"RADIOLAMP Rt RADIO- CRAFT's Listener's Table Receiver DX Forum See Page 648

HUGO GERNSBACK Editor

Constructing the In This Issue "RADIOLAMP rt RADIO- CRAFT'S Listener's Table Receiver DX Forum See Page 648

Broadcast Station List - Constructing A Micro- Midget Analyzer Rewiring Sets For 2 -Volt Tubes -A Battery- Operated Midget RADIO'S LIVEST MAGAZINE M`MU LVER

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Street

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PA YAFTERYOUGRRADUAiE I am making an offer that no other school has dared to do. I'll take you here in my shops and give you this training and you pay your tuition after you have graduated. Two months after you complete my course you make your first payment, and then you have ten months to complete your payments. There are no strings to this offer. I know a lot of honest fellows haven't got a lot of money these days, but still want to prepare themselves for a real job so they won't have to worry about hard times or lay offs. I've got enough confidence in these fellows and in my training to give them the training they need and pay me back after they have their training. If you who read this advertisement are really interested A scent in the big, busy Radio Shops at Coyne. Here you see in your future here is the chance of a life time. Mail the fellows working on real Radios-not reading about them from coupon today and I'll give you all the facts. books or lessons. This is THE way to prepare for the big - money field of Radio! TELEVISION and TALKING PICTURES Television is already here ! Soon there'll be a demand for THOUSANDS of TELEVISION EXPERTS! The man who learns Television now can have a great future in this great new field. Get in on the ground -floor of this amazing new Radio development! Come to COYNE and learn Television on the very latest, newest Television equipment. Talking Picture and Public Address Systems offer oppoh ' .nities to the Trained Radio Man. Here is a great new Radio field just beginning to grow ! Prepare NOW for these wonderful opportunities! Learn Radio Sound Work at Coyne on actual Talking Picture and Sound Reproduction equipment. machines and Sound equipment. You learn Wireless Operating on PREPARE NOW and be actual Code Practice apparatus. We don't waste time on useless theory. We give you the practical training you'll need -in 10 ready for Radio's many short, pleasant weeks. MANY EARN WHILE LEARNING opportunities You get And don't let lack Forget offs Free Employment Service for Life. pay -cuts -lay- -unemployment! Don't be tied down to of money stop you. Many of our students make all or a good part an man's future. You - untrained NEED TRAINING IN A FAST of their living expenses while school and you should GROWING MONEY -MAKING TRADE. Here's going to if your chance of a need this help just write me. 33 Coyne lifetime to get it! Hundreds of now in to Coyne is years old. opportunities open Radio. Training is tested- proven beyond all doubt. You can find out every- My sensational offer, explained below, makes it possible for you thing absolutely free. coupon my to START AT ONCE! Just mail for big free hook! The right way to learn Radio is the Coyne way -not by books, H. C. LEWIS, Pres. RADIO DIVISION Founded I899 but by actual, practical work on actual Radio, Television and Sound equipment. Here at Coyne you'll service and operate scores COYNE ELECTRICAL SCHOOL of modern Radio receivers, huge Broadcasting equipment, late type 500 S. Paulina St., Dept.53-8H, Chicago, Ill. Television apparatus, Talking Picture machines, Code transmitters Mail and receivers, etc. In 10 weeks you can step into a BEAL JOB, Coupon Today for All the Facts a salary of week leading to $50 a and UP! H. C. LEWIS, President Radio Division, Coyne Electrical School ALL PRACTICAL WORK 500 S. Paulina St., Dept. S3 -eH, Chicago, Ill. I'ar Mr. Lewis: Send me your big FREE Book; details of At COYNE your FREE Employment Service; and tell me all about your in Chicago special ALL ACTL AL, PRACTICAL WORK. You offer of allowing me to pay for training on easy monthly build radio sets, terms after graduation. install and service them. You actually operate great Broadcast- ing equipment. You construct Television Receiving Sets and ac- Name tually transmit your own Television programs over our modern Television equipment. You work on real Talking Picture Address City State

RADIO -CRAFT for MAY, 1933 641 OUR JUNE ISSUE IS A SPECIAL AUTOMOTIVE RADIO NUMBER

THE See Page 652 /RdioaftFOR SERVICE MAN DEALER RADIOTRICIAN

HUGO GERNSBACK, Editor -in -Chief LOUIS MARTIN R. D. WASHBURNE Associate Editor Technical Editor

CONTENTS OF THE IN OUR NEXT FEW ISSUES: MAY, 1933, ISSUE HOW TO MAKE AN ULTRA -MIDGET CAR RADIO SET. Because VOLUME IV NUMBER 11 of the extreme adaptability of the little A.C.-D.C. ultra -midget sets, many set makers have provided for their use with battery supply, and are recommending their use as an automotive re- Editorial -DX Listening Hugo Gernsback 647 ceiver. However, while most of these sets are extremely convenient to use, due to their portability and ready adaptability How to Build the "Radiolamp" Table Receiver to any convenient 6 V. current outlet, such as a dash -board or instrument - Clyde Fitch 648 board light socket, they lack the extreme sensitivity and A.V.C. The Latest Radio Equipment 651 feature of most automotive sets. To meet this demand, there has been designed a new "ultra- midget ": a car radio receiver which the The Vest -Pocket, Seven -Tube Superhetero- Ultradyne.. average set builder will have no difficulty in constructing. Build Ulysses Fips 654 this new "money maker." Building a Battery- Operated "Personal" Receiver H. G. Cisin 657 THE AUXILIARY ANALYZER AND TUBE TESTER. This interesting device picks up the problem of set and tube testing where older Building a Laboratory- Standard Analyzer analyzers leave off, and enables the Service Man to continue the Leon J. Littmann 658 use of his old tester in the service of new sets and tubes.

Making Money with Amplifiers, Part V Hubert L. Shortt and Frank Lester 660 RADIO -CRAFT is published monthly, on the fifth of the month preceding Constructing the Micro- Midget Analyzer that of date; its subscription price is $2.50 per year. (In Canada and George G. Serotta 662 foreign countries, $3.00 a year to cover additional postage.) Entered at the post office at Mt. Morris, Ill., as second -class matter under the act of The Volt- March 3, 1879. Trademark and copyright by permission of Gernsback Multitester -A Ohmmeter and Milliam- Publications, Inc., 98 Park Place, N. Y. C. meter Milton Reiner 664 Text and illustrations of this magazine are copyright and must not be reproduced without permission of the copyright owners. We are also agents for WONDER STORIES and WONDER STORIES QUARTERLY. Readers' Department - 665 Subscription to these magazines may be taken in combination with RADIO -CRAFT at reduced Club rates. Write for information. Operating Notes Bertram M. Freed 666 Copyright 1933. GERNSBACK PUBLICATIONS, INC. Rewiring R.C.A. and A.K. Sets for 2 -Volt Tubes David Hoyle 668 HUGO GERNSBACK, President J. M. HERZBERG, Vice -President S. GERNSBACK, Treasurer I. S. MANHEIMER, Secretary RADIO SERVICE DATA SHEETS: Published by TECHNI -CRAFT PUBLISHING CORPORATION. Pub- No. 89 R.C.A. Victor R -27, and Philco 53 Ultra - lication office: 404 N. Wesley Ave., Mount Morris, Illinois. Editorial Midget A.C.-D.C. Receivers 670 and Advertising Office: 96 -98 Park Place, New York City. Chicago Advertising Office: 737 North Michigan Avenue, Chicago, Ill. No. 90 Fada 103 Fadalette, Stewart -Warner Series Western Advertising Office: 220 No. Catalina St., Los Angeles, 108, and DeWald 54 Dynette Sets 671 Calif. L. F. McClure, Chicago Advertising Representative. Loyd B. Chappell, Western Advertising Representative. Broadcast Stations of the U. S. 672 The DX Listener's Forum 675 London Agent: Hachette A C :a., 3 La Belle Sauvage, Ludgate Hill, E.C. 4 Paris Agent: Hachette & Cie.. Australian Agent: McGill's Agency III Rue Reaumur 179 Elizabeth Radio Craft's Information Bureau _ 676 St., Melbourne A Super -Sensitive All -Wave Crystal Set J. M. Nighswander 680 Quasi -Optical Home Experiments John B. Brennan, Jr. 682 Book Review 697

642 PLACE RADIO -CRAFT FOR MAY, 1933 704A POST CARD lc STAMP

HERE Tricks of a "Sound" Wizard Since sound effects are to radio dramas what scenery is to the stage, one of the most important roles in any radio program is that enacted by a star performer who is neither personally heard nor seen by the listening audience. Yet his task is of the utmost importance if the background of' microphone-play is to seem realistic. Such an invisible wizard is Albert J. Sinton, sound director of the World Broadcasting Mr. J. E. Smith, President System, whose ingenious effects have added materially to the living realism achieved by that organization in the reproduction of its popular electrical transcriptions. Institute Born in England, Sinton carne to the United States when five yeast National Radio old. and soon after his school days developed an ear for music. It was as a drummer in a theatre orchestra in Utica, New York, that he began Dept. 3EX his unique career and later with the advent of the silent screen was engaged by a local motion picture house to watch the pictures shown, and with his drum and varied gadgets, produce the sound of winds and Washington, D. C. waves, railroad and steamboat whistles, and similar effects as the films un reeled. During the course of that experience, Sinton devised an unique sound effect cabinet operated by electricity and compressed air. Installed in this console cabinet were the means of making about fifty standard sound effects such as those of trains, airplanes. automobiles, and like familiar noises, and soon thereafter Sinton found himself being referred to as "the wizard of sound." Operated by push buttons from a control board, PLACE this device was at once adopted by the screen when the talkies came into being. It then came to the notice of the W. B. S. and Sinton was POST CARD lc of Sound Technician in the New York studios offered the post Chief STAMP of that organization. In addition to his magic cabinet, however, Sinton is the originator of HERE the means of realistically producing many sound effects now familiar to the ears of the listening audience. For instance the effect of footsteps crunching in the snow as required in making broadcasts of the adven- tures of the Northwest Mounted Police more thrilling. This colorful effect is produced by crunching the fist enclosed in a glove in a bowl of cornstarch. Not only do many of Sinton's devices add realism but reduce production expense. Before he set to work to solve the problem, scripts that Lincoln Radio Corporation called for the sound of marching feet required the presence of as many i supers as the W. B. S. studios could hold. Naturally this was costly as Dept. E335 well as inconvenient, so Sinton invented an apparatus which gave the illusion of a marching host quite as well, if not better, than the footsteps of an actual mob. His invention was a frame about eighteen inches 329 South Wood Street square with a number of wooden blocks suspended from its center. By Chicago, Illinois

PLACE POST CARD le STAMP HERE i Mr. H. C. Lewis, President Coyne Electrical School, Dept. 53 -8H 500 South Paulina Street Chicago, Illinois

PLACE POST CARD lc STAMP HERE

E. H. Scott Radio Laboratories, Inc. In this view, Albert J. Sinton, sound genius of World Broadcasting System, is shown surrounded by some of his numerous inventions for foxing the public via the "air" lanes. At the moment, he is producing Dept. C -53, the sound effects incident to the whine of shells in the course of a World War drama for the micrephoue. "You can't judge an effect by its sound!" 4450 Ravenswood Avenue CHICAGO, ILLINOIS i May RADIO CRAFT

Mr. J. E. Smith, President RADIO -CRAFT FOR MAY, 1933 704B National Radio Institute Dept. 3EX, pounding these blocks on the floor with a rhythmic movement, the sound Washington, D. C. of the tramp of many feet was perfectly produced. "Sometimes," said Sinton, "the effect of applause is reproduced from Without obligating me, send free book about spare time and full time a previous electrical transcription of the approval of a living audience

Radio opportunities and how I can train for them. and "dubbed -in" on the transcription being made. Other times it is found more satisfactory to have an actual gathering In the studio to laugh and clap their hands. "One of the most difficult effects I have ever been asked to create was Name the squeak of the chains of a porch hammock. I tried all sorts of things, including a real hammock swinging in the studio," Sinton continued, "but none sounded natural over the mike, for all too frequently that temperamental instrument absolutely refuses to reproduce actual sounds Address realistically. So in the case of the hammock chains, I finally won out by drawing a tooth -pick back and forth across the teeth of a small nail

Another novel method this "wizard" has devised is the scraping of City State a wire brush over a piece of corrogated tin mounted on a resonating box. The result is a perfect simulation of a locomotive going at full speed over a bridge! Not satisfied with that, however, Sinton desired a complete cabinet of railroad noises, so it was arranged that he might actually ride in an engine cab with his notebook as his companion. Dur- ing the trip. Sinton took notes on the various sounds he heard while the train was in motion -the engineer's signal. the shoveling of coal, click- ing of wheels on the rails, the steam exhaust, whistles and bells- every- thing which would add realism to a thrilling series of railroad broad- Ma RADIO CRAFT casts. Then after weeks of experiment, he solved each need and achieved his "railroad" cabinet. Lincoln Radio Working with him, Sinton has a trained crew of sound producing Corporation experts, the forte of one of whom is animal imitations. In spite of that Dept. E335, 329 assistance, however, Sinton once found himself stumped by the need to produce the sound of horse's hoofs. He rt last achieved it with a rub- Chicago, Illinois, U. S. A. ber plunger, auch as is used by plumbers, but at the close of the program a colored porter burst into the studio and called out "Oh, Mr. Sin - Please send me Free Technical description of the ton, lend me one o' your horses. The sink outside's plugged up!" Still other devices of Sinton's are apparatus to create the illusion of waves and R -9 SW -33 the splash of swimmers diving into water. Another is his "rain making" machine which performs its task by dropping sand on parchment paper, while his wind -maker is a motor shaft equipped with rattan sticks which revolve and fan the studio air. In one script where an automobile starter was required to be heard, Sinton found that except Name for having an actual starter mounted, this effect was a tough nut. But he stumbled across its solution in the form of an emery wheel mounted and in motion. Once asked if he could give the effect of falling snow, i Sinton replied that he could and stood silent without moving. "Perfect!" pronounced the director and Sinton took a bow. At the present time, Address however, he is experimenting with the feasibility of an actual electrical recording of wind and other natural sounds. Up until a short time ago, sound effects previously recorded for "dub- bing in" were fed into the electrical transcription disc by telephone line and as a result were not heard by the actors in the studio. Consulting City State with the directors Sinton thought the players' performance would be more convincing if they could hear these background effects. So he devised a turntable and phonograph pickup, with an associated amplifier and reproducer which would enable his sound discs to produce the desired effect in the studio and feed them to the transcription disc only via the studio microphone in the hearing of the cast. At present Sinton is engaged in a fascinating task assigned to him by the W. B. S. which is sending him to various sections of New York Mar RADIO CRAFT and its environs, in a car equipped with electrical transcribing apparatus. The purpose of these trips is to capture at first hand harbor noises, sub- way sounds, the rumble of freight cars. the blast of steam shovels, steel Mr. H. C. Lewis, President drills and all of the noisesome background familiar to Manhattan. Coyne Electrical School (See also the very interesting article, "How the Robot Fools You." in the April. 1932, issue of EVERYDAY SCIENCE AND MECHANICS, pg. 410. Dept. 53 -8H, 500 So. Paulina St. Technical Editor.) Chicago, Illinois Without obligation send me your big free catalog and all details of Rail- road Fare to Chicago, Free Employment Service, Radio, Aviation, Elec- A "Talking Fiddle" tricity, and Automotive Courses, and how I can "earn while learning" as A New York musician has devised a sound amplification system which 1 your in RADIO -CRAFT. he claims will produce the effect of a full symphony orchestra, although per advertisement a number of string instruments are eliminated. ALSO TELL ME ABOUT YOUR "PAY AFTER GRADUATION OFFER." Instead of utilizing the usual large number of first and second violins, only two first and two second violins are employed. Each violin is equipped with a Universal model W watch -case type microphone, at- Name tached to the bridge of the instrument. In addition two large model LL Universal microphones are used to pick up the orchestra as a unit. Only a single amplifier is necessary. The number of speakers, as well as their arrangement, is determined by the acoustical conditions of the auditorium. Address. There is a mixer between the microphone and the amplifier, which permits separate volume control for each of the six microphones. In this way, the volume of the four violins may be amplified above that of the other instruments, to as great an extent as desired. City State Using this plan, the orchestra is under the direction of a leader who directs the musicians and also controls the mixing panel, increasing the volume of the first and second violins as compared to that of the other instruments, to give the effect of a complete symphony orchestra and also to suit his individual interpretation of the way in which the selection should sound. Modifications of the above plan have been susvested, whereby additional microphones could be used in connection with the reproduction of other instrument sounds. slay RADIO CRAFT (See also "The Radio Violin" in the December, 1931, issue of RADIO- CRAFT. pg. 358. Technical Editor.) E. H. Scott Radio Laboratories, Inc. Dept. C -53, 4450 Ravenswood Avenue, Chicago, Illinois A "Padded Cell" for Sound Tests In the general Engineering laboratory of the General Electric Com- pany Send me all details regarding the SCOTT ALL -WAVE DELUXE RADIO, at Schenectady there is a padded cell-a room, within a room, of such construction that outside sounds, and even building rumble, can- including technical data, performance proofs and prices. This is not to not enter. obligate me. The outer wall is of sound -absorbing plaster; next within is hollow tile: then an air space; felt; another wall of sound- absorbing plaster; more air space; sheet iron; air space; lath -work, and then a thick layer of cotton waste -with a total thickness of about 18 inches. The ceiling of the inner room is similarly constructed; and the floor is supported on Name a felt blanket. Heavily padded double doors isolate the room. Within the room -where lack of reflections causes one's voice to sound strange-are conducted experiments to determine the amount and type of noise produced by motors, fans, and many other kinds of equipment Address The measurements are made with a noise meter which is a product the same laboratory. oY

City State SCOTT TAKES 20,000 -MILE CRUISE TO GIVE RADIO ANOTHER HARD TEST

Research To Prove Perfection Of Scott All -Wave Deluxe

E. H. Scott, whose genius created the marvelous SCOTT ALL -WAVE DE- LUXE RADIO, sailed recently on an ad- venturous 20,000-mile voyage to give his receiver still another series of gruelling reception tests. Thousands of miles from any land the SS. Maunganui plows her way down the trackless Pacific enroute to New Zealand. Her as E. H. Scott, designer and builder of the famous Radio Receiver bearing his name, passengers are gay boards the SS. Maunganui to start 20,000 -mile cruise. they gather in the luxu- rious Grand Salon each evening. They enjoy an WORLD -WIDE RECEPTION GUARANTEE excellent dance orchestra's rhythms. The tunes BASED ON CONSISTENT PERFORMANCE come from a loudspeaker that reproduces Backing the Scott All -Wave Deluxe Radio the music of orchestras with a positive guarantee of consistent world -wide Id. H.SC°Tr reception, with loud speaker volume, of foreign six or seven thousand stations 10,000 miles or more distant, was not miles away, back in "the States." justified by scientific laboratory tests alone. Rather To E. H. Scott, and the world's- record -shatter- such tests, under actual owner -operated condi- ing receiver which he designed and builds, must every pro- tions, as the reception in Chicago of go all the credit for this exceptional feat. But gram broadcast from VK2ME and VK3ME in music, daily news flashes and other radio an bringing Australia (9,500 miles distant) throughout treats to the Maunganui's company is but a small conclu- entire year's time, were considered more part of the thorough research Mr. Scott is carry- than 19,000 verified sive. Likewise were the more ing on during his cruise to test his receiver. From by owners undertaken foreign reception logs submitted Scott Here is the route of E. H. Scott's long cruise, his experimentation with the Scott All -Wave De- contributory to the to test reception under most difficult conditions. within a six months' period luxe, which is his most important piece of bag- with such a maker's decision to back his receiver gage, will come new inspiration and still further startling warranty. On his present 20,000 -mile justification of the consistent world -wide recep- RECEIVER will cover many WORLD- TRAVELING experimental cruise Mr. Scott tion guarantee under which this radio known as where reception is extremely diffi- localities radio "The World's Finest Receiver" is sold. cult. He is wholly confident that even in these final so- called "dead spots" his set will function per- The radio-wise will watch with interest for fectly for him as it is doing for many owners in reports of Mr. Scott's research. They confidently places where radio reception was always before expect news of the breaking of still more reception considered impossible. records as one outgrowth of this long trek. ENTHUSIASTIC OWNERS CONTINUE TO LAUD PERFORMANCE OF ALL -WAVE DELUXE Letters expressing perfect satisfaction with the like such a set -the ultimate in radio ability- marvelous Scott All -Wave Deluxe Radio pour why not send NOW for all details regarding it? into the Scott Laboratories daily. Here are ex- This Scott All -Wave Deluxe Radio which Mr AT ONCE! cerpts from a few recent ones: "Most sensitive SEND COUPON Scott is using on his research trip is an exact r of the custom -built sets sold to discrim- radio I have ever seen," SGP, Ala.... "Nothing duplicate E. H. SCOTT RADIO LABORATORIES, INC. receives broadcasts on all wave finer in tone -in fact, perfect in every way," FW, inating buyers. It 4450 Ravenswood Ave., Dept. C -53, Chicago, Ill. lengths between 15 and 550 meters. Of true one- Calif.... "Stations all the way from Berlin to Send me all details regarding the SCOTT ALL - dial type, it uses no trimmers or auxiliary tuning Tokio and Australia," ... JBT, Conn...: "For- WAVE DELUXE RADIO, including technical dials, and has no plug -in or tapped coils or other eign reception every day. France best -Rome, data, performance proofs and prices. This is not to old- fashioned wave band -changing devices. It is England, Germany and Spain come in very good," obligate me. visual equipped with automatic volume control, RPH, Conn.... "Tone cannot be improved -it tuning, static reducer, and every new scientific Name is already perfect," GL, N. Y.... ''Australia betterment of proved value. Despite its tremen- Address dous distance range, high selectivity, abso- with the volume of a local station," Dr. HPC, lutely natural tone, and general excellence, it N. Y.... "Amazed at results -would not take LTown State is sold at a remarkably moderate price. $500 in exchange for it," JLH, Pa. If you would .s

RADIO -CRAFT for MAY, I 933 643 Rdioaft FREE SERVICE

5. CLAROSTAT CONTROL HANDBOOK. A fart:,' 96. TORE. FILTERIZER AND CONDENSERS. The 32 -page book containing detailed specification- Tobe Deutschmann company is now catering to volume of controls, attenuators, constant -im- the Service Man with an extensive line of filter. pedancs controls, phonograph tops' READERS' BUREAU pickup faders, by -pass and line condensers and radio noise controls, line ballasts, rheostats, potentiometer - On this eliminators. Their latest catalog. describing the and fixed resistors of various kinds, together page are listed manufacturers' complete line, has just come off the press. A with valuable circuit -design catalogs and booklets, chosen because data. Contains many full page is given to the new "Fílterizer" noise diagrams and charts, and a guide of replace- they are of interest to readers of eliminating antenna system, an item of par- ment volume and tone controls for many com- RADIO CRAFT. Many of them con- ticular interest to Service Men because of the mercial receivers. Claroatat Manufacturing COO, - money -making opportunities offers. Tobe pony, tain valuable technical data in the it Inc. Deutschmann Corporation. form of charts, curves, tables, etc., 6. MEASURING RESISTANCE BY THE DEFLECTION and are therefore worth having and METHOD. The conventional method for the mea-- saving. You can obtain copies FREE 97. ARco TUBE BULLETIN. A descriptive urement of resistance involves the use of tl.. by using the coupon below. folder giving full technical characteristics on the Wheatstone bridge, a costly piece of apparatus. complete line of Arco radio receiving and trans- However, there are other methods which provide mitting tubes, photo -electric cells. television a fair degree of accuracy, enough for all prac- lamps, hot and cold cathode tubes, cathode ray tical purposes. The least expensive is the de- dealers and Service Men, for whom the volume tubes, rectifiers and charger bulbs. This can be flection method, which makes use of popularly is specifically intended. posted for easy reference. Arco Tube Company. priced milliammeters and fixed resistors. This A large amount of is bulletin describes the method completely, and apace also given to replacement power should be very useful transformers, condensers and to Service Men and ex- 98. How TO USE NOISE REDUCING ANTENNA perimenters with limited meter equipment. resistors for ordinary service work. This catalog is well SYSTEM ON BROADCAST WAVES AND SHORT WAVES Shallcross Manufacturing Company. prepared and is worth saving. Coast -to- Coast Radio Corporation. is the title of the latest booklet on this important subject. In addition to covering the theory, the practical application of the various noise- reduc- 11. SUPREME INSTRUMENTS. Contains lengthy 1. ing systems available for broadcast descriptions of the Supreme service instruments, 81. R. C. REStstoR CATALOG. This sixteen - and short wave use, is described also. Lynch Mfg. Co. including the AAA1 Diagnometer, which is five page catalog describes a very complete line of fixed instruments in one, the model 90 analyzer, the resistors for radio purposes. It includes model 40 tube tester and the models 60 and 70 full performance characteristics, so that a Serv- 99. AMPERITE CHART. Service Men will oscillators. Interesting to the Service Man be- ice Man or an experimenter with a particular find this chart very valuable, as it shows cause it tells how his work is facilitated by requirement in mind can select exactly the right the correct Amperite line voltage regulator ingeniously -designed test equipment that indi- unit for his purpose. A section in the back to use with any of several hundred different cates the condition of an entire set in a few contains valuable data on the conversion of broadcast receivers. An accompanying pamphlet minutes. New test apparatus to take care of milliammeters into ohmmeters and voltmeters, explains how overloaded condensers and the new tubes is also described. Supreme In- and on the extension of voltmeter and ammeter resistors may be the cause of crackling strument Corporat ion. ranges. This catalog is well worth saving. noises and poor reception. Amperite International Resistance Company. Corporation.

19. A BAPTISM or FIRE. Centralab fixed re- 100. WHOLESALE RADIO SERVICE CATALOG. sistors are made by forcing a carefully calibrated The 93. DUBILIER CONDENSERS. The 1933 catalog new Spring 1933 Wholesale Radio resistance material through a ceramic catalog con- plastic of Dubilier condensers is a large 16 -page booklet tains 152 pages, and is probably material, and then baking both under terrific the largest describing fixed condensers for every conceivable mail order catalog of its kind in heat. This booklet describes the manufacturing print. It is ex- application. These range from little mica units ceptionally complete. and includes process in detail, and lists the advantages everything for receiving circuits to man -high assemblies for from soldering lugs to all -wave claimed for fixed resistors of this type. It is receivers. It is transmitting work. A useful catalog to all radio of value to dealers, Service interestingly written and illustrated, and makes Men and experi- men. Dubilier Condenser Corporation. menters for reference and ordering purposes. good reading. Central Radio Laboratories, Du -. Wholesale Radio Service Co. Inc.

21. READRITE RADIO INSTRUMENTS. This six- 94. ELECTRAD PRODUCTS. The newest and 1 teen- page pamphlet contains some valuable hints latest catalog of Electrad products contains RADIO -CRAFT 5.108 on the testing of 'electrolytic condensers, as well twelve pages and lists many types of fixed and Readers Bureau as descriptions of the full line of popular- priced variable resistors and five different kinds of 96 -98 Park Place, New York, N. Y. Readrite instruments. Worth having. Readrite amplifiers for public address purposes. The Please send me free of charge the fol- Meter Works. lowing booklets indicated by numbers popular Truvolt resistors have been improved in the published list above: by the addition of insulating shields and heat 22. How To TEST PENTODES. This is a reprint radiating covers, and a number of new sizes have No. of an article of the same name that appeared in been added to the line. The catalog also con- the September, 1931, number of RADIO- CRAFT. tains some valuable data on the application of accompanied by descriptive matter on the resistors to radio receivers, transmitters, ampli. adapters specified for the purpose. If you missed fiers and sound systems. and suggestions on how Name the original article study the reprint; it contains to compute the value of resistors. A handy and much useful data for owners of teeters or useful catalog. Electrad. Inc. Address analyzers not already equipped to test pentodes.

Alden Manufacturing Company. City - State 95. CARDWELL (Please check the following) CONDENSERS. This is a con- I am densed four -page catalog of the well known Card- (1) Service Man (2) Experimenter 76. THE COAST-TO-COAST "BRowpcwaT." The well "Midway" variable condensers for trans- (3) Dealer (4) Jobber "Broadcast" is the ball 1932 edition of a 100 - mitting and receiving. These are small but not (5) Radio Engineer page mail order catalog is (6) Licensed Amateur that a veritable en- "midget" size instruments designed for purposes (7) Professional or Amateur Set cyclopedia. Its listings are very varied, and run where extremely light weight and reduction of Builder from soldering lugs to complete 100 -watt public bulk are desirable. Complete and detailed speci- This coupon will not be honored unless you check off your address amplifiers. Every article is well illus- fications are included for the assistance of con- classification above. trated and described for the benefit of radio structors. Allan D. Cardwell Mfg. Corp. L

644 RADIO -CRAFT for MAY, 1933 BE A RADIO EXPERT Many Make siOO ) 50 t° a Week You rnYourSpare ¶me J. E. Smith President. III ah, at Home National Radio Institute the man who has directed the Home -Study training of more men for the Radio Industry than any other man in America. /orlblDIO 'TELEVISION TALKING MOVIES

Set Servicing Broadcasting Ship Spare -time set serv- Stations Operating icing has paid many I. men to Employ t r a , .I Radio operat r.. on N. R. $200 world $1,000 a year. Full - m e n continually .hips see the make as for jobs paying as free and get good time men pay plus expenses. much as $65, $75. much as $5,000 a Here's one enjoy- and $100 a week. year. ing shore leave.

Aircraft IF you are dissatisfied with your present job, if Many Make SS, St% its a Week Extra in Spare Time you are struggling along in a rut with little or Almost at Onee no prospect of anything better a pay The day you enroll with me I send you instructions Radio is making than skinny doing 28 jobs flying safer. Radio envelope-clip the coupon NOW. Get my big FREE which you should master quickly for book on the opportunities in Radio. Read how common in most every neighborhood, for spare -time operators employed I you informa- through Civil Serv- quickly you can learn at home in your spare time money. Throughout your course send to be a Radio Expert good jobs my graduates tion on servicing popular makes of sets! I give you i c e Commission -what made $200 to $1,000 $1,620 to have been getting -real jobs with real futures. the plans and ideas that have earn a year for N. R. I. men in their spare time. My $2,800 a year. for itself. Many Radio Experts Make to $100 a Week course is famous as the course that pays SSO Talking Movies, Television, Short Wave, Mosey - In about ten years the Radio Industry has grown Back Agreement Included from $2,000,000 to hundreds of millions of dollars. Special training in Talking Movies, Television and Over 300,000 jobs have been created by this growth, Home Television experiments, Short Wave Radio, and thousands more will be created by its continued Radio's use in Aviation, Servicing and Merchandising development. Many men and young men with the Sets. Broadcasting, Commercial and Ship Stations right training -the kind of training I give you in are included. I am so sure that N. R. I. can train the N. R. I. course -have stepped into Radio at two you satisfactorily that I will agree in writing to re- and three times their former salaries. fund every penny of your tuition if you are not satisfied with my Lesson and Instruction Service upon Get Ready New for Jobs Like These completion. Broadcasting stations use engineers, operators, ê4-yage Beo S Information station managers, and pay up to $5,000 a year. Man- Talking Get your copy today. It's free to ufacturers continually employ testers, inspectors, States Movies foremen, engineers, service men, buyers, for jobs all residents of the United made and Canada over 15 years old. It An invention paying up to $6,000 a year. Radio Operators on tells you where Radio's good jobs possible by Radio. tells you Employs many well ships enjoy life, see the world, with board and lodg- are. what they pay. men ing free, and get good pay besides. Dealers and job- about my course, what others trained Radio doing and for jobs paying 875 bers employ service men, salesmen, buyers, managers, who have taken it are to $200 a week. and pay up to $100 a week. My book tells you about making. Find out what Radio these and many offers you without the slight- other kinds of interesting Radio jobs. est obligation. ACT NOW l SPECIAL Radio Equipment for Broad Practical Experience Given Without Extra Charge qty coo rhe is not all theory. 1.11 .how you how to too my special Radio Equipment for conducting experiment, :.nd building circuits which illustrate important prin- J. E. SMITH, President Television . iples used in such well known sets as Westinghouse. National Radio Institute, Dept. 3EX General Electric. Philco, R. C. A., Victor, Majestic, and The coming field others. You work out with your own Washington, D. C. of many great op- hands many of the things you read in portunities is cov- our lesson books. This 50 -50 method of Without obligating me, send free book training makes learning at home easy. about spare-time and full -time Radio oppor- ered by my course. interesting, fascinating. intensely practical. You learn how sets work, tunities and how I can train for them at why they work, how to make home. them work when they are out of order. Training like this show, up In your pay Nance A y. envelope - who, YOU graduate yuu hare had train Address..._ Ina and experi ,.nee -yoú re Imply look[,, for Job when City State YOU can get e, ariette. RADIO -CRAFT for MAY, 1933 645 This

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GERNSBACK PUBLICATIONS. Inc.. 96 -98 Park Place. New York. N. Y. 2,300 Pages iient hmen: nee a$uiwith your Special Offer, 1 entitle.. herewithIn $3.3.00 as arat payment toward the One 5,500 Illustrations Volume Radio Manual. Please forward it to n OVER promptly. Upon receipt of the book, I shall par express company 65.00. Thirty days later I shall end you $3.00. and sixty days after receipt ut book. I shall send you my last payment of $3.00. If you want to take advantage of the Special DI. count , of 104 }, remit only $12.60 with ihN rv.upw: THIS IS THE GREATEST SINGLE Name VOLUME RADIO BOOK IN PRINT TODAY Address GERNSBACK PUBLICATIONS, Inc. City State 96 -98 Park Place RC-333 New York, N. Y. I. ZZ Z //// / /// / /// //ZZ /ZZZ/ Z/ ZZZZ // ZZ // //Z/ // ZZ/ZZ /// // / /// / // / //Z // / ZZ i zZ/ z 646 RADIO -CRAFT for MAY, 1933 adio@ffTHE FOP SERVICE MAN DEALER RADIOTRICIAN "Takes the Resistance Out of Radio"

Vol. IV, No. II, May, 1933 Editorial Offices: 96 -98 Park Place. New York, N. Y. HUGO GERNSBACK, Editor

DX LISTENING

An Editorial by HUGO GERNSBACK

of listening to stations in Australia and s I HAVE often remarked before, radio has always thinks nothing moved in cycles. Everything that is connected other parts of the world. with radio moves in an endless cycle. When broad- The main remarks in this article, however, refer to casting first became popular, there developed a broadcast listeners on the broadcast wavelength from 200 "DX" listening. (For the benefit of new- to 545 meters, and there are, therefore still a great many great itch for to get. The mere fact that comers, the initials "DX" are an abbreviation, used origi- worlds to conquer and thrills and meaning "long distance. ") it is difficult to get reception from really great distances nally for code purposes, all the more exciting. When people were building their own sets, in the early on broadcast sets makes the sport '20's, the favorite pastime was a one -tube set with which The rule of the game seems to be that the ordinary com- you could listen to stations hundreds of miles away. People mercial set, generally, is not suitable for extreme distance used to sit up all night trying to get the distant stations. reception; but there are notable exceptions to this rule. Then, at the end of the '20's, the DX interest lagged some- Some of the very fine high -priced commercial sets have what, and by 1930 it seemed to have completely died down, been able to bring in real distance. As a rule, only really except for a few professionals who kept at it with unabated high -class, custom -built jobs, and those sets built especially vigor. with a view to bringing in distance -usually of the super- Of late, when people have again become more sane, and heterodyne type -seem to get the best results for their are staying at home more than formerly, the "DX bug" owners. The reason, of course, is that all the circuits seems to have infected a large part of the community once must be peaked to their resonant frequencies, and the en- more; once again editors of radio publications are begin- tire set must work with maximum efficiency. The least un- ning to be flooded with DX accomplishments which, this balancing will make a set unsuitable for really great dis- time, are of no mean order. A few hundred paltry miles tance work. Some of the best manufactured sets on the are no longer of any interest. Your present DX listeners, market may normally get stations from 1,000 to 2,000 and I am now speaking of broadcast listeners only, are go- miles without any trouble, but will fall down when receiving out for REAL distance. Listening from one end of ing stations over 5,000 miles away. the country to the other means nothing. Middle- Western Remember particularly, that the problem is somewhat listeners have actually been able to pull in stations from difficult, because there are available only 96 broadcast Australia on normal broadcast waves; and a number of channels on which there are thousands of stations. Even other Eastern listeners receive European broadcasts, as if you get the broadcast-carrier frequency from a station well as those of other countries, such as Central America, 5,000 miles distant on your special set, the chances are that and even South America, regularly. you will not be able to identify the call letters; because a This might strike one as impossible at first, but there half a dozen foreign stations may be camping on the same are several good reasons for this: first and foremost, we wavelength at the same time. The trick, therefore, is to are now in the favorable position of a sunspot cycle, which pick out a time when most of the stations have gone off aids radio reception. This cycle is now decreasing, and the air; you will then be enabled to listen to the one sta- will reach its minimum, indicating favorable reception, in tion you are after. 1934. It will then gradually increase and decrease again Naturally, you are not going to do all this in a single and, by 1945, will be at another minimum. It is, therefore, evening. It takes many months of patient work; and then r possible to look forward towards better radio reception you must get verifications from the stations themselves to both for broadcast wavelengths as well as short-wave re- prove that you are right. during the next few years. ception, in broadcast The DX interest by the public at the present time is of Of course, not every radio set will bring more than passing interest to the Service Man, too. The from the Antipodes. You must first have a good stations you must more owners are using their sets, the better it is for the radio location; you must have a powerful set; and servicing fraternity. Many Service Men today are making hours for listening accordingly. The large choose your stations, are extra money by sending circulars to their customers call- cities, as a rule, cluttered up with broadcast ing attention to the fact that, by overhauling their sets, favorable for DX listening when it comes to real not to this rule. Just they may be enabled to listen to stations thousands of distance; although there are exceptions miles away. This gives a new incentive to owners, and is the best set, is also not quite clear; for sometimes what as well as many have become addicts to DX listening after they have a set with only a few tubes seems to perform been shown how to do it another set with ten or twelve tubes, which may not even excellent aerial and ground To be sure, not every commercial set will do it immedi- work well at all. Of course, an are often necessary. The set may are the first requisites; and, then too, the set must work at ately. Aerial changes if real results are to be expected. have to be recompensated, condensers lined up, and some- its maximum sensitivity changes effected to make the set work at On the short waves, DX listening is, of course, common- times structural set will bring in stations its highest efficiency. If the Service Man is able to show place; because a good two -tube set can now bring in stations a from the maximum distance on this planet, i.e., 12,500 the owner that his former are so common that every school- few thousand miles away, the customer will be glad to pay miles; and these records which should not be unreasonably high. boy in the United States today who owns a short -wave set the charges,

647

: K. yikis.:s:.ay,a..s.,e.y,.-,yrrj HOW TO BUILD THE "RADIOLAMP" TABLE RECEIVER

This article describes the construction of a miniature radio set combined with a table lamp -the lamp serves as the limiting resistor in the filament circuit.

CLYDE FITCH

N THE February, 1933 issue of RADIO- CRAFT there appeared the first complete description of one of the new miniature radio receivers. It seems as though, over- night, this type of set has earned its spurs, and has swept the country by storm. It not only fills a great public need, but, to the ingenious radio fan, it offers unlimited possibilities for home -made sets of novel design. For example, the "Radiolamp," illustrated herewith, was made possible by following the general principles of miniature Fig. A set construction and combining them with a lamp. Also, Front view of the Radiolamp ready for operation. Looks interesting, eh? the variety of new tubes now available, mainly 6 Well, it k ir,reresti, g. the -volt, .3- ampere automobile type, which is used in this set, makes possible many interesting set combinations for the home constructor. The As stated in a previous issue, this pub- Radiolamp, see Fig. 1, contains three tubes and a rectifier. The first tube is a type 39, R.F. pentode ampli- lication is sponsoring a drive for better fier, coupled to a type 36 screen -grid detector, which is, in and more novel turn, resistance coupled to a type 38 output pentode. The cabinet design. The rectifier is a type 12Z3. All of the tubes except the recti- receiver described by Mr. Fitch is an fier have a 6.3 -volt heater which operates at .3- ampere. The rectifier has a 12-volt filament also rated at .3- ampere. example of what we mean. It is a com- This tube has an indirectly heated cathode, and, although bination reading lamp and radio set; of the high- vacuum type, it has a low internal voltage drop, which does not cause any appreciable reduction in voltage the idea is simple, but for some available for the plates of the tubes. strange reason has never been pro- Miniature radio sets are made universal; that is, they operate on both A.C. and D. C. The filaments of the tubes duced commercially. The circuit is are connected in series and are connected directly to the standard, and should give no trouble 110 -volt line through a limiting resistor, thus avoiding the use of filament transformers. The limiting resistor causes to the average set builder. a voltage drop of some 85 volts, and, consequently, at .3- el ampere, it must dissipate about 25 watts of electrical energy in the form of heat. For this reason many miniature

Fig. I Schematic circuit of the receiver, Note its similarity to the International Kadette. SW. and R2 are gauged. 648 RADIO -CRAFT for MAY, 1933 sets get hot enough to fry eggs on! This condition is one important reason why the combined set and table lamp is a logical combination, as the limiting resistor is eliminated and the lamp bulb takes its place, thus converting energy which was formerly wasted, into useful light. A table lamp requires a shade. By making the lamp of modern design, the shade may be in the shape of a cone, thus making it suitable to serve as a loudspeaker diaphragm. Without the limiting resistor and the loudspeaker in the set, the set itself can be made smaller, so that there will be ample room in the base of the lamp for the set without making the base unduly large. Another important reason for combining the set and lamp is that a much larger cone can be used than is ordinarily used in a miniature set, and the tone quality is thereby considerably improved.

The Radio Chassis Figure 1 shows the schematic diagram of the receiver. The circuit is conventional and is typical of the type used in many commercial miniature sets. It is a simple set to wire, and one should have no difficulty in making the connections. One point to observe is that the type 36 detector heater is connected to the negative side of the line, assuming the set is plugged into a D.C. outlet. This is important in order to reduce hum to a minimum when the set is used on an A.C. line. From the negative side of the line the current passes through the detector heater, then the type 39 R.F. tube heater, into the type 38 A.F. tube heater, and through the rectifier tube filament into the lamp filament and back through the switch to the other side of the 110 - volt line. A 40 -watt Mazda lamp is the correct size to use with this set. - We can also trace the plate supply from one side of the Fig. B line through the switch to the rectifier plate, out through View of the speaker.lamp construction with the "shade" removed. the cathode of the rectifier to the filter choke L5, and on to the other tubes. About 95 volts are available for operating these tubes, whether used with an A.C. or a D.C. light - 14" line supply.

Another point to observe is that the screen of the detec- A tor tube is connected to the cathode of the type 38 tube LOuOSP.EAKER i CONE LOUDSPEAKER. so that a positive potential is obtained for the screen which UNIT is equal to the grid bias of the type 38 tube. -41kp. i.1 All of the parts are marked the diagram with the NS 10 -32 same symbols as used in the other illustrations and in the THREADED CIRCULAR ROOS Note that the metal chassis is insulated RUBBER List of Parts. TUBE B'I LONG from all of the wiring by means of the insulating condenser C3. This procedure is followed to avoid any possibility of a short circuit or serious shock should the metal chassis become grounded accidentally, as usually one side of the light line is grounded, and the negative "B" supply is connected directly to one side of the line. For this reason l6" it is important, in mounting the two -gang tuning condenser, Cl and C2, and the electrolytic filter condensers C9 and C10, to use insulating bakelite washers under the screws and make sure that the mounting screws do not touch the metal N? 1W control, R2, is mounted on BRASS iRE chassis. The volume a bakelite LAMP / RAME SOCKET support for the same reason. For the values of the parts, BUSHING the reader should refer to the List of Parts. For the locations, the photographic illustrations, mainly Figs. C and D, should be observed. The metal chassis and lamp frame -work are clearly N4 6-32 - illustrated in Figs. 2 and B. Fig. 3 shows a plan view of TAPPED MOLES ALUMINUM the radio chassis with the location of the holes for the tube sockets indicated. One sixteenth -inch aluminum shield can material is used throughout. All of the important dimen- sions and other information are given in Fig. 2. Note that the holes in the top and bottom part of the lamp base, the Fig. 2 bottom of which is also the radio chassis, are threaded so Construction details of the "shade" pictured above, in Fig. B. that the sides, front, and back plates may be removed easily. The top of the lamp base is made exactly the same size as the radio chassis, or bottom. The small chassis Fig. 4. Ordinary lamp shade parchment should not be used mounted on top helps support the two rods which support as the oil it contains deadens the sound. The white draw- the loudspeaker unit and the wire frame for the shade ing paper works very well for both lamp and speaker, and and, also, improves the general appearance of the lamp. may be given a coat of white shellac to improve its appearance. The shellac should be applied after the border de- The "Radiolamp" sign, if any, has been painted. The design itself may be The combined lamp shade and loudspeaker cone is cut made to suit the builder's fancy. After the paper is cut from a piece of white drawing paper to the size shown in out as shown in Fig. 4 and decorated and shellacked, it should RADIO -CRAFT for MAY. 1933 649 be glued along the seam with rubber cement, forming it into a cone. The tip of the cone is clamped with metal apexes similar to those used in cone -type loudspeakers. This allows it to be attached to the drive pin of the loudspeaker unit. When assembled, the cone rests on a ring support made of No. 10 brass wire covered with a soft rubber tube. This ring is 131 inches in diameter and is supported at the lamp base in four places as shown in the photographic illustration, Fig. B. This wire support is soldered together. The loudspeaker unit was taken from a Premier miniature cone speaker and mounted directly on the threaded rods as shown, using the mounting holes already in the unit. The was drive pin extended to fit the new cone by soldering a longer one to it. In assembling the complete unit, the radio chassis, of course, should be built and wired first. Two wires are unit run from this up through holes in the top to the loudspeaker, and two more run up to the lamp. A lamp cord enters the chassis back of the through which connection to the line is made. The aerial lead is attached directly to one of the coils and extends through a hole in the back. The loudspeaker lamp shade assembly may then be mounted to the top of the lamp base and the two side pieces attached. This supports everything, and the connections to the lamp and to the unit may be made, making sure that enough slack in is left the wires so that the chassis may be removed without dis- connecting them. The front can then be drilled for the volume control and tuning dial shafts, and a window cut in to show the tuning dial readings. The tuning dial is simply a celluloid forced dial onto the condenser shaft and cemented on the shaft. This Fig C touch practically completes the construction of View of the receiver with the unit. The all parts labeled for convenience. reader should carefully study the various illustrations and note especially how the coils are mounted directly 119 on the tuning condenser with LiAL®ZAI- MIED small brass supports. They are mounted at right angles so as to reduce oscillation.

CORD TO CORD TO Operating the Set LOUD SPEAKER LAMP The operation of this set is quite simple. While it may not be as selective 0 as larger T. R. F. or superheterodyne receivers, or give the power output, it is extremely sensitive and picks up many stations with a small indoor aerial. No shielding of the tubes is shown in the illustrations. In some cases, if . oscillation becomes serious, it may be T)l a advisable to place a métal t shield around the detector tube and also to shield the detector , control -grid lead. The con- ,67. ...f1=' denser has a shield built in it between the two units. This feature and its ¡ small size and specially cut plates fa- VZrMEMIM cilitate tuning considerably, making it Fig. D ideal for this type of receiver. The Under -view of the receiver and alumincm case. All values are shown. coils also are so compact that shielding is usually not required. If a very long aerial is employed, it is advisable to connect a .0001 -mf. fixed condenser t in series with it.

List of Parts One Cardwell two -gang midget condenser .00035 -mf. Cl, C2; One Sprague fixed condenser .1 -mf, C3; One Aerovox fixed condenser .01 -mf., C4; One Aerovox condenser .5 -mf., C5; One Aerovox fixed condenser, .0001 -mf., C6; One Aerovox mica fixed condenser, .02-mf., C7; One Solar electrolytic condenser, 4 mf., C8; Two Aerovox electrolytic condensers, 4 mf., C9, C10; One Aerovox pig -tail resistor, 150 ohms, Fig. 4 Fig. 3 Rl; Construction details for the cone -shade. Main drilling layout for the chassis. (Continued on page 685) 650 RADIO -CRAFT for MAY. 1933 THE LATEST RADIO EQUIPMENT

ALL PURPOSE METER REMINGTON AUDIO AND POWER TRANSFORMERS RADIO SERVICE MEN will be interested in the announcement of the Westinghouse Electric & Manufacturing Company of the addition of a "universal" meter to its line of switchboard and laboratory instruments. This will be supplied with an externally mounted, factory matched "Rectox" rectifier to permit maximum flexibility of application. The new meter is of the flush type, with a bakelite molded case measuring 3'/s inches in diameter and 2 7/a inches deep. The scale has calibrations al- ternately colored in black and red for three D.C. voltage ranges, one re- range, and one A.C. voltage sistance A, power transformer; B, input transformer; C, output transformer, by Remington Radio. range. By the use of multipliers and shunts, A.C. and D.C. ranges of 5, line of all- purpose transform- center tapped: 1% volts, 6 amps.; 10, 50, 100, 250 and 1000 volts, and ANEWers designed for experimental and and 5 volts, 3 amps. Odd voltages resistance ranges of 10,000 and 100,- laboratory purposes has been brought may be obtained by connecting the 000 ohms, may be obtained. out by the Remington Radio & Electric various windings in series. This trans- In order to provide for easily con- Corporation. former can be used with rectifiers of structed shunts, the resistance of the The universal power transformer, the 80, 5Z5, 81, 82 and 83 types. meter movement itself has been made (A in the illustration above) has a The universal input transformer (il- comparatively high, 80 ohms. tapped primary, for 100, 112 and 125 lustration B) is enclosed in a copper The sensitivity of this instrument is volts, 50 -60 cycles, A.C. The follow- shielded, hermetically sealed iron case. 1000 ohms per volt on direct current ing high voltages are available: 900, Three primaries are provided, for and is appreciably higher on alternat- 850, 750, 650 and 550 volts, all cen- single and double "mikes," phono- ing current. This permits accurate ter tapped. The total current capac- graph pick -up, etc., and a single sec- measurements of voltages in circuits ity of this winding is 125 ma. The ondary for conventional connection to where lower resistance types of meters 5'I voltage regulation permits the use the input circuit of an amplifier. would give erroneous readings. of this transformer in all class A, A- The universal output transformer prime, and class B audio circuits. The (illustration C) has two primaries and following additional center -tapped sec- the equivalent of nine secondaries, and ondaries are available: 5 volts, 3 is suitable for all known types of A.F. amps.; 2'Fz volts, 3 amps.; 2% volts, circuits, all types of tubes and all 12 amps.; 1% volts, 3 amps. The fol- types of speakers. These are truly lowing filament secondaries are not versatile instruments. CARDWELL MIDGET CONDENSERS N response to the demand for smaller The new condenser is shown at the radio parts, the Allan D. Cardwell right in the illustration below. The Mfg. Corporation announces a new accompanying condenser is a double two -gang "Midway" featherweight spaced transmitting unit, 4% inches variable condenser of extremely com- deep. The size of the "Midway" con- pact design. Each section has a maxi- denser may be judged by comparison. mum capacity of 350 mmf. Although adequate for replacing full DUBILIER CONDENSERS size receiving condensers, the new The Dubilier Condenser Corporation "Midway" is only slightly larger than announces a new series of pyranol im- many so-called "midget" condensers. pregnated high- voltage condensers for space is 3 by New Westinghouse "Universal" meter. The overall mounting filter purposes. 2% inches. Cubic volume for standard capacity sizes has been reduced considerably through the use of pyranol, a patented, non-in- flammable i m - pregnator. Ca- pacities from '/a to 10 mf. in voltage ratings from 5,000 to 20,000 volts available. Left, Cardwell transmitting condenser; right, new "Midway" unit. RADIO -CRAFT for MAY, 1933 651 ALDEN TUBE ADAPTER THE Alden Manufacturing Company has added several new items to its already large line of adapters for analyzers and tube checkers. Service Men owning tube checkers more than a few months old will be particularly interested in the model 950XYL adapter, by means of which any tube checker may be brought up to date. It is very simple to operate, and there is only one toggle switch, and no plugs or jacks to bother with. It incorporates the proper resistance network to protect sensitive diodes against excessive currents as well as to safeguard delicate meter movements from the high current of mercury -vapor rectifiers. The case is of molded Makalot. With this new adapter a total of 70 different types of tubes may be tested. There are as follows: 1, 2A5, 5Z3, 14, 15, 19, 29, 33, 36, 37, 39, 41, 42, 43, 44, 46, 47, 48, 49, 52, 55, 57, 57A, 58, 59, 64, 65, 66, 67, 68, 69, 70, 76, 77, 78, 80, 82, 83, 84 85, 88, 89, 90, 92, 95, 98, 291, 283, 295, 985, 986, C2, C4, G2, G4, GA, KR1, KR20, KR22, KR25, Inside and outside views of the Alden adapter and its protective resistors. KR28, LA, PA, PZ, PZH, Wunderlich, AR, AF, AG.

GOLDENTONE MIDGET SCRATCH REMOVER THE "GOLDENTONE" midget shown SERVICE Men can readily earn a below is a product of the Fordson IN OUR JUNE ISSUE few extra dollars in their outside Radio Mfg. Corp. It is a six tube work by touching up cabinets in addi- superheterodyne incorporating auto- In the Spring, the radio man'; tion to repairing the radio instruments matic volume control using a duplex - themselves. The handy scratch remov- diode triode, tone control, "spotlight" fancy should turn to automo- er kit marketed by the Erwin-Rabeck tuning, and dynamic speaker. The in- Company (illustrated below) can be termediate frequency is 456 kilocy- thrown tive radio -and it will! The June into a corner of the tool bag. cles. The material is a filler that seals The set is housed in an attractive issue of Radio -Craft will contain itself in a few minutes and leaves no cabinet measuring 16 inches high and noticeable marks or lines. 12 inches wide. The chassis is gold lacquered and has a distinctive appear- a comprehensive treatment of all ance. The controls are conveniently located, and the scale figures are easily phases of automotive radio. read. Get your copy early!

" CORDOHM" WIRE THE "Cordohm" resistor cable, a 1 product of the Ohmite Mfg. Co., looks like an ordinary lamp cord, but consists of three wires: two copper and one resistance. The copper wires carry the 110 -volt circuit and the resistance lead reduces the voltage for the filament circuit.

The new Goldentone Midget super. The "Cordohm" connection cable. The scratch remover in action.

GRENPARK P. A. AMPLIFIER THE Grenpark -RCA public address amplifier is a two - stage outfit employing rapid heating tubes -one 26, one 50, and two 81's-and is especially valuable for inter- office communication systems wherein the amplifier must function within a second or so after it is turned on. All parts are extremely rugged, and are mounted on a % -inch wrought iron chassis measuring 17% by 12% by 7% inches; total weight is 58 lbs. This amplifier furnishes sufficient field current to energize four 12 inch dynamic speakers, which may be placed in advantageous positions to cover indoor or outdoor audi- ences. In addition it will operate as many as three dozen permanent magnet speakers. It also furnishes plate currents for a radio tuner. All filter components are sealed in cans to facilitate replacement and to reduce the effects of temperature changes. The Grenpark amplifier is -a- husky instrument. 652 RADIO -CRAFT for MAY, 1933 CARTER 32 -VOLT GENEMOTOR OWNERS of 32 -volt farm lighting systems have been more or less overlooked by radio engineers, and have been forced to use "B" batteries while other people enjoyed the advantages of power operation. The Carter Genemotor Corporation has come to the rescue with a new 32 -volt "Genemotor," which is a small efficient machine of the dynamotor (rotary) type. On the input side it consumes only-half an ampere; on the output side it delivers up to 30 ma. at 180 volts. No oiling is required, as ball bearings with sealed -in lubricant are used. A double filter system eliminates electrical noise in the radio set. It is furnished in a dirt proof case, complete with connecting cord and line switch, and may be connected in place of "B" batteries. The Carter Genemotor out of its case.

MERSHON CONDENSERS ANSLEY DYNAPHONE RADI- AERIAL T HE new Mershon wet electrolytic RDIO\ dealers and Service Men are "Radi - Aerial" of the Western I filter condensers illustrated below waking up to the possibilities of THEHE & Electrical Company connects are designed to meet present day de- the portable electric phonograph-not to the ground and in many locations mands for low cost in set construction merely a turntable, but a complete out- satisfactorily replaces the outside without sacrifice fit. To meet the growing demand, the aerial. in performance. Ansley Radio Corporation has brought - They are punc- out a well designed instrument called i g ture proof, self - the "Dynaphone," illustrated below. healing and free This is a true portable, operating on from mechanical either A.C. or D.C. It has a self -con- leakage. They are tained turntable, audio amplifier and available with dynamic speaker, with provision for either stud or microphone connection. Space is also clamp mounting, provided in the hinged cover for a in a wide variety stock of records. of capacities to The case opens as shown, the cover meet circuit re- being held upright by a strong arm. quirements. When not in use, the pickup arm is clamped down to protect it from in- CHROMOXIDE WIRE jury. The Radi -Aerial is small and compact. The opening for the speaker at the HROMOXIDE" wire, manufac- front; the tubes and amplifier are di- Enam- tured by the American rectly behind. "COSMOPHONE" PICKUP eled Magnet Wire Co., is a copper wire having a hard, chemically deposited in- THE Winchester Company's "Cos - sulating coating. It is suitable for mophone" pickup is constructed of many radio purposes. polished bakelite and is equipped with micrometer adjustment for regulating the pressure on the record.

" Chromoxide" wire has a darkened appearance. The Dynaphone in operation. The "Cosmophone" pickup.

ALDEN ANALYZER PLUG SERVICE Men, experimenters, and engineers who are now finding it necessary to revamp their old test equipment or build new outfits will be interested in the new Alden seven -prong latch -lock analyzer plug, with its attached five -foot, eight wire cable, the seven hole to six - prong adapter, seven hole to five-prong adapter, and seven hole to four -prong adapter. The analyzer plug is long enough to fit into all standard tube shields. Caps are provided on the side for the cap connections of screen -grid tubes. The latch lock anchors the various adapters securely to the main plug, and pre- vents separation of the units, which is extremely annoying in sets having fixed tube shields. For additional information on Alden adapters suitable Alden analyser plug and adapters. for all types of testers, see past issues of RADIO -CRAFT. RADIO -CRAFT for MAY, 1933 653 ULYSSES FIPS (Staff Reporter)

The completed receiver. Its size may be estimated by reference to the pocket watch. A Revolutionary Radio Development THE VEST -POCKET, SEVEN -TUBE SUPERHETERO- ULTRADYNE

T11E President of the great Westingmouse Radio & "I am sick and disgusted of imitating other fellows who Mfg. Company was pacing his office in an agitated skim off the cream, leaving us to hold the bag, by forcing manner. Every once in a while he stopped in front us to dump the sets upon the market at less than cost when of a chart which had curves on it, all of them point- the shouting is over. ing downward; every time he stopped and looked, he gave "Now I'll tell you," and here he swung a thick finger a nasty snort and resumed his pacing. Finally, he seemed under the nose of the unhappy engineer. "I am through to have come to a decision, and he pressed a button. A imitating. I want action, and I want originality. secretary appeared, to "If sets are going to be whom was given a hurried smaller, ours will be the call for the Chief Radio V4 V3 V2 Vy first radio tr . plant to make Engineer. This worthy in- them. I'm not going to dividual entered somewhat wait until some watch- breathlessly i n t o the maker in Hicksville turns august presence of the out a vest pocket set and President and blanched vi- captures the whole United sibly when he noticed his States. I'm going to be chief's scowling appear- the one who is going to ance. make the first," he shouted. "Sit down," bellowed the "Now here are your Chief, "and listen. orders: Within thirty days, "For a number of I want a vest pocket set. years," he began, "our Mind you," he said sternly radio set department has to the trembling engineer, been the joke of the country. "when I say a vest pocket Here we are with the re- set I don't mean coat sources of the greatest pocket. I want a seven radio manufacturing corpo- tube set small enough to fit ration in the country, and into your vest pocket. what do we do? We wait There is a tremendous until some little manufac- market for such a set. turer in a jerk -water town Every woman will wish to hits upon a good idea about carry one in her handbag. a radio set, and, after he Every man will wish to has captured the market, Photograph illustrating the sire of the set in comparison with the hand. All carry one in his vest we go and imitate him, and components ara mar ked for convenience. pocket, attached to his turn out a similar set. All watch chain. Children will we have been doing is imitating the other fellow. We want them. A tremendous market exists in jewelry stores haven't produced an original set since the radio boom in alone. People are already tired of even the little radios 1922. From that time on, every set has been an imitation which go into your desk drawer. Nor do I want a set that of someone else's. First the table models, then the con- requires an aerial. soles, then the midget sets, now the little radios. "Have you wise engineers ever heard of super-regenera- "What, may I ask, is our research department for? Are tion, where amplification is so great that an aerial is not you fellows men or mice? Have you all one -track minds really needed ?" without return ticket privileges, and is originality dead in "But," faltered the flabbergasted engineer, "where will your laboratories? you get a loudspeaker small enough -" 654 RADIO-CRAFT for MAY, 1933 THE present extraordinary radio development, which appears for the first time in any publication here, is the logical outcome of small sets. When the midget set first was announced, the radio industry threw up its hands in horror because they could not conceive that a radio set could be built in such a small space. Then came along the four -tube little radio sets, small enough to put into your desk drawer. How much smaller can radio sets be made? The present receiver seems to furnish an answer to this question. While this set is small enough to fit into the vest pocket, he would be a rash prophet who would dare say that it is the ultimate. Sooner or later, someone will probably build a radio set which, complete with tubes and speaker, will be the size of a watch. That may, or may not, be the ultimate. It looks, however, that the radio industry will soon have to put watchmakers to work in order to assemble these microscopic sets, if present indications are right -and the facts are that present indications are right!

and set upon "Silence," bellowed the boss of the great works, "who -into the presence of the august President, must you fellows always his desk the set here shown by actual photographs. The talks of loudspeakers? Why and wear grooves in your one -track minds? Why not be orig- engineer plugs the line cord into the nearest outlet never heard of 'singing arc lights? Have tunes in a station. The new set called, "The Vest Pocket inal? Have you seven -tube affair, you never heard of the talking electric lamp bulb? Where Seven Tube Superhetero -ultradyne," is a there? Is it written anywhere that and, by actual measurements, is found to measure only was your loudspeaker vest pocket. you must have a loudspeaker such as you understand the 4 "x2 ", just small enough to fit into your to get sound? The President beams as the term in order when Have you ever heard of a set is demonstrated, talking condenser? Have station after station, local talking as well as distant, is tuned you ever heard of a work," glove? Have you ever in with ease. "Good dyna- says the Boss of the heard of the singing the Chief mo which emits sound Works, slapping vibra- Engineer on the back. I due to molecular and I tions? All you fellows do knew it was in you is to putter around knew right along it could all day How much do in your laboratories, note be done. for ? ". all these peculiar effects, you think it will sell but never translate them "About $5.00 or there- into action. There are ways abouts would still net us a and means to make a radio good profit, but before we set sing and talk without go into that," he said with and it is up a twinkle in his eye, "watch loudspeakers, engi- to you to use the best this." And now the means. neer played his trump card. "Now, before I lose my He gave a jerk, and off patience, get out and break came the lamp cord con- the news to your fellow re- nection which had been search imbeciles and de- plugged into the lighting liver a rest pocket set to circuit. From his pocket me within thirty days. he pulled out what looked Here," he said, "is my desk like a sub -base of the radio calendar." And taking a which he fastened to the red crayon, he marked the bottom of the Lilliputian 5th of the month, when the set. Immediately the set set was to be delivered. started to play as before. The head of the big corporation was astonished, and began to ask questions. Here the curtain de- "Let us begin at the be- scends for a lapse of thirty ginning," said the enthu- days, at the end of which siastic engineer. "This set is both for A.C. and D.C., the chief engineer and his The tube! Note its similarity to the filamentless tube described in the March assistants, smiling, walk issue of RADIO -CRAFT. It will become as famous as the APR I. as well as battery opera-

Read This Article Now! The Amazing Possibilities of Vest Pocket Receivers Will Take Your Breath Away. It is the Ultimate Set for Years to Come

RADIO -CRAFT for MAY, 1933 655 The receiver described by our star reporter, Mr. Fips, represents one of the greatest advances in the radio art. Mr. Fips, who for the past twenty -five years has been associated with radio, considers this receiver to be the pinnacle of his radio achievement.

tion. The thing which you take for a sub -base is really does away with overlapping frequencies and, as you will the "A" and "B" supply. No aerial nor ground are needed. also have noticed, the set is exceedingly sharp in tuning. You take the little set out of your vest pocket anywhere, For that reason too, it has no dead spots. Because and you get, not only it uses no aerial, very broadcast reception, but, if little man -made static is necessary, with a little experienced. There are, extra addition, we can also L3 LI therefore, no extraneous bring in the short waves by noises which, so far, have pulling this little switch in been the the bane of radio. Of bottom. course, everything had to Of course, many prob- be worked out with watch- lems had to be solved. maker's precision; but, all First, we had to get a problems have now been special miniature vacuum solved, tube. and, after tooling None were existent. up, we will be in a posi- There was no reason to LINE CORO tion make to offer the set as the vacuum tubes as greatest radio marvel of large as they have been the age within the next made, so we proceeded to thirty days, should you make new tubes of a Rear view of the set. Again, all valu es are marked for the convenience of the constructor, should he wish to buil d the set. The think this to be necessary. special tubes become a loud. nature which re- spec ker. And, of course, the price quire no filament but work is highly attractive, too; on the principle of cold electronic emission"'. This tube with a list price of $5.00, actually millions of people will is very economical, and uses but little current. Several buy, not one, but numbers of these new principles sets." had to be incorporated into the tube While the chief engineer kept on talking enthusiastically because the tubes themselves become a sort of loudspeaker. in this manner, the Big Boss's face became darker and You will note that the new tubes themselves are all cloudier. He took a pad of paper and did some figuring. carried on a special diaphragm, and by molecular action, The more he figured, the more perturbed he became. their vibrations are carried to this oblong vibrating dia- "This is a fine set," he sneered, "but phragm from unfortunately, the which the sound issues. The tubes them- economics connected with it do not seem to work out so selves, as you will notice, are quite microscopic in size; in nicely. As a matter of fact they are super -lousy. Even fact, they measure only one inch overall by % inch in di- with the old midget sets selling for $75.00 we couldn't ameter. There are seven such tubes in this set. As to the make any money, and with all the radio set itself, little sets selling it is not very complicated, as you will see from the for $25.00 we can't make money; now, how much do you blueprint here. think we can make on a $5.00 set? As a "The matter of fact, set uses super- regeneration in addition to triple re- I think that while you have produced a marvelous con- generation of a special nature worked out by our research traption you were thinking only of price instead of qual- laboratories. The tuning condensers presented a little ity. Instead of making a higher priced set, you have con- difficulty in order to get the wave range, but here again centrated on the price angle. Fools like you are the ones our engineers did wonders. You will note that the tuning who kill the radio industry." condensers are so minute it would not be possible to cover With rising anger, and his face turning from red to the entire broad- a purple, he cast waveband. grabbed the set We, therefore, NEW THORIUM ALLOY EMITS ELECTRONS AT ROOM TEMPERATURE INSTEAD Or AT INCANDESCENCE and hurled it at resorted to a new 49260 0NM5 / ELECTRONIC ARC STABILIZING ELECTRODE the unhappy en- trick, and that is, ALL APRI RIES vRIo' MAGNETO- gineer who col- we work this set COST -1/ STRICTION lapsed on as the re- harmonics OSCGLL TOR sult of the im- only. NiT POTTER TRANS PT pact. "As is well I r The crest- known, practically every broad- Eta fallen and totally cast station can I crushed engineer Mr l l } I(I awoke with a be received on t r - ' oi 3v1 2 start, short wave sets and found ULT m: - Ii E that his cat had due to harmon- ° tgir Ti TUNE0.l ics. We utilize st If www jumped on his 567.0 I EATTER V ALL DIRECT --1-u CONNECTIONS chest just a this principle and L PKPCOILHUIMpl(y simply boost up (OPTIONAL) minute before x)e- MAGNETIC the harmonics RMONIC MOLECVMR the alarm clock TUNER MPUPIER went again in inverse t10 v off. He 60 ti looked around ratio. This, in DC OR CLOSE WINO THIS HALF practice, works COIL ONE WAS ANC HALO THE OTHER A C sleepily and his excellently, and wandering eye lit upon Complete schematic circuit of the receiver. The electromagnetic waves from the ether (if there is such the calen- "Read RADPO -CRAB, a thing as the ether) impinges upon the input to the receiver causing the magneto -striction oscillator dar. He noted the March issue for fur- to beat with the supersonic frequencies of the magneto -molecular oscillator, giving rise to the Super- date and ther information on hetero-ultradyne. It is interesting to note that the fundamental principles employed in this receiver groaned. have never before the principle of this been utilized In any commercial receiver. Magneto -striction oscillators have been IT WAS APRIL used so have magneto -molecular oscillators. but the combination of the two is, indeed, rare. Note tube. the unique method of winding the coil. FIRST!

656 RADIO -CRAFT for MAY, 1933 BUILDING A BATTERY -OPERATED "PERSONAL" RECEIVER

A battery- operated midget receiver of the "personal" type. It may be used in a car or at home, at will. All details are given.

Fig. A Top view of the chassis showing the location of all parts above the deck. H. G. CISIN, M.E.

of 700 milliwatts at 135 volts on the plate. Volume is controlled by means of a tapered potentiometer in the screen -grid circuit of the R.F. tube. Reducing the screen - grid voltage below 67', gives smooth, uniform control of the volume. The amperites (6, 13, 21) in one of the filament leads of each of the three tubes serve to reduce the filament voltage from the 6 volts supplied by the storage battery to the 2 -volt value specified for the tubes. They also provide automatic filament voltage control, as the storage - battery voltage drops. For this reason they are far preferable to ordinary voltage limiting resistors. If there is a short in the filament circuit, the amperites function as Fig. B fuses. Under -view of the receiver. The designations refer to the circuit, Fig. I. As an additional inexpensive, but valuable, protection to the receiver, a fuse is placed in the "B- minus, A- plus" THE "Personal" receiver is a versatile 2 -volt battery - line, as shown in the schematic diagram, Fig 1. This operated set. If energized entirely with dry cells, it fuse gives both "A" and "B" protection. The fuse should makes an excellent portable, since it is one of the always be left in the circuit, regardless of the type of "A" smallest, lightest battery sets ever designed. It makes battery used. an ideal air -cell receiver, as the total filament-current drain The chassis is bent from a 13% x 4 inch sheet of No. 14 is less than .4- ampere. Through the utilization of amper- gauge aluminum. The three socket holes should be drilled ites, the Personal set can be powered, if desired, by a before making the four bends. A rectangular cut is also standard 6 -volt storage battery. Three 45 -volt "B" bat- made at the front end of the chassis, prior to bending, to teries are required. The total "B" current drain is less permit the speaker cone to extend below the chassis deck than one -fortieth of an ampere. See Figs. A, B, and 1. and to be flush with the front. This cut is 4'/z inches The keynote of the "Personal" receiver is simplicity: it long x % inches deep. It is shown clearly in the under - uses but three tubes. These tubes are employed in an chassis view, Fig. B. efficient circuit requiring comparatively few parts; non- After the chassis is bent, the three sockets are mounted. essentials have been eliminated; no transformers are used; (Continued on page 685) the speaker is connected directly in the circuit, thus dis- pensing with speaker plug and socket. Even antenna and 4' ground binding posts are not used-the antenna is con- REE)5LE cNASAS -sii .09' LEAD TO Mn4r.E,iC wire coming from the set. The ground ANTENNA toEnreR nected to a flexible I 32 a J1e/ 33 22 connection is made at the negative terminal of the "A" ¡ad I 34 (7) in1 r battery. (16) Through the application of modern design principles and fla), m) through the use of the latest two -volt pentode tubes, and also of other improved components, this little sub- midget outperforms old -style battery sets taking up to four times as much space and using twice as many tubes. The three - tube circuit consists of a tuned R.F. stage employing a 34 11101=11011141111121. variable -mu pentode, a tuned detector stage using a 32 I MOW screen -grid tube, and an audio output stage using a 33 tiMIFIMie cHA5LS FUSE power amplifier pentode. (261 (2S)) Description of Circuit C-7) C:C- f 4 s v. 13.SV. 8- 135v The detector is coupled -to the output stage by resistors. ENT. CNO. The 33 output tube gives undistorted high gain with low Fig. I signal inputs. This tube has an undistorted power output Complete circuit of the "Personal" receiver described by the author. RADIO -CRAFT for MAY, 1933 657 1 BUILDING A LABORATORY STANDARD ANALYZER

A description of a one -meter analyzer suitable for numerous laboratory purposes. This tester is designed for use with the new Westinghouse meter and external rectifier. It tests all tubes and is suitable for point -to -point resistance measurements, and impedance measurements. If is extremely flexible in operation.

LEON J. LITTMANN, E.E.*

THE analyzer herein described has their testers neither allowed them to out any difficulty, this portable been designed with the lab- dominant analyze the ever increasing number of oratory at a relatively low cost and thought in mind of incorporating new tubes, nor allowed them to make with astonishing ease. as many as possible of the advan- many of the now vital tests that are so Rather tages and improvements than to go into a lengthy possessed by necessary today. discussion of the numerous handicaps analyzers now on the market. There The analyzer to be described was de- encountered in have also been incorporated other test apparatus, in this new signed, then, to satisfy the demand for this detailed description will instrument many other radically new be con- a truly all-purpose instrument as re- fined to a discussion of the finished and vital features not usually found in quired by all present -day, product, modern as well as which has been designed with analyzer equipment. This an- future, laboratories, Service Men, tech- all of the aforesaid alyzer can thus be used in conjunction taken into consid- nicians, sound engineers, etc. The de- eration and which incorporates the with any one of the new tubes, even fects though such that are so numerous among most features given below. tubes should be used in present -day service and conjunction with A.V.C., resistance, or analyzer appa- Here is a list of some of its out- direct -coupled circuits. ratus were, of course, minimized, to standing features: As a matter keep step with modern progress. (A) This analyzer is primarily in- of fact, many, many Full letters were received from Service Men schematic and picture diagrams, tended to be used with the new West- who complained that their test instru- as well as detailed explanations of the inghouse meter that has been especially ments had become obsolete, in that various test circuits and testing appli- designed for this tester, although enough cations, and a list of parts are given information is given in this article to *Chief Engineer, Coast -To -Coast Radio Corp. herein to enable anyone to build, with- enable the optional use of any similar

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Fig. A Fig. B Photograph of the panel used to house the resistors Panel view of the tester with all controls marked. See Fig 2, also. as explained in the text and in Fig. 2.

658 RADIO -CRAFT for MAY, 1933 BPI --t. BP.9 j BP5 `GND Gt iC e5 F- G2 TO CAP 1 GS MA GI Far H F. iR4i) ,R2, r ; VT .3 -_yP, BRA 8P2 VT.4 VT2 - VT.L 1 CUR- --- RENT

CURRENT '--/-_`.\ %q 511 Ss`,Ge , 57 IS 'I 2O l ; a552 oc. REVERSE 1 ,V01.751 t E M, A.0 I 5 c- IOMAA.0- i FuSE$ I- A.P e GI -A, 5 P. I i ,FL F21, , 61, _ - : F I IMF GNO GEr-- I I t 1 AL.IMP .OFF G'.G2 SL ANAL. PLUG MFG GRID CAP 021.1$t, CuRRFN CuRRENT -} ie [. - SG 58 Rt< Q13 G2: IIRR TU a GRID TEST a . á}' K.N.S r GRID TEST ; BR BP3( R17 1 -'I 515 pI _ OHMS IG2 iJt /It AS as 16 512 ó ä+ BP6 BP4 r . VOLTAGE 41/2 VOLT RUSH + 4%2 VOLT _- - TESTS. %q 2 IOO- C BATTERY "C _ BATTERY 130V SWITCHES GS 102 S zP GI C Tc 7F- 510 A.0 EL \--r521 520 519 515 514 SIB 517 516 E2

Fig. 2 Complete schematic circuit of the varsatila taster with all values marked for convenience. meter (such as the Weston 0 -1 milliam- ual sockets permits a tube under test Analyzer. Its fundamental idea is to meter, D.C., equipped with a copper - to be quickly inserted into its easily be able to test D.C. or A.C. voltages oxide rectifier). This Westinghouse identified socket, thereby avoiding the with any one of the meter ranges be- meter which, until recently, was manu- use of adapters and the use of universal tween any two tube prongs (or between factured almost exclusively for switch- sockets that may get out of order any prong and ground or grid cap), boards and laboratory purposes, is now quickly, or break down under the high and to identify this reading immedi- available to readers of RADIO CRAFT. voltages applied. ately and unmistakably. So far, prac- (This meter is shown elsewhere in this tically all analyzers on the market issue.-Editor.) Principles Used in this Analyzer make, for instance, a plate- voltage (B) The front panel layout is given (C) The actual analyzer principles reading. But how is this reading ob- in Fig. A, and the rear view of the employed in this analyzer were form- tained? Is it measured between plate resistor panel is given in Fig. B. Note erly employed with great success by and filament, cathode, ground, or grid? the use of individual 4 -, 5 -, 6 -, and 7- the writer in designing the 1331 model The answer to this question lies usually prong tube sockets. The use of individ- of the Coast -to -Coast Radio Corp. (Continued on page 689)

ANALYSER CURRENT READINGS S, P. 0142. RESISTANCE -C- PUSH- e /u+TON5 FOUR SS, $6,57, MEASUREMENTS TNERE ARE SIMILAR SWITCHES'. 5B. Sn 520 319 SIS P A Oa / SIT SIR 9,----0 4 f A- 70 CORRESPONDING R6 200 OHMS ANALYZER PANEL 2,250 OHMS POLARITY TO TUBE SOCKET TEST ON PRONG Al WITCHCH 9 CABLE -A RS S9 D.C. METER1 R -' 2W OHM5 DC - AC 53 RA0 Ç SYATM 611 MILLI- .1 REVERSING ARANGE4 + 1\^-"1:',14 _1111 SWITCH (^ + SELECTOR BP3 Rx' 5P4 4.5 V --i SWITCH 11 IMPEDANCE MEASUREMENTS -D- p1 GAUD CAP THERE ARE TWO OF THESE OPD.T SWITCHES. 512. 513. 102 -525 V, Ot A.C. NORMAL ,YOns O--(. POSITION FUSE r 1. CYü ES If 60,000 OWNS , f / BC¡ 70 ANAL`rZER, i PLUG. GRID 1~TEE7 RIS ! P LOW POSITION RIB 50.000 C PRONG G20ß G2 / IMPEDANCE r 4.000 : OHMS RANGE 4I'l' TO ANALYZER OHM NIGH ) GNP -g- { SOCK[T,G41D WIRE-WOUNO IMPEDANCE WaF 62 E2 PRONG 51 OR RESISTOR _, G2 RANGE } Orr 2x G3 SP 9 1 SNP ROTART SELCmP Fig. I, right. Detailed connections of the analyzer section of the tester. ros+ SWITCH, Si SOCCET UNDER. PEEN Fig. 3, above. Simplified diagrams showing the connections for various uses. RADIO -CRAFT for MAY, 1933 659 MAKING MONEY WITH AMPLIFIERS Part Five of a series written for Service Men who want more business. In the present article the authors emphasize a portable amplifier and public- address system designed especially for use in small automobiles. This works entirely on the car's regular six -volt storage battery and draws only eight amperes.

HUBERT L. SHORTT and FRANK LESTER*

ETTERS received by the authors, as on the charging generator (an opera- where under the edge of the rear seat, a result of the previous four ar- tion that takes five minutes), or pick and perhaps a third on either step ticles of this series, indicate that up a small battery charger- they're plate, so that you have "juice" avail- L there is a widespread demand for extremely cheap nowadays -and keep able on the outside of the car. Use a simple, compact amplifier (and asso- the battery as near 1300 on the hy- the double contact receptacles for loud- ciated accessories for public address drometer as possible. This attention speaker and microphone connections, work) that will work entirely from the is good business all around: the bat- and mount them in a hinged, weather- regular six -volt storage battery of an tery lasts longer, the car starts easier, proof little box on the step plate or ordinary passenger automobile. and the portable amplifier will always under the running board. All these "Big sound trucks with expensive speak up at full volume. outlets are, of course, wired into the equipment may be all right in the big car so that when the Install Permanent Outlets amplifier is cities," write our correspondents, "but thrown in, the whole outfit can be in- in smaller cities no one can afford Don't wait for your first outside P. ter- connected by bridging A. job cables with such luxuries. When a portable or to do a lot of rush wiring in suitable plugs on their ends. The out- mobile amplifier is needed for most the car. Buy an assortment of single side outlets obviate the necessity for small -town 'jobs,' the family `bus' is and double contact flush mounting re- wires draped over ceptacles windows or through pressed into service and all necessary and mount them permanent- doors, and make the installation look junk must be thrown into the back. ly in convenient places. Use the single much more business -like. Incidental- Give us some hints on rough- and -ready contact outlets for battery supply. Put ly, beware of one the wires through doors. P.A. work of this kind." on dashboard, another some- Some one is sure to slam the latter, There are now a number of good and snip! go the wires. portable six -volt amplifiers on the mar- Carrying the loudspeaker or speak- ket. For the most part, these use ers in a small car is often quite a prob- tubes of the 6.3 volt series, with the lem. If you want to attract atten- filaments working directly from the tion, build a cradle of some kind to car battery, and the plates drawing fit the top of the car and carry the current from a small, specially de- speakers there. For outdoor work, signed dynamotor that, in turn, also speakers of the trumpet type are, of works from the storage battery. With course, desirable. "B" batteries eliminated, the major source of trouble with portable out- A Portable Amplifier fits is also eliminated, and maximum A representative portable output at all times is assured. six -volt amplifier, designed by the authors to Battery Condition Important meet the special requirements of small car work, is illustrated in the various The last statement must, of course, views on be qualified: The over-all operation these pages. This amplifier Appearance of the Lafayette six -volt amplifier; the is the new Lafayette Six Volt Ampli- of the entire P.A. system is depend- dynamotor that furnishes plate current is .in the fier. Measuring % ent on the condition of the car bat- housing behind the tube line up. Along the front only 10 inches wide, of the chassis are the following (left to right): 8% inches deep, and 7% inches high, uses his speaker jacks, three -position output impedance tery. If the Service Man own it is readily mounted car for portable work, he should in- selecting switch main supply switch, and micro- on the running no phone input jacks. The two tube shields cover the board or trunk rack, or may simply be vest half a dollar in a hydrometer and type 36 and first type 89 tubes, and guard against placed on a seat, take readings on battery external pick up. or the floor. The the at least pressed steel housing contains a com- once a week. Like the shoemakers plete three stage with run down heels and the bartend- amplifier, with the plate supply dynamotor mounted on ers who don't drink, many radio men rubber behind are very negligent of own elec- the tube line -up. This their dynamotor is a special little machine trical appliances, and are just the ones designed quiet who get stuck with dead The for running and maxi- batteries. mum efficiency. Making the plate sup- authors questioned a dozen Service ply an Men random, and learned integral part of the amplifier at that only keeps the high voltage safely confined. one of them owned a hydrometer, and With loose he used it in months! "B" batteries or a separate hadn't two generator, and with "B" minus If you use your car for short trips grounded to the around town on service calls, and the car through the grounded storage battery, there is like- battery doesn't get much of a chance ly to be plenty of fireworks when a to charge up respectably, do one or wire accidentally both of two things: advance slips. the charg- Six tubes are used in the amplifier ing rate by adjusting the third brush Back view of the Lafayette six -volt amplifier with one 36 the back housing removed to show the special six circuit: type as a voltage am- *Wholesale Radio Service Co., Inc. volt dynamotor and its soft rubber mounting. plifier feeding one type 89 pentode

660 RADIO -CRAFT for MAY, 1933 ..y r

driver, which in turn, works into four type 89's in class "B" parallel push - push. The output, which is close to ten watts, is enough to make voice or music heard at large outdoor gather- ings. A single large trumpet may be used, as shown in the photographs, or a triple trumpet fed by a single dy -. namic unit. Connections are provided on the amplifier for convenient connection of six-volt dynamic speaker fields, and also for the local microphone-current supply. A microphone control box, incorporating a gain control, is available separately. One of the features of this amplifier is a voice coil impedance matching switch, which has three positions rep- 15 resenting impedances of 4, 8, and ohms, respectively. This enables the user to adjust the output most satisfactorily to the particular loudspeaker or combination of speakers that he in- tends to use. An additional secondary winding on the output transformer has output impedances of 500 and 2,000 ohms, respectively. The 500 -ohm section is useful for line matching purposes, The authors operating the amplifier as part of a small public-address amplifier. Mr. Shorts is at the -ohm section is intended microphone, Mr. Lester is in the back. The mike control box and the amplifier itself are on the back while the 2,000 seat. The loudspeaker is protruding from the right side. for magnetic speakers. The use of a rotary machine of the type, instead of less expen- O1ME dynamotor v type, was S6 Mlf \4 ;` sive units of the vibrating 89 nu- 0 decided on by the authors after 12 tests had been made on repre- ú5 merous 0.5 ó sentative instruments of both classes. 500 oHMs this amplifier is entirely 11 The machine in 0.5 enclosed and is self-lubricating. Its MIS o are excep- X X 4 regulation characteristics o.s MF tionally good, and were made so to MEG meet the changing current require- ó00 800 e M 4 ments of class "B" audio amplification. 0NM5 ONUS

Ripple Eliminated sSIS 20.000 IS sen Commutator 0NU5 line, o switch in the six -volt tGMD. The single e MF marked SW in the diagram, controls the tube filaments, the dynamotor and 6V. A I the dynamic speaker field supply. + simple filter in the high voltage circuit, W. A.F.piOKE choke and a X consisting of an audio CICLO TO FILAMENTS OUTPUT pair of heavy by -pass condensers, X smooths out the commutator ripple and is responsible Complete schematic diagram of the Lafayette six -volt amplifier, showing the values of all parts. Note .-e from the generator that the class "B" output stage employs two pairs of type B9 pentodes with the plates, grids, screens for the absolutely noiseless operation and cathodes of each pair connected together. The output transformer 12 is provided with two sets of tapped windings for different combinations of magnetic or dynamic loudspeakers. The microphone of the amplifier. is connected to the input side of the amplifier through a coupling transformer, in the usual manner. In the diagram T1 is the push -push ,p input transformer, T2 the special output transformer with two tapped sec- There are many large travelling trucks ordinary broadcast or short wave re- ondaries. The tube filaments are all fitted with elaborate sound equipment ceiver, with a suitable coupling me- in parallel. that have more or less ruined this dium. The latter may take the form of angle of the business because they low ratio transformer if the detector Quickly Set Up overdo it. Up to a certain point the is of the triode type, or a coupling The accompanying illustrations show "ballyhoo," as it is delivered through condenser if the detector is of the this amplifier, with the mike control the speakers, is interesting, but when tetrode (screen grid) type. box and an aluminum trumpet, in ac- the racket starts disturbing sleeping For street ballyhoo work, a regular tual use in a Ford convertible sedan. children, invalids and the like, it must auto radio receiver will save much This outfit has been driven through be stopped. Don't wait for the po- wear and tear on the available phono- many parts of New York, and never lice to give your P.A. business a black graph records and also on the an- fails to attract an immediate crowd. eye by clamping you in jail for dis- nouncer's voice. Incidentally, this com- The apparatus is set up or removed in turbing the peace; use some discretion bination may be employed for the ex- about five minutes. It has also been and you'll get repeat orders. ploitation of the particular auto re- and a small used in a roadster, a sedan, ceiver the Service Man or his employer truck. Radio Operation delivery is handling. Instead of waiting for of the things Service Men must Of course, the application of an audio One people to come the consider in operating a mobile ampli- power amplifier of this type is not lim- to store to hear the fier of this type in an automobile, for ited to voice announcements or phono- set, bring it to their attention by way street "ballyhoo," is the sentiment of graph records. It may be operated just of the additional amplifier and loud the local police toward such stunts. as well from the detector stage of any speaker.

RADIO -CRAFT for MAY, 1933 661

'0:» jx-,*-o-r.t«=1;411.« ;. __ _ !+'y'4i6f110!b f:t,.. , ei.e.i E- , 04:-1.44:4* Y1Yta:t_ E rieee - ..e CONSTRUCTING THE MICRO -MIDGET ANALYZER

We have described many analyzers in the past, but the one featured here is extremely small, tests all tubes, and, by virtue of a new switch, is simple to wire. SW.5 -_-- SW -7 eir. GEORGE G. SEROTTA SW.8

Fig. A Photograph of the Micro -Midget analyzer described by the author. The small size is apparent by comparison with the meter and the sockets. IN DESIGNING this analyzer, I have endeavored to make it as simple, as inexpensive, and as highly accu- 'R7 -f SW4 r., rate as possible. This analyzer utilizes a Weston or B3 Jewell 0 -1 ma. milliammeter equipped with accurate re- YB sistors, and may be built for approximately $26.50. It is very simple to construct, as may be seen by inspecting the wiring diagram, Fig. 1, and is easy to operate. Because of the simplicity of the wiring, the operator may easily understand the various tests he is performing on a receiver, whereas in some other analyzers the wiring is so complicated that the average Service Man depresses push buttons and throws switches but does not understand how the meter is being switched about in order to test a desired circuit. An analyzer of the type to be described will take care of all existing tubes, and, if necessary, with very little change, may be made to take care of ten -, fifteen -, or twenty-prong tubes if they are ever manufactured! The cost of the analyzer may be reduced to SW.I about $21.50 if carbon resistors are used in place of the wire-wound resistors Rl, R2, R3, and R4, but the read- SW. ings would not be as accurate. , At the left side of the wiring diagram is the switching 7 - SW.S arrangement of the analyzer. This analyzer utilizes a S W. -_ --_/\ new type of switch, Sw. 1, which I have designed. This 8_-=--c switch does away with many expensive push buttons, thus SW .3 'r SW-":6-)4 saving much panel space, and, also, eliminates compli-

Fig. B cated wiring. This switch is not being manufactured; Rear view of the analyzer. The designations here, as well as those in Fig. A, but I will describe how it works, so that if any of you above, correspond to those in the List of Parts and the diagram, Fig. I. wish, you may build it yourself.

VI v2 The Special Switch 4 -,5-.6 -NOIE c COMPOSITE SOCKET 2G2 Figure 2 is a diagram of the switch, Sw. 1. Seven pairs of contact points are mounted on a piece of bakelite GRID w 0.K CLIP in a circular arrangement. Each pair of contact points are spaced equi- distant from each other. They are represented in Fig. 2 as the outer disc on which the plate, [OR ruTVRE filament, grids, and cathode lines are connected, and 8-0RoKO D.C. are TueES G represented in Fig. 1 as X. Directly over this outer disc of contact points is the inner movable disc on which are REVERSING swlTCx,sw.3 mounted six jumpers, or shorters. Each jumper shorts R7 a pair of contact points, GG, FF, PP, KK, etc. On this RS / RI R2 R3 R4 inner disc are also mounted two separate contact points, / < l < Pd K MR MM. The jumpers, or shorters, are represented in Fig. -SW 2 1 as the dotted lines connecting the X's. The two small of the inner disc are represented as fS 2 sw sw sw Sw contact points the ePROMG 5 c T arrow heads in Fig. 1, and are designated by the letters '-I -» PLUG TO GRID MM. Re CRP, el T11 1 a When the switch is revolved one position to the right, GSK r M G2 .4.5 VOWS 84 the jumper that is closing the G1 (grid No. 1) circuit moves over and closes the cathode circuit; the juniper Fig. I which has closed the filament circuit moves Schematic circuit of the analyzer. The connections of the special switch are over and shown in simplified form for convenience. See Figs. 2 and B. closes the plate circuit; the jumper which had closed the

662 RADIO-CRAFT for MAY, 1933 plate circuit moves over and resistor in shunt, through the POSITION OF SELECTOR SWITCH , SW. 1 closes the filament circuit (FF), low resistance meter, with the resistor selected by the push and so on. All jumpers move TUBE PLATE GRID GRID GRID CATHODE points, VOLTS 0121 011.2 249.3 VOLTI button; the entire arrangement over one pair of contact TYPE OR VOLTS VOLTS VOLTS OR while the two separate contact CUR. OR CUR. OR CUR. OR CUR. CUR. is in series with the circuit points, MM, of the inner disc 00 P 02. which has been selected by now in G2, or grid cir- 01A P G2 Sw.1; a current reading is auto- are the 10 P G2 cuit, and the meter is now con- wO II P 02 matically obtained on the nected into this circuit, reading W 12 P G2 meter. The value of current is 12A P G2 depends upon the voltage drop grid current. If the switch 20 P 62 again revolved to the right, fila- 22 P GI across the 1,000 -ohm resistor. ment current will be read, and 24 P G1 K When Sw. 2 is in the first posi- 26 P G2 so on. Later, I will describe 27 P G2 K tion, F, points MM are shorted, how voltage can be read with 30 P 62 and the voltage of any circuit the same switch. 31 P G2 (the circuit is chosen by Sw. 1) 32 P G2 G2 The right -hand side of the 33 P 02 K is read, referring to the fila- wiring diagram is the meter ar- 34 P G1 62 ment. The proper voltage scale A 35 P 01 G2 K is chosen by depressing one of rangement of the analyzer. 36 P 61 02 K dry -disc rectifier is utilized so 37 P 02 the push buttons. When Sw.2 + that A.C. readings may be read K is on the second, or K, position, S19, G1ó G2 K G3 with on the D.C. meter. This neces- P G2 all voltages are measured sitates using a triple -pole, 41 0 63 02 K respect to the cathode. It is 641 P 02 double -throw toggle switch, Sw. 42 P 03 62 K standard practice to measure 4. When A.C. voltages are to 44 P GI 62 K all voltages in heater-type switch is 45 P 62 tubes from the cathode. be measured, the 46 P G2 K to the A.C. side; when 47 P G2 K thrown External Measurements D.C. voltages or currents are to 4 P 02 K k 30 P 02 be measured, the switch is 55 P 61 K All meter ranges are brought thrown to the D.C. side. This 56 P G2 K out to four binding posts, Bl, 57 P G 1 G2 G3 K all triple -pole, double -throw switch 5e P 01 02 G3 K B2, B3, and B4, from which throws the rectifier completely 64 0 G2 external measurements a r e out of the D.C. circuit when 66 01 made. Placing Sw.2 on F, all 71A IS G2 the switch is thrown on the D.C. eD P D.C. and A.C. voltage ranges of side. In most analyzers utiliz- el o the meter are available between do e2 P B2. Plac- ing a rectifier, the designers 45 o 01 K binding posts B1 and not avail themselves of this 99 0 02 ing Sw. 2 on MA, all D.C. cur- the rectifier 6A of the meter are means of throwing BN rent ranges out of the D.C. circuit when LA P 02 also available between binding testing D.C. Because of this weNDeuICN 62. 61 posts Bl, and B2. Continuity SW .1 failure, the accuracy of the SET ON P-cOR A 6 F,ANIENT VOLTAGES ¡ SW1 and resistance measurements readings are impaired. SET ON G2 FOP 2Y4 PLATE TEST Or 60, 81102 TVBES are measured between binding Directly below the triple -pole, Fig. 4 posts B1 and B3. For resist- double -throw switch is the A chart showing the position of the switch for various tests. Others ance measurements, a 4,000 - may easily be added. A description of the switch is given in the meter reversing switch Sw. 3. test. ohm resistor R6 is used with a Four resistors, Rl, R2, R3, 5,000 ohm rheostat R7 and and R4, having values of a 4.5 -volt "C" battery; the 10,000, 100,000, 500,000, rheostat R7 is used to ad- and 1,000,000 ohms, are just the battery until the used to increase the meter meter reads full scale. scale by 10, 100, 500, and When this is done, the test 1,000 times when reading leads should be placed either voltages or currents. across the unknown re- Each scale may be selected sistor, the deflection of the by depressing one of the 65 63 meter should be read and push buttons situated di- Fig. 3 Fig. 2 then referred to the resist- rectly below the resistors. An enlarged sketch of The meter dial. The special switch used. ance scale, Fig. 3, to de- Switch Sw. 2 is a standard termine its value. Output bi- polar, t h r e e position measurements are made be- switch. I made this switch FEATURES OF THIS tween binding posts B1 and from two single selector B2. When a low output switches that I had in my scale is desired, measure- junk box. These selector ANALYZER ments should be made be- switches have six contact It is small, thus taking a minimum tween binding posts B1 points and an off position; and B4 ; rheostat R? should it is shown as such in the amount of space in the tool kit; be used. To use the 0 -1 photograph of Fig. B, al- It is easy to assemble and simple to ma. scale, place the test though I only utilize three leads between binding of the positions. When wire -a blessing to the man begin- posts B1 and B4; rheostat this switch is revolved to R7 should be in the "off" the last position, MA, it ning to service radio receivers; position. A scale may easily automatically inserts a Tests all 4 -, 5 -, 6 -, and 7 -prong tubes be calibrated for the meas- 1,000 -ohm resistor, R5, in urement of condensers. the meter circuit. without any adapters, except those Tests of condensers should When the measurement on the analyzer plug; be made between binding of current is desired, Sw.1 posts B1 and B2. Of course, is revolved to the desired May be used as an ohmmeter, volt- Sw.4 should be thrown to position, and one of the meter, the A.C. position for A.C. push buttons, Sw.5, Sw.6, milliammeter, and output voltage, current and con- Sw.7, or Sw.8, is depressed, meter. No shunts are required. denser measurements. thus putting the 1,000-ohm (Continued on page 888)

RADIO -CRAFT for MAY, 1933 663

>.l.rr .=y±'.Y}ä:á 1614,*0**-?'0°' 1!* h ]T, s L- -. .:+.. :a rf :e" x. . +,a: 1aa-*. Ak,. . N. s nAlt:r:w.: ar':AtAiiad.,r:rs7ë.A THE MULTITESTER

A VOLT -OHMMETER AND MILLIAMMETER UHMS x50000 \tidP 2 F/ N A description of a simple tester which measures voltage,

O current, and resistance. It has several unique safety fea- /N tures which further facilitate its utility. /MILLS SELECTOR MILTON REINER*

en place and which might occur in the and less is of considerable value in Panel view of the Multitester Showing the location of all panel controls. future, there is every reason to be- testing R.F. circuits; the second ohm- lieve that any meter that will measure meter scale is from 0- 200,000 ohms; voltage, current, and resistance in a while the third, or high range, is from successive series of scales will always 0- 2,000,000 ohms. Of course, it is THE importance of considering ob- be of maximum utility. With this possible to measure resistances up to solescence, adaptability, and econ- point in view, the Multitester has been 6,000,000 ohms and higher by putting omy has frequently been stressed designed as a compact, economical, external batteries in series as is some- when purchasing, designing, or self -contained testing instrument which times resorted to by a few manufac- building test equipment. With some is complete in itself, or may always turers. few exceptions, it seems that we in serve as the heart of a super -flexible All voltages are indicated directly the radio industry "never learn," as analyzer system, other units of which on the meter which has a sensitivity we constantly see new instruments an- will be described at some later date. of 1,000 ohms per volt. There are nounced that do not consider these The Multitester is so designed that three voltmeter scales: the lowest factors of prime importance. great flexibility is available for mod- range is from 0 -5 volts. Voltages of Experience has shown that circuit ern testing methods at maximum econ- the order of .1 -volt may easily be read. design changes rapidly with the fre- omy and efficiency so that it can al- The other voltmeter ranges are 0 -50, quent improvements and additions to ways be used as a multiple- purpose 0 -250 and 0-750 volts respectively. the various types of tubes. The voltmeter regardless of what changes may This gives a higher range and a better age and current ranges for measur- take place in the future. In short, it arrangement of intermediate scales ing instruments are entirely different is a multiple range, combination ohm- than is available in most moderate from what they were several years meter, voltmeter, and milliammeter, price commercial ohmmeters. ago. Yet, there are a large number all self -contained. The ohmmeter has The majority of commercial com- of the older sets as well as the mod- a triple range: the low -scale reading is bination ohmmeters are merely volt, ern ones to be serviced. from 0 -2,000 first Regardless ohms, the division (Continued on page 698) of changes that have tak- representing 3¢ ohm. The ability to *Chief Engineer. Radio City Products Co. indicate resistance values of tF ohn

TAPERCO SO MA ?SOMA SNuNT ZERO ADJUST SMUwt 0 -15 600 -6.000 SS ONM3 TOTAL 0.60 ¿.500 OMMS 5 MA. SMONi f _l_ I5.000 a OMMS 3

SeniON Na s

Sv ,I illy

0111111101 SECT.ECTION NE 2. w vor_

e1+ s lI

SEC T.O, M! O r iwREE SECTION 'EN G05iTiON SELECTOR SwITCN ®MILLSq QQ'v01t5-C 4+1oMMT;

A bo. e: Schematic circuit of the hluItitester with the values of all parts. Note the use of a triple -pole rotary switch. Right: View of the rear of the tester. The sirnplicity is apparent at once.

664 RADIO -CRAFT for MAY, 1933 READERS' DEPARTMENT A department in which the reader may convey his thoughts to other readers. Included in this department are letters, kinks, short cuts, and experiments. Send in your ideas.

THAT TABLE OF I. F.'s tubes all test good and we have aligned Disconnect the power transformer Editor, RADIO- CRAFT: the condensers with an oscillator. We connections and test the transformer I have been reading RADIO-CRAFT for have sold and serviced sets for seven for leakage of one of the windings to some time. In the December, 1932 is- years, but this one has us stopped. ground, or to each other. At the same sue there appeared a chart of inter- A. J. NORTHRUP & SON, time test each winding for rated out- mediate frequencies which took a load East Berne, N. Y. put voltage. Try another reproducer; off most Service Men's minds. I want something may have happened to the to thank you for this chart, and also To this communication we replied as present one. for the RADIO -CRAFT tube chart which follows: You aligned the tuned stages with an came out some time ago. Let's have Gentlemen: oscillator. Did you get average read- more of these charts. The circuit of the Windsor receiver ings on the meter in the plate circuit THEODORE CRITZON, is not in our files. of the detector? (This is an instance 4633 Eller y, Probably the simplest way to locate of the value of working with calibrated Detroit, Mich. the trouble in this set is to isolate each equipment.) If you did not, look for section and to work in that section leakage in coils or condensers (perhaps (This is about the 'steenth letter we alone. That is, hook up the set with dust or soldering flux is in places where have received concerning these tables an external power pack (another Wind- it does not belong). Leakage in the in RADIO- CRAFT. Thank you, kind Sirs. sor, if available) and note the opera- R.F. circuit could show up as reduced It seems that the service field greatly tion of the R.F. and detector section signal strength without the operating needed these useful tabulations. Any of the chassis. If this is O.K., try a voltages being off in the least, but the suggestions for more tables ? -Editor) different R.F. and detector unit (con- old mike test would show that the trou- nected to the power pack of the Wind- ble probably was in the R.F. chassis, as sor under TROUBLE IN A WINDSOR 70 S. G. suspicion). pointed out above. Put the aerial lead We are inclined to believe SET that you on the input to the detector, to check have a shorted bias resistor (although the operation of the R.F. circuits. Due to the exceptional interest in a this should show up in the readings of Do not miss one of these pointers. bit of recent correspondence, we print your set analyzer). Of course, you have Please advise us as to what you find below the pros and cons of the discus- checked over your tubes. Test for to be wrong with the set. sion, which concerned the Windsor correct grid bias voltages and operat- model 70 S. G. screen -grid T. R. F. set. RADIO -CRAFT ing plate currents. Do other sets work Technical Editor Editor, RADIO- CRAFT: satisfactorily on the same aerial and We have a Windsor model 70 S.G. ground? Check the filament voltage The 7 tube A.C., set (built by the National of every tube. Check all the condens- mystery was solved when we Transformer Co., of Chicago) which ers for leakage. Test all the resistors received the following letter. suddenly lost its volume, and the recti- to make sure they are not shorted or Editor, RADIO- CRAFT: fier tube started to heat. We replaced open, and that they are of rated value. The trouble was located in one of the condensers one of the power pack condensers which Connect a microphone into the de- in the resistance coupled was shorted and the volume. came up tector grid circuit of the set and note A.F. unit. This condenser tested O.K. to about two- thirds of what it was whether you get normal output from until being "shot" with an extra high formerly on local stations, but all other the reproducer when speaking into the voltage, when it finally emitted a light stations can just be heard and the mike. If not, check the detector and curl of smoke. It must have been par- rectifier tube heats a little more than it audio; never mind the R.F. If O.K., tially broken down and would alter- used to. All voltages appear to be cor- check the R.F. section of the chassis nately heal and break down. We re- rect according to our set analyzer; for accidental grounds. (CoSltinned on page 683)

TIME AND DAY CONVERSION TABLE FASTEN TO WALL OR BENCH TODA I BACK wilw WOOD SCREWS ...... 12 12 II 1{ If I 65 Nee Zealand i II 12 I! 14 If IS 1 150 Australia. 10 II 12 Ii 14 16 IS 1.4114 155 tapas 10 120 Chins. Philippine. ( t 10 II I! 2 11 15 If 105 Indu CON.. Sula. I NNemem 12 I`444,3t 90 Calton. I1 t II 11 12 13 11 15 1 t 10 II 12 12 II IS a6 1 60 M»ritus. Seychelles 6 t 10 II 11 12 11 16 16 I AOen. Somaliland. Yada(uuar 9 10 II li Il 16 16 4ttikE 50 South Arrlr. 10 II 13 3 14 16 IS i+ L.... tk 15 Geom., Illy, Norway. Swedes 14")..... t s I I0 la 2 12 11 15 16 t 0 E eared. Promo. 0.51 T I 10 II 15 I f 0 II II li 16 IS It 1 '.a 30 6 10 II II 13 14 IS IS 1 ` 12 13 14 16 1 45 east '` I lo II II 6a 6 Aram...e Rico I II 51 ys n. C. EST li lï ii ii is i6 1+1. ..._[[+a `_ i ii 3 95 au ' S.T IO IS Fig. 51ST ``` 1 i i: ii ii ii ii i6 A, bracket; E, hood; C, hook; D, 'Martial spring ISO Min ñ..tiap. PET .yl % t II II II 11 u u 1 li ii ii 150 Alaws ta S 1 t 10 11 11 IS 166 Sam a. {Mani 1 IS IS I I II II S/16 as Du GIBER ROC KNOB P -F.ST 160 !l Ii IS 2 - 11 l'ESTERDAY TODAY NOTEJA-01 Add one .belt boor for Now cari NOTES:-0 Y mldnlólt. I to /.00 AM.. ate. IS Is soo.. II i. Z land Time. ROO PILED TO FIT SOCKETS i I Nam. Subtract osotalf ho, Read Ga ammo column. ertmñly. lhes:-. hes II w li, noon tor y India St.ad.r11 oil Holiday In New York EST.. It Y 1.6o A.Y, as Tom ' oae.balf hour for 0..all.. day in Melbourne. Australia. SCREW ilraadbtr et Or vyv.oed.y Sia P.M DRIVEL SOCK TS Iv Zealand aeid 600a1 ® . yni N The Moire of d.rbvea.--A P.Y. to 6 A N. are .5.4,0,1 SOCKET uTt

Fig. I Fig. 2 A chart which indicates the time throughout the globe at any instant. Here is an aligning tool that's easy to make.

RADIO-CRAFT for MAY, 1933 665 THE ANALYSIS OF RADIO RECEIVER SYMPTOMS OPERATING NOTES

BERTRAM M. FREED

THE widespread use of automatic arrival, the usual questions produced similar voltage from the control grids volume control and silent tuning the information that the set made the of the R.F. and I.F. tubes, to chassis. control has made the servicing of same crackling noise at each of the This unusual situation caused no little .. radio receivers more difficult and three times it had ceased operating. conjecture, and the first thought was complex. So many situations, both A tube checker was plugged into the a primary- secondary short of either the unique and troublesome, have arisen, line and the chassis pulled out of the R.F. or I.F. coils. However, if this due to different failures and defects cabinet to test all the tubes as the first were so, then, it was thought, some in the A.V.C. and S.T.C. systems, that step toward clearing up the trouble. breakdown would result, as the plate the Service Man is placed on his The set switch was snapped on to pre- voltage impressed on the primary mettle. Schematic diagrams have been heat the tubes. would be short -circuited to ground or important in the past, but with the Balancing the end of the chassis chassis through the secondary; but servicing of modern receivers, they with one hand, an attempt was made when the schematic was consulted, it have become vital. The careful study to remove the control-grid cap of the was found that this condition of high of a diagram with only a few tests first detector, 35 tube, with the free voltage on the control grids of these has, in many instances, solved a hand. An attempt was made, but three tubes was possible without fur- knotty problem. Some of the situa- failed, for when this was done, the ther breakdown. The control -grid re- tions will be described herein. author became the unfortunate donee turns were connected in the A.V.C. of such a vicious "jolt," that any idea circuit, together with the A.V.C. plate Atwater Kent Model 99 of further tube -checking was aban- resistor; because of its high resistance, Some time ago, the complaint of doned for the time being. The term- the amount of current was limited "dead again" was received on an At- inals of a voltmeter were placed from thereby preventing a short circuit of water Kent model 99 receiver. The chassis to control grid of this tube and the entire voltage output. "again" conveyed the fact that the set a reading of nearly 400 volts was ob- The fact that there was no further had been serviced previously. Upon tained. The voltmeter disclosed a breakdown evidenced an unimpaired

NIMIO 011013 '401:e1.--f- 1.

... r \'.r... / lel 1 i:I' '/K -

G7:.. F.{f.

ey'.I'+J r n "far`fa_r

0t3. +ec. 1..001 0% seo SSS lose O : e 300 .Hs

0.t.we.

0-S.-ILO

IPp

o M '. >' CO. eoe 1r

Fig. I Complete schematic circuit of the Atwater Kent model 99 receiver showing the values of all parts. An explanation of each unit is also included.

666 RADIO -CRAFT for MAY, 1933 1.1N tZ:: ^

A.V.C. plate resistor, and, proceeding lady of the house offered the informa- on this theory with the aid of a low- WHAT THIS DEPARTMENT tion that the fading usually occurred range ohmmeter, the short was found IS FOR after the set had been operating for within the shield can of the first I.F. fifteen minutes or so. With this lead, It is conducted especially for transformer, by the process of elim- the Service Man settled himself down the In ination. This unit is located in the ex- professional Service Man. to make what might be termed a "lis- treme front right corner of the chassis it will be found the most unusual tening test." and to the right of the control tube, troubles encountered in radio With the volume control set for a a 24. When the shield of this trans- service work, written, in a prac- moderate degree of volume, WOR, one former is removed (this may be easily tical manner, by Service Men for of the most powerful and reliable done by pressing in the bottom of the you. broadcasters in the vicinity was tuned - can on two sides and then raising it), Have you, as a professional in. The receiver operated for forty slightest vari- a carbon resistor will be seen imbedded man, encountered any unusual five minutes without the ation in when the Service Man in the pitch which is used to impreg- interesting volume nate the primary of the I.F. coil. This or Service Kink that took his leave, the owner agreeing that resistor is shunted across the secondary may help your fellow workers? the set was now apparently perform- winding, also impregnated, of the same If so, let us have them. They will ing satisfactorily. However, after a unit. Whether due to vibration or be paid for, upon publication, few days, the same complaint was re- other causes, the resistor short -circuits at regular space rates. ceived. Another Service Man was dis- r to the primary winding, resulting in patched with strict instructions to de- the aforementioned condition of con- vote as much time as necessary to de- trol grids that "kick." termine the true cause of the fading To eliminate this defect, all that is SLATE condition, should such exist. necessary is to work the resistor out On this occasion, the Service Man of the pitch and move it a fraction of selected WJZ as the listening monitor an inch away, after wrapping a layer and the receiver behaved perfectly for of tape around the unit. Another in- over two hours. The owner then vol- VSCI LLATOR unteered the fact that he has never dication of this trouble will be the UNIT climbing of the neon tube glow to the ORANGE heard these powerful stations fade, and that it was only on the smaller top when the receiver is first switched BLACK on, then quickly falling to the bottom - stations at the high- frequency end of of the tube as the receiver tubes heat. the scale that the volume varied. With The schematic of this receiver is il- LACK this in mind, a 1280 kc. station was lustrated in Fig. 1. tuned in. This necessitated turning SHIELD SNORT up the volume control. After only a This same condition and effect has HASS 15CAUSED often been found on the model 96, the TROUBLE few minutes, the fading commenced. 2.O COIL, ZIP The station selector was then set at offending member being the secondary BA NO-PA SS resistor within the first I.F. trans- TUNER 1350 Ice. and the same condition per- SLATE Sn MU) sisted. 1400 kc., however, where former. In this model, this resistor is / On located at the back right -hand corner the volume control had to be turned of the chassis and in of the neon back, the receiver did not fade. front To negative any idea of faulty light adjustment. SHIELD RF padding or trimmer condensers, the dial 477:'S C0RME0. was turned to 600 kc., a distant sta- Atwater Kent 812 REO- tion, and the signal faded. This led A few cases of noisy and intermit- WHITE: L to only one conclusion; the volume tent reception have been reported on OREEN SHIELD control was at fault. When this con- this model. This receiver is a new WHITE trol was turned to the highest point, one, utilizing two type 83 rectifying 5HELO or, on the higher end, the slightest tubes and type 46 tubes in the output SHORT To CHASSIS CAUSED touch or vibration would cause the arm with 46 as a driver. In TROUBLE stage another SL Ait - to shift from one turn on the resistor all of these few cases, the trouble has 2ID. CO, Il - Sena -.ASS to the next. It was near the end of been traced to a loose connection be- TUNER. the resistor, where the winding was neath the sleeving of the wires con- least firmly moored, that this shift be- nected to one end of the 1450 mmf. PL AC came noticeable, resulting in the fad- condenser within the oscillator coil ing. An odd complaint, but after a shield. new unit had been installed, the fad- On this same model, erratic opera- Fig. 3 ing condition was remedied. Subse- tion of the silent tuning control has Detail of the tuning units and shields in the quently, two other receivers of the Stromberg Carlson models 2S and 26 receivers. been found to be caused by a loose The screws, shown above, were shorted to the same model appeared with similar element in one of the 57 tubes in the chassis, causing the volume to drop and the tuning complaints, which, because of the first, S.T.C. stage. A few sharp taps on dial readings to shift about twenty-five kilocycles. were speedily rectified. the glass envelope will soon disclose On this same model, many service this condition; or, to more readily as- calls have been made because of certain this fact, place the tube into DIAL DRUM slipping drive cables. A very simple one of the 58 sockets and repeat the arrangement is utilized on this re- tapping. ceiver, and although the trouble may RCA Victor 21 be caused by a stretched tension An interesting case was recently en- spring, which does not take up suf- countered on an RCA Victor model 21 ficient slack in the cable, it has been in DRIVE found that by taking another turn receiver: the complaint this instance CORD was fading. Following the usual pro- SunsCONO around the gang shaft, sufficient fric- cedure, the Service Man assigned to tion is obtained to clear up the dif- the job made a complete analysis of LOOSE ficulty. This may be done by releasing the receiver, checking the tubes at the the spring beneath the dial, so that same time, and a thorough inspection Fig 2 thee turn may be made with the loose Slipping cables are not an uncommon trouble on is of the antenna system for possible many sets. In the RCA Victor model 21 receiver, cable. The spring then fastened breaks, grounds, or corroded connec- this trouble may be remedied by loosening the into position and the dial restored to spring and taking an extra turn around the con- tions. All was found ship -shape. The denser shaft-not the dial shaft. (Contiued on page 684)

RADIO -CRAFT for MAY, I 9 3 3 667 REWIRING RCA AND A. K.

SETS FOR 2 -VOLT TUBES DAVID HOYLE

A practical description of the manner in which RCA and A.K. receivers have been rewired for two -volt operation. It is completely illustrated by diagrams.

THE list price of the 22 is 80 per grounded end and insert an additional socket to which this lead is connected, cent higher than that of the 32 resistor of 6 ohms at Xl, grounding, of two black leads through the (in chassis Canada), and in that compari- course, the free end. See Fig. 2. We lead to the plus filaments of the R.F. son lies an opportunity for the make these resistors of nichrome wire tubes. Break each (at X3 and X4) and Service Man. wound on a fibre strip; No. 28 wire has insert a 25 ohm grid suppressor or a The RCA 22 is a five -tube battery set a resistivity of 4.25 ohms to the foot. home wound resistance strip, 25 ohms originally using two 22's and three Allow a few extra inches above that re- each. 12A's (or two 12A's and one 71A). Re- quired, so that a little may be added in Using a fully charged storage bat- placing the 22's with 32's is a compara- the circuit if necessary on final voltage tery and an accurate voltmeter, make a tively simple operation in this set. The test. From 1.5 to 2 volts is the best all - careful test of all filament voltages. owner saves money and the Service around bias fóund in our experience, Minor adjustments are taken care of Man paves the way for a complete and the added resistance is sufficient. by the extra length left available in change to five, two -volt tubes and a lit- At the left -hand end of the same edge the bias resistor. (This bias is not criti- tle extra revenue. With two 32's, two of the set are two resistance strips side cal.) Rebalance the set. 30's, and one 31 in place of the original by side; each is 1.95 ohm (R2 and R3). The voltage amplification factor layout, of the total filament drain is cut to A yellow lead, A+ in the cable, is these newer tubes is given as 440 approximately one -third of its former soldered to the junction of the two. as against 300 for the 22. Both owners, value. This means, not only less cost Through one of these resistors, R3, for whom we have made the change, for battery charging, but, in the case of flows the current for the power tube believe it an improvement. One of these an owner located at a distance from a and the two R.F. tubes. Make sure you owners, for whom we made the change garage or radio service station, less in- have the correct one by tracing the lead eight months ago, and who keeps a convenience, since every battery charge (black) to the filament socket of the careful check of his storage battery means trouble, and perhaps one or two power tube. Take a 1.-ohm fixed resis- charging, insists that he is getting 30% days without reception. tor and short out one -quarter of it. In- or more extra service from the one sert this resistor between the end of charge though Installing 2 -Volt Tubes only the R.F: s have been the resistance strip and the power -tube changed and the three 12A's are still in Take out the chassis and turn it over; socket (at X2). When the 32's replace use. We judge this to be due, possibly, have the back edge toward you. Near the 22's, the total current flowing to the greater sensitivity of the 32 the center of the nearer edge is a flat through this resistance is reduced from when the battery is below normal resistance strip (Rl in Fig. 1A). This 514 ma. to 370 ma., and the 1. volt drop charge. strip is the bias resistor of 6.5 ohms for required (for power tube 5-volt cir- Little difficulty should be met in the two R. F. tubes. It is grounded at cuit) is given by the increased resis- making the change. The leads are easy one end. Disconnect the lead at the tance. From the plus post on the power to trace, no "wrecking" of the chassis is required, and there is ample room for the added resistance 32 32 12A 12A 12A strips. -A- Changing the Audio End of the Set (1) When the time comes to change the R1 audio and detector ends, proceed as fol- 6.5 OHM RES. 5 lows: remove the three -quarter ohm i + ® - or resistor previously inserted at X2 and INSERT replace with one of two INSERT OMM / .75 -OHM ohms. This 2 1 " . .. RES RESISTOR 60NM IdIMMINI x2 assumes the use of a 31 in the power RES. stage (Filament drain, .13- amp.), xl 25 Ohr Rs there- RES fore, four ohms (very nearly) in T OHM this I RES lead gives the required one -volt drop. CHASSIS - 112 (Total filament OHO 1.95 OHM - %,".1L+ 'YELLOW current is to be .13- RES. plus .12 -amp., for 32's, which will give the 32 32 30 31 required one -volt drop through the -B- four ohms.) Thus, changes in the previously added R.F. resistors are not needed. In series with the other 1.95 ohm re- RI ri 2$ JMMS 6.5 OMM sistance, R2, shown RES. 50 SO (ADDROX) in Fig. 1A, add an OMMS OHMS additional six ohms. The total resist- + + + REMOVE ance, now eight ohms and the .12 -amp. INSERT .7$OMM {OHM -X4 RES,INSEßT for the two 30's (detector and first au- RES 2 OMM dio), gives a one -volt drop. Now we EI -. x3 6RES.- OMM I RES need three volts drop for each of these T last three tubes. -ohm 02 1.95 03 1.95 Fifty grid sup- CHASSIS OMM RES OMM RESA .A+ YELLOW pressor (test them) for the plus leg of - >. both detector and first audio tubes will supply this. For the 31, a 25 -ohm Fig. I resistor is Schematic of the RCA 22 with only the R.F. end of the set changed at A; at B, the same set showing a bit high, but can be "doc- the changes for complete two -volt operation. tored" if required. As before, test 668 RADIO -CRAFT for MAY, 1933 everything carefully. We do not think REWIRING OLD RECEIVERS FOR NEW TUBES it wise to follow the original schematic and use a single resistor for two tubes; better give each tube a resistor of its "New tubes have made my old set obsolete," cries own, otherwise, if one blows, the other may follow suit. A diagram showing the owner of a two -year old radio. "How can I bring the changes to be made to alter the audio end is shown in Fig. 1B. it up -to- date ?" he pleads in the same voice. These The owner of one of these sets complained of harshness at high volume and many other similar questions pour into the edi- but did not care to use the 71A with its added "B" drain. We added a .002 -mf. torial offices of this publication every day. fixed condenser in parallel with the one already across the secondary of the first Our policy in answering such letters is to state that audio transformer and he was pleased. The 12A was retained. we are unable to forward design data by mail; but, When inserting the resistor in the we should we plus lead of the detector tube, be care- if secure same, shall be pleased to pub- ful to disconnect the pilot -lamp lead. lish it. We take this stand because we are not de- Run a direct connection to yellow "A" plus and use a 6 -volt lamp. sirous of indulging in pure theoretical speculations; Changing A. K. Type "Q" Chassis for 2 -Volt Tubes and, furthermore, when we give information, we want We have changed the R.F. end of the two Atwater -Kent Model Q chassis to be sure that it is correct. The practical Service for 2 -volt tubes. This is a seven tube battery set originally using three 22's Man will appreciate this viewpoint, we are sure. in the R.F. end. We have only replaced the 22's in the R.F. end, leaving the This article is an example of the type of informa- audio end alone. Remove the shields and tubes, and tion we want to publish along these lines. Therefore, turn the chassis over. Remove the bottom cover plate. With the R.F. end to if you, as a Service Man, have actually rewired re- your left, you will note that near the front edge (away from you) of the ceivers for use with new tubes, send in your manu- chassis a short yellow- covered wire leading direct from the minus on the script with all information. Details of the manner in first audio to a grounded lug on the detector socket. This lead is carrying which manuscripts are to be prepared will be mailed the filament current of the detector and audio tubes to ground. This lead need upon request. not be changed as the R.F. filament currents return to ground by other paths. Attached to the filament posts Z.o F DET Is? G F of the R.F. sockets will be seen the R.F. filament resistors and the R.F. bias resistors; they are long, thin, covered wires, black with white tracer. Remove them. They will be replaced by resistors (25- and 50 -ohm suppressors) as indicated in Fig. 3. Break the wire connecting the first audio filament plus to the third R.F. filament plus at B (Figs. 3 and 4). Insert a six ohm resistor. This resistor will carry the current for the three R.F. tube filaments, .18 -amp., and there will be a one -volt drop here. Now insert the 25- and 50- Fig. ) to made In reDirinq the A.K. "Q" chassis. ohm suppressors as shown in Fig. 4. Circuit indicating the changes be Note that the new resistance schematic follows the original one.

F4 . It is best to wind the six -ohm resistor PDwEÿ inserted at B. Allow a little extra, as . XS TO in the previous job. This will take care R.F (+1 SOCKETS of any final adjustment. Of course, this Is. K4 To resistor could be dispensed with, but we IAF . R.F.(-) SOCKETS had a bunch of 25- and 50 -ohm resistors Rs_ X2 1 Rl and used them in this way. alrii.

RADIOCRAFT for MAY. 1933 569 89 Radio Service Data Sheet

R.C.A. VICTOR R -27 AND PHILCO 53 ULTRA -MIDGET A.C. -D.C. RADIO RECEIVERS

R.C.A. Victor R -27 Universal VI 8 93 7-14 96 Now check the adjustment of the sensitivity This small radio set carries the following V2 3 34 6-12 14 condenser (at the immediate right of the specifications: Line voltage rating, 105 to 120 V3 4 100 3-26 94 L.F. condenser) with the receiver tuned to a V., D.C., or 25 to I38 cycles A.C. Power con- V4 _ 58-73 10 station near the H.F. end of the dial; turn this condenser sumption, 40 W. A feature of this set is the The total voltage applied to the filaments is to the right as far as possible extremely wide tuning range of 540 to 1,700 51 V. without causing circuit oscillation or a squeal. kc. Operating voltages at maximum volume, Repeat this adjustment on a station near the on a 115 V. A.C. line (on D.C., slightly less) All of these readings were taken from the L.F. end of the dial; if circuit oscillation oc- are as follows: underside of the chassis, using test prods and curs, turn the condenser to the left until this leads with a suitable high resistance meter; disappears. Tube Fil. C. -G. S.-G. Plate Plate the volume control is set at maximum and the At the rear of the chassis are four condenser Type Volts Volta Volts Volta Ma. station selector 550 kc. at controls, as follows (starting : 1 6.0 3.0 106 105 7 from the left) The following data concerning the operation L.F. condenser ; 2 6.0 0.76 11.0 .025 'sensitivity; I.F. primary, 450 60 of this set on 115 V. A.C. are furnished: kc.: and I.F. secondary. 450 3 6.0 11.0 100 95 5 kc. 4 6.0 _. 116 15 Tube Fil. C. -G. Cath. Plate Of exceptional interest is the use of the Impossible to measure on ordinary voltmeter. Type Volta Volta Volts Volts Volta new, type 77 tube. the externally- connected suppressor -grid 6.8 V. R.F. pentode. The type The left -hand knob is a combined volume V1 7 94 18 95 12Z3 rectifier has a 12 V. filament. The sec- control and power the V2 4 34 12 15 switch; station selector ond- detector, V2. is made slightly regener- is at the right. If the set does not work V9 4 102 10 94 within V4 ative at the I.F. In order to secure adequate a minute, reverse the position of the 112 112 filtration on A.C. line in the socket. circuits, the single filter - plug This particular type of The total voltage applied to the choke has connected to not only set should be so as filaments is it the usual positioned to permit full 49.9 V. input and output filter condensers, but also a ventilation at all times. shunt The most These readings are taken in the manner de- tuning condenser which, with the choke satisfactory length of aerial for coil, forms a trap this set is scribed for making D.C. tests. circuit. The chassis does to be determined by individual trial. not connect directly to the light line. In general, a length of about 20 ft. should be To obtain maximum sensitivity through the quite sufficient: use of the 80 ft. of antenna wire furnished The filter condenser bank is color coded as this length is the dimension follows: Black, of the lead which is supplied with the set. If with the set, it will be necessary to adjust the common; green, .09 -mf.: white, the antenna lead is bunched, or too antenna compensating condenser, the L.F. .25 -mf.: red, .76 -mf.; black and white, 0.2 -mf.: coiled, near the common lead connecta the set, circuit oscillation may occur. A similar compensating condenser and the sensitivity to the shield can effect may be produced if the volume control condenser in the following manner; unroll only through a condenser of .05 -mf. is advanced too far. When tuned to a local the 80 ft. of antenna wire to its full length The fiber screw at the back of the chassis station with the volume control fully advanced. (do not connect it to another aerial or ground should be adjusted at the time of installation. a condition may be observed where a certain while the following adjustments are being Place the set in operation, tune in a station amount of counter -clockwise rotation of the made). Tune to a station near the H.F. end of near the middle of the dial, and adjust this control will improve the quality of reproduc- the dial (between 1400 and 1500 kc.). With a screw, which controls the regeneration con- tion and actually increase the volume. This fibre adjusting wrench, adjust the antenna denser, C. until, by turning clockwise. a swish- condition is caused by overloading and may condenser for maximum volume. (This con- ing sound is heard where different stations are be corrected simply by setting the volume condenser is the second one from the front con- tuned In. Now turn the screw counter- clock- trol.) Wise until trol below the readily -apparent critical point. After this is completed, tune to a sta. the swishing sound just ceases. tion near the L.F. end of the dial (as near Continue to turn in the same direction about Philco 53 Universal Compact 600 loc. as possible) and then adjust the L.F. one -quarter turn. When correctly adjusted, condenser for the circuit will not break into oscillation voltages maximum volume (looking at at Operating at a line potential of 120 the back of the set. this is the unit at the any point in the tuning range. V.. D.C., are given below: extreme left) : retune to the H.F. station and As indicated in the schematic circuit, several Tube Fil. C.-G. S.-G. Cath. Plate do any necessary fine readjusting so as to changes have been incorporated in models Type Volts Volts Volts Volts Volta bring in the station with maximum volume. starting with run 6.

ANT. MAGNETIC REO4.004C64. C1 R F.1 -12-36S MMS T-002MF. OUT RS C14 A.F t MELT. 39 36 2 MEG. .002MF 36 Is 37 0.13 Ju .DDa-Mc 0006 MF

875 áws- \ R13 MEG 4-30 6lONSMS IF 430MMF. ~ I MNc Ll l2 ` 30 6 MIL own OHMS II BMA < R2 0.2 -MEG (romo CONTROL a vinous I t Z( --- C7 300 C11 ana C4 CM OHM - *- .05-MF C5 5 MF. ;MF 500 4 M Sw.l SECTI ON TR r 014M5Ì C6 R4 31,000 OMMS C12 5 MF R7 10 V. .05-MF. 1, R-2 OHMS r R2 AND SW.1 ARE GANGED A. C.04GC 4+ CHASSIS RCA vIC700. MODEL R -27 UNIVERSAL. ^ A.TwgTED N a4MEG. ÿ:tiy .D772 MAGNETO - DYNAMIC 4EOROO.CE4 wuas -- ._._._.- SOHNS A Ñ OR, I F LÓSC.Ir7 Fsj-;+ oóots òO17.7. 1 COMP DWG OHMS REGT 4O O$S5 F m) 12 Z3 f

.O5 -MF e 4 VOLUME dMF. COSTS a 11

SL 99.000 REMOVE) 000 ß.o5 -MF OHMS 0.05 185 OHMS ICONO. CAN OHMS 0 49 -MEG CH I t1OS,~ GROUNDED ACOR TO O.0 CHASSIS 10,000 OHMS COMOACT- (ü EFFECTNE WITM RUM Nt5) 1. F. 50 K.0 POWER CONSUMPTION A4.OR O.C., 45 W. R R SW. 1 ARE GANGED. - PMILCO MODEL 53 1/HIVERSAL

670 RADIO -CRAFT for MAY, 1933 Radio Service Data Sheet 90

FADA 103 FADALETTE, STEWART -WARNER SERIES 108, AND DE WALD 54 DYNETTE SETS

Tube Fil. C. -G. S. -G. Plate Plat,. Fada 103 Fadelette following approximate voltages should be read to the frame of unit C. (using a high resist- Type Volts Volts Volts Volts Ma. A tabulation of voltages in this set on D.C.: voltmeter). 2 Tube Fil. C.-G. S.-G. Plate Plate ance VI 6.3 2.15 103 103 Type Volts Volts Volts Volts Ma. Tube Fil. Cath. S.G. Plate V2 6.3 3 9 39 .1 V1 6.3 2.6 97.5 ,97.5 4.5 Type Volts Volts Volts Volts V3 6.3 9 103 98 10 V2 6.3 .... 7.5 ...... V1 6.3 1.5 107 107 V4, V5 6.3 .... 15 V3 6.3 7.5 92.6 96.5 4.8 V2 6.3 1.3 9 1.3 V4 2.5 ...... 37 V3 6.3 9 107 103 By means of suitable line resistors, or adap- A set of figures for A.C. line operation: V4 12.6 122 .... ters. this set may be operated on light -line or battery power. Tube Fil. C. -G. S. -G. Plate Plate These figures are for a 115 v., A.C. line: Type Volts Volts Volts Volts Ma. on D.C., the values will be slightly lower. V I 6.3 2.6 110 110 6 Circuit oscillation may be due to the an- V2 6.3 .... 9 ...... tenna being too close to the set ; oscillation at All sets of the "universal current" type now V3 6.3 9 104 102 7 low signal volume with maximum set sen- on the market require that the Service Man V 4 6.3 ...... 40 cord is check the position of the power plug in it: The D.C. and readings are a 110 sitivity is normal. The power naturally A.C. for socket to determine whether it is correctly V. line. Bias readings are taken across re- warm. Do not force V4 into its socket. This be on 110, 32, 12, or poled. It is seldom that the chassis frame con- spective bias resistors. The D.C. input is set i designed to operated systems. nects directly to the power line. Circuit os- 34 W., and the A.C., 36 W. 6 V. current- supply cillation at the high -sensitivity setting of the Stewarf- Warner Companion Chassis Series Pierce -Airo De Wald Model 54 Dynette volume control is normal in many models. The 108 and 108 -X, Models 10 to 20 The following tabulation of operating volt- results obtained with ultra -midget sets will With the volume control tuned full on, the ages is furnished by the manufacturer: greatly depend upon local reception conditions.

ANT. DYNAMIC 2550NMS ORANG FADA 34 REPRODUCER A L GREEN 001SMr r R.F1 DET 2MEG. .006+1F A.F.1 RECT. YEL. eLK L2 LI FINIS4 -I F 36 4,000 F25Z5 F 39 GQEEÑ.. I I OMM T FIELD I I 1 MEG j1 BRN mowJ. L--_ BLK." ` I .05 GREEN 111515m T3 I MF vl vo RFE2L-- V2 V3 - -J V4 1 RED,, PNM CM LINE 10 MF. NOISE 25 V,DC. 50,000 4:0/X ELAN SW! ( ELECT. )' F OHMS I NATOS. LL .af FLECT) GRIN-ELK - R 'BLACK ORANGE 'BLACK NOTE f Tk DO I .25-' 4 m 000 8m 110V, MF 1 000 OV,DC. 180v,DC. A.C.OR TNE COAS IS 01MF 1.500 OHMS 00PLUME CONTROL CNAS515 - 5w. 1-AND-R; ARE GANGED -RED 25v..D.0 BRH: GRN D.C. (ELECT) -FADA MODEL 103 i 40ALETTE -

-AO ANT MAGNETIC 10 I SPEAKER 1 - MSF .003- 11F R F.1 DV' 2.1 MEG. .003- 11MEG AFI BATT'V. l 39 36 MF 38 PLUG,. s ) 1223 J ( 1 Ll IL BATTY (ORY ELECr) { BROWM SOCKET 4 MF 150v 1 (EACN) . ow/ S V4 , c 53 F (PRY N DOWER .1MF SMFLECT) Z .003- LACK CORD) .1 -MF 20 V \ 100 100V RED M (DR ELECT) 1, á41

BLACK V, --a «0.25.140. VOL. CONTROL 29,000 0N14$ 16000HMS R1 ANC, SW.1 ARE GANGED. r A.0 OR D.0 +{- CNASSIS - STEWSRT- WARNER CHASSIS SERIES 108 AND 108.5, MODELS 10 TO 20 (INCLUSIVE)-

ANT., REPRODUCER - PIERCE -AIRO OE WALD MODEL 54 DYNETTE-

I R t Ll L2 I OICE RECTIFIERS DET AF1 COIL 39 J I 36 MF 36, 37 57 Í f o rr- o r--- -0E-, 9 o I I r - Ft-F-,i I V I -.r------/"": 3.5 l^y4,-t- J NY I MILLI I I F-j IUMFER IN FOR R520 I - 100MMF l I 1 I 1 VOLT L l GREEN 3-UG .01 250 MF OHMS ¡Ft {i çL- B- F2 ELIM- 1 011145 1 4 5CJ0 155 NATOR 1 HMS /I SW L 1 TMF BATTERY I BLACK +-1-7.-- ¡ 1 1014F 10145 I I YOWME CONTROL 35.000 i^ Ol- OHM$ L to Don ONM5 0411 AST l'IN1 1 DOTT CONNECTIONS IMOCATE C14CUIT ¡- RED 11 I FOR 0S. FARN-LIO4nN6 CURRENT FOR. 32 V. ONLY ,I -A 60R S2v.} 110TOt20V,ACARDC' YILLOW -J r.-CHASSIS I- x----

RADIO -CRAFT for MAY, 1933 671 BROADCAST STATIONS OF THE U. S. A list of all the broadcast stations in the U. S. as prepared by the Bureau of Standards. Abbreviations: T, location of transmitter; C. P., construction permit authorized; LS, power until local sunset. There is no wave -length table; the wave -length, however, may be computed from the frequency in kilocycles (kc.) by dividing 300,000 by the frequency in kilocycles. Thus, station KALE, operating on a frequency of 1,300 kc., has a wavelength of 300,000 divided by 1300, or about 230 meters.

Call Power Freq. Call Power Freq. Call Power Fry. Letters Location (watts) kc. Letters Lamaism (watbi ka Letters Location (watts) ke. KABC San Antonio, Tez 100 1420 KGDE Fergus Fulls, Minn 100 1200 KOIL Council Bluffe, Iowa lkw KALE Portland, 1280 Ore 500 1300 KGDM Stockton, Calif 250 1100 KOIN Portland, Ore lkw KARK 940 Little Rock, Ark 250 890 KGDY Huron, S. D 100 1200 T-Sylvan KASA Elk City, Okla 100 1211) KGEF Los Angeles, Calif 1kw 1300 KOL Seattle, Wash lkw 1270 K BPS Portland, Ore 100 1420 KDEK Yuma, Colo 100 1200 KOMA Oklahoma City, Okla 5kw 1480 KBTM Paragould, Ark 100 121K1 KOER Long Beach, Calif lkw 1360 KOMO Seattle, Wash 920 KCMC Texarkana, Ark 100 1420 KOEW Ft. Morgan, k1 Colo 100 1200 KONO San Antonio, Tex 100 1370 KCRC Enid, Okla- 100 1370 KGEZ Kalispell, Mont 100 1310 KOOS Marshfield, Ore 100 1370 KCRJ Jerome, Aria 100 1310 KOFF Shawnee, Okla 100 1420 KORE Eugene, Ore KOB 100 1420 Smta Barbara, Calif 100 1 501 KOFG Oklahoma City, Okla 100 1370 KOY Phoenix, .'riz 500 1390 K DFN Casper, Wyo I I IO 500 KGFI Corpus Christi, Tex 100 1500 KPCB Seattle, Wash 100 650 K DKA I'itteburgb, Pa 50kw gin KGFJ Lon Angeles, Calif 100 1200 KPJM Prescott, Aria 100 1500 TSaxonburg KGFK Moorhead, Minn 50 1500 KPO San Francisco, Calif 5kw 680 KDLR Devila Lake, N. D 100 1210 KIFL Raton, N. Mex 50 1370 C.P.T-Near San Mateo C.P.50kw (DYL Salt Lake City, Utah 1kw 1200 C. P. Rowell KPOF Denver, Colo 500 880 (ECA Los Angeles, Calif .. dkw 1430 KOFW Kearney, Nebr 100 1310 KPPC Pasadena, Calif 50 1210 (ELW Burbank, Calif 500 780 KGFX Pierre, S. D 200 630 KPQ Wenatchee, Wash 50 1500 (ERN Bakersfield, Calif 100 1210 KGGC San Franciscan, Calif 100 1420 KPRC Houston, Tex lkw 920 (EX Portland, Ore 5kw 1180 KGOF Coffeyville, Kann 500 1010 TSugarland 2!2kw -LS (FAB Lincoln, Nebr 5kw 770 T. South Coffeyville, KQV Pittsburgh, Pa 500 1380 (FAC Lcs Angeles, Calif 1kw 1300 Okla KQW San Jose, (FRB Calif 500 1010 Great Falls, Mont. lkw 1280 KGGM Albuquerque, N AL 250 1230 KRE Berkeley, Calif 100 1370 (FBI Abilene, Kane 5kw 1950 KGHF Pueblo, Colo 2.50 1320 KREG Santa Ana, Calif 100 1500 T- Milford KOHL Little Rock, Ark 100 1200 KRGV Harlingen, Tex 500 1260 (FBK Sacramento, Calif 100 1310 KOHL Billings, Mont 1kw 950 KRKD los Angeles, Calif 500 1120 (FBL Everett, Wash 50 1370 KOIR Butte, Mont 500 1360 KRLD Dallis, Tex 10kw 1040 (FOPS Beaumont, Texas 500 5191 I( 01W Trinidad, Colo 100 1420 KRUD Shreveport, Da 100 1310 (FDY Brookings, 8. D 5511 lkw KOIX Las Vegas, Nev 100 1420 KROW Oakland, Calif 500 930 IFEL Denver, Colo 500 920 KOIZ Grant City, Mo 100 1500 T- Itichmond 1kw-IA T- Edgewater KOKB Tyler, Tex 100 1500 KRSC Seattle, Wash 100 1120 IFEQ St. Joseph, Mo 21 kw 680 KGKL San Angelo, Te 100 1370 KSAC Manhattan, Kane 500 580 Boone, [FOG Iowa 100 1310 KOKO Wichita Falls, Tex 2.M) 570 KSCJ Sioux City, Iowa lkw 1:330 IFH Wichita. Kane 1k 1300 KGKX Sandpoint, Idaho 100 1420 KW St. Louie. Mo 500 MO IF! Los Angeles, Calif 50kw 640 C. P. Lewiston KSEI Pocatello, Idaho 250 890 T -Buena Park KOKY Scottsbluff, Nebr 100 1500 KSL Sit Lake City, Utah FIO Spokane, Wash 50kw 1130 100 1120 KOMB Honolulu, Hawaii 2.50 1320 T-Saltair FIZ Fond du Lae, Wm 100 1420 KOMP Elk City, Okla...... 100 1210 KSO Dee Moines, Iowa 100 1370 FJB Marshalltown, Iowa 100 1200 KONF North Platte. Yeux 500 1430 KSOO Sioux Falls, S. D 2'2kw 1110 FJI Klamath Fall., Ore 100 1210 KONO Dodge City, Kane. 100 1210 KSTP St. Paul, Minn FJM Grand Forks, 10kw 1460 N. D 100 1370 KOO San Francisco, Calif 7.,Akw 790 T-RadioCenter FJR Portland, Ore 500 1300 T- Oakland KTAB San Francisco, Calif FJZ Fort Worth, Tex Ikw 560 100 1370 KORS Amarillo, Te lkw 1410 T- Oakland FKA Greeley, Colo 500 880 KOU Honolulu, Hawaii 2yzkw 750 KTAR Phoenix, Ariz 500 620 FKU Lawrence, Kan 500 1220 KOVO Missoula, Mont 100 1200 KTAT Fort Worth, Tex T- Tongaooxle lkw 1240 KOW Portland, Ore lkw 620 T-Birdville :FK X- (See KYW -KFKX) T-Faloma KTBS Shreveport, La lkw 1450 .YW KGY Olympia, Wash 100 1210 KIFI Twin Falls. Idaho 500 1240 FLY Rockford, Ill 500 1410 KHJ Lae Angeles, Calif lkw 900 KTHS Hot Springs National Park, .FLX Galveston, Tex 100 1370 KHQ Spokane, Wash lkw 591 Ark 10kw 1040 FM Northfield, Minn 1kw 1250 KICA Clovis. N. M 100 1370 KTM Irae Angeles, Calif 51X) 780 .FIN Shenandoah, Iowa 500 890 KICK Red Oak, Iowa 100 1420 TSanta Monica Ikw-LS FOR Lincoln, Nebr 100 1210 KID Idaho Falla, Idaho 250 1320 KTRH Houston, Tex 500 1120 FOX Long Beach, Calif lkw 1250 KIDO Boise, Idaho lkw 1350 KTSA San Antonio, Tex lkw 1200 FPL Dublin, Tex 100 1310 KIOW Lamar, Colo 100 1420 KTSM El Paso, To 100 1310 FPM Greenville, Tex 15 1311) KIEM Eureka, Calif 100 1210 KTW Seattle, W'aah lkw 1220 FPW Ft. Smith, Ark 100 1210 KIEV Glendale, Calif 100 850 KUJ Walla Walla, Wash 100 1370 FPy Spokane, Wash lkw 134(1 KIFH Juneau, Alaska 100 1310 KUMA Yuma, Ariz 100 1420 FQO Anchorage, Alaska...... 250 123(1 KIT Yakima, Wash. 100 1310 KUOA Fayetteville, Ark 1390 FRC San Francisco, Calif k1 lkw 610 KJBS San Francisco, Calif 100 1070 KUSD Vermillion, S. D 500 890 FRU Columbia, Mo 500 630 KJR Seattle, Wash 5kw 970 KVI Tacoma, Wash 500 FSD San Diego, 570 Calif lkw 600 KLCN Blytheville, .Ark. 50 1290 T-les Moines FSO Los .Angeles, Calif 500 11211 KLO Ogden, Utah 500 1400 KVL Seattle, Wash 100 1370 FUL Galveston, Tex .... 500 1290 KLPM Minot, N. D 250 1240 KVOA Tueaon, Aria 500 1260 FUO Clayton, Mo 500 550 KLRA Little Rock, Ark lkw 1390 KV00 Tula, Okla 5kw FVD Lm Angeles, Calif 1140 250 1000 KLS Oakland, Calif 250 1440 KVOR Colorado Springs, Colo FVS k1 1270 Cape Girardeau, Mo 100 1211) KLX Oakland, Calif 500 880 KVOS Bellingham, W'aeh 100 1200 FWB Hollywood, Calf lkw 950 KLZ Denver, Colo lkw 560 KWCR Cedar Rapids, Iowa 100 1420 FWF St. Louis, Mo 100 1200 KMA Shenandoah, Iowa 500 930 KWEA Shreveport, La 100 1210 FWI San Francisco, Calif 500 930 KMAC San Antonio, Texas 100 1370 KWG Stockton, Cal 100 1200 FXD Nampa, Idaho 100 1200 KMBC Kansas City, Mo lkw 950 KWJJ Portland, Ore 500 1060 FXF Denver, Colo 500 920 T- Independence KWK St. Louis, Mo FXJ Grand lkw 1350 Junction, Colo 100 1200 KMED Medford, Ore 100 1310 T- Kirkwood FXM San Bernardino, Calif 100 1210 KMJ Fresno, Calif 100 1210 KWKC Kansas City, Mo 100 1370 UR Okl home City, Okla 100 1310 KWKH Shreveport, La 10kw 850 FYO Lubbock, Tex 100 1310 KMLB Monroe, La 100 1_001200 T- Krnnonwood FYR Bismarck, N. D lkw 550) KMMJ Clay Center, Neb lkw 740 KWLC Decorah, Iowa 100 1270 GA Spokane, Wash- 5kw 1470 KMO Tacoma, Wash 250 1330 KWSC Pullman, Wash lkw 1220 GAR Tucson, Aria 100 1370 KNOX St. Louis, Mo 50kw 1090 KWWG Brownsville, Tex 500 1260 GB San Diego, Calif lkw 1330 KMPC Beverly Hills, Calif 500 710 KXA Seattle, Wash 250 760 GBU Ketchikan, Alaska 500 900 KMTR Irae Angeles, Calif 500 570 KXL Portland, Ore 100 1420 GBX Springfield, Mo 100 1310 KNOW Austin, Tex 100 1500 KXO El Centro, Calif 100 1500 GBZ York, Nebr 500 930 KNX Los Angeles, Calif 25kw 1050 KXRO Aberdeen, Wash 100 1310 OCA Decorah, Iowa 100 1270 KOA Denver, Colo 12(akw 830 KXYZ Hesston, Tex 250 1440 OCR Watertown, S. D 100 1210 KOAC Corvallis, Ore 1kw 550 KYA San Francisco, Calif lkw 1230 GCU Mandan, N. D 250 1240 KOB Albuquerque, N. M 10kw 1180 KYW Chicago, III 10kw Wolf Point, 1020 OCX Mont 100 1310 KOCW ('bickasha, Okla 250 1400 KFKX T- Bloomingdale Townap. GDP) Mitchell, S. D 100 1370 KOH Nev Reno, 500 1380 WAAB Boston, Mass 500 1410 72 RADIO -CRAFT for MAY, 1933 Cali Power Freq. Call Paws, Freq. Cil Power Frog. Leiters Location (watts) kc. Letters Localise (watts) ka Letters Laa1Me (watts) kc.

T- Quincy WDAE Tampa, Fla lkw 1220 WHAT Philadelphia, Pa 100 1310 W AAF Chicago, Ill 500 920 WOAF Kansas City, Mo lkw 610 WHAZ Troy, N. Y 500 1300 WAAM Newark, N. J lkw 1250 WDAG Amarillo, Tex ]kw 1410 WHB Kansas City, Mo 500 860 WAAT Jersey City, N. J 300 940 WDAH El Paso, Tex 100 1310 T-North Kansas City W AA Omaha, Nebr 500 660 WDAB Philadelphia, Pa 100 1370 WHBC Canton, Ohio 10 1200 WABC New York, N. Y 50kw 860 WDAY Fargo, N. D lkw 940 WHBD Mt. Orab, Ohio 100 1370 WBOQ T- Rayne, N. J. T -West Fargo WHBF Rock Inland, III 100 1210 WABI Bangor. Maine 100 1200 WDBJ Roanoke, Va 250 930 WHBL Sheboygan. Wie 500 1410 WABO. (See WHEC -WABO) WDBO Orlando. Fla 250 540 WHBQ Memphis, Tenn 100 1370 WHEC WOEL Wilmington, Del 250 I1», WHBU Anderson, Ind 100 1210 WABZ New Orleans, La 100 1200 WDEV Waterbury, Vt 5001 55,, WHBY GreenBay, W'is 100 1200 WACO Wat°, Tex 1kw 1240 WONT Minneapolis, Minn lkw ID, T -Wet la Pere WA DC Tallmadge, Ohio lkw 1320 WOOD Chattanooga, Tenn lkw 1280 WHDF Calumet, Mich 100 1370 WAGM Presque Isle. Maine 100 1420 T- Brainerd 23kw -LS WHDH Boston, Magie 1kw 830 WAIU Ohio Columbus. 500 640 WDRC llartford, Conn 500 1330 T- Saugus WALR Zanesville. Ohio 100 1210 T- Bloomfield WHDL Tupper Lake, N. Y 100 1420 WAMC Anniston. Ala 100 1420 WOSU New Orleans, La Ikw 1250 WHEB Portsmouth, N. H 250 740 W API Birmingham, Ala 5kw 1140 T- Gretna T- Newington WASH Grand Rapide, Mich 500 1270 WDZ Tuscola, Ill 100 1070 WHEC- Rochtter, N. Y 500 1440 WAWZ Zarephath. N. J 250 1350 WEAF New York, N. Y 50kw 660 WABO WAIL Haaleton, Pa 100 1420 T- Bellmore WHEF Kosciusko, Mire 100 1500 WBAA W. Lafayette, Ind 500 1400 WEAN Providence. R. I 250 780 WHET Troy, Ala 100 1210 WBAK Harrisburg, Pa 500 1430 WEAO Columbus, Ohio 750 570 WHFC Cicero, III 100 1420 WBAL Baltimore. Md 10kw 1060 WEBC Superior, \\-is lkw 1290 WHIS Bluefield, W. Va 250 1410 T- GIenlMnrns WEBQ Harrisburg. ID 100 1210 WHK Cleveland, Ohio lkw 1390 WRAP Fort Worth, Tex 50kw 800 WEBR Buffalo, N. Y 100 1310 T-Seven Hills 23rkw -LS T-Grapevine WEDC Chicago. Ill I(0 1210 WHN New York, N. Y 250 1010 WBAX Wilkes- Barre, Pa 100 1210 WEEI Boston, Maas lkw 590 WHO Dee Moines, Iowa 5kw 1000 T- Plains Twp. T- Weymouth WHOM Jersey City, N. J 250 1450 WBC Brooklyn, N. Y 500 1400 WEEU Reading. Pa lkw 830 WHP Harrisburg, Pa 500 1430 WBBL Richmond. Va 100 1210 WEHC Emory, \'a 500 1350 T- Lemoyne lkw-1,8 WBBM- Chicago, Ill 25kw 770 WENS Cicero. Ill 100 1420 WIAS Ottumwa, Iowa 100 1310 WJBT T- Glenview WELL Battle Creek, Mich 50 1420 WIBA Madison, Rie 500 1280 WBBR Brooklyn. N. Y lkw 1300 .Americus, WENC Ga 100 1420 WIBO Glenside, Pa 25 930 T- R°eeville WENR- Chicago, Ill 50kw 870 T- Elkins Park WBBI l'once City. Okla 100 1200 WBCN T- Downers Grove WINN Jackson, Mich 100 1370 WBCM Bay City, Mich 500 1410 WEPS- (See WORC -WETS) WIBO Chicago, Ill lkw 560 T- llampton Two. WORC T-De Plaines 13 skw -IS WBCN- (See WENR -WBCN) WERE Erie, Pa 100 1420 WISU Poynette, Rie 100 1210 WENR WESG Elmira, N. Y lkw 1040 WIBW Topeka, Kane lkw 580 WBEN Buffalo, N. Y lkw 900 T-Ithaca WISX Utica, N. Y 100 1200 T- Martinsville WEVD New York, N. Y 500 1300 WICC Bridgeport, Conn 250 600 WBEO Marquette, Mich 100 1310 T- Brooklyn T- Easton 500-LS NB HS Huntsville, Ala 100 1200 WEW St. Louis, Mo lkw 760 WIL St. Louis, Mo 100 1200 WBIG Greensboro, N. C 500 1440 WE XL Royal Oak, Mich 50 1310 WILL Urbana, III 250 890 WBIS- (See WNAC -'BIS) WFAA tallas, Tex 50kw 800 WILM Wilmington, Del 100 1420 WNAC T- Grapevine T -Felge Moor WRNS Hackensack, N. J 250 1450 WFAB New York, N. Y lkw 1300 WINS New York, N. Y 500 1180 NBNX New York, N. Y 250 1350 T- Carlstadt, N. J. T- Astoria, L. I. NBOQ- (See WABC -WBOQ) WFAM South Bend, Ind 100 1200 WIOD- Miami, FIa lkw 1300 N ABC WFAN Philadelphia, Pa 500 610 WHBF T-Miami Beach NBOW Terre Haute, Ind 100 1310 WFAS White Plains, N. Y 100 1210 WIP Philadelphia, Pa 500 610 NBRC Birmingham, Ala 500 930 WFBC Greenville, S. C 100 1200 WIS Columbia, S. C 500 1010 NBRE Wilkes- Barre, Pa 100 1310 WFBE Cincinnati, Ohio 100 1200 WISH Milwaukee. \Vis 250 1120 NBSO Needham, Mare 500 920 WFBO Altoona, Pa 100 1310 WJAC Johnstown, Pa 100 1310 NBT Charlotte. N. C 25kw 1080 WFBL Syracuse, N. Y lkw 1360 WJAO Norfolk, Nebr lkw 1060 NBTM Danville, Va 100 I370 T- ('ollamer 24kw -LS WJAR Providence, R I 250 890 NBZ Boston, Magie 25kw 990 WFBM Indianapolis, Ind lkw 1230 WJAS Pittsburgh, Pa lkw 1290 T- Millis Twp. WFBR Baltimore. Md 500 1270 T-North Fayette, Twp. 2' ikw -LS N8ZA Becton, Mn er lkw 090 WFOF Font, Mich 100 1310 WJAX Jacksonville, Fla lkw 900 T -Est Springfield W FDV Home, Ga 100 1500 WJAY Cleveland, Ohio 500 610 NCAC Storrs, Conn 250 600 WFEA Manchester, N. H 500 1430 WJBC La Salle, III 100 1200 NCAD Canton. N. Y 500 1220 WEI Philadelphia, Pa ' 500 560 WJBT Red Bank, N. J 100 1210 NCAE Pittsburgh, Pa lkw 1220 WFIW Hopkinsville, Ky lkw 940 WJBK Detroit, Mich 50 1370 NCAH Columbus. Ohio 510 1430 WFLA. Clearwater, Fla 250 620 T- Highland Park N CAJ Lincoln, Nebr 5011 510 WSUN WJBL Decatur, III 100 1200 NCAL Northfield, Minn lkw 1250 WFOX Brooklyn, N. Y 500 1400 WJBO New Orleans, La 100 1420 NCAM Camden, N. J 500 1 280 WGAL Lancaster, Pa 100 1310 C.P. Baton Rouge NCAO Baltimore. Md 250 600 WGAR Cleveland, Ohio 500 1450 WJBT- (Sec WBBM -WJBT) VCAP Asbury Park, N. J 500 1280 T-Cuyahoga Heights lkw-LS WBBM T- Wlhiteeville WGBB Freeport, N. Y 100 1210 WJBU Lewisburg, Pa 100 1210 VCAT Rapid City, S. D 100 1200 GBC- W (,Ces W-NBR-WGBC) W JB W New Orle na, Lt 100 1200 VCAU Philadelpida, Pa 50kw 1170 WNBR WJBY Gadsden, Ala 100 1210 T- Newton, Square Co. WGBF Evansville, Ind 500 630 WJDX Jackson, Miss lkw 1270 VCAX Burlington, Vt 100 1200 Pa WGBI Scranton, 250 Stn WJEJ Hagerstown, Md 100 1210 VCAZ Carthage, Ill 50 1070 WGCM Mississippi City, Mise 100 12W WJEM Tupelo, Mies 510 990 VCBA Allentown, Pa 250 1440 WGCP Newark, N. J 250 125?, WJEQ Williamsport, Pa 100 1370 VCBD Zion. Ill 5kw IOSO WGES Chicago, Ill 500 1360 WJJO Monecheart, Ill 20kw 1130 VCBM Baltimore, Md 100 1370 Newport WGH News, Va 100 13W WJKS Gary, Ind lkw 1360 CBS Springfield, 100 1210 Il WGL Ft. Rayne, Ind 100 1370 WJMS Ironwood, Mich 100 1420 VCCO Minneapolis, Minn 50kw 810 WGLC Glens Falla, N. Y 50 1370 WJR Detroit, Mich 10kw 750 T -Anoka C.P. Hudson Falls C.P.100 -LS T- Sylvan Lake Village VCDA New York, N. Y 250 1350 WGMS- See WLB -WOMS) WJSV Alexandria, Va 10kw 1460 T -Cliff ide. N. J WLB T -ML Vernon Hills VCFL Chicago, Ill 13A 970 WON- Chicago, Il 25kw 720 C.P. Near Alexandria, Va VCGU Brooklyn, N. Y 1400 500 WLIB T -Elgin WJTL Oglethorpe University, Ga.... 100 1370 T -Long Island City W G NY Chester Township, N. Y 50 1210 T-Atlanta VCKY Covington, Ky 5kw 1490 WGR Buffalo, N. Y lkw 550 WJW Akron, Ohio 100 1210 T- Creseent Springs T- Amherst WJZ New York, N. Y 30kw 760 VCLO .Zanesville, Rte 100 1200 WGST Atlanta, Ga 250 890 T -Bound Brook, N. J. VCLS Joliet, III 100 1310 WGY Schenectady, N. Y 50kw 790 WKAQ San Juan, P. R lkw 1240 VCDA Pensacola, Fla 500 1340 TSouth Schenectady WKAR E. Lansing, Mich lkw 1040 VCOC Meridian, Miss 500 880 WHA Madison, Wm 750 940 WKAV Laconia, N. H 100 1310 VCOD Iarrisburg, Pa 100 1200 WHAO Milwaukee, Witt 250 1120 WKSB Joliet, III 100 1310 /CRW Chimp, Ill 100 1210 WHAM Rochester, N. Y 5kw 1150 C.P. E. Dubuque C.P. 1500 V CSC Charleston, S. C 500 1360 T- Victor Twp. C.P. 25kw WKBC Birmingham, Ala 100 VCSH Portland, 1310 Me lkw 940 WHAS Louisville, Ky 25kw 820 WKBF Indianapolis, Ind TSearboro 500 1400 23 ¡kw -LS TJeffereontown T-Clermont RADIO -CRAFT for MAY, 1933 673 Call Perm Freq. Call Fewer Frq. CaN Power Free. Latter Location (watts) ke. Letters Location (watt$ ) ke. Latin Location (watts) ka

C.P. T-.Nr. Indianapolis WNBH New Bedford, Magie 100 1310 WRDW Augusta, G 100 15011 WKBH Ls Crease, Wis 1kw 1380 T- Fairhaven 250-LS WREC- Memphis. Tenn 500 600 WKBI Cicero, III 100 1420 WNBO Silverhaven, Pa 100 1200 WOAN T- SVhitehaven Ikw -IS WKBN Youngstown, Ohio 500 570 WNBR- Memphis, Tenn 500 1430 WREN Lawrence, Kane 1kw 1220 WKBS Galesburg. Ill 100 1310 WGBC T- Tonganoxie WKBV Connersville, Ind 100 1500 WNB Carbondale. Pa 10 1200 WRHM Minneapolis, Mim 1kw 1250 WKBW Buffalo. N. Y 5kw 1480 WNBX Springfield. Vt 250 1260 T- Fridley T- Amherst WNBZ Saranac Lake, N. Y 50 1290 WRJN Racine, Wis 100 1370 WKBZ Ludington, Mich 100 1500 WNJ Newark, N. J 250 1450 WRNY New York, N. Y 250 1010 WKFI Greenville, Mise 100 1210 WNOX Knoxville. Tenn 1kw 560 T- Coytesvilie, N. J. WKJC Lancaster, Pa 100 1200 WNYC New York, N. Y 500 570 WROL Knoxville, Tenn 100 1310 WKRC Cincinnati, Ohio 500 550 WOAI San Antonio, Tex 50kw 1190 WRR Dallas. Tex 500 1280 WKY Oklahoma City, Okla 1kw 900 T-Selma WRUF Gainesville, Fla 5kw 830 WKZO Kalamazoo, Mich 1kw 590 WOAN- (See WREC -WOAN) WRVA Richmond, Va 5kw 1110 WLAC Nashville, Tenn 5kw 1470 WREC T- Meehaniesxille WLAP Louisville, Ky 100 1200 WOAX Trenton, N. J 500 1280 WSAI Cincinnati, Ohio 500 1330 WLB- Minneapolis, Minn Ikw 1250 WOBU Charleston, W. Va 250 580 T-Mason Ikw -LS WGMS TSt. Paul WOC Davenport, Iowa 5kw 1000 WSAJ Grove City, Pa 100 1310 WLBC Muncie. Ind 50 1310 WOCL Jamestown, N. Y 50 1210 WSAN Allentown, Pa 250 1440 WLBF Kansas City, Kans 100 1420 WO OA Paterson, N. J Ikw 12.50 WSAR Fall River, Mass 250 1450 WLBL Stevens Point, Wis 2kw 900 WOD% Mobile, Ala 500 1410 WSAZ Huntington, W. Va 250 580 TNr. Ellis TSpringhill WSB Atlanta, Ga 5kw 740 WLBW Erie, Pa 500 1260 WOI Ames, Iowa 5kw 640 WSBC Chiu-ago, Ill 100 1210 T-Summit Township Ikw -LS WOKO Albany, N. Y 500 1441) WSBT South Bend, Ind 500 1230 W LBZ Bangor. Me 500 620 WOL Washington. D. C IW 1310 WSEN Columbus, Ohio 100 1210 WLCI Ithaca, N. Y 50 1210 WOMT Manitowoc, )Vis. 100 1210 WSFA Montgomery, Ala 500 1410 WLEY Lexington, Mass 100 1370 WOOD Grand Rapids, Mieh 500 12711 WSIX Springfield, Tenn 100 1210 WLIB (See VGN -WLIB) WOPI Bristol, Tenn 100 1510 WSJS Winston-Salem, N. C 100 1310 WGN WOQ Kansas City. Mo. 1kw 1310 WSM Nashville, Tenn 50kw 650 WLIT Philadelphia, Pa 500 560 WOR Newark, N. J 5kw 710 T- Franklin WLOE Boston, Mass 100 1500 T -Kenny C.P. 50kw WSMB New Orleans, La 500 1320 T- Chelsea 250-LS WO RC- Worcester, :Hass 100 1210 WSMK Dayton, Ohio 200 1380 WLS Chicago, Ill 50kw 870 WEPS T- Auhurn WSOC Gastonia, N. C 100 1210 T- Downers Grove WORK York. Pr Ikw 1000 WSPA Spartanburg, S. C 100 1420 WITH Brooklyn. N. Y 500 1400 T -W. Manchester WSPO Toledo, Ohio ikw 1340 WLVA Lynchburg. Va 100 1370 WOS Jefferson City. Mo 500 630 WSUI Iowa City, Iowa 500 880 WLW Cincinnati, Ohio 50kw 700 WOV New York, N. Y Ikw 1130 WSUN- (See WFLA -WSUN) T -Mason TSecaucus, N. J. WFLA WLWL New York, N. Y 5kw 1100 WOW Omaha, Nehr Ikw 590 WSVS Buffalo, N. Y 50 1370 T- Kearny, N. J WO WO Ft. Wayne, Ind 10kw 1110 WSYB Rutland, Vt 100 1500 570 WMAC- . (See WSYR -WMAC) WPAD Paducah. Ky 100 1420 WSYR- Syracuse, N. Y 250 WSYR WPAP- (See WQAO -WPAP) WMAC W MAL Washington, D. C 250 630 W QAC WTAD Quincy, Ill 500 1440 WMAQ Chicago, III 5kw 670 WPAW. (See WPRO -WPAW) WTAD Worcester, Mn es 250 580 T- Addison WPRO WTAM Cleveland, Ohio 50kw 1070 WMAS Springfield, Mass 100 1420 WPCC Chicago, Ill 500 510 T-Brecksville Village WMAZ Macon, Ga 500 1180 WPCH New York, N. Y 500 810 WTAQ Eau Claire, Wig 1kw 1330 WMBC Detroit, Mich 100 1420 T- Flushing T-Twp. of Washington WM80 Peoria, Ill 500 1440 WPEN Philadelphia, Pa 100 1500 WTAR- Norfolk. Va 500 780 T- Peoria Heights Ikw -LS WPFB Hattiesburg, Mise 100 1370 WPOR WMBF- (See WIOD-WMBF) WPG Atlantic City, N J 5kw 1100 WTAW College Station, Tex 500 1120 WIOD WPHR Petersburg, Va IW 1200 WTAX Springfield, Ill 100 1210 WM80 Richmond, Va 100 121u T- Ettrick WTBO Cumberland, Md 100 1420 WMSH Joplin. Mo 100 1120 WPOR- (See WTAR -WPOR) WTEL Philadelphia, Pa 100 1310 WM81 Chicago, Ill 5kw 1080 WTAR WTFI Athens, Ga 500 1450 T- Addison WPRO- Providence, R. I 100 1210 WTIC Hartford, Conn 50kw I060 WM80 Auburn, N. Y 100 1310 WPAW T-Cranston T-Avon W MBQ Brooklyn, N. Y 100 1500 WPTF Raleigh, N. C 1kw 680 WTJS Jackson. Tenn 100 1310 WMBR Tampa, Fla 100 1370 WQAM Miami, Fla Ikw 5110 WTMJ Milwaukee. Wis Ikw 620 'NMC Memphis, Teon 500 780 W QAN Scranton, Pa 250 880 T- Brookfield 2SSkw -IS T- Bartlett Ikw-L.8 W QAO New York, N. Y 250 1010 WTOC Savannah, Ga 500 1260 w MCA New York, N. Y 500 570 WPAP T-Ciiffside, N. J WTRC Elkhart, Ind 50 1310 T- Flushing W QBC Vicksburg, Miss 500 1300 WTSL Laurel, Mim 100 1310 W MIL Brooklyn, N. Y 100 1500 WQOM St. Aflame, Vt 100 1370 WWAE Hammond, Ind 100 1200 WMMN Fairmont, W. Va 250 890 WOO X Thomasville. Ga 100 1210 W W J Detroit, Mich Ikw 920 WMPC Lapeer, Mich 100 1500 WRAK Williamsport,ort, Pa 100 1370 W W L New Orleans, La 10kw 850 WMSO New York, N. Y 250 1350 WRAM Wilmington, N. C 101 1370 T- Kenner e. WMT Waterloo. Iowa 500 600 WRAW Reading. Pa 100 1310 WW NC Asheville, N. C 1kw 570 WNAC- Boston, Mass Ikw 1230 WRAX Philadelphia, Pa 250 1020 WWRL Woodside, N. Y 100 1500 WBIS T-Quiney WRBL Columbus. Ga 100 1200 WWSW Pittsburgh, Pa 100 1500

WNAD Norman, Okla 500 1010 WRBX Rnmrke, Va . .. . 250 1410 T- Wilkinshurg 250-LS WNAX Yankton, S. D. Ikw 570 WRC R';,,hliien.,,. It r' 500 950 WWVA Wbeelhig. W. Va 5kw II60

WN F Binghamton, N. V 110 1500 WRDO .. 100 1370 WXYZ Der ri \lieh. . 1kw 1240 POLICE STATIONS ALPHABETICALLY BY CALL LETTERS

Call Freq . Call Freq. Call Freq. Call Frei Letters Location ka Latin Location ke. Letters Location ka Letters Location ke. KGHO Des Moines, Iowa 1534 KGPX Denver, Colo 2442 WPDH Richmond, Ind...... 2442 WK DU Cincinnati, Ohio -- 1712 KGJX Pasadena, Calif 1712 KOPY Shreveport, La 1574 WPDI Columbus, Ohio 2430 WM DZ Indianapolis, Ind 2442 KGOZ Cedar Rapids, Iowa 2470 KOPZ Wichita, Kane 2450 WPDS St. Paul, Minn 2416 WMJ Buffalo, N. Y 2422 KGPA Seattle, Wash 2414 KOZG Houston, Tex 1712 WPDW Washington. D. C 2422 WMO Highland Park, Mich 2414 KGPS Minneapolis, Minn 2416 KOZO Sen Diego, Calif 2430 WPDX Detroit, Mich 2414 WMP Framingham, Maas 1574 KGPC St. Louis, Mo 1712 KOZE San Antonio, Tex 2506 WPDY Atlanta, Ga 2414 WPDK Milwaukee. Wis 2450 KGPD Sen Francisco, Calif 2470 KOZF Chanute, Kama 2450 WPEA Syracuse, N. Y 2458 WPDL Lansing, Mich 2442 KGPE Kansas City, Mo 2422 KGZH Klamath Falls, Ore 2442 WPEV Grand Rapids, Mich 2442 WPDM Dayton, Ohio 2430 KGPO Vallejo, Calif 2422 KGZI Wichita Falls, Tex 1712 WPEC Memphis, Tenn 247 WPDN Auburn, N. Y 2458 KGPH Oklahoma City, Okla 2450 KGZM El Paso, Tex 2414 WPEE New York. N. Y 24: WPOO Akron, Ohlo 2458 KGPI Omaha. Neb 2470 KVP Dallas, Tex 1712 WPEF New York, N. Y 24.50 WPDP Philadelphia, Pa 2470 KGPJ Beaumont, Tex 1712 KSW Berkeley, Calif 2422 WPEG New York, N. Y 2450 WPDR Rochester, N. Y 2458 KGPL Los Angeles, Calif 1712 WCK Belle Island, Mich 2414 WPEH Somerville, Maas 171? WPOT Kokomo, Ind 2470 KGPM Son Jaee, Calif 2470 WPDA Tulare, Calif 2414 WPEK New Orleans, La 2422 WPDU Pittsburgh, Pa 1712 KGPN Davenport. Iowa 2470 WPDB Chicago, Ill 171^ WPEP Arlington, Mass 1712 WPDV Charlotte, N. C 24.58 KGPO Tulsa, Okla 2450 WPDC Chicago, Ill 171.' WPFC Muskegon, Mich 2442 WPDZ Fort Wayne, Ind 2470 KGPP Portland, Ore 2442 WPDD Chicago, Ill I7t WPFD Highland Park. Ill 243 WRDH Cleveland, Ohio 2458 KGPS Bakersfield. Calif 2414 WPDE Louisville, Ky -211' WPFF Toms River, N. J 243 WROR Gram Point Village, Mich. 2414 KGPW Salt Lake City, Utah '470 WPDF Flint, Mich "11 WPFH Baltimore, Md 2414 WRDQ Toledo, Ohio 2470

674 RADIO -CRAFT for MAY, 1933 THE DX LISTENER'S FORUM

This department is devoted exclusively to the DX radio listener on the broadcast band. In this department are letters from those listeners who achieve unusual results in long- distant reception. We invite all readers of this magazine to forward their list to us for publication. Only the best lists will be published.

OH BOY! WHAT RECEPTION! WOC, Davenport, Iowa ; WORK. York, Pa.; WMBD, Peoria Heights, Ill.; WOKO, Albany, WHN, New York, N. Y.; WRNY, New York, N. Y.; WSAN, Allentown, Pa.; Editor, RADto- CRAFT: KTBS, Shreve- N. Y.; KYW, Chicago, Ill.; WRAX, Philadelphia, port, La.; WGAR, Cleveland, Ohio; WHOM, I would like to take the opportunity to com- Pa.; CFCF, Montreal, Que.; KRLD, Dallas, Jersey City, N. J. ; KSTP, pare my DX record with St. Paul. Minn.; others you publish. Texas; KTHS, Hot Springs, Ark.; KFBI, Mil- WJSV, Alexandria, Va.; WLAC, This record is honest and on word Nashville, my of honor ford, Kans. ; KNX, Hollywood, Calif. ; WBAL, Tenn.; KFJF, Oklahoma City, I have heard every station on this list which Okla.; WKBW, I Baltimore, Md.; WJAG, Norfolk, Neb. Buffalo, N. Y.; WCKY, Covington, Ky. am enclosing. These stations were heard in the WTIC, Hartford, Conn.; WTAM, Cleveland. WPEN, Philadelphia. space of one year Pa.; WWRL, Woodside, and I know of some people Ohio; WBT, Charlotte, N. C.; KMOX, St. Louis, N. Y.; WWSW, Pittsburgh, Pa.; who never get some of these stations W2XR, Long in five Mo.; WLWL, New York. N. Y.; WPG, Atlantic Island City, N. Y.; W3XK, Wheaton, years. My best pickup in daylight was Md.: KFBI, City, N. J.; WRVA, Richmond, Va.; CFCA, WEY, Boston, Mass.; WRDS, Ingham, Milford, Kansas, at seven o'clock in the morn- Toronto, WDBO, Mich.; Ont.; Orlando, Fla.; WDEL, WTOC, Savannah, Ga.; KFBB, Great Falls, ing, and WKBC a 100 watter at Birmingham, Wilmington, Del.; WISN, Milwaukee, Wis.; Mont. Ala., at about 6:30 A. M. KSL, Salt Lake City, WJJD, Utah; Mooseheart, All these stations were received with a If you will notice there are quite a few 100 - Ill.; KVOO, Tulsa, Okla.; WAPI. Birmingham, "Zenette" seven tube super with band pass and 250 -watt stations in this list and a few of Ala.; WHAM, Rochester, N. Y.; WOWO, Ft. filter and four gang condenser ; table them are out of this country. The idea must not Wayne, Ind.; model. WWVA, Wheeling, W. Va.; W. M. EASrw000. be assumed that these stations can be pulled in WCAU, Philadelphia, Pa.; KOB, State College, Baltimore, Md. at any old time because I have lost many hours N. Mex.; WINS, New York, N. Y.; WOAI, San of good sleep staying up to three o'clock in the Antonio, Texas; WCOD, Harrisburg, Pa.; morning. I find the best time to listen for DX WFAM, La Porte, Ind.; WLAP, Louisville, Ky.; "THE FOOL OF LONG programs is on Saturday night and ISLAND" Editor. RADIO -CRAFT: Sunday morning. Early west -coast In our issue of November, 1932, we asked Breathes there a man stations come in very good at that our readers fo contribute letters With soul so dead time. KFI comes in regularly every giving the results of their DX experiments. Who never to his night providing the weather is good. This new department is to further efforts in this direction. radio bath said "Step out, baby, As this set is only a seven tuber, I There has been an increasing interest of late in long dis- and pull 'em in." am very proud of this record. tance reception, What particularly in the broadcast field, and there With apologies do you think of it? to Robert Burns seems to be a race at the present time between owners of (Great Scott Ed.) broadcast l!- -I must con- sets and short wave sets to outdo each other in fess I'm not that soul -less individual List of Stations DX performance. for I am a firm believer that distance Many people probably do not realize that thousands of lends enchantment. And believe you CKOK, Windsor, Ont.; WGR, Buf- broadcast listeners are making records almost daily, and even me, I've been puh -lenty enchanted falo, N. Y.; WKBC, Cincinnati, Ohio; twisting the broadcast reception from Australian stations received in the dials of my "magic car- WFI, Philadelphia, Pa.; WLIT, Phil- pet" and soaring over United States is not impossible today. the hertzian adelphia, Pa.; WQAM, Miami, Fla.; waves to here, there and mostly WEAO, In this department, we will publish ev- Columbus, Ohio; WMCA, monthly letters from erywhere. I say mostly everywhere New York, N. Y.; WIBW, Topeka, DX listeners relating to their experiences and all letters for because my DXing activities are Kans.; WOBU. con- Charleston, W. Va.; publication must be sworn to by a Notary Public to make fined solely to the broadcast bands WSAZ, Huntington, W. WTAG, Va.; sure that our readers get only such data as are authentic, so between 1,500 and 540 kilocycles; Worcester. Mass.; WEEI, Boston. far as this can be done. since I frown on short-wave DXing as Mass.; WOW, Omaha, Neb.; WCAO, being too easy. I employ an 8 tube Baltimore. Md.; WMT, Waterloo, We shall try to publish as many of the letters as we can; but it may be impossible -creen-grid super (G. E.) with which Iowa; WDAF, Kansas City, Mo.; to publish all of them. in my would air travels I have visited the WIP, Philadelphia. Pa. ; WFLA, Clear- We be glad to have your comment on this new de- forty -eight states (many water, Fla.; partment. times) : all WTMJ, Milwaukee, Wis.; the Canadian provinces; several Mex- CKOC, CMCJ. Hamilton, Ont.; Ha- ican states; Bermuda, Cuba, the Ba- vana. Cuba; WGBF, Evansville, Ind.; WMAL, WNBO, Silver Haven, Pa.: WORC, Worcester, hama Islands. the Land of the Rising Washington, Sun, D. C.; KFI, Los Angeles, Calif.; Mass.; CFCO, Chatham. Ont.; KFVS, Cape Australia, Alaska, Central and South America. WAIU, Columbus, Ohio; WSM, Nashville, Tenn.; Gerardeau, Mo.; WHBU, Anderson, Ind.; Appearing in my log are these varied WEAF, calls from New York, N. Y.; WMAQ, Chicago, WOMT, Manitowoc, Wis.; WPRO, Providence, many widely separated locales: JOCK, 2VA, Ill.; KPO, San Francisco, Calif.; WPTF, Raleigh, R. I.; WSBC, Chicago, Ill.; WSEN, Columbus, LR4, LR3, YV1BC, KGU, RCS, XEFC, HIX, C. ; Toronto, ; N. CFRB, Ont. HIX, San Dom- Ohio; WCAD, Canton. N. Y.: WCAE, Pitts- WKAQ, CMCY, CKMO, CJOR, CKWX, KGBU, ingo, WLW, WOR, Haiti; Cincinnati, Ohio; burgh, Pa.; WDAE, Tampa, Fla.; WFBM, In- V PU and HHK. Quite a galaxy you will admit. Newark, N. XEN, Mexico J.; City, Mexico; dianapolis, Ind.; WNAC, Boston, Maas.; WXYZ, My log totals 720 stations with 659 verified re- WGN, Chicago, Ill. ; CHYC, Montreal, Que.; Detroit, Mich.; WAAM, Newark, N. J.; WDSU, ceptions and more trickling in weekly. And I CKAC. Montreal. Que.; CMK, Havana, Cuba; New Orleans, La. ; WODA, Patterson, N. J.; shall have been DXing only 2 years this coming XER, Villa Acuna, Mexico; WSB, Atlanta, Ga.; WLBW, Oil City, Pa.; KVOR, Colorado Springs, December. But with all my success there's WJR, Detroit, Mich.; WJZ, one New York, N. Y.; Cob.; WF'BR, Baltimore, Md.; WCAM, Camden, thing I can't fathom and that is: Why no Euro- WBBM, Chicago, IIL ; WMC, Memphis, Tenn.; N. J.; WIBA, Madison, Wis.; WJAS, Pittsburgh, peens ? (Perhaps some Radio-Craft DXer may WTAR, Norfolk, Va.; WGY, Schenectady, N. Y.; Pa.; WBBR, Brooklyn, N. Y.; WIOD, Miami. be able to enlighten me.) WBAP, Fort Worth, Texas; WFAA, Dallas, Fla. The DXing Fool of Long la., Texas; WCCO, Minneapolis, Minn. WGH, Newport News, Va.; WKBC, Birming- CHARLES WHAS, Louisville, KOA, MARTIN, JR., Ky.: Denver, Colo.; ham, Ala.; WOL, Washington, D. C.; WADC, ff7 -11 Burgoyne Ave., WEEU, Reading, Pa.; WHDH, Boston. Mass.; Akron, Ohio; WSMB, New Orlean, La.; WDRC, Springfield, L. l., WRUF, Gainesville, Fla.; CKGW, Toronto. Ont.; Hartford, Conn.; WSAI, Cincinnati, Ohio; KWKH, Shreveport, La.; WWL, New York. New Orleans, WSPD, Toledo, Ohio; KWK, St. Louis, Mo.; (Well, men, how about telling this "fool" how La.; WABC, New York, N. Y.; WENR, Chi- WAWZ, Zarephath, N. J.; WCDA, New York. to bring in the stations from across the pond: cago, Ill.; WLS, Chicago, DL; WCOC, Meridian, N. Y.; WEHC, Emory, Va.; WFBL, Syracuse. Editor.) Miss.; WGBI, Scranton, Pa.; WSUI, Iowa City, N. Y.; WGES, Chicago, Ill.; WJKS, Gary, Ind.; Iowa; CMX, Havana. Cuba; KFNF, Shenandoah, WCBM, Baltimore, Md.; WDAS, Philadelphia, Iowa; WGST, Atlanta, Ga.: WJAR, Providence, Pa.; WRJN, Racine, Wis.; KQV, Pittsburgh, BUT. FOR A CRYSTAL- R. I.; WBEN, Buffalo. N. Y.; WJAX, Jackson- Pa.; WSMK, Dayton, Ohio; KLRA, Little Rock, Editor, RADIO- CRAFT: ville, Fla.; WKY, Oklahoma City, Okla.; XEW, Ark.; WHK, Cleveland, Ohio; WBBC, Brooklyn, I built a crystal set using J. H. Nighswander's Mexico City, Mexico; HHK, Port Au Prince, N. Y.; WCGU, Brooklyn, N. Y.; WFOX, New circuit in the December issue of RADIO CRAFT, Haiti; KPRC, Houston, Texas; WWJ, Detroit, York. N. Y.; WKBF, Indianapolis, Ind.; WLTH, and it does all he claimed for it, and much more. Mich.; CMCD, Havana, Cuba; WBRC, Birming- Brooklyn, N. Y.; WAAB, Boston, Mass.; I added audio amplification and get full loud- ham, Ala; WDBJ, Roanoke, Va.; WCSH, Port- WBCM, Bay City, Mich.; WHIS, Bluefield, W. speaker volume on many stations. land, I pick up Me.; WFIW, Hopkinsville, Ky.; WRC, Va.; WRBX, Roanoke, Va.; KICK, Red Oak, many distant stations. Here are Washington, a few: KGO, D. C.; KMBC, Kansas City, Mo.; Iowa; WHFC, Cicero, Ill.; WILM, Wilmington, 750 miles; KSL, 630; KOA, 380; WOW, CKNC, Reynosa, 1.130; Toronto, Ont.; RED, Mexico; DeL; WTBO, Cumberland, Md.; WCAH, Colum- XER, 1,660; WLW, 1,780; WLS, 1,580; WCFL, Chicago, KDKA, KNX I4; Pittsburgh, Pa.; bus, Ohio; WHP, Harrisburg, Pa.; WNBR, and KFI, 930 miles; police stations KGPP, Port - WBZ, Boston, Mass.; WHO, Des Moines. Iowa; Memphis, Tenn.; WCBA, Allentown. Pa.; (Continued on page 693)

RADIO -CRAFT for MAY, 1933 675

-- A RADIO -CRAFT'S INFORMATION BUREAU

SPECIAL NOTICE TO CORRESPONDENTS: Ask as many questions as you like, but please observe those rules:

Furnish sufficient information, and draw a careful diagram when and the appearance of its answer here. needed, to explain your meaning; use only one side of the paper. Replies, magazines, etc., cannot be sent C. O. D. List each question. Inquiries can be answered by mail only when accompanied by Those questions which are found to represent the greatest general 25 cents (stamps) for each separate question. interest will be published here, to the extent that space permits. Other inquiries should be marked "For Publication," to avoid At least five weeks must elapse between the receipt of a question misunderstanding.

CRAFT Set assembled. In connection with scales of the PHILCO B-86 "B" UNIT Analyzer and have it all the A.C. Everything is O.K. but the A.C. scale. I type used in the set analyzer, it must be re- (191) Mr. Alfred Peters, Ione, Wash. have checked the readings with a Jewell Pat- membered that the resistance of the recti- (Q.) I would like to know the wiring cir- tern 74 -A A.C. voltmeter, scale 0- 3/15/150 V. fier varies considerably from unit to unit, cuit of the Philco Socket Power "B" Elimi- The 0 -5 V. reading is 1% V. less; the 0 -10 and that it is very difficult to get two recti- nator, A.C. type B -86. What is the electrolyte V., 4 V.; the 0 -60 V., 241 V., etc. The fier units that will act exactly the same. used in this instrument? On the voltage taps, 88,000 ohm series resistor for the 0 -50 V. If you refer to the accuracies specified by what is the K tap for? Where can the alu- scale is off. Please let me have the correct the leading analyzer manufacturers, you will minum electrodes be obtained? value of resistors for the A.C. scale. find that the A.C. scale is always less accu- (A.) The schematic circuit of the Philco Incidentally, are not the S. -G. and Sup. rate than the D.C. scale for the reasons stated types B -86 and B -82 Socket power "B" Elim- -G. leads reversed on the schematic circuit? above. inators is shown in Fig. Q. 191. The electro- (A.1) The diagram as published in the (Q.2) 011ie E. Winfrey, Denver, Colo. lytic solution is a trade secret which the September, 1932, issue of RADIO -CRAFT is cor- Will you please advise me the method used Philco Company has not as yet divulged. The rect; there are no errors, to our knowledge. in computing the value of the A.C. multi- components of the "B" unit may be obtained We cannot understand the discrepancy of plier resistors used in building the RADIO - from the manufacturers. The following ad- the 0 -5 V. scale. The error in this case is CRAFT Set Analyzer, described in the Septem- ditional data concerning this device is avail- 30 %. and we suggest that you check over ber, 1932, issue? able: the calibration of your test meter in order Assuming that at the 600 V. and 1,000 V. Prepare for use by pushing ranges the resistance of the rec- corks down into Philcotron cells. tifier is disregarded, the re- If using the Socket Power "B" sistance required is 900 ohms alone. snap switch on or off each per volt. At the 5 V. range this time radio set is turned on or would require a total resistance off. If using Socket Power "B" of 4.500 ohms in the circuit. with Philco Socket Power "A" or As a multiplier of 8,900 ohms Phlleo Trickle Charger leave is used, I subtract this from

switch of "B" turned on; the VOICE 4,500 and get 600 ohms as the switch on Socket Power "A," or COO resistance of the rectifier (disre- Trickle charger, controls the garding the 50 -ohm internal re- "A." the "B." and the radio set. sistance of the voltmeter which Ea The variable resistor should C,aLe PO. must be considered with the never be changed, when once rectifier anyway). Now, on the set. as directed in the "complete Er4114 4RE. 10 V. range the total resistance w instructions." Never add water VOICE should be 9,000 ohms and sub- á a ,E l I ""'--1-14., to "B" Philcotron cells, nor put ciao -rRuErI tracting 600 ohms leaves 8.400 into operation before opening Caa pan Y x -A - ohms as the correct resistance the vent hole in each cell. value -yet, the parts list calla PT. vuaaTo-aa Mr °- M The type B-86 unit is de- I Cp1T,A Pw. for 8,100 ohms, The 60 V. mul- signed only for 60 to 60 cycles, tiplier should be 44,000 ohms 106 to 125 V., A. C. The type instead of 88,000; but, assuming

B -82 eliminator may be used on E this to be in reality a 100 V. a 25 60 COMMECnM supply of to cycles, 105 FIELD COIL' VOL CaMTIIOL range, the resistor should be 2 a p,rE aixMaseeorcEmrTi to 126 V., A. C. ú,óú9ri. 89,400 ohms instead of 88,000 Complete instructions: With ohms. On the 250 V. range the Q. 196 the apparatus completely set up, Fig. resistor used is 220,000 ohms turn on the set filaments, adjust Schematic of the Bulova model 751 clock radio requested by Mr. Fairing. while to me it seems that it the volume control to maximum should be 249,000 ohms. and tune in a distant station; then, adjust the to see whether it is indicating correctly; if If the values used in the article are cor- variable resistor of the "B" unit to secure it is not, then re -check the value of the mul- rect please advise me the method used to best results. tiplier resistors which are used to obtain the compute them as I intend building this an- If a strong hum is heard, try reversing the various rangea. nine ranges of 1,000, 500, 250, alyzer with line plug, change the position of the "B" The 10 and 60 V. scales only read, accord- 100, 50, 25, 10. 6 and 1 in A.C. V., D.C. V.. unit, or use the "anti -hum" terminal K-con- ing to your statement, %. and 214-V. off, and D.C. ma., using a 8 -pole, 9 -point switch. neet it to the negative "B" terminal of the respectively. This represents an accuracy of I think this is simpler than the combination eliminator. Use only a high -resistance meter 5%. which is probably within the accuracy, used in the article. when taking voltage readings. Once the Phil - or tolerance, of the multipliers used, and this (Incidentally, this is the beet set tester cotrons cease to function they must be re- should not cause too much worry; more ac- that I have seen and I have been building M placed in their entirety. curate calibration would require the use of them for a good many years.) resistors having closer tolerances. (A.2) The values of the resistors used as The published values of resistors is cor- multipliers in this analyzer are correct. The RADIO -CRAFT SET ANALYZER rect, and our only suggestion is that you re- reason for the apparent discrepancies lies in (192) Mr. P. O. White, N. Jackson, Ohio check them to be sure that they are within the fact that the impedance of the rectifier (Q.1) I have sent for parts for the RADIO the accuracy specified. unit varies considerably. This variation in

FACET Po. Cop .IMnMP)

r aaVeEJ M

w áaunt Tap .! M

ÿ!0 Mll - Tap LNay Cr. p.TO Fig. Q. 19 OSCaLATOI FIL Schematic circuit of the Bur:less Micro -Relay requested by Mr. Lintatt. This c rcuit, with the relay, Fig. Q. 195 Fig. Q. 191 is designed to close a circuit -or open one- carry- Circuit of the Amrad "S" tube. Incidentally, Schematic of Philco types 11-86, 8.82 eliminators. ing 6 amperes at 220 volts. Input, I microamp. this tube is the first commercial filamentless tube.

676 RADIO -CRAFT for MAY, 1933 the resistor must be compensated for by hazard of variation or uncertainty of contact 1932, issue of RADIO- CRAFT. The transmitter changes in the value of the multiplier. There due to sparking, arcing, or oxiddation is no rigid mathematical method of con- works fine and also the receiver; but, when of comput- tacts in the operation of meters, industrial same is passed ing the amount of variation; that must be de. over metal, there is no effect. equipment, etc. The contact elements con- The adjustment was made according termined by trial. (We are glad you like stitute the Burgess Vacuum to in- the design.) Contact unit structions; that is, the receiver was tuned to which therefore may be operated in places a transmitter. then the transmitter where explosive gases was set at exist, etc. A time an angle where no signal was heard, but, when lag of 0.5 -sec. eliminates chattering of the passing the transmitter over POWER TRANSFORMERS-BUR- device; it may be operated a metal object, on 110 V., A.C. the signal was not brought back in. We GESS MICRO - even went so far as to RELAY walk up to an automobile without any 1193) Mr. R. effect being obtained Lintatt, Vancouver, until B. within only a C. few inches from the (Q.1) Could you car. The only change give me coil data for made in the equip- a power transformer ment from that out- to be made from an lined was that we old Philco "B" elim- used large -size 350 inator transformer? mmf. tuning con- Also, coil data for a densers instead of 10 V. bell -ringing the midget. 250 transformer u s i n g mmf. units specified. wire and laminations This should not af- from A.F. transform- fect the results, as ers. far as I can see, ao (A.1) Complete long as the trans- information on the mitter is working construction of pow- and the receiver will er transformers has pick up the radia- been covered in an tions. article on the sub- Will you kindly ject, which appeared offer suggestions and in the September. advise what is the 1931, issue of RADIO- smallest amount of CRAFT. Back issues metal that should may be obtained affect t h e instru- from the Circulation ment? Do you think Department. a quart fruit jar filled (Q.2) What is filled with coinss the schematic cir- L. would distort the cuit of the Burgess electromagnetic field Fig. Q. Micro -Relay? I un- 197A of t h e transmitter derstand that this Photograph of the RCA Victor A.F. modulated R.F. oscillator. enough to register a device is capable of signal in the receiv- closing a 1% "electrical horse -power" circuit er ? or D.C. The unmarked resistor has a value (A.1) Perhaps the trouble which is being with an input power of only 1 "fly- power." of 100 ohms. experienced in connection (A.2) The circuit of this device is with the RADIO- shown CRAFT "Treasure" Finder, in Fig. Q. 198. The relay is designed to open which aroused such tremendous interest, is in or close a circuit carrying 6 A. at 220 V. with THE RADIO "TREASURE" FINDER due, part, to a slight fault which occurred in the circuit a control- circuit current of only 1 micro- (194) Mr. W. L. Patrick, Laurel, Miss. diagram of the type 33 pentode, V8; the cor- ampere (through as much as 20 mega.). This (Q.1) I have built the minimum current requirement Radio "Treasure" rected circuit, and a lengthy description of eliminates the Finder as described on pg. 716 of the June, (Continued on page 687)

12A 30

EXT. MOD, 18

2 16 BROWN - RED BLACK GREEN YELLOW- r REO TR 19 BLACK -, GREEN -) 17 20 - 1- BROWN BROWN- 3 BROWN YELLOW 31 BLACK YELLOW 24 , 33 YELLOW Y ` 4Q_ß0 006-J r". 25-- 26 005`1` 11 BROWN/ Ir1

INT BLACK 27 28 29 13- ZZ BLUE INCREASE -e 35 IMQ 111 38 EXT. 6 BLACK 7,. ./ GREEN -s YELLOW, O6Ò ON YELLOW-RED TR -. 39 / 11t - YELLOW-RED TR. I YELLOW -- .3000 OHMS WOO OHMS 300 +13 i , , OFF IQOOOOHMS . Ms o YELLOW e+ Spÿ )00aM5 +9011 A1.MU, w.n I NIG o .3 oHMs 4o1I 21 23 43 0.4- /0 I ME4 GND BLACK 41 1o4M I BLACK RED BLACK O Np1TTT 42 I 8 9 10 YELLOW/ L I ) __ TiYELLOW

Fig. Q. 197 Complete schematic circuit of the Model TMV -18 -C oscillator having a range from 90 to 10,000 kc. Use this on your midget receiver) RADIO -CRAFT for MAY, I933 677 for MEMBERS

An i Important Message Irnilít'rhi Qrrtitirair to Radio Service Men this Is It a.,,a, DIM é7osepb F.lUaiet SINCE the manufactured radio broad- EVERcast receiver became an accepted neces- ... sity in the household, the Radio Service Man d..1,.,.. has been an essential factor in the radio ePodd 7!LJM &rddIDmitta.idieg trade; and, as the complexity of electrical 2.rv svL..{IL.Ca....I.LL...y..4 and mechanical design increases, a higher and higher standard of qualifications in the Service Man becomes necessary. a .me. . eol The need for a strong association of the technically qualified radio Service Men also A..'tat becomes more pronounced as the industry two. tat ... progresses. This is the fundamental purpose of the OFFICIAL SERVICE MEN'S ASSOCIATION, No. 14 -50e each which is not a money -making institution, or (Plus 10e for postage) No. 3-60e per pad of 50 organized for profit; to unite, as a group, $3.00 per ten pads, each of with common interests, all well qualified 50 Radio Service Men; to make it readily possible for them to keep up with the demands of their profession; and above all to give them a recognized standing in their profession, and acknowledged as such by the entire radio industry. Recently, at a meeting of the membership committee of the ASSOCIATION, a new group of members was started. Formerly, all ap- plicants for membership were required to pass a rigid examination to prove their ability to cope with any servicing problem. How- ever, there are a number of capable Service Men who either through lack of time or other causes cannot take the examination, 100 and in order to permit these men to enjoy No. 4-50e per the advantages of membership, until such a $3.00 per 1000 time that they can pass the full membership examination, on associate membership was created. No. 11 -50c set of three cards .In order to become an associate member, the applicant simply has to fill out a form listing his past experiences, type of test -instruments used, etc. He is then immediately accepted as an associate member and may obtain any of the essentials shown on this page. The essentials for the associate member differ only in the specification of Asso- ciate Member in place of Member as shown oog RADIO 5U It( in the illustrations. SSE The Service Men's Essentials are sold only to members and associate members. Service ALL WORK Men are therefore urged to clip the coupon below and send it to the OFFICIAL RADIO GUARANTEED No. 8-40c each SERVICE MEN'S ASSOCIATION, Inc. REASONABLE CHARGES WALTER SLOCUME Be sure to specify whether you desire the RADIO ENGINEER 2159 BROAD STREET THE RADIO application for full membership or associate Tel. Broad 8618 EDOEWDOD, R.I. member. SERVICE MEN'S Assortment Package r No. 12 -$3.00 set of 25 cards In order to facilitate new members in getting started, Application for we have made up an assort- Membership in ment of essential materials, ORSMA as follows: Executive Secretary, ORSMA 100 No. 1 Letterheads 98 Park Place, New York. N. Y. 100 No. 2 Envelopes Kindly send an application blank for These DISPLAY SIGNS 1 pad (60) No. 3 Record Full Membership Cards are printed in attractive colors 100 No. 4 Inspection Labels Associate Membership 1 No. 6 Gold Filled ORSMA and they are certain to help Lapel Button Name Service Men in their business imprinted with your name, address, city and telephone if they are placed in local number or Box Street stores where they can be seen Price Prepaid per set vI City State and read.

678 RADIO -CRAFT for MAY, 1933 Radio Service Men's Essentials oftheO R S M A

SERVICE MEN'S ESSENTIALS 111E OFFICIAL ItA1 101 SERVICE MEN'S ASSOCIATION has made arrange- ments 1 associateaassso men hers. Only member. and axeociate members ican buy these items; he. are not sold to others. Thee esientials a priced at act, plus a small additional fee which in the only source of income that the Association has. No one obtains any or benefit. Association profit except the itself. Whatever profit accrues, is reinvested for the furtherance and en- largement of the Aseocistion. By using the letterheads, hillheads, etc., you present the business -like appearance to your customers, so essential to successful servicing. In addition, the Ansoriation 1 ae made rangements with most of the prominent manufacturers discounts to allow special tumemlerr , providing ORSMA letterheads are used when orderieg.

No. I ORSMA LETTERHEADS These letterheads, shown on the right, are furnished with your name,addremand phone tele- nunder, printed on excellent paper. They are sold in lots of 100 or multiples thereof. with a distinct saving for single orders of 1,000 or more. You pay many uld have to times more if you ordered small lots from your local printer. w Per 100, 00,,; per 1000, R7,00. No. 2 ORSMA ENVELOPES Thee are furnished to match the letterheads, printed with your name and address, and seal of the Association. They go hand -in -hand with the letterheads and are usually No. 9 -75c each, large size ordered in the same Quantity. Per 100, 00r: per 1001, 13.00. 9A -60c each, small size No. 3 ORSMA SERVICE RECORD CARDS They serve a doubler e. whenever you e. !Q,lete x doh you 1111 out the report and hand -bill eit p, the r p.sthis is the "psychological , n, cdlcrt. Ily the use f casheo paper tw.u,ene,t r rd i- kept which i a vskiale asset to your business.. No. 1-60c per 100 They are furnished with your mblress and olepnumber.one number. l'er pad of 50, 00:; per 10 pads, each of 50, $310hc $3.00 per 1000 No. 4 ORSMA INSPECTION LABELS The label is to he filled in with the proper dates, and pastel inside the set or cabinet where the customer will see it. It in a Continuous reminder to him that, when service is needed, he can Fall you stain. The advantage is apparent. Per 100, 50e; per 100. 93.00, 10 ® No. 5 ORSMA LAPEL BUTTON

At the suggestion of many members a hand. , lapel button bearing the name and emblem of the Association has Iwen designed. It signifies to your fellow member. that you belong to the same Asciatiotsoo -and in addition it gives your customers letter appreciation of the professional nature of your work. 50c each. No. 6 ORSMA BUSINESS CARDS These are furnished on a fine grade of paper in two colors with a blotter lark. Thus they present an added incentive to your cu,pmr« to keep then, la a prominent place, where they will do the most good. They are printed with your name, address, and telephone and bear the official seal of the Association. l'er bah 75c:; per 1010, 94.00. No. 2-60c per 100 No. 7 ORSMA EMBOSSED STICKERS $3.00 per 1000 Ideal for use in sealing package,,. .relines, etc., or for IIMC m poet cards. They give your letters or cards a professional pater t. They are sold in Hots of 100 or moro. Per 100, BSc: per 1000. 10.00. No. 10-75c each, large size No. 8 ORSMA RUBBER STAMP 10A each, -60e small size A handy addition to s ember's em,ipment. The first line of the stamp beans Your o and the second reads - Member Official Radio Service Men's /teen. 'mu stamp ban many uses in the everyday life of a Service Man. 40c eatd,. STEPHEN MARKO Nos. 9 & IO ORSMA EMBLEM CUTS Thew cute for printing, advertising, etc., are furnished in two styles and sires. They may 1» unei for newspaper or telephone-book advertisements r for printing of any 139 Brithton Dose kind. Large sae, 1%x! in., 75e each; small sine, in., N Ns N ate each. Tel. 3 -0672 AttRon,O. No. I I ORSMA MEMBERSHIP SIGN 1 A set of three of thew signs. printed on heavy cards, and having holes punched in to hang in your once or tore, and x sold to member+ and associate members. No. 6-80e per 100 Torderhey are large enough s, tlet they are u,'ue.50c. usinent and the two tone effect makes a very attractive appearance. Set of three. $4.00 per 1000 No. 12 ORSMA ADVERTISING DISPLAY SIGN A two actor sign printed in large letters with your name. address and telephone, with the seal of the Association. l'I,i+ sold in quantities of 25 o end is ideal for hanging in stores, office-, err., for .lvertising purposes. Set of 25 card , 13.00. No. 13 RADIO SERVICE MEN'S ASSORTMENT PACKAGE This includes one gold filled lapel button, 100 letterheads, 100 envelopes, .50 se cards, and 100 labels printed with your o and address an described above. Trecordhe whole assortment costs only -13.00- -a worthwhile roving. Complete, 93.00. No. 14 ORSMA MEMBER CERTIFICATE No. 5 -50e each A hamleome diploma -like certificate engraved on stiff vellum- bored. The certificate is personally signed by the President and Esecutive Secretary and the corporation stamp No. 7 -85c per 100 of the Association is improved on a red seal attached to it. Your name, certificate number and date of registration are lettered by hand and the Certificate is trailed inacardlxard $6.00 per 1000 tube to insure safe delivery. Each 50r, plus Rhc for postage.

OFFICIAL RADIO SERVICE MEN'S ASSOCIATION 98RC Park Place, New York, N. Y. me Please send the following RADIO SERVICE MEN'S ESSENTIALS which I have selected front this advertisement. My remittance for $ is enclosed. Send remittance in form of check or stoney order. Register letter if it contains. cash currency or unused U. S. Postage Stamps

Name ORSMA No Address City and State

RADIO -CRAFT for MAY, 1933 679 A SUPER -SENSITIVE ALL -WAVE CRYSTAL SET J. M. NIGHSWANDER

A description of a crystal receiver designed for all -wave reception. This set is an outgrowth of the original set described by the author in our December, 1932 issue. It is especially designed for the man entering the radio field.

As all -wave 'planes, Iolice, and some S. -W. stations, Use No. 18 or 20 S.C.C. or D.C.C. wire, crystal set using plug -in -coils using about a 60 ft. antenna and a 60 spaced about 18 turns to the inch. was developed by the writer ft. counterpoise and tapping the coil The large coil, L2, in Fig. 1, has 54 and described in the Decem- at 3 and 9 turns from the ground end.) turns, tapped, from the ground end, at ber, 1932, issue of RADIO-CRAFT, page What the set has done: In a few 6, 15, 27, and 40 turns. This coil goes 354. Now, a new has been circuit days operation this set has in far below the broadcast band. For the brought out which is much more sensi- brought police calls from Seattle, Portland, San real short -wave band the coil L2 should tive and selective than the earlier de- have 15 turns, tapped at 3, 6, 9, and sign. latest Francisco, Berkeley and Denver; air The arrangement uses but ports in Oregon, Washington, Idaho, 12 turns from the ground end. This two plug-in coils (taken old from an Wyoming, Utah, Arizona, Colorado and coil, using a counter -poise, goes up S.-W. set), one for each wave band, into the broadcast band and separates and California, with many 'planes in flight. there is but one basic change in Heard: Amateur 'phone from half stations better, with good volume, than the circuit. The improved circuit de- across the large coil. It is not known how far sign is the U. S. and two S. -W. broad- shown in Fig. 1. cast stations upon channels this coil will tune below 46.96 meters. Using the set with a long adjacent on antenna the of Feb. 7. Coil Ll, the untuned, fixed, 11 -turn and a ground connection, night (Caught the call KFI (640 kc.) of but one at M. primary, is made in the general manner was highest possible to be 8:01 P. [Pacific the station time], W3XL, 6,425 kc., 46.96 meters, described for coils L2; coil Ll must be tuned in. The lower part of the broad- made just small enough to slip inside band and -wave Bound Brook, N. J., playing marimba cast short stations are solo, La as for and at the ground end of either of the received with the new much Sorrella.) And code, set with as some nights it's like a bee hive! coils which are used as L2. (This pri- volume and far better selectivity than mary is not a very important winding could be obtained with the old set by The relative broadness of tuning on and is used but little, although, if using this long outdoor antenna; in- this set is an advantage in finding S.W. loosely coupled when using a ground, it stead of a ground connection, a 50 ft. broadcasts and other voice signals, al- results in increased selectivity on loud indoor antenna is used as a sort of though, as a crystal set goes, it tunes signals.) counterpoise. This counterpoise lowers sharp. The same station will come in on the tuning limit somewhat. Building the Set several taps, but use the one which (Other builders of the old circuit re- The coils can be built on celluloid, places the station lowest on the tuning port distant reception of air ports and bakelite, or paper forms 3 ins. in dia. (Continued on page 687)

THE RADIO BEGINNER In this department we shall print every in experimenting with home -made sets. The month simple, but effective radio sets and new instruments, as well as the new tubes, make circuits, and other information for radio begin- this endeavor of particular importance. ners, or those just starting in radio. There are If you build the sets described in these thousands of radio fans and experimenters who pages, won't you be good enough to advise us are still interested in building their own, and what results you are getting?

Fig. I, loft. Schematic circuit of the receiver described. Fig. 2, above. Sketch of the tuning coil. Two coils are needed to cover both the broadcast and shortwave bands.

680 RADIO -CRAFT for MAY, 1933 AT LAST! WORLD -FAMOUS COYNE TRAINING IN ELECTA I CITI Aoloble For HOME STUDIE NOT The Ordinary The practical, simple, easily understood instruction material that has made COYNE famous for 34 years is NOW -for the first time in history -available for Correspondence YOU to study AT HOME! Never before has this instruction material been avail- Course able for any but regularly enrolled resident students and graduates of COYNE. But now, compiled by the entire COYNE staff assisted by many of the world's The 1,000 page COYNE is available for Standard Reference Set, with outstanding electrical firms, this rich store of electrical knowledge its more than 1500 illustra- you in convenient book form -to study at home. tions, is NOT the usual cor- espondence course. It is so INCLUDED arranged that, instead of get- FREE CONSULTATION SERVICE ting one or two lessons a Es co owner of thi, wonderful book- -The Standard COYNE Reference Set -will be entitled month from which to answer a to the privilege of freely consulting with COYNE Expert Instructors in the solution of any few simple questions, you get electrical problems that may arise in studying and using this home training net during an entire year's time. This feature alone is worth many times the small price of the book ... the whole complete volume at as hundreds of working have made use of this unique service. once, so that you can refer to testified by electricians -who advanced sections and different branches of electrical work at will, going ahead as fast or Here's WhylAm Taking This Step! slow as you please. And the It means a great deal to me to break a tradition and change a well- estab- book itself is always valuable lished policy after 34 years. That's what I am doing when I offer COYNE for constant reference and re Training to you AT HOME. instead of ONLY here in our great shops. But view. these are unusual times, and have created unusual conditions. Many ambitious men who would be here at COYNE now-preparing them.elces for a useful, profitable life work in eletricity -eannot come because of finan,ial diffirultle, it is my thought that by offering this COYNE Training to them for home study at ridiculously low be price, they will Yo Previous Experi- able to earn from what they learn. and soon be financially able to come to COYNE later If they deride they still scant this superior electrical training world that Is known the ence Needed To over for Its practicalness and thoroughness, Not that getting this book means the buyer has to collie to COYNE . It la simply my hope earning that the knowledge and power gained from this book will Inpite > u to taint the complete training Succeed that can come only from attendance at COYNE. Advanced education or pre - H. C. Lewis. President. ,ious experience is not needed to make a success of COYNE Electrical Training. Every- Don't Delay -Get Started NO thing is given in simple, easily 11TI understood language, illus- This big book of more than a thou- trated thoroughly by photo - sand pages -- crammed full of practical zraphs and diagrams. If you electrical knowledge illustrated by more an read and understand simple than 1500 photographs. diagrams. etc., 00 English you can learn all about shows you how to do real electrical WITH ORDER the operation, care, service, of every a d repair, etc.r of practical elec- jobs kind from installing 52 A Month , switches and wiring houses to connect- ° , oc trical equipment from this 4 Until full arie Oc-, s ing. testing, operating of $12 L, ' wrest book. and repairing uabd. Sr Sa.75 ea.li tbpcc¡pvaÿ4 A. C. and D. C. motors, controllers, to advance. e generators, and switchboards. Get it e ireet4sp4`o Immediate Profit. AT ONCE-you'll be delighted with the ÿo i°°ea ease and quickness with which you F°esi From This Book! c learn and can get to making real money o '4'e You will find it possible to out of spare time electrical work. Send e,...-0(,...4., c 5 4r learn to do real electrical jobs your order on the coupon NOW ! I 96 almost immediately upon re- , rw ceiving your COYNE Standard `¿p4 c¢c ooyo+' 43;r Reference Set book. There are / Gei, +4 t,9 many excellent opportunities to aa`ti' '''.$. oe / earn good money from spare COYNE r , b eao4 ce °e0e. time electrical work right in i' (9' q. 9aF your own neighborhood while .c,póQc4 s. r coa1 you are studying. This is not ELECTRICAL SCHOOLS . ; idle talk -but the actual expe- eay

RADIOCRAfT for MAY, 1933 681 FREE! Quasi -Optical Home Experiments AN IMPORTANT NEW John B. Brennan. Jr. IT was the intention of the author in this fifth ed a piece of thin rubber sheeting. On the of the series explaining simple home experi- upper surface of this rubber sheet there is de- IRC SERVICE HELP ments in the quasi -optical field to describe in posited a metal film which comprises the other If your name isn't on the IRC mailing detail the various experiments which could electrode, or charged body. Now. when these list, better get it there-quick! Beginning be conducted with the apparatus previously de- two bodies are charged, we must sensibly come with April the makers of the famous IRC scribed in this department together with a length to the conclusion that the rubber sheet. on Metallized and Power Wire Wound Re- of quartz tubing -that glass -like material which which is deposited in metalic form the one elec- sistors and Motor Radio Suppressors will possesses the unique property of confining with- trode, will give way more issue one of the finest, most readily than the useful helps in its walls a beam of light, so that no ribbed ever prepared for the radio service man-a matter metal plate because of the former's monthly publication known as the "IRC how the tubing is bent, the light rays will fol- greater resiliency. If the rate of charge be al- SERVICE CALL. ".. Far from being a mere low this winding path and be emitted at the tered, or varied. rapidly at an audio frequency "puff sheet" this little magazine will con- other end. rate it is easy to understand how the rubber tain more interesting, more helpful infor- Upon investigation, however, it was found sheet electrode or diaphragm pushes the air in mation than you'd that, relatively speaking, the sources of supply front of it to cause sound. imagine could be gar packed between two for quartz tubing were so few and the cost, Now this principle, after a fashion, is also covers. You'll not only in many cases, so prohibitive, that only a gen- used for the modulation of a beam of light, es- -e read it and enjoy it eral explanation of this experiment should be pecially in the talking movie field. Wokl BUT YOU'LL PROFIT given, merely to illustrate the peculiar prop- Two strips of metal, both resilient to a cer- /-`. FROM EVERY ISSUE. erties tain degree and R of quartz tubing. Of course, those expe- insulated from each other by 1 Drop us a line on rimenters whose pocketbook is sufficiently some film or coating are placed your business station - large protecting par- KF.SISTORC ery- today. Don't miss muy wish to indulge in this luxury and per- allel to each other and in such a position that it! form the experiment. in a state of rest, or without any energizing INTERNATIONAL RESISTANCE CO. So far, in this department, there have been voltage. they are so close together as to prevent 2006 Chestnut St., Philadelphia, Pa. described a high quality audio channel to whose the passage of a beam of light between them In Canada. TS Welbnp,on SL. w.. Toronto. Ont output could be connected the conventional tel- from an exciter lamp. Keeping in mind the ac- vision tube, or crater lamp, and a photo -elec- tion of the electrostatic loudspeaker, it is easy to tric cell with its associate amplifier and loud understand how the output from an audio am- speaker. The only additional piece of apparatus plifier would cause these two parallel ribbons NATIONAL required for the experiment is the quartz tubing, of metal to move away from each other in a bent into repelling action, thus allowing more or less light STEWART WARNER some peculiar shape, such as a U- shape, L -shape or S- shape. G9CVtt Now, if the high quality audio channel has BOSCH its input fed by some form of audio frequency, LINCOLN either from a phonograph pick -up or from a radio receiver, then there will be produced in Rammarlund the television neon tube, or crater lamp, minute variations of light intensity, entirely too rapid SILVER- MARSHALL for the eye to follow. OWNERS If the quartz tubing be placed so that one NOW of its open enda be near this neon tube while In Inereutng bers its other end CLAIM BETTER RECEPTION be placed near the photo-electric sIth the NEW not se -free cell. to which is attached its amplifier, then, regardless of the peculiar excursions of the to pass through the gate thus provided. depend- shape of the quartz tubing, the light entering it ing of course upon the variations of the energiz- LYNCH at one end will. with all fidelity, be emitted at ng source. Short Wave Antenna System the other end and energize the photo-cell so that 55,60 the light variations can be changed to electrical Some experimenters may wish to feed their Complete Kit current variations, and so be reproduced and high quality audio channel with audio fre- At All LYNCH Jobben and Dealers amplified, finally actuating the loudspeaker. quencies other than those obtained from a phonograph pickup or from a radio receiver. In such If your Jobber. Dealer or cannot serviceman cases one of the simplest and most supply you. order direct from u s. Sent post. last inexpensive peed. with Instruction Cockle?. upon receipt Continuing month's discussion on the devices is a home -made microphone, of manufac- SS. various types of mechanical and electrical light tured on the well -known kitchen table modulators with the Free Descriptive Folder upon request. with which experiments can be con- aid of one of the far famed Skindervikken but- ducted, one more such modulator is described tons. So numerous are the ways in which LYNCH MANUFACTURING CO.,Inc. here. this 71 button can be used, and so varied are the tRP- General Moto,, Bldg., New York, N. Y. Probably cir- all of us are familiar with the short- cuits in which it can be employed that to at- Maker, of ihr Famous Afrlaiii.rd Rauions lived electrostatic loud -speaker of a few year. tempt to describe even a few would be mere ago. The principle of its operation was based duplication of effort, especially when space in on fact that the two charged bodies of similar this department is at such a premium. For polarity tended to repel each other: and, if the detailed information motivating concerning its many uses ONCOURS force be altered, or varied rapidly. the reader is referred to the descriptive pamph- then would there be a coincident movement in let which accompanies each one of these Skinder- New-Improved-Simplified one or the other of the charged bodies. vikken buttons. In the electrostatic loudspeaker one of the Next month ... talking movies and their re- charged bodies usually assumes the form of a lation to light sensitive and light modulating de- ELECTROLYTIC ribbed rigid metal plate, while over it is stretch- viees. a CONDENSER for sub -panel one -hole NEW SYSTEM OF NUMBERING TUBES mounting. Designations for new Can be used in either tubes are now being Five Volt Filament Type Triode (Second assigned by most manufacturers in accordance of such a group)- 5B3 new radio sets or for re- with a system recently adopted by the Radio Two Volt Filament Type Triode (First placements. Manufacturers Association. A new system has one) _ 1A3 Eliminates threaded nipple become necessary because practically all of the Two and One -Half Heater Type Triode and large hexnut. Makes a available two and three digit combinations have (Second. one).___ 2B4 more rigid contact to been utilized. Six and Three Tenths Volt Heater Tetrode chassis without the usual The new method. which provides for further (Third one) 6C5 mechanical strain on the expansion of tube types, ordinarily requires only Six and 'three Tenths Volt Heater Type thin metal container. three symbols. These are arranged with the Pentode Suppressor Connection Internal numeral first, then a letter followed by a nu- (First one) ...._...... _...... _ ...... _...._.... -..._ 6AS Send in your request meral. The first numeral indicates the filament Six and Three Tenths Volt Heater Type for our complete or heater voltage by one -volt steps ; thus 2 of the Pentode Suppressor descriptive catalog Connection to Base example "2A5" covers any voltage from 2 to Pin (Second one) _...... __.- ...._ 6B6 err UR -..._ 2.9 volts. The last numeral indicates the num- Five Volt Filament Type Full Wave Rec- " r" CONCOURSE ber of usable tube elements with external,con- tifier (First one) _ 5Z8 nections: thus the 2A5 has five such elements. Two and One -Half Volt Heater Type Dou- ELECTRIC CO. INC. The letter is an additional distinguishing sym- ble Diode and 389 -409 Wales Ave., N. Y. City Triode Combination (Sec- bol which is arbitrarily assigned for each new ond one) 2B6 tube type. It shall be standard in a multiple grid tube Following are some examples of hypothetical to number the grids consecutively according to On page 646 of this issue will be found an im- tubes: portant announcement of the CONSOLIDATED their location proceeding from the cathode toward RADIO SERVICE MANUAL. It is worth your Type the anode. The grid shall be thus designated: while to spend a few minutes reading this ad- Description Number No. 1 grid, No. 2 grid, et cetera. Co-planer or vertisement which tells how you can buy this Five Volt Filament Type Triode IFirst of twin grids shall be designated: No I -A grid, No. book on our new purchase plan. such a group)___ 5A3 l -B grid, et cetera.

682 RADIO -CRAFT for MAY. 1933 RADIO -CRAFT READERS' DEPARTMENT (Continued Irons page 665) Westinghouse placed it with a new one and the set was O.K. for about a month, when the other RADIO INSTRUMENTS (smaller) condenser of this unit also gave out. After replacing the second faulty unit the set . are used in the new Coast -To -Coast functioned perfectly. Radio Corporation Circuit Analyzer re- From our experience in servicing these sets cently introduced. we would advise the Service Man to check used very carefully all bypass condensers- partic- The Universal AC -DC instrument ularly those in the resistance -coupled A. F. in this analyzer is one of a complete unit, because when any of these let go, the Westinghouse line which includes Am- set will still work, but very weak, the tubes meters, Voltmeters, Milliammeters, and win overheat, and the dynamic reproducer Radio Frequency Ammeters and Milli - case will get hot. ammeters. They cover all the require- A. J. NORTHRUP & SON. Service East Berne, N. Y. ments for Radio Engineering, and Research, Television, Sound Re- cording, Photo -cell applications and for WORLD -WIDE RADIO TIME Public Address Systems as indicators of In Fig. 1 is reproduced, by courtesy of QST power level and other important char- Publishing Co.. a useful chart which indicates acteristics. at a glance the time which exists at various points throughout the globe, at a given mo- A NEW DEVELOPMENT ment. During the winter, reception condi- A new line of Westinghouse small -size, tions are particularly good in the 200- to 550 - super- sensitive instruments has just been completed. meter band; but, during the summer months. the shorter wavelengths become extremely ef- Known as types MX and NX, these instruments fective, and, therefore, beginners in short- are available in 21/4 and 31/2 inch sizes, flush mount- wave radio reception will find this reference ing. "Moldarta" molded cases of pleasing appear- valuable at this time. It is pointed out that ance. Their sensitivity is so great that for the first distant signals above 88 meters are not re- time a 2 -inch instrument is available with 20 micro -amperes ceived well in daylight. and distant signals full scale deflection. below 25 meters do not come in well at night. For prices and complete information, see your local Westinghouse dealer, or write to the Coast -To-Coast Radio Corp., 123 West 17th Street, New York City. A SOCKET -TYPE ALIGNING TOOL SERVICE MEN Alvin C. Porter Write for your copy of COMPLETE CIRCUIT Most Service Men have in their tool kits DIAGRAMS showing how to construct and wire the above illustrated Analyzer. All constants given. a socket wrench equipped with several remov- Furnished gratis. able sockets for different size nuts: also, a screw driver socket. By using these sockets Westinghouse Electric & Mfg. Company on the end of a Ps -in. fiber rod, about 8 ins. long, a practically unbreakable neutralizing Room 2 -N East Pittsburgh, Pa. and aligning tool can be made; and one that will fit almost every aligning condenser. A small knob on the other end of the rod makes `One House of COAST- TO-COAST- for t.t

QUICK WATSON, THE PEAKED CAPI Editor. RADIO -CRAFT:

I have been a reader of your magazine for fi many years and have obtained a lot of helpful tips from your department known as "The Service Man's Forum." Because we have received so many little helpful hints, we thought perhaps someone ,. d complete with else might be benefited by the results of a .,ta herewith. case we ran across the other day. LIST OF Four" were called service one of PARTS.-.+ Tote' We to the early Individual parts as lisled In the right may be purchased model Freshman sets on which the complaint separately, at vices quoted. Two One was "no volume." The set, tubes, and aerial One "a 'I L It were checked and found to be in or- One " 11 perfect one " " a ni., der, but still the locals could just barely be Two "Yoles "I tr I. P-, heard. We were about to take the set into SilushaMou"Bú Flesh \lounr Pu.h Set the shop when we noticed a peculiar thing. One Ìanel Board for I, This had come out very rough One -ED/toad- ut set with com- One 'El,voad" oat position sockets and the owner, while trying One "Alden- r to 6 Pr'. Pin end Grid Cap toI, to insert the tubes in the dark, had rubbed off Three "Alden' Analiter PI < .\.I..i.i.-r.. a One Pair of "C -T -C' Needle l'oint Tut lent, quite lot of the soft solder which was on Band derma Chuck Hoge the prong ends onto the sockets. caused One "C-T'C Port/able C.., This One "C -T -C" Analyser Panel. Dolled and Elute,...l a leakage across the sockets, and the conse- Se of Blueprint. Ch...,, I..tinnaone ate Mitswllaneous cables. Wire. Hardware. Batter+., etc. quent loss of volume. After this lead was p cleaned off, the set worked normally, and an- 9t 1e r0` Total was CONTAINS THOUSANDS OF Complete Kit Purchased at One$6 s o other customer satisfied. 9s W. C. BURY, LISTINGS FROMA LUG OR Time - Special Inducement- Completely. $79.50 Lagoon Radio Serrire, SCREW TOA IOU WATT DUAL eeay fóneiate üera°a 2805 Henn. Ave., Minneapolis, Minn. CHANNEL RACK AND PANEL AMPLIFIER! (Our Radio Detective is with us again, and, curved pipe or not, he successfully ferrets COAST- TO-COAST- RADIO -CORPORATION . out the leak. (Hi!)-- Editor.) 123R-WEST I7TN STREET NEW YORK, N.Y. (Continued on page 691)

RADIO -CRAFT for MAY, 1933 683 OPERATING NOTES (Continued front page 667)

its place. Some repairmen use melted tallow Zenith 240 on the string but this soon wears away and A number of Zenith model 240 receivers another service call must be made. See Fig. 2 have for details. been serviced because stations were not received on the proper point on the dial. Although some A rather common complaint on this model is were rectified by distortion re- alignment of the oscillator at low volume. Although this condi- trimmers. it was necessary to adjust the cellu- tion has been caused by an open 500,000 -ohm loid dial scale on most in order to obtain the resistor in the first R.F. secondary return (which proper frequency settings. AD- A- SWITCH fact will be evidenced by a lack of control -grid Many dealers are installing this chassis in is the Emergency voltage, which, in any case, is very small be- custom -built cabinets. Where cause of the high this is done, and Control! resistance in the circuit). this the mounting board is not as thick as that used distortion has been cleared by the insertion of in the manufacturer's cabinet, the With a skeleton stook of CLAROSTAT suitable resistors back left to reduce the heater voltage of mounting bolt, if screwed too tightly, will pass AD- ASWITCH Controls over 70%p of vol- the A.V.C. tube to 1.5 volts, which, at the same ume control replacements can be handled. up too far and short to the biasing resistor, time, will render the receiver more stable. causing distorted and weak reception. because ane control can serve either for plain or RCA Victor 50 Zenith 244 switch type - the shaft ie completely insulated from the This model has necessitated more service calls Recently a Zenith 244. a twin reproducer re- contact arm- for fading than for any other condition. With ceiver, presented the problem of poor and dis- the combined length of shaft (with the all operating voltages correct, tubes perfect, and torted tone at low volume. This mounting bushing) is 1 54.--sufficient to condition, in take ears of most requiremente- all component parts tested, this condition had several previous cases, had been found to be Standard Ad- A-Switch Controle are avail- persisted in spite of all efforts to locate the due to a A.V.C. 57 able in as tapers and electrical char- poor tube. Replacement of t tariatior. source. After a good deal of trial and experi- this tube, however, was barren of results. It AI)-A- SWITCH is recognised and adopted mentation, it was found that by reducing the was only after much testing and routine work as the only ewrrreenev. Control rendering heater voltage u n servire with minimum mveat- of the A.V.C. 27 tube. the fading that the complaint was finally traced to an im- mwu. was eliminated. As in the case of the model 21, properly centered voice coil on the larger repro- A helpful VOLUME CONTROL and RE- the heater voltage was reduced to 1.5 volts by ducer. The aid of an offset screw driver will be SISTOR GUIDE is available upon request. means of filament resistors. found necessary to adjust the voice coil on this ...IPA-SWITCH" uw4 w.v,rntd tv am If the high heater voltage on the A.V.C. tube dynamic unit for proper clearance, as the spider caused the fading on this model (it must be is anchored by means of screws not easily ac- remembered that fading may be caused by any cessible with the ordinary screw driver. number of reasons), a certain and definite test CLAROSTAT MFCaCo. be may made to establish this fact. When the Stromberg Carlson 25, 26 receiver has been switched off for a minute or 285-287 N. 6TH ST.BKL1fN. NY. two after operating A stubborn case of fading and very erratic at moderate volume on a was weak station and then switched on again, a operation encountered on a Stromberg sharp increase or decrease in volume without Carlson model 26, 26 receiver, The symptoms in any change in the volume control setting will this instance were peculiar. After some minutes of normal reception. volume would suddenly mean that a reduction in the A.V.C. heater volt- lower, age must be made to eliminate, or clear up, the control of volume would become poor, SERVICEMEN, difficulty. and it would become necessary to readjust the station selector about twenty to thirty kilocycles DEALERS. RCA Victor RAE-26 from the regular band setting; some of the more YOUR PROFIT A frequent cause for low volume on the phono- powerful broadcasters being received on two graph of the RCA Victor RAE -26 phonograph points on the dial, some twenty kilocycles apart. ``/, GUIDE combination has been to shorted This setting would vary every few seconds. a_t traced a portion of the phono input transformer primary. There Although the bi- resonator condensers are a , are five terminals on this unit. of which only common cause for fading and no control of vol- FREE ume, on this model it was highly improbable EVERYTHING NEW four are used. The shielded conductor connecting to terminal No. 2 is often found resting that failure of these - 04 -mf. units would result against the unused terminal No. 3, shorting a in the erratic two -spot tuning that was experi- Send Today section of the primary that is not used, and re- enced. However, a quick check was made to w K ta`(PaVY n.nnl.l for this sulting in the complaint of poor record output. determine this condition in the manner described It is but a simple matter to tape up either the by the writer in the August, 1932, issue of BIG CATALOG terminal or the shielded cable to prevent a RADIO -CRAFT. The resistance of the R.F., I.F. If you haven't a copy of the RADOLEK recurrence. and first- detector secondary circuits were meas- 1933 PROFIT GUIDE ured with an ohmmeter connected respectively you are without the Radiola 67 biggest and most complete catalog of Radio from the control grids of the R.F.. I.F., and first Merchandise ever compiled by a house ca- Some months ago, the complaint, "no control of detector tubes to chassis. The reading obtained tering exclusively to Radio Servicemen and Dealers. volume," was received on a Radiola 67, a phono- from the control grid of the R.F. tube to graph combination employing automatic volume chassis was correct, approximately 100.000 ohms; NEW MERCHANDISE AT control. This complaint immediately brought to but the reading, well under 100 ohms, obtained LOWEST WHOLESALE PRICES mind a similar condition recounted in the July, from the first detector and I.F. control -grids to 1932, issue of RADIO- CRAFT, where an open con- Attach this ad to your letterhead or enclose chassis designated trouble in the secondary re- your business card and mail to tact of the phono-radio transfer switch was turn of these circuits. found to be the cause for an inoperative re- Ordinarily. this low reading is indicative of THE RADOLEK ceiver. When the A.V.C. 27 tube was with - leaky or partially shorted bi- resonator or .3 -mf. CO. drawn, the receiver would function but without bypass condensers, which would have produced 123 Canal Station. CHICAGO, ILL. any control of volume. In this case, however, the complaint of poor control of volume, more withdrawal of the A.V.C. tube made little or than any other condition. After these units no difference. The contacts of the transfer were tested and found perfect, the 100,000 -ohm switch were found in proper working order. The carbon resistor in the same circuit, located latter fact definitely pointed toward some defect under the volume control, and which often has RADIO MEN:-NOW!! in the A.V.C. system. Proceeding on this theory, been found shorted to chassis resulting in no EVEREADY SERVICE CEMENT the chassis was removed from the cabinet. control of volume, as well as the second 100.000 - ilrrée what `ou have needed. e As the first step toward solving the problem, ohm resistor, was checked, despite the fact that fart drying. [halide. vibre waterproofwiderw and proof the voltage divider and associated resistors in this resistor had checked satisfactorily because for repairingn. stater .. lend,. coils. the A.V.C. system were checked for continuity it is also in the secondary return circuit of the Itasca. manner, by the R.F. tube. ' :and other ureause. where °a in the usual placing continuity deppeendable needed. tester or ohmmeter across each section of the With the aid of a low -range ohmmeter, the Thin le pupure Ì'YItOCILYN ('E\IENT. ..taffy mad voltage divider resistors. This method, although difficulty was finally found within the condenser fee and uoee THINNEa.e ordinarily satisfactory, was the cause of a good gang housing shield. A close inspection will Price to Radio Men $.35 deal of trouble in locating the defective unit. reveal a screw that passes through the third See your jobber or send 35c to: an open 310 -ohm section of the voltage divider. gang section shield and which has been insulated is shield GENERAL CEMENT MFG.CO. One end of this section grounded, and be- from the by means of some wax, or com- ROCKFORD, ILLINOIS cause the entire divider is only several thousand pound. This screw. see Fig. 3, which is con- ohms above ground, an erroneous effect was ob- nected to the stator of the third tuning con- World -Wide Two Tube Short Wave Receiver tained when the continuity meter was placed denser, had shifted in the wax and was shorted 12,500 Mile reception record / 75 across the open section. Little thought was at to the shield, obtaining the strange effect as eetahliehedl Tunes front 15 the high outlined. The wire to the screw from to 200Metere. Gets foreign $ first given to reading obtained across the con- broadcasts, police call, air- this open section for the reason that the middle denser was disconnected and the problem was planes, arnateumetr. DIRECT! Complete section is only about twice the physical size of solved. KIT (no drilling/ with clear instruction to build this remarkable 2 tube receiver .14.75 the end one, although more than ten times This receiver employs another such screw Dry mH or AC model. larger. electrically. Again, a careful analysis of passing through the first gang section shielf. Send $1.00. Balance C.O.D. Satisfaction Guaranteed! the schematic brought the error to light. A and connected to the stator of the first tuning Short Wave Catalog R -S FREE repair was effected by replacement with a 300 - condenser. This screw cannot easily be seen HARRISON RADIO CO. 142 Liberty SI. New Twit Cry ohm, 25 -watt wire -wound resistor. because of the location of the trimmer condenser.

684 RADIO -CRAFT for MAY, 1933 v

which is mounted directly above this screw. The the tone control with the volume control, as same shorted condition has been encountered on both controls are identical, each being 500.000- several occasions. ohm units. Although the manufacturer may have intended some use for these screws, their removal from Stromberg Carlson 38, 39, 40, 38A etc. not impair operation the circuit did the of the The volume controls of these receivers are receiver. To substantiate this fact, both screws often changed because of noisy operation. In were a set that was disconnected in operating most cases, these units are really bad and must and no apparent difference was satisfactorily be replaced, but many instances have arisen noted. where this noisy action has been cleared without Stromberg Carlson 29 replacement of the volume control by changing The line switch on this model has been a fre- the first audio tube. If the tube in this stage quent offender. As in many other receivers, is gassy and draws too much plate current, this the switch is incorporated in the tone control. noisy effect is produced. If the owner is not, or does not, intend using Strong resonance hunt on these models has the set for phonograph reproduction. a repeat been found to be caused by leakage between service call may be eliminated by interchanging cathode -heater of the type 58 tubes. BATTERY -OPERATED PERSONAL RECEIVER

The chassis is then turned upside down, and the One Aerovox .1 -mf. cartridge condenser, type parts below the deck are fastened in place. The 281. 4; antenna coil (1) is fastened to the inside of the One Aerovox .25 -mf. cartridge condenser. type right chassis wall as shown. Coil (7) is fastened 281. 8: to the underside: hence the fields of the two One Aerovox .00025 -mf. mica condenser, type coils are at right angles and cannot interact. 1460, 10: No shielding is necessary between them. Two of One Aerovox .001 -mf. mica condenser, type 1460, the amperite mountings. (6) and (13), are se- 16; cured to the inside left chassis wall. The third One I.R.C. 30,000-ohm, 1. watt, metallized resist- amperite (21) is fastened to the underside of or, type F-1, 25: the deck, near socket (20). One I.R.C. 100,000 -ohm, 1. watt metallized resist- The cartridge condenser (2) is mounted ver- or, type F-1. 17; tically, having one terminal soldered to the back One I.R.C. .25 -meg.. 1. watt metallized resistor. lug of the antenna coil secondary and the other type F -1, 19; terminal grounded to the chassis. One ter- One I.R.C. .5 -meg., 1. watt, metallized resistor, minal of the mica condenser (10) is soldered to type F -1. 14; the plate lug of socket (5) ; its other terminal One I.R.0 1. meg., 1. watt, metallized resistor, is soldered to resistor (11). Unit 16. a mica type F -1. 11: TESTER condenser lies flat against the underside of the Two Amperites. No. 630 with mountings, 6, 13; chassis and is soldered to the plate terminal of One Amperite, No. 633 with mounting, 21: -tcrdat4 socket (12). Its other end is soldered to a lug (Note: above amperites are used with 6 -volt NO. 710 which is grounded to the chassis by means of a storage battery. If 2 -volt air cell battery is used, socket fastening screw. One terminal of con- substitute 4V -199 amperites for the two No. A Remarkable Instrument denser (18) is also connected to the plate lug 630's and omit No 633.) of socket (12), while the other terminal is One Trutest 5 -prong wafer -type socket, 20: Al a Remarkable Price soldered to the control -grid lug of socket (20). Two Trutest 4 -prong wafer -type sockets, 6, 12; new and improved tester is designed Cartridge condenser (8) is placed near the One Trutest 5 -inch midget magnetic speaker. 22; THISfor testing any radio, whether an up- to -the- speaker cone, being connected at one end to the One .5 -amp. Instrument Littelfuse, No. 1007; minute model or any old model. It is equipped yellow terminal of coil (7) and at the other end One Littelfuse Gryp Connector, No. 1039, with a practical selector switch for checking all parts of the tube circuit by to the metal chassis. The five resistors are next Raytheon type 34 connecting to One tube, 6: the set sockets. It is so designed that selec- soldered as near as possible to the other com- One Raytheon type 32 tube. 12; tion can be quickly and accurately made for ponents with which they function. A piece of One Raytheon type 33 tube, 20; testing voltages of plate, grid, cathode, sup- flexible braid is soldered to the blue terminal of One fiber terminal strip with six soldering lugs: pressor grid and screen grid. Plate current, coil (1). This wire is then tied to the chassis Two screen -grid clips: filament volts, line and power supply volts are also measured. by means of a small eyelet, so that any pull or One Blan aluminum chassis, 9t6, x 4 inches x ISC Capacity and resistance charts are furnished strain on it will not affect the connection to the inches high. No. 14 gauge: showing use of instruments for testing con- coil. Of course, it must be well insulated from Three 45 -volt "B" batteries; densers and for measuring resistance up to the chassis. The chassis is now turned right - Three 41 -volt "C" batteries. 100,000 ohms. side up and the two -gang condenser is secured Optional Equipment: Both A.C. and D.C. filament voltages are to the deck at the right side. The combined accurately measured on the one meter. Con- One Crowe ornametal metal cabinet, outside di- tains new wiring and socket volume control and switch is mounted on a right- for taking care of mensions 10x6tux4% inches deep: new small 7 -prong tube as well as larger 7- angle bracket at the left as illustrated. front, One miniature vernier dial. prong tube. It is equipped with a small diam- The midget speaker is mounted at the front cen- eter -adapter views plug for testing in new sockets. ter by means of small right angle brackets. (Under of this receiver may be obtained Try this amazing tester one day and you'll by sending 5 cents to the author.) wonder how you et or cot along without it. Wiring the Receiver The set is now ready for wiring. The filaments are wired in first, the negative line being THE "RADIOLAMP" TABLE Only $15.00 Dealers grounded to the chassis. Switch (23) is wired (List in series with the line. Grid and screen -grid cir- RECEIVER 525.00) cuits are wired next, then plates. bypass con- Your jobber can supply you. If not, or- densers, etc. The flexible wire with screen -grid (Continued from. page 650) der direct. We will ship the No. 710 Tester directly to you -when re- clip which goes to the cap of tube (5) is soldered One Acratest volume control with switch, 250,- mittance accompanies your order at to the stator of condenser section (3). The 000 ohms. R2; the dealers net price, $15.00. other flexible lead to the cap of tube (12) is One Aerovox resistor, 50,000 ohms, R3: brought to the deck through a hole in the chassis. One Acratest resistor, 2.5 megohms, 114: a fiber terminal strip is used as If shown in One Aerovox resistor, 1. meg., 125; READRITE Figs. A and B, this should be put on after corn - One Aerovox resistor, 1,500 ohms, R6: pleting as much of the wiring as possible at Two Find -All aerial couplers LI, L2 and LI. L4: sockets (5) and (12). This strip is fastened One 15 henry choke, L5; Meter Works about % inch from the underside of the chassis One type 39 tube; 53 deck by means.of 1 -inch screws which also serve One type 36 tube; College Ave., to fasten the wafer sockets (6) and (12). After One type 38 tube; Bluffton, Ohio the wiring has been completed, the correct am- One type 12Z3 tube: perites are inserted in the mountings and the One 40 -watt lamp; three tubes are put in their respective sockets. One Premier loudspeaker unit; Readrite Meter Warka, The batteries are hooked -up to the set and the Three five -prong sockets : 53 College Ave -, antenna and ground are also connected. One four -prong socket; Bluffton, Ohio One lamp socket with List bushing: of Parts One cord and plug; Gentlemen: One Cardwell dual midway, featherweight vari- One celluloid dial: Please send me informa- able condenser, .00035 -mf. each section, type tion about Readrite No. 710 Cone apex, cone and fittings; Tester. Also catalog of other servicing in- 407 -CS. 3. 9: Two Blan chasses, 5% by 6% by 1%, ins. deep, struments. One Find -All antenna coupler, 1; %n aluminum: One Find -All impedance coil, 7; One Blan chassis, 8% by 8% by 1 in. deep; Name One Electrad 25.000 -ohm tapered volume -control Two Blan sides, 5% by 6 by is ins.: potentiometer, type 121280 -P, 26 with switch One Blan back 5% by 6 by tá ins.: 23: One Blan front 5% by 6 by tie ins.; Street Address Three Aerovox .02 -mf. cartridge condensers, type Two No. 10-32 threaded brass rods, 8 ins. long; 270, 2. 15, 18: Screws, nuts, etc. City State

RADIO -CRAFT for MAY, 1933 685 HEADQUARTERS THE 37 "RECTIFIER" for Service Men's & Dealer's William Rankine* phis Jiandy In view of the rapidly increasing popularity 6s- of the so- called "Universal" receiver, tube manu- Replacements Repairs facturers have been giving consideration to the Power Tron. ro,er, rewound at lowest w"t; all types of impedance rcl,ius d I,ne tr n.formen for broadcast .teas use nuke trans- development of special types of tubes for use as formers all of amplifier transformers. or .oyes otherther ' is wound wrihlpw w or. tell us what yo, .ant.. we will engineer rectifiers in receivers of this nature. While it is MAGAZINE you roll. without extra possible that satisfactory operation can be se- We design all ty of precision .wound choke. indoclane.. and I.F. Coil. for any frequency. cured from these new tubes, it is also desirable Loom Enohn era -A -'r ,m el lute. n de from the standpoint of economy, to keep the ,. .tall- r r impedanceo used in L 1 ed -brae. f, number of different types of tubes on the market mated lir osoldered tout... .91.9S Per na- for as low as possible. This is desirable for two Binder A a 1f' t 'ondw,er Mike Head for only $16.65. Thh is n precision herd; reasons. and serv- In , hat curve from 3e to 7 Mr ycl o wt of 7200 ,N\ik' specific First, the dealer the headnw i performance. A new simplified design nukes this r possible. iceman is not compelled to carry too large an in the consumer Mr, o, n,! a r e Stretched diaphragm mikes investment stock and secondly, converted IMO otlel r hads..ender a mike for s may always be assured of satisfactory service in for all copies of 1 1 you .bl. n Ilyd'an. Amphh . Transformer lireurn or dojos t dur . for estimates.,ate.. the event of his receiver becoming faulty. We arc i.md for rall V testingt n the tel.et e From a standpoint of the Service Man, the 11 y need w either for radio or n amplifiers. dealer or the radio set owner, there are four nn°ïIda nnue give °hn.rá;. hrt sedi.:.`i°:,. it. nut write essential points to be considered in the selection RADIO -CRAFT For 31.50 . aal send y ,id, calibrated eeLa ",for the ee de. of ado neffr ndr `chu .II,"\II of a tube for any particular function in flu ma u.lmr ore eh.ulutely guaranteed to be retrwnnted receiver. The first is that the type is of a standard nature and one on which renewals may .send ee.Manee in form of check or n v Order. easily be obtained, as a result of complete dis- RADIO RESEARCH LABORATORIES tribution. It should be not more expensive than Manufacturers, Designers, Consulting and the type which it replaces. It should, as far as Experimental Engineers possible, either reduce the number of component noun California Ave., Ft. Wayne, Intl parts required for the circuit or at least it 20 yearn in the electrical and radio field should not require additional parts. The fourth and possibly most important point is to determine whether or not the tube will give a satisfactory account of itself throughout its life. Following the test made in the laboratory of RCA, on tests made with the type 37 tube, for Short Wave use in rectifier circuits of this nature, we have come to the following conclusion and have, therefore, determined not to introduce another type Specials of rectifier to accomplish this purpose. The circuit characteristics of these small receivers are now quite well known and, since it is not RESCO 3 Resco S. W. 5 necessary the rectifier tube to supply morn RECEIVER Tube A. C. for than approximately 20 ma., it is not necessary 1 -34 .Meteco Grid an.l Receiver 2 -30 tube.. constructed u for us to use one of the mercury vapor tyln,- qua lity Pa ihroughou. ,ring (2) 57'8- capable the aluminum "cheeia n d 21 We and ti) rectifiers or a rectifier of delivering d. Vernier dl.l. range 280 rectifier. Alu- amount of power which we can take from a is_a0 M. minum chassis and AaaerraNd, Wired and vernier type 80 high- vacuum tube. áúel with RADIO CRAFT Tegtad L Special For the purpose of our test, however, we de- $9.75 less tubes 517.95 less tubes cided to put the tube on a life test which would is not a magazine which is read hast- be much more severe than it would ever en- ily and then discarded. Readers keep SHORT WAVE BARGAINS counter in practice. The tests were conducted with a drain of 40 ma. at 135 V., D.C. be- their copies for years -use them re- 34 V. 8amp. hl. Oran.. ''wail 81.69 Set of 4 .hart wave plus -in eon. 1.79 tween the heater and the cathode. Under these rondos head phones per pr 1.36 peatedly for reference, for "dope" on Bakelite dhd. .la conditions, the filament voltage applied to the ' Bakelite Vernier arils A9 new tubes, for service hints and short aakeate coil form. rihhed I9 type 97 tube was 6.3 and the filament current Wafer akRey¡. 5 or 6 P...11 - .9 -A. The maximum voltage applied was Telegraph plate cuts, for kinks, etc. 125 and the drain approximately 40 ma. All Merchandise Guaranteed Several types of "universal' receivers were Now the publishers make it possible Radio Electric Service Co., Inc. operated with the type 37 tube as a rectifier with the following results. Where the load was for you to save every copy and for L.E. Cor. 7th & Arch Sts. Phila. Pa. 20 ma., the average D.C. output of the tube was this purpose a special binder has been 103 volts. The maximum voltage delivered by any of those tubes tested was 108 and the designed to preserve twelve issues. minimum was 97.6. This variation was noted This handy binder is made of a in about 10% of the tubes and even with this material and is variation it was found that there was no appre- heavy, substantial ciable difference in either sensitivity or power covered with black grain leatherette. USE OHIOHM output. Furthermore, it was found that the The name RADIO -CRAFT is hand - SETS use of the 37 eliminated the generation of R.F. SPARK SUPPRESSOR noise, which sometimes occurs when other types 'omely stamped in gold on the cover. for eliminating Ignition Inter- of rectifiers are used in these receivers. and it ference on Automobile Radios was therefore unnecessary to use the R.F. choke, An ingenious mechanical arrange- required when the other types of tubes were ment is provided which makes it pos- used. Of course, when the 37 is used as a For 4, 6 and S cylinder cars. Furnished complete with condenser and necessary rectifier, the plate and grid elements are fastened sible to hold copies flat when reading spark suppressors. Lasts the life of the together. This may be done by tying the two from the binder. car. Special non -shorting, and temper- terminals of the tube socket together with an resisting features. ature and vibration ordinary piece of bus. bind- Cash in on this growing market. Therefore, we are of the opinion that when The RADIO -CRAFT design engineers recognize the fact that this er is shipped anywhere in $ 2 5 THE OHIO CARBON CO. tube will perform all of the necessary functions LT. S. prepaid for only $125. for the "universal" or "A.C..D.C." type of Canada and foreign 25c ex- Cleveland, Ohio receiver, it will rapidly come to replace those special tubes which have been developed to take tra. Use the coupon below to order. care of this job. - -Mail This Coupon Today- - 'Engineering Dept., Triad Mtg. Co. RADIO -CRAFT Magazine AUTOCRAT AUTO RADIO 96 -98 Park Place, New York, N. Y. A. C. OHMS LAW? Fn9need you will find my remittance for E1.25 6 TUBE Many set constructors and Service Men do net It'Irerk. stamps or money order accepted) for uhirh seem to realize that Ohm's Law applies to A.C. u are to send me, postage prepaid. the RADIO - Quality -Tone - Selectivity H Power l'ItAFT BINDER. large enough to hold twelve Issues. filament circuits as well as to other portions of Complete 529.40- includes set. remote control. suppressor (Canada and foreign add 25e extra.) kit. tubes, mounting brackets. dynamic pkr.- antenna. the radio circuit. They use thin wire for the Set only $10.78. Also 4- 5- 6Tube Midgets with latest heaters -usually about No. 18-and then wonder Dealers wanted. Write today. tubes at low prices. why the tubes at the end of the line show low AUTOCRAT RADIO CO. filament voltage. 3655 N. Hamilton Ave., Chicago, Ill. Tubes of the 2.5 -volt series draw an average of 1.75 amperes each. Eight such tubes will thus take a total of 14 amperes, which is a lot can be of current, anyplace. No. 14 flexible wire BACK ISSUES of RADIO-CRAFT in had at the price of 26c each. Address should be used, or two strands of No. 18 State RADIO -CRAFT, 98 Park Place, New York City. parallel will do.

686 RADIO -CRAFT for MAY. 1933 INFORMATION BUREAU THE WHOLE WORLD SPEAKS - (Continued from page 677) other possible causes of mat- performance, are contained in the October, 1932, issue. pg. 229. Thru As the corrected circuit indicates, the screen - grid of V3 should have been connected to the battery side of the output load (headphones). instead of the plate side. (Q.2) F. M. Moran, Bessemer. Ala. On Pg. 716 of the June, 1932, issue of RAnto -CRAFT you gave a description of how to build a radio "treasure" finder. I have completed one as described in the magazine and have tried it out. It works O.K. on a buried six -inch waterpipe, but I have not had any luck on anything smaller on account of ground capacity. I have buried a cast iron water kettle but I cannot detect the difference in sound by ear. There are body and ground capacity effects which prevent my getting the desired result. I have worn rubber hipboots and this cuts down some of the capacity effect. I am The New thinking of using a galvanometer in connection with the ear phones. There is a machine that they claim will ADMIRALTY SUPER -15 locate gold and silver. I was talking to a MULTI -WAVELENGTH SUPERHETERODYNE man the other day and he said that he could engineering. the world's most advanced Radio Receiver. This great locate a bulk as small as 18 silver dollars. In design and new 16 -Tube Model opens up a vast new stage of magnificent entertainment. He saw the machine that I built and said Dependable long distance reception with the lure of overseas programs via short that if I could get rid of the sound only waves, as well as your favorite broadcasts as they originate at the station. This when I came in contact with metal, it would is the true Romance of Radio that awaits you. work O.K. The Admiralty Super -15 provides the maximum in sensitivity. selectivity and Please tell me how I can make the ma- quality of reproduction ever promised. chine silent only when I come in contact with Corn pl, t e tits rn to rr nvn t on rrq test Address metal. (A.2) Note the reply, above, to Mr. W. NORDEN -HAUCK ELECTRIC & MFG. CO. L. Patrick. 402 Cherry Street, Philadelphia, Pa. U. S. A. We see any wanting a cannot logic in -Builders Of the Highest Class Radio Apparatus in the fl'orld." machine that would operate only when "contact" had been made to metals. If you could come that close, what would be the use of a "locator"? RCA VICTOR A.F. MODULATED Taking the view that what you want is a R.F. OSCILLATOR more sensitive arrangement, we suggest that you add one more tube to the output circuit (197) Mr. Paul Connelly. Duboise, Ia. of the receiver,, and connect in the output (Q.) What is the schematic circuit used circuit of this added tube a sensitive "out- in the R.C.A. Victor "Standard Signal Gen- put meter." These meters are now obtain- erator"? able for use in servicing radio receivers, (A.) In Fig. Q.197 is illustrated the cir- where an accurate, sensitive instrument is de- a signal generator design. The con- sired to indicate the exact point in the ad- cuit of nections are those of the R.C.A. Victor type justment of a circuit when maximum (or min- TMV -18 -C Standard Signal Generator. By imum) reading is obtained. You may keep plug -in coils the R. F. range your headphones in the output circuit of the means of six extends from 90 to 10,000 kc. The A.F. preceding tube, as usual, in order to "mon- the fixed frequency of the "treasure" finder. modulation is 80% at itor" the operation of The output voltage range extends We wish to point out that continued use of 400 cycles. from 14-microvolt to 2 volts. The output the finder will enable you to Improve your attenuator, except for the technique and thus more readily secure good impedance of the results. higher multiplier values, is 0.7 -ohm. External modulation may be conveniently used. Ther- mocouple 42 is of high -resistance type and AMRAD "S" TUBE provides a means of accurately measuring the voltage input to the attenuator even at the (195) Mr. Charles Parker, Buffalo. N. Y. extreme high frequencies. All available data (Q.) What are the characteristics of the appears in Fig. Q.197. A front -view illustra- old Amrad "S" tube, and how is it used? tion of the instrument is Fig. Q.197A. (A.) The Amrad "S" tube was one of the r. first filamentless or gaseous rectifiers, and is I classed with the better -known "Raytheon" group of tubes. A SUPER SENSITIVE ALL -WAVE The model 3000 S tube is a 20 watt, half - CRYSTAL RECEIVER wave rectifier tube designed to deliver 50 ma. at 800 to 750 V.; approximate life, 3,000 (Continiod from pope 68o) hours. The S tube fits a standard screw condenser setting for loudest signals. base. Operating normally, the S tube is just To tune to the higher frequencies, move the too hot to touch; however, when the tube right -hand switch (marked "right" in Fig. 1) becomes overheated due to overload, the in- forward, clockwise. one to three taps before terior of the glass stem becomes conducting advancing the left -hand switch arm. The effi- in both directions. The primary of the power ciency of this set seems to lie partly in the transformer must be protected by 3 A. fuses. low -loss coils, but mostly in the one basic the new 50e A schematic circuit incorporating two S change in the circuit, in which the detector is tubes in a full -wave connection is shown in connected permanently to the last turn (from Cent eolith Vol III Fig. Q195 Around) on the tapped colt Control Guide of Parts BULOVA CLOCK-RADIO List Thousands of these new Guides are now One Puretone or Rotorit crystal detector (or doing signal service in helping serv- (196) Mr. Ernest A. Feiring, Akron, Ohio. a good piece of galena); icemen to do a more efficient and satis- (Q.) In the April, 1982. issue of RADIO- One tuning condenser. 500 mmf., Cl; factory replacement job . . . with, of CRArr, on pg. 656. appeared an illustration of One fixed condenser, .001 -mf., C2; course, added profits. the Bulova clock -radio set. Has the sche- One set of coils (see text) LI, L2; Send for the Centralab Guide on your matic circuit of this receiver ever appeared One pair of headphones (Baldwin. Brandes, stationery Address Dept. C. in RADIO -CRAFT? How does the clock operate etc.) ; radio set? to control the tap switches, "right "; (A.) The schematic circuit of this in- Two "left." strument, the Bulova model 751 clock -radio Eleven taps; set, is shown for the first time in RADIO-CRAFT One baseboard, 7 x 12 x % -in; CENTRAL RADIO LABORATORIES in Fig. Q.196. This circuit tells the story. One panel, 7 x 7 x Vs -in.; (Continued on following column) Hookup wire, screws, etc. 930 E. Keefe Ave. Milwaukee, Wis. RADIO -CRAFT for MAY, 1933 687 SERVICEMEN THE MICRO -MIDGET SET HERE ARE YOUR LATEST NEEDS ANALYZER GET,THIS ADAPTER TO MODERNIZE YOUR TUBE (Continued from page 663) CHECKER SSOXYL Universel Tube Cheek- NOW No adapters ' Adep caeca per NE are required with this analyzer, TUBES. tNei - re. -,n f° Jr ó except the analyzer adapters which are P i 1)4 toiope.ot ir. plug of tt du and direction hat- the 6.4, 6 -5, and the 6 -7 type. The analyzer ing overo s0 NEW TUbEi with e ee recording aie e el plug is a six -prong plug. Only two sockets h.e and fu t der eg Plod are used to take care of all tubes; one socket .. with all order. .00 READY l'I '1I Prise $6.00 is a 4 -, 5 -, 6 -hole composite socket, and the 11 itch the 96490E adapterrmust heused on the other one is a 7 -hole socket for testing bas of the 950x11; 9645CL UY UX 7 -prong tubes. botp,m -with C. G, Icud. 1.1.1 l'rire y 1.25 EQUIP YOUR ANALYZER WITH THIS All parts are mounted on a panel measuring PLUG AND BRING IT UP TO DATE. 7x7% in. I used an old Music Master DIAGRAMS AND DIRECTIONS SENT panel: 17tß FREE WITH ALL this panel incidentally cost me 20 cents. thus 907LC Famous Ns-Ald Latch Lock saving myself about 78 cents were I to buy Analyser Plug with Twin C. O. Handle and Bfivpe feet of eight -wire made attached. a new one. RADIO -CRAFT f077WW1. (a.W,uvutebeddi Lit Pric...í3.5Ó The photograph of Fig. B shows the posi- The 907WL basic ploy fits the 59 even prong 97be socket. For U X 4 hole ,chetg. he tion of the various parts that go into the 4153adapter Is snapped onto he plug:' ter construction of the analyzer. Yt6 hole sockets. the 97511$ is used: for 6 con- The meter is tact Inc 9701)1 and for the new email mounted bear the center of the panel (see else 77mntaet Imebt t omit for the 247 -U7. ul,s. ,e 9 -]U5 dopnt M tired. Fig. A, also); Sw.1 to the left of the meter; All o/t the .In,.'e f" , 9 74111. 761)i, 07004 INDEX 1,77115 Sw.2 to the Ar,ciate Adopters. right of the meter; the battery contains a an Sl.2S itch adjuster It thorough, alphabetical and topical rheostat, R7, and the A.C. -D.C. arrangement of EVERY article and subject REPLACE YOUR OBSOLETE switch, Sw.4, are placed above the meter. which has been SOCKETS AT EST published in all the issues of COMPOSITESOCkf 1 The seven-prong socket is placed to the right RADIO -CRAFT from July, 1929 to June, 1932 'tan of 10110. the A.C.-D.C. switch. The 4 -, 5 -, 6 -hole composite socket is placed to the left of R7. Radio lien hare conclusively proved to us the need and -i prertlrability for a book with h has Included In it, a com- The 1,000 -ohm resistor, R6, and the 4.000 -ohm prehensive and complete listing of eery article which has resistor, R6, are placed on top of the meter. thus far been published In RADIO-CRAFT. A book which has each topic while beneath the two resistors is placed the so sub- divided and cross - indexed small that a mere glance at a subject will glue you any num- rectifier. Directly below the meter are brr of classifications and uses of R. For example, if shown the four push button switches: the you look at tubes, Volt find under this topic, various sub- titles. power, reversing switch is in the center, as are also general, transmitting. photo -relis, testing of tubes, thyratone, etc. Every article or notice in the Price. the four resistors, Rl, R2, R3 and R4. The book has been considered so deeply Important that when you refer to a certain classification, dot four binding posts are mounted on the sides listed below the uln topic, you will find perhaps a dozen or more articles of the panel above the meter. The 4.5 volt treating !nr'11 n -I the subject from different angles. Tie author In rase ..le sicket. Litt Prue :1,500 "C" battery is placed in a separate box. arb Is given -tiro exact issue in which the article Price. appeared, and on what page it Is to be found. So hole The position of the switch when making ac- 47,) sehet, Lief . ,f0 curately compiled, by C. W. Palmer, one of radio's fore- 437 7 hole peter, Litt Prim. .35 tests is shown on most writers, 436 6 hole wicket. ddat,Prim. .25 the chart in Fig. 4. When that in less than two minutes you can turn 425 6 hale Pocket. List Pries .2B using the chart, the following should be ob- to any rticle- needless to wade through all the Issuer 424 4 hole wehet. List Price .2S of RADIO -CRAFT which. have been published during the served: past three years. TREAT YOUR OUTPUT METER TO J THIS ADAPTER The RADIO (1) The left column refera to the type of -CRAFT INDEX is exactly the same size e the monthly tube under test; magazine -it hoe 21 pages. It can be con- kept on file with the copies of the magazine-- (2) All letters in the other columns refer venientlyready for quick reference. The Index is printed on good to the position to which the switch Sw.1 paper with self covers. This book is sold 9144 e Su must be rotated in order to obtain the read- only by the publishers at 25,' the ing indicated r tar. 11.11 coupon below for your copy of the RADIO- 'q! NFRF'G TM- DO1CNFST.-tOWfST at the top of the column; CRAFT INDEX. :rp. COST tIOmRNInNO / mYOUH p0f (8) Grid No. I is the input or control .3a 9GSDw grid: Briefly outlined below appears only a partial . 53.50 (4) Grid No. 2 is the screen grid; contents of the book 9T, 965DSw I i9h50w Mw (5) Grid No. 8 is AMPLIFIERS V S2.6Ö the suppressor grid. PATENTS s7sow ANTENNA SYSTEMS- - n - PHONOGRAPH ,' CABINETS REPRO- tt 975DW I - 13.00 List Parts CIRCUITS-- DUCTION A N D RE- . of ë ïosw .a -al, hwk,ng Fwd. CORDING t V CODE - - cessa . One Tau -Rex copper -oxide rectifier; COILS AND TUNING POWER SUPPLY AND Send lugs, cow - - BATTERIES 111 One Jewell model 88 or Weston COMPONENTS - l eg all kinds of socket: P con - model 801, - RECEPTION 9rIOW coil toron, etc. Bs, COOPERATIVE LABORA- - tan. 0 -1 ma, milliammeter; REMOTE CONTROL Send a dime for the Na -AM Adapter Data Sheeteshcw- TORY - - diagrams of over 300 different adapters for even One special switch, as described, Sw.1; DETECTORS AND SELLING AND MONEY y RECTIFIERS MAKING SERVICING aringdapter s fo r.piCkups. s microphones. ououtput aerss,meters, tone One Eby double-pole, three -position switch, EDUCATION - SET CONSTRUCTION - controls. short wave converters. tube hecken, t an- - - yeen, etc., directions for modernizing obsolete set Sw.2; INTERFERENCE AND SPEAKERS AND REPRO - HUM DUCERS- analyzers, new tube -prong connections. etc. One Yaxley double -pole, double- throw switch, ELIMINATION - on test the 25_and 30 volt KINKS - TELEVISION - tubes )with any tube. e ckerto Sw.3; MANUFACTURING TONE AND VOLUME METERS - Servicemen s Discount 33% One Yaxley -pole. double AND TESTING CONTROL- On orders amounting to List .. 40% triple -throw switch, EQUIPMENT- TOOLS $10.00 Sw.4: MISCELLANEOUS- TRANSFORMERS- MOTION P ETT ALDEN PRODUCTS CO. Four Yaxley single -pole. single -throw push- I C T U R E TRANSMISSION - Dept. R -5 715 Center St. RECORDING AND TRANSMITTERS. -ALLA button switches, Sw.5, Sw.6, Sw.7, SW.B PROJECTION TUBES CA V BROCKTON, MASS. MUSICAL - - One Precision 10,000 -ohm resistor, type A, INSTRU- LIST OF BROADCAST. MENTS - SHORTWAVE AND R1; NEUTRALIZING- TELEVISION NOVELTIES- S T A - One Precision 100.000 -ohm resistor, type A, TIONS- 5eirsilia4 R2; 7ol4*4 ABSOLUTELY NOTHING SHl1RE One Precision 500,000 -ohm resistor, WHICH HAS APPEARED type A, IN RADIO -CRAFT HAS BEEN OMITTED FROM MIROPONES RS; THIS VALUABLE COMPILATION One Van I. meg. resistor, R4; One Acratest 1.000 -ohm resistor, wire wound, Clip and Mail Coupon SHURE BROTHERS COMPANY R5; Today! Manuleeturerr- re4hee,. One Acratest 4,000 -ohm resistor, wire its SHURE, P.. wound. r WEST R6; 337 MADISON ST CHICAGO, ILLINOIS Publish, -ri of RADIO CRAFT. RC -:33 One Clarostat 5,000 -ohm rheostat, R7; tub us )'ark )'lire, New York, N. Y. One General Electric 7 -wire cable; Enclosed you will find my remittance of 2.. -m (check, .tangle r looney One Federated 6 -prong analyzer plug; order al rented) for wkhh you a BINARY LOGARITHMS to d me, postage prepaid one tont of the (Base 2- Octaves) One Eby 7 -hole socket; Vl; RADIO -CRAFT INDEX. Pamphlet of 24 mimeographed sheets. Bilogs One Na -Aid 4 -, 5 -, and 6 -hole composite of 1024 integers with data for all numbers. socket. V2; Simplest system for comparing periodicities- One bakelite panel, 7x7,/4 in.; Name sound, electromagnetic, etc. Reduces array of Four non -removable binding posts, BI, B2, integral ratios to greatest possible simplicity. B8, B4. TWO DOLLARS. One 4.6 -volt "C" battery; G. H. POHLAND, 1149 Felton Court, CHICAGO One pair of test leads; One Eby 6 -to -4 analyzer plug adapter; One Eby 6 -to -5 analyzer plug adapter; City One Na -Aid 6 -to -7 analyzer plug adapter; There hall been rumor circulated by our com- acne that Lae Mark death, it har been grossly We Wisely moved Wedo not NM State...... _..._...... - ...... _._..._..._..._..... lo Eagpeerimenten. catalog but luv. the`G. selection W aid d 'AVEN'T YOU? . new rads rt. in the wo THIS BOOK CANNOT BE MAN, One of the saddest letters ever received BOUGHT ON THE NEWS- 171 SreedmiSIIi St ,W ow York, N. Y. by the B. B. C.: -"I 'ave a license since STAND -ONLY DIRECT 25c four years and 'ave not heard nothing." FROM THE PUBLISHERS THE COPY (Wireless Weekly)

688 RADIO -CRAFT for MAY, 1933 BUILDING AN ALL -PURPOSE TESTER (Continued from page 659) in the dark so far as the average Service Man "Milli -Amps" Switch, S3, permits the selection is concerned -especially when new tubes, auto- of any one of the following ranges: 0-1, 0-5, matic volume control, and complicated circuits 0 -20, 0 -100, 0 -260 milliamperes. The reverse are involved. All this guesswork has been switch previously mentioned can also be used eliminated which not only makes this analyzer for the current readings. simple to build, but easy to operate. in a self - Parallel shunts for the current ranges are instructing manner. in parallel with the meter resistance, thus mak- A -C -RADIO The various socket holes, looking up and going ing the total resistance of the corresponding TELEVISION the EVERT ELECTRICAL clockwise, are correspondingly identified as fila- milliammeter ranges even smaller than SUBJECT COVERED ; is a decisive ad- ment plus. (FX) : plate. (P) ; grid, (G1) grid, shunt resistance itself, which Here's great news for anybody interested in vantage, especially when tubes (G3) ; screen, (S) ; cathode, (C) : filament minus testing output Electricity. BRAND NEW 1933 edition of Ap- (F -); and grid 2. (G2). the latter denoting the having large plate currents. (Providing that a plied Electricity brought right good. low- resistance shunt switch is employed, grid cap. The ground binding post is identified FOR down to date with every NEW as Gnd. (See Fig. 2). the milliammeter ranges may be extended into Electrical subject fully covered. several amperes.) This makes the milliammeter AND EXPERTS The various tube elements being thus identified Over 3000 pesen 10 big Volumes and all shipped are all connected to two sets of switches. which. of the low resistance type, having less than 1 -hundreds of FREE for examination. in turn, are connected to the meter terminals. ohm resistance for the 0 -1000 ma. range, and illustrations - tube currents under the in n,t One of these switches consists of a rotary switch permitting the reading of plete erk of it BIG FIELD! Big Demand! named This switch is usually actual operating conditions. tied ever pn + wl, o ,. Sl "Analyzer." II- .ed. 'e Big Pay! in a certain position, such as the one (G) To make resistance tests, employ the ahtlen i,nd kept motors.t , -'de, right in thn uwnndla marked "Gnd." The other switch (S14, S15 ... two lower right-hand binding posts, BP3 and 4, hi- tries . Auto, e ea machine as a bank of with the rotary "Testa" Switch, S4, in the diesr, t s- lira. tirai! every industry l 21) can be easily identified push- everythier on eleetrie,ty and men who button switches on the bottom of the panel, Fig. "Ohms" position. A self- contained 4% -volt "C" Ir, tricnl w' this asLie,t ranks big A. Once a certain voltage range has been battery and a bridge circuit are employed (as Isined heant, fascinating work, to ,Wynne I,v,rn and do: learn key with these 1 on as chosen with the "Volts" switch in Figs. and 2, described further and shown in Fig. 3C). ,ado rstnud Ino,kn. Send coupon for e +,t for it is merely necessary to push any one of the insuring permanent accuracy of the scale cali- FREE exxnnnau.m and see for your- switches just referred to (S14, 16...21) to bration, even should the battery voltage drop. If obtain the desired voltage reading to ground. A rheostat is provided to compensate for the A ye r consulting membership in tie. Amer ,. , Terha .al i n now given tee 0 Of course, all the readings can be obtained with latter. The scale is calibrated from to 100,000 n,l r ,d,. .dt /o, bu - I'vrIene,din FREE :1e , ',I ..flint'. Dilli respect to the cathode: for instance, by turning ohms. By turning the rotary "Tests" switch, .. the "Analyzer" switch, Si, to the C (Cathode) S4. in the R /10 position, the range is reduced , position. It might be well to mention that all to 0- 10,000 ohms, permitting the reading of such AMER CAN TECHNICAL SOCIETY Dept. ES36, Drexel at 58th St.. Chicago these voltage readings may be either A.C. or D.C. low resistance values as 5, 10, and 15 ohms. and that the polarity reversing switch, S9, can (Of course, much smaller values of resistors as AMERICAN TECHNICAL SOCIETY, also be used for them. well as resistors ranging up to several megohms, Dept. E536, Drexel at 55th St.. Chicago can be measured with a suitable external voltage Bend for 10 day, free n e, BRAND NEV. ' 10 V01011%1, set of (D) Current readings in four different tube Electrical Engineering. s In return far mailing this coupon element circuits may be obtained by bringing the source in conjunction with the largest current n,,,,nntb, send absolutely Gee, certificate of membership in the American Technical Society entitling me to free consulting S4, into the M.A. (milli- and voltage ranges of the analyzer.) rotary "Tests" switch. privilege for one year. 1 will pay Use few rents delivery ampere) position, and by throwing any one of (H) To make impedance tests, use the two charges on the taroks. If I wish 1 nmr return them in 10 day+ M.A. toggle switches (S5, 6, 7. 8) in lower left hand binding posta BP7 and 8, with and o .e you nothing. but if I keep men, I will send 52.00 the four after 10 day., then $3.00 a month until the Special sale price the "on" position. The "Milli -Amps" rotary the rotary "Tests" Switch, S4, in the "Imped- of only $29.80 is paid. switch, S3, permita the selection of any one of ance" position. For making these tests it is Name 0 0 -100, necessary to employ 100 -125 -volt, 25 -60 cycles, five milliampere ranges: 0 -1. 0.6, -20, Addrem 0 See Fig. SA. Two push -buttons (S12 A.C.: hence the necessity of a conventional line -250. City State and S13) identified as "Grid Tests" permit the cord and plug. A rheostat "Impedance -Ad- Employed by so- called grid tests to be made. A separate juster' makes a zero impedance adjustment pos- 4%-volt "C" battery, E2, is provided for this sible in order to compensate for various A.C. Addrew purpose. (This battery insures greater circuit line voltages. As will be outlined further on, simplicity and less interdependence of one test it is possible to measure capacity, and the im- setting upon another: it also practically doubles pedances of choke coils, transformers, etc. The the life of one battery.) By pressing one of circuit is given in Fig. 3D. these buttons a change in plate current read- For large impedances such as that of an ings may be observed, which change in reading impedance of a 0.01-mf. condenser, the unit is commonly considered as the most satisfactory under test is placed in series with a 50,000 -ohm P index of a tube's condition. (See Fig. SB.) All resistor and the A.C. line voltage. The meter R D.C. and A.C. voltmeter ranges are protected itself has a 50,000 ohm series resistor, thus act- by two suitable 10 -amp. fuses, insuring endless ing as a high resistance voltmeter and measur- o life to the meter and rectifier. ing the A.C. voltage across the impedance under VE Fleure 2 serves not only as a complete schema- test. This impedance may be that of a resistor, tic diagram, but. as it shows every single lug of of a choke coil, of a transformer winding. of a all the parts used, it becomes at the same time condenser, etc. When the impedance toggle I a layout point -to-point diagram. Referring to switch S10 is thrown to the low impedance range. N. the four pole rotary switch, 54. all indexes No. the impedance under test is placed, in aeries with 1 refer to the first rotary section, all indexes a total resistance of 100,000 ohms, across the No. 2 refer to the second rotary section, etc. A.C. line, and the meter is acting now as a low - All letter indexes refer to the same contact voltage voltmeter. (Should a fully charged con- FLACON number of each rotary section. denser be placed directly across the meter, it is A further inspection of the panel will reveal protected against injury by a 1 /100 amp. fuse, TYPE "B" DYNAMIC UNITS four pairs of uniquely designed binding posts F2). have been proven in the field identified as "Volts," "Milli -Amps" "Ohms." The meter scale itself is not calibrated in and "Impedance." Into these parts test prods terme of impedances, but impedance curves can must be inserted in order to obtain the cor- easily be drawn up with the aid of a few known Compere these features: responding external tests as follows: values. (E) To make external A.C. and D.C. voltage (I) The types of novel three -in-one binding Peak Power -50 watts tests, use the two upper right hand binding posts and test -lead jacks employed are of in- Continuous Power-30 watts terest; the tops of the binding posts used Five types for every purpose posts, BP 1 and 2, Fig. A, with the rotary switch on the Cadmium -plated -all metal S4, in the "Volts" position. The rotary switch, panel are equipped with tight gripping, self - Wide -range quality. S2, marked "Volts," permits the selection of contained jacks, into which can be inserted the any of the following voltage ranges: 0 -5, 0.10, spring constructed test -cord plugs. They allow Effective March 1, 1933, new lower 0 -50, 0- 100, 0 -250. 0 -500, 0 -1,000 volts. To the almost instantaneous changeover from one test price. on all units- Illustrated above left of this switch is a semi-rotary switch, Sll. to another, by merely removing the test -cord -the type B Master -50 watts peak - 340.00 list. which permits a choice between D.C. or A.C. plugs from one set of binding posts and insert voltage readings. A polarity switch, SO. denoted ing them into another. Both the binding posts Write Dept. RC -3 for latest catalog as "Reverse." reverses the meter reading, should and test jacks are multi- colored, making the of p. a, horns and units. the test leads be used in a wrong manner. polarity indication automatic. The binding post heads are, at the same time, of the screw -down Heron horns and Units are toveral by l'. S The various voltage ranges are obtained with Patents Nos. 1.507.711: 1,501,032: 1.577.2711 the aid of the rotary voltmeter switch S2, shown type, and permit the horizontal insertion of any 73.217: 73.218. 1.722.448. 1.711.514; 1.781,489 1, various resistors in test leads, either through a traverse hole or by 1.832.808; 1,831.327; 1,835.739; 1.815,210 in Fig. which introduces 1,,78,3611; 1,888.112. series with the meter. As the meter employed twirling around the threaded stem. When the is an 0 -1 milliammeter, the voltage rangea ob- test jacks are engaged into the binding posts, tained all have a total resistance of 1,000 ohms no metallic surface is electrically exposed, and RACON ELECTRIC CO., Inc. per volt on all D.C. ranges, and somewhat more loose metal parts or wires may fall safely on New York, N. Y. on all A.C. ranges. the analyzer panel without causing any electrical 52 East 19th St. (F) To make external current tests, employ disturbance whatsoever. the two upper left -hand poets, Fig. A, BP5 and (J) Point -to -point resistance measurements 6, marked "Milli- Amps." With the "Tests" can be made in any chassis under test with this switch, S4, in the M.A. position. A rotary (Continued on following page)

RADIO -CRAFT for MAY, 1933 689 analyzer with relative ease, due to the fact Build a that all the analyzer tube sockets are normally electrically disconnected from the meter. In order to make these resistance tests, simply insert the analyzer plug, AP. directly into 8.100.00 any receiver TREASURE or amplifier socket. Now insert the teat plugs into the "Ohms" binding posts. BP3 and 4. IN PRIZES! With the test prods fitting snugly into any two FINDER! analyzer socket prongs, the D.C. resistance can be read directly on the meter. (If the test jacks are inserted into the "Im- pedance" binding posts. the corresponding A.C. resistance can be obtained.) WHAT (K) A ground binding post is also provided is the on the teat panel with a corresponding lead and battery clip to permit similar resistance meas- BEST urements between any one of the prongs and the ground or chassis connection of the unit under test. A great amount of time is saved thereby while trouble shooting, because it becomes now unnecessary to remove the unit under Title test from its original location in a cabinet or to be forced to get with the test prods into some practically inaccessible area. for the Ordure helm.? List of Parts t )rle Coast -to -Coast portable leatherette ca,. feie .t COPY 12%x13x4?á ins.; One Coast -to -Coast black bakelite panel, drilL,d and engraved, 10x12x3/16 ins.; One Westinghouse 0 -1 ma. universal Rectos rectifier, (calibrated in A.C. volts, ohms, and D.C. volts), model CX, M: One Eby bakelite base mount, 4 -prong socket, model 5086, VT1; One Eby bakelite base mount, 5 -prong socket, model 5087, VT2: One Eby bakelite base mount, 6 -prong socket, We model 6187, VT3; supply One Eby bakelite base mount, 7 -prong socket. model 6187a. VT4; all Parts for Building Eight Coast -to -Coast special three -in-one hind - ing posts, type BPE619, BPI.. 2, 3, 4, 5, 6. 7. 8: Electrical One Carter single -pole. nine -position rotary and Radio switch, model 4075, Sl: One Carter single -pole, seven -position rotary TREASURE switch, model 4074. S2: One Carter single -pole, five -position rotary LOCATORS switch, model 4073a, S3; One Carter four -pole, five -position Radio, Audio. Ground Potential rotary switch, Measurements. Hughes model 4080, S4: Induction Balances and other types; including Oscillators Five H &H D.P.D.T, toggle switches, and amplifying systems. model 8351, S5, 6. 7, 8, 9; We supply all materials needed for building end oper- One H &H S.P.D.T. toggle switch. model 2196, ating any of the recognized treasure finders. S10: The following standard circuits are described in our One Carter T.P.D.T. jack switch, model 72:10n. bulletin: S11; At No. I. Ground Potential. Leap -Frog Method. Two Carter D.P.D.T. push- button switches, All 4 -Color Cover model 7237a, S12, S13: Large 9 "x12" in Size No. 2. Hughes Induction Balance Type A. Newsstands Over 200 Illustrations No.3. Hughes Induction Balance Type Two Carter On- and -Off locking -type push-but- B. tons, No.4. Sensitive Hughes Induction Balance. modela 5081e, S14, S15: R.t PIDLV increasing each day-are the nurnber of ex No. 5. Simple Super-Sensitive Hughes Balance Circuit. Six flush -mount buttons, model 4082, S16, 17, in -Ware field-developments 18, 19, 20, 21; sbilet r rr to thist branch of radio thousands of No. 6. Radio Frequency Oscillator Circuit. new "thrill seekers." Experimenters. as In the early No. 7. Audio Oscillator Circuit. One Cinch ground binding post, model 3283, days of Radio, again hare the opportunity M bring about stirring new Invent ions. In No. 8. BP9; head, SHORT WAVE Single Search Coil Hughes Induction Balance ('It AF ^r, the Experimenter's Magazine, how you can build with Audio Amplifiers. One Coast -to-Coast resistor, 19.75 ohms. RI; your own Short -M'ave Bets. both transmitters and receiv- No. 9. Combination Radio Transmitter and Receiver One Coast -to-Coast resistor, 4.16 er,. SHORT WAVE ('RAFT is exclusively a ,hart -wave ohms, R2; magazine circuit. One Coast -to-Coast resistor, 0.798 -ohms, R3; -the kind you have wished for so long. One Coast -to-Coast resistor, 0.317-ohms, R4; Also accessories such as Higb Frequency Buzzers, One Coast-to-Coast resistor, 275 ohms, R5: Interesting Articles in the Current Issue Audio Oscillators, Differential Current Trans. One formers, Two Stage Audio Amplifiers, etc. Coast -to-Coast resistor, 2,210 ohms, R6; A Three Tube "Stand -By" From A Radiale V, by A. R. One Coast -to -Coast resistor, 2,000 ohms. 127; Ap pelman. One Coast -to -Coast resistor, 2,500 ohms, R8; A "Plug- less" 3 Tube S -W Receiver. IVlih any one of these systems you can locate burled A Brand New Style ShortWave treasures. metal war relies, mineral deposits. subter- One Coast -to-Coast resistor. 5,000 ohms, 129; Call List, With Calls. ranean seater veins, Frequencies, etc., In bold type. buried gas and water piles, and One Coast -to -Coast resistor, 40.000 To lost objects, tools and treasures sunken In water, etc. ohms, 1110; How Get A License For Amateur Radia Stations, by One Coast -to-Coast resistor, 60.000 ohms, R11; "Bob" Hertzberg. 12,500 Mlles Write for pamphlet airing history and theory on this One Coast -to-Coast resistor. 150.000 On "Loud Speaker"-All On 2 -Tube interesting subject. All above circuits and systems are ohms, 1112; Oscillodyne- Verified by the Editors. One Coast -to-Coast resistor, 250,000 described and explained. List of parts and prices In- ohms, RI3; New "Dual Channel" S -W Receiver -which permits you cluded. (Price of pamphlet 10e.) One Coast -to -Coast resistor, 600.000 ohms, R14; to hear 'both ends" of phone talk. by C. E. Denton and L. W. Two Coast -to-Coast resistor, 50,000 ohms, 1215, Orton. 1216: The "Easy -Build" S -W Super -regenerator. Mail Coupon TODAY! S5.00 Monthly Prize For Best S -W Kink.. One Coast- to-Coast resistor panel; Short -Wave "Question and Answer" Bas. One Electrad 200-ohm, wire -wound rheostat, Short -Wave Beginner, by C, W. Palmer. GRENPARK COMPANY Dept. RC R17; 245 Greenwich St., New York. N. Y. One Electrad 4,000-ohm, wire-wound potentio- SPECIAL OFFER Enclosed find 10e for which kindly rend me COUPON pamphlet on Treasure Finders. meter, RI8; One Alden 7 to 6 -prong analyzer plug with SHORT WAVE CRAFT RC533 center pin and grid cap, model 7218a, with 9- 98 Park Place, New York. N. Y. wire cable, 5 -feet long: GET ACQUAINTED OFFER Newt One Alden 6- to 7 -prong adapter, model 72216; One Alden 6- to 5 -prong adapter, model 7221a: and foreign $120) for enter my ubsulptiona to SHORT-WAVE ('RAFT for g months. One Alden 6- to 4 -prong adapter, model II understand 7222; that your regular rate for a year's subscription Is One pair Coast -to -Coast test leads with hand- Mall me a sample copy of SHORT WAVE CRAFT for spring chuck prods; which I enclose 150 (U. S. Stamps or coin accepted). Two Burgess 41/2-volt "C" batteries; One line cord with rubber plug: Name Two Littlefuse .01 -amp. fuses, type 1001, FI, F2 ; Address State One Coast -to -Coast impedance chart, output meter chart. Cit» State 690 RADIO-CRAFT for MAY 1933

ì ta, 14,a4 _ ., e:; s ; 7. ». ::a a t-. ff SyKal ; Here's a book READERS' DEPT. every Radio Man will (Continued from page 583) M U LTITESTER refer to dozens of times A 1 10-VOLT D.C. "MEGADYNE" every Editor, RADIO- CRAFT: Knock day- I built your one-tube loudspeaker set published down 15 in RADIO -CRAFT. However, I did not want to be kit, net ... bothered with batteries, so I incorporated a few (lees batteries and extra parts and hooked it all up for 110 V. D.C. teat prods) operation as per Fig. 2: and I must say it is List $27.50 all that you claim for it. Selectivity is fair, plenty of pep, and has absolutely no hum. The value of resistor R, for the filament, was a bit Completely troublesome. so I tapped along a 2,000 ohm, bare wired and wire -wound resistor, using a meter, until I got assembled, (20 just 6 V. on the filament. I should say this set net ..._ IMU e SCION is a little wonder. Would you mind passing it (Includes batteries on to the boys? and test Prods) J. DACOSTA, 223 E. 117 Street, New York City. FEATURES - Triple Range Ohmmeter, Ye to (Here it is. We are glad that Mr. DaCosta 2.000,000 ohms Four Range Voltmeter, 1 /10 to has had such success in revamping the "Mega - 750 volts- Triple Range Milliameter, 1 /10 to dyne." originally described in the July, 1932 250 milliamperes -1000 ohm per volt sensitivity Teehnicat Editor.) -Automatic Selector Switch connecta meter to issue of RADIO- CRAFT.- proper circuit and scale and totally disconnects from all others. Double Range Ohm Meter and Circuit Tester !_ to 200,000 ohms Complete 51195 Net Super Test Unit Super-flexible analyzer A Valuable RADIO BOOK! unit for use with any HERE is one radio book that answers every meter or with Multi - conceivable question on interference. It teeter. Permits all point $135° to point resistance List .$25.00 contains 76 pages, 85¡x1l inches, chock full measurements and all with wiring diagrams, drawings and photo- voltage -- current measurements. 36 different graphs showing where interference originates voltage or resistance readings available at one -how it is distributed, and how to eliminate socket. Spare provision for 9 more readings. it. This is a wealth of information needed by Includes 7 prong analyzer plug with adaptera every radio listener, dealer and Service MF. and 10 wire cable. Man. r % N.-e Send for bulletins on Testing Equipment. Send fifty cents in stamps lid- A.01010E or check for this book. 110V, D.C. KENYON IOW-RESISTANCE, RADIO CITY PRODUCTS CO. 48 WEST BROADWAY NEW YORK, N. Y. thematic circuit of the D.C. power -operated RADIO -CRAFT MAGAZINE Megadyne receiver. We hay. received so many 96 -98 Park Place New York, N. Y. equests from readers who desire to operate this excellent receiver from D.C. power supply, that we are pleased, indeed, to incorporate this circuit in our pages. AERO INTERNATIONAL CONCERNING "MORE TUBES ?" ALL WAVE 11 -TUBE Editor, RADIO -CRAFT: I for one am heartily in accord with your SUPER- HETERODYNE DE LUXE suggestion as to the "Portable Series of Tubes." Completely Assembled My idea is that the filament current be made With 2 Matched as low as tube efficiency will allow. The voltage Dynamic of course should be such as to permit the tubes Speakers _ ...... -..ia1 to be operated from one or more dry cells in At last! World wide re- parallel. ception at a sane price. Gives inside information Now let me ask some questions about a tube. 15 to 550 meters. Besides on all running machinery In the May, 1932, issue, Mr. Martin told of a the regular broadcast new combination detector -oscillator tube, which band, it brings in for- Build it yourself he called a septode. In this section of the coun- eign programs. amateurs. All you need Is an old Flashlight, a SKINDERVIKEN nothing has been seen or heard of it to date. police calls, ships at sea and aeroplanes. One Button and a phone receiver. try coils. Latest super - as yet? If so, dial control. No plug in Full details of instruction and blueprint showing where Is this tube in production phonic tubes. and how to listen, also chart Indicating character of could you tell me the manufacturer's name and noise in automobile chassis and motor. also the list price of this tube? If this tube is OTHER USES FOR not now manufactured, is it dropped permanently AERO 4 -TUBE MIDGET SKINDERVIKEN TRANSMITTER BUTTONS: or temporarily? RADIO AMPLIFIER PHONOGRAPH AMPLIFIER for asking I am considering $10.95 less tubes DETECT)GRAPII TELEPHONE AMPLIFIER As to my reason (pictograph) LOUD SPEAKER AMPLIFIER building the cheapest, most sensitive "super" $2.95 kit of tubes HOME RECORDER CRYSTAL SET AMPLIFIER possible, and would like to get this tube, as LAPEL MIKE The lowest. priced quality otherwise I will have to use a type 57 tube as Midget Receiver on the mar- the detector-oscillator. ket today. Very selective, 16 PAGE INSTRUCTION BOOKLET H. MCKNIGHT, containing suggestiens and diagrams for brings in long distance like R. F. D. 4, local stations. innumerable uses, furnished with each 95c Skinderviken Button Buhl, Idaho. ONLV (The aaboratory-model tube to which Mr. Mc- AERO 5 -TU8E MIDGET.... =11.90 Our Microphone Transmitter is the original SKINDER- Knight refers was changed slightly in the pro- AERO 6-TUSE MIDGET._- 18.50 VIKEN Button: it is the smallest micron one made, duction model and is now available as the type measuring only k inches In diameter. It la filled with the finest polished carbon grains obtainable. 55 with a 2.5 V. filament. and the 85 in 6.3 V. AERO WORLD WIDE -ULTRA SENSITIVE- design: however, the low mu (about 8.3) of USE COUPON -SEND NO MONEY the triode section resulted in the development I -Tube SHORT WAVE When the postman delivers your order you pay him for û SET for Head- whatever you have ordered. plus postage. of the still more recent type 75 tube (with a Operation mu of 100) described in the April, 1933, issue of $5s .95 phone PRESS GUILD. Inc. Its- -533 RADIO -CRAFT.- Teehnicat Editor.) Listen In DIRECT to Lon- 16 Murray St.. New York, N. Y. don, Paris, Berlin, Buenos Please mall me at once as many of the following Aires and other broadcut- 1n{ throughout the Shinderrlktn Microphone Buttons as I have indicated. .tatlons ADDING A BAND -SELECTOR TO world la short wares. Your CI One for 95c: Two for 91 75: ordinary receiver cannot tune Three for $2.50 0 Four for $3.20 THE "PENTODE PORTABLE" In these low wave stations. I will pay the postman the cost of the Items as speei - WORLD -WIDE RECEIV- fird, plus postage. Editor, RADIO- CRAFT: ER Fete 15 to 500 meter.. have read from time of the different Aero 2 -Tube Short Wave Set i time to .75. The same as abov Name versions of the justly popular "Pentode Port- set but It has I stage of Audio Frequency added to Its able," and so wish to pass on to others what I Write for Complete Catalogue Address have been doing along the same line. City State (Continued on following page) CHARLES HOODWIN CO. 4240 Lincoln Ave, Dept. B -17 Chicago RADIO -CRAFT for MAY, 1933 691 Here in Pittsburgh, I found that after building this set I didn't have the selectivity that I wanted. so I added a band -selector feature. Then, being a short -wave fan, I added a D.P.D.T. THE switch, and then could tune down to the police waves and the 160 meter band for amateurs. The result is'a set that can do more than some of its big brothers. The circuit. below. is the usual band -selector ORSMA arrangement. Coils Ll and L2 have 44 turns of No. 30 D.C.C., tapped at the 20th turn from the ground end. A D.P.D.T. jack- switch covers the two coil ratios. The tickler. L3, has 20 turns of 30 D.C.C., although experiment is advisable. The rest of the set is the same as the original "A.C. Pentode Portable," described in the Sep- tember, 1931, issue of RAIDO. CRAFT. The spacing between the whole of Ll and L2 is one inch for the broadcast band. When the set is switched to the low -wave position. this THE BIGGEST NEWS- MAGAZINE IN n distance is greater, giving desired selectivity on THE RADIO INDUSTRY the 160 meter amateur band. By bank -winding L1 and L8, the original Issued Monthly for Radio compactness is preserved. and the only addition Service to the original set would be the midget two -gang Men condenser and D.P.D.T. switch. This new magazine is filled with inter- I hope that this version will be of interest to esting service information; plans of your readers. and that they have as much fun the Association; Service Men's expe- out of this design as I have. riences; answers to inquiries about RICHARD O. LAMB, servicing; hints on 1039 S. Trenton Ave.. making extra Wilkinaburg, Pa. money in the servicing field, in short, (Mr. Lamb has added his name to the very it is a magazine written for and 'by long roster of those who are "tickled pink" with members of the O R S M A. It is No. 2 the performance of their "Pentode Portable," the voice of the Association in which FUNDAMENTAL PRINCIPLES the original description of which appeared in the the problems and suggestions of the August, 1931, issue of RADIO-CRAFT in the article, individual members are presented for OF RADIO "The RADIO-CRAFT Pentode Portable. "- Trchnicrtl review Radio Simply Explained -Its Origin, Nature and Functions Editor.) and discussion among the fra- By LOUIS MARTIN ternity. It is a magazine for, Prepared with special consideration giren to young of and members in the radio profession. and those who hale by the Service Man, edited by the staff gained their experience in haphazard fashion. 'fait radio primer is handy fundamental aid for "rheeking of RADIO -CRAFT Magazine, sponsors up" and systematizing your knowledge of radio. Re- of the OFFICIAL RADIO SERVICE gardless of how much you know about the subject. you should read this book. MEN'S ASSOCIATION. PARTIAL CONTENTS: In appearance this Chapter I- Fundamentals of Radio: Electricity. Resistance. BULLETIN is Batteries, The Magnetic Cinvii. The Magnetic Field. In- made up in the style and size of a ductance. Condensers. A.C. Circuits, Propagation of Radio Waves: Chapter II-The Simple Radio Set, Single. Two, tabloid newspaper. It contains up -to- and Three-Circuit Tuners, The Battery Set, Vacuum the- minute service information. A Tubes. Electric Seta. Loud Speakers: Chapter III -Dia- grams, How to Read Them; Chapter IV- Amateurs and partial contents of the average issue is Broadcast Stations, Talking Pict urto, Television. found below: No. I EDITORIAL: -Advice to the young Service Man How to t started. - FORMULAS and RECIPES SERVICING EXPERIENCES: -The methods used For the Practical Man to overcome unueuSI and difficult service jobs. By S. GERNSBACK SERVICE MEN'S EQUIPMENT:- Favorite test- a, An extremely helpful book shooing you how to save Nt. SO C C. coa ing units of " " Service Men. ALL CO LS Ga ANT44T ONO. EXPOSING THE SERVICE "GYPS motley by snaking In your tool home- at a fraction of the D44 T.64°. ": -A continu - regular cost, the hundred and one preparations which you tion of the war against dishonest service work. now buy for use at hone or husine.s. THE SERVICE MEN'S OWN FORUM: Thera the PARTIAL CONTENTS: III views and problems of the members may be 2%xw. T-L3 3 ot. 1. Adhesives: Glues, Cements. 2. Cleansing: Stain Re- mA "aired." movers. Bleaches. 3. Metal Craft: Coloring, Oxydizing, xoT. Die ELECTRIFYING AND MODERNIZING OLD RE- Plating, Polishes. 4. Paints: Colora, Stains, Varnishe, CEIVERS:-As source of income for she Serv- 5. Glass -Working: Cutting, Drilling, ice Man. Boring. Stetting. MAKING MONEY AT Wood-Craft: fauna L3 TO TAD SERVICING:-Methods of BM Mo. Os) advertising and extending business employed ro Furniture Polishes. p , Insk Sympaheti,athecHateprooiing, 1m- Bible. Hectograph. b successful Service Men. 8. Photography: Developers, Emul- THE sions. Fixers. 9. Antidotes for Poisons. Remedies (ta- RADIO SERVICE MEN'S BUYING GUIDE: ttoos and Scalds. Disinfectants. -A classified directory of radio manufacturers 10. Preparation. and 5tanipulation. Handling, Mixing, Tables of Weights and RADIO -LANGUAGES' STEAM supply companies which allow special dis- Measures, Useful Tables. counts to Members. ROLLER THE QUESTION BOX: -Question asked by Na. 3 Service Men and the answers. Radio will in time polish off local dialects and EMPLOYMENT SERVICE: -Ads Inserted by com- ELEMENTARY panies in need of Service Men and Members MATHEMATICS at the same time make the common language looking for employment. for the Technician and Craftsman richer in words and their use more accurate, By C. SHAINMARK Subscription Rates for t he a This manual has been especially prepared for the an predicts Professor Otto von Friesen of the Uni- who wishes to acquire a working knowledge of the ele- versity of Upsala, who is an internationally ORSM :1 BULLETIN mentary principles of mathematics. A complete treatment of the subject is given by the author, Mr. C. Shaintnark, known linguist and a member of the Swedish with special attention to the use of mathematics in Radio Academy which annually picks the winner of [t It S N Non -Mem- and other technical work for those who employ its for- 5lernbera mulas daily. the Nobel Prize in literature. What he says bere PARTIAL CONTENTS: about the effect of broadcasting in Sweden holds 50c one year $1.00 i I- .trithmetle: Addition. Multiplication. Subtraction. Di- true, of course. in other countries. ision. How to t'se Decimals; Fractions, $1.00 two years $1.75 I'l- Pernmtages, Like most lands Sweden has Hallo and Proportions; Ill- Powers and Roots; IV -Tbe many dialects $1.50 three years $2.50 Metric System; V -How to Measure Sudan., and Vol- and when a person speaks on the national radio umes; Mathematics for $2.00 VI- the Manual and Technical program is often possible four years $3.00 Craftsman; VII-Special Mathematics for the Radio it to tell from his Technician; VIII -Commercial Calculations. Short -rot enunciation what province he comes from. It $2.50 five years $3.75 Arithmetic, Interest Calculation, Discounts; IX- Weights is the deliberate policy and Measures; X- L-seful Tables. of the Swedish broad- Price of Single Copy 10e casting service, which is under the control of the All our books are of uniform sire, 6 x 9 inches, ami press, to admit all and every dialect and contain 64 pages. The books are printed on strong paper not attempt any restriction of its speakers to Subscript- Blank Nth st iR colored rovers. those who were born In Stockholm, for instance. speech has In Germany the of the stage be- Executive O. R. S. PRESS GUILD INC., 16 Murray Secretary M. A.. St., New York. N. Y. come the standard for good spoken German, and 98 Park Place, New York, N. Y. ANY TWO 1100E8 FOR 850 how much more important the radio broadcast ALL TIIREE BOOKS FOR $1.251 postPald. Enclosed and my remittance of S for idch which reaches so many more people, will be please enter my subscription to your BULLETIN for Enclosed find $ for which mall me postpaid the following books: for the future development of our tongue. Not -years, o member Association and my Member- No. 1 No. 2 No. 3 that we may look forward to anything that shin C of The Single copy 50e Postpaid might be called "Radio Swedish," but the radio I am not a member, but would like to receive your will gradually smooth out the various dialects application blank to join the O. R. 8. M. A. (no fees-no dues to be by me). and intonations into a more national speech. paid The country have preserved many dialects also Name..._..._...._...._..._...._..__._.._ .__._...- ..._...._..._..._...._ old words which the national language has Address dropped and radio may bring back those which Address..._...._....._...-...._- -._.. _.._._-....-_..- still serve a purpose. The Swedish radio chiefs believe. the t'Ity and State. ..__.._...... __...... _...._.. _.._...._...... _...... _... furthermore, that pronunciation of CIV State.. RC -533 foreign words will be improved by the radio. 692 RADIO -CRAFT for MAY, 1933 LISTENER'S FORUM (Continued from pope 675) RCA INSTITUTES Recognised Standard In Radio Instruction Sinai 1909 CLASSIFIED land, Ore.: KGPA, Seattle. Wash.; KGPW, Salt Technical Training Courses Lake City ; KGPE, Kansas City, Mo.; KSW, ADVERTISEMENTS Berkeley, Calif. ; KGPX, Denver, Colo.; and many in Radio and Associated more. Electronic Arts Advertisement. In this section c ins. reed at the I also get airplane and airports, some, far cod of ten ants per word for each Insertion -name, East. The set is a wonder. I use the crystal set Practical Radio Engineering Initials and address each count as one word. Cash should accompany all classified advertisements un- as a tuner unit, no R.F. amplification whatever. Sound Engineering less placed by a recognised advertising agency. No H. H. HOLME, Broadcast Transmission less than ten words are aeceptcd. Advertising for Clenyon Ranch. the June 1933 1.sue should be received not later Radio Servicing 9th. Poet Fans, Idaho. than April Commercial Radio Operating Resident Cahoots at New York andehlaaso CHEMISTRY HE KNOWS WHEN TO HUNT EXTENSION COURSES for HOME Editor, RADIO- CRAFT: BECOME A TRAINED CHEMIST. Thousands STUDY under new "no obligation" plan, career. Learn at In reply to your request for unusual DX rec- of opportunities -fascinating ords, allow me to tell of the unusual record I with privilege upon graduation of 2 weeks' home. Complete experimental laboratory outfit intensive practical training without given. York. Insti have made. My Majestic table model is just 20 charge 19 Park Place, ' Dept. RC, New days old. Without ever experimenting with the at either Resident School. aerial, except to shorten it, and without DXing DOGS in the early morning, I have increased my DX Mail Coupon for Illustrated Catalog in 14 countries. bull pups, $15. Bull- total from 205 to 860 stations BEAUTIFUL Registered as follows: CPX, Bolivia: dogs. 501 -RC, Rockwood, Dallas, Texas. My best catches are RCA INSTITUTES, INC., CX20- Uruguay; YV1BC, Venezuela; LR4, Spain; Dept. RT -5 INSTRUCTION Buenos Aires; LR6, Buenos Aires; EAJ7, 75 Varlck Street, New York, N. Y. Radio Budapest (545 Kc.) SCW, Sweden; equipped radio 1154 Menhandise Mart, Chicago. lII. CANADA'S Oldest and best SCK, Sweden (250 watts) ; all before 11 P. M. school offers complete course covering Radio, Please send with no obligation to me: in the evening. resi- Television, Sound Amplification. etc. Approved when ( ) Illustrated catalog and information about by leading radio manufacturers. No duty or My success is due mainly to knowing dent school morses. to look stations, the new tubes, courses for study exchange to pay. Radio College of Canada. and where for l 1 Information atout extension Limited, 310 Yonge St., Toronto. and a bi- directional aerial, and luck, not skill. at home, together with illu,uated catalog. ROBERT ROSENBERGER. MEN -WOMEN, 18 -50 WANTED. Qualify for future Government Life Jobs. $105.00- 17 Janssen PI., Name Age. 8175.00 month. List positions FREE. Write Kama. City, Mo. Dept. J77, have today eure. Franklin Institute, (Here is a real goal to shoot for. You'll Address .. Rochester, N. Y. to do some fancy tuning. Editor.) RADIO Citv Stete J MAGNETIC Speakers rewound and adjusted, SOME LOW POWER CATCHES $1.25. Radio Service. Flora, Indiana. Editor, RADIO- CRAFT: "Pocket Radio," $2.00. Cata- I am writing to tell you about the results 1 GUARANTEED I had my log, 10c. Neil Tasker, Shamokin, Pa. have enjoyed with my radio. have NEW set for thirteen weeks; I bought it second hand THE TRANSFORMERS REWOUND, varnished, and to date 111 stations have been tuned in. baked, guaranteed, reasonable cost. SPEAKER REPAIRING, magnetic $2.00. $2.50; dynamic, Here are some of the best -WPEN, Phila- SHALLCROSS voice coils, fields, etc., reasonable charges. Clark delphia. Pa., 250 watts; WOL, Washington, Bros. Radio Co., Albin, Iowa. D. C., 100 watts; WSPA, Spartanburg. S. C., A.C. UTILITY METER 350 watts; No. TRANSFORMERS AND SPEAKER FIELD 250 watts; CMBY, Havana, Cuba. 685 COILS rewound or made to order. Trans- and KFVD, Los Angeles, Calif., 1000 watts. former and complete instructions on rejuve- Station KHJ in Los Angeles, Calif., and station C_ 1PACITY nating of AC tubes $4.00 postpaid. 5 hours XER in Villa Acuna, Mexico, can often be picked - .0005 Mid. U IO Mid. service. Pembleton Laboratories, 921 Park up before 9 p. m. Wayne, Indiana. view, Fort I have heard every channel except 10 of them. SENSATIONAL MICROPHONE V A L U E- They are 1440, 1840. 1280, 1180, 1120, 1050, 1030, INDUCTANCE Universal Model "Y "- Experimenters single - 1010, 960 and 560 kilocycles. I have only used .5 Henrys U 10,000 button, watch model type. 200 ohms. Pure the set for a little over two months, though, Nutria Gold Spot Center Diaphragm. Only $2.00, including valuable 1988 general catalog with dia- and I hope to have a station for each channel grams. Universal Microphone Co., Ltd., In- before long. RESISTANCE glewood California. I would like to hear from other DXers to com- 25 ohms to 5 megehms. MAJESTIC "A" AND "B" ELIMINATORS pare records and swap experiences. A.C. voltage ranges cheap. E. Tischler, Plymouth, Pa. J. S. CORAL, 0- 10.125. 500 -1000 Latrobe, Pa. (Thanks for your letter, J. S. You have a t000 ohms per volt. very record for such a short time. Your good This instrument is very easy to build. request for letters from other DX fans is a The important parts required are a 1- milli- good one. Anything that will bring listeners ampere A.C. (rectifier type) meter and the CHEMISTRY closer together will certainly be for their benefit. SHALLCROSS Resistor Kit No. 685 with A New Plan fo Become a We might add that we will be glad to forward meter scale. any letters addressed to Mr. Goral or any other Rend dc In stamps for Bulletin 683 -P TRAINED CHEMIST contributor to this column. Just address the describing this useful test InatrumenL 6.25 By taking only one step at a letters in care of the DX Editor, RAmo.Ca *rr, means 98 Place, New York. SlialtnssPdke®uupag STARTS YOU time -as your permit - Park Editor.) twit e you can give yourself the benefit ELECTEICAL SPECIALTIES thorough -going, up-to- wt, , .. leglW of the most complete, 4'tslBngdale-Pa.r>. the- minute education for skilled well -paying TOBE PRIZE CONTEST professional work, in the most fascinating of all scientific fields, through our famous Every radio dealer and Service Man will be COURSE IN PRACTICAL CHEMISTRY interested in the news that a prize contest, entirely within the radio industry, is to be Writs TODAY For Information sponsored by the Tobe Deutschmann Corporation Chemical Institute of New York, Inc. of Canton, Massachusetts. This contest., which Founded 1921 is open only to bona fide radio Service Men and HOME EXTENSION DIVISION dealers, will result in the distribution of one Place New York, N. Y. hundred valuable prizes, including the latest 19RC Park types of radio interference locating apparatus, WANTED service instruments, condenser kits, radio magazine subscriptions, etc. Smart service men who realize The object of the contest is to familiarize the money possibilities in the radio industry with the newest developments TO ALL RADIO MEN! in the Tobe condenser line. Although many plugging Amperite. It im- radio men. especially the younger ones, know proves the sets you service; The advertisements which appear on the Tobe Deutschmann Corporation chiefly saves the customer at least pages 688 and 689 of this issue is ex- through its radio noise eliminating devices. this 10% on electric current. You concern has been high quality tremely important. Everyone should manufacturing make $1.85 clear profit on condensers for many years. Corpora- turn to these pages NOW and read Full details of the Tobe Condenser Contest each sale. Amperite tion, 561 B'way, New York. them carefully. may be obtained from leading radio parts jobbers or by writing- to the Contest Director of the Tobe Deutschmann Corporation.

RADIO -CRAFT for MAY, 1933 693 HAMMARLUND "AIR-TUNED" TRANSFORMERS A departure from present design is presented in a new group of air -tuned intermediate frequency transformer and oscillator units developed by the Hammarlund Manufactur- ing Company, 424 West 33rd Street, New York, N. Y. The transformer is of the tuned primary - tuned secondary type, with both plate and grid coils tuned to resonance by means of air -dielectric variable condensers of special design. These condensers are mounted on an Isolantite panel Iii" in diameter. The rotor is carried in a single bearing in the Isolantite panel and consists of two circular and three semi -circular brass plates of %" radius riveted to the rotor shaft. The stator, also of brass. consists of two circular and two semi- circu- lar plates soldered to stator support rods, which in turn are soldered in the bushings in the Isolantite panel. Contact is made to the rotor plates by phosphor bronze spring under considerable tension. No locking device is necessary. as the tension of the contact spring is sufficient to maintain the setting of the rotor even where extreme vibration is present. A screw driver slot is provided in the end of the rotor shaft to facilitate tuning. The use of these air variables practically You want to get the exact and technical meaning of a word or phrase in radio! You eliminates the varia- in are doubt about a radio formula or radio circuit! You look through a maze of hooks tions in gain and selec- and magazines losing your time and your temper. tivity Why not have at your desk or in your library a copy of inherent in I.F. transform ere in which the coils are tuned by means of adjustable con- S. GERNSBACK'S densers of the compression type using mica dielectric. Even RADIO ENCYCLOPEDIA when such condensers are built on Isolantite bases and the highest THIS book is the NEW EDITION OF THE FAMOUS FIRST RADIO ENCYCLO- grade mica is PEDIA by S. Gernsback, the first book of its kind ever published in America. used. The new Second Edition is fully revised, rewritten, and enlarged. It is abso- variations in tempera- lutely the upto- the-minute new model of ture and relative humid- r- the pioneer First Radio Encyclopedia, ity causes changes in 1 which became the stand -by of all radio both the capacity and S. GERNSRACK CORPORATION, men in every pan of the world. 98 Park Place. New York. N. Y. power factor sufficient 2,201 RADIO DEFINITIONS to render them unfit for use in precision 1,253 TECHNICAL ILLUS- equipment- The change in capacity is es- NEW SELLING PLAN TRATIONS pecially troublesome in transformers operating 34 TABLES AND CHARTS at 24 PAGES OF APPENDIX the higher intermediate frequencies, where Send me one ropy of the neo Seront a given percentage change Edition S. Gernsback'* Radio Encyclopedia Red Morocco-Berate! Flexible in capacity causes a lilt the privilege of Inspection. If I Ilke Binding a relatively great change in I.F. transformers the volume, I will pay Expressman $3.98 Printed on when expressed in kilocycles. plus shipping chargea. strong ledger paper. $3.98 Loose -Leaf Arrangement For instance, variations in capacity of as 352 pages. 9x12 in. Weight 3 lbs. much as 3% between the six compression Address -...... _..._..-._. type mica condensers used in a two stage (3 transformer) intermediate amplifier are Rt'533 39,000 Bought the First, Edition! not uncommon during a spell of high relative humidity. Since the percentage change and resonant frequency of a circuit is equal to one -half the percentage in capacity, for small changes only, this represents a frequency drift of 1!tz % or 7 kc. in the case of a 465 kc. amplifier such as is used in the "Pro." A FOR SALE, BARTER AND EXCHANGE large increase in losses invariably accompanies this capacity change As an aid to our nmlers, all ads ort i+emvnts to be inserted in due to moisture this department are absorption. The accepted at 2c a word; name, address, street number. etc.. each counting for one word. mis -tuning, plus the increase No advertisement for less than fifteen (15) words accepted. in power factor, causes a marked decrease in both selectivity The Publishers are not responsible for difficulties arising out of the trades. In and amplification. this department, only advertisements for private individuals can be accepted. RADIO -CRAFT reserves the right to reject any advertisement that conflicts with the CHECK FILAMENT DRAIN* policy of this magazine. Send all "Swap" advertisements to RADIO-CRAFT, 96 -98 Park Place, New York. N. Y. When tubes are used in a parallel connection the variation in filament current does not play auch an important part upon their Have one Larault l'Itradyne, one of the finest Super - One television scanner comprising synchronous mo- life. However, when tubes are connected in het.s made. Famous for long distance receiving. Have tor, 00 hole scanning disc, come, also small Short Wave Converter. Send $25.00 cash first first served. series the filament current draw every $7.00. Hove on brawl-limy Workrite short wave con- for for Loth. Write. T. Epstein, 7 West 22nd Street. tube should be identical. otherwise, Suite 1009. New York, N. Y. verter $65.00. tint check for $8.00 takes It. Ellis, the tube North Central Ave., Ramsey, N. J. designed to carry the smallest filament cur- Have 72 -Inch R.C.A. Victor exponential horn. with rent will be subjected to the greatest strain electric and acoustic tone -arm pick -ups. First check and is likely to burn out long before it would $ 5.00 takes It. Crossman air gun. 22 calibre ahaas HASIMAI(Lt-ND HI -Q 30, Iv C. model, for sale. like a regular bullet Mlle. cost $17.50 -will sell for Seven tubes: two 227's. two 221's, and two 255's In under normal conditions. $7.00. H. Ackerson, Island Road, Ramsey. N. J. push Dull. ['.ses dynamic speaker and has facilitle: Some tube manufacturers are turning out for phonograph connections. A r narkably sensitive 6.8 volt heater type with a rated filament StewartWarner 8 -tube broadcast set, tattle model P1 receiver. List of chassis. $1.50. Will sell for $10 current of 400 mils while others No. 80111. original price $50.50. Will sell for $12.00. rash. A real bargain. L. Abitsch, 136 West End are rating ltentbert Short Ware Converter. 3 tubes. with power Ave., New York City. their filaments at 800 mils. Where these supply and automatic switching arrangement. 10 to tubes are connected in series, the 300 mil 200 meters. brand new, never used. cost $2225.00. will tubes are seriously overloaded ULTRA-MODERN SUPER. All parts for this fa- if enough cur- sell for $7.50. Zenith. model '8E220 chassis. 36 in. rent is passed long. 10 tubes, T.II.F., slightly used. Including mous set mounted on a cadmium -plated chassis and through the circuit to opera- tubes, equipped with too horns. conies with model partly wired. for sale. Only manufactured parts used; aI te the 400 mil tubes normally. 'LEI battery eliminator. with Raytheon tube. also everything in excellent shape. Set described in Oc- Even where tubes are connected in parallel original tober Issue f this magazine, $22 Westinghouse Rector trickle charger. price Price. 20.00. First and all are supplied by a given voltage, fila- $500.00. will sell for $40.00. A. Rlbarsky, ISO Rir- money takes oit -a real buy. Z. Martin, 415 Lefferts ments having erside Drive, New York City. Ave.. Bnakbm, New York. too low or too high a resistance will change the performance of the receiver very materially. *Triad Mfg. Co. 694 RADIO -CRAFT for MAY, 1933 MERCURY -VAPOR TUBES Build the NEW Since the type 82 tube has a 2t_ V. filament, it is necessary to make some slight ad- RADIOLAMPCombined a Practical justment in the receiver as to voltage supply The Finest A.C. -D.C. Radio With Table Lamp -Ideal la Bedside. Table or Desk THE to rectifier tube; although, similar compensa- This Universal Set can he tion may be applied externally by using an used wherever the is AMERICAN current, a 5 V. It MOTEL adapter. Since the type 80 tube has either A.C. or D.C. It filament, it is necessary to drop this potential to employs the latest circuit, 275 ROOMS the 2% V. required for the 82 by connecting tubes and parta. The BATH large lamp shade speaker WITH into the filament circuit a .75-ohm resistor with gives full, rich tono ouel- Up of 10 to 15 watts. ity. hitherto unobtain- $2.00 a rating able miniature receiv- Further information concerning the type 83 ers. .Úl part, for bug same the RADIOLAUP are tube which employs a 5 V. filament, the furnished in a complete as the SO, is given by Mr. Walter R. Jones. KIT, with full instructions and simplified plans. writing in SYLVANIA News, as follows: Servicemen! With the new type 89 tube, much damage As soon as your custom- THE may be done by inserting the tube in the 80 ers andfriends see and socket without thinking. If this is done, pro- hear your RA DIOLANI P. ANNEX they will want one just viding nothing burns out in the receiver or like it. money sup- i 226 ROOMS up," the receiver will give considerably plying this demand. The RADIOLAM P can be assembled "blows WITH BATH d completed few hours and wells on eight for $25.00. better performance than it did in the past. This COMPLETE RADIOLAMP KIT -Containing all Parts 15 Up Performance, however, is not likely to last long, Necessary RADionsAUP + since the increased voltage will sooner or later (less tubes). Full Instructions and 1 Simplified Plans. only 3e75 blow one or more of the filter condensers in a ESSENTIAL KIT-Containing Set t Find-All Celle. Drilled tame Base CImw4 and Lamp ShadeöbWa öpp4er s.r0 power unit. If this condenser simply opens up, Find -All Coila. per wt 5.00 loud annoying hum will result. If, Lamp Beet Chor.4 2.00 a very and 1 Shade kNr 2.00 however, as is more than likely to occur, the Full PlenapFr euh Compleir ait -Othe 1.00 All Prices r.o.e - New York -All Parts eFully Guaranteed condenser shorts, the power transformer in the fend Check or Money Order or Pay Postman pon Delivery receiver will be burned out unless the tube is THE RADIOLAMP COMPANY Instantly removed from the receiver. In addi- Suite 541 88 Park Place New York. N Y. tion to this, if anything should happen to the tube for even an instant it is quite likely that it would burn out the transformer before the tube could be removed. For this reason prac- Food has made tically all receivers which are designed to em- Our ploy the new mercury vapor rectifier tube are our Reputation provided with a fuse. so that in the event of SERVICE MEN! COFFEE SHOP OPEN UNTIL MIDNIq,at any momentary tube failure the fuse will be blown instead of ruining the power transformer. Send for our new 1913 some advertising In the past there has been Catalog . Just off the which recommends the substitution of a mer- press. Everything in re- cury vapor rectifier tube for the type 80 tube placement parts. Tubes. which is now in the receiver. A safer way, if Batteries. Latest Sound you are not satisfied with the performance of Systems, Automobile HELLO AMERICA!! buy receiver Sets and Electrical your present receiver, is to a new 6000 differ- and modern Supplies. IT'S HERE! which is equipped with the new ent Items at lowest tubes rather than to attempt to change the re- wholesale pr i c e e. NEW YORK'S MOST ceiver over to hap-hazardly use some of the new Prompt. reliable serv- SENSATIONAL tubes. This sort of change is much like the ice. Send forthls big change which often is made with the model T FREE Catalogue today. You need It. Cabaret Restaurant Ford of substituting a model A hood and expect- FEATURING ing your car to run as a model A or a model B car does. JAMES HALL D. T. SIEGEL. General Manager of the Ohm - ALLIED RADIO CORP. (Movie of ite Manufacturing Company, announces that 833 W. Jackson Blvd., Chicago, Ill. AND S MARDI GRAS ORCHESTRA this company is now making two special value Please send me FREE your new 1933 Dine in an Atmosphere of Far Away Monte in the Red Devil line. These units have resist- catalog. Carlo While You Enjoy Bobby Sanford's ance values of .4-ohm and .83-ohm and are Name WHEEL OF DREAMS intended for use in replacing two type 81 tubes Address Broadway's Smartest Floor Show With a in a power pack with a single type 83 tube. Host of Popular Favorites and These special value resistors are now carried City State 40- GORGEOUS GIRLS -40 in stock by many distributors. Phone Anyone -Anywhere from the Tele- phone On Your Table The use of the 83 tube requires enough re- DINNER -51.5o sistance to be inserted into the filament line to volts. On drop the voltage from 7.5 to 6.0 announces a new and better Bridget radio Monte Carlo Casino sets which have a single filament winding on the AT THE LOWEST PRICES EVER 48th Street West of Broadway power transformer, the .83-ohm resistor is in- QUOTED! Reservations -Lackawanna 7111 serted in the filament line. For sets which have THE NEV SIX TUBE a center -tapped winding, it is better to use a l NO COVER CHARGE EVER .4-ohm resistor in each side of the filament line. goCDentone This keeps the transformer in balance and pre- TRADE M.tRK vents hum. Superheterodyne be nega- With automatic For sir tube chassis An R.F. choke must connected in the and dynamic speaker -The Hotel Royal- tive or positive lead, with the 89 tube; this volume control The HOMELIKE Hotel of Philadelphia should be about 6 henries, 260 ohms, and able Mass production enables us to quote the 100 -150 was de- lowest prices. Buy direct from manufac- at Broad St. & Girard Ave. to pass mils. (This "kink" scribed by Jack Grand in the "Over- the -Counter" turer. Philadelphia, Pa. column of RADto- CRAFT.- Tcchuicel Editor) WE REFUSE TO BE UNDERSOLD! Combines every convenience and home The main reason for using the 88 tube, aside FREE COMCPLETE INFORMATION comfort and- commends itself to peo- from the more satisfactory operation. is the of refinement. saving in The list price of a pair FORDSON RADIO MFG. CORP. ple great price. Ave. of 81 tubes is $10.50, while the list of the 83 11700 Livernois Detroit, Mich. WITHIN 5 MINUTES OF CITY HALL is only $1.55 which is a worthwhile saving. The cost of the resistors and chokes is very small Rates as loin as compared to this saving. jsi.50 $2.00 $250- Single SFORMERS 1 2.50 3.00 & up- Double) RAN Ore r 1 ag EVERY DESCRIPTI M NUFACTURER FROM THE MpIVEY/ We make it our business to please RADIO CHASSIS-NEE BUY DIRECT - AND SASE' BIGMANUFACTURERS A Afor Mr. Smith, Mgr. MARQUETTE SET and AMPLIFIER FOR RS- SERV/CEMEN..t1'RRTE TED contusion 1 D£ALE PRICES-QUO Due to the resulting from the use Containing LOWEST RADIO SERVICE MEN of the name "Marquette" which it appears had FREE CATALOG end Sales Represent- never been properly protected in so far as Type Distributors -DEPARTMENT.. Be sure to read the announcement on Page 692 of Highest Our SALES the Marquette Radio Company was concerned. atives Should Contact this issue which tells about the new ORSMA BUL- they have changed their name to Radio LETIN. It is the most up -to -the- minute news tabloid Chassis, Inc. There have been no changes R pp1ÖÊLËCTRICvay.YORK REMINGTON 17en St.NEW for all radio Service Men. made in the corporate set -up whatsoever. 121 R' W EST H,

RADIO -CRAFT for MAY, 933 695 2,USEFUL RADIO BOOKS WET OR DRY?* WHICH EVERY The "wet" electrolytic has the ability to viand a tremendous amount of abuse in the EXPERIMENTER NEEDS IN HIS LIBRARY form of overloading without excessive shorten - ing of life and without much danger There is not a radio man in the field. experimenter. service man or dealer. who will of per- not want to read these two books. Right up to the minute with ou[stand ing manent breakdown. due to the fact that such meats in short -wave radio -new methods and apparatus for quickly learning how to condensers, because of their construction, can become a practical radio operator. Each book is authoritative. completely illustrated and not too highly technical. The test is easily and quickly grasped. dissipate a large amount of internally gener- ated heat and are continuously self- healing as How to Become An Amateur Radio Operator long as liquid remains within the unit. "e .hose LIORI Fun- Myron P. Eddy to write this book be, aoye his long years of damentally, such condensers have a somewhat experience In the amateuralcur Livid have made him pre -eminent In this line. For higher Many years he was l instructor of radio telegraphy at the It. C. A. Institutes. He power factor than the dry type of unit Is a member of the I.R.E. (Institute of Radio Engineers), elm the Veteran although it is possible to make even com- %Tireless Operators' Association. mercial wet If you Intend to become a licensed rode operator. if you wish to take up phone electrolytic condensers with power work e tually. if you wish to prepare yourself for this Important subject factors as low as 10% at operating voltages this la tho book you must - get. of 400 and peak operating voltages as high Partial List of Contents as 500 may be obtained with the wet type of Nays of learning the code. A system of sending and receiving with neces- unit without inherently increasing the sary drill words Is supplied so that you may work with approved methods. factor power Concise. authoritative definitions of radio terms, units and lass's, brief beyond the safe maximum limit for this descriptions of commonly used pieces of radio equipment. This chapter type of device. gives the working terminology of the radio operator. Graphic symbols are Due to the mobility of used to indicate the various parts of radio circuits. General radio theory any impurities which particularly as it applies to the beginner. The electron theory Is ariefiy may remain within the wet condenser after given, then waves -their creation, propagation and reception. Funda- fabrication, such units must be constructed mental laws of electric circuits, particularly those used in radio. with extreme are explained next and typical basic circuits are analyzed. care if good shelf life and good Descriptions of modern receivers that are being sled with operating characteristics are desired and the success by amateurs. You are told how to build and operate worth of this type of condenser these sets. Amateur transmitters. Diagrams with specifica- can be very lions are furnished so eonstruction la made easy. Power largely determined by determining the history equipment that may be used with transmitters and receivers. of the company making such a product and rectifiers, filters, batteries, etc. Regulations that apply to what their reputation is Amateur operators; the International "O" signala, etc. for care in this matter. The wet condenser is very desirable for use Hotly to Build and Operate as a first stage filter condenser, especially in Short Wave Receivers units of high power output and where a high is the best and tad up to -dote book on the subject. It Is value of ripple is imposed on the condenser. edited and prepared by the millars of SIIORT -NAVE CRAFT. Considerable and contains use has also been made of the wet SHORT WAVE a wealth of material on the building and oper- condenser, CRAFT ation, not only of typical short -wave receivers. but short wave largely because of its ability to 96 -98RC Park Place, converters as well. radiate New York, a greater amount of heat without N. Y. Dozens of short -wave sets Gentlemen: are found in this book, which con- breakdown, as a voltage regulating device I enclose herewith S tains hundreds of illustrations; actual photographs of sets built. for for which please send me, prepaid a copy of (look -ups and diagrams galore. the "B" supply in addition to its normal the book checked. The book comes with a heavy colored cover, and is printed function of filtering. This action is of course ( ) HOW TO BUILD AND OPERATE throughout on first -class paper. No expense has been spared to a function SHORT -WAVE RECEIVERS -50x. make of the leakage current of the con- this the outstanding volume of its kind. The book meas- denser which increases ( ) ROW TO BECOME AN AMATEUR urea T%o10 inches. rapidly above the so- RADIO OPERATOR -50e. This book Is sold only at such a ridiculously low price be- called breakdown point. The breakdown cause po- Send money order, check, cash or new U. S. It is our aim to put this valuable work Into the hands tential of a wet electrolytic condenser, it might .tamps. Register letter If It contains stamps of every short -wave enthusiast. be mentioned, or currency. We knew that If you are at all Interested in short waves you is a function of the solution and will not wish to do without this book. It is a most im- not primarily a function of the formation on portant and timely new radio publication. the aluminum as is the case with the dry type Each Book Contains Over Ise Illustrations of condenser. For this reason, the wet con- 711 Pages 7 : ie Inches Not Sold on Newsstands denser does not re -form to a voltage higher than its normal breakdown voltage City Mail Coupon in use as State at Left for Books! is very apt to be the case of the dry type. Recent refinements in the construction wet of DID SERVICE LECTRIC/ electrolytic condensers have resulted in a YOU SAY unit which can be made to sell at a very low efriyereaíorse price that will stand a tremendous amount of BARGAINS? abuse and that will show no evidence of the In your ettnittnntity there are dozens of leakage of liquid that used to be so common electric refrigerators to be serviced. THATS WHAT /SAID Many need Immediate repairs which can among former devices of this type. be made quickly. with little expense -and aWelt you can repair with the aid of this authori- The "Dry" Condenser BARGAINS.' tative Refrigeration Service Manual. Make many extra dollar.. together with other repair work. Elec- The "dry" electrolytic condenser offers the tric refrigeration servicing Is a well -paying busi- advantages ness -start in ,tour spare time-before long you will of extreme compactness, relatively Publisher's Samples and devote full time to R. One or two ions pays the low power factor, extremely low cost, and Bindery Relents small cost of the OFFICIAL REFRIGERATION multi -unit construction within SERVICE MAN1'A L. one container. We have on band few hundred copies of the .Sta'OND It is but little affected by slight overloads as EDITION S. ' JEANSBACK RADIO ENCYCWI.i.I TA, 96 Pages of New this type of condenser will form which we are going to sell as quickly as possible at a marvel- Data up to about ous bargain price. Have Been Added to the 10% above its rated operating voltage and in We are going to call it s sale of " shopworn" book,. some cases even more than this, where the These books are actually, however-every one of them OFFICIAL REFRIGERATION overload is new books. and for all practical purposes as (rood as any copy- not too abrupt and where the me- you could buy. They are copies that have been used by the SERVICE MANUAL chanical structure of the condenser is such publisher as display and salesmen's samples, as in bookstore that this increase in voltage does not i lows, expositions, etc. Some were set aside because of To bring this us.fol ...miss brim, ri h, . ,late. Mr. L. K. exceed bindery imperfections, such as a slight defect in the gold- Wright. he editor of t. I OFFICIAL REF lois s E it.ATION SERV- the limits calculated to cause arcing within stamping, or a small ICE MANUAL. has a,i,ieÁ wealth of materiel on new lectric irregularity in the texture of the cover rs and older mnIclle as w -II. As1omaI rarer rehiferator the device. -toad of then blemishes being so slight an to be scarcely Fqu been ae ra sly denerihed Orso, the s,se ,i,t f rvwmg- The noticeable on ordinary inspection. The text pegee are per- ill dry type of condenser can be manu- cangeasiÌy ho mad . The rt rppst fect. The 1 ks are not in any way marred, but merely not addition al l,enern nee n factured in such a way as to have very low im- fresh enough to be sold as new Is,oks. trews the cost of the book to how who order their copy now. pedance relatively This Second Edition Radio Encyclopedia consists of 352 at high frequencies and is Pages, weighs 3 lbs., bound in red Keratol flexible binder. Han Ars Some of The Important Chapters: therefore an excellent unit for bypass pur- 9x12', containsn 2.201 Radio Definitions: 1,253 tech. Introduction to the Refrigeration poses. Such unite are also ileillustrationslu and 31 table, and charts. Servicing ea.ine. made with both We are disposing of these very fine books at the ridiculously History of Refrigeration electrodes filmed over so that they may with- low Fundamentals of Refrigeration. price of Description of All Known Typo of stand A.C. without the application of any Refrigeration. polarizing voltage and in the field of A.C. $2.00 per copy Motcal ap- New leeks of stock Trouble shooting. plications, especially at low regular are selling currently at $398 Unit tiara. Valves and Automatic and medium pow- This offer of course will hold only so long As our special ers, the dry electrolytic condenser is making souk holds out -first come. first served' Mabee and Specifications of Uoila. Manufacturers of Cabin rapid strides. We have also on hand few hundred remaining Refrigerants and Automatic Enuip- Many Other Important Due to the possibility of winding multiple copies of the unbound volumes of the FIRST EDI- Chepterti TION of this encyclopedia, which we have been unit dry condensers in a continuous roll, form- selling out very apidly. at the close-out price of OYESP1,200 DIAGRAMS ing several separate units either with or without flealblet seleal Gunder 69 r a copy a common cathode, or common anode section. Complete Service Data or connection. within The size of the look is 9 by 12 inches. it contains Mail Coupon Today! the condenser, the dry 108 pelves, and is printed on the finest book paper unit becomes e. very versatile and flexible obtainable, it contains over 1,930 definitions. 519 r type of device as various multiple sections photo repr,lnrtions, drawings, and diagrams. GERNSBACK PUBLICATIONS. Inc. RC -533 can 96 -98 Park Place, New York, N. Y. be made by ingenious manipulation of the Don't send any money. Delivery win be onowinlan, made to you on th I encl., herewith my remittance for 85.00 electrodes at a very low cost per unit for the (cheek. stamps or Money Order accepted) for completed SKOR PRESS1Inc., 19 Park Place, New York, N. Y. ITC which you are to send me. podase prepaid. one condenser. lease send me copy of the OFFICIAL ItEFItIGE RAT' ON The dry electrolytic condenser is rather su- SECOND EDITION. 8. Gernsback Radio Encyclo-t 2 SERVICE MANUAL. together with the extra perior to the wet for use at low voltages and pedie. of your special "shopworn" sa te lot, at ii 96 sages of new material at no extra cost. FIRST EDITION. 8. Gernsback Radio Eacyclo 69c also has some advantage when used in lo- podia. of your unbound special lot Name cations where very low temperature ranges I will pay the postman the amount indicated above on del- are ivery of my order. plue the small postage charge. Address experienced as for automobile radio receivers Name City and the like. Address City State *Courtesy, The Magnavox Co. 696 RADIO -CRAFT for MAY. 1933 NEW ELECTRICAL AIDS TO NAVIGATION How inaudible sounds are used to measure measured to 3,000 fathoms or more, nearly 81 ocean depths while the steamer speeds on: how miles of water! mariners locate their positions by radio waves; how light houses and harbor beacons are auto- Beacons and Electric Eyes how ships matically turned on at nightfall; The Macneil "fog-eye," an infra -red instru- in the dark through may detect unseen icebergs ment which enables the mariner to be warned thick fog; and how the new automatic SOS recently described (and of fog -obscured ice -bergs, ships, beacons, etc., receivers work, were dense on em- CONDENSER Dr. Herbert Grove Dorsey, even through fogs dark nights, demonstrated) by ploys for its operation the infra -red waves or Principal Electrical Engineer, U. S. Coast & the Science heat vibrations just beyond visibility. These Geodetic Survey, who addressed being longer than the light PRODUCTS York Electrical Society. infra -red rays. Forum of the New waves, come through and around the fog paris are unexcelled The fathometer, for instance. he stated. ticles unimpeded. (The system was described use in now used on hundreds of ships measuring 1931 issue of RADIO-Camer.-Tech- for In in the May. fathoms whenever the captain wishes. stical Editor) days, he would have to slow up the former Radio beacons along our coasts enable mar- Radio Servicing ship. if the water were shallow, or stop if it iners to locate their own positions by tri- were deep. But now he presses a button, the Systems from unseen points on shore, great- Public Address fathometer starts and after a few readings he angulating himself that he has plenty of water. ly extending the influence of the ordinary assures lighthouse service. Amateur or Broadcast It is all finished in a few seconda, even though the depth be a thousand fathoms! By the Every ship which comes up New York Har- Transmitters method of lowering a wire to measure such a bor after nightfall, steers its course by range depth, the ship would have to be stopped at lights which are turned on, each dusk, by elec- This complete line is now catalogued least a half hour, while now it can proceed at tric eyes (photo -electric cells! and also ex- and stocked by full speed, twenty to thirty knots, and in any tinguished automatically at daybreak. kind of weather, day or night. With the (An interesting description of the "talking LEADING JOBBERS the pilot house, the skipper fathometer right in light beam" appeared in the April, 1933 issue Ask your jobber for a copy of his catalog about the depth. has no anxiety of RADIO-CRAFT.- Trchnicai Editor) including the complete TOBE Line, or full details of the ocean bottom now With us the TOBE dis- given in our charts, navigators are finding write for the name of them much more useful than just mere road tributor nearest you. maps of directions at sea. The bottom is sel- BOOK REVIEW dom flat for any considerable area and, if a navigator is lost in a fog. he can keep his RADIO OPERATING QUESTIONS AND AN- Tobe Deutschmann Corp. fathometer running a few minutes, mark the SWERS. by Arthur R. Nilson and. J. I,. Hor. indications on a piece of thin paper, and by nung. Published by McGraw -Hill Book Co., Canton, Mass. moving this around over the chart, keeping Inc., New York, N. Y. Fourth Edition, it parallel with his course, he will find some 51/2x8 in.. 350 pgs., 96 illustrations, cloth. line on which his soundings will agree with Price $2.50. not only his posi- RADIO OPERATING those of the chart, locating The Fourth Edition of this volume intro- and of travel, but giving also T' tion direction duces a broader review of radio operation RADIO SERVICING his speed. So vivid are the fathometer indi- - new broadcast, marine, aeronautical, police Prepare for the cations when steaming over rapidly changing and ama- Government Radio depths that it is almost like seeing the bot- teur-as compared with previous editions which Operating license ex- tom rise and fall, as do the hills and valleys covered only commercial operating. aminations; Radio Operator, M a r i n e by the road side as you ride along in an auto- The volume includes over 600 typical ques- a n d Broadcasting. mobile. tions, based on actual examinations, with full, Also radio Amateur Describing the Fathometer illustrated answers. The knowledge contained Telegraph and Tele- phone. Resident In one part of the equipment, called the in- in this volume makes the reader familiar with Write for dicator, there is a small motor with a governor the essentials of all license tests, both commer- which, through a system of gears, rotates a cial and amateur. For the technician who wishes "Opportunities black disc four times per second. Attached to pass any type of radio license examination, back side of the disc is a tiny neon in Radio" to the or for the general experimenter desiring to in- a small edition of the same tube TRADE tube, just crease his knowledge of radio facts, WEST SIDE YMCA used in advertising signs and in television. this volume is very valuable. & TECHNICAL SCHOOL When this neon tube is illuminated its red 7 West 63rd Street New Week City light shines through a slot In the disc, but it is lighted only now and then. In front of the disc is a sheet of glass on which is paint- A NEW FOR ALL RADIO SERVICE MEN ed a circular scale marked in fathoms from Here is big news for every Radio Service Man. If you want diagrams zero to 100. Every time the neon tube passes of commercial radio receivers, we are now prepared to give you the zero point of the scale, an electric current SERVICE passes through a sounder bolted to the bottom RUSH SERVICE of the ship and a sound is produced as a short In into the three OFFICIAL RADIO SLRVI(.li MANUALS published by w so whistle blast. Only these sounds pass far, we are listing almost 5,000 diagrams of commercial radio sets manufac- the water: no wire is lowered, nothing is tured in America. dropped. no connection with the bottom is Heretofore you could get these diagrams only by buying our OFFICIAL made. The sounds themselves do the work RADIO SERVICE MANUALS. by being reflected from the bottom of the We have, however, had an increasing demand of late from Service Men who ocean as echoes. are not owners of any of the MANUALS but who wish to get one or more As the echoes return to the ship they are diagrams. We are now repared to send you such diagrams on a rush order plan. We realize that if you want one these diagrams you wart¡ "heard" by a receiver of submarine sounds, of it quick. called, and For that reason, we now have a special staff to send any special diagram or "electric ear" as it might be to you ¡be same day ¡bat your order is received. an using thermionic tubes increases amplifier you live a distance away us, and cannot wait the echoes so that the elec- If from for regular mail, the loudness of the send us 8 cents extra, and the diagram will be sent to you by Air Mail. trical energy will cause the tiny neon tube These diagrams come to you on bond paper, size 9x12 inches. We are to make a single brilliant instantaneous red prepared to furnish practically any diagram you possibly can ask for- flash of light as the tube whirls around with IMMEDIATELY. the disc. This flash will shine through the HOW glass, opposite some mark on the scale, six TO ORDER fathoms, for example, if that happens to be Just tell us what diagram you want, giving us the name of the radio set depth of water through which the ship is and model number. It is absolutely necessary for us to have the model the number, as without this there is no way of identifying the set. A mere a second the red light passing. Four times description of the receiver or a list of the tubes it uses is of no help. We flashes at six fathoms, thus measuring a time will immediately mail you the diagram, if it is available, the same day interval of only fifteen thousandths of a your order is received. Note: Question coupons are not acceptable for second. and you read the depth as easily as these diagrams. you read time on a clock. Now, as the ship travels through deeper water, the red flashes WZ HAVE A UNIFORM CHARGE FOR THIS SER- will occur at later intervals, making the indi- VI= AND THAT IS 2Sc FOR EACH DIAGRAM cations move along the scale to show increasing depths. In going from deep water to shal- If you wish more than one diagram, the price is still 25c each. low, of course the red flashes will follow the but if you order six at one time, the price will be $1.00 for the six, providing all are ordered at one time. scale backwards just as well as forwards. If the depth increases to more than a hundred GERNSBACK PUBLICATIONS, INC. fathoms a handle is turned shifting to a slower C speed and another scale. so that, while the (Special Diagram Department) indications come less often, the depths can be A DIAGRAM 96 99R PARK PLACE NEW YORK. N. Y.

RADIO -CRAFT for MAY, 1933 697 THE MULTITESTER- VOLT -OHMMETER -AMMETER (Continued from page 664) ohmmeters, and the owners must use another cuit is arranged so that less than instrument 50 milli- the diagram. Connect all the tip jacks to the for measuring current. The Multi - amperes is momentarily flowing when testing circuit as shown: tester, however, is also a milliammeter, and has very low resistance values. For medium and (9) Connect the battery terminals to the se- current ranges and scales 0 -5, 0 -50, 0 of and -250 high resistance values, less than one milli- lector switch section 2. milliamperes. No. Be sure that all leads ampere momentarily flows through the circuit. to the battery terminals are securely fastened There is no confusion about selecting the The batteries, which are self- contained, will, and that there is no danger proper terminals, or tip jacks, of a short circuit. for making therefore, last practically their "shelf life." (10) Check the entire mounting and wiring measurements, as the one and one only set of The wiring diagram is shown in the figure. very carefully. If everything is O.K., secure the terminal -voltage is used jacks for all scales. It will be seen that only 1.5 volts is applied panel in place by means of mounting screws. This pair of terminals is of the non -shorting for the 0- 2,000 -ohm scale, and 3 volts for the See that the pointer on the meter is in zero type. and the positive is denoted by being 0- 200,000 ohm scale, while 30 volts is used colored for position. Adjustment may be made by means red while the negative is colored black. the 0- 2,000,000 -ohm range. The circuit is Similarly, only sim- of a tiny screw driver to turn the small zero one set of polarized jack ter- ple; but, when wiring, one must be sure to minals is adjusting screw protruding through the meter used for all current measurements re- have all connections soldered to lugs on the vari- glass. gardless of the scale selected. All ohmmeter ous terminals. The instrument is now ready measurements are available for use. When at the pair of used as an ohmmeter, turn the selector switch non -shorting jack terminals Instructions marked OHMS. to the proper scale. Always short circuit the A feature of the design is the single, simple (1) Fasten the meter to the ohmmeter selector switch panel by means terminals (through the test leads) which can be instantly set to of the three mounting screws and nuts: and turn the zero adjusting use the instrument rheostat for full - at any desired scale as (2) Secure the zero adjuster rheostat to the scale deflection of the needle. This balances either a voltmeter, ohmmeter, or milliammeter. panel by means of the locknut An provided. Mount the ohmmeter calibration so the resistances advantage of this design and switching ar- the knob on its shaft so that its rangement pointer is at may be accurately tested. is that the meter is automatically the left mark on the "low" position when the disconnected from all scales and circuits ex- rheostat is turned to its extreme left; List of Parts cept the one in which it is definitely indi- Fasten (3) the selector switch to the panel by One Beede 0 -1 ma. meter having scales of cated by the position of the selector switch. means of the locknut, and attach the knob 0 -2,000 ohms and 0 -5- 260 -750 volts -ma.; There are many instances where instruments so that the arrow points to the have 2,000-ohm One Supertest selector switch, 3 sections, 10 been ruined due to a bit of carelessness marking on the panel when the switch combined with the arms Positions: fact that one side of the are in position No. 1: One Supertest meter was also connected tapered rheostat, 15-600 -6,000 to some other circuit (4) Insert the tip jacks and fasten them to ohms. or battery. the panel. Follow the diagram as to red and Three Supertest shunts for 6 ma., 50 ma. and When not being used as an ohmmeter, all black color battery scheme. Be sure to use the insulated 250 ma. readings; terminals are entirely disconnected bushings when mounting the jacks; from the meter so Four Supertest multipliers, 5,000 ohms, 50,000 that incorrect use of the (5) Mount the shunts and multipliers ohms, 200,000 terminals cannot cause on the ohms, 500,000 ohms; damage by the self- sub panel as shown. Wire the shunts Three resistors, contained battery. The zero to the 25 ohms, 2,500 ohms, 25,000 adjuster used meter and to the selector switch terminals of ohms; for setting the ohmmeter is a tapered winding section No. 1 as per wiring diagram; Two knobs; to give smooth and gradual adjustments. (6) Make It the inter- connections between ter- Six Supertest insulated tip jacks, 3 red and 3 consists of a sectional rheostat with 15,600 minals of selector and 6,000 switch section No. 2 as shown black; ohms in each one -third of the wind- in the wiring diagram. Connect ing space, respectively. terminal 9 of One sub panel for mounting shunts and mul- section No. 1 with terminal No. 1 The knobs used to operate of section No. tipliers; the zero ad- 3 as shown; Two teat prods and leads; juster and selector switch are of the large, (7) Wire the resistors having values of 25 One 30 -volt set of batteries. low type, which provide a comfortable and ohms, firm grip. 2,500 ohms, and 25,000 ohms as indicated. One Supertest panel, drilled and etched, The white arrow pointer on the Connect the zero adjustment knob clearly indicates the operating rheostat according 5,4 x 8'4 inches; position to the diagram; One Supertest crystalline -finish metal case, of the switch on the etched panel. The dr- (8) Wire the voltmeter multipliers, following 5,4 x 3!4 x 4 inches; Sensationa lly puzzles! Sa o Neve in Jig The Front Cover of this Magazine in a ISO piece cut-out A BEAUTIFUL 4 -COLOR PIUZZLE JIG SAW PUZZLES will come turning each piece to complete MAIL THIS and go-but here is one that's this 150 piece puzzle. going to last a lifetime-It's COUPON none other than the cover of Send for your Jig Saw Puzzle TODAY WITH 2.5c Radio -Craft, in four colors, today- there's hundreds of and painted by Brown, the fa- hours of fun for only a quarter Radio -Craft Magazine mous -just 25 cents in stamps or 96 -98, Park Place, artist. New York, N. Y. coin. The coupon below makes Enclosed you will find my remittance for Here are many hours of fun it convenient to order your 2. cents (Stamps or money order ac- for every member of the fam- puzzle. It also insures cited) for which please send me a Jig speedy Saw Puzzle of the May cover of this ily-one, two or three hours of delivery. Clip and mail today. magazine, in 150 pieces. pleasant pastime, juggling and Name

Address RADIO -CRAFT MAGAZINE 96 -98 Park Place City State New York, N. Y.

698 RADIO -CRAFT for MAY. 1933 The latest addition KEEP YOUR CUSTOMERS AD- VISED OF GOOD PROGRAMS UNIVERSAL to the R_uu10 - CR.4LFT Few Service Men follow the program weeklies Protected very closely: yet, undeniably, one of the best Diaphragm Type ways of making customer -friends is to point Library Series out the better programs which may be regularly 1933 Model "BB" received. The following paragraphs, part of a Damage proof diaphragm pro- by James M. Skinner, president tection is now added to the talk delivered of Model BB & Corp., before a superdependability per- of Philco Radio Television formance. Brand new ahead- of -the- meeting of the Policyholder's Service Bureau times design. Double- weight, in -built of the Metropolitan Life Insurance Co., indi- ruggedness. The new 1933 Model BB cate the great lengths to which some organiza- offers a new conception of what micro- tions will go to meet the best interests of radio phone values No listeners. (Spot broadcasting, it will be re- prices. Model BB still at 82 5.0a called, has been described in RADIO-CRAFT e8 the list. method which uses special 83 1/3 r. p. m. elec- Universal Microphone Co., Ltd. trically- recorded. long- playing program recorda 424 Warren Lane Inglewood, Calif., U. S. A. POINT in lieu of the actual orchestrations, etc.) 'DINT TO " We were able recently to organize in less than a week's time, a program of spot broadcasts using a hundred and twenty -three tESISTANCE stations every night for five consecutive nights to promote a nationwide word building contest. Thus we used six hundred and fifteen broad- SERVICE cast periods in five days which the broadcast- 4EASUREMENTS ing companies tell tas is a record. MEN Like Modern Method "We always have used spot broadcasts, or at The least our dealers have, with more or less con- These Handy of Servicing stancy, but these again have been governed by VOLUME CONTROLS the advice of our local agencies. During the Standard end d coven with power- Radio Receivers past year, our principal broadcasting has been switch ssemblyvare instantly interchange, ble. A great convenience and time -saver. the concerts of the Philadelphia Orchestra under eut to desired E. Denton Long, aluminum shafts, easily ire Clifford direction of Leopold Stokowski using all sta- length. and supple- tions in a coast to coast system Write Dept. RC -S for complete catalog 50c mentary short -wave transmission to carry these The concerts to foreign countries. !75 Varick St.. New 'York. N.Y. Cops "Our object in selecting Stokowski and the Philadelphia Orchestra was because we believed EECTItAD it advisable, almost our duty to broadcasting and to radio, to give the music loving radio owners of the world an opportunity to enjoy often. the -ANOTHER VALUABLE BOOK FOR world's finest music under direction of America's SERVICE MEN greatest musical director. These were not studio full length concert broad- Of the difficult problems which Service Men face broadcasts but actual and today when repo! ring n-rei vers. the greatest is that casts direct from the Academy of Music while for PROFITS of replacing Proper resistance 'mutes In sets. the distinguished and colorful audience was pres- This task becomes even More difficult when the ent. PER FOR MANCE values of resistors are unknown: and manufacturers of many Mnndnrd sets do not pass this In- "With these broadcasts, we held the air for Dealers and Service Men formation ou to Service Men. an hour and three -quarters, (first) to avoid cut- In this new book. "RESISTANCE MEASURE - ting the concerts to fit a predetermined program MAKE BIG MONEY! MENTS." radio men will find t he information radio make (second) to impress upon the public o 4 and I GI rtube Place in normal Period: n1 Ilbettero grade ntsehel to quickly n receiver set guaranteed. tarok cuts In half, the as well as upon other broadcasters, the quality midgets -of super construct ion -every operating condition. This Important details upon request. Moe usually required to adJusit the %vent ge set. of program that today's broadcasting and receiv- Excellent reception. turn devoted to the elementary 4 tube. 2 circuit with tubes 311.000 Sufficient space hits ing facilities make possible: and (third) to a tube. 3 circuit with tubes 13.00 problems and the theory or electricity as It is 5 tube. Super with tube... - prove our contention that it is not good busi- 6 tube.Short Wave Bin.) Switching. 13 to 200 mete 20.00 applied to resistance measurements SO that the cycle) of ( i lo voir. AC--00 21 00 Service Man will hn ve a comprehensive Idea as to nose to originate too large a percentage pro- a tube Auto Radio and O Eliminator. complete how to overmany this problem. grams in the studios nor to have the listening Regular 3 months guarantee. Write today. Below you will find a partial list of the con- hours cut up into so many short periods. We TRUMAN RADIO COMPANY Chicago. Illinois tents w'laleil will appear in this new btmk . . . believe that a program must be of a quality to 7411 -(' Stewart Avenue. prepared by one of radio's foremost service writ - and to hold an audience, ers. E. Denton. attract an audience Clifford and we think there should be enough of it to Only by these qualities do Extra Special Partial Contents of satisfy an audience. 4= POINT -TO -POINT RESISTANCE MEASUREMENTS we believe that a program will impress its spon- AUDIO AND POWER CHAPTER 1- INTRODUCTION. Advantages of Re- sorship enduringly upon a listening audience. SAMSON SUPPLY COMPONENTS Ftunce Measurement Method of Servic- "We do not infer by this that all programs At Considerable Price Reductions ing for Radio Work. but A FEW EXAMPLES LISTED HERE 2 Principles. should run for an hour and three -quarters CHAPTER -Baste Our Measurement. we are mindful of the fact that vaudeville lost a.iat ('IIAI'TER 3- Methods of Resistance Title Price Price CHAPTER 4- Resistors in Radio Receivers and Am- its hold on the public. We think the vaude- Cat. No. plifiers. villian rapidity of act presentation should be s Symphonic Audio Trenaformor.. ..810.00 $1.69 a. CHAPTER 5 -Point to Point Resistance Measurements hope Y Input or Inter-nage Push Pali A.1'.. 14.00 1.95ea. in Typical Radio Net using Ohmmeter. avoided in radio because listeners usually 04-07 -08 Output Tratmformera 10.00 1.45ea. 3loulern to settle down, relaxed, for a considerable period M.L. Mike to Line Transformer 30.00 2.95 CHAPTER G- Resistance Measurements using 30.00 2.95 Tester. changes TL Tuile to Line -perhaps an entire evening. When LT Line to Tube 30.00 2.95 CHAPTER 7- Routine Testing where Circuit Diagram so frequent 2.50 .69 are from one program to another are R.F. Choke 85, 3LH is Available and where Re. Istattces and Radio Scratch Filter 2.50 .69 Known. as to get the listener all jittery. radio, it seems Phono CHAPTER 8- Routine Testing where Circuit Diagram to us. is being abused instead of used." ALMOST ALL SAMSON NUMBERS IN STOCK f Is Not Ara liable and where Resistances Write for information on any Samson Are Unknown. products not listed here CHAPTER 9 -The Relation of Voltage Testing Methods Measurement. ALAN RADIO CORP. to Resistance New N. Y. CHAPTER 10- .tPPENDI N. Resistance Charts, etc. FOX HUNTING BY RADIO 83 R. Cortlandt St. York, That well -known columnist, "Ariel," writing 64 PAGES - 6x9 INCHES TRADE MARKS in a past issue of POPULAR WIRRLESS, laments OVER 100 ILLUSTRATIONS COPYRIGHTS as follows, anent the use of radio in pursuing PATENTS Br'er Fox. "Lillie Ideas May hire Big Commercial f'ossibililies" BY that in connection with a radio PROTECT THEM Mail Coupon Today! It is reported Send for our Free hook. "Ilan to Obtain a Patent" and display at Pardubice, Czechoslovakia, wireless "Retord of Invention" blank. valiant Prompt Service -Rea semble Charges- Deferred Payments GERNSBACK PUBLICATIONS, Inc. RC -533 is to be used on aeroplanes to signal to NI 9698 Park Place. New York, N. Y. huntsmen in motor -cars the position of a fox, VICTOR J. EVANS E! CO. Eta Imp' you will find my non lot anse of Fifty Cents which will then be hunted by the aforesaid he- Registered Patent Attorneysa-Established 1898 It heck. stamps or money order accepted 1, for nhirh you sorry! Radio has 650:EE VICTOR BUILDING WASHINGTON, D. C. are lo send me One Copy of POINT-TO-POINT RE roes till it is killed! I'm SISTANCE 31EASI IIE31ENTS, by Denton. done so much that is useful and pleasant that EASY WAY TO to turn it to the purpose of assisting a small animal to be harried to death hurts my pride MAKE MONEY IN RADIO Name of the human being. My full New training' wet hmi and :errire egui i purent 'uffrr star, in the nobility you earning quickly. Covers all the Ist est development and uncensored opinion of fox -hunting by In radio science. preparing YOU quickly and thoroughly would not be printed for gord positions or independent bu-Ines. career. Semi horse and hound alone NOW for all particulars to by any editor I have ever met or worked for. My opinion of a radio fox hunt would singe Radio Training Association of America the very paper! Dept. RCA -5, 4513 Ravenswood Ave., Chicago, III. RADIO -CRAFT for MAY, 1933 699 The dioaft ibrary Series is handy for reference! Presented on this page are the new tained in these books will increase your books subject -each is thoroughly familiar of the RADIO -CRAFT LI- knowledge; you will find them a real with the field which he represents. BRARY -the most complete and au- help in your work and they will thentic set con- This is perhaps the first real oppor- of 'volumes treating indi- tribute to your money earning capac- tunity that you have ever had to build vidually, important divisions of radio. ity. Read these books during your radio Each book a library of books that are au- has been designed to give spare time at home. thentic, right- up-to- the -minute and radio men the opportunity to specialize The authors of these books are well - written in one or more so that they are easily digested of the popular branches known to everybody. Each one is an and clearly understood. Mail coupon of the industry. The material con- expert radio man; an authority on the below for your books,

TO Beek N.. I THE RIGHT Book No. Book No. 7 Beak Ne. le WILL BE FOUND RADIO SET MODERN RADIO RADIO KINKS AND HOME RECORDING A SHORT RESUMÉ ANALYZERS HOOK -UPS WRINKLES AND ALL ABOUT IT And How To Use Them The Best Radio OF EACH BOOK Circuits For Service Men and Expert A Complete Treatise on Instan- menters taneous With Full Instructions end De- A Complete Compendium of the Recordings. Micro- phones. Recorders. Amplifiers, scriptions of Set Analyzers. Most Important Experimental A Complete Compendium on the Tube Checkers, OaelDeters, Eta. Latest Commercial Machines, Serv- and Custombuilt Receivers Radio Short -Cuts and icing. etc. Money - Savers By L. VAN DER MEL By R. D. WABHBURNE By GEORGE 1. By C. W. PALMER SALIBA This book explains thoroughly It Is fascinating to the experi- the operation of set analyzers. If there is one subject that menter. or even to the up-to -date If often becomes necessan for Is fascinating time checkers, oscillators and Service Man, to take commercial experimenters anti Service to every radio other Men to man. it Is that of Home Re- testing equipment. For set and to change It Into one us- call upon their memory for some esery radio man this book cording. Of course, this volume is ex- ing a famous hookup that Is not short cut or radio wrinkle that lo not tremely helpful. It covers every found in any all on "Home" record- manufactured set. will solve a problem quickly. In ing. but the Information Phase of testing and gives you Many excellent circuits have nev- business, "short eats" mean con- valuable short cuts; time tained therein is important to completely i been commercialized but lim- and money saved, and to the Serv- commercial illustrated with photographs and ited radio men. studio only to home set builders. ice Man "time saved" means operators. engineers diagrams to facilitate the use of Thousands of these popular cir- money earned. and others modern tc iers. hnereited ln this phase of ra- cuits have been requested from This book dio. lime to time, and is a compilation of ln this book important radio kinks and we have Included over 150 cir- wrin- The art of recording and re- cuits. which kles and discusses only such items producing broadcast Include the famous as are constantly selections is Peridyne, Cash-Box A.C. -D.C. Used today. becoming more important even Set and others. day to radio men, experimenters Beek Ns. 2 and Service Men. Equip- ping dance lulls, auditoriums, churches restaurants and homes MODERN VACUUM with public address systems and Book Ns. 5 amplifiera TUBES Book No. brings many extra t dollar, and often an excellent And How They Werk HOW TO BECOME A Income. RADIO SERVICE MAN RADIO QUESTIONS With complete Technical Data on AND ANSWERS All Standard and Many Special How to Get Started and Now to Tubes Make Money in Radio Servicing A Selection of the Most Impor tent By ROBERT of 5.000 Questions Submit- HERTZBERG By LOUIS MARTIN ted by Radio Men During the Course of One Year MODERN VACUI'SI TUBES The ambition of many men in BIG describes the fundamental elec- radio today Is to become a firat- By R. D. WASHBURNE tron theory which Is the basis of grade Service Man. vacuum It Is not as DISCOUNT all tube operation, and difficult as one might believe. but There have been collected a wide goes progressively from the elm - it cannot be done In a few short variety of questions which have pleat two- element tubes right co months. Following very earefully come into our ',Mortal offices dur- OFFERED to the latest pentales and thyra- the advice of Mr. Martin. who ing the past two years, and only Irons. It Is written in clear. has dealt with the problems of those whose answers would benefit In order to make it possible simple language and Is devoid of thousands Service the majority of men engaged the of Men. this In for everyone to buy these books, mathematics which is usually hook deals very carefully with radio have been incorporated in so confusing. Valuable the the fifty (501 cent price has reference essential stages in the prepara- this amazing question and an- been made uniform for charts and characteristic curves swer hook. all vol- tion for qualifying as a Service A tremendously long umes. You can buy these books of standard and special tubes are Man. list of topics Is treated. separately, lo be found, also diagrams of but you should take sockets and pin connections. advantage of our special offer: When Five (5) Books Book No. S or More Are Ordered BRINGING ELECTRIC Book No- S Deduct 20% Book No. 3 SETS UP TO DATE AUTOMOBILE RADIO from Your Remittance THE SUPERHETER- With Pentodes, Multi -Mua, Dy- AND SERVICING namic S pea ken-Complats In- Simply fill in the coupon be- ODYNE BOOK formation How to Modernize A Complete Treatise on the Sub- low, and mall it to us together A. set (levering All Phases from with your All About C.. O. C. and Battery Oper- remittance. (' licita. Superheterodynes ated Receivers Installing to Servicing and SUMP, or money orders accepted. Maintenance How They Work, How to Build By CLIFFORD E. DENTON and How to Service Thom By LOUIS MARTIN By CLYDE In this country there are over FITCH ten million electrically operated Automobile radios are up and ALL BOOKS receivers that , Id be molern- coming. and someone has to serv- There is no moro fascinating a ice them properly. euldect in the large array of radio lud-by placing oin them new type It therefore tubes, new speaker equipment and behooves you to read this 1m- UNIFORM ircuite than the famous super- meneely heterodyne circuit. Whether other modern improvements. This important new book on you the art of Automobile Radio. The The hook.; In the new It.tDIO- are a Service Man or experiment- business of improving old seta CIt.IF'r LI ItRARY can go to the experimenters and book is concise. and full of illus- e all er, first -hand knowledge about the trations, strictly up-to -date, and written construction of superheterodyne re- Service Men if they will quickly photographs, diagrams by men who jump into action. and hookups. know their sub- -elvers 1s very important. The jects. The volumes are all book on Superheterodynes gives Read in this book by Mr. Den- A few of the really interesting uniform size, 0 :0 inches, and underlying principles of their con- ton, how easily you can modern- chapters: introduction; Automo- contain on an average of 50 to struction, right from the very first ize any obsolete set, and with tive Radio Installations; Complete t0 Illustrations. Each book Descriptions set made. little additional costa. of Commercial Auto- Ì printed on tine book paper. motive Receivers; Servicing Auto- expense has been spared motive Receivers: The ignition to make It an outstanding value, System; General Service Consider- for its editorial contents as %sell ation; Effects of Temperature on as from the mechanical stand- Clip Coupon and Mail Today! Power Supply; Conclusion. point.

GERNSBACK PUBLICATIONS. INC., 96.98 Park Plats New York, N. Y. 1 have circled below the numbers of books in the RADIO -CRAFT LIBRARY, which you are to send me, and have deducted 20% for ordering five (5) books or more. 1 have included my remittance in full, at the prlco of 50c each, when less than five books are ordered.

The amount of my remittance Is._ .__.(Stamps, cheeks or money orden accepted.) numbers wanted: Circle 1 2 3 4 5 8 7 8 B 10

Name ... Address _.____....._.__....___.._...__.

City State RC -5 -33

700 RADIO -CRAFT for MAY, 1933 roj TWO STAGE 250 SUPERPOWER A e AUDITORIUM- SOUND TRUCK and to PIJBLIC'ADDRESSeAMPLIFIERS X FACTORY WIRED } READY FOR Alent tt/ IMMEDIATE US6 I y> l'so vte for " IJ ; ? t ` ® - ; 'I ___-- TI' TUN E R ss I pD HoHo t lY, cK vp w " p 'IRE°aa25o7 AI CROPH ONE rBiTb;iB' 0epw MpIIFICAIl°1 G ÙiiY SPEAKERS. Note with Victor 2 -1000 ohm, or 4 -2500 ohm (110 Volt D.C. TSpe) DYNAMIC This Amplifier Is the original AP -736 Mall (which was furnished -' transformer is required, as our heater action of the that if only hoe Steaker will be used. then no output I(leclrolas selling as high s 61.000.00:). Due to the "quick transformer. Constructed upon do the Model. that amplifier is Speakers are equipped with a suitable matching Ist A.F. Tube, and in fact of all the tubes 68.95 of great strength. handsomely duro sprayed, -OFFICE COMMUNICATION SYSTEMS. or % in thick malleable Iron chassis idea =peciaily valuable for use in INTER 17% in. long 12% in. wide and 7% in. tall over -all. An imposing is necessary to operate an amplifier "the montent" it is turned on! measuring transforme: ,herever it high and low of its contents can he gleaned by its weight of fully 68 lbs.! The power the two stage 68.95 model employs 1 -228 input tube (and associated even over cor, into a 250 tage Is of heavy -duty design, and will function practically indefinitely. .o pedanee input transformen), which is audio transformer coupled is also foolproof. Rectifiers. An output transformer furnished tinuous operating periods. The filter condenser system practically :id utilizes FULL WAVE 2 -281 to of Its being rated as high as 1.500 volta! Perfect impregnation to 15 voice roil of any dynamic speaker. The three stage highly due some units of matches an 8 ohms VOLUME of components makes same impervious to the ravagea of both extremes improved $19.50 model comprises the Isllewing: A UNIVERSAL INPUT vital clever automatic and . even Ideal for use in the tropics! A the circuit of the first 'pre- amplifier" 56 tube. the output of climatic changes on when coNTROL is in gril is arrangement the amplifier should it be turned Wit is resistance coupled into a second 56 A.F. Stage, which in turn PUSH- fool -proof switching protects to 30', 250 TIRES! Its Is temporarily disconnected. Another switch permits selection of 90 'I'LL TRANSFORMER COUPLED to TWO SUPER-POWER speaker for an A.C. DISTORTION -FREE and amazingly faithful In Its Volt or. 105 to 120 Volt A.C. operation. Receptacles are provided enormous output el 13 web is field current outlet. All conned Sheer realism of fidelity. By virtue of its employment of THREE HIGH GAIN Line Cord Male Plug and for a convenient speaker is enormous nd makes engraved on readily accessible bakelite terminal strip t.F. STAGES, microphone and phono pirk.up amplification lion terminale are clearly LIFE- his amplifier accordingly extremely valuable. (Its D.B. Gain Is rated ate 92 D.B.) PRODUCES GIGANTIC DISTORTION -FREE VOLUME. REMARKABLE (he input terminals may be connected to any secondary winding of any input trans- LIKE REPRODI'CTION! You will be Immensely thrilled by the aimoat uncanny It as a farmer (generally contained In control boards) or to a radio tuner output plate Ir- reproducing qualities at these amazingly powerful amplifiers- elther using It. high impedance phono pick -up. etc. Both the 68.95 and 619.50 model furnish phonoonph or Radio Tuner amplifier! We want you to expect the most, Dynamic Speakers. Connection microphone, D.C. Field Current Excitation to from One ta Four for. you will not he diaappointedl diagrams are furnished showing how to connect the field coils of 1.2500 ohm, 1 or SUPER -POWER 250 MODEL Three Stage 250 Push -Pull 13 Watt Model TWO STAGE Less Tubes with GEM. I\l. STAGE AMPLIFIERSWith Four 3a STAGE AMPLIFIER TWO STAGE AMPLIFIER Less TWO 3 STA uE AMPLI TIER. Tubes end choice and Speaker Ready RCA tg your Tubes and Speak- off one Wright De $1750 For Immediate Op- in- er Ready For n C Coster or Jensen Dy- erotica 950 Costes Jansen 7 Opera- tr 9 t5 namic Speaker a $3350 Immediate Dynamic Speaker... fion 3 AMPLIFIER, with ais Genu- 3 STAGE AMPLFIER Equipped STAGE TWO STAGE AMPLIFIER ine RCA tube. d including your GENUINE TWO STAGE AMPLIFIER With Four With SIX GENI hoiea f TWO CO Equipped With FOUR RCA Tubes and choice DINE RCA TUBES Wright Da Cosser or J RCA TUBES of two Wright D. $2 25 (2_$g. 2 -25 O. $2650 Jensen Dynamic 38 1 Jensen Dy- (1 -228, -250, J Coster or 2 -281) Speakers 2 -281) namic Speakers Ratings Soo ohms, 1!3. 7th -334 ohm.. 93.95 Special Output Transftormer- Matches voice coil. of from 2 to lb Dynamic Speakers. 13 Output Complete P.A. Installation Auditorium or Sound Truck RCA Amplifier Watt Consist of: thought of our P.A. Engineering Deli t. Complete I nt.11etion RCA Amplifier Complete As Tou may purchase this complete system 1 Three -Stage g26.5o 1 Set of Si. Genuine RCA Tubes assurance of obtaining maxi- with every 4 D.C.Dynamic Wright Illustrated mum sound coverage and perfection of De Coster Speakro reproduction. Each speaker field is ener- at $7.35 29.40 and a SUIT- I SPECIAL OUTPUT TRANS- gized from the amplifier 3.95 $8950 VOICE COIL MATCH- FORMER OUTPUT ABLE Ipihone Double Button Micro- ING TRANSFORMER Is furnished as 12 50 well. Note that the ALL PURPOSE tae "Miki' 7.95 Rightfully Consid. PHONO-MIKE- RADIO" Input Control 1 Stand tand Ring ered the Biggest blending. fading and 1 Purpose Input Control Box permits perfect "All- 17.50 Value in America super -imposition of voire across a phono. Box also permits the sepa- 13356 and 78 R.P.M. Dual Speed Today! record. etc., etc. It 9.75 rate placement of the amplifier proper 110 volt A.C. Phono Motor Careful selection of c- box. Speed Pick- up 6.75 ssory equipment to from this very efficient Input control 1 Dual these may Dynamic Speakers are de- QPhdono Any of Accenoriee ro pries a perfectly only Total $uä.30 be Purchased Separately matched P.A. System (If twt $10.00 SP elmené $07.50 at Prices Quoted Herewith! was the dominant cost price shown to the right. One -Dollar -Series Audio Transformers Servicemen and Set Build- ers: Employ These High Westinghouse Grade Transformers Exclusive y! Audio and Input Push - Output Transformers YOUR l'hese transformer: are all designed on a Pull Transformers From 1 -171, 245, 250, eta. to Voice Coil in. square core of high Silicon steel. S to 1 Audio 3 to 1 Audio 8-15 ohms CHOICE 1 59, 233, 238, etc., to l'he core Is securely held In a rigid steel 2 to 1 Audio From -247, henni Otrora. Designed In accord.. e Input Push -Pull 8-15 ohm. Voice Coil Juh the latest technique: they can he de- Input with Spit From 2 -171, 245, 250, etc., to -Pull 8-15 ohms Voice Coil ,e dei upon to give very satisfactory re- ua to 'tilts! The 6 inch leads are made of Inter -Stage Push -Pull From 2 -247, 59, 233, 238. etc., easily Insulated wire and bear the R. M. Microphone Inputs 8-15 ohms Voice Coil A. standard celer ceding. The colis are Single Button -200 ohm Inputs clentifirally treated to be impervious to Phono -Pickup $100 Double Button -200 ohm ,11 atmospherics -a very valuable and Low Impedance ::ry feature. The overall measure - Line Transformers High Impedance Each enls of all the transformers are 3% in. 500 ohm line to Grid Filter Choke 2 in. wide. 2 in. tall. There is Plate to 500 ohm Line Box to 500 ohm Line 30 Henry, 200 ohms, 150 mil no 4 better quality transformer available! Control is required with every order. Balance All offers are F. O. B. New York, and subject to prior sale. Terms: A deposit of 20% may be paid on delivery. Or, deduct 2% if full amount is sent with order. GREEN STREET, Dept. RC GRENPARK CO, N245 YO K,

RADIO -CRAFT for MAY, 1933 70 I Make Try-Mo Your Short-Wave Headquarters

For Many Try -Mo'a ade- Years Try - -, NI- quate staff of Mo Has Been I/, Short - Wave The "Ham's" Experts a r e Headquarters always at F o r Short- your service to assist you Wave Re- in your prob- ceiving and lems on re- Transmitting ceiving a n d .Apparatus. transmitting.

Years of diligent experiment. in the POWERTONE "LABS" have finally produced SHORT -WAVE RE- Powert one CEIVERS that have earned a TRULY ENVIABLE REPU- A. ve especiala 1 TATION in their RECEPTIVE QUALITY -CAREFUL filheri CONSTRUCTION -BEAUTIFUL APPEARANCE oP y ten -and which edw - UNSURPASSABLE QUALITY PARTS. hum to . minimum Lhu,affurd- POWERTONE has Leen turtle a WORLD- FAMOUS NAME l.y their production of ONLY QUALITY EQUIPMENT. Youn elem. loud re- n ception. have the UTMOST FAITH in a GUARANTEED POW ER- All :°listed are complete TONE SHORT -WAVE RECEIVER. four covering lenwith 5 to meters. All seta complete with 6 mo.. guaranteed SYLVANIA Tube.. 2 -Tube Battery Operated 3 -Tube Battery Operated 3-Tube A. C. 4-Tube A. C. 5 A. A "peach" of a set for the "Br- 1...o- the new 234 R.P. -Tube C. pentode Puer the latest '58 general nor- Utilise, one '56 triode Experience the thrill mite which is noted for its sen -i. mise mod! and a '57 triplegrid tube. a The Paramount of Powertonc of` Real '58 triple grid R.F. amplifier Short -Wave Reception tivity in picking up weak signal.. amplifier tube. Quiet, hnnde,s tube, Receivers. With this master- Police Signals! Amateurs! Two 230's follow teatn ir. a '47 pentode power ampli- hurt-wave reception. An 'h0 fier tube, and an '80 piece of engineering you can LTo-Shore Signals! C. W.I detector anda d tl other is used type recti- typa tube for rectifica- fier tithe. Uses. reach out to the distant corner- sensitive 232 screen grid usaed as audio. tion. }Iinged OCTO form top on cabinet coils that covera length of the earth for new and dif- I 233 p,werlrentodooutput Wired, with tubes ó,ilitates removal ofcoils and Rom volt tube.. odes. 15 to 200 meters, Cabinet ferent thrilLs. Use, two 258 (lees hatteria,) .. S 1 95 with hinged top for easy o. sed. with tubes re- triple grid amplifier tubes, on, $9.95 of Parts with Wired, with I of coils. ba Kit 10.75 '58 triode, one tubes fleas batterie,) tubes 514.95 Wired. with '50 triple rid I It of l'ert., with tubes S19.75 power amplifier tube.' and batteries/ Complete set of Lat- hit of Parta, with . 7.5 2.75 Kit of Parts. 80 type rectifier. tsrio- 12.75 with 16.95 Iodate set of Lar- 2.75 ALL SETS COMPLETE WITH TUBES ireCIt th tutte., At OTformO coit i 24.95 Sagret$c New 1933 "ROCKET" 2 -Tube Short Wave R, C. A° ! n..design ofthe "ROCKET" re.utts FARRA Cassis e the keyword, the name (Permanent ibesrt alitydparts .ticlmp0prs ke, lowe.tpriceswere kept in mind. Clear GUAR Magnet) S4eake WA, te t, wing the Dyn R construction of 7ED PARR anle the " are furnished with No C It' ,am'tt all kin.. The kit contains every con - an ha SSis it 'table necessary part for assem- Ifi renn°t, p\° bling a complete :Rum-Wave Re, eier. 6eao"td -including HAMMARLUND Tuning a- Condenser: drilled and punched fyt metal panel which eliminate, hand tIÑJ ehe^re capacity: drilled bane for mounting of sockets. etc.: Your plug -in coils t MU4oaio n!" ' , ehe covering wave lengths from 15 to 200 n ehrp l' two 230 type two-volt tubes. Dimension. Ìo,w°i °'ilÌ regie., mu of panel: 55 high. 0' wide. h/ Complete kit of :.,rt.. with blueprint Rhes Set of two 230 lvania f4.25 l oeh deve nvost tubes 1.a0 ortyr.unnevYt Set of batteries 2.25 l'le e, d I ,ludo- two "B" batteri.,, two dry celle) fur Lightweight Ilea,lphunea eich,.,. completely wired odef $4.95 "Beginner's Twin" NOW ! Se95 BOSCH Short Wave Speaker Cabinet Receiver Stromberq- Carlso A beautiful walnut cabinet ( Batten Operated) t mat actively finieled . \. de.rrited and hand-rubbedrubbed to a soft. in the New York MAGNETIC satiny sheen. Will ac- Sun. March 4th. commodate any speaker np 1933. Designed PICKUP to and including 10' i by a famous diameter. Will materially radio engineer. enhance any ..nrrn utingra Not a make- OUTFIT to which it is plated shift affair, but a carefully built Price $1.95 kit that Redly A genuine Strom - Brings In berg- Canaan Phan Short W ve Station.. Ex- rph Outfit In orig- treme inal carton., selling Jensen D -7 A.C. of the circuit now for only the major factor of the "Beginner's Twin." thus 50 It seen. Dynamic Speaker eliminating any complications in the hookup. incredible, yet figures d.,. Recommended for those who fit which we have Aiways sold for 9 :. -...... I. Dmigned for all of people are interested in exeterimenting on short- waves, but who donnot wish time for $5.50. Thousands have be .old at the former mpb!ter to systems and to spend too much This is price particularly use kit not only very and acclaimed by all e. superb value. Can you for with how in price, but of on ch simple construction that it imagine the value you are getting with i late model receivers re- requires o practical knowledge the price practicnll quiring of radio to ensemble an ('. Dynamic it. Noweveryonen interested in the new "short speaer. ConeA. is -wave IOü fad" can afford to try hi, hand at building arecreceiver ook what you Orel diameter-overall height of his own that will receive short wave etatlona.The 13'. An 8 ofd. Stromberg- Carlson Pick -Up with Built -In Velum, . electrolytic kit ie comprised of nationally- known, standard part., cnden used to mint Kit of parts with blueprint and Control A. C. ham tubes $7.95 any Wined with Sylvania tubes 8.95 Stromberg-Carlson Input Transformer rre (with complete net of batteries 2.50 20 Ft. Insulated Extension Cord tube) $8895 New, Improved Pick -Up Plug

` = TRY-MO RADIO (O.INEÓS Conlandt St.NewYorki,

BRANCH deposit must ac- STORES 20% 178 Greenwich St., N. company all C. O. D. Y. C. 179 Grcr,taieh St.. N. Y. C. ,Send for Our New Bar- orders. Near Dey St. Near C"rtlandt St. gain C'ataloy replete with Note: Send Mail Order. to Dept. C5, 85 Cortlandt St., New York City. Radio Parts.

702 RADIO -CRAFT for MAY, 1933 Modulated .Oscillator illa ror

m4waeae t` d.fp A. ikea,td A.Q tuba.. fede..l.

wt, 3 dry . 7i4 ,., .. . 76 ...... ,...... 11' 9ater.... $6.53 l. 14netb .00035 Variable H R Prime A. C. Phonograph 'I} ss Motor jet .1 Condensers eturdv. KELLOGG NEW BEEDE METERS r SINGLE BUTTON HAND D'Arsonval Movement ] "MIKE" Lowest prices!! I

Sí.45 S5.50 95c FLECTHEIM 0-500 Voltmeter Powertone Microphone Input Stage Powertest 3 Gang tir net Condensers .00035 toll. t`.c. Afff onlyt'urtnble 5 mil,. q,w, 11-50. i\\\\ tratm o-sou volte U. C. Itishlr $4.12 53.25 ikelpd 4.12 3.25 heavy L 4.12 3.25 ,lu d 4.12 3.25 $1.35 3.25 3.25 3.25 3.25 3.25 3.25 54.95 3.25 3.25 Powertest .00014 3.25 Universal Midget Power Condenser 3.25 Transformer tic {3.25 Farrand Magnetic Speaker Chassis R. M. A. a rrand I Watt Color han.ie one of the finest of o magnetic Coded Re- speaker chassie a ail - able today. Itt sistance Kit 95c a balanced armature which nablea the chassie to handle a large moonlit mi volume without dis- Sangamo Push Pull Input torting or rattling. and Output and Audio Transformers ICCIIAL $1.95

Powertone Midget POWER TEST Variable Dynamic Speaker Midget Condensers

Si.25 S2.45 $3.45 $1.45 FREE! $1.95

h"e ha. e tril BRANCH STORES nrarew ilow tilthe 17$ Greenwich St., N. Y. C. 2» Greenwich It., N. Y. C. u deed, hided St. ,i.' rite pricer Near Der St. Neer Cortlandt i.trin ir: TO ` i Note: Send Mail Orders to Dept CS, 85 Cortlandt Sr., N. Y. C.

701 RADIO -CRAFT for MAY, 1933 MAY SPECIALS!! EVERY month we list on this page certain STAR items, which are STOP SHOPPING. The lowest prices are right on NOT LISTED IN OUR CATALOG. These are all specials this page. No one the of which undersells us. We meet any price on ANY NEW Merchandise. Order quantities on hand are not sufficient to catalog them. Once sold out, direct from this page and nave money. no more can be had. First 100% satisfaction on every trans- come, first served. ORDER NOW, TODAY. action. Take advantage of these special offers. ORDER NOW, TODAY. Only $ óly S Greatest Buy In America! $ * "PEERLESS" 8 -TUBE SCREEN -GRID T.R.F. RADIO RECEIVER Complete with Full Dynastic Speaker

Ha, w i,,nt 5o Limited Supply-Only as Long as They Last -Order Today IF LVEIt there ware a greater salt, n this offered before, be have yet to be It. silicify. Many The s of our -fooleryn Inform us that a . variety of dia ant seleriinify and 1 -tube nsitivity ul receiver due to Ile tour tuned stages stations a I, 'I mine I re as sharp as In like i.r,r quality, too, Is extraor in..HH l> line. Despite the just those of an rrrvu -ire 11 -tube Superheterodyne riseiver. The maze of two' tubes or IV s rc hit." upon the market. it i ally conceded tins strurt Ion of this receiver is best Ie,crilanl as "standard." Ito circuit Is none for verace home use other than 'good push pull '45's supply adequate power s with the least distortion. the old standby" TILE type which la the most rem table and the Why build a set when a most foolproof ever designed. It Incorporates mtplele receiver, xi red and ready to use. and rmupletr three stages of tunedne ILK angdierr with speaker. ran be bought tat this phenomenally low prim? is 1 ion using type '21 Screen -grid tubes; the pox er detector Is a a Here an excellent "1; single stage tppernmity for x ide -awake e v lee men to "lean up." There are little mare than of AN voltage amplifiration utilizing the type '27 tube. feeds a pair of 45's In push 1no of these receivers left and at pull, the full bare resticer Is an N0. All provisions ' this low price, they are bound to give t In very are made for supplying field short order. Experimenters 111 find in maser for the 0 Inch TCA this chassis the laboratory 'monitor" they (Transformer Corporation of America) full dynamic have been batting to buy "bben things got cheaper." -weaker. Both cone and spider of this excellent reproducer are tootle of Mutes to Remember that the supply is limited. hence. "first cone first x r d." The moral is don't delay. order improve the high note response Ibrilliance) b- ithout impairing the low note Ion. today. praluct Os erall size 21" x 8" 2 8 :4'. (set only). Ship. wt. 45 lbs. Tuning is extremely simple. the tuned ti reuits being controlled by single central knob; a vernier drum -type Illuminated tuning dial is employed. The second knob List Price $75.00 cnmrols the on -off switch and the third, lite one on the right, volume control. Coils, -condenser -ivid. alter Added. r bank, output elf and by-pass condenser NO. SP -2000 Peerless 8 -Tube TRF Receiver bankis :ink are all individually shielded. The chassis itself is made of nun- xiuminum. magnetla YOUR PRICE with speaker but less tubes . \l \Ipea {x/aJ The use of four tuned circuits. mewl.) ing screen-grid tubes and high gain B.F. LIMITED SUPPLY-ORDER TODAY- TOMOR- 85 ri.w.(nrn,r- to s i l l r is iris ,.1 'efts Mg. and by- passnc, reso It lu high sin ROW MAY BE TOO LATE Build Your Own "Dependable" Tube Tester! Doerle 12,500 Mile ShortWave Set Ate. Sold r time be pre-emit a eomplete Although in Kit Form kit lit ei the Doerle is a low -priced re- 1 .oiiug all mil a need "DEPEND- ABLE'. 1111,5 ceiver, yet it pulls in short l' -n, -:m imtrument sshlrh is MOD- -wave stations ERN In every s t -o of the bad. Will test all the from all over the world. REGULARLY. in latest type tube Ìm4uding those with 4, 5 and 7 practically any location, not only in prongs- DIRECTLY- wITIIOt-T TIIE USEE (5F A this SINGLE ADAPTER. Complete details for eons! 'ust- country, but anywhere. Thousands of ex- log rids instrument here printed In the RADIO perimenters have built their own, and have C1t.11.7 magazine for April. (skimpy of this magazine obtained miraculous results. All the usual bill be given FREE sa It h each purchase. I Complete in:truejinm are also furnished bith each kit. "bugs" have been ironed out by us in such The "DEPENDABLE." despite Its high degree of a way that you may order every receiver accuracy. is ESTItE.3IELY SIYIPLE Tll OPERATE. with full confidence, that "it will do its Bulls plates of the 80 -82 -83 and other reel icera stuff" anywhere. are readily tested Without the use of a "second It is possible for us to Plate" button. 'roe condition of a given tube Is sell cheaper parts for the complete receiver manifesto' by Its mutual co du el once (em ',skipr at a lower price. But then we could not hararterist le. 'hick ie clearly indicated on the me- its performance. wl. t:nihlrc- ..nit, type meter guarantee Therefore only ,. ... n ic ter at an First Class Material Is Used. '1'11 I a rertiver is exactly as (Please specify which when metre Illustrated. for which is Si,. of IuuJnum panel i, t) x "SHORT" test satcgt:u. the Iii, Invites ; of the meter. Shorted tubes are ulumaticall> E RADIO AND SHORT base if fits Inches. List of material E used: 2 llammariund .001114 indicated on a pilot light. Condensers; 1 Car- ter 20 tun Rheostat Sbiteh r. Operates on IOS 115 -123 volts A.C. with WAVE TREATISE and ; 1 st raw[. un the Indio Transformer; 2 Kurtz -Kirsch V. -' Dials; 3 ONLY Bakelite Low Loss Sorkets; 1 Mi.. FIRST-CLASS PARTSv ARE USED The ne. Winery. 1.3 edition of sur Radio Equalizer THROUGHOUT. The is sold complete bills Antenna Condenser; 1 -.0001 kit and Short-Wave Trent*. Nu. m. has as Fixed Condenser; beautifully lithographed panel and handsome came n tune-104 ad pages 1 -5 iegohm Osrbor.. useful a Grid Leak; 2 Telephone Pin I leatherette ease with deluxe trimmings. Over- kÑonnetlon rad Items d.- Panel; (arks; Alun. grams and iintratons.l ro iii.d . he i Veneer Baseboard; 1 Bakelite Stln all dhnensiuna of completed tube checker in Knob; - double binding :Ise 11" 9" x 5 ". Ship. ut. 8 lbs. ANOTHER posts; 1 set of 1 e CATALOG Md oon 1 aUi íT1 Loss y,. ge elfisori.1 a.stiii Short Wave Plug-in (oils; 4 -page h:- Here is what you receive: and litho- b,o,le i - tion 1- drilled wti.n to pamphlet and blue prints; 1 Set of n graphed panel 10" 8 "; 1-filament trans- n h.. heen sxare, Wire, Ne Complete radio hipping - ight former; 1-0 -15 MA. specially calibrated mag- ,laiefurìn No. 2111. TWO TUBE 12.500 MILE DOE: netic -vane meter (or moving coil meter -see inn hated are thehfollow SHORT-WAVE RECEIVER. completely s hove): 1 -7 point filament selector ss Itch; 1- and tested as per above specifications. 4 line voltage selector 1 point switch; -6 -leaf HERE IS A PARTIAL LIST OF VOUR PRICE jerk switch; 1 -3 -leaf momentary roneut CONTENTS - 88.00 switch: 1-- S.P.D. T. toggle switch; I1eldeu l..l Nn. 2141. TWO 1- u': Fundamental Principles of Radio TIRE 12.500 MILE I)OERL}I soft rubber plug and rable; 10 -wafer sockets Oh La Discuss,on at New- rhIOItT WAVE RECEIVER KIT, isith all parts for 4-5-61 and 7 prong tubes; l-3 watt 7.000 :epe lln'NIe1n Tub -Con t u t,ng a' Triple- Twin" as specified above, but not A wired, with blueprint olun 1 ^- pliller -All about Superbetero- orner[ Ions resistor; -10 watt 900 ohm resistor; .^,OTRiCiANS dy at and Instructions for operation. Com 1 -E limin ins Man.Mdae plate bakelite indicator knobs; -l5 w att pilot lamp Stalic- Constructing a Two shipping weight 5 lbs. amt socket: 2-switch DEALERS -Tube buttons; 1-screen-grid - Trotter" YOUR PRICE rap and wire ; 1 -teat here, e case; assorted i. r'v1 ant5 -$3.00 OPrize SuggestionRS- $7.70 hardware, wire. etc. Ship. at. Bs lbs. Raceiverdio Rinks, etc., etc. No. LIST PRICE t$2758 ;,, TRADIh( Co. rag the 4following: 2 }si }gym oohs guaranteed tNeon- Iron type No. 230 tubes; one a t of No. No. WRITE TODAY. Enclose 4 1678 301 Dependable Tube Tester Kit tees Matched Ileadphonea; 2 No. 6 standard YOUR l'RI('F BZZ45 Over 100 New Hook -Ups. cents for postage. Treatise dry relis; 2 standard 45 -volt "B" batteries. Colo - No. 301A Same as above but with IC Etc. 1000 Illustrations. sent by return mail. piel. shipping wish[ 22 lbs. Moring loll Meter. YOUR PRICE... SIS7w7 ro1'n PRICE ...... _....__.._..._ $5.40 WE ARE A WHOLESALE HOUSE AND CAN- NOT ACCEPT ORDERS FOR LESS THAN I ORDER FROM THIS PAGE. You will find spe $3.00. dial prices from time to time this If C.O.D. shipment is desired, please remit 20% Radio Trading Co. Get our magazine. remittance. which must accompany all orders. big FREE catalog for the greatest Radio If full cash accompanies order, deduct 2% dis- 102. Park Place (Bargains.Should you wish count. Send money order-certified check -U. S. goods shipped by parcel post. Flamps. be sure to include sufficient extra remittance for New York, N.Y. I same. Any excess will be refunded.

704 RADIO -CRAFT for MAY, 1933 They Have Copied Everything Except TRIAD Quality

IT IS WRI'r' FEIN - "Imitation is the sincerest form of flattery"

TRIAD Appreciates the compliment it receives each month from other tube manufacturers who have copied our sales plan -our method of advertising -our discount schedules TRIAD Was first to recognize the Service Man TRIAD Was first to make double-tested tubes TRIAD Was first to offer a plan which really makes money for the dealer and Service Man

OTHERShave made every effort to do the same thing BUT THEY HAVE NOT BEEN ABLE TO DUPLICATE TRIAD-'Quality TUBES

A NEW DEAL yluuufucluriug Cu. Some of our Service Men and Dealers have wanted to buy regular Triad Pawtucket, R. I. Tubes to meet ordinary competition - TRIAD We have worked out a special proposition with most attractive discounts. Gentlemen: and will be glad to supply the details upon request. Please send me the outline of the TRIAD Sales Plan for Dealers and Service Men. With regular Triads you can beat any kind of competition. Triad Dealers and Service Men everywhere have sold many thousands of Name._ these tubes, they are making money -there hasn't been a single complaint. Mail the coupon today and learn how you can sell these super-grade tubes at a real profit. Address We protect you in your territory and you are sure of all of the inducements offered by itself. GET THE by other manufacturers, plus quality which is in a class ('ity State FACTS! My I head or business card is attached Announcing the New Idea in DX

LINCOLN R -9 9 -200 METERS

The new R -9 has what one might say -a Don't forget you have the choice of the dual personality. In the hands of an ex- famous DeLuxe SW -33 all wave, if you pert commercial operator, the high sen- prefer, which radio engineers, Army offi- sitivity brings in CW and voice signals, cers, and millionaires claim the greatest re- impossible to hear on many receivers, with ceiver they ever operated. The new super any volume you want. It has been a sen- powered DeLuxe SW -33 cuts like a knife, sation to every "Ham" who worked it on absolutely 10KC from the powerful locals. the air. Sensitivity beyond practical measurement and a new fidelity hard to equal in the In the hands of the "dyed in the wool" finest amplifiers. DXer it has filled the bill 1007c. He can be the proud possessor of the most power- Just drop me a line and tell me what ful strictly short wave receiver which he you want. If you are a licensed operator, can demonstrate to his friends without in- please give call letters. I will send com- terrupting the family broadcast receiver. plete information on your request.

If you could bring in just half of the Cordially yours, stations we bring in daily, regular as clock work, you would be just as enthusiastic as we are. W. H. Hollister, President.

LINCOLN RADIO CORPORATION, 335 S. Wood St., Chicago

LINCOLN RADIO CORPORATION Dept. E,335 S. Wood St., Chicago U. S. A. Please send me Free Technical lit. Sl riptiun of the R-9 SW -33 LINCOLN Name Street Deluxe Receivers City State