RADIO'S LIVEST MAGAZINE September 25 Cents Canada 300 HUGO GERN Editor Describing the New RADIO GARAGE DOOR OPENER See Page 138 A New Triple -Twin Tube - Direct Coupled Amplifiers -A "1- Tube" Super A Quality Audio Amplifier - Design of Test Instruments - Adapters CANDOHM RESISTOR REPLACEMENT CATALOG MUTER opens a new field for Deal- STANDARD EQUIPMENT ers and Service Men -a plan which IN LEADING SETS enables radio men to do a thorough The Muter Candohm Resistors are service job, to effect proper resistor absolutely permanent in values, and replacements, and to make a good are not subject to "breakdown" in profit. normal service. All Candohms (ex- The selection of Muter Candohm Re- cept type FH), are wire wound on a sistors, since 1929, for use in leading bakelite core with Armite insulation ; receivers proves conclusively, that the type FH is wire wound on a spe- character- cial asbestos core. Candohms de- their design, engineering signed for particular set models are istics, construction and longevity equipped with the required special have, in every way, passed the rigid mountings. Set manufacturers have tests of set manufacturers. standardized on Muter Candohm Re- Muter Candohm Resistors are stand- sistors because of their accuracy, ard equipment in several hundred liberal heat dissipation and absolute receivers manufactured by over fifty freedom from trouble. When neces- Candohm sary to replace a Candohm Resistor, leading set manufacturers. obviously the set will perform much Resistors are heavily armored so better if a genuine Candohm is used, that the Service Man can convenient- made to the set manufacturer's ly carry an assortment without specifications. danger of damage. A supply of stock OUTER PROTECTIVE STEEL INSULATED MOUNTING values of Candohm Resistors, when COVERING MAKING UNITS LUGS FOR alt SCREWS LBSOLUTELY DAMAGE PROOF used singly or in combination, are U. S. PATENT NO. t TN.IY sufficient to attend necessary resistor service work on a large majority of to replace sets. It is advantageous RESISTANCE WIRE WOUND ON GENUINE BAKELITE CORE. ordinary resistors with MUTER TERMINALS OF ARMRE INSULATION BEST GRADE COKE PLATE CANDOHMS. 'SBB VOLTS A. C FOR EAST SOLDERING NEW, COMPLETE CATALOG READY FOR DEALERS AND SERVICE MEN Mail Coupon Today! The coupon in the lower left-hand corner, com- CAND0HM pletely filled in, will bring to you the Muter RSSTpR 1933 Candohm Replacement Catalog, and com- .-The Muter Company. Dept. RC. plete information on other dependable Muter ReP/acemen[ 1255 South Michigan Avenue. products for dealers and service men. Write Ca taio Chicago, Illinois today Dept. RC. The Muter Company, Candohm -address Please send me the Muter 1933 1255 Michigan Avenue, Chicago, Illinois. Replacement Catalog listing the seta in South 1933 9' which Candohms are standard equipment. Name MUTER DEPENDABLE PRODUCTS Address City State Service Man [-] Dealer Jobber OPPORTUNITIES are many for the Radio Trained Man Don't spend your life slaving away in some dull, hopeless job' Don't he satis- fied 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 Prepare for jobs as Designer, Inspector and Tester -as Radio Salesman and in 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 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 lat- est and newest Television apparatus, Talking Picture and Sound Reproduction equipment, Code Practice 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 Employment Service for Life. And don't let to do. I'll lack of money stop you. Many of our students make all or 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 course you make your first payment, and then you all doubt. You can find out everything absolutely free. have ten months to complete your payments. Just mail coupon for my big free book! There H. C. Lewis, Pres. are no strings to this offer. I know a lot of honest fel- RADIO DIVISION Founded I89q 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. SOO S. Paulina St., Dept.63 -9H, Chicago, Illl. I've got enough confidence in these fellows and in my Mail Coupon Today for All the Facts training to give them the training they need and pay me p back after they have their training. _- --- - - tmom -aim you -- If 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. 63-9H, 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 SEPTEMBER, 1933 129 (Rdio.af ERVICE MAN - DEALER RADIOTRICIAN HUGO GERNSBACK, Editor -in -Chief LOUIS MARTIN R. D. WASHBURNE Associate Editor Technical Editor IN OUR NEXT FEW ISSUES: CONTENTS OF THE WHAT EVERY YOUNG SERVICE MAN SHOULD KNOW ABOUT SEPTEMBER, 1933, ISSUE THE INSTALLATION OF PLAYHOUSE SOUND SYSTEMS. How much does it cost to install an efficient sound system in a theatre? What apparatus will be required for a house with a capacity of VOLUME V NUMBER 3 1,000 people; of 5,0007 What are the probable difficulties one would encounter in installing the system and how could these faults be overcome? These and many more questions of a similar nature Editorial: Our Changing Radio Hugo Gernsback 137 are answered in a practical manner in this multi -article by an authority on the subject. This series alone will be worth the price Describing the Radio Garage Door Opener of many subscriptions to RADIO -CRAFT. R. D. Washburne 138 HOW TO MAKE A UNIVERSAL A.C.-D.C. AUTO RADIO RECEIVER. Latest Radio Equipment 140 A feature of this ultra midget set design is the high gain attained through the use of modern tubes; including the type 6C6. Other A New Deal in the Radio Industry 141 considerations of interest to everyone are its low cost of construc- tion and simplicity of design. Provisions are made for phonograp! A Decade of Progress 141 pickup or microphone input. The 2B6-A Duplex Triode L. van der Mel 142 THE MAINTENANCE OF CARBON MICROPHONES. Nearly every Constructing the All -Wave Midget "Four" radio technician has viewed the carbon microphone with a sense of awe, presuming that, since the instrument was one of the moss H. G. Cisin 144 expensive, small-size units in his equipment, only a gifted few Constructing A Complete 26 -Watt Dual Channel could successfully service it. In this article the author clearly dis- closes the foibles of the device and the correct repair procedure P.A. System 146 Louis Gancher to be followed by a technician having average ability and good The Design Principles of an All- Purpose Tester judgment. Floyd Fausett 148 Quality in Audio Amplifiers W. H. Hollister 150 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 Features of a Modern 50 K.W. Station 151 foreign countries, $3.00 a year to corer additional postage.) Entered at the post office at Mt.