u THE ELECTRICAL IJIT/ENTIOWS OF Dl. JAI-ffiS liARHIS HOGERS OF HYATTSVILLl^;:' A thesis prepared by Edwri.rd Ellesmere McKeige as part of his initiation into Phi Mu, the Honorary Sngineering Fraternity of the University of Maryland. Aaril 50, 1925, Dr. ■Rosters and his transmitter that has been heard in Europe. Note the corrugated iron sheath- ing on the walla to exclude ether waves. -1- THE ^L'RCTRICAL IICVENTIONS OF DR. JAJvES MRHIS HOGE:^ OF HYATTSVILIiS In his picturesque old mansion at Hyattsville, Dr. Ja^ies Harris Rogers continues ^ despite advancing years, to co'ivert the ideas of his fertile brain into lasting "benefits to mankind. From boyhood until toda7/ he has never ceased to be active and origi- nal. In the course of his life he has been granted well over firty patents. ■While still a young man he attracted so much attention that he vreis made the chief electrician of the Capitol building at ''(Vashington, It vr&s while he held this position that several of his inventions Vfere made. ELECTRIC LIGHT Probably his earliest development was a form of electric arc light. Although the arc light was not invented by Dr. Rogers his improvement was a great step in its development. This light was in- stalled on the Capitol dome and on Nev/ Year's Eves it was played up and down Pennsylvania Avenue on the crov/ds that gathered to witness the strange spectacle of electric light. THE T^KmiOTRLE IffiTER Another invention perfected during his stay at the Capi- tol was the "Thermotele Meter." This device was used for indicating the temperature in different parts of the building to the operators in the engine room. Forinerly, messenger boys v/ere employed to make the rounds and note the temperatures. With the new systen, however. -2- the operation of a selective switch indicated anjf teinperature in the building. The device consisted of a column of mercur;;' which tipon ex- panding and contracting changed the resistance of an electric circuit. A voltmeter in the engine room calibrated in degrees of temperature, was used to determine the resistance of the circuits. By this method the temperature control of the great building was greatly facilitated, A SUBMARINE CABLE A submarine cable requiring no insulation is another inter esting development of thin genius. The C':ble consisted of two v.-ires, one of iron and one of copper. V/!ien these are immersed in v/ater they form a sort of battery. A key at one end of the cable could be oner- ated to short circuit this battery and there- by cut off the voltage at the other end. . A galvanometer at the receiving end indicates ¥/hen tjie key is open or closed. The symbols of the M^rse Code v;ere sent p.n this manner across the Hudson Hiver at New York. The system, however, proved unsatisfactory for long distances, due to the resistance of the Yidres cutting do^vn the short circuit effect. TELEPHOIfflS Dr. Hogers also did considerable T7ork in the early develop raent of telephones. As with the arc light his contributions to the telephone industry were stepping stones leading to the modern highly developed systems. C<»»e«- -T* TEiva*- fln uninsulated 5u bmarine cable . -3- THS PHIIITING TILEG^UPH Another interesting invention tha^. vtbls of great iitiportance in its time was the printing telegraph. Dr. Rof^ers dissected and an- alyzed the letters of the Homan alphabet and found that they could all be inade up of eight elenentary characters as shovm in the diagram. The receiving device consisted of a sort of si-iDle ti'-pevrriter with liffht keys ooerated by electro-roagnota. At first it would seem that nine wires Would be required between stations; one for each of the magnets and a common return. However, only one is used as will be ex- plained later. The first step in the transmission of a message ^vas the perforation of a tape. This was accomplished by an esoecially de- signed machine operated from a typev/riter. The tane vdth its per- forations passed on a metal roller under eight contact tips, V/hen a tserforation came under one of the tins it nmde contact vfxth the roller. An electric current flowed over the line and operated the corresponding man;net at the receiver, thereby printing one of the symbols. In order to save expense in the 2!^ "TTle 8Chciractef3. ^ECUEFilHIJ KLMNDFDR XTUVWXXZ IFie Telegraph fllphatoet. transmission line, Dr, Hogers originated a >'5ys- tem whereby the single line v/ire '^s transferred in suces- II *'. fc-o° f^ — L CjTQuffl Co»i»ec*i<»iS Datteiy , — Elemen'tary Corunec^a^y of FVin+i'n^ Te.(e<j/Qph -4- sion to each of the eight circuits. This ivas accomplished ty connecting the eight wires at each end to segments on a stationary ring or commu- tator. The line connection was led to a brush on a revolTing wheel which Wide contact v;ith each of the segments in succession. The next difficulty was to make the wheels at the sending and receiving stations to revolve in exact synchronism. If this did not occur the circuits would get mixed and ^fl wire at the sender might be connected to some other circuit at the receiver thereby spoiling the transmission. The method of obtaining synchronism is therefore the heart of the system. The machines are so built that when one r/heel reaches a certain position it causes a spark to occur at a small gap on the rin of the other wheel. Now if both wheels turn at exactly the same speed the spark will take place at the sf'.me point in each revolution and the spark will appear to be stationary. If the tvro wheels are not re- volving at equal rates the spark will occur before or after the point it occurred in the previous revolution and the spark appears to travel around the rim. The direction of this travel indicated to the operator whether his wheel is slow or fast and he regulates it accordingly. By this system one letter is transmitted per revolution of the wheel. It vfas found possible to send as ftist as two hundred words a minute, whereas the average telegraph operator can send only twenty. Other advantages were that strict secrecy of messages was obtained, as the only person vrho could possibly intercept one wb,s the tape puncher. Also it would be impossible for errors to occur, as transmission ivas entirely mechanical. -5- It is interesting that this printing telegraph, nlthough considered as one imrention is covered b;;- four patents. One covers the means of obtainine; synchronism, the second the tape perforating machine, the third the printing device, and the fourth the elect- rical carriage upon which the copy is printed at the receiver* In perfecting the system Dr. ^logers worked through eighteen years of hopes find disappointments until suoces was finally attained, A company was organized in 1895 to use this system, A line was successfully operated betvfeen Washington D. C. and Baltimore for some time. Although the system is not used today, Dr. Rogers' in- vention for attaining synchronism is employed in the transmission of pictures by radio. UNDERGROUITO HADIO The most important of Dr. Rogers' inventions is the under- ground radio. As far back as 1902, when Marconi sent his first message across the Atlantic it occurred to Dr. 'Rogers that the earth, not the air, was the conducting m-sdium that carried the impulses. To his mind it was much more logical that the earth, a conductor, carries these im- pulses than the air, w'-ich is an insulntor. After many years of experi- menting. Dr. Sogers now believes that, while some of the energy radiated by a transmitting antenna is propagated through the air as Hertzian t'lnaves the major portion of the energy reaching the receiver is due to the ground waves. Dr. Hogers altogether discredits the Heaviside theor;/. This Theory states that a height of about 100 kilometers there is a layer (known as the Heaviside layer) which will not carry the Hertzian "waveB -6- but reflects thera as a mirror reflects li^ht. The wavea are STipioaed to be reflected from the transinitting aerial, thus passing &• round the bul^e of the earth's crust. In the yUgvigJ^ Uayer -ft*"* daytime the wives do not reach ^"^ 'S<'<^'° ^^^^^ ^^"^ around +k«^ earrtiV curuatufe according += Hc^viside. the Heaviside surface as pfxrt of the air between it and the earth is ionized by the action of the sun. This is supposed to account for the non-reception of distant stations in the daytime. Fading is believed by Heaviside adherents to be due to changes in the shape of this layer sometimes focusing considerable energy on the receiving aerial and then again leaving it almost devoid of energy. Those v/ho do not belie"ve in the Heaviside theory say that this does not account for the difference in fading of t.70 stations in a straight line from the receiver. T'liS phenomenon laay be observed most any night by a listener-in. Dr, Sogers says that the v/aves propaf;ated by the aerio.l of the trans?nitter travel in straight lines through apace and the only iTay messages are heard for great distances around the earth's curvature is by ground waves. f Experiments bearing ^ i / •c,'*'^ out his beliefs have been conducted y^ \ j '^^o^^ in his laboratory -.vlth a oowerful receiver connected to a loop antenna. A well was constructed under the lab- — _-^ \// ^^^-si'ii-'^^ ^'i-iSitAc Wqw ^adio Waues gei- arourvi five -7- JTTTT- oratory and carefully shielded with metal on the top and for a short dis- tance down from the surface. This arrangement excludes all eners^y that might reach the well from the atmosphere. By letting the loop dovm into the well nany of the long wave European stations were heard, \Ihen the loop was removed from the well and placed in the room these stations could not be heard at all. This proved that ground waves are responsible for long distance reception, ^'^hen asked how the commercial stations receive these sig- nals, Dr. ^gers explained that it was done with an aerial and ground system, and that the ^roimd vraves were picked up by the .,roand connection, and that O^dcrgrcur^ Ifeception wiM a Locf? the aerial itself is of little, if any use at all, except in tuning the primary circuit. The existence of "dead spots" in radio coimunication may be explained by the underground theory. For instance, the dead s'jot l etiivoen Washington D, C. and Baltimore is probably due to the large deposits of iron ore between the cities. This tends, to absorb the energy of the ground waves which, if they do get through, are considerable weakened. In recent tests betaveen America, France and Warsaw, the speed of radio waves was calculated by exTDert engineers and scientists to be 165, OuO miles per second. The speed of waves in the ether is 186,000 miles per second. This fact is additional evidence that the atmosphere is not the medium for long distance communication. The use of underground radio practically eliminates fading and static, the two bug bears of ordinary reception, Ur. Rogers never -8- rec©iTr©s reports of "Q S S", or fadinff, from anateurs with vthon. he coinnnjni- cates by means of his station 5 X R. The system is also "very little effect- ed by daylight and dark, The ran^e of such a system compares very well v/ith other systems. In this country 3X H has been heard fro-' Maine to Georgia, and from the At- lantic to the ^pacific. Just recently came the v/ord that listeners-in in Fr-^^nce have also picked up Dr. i^ogers • station which used only -vory moder- ate powe r . The type of antenna used for both transmission and reception at 3 X S is a copper tube supported in a terra-cotta pipe. This pipe is buried with its top surface about a foot below the surface of the ground. The /^ 7^\ |} L ^ -TefTn-^rVt copper tube is supported in the center '^^'f of the pipe by ^yralin rods . The -an- — >/ tenna system used for short waves Um) consists of two such conductors 50 mm myM/Mm^j ^ ^^ ^^/^^/^/y^^^yy^^^^ ^ ^ feet long stretching in opposite "* ^ ^ "*" '^ ^ directions from the set. ^^*'^ ^^ Underground flhtenra. This type of antenna is very directional practically exclud- ing stations in a line perpendicular to its I'sngth. In order to receive from all directions another saitenna is used perpendicular to the first. These antennas may be used together vrhen listening for calls, thus re- ceiving equally well in all directions, or they may be used separately thus excluding possible interference by other stations. The reason for this directional effect is quite apparent. -9- Imagine a imve advancing through the gro\ind in the form of a huge circle, whose center is at the transmitter. ■P^ Station of firitennas After travelling any but the small- est distances. any portion of the ■wave is practically a straight line advancing perpendicular to its front. ?Jow if it strikes an antenna parallel to its front evei-y part of the antenna vlll have its potential chanp;ed the same amount and no current will flow, since a difference of potential is necessBry for the production oi' current. However, if the vmve first strikes one end of the antenna the potential of that end is changed with respect to the other, and a current flows which may be used to operate the receiver. ^ ^ Underground radio . — "T — Tras used by the American Army in France during the World War. Its effectiveness, both day and night, and the ease of construct- ing and concealing the antenna made it ideal for use in the trenches. The greatest value of the invention, however, is its use on sub- marines. Ur. Rotters discovered that the ground waves are equally as ef- fective in water. The problem, though, ivas to oerfect a t^/'pe of antenna that might be used under water. The ordinarj^ types failed because of the nearness of the metal hull and the current carrying capacity of s^lt ^*'»wc Front + D\recJiar,ai Eff<2ot of water. After trying many different types with no success the idea of -10- of making a loop antenna with ':h6 hull of the boat for one side vma tried. This plan was a great success and by means of it subnorines vrere able to transmit and receive messages while sub- merged, a fset Drev- ronn«^""> ■h, Kui/ — ^ iously declared irn- possible, Vath this Ihe Submarirre flntenna. arrangement a submarine submerged off the American coast heard the German station at Nauen. One of the naval officers who ■wss prominent in the testing of this device stated that in fresh water the subnerged antenna would v/ork at any depth. In salt vraterj hovrever, at a depth of 20 feet, only the longer ivaves above 10,000 meters could be heard. The shorter waves could be received by decreasing the depth. Many Kavy Stations used the underground and undersea system during the war. At Belmar, New Jersey .during most of the 7far, six oper- ators ivere constantly "listening in" and receiving messaf!;es from the Allied stations in Surope, Soraetioes even the German official reports on battles and submarine operations were heard, Dr, Rogers unhesitatingly lent his inventions to the Navy during the war, even before he had patented some of them. The submarine antenna system was one of these. About this invention a long legal battle was fought between Dr. iiogers and certain departments of the government vrhich tried to defraud him of his invention as a result of its not having been patented. At gre^t e:xpense to hiiself , Dr, Hogers finally won his case after yee,r3 of legnl fighting. . -11- TH5 ROGERS LOOP . The latest imrention of this genius is also in the radio line. It is a loop antenna of great efficieno;^/' and selectivity. In amateur radio circles the success of the "cage" antennn is well knovm. This t;'/pe of an- tenna is a single conductor made up of a number of parallel wires, usually arranged to resemble a long sqiiir'rel cage. The principal advantafre of this antenna is its lov/ ohmic resistance, due to th© parallel connection of a number of v/ires. Dr. Hogers reasoned that this principal could well be apolied to the loop antenna. The result of his reasoning is the Rogers Loop, which is the ultimate in loop antennas. The Cage ^nt-env^a. This device consists of ten turns of a conductor made up of ten vares. These wires are supported from a six spoke wooden frane by pyralin disks, with holes bored for t-ie individual wires. In a receiving set, especially, low resistance of the circuits is an absolute necessity to sharp tuning, and loud signals. Hence the Rogers Loop, with its low resistance is ideal for recep- tion. The Rogers Loop, -12- HOKOHS Dr. Hogers received the degree of Doctor of Science from the Maryland State College in recognition of his ftchievements. He vms elected to the lAiryland Acaderr^y of Sciences in 1919, In 1920 he received an es- pecial vote of thanks from the General Assembly of >/iaryland for his notable achievements during the war. His work vf&s at one time before the Nobol Comraiasion in Stockholm, However, it did not see fit to make him any aw^rd. Dr, Hogers' says that he orizes the thanks of the Ida ry land Assembly more highly than he would a Nobel Prize. Thus his patriotism for Mar^^land is shown. It has been related how he gave up his inventions to the Wavy during the war vdthout even patenting them. This is proof of his great patriotism for his country ^ In view of his pride in his Co'iontry and State, it is only fitting that they should be proud of him, Maryland may indeed honor this inventor who has brought her fame and honor and the nane of Janes Harris Hogers will go dovm in History with Carroll and Howard and "all her slurob'rers with the just," NOTE: All the material used in this thesis wff.s obtained directly from Dr. Rop;ers himself. As far as I know there is little material available on this subject at the present outside of patent office records.