Radio Psychometry See Page 264

RADIO'S LIVES/T MAGAZINE

r November 25 Cents Cando 30t

HUGO GERNS1L&CK réíter

WA DO OU NAT Experiments in Radio Psychometry See Page 264

Broadcast Station List -A Home Radio Robot-The "Resonator" Loudspeaker Making Transformers and Chokes - "Dry Cell" Tubes in A.C. -D.C. Receivers READR1TE EQUIPMENT ÁMOVED \ WOK., of 9riiz 6 . ciyy

OW is the time to cash in on the widespread public interest that is being aroused by the sensa- t.onal Radio Prosperity Campaign. And you, as a Radio Service Engineer, No. 710 can cash in best by using the Readrite READRITE TESTER testers shown here. They will make money for you and save you money! You can afford to standardize on Readrite instruments. They are popularly priced. They enable you to make more calls at less cost per call ... they make it easy for you to meet every servicing requirement .. . they withstand the hardest kind of use and abuse ... they insure that your equipment dollar stretches much farther.

No. 710 READRITE TESTER No. 550 This all- purpose tester fills every need of both the ex- READRITE pert service man and the beginner. It is designed for OSCILLATOR the testing of new and old radios. Equipped with a practical selector switch for checking all parts of tube circuits by connecting to the set sockets. Selection for testing voltage of plate, grid, cathode, suppressor grid and screen grid is quickly and accurately done. Plate current, filament volts, line and power supply volts, resistance and continuity are Here's measured. Battery is used for continuity testing of transformers, chokes, Proof of etc. Handles most advanced circuits and newest tubes. READRITE The No. 711 Readrite Tester is the same as the No. 710 except that it is Leadership. equipped with the new Triplett D'Arsonval Volt -ohmmeter, which has 1000 ohms per volt resistance. The readings are 0- 15 -60- 300 -600 - --0 to 300,000 Write ohms. Ohmmeter reading is secured with the 4% volt battery, which is furnished. for your copy No. 550 READRITE OSCILLATOR TODAY! This signal generator furnishes a modulated signal of constant frequency for REACH FOR the alignment of all modern radios. It is used to align r. f. transformers, IME JOY OF LIVING No. 410 check oscillator stage, compare gain in tubes and determine the sensitivity TUBE TESTER of a receiver. TIE IN No. 410 TUBE TESTER WITH/ THE NEW Used for checking new old in receiving sets. de- PROSPERITY and tubes Simply let. Pall signed, compactly constructed, this tester is ideal for both outside CAM PAIGN work and for counter use. A push button provides two -plate current readings for determining the conductance and worth of a tube. For those wanting a longer-scale instrument, the Model 416 Tester, with a Triplett D'Arsonval Flush Mounted Meter is offered. This instrument does not have illuminated dial, but in other respects is

the same as the No. 410. I READRITE METER WORKS, I 81 College Ave., A Bluffton, Ohio. YOUR JOBBER CAN SUPPLY YOU Centlemea: See him today, or send the f Send me catalog on Readrite Instrument No. ( 1 u. well as folder giving proofs of Readrite Leadership. coupon for descriptive catalog. Neam READRITE METER WORKS Street Address...... _. City.. State 81 College Ave , Bluffton, Ohio OPPORTUNITIES are many for the Radio Trained Mari Don't spend your life slaving away in some dull. hopeless job! Don't he satisfied to work for a mere $20 or $30 a week. Let me show you how to get your start in Radio-the fastest -growing, biggest money -making game on earth. Jobs Leading to Salaries of $50 a Week and Up jobs as Designer, Tester Prepare for Inspector and -as Radio Salesman and in G Service and Installation Work -as Operator or Manager of a Broadcasting Station -as Wireless Operator on a Ship or Airplane, or in Talking Picture or Sound Work- HUNDREDS OF OPPORTUNITIES for a real future in Radio!

TenWeeks of Shop Trainin - Pay Your Tuition After Graduation g We don't teach by book study. We train you on a great outlay of Radio, Television and Sound equipment-on scores of modern Radio Receivers, huge Broadcasting equipment, the very latest and newest Television apparatus, Talking Picture and Sound Reproduction equipment, Code Iractice equipment, etc. You don't need advanced education or previous experience. We give you -RIGHT HERE IN THE COYNE SHOPS -the actual practice and experience you'll need for your start in this great field. And because we cut out all useless theory and only give that which is necessary you get a practical training in 10 weeks. TELEVISION and TALKING PICTURES And 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 opportunities 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. don't waste time on useless theory. We give you the prac- PAY FOR YOUR TRAINING tical training you'll need -in 10 short, pleasant weeks. After You Graduate MANY EARN WHILE LEARNING I am making an offer that no other school has dared You get Free Enii'lo%ntent Service for Life. And don't let lack of money stop you. Many of our students make all or to do. I'll take you here in my shops and give you a good part of their living expenses while going to school this training and you pay your tuition after you and if you should need this help just write to me. Coyne have graduated. Two months after you complete my is 33 years old. Coyne Training is tested -proven beyond all doubt. You can find out everything absolutely free. course you make your first payment, and then you Just have ten months mail coupon for my big free book! to complete your payments. There H. C. Lewis, Pres. are no strings to this offer. I know a lot of honest fel- RADIO DIVISION Founded i1199 lows haven't got a lot of money these days, but still want to prepare themselves for a real job so they COYNE Electrical School won't have to worry about hard times or lay offs. S00 S. Paulina St., Dept. 83 -8H, Chicago, Ill. I've got enough confidence in these fellows and in my Mail Coupon Today for All training to give them the training they need and pay me the Facts back have after they their training. I If you who read this advertisement are really interested H. C. LEWIS, President in your future here is the chance of a life time. Mail the coupon today and I'll give you all the facts. Radio Division, Coyne Electrical School 500 S. Paulina St., Dept. -811, Chicago, III. ALL PRACTICAL WORK Dear Mr. Lewis:- Send me your Big Free Radio Book, and At COYNE in Chicago all details of your Special Offer. ALL ACTUAL, PRACTICAL WORK. You build radio sets, install and service them. You actually operate great Broad- Name casting equipment. You construct Television Receiving Sets and actually transmit your own Television programs over our modern Television equipment. You work on real Talk- Address ing Picture machines and Sound equipment. You learn Wireless Operating on actual Code Practice apparatus. We City State ---

RADIO -CRAFT for NOVEMBER, 1933 267 /idio.aft\ FOP THE

SERVICE MAN - DEALER RADIOTRICIAN

HUGO GERNSBACK, Editor -in -Chief C. W. PALMER R. D. WASHBURNE Associate Editor Technical Editor

O, 041117 IN OUR NEXT FEW ISSUES: CONTENTS OF THE MAKING YOUR OWN VELOCITY MICROPHONE. Almost everyone is interested either professionally or experimentally in micro- NOVEMBER, 1933, ISSUE phones. Therefore, we believe that an article giving complete information on the construction of an instrument of the high - VOLUME V NUMBER 5 quality "velocity" type will be received with exceptional interest. Particularly, in view of the fact that the few components which require moderately precise machining will in form Editorial: The Radio Set of 1950 Hugo Gernsback 263 be available kit for the technician who is not blessed with a junior edition of a Radio Psychometry 264 machine shop.

Latest in Radio 266 DETAILS FOR MAKING A REAL AUTOMOTIVE RADIO RECEIVER. Although most previous articles concerning the construction of International Radio Review 268 automotive radio sets have been confined to the more essential The New "Resonator" Loudspeaker rudiments of instrument design, this article described every detail. Only standard parts are used. The 7 -tube superheterodyne Pierre Hemardinquer 269 circuit incorporates automatic volume control, variable -mu R.F. pen- A Radio Robot -In the Home todes in the R.F. and I.F. stages, and two pentode tubes in push - Arnold G. Ferdon 270 pull. A 3- section gang condenser with shaped -plate oscillator tuning sections is used. The dimensions of the overall chassis box A Wired -Radio Public Address System are only about 9 x 712 x 7 ins. high. David R. Freeling 272 AN ELECTRO- ACOUSTICAL WAVEMETER. Helmholtz or Koenig An Introduction to- "Servicing the 'Talkies'," Part I resonators have been used to defect sound and to determine the Aaron Nadell 274 pitch, but instruments of this form have the very great disadvantage that the ear is employed to determine when The Newest Design in All -Wave Superheterodyne resonance exists. But the new electro- acoustical wavemeter is independent of the Receivers .. _ McMurdo Silver 276 ear and lends itself to accurate and convenient sound measure- How to Convert A.C. -D.C. Sets for "Dry Cell" Tubes ments. Richard Silberstein 278

How to Make Your Own Transformers and Chokes, RADIO -CRAFT is published monthly, on the fifth of the month preceding that of date; its subscription price is $2.50 per year. (In Canada and Part I Lester H. Carr 280 foreign countries. $3.00 a year to cover additional postage.) Entered at the post office at Mt. Morris. III.. as second -class matter under the act of A 26 -Watt P.A. System, Part III Louis Gancher 282 March 3, 1879. Trademark and copyright by permission of Gernsback Publications. Inc.. 98 Park Place, N. Y. C. Text and illustrations of this magazine are copyright and must not be Broadcast Stations of the U. S 284 reproduced without permission of the copyright owners. We are also agents for WONDER STORIES and EVERYDAY SCIENCE AND MECHANICS. Sub- scription to these magazines may be taken in combination with RADIO - The Maintenance of Carbon Microphones CRAFT at reduced Club rates. Write for information. Albert R. Kahn 287 Copyright 1933. GERNSBACK PUBLICATIONS, INC. Operating Notes: Eliminating Auto -Radio Noise.... R. L. Dougherty 288 HUGO GERNSBACK, President J. M. HERZBERG, Vice -President S. GERNSBACK, Treasurer I. S. MANHEIMER, Secretary Readers' Department 289 Published by TECHNI -CRAFT PUBLISHING CORPORATION. Pub- RADIO SERVICE DATA SHEETS: lication office: 404 N. Wesley Ave., Mount Morris, Illinois. Editorial No. 101- Majestic Chassis Model 460 6 -Tube and Advertising Office: 96 -98 Park Place, New York City. Chicago A.C. Superheterodyne 290 Advertising Office: 919 North Michigan Avenue, Chicago, Ill. Western Advertising Office: 511 So. Alexandria St., Los Angeles, No. 102- Colonial Models 250, 279 and 300 5- Calif. L. F. McClure, Chicago Advertising Representative. Loyd Tube A.C. -D.C. Superheterodynes 291 B. Chappell, Western Advertising Representative.

The Beginner's "Unit Chassis" Receiver London Agent: Hachette & Cie., 3 La Belle Sauvage, Ludgate Hill, E.C. 4 Paris Agent: Francis R. Harris 292 Hachette & Cie., Australian Agent: McGills Agency 111 Rue Reamur 179 Elizabeth St., Melbourne RADIO -CRAFT'S Information Bureau 294 Book Review 316

258 !1 BE A RADIO EXPERT -- f Many Make $15 $40 $ aweek

J. E. Smith. President, ¡il sah, % at Home rnYourSpareTine National Radio Institute the man who has directed the Rome -Study training of more msn for the Radio Industry than any other man in America. forMDJO -TELEVISION 'TALKING MOVIES

Set Servicing Broadcasting Radio Factories Span -Till t - I t n fir - liwplp t -ITS, in. ing pays many N. I;. I. Stations Employ m:un.,._. spectuns, iremtn, men $5, $10, 815 a engineers. ....r- engineers, service- week extra. Full -time aon, insial lad inn und mxiutruauor men, for jobs pay- men make as much as nun fur suis pap- ing up to $7,500 a $40, $00, $75 a week. s till lu :;,Unit a sear. Aircraft

If you are dl ,,al l sued with job; are st niggling s Radio your present If you and it it rurentent are taking Ptare. Here Is a real future for thousands slang In a rut with little or no prospect of anything better than a and thousands of men whn really know Radio. Ost the training that skinny p:uY Metope- tito the vottoon NO',V. (het I v big FIIEE Mom, the road to g,anl pay and send the eanpon now and get is bask on the opl.ornmlthe, In quL ran Radin making Italia. Read how -kly lull pal'lirulars nit hoe a and t interesting 1 make learning at hone. lean] at honor \ be h flying safer. Radio in spare Ilene 10 . Radio Expert- what good Itend the letters from graduates who are today earning good uoncy In opwml or- employed jolts my graduates have been getting -real jobs with real futures. Ibis fosrinating industry. through Civil 5,r- vire t., nnnìssion Many Radio Experts Make 840, SSO, cant $1,1120 to S75 a Week Many Make SS, SIO, SIS a Week Extra $2,800 a year. in Spare Time Almost at Once In about ten years the Radio Industry has grown fmnr few million dollars lu hundreds of million annually. Over :Pn1.Uno My book also tel how Many of my stnients made 45. $10 and $15 jobs have been created by tills growth, and thousands more will be a week extra sen Icing sets In spare t line, soon after they enroll., l. a led by continuedntinued development. Manyliand men voting lion give you plans and Ideas that hate made goad spare -time tnoney- wrilh for right training -the kind of training give you in the $!llll to moon a year -for hundreds of fellows. My Course is N. It. I. Course - -hone stepped Into Radio at two and three times famous as "the one that pays for Itself." their former .salaries. Real Opportunities Ahead in Radio Money Back if Not Satisfied

for Trained Men I am os sure that N. it. I. ran. train you at home sat l sfacinrily that I will agrrr In writing to refund met, penny of ,pour tuition It's hard to and a geld with more opportunity awaiting the if vat are not satisfied with my Lessons no' Itrtruel ion Senire apcn trained mar. Why in l0:í2 -the worst v ar of the depression -the completion. You'll get a copy of this Agreement with my book. Ratio Industry sold $21111.111111.000 wart h of sets and pans'. 'larirl- faeturers alone employed nearly l00,u011 people! About 300,11110 people worked In Iht hulu.ir,. In 1932, broad.a sting had Its most 64-page Book of Information profitable year It's a glgantir b usines s. P I Irl the tt,tn business Free years! And liek what's ahead' 311111os of sets becoming obsolete Oet mils 101111y. Talking annually. 17,0011,1100 sets in opera inn that need see lying from your It's free to any ambitious fellow over 15 years old. time to time! Orrr 01111 great bro deasting stations furnishing It Movies entertainment and news to 10u.000.000 people. These figures are tells you about Radio's spare -tine and full -time opportunities; 11 you An invention made so big that they are hard to grasp! 1" el they are all true! lloro job tell- possible by Radio. Is r Industry that has grown quickly Into a couwrrialn giant. all about titi Course: what others wio Laye taken It are doing and Employs many No ywonder great busier -s leaders predict a brilliant future for this making great and growing business. Find out what Radio Meer, rYOU well -trained Radio without the slightest obligation. men for jobs pay- NI.VL THE í'(11'141.0 NOW. ing $75 tu $200 a Get Into This Yield With a Future week. J. E. SMITH, President There's opportunity for you In Radin. 11s future is certain. National Radio Institute Television. short wine, pollee Radin, automobile Radin, midget sets, Dept. 3MX speaker systems,' aircraft Itadl. III brand,, deerloPments laud event Washington, D. O.

4 28 MONEY MAKING HINTS FREE

Mail the coupon. I'll send you one copy of my a= IMO SIM valuable 56 -page Reference Book "28 Tested Television Methods for Making Extra Money." I'll do it to prove that my training !s easy to understand J. E. Smith, President The coming field and use -that it is practical -that it is full of National Radio Institute, Dept. 3MX of many great Washington, D. C. op- money - making informa- portunities is cov- tion right from the start. ered by my course. This book shows you how Dear Mr. Smith: I scant to take advantage of your Special Offer. :end me your two books. "28 Tested to (lo 28 Radio jobs corn - Methods for Making Extra Muter" and "Rich Rest-anls in mon in every neighbor- Radio." I understand this does not obligate me. hood - tells you how to (!'LEASE PRINT PLAINLY) get these jobs. Hundreds of my students have made Name Age $5, $10, $15 a week in spare time while learn- Address ing. Prove to yourself 1Js -1 that you can do it too. RI ate Mail coupon now. RADIO -CRAFT for NOVEMBER, 1933 259 YOUR COPY OF THE 1 9 3 4 OFFICIAL RADIO SERVICE MANUAL IS READY!

In preparing this new edition many of As in previous years, the 1934 Man- THE necessity of GERNSBACK ual will also include a FREE QUESTION field has been the outstanding problems of the Service Manuals in the radio Men have been considered -methods of AND ANSWER SERVICE. In each book shown by the fact that the total servicing, the new equipment constantly will be found 25 coupons, which en- ::ales of the first three OFFICIAL needed to cope with new tubes and sets, title you to free consultation on any radio RADIO SERVICE MANUALS, includ- and the other fields of radio, such as pub- service topics. These coupons give you a ing the new CONSOLIDATED EDI- lic- address systems, short waves, auto radio complete mail service -questions on servic- others. ing and operating on any set or circuit TION, now exceed 80,000 copies. and are answered promptly and ac- Radio Service Men and curately by the editors. Re- others engaged in various member that, at the regular branches of radio know the rate of 25c per question which importance of such books, of the 1934 Manual in Brief is usually charged by radio and how they must depend Contents magazines, this service alone upon them for reliable in- Diagrams and service notes, more complete than ever before in is worth $6.00. And for the any MANUAL. Not merely the schematic hook -ups will be found. Manual, we charge only $3.50. formation. Whether for but also chassis drawings showing parts layouts, positions of trim- public- address work, tube mers, neutralizers, etc. It is quite evident that the or a circuit all sets, as an aid in checking 1934 Edition of the OFFICIAL information Voltage readings for practically RADIO MANUAL diagram, the material tubes and wiring. SERVICE - will be a decided improvement needed is certain to be All values of intermediate -frequency transformers used in super heterodynes, with the manufacturers' own suggestions as to correct over previous volumes, and found in one of the OF- balancing. will even surpass the high FICIAL RADIO SERVICE Detailed trouble -shooting suggestions and procedure as outlined standard of the former Man- MANUALS. The GERNS- by the manufacturers' own engineers -in other words, authentic uals. BACK Manuals have been dope" right from headquarters. WE WILL constantly used in refer- Values of all parts indicated directly on all diagrams. ORDER YOUR COPIES NOW ence work by leading radio POSITIVELY NOT INCLUDE DIAGRAMS FOR WHICH PARTS VALUES CANNOT BE OBTAINED. It is important to every set manufacturers, mail- to A.C.-D.C. cigarbos midgets. order houses, jobbers, deal- A special section for reference Radio Service Man and Dealer A special section for reference to automobile radio. that he receive his copy of the ers and, most extensively. s. A special section for reference to public -address amplifie: 1934 OFFICIAL RADIO by Service Men, for whom -wave receivers. these books are invaluable. A special section for reference to short SERVICE MANUAL as soon A special section for reference to remote -control systems. as it is published. The new In the planning of the data, covering both the 1934 OFFICIAL RADIO A complete compilation of radio tube book will prove itself to be in- old and the many new types. volumes of SERVICE MANUAL many analyzers, etc., with valuable as those A special section devoted to test equipment, book as things have been taken into full diagrams and other valuable information. previous years. The you consideration. First, how we A complete list of American broadcast stations with their fre- usual comes to postpaid quencies kilocycles; useful calibrating and checking and free of additional charges. could reduce our own costs, receivers and in turn pass these sav- tsoscillatorsand n calibrating No need to delay sending us Free Question and Answer Service. the same as in our last two ings on to our readers. Manuals. your order -the 1934 MAN- is Second, what information No theory; only service information in quickly accessible form. UAL, like its predecessors, not contained in previous Absolutely no duplication of any diagrams; nothing that appeared a necessity in your business. editions of the Manuals in any of the previous Manuals will appear in the 1934 MANUAL. We strongly advise you to or- must be incorporated in This we unconditionally guarantee. der your copy today, and then the 1934 edition and would A handy. easily- consulted master Index making it easy for you you will be certain to get one to find almost anything to your service problem in- be of utmost importance to stantly. This indes will includenclude all the diagrams published in all from the first printing of the its users. Third, what ad- the previous GERNSBACK Manuals, as well as the 1934 diagrams. hook. The 1934 Manual is now vance information we could A big convenience and time I ready for delivery. print that would be useful in the future. Mail the coupon today. After careful analysis we The illustrations in the 1934 Manual will r GERNSBACK PUBLICATIONS, Inc. found that the total cost of producing be more explicit than before; inasmuch as 96 -98 Park Place, New York, N. Y. the 1934 Manual would be consider- the diagrams will not be limited to the years, and but other illustrations Gentlemen: Enclosed you will find my ably less than in former schematic circuit, remittance of $3.50 for which you are that at this time we could reduce the price will show the parts layout, positions of to send me One Copy of the 1934 of book to our readers. The Fourth neutralizers, etc. There will be OFFICIAL RADIO SERVICE MAN- the trimmers, UAL as soon as it comes off the press. Edition of the OFFICIAL RADIO SERV- hundreds of new circuits included, and not [Send remittance by check or money sell this year for,$3.50. any previous edition of the man- order; or register letter it it contains ICE MANUAL will one from cash, currency or unused U. S. Postage The book will be published like the 1933 uals will be repeated. This we uncondition- stamps.) Manual -the volume will be sent to you ally guarantee. complete. As usual, we urge that all our The number of pages in the new Manual Name readers place their order early so that will exceed 400, with hundreds of illustra- they will get a copy of the first printing. tions, including diagrams, charts, photos, Address Usually, at the last minute a tremendous picture layouts, etc. The size of the Man- as former number of orders come to us and quite ual will be the same that of the City State often orders are held up while the book volumes -9x12 inches, with a flexible, is going through a second printing. loose -leaf binder. L 1933 260 RADIO -CRAFT for NOVEMBER, . . . say these 30 Leading Radio LET THESE ENGINEERS RIGHT FROM THE HEART Manufacturers OF THE BIG RADIO INDUSTRY J ra i ny .. to their 40,000 oz t cam- Name, r DISTRIBUTORS and DEALERS throughout United States GOOD PAY RADIO WORK and Canada To the man who wants to make $35 to $75 a then on into the new and larger field of week and more- Here's a Message for You! Electronics-Sound Pictures, Public Address "The great Radio Industry, today - Systems, Photo Cells, and Television. This AMERICAN BOSCH more than ever before -is on the look- feature alone makes R. T.1. the outstanding AMERICAN TELEVISION out for PROPERLY trained men to fill home training in Radio. ARCTURUS TUBES its more responsible jobs. These are the better- paying jobs in Radio , YOU GET "QUICK RESULTS" BALKEIT BRUNSWICK jobswhich give steady work at good pay, CAPEHART as a starter; and an early advancement C. E. Head, 431 Third St., Alexandria, La., CLOUGH -BRENGLE to still better -paying jobs,as a future." Says: "Made my first money 11 days after CO. starting your training-cleared $14.25." CROSLEY CLARION HERE, THEN, IS REAL OPPORTUNITY Frank E. Klemann, DAYRAD DeFOREST Lisle, Ill., writes : "Doubled But my pay in less than six months." ECHOPHONE to qualify for these better- paying jobs, men must be PROPERLY "trained" -they Harry L. Stark, Ft. Wayne, Ind., writes: FADA GREBE HOWARD must know the theory of Radio, as well as "Now making three times as much money HAMMERLUND the practical side, and be able to teach as I was making when I started your training." KENNEDY KOLSTER LYRIC other men some of the things they know. So, if you MAJESTIC PHILCO The Radio Industry, itself, has no time to want to get out of a small pay, no- train these men. That's why the Radio & Tele- future job, and into good pay, big - future SANGAMO ELECTRIC vision Institute, of Chicago, is doing the job. work - get into Radio. But let these big SENTINEL SHELDON You'll be trained at home - in your spare engineers direct your training. SILVER -MARSHALL time -easily and quickly, and at a cost of STEWART RADIO only a few cents a day. And as you are MAIL COUPON FOR STEWART- WARNER taught to "earn as you learn " - R. T. I. FREE BOOK Training need cost you nothing. STROMBERG-CARLSON Let me tell you more UNIVERSAL MICROPHONE R.T.I. IS "SHOP about this amazing- TRAINING TRAINING" ly easy Shop -Type ZENITH FOR THE HOME home- training, It comes to you right from the Radio Industry and more about the wonderful The need for men, PROPERLY trained, is one -right out of the factories where Radio sets opportuni- of the Radio Industry's major problems, today. and other vacuum -tube devices are made. It ties for the R. T. I. TRAINED man in In fact, the very future of the Radio Industry was planned and prepared for you by big radio this is dependent on the industry having available, engineers IN these factories, most of whom -the world's fastest at all times, an adequate supply of PROP- are the Chief Engineers of these great' Radio growing industry. Everything is fully explain- ERLY trained men to install and service - plants. And NOW these same engineers are ed in my big, new booklet ... "RADIO'S not only the present-day highly complicated actually supervising R. T. I. Training. Which FUTURE, AND YOURS." Send today for Radio and Electronic equipment the -but still means that trained the R.T.I. way, you'll be your copy. The book is free. more complicated equipment that will be brought out by the Industry, from time to time. trained as the Radio Industry wants you trained - just as the Radio Industry, itself, Ray D. Smith, President, The above 30 manufacturers realize this. would train you if it was doing the job. Dept. 68 Radio and Television Institute, Chicago They know that under such circumstances, no ordinary Radio Training Is going to give them You learn by doing, of course, because that's Ray D. Smith, President, 7 the type of "trained" man they want. Only a the Shop Way of teaching. But you also learn RADIO and TELEVISION INSTITUTE, (R.T.I.), Training that is right- up -to- the- minute, and the theory of Radio - without which you 2130 Lawrence Ave., Oept 68 Chicago, Ill. properly prepared, highly practical, and prop- can't hope to go far, or make much money, Without obligation of any kind please send me a erly supervised, will answer their purpose. in this copy of "Radio's Future and Yours." I am inter- great industry. ested in home training and Radio and Television Institute your the opportunities home.training you say exist in the great the has field of Radio for successfully met their every test. That's ELECTRONICS -SOUND PICTURES R.T.I. Trained man. silty these manufacturers recommend R. T. I. Training, not only to their own men, every- P. A. SYSTEMS -PHOTO CELLS - where -but to all men who want to get some- Name where in Radio. TELEVISION -all included Address 'This message approved by the above Radio service is just the starting point in R.T.I. thirty Radio Training. From there we take you up through Manufacturers. City Copyright 1933 by R.T. I. the very latest developments in Radio, and State- _____

RADIO -CRAFT for NOVEMBER, 1933 61 This

Radio's GREATEST tinnpl

Buy this Rig Volumua on our New DEFERRED PAYMENT PLAN Here are two of the most surprising announce- ern, up -to -the- minute, and which contains so Now ments that we have ever made to the radio trade much useful you can get the information as is to be found in 1931 and we know that it is such good news that this single volume. It is a book that will outlast OFFICIAL RADIO SERVICE MANUAL, every radio man will be greatly enthused. any other radio book in print. Look carefully with Supplements, FIRST -that the three editions of the OFFI- at the illustration of the complete edition on 1932 OFFICIAL RADIO SERVICE MANUAL, CIAL RADIO SERVICE MANUALS have the top of page. It measures 9" wide, 12" with Supplements, now been combined into one big volume of long, 4' thick. and the 1933 OFFICIAL RADIO SERVICE over 2.300 pages. Included MANUAL Complete SECOND-that this new single volume of con- in this volume is a complete radio servicing course. This course covers every step at a big saving. solidated radio circuit diagrams and complete needed to learn radio servicing course can be bought on a de- the servicing business . from THE SPECIAL NEW PRICE FOR ALL THREE starting in business . ferred plan -and at a big saving. materials needed . MANUALS. WITH SUPPLEMENTS, IN ONE payment and how to go about servicing receivers and re- VOLUME, WITH It is needless to say how valuable the OFFI- pairing HEAVY BINDER IS ONLY CIAL RADIO SERVICE MANUALS have been other radio equipment. This course in itself, is actually worth the price of the entire to members in every branch of the Radio In- book. dustry. and how many thousands of each edition have been sold to manufacturers, jobbers, Our new plan now enables every radio man to $14.00 dealers. Service Men and experimenters. But get this single volume --a Complete Directory of You buy this book this way - we must emphasize this one fact: Service Men all Circuit Diagrams, of over 2,300 pages, on Send $3.00 with order - now realize that they are tremendously handi- deferred payments. You can order this book Pay $5.00 to Express Company upon receipt of capped without the full set of Gernsback Man- immediately -get it in a few days. and use it book. uals. So much so, that those who have pur- while you are doing servicing work. You can Send $3.00 thirty days after receipt of book. chased only one or two volumes, are NOW OR- make the first few calls pay for the entire cost Send $3.00 sixty days after receipt of book. DERING THE MISSING BOOKS. They want of the book. Total $14.00. their files to be complete. For you to get this book is quite simple and it IF THE ENTIRE AMOUNT IS SENT WITH The complete book gives you a volume of over is sent to you as soon as your order is received. YOUR ORDER, WE WILL ALLOW YOU A 2.300 pages with over 5.500 diagrams, charts You pay for it in small monthly amounts which 10% DISCOUNT. THIS CAN BE DEDUCTED and photos. There are absolutely no pages or can be taken from your earnings. If you were FROM YOUR REMITTANCE. illustrations or diagrams duplicated. There is to buy the three volumes separately, the total no radio book published today which is so mod- cost would be $17.00, including the supplements. IMMEDIATE SHIPMENT Mail Coupon. Today! 112.300 Pages GERNSBACK PUBLICATIONS. Inc.. 96.99 Park Place. New York. N. Y.

r I not lnmrn 5,500 Illustrations In accordance uith your Special Offer. I enclose OVE heren It h $3.00 as first payment tocard the One- Volume Radio Manual. Please forward it to me promptly. Upon receipt of the lesk, I shall pay express rom piny 21.00. Thirty days later I shall send nu m$3.00, and slaty days after receipt of book. Ì shall send you my last payment of $3.00. If yOu want to take advantage of the Special 014- THIS IS THE GREATEST SINGLE count of 10r;ß, n-mit only $12.60 iritis this coupon.

VOLUME RADIO BOOK IN PRINT TODAY Name

.tddre.as GERNSBACK PUBLICATIONS, Inc. 96 -98 Park Place New York, N. Y. l'Ity State ...... ///////i i i i i i i i i i //// i i i i i i i i i i i i i i i i i i i i i i i i i i // ii i i i i i i i // ii i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i /// i i i i i i /// RC -11 262 RADIO -CRAFT for NOVEMBER, 1933 dio@fíFOR THE

SERVICE MAN - DEALER RADIOtRICIAN "Takes the Resistance Out of Radio"

Editorial Offices: 96 -98 Park Place, New York, N. Y. HUGO GERNSBACK, Editor Vol. V., No. 5, November, 1933

THE RADIO SET OF 1950 An Editorial by HUGO GERNSBACK

IHAVE been asked a number of times during the past few that, by not having to worry with a filament supply, the set months, by readers of RADIO-CRAFT, as to my ideas on the is simplified a great deal. radio set of the future. I have, in the past, made many The tubes themselves will be vastly more efficient than prophecies in connection with radio, a number of which those which we have today. By that time no doubt a real have come true; and, since the radio set industry has been detector tube will have been evolved; one that is far more more or less in a state of chaos during the depression period, efficient than tubes in use today. The sensitivity of the tube it is not surprising that radio people should want to know itself will have increased several hundred per cent over what the future radio set will be like. what we have today. The result will be that the radio set of 1950 will require no ground, no aerial; that means less While I do not claim to be endowed with supernatural extraneous noise and static pick -up. Each set will have built powers, I believe that my guess as to the set of the future a real filtering system -not the filter will not be very far out way right into the chassis of the in time to come. When which we use today, but something radically different, which I speak of the set of the future, I am not thinking of next 90 to 95% of the line noises that or even will effectively kill from year's set, the set of five years hence; but let us enter the set today by way of the power supply. look at the radio set of, say, the vintage of 1950. The loudspeaker of the future set will not bear the slight- It is safe to say that the 1950 radio receiver will not be a est resemblance to the one of today. It is almost certain that midget set, nor a cigarbox type, nor a coat -pocket model. it will be of neither the magnetic nor the dynamic type; The chances are that it will stand at least four feet high, most likely, it will be a crystal type or a condenser type, and possibly taller. It will not, however, look even remotely or a combination of both. There is even a chance that the like the radio set of today; it will certainly not be a piece set of 1950 will have a multiplicity of loudspeakers, each to of furniture, nor will it be disguised as a bookcase or as a take care of a certain band of audio frequencies, in order to chest of drawers. It will be large, because the television cover the complete range from the lowest to the highest tones. angle will have been solved, and it will have either an open By 1950, it is most probable that the present broadcast or concealed, ground -glass "faceplate," upon which the images band will be abandoned, and that broadcasting will be done appear. Most likely, there will be a sliding -panel arrange- generally on wavelengths below 200 meters. If television is ment to hide the ground -glass television panel when the set finally perfected, as it will be, the present broadcast wave- is not in use. The television panel will be presented at a lengths will be useless. Television broadcasting must be on convenient height for you, when you are sitting in a chair wavelengths below 50 meters, and that is what the set of to watch the performance. Most likely the set will be swiv- 1950 will be tuned to. Every station will broadcast tele- eled; that is, the top, which contains the television ap- vision and sound, both on the same frequency. This I pre- paratus, will turn in such a manner that (since the image is dicted in May, 1926, editorially, and it first came about in projected on a straight surface) it will not be necessary to April, 1932, when the New York station of the Columbia move the entire set when you wish to view the image from Broadcasting System accomplished simultaneous sight and a different part of the room. If you move to the right, near sound broadcasting. the window, you turn the top part of the cabinet so that the There will be radio networks, like those of today; with television panel is at right angles to your line of vision. the difference that almost every town will have its own local The tubes in this set will most likely be of the cold or broadcasting unit to supply the radio sets of its locality. filamentless type. They will be much smaller; probably On the television end, we will have, of course, no moving not much larger than a thimble. parts in the set of 1950. A somewhat overgrown radio tube will project the image on the ground -glass screen. (This The chassis of this set will be radically different from any- screen will vary in size, but will never be smaller than thing we have today. For quicker servicing. all parts will about 9 x 12 ins. More elaborate sets will naturally require be demountable almost instantaneously. Radio engineers larger faceplates for larger projections.) There will be no will have come to recognize the fact that, no matter how flickering, no crossbands, on the television screen of the set well you build a set, certain components (such as transform- of 1960. The image will be better and steadier than the ers, condensers, coils, and the like) will not last forever, picture which you see in your motion -picture house. and must be replaced. At the present time, this means rip- The set will of course have its output controls, whereby ping the set apart. The set of 1950 will have most of the sound and sight can be regulated to your full satisfaction. components mounted as we mount tubes today. There will Inasmuch as its television screen will be tremendously bril- be sockets, similar to the present radio tube sockets; or of liant, you will never turn it on full (except in bright day- the bayonet type, so that by a twist of the wrist you can pull light) because the great output of light from the television out every transformer and every condenser to replace it. your eyes. same tube would cause the image to hurt The will be the case with the small fixed condensers, As the broadcasting stations will televise and transmit in resistors, etc. full color everything that is going on, some of the more I can hear some of the present -day radio engineers throw elaborate sets of 1950 will have color-television attachments up their hands in holy horror at this suggestion. They will to reproduce the image in full colors. The lower -priced sets say that you have such a multiplicity of unsoldered contacts will reproduce black and white; while the better sets will that you will hear nothing but noise. They forget one im- reproduce the three primary colors, red, blue, and yellow, portant point, and that is that the radio tubes themselves, giving all necessary colors in a full "halftone" effect.. the heart of the radio set, are not soldered today; in a ten - The cabinet of the 1950 set will probably be all- metal. tube set you will have as many as sixty "loose" contacts if The entire set will be enclosed in metal, in order to keep the tubes have six prongs each. If the contacting arrange- out extraneous noises that otherwise would be picked up ment is well engineered, we should have no fear of loose or by the chassis. The set itself will positively not be open microphonic contacts. Service Men will be able to replace in the back to collect dust, as they are nowadays; it will be parts in practically no time. It should also be remembered sanitary.

263 That the quotation, "There are more things in heaven CAPACITY - and earth, Horatio, than are PLATE TABLE dreamt of in your philoso- phy," is a truism, becomes more obvious the more we learn. New developments in sensitive test devices have unearthed hitherto unknown psychic phenomena - a phase of radio technique A. F. which still is in the embryonic AMPLIFIER stage. The following article describes several interesting Fig. A experiments. Mechanical arrangement of the "open grid" indicating circuit. RADIO PSYCHOMETRY

ONSIDERABLE interest was recently created when needle point on the end of the lever is arranged to press \lajor Raymond Phillips, an English scientist, ex- lightly against the cylinder and the other end rests on the hibited an instrument called a Radio Psychometer. center of the parchment head of the tambourine. This instrument is so sensitive that it is affected by It is pointed out that some people could not influence the anyone standing near, although a more pronounced effect is needle point until the lever was very carefully adjusted, produced by placing ones hands near a copper plate con- while others simply had to hold their hands near the tam- nected to the device. Although no actual contact is made bourine head to cause the line on the smoked drum to move with the apparatus, the effect is such that model trains can irregularly up and down as the latter revolved. be set running and the motion only ceases when the hand is removed from the vicinity of the copper plate. One experi- The Psychometer ment is illustrated in Fig. A. A diagram of the circuit used by Major Phillips is shown at A in Fig. 2. It will be noticed that the output of the Hand Capacity? amplifier is arranged to control a model electric train. The There has been much speculation regarding the cause of amplifier consists of a transformer coupled unit, the first the phenomenon. At first, it appears that it is a simple case tube of which has an open grid circuit, with a copper plate of hand capacity, which changes the grid-to- filament capacity attached at A. Filament resistor Rl regulates the filament of the first tube of the A.F. amplifier -thus causing a change potential on tube V1, while the remainder of the tubes are in the plate current. controlled by an automatic filament ballast resistor, R2. A However, Major Phillips points out the recent experiments 400 ohm resistor is connected in series with the plate supply of an eminent radiologist who, with novel apparatus of his circuit to control the plate voltage. The "B" circuit is own design confirmed the existence of an "electrical field" shunted by a condenser of 4 mf., labeled C in the diagram. about the human body. He stated that many of the effects Relay No. 1 is wound to a resistance of 8,000 ohms and in radio communication attributed to "hand capacity" are is connected across the output impedance T3, so that a probably due to this "electric field." change in the plate current will actuate it. Relay No. 2 is It is well known that the electrical resistance of the human an ordinary low resistance unit with a winding of about 6 body varies with motion. Delicate instruments have recorded ohms. The main relay also has a resistance of 6 ohms and the effect on a person of a sudden shock. It therefore seems the armature is arranged to open or close the circuit to the reasonable that some of the "capacity" effects may be due model train. to other phenomena. When a person places his hand near the copper plate, A, Several simple experiments may be tried to show the the relays close, thus starting the train. When the hand presence of this field surrounding the human body. The is withdrawn, the plate current returns to its former value, first of these shown at A in Fig. 1, was tried in the offices and the relays open. of RADIO-CRAFT, but did not show any marked effects, perhaps In the first part of this article, it was pointed out that due to the haste with which it was tried. It consists of a the instruments developed by Major Phillips operated differ- mahogany board 36 x 10 x :y, -in. thick, carefully balanced on ently when different persons approached them. It has been a knife edge. It is explained that when a person's hand is found that the same thing applies to this instrument. held over one end of the board, the latter (if it is carefully To check the experiments of Major Phillips, an amplifier balanced) will, after a short time, oscillate slightly. Some unit was set up in RADIO -CRAFT laboratories. The circuit people. it is said, appear capable of producing stronger effects of this amplifier is shown at B in Fig. 2 and a photograph than others. of the set-up is shown in Fig. A. Since Major Phillips ex- The second experiment described is shown at B in Fig. 1. plained that different persons affected the device differently, The apparatus consists of a phonograph motor, D, a tam- we arranged the unit with a sensitive current meter in the bourine, B, a lever with a needle point at one end, A, and a plate circuit of the output tube. This meter measures the cylinder of glass covered with soot, C, suitably mounted on difference in plate current when different persons place their the phonograph motor so that the cylinder will revolve. The hands near the plate.

264 RADIO -CRAFT for NOVEMBER, 1 ?33 LAMP 57 A.FT. 45 OUTPUT ' RESISTANCE RELAY RELAY PLATE NE. 2 N4. 1 TRANS. MODEL i L A ,LwAY I ao / o ó! OUTPUT ó j l LMF. V1 MAIN RELAY IL 1- II 4 A TERMINALS T COPPER. 6v A OR TESTING 1.000 --ti PLATE BATTERY PURPOSES, SW. D.T. 1 - -OHMS

2.5 V. 1

1,650 OHS o as 2.5 V. 1 1ME Tt T3 R2 Vl TINT CH.-) MILL A MMETER 2 "A+" -1 5 V.

R , c 37SV. 20,000 'B V3 a R3 ON .375 V. \ i r %r o ( 4 MF 8 MF 4MF 60v. 110 , A C 80 R FILAMENT BALLAST. IP -

Fig. 2 At A, schematic circuit of Major Phillips' radio psychometer; the circuit at B shows electrical connections followed in the set-up shown in Fig. B.

THE 1934 ULTRA -MODERN SUPER. 10' In reading the above title, readers of RADIO -CRAFT will immediately recall the article, "Building and Operating An Ultra- Modern TEETER Super.," which appeared in the October, 1932 issue of RADIO -CRAFT. BOARD r 6' To these tecnicians, particularly, we call attention to a construction -A- 12 - -.7/ - article on the modernized version of this instrument which is to appear in a forthcoming issue of RADIO -CRAFT; owners of broadcast receivers built in accordance with the older design will find it particularly convenient to convert their chassis to the newer construction, since they will have most of the equipment on hand. The new type 2A7 tube is used as the combination oscillator and first- defector. The new 2A6 is used as a second -detector and in order to obtain improved A.V.C. operation. Meter tuning is now incorporated in the design. Also, interstation noise suppression is included in the form of a silent- tuning switch. Fig. 1 Two of Major Phillip's psychometer units.

The circuit of the amplifier unit used in our tests is a completely across the scale. This battery, which may be an straight transformer coupled arrangement, using a screen - ordinary 41%, V. battery, is connected to "buck" the normal grid tube for the input tube, and feeding through an audio flow of plate current through the meter. The positive term- transformer with a high- impedance primary to a triode out- inal is connected to the plate of the 45 tube, while the nega- put tube. tive end is connected through a 0.5 -meg. variable resistor to The unit has a self-contained power unit of conventional the other terminal of the meter. The 0.5 -meg. resistor is design, using a type 80 rectifier tube. The usual power trans- then adjusted to the point where the indicating pointer is at former and filter arrangement used in practically every A.C. zero, when the amplifier is in operation. A switch should be power unit, are employed. The values of all the parts are provided, to break the connections of the bucking battery shown in the diagram, Fig. 2B. to the meter, so that current will only flow when the unit As a means of controlling the sensitivity of the unit, a is being used. potentidmeter, R, is employed as a combined bleeder resistor Its trying the device out, an arrangement was used (not and voltage control for the screen grid of the 57 tube. A shown in the photo) so that the proximity of the hand to point will be found on this potentiometer scale that effects a the plate was always the same, to prevent this from affecting compromise between stability (to prevent the unit from the results obtained. Varying current readings were noted starting parasitic audio oscillations) and sensitivity (to re- for different subjects. tain sufficient to show an appreciable change in plate current We will not attempt to detail the results of our experi- when the "capacity plate" is approached). ments, However, we might point out that as different persons affect the unit differently, a field of The current meter, which may be either a sensitive milli - éxperimentation is ammeter opened up for those interested. It is quite possible that the or a galvanometer is connected across the primary system winding of the output transformer. could be used as suggested on our cover, to classify people according to their nervous temperament, or according No connections are shown for the secondary of this trans- to their mental activity, etc. former, but if desired, a loudspeaker may be connected to it, We will be interested in learning of the results obtained to give an audible indication of whether the amplifier is by experimenters who try any variation of the Radio Psycho - oscillating or not. This will permit the operator to adjust meter. R to the point of greatest sensitivity of Vl. (Credit is hereby given to AMATEUR WIRELESS, a recent It may' be necessary to connect a "C" battery and resistor issue of which English publication contained an article men- across the connections to the current meter, to prevent the tioning many of these experiments; the explanations are normal plate current from throwing the indicating pointer quoted.)

RADIO -CRAFT for NOVEMBER, 1933 265 LATEST RADIO EQUIPMENT

A DUAL -USE "FILTER" THIS handy unit for the Service Man's kit is shown below. It is a combined line filter t for reducing noises introduced through the power supply), and aerial coupling unit. For the first -mentioned application the unit may be plugged into the line, either at the receiver or at the offending Dual-scale resistance indicator for determin- electrical device. ing replacement resistor values (No. 151) Two new radio instruments (No. 147) The aerial coupling unit may be used to increase the selectivity of sets by NEW RESISTANCE -TEST UNITS adjusting the knob (between the two RESISTANCE INDICATOR TWO handy servicing units are shown binding posts); or for replacing the out- THIS dual -scale indicator, illustrated above. The first, A, is a decade re- side aerial by connecting the aerial above, is used in determining resistor sistance box supplying ten resistance terminal on the set through the unit replacement values. Two clips are con- values from 0.1 -meg. to 1. meg. to ground. nected across the burned -out resistor, The second, B, contains a calibrated, and the radio set turned on. The special, 0-0.1-meg. resistor unit consisting of a rounded contact is then gently run special 25,000 ohm potentiometer and along the high- resistance scale, starting three 52,000 ohm carbon resistors. from the 0.1 -meg. end. When the set These handy servicing items which functions correctly, the desired value of are each mounted in small bakelite the replacement resistor is read from boxes are useful for substitution in cir- the scale; for values below 1,000 ohms cuits under test and for measuring re- the low- resistance scale is used to sistance values by the substitution obtain greater accuracy. method. Noise filter and aerial connector (No. 149)

VOLT -OHMMETER CRACKLE -FINISH RADIO PAINT ANEW instrument, shown below, has THE radio constructor and the Service been designed to meet the need for Man who prides himself on doing an point -to -point service instruments. An unusually good job will find these paints outstanding feature of the new unit is indispensable. (Part of a dealers' dis- its automatic vacuum relay which pre- play "board" is shown below.) vents costly burn -outs of meters or cir- The paint is applied in the usual cuits -the relay automatically throws manner, by brushing lightly over the the circuit open, then closes it when the surface, and after about 20 minutes the overload is removed. Replacement transformer kit (No. 150) surface crinkles and forms itself into The instrument weighs only 212 lbs.; beautiful designs which enhance the it is 7 x 4 x 3 ins. deep. The voltage appearance of any object. A KIT OF TRANSFORMERS ranges are 3; 30; 300 and 600. The re- Both transparent and opaque paints sistance ranges are 0 to 1000; 0 to 0.1- o meet the urgent demand of Service are available for surfaces in amber, meg. and 0 to 1. megohm. The basic T Men for immediate service on the blue, red, green, white, black and gold. meter reads 0 to 1 ma. replacement of transformers without . maintaining a large stock, a kit of multi -tap transformers, shown above, has been introduced. Slotted frames permit easy mounting. The designs "fit" over 90% of the sets. These replacement transformers may r be installed as permanent equipment. - BUY IT _ TRY IT « Four power transformers are included AMUR OWE FCO WN11E eftlEll in the kit, one for 4 -tube sets, one for 5- or 6 -tube, one for 7- or 8 -tube, and one for 9- or 10 -tube. The fifth unit in the kit of six transformers is an A.F. output transformer 4i44411 with various tap combinations to couple from single or push -pull stages to any voice coil from 2 to 30 ohms. The sixth unit is a universal A.F. IP input transformer which can be used JIM" .LLU Volt- ohmmeter unit No. 148 in push -pull or straight A.F. circuits. Radio paint for "crackle" finish (No. 152) Name of manufacturer of any device will be sent on receipt of a self -addressed, stamped envelope. Kindly give (number) in description under picture.

266 RADIO- CRAFT for NOVEMBER, 1933 Above The circuit of the I.F., R.F. oscillator. Right Above The rear view showing the trimming condensers. The latest in test oscillators (No. 153)

A NEW TEST OSCILLATOR controls are sealed while the zero-beat is maintained. ATEST oscillator for the radio Service Man, having the The power cord contains a resistance element and will frequency stability of a laboratory -type signal generator, heat somewhat in normal operation. has just been announced. It is illustrated, above, by picture It is not essential to ground the case to secure satisfactory and diagram. operation, but the connection serves as a static drain on The usual self- modulated oscillator circuit is not used. The the line filter condensers within the instrument. unit employs three tubes; (1) the R.F. oscillator stage; A shielded cord is supplied for connection of the oscillator (2) a separate modulator stage; and, (3) a rectifier tube, to the receiver under test; the sheath of the cord (the black for this instrument operates from any light socket, A.C. or unshielded tab) connects to the ground connection of the D.C., eliminating battery cost and weight. oscillator and the ground post of the receiver. The tip from The "electron- coupled" oscillator circuit gives freedom from the inner shielded wire should be inserted in the jack marked frequency variation due to voltage changes or input circuit HIGH or LOW, in accordance with the nature of the test conditions. Complete coverage of all intermediate broad- being made. Note that the attenuator control marked R.F. cast- and short -wave bands is provided, including the new OUTPUT is effective only with the tip in the LOW jack. 546 and 477.5 kc. intermediate frequencies used in the latest When placed in the HIGH jack, a potential of about 0.5 -V. sets of foremost manufacturers. and of fixed value is imposed on the cord. Also, it is then The whole unit is contained in a single steel housing, with possible to make A.F. tests directly by 'onnecting the other a black crackle finish. Output frequencies are adjusted at end of the shield wire into the grid of one of the A.F. tubes. the factory to zero -beat against a crystal oscillator; the (Continued on page 295)

operates from 6 V., D.C., and furnishes NEW TUBES the high voltage (250 V. at 75 ma.) required by the amplifier. THE type 1A6 tube, shown below, is This device draws only 4.7 A. from a "pentagrid converter" designed primarily for use the 6 V. storage battery and requires as a combined oscil- no thermionic tube for rectification; lator and mixer in battery- operated mechanical rectification obtained superheterodyne receivers. The 1A6 is by possesses means of an extra set of contacts on the many operating advantages vibrator assembly. The complete me- over the oscillator -mixer combinations chanism is mounted upon an air -cush- hitherto employed. Among these advantages are: economy in "A" current A 13 W. P.A. amplifier (No. 154) ioned rubber base and provided with two electrostatic, electromagnetic and drain, greater operating stability, high I.F. gain, higher A 13 WATT P.A. AMPLIFIER sound -proofing shields. The device is and more uni- THE use of a class not only quiet and fool -proof, but B audio circuit oper- form transla- together with carefully designed ates with approximately 30% more effi- components ciency than can be obtained from most tion gain, vol- have provided the P.A. am- ume control plifier shown above rotating machines. ef- with many desir- fectiveness com- able features -especially for a portable When the system is operating from or mobile sound parable with system -such as light 110 V., A.C., the type 83 rectifier em- that of a vari- weight, compactness, high output with ployed produces not only sufficient cur- able - mu ampli- fairly small tubes operating at low plate rent for the amplifier requirements, but voltages, fier in an I.F. and economy of power con- also furnishes field current for as many stage, reduction sumption. as six, 2,500 ohm dynamic speaker fields. or elimination An exclusive feature in the design of By employing dual -field dynamic this amplifier of the inter - provides for a rapid speakers (containing both a high volt- coupling effect change -over 6 from V. storage battery age -2,500 ohm-and a 6 V. field wind- between the sig. operation to 110 V., A.C., or vice -versa, ing) it is possible to excite the speakers without nal and the os- changing any tubes -or using from either a 6 V. storage battery or cillator circuit, adapters. It is only necessary to insert from the amplifier (when it is operating almost entire the 5 -prong plug into either one of two from 110 V., A.C.). elimination sockets mounted of on the right -hand end The first A.F. stage uses a type 78 radiation from of the chassis. The front socket is used tube; the second, driver, an 89; and the the local oscil- for 110 V., A.C. operation, while the third, class B output, two 79's. lator, rear socket simplicity is used when the amplifier A combination 6 V., D.C. and 110 V., of oscillator cir- is operating from a storage battery. A.C. operated phono. motor and turn- When cuit adjustment, the amplifier is being powered table are also available to complete the and economy from a in storage battery, it utilizes a universally- operated accessories for this (Continued on vibrator -type converter -rectifier which amplifier system. page 296) The 1A6 tube (No. 155) RADIO -CRAFT for NOVEMBER, 1933 267

INTERNATIONAL RADIO REVIEW

HERE is what the radio experi- a if of the signal fed to the A "Self- Tuning" Circuit menter has been wanting for the frequency re- coil Ll is altered, the effective induct- RECENT issue of Popui..tR WntE- long time -a semi -technical view of the thousands of new ance of Z in the plate circuit of that Lt:ss, London, England, contained tube will also change, and in turn will discussion of a new ideas which are continually ap- an interesting vary the grid -to- filament capacity. in which the radio pearing in overseas publica- method of tuning, Of course, without some further con- Each there are re- frequency circuits automatically tune tions. month trol, the tuning would tend to adapt thenisclres to any applied frequency! ceived at the offices of RADIO - to several stations at once. To called itself The action depends on what is CRAFT hundreds of daily, weekly prevent this it is necessary to use a the "Miller effect." and monthly magazines orig- single pre -selector or band -pass circuit is a defin- As everybody knows, there inating from every point on the coupled to coil L2 as shown at B, Fig. 1. ite electrostatic capacity across the elec- face of the globe. This eliminates the need for multi - trodes of a tube which in the days before ganged controls. screen -grid tubes gave a lot of trouble SINCE the cost of subscribing by causing self -oscillation. Some years to each of these would be pro- ago a physicist named Miller discovered hibitive for most radio men, we A Novel P.A. Amplifier that this capacity effect is not the saine have arranged with technical RECENT issue of WIRELESS when the vacuum tube is lit as when it translators to prepare for our WEEK 1Y, an Australian radio i.5 cold. Not only does the apparent readers reviews of all the really magazine, contains a rather interesting for P.A. rapacity between electrodes change, but important, new developments il- form of push -pull amplifier work. The 180 -degree out-of -phase po- its value depends upon the kind of cir- lustrated and described each cuit of the tube. In tential for push -pull operation is ob- used in the output month in these international short, the effective grid -to- filament ca- tained from the cathode or grid- return" pacity varies with the effective imped- radio periodicals. circuit. ance of the output circuit. NOTE that the only available in- It consists of a 3 -stage amplifier, Now, since the effective inductance in formation is that which is pub- shown in Fig- 2. A diode -triode tube, the plate circuit of a tube automatically lished; the experimenter must V1, is used, so that the amplifier can increases with the frequency of the sig- adapt the ideas to whatever be adapted for radio work by the addi- By using nal it is handling, it follows that the equipment he has on hand. tion of a simple tuning unit- Miller effect on the grid -to- filament in- the diode type of detector, it becomes ter- electrode capacity also will change. feasible to retain the fidelity possible One can, therefore, imagine an inductive with the amplifier, when working on output circuit so designed as to increase the grid -to- filament radio. But for the amplification of pick -up from phonograph capacity inside a tube on long wavelengths and to decrease records, the audio section (triode portion of the diode -triode) it on short wavelengths. of ßr1 is used, being resistance coupled into a pair of 56 type This occurs in the circuit shown at A in Fig. 1, The tubes in push -pull. input circuit to the screen -grid amplifier is untuned, hut the (This change from single tube to push -pull without the coil Ll is shunted by a tube, V1, the plate of which is con- use of an input transformer is the most interesting part of nected to the "B" supply through an inductive load, Z. Now, (Continued on page 299)

50.000 00M5 .02- Mr .Ot-MF. V2 Va (Hewn) V1 J

0 1MEO A J B. MEO C 05M FG D.

A A 0.;411

L T1 óMs 0.046 0.1 -MF 25 MC S- 5,000 .0l- MEO OHMs MF = VS Fig. 1 V3 - 10.000 Inter -electrode OHMS capacity, C, variation In V1, tunes Ll. 8MF 50.000 =CEAC)= CIELO OHMS 20 COIL CMSti C6 011 v.d[S.-_-- ¡I 520 CI NOTE A A 9 4,5 nCM. 06 A,gkD- FOR 5e5v )ií RADIO RECEIVER Ili ....C i . ë Ca, O- FOR PT PH0N0.PK2CVP Sw

s1 l"jTr rs Fig. 2, Above This novel push -pull amplifier requires no transformer to obtain the - 0ni vt 1: counter -phase potential, which is derived from the grid- return circuit If of Vl. JJî; u:;i,b 02 Fig. 3, Left vuS.. The quality" receiver-brought up to date. Stage A.F.1 _- ,0 -w. S,a,NC, SCiIC.CCS evu . ,.2 "perfect secures push -pull output performance without the use of a transformer.

268 RADIO -CRAFT for NOVEMBER, 1933 THE NEW "RESONATOR" LOUDSPEAKER

The author describes the use of a system of tubes, resonant at one or more points in the audio scale, for reenforcing the output of a dynamic reproducer.

ALL loud speakers incorporate a motor unit which transforms the electrical vibrations in an A.F. circuit into mechanical vibrations of a diaphragm moving in air. But although the electric input to the motor unit may be "perfect" within practical limits, so many factors are introduced in the subsequent steps that seldom do we find the tone quality of our air vibrations to be mechanical replicas of the electrical waveform. Let us consider the instance of an electro- dynamic reproducer with a free cone, one of the best types of reproducing devices in general use. To correctly utilize the "dynamic," Fig. A we must use a "baffle," as large in proportion as the lowest The "Resonator" speaker. frequency to be reproduced, to separate the fore part of the cone from the back. Although this construction successfully prevents the compression wave produced by the front, con- cave part of the cone from being cancelled by the expansion PIERRE HEMARDINQUER* wave being produced simultaneously by the convex part, we are utilizing only a part of the available energy -only that which is produced from the front of the cone. Another cone; and vice versa. These sources of faulty reproduction disadvantage is the directional characteristic which results explain in part the need for tone "compensation" and "cor- when a baffle is used. Further, it is generally recognized rection" in modern sets and reproducers. that a dynamic reproducer having a small cone is not as The simplest of all resonators is made of air held in a efficient in reproducing the low notes as one having a larger hollow box. Then there is the classical experiment, illustrated in Fig. 1, of holding a vibrating diapason (standard Frunee, corrospm,dent. (Continued ou page 299)

LOW- FREQUENCY TUBES

NIGH- FREQUENCY TUBES T

C2 ® r DYNAMIC -A- REPRODUCER. -B-

Fig. 1 Fig. 2 Demonstrating resonance effects. At A and B, front and side views, respectively, of the new speaker.

RADIO -CRAFT for NOVEMBER, 1933 269 A RADIO ROBOT IN THE HOME

ARNOLD G. FERDON*

Fig. A Domesticating the radio robot.

ARADIO "Utopia" is probably the with a remote control unit at each best expression to use in de- speaker. Mr. Powers is shown in Fig. scribing the radio system in- A, operating one of the remote controls. stalled for Mr. A. J. Powers, However, remote operation is not the president of a New York firm, who has only feature of the system. Two Landis his offices and apartment in the same program machines are used in conjunc- office building in the heart of the tion with a Stromberg- Carlson Master metropolitan district. On the roof of Electric Clock to turn the receiver on the building, he has one of the most and off automatically at any pre- deter- complete indoor and outdoor gym- ined time. (The electrical units with nasiums in the city and a roof garden their various relays and timing devices that is certainly a pleasant surprise to for the Stromberg- Carlson Master Clock anyone viewing it for the first time. are shown in Fig. B.) Programs can Mr. Powers' offices and home have be selected a week in advance, and the every possible modern convenience to radio may be turned on for any length make life and work more enjoyable. He of time! The program machines are spares no cost in keeping up to date; equipped to make and break 16 separate as he says, "I believe in being not only circuits at one minute intervals over up to date but ahead of the times." a period of 168 hours, or one week. At the beginning of each week, Mr. Powers A of the above very good example indicates on a radio schedule the pro- is shown in the radio installa- attitude grams he wants to hear. A secretary This system is an elaboration of tion. then adjusts the program machine so which was described the telektor system that the receiver is automatically turned in the May, 1932 issue of RAmo- CHAr°r. on before the program begins. Primarily, it consists of a combination radio and phonograph, equipped with However, Mr. Powers is not satisfied three speakers located at various points, with having the radio turned on and off in this manner. He desires to be Fig. B Master Clock relays and timers. -Ihmr IAulio Crrviec, Inc. reminded before the program starts, so

MASTER CLOCK PROGRAM ` MACH INES SPEAKER AND CONFERENCE ROOF GARDEN TELE KTOR ROOM 7 t GYMNASIUM TEL D.C. FOR SPEAKER FIELD

GONG IN APARTMENT

500 W. CONVERTER [qJ APART M1-** RADIO AND TELEKTOR SET ELECTRIC SPEAKER. AND PHONOGRAPH WITH SELECTOR, SPEAKER TELEKTOR REMOTE eC A.C. RELAYS CONTROL SYSTEM. 1111 111111111

Fig.1 A block illustration of the equipment and its hook -up in the domestic version of the radio robot.

270 RADIO -CRAFT for NOVEMBER. 1933

Few radio technicians are aware of the strides which have been made in the practical application of radio principles. Consequently, \ 641i1 we take pleasure in present- REMO I ( ing the details of an ultra- CONTROU modern radio installation in 1 the home. Progressive radio Service Men will show this article to neighborhood prospects. .... 1r,. ii \' +'

Fig. F Dynamic reproducer and remote control unit. The gymnasium and running track are at the left; at the right are the tennis courts; and Immediately in front, the roof garden. that he can walk leisurely into his "conference room" and sit in comfort while the program progresses. To accomplish Fig. C, the large cylinder is perforated this, the program machine is again over its entire surface. These perfora- called into service; a gong is installed tions are for a specific purpose -when in his private office and his apartment. pins are inserted in the holes, a contact These gongs chime one minute before is made at a given minute, hour, and a program starts. day, so that the various circuits in- The program machines which are the volved may be completed. "heart" of the system are very interest- One program machine turns the radio ing units. One of these devices is shown off and selects the station, while the in Fig. C. It consists of three selector second turns the outfit on, selects the cylinders, the largest one of which speaker or speakers to be used, and shifts each minute when the electrical sounds the chime which announces the impulse from the Master Clock is re- program. Pins inserted in the large ceived; a smaller one which shifts once cylinder control all of these operations, each hour; and a third which shifts for any period of time from one minute to 168 hours. once every day. As you will notice in Fig. H (Continued on page 298) A close-up of the speaker shown in Fig. F.

(141!15i aaanneda CIRCUIT SELECTOR

CONTACT PINS SELECTOR DRUMS

Fig. E The remote control radio set.

TIME DELAY RELAY

MOTf1R

Fig. C, above Week -adjusted program machine. Fig. D, right Fig. G A two -room speaker installation. When the A bank of speaker- selector relays. It is these doors on either side are closed nothing units that determine which speakers operate. can be heard. RADIO -CRAFT for NOVEMBER, 1933 271 ANNOUNCING - An entirely new system of P.A. operation. An audio frequency modulated radio amplifier is used to "power" the entire electric light wiring system of a room, a home, or even an entire hotel. To receive the "broadcast" it is only necessary to plug an ordinary radio receiver or suitable detector - and- amplifier unit into any electric light connection in the room or building, as the Fig. A may be. The new wired -radio public address amplifier in service, "broadcasting" over a hotel's lightpower lines. case A WIRED -RADIO PUBLIC ADDRESS SYSTEM

novel and highly efficient device pose is fundamentally that of a Hartley radio receiver or suitable amplifier. illustrated in Figs. A and B has oscillator with Heising modulation using The amplifier ordinarily used with for its purpose the elimination of a type 45 tube as an oscillator and a the system is especially designed for T11Eall the usual wiring, either tem- type 27 as a modulator. Adaptation to "line operation." For this purpose it porary or permanent, between the mi- the electric lighting system is accom- has a special coupling device built in crophone and public address amplifier plished by capacity coupling; several ahead of the first stage. See Fig. 2A. with no limitations in the distance novel features are incorporated. Both This device consists essentially of a between the two. The advantages of not sides of the A.C. line are used and a fixed inductance with a variable con- having to wire for sound will be at once ground potential is established through denser. C17, connected across it. A type apparent to any engineer or Service the BX conduit and piping in the build- 27 tube, V4, serves as a detector and Man who has occasion to lay out yard ing. Radiation from the instrument is rectifier of the high- frequency carrier - sifter yard of multi -conductor cable prevented by enclosing the entire ap- wave; three 0.1 -mf. high- voltage con- through corridors, rooms, stairways, air - paratus in a metal cabinet and ground- densers are used for coupling this unit shafts -and at the same time prevent ing it. The power pack, Fig. 2B, is of to the line. unwary feet from tripping over it. Any- conventional design with the exception While designed primarily for pro- one who lias experienced these and some of two large R.F. chokes in the input fessional sound applications, the wired- of the added difficulties of hurried con- of the power supply to prevent R.F. radio P.A. system has a multitude of nections, will appreciate the advantages feed -back and two 0.1 -mf. condensers to other uses. For instance, due to the of this newest development in sound act as a bypass to ground. An efficient small amount of power used and because engineering. matching transformer and a two- button its radiations are confined to the electric This versatile device is based upon microphone with button current fur- light wires by the natural shielding the application of certain well known nished by a small "C" battery completes effect of the iron conduit through which principles in the radio art. It takes the the ensemble. all light wires are run, the wired -radio P.A. system may be used in the home place of the usual preliminary amplifier Operation and differs in function from it only in- without fear of outside radiation. sofar as it is designed to operate over Operation is very simple. You simply To use your radio set as a powerful the electric light lines, by generating plug the "unit" into any convenient public- address amplifier, simply discon- and superimposing a carrier -wave upon 110 V., A.C. socket or receptacle, press nect the aerial at the set, replace it with the wires. a button and talk. The modulated car- the ground wire, and your radio receiver rier-wave is instantly impressed on the is then ready to pick up speech or music Circuit lighting system and the voice modula- as "broadcast" from. any place in the The circuit, Fig. 1, used for this pur- tions carried over the wires to a remote house where you may have plugged in

272 RADIO- CRAFT for NOVEMBER, 1933 27 R4,4MEGS TOMOV,AC. C21 if C20 j 0.1- 0.1- U. MF. TO INPUT OF 60T D.A. N422 wnaE

C17 / C19 -a -A- 350MMF. 0.1-MF.

Fig. 2, Above At A. above. is shown an input detector uni suitable for use with any type of power amplifier at the "receiving" end of the R.F. P.A. system. At B is shown the power pack required for the wired -radio P.A. unit. illustrated by diagram in Fig. 1. In Fig. 2A, coil L2 is the 60 T. unit. Fig. B, Right An interior view of the wired-radlo P.A. unit. The small components are underneath the chassis. the P.A. unit. Leave the radio set connected as described and conceal the R.F. P.A. unit in a room and you can create endless amusement at parties by arranging to listen-in on any conversation that takes place at the remote point. Replace LIST OF PARTS the microphone (attached to the sys- Modulated Oscillator P,wor Pack tem) with any electrical phono. pickup Our cnirr- t:gq,rd inductance coil appnrxi- One poker transformer, with two 2.5 V. and you can broadcast your favorite mately 60 fonts Of No. 22 U.C.C. wire Iilnmeat windings, a 5 V. winding, a (anicnua coupling, 111 turns), L1; 750 V. winding with center -tap, and records over the home electric lighting One 350 mint. variable condenser, C1; equipped with an electro-static shield, system to your radio receiver. Une 2 meg. grid leak. R1; PT; These are but a few of the many ap- One 250 mmf. condenser, C2; Four 0.1 -mf. condensers, CI I, ('12. CI 3, Thur 0.1 -mt. endeu.rm, C3, C4, C5; C14; plications of this new and useful device. Two .006 -mf. condensent. CO3 C7; Two S mt. electrolytic condensers, ('15, Constructional Data One .01 -mf condenser, CS; C16; In building the R.F. P.A. transmitter One 5 mt. condenser, CO; One A.F. choke, Ch. 2; One .25 -mf. condenser, CI0; One 4 -prong sot -ken for V3; and amplifier coupling device, it is not One 30,000 ohm resistor, 122: One type SO tube, 173; necessary to do any special coil winding One 2,000 ohm resistor, 113; Two 30 A. fuses; or machining of small parts. Standard One R.F. choke, S5 mhy., R.F.C. 1; One flue block; One 4 -prong socket, for VI; One power switch, Sw. 2; parts may be used throughout. For this One 5 -pr,ng socket. fer V2; Two hank -wound coils, No. 22 O.C.C. wire, reason, no detailed description of the One type 45 tube, VI; used as R.I.% chokes in A.C. line. R.F.C. construction has been attempted. One type 27 tube, V2; 2, R.F.C. 3. 30th One microphone transformer, Tl; Pickup Unit Coil Ll is tapped at the turn; One coil of approximately 60 tuons of No. LI and L2 are tight -wound (except One microphone, 5IIC; Ll One cord, plug and socket for microphone; 22 O.C.C. wire, L2; One Variable condenser, 350 mmf.. C17: antenna, whose turns are spaced r, -in.); One "C" battery; Olio fixcl e tenser, 250 mmf., No. 22 D.C.C. wire is used for all coils; One battery "C" switch, Sw. 1; Three 0.1 -mf condensers, C19, C20, C 21: the winding form is a tube 2 ins. in One chassis; one 5 -prong socket, for V4; diameter. For R.F.C.2 and R.F.C.3, One 6 ft., two- conductor cable and plug; One type 27 tube, V4; random -wind 500 T. of No. 22 D.C.C. One A.F. choke, A.F. Ch. 1. une 4 meg. grid leak, R4. wire on a tube 2 x 1 in. in diameter. Ordinary 30 hy. filter chokes are suitable as Chi and Ch.2. The amplifier illustrated and described TO ILO V, A.0 T1 R2 Rt was a model. A "commercial" R F.C.1 "hand" MICROPHONE 2ME65OÌMf now available, the TRANS. 27 ( OHMSO 85 Miiv. 45 411-MF model, is called MODULATOR s OSC. j T cs "socket mike" and looks just like a con- 06)` denser mike and head -amplifier; the principle of operation however is the same as indicated in Fig. 1. The simplicity of the Hartley oscillator circuit and Hefsing modulation L system is such that the pictures, dia- Cl grams, and lists of parts, should be all fi CO that are necessary to enable anyone to .25 MF. N.V 006-MF CO r / build and operate the system. The X (EH)AC - .01-MF. t3./SMp. writer will be very glad to answer any "legitimate" inquiries concerning this device, which fills a long -felt need in Fig. 1 several fields. Schematic circuit of the new wired -radio public address system.

RADIO -CRAFT for NOVEMBER, 1933 273 Intimate in Character The Daily Newspaper International in Scope Of Motion Pictures Independent in Thought Now Fifteen Years Old

VOL. EXI1. NC. 77 NEW YORK. FRIDAY. JUNE 31 , 1'433 5 CENTS Fox Announces 43 of 54 Titles For Next Season

"OPEN MARKET" ON EQUIPMENT PARTS Defer A '" pro sed N. Y. Building Code to Fall T Decision Finds Illegal Electrical Research Aldernr,._. Products Clause Restricting ,call Talk M Buying- _ICOATE Following Producers Win Important Point the Board , .. ,aermen, at which re In one of the most one does not need a Article 2 of the proposed building far -reaching court decisions in the annals come to the jolly conclu- code which would prohibit marquee of the film industry, Judge John P. Nields of the U. S. Dis- erry old industry is whirling signs of more than two feet in trict Court, Wilmington, Del., has handed down a decision which d. Thins are oing, height was considered; an 'ourn- allows exhibitors to buy sound reproducer parts in the open market, regardless of their tying agreements with Electrical Research Products, and permits producer licensees to sell their pictures to exhibitors other than Fig. 1 !those using Western Electric Equip- "Exhibit 'A'" in talkies servicing. Opinion on Page 9 note

AN INTRODUCTION TO

1-.CENT developments, culminating SERVICING in a decision handed down in a United States court a few weeks ago, have effectively opened to the radio dealer and Service Man the field of supplying parts THE "TALKIES" to motion picture sound equipment! It is a profitable field. The radio man PART I who can "line up" three or four local AARON NADELL theatres as customers for his electrical Parts and his technical knowledge will find he has a very nice or some similar trouble which the local radio Service Man side line to add to his radio business. If he can line or up six might easily have repaired, with good profit to himself, at eight such theatres (possibly all under one ownership) -tenth he will oar the cost! find he can afford to consider his radio business a If side line. Approximately these prices and practices seem fantastic, it must be 17,000 American theatres are now understood 'vrire(t for sound." that to the theatre the sound equipment is its stock in trade, which must operate at all costs. Unlike the Parts Replacements Charges radio owner, who has no reason to be troubled if his radio is silent for a day or two, the theatre Theatres are accustomed to paying prices for their supplies cannot afford to shop that will remind the radio man around for lowest prices. of the days of '22 and '23. The theatre manager, Sixty dollars for a rectifier tube capable and the projectionist, the two persons of passing 200 ma. who are directly responsible was not an uncommon price until very recently, for the performance of the sound and some equipment are, for reasons which theatres are still paying it. (Sixty-not six- dollars.) will be explained later, not average An always technically equipped, by experience or theatre will spend several hundred dollars a year previous train- for tubes alone. ing, to understand precisely what repairs are needed in an emergency, or how These prices fade into comparative unimportance much those repairs should cost. when Today, by decision of a United compared with the cost of replacing a burned -out transformer, States court (see Fig. 1), or some similar part as well as by certain internal changes (to be described) in in an amplifier. Often, in the past, the theatre such amplifiers have been returned industry itself, the local radio man is at liberty to the factory for com- to make those repairs plete overhauling, at a cost of $100 and to sell the necessary parts for them. or more, because of a That he can do this at excellent damaged A.F. transformer, a short-circuited condenser profit to himself, and still block, save the theatre much money, as compared with the prices 274 RADIO -CRAFT for NOVEMBER, 1933 It is accustomed to pay, is, to this factory, and in general leaving no room writer, unquestionable. The only ques- at all for the local radio man to be of tion involved is convincing the manager the slightest use. That set-up is now and the projectionist of that fact. broken down. The large chain proved There is where the catch comes in. uneconomical-the overhead ate up the Those gentlemen are tough people to profits-and is everywhere in discredit. convince; and the man who attempts to Small chains, composed of three, four or of do it must know very thoroughly just a dozen theatres are the backbone show what he is about. He must not only business today. They constitute know sound equipment technically (it is the local radio man's most promising very similar to radio equipment) but he prospects. Skeletons of the larger must also know show business, and its chains still remain, for the most part peculiar requirements. Most important broken down into smaller operating of all, he will need a good and deep groups which the radio technician can insight into the psychology and habits contact with profit both to himself and to them. of thought of both the projectionist and the manager, or he'll never get to first The full story of the recent changes base. If he doesn't know how to ap- in the theatre industry is more compli- proach those gentlemen, the fact that cated Fig. 2 than this brief outline indicates, actually he can help them and save them but the complications Up A 'frame" from a sound -movies film. will be taken money won't mean a thing -as will be in detail in their proper place. At this seen. point, enough has been said to point It is proposed in this article and in out that an opportunity never before others to follow, to outline both the open to him is awaiting the local radio technical and the commercial aspects of SERVICE MEN dealer when the show season "opens" the new opportunity which is now open this fall and winter, provided he has to alert radio technicians. At the pres- Do you know that there are equipped himself with the necessary ent moment it may be as well to pause approximately 17,000 Amer- knowledge to take advantage of it to explain how is that oppor- it that ican theatres now "wired for tunity is now open; and why, until very Do you know that Forthcoming Articles recently, the chances of the local radio sound "? man to be of service to his community's these theatres have been ac- It simply will not work to ask for theatres were extremely dubious. customed to paying as high as the manager at the box office of the Two developments have contributed $60.00 for a rectifier tube? local theatre and offer in some vague to the creation of the present set -up. Do you know that simple ser- way to be helpful in his sound prob- One is the court decision already re- vice jobs on talking motion lems. The radio man who aspires to ferred to- handed down by Judge John picture equipment have cost service and supply his local theatre P. Nields in the U. S. District Court at $100.00 and more? However, must know precisely what function he Wilmington, Delaware; and the other it is only within the last few intends to perform. He must know ex- is the breakdown of the large theatre months that changes within actly and in detail how and why his chains. intervention will the theatre structure have be advantageous to that manager. More important still, made it possible the for In. know Contracts and the Federal Court must how to make his inter- independent radio Service vention welcome, and not objectionable, There was only one company equipped Man to handle calls for service to the projectionist. Lastly, he must and ready to supply the sudden and on talkie equipment. In this learn enough about that very peculiar urgent demand for "talkie" apparatus and subsequent articles in a enterprise, unlike any other, which is when talking pictures began, and every new series, Mr. Aaron Nadell, called show business, to enable him to theatre in the country was shouting for who is an authority in his interfere in it successfully and with- the necessary equipment "immediately chosen field, will show the out. "gumming up the works." if not sooner." That company natur- radio Service Man the exact But before everything else, he must ally got the cream of the business, on steps necessary to successfully know what sound equipment is all their own terms. They did not sell, about, what enter a newly opened, highly it is like and how it differs they leased. The terms of the lease from profitable Servicing ordinary radio equipment. At provided that the same company was to field- the least enough about sound Talkies. installations supply all tubes and other spare parts, not to become confused when he con- no matter how much more cheaply they fronts a rack -full of apparatus reaching could be purchased elsewhere. There from floor to ceiling and is told the was also a servicing clause, which will whole business is only an audio ampli- be discussed later but which is of no immediate concern fier with ten watts output! here. It is that leasing contract that the Federal court at In the articles to follow it is proposed: Wilmington upset. In consequence any radio man is now (1) To discuss the elementary nature of sound equipment, free to sell tubes or other supplies to theatres (amounting to from a moderately technical point of view. Any experienced about half of all talkie theatres in the country, and including radio man will grasp the essentials of this description with- nearly all the larger and wealthier ones) which use that out the least trouble. company's electrical equipment. Other legal actions along (2) To describe the problems, functions and average psy- related lines will be described later in this series. chology of the theatre manager, together with some attention Until a short while ago the majority of the country's to the unusual nature and problems of theatre enterprise. theatres functioned under the chain system, which meant (3) To deal with the background, psychology and problems that a thousand or more theatres were, like so many grocery of the average projectionist (without whose co-operation the stores, under one ownership, and operated from a central radio man will get nowhere) -and especially with the ex- office in New York, Chicago, or some other large city. Pur- ceptionally delicate situation of contacting the unionized chase of supplies for sound equipment, and supervision of projectionist. the service such equipment required, were handled by the (4) To outline, in considerable detail, just how the radio "home office." Staffs of sound engineers travelled about the man can offer superior service and assistance to neighboring country inspecting theatre apparatus, contacting manufac- theatres, and in particular how his peculiar advantages turers, buying tubes and other supplies directly from the (Continued on page 302)

RADIO -CRAFT for NOVEMBER, 1933 275 THE NEWEST DESIGN IN ALL -WAVE

PART McMURDO SILVER*

Fig A At the left is the complete set in its chromium cabinet while at the right the power supply, amplifier and speaker.

TO THOSE familiar with the original Masterpiece all - stations! wave superheterodyne receiver two changes are out- The control knobs are, looking at the front panel, Fig. A, standing upon looking at Fig. A. The first is the upper two, the main tuning knob and dial at the right, and polished chromium shielding "cabinet" over the entire the vernier or band spread dial and knob at the left; the receiver chassis, shown at the left. This cabinet contributes visual tuning meter is at the top- center. The four lower additional shielding over and above that of the individual knobs are, left to right, audio volume level control, manual circuit elements, helping to eliminate extraneous noise, and tone control; at the lower center, the audio beat oscillator also keeping dust and dirt out of the set. toggle switch, inter -station noise suppressor or sensitivity Simplifying the Tuning control, and the four -position, positive -acting wave change The second change is the use of two tuning dials instead switch. of one. The receiver is completely tuned by the right-hand Sensitivity Control dial and its single knob, as was the first Masterpiece. The In any sensitive receiver using an A. V. C. system, sensi- second dial is simply a vernier, or "bandspread" tuning tivity will rise to a maximum in the absence of a carrier dial to permit he short -wave bands such as the 6,000, 9,500 signal, and the local noise is bound to be heard between and 12,000 he. short -wave bands (which are assigned for stations, if a "squelch" circuit is not provided. This is par- broadcast services) to be spread out over a whole full dial ticularly annoying in the daytime, when many channels are scale. It may otherwise be used to spread the four amateur bound to be dead, and noise will be heard as the set is tuned bands -or even small segments of the broadcast band, for between the stations normally heard in the daytime. easy tuning. The special "squelch" circuit used in the first Masterpiece The 28:1 dial ratio used in the first receiver was too had two disadvantages. It required an extra tube, and its slow in operation; even more important, it did not permit cut -off level had to be set at some arbitrary point. Also, it was found that many stations constituting good sufficient band -spread for easy reading. Using the new band - noise -free spread dial, the main tuning dial need only be set at, say, entertainment, would, in the course of the normal and con- 6.2 for the 6,000 kc. or 50 meter short -wave broadcast band, tinuous slight fading, fade across any arbitrarily established cut -off and all the stations in this band will be found spread out level, resulting in a periodic cut off of reception, or nicely on the vernier dial-for the first time, actually making if fading was rapid, in choppy and distorted reception when the squelch circuit was short -leave tuning easier than is broadcast band tuning on in use. ordinary receivers. Therefore, an R.F. sensitivity control has been substituted for the squelch Tuning is rendered difficult by any high -ratio tuning dial, circuit. It can be adjusted to local noise conditions; also, which will necessarily be mechanically stiff. By the use of it entirely eliminates the possibility of 6:1 automatic take -up gear drives with choppy reception of stations fading slightly across the silent opposed gears (an tuning equivalent of the beautifully smooth helical gear control) control cut -off level. It permits of adjustment, when the mechanical operation not only is smooth desired, of the R.F. and I.F. gain to the exact degree desired, and entirely almost free of slippage, wear or backlash, but the control knobs wholly independent of the actual loudspeaker volume desired, and over all turn with extreme ease. This simple mechanical change is ordinary operating ranges has no effect on the A. V. invaluable, and in the hands of a novice can make all the C. action, or on the operation of the A.F. vol- difference between skipping over foreign short ume level control. -wave stations, Thus the and having them actually easier to find than broadcast band revised tube circuit line -up in the receiver chassis is: a type 58 R.F. stage; a 2A7 combined first detector and President, McMurdo- Silver, Inc. electron -coupled oscillator (the first combination tube so far 276 RADIO -CRAFT for NOVEMBER, 933 SUPERHETERODYNE RECEIVERS

Since the author started building the Masterpiece 13 to 570 meter custom -built superheterodyne, hundreds of these receivers have gone into use all over the world. Now, one year later, and as a result of analyzing a cross -section of comments and suggestions, an improved instrument has been developed. These improvements are simplifications of an electrical and mechanical nature, calculated to render the results previously obtained easier to secure, both for the novice and the experienced engineer alike.

Fig. C Fig. B The band -spread dial on the left simplifies tuning on the short wave bands. The underchassis view of the set coils and band switch. An overall metal cabinet entirely eliminates extraneous pickup by the wiring.

introduced which gives actually better results than separate for 9 ke. selectivity is needed in Europe where broadcast - tubes performing the same functions); three type 58 I.F. band stations are separated by 9 kc. instead of 10 kc. as in stages (the third stage used for selectivity, not for gain -its this country. This does not affect the fidelity unfavorably, additional gain cannot be used); a 56 first A.F. stage; two which is still flat to 5 db., from 50 to 4000 cycles- better type 2A3 tubes connected in push -pull class A, and delivering fidelity than is had by any competitive set today available 15 W. of output power; and a 5Z3 rectifier. not resorting to excessive A.F. compensation with consequent annoying hiss. Changes in the Power Stage Another change which results in improving the signal -to- A pair of type 45 power tubes operated in the class A noise ratio is the use of the tuned R.F. stage on both broad- prime system developed in the writer's laboratories was used cast and short waves. This is a development made possible in the original Masterpiece to produce 10 W. of undistorted by research work done by the writer in the past year which output power. Refer to "Pentode, Class B or Triode Audio resulted in the ability to accurately track the tuned R.F. Systems ?" by the writer, in the July, 1932 issue of RADIO- stage with the first -detector and oscillator circuits. The CRAFT.) This class A prime development had so much merit additional gain of this stage cuts down oscillator hiss found that another manufacturer desiring to obtain its result, but in other sensitive receivers, and results in the best inherent loath to bow to the more advanced research work of a com- signal -to -noise ratio so far obtained in any sensitive all -wave petitive laboratory, insisted that RCA develop a larger, radio receiver. It also eliminates the repeat spot or image straight class A tube to give the same results. The result was interference on short waves found, the writer believes, in the new 2A3 tube, a pair of which when operated in class A every other custom -built all -wave set made today. connection will turn out 15 W. of undistorted A.F. power Separate antenna coupling coils for each of the four bands at reasonable operating voltages; these tubes possess the permit the use of a tuned or transposed antenna or lead -in advantage of requiring only voltage, not power, from their system. driving stage; whereas, the 45's in class A prime require Still another point of improvement lies in the arrange- power to drive them to full output, hence the use, in the earlier ment of circuit constants to permit the 12,000 kc. short -wave design, of a pair of 56's in push -pull as a power -driver stage. band mostly occupied by foreign stations to fall at the low Through the present use of a pair of 2A3's the maximum tuning capacity end of one tuning range. This low C/L power output is increased 50%, (this consideration is un- ratio circuit gives better signal strength than does a high important, since 10 and 15 W. is less than about 2 db., or C/L ratio circuit, making for more consistent and satis- the minimum variation ordinarily perceptible to the human factory reception of 12,000 kc. and 9,500 kc. band foreign ear.) The important point, however, is that the 2A3's require stations. no driving power but may be fed by a single 56 voltage In conclusion, the writer desires to express appreciation amplifier. to Masterpiece users for their helpful suggestions; and par- The 15 tubes used in the original receiver's A.F. amplifier ticularly to Professor William Bostwick of Cornell University and power unit are now seen to be cut to eleven, more who, in his search for the ideal all -wave receiver, and in efficient ones. Actually, however, the improved and simplified attempting to satisfy the University's rigid requirements, receiver uses 12 tubes, the twelfth tube being a 58 in the has been of great help in brining the latest model to its added, dual -tuned I.F. stage. This tube is added only be- present high state of perfection. cause it is the simple and obvious means of coupling the A schematic circuit of this receiver and a more detailed two extra tuned circuits added to the I.F. amplifier to set technical discussion will appear in a forthcoming issue of the selectivity up to absolute 9 kc. instead of absolute 10 kc., RADIO- CRAFT.

RADIO -CRAFT for NOVEMBER, 1933 277 HOW TO CONVERT A.C.-D.C. SETS FOR "DRY- CELL" TUBES

RICHARD SILBERSTEIN

Fly. A TI-.0 r.

The modern A.C. -D.C. ultra -midget radio receiver unfortunately cannot be used in places where there is no power supply - a completely self- contained set is required for use on the beach, in camps, on small craft, and in canoes. The author describes a "converted" receiver which weighs only 12 lbs., complete with batteries, and which can easily be fitted into a knapsack for purposes of transportation. The filament drain from the three tubes is only 180 ma. so that frequent "A" battery renewals are not necessary.

THOSE of us who bought an early is to remove the plate choke, the fila- the R.F. coils wrapped in cloth tied with 4 -tube T.R.F. midget set with a ment drop resistor and all the electro- rubber bands in order to avoid scratch- magnetic speaker may have won- lytic condensers. Electrolytic condens- ing the delicate enamel insulation. dered what to do with the old set ers have a continuous leakage current The socket nearest the variable con- now that a new 5 -tube superheterodyne and therefore must not be used on sets denser is to be used for the 32 R.F. midget reposes on the living -room table operated from "B" batteries unless these amplifier tube. Since the bulb and (or ought to!). Here is a way to make are disconnected whenever the set is base of the standard type 32 are larger the old set perform in a brand new not in use. Nearly all the wiring in than those of the 39 which it is replac- role- entertaining a canoeist, for in- the under part of the chassis, except ing, it will be found that the variable stance, as illustrated in Fig. A -at the the common negative bias connection condenser plates will hit the tube unless additional cost of only a few tubes, of the R.F. coils must be undone. This the whole unit is moved forward. This batteries and other small items. Al- last can be used as a connection for the is accomplished very conveniently by though the description will cover spe- 3 V. "C" battery negative. moving the unit forward a distance cifically the Emerson Compact set, it It is well during this procedure and equal to the distance between the two applies in general to any of the earlier in fact all through the work, to keep mounting screws, namely 1 5/32 ins. "universal- current" radio receivers, the primary requirement being a magnetic speaker, which is essential to a light, ANT, REGENERATION MAGNETIC r CONTROL REPRODUCER battery -operated set. A front view of COUPLING r TICNLER, C9 the completed conversion is Fig. B; and /GOND. R F. R3 .0I-MF I 32 0Er % a rear view is Fig. C. cl ! 32 I Briefly, the conversion consists of I- substituting a type 32 tube for the 39 I II in the R.F. stage, another 32 in place ce of the 36 a 30 of A- detector, and instead ¡ Cî,.05,MF the 38, in the output stage. Coupling d e R FC R4 between the detector and the audio out- Rf C5i :05NIF put stage is accomplished by means of GND la co. C3,.OS MF l RS an R.C.A. 700 hy. detector choke. Re- III 'MMWIIIEMIIIIMEMI generation is provided in the detector circuit by means of a 50 -turn coil u 1 r-414.-IF coupled to the grid coil. The "con- SW C. IM verted" circuit to be followed is shown 1 in Fig. .1. Items not labeled are the CNA SIS' (INSULATED) "8+` a +- f A+' same as in the original set. 45V 67V 90v 3V. 4 5v 'C +" Step -by -Step Procedure Fig. 1 The first thing to do on the old chassis The Emerson "Compact," rewired for dry -cell tubes.

278 RADIO -CRAFT for NOVEMBER, 1933 It is then necessary to drill only one occupied by the 38 but this was not new hole in the chassis, a 1/4-in. hole done because experiments with a fourth at a distance of 15/32 -ins. toward the tube gave poor results.) Two type 30 front. Then the condenser is re- mounted tubes in parallel gave a slightly weaker with the forward bushing in the new and more distorted signal than one, hole and the rear bushing in the hole probably because their combined plate previously occupied by the forward impedances did not match the speaker bushing. In this process the leads to impedance. An additional stage of re- the condenser must be removed and sistance coupled amplification was soldered back again. abandoned because of detector tube Now the condenser plates will clear microphonics. the tube but it may be necessary to The chassis Is left free as in the hammer in the flange of the loudspeaker original set, being tied to the negative frame for a short distance so that the end of the 3 V. battery only by means plates may pass without touching. It of a .05- mf..condenser. This is better will be found that the antenna series than making a direct connection since condenser mounted on the frame of the it minimizes the chance of a short - tuning condenser protrudes past the circuit while the set is being tested. front of the chassis. This is now re- In "universal" or A.C.-D.C. sets the moved and placed under the chassis in ground connection is made through the part of the space formerly occupied by power line, but since there is no power the filament drop resistor. line in a battery set it is necessary to Fig. B The 32 detector tube takes the place have an actual ground connection, or Front view of the completed irstrument. of the old 36 tube. Instead of the else a "counterpoise" consisting of about "plate" detection scheme previously 25 ft. of wire, for use in places where used, the "grid -leak and condenser" a good ground is not to be had. This type was employed in order to obtain ground or counterpoise is connected di- higher efficiency on weak signals. The rectly to the chassis when the set is 250 mntt condenser is mounted under in use. the chassis in the middle of the space The filament current is controlled by formerly occupied by the filament drop means of special ballast-resistor car- resistor and the control -grid lead tridges. Space limitations required that brought up to the detector tube. these also be carried in the battery box Although the R.C.A. detector plate and to minimize the number of connect- choke, R.F.C.. was the smallest choke of ing wires they are arranged in parallel. its kind obtainable, no space was found For the preliminary test and for final on the chassis into which it could be mounting, eight leads must be brought fitted. Hence it was necessary to mount out from the chassis through the per- it outside of the chassis in the battery forations at the rear. (These leads are box. For this reason one must now clearly shown in the rear and underside solder a long, insulated lead onto the views of the chassis, Figs. D. and E, plate connection of the detector socket. respectively.) They are the seven battery leads shown in Fig. 1 and one Fig. C Adding Regeneration more lead, X (from the detector plate), Lead connections to the batteries. for the R.F. choke. The other end of or tickler coil Ll The regeneration the choke goes directly to the "B+" consists of 50 turns of No. 30 enameled 90 V. tap in the battery box. wire on a q -in. form. The wire is wound as close as possible to one end The Power Supply of the form so as to secure close coupling to the detector circuit. The coil is For the sake of portability it was de- mounted directly on top of the detector cided to use only 90 V. of "B" battery. grid coil. A handy way to do this is to The smallest batteries obtainable are obtain a small piece of fiber about 20 45 V. units made by a company in Cleve- thousandths of an inch thick and cut a land, Ohio. The batteries measure 3% strip about I/_ -in. wide. Curl this strip x 2% x 31, ins. The same company in the manner of a stiff collar and slip makes a 3 V. "A" battery having dimen- it into the end of the regeneration coil sions of 3% x 1% x 4 :y4 ins. For the so that it protrudes about t/4 -in. above 3 V. "C" battery a small flashlight bat- the end all around. A little Duco tery was used; for the 4%/2 V. "C" bat- Household Cement or Ambroid Cement tery another type was employed, al- will hold it in place. Now push this though a flashlight battery would have assembly into end of been satisfactory in this position. the the detector Fig. D coil, smear a little of the cement onto The battery box can be made to suit Rear view of the battery -type ultra -midget. the fiber and permit to dry for a short the individual's "taste." One method time. would be to have a separate battery box To provide for regeneration control, joined by a multi- colored cable to the remove the volume control potentiom- main outfit. In this set the battery box eter and substitute a 20,000 ohm po- was built of 474-in. pine directly onto tentiometer with an off -on switch, con- the set, using the bottom of the cabinet necting it into the circuit across L1 as the top of the battery box. The four as shown in the diagram. The off -on bolts which pass through the bottom switch breaks the negative filament of the cabinet to hold the chassis in circuit. place were used to hold four 1 in. brass The 30 audio tube is mounted in the angles to which were bolted the ends of space formerly occupied by the 37 recti- the box, measuring 4 ins. along the cab- fier. (It would have been possible to inet bottom by 41/2 ins. deep. Around Fig. E put a fourth tube in the space formerly (Continued on page 301) Urtderview of the altered chassis.

RADIO -CRAFT for NOVEMBER, 1933 279 HOW TO MAKE YOUR OWN TRANSFORMERS

AND CHOKES PART I

LESTER H. CARR*

ItANSFOR\IERS are only as good as their poorest feature, both in design and construction. It is T very important to take great pains not only in designing and laying out a transformer but also to use equal skill in its construction. Since the subject of design has been covered quite thoroughly in previous issues of RADIO-CRAFT only a few of the important points of design will be re- viewed. For maximum efficiency in operation, the core loss of any transformer should equal its copper loss, the ratio of the weight of iron to the weight of copper in the average power transformer, using a high grade of steel, being approximately 81/.-,. The allow- able current density in the copper for continuous operation is between 1300 and 1500 c.m. (circular mils.) per Fig. A ampere. Due to the fact that the eddy A low -power transformer, showing primary electrostatic shielding tape. current loss in the conductors increases as the square of the thickness of the case of a poor oxide wire, it is not advisable coating. In the windings. Light material having a high to use wire event that an additional insulator is dielectric much larger than necessary, if this loss strength is preferred. If used only a very thin coat should be heavy insulation is to be kept at a minimum. However, is used or if too much applied. This is done by dipping the is put in windings, this is more important in reactors the hot spots will laminations in a thin solution of in- be due (choke coils) than in transformers. The present to the poor heat con- sulating varnish or its equivalent. In ductivity from the inner portion of the hysteresis loss in the core varies as B1.6 building up the core it is inadvisable to coils. This may prove and f, where B is the flux density and as disastrous as use butt joints and it should be inter- under -insulating, f is the frequency of the current. The due to the insulation leaved with as few joints as possible. carbonizing from the heat and breaking eddy current loss varies with B2, f2, and In small units it is possible to stamp down. On narrow coils t2, where t is the thickness of the lam- heavier insula- out the laminations, although in the tion can be used without this danger inations. From this it can be seen that larger sizes to it is usually necessary to and is to be favored due to the strength- keep down the losses in the core the build up the core from flux density strips. In either ening of the winding. If the windings should be kept down within case, even interleaving is limits and also the laminations used to keep are to be impregnated (and all high should the reluctance of the joints as low as grade windings be very thin, usually 26 or 28 gauge. transformer should be) possible. If the reluctance of the core cotton tape is used to wrap the coils. Good Construction Design is increased very much by poor joints, This makes a good binder for the im- the magnetic Now let us turn to the construction leakage in the windings pregnating compound. The winding is proper. will increase, resulting in poor trans- then placed in a vat and heated. the air First, the cutting of the transformer regulation. former steel should be done with sharp pressure being reduced to help draw A very and close -fitting tools to prevent drag- important rule to remember out all moisture. The coil is then ging the edges. If in both design and construction is that placed in hot resin compound and the this is not done the the turned edged will break through the mean turn length of both the steel pressure raised to drive the impregnator oxide scale on the adjoining laminations and the copper should be kept at a well throughout the winding. It is then minimum; from which and cause a large increase in the eddy one deduces that wrapped with empire cloth for addi- current loss. Care should the ratio of the space occupied by the tional external insulation. By impreg- be taken copper not to injure the oxide to the total winding space should nating not only is the insulating quality coating of the be as large as steel by bending or chipping possible. This ratio is increased but the coil is strengthened as this known as the space factor. oxide affords the only insulation to the greatly which prevents insulation rupture due to stress on the winding eddy currents, unless the laminations Coil- Winding Details at are dipped in times of sudden shock loads or short - an insulating varnish. It is highly desirable Usually this is not necessary except in to use "pi" circuits. windings wherever possible, because of the need of special construction or in Mica is often used as an insulator better insulation, cooling and symmetry between primary and secondary wind- Consultant Engineer, Franklin Transformer in tapping. Care should also be used ings because of the necessity of having Company, in selecting insulating material for the close proximity of the primary and

280 RADIO -CRAFT for NOVEMBER, 1933 Although past issues of RADIO -CRAFT have contained considerable information concerning the design and construction of power transformers and chokes, and A.F. transformers and chokes, a good part of this information has been entirely theoretical; and previously published practical data in many instances has not taken into consideration the newest "tricks" as used by manufacturers. Consequently, this article by Mr. Lester H. Carr will be of exceptional interest, since it combines both the theoretical and practical viewpoints in the design and construction of units in power and A.F. circuits.

able, its core may be used. Figure 1 shows a standard "shell" type of stamped lamination commonly used; also it shows how the core is built up from the laminations by reversing each adjoining piece. Once the core size is known, work can be started on winding the coils. The cross -section of the core, "Core Sq. In. X- Section," in Table I is obtained by multiplying the dimensions selected for measurements A and B in Fig. 1. Make a winding form out of a piece of soft wood whose outside dimensions are approximately t/s in. larger than the core piece. (This is to allow for insulation between the coil and core.) The piece of wood is cut to a length suitable for mounting in a winding jig or lathe. If such facilities are not available the turning can be done by hand with a little additional help. The block Fig. B should be waxed or varnished so that A medium -power transformer. The primary and secondary windings are tapped. the coil will slip off easily after the winding has been completed. Wrap a secondary windings if magnetic leakage set front the power lines. couple of layers of empire cloth or is to be kept low. Figure B shows a flexible design of tough paper around the form and hold The leakage reactance caused by this high -voltage power supply transformer in place with a small piece of adhesive leakage flux is equivalent to an induct- with variable taps on both the primary tape. Cut a piece of cotton or friction ance added in series with the primary, and secondary for voltage adjustments. tape 1% or 2 ins. long and lay it length- and, consequently, greatly impairs the The clamping manner of holding the wise on the form at the end where the voltage regulation of the transformer. core of the high -voltage unit is prefer- winding is to start so that the first A design feature is to enclose the able to the method used in the unit turn is nearly in the middle of the strip. primary winding in copper foil, care illustrated in Fig. A. When the method Wind two turns and then double back being taken not to have a short- circuit- of clamping with a bolt through the the loose end of the tape outside the ing turn. (Opening up the foil in one core is used, small brass bolts with bush- first turn, pulling it tightly over the or more places and insulating will safe- ings should be used to minimize the two turns and continue the winding guard against any trouble of this kind.) eddy current loss. over the two layers of tape. This binds If the transformer is used where there Some of the above steps, employed in the first two turns, preventing them are any R.F. currents which might leak high -grade transformer manufacturing, from slipping. This procedure is used into the windings, this shielding pre- may be impractical for the reader to on each layer and at both sides of the vents it from getting into the low-volt- use in building up individual units. It coil. After the first layer is wound. . age primary where there would be dan- is, however, possible to use more simple wrap one layer of thin, tough paper ger of its rupturing the insulation and methods which will produce good trans- which has been boiled in paraffin over rendering the transformer useless. formers if exceptional care is taken. (Continued on page 306) Commercial Transformers Home -Built Transformers Figure A shows a low- voltage type of For those wishing to build up a spe- unit having several secondary windings, cial transformer or to rebuild a burned and having a shielded primary. A out one, let us cover a simplified con- primary winding is shown, illustrating struction. the manner of enclosing the coil in cop- It is advisable to obtain the core from per. The steel case, illustrated, effec- a reliable house to insure a good grade tively short -circuits any stray flux from of steel. Either obtain it all ready cut the transformer which would tend to to shape, or take the sheet steel to a tin interfere with other equipment. It shop and have it cut or stamped out; might be mentioned that primary shield- however, you will save time and money ing of radio receiver power transformers by purchasing stamped laminations. In is highly desirable inhere electrostatic case an old discarded or burned -out Fig. 1 interference often tends to feed into the transformer of the right size is avail- "Shell -type" core laminations.

RADIO -CRAFT for NOVEMBER, 1933 281 CONSTRUCTING A COMPLETE 26 -WATT, DUAL CHANNEL P. A. PART Ill SYSTEM Detailed data in reference to the input mixer, 2 -speed phonograph turntable, turntable power supply, dual -field dynamic reproducer, and the reproducer field coil exciter required to complete the optional power line or battery 26 W. amplifier. This concludes the series. LOUIS GANCHER*

THE man who is looking forward our 26 W., dual -channel P.A. system, BP3 and BP4, also located on the rear to making a couple of extra dol- the unit illustrated in Fig. F has been of the case, are used to couple radio lars in the P.A. field by building designed. tuners through the control box into the and using the universal 6 V., D.C., By reference to Fig. 7, the schematic amplifier. A selector switch, Sw.4, and 110 V., A.C., 26 W. portable P.A. circuit employed in this mixer, it will feeds the output of either the phono. system discussed in previous install- be seen that the 2- button microphone, pickup or radio tuner units into the ments of this series, has only a few M1, is connected to a polarized, 3 -way volume control, R3, leaving the micro- more points to consider and then he male plug, PP1, which may be conveni- phone available, in either instance, for may write "finis" to his acquisition of ently inserted or removed from the impromptu operation. Thus, by man- the necessary apparatus. For, it will polarized, 3 -way female outlet, PP2, ipulating both volume controls, R3 and be recalled, the system is based on the mounted on the rear of the control unit. R4, separately or simultaneously, the use of a number of inter -locking units, Each of these double- button microphone microphone input signal may be mixed not all of which have as yet been de- circuits are connected through their or faded onto a phono. record or radio scribed. This will be evident by refer- respective microphone current controls, tuner program. The tone control, TC, ence to Part I, in the September, 1933 R1 and R2, and microphone current modifies any undesirable defects of the issue, where the complete system is reading switches Sw.1 and Sw.2. input signal and permits the "mixed" shown mechanically locked together, in Snap Sw.1 to the ON position and ad- signals to be compensated to best ad- Fig. C, and "strewn about," ready for just RI for an approximate reading of vantage. business, in Fig. A (the manner in which 8 to 12 ma. Then, to the OFF position; Two wires leading from the output the complete P.A. system is electrically repeat the procedure using R2 and Sw.2. posts, BP5 and BP6, are the only neces- connected is shown in the block dia- The S.P.S.T. battery switch, Sw.3, opens sary interconnecting links between the gram, Fig. 3). the circuit of battery B1 when not in control box and the amplifier. A single "Checking up," we find that detailed use. (Two similar, 100 ohm single -but- shielded wire, up to 50 ft. in length, data is lacking in connection with the ton microphones may also be used with may be used to connect the output of following units: the input mixer, the this system for remote dual pickup by the control box to the input terminals 2 -speed phonograph turntable, the turn- connecting them in series as shown at of the amplifier, the outside metallic table power supply, the dual -field dy- A in Fig. 7, and using an additional, shield itself acting as one of the term- namic reproducers, and the exciter for polarized male plug identical to PPl. inals and ground at the same time. the high- resistance fields of these repro- The output of the microphone trans- All of the controls and equipment, ducers when they are operating on 110 former, TI, is connected to the modified with the exception of the 41t, V. "C" V., A.C. "T" pad type constant impedance con- battery, are housed in a No. 18 gauge, trol, R3, which provides for the com- crackle-finished steel case, 6 x 514, x 6 The Input 'Mixer' Control Box plete attenuation of the microphone in- ins. high. For a portable P.A. system to be put signal while maintaining a constant of output impedance. truly versatile it must be capable The Two -Speed Phonograph attenuating, accentuating, fading and Two phono. input binding posts, BPI mixing voice, phonograph and radio and BP2, mounted on the rear of the In order to make the entire system programs. To secure these effects in case, are connected to the primary of operative from either 110 V., A.C., or the tapped, phono. pickup input trans- from a 6 V. storage battery, particularly President. Coa t- t" -C,w >t Rodio Corp. former, T2. Two additional terminals, for use in sound trucks, automobiles,

Fig- F, lef ; Fig. 8. above At the left, In Fig. F, is illustrated the input mixer. Its circuit connections are shown in Fig. 7, on the following page. Above, in Fig. 8, are shown in A and B the phonograph turntable and 'dynamic reproducer field coil power supplies pictured in Figs. H and I, respectively.

282 RADIO -CRAFT for NOVEMBER, 1933 boats, or wherever 110 V. A.C. is not MICROPHONE DYNAMIC available, it was necessary to design CHANNEL NE.1 SPEAKER. N2.1 the special light weight induction -type 6 V. phonograph motor shown in Fig G. PHONO. It requires only 2.8 A. at 6 V. and is PICK UP V capable of continuous operation in a INPUT 26 WATT (COKE MIXER : COIL closed carrying -case without over -heat- .DUAL-CNANNEL TO 6V CONTROL LEADS) .DUAL-OUT PUT BATT ing. The motor is of the dual -speed BOX _CLASS'B" . -- J variety, operating at either 33 1/3 or 78 PHONO. TOR AMPLIFIER --f-i PONER SUMOPPLY A speed- selector cam switch CONNECT TO ; 1l0 V. A.C. r.p.m. DYNAMIC ' I -y FIELD .: V. PHONO. MOTOR SPEAKER. switch provides for instantaneous `6 ExCITER : change -over from one speed to the NR 2 other. A smooth, vibrationless gov- 6 V. SUPERHET. STORAGE ernor control permits slight variations RADIO TUNER.. BATTERY from standard speeds to suit special conditions. In order to insure abso- 6 V. TO6V. STORAGE CHANNEL N4.2 BATT ) lutely silent and permanent operation 8AT TERM under the most adverse handling condi- TO 10 V., A.C. tions, all of the spiral gears are cut Fig. 9 from laminated bakelite, housed in dust - A block diagram of the manner in which the accessories are interconnected. proof cases, and arranged to run completely submerged in oil. Self- lubricat- The Reproducer Field Coil Exciter o POI PP2 T1 R3 ing, oversize bearings eliminate the The standard equipment for this "in- necessity for constant attention to any terlocking portable P.A. system" in- part of the motor. A unique construc- cludes two 12 in. "P.A. Auditorium" dy- tional feature provides for sufficient namic reproducers, equipped with a Mi torque (for instantaneous start) and unique dual field coil system composed constant uniformity of speed regardless of two separate windings, one of 6000 R2/ of severe voltage variations or record ohms which requires 50 ma., and another 100 OHM drag. The complementary equipment winding of 3 ohms which requires only MICROPHONE NR.1 12 in. - of the motor includes a felt 2 A. at 6 V. for full field excitation. It RPOINTSEMOTE covered turntable, and all necessary should be remembered, however, that hardware. An automatic stop is avail- only one of these fields need be excited C POLARIZED -i / 3-WAY PLUG able and may be added to the control for the correct operation of the speaker. mechanism if desired. The phonograph BPS Both fields are designed to produce the MICROPHOI000NMNE pickup should preferably have an im- `PHONO correct number of "ampere turns" for DHOHO 6 DKxuD. : BPI T2 BP pedance of 200 ohms. maximum sensitivity. In fact, there is no difference in the performance of the Phono. Motor A.C. Power Supply speaker operating from 6 V., D.C. or I.BP2 In order to operate the 6 V. D.C. 110 V., A.C. motor of this turntable from 110 V. If only one speaker is to be used with fBP3 _ A. C. it is necessary to use the power the equipment, then the speaker field Fig. 1 becomes unit shown in Fig. H. As shown at A coil exciter shown in BP 4 in Fig. 8, it consists of a step -down merely an optional accessory, as this -duty, one speaker may obtain its field excita- Fig. 7 transformer, PT2, and two, heavy Schematic circuit of input mixer. copper -oxide rectifiers, RE1 and RE2. tion (when the system is operated from connected in parallel. The rectifiers 110 V., A.C.) from the amplifier itself, convert 13.5 V. output of PT2, into by connecting the field coil directly the ree CA 6 V. D.C. which is shunted with a 2000 across the output of the rectifier system. mf. electrolytic condenser C27 to pre- This method however, is not recom- vent the ripple, in the pulsating recti- mended for the following reasons: fied current, from being applied to the first, because it imposes too great an phono. motor. Two flush -mount recept- additional drain on the amplifier power acles, RC1 and RC2, are provided for supply; and, second, because unusual connecting the phono. motor to the precautions have to be taken in the power supply; RC2 may be used for installation and placement of the providing field excitation to a 6 V. speaker because of the dangerously D.C. dynamic reproducer providing the high potential of 300 V. developed across latter does not consume more than 2 A. (Continued. on page 307) Fig. J The dual -field speaker assembly.

Fig. G, above The 2-speed phonograph turntable.

Fig. H. center Phonograph turntable power supply. RC I RC2 SW.5 RC3 RC4 5W.6 CH.IO SPEAKER FIELD EXCITER ' PHONO. MOTOR RECTIFIED CURRENT Fig. I, right SUPPLY Speaker field coil power supply.

RADIO -CRAFT for NOVEMBER, 1933 283 BROADCAST STATIONS OF THE U. S.

A list of all the broadcast stations in the U. S. as licensed by the Federal Radio Commission and brought up to date to Aug. 15, 1933. Abbreviations: T, location of transmitter; C. P., construction permit authorized; LS, power until local sunset.

Wave- I Wave- Wave- Power Prep Call Power Freq. Call Location Power Freq length Call Location length Location length Letters (watts) (kc.) (mews (watts) Ike. . Letters (watts) kc. meters Letters meters'

'4'0 KO II Phoenix, Ariz -LS 1391 KABC San Antonio, Tex 100 1420 211.3 KGER Long Beach, Calif 5kw l360 1 ; Ikw 215.8 KALE Portland, Ore 500 1:300 230.8 KGEZ Kalispell, Mont 110 1310 2w!' KPCB Seattle, Wash 100 650 462 KARK Little Rock, Ark 250 890 337.1 KGFF Shawnee, Okla 100 1420 211 :; KPJM Prescott, Aria 100 1500 210 4 ASA (ilk ('its,, Okla IO) 1210 247.9 KGFG Oklahoma City, Okla. 100 1370 2l0 KPO San Francisco, Calif... 5kw 680 441 KBPS Portland, Or 100 1420 211.3 KGF( Corpus Christi, Tex... 100 1500 20' T -Year Belmont C.P.50kw 4BTM Paragould, Ark 100 1200 250 KGFJ Los Angeles, Calif 100 1200 2511 KPOF Denver, Colo 500 880 341 (CMG Texarkana, Ark 100 1420 211.3 KGFK Moorhead, Minn 100 1500 ''IN, KPPC Pasadena, Calif 50 1210 247.9 (CRC Endid, Okla 100 1370 219 KGFL Raton, N. Me 100 1370 2l9 KPQ 1Venatebee, {Wash.... 100kw 15001 200 tCRI Jerome, Ariz 100 1310 221) T- Roswell KPRC Houston, let Ikw 9211' 326 (DB Santa Barbara, Calif 100 1.500 200 KGFW Kearney, Nebr 100 1310 229 l'- SUgarland *Am-LS (DFN Casper, 1Vyo 500 14-10 208.3 KGFX Pierre, S. I) 200 630 476 KQV I'ittsburgh, l'a 500 1380 217.4 (OKA Pittsburgh, 1'1, 50kw 980 306 KGGC an Francisco, Calif... 100 1420 211 4 KQW San Jose, Calif 500 1011) 297 T- Saxonburg KGGF Coffeyville, Kans 500 1010 29 7 KRE Berkeley, Calif 100 1:370 211 (DLR Devils lake, N. D.... 100 1210 247.9 T -S. Coffeyville, (Okla. KREG Santa Ana, Calif 100 15011 210 (DYL Salt lake City, (tab.. Ikw 1291 232.6 KGGM Albuquerque, N. M... 250 1230 24:: 9 KRGV Harlingen, Tex 500 1226)) 238.1 (ECA Los Angeles, Calif.... Ikw 1430 209.8 KGHF Pueblo, Colo 250 1321) 227.3 KRKD Los Angeles, Calif.... 500 1120 2117.9 (EIW Burbank, Calif. KGHI Little Rock. Ark 100 1200 2511 KRLD Dallas, Te .. 10kw 1041) 288.5 (ELW Burbank, Calif 500 781) 385 KGHL Billings, Mont Ikw 950 3111 KRMD Shreveport, La 100 1310 229 CERN Bakersfield, Calif 100 1200 250 KGIR Butte, Mont 500 1360 20í ': KROW Oakland, Calif 500 930 323 (EX l'ortland, Ore 5kw 1180 254.2 KGIW Trinidad, Colo 100 1420 21 I :: 'f- Richmond Ikw-LS (FAB Lincoln, Nebr 5kw 770 390 T- Alamossa KRSC Seattle, Wash 100 1120 267.9 (FAG Lus Angeles, Calif.... Ikw 13181 2311.8 KGIX Las Vegas, Nev 100 1420 211 : KSAC Manhattan, /Cans..... 5110 580 517

(FBB Great Falls, Mont.... Ikw 1280 234.4 KGIZ (;rant City, Mo 100 1500 2161 KSCJ I Sioux City, Iowa Ikw 1330 225.6 (FBI Abilene, Kans 5kw 1050 285.7 KGKB Tyler, Tex 100 1501 2110 KSD St. Louis, Mo 500 550 545 T- Milford KGKL San Angelo, Tex...... 100 1370 21'.1 KSEt Pocatello, Idaho 2.50 900 333 (FBK Sacramento, Calif..... 100 1310 229 KGKO 1Vichita Falls. Te 250 576 :126 KSL Salt Lake City, IAA.. 50kw 1130 265.5 (FBL Everett, Wash 50 1370 219 KGKY Scottsbluff, Nebr 100 1561, 21e1 'l'-Saltair (FDM Beaumont, Texas 510 560 53(1 KGMB Honolulu, Hawaii 250 1321 _27 ., KSO I) es I(loiner, Iowa.... 100 1370 219 ;FDY Brookings, S. D Ikw 550 545 KGNF North Platte, Nebr... 500 143111 211'.1. KSOO Sioux Palls, S. I) Ikw 1110 270.3 IFEL Denver, Colo. 500 420 326 KGNO Dodge City, Kans -. 250 13411.2 ., KSTP St. Paul, Minn 25kw -1.5 1460 205.5 T- Edgewater KGO San Francisco, Calif... 71 akw 790 :h,, 11-1tadio Center :FEO St. Joseph, Mo. .?!.;,kw 680 441 T- Oakland KTAB Sas Francisco, Calif Ikw 560 536 ,FGQ Boone, Iowa 100 13111 229 KGRS Amarillo, Tex Ikw 1416 21. 'r- Oakland ,FH Wichita. Kars Ikw 13011 230.8 KGU Honolulu, Hawaii 21 zkw 7511¡ 41111 KTAR Phoenix, aria 500 621) 484 .FI Los Angeles, Calif. ... 50kw 640 469 KGVO Missoula, Mont 1(8) 1200. 2.511 KTAT Fort Worth, Tex Ikw 1224(1 241.9 T -Buena Park KGW Portland, Me ... Ikw 620 48( T- Birdville ;FIO Spokane. Wash 100 1120 287.9 T- F'aloma KTBS I Shreveport, La Ikw 1450 206.9 ., ,FIZ Fond du Lac, Wis.... 100 1420 211.3 KGY Olympia, Wash 100 12111 17 KTFI Twin Falls, Idaho.. Ikw -LS 1241) 241.9 FJB Marshalltown, Iowa... 100 1200 250 KW Loe Angeles, Calif Ikw 9119 :.... KTHS Hot Sp. Nat Pk, Ark. 10kw 1040 288.5 FJ1 Klamath Falls, ore... l00 1210 247.9 KHQ Spokane, Wash Ikw 5I 1, 500 KTM Lm Angeles, ((aid.... 510 7811 385 FJM Grand Forks, N. I)... 100 1370 210 KICA Clovis, N. M 1011 1370 21, 'r -Santa Monica...... Ikw -1.S FJR Portland, Ore ...... 500 1300 230.8 KICK farter Lake, Iowa 110 1420 211 :: KTRH Houston, Te[ 5(0 1120 267.9

FJZ Forth Worth, Tex 191 1370 219 KID Idaho Falls, Idaho 250 1320 _27 ; KTSA Sao Antonio, Tex..... Ikw 1290 232.6 FKA Greeley, Colo 500 880 341 K 10 Boise, Idaho Ikw I350 t'_ KTSM 1I l'an, Tex 100 13111 229 'I FKU Lawrence. Kan 500 1220 245 KIDW Lamar, Colo 100 I420 711 ., KTW 'rattle, Nash Ikw 12201 245.9 ., T- 'l'onganoxie KIEM Eureka, Calif 100 12111 .0 KUJ Walla Walla, Wash... 100 13711 219 KIEV Glendale, Calif 100 Bau a,,, KUMA Yuma, Aria 100 1420 211.3 FLV Rockford, III 500 1410 212 KIFH Juneau, Alaska 100 13111 KUOA Fayetteville, Ark k1 1260 238, I K FNF Shenandoah, Iowa.... 500 890 337 KIGY Lowell, Aria 110 1200 7]1, KUSD Vermilion, S. D...... 510 891 337 , FOR Lincoln, Nebr 100 1210 247 1I KIT Yakima. Wash 110 1310 -- KVI Tacoma, 11'ssh 500 5714 526 K FOX Long Beach, Calif..... Ikw 1250 240 KJ BS San Francisco, Calif 100 1076 2,1, I 'l' -Des Moines FPL Dublin, Tex 100 1310 229 KJR Seattle, Wah 5kw 4;1, .,,, KVL Seattle, Wash 100 13711 219 K FPM Greenville, Tex...... 15 1310 229 KLCN Blytheville. Ark 100 1296 7.1 a KVOA 'Tucson, Ariz 50k) 1268) 238.1 K FPW Ft. Smith. Ark 100 1210 247.9 KLO Ogden, Utah 500 1400 211 :: KVOO 'Pula, Okll 5kw 11411 263.2 ., K FPY Spokane. Wash Ikw 1340 223 0 KLPM Minot, N. 1) 251) 12411 711 KVOR Colorado Spgs.. Colla.. Ikw 1270 236.2 K FPO Anchorage, Alaska.... 254) 600 510 KLRA Little Rock, Ark Ikw 13'.19 717, KVOS Bellingham. Wash..... 1110 12101 250 FRC San Francisco, Calif Ikw 610 4112 KLS Oakland, Calif 250 14411 _ ., KWCR ('edar Rapids, Iowa... 100 1420 211.3 K FRU Columbia, Mo 500 630 476 KLUF Galveston, Tex 100 1:170 21, KWEA Shreveport, 1 s 100 12111 247.9 K FSD San Diego, Calif Ikw 600 5110) KLX Oakland, Calif Ikw 880 341 KWFV Hilo, Hawaii 100 1210 247.9 K FSG Los Angeles, Calif..... 500 11211 267 9 KLZI Denver, Colo Ikw sial) 536 KWG Stockton, Cal 100 1200 250 K FUO Clayton, Mo 5181 550 54:1 K M A Shenandoah, Iowa.... 700 9:01' :1'21 KWJJ Portland, Ore . 7081 1060 283 FVD Los Angeles, Calif 250 1006 31)11 KMAC San Antonio, Tex..... 110 I3711 I'1 KWK 1St. Louis, Mo Ikw 134) 222.2 l 41,, K FVS Cape Girardeau, Mo.. 100 1210 247 '.1 KMBC Kansas City, Mo Ikw ll T- Kirkwood K FWB Hollywood, Calif Ikw 950 316 7'- Independence KWKC Kan.,. City, Mo 100 1370 219

FWF St. Louis, Mo MO 1200 250 KM ED Medford, Ore 100 1310 = - KWKH Shreveport, I 10kw 8511 :153 K FW1 San Francisco, Calif... 500 930 32:3 KMJ Fresno, Calif 500 580 517 T- Kennonwood K FXD Nampa, Idaho...... 100 1200 2:10 KMLB Monroe, La 100 1200 2.M KW LC I)eeorab, Iowa 100 12711 236.2 K FXF Denver, Colo. 500 9'20 :126 KMMJ (lay Center, Neb..... Ikw 740 4(15 KWSC Pullman, Wash Ikw 1220 24.5.1) K FXJ Grand Junction, Colo. 100 1200 2511 KMO Tacoma, Wash 250 1330 225.6 KWWG Brownsville, Tex 500 12601 238.1 FXM San Bernardino, Calif. 100 1210 247 9 KMOX St. Louis, Mo 50kw 1090 275.2 KXA Seattle, Wash 250 760 345 K FXR Oklahoma City, Okla. 100 1310 224 KMPC Beverly Hills, Calif.... 500 710 423 KXL Portland, Ore 100 1420 211.3 K FYO Lubbock, Tex 100 1310 29 KMTR lus Angeles, Calif .... 500 570 526 KXO 11 Centro, Calif 100 1500 200 K FYR Bismarck, N. D Ikw 550 51.5 KNOW Austin, Tex 100 1500 21H) KXRO .lb Been, Wash 100 1310 229 2511 K GA Spokane, Wash 5kw 1470 2114 1 KNX Loe Angeles. Calif..... 25kw 1050 285 7 KX YZ Houston, Tex 1440 208.3 K GAR Tucson, Ariz 100 1370 211 KOA Denver, Colo...... 121 ¡kw 830 311 KYA San Francisco, Calif... Ikw 12:311 243.9 K GB San Diego, Calif Ikw 1330 225 6 ROC Corvallis, Ore ]kw 550 545 KYW Chicago, Ill 10kw 10211 294.1 GBU Ketehikan, Alaska.... 500 900 33:: KOB Albuquerque, N. M... 10kw 1180 254 2 T- Bloomingdale Twsp. GBX Springfield, Mo. 100 1310 224 KOCW Chickasha, Okla 250) 1400 214 :: WAAB Baton, Mass 500 1410 212.8 K GBZ York, Nebr 500 930 323 KOH Reno, Nev 500 1380 217 4 T- Quincy GCA Decorah, Iowa 100 1270 2 KOIL Councils Bluffs, Iowa. Ikw 1210 23.11 I WAAF Chicago, III 500 920 326 K GCR Watertown, S. D 100 1210 247.9 KOIN Portland, Ore. Ikw 9411 319 WAAM Newark, N. J Ikw 1250 240 940 319 K ctu Mandan, N. D 250 1240 241 '.I KOL Seattle, Wash Ikw 1270 2:36 7 WAAT .leray City, N. J 500 K GCX Wolf Point, Mont .... 100 1310 229 KOMA Oklahoma City, Okla. 5kw 1480 2112.7 WAAW ( Imaha, Neb. 500 6601 45.5 K GDE Fergus Falls, Minn... 100 1200 2511 KOMO Seattle, Wash 1kw 920 39; W ABC- New York, N. Y 50kw 860 349 GDM Stockton, Calif 250 1100 272 KONO dan Antonio, Tex..... 100 1370 2111 WBOQ 'I'- Wayne, N. J. K GDY Huron, S. I) 250 1340 ?23.!1 KOOS Marshfield, Ore 100 1370 214 WABI Bangor, Maine 100 12181 250 K GEN Yuma, Colo 100 1200 250 KORE Eugene, Ore 100 1420 211 1( WACO Waco, Tex Ikw 1240 241.9

284 RADIO -CRAFT for NOVEMBER, 1933 Wave- Wave- Power Frey. length Call Location Power Freq. length Call Location Power Freq. length Call Location (kC.) i Letters (watts) Letters (watts) (ke.) (meters) Letters (watts) (kc.) (meters) )meters)

Gretna 250 1010 297 WADC Tallmadge, Ohio Ikw 1320 2 27 . '6 T- WHN New York, N. Y 250 1450 2009 WAGM Presque Isle, Maine... 100 1420 211 :3 WDZ Tuscola, III 100 1070 280.4 WHOM Jersey City, N. J..... 209.8 WAIU Columbus, Ohio 50) 640 469 WEAF New York, N. Y 50kw 660 455 WISP Harrisburg, Pa 500 1430 WALR Zanesville, Ohio 101 1210 247.9 '1'- Bellmore T- Lemoyne Ikw-LS 1310 229 WAMC Anniston, Ala 100 1420 211.3 WEAN l'rovidence, It. I 2.50 780 :3 &5 WIAS Ottumwa, Iowa 100 WAML Laurel, Misa 100 1:310 229 WEAO Columbus, Ohio 750 570 526 WIBA \sadhon, Wis. 500 1280 234.4 323 WAPI Birmingham, Ala 5kw 114 J 263.2 WEBC Superior, 'Wis Ikw 1290 232.0 WIBG Glenside, l'u 25 930 WARD Long Island Cy, N. Y. 500 1400 214.3 WEBQ Harrisburg, Ill 100 1210 247.9 T- Elkins Park WASH Grand Rapids, Mich.. 500 1270 236.2 WEBR Buffalo, N. Y 100 1310 229 WIBM Jackson, Mich 100 1370 Y19 247.9 WAWZ Zarephath, N. J 250 1350 222.2 WEOC Chicago, Ill 101 1210 247.9 WIBU l'oynette, Wis 100 1210 517 WAZL Haselton, l'a 100 1420 211.3 WEED Greenville, N. C 100 1420 211.3 WIBW Topeka, Kars Ikw 580 250 WBAA W. Lafayette. 500 14(0 214 3 WEEI Boston, Mass Ikw 590 509 WIBX Utica, N. Y 100 1201 Ind.... 50) WEAK Harrisburg, Pa...... Ikw 1430 209. T- Weymouth WICC Bridgeport, Conn 250 600 WBAL Baltimore, Md 10kw 1060 2..3 WEEU Reading, l'a k1 830 361 T- Bridgeport 500-LS 250 T- Pikeville, Md. WEHC Charlottesville, Va 500 1350 222.2 WIL St. Louis. Mo 100 1200 337 WBAP Fort Worth, Tex 50kw 800 375 WEHS Cicero, Ill 100 1420 211.3 WILL Urbana, Ill 250 890 T.Gmpevine WELL Battle Creek, Mich.... 50 1420 211.3 WI LM Wilmington, Del 100 1420 211.3 WBAX Wilkes -Barre. l'a 100 1210 247.9 WENC Americus, Ga 100 1420 211.3 T -Edge Moor 536 T- )'laina Twp. WENR Chicago, Ill 50kw 870 34.5 WIND Gary. Ind Ikw 560 254.2 WBBL Richmond, Va. loo 1210 247.9 1'- Downers Grove WINS New York, N. Y 501 1180 WBBM Chicago, Ill 25kw 770 390 WESG Elmira, N. Y Ikw 1040 288.5 T- Carlstadt, N. J. 'kw 230.8 T- Glenview T- Ithaca WI OD- Miami, Ila 1300 WBBR Brooklyn, N. Y Ikw 1300 230.8 WEVD New York, N. Y 500 1310 230.8 WMBF 7' -Miami Bench 492 T- Rosxiile 'l'- Brooklyn WIP Philadelphia. l'a 500 610 297 WBBX New Orleans, La 110 1200 250 WEW St. Louis, Mo Ikw 760 395 W15 Columbia, S. C 500 1010 267.9 WBBZ Ponca City, Okla 100 1200 250 WE XL Royal oak, Mich..... :) 1310 229 WISH Milwaukee, Pi 250 1120 229 WBCM Bay City, Jlich 500 1410 212.8 WFAA Dallas, Te 50kw 800 375 WJAC Johnstown, l'a I00 1310 283 T- Hampton Twp. T- Grapevine WJAG Norfolk, Nebr. Ikw 1060 337 WBEN Buffalo, N. Y 900 333 WFAB New York, N. Y Ikw 1300 230.5 WJAR Providence, It. I. 250 890 k1 232.0 'l'- Martinsville T- Carlstadt, N. J. WJAS Pittsburgh, I' Ikw 1290 WBEO Marquette, Mich. .... 110 1310 229 WFAM South Bend, Mud...... 100 1200 250 T -No. Fayette, Twp, 2!.kw -La 333 WBHS Huntsville, Ala 100 1200 250 WFAS \\Lire )'lairs, N. Y.... 100 1211) 247.9 WJAX Jacksonville, Fla...... Ikw 900 492 WBIG Greensboro, N. C. 500 1440 208.3 WFBC 1reenville, S. C 100 1200 250 WJAY Cleveland, Ohio 510 610 WEBE rineineati, Ohio 100 1200 250 WJBC La Salle, III 100 1200 250 247.9 WBNX New York, N. Y 250 1350 2!2.2 WFBG Altoona, l', 100 1310 229 W161 11n1 Bank, N..1 100 1210 50 219 WBOQ (See WABC- \VBOQr WFBL Syracose, N. ) Ikw 1360 220.6 WJBK Detroit, Mich 1370 WBOW Terre Haute, Ind..... 100 1310 229 T- l'ollanrer 21 kw -I.S T-Highland )'ark WBRC Birmingham, Al..... 500 930 323 WFBM Indianapolis, Ind.,... Ikw 123(1 243.9 WJBL Decatur, Ill 100 1200 250 WBRE Wilkes -Barre, l'a 101 1311) 2 WFBR Baltimore, Md 500 1270 236.2 WJBO New Orleans, La 100 1420 211.3 WBSO Needham, Miss. 501 9!11 326 WFDF I lint, Mich 100 1311) 229 C.P. Baton Rouge 12(X) 250 WET Charlotte, N. C 25kw 1080 _77 WFDV Rome, Ga 100 1500 210 WJBW New Orleans. La 100 WBTM Danfille, Va 100 1370 21!r \ WFEA >lauchester, N. 11 500 1430 209.8 WJBY Gadsden, .11n 100 1210 247.9 WBZ Boston, Mass 25kw 990 303 WFI lhiladelphia, l'a 500 511) 536 WJOX Jackson. )lise Ikw 1270 236.2 T-Millis Twp. WFIW Hopkinsville, Ky Ikw 940 319 WJEJ Hagerstown. Md 100 1210 247.9 900 WBZA Boston, Maas Ikw 91X) 303 WFLA- Clearwater, Fla 250 620 48: WJEM Tupelo, Miss 501 303 T-East Springfield WSUN WJJD \fooseheart, III 120kw 1130 265.5 WCAC Storrs, Conn. 2:0 601 500 WFQD Anchorage, Alaska.... 600 500 WJMS Ironwood. Mich 101 1420 211.3 Mich 750 WCAD Canton, N. Y 500 1220 245.9 WGAL Lancaster, l'a 100 1310 229 WJR petrol:, IOkw 400 T-Sylvan lake Village WCAE Pittsburgh, Pa...... k1 1220 245.9 WGAR Cleveland, Ohio :011 1451) 2096.9 WCAH Columbus, Ohio 50I 1430 201.8 T- Cuyahoga Heights Ikw -1.8 WJSV Alexandria. Va...... ' 10kw 1460 205.5 WCAL Northfield, Minn Ikw 1250 240 WGBB Freeport, N. Y 100 1210 217.9 WJTL :)glethorpe Univ., Ca 100 1370 219 WCAM Camden, N. J :00 1280 234.4 WCBF Evansville, Ind. 500 6311 476 T- Atlanta WCAO Baltimore, Md 250 600 500 WGBI Scranton, l'a 250 880 :341 WJW Akron, Ohio 100 1210 247.9 Mississippi 101 1211E 247.9 WIZ New York, N. Y 50kw 760 395 wCA Asbury Park, N. J.... 500 1 280 234.4 WGCM City, Miss. T-Whitesville WGCP Newark, N. J 250 I250 240 9 -Bound Brook, N. J. 51111 San Juan, P. H Ikw 1240 241.9 WCAT Rapid City, S. D..... 100 1200 250 WGES Chicago, Ill 131,0 220.6 WKAQ WCAU lhiadelphia, Pa 50kw 1170 256.4 WGH Newport News, Va.... 1011 1310 229 WEAR E. Lansing, Mich Ikw 1040 288.5 T- Newton, Square Co. WGL Ft. Wayne, Ind 100 1370 219 WKBB Joliet, Iii 100 1310 229 WCAX Burlington, Vt 100 1200 250 WGLC Hudson Falls, N. Y... 100 1370 219 C.P. E. Dubuque C.l'. 1500 WCAZ Carthage, III 50 1070 280.4 WGN Chicago, Ill 25kw 720 417 WKBC Birmingham, Ala..... 100 1310 229 w0 BA Allentown, l'a 250 1440 208.3 T-Elgin WKBF Indianapolis, Ind..... 500 1400 214.3 Indianapolis WC BD Zion, Ill 5kw 1080 277.8 WGNY Chester Twsp., N. Y -. 50 1210 247.9 T-Nr. La ('ronce, Wù 1kw 1380 217.4 WC BM Baltimore, Md 100 1370 219 WGR Buffalo, N. Y Ikw 550 545 WKBH Cicero, 111 WO 1420 211.3 WC BS Springfield, Ill- 100 1210 247.9 T- Amherst Twp. WKBI Ohio 500 WCCO Minneapolis, Minn.... 50kw 810 370 WGST Atlanta, Ga. 250 890 337 WKBN Youngstown, 570 520 T -Anoka WGY Schenectady, N. Y.... 50kw 790 380 WKRV Connersville, Ind 100 1500 200 WCDA New York, N. Y 250 1350 222.2 T -South Schenectady WKBW Buffalo, N. Y 5kw 1460 202.7 T- Cliffside, N. J. WHA \fadiwn, Via Ikw 910 319 T- Amherst Tap. Ludington, Mich 100 1500 200 WCFL Chicago, Ill 1, ..)kw 970 3119 WHAD Milwaukee, Wù 250 1120 267.9 WKBZ WHAM ItocheMer, N. Y 5kw 1150 260.9 WEEU la Grange, Ga 100 1500 200 WCKY Covington, Ky 5kw 1410 201.3 T- Victor Tap. C.P. 25kw WKFI Greenville, Misa. 100 1210 247.9 T- Crescent Springs WHAS Louisville, Ky. 25kw 820 366 WKJC Lancaster, 1'a 100 1200 200 WKOK 100 1210 WCLO Janesville, Wi 100 1200 250 T- .Ieffersontown Lewisburg, l'a. 247.9 RC Ohio 500 WC LS Joliet, Ill 100 1310 229 WHAT Philadelphia, l'a 100 1310 229 WK Cincinnati, 550 545 Okla. Ikw 900 WCOA Pensacola, Fla 501 1340 '2'23.9 WHAZ Troy, N. Y 500 1300 230.8 Wit Oklahoma City, 333 wEoG Meridian, 0ùs 500 880 341 WHB Kansas City, Mo.. ... 500 860 349 WKZO Kalamazoo, Mich Ikw 590 509 Tenn 5kw 1470 WOOD Harrisburg. l'a 100 1200 250 T -North Kansan City WLAC Nashville, 204.1 WCRW Chicago, BI 100 1210 247.9 WHBC Canton, Ohio. 10 1200 250 WLAP Louisville, Ky 100 1200 250 Ikw 1250 240 WCSO Charleston, S. C 500 1360 220.6 WHBD Mt. Orab, Ohio 100 1370 219 WLB Minneapolis, Minn.... T -St. Paul wCSH Portland, Me Ikw 040 319 WHEF Rock Island, Ill 100 1 213 247.9 WLBC Muncie, Ind 50 1310 229 T- Scarboro 2, íkw -1...S WHBL Sheboygan, Wi. 500 1410 212.8 WLRF Kansas City, 100 1420 211.3 wDAE Tampa, Fla 1kw 1220 245.9 WHBQ \Memphis, Tenn 11X1 1370 219 Kans.... 9 Stevens Wis... 2!2kw 900 333 WOAF Kansas City, Mo..... Ikw 610 492 WHBU Anderson, Ind 100 1210 247 WLBL l'oint, WOAG Amarillo, Tex Ikw 1410 212.8 WHBY Green Bay, Wi 100 1200 250 T-Nr. Ellis wLeW Erie, l'a 500 1260 238.1 WDAH F:1 Paco, Tex 100 1310 229 T -)Vest De Pere Ikw -I S WDAS Philadelphia, Pa 100 1310 219 WHOF Calumet, Mich 100 1370 219 T- ummit Township Me 500 620 WDAY Fargo, N. D Ikw 940 319 WHDH Becton, Mass k1 830 361 WLBZ Bangor, 484 50 T -West Fargo 'F- Saugus W LCI Ithaca, N. Y 1210 247.9 Erie, l'a 100 1420 211.3 WDBJ Roanoke, Va 2:0 930 323 WHDL Tupper lake, N. Y. 100 1420 211.3 WLEU Lexington, Mass 100 1370 219 WDBO Orlando, Fla 250 580 517 WHEB 1'orLcmouth, N. 11..... 250 740 405 WLEY WDEL Wilmington, Del 250 1120 267.9 T- Newington WLlT Philadelphia, Pa 500 560 536 Macs 100 WDEV Waterbury, Vt 500 550 545 WHEC Rochester, N. Y 500 1440 208.3 WLOE Boston, 1500 200 250-LS WDGY Minneapolis, Minn.... Ikw 1180 254.22 WHEF Kosciusko, Mis 110 1500 200 T- Chelsea WLS WOOD Chattanooga. Tenn... Ikw 1280 234.4 WHET Troy, Ala 100 1210 247.9 Chicago, Ill 50kw 870 345 Downers Grove T- Brainerd 21!kw -LS WHFC Cicero, 111 100 1420 211.3 T- Va 100 219 WDRC Hartford, Conn 500 1330 225 6 WHIS Bluefield, W. Va. 250 1410 212.8 WLVA Lynchburg, 1370 T-Bloomfield WHK Cleveland, Ohio Ikw 1390 215.8 WLW Cincinnati, Ohio 50kw 700 429 WDSU New (cleans. La Ikw 1250 21 T.Seven Hills 2!¢kw -LS T-Mason

RADIO -CRAFT for NOVEMBER, 1933 285 Wave- length Wave- Call Power Freq Location length Call Location Power Frc. length Call Location Power Fr e4 Letters length (watts) (kc.) (meters)meters) Letters (wafts) (kc.) (meters) Letters (watts) (kc.) (meters) WLWL New York, N. Y 5kw 1100 272.7 WOP1 Bristol, Tenn 100 1500 200 WSAI Cincinnati, Ohio 500 1330 225 .6 T- Kearny, N. J. WOQ Kansas City, Mo..... Ikw 1300 230.8 T -Mason Ikw -LS WMAC (See WSYR-WMAC) WOR Newark, N. J 5kw 710 423 WSAJ Grove City, Pa. 100 1310 229 Washington, WMAL D. C 250 630 476 T- Kearny C.P. 50kw WSAN Allentown, l'a 250 1440 208.3 WMAQ Chicago, Ill 5kw 670 448 WORC Worcester, Mass. 100 1200 250 WSAR Fall River, Mac 250 1450 20i.9 T- Addison T- Auburn WSAZ Huntington, W. Va 500 580 517 WMAS Springfield, Mass..... 100 1420 211.3 WORK York, NI Ikw 100(1 300 WSB Atlanta, Gx 5kw 740 405 WMAZ Mason, Ga 500 1180 254.2 T -W. Manchester WSBC Chicago, Ill 100 247.9 wmeC 1210 Detroit, Mich 100 1420 211.3 WOS Jefferson City, Mo.... 500 634) 476 WSBT South Bend, Ind...... 500 1230 243.9 WMBD Peoria, Ill .. 500 1440 21)8.3 WOY/i New York, N. Y Ikw 1130 265.5 WSEN Columbus, Ohio 100 1210 247.9 T- Peoria Heights Ikw -LS T-Secaucus, N. J. WSFA Montgomery, Ala 500 1410 212.8 WMBF (See WIOD -WMBF) WOW Omaha, Nebr Ikw 590 509 WS'X Springfield. Tenn 100 1210 247.9 WMBG Richmond, V 100 1210 247.9 Wow() Ft. Wayne, Ind 10kw 116(1 258.6 WSJS Winston-Salem, N. C.. 100 229 WMBH 1310 Joplin, Mo. 100 1420 211.3 WPAD Paducah, Kv 100 142(1 211.3 WSM Nashville, Tenn 50kw 650 462 WMB' Chicago, Ill...... 5kw 1080 277.8 WPAP (See WQAO -WPAP) T- Franklin Addison T- WSMB New Orleans, la 500 1320 227.3 WMBD .Auburn, N. Y...... 100 131(1 229 WPCH New York, N. Y 500 570 526 WSMK Dayton, Ohio 200 1381 217.4 WMBQ Brooklyn, N. Y 100 15191 200 T- Flushing WSOC Gastonia, N. C 100 1210 247.9 WMBR Tampa, Fla 100 1370 219 WPEN Philadelphia, Pa 100 1500 200 WSPA Spartanburg, S. C 100 1420 211.3 WMC Memphis, Tenn 500 780 385 WPFB Hattiesburg, Miss.... 100 1370 219 WSPD Toledo, Ohio Ikw 1340 223.9 T- Bartlett Ikw -LS WPG Atlantic City, N. J.... 5kw (LIN) 272.7 WSUI Iowa City, Iowa 500 880 341 WMCA New York, N. Y 500 57,) 526 WPHR Petersburg, Va 100 1200 250 WSUN (See WFLA -WSUN) T- Flushing T- Ettrick wsys Buffalo, N. Y 50 1370 219 WMED Florence, Ala 100 1420 211.3 WPRO Providence, R. I 100 1210 247.9 WSYB Vt WAIL Rutland, 100 1500 200 Brooklyn, N. Y 100 1500 200 T- Providence wSYR- Syracuse, N. Y 250 570 526 WMMN Fairmont, W. Va..... 250 890 337 WPTF Raleigh, N. C. Ikw 1'81) 441 WMAC WMPC Lapeer, Mich...... 100 1500 200 w4AM Miami, Fla 1kw 513) 536 WTAD Quincy, Ill. 500 1440 2(18.3 WMSG New York, N. Y 250 1350 222 2 WQAN Scranton, l'a 250 8811 341 WTAG Worcester, Mass 500-IS 580 517 WMT %urate. loo, Iowa 500 600 500 WQAO- New York, N. Y 250 1010 297 WTAM Cleveland, Ohio 50kw 1070 280.4 WNAC Boston, Mass Ikw 1230 243.9 WPAP T- Uliffside, N. J. T -Brecksville Village T- Quincy WQBC Vicksburg. Miss 500 1360 220.6 WTAQ Faun Claire, SWis Ikw 1330 225.6 WNAD Norman, Okla 500 1010 297 ' w4DM St. Albans, Vt. 100 1370 219 T -Twp. of Washington WNAX Yankton, S. D 212kw-LS 570 526 WODX Thomasville, Ga 100 1210 247.9 WTAR Norfolk, Va. 500 780 385 WNBF Binghamton, N. Y.... 100 1.500 200 Ì WRAK Williamsport, l'a 100 137(1 219 WTAW College Station, Tex.. 500 1120 267.9 WNBH New Bedford, blahs... 100 1310 229 WRAM Wilmington, N. C 100 1370 219 WTAX Springfield, Ill. 100 1210 247.9 T- Fairhaven 250-LS WRAW heading, l'a 100 131(1 229 WTBO Cumberland, Md 100 1420 211.3 WNBO Silverhaven, ' l'a 100 1200 250 WRAX Philadelphia. Pa 250 ((1LNI 294.1 WTEL Philadelphia, l'a 100 1310 229 WNBR Memphis, Tenn 500 1430 2011.8 WRBL Columbus, Ga. 100 1200 250 WTFI Athens, Ga. 500 1450 216.9 WNB Carbondale, l'a IO 12191 251 WRBX Roanoke, Va 250 111(1 212.8 WT IC Hartford, Conn 50kw 1060 28:3 Springfield, WNBX Vt 250 12611 _.,. I WRC {Washington, U. C..... 500 950 316 T -Avon WNBZ Saranac 2t. Lake, N. Y.. 50 12'm a WRDO Augusta, Me 100 1370 219 WTJS Jackson, Tenn 100 1310 229 WNOX 569 Knoxville. Tenn 2kw -LS 5.16 WROW .Augusta, Ga 100 tsoo 2710 WTMJ Milwaukee, Wig Ikw 620 484 WNYC New York. N. Y 500 810 370 WREC Memphis, Tenn 500 600 500 T- Waukesha 2l2kw -LS

WOAI San 0 Antonio, Tex..... 50kw 11( 252.1 1'- Whitehaven lkw -I.S WTNJ Trenton, N I 500 1280 234,4 T -Selma WREN, Lawrence, Kans Ikw 1220 245.9 WTOC Savannah, Ga 500 1260 238.1 WOBU Charleston, W. Va.... 250 581 517 T- Tonganoxie I WTRC Elkhart, Ind 100-LS 1310 221 woc Mitchellville, Iowa.... 501)w 1000 300 WRHM Minneapolis, Minn.... Ikw 1250 240 WWAE Hammond, Ind. 100 1200 250 T- Fridley WWJ Detroit, Mich Ikw 920 326 WOCL Jamestown, $. Y..... 50 12111 217 9 WRJN Racine, Wis. 100 1370 219 WW1. New Orleans, La 10kw 850 353 WODA Paterson, N. J Ikw 12511 240 WRNY New York, N. Y 250 1010 297 T- Kenner WOOX .Ala Mobile, 500 14101 212 8 T- Coytesville, N. J. wwNC Asheville, N. C Ikw 570 526 T- Springhill) WROL Knoxvile, Tenn...... 100 1310 229 WWRL Woodside, N. J 100 1500 200 WOI Ames, Iowa 5kw 640 469 WRR Dallas, Tex 500 1280 234.4 WWSW Pittsburgh, Pa 100 1500 200 WOKO Albany, N. Y 500 1440 208.3 WRUF Gainesville, Fla 5kw 830 361 T- Wilkinshurg 250-LS WOL Washington, D.C..... 100 13111 229 WRVA Richmond, Va 5kw 1110 270.3 WWVA Wheeling, W. Va ,5kw 1160 258.6 Wie 217 ', womT Manitowoc, 100 I219 T- Mechanicsville WXYZ Detroit, Mich Ikw 1240 241.9

WOOD Grand Rapids. Mich. 510) 1 ' 2 7 6 2 1 , _ POLICE STATIONS (Alphabetically by Call Letters)

Call Location Freq. Call Location Frey Call Location Freq Call Location Freq. Letters Ike.) Letters kc. Letters kc. Letters Ike.) I KGHO Des Moines, Iowa 1534 KGZI Wichita Falls, Tex 171: WPDH Richmond, Ind 2142 WPES Saginaw, Mich. 2442 KGJX Pasadena, Calif 1712 KGZJ Phoenix, .tria 2430 WPDI Columbus, Ohio 21311 WPET Lexington, Mass 1712 KGOZ Cedar Rapids, Iowa 247(1 KGZL Shreveport, La .. 17i: WPDJ Passaic, N. J 24111 WPEW Northampton, Mass. 1574 KGPA Seattle, Wash 2414 KGZM AEI Paso, Tex 711 I WPDK , Milwaukee, Wie 2450 WPEY Chattanooga, Tenn 2470 KGPB Minneapolis, Minn 2416 KGZN Tacoma, Wash 2414 WPDL Lansing, Mich 2442 WPEZ i ramingbam, Mass 1574 KGPC St. Louis, Mo 1712 KGZO Santa Barbara, Calif 2414 WPDM Dayton, Ohio 2430 WPFA Newton, Mass 1712 KGPD San Francisco, 2470 Calif KGZP Coffeyville, Kan, 24511 WPDN Auburn, N. Y 245F WPFC NI uskegon, Mich 2442 KGPE Kansas City, Mo 2422 KGZQ Waco, Tex 1712 WPDO Akron, Ohio 245. WPFD Highland Park, Ill 2430 KGPG Vallejo, Calif 2422 Salem, KGZR (re 2442 WPDP Philadelphia, l'a 247(1 WPFE Reading, Pa 2442 KGPH Oklahoma City, Okla 2450 KGZS McAlester_ Okla 2450 WPDR Rochester, N. Y 245E WPFF Toms River, N J 2430 KGPI Neb Omaha, 2470 SIDA Seattle, Wash 1574 WPDS St. Paul, Minn 2416 WPFG Jacksonville, Fla 2442 KGPJ Beaumont, Tex KSW 1712 Berkeley, Calif 2422 WPDT Kokomo, Ind 2470 WPFU Baltimore, Md. 2414 KGPK Sioux City, la 2470 KVP Dallas, Tex 1712 WPDU Pittsburgh, l'a 1712 WPFI Columbus, Ga. 2414 KGPL Los Angeles, Calif 1712 WBA Harrisburg, Pa .. 257 WPDV I Charlotte, N. C 2458 WPFJ Hammond, Ind 1712 KGPM San Jose, 2470 Calif WBR Butler, l'a 257 WPDW Washington, I). C 2425 WPFK Hackensack, N. J 2430 KGPN Davenport, lows 2470 WCK Belle Island, Mich 2414 WPDX Detroit, Mich 2414 WPFL Gary, Ind 2470 KGPO Tulsa, Okla 2450 WDX Wyoming, l'a 257 WPDY Atlanta, Ga 2414 WPFM Birmingham, Ala...... 2414 KGPP Portland, (re 2442 WEY Boston, Mass WPDZ Fort Wayne, Ind 24711 WPFN Fairhaven, Mass 1712 KGPQ Honolulu, 'I'. H . 2450 WKDT, Detroit, Mich .. 1371 WPEA Syracuse, N. Y 2458 WPFO Knoxville, Tenn 2470 KGPR Fort Worth, Tex 1712 WKDU Cincinnati, Ohio . 1712 WPEB ((mnd Rapids, Mich...... 2442 WPFP Clarksburg, W. Va 2414 KGPS Bakersfield, 2414 Calif WMB heading, l'a 257 WPEC Memphis, Tenn 2470 WPFQ Swathmore, l'a 2470 KGPW Salt Lake City, Utah 2470 WMOZ Indianapolis, Ind 2442 WPED Arlington, Mass 1712 WPFR Johnson City, Tenn. 2470 KGPX Denver, Colo 2442 WMJ Buffalo, N. Y 2422 WPEE Brooklyn, N. Y . 2450 WPFS Asheville, N. C 2458 KGPY Shreveport, la. 1574 WMO Highland Park, Mich . 2414 WPEF New York, N. Y 2450 WPFT Lakeland, Fla 2442 KGPZ Wichita, Kane 245(1 WMP, Framingham, Mass 1574 WPEG New York, N. Y 2451 WPFU l'ortland, Me 2422 KGZA Fresno, 2414 Calif WNDA Miami, Fla 2442 WPEN Somerville, Mass 1712 WPFV Pawtucket, R. I 2470 KGZB Houston, Tex 1717 WPDA Tulare, Calif 2414 WPEI E. Providence, It. I 1712 WPFW Mt. Pleasant, N. Y 2414 KGZC Topeka, Kane 244! WPDB Chicago, Ill 1712 WPEJ Brookline, Mass 1712 WPFX l'alm:Beach, Fla 2442 KGZD San Diego, Calif 2430 WPDC Chicago, Ill 1712 WPEK New Orleans, la 242! WPFY Yonkers, N. Y 2414 KGZE San Antonio, Tex 2506 WPDD Chicago, Ill 1712 WPEL W. Bridgewater, Mae. 1574 WROH Cleveland, Ohio 2458 KGZF Chanute, Kane 24511 WPDE Louisville, Ky 244:- WPEM Woonsocket, R. I 2470 WRDQ Toledo, Ohio 2470 KGZG Des Moines, la 2470 WPDF Flint, Mich 244'_' WPEP Arlington, Mass 1712 WROR Grosse Point Village, Mich.. 2414 KGZH Falls, Ore Youngstown, Klamath 2442 WPDG Ohio 245, WPEA Baton Rouge. la. 1571 WRDS Fwt Lansing, Mich. 1574

286 RADIO -CRAFT for NOVEMBER, 1933 THE MAINTENANCE OF CARBON MICROPHONES

Even the best of carbon microphones has a very definite and limited life, especially when subjected to the rough handling usually encountered in broadcasting and sound work. Mr. Kahn describes the best rejuvenating methods.

ALBERT R. KAHN

I1 WAS not so very long ago that microphones were conventional method of constructon. The buttons are held treated, quite respectfully and were viewed with not a in place by a front and back bridge, A and B, both of which little mystery even by those who used them. However, are removed by taking out the screws holding them to the with the increasing use and demand for public address frame. The old carbon is then discarded. Taking extreme equipment the microphone has come to be considered as an care not to injure the felt carbon -retaining rings, C and D, ordinary piece of equipment, and handled as such, and the clean the buttons well with carbon tetrachloride, ether or requirements of microphone service have become increas- chemically -pure alcohol. Use cotton or a soft cloth for this ingly severe. operation to insure freedom from scratching the surfaces. Sound trucks, with their jar and vibration cause premature In the event that the felts are injured, new ones may be cut aging. Wobbly speakers' platforms do their part in further- from a cheap grade of cotton batting if care is taken to get ing the microphone repair industry. And the old, iron -clad the same thickness as the original. rule, "never move a microphone with the current applied" is The diaphragm, E, next gets attention, and is cleaned in difficult to impress upon public speakers and performers. the same manner as the buttons. Care must be taken not to Fortunately, for the sound engineer, the life of a micro- rub through the gold coating in some makes of diaphragms. phone can be renewed by the replacement of grains, in most If the buttons are burned or have lost their polish beyond instances. If the instrument has had long periods of high use, it is good policy to replace them with new ones. When current or been subjected to extremely hard usage, the re- doing this, maintain the original distance between the button placement of buttons and diaphragm is necessary. face and the diaphragm, as this has a very definite bearing In use, the button current is applied to a double -button on the sensitivity and quality. The retaining felt should carbon microphone through a center -tapped microphone in- have no real pressure on the diaphragm but should just touch put transformer primary. The current flows from the but- it firmly enough to prevent the grains from dropping out. tons through the grains to the diaphragm which is at ground If an examination discloses that the diaphragm is burned, potential. While operating, the grains are moving con- dented or otherwise in bad condition, this too, should be stantly, being actuated by the diaphragm or by the shaking replaced. As shown in Fig. 1, the outer edge of the dia- of the microphone, itself. This movement of the carbon phragm is clamped by the frame. Stretching -ring G exerts grains a microscopic which causes arc will, in time, burn the a it and holds it in a stretched position. The polish pressure on from the surface. The greater the movement and degree of stretch depends upon the diaphragm material used. the higher the current, the faster the wear. Unless the mi- in some of the lower- priced instruments crophone Steel, which is used has been used at high values of button current, the needs little as the weight of this material helps to damp the diaphragm and buttons will not burn in this manner but will movement. Duralumin needs more stretching because of gather a film of corrosion. All of this tends to reduce the the lightness and is in the order of three -quarters of its sensitivity and output and increases the noise level. It is limit. In other words, a diaphragm can be over- sometimes difficult elastic to get sufficient current through the micro- and cause a reduction of the sensitivity, especially phone and to get the buttons to "balance." stretched on the lower register. For one not having access to equip- The method of replacing the grains depends, somewhat, upon the design of the instrument. Figure 1 illustrates the ( Continued on page 305)

CARBON GRANULES

GLASS PLATE FELT RETAINING CARBON RING GRANULES

BUTTON CUP FELT RCTAINING RING Fig. 1

Fig. 2 A cross- section of a two -button microphone, detailing the important parts. Note that the The method of measuring carbon grains. diaphragm, E, is suspended between carbon cups H and I.

RADIO -CRAFT for NOVEMBER, 1933 287 THE ANALYSIS OF RADIO RECEIVER SYMPTOMS OPERATING NOTES

R. L. DOUGHERTY

balanced. This is really important. ELIMINATING Never under any consideration take a AUTO -RADIO NOISES PRIZE WINNING new set out of a carton and slap it into a car. Go over the set thoroughly. If ARTICLE if it is a superheterodyne of the latest Wl'I.II t he lower pricing of with everything in one case, this .,atonobile radio sets, and To Mr. R. L. Dougherty of make Neptune, N. J., goes the honor simply means connecting a suitable the fact that conditions are connecting the remote more prosperous of winning the first prize of storage battery, getting controls, and tuning the set. Do not throughout the country, the sale and $15.00 in the $50.00 prize con- installation attempt to balan.e the set on an outside of these units is taking a test held recently by Federated aerial. set is to big jump. or regulation set If the This is everywhere evident Purchaser, Inc. By special ar- be installed in a garage or place that is in the number of queries concerning this rangement with this company, fairly well shielded, connect the antenna work, and the of noise elimina- amount we are please to be able to pub- that you are going to use, and supple- tion that writer called the has been lish this article in its entirety. ment it by laying on top of the antenna upon to do. As of work is this type a length of insulated wire about thirty not new me, majority (For further information on the to but is to the to fifty feet long to increase the pickup of radio men, this article is addressed elimination of noise in automotive radio receivers, readers are to normal. If the shop is to specialize to those who "would like to know" but in installation, it would be a good idea cannot out. referred to past issues of tint to use two plate antennas spaced about The first time that the average radio RADIO -CRAFT, and to the very t/., -in. apart, one being connected to a Service Man or technician attempts to complete book, "Automobile and the other to install regulation aerial, the an automobile radio set it is a Radio and Servicing," by Louis set proper. A ground is not necessary case of "imagine my embarrassment" Martin. -Technical Editor) and in the shop is not used. Balance when, the set has been nicely and after the set accurately by means of a cali- firmly placed, the nice new suppressors brated oscillator after the fashion of a installed, condensers wired into circuit, house radio set, and note the noise level possibly an under -car aerial con- and of the particular set. It is the habit of nected that, the motor being turned on, there is a faint sound of music subdued a majority of the newer sets that are in a "foreground" of ignition static! If being built in one unit (with a vibrator - he is the average Service Man, he has type "B" eliminator) to be very "buzzy" doubtless been queried countless hun- sometimes when first hooked up. If dreds of times about removing static - the set seems to be exceptionally noisy and here he is, after swearing that it is in this respect, change it. Otherwise, if not possible, with the prettiest bunch there is just a slightly noticeable buzz of localized static in the world to re- it will wear off after breaking -in of the move. Oh well, that's what he gets for eliminator contact points. being a "radio master mind." Then there is also the fact that the Fig. 1 With car sets using the "dynamotor" newer sets are so greatly advertised as Details of car radio service. for furnishing the high "B" there should being "Installed in less than three - be no ripple at all and the sound of the quarters of an hour -even by a novice." Blah, and more motor itself should be just barely noticeable when you stand blah! It generally takes more than two to three hours of about two feet from the unit. If there is any ripple at all in continuous and steady work before the job is fully completed. the speaker when the set is tuned to the frequency of a local If you don't believe that, here is a positive shop record of station -replace the unit. a professional "auto- radio" man over a period of a week. Seventeen cars, thirteen of which were current models, Installing the Set one was one year old, a second two years old, and two more Select the location for the set, watching that you have were three years old but of a make which "doesn't get old plenty of room on all sides, and making sure that the remote with the years." In these seventeen cars four different cable from the steering column will reach to where you are makes of radio sets were installed- Philco. RCA, Motorola going to place the set. After the actual installation of the and Atwater Kent. From actual shop time records with set, control, eliminators or batteries and before the antenna every minute of actual work accounted for (no time off for of the set is connected, put on the suppressors, distributor smokes or going next door to get additional parts) the aver- and generator cutout condensers, and with the battery con- age time for the seventeen sets was three hours and fifty nected, turn on the set to allow it to warm up. Coil the minutes! Furthermore, as a check, fully three -quarters of antenna lead from the set around on itself to neutralize that tinte was marked down to noise elimination. Also, take outside pickup and turn on the motor. Nothing will be into consideration the fact that as a specialist, all the heard as far as a signal goes but plenty of noise will be necessary equipment, wrenches, shielding and all tools neces- heard. sary to a neat, speedy and efficient installation were right at llave a couple of spare condensers handy. One equipped hand. with test prods as shown in Fig. 1 is a very handy tool. If Routine Procedure the noise sounds excessive, this shows that there is a great In all cases a set routine should be followed. First and amount of ignition noise getting into the circuit through foremost the set should be placed on a bench, hooked up and (Continued on page 308)

288 RADIO -CRAFT for NOVEMBER, 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.

vice Man who is working with auto- BRINGING THE MOUNTAIN TO AUDIO TRANS. MOHAMMED -1933 VERSION mobile "radios." PHONES ALVA H. CLARK I(AIIlo ('it i r: Editor. Linden. A. C. R1 In this day and age one has really 1 C! his services in order to reach to clarion A SMALL LIGHT FOR BIG JOBS the consumer. This business of putting O O -hole in Fig. 1, out a "shingle" and then waiting for The peep light shown is extremely valuable for searching out business to overwhelm you is a thing of R2 fi small parts of equipment to be repaired the past. One very good way to put a Cx or It repairman few extra dollars in your pockets is to inspected. enables the 1 to thoroughly inspect the bearings. oil fill up the service car with your com- 111111 -B- rings and small parts of motors and plete equipment and start out "house - other equipment without disassembling. to- house." Fig. 2 Installed at the East Pittsburgh works This scheme has a number of advan- for condenser measurements. A capacity bridge Electric and Manu- tages. One is that the job is done at of the Westinghouse Company, this inexpensive the house and there is no more bother facturing the corner is to hop into a service truck, spot was with sets around the shop. Of course, miniature light constructed buzz around the corner, and find out. pen type there will be a few which will have to from an ordinary fountain This is a good tip for the fellow with flashlight. It is attached to a flexible be taken out. In the summer time or enough ambition heft Io try it. Editor.) cord arm in a convenient position in warm climates all jobs can be done and over the bench and is energized with in the car, if you have a large truck A RURAL COMMENT a small transformer mounted on the with a regular service-panel layout. Editor, 1LAll10- CuAFT: Another advantage is that you can get wall. As the ordinary extension light After all, I see that there are a few is rather cumbersome and cannot be the business of the customer (and there Service Men left in the country dis- are lots of them) who does not want used for getting into the interior parts tricts. I was beginning to think there of small apparatus this trouble light the set taken away. was A.C. or D.C. power everywhere ex- Some idea of the equipment required has proven itself to be a time saver and cept here, as all of the radio publica- a valuable addition to the inspection for this method of radio service can be tions have just about quit publishing had from the following list: bench. When not in use the light may helps for those who have to stick to be placed in the receptacle at the end One service truck or car, set analyzer battery- operated sets. If it were not and oscillator; a large assortment of of the arm and swung aside until for R.tnlo- CieAr-r and Snow'. WAVE CILAFT, needed. parts, such as, power transformers, filter we would be "out," sure enough. They and smaller condensers, resistors, vol- are the tiro best radio magazines on the ume controls, etc.; a complete set of market today -I never miss a copy of MEASURING SMALL CAPACITIES tools; dynamic and magnetic speakers; a either. \-r'ry often I have needed sonic means complete set of tubes; a small rug to Mr. Robert Rogers in his letter in the of measuring the capacity of a con- spread on the floor. July, 1933, issue of Kamm-CRAFT ex- denser. However, the usual arrange- 1 think the Service Mat will find this pressed my feelings exactly. ments require expensive apparatus that money idea will net him a little extra Thanks to Mr. Ray L. \\-orderly, also, I do not possess. Therefore, I evolved and will be well worth his time. for his suggestion about changing model the circuit shown in Fig. 2. Cr. A ar :NcE E. SWISH 67 Atwater Kent to use 2 V. tubes. I The tube and A.F. transformer form 921 k; O. Illinois Ave. ran up with this problem today and an oscillating circuit. The resistors RI Villr, Park. Ill. expect to try his suggestion. and R2 are the two parts of an ordinary CRAr-r is worth many times wire -wound potentiometer. CI is a (Mr. believes the way to June RAmo- Swink that pile.. to the Ser- (continued 00 pa-m' 3151 find out whether "prpsperity" is around a year's subscription

-FRONT. DE CNAMGER FOP ,FLtlllsl,t : Z. -.l f CHUCK LEAD :: I~ C TODFER -E 1 "tI' 1 X". BRACE f " root- ., (MAKE ON[) HOLDE4 V 11 (tArn 11 -T -B- L/R ,.- ORLbEOO - REAM TO IA' ®- II4'SFT- ',G'SFT- SCREW 1 I 1 SCREW ROUMO OFF i I FRONT SIDE -_ EDGES %4 A. 24+ L 9E o /èL T D _ 11:- 1- A- _ l , .51- 4 %6 I 5E r/4.ORILL CUTTING

( ENLARGED ROO TOOL METAL FOUNTAIN PEN FLASHUGT ,, -C PILOT ROD PANEL TAP FOR /4.SET' SCRews Ni CuTT NG -PILOT -HOLDER- (MAKE ONE, IRON OR ireEL) TOOL (MAKE ONE) - SOCKET CUTER IN USE- Fig. 1 l A light that is handy for the service bench. Fig. 3 An A.C. transformer supplies the spot -light current. Constructional details for making a "fly" cutter for drilling socket holes.

RADIO -CRAFT for NOVEMBER, I933 289 101 Radio Service Data Sheet

MAJESTIC CHASSIS MODEL 460 6-TUBE A.C. SUPERHETERODYNE

(The model 460 chassis is used in receiver models 461 and 463. The chassis incorporates new tube types including the G -2A7 -S pentagrid converter, G -55 -S duodiode -triode, and G -2M pentode. Also, an exceptionally selective input circuit, delayed A.V.C., line noise filter.) The 31ajestk model 460 chassis is most less for un output signal of 1011 milliwatts nuubI 460 chassis fellow's the modern trend readily recognized by the modernistic de- ut :;oie modulation, of having an improved over -lo :ld und A.V.C. signs of the cabinets of models 461 and 462 Three colored dots on a mica condenser action. but without the customary disad- receivers in which It is incorporated. The indicates its capacity and the two co Iured vantages of the more conventional circuits. It's by improved pre -selector teuit results in very dots, its 1 ).l', working voltage. The cul 'This is accomplished utilizing one diode high inmge attenuation and greater stage have been assigne11 its follows; 0. black : I. plate of \'4 for .\.F development only, and gain. with consequent lowered percentage of brown : 2. red : orange: 4. yellow : 5. the other for A.V.C. voltage only. It is, noise. for a given output level. green; li. blue: 7. purple; S, gray: 0, whil1'. therefore, possible to design an A.F. circuit Tube voltage characteristics are as fol- Un condensers having three dots ou 11111' slid an A.C.C. circuit of optimum constants lows: S1111' motta two ou the other, the desigu( t tuns vita t any sncriti ce of tone to aid the other Tube tath. S. -r,. Plate ore to be read with the capacity rating t3 as has been the r:tse in previous receivers. Type Colts Volts Volts dots) at the bottons, while ou condensers 'l'Ire result of this design is m much greater V1 4.2 :12 _fro having all live dots on nue side, the designa- power output for very weak. as well as C_ 4.2 :13 219 tions are to be read with the capacity rat- strung. signals and a very constant output V:; 4.2 :12 21:0 ing at the top. hvel over an extremely mid, I.amigo of sig- Referring tu this code, the first color in- nal inputs, which effectively Inv'reomos fad- 2d11 24:; dicates the first digit of the capacity x- ing. 'the speaker field measures 1.070 ohms, 3lrnhttutu' figures mure tabulated: oscilla- pressed in man f. The second color indicates The 1 :- 2. 17 -S pentagrid converter tube, \'2, tor S. -I: volts n and plate volts. 02. the second digit of Ilse capacity. also ex- is used for two definite reasons. first, it Art mal triode plate voltage 'flits rend pressed in nun f. The third color indicates gives a very flat sensitivity over the band ing will be much lower If a lowarsisla nee the number of ciphers following the second covered and, second. it mikes it possible to voltMeter Is used. dne to the drug across digit of the eaymcity. The following ex- control this stage with the A.V.C. voltage. it:;. The rectified filament-to-ground pnh'u- amples are given : red, green and brown The 1: -2.\5- pentode is capable of giving tial is 240 V., iIC.: line voltage. 115 V.: (lots. 2311 mud.: brown, black and red dots. it large pourer output with a eclat ively small volume cmntaul in maximum position. LOta) nun f. Again refering to the code. input signal voltage. The power handling When aligning the receiver circuits, the first colored dot indicates multiples of ability of \ :3 Is essentially the saune as that manual volume control ail most be ht the fou C. and the sicomd tint' indicates nudtt- of the G.d. with 1..111 rte connection. maximum volume position. Supply n 175 ples of 10 V. Examples.: orange and green The letter S ais the last letter 011 31ajes signal to the grid of V2 and adjust the doh, 350 V., blue and black dots, tan) V. tic tube type numbers indicates that the trimming condensers in shunt to the 1.1,. We wish to roll the attention of Service tube is spray- shielded. 'Phis shield Is transformers for mnxlmutn nntpnt. Finally. Men to at forward step taken by Majestic grounded to the en t huile. as shown in the set the ° -gang condenser to the minimum - t,iVttid the develo! 'ut of is 'basis- rriiap schematic circuits, capacity position and supply n 1,7311 ke. color code. Tell ta sper ilicattons are its signal to the input of the receiver and align follows: the trimming condensers for maximum out- Blue. yellow Urn, -1'r- -high V. from rectifier put. hais hems After the receiver aligned. flitter input) ; the sensitivity should be li) microvolts or Ifesi -"1t" plus; Orange- cathode : White-screen-grid ; ]flue -filament; Black-filament and ground; I; reen -grid return: I fro wn-ca th ode ret urn Black, red tracer -control -grid; White. red tracer-rontrol -grid (condenser); Orange, black tracer- suppressor -grid; Black, yellow tracer- special plate; Bitte, red tracer -- special screen; Yellow -all plates; \\'hire It.l'.- . \. \'. C, circuits; Yellow It. C.- sprriul A.V.C. circuits; Black and red twist1'i -pilot lamp. (For sonie tittle to r there will he east's where substitutes will be 11111110 for the purpose of using up inventory. Theie may also be casses which arise where it will be 1l1i1)Ilii impossible to obtain the specific wire when needed, In which case a substitute will be made. In general. lin leveret', the above code ¡rill be strictly adhered to.) The modernistic model 463 receiver The A.V.C. circuit incorporated in the The new model 461 superheterodyne. DYNAMICsootoC MI CE 4 Oft t OEr 2 .MSF. -1 VOICE COIL i OSC G-56-S E,AVC wONaif G2AS G2A7.5 rr553 .005- ¡MUM -lUCs COIL l2) I I / 02 1.25- Mf MF ` MEG T AMT tFT1 LFT.c I psis 3w -D I

Ct x pr`OTL L r 01- ffCT. v2 V3 s aND X X X x

f2 a I ID Mf r

MANUAL M VOLUME CONTEOL 0.2 -MEG., GI r FIE D w.r.ti16MF. .25- .25- CO., MF ti O.SMEG (i 8 MF. 1 IF 175 KC 110V, 13A / ("1 300 360 t 9.000 t 10.000 A.C. OHMS 05M! OHMS OHMS OHMS

290 RADIO -CRAFT for NOVEMBER, 1933 Radio Service Data Sheet 102

COLONIAL MODELS 250, 279, AND 300 5 -TUBE A.C. -D.C. SUPERHETERODYNES

(Two chasses, types 128A and 128B, cover these three receivers. The following features are incorporated in both chasses: a voltage- doubler rectifier connection; uses types 6A7 and 6B7 tubes as oscillator and first- detector, and I.F. and A.V.C., respectively; A.V.C. )

Numerous features in the Colonial modela on the ('littssis are wired as shown in the 250, 270. and fia) (illustrated; the case is indicated circuit below; "II' rhasses aie molded ha ke li tel receivers, tunke the techni- wired as per the other diagram, below. cal data concerning them of exceptional in- .111 metal parts of the chassis. including terest to the Service Man. Sw. 1, are at high potential to ground, An A.C.-D.C. switch. Sw. I. controls the Therefore, do not ground the chassis; also, circuit for hest operation under the condi- do not touch the chassis while the power tions of power line voltage plate supply in Cord is plugged into the power outlet. the U,C', I)ed tion, and the increased voltage The loudspeaker may be removed for re- obtained from is "voltage doubler" circuit placement by taking off the V2 tube shield in the A.C. position. Because the 0.17 tube and removing the three speaker mounting is used as a combination oscillator and that screws. He certain that the speaker leads detector, and the 0117 as an A.V.C. and I.F. color code is followed. Incorrect connection amplifier, the receiver is est uicil telit to a set of the leads wilt cause the hum voltage in using se Ven tubes. The It.I'. coils are spe- the hunt -buck coil to cause an increase in cial, litz -wound units having an exception- the audio hum level instead of cancelling it, ally high Q factor and low It. The dial is Referring to the diagram of chassis 128.1 calibrated in kc. The power cord incorpo- it will be noted that in the A.C. position of rates resistor 116. The reproducer field coil Sw. 1. the rectifier filament and cathode .52 also functions las the only choke coil in the differ in voltage by the maximum voltage filter system. Tube operating voltage and output of the voltage doubler circuit. This current chit racteristies are given below. condition has been corrected in the circuit The field coil potential is 70 V. Measure- shown for chassis 12511, where the maxi- ments were made with a 500 V., high- resist- (;rid No. 1, 5 V.: No. 2, 105V.; Nos. 3 mum potential] difference between the fila- ance meter: line voltage, 118 ment and maximum-voltage V., A.C.: set and 5, 55 V.; No. 4. 1 V. Current figures: the cathode has detuned. and speaker field "hat." Care grid No. 2, 1.:1 ma.; Nos. 3 and 5, 1.2 mn. been reduced to the line potential. should be used when taking readings with In both circuits, first -section plate Ai and a set analyzer capacity The negative voltage drop across 112 and as the of the cables I. tenser C5 are imperil [ ive in the 11.t. may cause It:l is applied to the control -grid of VI ; the circuits to oscillate, resulting in position of switch Sw. I. However, the sec- erratic readings. (Usually. negative voltage drop across lt:l is applied touching the ond section. Iti, 1I 7, of rectifier VS has or plate to the control -grid of V2. Residual bias far been grid will stop oscillation.( rewired so that Instead of passing the 1.1 is furnished by its ; and for V2, by 114. total Tube C.41. SA:. Plate SA:, ('late current required by set The the (including the Type Volts Volts Volts Mn, Ma. A.V.C. action can be rendered inop- current for the field coil) with the rectifier VI 7 55 110 0.2 0.4 erative when peaking the 1.1". transformers section in the negative leg of the high -volt- V2 22 50 by unsoldering one side of C. which is -1.5 .04 0.1 age circuit Cars shown in the circuit of V8 -10 120 100 5A mounted across the sinket of 1.2. 'trimmer's 20 chassis I 28 1 it is in the positive leg, as V4 C'1 C4 are accessible 2 to from the front of shown In the circuit of ehaasis 12811. (In- '.5" - - - - the chassis. - - - 40 stantaneous polarities of the power line are Indicates high resistance. Receivers which are rubber Stumped 128:1 shown iu parentheses.)

DVNAMIC DET1 REDRODUCEt R6,1540NM5.sF A i OsC ivC DET2 .002 -MF AF 6A7 CI 1FTl C2 687 C5 IFT2 (4 77 43 ¡1 .0S-MF OICE e C )ErI cOIL 2525 RECT % ì a 250 sum 6' 41 rMG BUCaaNG J ) - COIL I T AC V4 15 0.4- E F Swl Nil_] EG MEG tat 0.5 ti 0.2- d- : CNA GND o 1 55,5 0.5 L1E0 MEG MEG J 3.000 Q 250 J VOLUME ...BLACK o CONTROL o1-MF 1 0.1-MA R Rl (EATN) 1.600 0 MS 0.1- Cso al -)At. at- FIELD COL MF. owns MF `(ELE[) r -RED - C7 L2 R4, 7o0 2Ò.00o 1 MEG. r CNASSIS 128 A ONUS 0NM5 (EACN) 5w 2.F175NC 0.1MEG1 r4000NM5 elOV,AC;OC^

7 rcóñvéa DYNAMIC 154 F DET 1 002-F iSNaELO AF VOCRODUCEt ONMS, A OSC DET 2 50.000 R6 6A7 0555 . 43 VOICE ¡ i (1 1FT1 C2 _ I /COIL 2525 0.2. RECT. MEG

NUM 006 618156 MF COIL

T V4 0.5. E F Swl M G 'i 0.1 M

R 50.000 ONMS i 1,600 00t 0.1- MF MEG. BLACE' CIELO COIL

50.000 15.000 OHMS ONM5

RADIO -CRAFT for NOVEMBER, 1933 291 THE BEGINNER'S "UNIT CHASSIS" CRYSTAL AND 2 -TUBE RADIO SET

Previous "Beginner's" articles in RADIO -CRAFT have been devoted almost exclusively to the design of "bread- board" radio receivers. In the following article the author dis- cusses further the "chassis- type" design which more closely follows standard radio set construction. One more tube has been added to the chassis described last month.

PART II FRANCIS R. HARRIS

HASSIS construction is universally used in modern with the addition of a second unit practically identical; the radio apparatus for a number of very good reasons. schematic circuit is Fig. 1. These chasses, and others like In the first place shielding is necessary in any receiver them, will be used in future layouts for all kinds of circuits. with more than one stage of R.F. amplification, especi- Expense, therefore, due to the fact that the same material ally with modern high -gain tubes. This shielding, to be effec- is used over and over again, will be very slight. tive, must be thick, at least one -sixteenth inch; material of As for difficulty, that is largely a matter of getting used this thickness has considerable mechanical strength, hence to the idea of working metals and of getting the "feel" of its use as a base on which to mount all the apparatus. handling them. Most of us have worked with wood a great Furthermore, chassis construction allows of placing units deal, we had manual training in grade school, it is a familiar which are wired together one over the other and makes (Continued on page 312) possible a compact construction while at the saine time sacrificing electrically, in fact in many cases a T PHONE nothing r 250 CRYSTAL -_-0..0.CHOIES/ JSCK of J4 WAN 0[7[004 331 distinct gain is secured through the use short, direct leads. I J II INSULATEO In other words, chassis construction is lighter, stronger, FROM I CHASSIS electrically superior, more compact and gives a more work- ( I Cs manlike appearance to the job on which it is used. I SOOMMC In spite of these obvious advantages it is very seldom that MORE aF I Er nus one finds a beginner in radio work using this type of construction; probably because he has the mistaken idea that ego. O Nor 4MF. it is expensive and difficult-mistaken because, while both osso) z thoughts are true to a certain extent, expense and difficulty 135 can both be minimized by proper design such as has been employed in laying out the beginner's chassis described below and in last month's issue. was open market MICHANICALLY CONNECTED Some years ago there available on the Sw- - r.,_lF a unit chassis so constructed that a large number of experi- .4. Ì t Iy mental circuits could be wired up without changing the me- I ENT. ONO. SOCKIT I FtD6 layout. Somewhat the same idea has been followed L 2 v. chanical UNIT 2 UNIT I , in laying out this series. + CONNECTION TO CHASSIS The chassis described last month, for instance, is used Fig. 1 (with only slight changes in the wiring) again this time Schematic circuit of the crystal and 2 -tube receiver.

Fig. A The front view of the receiver showing the two panels blocked together as a complete unit. The beginner's "unit chassis" crystal and 1 -tube radio set described in the preceding issue of RADIO -CRAFT is the panel shown at the ex- Fig. B Fig. C treme right. The rear view of the two chasses. The underside view, disclosing the wiring.

292 RADIO -CRAFT for NOVEMBER, 1933 The Best NEWS of the Year

Your Copy

is Ready!

Every man connected in any way with the boom- ing auto-radio business will want a copy of this book immediately. It is devoted exclusively to auto-radio service "dope," in complete, understandable f o r m. The OFFICIAL AUTO-RADIO SERV- ICE MANUAL contains schematic diagrams, chassis layouts, mounting instructions, and trouble-shooting hints on all 1933 and many older model auto- radio receivers. This Manual contains a "gold-mine" of information. Over 200 Pages Over 500 Illustrations 9x12 Inches Flew'blt; Loose- Leaf Cover

MAIL THIS COUPON TODAY! I Order Your Copy Today! (IERNSIIWK PI1ILICATIONS. Inc. PoI-I You have the opportunity to get your copy of Patk rho, New tort. N. Y. the 1933 OFFICIAL AUTO-RADIO SERVICE Entitcted Not i, ill find my remittance of $27.0 for onion Idea e 'mid tor Inte Cony or the it,: t OFFICIAL At To-IcAmo SEIIVICE MANUAL from the first printing of which we MANUAL. IScrol rend/Lime in 11114k or trinity order. Itcliater have copies on hand. The Auto-Radio Service lett, It it contains join or tootles./ Manuals are selling so quickly that already another print order has been authorized. We urge you to get your copy now so that it will not lo Name neees.lry f.,1 .11 it, be without a copy of thi, manual.

Address . GERNSBACK PUBLICATIONS, Inc. 96-98 Park Place New York, N. Y. City slat,

RADIO-CRAFT for NOVEMBER, I 9 3 3 293 RADIO-CRAFT'S INFORMATION BUREAU SPECIAL NOTICE TO CORRESPONDENTS: Ask as many questions as you like, but please observe these rule:.:

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 25 cents (stamps) for each separate question; answers are subject Those questions which are found to represent the greatest general to subsequent publication, if considered of exceptional general interest will be published here, to the extent that space permits. interest. At least five weeks must elapse between the receipt of a question Other inquiries must be marked "For Publication."

ELEVATOR LEVEL CONTROL In order to obtain correct bias in the lobe circuits, it is essential that four dry rolls J1) Mr. Barbier Chase, Miamisburg, NM ANO PC. CELLS / OUNfCD ON be used in order to obtain a O V. filament Unie. supply. However, some constructors have Iii.) How are photoelectric cells used to failed to follhw the directions which call for bring an elevator to a stop exactly at the the use of three, type (1-30 filament ballast Boor level? 41' Ilk- resistors -result, a complete set of burned (A) The following information in connec- ELEVATOR. feuT'AR,>,;I out tubes. Ito not try to eliminate these re- tion With the Westinghouse Electric. Elevator PECELL CONTROLLED sistor,' by reducing the filament battery volt- Company's installation in the RCA building age through the use of a fewer number of at Rockefeller l'enter discloses the system cells. used in photoelectric levelling of elevators. The metal box should be as solid as pos- The arrangement of the mechanism is sible: the writer recommends 1 //113 -in. alum- Shown in Fig. (Y2 1.\, The three respective inum with the edges solidly bonded. In fact, positions which the appai troths may assume it was essential to put ply -wood on the sides during the leveling of a car are shown in of the locator illustrated in the article since Fig. Q222113. the case of that port tcnl:t r instrument wag A small automobile headlight bulb is made of copper which sprang slightly and mounted upon a control panel on the side caused n change in wavelength as its rela- of the car. An "up" controlling photo- tions to the detector coil varied. The joints electric tube is mounted 3 ins. from, and on of the copper can were welded in order to a horizontal line with the light bulb. A. A- make a water tight container. "down" bulb is mounted in a similar position Further points of vital Interest in the on the opposite side. When the rays of light ErCItER operation LAMP construction and of the metal lo- fa11 upon the "up" tube, the usual amplifier cator described in the July. 1933 issue of circuit is put into operation and the ear n UP-CONTROL It.tDto- ('iAr^r are the following: moves upward: when they fall upon the PAwN.sotE GELL P E. CELL (1) Be very careful to do n neat wiring "down" tube, the car descends job, soldering every joint perfectly and hie- Metal cames fastened to the walls of the Fig. Q. 221A ing every wire down tightly in position. shaft. shown In Fig. Q221.\ and It, control P. E. cell control of elevators. Use only stranded, rubber- covered hook -up the movement of the elevator. They allow wire: be sure the wire Is well tinned. Do the light rays to fall upon only one of the not try to use single -conductor wire, two light -sensitive tubes as the car slows (2) t'se all the precautions customarily down, a nil L"mpletely intercept the rays A- OPAQUE VANES used in wiring high -gain superheterodyne when the ear (rASTENEO TO reaches the correct floor level CLLVATOR SNAET) radio receivers against undesirable radio Pre. The photoelectric control does not begin l:/ é quency coupling. to function until the car, slowing down ir CAR AT FLOOR LESSI FLOOR LEVEL (3) Ton will note a discrepancy in the enters a stop, the zone of the metal vanes. illustrations used in the original story : ono If the car is descending, the upper vane. en- WIN UP AND DOWN PE CELLS!. EXCITER illustration, 2, shows PE CELLS DARN - LAMP MOUNTED Fig, the monitor oscil- countered first. prevents the light rays from CAR REMAINS STATeONARY ON CAR ROOF lator coil mounted in the floating oscillator falling upon the "up" controlling tube. When shield box: this is not correct as the monitor the ear, still slowing down. reaches the lover oscillator coil natant be mounted in the moni- vane, the "down" tube is cut off and Ilse car - -FLOOR LEVEL tor shield box together with its tuning con- immediately stops. The control works In a denser and associated parts, as shown in CAS iELOW ROOK similar mauser in stopping an ascending car. LIVEL -o- Fig. 1. (4) The use of brass strips to mount the PP - CONTROL RAYS FALL UPON LIP CONTROL coils LI, L2. as shown. is not a recommended "THE NEW 'TREASURE' FINDER" - E CELL RE. CELL - CAR MOVES UPWARD practice as the added capacity caused by the proximity of the brass to the windings may CORRECTIONS -C- seriously affect the tuning and energy radiation of the floating oscillator. A better (222) 1lr. W. l'. Itavis. Springdale, Ark. CAR MOTE PfOOR MIL O-- Irk method is to place n block of wood against I0.1 I have built the -treasure" tinder /I \ FLOOR LEVEL the .end of the cabinet where the coil mounts described by \1r. 1 :. Franklin Sarver in the in such n manner that the coil is held about .1iily, I11:::; 1 Issue of ItAmO.'u.trr, but have LION? RAYS MU. UPON 2 ins. away from metal DOWN - the box; and fn been unable to get the circuit to oscillate. CONTROL PE. CELL - DOWN CONTROL position. by leather straps, CAR MOVES DOWNWARD PE. CELL Please advise what may be the trouble. 1:0 The copper screen shield around LI, (.\.) We have received so many hundreds f.^. is a narrow strip. 1 -in. wide, and is placed of inquiries concerning the metal locator de- on the outside of the coil form. The instru- veloped by \Ir. Sarver we have Q. that asked Fig. 2218 ment is somewhat more sensitive anus him of and to prepare for the renders lLttaO- ' Blinden" control the exciter lamp rays. more penetrating power without this shield. ('n.tpr a series of comments concerning the Without the shield, however, the instrument hoist likely troubles the constuet,sr nifty Is more "tricky" In its operation. The author encounter in building this sensitive iustru- ear of the operator might be left free to hear was able to handle the instrument nicely nient. The information furnished to us by other sounds in the surnnnoting territory. without this screen shield after about Mr. Sarver two is as follows. good results are not obtained if the I- weeks field practice and made most suc- Lark the of appreeia tion. on the part of build- tor brats against the fundamental freyueu l y cessful deep locations without ers of the heterodyne it. metal lneator. of the of the Flog ling oscillator. Willi the instru- tan Senegal builders ha tee written prerisiou to the required in constructing apparatus ment I am using. the monitor beats against author stating that the instrument does not of this nature, is the foremost "fault," if the sixth harmonic of the floating oscillator, oscillate. This may be due to one or more we may call It such, In operation of the this note being much softer and easier to reasons. Try reversing the leads on the derive. listen to: also. n greater frequency change monitor tickler coil I.4: this oscillator is 'Else writer has added a midget variable is caused by the given change of indueta nee. nothing more than the old familiar regenera- r 'tenser to the tuning system of the monitor The chief trouble that the writer experi- tive detector operating nt the point sus- order of in to secure smoother action in con- ences seems to be In a slight drifting of the tained oscillation. Place a short piece of trolling the beat note, the monitor tuning monitor which makes an adjustment necessary copper wire attached to the plate of VI, capacity now consists of n compression -type al every seven minutes: experinmn is are near n radio set antenna and tune the radio mica tosii.sisen . of ^..0 mmf. maximum capa- under way to prevent this drift. However, set until a (rent note is heard from the city. plus the midget variable condenser. the latest "record" achieved by the writer monitor in the radio speaker: if a whistle one of the headphones has been removed with the n ppa ra tuts described was the loca- is heard from the radio set. reset the monitor and an impedance of equal value has been tion of a gold watch at a distance of about tuning condenser and try again. Do this substituted in the instrument, so that one 40 inches. (Continued on page 313)

294 RADIO -CRAFT for NOVEMBER, 1933 A NEW OSCILLATOR (Continued from pape 267) If the A.F. circuit is functioning from that point on, the 1,000 cycle note will be heard in the speaker. For I.F.:mtplifier tests the oscillator should be set tu the correct frequency aull the test lead ...toweled Iii the grist of tir tirstdete,.- tor. III so lo - ce t%rr,. du, to the natme of :11'y the A.1'.,', , i ,nit. il may be lneteSN to .111 between connecta " -end -u r f al t -mf. the test lead and the grid to prevent shorting of the Lias circuit. With the above connection. it may be found That the signal cannot be hard or detected with the ewd in the 1.411V jack. If so. it in. dicates that the receiver circuits are badly out of alignment and the II11 :11 jack should be used until the alignment is sattìci,Itly good to allow hearing or seeing an indication of the signal with the line tip lu the Llut% jack and tile It.F. output control set at nu, mum. As the varions trimmers are bi..ii : Io the point of resonance, the It. F. output control should be retarded, always using the lowest value of oscillator output that will a give a satisfactory resollanc, indication. For ILF. alignment. the line cord should he cunneeted to the antenna post through a condenser to simulate an antennal. The receiver manufacturers bulletin should be (.ouslllunI as to the correct size of condenser to use: or. in the absence of this information a Vitt mont. Milt is suggested for use with standard broadcast receivers and 100 mmf. with auto- radio receivers. The same general procedure is followed In making this test that was used Noucr 666 in taking the I.F. test. using always the . tn.nt.t Sr,.gtNaa minimum possible setting of the 11.F. output control. The dial at the lower left-hand side of the panel Is calibrated In k'. off resonance. Io other words. with the seleelur dial set at 175 ke. and the selectivity dial set at O. the frequency emitted by the oscillator is exactly OBSOLESCENCE WORRIES ARE ENDED 175 Ice. and the selectivity dial set at 0. the to the left Io divisions, the frequency will he 175 minus 10, or 165 ke. In the same way, if the selectivity dial is turned to the right uíith this- new test equipment -say 5 divisions -the frequency will be 175 plies, I.r ISO la% The same action of the selectivity dial o!Iains at all settings of the Here is new test equipment that will never gather cobwebs because of selector dial. Il,i.s unique feature permits ob >olescence; never cost you real money in order to keep it up -to -date. the testing of the receiver for selectivity. The reasons are obvious: Many receivers are arranged in such man- The Weston Model 665 Selective Analyzer contains all the necessary ner that it is possible to stagger or distort voltage, current and resistance ranges. Separate Socket Selectors are selectivity carve very easily in the coin,. the provided to accommodate all 4, 5, 6 and 7 prong tubes. You merely of what scetns to be a normal alignment. aids is "flat toll' resnntae, as contrasted attach the proper Socket Selector to the Analyzer, and insert the plug with "peak" resin inse.-7'celtaical Editor) into the tube socket of the radio set. Then, by plugging into the This ran easily he detected, by aligning the proper jacks, voltage, current and resistance may be read in any part 1.F. unit at, fur example. 175 kv. and then of the entire network leading to the tube socket. New tube bases shifting the frequency equal amounts to either merely mean a new, inexpensire Socket Selector. side of Ili. reort :n1re peal:. anti noting wheth- The Weston Model 674 Tube Checker is a real tube merchandiser. er the Lulling art in response is equal on both shows sides of the resonance encre. as noted in the It good tubes as "GOOD ", and is beautifully finished in three output deck,. 111 addition. the scie,I ivity distinct tones of brown. Provides for testing all present tubes; and Ilia I Can he use] for obi a juin, settle of ill, bas seven spare sockets which can be quickly wired in to test some 11,s -used interun -diate freq tendes if they are fifty -odd additional tubes when and if offered. All reference to or within ten ke. .,f the standard frequencies. knowledge of tube characteristics is avoided. Quick and accurate indi- For example, th Is3 1c. test frequency eau cation is obtained by simply following the few concise steps on the be obtained by .,Ming the dial at 175 and tube limit chart. Other features make it today. selectivity dial at plus 10 kc. the outstanding value the Weston Model 666 Socket Selectors can be used with any and all Feusiticitlr tuts also may be made with makes of Analyzers. Your present Analyzer can be brought up-to -date, this unit as the It.I'. output at tenuatur is an and kept that way, with these inexpensive units. accurately coat olhnble lust rumeur and the simple, operator will 1.11 11 it posstlde ta tunke notes These and other Weston Radio Instruments are illustrated and described in on the response of receivers in ternis of the the new bulletin HA. Send the coupon today, and receive your copy...Weston setting of the altenattior. This means that Electrical Instrument Corporation, 599 Avenue, Newark, N. if the setting of the It.F. output routal tutees- Frelinghuysen J. stirs to give a certain output from the receiver is rertarle.1. Ihese vaines may be used for comparison of the sensitivity Of the same receiver, or one of the same type, at a future date. Aecuuulat ion of data of this type is of great value to the i

RADIO -CRAFT for NOVEMBER, 1933 295 A E R I A L FILTERIZERS have helped thousands of radio listeners to obtain noise -free radio reception in locations where radio noise made even the best of sets useless. This remarkable product of the acknowledged authority on radio noise -the TOBE DEUTSCHMANN CORPORATION-guarantees satisfaction and real

!:IC /rrAnlr.utuP profits for you. Do not accept imitations or substitutes -insist on genuine tU/w1r0(War OF t./(LOW uaav. TOBE FILTERIZERS, made by the one organization that has specialized 15157(M1./n0(0 WO w MVO (unA in noise elimination and whose products are recommended by leading manufacturers throughout the nation. We stock the complete line of TOBE FILTERIZERS and FILTERETTES, and are now the noise headquarters for the eastern United States. Send us all your noise questions and our noise experts working with Tobe interference engineers will tell you just how to stop the noise and make a profitable Filterette or Filterizer sale.

Eastern Headquarters R I Filterette Division for Tobe tI !f WHOLESALE RADIO SERVICE COMPANY, Inc. 100 SIXTH AVENUE NEW YORK, N. Y.

I lowever, In designing us/-il to tar coils for the gi Ve satisfactory operation of the lA6, The NEW TUBES 1.16, the coupling between the oscillator grid mils are suitable for use with an IX. of 175 (Continued from paie 267) coil and plate coil may be slightly greater kc. in a broadcast -baud set. 'Che use of other chassis space requirements:. than that commonly used with triode oscil- intermediate frequruci(s wItI necessitate Resembling in both function and operation. lators. changes ill the inductance of the coils. Usu- the 2.\7 and 6.\7 described in the July 19:::: In the illustration at the top of Fag. 1 are ally coils which are suitable for the 2A7 or tube. issue of ItAUto-t1t.5 vr, the 1 .\6 is subject to shown three standard methods: A, It, C, for OAT will be satisfactory for this the same general operating requirements no constructing the oscillator coils. Each of the The oscillator anode -grid voltage must not anode -grid is those applying to other Oen to grid converters. hrec coifs shown has an M /I. ratio (the mu- exceed 135 V. If the oscillator The following operating conditions may be tual inductance, M. bet wecu the oscillator supplied from a plate voltage source of more taken as typical. for two plate Voltages. I le- tuning coil. 1.2. and the oscillator than 135 V.. a voltage, dropping resistor mast Plate voltage I::.. loo V. grid -tuning coil, 1.I, to the inductance, L, of be used. With ISO V. plate supply, a 211,000 Screen -grid Volt- the oscillator grid- tuning coil, L1) which will ohm voltage dropping resistor in serles with age (g rt(tO the oscillator anode-grid. and shunted by an Nos. 3 and 5) 67.5 67.5 V. 01 -mf. condenser. will reduce the voltage to (grid q.t. a pentu lssible Value. .\ le-grid I1/PUr úw°t, LAG No. 2) 135 135 V. rT In general, decreasing the voltage on grids Control-grid Nos. 3 and 5 from 67.5 \'. will decrease the 11 :rid No. 4) -3 V. gain. The screen -grid voltage must. however, tisc :grid (Grid never exceed 07.5 V. wider any conditions of No. 1) rests - operation. The optimum value fo screen -grid tor 50.0011 11104111 u111110 Voltage is dependent un the other electrode Plate current 1.2 1.:: ma. Voltages and on the circuit constants. 'l'hus, Screen -grid cur- all currents will increase with Increasing rent _.l 2.4 ma. screen -grid voltage. .\ reduction in the os- .\node -gr(d cur- cillator grid -leak resistance 1114 ceases the gain rent 2.3 2.3 rout. und at the same time. the currents. .\ucl an oscillator -grid increase ill the 11 /t, ratio of the oscillator en rrent 0.2 (1.2 ma. SIGNA - A1/OOE.GRID RL,/ SCREENGAID PLATE cuti operates In the stele way. Total cathode GRID EIAS SUPPLY Su PLY SUPPLY SUPPLY 'Che total cathode current in the 1.\6 should current 6.2 6.2 too. NP. 52, PLATE COIL,SST LATE COIL AST. 1/..52 LATE COIL 45T. never exceed 9 oat. Varying operating condi- Plan, resistance 0.4 qa megohm WOO COAX T. ! GRIP COIL Nn. I¡, OPIOC R SIT. tions to rals the cathode current above 6.2 L 1/1.72 Filament volt- 11111., as shown in the circuit, in Fig. 1, rLtJ Ip for age 251 2.0 V. ó1ó: TT :ólß _ typical operating conditions, usually (E1/AM W will not l'i la nl en t cur- N1.32 -G- *um) increase the gain appreciably. t'onsequently, rent o 06 0.06 ¡ more operation of G4 satisfactory the 1.\6 is ob- Conversion con - G2 61 PLATE tained with approximately 6 nut. cathode cur- ductanre _"75 300 mierondros GS rent, since IIigher caltes tend 64 to xhorirn flee Con Version con- Gs - (CAP) life of the tube. ductance at In the lover part of Fig. 1 are shown, left, Gl 2.5 volts PLATE the socket connect tous, and, at right, the tube on No. 4 4 4 micrombos grid (Tao VIEW elements of thu- 1.111, .\ "en t tende effect" ex- The design of a su perlet erudyne receiver OF lots het wren 442 and G3. This is the "virtual employing the I .\ti is convent iounl. There HEATERS SOCKET) ea thude" described, and illustrated in Fig. 31,, are no unusual features which must be taken in the .holy issue of RADIO- ('It.\ITT previously into consideration. The It. F. input circuit. anent toned. t lie t.F. transformers and the gang-tuning Fig. 1 Referring again to the schematic circuit in condensers are designed in the usual manner. Circuit and coil details for the 1A6 tube. Fig. 1, the ganged condenser C'1 and C2 are

296 RADIO -CRAFT for NOVEMBER, 1933 standard signal and oscillator-frequency tuning units, respectively. Condenser C::, a -padding" unit. is not required if condenser C2 is "shaped." Con- densers C4 and t:5 are the usual I.F. trimmers, with a minimum capacity of 50 mint., as stated below. Complete shielding is essential to prevent interstage feedbark. The filament voltage voltage should never be permitted to exceed 2.1: V. 'l'Ite bias voltage applied to grid 4 can b,' varied over relatively wide limits to contra the translation gain of the tube. For example. with 07.1 volts on the screen (No. and No. :. ), the bias voltage luny be varied from -3 to plate current cut -off iapproxi- mately -_5 volts t. With lower screen voltages, the cut -off point k proportionally less. The extended rut -off feature of the 1.10 in combination with the similar chttrncteristics of super- control tubes cant be utilized advan- tageously to adjust receiver sensitivity. Since the capacity between grid No. 4 and plane is in a parallel path with the capacity Rod inductance of the plate load, PI. it is important to use a load capacity, C4. of suf- lithot size to limit the magnitude of the It.F. voltage built up across the load. If this is not done, 1LF. voltage feed -back will occur between plate and grid No 4 to produce degen- erative effects. For this reason. the size of the load condenser in the plate circuit should be not less than 7.0 nun f. THE Converter circuits employing the 1AO may easily be designed to have a translation gain of approximately 40. The typical sehematie elrcnit shown in Fig. 1 provides exceptionally uniform oscillator output over the entire grid - PHILO bins range. The 6C6 Another new tube is the Cl'O triple -grid- SET TESTER amplifier and detector: it is an efficient ILI''. pentode having a sharp cut -off. It is similar to the type 57, except for the heater rating. This tube is reeommended for lase as a detector, or as a second -detector- oscillator in uses superheterodyne receivers: also as n control the Westinghouse Universal Instrument tube und as an A.I'', amplifier with resistance coupling. Typical operating characteristics for this THE instrument used in the Philco 3 ohmmeter scales -1500, 0.150,- tube as a class A amplifier are as follows: "All -Purpose' Set -0 Heater voltage 0.:: V. Tester is a stand- 000, and 0- 1,500,000 ohms. Plate voltage 250 V. ard Westinghouse universal Rectox mil - 5 a-c. output scales. Screen voltage 10o V, liammeter. The instrument is flush -mounting, in Crid voltage (for cathode This instrument provides, by the use of a molded case 3% inches in diameter, cut -off l -7 V. shunts and resistors: and 2% inches deep. D -c. scales are Grid voltage -3 V. 5 a -c. voltmeter scales -0 -10, 0 -20, black and a -c. scales are, red, for quick Plate current 2 ma. 0 -100, 0 -200, and 0 -1000 volts. identification. Screen current 0.5 -tua. When used as a voltmeter, 5 d-c. voltmeter scales, in the same the sensitivity is 2000 ohms per volt. Ac- Plate resistance 1,5 megohms ranges as for a -c. Amplification factor 15.10 (min.) curacy is within 2 per cent. As a biased detector, 3 d -c. milliammeter scales- 0-0.5, Send the coupon today for more cortt- the GCC has these 0 -1, and 0-100 milliamperes. characteristics : plete data and prices on this instrument. Heater voltage 0.3 V. Plane voltage 250 V. Se reel voltage 100 V. SEND FOR INFORMATION grid voltage -G V. estinghouse Plate current 0.1 -ma. Westinghouse Electric & Mfg. Company Plate load. 0.25 -megohm or a 500 hy. choke Quality uorkntanship Dept. 108, Room 2 -N -East Pittsburgh, Pa. sh nu t ml by an nugah m resistor for re- guarantees every Westinghouse product Gentlemen: Please send me information on: .sktnnce load; theu;3- plat' voltage will be the Philco Set Tester. plate supply voltage minus the voltage drop U Universal Rectox Instruments. in the load, depending on the plate current. Name Address T 79711 The 6D6 City State RC 1133 'l'hen there is the new 6110, a triple -grid Be sure to turn to page 293 of this issue and read about the new 1933 OFFICIAL variable -mu amplifier: it is n remote eut -oaf AUTO -RADIO SERVICE which is now published. tube. otherwise similar to the OCI:. It is de- MANUAL signed for It. F. n nil 1.F, amplification, or far use as a first- detector in superheterodyne receivers. In this latter service, the transla- WANTED ! tion gain Is lower than obtained Jobbers- -Mail Order Houses and Representatives WANTED that from in all Territories the Ih 6, lint ANA'.('. potentials may Ile applied -every radio service man, set builder and to this tube to seeure increased range of con- TWO FAST MOVERS experimenter to have the helpful Ilammar- trol. Except for the beater rating this tube lund Catalog of precision products. Write i- similar in operation :nul characteristics to D.-pt. RC -11 for free copy. . \lso, if inter- the 5S tube. ested in the most efficient shortwave 'l'ypical receiver operating couditions for the CDC ever devised, ask abord the COMET "1'110" tire given below. Snperheterod) ne c,ith Crystal Filter. Heater voltage C. V. Plate voltage 250 V. HAMMARLUND MFG. CO. Sown voltage 100 V. c 424 W. 33rd Street Grid voltage --3 V. Free Edge Cone and Voice And-Field Coils for all New York, N. Y. Plate carrent 9.2 Coil Assemblies Dynamic Speakers ma. We also Manufacture Various Types of Rrll'ca current 2 ma. Magnetic Speakers Plate resistance 0.3 megohm We em Sunnis. and Remedy Your Speaker Nee I, Amplification factor 28 Speaker liftes. Since 1921 ámmarlund LEOTONE RADIO P ',SEC /.^..ON Mot ual eondncta nee iI1;110 inirromhns CO., 63 Dey St.,NewYork.N.Y. PRODUCTS RADIO -CRAFT for NOVEMBER, 1933 297 An even more recent series of tubes that are spray shielded permit the design of receivers which do not require the use of external shield caris. These tubes are desig- nated as the (C7, 01)7, and 6E7. The 6C7 The 6t'7, n duodiudc- triade tube, is Identical to the type s.1. but is equipped with a shield of molten metal sprayed on the glass envelope. This shield is eunuerted to an extra prong .11 the tube base, between the diode plate Una rest the ea thude, and IIle eat thude, which

I eressita t cs the use of a 51,1,111 7 -prong socket. The 61/7. a triple -grid amplifier and detector tube. is similar to the 6C6, described above, except for the addition of a spray Books and lectures ois the marvelous accom- shield on the glass env(1lope. 'Phis shield is plishments of the Photo-electric cell must connected tu an extras prong on the base. be- Inspire you. but only by experience with the actual device can you get the FEEL of a tween the suppressor -grid and the cathode. Photo -cell; only by owning and working with .\ small 7 -prong socket is required. the tools of Photo-electricity (a complete kit) The 6E7, triple -grid super- control amplifier can this science become a powerful reality tube, 1s similar to the 6106 described above, rather than the intriguing mystery that it except for the addition of the spray shield must be to you now. and Its connection 1,,,,1"r. Years of experience manufacturing Photo- cells and allied instruments have Placed us in a position to supply the most dependable apparatus known. The Kit we offer consists A RADIO ROBOT of only the highest quality merchandise; a Centralab (Continued from paye 271) Photo -electric cell, amplifying tube, magnetic relay, condenser, resistors, socket; everything FIXED RESISTORS Installation Difficulties that is essential for the ideal unit, though While operation of this system sounds your problem is to control illumination, de- the tect burglars, count articles in production, complicated, it is really simple, compared to guard machinery or accomplish any of the More and more servicemen the task of designing and Installing it. In Innumerable feats which are practical for are being "wised up" to the the first place, the building Is located in a Photo -cell control. U.C. district. Both the telektor units and Our price is an achievement in itself. fact that they can do a better the combination radio and phonograph are 38.00 the complete kit. job with CENTRALAB Fixed designed for A.C. operation, which neeessi- totes of a converter A -watt THE CLARK INSTRUMENT Co. Resistors. For these sturdy, the use unit. 500 motor- generator set Is used for this purpose. CAMDEN, N. J. dependable resistors are BAP- However, this latter device could not be WITH FIRE and turned on separately as this would complicate TIZED the operation of the system. (It must be re- stand up under strains and membered that the radio equipment was in- PRACTICAL abuses that would make the stalled for people who know nothing about RADIO ENGINEERING the technicalities of radio.) To overcome the average resistor give up and difficulties involved. a special master relay An opportunity for quit. So be sure to specify has been installed to the receiver and is con- RADIO MEN to en- fleeted to the various telektor unite as well large their scope of CENTRALAB when next you as the program machines. This relay is op- training. order your stock of replace- erated by the U.C. line. and as soon as the Whether elementary' radio prin- contact to the converter unit is made. the elples or advanced subjects, .maul avid i- ment resistors. cations or practical radio engineering. B.C. circuit is broken and the contact held RCA Institutes is prepared to give you by the A.t', output from the converter. All the instruction you red. other circuits l except the field current for RESIDENT SCHOOLS NEW YORK AND CHICAGO one of the loudspeakers) are opened from with modern standard equipment EXTENSION COURSES FOR HOME STUDY this converter. under convenient "no obligation" plan. CENTRAL RADIO LABORATORIES To understand some of the difficulties In- Illustrated Catalog on Request volved in engineering the installation of this MILWAUKEE WISCONSIN vystem, a block layout, Fig. I. bits been made. R C A INSTITUTES, INC. This layout does not show the actual wiring, Dept. RT -II 75 Varick Street, New York it is naturally- much more complicated 1154 Merchandise Mart, Chicago than the diagram shows. It will be noticed that the radio set. one reproducer, and one Give SERVICE telektor unit are located in the "conference SOW'S THE QUALITY? room "; the master clock. gong, and program 'l'une quality Is ton precious to sacrifice. It should I . . . . with a Small Inventory machines are in the office. The speaker be your first enn.ideration In purchasing condenser second microphones. It Is the first consideration of Chri sell- :I and located is the best Volume Control Proposi- telektor are on the roof. while Acoustic Laboratories in building them. That Is Here the third speaker and telektor, together with by we can say "Compare the ('hrhell -A roost it tion on the Market. Here are the reasons the second gong. are located in the "apart- microphone with any other. evene at twice III.. price. lour money refunded if you a mien., . c of why? ment." better tone quality." 1. Over 400 "exact duplicate" controls The speaker selector relays which are to -WE ARE PROUD OF OUR PRODUCT9- 1hß . we kmw r..k L.r .Lill. ,i.,. . ; 1 in the "X' series. rated on the fluor below the apartment and 2. Yet with SIX controls in the origi- /dikes are shown in Fig. U. The eomplien- of from nal-AD - A - SWITCH - SERIES 477 tlons the installation are apparent bmllt, p,r.-ii.m l.lm,d lit :ul. sets can be serviced. this photograph. You will note that there la.qmered abu.hum shrll sbields a b.., are twine armored cables running from these reaneaner < I..1..-: , I in both erated. Itei.,.. 1 ^^ \!! 3. By combining controls t hr..e relays with the associated con necb lr . requirement can be met tiwuy. I lines any . black. .., with minimum stock investment. The Three Outlets ply. Very a.tr.r. pu., AAi. - F" Ì; describing this ,nle,.,,, . i`r ,L;,` in- 1 4. Clarostat with its two separate .ts ire mentioned before. three speakers cluding bu1I,1-y our-ow n kits. Folder It.\' lines offers the widest range of with their associated telektor units make up CHRISELL-ACOUSTIC LABORATORIES L9260 Filth Avenue 8rooklyn, N. V.1 controls to choose from. the remote control feature of the installation. 5. Clarostat Controls are inseparable The mechanical installation of these speakers from Quality Service Work. f: novel. The radio Set, shown in Fig. E, one Sr TO COAST itA.t". COAST TO COAST R- ,IO fi flares( at "X" line has over 900 controls to choose from reproducer and the telektor unit shown In CONTAINS TOO MGMÿ taper. bushing Fig, located / S.000 LISTINGS 2.000 NEW r -exact as to electrical overall resistance. A, are in the "conference room," ILLUSTRATIONS shaft length, and will fit Into exact space In set. VALUASLI However, the tuning controls on the receiver DIAGRAMSNAME US TORE Ti Clarostat Ad- A- Switch line comprises the maximum are never touched as the location of the telek- M/IpRYAIrrAJ 5a5 RUILIC O ut pity with minimum stock investment. Series W (Wire A00RESS AMPLIFIERS isoln Wound) obtainable from 50 to 50.000 ohms. Series C tor box is much more convenient. Those who EQUIPMENT, IO (new composition element obtainable from 10!100 to have read the previous article describing the 5.000,000 ohms. Ihnh lines obi a Liable in all tapers - insulated shaft 115" long. With r Is indicated as fol- telektor system know how simple It is to lows: tV -28 will service 12s so -: ._e will service 106 turn the set on and tune to the stations for Ind v; LV -29, 77 sets; C-59, ,.,, nr., etc. which the unit has been set. COAST-TO-COAST- RA IO-CORPORATION. inn wfrr.r.STnr, - -_ -__ NEw vOe,,,N.v _O rR9 NEW CONTROL The second speaker is located on the roof. REPLACEMENT GUIDE midway between the gymnasium and the roof THE CONSOLIDATED OFFICIAL RADIO SER- ON REQUEST garden. As shown in Fig. F. it is equipped VICE MANUAL is the only complete, right -up. to- the. with a long cable which winds itself auto - minute ONE VOLUME BOOK on radio servicing. CLAROSTAT MFG. CO., INC. on a reel. feet of 3 It contains over 2300 pages. over matically spring Thirty 5.500 diagrams, charts and 2117 N r.rth 11th Street. Brooklyn. N. Y. conductor cable are provided on the reel, and photos. At .A -A55! l.'ll was originated by ClarostaL Full details about this great book will be (Continued on paye 301) found on page 262.

298 RADIO -CRAFT for NOVEMBER, 1933 should be no signals hearil in a pair of phones RADIO REVIEW connected, as shown in dotted lines, to the ,Iinn,d fion page _05) center-tap. Z, of resistors ltlx and 1119 across the output transformer. This arrangement the amplifier. It will be noticed that one Is virtually the same as in the first stole°, of the type :,fi tubes. VS, lias its grid con- except that the heavy plate current of the nected. through C. into the cathode circuit output stage is prevented from flowing of the diode- triode. V1. As the current haw- through the phones, the point Z being at ing in this circuit is 180 degrees out of the same .\.t', potential as the center -tap phase with that in the plate circuit, the of the primary of the output transformer. necessary phase opposition is achieved, - It Is interesting to note that If 119 is Editor). varied, so that an oat -of- balance of, say, 20 These in turn, drive a pair of 47 type per cenI 1s produced to guessi instability la pentodes. 'rite 200 ohm ai rewound resistor noticed lin its effect on the quality of repro - is called neon carry a ta fairly heavy cur- ductlon, and if this value is exceeded motor - rent. and on this account needs to be rated boating will set in, especially when the ampli- to carry 100 nut. The remainder of the fier Is working as a local-station receiver. resisters should be of 1 W. sire. The values of parts for the set are a- N.U. Scientist Perfects (tenders will nut ire that the tube types foliows: 'rubes - 11114's In the first stag,. mentioned are the sanie as the American with 1'X4 output tubes t not obtainable in types. American tubes are used almost ex- the i'. F.i : however. other [Horn nvnilai.: Ultra Violet Lamp clusively in .\ust ralia.- fiditer). tubes may he used. Resistors l'1, 1'2, -at. 011111 potenti dens: TRI. 112, ROO ohms; 115, 250 ohms: 114, :í10 ehnts : 115, 4011 ohnis Special The : Installations Seen As international Radio Review Rh, 117. Ií15, ^n.nno lites: its, RIO. 1112, 'l'IIL April and May, 1[1:11, Issues of RADIO- lais, 1114. 1117, 12I. .4.- nughom : 1:11. 311,111111 Money Maker for Service Men I ('a.i r we described ii radio receiver de- ohms : 1111. 2 legel0us : RIO, 20.(1011 ohms; signed by the British Broadcasting I'oin- Ills, 1119. 1:22. I._ -. 10.0110 ohms; 1120. 1121, Chief Engineer, Dr. E. A. Lederer of National pany's vie:Meer :s (which was made to produce 100 ohms: 1 :25, lu ohms. Condensers l'1, Union has developed a constant source of vital ultra violet wave as nearly prefect quality fis possible. The 1'2, 1112 -1114 ; l'::, t'4. (6, 2 inf.; t'.,, .all -mf. ; lengths in the new Lederer Ultra Violet lamp types D -30 and X -30 announced this descript fou of C7, .115-mf.: ('N, :0)0 nanti. ; C9. C10, this receiver ,rivaled such 309 month by National VitaLite Corporation, affiliated ('11, ; marked i u t crest that we are sure many of mint.; 100 moat. ('12, .01 -mf. with National Union Radio Corporation. our renders will be pleased to study the These lamps are the crowning achievement of two new circuit of this simplified "Perfect generations of scientists. Work on the Lederer (Quality" receiver, which appeared recently THE "RESONATOR" lamps was started in Vienna, Austria. about 1910 in WIRE!ti ss \ \'oln.u. London. England.nd. by Dr. Anton Lederer, father of National Union's The diagram. Fig. si is the general (continued front pape 2091 Dr. E. A. Lederer. The developmental work was arrangement of the set it Is not proposed picked up by Dr. E. A. Lederer at the time of his of pitch. in this instance, father's death in 1932. a tu deal with the power unit as this unit a tuning fork) With background of over a Ions experience with Westinghouse in vacuum follows tonventinu and an of test tube, and pouring monitory tube and gives output or water tube: lamp engineering, dating back to 1921, the son ,Lau i'., filtered D.C. into the there conies a moment when the tube vibrates very was well equipped to carry through the father's The debstar arrangements are also quite strongly work. Applying his highly and considerably reinforces sound specialized modern normal and the lt.F, side is designed to the which radio knowledge against the background of his Is being by the diapason. r°cei ve only two local English stations; a produced If one father's hundreds of experiments, Dr. E. A. Led- continues pouring the liquid, system erer produced two single- circuit tuner was used, this bring de- the types of lamps approaching the stops resonating ideal for ultra violet wave Both lamps normal, and the It. F. side is designed at the fundamental fre- production. to quency of the diapason are the same in basic construction, the difference Arable because the receiver was designed but reinforces, in for succession. other musical being in the kind of glass used in the bulb. fixed tuning, switching from one station to notes which are the odd harmonics of the fundamental note. The Lederer D -30 is a medium fast tanning lamp the other being accomplished by relays which and the X.30 a .\ similar experiment may be demonstrated fast tanning lamp. They operate switch in fixed condensers. at low voltage and therefore require the Lederer by using as the resonator a two- section In order to obtain push -pull operation from pipe Type T -30 Transformer to permit use on 110 volt open at both ends and sliding one section 60 cycle a pair of output V1teuunt tubes it is necessary alternating house current. back and forth inside the other. In this to introdtee a "lag" of ISO degrees in The Ultra Violet waves are produced when a rare the manner it is possible to reinforce grid voltage of one of them so that the entire gas with which the lamps are filled comes in con- it will sequence of harmonies tact work opposite the other. In other words the of the funda- with mercury vapor created by heat from the mental note. It is In the application of two electrodes in the bulb. when one grid ris..ives a positive impulse, these general principles upon which are hosed The Lederer lamps are safe and as easy the other sh,rnld rerelVe a negative one. With to operate tnnuy musloal instruments such as the key - as an ordinary house bulb. the usual . \.I', transformer type of coupling. bugle, saxophone, trombone, clarinet, flute, Individual parts can be purchased this is easily obtained by using a center- separately so limiting horn. organ- etc. that with a few necessary parts the tapped transformer. but. where resistance service man In passing, it may be well can make special home installation at a minimum coupling Is used. this eau be to mention that effected by tak- a very narrow pipe resonates only cost. ing advantage of the priniiple the A.C. to the that harmonics of the exeltilig sound broad Every service man should investigate as a source voltage component on the plaste of while all ampli- pipes resonate only at the fundamental fre- of additional revenue. fying tube is 180 degrees out of phase with quency ; organ plows reinforce Further details will be supplied upon request ad- that on the only the funda- grid. mental sound. 'l'he the d d to National VitaLite Corporation, 400 Tho input Voltage timbre of exciting Madison Avenue, New York, is applied. therefore, to sound is materially changed by the N. Y. the grid of one tube. say to point charac- Y in the teristics of the resonating system and tiffs diagram, and a portion I case lit this about modification is dependent upon the following 4 per vent 1 of Voltage. the amplified which factors: (1) The shape of the hollow in SHOP EQUIPMENT is now Is,) degrees out of phase. Is coupled, the pipe; the rigidity of Its sides; the in- through f'3. Into the control -grid circuit of ternal polish of the pipe: and FREE THRU N. U. the second °hala of amplifying the ratio be- tubes. Tilts tween the diameter and the length of the is accompli shed by ha piling off a portion of pipes. National Union offers the new Hickok Simplex the Voltage difference between the tube plates Portable Tube Tester, an Automobile Radio Ser- Most reproducers have a number of dead of the first stage by means of potentiometer vice Manual, Supreme Model 333 Combination spots at the high -frequency end of scale Set Analyzer and litt. the Resistance T , three Radio at which the sound output is so feeble Service Manuals, ABC Unameter 'fhe suceess of of as to Tube Tester. the operation the am- considerably change the timbre of reproduc- Oscillator and Output Meter, Bench Kit Box and plifier depends on the correct balancing of tion. This is particularly a Readrite Tube Tester, FREE with purchase of noticeable when National the circuits-that is to say. considering the listening to vocal and instrumental soloists. Union tubes. Deposit on some items. first stage, the audio frequency Send coupon for full details. voltage on However, it is possible to build a system the of one grid tube must be equal and of resonators so designed as to reinforce opposite to the A.F. grid voltage on the these particular weak points in the repro- For your convenience -National Union other. If this is done, the A.F. voltages on duction. jobbers stocks are complete! types the plates of these tubes will be equal and A big step forward in this All at opposite proriding direction was in phase, that the amplifi- Dr, Volf's use of a dynamic reproducer all times. of each in cation tube with its associated con- conjunction with an exponential horn nod densers and resistors is the sanie. a resonating system. as described be Laur- similar remarks. of curse, apply to the All offers subject to withdrawal without ence M. Cockaday in the article, "Near 1 oe- output tubes. If correct balance is attained velopments in Reproducers," which appeared notice! In this part of the circuit. there should be in the May, 19 :10 issue of ItAD10- ('aAFT. no .\.F. u ur'eIl is in the common positive feed More recently, there tins been developed a National Union Radio Corporation to any stage: or in the common negative system of resonating tubes which of N. Y. corre- 400 Madison Ave.. New York, N. Y. feed frn,,a the stage. This is easily tested spond precisely In their fundamental fre- in the first stage by the insertion of a pair Gentlemen, quencies with the notes of the chromatic Tell , o how I can take ad- of phones at the point X, and the potentio- scale, and a standard Vantaxe of yuur equipment offers. dynamic reproducer, RC11 meter 129 is moved so that a minimum signal as illustrated in Fig. A. A more detailed is heard NAME in the phones, the tubes having been illustration is Fig. 2, which shews the man- temporarily removed from their sockets. If, ner in which the dynamic reproducer is placed STREET now, the tubes are replaced and if each am- In relation to the resonating tubes. As CITY plifies the signal to the same extent, there shown In Fig. 2, the reproducer is placed STATE RADIO -CRAFT for NOVEMBER, 1933 299 ou a horizontal baffle in such a marner that

I h.. Sound waves, heaving the front of the mom. tue ca11Sed to directly actuate a bank Another TRUMAN r.f high -frequency resonant tubes placed RADIOft1934 Fee; ly abo ce. 'i'br tore- frequency output from the opposite .ide of the conical di:ynhtmgnt AUTO MODEL NO SERVICEMAN DEALER Nets into Libra t ion it Set tif low-f resiliency lithos located at the periphery of the battle. OR SET BUILDER CAN AFFORD 'l'he relation of these two sets Of tubes is 7-TUBE SUPER understood by euutp:uitig the front i'russ- 6" Speaker Seel iuu View, .1, wit It the side rroSS- SCIti11n TO BE WITHOUT THIS BOOK View. It. Ruth Sels of I lilies arc Id:Wed List Price R 15.00 p:tallel lo each lit hrr :Ind in a vertical Send for the most plane: the relation of each taire With regard Short Wave and Broadcast Midgets cone e:Illnlold,d Sil Ihat it Torre valuable book in to the is Write for Dealers' Discounts Radio. Packed .p tiuds lo the best persil ion in which It iS 1 of musical with quality and Ili be Ilriceu tubes Ilrieltbit'iag tai titionriez tuer e,1 :11,11 1111 S3'111111111 Ilea ex- TRUMAN RADIO SHOP value. Lists the tremities. In this way there is no lose of 7443 STEWART CHICAGO, ILL. most complete sound eul't and. on niionut of Ille length line of radio re- Of the re"siting tube, them e:tll be no stir of Sourd. placement parts ill le Iitsve,ti Iwo err. MAKE A LOUD SPEAKER SYSTEM for any service re- out a any Radio Sit haling a pal. aragtaph ro 'l'he aeons( rumpling bel weer I upper it if --- - MODEL CRXF quirement. Fea- :utl Imier .oued- choulber5, 4.'1 and 1'2. ri' ttnsts:s of n hit otduote. tures latest type spectively, and both vets (if resonators, um3' atoll enter. (idiotic ,oilr,.l uJ b :atel, ,ita,ti' ;ti' set -building kits, tory: it is only necessary 111 bauge the ar ly a ,darned in a test instruments, ptisil ion of a mtiriug il It that 4111s1 it Iles Long and Short the "Iltior' tri the tipper ria other and the Wave Radios, "coil ils)" tit the looser eu,, \\'iih t hr a(rn'e- tnentitiur,l design I he dy nttulil Bris iflu 11 11 ií I h,aii a a Sound Systems, retults. Na. reduced to is uv11'kiug in aI ulosrq tu'i'a : '11141 the etc. for this $ .50 List. Write fu11tI 11111s :IS a Piston. '1'114 resonating standard FREE Catalog to- er of the )i .bi' :tit tnlss required tu all the notes UNIVERSAL day! r y in Sire from ltd ft. for piano scale range t Microphone CO.. Ltd. low 1' G12 rye les t to 'a -ft. for :1 In the I 020 Warren Lane, Inglewood, Calif.. U. S. A. 4, SiNth oc0l ye 1 : :.: :.1-I cycles ALLIED RADIO CORP., .11thongh this reproducer design may be Dept. D, 811 W. Jackson Blvd. used in small models, hest results are ob- World -WideTwoTubeShortWaveReceiver 12.500 5llle nit-cotton re Chicago, Illinois. tained ts'hn the lust rntntut is designed for rd e.lablóhc,1' Trio $4,75re, O Please send me FREE your New 1934 a polder input to the motor Unit of about 5 from 13 a Jeu 31, Radio Book. W., minimum. l'or best reproduction of the Get, tr,o iem hr'liti'.t r'liee ,:ill. ,irelane,. err, t n. agi Irai) very low notes, the optimum height for the 1411í1:4"I" d Ili(. aI I't Imo demi tubes must be used. 'i'hus, the tinkled re- ..II. clear 4 ,, >lla. i..: t baud this u,,. b ini,,- r h h $0.75 may range in size Trou Ina sua 11 Address pruduret 'l 01 , !ti'' ode; .1 a instrument illustrated in 1.12..1, which urea. - d r. i :rrtrrr C.O.D. Satin! nnm GM. ,1 air rdl City ures :14 x -lu ins. high. Irt larger models Send for FREE Short Wave Catalog measuring about .l x Iii ins, high. Conse- Harrison Radio Co.. Dept. R11. 102 Liberty St., N.Y.C. quently, the Ilsonalnr loudspeaker, as rle- .iined at present. is best adapted for us, in theatres, hails. and wherever rise (lies, PIos PAG E f:l et ors of large dimensions :nml high power output are desirable turd convenient. A p:u- I933 RADIO tiettlarly satisfactory installation of a resonator reproducer includes the use of i is,, dit CATAaepplets with BARGAINS GALOREo for ielent units, one dasigud L'or voice r.pi...lnr- DEALERS ^ SERVICEMEN -A MATE URS lion and the other for orchestral frequencies. Send for Your Cop TODAY .1 tine musical instrument may be nmldr bp TRY -MO RADIO :F: 81CCe°erL(tND?}T Dept. C. ..ontbiuiug a resonator reproducer with it high quality microphone, an A.P. amplifier. is what everybody says and it harmonium of gaol quality with 24 SERVICEMEN! slops, ! kty -boau'ds. and a pedal. Such an THE MOST COMPLETE LINE OF CONDENSERS when they read this letter RESISTORS FOR EVERY RADIO USE runugtt iras the avinstic NMI lily and power AND isst Writs for our now . -pan Cabog folder cree 01 charge output of it i:u'ge organ of whirl', with its J. T. W A R I N G / dr,uhle key. board. ped :t1 11Peration, oar.. it ISO Southern Blvd. N. Y. C. has the outward appearance. Still, It has for .lulu 21 -t. 1333 of amplitude., Mr. Arthur 11. Lynch, the pla3'er a larger variation Lyn,rb MN. Co., Inv. than can be obtained in the ordinary organ I 51 Percy Ht.. N. Y. C. by operation of tune tout rois in Dear \I r. Lynch: also, the v: 7i Washington Strwt Brooklyn. N. Y. It is not this writer's cut - the ei.,- triral 61,111ís, It is pussibla tu n'y lour In hand ion !lottery the tone quality within wide limits. 'I'h, phrases 1 or nupllnsent, Pro- smite ideas may Ile applied to an to factiously. 1 Roo ever. your general I rodmrl- : po, it14ely THE ordinary piano. lent at'rtim: it into what SERVICE MEN: New! EX. beet that we have eier used. might be aptly t,r11e11 :1 "Saper' Ilin11u. We hale been engaged In STAT 20 -watt wire -wound re- research ork on sistors. Same size as ordinary dal powerplayer a plltler-art tit lilts 1ng Class 'A" l'riiu Am. 3 -watt resistors. Post card to- plmratiol In so doing hate expel lowed lsiderahle day brings bulletin. tutti, uhy i;l I Nina nisi did.. A NEW OSCILLATOR Tilton Manufacturing Co that we (hate been using. Ito, etti y. brnverrr. u tit itched 17 East 26th Street, New York to l.ymh Iteslhm rand It it pleasure to Inform you that wei e than pleased icllh eeulls. With lie_, wishes for con-un rtinrenill with Ih, 1_n0u kt. and 1.5011 s GET THE tinued test I'rrqueliies. The ha rmonilS of the 1,111111 gIG RADIO CATALOG Very trulyiii liv. f Now, uy' aine nom vomi rent ly I Megacycle (Signed) J. 'T'ur\t'at litt IN 148 BIG PAGES SI. that il is 11:1 11113: 10 cart testing a1111 -THE RADIO SUPPLY WORLD apart. , lost out fer 1.0'11. \lake a fu, it em libration nl _.111111 hr 11111 the receiver. Healer S, oors. Es; ut eli :;111111 `eletterheads. Outre ro A. r liait Lis ent Wit 11 1111. )oirai lurnterl. 1 h ke. rnlibra- sinalvtle t!a lis IL e. i Sua, 'y , sh iconic Point. 1itil is Itic:ut11 trout I he tbi rd lm calmir of the 4.111111 CO. OEM I,rlru kr, test 111,1 e '1ti win tiiS polit. BURSTEIN -APPLEBEE Dept. A.1 1012 McGee St. KANSAS CITY. MO. Universally Accepted the Seirrlor dial 11111 be e11:11lgrd lu 1.:.110 Sc. where the BEST is 14 e if the se emol harmonie tif this note is standard beard at the .nlo,/ point on the receiver dial. 'l'he S,br1,0' i- m -set :u 1.n1111 kr. and do- Prices of LYNCH Resistors :0111111 011 un the to Jobbers, Dealers and -moot Re. :nid Re. points rr- astliv!! Servicemen no higher than e, i c,.r d i a l l io n toil. At uJnm kc., the actual S ÚRE T`°44 t prices of ordinary resistors. I_ ret achy ell again he dWiuitrly eSlablishwl by itriug 640h the 1!I011 and 1.:5011 kv. inter MICRO;P ONES l4 be 11.1' Ulin of the actual hatDOUie flint Is Free Descriptiot Folder Upon Request - l 11eim1Z used. '''his convenient method of elleek- SHUPE BROTHERS COMPANY LYNCH ine the order of the harmonie being used MANUFACTURING CO.Inc. MICR( 4111 NIS crises 7Ma 51 Vesey el tumuli tes tally possible errors due to the ad-- Street', NewYorh, NY taking of :guidons responses of the receiver 2IS WEST MINOR ST. CIIICAGO. ILLINOIS

I for net mal ha rmmtli1, of the oscillator.

300 RADIO-CRAFT for NOVEMBER, 1933 the beirar'ior of the set moist be observera in A RADIO ROBOT the ¿whin'''. Also these tests toast be made A N N O U N C I N G (Con Nei:id )coo" any, _as) with the ground connection on. sine,. then an additional 50 -foot cable may be attached the antenna will absorb the same amount of Triplett Fine Instruments so that the speaker may be moved to any part energy as it will in actual use. of the spacious roof. The telektor unit is The resistor ilI in the grid return of the .at detector stage &"'° prOvided with n 1I) foot. flat canvas connec- is an important item in the Í tor strip and may be used either in the roof limit adjustment of oscillations. This is garden. or the outdoor or indoor gymnasiums. knutt-n as a suppressor and serves to isolate ' T F you choose precision in- by passing it through the small doors pro- the detector grid circuit. Values up to 1 struments on the basis of vided for tilts purpose. r ¡ -uug. may be tried. 'l'oo small a value The third speaker is heated in ML, Powers' may result in incidental oscillations and too r their features and perform- apartment and is cleverly installed in the large a value will male regeneration threugh- ance, you will find that Triplett wall so that it may be heard either in the out the range impossible. In the particular Instruments val- bedroom or the hallway leading to the bath. set tried, about 7:,000 Maus proved to be are outstanding It was originally planned to install Individual the best value. ues. Competitive tests and a point speakers in these two 1oems. but this phut The regeneration coil, become of accidental by point analysis prove their su- was abandoned when it was diieovered that coupling between the plue and grid circuits, the fourth speaker would complicate the in- will permit controlled oscillations throughout periority. These instruments are stallation n great deal. a large inlet of the tuning range no matter advanced in design, rugged in A compromise was made by installing celo- where it is mounted, but in order fo obtain tex -lined doors in the wall behind the bed- oseillat ions at the loir -f eminency end it iß construction, absolutely depend- room speaker, so that the programs ...alai be tr rr'.++w rp to hare it ca rep i..l close to lier prid able, give the close readings re- heard In the bathroom when desired. by sim- coil of the del eel ,o' as p rra iwusly described. quired for fine work and are ply opening the doors. This arrangement is ']'hen too it will be ncee -s:n'v to try reversing shown clearly in Fig. G. the leads from It tu the potent iotneter tu make popularly priced. Figure II shows the roof speaker and telek- the set regenerate at the luta- frequency end. tor units i operation in the roof garden. .\fier these tests are completed fasten the Triplett Electrical Measuring Instru- Beth units slide through the doorway shuwn cluisais in the cabinet and assemble the bat- ments are made in a complete range of t., the right of the speaker.er. The small open- tery box. There must be right holes in the sizes: 2 ", 31 ", 5% " -in A.C. and D.C. ing within this doorway permits the telektor back Of the bluter,¿ box te areotnmodate the voltmeters, ammeters, milliammeters, to be moved into the roof tennis court,. eight battery lends coming down fries the millivoltmeters and D.C. micro- ammet- In commenting nbont his radio Installation, chassis, These leads are tu be out as short ers. Triplett also offers thermo- couple Mr. Powers said that it was worth at least as convenient. Insert all batteries, tanking and copper -oxide A.C. Universal instru- $1I1.000 to him and while the actual installa- sure to wedge them its with small pieces of ments tion did not cost this much. it is evident from wool so that they will not slide around and and sensitive relays. The D.C. the description above that this complete radio short to one another. units are equipped with a D'Arsonval moving system cannot be compared with ordinary "The Proof of the Pudding coil, while the A.C. units are radio installations. ..." of the double iron repulsion type. Port- As the set is now, ready for use, its over- however, Mr. Powers is not yet satisfied able, flush and projection panel style all dimensions are approximately 12 x 12 X with the installation and has many ideas for cases are furnished. improving it. One of these Is to use the 5 ins.: it is easy tu carry it in an average- program machines for other purposes than size knapsack. Brass chest handles mounted Here are some of the superior features set on and awaken- on either side of the cabinet and a belt turning the radio and off stretched of these instruments: Sapphire jewels, ing him in the morning. Ile proposes to in- through them across the top makes a convenient arrangement for lifting the set. non -fatigue springs, extra light- moving stall a system in the penthouse so that the element, special steel magnet, windows to the sleeping porch will main auto- The first test of actual usage was made white matically at 10 P.M. and close at 6 A.M. in a canoe on heal Lake at Asbury Park, metal dials with extra long scales. Also. electric -steam heaters will automatically N. d.. where all the New York stations were start at 6 A.yi.. so that the roosts will be brought in with good loudspeaker volume. Your Jobber The set was mounted in the center of the Can Supply You heated when he arises. The electric -steam It will pay you radiator is con tens ila red because the build- boat and the end of the aerial who tied to to specify Triplett Fine ing's steam heat is not turned on until later. the handle of a canoe paddle jutting into the Instruments. Ask your jobber to show air from a position forward of the bow seat. them to you. Write for literature and At first, a trailer consisting of 25 ft. of bare additional information. copper braid with a sinker on the end was A.C. -D,C. SETS used for a ground. This proved hard to Triplett Electrical Instrument handle and continually caught on the bot- Co. tom of the lake. It was then found that 16 Main Street Bluffton, Ohio this assembly the rest t Ito box was built. fairly satisfactory reception was obtained the sides and bottons being screwed on, since with the whole trailer ciiiled tep in the bot- it is necessary tu drop the bottom in order tom of the boat. .lust barrio dipping the end to unscrew the chassis bolts. The inside di- of the troller trifle the sinker into the writer mensiens of the box were 4 x 41/2 x 9% ins., fn" le ell in i elm trebled the oalpn t, 'whirl, tram which was ample spar.. The choke was lam ers good as "rhea the f r, ilex was all fiii noun ted nt about the middle of the cabinet wag ant. Therefore all that is no. ossa ry for l,nt torn (note the top of the battery I,oxl and n "ground" in n beat is fem. or five feet of the filament ballast resistor cartridge holders wire with a sinker on the end. ou one of the ends. In Central ]'ark. New York, a test was Before final assembly it is necessary to made with the aerial wire strung over the Iliad: the oink up temporarily to adjust the limb of a small tree and a counterpoise con- timing condenser tri uuners. which is a minor sisting of about 20 ft. of wire stretched out matter, and also to adjust regeneration, tin the grossi, ]teen se of the absence of which is Vlore difficult. steel fra mewerks the signal intensity was about ten times as great as with a similar Sensitivity Control arrangement tried on the 12th story of ml Adjusting the regeneration, which deter- ¿Ilant't Men smoke (,¿:ilia' not more than 100 mines the sensitivity and, to a e)ti side rn l de yds. away! extent.. the ntput volume. resolves itself into two, ,jet's, namely: (a) getting rid of bici- List of (Additional) Parts nr denfai parasitic oscillations; and, (b) Une resistor, 75:000 ohms li - \ \'.. Ill : re- inserting controlled oscillations. TWO resistors meas.. 0.5-W., I:2. 1 :4 : Ineblentall useillauiens occur at the high - MO put rot ianu'ter with switch. 211.111111 Ohms, NO. 331 NO. 321 fregm,ney end of the tuning range with the 1:3 and Su'.: plates of the tuning condenser nearly all the Three ballast resistor cartridges, No. 4V- lt)t), MAIL TODAY FOP. DETAILS way ant. To s c if they are present it is It.l, I:O, It7 ; of course necessary to cut the regeneration Two cartridge condensers, ,05 -mf., 200 V., coil entirely out of the circuit. These useil- C4. C5; lan nun are caused by incorrect bypassing, I ne mica condenser, 250 nun f., C7: Triplett Electrical Instrument Co. and inadcq ua te isolation of the tuned circuits une mira condenser, Sou muff., ('S; 16 Main St., Bluffton, Ohio and the antenna circuit. One Ill'A detector plate choke (replacement Gentlemen: -Please send me catalog on Triplett An important thing to remember is that part for lied iolas 44, 40 and 47), 700 by., the set is to be used ii tin hiy in a cabinet. It.F.C.; Instruments. I an, interested in In one stage of the experimenting, a set Three 4 -prong sockets with mounting holes which would not stop os. illat ing at the high on IV, in. centers; Name frequency' end of the ratage wino the chassis Two type ::2 2 V. tubes. V1, V2; was outside the cabinet and gave good con- One type :t0 2 V. tube, VS; Street Address trolled regeneratino throughout the range, une 4!_. V. "t "' battery : would not Oscillate through more than halt One 3 V. flashlight battery; the tuning range when it was inserted In the Two 45 V. "ll" batteries; City cal,iuet! Therefore, after each adjustment One 3 V. "A" battery.

RADIO -CRAFT for NOVEMBER, I 9 3 3 301 SERVICING "TALKIES" WORLD'S FINEST PHOTO - INSTRUMENT (Co/di/11U(d fruut page 575) permit him to offer to the theatre, services and benefits which no one else has ever been able to make available at a reasonable cost. (5) To suggest methods of sales approach to both manager and projectionists, methods A -C -RADIO suited to their psychology turd problems, which will help the radio man to secure an TELEVISION audience, and to lay before those gentlemen, BIG BOOKS Every Electrical Subject C d in the most favorable possible light, the superior service's and assistance, mentioned Here's gr.al a nc t,'11.1. anybody int...... sled render. edi- above, which he is in a position to in Electricity. BRAND NEW 1933 Cover- 4 tion of Applied Elect riel ty In this installment current price lists brought right down to date with lug theatre parts and services will Ix fur- -L1 r FOR every NEW electrical subject nished, indicating to the radio dealer, just BEGINNERS big Volumes prices him to In all the World No Other Camera Like This! and EXPERTS fully covered. lo what will constitute fair for Over 3000 pages and all shipped FREE for ex- ask. of amination. -hundreds An outline of the more important factors The only Quick- Acting. Automatic Winding. Ground Illustrations - (ilass Standard F11111. n- of the above headings -an outline to be filled Focusing Causera unt Roll the most Goud for all punwses. No Separate or At- work of BIG FIELD! Big Demand in in greater detail iu subsequent articles Parts - t aclmnent s are Necessary! i1etskindever Men understand I follows below. P ul, l l shed. BIPag Y clear Icy are urgently Dynamos, Mo- needed right now in thousands of tors, p o w er industries. Autos. airplanes, ma- No Double Exposures with "PAL KO "1 1. The Nature of Sound Equipment stations. radi- chine Shops -pram 'rally even' Indus- t THINKS and COUNTS for you. Used by o television. try depends ini electricity and men enerything tier. who know this subject make big Essentially, and stripped of complications U. S. Government, Eilueat innai Experts and trical explained money. Pleasant. fascinating work, of every kind, sound equipment Is au audio Leading Publications. simple! I''si iveI De- clearly so any- ettoY to learn and do: learn quIckly amplifier. The complications, however, are pendable! 3 Cameras in One! "PAL Ell takes Olin can un- with these books. Send coupon for full postcard SA, or 2/d or 1/3 this size -19 derstand them. a set for FREE examination and more important than this simple feet. The pictur' of a six exposure film! we f r yourself. Input to this amplifier is drawn from three SAVINGS ON FILMS ALONE WILL A year's nsulting membership In the sources. One is an announcing microphone SOON American r Technical Ssx1ely now given PAY FOR "PAL KO" Cyclo- lin some theatres). .Another is a phonograph FREE free to all readers of this famous SATISFACTORY PERFORMANCE GUARANTEED pedia of Eleetrirtty. Many say. "That's pickup (now seldom 11811111. The third. and OR MONEY REFUNDED! north than cut of Looks." more by far the most important, is a photoelectric SOLD DIRECT FROM MANUFACTURER TO YOU AMERICAN TECHNICAL SOCIETY cell. A special lamp shines through the WRITE TODAY FOR FREE CATALOGUE Dept. E826, Drexel at 58th St., Chicago "sound track" at the side of the motion pic- AMERICAN TECHNICAL SOCIETY. ture film. As the film moves, the amount PAL KO, Inc. Dept. E826. Drexel st 58th St.. Chicago of illumination that can pass through the Send for to days' free u BRAND NEW 10 volume set 817 Wash. Blvd. CHICAGO Dept. R -2 of Electrical Engineering. In return for mailing this film and reach the "l'.E," cell changes at coupon promptly. send absolutely free certificate of mem- audio frequency; the corresponding changes bership in the American Technical Society entitling me in cell's output are amplified to free consulting privilege for one year. I will pay the the electrical Here's a book every Radio few cents delivery charges on the brooks, If I wish I may and supplied to loudspeakers. One complete return them in 10 days and owe you nothing. but If I "frame" of sound film is illustrated In Fig. It. Man will refer to dozens teen them I will send $2110 after 10 days. then 03.00 The same type of amplifier Is used in month until the special sale price of only 529.511 is paid of times every day- Name many theatres, but the number of loudspeak- Address ers in any given theatre depends upon its City State size and shape; therefore the amplifier out- Employed by put is commonly equipped with a tapped Address transformer or similar arrangement to meet the impedance requirements of any number of loudspeakers. Theatre amplifiers are commonly larger Try this FORMULA heavier you design or build that new Set Analyzer. and in construction than those WHENDecade Hoa, Bridge, Ohmmeter or High Resistance familiar to the radio man, and for conveni- Voltmeter why, not try this F'ORA11MA: ence in transportation and in making repairs t1 +A +MD PwwR are often divided into two or more parts. LC each of which Is called an amplifier. 'Thus When Q equal. QUALITY end A eouals ACCURACY MD equals MODERN DESIGN and I.0 equals LoW there may be as many as four amplifiers in COST and LAST COST then PW W It to always PRECI- cascade, all, naturally, constituting one large SION WIRE WOUND REStSTc1RS. a mplifìer. RESISTANCE RANGE: .25 Ohm to 1 Megohm fewer supplies vary greatly. Storage bat- TYPE "F" TYPE "D" teries and "H" batteries are still used, but Normal Rat - N,rm,al hat- are rapidly being replaced by rectifiers, which ing t''i watt --homld prove one fruitful source of income AIogiWuttt AI n u to A Length " Length the radio man. rectifier installation Al ai I m um Al a ni In to replace storage batteries in a sound system Diatoter Diameter will sell for several hundred dollars. Length of Length of One technical problem of great importance Leads 1's leads I' t" in Ilea l res, but not often troublesome in Fu shed Furnished with No. I5 with No. IS connection with radio receivers, is that of 'I'inned Tinned acoustics. More will be said of this later. Copper C o o p e r 1ead, Lad.. At present it is sufficient to note that sound tan air wave) travels at approximately 1,000 A Valuable RADIO BOOK! Free Booklets and Price List feet per second and is reflected by walls or HERE one radio book that answers Precision Custom Built Wire Wound other hard surface's. :At torch such reflection, every Resistors, Mfg. by the sound wave loses some of its energy. In conceivable question on interference. It the average living room. where walls may contains 76 pages. 8'_xl1 inches, chock full e, PRECISION RESISTOR CO. perhaps he ten feet apart, sound will undergo with wiring diagrams. drawings and photo- 334 Badger Ave. Newark, N. J. a hundred reflections per second and lose all graphs showing where interference originates its energy in that length of time. Conse- -how it is distributed, and how to eliminate quently, celw and reverberation give little it. This is a wealth of information needed by trouble in radio installations. But in a every radio listener, dealer and Service Man. STEWART -WARNER theatre, where the walls may be a hundred Send fifty cents in stamps or check for this book. feet apart. the sound, undergoing only ten FACTORY CO- OPERATION reflections per second. may retain its energy RADIO -CRAFT MAGAZINE and therefore its audibility for two or three 96 -98 Park Place New York, N. Y FOR SERVICE MEN seconds or more, confusing new sounds that Service meetings to be held all over country follow. This condition is known as reverb- by special factory radio field engineers. Com- eration and is sometimes very troublesome. plete diagram talk on new Stewart- Warner Its treatment will be described hereafter. circuits will show you the easy way to service Another technical problem, somewhat StewartWarner radio sets. Service manuals familiar to television enthusiasts, Is that of on all new Home and Auto Sets will be given free. controlling the speed of the motor which For time and place of meeting, write drives the sound film. If this speed is not Service held the frequency of the sound will shitt- ia, Department a of rt .ni.rnaan. b nnl»rw-electrical form distortion very annoying to the characteristic..Áao Üvr.periti.e.:.á are trained In STEWART -WARNER ear. Several methods are used to control m within t"TnT free.~ CORP. interestingI n.Tr iC.lR.a and `/Tr Trans- 1826 Diversey Parkway - e Chicago motor speed, some of which Include intricate om... i1vR"Pr.Ñ . 1JJp". pr r. vacuum tube circuits. az1 ParkviMvenueaÁLABORATORIES o ayne, Indiana

302 RADIO -CRAFT for NOVEMBER, 1933 2. The Theatre Manager. This is tilc ie111011 w'hn guards the por- Get Our Readers Say- tals of theta it business: his .dyttotume mr r/u "The RADIO -CRAFT INDEX makes it easy to nppro re hit per, riot's 1,r rn'derx for work r and the exact location of any article or topic be done. But he is a difficult man to ap- which appeared in RADIO -CRAFT. Without proach, being in general quite sophisticated. any loss of time, you can locate quickly, the article needed. This book is a big help to every if not hind boiled. lie uses extravagant sales radio man." eiii¡iila in his own business ton frequently to be nnuh impressed by anyone trying to sell him anything, however good the offer FREE may sound. Ile Is, however. very keenly on the lookout for every weans of cutting hi- Th Ea expenses or of insuring his equipment again breakdown. The key to his good I.0 service graces not be discussed nosy. After the bnckgruil r. 1t.111111-CItAFT of his business problems is made plain, l, proper method of approaching hint will I, come dear. BULLETINS! INDEX 3, The Projectionist, The approval of this gentleman is vital. IIe is officially responsible for the operai it n' It contains a thorough, alphabetical and topical arrangement of EVERY article and subject and condition of the equipment in the Fri which has been ublished in all the issues of jection booth. Moreover, he Is a responstlr Keep up -to -date on new facts RADIO-CRAFT from July, 1929 to June, 1932 person in every sense of the word. lu mar,ii states he is licensed only after a string... and methods discovered every Itaillo Niel) have eonelusively pro, rd to u. the need and examination. Ile deals with highly inflam- era.tirabtlly fur a book whiell ha. included In it a prehriui mr and complete Ming of emery article which ihas mable film, anti a moment's carelessness on month by other service men. Ilia. tar been published In lt.'1/l0- t'1t.t }T. .t hook his part can cost n hundred lives. Ile will nherb Ims .a h 101/1e SO sub -Jh ldcd :end s- Indexed not be pleased w'Itlr any who comes in that a glance at a whiert will give your any num- Lrr of cla sitiratinis and i 1,r It. Fur example. If proposing to .stony hint huIV to do his work : -Sylvania News" brings all the 011 look at tubs,e yout find , this tapir. various snh- but the fact remains that he can, in most t ille -. general. power. transmitting. Idpno-eells, testing latest news of radio sets and serv- of lobes. tai rams:, err. y:me entitle or make in the cases, use the cuoperat hull the local radio Mack has been emsidered sac deeply Important that myhrn man can supply, and will welcome it is icing. In every issue, there's a certain if it you refer to a classification. listed below the main offered tactfully. ' l'Ite problem of dealing tople. you sill find perhaps a dozen it more articles full page of useful servicing tips treating the -object foes different angles 'rile author in with hint is complicated by the fact that from men in earn ; Ilse is given the exalt issue In which the article some theatres employ nn loo projectionists, other your business. atNeared, and on what page It Is to be found. go a some, men umIt Fill in rustily compiled. by P. W. Pa litter, u e or radio's fore- and who are members of any and mail the coupon and writers. that In less than two minutes you can turnmost nuhttt. Most of the larger and wealthier you'll get this valuable service to any art isle- nee'lless to wade through all the Issues theatres employ union men. whose wllaries in or RADIO, RAFT wadi have hero published during the FREE each month. No obliga- past I tree years. the larger cities run to a hundred dollars a week or more. It is n fact that many tion . . it's a complimentary serv- The RADIO -CRAFT INDEX H exaetb' the same size as of these men learned what they know abort the monthly magazine -It has 21 pages. It con be con- ice offered by the makers of lenient ly kept .n ale with the routes of ate magazie electricity in the flays before sound came to ready for lui k reference. The Index Is printed on goad the theatre and have never acquired an easy Sylvania Tubes. paper with self voters. fantlliarily In dealing with vn(uunt udie This book I sold only by the publishers at 25 tho equipment. Not that they need help in run- And here's a chance to cash in on rulw. ]Fail -vnpon below for your roan' II the 11AD10- ning their ,lobs, for «bleb they are pall, but t'It.tpT INDEX. often they can use it, If it is of the right your experience, too! Send in Briefly outlined below appears only a partial kind, and properly offered. Approaching and your own servicing tips. For contents of the book dealing with these is a most vital factrue in every one that's printed in "Syl- securing theme business -one that will de- AMPLIFIERS - PATENTS- serve it full article, devoted to notlihm vania News," you get a free Syl- ANTENNA SYSTEMS - PHONOGRAPH REPRO- CABINETS- DUCTION A N D RE- and offering many concrete sugc vania Tube ( any type you select CIRCUITS - CORDING - to methods of approach. CODE- POWER SUPPLY AND up to S3.O0 in value!) COILS AND TUNING - BATTERIES - COMPONENTS- RECEPTION - 4. The Radio Man's Function in the COOPERATIVE LABORA REMOTE CONTROL - TORY- SELLING AND MONEY Theatre. DETECTORS AND MAKING SERVICING- RECTIFIERS - SET CONSTRUCTION - Why It is that, when the projertioai si :- EDUCATION SPEAKERS AND REPRO - INTERFERENCE- AND DUCERS- capable of making his own repairs Ile HUM ELIMINATION TELEVISION trained man's servicls will be helpful to him - AND - KINKS - TONE VOLUME (and can become indispensable) be MANUFACTURING - CONTROL - will not METERS AND TESTING TOOLS 11111, clear until after the peculiar nature of EST E D RADIO TU BE EQUIPMENT- - theatre business has been %4T TRANSFORMERS- discussed, and MISCELLANEOUS TRANSMISSION will be M O T I O N P I O T U R E - therefore explained more fully. AI A PRODUCT OF' HYCRADE RECORDING AND TRANSMITTERS - this point the radio reader may, if be Asir. SYLVANIA CORPORATION PROJECTION- TUBES- accept the statement that he can be of nit- MUSICAL INSTRU- LIST OF BROADCAST. vital service. as n subject to last. MENTS- SHORTWAVE AND fact. NEUTRALIZING - TELEVISION STA - elaboration. The crucial point is that mess. NOVELTIES- TIONS- to repair theatre equipment is not enoa_l ABSOLUTELY NOTHING WHICH HAS APPEARED it must be repaired. when it breaks doom n IN RADIO -CRAFT HAS BEEN OMITTED FROM is a great Inrr'ry. The radio teclmiei: THIS VALUABLE COMPILATION offers the theatre his experience, his metal his stork of parts, and his instant avallabi ti t., Clip and Mail Coupon Today! as a resident of the community. In aped instances no one but himself can give the 9 theatre all these advantages. MAIL COUPON TODAY! Pnbn'bers cf It.tl /TO-CRAFT, Ins' -I1 96.98 Park Place. New York. N. Y. 5. Sales Approach. Enclosed Son will find my remittance of 2 e (rherk. Hygrade Sylvania stamps or ',nney order accepted) for wldch you aare That the sales approach to the theatre Corp. A-4 tu end ate, -lige prepaid, of po mte copy must be tactful and not clumsy : that it Emporium, Pa. RADIO-CRAFT INDEX. should not be undertaken on the spur of the moment but carefully engineered with a full Dear knowledge of all the details of the sales Sirs: Naine resistance that normally will be encountered, Please put my name on the mailing should be sufficiently plain from the fore. Address going. Concrete suggestions will follow. list for your free radio bulletin. "Sylvania News." CRY Theatre Problems Are Interlocked I will be seen from the above that ninny Name Stale of the problems a radio technician may expect to encounter in seeking theatre business THIS BOOK CANNOT RE Address tl'AHT Interlock with each other: therefore it was Ill ON THE NEWS- thought STANDS - ONLY DIRECT well to preface a detailed discussion FROM THE PUBLISHERS 25c f each with this general outline. when City State THE COPY the subjects described above are taken singly In greater detail, reference to this outline

RADIO -CRAFT for NOVEMBER, 1933 303 should indi.mte how each of them relates to the others, and so make for more thorough understanding. But before any of them can he taken up fully It will also be necessary A conception of for the retteler to have some u..... that extraordinary nature of show busi Revelation which underlies them all. IN .lust as no one of the above subjects - some reference to lull.. Short Waves be made clear without et' miore of the sut hers, so none of them, not ,\1'n 1111' technical nature of the apparato. Ina adeuluately b. grasped without constant "Cooking By reference to the nnnsnal problems of tale theatre industry. The special nature of that Short Waves" Catalog industry is described below. mud should alrrtn.v he retimmItered through everything of1O, 000 that follows. The high prices paid by Complete Details in the November theatres for projection noon sipplls and issue of SHORT WAVE CRAFT RADIO labor. the psychology of the theatre manager :IS it 11ustuess 1111111. and malty other peculiari- ties the radio reader will find mentioned in FOR 25c A COPY BARGAINS: in without thin great the articles to follow, and will encounter Y.,11 ....III vet along es. Radio Bargain Itook Mare than la.unn practical t'ontatt with his local Meat Items are listed! Anything and everything are all .xpl11ined Ii3" the fort that the mown.- 'night eier tired is here! SETS. that you in rh'tusf¡1, ally different front T1 lIES. SPEAKERS. IcEl'l.a(F'yl ENT no, al huxinrxx !'.[ITS. K I 'ES. etc. F:h rev latest vieveluo- ,urn °tit,',' huxinrxx trh,tixuerf'E. Picot -Ev cry innovation at lowest whelesala prices! The butcher. baker and radio denier all limitermater what you want we have It. We sett tangible. r .rote alerrhaud ¡so, that can hare the target stock of ronlacemetd WW1, b' very kronen be carried away. that ran i.e weighed. meas- 1111 world-- u'pl :uruont pan, for radio \ set! Save time and money by totngtng 1n'etl. txam111Ni. 'l'ho then hr's tastuwers s to WiloLESALE RADIO your requitement e :n'ry nothing astray feu Its doors, unless SERVICEF. 'SHORT WAVE FANS! they carry it in their heads. The theatre If you're interested in Sher, Wave. he sure to sell oven its seats. It rents them of Bar- does not get this great raining. It lists hundreds being: time is what it sells. gains In Sets. Converters. Coils and Equipment. for the time Prominent makes such as NATIONAL. ll.tyl- and w-llut it gives in return for the nwWy rte.. are featured' MARIA 'NIL I.AFAYETTE, it takes is tt ntrrod --at very difficult thing Buy from this 12 ea old r moot -the ex- HOUSE OF RADIO ItELLUll LITY -where for the customer to weigh, measure or your satisfaction is guaranteed! uuthie'. 1 IoW 01111 the customer ever tell that NO CONNECTION WHATSOEVER WITH he is getting his money's worth? So many ANYOHER ! little things prevent hint from getting it. A inn mny ensily buy his admission and enter the theatre in a state of mind lleit prevents him from onto y -in_ the show. Dept. C -113 state of mind In w'hieh n man enters a rain.. your Big New Catalog to ma at once. Rush store doesn't matter .suite .so much, If he Naine bur's a tube. at least he eonss Out with the he buys tuentre enterhtinment Address I fake. lint If while he is in the wI wood to enjoy it. State -J he eo uus out with nothing and holds it - grudge against the theatre. Therefore the manager, unlike most other business men. mast ea.Ìale his customers before they bet: All 4 -Color Cor r Truly Remarkable Reception his customers: Must dress up his front with At 9 "sl2" in Site lights. anti al tractive Piet ores. put nnifnrats Large Newsstands Over 220 Illustrations "the DUMONT Aerial loll his cnshlrr :niel doorman, decorate his lobby. awl do aunty other of vestibule called the n['114.1- Increasing each tar are the number Static Eliminator ! things not thought of by other business men. 1'..a nowt + In the Nhon -wan. Colt -develoetm and i' loir tt c bringing tu this brunit of r,.ullo lhausand. ..f no Once the customer is inside small an- now .'thrill seekers." tahetimenter -. u in the rattly noya11ee fury Ile 110111111 1011. In the well It bier d,,n. of Itnr»» again hase the m bring :d.VE seats. .'bring inventions. Raga slime!' w'.tt'E theatres, the lighting. the carpets, the y..or the Experimenter's Magazine. barnNMI n [mild the drinking fountains. the rest rooms, the ow it shonw':ne set,. j,,''s re. eh eery lone of voice of the ushers. are given SHORT w'lti! U 1- es Ilu -i. r'. : !short-wave magazine -tire kind you have uL-he.l t long. minutest attention -thousands of Ilol- . illustration the lar. are spent on 1St tit slain. tO 0110 Ilot ill sun \\9 eliml- Feature Articles in the November Issue t he business, to be the merest trifle.. The w' It It natur theatre is Mashies, to make money, not Cooking With Short Waves. leads and it to away. hilt even a 51111111 annoy - attach- throw it The Short Wave Scouts- handsome trophy Plug :nmr may ipset the patron's ru,loytneut of meats cup given monthly -by Hugo Gernsback. st= f hat Inttnigible, uunlensarablc thing rolled entertainment, for which he has pawl his Ham and Yeggs, by W. H. Fraser- Short- Here at last is a device made to eliminate com- curie pletely man -made static, the typ of noises that so money, and then he is less likely to Wave Fiction. of eons often causes discomfort to radio e listeners. Quickly hack, a large proportion movie pat Phone Amateur Transmit- as everyone knows. Adding To The it reduces it to a minimum, disturbances caused by ire w al. Mid the lali..s. and diagrams, by electrical appliances and aerials of all descriptions, ore Sonletimrs very fussy about very slim11 ter-With full details and in reception with clear, and excellent Leonard Victor, W2DHN. brings titles, 111111 11111113" 1110401 by them. results. Can be connected in five minutes. Elimi- Radio nates all roof aerials. The mural of the above is that: a slight World's Tiniest Tube. mount is a crime: a distract- Service Men and Dealers add this money -making .11st..r1 ion in the A 4 -Tube "5 and 10 Meter Receiver - radio device to your line -install the Dumont ing noise in the sound is a sin: nod inlrr. with Optional Super Regeneration! By Eliminator in every home where you call to service Hirt i.,n of the show ix Ihioh frenxnn! .s George Shuart, W2AMN. the set. A lifetime of service is guaranteed for t hntre will o great length.. and spend every Dumont Eliminator. large sums, to avoid any of Ihuse things. The Best Short Wave Station List in Each Clip Coupon and Mail That Pict will be ,hearer svh.n it is realized Issue. that theatre busines s. Iike the baker's anti SPECIAL OFFER COUPON rDUMONT ELECTRIC COMPANY, Inc., RC untlil:e the radio unl's. i- . ss,nthtlly repent 453 Broome Street, New York, N. Y. bnsiuess -the vigil problem is "to make thew SHORT WAVE CRAFT RC -II 98 Park Place. New York. N. Y. Enclosed you will and cheek or looney order 611 " coon ba." lift dill'eriug from the bake- nouns of $2.81 (Regular 1.1,1 l'rtee $5.1i01. shop. the theatre does not purvey a necessity GET ACQUAINTED OFFER oMelt -end me. prepaid one Dumont Static Elba. n $1 00 Tor, with complete operating instructions. The problem of the baker is to insure that I As per your special Offer. T en.!. ''Roads his rust 1's will rturt to hint. instead of ml backn sl._ul fur which enter soh:rein, ion to 3 t enn. 'n Name SHORT WA t'l' EIt.s FT fur Il undrnuunl going to some other bakery. The problem 111,a \ :War ruile for a ad. -rip. ion is 1Y.5n.] Address Mail eopy'y of the theatre Industry is to make customers I 1 o mule Yd .snotty WAVE rlt.Ai"r 'Ity .tai' tome to the theatre at all. This is one of for ohick I enclose 15e W. S. st:wn. ur nui a,rpte.h. J why, in theatre code, a distract- the reasons N...nr ing nntse In the sound is a sit. and Interrup- Read the announcement on page 293 tion in the show unpardonable. It is also .td.!n - about the new OFFICIAL AUTO- one of the maSons Why advertising is of the RADIO SERVICE MANUAL. This most vital importance to show business mid is the greatest book of the year for why yon will ti nd the Manager, when yon Radio Service Men. go to see hint, touch more interested in the

304 RADIO -CRAFT for NOVEMBER, 1933 pictures he expects to dress his lobby with for the next show than in anything yon tan say about saving him money in the projection room. It hi also the reason why you SERVICE PROFITS In your community tnere are have a very good chance to sell him no dozens of electric refrigerators amplifier and loudspeaker to use outside his Ft'to be serviced. Many need im- front door for advertising purposes. which can be made mediate repairs High Treason -and Worse! ASSURED quickly, with little expense -and which WITH THE you can repair with the aid of this au- Theatre people say: "The show must go thoritative Refrigeration Service Man- tai" -flit," they mean it. The show meal RADIOTRON ual. Make many extra dollars, together on -one excell,ut t'insola is that if it doesn't RCA with other repair work. Electric refrig- the audience asks for its money hack. Non . CUNNINGHAM RADIO TUBE eration servicing is a well -paying busi- this is "e expensive in show business than ness -start in your spare time -before in any other. Because -if a dissatisfied cu-- will devote to it. One long you full time tomer brings hack 11 radio reeei ver, rind ask- SERVICE SYSTEM or two jobs pays the small cost of the for his money. the radio store loses a sale: OFFICIAL REFRIGERATION SERV- tuuugh. hilt least the that's had at it gets TIO 14 Olio ow, ICE MANUAL. receiver back, and eau sell it some other Data time. But when the theatre gives refund- 96 Pages of New to its patrons because the show lots stupprd. Have Been Added to the it gets nothing bath, for the theatre does not sell seats, but "time." and rents the seats for OFFICIAL REFRIGERATION the time involved in ono show. The next show is a new sl with new seats, or SERVICE MANUAL rather new time, to be sold. Ì'iwe is the To bring this useful service manual right theatre's stock in trade. 1111,1 it cannot be up -to -date. Mr. L. K. Wright, the editor of taken back when the customer is given his the OFFICIAL REFRIGERATION SERV- money back : the theatre that has to refmtd ICE MANUAL, has added a wealth of mn- admissions is In precisely the condition of terial on new electric refrigerators, and older models as well. As usual every re- it radio store that had to refund the price frigerator has been accurately described of a defective radio receiver -if the customer from the viewpoint of servicing-diagram, kept both the radio set and his money. It to illustrate the essential parts, so simpli- has lost part of its stock in trade without fied that repairs can easily be made. The any return. Therefore the show MUST go addition of these new pages will not in- be spent in crease the cost of the book to those who on. And whatever money must order their copy now. the projection room to see that it goes on, must be spent -if tubes cost $7.1, apiece. that's Mere Are Some of The Important Chapters: just too bad ; it's a lot cheaper to keep 8pares Introduction to the Refrigeration Servicing Rusin.0 Ucua to A arc a breakdown. 111 +tory of Ref, leeralion In these recent years of depression not all Fundamentals of ltrfrigerat ion as much as they usually Des.r lotion of All Known T5'pes of Refrigeration theatres have done Moto, do to avoid slight distractions to the patron: Troullie Shoot lug not all of them have done as mach as they FORM Unit Parts. Valves and Automatic Equipment of SERVICE ORDER \takes and Stur.ifirst Ions of l'nits usually do to Insure against interruption (Similar Form for Cunningham) Manufacturers of Pahlnel+ the en termin mcut: but the above describes Refrigerants atiii tutnntaW' Frill preens and Many condition of theatre operation In Other lmport.t I' I'Iw Deers the normal the United States, and a condition that has The-Service Order Form is one of been fairly well appruxituated even in these the most popular features of the hardest times. The chief difference the de- RCA Radiotron - Cunningham Ser- pr,- .scion has made is that G1rmerlp the man- vice System, comprising also a ager was so Interested In his advertising that Prospect, Sales and Service Record he ordered what he was told was the best Form, Service Billhead, Not -at -Home for his projection roost, and didn't care Service greatly if it cost a bit too mach. Now he bus Card, Service Post Cards, formed the habit of being ex traonlinau ily Advertising Mats and numerous keen to save any slight operating rust he other profit -building items. 1.1111- -hat 11111 at the expense of 10111101 annoy- ance or -above all-of a stop in his show. Thousands of dealers and service men are staking money on service, right this minute, with the aid of' CARBON MICROPHONES the Service Order Form. tritli,tut,l fro, u ,I,, 2'7 I This form offers the service man a latent determining optimum -t ;' -h "cot and simple, complete, accurate method try" is the best method, of making charges and recording 'l'hc 1111.11011 cups. Il and I are lilted half full of carbon grains. the grade dep,'tdenl on service work done. the use tu which it is to be put- Number CO IS lue0mtutnded for hard usage: Nit. SI) is Its very completeness stimulates the Used for general work and is selected in most service man to do a thorough job. instances: No. 100 is best for extremely high Space for "complaint" is a time quality reproduction. The latter packs quite saver because as many facts as Over 1,200 Diagrams easily and has at slightly higher background in advance. noise; and Is suitable for use where the possible are ascertained 450 Pages mieruphone is thoroughly protected from Flexible Looseleaf Binder bumps and vibr:ulula. Complete customer information is Figure 2 shows the procedure in filling the compressed into one line with the Complete Service Data button cups. A flat piece of glass is held use of symbols. cettirally, aillas the front of the button and lightly settle the Car- the button tapped fo 50 triplicate sets to a pad. Radio - Today! bon. The amount of grains can Ile viewed Mail Coupon and the same amount put in each one. If iron Item No. 319. Cunningham the pressure of the button felts un the dia- Form No. 1180. Price, imprinted. GERNSBACK PUBLICATIONS. Ins. ItC -ll phragm is equal, the buttons will be halaneed, with six sheets of carbon paper, 96 -98 Park Place. New York. N. Y. electrically. 3 pads for $1.25. I eranre harm ith my remittance fur f.,. no trhe,ß. The damping plate (l', in Fig. Il is spaced clames or Money order a tieutedt for ohich you of inch from e to send me. portage prepaid, copy of the from one to two thousandths nu PROMOTION DEPr.. R, C. OFFICIAL, IE'tt(IEtATI(S SRVItEE MAX - the diaphragm. If several grains of 111110111 R(lt, Camden, N. Jl 96 et new s..- 1 AL. together with the extra pares or dust are permitted to remain ou this, it is I enclose $1.:5 (cash) (check) (money terial at no extra test. obvious that they will touch the il ta pli t'a gill order). Send me 1 flet of Service Order and damp the movement. The damping plate Forma (3 pads). Same should be cleaned immediately before as- Dealer 0 RCA Radlotron sembling. Service Man D Cunningham The buttons replaced the micro. Address are and phone is again ready for an user- enthmia.Iie Name./ political speaker an excited orchestra It ;n h'r Street I 10 Slate or a utili neing sound truck to start it on its downward path. City State

RADIO -CRAFT for NOVEMBER, 1933 305 MAKING CHOKES, ETC. `Best for Every Test" (Crntlirnn,! New Model 401 _ the layer and continue the winding 111,01:10011. MULTITESTEIt Tapping the Transformer A Leader in Design -A Champion in Performance -A Winner in Price! it is much easier in taking laps ore tatoo windings to tank then( utT at the outside turn PRICE ONLY ¡rather than In bring theta from Within the . w-in11i110 1 and by Juggling the number of layer. 111111 the inrna per layer this 1.111 usun Ily s1500 I.. arronps11s11e,1. if the uunlber of hips needed NET i+ nut too great. This wIll, of rnuts,., htucr A Symbol fo be planned oat 110fore the eons inn he- Knock -Down t ins. If it is found necessary 10 bring 0111 THE Yule log-symbol of' Christ- KIT I a lis within the coil, great ea re should be mas through the ages. On the taken not to weaken the insulation. The great holiday the lord of' the manor (less batteries) tarn to be tapped should be pulled up slightly threw wide the doors, and misery Complete with and al strip of empire cloth pliteed under the and squalor were forgotten in the

Instructions 1 snot where 111. lead is to he soldered on. The cheer of the boar's head and was- .Vet to Dealers lead running out of floe eon should I.. in- sail. and Servicemen sulted with condole tubing nod ha r snips ut ugtir cloth 011 each side. Wiwi' I List the pri- Customs change, but the Christmas $27.50 m:n;y winding - IT:Ic leads herall« It wall never b tins been ronipl4Id, hind Ilu- spirit is ageless. Today millions ex- II excella in Performance because last turn in much the ',ante 11111 its be- fool dog, mealy. press it by the purchase of Christ- nuhker and better th.. fore; use n longer piece of tape for doubling other te,rs.te Nevertheless, the prlre Is lower mas Seals -the penny stickers that that of crlinary back, and a strip of adhesive 110111 testers. to it in fight tuberculosis -still the greatest This high -anal fly Instrument Includes a Triple Range place until the secondary binds if, Phi he Ohmmeter. 'a to 2 million ohms. ,.,lnplttely srlf- one public health problem. Your pennies or two layer. of empire viol 11 a reuuli talnrd; a rotor Range Voltmeter. d -5. 511. 2511 -75to Ile winding and fasten n will help. vt.olts. at loot ohms per olt; a Triple Range 311111 - it by small strip ammeter, 0- 5- 2111-750 mils. of tape around each side. If n static shield An Automat h Selector Switch Instantly connects to I, desired It ritt) Ile made of a very thin sii. -el the desired Hruit and range, at the sale lime dls- of copper etnnerting the Meter trout all other tHreuils and about % -lu wider than the wind ranges. This safety teal lire prevents short cin-u Its Ina and rut to a length such that it lacks and burn -ours. The meter employed Is a 3'0" approximately % -In. of clear auuu11d D'A rsonval type moving roll instrument. Ali urary going the primary. 'Phis, can be u Rhin 2 percent. A tapered compensator gives held in place while smooth zero adjustment on all ohmmeter ranges. one or IWO lay's of 1mpire Cloth are wrapped The 31011 lester Is mounted In an atlrael lee, com- over it and fastened In pine, with as little pact, . ry dal li ne finish case -Say "x$ "c xl ". Panel tap.' as is clearly ebbed. necessary. E't' i -I hiug is now In A set of high -grade test pant. BUY CHRISTMAS SEALS lh det.a bah le readiness to start winding the alligator spring clamps indu. le I sevulitia it 311.1Hmeter. with sAIdc11 is eoust'urt ed the saute ;Is 1114 primary. Assembled, wired and ready to use $20 net to deal - When eIs and servicemen. List $37.50. the winding is finished and bound completely, wrap IIle tfite coil with cotton THE "DEPENDABLE" TUBE TESTER tape, the wrapping being done perpendicular NEW MODEL 303A to the [vile. The roil is then immersed in a Will Always Be Upto -Date hot of Certainly It lest e en. e tube-Mole Ihall I:nl mixture beeswax and resin and slwh are w xtrd on the panel. Fut - boiled for fifteen minutes. The coil is again pro, He. for testing 50 more new completely wrapped. t 's oe Perpetually up- this line wil h sit lua tudale. it has Juan) (1140011 r res. rues high -quality 11'.trsnnr a or empire tape. Build the core up III mew. Teds all tulles more a as shown in l -rig. I rctely 1. it shtntped la titilla a Hulls amt erdeaa l orally. Only two sele,-tor of tills type are used, n Itches to adjud. Has short tester, moulded and slip pieces of - para0ined s.tkets imiuding large and small 7 -prong cardboard between the coil and ,Is, pllo sack - the light Indicator, gas test se, ond plate core. The coil can he tightened onto the Cure all r - Offers, line voltage a.bu.oncnt. heaut I_ by carefully driving Der r. I panel, light rompait. go,(l.a.king very narrow wet lges. .orying rase. from each side of the transformer, between the core and 818.75 net to dealers and servicemen-List $35 the cardboard. The core shun Ill Ah. :,a l lable in Knock Down Kit Form Com- br rery lightly Clumped to prevent excessive plete with Instructions $14.75 vibration: angle irons or bulls are suitable for this pit rpeso.

E free data sheets on complete line of test equipment, Mounting the Transformer RADIO CITY PRODUCTS CO. Utie of the ea siest and must effect two inetln- 4i1 Broadway West Dept. RC New York, N. Y. nds for mounting such a unit is to place it in n can .4i11ä(:11' l0 the type shown in 1.1g..%. .After the transformer Is placed in the Can. I Ile Pall should be filled with hot asphaltum I II or tesltl euulpound to seal the unit. The fol- SOLVED lowing table. I, of average design factors. Wave F,u.s _. md.1u1 .- :ices the desirable set -up for use in building of ford a teal mnerelat S.W. di na ry transformers of conservative ra ('anal is now offer- ling. Receiver, although the values can be varied up to ten log the international Pro- per fessional. A pmerful and cent, and still be within working limits. selectee. 'Jabotamn built 9 It is advisable to use single -cotton. enameled tube A.C. Narrt wave stoper- employs wire for this Class of work as it has beten.tgne. It a insulating high tuned 11. F. stage. instan- qualities and cannot be do nna gel taneous band spread. new as easily as plain enameled or plain double- dra r tv 1,e .ii ls. audioa C.W. o.a, elect ran coupled ose.. cot ton-covered 3 wa tt nonce and other professional tenures. Depend- wire. able world wale reception. Kit .r lahmana, 1, THE MAGAZINE OF SEX SCIENCE wired. Ile. tilled in November Radio News C J.a SEXOLOGY, foremost alurat lot sex magazine,agazine, lo J October short wave Craft. T.till.l: 1 I Average Design Faetorsl i'ri II en in simplet language and can he read by Write immediately for diagram description every member of the family. It Is Instruct He. en- fl! Rating Core. Sq. In. Wire Size Turns lightening and special offer to Radio Craft Readers. Watts Tuas /Volt -not a risque bark- eontalns no jargon \- Section PO. I'rl. l'rl. or sec. hevmtrd to st -levee of health Hygiene. LIBERTY ST. 50 Cunbdnni _, important POSTAL RADIO NEW YORK, 2.0 sq. In. 23 500 art Ivies on Sex Selene , Fa pages. oath luratee two -eolor cover. Itere are a 2 21 42.E 4.57 few of 100 the more Important art lu-les; ('regnant men: :.4 " " 20 350 3.1 R Sex Starvation; Cinmeelslon of Women: Men 1r Who 150 2.7 " 18 310 2.86 Suckle Infanta; Chunh and Sexual Rduration; xlen- r1 strnalIon In Monkeys; the Itirth of Stone Itabies; 200 3.3 18 295 Sex /trimes; TAUREX Meter Rectifier ti 2.52 A Boy or a Girl'!; Sexual Selection: 300 4.0 " 14 Control of Syphilis; Sexual I '. any D.C. Milliamnreter into a Sensitive 245 22 helriencies; Impotency A., ree at in Young Men; White Man Turns Negro. >l MADE FOR METERS -Size 11 In. by 400 4.4 " 13 etc. 190 1.75 Get a ropy ?¡. n FULLY GUARANTEED. " 61 of SEXOLOGY on any newsstand. or. 600 5.5 11 135 If your Fan be em! in Set Testers, Analyzers and for 1.23 dealer cannot supply you, send 25e in stamps 800 for a ropy f the many other purposes. See article on Universal 6.0 " " 10 120 1.09 current Issue. SEXOLOGY Analyzer in tha. Issue of Radio- Craft. TAUREX 1000 7.3 ' " 9 110 1.00 25R West Broadway Now York, N. Y. all he shipped postpaid promptly upon receipt of $5 hhe -k nr money -order -or order 13.0 D. and 1,:n Furnished Complete with Diagrams Although different transformers will require slightly varying Read - methods the Ti-. MASTERDIAL- Installed on your 0 to of eonstrur- announcement on page 260 t I t ion, by ,I n. n ter enables you to read Si exerting raue and discretion, highly about the new 1934 OFFICIAL I RADIO A. ( . .I ;I Voltage. Resistance and Capacity satisfactory transformers will result. itatLae.. ('rie $2.75 postpaid. SERVICE MANUAL. This is the great- Leo Tommie. 3245 37th St.. Lens Island City, N.Y. I'l'ls next article will cover A.F. trans- est book of the year for Radio Service formers.) Men.

306 RADIO -CRAFT for NOVEMBER, 1933 A 26 -W. "INTER- LOCKING" P.A. SYSTEM A Tip for SERVICE MEN THE name " ELECTRAD" on a replacement Resistor, Volume Control or the speaker field. Th,qefoi. it is recommended always meant the at the LOWEST that the semi rate ex t erna I speaker field exciter. Amplifier has HIGHEST QUALITY shown in Fig. I. be employed. POSSIBLE PRICE. ELECTRAD products were the best obtainable when radio This unit as shown at B in Fig. 8 is com- the best today result of pioneering and posed of a heavy -duty power transformer. was young, and they are -the nrra nged in a full -wave rectifying cir- specialization. cuit employing a type s:; mirez ry vapor recti- to fier V I(t I which produces sufficient current folly energize tiro t;.0(10 ohm field coils), together with a 15 hy-., 2110 olio[, 120 ma. choke Ten coil, Ch10, and an S uhf., 5u0 V.. dry electrolytic condenser. t_l. The latter two units remove all audible filter ripple from the Watts speaker fields. Flush -mount female receptacles RC3 and RC4 provide for convenient Plain an d switch covers in- connection of the two speaker fields to the of stantly interchangeable. exciter. snap nne nut and tir nth--r By using this special field exciter the versa- RESISTOR PERFECTION tility of the system is vastly increased. It l i e y The Handiest provides for the use of an additional speaker Ivre ssilz- ss.nund, it re,,Ins.cuanlele.l ter scatter that is compact, beautifully made, long - at any future time (if the initial purchase lived and remaille constant in resistance value. VOLUME CONTROL includes only one) without making any 'I'he price is so low there.is no longer any cx- changes, and also simplifies the installation ruse for using non- wirewound resistors of low Without distnrhing control of either one or two speakers at any distance wattage, when you can have the extra safety tions, ELECTRAD Replacemer.. .f. only voice -coil factor without extra cost. time' Controls may be converted to froni the amplifier, since the power- switch type merely by re- connections need be run from the amplifier he electrical industry has recognized vitreous the nameling as the finest type of insulation for moving the standard end -cover and to the speaker, while the 110 C., A.C. con- more than fifty years. snapping the switch assembly in its nections for the exciter may be taken from \lone) Metal contact hands and lugs resist psi. place. any A.C. outlet adjacent to the speaker. dation and eliminate expansion strains. Equipped Long. ALUMINUM shafts are easily IThe manner in which the accessories are also with pigtails. cut to desired length. Just five types connected to one another is illustrated in the ?itme type made in three .sites, three ratings and required to service 799 standard block diagram, Fig. 9.) 67 values. model receivers. It should he borne in mind that one of these exciters is required for every two speak- Irrite f)ept. RC -11 for If four or eight dynamic speakers VEST -POCKET FREE GENERAL CAT 4 ers; thus. LOG and VEST- POCKET are employed, then two or four excitera re- VOLUME VOLUME CONTROL spectively, must be used. Figure J shows GUIDE. how both the speaker exciter and miette, turn- CONTROL table power supply are temporarily mounted ITS Vertek et. New York. N7 in the cover of the speaker case. Both units GUIDE nee readily demountible for use at remote points. FREE Write for FREE Copy ELECTRAD lu conclusion, the writer expresses the hop.. that this unique and highly versatile 1'.. %. System will be the means whereby radio dealers and Service Men will considerably increase their incomes. either by entering, or by branching into the highly profitable "industry" of renting or selling P.A. amplifiers. The author will be pleased to answer any queries that ltxmo- Cass'r readers may address to his attention. The Source of Supply List of Parts FOR Input mixer control box One Remington double -button microphone transformer, type EdTO, Ti (me Iteniington photo. pickup transformer, type E670, T2: Two Electrad rheostats, 400 ohms. III, 112: AMPLIFYING EQUIPMENT Two Electrad moditied "T" type attenuators. 0.5- nleg.. 118, 114 Two D.P.l I.T. toggle switches, Sw. 1, Sw. 2, here you can get everything front the small Portable one S. P.S.T. towel,. switch. Sw. Public Address outfits to large Rack and Panel combina- One S.i'.II,T, toggle switch. Sw. 4: tions for theatres. auditoriums and schools. All. types, sizes and prices of units for indoor and outdoor fixed or One Remington time control, 'r(' of them carried regularly- in Reed ri te mill ismmeter, 0 =2:. ma.. \l2: movable installations -many One stock ready for immediate delivery. One :i-way polo rized plug and outlet. PP2; Mixing Panels, Transformers, Booster Devices. Cen- -Coast chassis; Misc. assemblies, Radio and Phonograph, Screen One Coast -to drilled tralized control equipment I ;rid . \tulio. Pentode Amplifiers and special hardware assortment. every unit in this wide well Phono. Motor Power Supply ouilt to order. Rack of WANT IT? balanced line k the Webster laboratory and the Webster One Remington power t ra nsformer, type 1,[70. and statements are de- (omit/etc ll'e('ster guarantee. Webster equipment pendable. One electrolytic condenser. 2,0110 mt.. C27: cofa top shereiun hale,' XII-11i, ltl ?I types of amplifiers ami i,oattions invited. Two copper -oxide rectifiers. type other nd equipment. RE2; eilt "l en regi,CSI. Two flush -mount female receptacles, RCl. RC2: One S.P.S.T. "on -off" switch, Sw. i; One fuse, 2 A., F2; THE WEBSTER COMPANY One Coast- tn- I.iast drilled eha ssls; >1i hardware assortment. Speaker Field Coil Exciter C H I CAG O, I LLI N O I S One Remington power transformer. type 1:. .. rT3; One Remington filter choke, type I1170, Chlo; One 3 mf. electrolytic condenser, ('28; Two female flush -mount receptacles, ItCS. RC4: BACK ISSUES OF RADIO -CRAFT One 20 ohm C.T. resistor, R20; which you might need to complete your files, can still be had at the price of 25: par c :ny. One S.P.S.T, toggle switch, Sw. 6; with your remittance in check or money order. One fuse, 2 A, F3; Send us your requirements, together New York, N. Y. One Coast -to -Coast drilled chassl ; Misr. RADIO -CRAFT 98 PARK PLACE hardware assortment.

RADIO -CRAFT for NOVEMBER, 1933 307 CAR -RADIO NOISE (Continuo,' from p,nfr 1g.v) CLASSIFIED Internal pickup. battery lead, remote control lead, etc. This should be minimized before ADVERTISEMENTS c. anything Is done about uecting or locating Ahrilnrauroi. Ilii; sr: are hurried the antenna. Shunt one of the "spare" con- ,.I of Issthe rots per rd tar each 7 h BRUNO SUPERIOR densers from the key side of the Ignition coil bailie. initials and address math count as t r t'ash .should arrwapany all classified advertbelt. t.. VELOCITY MIKE is "so su- to ground. Likewise try a connection from unless placed by a recognized advert lsing agency. No perior to the average micro- the gas indicator side: also, the battery side less than ten words are anteitted. Adserti.mg p,r hone used by amateurs the )/cumber 19:13 issue should be received nut later that of the coil, If It is a three -contact coil. Do than here is Ho amber 9th. comparison," says not try to connect a condenser from the mid- a well -known radio expert. of because, Excellent for public address point the coil to ground besides it studio. Rapidly replacing getting a nasty "shot in the arm." you will carbon mikes. Voices come "kill the motor." since high- tension current AUTO GENERATORS thru lifelike. Says Mir. goes through a small condenser like sand sissippi. not "\lith-i.yippi ". through a sieve, and a puncture is liable to . Response .30 to 14,000 cycle.,. happen to the low-pressure condensers used A.C. AUTO GENERATOR -Convert Ford gen- List Price (Kit) $10.00 for the purpose. Bypassing one or more of erator into 110 -volt, 250 -watt, dependabel A.C. Ute points mentioned should bring the noise generator. Driven by fan belt on car. Adaptable down decidedly. for public address, radios and home, camp or BETTER RECEPTION flood lighting. Simple instructions with complete WITH THE AMPERITE If the ignition coil is mounted under the drawings. Only $1. Autopower, 410 So. Moyne. dash-hoard, on the set side of the bulkhead, it Chicago. The only automit.c eltace regula- 18 best not to waste time but to remove the tor. Keeps set at the required volt- roil and place age. Prevents nverltt :el imp and unit in the motor compartment. POWER SUPPLIES timrh burnouts. as near to the distributor as possible. It - sometimes happens when the switch is an in- /AMPERfTE Grporation 36N WOYORKAY tegral part of the roil, tliat when the coil is \,C. POWER, less than $3.00. Built) a 300 -watt. removed it will be necessary to obtain a sepa- 110 -volt, 60cycle, public address or light genera- rate switch and put it on the dash: then. tor. Complete plans $1.00 or A.C. Power. P. O. Inox 382, Vincennes, Indiana. lock the original key In the coil and solder It in place in the locked position. Bring the FINAL BIG CLOSEOUT OF leads from the new key to the coil by using RADIO ordinary, heavy -duty twisted lamp cord, ilrOt JEWELL TUBE CHECKERS sheathing it in copper Shieldmg. RADIO PARTS -WE CARRY EVERYTHING J e w e l l 538 tube Connect up the coil. close the hood and, seller. This is the for receiving and transmitting. Wedel Company, one that every using a coil of fifteen or twenty feet of in. Inc.; Wholesale, Seattle, \\'ashington. wants. Now sulated wire connected to the antenna lead you ran afford to and on the outside car, buy two r more at Ihrown ground the CRYSTAL SET- Something new. Separates all this special price. tune in a station and note the noise level stations. Operates speaker. 750 miles verified. Only 25 left. Each with the motor running. Unless the car Blueprint 6 others, 25c coin. Modern Radiolabs, set furnished with 151.11 Liberty, San Francisco, Calif. the N a -A I d is a Buick or a SItllllttt' ell l' which has every- NYL single thing practically inside the motor block, it is adapter. O u r price to be expected that noise will be heard. but it S2975 should be decreased to some extent. MAILING LISTS e.13 112A 33 42 57 81 "Trimming the Rotor" 2.13 120 34 44 58 82 5Z3 22 35 95 59 83 The next procedure is "trimming the ro- Pave the way to more ales with actual 15 21A 311 44 7IA 84 names and addresses 19 ^' t7 47 75 85 tor" of the distributor. Remove the cap on of Live prospects. 01A 21 t8 98 88 the distributor head and take out the -rotor Get them from t 3n t9 '0 78 t'XII19 the original compilers ( t hat little gadget which goes 'round and I l0 al III 55 80 of basic list information-tap to date w'hl" 32 41 56 'round and actually distributes the "kick "). actuate- guaranteed. Lightly dress down the ruuttiug-edge with a 51.UL ORDERS file to remove corrosion from the tiring Tell us about your business. We'll help SAME the you find FILLED side, and then carefully up with hard the prospect.. No ob- DAY. C. O. D. Or- build it ligation for consultation service. ders must be accom- solder as shown in Fig. lit so that it makes panied by 10r;í de- an actual wiping rentnct with the spark plug Perk. Include postage. point 45D Vetey Street contacts. Sam. cars use a rotor which NEW YORK. N. Y. makes an actual wiping contact by means of t°^ 60 page Reference N. Y. Headquarter: for Transmitting Apparatus a spring slider. In this case simply dress up the cap contacts and rotor with very tine Book and Marlins eatery cloth or, preferably sandpaper, until LIST CATALOG shiny. HIGH -FREQUENCY LOUD Gives counts and prices on In the case of fixing the rotor, it need not 8,000 lines of business. Shows how get SPEAKER be stated to use extreme care, because if a you to special lists by territories and line of business. Auto lists of slight amount too must solder or a sloppy all kinds. job of soldering is done on the point there Shows you how to use the mails to sell Efficient, prerlalon -built dynamte Is a very great chance 3unit to rover audio band from of the distributor cap your products and services. Write today. 1100 to 12.600 eyries. Stier laity being split the first time the motor is started designed hunt included with unit. up. .1 few tests will generally show how Perfect for wide -range reproduc- R. tion. Can be used with large horn much to use in each Individual case. It is L. POLK & CO. or one speakers and filter listed better to make several tries each time, adding Polk Bldg.- Detroit, Mich. below. a little until it just makes a light contact. Branches in Principal Cities List $25.00 than It Is to spend time and money buying World's Largest City Directory Publishers your customer a new cap for his distributor. Special high and !m- Mailing List Compilers. Business Statis- esas alter with coup- The placing of the "A" battery lead can tics. Producers of Direct Mail Advertising. ling transformer, for amplifier output. Cart also cause at goodly amount of pickup. Try a le m lnu nt rare and all three suitable places for the leas) amount coupling transformer. of "buck up" namely the positive "A" of the battery, the starter positive and the ammeter List $25.00 positive. When the best place is found, make that lead as short :Is it Is possible. The Write Dept. -The Hotel Royal- RC -II for Data writer has found cases where a healthy -size ILK choice properly bypassed to ground helped The HOMELIKE Hotel of Philadelphia RACON ELECTRIC CO., Inc. immensely. For ibis purpose a simple choke 52 East 19th Sweet, New York, N. Y. is made up from annunciator wire wound on at Broad St. & Girard Ave. a suitable form. from to ? pound of No. SUPER TESTI NG KIT! 14 is sufficient. WITH PENCIL TYPE HANDLES Philadelphia, Pa. r i -r hs pr Parois With all these tests made, install the an- :l nuble 'rip Contliues every convenience and home com- Kit mvlclr with 2 )'lug -In- tenna which is to be used, and again compare cummends itself Prongs, 2 Alligator Clips, 2 fort and - to people of Needle Point Phone Tips, and the reception with that when the outside refinement. Spade Lugs, Long. Thin wire w'iIS being used. It the noise level goes Pemdl -Type handles for easy up means WITHIN 5 MINUTES OF CITY HALL testing in tight places, Ideal it that your aerial is either inef- for testing Long and Short. ficient or insufficient. If you are using the Rates as low as wave Sets. Coils, Condensers. antenna supplied with the car, in the roof Etc Complete kit. Introduc- of the tonneau, try supplementing it with an $1.50 $2.00 $2.50 -Single tory Price Now $1.00 Prepaid. 2.50 3.00 & up- Double American Radio Hardware Co. under -car aerial; also try using just an un- 137 Grand Street dereur aerial alone, We make it our business to please New York N. Y. not using the car aerial Write for Free Pans Catalog at all. With due respect to the manufactur- Ask for Mr. Thatcher, Mgr._ 308 RADIO -CRAFT for NOVEMBER, 1933 ers of the cart;, they sometimes make Tory good noise pickups out of what was meant to be an efficient radio aerial. PORTABLE PUBLIC ADDRESS EQUIPMENTS! Next bond all the pipes, wires and control rods coming through the bulkhead, on both TYPE PG -62-A complete Portable Public sides, grounding both securely and soldering Address System, including the famous VELOC- ITY MICROPHONE a high grade Class B all connections. (;round the elect rolock cable 20 watt amplifier, and two modern dynamic as well as the speedometer cable at several loudspeakers -all selfcontained in one con- places along their lengths -first making sure venient carrying case. Operates on 110 volt that the metal you are grounding it to really AC and is designed to faithfully reenforce is a ground and not "above," or just hanging speech and music. Has provision for electric onto a wood frame -piece. phonograph input. If after all these precautions have been made a great deal of the noise is not removed. obtain a piece of copper screen and place it under the floor mat, directly beneath the lo- catiuu of the set, and ground this securely to TYPE PG -63 -A smaller and lighter design the bulkhead. If an overhead antenna is be- including close talking carbon microphone, ing used, make sure that the springs in the Class B 6 watt amplifier and dynamic loud - well speaker -all self-contained in one convenient seats and back of the seats are all carrying case. Operates on 110 volt AC and bonded together and grounded to the chasses is designed to reenforce speech and music, of tiie eats; as well, ground all the metal ate - and has provision for electric phonograph cessorics which may be placed ou the car. input. The robe -rail of one particular open car caused two men to spend over three-quarters of an anxious hour on n ear only to find out Mat this member was screwed Into a w lea A full line of high quality sound reenforc- back -post and was not grounded. When this ing equipment is available for permanent in. Surveys and estimates furnished on request rail was grounded securely- to the chassis, a atallations. and without obligation. was drop in the ignition noise level which Write really uubel leviable was noted. for descriptive literature. ANYTHING IN SOUND REPRODUCTION 'l'he writer has n penchant for under -car ,]R aerials. Whore:Is the overhead antenna may PIminp ¡nnc Di,isiun be Imam- (tlioient in same instances -I like to know that toy results will be the satue all the R C A VICTOR COMPANY INC. time, so for that reason always use the same style antenna, supplementing it from time to "Radio Ileada/unrlers" CAMDEN. N. J. time with the ear aerial furnished when it proves to he as good as the under -oar aerial. The aerial used is simply as piece of copper screening a foot and a half wide and from six to seven feet long. set in at flat bag made of top material Iwo ier- proof, of course) and with a tape at each of the four corners. WAKE UP ..., Fastened between the front mid rear axle of n oar they are neat. elea n, efficient and cost but 45 to 50 cants to make up. STOP DREAMING The following are some of the methods regularly usail to eliminate 1111i se in some of the most popular awakes of cans on the mar- Radio Offers a Real ket. To list all of the cars would be too great Future it task, ban the few popular ones noted cover about all the methods used. For Ambitious Men - ltriCK.- Itattery lend installed in shield, antenna wire shielded, suppressors and con- To the man who has time on his hands just densers connected. _k small piece of screen- now -the man who wants to put that time on fluor car under set, ing sometimes used of to thinking of the future-CREI offers a securely grounded to frame. This will gen- complete home study erally eliminate all of the noise in these ears FREE .. course in Practical as they are the easiest to work on, everything Illustrated Radio Engineering. electrical about the car being shielded and the spark plugs being encased In the block. Booklet Not only is this extension course prepared for the average radio- minded man, but it ('IIl-VItOI.I,l'. -('oil moved up and fastened Conta;saiaag complete consists of a series to motor block In eluse relation to distributor. information regarding of instructions in specialized training for those radio men who know Lends from switati to roll being run in a o variants eourses- that technical training will give them that twisted pair. shielded in copper shielding. a.ite' for it (loft"! This lead should be run in such fashion tie, needed knowledge and ability to forge ahead It passes low on the unItur block alongside .:i to bigger things! the distributor. Build up the rotor of the distributor. Ilond all wires. pipes and control rods coming through the bulkhead on ENGINEERING both sides and ground well. Install sat on CAPITOL RADIO INSTITUTE right side of car. US.' all su ppressurs and 14th and Park Road, N.W. (Dept. RC -I I) Washington, D. condensers. and if at slight noise is still heard C. use a condenser on the switch or battery side of the coil. Un some of the earlier models of ear, notably the I930 and 1031. It was this THE NEW necessary to Install at fairly heavy It.h, choke in the 'A" lead, bypassed to ground. PDXTIAC. -Place toll in motor compart- SHALLCROSS ment near distributor and follow precautiou- WHEATSTONE as outlined above for the "Cherry" In ad: BRIDGE (No.630)

dltion it is sometimes necessary to bond and >ptinFe. r 4a ground all the cushion springs and rube racks. 111.41111.411111..01 i be ,dbar.I. Jrllr,I1 An under -car antenna is generally more ef- elr.trh al trrnhdan. Cuml a is .. rg by rm.nPluring a Id aml a : ficient ou the snarler closed models and road- sll.LlRbss Itl- emtaa ster jobs of tuais make. -ilhr l. h N tlan:un.i:m1.,. -car an- Ramat. .01 ohms to lit MeOohms I)OUalli. -i'se highly efficient under Kt o.l he in xlamp. for Bulletin tenna and extremely short leads f coil to ranlatinion full nJormn- distributors. Shield all Ignition lends from lion and ettaixt waelioa alitnily. switch and use condensers on switch side of SHALLCROSS MFG. CO. poll to ground. For some undecipherable rea- 709 MaeDade Bhd. Collintdate. Pa. son it is sometimes necessary to run the wires from the distributors to the plugs in shielded wire. When this is being dune make sure however that there Is sufficient space On page 305 of this issue you will find an important announcement which tells about left between the suppressors and shield to the OFFICIAL REFRIGERATION MANUAL and the new material added . . now avoid a jump -over to ground. Regulation bringing this valuable book right up to the minute with new servicing material. Packard "Lackard" shielded Ignition wire

RADIO -CRAFT for NOVEMBER, 1933 309 split for about an 11101 or so and that part of the shield removed, is generally O. K. BOOKLET Ground all shielding well but take care that In doing it no chance of grounding due to Rdio'aft FREE SERVICE rain is possible. CIIItVSLEIL -Coll moved up next to distributor and all wires on both sides of bulkhead shielded and bonded. as descriptions of the full line of popular -priced Coil bypassed and Readrite instruments. Vs orth having. Rcadrite a goodly portion of shielding used under floor READERS' BUREAU Meter Works. mat in region of set. Under -car aerial preferred. On this page are listed manufacturers' catalogs and booklets, chosen because they are of in- 76. THE COAST -TO -COAST "BROADCAST." The l'ACIC.1llD. -Rest results are met with the terest to readers of RADIO-CRAFT. You can "Broadcast" is the Spring- Summer 1933 use of an under-car aerial in addition to the coupon below. edition obtain copies FREE by using of a 100 -page mail order catalog that is a veri- overhead aerial when ear is furnished with table encyclopedia. Every article is well illus- sa nu. Thoroughly bypass all coil leads and trated and described for the benefit of radio shield ignition wires from coil to distributor. dealers and Service Men, whom volume for the Some of these Jobs have had halve 5. CLAROSTAT CONTROL IIANDROOE. .1 large is specifically intended. Coast -to -Coast Radio to the coils 32 -page book containing detailed specifications Corporation. moved up to the front of the motor black. of volume controls, attenuators, constant -im- There a re a great ninny custom -built body pedance controls, phonograph pickup faders, tone Jobs in this class and great care will have to controls, line ballasts, rheostats, potentiometers be taken in bonding 94. ELECTRAD PRODUCTS. The newest and the cushion and back and fixed resistors of various kinds, together springs. Bypass with valuable circuit- design data. Clarostat latest catalog of Electrad products contains all donne light leads at the Manufacturing Company, Inc. twelve pages and lists many types of fixed and light. and ground t horougl It not only the variable resistors and five different kinds of protective cable on spotlight but also the amplifiers for public address purposes. The standard used to hold the spare popular Truvolt tire in the resistors have been improved fender "well" On the sport jobs. by the addition of insulating shields and heat 6. MEASURING RESISTANCE BY TIIE. DEFLECTION radiating covers, and a number of new sizes have AT-TCT -RN.-One of the toughest cars to METHOD. The conventional method for the meas- been added to the line. A handy and useful work on catalog. Electrad. Inc. is this job. 'Phis is especially true urement of resistance involves the use of the of the models which encase the leads coming Wheatstone bridge, a costly piece of apparatus. from However, there are other methods which provide the distributor in an aluminum- topped a prac- hood. It is necessary to spare no pains or fair degree of accuracy, enough for all 96. TORE FILTERIZER AND CONDENSERS. The de- clipper shielded wire on en tical purposes. The least expensive is the Tobe Deutschmann company is now catering to this r. as every flection method, which makes use of popularly the available had must be thoroughly shielded, This Service Man with an extensive line of filter, priced milliammeters and fixed resistors. by-pass and line condensers and radio noise every control rod bonded and grounded, and describes the method - bulletin completely. Shall eliminators. A full page is given to the new the coil placed in close cross Manufacturing Company. relation to the dig. "Filterizer" noise eliminating antenna system, an tribe tor. Also ground all metal floor panels item of particular interest to Service Men be- that are not already grounded. Item the ".," cause of the money- making opportunities it battery offers. Tobe Deutsclhman» Corporation. lead -in shield from the ammeter lend or starter positive. Make sure that every 11. SUPREME INSTRUMENTS. Contains lengthy piece of metal In the chassis, even down to descriptions of the Supreme service instruments, the window including the A:1A1 T)iagnometer. which is five 97. Asco Tuae BULLETIN. raising me'hn n ism is grounded, A descriptive as instruments in one. the model 90 analyzer, the folder giving full technical characteristics on the well as grounding thoroughly the frame mortel 40 tube tester and the models 60 and 70 complete line of Arco radio receiving and trans- holding the spare tires. If the car uses a oscillators. Interesting to the Service Man be- mitting tubes, photo-electric cells, television tonneau windshield as so nub ny of this make cause it tells how his work is facilitated by lamps, hot and cold cathode tubes, cathode ray do in the Open cars. ground this and the ingeniously-designed test equipment that indi- tubes. rectifiers and charger bulbs. This can be meta I back of the froot sent thoroughly, not cates the condition of an entire set in a few posted for easy reference. Arco Tube Company. minutes. Supreme Instrument Corporation. being content with merely grounding the metal back and relying on the screws holding t he windshield to bond it to the back. TO 98. How TO USE NOISE. REDUCING ANTENNA the Service Men who can lick an .Auburn com- SYSTEM ON BROADCAST WAVES AND SHORT WAVES pletely is the title of the latest booklet on the first "crack" belongs the title 19. A BAPTISM OP FIRE. Centralab fixed re on this important complete sistors are made by forcing a carefully calibrated subject. In addition to covering the theory, the ''l'he ':auto-trician." It has been resistance material through a plastic ceramic practical application of the various noise- redue- done, but generally if an Auburn comes into material and then baking both under terrific mg systems available for broadcast and short the shop the owner is given to understand heat. This booklet describes the manufacturing wave use, is described also. Lynch Affg. Co. that snore little noise may be present "at process in detail, and lists the advantages times." This is to forestall calls when the claimed for fixed resistors of this type. Central owner finds other, less Radio Lab.lratorics, Inc. expensive cars with 102. .1MF.RICA'S OLDEST RADIO SCHOOL. This little or no noise at all. It can be reduced attractive 16 -page catalog describes the various to n minimum by careful course instruction work and attention of available at the RCA In- to details as shown in stitutes in New York and Chicago. Training is the first part of the Riven in the following subjects: radio broadcast- article. 12. RFADRITE RADIO INSTRUMENTS. This six - ing. radio operating, radio servicing, and sound FORD. -This is another teen -page pamphlet contains some valuable hint. and public address work, Home study courses easy car to work on the testing of electrolytic condensers, as well are also offered. RCA Institutes, Inc. on, especially some of the older model A's, as all that is necessary in these cars are the suppressors, and condensers. and shielding of r the coil lends, In the later models the 4's 1 103. MILES PUBLIC ADDRESS SYSTEMS. A con- and VS's it IN n littl' ha rile r as RADIO -CRAFT 5 -107 cise 8 -page catalog listing the distribu- microphones, loud tors will have be Readers Bureau speakers, power units, amplifiers, transformers to dressed down and the coil someti nit's ed up. Bonding 96 -96 Park Place, New York, N. Y. and incidental accessories. 3liles Reproducer Co., and Ina. grounding of all wires and control rods is of Please semi me free of charge the following course part of the job. In the two -door sedans it H best to supplement the overhead booklets indicated by numbers in the published 104. WESTON STANDARDIZED SERVICE. UNITS. antenna This with an under-car aerial, and also list above: folder describes a complete series of stand- bond and ardized service units, consisting of an analyzer, ground the springs of the back seat. tube checker, oscillator, volt- ohmmeter and ca- PLYMOUTH, -Coil should he pacity meter. Weston Electrical Instrument Corp. moved up to No. w. the distributor or placed as far front as possible. Shield and bond a'ir's on both sides of bulkhead. Not much trouble. However, 105. RADIO BARGAIN NEWS. This dealers' and on account of the "floating power" Service feature of Men's mail order catalog is a veritable these cars some trouble is experienced Name buyer's guide. Among the hundreds of items due to incomplete electrical bonding of the block included are auto radio sets, mobile sound ampli- to fiers, dynamic speakers and replacement parts the chassis. A copper bond strap made Addrr.rs of every description. Federated Purchaser, Inc. from shielding, fastened under one of the bolts and thence to frame will lick it easily. City State Now a word at this time about the care necessary when (Please check the following) 106. EXSTAT SPECIALTIES POR RADIO SF.RVI..E working on and around igni- TECHNICIANS. A useful catalog tion systems. .1 "short" plays I am of resistors, havoc with n condensers and volume controls, prepared espe- car battery and if when changing coils around cially for the Service (I) Service Man (2) Experimenter Man. Of particular value and rewiring ignition systems for new is a ten -page section listing the correct replace- switches ment volume controls there is any chance of a short, take (3) Dealer (4) Jobber for numerous radio re- the time first to disconnect ceivers dating hack as far as 1926. Tilton the positive lead (5) Radio Engineer Dlasurfacturing Company. from the battery and then go on with the (6) Licensed Amateur work. Remember also, that a grease spot on (7) Professional or :Amateur Set Builder the upholstery leaves a had impression on the 107. SHORE TECHNICAL BULLETIN. customer, besides showing you up as a This coupon will not be honored unless you A 4 -page bulletin published monthly. and devoted exclu- careless worker. If you want repeat busi- check off your classification above. sively to the advancement of microphone tech- ness the surest way of getting it is to do nique. Shure Brothers Co. good. clean work and let your own customers

310 RAD 10-C RAFT for NOVEM BE R, 1933 send around their friends. Fully 75 per cent of the work done last fall was on recommen- dation in the shop. simply taconite the men were clean and courteous. Where a man secs WEADQUARTERS FORS a fellow in a nice clean snit of white cover- alls and with clean hands working on his car, and the upholstery rt,ve retl over with PUBLIC ADDRESS AMPLIFIERS nice greaseproof covers, the wheel covered UYD C om A UFA GAR a p d with a cloth, and a shield over the painted B /RE Tfi M N CT UR 5A VE 8/6 MONEY. parts -it leaves an indelible impression. r/frj wo ..Nodels_se9r>ai/a61e or use omobcles axa If you are going to specialize more or less is 0110 of in this installation work -and it all I ndoorand Outdoor/nsfa//a/rons suehas UKiaersall Povaered71odels the few branches of radio now really active - , get n complete set of Wrenches suitable for Operatrnorn I10lIo1lACorDCorfoma 6oltlotageßalc the removal of the bolts and nuts on the motor and chassis. :fist, make sure that each With PvWeR VUTPUTS RANGING from 3 TO /00 WAT! job is really finished to the best of your ability before It is turned over as completed. It Victor Push-Pull 245 Amplifier is far better to advise a customer that "It @ Esrrl lent For All Microphone. Phono Pickup was impossible to complete the entire Job to- Anil Radio Tuner Amplification Applications. i, ES$ day to my satisfaction -I will finish it at Tuet sI ltn.1. n taneou. Heater Amplifier . I.. "Call ¢ lei i'J spIAg'A it i< your own convenience tomorrow," than I St.,n,lar.1 Mortel i I -.V:. 2-245. 1--290. SET OF $169 to let a customer go out with the idea th:c ohm yoke coal.. and TUBES you have not done the job right and be fora , . a sá00.4..11110 Colt MATCHED 95 to come back. ..W ul,u Cu .ylei, I, : n,hled kit:.nybtdr can DYNAMIC Make positire -and the italics should be thi. smplìher dù[rnn,.frm,i,lud. 110. -,1t .tata.. 0U eyrie. SPEAKER [ hearkened to -that when you work on a cal nothing is haft undone when the job is to rue -To- COAST- -CORP. ever. All bolts and screws should be as ticl COAST RADIO as they were when you got the ear, and eve: 123 K-WEST 17TÚ STREET . NEW YORK.N.Y. wire should be properly installed so that the shielding cannot possibly short out anything and cause any trouble. For emphasis, let me state a case in point. An owner of a car to Packard, to be exact) had one of his neighborhood radio men install a radio set in his car. The job was Amazing turned back presumably finished. But -the Announcing next day the same radio man was visited by an irate car owner and his attorney! In doing his work the mot had loosened up a bolt on the steering column to enable him to bolt Typewriter Bargain the set into the corner "out of the way." This bolt was not put back securely and that evening when driving the bolt had dropped Portable only 10c a Day out, the steering column became louse And New Remington an accident bad ensued. The man was held 10 -DAY FREE TRIAL OFFER 1 liable because it seas afterwards proved that (lily u a day buys this latest it Was his negligence which had caused the model Remington PortableI trouble and he had to "soak tip' $700 for Not a used typewriter. Not n re- the damage. So -o-0 -0 (to emulate that tire- built machine. It's a brand new, whistle of the air, Ed. Wynn)-when you regulation Remington typewriter. does the fin- take off, put back so tight that the next Simple to operate, yet MAIL it it est work. Full set of keys with large fellow will have trouble taking it off again. and small letters. COUPON Some cars have double Ignition systems, Try this typewriter in your home and these contrary to the first notion will not or office on our 10 -day FREE TRIAL for full facts about be as hard to work on as a first glance would OFFER. If at the end of to days seem indicate. however a word about you do not agree that this Rem- this astounding offer to ington Is the finest portable at a. these: don't "fool" with the spacing of the any price, you can return it at RFÚIINOTON RAND INC., Dept. RC -4 points of these systems, as a fraction of an our expense. Don't delay. Don't BUFFALO, NEVC YORK. Inch placement means namable with coupon in their put it off. Mail the today. Please tell me how I can buy a new the car. Building up the rotor Is O.K., but Or use postcard if you prefer. our new catalogue Remington Portable Typewriter for do not try to dress the points down or but her Write for only 10e a day. Also enclose one of with adjustment unless you are all tg- showing the most complete new catalogues. their line of portable and desk your ililt,n specialist and have worked on double models ever offered. ignition before. Tame As a final word, the actual mounting of FREE TOUCH Address the set in the ear is simple, but before you TYPEWRITING COURSE promise the complete installation in "ow.) lour" prepare to have a half -dozen experts ready to Work on the car so that it 4:111 be FLASH -OVER IN 83 TUBE done. Ask a fair rate per lour fur outside work and keep in touch with the neighboring DUMONT Hue., :1 ,1 aloof nr -;:[n-u By Test" automobile sales agencies. Do their work been purzleà by the (lash oser Which sana "Best for then) and s e how tunny of the friends of occurs the S° -wave un Dumont's complete line of Electro- times in type full Paper and Tubu- the owners of now cars will come ul't,111111 and rary vapor rectifier tithe. lytic Condensers. "get one put in.. lar, enable Service Men to make This condition is explained as follows ' the matter of just what charges should replacements in an unusually large In . the National 1 -ni.n Radio Corp.: -In :I number of radio receivers. includ- be made, a deal will of course depend great hautdling 11111 shipping of the $:: tube. I ing all late model auto -radios and upon your Inca riun. For the average instal- excess mercury often deposits itself in a IiiI midget sets. Dumont Condensers lation of a new set a charge of $lit is made across the stem of the tube thus forming are recognized by their superiority, to the rust oil e. Where the work comes elect rival path between the electrode run, quality and permiability in retain. ing their values. from one of the automobile agencies Who most dons. It Is the burning away of Ulis 'I' naturally have to be "counted in" on the posit which causes the Dash over. labor, there is a tacit understanding that For tea Ily ideal operat inn. the tulani' MODERN RADIO customer they ¡tre to bill the for this ant0unt unlit sllonld he allowed to burn for a pea an nil their commission of $5.+11) is deducted of three or four minutes. After this II. ACCESSORIES from this figure. plate voltage may be sil rely applied. Ti,, The wide variety of replacement On all outside work where pry parts carried by Dumont permits it is sit burning of the ii lament will warm the I "noise eli nmination :" a Oat ratte of $1.00 per Dealers and Service Men to pur- tu drive off the condensation chase Standard replacement parts hour is fair. This should be adhered 10 in mercury un the st em. at prices which are exceedingly low. all cases and no cut rates given. It will be The type s:: tulle is designed to stand an The quality of Dumont's products found that a great deal of this work ran la. applied voltage of 510 \'.. ramas. per plate are only of the finest. obtained. Especially-, from car owners who mill deliver 5.10 nia. D.1'. output. Providing Send for free catalog listing hon. have had their sets installed in an unsatis- the tube is operated rating, deeds of replacement parts, for within this ex- standard radios. factory manner and have never received satis- cellent life will be secured, but overloading faction from the original installation man - will ea titi' early failure. The application of either because of lack of knowledge ou his Dumont Electric Co., Inc. higher A.C. voltage than 500 V., per plate York, Y. part as to the correct procedure, or because cause 453 Broome St.. New N. will electrolysis in the glass stem Jobbers and Sale, Territory Open of na desire to satisfy the customer. Whlell 11,4114 it in stem rupture."

RADIO -CRAFT for NOVEMBER, 1933 311 BEGINNER'S on tete diagram as you put It in place and SUPREME MODEL 333 2-TUBE you will avoid mistakes and omissions. (Continued front page 302) If you are adding to last month's unit the following changes will have to be made in the subslauhe to us, we are used to the "feel" eireuit of the origlnnl unit and had best be of it and would prefer to use it for base- made before proceeding with the wiring of boards. But it is a very poor material for the new unit. ,adio construction. so bet's get away from it. Change the it.I", choke and its associated Uuminum, being a very soft metal, can be bypass condenser, from the grid to the plate handled Just Synod like in many- ways. it can circuit of the output tube. as shown. ('nun - be worked with regular wood working tools. pletelp disconnect the primay of the 3 -elr- and it makes for fou' superior construction. cult tuner and leave it "floating"; also disconnect the antenna wire from this coll. Wire Construction the tickler of the :'circuit tuner Into the The first job Is to make up the chassis as plate circuit of the output tube, as shown. shown in the drawing, Fig. 2. if you built Remove the 750 ohm bias resistor and wire the circuit shown last month you have only in the too ohm and volume control resistors, one to make, Otherwise you must build them as shntvu. The power (table is made by cut- both. I/o your work carefully and exactly ting fuir wires (with differently colored in- and hold as closely as possible to the dimea- sulation) as long as required to reach from sluns giren, since these same units must "tie the set to the batteries, and soldering the end up" in the future with other units built to oP each lulu une of the four prongs of an old tube base, The Biggest $39.50 Worth of Analyzer Anywhere go with then[. It is ad y i stalde, also, to build braiding the wires together and pouring Insulating wax into base The new Model 333 is a modem Analyztr t+mbined with two separate units as Shown because. while the tube to it hold wires -to- point r the in place. paint tester. and enable, Ile nnpiete point. they are side by side a his COOP Svc may decide to -Point red;I anre, cottage. nd current analysis. (21 to take them apart for layout. lobe testing front the r..114 n cachet with .ri(- rontaineI MI./titer slid hift batters. sali capacitor leakage teas, Includ- First cut out the four pieces required for Operation ing elerl roly'le capacitor:. II, use of head- Phones. loud the two panels and two (-tissues, then lay speakers, nderophones. etc, connection. tue all udseel. .\fter all the wiring is In pince and you luneous tests and (5, sis range output meter available them out with a scriber and center -punch, are sure, and doubly sure, that everything Is for convenient use without the necessity of troublesome anal "slut" all holes It small output with drill, say O. IC., you are ready to put the set Into adapters. about I -in. In using the Model 353 It 1: unneeessury to remove the /10 Then, drill through all the operation. -(rassis of the radio or to dismantle it In order to gain holes uu the panels, and all except the socket Plug in the phones, tubes, power cable and to the circuits for "point -to- point" tests with holes on the sub -panels. Next, bend crystal te probes as Is n with the usual point -to- up the detector, staking sure that the little point"is sub -panels, being set tester. Any n meter range may be applied sure to make sharp corners wire Ill this last unit is making contact thin the with analyzer cable bol using dare for resistance and exactly on the dotted "bend lines" On the output measurements. ¡'rouie: A.C., U.C., M.A., out- ishow'n crystal, and attach the ° \" battery uuul put ranges of 0/5 25/155 /Z59/5110 /brat mils or volts; the drawings) and cut out the socket holes. the negative side of the "It" battery. When Resistance ranges of o l,00u /11).01)1) /lnn,ao0 /1.1)00e00ó After this the panels and sub -panels be the volume ..Irinns; and may control knob is turned to the "on" repen-u y ranges of 0/.12..'1.2.5/12.5 Huas. bolted together and a All readings direct o mener -no chart+. Fers Suprente't stnall piece of al i- position of the filament switch the tubes lium I Axciusite FREE REFERENCE POINT SYSTEM OF about in, x y, -in. wide may be bent should light with a very dull red glow. NALYSIS. es. If 60 le. lengthwise into an angle and used to hold the they don't, lind out why before proceeding Dealers Net Cash two units $ together by being bolted below the further. Wholesale Price 39.50 sub -panel to one of the bolts, on each unit, Now turn the volume control to the full Ask your Jobber for demonstration-writs for that hold the panel In place. This angle will "un" position and snap the positive "B" wire complete Catalog. Order now- higher prices he all that is necessary, though if you insist across the battery post. A sharp click in the on an unusually . are certain. solid job you may also place phones and BO large spark indicates that the another similar angle between the two units circuit Is probably wired correctly and the Supreme Instruments Corp. at the bark of the sub -panel, connection may be made permanent. 478 Supreme Bldg. Greenwood, Miss. :After the chassis is couapb tety assembled Make a temporary ground connection the you to may take the available apparatus for unused primary of the :;- circuit tuner and which holes could not be speri led )since they attach a good, outside antenna to the other mount in such a wide variety of ways), such end. Moving the adjustment of the crystal Be coils and tuning condensers, and arrange detector should now result in clicks and them on suss NEW AMAZING the chn in the most convenient scratches in the head phones and when a w'ay. Ile sure to keep the tun tuning coils, sensitive spot Is touched you will boar the I,I, 1,2. and the two R.P. chokes as far trim familiar rushing sound always present, due each other as AERO possible. and with their axes utt to II t mospherics. When such a spot is found right angles In order to a leave the detector After dd feed back. alone and "fish" for a sta- everything is arranged t your satisfaction with the tuning anti regeneration con- INTERNATIONAL tion mark out and drill the counting holes trols. One position or the other of the tick- and fasten everything down, ler with its axis parallel to the main coil ALL WAVE If you built the unit sin vn last month will give regeneration and the whistling chal'- mad are adding to it. it n-ill lt. necessary to ((.,ilinatcd on pape :14) 11 TUBE remove the filt TM' nt switch troni the panel SUPER and substitute for it 4 De LUXE the combined switch and volume control TNESE taus IN ONE ' PANEL ONLY Here now! world which Is being used in Wide (2 PANELS REQUIRED, ReceptIOn. No this circuit. ONE BLANK) 115'; .. ping In coils. Auto- i t%- vuntie volume con- Completely Assembled Wiring 2. ol . shielding -tOO With 2 Matched Full 1 -new superpphonte If yon are starting BEND NEW pulsa. Cet Dynamic ALI, the 5 a brand 11100' jab pun fl Speakers / wave - hart . -J eJ 1 only now proceed e br r- 5775 8 with Ibo m , , : a nil. 7..- Tubes the uutrkub!ç wiring. making Itt p.' gaud, solid soldered L. AERO WORLD WIDE .joints especially in the CO so of bypass 1-Tube Short Wave condensers where t Ie SC ee7 s,1 hew I Operative pig mils are depended r- e the thrill of listening upon to hold the con- Il i It taut to Buenos Aine. densers in place. me- -susPANLL- L"udno. Berlin. Paris. and elm nil hrnadcaet ing stations fe NOTE: htCher rnughout push -baaek the world, via I'st solid, TIDE NÖLE .mods,' WAVES. The wire throughout. IN ONE SUBPANEL AERO w'OIt1.1) WIDE Vice ONLY. (A) Rl ;Cl'ivER gets 15 to 550 in the filament circuit meter :- (2 SUB- PANELS For the pa ct seven first. then the grid - REQUIRED) 1 t his little wonder set e has bet-11 one of the biggest wiring and finally the X 2eot SUB -PANEL (A) a the ah rt ware plate wiring, - X FOR SUBPANEL Field. keeping 'VC (B) all leads as short and Complete line of radio sets and transmitting apparatus direct as possible, and Write for FREE Catalogue b r i n g pa l-- rtirnlan¡y Je- pETecroR .- S'J "r-ly careful to avoid run- }}S/ - MOVNTINQ 4 CHARLES HOODWIN CO. ning the grid wiring BEND NERE 4240 Lincoln Ave., Dept. G-15 Chicago close, and parahlrl to á' Please send .. your NEW 1933 Flo i I .t'1':1LOGUE, the plate wiring at ya' Va' %" Name any point as this will (-aase feed back and street unstable operation. Fig. 2 Town Mark out each wire Details for making the aluminum panels and sub -panels. L_ State J 312 RADIO -CRAFT for NOVEMBER 933 dial. Although this means 100 x 100 or I INFORMATION BUREAU 10,000 tests to find the most sensitive setting of the instrument. the results are well worth (Continued front no a 12941 the effort and time involved. SUPREME MODEL 444 testing with the floating- oscillator tubes out Switch Sur:: is used to cut out the grid Five Unit Radio Tester bias on the two floating- oscillator tubes, per - of their sockets. mitting similar tests sh ou ld be performed with the thein to run "wild" and thus causing floating oscillator, reversing the leads of Isl. a heavy plate -current flow through coil I._. This creates D.C. if necessary. When it has been determined a magnetic flux and if the that both oscillators are oscillating. try again tube circuit Continues to oscillate it varies this I1.('. flux some an to get a brat tote in the instrument receiv- from point above arbitrary zero. On saute frequencies ers. It nta y be necessary lo add to Or re. the in- of wire from coil 1.:., be- strument performs best when operated in Ibis move a few turns manner. Callao variations in mounting this Coll with If any further trouble is encountered in reaped to the shielding surface will vary constructing its characteristics sufficientlyciently to throw it out this metal to, -a tor, the writer will be glad to answer of tune. It should not be necessary to add inquiries. turns to 1.4 if WI k up to par and 1s being Franklin operated at Its rated filament potential E. Sarver, rcheck this point, by means of an accurate 2923 Harrison . freef, volt met er). Kansas ri!rt, .lfo. Complete Laboratory Equipment (Tt Many builders seem to be having trouble getting parts to build the outfit: at a Popular Price be glad to any desired the author will give PHILCO SHORT -WAVE CONVERTER The new Model Ill Floe bolt Radio Te-ter Incorporates assistance in this connection. Ille functions of a Ilndern anal) zer, un A.C. tube tester, IKI The values of component parts shown \Ir. John ICraumr. ,h,r,.y City. N, .1. .t shielded oscillator all olunnlegohumaAer. and a narl- tor tester. The anahaer otters FREE REFERENCE In Fig. 1. the schematic circuit, are satis- (Q.I.1 What is the power eloisuniption .r COINT SYSTEM OF ANALYSIS. pent hang A.C., D.t'.. factory: however. units ('I.\ and t`:.\ may the l'hllco short-wave converter, model 4, \I..\., output mans nr le /5 /25 It i /X511/500 /1250 ells or roll s Resistance ranges of 0 -1 !100 /10.000 loi,Ólll n broadcast be changed to conventional trimmer con- When used with receiver? /1,ouIIt,a1Nl nions and rapacity ranges of u.í_5'1.25/12.5 densers of smaller capacity. (.1.1.) The Pliilen model 4 short -wave con- lords. Tube tester accommodates all tubes ¡minding the est types without adapters. a special 11 -point 6 -pin The schema tie circuit shnsvn as Fig. 1 in verter Consumes 50 watts maximum. This selector, -witch Is used so that only four sockets are re- the July, 19 issue has be,n modified slight- converter has Its own paver supply unit. and quired for accommodation of all 4. 5. A. mati and Targe ly to secure imp ro veti nperat loo, ns mentb died for this reason. the type of set with which base 7 prong tubes. Tests all A, it, C. I), Y, Z. series Including duo -diode connections. Provides filament heater a1ove. Therefore. the t'ircuit has been com- it is used has no effect on the current con- voltages of 1.5, 2.0. 3.3, 5.0. 0.3. 7.5 12, 14, 25 and 30 pletely checked owe r and these slight revisions sumed. volts. The A.C. 1).C. see,Iatb' stabilized and completely (Q.2.1 Why is necessary shielded 111e!'r modulated oscillator Insures utmost ac- included in the circuit shown here as Fig. it to s.'t the dial curacy from 130 to 1$75 kilocyrtea covering the 20, 411 Q, 2 Note that in this Circuit the capaci- of the broadcast receiver at 1.000 kc. when and 80 meter short -ware bands. Complete laboratory ties of the tuning condensers in shunt to using this converter? ettiptrsent engineered into a single Instruu)ent. 1,1 -1.:. TL: have been inerea slot because the (. \::.t The Piffle. medei 4 converter con- Dealers Net Cash tains first $ QAe50 prow ions va Ines were so near the dead-line of the -detector and oscillator circuits Wholesale Price A+i inoperative chn ra tteristies that the instrument of a short -wave superheterodyne receiver. and was extremely difficult to adjust In order to the broadcast receiver becomes the I.F. am- Ask your Jobber for demonstration -write for secure n bent note. The values are: t'1, :150 plifier. second -detector and audio amplifier of complete Catalog. Order now -higher prices ever.. variable. with vernier dial: t'1.\ omit- the system, when connected with the con- are certain. ted : l'2, .0015 -mf.: ('2A. ::7,0 aunt.. variable. verter. As the short -wave portion of the set with insulated shaft and vernier dial, Since is designed to operate with an I.F, amplifier Supreme Instruments Corp. several roust root n rs have stated that they of 1,0(1(1 ku., the broadcast receiver must had considerable difficulty in locating the fila- naturally be set to this frequency. 477 Supreme Bldg. Greenwood, Miss. ment ballast resistors, the ei mutt has been re- (Q.3. llow Is vernier tuning on the short- wired so that any tutr -e 2 V. tubes drawing wave converter made possible by using the equa I amounts of rot-rent can Ile used without broadcast station selector? n lihtment series resistor. (.1.::.1 When the broadcast receiver dial The two milli musters are of light weight. setting is changed, the tuning of the short- inexpensive type and are used merely as in- wave circuit is changed by an equal amount. dicators. When the set is first turned on. For instai nee, if the short -wave dial 1s set ail they show a heavy flow of Current : then, the 2 megacycles with the broadcast dial at LOUI falling off of current flow indicates that the kr., a 2 megacycle signal can be received. system fed t h ran gh the meter has started Now, if the broadest feeiver dial is changed ADIO osrfllilting. to 1,010 kc,. the tuning of the short -wave ar.n. The large amount of variable capacity in converter will be changed to 1.99 megacycles, the tuning circuits makes possible the selec- although the short -w'in'e dial still remains na tion of a large number of frequencies and the 2 megacycle setting. Therefor it ¡- here a surprising condition is noted, Some much easier to make such a 10 kr, change in ton aI bi)Mfiotta of frrye ,n Vies 7i cc far greater lute toning of tiro broadcnst receiver than th penetration and response Hew of At vs. livery short -w'tu ve converter. Thus, vernier tuning point on the tlnating- osrillntnr should dial be by means of the brnatca st station selector li3,.,, ,ttI n, worked against every point .n the monitor is made possible. loge. powerful iiti ion of radio -Lang, YOU up to date on nil ineprovement- radio. television. sound engineering, and keeps you among the real money-makers in th t. 0-1.MEG. MONITOR OSCILLATOR-1. tOOMMF.1 .00:5-MF.,C F OATING OSCILLATOR expanding held. trnles' you has REG. -_ IMil high -type pr.,,sai,nn! t' cow- Lr ------i g yon will find it hard , 250 MMF. = E a r\ Li, BT. TROL TRIM)iAER. of the poorly paid "ti nk ener'1 .1.MEG. T T N!!.26 14 I D.s.c. 201. T et3.5C2NANtF. 1 New -Type Set Analyzer NO.26 l WIRE DS.C. 24' DIA, WIRE -r 30 .30 Al part ,f Il't. A. training Youot Kee this up- teo--rh 30 I 1 uute Set Analyzer and friable Shooter. Alter a OAF. T 12, Sr. few en.V lee+nna you ere ready to n e it for immediate / 53.26 uey- raking, competing with 'old- limer.'without L3, BOT. I .002- fea With this wonderful phew of esp,ipu,ent. larked MF, 0. S.C. by r. run need have no 40.26 DS C -I '/ WIRE WIRE V2 V3 heir , worry over toe future. Even though there 24" DIA. sl htrnever lase n radio net constructed-or t" DIA p not r nanother uprovementc adio made -there are enough - ri e that need frequent attention to a 0 VI B sure You good money ea :tempted Radio-technician. ' l Start Money- Making Quickly `R.F.C. R.T..A Tra' i th 1,-, red - nd q n ate n` 250 MMF. iSMIELO tb. ,ndha achee Ì ad,., 'el le ,he world-te te I NS she ,Iole end f cadì, Siv. IIt ,., / I.0 a aLdnw . rth ,cori rÌ,0 eelai are alar R. F. C. MÄ° r I '. n r. ...i .,e lu J,Ì , ll tree delay I _O -too your Yard e.a, N',-i t . d ,ila ohi. hhr a MA. the The dv eof - yo r- own that nay own up . ne,.. Jepr ash h, yrrwt futura lue y ^ú 2 MF k A.FCH, - --y I i p16+y I1I1I WATERTIGHT _if SHIELD 3/r6-TNICK RADIO TRAINING ASSS. OF AMERICA, ALUMINUM 4513 Ravenswood Av.. Depot. RCA11, Chicago, III. PHONES me all , )'v'TA T YBr,4570135V.+I,I'I,I'I,I+ ,l, ,^ir i,^for rTknon about pi u ln,nimne.ne, aim %n a.T.A.rRWi eel, ,runa today. NAME Fig. Q. 222 ADDRER9 The "treasury' finder diagram as revised by Mr. Sarver. L .1 RADIO -CRAFT for NOVEMBER, 1933 313 BEGINNER'S 2 -TUBE BARGAIN (C'on fitulcd from pape 312) acteristic when a station carrier is passed. Tune to the silent setting between the descending and ascending whistles and slowly SALE rotate the tickler control until the whistle st ups and the voice or music is heard. With everything set thus, adjust the .lo- teetor to its most sensitive point. Now dis - of 3000 connect the antenna and transfer it to the regular antenna post and tune in the saine station with only the first tuning condenser. When you have done all this you have WESTINGHOUSE checked the ttperat issu of the receiver and logged your first station. Keep a record of Power Generator it and go to it to see how many more you can log. Aircraft Transmitters Troubles If you have wired the receiver carefully according Hundreds of Uses for to the diagram and illustrations Outside View View of Aircraft you should have no trouble In securing im- of Radio Experimenters Generator with mediate and satisfactory operation. however, Aircraft Generator a few hints covering the most likely troubles Hood Taken Off may help. Absolute silence in the phones with the filaments properly lit indicates an open "B" The Government Paid Originally $147.00 Each line somewhere A buzzing noise indicates that the grid circuit of the output tube is open -probably at for these Westinghouse Generators the crystal detector. trashes and rattles which occur intermit- tently, with the antenna disconnected, often indicate an old, run down "B" battery. This can be cured to some extent by the use of the OUR PRICE 95 4 mf. bypass condenser shown dotted in the AS LONG AS SUPPLY LASTS diagram; but the best cure Is, of course, a EACH new battery. Inability to obtain the squeal or whistle Technical Specifications when It station is tuned in indicates lack of The special generator illu d is of the threaded for distance of At the end sufficient regeneration and may be due to a self- excited inductor type. The rotor serves two opposite from the drive the shaft extends a/c.in. number of different causes: a poor tube, entirely low distinct purposes: 1. It carries the in- Case dimensions, exclusive of the shaft, 4t.:2x61/4 "11" voltage, exeessIve bypass effect due to ductors for the A.C. generator, which has sta- in. in diameter. the plate wiring being too close to the tionary field and armature coils. 2. It carries The output of this self- exciter generator is grounded the D.C. armature, which corresponds 'a the fed to chassis, a defective R.F. choke or step -up transformer which, in turn, is bypass exciter in other machines. fed to 12 -point synchronous rotary spark -gap; condenser, or insufficient tickler turns. There are a rocker per. The remedies to these faults are obvious. two pairs of mita the single In extreme cases it may be necessary to con- poles stator - ANT. stator point to siderably increase the size of the 600 tnurf. PIP-UO two North .TUNE. be accurately R.F. bypass condenser, but and two this should not be South. adjusted to made any larger than necessary since it will Around these phase the spark affect four poles are the audio and cut down the volume. and the power may wound the supply. It also be necessary to wire the tickler The and unused four field coils spark - gap primary in serles as was done which, is last mouth when SPARK i included in a in the antenna circuit, this should energized, pro. GAP secondary that give enough coupling to make the most stub- duce poles of L_ / AMINO comprises a born circuit oscillate. alternate po- H CON. 'ALLOW mica fixed con- Excessive regeneration can most easily be larity. Each ceKET METAL SNEI.L BAKELITE denser, and reduced by decreasing of these poles aeo SNELL the size of the 50U tapped tuning rand. lt.I ". by-pass condenser. is provided --GYVE STARTING BATTERY However. if the inductance ad- oscillation should with four slots justable in the continue. even with the into which are range of 250 tickler shorted completely out of the circuit fitted the A.C. windings. The rotor is a 12 -tooth to 550 meters. This coil conti is of 25 turns of the trouble is in the 11.1". amplifier stage and inductor that carries the D.C. exciter current re- of No. 14 wire wound on a thre ded bakelite form other remedies must be used. quired by the alternator; a built -in commutator 3 ins. in diameter and 3 ins. ong; the over -all The most common trouble in this case takes off the generated D.C. Three leads extend length is 41/4 ins. One set of aps is brought to would be coupling in the wiring. Check through the casing to permit a t,_ V. flashlight - a contact at one end and this plate provided with a carefully. If moving type battery to be switched into circuit for start. switch; the other set is brought to a contact plate any of the wiring around with a piece ing, and to control the A.C. output of the gen. at the opposite end and provided with a pair of of wood or other insulator makes erator. Rotated at its normal speed of 4,500 laboratory- adjusted contacts. A stream -lined a change In the pitch of the note this wire is r.p.m., the output is 200 W., at 115 to 125 V. bakelite housing slips over the entire transmitter the trouble maker which must be cured. even (on open circuit), 900 cycles. assembly. The over -all length of generator (ex- )s, the extent of shielding that particular Manufactured by Westinghouse for the U. S. clusive of shaft) and transmitter is 18 ins. wire. Weight of complete outfit, Signal Corps, the sturdy construction of this in- 20 lbs.; shipping A tube strument recommends it to the technician. The weight, 35 Iba. shield, or a shield between the two units alcove rotor turns in ball bearings. In order to per- the sub -panel may sometimes bu fectly withstand the extremes of temperature and necessary. humidity encountered in air -craft service all the WELLWORTH TRADING COMPANY If the coupling app,a rs to exist between coils are thoroughly impregnated with a special the phone cord and other parts of the circuit compound and then baked. Shaft Dept. RC-11 length (driving the It. F. choke In the output plate is dc- end), 2 ins.; diameter, 9 /16 -in.; the end is 111 West Lake Street CHICAGO, Illinois feet ve. It is quite impossible to list here every THESE GENERATORS type of trouble that all of you may run into, HAVE NEVER BEEN USED AND ARE SHIPPED IN but enough has been said to point the way THEIR ORIGINAL PACKING BOXES. THEY ARE FULLY GUARANTEED and a little sound, common sense together with a working TO BE AS DESCRIBED ABOVE. knowledge of the operation of radio circuits will enable you to lick any problem which can arise. Remember, always, that every WELLWORTH effect has a definite and logical TRADING CO., Dept. RC -11 Pause. and if you can't thin t he cause-that's your 111 W. Lake Street, CHICAGO, Illinois fault ; yen 11011.t know enough to Lind it tel the renud I'n Iha1 is ..I ndp, Enclosed find $4.95 for which ship by express collect one Westinghouse Power Generator Aircraft Transmitter as per your description. List of Parts I 3- circuit tuner I'm ::au mmf. NAME L2; condenser, I one 2-circuit ADDRESS - -- - Ll; tuner for :iis ntmf, condenser, CITY STATE Two :150 mmf. tuning condensers, Cl, C2; Two 85 mhy. It,F, choke ,oils, L3, L; Two Bit mhy, 11.8'. ch,,l;, ,ails, 1.3, L4;

314 RADIO -CRAFT for NOVEMBER, 1933 One 250 mmf. mica condenser, C3; One 500 mint% mica trnldenser, C4; One double unit, 0.1 -mf, paper condenser, °50 V., C5, C6; HIER Une single 0.1 -mf. paper condenser, 250 V.. C7; I tue 25 mf., 25 V. electrolytic condenser, CS; A NEW MONEY MAKING (tile 4 Inf. 250 V. paper bypass condcuscr, C'9

1 ipl ütmi11 : 11ne 70111111) ohm; ![. -..', resistor, RI; BUSINESS Une 100 ohm, 1 W. resistor, 102: Une 7,00 ohm volutne venire.' potentiometer, with switch attached. 1t:. fm- Radio Service Men Une Ifeterit crystal detector; 1Me typa 34 tube. VI : line type 6 :; lobe. V2' c all ear-roundr -round money r king uppor- line 5 -prong walla' socket; tuults for a who hove sbion and foresight. 'I'1vO 4 -prong water socket trill the Legal ..de id beer now prorli :ally established s in r state. and ra pidly graving into a large scale one open -circuit jerk and insulating bushing; .l bolo is,.. all re:taurant, cafes, bars. clubs and hotels Une .\ill. -1 :rd. binding post strip; are fared null the problem or hnq,crly rondltlimed equiph men to keep omit beer from sourness. bad late and tine power plug nad 4-wire cable; other deterioration resulting from uncleanliness. Une 2 V. storage cell; 'rim, pipes and eons through which beer is Pu'l'ped have Three 45 V, "11" be. tlrits: to he kept milieu lously clean. In ninny stales there 'I'w'n aluminum panels. 4 x T x Irari, regulating linos as to Imlw many tinter ear ls week all beer pipes and rolls have to be cleaned Two aluminum sub-panels. 4 x S°d x I/16 -ií1.: in any establishment where beer is sold. l I Inc nkelit' detector mean' ing, . x 5e, , -x- !tl- .and here Is where you Seri ice Men come in to stake ol' :; /l(i -111.: money: No. 6/32 brass machine screws, nuts and SET YOURSELF UP IN THE BEER -PIPE ('LEAN- ING BUSINESS. hook up wire, Ail Dat need is our new. unique, compact, portable (BEER i'Ì PE-. ''LEANER. Go and ti -it your Meal restaurants, cafes. bars, clubs, and boteis, and make a sert ice contract with the pro- prietors to citan their equipment once or Mire a weea. o r oftener, at a fixed charge. READERS' FORUM II IIII/ lia 1 Ifetu ,uiC sil "HAVE YOU SEEN IT 2" known condenser value and ('x 1s an un- Filled with valuable data. Character- known. istic of all RCA-Cunningham, Majestic, In operating and other tubes. Dozens of circuit di- the circuit. the potentiometer Public Address circuita i,. adjusted until no sound agrams. Finest is heard in the and parts. Volume control guide - phones. Now the resistance- rapacity bridge is most complete ever published- volume Cl 112 controle for every set on the market. balanced so that -= - tat first the ratio Resistance Tables -all sizes of wire and ('2 It l composition resistors. Neu test equip- appears inverted but ment-exclusive Radolek design. Na- the reactance of a con- tionally known radio sets. This is a denser varies inversely as the capacity.) real Profit Guide -s radical departure With the 0011 ohm potentiometer III, R2, from every other publication in Amer- and 2.000 ohm pl -s I used, condensers be- ica. Your copy is free. Please enclose low .OIi -m t. did not give accurate results. business card or letterhead. Write now- However, by using more sensitive planes or a higher resistance piton t iometer, smaller con- The price vet. pay for rime BEER PIPE -COIF, densers could be tested. The same result V10 CLEANER will mine bark to you In car i ngs in a very few dar, of not k, and every cent you take in alter that might also Ile obtained by arranging an audio will be clear profit -BIG MONEY FOR YOU! oscil ln ter of higher frequency or more power. SELECTION The BE'lit PIPE -''OIL t 'I, E.t NI.: It here described Is Any type if triode may be used in place of 'rnl ificall> en .depied to du a thwrongh job of elean- the 90; adjust and "R" for best opera- ing beer piped lies, rolls, and faucets. It Is mggeillY "A VOeS built for bard n and long son ire. There Is nothing tion of the circuit, and tube selected, to get of under, out WitittM A. EDSON. He full' gu:oanlee every one of our ItEEIt PRICES COIL CLEANERS :igolnst didn't: In either material or Olathe, Kerns. w orlauausun p. This portable apparatus consists of a r R.P. motor, `11.4(3- a 1IIlt Et "I' i tUVE rwnnpressur, and a water -tank. The lank is prof ided triti aster- Intake plug; pressure rauf.; 60 -Ih. safety :ale, water nutlet lam et and bore flat- A METAL HOLE CUTTER nett tune for ''obi. The entire equi hurlent weighs 42 iI,,., SERVICE I s RADOLEIt 131 and nl 25" Du length_ 11" in width and Is" in The hone cai s t'uetor of radio receivers en- CO., Canal Station, Chicago height. a`Shilgdag weight 55 lbs. I am a Dealer Set, In man counters a long. hard job. when he under- r. 'rime whole ,rot fit Is portable, and mounted on a bane I utnrate tronc Shop or Store O; from (tome D own following coui vtnd iv Rh - null t'iaels. takes to cut the tube socket holes in a metal I the Test Equl tnnent ..... To use the apparatus, all you have to do is to plug chassis hi'sperially iron or steel). My training and experience is: your motto into ally A.C. light woke', fill the tank The writer, a tout designer. first tried to three -quartets full of hot or cold water to which you make one by hand may add ammonia. sad stola, or any cleansing , entirely using only the pounds, start sour motor until your gauuge shows about tools to be found in an average home work- Name 40 Ms, of air pre -sure. c. w.a the empty beer line with shop and found that a strong, service- Address your tank, open the beer faucets and forte the cleansing good, liquid through the pipes and rolls. Repeal the opera - able one NV as practically impossible to make. tlmt with clear water, and blow out the coils and hopes The holder shown in Fig. a, is easily cut wish air. This is all there is to it. out of iron or steel with a hack -saw, but the Under our Intrndnrtory offer-here announced for the holes - first tame -Ihi, whole senire equipment de- eribed alas require the use of n power -driven drill will be sold ;vl a 'limited time at the aheclaI trice of press. 'l'he reaming of the two holes can im' omitted provided a careful job of drilling is dine by a good mechanic. If the holes are pepetttluble $37.50 reamed. a drill about twenty thousandths (Shipped by Express or Freight Collect/ smaller than % -in. is used to bore them first, - then a % -in. reamer Is used. If the holes are In any n v business venture. one of the prime ele- Q#lçof(Ofiúl ait, of su ss is to get in on the grouIld door. Ito not reamed, a Ya -in, drill Is used to finish out the first Mae in your rite to start this new service bust - the hole to size. These two holes should be a 0rffifilla nett- ! lash in on the start ! If you work it right. you sliding lit on the rod r will make a lot of money, and you still Irate work to drill that tits Into them. e keep you busy summer and winter. A good merhnnic will out out the holder, lay ..I,1UD Send us >our order now, using the order blank below. out and spot the holes, then set the holder in n hand vice to drill and ream the two holes LOUD SPEAKERS ORDER BLANK - at one setting fto get them to run parallel). ORMAL efficiency 2!_ to 25 watts - --- peak rape. Ili ., w ills! BC Ie's The cutting, end of the tool and one end of diaphragm and voire roll a. WELLWORTN TRADING CO. the pilot rod should be hardened. The har- -sure higher efficiency and ' far (l1 W. Lake St., Chicago, 111. RC.II dening of the cutting tool must be very care- r dependability! write for Ill- . o n 111'1) milts, all aluml- Enclosed find $32.50 for whkh please slip me by fully done, for, If left too hard it will break; oeulherprwf "NATURAL -- express or freight one of your libElt PIPE-COIL if too soft it will dull rapidly. The harden- I:\I;'t,trumpets, microphones, oz. air mimeo horns. l'LilANElt outfits, ing Is done by heating whet be will the cut- Get dc t a ils of Fite -Day Free Trial and Information ting end over It flame until dull red, then MI nor new high ireouenev theatre unit. Name plunging it into thick oil or warm water. After which the end is polished bright with BUD CO. Address emery cloth and re- heated over a smaller SPEAKER flame until it is a very dark brown, just turn- DORR ST City Slate ing purple; it is then plunged into water. TOLEDO OHIO- U.S.A. RADIO -CRAFT for NOVEMBER, 1933 i 315 nie tools are cut to shape with a tile, befor hardening, of worse. .SERVICEMEN In using the ratter the sork,is are first II. to air Ile ' lulpmled a ++rntlai parts for the Revised Rado -r :tit Universal Analyzer: laid out, and their centers spotted with a Index to Advertisers 907W LCA ' .:III 7 -pin Latch-leek Analyzer prick -punch. 'l'hen a ly -lu. drill Is used to l'lltg ' s -wire $5.511 ti. cable List bure a hole at prick -punch 974DSA. u A. 976DSA, and 977DSA 1.lst 5.00 the mark, aft, -r- 4568 I c Bottom Socket List .50 wards reboring the hull' Wit 11 a ,, -in. drill. 427 SI.n .,. 1 main Sorkrt List Finally, the pilot of the iule cutter is placed 427A ,all I limos aket t .\ero'ox C'orpor:ni,nt .. _. _.. Lid in the hole socket 91 De Lull. I: ed 1 -1:rid and the hole cut. \ 'ill List Alden 511a. Co. . ... Now nist I the time to modernize Some folks prefer a socket hole wills a dia- .% Hied Iladio ('a,p. all of your test equipment. Don't meter of delay any longer. Here are kits I1, in., while others want une 1% .\m,rie:m Itadiu Itardoare l'anlh:wy priced to 0t every serviceman. In.: I have split the oith this tool .1npriran Red Co.,- and diagrams Directions includ- an duladC it 1 /Il] fus. iu diameter. American 'rrrhniraI n, vielr' ed with all outfits. Each adap- Atom-rite Corporation I IN it'' LAIlAnt', ter has a bi -rotor ring with .4utonpdr \Ilg. ('o distinctive color, hand between :11: Ittl itlrtt Lane, heater holes to enable any adapter to be quickly joined to the Ils Lltje'port, (tuna. B analyzer plug. Itud Speaker Company 315 Here is the o rot ..ion :d m "del. lsrd in, Ifulslrii,- .\pplelee t'o, 300

.Ir,yrll. 1 , tester.. II C get. tins 1,11 II BOOK REVIEW Na-Ald l.ap tc1. l'.tpilai Radi I _, 11'1111g Institute 3 O I e lease. I,, TELEVISION ET SES PROGRESS C'aaBrd It:ldi' I. .it elics o4 9117 Wl..\ !, Net'' l'L11.' II- \ '., L.. . 294 pnnlg Loci -iasua (Television and Its Progress), by P. 2114 b'zer flog t, ill] 'font. 1.i C. G. Handle Henlardin(juer; preface by A. Blondel. 211Y I' liiS;\ 7A to 1-prong 1.:1t1'íí AMMO, oOS, 311 :. iISA TA to 5-prong latch .\dallier Published by Dunod, Paris, France. Coyne I:Icrl.rl", -. 257 7,1/S.\ 7:\ In I:- prong l.an11 Adapter 51/2 x 8% ins.; 244 pages, deckle edge, .:7S.\ 7A to 7 -1001ng Lath Adapter I) 150 illustrations, paper covers. ,u :\CI..\ KIT Complete shown çs - Ikuladnn:nul Corp. 290 Here ls is the set for those who 1111e outstanding fault to be found will] pre- Dumont Electric Co. 304, 311 want the lowest possible prig. Uses the Handle plug ,citi cious works on the sub,ieet of television was ni red u. pr "NI ake- t'"ur -u t he biased manner in which they were pre- E a dl,lartr, 1'1 .1, pared; there was obvious, Elrrtnd, Lite. 307 tesrn. in rd :nlaph an effort to "sell" sad a pa it i,Ubir system, peatnits .ax.1 rG. television or the aulhur G In socket. end permitted his patriot ism to OVershadaty luis choice of Greupark Company 319 977r 7 -prong Plalu -'I. ma feria I. In pleasant you 1%1Si with Analyzer Plug I I. is .15,11 of affairs Is -1.a 'l'elevi.i,m et ses 4 4741\' , -prong . H to Wu f cog re. >" which. n11hongh written in Adapter the 11anmuuun )Itg. l'ompany 297 97 :.w 7 to .1.pí one Preach Inu_uage. contains a wired eunuk:l Illy eels. Harrison Radio Co.. _.. 30.1 Adapter unglolitan rev ietr of the etti ire field of 971W 7 to 6 -prong tele- Ilnodsciu 1'omp:u,y, Chet. 312 WItesi vi:i,nt. Adapter Il% a'ade s., 303 977WA to 7Aprong l'1.rhn l,a 11 is aol too much to hope for an Wired Adapter I :nglisp ce (Shill of this hook. Iiuwv -v,r. that L 9771 KIT Complete as should non prevent the amhilluus tPelsttkill I.erds It:ulio ('onlp:nty 304 410011 gleaning wino lie may from This we II- ill ts- Leut Itadiu Campauy 17 8 -Wire Rraid- Covered Ana is zr Cablr...i.ia í10- tra1ell volume tvhi,ly nil hough lea Lynch Mtg. C'unlpa0y 3110 REPLACE YOUR OBSOLETE SOCKETS WITH writ in THESE LATEST COMPOSITE SOCKETS french. is tan remelt' host roil ve, as is luth- M Ora: 4.5 -n Contact Cuum1'Shr Soa- ket.... l.i-t :111, . eated liv t he following review of the chap- 177 7 -7 l'ontnrt lbuyxnile Surkel I.i -t rot, ters. S,idwest Radio (imp Baci: Cov,r ht's here at last 1 -The - - - I i i Tb hixlnrn nail rxxenlinl prinriplex 51 :Ike - Y ,ur Own" r- -r -- .r -1,.. nJ N Adapter Isle. All the . - ."ra felerixioa, This Chapter starts Willi a lie - Na I iot,:ll Radio íu t it nt 270 part, for taking , r -I- - -?f;.. seriptinn of the eleeno -c hemital picture ,Iii red Eusse, i,s foi is Irans- Sad ion :d Ilion Radio Cott' Mission exptrimtals of Italia and Blackwell. around the year 1570, and concludes with a P discussion of I he Met' Zworykfn cathode-ray)' l'al Ko, Toe. 302 sy.sltm of television. l'eml,let n L;da,r.Joties 3..2 12 'l'Gy pro/dewsv of le lecixioa disti tilx "pi i- Volk A Co., R. I ani 'üp. col ts-n,/ ciccl rival elijlicullic. In this ehnpter Popular Ib.nk Con. 3''4 I'oslal Radio C'nrl, 311 and lead X11 , i res. moo the Mmhur rh:n'l y shows the rtnsuus for Precisionision Resislar Co 303 "Slake - Your Own' numerous effects eu ,'ulll114.1141 Adapter Kit complete. in television re- 1.1,4 S2.50 coPlloll and U'answissi,tn. R Bought ai,a ralely ratel 1. I:: ) 7'1,1 , If 1t llnvt ,qu 5. rnlioax of It lrri- Ramon Electric C. :1'4 and small 7 tue xi,ot. >1a'st r t han section lids al r' adrrs of the yu111111e' will ure Radio City l'naluets ('a Rnr, 25e each 11111t the this is 100.1 furl 'r, -tin, cbapter.í Radio R Teleris Institute !dl GET TO 'Phis :12,1 THIS ADAPTER MODERNIZE YOUR tine, pnrli,11111 HS% ill the Inridii - with Radio Trading Company TUBE CHEG.KER I Radio . \s-orialiun 313 which n l Training 950XYL lu :nn her bn t u le, I l e s a l l i _ n i a g suh- l'nitersal Tube Radolek Compi uc :115 Check ow Ad :q,ter teso over jeci oÌ the I:Crr cell and Ni, 1 1 1 prism i n cuu- Ina NEW TI'Itl'S. No, wires IRC.% Cunningham '11íb'' l'oro 3o 5 Heel ion with t h e poly rival1 ion, of li_ht. - uo Ira',+ lark.- ,c ry RCA Inn il ones, In, _. 204 1 4 1 7'G. e t , l +h,'ple to ala'l ralrv_ r lrrnit Mme >sutix.vioo ,rod r p i o of ltie- RCA Victor Co., Inc 3.19 eli:nr:uu mill direction t isinu. All Ow various types studio ar- Iteadrite \tetre Works hoside Front l'ae, r riot Insult, t non r:la_tnlenls iui 311 NEW TIIIES with r shove, followed cu rim's cone U'ips :I rte Remington Rand, lue. for r rding tt:utings I111,, tiscribed. with pa rl it'll lnr 1,1%m ce I.1 the 1101.1 Royal ..... 30ì a d fnulure tubes a tout-d lechid e:II features peculiar to each system all unlit, List l'aaire 56.00 r 4 151 $ It your lobe checker has no 111:, Rndiot'iteiuss fc,' Ins r ,,,,,,s trier. Tl:e Soxedogy rot- ,tdlge ncilrb the 9',lSOl, :r L'pier mot be used . \ineri,nn reader of this Mud: will he quite 305, lie k:u ut the 1.511X5 1,, 9 ".lsnl, t'y aaolmded tit the wealth of information which Sballcros- Nit,. Co 353 1,111 01111 1. 1:. 10.1 Li ,l 1.11, .., 51.25 author Slntrr Bret lese, t'1'nglnu' nn the has Compiled ronn1ramg nano lCe[ silver. '15OTR TRANSFORMER-TYPE TUBE- CHECKING 51,for- go lue In -ides. hack lover ADA t- I,vlsiun rtlnipmcal bn.o4 1,u um n) ditÍ,rent .1o1ms,m Sodi, 11 ' C. :117 I. :cif -cuntairJ ma- television si-stenls. soul :n ailnhll ill the c.uD- SItwarl %Varner 1 "I'll 3119 +a transformer a n d I, age switch for testing Iri's Ut which I hey ur1 iudigl uous, Snpr.me Instnunl its Coll' '; L 4, 31:1 in to 311 tell lobes 1111 l'ulln.,lr -rap tel)rixion. tr IS of inter- One 21 l uberhrrker est to obscr'e T o`ker Can rhrrk that the nothur has Ile voted

1 ... 21Z5. 1:1. tI 1. 12''43, CoMSiderahll spa CC In the sub,ir,'t which Is go- T:nnsig, t." .. :ton II. lit A22. A25. lug to reeei'.. the greatest attention in the 'l'ilton \Itg. l'onopoiroy cis, A311. A32. M0. Triplet Elec. hot lone rot Co, or t AE. HZStt. RAI, next hro years. For, television by 'l'rum:n, Radii, Shop 9r., 21 :2. I',1. 25'/,3. means of S114.1111111 tube p11-1 ue disseutidtng and ,n !.\. el,. If not. Try Mo Itndio l'1'., In,. o cd the 9.o'r1t adaptr. relou111iufng suits Oppea rs Ili b, the most logl. r cet non and reoul ehart on hase of ndapter. cal sysiol SO far proposed: ihr advatil :lgts U and be aile to Iitrrk ne,v high all the offend by. for instance cal -r:iy Siien phnu, 1'" 5Ae) soilage tune+. List frire $6.00 lde tubes are Universal not.ntr-irrmrn's Discount nume'ruus. as the :nn how shows in this clmp- e orders amounting to glom. LI -t frire lu e4 ter In which the latest ideas are described. w HERE'S THE DATA YOU WANT ITs : u4 Iwo stamps for new Buckle, -hotting Illne. 7'1tr Prof/ry of IrIry beiun, Intel'ua- Webster ('onq,:utv, 'Fla - lt Trading Company' '.'fed Lobe socket , o1 different tIonnhl)' known pioneers in t, -hi'r isiun tell Ilse \1'ellwnui :.II. I-, of data uwetiontn, rwiring Obsoleteb otau art :uwq'z- reader, hl this concluding' chapter. just what \\'rstiaghrn'.e Elee. A.; ?Dg. c.1 ' o and using new tube: In plue'' of old types. In- Weston I:11.4 Insl run. nt (',.ti '- develnpme'Mts we may expect of atalog Pages on all kinds of Moll.d anal alrl In the field \1'holes:de Rarlio Senicc Cn .:u4 sockets. speaker slugs. connector, s ot television within the !lest few years. ()no- u d plugIn rolls, roll winding data al, tations 11-C receler circuit, ete. In14ude the opinions of tin rt belrmy. IDennt. I hilly Oiler, l:duunrd Henn. \InrC ALDEN PRODUCTS CO. (While every pnr:rdion is taken Io Moore ar- Chnut9rrre, Ren, Its ray, Van 1 )yek. \buufred DepgROCKITONIS SL eracv, s'e ea t guarantee again.) ehe NA-ALIA won .1. tes-i_ MASS. Ardenne, 1.. IWird. lingo flernsback, hilily of un occasional change ur ortti,,,iun in the and V. K. Zworykin. pnq.ard ion of this index.)

311, RADIO -CRAFT for NOVEMBER. I 9 3 3 NEARLY 3 FEET BOYS! t THROW YOUR VOICE SOLAR TELESCOPE $1.25 LONG S 7, Into a trunk under the bed or Y anywhere. Lots of fun fooling teacher, policeman or friends. THE VENTRILO The new Excelsior Solar Telescope is a large and serviceable intro: I made and accu- a little instrument, fits in the rately fitted. When extended it is almost three feet in length, and wtnl -..I measures not quite mouth out of sight, used with - twelve inches in length. Telescopes of this size usually sell for ninny titles this price, but by above for Bird Calls, etc. Anyone can use it. importing them direct from a large European manufacturer, we are enabled to offer them to our Never fails. A 16-page course on Van. customers for ONLY $1.25 each, at which price they ought to sell readily. The lenses are well triloquism and the Ventrile. All for 10e postpaid. made, the sides are brass bound, and the four sections are perfectly fitted. Here is your chance to obtain a Telescope for a nominal sum. It will be sent postpaid to any address upon receipt of $1.25 in any convenient form. Postage stamp, at't erted if more convenient.. arts Nam 1Ìuit"sellerer only MOTOR us. 10 C ELECTRIC MAKE YOUR OWN RADIO 1 An Electric Motor for Only 10 cents. Pistol Reim I ;, Sound- a lmo.t unbelievable but it Blank Cartridge w., Ne. i is pet featly true. For ONLY 10 Dry STYLE Ó n.,' Wad news. cents we send v'm all the parts REVOLVER e tc. Thal Eat necessary packed in a neat box with Prices belt tar, full printed and illustrated direc- `i 1 VICIENT for assembling. No trouble tions 50c n o. bow rtaaooaks at all putting the parts to- d ° rte tocs. gether. in fact it is Ft's. $100 peul Rwur Bete. W .. tech f hick be Just follow a few simple rehmsd 1 ries Alao how to build instructions :mil in a 0 Ravin. sur bringing ÌIn foreign Nano.. few minute: the motor pollee ana. ships st r, eta. ONLY 10e.postpaid. is ready to runt. IOc postpaid. Well made and effec- SILENT DEFENDER tive: modelled on late3'. Used by po- WONDERFUL type Revolver; appearanco lice oaken, de- 35¢ alone enough to s) are a teetives,eberiffe, LOOK INSTRUMENT burglar. Fires C night watch- Blank Cartridge -2 obtain- men and others Greatest t It i n g yet. able everywhere. Pries 50e. or better make and as a means of Nine separate articles superior knish $1.00. Blank Cartridges 50e per self -protection. an one. Odd. Curious 100. Holster (Cowboy type) for Blank Very effective. Interesting. hots Cartridge nd Pistol 50e. Shipped by Ecpresa only. Cannot go by parcel Easily ate the of as well hi pleasure poet. 770 page Catalog of firearms, sporting goods, novelties, hand, the fin- very useful. Can be ate., 10e. gers being graepos In the tour holes. Very -d as a Magnifying (Haa. alumi- Opera Glass. 3 .Stereo :rope, numtheynare every` light, weighing a Burning lens, a Reading Olas. a Tele- than 2 ounces. Bandy pocket size scope. a Compass, a pocket Mirror. and BAG O' TRICKS 15c always ready for (natant use. PRICE laryng) .r iff..Ar : m ining rye, ra . nosee throat. It 25e each, 2 lee 4Se postpaid. Catalog toe. is wort!. a.1 toe a uut to lnate t venur a painful cinder in It Is great furl mys Cu. Folds flat and al's Gt, pA -ket. Price, 35e, or 3 tor 51,00. tiring your friends. WONDERFUL X -RAY TUBE -- Get tills Bag O' Tricks A wonderful little Instill- 15° and be the cleverest ment producing optical fellow in 3. o u dis- Illusions both surprising trict. Cons-alms eappara- RAY and startling. With it tus and directions for you can see what M FOCR FIRST CLASS apparently the bones of Make Your Watches, Clocks, Etc., TRICKS. i n c l u d i n g the your nose= the lead In a lead pencil, the Visible by Tbe«,I.t..tdi...>isthseeleuee MAGIC l'A GULF: (mystify Interior opening In a pipe stem, and many Night your friends by making other similar illusions. 31er 25e. dene.a nierbilant stW. w e be SI last oroesnd dlbv,;,áurm< tpb,lel fe.rknbl. Facelift, LUMINOUS PAIN r, which, IpplW to thew... of any: aril.. melts. of eels. neat. match :tick jump from It perfectly 1.141e se th. dark. THE THE NIGHT, THE MORE NM. one hole to the other). Exploding Matches LÌden.AHT IT SHINES. Quit. .,mole Io un. A. so > en do it. A bias paned b the dial t h e TANTALIZING N your t.. or s.1 subi. you tell the time by eight. You r.n ea pu. but- Moro tap Oboe 46tä mob i CROSS TRICK. HINDU win. look like tons f H. li.bm tel bone , sad Ionumenble other ankle.: T1.y pat i w n Luminous Onelaa LansawR k. ate. Bottle containing waeiert to M Y ST IC SQUARE yourdinar but plod. reel .10.11 . fine. PAea 2Se. Cra.r.ireSO< and $1.00 00.19,14. with loud bent when lie 11 TRICK. and the NITS - eastehee to boa. rE1t101'S RATTLING pow bow 3 brae 35e. 7Ñ STICK TRICK. Full instruc- lOc mailable. BIG tions with each trick. No skill Weed by Ezprlonly. ENTERTAINER required. Everything complete for 180 Jokes and Riddles. 34 ISe postpaid. ITCHING der Magic Tricks, 54 Parlor Games. ,.ra.rP000w 73 Toaste. 15 Tricks with Cards. / tlWyok»jpta Ipt.n.iroNSo- 50 Money- making Secrets. 10 oó 'Dpt té.mc w1 Funny Readings. 3 Afonologues. Electric Telegraph Set 15c rough enjoyable. I7 a are boys! A ele.'OrtC tole - 21 Puzzles and Problems. 5 you private Ite- graph set of your owe for Ifat Lots of fun nod- r'' MlÌolltngÌ.W¿¿detpe Comic Recitations. tie Cut-outs for ins ages to your friends. Get two sate. 'iÉ teiá°ndpotbepowdu Checkers an o ese, Dominoes, Fox and Geese, O Men Morris, book them up as how* in the directions. for v400ew.roplelch. Spanish Prison Puzzle, Game of Anagrams, etc. All fort.% postpaid. two-way mensa.a for wending and wt. Tb. Melt V ÌÉ é some receiving. No trouble at all to doaemaemtlé0'pÁ`bs t:ór.a..` operate with tbssimuleinstruction. foril`/depd.:: that accompany each set. HYPNOTIZE! J` Operates on any standard ANARCHIST BOMBS dry batteryobtainableevery. Pe One t Mew .. Thr Fl.eebook With this outfit r Enured woe fall ót il abo,f I .an learnar to wtram ,it oo ill mammary PLAY PIANO ed et` ternatlon than a Bmbortw. hypnotize. l by the cheese. The mall entirely Mon. Interruttnnal Cud , isapwwn In snort time. INONEHOUR nd in vary abort time /DOTN'DASN IOC. yy 500,1 a with [hi. new VAMPING been an pert o'er- myrPA s . The BOY for SSC., ree p.r dog ROARD. No tencher needed. Elaetrkian a arda per `haprieinny amnia. Place the °'°gee =ogee Ero.gross aotN. BWpWd e..: t:wiriiwiaáti.: R. ö upright `vet el.a ear.ru ti t t s 100 by Eapias. Not Prepaid. GOOD LUCK RING ha ppiiaann amp brut. complete r 1 ry Add 106 for 64 thou... of woes, witheh key. // .g V. allot Inn d eounuer. f a - rdf Cea book II NEEZING m .11.d. welt , for trot.. ra.: men., POWDER Ali,., eon: d s 4p F about ae 500 of al she ntaat tricks In male. then novelties. sorti.. gam.. .tog gone. robberber ON wandnlommint book. r.reooHlosin weds end ADDRESS ORDERS FOR ALL GOODS THIS PAGE TO Mime Mca or . E. Prot.: Stamm. articles wt.d . cannel. MO e>, Mom. and frontal Mete. we..ted Al clevere rate of Fachnone. jOHNSON SMITH B CO. °e!. Racìne,Wie.

RADIO -CRAFT for NOVEMBER, 1933 317 The kadio.eaft Library Series covers accurately every branch of Radio -anti thoroughly, too

Presented on this page .ire the new hooks of in these hooks will increase the RADIO your knowledge; you familiar with the field which he represents. -CRAFT LIBRARY -the most com- will find them a real plete help in your work and they This is perhaps the first real opportunity that and authentic set of volumes treating indi. will contribute to your money earning capacity. vidually, important divisions of radio. you have ever had to build a radio library of Each book Read these books during your spare time at hume. books that are authentic, right has been designed to give radio men the oppor- -up-to- the -minute The authors of these books are well-known to and written so that they are easily digested and tunity to specialize in one or more of the popular everybody. Each one is an expert branches of the radio man; clearly understood. Mail coupon below for your industry. The material contained an authority on the subject-each is thoroughly books.

Book No. I TO THE RIGHT Book No. 4 Book No. 7 Book No. IO WILL BE FOUND Radio Set Modern Radio Radio Kinks and A SHORT RESUME Analyzers Home Recording and OF EACH BOOK Hook -Ups Wrinkles All About It And How To Use Them The Best Radio Circuits For Service Men and Experi- A Complete Treatise on Instan- menters taneous With Full Instructions end De- A Complete Recordings, Micro Compendium of the phones. Recorders. Am pliheri, scriptions of Set Analyzers, Most Important Experimental A Complete Compendium on the Tube Checkers, Oscillators, Ete. and Commercial Machines, Serv- Customhuilt Receivers Latest Radio Short -Cuts and icing. etc. Money -Savers By L. VAN DER MEL By R. D. WASHBURNE By GEORGE 1. By C. W. PALMER SALIBA This book explains thoroughly It is fascinating to the experi- there is one the operation of set analyzers. menter. or even to If subject that the up -to -date It often becomes necessary for is fascinating to every radio tube checkers, oscillators and Service Man, to take a commercial experimenters and Service Men to man, it Is that of' Home Re- other testing equipment. For set and to change it into one us- il upon memory every man book their for scone cording. Of course, this volume radio this Is ex- ing a famous hookup that Is not short cut or radio wrinkle that tremely helpful. It covers every is not all on 'Home" record- found in any manufactured set. will solve a problem quickly. In ing. phase of testing and kites you Stan excellent circuits business. but the information con- valuable have nev- 'short tuts" mean time tained therein is important to short cuts; completely er been commercialized, but lim- and money saved, and to the Serv- illustrated with photographs and commercial radio men, studio ited only to home set builders. ice Man "time saved" means operators. engineers diagrams to facilitate the use of Thousands of these popular Ir- money earned. and others modern testers. Recently reprinted. interested In this phase of ra- cults have been requested from dio. time to time, and in this book The art of recording and re- we have Included over 150 cir- Book No. 2 cuits. which Book No. S producing broadcast selections I. Include the famous becoming more Important Peridyne. Cash-Box A.C. -D.C. every Set Radio Questions day to radio men. experiment- Modern Vacuum and others. ers and Service Men. Equip- Tubes and Answers ping dance halls, auditoriums, churches, restaurants and homes A Selection of the Most And How They Work Book No. 5 Impor- with public address systems and tant of 5.000 Questions Submit- amplifiers brings many extra ted by Radio Men During the With complete Technical Data on Hew to Become ollars and often an excellent All Standard and Natty Special a Course of One Year income. Tubes Radio Service Man By R. D. WASHBURNE By ROBERT HERTZBERG How to Get Started and How to There have been Make Money in Radio collected a wide Bak No. MODERN VACI'l'M TIRES Servicing variety of questions which have II describes the fundamental elev. By LOUIS MARTIN come Into our editorial offices dur- Iron theory which Is the basis of ing the past two years. and only Point -to -Point Resist- all vacuum tube operation. and The ambition of ninny men In those whose answers would benefit ance Measurements goes progressively from the sim- radio today is to become a first- the majority of men engaged in plest two- element tubes right LP gradede Service Man. It is not as radio have been incorporated In The Modern Method of Serail. to the latest pentodes and thyra- difficult as one might believe. but this amazing question and an- ing Radio Receivers Irons. It is written In clear. it rennet be done In a few short swer book. A tremendously long simple laneuage and is devoid of months. Following very carefully list of topics is treated. By CLIFFORD E. DENTON the mathematics which is usually the advice of Mr. north). who Of so confusing. Valuable reference has dealt with the problems of the dIMcult problems which charts and characteristic curves thousands of Service Men. this Service Men face today when of standard and special tubes are book deals very carefully with the Book No. 9 repairing receivers. the greatest to be found, also diagrams of essential stages in the prepara- is that of replacing re- sockets and tion swans. vamorn in 'tpr11iimper pin connections. for qualifying as a Service Automobile Radio difficult when the valve Man. `s, ntesw unknown: and mano- and Servicing r ° n standard se s doanot this f Book N.. 3 A Complete Treatise on the Sub- InThi. hook ionmen w i1Ì findleh. ject Covering All Phases from informallon needed to wdeury I.ee'. Book No. 6 operating Installing to Servicing and rñu book' cuts The Superheterodyne Maintenance in lhot time u:unii Bringing Electric required to odium the a rat t. Book Sets Sufficient apace has been denot dto the Up to Date By LOUIS MARTIN elementary problems a d the theory of All About Superheterodyne, elee is applied to Automobile measurements thethe, et Man With Pentodes, Multi -Muss Dy- radios are up and a How coming. and someone has to serv- ve ,mprehens idea a to how They Work. How to Build namic Speakers-Complete In- to overcomee im ohlem and How to Service Them formation How to Modernize ice them properly. It therefore will find a partial list of the behooves contentsn whkh will A. C.. D. C. and Battery Oper you to read this im- appear in this new By CLYDE FITCH mensely important new hook on atad Receivers INTRODUCTION. Advantage of Re- the art of Automobile Radio. Thy iMÌMarine Measurement Method of Serv- There is no more festinating a book subject By CLIFFORD E. DENTON Is concise. and full of illus- icing Radio Work: Beale Principle: In the large array of radio trations, photographs. diagrams ethod. of Resistance Measurement: circuits than the famous super- In this country there are over and hookups. R to in Radio Receivers and Am- plifier.: Poin o.loint Reai.tar`e- heterodyne circuit. R'hether you ten minima electrically operated A few of the really interesting are a Service Man or Typical experiment- receiver.: that t dd be modern - chapters: Introduction; Automo- toeing "Ohmnet e ce ]..sure. er. nest -hand knowledge about the ized-by placing Modern Tester: Routine construction vin them new trim tive Radio Installations; Complete of superheterodyne re- tubes. new speaker equipment and Descriptions of Commercial Auto- Tertian where Circuit Diagram ú Araib ceivers is very Important. The other modern Improvements. l e and her e R e : book on This motive Rereivero; Servicing Auto - Ñ Testing where Su!erheterndrnes gives business of improving old sets nt ive Receivers The Ignition it Available l e underlying principles of con- knerwhodts hn. irRte leomietienasn n their tan go to the experimenters and System ; General Service Consider- eeÌtvss e struction, right from the very first Service Men they Twinne n eae Mkvennobsswsr,s set made. if will quirky ations; Effects of Temperature on mein; APPENDIX. Hesisare Chart. mop Into art ion. Povrr Supply: Conclusion. etc.

ALL BOOKS The hookas in the new RADIO -f tt.F'r LIBRARY are all strbtly up-to-date. and written by men who know their subjects. The v, lumen ant all uniform size. Gx9 Inches. and rontain un an average of 50 to UNIFORMtlustratinns. Lush hook Is prhued mt lint- book paper and m expense has been spared to make tt ,ad.t:mding s'alite. fist It: ,' frontal ,imnrnls as scull as tram they metlianfral standpoint. Clip Coupon and Mail Today!

Big Discount GERNSBACK PUBLICATIONS. INC.. 96-98 Park Place, New York, N. Y. 1 have tirrled below the numbers of books In the RADIO-CRAFT LIBRARY. which you to You are to send me, and have deducted 20% for ordering five (51 books or more. I have Included my remittance In full, at the price of 50c each, when less than five books are ordered. in order to make it poi -i bit for Itnow to buy these book.. the fifty (501 cent prime has limn made uniform for all volumes. You can buy these books separately, but you should The amount of my remittance le._ (Stamps, checks or money orders accepted. ) take advantage of our special quer: Circle numbers wanted: 1 2 3 4 5 6 , 8 it 10 11 When Five (S) Books or More Are Ordered Deduct 20% from Your Remittance Name -- Address Simply fill in the coupon at left. and nail it to us together Pith your remittance. ('heck, stamps or money orders acre Pted env _ Slate SC-11-33

318 RADIO -CRAFT for NOVEMBER, 1933 $50,000 SPEAKER CLEARANCE SALE! SP CL t i, - S.1 t i - FEAT!s ri FARRAND INDUCTOR DYNAMIC Absolutely Farrand: The Ideal Short Wave Receiver Speaker: Genuine Eliminates Hum and Line Noise: Compact in Size: Brings in the Very Weak Short Wave Draws Less Current: Stations: Do not confuse this model with the various similar types on the market, posing as Farrands. This is the true Farrand Inductor Dynamic. Its adap- tion to Short Wave Radio Receivers has proven a popular step. The most inaudible stations are brought in with remarkable clearness without the customary noise and hum of regular dynamic speakers. Has two magnets parallel to each other with a bracket placed between them to facilitate mounting. Overall 9 ". $3.95 BOSCH FARRAND SPEAKER CABINET Limited Quantity! 12 .' MODEL Will a,., n nu.late act INDUCTOR magnetic, tir' orr ehnatnit up 1n" ir. GENUINE diameter. .t bed e . :u',,. C DYNAMIC Janet R A ally anti ,p. .i, . j tinishe.tl. It The 12" models have two 1r nets standh!g umrighl. by c of the forces, manufacturers of cabi- MAGNETIC ith a bracket ton the bet- nets. (;rill contain. n to ease nu!oIing. DI- nalons of the 12" model: gold limoge cloth F. untrastlsg ^' high and 6%" deep - color CHASSIS t12" scheme. 11miell htuh, 12" wide, 10" deep. This chassis is the 'dent ieal Our Price $5.95 $1.75 une used in the I(.C.A. 1011.1- 101111 and 10:3 Speakers which list fur as high as $35.011. Note built -in t mgmt transformer OXFORD JENSEN which permits use of 450 volts without distortion, rat- A.C.and D.C. Model D7,A.C. ( ling Llasting. Generous oversized niagiet Pile thick armature is accurately centered, the CONCERT DYNAMIC -I urdy medal trame is lined wi 1 a special self - tic .,1 as all ad- batfliig fabric, greatly improving mletic I,.. line" note rt rodrl. lit i.mal speaker le Three nits nt this sellait halal speaker. ' Note th -. point suspension Many hones. ai well : slanted !igatnl surface of the cone, an exclusive fe..' cone types. A.C. 110 public address .a ar280 rectifier. D.C. tu h :niter's perfertis mal ion quai IhI. tents. Will handle ) all npnsluct dels have a field enormous amount -idertddy; most Compactly made; 9' resistance of 2.5110 volume tvlthent distort - .. Ineter, 11 /_" deep overall. dons. Output traw- Ing or null' Prive $2.75 l-timerangle be had ped with - - or push tube. The roll output tubes. ch. WI" wide. and : required, I6 ". Supplied n. Piero t C. with Tube $5.75 n.f. Model $4.50 $8.95 D.C. Model $6.95 Price Going Up. Buy Now! OXFORD PEERLESS Carlso D.C. Stromberi A.C.or D.C. 0.--00111 A.C. and DYNAMIC MAGNETIC Auditorium SPEAKER PICK UP- DYNAMIC CHAS SIS nbl ie ad- .I wpl OH at ion is Adaptable f..r the miat.a itaa here. For perfect tonal baket 2Rle it )amerful amplifier. Equally willed quality and service insist on a genuine STROM (tit a 120" use with BERG- CARLSON PICKUP. Little has to be ,truing. litte n' /. for any re- with . eriser employing the al dut it rombenr -Ca rie'n quality is knots, tunes average type nit audio world over. Prier includes a St romberg-1 amplification ay'st ell the field Head, Ann, Matching Transformer, l'iek u p l'i u_ Hs,hirh gives me using ai low ai 911 volta "It" current. D.C. model shunt' and 20 -Fait Insulated Extension Cont. raher higher field strength and p -- greater r . s 1.000 choit field and a pu output troma- BUY NtOR'! a rgizatlord ILC. model has a I Ica field nouur; A.C. nettle! nird a dry rertiller system with This Lmw Price For Short Time whieh ran he energized from the ; a hum condenser for minimum A.C. han. I f Iv ticks of amplifiera or front 110 volt D.C. line. Dimensions -12" high. 8" deep. Price Complete $5.50 A e' '1'-1.0. 0 -1 e.$1.951I C. Model prics.$6 9 5 A.C. with 280 Tn!., $9.95 $7,95 D.C. Model ...f ..95

a1 -n ure F. O. B. New York, and ot to prior sale. Terme: A deposit On% is requi -ed with every order. Bal- . ..i.l on deli,.... Deduct GRENPARK COMPANY roll is sea.! 'th order. RC DO NOT SEND FOR CATALOG 245 Greenwich St. Dept. New York, N. Y.

RADIO -CRAFT for NOVEMBER, 1933 317 RTC's Big November SPECIALS

Every month we list oil this page a STOP SIlv1'l'I,v(; -the lulccst prices few STAR* items which are not listed are right on thi< page. No one under- in our catalog. These are all specials sells us. We meet any price on any on which the quantities on hand are No One in Radio new merchandise. Order direct from not sufficient to catalog them. Once this page and save money. 100'', satis- sold out, no more can be had. ORDER Undersells Us! faction on every transaction. Take ad- NOW -TODAY. vantage today of these special offers.

7 TUBE SCREEN -GRID 11 TUBE * "FARADAY" RADIO RECEIVER BITED "NEW DEPENDABLE TESTER Complete with Full Dynamic Speaker Sold Either Wired or in Kit Form ONLY loo -NO MORE WHEN GONE Ilere indeed Is 161, 1111r14 tub,' rhrrk, inSV. ehirh I lllllsf:ItN i el t III -1 :ill the latest t>pe ` tube.. art wll'a;; tluc gill, AND s l'ILI/NIGs -- 1,1 1(} ;t"i'1.1'- uitlmuL the u l .gle adapter! The il .Ni :1C DEl'ENl1.ABI.E." despite Ito high de- ., e of al curacy. i ISl tensely slulple to operate. Roth of the N11-52 Fa :OBI BIB, ter! liter tulles : hily tested willow* the use at a ,u0ud plat,' Tile Instrument employA a Mall- era do. D'A It- s,INV.%1. TV l'E, 3103'1Nä -COIL. I1 E'l'Elt. insuring r hy etlrrmt ccuracy. Thi. in- trmueut tilt "k mure than 120 different tube: and e n ttn.r IL h hare IRA a vet been placed on theft arlso. 'l'le. tlll.e le.ter ,11 unpl) guar led against lithe mn:," %Lich condition Is Indhtiled by the flash- of a small pilot light. All IvanponenI parts are and on 1 beautifully etched panel and the entire Insn ument tilted In a start i ly , Ifrd. Zeal heret r-rovrred. carrying I,, C. For o,'ertl.11 I t 10:. I2, volts. 7.0 e. Tilts instrument I' arallattle either In kit form or f onteh i 'i) wired auI arty to Ire. $blppine neigh, !, Ina. N0. 303 "New Dependable" Tube Tester. NO. 303 A "New Dependable'' Tube Tester completelyrI wired and in kit form. tested. V{ 11 ever there se.s a renter value thnn t1d. Imf..re, have yet to see it. The wir :1, 1 13 d of . :4 YOUR PRICE..._...... $14.13 .ennillrity lid- i lithe n dn'. to it- toned _tan,- .r. ¡tact 5, 'Intro :V' tl..e.. YOUR PRICE nnl.er-helrn.b'ne r...iv r 'l'Lr uet'ou ..f 11.f- -et Iw"I de.rril.-d n. ' tnndar.L.. il.. r nit i other than Ow ..Ldd--lnudlF" T. lf. P. t,rP xhieb t. the ` f..l pro"( ever de.ignrd. It i r..l- tw'..l:1ce. of t I It. l'. : n.nliti.atou twang type ^t rwtud rid bd. n 4Tr 24't.'..r .I.teetor: e u-Ir -ripe tpw. =- A. F. Voltaire .tlir thou tinnily n pt.t.-pull .tng, u.u.c 2-45 tnlw. The 1 o- ..dd}. wVlet: with n ua.tel.e l, lull dynamic .penker. E X T R A S P E C I A L Ta extremely . unde, 7'he kn..b , the left i mLin:aioni volume control n1.1 p..werlw¢toh. The knob rn the riehl ì- the 11:.ti.n....t.Inrr,TLr locale witch in the n Baird Universal Short Wave and Television Receiver 1:J.le- >,1n t. e. ..dr..l th. ia..e fo1.11 hich trel.le to doe. 1.:,-'. f'..il. t.raiaa-.+.mLen.rrr-rnu.r I L.. 1.1.nE 111.._ . L..I,...... ,...... ,L.r.-..r-. rle., :.n :dl ILor.nlcLly .LirlJa.i. The Seven Tubes-IS to fai Meters Th.,,...... , not , a,u.le.lp pc. It .Inll.- .d.1,,....L ..Ih ..I;id:: , AIRr..nn.l Only 20 at This Price

. 1 . 1 . M i t t . . , e r . , . . 1 1 1 1A f . k1,- , ..1.

a?, ìlnu No. SP -2001. "Faraday" 7 Tube Screen Grid T. R. F. J

l I ' 1 d . .. Receiver including dynamic speaker but 4.!¡° .I less tubes $11.95 fA I II II 1 t. 7 IIF I I YOUR PRICE . I 1 I 1 d I 1 - 1 12 51.5/45 roil, 1 I I 5oli tl... i I . . : (n 11 1h .I I a na nddìil ..1lta ..il. Il Ì..r rl1... nÌl 111.. 1 I II IJunnlr. J I n In 14tNTAINF 1\AIIANtt\le \1 ll\ l. T 1., .,11. 11 it' .,t Il. id, [wing oo tsUOl Act List rau d.elre to tale ndrsl,tvn. l tl.'. , t. . 1.1.. LIST PRICE $80 ONLY AND SHORT RADIO No. 35 Baird Universal Short Wave and Television Receiver E WAVE TREATISE YOUR PRICE $22.48 alb e NEW READRITE MODEL 710 ANALYZER :í °.aua. TESTS LATEST TYPE 6 AND 7 PRONG TUBES i;i, ; NINE METER SCALES AVAILABLE RADIO JUST ANOTHER CATALOG SHORT WAVE TREATISE HERE 1CONTENTSA PARTIAL LIST Principles of RadÑew Fundamental Dlsc usston er. y T,....r.11l. r.110 .1r..111. Ohm's law - Tee Tubes_ COnstruttinga"Tt1pt o- dynetier E1 mlin tine S Men -Made CONVENIENT SELECTOR SNITCH Constructing a Two -Tube Static - Globe- TrittteT" Short -Wave RC' RaIrer -53.íe P.et d10 sinks: etc.. etc. ST nENTnOES- MUS WRITE TODAY. Enclose 4 -80 RECTIFIERS. tt<-. i' postage. Treatise II1r:,i cents for 100 New. sent by return nail. Etc. 111111 uularnln.n..

..1,.aF nI.ntl.. .1.1,. Model 710 4..ä1\ ter. lint Put c. 527. SO. YOUR PRICE $16.17 WE ARE A WHOLESALE HOUSE AND CAN NOT AC ODDER THIS PAGE Yuu will find special prices from time to CEPT ORDERS FOR LESS THANOU [3.00. ORDER FROMl-1 1111.7 71'i time. in this magazine. Get our big FREE If C.O.D. shipment is desired. please remit 20% remit- catalog for the which must accompany all orders. greatest Radio Bargains. lance Should wish goods shipped by parcel be sure include extra 11 full cash aetified ies order. deduct 2°L discount. Send you Roo post to sufficient remittance money order -- certified check -U. S. stamps. for same. Any excess will be refunded. Radio Trading Company 102 Park Place New York, N. Y.

320 RADIO -CRAFT for NOVEMBER, 1933 McMurdo Silver now presents MASTERPIECE II Designed especially for Admiral Byrd,

from specifications developed in col- laboration with the research and engineering departments of Harvard and 'another great eastern University.

Admiral Richard E. Byrd, U.S.\., asked Dr. \IcCaleb of Harvard University which radio receiver would be best for his next Antarctic expedition. In substance, Dr. McCaleb replied, "Mc \Iurdo Silver's Masterpiece, with certain additions." Immediately, the engineering department of Harvard made certain suggestions to Mr. Silver, as did the engineering research department of another great eastern university, to produce, for Admiral Byrd, the greatest, most complete, most thoroughly able all -wave radio receiver the world has ever seen. Masterpiece II is the result. The specifications of Masterpiece II, as you can readily see, promise a quality and extent of performance often dreamed of, but never seriously considered as either probable or possible of attainment. Yet, Masterpiece II actually meets them, to the letter, and its performance, very con- clusively asserts the fact that an entirely new era of transoceanic radio reception has been born. Duplicates of Masterpiece I I ... exact duplicates of the very receiver that is going into the Antarctic with Admiral Byrd, are now available. A completely descriptive, fully illustrated book will gladly be sent upon receipt of the coupon below. BRIEF SPECIFICATIONS Wave length Range 10 to 570 Automatic volume control holds all meters or 520 to 30,000 kc. Four stations 20 microvolts and up at position wave change switch. constant volume to the ear. (External unit extends range from Selectivity absolute 9 Kc. for t'Q 700 to 2000 meters.) Europe, better than U. S. needs (21 Kc. wide 10,000 times e:l1 - Tuned R. F. stage on both Broad- down). Pt,,, ;: cast and entire Short Wave range Fidelity perfect over 30 to 4,000 .7...) yet single dial tunes the receiver. cycle audio range. Greatly improves signal -noise Undistorted power output, 15 watts. ratio on 12,000 mile reception. Automatic and manual tone con- Band- spread tuning on short waves. trols. Makes short wave tuning act wally Special Impregnation for tropical easier than broadcast tuning. climates. 3 air -tuned intermediate stages. Built-in beat oscillator for easy Most accurate intermediate am- finding of S.W. and weak broad- plification ever developed. cast stations. ('hromium Sensitivity better than ) micro- plated steel shielding volt absolute average. case eliminates need for cabinet. 10 day trial in your home. Open- Interstation noise suppressor ad- and-shut guarantee. Money back justable to exact location require- instantly if you are not absolutely ment. satisfied-no questions asked. Hare are illustrated the Master- piece lI Super speaker that de- velops 4 times the poire output of any other... and the slightly smaller "auditorium" sçseaker usualh McMurdo Silver, Inc., Belmont Ave.. Chicago, furnished by custom set makers. Either is furnish,.' 1735 U.S.A. opriomd!, u irh Mast er!iwe I!. Send me full technical information on Masterpiece II. Nance McMURDO SILVER, Inc. Street ..._ ,.. 1736 BELMONT AVENUE - - - CHICAGO, U. S. A. Town State Naves Seen Equal ' Reyend Iant Ne Other Sat Compares Fine Results "You certainly know how to "The \lidweet, 111 -Tube Ra- .'I am well pleased with the *lagged ral Central sad had American and e Mexican sta- build All -Wave Radios. I dio is all you said and more Midwest-IC bane pleased beyond 1l my ( world-wide receiver). I some One resulta with i tions short and long wave. am we FYA. France. Erect elpeetations: have been lis- don't believe there is another Sunday afternoon were Get listening to a Rugby seen anything to equal t h tening for two hours to CSB act on the market tocay with game new Midwest -I6 for taon in England. 12110. and Pon - the tone and selectivity of between Ireland and Eng- ,d,tentgen- toise. France."-Dayton H. Midwest 18 -Tube Radio." land. being broadcast from fidelity and J. (tart. 41 'tivity. " -T. o N. Stewart. Lesher, 267 Sylvan Ara-. -Mr. C. L. Gietl. 415 E. S. Iondon."-li. Vero Beach. Florida. Waterbury. Coon. Grand Avo,, Springfield. Ill. west SA. Cromwell. Coon. THOUSANDS ARE fflotyooiiil OvEli11115 9T0 . 2,000 METERS

1AYS E

World Wide t, Reception MIDWEST startles radio world by offering this 16 -tube De luxe ALL -WAVE radio... finest development of it 14 years of experience as leadi ng radio manufacturer ...at sensationally low price of only $49.50. Buy this / bigger, better, more powerful, clearer -toned radio...direct WORLDS GREATEST from Midwest Laboratories... at a positive saving of 30% to 50 %. RADIO VALUE Brings in broadcasts from stations 10,000 miles and more away. Gives complete wave length coverage of 9 to 2,000 meter (33 megocycles to 150 KC). This powerful, super -selective, radio has FIVE distinct wave bands . ultra short, medium, broadcast and long ... putting whole world of radio TERMS at your finger tips. Now listen in on all U. S. programs... Canadian, police, amateur, commercial, airplane and ship broadcasts...and world's AS LO W AS finest stations as: DM Nauen, Germany -REN, Moscow, Russia -EAQ, Madrid, Spain -12R0, Rome, Italy- VK2ME, Sydney, Australia. Never 1100 you DÓWN / before so much radio for so little money. Don't buy any radio until learn about this greatest of radio values. Send today for money -saving facts! with 40 NEW 1934 FEATURES New Try this Midwest radio...in your own home...for thirty days before you decide. See for yourself the 40 new 1934 features De/u.reAudiforium Type that insure amazing performance. For example -Automatic SELECT-O-BAND (exclusive with Midwest), simpli fies short wave tuning, instantly pointing out the wave length of the station. SPEAKE R Other features include: Amplified Automatic Volume Control, New Type Tubes, Superheterodyne Circuit, Velvety Action Tuning, Super We will send you copies of letters like those 16 Tubes, Balanced Unit They'll convince you Power Class "A" Amplifier, 29 Tuned Circuits, New Duplex-Diode-II igh Mu Pen- Illustrated at top of page. Full Rubber Floated Chassis, Variable that Midwest radios are sensational values tode Tubes, No-Image Heterodynes. radio Tone Blender, Centralised Tuning, 7 KC Selectivity, New Thermionio Rectifier, They prove you can order your Midwest Totally scientifically shielded (coils and switch eat acomhed)etc. These and many by mail with as much satisfaction as if you additional features are usually found only in sets selling from $100 to $150. were to select it in our great radio laboratories. DEAL DIRECT WITH IABORATORIES RUSH THIS COUPON FOR Increasing costs are sure to result in higher radio AMAZING 30-DAY FREE TRIAI prices soon. Buy before the big advance...NOW, NEW STYLE CONSOLES while ou can take advantage of Midwest's amass OFFER AND NEW 1934 CATALOG The new, big Midwest cata- ingly low prices. No middlemen's profits to pay! log shows a complete line of You save from 30% to 50% when you buy direct JIVE ...... de luxe Dept 312 r Make Easy beautiful. artistic, from Midwest Laboratories -you get Cincinnati, Ohl*. r 1 Consols In the new mo- 30 days FREE trial as little as $5.00 Late. Manny ... - Without obligation on my part send 1 daruistio designs and down puts a Midwest radio in your your 1934 catalog. and tom- CheckCheek HereHer priced you 30" to UP me new for Her to save as home. Satisfaction _guaranteed or your ['fete details of your liberal 30-day 1O ó. Hand made by Mas- money back! FItI:E catalog shows sen- FREE trialonor. Tina b NO F an order die - ter Craftsmen, they lend v a- val ors. write T() DAY ! TO Unction and dignity to any ovsrur satioaal radio home. Mail coupon today. Sian and mall ...or. send name and ad. .ens on postal card... NOW! Name

Address City Stata DEPT. 312 OHIO, U. S. A. 1 - CINCINNATI, 1 f aoi,' tied 1920 Cable Address Mireco. ABC 5th Edition