,  to  St.  John's, 
Newfoundland,  a  distance  of  1,800  miles,  and  in 
1909  the  Glace  Bay-Clifden  circuit  had  already  been 
in  commercial  operation  for  two  years.  In  Eng- 
land the  year  1902  saw  the  invention  of  the  Fleming 
valve,  to  which  the  grid  electrode  was  added  in 
1906.  by  De  Forest  in  the  United  States.  In  the 
same  year  Professor  R.  A.  Fessenden  was  working 
at  Brant  Rock,  Massachusetts,  on  his  high-fre- 
quency alternator  and  numerous  other  inventions. 
Even  radio  telephony,  or  aerophony,  as  it  was  fre- 
quently called  at  the  time,  had  made  appreciable 
progress,  although  the  quality  of  transmission  had 
not  yet  attained  any  celestial  heights.  In  1907 
De  Forest  made  experiments  in  wireless  telephony 
on  various  naval  vessels  and  succeeded  in  trans- 
mitting, on  occasion,  over  distances  up  to  sixty 
miles,  using  arc  sets.  The  Poulsen  arc  was  fairly 
well  developed  by  1908,  and  Marjorana  telephoned 
with  an  arc  modulated  by  a  water  microphone  from 
Rome  to  Sicily,  a  distance  of  300  miles. 

In  1909,  the  great  Nauen  station  was  already  in 
operation  in  Germany,  and  preparing  for  communi- 
cation with  the  United  States.  It  had  a  33O-foot 
tower,  an  umbrella  antenna,  and  325  kw.  alternator. 
Messrs.  Slaby  and  Arco,  the  chief  engineers  of  the 
Telefunken  Company,  working  on  the  inventions 
of  Wien  and  others,  had  produced  a  complete  and 
efficient  quenched  spark  transmitter,  which  was  as 
far  ahead  of  the  straight  gap  sets  of  the  day  as  the 


modern  tube  transmitters  are  ahead  of  it  now. 
In  the  neighborhood  of  New  York  things  were 
lively  enough.  The  42  Broadway  station  of  the 
United  Wireless  Company,  call  letters  NY,  erected 
in  1904,  was  in  full  operation,  and  many  operators 
still  remember  its  snappy  250  cycles  calling  AX 
(Atlantic  City)  in  American  Morse,  under  the  ca- 
pable fist  of  Mr.  J.  B.  Duffy.  The  Waldorf  Astoria 
roof  bore  two  towers,  and  Mr.  Pickerill  presided 
over  the  station,  which  had  the  call  letters  WA. 
There  was  also  a  2  KW.  transmitter  on  the  Hotel 
Plaza,  with  the  spark  gap  placed  in  a  wooden 
"safe"  to  prevent  it  from  disturbing  the  slumbers 
of  the  guests.  Its  call  letter  was  "p"  and  that 
was  all  it  needed;  the  day  of  four-letter  calls  was 
still  far  in  the  future.  Whether  "DF,"  the  Man- 
hattan Beach  station,  was  still  in  operation,  I  do 
not  recollect  at  this  instant,  but  De  Forest  had 
been  making  experiments  on  the  incompleted 
Metropolitan  Tower,  and  in  1909  he  declared,  "I 
feel  certain  that  within  a  short  time  we  will  be 
able  to  be  in  wireless  communication  with  the  Eiffel 
Tower  in  Paris,"  a  prophecy  which  was  not  fulfilled 
until  1915,  and  then  by  the  American  Telephone  and 
Telegraph  Company.  There  was  also  a  fine  an- 
tenna on  the  7  ist  Regiment  Armory  in  New  York. 
I  recollect  seeing  it,  but  the  call  letters  escape  me. 
Nor  were  other  sections  of  the  country  much  be- 
hind. On  the  Great  Lakes,  there  were  stations  at 
Port  Huron,  Detroit,  Toledo,  Cleveland,  and 
Buffalo.  In  California  there  were  stations  at  San 
Francisco,  Mare  Island,  Sacramento,  and  Santa 
Barbara.  On  Cape  Cod,  MCC,  operated  by  the  Mar- 
coni Wireless  Telegraph  Company,  was  in  opera- 
tion not  much  later,  and  the  Navy  had  a  station 
at  Key  West.  These  are  only  a  few  among  many 
deserving  mention,  and  no  doubt  many  of  the  old 
operators  will  feel  aggrieved  and  write  me,  "What 
about  Cape  Race,  and  this,  that,  and  the  other 
station?  "  Radio  was  still  in  its  days  of  struggle,  and 
there  was  little  money,  and  a  vast  amount  of  ignor- 
ance, but  it  was  moving,  here  was  no  doubt  of  that. 

Microphone  Miscellany 


A  Free  Bath.  Advertisement  of  a  manufacturer 
of  condensers:  "By-Pass  Condensers  do  a  double 
job.  They  filter  the  fluctuating  B  battery  current. 
They  provide  a  free  bath  for  the  radio  frequency 
currents.  .  .  ."  Yes;  it  was  printed  that  way 
in  at  least  two  magazines. 

Imagination  Is  a  Great  Thing.  Ingenious  blurb 
issued  by  the  press  agent  of  a  chain  of  stations: 

Those  who  are  not  fortunate  enough  to  be  able  to 
spend  their  summers  by  the  sea  at  least  can  have 
some  compensation  Sunday  nights  during  July  and 
August  when  programs  are  broadcast  direct  from  the 
Steel  Pier  at  Atlantic  City. 

The  refreshing  sounds  of  the  surf  beating  on  the 
shore  will  be  relayed  from  the  famous  resort  and 
sent  out  to  keep  the  radio  fan  cool  in  sultry  weather, 
a  specially  constructed  microphone  being  housed 
under  the  furthermost  point  of  the  Steel  Pier,  di- 
rectly over  the  surf,  for  that  purpose. 


Shrewd  Comment  on  Things  As  They  Are 


773 


i 

C^-l 

I 


1      o  Suspended 
•_*.  microphones 
(Uncased) 


microphone- 


Conductor 


Side  Vj 


Suspended  microphones 


Close 
microphone 


FIG.    4 

The  microphone  set-up  used  by  the  American  Telephone  and  Telegraph  Company  in  picking  up  the  Goldman 

Band,  playing  at  the  stadium  on  the  campus  of  New  York  University.     The  WEAF  engineers  have  done  the 

work  of  installation  and  the  programs  are  broadcast  through  a.  chain  of  stations 


Thus  refrigeration  by  radio  has  become  a  reality. 
Can  one  take  one's  baths  that  way  also?  Will  not 
a  microphone  suspended  in  some  lobster  palace, 
carrying  the  sounds  of  mastication  and  imbibition 
to  the  radio  audience,  satisfy  the  hunger  of  the 
listeners  and  save  heads  of  families  several  kopeks 
a  day?  Must  we  breathe,  when  an  air-compressor 
can  be  set  up  to  make  respiratory  sounds  for 
everybody  with  a  radio  set?  Go  to  it,  boys,  the 
idea  has  endless  possibilities. 

The  Age  of  Radio  News  Items.  A  woman,  by 
the  expedient  of  not  telling  her  age,  need  never 
grow  old;  and  as  long  as  journalists  know  little 
about  radio,  the  same  holds  true  for  news  items  in 
this  field.  In  the  last  few  days  the  papers  have 
carried  headlines  telling  about  two  German  ships 
which  communicated  by  radio  telephony  over  a 
few  hundred  miles;  the  phonograph  recording  of 
radio  signals  in  Vienna,  and  the  use  by  the  New 
York  Edison  Company  of  a  radio  storm  detector 
operated  by  static  disturbances.  The  last  named 
is  about  12  years  old,  and  the  other  two  achieve- 
ments are  not  so  much  younger. 

Radio  and  Audio.  An  unfortunate  man  was  trap- 
ped in  a  Kentucky  cave.  It  was  found  possible  to 
run  an  electric  light  close  to  him,  but  later  the  crevice 
through  which  the  wires  had  been  passed  closed 
up,  and  communication  with  the  entombed  man 
ceased.  Two  newspaper  men  connected  a  two- 
stage  audio  amplifier  to  the  wires  leading  into  the 
cave,  and,  hearing  a  noise  in  the  head-phones  con- 
nected to  the  output  of  the  amplifier,  concluded 
that  the  captive  was  still  alive.  Although  the  ex- 


perimen-t  had  absolutely  nothing  to  do  with  radio, 
all  the  newspapers  referred  to  the  two  reporters  as 
"radio  experts." 

Again,  an  announcement  appears  in  the  papers 
that  during  an  outdoor  opera  production  at  the  Polo 
Grounds,  a  "radio  amplification  system"  is  to  be 
installed.  A  public  address  system  is  also  radio, 
therefore;  in  short,  everything  that  comes  out  of  a 
horn  is  radio. 

Further  Stirring  Up  of  a  Delicate  Subject.  This  is 
written  on  a  night  in  July  when  static  is  in  evi- 
dence, and  I  have  to  take  it  just  like  any  common 
listener.  What  we  should  get  into  our  heads  is 
that  static  does  not  accompany  heat,  but  changes 
in  temperature,  and  in  general,  those  conditions  that 
make  for  lightning  storms.  During  the  extreme 
hot  wave  starting  June  ist,  and  lasting  about  a 
week,  there  was  little  static  on  medium  distance 
stations,  and  none  on  locals,  although  temperatures 
far  up  in  the  nineties  were  the  rule.  It  is  when  hot 
changes  to  cool,  or  when  the  humidity  is  very  high, 
that  the  static  tends  to  become  rambunctious. 

Statement  of  a  manufacturer  of  audio  trans- 
formers: "Static  is  diminished  in  proportion  to  the 
amount  of  volume  which  a  radio  set  delivers,  ex- 
perts agree."  This  is  awarded  the  grand  prize  for 
the  month's  most  brilliant  climax  in  the*  dissemina- 
tion of  radio  piffle — a  fresh  pretzel,  four  and  a  half 
inches  inside  diameter,  stuffed  with  highest  quality 
garlic.  An  unspecified  reward  is  also  offered  to 
every  "radio  expert"  who  will  come  forward  and 
publicly  "agree"  with  the  above  contribution  to 
technology. 


Notes  on  Chemical  Plate  Supply 

Units 

An  Unusually  Complete  Discussion  of  the  Problems  of 
Building  and  Operating  a  Chemical  Unit  for  B  Supply 

BY  JAMES  MILLEN 

rHIS  article  should  be  of  great  interest  to  ihe  large  number  of  constructors  who  are 
experimenting  with  the  chemical  rectifier,  for  it  is  full  of  the  experimental  "dope" 
which  delights  the  heart  of  every  genuine  experimenter.  While  ihe  author  has  given  his 
attention  especially  to  the  problems  presented  by  the  rectifier  he  described,  the  general 
remarks  on  the  chemical  type  of  rectifier  have  never  been  presented  so  completely  and 
helpfully  before.  The  Chemical  Plate  Supply  Unit,  described  in  RADIO  BROADCAST 
for  June,  has  been  assembled  by  many  readers  and  their  many  letters  have  echoed  their 
great  satisfaction  -with  the  device.  That  unit  can  he  built  for  about  $20  and  will  furnish 
as  much  as  120  volts  and  plenty  of  current  for  any  receiver. — THE  EDITOR 


THE  question  of  rectifying  but, half 
of  the  a.  c.  cycle  by  means  of  a  single 
rectifier  cell  instead  of  the  four  cells 
for  double  wave  rectification  as 
described  in  connection  with  the  Chemical 
Plate  Supply  Unit  in  June,  1925,  RADIO 
BROADCAST,  has  arisen.  It  can  be  done,  but 
the  complete  outfit  is,  in  the  end,  larger  and 
more  expensive.  Furthermore,  such  an  ar- 
rangement will  only  be  satisfactory  when 
used  with  radio  sets  drawing  little  plate  cur- 
rent, the  upper  current  limit  being  about  ten 
milliamperes.  The  increased  cost  and  size 
of  a  single-cell  plate  supply  over  the  four- 
cell  outfit  described  in  the  June  RADIO 
BROADCAST  is  due  to  the  very  much  larger 
and  more  effective  filter  system  required.  In 
an  experimental  model,  a  total  capacity  of 
thirty  microfarads  and  an  inductance  of 
thirty  henries  was  used.  There  was  no  hum 
present  in  a  set  drawing  twelve  milliamperes 
and  perhaps  a  slightly  smaller  filter  might 


have  been  satisfactory.  The  point  to  be 
emphasized  is  that  the  filter  used  in  connec- 
tion with  the  four-cell  outfit  is  not  effective 
enough  for  use  with  a  single-cell  outfit.  Much 
more  capacity  must  be  added.  For  the  benefit 
of  those  who  might  care  to  experiment  with 
a  one-cell  device,  the  hook-up  is  given  in  Fig. 
i.  The  rectifier  cell  is  identical  with  those 
used  in  the  four-cell  B  battery  substitute. 

Another  limitation  to  the  use  of  a  single- 
cell  outfit  is  that  the  voltage  supplied  by  it 
must  not  exceed  about  seventy  volts.  To 
increase  the  voltage,  it  is  necessary  to  connect 
two  cells  in  series  as  shown  in  Fig.  2.  The 
double  rectification  four-jar  unit  will  supply 
an  output  d.  c.  voltage  as  high  as  1 10  or  120 
volts.  The  reason  for  the  higher  voltage  being 
permissible  in  the  four  cell  outfit  is  because 
the  total  a.  c.  voltage  is  always  divided  be- 
tween two  cells.  Consequently,  the  voltage 
per  cell  never  exceeds  the  practical  maximum 
limit  of  about  eighty  volts  a.  c. 


FIG.     IA 

An  experimental  model  of  a  current-tap  with  single  wave  rectification 


Notes  on  Chemical  Plate  Supply  Units 


775 


INCREASING    THE    VOLTAGE    OF    THE    CHEMICAL 
PLATE    SUPPLY    UNIT 

A  NUMBER  of  the  readers  of  this  maga- 
*»•  zine  who  are  using  resistance-coupled 
amplifiers  have  inquired  of  the  writer  about 
ways  in  which  to  increase  the  voltage  supplied 
by  the  original  unit  from  no  to  150.  A 
current-tap  supplying  150  volts  will  require 
eight  rectifier  cells  in  place  of  four.  Fig.  3 
shows  how  they  are  connected.  The  number 
of  turns  on  the  transformer  secondary  (using 
NH3  H2  PO4  electrolyte  in  rectifier  jars)  must 
be  increased  from  1035  to  1300.  The  con- 
stiuction  of  the  cells,  the  choke,  and,  in  fact, 
all  other  parts  remains  the  same. 

It  is  also  possible  to  raise  the  output  d.  c. 
voltage  by  adding  capacity  to  the  line  side 
of  the  filter.  As  filter  condensers  are  rather 
expensive,  it  will  be  found  more  practical  in 
this  case  to  employ  the  method  of  voltage 
raising  suggested  above. 

THE    AMMONIUM    BORATE    RECTIFIER 

IT  HAS  been  found  that,  when  a  cell  with 
ammonium  borate  electrolyte  stands  idle 
for  a  long  period  (a  month  or  so),  its  internal 
resistance  increases  to  such  an  extent  that 
the  output  voltage  of  the  current-tap,  when 
again  put  into  use,  is  somewhat  lower  than 
originally.  This  voltage  will  increase  to 
normal  again  after  about  three  hours'  use. 
This  phenomenon  does  not  occur  when  an 
electrolyte  of  primary  ammonium  phosphate  is 
used.  Should  the  experimenter  have  any  diffi- 
culty in  securing  CP  primary  ammonium  phos- 
phate, CP  secondary  ammonium  phosphate 
may  be  used  with  equally  satisfactory  results. 

IMPROVING   THE    CATHODE 

A  NOTHER  peculiarity  of  the  rectifier 
•**•  cell  using  an  electrolyte  of  ammonium 
borate  which  can  not  be  observed  when  one 
uses  the  ammonium  phosphate  electrolyte 

Rectifier 


is  the  deterioration  of  the  lead  electrode, 
whose  surface  is  oxidized  to  lead  peroxide 
which  crumbles  off  and  falls  to  the  bottom  of 
the  jar.  This  action  is  readily  prevented  by 
removing  the  lead  electrodes  after  they  have 
been  used  for  five  or  ten  hours,  and  hammering 
them.  An  old  flat-iron  makes  an  excellent 
anvil  for  this  purpose.  The  round  shape  of 
the  electrodes  may  be  retained  by  rotating 
them  on  the  anvil  during  the  hammering 
process,  or,  they  may  be  hammered  until 
they  have  a  square  or  slightly  rectangular 
cross-section.  The  reason  for  this  treatment 
is  to  force  the  first  coating  of  lead  peroxide 
into  the  surface  of  the  metal  and  thus  form  a 
protective  coating  for  the  rest  of  the  elec- 
trode. No  more  trouble  will  then  be  had  with 
lead  electrodes  which  have  been  treated  in 
this  manner.  As  previously  stated,  this 
deterioration  takes  place  only  when  the  am- 
monium borate  electrolyte  is  used. 

Of  course  this  process  is  not  necessary  as  it 
will  take  a  long  time  for  an  untreated  lead 
rod  to  be  completely  changed  to  lead  peroxide 
powder.  The  real  objection  to  the  lead 
peroxide  is  that  it  settles  to  the  bottom  of 
the  jar  and  may,  in  time,  short  circuit  the 
two  electrodes. 

THE    ANODES 

THERE  is  no  satisfactory  substitute  for  CP 
aluminum  rod  for  use  as  the  anode.  If 
one  cares  to  take  a  chance  with  commercial 
rod,  he  may,  or  may  not,  secure  a  good  set  of 
electrodes  the  first  time.  The  chances  are 
that  he  will  not.  Some  parts  of  a  commercial 
rod  are  almost  (but  seldom)  quite  as  good  as 
the  CP  rod,  while  other  parts  of  the  same  rod 
are  worthless  as  rectifier  anodes.  The  strange 
part  about  the  commercial  rod  is  that  it  ap- 
pears to  improve  slightly  with  use,  but  it  is 
rather  poor  during  the  first  few  hours.  The 
CP  rod  is  good  from  the  very  start. 

30  Henries 


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Primary 
800  Turns 

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FIG.    I 

The  fundamental  circuit  diagram  of  the  current-tap  illustrated  in  Fig.  i  A.     The  transformer  is  not,  from 

an  engineering  point  of  view,  essential,  but  is  required  by  the  fire  underwriters,  as  if  it  were  not  used  and 

the  connection  to  the  i  lo-volt  line  reversed,  a  short  circuit  of  the  i  lo-volt  line  would  result 


776 


Radio  Broadcast 


30  Henries 


110V.A.C. 

Primary 
800  Turns 


O12CH 


Transformer  Core  I  Sq.  in. 
Sectional  Area 

FIG.    2  ~W 

When  higher  voltages  than  those  supplied  by  the  single  cell  outfit  illustrated  in  Fig.  lA  are  required, 
two  cells  must  be  connected  in  series  and  the  number  of  transformer  secondary  turns  increased 


Some  tests  were  made  using  aluminum  weld- 
ing rods  (aluminum  alloyed  with  about  2 
per  cent,  copper)  as  anodes.  These  electrodes 
were  very  much  more  resistant  to  corrosion 
when  used  with  high  currents,  as  in  rectifiers 
for  battery  charging,  but  the  cells  employing 
them  had  quite  a  leakage  current  when  used 
in  a  current-tap  device.  Leakage  current 
was  determined  from  oscillograms.  The  os- 
cillogram  of  the  output  of  an  unfiltered 
chemical  rectifier  with  CP  aluminum  elec- 
rodes  never  dropped  down  to  the  zero  line,  due, 
probably,  to  the  filter  action  of  the  high  in- 
herent electrostatic  capacity  of  the  rectifiers. 
As  would  be  expected,  the  d.c.-a.c.  current 
ratio  was  very  much  better  for  the  CP  rods. 
Welding  rods  are  certainly  not  suitable 
for  a  current-tap  device. 

Sheet  aluminum  electrodes  have  been  used 
quite  successfully  but  are  not  as  satisfactory 
as  CP  rods.  A  sheet  of  supposedly  CP 
aluminum  obtained  from  a  large  chemical 
supply  house  was  found  to  be  impure  and 
unsatisfactory  at  one  end  and  not  a  bit  better 
than  the  purer  grade  of  commercial  sheet. 

In  any  event,  poor  electrodes  are  easily 
detected  when  put  into  use.  Either  the  cur- 
rent-tap will  not  work  properly  (There  is  a 
"hum,"  or  the  d.c.  voltage  is  much  lower  than 
theoretically  calculated)  or,  if  it  appears  to 


work  properly  at  first,  the  cells  will  soon 
over-heat  and  then  the  unit  will  cease  perform- 
ing. The  presence  of  a  very  soft  white 
cloudy  precipitate  which  seemingly  floats 
around  in  the  bottom  third  of  the  jar  gener- 
ally denotes  the  presence  of  impurities.  I 
have  never  seen  it  in  cells  using  distilled 
water  and  made  from  good  materials.  It 
nearly  always  occurs  when  tap  water  has  been 
used  in  place  of  distilled  water  in  preparing 


The  Plate  Supply  Unit  described  in  the  June  issue  may  be  altered 
so  as  to  supply    150   volts  to  resistance-coupled    amplifiers 


FIG.   4 

A    pair    of    electrodes,    showing    the 
rubber  insulating  sleeve  on  the  anode 

the  electrolyte.  As  a  rule,  however,  it  does 
not  cause  much  trouble,  although  the  cells 
containing  such  a  precipitate  seem  to  run 
warmer  than  others.  Always  use  distilled 
water. 

This   precipitate   should   not   be  confused 
with    the    solid    crystalline    deposits    which 
are  due  to  an  excess  of  ammonium  phosphate 
or  borate  in  the  electrolyte.     Such  precipitates 
are  not  injurious  in  any  way 
whatsoever.     It   might  be 
well   again  to  warn  against 
impurities  in  the  electrolyte. 
Even  the  smallest  quantity 
of  ordinary  table  salt  (NaCl) 
will  seriously  interfere  with 
proper  rectifier  action. 

Properly  operating  cells 
made  from  good  materials 
are  easily  detected  by  ob- 
serving them  when  operat- 
ing in  a  dark  room.  The 
aluminum  electrodes  will 


Notes  on  Chemical  Plate  Supply  Units 


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FIG.    5 
Details  of  the  shell  type  power  transformer  core 

glow  with  a  pale  yellowish  green  light.     Cells 
which  do  not  so  glow  should  be  replaced. 

Overheating  of  the  cells  is  generally  due, 
as  previously  mentioned,  to  the  use  of  impure 
materials,  but  may  also  be  caused  by  trying 
to  get  too  high  a  voltage  out  of  the  unit  (by 
increasing  transformer  secondary  turns,  etc.), 
The  maximum  filtered  d.  c.  voltage  from  a. 
four-jar  unit  must  not  be  over  120  volts  and 
should  preferably  be  between  90  and  100  volts. 
The  greatest  allowable  temperature  of  the 
electrolyte  is  about  50°  centigrade  or  122°  F. 
As  this  is  above  body  temperature,  a  properly 
operating  cell  may  at  times  feel  rather  warm 
when  touched. 

ANODE    INSULATION 

AN  IMPROVEMENT  over  the  collodion 
film  insulation  for  the  anode  as  de- 
scribed in  the  RADIO  BROADCAST  for  June  is  a 
film  made  from  modified  aeroplane  wing 
"dope."  This  "dope"  is  prepared  by  de- 
solving  some  celluloid  (secured  from  old 
photographic  negatives,  etc.)  in  acetone.  Ace- 
tone is  the  solvent  used  by  motion  picture 
operators  for  joining  film  together.  It  may 
also  be  obtained  from  any  druggist.  Very 
little  is  required. 

A  still  better  insulation  is  obtained  by  the 
use  of  short  lengths  of  live  rubber  tubing. 
The  inside  of  the  tube,  which  should  be  some- 
what smaller  than  the  aluminum  rod  is  coated 
with  vaseline  and  is  then  stretched  over  the 
upper  end  of  the  aluminum  rod  and  pulled 
down  to  the  proper  position.  This  insulation 
is,  of  course,  put  on  before  the  rod  is  fitted 


into  the  stopper.  .  The  length  of  the  electrode 
exposed  to  the  solution  should  be  one  and 
one-half  inches  and  the  rubber  insulation 
should  extend  below  the  surface  of  the  liquid. 

ADDITIONAL   TRANSFORMER    AND   CHOKE    DATA: 
THE    CORES 

HP  HE  transformer  and  choke  coils  are  cut 
1  from  silicon  steel  sheets  of  from  ten  to 
seventeen  mils  (thousandths  of  an  inch)  in 
thickness.  Fig.  5  gives  the  shape  and  di- 
mensions of  the  toy  transformer  core  rec- 
ommended in  the  previous  article.  As  it  is 
almost  impossible  to  cut  such  shape  lamina- 
tions by  hand,  the  type  of  core  illustrated 
in  Fig.  6  may  be  used.  The  sectional  area 
of  the  magnetic  circuit  of  the  manufactured 
core  (Fig.  5)  is  .75  square  inches,  but  if  a 
home-cut  core  of  the  type  illustrated  in  Fig. 
6  is  used,  the  sectional  area  had  better  be  one 
square  inch.  Each  lamination  should  be 
given  a  thin  coat  of  shellac  arid  allowed  to 
dry  before  assembling. 

TRANSFORMER   WINDINGS 

FOR  either  type  of  core,  the  transformer 
primary  winding  consists  of  800  turns  of 
No.  26  enameled  copper  wire  and  the  second- 
ary of  either  1030  or  1 125  turns  of  either  No. 
28  or  No.  30  wire. 

The  primary  is  layer  wound  on  a  square 
cardboard  tube  which  fits  snugly  on  the  core. 
Use  thin,  waxed  or  glassine  paper  between 
layers.  Several  layers  of  heavy  paper  or 
Empire  cloth  are  wrapped  over  the  primary 


FIRST  LAYER  AND  SECOND  LAYER  AND 

ALL  ODD  LAYERS  ALL  EVEN  LAYERS 

FIG.  6 

If  the  power  transformer  core  is  to  be  hand-cut,  the 
type  of  core  illustrated  in  this  Figure  is  recom- 
mended 


778 


Radio  Broadcast 


before  starting  the  secondary.  Care  should 
be  used  in  bringing  out  the  lead  wires  to  see 
that  they  are  well  insulated  from  each  other 
and  from  the  core. 

The  choke  coil  core  requires  no  air  gap, 
as,  due  to  the  low  current  used  in  current- 
tap  devices,  the  core  is  operated  well  below 
the  saturation  point. 

It  might  interest  some  to  know  that  at 
this  time  the  particular  current-tap  shown  in 
the  illustrations  in  the  June  RADIO  BROAD- 
CAST is  still  being  used  every  day  and  as  yet, 
after  six  months,  has  required  absolutely  no 
attention,  not  even  the  addition  of  distilled 
water. 

The  oscillogram  shown  in  Fig.  7  was  made 
of  this  same  current-tap  under  the  exceed- 
ingly heavy  load  of  60  milliamperes.  Fig.  8 
shows  the  effect  of  insufficient  capacity  in  the 
filter  system. 

WHAT    AN    OSCILLOGRAM    IS 

AN  OSCILLOGRAM  is  a  visual  indication 
of  how  current  or  voltage,  as  the  case 
may  be,  varies  with  time. 

A  variation  in  the  output  of  a  double-wave 
rectifier,  which  is  operated  from  60  cycle  a.  c. 
would  be  very  noticeable  in  the  loud  speaker  of 
a  receiving  set,  in  the  form  of  a  6o-cycle 
"hum."  This  "hum"  would  usually  be  in- 
dicated by  the  periodic  variations  in  current 
as  indicated  by  the  curved  line  in  Fig.  11. 
The  time  interval  between  peaks  is  -fa  of 
a  second.  Current  at  any  instant  is  pro- 
portional to  the  vertical  distance  of  a  point  on 
the  curve  from  the  straight  horizontal  "zero" 
line. 

In  Fig.  7,  the  current  is  steady,  as  shown  by 
the  upper  horizontal  straight  line,  and  as  a 
result,  no  hum  is  heard  in  the  "loud  speaker." 

The  allowable  periodic  variations  in  the  cur- 
rent is  about  i  per  cent,  although  some  people 
do  not  object  to  a  "hum"  caused  by  as  much 
as  5  per  cent,  current  variation.  This  latter 
condition  is  approximated  by  Fig.  8. 

Oscillograms,  such  as  those  accompanying 
this  article,  are  made  by  a  photographic  proc- 
ess in  which  a  fine  beam  of  light  is  caused  to 
move  up  and  down  with  variations  in  current 
on  a  strip  of  photographic  paper  mounted  on  a 
revolving  drum,  thus  tracing  the  white  lines 
shown  in  Figs.  7,  8,  and  1 1. 

The  neat  and  compact  arrangement  of  the 
rectifier  jars  shown  in  Fig.  9  was  made  by  one 
of  the  readers  of  RADIO  BROADCAST,  Mr.  F. 
A.  Dede.  The  jars  and  electrodes  are  similar 
to  those  used  in  the  original  outfit.  The 
straps  around  the  top  and  bottom  are  made  of 


zinc,  although  any  other  material  would  have 
been  just  as  suitable.  The  top  is  sealed  with 
battery  wax,  which  may  be  obtained  from 
any  storage  battery  service  station.  Four 
Fahnestock  automobile  ignition  cable  clips 
are  used  on  the  four  electrodes  to  which  con- 
nections are  made.  All  wires  between  cells 
as  well  as  the  tops  of  the  four  electrodes  not 
fitted  with  clips  are  concealed  in  the  wax. 
Two  small  glass  vent  tubes  are  provided  for 
each  cell,  one  for  filling  and  the  other  for  the 
escape  of  air  in  the  jar  while  it  is  being  filled. 
The  electrodes  were  held  in  place  by  means 
of  cardboard  discs  fitted  into  the  necks  of  the 
salt-mouth  bottles.  The  hot  wax  was  then 
poured  over  and  allowed  to  harden.  The 
cardboard  discs  also  preventing  the  melted 
wax  from  running  down  into  the  bottles.  The 
Fahnestock  clips  facilitate  the  easy  removal  of 
the  rectifier  as  a  unit  from  the  current-tap 
cabinet  for  occasional  inspection  and  addi- 
tion of  distilled  water. 

While  describing  unit  arrangements  of  cells, 
it  is  well  to  emphasize  the  fact  that  the  jars 
must  not  be  completely  sealed  in  a  small  box 
or  other  such  container  which  would  seriously 
reduce  the  heat  radiation  and  thus  cause  the 
temperature  of  the  electrolyte  to  rise.  The 
arrangement  shown  in  Fig.  9  does  not  violate 
this  rule  as  air  can  circulate  around  each 
cell. 

The  majority  of  commercial  B  battery  sub- 
stitutes, especially  those  employing  vacuum 
tubes  as  the  rectifiying  units,  show  an  unfor- 
tunate drop  in  voltage  with  increased  loads. 
Thus  the  voltage  supplied  to  a  single-tube 
set  by  such  a  device  might  be  nearly  one- 
hundred  volts  whereas  the  voltage  supplied 
by  the  same  unit  to  a  superheterodyne  with- 
out proper  C  batteries  might  be  but  thirty  or 
forty  volts. 

Such  trouble  is  not  had  with  the  Chemical 
Plate  Supply  Unit  as  the  drop  in  voltage  due 
to  increasing  load  is  slight  owing  to  the  rela- 
tively low  internal  resistance  of  the  chemical 
rectifiers.  This  phenomenon  is  illustrated 
by  the  curves  in  Fig.  9.  Curve  A  is  for  a 
commercial  B  battery  substitute  using  a 
uv2oiA.tube,  while  curve  B  is  for  the  Chemi- 
cal Plate  Supply  Unit  described  in  the  June 
RADIO  BROADCAST. 

THE  EXPERIENCE  OF  A  READER 

MR.    R.    E.    GRAVES,    in   the    following 
letter,    gives    some    information    which 
may  be  of  value  to  those  who  have  built  the 
Chemical    Plate  Supply   Unit   described   by 
the  author. 


Notes  on  Chemical  Plate  Supply  Units 


779 


Referring  to  the  B  battery  substitute  described 
in  your  June  issue,  I  have  recently  made  one,  and 
the  results  it  gives  are  excellent.     However,  for 
your  information  and  to  help  you  in  answering 
inquiries,  I  will  give  you  the  following  information, 
Instead  of  following  out  your  transformer  speci- 
fications, I  had  the  Thordarson  Elec.  Mfg.  Co. 
of  this  city,  make  the  transformer  which  steps 
1 10  volt  a.  c.  up  to  150  volts,  but  I  found  that 
with  this  high  voltage  the  aluminum  will  not 
hold  its  film  and  it  was  necessary  to  put  a  re- 
sistance in  the  input  to  give  me  an  output  of 
about  125  volts. 

The  transformer  has  an  extra  winding  for  a  6- 
volt  automobile  lamp. 

These    people    carry    a    jo-henry    choke    coil 
wound  with  large  wire  which  I  found  very  good. 
Instead   of   purchasing   salt   mouth   bottles    I 
bought  four  B  battery  chargers  at  the  ten  cent 
store.     These  come  complete  with  rubber  screw 
tops  and  the  lead  and  aluminum  rods. 
Below  is  the  cost  of  the  special  parts: 
Thordarson  Transformer     .     .      .     $6.00 

Choke 4.00 

Rectifier  jars  complete         .     .     .     .    25  each 

Primary  ammonium  phosphate  can  be  purchased 

In  Chicago  from  Schaar  &  Co.  556  W.  Jackson  Blvd. 

The  transformers   specified    in  your   June   issue 

are  not  to  be  found  in  Chicago. 

The  price  of  salt  mouth  jars  and  accessories  if 
purchased  here  would  put  the  rectifier  cost  to  about 
$3.00  as  compared  to  fi.oo  if  bought  at  the  ten 
cent  store  while  the  primary  ammonium  phosphate 
can  be  purchased  at  only  two  places  in  Chicago  and' 


FIG.    7 

Even  when  an  exceed- 
ingly heavy  current 
(50  milliamperes)  is 
taken  from  the  Chem- 
ical Plate  Supply  Unit 
described  in  the  June 
RADIO  BROADCAST,  the 
output  is  very  well 
filtered  as  shown  by 
the  smooth  oscillo- 
gram  of  the  output 


FIG.   8 

This  oscillogram  is  a 
visual  indication  of  what 
occurs  when  the  con- 
structor attempts  to 
economize  in  the  con- 
struction of  the  filter  by 
using  a  total  electro- 
static capacity  of  4 
microfarads  rather  than 
eight.  The  load  here  is 
adjusted  for  a  current  of 
60  milliamperes 


FIG.   9 

A  compact  way  in  which  the  four  rectifier 
cells  may  be  combined  into  a  single  unit 

1  might  add  that  the  amount  of  phosphate  as 
specified  in  your  article  did  not  make  a  fully  satur- 
ated solution. 

I  am  very  pleased  with  the  outfit,  although  from 
the  start  I  knew  that  it  would  work  or  it  would  not 
have  been  published  in  RADIO  BROADCAST. 
Respectfully  yours, 

R.  E.  GRAVES. 
Chicago,  Illinois. 

WHERE      SUPPLIES      FOR     THE      UNIT     CAN      BE 
SECURED 

AS  MANY  of  our  readers  have  written  that 
they  have  been  unable  to  secure  the 
chemical  supplies  listed  in  the  June  RADIO 
BROADCAST  at  reasonable  prices,  we  have  in- 
vestigated the  situation  further  and  found 
that  the  material  may  be  obtained  from  the 
following  concerns: 

Empire  Laboratory  and  Supply  Co.,  Inc., 

218  East  37th  Street,  New  York 
Strahs  Aluminum  Co., 

48  Franklin  Street,  New  York 
Aluminum   rods  only 

The  prices  for  the  complete  set  of  parts  as 
listed  below  range  from  a  high  value  of  $2.61 
to  a  low  value  of  $1.75: 


y8o 


Radio  Broadcast 


FIG.     I  I 

Due  to  the  high  inherent  electrostatic  capacity,  the 
unfiltered  current  supplied  by  a  double-wave  electro- 
lytic rectifier  does  not  drop  to  zero 


4  3  oz.  salt  mouth  bottles. 

4  No.  6  rubber  stoppers 

i  2-ft.  length  iV  diameter  CP  Aluminum  rod. 

I  2-ft.  length  iV  diameter  lead  rod. 

i  6-inch  length  glass  tube  for  vent 

i  oz.  primary  or  secondary  ammonium  phosphate. 

Any  of  the  individual  items  may  also  be  obtained 

separately. 

As  the  price  of  lead  rods  still  seems  most 
unreasonable  when  obtained  from  chemical 
supply  houses,  the  cathodes  should  be  made 
from  sheet  lead  which  is  readily  obtainable 
at  a  very  much  lower  price  from  your  local 
plumber.  Such  lead  should  be  cleaned  with 
sand-paper  before  using. 


45 


40 


35 


30 


Chemical  Plate  Supply  Unit 
After  500  Hours'  use. 


Commercial  B  -  eliminator 
Employing  one  V  U  201-A. 

Commercial  B  -  eliminator 
Employing  two  V  U  201-As. 


Ohmic  Resistance  aC 
Rectifier  &  Filter 


All  Tubes  New 
Curves  Very  Much 
Poorer  for  Old  Tubes 


25 


20 


15 


10 


50 


90 
D.C.VOuTS 

FIG.    10 

These  curves  show  how  the  voltage  supplied  by   several 
different  types  of  current-taps,  drops  as  the  load  is  increased 


Single-Control  For  Your  Present 

Receiver 

A  Geared  Condenser  Unit  Which  Can  Be  Applied  to  the  Roberts 
Knockout,  the  Phonograph  Receiver,  the  Browning-Drake, 
the  Super-Heterodyne,  and  Many  Other  Popular  Receivers 

BY  ALLAN  T.  HANSCOM 

?HpHE  methods  so  far  brought  out  for  single-control  of  radio  receivers  have  all 
1  been  those  which  used  a  group  of  condensers  all  tuned  by  one  dial — which 
simultaneously  varied  the  frequency  (wavelength)  of  each  circuit  in  which  the 
various  condensers  were  connected.  This  method,  due  to  Hogan,  is  quite  work- 
able, but  it  allows  nothing  for  variations  in  the  individual  coils  in  the  circuits.  The 
unit  described  here  may  be  applied  to  any  circuit  in  which  two  coils  of  approximately 
the  same  value  are  tuned  by  condensers.  Due  to  the  ingenious  cam  arrangement 
on  the  first  condenser  of  the  single-control  unit  described  in  this  paper,  any  irregular- 
ity in  the  first  secondary  coil  of  the  circuit  to  which  this  unit  is  applied,  may  be 
compensated  for  by  a  preliminary  adjustment  of  the  first  condenser.  This  is  not  a 
how-to-make-it  article  but  the  elements  of  the  device  are  standard.  The 
mechanical  features  of  the  complete  unit  could  only  be  made  by  a  constructor  with 
more  than  ordinary  mechanical  ability  and  a  good  machine  shop  at  his  command. 
The  single-control  element  should  prove  so  helpful  to  the  home-assembler  that  we 
feel  no  hesitancy  in  publishing  this  article,  although  the  unit  cannot  be  made,  but 
must  be  bought. — THE  EDITOR 


THE  necessity  for  selectivity  in  radio 
receivers  is  becoming  more  evident  as 
more    stations    take    the    air,     and 
radio  listeners  will  probably  welcome 
a  more  simple  method  of  tuning  which  will 
not  in  any  sense  detract  from  the  efficiency  of 
their  receivers. 

The  ultimate  in  receiver  design  should  have 
one  station  selector,  one  control  for  volume 
and  one  control  to  turn  the  set  on  and  off. 
The  old  single-circuit  receiver  approached 
these  requirements  but  did  so  at  the  expense  of 
the  selectivity  which  is  an  urgent  requirement 
nowadays.  The  single-circuit  set  radiates 
most  distressingly  and  so  it  has  been  gradually 
superseded  by  sensitive  receivers  of  more 
desirable  types. 

Practically  the  only  possible  way  to  secure 
selectivity  in  the  receivers  in  general  use  to- 
day, is  by  means  of  two  or  more  tuned  circuits. 
Now,  since  each  circuit  must  be  tuned 
separately,  we  have  two  or  three  tuning 
controls  on  most  of  the  receivers  now  popular. 
It  was  early  apparent  that  this  difficulty  could 
be  overcome,  provided  the  two  or  more  tuned 
circuits  could  be  controlled  simultaneously 
with  a  single  knob  or  dial.  To  do  this  suc- 
cessfully required  laboratory  methods  which 
can  not  be  adopted  by  the  average  constructor, 
and — more  important — do  not  go  hand  in 


hand  with  quantity  production  in  manufactur- 
ing. 

With  these  ideas  in  mind,  the  writer  has 
developed  a  method  which  permits  of  the 
simultaneous  tuning  of  two  circuits,  and  at  the 
same  time  makes  possible  a  slight  variation 
of  one  circuit  without  disturbing  the  other, 
in  order  to  compensate  for  slight  variations  in 
the  two. 

This  makes  the  reduction  of  one  tuning 
control  possible,  and  in  the  case  of  the  standard 
neutrodyne  or  other  tuned  radio  frequency  re- 
ceivers, the  number  of  controls  is  thus  reduced 
from  three  to  two.  In  sets  using  a  single  stage 
of  tuned  radio  frequency,  such  as  the  RADIO 
BROADCAST  three-  and  four-tube  Knock- 
outs, the  Browning-Drake,  etc.,  as  well  as 
most  super-heterodynes,  the  number  of  tuning 
controls  is  reduced  to  one,  and  the  simplicity 
of  the  tuning  is  a  pleasant  surprise  to  a  person 
operating  one  of  these  sets  for  the  first  time. 

The  essential  feature  of  this  assembly  con- 
sists of  two  Remler  condensers  mounted  in 
such  a  manner  that  their  capacities  may  be 
simultaneously  varied  with  a  single  Marco 
dial  reading  through  180  degrees.  In  addition, 
one  of  the  condensers  may  be  varied  through 
20  degrees  of  dial  movement  without  disturb- 
ing the  setting  of  the  other  condenser.  At  the 
mid-point  of  the  vernier  setting,  the  two  con- 


782 


Radio  Broadcast 


.0005 


t  .00025 


40         60         80        100        120 
DIAL  SETTING 

FIG.    2 

The  curve  in  the  center  shows  how  the  capacity  for 
one  condenser  will  increase  or  decrease  with  respect 
to  the  dial  readings.  The  dotted  curves,  A  and  B, 
depict  how  the  values  vary  as  the  vernier  is  adjusted 
between  maximum  and  minimum  points 


RADIO  BROADCAST  Photograph 

The  gearing  arrangement  of  the  two  Remler  Con- 
densers is  clearly  shown  in  this  rear-view  photo- 
graph. The  dial  shaft  gear  can  be  seen  in  the  center 
between  the  two  pieces  of  bus-bar.  The  cam 
controlling  the  vernier  motion  of  the  right  hand 
condenser  is  not  included  in  the  photograph 


densers  have  equal  capacity  at  any  dial  reading 
and  the  vernier  gives  a  plus  or  minus  variation 
sufficient  to  cover  the  ordinary  inequalities  of 
tuning.  This  arrangement  has  the  following 
important  advantages: 

1.  Dial  may  be  logged. 

2.  Straight  line  wavelength  curve  of  the  con- 

denser spreads  stations  evenly  on  the  dial. 

3.  Vernier  variation  at  any  setting  is  propor- 

tional to  wavelength. 

4.  The  main  dial  and   vernier  not  electrically 

connected,  thereby  avoiding  hand  capacity 
effects. 

5-.     Condensers  each  have  separate  terminals  and 
may  be  connected  independently. 


-     Gnd 


FIG.    3 

The  application  of  the  single-control  feature  described  in  this  article,  may  readily 
be  applied  to  the  Roberts  Knockout  receiver,  a  diagram  of  which  appears  above 


Single-Control  for  Your  Present  Receiver 


783 


Remove 
Jumper; 


.  Grid 
fTubel 


Tube  2 


+  A'  -A; 

REAR  VIEW  SHOWING  CONNECTIONS 

FIG.    4B 

If  the  idea  suggested  in  Fig.  4A.  is  tried  out,  the  fan 
can  follow  the  connections  marked  in  this  diagram 
for  the  two  condensers 


6.     Side-by-side  mounting  saves  space  and  con- 
forms to  layout  of  set. 

The  applications  of  the  single  control 
capacity  element  to  various  circuits  will  be 
taken  up  at  length,  and  a  description  of  the 
device  is  first  presented  in  order  that  the 
details  may  be  made  clear.  From  the  photo- 
graphs we  see  that  the  two  condensers  are 
mounted  so  that  the  gears  will  engage  with 
each  other  and  consequently  the  rotation  of 
one  condenser  will  affect  the  other  one  simul- 
taneously. The  dial  shaft  gear  is  shown  in 
Fig.  i.  This  drives  the  left  hand  condenser 
which  in  turn  is  geared  to  the  one  on  the  right. 
The  cam  which  controls  the  vernier  motion  of 
the  condenser  on  the  right  can  be  seen  in  the 
photograph  of  the  back  of  panel  view  of  the 
four-tube  RADIO  BROADCAST  phonograph  re- 
ceiver. The  condenser  is  mounted  so  that  it 
may  be  raised  or  lowered  by  the  motion  of  the 
cam  and  yet  the  position  of  the  gear  which  en- 
gages with  the  left  hand  condenser  remains 


fixed.  If  the  main  dial  shaft  is  rotated,  both 
condensers  will  be  affected,  but  the  motion  of 
the  shaft  containing  the  cam  will  vary  the  cap- 
acity of  the  right  hand  condenser  but  will  in  no 
way  affect  the  one  on  the  left.  Fig.  2  represents 
the  curve  of  one  condenser  and  if  the  vernier 
is  set  at  the  mid-point,  the  other  condenser 
will  have  an  identical  curve.  In  Fig.  2,  A  rep- 
resents the  curve  of  the  right  hand  condenser 
with  maximum  adjustment  of  the  vernier, 
while  B  in  Fig.  2  represents  the  minimum  ad- 
justment. 

In  the  application  of  this  device  to  a  receiv- 
ing set,  it  is  necessary  to  bear  in  mind  certain 


FIG.    4A 

The  Browning-Drake  and  Silver  circuits,  which  are 
almost  identical,  have  two  variable  condenser  con- 
trols, and  it  is  possible  to  cut  this  down  to  one  con- 
trol by  employing  the  system  outlined  by  Mr. 
Hanscom 

fundamentals  which  apply  to  tuned  circuits. 
For  a  given  frequency  (wavelength),  a  certain 
value  of  C  (electrostatic  capacity)  must  have 
a  definite  value  of  inductance,  the  frequency, 
(wavelength)  being  a  function  of  the 
product  of  these  two.  If  we  increase  the 


NOTE:  6 u>  Rheostat  Between  +  A  -  B  Post  and 
+  A  of  all  Tubes 

FIG.    5 

The  single  control  unit  may  readily  be  applied  to  the  RADIO  BROADCAST  Phonograph  Receiver.     In  this  way 

only  one  control  will  be  necessary  for  the  condenser  shown  across  the  secondary  tuning  coil  and  that  across 

the  secondary  of  the  r.  f.  transformer.     The  connections  in  Fig.  48  apply  in  this  instance  also. 


784 


Radio  Broadcast 


inductance  we  must  decrease  the  capacity  in 
order  to  tune  to  the  same  frequency  (wave- 
length) value.  It  should  therefore  be  ap- 
parent that,  if  two  circuits  are  going  to  be 
tuned  with  this  capacity  element,  the  induc- 
tance of  each  circuit  should  be  approximately 
equal.  When  these  inductances  are  equal,  it 
will  be  found  that  the  adjustment  of  the 
vernier  is  unnecessary  throughout  the  entire 
frequency  (wavelength)  range,  but  the 
vernier  makes  possible  the  necessary  correction 
for  differences  in  inductances  and  distributed 
capacity  of  the  circuits. 

APPLICATION  TO  THE   ROBERTS   KNOCKOUT 
RECEIVER 

FIGURE  3  represents  the  Roberts  circuit, 
which  consists  of  a  stage  of  tuned,  neu- 
tralized, radio  frequency  amplification  and  a 
tuned  detector  with  tickler  feed-back  together 
with  a  stage  of  reflexed  audio  amplification.  As 
applied  to  this  circuit,  this  single-control  ca- 
pacity element  should  be  connected  so  that  the 
condenser  which  is  controlled  by  the  vernier 
will  tune  the  first  radio  frequency  stage.  It 
is  suggested  that  a  small  fixed  condenser  be 
connected  between  the  antenna  and  the  tap 
on  the  first  tuning  coil,  particularly  if  the  set 
is  used  with  a  long  antenna.  If  the  single- 
control  device  is  applied  to  a  Roberts  Knock- 
out set  which  is  already  in  use,  it  is  well  to 
make  the  necessary  adjustment  in  order  that 
the  two  dials  will  read  alike  before  the  element 
is  installed.  If  you  find,  for  instance,  that  the 
antenna  tuning  dial  is  always  lower  than  the 
second  dial,  this  should  be  corrected  by  insert- 
ing a  small  fixed  condenser,  from  .0001  to 
.00025  mfd.  in  the  antenna  lead.  If  the 
dial  still  tunes  low,  this  may  be  corrected  by 
removing  a  few  turns  from  the  antenna  tuning 
coil.  This  is  necessary  only  in  extreme  cases, 
and  if  the  dials  can  be  made  to  read  within 
four  or  five  points  of  each  other,  you  may  in- 
stall the  single-control  without  any  change  in 
the  set.  In  most  Knockout,  receivers  this 
change  is  brought  about  by  means  of  the  an- 
tenna switch,  which  compensates  for  antennas 
of  various  lengths. 

It  is  suggested  that  the  plates  of  the  two 
condensers  which  are  nearest  each  other,  should 
be  connected  to  the  filament  end  of  the  re- 
spective coils  to  avoid  coupling  effects.  The 
single-control  capacity  element  has  a  flexible 
connection  between  these  two  sets  of  plates, 
and  in  the  case  of  a  positive  return  to  the  de- 
tector filament,  this  connection  may  be  re- 
moved and  the  wiring  then  made  in  the  usual 
manner  care  being  taken  to  supply  flexible 


leads  to  the  left  hand  condenser.  The  single- 
control  capacity  element  is  mounted  on  the 
rear  of  a  panel  by  means  of  three  screws  and 
nuts,  and  the  template  gives  the  location  of  all 
the  necessary  holes. 

SINGLE-CONTROL    FOR    THE     BROWNING     DRAKE 
RECEIVER 

THE  Browning-Drake  receiver  (completely 
described  in  RADIO  BROADCAST  for 
December,  1924),  is  deservedly  one  of  the  most 
popular  circuits  in  use  to-day,  and  it  has 
earned  this  popularity  through  the  excellent 
results  which  are  obtained  with  it.  This  cir- 
cuit differs  from  the  Roberts  only  in  the 
method  of  neutralization  and  in  its  lack  of 
reflexing.  Some  of  the  kits  which  are  on  the 
market  for  its  construction  are  provided  with 
a  .0005  mfd.  variable  condenser  for  the  first 
stage  and  a  .00035  mfd.  condenser  for  the  sec- 
ond stage.  This  results  in  the  left  hand  dial 
reading  lower  than  the  right,  particularly  on 
the  lower  frequencies  (longer  wavelengths). 
In  most  cases  however,  the  single-control  ca- 
pacity element  can  be  installed  in  the  regular 
manner.  If  it  is  found  that  the  vernier  must 
be  turned  to  the  extreme  position  so  that  the 
first  condenser  has  more  capacity  than  the  sec- 
ond for  any  given  setting,  this  may  be  cor- 
rected by  lengthening  the  antenna  or  by 
connecting  it  to  a  tap  on  the  coil  a  few  turns 
nearer  the  grid  end  of  the  winding.  If  it  is 
found  that  the  vernier  works  best  in  the  other 
extreme,  where  the  first  condenser  has  less 
capacity  than  the  second,  it  can  be  corrected 
in  one  of  three  ways.  One  can  shorten  the 
antenna;  connect  a  fixed  condenser  .0001  to 
.00025  mfd.  capacity  between  the  antenna  and 
the  tap  on  the  first  coil,  or  move  the  tap  on 
first  coil  nearer  the  filament  end.  It  will  be 
found  that  the  original  inequalities  can  be 
taken  care  of  with  the  vernier,  but  bear  in 
mind  that  the  proper  adjustment  of  these  in- 
ductance and  capacity  values  will  make  the 
vernier  almost  superfluous,  leaving  only  one, 
frequency  (wavelength)  control. 

SINGLE-CONTROL  FOR  THE    SUPER-HETERODYNE 

THE  super-heterodyne  circuit  consists  es- 
sentially of  two  tuning  controls,  one  to  ad- 
just the  loop  or  antenna  coupler  and  the  other 
to  vary  the  oscillator  frequency,  the  latter 
to  produce  the  proper  beat  for  the  intermediate 
amplifier.  The  single-control  capacity  ele- 
ment lends  itself  admirably  to  this  type  of 
circuit,  because  the  proper  value  of  loop  induc- 
tance may  be  obtained  by  using  the  proper 
size  and  number  of  turns  on  the  loop.  To  do 


Single-Control  for  Your  Present  Receiver 


785 


RADIO  BROADCAST  Photograph 
FIG.    6 

This  illustration  depicts  the  second  harmonic  super-heterodyne  described  by  Mr.  Hanscom  in  the  Novem- 
ber,  1924,  RADIO  BROADCAST.     The  single-control  capacity  element  has  been  found  ideal  under  actual 

working  conditions,  in  this  type  of  receiver 


this,  it  is  only  necessary  to  vary  the  loop  turns 
until  a  point  is  reached  where  the  desired 
frequency  (wavelength)  range  can  be  covered 
with  the  least  possible  variation  of  the  vernier. 
The  super-heterodyne  is  different  from  the 
tuned  radio  frequency  set  in  the  respect  that 
it  depends  for  its  proper  action  on  the  constant 
difference  of  frequency  between  the  two  tuned 
circuits.  It  is,  therefore,  only  necessary  to 
provide  the  same  tuning  range  in  each  of  the 
circuits  and  the  vernier  can  be  set  so  that  one 
condenser  will  always  provide  more  capacity 
than  the  other,  thereby  providing  the  desired 
beat  frequency.  It  is  possible  to  calibrate  a 
super-heterodyne  for  either  the  upper  or  lower 
setting  of  the  oscillator.  Below  is  given  the 
dial  settings  of  a  two-dial  super-heterodyne 
with  a  given  loop. 


1 199  kilocycles  (250  meters)  .  . 
999  kilocycles  (300  meters) .  . 
833  kilocycles  (360  meters) .  . 
750  kilocycles  (400  meters)  .  . 
600  kilocycles  (500  meters)  .  . 


LOOP 

..8 
..  16 

..27 


OSCILLATOR 

"I 

24 

382 
48 

73 


This  shows  a  total  dial  movement  between 
the  limits  specified,  of  43  points  for  the  loop 
tuning  and  61  for  the  oscillator.  To  correct 
this,  three  turns  were  removed  from  the  loop 
after  which  the  readings  were  as  follows: 


1 199  kilocycles  (250  meters) 
999  kilocycles  (300  meters) 
833  kilocycles  (360  meters) 
750  kilocycles  (400  meters) 
600  kilocycles  (500  meters)  , 


LOOP      OSCILLATOR 


•39 
.50 

•75 


24 


73 


It  will  be  noticed  that  there  still  exists  a  con- 
siderable difference  in  the  dial  readings,  but  the 
total  scale  movement  for  each  condenser  is 
the  same,  and  the  vernier  adjustment  may  be 
set  at  a  position  which  will  give  uniform  results 
throughout  the  entire  scale.  On  practically  all 
super-heterodynes  the  oscillator  tunes  sharper 
than  the  loop,  and  the  single-control  capacity 
element  should  be  connected  so  that  the  right 
hand  condenser  will  tune  the  oscillator,  leaving 
the  vernier  for  the  fine  tuning  adjustment  on 
the  loop. 

SINGLE-CONTROL    FOR    THE    RADIO    BROADCAST 
PHONOGRAPH    RECEIVER 

THE  popular  Roberts  Knockout  circuit  is 
the  basis  of  the  set  which  has  been  fea- 
tured by  this  magazine  as  being  the  best  re- 
ceiver for  the  money  that  can  be  built  by  the 
home  constructor.  By  utilizing  the  capacity 
element,  a  phonograph  receiver  can  be  con- 
structed as  a  true  one-control  set.  A  simple 
receiver,  made  to  specifications  supplied  by 
RADIO  BROADCAST  and  incorporating  this  de- 


786 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 


FIG.    7 

A  variation  of  the  RADIO  BROADCAST  Phonograph  Receiver  employing  the  single  control  capacity  element. 
The  cam  which  controls  the  vernier  action  of  the  condenser  on  the  right,  is  shown  beneath  that  condenser 
and  is  partly  hidden  by  the  detector  tube  socket.  A  Claratuna  unit  is  employed  for  the  r.  f.  coupling. 
This  unit  comprises  a  radio  frequency  transformer  to  which  is  tightly  coupled  the  tickler  coil.  Regeneration 
control  is  accomplished  by  a  variable  resistance  incorporated  within  the  Claratuna 


vice,  is  shown  in  the  photograph.  There  are 
four  tubes,  consisting  of  one  stage  of  tuned 
radio  frequency,  detector,  and  two  stages  of 
audio.  The  front  panel  measures  only  1 2§  by 
8  inches  and  the  sub-base  measures  5  by  10 
inches.  This  is  supported  to  the  front  panel 
by  means  of  Benjamin  brackets.  The  binding 
posts  are  mounted  along  the  rear  of  the  sub- 
panel  and  the  Thordarson  audio  transformers 
are  fastened  beneath  it.  The  Sickles  antenna 
coupler  contains  a  four-point  switch  to  com- 
pensate for  various  lengths  of  antennas,  and 
the  coupling  element  between  the  radio  fre- 
quency tube  and  the  detector  is  a  coil  with 
fixed  tickler,  known  as  the  Claratuna,  mounted 
beneath  the  tuning  element.  The  regenera- 
tion is  controlled  by  a  carbon  resistance  shunt- 
ing the  tickler  coil.  This  gives  a  smooth 
even  control  without  the  necessity  of  moving 
coils,  the  space  required  for  the  radio  fre- 
quency unit  being  reduced  to  minimum.  This 
receiver  gives  excellent  volume,  distance  and 


selectivity,  and  the  simplicity  of  tuning  is  a 
revelation. 

Fig.  5  shows  the  wiring  diagram  of  this 
phonograph  receiver.  The  negative  filaments 
of  all  tubes  are  connected  together  and  to  the 
ground.  Use  of  the  complete  antenna  coupler 
and  the  coupler  between  the  first  and  second 
tubes,  makes  the  wiring  of  the  set  a  simple 
matter.  The  audio  transformers  are  mounted 
with  the  cores  in  line  and  not  at  right  angles, 
and  the  metal  shieldings  of  the  transformers 
are  connected  together  and  to  the  ground.  A 
Chelten  Midget  condenser  is  used  for  neutral- 
izing and  its  position  is  not  critical.  It  is 
located  on  the  sub  panel  at  the  end  nearest  the 
antenna  coupler,  which  is  clearly  shown  in  the 
photograph. 

EDITOR'S  NOTE 

*T*HE   opinion  is   prevalent   among  some  broad- 
*•  cast  listeners  that  the  use  of  straight  line  fre- 
quency, or  wavelength,  condensers  will  relieve  most 
of  the  present  difficulties  in  tuning.     There  are  cer- 


The  New  Size  of  "Radio  Broadcast"  for  November 


787 


tain  things  that  these  condensers  will  do,  and  natur- 
ally others  that  they  cannot  do.  What  the  phrase, 
straight  line  condenser  means  is  that  a  given  num- 
ber of  degrees  on  the  condenser  dial  represents  a 
certain  number  of  kilocycles,  or  wavelengths,  re- 
gardless of  which  end  of  the  scale  is  being  used. 
This  is  of  distinct  value  at  the  higher  frequen- 
cies (lower  wavelengths)  and  will  enable  the  user 


to  distinguish  many  of  the  stations  now  in  class  A. 
Condensers  of  this  type  will  not  eliminate  the 
heterodyning  of  two  stations  that  stray  from  their 
assigned  frequencies;  they  will  not  separate  two 
stations  that  are  on  the  same  frequency,  as  many  in 
Class  A  are,  and  they  will  not  eliminate  any  of  the 
tuning  troubles  that  arise  at  the  transmitting  sta- 
tion. 


FIG.    8 


RADIO  BROADCAST  Photograph 


A  front-of-panel  photograph  of  the  receiver  shown  in  the  preceding  diagram.  The  apparatus  on  the  panel, 
reading  from  left  to  right,  include  a  voltmeter,  the  single-control  dial,  rheostat,  and  (bottom  row)  vernier 
control  knob,  resistance  control  and  phone  jack.  A  Hoyt  filament  voltmeter  is  included,  and  the  use  of  fila- 
ment meters  is  recommended  in  all  receivers.  Operating  tubes  above  their  rated  voltage  very  materially  de- 
creases the  life  of  a  tube 


The  New  Size  of  "Radio  Broad- 
cast" for  November 


WITH    the  November  number,  RADIO 
BROADCAST  will  be  three  and  a  half 
years  old.      During  its  career  the  pub- 
lishers have  tried,  through  every  means 
in  their  power,  to  produce  a  magazine  which,  from 
the  reader's  point  of  view,  should  take  the  leading 
place  in  the  radio  field.     Judging  from  letters  which 
from  time  to  time  trickled  into  our  office — letters  of 
gratitude  from  our  readers,  backed  up  by  healthy 
circulation  figures,  it  appears  that  we  have  not  failed 
altogether  in  this  respect.     It  has  been  our  constant 
endeavor  to  make  the  word  "quality"  synonymous 


with  both  our  editorial  and  advertising  contents. 
Now,  it  is  not  our  custom  to  celebrate  a  birthday 
every  six  months,  but  nevertheless  it  happens  that 
in  November,  we  shall  signalize  the  occasion  by 
introducing  RADIO  BROADCAST  in  a  new  form.  The 
public  support  and  approval  of  the  magazine  has 
been  so  unqualified  that  its  physical  size  and  ap- 
pearance must  be  improved  in  addition  to  the 
improvements  which  from  time  to  time  we  are  con- 
stantly effecting  in  the  editorial  pages.  November 
fifteenth,  1925,  will  be  our  red  letter  day  then,  and 
we  hope  that  our  readers  will,  by  their  universal 


Radio  Broadcast 


approval,  help  us  to  celebrate  the  occasion  when 
the  new  RADIO  BROADCAST  appears.  We  contend, 
and  that  is  only  because  our  readers  contend  too, 
that  our  contents  are  exactly  what  the  readers 
desire,  and  it  is  for  this  reason  that  every  one  of 
the  popular  features  of  the  present  magazine  will 
be  retained  in  the  larger  size. 

Our  constructional  articles,  as  most  of  our  readers 
know,  are  not  printed  merely  because  they  provide 
another  way  to  build  a  receiver,  or  worse  still — 
because  they  afford  another  outlet  for  parts.  The 
criterion  by  which  we  judge  our  construction 
articles  is:  first,  are  they  authoritative?  second,  are 
they  helpful?  third,  do  they  provide  information  on 
construction  which  is  not  available  elsewhere? 
fourth,  are  they  complete?  These  aims,  we  think 
we  have  attained.  Our  readers  tell  us  we  have  done 
so,  and  after  all  is  said  and  done,  it  is  the  reader  who 
is  in  the  most  advantageous  position  to  judge. 

The  authors  who  write  for  RADIO  BROADCAST 
are  men  who  know  what  they  are  writing.  They 
are  in  the  best  positions  to  obtain  information 
.  .  .  shall  we  call  it  dope?  .  .  .  which  is 
most  interesting  to  our  readers.  Their  names  are 
veritably  ones  to  conjure  with  in  the  vast  field  of 
radio.  Ever  since  the  first  number  of  the  magazine 
was  placed  on  sale.it  has  contained,  month  by  month, 
that  engrossing  article  "The  March  of  Radio" 
specially  prepared  by  Professor  J.  H.  Morecroft, 
of  Columbia  University.  This  editorial  record  of 
radio  progress,  which  nearly  everyone  of  importance 
in  the  radio  industry  reads,  will  naturally  continue 
in  the  new  RADIO  BROADCAST.  Mr.  Morecroft 
occupies  a  high  position  in  radio;  a  Professor  of 
Electrical  Engineering  at  Columbia,  a  Past  Presi- 
dent of  the  Institute  of  Radio  Engineers,  and 
author  of  a  standard  text  on  radio,  The  Principles  of 
Radio  Communication,  Mr.  Morecroft  has  a  weight 
of  knowledge  and  authority  behind  his  editorial 
comment,  which  is  nationally  quoted  every  month. 

Then  there  is  Carl  Dreher,  one  of  the  most 
able  broadcasting  engineers  in  the  country.  He 
tells  us  monthly  what  the  broadcasters  are  doing 
and  how  they  are  doing  it,  and  in  his  inimitable 
fashion — which  has  won  him  recognition  in  other 
fields  than  his  chosen  one — relates  the  opinions  and 
comments  that  are  prevalent,  about  the  latest  de- 
velopments in  the  radio  field. 

The  broadcast  listener  is  represented  in  that 
popular  feature  "The  Listener's  Point  of  View," 
which  has,  again  judging  from  correspondence 
alone,  a  very  large  following.  We  aim  to  cater  to 
the  fan  of  every  stage,  from  the  veriest  of  embryos 
to  the  most  technical  of  them.  For  the  former, 
Zeh  Bouck  conducts  a  department  calculated  to 
interest  the  beginner  but  written  interestingly 


enough  to  be  followed  by  the  more  technical  man. 
He  sets  out  to  guide  the  beginner  sympathetically 
and  carefully  through  the  early  and  confusing  mazes 
of  radio,  and  in  this  he  succeeds  admirably. 

And  as  regards  advertising.  The  high  standard 
of  admissibility  to  our  columns  is  the  reader's  as- 
surance that  everything  advertised  is  exactly  as  it 
is  described.  Our  policy  is  first  to  be  sure  and  then 
go  ahead.  For  that  reason  the  star  of  approval,  ap- 
pearing on  all  the  advertising  pages,  was  established 
many  months  ago.  It  is  a  way  of  telling  our 
readers  that  the  apparatus  advertised  has  been  given 
a  thorough  test  by  the  laboratory  and  was  found 
satisfactory.  The  man  not  behind  the  editorial 
scenes  cannot  realize  what  an  effort  it  has  to  main- 
tain strictly  this  advertising  policy  under  all  con- 
ditions, but  we  feel  sure  that  we  have  not  failed  in 
this  respect.  Our  laboratory,  we  might  add,  is, 
in  technical  equipment  and  staff,  second  to  none 
in  the  country. 

In  addition  to  its  new  size,  which,  by  the  way,  will 
be  eight  ancl  five  eighths  by  ten  and  a  half  inches,  the 
magazine  is  to  be  printed  on  a  more  expensive 
paper,  a  heavy  white  paper,  which  will  greatly  en- 
hance the  appearance  of  the  illustrations  and  make 
the  diagrams  even  clearer  than  is  possible  at 
present. 

A    NEW   COVER 

A  PRIZE  of  $500  was  offered  for  the  best  cover 
•**  design  for  the  new  magazine,  and  one  has 
been  chosen  by  the  judges,  which  we  think  our  read- 
ers will  agree  is  particularly  pleasing  and  attractive. 
It  was  painted  by  Mr.  Fred  J.  Edgars  of  Tenafly, 
New  Jersey,  and  was  picked  from  innumerable 
others  submitted  from  cities  all  over  the  United 
States. 

-In  the  November  RADIO  BROADCAST  we  are 
planning  some  features  of  particular  interest. 
Robert  H.  Marriott,  the  first  president  of  the 
Institute  of  Radio  Engineers,  has  written  a  fascinat- 
ing story  of  radio  development,  which  will  be  run 
serially.  Keith  Henney  will  continue  his  engross- 
ing articles  on  "What  Is  to  Become  of  the  Home 
Constructor,"  and  there  will  be  more  phonograph 
radio  receivers  for  those  interested,  in  future  issues. 
There  will  be  an  article  on  a  high  quality  audio 
amplifier  which  operates  direct  from  the  a.  c. 
mains;  latest  information  on  short  wave  work, 
gleaned  from  the  operators  of  RADIO  BROADCAST 
station  2  GY;  plans  for  the  third  International  RADIO 
BROADCAST  Tests,  and  a  host  of  important  con- 
structional material  exclusively  written  for  this 
magazine. 

In  November,  RADIO  BROADCAST  will  greet  you, 
bigger  and,  we  are  sure,  better  than  ever. 


High  Radio  Adventure— On  Short 

Waves 

The  Romance  of  Code  Communication  Far  Below  the  Broadcast  Channels- 
Something  About  RADIO  BROADCAST'S  Experimental  Transmitting  Station  2  GY 

BY   KEITH    HENNEY 

Director,  RADIO  BROADCAST'S  Laboratory 

FOR  some  months,  the  RADIO  BROADCAST  Laboratory  has  been  hard  at  work — among 
its  many  other  activities — in  installing  a  high  frequency  (short  wave),  low  powered 
transmitting  station  to  operate  in  the  communication  bands  assigned  to  amateur  experi- 
menting. The  field  of  high  frequency  (short  wave)  transmission  offers  one  of  the  most 
fascinating  fields  for  experiment  in  all  radio— as  any  amateur  operator  will  tell  you  with 
a  sympathetic  optical  twinkle.  We  lime  no  desire  to  encroach  on  the  field  already  well 
covered  by  our  excellent  contemporary,  QST,  and  on  the  work  we  expect  to  do  will  be 
along  somewhat  different  lines — although  none  the  less  fascinating.  In  an  early  num- 
ber of  the  magazine  we  shall  have  an  announcement  of  very  great  interest  about  this  work 
and  our  station,  2  GY.  A  goodly  number  of  advanced  broadcast  listeners,  if  we  are  any 
judge,  are  becoming  more  and  more  interested  in  what  is  being  done  on  other  communi- 
cation bands  than  the  broadcasting  and  this  article  presents  some  of  the  romance  and 
interest  of  that  new  territory  for  radio  exploration. — THE  EDITOR 


A  VENTURING   into  the  radio  region 
below  about    1500    kilocycles    (200 
meters)   is  like  exploring    unknown 
territory.     It    is   impossible   to   say 
what  will  be  found  there  and  no  guess  is  too 
wild.     From  this  frequency,    1499  kilocycles 
to  be  exact,  down  to  goodness-knows  where, 
is  a  region  so  vast  that  all  existing  stations 
could    be    placed    in    it    without    crowding. 
"DX"  exists  there  that   is  undreamed  of  on 
the  longer  waves,  and  it  is  a  territory  into 
which  any  one  may  venture  with  the  certainty 
that  hejvill  discover  interesting  things. 

A  few  years  ago  there  were  no  stations 
working  between  the  amateurs  and  the  com- 
mercial stations  operating  on  1499  and  499.7 
kilocycles  (200  and  600  meters)  respectively. 
Then  the  broadcasters  filled  the  gap  and  grad- 
ually moved  down  toward  the  "hams"  until 
they  are  now  next-door  neighbors.  The  ama- 
teurs, by  government  fiat,  moved  down  into 
the  "no  man's  land,"  employing  frequencies 
of  from  1499  kilocycles  up  (200  meters  down). 
Leon  Deloy  of  Nice,  France,  an  enthusiastic 
amateur  experimenter,  is  one  of  the  individ- 
uals who  really  started  the  short  wave  affair 
going  on  a  grand  scale.  Sporadic  attempts 
had  been  made  to  entice  amateurs  into  this 
territory,  but  when  this  Frenchman  established 
communication  across  the  Atlantic  on  a  fre- 


quency of  about  3000  kilocycles  (100  meters), 
it  was  the  signal  for  great  amateur  activity 
with  the  short  waves  that  had  once  been 
thought  useless.  Now  the  amateurs  not  only 
occupy  a  band  from  1999  to  1499  kilocycles 
(150  to  200  meters),  as  of  old,  but  they  are 
working  in  bands  around  3748,  7496,  14,991, 
59,964,  428,314  kilocycles,  (80,  40,  20,  5,  and 
.7  meters). 

After  Deloy's  success  it  was  not  long  until 
England,  Denmark,  and  The  Netherlands 
amateurs  had  communicated  with  America, 
and  now  there  are  few  civilized  nations  whose 
radio  citizens  are  not  in  personal  touch  with 
other  foreign  countries. 

Below  1499  kilocycles  (200  meters)  is  a 
paradise  in  which  nationality,  language,  and 
distance  are  of  no  importance,  nor  is  a  limited 
pocketbook  an  excuse  for  staying  away  from 
the  most  interesting  region  of  radio.  There  is 
the  record  of  the  Massachusetts  boy  who 
spoke  with  a  fellow  amateur  in  Australia  with 
a  lone  5-volt  receiving  tube  which  cost  him  $3. 

Remember  how  few  stations  you  can  hear 
on  your  broadcast  set  in  the  summer  time  at 
night — and  how  very  few  in  the  day  time. 
Now  suppose  you  sit  in  with  the  operator  of 
2  GY,  the  experimental  transmitting  station 
operated  by  the  RADIO  BROADCAST  Labora- 
tory. 


790 


Radio  Broadcast 


AN    AIR   TOUR 

IT  IS  Saturday,  June  27th.  The  weather  is 
not  particularly  favorable.  At  9:40  A.  M. 
we  tune  the  receiver  to  7496  kilocycles  (40 
meters)  and  at  9:43  we  hear  8  NX,  Walter  J. 
Barnwell,  Lansing,  Michigan,  calling.  We 
converse  with  him  until  after  10  o'clock  when 
he  says  that  our  signals  are  somewhat  wobbly, 
probably  due  to  weather  conditions  between 
the  two  stations.  At  that  time  we  hear9EK, 
the  Burgess  Laboratories  Station  at  Madison, 
Wisconsin,  calling  us,  and  for  the  next  hour  we 
try  to  get  together  without  success.  He  can- 


not hear  us  and  his  signals  waver  too  much  for 
comfortable  reception. 

At  10:58  we  hear  WNP,  S.  S.  Bowdoin, 
Commander  MacMillan's  vessel  sending  a  long 
message  to  i  NT,  Norman  C.  Theobald,  Attle- 
boro,  Massachusetts.  We  copy  all  but  two 
words  and  when  the  Bowdoin  has  difficulty 
in  hearing  i  NT,  we  step  in  and  call  him  our- 
selves. He  is  troubled  with  near-by  inter- 
ference and  finally  replies  2NY  instead  of  2GY 
so  we  are  not  sure  that  we  worked  him  after 
all. 

Not  long  after,  9EK  calls  us  again,  and  after 
some  attempts  to  get  together  he  broadcasts 


FIG.     I 

The  installation  at  2  GY  showing  the  5O-watt  transmitter,  receiver,  wave-meter,  and  batteries  for  plate  voltage. 
Strangely  enough  the  "  5  waiter"  transmitter  operating  entirely  from  batteries  so  far  has  done  about  as  good 
work  as  the  big  transmitter.  The  big  set  requires  130  milliamperes,  the  small  one,  60  mils.  The  receiver 
was  made  by  U.  B.  Ross  of  2  UD,  and  the  wavemeter  constructed  to  Bureau  of  Standards  specifications. 
Although  the  map  doesn't  show  it,  there  are  pins  in  California  and  Dakota 


High  Radio  Adventure  on  Short  Waves 


791 


a  message  to  our  Chief,  Mr.  Frank  N.  Double- 
day.  It  says: 

Greetings  from  Burgess  Organization  via  our  two 
stations.  Hope  to  cooperate  with  Lynch  to  aid 
short  wave  work. 

After  telephoning  the  MacMillian  message  to 
the  Western  Union  for  transmission  to  the 
National  Geographic  Society  at  Washington, 
we  sign  off  for  luncheon.  MacMillan,  at  that 
time,  had  just  left  Nova  Scotia,  and  was  on 
the  second  lap  of  his  polar  journey. 

The  next  day,  Sunday,  June  28,  we  arrived 
at  the  station  at  6:25  A.  M.  to  see  what  was 
going  on  at  that  hour.  It  is  raining  slightly 
and  there  is  some  static.  The  first  thing  we 
hear  is  6cHZ,  Wallace  S.  Wiggins,  Los  Nietos, 
California,  calling  NPO.  Now  NPO,  if  you 
please,  is  Guam  Island,  in  the  Northern  Pacific 
(6000  miles  from  California).  At  6:39  we  hear 
6  BUR,  L.  E.  Smith,  Whittier,  California, 
6ccw,  K.  L.  Riedman,  Long  Beach,  California, 
and  5  UK,  Charles  A.  Freitag,  New  Orleans,  all 
working.  A  minute  or  so  later  we  hear  a 
strange  note  pounding  away  at  great  rate 


working  with  2  MU,  William  Schick,  Brooklyn. 
It  turns  out  to  be  NVE,  U.  S.  S.  Utah,  bound 
from  Panama  for  San  Pedro  and  now  off  the 
coast  of  Lower  California.  He  has  a  load  of 
Annapolis  midshipmen  aboard.  Turning  the 
tuning  dial  a  bit  we  stumble  into  NPM,  Hono- 
lulu, calling  NPN,  Cavite,  Phillippine  Islands. 
At  7:25,  one  hour  after  we  arrived  at  the 
station,  we  hear  QDED,  Ralph  R.  Williams, 
Denver,  Colorado,  calling  NPO.  In  that 
short  space  we  have  heard  three  amateurs 
on  the  Pacific  coast,  we  have  heard  the  U.  S.  S. 
Utah,  a  cool  2500  miles  away,  and  we  have 
heard  Honolulu  approximately  5000  miles 
distant.  Not  bad  for  one  hour!  It  has  been 
broad  daylight  all  the  time — traditionally  bad 
for  radio  work. 

AUSTRALIA — IN    ONE   JUMP! 

CRIDAY,  July  10,  we  come  to  the  station 
*  early  again,  and  at  6:30  A.M.  we  send  a 
message  to  our  home  via  8cz,  Loren  G.  Win- 
dom,  Columbus,  Ohio.  We  also  have  a  mes- 
sage for  Australia,  but  do  not  havethe  nerve  to 
transmit  it  to  this  amateur  in  Ohio,  only  800 


FIG.    2 

A  close-up  of  the  5O-watt  transmitter  and  the  4O-meter  inductance.     The  small  coil  on  the  left  is  a  choke  coil 

to  keep  radio  frequency  voltages  out  of  the  plate  supply,  and  the  mouse  trap  arrangement  on  the  right  is  an 

external  shunt  for  the  kilovolt  meter.     A  double-spaced  Cardwell  condenser  is  used  for  tuning 


792 


Radio  Broadcast 


miles  away.  A  half  hour  later  we  hear  Aus- 
tralian 2 CM  working  8cz.  What  hard  luck! 
Had  we  given  the  message  to  the  Columbus 
operator,  it  would  have  been  in  Australia  in 
one  half  hour,  better  than  any  cable  could  do. 
It  is  9  P.  M.  in  Australia,  5  o'clock  Central 
Standard  Time  in  Ohio,  and  7  o'clock  Eastern 
Daylight  Saving  time  in  Garden  City. 

Honolulu  is  on  again  this  morning  as  well  as 
4RL,  Mario  Castro  Fernandez,  Santurce, 
Porto  Rico. 

The  next  time  we  listen  is  on  July  29  at 
9:20  P.  M.  We  hear  i  CKP,  George  H.  Pinney, 
South  Manchester,  Connecticut,  calling  WNP. 
There  are  thousands  of  amateurs  on  the  fre- 
quency band  of  about  7500  kilocycles  (40 
meters),  all  pounding  away,  working,  or  try- 
ing to  work,  with  each  other.  In  this  bed- 
lam of  signals  it  is  difficult  to  pick  out  any 
particular  one.  We  call  several,  but  not  until 
10:30  do  we  raise  any  one.  It  is  i  BQU,  Alden 
C.  Eldridge,  Buzzards  Bay,  Massachusetts, 
and  we  converse  for  a  half  hour.  At  1 1 152 
we  connect  with  SAMS,  Albert  H.  Buch,  Tawas 
City,  Michigan.  This  is  better  and  we  have 
hopes  of  reaching  out.  Nearly  an  hour  later 
we  communicate  with  9MN,  Robert  C.  Berry, 
Louisville,  Kentucky,  and  then  with  9EK,  our 
frjends  at  the  Burgess  Laboratories,  Madison, 
Wisconsin.  We  feel  pretty  good  over  this 
communication,  for  we  have  been  trying  for 
a  week  to  get  together.  We  give  him  a  mes- 
sage from  Mr.  Doubleday. 

It  is  now  2:00  o'clock  and  our  ears  hurt 
from  wearing  the  phones  so  long  so  we  take  a 
brief  rest.  A  half  hour  later  we  listen  in  again 
and  note  that  many  stations  have  dropped  out 
of  jfhe  hunt  for  "dx."  It  is  possible  that  we 
shall  work  the  coast.  Our  signals  are  answered 
by  gNN  soon.  He  is  Chas.  R.  Jarosewicz  at 
Chicago  and  a  few  minutes  later  we  connect 
with  9AMM,  James  Gwynn,  Shenandoah,  Iowa. 
This  is  "out  west"  from  Garden  City  and  our 
hopes  rise  again. 

Seven  minutes  elapse  before  we  touch  the 
key  again  and  then  we  send  out  a  general  call, 
"CQ."  Who  should  come  back  but  6TX,  R. 
M.  Thacker,  Baldwin  Park,  California!  We 
have  worked  the  coast.  In  twenty  minutes, 
3:24  A.  M.  to  be  exact,  we  click  with  another 
Californian,  6jp,  Oscar  Roediger,  San  Fran- 
cisco. He  says  "FB,"  which  in  amateur 
language  means  "fine  business." 

At  4:25  we  get  a  long  message  from  4ASK, 
Florida,  which  we  try  to  phone  to  the  Waldorf 
Astoria  Hotel.  The  telephone  operator  there 
says  she  is  not  in  the  habit  of  getting  telegrams 
phoned  to  her,  especially  telegrams  that  relate 


to  Florida  real  estate  and  a  young  lady  who 
wants  to  marry  somebody  now  at  the  Waldorf. 
If  it  were  not  illegal  we  would  pass  this  whole 
message  on,  for  it  is  a  good  one,  but  that  is 
impossible,  since  it  would  violate  the  oath  of 
secrecy  assumed  by  every  licensed  operator. 

It  is  now  5  o'clock  and  we  are  hungry,  sleepy, 
and  happy.  We  have  worked  two  stations  in 
California  and  many  at  less  distance. 

THE    RESTRICTED    BRITISH    AMATEUR 

THIS  night's  work  was  so  successful  that 
we  try  it  again,  the  next  evening,  July  30. 
At  10:00  we  get  in  touch  with  9BBj,  James  R. 
Freyermuth,  South  Bend,  Indiana,  with  whom 
we  have  talked  before.  At  10:20  we  work  with 
8000,  Robert  L.  Miller,  Royal  Oak,  Michigan. 
We  now  sweep  all  the  amateur  wavelengths 
for  WNP,  for  we  have  messages  for  MacMillan. 
We  do  not  hear  a  sign  of  him,  but  hear  British 
2  sz  calling  WNP.  In  a  half  hour  this  Britisher 
is  working  WNP  and  telling  him  that  British 
regulations  would  not  permit  him  to  take 
messages.  Stupid  regulations,  we  think. 

It  is  not  a  good  night  and  it  is  after  i  o'clock 
before  we  connect  with  SCCM,  Eugene  Rup- 
precht,  Grand  Rapids,  Michigan.  Not  much 
later  we  click  with  9 CCA, 'Kurt  T.  Johnson, 
Chicago,  Illinois,  and  finally  work  6cpp, 
Bryson  Walker,  Hollywood,  California.  There 
are  many  Californians  on  the  air  and  also 
7 IT,  A.  C.  Dixon,  Jr.,  Stevensville,  Montana. 
Finally  9  EPS,  Lee  Jensen,  Marshalltown, 
Iowa,  tells  us  that  a  bad  thunder  storm  is 
raging  out  his  way  which  explains  why  so  few 
Western  stations  answer  caUs  from  2GY.  NVE, 
the  Utah,  is  on  again  and;?working  a  number 
of  Eastern  stations.  The  Zenith  station,  9XN, 
at  Chicago,  is  working  with  WAP,  S.  S.  Peary, 
the  second  MacMillan  vessel  now  in  the  Arctic. 

The  next  night,  July  31,  we  have  fair  suc- 
cess with  the  transmitter,  working  down  into 
several  Southern  states.  The  receiver,  how- 
ever, is  doing  remarkably  well,  for  we  log  New 
Zealand,  2  KF,  British  2NM,  Chilean  i  EG,  Aus- 
tralian 3  BD,  and  Mexican  i  AA,  and  i  B.  All 
of  this  is  around  40  meters — and  is  only  an 
extremely  small  part  of  the  frequency  spectrum 
above  1490  kilocycles  (below  200  meters). 

The  station  operated  by  the  RADIO 'BROAD- 
CAST Laboratory  came  on  the  air  for  the  first 
time  June  18,  1925,  and  by  August  loth  had 
worked  amateurs  in  twenty  states  and  two 
provinces  of  Canada.  Many  of  these  stations 
were  worked  in  the  daytime,  feats  of  trans- 
mission and  reception  that  would  be  impossible 
on  the  lower  frequencies  (longer  waves).  The 
power  required  to  carry  on  these  communica- 


High  Radio  Adventure  on  Short  Waves 


793 


tions  has  never  exceeded  130  watts,  and  to- 
gether with  that  required  to  heat  the  filament 
of  the  "50  waiter",  totals  less  than  200  watts. 
The  average  electric  iron  requires  400  watts  of 
energy.  The  cost  of  the  apparatus  has  been 
about  $200,  a  sum  required  for  a  good  receiver 
with  its  accessories.  At  the  time  this  is  writ- 
ten, in  August,  very  successful  communication 
is  being  maintained  over  800  miles  with  a 
power  totaling  less  than  40  watts,  and  some 
very  good  results  have  been  secured  with 
ordinary  5-volt  receiving  tubes  used  for  trans- 
mitting purposes. 

THE    B.    C.    L.    IS    MISSING    SOME    GREAT    RADIO 
SPORT 

I MAGINE  sitting  in  your  home  with  appara- 
1  tus  as  inexpensive  as  that  of  2  GY  and  con- 
versing with  fellow  amateurs  in  England,  or 
Australia,  or  South  America!  Is  it  any  won- 
der that  the  17,000  licensed  amateurs  in  this 
country  think  that  broadcast  listeners  have 
something  yet  to  learn  before  they  have 
tapped  the  greatest  source  of  radio  interest? 


The  transmitting  tube  is  somewhat  different 
from  those  with  which  broadcast  listeners  are 
familiar.  Its  filament  requires  10  volts  and 
burns  up  6  amperes!  Its  plate  battery  re- 
quires 25  of  the  ordinary  45  volt  B  batteries, 
1 100  volts  in  all.  The  average  plate  current 
is  100  milliamperes,  or  about  that  required  by 
five  average  broadcast  receivers.  Another 
source  of  high  voltage  that  has  been  used  suc- 
cessfully is  an  "S"  tube  rectifier  also  shown  in 
the  photograph  below. 

The  antenna  system  has  suffered  many  vi- 
cissitudes. It  has  consisted  of  nearly  every- 
thing from  a  brass  gas  pipe  to  a  fan  of  wires 
stretched  between  the  two  Sj-foot  masts. 
At  the  present  time  it  consists  of  a  single  ver- 
tical wire  one-half  wavelength  (65  feet)  long. 
It  is  "fed"  from  the  transmitter,  which  is 
actually  some  distance  away,  by  a  single  wire, 
and  although  one  half  ampere  of  current  flows 
in  the  center  of  the  antenna,  there  is  very  little 
energy  in  the  "driver"  wire  itself.  It  is  a 
curious  arrangement,  but  it  works. 

At  the  time  this  is  written,  plans  are  being 


FIG.    3 

An  S  tube  rectifier  and  filter.     The  S  tubes  are  in  the  cage  together  with  an  Acme  i  joo-volt  transformer 
and  control  resistances.     The  filament  transformer,  behind  the  R.  C.  A.  filter  coils,  is  a  home-made  affair. 
The  filter  condensers  are  high  voltage  paper  condensers 


794 


Radio  Broadcast 


formulated  for  a  complete  investigation  of 
the  phenomena  underlying  transmission  in 
this  very  high  frequency  (short  wavelength), 
region.  It  is  an  adventure  into  unknown 
fields.  There  are  many  amateurs  on  their 
narrow  bands  down  there,  and  a  few  commercial 
and  naval  stations  are  carrying  on  long  dis- 
tance communications  down  there  also.  Mar- 
coni is  experimenting  with  "beam"  transmit- 
ters, and  there  are  a  few  broadcasters  like  KDKA 
and  WGY  who  have  high  frequency  (short  wave) 
channels.  There  are  many  harmonics  from 
broadcast  stations  down  there  too — but  there 
are  thousands  of  wavelengths  and  only  a  few 
to  use  them  at  present. 

This  experimental  work  will  be  carried  out 
jointly  by  the  Laboratory  of  RADIO  BROAD- 
CAST and  the  National  Carbon  Company  and 
will  include  the  building  of  accurate  frequency 
meters,  short  wave  transmitters  and  receivers, 
especially  low-powered,  battery-operated  af- 


fairs. The  interesting  things  that  occur  down 
in  this  strange  territory  are  too  many  for  the 
broadcast  listener  to  pass  up  entirely,  and  from 
time  to  time  the  Laboratory  will  conduct  a 
small  pictorial  and  verbal  tour  for  our  readers. 

For  the  benefit  of  amateur  readers  it  may  be 
said  that  2GY  has  an  operator  on  duty  all  day 
and  night.  The  station  will  be  glad  to  com- 
municate with  any  amateur  on  any  wavelength 
at  any  time,  to  relay,  or  deliver  messages  or 
to  carry  out  tests  that  may  be  mutually  in- 
teresting. The  station  will  be  glad  to  check 
amateurs  on  their  transmitting  frequency 
(wavelength),  and  it  is  possible  that  a  calibrat- 
ing service  will  later  be  organized  so  that 
wavemeters  or  receivers  may  be  accurately 
calibrated  for  amateurs  who  desire  the  service. 

Reports  of  the  reception  of  signals  from 
2  GY  will  be  greatly  appreciated.  They  should 
be  sent  to  the  Director  of  the  Laboratory, 
RADIO  BROADCAST,  Garden  City,  New  York. 


FIG.  4 

The  "shack"  which  houses  2GY.  This  was  built  originally  for  the  International  tests,  but  is  now  used  for 
short  wave  transmission  and  reception  entirely.  In  the  spring  the  arbor  is  covered  with  roses  and  wisteria — 
but  they  have  little  to  do  with  short  waves.  The  insert  shows  some  of  the  effort  which  has  been  expended 
on  the  masts  and  gives  an  idea  of  their  size.  The  cage  has  been  replaced  by  a  single  wire  receiving 
antenna  and  a  variety  of  transmitting  antennas  are  [used,  strung  from  a  rope  between  the  two  85-foot 
masts  1 50  feet  apart.  A  single  wire  40  meters  long,  hung  vertically  downward,  seems  to  be  as  efficient  a 

radiator  as  any  other 


For  the  Radio  Beginner 


ii imiiiiimtiuiiiiiiiiiue 


How  to  Build  a  Simple  One-stage  Amplifier 


rHE  "  Radio  Beginner"  this  month  guides  the  newcomer  through  the  construction 
of  a  simple  one-stage  audio  frequency  amplifier.     The  addition  of  this  amplifier 
will  add  no  little  bit  to  the  possibilities  of  the  crystal  and  single-tube  receiver,  while  its 
construction  will  contribute  a  valuable  fund  of  practical  knowledge  to  the  experience  of 
the  builder. 

In  the  elementary  theoretical  section  of  this  department,  Zeh  Bouck,  its  editor,  dis- 
cusses the  fundamental  action  of  the  vacuum  tube  in  preparation  for  future  articles  on  its 
action  as  a  detector  and  amplifier.  References  for  outside  reading,  treating  on  the 
material  covered  in  "  The  Radio  Beginner"  this  month,  are  suggested  to  the  student 
reader. — THE  EDITOR 


THE  output  of  any  of  the  receivers  we 
have  so  far  described  in  the  past  nurn- 
bersof  this  magazine  (for  July,  August, 
and  September)  can  be  amplified,  or 
made  louder,  by  the  addition  of  a  simple  audio- 
frequency amplifier.     The  conventional  ampli- 
fier consists  of  some  means  of  coupling  the 
output  of  the  radio  receiver  proper  (a  trans- 
former in  this  case)  to  an  extra  tube,  where  it 
is  amplified  by  means  of  the  well-known  relay 
characteristics  of  the  tube. 

The  following  illustrations  and  text  show 
how  such  an  amplifier  can  be  built  up  on  a 
baseboard.  The  task  is  well  within  the  ex- 
perience and  ability  of  the  beginner. 

LIST   OF    PARTS 

THE  electrical  parts  necessary  for  the  con- 
struction   of    the    amplifier    are    photo- 
graphed in  Fig.  i  and  are  as  follows: 


IN    FIG.    I  DESCRIPTION  APPROXIMATE 

PRICE 

No.  i  Standard  socket $  .25 

No.  2  lo-ohm  rheostat  (base 

mounting  type)  ....  .25 
No.  3  6  binding-posts  at  5  cents 

each .30 

No.  4  Audio-frequency  amplifying 

transformer 4.00 


Total 


4.80 


The  parts  designated  are  designed  for  use 
with  a  standard  five-volt  tube.  If  it  is  desired 
to  use  a  three-volt  tube,  which  is  quite  satis- 
factory in  a  single  stage  of  audio  amplification, 
a  thirty-ohm  rheostat  and  a  socket  for  the 
small-based  three-volt  tubes  should  be  substi- 
tuted for  the  parts  listed. 


RADIO  BROADCAST  Photograph 


FIG.    I 

The  electrical  parts  used  in  the  construction  of  the  simple  amplifier 


796 


Radio  Broadcast 


Any  reliable  make  of  amplifying  transformer 
will  give  satisfaction.  A  Jefferson  transformer 
was  employed  in  the  amplifier  photographed 
and  described.  When  purchasing  the  parts 
specify  a  three-to-one  ratio  transformer.  This 
means  that  the  secondary  winding  will  have 
three  times  as  many  turns  of  wire  as  the  pri- 
mary, a  ratio  the  writer  recommends  for  all 
around  amplification.  A  higher  ratio,  how- 
ever (up  to  six  to  one),  will  work  satisfactorily 
in  the  first  stage  of  amplification. 

The  parts  are  mounted  on  a  wood  base  five 
and  one  half  inches  long  by  five  inches  wide, 
according  to  the  layout  suggested  in  Fig.  2. 
The  radio  beginner  will  find  it  worth  while 
to  sandpaper  the  base,  bevel  the  upper  edges 
slightly,  and  to  stain  it  a  dark  green. 

WIRING    IS   THE   NEXT    PROCEDURE 

EPICURE  3  shows  the  wiring  diagram  in 
•  two  forms.  Diagram  A  is  the  standard 
schematic  arrangement  employing  the  usual 
electrical  and  radio  symbols.  Diagram  B  is  a 
pictorial  layout  of  the  same  hookup  which 
may  be  of  greater  significance  to  the  beginner. 
Comparison  of  these  two  sketches  will  explain 
Fig.  3A.  The  reader  should  familiarize  him- 
self with  this  system  of  circuit  diagramming. 

Examination  of  the  transformer  will  show 
four  binding  posts  or  connecting  terminals. 
These  are  generally  grouped  into  two  on  each 


TT 


Audio 
Transformer 


side,  one  group  marked  P  (indicating  the  pri- 
mary winding),  and  the  other  S  (designating 
the  secondary  winding).  One  post  in  group  P 
is  marked  "P,"  which  indicates  that  this 
terminal  should  be  led  through  to  the  plate  of 
the  preceding  tube.  The  remaining  primary 
binding-post  will  be  marked  either  with  a 
plus  sign,  or  "B"  or  "B  Bat,"  meaning  that 
this  post  should  connect  with  the  positive  ter- 
minal of  the  B  battery.  The  secondary  posts 
will  be  marked  "G"  and  "F"  or  "G"  and  a 
minus  sign,  signifying  respective  connections 
to  the  grid  of  the  amplifying  tube  and  the 
minus  side  of  the  filament  lighting  or  A 
battery. 

There  will  be  four  posts  on  the  socket 
marked  "P"  for  plate,  "G"  for  grid,  and  two 
marked  "F"  for  filament.  Occasionally  plus 
and  minus  signs  are  substituted  to  indicate 
the  filament  binding-posts.  The  rheostat  will 
have  two  binding-posts,  unmarked. 

Binding-posts  i,  2,  3,  4,  5  and  6  (Fig.  3)  are 
wired  respectively,  by  the  shortest  possible 
routes,  to  the  "P"  transformer  connection; 
the  "B  Bat"  transformer  terminal;  one  fila- 
ment post  on  the  tube  (plus  if  marked),  to  the 
rheostat  and  "  F"  terminal  on  the  transformer; 
and  to  the  plate  of  the  tube.  Post  6  is  left 
blank. 

The  remaining  post  on  the  rheostat  is  wired 
to  the  second  filament  terminal  on  the  socket. 
The  "G"  post  on  the  transformer  is 
wired  to  the  similarly  marked  socket 
post,  completing  the  wiring  of  the 
amplifier. 

Bare  No.  18  copper  wire,  covered 
by  black  spaghetti,  lends  a  neat  ap- 
pearance to  the  finished  amplifier, 
shown  in  Fig.  4. 


e 


© 


FIG.    2 

Dimensions  of  the  baseboard,  indicat- 
ting  the  positions  of  the  various  parts 


HOW   THE    AMPLIFIER    IS   CONNECTED 

THE  amplifier  we  have  described 
is  designed  for  operation  immedi- 
ately after  a  crystal  or  bulb  detector, 
or  following  the  single  tube  on  the 
RADIO  BROADCAST  One-Tube  Reflex 
receiver  and  similar  sets.  It  should 
not  be  used  as  the  last  step  in  a 
multi-stage  amplifier. 

The  principle  of  connecting  the 
amplifier  is  the  substitution  of  the 
input  posts,  I  and  2,  for  the  telephone 
receivers  in  the  original  circuit  by 
phone  plug  or  binding-posts.  The 
telephone  receivers,  or  loud  speaker, 
are  then  connected  at  the  output 
posts,  5  and  6. 

Fig.  5  shows  how  the  amplifier  is 


The  Principle  of  the  Vacuum  Tube 


797 


connected  to  a  crystal  receiver,  such  as  that 
described  in  "The  Radio  Beginner"  for  July. 

A  suitable  A  battery  for  the  tube  used — 
six  volts  for  a  standard  five- volt  tube  or  4.5 
volts  for  a  three-volt  tube — is  connected  with 
the  positive  terminal  to  post  3  and  negative  to 
post  4.  The  minus  side  of  a  90- volt  B  battery 
(built  up  of  two  45-volt  blocks  or  four  22.5- 
volt  blocks  connected  in  series)  is  connected  to 
the  plus  terminal  of  the  A  battery.  The  posi- 
tive side  of  the  B  battery  is  led  to  post  6,  thus 
completing  all  connections  to  the  amplifier. 

The  connections  to  a  single-tube  receiver  are 
fundamentally  the  same.  The  A  battery  that 
lights  the  detector  tube  can  also  be  used  to 
light  the  amplifying  tube.  In  order  to  sim- 
plify this,  the  same  type  of  tube  should  be  used 
both  in  detector  and  amplifier.  The  battery 
connections  to  the  amplifier,  when  inputted 
from  a  bulb  set,  are  shown  as  heavy  lines  in 
Fig.  6.  If  a  tube  detector  is  employed,  it  is 
probable  that  only  22.5  volts  will  be  used  on 
the  plate  of  that  tube.  A  larger  battery  is 
therefore  added  to  the  detector  B  battery,  to 
supply  plate  current  to  the  amplifier  only. 
If  the  one-tube  reflex  tuner  is  used,  the  plate 
battery  will  probably  already  have  a  voltage 
of  90,  and  the  extra  battery  will  not  be  re- 
quired. 

In  both  crystal  and  bulb  receiving  sets,  the 
amplifier  will  function  best  when  the  primary 
of  the  transformer  is  connected  in  a  certain 
electrical  direction  (when  P  is  connected  to 
the  plate  of  the  preceding  tube  in  the  case  of 
a  bulb  set),  and  the  connections  to  posts  i  and 
2  should  be  reversed  experimentally. 

If  any  reader  of  "The  Radio  Beginner"  is 
in  doubt  as  to  how  his  amplifier  should  be 
connected,  the  technical  editor  will  be  pleased 
to  indicate  the  connections,  if  a  diagram  of  the 
tuner  is  submitted  to  him. 

OPERATION 

THERE  is  no  tuning  or  other  adjustment 
on  the  amplifier.  The  filament  should  be 
turned  up  to  the  proper  brilliancy,  as  evi- 
denced by  satisfactory  operation,  after  which 
the  amplifier  functions  without  attention. 

Used  with  a  bulb  detector  set,  the  one-stage 
amplifier  will  give  fair  loud  speaker  signals. 
In  conjunction  with  the  one-tube  reflex,  the 
signal  strength  will  be  sufficient  for  dancing  in 
a  small  room.  Inputted  from  a  straight  crys- 
tal detector,  volume  will  seldom  be  sufficient 
for  loud  speaker  operation,  but  will  give  com- 
fortable ear  phone  reception  on  signals  that 
are  very  weak  unamplified. 

The  intensity  with  which  distant  stations 


B 

FIG.    3 

How  to  wire  the  amplifier.     Diagrams  A  and  B  are 
identical.     The  reader  should  endeavor  to  fami- 
liarize himself  with  the  schematic  system  (A)  of  cir- 
cuit diagramming 

can  be  heard,  is  increased  slightly  by  the  ad- 
dition of  the  RADIO  BROADCAST  Beginner's 
Amplifier. 

-Jjiiiiiiiiiiiiimiimmiiiiiiimimiiimmiiiiiiimiiimiiiiimiiiiiiimmmiiiiiiimniimiliiiiimiii 

THE  RADIO  PRIMER 

* 

|Fundamental  Ideas  behind  the  Vacuum  Tube| 

"I nmnimillimnmmllimilllllllimmilllNlllllimilllllllimilllllimillllimnillllllllllllirH 

AWE     analyze     matter — going    down 
through  the  molecule,  atom,  and  ion 
— we  arrive  at   what    appears   to   be 
"the  thing  itself,"  the  fundamental  component 
of  all  matter  further  than  which  science  of 
to-day  has  been  unable  to  guess  or  travel. 
All  matter,  from  bricks  to  sewing  machines,  is 
apparently  built  of  these  tiny  philosophical 
bricks  known  as  electrons,  which,  so  evidence 


798 


Radio  Broadcast 


FIG.  4 

The  completed  amplifier.     Black 

spaghetti-covered  wiring   adds  a 

neat  professional  touch 


tells  us,  are  infinitely  small  charges  of  negative 
electricity. 

We  have  reason  to  believe  that  whenever 
electrons  move  in  a  cooperative  motion  away 
from  the  atoms  with  which  they  have  been 
associated,  their  movement  is  evidenced  as  a 
current  of  electricity.  A  haphazard  motion, 
or  a  regular  movement  within  the  atom  does 


RADIO  BROADCAST  Photograph 


not  give  rise  to  this  phenomenon;  for  electrons 
are  continuously  moving  about  in  this  manner 
— in  the  paper  on  which  I  write,  in  the  maga- 
zine which  you  are  reading,  and  in  millions  of 
other  things  that  at  this  moment  exhibit  no 
electrical  characteristics.  This  perpetual  ac- 
tivity of  electrons  within  the  atom  is  stimu- 
lated by  temperature.  The  higher  the  tem- 


FIG.   5 

Connecting  the  amplifier 
to  a  crystal  receiver 


*"  45  V 

The  Filament  of  the  Tube 


799 


To  Phone 

Binding  Posts 

or  Plug  on 

Receiver 


Extra  Battery 

FIG.   6 

The  amplifier  connected  to  a  bulb  set.     The  heavy  wires  indicate  the  battery  connections  to  the  amplifier 


perature,  the  faster  these  unimaginably  tiny 
negative  charges  move.  If  the  temperature 
is  made  sufficiently  high,  the  electrons  will 
move  so  rapidly  that  many  of  them  will  fly 
away  from  the  atom — like  mud  from  a  rapidly 
revolving  wheel. 

For  instance,  the  sun,  hotter  than  anything 
of  which  we  know  on  this  earth,  is  throwing 
off  electrons  in  vast  trillions.  Many  millions 
pass  the  earth  each  second.  Above  ground 
they  "occasionally"  (countless  times  per 
second)  hit  atoms  of  air.  The  collisions  are 
visible  as  light;  we  see  it  thousands  of  miles 
away.  We  call  it  the  aurora  borealis.  The 
reason  the  air  below  is  not  ionized  (which  is 
the  scientific  term  for  this  generation  of  light) 
is  that  the  atoms  of  dense  atmosphere  down 
where  we  breathe  are  too  close  together  and 
would  merely  stop  the  motion  of  the  electrons, 
instantly  lowering  their  velocity  below  the 
high  speed  required  for  ionization. 

If  we  heat  a  wire  sufficiently  by  holding  it 
over  a  candle  flame,  it  will  give  off  electrons. 
If  a  plate,  or  sheet  of  metal,  is  placed  close  to 
the  heated  wire,  and  a  powerful  electrical  posi- 
tive charge  is  applied  to  it  as  shown  in  Fig.  7, 
the  electrons  will  be  attracted  over  to  the 
plate  (remember  that  unlike  charges  attract 
each  other).  In  other  words,  an  electric  cur- 
rent will  flow  through  the  circuit.  The  cur- 
rent will  be  a  very  small  one  due  to  the  ob- 
structing effect  of  the  atoms  of  air.  However, 
if  the  plate  and  hot  wire  are  sealed  up  in  a 
vacuum,  the  electrons  will  have  a  free  path  to 
the  plate  and  comparatively  high  currents  can 
be  passed.  This  is  done  in  the  vacuum  tube 
whose  constructional  principles  are  sketched  in 
Fig.  8. 


It  is  impossible  now  to  heat  the  wire  with 
a  candle  flame,  so  it  is  made  hot  by  passing 
through  it  a  current  of  electricity,  just  as  a 
similar  current  heats  the  filament  of  the  elec- 
tric bulb  in  your  reading  lamp.  This  current 
is  supplied  by  the  filament  or  A  battery.  The 
positive  charge  is  applied  to  the  plate  or 
"anode"  (positive  electrode),  by  the  B  bat- 
tery. 

When  the  filament  is  heated,  generally  to 
fair  brilliance,  electrons  will  be  freed  to  fly 
to  the  plate  through  the  vacuum  and  a  current 
will  pass  through  the  tube. 


Plate  Near.., 
Heated  Win 


.Wire 


Battery 


FIG.  7 

The  principle  of  the  filament  in  a  vacuum  tube. 

The  filament  battery  is  applied  to  heat  the  filament 

to  a  high  temperature 


8oo 


Radio  Broadcast 


UNILATERAL 


CONDUCTIVITY 
TERM    MEANS 


WHAT      THE 


IT  WILL  be  observed,  in  the  arrangement  we 
have  sketched  and  described,  that  electrons 
will  flow  only  from  filament  to  plate,  because 
there  is  no  reversal  of  conditions  to  make  them 
go  backward.  In  other  words,  the  vacuum 
tube  can  pass  electricity  in  only  one  direction. 
Thus,  if  an  alternating  e.  m.  f.  (electromotive 
force)  were  applied  to  the  plate  of  the  tube, 
current  would  flow  through  the  circuit  only 
when  the  plate  was  positively  charged — that 
is,  one  half  of  the  time.  In  this  respect  the 
bulb  is  similar  to  the  crystal  detector  that  we 
discussed  in  this  department  for  August,  and 
it  can  be  substituted  for  the  crystal. 

It  is  readily  understood  that  this  rectifying 
action  is  comparable  to  a  valve,  which  shuts 
off  the  current  on  one  half  of  the  cycle  and 
passes  it  on  the  other.  This  type  of  tube — 
a  two-element  (filament  and  plate)  bulb — has 
been  named  the  "Fleming  Valve"  after  Dr. 
J.  A.  Fleming,  the  English  scientist  who  first 
applied  it  to  the  detection  of  signals.  Modi- 
fications of  the  Fleming  Valve  have  several 
uses  to-day,  the  most  common  among  which  is 
the  "Tungar"  bulb  used  to  rectify  alternating 
current  in  battery  chargers. 

Mr.  Lee  De  Forest  gave  us  the  vacuum  tube 
used  in  modern  radio  when  he  inserted  a  third 
element,  the  grid,  which  is  a  wire  screen  look- 
ing something  like  its  diagram  symbol  shown 
in  Fig.  9,  between  the  filament  and  plate. 

But  it  is  another  matter  when  an  electrical 


Vacuum 
Tube 


FIG.  8 

The  two-element   vacuum  tube,  sometimes  called 

the  "  Fleming  valve"  after  its  inventor,  Dr.  J.  A. 

Fleming 


FIG.   9 

How     the     usual    three- 
element  tube  is  indicated 


charge  is  placed 
upon  this  grid.  If 
a  negative  charge  is 
applied  to  this  third 
element,  it  will  repel 
the  electrons  (it  is 
an  old  electrical 
axiom  that  like 
charges  repel  each 
other)  and  none  can 
pass  through  to  the 
plate.  Thus  the  cur- 
rent through  the  tube — or  "plate  current" 
as  it  is  called — will  be  decreased  or  stopped. 
On  the  other  hand,  if  a  positive  charge  is  im- 
posed on  the  grid,  more  electrons  would  be 
drawn  from  the  filament,  and  by  the  time 
they  travel  as  far  as  the  grid,  most  of  them  are 
attracted  by  the  greater  positive  potential  on 
the  plate  and  will  pass  through  to  it.  The 


<-  Electrons -. 


FIG.     IO 

result  is  an  increased  plate  current  in  the  cir- 
cuit plate  to  B  battery  to  filament.  The 
sketches  in  Fig.  10  serve  to  illustrate  this 
interesting  action. 

In  A,  the  grid  is  at  zero  potential  and  an 
average  number  of  electrons  flow  to  the  plate. 
As  the  grid  is  given  a  negative  bias,  in  B,  the 
flow  of  electrons  (which  causes  the  current  in 
the  plate  circuit)  decreases,  to  change  to  a 
comparatively  large  current  with  the  plus 
charge  in  C. 

The  commercial  tubes  with  which  you  are 
familiar  have  these  three  elements — and  func- 
tion in  the  manner  we  have  described. 

They  can  be  obtained  in  various  types 
having  minor  differences  in  electrical  charac- 
teristics such  as  filament  potential  and  cur- 
rent, but  the  fundamental  action — the  control 
of  the  plate  current  by  the  grid  charge — re- 
mains the  same.  This  control  action  is  often 
referred  to  as  a  "trigger"  or  relay  action,  for 
like  the  trigger  in  a  pistol  or  a  relay  in  any 
electrical  circuit,  a  variation  in  the  charge  on 
the  grid  can  be  made  to  control  or  set  loose 
much  greater  power  in  the  form  of  plate  cur- 
rent variations.  It  is  also  a  relay  action  in 


References  in  Radio  Text  Books  Relating  to  the  Tube          80 1 


the  sense  that  the  current  in  one  circuit  can  be 
shut  off  by  the  impulses  in  another  and  totally 
different  circuit.  For  instance,  in  Fig.  n, 
in  which  A  is  a  magnetic  relay  circuit  and  B 
is  a  vacuum  tube  circuit,  the  closing  of  key 
K,  in  either  system,  will  break  the  circuit 
through  the  telephone  receivers.  In  A,  the 
lever  will  be  pulled  down,  opening  the  circuit 
at  S,  and  in  B,  the  high  negative  charge  sup- 
plied to  the  grid  will  open  the  circuit  at  S. 

jimiimimmimiiiniiMiiimiiimiiiiiiiiiiiimiiiiiiiiiimiiiiiiiiiiiiiiiiiiiiiiiimiiimiiimiiiimip; 

THE    RADIO   LIBRARY 

^mnimiiMiiiiimnmmiinmiimnimmiiitimmiiiiiimiimiimiiiimiiimiiiiimiimmiiiimiT 

fundamental  action  of  the  vacuum 
tube  is  explained  in  almost  every  modern 
radio  book.  The  student  reader  will  find 
the  following  bibliography  of  interest  and  as- 
sistance: 


T! 


The  Outline  of  Radio,  by  John  V.  L.  Hogan, 
Chapter  eight.  An  easily  understood  exposition 
of  detection. 

The  I.  C.  S.  Radio  Handbook,  pages  216  to 
237.  This  is  less  elementary  but  should  be  easily 
followed  by  the  reader  who  comprehends  most  of 
what  he  has  so  far  read  in  "The  Radio  Beginner." 

Vacuum  Tubes  in  Wireless  Communication, 
by  Elmer  E.  Bucher.  Parts  One  and  Two. 
Less  elementary. 

Principles  of  Radio  Communication,  by  J.  H. 
Morecroft.  Pages  364  to  page  467.  This  par- 
ticular book  is  recommended  to  the  engineering 
student.  While  starting  with  the  simple  ele- 
ments of  the  vacuum  tube,  it  rapidly  develops 
into  a  mathematical  exposition  of  the  subject. 

Vacuum  Tubes,  by  H.  J.  Van  der  Bijl.  A 
similarly  exact  but  perhaps  more  thorough  re- 
search than  the  excellent  chapters  by  Professor 
Morecroft. 

SI MIIIIII iiiiimimiimiimimim mini iiiiiiiniiiii Humming 

THE   RADIO   LEXICON 

I  i 

Sunn imiimmi iimiiiimmmiiimiimiiiimii iiiimmmiimimmmmiiS 

IONIZATION:  A  phenomenon  caused  by  the 
passage  of  current  through  gases — generally 
rarified.  Mechanically,  it  is  the  result  of  re- 
peated collisions  between  the  infinitely  small 
particles  of  which  we  believe  matter  to  be 
composed.  It  is  usually  evidenced  by  a  visible 
glow  or  haze. 


FILAMENT:  The  wire  in  a  vacuum  tube  which 
is  heated,  generally  to  incandescence,  and 
which  in  this  condition  throws  off  electrons. 
PLATE:  The  metal  "anode"  or  element  in  a 
vacuum  tube  upon  which  a  positive  charge  is 
placed  to  attract  the  electrons  from  the  filament. 
TUNGAR  BULB,  RECTIFYING  TUBE,  FLEMING 
VALVE:  Trade  and  technical  names  for  a  two- 
element,  plate  and  filament,  vacuum  tube. 
GRID:  The  third  "element"  introduced  between 
the  filament  and  plate  by  Mr.  Lee  De  Forest. 
It  controls  the  flow  of  electrons  from  filament  to 
plate  by  means  of  the  electrical  charge  placed 
upon  it. 

PLATE  CURRENT:  The  current  through  a  vac- 
uum tube  which  flows  from  filament  to  plate. 
SPACE  CURRENT:  Generally  the  same  as  plate 
current,  but  occasionally  used  in  reference  to  a 
current  between  grid  and  filament  or  plate. 
A  BATTERY:  The  cell  or  battery  supplying  the 
filament  lighting  potential  to  a  vacuum  tube. 
B    BATTERY:  The   battery   applying   the  high 
positive  potential  to  the  plate  of  a  vacuum  tube. 
(Usually  of  from  22.5  to  135  volts). 
RHEOSTAT:  A  variable  resistance  of  compara- 
tively low  maximum  ohmage.     In  radio,  it  is 
generally  used  to  regulate  the  voltage  applied 
to  the  filament. 


RADIO  BROADCAST  Photograph 


FIG.     I 


Tubes  of  many  manufacturers.  The  round  one  in  the  foreground  is  a  Western  Electric  2i6-A,  particularly 
adapted  for  use  in  the  last  audio  amplifier.  Two  "  high-mu"  tubes  are  shown,  one  from  the  Cleartron  Tube 
Company  and  the  other  sold  by  the  Daven  Radio  Corporation.  The  others  are  standard  3-  and  5-volt  tubes 


How  to  Judge  Radio  Tubes 

Signposts  to  Tell  What  Factors  Make  a  Good  Tube- 
Results  of  Laboratory  Tests  on  Many  New  Tubes — Two 
New  Batteryless  Receivers — A  New  Current  Supply  Device 

BY  THE  LABORATORY  STAFF 


THE  tube  and  its  batteries  are  the  only 
things  that  should  wear  out  in  a  modern 
radio  receiver,  and  the  economics  of  the 
tube  is  an  important  consideration  when 
the  broadcast  listener  is  on  purchasing  bent. 

In  the  usual  five-tube  set  the  vacuum  tube  per- 
forms the  functions  of  radio  frequency  amplifier, 
detector,  and  audio  frequency  amplifier.  In  some 
receivers,  such  as  the  super-heterodynes  or  the  re- 
generatives,  the  additional  task  of  oscillation  is 
ptaced  on  the  tube,  and  in  reflex  sets,  some  of  the 
tubes  do  two  tasks  at  the  same  time.  It  is  no  won- 
der, then,  that  broadcast  listeners  should  be  careful 
of  the  tubes  that  they  buy. 

Within  the  last  few  months,  the  RADIO  BROAD- 
CAST Laboratory  has  received  samples  of  receiving 
tubes  manufactured  by  many  of  the  100  manufac- 
turers now  in  this  business.  Some  of  these  tubes 
have  been  worthless,  some  very  good.  The  data 
printed  this  month  represents  71  tubes  from  11 
manufacturers  and  are  the  best  of  the  many  that 
have  been  tested.  The  average  of  these  figures  is 
an  interesting  and  useful  standard  by  which  tubes 


may  be  compared.  One  assumes  that  in  both  manu- 
facturing and  purchasing  a  tube,  the  most  important 
question  which  arises  is  "what  is  a  good  tube?" 

The  answer  involves  two  factors,  the  electrical 
characteristics  of  the  tube  and  the  factor  of  eco- 
nomics. How  long  will  the  tube  last? 

Electrically  speaking,  there  are  three  factors 
which  completely  define  any  particular  tube:  the 
amplification  constant,  the  plate  impedance,  and 
the  mutual  conductance.  These  terms  may  not  mean 
as  much  to  the  radio  buyer  as  "stroke,"  "bore," 
"wheel  base"  and  other  similar  ones  do  to  the  auto- 
mobile purchaser,  but  they  are  tremendously  im- 
portant to  the  shopper  for  tubes. 

AH  three  indicators  are  bound  up  in  the  mechani- 
cal construction  and  placing  of  the  elements,  and 
the  efficiency  of  the  filament.  The  construction  and 
location  of  the  elements  are  really  a  manufacturing 
detail;  the  efficiency  of  the  filament  is,  then,  the 
vital  factor  upon  which  the  value  of  the  tube  de- 
pends. Unfortunately,  the  production  of  filament 
wire,  especially  modern  oxide  coated  or  thoriated 
wire,  is  not  a  simple  task.  It  is  said  that  much  of 


How  to  Judge  Radio  Tubes 


803 


RADIO  BROADCAST  Photograph 


FIG.    2 


Tube  life  tester  used  in  the  Laboratory.     Meters  are  provided  for  maintaining  the 
filament  voltage  at  proper  value  and  for  reading  the  plate  current  at  regular  intervals 


the  wire  in  present  tubes  is  said  to  be  stolen  from 
the  large  manufacturers  who  own  the  patents  and 
processes  for  making  the  wire.  Some  of  the  wire 
in  tubes  not  made  by  those  who  control  the  manu- 
acture  of  this  filament  wire  is  imported,  some  of  it 
is  made  for  independent  concerns  by  men  who 


have  been  enticed  away  from  the  larger  laboratories. 
One  spool  of  wire  will  make  hundreds  of  tubes. 

The  amplification  factor  of  a  tube  is  a  measure  of 
the  voltage  amplifying  ability  of  the  tube  and  should, 
in  an  amplifier,  be  high;  the  plate  impedance  is  the 
electrical  impedance  which  it  places  in  the  circuit 


RADIO  BROADCAST  Photograph 


FIG.    3 


The  Radio  Receptor  Company's  batteryless  receiver.     This  receiver  will  operate 
from  a  loop.     The  rectifier  tubes  are  in  the  compartment  on  top-  of  the  receiver 


804 


Radio  Broadcast 


in  \vhich  it  is  used,  and  should  be  low;  the  mutual 
conductance  relates  to  the  importance  of  the  grid  in 
controlling  plate  current.  It  is  also  the  ratio  be- 
tween the  amplification  factor  and  the  plate  im- 
pedance, and  should  be  as  high  as  possible. 

In  general  there  is  no  object  in  a  tube  of  high 
"mu"  (amplification  constant),  if  the  plate  imped- 
ance increases  correspondingly,  although  for  resist- 
ance and  impedance  amplifiers  there  is  much  to  be 
said  for  tubes  with  high  voltage  amplification. 

For  audio  amplifiers,  it  is  highly  important  that 
tubes  of  low  impedance  be  used  from  the  standpoint 
of  quality  and  power  amplification  while  in  radio 
frequency  circuits,  tubes  of  low  impedance  will  give 
greater  gain  and  more  stable  operation.  The  future 
trend  of  tube  development  seems  to  be  toward  lower 
impedance  tubes  that  may  be  used  as  power  ampli- 
fiers with  plenty  of  grid  bias  and  a  high  B  battery 
voltage.  The  new  Radiotrons  will  do  much  to  fill  in 
the  gap  between  the  ordinary  j-volt  tube  and  the 
5-watt  power  tubes.  Several  independent  tube 
manufacturers  have  realized  the  need  for  semi-power 
tubes  and  it  is  probable  that  the  early  winter  will  see 
high  power,  high  quality  amplifiers  in  more  general 
use  than  has  been  possible  up  to  this  time. 

GOOD    FILAMENT   WIRE   MEANS   GOOD   TUBES 

HpHE  heart  of  the  tube  is  the  filament,  and  those 
*  manufacturers  whose  filament  wire  is  good  can 
make  good  tubes.  Otherwise  they  can  make  only 
mediocre  products  whose  characteristics  will  be 
erratic  and  whose  life  will  be  uncertain.  Many 


tubes  have  excellent  characteristics  when  placed  on 
test,  but  after  a  few  hours  of  service  the  supply  of 
electrons  has  been  exhausted  and  the  tube  is  dead. 

For  a  given  number  of  watts  expended  in  heating 
the  filament,  the  user  should  get  a  certain  number  of 
plate  milliamperes.  The  filament  efficiency,  on  the 
table  shown  as  "mils  per  watt,"  is  a  measure  of  the 
value  of  the  filament.  Tubes  with  high  filament 
efficiency  will  usually  have  a  higher  mutual  conduc- 
tance, as  the  table  plainly  shows. 

It  is  probable  that  all  of  the  tubes  listed  will  give 
comparable  results,  and  although  measuring  instru- 
ments will  show  that  some  give  greater  amplification 
than  others,  the  ear  will  not  be  able  to  distinguish 
the  difference.  None  of  the  poor  tubes  has  been 
listed  in  this  table.  Since  the  customary  practice  is 
to  run  amplifiers  at  90  volts  on  the  plate  and  nega- 
tive 4.5  volts  on  the  grid,  the  data  given  was  taken 
under  those  conditions. 

In  the  Laboratory,  these  characteristics  are  meas- 
ured and  the  tubes  are  then  placed  on  a  life  test. 
They  are  run  at  normal  filament  voltage  with  the 
grid  connected  to  the  negative  filament  and  with 
about  120  volts  on  the  plate.  At  the  end  of  200 
hours,  if  the  tube  is  still  "alive,"  the  characteristics 
are  again  measured  and  another  200  hours  test  is 
run  through.  For  this  reason  it  takes  considerable 
time  before  the  Laboratory  is  certain  of  the  qualities 
of  any  given  tube. 

Fig.  i  is  a  photograph  of  some  of  the  tubes  that 
have  been  tested  and  Fig  2  shows  a  tube  life  tester 
in  use  in  the  Laboratory. 


RADIO  BROADCAST  LABORATORY 

REPORT  ON  TEST  OF 

5-VOLT  TUBES 

MILS 

NO. 

F!L. 

FIL. 

PLATE 

PLATE 

AMP. 

MUTUAL 

TESTED 

CURRENT 

WATTS 

CURRENT 

IMPED. 

CNST. 

COND. 

WATT 

Ceco      .... 

2 

•25 

•25 

5.6 

4-5 

14,800 

7-2 

508 

Cleartron    .      .      . 

8 

•27 

•35 

7.03 

5-o 

IO,8OO 

7-3 

650 

R.  C.  A.      .      .      . 

IO 

•2  5 

•25 

6.0 

4.8 

I3,OOO 

7.0 

55° 

Diatron. 

5 

.27 

•35 

5-83 

4-3 

14,500 

7.8 

550 

Jove  

6 

.27 

•35 

6.7 

4-95 

IO.OOO 

5-6 

603 

Marathon    . 

9 

•25 

•25 

8-45 

6.75 

9,600 

7.0 

700 

Sea  Gull 

12 

•23 

•15 

6.7 

5-83 

10,000 

6.6 

660 

Silvertone   . 

5 

.22 

.1 

7.0 

6.35 

10,700 

7-2 

650 

Van  Home 

5 

.23 

•15 

5.8 

5-05 

i},6oo 

8-33 

615 

Elektron 

4 

•25 

•25 

4.6 

3.68 

1  7,400 

8-45 

483 

Goode    .... 

5 

•24 

.20 

6.8 

5.67 

12,000 

8.32 

704 

TOTAL 

7' 

Avg.  .244 

1.22 

6.0 

4-0  '. 

12,400 

7-7 

606 

CONDITIONS 

FILAMENT    VOLTS            PLATE    VOLTS            GRID    VOLTS 

5                               90                       —4-5 

Plate  Current  is  at  Zero  grid 

How  to  Judge  Radio  Tubes 


805 


With  each  tube  of  the  Van  Home  Company  of 
Franklin,  Ohio,  the  purchaser  gets  complete  data 
such  as  the  characteristic  curve,  the  plate  impedance, 
amplification  constant  and  mutual  conductance. 
This  gives  the  user  an  unusual  check  on  each  tube 
he  buys. 

BATTERYLESS    RECEIVERS 

IT  HAS  long  been  the  dream  of  radio  listeners  to 
'  possess  a  receiver  that  required  no  batteries  which 
U'ould  run  from  a  lamp  socket.  Two  receivers  of 
this  type  have  been  tested  recently  in  the  Labora- 
tory. One  is  known  as  the  Multiflex  and  manufac- 
tured by  the  Radio  Receptor  Co.,  Inc.,  New  York 
City,  and  the  other  is  called  the  Powerola  and  is 
manufactured  by  the  Terminal  Electric  Co.,  New 
York  City.  Neither  of  these  receivers  requires 
batteries  of  any  kind,  and  both  may  be  run  from 
either  direct  or  alternating  current,  both  use  stan- 
dard tubes. 

The  development  of  receivers  of  this  type  has  been 
interesting.  It  is  a  comparatively  simple  matter  to 
secure  proper  plate  potential  from  either  direct  or 
alternating  current.  The  many  B  substitutes  now 
on  the  market  attest  to  this  fact.  It  is  not  difficult 
to  operate  the  filaments  of  amplifier  tubes  from  alter- 
nating current  either.  The  great  obstacle  in  the 
way  of  a  battery  less  set,  however,  is  the  detector  fil- 
ament which  must  be  fed  from  pure  direct  current. 

Tungar  tubes,  such  as  are  used  for  charging  stor- 


age batteries,  are  one  solution  to  this  problem.  If 
two  of  them  are  used  to  rectify  both  sides  of  the 
alternating  current  and  if  the  output  is  sufficiently 
filtered,  the  detector  and  amplifier  filaments  may  be 
run  without  A  batteries.  In  receivers  utilizing  this 
means  of  filament  supply,  it  has  been  customary  to 
run  the  filaments  in  series  to  lower  the  current  flow- 
ing. If  3-volt  tubes  requiring  but  60  milliamperes 
filament  current  are  used,  it  is  possible  to  use  as  rec- 
tifiers, two  of  the  B  battery  substitute  tubes.  In 
this  case  the  entire  current  requirements  are  about 
70  milliamperes,  which  two  rectifier  tubes  should  be 
able  to  supply  for  considerable  length  of  time  with- 
out deterioration. 

Both  of  these  receivers,  which  were  previously 
mentioned  operated  successfully  in  the  Laboratory. 
The  Radio  Receptor  s?t  operated  quite  satisfact- 
orily on  a  bop. 

THE    A.    C.   TUBE 

TTHE  A.  C.  Tube,  which  is  attracting  considerable 
*  attention,  has  several  advantages.  In  the 
first  place  its  filament — which  is  not  really  a  fila- 
ment at  all — is  heated  by  alternating  current.  This 
means  that  no  A  battery  is  required  and  that  a 
person  who  has  a.c.  in  his  house  needs  only  a  small 
toy  transformer  to  operate  the  filaments.  No 
rheostat  is  required.  This  tube  is  the  outcome  of  a 
great  deal  of  work  by  many  engineers  on  a  "uni- 
potential"  cathode  tube,  which  means  little  or  noth- 


FIG.   4 

An  excellent  neutrodyne  which,  in  the  middle  of 
the  summer,  picked  up  several  Chicago  stations 
and  Miami  Beach  from  Garden  City.  It  is 
made  by  the  Howard  Radio  Company,  Chicago. 
With  it  is  the  Stewart  Warner  loud  speaker, 
which  is  a  very  good  horn,  and  an  interesting 
power  supply  unit  from  Balkite 


RADIO  BR 


8o6 


Radio  Broadcast 


RADIO  BROADCAST  Photograph 
FIG.    5 

A  close  up  of  the  Balkite  B-current  supply  and  trickle  charger.  These  units  are  very  compact  and  are  neat 
adjuncts  to  modern  radio  sets.  The  B  current  supply  takes  the  place  of  B  batteries  and  employs  a  chemical 
rectifier.  The  trickle  charger  may  be  left  on  the  storage  battery  at  all  times  when  the  set  is  not  being  used. 
In  this  way  the  battery  is  always  operating  at  top  efficiency.  The  Brach  switch  is  a  device  to  switch  the  A 
battery  from  "on-charge"  to  the  receiver,  with  very  little  effort  on  the  part  of  the  user.  The  component 
parts  of  the  B-current  supply  of  the  trickle  charger  and  tantalum  elements  are  clearly  shown 


ing  to  most  of  us,  and  is  an  important  step  in  a 
proper  direction.  With  such  a  filament  heater,  it 
should  be  possible  to  get  very  high  filament  emission 
with  consequent  high  mutual  conductance.  This 
should  be  a  great  advantage,  since  mutual  conduc- 
tance is  a  direct  indication  of  the  value  of  a  tube. 

A.  C.  tubes  tested  in  the  Laboratory  have  worked 
sporadically.  Sometimes  excellent  results  have  been 
secured,  sometimes  no  results  at  all.  The  chief 
trouble  has  been  noise  from  the  a.  c.  hum.  This  can 
be  ironed  out,  and  a  receiver  brought  to  the  Labora- 
tory by  the  Pathe  Radio  and  Phonograph  Company 
worked  beautifully  with  no  batteries  at  all.  The 
filament  emission  of  the  A.  C.  tubes  may  be  some- 


what higher  than  that  obtainable  from  standard 
5-volt  tubes,  but  the  mutual  conductance  of  a 
number  of  these  was  about  equal  to  that  of  the 
average  5-volt  tube,  although  they  were  not  so 
uniform. 

At  present  it  is  difficult  to  say  what  the  A.  C. 
Tube  will  mean  to  radio.  They  have  many  possi- 
bilities, and  may  prove  to  be  one  of  the  most  im- 
portant contributions  to  modern  reception.  On  the 
other  hand,  they  will  be  useless  to  thousands  of 
listeners  who  do  not  have  a.c.  At  the  present  time 
it  is  believed  that  they  have  not  reached  the  acme 
of  development  and  the  future  must  promise  a 
great  deal  for  this  new  tube. 


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1"NO\V/  I  HAv/E  FOUND.    ...     "I 

A  Department  Where  Readers  Can  Exchange  Ideas 
and  Suggestions  of  Value  to  the  Radio  Const  rue  &randOperator  I 


A  SIMPLE  SOLUTION  TO  A  COMMON 

PROBLEM   IN  ANTENNA 

CONSTRUCTION 

RADIO  fans  who  live  in  apartment 
houses  or  in  densely  populated  areas 
are  often  confronted  with  almost 
insurmountable  problems  in  the  matter  of 
erecting  an  antenna,  and  especially  in  the 
matter  of  bringing  the  lead-in  down  to  a  suit- 
able window.  A  receiving  set  capable  of 
operating  on  a  loop  is  usually  either  too  ex- 
pensive or  lacking  in  distance-getting  qualities 
to  be  satisfactory  in  such  locations,  so  an 
antenna  is  almost  a  necessity,  undesirable 
though  it  may  be. 

The  writer  recently  encountered  and  solved 
the  problem  of  bringing  a  particularly  difficult 
lead-in  down  the  side  of  a  large  building. 

The  antenna  was  strung  between  two  large 
electric  signs  over  the  center  of  the  roof  of  the 
building  and  the  lead-in  brought  down  to  an 
insulator  on  the  end  of  a  2  x  2  inch  piece  of 
pine  projecting  a  few  feet  (as  far  as  was  per- 
mitted) over  the  cornice  of  the  building. 
It  was  secured  with  lag-screws.  The  wire 
was  dropped  down  and  brought  in  through  a 
window  frame.  This  is  where  the  usual  snag 


Outside 
Wall  of 
Building 


//I  ^^5/,,    D»«»»   T..k.~. 


Brass  Tubing 


-Window  Frame 


FIG.    I 


was  struck.  The  trouble  lay  in  the  fact  that 
the  window  was  recessed  in  the  usual  manner, 
being  about  fourteen  inches  in  from  the  face 
of  the  building.  Directly  over  the  top  of  the 
window  was  a  tin  channel  bearing  a  series  of 
electric  lights  running  the  length  of  the  story. 
The  wire,  dropping  vertically  and  then  in- 
ward at  a  sharp  angle,  of  course  made  contact 
with  the  channel  and  swayed  back  and  forth 
between  two  of  the  sockets,  at  times  also 
brushing  across  the  upper  portion  of  the 
structure. 

To  carry  the  wire  out  away  from  the  build- 
ing with  a  stick  was  not  to  be  considered,  be- 
cause the  window  faced  a  busy  thoroughfare 
only  a  few  feet  below,  and  the  unsightly  con- 
glomeration of  braces,  guy  wires,  etc.,  neces- 
sary to  such  a  method  would  not  have  been 
tolerated  by  the  company  for  which  the  an- 
tenna was  being  erected. 

The  problem  was  at  last  solved  in  the  follow- 
ing manner:  A  porcelain  tube  was  run  through 
a  hole  in  the  window  frame  of  a  size  to  make  a 
very  tight  fit.  Through  the  center  of  the 
porcelain  tube  was -forced  a  three-foot  piece 
of  T\  inch  outside  diameter  brass  tubing,  so 
that  the  greater  part  of  the  latter  protruded 
outside  of  the  room  into  the  open  air.  The 
hole  in  the  brass  tubing  was  large  enough 
to  allow  the  antenna  wire  to  pass  through. 
In  this  manner  the  lead-in  was  carried 
several  feet  out  from  the  face  of  the  building 
and  entirely  away  from  the  electric  light 
sockets,  making  a  very  neat  and  satisfactory 
job.  The  details  are  shown  in  Fig.  i. 

H.A.  HIGHSTONE, 
Oakland,  California. 

A  SELF-SUPPORTING  "D"  COIL 

A  THOUGH  the  toroidal  coil  is   perhaps 
a  trifle  more  efficient,  the  ease  of  con- 
struction together  with  its  adaptabil- 
ities in  the  coupler  and  the  variometer,  make 
the  D  coil  preferable  in  many  cases,  and  the 
self-supporting  feature  adds  to  its  efficiency. 

A  good  wound-on-air  coil  of  the  D  type  may 
be  constructed  as  follows:  The  nails  or  wooden 
pins  which  serve  as  a  form  on  which  to  wind 


8o8 


Radio  Broadcast 


the  coil  are  inserted  in  a  soft  wood  board  in 
the  same  manner  as  that  used  for  making  low- 
loss  solenoids,  but  are  arranged  as  shown  in 
the  accompanying  diagram,  Fig.  2.  The  first 
turn  is  started  by  passing  the  wire  inside  pin 
i  and  outside  pins  2  and  4  and  then  over  1 1, 
9,  7,  5,  12,  14,  i,  3,  12,  10,  8,  6,  4,  13,  15.  At 
this  point,  two  turns  have  been  completed  and 
the  third  turn  is  wound  over  the  first  and  the 
fourth  turn  will  come  directly  over  the  second 
and  so  on. 

It  will  be  noticed  from  the  diagram  that  pins 
5  and  3  and  pins  1 1  and  13  are  relatively  near 
to  and  equidistant  from  pins  4  and  12  respec- 
tively. That  part  of  the  circumference  be- 
tween pins  5  and  1 1  must  be  divided  into  some 
convenient  number  of  equal  parts  of  even 
number  (6),  and  the  portion  of  the  circle  be- 
tween pins  3  and  13  is  correspondingly  divided 
into  an  odd  number  of  divisions  (5). 

After  the  desired  number  of  turns  have  been 
wound  on,  the  coil  is  slipped  up  on  the  pins 
far  enough  to  be  tied  at  the  intersections  of  the 
wire,  with  a  strong  linen  thread.  The  pins 
are  now  removed  and  a  very  firm,  efficient  coil 
is  the  result. 

HERMAN  M.  PATRIDGE, 
Newfields,  New  Hampshire. 

A  TUBE  LIFE-SAVER 

WHEN,  after  having  built  a  new  set, 
a  test  is  made  to  determine  whether 
the  plate  battery  is  accidentally  con- 
nected with  the  filament  circuit,  one  procedure 
is  to  try  a  regular  tube  in  the  different  sockets, 


10 


11 


6  Volt 

Automobile  Lamp 
Imbedded  in 
Sealing  Wax 


_  Old  Tube 
Shell 


FIG.    2 


FIG.  3 

and  if  it  doesn't  burn  out  in  any  of  them,  it 
is  safe  to  put  all  tubes  in  their  sockets,  and 
go  ahead  with  other  testing.  If,  however,  the 
plate  battery  has  been  wrongly  connected,  the 
cost  of  the  test  is  a  new  tube,  $2.50,  or  there- 
abouts. 

Take  an  automobile  lamp  socket,  either 
single  or  double  contact,  as  preferred)  and 
solder  two  leads  to  it,  connecting  this  lamp  in 
an  old  tube  base  with  its  two  leads  connected 
to  the  regular  filament  terminals  of  the  base. 
Fill  around  the  socket,  in  the  base,  with  seal- 
ing wax.  Thus,  using  one  of  the  small  auto- 
mobile lamps,  as  in  Fig.  3,  the  cost  of  the  test, 
in  case  of  a  wrong  connection,  will  be  reduced 
to  the  cost  of  the  small  automobile  lamp, 
about  30  cents.  This  will  no  doubt  appeal 
to  set  builders  who  have  had  to  replace  the 
"test  tube,"  as  I  have  had  to  do. 

W.  H.  MAYFIELD,  Miami,  Arizona. 

A   METHOD  OF  SCRAPING   WIRE 

A  KINK  that  I  have  never  seen  in  publica- 
tions, and  therefore  may  be  of  use  to 
this  department,  is  a  method  of  remov- 
ing insulation  (either  cotton  or  silk)  from 
magnet  wire.  Until  recently,  when  I  had  this 
to  do,  the  only  tool  that  occurred  to  me  was 
a  knife.  One  day  when  I  had  a  couple  of  feet 
of  wire  from  which  to  remove  the  insulation, 
I  had  no  knife  handy,  but  seeing  a  piece  of 
emery  cloth  lying  on  the  bench,  I  folded  it  and 
drew  the  wire  through  it  a  couple  of  times,  and 
since  then  have  never  used  a  knife  for  this 
work.  Try  it. 

W.  H.  MAYFIELD, 
Miami,  Arizona. 


RADIO  BROADCAST  ADVERTISER 


809 


JVhether  you  smile  or  cuss 
depends  upon  the  service 
behind  your  Radio** 


What  is  this  radio  service  which 
we  claim  is  so  necessary? 

Do  you  drive  a  car? 

Do  you  ever  have  little  things 
go  wrong  with  it? 

You  have  become  so  used  to 
minor  troubles  that  you  don't 
condemn  the  car  on  which  they 
occasionally  occur. 

No— 

You  go  right  to  a  service  man — 
a  man  who  knows  your  make  of 
car.  You  don't  go  to  a  handy  man 
who  claims  he  can  fix  any  car. 

That's  automobile  service,  and 
is  one  of  the  main  reasons  for  the 
auto  being  the  success  it  is  today. 

The  same  service  condition 
exists  in  radio — the  only  difference 
being  that  people  don't  yet  under- 
stand it. 

The  radio  instrument  which 
never  requires  service  has  never 
been  built — it  never  will  be. 

Like  automobile  manufacturers, 
the  better  radio  manufacturers  do 
all  within  their  power  to  make 
their  instruments  mechanically 
perfect.  Nevertheless,  like  the 
auto,  little  things  will  sometimes 
go  wrong — they  are  serious  to  the 
radio  owner  but  very  simple  to  a 
factory  trained  service  man. 


The  handy  man  who  can  fix  any 
radio  simply  experiments  until  he 
locates  the  trouble — such  a  method 
was  disastrous  to  the  auto  in  for- 
mer days — disastrous  and  expen- 
sive in  radio  today.  1 1  is  not  sound. 

Ozarka  instrumentc  are  sold 
only  by  Ozarka  factory  represent- 
atives, men  who  are  factory 
trained  in  sales  and  service,  men 
who  sell  no  other  radios  but 
Ozarka. 

These  men  don't  pretend  to 
know  all  about  radio  but  they  do 
know  all  there  is  to  know  about 
Ozarka — isn't  that  the  kind  of 
radio  service  you  want? 

Ozarka  instruments  are  sold 
under  a  very  definite  plan.  An 
Ozarka  representative  will  gladly 
set  up  an  Ozarka  in  your  home — 
he  won't  tune  it — he  won't  tell  you 
what  it  will  do — you  must  operate 
yourself.  If  the  results  you  receive 
by  your  own  operating  won't  con- 
vince you  that  the  Ozarka  gives 
you  the  distance,  volume,  selec- 
tivity, tone  and  ease  of  tuning  that 
you  demand  then  don't  buy  it. 

Ozarka  instruments  are  built  to 
sell  themselves  but  no  Ozarka  is 
sold  without  factory-trained  serv- 
ice behind  it. 


Openings  for  a  Few 

More  Ozarka  Factorv 

Representative  s 

rv 


E. 


UZARKA  Incorporated,  is  now 
entering  its  4th  year.  From  a 
beginning  with  one  engineer,  one  ste- 
nographer, one  salesman — our  present 
•resident,  the  Ozarka  organization 
»jas  grown  to  over  3,100  people.  There 
must  be  some  good  reason  for  this 
growth. 

Ozarka  instruments  have  made 
good — they  have  more  than  met  com- 
petition. Ozarka  representatives  have 
made  good  not  only  because  Ozarka 
instruments  were  right,  but  because 
they  have  been  willing  to  learn  what 
Ozarka  engineers  were  willing  ancl 
capable  to  teach  them — Ozarka  un- 
usual salesmanship  and  Ozarka  service. 

Send  for  FREE  Book 

Radio  offers  a  wonderful  opportun- 
ity to  men  who  are  willing  to  start  at 
the  bottom  and  build.  You  need  not 
know  salesmanship,  but  will  you  learn 
what  we  will  gladly  teach  you?  You 
may  not  know  radio,  but  we  can  and 
wijl  teach  you  if  you  will  do  your  part. 
With  such  knowledge  and  willingness 
to  work,  it  doesn't  seem  possible  that 
you  cannot  make  good.  Sign  the  cou- 
pon below,  don't  fail  to  give  the  name 
of  your  county.  Better  still  write  a 
letter,  tell  us  about  yourself  and  attach 
the  coupon.  If  interested  in  our  sales- 
man's plan  ask  for  "Ozarka  Plan 
No.  100." 


122  Austin  Avenue  B 
Chicago,  Illinois 

Gentlemen:  Without  obligation  send  book  "Ozarka  In- 
struments No.  200"  and  name  of  Ozarka  representative. 


Name.   .. 
Address.. 


122  Austin  Avenue,  B 
Chicago,  Illinois 


County State.. 


.City YOU'LL  KNOW 

THE  MAN  BY 


THIS  BUTTON! 


Gentlemen  :  I  am  preatly  interested  in  the  FREE  BOOK 
"The  Ozarka  Plan"  whereby  I  can  sell  yourinstruments. 

Name  ............................................  .................................. 

Address  .................................................  City  ..................... 

County  ..........................................  State  ......................  .. 


QUESTIONS  AMD  ANSWER/* 

>0 


QUERIES  ANSWERED 


WHAT  CARE  DOES  A  RECEIVER  ORDINARILY  RE- 
QUIRE? 

R.  J.  L.  Lincoln,  Nebraska. 

HOW  MAY  THE  BEERS  CHARGER  BE  USED  TO  CHARGE 
STORAGE     B     BATTERIES? 

T.  C.  N. — Hempstead,  New  York. 
WHEN  i  ADD  RESISTANCE-COUPLED  AMPLIFICATION 

TO    THE    ROBERTS    SET    THE    VOLUME    IS    LESS    THAN 
ORIGINALLY  ON  TWO  TUBES.      WHY? 

M.  L.  C.— Zion  City,  Illinois. 


RECEIVER    RENOVATION 

A  RECEIVER,  like  any  other  piece  of  intricate 
machinery,  needs  frequent  overhauling  and 
renovation.  It  is  just  as  unfair  to  assume 
that  a  motor  will  function  without  oil  as  it  is  to 
assume  that  a  receiver  will  operate  satisfactorily 
without  frequent  cleanings. 

Look  over  your  condensers.  If  they  have  a  pig- 
tail connection  so  much  the  better  for  them.  If  they 
have  not,  then  it  should  be  observed  whether  a 
thin  film  of  grease  produced  by  moisture  and  dust 
has  got  into  the  bearings.  Never  use  oil  to  lubri- 
cate a  hard-turning  condenser.  Rather,  try  to  loosen 
up  on  the  pivots — or  get  a  new  condenser. 

If  your  condenser  is  composed  of  a  section  of 
stator  plates  which  are  cut  out  of,  or  assembled  into, 
a  solid  block,  it  is  absolutely  essential  that  every  so 
often  the  spaces  between  the  plates  be  cleared  of 
collected  dust.  A  pipe-cleaner  is  well  suited  for 
this  work,  and  it  is  not  a  bad  stunt  to  clean  all 
condensers  irrespective  of  their  peculiar  assembly. 

How  are  your  coil  units?  Is  the  wire  merely 
wound  on  the  bakelite  or  cardboard  tubing  without 
any  binder?  If  so,  and  the  coil  is  loosening  owing 
to  shrinkage  and  drying,  put  the  wires  back  into 
place,  tighten  the  turns  and  then,  at  the  start  and 
finish  of  the  coil,  put  a  dab  of  collodion,  shellac  or 
varnish — this  to  keep  the  winding  permanently  in 
place.  Do  not  coat  the  whole  coil  with  this  binder 
as  the  resistance  will  materially  increase  affecting 
the  overall  efficiency  of  the  receiver  in  which  it  is 
employed. 

Take  a  look  at  your  sockets.  Have  the  binding 
posts  on  them  become  loose?  If  so,  you  can  credit 
them  with  causing  some  of  the  scratchy  noises  which 
you  have  undoubtedly  heard.  Also  look  at  the 


HOW  MAY  REGENERATION  BE  ADDED  TO  MY  NEU- 
TRODYNE? 

T.  C.  R.— Butte,  Montana. 

HOW  ARE  THE  W.    E.  TRANSFORMERS   USED  IN  THE 
ROBERTS    CIRCUIT? 

I.   K.— Brooklyn,  New  York. 

WlLL    YOU    PUBLISH    A    TABLE    OF    SCREW    SIZES, 
DRILL   GAUGES   AND   TAP   SIZES? 

C.  B. — Philadelphia,  Pennsylvania. 


contact  blades  of  the  sockets  and  see  that  they 
have  not  been  bent  down  so  far  that  there  is  no 
contact  between  them  and  the  tube  prongs.  Brighten 
the  surface  of  the  tube  prongs  and  be  sure  none  are 
loose. 

If,  in  the  construction  of  your  receiver,  there  has 
accumulated  between  the  battery  terminals,  or 
any  other  contacts  in  the  receiver,  a  deposit  of 
soldering  paste,  remove  it  with  a  washing  of  alcohol. 

Don't  let  your  batteries  get  dusty,  especially 
between  the  terminals,  and  be  sure  to  coat  the  ter- 
minals of  your  A  battery  with  vaseline  to  prevent 
corrosion.  Phone  and  loud-speaker  cords  often 
become  wet  or  if  they  have  come  in  contact  with 
the  top  of  the  A  battery  the  insulated  cotton  cover- 
ing becomes  rotted  and  soon  a  short  circuit  between 
the  tinsel  wires  occurs. 

CHARGING    A    AND    B    BATTERIES 

THE     Beers    universal    battery    charger    de- 
scribed in  the  September  RADIO  BROADCAST 
may,  with  the  addition  of  a  lamp  and  a  few 
wires,  be  made  to  conform  with  its  name  and  be 
employed  as  both  A  and  B  battery  charger. 

No  change  in  the  original  circuit  is  necessary  and 
it  was  found  by  experiment  that  both  A  and  B 
batteries  could  be  charged  simultaneously.  Of 
course,  when  a  6-volt  battery  is  charged  at  the  same 
time  as  a  B  battery,  the  amount  of  current  passed 
into  the  B  battery  is  lower  than  when  only  the 
latter  battery  is  on  charge.  The  output  charging 
rate  of  2  amperes  will  be  divided  proportionally  be- 
tween the  two  batteries. 

With  a  2oo-watt  bulb  it  was  found  that  a  charging 
rate  of  .7  amperes  was  obtained  on  a  48-volt  B 
battery,  and  with  a  50-watt  lamp,  .18  amperes. 


RADIO  BROADCAST  ADVERTISER 


MODEL  L-3 


All  Ultradynts  are 
guaranteed  as  long  as 
Mr.  Lacault's  mono- 
gram seal  (K.E.L.)  on 
the  assembly  lock  bo/Is 
remains  unbroken. 


NoDials-NoPanel 

°r 


IF  the  Ultradyne  Model  L-3  were  merely 
another  new  receiver,  its  influence  in  the  in- 
dustry would  be  little  felt. 
But  it  is  in  reality  the  first  step  in  the  general 
revision  of  radio  receiver  design  which  is  bound 
to  follow  its  advent. 

For  the  new  Ultradyne  Model  L-3,  is  an  entirely  new 
type  of  receiver — radically  different  in  appearance  and 
method  of  operation — gives  finer  results  from  finer  engi- 
neering. Employs  six  tubes — is  completely  assembled 
and  wired,  ready  for  the  tubes  and  batteries. 
It  has  no  dials — no  panel — no  needless  controls.  Two  le- 
vers, an  exclusive  Ultradyne  feature,  give  you  control  of  the 
entire  broadcast  program.  Its  operation  is  practically  au- 
tomatic— simply  slide  the  pointer  to  the  station  you  want 
and  adjust  the  volume  control,  soft  or  loud  as  you  like  it. 
Loud  Speaker  and  "B"  Batteries  self  enclosed  in  a  beautiful 
cabinet  that  is  far  from  mechanical  in  design  and  is  an  ideal 
mahogany  furniture  piece  for  the  most  charming  home. 
Ask  your  dealer  for  a  demonstration. 


Write  for  descriptive 
folder         A 


PHEMX    RADIO 
CORPORATION 

116-C  East  25th  St. 
N.  Y.  CITY 


Tested  and  approved  by  RADIO  BROADCAST 


8l2 


Radio  Broadcast 


FIG.    I 

With  the  A  battery  on  charge  at  the  same  time,  the 
current  in  the  B  battery  circuit  was  cut  to  about 
one  third  its  former  value. 

To  charge  B  batteries  it  is  only  necessary  to 
connect  the  positive  terminal  of  the  battery  to  the 
graphite  electrode  of  the  tungar  tube,  i.e.,  the  lead 
coming  out  of  the  top  of  the  tube. 

The  negative  side  of  the  battery  connects  to  one 
side  of  the  a.  c.  line.  The  other  side  of  the  a.  c 
line  connects  to  the  positive  output  terminal  of  the 
A  battery  charger.  In  the  circuit  diagram  Fig.  i, 
the  heavy  lines  indicate  the  new  connections  for  B 
battery  charging.  It  is  obvious  that  by  varying 
the  size  of  the  lamp  in  the  charging  circuit,within 
the  limits  specified,  the  charging  rate  may  ac- 
cordingly be  varied. 

The  above  specifications  hold  good  only  for  a 
48-volt  B  battery.  Do  not  try  by  this  method  to 
charge  a  96-volt  or  larger  bank  of  B  batteries. 

RESISTANCE    COUPLING    IN  THE   ROBERTS   KNOCKOUT 

MANY  constructors  have  endeavored  to  add 
resistance-coupled  amplification  to  their 
two-tube  Roberts  receivers  with  varying 
results.  Some  were  successful,  others  not.  If  the 
circuit  is  observed  and  analyzed,  it  will  be  noted 
that  the  input  connections  to  the  first  resistance 
coupler  are  not  like  that  of  a  transformer-coupled 
amplifier.  The  detector-plate  resistance,  having 
B-battery  current  flowing  through  it,  is  isolated 
from  the  grid  of  the  next  tube  by  an  isolating  or 
blocking  condenser.  These  points  are  brought 
out  in  Fig.  2. 

Now  supposing  a  pair  of  leads  are  brought  from 
the  output  of  a  tube,  such  as  at  1-2  Fig.  2,  and  are 
connected  to  the  plate  resistance  of  the  resistance 


coupler.  If  by  any  chance  these 
connections  are  so  reversed  that 
the  plate  lead  of  the  first  tube 
connects  to  the  end  of  the  resistance 
not  common  to  the  isolating  con- 
denser, then  a  circuit  such  as  in  Fig. 
3  will  result. 

Here,  a  B-battery  potential  will 
be  applied  to  that  end  of  the 
plate  resistance  connected  to  the 
isolating  condenser  and  the 
effective  voltage  drop  across  the 
plate  resistance  will  not  be  real- 
ized. 

Those  who  employ  resistance-coupled  amplifica- 
tion in  their  receivers  are  cautioned  to  check  over 
the  connections  to  this  part  of  the  amplifier  as  satis- 
factory operation  of  the  receiver  is  entirely  depend- 


FIG.    3 


FIG.    2 


FIG.   4 

ent  upon  the  correct  hookup  of  the  plate  resistance. 
In  Fig.  4  the  incorrect  circuit  is  shown  in  another 
form  and  as  it  would  be  recognized  in  a  receiver. 

While  on  the  subject  of  resistance  amplification, 
it  is  well  to  state  that  the  output  amplification  of 
the  unit  may  be  unquestionably  increased  with  the 
use  of  the  new  high-mu  tubes  especially  designed 
for  use  in  resistance-coupled  amplifiers. 

ADDING  REGENERATION  TO  THE  NEUTRODYNE 

IT  HAS  generally  been  assumed  that  the  addi- 
tion of  regeneration  to  a  receiver  was  theoreti- 
cally equal  to  the  addition  of  a  stage  of  radio- 
frequency  amplification.     Furthermore,  in  the  use 


RADIO  BROADCAST  ADVERTISER 


813 


.oo\ 


_     Micadons 

standard  fixed  radio  condensers 

NEARLY  all  of  the  leading  manufacturers  of 
radio  sets  have  adopted  the  Micadon  as  their 
standard. 

A  layman  might  be  fooled  —  not  so  these 
manufacturers.  They  need  fixed  condensers 
with  accurately  matched  and  permanent  ca- 
pacities, and  they  know  which  are  the  best. 
Year  after  year,  they  buy  millions  of  Mica- 
dons.  This  overwhelming  preference  is  your 
assurance  of  quality. 

Send  10  cents  for  32-page  booklet  "ap- 
plications of  Dubilier  Condensers  in 
Radio  Circuits."  Address  Dept.  H-2. 
ronx  Boukvard,  New  York  City 


Dubilier 

CONDENSER    AND   RADIO    CORPOHATIOlj 


Tested  and  approved  by  RADIO  BROADCAST 


8i4 


Radio  Broadcast 


x.  Capacity  Feed  back 
Condenser 

FIG.    5 


of  regeneration,  it  is  possible  to  tune  a  receiver  by 
the  squeal  method  which  is  admitted  to  be  practi- 
cally the  easiest  system  in  use.  In  the  standard 
neutrodyne,  unless  the  receiver  be  improperly 
neutralized,  it  is  not  possible  to  realize  the  benefits 
from  such  a  system  of  tuning,  and  often  a  station 
is  passed  by  simply  because  the  peculiar  whistle 
is  not  present. 

To  include  regeneration  in  a  receiver  of  this  type, 
it  is  possible  to  choose  from  two  systems — namely 
capacity  feedback  or  inductive  feedback,  otherwise 
recognized  as  "tickler  regeneration."  The  former 
has  the  advantage  over  the  latter  system  in  that 
the  adjustment  of  regeneration  is  independent  of 
wavelength  and  does  not  affect  the  tuning  properties 
of  the  receiver. 

In  tickler  control  a  readjustment  usually  throws 
out  the  main  tuning  control  a  trifle.  Inductive 
feedback  is,  however,  the  more  common  form  in  use 
to-day  and  usually  consists  of  a  coil  of  wire  located 
in  the  plate  circuit  of  the  detector  tube.  It  is 
coupled  to  the  detector  secondary.  Another  method 
of  doing  the  same  thing  is  to  employ  a  variometer 
in  the  plate  circuit  of  the  detector. 

The  capacity-feedback  system  has  only  lately 
come  into  extensive  use  and  is  the  one  described  here. 

The  usual  secondary  coil  in  a  neutrodyne  consists 
of  about  60  turns  of  wire  wound  on  a  cylindrical 
form.  To  this  coil,  at  the  filament  end,  must  be 
added  from  one  third  to  one  half  the  number  of 
turns  already  on  the  secondary.  Then  at  the  new 
lower  end  of  the  entire  coil  is  connected  one  ter- 
minal of  a  variable  condenser  the  other  contact  of 
which  connects  to  the  plate  of  the  detector  tube. 
The  circuit  is  shown  in  Fig.  5.  The  heavy  lines 
indicate  that  part  of  the  circuit  which  is  new, 
comprising  the  capacity-feedback  system. 

For  individual  receivers  it  may  be  necessary  to 
experiment  with  additional  coils  having  various 


turn-values.  Also  the  experimenter 
will  find  that  with  some  coils  a  small 
condenser  is  satisfactory  where  in 
other  cases  only  a  larger  condenser 
will  do. 

The  most  satisfactory  and  success- 
ful arrangement  is  that  where,  with 
a  given  number  of  turns,  regenera- 
tion over  the  whole  wavelength  range 
of  the  receiver  will  be  obtained  over 
the  whole  scale  of  the  capacity-feed- 
back condenser  dial. 

The  experimenter  may  wind  the 
additional  coil  in  any  way  convenient, 
according  to  the  mechanical  and 
physical  limitations  of  the  particu- 
lar part  of  the  receiver  where  the 
coil  is  to  be  placed.  It  may  be  bank 
wound,  random,  or  in  any  of  the 
concentrated  forms  such  as  basket 
weave,  diamond  weave,  or  spider- 
web.  The  latter  offers  greatest 
possibilities  because  of  the  space 
saved  in  its  use.  One  important 
thing  to  remember  is  to  wind  the 

new  coil   in    the   same   direction   as    the   original 

secondary. 

WESTERN    ELECTRIC    PUSH-PULL    TRANSFORMERS 

SINCE   the  publication,  in   the   July   "Now    1 
Have    Found    Department,"    of    the    article 
by   Mr.   H.  Q.  Horneij,  describing  the  con- 
struction of  a  four-tube  Roberts  receiver  employing 
a  brace  of  Western  Electric  power-amplifier  trans- 
formers, we  have  been  asked  where  the  transformers 
might  be  purchased  and  why,  from  a  "new  idea" 
standpoint,    the    article    appeared    in    the    above- 
mentioned  department. 

To  answer  the  last  question  first,  the  article  was 
presented  to  our  readers  because  the  use  of  Western 
Electric  transformers  guaranteed  nigh  on  to  perfect 
loud-speaker  reproduction  of  voice  and  music. 


Battery 


AAAAA\  WE  Tapped 

VvVVV    I  Secondary  Audio  Transformer 


To  Tickler 


FIG.    6 


o 

8+45 


RADIO  BROADCAST  ADVERTISER 


815 


EVEREADY   HOUR 
EVERY   TUESDAY    AT   9    P.  M. 

Eastern  Standard  Time 

For  real  radio  enjoyment,  tune  in  the 
"Eveready  Group."  Broadcast  through 
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WE  El  Boston 

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ECONOMY 

No  ONE  size  or  type  of  battery 
can  be  economical  on  every  type 
of  receiving  set.  That's  why 
Eveready  Radio  Batteries  are 
made  in  different  sizes  and  types 
• — so  that  every  radio  user  can 
enjoy  the  economy  that  is  to  be 
had  by  fitting  exactly  the  right 
Eveready  Battery  to  his  receiver. 
For  owners  of  sets  with  five,  six, 
eight  or  more  tubes,  and  power 
amplifiers,  there  is  the  extra- 
large,  powerful  and  unusually 
long-lasting  Eveready  "B"  Bat- 
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Canadian  National  Carbon  Co.,  Limited 

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Radio  Batteries 

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Many  owners  of  receivers  already  had  in  their 
possession  the  old  Western  Electric  power  amplifier 
and  here  was  a  good  chance  to  incorporate  it  in  a 
receiver  of  the  highest  type. 

The  tapped  secondary  of  the  first  stage  presented 
an  opportunity  to  use  this  transformer  for  the  control 
of  volume  in  the  Roberts  receiver,  when  used  in  the 
audio-reflex  stage.  This  application  is  embodied  in 
the  circuit  diagram  Fig.  6. 

Naturally,  the  use  of  the  w.  E.-2i6-A  tubes  is  es- 
sential to  undistorted  output  inasmuch  as  the  use 
of  UV2O1A  tubes  with  the  Western  Electric  trans- 
formers would  be  a  poor  combination  resulting  some- 
what in  a  loss  in  volume  and  clarity  of  output. 

SCREW    THREADS    COMMONLY    USED    IN    RADIO 

THE  fan  who  makes  his  own  must  often 
rely  upon  the  data  contained  in  radio  pub- 
lications for  the  correct  sizes  of  drills,  taps  and 
screws,  to  use  in  the  assembly  and  general  con- 
struction of  his  receiver  and  other  radio  apparatus. 

Many  can  boast  of  a  steel  tap  and  drill  gauge  in 
their  collection  of  tools,  and  with  this  handy  adjunct 
to  the  constructor's  shop,  it  is  possible  at  a  glance  to 
know  the  proper  size  drill  to  be  used  by  merely 
inserting  the  screw  to  be  used  in  the  hole  in  the 
gauge  in  which  it  properly  fits. 

However,  not  all  have  these  gauges  and  so  in 
Fig.  7  is  shown  a  table  which  lists  the  screws  and 
threads  most  commonly  used  in  radio  apparatus 
construction,  with  the  corresponding  clearance  drill 
hole  sizes  and  tap  drill  sizes. 

The  column  on  the  left  lists  the  screw  sizes. 
The  center  column  shows  the  tap  drill  sizes  which 
naturally  are  smaller  than  the  clearance  holes, 
which  are  listed  in  the  last  column. 


SIZE  OF 
SCREW 

TAP  DRILL 
SIZE 

CLEARANCE 
DRILL  SIZE 

256 

48 

42 

3-48 

44 

37 

4-36 

41 

31 

540 

36 

29 

632 

33 

27 

732 

30 

22 

832 

28 

18 

9-32 

24 

13 

1032 

20 

9 

10-24 

23 

9 

11-24 

19 

3 

12-24 

15 

1 

1424 

6 

fc 

1420 

10 

k 

FIG.    7 

If  it  is  desired  to  tap  a  piece  of  brass  or  bakelite  for 
a  6-32  machine  screw  then  a  No.  33  drill  is  used. 

If  the  screw  is  to  be  used  to  clamp  two  pieces  to- 
gether, then  a  clearance  hole  is  drilled  to  allow  the 
screw  to  pass  through  and  into  the  hole  with  ease. 
In  this  instance  a  No.  27  would  be  used  for  the  drilling. 

Where  a  hole  to  be  threaded  does  not  go  through 
the  material  but  only  is  drilled  for  part  of  the  way, 
then  a  tap  having  a  blunt  end  with  a  uniform  diame- 
ter is  more  satisfactory  because  if  a  tapered  tap 
were  used  the  threading  would  not  be  complete  at  the 
bottom  of  the  hole.  Where  the  hole  does  go 
through,  then  a  tapered  drill  may  be  employed. 

I  n  all  tapping  operations,  only  work  the  tap  for  two 
or  three  threads,  working  it  back  and  forth  and  then 
remove  it  so  that  chips  or  dust  may  be  taken  out. 
Repeat  the  operation  which  will  insure  a  clean  thread. 


When  writing  to  the  Grid,  please  use  the  blank  printed  below. 


GRID  INQUIRY  BLANK 
Editor,  The  Grid, 

RADIO  BROADCAST, 

Garden  City,  Njew  Tor\. 
Dear  Sir: 

Attached  please  find  a  sheet  containing  questions  upon  which  \indly  give  me  fullest 
possible  information.     I  enclose  a  stamped  return  envelope. 

(Chec}{  the  proper  square) 

CD  I  am  a  subscriber  to  RADIO  BROADCAST.     Information  is  to  be  supplied  to  me  free 
of  charge. 

CH  I  am  not  a  subscriber.    I  enclose  $1  to  cover  costs  of  a  letter  answering  my  questions. 


My  name  is . 


My  address  is. 

G.  O. 


INDEX 


(*  Illustrated  Articles.    Editorials  in  Italics) 


//DVERTISING,   Reform   Is  Needed   in 

-/?  Radio 490 

*All-Wave  Tuned  Radio  Frequency  Receiver, 

An  (Zeh  Bouck) 581 

Amateur  Can  Try  Radio  Pictures,  The 595 

Amateurs,  The  World  Conference  of 339 

American  Radio  Tubes,  There  Are  So  Few ....  339 

*Among  Our  Authors 116 

*And  Now — The  Radio  Lighthouse  (James  C. 

Young) 719 

*As  the  Broadcaster  Sees  It  (Carl  Dreher) 

74,  229,  350,  500,  610,  761 

Associated  Press  Recognizes  Broadcasting,  The.  337 
*Audio    Amplification,     Some    Remarks    on 

(George  C.  Crom,  Jr.) 745 

*OEAM  Stations  Revolutionize  Radio?  Will 

-D  (Guglielmo  Marconi) 323 

Better  Receiver  Contest,  The 250 

"Bootleg"  Tube?     What  Is  a 335 

Broadcast  Licenses  Should  Be  Granted  Only  on 

Petition 38 

Broadcast  Situation,  The  Tangled 201 

*Broadcast  Stations  Interfere,  When  (C.  B. 

Jolliffe)  586 

Broadcast  Wave  Is  Best?  What .595 

*Broadcasting,  How  the  Government  Is  Reg- 
ulating Radio  (R.  S.  McBride) 27 

*Broadcasting  in  England,  The  Story  of  (F.  J. 

Brown) 175 

Broadcasting,  The  Associated  Press  Recognizes .  337 

Broadcasting,  The  News  Value  of 736 

/^ AN ADA  Showing  Us  the  Way?  Is 738 

^  Channel  Cable?  Where  Is  the 741 

*Chemical  Plate  Supply  Units,  Notes  On 

(James  Millen) 774 

*Coils  and  Condensers  (By  the  Laboratory 

Staff) 524 

*Coils,  How  to  Design  Radio  (Homer  S.  Davis)  46 

Contest,  The  Better  Receiver 250 

Crime  of  a  Radio  Manufacturer,  The 335 

*Cutting  Down  Spark  Interference  on  the 

Great  Lakes  (Corley  W.  Kirby) 590 

A  Y  of  Good  Music,  The.  .                 42 

Distance  Fiend,  The  (A.  H.  Folwell) ....  35 
*Do    Weather   Conditions    Influence   Radio? 

(Eugene  Van  Cleef) 90 

T7  LECTRICAL  Exports  Are  Increasing 207 

J-*  *England,  The  Story  of  Broadcasting  in 

(F.  J.  Brown) 175 

"Ethics"  in  Radio.  .                 599 


F 


I RST  Presidential  Radio  Inaugural,  The..       37 
*For  the  Radio  Beginner:   (Zeh  Bouck) 
Adding    a    Bulb    to    the    Beginner's 
Crystal  Set 492 


Construction    of    a    Simple    Audio- 

Frequency  Amplifier,  The  .........  795 

Fundamental  Ideas  Behind  the  Vacuum 

Tube  .  ..........................  797 

How  to  Build  the  R.  B.  One-Tube 

Knock-Out  Receiver  .........  ....  623 

How  to  Make  a  Receiver  for  $1.82  ...  366 
How  to  Make  a  Simple  Low-Loss 

Coil  ............................  372 

Radio  Terms  Denned  .......  497,  631,  801 

References  to  Good  Radio  Text 

Books  ..............  ......  496,631,801 

Vacuum  Tube  As  An  Amplifier,  The  628 

What  "  Detection  "  Means  ..........  494 

frauds  in  Manufacturing  ...................  597 

*From  Figures  to  Fame  (Myra  May.)  ........  451 


,  The: 
Adding  R.  F.  Amplification  to   Re- 

generative Receivers  ......  .......  107 

Adding  Regeneration  to  the  Neutro- 

dyne  ...........................  812 

Audio    Amplifier    Circuits    for    the 

Roberts  Receiver  ................  108 

Audio  Transformer  Markings  ........  110 

Charging  A  and  B  Batteries  .........  811 

Code  Instruction  ...................  548 

Coil  Winding  Chart  for  Calculating 

Capacity,  The  ...................  276 

College  Radio  Correspondence  Courses  108 

Corrected  Dimensions.  ....'..'  ........  278 

Crystal  Receiver,  A  Good  ...........  668 

Four-Tube  Crystal   Reflex   Receiver, 

The  ............................  414 

Ground,  A  Good  ...................  666 

High  Mu  Receiver  Versus  the  Rob- 

erts Knockout,   The  .............  412 

How  a  Detector  Tube  "Detects  "  ____  272 

Home  Made  Coils  for  the  Roberts  Re- 

ceiver ..........................  540 

How  to  Charge  B  Batteries  from  A.  C.  542 

How  to  Compare  Loud  Speakers  .....  666 

How  to  Tell  the  Condition  of  Vacuum 

Tubes  ..........................  664 

Impedance-Coupled    Audio    Amplifi- 

cation ..........................  276 

Lynch  Lead,  The  ..................  418 

Making  Transformers  for  the  Super- 

Het  ............................  668 

Meters  and  B  Batteries  .............  107 

Needed   Reform   in   Radio  Standard 

Practise  ........................  546 

Neutrodyne  Circuit,  A  ..............  416 

Notes  on  the  Roberts  Circuit  ........  112 

On  Matching  and  Unmatching  Tubes  672 

Receiver  Renovation  ...............  810 

Resistance  Coupling  in  the  Roberts 

Knockout  .......................  812 

Rheostat  Location  .  .  542 


INDEX— Continued 


Roberts  Neutralization  Method  Ap- 
plied to  the  Neutrodyne,  The 542 

Screw   Threads   Commonly   Used   in 

Radio 816 

Selecting  a  Storage  Battery 412 

Something  About  Loops 411 

Staining  and  Polishing  Cabinets 276 

Three-Tube     Double     Reflexed     Re- 
ceiver, A 668 

Tools  for  Radio  Construction 416 

Toroids  for  Neutrodynes 670 

Transmitter-Receiver  Circuit,  A 544 

Tube  Protector,  A 276 

Western    Electric    Push-Pull    Trans- 
formers   814 

What  Wavelength  Means 411 

Why   the   Hanscom   "Super"   Won't 

Oscillate  on  Low  Waves 544 

*Guiding  the  Good  Ship  Radio:  An  Inter- 
view with  W.  D.  Terrell  (Dwight  K. 

Tripp) 743 

T7IGH  Commissioner?  Does  Radio  Need  a  489 
JL 1  *High  Radio  Adventure  on  Short  Waves 

(Keith  Henney) 789 

Horizontally  Polarized  Wave,  The 732 

*How  the  Government  Is  Regulating  Radio 

Broadcasting  (R.  S.  McBride) 27 

How  the  League  cf  Nations  Aids  Radio 735 

How  the  Propagandists  Work  in  Radio 332 

*How  to  Be  a  Good  Radio  Neighbor  (Hogan- 

Goldsmith) 359 

*How  to  Build  a  Two-Stage  Detector-Ampli- 
fier Unit  (John  B.  Brennan) 458 

*How  to  Build  a  Two-Stage  Radio-Frequency 

Amplifier  (John  B.  Brennan) 49 

*How  to  Build  Radio  Broadcast's  Phonograph 

Receiver  (Arthur  H.  Lynch) 393 

*How  to  Design  Radio  Coils  (Homer  Davis)  46 
*How  to  Judge  Radio  Tubes  (The  Laboratory 

Staff) 802 

*How  to  Make  a  Chemical  Plate  Supply  Unit 

(James  Millen) 220 

*How  to  Make  a  Universal  Battery  Charger 

(Roland  F.  Beers) 640 

*How  to  Solder  (William  F.  Crosby) % 

IMPORTANT  Announcement . .  112 
"IntheR.  B.  Lab.: 

Better  Loud  Speaker  Connection,  A. .  241 

Building  Your  Own  Lab 73 

How  to  Record  Radio  Signals 68 

Improved  Knockout  Amplifier,  An. .  240 

Shooting  Trouble 70,  239 

Simultaneous  or  Tandem  Tuning ....  236 

Unique  Loop,  A 242 

In  Which  Some  Discrepancies  Are  Cleared  Up  759 

Increasing  Use  of  Short  Waves,  The 593 

induction  Loud  Speaker,  An  (C.  W.  Hewlett)  508 
Interesting  Things  Interestingly  Said 

44,  207,  341,  491,  603,  742 

Is  Canada  Showing  Us  the  Way? 738 

*Is  the  Radio  Newspaper  Next?  (James  C. 

Young) 575 

LATEST      Alterations      in      Broadcasting 

Wavelengths 99 

League  of  Nations  Aids  Radio,  How  the 735 

"Lighthouse,  And  Now — The  Radio  (James  C. 

Young) 719 

listeners'  Point  of  View,  The  (Jennie  Irene 
Mix) 62,  213 


*Listeners'  Point  of  View,  The  (Kingsley 
Welles) 469,  632,  751 

*"Low  Losser",  A  Fifteen  Dollar  C  W  (C.  S. 
Mundt) 658 

*A /TAKING    a    "Super-Het"    from    Your 
1VJL       Neutrodyne    or    Single-Circuit    Set 

(A.  O'Connor) 516 

*Making    Radio    Receivers    More    Selective 

(Keith  Henney) 189 

Making  Radio  Transmission  Surer 42 

*Making  Your  Receiver  a  Super-Heterodyne 

(A.  O'Connor) 254 

*March  of  Radio,  The  (J.  H.  Morecroft) 

36,  198,  332,  483,  593,  732 

Meaning  of  the  Star,  The 94 

*Method  of  Radio-Frequency  Amplification, 

A  New  (C.  L.  Farrand) 387 

*Method  of  Transmitting  Pictures  by  Wire  or 

Radio,  A  New  (Charles  C.  Henry) 19 

Mr.  Sarnoff  As  An  Optimist 44 

Misuse  of  a  Municipal  Broadcast  Station,  The      739 

Month  in  Radio,  The 202,  340,  738 

*More  About  Radio  Broadcast's  Phonograph 

Receiver  (Arthur  H.  Lynch) 529 

More  Facts  About  Radio  Transmission 205 

Music  Publishers  Oppose  Broadcasting,  The . .       602 

\TAVY  Establishes  an  Amateur  Radio  Re- 

JM       serve,   The 202 

*New   Developments  and  Experiments  with 

Receivers  (Keith  Henney) 725 

*New  Equipment: 

Acme  Battery  Charger 420 

Amplion  Loud  Speaker 114 

Andrews     Paddlewheel     Coil,     The 

(Radio  Units,  Inc.) 114 

"Ballgrip"    Binding    Post     (Quality 

Moulded  Products) 280 

"Ballgrip"  Socket  (Quality  Moulded 

Products) 114 

Belden  Loop  Wire 280 

Bradleydenser 420 

Erla    Rheostat    (Electrical    Research 

Laboratories) 420 

Hercules  Aerial  Mast  (S.  W.  Hull  & 

Co.) 420 

Kellogg  Condenser 114 

Kellogg  Reproducer 280 

Sangamo  Fixed  Condensers 420 

See-Ess  Winder  (Wireless  Electric  Co.)     280 
Toggle  Battery  Switch  (Cutler-Ham- 
mer Mfg.  Co.) 114 

Velvet  Vernier  Dial  (National  Co.) ...     280 
*New  Fashions  in  Radio  Programs  (James  C. 

Young) 84 

*New  Method  of  Radio-Frequency  Amplifica- 
tion, A  (C.  L.  Farrand) 387 

*New  Paths  for  the  Short  Waves  (Kenneth 

Bolles) Ic3 

New  Size  of  "Radio  Broadcast"  for  Novem- 
ber, The 787 

News  Value  of  Broadcasting,  The 736 

*Notes    on    Chemical    Plate    Supply    Units 

(James  Millen) 774 

*"Now,  I  Have  Found": 

Alternating  Current  as  a    Source  of 

Filament  Supply  (J.  B.  Clothier,  Jr.)     103 
Automatic  Potentiometer  Cut-Out,  An 

(K.  W.  Root) 661 

Coil  Mount  for  the  Roberts  Coil,  A 
(H.  Batchelder) 407 


INDEX— Continued 


Convenient  Mounting  Strip,  A  (Harry 
W.  Gilliam) 104 

Crystal  Detector,  A  Handy  (Frank 
Master) : 663 

Determining  the  Polarity  of  a  Battery 
with  a  Potato  (L.  B.  Robbins) 410 

Dull  Finish  for  Panels  (Harry  W. 
Gilliam) 106 

Fifteen  Dollar  CW  "Low  Losser."  A 
(C.  S.  Mundt) 658 

Filter  Condenser.  A  Good  (C.  E. 
Seifert) 105 

Four-Tube  Roberts  Receiver,  A  (H. 
Q.  Horneij) 406 

Helps  for  Constructors  (John  V. 
Frederick) 537 

How  to  Make  a  Low  Melting  Point 

Solder  (G.  D.  Robinson) 407 

Making  a  Neutralizing  Condenser 
(Carl  Roberson) 662 

Making  Hard  Rubber  Spiderwebs  for 
the  Roberts  Set  (Wayland  S. 
Bailey) 539 

Making  Your  Own  Cabinet  (Welsford 
A.  West) 106 

Method  of  Scraping  Wires,  A  (W.  H. 
Mayfield) 808 

Neutralizing  the  Roberts  Knock-Out 
(M.  B.  Whitney) 535 

Oscillator  in  Your  Super-Heterodyne, 
The  (F.  W.  Hutton) 408 

Phone  Circuit  Test,  A  (L.  T.  Phelan)      409 

Radio  Lightning  Arrestor  Made  from 
Spark  Plug  (L.  B.  Robbins) 538 

Rheostats  and  Verniers  Controlled 
with  Horizontal  Dials  (J.  T.  Carver)  538 

Safe  Homemade  B  Substitute  Using 
110  Volts  A.  C.,  A  (James  B. 
Hayes) 537 

Screw  Starter,  A 103 

Self-Supporting  "D"  Coil,  A  (Her- 
man M.  Partridge) 808 

Seven  Construction  Ideas  (F.  L.  An- 
derson)    662 

Simple  and  Efficient  Form  for  Wind- 
ing Your  Own  Coils,  A  (Ralph 
Palmer) . 536 

Simple  Solution  to  Problem  in  An- 
tenna Construction,  A  (H.  A.  High- 
stone)  807 

Single  Bearing  for  Rotor  Coils,  A 
Good  (Gerald  Gray) 663 

Tickler  Kink  for  the  Roberts,  A  (J. 
Bell) 106 

Tool  to  Drill  Holes  in  Glass,  A  (C.  J. 
Eisen) 661 

Tube  Life-Saver,  A  (W.  H.  Mayfield)      808 

Two  Shop  Tricks  (Welsford  A.  West)      660 

When  Working  Bakelite  (Carl  Pen- 
ther) 106 

*^VBITUARY  Notice  of  Miss  Jennie  Irene 

\J      Mix 343 

On  Our  Birthday 82 

""Operating  Your  Radiating  Receiver  Without 
Squeals  (Alfred  N.  Goldsmith) 363 

*PHONOGRAPH  Receiver,   Radio  Broad- 
cast's (Arthur  H.  Lynch) 263 

*Programs,  New  Fashions  in  Radio  (James  C.  . 

Young) 84 

Progress   of   International   Broadcasting,    The     204 


nADIO  a  la  Carte 3g 

-A.  Radio  Broadcast 's  Phonograph  Receiver : 
*How    to    Build    Radio    Broadcast's 
Phonograph   Receiver   (Arthur  H. 

Lynch) 393 

*More  About  Radio  Broadcast's  Pho- 
nograph    Receiver     (Arthur     H. 

Lynch) 529 

*  Radio  Broadcast's  Phonograph  Re- 
ceiver (Arthur  H.  Lynch) 263 

Radio  Broadcast's  Phonograph  Receiver  489 

Radio  Comes  to  the  Russian 594 

Radio  Conference  Postponed?    Why  Is  the  602 

Radio  Corporation  Announces  a  Deficit,   The  741 

Radio  Dispute  in  Cincinnati 41 

Radio  in  Foreign  Countries 737 

*Radio  Newspaper  Next?  Is  the  (James  C. 

Young) ;..  575 

*Radio's  Part  in  the  Sargasso  Sea  Expedition 

(Alfred  M.  Caddell) 209 

Radio  Quality  Will  Count 40 

Radio  Receiver  of  the  Victor  Company,  The. .  . .  487 

Radio  Service  Needs  Money,  The 598 

Radio  Sets  Must  Meet  the  Claims  Made  for 

Them 337 

Radio  Situation  in  South  America,  Thz 596 

Radio,  the  Handmaiden  of  Explorers 733 

*Radio-Frequency     Amplification,     A     New 

Method  of  (C.  L.  Farrand) 387 

Receiving  Is  Good  in  California 596 

"Revelations  of  Enoch,  The  (W.  R.  Bradford)  100 
*Revolution   in   the   Art   of  Teaching,    The 

(Frederick  P.  Mayer) 477 

*QHALL  I   Run  My  Set  from  the  Lamp 

O      Socket?  (Laboratory  Staff) 651 

*Short  Waves,  New  Paths  for  the  (Kenneth 

Bolles) 183 

Short  Waves,  The  Increasing  Use  of 593 

*Single-Control    for   Your   Present    Receiver 

(Allan  T.  Hanscom) 781 

"Single-Control  Receiver,  A  (C.  L.  Farrand)        620 
*Some  Facts  About  Sound  Waves  (B.  F.  Mies- 

sner) 243 

*Some     Remarks    on    Audio    Amplification 

(George  C.  Crom,  Jr.) 745 

*Super-Autodyne,  The  (McMurdo  Silver).  ...     334 
Super-Heterodyne : 

*Making  a  "Super-Het"  from  Your 
Neutrodyne   or   Single-Circuit  Set 

(A.  O'Connor) 516 

*Making    Your    Receiver    a    Super- 
Heterodyne  (A.  O'Connor) 254 

*Super-Autodyne,    The     (McMurdo 

Silver) 376 

Super-Power  Is  Almost  Here 334 

Supply  and  Demand  in  Radio 598 

""TVAKE  Your  Radio   Set   to  the  Country!  252 

J-    Tangled  Broadcast  Situation,  The 201 

There  Are  So  Few  American  Radio  Tubes 339 

Transatlantic  Telephony  Is  Not  Yet 204 

Transmitting  Pictures  by  Wire  or  Radio,  A 

New  Method  (Charles  C.  Henry) .  1 19 

*T  TNIVERSAL   Battery   Charger,  How  to 
^       Makea  (Roland  F.  Beers) 640 

T/'ACUUM  Tubes  in  Another  Legal  Tangle  41 
r       Victor  Company  Joins  the  Radio  Ranks, 

The 338 

Victor  Company,    The  Radio  Receiver  of  the  487 


INDEX— Continued 


WAVELENGTH    or    Frequency— Which? 

(J.  H.  Morecroft) 498 

We  Need  More  Delicacy  in  Radio  Advertising  206 

"  Weeding  Out "  in  the  Radio  Trade 736 

*What  Are  the  Royal  Roads  to  Radio?    (Keith 

Henney) 344 

What  Broadcast  Wave  is  Best? 595 

What  Does  the  New  Allocation  of  Broadcast 

Wavelengths  Mean? 36 

What  Is  a  "Bootleg"  Tube? 335 

What  Is  the  Radio  Receiver  of  To-morrow? ....  485 
*What  Is  to  Become  of  the  Home  Constructor? 

(Keith  Henney) 604 

What  Membership  in  the  Institute  of  Radio 

Engineers  Means 37 

What  Our  Readers  Write  Us 374 

What  the  Radio  Corporation  did  in  1924 43 

*When  Broadcast  Stations  Interfere   (C.  B. 

Jolliffe) 586 

When  Great  Men  Speak  of  Radio 488 

When  Radio  Aided  Politics 200 

When  Trains  Are  Run  by  Radio 204 

Where  Is  the  Channel  Cable? 741 

Who  Will  Protect  the  Radio  Listener? 597 

Why  Does  Congress  Refuse  to  Broadcast  Its 

Proceedings? 198 

Why  the  Radio  Industry  Will  Not  Be  Revolu- 
tionized    483 

*Why  Your  Receiver  Squeals   (John  V.   L. 

Hogan) 359 

*Will   Beam   Stations  Revolutionize   Radio? 

(Guglielmo  Marconi) 323 

Will  the  British  Receiver  License  System  Fail?  39 

Wireless  Vision  Achieved 205 

Work  for  Hcover's  Third  Radio  Conference ....  340 

World  Conference  of  Amateurs.  The 339 


PORTRAITS 
(*Portraits  in  "The  March  of  Radio") 

*Alexanderson,  E.  F.  W..  .  44 

*Allen,  G.  Y 208 

Allen,  Ida  Bailey 633 

Anderson,  Carl 635 

*Baldwin,  Stanley .  .  739 

Beebe,  William 210 

Belin,  Edouard 595 

Bellows,  H.  A 601 

Bowman,  John  G 481 

Brard,  Magdeline 66 

Breen,  May  Singhi 473 

Brennan,  John  B 252 

Brown,  Marshall  S 64 

Burrows,  Arthur 598 

Campbell,  Howard  E. .  .  353 

Carson,  D.  B 33,  491 

Christiansen,  Red 86 

Clay,  Ten  Eyck 475 

*Corridon,  L.  A 734 

Crosby,  W.  F 116 

*Crosley,  Powel,  Jr 341 

Davies,  Marion 471 

Davis,  Stephen  B 31 

Dellinger,  J.  H ' 33 

De  Luca,  Giuseppe 230 

De  Rose,  Peter 473 

*Downey,  W.  E 339 


Eccles,  William  H 228 

Elder,  James  A.  M 602 

Farrand,  C.  L. .  .  .  390 

*Foster,  Robert  M 489 

Ganz,  Rudolph 753 

*Gerhard,  Anthony 204 

*Gilbert,  J.  C 490 

Goldman,  Edwin  Franko 634 

Greene,  Roseline 65 

Hazeltine,  Louis  Alan.  .  .  .451,  453,  455 

Henry,  C.  C 116 

Hill,  Luke 216 

Holman,  John 67 

Hoover,  Herbert 31 

*Jewett,  Edward  H 741 

*Kellaway,  F.  G 737 

Knecht,  Joseph 62 

*Latour,  Marius  C.  A 207 

McDonald,  E.  F.,  Jr 718 

MacMillan,   Donald 718 

Marconi,  Guglielmo 325 

Mix,  Jennie  Irene 343 

*Molinari,  Bartholomew 186 

Novak,  Joe 756 

Philput,  Mary  F 479 

Pinto,  Anna 63 

Rassouchine,  Vladimir 213 

Reinartz,  John  L 185,  718 

Reiner,  Fritz 469,  753 

*Reith,  J.  C 737 

*Rice,  Martin  P 45 

*Rogers,  J.  Harris 42 

Ross,  Nellie  Taylor 470 

Sarnoff,  David 32 

Sayler,  Oliver 751 

Schneider,  Bennett  B 637 

Schnell,  F.  H 186 

*Shaw,  George  Bernard 206 

Skrznski,  Alexander 754 

*Smith,  Alfred  E 632,  740 

*Smythe,  Joseph  C 204 

Sokoloff,  Nikolai 753 

Steele,  George 718 

Stern,  Florence 219 

Stevens,  A.  W 342 

Summers,  Lola 67 

Taylor,  A.  Hoyt.  .  599 

Terrell,  W.  D 743 

Turner,  Fred  J 638 

Van  Cleef,  Eugene 116 

Van  Hoogstraten,  Willem 753 

*Weagant,  Roy  A 39 

AUTHORS 

Anderson,  F.  1 661 

Bailey,  Wayland  S. .                    539 

Batchelder,  H 407 


INDEX— Continued 


Beers,  Roland  F 640 

Bell,  J 106 

Bolles,  Kenneth 183 

Bouck,  Zeh 366,  492,  581,  623,  795 

Bradford,  W.  R 100 

Brennan,  John  B 49,  458 

Brown,  F.  J 175 

Caddell,  Alfred  M..  .  209 

Clothier,  J.  B.,  Jr 102 

Crom,  George  C.,  Jr 745 

Crosby,  W.  F 96 

Davis,  Homer  S 46 

Dreher,  Carl 74,  229,  350,  500,  610,  761 


Eisen,  C.  J. 


661 


Farrand,  C.  L. .  .  .  387,  620 

Folwell,  A.  H 35 

Frederick,  John  V 536 

Carver,  J.  T..  ..  538 

Gilliam,  Harry  W 104,  106 

Goldsmith,  Alfred  N 363 

Gray,  Gerald 663 

Hanscom,  Allan  T 781 

Hayes,  James  B 537 

Henney,  Keith 189,  344,  604,  725,  789 

Henry,  Charles  C 18 

Hewlett,  C.  W 508 

Hogan,  J.  V.  L 359 

Horneij,  H.  Q 406 

Hutton,  F.  W 409 


Kirby,  Corley  W 590 

Lynch,  Arthur  H 82,  263,  393,  529 

McBride,  R.  S 29 

Marconi,  Guglielmo 323 

May,  Myra 451 

Mayer,  Fredtrick  P 477 

Meister,  Frank 663 

Miessner,  B.  F 243 

Millen,  James 220.  774 

Mix,  Jennie  Irene 62,  213 

Morecorft,  J.  H 36,  198,  332,  483,  498,  593,  732 

Mundt,  C.  S 660 

O'Connor,  A 254,  516 

Palmer,  Ralph. ...  536 

Penther,  Carl 106 

Phelan,  L.  T 410 

Robbins,  L.  B 410,  538 

Roberson,  Carl 662 

Robinson,  G.  D 408 

Root,  K.  W 661 

Seifert,  C.  E 104 

Silver,   McMurdo 376 

Tripp,  Dwight  K 743 

Van  Cleef ,  Eugene 90 

Welles,  Kingsley . .  . .  469,  632,  751 

West,  Welsford  A 106,  660 

Whitney,  M.  B 535 


Jolliffe,  C.  B 586     Young,  James  C. 


.83,  575,  719 


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All  circuits,  resistors,  and  condensers 
are  securely  soldered  within  the  base, 
leaving  no  exposed  part*. 

Another  outstanding  feature  is  the  use 
of  Bradleyunits  (Molded  Resistors) 
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Instead  of  passing  the  incoming  sig- 
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it  through  two  of  the  three  tubes  several 
times,  each  time  building  up  its  strength 
and  adding  to  its  volume. 

Even  the  technically  uninitiated  can 
see  the  advantages :  simplicity  instead  of 
complexity;  fewer  dials  to  adjust; 
sharper  accuracy  in  selecting  stations; 
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This  simplicity  of  design  combined 
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under  the  most  exacting  conditions  and 
you  will  understand  why  it  represents  a 
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Crosley  manufactures  receiving  sets  which  are  licensed  under 
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BETTER-      COSTS        LESS 
THE  CROSLEY  RADIO  CORPORATION  CINCINNATI,  OHIOJ 

•^  Tested  and  approved  by  RADIO  BROADCAST  if 


THE  COUNTRY  LIFE  PRESS,   GARUKN   CITY,   NEW  YORK