engineering & manufacturing...that translate experience into action. back in 1934, for exam-ple,...
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JULY
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* Edited by M
. B. S
leeper *
a zeta& jot idling. ekiadtzi ;cut.IN peacetime, the ability
to deliver required re-sults quickly saves money.In wartime, this abilitysaves lives!
REL has the engineeringknow-how, backed by lab-oratory equipment andmanufacturing facilitiesthat translate experienceinto action.
Back in 1934, for exam-ple, when other manufac-turers were declaring that2 -way police communica-tion was impractical, RELwas producing and install-
ing 2 -way mobile equip-ment.
In 1940, while otherswere wondering if it couldbe done, REL built andinstalled the first of a seriesof 50 -kw. FM transmitters.Up to the present time, noother company has deliv-ered a single FM transmitterof more than 10 kw. output.
Repeatedly, under Warconditions, REL has beencalled upon by the U. S.and allied governments toperform unusual servicesbecause "REL has a knack
for getting results fast."Every man in this organ-
ization is doing his utmostto maintain this reputationin the service of our ArmedForces.
RADIO ENGINEERING LABS., Inc.Long Island City New York
Sales Offices:5334 Hollywood Blvd., Hollywood, California2040 Grand River Ave. W., Detroit, Michigan
310 Fifteenth St., Denver, Colorado
,171eSSAge -And anexplanation to the readersof this publication:
LAST SPRING, THE EXIGEN-cies of War activities delayed thepublication date of this Magazine.I regret any inconvenience orconfusion that this has caused.
The delay resulted from takingon additional responsibilitiesconcerned with the War effort,and from the need of readjust-ments such as almost every engi-neer has had to make who isengaged in the development andproduction of military radioequipment.
It would have been easier todelegate the work of editing thispublication to someone else forthe duration of the War. How-ever, I felt that a radio -electronicpaper, published in the service ofengineers and executives engagedin wartime radio activities, re-
quired an editor who possessed an
understanding of what is going onin the industry from actually par-ticipating in it himself.
Much of the most interestingmaterial cannot be publishednow, because of military limita-tions, but someone in the positionof an outsider, forbidden to passthe doors marked Visitors NotAllowed, would be at a loss tosecure permitted material of inter-est to the readers of this Journal.
In order to reestablish the regu-lar publication date, this issue,mailed on August 20th, has beenindicated as the July -August num-ber. The September issue will bemailed on September 20th, andthis date of issue will be main-tained in the future. Every sub-scription will be extended oneadditional- month.
M. B. SLEEPER
RADIO -ELECTRONIC ENGINEERING 86 DESIGN
1
AA'WHETHER you are interested in
Industrial Rectifiers from 1 volt
to 250,000 volts and from 1 Mato 2,500 Amps
OR if you are interested in
small transformers in our Ultra -Compact, Ouncer or Sub-Ouncertypes (our smallest units weigh only
one-third ounce)
OR if you require high powertransformer equipment for a 500Kw. transmitter
OR an industrial application ora special Varitran or VoltageRegulator to suit a specific re-quirement
F.
WAVEVA RI TR AN
MAY WE ASSIST YOU IN YOUR PROBLEM?A note to our Engineering Division will bring a quickresponse with details on units to your requirements.
EXPORT DIVISION: 100 VARICK STREET NEW YORK. N. Y. CABLES: 'ARLAI"
RADIO -ELECTRONIC
ENGINEERING &DESIGNCOMBINED WITH: APPLIED ELECTRONIC ENGINEERING
VOL. 2 JULY -AUGUST, 1942COPYRIGHT 1912, M. B. SLEEPER
CONTENTS
NO. 9
WFIL HELPS NAVY APPLICANTSLieu.. Arnold Nygren, U.S.N.R. S
HIGH -FREQUENCY IRON CORES, Part 1
Austin C. Lescarboura 7
SHORT-RANGE FM EQUIPMENTFrederick T. Budelman 10
SPOT NEWSItems and Comments 12
NEWS PICTURERadio -directed Cutter on Sub Hunt 13
LONG-DISTANCE FM RECEPTIONL. W. Stinson 14
CW & PHONE TRANSMITTERFrank A. Gunther 16
LIMIT BRIDGEM. Lieblich 18
VACUUM TUBE REVIEWOffl:ial Tube Data 19
RADIO -ELECTRONIC PRODUCTS DIRECTORYRadio Engineers' & Purchasing Agents' Guide 26
DIRECTORY OF REPRESENTATIVESAdcresses & Phone Numbers in War Production Areas 30
THE COVER DESIGN AND CONTENTS OF FM MAGAZINE ARE FULLY PROTECTED Ni U. S.COPYRIGHTS. AND MUST NOT BE REPRODUCED IN ANY MANNER OR
IN ANY FORM WITHOUT WRITTEN PERMISSION
* * * * * *M. B. SLEEPER, Editor and Publisher
S. R. COWAN, Advertising Manager
Published by: FM COMPANYEditorial and Advertising Office: 112 East 36th St., New York City, Tel. LE 2-8070Chicago Advertising Representative:
Howland & Howland, Inc., 360 N. Michigan Ave., Tel. STAte 4439FM Magasine is issued on the 20th of each month. Single copies 250- Yearly sub-scription in the U. S. A. 83.00; foreign 84.00. Subscriptions should be sent to FMCompany. 112 East 36th St., New York City.A charge of 250 each will be made for duplicating copies returned because of sub-scriber's failure to give change of address.The publishers will be pleased to receive articles, particularly those well ill edwith photos and drawings, concerning all phases of FM developments. Manuscriptsshould be sent to the publication office, at New York City. Contributions will heneither acknowledged nor returned unless accompanied by adequate postage, pack-ing, and directions, nor will FM Magasine be responsible for their safe handling inits office or in transit.Advertising correspondence, copy, and cuts should be addressed to the advertisingoffice at New York City.
wroi-npos two SHUNS ' .I er unnarvisii..-11 JOURNA OF WARTIME RAM -ELECTRONIC IEVELIMIENI.
EATIAEERIM6 k MANUFACTURIII6 Ed..ed b. M e s,..
COVER PICTURE
Rapid and continuous prog-ress of radio development isbringing out many new me-chanical designs of strangeappearance. Much of this isdue to increasing use of ex-tremely high radio frequen-cies, and to the application ofradio to unusual services.
An interesting example isthe new ,Jefferson -Travis flexi-ble mobile antenna, motor -tuned by remote control,shown on this month's cover.At left is Edward J. Hefele,chief engineer, and Walter C.Hustis, both of J -T Corp.
0 THE U. S GOVERNMENT
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FREED RADIO CORPORATION CONTRACTORS TOrn
IT HAS NOT BEENdifficult for the FreedRadio Corporation tochange over from ci-Nilian to military pro-duction.
Manufacturing phonograph combi-nations equipped for FM, AM, andshortwave tuning, priced from $265to $1,250, our established engineer-ing practices and production meth-ods were generally in accord withArmy and Navy requirements.
The enlargement of our very capableengineering department and furtheradditions of laboratory and testingapparatus were under way beforePearl Harbor.
New machinery and manufacturingfacilities scheduled originally for in-creasing civilian set production arefinding use, instead, on militaryequipment.
Quickly, smoothly, and effectively,our organization has gone all out inthe service of our Armed Forces. Weare producing transmitters, receivers,test instruments, and special equip-ment on prime Government con-tracts. Meanwhile, we are steadilyincreasing our capacity, in order toplay a still larger part in the Battle ofProduction.
ARTHUR FREEDGeneral Manager
-(1/Feeid-e(jefflOW41/FREED RADIO CORPORATION
Engineers and Manufacturers
39 West 19th Street New York City3
AT SCHOOL DEDICATION. LEFT TO RIGHT- LT. -COMDR. LUDLAM. ROGER W. CLIFF, COMDR. S W. TOWNSEND. COMMUNICATIONSOFFICEF. SAMUEL R. ROSENBAUM. WFIL PRESIDENT. AND LT. K. B. EMMONS, IN CHARGE OF NAVY RECRUITING IN PHILADELPHIA
Will HELPS NAVY APPLICANTSStation's Code School Training Gives Men Head Start on Navy Radio Careers
BY LIEUT. ARNOLD NYGREN, U.S.N.R.
THE idea behind the WFIL radio codeI school is to serve the dual purpose ofhelping the IT. S. Navy in its urgent needfor more radio operators, and to helpyoung men who are interested in thisbranch of the service, particularly thoseclassified as IA, to get a head start in theirtraining before enlisting in the Navy.
The plan of the school, conceived byRoger W. Clipp, general manager andvice-president of WFIL and W53PH, andLieut. K. B. Emmons, in charge of recruit-ing in the Philadelphia District, is pre-sented here with the hope that it will en-courage other broadcasting stations toorganize similar training classes, withtheir engineers serving as the faculty.
Purpose of the School * Speaking over WFILduring the dedication ceremonies, Com-mander S. W. Townsend, district Com-munications officer, summarized the pur-pose of the school in these words: "WFILhas given us a ready and extremely prac-tical answer to the acute need for radiooperators by creating here in its studios aschool for training men for the highly
*Formerly chief engineer, Station WFIL, Phila-delphia, Pa.
necessary radio operating duties of ourNavy. The WFIL radio school for Navalapplicants is highly valuable for two im-portant reasons.
"First, it trains men in the very atmos-phere of radio, going on twenty hoursevery day along the most modern lineshere in WFIL's commercial broadcastingstudios.
"Second, these men, in a few briefweeks, will be taught to copy Continentalcode up to twenty-five words a minute,and to copy on a typewriter. When theyreach this standard, a large part of theirprimary training as Naval radio operatorsis accomplished.
"The graduates of this radio school willgo to the Navy Recruiting Service andstart on the road to becoming petty offi-cers in the Naval Communications Serv-ice.
"The shortage of trained radiomen ofthe Navy is in the thousands, and themanagement of WFIL is to be commendedfor taking the initiative in establishing thisfine school."
Benefits to Students * In addition to obtain-ing men of technical aptitudes for radio
training who might otherw se be calledup in the draft as privates, this schoolaffords a very practical service to thestudents. Those who complete the courseare ordinarily accepted for the V-3 (radio)rating by the Navy, and receive $78 amonth as radiomen, third class, insteadof the regular apprentice seaman's pay of$50. Many of the men starting this courselook upon it as a preparation for betterjobs when they return to civilian life.
Class Instruction * The instructors at theWFIL school are members of the staffwho have volunteered their services. LouLittlejohn, director of the school and nowacting chief engineer of the Station, hadan amateur license at the age of 13, andlater went to sea as an operator on tank-ers, freighters, and passenger ships. FredMoore was radioman on a sub -chaser inWar I, and put in It years in the U. S.Navy. Charles Coleman has many recordsto the credit of his amateur station. BillNeill, William Lovainy, and Tony Wheelerhave had both commercial and amateuroperating experience.
These men, typical of the engineersavailable at the larger broadcast stations, 5
put in a full week's time on their regularjobs, and then run the school after hours.They enjoy it, too. Fred Moore remarked,after his first night of teaching: "I haven'thad such a thoroughly enjoyable threehours in a long time!"
The radio school is located in a largeroom adjacent to the FM studio. As theaccompanying illustrations show, theroom is equipped with code transmittingand receiving apparatus and typewritersfor t4 students.
No difficulty was encountered in ob-taining the equipment necessary. Itcomprises:
1. Automatic Tape Transmitter - pur-chased by WFII. from McElroy. of Bos-ton.
Keys and Incidentals - purchased byWFIL locally.
3. Control Board, to enable instructor tokeep in touch with individual students -designed and built by WFIL engineers.
4. Marine Receiver - donated by one ofthe engineers.
5. Tables for the students - donated byLit Brothers, local department store.
6. Typewriters with blank keys for teach-ing touch typing - donated by StrayersBusiness School.
Code reception is taught by hand andtape transmission starting, of course, atgreatly reduced speed. The tape trans-mitter, employing a photo -electric cell,permits the instructor to increase thewords per minute very gradually. Thecontrol board enables the instructor toconnect with any pair of headphones.
Coincident with code practice is instruc-tion in touch typing, which is of equalimportance to Navy operators. Locationsof the letters on the keyboard arc shown
only by the wall charts. Typing instruc-tion is given by Mrs. Alice Faust, secre-tary to Mr. Clipp.
Advanced code practice includes prac-tical problems in transmission and recep-tion of message traffic, and tactical opera -
average in intelligence, and share a sin-cere enthusiasm. In short, the applicantsare fine material for training.
The age limit imposed by the Navy is18 to a. Those with this age group whowrite or stop in at the Station are told to
FROM THE START, STUDENTS MUST TRANSCRIBE CODE BY TOUCH TYPING
tions, during which each man at his deskis a "ship" in a squadron. An incidentalbut important part of the course is thestudy of geography.
Selection of Students * Applicants for theWFIL school hear about this course fromannouncements on the air, from news-paper items, or from their friends. Theyapply by letter or in person. They comefrom all walks of life, and range in agefrom 16 to 60. They are generally above
VERNA STAIR AND LOUIS LITTLEJOHN AT THE CODE TRANSMITTER DESK
report to the WFIL Educational Director.He interviews them, and checks on theirqualifications. Lads under 81 must havetheir parents' consent. Married men musthave the consent of their wives.
If passed by the Director, the applicantthen goes to the Navy Recruiting Officeat the Philadelphia Customs House. Therehe is put through the regulation physicalexamination. About one man in threefails to meet the Navy requirements, andhis name is dropped at the school. Thosewho pass are told to go back to the schoolwhere they then learn how soon they canstart the course. Usually, this is the fol-lowing Monday.
Since classes are held at night, thosewho are employed can continue to workright up to the time they have finishedtheir training and are taken into theService. On the other hand, if a studentfinds he is not fitted to serve as a radiooperator, his regular work has not beeninterrupted.
After a student starts, he must attendevery one of his classes, five nights a week,for the first three weeks. This length oftime is usually sufficient to eliminate thosewho started with nothing to back up theirinitial enthusiasm.
Students may enlist in the Navy at anytime up to, and including, the date theygraduate from the course. However, theyare not accepted for active duty untilthey meet the required sending and re-ceiving speed of 45 words per minute. Atthis time of writing, nine men in theschool are already enlisted in the Navy.
(CONTINUED ON PAGE 24)
HIGH -FREQUENCY IRON CORESPart 1, Better Characteristics and Greater Uniformity Result from Thoroughly Americanized
Materials and Production Methods Forced by War
BY AUSTIN C. LESCARBOURA
EGARDING high -frequency iron core:-.as with many other items deemed vital
to the successful prosecution of the war,this nation has declared its completeindependence. We no longer need Euro-pean or other outside aid. We now pro-duce our own powdered -iron cores. Suchcores are made from domestic materials.We have evolved a production techniquethat provides provably superior ironcores. Our output today is on a fantasticscale as regards volume, coupled withgreat precision of production control,which is to say that it has become a full-fledged American wartime industry.
Old Idea in New Dress * The purpose of thepowdered -iron core is to reduce high -frequency losses by minimizing the pathor length of travel of magnetic currents.The finer the iron particles the lower thelosses at still higher frequencies, otherfactors being equal. The iron particlesare held together by a suitable binderand molded into solid shapes. An earliertechnique of coating paper with powderediron, has long since been abandoned infavor of molded cores.
The powdered -iron core artgoes back to 189i and probablyas early as 1878, when iron fil-ings imbedded in shellac orresin were used for high -fre-quency applications. Some ofthe early superheterodyne re-ceiver kits featured powdered -iron core IF transformers inwhich iron filings were held inshellac or plaster of paris. Morerecently the art has been givena fresh start, first in Germanyand other European countries,particularly Czechoslovakia,and later in the United States,notably in the development ofnew forms of powdered ironand alloys, better binders, andmore critical control of the re-quired electrical characteristics.
For years, the better gradecores were imported from Ger-many. Later, German powderswere imported for American -made cores. With the outbreakof the present war, however,overseas supplies were sooncut off. Then Crowley engi-
In collaboration with the Engineer-ing Department. Henry L. Crowley &Co., Inc., West Orange, N. J.
!Leers, already pioneering in ceramic orsteatite parts, which had much in commonwith iron -core production, gave the pow-dered -iron technique an entirely newdirection.
General Considerations * To appreciate whatI lcen accomplished, it is necessary tounderstand the general conditions in-volved. To begin with, the Q of a coil iscontrolled not only by the loss in its corebut also by the permeability of the corematerial. As the particle size is decreasedbeyond a certain point, the gain (lowerlosses) from reduction in particle sizetends to become proportionately less andless, while at the same time the net effec-tive permeability tends to drop at an in-creasing rate. This results in the crossingof these two lines at some point, afterwhich further reduction in size becomesnegative in its effect upon coil qualityor Q factor.
At this point special production meth-ods must be resorted to, and even theseof course only change the point at whichthe two lines cross. Hence reduction ofparticle size is limited and, for given ma-
terials, there is an optimum size depend-ing upon a ratio between effective permea-bility and loss. Loss consists of hysteresisloss and eddy current loss. With particlesize reasonably small and operating athigh frequencies, hysteresis is the moreimportant. By increasing specific resistiv-ity, we are able further to reduce eddycurrent loss.
Crowley engineers therefore aimedtheir efforts in a new direction, namely, todecrease hysteresis and, if possible and atthe same time, to increase permeability.In considering the possibilities. it seemedreasonable to expect lower hysteresis inmaterials whose atomic or molecularstructure was least dense and, conversely.to expect permanent magnetic effect andhigh hysteresis in the denser structures.
Without going into these specific metal-lurgical specifications. it can be said thatthe objectives have been attained. Crow-ley Nlagicore alloys show higher effec-tive permeability at higher frequencies,together with lower losses, than do ma-terials which are better at lower frequen-cies. Also, the method of insulating theparticles was carefully considered and an
entirely new technique finallychosen. The difficulties andshortcomings of resinous bind-ers at high frequencies are toowell known to require discus-sion here. Suffice it to state thatthe dimensions of the insulatingcoatings are quite minute, andin this regard again the back-ground of ceramic experiencehas been of great help.
FIG. 1. CHECKING CCRES ON PRODUCTION TYPE 0 METER
Mechanical Considerations * Of asgreat intlncrtancc a. electricalcharacteristics are mechanicalconsiderations. Here the stressis definitely placed on the use ofstandard or established shapesand dimensions as far as possi-ble, for which (lies are available.Sample specification forms areavailable, showing what infor-mation is necessary as to di-mensions, screw inserts, slots,tolerances and other details.
Mechanically, powdered -ironcores are made of powderedferrous particles held togetherin a hard metallic mass by asuitable binder. Various mold-ing techniques are employedfor shaping the cores. Cylindri- 7
8
cal cores, tubes, cups and similar shapesare formed in automatic presses whichdeliver a high production rate and re-markable uniformity of pieces and char-acteristics at low cost.
In addition to basic molding operations,iron cores can be further shaped or fabri-cated by various machining operations.Drilling, threading or tapping, milling,grinding, slotting and other operationsare permissible. some materials lendingthemselves to such machining better thanothers, although all Crowley iron -corematerials can be ground or cut to shape.
Typical Core Shapes * Small cylindrical coresor "slugs.' constitute the major portion ofcore production today, and a wide arrayof standard sizes have already been setup through usage. For IF transformers,cores from .2.55 in. in diameter by 36 in.long, to .370 in. in diameter by 3% in. longare generally used, depending again uponmaterial used and range -circuit require-ments. For push-button receivers, coresfrom .2.55 in. in diameter by in. toin. long to .310 in. in diameter by IA in.to 1 in. long are mostly used. dependingupon the material and the range -circuitrequirements.
Cup -shaped cores are also widely em-ployed. from .500 in. inside diameter by.187 in. inside depth (for each half) and.937 in. outside diameter by .310 in.outside depth (for each half). A center coreor slug slips through the two cups. forminga closed -core transformer in combinationwith the coil that fits inside the cups.
Powdered -iron tubes or sleeves are usedfor shielding coils in high-grade receivers.anti can be supplied in any of the corematerials. Also, large cores, 1 in. in diam-eter by 4 ins. long, are employed fortransmitter inductances. They improve
FIG. 2. PLUNGER CORES, WITH THREADED INSERTS, FOR PERMEABILITY TUNING
the Q of the circuit anti decrease the phvsical dimensions of the inductances required for any given range. By means of atapped inductance and such a core, novariable condenser is required. thus re-ducing size anti weight still further.
Powdered -iron cores are also made inI-shapes similar to transformer lamina-tions, for carrier -current coupling func-tions and fur high-fidelity transformers.
Again, large toroidal cores are made forcarrier -current work and other similar I. av-frequency audio equipment. Recently.there has been a growing demand for largecore shapes. especially in cylindricalshapes with a length to diameter ratio ofIT, or 2 to 1. In high -frequency circuits.Q's Of 300 are by no means uncommon.with an effective permeability of approxi-mately 2. These large cores can be pro -
FIG. 3. SOME SPECIAL-PURPOSE CORES. LARGER PIECES ARE FOR EQUIPMENT DEVEL-OPED FOR CARRIER -CURRENT COMMUNICATION SYSTEMS
deiced with special binders which preventover -heating with large power output,therchy permitting their use in tank cir-cuits of transmitters having high -poweroutput. Other applications include large -size cores in the design of filter chokes in-tended to carry DC anti at the same timeto filter out high -frequency currents.
Desirable Characteristics of Cores The charac-teristics desired for core materials are highpermeability and the control of losses andQ. so as to predetermine the Q. There is avery definite demand for increased per-meability, and this constitutes a trickyproblem because of the high frequenciesand the very low applied voltages. Thisrequires that the I'HF curve start rela-tively high and he quite flat. In otherwords the permeability must be high, andrelatively unaffected by the degree ofloading. It is interesting to note that un-der these conditions and frequencies, somepowdered core materials are superior tosuch excellent materials as permalloy.
In some applications, it is desirablethat the Q of coils remain practically con-stant with or without the core. This per-mits the designing of a circuit providingfor any change introduced by station se-lection at one or the other end of theband: in other words. with the core all theway in or out.
In other applications it may he desira-ble to have a distinctly different condition,so that the selectivity is increased at oneend of the band or the other. In fact. boththese conditions are sometimes met indifferent circuits. Nlaterials have been de-veloped for these opposite purposes. Theexpanding of the band with higher fre-quencies is another requirement in somecircuits.
Incidentally. at high frequencies wherehigh Q is desirable, this objective can Ieobtained by proper proportioning of thespace between the core anti the coil. It is
a fairly good rule that the higher the
frequency with ordinary coils, the greaterthe space between core and coil walls, andthe less the weight of core material thatshould he used.
Iron Cores in Receivers * The use of powdered -iron cores in broadcast receivers was givenan impetus by the introduction of push-button tuning. Iron cores have been usedfor oscillators, wave traps, antenna cou-plers and other components. They wereused not only for increasing Q and sharp-ening tuning, but also for stability and forbroad band passing. Couplings intended topass all frequencies without critical pointsor great variations in the degree of cou-pling are made possible by means of spe-cial core materials now available and ingeneral use. The use of completely closedcores or cups of the proper material is es-pecially favorable for such functions.
In the short-wave field it is frequently
tion at will or change from one station toanother on a given push button, withoutrequiring skill or instruments, therebyeliminating the usual service calls whichmost other means require, especially withtrimmer condensers.
The first and simplest method of usingcores in two -stage tuning is with twoseparate cores, each with a screw moldedtherein, moving in coils adjacent andparallel to each other, one for the oscil-lator and the other for the antenna, con-nected by means of a metal yoke to whichis attached a screw that comes forwardthrough the panel and underneath theproper push button. The usual push-button switch is used, so that when thebutton is pressed in, the two coils are cutacross their corresponding portion of thecircuit.
In the normal routine of adjusting a setat any frequency within the band, the
FIG. 4. CUP CORE AND SLUG ARE USED FOR INTERMEDIATE FREQUENCY TRANSFORMERS.LONG PLUNGER IS FOR PERMEABILITY TUNING
desirable to have a core that will not re-duce the Q of a coil materially when in-troduced therein. This type of core is par-ticularly important in permeability tuningof the vernier adjustment. For this pur-pose, special materials such as HF-7 and0-9 were developed. For very high fre-quencies (30 to 300 megacycles) coresmade with conventional binders some-times burn up. For such applicationsCrowley engineers have worked out newhinders that will withstand the heat pro -/111(4.d by busses at those frequencies.
Push -Button Tuning * Pre-set station selec-t ion at broadcast frequencies is relativelysimple by means of coils with adjustableiron cores. There are several major ad-vantages gained by this method. One ismaximum stability over a long period oftime, regardless of temperature and otherclimatic conditions, as well as severe me-chanical jolting. There is also the advan-tage that the operator can select his sta-
push buttons arc depressed successivelyand the two corresponding cores movedseparately until they track. This bringsthe antenna and oscillator coils into align-ment. Then the user can adjust the twotogether by means of a screw fastened tothe yoke. Other mechanical methods can,of course, be employed to achieve thesame end.
In order to track the oscillator with theantenna coil by the same movement, theoscillator coil can be either wound differ-ently in shape or size from the antennacoil, or the iron core can be made shorter.A more expensive way is to shape the ironcore. In some instances, two cores aremade of different permeability, but hav-ing the same physical dimensions, so as toarrive at the same results.
The recommended cores are less thanthe usual standard size. In other words,instead of using % in. by 1 in., or 3% in. by
in., the cores recommended are s f6 in.or even 1/4 in. in diameter and cot,
respondingly shorter. The core 3is in. indiameter by N in. long represents a mosteffective size.
Permeabi' ity Tuning * This method of tuningis similar to push-button tuning in that aset of cores is used to replace the variabletuning condensers. Generally this is ac-complished by a quite heavy or high per-meability core, from in. to 17/8 in.long, placed in the axis of a long solenoid,and moved back and forth by mechanicalmeans. Frequently a powdered -iron coresleeve is placed around the coil to increasethe tuning range and to improve shield-ing, and dispensing with aluminum shield-ing. It is also feasible to place coils aboveand below the chassis, with respect toeach other, as a further shielding means.
Each coil represents a stage of tuning,so that for three -stage tuning there wouldbe three separate coils and three separatecores, w ith some mechanical means for thegroup movement of the cores. Such a tun-ing unit replaces the usual variable tuningcondensers. Its obvious advantages arelower cost, more accurate tuning, bettertracking and high average output.
Part 2 will present Q -frequency curvesfor various core materials.
FM SERVICE AT BINGHAMTON
DRELIM I RY tests on the recentlyI- installed \V49BN transmitter have beencompleted, and the station is now inregular operation.
The equipment comprises an RELmodel 519DL transmitter of 3 -kw. output,operated with a vertical coaxial antennamounted above a 107 -ft. mast. Totalheight above sea level is approximately1.800 ft.
For the present, the transmitter isrunning at about 1,970 watts input, whichis the calculated value to overcome thelosses in the power amplifier and trans-mission line, and to assure 1 kw. of an-tenna radiation.
This power and the antenna at W49BNassure the field strength calculated fortheir service area. The actual fieldstrength in many of the towns located ina 50 -mile circle was surprisingly good.This is another one of the areas where thebroadcasters receive very poor signals onstandard AM frequencies.
Some of the dealers were attempting todemonstrate poorly designed receivers,which did not provide proper limiting cir-cuits. Reception from these sets, I mustadmit, was not up to FM standards ofquiet, high-fidelity performance.
However, correctly designed sets, usinga stage of tuned RF and adequate limiters,proved that W49BN is putting out thekind of signals that listeners want. Beyondthat, it is up to the dealers to see thattheir customers buy the right receivers,and have them installed properly.
Frank .4. Gunther 9
10
FIG. 2. MODEL 5FRX-W IS COMPLETELY CONTAINED IN A STEEL CASE
SHORT-RANGE FM EQUIPMENTAC -DC Circuits Afford Economies and Conveniences Where
Higher Power Is Not Necessary
BY FREDERICK T. BUDELMAN
EOR many of the new applications of[FM transmission, it is not necessary touse as much power as is delivered by thestandard 25- to 50 -watt mobile units.In many cases, too, there is need for ex-tremely simple apparatus that can be setup anywhere, under any conditions, at amoment's notice.
Design Features * To meet these new re-quirements, F. M. Link has developedand is now producing a design whichcombines, in a single unit, an FM trans-mitter, receiver, 6 -volt DC power supply,and a 115 -volt AC power supply.
The unique feature of the built-in dualpower supply provides a design that issuitable for either fixed or mobile use.The compact arrangement makes theunit easy to handle and quick to installfor, whereas the four elements of theequipment are usually mounted sepa-rately, in this design they are combinedinto a single piece of apparatus.
Two models are available. One is thetype 5FRX, which comprises the trans-mitter and receiver unit, as shown in Fig.1, with a separate control box, loud-speaker, push -to -talk handset and hang-up bracket, antenna and mounting, con-trol -box cable, and mounting hardware.This type is intended primarily for mobile
*Chief Engineer, F. M. Link, 125 West 17thStreet, New York City.
use, although it can be used for fixed in-stallations. The case shown in Fig. 1 isonly 13M ins. long by 11 ins. wide.
Type 5FRX-W, Fig. 2, combines allthe equipment listed above in a weather-proof metal cabinet which carries theantenna mounting on the end, and haslouvres behind which the speaker issecured. A cradle inside the cabinet holdsthe handset during transportation.
The weather-proof cabinet, of heavy -gauge steel, measures 21 ins. long, 15ins. wide, and 83% ins. high. The cover,fastened with quick -opening trunk catches,has a key and lock, so that the equipmentis kept tamper -proof.
The loudspeaker has a neoprene dia-phragm, so that moisture cannot enter thecabinet through the louvres. A slot inthe case allows the handset cable to bepermanently connected inside the cabinet,and yet the handset can be used ex-ternally with the cover closed. On -offswitches and pilot lights are mounted oneither side of the speaker. No other con-trols are on the outside.
At the opposite end from the speakerand control switches are mounted aninsulated antenna base and a coaxialline fitting. In many past applications ofthis 5FRX-W equipment, a quarter -wavewhip antenna, mounted directly on thecase by means of the antenna base, provedto be a satisfactory radiating system.Then only a 115 -volt AC or 6 -volt DC
power source was necessary to completethe communications system.
In both types, the receiver portion isidentical to the standard Link 11UF Ed. 3super -sensitive receiver which utilizes litubes in a time -proven circuit of highsignal-to-noise ratio and dependability.
With a total receiver and transmittertube complement of only 16 receivingtype tubes, including one rectifier, the5FRX is hardly larger than other FMreceivers, and actually has less drain.In either the receiving or transmitting po-sition, the unit draws approximately 11amps. at 6 volts DC, or 90 watts at 115volts AC.
Tube Complement * The tubes and their usesare as follows:
7F7 Crystal oscillator, phase modu-lator
7W7 Quadrupler7C5 Quadrupler7C5 Doubler, power amplifier
6AC76K86V6GT6SH76K86SJ76AC76H661166SL7GT6K6GT
RF amplifier1st detectorCrystal oscillator, multiplierIF amplifier2nd detector, crystal oscillator1st limiter2nd limiterDiscriminatorAVC, squelch filter1st audio, squelchAudio output
6X5GT Power supply rectifier
Transmitter and Power Supply * The transmit-ter ha, an vittirel m circuit of onlyfour tubes, utilizing the phase -shiftprinciple of producing frequency modu-lation with direct crystal control. Thisnew circuit contributes to the compact-ness and simplicity of the transmitter.Frequency multiplication of 32 times isused to produce the standard maximumswing of ±15 kc.
The built-in power supply operates in aconventional manner on 115 volts, 50-60cycles. When operation from a 6 -volt bat-tery supply is desired, a built-in vibratoris switched into the circuit, utilizing thesame power transformer, rectifier, andfilter components.
Transfer from one source of power tothe other is accomplished instantaneouslyby means of switches located on the out-side of the chassis.
This latter feature makes the set idealfor normal operation on AC, with astorage battery as an emergency powersource. At the same time, it is equallyeffective as a high-performance, low -power mobile set.
Control of all facilities is accomplishedfrom a control box which is eithermounted remotely when used with thetype 5FRX or inside the cabinet of the5FRX-W.
The 5FRX runs on 6 volts DC or 115
.1,
14,111***,..
FIG. 1. THE 5FRX FM TRANSMITTER, RECEIVER, AND THE 6 -VOLT AND AC POWER SUPPLIES ARE COMBINED IN THIS SINGLE UNIT
volts AC, depending upon the positionof the two power toggle switches at therear of the right hand side of the chassis,behind the power plugs. When theseswitches are up, the set operates on AC.When they are down, it operates on DC.The set will work without regard to thepolarity of the DC source.
Characteristics * The principal characteris-tics of the transmitter and receiver areas follows:
Transmitter Powernominal
Frequency Rangetrolled frequencymc.
Type of Emission - Frequency modu-lated
Frequency Deviation - ±15 kc.Audio Range - 300 to 3,000 cycles with
high -frequency pre -emphasis and sharpcut-off filter at 3,000 cycles
Power Source - Dual 6 -volt DC or 115 -volt AC supply
Power Input - 11 amps. at 6 volts DCor 90 watts at 115 volts AC.
Transmitter Output Impedance - Anyusually fed into concentric line
Control - Remote, by self-contained re-lay
Receiver Output Impedance - .500 ohmsReceiver Power Output - 1 watt
While the frequency range of the stand-ard unit is 30 to 40 mc., it is readilypossible to provide either a higher orlower operating frequency for special ap-plications. Police and guard systems,emergency services, and most other appli-
Output -3 watts.
- Any crystal -con -between 30 and 40
cations of this equipn4 t are in the 30 -to 40-mc. hand.
Applications * The 5FRX-W is well suitedto any kind of a temporary mobile in-stallation in an open car, jeep, or stationwagon. The 5FRX is more satisfactoryfor a permanent mobile installation, asthe remote control unit and handset canbe mounted on the dash and the speakerplaced for best audibility.
For guard house, patrol booths andsimilar installations, either the 5FRX-Wor the 5FRX can be used. If a 5FRX isused, the transmitter -receiver can beplaced convenient to the antenna, whilethe speaker and control can he mountedwherever convenient to the operator.
Both types are ideally suited to marineinstallations, and are applicable to boatsof all kinds. Where the equipment ismounted in the pilot house, the whipantenna can be mounted readily over-head, with a coaxial transmission linelead to the transmitter. Where thequarter wave rod or whip is mounted onguard house or deck house, a large metalplate or screen should first he put on theroof to act as a ground, with the antennaat the center. For longer ranges, theantenna can be mounted on a mast oryard arm.
The 5FRX-W, in addition to havingthe universal mount on the side of thecase, has a coaxial line fitting so thata coaxial transmission line can be con-nected to feed either a quarter -wave whipor a half -wave coaxial antenna. A newdesign of "hang-up" coaxial antenna isavailable which can be fed by a new type
of flexible coaxial transmission line.These accessories further widen the ap-plications of the versatile 5FRX and5FRX-W.
The low power of the transmitter is nocriterion of its capabilities. The consistentrange is 3 to 10 miles, but it gives veryacceptable service over distances greatlyin excess of these figures. In many waysit closely approaches the performance ofhigher powered mobile equipment, atvery much less battery drain and withthe additional advantage of being opera-ble on AC.
A complete system of fixed station andmobile equipments can be engineeredusing this unit only, making for economyin first cost and minimum cost in main-tenance spare parts.
The unit has so many advantages andis capable of so many applications thatit already shows promise of out -strippingheavier and more elaborate equipment.
Many interesting applications havealready been made but these cannot bediscussed at the present time for obviousreasons. It is easy to understand, how-ever. just how this unit can be applied inliterally hundreds of different ways afterconsideration of the characteristics andthe make-up of the equipment.
In Preparation: A comprehensive anal-ysis of automatic frequency control cir-cuits applied to FM receivers is scheduledfor the September issue. The material isbeing prepared by Murray Weinstein,who has achieved notable success withAFC for FM reception. 11
12
SPOT NEWS NOTESSavings: Stoppage of civilian radio set pro-duction is estimated by WPB to have ef-fected an annual saving of 70,000 tons ofsteel. 10.500 tons of copper, .2,10(1 tons ofaluminum. .280 tons of nickel.
S.W. Interference: FCC has approved tem-porary frequency shifts of short-wavebroadcast stations on occasions whenother stations interfere with reception atforeign points. In most cases. change willbe only a few kilocycles.
A -N Production Award: Conferred on Philcofor "high achievement in production ofwar equipment." Philco is delivering com-munications equipment for planes andtanks. and also shells, fuses, and heavy-duty storage batteries.
John Shepard, 3rd: Honored by a citation forpoldie service by the Commonwealth ofNlassachusetts on the 40th anniversary ofstation WNAC. Presentation was byLieut.-Governor Horace 'I'. Cahill. Otherspeakers included Boston's Mayor Tobinand FCC Chairman Fly, who sent a tran-scribed message from Washington, I). C.
No Tires: Radio distribu-tors, dealers, and service-men and those providingtransportation for therepair of any portablehousehold effects havebeen dropped from thelist of eligibles for newor recapped tires.
WFIL: Although locatedon the top floor of theoffice building which car-ries Philadelphia's talleststructure (their FM an-tenna) the WTI I. studioswere flooded during adeluge of rain which fellon July 27th.
Draft Deferment: 11(.0)111-
[11(.11,1m by War Man-power Commission forthose engaged in produc-tion of communicationequipment, and in com-munication services. Ra-dioequipment assemblersand electrical and radiotesters are listed amongoccupations essential toWar production.
Cooperation: In response torequests of U. S. troopsacross the Pacific, GE'sSan Francisco station
KGEI is short -waving CBS shows whichfeature popular orchestras. Coverage in-cludes Alaska, Hawaii, Midway, China,Burma, Australia. New Zealand.
Lifeboat Radios: No use spending time de-signing clever lifeboat radios to call helpwhen ships are torpedoed. Reason is thatif submarine sees anything that looks likean antenna, they machine-gun the boatand crew because radio call would discloselocation of submarine.
MA: Replaces W2XOY as call of GEstation at Schenectady. Schedule is from:1:00 to 10:00 P.NI. daily.
Radio Set Sales: .11I -time record excise taxesof $13.051,313 were collected in first sixmonths of 1941. At 10%, this indicates netsales of $130,528,250, or retail sales ofabout $260.000,000. In corresponding1941 period, taxes at 532% were $3,(182.-340. indicating net sales of $.56,046,200.or re -tail sales of about $111.000.000.
TO CONSERVEBLATTERMAN
RF CHOKES
MATERIALS AT KFI, H. L.NOW EVEN WINDS HIS OWNIN STATION'S WORKSHOP
Items and comments, personal and other-wise, about manufacturing, broadcasting,communications, and television activities
Editor's Note: How much more enjoyment isprovided from original music by FM in-stead of AM reception was brought hometo your Editor when one of the tubes letgo in the FM end of his set, and he hadto listen to the last half of the NBCSymphony Orchestra, conducted by Ar-turo Toscanini, on AM. Frankly, thepart heard on AM sounded, by com-parison with FM. decidedly dull andHat, and of not much more importancethan any recorded program of averagequality.
New RMA Members: Latest additions areWestinghouse, with radio plants in Pitts-burgh, Baltimore, and Bloomfield. N. J.;Remington -Rand, Inc.. Electronics Divi-sion of New York City and Middletown,Conn.; Radio Engineering Laboratories,Inc.. Long Island City; Technical Radio,Inc.. San Francisco.
New Plant: Of 40,000 sq. ft. has been openedby National Union Radio Corporation ofLansdale, N. J. Formal inspection wasmade by Major Kenneth I). Johnson, ofWashington. Training classes for skilled
and unskilled workers arenow in progress.
Mexico: Major Jose ClarkFlores, Chief Signal Sec-tion, Mexican Army, an-nounces from MexicoCity that his Govern-ment is purchasing largequantities of U. S. radio.telephone, and telegraphequipment.
Resistors: New catalogshows Lectrohm line offixed, adjustable. "Rib-bon -edge" and ferruletype resistors. and asso-ciated hardware. Alsolisted are power line andRF chokes, and smallsolder pots of 134- and4-1b. capacity for pro-duction service. Lec-trohm, Inc., Cicero, Ill.
Domestic Mica: Of goodelectrical grades is avail-able in the [SA, contraryto prevailing opinion.Lacking penny -a -day la-bor market of India, itwas not practical to op-erate domestic mines,since only' 8 to 10% oftonnage splits into sheetsfor condensers. Now,(CONTINUED ON PAGE 24)
400010r
NEWS PICTURETii; Coes' [ind Cutter. wheeling tc attack asuspected submarise while guarding atraasatlanic convoy, is giJen greatlyircressed effectiveress by newly devl-
opec radio commimicr,:ions and signs..it-1gequpment. Action is so fast, that whensubmarine is lova7ed. coordination andspeed of men awl ir_achines determinessuccess or failure in the protection ofconvoyed vessela
'Lie fact that -3bc halve not lost a singletransport from oar Artlarrtic convoys isgreatly to the credit of the manufactt rers
who are building ratio ucaimacnt -7or theU. S. Navy.
If Navy radio aad in-spection sometimes seem :even, ttey arewell-grounded on experimce, ard areamply jus-ifiec by the fat that otianequipment fails, -it 2ons: tites a liablityto the mer who depend Ipon it to carryout their duties. 13
14
LONG-DISTANCE FM RECEPTIONReception from Eastern FM Transmitters, as Recorded at Station KVOO, Tulsa
As a matter of curiosity, if nothing more.M the appended charts may be of someinterest to the readers of RADIO -ELEC-TRONIC ENGINEERING.
The same recordings and the chartsshown in the accompanying illustrations,summarizing the field intensities recordedat station KVOO, Tulsa, Oklahoma. were
*Engineer, Station KVOO, Tulsa, Oklahoma.
BY L. W. STINSON
made during the past year, in an attemptto get a limited amount of factual, quan-titative information on high frequencysporadic transmissions. From these ob-servations, certain deductions are fairlyevident.
For instance, it seems certain that areasonable amount of sporadic interfer-ence can he anticipated well within the
fifty microvolt -per -meter contours ofsame -channel FM stations when the useof such stations on high power becomesgeneral throughout the country. This in-terference is to be expected, unfortu-nately, during the months of June, Julyand August, months during which static -free reception by FM is a strong argu-ment in its favor over AM broadcasting .
RECEPTION FROM DETROIT, NASHVILLE, NEW YORK, BOSTON, AND ROCHESTER AS RECORDED AT SUMMERTIME INTERVALSWO -
100
SO-
25 -
10 -10
to-
-0
10
SOD-
103-
23-
; Wo
1540-
U100-
I 50_
0
10 : 11111111111111M111111r:
ILIILIM1111WirlaillilallallilleartallaUVIC 490
010 7
S AUGUST 8 3 2
SCO
SO -
26
10
JUNE 24
JUNE 26 3 2
PIA 12 AM EST
PIA 12 AM EST
111 IS AM EST 11
0 6 AUGUST IR 3 a I PIN 12 AM
GRAPHIC CHARTS OF SKY-WAVE RECEPTION OF FREQUENCY MODULATED STATIONS AS RECORDED AT TULSA. OKLAHOMA0000 ENO. OM - acrroalta 11141 RECORDER TUNED TO W2 XMN EXCEPT AS NOTED
10
2 CC
50
5 25
3
0
V
2
03
0 0 0 1 0 0 x 0 11 0 0 II 0 0 0
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
JULY
k.
- I _ _
oliLo lof 0 o lo o o o o o0 I o I Id! x ggi. I
50
12
p
I 3 4 5 9 7 8 10 11
DAILY PERIOD ON CHART REPRESENTS TIME
12 IS 14 IS -
AUGUST7AAi TO 12Pu EST WITH DURATION AND HOURS OF RECEPTION APPROXIMATELY
O- NO SIGNALS INDICA-ED ON RECORDER CHART THIS DATEX - RECORDER INOPERATIVE THIS DATE
SHOWN
INTENSITY AND OCCURRENCE 0= SPORADIC -E SKY -WAVE SIGNALS =ROM W2XMN1 ALPINE N.J.,
AS RECORDED AT TU-SA OKLAHOMAfy00 ENG DEPT-- SEPT 1941.
CAREFUL STUDY OF THIS DATA IS REQUIRED TO DETEFMINE THE TRUE SIGNIFICANCE OF THE [DEGREE OF INTERFERENCE SHOWN
The periods of reception of these signalshave been checked against the reports ofvertical incidence measurements of theBureau of Standards, and have been foundto agree quite well. This indicates that ananalysis of their measurements over thepast few years should be useful in pre-dicting the average annual interferenceto be expected over various distances.
The recording program will probably becontinued this year again, as receptionduring the first days of June has indicatedthat a great many of the distant signalsare coming through with high intensities.
Editor's Ncte: The records made by Mr.Stinson and presented here prompt thesuggestion that the War period offers anopportunity to collect complete data onpotential FM interference which willserve as a guide to the allocation of fre-quencies and specifications of power out-put at the time when new broadcast sta-tion construction is permitted again.
If there is going to be an interferenceproblem on FM channels, this preparationwould eliminate changes and alterationssuch as the AM stations have had tomake. On the other hand, if it is knownfrom year-round observations that therewill be no serious interference problem,the FCC can be more liberal in allocating
the same frequencies to several stations.In either case, such data will provide a
sound basis for planning the expansion ofFM broadcasting.
Mr. Stinson's data is reassuring insofaras it shows potential interference, duringwhat he has observed as the worst months,to be decidedly sporadic. Compared toconditions on AM broadcast channels,where eastern stations, for example, andthose in Texas and on the west coastsqueal with one another, the FM pictureseems highly reassuring.
Listeners in the rural sections, particu-larly, would be grateful for the absence ofthe AM squeals which come in at so manypoints during the evening. If, on FM,powerful signals from a remote stationshould take over temporarily a channelalso occupied by a local station, receptionwould be clear, at least, and fit to hear.Reception might change at intervals fromone station to another, as the remote sig-nals swing in and out, but not to the ac-companiment of shrieks and howls whichcharacterize AM interference.
Some engineers feel that, with the ex-pansion of FM service, a serious inter-ference situation may develop.. Otherstake the position that it is reasonable toexpect trouble.
Radio receiver manufacturers will wantto know about this matter when theystart their preparations to resume civilianproduction. So will the companies build-ing transmitters, and the men who will becalled upon to finance the erection of FMstations.
Gathering FM transmission data at thisopportune time will not involve the use ofa burdensome number of engineeringman-hours. Most of the data required canbe taken by unattended recording devices,such as used at station KVOO. Perhapsarrangements for gathering informationcan be organized by the engineers of theFCC. Coordinated efforts are needed toassure the collection of data that can heintegrated readily.
U.S. SIGNAL CORPS APPOINTMENT
New chief radio engineer of the SignalCorps is Robert M. Morris, one of theoriginal staff of WEAF when it was estab-lished by AT&T in 1944.
He moved over to NBC, as chiefdevelopment engineer, when that Com-pany was organized in 1947, and con-tinued in that capacity until he was madebusiness manager of the NBC Radio -Recording Division, in 1941. 15
16
CW & PHONE TRANSMITTER
500 -Watt Self -Contained Transmitter Features Versatile
Tuning Circuits and Instantaneous Frequency Selection
BY FRANK A. GUNTHER
REQUIREMENTS for many of the newtypes of special-purpose radio appa-
ratus are giving radio engineers widerscope for the use of new ideas than hasbeen possible within the limitations of themore conventional prewar specifications.
The 500 -watt AM transmitter illus-trated here falls within the category ofsuch new types.
Electrical specifications called for theinstantaneous selection of any one fre-quency from a number up to five between300 kc. and 43 mc., for either phone or CWtelegraph. Mechanical requirements werefor extremely rigid single -unit construc-tion, using a dust -proof steel cabinet,with only the microphone, telegraph key,and desk -type amplifier and operatingcontrol to be mounted separately. Fullprotection against extremes of tempera-ture and humidity were also specified.
General Description * Figs. 1 and show howt lie design was worked out in the finishedtransmitter. It is designated as the RM.type 4C1A, and is now being produced asa standard model.
The equipment is divided into five sec-tions, as shown at the right, in Fig. C.These carry, from bottom to top: (1)power supply circuits and blower for air-cooling the tubes, (i) speech amplifier.(3) crystal oscillator and buffer stages,(4) power amplifier, and (5) antenna linecoupling condensers.
Circuit elements in these sections whichrequire adjustment can be set and lockedwhile the safety door is closed, as shownin Fig. e. right.
While the particular transmitter illus-trated is equipped for only three operatingfrequencies, provisions are made to addcircuit elements for two more frequenciesif and when they are required.
All vertical wiring for interconnectingthe sections is cabled and run in channelsformed by the corner uprights of thewelded steel frame. Welded constructionis used throughout to eliminate nuts andbolts except where parts must be remov-able. The result is an absolutely rigidframe that cannot become loose in transitor under any adverse operating con-ditions.
* Vice president in charge of engineering, RadioEngineering Laboratories, Long Inland City. N. Y.
Power Supply * All the heavy component,of the power supply circuits and the rec-tifier tubes are located in the bottomsection. Here, also, are the blower motorand, against the rear of the cabinet, thespun -glass filter for the air intake. Theair blast is directed upward to an outletat the top of the cabinet.
Altogether there are five supplies inthis transmitter. They are:
1. C bias supply, furnishing 150 voltsfrom a type 80 tube.
C. The 300 -volt oscillator supply, alsousing a type 80 tube.
3. Next is the 500 -volt doubler supply,which uses a 57,3 tube.
4. 'Fwo 87i -A tubes furnish '2,000 voltfor the modulator and amplifier.
.5. Finally, a 5Z3 supplies power furthe AF stage.
Starting time -delay and plate overloadand underload relays and other AC con-trol equipment can be seen in the bottomsection.
An auto transformer is provided so thatthe transmitter can be operated from any50- to 60 -cycle single-phase line capableof delivering 3 kw. at 190 to e70 volts.The auto transformer has CO steps forvoltage adjustment. All circuits after thetransformer are designed for CIO -voltoperation. Accurate regulation of the fila-ment voltage is obtained from a manuallyoperated regulator.
Audio Section * The speech amplifier andaudio section are located above the powersupply. The audio tube complement com-prises a pair of 76's in push-pull, drivingfour 6A3's in push-pull parallel, which feeda pair of Eimac 100TH tubes in push-pullclass B, serving as modulators.
These latter are mounted at the center ofthe section, where they are cooled by theair stream from the blower below.
On this section, too, are mounted themain circuit breaker and controls for theplate voltage and primary voltage. Theknobs are accessible when the safety dooris closed.
Oscillator and Butter * on the center sectionthere are two separate chassis, one at theleft for the crystal oscillator circuits, andone at the right for the doublers.
FIG. 1, REL MODEL 421A 500 -WATT UNIT,WITH QUICK -CHANGE FREQUENCY
CONTROL
The views iu Fig. L show the lockeddials for the three separate crystal oscil-lator units, and the oscillator plate currentmeter. Each unit has its own crystal con-trol. Three Leach relays, just visibleabove the panel, select the required oscil-lator circuit and connect it to the soetube.
Three corresponding buffer circuitsare located at the right, each with its platetuning condenser and relay to cut in theunit required for the working frequency.The tube is another 804.
The meter on the left shows the buffergrid current, and the one on the right,the buffer plate current.
Controls for the modulator bias voltageand buffer screen voltage are located be-hind the Bakelite plate at the center.
On both the crystal oscillator anddoubler panels there are holes at the left and right for the shafts of additionalcondensers, in case more than three tuningunits are required for additional operatingfrequencies.
Power Amplifier * Two HK257 power ampli-fiers and the corresponding tuning circuitsare mounted on the next section. The platecircuit coils have separate shields. Dialsfor the plate tuning condensers can beseen at the front. Here, again, provisionsare made for extra tuning units.
Antenna Tuning * The antenna line couplingare located in the top section.
Across the front are jacks into whicheither an RF meter panel or a blank panelcan be plugged. For reasons of economy,only one meter panel is furnished. When itis desired to read the antenna current forany frequency, the meter panel is pluggedin at the corresponding position. Thisputs a meter in each side of the balancedline.
Sections at the left and right are providedwith removable blank panels if additionaltuning circuits are used.
The antenna is fed by an open trans-mission line of 400 to 600 ohms. A sepa-rate antenna is required for each operatingfrequency.
Meters * The five meters at the top of thecabinet show, from left to right, the poweramplifier filament voltage, power ampli-fier grid current, power amplifier platecurrent, modulator plate current, and thepower amplifier plate voltage.
Control Unit * A sloping -front control unit,connected to the transmitter by a 40 -ft.cable in Greenfield covering, contains themicrophone pse-amplifier with its ownpower supply.
Both the microphone and telegraph keyplug into the control unit. Either a crystalor dynamic microphone, controlled by agrip -to -talk switch, can be used. Gaincontrols are provided for the microphoneand for a separate 500 -ohm input line.
The unit also carries the controls neces-
sary for starting and stopping the trans-mitter, and selecting the transmitterfrequency.
When the CW telegraph key is pressedor the microphone switch gripped, thetransmitter circuits are operated auto-matically. Breaking either circuit killsall the power in the transmitter, permit-ting the receiver to function without in-terference. Also, suitable relays in thetransmitter shunt out the plate and screenwindings of the class B modulation trans-former when the telegraph key is oper-ated, and light the filaments of the audioand modulator tubes when telephonetransmission is employed.
The audio system is essentially dis-tortionless, and has a flat response, ±3db, from 150 to 6,000 cycles. This meas-urement is from the microphone inputterminals to the antenna terminals, with100 per cent modulation of the RF carrier.
Dimensions * The transmitter cabint meas-ures 76 ins. high, 39 ins. wide, and i5IAins. deep, and weighs 1,460 lbs. complete.The control unit is 18 ins. long, 9 ins. high,and 101/2 ins. deep. It weighs N lbs.
Application * The type 4e1A transmitter islilt (.11( 1(.11 primarily for communicationsservices, and as such it is an extremelyversatile design. The quick -change fre-quency control makes it admirably adaptedfor a central station, handling traffic witha number of distant points. It can be
used for speech transmission under normalconditions, and switched to CW telegraphin case of atmospheric interference. Allcomponents are intended to stand upagainst salt water dampness, making it aswell suited to use at sea as on land.
CANDY FACTORY TO MAKE CONDENSERS
One of the oldest candy manufacturersin the east is preparing to convert part ofits plant into paper condenser production.This will take up slack resulting from re-duced supply of cocoa. The concern is theNew England Confectionery Company, ofCambridge, Mass.
This may seem far fetched at firstthought, but it is actually a practical usefor an air-conditioned factory employingwomen workers of great manual dexterity.Production of paper condensers, particu-larly of the oil -filled and oil -impregnatedtypes, continues to lag further behindrequirements, despite the enormously in-creased facilities of the established con-denser manufacturers.
The idea of bringing in a non-competi-tive company is a practical way to meetthe emergency for, when the War is over,the candy manufacturer will simply junkwhat will probably be worn-out machin-ery, and go back to making chocolate bars.
It is understood that the WPB, spon-sors of this plan, has obtained the coopera-tion of Tobe Deutschman Corp., Canton,Mass., to expedite the conversion. Produc-tion is scheduled to start September first.
FIG. 2, LEFT: APPEARANCE WITH SAFETY DOOR OPEN. RIGHT: INTERCHANGEABLE TUNING UNITS AND METER PANEL CAN BE SEEN HERE
17
USE OF THE LIMIT BRIDGEFor the Rapid Determination of Percent Variation from Resistance Standard
CXACT specifications of allowableL
per-centage of variation for so many of the
resistors used in military equipment havebrought about the widespread use of thedirect -reading resistance limit bridge.This instrument is the most practicalmeans for checking resistors accuratelyand rapidly in large quantities.
It has the added advantage of classify-ing resistors as to resistance variation sothat they can be sorted finally by a singletest. That is, if the allowable tolerance fora given value for a specific purpose is ±4%, resistors of larger variations can besorted during the initial inspection, andset aside to be used in other applicationsfor which they would be acceptable. Thiseliminates the need for subsequent re-checking and reclassification.
Fig. 1 shows the Radio City Productsmodel 670 limit bridge, and the circuitdiagram is given in Fig. R.
No skill is required to operate the in-strument beyond accurate observation of
* Chief Engineer, Radio City Products Company,Inc., 127 West 26th Street. New York City.
FIG. 1. THIS RESISTANCE LIMIT BRIDGE IS
18
BY M. LIEBLICH
the scale reading. The zero -center scaleindicates the percentage of variation ofthe resistance under test from a standardresistance, up to 10%, with an accuracyof ± .1%. The 4 meter, having asensitivity of 25-0-25 microamperes, isfitted with a scale calibrated .5% perdivision, permitting very accurate read-ing.
Either an internal or external standardresistor can be used. A specified standardis furnished with each instrument. Anyother standard value can be connected tothe binding posts at the right hand edgeof the front panel. Then the switch, justabove the binding posts, must be thrownto the EXTERNAL position.
Four dry batteries, carried within thecase, furnish the filament current and theoperating voltages. In addition to theON -OFF switch at the right, there is asafety switch, above the meter, that opensthe filament circuit when the cover isclosed. A pilot light on the left of thepanel shows when the filaments are on.
Binding posts and a switch are provided
OPERATED BY SELF-CONTAINED BATTERIES
at the left for connecting an externalbattery in case a resistance standardvalue is used which requires a higher volt-age than the 7A -volt battery in the case,to give full-scale deflection at 10% varia-tion when the zero adjustment, below themeter, has been turned to its limit.
Operation * To test resistors against theinternal standard, the following proced-ure should be carried out:
1. Put the control switch at the ON posi-tion, and BATTERY and STANDARD switchesin the INTERNAL positions. Allow 30 sec-onds for the tubes to reach a stable condi-tion.
2. If necessary, reset the ZERO ADJUST
knob so that the pointer is at zero on themeter scale.
3. Connect the unknown resistor to theR. posts at the bottom of the panel.
4. Press the PRESS TO READ button at theleft of the binding posts.
5. Read the plus or minus deviation fromthe standard directly on the scale of themeter.
When an external resistance standardof a different value is used, it is necessaryto readjust the potentiometer mountedbehind the front panel. This is R6 inFig. e.
The procedure is as follows:
1. Remove the instrument from the case.
2. Put the control switch in the ON posi-
tion, and STANDARD switch in the EX-
TERNAL position. Allow 30 seconds for thetubes to reach a stable condition.
3. Connect the new standard resistor toEXTERNAL STANDARD.
4. If necessary, reset the ZERO ADJUST so
that the pointer is at zero on the meterscale.
5. Connect a resistor of exactly 10%more or less resistance than the standardto posts R..
6. Adjust the potentiometer mounted be-hind the panel, using a screwdriver, untilthe meter reads exactly 10%. This will bethe correct reading, since the test resistorvaries exactly 10% from the externalstandard.
7. If the 10% reading cannot be obtainedby adjusting the potentiometer, it will he
(CONTINUED ON PAGE 25)
VACUUM TUBE REVIEW
829-APush -Pull
Beam Power Amplifier
PU2 Pui
G2HCENTER
TAP
INDEX DOSSON !UGC
PLANE OF ELECTRODES OF EACH UNITIS PARALLEL TO PLANE THROUGH AXIS
OF TUBE AND AA'
BOTTOM OF TUBE
829-A is a push-pull beam power transmit-ting tube of the heater -cathode type. Itcontains two beam power units in one en-velope. Total maximum plate dissipationis 40 watts. The exceptional efficiencyand high power sensitivity permit fullpower output with very low driving power.For example, a single tube operated in
058. °°2-OIA
TANK.
I
,,e. 002"
0;AMS.--\PINS 2d-1-20.
NOM.
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SP
_41; MIN.
INTERNALSHIELD
311"MAX.
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-INDEX BOSS
.10.°11PATPIN iTIPS
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JVITTEMA VIEWAfton, rmlarlsos UINTA Polls API nuts TO TWA-AAOIS SUCH 'NAT PIP,I OILL I, GMAT mAy1PG On,0.0W- POLES APO 00I 0.115' POLO 44444 GAD AT 'RACYNIGLIO OP LOW C.AOLI
push-pull class C telegraph service is capa-ble of handling a power input of 140 wattswith less than 1 watt of driving power atfrequencies as high as NO mc. The 829-Acan be operated at reduced ratings at fre-quencies as high as 450 mc. Plate -to -plate circuit resonance of the tube is 750mc.
The exceptional efficiency of this tubeat the ultra -high frequencies is made pos-sible by the balanced and compact struc-ture of the beam power units, excellentinternal shielding, and close electrodespacing. The internal leads are short andheavy in order to minimize internal leadinductance. The terminal arrangementprovides excellent insulation and is de-signed to facilitate symmetry of circuitlayout. Neutralization of the tube is un-necessary in adequately shielded circuits.
The heaters are arranged to allow op-eration from either a 12.6 or a 6.3 -voltsupply.
CHARACTERISTICS AND RATINGS
Unless otherwise specified, the followingvalues are for both units:
Heater:Voltage, AC or DC, per unit. .6.3 voltsCurrent, per unit 1.125 amps.
Transconductance for plate current of 60milliamps., approx 8,500 Amhos
Grid -screen mu factor 7Direct interelectrode capacitances. each
unit:Grid -plate, with external shielding,
maximum .1 ALAInput 14.5 Ad.Output 7.0 pd.
Screen -cathode capacitance, including in-ternal screen bypass condenser, approx.
65 Ad.Bulb T-16Terminal mounting . . . See INSTALLATIONType of cooling See INSTALLATION
MAXIMUM CONTINUOUS COMMERCIALSER4ICE RATINGS AND TYPICAL
OPERATING CONDITIONS
Following maximum ratings are abso-lute values:
As GRID -MODULATED PUSH-PULL RFPOWER AMPLIFIER, CLASS C TELEPHONY
Carrier conditions per tube for use witha maximum modulation factor of 1.0:
DC plate, max. 750 voltsDC screen, grid 2, max 225 voltsDC grid, grid 1, max -175 voltsDC plate, max HO ma.Plate input, max. 60 wattsScreen input, max. 6 wattsPlate dissipation, max. 40 wattsTypical operation with modu-
lation factor of 0.7:
A reference index of tubes listed in previous issuesof Radic-Electronic Engineering will be found on
page 24. A revised index is published each month
DC plate 500DC screen NODC grid -38Peak RF grid -to -grid . . .82Peak AF grid 17
DC plate current HODC screen 10DC grid, approxDriving power, approx.' 0 5Power output, approx.. . 23
750 voltsNO volts
-55 volts104 volts15 volts80 ma.5 ma.0 ma.
0.7 watt21 watts
As PLATE -MODULATED PUSH-PULL RFPOWER AMPLIFIER, CLASS C TELEPHONY
Carrier conditions per tube for use with amaximum modulation factor of 1.0:
DC plate, max 600 voltsDC screen, grid 2, max. 225 voltsDC grid, grid 1, max. -175 voltsDC plate, max 212 ma.DC grid, max 15 ma.Plate input, max 90 wattsScreen input, max. 7 wattsPlate dissipation, max 28 watts
Typical operation:DC plate 425 600 voltsDC screen voltage of eoo NO volts
from series resistor of 2
6,400 13,300 ohmsDC grid voltage of . . -60 -70 volts
from grid resistor of 3
5,500 5,800 ohmsPeak RF grid-to-grid 154 172 voltsDC plate 212 150 ma.DC screen 35 30 ma.DC grid, approx 11 12 ma.Driving power, approx 0.8 0.9 wattPower output, approx 63 70 watts
As PUSH-PULL RF POWER AMPLIFIER ANDOSCILLATOR, CLASS C TELEGRAPHY
Key -down conditions per tube, withoutmodulation 4:
DC plate, max 750 voltsDC screen, grid e, max. 225 voltsDC grid, grid 1, max -175 voltsDC plate, max.... 24DC grid, max. 150
mma.a.
Plate input, max. 120 wattsScreen input, max. 7 wattsPlate dissipation, max 40 wattsTypical operation:
DC plate 500 750 voltsDC screen voltage:
from fixed supply of NO NO voltsfrom series resistor of
9,300 18,300 ohmsDC grid voltage:
from fixed supply of-45 -55 volts
from cathode resist. of160 270 ohms
From grid resistor of 3
3,750 4,600 ohmsPeak RF grid-to-grid 124 140 voltsDC plate 240 160 ma.DC screen 32 30 ma. 19
20
DC grid, approx leDriving power. approx.
0.7Power output. approx.83
14 ma.
0.8 watt87 watts
At crest of AF cycle, with modulation factorof 0.7.
2 Connected to modulated plate -voltage supply.a The grid circuit resistance should never exceed
15,000 ohms total per tube, or 30,000 ohms per unit.If additional bias is necessary, use a cathode resistoror a fixed supply.
Modulation essentially negative can be used ifthe positive peak of the AF envelope does not exceed115% of the carrier conditions.
INSTALLATION
The 849-A may be mounted by meansof a special socket having floating con-tacts, such as the RCA N. 9934 or 9935.
tinuous operation of the tube so thatforced air cooling is recommended. Forcedair cooling is not required for the 849-A inintermittent service where the "on" pe-riod of plate power application is ordi-narily not more than five minutes, andwhere the "off" period is not less thanthe "on" period.
The heaters of the 8'N -A are connectedin series within the tube. The center con-nection is brought out of the bulb to aseparate pin terminal to permit eitherseries operation from a 1e.6 -volt supply orparallel operation from a 6.3 -volt supply.Either an AC or a DC supply may beused. Under any condition of operation,
71-FDRIVER
ULTRA -HIGH -FREQUENCY PLATE -MODULATEDPUSH-PULL R -F POWER AMPLIFIER(OPERATING FREQUENCY APPROY. 200 Mc)
0-250 MA.
+8
1 1HEATER SUPPLY
12.6 V.
"ce
RCA -829-ARI
RZ
2 'Mr cs 00.6 R3
C3 A4 0-75 TI
`2T-MA.
TC4
1-B +440 V.
( WITH CATHODEBIAS)
TOANTENNAFEEDERS
0-54.10 C7MA.
TOMODULATOR
NOTE 1: Adjust coupling of Li, Ls, and Ls, Li for op-timum grid excitation.
NOTE 2: Grid resistors should be adjusted on La, L.at voltage node.
CI 1.2 to 10 ma. per section.CS 25 mfd., 200 volts.Ca 500 µµf. mica.C4 500 pg. mica.Cs 500 pal', mica.Cs 500 µµf, mica.C2 3 to 35 j.j.f.C', 3 to 35 w.f.
No. 9934 (UT -106) is made for use at fre-quencies below 60 mc. No. 9935 (UT -107)has built-in by-pass condensers for theheater and the screen and is designed foruse at frequencies above 60 mc. Theplate terminals take clips with flexibleleads.
Flexible leads are necessary so that nor-mal expansion will not place a strain onthe glass at the seals. Each lead should heconnected to its clip before the clip isplaced on the plate terminal. Connectionsshould never be soldered directly to thetube terminals because the heat of thesoldering operation may crack the leadseals. The 849-A may be mounted in avertical position with the plate terminalseither up or down. It may also be mountedin a horizontal position provided the planeof each plate is vertical (on edge).
The bulb becomes very hot during con -
RI 7,500 to 15,000 ohms, I watt.R, 7,500 to 15,000 ohms. 1 watt.R3 60 ohms, 10 watts.R. 6,400 ohms, 15 watts.Ti Modulation transformer.L. Dimensions dependent on type of driver tube. Ap-
proximately same as L5, Li.La Same as above.Li X" diameter copper tube, approx. 10" long, spaced
X" between centers.L. Same as above.Lb %" diameter copper tube, approx. 7" long, spaced
4" between centers.L. Same as above.
the heater -voltage should not deviatemore than ±10% from the rated value.
The cathodes of the 8e9 -A are con-nected together within the tube. The cath-ode circuit should be connected to theelectrical mid -point of the heater circuitwhen the heaters are operated from an ACsupply, or to the negative heater -supplylead when the heaters are operated froma DC source. In circuits where the cathodeis not directly connected to the heater, thepotential difference between them shouldnot exceed 100 volts. If the use of a largeresistor is necessary between heater andcathode in some circuits, it should be by-passed to avoid the possibility of hum.
The plates of the 849-A show no colorwhen the tube is operated at its maximumplate -dissipation rating.
The screens of the 849-A are connectedtogether within the tube, and they are by-
passed by means of a 65 pa. condenserconnected inside the tube between thescreens and cathodes. Screen voltage maybe obtained from a separate source, fromthe plate supply through a series resistor,or by means of a voltage divider. Thechoice of method depends on the servicein which the tube is used (see APPLICA-TION). When the screen voltage is ob-tained from a separate source, or from avoltage divider, plate voltage should beapplied before or with the screen voltage.Otherwise, with voltage on the screensonly, the screen current may rise highenough to cause excessive screen dissipa-tion. When screen -voltage regulation isnot an important factor, the series resist-ance method for obtaining screen voltageis desirable because of its simplicity andbecause it limits the DC power input tothe screen. A DC milliammeter should beused in the screen circuit so that the screencurrent can be measured and the DCpower input to the screen determined.The screens should not be allowed to at-tain a temperature corresponding to morethan a barely perceptible red color. Thistemperature corresponds to the screen -input values shown under CHARACTER-IST1( S.
The screen current is a very sensitiveindication of plate -circuit loading andthe screen current rises excessively (oftento the point of damaging the tube) whenthe amplifier is operated without a load.Therefore, care should be taken when tun-ing an 849-A under no-load conditions inorder to prevent exceeding the screen -input rating of the tube.
A protective device, such as a high -voltage fuse. should be used to protectboth the screens and plates against over-loads. When a bleeder resistor of poorregulation or a series resistor is usedfor obtaining the screen voltage, thisdevice should be placed in the commonpositive high -voltage supply lead. Itshould remove the high -voltage supplywhen the DC plate current reaches avalue 50% greater than normal. When thescreen voltage is obtained from a separatesource or from a voltage divider of goodregulation, a protective device should alsobe placed in the screen -supply lead. Itshould remove the screen voltage when theDC screen current reaches a value of 50%greater than normal.
Shielding of the RF amplifier stageemploying the 849-A is required for stableoperation. A convenient method of shield-ing is to insert the plate end of the tubethrough a hole in a metal plate so thatthe edge of the opening is in close prox-imity to the internal shield of the tube.An alternative shielding and mountingarrangement is to insert the grid end ofthe tube through a hole in the shield andthen clamp a ring or cup to the chassis soas to complete the shielding and lock thetube in the mounting.
RF by-passing of the 8e9 -A at its ter-minals is necessary in order to realize the
DEATH before DISHONOR!
Observation of the stress points on glass esettaseals around vacuum tube leads is made iththis detice. Close-up photo above shows tit? ac-tual view of a faulty lead. Note the change inpolarized light creating distorted shaa.owswhich show up stress and strain in beads. suchstrain ssmetimes occurs where metal and glassare seaeed together.
Inspecting the entire glass bulb with the help ofa polarized light. This device shows up stressand strain on the glass which might be createdduring the shaping operations.
Casual observation of a vacuum tube does not reveal its flaws.That's why Ei:nac engineers have developed many devices for thepurpose of ex-3osing even slight weaknesses in construction. Theabove is not a dungeon window, but a close-up photo of a faultybead on a filament stem as viewed through a specia_ bead testingdevice. Needless to say, this stem willnever reach final assemEly . . . better"death before dishonor" to the Eimactradition of dependability.
Such care in production plus constantresearch into the phenomenon of theelectron tube assures you of the utmostin performance from every Eimac tube... provides the answer to why Eimactubes are first choice by most of the lead-ing engineers throughout the world.
Export ,Agents :(FRAZAR & CO., LTD., 301 Cloy St.)
San Franc sco, California, U. S. A.
Mfg. by Eitel- McCullough, Inc., San Bruno, California, U. S. A.
22
full capabilities of the tube at the ultra-high frequencies. Conventional by-passingmethods and grounding are not adequate.One convenient method of by-passing is touse ribbon heater and screen leads to thetube terminals and to insulate the leadsfrom the external shield plate by meansof mica spacers to former by-pass con-densers right at the tube terminals. It isimportant that the grid, plate, and screencircuit returns are made to the commoncathode connection in order to avoid RFinteraction through common return cir-cuits.
It may also be advisable in some ap-plications to supplement the action ofthe by-pass condensers by RF chokesplaced close to the condensers in the volt-age supply leads.
In order that the maximum ratingsgiven under CHARACTERISTICS are not ex-ceeded, changes in electrode voltages dueto battery- or line -voltage fluctuation,load variation, and manufacturing varia-tion of the associated apparatus must bedetermined. An average value of voltagefor each electrode should then be chosenso that under the usual voltage variationsthe maximum rated voltages will not beexceeded.
When a new circuit is tried or when ad-justments are made, it is advisable to re-duce the plate and screen voltage. Thismay be done conveniently by means of aprotective resistance of about 2,000 ohms(total) in series with the screen lead and aprotective resistance of about 2,000 ohmsin series w i ill the high -voltage supplylead.
APPLICATION
In grid -modulated class C telephoneservice, the 829-A is supplied with un-modulated RF grid excitation voltage andwith a DC grid bias which is modulated ataudio frequencies. Grid bias should pref-erably be obtained from a fixed supply.The plates are supplied with unmodulatedDC voltage. The audio power required inthis service is very small and need besufficient only to meet the peak powerrequirement of the grids of the class Camplifier on the positive crest of the inputsignal. The actual peak value is generallynever more than 0.15 watt. The screenvoltage should be obtained from a sepa-rate source or from a voltage divider con-nected across the plate supply.
In plate -modulated class C RF ampli-fier service, the 829-A can be modulated100%. The screen voltage may be ob-tained from a separate source; a voltage -dropping resistor in series with the modu-lated plate supply may be used also. In anycase, the screen voltage must be modu-lated simultaneously with the plate volt-age so that the ratio of screen voltage toplate voltage remains constant. Modula-tion of a fixed screen -voltage supply canbe accomplished either by connecting thescreen lead to a separate winding onthe modulation transformer or by con-necting it through a blocking condenser toa tap on the modulation transformer orchoke. With the latter method, an AFchoke of suitable impedance for low audiofrequencies should be connected in serieswith the screen -supply lead. Control gridbias should be obtained from a grid re-
sistor or from a combination of either gridresistor and fixed supply, or grid resistorand cathode bias resistor. The combina-tion method of grid resistor and fixedsupply has the advantage of not onlyprotecting the tube from damage throughloss of excitation, but also of minimizingdistortion effects by bias -supply com-pensation.
In class C RF telegraph service, the829-A may be supplied with screen voltageby any of the methods shown underINSTALLATION. When a series screen re-sistor is used, the regulation of the platesupply should be good enough so that thescreen voltage will not exceed 600 voltsunder key -up conditions. Grid bias maybe obtained by any convenient method.
The 829-A may be operated at maxi-mum ratings in all classes of service at fre-quencies as high as 200 mc. The tube maybe operated at higher frequencies pro-vided the maximum values of plate volt-age and power input are reduced as thefrequency is raised (other maximumratings are the same as shown underCHARACTERISTICS). The tabulation belowshows the highest percentage of maximumplate voltage and power input that can beused up to 250 mc. for any class of service.Special attention should be given toshielding, cooling and RF by-passing atthese frequencies.Max. permissible percentage of max. ratedplate voltage and plate input:
Class C 200 mc. 250 mc.grid modulation 100% 94%plate modulation . 100% 89%telegraphy 100% 89%
NEW BOOKS ON RADIO
BASIC RADIO - The Essentials of Elec-tron Tubes and Their Circuits, by J. Bar-ton Hoag, Ph.D. 379 pages, profusely il-lustrated, 834 by 6 ins. Published by 1).Van Nostrand Company, Inc., 250 FourthAvenue, New York City. Price, 83.25.
In the preparation of this text and theexcellent illustrations, Dr. Hoag has donea highly useful job for the great numberof new radio -electronic students who, withonly a limited knowledge of physics andmathematics, must gain a working knowl-edge of vacuum tubes, their circuits, andtheir functions.
The hook is up-to-the-minute in thesubjects covered, making it of specialvalue to students of military radio -elec-tronic equipment. With practically nomathematics, the functioning of moderntubes is made clear, and then related, insubsequent chapters, to feedback ampli-fiers, receivers and transmitters, signalgenerators, television equipment, oscillo-scope testing, alignment of superhetero-dyne circuits, frequency modulation,direction finders, UHF circuits, and micro-wave apparatus, including the Klystron.
Twenty-two pages of problems andquestions, comprising a practical review,
ENGINEERING SUBJECTS
were prepared I \ E. B. Red ington, Instruc-tor in Charge. Radio Engineering andMaintenance School, U.S.C.G. The au-thor holds the rank of Lieutenant Com-mander as head of the Department ofScience, U. S. Coast Guard Academy, atNew London.
This hook is recommended highly to allstudents preparing for civilian or mili-tary radio work.
DEFINITIONS OF ELECTRICAL TERMS,compiled by the A.I.E.E. Standards Com-mittee. Over 300 pages, 8 by 11 ins. Pub-lished by the American Institute of Elec-trical Engineers, 33 West 39th Street,New York City. Price, $1.00.
Standards Committees of 31 engineer-ing societies and organizations, includingthe Bureau of Engineering, IT. S. NavyDepartment, have collaborated in estab-lishing the American Standard Definitionsof Electrical Terms, under the procedureof the American Standards Association.
Definitions are arranged in groupswhich cover fundamental and derivedterms for: Rotating machinery; Trans-formers, regulators, reactors, and rectifi-ers; Switching equipment; Control equip-ment; Instruments, meters, and meter
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In the group of Electrocommunicationdefinitions are those related to instru-ments for conversion to and from electricwaves. circuit elements, networks, lines,antennas, radio transmitters and receiv-ers, direction finders, television, telephonesystems, stations and sets, lines and trunks,switching systems and apparatus, andtelegraph systems.
Electronic definitions cover vacuumtubes and electrodes, electrode voltage,current, and power, electrode impedancesand admittances, amplifiers, gas tubes,phototubes, cathode-ray tubes, and X-raytubes.
At a time when great emphasis is beingplaced on simplification and time conser-vation through technical standardization,every engineer will benefit by a carefulstudy of the data concerning his particularactivities which is presented in this vol-ume.
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VOLT - OHM -- MILLIAMMETER
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WFIL HELPS NAVY APPLICANTS
(CONTINUED FROM PAGE 6)
After completing this course, the menare sent to the Navy Radio School atNewport, R. I., for advanced instructionand training in radio theory and practice,in preparation for going to sea.
Additional Information * The Navy hopes thatother broadcast stations will establishsimilar courses, so as to make instructionavailable in all parts of the Country tomen who are potential operators. Com-menting on this plan, Roger Clipp said:"If the radio stations of America willtarry on the work started here, we canmeet the Navy's need for technical menin this field. I shall gladly place at thedisposal of any interested station all theinformation as to the organization andmaintenance of a Navy code school."
SPOT NEWS
(CONTINUED FROM PAGE 12)
however, production of Mycalex, usingground mica scrap, has risen to a pointwhere sale of waste makes US mica min-ing profitable.
50 -Watt Rheostats: Are now being producedby Clarostat Mfg. Company, of Brooklyn,N. Y. Resistances up to 10,000 ohms areavailable. Design is similar to Clarostat's25 -watt line, with element embedded inceramic housing. Shaft is completely in-sulated from rotating contactor.
Lock Washers, Terminals: Shakeproof, Inc.,of Chicago, is now standardizing on re-duced number of lock -washers and lockingterminals, according to sales manager E.W. Fuller. Discontinued types will besupplied until exhausted. Stock types,listed in new catalog sheets, cover 90% ofradio and electrical applications.
Chicago: Surface lines are using a Motor-ola FM installation to reach the servicetrucks around the City, so as to speedthem from one job to another.
Condensers: Oil -filled and oil -impregnatedpaper condensers, encased in metal tubes,are listed in all values and voltages in anew catalog released by Solar Mfg. Cor-
poration, of Bayonne, N. J. Demand forsuch types of paper condensers has in-creased enormously because they are sowidely specified for Army and Navyequipment.
UHF Bibliography: A 52 -page reference bookon this subject, compiled by E. Kelsey,has just been published by Zenith RadioCorporation, Chicago. Books and paperslisted include those published abroad. aswill its in the USA.
Franklin M. Doolittle: General manager of\V DR(' and has been appointedtechnical FM adviser to Board of WarCommunications, at Washington. He willrepresent FM Broadcasters, Inc. in thiscapacity.
Use of Silver: Is saving huge quantities oftin at General Electric, according to vicepresident Harry A. Winne. G.E. usedabout 500 tons of tin ill 1940. This year,with output doubled, tin consumption willnot increase, due to substitution of silverfor tin in soft solder. In the past, soft sol-der has ranged from almost pure tin to40% tin and 60% lead. Now, compositionsrun from 20% tin, 1% silver, and 79%lead to 97.5% lead and 2.5% silver. Braz-ing instead of soft -soldering joints andconnections is saving copper, too. Widelyused brazing alloy was mainly copper,with small silver and phosphorus content.Now, typical brazing alloy hasper, 50% silver, 16% zinc, and 18%cadmium.
Indianapolis: W73IN will be on the airshortly, using transmitting equipmentordered and built before the freeze orderwas put into effect. So says R. M. Cran-dall, president of Associated Broadcasters,by whom the FM station will be operated.
Correction: Last month, on the Spot Newspage, W49BN was referred to as aRochester station. As the call letters indi-cate, this station is located at Bingham-ton, N. Y. It is affiliated with WNBF.
Reference Index:Vacuum Tube
ReviewsComplete design data on the following tubes
has been presented in Radio -Electronic Engi-neering to date'
1635 Class B twin amplifier June. 19421642 Twin triode amplifier June, 19429004 UHF diode May.19429005 UHF diode May, 1942
1A3 HF diode Slay, 19423A4 Power amplifier pentode May, 19423A5 HF twin triode Slay, 1942829A P -P RF beam power amp July, 1942
6C4 HF power pentode Slay, 1942
9JP1/180914 9 -in. cathode ray.... June, 1942
1L4 RF amplifier pentode May. 1942
VI IN
EX T.EXT. BAT.
FIG . COMPLETE CIRCUIT OF THE DIRECT -READING RESISTANCE LIMIT FRIDGE
USE OF THE LIMIT BRIDGE(CONTINUED FROM PAGE 18)
necessary to use an external battery ofmore than the 7 -volt battery VI. Inthat case, put the battery switch at EX-TERNAL, and connect a voltage greaterthan 732 to the EXTERNAL BATTERY postson the panel. The exact value must bedetermined experimentally by readjustingthe potentiometer until, with a test re-sistor varying 10% from the standard, themeter reads 10%.
Calibration Check * From time to time, afterthe batteries have been in use for severalmonths, the ZERO RESET should be ad-justed and the meter reading checkedagainst a resistor varying 10% from astandard value. If the meter does not readexactly 10%, the potentiometer behindthe panel should be adjusted. If this is notadequate to correct the reading, the bat-teries should be replaced, and the read-justment process repeated.
Circuit Data * The four batteries shownin Fig. 4 are:
V, - 7.5 volts, Burgess F5BP.V2 - 1.5 volts. Burgess 4FA.
-9 volts. Burgess X466.V4, V4 - 45 volts, Burgess 5308, grounded
at the center tap.
Other values of components in the wiringdiagram are:
R -STD - Internal standard resistance.R, - 1,000 ohms.112 - 1,000 ohms.113 - meg.R, - 50,000 ohms.It - 20,000 ohms.
- 2,000 -ohm potentiometer.RE - 15,000 -ohm zero reset.C, - .01 mfd.tin - Press -to -Read switch.S2 - Safety switch.
53 - ON -OFF SiViteli.M - 25-0,-25 microamperes.VT, - 1CSGT tube.
The size of the case, with the coverclosed, is 143/1 ins. high, 10% ins. wide.and 8 ins. deep. Weight, including bat-teries, is 194 lbs.
BOOK REVIEW
ULTRA -HIGH -FREQUENCY TECHNIQUES,by J. G. Brainerd, editor, Glenn Koehler,Herbert J. Reich, and L. F. Woodruff, pro-fessors at University of Pennsylvania,Wisconsin. and Illinois and at Massachu-setts Institute of Technology, respec-tively. 535 pages, 316 illustrations, by
ins. Published by D. Van NostrandCompany, Inc., 250 Fourth Avenue, NewYork City. Price $4.50.
Here is another book based on wartimeneeds for technical literature. The fourauthors who collaborated in the prepara-tion of this text were members of the con-ference held at M.I.T. in November, 1941,to consider the need, engendered by theWar, for engineers trained in the ultra-high -frequency field.
Discussion at this conference broughtout emphatically that lessons learnedfrom our allies and our enemies indicatedthat a serious shortage is developing inspecialists trained in electrodynamics andultra -frequency techniques. This demandhas been brought about by the introduc-tion of radically new weapons, battle tac-tics, and military and naval devices, allrelated to the vital role of radio communi-cation.
Men who have had this extra trainingare needed for (1) various branches of theArmy, Navy, and Marine Corps, (2) Elec-tronics Training Group Replacement, forservice in England, (3) Government re -
(CONTINUED ON PAGE 27)
PRONG-BASE
ELECTR OL YTICS
This already popular type ismade still more popular becauseof certain Aerovox refinements.Indeed, it will pay you to checkthese refinements for yourselfwhen considering prong -baseelect rolytics.
Check these features for yourself.Sample cheerfully submitted. Let usquote on your requirements. Litera-ture on request.
EROvoxco."0",--
NEW BEDFORD. HMS., U. S. A.
In Canada: AEROVOX CANADA LTD., Hamilton, Ont.
EXPORT: 100 Varick St., N. Y., Cable 'ARAB' 25
26
RADIO -ELECTRONIC PRODUCTS DIRECTORYThe Radio Engineers' & Purchasing Agents' Guide to Essential Materials, Components, and Equipment
* Indicates that addresses and phone numbers of representatives in War Production centers are listed at the end of the Radio -Electronic Products Directory
ANTENNAS, TransmittingBlaw-Knox Co., Pittsburgh, Pa.Lehigh Structural Steel Co., 17 Battery
Pl., N. Y. C.Lingo & Son, John E., Camden, N. J.Truacon Steel Co., Youngstown. 0.Wincharger Corp., Sioux City, Iowa
BEADS, InsulatingAmerican Lava Corp., Chattanooga,,,
Tenn.Dunn. Inc., Struthers, 1321 Cherry,
Phila., Pa.Star Porcelain Co., Trenton. N. J.Steward Mtg. Co., Chattanooga. Tenn.
BOLTS, NUTS & SCREWS, MachineAmerican Screw Co., Providence. R. I.Bristol Co., The, Waterbury. Conn.Central Screw Co., 3519 Shields Av.,
ChicagoChandler Prods. Corp., Cleveland. 0.Continental Screw Co., New Bedford,
Maas.Corbin Screw Corp.. New Britain, Conn.Harper Co., H. M., 2609 Fletcher, Chi-
cagoInternational Screw ('o., DetroitLamson & Sessions Co.. Cleveland. 0.National Screw & Mfg. Co., ClevelandNew England Screw Co., Keene, N. HOhio Nut & Bolt Co.. Berea. OhioParker Co., Charles. Meriden, Conn.Parker-Kalon Corp., 198 Varick, N. Y. C.Pawtucket Screw Co.. Pawtucket, R. I.Progressive Mfg. Co., Torrington, Conn.Republic Steel Corp., Cleveland, 0.Russell. Burdsall & Ward Bolt & Nut
Co., Port Chaster, N. Y.Scovill Mfg. Co., Waterbury, Conn.Shakeproot, Inc., 2501 N. Keeler, Chi-
cagoSouthington Hardware Mfg. Co., The.
Southington, (NDrin.Whitney Screw Corp., Nashua, N. H.
CABLE, CoaxialAmerican Phenolic Corp.. 1830 S. 54 Av.,
ChicagoAnaconda Wire & ('able Co.. 25 B'way.
N. Y. C.Andrew Co., Victor J., 363 E. 75 St.,
ChicagoBelden Mfg. C'o., 4673 W. Van Buren,
ChicagoBoston Insulated Wire & Cable Co.,
BostonCommunications Prods. Co., Jersey City,
N. J.Cornish Wire Co., 15 Park Row. N. Y. CGeneral Cable Corp., 420 Lexington,
N. Y. C.Doolittle Radio, Inc., 7521 S. Loomis
Blvd., ChicagoGeneral Insulated Wire Corp., 53 Park
PL, N. Y.('.Simplex Wire & ('able Corp., Cambridge.
Mass.
CABLE, Microphone, Speaker &Battery
Alden Prods. Co.. Brockton, Mass.Anaconda Wire & ('able Co., 25 Broad-
way. N Y. C.Belden Mfg. Co., 4633 W. Van Buren.
ChicagoBoston Insulated Wire & ('able Co.,
Dorchester, Mass.Gavett Mfg. Co., Brookfield, Mass.Holyoke Wire & Cable Corp., Holyoke.
Mass.
CASTINGS, DieAluminum Co. of America. Pittsburgh.
Pa.American Brass Co.. Waterbury, Conn.Dow Chemical Co., Dowmetal ,
Midland. Mich.
CERAMICS, Bushings, Washers,Special Shapes
Akron Porcelain to.. Akron, 0.Electronic Mechanics, Inc.. Paterson,
N. J.Isolantite, Inc., Belleville. N. J.Lapp Insulator Co., 1.eroy. N. Y.Louthan Mig. Co.. F. Liverpool. 0.Star Porcelain Co.. Trenton. N. J.Steward Mfg. Co., Chattanooga. Tenn.Victor Insulator Co.. Victor, N. Y.
CHOKES, RFAladdin Radio Industries, 501 W. :35th.
ChicagoAlden Prods. Co., Brockton. Mass.American Communications Corp., 306
B'way. N. Y. C.Barker & Williamson, Upper Darby, Pa.Coto -Coll Co., Providence. R. I.D -X Radio Prods. Co., 1575 Milwaukee,
ChicagoGeneral Winding Co.. 254 W. 31 St.,
N. Y. C'.Guthman & Co., Edwin, 400 S. Peoria.
ChicagoHammarlund Mfg. Co., 424 W. 33 St..
N. Y. C.Johnson Co., E. F., Waseca, Minn.Lectrohm, Inc.. Cicero, Ill.Meissner Mfg. Co., Mt. Carmel, Ill.Miller Co., J. W., Los Angeles, Cal.Muter Co.. 1255 S. Michigan, Chicago
National Co., Malden. Maas.Ohmlte Mfg. Co., 4835 W. Flournoy St.,
ChicagoRadex Corp.. 1328 Elston Av., ChicagoSickles Co.. F. W., Chicopee. Mass.Teleradlo Eng. Corp.. 484 Broome St.,
N. Y. C.Triumph Mfg. Co., 4017 W. Lake St.,
Chicago
CLIPS, C forMueller Electric Co.. Cleveland, 0.
CLIPS & MOUNTINGS, FuseAlden Prods. Co., Brockton. Mass.Dante Elec. Mfg. Co., Bantam, Conn.Ilsco Copper Tube & Prods., Inc..
Station M, CincinnatiJefferson Elec. Co.. Bellwood. Ill.Jones, Howard IL, 2300 Wabansla, Chi-
cagoLittlefuse, Inc.. 4753 Ravenswood, Chi-
cagoPatton MacGuyer Co., Providence, R. I.Sherman Mfg. Co.. H. B., Battle Creek.
Mich.
CLOTH, InsulatingAcme Wire Co., New Haven, Conn.Brand dr C'o.. Wm., 276 -4th Av., N. Y. C.Endurette Corp. of Amer.. ClIffwood,
N. J.Insulation Mfgrs. Corp., 565 W. Wash.
Blvd., ChicagoIrvington Varnish & Insulating C'o.,
Irvington. N. J.Mica Insulator Co., 196 Varick, N. Y. ('.
CONDENSERS, Fixed* Aerovox Corp.. New Bedford, Mass.American Condenser Corp., 2508 S.
Michigan. ChicagoArt Radio Corp., 115 Liberty, N. Y. ('.Atlas Condenser Prods. Co., 548 West-
chester Av.. N. Y. C.Automatic Winding Co., East Newark,
N. J.Bud Radio. Inc., Cleveland, 0.Cardwell Mfg. Corp.. Allen I)., Brook-
lyn. N. Y.Centralab, Milwaukee. Wis.Condenser Corp. of America. South
Plainfield, N. J.Condenser Prods. Co., 1375 N. Branch,
ChicagoCornell-Dubiller Elec. Corp., S. Plain-
field. N. J.Cosmic Radio Co., 699 E. 135th St.,
N. Y. C.Crowley & Co., Henry L., W. Orange.
N. J.Deutschmann Corp., Tobe, Canton,
Maas.Dumont Elec. Co. 34 Hubert St.,
N. Y. C.Electro-Motive Mfg. Co., Willimantic,
Conn.Erie Resistor Corp., Erie, Pa.Fast & Co., John E., 3123 N. Crawford.
ChicagoGeneral Radio Co.. Cambridge, Mass.Girard -Hopkins, Oakland. Calif.II. R. S. Prods., 5707 W. Lake St.,
ChicagoIllinois ('ond. Co., 3252 W. North Av.,
ChicagoIndustrial Cond. Corp.. 1725 W. North
Av., ChicagoHemline Corp. of America, Long Island
City. N. Y.Johnson Co., E. F., Waseca, Minn.Kellogg Switchb'd & Supply ('o., 6650
Cicero, ChicagoMallory & Co.. P. R., Indianapolis, Ind.Micamold Radio Corp.. Brooklyn, N. Y.Muter Co., 1255 S. Michigan, ChicagoPotter Co., 1950 Sheridan Rd.. N. Chi-
cagoRCA Mfg. Co., C'amden, N. J.Sangamo Elec. Co.. Springfield, III.Solar Mfg. Corp., Bayonne. N. J.Sprague Specialties Co., N. Adams.
Mans.Teleradlo Engineering Corp., 484
Broome St.. N. Y. ('.
CONDENSERS, Variable ReceiverTuning
Alden Prods. Co., Brockton, Mass.American Steel Package Co , Defiance.
OhioBarker & Williamson. Ardmore, Pa.Bud Radio, Inc., Cleveland, 0.Cardwell Mfg. Corp.. Allen D., Brook-
lyn, N. Y.General Instrument Corp., Elizabeth,
N. J.Hammarlund Mfg. Co.. 424 W. 334d St.,
N. Y. C.Insuline Corp. of Amer., L. I. (AY. N. Y.Meissner Mfg. Co.. Mt. Carmel, III.Millen Mfg. Co., Malden. Mass.National Co., Maiden, Maas.Radio Condenser Co. Camden. N. J.Reliance Die & St'p'g Co., 1260 ('ly-
bourn Av., Chicago
CONDENSERS, Variable Trans-mitter Tuning
Barker & Williamson, Upper Darby. Pa.ltud Radio. Cleveland, 0.Cardwell Mfg. Corp.. Alien D, Brooklyn,
N. Y.Hammarlund Mfg. Co., 424 W. Xi St..
N. Y. C.Insuline Corp. of Amer.. L. I. City, N. Y.Johnson. E. F., Waseca, Minn.Millen Mfg. Co.. James. Malden, Mass.National Co.. Malden. Mass.
CONDENSERS, Variable Trimmer* Aerovox Corp.. New Bedford. Mass.
Alden Prods. Co.. Brockton, Mass.American Steel Package Co., De-
fiance. 0.Bud Radio, Inc., Cleveland, 0.Cardwell Mfg. Corp., Alien, Brooklyn.
N. Y.('entralab. Milwaukee, Wis.General Radio Co., Cambridge. Mass.Guthman. Inc., E. I., 400 S. Peoria.
ChicagoHammarlund Mfg. Co., 424 W. 33 St..
N. Y. ('.Insuline Corp. of America. Long Island
City. N. Y.Johnson Co., E. F., Waseca, Minn.Meissner Mfg. Co., Mt. Carmel, Ili.Millen Mfg. Co., Jams, Malden, Mass.Miller Co.. J. W., Los Angeles, Cal.Muter Co., 1255 S. Michigan Av.,
ChicagoNational Co., Malden. Mass.Potter Co., 1950 Sheridan Rd., N.
ChicagoSickles Co., F. W., Chicopee, Mass.Solar Mfg. Corp.. Bayonne. N. J.Teleradlo Eng. Corp., 484 Broome.
N. Y. C.
CONNECTORS, CableAero Electric Corp., Los Angeles. Calif.Alden Prods., Brockton. Mass.Amer. Microphone Co.. 1915 8. Western
Av., Los AngelsAmer. Phenolic Corp., 1830 S. 54th St..
ChicagoAmerican Radio Hardware Co., 476
B'way, N. Y. C.Andrew, Victor J.. 6429 S. Lavergne Av..
ChicagoAtlas Sound Corp., 1442 39th St.,
Brooklyn, N. Y.Birnbach Radio, 145 Hudson St.,
N. Y. C.Breeze Mfg. Corp.. Newark, N. J.Brush Development Co.. Cleveland. 0.Bud Radio. Cleveland, OhioCannon Elec. Development, 3209 Hum-
boldt, Los AngelsEby, Inc., Hugh H., PhiladelphiaElectro Voice Mfg. Co.. South Bend,
IndianaGeneral Radio Co.. Cambridge. Mass.Insuline Corp. of Amer., I.. I. City, N. Y.Jones. Howard B.. 2300 Wabansla,
ChicagoMallory & Co., P. R., Indianapolis. Ind.Radio City Products Co., 127 W. 26 St.,
N. Y. ('.
From month to month, new companies are enter-ing the Radio -Electronic field. Older concerns areadding new products. Accordingly, this Directorywill be revised each month, so as to assure engi-neers and purchasing agents of up-to-date in-formation. We shall be pleased to receive sug-gestions as to company names which should beadded, and hard -to -find items which should belisted in this Directory.
CRYSTALS, QuartzBausch & Lomb Optical Co., Rochester,
N. Y.Bellefonte Eng. Labs.. Bellefonte, Penna.Bliley Elec. Co., Erie, Penna.Burnett. Wm. W. I., San Diego, C'al.Collins Radio Co.. Cedar Rapids, IowaGeneral Electric Co., Schenectady. N. Y.General Radio Co.. Cambridge, Mass.Harvey -Wells Communications, South-
bridge, Mass.Hipower Crystal Co., 2035 W. Charles-
ton, ChicagoHollister Crystal Co., Merriam, Kan.Hunt & Sons, G. C.. Carlisle. Pa.Kaar F:ngineering Co.. Palo Alto, Cal.Miller, August E., North Bergen, N. J.Peterson Radio, Council Bluffs, IowaPrecision Crystal Labs., Springfield.
Mass.Precision Plezo Service. Baton Rouge,
La.Premier Crystal Labs., 63 Park Row,
N. Y. C.RCA Mfg. Co.. Camden, N. J.Scientific Radio Service, Hyattsville,
Md.Standard Piezo Co., Carlisle, Pa.Vaipey Crystals, Holliston, Mass.Zeiss, Inc., Carl, 485 Fifth Av., N. Y. C.
FELTAmerican Felt Co., Inc., Glenville,
Conn.Western Felt Works, 4031 Ogden Av.,
Chicago
FIBRE, VulcanizedBrandywine Fibre Prods. Co.. Wilming-
ton, Del.Continental -Diamond Fibre Co., New-
ark, Del.Insulation Mfgrs. Corp., 565 W. Wash.
Blvd., ChicagoMica Insulator Co., 196 Varlck, N. Y. C.Nat'l Vulcanized Fibre Co., Wilmington,
Del.Taylor Fibre Co., Norristown, Pa.Wilmington Fibre Specialty Co., Wil-
mington, Del.
FILTERS, Electrical NoiseTobe Iteutschmann corp..
Mass.Canton.
FINISHES, MetalAirose Chemical Co.. Providence. R. I.Aluminum Co. of America, Pittsburgh,
Pa.Ault & Wiborg Corp.. 75 Varick,
N. Y. C.Hilo Varnish Corp., Brooklyn, N. Y.Maas & Waldstein Co., Newark, N. J.New Wrinkle, Inc., Dayton, 0.
FUSES, EnclosedDante Elec. Mfg. Co., Bantam, Conn.Jefferson Elec. C'o., Bellwood, Ill.Littlef use, Inc., 4753 Ravenswood Av.,
Chicago
GEARS & PINIONS, MetalGear Specialties, Inc.. 2650 W. Merlin.
ChicagoPerkins Machine & Gear Co., Spring-
field, Mass.Thompson ('lock Co., H. C'., Bristol,
Conn.Continental -Diamond Fibre Co . New-
ark, Del.
GEARS & PINIONS, Non -MetallicBrandywine Fibre Prods. Co.. Wilming-
ton, Del.Formica Insulation Co., Cincinnati. 0.Gear Specialties, Inc.. 265(1 W. Madill,
Chicago* General Electric Co., Pittsfield, Mass.
Mica Insulator ('o., 196 Varick St..N. Y. C.
National Vulcanized Fibre Co., Wil-mington, Del.
Perkins Machine & Gear Co., Spring-field. Mass.
Richardson Co.. Melrose Park. ChicagoSynthane Corp.. Oaks, Pa.Taylor Fibre Co., Norristown, Pa.Wilmington Fibre Specialty Co.. Wil-
mington, I)el.
GENERATORS, Gas Engine DrivenKato Engineering Co., Mankato. Minn.
HEADPHONESBrush Development Co., Cleveland, O.Conn. Tel. & Electric Co., Meriden,
Conn.Carrier Microphone Co., Inglewood, ('al.Cannon Co.. C. F., Springwater. N. Y.Carron Mfg. Co., 415 S. Aberdeen,
ChicagoChicago Tel. Supply Co., Elkhart. Ind.Connecticut Tel. & Elec. Co., Meriden.
Conn.Elec. Industries Mfg. Co., Red Bank,
N. J.* General Electric Co.. Pittsfield. Maas.
Kellogg Switchboard & Supply Co.. 6650S. Cicero Av., Chicago
Murdock Mfg. Co., Chelsea, Mass.Trimm Radio Mfg. Co., 1770 W. Ber-
teat). ChicagoUniversal Microphone Co.. Inglewood.
Cal.
Michigan's pioneer Frequency Modulation Station,owned and operated by The Detroit, News. AssociateA. M. Station WW1
4500 Penobscot Bldg.DETROIT, MICHIGAN
WHAT ISSUES OF FMMAGAZINE ARE MISS-ING FROM YOUR FILES?COMPLETE YOUR BACKNUMBERS. SEE SPECIAL
OFFER ON PAGE 29
BOOK REVIEW(CONTINUED FROM PAGE 25)
search and development in the RadiationLaboratory and Civil Service, (4) indus-tries engaged in War production, and (5)teaching, to enlarge further the reserveof trained specialists.
To aid the rapid progress of the trainingprogram, a new textbook was required forthe use of institutions giving the necessarycourse of instruction. Thus it came aboutthat four specialists in this field collabo-rated in preparing and editing the text ofT.1.11{1.-HICH-Fith:Q1 TEt
7
g:W0-140,1(:_°./;91109e,-eite
For Proven FM EfficiencyThe Lingo FM Turnstile Antennais our important
contribution tothe industry's FM accomplish-ments. The years that have beendevoted to developments,have al-ready borne fruit in the formof an outstanding
record of effi-ciency from an imposing list ofactual installations.Even now,while our plant is engaged in all-out Victory production, we con-tinue our development
efforts toassure even greater efficiencyindesign and performance to meetthe requirements
of a greater FMindustry tomorrow.
JOHN E. LINGO & SON, INC.ICENSED MANUFACTURERS OF PATENTED TURNSTILE ANTENNAS
In order to speed the publication of thisbook, the text was typed, and the pagesprinted by offset. Therefore the contentsis as up-to-the-minute as the fastest book -production methods could make it.
The fifteen chapters cover: Linear cir-cuit analysis; Fundamentals of tubes,power supplies; Amplification; Triggercircuits, pulse -sharpening circuits, andoscillators; Cathode-ray tubes and cir-cuits; Modulation; Demodulation; Radioreceivers; Transmitters; Ultra -high -fre-quency generators; Transmission lines;Radiation; Propagation; Hollow wave
Lalmr,t()n- manual.
FCC RELAXES FM REGULATIONSTHE FCC ha, announced a la-%% wartimeI policy for FM broadcast stations which
will have the effect of encouraging thosealready on the air to continue for theduration, and will enable several newstations, not yet in operation, to go aheadwith their plans.
The announcement from the FCCstates: "The Commission observes thatthe Communications Act does not con-template extensions of time within which
to complete roost ruction unless it appearsthat construction can be completed withina reasonable length of time. Nor is it de-sirable to continue the issuance of specialtemporary authorizations upon a shortterm basis. However, it is desirable to en-courage such service as is now possible tolisteners having FM receivers. Accord-ingly, the Commission will give considera-tion to applications for licenses to coverpartial construction of FM stations where
CAMDEN, NEW JERSEY
such construction has proceeded to thepoint where it is possible to provide alimited but satisfactory FM service. TheCommission will also consider applicationswhere construction has been completedand the permitee has been unable to secureequipment and technical personnel tomake measurements, required as a prereq-uisite to issuance of a license. Such li-censes will be granted on the definiteunderstanding that immediately the re-quired materials and personnel are avail-able, steps will he taken to comply fullywith the original construction permit."
In order for a station to qualify underthe FCC policy: it will be necessary foreach applicant to show:
1. diligence in proceeding with construc-tion and the reasons for failure to com-plete construction;
2. the actual status of construction whichthe applicant believes sufficient to pro-vide an acceptable FM service:
3. the materials and technical personnelneeded to complete construction and makeproof of performance; and
4. the applicant's determination to pro-ceed with the final completion in accord-ance with the Rules, Regulations, andStandards of the Commission when ma -
(CONTINUED ON PAGE 30) 27
LIMITED EDITION3 Essential RadioReference Volumes
forEngineering, Patent& Private LibrariesEach volume is a 300 -page record ofprogress in research and developmentduring the most significant period inthe history of radio progress. Theinformation and data contained inthese volumes are available from noother source.
Each volume has been bound in life-time pigskin, by the famous EggelingBindery.
A limited number of these volumes isavailable. Of the first, only 9 copies re-main. All are offered subject to priorsale at $5.00 each, postpaid.
F M COMPANY28 112 EAST 36th STREET, NEW YORK CITY
HORNS, OutdoorUniversity Laboratories. 195 Chrystie
St.. N. Y. C.
IRONS, SolderingIlexacon Electric Co.. Roselle Park,
N. J.
KNOBS, Radio & InstrumentAlden Prods. Co., Brockton. Mass.American Insulator Corp.. New Free-
dom, Pa.Chicago Molded Prods. Corp.. 1025 N.
Koimar, ChicagoGeneral Radio Co.. Cambridge, Mass.Imperial Molded Prods. Corp.. 2921 W.
Harrison. ChicagoKurtz Kasch, Inc.. Dayton. O.Millen Mfg. Co.. James, Malden. Mass.Nat'l Co.. Inc.. Malden. Mass.Radio City Products Co.. 127 W. 26 St..
N. Y. C.Rogan Bros., 2001 S. Michigan, Chicago
LABORATORIES, ElectronicResearch
* Browning Labs., Inc.. Winchester. Mass.
LIGHTS, Pilot or IndicatorAlden Prods. Co.. Brockton. Mass.Dial Light Co. of America. 90 West.
N. Y. C.Drake Mfg. Co., 1713 W. Hubbard.
ChicagoGeneral Control Co.. Cambridge. Mass.
* General Elec. Co., Lamp Dept., NelaSpecialty Dlv., Hoboken. N. J.
Herzog Miniature Lamp Works, 12-19Jackson Av., Long Island City, N. Y.
Kirkland Co.. H. R., Morristown. N. J.Mallory & Co.. P. R., Indianapolis. Ind.
LUGS, CopperMandy Engineering Co.. 459 E. 133rd
St.. N. Y.('.Dante Elec. Mfg. Co.. Bantam. Conn.Ideal Commutator Dresser Co.. Syca-
more. III.Ilse° Conner Tube & Prods.. Inc.. Sta-
tion M. CincinnatiKrueger & Iludepolil, Third & Vine,
Cincinnati, O.Patton-MacGuyer Co., 17 Virginia Av..
Providence. R. I.Sherman Mfg. Co., Battle ('reek. Mich.
MACHINES, ImpregnatingStokes Machine Co., F. J.. Phila.. Pa.
MACHINES, NumberingAltair Machinery Corp.. 55 VanDam.Numberall Stamp & Tool Co., Huguenot
Park. Staten Island. N. Y.
MACHINES, Riveting('hlcago Rivet & Machine ( '0., Bell, ..I
Illinois
MACHINES, ScrewdrivingDetroit Power Screwdriver Co., Detroit,
Mich.Stanley Tool Div. of the Stanley Works.
New Britain, Conn.
MAGNETS, PermanentGeneral Flee. Co.. Schenectady, N. Y.Mallory & Co.. P. ft.. Indianapolis, Ind.
METAL, ThermostaticBaker & C'o., 113 Astor. Newark, N. J.C. S. Brainin Co.. 20 VanDam, N. Y. ('.t'alllte Tungsten Corp., Union City,
N. J.Chace Co., W. M., Detroit, Mich.Metals & Controls Corp., Attleboro,
Mass.Wilson Co., H. A., 105 Chestnut,
Newark, N. J
METALS, Pr d PowderGibson Elec Co Pittsburgh, Pa.Mallory & Co., P R.. Indianapolis. Ind.
METERS, Ammeters, Voltmeters,Small Panel
Cambridge Inst. Co., Grand CentralTerminal, N. Y. C.
De Jur-Amsco Corp.. Shelton. ('onn.*General Electric Co., Bridgeport. Conn.
Hickok Elec. Inst. Co.. Cleveland. 0.Hoyt Elec. Inst. Works, Boston. Mass.Readrite Meter Works, Bluffton. 0.Roller -Smith Co., Bethlehem, Pa.Simpson Elec. Co., 5218 W. Kinzie,
ChicagoTriplett Elec. Inst. Co.. Bluffton. 0.Westinghouse Elec. & Mfg. Co.. E. Pitts-
burgh, Pa.Weston Elec. Inst. Corp., Newark. N. J.
MICABrand & Co., Wm., 276 Fourth Av..
N. Y. C.Insulation Mfgra. Corp., 565 W. 1Vash.
Blvd.. ChicagoMacallen Co., Boston. Mass.Mica Insulator corp.. 196 Varick.
N. Y. C.New England Mica Co.. Waltham,
Mass.Richardson Co., Melrose Park, Chicago
MICROPHONESAmer. Microphone Co., 101.5 Western
Av., Los AngelesAmperIte Co.. 561 B'way. N. Y. C.Astatic Corp.. Youngstown, D.Brush Development Co.. Cleveland. 0.Carrier Microphone ( '0., Inglewood, ( 'al.Elect. Industries Mfg. Co., Red Bank,
N. J.Electro Voice Mfg. Co.. South Bend.
Ind.
Kellogg Switchboard & Supply Co.,6650 S. Cicero. Chicago
Radio Speakers. Inc.. 221 E. Culierton,Chicago
Philmore Mfg. Co.. 113 University Pi..N. Y. C.
Permoflux Corp.. 4916 W. Grand Av.Chicago
Rowe Industries. Inc.. Toledo. 0.* Shure Bros.. 225 W. Huron St.. Chicago
Turner Co., Cedar Rapids. Ia.Universal Microphone Co.. Inglewoo(I,
Cal.
MONITORS, Frequency* Browning Labs.. Inc.. Winchester, Mass.*1.1nk. F. NI., 127 W. 17 St.. N. Y. C.
MOTOR -GENERATORS, Dynamo -tors, Rotary Converters
Alliance Mfg. Co., Alliance, 0.Air -Way Mfg. Co., Toledo, O.Bendix, Red Bank, N. J.Black & Decker Mfg. Co.. Towson, Md.Bodine Elec. Co., 2262 W. Ohio, ChicagoCarter Motor Co., 1608 Milwaukee,
ChicagoClements Mfg. Co.. Chicago, III.Continental Electric Co.. Newark. N. J.Delco Appliance, Rochester, N. Y.Diehl Mfg. Co.. Elizabethport. N. J.Dormeyer Co., Chicago, Ill.Eclipse Aviation, Bendix, N. J.Elcor, Inc.. 1060 W. Adams, ChicagoElectric Motors Corp., Racine, Wis.Electric Specialty Co., Stamford, Conn.Electrolux Corp., Old Greenwich. Conn.Emerson Electric ('o.. St. Louis, Mo.Eureka Vacuum ('leaner, Detroit, Mich.
* General Electric Co., Schenectady, N. Y.Jannette Mfg. Co., 558 W. Monroe,
ChicagoKnapp -Monarch. St. Louis. Mo.Leland Electric Co., Dayton, 0.ohlo Electric Co., 74 Trinity Pl..
N. Y. ('.Pioneer Gen -E -Motor, 5841 W. Dickens
Av., ChicagoRedmond Co., A. G., Owosso, Mich.Russell Co., Chicago. Ill.Webster Co.. Chicago, Ill.Westinghouse Elect. Mfg. Co.. Lima. 0.Wincliarger Corp.. Sioux City, Iowa
MOUNTINGS, Shock AbsorbingLord Mfg. Co., Erie, Pa.
S. Rubber Co.. 1230 -6th Ave..
MYCALEX* General Electric Co., Schenectady, N. Y.
Mycalex Corp. of Amer., 7 E. 42 St.,N. Y. C.
NUTS, Self -LockingElastic Stop Nut Corp., Union, N. J.Palnut Co.. Inc., Irvington. N. J.Standard Pressed Steel Co.. Jenkintown,
OVENS, Industrial & Laboratory* 1:e(leral Lice. ( Sellenerta(11'. N. 1
Trent Co.. Harold K.. Philadelphia
PHOSPHOR BRONZEAmerican Brass Co.. Waterbury, Conn.Bunting Brass & Bronze Co., Toledo. 0.Driver -Harris Co.. Harrison, N. J.Phosphor Bronze Smelting Co., Phila-
delphiaRevere Copper & Brass. 230 Park Av.,
N. Y. C.Seymour Mfg. Co.. Seymour. Conn.
PLASTICS, ExtrudedBlum & Co., Inc., Julius, 532 W. 22 St.,
N. Y. C.Brand & Co., Wm., 276 Fourth Ave..
N. Y. C.Extruded Plastics. Inc.. Norwalk. Conn.Irvington Varnish & Insulator Co..
Irvington, N. J.
PLASTICS, Laminated or MoldedAcadia synthetic Prude.,111:11 I ,g(11.11
Av., ChicagoAlden Prods. Co., Brockton, Mass.American Cyanamid Co., 30 Rockefeller
Plaza, N. Y. C.American Insulator Corp.. New Free-
dom. Pa.American Molded Prods. Co.. 1753 N.
Honore, (*Maw)Auburn Button Works, Auburn, N. Y.Barber -Colman Co., Rockford, Ill.Brandywine Fibre Prods. Co.. Wilming-
ton. Del.Catalin Corp.. I Park Av., N. Y. C.Celanese Celluloid Corp., 180 Madison
Av., N. Y. ('.Chicago Molded Prods. Corp.. 1024 N.
Koimar, ChicagoContinental -Diamond Fibre Co., New-
ark. Del.Dow Chemical Co.. Midland. Mich.Durez Plastics & Chemicals. Inc., N.
Tonawanda. N. Y.Extruded Plastics. Inc., Norwalk, Conn.Formica Insulation Co., Cincinnati, 0.
* General Electric Co., Plastics Dept.,Pittsfield. Mass.
General Industries Co.. Elyria, 0.Imperial Molded Prods. C0.. 2921 'A*.
Harrison. ChicagoIndustrial Molded Prods. Co., 2035
Charleston, ChicagoKurz-Kasch, Inc.. Dayton. O.Macallen Co., Boston. Mass.Mica Insulator Co., 196 Varick, N. Y. C.Monsanto Chemical Co., Springfield,
Mass.National Vulcanized Fibre Co., Wil-
mington, Del.Northern Industrial Chemical ('0..
Boston, Mass.Radio City Products Co.. 127 W. 26 St.,
N. Y. ('.Richardson Co., Melrose Park, Chicago
Rogan Bros., 180 N. Wacker Dr.,Chicago
Rohm & Haas ('o., PhiladelphiaStokes Rubber Co., Joseph. Trenton.
N. J.Surprenant Elec. Ins. Co.. BostonSynthane Corp., Oaks. Pa.Taylor Fibre Co.. Norristown. Pa.Westinghouse Elec. A Mfg. Co.. E.
Pittsburgh. Pa.Wilmington Fibre Specialty Co., Wil-
mington. I)el.
PLUGS & JACKS, Spring TypeEby. Inc., Hugh II.. Philadelphia. Pa.['chine Co.. Newtonvllle. Nlass.
PLUGS & JACKS, TelephoneType
Alden Prods. Co.. Brockton. Mass.American Molded Prods. Co., 1753 N.
Honore. Chicago(.'hicago Tel. Supply ( Eikart. IndGuardian Elec. Mfg. Co.. 1627 W
Walnut. ('hicagoJones, Howard It.. 23(H) Wabansla Av.
Chicago
PRESSES, Plastic MoldingKits Machine ( 3930 W. Harrison.
( 'hicago
PRESSESStokes Machine Co., F. J.. PhiladelphiaWatson -Stillman Corp., The. Roselle
Park. N. J.
RECTIFIERS, Current* Itenwood 1.1nze Co., St. Louis. Mo.
Continental Elec. Co., 903 MerchandiseMart, Chicago
Electronics Labs., Indianapolis, Ind.Fansteel Metallurgical Corp., N. Chi-
cago, Ill.*General Electric Co., Bridgeport, Conn.
International Tel. & Radio Mfg. Corp..E. Newark. N. J.
Mallory & Co., P. R., Indianapolis. Ind.Nothelfer Winding Labs.. Trenton,
N. J.rnited Cinephone Corp., Torrington,
Conn.Westinghouse Elec. & Mfg. Co.. E.
Pittsburgh. Pa.
REGULATORS, Temperaturethen -Bradley ( . Milwaukee. Wis.Dunn. Inc.. Struthers. 1321 Cherry,
PhiladelphiaFenwal Inc.. Ashland. Mass.
* General Electric Co., Schenectady. N. Y.Mercold Corp., 4217 Belmont, ( 'Meng°kfinneapolLs-Honeywell Regulator,
Minneapolis. Minn.Spencer Thermostat Co., Attleboro,
Mass.
REGULATORS, VoltageAcme Elec. & Mtg. Co.. Cuba. N. Y.Ferranti Elec.. Inc., 31) Rockefeller
Plaza. N. Y. C.* General Elec. Co., Schenectady. N. Y.
H -B Elec. Co., PhiladelphiaSola Electric Co., 2525 Clybourn Av.,
ChicagoUnited Transformer Corp., 150 Varick
St., N. Y. ('.
RESISTORS, FixedAcme Elec. Heating Co.. Boston. Mass.
* Aerovox Corp.. New Bedford, Mass.Alien -Bradley Co.. Milwaukee. Wis.Atlas Resistor Co., 423 Broome St..
N. Y. ('.('entralab. Milwaukee. WisconsinClarostat Mtg. Co., Brooklyn. N. Y.Conti Carbon. Inc.. Cleveland. O.I)aven Co.. 158 Summit St., Newark,
N. J.Dixon Crucible Co., Jersey City. N. J.Erie Resistor Corp., Erie. Pa.()lobar Div. Carborundum Co., Niagara
Falls. N. Y.Hardwick, Hindle, Inc., Newark. N. J.Instrument Resistors Co., Little Falls.
N. J.Intern'i Resistance Co., PhiladelphiaLectrolim, Inc.. Cicero. III.Ohmite Mfg. Co.. 4835 W. Flournoy,
ChicagoPrecision Resistor Co., Newark, N. J.Sensitive Research Inst. Corp.. 4545
Bronx Blvd., N. Y. C.Shallcross Mfg. Co., Collingdale. Pa.Sprague Specialties C'o., N. Adams,
Mass.Stackpole Carbon Co.. St. Marys. I'a.Ward Leonard Elec. Co., Mt. Vernon,
N. Y.White Dental Mtg. Co., 10 E. 40th St..
N. Y. C.Wirt Co.. tiermantown. Pa.
RESISTORS, Fixed PrecisionInstrument Resisters. Inc.. Little Falls,
N. J.Intern'i Resistance Co., PhiladelphiaOhmIte Mfg. Co., 4835 Flournoy St..
Chicago
RESISTORS, Variable* Aerovox Corp., New Bedford, Mass.
Allen-Bradley Co.. Milwaukee, Wis.Amer. Instrument Co., Silver Spring
Md.Atlas Resistor Co.. N. Y. ('.Centralab, Milwaukee, Wis.Chicago Tel. Supply Co., Elkhart, Ind.Cinema Eng. Co., Burbank. Cal.('larostat Mfg. Co.. Brooklyn. N. Y.Cutler -Hammer, Inc., Milwaukee, WisDeJur Amsco Corp., Shelton, Conn.Electro Motive Mfg. Co., Willimantic,
Conn.General Radio Co.. Cambridge. Mass.G -M Labs.. Inc.. Chicago. III.Hardwick. Hindle. Inc., Newark, N JInstrument Resistors. Inc., 1.Ittle Falls.
N. J.
Interri'l Resistance Co., PhiladelphiaMallory & Co., P. R.. Indianapolis, Ind.Ohio Carbon Co.. Cleveland. OhioOhmlte Mfg. Co., 4835 W. Flournoy
St., ChicagoPrecision Resistor Co., Newark. N. J.Shallcross Mfg. Co.. Collingdale. Pa.Stackpole Carbon Co., St. Marys. Pa.Utah Radio Prods. Co., 820 Orleans St.,
( 'hicagoWard Leonard Elec. Co., ML Vernon,
N YWirt Co I1erniantown. Pa.
RESISTORS, Variable, Ceramic BaseolimIte Mfg. Co., 4835 Flournoy St..
Chicago
RIVETS, Plaincentral --crew Co., 3519 Shields Av..
( Meng°Progressive Mfg. Co., Torrington, Conn.Republic Steel Corp., Cleveland, O.
SCREW MACHINE PARTS, Non -Metallic
oiditiental-Diamond Fibre Co.. New-ark. I al
SCREWS, Recessed HeadAmerican Screw Co.. Providence. It I
Bristol Co.. The. Waterbury, Conn.'handler Prods. Co., Cleveland, O.
Continental Screw Co., New Bedford.Mass.
Corbin Screw Corp., New Britain, Conn.International Screw Co., Detrsit, Mich,Lamson & Sessions. ('leveland. 0National Screw & Mfg. Co., Cleveland.
0.New England Screw Co., Keene, N. H.Parker Co., Charles, The, Meriden,
'onn.Parker-Kalon Corp.. 198 Varick, N. Y. (Pawtucket Screw Co., Pawtucket. It. I.Plieoll Mfg. Co.. ChicagoRussell. Hurdsall & Ward Bolt & Nut
Co., Port Chester, N. Y.Scovill Mfg. Co., Waterbury, Conn.Shakeproot, Inc., 2501 N. Keeler Av..
ChicagoSouthington Ilardw. Mfg. Co., South-
ington, Conn.Standard Pressed Steel Co.. Jenkintown.
Pa.Whitney' Screw Corp., Nashua. N. II.
SCREWS, Self -TappingAmerican Screw Co., Providence, R. I.Central Screw Co., 3519 Shields Av.,
ChicagoContinental Screw Co.. New Bedford.
Maas.Parker-Kaion Corp.. 198 Varick, N. Y. (Shakeproot. Inc., 2501 N. Keeler.
( 'hicago
SCREWS, Set and CapAlien Mfg. 1'0 Hartford. Conn.Parker-Kalon ( 'orp., 198 Varick.
N. Y. C.Republic Steel Corp., Cleveland. O.Shakeproot, Inc., 2501 N. Keeler Av.,
Chicago
SCREWS, Hollow & Socket HeadAlien Mhz , Ilartferd. coonI'ent ral Screw Co.,:i519 Shields, I 'hicagoParker-lialon, 198 Varlck, N. Y. (Standard Pressed Steel Co., Jenkintown.
Pa.
SELENIUM* Benwood Lime Co., St. Louis. Mo.
SHEETS, ElectricalAmerican Rolling Mill Co.. Middle-
town. 0.Carnegie -Illinois Steel Corp., Pittsburgh.
Pa.Follansbee Steel Corp., Pittsburgh, Pa.(Iranite City Steel Co., Granite City. III.Newport Rolling Mill Co.. Newport, Ky.Republic Steel Corp. Clevelanc, D.Ryerson & Son. Inc., Jos. T., Cnleago
SOCKETS, TubeAladdin Radio Industries, 501 W. 35th
St., ChicagoAlden Prods. Co., Brockton. Maas.Amer. Phenolic Corp.. 1831) S. 54th Av.
chicagoAmer. Radio Hardware Co.. 47C B'way,
N. Y. C.Birnbach Radio Co., 145 Hudson,
N. Y. ('.Bud Radio, Inc., t'leveland. 0.Cinch Mfg. Co., 2335 W. Van Buren St.,
ChicagoConri-Diamond Fibre Co.. Newark, Del.Eagle Elec. Mfg. Co., Brooklyn. N. Y.Eby. Inc., H. H.. PhiladelphiaFederal Screw Prods. Co., 26 S. Jeffer-
son, ChicagoFranklin Mfg. Corp.. 175 Varlck,
Ilammarlund Mfg. Co.. 424 W. 33 St.,N. Y. C.
Johnson Co.. E. F., Waseca. MinnJones. Howard B., 2300 Wabanida.
ChicagoMicarta Fabricators, Inc., 4619 Ravens-
wood, ChicagoMillen MIg. Co.. James, Malden. MassMiller Co.. J. W., Los Angeles, Cal.Nat'l Co., Malden, Mass.!fernier Co.. San Francisco. Cal.Smith Co., Maxwell. Hollywood Cal.
SOLDER, Self -fluxingGarden City laboratory, 2744 W. 37th
Pl., Chicago* General Elec. Co., Bridgeport. Conti.
Kester Solder Co., 4209 WrightwoodAv., Chicago
Ruby Chemical Co., Columbus, H.
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0 January, 1941 OctoberID February E November
Out of Print E December
March E January, 1942
April 0 February
0 May E March
June E April
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29
30
SOLDER POTSLectrohin, Inc.. Cicero, Ill.
SPEAKERS, Outdoor TypeUniversity 1.abs., 195 Chrystie St.,
SPRINGSAccurate Spring Mfg. Co., 3817 W.
Lake, ChicagoAmerican Spring & Mfg. Corp.. Holly,
M lob.American Steel & Wire Co., Rockefeller
Bldg., Cleveland, 0.Barnes Co., Wallace. Bristol. coma.Cuyahoga Spring Co., Cleveland, 0.Gibson Co., Wm. D., 1800 Clybourn
Av., ChicagoHubbard Spring Co.. M. D., Pontiac.
Mich.Hunter Pressed Steel Co., Lansdale. Pa.Instrument Specialties Co.. Little Falls.
N. Y.Muehlhausen Spring Corp., Logansport,
Ind.Peck Spring Co., Plainville. Conn.Raymond Mfg. Co., Corry, Pa.
SUPPRESSORS, ParasiticOhmite Mfg. Co.. 4835 Flournoy St.,
Chicago
SWITCHES, KeyTel. Supply Co., Elkhart. Ind.
SWITCHES, Rotary Tap, CeramicBase
Olinda, Attn. Co., 45:15 Flournoy St.,Chicago
TRANSFORMERS, IFAladdin Radio Industries, 501 W. 35th
St., ChicagoAmer. Transformer Co., Newark, N. J.Automatic Windings Co., E. Passaic.
N. J.Caron Mfg. Co., 415 S. Aberdeen.
ChicagoD -X Radio Prods. Co., 1575 Milwaukee.
ChicagoGeneral Winding Co.. 254 W. 31 St..
N. Y. ('.Guthman & Co., 400 S. Peoria St.,
ChicagoHammarlund Mfg. Co., 424 W. 33 St.,
N. Y. C.Meissner Mfg. Co.. Mt. Carmel. III.Millen Mfg. Co., James. Maiden. Mass.Miller Co.. J. W.. Los Angeles. ('al.Nat'l Co.. Malden, Mass.Sickles Co.. F. W., Springfield. Maas.Teleradlo Eng. Corp., 484 Broome St..
N. Y. C.Triumph Mfg co 1017 W. Lake.
Chicago
DIRECTORY
TRANSFORMERS, Receiver Audio& Power
Acme Elec. & Mfg. Co., Cuba, N. Y.Amer. Transformer Co., Newark, N. J.Amplifier Co. of Amer., 17 W. 20th St.,
N. Y. C.Audio Devel. Co.. N. Minneapolis. Minn.Cinaudagraph Speakers, Inc., 3929 S.
Michigan. ChicagoElectronic Trans. Co.. 515 W. 29 St..
N. Y. C.Ferranti Elec., Inc., 30 Rockefeller
Plaza. N. Y. C.Freed Trans. Co., 72 Spring St., N. Y. C.Gen'l Radio Co., Cambridge, Mass.General Trans. Corp., 1250 W. Van
Buren, ChicagoHalldorson Co., 4500 Ravenswood.
ChicagoJefferson Elec. Co.. Bellwood. Ill.Kenyon Transformer Co., 840 Barry St.,
N. Y. C.Magnetic Windings Co.. Easton. Pa.New York Transformer Co., 51 W. 3rd.
N. Y. C.Norwalk Transformer Corp, S. Norwalk.
Conn.Raytheon Mfg. Co., Waltham, Mass.Skaggs Transformer Co., Los Angeles,
('al.
Standard Transformer Corp., 15110 N.Halsted. Chicago
Superior Elec. Co.. Bristol, Conn.Thordarson Elec. Mfg. Co., 500 W.
Huron. ChicagoUtah Radio Prods. ('o., 820 Orleans St.,
Chicago
TUBE MANUFACTURINGMACHINES
Hilton Eng. Labs.. Redwood City, Calif.
TUBES, Cathode RayDumont Labs.. Allen B.. Passaic. N. J.Farnsworth Tele. & Radio Corp.. Ft.
Wayne. Ind.* General Elec. Co., Schenectady, N. Y.
Hygrade Sylvania Corp., Salem. Mass.Nat'l Union Radio Corp.. Newark, N. J.RCA Mfg. Co., Camden, N. J.
TUBES, Current RegulatingAmperite Co., 561 Broadway. N. Y. C.Champion Radio Works, Danvers. Mass.Hytron Corp. & Hytronic Labs.. Salem.
Mass.RCA Mfg. Co., Camden, N. J.
TUBES, Photo -ElectricBradley Labs., New Haven, Conn.Cont'l Elec. Co., Geneva.De Jur-Amato Corp., Shelton, Conn.De Vry, Herman A., 1111 W. Center,
ChicagoElectronic Laboratory, Lo, Angeles. Cal.Emby Prods. Co., Los r.iles, Cal.
OF MANUFACTURERS'
* General Elec. Co., Schenectady. N. Y.General Scientific Corp.. 4829 S. Kedzle
Av., ChicagoG -M Labe., 4313 N. Knox Av., ChicagoLeeds & Northrup Co., PhiladelphiaNat'l Union Radio Corp., Newark, N. J.Photobell Corp.. 123 Liberty St.,
N. Y. C.RCA Mfg. Co.. Camden, N. J.Rehtron Corp., 2159 Magnolia Av..
ChicagoRhamstine, J.. Detroit, Mich.Westinghouse Lamp 1)1v., Bloomfield,
N. J.Weston Elec. Inst. Corp., Newark. N. J.
TUBES, Receiving* General Electric Cu., Schenectady, N. Y.
IlYgrade Sylvania ('orp., Salem, Mass.Hytron Corp.. Salem. Mass.Ken -Had Tube & Lamp Corp.. Owens-
boro, Ky.Nat'l Union Radio Corp.. Newark, N. J.Raytheon Prod. Corp., 420 Lexington
Av., N. Y. ('.RCA MFG. Camden, N. J.Tung -Sol Lamp Works, Newark. N. J.
TUBES, TransmittingAmperes Electronic Prods, Brooklyn,
N. Y.Eitel-McCullough. Inc.. San Bruno, cal.Federal Telegraph Co., Newark, N. J.
* General Elec. Co.. Schenectady, N. Y.Heintz & Kaufman. S. San Francisco,
(al.Hytron Corp., Salem. Mans.Nat'l Union Radio ('orp., Newark, N. J.Raytheon Prod. Corp., 420 Lexington
Av.. N. Y. C.RCA Mfg. Co., Camden, N. J.Taylor Tubes, Inc.. 2341 Wabansia,
ChicagoUnited Electronics Co., Newark, N. J.Westinghouse Lamp Div., Bloomfield,
N. J
TUBES, Voltage -RegulatingAmperite Co.. 561 Broadway, N. Y. ('.HYgrade Sylvania Corp.. Salem. Mass.Hytron Corp.. Salem. Mass.RCA Mfg. Co., Camden, N. J.
TUBING, Laminated PhenolicBrandywine Fibre Prods Co., Wilming-
ton, Del.Formica Insulation Co., Cincinnati. 0.
* General Electric Co., Pittsfield, Mass.Insulation Mfgrs. Corp.. 565 W. Wash-
ington Blvd., ChicagoMica Insulator ('o.. 196 Varick, N. Y. ('.Nat'l Vulcanized Fibre Co., Wilmington.
Del.Richardson Co., Melrose Park, ChicagoSynthane Corp., Oaks. Pa.Westinghouse Elec. & Mfg. Co., E.
Pittsburgh. Pa.
Wilmington Fibre Specialty Co., Wil-mington, I)el.
TUBING & SLEEVING, VarnishedCambric, Glass -Fibre, Spa-ghetti
Bentley -Harris Mfg. Co., Conshohocken.Pa.
Brand & Co., Wm., 276 Fourth Av.,N. Y. C.
Endurette Corp. of America, ClIffwood,N. J.
* General Elec. Co.. Bridgeport. Conn.Insulation Mfgrs. Corp., 565 W. Wash-
ington Blvd., ChicagoMica Insulator Co., 196 Varick St..
N. Y. C.VARNISHES, Insulating, Air -
DryingJohn Dolph ( '0.. Newark. N. J.
VARNISHES, Insulating, BakingJohn C. Dolph Co., Newark, N. J.
VIBRATORS, Power SupplyTurner Cedar Rapids, Ia.
WIRE, BareAmerican Steel & Wire Co., Cleve-
land, 0.Anaconda Wire & ('able Co., 25 Broad-
way. N. Y. C.Ansonia Elec. Co., Ansonia. Conn.Belden Mfg. ('o., 4633 W. Van Buren.
Chicago* General Elec. Co.. Bridgeport. Conn.
Phosphor Bronze Smelting Co.. Phila-delphia
Rea Magnet Wire Co., Fort Wayne. Ind.Itoebling's Sons Co., John, Trenton,
N. J.WIRE, Hookup
Caret( Mfg. Co., Brookfield, MassWIRE, Magnet
Acme Wire Co., New Haven, Conn.American Steel & Wire Co.. Cleve-
land. 0.Anaconda Wire & Cable Co., 25 Broad-
way. N. Y. C.Ansonia Elec. Co., Ansonia, Conn.Belden Mfg. Co., 4633 W. Van Buren,
ChicagoElectric Auto-Lite Co., The, Port Ifuron.
Mich.* General Elec. Co., Bridgeport, Conn.* General Elec. Co., Schenectady, N. Y.
Holyoke Wire & Cable Corp., Holyoke,Maw.
Rea Magnet Wire Co., Fort Wayne.Indiana
Rockbestos Prods. Corp.. New Haven.Conn.
Roebling's Sons Co., John, Trenton.N. J.
REPRESENTATIVES & SALES OFFICES
IN RADIO WAR PRODUCTION AREAS
*These manufacturers' names are starred in the Radio -ElectronicsProducts Directory
AEROVOX CORP.Boston: 94 Portland St., Lafayette 3484Chicago: 4753 trway, Long Beach 0109Cleveland: 219 Film Ex. Bldg., Prospect
0719
Los Angeles: 1341 S. Hope St., Rich-mond 9121
New York: 347 Fifth Ave., Murray Hill5-7090
Pittsburgh: 918 Hill St., Churchill 0838
BENWOOD LINZE CO.Chicago: 549 W. Randolph St.Hollywood: 6406 Sunset Blvd.New York: 17 E. 42 St.Pittsburgh: 337 Ave. F. Forrest Hills
BROWNING LABORATORIES, INC.Address all correspondence to Winches-
ter, Mass.: 755 Main St., Win. 2121
GENERAL ELECTRIC CO.Boston: 140 Federal St., Hubbard 1800Chicago: 840 S. Canal St., Wabash 5611Cleveland: 4966 Woodland Ave., Endi-
cott 4464New York: 570 Lexington Ave.. Wicker-
sham 2-1311Philadelphia: 1405 Locust Ave., Penny -
packer 9000San Francisco: 235 Montgomery St.,
Douglas 3740
LINGO & SON, INC., JOHN E.Address all correspondence to Camden.
N.J.: 28& Van Buren Ave.,Camden 487
LINK, F. M.Address all correspondence to New
York: 125 W. 17th St., Chelsea 3534
RADIO ENGINEERINGLABORATORIES, INC.
Denver: 210 Fifteenth St.Detroit: 2040 Grand River Ave., W.Hollywood: 53334 Hollywood Blvd.Tampa: 115 S. Franklin St.Export: 89 Broad St.. N. Y. C.
SHURE BROTHERSChicago: 225 W. Huron St.. Delaware
8381Columbus: 85 E. Gay St., Adams 8928New York: 136 Liberty St., Worth
2-6550Philadelphia: 1343 Arch St.. Rittenhouse
9778San Francisco: 234 Ninth St.. Hemlock
2625Washington: 3308 Fourteenth St.,
N. W. Columbia 3938
FCC RELAXES FM REGULATIONS(CONTINUED FROM PAGE 27)
terial for further construction and neededtechnical personnel become available.
The following stations, totalling fifty-one, come within the scope of the FCCannouncement. In this list, CP indicatesthat the station already holds a construc-tion permit. PT indicates that the stationis now engaged in program tests. SA showsthat the station has a special temporary au-thorization, permitting it to be on the air.K31LA CP Columbia Broadcasting System, Holly-
wood, Calif.K37LA CP Earle C. Anthony, Inc., Los Angeles, Calif.K45LA SA Don Lee Broadcasting System, Los
Angeles, Calif.K6LA CP Metro -Goldwyn -Mayer Studios, Los An-
geles, Calif.
W53H PT Travelers Broadcasting Service, Hartford,Conn.
W65H SA WDRC, Inc., Hartford, Conn.
W47C CP WJJD, Inc., Chicago, Ill.W59C SA WGN, Inc., Chicago, Ill.W87C SA Columbia Broadcasting System, Chicago.W75C SA Moody Bible Institute, Chicago, Ill.
W79C CP Oak Park Realty & Amusement Co., Chi-cago, Ill.
W83C CP WHFC, Inc., Chicago, Ill.W71RF CP Rockford Broadcasters, Inc., Rockford, Ill.
W71SB CP South Bend Tribune, South Bend, Ind.W49FW SA Westinghouse Radio Stations, Fort
Wayne, Ind.W73I CP Associated Broadcasters, Inc., Indianapolis,
Ind.
W45BR PT Baton Rouge Broadcasting Co., BatonRouge, La.
W43B SA Yankee Network, Boston, Mass.W67B SA Westinghouse Radio Stations, Boston, Mass.
W77XL CP WJIM, Inc., Lansing, Mich.W45D PT The Evening News Association, DetroitW49D SA John Lord Booth, Detroit, Mich.
K51L CP St. Louis University, St. Louis, Mo.K59L CP Columbia Broadcasting System, St. LouisK49KC SA Commercial Radio Equipment Co. Kan-
sas City, Mo.
W39B PT Yankee Network, Mount Washington, N. H.W91NJ CP New Jersey Broadcasting Corp., Jersey
City, N. J.W95NJ CP Bremer Broadcasting Corp., Jersey CityW31NY CP Edwin H. Armstrong, Alpine, N. J.
W39NY CP Municipal Broadcasting System, N. Y. C.W47NY SA Muzak Radio Br 'dcasting Station, N. Y. C.W55NY CP William G. H. Finch, New York CityW59NY CP Interstate Broadcasting Co., N. Y. C.W63NY SA Marcus Loew Booking Agency, N. Y. C.W67NY SA Columbia Broadcasting System, N. Y. C.
W71 NY SA Bamberger Broadcasting Service, N. Y. C.W75NY CP Metropolitan Television, Inc., N. Y. C.W47A SA Capitol Broadcasting Co.,Schenectady, N.Y.W85A PT General Electric Company, Schenectady,
N. Y.W49BN CP Wylie B. Jones Adv. Agency, Bingham-
ton, N. Y.
W41MM SA Gordon Gray, Clingman's Peak, N. C.
W45CM SA WBNS, Inc., Columbus, OhioW49PH SA Pennsylvania Broadcasting Co., Phila-
delphia, Pa.W53PH PT WFIL Broadcasting Corp., PhiladelphiaW57PH SA Westinghouse Radio Stations, Phila-
delphia, Pa.W69PH SA WCAU Broadcasting Co., PhiladelphiaW73PH SA William Penn Broadcasting Corp., Phila-
delphia, Pa.W65PH CP Seaboard Radio Broadcasting Corp.,
Philadelphia, Pa.W75P SA Westinghouse Radio Stations, Pittsburgh
K51AM CP Amarillo Broadcasting Corp., Amarillo,Texas
K47SL CP Radio Service Corporation of Utah, SaltLake City, Utah
W55M PT The Journal Company, Milwaukee, Wis.
W51C Zenith Radio Corporation, Chicago, Ill.W45V Evansville On the Air, Inc., Evansville, Ind.W51R Stromberg-Carlson Telephone Mfg. Co.,
Rochester. N. Y.W47P Walker -Downing Radio Corp., Pittsburgh, Pa.W47NV National Life & Accident Insurance Co.,
Nashville, Tenn.
I /111 RADIO -ELECTRONICLW, ri a ENGINEERING & DESIGN
1117.iTHE JOURNAL Of WARTIME RADIO -ELECTRONIC 181111111011,
ENEISHRING & diANUFACTORING E3., Sy # Steep*.
0111 RADIO -ELECTRONICL A ENGINEERING & DESIGN
A
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THE 1111111MAL OF WARTIME 111111-EENTIINIC
ENCINEERINC & MANUFACTORINC Ed,ted b, a & s.w.w.
411111101-11110 Y41f MINNA I ZS VOW- 1.111MilleTIE JOURNAL Of WARTIME RAMO- AECTIONIC 11111.11PMENT,
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Position
Company
FREE: A copy of the second or third bound volume, as illus-
trated on page 28, will be sent you absolutely free if you
will make up a group of five subscriptions among your as-
sociates. Take advantage of this unusual offer without delay!31
The Right Answers
to Unusual
Radio -Electronic ProblemsFOR EXAMPLE: what is probably the most sensi-
tive, effective, and certain method of protecting
electric substation equipment, radio transmitters,
pumping stations, and similar installations is the
Browning Boundary Protection System.
Born of the wartime need of protection against
saboteurs, this system was developed and perfected
by the Browning Laboratories, in collaboration
with public utilities. It is capable of innumerable
applications where it is desired to signal, in any of
several ways, the approach of a trespasser to the
boundary of property requiring protection.
This is only one of many products of research which
has given the Browning Laboratories such a promi-
nent position in the radio -electronic field.
In personnel, equipment, and experience, this
organization, under the direction of Glenn H.
Browning, affords exceptional facilities leading to
sound and practical applications of radio -electronic
equipment for both military and commercial use.
* BROWNING *Frequency Monitor
Available with One to Four BandsPriced $125 to $185
The Browning Frequency Monitor, illustratedabove, is used as standard equipment for policeand public utility emergency radio systems through-out the USA. It provides the greater precision nowrequired by the FCC for all emergency transmitters.Suitable for both FM and AM, the Browning Moni-tor is built with one to four bands, for any frequen-cies between 1.5 and 60 mc. Prices:
Band $125 3 Bands $1652 Bands 145 4 Bands 185
BROWNING LABORATORIES, Inc.32 755 MAIN STREET WINCHESTER, MASS.
to the designers of ELECTRONIC EQUIPMENTLENZ is an organization of special-ists in design of wires and cablesfor electronic equipment. You'll findthousands upon thousands of feet ofLENZ standard and specially de-signed Wires, Cables and Cords inmilitary radio and wire communica-tions the world over-in Radar and
other types of electronic equipment.This specialized experience and
the facilities of the LENZ organizationare at your disposal for the solution cfyour wire problems. Call in a LENZWire and Cable Technician-with noobligation. Mail the coupon for a
LENZ Catalog.
ELECTRICAL CORDS, WIRES & CABLES
LENZ ELECTRIC MFG. CO.1751 NO. WESTERN AVENUE CHICAGO, ILLINOIS
IN BUSINESS SINCE 1904
MAIL THIS COUPON FOR LENZ CATALOG
AND TECHNICAL INFORMATION
Lenz Electric Mfg. Co., 1751 No. Western Ave., Chicago Please send me Lenz Catalog
Name
Address
City Stale
RUMFORD PRESSCONCORD. N H.
LINK MODEL 205 LINK CONTROL BOX, HANDSET,INTERMEDIATE FREQ. AM RECEIVER AND SPRING BASE ANTENNA
LINK MODEL 35UFMMOBILE FM TRANSMITTER
North Carolina goes 2 -way with
LINK FM EQUIPMENTAnother state-wide two-way radio com-munication system is being completed bythe North Carolina Department of MotorVehicles, Highway Patrol Division, underthe direction of Major J. T. Armstrong.
Link equipment, as illustrated, has beenpurchased for this project. North Carolinawas already equipped for one-way com-munication to Patrol cars, but this provedinadequate to meet the new responsibilitiesput upon the Highway Patrol by Warconditions.
Confronted with the need of conservingcritical communication equipment whileaugmenting the existing system to meetminimum defense requirements, the fol-lowing plan was adopted:
The present AM main station transmitterand car receivers are continued in service,and Link Model 35UFM talk -back trans-mitters are being installed in cars. FMpickup receivers are being set up at strategicpoints as necessary.
Tiflis with a minimum use of additionalcritical equipment, the system efficiencyis brought up to wartime requirementswith two-way communication, resultingin greatly increased effectiveness of theHighway Patrol.
The experience and knowledge of Link En-gineers are at the service of State, County, andMunicipal Police officials who are requiredto revise and enlarge existing or projectedsystems in accordance with wartime needs.
THESE LINK -EQUIPPED FM STATE-WIDE POLICE SYSTEMS NOW SERVE THE ATLANTIC SEABOARD
FM
CONNECTICUT MASSACHUSETTSDELAWARE NEW JERSEYMARYLAND
NEW YORKNORTH CAROLINAVIRGINIA
THE BEST -EQUIPPED MUNICIPAL POLICE SYSTEMS ALSO USE LINK EQUIPMENT EXCLUSIVELY
"3he Difficult we do Immediately-7he Impossible takes a little longer"
3red jt/1. fink 125 EST 17th ST., NEW YORK, N.Y.Telephone: CHELSEA 2-3838
Engineer Manufacturer