TELEVISION NEWS Section Ii!Ci -Itll\ II:S HUGO GERNSBACK, Editor Formerly ULM) I 0 Cita R-

See Special KAMM TELEVISION NEWS Section iI!Ci -Itll\ II:S HUGO GERNSBACK, Editor formerly ULM) I 0 Cita r- :

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YOU PRACTICE RADIO YOU PRACTICE RADIO SERVICING COMMUNICATIONS You build the modern Radio I send you parts to build the shown below as part of my Ser- Transmitter shown below as vicing Course. I send you the part of my new speaker, tubes, chassis, trans- Communications former, loop antenna, EVERY- Course. Conduct THING you need to build this actual procedure modern Radio Receiver. Use it of Broadcast Op- to make many tests, get erators, practice practical experience. interesting experiments, learn how to put a transmitter on the air.

YOU BUILD THIS TESTER as part of my I r Servicing Course, Will Train You at Home with parts N. R. I. sends. It soon with MANY KITS of Parts I Send helps you EARN Want a good pay job in the fast -growing or get a good pity Job in Police. Aviation Radio and Television Industries, or your or Marine Radio, Broadcasting. Public Ad- EXTRA MONEY own money -making Radio -Television shop? dress work, etc. Or think of amazing Tele- fixing neighbors' I've trained hundreds of men WITH NO vision opportunities. Already manufacturers Radios in spare PREVIOUS TRAINING to be Radio tech- are producing over 100,000 sets a month. nielans. Or now you can enroll in my New stations going on the air everywhere! time. NEW practical course In Radio -Television Television Is America's fastest- growing in- YOU BUILD THIS COMMUNICATIONS -learn to be a Broad- Ilustry and men who know tt will be to WAVEMETER casting and Communications technician. You demand. as get practical Radio experience with MANY part of my NEW Convnunicritins GET ACTUAL Course. Use it with KITS OF PARTS I send you in my train -at- LESSON AND BOOK FREE home method. All equipment yours to keep. My DOI -ISLE FREE OFFER entitles you Oscillator you also to actual SAMPLE LESSON and my 64 -page build that furnishes MAKE EXTRA MONEY IN SPARE TIME book. "HOW TO BE A SUCCESS IN RADIO An part of my Radio Servicing Co urse, -TELEVISION-ELECTRONICS," both basic power to I send SPECIAL BOOK - FREE. Mail coupon now. transmitter and de- LETS starting the day you See how quickly, easily enroll. Make EXTRA you can start. J. E. termines transmit- ot t MONEY fixing Radios In VETERANS SMITH. President. Dept. MI apare time while 9NX National Radio Insti- ter frequency. training. tute, Pioneer florae Study Then start your own Its- Get this training without cost Radio School, Washing- Ndio sales and service shop I TRAINED THESE ME under G. I. Bill. Mail coupon ton 9. D. C. Good Job In Radio Sigma Has Own Radio Business "Am Chief En- "Now have gineer of Ra- two Radio dio shops servic- Sttior. Mr. J. E. SMITH, WORD in ing about 200 President, Dept. 9NX charge of four seta month. National Radio Institute, Washington t, D. C. men. Owe all Have largest I know about Radio to service establishment in Mail me FREE Lesson and 64 -page book. NRI." -CLYDE J. BUR- Southeastern Missouri "- (No salesman will call. Please write plainly.) DETTE, Spartanburg, ARLEY STUDYVIN, De- South Carolina. Soto, Missouri. Name Age Address A TESTED WAY City ... Zone State TO BETTER PAY LÍ]('heck If Veteran Approved for Training l'nder G. I. Bill 4

Hugo Gernsback, Editor -in -Chief R.a1D I O - Fred Shunaman, Managing Editor I:lal:/:?It/1SII:S M. Harvey Gernsback, Consulting Editor formerly RADIO -CRAFT Robert F. Scott, W2PWG, Technical Editor InCnrnntne R. H. Dorf, W2QMI, Associate Editor SHORT WAVE CRAFT TELEVISION NEWS RADIO ISION Trademark reglotered U. S. Patent Umca I. Queen, W2OUX, Editorial Associate Chassis Lee Robinson G. Aliquo Angie Pascale, Production Manager General Manager Circulation Manager Wm. Lyon McLaughlin, John J. Lamson Robert Follath Pechnicol Illustration Director Soles Manager Promotion Manager Contents December, 1949 Editorial (Page 21) Electronic Experimentation by Hugo Gernsback 21 Broadcasting and Communications (Pages 22-23) Mid -Ocean Radio Stations ;Cover Feoture) 22 Test Instruments (Pages 24 -25) Test Instruments and the Technician by Herbert S. Brier 24 Television News (Pages 26-30) Filmed Television by Torrence Downey 26 How to Remove the 60 -Cycle Buzz from Intercarrier TV Receivers by L. S. Pearlman 28 Two -Week Course Teaches TV by Dave Gnessin 30 Audio (Pages 31 -33) Speaker Baffling Simplified by A. G. Sonders 31 Audio Squelch Circuits by John L. Gergen 32 UNIT DESIGN Theory and Engineering (Pages 34-37) Electron Shadows Map Force Fields 34 Lead -Pencil Mark Sets Off Relay by Victor H. Laughter 35 FITS ANY CABINET Microwaves, Part VIII -Receiving and Transmitting Antennas for Microwave Communications by C. W. Palmer 36 The most versatile television Construction (Pages 38 -39) Receiver Fits Shirt Pocket by Thomas J. Judge 38 chassis yet designed! Three basic Amateur (Pages 40-41) units - power supply How to Become a Hom, Port III by George W. Shuart, W4AMN 40 chassis, RF chassis and deflec- Cavity Resonator by Rufus P. Turner, K6AI 41 tion yoke assembly - may be Servicing (Pages 42 -64) placed side by side, one above Radio Set and Service Review (Hollicrofters Model S -72) 42 the other, etc., to conform to Instrument Tests Battery Radios by William H. Brakes 44 in AF- Ultrosonic Frequency Meter 45 any cabinet. Simply plug Eight AM Detector Systems 46 the cable connectors. Each Several New Tubes 47 unit is soundly engineered and Advertising and Selling. . . . by T. W. Dresser 48 built to famous National Fundamentals of Radio Servicing, Port X- Triode and Tetrode Tubes standards of performance. by John T. Frye 50 Intermittent Filaments by Dove Gnessin 56 1. Choice of 10" (TV- I OC) or The Intermittent Headache by Mox Alth 60 I21/2" (TV- I 2C) chassis. 2. Tunes Foreign News (Pages 66 -70) all 12 channels. - European Report by Major Ralph W. Hollows 66 3. Wired, pre tuned and tested - not a kit. Electronics (Page 87) Messages Printed by Cathode -Ray Tube 87 4. RF stage employs tuned grid and Departments plate for maximum gain The Radio Month 8 Try This One 84 and optimum bond width. 5. Radio Business IO Association News 86 Unique 36 mc IF minimizes inter- New Patents 72 Miscellany 38 ference. 6. Fine tuning control New Devices 74 People 91 covers range of 2 -3 mc. for Question Box 76 Rodio Electronic Circuits.. 80 Communications 92 maximum tuning accuracy. 7. Technotes 82 Book Reviews 95 Improved intercarrier sound. ON THE COVER: Part of the superstructure of the Coast Guard's Ocean 8. Magnetic deflection and "fly- Station Vessel Spencer, showing the many radio and back's high voltage supply. 9. 72- radar antennas. Kodachrome by Avery Slack. ohm unbalanced and 300 -ohm

RADIO. ELECTRONICS. December, 1949. Volume XXI. No. 3. Publl Iwd monthly. Publication Office: Erie Ave. balanced inputs. 10. Supplied set und CI.Ma Ittr p C 1945. at lilt Wat ulnva at F to G Streets, 1'1l ladelph la 37. l'a. Matted at Nltlul,er with two six -inch PM speakers. Philadelphia. Pa.. under the Act of March 3. 1879. SUBSCRIPTION RATES: in U. S. and Canada. In C. S. 56.00 ; for three Sean; Poseeulune. Mexico, booth and Central American countries. iß.50; for two fd.00 athgle copies 3Uc. All other foreign countries 84.50 year, 98. 00 for two year.. $11.00 for three sears. Allow une Specify either stencil Imprerilon from a recent wrapper. nth for change of address. When ordering a change please furnish an address TV -10C or TV -12C $149.50 Gernsback. Pres.: M. Harvey Gernsback, Vice -Pres.; G. AllOUe. OWE. RADCRAFT PUBLICATIONS. INC. Hugo When ordering ( less picture tube) Contenu Copyright. 1940. by Raderait Publications. lac. Test and Illustrations must clot be reproduced without terml.eion of copyright owners. EDITORIAL d ADVERTISING OFFICES. 25 West Broad New York T. N. Y. Tel. REctor £ -0890 BRANCH OFFICES: Chicago: 308 W. W'a.hlnRmn Street. Telephone R.4ndnl,h 8 -7383. Loa Angeles: na'I,., It' I -9481. Ilarkc t. 1197 s' ilsld tC Blvd.. Tel. MA 6 12:1 San Francisco: Its 1ph W Rat k. r. 582 Market SI., Tel. G.t rtleld FOREIGN AGENTS: Great Britain: Alta. Publishing and Distributing Co.. Ltd.. 16 Bride Lane, Fleet St.. Lon : 37 Avenue l'Opera. don E.C.4 Australia: McGill'. Agency. 179 Ellzahelh Street. Melbourne. Brentano's. de Hook New 4.emv, I l'arts 2e. Holland: TrIlerrron. Heemeteed-she. lireer 124 Ilrrmslede. Greet, lolervIal bmal A Amerika Street. Athena. Se. Africa: Central News Agency. Ltd.. Cor. ItI..Ik A Commissioner Sts.. Johannesburg; 70 012 Lung Street. Capetown; 369 smith Street. Durban. Natal. Universal Book Agency. Harrison Street. Johannes burg. Middle East: SIIIIIISIxky Middle Kan .agency. Jaffa Road. .Ieruaalem. India: Stall Gupta I Olstnoutora Co.. Armin Baur Patrika Lt.. 14 Ananda Charterire lane. Calcutta. Broadway News ('entre. Poet Hait =5557. Udgr. Bombay =14. K. L. Kannappa Sludaliar. Sts General P Road. Mount Road. Madras 2. Pakistan: Pared'.. Book Stall. Opp. Regal Cinema, Preedy St.. Kararhl 3. NATIONAL COMPANY, Inc. M A L D E N . M A S S A C H Editorial and Executive Offices: MEMBER AUDIT SUREAU OF CIRCULATION 25 West Broadway, New York 7, N. Y. RADIO -ELECTRONICS for èB ; RADIO, TELE VISION and ELECTRONICS Master ACC Phases r Get Complete Training. You Receive and Keep All Equipment, Parts and Lessons. No Extra Charges. You will find all lessons easy to under- GOOD PAY stand because they are illustrated and Unlimited Opportunities throughout with clear diagrams and step -by -step examples that you work in JOBS LIKE THESE: out yourself. Every piece of the eqiup- ment and complete lesson material we Business of Your Own send you is yours to keep and enjoy. Radio Manufacturing, Sales, Service including the multifester, experimental Broadcasting, Telecasting equipment, all parts of the Superhetero- Television Manufacturing, Sales, Serv- dyne, ice tube manual, radio dictionary, Laboratories: Installation, Maintenance and complete, modern Television texts. You receive complete standard equip- of Electronic Equipment, All parts are standard equipment. ment, including latest type High -Mu Electrolysis, Call Systems Tubes, for building various experi- Garages: Auto Radio Sales, Service Shop Method Home Training ... mental and test units. You progress Sound Systems and Telephone Com- step by step until you build a companies; Oil Well and Drilling Com- Earn While You Learn plete Superheterodyne Receiver. It is panies; Engineering Firms With our practical resident Shop yours to use and keep. Theatre Sound Systems, Police Radio Method Home Training, you study in your spare time. You receive Spare And scores of other good jobs Time Work Lessons, which show you in many related fields how to earn while you learn. Service MANY neighbors' radios and TV receivers, ap- YOU CONDUCT pliances, etc., for extra money and ex- EXPERIMENTS LIKE THESE! perience. Many National students pay all or part of their training with spare Checking action of condensers time earnings? Experiments with AF and RF amplifiers Experiments with resonance DON'T DELAY! The Radio -Television Producing beat frequencies Industry needs trained men NOW! Calibrating oscillators YOU RECEIVE THIS Experiments with diode, grid -bias, grid - For quick action, PROFESSIONAL MULTITESTER! leak and infinite impedance detectors APPROVED mail coupon Practical You will use this professional instru- experience in receiver trouble FOR today and we'll ment to locate trouble or make shooting Application of visual tester in check- VETERANS! rush you full in- delicate adjustments -at home -on Check coupon below ! service calls. You will be proud to ing parts and circuits formation. own this valuable equipment. Com- Experiments with audio oscillators plete with test leads. Advanced trouble- shooting . . . and many, many others You construct the Transitron SIGNAL GENERATOR Signal Genera- by tor shown here. Complete Training Practical demonstrating NEW, ILLUSTRATED ( Transitron prin- Resident Trade School, Est.1905 OPPORTUNITY ciples in both The same highly trained faculty, in- R.F. and A.F. struction materials and methods used BOOK AND SAMPLE 1 stages. You here in our large, modern resident LESSON SHOW YOU study negative adapted to your training i type oscillators school, are HOW WE TRAIN at firsthand. in your own home. Shop Method Home Training has been proved by hundreds YOU ... SEND FOR of successful graduates. THEM TODAY! NO Both Resident and Home Study COST. NO OBLIGATION. AUDIO OSCILLATOR: Courses Offered An electronic device, which YOU produces audio - NATIONAL SCHOOLS frequency sig- LEARN BY LOS ANGELES 37, CALIF. EST. 190 nals for modulating R.F. (radio frequency) carrier DOING waves, testing A.F. )audio frequency) National amplifiers, speakers, etc. You receive Schools, Dept. 12 -RE Mail in envelope special labora- 4000 R tory experi- South Figueroa Street or paste on T.R.F. ment lessons Los Angeles 37, California penny postal. RECEIVER to show you Send me your FREE book "Your Future in Radio" and You build how to build the sample lesson of your course. I understand no sales- i several with your own man will call on me. 1'4 T.R.F. Re- hands various ceivers, one experimental NAME. of which, a 4- units such as ADDRESS...... __._...... _...... _...... _.._.._.._.._....-..... tube set, is shown those shown at --- here. You learn construction, align- left, and how CITY ZONE._._ STATE..._..._..._... ment, make receiver tests, and do to conduct Check here if Veteran of World War II trouble shooting. many tests. DECEMBER, 1949 6

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NOW - -you can afford to own the Service Data Library that is earning HAVE COMPLETE, ACCURATE DATA ON extra profits every day for more than 25,000 successful Service Tech- nicians! NOW -for the first time -the famous PHOTOFACT Library can ALL POST -WAR SETS YOU SERVICE! be yours with this new "Pay -as -You- Profit" Plan! Here's all you have to do: See your parts jobber. Order 4 or more PHOTOFACT Volumes. LYith the Easy-Pay flan, you can boost your earnings Pay only $18.39 down. You get your Library immediately. You use it now, using proved superior PHOTOFACT. Have complete, now. It earns for you -and you pay as you profit! If you're not already accurate, uniform data on all post -war receivers -own a money- making PHOTOFACT user. here's your easy -pay chance to own the only Radio and TV service data based on actual the most productive radio service data in the world. If you're already laboratory analysis of the equipment. Here's why using PHOTOFACT, here's your chance to complete your library by PHOTOFACT is better in every way. You get: 1. Exclusive filling in those missing volumes. Now that you can afford PHOTOFACT, TV coverage in easy -to -use individual envelopes. 2. don't be without its time- saving, money- making advantages a single Exclusive Standard Notation Schematics. 3. Exclusive day longer. See your parts jobber today! oscilloscope wave forms. 4. Photos of all chassis views with each part identified. 5. Full alignment instructions, plus circuit voltage and resistance analysis. fì. Complete parts lists and proper replacements. 7. Dial cord string- ing diagrams. 8. Disassembly instructions. 9. Record Changer service data. 10. Exclusive keyed data system right on schematic. There's nothing like RECORDING :4 -all values the 1948 PHOTOFACT! It pays for itself in saved time, bigger R tel 1-iEVI4sio T aN1EMM8 xeee work output and greater profits. To protect your future sosaHaNaAt in servicing, act now -own the PHOTOFACT )0'- } { tEIEVISna[U Lrso:l/sd Radio -TV v QII'E '°' Library the Easy -l'ay Way! SEE YOUR PARTS JOBBER *1. . . i*. / OR WRITE DIRECT TODAY CURRENT PHOTOFACT BEST -SELLERS The Recording and Reproduction of SOUND, by Oliver Read. The Com- plete, authoritative treatment of the entire subject of Sound, written HOWARD W. SAMS 8 CO., INC. by the editor of Radio & Television News $5.00 955 N. Rural SI., Indianapolis 1, Ind. Photofad Television Course. The book used by thousands; gives you a Send full Easy -Pay Details principles, operation clear understanding of TV and practice .$3.00 Send FREE PHOTOFACT Cumulative Index Television Ant . Shows you how to select and install the proper Send PHOTOFACT Folder for Set Model antenna, and how to overcome antenna problems $1.25 (FREE to Service Technicians writing in on letterhead; 50c charge to Experimenters) 1948 Record Changer Manual. Covers 45 models made in 1948, including new LP and dual -speed changers, plus leading wire recorders. Based on actual analysis of the equipment $6.75 Name Auto Radio Manual. Complete Photofact service data on more than Address 100 post -war auto radio models -a time-and-money-saver . .$0.95

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THE THREE BASIC CREI COURSES : CAPITOL RADIO ENGINEERING INSTITUTE Dept. 1512A, 16th S Park Rd., N. W. Washington 10, D. C. * PRACTICAL RADIO ENGINEERING course in all phases of radio- electronics Gentlemen: Send me FREE SAMPLE LESSON and complete Fundamental details of the TV and FM Servicing home study course. Als,, PRACTICAL TELEVISION ENGINEERING ,end brochure that explains the CREI self- improvement * program and gives complete details and outline of course. Specialized training for professional radiomen C am attaching a brief resume of my experience, education and present position. * TELEVISION AND FM SERVICING Streamlined course for men in "top- third" of field [ TV, FM 8 ADVANCED AM SERVICING Check PRACTICAL TELEVISION ENGINEERING Field PRACTICAL RADIO ENGINEERING of CAPITOL RADIO Greatest AERONAUTICAL RADIO ENGINEERING Interest r BROADCAST RADIO ENGINEERING (AM, FM, TV) ENGINEERING INSTITUTE RADIO -ELECTRONICS IN INDUSTRY An Accredited Technical Institute Founded in Iv ?7 NAME Dept. 1512A, 16th Street & Park Road, N. W. ADDRESS Washington 10, D. C. FREE BOOKLET CITY ------'- .-.-_------._ZONE --- ..STATE_ Branch Offices: plus 7 1 AM ENTITLED TO TRAINING UNDER G.I. BILL. New York (7) 170 Broadway Sae Francisco (2) 760 Markst M. SAMPLE LESSON DECEMBER, 1949 to Radio Business The Party Distributors' Conference Consisting of numerals, dollar signs, 4 GREAT BOOKS and Show will be held at the Hotel and bases, finished in black, red, and Stevens, Chicago, the week of May 22, yellow plastic, each pricing kit contains TO HELP YOU 1950. Dedicated primarily to the inter- six sets of numbers and six bases. Iden- ests of all electronic parts jobbers, it tification slips are also provided to note CET ANE4D will, for the first time, be open to the other information such as model num- industry without attendance restric- ber, terms, and down payment. tions, according to an announcement IN THE WORLD! by the board of directors of the Show Skiatron Corp. has opened offices at Corporation following action taken at 381 Fourth Avenue, New York City, What could be finer for Christmas than their August meeting in Chicago. ARTHUR LEVEY, president, announced. nooks that make it easy to learn worth i while. good -pay Mg trades -at home in spare JEROME J. KAHN of Chicago was The new company has been formed for time: Buy them for your friends -suggest to your own friends and relatives that noth- elected president, succeeding another the exploitation of certain basic televi- i ng they might give to you could please you sion patents formerly owned by Sco- more! Each of these famous books is com- Chicagoan, WILLIAM O. SCHONING, who olete, authentic. easy to understand. Our becomes secretary for the 1950 term. phony Corp, of America, in which IO.day money -back guarantee protects your lftl 11l e t.Í- rj WALTER W. JABLON of New York was Paramount Pictures, Inc., and General elected vice president, and LES A. Precision Equipment Corp. were par- CASH IN ON TELEVISION THAYER of Chicago was named treas- ticipants. The patents were freed only urer. after the entry of a consent decree in SERVICE PROFITS! The 1950 Show will be exclusively for the Paramount -General Precision -Sco- tiri where the big aerun phony antitrust was in tel. is ion! l'IIA(TICA I. -TEEM ISICON exhibitors' distributor customers, and suit, which based SERVICING by J. It. Johnson and J. li. upon the Government claim that "com- Melt( is a down -to-earth. :113-page book throughout the four -day session will that tells you step by .stele what to do. mercial development in this country of what pals, parts and eruilmetn to use- feature a comprehensive educational in short, hew to handle every phase of program for jobbers. Preliminary plans an important advance in the television the work eaelently. This how 1'V differs from radio: outlines servi.hlg prnoedules: include seminars and discussions on art has been postponed and the opening ntains ease histories f actual jobs. of a new field of public entertainment Makes TV Descriptions of eomman TV Wouldes and such subjects as ways and means of service easy their remedies make book doubly helpful. research, and education has been unnecessarily to learn! over 2111 Ilin.trations. Price only ft. stimulating sales, market cost accounting, merchandising, and delayed." Skiatron Corp. owns many of ABOUT FM inventory control. Emphasis, the direc- these patents outright and controls LEARN ALL tors said, will be placed on helping others through an operating agreement It Cabra more than ordinary radio ! with Scophony Corp. of America. edge to handle the ronlpllrated manufacturers increase distributor ptoblrm.r of FM rervIeing l EREQI'i ;', t "i business and, in turn, on helping dis- yR tuCL.ATIl1N. a new 449 -page hark by Speer Carbon Co. of St. Marys, Pa., Nathan Marchand is complete with over M ¡- tributors expand business with their 11 :Ina illustrations pins on- the -lob examples I customers. announces that it has acquired sole own- whlrh quickly help you understand things. ership of both Voters basic theory, circuits. trattenl uteri, the Speer Resistor Corp., receivers and mobile equipment. Gives full ate of St. Marys and of Angelica, N. Y., and America, Camden, details of modern methods of adiusting and Radio Corp. of Jeffers Electronics, Inc., with plants at repairing MM receivers Including circuit Modern FM N. J., has prepared a "Radio- Repair nrrol iadl lea, tuning Indicators, antennas. systems . Dubois and Driftwood, Pa. alignment and dozens of other subjects. and how to and Tune -Up" merchandising cam- Price only $5. service them. paign for the RCA Tube Department. Sheldon Electric Co., Irvington, N. J., With an estimated 10 million radio SPECIALIZE has entered the television field with a IN SOMETHING receivers now needing repairs in homes line of 10 -, 121/2 and 16 -inch flat -face, all over the country, the new RCA cam- -, DIFFERENT... Electric ,Motor Repair! all -glass television picture tubes. Shel- paign is aimed directly at the consumer on don has merged with Allied Electric Pe :cd chat I.tn be bvrue.l ,luIndre and strongly slanted to emphasize the boom front fills formas ELECTRIC Products, Inc., and is being operated %IieTOR REPAIR look, you r a n train for fact that, for relatively low cost, the as a division of that company. ,,rcpt. profitable service tom 'leallt' average noisy or inoperative radio can nY e-leetrie matir in lontmon t. -from Copie repairs to complete armature re- be restored to first -class condition. winding. is explained cleanly National Television Everything The purpose of the campaign is to Film Council has In text and by mure than 900 illustra- started a survey to correct "demoral- tions. Covers all AC nd DC motor stimulate new business for the radio Ideal for use types, also motor control s .Isleuli. Munk the aver- izing trade practices" in the of beginners. handle spec¡fi. service dealer by overcoming No previous galles show hotu to motion picture films by television sta- When a motor I i -t age consumer's impression that radio training tions. The Council aims at establishing required. look it up' 300 Parr, repairs are expensive. In addition, the standard film -rental charges based on campaign provides the dealer with the the population in the area covered by BE AN OSCILLOSCOPE EXPERT! ready -made means to merchandise and the station of on the station's price his services effectively and pro- time ray usel llographt properly and watch your rates or both. efficiency and earn Inds sear! 5101/ERs fessionally. "S('l1.IAIS(OPNS AND T11f:IR l'SEs by Jacob IL Rutter. Jr., of Alien P. Built around an eight -point "Radio Du Mont Laboratories teaches you how Motorola, Inc., Chicago, Ill, reports mathematiet -In a w Repair and Tune -Up Special," the cam- without insolved volume you can easily understand. Shows whur paign lists eight definite services and that dollar sales on television the oseilloncope Is, how it works and ev receivers in the month of September siOy how, where and why to use it or advertises the total price. To meet the Explains making connee- was up 424' over the same period in owe ¡lie jobs. Makes requirements of individual dealers, pro- tb.n., adjusting circuit enntponents, set- 1948. Unit sales were up 403%, ting controls. analysing mitt en ne. etc, 300 oscilloscopes vision is made for imprinting prices on to Pages. 100 Illnst rat lnua Including (invent easy to order. of pattern Idlmn.. relre only Ec.01d understand! the advertising material Covering all requirements for a com- Allen B. Du Mont Laboratories, Inc., 10 DAY MONEY -BACK GUARANTEE prehensive local promotion, the new dedicated in East Paterson, N. J., last B. Du peat. RE 129. MOestY KILL BOOKS. campaign ranges from direct mail to month what president Allen 232 Madison Ave.. New York 16. N. Y. window display material. Included are Mont called the world's largest and IIEnclosed find S...... foe I,onkt. checked: or u s ml C.O.I), for rhea n,a nt Pill. a colorful five -piece display kit, a most modern television assembly plant. stare M I nil y e.,fImarl. Mn (',11,0 v I 1 l'.SNA.I Meeks not Itsfachwt. itt 1. three -piece direct-mail campaign, a Covering 480,000 square feet, the struc- arrneet I mayn them in 10 data : m guarantee to refund m +'money. window streamer, newspaper ad mats, ture is located on the 58 -acre site of the ^ PRACTICAL 'VP FVISION :ERVICINC 1 RS I64.50 outside U.s.A.I and several radio -spot announcements. former Wright aeronautical plant. It = r: FREQUENCY M000I.ATION f.'. Ií5.50 outside t'.S.A.I In addition to the new "Radio Repair was purchased from the WAA. s3.F.CTRIC MOTOR REPAIR = fia Iú.50 outelde L'.C.A., and Tune -Up" campaign, the RCA

TIO I I: I ^_ MODEItNie .i Aveo /fd.i50go telle Tube Department is making available Crosley Division of Corp., Cin- a special pricing kit to enable radio cinnati, Ohio, is introducing its plan of Name service dealers to price clearly and at- "pay -as -you -see" television meters to Address tractively such window and counter New York dealers after successful tests City. .Zone. State ...... s merchandise as radios and appliances. in Cincinnati. RADIO -ELECTRONICS for 1

NOW,' Build and Keep Big Screen Top Quality Television Receiver at Home as You Prepare for a LEDProfitable job in I O N 10 -ELEC , Choice of 10,12% or 16 inch picture tube Oscilloscope Now you can get this amazingly prac- ceiver. Standardized chassis is adapt- tical aid for learning Television at able for a 10, 12'2 or 16 inch direct home, to help you get started toward view tube that gives big, bright, sharp,

FASCINATING WORK . . . GOOD steady pictures. This is an optional MONEY . a THRILLING FUTURE - training advantage- designed to pro- in a real job, or your own sales and vide the utmost in practical "learn -by- service business. When you complete doing" home training in Television. Mail our regular home training -described coupon for complete details. See why below -you can build and keep a top you owe it to your "Television Future" quality commercial -type Television Re- to enroll for DeForest's Training, Inc. Multimeter

You also build See how D. T. l.'s amazingly effective T-V circuit training, (2) and keep this methods help start you toward a double -range R -F SIG- GOOD JOB or your OWN BUSINESS NAL GENERATOR, (3) Piofessiona/ in one of America's most promising jewel- bearing MULTI- fields- including Television, F.M. Radio, METER, (4) quality 6 -tube Type Equipment Aviation, Train, and Taxi Radio, Broad- SUPERHET RADIO. Then cast Radio, Industrial Electronics. Get build and keep that big

modern lessons . . . plus 16 ship- new Television Receiver. ments of Radio -Electronic parts. Work Here's EVERYTHING YOU over 300 experiments and projects- NEED for real laboratory including building of (1) commercial - type training . . AT type OSCILLOSCOPE for practical HOME!

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If you prefer, you an get ALL When you complete your train- your preparation in our new, ing, our effective Employment Chicago training laboratories Service helps you get started 6 -Tube .. one of the finest of its kind. toward a real future in Tele- Receiver Ample instructors . . . modern equipment. Write for details! vision-Radio-Electronics. You also use NOME MOVIES! a D. T. I. Exclusive! DeFOREST'S D. T. I. alone includes the modern, visual TRAINING, 2533 INC. training aid . . . MOVIES . . . to help you North Ashland Avenue, Dept. learn faster, easier of home. See electrons on Chicago 14, Illinois RC-F 12 the march and other fascinating "hidden Without obligation, action " -a remarkable home training advan- give me how I may complete facts tage that speeds your progress. make my start in showing Television -Radio- Electronics. Name...... Age...... Street......

CHICAGO 14, ILLINOIS City ...... Zone ...... A DE VRY Institution State ......

DECEMBER, 1949 12

V-4 A NEW MODEL VACUUM KIT TABE VOLTMETER Y'

EXPORT DEPT. 13 East 40th St. COMPANY (16) HEATH NEW YORK CITY CABLE: ARLAB -N Y. ... BENTON HARBOR 20, MICHIGAN RADIO- ELECTRONICS for ?lest 1450 fTeattf4 PUSH -PULL EXTENDED RANGE 5" OSCILLOSCOPE KIT 9e4twect

The first truly television *selll Extended sweep range 1S cycles to Tremendous sensitivity .06 Volt RMS 70,000 cycles. per inch deflection. New television type mullivibrator Push -pull vertical and horizontal amplifiers. sweep generator. New magnetic alloy shield included. Useful fr range to 21/2 Mega- cycles. Still the amazing price of $39.50. The new 1950 Push -Pull 5" Oscilloscope has features that seem impossible in a $39.50 oscilloscope. Think of it- push -pull vertical and horizontal amplifiers with tremendous sensitivity only six one hundredths of a volt required for full inch of deflection. The weak impulses of television can be boosted to full size on the five inch screen. Traces you couldn't see before. Amazing frequency range clear useful response at 2 ' Megacycles made possible by improved push -pull amplifiers. Only Heathkit Oscilloscopes have the frequency range required for television. New type multi -vibrator sweep generator with more than twice the frequency range. 15 cycles to 70.000 cycles will actually synchronize with 250,000 cycle signal. Dual positioning controls will move trace over any section of the screen for observation of any part. New magnetic alloy CR tube shield protects the instrument from outside fields. All the same high quality parts. cased electrostatically shielded power transformer. aluminum cabinet. all tubes and parts. New instruction manual now has complete step by step pictorials for easiest assembly. Shipping Weight 30 lbs. Order now for this winter's use. CONVERSION FOR OTHER MODEL HEATHKIT OSCILLOSCOPES A conversion for all 03 and 04 scopes is available changing them to the new push -pull amplifiers (does not change the sweep generator). Complete kit includes new chassis, tubes and all parts. For a small investment. add the latest improvements to your present oscilloscope (Except C.R. Tube Shield). Shipping weight 10 lbs.

Order OS Conversion Kit No. 315. . $ 12.50

THE NEW ea l¢r HANDITESTER KIT MORE 9eatcuce't THAN EVER BEFORE Beautiful streamline Bakelite cose. Quality Bradley AC rectifier. h AC and DC ranges to 5,000 Volts. Multiplying type ohms ronges. I% Precision ceramic resistors. All the convenient ranges 10-30 - Convenient thumb type adjust control. 300-1,000 -5,000 Volts. 400 Microampere meter movement. Large quality 3- built -in meter. The instrument for all -the ranges you need -beauty you'll enjoy for years and you can assemble it in a matter of minutes -an instrument for everyone. The handiest quality voltohmeter of all. Small enough to put in your pocket yet a full 3" meter. Easy pictorial wiring diagrams eliminate all assembly problems. Uses only IN precision ceramic divider resistors and wire wound shunts. Twelve different ranges. AC and DC ranges of 10 30 300. 1.000 5.000 Volts. Ohms ranges of 0 -3,000 ohms and 0 300.000 ohms. Milliampere ranges of IOMA and 100MA. Hearing aid type ohms adjust control fits conveniently under thumb for one hand adjustment Banana type jacks for positive low resistance connections. Quality test leads included. The high quality Bradley instrument rectifier was especially chosen for linear scales on AC. The modern case was styled by Harrah Engineering for this instrument. The 400 microampere meter movement comes already mounted in the case protected from dust during assembly. An ideal classroom assembly instrument useful for a lifetime. Perfect for radio service calls, electricians, garage mechanics. students, amateurs and beginners in radio. The only quality voltohmeter under $20.00. An hour of assembly saves you one -half the cost and quality parts give you a better HANDY instrument. Order today. Shipping weight 2 lbs. OHMS ADJUST.

EXPORT DEPT. 13 East 40th S. NEW YORK CITY (16) CABLE: ARLAB -N. Y. e e e BENTON HARBOR 20, MICHIGAN DECEMBER, 1949 II Beauty Quality Economy

IMPEDANCE BRIDGE KIT A LABORATORY INSTRUMENT NOW WITHIN THE PRICE RANGE OF ALL

Measures Inductance from 10 microhenries to 100 henries capacitance from .00001 MFD to 1000 MFD. Resistance from .01 ohms to 10

megohms. Dissipation factor from .001 to 1. "O" from 1 to 1000.

Ideal for schools, laboratories, service shops, serious experimenters. An impedance bridge for everyone - the most useful instrument of all, which heretofore has been out of the price range of serious experi. mentors and service shops. Now at the lowest price possible. All highest quality parts. General Radio main calibrated control. General Radio 1000 cycle hummer. Mallory ceramic switches with 60 degree indexing - 200 micro -amp zero center galvanometer -y, of 1% ceramic non- inductive decade resistors. Professional type binding posts with standard ?.(" centers. Beautiful birch cabinet. Directly calibrated "Q" and dissipation factor scales. Ready calibrated capacity and inductance standards of Silver Mica, accurate to t/ of I ñ and with dissipation factors of less than 30 parts in one million. Provisions on panel for external generator and detector. Measure all your unknowns the way laboratories do - with a bridge for accuracy and speed. Internal 6 volt battery for resistance and hummer operation. Circuit utilizes Wheatstone, Hay and Maxwell circuits for different measurements. Supplied complete with every quality ELSE TO BUY part - all calibrations completed and instruction manual for assembly and use. Deliveries are limited. Shipping weight, approximately 15 lbs.

10,000 V. H. V. TEST PROBE KIT No. 310. Extends range of any 11 megohm VTVM to 3,000 and 10,000 Volt ranges. A necessity for television. T E L E V I S I O N Shipping \Vt., I pound. $4.50 A L I G N M E N T GENERATOR R.F. CRYSTAL KIT TEST PROBE KIT

No. 309. Kit to assemble. Everything you want in a tele- R.F. probe extends VTVM vision alignment generator. A range to 100 Mc. Com- wide hand sweep generator cover- plete with IN34 crystal ing all TV frequencies 0 - 46 Ship. Wt., I lb...... S6.50 54 to 100 - 174 to 220 Mega- cycles, a marker indicator covering 19 to 42 Megacycles, AM modulation for RF alignment - va- ELSE TO BUY riable calibrated sweep width Q - 30 Mc. - mechanical driven sweep. Husky II0V. 60 cycle power transformer operated step type output e inductive - Item attenuator with 10.000 to I range - high output on all ranges - band switching for each TOOL KIT range - vernier driven main calibrated dial with over 45 inches of calibration - vernier driven calibrated indicator marker tuning. Large grey crackle cabinet 16Sí3 "x 10 %g "x a tool kit Now complete Phase for single trace adjustment. Uses three high frequency triodes plus to assemble your Heathkit. 7- 3/16 ". control tuning condensers for greater efficiency and accuracy at high Consists of Krauter diagon- 5Y3 rectifier - split stator al cutters and pointed nose frequencies - this Heathkit is complete and adequate for every alignment need and is assembly pliers, Xcelite supplied with every part - cabinet - calibrated panel - all coils and condensers wound, screwdriver. 60 Wart 110V. calibrated and adjusted. Tubes, transformer, test leads - every part with instruction soldering iron and supply manual for assembly and use. Actually three instruments in one - TV sweep generator- Wt., 2 of solder. Shipping AM generator and TV marker indicator. lbs. Complete kit 55.95 TV

EXPORT DEPT. 13 East 40th St. CIO - IV Y NEW YORK CITY (16) w CABLE: ARIAS -N. Y. ... BENTON HARBOR 20, MICHIGAN RADIO -ELECTRONICS for ).5 all in HEATHKITS...

qatelder TUBE CHECKER KIT eae I. Measures each element individually 5. Checks every tube element 2. Has gear driven roller chart 6. Uses latest type lever switches 3. Has lever switching for speed 7. Uses beautiful shatterproof full view meter 4. Complete range of filament voltages 8. Large size 11' x 14' x 4' complete 9. Checks new 9 pin piniatures

Check the features and you will realize that this Heathkit has all the features you want. Speed - simplicity - beauty - protection against absolescence. The most modern type of tester - measures each element - beautiful Bad -Good scale, high quality meter - the best of parts - rugged oversize 110V. 60 cycle power transformer - finest of Mallory switches - Centralab controls - quality wood cabinet - complete sec of sockets for all type tubes including blank spare for future types - fast action gear driven roller chart uses brass gears to quickly locate and set up any type tube. Simplified switching cuts necessary time to minimum and saves valuable service time. Short and open element check. No matter what arrangement of tube elements, the Heathkit flexible switching arrangement easily handles it. Order your Heathkit Tube Checker today. See for yourself that Heath again saves you 3 and yet retains all the quality - this tube checker will pay for itself in a few weeks - better build it now. Complete with detail instructions - all parts - cabinet - roller chart - ready to wire up and operate. Shipping Wt., 15 lbs. ELSE TO BUY

eeezdtleit Item eeett tteeit NEW s'eae SINE AND SQUARE WAVE BATTERY SIGNAL TRACER AND AUDIO GENERATOR KIT ELIMINATOR KIT ' UNIVERSAL TEST SPEAKER KIT

Zett ELSE TO BUY $22Só

Experimenters and servicemen working with a square wave for the first time invariably wonder why it was not introduced before. The characteristics of an amplifier tan be determined in seconds compared to several hours of tedious The popular Heathkit has plotting using older methods. Stage by stage, Now a bench 6 Volt Power supplyPD Y kit signal tracer now amplifier testing is as easy as signal tracing. for all auto radio testing. Supplies 5 - been combined with a universal test speaker at The low distortion ( less than 1,4 1 and linear 7! , Volts at 10 Amperes continuous no increase in price. The same high quality output ( ± one db.1 make this Heathkit equal or 15 Amperes intermittent. A well fil- tracer follows signal from antenna to speaker or superior to factory built equipment selling tered rugged power supply uses heavy -locates intermittents -defective parts quick- for three or four times its price. The circuit is er -saves valuable service time greater the duty selenium rectifier, choke input filter -gives popular RC tuning circuit using a four gang income per service hour. Works equally well variable condenser. Three ranges 20.200. 200- with 4,000 MED of electrolytic filter. broadcast FM 2.000, 2.000- 20.000 cycles are provided by 0 - 15 Volt meter indicates output. Out- on - or TV receivers. The test selector switch. Either sine or square waves put variable in eight steps. Excellent for speaker has assortment of switching ranges to instantly available at slide switch. All compo- demonstrating auto radios. Ideal for match push pull or single output impedance. nents arc of highest quality, cased 110V. 60 servicing - can be lowered to find Also test microphones, pickups - PA systems cycle power transformer. Mallory F.P. filter con. sticky vibrators or stepped up to equiva- comes complete cabinet 110V. 60 densers, 5 2 - - tubes, calibrated color panel, grey easily cycle power transformer tubes, test probe, crackle aluminum cabinet. The detailed instruc- lent of generator overload - - tions make assembly an interesting and in- constructed in less than two hours. all parts and detailed instructions for assembly structive few hours. Shipping Wt., 15 lbs. Complete in every respect. Shipping and use. Shipping Wt., 8 lbs. \Vt., 18 lbs.

EXPORT DEPT. 13 East 40th Sr. NEW YORK CITY !I6) CABLE. ARIAS -N Y ... BENTON HARBOR 20, MICHIGAN DECEMBER. 1949 Ifi

1Ze« qeatl er BROADCAST AND 3 BAND SUPERHETERODYNE RECEIVER KIT BROADCAST MODEL BR -1 3 BAND MODEL AR -1 550 to 1600 Kc. 550 Kc. to 20 Mc. Two new Heathkit Superheterodynes featuring the best of design and material. Beautiful six inch slide $1950 rule dials - 110 V. 60 cy. AC power transformer operated -metal cased filters -quality output transformers, dual iron core metal can IF transformers - two gang tuning condenser. The chassis is provided with phono -radio switch-110 V. outlet for changer motor and phono pickup jack. Each kit is complete with all parts and detailed instruction booklet. Pic- torial diagrams and step -by -step instructions make assembly quick and easy.

Ideal AC operated superheterodyne receiver for home use or replacement in Enjoy the thrill of world wide short wave reception with this fine new AC console cabinet. Comes complete with attractive metal panel for cabinet operated Heathkit 3 band superheterodyne - amazing sensitivity 15 microvolt mounting. Modern circuit uses 12K8 converter, I 2SH7 input IF stage. 12C8 or better on all bands. Continuous coverage 500 Kc. to over 20 Mc. Easy to I output IF stage and first audio 12A6 beam power output stage, 5Y3 rectifier. build with complete step -by -step instructions and pictorial diagram. Attractive Excellent sensitivity for distant reception with selectivity which effectively accurately calibrated six inch slide rule dial for easy tuning. Six tubes with one separates adjacent stations. dual purpose tube gives seven tube performance. Beam power output tube gives over 3 watts output. The husky 110 V. cased power transformer is conservatively rated for long life. Separately assembled coil turret with band switch eliminates difficult construe. The illuminated six inch slide rule dial is accurately calibrated for DX recep- Lion. Conservatively rated 110 V. power transformer supplies full operating tion. Enjoy the pleasure of assembling your own fine home receiver. Has tone, voltages to all tubes for maximum reception. Has band switch, tuning, volume. i volume, tuning and phono -radio controls. Chassis size 21/4" x 7" x 121/2". tone and phono-radio controls. Chassis size 214" x 7" x 1212 " supplied to 3.4 ohm - Comes complete with all parts including quality output transformer complete - punched chassis - tubes - controls - transformers (quality out- voice coil, tubes, instruction manual, etc. ( less speaker ). Shipping Wt., 10 lbs. put to 3.4 ohm voice coil) - all small parts - hardware and instructions No. BR -1 Receiver $ 19.50. (less speaker). Shipping Wt., 10 lbs. No. AR-I Receiver $23.50. No. 135 Communications Type Table Modi Metal Cabinet $4.50 No. 335 Communications Type Table Model Metal Cabinet $4.50 No. i21) High Quality 4' I'M Speaker her above 2.75 No. 320 High Quality 5" PM Speaker for above 2.75 .>wx hew 1950 VERNIER TUNING R.F. geldtker SIGNAL GENERATOR KIT 7eaewcet {

New S to 1 ratio vernier tuning Cathode follower output for greatest for ease and accuracy. stability. New external modulation switch - 400 cycle audio available for audio testing. use it for fidelity testing. Most modern type R.F. oscillator. New precision coils for greater Covers 150Kc. to 34Mc. on fundamentals output. and calibrated strong harmonics to 102 Mr.

The most popular signal generator kit has been vastly improved -the experience of EXTER thousands combined to give you the best. Check the features in this fine generator and MODULA consider the low price $19.50. A best buy for any shop, yet inexpensive enough for hobbyists. Everyone can have an accurate controlled source of R.F. signal voltage. The new features double the value -think of being able to make fidelity checks on receivers by inserting a variable audio signal. Internal 400 cycle saw -tooth audio oscillator modulates R.F. signal and is available externally for audio testing. The new 5 to 1 ratio vernier drive gives hairline tuning for maximum accuracy in scale settings. The coils are already precision wound and calibrated. Uses turret type coil and switch assembly for ease of construction. The generator is 110 V. 60 cycle transformer operated and comes complete in every detail- cabinet -tubes -coils -beautiful two color calibrated panel and all small parts -new step -by -step pictorial diagrams and complete instruction manual make assembly a cinch even for novices. Why try to get along with. out a signal generator when you can have the best for less than a twenty dollar bill. Better order it now. Shipping weight 7 lbs $19.50 CONVERSION KIT FOR G -1 GENERATORS Conversion kit for G -1 generators for vernier tuning and external modulation includes new high band coil for greater output. Gives all the features of new G -5 listed above. Order G -5 Conversion Kit No. 316 $4.50

EXPORT DEPT. 13 East 40th St. NEW YORK CITY (16) CABLE: ARIAS -N. Y. e . e BENTON HARBOR lO, MICHIGAN RADIO -ELECTRONICS far 17

eatdit hiew featlf:4iZ`e ELECTRONIC SWITCH KIT FM TUNER KIT\ THE UTILITY OF ANY SCOPE DOUBLES A truly fine FM Tuner with the coils ready wound, all alignment completed -all that is necessary is wiring and it's ready to play - uses super regenerative circuit - 110V. 60 cycle transformer operated - two gang tuning condenser - slide rule calibrated dial - two tubes - complete instructions including pictorial enable even beginners to build successfully. Shipping Wt., 4 lbs. Beautiful mahogany cabinet for FM CABINET V 1475 Tuner (shown above) extra $3.75 ltdefteaf EXTRA ELSE TO BUY

An electronic switch used with any oscilloscope provides two separately controllable traces on the screen. Each trace is controlled KIT independently and the position of the traces may be varied. The CONDENSER CHECKER input and output traces of an amplifier may be observed one beside the other or one directly over the other illustrating perfectly any change occurring in the amplifier. Distortion - phase shift and other defects show up instantly. 110V. 60. cycle transformer operated. Uses 5 tubes (1 6X5, 2 6SN7's, 2 6SJ7's). Has individual gain controls, positioning control and coarse and fine sweeping rate controls. The cabinet and panel match all other Hcathkits. Every part supplied including detailed instructions for assembly and use. Shipping Wt., 11 lbs. ,Power factor scale Bridge type circuit Measures resistance Magic eye indicator eat/44t M leakage 110 V. transformer 3-TUBE All WAVE RADIO KIT Checks paper -mica- operated electrolytics All scales on panel Checks all types of condensers. paper- mica -electrolytic- ceramic over An ideal way to learn radio. This kit is com- a range of .00001 MFD to 1000 MFD. All on readable scales that plete ready to assemble, with tubes and all other read direct from the panel. NO CHARTS OR MULTIPLIERS from 110V AC. Simple, clear are parts. Operates condenser checker anyone can read without a detailed instructions make this a good radio NECESSARY. A training course. Covers regular broadcasts and college education. A leakage test and polarizing voltage for 20 to short wave bands. Plug -in coils. Regenerative 500 volts provided. Measures power factor of electrolytics between circuit. Operates loud speaker. Shipping Wt., 0% and 50 %. 110V. 60 cycle transformer operated complete with 3 lbs. rectifier and magic eye tubes. cabinet, calibrated panel. test leads $875 HS30 Headphones per set ....$1.00 and all other parts. Clear detailed instructions for assembly and use. 21/," Permanent Magnet loudspeaker _ 1.95 Why guess at the quality and capacity of a condenser when you Mahogany Cabinet _. _... . 2.95 can know for less than a twenty dollar bill. Shipping Wt., 7 lbs. CABINET EXTRA GCliltzit

H I G H F I D E L I T Y

S H I P V I A AMPLIFIER KIT FROM _Parcel Post HEATH CO. _Express

jotlrúrg B E N T O N HARBOR _Freight

ELSE TO MICHIGAN _Be 1 Woy BUY o... DESCRIPTION Price Total $1495 Build this high fidelity amplifier and save two -thirds of the cost. 110V. 60 cy. transformer operated. Push pull output using 1619 tubes (military type 6L6's), two amplifier stages using a dual triode (6SL7). as phase in- verter give this amplifier a linear re. production equal to amplifiers selling for ten times this price. Every part supplied; punched and formed chassis. transformers (including quality out. put to 3 -8 ohm vosee coil), tubes. controls, and complete instructions. Add postage for 20 lbs. 12" PM Speakers for above....$6.95 Mahogany Speaker Cabinet, ENCLOSED FIND CHECK ... MONEY ORDER FOR 14'i" 14'," 8' $8.75 PLEASE SHIP C O.D. ... POSTAGE ENCLOSED FOR POUNDS __.. :::... x..:..

EXPORT DEPT. 13 East 40th S1. AIL IVY NEW YORK CITY (I6) HEATH COMP CABLE: ARLAB -N. Y. . - - BENTON HARBOR 20, MICHIGAN

DECEMBER, 1949 18

BEN ... and YO can FROM 5 00 SRV'E9 do the same by P1`'A'Y AIGN GAM? ACTING NOW ! -SYLVAN Another of Sylvania's famous profit -building campaigns is getting under way! VRt WOGs I The campaign runs through the months of January, February, March and R April -with half -page ads like this in LIFE, THE SATURDAY EVENING POST, A / LOOK, COLLIER'S, and RADIO AND TELEVISION BEST. The ads tell your customers and prospects to come to you for radio and television service. But that's just the start! THEN ... you tie in with this national advertising by using Sylvania's complete kit of display and direct mail material -all built around the ads - designed for you -and ready for you now! Sylvania's previous campaigns paid off in a big way for thousands of dealers "rotear Suede eas aaNhl and servicemen. Be ready to cash in on this latest big push!

HERE'S WHAT YOU GET IN THE SYLVANIA KIT:

' ; r. .Nh : `i : 3>,

POST CARDS. O You get 4 sets of we Postal Card Mailings -one for use am b " each month in the campaign. eáommnd SYLVANIA--r and They're in 3 colors -imprinted TelevisionTubes with your name and address! You pay only the government postage on each card- that's © WINDOW DISPLAYS. You get 2 Window of/ you pay for the entire kit! Displays -featuring the same illustra- EVERYTHING ELSE IS FREE. tions as the Sylvania national ads. 3- dimensional-4 colors -2 by 3 feet. 2 COUNTER CARDS, too, 12 by 18 inches.

100t rot THIS SIGN Or minuet SANG sum AD MATS. You get 4 Newspaper Ad Mats -two sizes for each 2- month period. Sizes are one O STREAMERS. You get 2 Window Stream - Does your radio give our with squeals and grunts? Then and two columns wide, 7 inches ers-in 2 colors -11 by 26 Inches. Like call the re,vkenun who displays the Sylvania ,ign. Because deep. Easy way to tie your local the other items in the campaign, your radio needs expert cart, the kind this fellow is trained newspaper advertising in with Streamers feature both radio and tele- to give. He has Sylvania teat equipment to mot out rouble Sylvania's national ads! vision service. spots ... highqualiry Sylvania radio tubes to bring you the cry,ol.clear reception you want. Hear your old an perform as it did the day you bought it. Can it wed at the Sylvania © RADIO SPOT ANNOUNCEMENTS. You get 4 booklets of Radio Spot ,ign el dependable smite. Announcements -one for each of the 4 months in the campaign. When you've planned your schedule, just hand the spots to your local radio station- they're all ready to use!

SYLVAN IA Mail coupon today for full details on the complete campaign!

RADIO TUBES Sylvania Electric Products Inc. PaaDUCT Of SytVNIA eucTOic PDDDCTf INC, Advertising Dept. R -1712, Emporium, Po. Please send full details of your new 1950 January, February, DECALS. You get as many March and April Service Dealer Campaigns. Decals as you need -in 8 or 12 inch diameter. NAME Your choice of wording - RADIO SERVICE or COMPANY RADIO TELEVISION SERVICE. Sylvania's ads ADDRESS make these Decals nationally known -cash In CITY ZONE.... STATE on their familiarity! SYLV\NIA*E LE CTRI C LIGHT BULBS; PHOTOIAMPS RADIO TUBES; CATHODE RAY TUBES; ELECTRONIC DEVICES; FLUORESCENT LAMPS, FIXTURES. WIRING DEVICES, SIGN TUBING; RADIO ELECTRONICS Icy 19

They Packed a Pole Line Into a Pipe

Back in the eighties, telephone executives faced underground; by the early i9oo's even cities far a dilemma. The public demanded more telephone apart could be linked by cable. service. But too often, overloaded telephone poles Then Bell scientists went on to devise ways just couldn't carry the extra wires needed, and to get more service out of the wires. They evolved in cities there was no room for extra poles. Could carrier systems which transmit 3, t a, or even 15 wires be packed away in cables underground? voices over a pair of long distance wires. A co- Yes, but in those days wires in cables were axial cable can carry 1800 conversations or six only fair conductors of voice vibrations, good television pictures. This is another product of only for very short distances. Gradually cables the centralized research that means still better were improved; soon every city call could travel service for you in the future.

BELL TELEPHONE LABORATORIES EXPLORING AND INVENTING, DEVISING AND PERFECTING, FOR CONTINUED IMPROVEMENTS AND ECONOMIES IN TELEPHONE SERVICE

DECEMBER, 1949 20

Get Your FCC Ticket Which Jobs leading to Better Pay $3,000 to $7,500 (Average Pay Reported by FCC Nationwide Greater Security Survey) Do You are opening up A Nice Home right now for FCC Licensed Want? Happy Vacations A New Car and Travel Radiomen. How to Pass COMMERCIAL FCC RADIO OPERATOR

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ELECTROMC EXPERIIIE%TATIO1'

... There are now over one-half million electronic experimenters in the (' S

By HUGO GERNSBACK

SINCE the beginning of World War II -even previous which at night are lit so that the public may see if the to it- electronic experimentation in the United States taxi is occupied or not. At present the roof indicating has taken an extraordinary upsweep. lights are switched on when the taxi driver puts on the headlights consulted seem to be unanimous that and the taxi -meter flag is up. The driver, Authorities however, may forget to put on the driving lights when today there are in the United States well over 500,000 darkness comes with the result that the roof lights remain radio -electronic experimenters, of which we here name In only the major classes. dark. this case the taxi passes many would -be passengers because once the speeding taxi is abreast of you it is First we have the industrial laboratory experimenters too late to hail the cab driver. In the daytime nothing is who work for the large radio manufacturers and allied done for would -be passengers, who from a distance can- intemsts. An entirely new class of these sprang up in the not possibly see if the taxi is occupied or not. ear 0's, i.e. the atomic electronic research experimenters. This particular class is growing by leaps and bounds. What is needed is a simple, low- priced photoelectric system which puts on the roof lights automatically in fail- The next large body is connected with various institu- ing light- whether at night or in the daytime. On very tions of learning, such as universities, colleges, etc. Then cloudy or foggy days when it gets almost dark, few taxi we have the professional engineers who are given assign- drivers switch on their headlights. Consequently the roof ments for electronic research by various manufacturers, lights stay dark. business houses, architects and a vast number of others, for special devices needed for specific purposes. A photoelectric, automatic relay arrangement would solve this problem nicely. The same device then could also Our armed forces, the Army, Navy, and Air Forces, all be doing double service maintain large, ever growing staffs of electronic research - during daylight. It would switch experimenters. Further, there are the private experimen- on, say, an intense yellow searchlight on the right side of the taxi. This light could be constructed on the same ters who pursue their hobby for personal instruction. principle as the stationary red and green street lights Finally we come to the inventors. The latter class is by no which means small one and it is growing are easily seen during the daytime. Thus, a high - a apparently larger as power yellow light would mean that the taxi is unoccupied. time goes on. In case a yellow light is objectionable a different visual As electronic applications and new industrial r iuire- system could be operated by the photoelectric system. ments increase at an extraordinary pace, hundreds of Sew electronic devices are urgently needed almost daily. A list Such a system would be wholly automatic. It would, first, of several thousands of such applications and improve- be of great service to all taxi riders. Second, the taxi ments can be made up by anyone who knows the electronic owners would benefit from it due to higher revenue. In field. New York City there are over 20,000 cabs run by large fleets, all of whom are most interested in a device of this It would seem, therefore, that electronic experimentation type. The same is true in various percentages in other is an unusually worthwhile endeavor today. How far this cities. Independent taxi drivers are even more interested can be expanded not even the most enthusiastic proponent and would be glad to pay a fair sum for such a device of electronics can possibly foresee. Here are a few sug- because they know that their revenue would be increased. gestions for needed electronic improvements and devices, mdb given simply as examples. AIRPLANE PUBLIC ADDRESS. If you have used one of the fast airplanes you must have noticed the almost BLAST -PROOF MIKES. Recently we were sitting in one impossible of the largest motion -picture houses in New York. Our lo- performance of the planes' public address sys- cation was roughly tems. These are usually installed in the pressurized larger halfway back in the auditorium. A shrill planes so .{ female singer who had never been taught microphone tech- that the captain of the plane can speak to his nique passengers. Very often his information is important and put her mouth as close to the mike as was humanly it is always possible. This literally started to blast the audience out of interest to the passenger who wants to of their seats via know over what part of the country he is flying and hear the house public address system. The special news bulletins, weather result was physically painful to the eardrums, so much so reports, when the plane that a ten -year will arrive at its destination, etc., etc. The trouble with air- -old boy sitting next to us tightly clapped craft public address systems his hands over his ears. A number of persons walked out, today is that in a pressurized including the writer, when cabin the ears of the passengers become affected in such the blasting became unbearable. a way that they do not This is not an unusual performance, as many motion-pic- hear as well as at sea level. The pressurizing is usually made roughly equivalent to the ture houses which give stage shows work on the same deci- atmosphere at about bellow principle. It is also true in night clubs, concert 8000 feet altitude, although the plane halls, etc. may be flying at 20,000 feet or more. Also, when the plane begins to descend the air pressure gradually increases Some public address systems have been built with an to normal. All of this affects the public address loud- audio a.v.c. system (volume compression) so that the out- speakers and microphone adversely; it makes the trans- put into the loudspeaker system is automatically con- mission of speech often totally incomprehensible. What is trolled to keep the decibel range within comfortable limits. needed badly is an electronic equalizer which changes the These systems, however, are expensive and are therefore output in such a manner that it will automatically be not used universally. It should be possible to devise suited to the hearing ability of the simple, a passengers, regard- low -cost electronic system that, by the addition of less of changing air pressure. This need not be a difficult perhaps a single tube and a few other components, will assignment for an alert electronic experimenter. On ac- accomplish an automatic constant -level sound output. count of aviation procedure, it should badly needed. It is be remembered that not a great deal of extra weight can be added to existing PHOTOELECTRIC systems. This is the first thing that airplane TAXI INDICATOR. In most of our frown companies larger cities it used to be upon. The device, therefore, must be reasonably a problem to hail a passing taxi simple and above all because you never knew if it was free or not. After not be too expensive. Such an im- war, these cities made mandatory the provement is certain to find a ready sale and quick adop- a system of roof lights tion by all major airlines. DECEMBER, 1949 22I Broadcasting ANd Communications

Mid -Ocean Radio Stations

THE world's most compact assem- special signals produced by a tone Since the duties of the little Ocean Sta- blage of widely variegated elec- oscillator. tion Vessels are expanding continually. tronic and radio equipment is The power of the various transmit- such new equipment becomes necessary without doubt to be found on one ters ranges from .027 watt to 750 watts, regularly, and finding a spot for it is of the Ocean Station Vessels of the with frequencies anywhere between 300 work for a genius. United States Coast Guard. These little kc and 156 inc. Ten remote control Though the equipment itself may be ships -averaging about 2,000 tons in units permit operating transmitters jammed, its congestion is nothing com- displacement and 300 feet in length- and monitoring their receivers from pared with that of the signals -both are scattered over the Atlantic Ocean various spots aboard ship. For example, incoming and outgoing. The ships have to report on weather conditions and to some of the main radio room transmit- two masts about 100 feet apart, on or aid transoceanic air service. ters may be operated from the pilot between which all the antennas must be Crowded into the ship's 300 feet are house, plotting room, or emergency ra- mounted or hung. seven communications transmitters, 14 dio room. The resulting interference resembled communications receivers, fou r all - Most of the equipment is concen- a radioman's dream of Hell, and its re- wave broadcast receivers, five speaker - trated in the main and emergency radio duction called for even more equipment. amplifiers, three transceivers, five rooms, pilot house, and plotting room. By using multicouplers, eight receivers "handi- talkie" type transceivers, one Compactness of the installation be- are operated from one antenna. Band - beacon transmitter, one standard di- comes evident whenever it becomes pass filters keep the powerful beacon rection finder, one Loran receiver - necessary to install new equipment. transmitter signals on 312 -314 kc out indicator, three radars with their associated IFF equipment, a remote PPI radar repeater, and receivers and recording equipment for radiosonde transmissions. The Ocean Station Vessels of the Additional electronic equipment includes underwater echo -ranging equip- - ment and two echo sounders, as well U. S. Coast Guard perform a little as the internal communications system, comprising ten 10- station talk -boxes known service to ships and aircraft and a 250 -watt amplifier which drives a bull horn and 30 speakers in all parts of the ship, operating on voice and with RADIO- ELECTRONICS for Broadcasting and Communications 23 of the receivers tuned to the distress frequency at 500 kc. Tunable filters trap pulse interference which would otherwise paralyze receivers on the v.h.f. ranges, and automatic antenna changeover relays switch receiver and transmitter onto the same antenna in a number of operations. thus doubling the antenna efficiency. Complex patch panels enable the operator to choose between a number of antennas for any given transmission or reception, under varying conditions of noise level, signal strength, selective fading, or other circumstances. The equipment is used in carrying out the four main duties of an OSV: 1. Weather observations and re- porting; 2. Transoceanic aircraft check point; 3. Distress; 4. Preparedness. The Weather Service Weather data is gathered by RA- wind observations) in WINS (radio Official Coast Guard Photos which a balloon carrying a radar re- Masthead of one of the ships, showing assemblage of radio and radar antennas. flector is tracked by the ship's radars, or by RABAL (radio balloon sound- ing), a standard radiosonde with a large balloon which carries it to a every three or four weeks. Upon sight- in October, 1947. The 65 passengers of height at which the balloon bursts. The ing the relief ship, the ship to be re- that plane were picked up over a pe- RABAL transmitter operates at about lieved releases a helium -filled balloon riod of two days by the boats and rafts which a crossed -dipole 40 mc, and has been heard as long as carries target of OSV Bibb, patrolling station C, mid- three hours before reaching the burst- reflector. Both ships then engage in a way between Newfoundland and Ire- joint RAWIN (radio wind direction and land, though 35 -foot seas were running. ing altitude. velocity All weather reports, together with observation) with their air There have been many less dramatic temperatures and other meteorological search radar, as a check on the per- occasions when a plane or surface ship coded and transmitted formance of both plotting teams and has been assisted in emergencies, rang- information, are radars. to Coast Guard receiving stations on ing from medical treatment to the res- high- frequency bands near When the RAWIN is completed the new cue of the crew of a "ditched" plane. one of the ship officially takes over the station 16 mc, depending on the time The electronic personnel of an OSV 8, 12, or and places its automatic high -power of day, distance of transmission, at- consists of 15 persons. Of these, twelve other conditions. Some- aircraft beacon in operation. The bea- are on the operating staff-seven ra- mospheric, and which five out of every messages may be transmitted con, transmits diomen, four radarmen, and one sonar- times the fifteen minutes the ship is on station, on two frequencies to man. Commissioned deck officers and simultaneously is primarily to transoceanic air- reduce the effects of selective fading; useful petty officers are also called upon from or combination craft, and permits them to get auto- time to time to operate direction find- and when no frequency matic direction finder bearings as a of frequencies will get them to shore, ers, echo sounders, and radar equip- OSV. position check. As the aircraft nears ment. they are relayed through another the ship it reports departure, destina- Station vessels relieve each other tion, altitude, speed, course and other Radio Repairmen information by radiophone. The ship's radar picks up the aircraft The other three men are classed as and can give it an accurate check on its electronic technicians. On them devolves position, course, and actual speed. All the whole task of keeping the equip- information concerning passing flights ment in operating condition. A complete is recorded and saved, for it might be complement of test equipment is neces- of vital importance should planes be sary to maintain the variety of gear on off course, in trouble, or overdue at board. There are five frequency meters, destination. two signal generators, a wavemeter, Data on local surface weather and tube checkers, oscilloscopes, v.t.v.m.'s, the direction and velocity of winds at and special test sets for particular different altitudes are transmitted to equipment. Since frequencies vary from aircraft. Some station vessels in the ultrasonic to u.h.f. and types of trans- North Atlar.tic handle as many as 350 mission from c.w. through phone to aircraft on each patrol, and in some pulse, with equipment ranging from cases as many as 15 at the same time. kilowatt size down to hand -carried ap- Such cases require the highest degree paratus, an electronic technician on of teamwork in the plotting room. one of these vessels holds down an ex- Possibly as important as the ships' tremely interesting, if very busy, job. weather observations is their direct He has to know his stuff, and there is service to air and sea navigation. Con- plenty of stuff for him to know. Each tinuous watch is maintained on all dis- man must be extremely versatile and tress frequencies, both air and marine. an expert in each line. It is a carefully Coast Guard OSV's have participated selected and carefully trained man who in more than one spectacular rescue, holds a technician's position on an In the radar room of one of the OSV's. such as that of the Bermuda Sky Queen OSV. DECEMBER, 1949 241-- Test Instruments

By HERBERT S. BRIER

two common types of multitesters, one rated at 1,000 and the other at 20,000 ohms per volt. (See RADIO -ELECTRONICS for May, 1949, for complete specifications on 30 different models of multi - testers.) For general measurements on tube circuits, the 20,000- ohm -per -volt mod- a els are to be preferred, other things being equal, because they will measure across much higher resistances and will usually give more accurate voltage measurements. Table I records the readings that might be obtained with different meters at the plate and screen terminals of the 6SJ7 resistance - coupled amplifier which is diagrammed in Fig. 1. Obviously, different ohms -per -volt ratings and different scales can affect voltage readings. The meter resistance shunts the plate or screen resistance, lowering it considerably as far as the B- supply is concerned, and reducing the voltage appearing across it. To be ig- nored, the meter resistance must ex- Part of typical test bench shows manuals and some essential instruments. ceed the plate or screen resistance by at least 10 times so that its shunt effect is negligible. The a.c. voltage ranges of most multimeters are 1,000 ohms per volt, and are generally used for measurements only at the power -line frequency or across voice coils. There are more suit- Test Instruments able devices, which will be discussed later, for measuring audio and ri. voltages (signal voltages) in the receiver proper. Service data and Admittedly, a competent service technician can repair any piece of radio equipment without a service manual; he does so when necessary, but only at the cost of much time. Quoting two Igo technicians on the subject will make further comment unnecessary. the Technician In the November issue, John T. Frye, the well known writer, described the servicing of a radio -phono combination. The complaint was faulty operation of RADIO- ELECTRONICS for February, scribes, somewhat in the order of their the record changer, and the repair con- 1949, contained an article of importance, the service instruments the sisted of tightening a setscrew, a 30- mine, "Using Your Ohmmeter," average radio repair shop should have second job. But even to see the screw which outlined how the radio ex- on its bench. required disassembling the changer and perimenter with a good grasp of radio 1. Multitester (volt- ohmmeter). removing the motor from its suspension fundamentals could repair an ordinary 2. Service data. mounting. The importance of this story radio receiver with no equipment other 3. Signal generator (for AM is that Mr. Frye commented that his than an ohmmeter, a tube manual, and work) . service data saved valuable time by a small stock of parts. While this is 4. Tube tester. detailing trouble symptoms and by true, more extensive equipment is nec- 5. Vacuum -tube voltmeter. showing how the setscrew could most essary for anyone who expects to earn 6. Signal tracer. easily he reached. Every repairman can a living through radio servicing, and 7. Capacitor checker. cite a parallel case. this article will attempt to show the 8. Wide -range (television) sig- Another technician, who has been a reason why. nal generator with built -in radio trouble shooter for several air- The greatest value of test equipment variable sweep generator and lines and for a large manufacturer, on the average service job is that it marker oscillator. said that he would give up all his test enables the technician to do a better 9. Cathode -ray oscilloscope. instruments before parting with his job in less time, although it often spells manuals. "After all," he said, "if worse the difference between success and fail- Multitesters comes to worst, I can always substitute ure as well. While no two technicians Accepted almost universally as the good parts for doubtful ones and use will agree entirely, the following de- indispensable test instrument, there are the old spark method for checking volt- RADIO -ELECTRONICS for Test Instruments 125

ages, but without the service data, not TABLE I even the designer himself could figure out some of the things they cal! re- Meter _ 1,1(x) ohms /v ¿20,000 ohms /vr \'.t.v.m. ceivers." Scale Plate Screen Plate Screen Plate Screen volts volts volts volts volts volts volts Signal generators 50 20 7 off scale 20 off scale 25 The signal generator runs almost constantly in a busy service shop. 250 50 151 83 22 90 25 Aligning i.f. and r.f. circuits then becomes a simple matter of setting the 1,000 741 202 891 242 90 252 generator to the proper frequency, 1 Difficult to read accurately. 2 Impossible to read accurately. coupling it to the various control grids in sequence, and adjusting the appro- revealing such things as unbalance in quencies of the circuits being adjusted priate trimmers or slugs. push -pull stages, leaky coupling capaci- are high radio frequencies with band- Service manuals, incidentally, are tors, defective i.f. or r.f. coils, and im- widths measured in megacycles, the almost a necessity for getting maxi- properly functioning oscillators. signal generator is invariably swept at mum utility from a signal generator, The v.t.v.m.'s high sensitivity is not 60 or 120 cycles per second. As it is the because they list the various frequen- obtained at the cost of durability. It is rate of sweep and not its width that cies to which to set the generator, and less likely to be damaged through ac- determines the modulation frequency of give special alignment instructions for cidental overloads than are less sensi- an FM signal, and the majority of tele- individual receivers. tive straight multimeters. vision alignment procedures are based

Tube testers Signal tracers ooi 270 ------I With a good stock of tubes to substi- Although some technicians claim that TO CiRCURS TO VERT AMPL tute for doubtful ones, the tube tester signal merely duplicate the BEING tracers ADJUSTED OSÚLLEGCOPE can be dispensed with temporarily. work done by other test equipment, However, no successful technician others like the speed a tracer allows would attempt to operate very long in diagnosing a receiver's ills. The sig- Fig. 2-Simple probe rectifies TV r.f. without one, if for no other reason than nal tracer is moved, stage by stage, or i.f. for feeding to scope amplifier. that the customer expects him to have from the antenna terminal toward the it. Besides, a tube tester is convenient speaker, revealing exactly where the on connecting the oscilloscope to the and a potent seller of new tubes. signal disappears. The tracer may even output of the video detector, it can be Unfortunately, practically every tube tell the experienced user the exact de- seen that the oscilloscope trace is also tester on the market occasionally mis- fective part. And it is especially useful 60 or 120 cycles. Those alignment pro- judges a tube, especially oscillator tubes in tracing hum, particularly in a.c.-d.c. cedures that require the oscilloscope to and noisy and intermittent ones. As a receivers where individual tubes can- be coupled to individual tuned circuits result, a good technician never hesi- not be removed without disabling the are handled by a simple diode in a probe tates to substitute another tube for one entire receiver. (see Fig. 2) to convert the signal gen- that tests OK in a checker, but in a erator output frequency to one that will Capacitor checkers be passed by the built -in oscilloscope Here again, there is considerable di- amplifier. vergence of opinion. Depending on per- With almost every new test instru- sonal preference and on what other test ment conies an auxiliary piece of equip- equipment is available, capacitor check- ment that may double or triple its use- ers are often rated by service techni- fulness; yet, oddly enough, many tech- cians on the answers to questions like nicians throw it away with the packing. these: 18 it easier to check a coupling This gadget is the instruction manual. capacitor with a checker or with a Not only does it tell how to use the in- v.t.v.m.? Is it faster to bridge another strument, but, equally Fig. 1 -Table 1 shows results of meas- important, it urements on this voltage amplifier. filter capacitor temporarily across one tells what the instrument cannot do. that is suspected of having dried out More can be learned about the com- receiver where everything is apparently than to unsolder it and test it on a parative merits of various types of normal still does not operate properly. checker? Why measure the character- equipment through reading and com- istics of a capacitor in a receiver when paring instruction manuals than in any Vacuum -tube voltmeters service manuals give full data on all other way except actually using the Some technicians prefer a good vac- of them? equipment or "asking the man who uum -tube voltmeter t v.t.v.m.) above No matter how these questions are- owns one" -and not even he can always any other single test instrument be- answered, almost all technicians will be depended on for full information. cause of its versatility. A good one admit the value of a capacitor checker The importance of reading the in- may measure resistance between 0.1 in culling defective and mislabeled re- structions accompanying even familiar, ohm and 1,000 megohms; d.c. and a.c. placement units before they are placed simple types of test instruments is well voltages up to low radio frequencies, in a set. Too, most capacitor checkers illustrated by the following incident. from a fraction of a volt up, at a re- will measure inductance and resistance Some weeks ago I helped a service tech- sistance measured in tens of megohms; as well. nician test several hundred tubes. Fol- and with a high- frequency probe, it can lowing exactly his instructions for measure r.f. voltages above 100 mc, Sweep generators; oscilloscopes using his tube tester, we had tested just to mention a few of its uses. A suitable sweep- frequency signal about half of the tubes when I became Comparing the third column of Table generator tunes between at least 2 and certain that there was something amiss. I with the other columns shows the 216 mc, and can be swept (frequency - He dug out the instruction sheet, and value of the v.t.v.m.'s high input re- modulated) from zero to 10 mc or more. we discovered that we were using the sistance, as does the fact that it offers Also, it has provision, preferably built wrong procedure for testing for shorted the only practical method of measuring into the same cabinet, for providing elements. Retesting the previously a.v.c. and similar low d.c. voltages de- accurate, unmodulated marker points. O.K.'d tubes, we found many that had veloped across high resistances. Being The requirements for the cathode -ray shorts between two or more elements! I equally sensitive on the a.c. scales, the oscilloscope are not too severe. Any hesitate to think of how much extra v.t.v.m. will also measure signal volt- good one, with amplifiers of reasonable work this technician made for himself ages (using the high-frequency probe gain capable of passing audio frequen- in the year or more he had been using for r.f.) right at the tube elements, cies, is adequate. Although the fre- the tester in this manner. DECEMBER, 1949 281 Television News How To Remove The 60 -Cycle Buzz From Intercarrier TV Receivers

A known disadvantage of intercarrier receivers is a possible 60 -cycle buzz. It can be removed easily.

By L. S. PEARLMAN

INTERCARRIER sound i.f.'s tor tele- detector and amplifier should pass up for the maximum volume and a strong vision receivers have several decided to 4 me and then cut out the higher signal for minimum buzz. In most cases advantages over separate video and frequencies. For intercarrier, some 4.5- that alone will cure the trouble. sound i.f.'s. There is a saving in the mc signal should go through the peak- The primary and secondary tuning total number of tubes in the set, free- ing coils and be taken out of the picture adjustments on the ratio detector can dom from drift problems, and ease of by a trap which feeds the 4.5 -mc am- be recognized by their effects. Tuning tuning. But their use brings up one big plifier and ratio detector. A good ratio through the primary will gradually in- problem: a 60 -cycle buzz in the sound detector will go far toward cutting crease and then decrease the sound out- due to sync and picture modulation. down the buzz. put without too much distortion off Good design in the set and good service The 4.5 -mc beat must pass through tune. Tuning through the secondary in the field when necessary will elimi- the front end, i.f.'s, and video contin- from off tune will increase distorted nate this buzz. uously. If any tube, such as the last i.f. sound to a maximum, clear the sound Fig. 1 is a block diagram of a re- stage or the video amplifier, cuts off on and reduce noise to a minimum, distort ceiver using the intercarrier system, peaks of sync signals or picture whites, and increase noise, and then drop off sound and picture carriers being ex- the beat note will be cut off at the same the distorted sound volume. Align the actly 4.5 me apart on all channels. If time. This will cause a buzz in the sound takeoff coil or transformer and sound and picture carriers are both sound that cannot be removed by any the ratio detector primary for maxi- passed through the i.f. strip, a 4.5 means except changing the bias or mum on a weak signal and the ratio me beat note appears in the video de- other voltages or the signal strength detector secondary for maximum un- tector. This beat note is frequency - to correct the stage that is cutting off. distorted quiet sound. If the set is modulated like the sound carrier and This should not be necessary in a well badly off alignment, a signal generator This should be amplitude -modulated like the picture; designed set unless some component is will have to be used. the amount of each modulation and the defective or changed in value. fed into the video amplifier grid. Care- strength of the 4.5 -mc beat note de- Sena pends on the strength of each carrier VIDEO AMPL. at the detector. Picture carriers are modulated downward as much as 95% 4s C AMPL. AUDIO AMPL. 41 AUDIO OUT. for the brightest whites in the picture. of only 5% of the So you can be sure Fig. 1 -Block diagram shows how intercarrier works and why it is economical. picture carrier being there all the time. The sound carrier in the i.f. stages Other ways to minimize the buzz are fully retouch the ratio detector sec- should be way down on the slope of the by making the 4.5-mc amplifier a lim- ondary on a strong signal for minimum over -all response curve, no more than iter, by using a good ratio detector, and buzz and distortion, and then touch up 1/20 (5%) of the flat -top maximum, to by keeping the sync circuits physically the primary and the sound takeoff coil. beat note as free from picture and electrically away from the inter - If the buzz persists, front end and keep the aim here is modulation as possible (see Fig. 2). It carrier i.f. and audio stages. Decoupling i.f.'s should be tried. The to sound on the right should not be too much less than this so the sync- circuit B -plus supply helps. get the carrier will be enough 4.5 -mc signal In servicing an intercarrier televi- portion'of the over -all bandpass curve. that there fine tuning control in the mid- to give adequate sound volume. The sion set to eliminate buzz, touch up the Set the traps, and alignment ratio detector first. The primary should dle of its range. Adjust the oscillator front end, i.f.'s, sound in the should be designed with be tuned for maximum sound volume on a station, tuning until frequencies the picture. The mind. and the secondary for minimum buzz, picture wipes out this in sound will be loud and clear. Back off The 4.5 -mc beat note is normally which will also be close to maximum the video amplifier. sound volume. Those adjustments on the oscillator adjustment until the trapped out after picture is clear and sharp without In well -designed receivers the video should be made on a weak signal first RADIO -ELECTRONICS for Television News 129 sound or 4.5 -mc interference. The in- simpler correction is to reduce the cause a 15,750- c.p.s. note. Practically terference in the picture looks like gain of the i.f. strip below overload by all commercial television receivers have about 300 fine vertical lines, causing increasing the cathode -bias resistor in a narrower audio response than that, the picture to appear out of focus. Tune an i.f. stage that does not have a.g.c. and the high- frequency noise and note the oscillator back and forth slightly applied, usually the last i.f. stage. This are cut out in the audio stages. This from this point for minimum buzz. If resistor can be increased to several can't be done for the 60 -cycle buzz. The the adjustment for minimum buzz is times its normal value as long as the 60 cycles can't be eliminated merely by tube is not biased close to cutoff. keeping the low- frequency cutoff of the Another cause for buzz is electrical audio system above 60 cycles. The buzz coupling through the power supply. in the sound is due to a sharp pulse Usually not encountered in well de- with many strong higher harmonics. signed receivers, this is not peculiar to Raising the low- frequency cutoff of the intercarrier sound but might be present amplifier above 60 cycles would dimin- in any television receiver. To test for ish the fundamental but would still this, connect an oscilloscope to the permit the higher harmonics to come 1 kr ems WIDTH -4 SOUND I I Pi% B- supply of the audio and 4.5 -mc through. CARRIER 14- 4.5 MC -I CARPER stages. Examine the waveform for ver- This article has covered a large num- tical sync pulses or vertical sweep. If ber of causes and cures for intercarrier response. Fig. 2- Desired receiver i.f. more than 1 volt peak -to-peak of these buzz. Don't be overwhelmed. In a nor- receiver, gives a waveforms is present, decouple the sup- mal, well -designed touching not at or near the point that ply of the sync vertical up the alignment of ratio detector picture, i.f.'s and end amplifier, the the clear the front blocking oscillator, or the vertical out- or oscillator and checking tubes and will have to be realigned. r.f. put tube, depending upon the waveform components will be all the servicing nec- For realignment, connect an in supply. essary in the vast majority of cases. sweep generator to the antenna ter- found the power When this is too difficult, the decoupling be The of the information may be and a 'scope to the video detector could rest minals applied to the 4.5 -mc stages and the found useful for a more general under- output. Set the output of the sweep about the same a.g.c. audio. It is best to decouple the source, standing and in occasional difficult generator to give however. servicing jobs. Remember, there voltage or d.c. voltage at the video de- in as the average station would in We've been talking only about elimi- shouldn't be any annoying buzz an tector of 60 -cycle buzz. The same fac- set; for it have This is important, nation intercarrier all causes the particular area. covered in this will also cures. because in many sets the bandwidth tors article their changes with a.g.c. Getting the right curve with a standard value of fixed or a.g.c. bias might not mean much as far as actual operating conditions are ANNUAL TELEVISION NUMBER i.f.'s and front concerned. Align the next month end to get the desired curve and band- to be published by RADIO -ELECTRONICS -will carry sheets articles on all phases of the fast -moving industry. This special 146 - width, as described in instruction receivers, tele- In 2.5 -mc band- page issue will feature complete directories of television on the set. general, -3 vision of identifica- width half way down the curve is aver- antennas, lists of TV stations and illustrations their tion signals, stories on intercarrier, color, receivers, remote viewers, for 7 -inch television receivers and age improving old receivers, and many others. Don't miss this big 146 -page 3 3.8 me for 10 -inch receivers. to issue! Reserve a copy at your dealer today. Don't try to obtain full 4 -mc bandwidth on a receiver unless there is a trap to attenuate the sound carrier. Otherwise it will not be possible to get the sound carrier far enough down on Reports on Television DX the curve. After alignment, check the sound and picture carriers. When the Long distance (several- hundred -mile) tady, N. Y.; and WPTZ, Philadelphia, picture carrier is set half way up one reception of television signals is very Pa. -and there are more. side of the bandpass curve, the sound undesirable from the standpoint of the William A. Riaski of Guthrie Cen- carrier should be far down the slope FCC allocation engineers, since it ter, Iowa, experimented with a number of the other side, less than 1/20 of the means that interference from a dis- of antennas atop a 60 -foot pole and flat top height. After the i.f.'s and r.f. tant station may suddenly wash out a found that the circular loop described have been aligned and checked on all local one. When the dx does not create by Noll and Mandl in the June, 1949, used channels, the oscillator should be interference, it, like any other freak issue of RADIO-ELECTRONICS (page 26) adjusted, as mentioned above, on the phenomenon, is of great interest to gave the best results of them all. His air. some television fans. Many set owners farthest dx was Los Angeles. He gets In strong- signal areas the buzz may -especially in areas where there is good results about five nights out of persist because of overload. Check the little local reception -spend a good seven with Omaha, Nebr., stations, components and voltages in the last deal of time seeking out TV dx. For about 85 miles away, which are the i.f. stage and the video amplifier. Then the benefit of dx'ers. we ran in the nearest ones to him. Mr. Riaski's report attenuate the signal by using a pad in November issue a list of U. S. tele- on the loop should be of interest to the antenna, reducing it to give less vision stations as well as a call for others looking around for an antenna than a good picture at full contrast. If reports. that will really pull in a picture from this clears up the buzz, it indicates The November issue is not yet off the a distance. overload. This can be corrected by pad- press as this is written, but even the A. B. Cooper of Rochester, Minn., ding the antenna, if the net picture few letters on hand show what can be reports receiving KOB, Albuquerque, signal strength is adequate. Or else the done. J. R. Pewitt of Nashville, Tenn., N. M. His receiver was an Emerson a.g.c. voltage could be increased by infor instance, reports reception from 611 and the antenna a Ward TVS -6 creasing the value of the a.g.c. bleeder several distant stations, the farthest low -band, stacked array. resistor if one is used. of which was WBZ -TV, Boston, Mass., We hope to receive many letters from The cathode -bias resistor in the vi- 950 airline miles away. He used a dx'ers all over the country and to re- deo amplifier can be adjusted up and Garod model 900 receiver and a Radi- port on them in the January issue. down, depending upon whether the art stacked -dipole antenna. Other sta- When you write, don't forget to give us overload is driving this stage to cutoff tions Mr. Pewitt has received include all the information on receiver, anten- or toward saturation. The determina- WMAR -TV, Baltimore, Md.; WBEN- na, times, distances, channel numbers, tion of this point is more difficult. A TV, Buffalo, N. Y.; WRGB, Schenec- and so on. DECEMBER, 1949 Television News

Two -Week Course Teaches TV

By DAVE GNESSIN

IT is not unusual for a young man community. The dim rumors of only 20,000, where 450 volts used to be max about to enter the radio field to a few months before now become stark imum rating on the power supply. register at one of the many good reality. Showers of Sunday advertising Unfamiliar new terms, such as raster, radio service schools, buckle down herald the opening of a TV relay out- sync, sawtooth, sweep, scan, and re- to a regimen of study, and remain in let. The chain department store has storer, clog the tongue. Regular test residence at the school for several a hastily prepared window set up equipment becomes obsolete. Regular months -or even years if need be -to with the first TV receivers ever seen methods are inadequate Regular radio learn the trade properly. in town. Our small radio dealer studies information is now insufficient. On the other hand, a settled family his first TV schematic. Can the corner radio service dealer man no longer young in years, with What strange world of radio is this go back to school? 10 or 20 years of practical radio ser- new field? There are more tubes in the Armed with pencil and scratch pad, vicing behind him and a steady busi- smallest TV set than in the largest with lunch bag under his arm, the ness taking his full time, views with combo ever seen before. The C -R tube middle -aged radio man is going back to alarm the onset of television in his votages run from 2,000 to better than school. In the pictures on this page the students are all well over 30 years of age. All are married. All are experienced service technicians. Faced with the positive certainty of television in their community, they realized that the only way to handle the new field properly was to go to school and learn it. So these men took a "vacation" from their work bench and started to study. Different communities have different setups. This group in Columbus, Ohio, made a cooperative deal with the local Philco outlet, Bennett Distributors. The distributor furnished the factory instructor, school space, test equipment, and TV receivers for study, while the service technicians furnished their full time from 9 to 5 for two weeks. A fair deal? The distributor thinks so. So do the technicians. I v Class works on actual receivers. Author left. hand in pocket) check, lt.ic. Limited to 12 men to a class, the school has a long waiting list At this writing more than 50 radio men from Columbus and surrounding towns have completed the course -tuition -free. Can the average service technician learn TV in two weeks' full time? Ben- nett thinks so. The graduating students confide they never realized how basic the whole idea of TV is until it was slowly and carefully explained in class, followed up by (not laboratory, mind you -but) work -bench practice. High - voltage is respected, but no longer feared, for these men have now handled it. Sweep, scan. and raster are permanent additions to the radio man's working jargon, for he can now use the terms meaningfully, having adjusted and observed the action of each of these elements. Having touched, felt, and seen at first hand the TV chassis on the bench, the technician now rec. ognizes it well, and welcomes it. Gentlemen, this TV is good business. The distributor, it may be noted, has bought himself a fistful of good -will. He has invested in the ultimate salesman, the small radio shop owner. He has built up a crew of TV men who can now take care of their own. These TV confidence. Gnessin, himself a student, shows friend alig .nt method as instructor watches. men will push with RADIO -ELECTRONICS for Audi. Speaker Baffling Simplified

The best speaker needs good baffling to realize its full range and output efficiency

By A. G. SANDERS RCA Photograph High -fidelity, low -cost speakers, like the one held by Dr. H. F. Olson, are now available to the baffle builder to form complete units.

ASP is instrument by side (front or rear) do not immediately cycle into the distance in inches that means of whanwhichich the electrical reach the other side, but are retarded sound travels per second. (Velocity of signals picked up by the radio by having to travel around the baffle. sound in air at 68 degrees F. is about or phonograph are made un- It is possible to control the travel time 1,127 feet per second, or 13,524 inches.) derstandable to the human ear. It acts of sound from one side of the cone to The diameter of the speaker opening as an interpreter, converting pulsating the other by variation in the size of is then added to the sum, giving the audio -frequency currents into air vibra- baffle. over -all diameter of the baffle. tions, or sound waves. If the dimensions of the baffle are From the foregoing it can be seen Despite the importance attached to correct for reinforcement of any given that the speaker can be acoustically/ its operation, the speaker is not yet frequency, a sound wave from the front loaded at any given frequencies. Since anywhere near as efficient as other of the speaker will arrive at the rear we are chiefly concerned with low - radio components. While the cone or of the cone at the exact moment the frequency losses and the baffle is the diaphragm can be so designed that it next outward thrust begins. The mov- only means of correcting them, the follows the changing audio currents, ing wave will then push against the acoustic load of the speaker should be more or less faithfully, it is incapable cone in the same direction as the voice at, or very near, the lowest frequency of forcing the relatively heavy mass coil is pulling, resulting in assistance to be reproduced. of air to do likewise. Consequently, the For reproduction of speech only, the resulting sound wave is more or less a low frequency may be 300 cycles per we compromise, or distortion, of the orig- second (350 cycles for limited speech), inal sound wave, the distortion varying making possible the use of a flat baffle in degree with the quality of the with an over -all diameter of 32 inches, speaker. as in Fig. 1. However, music extends .4 Losses occur at all frequencies of the the lower range downward to 100 cycles audio spectrum but are more pro- and less. If we are to change the acous- nounced in the upper and lower regions tic load of the speaker to 100 cycles per than in the middle. High- frequency second, the diameter of the baffle must losses can be minimized somewhat with be increased to '77 inches. The larger electrical networks and a properly de- size is impractical; therefore, we must signed speaker. Low- frequency losses look around for designs that will re- can be compensated only by using that place flat baffles. auxiliary structure known as a loud- Since sound waves from either side speaker baffle. of the speaker tend to cancel each other, When a speaker is operated in the it would appear that a simple solution open and unattached to a baffle of any of the problem would be to enclose kind, sound waves generated at the tightly the rear of the speaker in a front and rear of the cone cancel each sound -proofed cabinet. Theoretically other because they are out of phase; 32" FRONT VIEW this is an infinite baffle. that is, their direction of travel is op- Actual tests have shown, however, posite and each one is bucking the Fig. I -Flat baffle is simplest. Round types that the behavior of the speaker does other, or rather, the pressure wave at are not os common as the rectangular ones. not conform to the theory of infinite the front flows around and cancels the baffles under these conditions and op- rarefaction wave at the rear of the to the voice coil instead of resistance to eration becomes erratic and highly va- cone. With the speaker bolted to a cir- its action. The two forces are working riable. The reason is that the air within cular board, or flat baffle, with an open- together in series, or in phase. the closed compartment is not free. ing in the center for radiation of sound The diameter of flat baffles is calcu- Each movement of the cone raises or waves, those waves generated at either lated by dividing the time of one -half (Continued on page 32 ». DECEMBER, 1949 32 Aodiu Audio Squelch Circuits

By JOHN L. GERGEN

IN installations where a receiver must unscheduled broadcasts. However, de- in Fig. 2. Only two additional tubes are remain on for long periods of time signers of high -quality receiving equip- required, the most convenient arrange- even though no signal is present at ment can use the squelch circuit to good ment being to use a dual- triode. The the antenna, noise and background advantage to silence between -station 6SL7 -GT was chosen because it has a hiss (present in any receiver no mat- noises while tuning. A squelch circuit sharp change in plate current for a ter how well designed) are amplified would be impractical for this purpose change in grid voltage of from 2 to 4 through the i.f. and audio stages and in a communications receiver when lis- when the plate voltage is 250. cause annoying noises at the loud- tening to signals which fluctuate rap- speaker. A squelch circuit is a control idly at random due to atmospheric How the squelch works arrangement, usually operating from conditions, but it offers improved per- The circuit of the squelch is very the a.v.c. voltage, that silences the re- formance for FM and broadcast much like that of a direct -coupled am- ceiver when no usable signal is being reception. plifier: a voltage divider is placed received. The diode detector VI of a conven- across the power supply, and the two tional AM receiver, such as that in stages -plates, cathodes, and grids- Fig. 1, furnishes two output voltages. are placed at various points along it. An a.f. signal, from which r.f. has been Fig. 2 is drawn so as to show clearly removed by Cl, appears across Rl. This the voltage- divider effect provided by is applied through C2, which blocks the the three resistors R4, R5, and R9 d.c. component, to the volume control across the power supply. (not shown), the arm of which is con- The voltage appearing across R9 is nected to the grid of the first audio applied as plate voltage to V2 -b, an amplifier. The rectified d.c., filtered by ordinary cathode- follower amplifier. R2 and C3, is negative with respect to The a.f. signal from the detector is ground. It is brought back to one or applied between grid and ground. Out- more r.f. and i.f. stages as a.v.c. put is taken from across the cathode Since the a.v.c. voltage is the result resistor. ÎC 3 of rectifying the r.f. signal, its magni- The bias on V2 -b, however, is con- tude depends solely on the signal trolled by V2 -a, which, in turn, is con- Fig. I -The sources of a.f. and a.v.c. strength, not at all upon the modu- trolled by the a.v.c. voltage. Squelch circuits are used frequently lation. When no signal is being received, in military and police receivers; such The a.v.c. voltage may also be used there is no a.v.c. voltage; therefore equipment must remain on to receive to control a squelch circuit, as shown there is no voltage between grid and

SPEAKER BAFFLING SIMPLIFIED (Continued from page 31)

lowers the pressure of air within the comes greater, until a point of minimum cabinet, which in turn stiffens the cone. efficiency is reached along the plane of The more rigid cone is unable to follow the cone. the pulsating current in the voice coil with any degree of accuracy, especially on transients and at the higher audio c.'. frequencies. Many designs have been created in `.:. the attempt to find suitable means of 20.1/2"1066 and not have ex- OPENING baffling the speaker TO cessive bulk or size. One of these is the ROOM Jensen Bass -Reflex speaker housing shown in Fig. 2. This is essentially a sound chamber of several cubic feet, having a second radiation vent near the speaker opening. A limited amount of TOP VIEW 1 OPEN I sound insulation used on the inside walls absorbs high frequencies, but has little effect on low frequencies. This type shows a marked improvement over r Courtesy Jenne. Mfg. Co. the average baffle, particularly radio a6 Fig. 2 -A Typical bass -reflex speaker. cabinets. Another type recently introduced is $pkr. Vol- Port wall Lt. dom. ume area A B C D E F a corner baffle utilizing adjacent tin.) 1in.) lins) surfaces as part of the sound channel. channel GRILL 10" GRILL ,...ILL 18 12,600 87 1534 1434 26 33 15iá 553 Fig. 3 shows how the sound within the cabinet is "folded" as in a 1313 4",, 15 9,080 85 13 rí 12 23'4 3174 re- horn, eliminating much of entrant i 6 30" 6. 12 6,990 60 10 3g II 22 28?é 10Fí 53, the objectional size. Location of the "tt- effi- 10 5,440 37 8 7e 1013 19'4 2644 81, 414 cabinet is also an advantage. The ciency of the speaker is maximum di- LOOR FRONT VIEW 8 3,210 25 6s? 91316 224, 614, 34 rectly in front, or along the axis, de- Fig. 3-Co-nor-type speakers like this 6 2.100 19 51, 7S 14 19% 51,4 31,, creasing as the angle of distribution be- one are becorn:ng increasingly popular. RADIO -ELECTRONICS for Audio I33 cathode of V2 -a, except a small bias condition necessary for operation of audio is heard. Tuning off the station furnished by R4. The grid is connected the d.c. circuits just described. should silence the speaker. When any to the negative end of the power sup- other station is tuned in correctly, it ply (through R3, in which there is no Construction should be heard; but, when tuning be- noise, hiss, inter- current flow and therefore no voltage The squelch circuit can be installed tween stations, all drop), while the cathode is connected in any receiver which has a.v.c.; the ference, and so on should be inaudible. diagrams show the to the top of R4, which is a more posi- detector need not be a diode. The 6SL7 - Though the an AM re- tive point on the voltage divider. The GT and its resistors and capacitors can squelch circuit used with grid is slightly negative for that rea- chassis. ceiver, it can be especially valuable usually be installed right on the silence son, but plate current flows. Connections made to the receiver's with an FM set, particularly to are on The plate current of V2 -a flows B- supply, filament supply, and to the the loud hiss heard between stations through its plate -load resistor R6, detector's audio and a.v.c. outputs. sets which use limiter- discriminator which has a high resistance. The cur- The only change necessary in combinations. All that is necessary actual which is rent flows through R6 from plate to the receiver circuit is to disconnect the is a negative d.c. voltage supply, which means that the plate end audio output of the detector from the present when there is a signal and is negative with respect to the other top of the volume control and lead it absent when there is none. The grid end. The negative (plate) end of R6 to the of V2 -b. The a.f. voltage of the limiter satisfies this re- instead grid to the is connected (through R7, in which output from the cathode end of R8 is quirement and may be connected there is no voltage drop) to the grid top of R3 to control the squelch. With then connected to the top of the vol- not of V2 -b, and the positive end (through ume control. Because V2 -b is a cathode other types of detectors which do R8, in which there is no drop when follower, it has no gain and the output need limiters there is generally a way V2 -b is not conducting) to the cathode receiver will be about the of obtaining a d.c. voltage. Sets which volume of the no of V2 -b. same as before. It may be slightly less have a.v.c. will, of course, present When V2 -a is conducting (when because the cathode- follower gain may problem, as R3 is simply connected to there is no a.v.c.), V2 -b is biased by be slightly less than 1, but there is not the a.v.c. line. the voltage drop across V2 -a. This is enough loss to cause trouble. sufficient to cut V2 -b off completely. Only one adjustment is needed. The MATERIALS FOR SQUELCH 10,000, IS,000, 100,000 Therefore, it cannot amplify the audio magnitude of the a.v.c. voltage devel- Resisten: I -200, I- I- I- 100,000 ohms, 1 ohms, 1 -2.2 megohms, Vs wat; I- signal impressed on its grid by the de- in receiver depends on the oped the watt; 1 -500,000 -ohm potentiometer. tector, and the loudspeaker is silent. proximity and power of the stations When a signal appears, it creates a listened to. The weakest of these should Capaciten: I -.01, 2-0.1 pt, 600 volts, poper.

+250 2 be tuned in and R3 adjusted until V2 -a V2. MIscelleeeees: I- 6SL7 -GT; I -octal tube socket; just cuts off -that is, until normal necessary hardware. R9 IOOA eíe ' I AF FROM OEhVII

New Electronic Music Vibrato Circuit

A novel electronic musical instrument one triode of the 6SL7, which is con- recent issue of Elec- nected as a phase -shift oscillator whose AVC VOLTAGE FROM was described in a 12 220,000 - CET (VI) tronics. The instrument consists of frequency is controlled by the tone -generator channels and an audio ohm resistors and the .05 -uf capacitors. 5OON amplifier. A switch frame is fastened The other section of the 6SL7 is a buffer 65LT across the keyboard of a standard piano amplifier. is elec- 7I I6 so its keys close appropriate circuits in One section of the 12AX7 an the electronic -organ tone generators tron- coupled oscillator whose frequency and both instruments are played at is controlled by the values of the iron - Fig. 2 -Where squelch tube is inserted. once. cored inductor L and the capacitor C Each tone -generator channel consists shunting it. The signal from the buffer certain amount of negative a.v.c. volt- of an electron- coupled sawtooth oscil- amplifier is applied to the grid of the age, which appears across R3. Enough lator and a series of four cascade fre- remaining triode of the 12AX7. The of this is tapped off R3, by the setting quency- halving multivibrators. Each of strength of the vibrato signal is con- of the movable arm, to cut off V2 -a. the oscillators can be frequency -modu- trolled by varying the 27,000 -ohm re- Since there is now no V2 -a plate cur- lated to produce a vibrato effect. Fre- sistor. The value of this resistor is rent passing through R6, there is no quency modulation is produced by ap- altered by switching in parallel resis- voltage across it and the cutoff bias plying a 6 -cycle signal to the grid of tors in the original circuit. it had applied to V2 -b is removed. Be- a reactance tube across the oscillator The signal from the buffer -amplifier cause the only resistors between the of each of the tone- generating channels. could be applied to the suppressor grid grid of V2 -b and the bottom of its cathode resistor are now carrying no 6SL7 I2Ax7 current, these two points are at the 5 +2650 same potential. The only d.c. voltage appearing between the grid and cathode TO FRED Di0CE0S of V2 -b is that caused by the usual voltage drop across the cathode resistor R8, which gives the correct bias for normal operation. The a.f. plate current of V2 -b causes a.f. voltage variations across R8. The a.f. voltage is fed out to the following V' audio stage through C6, which blocks i the d.c. component of the cathode volt- 6 CYCLE OSC t AMYL TONE 05C L REACTANCE TUBE age. The lower end of R8 is bypassed to ground for a.f. by C5, so that the The low- frequency oscillator and a of a voltage amplifier in an audio am- audio output is effectively 10,000 ohms single tone -generating oscillator and re- plifier used with electric guitars and above ground, while the entire tube is actance tube are shown in the diagram. similar instruments to produce a vibrato actually far above ground for d.c., a The vibrato signal is generated in or tremolo effect. DECEMBER. 1949 Theory and Engineering 341

Electroii Shadows Map Force Fields i

New technique makes magnetic and electrostatic fields risible to the eye Fig. 1- tintouehed beans throws mesh pattern on photo plate. Fig. 2- Magnetized wire in path of beam distorts grid line..

NEXT time you see a light shining Between the crossover and the photoelectric and magnetic fields of very against a wall and decide to im- graphic plate or fluorescent screen is a small size, its special value being that prove the opportunity by mak- mesh of fine wires, so that the plate field strength at any point can be ing hand shadows resembling shows an enlarged gridiron pattern. measured. Many of these fields could ducks and rabbits, you may feel a little The field to be analyzed is placed be- never before be evaluated because a kinship to serious -minded scientists of tween the point electron source and the probe any larger than an electron dis- the National Bureau of Standards. magnetic lens..Fig. 2 illustrates what turbs the field. Investigation of the These men are using shadow pictures happens when a piece of recording wire too, though for a purpose far removed which has been magnetized by a series from innocent enjoyment. Their shadow - of evenly spaced short pulses is exam- casting rays are not light, but electron ined. The magnetic field around the streams projected on a fluorescent wire distorts the rays from the source screen or photographic plate. And the before they reach the lens, the amount shadows, cast by electric and magnetic of distortion at any point depending fields in a technique developed by the on the intensity of the magnetic Aeld at Bureau's Dr. L. L. Marton, are yielding that point. important information on hitherto in- Because electron rays have been dis- visible phenomena. placed, the focus at the crossover is Figs. 1 and 2 show how one typical disturbed. It becomes larger, and the experiment was conducted. In Fig. 1 a virtual source of electrons which it stream of electrons emitted at the left forms is no longer simple. When the is focused by a magnetic lens, much as diverging beam reaches the wire mesh a glass lens would focus light. The and casts its shadow on the screen, the beam then converges at the focal point: even pattern of the mesh no longer ap- r the electrons deflected downward by the pears. The disturbed rays of the source lens continue to travel downward and make curves and aberrations in the those deflected upward continue up- gridiron, vary of focus, the sharpness Fig. Pattern of a horseshoe magnet. ward. The focus at this "crossover" and make strange -looking whorls. 4- point is very sharp. Thus the crossover An enlarged photograph of the fundamental nature of ferromagnetism, is a virtual electron source. screen of Fig. 2 is shown in Fig. 3. for instance, is now under way at the Another picture, the pattern distorted Bureau of Standards. Space - charge this time by an ordinary horseshoe fields, fields produced by contact poten- magnet (you can see the magnet's tials, charge distribution in gaseous shadow), is Fig. 4. With the aid of plasma, waveguide problems-all these complex mathematical formulas, re- and more will yield their secrets to the t lets" searchers can measure and evaluate probing electron ray. f v!arlw.ÑG?1 the distortion of the mesh pattern and One of the important fields the tech- \//i\M/.i determine exactly the strength and na- nique may be applied to is waveguides. ture of the magnetic field set up. Even Often the shapes of waveguides are too fff1Nf/:Ái%i//a3i without a scientific background, how- complex to allow mathematical analysis J ever, it is easy to see the bulges above and the engineer depends on experi- ...... Nf..Nj/,//Offlf/fl - _nail - and below the shadow of the wire in ment. By measuring the fields in wave Fig. 3, indicating the alternating mag- guides of various sizes and shapes with (affafaff 111J netic field induced by the recorded electron shadows, it may be possible iiiifff.A/ rue pulses. to set up formulas to predict perform- i:f/.J/t./. and eliminate much rf The electronic "shadowgraph" is ex- ance accurately Fig. 3- Pattern of he magnetized wire. pected to allow exploration of complex guess work. RADIO -ELECTRONICS for Theory and Engineering

Leal- Pencil Mark Sets Off Relay

7'11yrutron and two delay relays maize simple responder

By VICTOR H. LAUGHTER

THE pencil -mark responder is a device that operates a relay when a pair of contacts passes over a pencil mark. Because the resistance of pencil marks is not only high but very variable, the current through the marks is neither great nor constant enough to operate a relay directly; and if the pencil marks travel under the contacts at any but the very slowest speed, the contact does not last long enough to operate a relay even through Responder chassis. The large filament transformer is not necessary. a vacuum tube. was used The model described here nism blank out until the next item was remote it may in which holes control circuit, whatever with a traveling tape reached. Other possible be. record store pur- applications in- Its s.p.s.t. contacts close, sending had been punched to clude computing devices and B- name of each item pur- grading current through RY2. chases. The machines for school examination pa- RY2, however, is a slow -make relay. chased was printed on the tape and the pers. In either case, combinations -of (The - worked in conjunction model used a surplus Clare time following holes contacts on to indi- connected to separate relays delay type with a copper slug the with mechano -electric selectors would be needed. end the de- up prices. When a pur- armature of coil.) Closing cate and add The diagram and photographs show lay for RY2 may be which holes had been punched adjusted up to chase for the basic unit. The U- shaped contacts about 0.1 second. had to be canceled, a line was drawn were quickly made name. When the for experiment but When RY2 closes, the current supply through the printed should be much improved for continu- to it, to RY1, and to the 2050 passed over the pencil mark, plate is contacts ous duty. The 2050 is a thyratron. interrupted. RY2 immediately responder relay opened long enough opens the The potentiometer R1 across bias but by this time the tube has deionized, to make the price -calculating mecha- the battery is normally set so that the gas the negative grid has resumed control, REMOTE CONTROL ORCUITS in the 2050 does not ionize and the tube and the tube is again at cutoff. /1w is cut off. Plate voltage is supplied to RY1 is a slow -release relay (another 220K the R4 tube through the coil of RY1 and surplus Clare unit). After a time ad- SLOW MARE R5. Positive voltage is also supplied to justable up to about 0.4 second its con- the contacts through R9, an isolating tacts release. The control circuit is re- CONTACTS resistor. turned to its original condition, and When the contacts hit the pencil the circuit is ready for another con- 22.5V RO I mark, positive voltage is applied 5DK R tact. R5 through R4, the pencil mark, and R3 The speeds to which the relays should 500 (another isolating resistor) to the 2050 be adjusted depend on the maximum IOW grid. Because the resistance of R2 and speed at which pencil marks are ex- SLOW RELEASE Rl is fairly high (330,000 24VDC /Inn ohms mini- pected to hit the contacts. The com- .005 mum, actually much more because the bined relay delay times should be 1600V potentiometer arm is some distance slightly less than the time between 2050 from the positive battery terminal), marks. very little current is drawn from the Contacts have been placed as far plate supply through the contact net- apart as 4 inches with stable operation, work. The positive voltage, even when but probably the ideal distance is there is K /i0W SEL RECT considerable resistance in the around tiffs inch. The selenium- rectifier pencil mark, is high enough to raise the supply shown in the diagram was grid above the triggering point. The selected for simplicity, and is thor- SRST SW gas then ionizes, and the tube conducts. oughly satisfactory. The contacts shown As soon as the tube conducts, or fires, are a pair of bent wires lashed to a 117 VAC plate current is maximum and the grid piece of polystyrene with Scotch tape. loses control. RY1, in series with the Adjustment of the unit merely requires plate and the B- supply, closes imme- setting Rl at a point just negative Schematic of the pencil -mark responder. diately. Its s.p.d.t. contacts actuate the enough to keep the tube from firing. DECEMBER, 1949 Theory 111111 I:ulliueeriu9 MICROWAVESi

Part -// /- /t('rt'irini/ and Iranxmi//ina, an/ +rnnax for aiiirmraro' communication

By C. W. PALMER

OUR study of microwave com- and reflector. These are stacked arrays. ponents cannot be called cottt- The increased efficiency of narrow - plete until the subject of beam transmission permits the use of antennas, both for transmit- very low -power transmitters, because ting and receiving, has been thoroughly the power is concentrated rather than explored. being spread over a large area. This is The usual considerations for antenna fortunate because it is difficult to gen-

pearance). Thin strips of metal are in- a dipole receiving antenna with either serted into slots cut into the foam in a a flat or bent plate or rod reflector is predetermined pattern. The lengths and probably the best. It is simple and fair- positions of the metal strips determine ly efficient. the sharpness and other characteristics of the beam. Antenna Matching The construction of the lens is shown For both receiving and transmitting in Fig. 5. it is necessary to match the impedance of a microwave antenna to the feed line End -Fire Antennas for efficient operation. Let us consider Microwaves follow a plastic rod just a typical antenna consisting of a dipole as light waves follow a lucite or fused - mounted in a parabolic dish reflector. quartz rod. This phenomenon has been The position of the antenna in the used to demonstrate the action of the dish is set for maximum gain and mini- waveguide many times, but has found mum side lobes. The side lobes are sec- little application in practical micro- ondary responses which are always wave work. present in this type of antenna and, if However, one radar device developed large enough, will destroy its direc- Itrll Lohorotorirx photo during the war and used commercially tional characteristics as well as reduce Fig. 5- Putting together a metal lens. for point -to -point microwave communi- its efficiency. Fig. 7 shows a typical cation is the end -fire antenna, which antenna field pattern for a highly di- put power, which in most cases is well under 100 watts. Using higher power is unnecessary because receiver gain - especially in the i.f. and a.f. sections- can be upped as needed, provided the signal at the receiving antenna exceeds the noise by a reasonable ratio. At- mosphéric noise is a very minor problem at microwaves. Microwave Lenses While the reflector plates and rods described above follow to some extent the principles of optics in focusing a radio beam (somewhat as do the reflectors used in auto headlights and in searchlights), an even more striking TAPERED POLYSTYRENE similarity was recently demonstrated RODS in by the Bell Telephone Laboratories Bell I.aborotoriem photo disclosing their new microwave lens. Fig. Ó---ln this wa end fire al ray. the rowaves follow plastic rods. Microwaves are focused in beams by being bent through sheets of insulating material and metal strips of the correct makes use of this ability of plastic ma- rectional beam with the main lobe and dimensions and shapes. Just as light terials to guide waves. the side lobes marked. waves can be bent in a glass lens to Fig. 6 shows a wartime version of the The antenna is matched to the feeder focus on a small spot, the microwaves end -fire antenna. It contains three rows with impedance -matching transformers were discussed earlier in this are bent in this easily controlled focus- of polystyrene rods, 42 in all, each of which ing device, which produces efficiencies which is fed by a waveguide from the series. For co -axial type feeds a quar- even higher than the reflectors and transmitter. ter -wave transformer on the inner con- which is capable of handling a much Such an antenna displays a remark- ductor is ordinarily used. Waveguides greater bandwidth. able ability to beam microwave signals are matched by inserting a matching This is not to be confused with the and is easily controlled by correctly "window" at the proper place. A prop- earlier Bell electromagnetic lens, pic- dimensioning the plastic rods. The erly matched antenna feeder should tures of which have been published in number of rods, their length, and spac- have a standing -wave ratio of less than this magazine and in many Bell adver- ing depend on the width of the beam 1.2 after final adjustments. tisements, especially around 1946. That required and the power to be trans- lens worked on a waveguide principle mitted. These antennas have gains up and its frequency range was limited. to 17 db. The new lens might be called a true optical type, and the strips (or beads Receiving Antennas ANTENNA SIDE LOBES MAIN BEAM in some models) of metal in the lens The subject of receiving antennas Fig. 7 -Ideal result is a narrow betun. look to the radio wave much the same can be covered very quickly: in most as the molecules of glass in a standard microwave installations the transmitter It is desirable to keep the r.f. feeder optical lens look to the much shorter antenna is also the receiving antenna. as short as possible to avoid losses. In waves of light. Thus all the factors mentioned above many microwave installations, notably Fig. 3 shows four of these lens an- except power -handling ability apply radar systems, the r.f. generator or tennas installed at a television relay also to receiving. transmitter is located very close to the station. At the base of the horn -shaped When separate receiving antennas antenna, with cables carrying d.c. shield is the waveguide feed which sup- are used, they usually take the form power and modulation (voice, keying, plies the r.f. power. The shield allows of a dipole backed up by some form of or pulses) to the r.f. tubes. While this the waves to spread out over the entire reflector. Where extremely sharp beam- may seem troublesome to the amateur surface of the lens which then focuses ing is needed, the parabolic reflector or experimenter, the results pay many them into the narrow beam (vertically "dish" is generally employed while in times over for the increased construc- polarized) needed for the transmission the case of extremely wide -band work, tion difficulties. Care taken in building path. such as television link receivers, the the r.f. generator will keep it small As shown in Fig. 4, the lens consists lens -used with either a waveguide or and light enough to mount right on the of slabs or sheets of polystyrene foam a dipole -is preferable. antenna mast or in a container at its (somewhat like sponge rubber in ap- For the amateur radio experimenter, base. DECEMBER. 1949 :18 Construction Receiver Fits Shirt Pocket

Subminiature tubes in a standard regenerator

By THOMAS J. JUDGE

Whole receiver is no taller than a standard fountain pen.

THE set described here was built tector tube. The other winding is in A certain amount of time should be around three subminiature tubes, series with the loop antenna. This ar- spent learning how to bend and cement using an orthodox circuit consist- rangement provides very good gain and plastics, which, with a little practice, ing of a regenerative detector fol- at the same time reduces to a minimum are very easy to work with. lowed by two stages of audio amplifica- the effects of detuning caused by body The complete circuit is tion. shown in the Permeability tuning, used with a capacitance. drawing. The photographs reveal how built -in loop antenna, covers the entire The smallness of the receiver can be most of the connections are broadcast made. The range from 550 to 1,500 kc. A readily seen in the photograph of the loop consists of 14 turns of No. 34 small 221 -volt B- battery and two assembled set and a standard fountain enameled wire wound on the ?4s x %- standard penlight cells (used in paral- pen. The other photos show the chassis, inch strip cemented around the outer lel) provide the power supply. All parts both front and back views, when re- edge of the chassis. The regeneration are mounted on a Ms -inch phenolic plate moved from the case. Note that the transformer consists of a drilled and and enclosed in a case of Ms -inch black bottom portion of the case is cemented tapped powered -iron core % inch in di- Plexiglas. A slide- rule -type dial is to the chassis. ameter and ')is inch long. A single layer mounted on the top end of the chassis. Construction of a really small re- of Scotch tape was first wrapped around adjacent to the three control knobs. ceiver such as this presents a number the core, and the plate winding, 60 The over -all size of the unit is only % of problems not usually encountered. turns of No. 40 enameled wire, was x 2% x 5% inches. Because of the small working space then wound. Coil dope was painted on, To keep the size of the unit to a each part must be added with great and, after it dried, grid winding, of 25 minimum and also to provide a simple care. turns of the same size wire, was added. and neat -looking job, no wiring was Anyone interested in building such a All leads were left fairly long until used to make connections. Instead, all receiver should first acquaint himself after assembly to the chassis and until connections were cut from a piece of with each component to be used. With after all the necessary operating tests .012 phosphor bronze, after which each patience and care, a scale drawing were made. piece was tin -plated. Small silver- should then be made showing the exact The permeability tuner consists of a plated eyelets and small turret -type location of each component. This draw- phenolic tube of 1k inch outer diameter lugs were used to fasten the various ing can be used as a guide in forming and 111'16 inches long. Small pieces of pieces to the chassis and also to pro- and drilling the chassis and case. Plexiglas 1 %6 inch thick and y inch vide means of anchoring the- resistors 2E41 2E31 .001 2E35 .03 and capacitors. Subminiature sockets were cemented to the chassis to provide a ready means of replacing the tubes. In addition, fixed clips are provided for the batteries, simplifying replacement. All components are so arranged that replacement can be made with the utmost ease. The circuit used in this set is quite orthodox with the exception of the method employed for regeneration. Re- O PLAIN EYELET ferring to the circuit diagram, note TURRET TYPE LUG that one winding of the feedback coil SOLDERING TERMINALS ON VC UNIT is in series with the plate of the de- Circuit is almost standard regenerative set. Tubes are Raytheon submimatures. RADIO- ELECTRONICS for Construction --I 39 square were drilled and cemented to both ends of the tubing for mounting. The space between the two end pieces was covered with a single layer of No. 43 enameled wire. A powdered -iron slug 1% inches long and I;ia inch in diameter provided with wire hooks on both ends completed the unit. For good efficiency the slug must fit snugly within the tubing. Start with an oversized slug and carefully turn it dowr until a snug tit is provided. Small grooves Vol inch wide, % inch long, and 1, :12 inch deep are cut in the chassis, after which the ends of the tuning unit are placed and cemented to the chassis. The driving element of the tuner consists of standard dial cord, tension spring, a small piece of black Plexiglas, and a drive pulley. Turret -type lugs are used to guide as well as to retain in phis side of eha.sis show. now 111e tube 'pus.' are bent ance pushed in sockets. place the dial cord. The pointer is made from black Plexiglas cut in a U shape. The upper side of the piece acts as the pointer, while the lower half connects to the dial cord. The drive pulley was turned down from a piece of 'Q x %- inch brass rod. It is % inch outside diameter and % inch wide, with a groove approximately %rt inch wide and 1.30 inch deep. The balance of the rod is turned down to % inch and the tuning knob is mounted on it. In mounting the drive pulley, a ! n inch piece of Plexi- glas was riveted to the chassis to provide sufficient bearing surfaces. This can readily be seen in the lower photograph at right. The tuning knob was made by using the outer part of a standard IRC mini- .if , c"" ature volume control with a piece of ' 'IHHlxlnn phenolic plate cemented on the inside. A hole approximately '/s inch in diameter was then drilled through the center. A small drilled and tapped hole provided a way of securing the knob Chassis is fat piece of phenol plate. Noie metal strips used for connection. to the tuning shaft. The trimmer capacitor was made ton; piece to provide a satisfactory fit- point of a pencil in the hole. pushing from a !1,; x '/4 x I:Yto -inch phenolic ting between the case and the bottom the spring away from the chassis and plate, two pieces of .012 phosphor piece. releasing the lock. bronze, and a thin piece of mica taken The upper portion of the case is also Ports from a small standard trimmer. After made from t -inch black Plexiglas. Af- list for Three -tubs Rodio various pieces, Resistors: 2 -S.I, 1 -2.2, 2-1 megohm; I- 150000. cutting and forming the ter cutting the necessary openings for 1- 68000, 1- 56.000 ohm, I/3-watt. 1- 500,000 -ohm a hole was drilled and tapped in the the three knobs, an opening % inch control, IRC type H.

Capacitors: 2 01, 1 1 chassis as well as in the additional wide and 1% inches long was provided -.03, 2- -.001, -.0005 t, 100 - volt. paper, heoring -aid type; 1-80 uut, 2 -.001 f, piece of phenolic plate. The pieces were for the tuning dial. A piece of clear ceramic. fastened to the chassis with small eye- Plexiglas 1jo x '/4 x 194 inches was used Miscell : 1 1R type SH fingertip switch, hearing- I- lets, a small brass screw providing for the face of the dial, with the num- oid -tvpa crystal phone; 1- Raytheon 2E31, 1 -2E35. 1 -2E41 subminiature tubes. 1- Eveready Noe means for tuning. hers 5, 7, 9, 13, and 15, properly spaced, 412. 22.5 -volt hearing -aid battery or equivalent. 2- The photographs show the method of type 915 or equivalent penlight cell, assorted eyelets engraved on it. This piece was cemented and turret -type lugs. completing the various connections with over the opening mentioned above. To the phosphor bronze strips. These con- provide sufficient space for the dial nections are cut and drilled in accor- pointer, it was necessary to remove a SLUG -TUNED PUSH -BUTTONS the scaled drawing. dance with They small portion from the underside of the A number of receivers use slug - should then be tin -plated to prevent top piece adjacent to the opening pro- tuned push -button tuning assemblies corrosion. vided for the tuning dial. After this, consisting of a number of coils, each Referring to the photos, you will note the top piece was cemented to the main tunable over a narrow sector of the that the bottom portion of the case, a body of the case. broadcast band. Frequently it is desir- piece of ' -inch black Plexiglas, is fas- The chassis slides into the case from able to increase the resonant frequency tened to the chassis. A groove !Sa inch the bottom and they are locked together of one or more of these coils. wide, ií0 inch deep, and 2% inches long with a small phosphor bronze spring To do this, cut a small brass slug was cut in this piece. The chassis is attached to the chassis. This spring from a volume control shaft or other made long enough so that its bottom engages a slot cut on the inside of the round stock and insert it into the coil end can be inserted in the groove and case. A small hole, large enough to ac- form. Locate the best position for the cemented in place. After the body of the commodate the point of a pencil, is slug, tape it for a snug fit, and cement case was and formed cemented together drilled through the case opposite the it in place. Use the powdered -iron core a section ?tig inch wide and %6 inch deep spring. To remove the chassis from the for precise tuning. was cut off the inner edges of the bot- case it is necessary only to insert the -B. F. LaDue DECEMBER, 1949 Amateur -gai to ge colte a frill and application st>

ow la° Ill W4AW40011 W. SHUART. + GEORGE By

don't know the exact facts. The Radio Amateur's License Manual (available from ARRL) contains many pages of fenses mean permanent loss of license typical questions and answers, and is and no more hamming! the ideal text for this examination. Amateur regulations may be found Some people say you don't have to in various amateur publications, but know much about radio to be a success- THE rno.st urgent problem once you the safest procedure is to get the in- have decided to be an amateur is ful amateur. These people (who usu- formation right from the horse's ally have lots of money) go to a store how to persuade the government mouth. That means putting 15 cents you operator and buy all their equipment, and then to give station and (in coin) in an envelope addressed to persuade licenses. The accepted method is to go another amateur to set it up the Superintendent of Documents, Gov- and show to the nearest Federal Communications them how to turn it on and ernment Printing Office, Washington off. When they get on the air, they find Commission field office on a day when 25, D. C., and asking for FCC Regula- amateur examinations are scheduled, that just about every other amateur tions, Part XII: Rules Governing the wants to talk about equipment and and prove your fitness to hold an ama- Amateur Radio Service. You will re- technical call by sending and receiving code matters. There is little room teur ceive a copy of the basic rules plus any in hamdom for those who 13 words per minute and by taking don't care to at recent amendments, which will bring learn at as much written examination. If you practice least about technical a you right up to date. matters as the average radio receiver code long enough, remembering the technician. hints given last month, you'll have lit- Technical questions tle trouble sending and receiving at that speed. The second and major portion of the Where to find the answers The written examination covers two written examination will tell the Com- Learning radio is not hard. If it isn't main subjects, the first of which is mission whether you know enough a pleasure, you have no business trying rules and regulations -when, how, and about the technical side of amateur ra- to get an amateur license. You can get on what frequencies amateurs may dio to operate a transmitter and re- all needed knowledge at the experi- transmit, technical standards, traffic ceiver without transgressing the regu- menter's workbench, and you can get rules, and the many other restrictions lations. To pass this section you must most of it from reading. The best way and procedures which govern all sta- know basic electricity and electronics, is a combination of the two -read about tions and ham stations in particular. and be familiar with antennas and it, then try it. Entirely aside from the immediate common transmitting, receiving, and One book every amateur and pros- problem of passing the examination, a amplifying circuits, as well as being pective ham should own is The Radio thorough knowledge of regulations will able to make simple calculations in- Amateur's Handbook, published yearly do as much for you as knowledge of volving nothing more complex than by the American Radio Relay League traffic regulations does for an automo- basic algebra. You must, of course, and available (like all League books) bile driver; it may prevent loss of your know the important radio formulas on either directly from ARRL in West license. which the calculations are based. Hartford, Conn., or from your local or A "pink ticket" in a ham's mail any The FCC's use of multiple- choice mail -order parts dealer. A basic text morning will probably spoil his whole questions (instead of writing down an on amateur radio, it contains instruc- day, for it. tells him he has been dis- answer, you indicate which of several tions for building every item of ama- obeying the rules. Usually, if the of- printed answers is correct) simplifies teur equipment. Another book, similar fense is not very serious, he is given the task to some extent. If you arrive to it, but different enough to give addi- several days to clear up the violation at an answer that differs from all of tional help, is the Radio Handbook, if it is a technical one. He must then those given, you know it is wrong and published by Editors & Engineers, Ltd., reply to the FCC's notice, detailing all can try again. In many cases, you can Santa Barbara, Calif. These two texts the steps he has taken to prevent fur- make an "educated guess" if you are are most helpful if you already have ther violation. Serious or repeated of- fairly familiar with the subject but some knowledge of radio in general. RADIO -ELECTRONICS for Amateur I41

For the real beginner, there are parts of it -or if you never took the well as in the license exam; it will many elementary books as well as subject, dig into a good elementary pay you well to brush up on your fig- magazine articles. John T. Frye's se- textbook. uring. ries, "Fundamentals of Radio Serv- A more complex formula, the basic When you consider yourself fairly icing," currently running in RADIO - one for resonance in a tuned circuit, is well along the road to the necessary ELECTRONICS, is excellent. The series 1 knowledge, get really interested in the started in the February, 1949, issue. f= -- ARRL License Manual. You will find Additional texts and references are 2vr V LC il: it questions similar to those on the given in the table below. The symbol f represents resonant fre- FCC examination. Each question is fol- Whether or not you do much reading, quency, L the inductance of the coil, C lowed by the correct answer. Go you will be unable to get the "feel" of the capacitance of the tuning capacitor, through the book covering the answer radio without doing some practical and r= 3.14. By the same algebraic to each question with a 3 x 5 -inch in- work. Any issue of this magazine will rearrangement process, we can find L dex card while you try to figure it out give you material to work with. Try building a simple receiver or a photo - tube relay or any one- or two -tube gadget. When you have made it work, USEFUL TEXTS AND REFERENCES try something a little more complicated. Each time you build something, Radio Physics Course Alfred A. Ghirardi try to find out why it works as it does. F un(talnentals of Radio Frederick E. Terman Use both your books and your brains. To illustrate how much experimenting Radio Fundamentals W. L. Everitt is necessary for an understanding of How to Become a Radio Amateur L. radio, notice typical magazine articles A. R. R. that direct the reader to use some Radio Amateur's License Manual A. R. R. L. component or other from the "junk Learning the Radiotelegraph box." It's a rare radioman who doesn't Code A. R. R. L. have a pile of parts left over from past 7 he Radio Handbook Editors and Engineers experiments. Before you can consider yourself qualified, you'll have one too! The Radio Amateur's Handbook A. R. R. L. A very great part of radio -the most Mathemaats for Radiouren Nelson M. Cooke important part -is concerned with tubes. Every handbook covers tube op- The Radio Amateur , \ercconier Editors and Engineers eration, of course, but you will need a tube manual as well. A "best buy" is the 35 -cent RCA Receiving Tube Man- ual, which lists the characteristics of or C if the other two factors are yourself. The ones you do well on, all receiving tubes and also contains known. In this case, the squares and leave alone. The ones you miss, mark many pages of general information square roots dealt with require a little it the margin and use as a study guide. about tubes and their use. This infor- more experience and knowledge than When you can answer every question mation should be read thoroughly -it the simple Ohm's law formulas. in the License Manual, you can pass is one of the best and simplest texts Believe it or not, these calculations the examination. on the ail- important radio tube. are really necessary in ham work as Good luck!

Radio mathematics Sonic experimenters have played with CAVITY RESONATORS radio for many years without ever learning Ohm's law -but no amateur SINCE the war, with information Maybe somebody has an explanation ever went on the air so sadly ignorant, being released gradually by the for this sudden interest and this sur- it for no other reason than that he had authorities, large numbers of ra- prising disregard of physical size. We to know it to pass the examination. dio men apparently have been haven't. At any rate, in an effort to be The necessary math is not hard. The catching up on their reading. Believe it of service, the accoml,anying table has basic formula that deals with current, or not, many who were not in the been prepared to show the sizes cavi- resistance, and voltage, for example armed radio services or in secret civil- ties would have to be for the 1 -, 2 -, and (these factors are dependent on each ian war work are just hearing about 6 -meter bands. The reader can see from other) is E = IR, which means that cavity resonators and think these are that just how big the things must be the voltage across a resistance (sym- swell gadgets. Highly technical radio and can draw his own conclusions. bolized by the letter E) is the product of treatises explained these devices (and In each case, the center frequency of current (I) times resistance (R). Note waveguides too) several years ago, but CAVITY -RESONATOR TABLE that we could have written this E = I in mathematical language that fright- Frequency Cylinder Cube Sphere X R, but, as in any algebra, the "times" ened away the practical boys. (me) (diameter- (box with (diameter height canal sides, 1 sign may be omitted between symbols. For some unexplained reason, the immaterial) each side ball) in ' ches) If we know the values of E and I author's mail lately has included a re- 220 -225 40 6" 37.3" 46.59" and want to find R, rearrange the spectable number of requests for the 235 -240 38 2" 35.2" 43.7" 144 -148 62" 57 2" 71" formula by dividing both sides by I: dimensions of cavity resonators for use 50.54 14'6" 13'5" 16'7" E IR E in transmitters and frequency- measur- the band has been selected for calcu- or R= -- ing gear in the amateur 1 -, 2 -, and 6- lating the cavity size. We do not be- I I I meter bands! We advised the inquirers lieve amateurs are interested in any Another rearrangement that a cavity for even the 1 -meter band but the simplest shapes -cylinder E is a cumbersome thing, that you just (can), cube (box), and sphere (ball). can't do the job with a beer can or We also doubt that anyone will be hon- R lunch bucket, and that there are sim- estly interested in a 6 -meter cavity, serves for finding current when you pler ways to tune up in those bands. since it would have to be as big as a know the voltage and resistance in the But the reply keeps coming back, "So room. (But a few years ago, we did not circuit. it is as big as an ash can. All right - think amateurs would be interested in If you don't remember your high - tell me the exact size. I still want to ranch -sized rhombics!) - Rufus P. school algebra -at least the simpler know." Turner, K6Á1 DECEMBER, 1949 12 Servicing Radio Set and Service Review

Ilallicrafters Model S -72

a loop antenna for broadcast reception one of the first off the production line, and standard antenna coils and a tele- the bandspread capacitor is a compres- scoping rod for shortwave. sion -type mica trimmer (C37 in the The oscillator is connected as a tri- diagram) shunting the oscillator sec- ode with grids Nos. 2, 3, and 4 con- tion of the tuning capacitor. The shaft nected to the plate. A 7 -µµf capacitor of this control has a metal projection 'like S-72 is a portable 1-band receiver. and 47 -ohm resistor connect the oscil- which opens the tone switch S3 when lator plate to the mixer grid to provide the bandspread control is set at zero model S -72 is local oscillator injection voltage. Re- for normal broadcast reception. Moving an eight -tube, four -band, three - sistance coupling being used between this control through six divisions on way portable receiver of AM the i.f. stages, there are only two i.f. the dial closes S3 and connects a 470- HALLIcRAFTERSand c.w. signals between 550 kc transformers in the set. The second de- µµf capacitor between the plate of the and 30 mc. Housed in a brown leather- tector and audio sections of the set are first a.f. amplifier and ground. The ette-covered case 121/4 inches high, 14 conventional. The phone jack discon- manufacturer states that the tone inches wide, and 71/4 inches deep, it nects the speaker when the phones are switch has been eliminated and a three - can be operated from 117 -volt a.c. or plugged in. Phones of 500 ohms or section bandspread capacitor installed d.c. lines or from its pack -type battery. higher impedance can be used. on models now in production. This set has such features as electrical The b.f.o. is a triode- connected 1U5. The VOICE -CODE control is a combina- bandspread, automatic noise limiter, Stray capacitance (and possibly feed- tion r.f. gain control and a.v.c.- b.f.o. b.f.o., and phone jack, but it is definitely back through the power supply) pro- switch. When it is turned clockwise as not a full -fledged communications re- vides coupling between the second de- far as it will go, the set operates at ceiver as were the Sky Traveler and tector and b.f.o. maximum sensitivity because the r.f. Sky Ranger. The automatic noise limiter is a and first i.f. screens are operated at The tube line -up consists of a 1T4 shunt -diode type using the diode of the the full voltage developed across R8. r.f. amplifier, 1U4 mixer, 1R5 oscil- 1U5 b.f.o. tube. the r.f. gain control. Switches S2 -b lator, two 1U4 i.f. amplifiers, 1U5 sec- The controls are TUNING, RANDSPREAD (a.v.c.) and S2 -c (b.f.o.) are open. ond detector, first a.f. amplifier, and TONE, BAND SELECTOR, VOICE -CODE, ON- Turning the control counterclockwise a.v.c., 3V4 power amplifier, and 1U5 OFF- VOLUME, and A.N.L. (automatic applies B-voltage to the b.f.o. and b.f.o. The r.f. amplifier is wired to use noise limiter). In the model examined, grounds the a.v.c. line. Although the S -72 is primarily designed as a general- purpose portable, fa- its electrical bandspread and b.f.o. put it several jumps ahead of others in the same class. It was compared with sev- tr eral a.c.-operated communications receivers and was able to hold its own on almost any signal which did not require a Q -5'er or crystal to pull it in. A good long -wire antenna increases the average signal level about four S- points over the whip antenna and brings weak signals well above the noise. The model tested has a tendency to be microphonic when the speaker is used while receiving signals in the 11 to 30 mc range. This is caused by acoustic feedback between the speaker, the oscillator tube, and its section of the tuning capacitor. This set could be adapted for amateur service by taking the b.f.o. and a.v.c. switches off the r.f. gain control and replacing them with a d.p.s.t. switch. The addition of a standby switch and provisions for a doublet - type antenna would make this receiver A .ingle pack .upplics A- and ISywwcr. A broadcast loop is inside bark cover. ideal for field -day operations. RADIO- ELECTRONICS for Servicing I45 Turn dial across local stations. A dip in the total B- current indicates normal AF- Ultrasonic Frequency Meter a.v.c. action. (This is some help in alignment.) DESCRIBED in The Reriew of The square waves are applied to a With class -B- output sets, tune in a Scientific Instruments, this elec- 6H6 discriminator through capacitor C, local station, and increase volume. One tronic frequency meter measures which is charged through diode V2 -a, look at the heavy peaks of B- current frequencies between 20 cycles resistors R3, R4, and the output im- will show your customer how to con- and 160 ke, independently of amplitude pedance of the second 6SJ7 clipper dur- serve B- batteries by holding volume and waveform. ing the positive half of the square down when not required. 'l'he signal is applied to the input wave. During the negative half of the To check for open filaments in indi- terminals and amplified by two 6SJ7 cycle, C discharges through V2 -b, the vidual tubes, turn A- voltage to about 1 high -gain amplifiers. A 6V6 is driven meter, and the clipper impedance. If volt. Remove tubes one at a time. A beyond cutoff and to saturation so it the time constants of the charge and clips the positive and negative halves of discharge circuits are equal, the meter 90V SOURCE the signal and produces square waves current is determined by the size of C of the same frequency as the input sig- and the frequency of the square wave. 2K nal. The square waves are differen- Therefore, the meter can be calibrated tiated and applied to a diode clipper VI to read directly in cycles per second. 2 INT EXT which removes the positive pulses. The Ranges are switched with a -cir- negative pulses are applied to the con- cuit, eight -position rotary switch that trol grids of a pair of 6SK7's in a changes the value of the charging ca- modified Eccles -Jordan multivibrator pacitor C and the meter shunts. The circuit. This circuit is so connected that high- frequency ends of the ranges are one tube is cut off and the other con- 160, 800, 1,600 cycles and 8, 16, 40, ducting at all times. The multivibrator 80, and 160 kc when C equals .05, .01. "flips" when a negative pulse is applied .005, .0019, .0005, .00025, .00018, and to the grid of the nonconducting tube. .00009 ttf. All meter shunts are 500 -ohm A positive pulse has no effect on the potentiometers.

A SOCKE T B SOCKETS circuit. The first negative pulse "flips" To adjust the instrument, apply an the multivibrator and the next makes it audio signal to the input terminals. Fig.. I (left) and 2 -A and B circuits "flop;" thus, two negative triggers are Use a scope to check the triggering of the battery receiver testing panel. required to make the multivibrator go pulses at the grids of the 6SK7 multi - through one complete cycle. vibrators. A sharp negative pulse increase in A- voltage each time slight The output of the multivibrator is a should be observed. Adjust R2 for a a filament. indicates closed square wave one -half the frequency of square wave when the scope is con- the input signal, thus simplifying high- nected between ground and either plate Testing batteries f requency compensation and increasing of the multivibrator. Adjust RI for re- One -and- one -half -volt cells of all the useful range of the meter. Because liable triggering action. Adjust R4 until kinds may be tested across the A -ter- the multivibrator output is distorted at the meter reads off scale (about 100 µa) minals (Fig. 1). The rheostat must be high frequencies, it is fed to cascade - at the full -scale frequency of one of in the off position. B- batteries may be connected 6SJ7's working as clippers. the ranges. Bring the meter back to full tested by throwing the switch in Fig. 2 These produce square waves whose am- scale with the appropriate shunt. Cali- to EXT and connecting the B-bat test plitude is constant, regardless of the brate the scales with a wide -range a.f. terminals to the battery. One thousand input frequency and amplitude. signal generator. ohms in series with any milliammeter converts the latter to a voltmeter of the 50µµf MICA same scale. Hence, a 50 -ma meter, for 6SJ 7 6SJ7 6V6 instance, becomes a 50 -volt meter, and .I/500V330K 3 draws sufficient current to throw a good o-1 test load on the suspected battery. A 2,000 -ohm, 5 -watt resistor may be used IMH t1, measure to 100 volts. 25

25v 1----77757 31K Two -volt sets 15 %45014 15/450W 310K 20W IOW 450v1 RI .5K 330K 330K IS. 450V 5K IOwI If 2 -volt sets are commonly serviced, a 2 -volt storage cell should be used for 20K 20K A- supply. This will also serve for 1%- 70µH volt tubes. For really old models, an 40yµ1 MICA 40µyfOKA extra B- socket may be necessary (there is one on the panel in the photo), and 6 SJ 7 C voltage taps at 22'íz and 67í/z volts.

For car radios and 6 -volt vibrator TESE 240 sets, a 6 -volt supply may be connected 240 to terminals on the panel, in series s 330K iY 2tIRC 750 1 PO with an old -style automobile ammeter. SW Shorted or open A- connections, sticky vibrator and bad or filter v2-b points, buffer 6H6 capacitors may be detected by observ- ,Ii600v- ti w ing the current drain. 0.B0yA Modifications or improvements of R2 this arrangement will suggest them- 250K ww 15K/IOW selves to the individual technician. Cir- A11 W. V2-. 1 22K/IOw 22K/10w cuits could be installed for other types 0 0 0 0 0 0 0 of sets using 4'12- or 9 -volt A- batteries. -O - REGULATED +150 0- I +300v METER SHUNT An alternative is to install a switch to I FOR EACH RANGE -SEE TEXT FIL open the voltmeter circuit, or to put a PINS 2.7 multiplier resistor in series with it. This instrument indicates the frequency of signals of any waveform or amplitude DECEMBER. 1949 Servicing

Eight AM Detector Systems

These detectors have stood the test of time

Detector stages have been various resistor 220,000 instead of the 750,000 high quality. The following tube may and numerous, and we print here dia- ohms indicated in the diagram. This be a 6V6 or 6F6, with point G connected grams of those which have continued modification for the 6V6 is equally use- to its grid. Transformer coupling may in use. Diode detection is almost uni- ful in the diagrams to follow. be used with the grid detector of dia- versally used today; nevertheless, pen- gram 1, but not with pentodes, unless tode and triode detectors are occasion- No. 2- Pentode plate detector they are used as triodes. In that case, ally employed and have advantages un- The same tube is used. Since the a 6J7 may be used by connecting the der certain conditions. In all the dia- plate resistor is only 100,000 ohms, re- suppressor to the cathode and the grams the tubes are: diodes, 6H6; production of high frequencies is better screen to the plate. diode -triodes, 6Q7 or 6SQ7; diode- pen- than in diagram 1. todes, 6H8; triodes, 6C5 or 6J5; pen- If the pentode is replaced by a triode, No. 4- Standard diode detector todes, 6J7 or 6SJ7. the cathode resistor should be between Either a single element of the 6H6 15,000 and 30,000 ohms. In diagram 1, or its equivalent, or the two elements No. 1 -Grid detection however, no modification (other than in parallel, may be used. The point K A 6J7 or equivalent tube is used. At omitting the screen resistor and capaci- may be grounded or -if the other diode the input end is the primary of the tor, of course) is required if the pen- is to serve for delayed a.v.c. -it may he last i.f. or r.f. transformer; at the out- tode is replaced with a triode. attached to the cathode of the preced- put, the resistance -capacitance coupling ing i.f. or following a.f. tube. elements to the first audio stage. If the No. 3-Triode with transformer Point G is, of course, the output to following tube is a 6V6, the capacitance This type of plate detection gives the a.f. grid. If there are two following may be .03 instead of .01, and the grid good results if the transformer is of stages of audio, the 510,000 -ohm resistor may be replaced with one of only 220,000 ohms. .o .ol (This rule can be fol- 1 lowed in all the diagrams.) IMEG 0003 OON I 0003 ICON .0001 1 8+ nH s+ . -. No. 5 -Diode push -pull detector SIGN iSGN. 750N 750N This circuit makes it possible to re- LVJ ® 5 duce the values of Cl and C2-or even --- IOON .5 to eliminate these capacitors altogether, eN as well as R. Thus reception of high 1 2 frequencies may be improved. This advantage is not obtained free, for the audio output voltage is only half as .0003 great as that obtainable from the stand- 1 1 ard diode detector.

°+ No. 6-The diode- triode 25 .02500Ny,yTO IMEG If the tube is a 6Q7 (or 6SQ7), RI 510N I may be 3,000 ohms and R2 100,000 OOÓI - ohms. The C 3 4 values of and R are the same as in diagrams 1 and 2.

172 B+ No. 7- Double diode-pentode .0003 The tube is a 6H8 or similar type. il 0 -^ y C The low -value plate resistor assures uniform amplification up to approximately 10,000 cycles. The 500 -ttttf ca- 11--VvV1/ti pacitor which shunts the plate resistor F 51N may be reduced to a size just large Á00i 25 In enough to prevent distortion. ,t ci cz 5 .02 IMEG - 6 No. 8- 1.f.- detector stage 20N 8+ G In this circuit, the pentode portion

.GOGS t of the tube is used as an i.f. amplifier. E 3 Point G is connected to the grid of the A 500N a \ G r .02 first a.f. stage, which may be 6J7 or 200 N N ' B + SIN 510K equivalent. The potentiometer may be I megohm instead of the 500,000 ohms SN

IOON .1 indicated. The cathode resistor may be 25 .I 300 .0001 SIN SION 25 increased or decreased from the 300 - I AvC .1 B+ ohm value given, depending on tenden- .0001 .0001 .02 I MEG cies toward oscillation in the i.f. sec - 7 - 8 tion.-Toute La Radio (France) RADIO- ELECTRONICS for Servicing 17

Several New Tubes TUBE manufacturers have been 200 mw at 90 plate volts. The D'3 particularly busy with new types (same photo) is an amplifier or oscil- during the last few months, and lator triode with a µ of 14.5. The cen- have issued a number ranging ter tube is the 5722, a noise -generating from a 10 -stage multiplier phototube diode suitable for measurements at to a subminiature ballast. frequencies up to 500 mc. An array of new Sylvania miniatures The RCA 5819 (Photo 4) is a 10- appears in Photo 1. They include types stage multiplier designed especially for 6BT6 and 12BT6, identical with 6AT6 use in scintillation counters and other 2 and 12AT6 except for better rectifica- applications involving low- level, large - tion efficiency of the diodes and lower area light sources. At 90 volts per stage, internal capacitances; 6BÚ6 and multiplication of feeble currents pro- 12BC6, miniature duo -diode triodes like duced by weak illumination is about the 6BF6 except for improved diode 400,000. The 5823 in the same photo is charactet istics; and the 6BK6, 12BK6 a miniature glow- discharge, cold -cath- and 26BK6, miniature duo -diode high - ode triode designed as a relay tube for mu triodes like the 6AV6 but with im- on -off control. proved diodes. The 26BK6 has a 26.5 - The General Electric CL -5824 (Photo volt, 70 -ma filament. 5) is electrically and physically inter- Photo 2 shows two cat hode-rav tubes changeable with the 25B06, hut is con- for oscilloscope use. The Du Mont 5XP structed to give more dependable serv- series has a high -sensitivity deflection ice. system permitting deflection of 1 inch Raytheon's new 8BP4 (Photo 6, for 24 to 36 volts. The RCA 3KP11 is right) is an 8,4-inch tube which elec- electrically equivalent to the 3KP1, with trically is a direct replacement for the a high -intensity bluish glow especially 7JP4 (left in same photo) but has a intended for photographing. considerably larger screen area. . The Sylvania 1W4 (at left in Photo The Amperite subminiature ballast :3) is a pentode power amplifier with (Photo 7) can be supplied to dissipate an output of 35 mw at 45 volts and power up to 3 watts. Maximum current is 0.9 ampere. Other new tubes are the Raytheon 1X2, a high- voltage television rectifier, the Sylvania 1L6, a pentagrid converter for portables, the RCA 6AB4, a high - mu triode for grounded -grid service in FM and TV sets, RCA 6AH6, a sharp - cutoff pentode for use in video i.f. and video amplifiers, and the '7X6, a Syl- vania rectifier with 150-ma output and separate cathode leads.

7 DECEMBER, 1949 Servicing 181

ITH few exceptions radio technicians look on advertising as sheer waste of money. They reason that the return Advertising is not worth the expenditure, and consider that their reputation for good honest work at a reasonable figure should ensure them their fair share of the neighborhood's radio business. Of course, a sound reputation built up and Selling over a period of years will ensure a steadily increasing trade. But it is a slow process and uphill work; and one dissatisfied customer- whether his complaint is justified or not -can do more A distinctive advertisement harm to such a business than the good done by two completely satisfied ones. that tells a definite story The reason advertising is looked at askance by most radio technicians is increases sales and profits simple. Their advertising, as it stands, does not pay. I have studied thousands, probably tens of thousands, of service - By T. W. DRESSER dealers' advertisements. Not one in a thousand was worth the money spent on it. They are stereotyped in their layout and in the style of type used. Interest- ing facts that could have been brought out are submerged in an unattractive assembly of garden -variety illustrations and wording. That is not advertising; it is philanthropy- giving money away! Publicity, like anything else worth doing, must be planned. Its only purpose is to bring together in favorable circumstances the prospective customer and the salesman; that is the sole aim of advertising, and it is worth remembering. It is worth remembering be- When your radio goes blooey, bring, Our engineer calls promptly. If neces- cause today publicity is high pressure.

phone, or write an S -O -S to DIXON'S. sary, he takes set to our repair she Hundreds of thousands of firms and

l i a, people are aware of its value, and your I -1'II advertisement will be submerged in the flood of mediocre publicity -unless you li make it outstanding! Generally, radio technicians' advertisements fall down because they are not attractive enough to warrant reading through, or because Nero set is labelled for indntifica- ...repair technician in special room they attempt too much in a small space. inevitable result is tien, vacuum- cleaned, and passed to... equipped with the latest instruments. The that the adver- tiser gives it up after a period of poor results and thinks that advertising is a much overrated business. The aim of any well-organized dealer is to "feed" his staff -or himself in the case of a one -man business -with a steady succession of new prospects whose interest has already been inspection Before set is returned to you, French- After repair, radio goes to is the only possible way to it shine like newl aroused. It deportment for actual on -the -air test. polish experts make run a successful business, and it cannot be done by good will alone. Only That's this story -the way your radio good publicity can supply such a flow of new prospects. Figure one is an example gets the A -to -Z treatment by experts. of good advertising by a service tech- in our work; you'll be We take pride nician, which stands out by virtue of proud of your radio. You'll say... its distinctiveness; it looks interesting "GO TO DIXON'S. I'M GLAD I DIDI" and invites the reader to scan it again. In fact, its attention -compelling angle is comparable with that of the daily 1;a dio A G E N T S F O R comic strips. Dixon's EMERSON R.C.A. PILOT Having drawn the reader's attention, Whichburg PHILCO ADMIRAL this advertisement then forces its point ROGERS -MAJESTIC Phone 72272 home. The gist of its story is that, if the reader's radio is defective, he should take it for servicing to the This atI ertisement tells a story with pictures. Readers will see and scan it dealer whose name appears at the foot of the ad. The other illustrations show RADIO -ELECTRONICS for Servicing f9 what will happen to the radio while in with a well -arranged window and an INEXPENSIVE FREQUENCY the dealer's hands, and are calculated attractive colored fluorescent lighting STANDARD to inspire confidence in the work done. scheme-has brought this technician- An economical little frequency stand- The appeal is then extended to cover dealer the major share of the radio ard for the experimenter's workbench, new sales by explaining in the final business of a town of 300,000 inhabi- this unit can be used with any crystal paragraph that "We take pride in our tants. Yet four years ago he was al- whose fundamental frequency is suita- work; you'll be proud of your radio. most unknown in this city! Such suc- ble for the purpose. A number of stand- You'll say ... 'Go to Dixon's. I'm glad cess is an outstanding example of the ard-frequency crystals have been avail- I did.' value '" of rightly handled publicity. able at very low prices on the surplus Another form of publicity with a de- In advertising new radios far more market. cided pull is that in Fig. 2. The appeal emphasis should be placed upon the The parts values are not critical; of this advertisement lies principally in value of demonstrations at the dealer's they can vary approximately 20% from the fact that -superficially at least-it premises or in the customer's home. the values shown on the diagram. The offers "something for nothing." It in- Many dealers' advertisements fail to tuned circuit is not absolutely necessary vites readers to phone and stresses in stress how much such demonstrations and can be omitted if the points X -X the most effective manner possible that can help the customer make a wise are connected together. However, the there is no obligation. In consequence choice. Others fall down in their appeal resonant circuit gives more "kick" to the reader feels that, if he does phone the output, enabling the operator to or write, he can ignore, without em- secure usable harmonics up to 30 me barrassment or cost, whatever advice is with a 100 -kc crystal and much higher. tendered. In other words, he feels he is of course if higher- frequency crystals under no obligation. Repaired are used. Service-dealers' advertisements may Suggested values for L and C for be based on this model, although they different crystal frequencies are: should not copy its (or anyone else's) by format slavishly. Designed to bring in- Crystal L (mh) C (µµf) quiries, it ultimately ensures a regular 100 kc 20 120 flow of both service and new sales. Once SHAW 200 kc 5 120 the contact has been made between the 500 kc 2.5 40 "prospect" and the dealer, personal 1 mc 2.5 10 and salesmanship demonstrations should "The Radio Doctor" 2 mc 1.25 5 produce that flow of sales and serv- 5 mc Omit L and C and short X -X icing. Showcards, letterheads, and window Standard r.f. chokes and small vari- lettering can all contribute at a small able Fig. People remensber shop's slogan. capacitors are built into plug-in outlay a substantial quota to the appeal 3- forms. Other combinations of induc- to the prospective customer. Fig. 3 to the reader to take some definite actance and capacitance can be used if shows the slogan used by a highly suc- tion. Most people already know that they tune to the frequency of the crys- cessful service -technician- dealer in this any modern radio showroom will gladly city [Bradford, England]. His letter- demonstrate receivers in stock, but head and business card carry the same there is a vast difference between sub- wording and on each repaired radio conscious awareness and active interest. ~Ai 1006 .02 in his shop stand small cards printed RF OUTPUT Good advertising will burgeon this in- 3 tt active knowledge into real interest. To 117L7-GT this end the dealer's publicity should stress the advantages to be derived 4 5i0i2w IS YOUR RADIO IN from demonstrations, while indicating J-xTAL 5.1 8 that they imply no obligation what- = MEG 2 7 TROUBLE ? ? ? IH I~15ÓVT ever on the prospective customer's part. .1/2008 4;300 117VAC I can't get WBZ. Whenever and wherever possible Interference spoils program. manufacturer- dealer campaigns should FOR L, C & XTAL SEE TEXT Do I need an antenna? be used to their fullest. Such publicity -while essentially concerned with the Why can't I get FM? products of one particular manufac- tal they are designed to work with. The We are asked similar questions sev- turer-does succeed in bringing in po- 1.25 -mh inductor may be half of a 2.5- eral times each day. Our advice is tential customers, and the dealer need mh r.f. choke. Harry C. Aichner, Jr. given free and without obligation. not refuse a sale if the customer re- If you have radio trouble ask our jects the advertised brand. Sales aids LRTA INDUCTS OFFICERS help. It doesn't matter what make supplied by manufacturers also help Michael Csigi was installed last or type or where you bought it. Our greatly in making an attractive win- month as president of the Lackawanna technical dept. is at the service of dow display, an essential in pulling in Radio Technicians Association in Scran- all listeners. the casual passerby. ton, Pa. Other officers of the Associa- There is no doubt that intelligent, tion inducted at the ceremonies were: TECHNICAL DEPT., well handed publicity pays handsomely August Cianchetti, first vice -president; DIXON'S RADIO in the radio trade, more so perhaps Merrill Greene, second vice -president; Whichburg than in many other industries. The James Jerome, treasurer; Howard E. Cal', rite or phone 72272 dealer with initiative will use it to the Greene, secretary; Homer Kinback, as- limit to boost his steady trade in sales sisting secretary; and Louis Perna, Ste- and servicing, to take advantage of phen Csigi, and John Riegel, trustees Fig. 2 -This ad invites free inquiries. periodic booms such as television is ex- of the Association. periencing at the moment, and to buffer The second semester of LRTA's tele- as in the figure. This reiteration of a the slack periods. vision school started on October 10. Ses- theme subconsciously impresses itself His reward will be an increasingly sions are held in Scranton Technical on the mind of all who encounter it, steady trade, constantly building up, High School on Monday and Friday and in time they associate automatically for advertising does not stop when the nights under Kenneth Cooke, the in- any mention of radio with the name campaign is over. Satisfied customers structor in charge. Expenses (includ- of the dealer - in question. brought in by his publicity -tell others; ing instructor's salary) are paid by the The same theme is carried into the thus advertising is the most satisfac- State Board of Public window Instruction and lettering and -in conjunction tory "snowball" in the world. the Scranton School District. DECEMBER, 1949 Servicing Fundamentals of Radio Servicing

Part X- Triode and tetrode tubes By JOHN T. FRYE

S POINTED out in a previous But the filaments or cathodes of most ing plate to attract a larger current. chapter of this series, the radio and TV receiving tubes are coated Father Adam of all electronic with a mixture of barium and strontium Enter the triode oxides on a nickel -alloy base. They tubes is the two -element diode. The early radio engineers, viewing One of the elements, the plate or anode, need be heated to only approximately steady flow of from cath- 700 to 750 degrees C to make enough this electrons is simply a piece of metal without any feel small makeup. But electrons boil out. ode to plate, began to like special fussiness in its boys coming is There always has to be a villain in watching the stream out the other, the cathode (or filament), a wanted elec- piece though, and the mustache- of garden hose: they to stick the key element in almost every the into the and see twirler of electron -tube flow is something current tron tube -no matter how complicated current would boiled the space charge. Picture the stage set what happen. The something it may be- because the electrons they inserted was a grid, and that is out of it make up the emitted current for plate-current flow: the filament is the tube. In tube de- heated and a positive charge from the how the triode tube was born. that goes through The grid is a mesh of fine wire wound material is extremely B- battery or power supply is connected sign the cathode around supports so that it surrounds important, so let us dig a little deeper to the plate. Some of the electrons cathode. The photo of a broken - into the subject of cathodes. emitted from the cathode are pulled the across to the plate by its positive open triode shows the grid wires plain- charge. But other emitted electrons are ly. The drawing of Fig. 1 shows the ele- not reaching the plate because the B- ment structure of a typical triode vac- voltage simply isn't high enough; and uum tube. they are just standing around between The control grid, as its full name the filament (or cathode) and the plate goes, is usually biased negative with doing nothing. This little cloud of not - respect to the cathode; that is, a nega- so- innocent bystanders is called the tive d.c. charge is permanently placed space charge; being composed of elec- on it. Sometimes a small battery is trons, it is charged negatively. used, at other times the negative ter- Now, as the heat of the cathode boils minal of an a.c: operated power supply, out more electrons from its surface, and in still other cases other methods the space charge tries to push these are brought into play. But the net result is that the grid is more negative IV; electrons back onto the cathode -the negative space charge repels the nega- than the cathode. The triode tube has only a single grid. tive emitted electrons. The positive If the grid were positive, it would plate is shouting, "Come on over!" to act somewhat like another plate -it the electrons, but the space charge is would attract electrons, and there commanding, "Get back on that cathode!" The space charge is nearer the cathode than is the plate, so the newly emitted electrons feel the effects of the space charge much more than those of the plate. Result: fewer electrons get to the plate and plate current is low. One way to cut down the bad effect of the space charge is simply to cut Note screen grid in this tetrode photo. down the space. In the 25Z6, for instance, the cathode and plate are only In most tubes, the only way to make .02 inch apart. Another way is to put a cathode emit is to heat it. As with a little mercury in the tube. When the incandescent lamps, tungsten is the filament heats, the mercury vaporizes only wire that can stay hot enough to and becomes a gas. When an electron on emit any practical quantities of elec- its way to the plate hits a mercury - loose one trons without melting. Pure tungsten vapor atom, it knocks of Fig. Arrangements of cathode and in many large trans- the mercury atom's electrons, which 1- filaments are used and plate in triode tubes. mitting tubes; they are heated to a promptly beats it over to the plate like filament, grid, dazzling white -to over 2,000 degress C. a little boy at the end of a school day. Tungsten, while it stands up under The mercury atom now is missing one would be a grid current just as there heat, is not the best emitting material, electron. Looking around, it discovers is a plate current. Although the grid and therefore many medium -sized the space charge and snatches an elec- is positive in a few rare circuits, it is transmitting tubes have tungsten fila- tron from it. The mercury atom is negative in most applications and does ments coated with thorium. These whole again-and electrically neutral not attract any of the emitted electrons thoriated filaments liberate plenty of -but by gobbling up that electron from to itself. when they are heated to a the space charge, it has reduced the Like a water -logged life preserver, electrons is bright yellow -about 1,700 degrees C. space charge and aided the hard -work- a negative grid not only is no help, it RADIO- ELECTRONICS for 51

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IT'S YOUR 411/ED 196-PAGE VALUE- PACKED CATALOG! SEND FOR IT TODAY Allied r.,.,s,:: Radio in . ::,:::::,::::::;:: Get Radio's Leading Buying Guide Here's the Buying Guide to everything in radio for everyone in radio! It's the one complete catalog, preferred in the field because it fills every TV, Radio, and Electronic supply need. It's packed with the world's largest selections of quality equipment at lowest moneysaving prices. See the latest in TV, AM and FM receivers; radio -phonos; new Sound Systems, P.A. equipment and high -fidelity sound components; recorders and accessories; full selections of newest Amateur receivers and station gear; test instruments; builders' kits; huge listings of parts, tubes, tools, books, diagrams. ALLIED gives you every buying advantage: speedy WORLD'S LARGEST STOCKS delivery, expert personal help, lowest prices, assured Radio Parts Unlimited satisfaction -plus the most liberal Time Payment plan Test Instruments -All Makes in radio. Get the 1950 ALLIED Catalog --it will save you Television time and money. Send today for your FREE copy! & Home Radios P. A. and Hi -Fi Equipment Amateur Station Gear HEADQUARTERS Experimenters' Supplies IS YOUR TELEVISION ALLIED on ALLIED! QUICK, EXPERT SERVICE TV when you depend You keep up with stocks for the latest releases Count on us and largest picture tubes, component tunersnd Send for Radio's Leading Buying Guide of latest in TV receivers, -plus the stock! So accessories in TV -we have it in kits. If it's anything and ALLIED First! remember -for TV -it's ALLIED RADIO CORP. 833 W. Jackson Blvd., Dept. 2 -M -9 ALLIED RADIO Chicago 7, Illinois Send FREE 196 -page 1950 ALLIED Catalog.

THE WORLD'S LARGEST RADIO SUPPLY HOUSE Name Address Ecientitio9 et Ra.dia,Tla.ssd Eleetna.rica City Zone. State

DECEMBER, 1949 52 Servicing How to build this modern service bench a hindrance -it not only does not pull vary the plate -voltage control until the for your shop! electrons away from the cathode but current is 5 ma. A look at the plate pushes them back! voltmeter shows 210 volts. Note that So here we have the plate pulling a 40 -volt plate-potential change was electrons from the cathode and the grid necessary to get the sante effect on the pushing them back on. The question is: plate carrent as was obtained with who has the most to say in this war of only a 2 -volt grid change! The ratio of purposes? Answer: the grid. Reason: the two, 40/2 or 20, is the amplification because it is so much closer to the factor (mu or It) of the tube. cathode than is the plate. To make practical use of the tube as When the grid goes negative, it is like an amplifier, however, we must have a traffic policeman putting up his hand some way of taking the amplified volt- -traffic slows down or stops, as de- age changes and feeding them to other sired. When it goes more positive (or points in the equipment. The plate load less negative), you can imagine the resistor in Fig. 3 is the gimmick that policeman vigorously motioning all the solves the problem. As the plate cur- cars to move on. When the plate volt- rent changes because of grid -voltage age changes, however, it's as though a changes, the current rising and falling policeman 10 blocks away were direct- through the resistor creates a changing ing the traffic. There is some effect on voltage drop across it. If the tube is the electron traffic around the cathode operated correctly, the voltage changes C ¡stele plans and illustrated instruction. in the Janu- but not much. across the load duplicate exactly the of RADIO DISTRIBUTION t \Il MAINTE - \ t\t`El Build this efficient, time money saving When the grid does become less nega- voltage changes at the grid, except that

1 h that will make a attractive addition to your service tive and lets the plate pull electrons they are much larger. h..p. Easy to assemble. low cost, large enough to ae away from the cathode, the electrons They are not 40 times as large, co nodate big Ty chassis: This bench has been carefully designed to he ultraeairient as to working pass right through the spaces in the though -there's a fly in the ointment. -pace. mol location, etc. Don't miss this valuable feature Every time the plate current rises, the the issue 6J5 January of: drop across the resistor rises too . it must to furnish output. But the voltage on the plate is now less because much less than the full battery voltage RADIO QII® reaches the plate. Of course, the less- AND maanusavamem ened plate voltage does not entirely The plete trede journal devoted to ale, and service nullify the effect of the more positive of Radio, video. Audio. Fig. 2-Test setup shows nut of a triode. grid voltage, because, as you remember, plate voltage is not anywhere near Single Copies .25 grid mesh, just as the cars in traffic as effective in controlling the tube as go by the policeman. is grid voltage. It does cut down the $3.00 Per Year $5.00 2 Years With all this in mind it is easy to amplification somewhat, however, and, see why the grid voltage has much more on the values of resistance SALE NOW depending DECEMBER ISSUE ON effect on the plate current than the and voltage used, the output voltage is Get your copy today and ask about the plate voltage has. To state it another only about 14 times the input. SPECIAL OFFER PLAN way, a small change in grid voltage and save money on your subscription! produces a change in plate current which could only be duplicated by a VIDEO NAND BOOK much larger change in plate voltage. Now in one great book -all the es- You can prove this yourself with sential knowledge of tetet ilion for laboratory technician-experiment- equipment no more complicated than er - . . . everyon in- that shown in Fig. 2. The 6J5 is ar- terested i working at television! Complete. up -Iothe -minute info, ranged so that both grid and plate arranged for quick reference voltages can be varied and plate cur- v to read . . , no mathematics. rent read on the milliammeter. CHIME HEATER CONTROL GRID SCREEN GRID PLATE Oser 9110 pages . .. e than 8015 photograph.. diagram.nrand draw. Suppose we start with -8 volts on Fig. -I- Screen between grid and plate. ing-. Here are e of the objects the grid and 4 -250 volts on the plate. suarrd: Fundamental.. the T\' , the receiver, antennas, pro- Because of the construction of the tube, There is one point to get straight: gramming. installation. s , test the plate current is 9 ma. the tube equipment, data. terms. etc.. etc. $5.00 does not take the input volt- 4-.BLOCKING OR age and stretch it in some mysterious RADIO DATA BOOK COUPLING way to get a bigger output. The tube CAPACITOR AC INPUT Ilse mil. radio handbook of its PLATE really does not amplify at all! It is a LOAD kind! Covers es er.thing in Radio control device. It works similarly to i- RESISTOR for lab technician. -experimenters GRID BIAS the filling station hoist that sends your -- and BATTERY AC up in so re! Over 900 pages. 12 big section- OUTPUT car the air the garageman can with hundreds of draw Me, and llllllllll work underneath it. The attendant grams. Sonic of the subjects covered works a little valve -and presto! your are . . . Testing. Measuring ainsi is 3,000 -pound automobile rises before Alignment . All about Antennas Fig. 3 -A plate load resistor added. ... Sound Systems ... Recording your eyes. It isn't the attendant's hand Complete Test Equipment Now we change the grid voltage to that does the work, of course. It's the Data . . Complete Tube Manual -10. The milliammeter reads 5 ma, compressed air stored in a tank, re- . . . Charts. Graphs and Curves in by the $ 5.00 . SO Tested 1:irn,it. .. , Codes. which agrees with the idea that making leased the desired quantity Ssmbols and Standards . . . ISO Basic Circuits . . . the grid more negative pushes more little hand valve. Dictionary of Radio Terms . . . etc.. etc. electrons back on the cathode so they A vacuum tube is just like the little Remember, then, valve and the plate or B- battery like All products of can't reach the plate. that to decrease the plate current by 4 the stored compressed air. The incom- BOLAND & BOYCE INC., Montclair 3. N. J. ma, we had to make a 2 -volt change in ing signal on the grid simply releases are available at your grid potential. and dams up the stored electrical en- local distributor's counters. Order now! Now reset the grid voltage to -8 ergy in accordance with its desires. (so that 9 ma is flowing again). This There is no grid current, so no power time the object is to see how much the is taken by the grid either from the plate voltage must be changed to get batteries or from the controlling input plate current down to 5 ma. So we signal. The output voltage -every bit RADIO -ELECTRONICS for Ì M O N E Y BACK GUAR A N TEE - We believe units offered for sale by mail order should be sold I only on a "Money- Back -If- Not-Satisfied" basis. We carefully check the design, calibration and value 1 of all items advertised by us and unhesitatingly offer all merchandise subject to a return for credit or ; `.refund. You, the customer, are the sole judge as to value of the item or items you have purchased.

A COMBINATION Specifications: Specifications: The New Model Tests all tubes including OHMS PER VOLT * 20,000 MULTI -METER i) D.C. Voltage TV -10 TUBE TESTER 4, 5, 6, 7, Octal, Lock -in, Ranges: (At Peanut, Bantam, Hear- 20.000 ohms per and TELEVISION KILOVOLTMETER Volt) ing -aid, Thyratron, Miniatures, Sub- Minia- The New Model 0. 2.5.10 50/100/ Novels, etc. Will TV20 250/500/1.000/ tures, 5.000 / 50,000 also test Pilot Lights. Volts) * Tests by the well- entaba 8 A. C. Voltage lished emission method Ranges: (At I. for tube quality, directly Ouu ohms per read on the scale of the Volt) meter. U -2.5 10'50/ IOU 'Pests for "shorts" and 250 500 1.000. * 5.000 Volts '-leakages" up to 5 Meg - obms. 5 D. C. Current Uses the new self- clean- Ranges * Lever Action U -5U Microamperes ing Switches for individual 0 -5.50 500 Milli- amperes element testing. Because all elements are num- 0 -5 Amperes bered according to pin - 4 Resistance number in the RMA bee Ranges: numbering system, the 0-2.000 t 20.000 user can instantly iden- ohms. U 2 2U tify which element is Megohms having D. B. Ranges: under test. Tubes Added Feature: In 7 tapped filaments and eludes an Ultra High (All D. B. frequency Voltmeter ranges based on tubes with filaments ter - OUb on- The Model TV -10 operates on 105.130 Probe with a frequen =I Mv. minating in more than to a 800 ohm Volt 60 Cycles A.C. Comes housed Ina 5 cy one pin are truly tested range up to I.000 lino) beautiful hand - rubbed oak cabinet cam- 9NET M E G Al: Y CLLS.When Clete with portable with the Model TV -10 as plugged into the Mod- - 4 to + ID db any of the Pins may be paced in the neutral position when necessary. + 8 to Oh el TV -20. the V. H. + 22 The Model TV -10 dues use type sockets. Instead converts the unit + 22 to + 36 db * not any combination Probe is impossible Into a Negative Peak - + 28 to + 42 db individual sockets are used for each type of tube. Thus it Reading H. F. Volt- + 36 to + 50 db to damage a tube by inserting it in the wrong socket. meter. + 42 to a 50 db Free -moving built -in roll chart provides complete data for all tubes. + 48 to ,. 62 db * The Model TV -20 operates on self -eon * Newly designed Line Voltage Control compensates for variation of any tained batteries. Comes housed in beau 7 Output Voltage line voltage between 105 Volts and 180 Volts. Mull hand -rubbed oak cabinet com- $39.95 ranges: plete with portable cover. Built-In High 0 to 2.5 lu 50 Voltage Probe. H. F. Probe. Test Leads OM 250 500.- The and all operating instructions 1.000 Volts 7,72:0" TELEVISION SIGNAL GENERATOR The Model 88 -A Combination Enables align- SIGNAL GENERATOR ment of Tele- vision I. F. and front ends with- and SIGNAL TRACER out the use of an Oscilloscope Signal Generator Specifications: *Frequency Range: 150 Kilo- cycles to 50 Megacycles. The Specifications: R.F. Signal Frequency is kept completely constant at all out- Frequency put levels. Modulation is ac- Range: 4 Bands complished by Grid- blocking ac- -No switching. tion which equally effective 18-32 Mc. 36- for alignment of amplitude and 65 Mc. 54 --08 Mc. frequency modulation as well as 150 -250 Mc. Au- for television receivers. R.F. ob- dio Modulating tainable separately or modulated Frequency: 400 by the Audio Frequency. cycles (Sine Signal T Specifications: Wave). Attenu- 'Uses the new Syhania IN34 Ger- ator 4 position. manium rryvtal Diode which com- Model TV -30 ladder type with constant impedance con- bined with a resistance- rapacity net- comes complete trol for fine adjustment. Tubes Used: work provides fre- with shielded co- 11C4 quency range as axial lead and as Cathode follower and modulated 6C4 qrn. 1° rat Megacycles.cl' 11 all operating in buffer. as R.F. Oscilator. 6SN7 as S9 8N85 struetiona. Audio Oscillator and power rectifier. The test ds atnd 'gerating instructions. ONLY The New Model 770 -An Accurate PocketSiae The New Model 670 VOLT -OHM MILLIAMMETER SUPER METER (Sensitivity: 1000 ohms per volt) CumIact- mensures 314" x 55ís" x 2% ". A Combination Uses latest design 2,', accurate 1 Mil. VOLT - OHM - MILLIAMMETER D'Arsonval type meter. Same zero ad- plus CAPACITY REACTANCE. justment holds for both resistance ranges. INDUCTANCE and DECIBEL It is not necessary to readjust when 51 EA SI' REM ENTS. switching from one resistance range to D.C. VOLTS: o - another. This is an important time-sav- 1'011 A C VOLT, ing feature never before included in a t'en TI'V T V.O.M. in this price range. Housed in VOLTS round -cornered. molded case. Beautiful DC CURRENT I to III Amps, RESISTANCE: 0 to hlick etched panel. Depressed letters Io0.0011 0hme. O to In Aesohtnn. CA filled with permanent white, insures PACITY: onl in 5161.. 1 lu t \I' long -life even with constant use. Quality tea for elect rolyflr13 REACT Specifications: 6 A.C. VOLTAGE RANGES: ANCE: 700 10 27.nun Ohm.; 13 -goo uOmo o. I :;n; I',n 30 13110/30011 colts. Meanhme. 6 D.C. VOLTAGE RANGES: 0 -7tz /1:/7 I3INDUCTANCE: 1.75 to 70 Henries; 150 :-o I ion Its. Di N eon Ilenrlea. 4 D.C. CURRENT RANGES: 0 -It4/15,1511 DECIBELS: -10 to +18. +10 to +30 . Ma n -1 t Amps. +30 to +58. 2 RESISTANCE RANGES: 0 -500 Ohms. 0 -1 The model 670 comes housed in a rutted Megohm. crackle -finished steel tab- inet complete with test The Model 770 comes complete 9U leads and operating in. 40 with sell -contained batteries. struetiona. Size 51 /e- x a NET test leads and all operating NET 7' r 3 -. Instructions. x20 °á DEPOSIT REQUIRED PLACE GENERAL ELECTRONIC DISTRIBUTING CO. NEW YORK SARK N.

D E C E M B E R , 1 9 4 9 e.I Servicing

of it -is energy from the B- battery. If Now the tube works just as before, there were no grid signal, there would with this exception: while the plate PRESENTS just be a steady d.c. voltage across the voltage changes periodically (just as it load resistor. There would be no output did before), the screen voltage does not. because the capacitor prevents d.c. from And because the screen is closer to the OUTSTANDING PRECISION passing. But when the grid signal starts electron source (the cathode) than the repelling and passing elec- plate, its pulling power is greater. As INSTRUMENT KITS alternately trons. the d.c. across the resistor rises a result, the plate voltage changes don't and falls with the plate -current have anything approaching the effec- changes. That gives it an a.c. charac- tiveness they had before in cutting MODEL 221-K ter, and it passes through the capacitor. down amplification. Even when the 111IM KIT plate voltage is low, there is almost as lirait Solid this The screen grid much positive force pulling electrons register's Ven- m Tube Y'olt- through the tube as when the plate 15 dlRet- You remember that, while the am- neter. AC voltage is high. The amplification of a mt rang.(, plification factor of the 6J5 is 20. we DC range, std /200 /500 tetrode, as this tube is called, is many 11/5/10 ono; - could get a real amplification of only /1000 vota, .. times higher than that of a simple tri- meter range: 14 times in the practical circuit of Fig. ohms to 1 megohm' 3 because plate -voltage changes gum- ode. Zero Center t' t TV diseron'Ric med up the works. The cure is to add Another advantage of the screen is alignment. meter cannot another grid to the tube. Called the its reduction of grid -to -plate capaci- Oh' Double burn out reed bal anee.l sobre. 0515!') Rocco grid (or simply screen), it is tance. Those two elements form the triode elect( assures 43501A bridge //133n Y. ._-r,U located between the control grid and plates of a small capacitor through peAurmancI 6' a corlo. Size tl 7 /1T a fíVTVM which some of the tube's output can -WIRED wlretl. the plate, as in Fig. 4. FACTORY ro nP r Setae, our The screen operates all times with feed back to the input, especially at Mo d e 1 21. at .Jibs.(: J. and le a positive voltage on it, a voltage about higher frequencies. Feedback can pro- half that of the plate (more or less). duce all kinds of hair -raising effects, as You Build 'Em In One Evening - The hookup appears in Fig. 5. The we will find later on, but the screen THEY LAST A LIFETIME! grid, placed right in the middle of the grid -plate capacitance, breaks it up by TV -FM NEW! Sensational INPUT OUTPUT acting like a shield or screen (hence SWEEP SIGNAL its name) and reduces the capacitance GENERATOR KIT (which may be several micromicrofar- Model 360 -K. I'm »'1 ads in a triode) to something less than marker oscillator with r - Ifhhll r table amplitude. Cos. .01 µµf in the tetrode. all TV and FM aliento ' a Irequencles between Fig. 5- Circuit of tetrode amplifier. In the next chapter we will take a ke and 228 me. Sweep width variable from 0.35 screen voltage is fixed and (loes not quick glance at a couple of more tube me. with tnehaulcal Inductive sweep. All TV and wade FM Channels marked directly on panel for Ins an- vary with the plate current. Because it types and then into tube charac- t:oleo . reference. Provides for injection w itb rile nal teristics. Knowing the characteristics signal generator marker. Phasing control Melu led. is positive, it helps the plate attract Vernier driven. toning dial for minter me ll star of a tube is just like having a trusted directly calibrated in frequencies. -co lm et -bed electrons from the cathode; most of the panel, and durable steel rahlnet. Complete n itl all electrons, however, pass through the friend give you the lowdown on a corn- tubes: 6X5GT. 12:í177, two OC4's. Crystal not In- ing blind date: it you cluded. Sloe: 10' x 8' g 6%'. $29.95 screen wires and go to the plate - tells exactly what Complete Kit, only is kind of a you FACTORY -BUILT AND TESTEDS39.95 screen current very small. performance can expect! MODEL 360. Ready to use If" SCOPE KIT SERVICE SHOP HAS ROLLING TEST CABINET Model 400 -K. LabonlnrY precision .rope. for F)1. sol & TV servicing. De fleet tar sensitivity: .05 volis per inch full gain. Horizontal sweep circuit. 15 Io 30.0011 cycles. Fre- quency response of horizontal and vertical amps is frum 50 tu 511.000 cycles. Graph screen. Op- erates on 110 to 130 volts AC. 50.60 cycles. 3-ulur ebbed, rub -prao panel. Size: 8$'g 17" n la- bleb. 3 -valor etched panel $39!5 FACTORY -BUILT OSCILLOSCOPE Model 400. Fully wired. a ...entitled. and rar -trd 569.95 SIGNAL GENERATOR KIT Model 320 -K. For ,enire, Ian, anti School d.c ill Fyl- AM alignment and to provide TV marker frequenrles. Ceramic Insulated variable condensers. Highly Stable Hartley oscillator his range of 150 kr to 100 me with fundamentals to :N nid. I'ol- % pills audio asri tiaras supplies pure 400 cycle sine woe voltage for modulation. Large 0' did. Easy -to -read calibrations. Easily aligned. Complete with tubes. 10' g 8' a 4,4'. 3 -rolor $1ae.73J etched panel FACTORY WIRED AND ALIGNED Model 320. Ready to use f29.9S SEE YOUR AT ELOCALR JOBBER. Complete simplitled instructions and illustrations ncome with every Elf. Instrument Kit. it pure eninr- nr t to build your own equipment. Nothing more to buy. anyone can build Photo by J. J. Cook them. Write for catalog C. This is the service -bench sect' of Ward Cust built Radio in New York City. ELECTRONIC INSTRUMENT CO., INC. The test cabinet Iras four panels of instruments and is tiro red ou a roll table All tables and racks are 'stade of steel. Fuses 276 NEWPORT STREET so that it can he used where needed. for all bench a.c. outlets and a master switch turns off all power. are provided spots. BROOKLYN 12, N. Y. An adjustable fluorescent lamp over the bench illuminates the critical RADIO -ELECTRONICS for 5.55

'2 Great à&vette Mail Centers RADIO ELECTRO EWS and 7 Stare Outlets to speed orders

* * * * 29 YEARS SERVING & SAVING MONEY AND TIME FOR 500,000 HAPPY CUSTOMERS * * * * FREE! GET YOURS QUICK! (IF YOU DELAY THERE MAY BE NO YE LEFT_ SO MA IL COIIPOIV NOW!) SUPERB CHASSIS BRINGS WIDE ACCLAIM NEW 1950 CATALOG GOING FAST COMPLETE AM -FM RADIO 164 PAGE BOOK Static -Free FM Brimful of Best Buys in

8 Tube Superhet J TELEVISION 10 Inch Speaker J AM IL FM RADIOS J HI -FI SYSTEMS J PA EQUIPMENT ONLY $47 50 with Tubes J ELECTRON TUBES J RADIO PARTS Here's a powerful, deluxe FM-AM chassis that brings in regular broad. cast programs plus brilliant, staticles FM - a two-band receiver for J HAM EQUIPMENT the price of one) This complete unit includes e built -in power supply, J PHONOGRAPHS 10 speaker and loop antenna for AM reception...ready for installation in. a suitable cabinet. Highly selective and sensitive circuit covers J APPLIANCES 550-1600 KC and 88-108 MC bands. Connection is provided for an ex- ~*w44. ternal FM antenna, and an input jack for record player attachment. He J TEST EQUIPMENT °^w,y ^¡;r 3- position tone control. Tubes: 12AT7, 6BE6, (2) 6BA6, 6AQ5, 6AT6, J XMAS GIFT IDEAS 6X4 for 110v. AC. 6AL5, rectifier 50/60 cycles Plus 1N820R -With Tubes...Shipping Weight 20 lbs ...... 47.50 A BIG 16 PAGE BARGAIN SECTION HI-FI MADE EASY FM -TV SWEEP GENERATOR Every mail brings us hun- the vast electronic field. with SPEAKER COMBINATION dreds of new requests for Mail coupon for yours NOW WOOFER -TWEETER $20.36 this latest and greatest - also start saving money at once by using the coupon (Available Separately) Lafayette Catalog - bulging with the biggest to order items on this page. 12 "WOOFER bargains we've EVER offered in over Remember, Lafayette's fa PM dynamic with mous 30 -day money 29 years of leadership in -bock I voice coil; 6- guarantee insures your satis- 8 ohms imped- the rodio industry. it's ance. 6.8 ox Al- - faction!Get your FREE copy nico magnet. Ca- practically a free encyclo- before this edition is ex- pcity 14 -18 Complete FM-TV frequency cov- pedia of everything new in exhausted. watts. erage from 2 -227 MC on 3 bands. Sweep width 500 KC to 10 MC. 99N710R 5.95 Dial calibrated directly in fre- TYPICAL CATALOG BARGAIN HAS MANY USES

quency. Maximum output 500,000 TWEETER microvolts. Built -in power line 5 TUBE HIGH GAIN PRE -AMPLIFIER High Freq. Adaptor filter. Generator output can be Response over used either FM or pure RF. 105- 5 -tube, four stage preamp. In. ONLY 15,000 cycles. 125 volts, 50/60 cycles AC. Steel put suitable for high impedance cabinet finished in gray wrinkle low output pickups and high in r Impedance (units pedance mikes. lias single cin,. in series) 6 -8 enamel. Stpg. Wt. 16 lbs. .$X95,` ohms. Power cuit mike jack, volume and tone VVV rat- 25N21736R 34.95 control and replaceable fuse. ing 8 Watts. Sup- Shipping Weight: 10 plied with mount- lbs. screen for 12 ELECTROLYTIC speaker. No filter 99N9604R -Less Tube...8.95 network or additional space re- CONDENSER SPECIALS IMP quired. i, 1« 22N19384R -Wt. 3 lbs 14.41 SI ter DUAL SPEED ADAPTOR 1 LAFAYETTE RADIO, Dept JI.9 Adapts Prong Mounting Can Type 901 %. Jackson Blvd., Chicago 7 stand- 100 Sixth Avenue, New York 1S armed 78 RPM Each 25C 10 for $2.2S record Check here for FREE Catalog (Please don't check if player for Stock No. Capoc..r Mid. Vol soa. you already have the new 45 your catalog.) and 33 1/3 .1 , 99N34e2F 30.5: 25'ICC ... .. IC Please fill attached order.) enclose $ RPM records. Kit includes speed 99N3494F 10-10.70/2C 450.'S`.: :. in post- reducing table, special 99N3491R 10.30.15/30 45 5. al note, money order or check. (Include estimated assembly and pickup. shipping on 99N3469R 30/20'20 350/300 25C charges based weight and zone.Overpay- ments promptly refunded). 34N22610R -Wt. 5 lbs 11.95 99N 3441 R 30.50' 100 150.'21 NAME SHOP IN PERSON AT LAFAYETTE OUTLETS NEW YORK: 100 Sixth Avenue & 542 E. Fordham Rd.(Bronx) ADDRESS CHICAGO:901 W. Jackson Blvd. NEWARK:24 Central Ave. BOSTON: 110 Federal St. ATLANTA: 265 Peachtree St. CITY ZONE...STATE

DECEMBER, 1949 Servicing MID- AMERICA'S UNBEATABLE Intermittent Filaments

LOW PRICES By DAVE GNESSIN Terrific Value! REMOTE CONTROL & INTERCOM MAnli 56.95 , !nil ml Eolio THE elusive intermittent is the series filaments, both terminals of the Eitbri main [ono,r tun; bane of the serviceman's life. It neon bulb across the open filament are ed above may be used lu operate. modu- follows no rules and keeps no at full line potential (117 volts). The late ul Illullilur radio hours. The raucous noise that ema- neon tube immediately ignites and stays sels. Interphone Pro- vided 1 r the two units over distances tip to I. nates from the rear of most service lit as long as the filament of its asso- mac! 1{t.n'lh ing brand new and in original park. ang; Imitate. 01811111.11011 laalks for operation and shops is due largely to receivers operat- ciated tube is open. maintenance and data -strong canvas ma rryhma case -blast in normal Note only the neon hq which y ai'll rind a nu ltitudeof uses. Set r ing open, full (just as that lamp across with sternal, 1 I a plate load relay. cords operation in the home!) in the hope that the open filament lights. The other in- IPI l fi arrsgand 1'1. -551plugs. sealed suant transformera, 'her tine. parla. Required for operation but not sup - the intermittent may be at least located, dicators still have low- resistance fila- 44-41 a ninexpensive T -1: nt niphonea. headsets PC from ordinary flashlight tells. Main if not repaired. Many's the kilowatt ments across them, shorting them out of St_'x4 41. -x4 s. -; ante measurea the It's a bargain for luban.tn and expert- consumed by electric radiant heaters circuit. Thus the open circuit, ,,,,L quantity a,.4; hi+.. operating on radio equipment on the whether intermittent or permanent, is T -17 service bench, in the hope that applying immediately marked. Remove the lit MICROPHONES excess heat will open up the intermit- neon adapter and faulty tube. Replace tent. the faulty tube. Now watch the circuit MA1601 ..69c Famous earhon Like the poor, the intermittent will for a while to see if any other neon in- mike with 01111t- in hiss probably always be with us. But the dicator flashes. If all is quiet, the lateh ruolito -talk button In handle; 5-foot rubber covered cable with PL -6S plug. Used but recondi- malady will prove less virulent if we trouble has been spotted and repaired. tioned and a great buy at our rink-bril tole low price. (in -at for imialeur mobile equipment. PA and for attack the disease with all the weapons 41.r will, CC-261 above at hand. TINY 60 RPM One such weapon is described here. Synchronous Motor Its purpose is to indicate immediately when a tube filament is open, be it even M A 1723 $1.89 for a period hardly long enough for the TaBE 1 - J by model makers. display NEON manor:tourers. etc Turns at 60 receiver to go dead, cool off, and then let ltisi with 26 -I(5 colt. 60 cycle topul. operates aura 110 -120 volt the filament wires fall together again. At' wilt transformer w supply. This condition accounts for a fair pro- 1,5- deep with 1a.' diaun ter; has ' shoal 1- lung. Made by Cramer and worth far more than our low portion- though by no means a major - price for both units. ity-of intermittents, and represents a ADAPTER Universal type very hard to find. Matching Transformer CABLE BROUGHT iNvO r SOCRE T Other uses will be found for the de- ADAPTER ON AErwar SIDE which in TO BE NEAR fILSOtNT P1ó5 MA -2597 89c vice, such as indicating tube a series filament string is open. This Baled 25 watts with c'i ro i fre- 1 quency range to 10.000 IPS. ylatrhes quick technique might be applied as speaker voice colle from 3 to 15 ohms with line ina- pt danres from 50 to 0400 ohms in eight steps: Maher to all transformerless standard practice Fig. 1 tube tattoos possible by parelleling taps. widely used -A in the adapter assembly. o f line or plate lo robe roil circuits. Shielded and receivers arriving at the shop with fila- net irally sealed: measures only 3-x2%:13.'. ments out. -way 1 v Maint for set -builders, sus icemen. experimenters, Two octal and other adaptors are An octal (or loctal or .niniature) available. They,come apart for wiring. F _ Big Savings! adapter, with prongs on the bottom and It may be necessary to drill a hole in MATCHED PAIR an octal (or boas! or miniature) socket the cover of the assembly to accommo- IF TRANSFORMERS on top is opened to admit the pair of date the neon-indicator wiring. If no N(' for aupr sets. 24$- high. 11,- square. pad' lug rotang. Color coded leads. wires from a miniature neon test light. adapters are available, they can be MA-502235 Il Input 29x( \latched This pair is connected to the filament MA- 502236- OUlput 29e1 l'air 45c home -made, using old tube bases and 455 Kt' standard. 3- high. I3.- sq. Spade lugs. prongs. (Different tubes have different sockets. Make them sturdy; they will Coded leads. Input IF with grid cap lead. filament terminals. Adapters should be undoubtedly be plugged in and out MA-502222-23 N.nrhr -I F.1 Ni'-IF pair, only 49C prepared and marked on the base for very frequently. STANCOR TELEMATCH ready identification). A whole set, cer- ford tu be made NEON NEON Regular Lot $1.95 tainly no less than six, should NEON NOW ONLY up. 1''eri by TV set owners everywhere! Increases an- eltai ncy, minimizes ghost hnages, rejects ad- In using the device, the tube is re- vent channel interference. .Attaches to antenna t ats of set with 300 -olnn twin lead provided; moved from its socket and the correct hat's all there is to installation! Brand new. oral- is a.' display canons; complete with Instructions. neon adapter is plugged in. The tube then inserted into the adapter, with the

STANDARD MICA CONDENSERS neon indicator hanging out. See Fig. 1 11V5< Bargain Low fric r -10c Falb for the setup. This is done for all the 25 of One Type for $2.00 50 of One Type for 3.49 tubes in the receiver. Fig. 2 shows the 100 of One Type for 5.69 ron01'. .151004 .1100 12 .1111117 .0033 application to three tubes; it holds for Fig. 2 -Lamp shows up the had filament. .000041 .1141022 .0006 .11116 are in the receiver .00006 .01013 .ont 011116 as many tubes as .4100066 .00066 .002 being tested. This information is made available The neon indica- with the permission of Fred Colton, ORDER FROM THIS AD! How does it work? 90 volts. tube who has used the procedure for some All prices f.o.b. Chicago. 25u0 deposit required on tors fire at about Since C.O.D.. orders. pay balance plus postage on delivery. high, the indi- time in his Columbus, Ohio, service shop. order filaments don't rate that Send orders to Desk RC - 129. Minimum $2.50. cators normally will not ignite. When (Another quick way of checking a filament string is to measure ' they don't light up, they don't draw cur - suspected MIDAME rent. Hence, they will not affect normal all filament voltages with an a.c. volt- operation. If one tube is open, as in Fig. meter. An abnormal tube will often 5405E WARENOUSt 3, the filament string is broken. The show surprisingly (to the uninitiated) 2412 S. Michigan Are. 2307 S. Archer Ave. high low voltage across the filament. Chicago 1e, in Chic,* IS. III. series filaments will not light. or \\'ith no current flowing through the -Editor.) RADIO- ELECTRONICS for 57

INDIANAPOLIS ESSE RADIO CO. INDIANA sse s Specccr - Wer HASH FILTER ESSE Mounted on strip 31/2" x I ". Contains two hash WILL BUY ANYTHING ELECTRONIC chokes & one dual .35 MFD 400 Volt bathtub Attention Factories, Hams, Dealers, Individuals condenser. Price ...... 50 .. . just Auybod3 Some of the equipment listed below is urgently needed by our company to meet the demands of customers and we will pay the highest cash prices. Send letter with full description describing condition and quote price. We will immediately answer and if we can use your equipment, we will authorize you to send it to us COD. We are dealers in surplus electronics and we are interested in anyttiing dealing with radio or television. We are especially inter- APQ -9 RECTIFIER -POWER UNIT ested in large quantities of surplus and anything that can be PP -5I

400 cycle I I5 V. Contains 4 -5R4GY tubes, bought at a bargain price. Please don't hesitate to write us im- 2-4 Mfd. 1000 V. DC condensers, 2 Mfd. 1500 V. us what have -I mediately. Quote prices on you and give us a full DC condensers, 400 -2600 cycle transformers, pow- detailed description. We will not answer any letter unless deer resistors. etc. Weight 38 lbs. Size 2I "L x

scription and price is quoted. 5 -I /3 "W x 75,4' H .. . S4.95 WE NEED AT ONCE! We Are Especially Interested in Large Quantities BC -348 Receivers, AC or DC models Large stocks of condensers EC -312 Receivers Large stocks of resistors BC -22I Frequency Meters Large stocks of speakers BC -224 Receivers SCR -522 Transmitters & Receivers BC -342 Receivers Hallicrafters BC -610 Transmitters TURBO AMPLIFIER Police type VHF transmitters and re- Any factory built transmitters and receivers for mobile application Used for ports- shipped complete with the fol- ceivers such os Hallicrafters, Na- lowing tubes: 2- 7C5's, I -7Y4, I -7F7. tional, Temco, Collins, RCA, RME, Collins ART -13 Transmitters Price 51.00 ea. Hommerlund, Millen, Meck, Har- A PS -13's vey- Wells, Meissner, Sonar, Mc- SCR -269F or G Fairchild or Bendix BC TRANSMITTER AND Murdo- Silver, Gonset, Stancor, Bud, ADF's -1158 etc. Headphones in quantify lots MODULATOR for Amateur or commercial sets Microphones in quantity lots Mode by Bendy airborne operation. Designed for remote control. Power source 28 V. DC input stocks large of tubes Field telephones (not included ). Operates in any place in the Large stocks of transformers Sound -powered telephones 53 -60 Mc. and 80 -88 Mc. frequency band. Is crystal controlled (crystals not included). Has We are especially interested in any factories, dealers or other outlets giving RF stages, amplifier and driver section, contains us a list of surplus electronic equipment that is for sole so that we may submit 4-815's and 10 -12SN7 tubes, I -0/150 DC milliamp our bid. Weston meter which can be switched to various circuits. Hos exhaust fan for ventilation. Can easily be converted to operate on several fre- AUTOMATIC DIRECTION FINDER BC -221 FREQUENCY METER quency bands. Size 12" x 8" x 18 ". 45 lbs. Limited Covers 125- 20,000 Kc. Battery or 110 V. quantity 527.50 RADIO COMPASS SCR -269 -G AC or vibra -pack operated. A beautiful Brand new in origins crates. Made by Bendix. Complete, a truly magnificent buy for airplane instrument. The finest we hove ever had. owners or boat owners $125.50 569.50 A TREMENDOUS BARGAIN Quartz Crystals without Holders CABLE CONNECTORS AND PLUGS Get an assortment of these and grind to your own frequencies or use them they are. .5x.6" Choice .25 - All Brand New as B -cut lopped faces Manufacturer Type Price on and squared on edges. Ampheno ... AN3101-16-10P 25c each (Ready to use). We will give you an assort. Ampheno ... AN3101,18-18S 2Sc each ment of these from approximately 13 thou- Ampheno .. AN3101-22-5S 25c each sandths of on inch to 24 thousandths of an inch Ampheno . . AN3102-22-15P 25c each Ampheno AN3102-28-10P 25c each whereby you can grind to frequencies desired.

Ampheno ...... AN3102-32-5P 25c each T-11 -B Carbon These crystals are now ground to the approxi- Ampheno ... . AN3106-18-115 25c each mate following frequencies: Ampheno _. AN3106-18-18P 25c each Microphones Ampheno AN3106.24-6S 25c each (Handmike) (New) 3880 4640 6225 7300 Ampheno .. AN3106-24-7P 25c each $1.75 3900 4900 6275 7400 Ampheno AN3106-32-SS 25c each Army Phones Harwood. AN3-08.145-e 25c each 4140 5300 6700 7500 Aero...... AN3108.145-2S 25c each Low Impedance 4600 5580 6850 7800 AN3108-14S-2S 25c each Cannon. Used. With short cord and plug 4650 5800 6900 7900 Amphenol . . AN3108.14S-25 25c each PL -354 and cushions. Amphenol _ .. . AN3108.18-12P 25c each Price $2.50 Formula for converting thicknesses of B -cut Amphenol. .... AN3108-22-5S 25c each crystals to frequency is as follows: Frz98.4 /T Cannon...... AN3108-22-55 25c each Magnesxn Indicator

. F Amphenol . . . AN3108-24-6P 25c each To be used for beam antenna. where is frequency in kilocycles and T is thick- Amphenol AN3108-24-16S 25c each Practically same os I -BI -A Selsyn ness in inches. Cannon...... AN3108-24-16S 25c each indicator. 15 -25 V. 60 cycle AC. Arnphenol _..... AN3108.32-5P 25c each 3" size. AN ASSORTMENT OF 20 Amphenol .. AN3108.28-10P 25c Excellent each condition $1.25 ea. DIFFERENT THICKNESSES . 51.50 Pwg for connection .50

DECEMBER, 1949 ei3t t$Sf skedatli

SCR -625 MINE DETECTOR Brand New Metallic Objects Only Used by the Army to detect buried metallic mines. Its private use suggests the location of underground or underwater pipes, cables and ore bearing rock, the location of metallic fragments in scrap materials, logs, etc., and the screening of personnel in plants for carrying of metallic objects. Here's a Special Bargain The unit consists of a balanced inductance bridge, a two -tube amp. and a 1,000 cycle oscillator. The presence of metal disturbs the bridge bolanc, we are able to offer to resulting in a volume change of the 1,000 cycle tone. The tubes used are INS. The circuit may be modified & Cus- low- battery drain types such as IG6 and our many Friends for control of warning signals, stopping of machinery, etc., when metal is tomers: the famous HER detected. Operates from two flashlight batteries and 103 V. "B ". However, a power supply operating from 110 V. may be used. Comes complete with MAJESTY" soore tubes. spare resonator and instruction manual -in wooden chest 81/4 "1281/4 "x16 ". Weight in operation is 15 lbs. New, complete in original overseas pocking container. Originally sold by War Assets for 5166.00. The U. S. Forestry Service has recommended procedure for using the SCR - AUTOMATIC 625 Mine Detector to find concealed metal in tree logs and other timber products. Price $59.50 1

DISHWASHER Batteries - $4.00 extra Clean. Sparkling Dishes in 2 Minutes Flat Now you cars free yourself of the everlasting drudgery of Tetrad 18 -A Frequency Standard 'em in "Her Majesty" washing dirty, greasy dishes! Just put Checks signals in the ronge of 100 Kc. to 45 and forget TELRAD Automatic Dishwasher for a couple of minutes Mc. with a high degree of accuracy. Self - 'em! No more chopped, dishpan hands, no more dirty dish contained power supply is 110, 130, 150, 223, re towels! Not only does Her Majesty" save you lots of time and 250 V 25 -60 cycle AC. Complete with and trouble, but it saves on soap. Just o thimbleful of deter- tubes, dual crystal and instruction book. gent does the trick ... thoroughly! You'll be amazed ... and Brand new. Price $24.95 delighted at the job "Her Majesty" does. "HER MAJESTY" DISHWASHERS NOW GIVEN AWAY ON THESE COAST - RF TRANSFORMER TO -COAST RADIO PROGRAMS: For experimental use. Covers four bonds. Trove!e," -Times o "Second Honeymoon," "Welcome Range unknown. Measures 4" s 47/r" s 21/4". Wasting," "Take o Number Brand new. Price $.50 A Wonderful Xmas $20.00 ven e. celeste Gift for her . . . each COLLINS AN /ART -13 XMTR. This is the most stupendous Look at these A compact, lightweight, modern, highpowered transmitter. Frequency bargain that we've ever of- Sensational Features range 2.113-1 Mc. on any of its II auto -tune crystal controlled or master fered. These dishwashers were Dishes Dry by Themselves! as channels. Dec. 1947 "Radio" gives conversion data for convert. V. made to sell for many, many Easy to Use -Slip hose on V. in fine con. tested in our faucet . . put in dishes DC operation to 110 AC ore exceptionally more dollars thon what we are turn on the water! lobs. Weight. (Dynamotor included) $234.50 asking. They are brand new: in Fits on Droinboard fact, still packed in shipping Holds 16 Dishes at once Extra Basket for cups, BL- SELENIUM RECTIFIER boxes. saucers and silverware. 2 these for full -wave circuit converting Because of the low price that No Motor . . No Electricity Type 23751, holf -wave. Use of we are selling these dishwashers . No Expensive Plumbing! 110 V. AC to 135 V. DC at .75 amps. or parallel for higher current Light Weight (only 12 lbs.) we absolutely do not offer ratings. Voltage output controlled by condenser across output. for, Rust - Proof Aluminum with any guarantee or refund what- Baked -on Finish. Brand new. Price..... _. $1.75 ea. soever. Double-Action Spray.

RECORDER COMBINATION AUTOMATIC RECORD CHANGER 4 MODEL GI -130 or RC130L play records, cut records Manufactured by General Industries Corn- pony, this unit is ideally suited for installation in your phono-combination or can be used with any amplifier having approximately 5 watts output (although a power level of approximately 1/4 watts is all that is required for satisfactory cutter operation). Cutter head is an Astatic Crystal X -26. Record player mechanism is automatic and plays twelve 10 -inch records or ten I2 -inch records. Pick -up head is a sure crystal. These mechanisms are brand new in original shipping boxes and we are selling them at a fraction of their original cost (original price $79.50). Our Price, complete with operating and service manual, brand new, Close -out sale. ESSE RADIO CO., 40 W. South St., Indianapolis, Ind.

RADIO -ELECTRONICS for 59

INDIANAPOLIS, ESSE RADIO CO. ¿iie$ Specta t Offer INDIANA 15 WATT POWER AMPLIFIER UNIT -Brand New

line -up is I -2D21, I -6AL5, I -6SJ7, I -6SN7, 2-

6L6G's, I -5U4G. The total power drain is 300 watts

from the I IO V. 60 cycle AC power source. Treble, bass, vernier volume and master volume controls are provided. This amplifier is beautifully designed and is sturdily constructed with the best of components. It can be used for continuous day and night service. Deluxe features such os high -low AC line switch, AC line fuse, good ventilation of chassis and cover, external carrying handles, lock and key, and heavy duty AC line cord are provided.

You can use this unit for microphone, phonograph, or radio input or fix it for combinations of such inputs. It will make an Model F Power Amplifier Unit manufactured by excellent foolproof and Personal Music Company, Newark, New Jersey. trouble -free unit for dance bands, lecture halls, Formerly sold to jobbers at $129.50 each. schools, sports events, for rental purposes, for inter- office communication. It will handle a number of Chassis size 1 11/2" x 171/2" x 21/2" high (with cover loudspeakers. Originally sold for $129.50. Our price 111/2" x 171/2" x 71/2" high). Net weight about 50 lbs. Gray crackle finish. This amplifier delivers 15 watts of undistorted audio $3 Brand New power with excellent frequency response. The tube 5.0° Complete RADIO TUBES 38c ea. Your choice in quantifies of 1000 Brand New. Individually, attractively boxed. Un- Your choice. Mix up the types, we don't care. conditionally guaranteed against anything except Price each $ 50 breakage, for 90 days. Any tubes found not satis- 100 or more 45 ea. 250 or more 42 ea. factory, return to us for credit. 1000 or more 38 ea.

OZ4 2A7 6AK5 6K6 617 2AT7 25N7 37 84/6Z4 MGT 3A4 6A L5 61(7 6T8 2AU6 2507 38 85 A7GT 3A5 6AOS 6K7G 6U6G 2AU7 25R7 39/44 89 B5 387 6AT6 6K8 6U6GT 2AV6 207 40 117P7 CSGT 3D6 6AU6 6L6 6U7 2AX7 2Z3 41 .117Z3 C6 304 6AV6 6L7 6v6 28A6 4A7 42 I17Z6 DB 305 684G 6N7 6W4 28A7 407 43 VR90 G4 354 688 6P5GT 6W7 28E6 4X7 46 1619 HS 3V4 6BA6 607 6X4 28F7 9 47 VR ISO H5GT 5FP7 6BA7 6R7 6X5 2C8 918 50 1828 16 5R4G 68E6 6S7 6Y6 2F5 14A 5085 183 16G ST4 68F6 6S7G 6Y7 2H6 25A6 SOCS 4828 L4 5140 6806G 658 6ZYS 215 25AC5 SOY6 483 LC6 5U4G 68H6 65A7 7A4 117 2516 51 954 LH4 5V4 6816 6507 7A7 2K7 25Z6 53 717A LN5 SW4GT 6C4 6SD7 7A8 2K8 26 56 955 NS 5X4 6C5 6SF5 786 207 27 57 956 05 5Y3G1 6C80 6507 7C4 2SA7 30 58 957 R4 5Y4G 6D6 6S H7 7C5 201/7ES 31 70L7GT 1005 RS 523 6D8 6517 7F7 258 3217 71A 1626 55 5Z4 6F5 65K7 7H7 2507 35 75 1629 14 6A3 6E6 6SL7 7Y4 25E5 35/51 76 2051 Ts 6A4 6F8 6SN7 7Z4 25F7 3585 77 2050 U4 6A6 61-16 6507 IOY 2SG7 35W4 78 9003 US 6A8GT 615 65127 12A6 2SH7 35Z5 80 CW931 V 6ACSGT 616 6SS7 12A8 2517 35Z6 81 307A 2A5 6AF6G 617 6517 12AT6 2SK7 36 83 9001 2A6 6A GS 618 6SU7

Unless Otherwise Stated, All of This Equipment Is Sold As Used CASH REQUIRED 40 W. South St. WITH ALL ORDERS $1449(1. Orders Shipped F.O.B. Collect Indianapolis 4, Ind. DECEMBER, 1949 Servicing

The Intermittent Headache

By MAX ALTH

NOTHING on a service bench will change in the set's output, or may even turn a man's liver a brighter cut the oscillator off completely. shade of green than will an in- When you have cleared the installa- termittent receiver. Other prob- tion of suspicion, then everything else lems can be solved with time, special is suspect, including the extension equipment, money, and even with sweat speakers, record player attachments, -but the only things to which an inter- telephone cutoffs, etc. First consider the mittent radio respond are hair tearing, chassis in relation to its cabinet. Some- nail biting, and tears. one may have stuffed papers inside, This is the case inevitably whenever causing the temperature to go too high. the service technician uses the wrong Anything can have happened, including approach. But there is a right one. a visit from a family of mice. It is very The very first thing to do when set will well on MICHAEL S. COLAIANNI, a possible that the play customer says, "My radio set fades," is where, well ventilated, Globe Radio and Electronic Co. your bench it to rush out of his house and get your- ope.ates relatively cool. Won't you be "I got a New Deal when I modern - self a Sherlock Holmes hat the the embarrassed one when you return red my service shop through the -that's N.U. Dealer Equipment Plan double-ended job in green plaid-and a the set, and it still fades, running hot . best of all AT NO COST meerschaum pipe. The second thing to in its cabinet? If possible, take the cab- TO ME. My new equipment helped increase do is to return to the scene of the inet to the shop with you. If not, run radio and TV service crime, slip your feet under the Morris set, of its and sitting on earnings and brought the out cabinet in new business too. chair, and prod the victim into talking. the floor, and see what happens. Now that 1 know Let him talk all he wants, but don't Bear in mind during all these she- about the N.U. Plan, I'll get all my equip- believe a word he says. Then tell him, nanigans that you are not trying to be ment this easy way." "Show me." Get him to turn the set on the fair- haired boy of the radio service ... tune in the disappearing radio pro- world, but that you are trying to sim- gram. Then wait for it to fade. plify and localize your trouble by elim- Sure! Mr. Colaianni is All this may seem a silly waste of inating one possible source of fading enthusiastic about the time, but believe me it is not. The prob- after another. N.U. Dealer Equipment lem of locating the causes of fading Plan ... just as enthu- and intermittency is one of detection; Up fo this point: siastic as thousands of and, if a Sherlock Holmes hat and pipe You have established by personal ob- other service tech- will help you think and act like a de- servation that an actual defect exists. nicians throughout the tective-go get them! You have cleared the installation. U.S.A. who were award- Make certain that the set actually You have cleared the line voltage. fades, and that it is not tuned to a You have cleared the chassis -cabinet ed equipment ... at no weak dx station which carries a pro- cost. combination. gram similar to the local one, and You know that a defect exists in the whose fading is caused by normal con- Now! Any Serviceman Can Get New set proper -the chassis. ditions outside the set. Do not yank the set until you have Equipment Thru the N.U. Dealer If the set doesn't fade in your pres- made all the foregoing checks. Equipment Plan ence, you can suggest to the customer When you do take the set to the shop, that he wait until the fading becomes do so very carefully as not to jar it All YOU need do is tell your more pronounced, in which case your into normal operation accidentally. If N.U. Distributor, "I want to go job will be much easier and you will be you do jar the set, you won't know on the N.U. Dealer Equipment able to charge much less for the repair. what's up when you get it on the bench; Plan." Select the equipment Assuming that the customer's set and what's worse, you may jar the set you want from your N.U. Dis- really does fade, you may have a suspi- again on returning it -and start it tributor's stock get on -the- cion as to what is causing it. Keep your fading again! (Continued on page 62) ... is where spot delivery and your day - suspicions to yourself! This ... many a good radio technician goes by -day purchases of N.U. Tubes wrong. Your guess may be very good automatically make it yours: - but don't yank the set until you are cer- ANNUM. N.U. has household, sports tain the trouble is not due to the RfOTO and travel gifts for you too ... installation. CONTEST same under the plan. Maybe it's not the set Notional Union takes the money that ordinarily goes for extr t consumer mag- The fade may be caused by a defec- azine advertising and gives it to you in the form of vital service equipment and valuable tive antenna, a loose ground connection, luxury gifts. or even a low and changing line volt- Use Premium Quality N.U. Tubes age. Make certain of it by disconnect- and Build a Bigger -Better Business ing the antenna and using a length of bell wire as a temporary antenna, for example. Disconnect the ground completely, and put a voltmeter across the 0-2 See Ilim or write us today line when the set is at its nadir. A radio will play very nicely when the line voltage is high. But, when the line voltage Suagretrd by Arthur A. Henrikeon, Chicago. IU. NATIONAL UNION RADIO CORPORATION is low, there is a critical point at which "See dear! I told you our television set a slight variation will make a great would pay off!" RADIO -ELECTRONICS for li 1

ALLIED is your leading supplier of NATIONAL

the world's greatest communications receiver dfo VALUES!

BUY ON RADIO'S MOST LIBERAL TERMS k -"NC-57 ONLY 95 AMAZING ALL -WAVE DOWN RECEIVER VALUE

A popular communications receiver for Amateur or SWL- featuring famous National performance at low cost. Tunes 540 kc to 55 mc continuously for broad- 4t' cast and world -wide short -wave reception. Frequency ONLY bands: 540 kc to 1.6 mc; 1.6 to 4.65 mc; 4.65 to 13.5 mc; 13.5 to 35.0 mc; 35 to 55 mc; (tunes Amateur 6 meter band). Features: calibrated main and electrical bandspread dials; RF trimmer; noise limiter; adjustable beat oscillator; 3- position tone control; relay 575DOWN terminals; "S" meter socket; universal antenna input; NC-33 SENSATIONAL voltage -regulated converter, oscillator and RF circuits; built -in PM speaker; standby Switch; 2,1/2 watts LOW -COST PROFESSIONAL MODEL audio output. Uses following tubes: 6SG7 RF, 6SB7Y converter, 2 -6SG7 IF's, 6H6 ANL -2nd det. -AVC, Here is the highest -quality communications receiver ever available 6SN7GT 1st audio -BFO. 6V6GT audio output; VR at so low a price! Here's the most for your money in every way! 150 voltage reg. and 5Y3GT rect. Steel cabinet fin- Four band tuning covers 500 kc to 35 mc continuously: band D. 500 -1420 kc; Band C. 1420 -4200 kc; Band B, 4.0 -12.0 mc; Band A. ished in smooth gray; 16!,.¡" x 83.¡" x 11h ". For 105- 12.0 -35.0 mc. Separate main tuning and bandspread dials provide 130 v., 50 -60 cycles AC. Complete with tubes. Shpg. either general coverage or bandspread for any portion of any fre- wt., 33 lbs. $8950 quency range. Modern circuit uses: 12SA7 converter, 12SG7 IF 97 -595. Cash Price F.O.B. Chicago amplifier, 12H6 2nd. det.- AVC -noise limiter, 12SL7GT 1st audio and beat oscillator, and a 35L6GT audio output. Uses 1- 35Z5GT Terms: $8.95 down, $7.12 monthly for 12 months. rectifier. Professional features include: automatic noise limiter, code -phone switch, band -selector, adjustable pitch beat oscillator, headphone jack, built -in 5' PM speaker, and universal input for single wire or doublet antenna. Calibrated main tuning has all important amateur, police, and FOR YOUR foreign broadcast bands plainly marked. The NC -33 is finished in SEND smooth gray enamel, with glareless translucent dials, and chrome 1950 196 -PAGE trim. Size. 16 9t,'x 83," x 812'. Operates from 105 -125 volts, 40 -60 cycles, AC, or 105 -125 volts DC. Shpg. wt., 18 lbs. $5750 CATALOG 97 -596. Cash Price, F.O.B. Chicago ALLIED Terms: $5.75 down, $5.49 monthly for 10 months. Buying Guide du-..d eed Radio's leading ALLIED RADIO CORP., Dept. 2 -MM -9 Buying Guide Radio all of 833 W. Jackson Blvd., Chicago 7, Illinois Get the only complete that fills one book sup- in the field -the Electronic and at Enter order for National Model your Radio, Television advantage Get every buying Enclosed Full Payment ply needs! stocks of quality --world's largest prices ALLIED $ Part Payment. Balance C.O.D. ALLIED of lowest moneysaving atten- equipment personal Send Time Payment Form expert shipment, order. _speedy, on every Send FREE 196 -Page ALLIED Catalog complete satisfaction today! tion, ALLIED Catalog Get your FREE RADIO Name Address City Zone State

DECEMBER, 1949 62 Servicing (Continued front page 60) A number of tools on the market are designed to aid in the servicing of fading radios. The best of them is perhaps the Chanalyst, or channel analyzer. This five -eyed monster that never sleeps can watch five sections of your radio for you. In effect, it is five vacuum - tube voltmeters. You hook one section 40UTSTAND G of it to each section of your set, and let her rip. When the set cuts out, you ONLY $8299 IS THE COST look into the electric eyes, and learn for the sensational -new- improved immediately whether it's the r.f., mixer, T E L E K I T i.f., output, or power supply that has lain clown on the job. TELEVISION KIT While this instrument is very good, a Operates the IO ". 12 ". IV2. IS' and Ifi" picture tube. better instrument is still that brain Complete with new builtin- pretuned and aligned 13 supposedly lodged channel tuner, all parts and easy step-by -step inslruc beneath that detec- lions and schematics. $82.99 less tubes, complete set of tive cap. Even after the Chanalyst has tubes. including 10 BPI picture tube $49.50, special designed 10' cabinet $21.50. put the finger on the fading stage, or An surtaxing value, even a beginner can assemble one of group of stages, you still have these fine, new, improved television kits. Uses the new I I to locate channel tuner, prewired and factory aligned for the en- the offending capacitor, coil, solder, tire television spectrum. Highest quality parts and excel. Same quality and tea ures tor 7' lent Circuit assure perfect performance. Circuit desi gnrn joint, wire, rosin drop, or whatever is stage. oscil. k it. complete, less tubes ó59U.5i by outstanding TV engineers. Contains RF lator and mixer. Uses new IF coils, providing maximum causing the trouble. That component Complete with tubes. $99.50. special designed pain and picture definition. Sound reception is high may well be cabinet ...... $19.50 quality FM for years of listening pleasure. in another portion of the circuit. And very often, the set will THE MODEL 999 -A COMBINATION leap back into action when you try to clip the test lead on the first suspected SIGNAL GENERATOR component and not fade again for several minutes, or in some horror cases, several hours. AND SIGNAL TRACER Signal Generator Specifications: Frequency Range? 150 Kilocycles to 50 Megacycles. The R.F. Signal A few possible clues Frequency is kept completely constant at all output levels. Modulation is accomplished by Grid -blocking action which is equally effective for The alignment of amplitude and frequency modulation as well as for tele- experienced technician can some- vision receivers. R. F. obtainable separately or modulated by the times guess Audio Frequency. the trouble by listening Signal Tracer Specifications: to the set cut in and out. Here are -Uses the new Sylvania IN34 Germanium crystal Diode which combined with a resistance -capacity some characteristic sounds, and their network pnvides a frequency range of 300 cycles causes: to 50 Megacycles. $2$NE85T The Model 999 comes complete with all test leads Breaks in the front end of the set, and operating instructions. ONLY antenna, and r.f. stages cut in and out THE NEW MODEL TC -75 TEST CRAFT with a cleanness, or lack of thump, A COMBINATION TEST which is very distinctive as compared to rear -end breaks. Breaks in the audio * & SIGNAL TRACER usually have a heavy- footed thumping ti SPEAKER accompanying them. plus speaker plus substitute 100 V. substitution D.C. power supply An oscillator cutting in and out can .a. plus resistor tester plus field substitutor be spotted by the signal's disappearing, plus condenser tester plus voice coil plus resistor substitution an increase of rush, and a seeping in of substitutor plus signal tracer all stations, especially if the set is plus an experimental one plus condenser substitutor stage audio amplifier tuned toward the high- frequency end 0 plus universal output of the broadcast plus output indicator band. }ransformer When $29 NET Complete including signal tracer probe and full Instructions. an r.f. stage cuts out on sets A must for every radio serviceman and engineer. having a.v.c., the signal may or may not hold its level, but the background CRAFT THE NEW MODEL TC -50 TEST noise may increase as the a.v.c. turns up the gain. The same thing happens when an i.f. stage cuts out. TUBE & SET TESTER When one of several audio stages A complete laboratory, all purpose test -instrument, cuts out, the set performs normally this versatile combination tube and set tester will with the exception of a great loss of tubes. The accurately test all up -to-date designed volume. is multimeter section affords many necessary measure- But the signal clear and un- ments for everyday's service work. distorted. Interstage coupling due to the existing wiring feeds some of the The New Modal TC -50 Tube and Set Tester combines seven instruments, D.C.V., A.C.V., D.C.M.A., Ohms. Out- energy around the dead stage, making put Meter, Decibel Meter and Tube Tester. Full scale it harder to locate the trouble. accuracy to 2%. English Reading GOOD and BAD scale If the set cuts out when the volume for testing tubes. Obsolescence reduced to absolute minimum. Simple and quick reading charts for tube is turned way up, very possibly the testing. Multimeter section affords most popular every - speaker voice -coil leads are making day's measurements. poor contact. If there is no hum what- be Complete with test leads, tube charts ever in the speaker, you can certain and oll detailed, operating instruc- 50 the break is there. When one or more of the filter capaci- tions. 39 NET Size 8" a 101/2" a 5" tors opens up, there will be-in addition to an increase in hum -the possi- Immediate delivery from stock. 20% /e deposit required on C.O.D. orders. bility of decrease in volume (due to a voltage) of audio METROPOLITAN ELECTRONICS & INSTRUMENTS COMPANY lowering of plate oscillation, motorboating, r.f. and i.f. 106 FIFTH AVE. DEPT. RC -12 NEW YORK 11, N. Y. oscillation, because of lack of the filter RADIO -ELECTRONICS for 63 hallicrafters 11 -TUBE FM AM CUSTOM CHASSIS ONLY $59.95 * WORLD'S FINEST CHASSIS VALUE, REGULAR NET WAS $110.00 * OUTPUT MATCHES 8 OHM VOICE COIL. * PRICE WITH 12" COAX. P. M. SPEAKER $69.95.

Model 5.55 Nallicrafters, 11 tube AM -FM radio receiver chassis for broadcast and FM 88 to Onler your S -56 complete with 108 1... Aut.matic frequency control on FM. holds the receiver in perfect t Phono co - 533.50 list Clnaudagraph 12 Inch co- rtlun`o of chassis. Full range tone control with bass boost. Push -pull OKB tubes ill axial PM speaker. Combined shipping audio system. a Frequency response essentially flat. from 5 to 14,000 CPS. Wide vision ecru. o weight 35 lbs. Both only rately calibrated slide rule dial, with preselection n /broadcast band. Output transforer for $69.95. nuncio., n PSI speaker. 4 antenna terminals. two for AM and two for FM. This is the i o that we know of balay. Better get y order in early. Designed to be .. :odic selling In the $400.00 to $000.00 class. The regular dealers net 110.00. However a lucky purchase enable. us to offer these brand n hot. Ildlicrafters chassis. complete with tubes and operating instructions! et S -56 Hltcrafter FM /AM custom chai. J on1, 559.95: ,'aker. Chassis size 123/4 x 10 k 73/4". Weight 12 lbs. Brand new factory sis. Matches any 8 ohm PM speaker. $ carte :e,l. Ito, your 5.56's with wide range 12' coaxial PM speaker. Both for Only $69.51. Only $59.95.

6 TUBE 8 -TUBE HALLICRAFTERS MODEL S -59 AC DC KIT COMPLETE WITH 12" COAXIAL SPEAKER $42.95 $9.95 Model S -39 Ilallirraflers, hich fidelity. S tube PM AM chassis, for custom 540 17011 ke and FM 88 to 108 mc. Size using pfulS siisel lui,eai used in a Farm installations. Receives broadcast to ItOr plastic cabinet. with .ode rule cal. 126_ x 71.:. x 9 ". An excellently engineered chassis, with accurately cali- t.f. stage, 2 gang condenser. loop antenna 60 14,000 CPS and 5 ,eaker. This makes factory like brated slide rule dial. Variable tone control and to wide range radio. The cadmium chassie is ready punched audio. 1Push -pull 6K6'sl 8 ohm output transformer will match most and sockets are installed. This type of kit fuusually sells for at least 515.00. All parte speakers. No special output transformer required. Loop antenna built on for rnishedd. including tubes: 121(4. 2.12SK' broadcast reception. Includes tubes: 2 -6BA6, 6BE6, 6AL5, 6SQ7, 2 -6K6 and 12.SR7. 351.8 and 3525. Complete with we diograme and photon. Kit M. +del P8.0. Wt. 5Y3. This is without a doubt the most radio chassis have ever been able to 8 lbs. .5.95 offer. Better rush your order now. We have them. Price less speaker $32.95.

S 8 tube custom 3 Hellirrafter -59. Hallierafter S -59. custom FM /AM -WAY- with Cinaudagraph FM /AM chassis. chassis. output matches any 8 ohm PICK ME UP 12 inch fidelity coaxial PM high PM speaker. Priced less speaker, speaker. BS pictured. Shipping weight PORTABLE shipping weight 18 lbs. Net $32.95. RADIO 28 lbs. Both for $42.95. ONLY ACCESSORIES FOR S- 5616S -59 CONSOLE CABINET FOR S -59 $19.95 $9.95 . \.l... a with micro. Beautiful blond consoleisole cabinet. 33' high. 17' front to hack and 21- I. ..`nick Up. Dual our. wide. The lower half Is Ser.tonal New 3Way Portable Radio Kit. in divided for record anion.. A hinged lid plua lvoredr an whoa to t. tin- nners the radio changer compartment. Changer apace 12 x 15'. leatherette` casse made ,.n,l:lI.'I.ut lacks for ' General Radio Is ready Electric varlal,le reluctance pickup and crystal or panel cut for the Hallierafter 5.50. Use any speaker by Farnsworth, o lid with loop antenna re d'y with t40 Stock built-in. Si. 5 9 a 6 -. Build yourself dynamic mike. This makes your 5.50 a home cut blond cabinet. professional looking raoradio w lh this kit. P. A. . nn : Iripnint weight 2 Ms. Sise fur Sh59,1 uncutunco r hanger boaN. Net x Every piece furnished Including tubes: 1115. 3 _ X I yx r1". Net $3.95. 1:M speaker $2.95 extra. 1T4. 185. and lh'y4. Il as ea to fol- broadfalt Shure 708A. regalar $22.00 lint crystal mike Stock No..111.55. above blond cabinet with blank radio panel (radio low diagram an This .wReceives dWith cord. S8 a'. extra. Adlustahle banquet type area S x 15 -, changer area 12 x 15'., Net SII1.95. two gap` euperttet. that"looks Ilk. 540.00 esk stand $2.95. .extra. Stock No. P.1000. above blond cabinet, changer area 15 s 15, radio area 5 x 15 ". e -din. We should ask 317.0., for this kit. Build over to suit your needs au record player or combination. However, lise 9rsduetloe makes tab 59.95 Net $14.95. possible. Stock No. EP-4X. complete kit le Wineries.. Shipping weight 9 luis. Set pria $9.95. Hit of betterles. 6713 TELEVISION MAGNIFIER volt R and 'A ". 53.13 ex t., "COAXIAL" $7.95 Regular $25.00 -FOR ONLY Reg BUILD YOUR OWN 532.50 stock Ni,. and oti vlsw,t Magnifier. rystal Il.il,rh s ti7'l i ailed. Magnifies List P.M. present 10- 12.inch television picture up to RADIO STATION four We ffer `you new factory SPEAKER magnifiers. You provide your own of mounting to MINIATURE TV ilue Y, uset cord. This lens[rIs`a $25.00 va Mat McGee s i BROADCAST offers it to you for only $7.05. When ordering. Include postage for 22 tbs. r t J STATION .c' " KIT 56.95 Sarkes Tarzian TELEVISION POWER TRANS. kit Model DK.OX. Bu..., $12" 110 Volt AC-DC 13 CHANNEL ilStales K , -i f,, n, $2.95 Crystal Mike or photo,, ,,I r, th,. T.Y. TUNER aVZ -50 Power Transformer. transmitterHitter must I vil . cis only a oho lion. ,. a nationally/ally known speaker rom- (- 04230'%. A 135 m tapped otherwise you will ",..oilcan( two or ONLY $7.95 110 volt primar. äänó,ilex pant'. I Response 40 CPS. three miles). Complete kit with tubes. dia- to 17.000 Just Sarkes- Tars,... 13 channel tuner for Tele. piffle voilag¢e and filament Trani and operating instructions. Weight 4 nmk in place of any 8 ohm PM speaker vision This 3 tube front rot is 1. p t f i' th T. V. Ms. Model 0F. -65. Net 59.93. wired, including tube sockets. The same TV jolts chassis. 375 volts D.C. 6.3 and have the finest tone quality. Shipping fallront end as used by several nationally known en t. A dJUhhe tepino . SW Minialitre Radio Trans. ze. S i. Model DE-6XWT weight 8 lbs. Struck No. CR In h miner wired ready u operate. Not 35.95. -13X. Net GgY %.8U T. V. Ofered ith printed schematic diagram. wérl5 t3/ Ill. ers Crystal Mike & Desk Stand $4.93 extra. 312.95. Two for $2a Priced complete` with 3 bes: fit '4 op 53.93 0005 mixer anand 0RH8 RF amplifier. This n t is worth twice , price. All wired. JEFFERSON T.Y. PWR. TRAN t Is be v 'Ideoochannel. COMPLETE AMPLIFIER KITS t, feil Inh, T.V. power Transformer, Imilar to Hi -Fi OUTPUT Ii We i ed mal l eitwith t c Fnnns, R.C.A. worth GL'2.00 hassis. dvertised below. 200 ma. 110 stilts SC cycle. 700 volts FOR P.P. 626 Weight 2 Ins. Stock No. SK -T3. Net price. at 13 channel tuner with 3 3 pens ,oeil 0.3 volts s 8amp,. Trennt` 3:44 x 4ty X 5t/ ", Shi1,yl reg weight. $6.95 tubes $7.95 1Ize2 Ins. Stock No. Net price..59.95 Why pay $20 or $30 for an putout' Our lab teat Television proved this best G.I. T.Y. FRONT END SCOOP Vertical Deflection O Trans. $1.95 former. Shipping weight 'J lbs. Stock No. spon se'fr"r 1day.. Channel T.V. front V0.5000. Net to cycles. 6600 price...... $1.55 20.000 tube10C4 2 tuRequires Television Focus Coil. Top quality for 10 tir ohms plate to plate with 4.8 -15 -250 and ,ripedamaged r the 12- tubes. Similar to R.C.A. No. 20201. KIT 500 hot omlan..S ,i,11112. weight 8 lbs. me r and lfor building TV boo Net price $2.49 12 WATT KIT 20 WATT Stork Nn. A.403. Net t ..,i... Also for school class room aids train- for Norisentel Oscillator T . Stock TM -12 $10.95 TM-20 515.95 ing. Stock No. MA -13XT weight 4 lbs. net 11.MA. Net price Nit Watt r kit. $1.95: Kit of 3 tutors Ste extra. 99e deal highh qualityrecord play r CAPEHART P.A. System or recording amplifier. Matcher RCA Type 21 IT3 Horizontal Deflection Out. component chassis. T. V. put and High Voltage Transformer. Sale ontrol(adca md1m phono to mike l put TWO POST SCOOP $5.95 regular $5.70. Net 54.49. rcompensation for G.E. Variable Reluctance L Farnsworth Television RlaCA 20303 Permanent Magnet Ion Trap. ek Output mulch. 8 .,hm Voire Coil. RECORD .t 1 ¡1ÿ5;t { Chassis Model GV 280 par- Sale Price 99c. 00 MillMi. Power Transformer Complete with ' built up Chassis tubes. diagram seal photos. 2-850. 2 -12427 Si. RCA 220101.20108 Deflection Yoke. Sale rectifier. Variable tone control. Model CHANGER $6.95 12x17. Has 16 Tube 51wk. Price regular $4.50. Net 53.49. TÁa Net 10l5P4 Picture Tube. Manufacturer says Ì11/? mike andOdes"k 65 1611,e Atounrot oar. Condenser,. these tubes ere guaranteed Perfeet s4 extra. ls or Transformers or attuning i Sweep except Model TM -12WT plifier It TM-11 x kit Ca hart Cbaniar Scoop. t quite to their rigid specifications. wired ready operate Used on famous, 1 o,ne. rin cult. are rl partially wired up. 9.9.5p to net 514.95. high combinations. " priced These changers This T.V. Chassis is deal for the student Genuine dons. Kit Model TM20. A (nigh quality 20 Wall nine been removed from Seto: to be . and exparmenter. Learn T.V. building All In Audio Amplifier(pe Tramp t,l:.re,l unit twin speed changers. Require by factory[cl /SalePrice 01.5`ní Inputs for mike .finir Repair. These have Capehart true. from. 'Furnished with 1948 regular 53.00 or Mangono pickup. Compensation for G.E. t nl.r,e variable resistance cartridges. Re. Wbl rratlp Television Manual, Variable Reluctance pick up. Tone and fader e gain as the G.E. VR cartridge. which ha lete schematic thi TELEVISION COURSE controls. Has heavy duty universal output l'umur(mg instructions hasch as well r'as 9 pages of service in- $3.00 ransformer to match one furnished. Base Sam's Television Course look. 216 pages. or two speakers. sire 1414 - x14,4'. Weight 23 tbs. Stork formation. T.í'. ,lai. to you in everyday language. Ready punched chassis. Price includes tulles, NK 3. 59.95 ea. If Brau want to play with Television here We (Minnk diagram and ohm. 2 -nl0 .,-7N7.7. 774 . is Name to t started. Net it's the finest ` value today. Frequency response 50 F.xtr:, tone arm. with 511.4.1 to 12000 Coe. Kit Crystal car- Farnsworth C. t'2Ì1" partially hui t up Chassis 17.401.L Television antenna. Stacked high Model TM 2n. Weight 20 lbs. Net Is $15.95 tridge and permanent needle. $1.00. extra. and 4N Supreme T.l Manual for Model 1'M -2UWT all 35.9$ and low hand folded dipoles. With reflectors npiiriyt TM -2U kit Extra tone . with G.F. 11PX.010 varie Include tage for 11 b5. GV260 Chaseb wired really to operate ne 320.95. aile relmtnme cartridge. 52.95. extra. only 52.95. and mast. Regular 515.00 net. McGee'$56. sale YPrices P.0.5. N.C. send (see deposit WRITE FOR BARGAIN FLYER. McGEE with order. sal. sent C.O.D. With Parcel o RADIO COMPAN Post 0 include Postage. 1424 Grand Ave., Kansas City, Missouri DECEMBER 1949 lil Servicing capacitor's bypass effect on a.f. and r.f. the capacitors on or in the defective currents. circuit. That is, if the intermittent When one of the cathode bypass ca- capacitor seems to be one of the filters pacitors in an audio circuit opens, there -out with all the filters! If it is one will be an apparant loss o. bass and of the bypasses in a tone network - pos;ib:y a great :ass of volume in the out with all of them; and so on down Iou is oeak. . the line. A MESSAGE TO Intermittent capacitors often react Your next move, if none of the fore- to line -voltage fluctuations. Switching going approaches are practical in the on lights in the same room makes them given case, and you believe the fault to Service -Dealers: cut in or out. Cold -soldered joints, on lie in one of the capacitors, is to try the other hand, are very susceptible to and find the faulty one. The problem vibrations. is that the capacitor at fault won't lie WORRIED ABOUT The cycle of fading should be care- down and stay dead, but gets up and fully noted. A short cycle is more often works when you approach with your COMPETITION? due to a tube. A long cycle is possibly test leads. Therefore, you have either due to some heating or thermostatic to locate it by way of its associate cir- effect. cuits or by forcing it to lie down and Become the stay down. A good stunt (if you can't Systematic procedure replace all the capacitors) is to un- These are but some of the many ways solder the hot end of each suspected TV SALES fades give themselves away. However, one. When disengaging a capacitor before you touch any of the set's com- duplicates the fade exactly, you may ponents- unless the trouble is staring be a little nearer the solution of your you plumb in the face-clear the tubes mystery. and SERVICE first. Replace them with another set Some technicians test pigtail capac- by known to be good. Do not depend upon itors wriggling them while the set is in a tube tester to check tubes suspected operation. Other equally com- CENTER of fading. Most testers merely check petent men will tell you that wriggling the emission of the tube, and none of will send them on their way to inter- IN YOUR COMMUNITY them duplicate toe exact conditions mittency. it encounters in actual operation in a Some bring a hot soldering iron near Beat competition at a profi }. the suspected capacitor, and hope the receiver. additional heat will cause it to act up. Stop being undersold by Check the tubes by substitution be- - Some use a loop coupled to a high - anybody! cause a tube can, and often does, re- power, high -frequency generator in the act exactly like a cold -soldered joint or belief that the induced current will re's o real opportunity to MAKE MONEY intermittent capacitor. cause the intermittent to become perma- next step is to the sol- in Television. If you can qualify, you can Your check nent. dered This is very important in orne the Transvision Television Center joints. Others drop one corner of the set a new sets where a cold -soldered joint few inches to jar the components, and your community - and BUY TV and is much more common than in an old RADIO PARTS AT JOBBER PRICES. Prac- still others warp the chassis with their one. (Obviously, if the old set had a bad hands, to put mechanical strain on the ally no investment required. This offer joint, it would have caused trouble set. open only to service -dealers in territories before.) The most successful are those who here we do not hove an authorized dis- Go over the joints with a hot iron. toss the set out a ten -story window and ,ributor. This seems to be a lengthy method, but quit the business. For the replacement Contact Transvision at New Rochelle. is a wise one. For one thing, the hot of less than all the capacitors on an iron marks the joints you have inspect- Y., for details on Tronsvision's "TV old set is a compromise -and just when ed. For another, it is slightly impossible P on. DO IT TODAY! to compromise depends upon the serv- to spot a bad joint by eye -or any other iceman's judgment. No hard and fast NO FORCED PURCHASES way! rule can be laid down here or anywhere NO "TIE -IN" DEALS With the accessible joints cleared, else. next have a go at the wires. Tug and NO CAPITAL PROBLEM pull on them, keeping in mind the fact Other components NO INVENTORY PROBLEM that a wire has two (or more) ends, and that pulling on one end also moves With the tubes, joints, wires, and Get the FACTS about the amazing Trans - the others. capacitors cleared we can go on to test- vision Dealer Plan. It will give you a big Next in line come the capacitors. If ing the remaining components in the stoke and big future in television. you have more or less located the de- receiver. fective capacitor (or capacitors) with by momentarily 1'I1.1. otT s \It sI %II. THIS Coils can be checked COI ru\ \met instruments, replace it (them) and flashing a high voltage through them. check by listening. However, replace- The theory is that the overload will ment of capacitors is not a simple prob- either make them or break them (either TRANSVISION, INC. lem, with one exception. If the set is weld the break permanently together or NEW ROCHELLE, N. Y. fairly new, you can safely assume that melt the ends further apart.) Other the defective capacitor is an accident, components will have to be tested indi- and that the rest of them are up to vidually in fashions depending upon Yes, I want to MAKE snuff. their nature. MONEY in TELEVISION! nr. -12 If the set is an old one -and a midget Continue in this way, clearing part -your best bet is to rip tlu-rn all oat, after part; follow a definite, systematic Send details of TV CENTER PLAN. excepting micas (they seem to last for- plan until you locate and arrest the ever) and not waste time testing each offending part. Nome one. If the set is old. but huge, 'ott are you follow this Sherlock Holmes (please print) If definitel, faced eith the rod of a e system, you will eventually locate the Address pletc capacitor repIaeein. nI. lour hest trouble. But if you cross your fingers. and safest bet is to seII .our eus r on trust to luck and your technical skill. may City & State the idea. and jump around in the set, you Your next best bet is to replace all never, never find it! RADIO -ELECTRONICS for Repair Electrical Appliances and Utilities with the aid of THE AMSTERDAM MODEL 100 ELECTRIC TESTER A NEW KIND OF INSTRUMENT FOR TESTING ALL ELECTRICAL CIRCUITS AND APPLIANCES SUCH AS-

RANGES VACUUM CLEANERS SHAVERS AIR CONDITIONERS HEATERS REFRIGERATORS IRONERS SUN LAMPS

WASHERS CIRCUIT BREAKERS FANS LIGHTING SYSTEMS ETC.

THE MODEL 100:

Will accurately measure all Voltages both A.C. and D.C. between 70 volts and 660 volts.

Incorporates a Continuity Indicator which is used for locating breaks in wiring, and "shorts" and "opens" in switches.

Will indicate excessive leakage between a motor and a line up "O LT 7 to 10 Megohms. Will indicate if an appliance, motor, etc. connected CONTINUITY in a line is "open."

Will indicate when a three phase motor is running erratically due INDICATOR to o "blown" fuse. Will indicate whether the current is A.C. or D.C. and if the frequency is 25 cycles or 60 cycles.

Is the ideal trouble -shooter as if will instantly locate opens, shorts and grounds.

Will test all bulbs, radio tube filaments, pilot light lamps, Compact -Measure;: 3118" . S?a" x 21%4" all fuses including cartridge, screw, etc., fluorescent bulbs, etc.

Will test condenser for both opens and shorts. Will check field coils for opens and shorts. ONLY $ 00 Will indicate when one side of an appliance or motor con- The Model 100 Electric Tester comes housed nected to the line under test is "grounded." in a round cornered molded bokelite case. Complete with all Will instantly identify the "grounded" leg of any electric line. test leads and operating instructions. SHIPPED ON APPROVAL! NO MONEY WITH ORDER -NO C.O.D.

TRY BEFORE YOU BUY! Yes, you need send no money with order or pay anything on delivery. Simply fill out this order form and mail it today. Try the Model 100 for 10 days. If completely satisfied remit $5.00. If not, return the instrument -no explanation necessary

AMSTERDAM SALES CO. Dept. RC -12. 98 PARK PLACE, NEW YORK 7, N. Y. FREE PREMIUM!

Gentlemen: Please rush one Model 100 Electric Teste-. I will either remit $5.00 Check here if you include $5.00 payment with order. after a 10 -day trial or return the instrument via Parcel Post. In return for saving due to bookkeeping, we will include a set of 6 assorted key chains with your Model SHIP TO: -Name 100. If the Model 100 does not meet with your whole- Address hearted approval after a l0 -day triol, return it for full immediate refund of $S.00 -keep the premium for City State your trouble. DECEMBER, 1949 61: Foreign \cWs European Report By Major Ralph W. Hallows

SUPERIORITY RADIO -ELECTRONICS LONDON CORRESPONDENT AT A GLANCE! Britain has had a big slump in radio The vertical response sales for some months now for several of this economy TV interesting reasons. First, there's scope is usable to shortage of cash. Next comes purchase 5000 kc, not 50 kc. tax. This ups the cost of new radio by Response is flat to about 25r/, -and an increase of that 750 kc, down 3 db magnitude is a pretty serious consid- at 1000 kc. Amplifier eration. The radio manufacturers had supplies a voltage A R-3 a seller's market for a year or two af- gain of 20 at 5000 kc. ter the war; hardly any domestic ra- Check this necessary feature before you buy dios having been made between 1939 any scope for TV use. and 1945, when the war was over, there were hundreds of thousands of homes The R.S.E., AR -3 Scope has been built by Ross Armstrong to our rigid specifications. It's a in which the old radio set was just complete unit that embodies standard hori- worn out and simply had to be replaced, zontal amplifier and sweep circuits with willy -nilly. normal sensitivity. ELEVISION Those are all contributory causes of The case is 8e high x 50 wide x 140 long, is said to have the slump, but the chief one is that the attractively finished in "hammered" opalescent stolen the radio manufacturers decided, for some blue enamel. on standard 110 volts Operates show at Ra- queer reason, not to hold an exhibition -60 cycles -40 watts. Tubes, 3BPI.6AC7- last year. Publicity is the life blood of 6517. 6X5- 5Y3.884. Instructions included. diolympia this modern business. If you don't keep on Complete specifications upon PRICE year; in a way request. Satisfaction or your perhaps it did. TV still has a big telling the man in the street what money back. $4995 novelty appeal and demonstrations of you're doing, keep on showing him AVAILABLE TO JOBBERS televisers on the stands and in the spe- F. O. B. IN QUANTITY cial rooms were bound to be DETROIT viewing more exciting than those of plain and simple radios. Nevertheless not more INTERCOM & RADIO than half of England's population will AT A be served by TV when the Birmingham transmission is added at the end of the PRICE years to the existing London transmis- THAT sion. Of that half, only a comparatively small proportion can even think about This pickup lia. inlrrrhangvable rlip -on CAN'T affording the price of a TV receiver. head. for Isla. ing butts Aland:tri a Id IT Hence, the majority of the tens of thou- BE BEAT records. t1 sgn et ir. it ha. high output. sands of folk who kept the exhibition 6 Tube superhef -3 tube packed from start to finish went to it WHILE THEY LAST what it means to him, and keep on giv- with the idea of window-shopping at intercom permits coming him reasons why he should spend the television stands and of selecting munication between ra- his hard -earned money on your prod- $2995 at the others the new radio receivers dio- master and up to 4 ucts, he just dries up as a source of With 1 sub -station that they are going to have now or sub -stations. and 50 feet of cable revenue to you. The Radiolympia that Extra Sub -stations hope to have shortly in their own living didn't take place last year was a loss Original cost $64.50 53.95 each rooms. indeed, but the exhibition that did come There's no disguising the fact that off this year has put the new radio re- PUSHBACK ceiver right back on the map for the ordinary man and woman. It gave visi- WIRE tors a thousand and one practical Y. demonstrations to show that the old 25% BELOW MILL COST! radio receivers in their homes weren't 1st class, Essex or Lens. ALL SOLID tinned copper, double cotton serve, waxed finish. up to the task of bringing in today's radio programs as they deserve to be 1000 Precise- SIZE COLORS 100 feet lion Reel reproduced. 22 ILACK.SROW N .39 3.79 I. 49M It showed them three more important 20 RED -WHITE -SLOE .49 4.49 3.SgM 18 SNOWS .69 8.98 things : 1. New radios cost much less now than a year or so ago. This year, radio ORDER INSTRUCTIONS set prices average about 15% less than Minimum order - $2.00. 75% deposit last year. with order required for all C.O.D. ship. 2. Those endowed with critical ears cents. Be sure to include sufficient post. Demand This age -excess will be refunded. Orders can now obtain at reasonable cost far Seal of Quality received without postage will be shipped more faithful reproduction than was express collect. All prices F.O.B. Detroit. possible at a comparable price in recent Quantity and Export years. Orders Solicited 1 t k 1 3. The radio receiver can be as pleas- ing to the eye as it is to the ear. British SUPPLY & radios of today, with their cabinets KHVIV made of lovely woods or of beautifully ENGINEERING CO., Inc. are designed Saur and Moore hearing aid doubles as colored plastic materials. 85 SEIDEN AVE. DETROIT 1, MICH. ceased to be a broadcast receiver for one station. by artists. They have RADIO -ELECTRONICS for 67 Now, For the First Time GUARANTEED TEST INSTRUMENT KITS * READ DETAILS OF UNPRECEDENTED GUARANTEE IN BOX AT BOTTOM OF THIS PAGE w

MODEL7(T -40 VACUUM TUBE VOLTMETER FEATURES SPECIFICATIONS

I I resistance) 0 3 - Uses 4,,e -2.6 accurate IT Arsonval type Meter with high D.C. VOLTS: (At mephitis input to 30 torque movement and Alnico V slug. 150 750/1.500 Volts. Meter guaranteed against burn -out on ALL electronic ranges. A.C. VOLTS: (At 1.000 ohms per Volt) 0 to 3/30.150,- Meter will not be damaged even when improperly switched 750 1.500 Volts. to higher range. RESISTANCE: 0 to 1.000 ;10.000 /100.000 ohms. 0 to 10 Stabilized degenerative circuit results in linear D.C. stale. meguhms. 1.000 megohms. Isolating test -prod tor all D.C. Voltage ranges. D.B. Based on 0130 equals .006 watts (6 mllliwates) into a 500 ohm line. Megohm input resistance on all D.C. ranges. - 24 d to r 4db + 10 d to +38db Ohmmeter accurately measures Irom 1 10th ohm to I bil- lion ohms. - 4db to + 24 db + 30 db to + 58 db

Model MT Kit cornea with KT -40 COMPLETELY WIRED 0 complete MODEL all Darts including test leads. V.T.V.M. a19so c,rcu,t, READY TO OPERATE $29.50 I P end. operat,ng Instructions, tc. NET

THE NEW MODEL 247 T UB E TESTER Check octals, loctals, bantam ir. peanuts, television miniatures, magic eye, hearing aids, thyratrons, the new type H. F. miniotures, etc. FEATURES Newly designed element selector switch reduces the pas Otte of the most important improvements. we believe. sibility of obsolescence to an absolute minimum. is the fart that the 4- position last action snap switches are all numbered in exact accordance with the standard When checking Diode. Triode and Pentode sections of element ter- multi -purpose tubes, sections can be tested individually. R.M A. numbering system. Thus. If the a test. button A special isolating circuit allows each section to be minating in Pin No. 7 of tube is under is tested as If it were in a separate envelope. No. 7 used tor that lest. The Model 247 provides a supersensitive method of checking for shorts and leakages up to 5 Megohms between any and all of the terminals. model 247 rtlt comes with all P ares. new speed-read chart. handsome nand-rubbed oak

TMODELHENEW SIGNAL -. 8 -450 GENERATOR SPECIFICATIONS Frequency Range: 150 Kilocycles to 50 Megacycles. The R.F. Signal Frequency Is kept completely constant F.M as well as A.M. receivers can be speedily aligned at all output levels. This Is accomplished by use el a with the aid of the Model B -450. Modulation in the 'pecial grid loaded circuit which provides a constant load E B -450 is accomplished by F,rid. blocking action which has 1 the oscillatory circuit. A grounded plate oscillator proven to be equally effective for alignment of amplitude is used for additional frequency stability. as well as for frequency - modulated receivers. D' -et reading -all calibrations are etched on the front R.F. is obtainable separately or modulated by Anoto panel. Frequency. Positive action Attenuator provides effective output control at all times. Model 0' 450 Kitcomes complete ...PP all its inctuddlo ei. test leads, etc. Mottling else o MODEL B -450 COMPLETELY WIRED our READY TO OPERATE $24.50 j S'8 NET *UNPRECEDENTED GUARANTEE!! All kits advertised on this page ore offered subject to the following guarantee: If, after completion, me Ir Il, ment does not operate to your fullest satisfaction, you may return it and we will ship you a brood new factory wired and tested model for only the difference between the price of the Kit and the price of the complete Instrument. Full credit will be given no matter what stage of completion has been reached in wiring the Kit.

20 °o DEPOSIT REQUIRED ON ALL C.O.D. ORDERS

Dept. RC -12, 98 PARK PLACE GENERAL ELECTRONIC DISTRIBUTING CO NEW YORK 7. N. Y. EXPORT DEPT. MARITIME INTERNATIONAL CO. 10 BRIDGE ST -, NEW YORK 4, N. Y. CABLE: FOXCROFT

DECEMBER, 1949 Foreign News

things that must be tolerated in an otherwise delightful living room be- rHARD-TO-GET PARTS-N cause one cannot get anything better. JOBBERS! POWERFUL ALL -PURPOSE INDUCTION On the contrary, these are models MOTOR which are either so small and unobtru- IDEAL FOR EXPIRIMCNTCRS -1O1 USES unno- st andard,e this self starlit, V' shaded WHOLESALERS! sive that their presence passes is ow. Pole A.C. induction motor so erful enough for number ticed, or which are in themselves of rte are: Tint- ing Devices. Current Interrupters. beautiful that they add to the attrac- Electric Fans, Electric Cn,ms. RADIO & TELEVISION Window Displays. holoclI Control tiveness of their surroundings. Devices, Electric Vi . Small or,ndrs. Suffers and Polishers. To take one example, the peacock is Miniature umis.therMechanical Mod. Ms, ies. and ppliral a glorious bird when you see him full - Consume. 15 walla n1 power d has peed td 3.0011 face with his tail fanned out. If, sturdy unit this sturdy unit "will Conslantry though, you happen to be behind him, ate an S turntable loaded with dead rowel be nigh wide:dshaft TUBES his southern aspect leaves much to h.:Dimensions Is ISdhne studs: shaft mountinghloo ",t g t11- So most radios: their by 3 / &diameter d s desired! with retaining bearing". Designed für 1110-20 volts. 50.80 fronts pass muster, but their far -from- slip. Wt. 2 Ib.. AVAILABLE AT ITEM NOi4ïly. $1.95 beautiful backs must be placed out of YOUR PRICE DEFINITELY sight against the wall, which very ULTRA MAGNET the positions they can oc- urn MORE THAN 20 TINES much limits ITS OWN WEIGHT cupy as pieces of household furniture. LITTLE GIANT MAGNET Lifts 3 lbs. ily. Weighs 4 . LOWEST PRICES One of the newest nonbattery portables Made of ALNICO new high- magnetle eel. Complete with keeper. World' is housed in a molded plastic cabinet, most powerful magnet ever made. The experimenter and hnhbyl.t will with front and back identical in ap- And hundreds of excellent uses for IN COUNTRY this nigh quality Permanent. magnet. pearance. Even the tuning scale ap- Measures 1L i 143..' Ship. SWt. both sides of the set. can ITEM NO. 15 pears at It TOUR PRICE B $1 .25 thus stand anywhere in the apartment. Following is a list of television GENUINE MICROPHONE TRANSMITTERS Regular telephone Ira.. small receivers mitten taken from a r tubes available in large quantities. Some company A perfectly Some tiny receivers were on view at on 2 dry cells. Can be Each tube is individually boxed used on P.A. systems. call the show. The ''world's smallest super - om. Inter.com munlea. acts. short-line tele. and tested and also carries a het" is a four -tube midget measuring phone or farm o farm only approximately 10 x 4 x 3 inches. lines. also to talk money -back guarantee. through your own radio or as concealed dicta... There were portables and personals Useful replace. the fullest use of miniature n battery-ratednl,e 1 B3 making oral' telephone Ines. 6X4 6W4 THESE ARE GENUINF. tubes and components and weighing as TRANSMITTERS. NI *DE 0V 5U4 6BJ6 12AX7 KELLOGG. WESTERN ELECTRIC AND STIIOMnERG little as 31/2 lbs., including all batteries. excellent a. remarkable and oneu sell m offered ' in1 "these 5V4 6BH6 12AU7 set shown, meas- tii t(.5. Shop. Wte 1' lb. An automobile radio ITEM NO. 1E0 YOUR RICE + 618 6.16 12BA7 uring 92/a x 51/z x 6% inches and $1.9595 WATTHOUR METER 6BA6 6AK5 12AT7 Cnmpletelr erhauled and ready for Immediate service Designed for regular 100 -11 to 6AU6 6AG5 1258 volt. flu c e 2 -were A.C. circuit. Simple to Install: .2 wires from the line and 6BE6 6BF6 12BF6 2 wires to the load. Stunt Ilv nstructed In heay. ttase. St high. flti, 6AT6 6BA7 12SN7 wide.metal S- sleep. Westinght,tl,e. G. E. Fort Wayne. Srrngarno other mailableav make. Shp 6AQ5 6A L5 19T8 W I. la Ms ITEM NO. 33 6BG6G 6V6 19BG6G YOUR PRICE $4.95 658 6SN7 35B5 AMAZING BLACK LIGHT!! automobile radio receiver, said by Powerful 230-Watt Ultra- violet Source 6C4 6SL7 117Z3 This The best and most practirnI maker, Masteradio, to be light for its Britain's real experimental' and smallest, is 9% x 51/4 x 61 inches. tlnmenteu . Make. all flunree. types of radio and cent a hatanres brilliantly lumi- Many other kient. No transformers of a nd needed. File any standard television tubes available. Write lamp socket. grinds out beau. weighing only 10 lbs. (see photo), is IIful opalescent hues In van's.. type. of m lerlal.. Swell for complete information. particularly useful in the 7-15- horse- amateur panic..I lays etc.: to for lrtain unique lighting effects. power autos of which we make so B ulb only. Shp. Wt. 2 lbs. NO RETAIL much use on this side of the Atlantic. YTOURR PRICE 51.95 spare and ACCEPTED They haven't much room to ORDERS these small radios fit in where others WESTERN ELECTRIC BREAST MIKE This is a tine light. weight air. craft carbon mlcrophorte. It weighs won't. In any case, though, why carry only I lb. Mike with brestplal Indiana a large and heavy automobile radio if mounting and ' has 2 -way swivel- All inquiries horn the State of fn aalntment that It can be a small, light outfit does just as well? adjusted W any desired position. should be forwarded to the ESSE RADIO There are 2 woven straps: onedge -ues Speaking of the radio set as a piece around neck. other 4. Ind. chest. Straps can b snapped on CO., 40 W. South St., Indianapolis of one model interested me off quickly by an "infemou. furniture, ar K This excellentcent mike be considerably. This is built rather on adapted for horn. broaarasti,,g or private By the lines of the expanding bookcase on dismounting brrelastplate Y lte can be used o desk the add -on system. Start, if you like, complete with fl.toot [toed and hard rubber plug. Finlahed lsherardlsed place. a smallish table radio. Add a big- wean i á with ITEM NO 152 NEW JERSEY ger loudspeaker in its own cabinet and YOUR PRICE S1.00 When this becomes a console model. HUDSON SPECIALTIES CO. RADIO AND next your bank balance is again right, 40 West aroidway. Dept. RE- I2 -43. New York 7. N.Y. I have circled below Gut number of the items l'n, a new unit makes the whole a radio - ordering. cis 1 harge.) ñ Inard (NO CO.O. phonograph. An automatic changer and ORDERS UNLESSeACCOMPANIED WITH A DEPOSIT.I TELEVISION OR y depuat of I Is enclosed lure a storage cabinet for records can be required). Ship order C.O.D. for flalan,:e. NO Ç.O.O. ORDERS FOR LESS THAN 53.00. SS SUMS TO IN. added as time goes on. Another add -on CLYDE SHIPPING CHARGES. Circle Item No. wanted, 132 TUBE COMPANY unit provides television. Thus, from 147 111111 IGO 87 33 quite a simple start can be built up Name 715 ELIZABETH AVENUE progressively an instrument giving ev- ELIZABETH 4, N. J. ery facility for home entertainment Adores Wee. Print Clearly provided today by electronics. city TEL. ELIZABETH 2 -5180 (Continued on page 70) J RADIO -ELECTRONICS for 69

tk hiv`J tONST 12Ca.94z4 Pzeoeotrd

c l le,n t k \`t1 /I Ilnx F,t^d 1n o 111 11.aain'ari,ar a tu c Nt tla ginerxg t tpl v Earl t Tua11 odf #33. txl.Doavtnsuel vg Tail re GIFT ITEMS receiv s ia will nilIh no bitsx -rail .ntr ilAuthors s Oblisbet ,b but 55p0inrauh. t rmpdvendor Is at GIVE -AWAY PRICES! any arr 50 words rods. in rad.tr,_ .altTaln Niagara radio ' Tae it 'Tail t, , to All -Tall Niaga ra Iebwt. t1 SUPER SURPLUS SPECIALS NIAGARA'S Inr lNDC[Iy become GOLD -PLATED :aDDL CurD. HEART !: SPECIAL!

OF THE \n ultl.: 1,1 Ii trr,i. I:.,I1 Plated I it) Resonator "ONCEINA- LIFETIME" VALUES BC -221 oltl a range of 234 25s P. Slit.I Fully u'invl. Includ- FREQ. Á ing Isms 457, wont tithes. Ilesi ansd by the navy for Such as THESE! METER P. use + a namable modm lateda tot .,awilLdnr. S .arm I,\\ Check Every One! 'Phis Vr() -Px HE USED AS hl)'. used I. i., 221 A S1111H'1..STEU SIGN. L (.EN- L.M. FRED. METER, slat. hook. mod. IX, $90.00 }at.\TRN. Battery rtmpariment is large nova] to TRY NAVY c l0 mu. It complete Freq. Melt iIealb'!s house speech A amnia er 44.95 sidled tar dc tar/,, equipment and power +uPVU. n aking HANDY In meter , mere r 24 .95 it a deirahl, portable for at rurlhm of l'lIF Transmitter (lam BEACH model 17000 NO meterI \ }r' ( 0 tex' I9 S 5 use. fame hie oath toning ach. tuhes. trod CON-SET 50-54 Mes. 27.50 antenna. and wi rendi cev'rrtrr. Ilk.. new nei tits. Foundation !.I diagram onn indite cover. Black HUDSO With 'IkE 79.95 rinkle finished iahinet measures 3 Portable Transmitter 91ÿ f14 x HUDSON MARINE 6 Thau. TOW soir-rear SI !,s Thr Ruv 01 f.i J. fin's' NEW 4-Replacement for Id' -221 Cat. No. N -257 contains two temperature A moisture Itotionaaf 9t. BE UNITS V f.. .. 3.95 : l'out Special .. $3.95 GE MOBILE XMTR. S ì0e rolls. water switch, 3 tarlal.le .undrnaru, r ham. lisisouns. N sliver mira enndenaen. Y reads . SILVERR vol r,.xt mir. osso I mounted un sturdy alnminnnt sui alcpala. rrad)j 1 l L i t .329..989 'ffi 4, for installation. Itrand new do original par-kima. GIBSON GIRL "nogg. rns NEW 5 N-276 WAVE ATD NAVY 50 Watt amis. la ba NEW 49.95 '" TRAPS Very special. 36.95,. NAVY 6v, portable audio amip l lf. kY tip. 9.95 'traps consist of two slog -tuned oil - C 221 N. is i. nor. u,'xtal & r. book, EXC. 75.00 ertrnl rolls and two ceramic con - BC t r. NAVY wtraoli., or. r 75.00 BT CUT 1000 KC XTAL e. dinaers. All haunted MI a cadmium NAT'L I -10A RCVR x rail., listt par. undo ..When used in alane assembly, will make a full). plated brarkel conveniently drilled 1. N 42.00 ,l s,lI contained ]ammonir generato' front 125 RI' tal. and ready for mounting. May be used CRV NAVY Rear. tam -Gnu ke. x lobes. into 6C. f. Ver)' .. 14.95 to eliminate F51 sound bars In T\' Sa11IN :11'9 +,'t;. eliminate amateur interference 12 -27 ISM resistance bridge Iw:ealeannmlr.I 75.00 al 34.956: ,e Speri .. "hark excitalbol in Rears. BC -614 -D speech amplifier for 111f -610. NEW«r', 45.00 TV S1atth -Lo antennas, and W 1252 electronic wavemeter, 2'2 -30 Ales. Est 49.95 r "p .....0: e,.. Ili TV d,n.- F` af other uses In numerous to no noon. They're going fast. so order 5 WATT AUDIO AMPLIFIER tour- Cat. No. N128 Special 11'. 39c Each, 3 for $1.00 T -17 MIKE

I...., e.r 1'111.. I.re, ' $Ii4hlly med. guaranteed perfect and clean. Single TINIEST V.O.M. button carbon Ilandmike. Light Ott IN THE WORLD dent. 2011 ohms. Press to-talk snitch. 5 -11. rpylher nrcd with 1'7. -66 plug

a ilaclled. Cat. Na. N -249 Sp, 1ì.d 69e

.\laid amplifier iNU'r .\ I:rn ,leUrrrina full c e411,. One tune and frtgmney response. Complete with tubes. output transformer, volume and pue r nirnd '; $1,000,000 STOCK (teal quality equipment not 10 be +tl u.. 11 lib ,\t'- 111' amplifiers fil' mmdrsrript vain- 11 v 60 (y. Inmi Cat. No. N.185 s1 2.so BRAND NEW TUBES Your cost L I F.UIUI'S BRANDS .. ALL BRANDED it ANI) BOXED SMALL PARTS

CABINET REDUCED lntatllre I, iii (rawer -5 -riling rabbi." lot ,null ,6 3lí% MORE THAN /o í parts. Three drawers dl- 1. 50 vide Into 6 compartment 1S4 RECEIVING fourth has Mir emopart- S. ''f E1148NSMITTIS 1115(:T 3 .55 mein for larger Rents. f NI.rli:\It.\ ex IusieolY Presents the -Universal e,:I 2C26 .28 3A4 Slade of durable. snot- it Ratty Tester." measuring 37.' 2!w x Iß, ,f welded Meet steel. Fin- 't' , 1.70 . '. Sc C.mlalus a sen r l t ire 0-240 mirmanleter with the. is 1. ished in green baked ldlorr int. tang "f OY 1 .28 3D6 .29 ,enamel. Meast". 5a.' 0 -15 V AC or DC ,a s! 211 6(14 .2829 i; i'- v1 ,h .28 /; 11 -150V A1' or Ile' 93 803 3.63 6AR5 .54 jr. right 4 Its. 52.24 0 -750V ,1C or DC e:`- 805 3.63 6D6 .55 Cat. No. 277 Your cost 1(61 813 6.90 6K7CT .54 Ì' ohms slum adinat and-100.1100 '' 815 1.37 6SH7 .27 , n iN'A'olimrI' rx'Itch. Includes k. e4 STEEL 1 pair tea bvnls. Will fit Into Your watch pocket {{ 841 .38 6SS7 .53 A it)f 954 .18 7('4 .28 f Cat. Nô.ahN -258 TOOL CHEST Special $8.95 6'`''a 955 .18 12A6 .28 1` , 57 .18 .29 Nationally knutu 4 9 11 H6 tool chest with aillumai ".. f 958A .18 1. K7f,T .33 l. l etraillug Ir:ü'. 1!. ,.. 0 1619 .18 12S147 .29 1 length Plano -type bin. with water (t ,f Ifi25 .18 12SR7 .29 v shed. } . 1626 .18 28D7 .29 h :dominion handle. di ao mill with padlock , .,.; ¡! 7193 .47 35r.6CT .53 jr; NIAGARA RADIO SUPPLY CORP. ninfnreed corners. 1 an .18 50B5 .53 he opened wild]w tar hand L.r -.II NOT pen unin- Dept. C129 9006 .18 50L6GT R fr:A. `! 54 tentionally. - Finished in gem: enamel. Meas. 160 Greenwich St., New York 6. N. Y. a? ALL QUANTITIES LIMITED s 16' s ; Nhfnuing rrgl. ; its. a g Cat, No. 278 r 5 ,98 S' a .. r;. r;r s`s7SC Your cent IMPORTANT NOTICE: Please 71tß. -li ir. .n attache.( list. ,&t,. .the an, deposit alti, (.0,0. , derv, natevn rated. I)nlers received without ....tag. he sha v a sit: Pm'ih ailwayeexpn't 'falter(. .S'.,,.1 us Four In uiriwv today. 0'e et1 odo In English. D flair ins n t' on mailing list to receive special xpal. 'Ish, 1 trench. tali:,... r 1..bsn Ihtninol:ai. Rehrex. re an. Portuguese, .elf. Prices s ñiert to change hnlli-i ins .d rhliudled- bargains. (' i guanlily sill,o ..h All stork i iii v. i', Y.4 Nam. Vt

µt.5 .\ddnar _¡l

...State L J DECEMBER, 1949 70 Foreign News (Continued from page 68) clearly marked and tuning mechanisms WHERE TO BUY IT ... I like. too, the idea of several firms are so simple to operate that buttons on that it is their job to provide nothing a radio are very nearly as rare as WHOLESALE RADIO but the "works" of the radio and that crowsfeet on the face of a motion pic- of Baltimore other firms (of which there are many) ture actress! should supply whatever kind of cabinet the purchaser, and particularly his bet- Use for mine detectors ter half. may fancy. Anyone who buys Recently the owner of a valuable T. V. ANTENNAS a good -looking, expensive radio is liable herd of pedigreed cattle found that one to find that its trade -in price, after he of his best cows was ill. In spite of all AND ACCESSORIES has used it for a year or two, is pretty his treatment, she grew daily worse and small in view of its excellent cabinet. worse and the veterinary was called in. Complete Stock! Low Prices! II' the radio is to be, as I think it Having made a very careful examina- We've got the right antenna and the nlld, an important part of the fur- tion, the vet came to the conclusion right accessory for any installation niture of any home, a high -quality cab- that the trouble was due to the presence tE of some foreign body in the animal's Sensational Antenna Buy! stomach. He deduced that she must have swallowed something -possibly a SNYDER HI -LO ARRAY piece of metal -while grazing. Being Model TV 21 a man of ideas, he recalled that a friend of his had recently bought a war -sur- rpd a liner antenna : Mier,- or Ihle low pri plus mine detector. This friend was r,,,, folded diodes MIl summoned by telephone and arrived y L'au ulte rene.: Complete with two St l' with the apparatus. When placed over 595 ea>I ,e,6m.. In E. nand , the cow's stomach, it gave an instant , ,manu?. ,tear,)' for en:y, 'pu :uatmn. In Inc s,7. strong response. An operation disclosed

T.V. ANTENNA ACCESSORIES TV Lightning Arrestors `scanner unit of the Ekeu cloud and col - rake twnl lend coilAuit lision warning radar. This is 3 -ens sys- cable. No wire .trim'e tem designed to warn aircraft pilots of u 300 ohm. ' moo. ty11e. Model LA-1.' storm el Is and other aircraft as far 53c ii.9ö away as fl) miles. The entire radar set - Up consists s,' \/'n separate . E. . 10 It of STEEL EXTENSION POLES. 11 - Il'. weather treated...... 1.95 K. Cole. I.td., manufactures the system. WIVEL SASE. AII,nnm .39 DYYWIEE. 0 -t nnle.l 5.. 20. Per .39 24 mole. 51/ fl. each. Interco...... l -,l.. 6.00 72 OHM COAXIAL CARLE ROSSU 14e per Il. inet that has been carefully chosen Per Imo fl. . 3.75 300 OHM TWIN LEAD SI.1.- r 100 II should not have to be discarded after a 1000 lit. I I.75 CHIMNEY MOUNT BIl of ee comparatively short period of service. :411,111N . 1.59 NI -RAAND ADAPTER. I :.i A good cabinet doesn't, after all, de- ,,:. fluelor. cla, n. r 3.00 ]I/a- -30_30 0 OHM STAND 'or iN5ULA,1R5 teriorate rapidly in value; it continues T 3.25 SAMS TV ANTENNA Mnun, 1.25 to please the eye, and all that it needs to please the ear as well is a renewal T he recording plats back New Low Price! Famous or time of tlsio of the radio or radio phonograph in- magnetic recorder is Ito minutes. It em- 10' TELEVISION side it. ploys u 1,000 -card -long plastic tape. model 513 Buy a cabinet to fit in with the furniture of any room and, as time goes a 3 -inch nail in the cow's stomach. ------$174.50 on, discard the old radio or radiophono- Thanks to the use of the mine detector 1 as a surgical aid, the cow is this VI:;1 , 1111111 graph chassis and replace them with now as TV Iteeeleer aith 61 well as ever. In. surren up -to -date models. Just think of the uaa me moo Ito saving you'd make! hllah,11,0 I e (n : : SONOBUOYS TRACK SUBS Ill 10¡111 pine w: It is curious and interesting to notice In any future war submarines :: re, t di., are lobe and one have died Mwdern de.icll pia.. how many -time "stunts" likely to be an even greater clanger to o h{nel. I6- w hie: I: high and 1'1'r- deep. 1 surface shipping than they were in the rhauuela. last because, with some sort of Schnor- Save Money! Get Top Quality kel device they will be able to use their Sheldon Custom -Made "Telegenic high -speed Diesel engines while sub- T.V. PICTURE TUBES merged. The London Illustrated News Flat Face. Magnetic focus and deflection 108P4 -10" $23.97 points out in a recent issue that Sono - 12LP4 -12" 31.00 buoys may prove even more valuable 16LP4 -16" 48.50 13 MONTH GUARANTEE in any future war than they already have in the last one. Lowest Prices! Highest Quality The Sonobuoy is a metal cylinder con- HIGH VOLTAGE, TV taining a radio transmitter and an un- TUBULAR CONDENSERS .0005 n.Id. 6000 V. 19e derwater microphone. It has been used .001 ofd. 6000 V. 19e to indicate to a listening plane the pres- .005 mid. 6000 V. 23e .03 mid 6000 V. 35e ence of a sub. In the new system, sev- .05 ofd. 6070 V. 39e .0005 mud. 7500 V. 39e eral Sonobuoys, each operating on a .001 mfr. 10.000 V. 49e different frequency, will be dropped by portable broadcast receivers parachute in the neighborhood of a sub- WRITE FOR FREE "FYI' BULLETIN One of the Or Phone Mulberry 2134 displayed at Radiolynspia, this del is marine. The aircraft pilot plots the po- operates sad - Address orders to Dept. OR.95 rasade Ir. Roberts Radio. It sition of the submarine by tuning to isfactorils esen wills the case closer,. each buoy and noting the volume of the The coser is sold as part of the radio. sound its microphone is picking up. The WHOLESALE a natural death. One of these is push- nearest to the submarine will, of course, in RADIO PARTS CO., Inc. button tuning. Time was when there give the loudest sound, and so on. Thus 311 W. Baltimore St. were radios with almost as many but- he can track the sub until surface craft 1, MD. tons as a hell -hop's uniform. Now tun- arrive to take over the hunt and male BALTIMORE ing scales have become so large and the kill. RADIO -ELECTRONICS for 71

SWITCHES AND CIRCUIT TRANSFORMERS RADIO RADAR BREAKERS MODULATION & DRIVER XFMRS- RCYRS- XMTRS- COMPONENTS Heinemann circuit breakers RC 1206 mod. xfmr., 815 class AB2. BC 223 AX Transmitter -BRAND NEW- 56W. RC1205 801 oscillators and 801 PA's, 46 110 -15 amp. 1.49 audio. driver xfmr. (2) 110 -20 amp. __. -. 6SN7 to 815, class AB -2 (com- mods. L (1) 46 speech amp. 4 xtal 1.49 RC 1206). Both }regs. and master osc. on selec 110 -5 amp. .95 panion to units for or only $4.95 switch -tone voice or CW mod., 10 -30 SCOPE XFMR. -pri. 110V -60 cy., W. output. Ideal for 80 meter band. sec. 4000V. at 10 ma., 6x41(3/" 3.95 Complete with 2 colis TU 17A 2000.3000 Aircraft ckt. breakers AUDIO OSC. XFMR. with FEED- kc. TU -25 3500.5250 kc. -black crackle 24V.20 amp. and .95 case. Two cases to store amp. -AN 3160 -Square D BACK OUTPUT windings extra tolls. Co.__. .51.49 IF XFMR -5 MC with air trimmer -im- Freq. chart and tubes Incl., packed in pedence coupled. mounted in Alum. orig. cases, less stale. $39.95 shield can .95 DISCRIMINATOR XFMR. to match BC -702 A HIGH FRED. RADAR XTMR. DPST 30 amp. toggle switch- bakellte (4) 2x2 tubes; case IF xfmr. above .95 squirrel cage blower, 12- .39 FILAMENT 110-60 24V.; 25MA, meter; DPDT 110V. slide XFMR. pri. cy.. 2" 028000V cond.; switch .19 sec. 4 volts 16 (2) .01.500V DPDT Toggle switch at amps. and 2.5 tonds.; .001.9500V. .39 volts at 1.75 amps. INSULATED cond. ___ $14.95 FOR 5000 volts. Ideal for 2x2 and 826 tubes. Hen- etically sealed. BC -AR230 TRANSMITTER with 4 tubes 6x31 /zx4 %z" 1.95 and RF ammeter. RELAYS IF XFMR., 30 MC, silver slugged .35 Potter 6 Brumfield OVERLOAD relay 500 ohm to GRID matching xfmr. BC AL229 RECEIVER with 6 tubes -air- relay No. 1 is 5000 ohms, coil No. 81749 (used with T -17 mike) .69 craft equipment, both units $9.95 current 10 ma., relay No. 2 Is 110V 60 cy. Ac coll. SPDT $1.95 785 'APT-5 UHF NOISE MODULATED JAMMING XTMR -With these tubes: Telephone type, plate sensitive relay - (2) 6AC7. (1) 6L6, (2) 829. 11) 931A, 7000 ohm, SPDT 1.95 TUBES (1) 6AC7, (1) 522 blower- cooled UHF 3047L-Ideal for 1 KW final. Induc- oscillator tube. This unit contains a Plate sensitive relay -5000 ohm coil tion heater or dielectric heater. lecher -line tuned cavity with tunable contact DPST ______1.49 Efficient operation at 1500.3000 V. plate. grid. and cathode lines. Lecher. -typical operation 2500V. at 400 line settings are read directly in CM on BK.22K relay -used In conjunction ma. $ .75 front panel with veeder type counters. with SCR- 269 -F- contains 28V step Neon resonance Indicator. Filaments relay. 5 deck, 6 pos. switch -12V operate from 115 VAC. No plate supply. DPST 2.95 CATHODE RAY TUBES Packed in orig. case with instruction book. Wt. 118 lbs. .$95.00 i A P 1 $2.9' 3 B P 1 2.95 5 F P 7 2.95 BC375 XTMR TUNING UNIT- Approx. RESISTORS 7 B P 7 65 MMFD cond., coils, RF chokes, dials. and RHEOSTATS 3.95 assorted micas, 25WVDC and many other POWER RHEOSTATS- 25W -25 ohm - 9 L P 7 4.95 5 B P 1 parts $2,50 1 amp. max.__. 5 .69 2.75 POWER RHEOSTATS- 5 G P 1 5.95 25W -25 ohm - ARR7 AIRBORNE HALLICRAFTER 1.7 amp. max .95 3 G P 1 3.50 75.000 ohm. 200W. VERSION OF SX28A- Search rcvr., bleeder .95 with tubes, less power supply. 11.296 ohm. 100W. bleeder. IRC type complete In sealed cases_. $129.00 tapped at 750-23-23.7500-3000 __. . .49

1 Meg. 1 multiplier, ° -, tolerance.. .89 TRANSSEIVER 20.27.9 MC, Thyrite discharge resistor type 5F CE PHOTOCELL -for use In projec- BC620A- - HE 130V tors or burglar alarm .95 dual channels, builtIn M. and plate AC /DC .95 as follows: 100 % PHOTOFLASH TUBE 12.000.000 lu- meters, with tubes (4) assorted watt resistors In 1LN5. 11LC6. (1) 1LH4, (2) 1291, (4) popular sizes ._ 1.49 mens output. Ignition coil Included on back of bulb. 10,000 1299. (1) 1294 -Ideal for use between flashes - good diagrams furnished on request 5.95 boats. vehicles, etc. Used, in con- Complete Photoflash kits -Write for dition. less power supply. Wt. 38 -lbs. SILVER Information Complete with carrying case and dia- CERAMIC CONDENSERS Complete Stock of GE Photoflash Tubes grams. 500 W.V.D.C. 10c ea. 12 for 51.00 Available capacity (MFFD's), 2, 3, 4, 5, GE CONTROL BC1103 -Contains fuse 7. 8. 8%, 10, 11, 12, 15, 24, 25, 30, 40, PLUGS AND CONNECTORS F301, indic. lamps 1301, 1301A. recep- 100, 120, 125, 140, 3 Russell 232, 350, 375. 400, 470, AN-3102-24-3P SK-C16-326 tacles as follows: pole Stole 45, 50, 61, dual 60. 70, 72. 75, 80, 81. 95. PL065 No. 6852. 2 pole Hart and Hibeman 500. 1000 and 5000. SK-C16-23- No. F7723, 4 pole Russell Stole No. AN3106.36.1S z ACAN A N-3108.36-155 M359-A 8087. Also relay 120V., 60a Struthers - AN-3108282S AN-3100.32.6P Dunn No. AS8X1, Switch, AllenBrad PL-OZ7 10H-529 le) cat. 2AS, and 250V. 10 amp. inter- CAPACITORS AN3106.24.2S AN-3057.24 lock $4.95 2MFD -6000 V. paper oll type AN-3106.28.2P AN-3102-1451P 58.95 SCR -(25 Mme Detector, used $39.50 2MFD7500 V. paper oll type ... 12.50 AN-3057-16 PL-147 1MFD -5000 V. paper oil type 2.95 AN3057.8 AN-3106.32.1015 1MFD6000 V. paper oll type 4.95 UG21/U AN-310218-20S .1 MFD -7000 V. Sprague tubulars 1.95 PL-0171.1oH/414 U-16/ 2 MFD -1000 V. 5 .89 AN-3108145-2S PL-112 METERS and INDICATORS 1 MFD1000 V. .44 AN-3102-14S-2S PL-118 Remote position Indicator -I.82, 6.12V. 8 MFD-600 V .95 AN3108-40-1S AN3102-2027P 400 cy.. 5" indicator with 0.360 degree 4 MFD -600 V. .69 PL-18210H/258S MC-136 dial $4,95 2 MFD-600 V. .49 AN310822-17P ARC-9589 Azimuth control MN -52H -360 degree dial - 20 MFD2500VDC PK. Type No. 775. AN-3108-24-19P AN310222-14P 60 to 1 ratio crank control -Ideal for 65W. Sec.- PHOTOFLASH 9.95 AN-3106-22.1S AN-3102.148.75 antenna rotating indicator. used $ .49 32 MFD2500VDC PK. No. 777. AN310218.55 AN-310618.125 Meter -3. z" cross pointer. Two 200 micro - 100W. Sec.PHOTOFLASH 14.95 2255.26 AN-3106-165.1P amp movements, brand new $2.95 .01 MFD 8000V. 16.20 Amps. Aerovox PL-419 AN-3057-S METER. type DO -41. 0.1 mil. movement. mica LS-217-1000-3000 KC 4.95 AN3106-18-8e AN3102.36.8P scales 0.5 DC Kilo V. and 0.10MA .002 MFD -3000 VDC Mica .69 DC ___$2.95 3x.05.300VDC round can 1 "x1 ", paper Doz. 1.00 50 -30 MFD, 150V. tubular electroly- 45e each tics, well known brands .49 MISCELLANEOUS .008 Buffer 1600 -V _ .29 BUILD YOUR OWN GEIGER COUNTER. BN IFF Antenna duplexer, 156.157 Assorted micas per one hundred 1.95 Detects both Beta and Gamma rays. MC $5.95 All parts, batteries, diagrams and BN IFF non directional doughnut an- instructions, nothing else to buy. This tenna 5.95 is the famous 49'er Geiger Counter. Voltage REGULATOR, carbon pile. VARIABLE as described in Sept. Radio Electronics. magnetic type, coil current 105 ma.- CAPACITORS 349.50 max. 5 amps at 18.25 volts .95 5 Gang variable, approx. 50 MMFD THERMOSTAT, per sect. DETROLA RECQRD CHANGER,. normally opens at Individual air tuned pad - au 95 deg. F.. No. F85.1/H5 .49 ders-18 to 1 tomatic changer for 12 10" 10 vernier drive-shiel- or BLOWER, 400 cy., 115 Volts Type ded _ 12" records __ 9.95 $1.95 FL, style No. I 171145C, 6 Gang variable- silver plated -sec. 6700 RPM. Westinghouse - 1.95 1: 350 MMFD, sects. 2, 3, 4, 5: AIRCRAFT COMPONENTS 60 MMFD, BLOWER, squirrel cage, 110/60 cy. sect. 6: 80 MMFD .89 A5 SPERRY DIREC. GYRO. part No. AC. 2" outlet. silent oil lite bearing BUTTERFLY WAVEMETER AND 656029115V., 400 OSCILLATOR cy., 3 ph. $9.95 motor. with mtg. bracket 7.95 CONDENSERS MK 18 Eastman Kodak gunsight 2.95 Eclipse 24 V. carbon pile type, GE TN-2A 106.300 MC Antenna conden- MK 4 Bank and Climbgyro ser -with acorn control Voltage REGULATOR, brand new. socket $3.95 head for MK 4 autopilot . 9.95 TN -20 76-300 Ci lbs. _ ,95 MC oscillator 3.95 A 5 Autopilot Serve', 100 Ib. max... 9.95 TN -3A 300-1000 MC Detector (uses 1N29 XTAL 2.95 TN -30 135.485 MC Oscillator TN 300-1000 MC oscillator (uses 368A5 doorknob HERSHEL RADIO CO. tube) _ Free Ceramic 3.95 sliver padders -dual 3 to 12 DEPT. R. E. 12 MMFD or 3 to 20 MMFD .19 Catalog 5249 GRAND RIVER DETROIT Ceramic mica gadder- single 5.20 8, MICHIGAN MMFD per doe All orders F.O.B. Detroit- Minimum order $2.00- Michigan customers .50 add 3 °s sales tax -20 °e payment must accompany all orders.

DECEMBER, 1949 72 New Patents R.F. POWER MEASUREMENT S. For example, assume that there is an increase ITEM OF THE YEAR in load current. Usually this means lower poten- THE HOTTEST Potent No. 2,465,683 tial across the output terminals. In this circuit. Rudolph N. Griesheimer, Belmont, Mass. takes As the load 130 TV CHASSIS WITH VOLTAGE DOUBLER however. the following place. (assigned to the U.S.A. as represented by takes more current, there is greater flow through R and therefore a drop across it. The A READY -TO PLAY 16 31 -TUBE RECEIVER the Sec'y of the Army) greater The bridge method is one of the simplest and grid side of this resistor goes more negative, thus most sensitive for measuring ref. power. Three raising the grid bias and decreasing plate current. of the arms are resistive and the fourth contains As a result there is less voltage drop across S a tiny bead thermistor. First the bridge is bal- which is also in series with the load. Since S is anced without ref. applied. When ref. current much larger than R. it controls the output volt- flows through the thermistor, the bead material is age. The smaller drop across S makes available heated and its resistance lowered. A microam- more voltage at the load. P should be adjusted meter measures the bridge unbalance and in- until the compensation is complete. dicates the amount of r.f. power. A similar effect takes place if the source voltage varies. For example, if it is reduced. less current flows through the plate circuit. Again there is less voltage drop across S. making available a greater potential for the load and compensating for what would otherwise be a lower output. STATIC DISCHARGER AND IND:CATOR Potent No. 2,475,356 LICENSED Emery Meschter, Towanda, Pa. (Assigned to E. I. duPont de Nemours St Co.) By RCA The static electricity generated on sheets of paper, plastic material, or cloth moved rapidly along rollers is dangerous and troublesome. ATTRACTIVE DEALER PRICES Unfortunately the bend is affected by changes Sparks may ignite nearby material. Raw pho- in ambient temperature as well as current flow. tographic film may be spoiled by exposure to WRITE WIRE PHONE For example, if there is a drop in room tempera - 1119/lOW LAMP tuve, the resistance of the bead drops. In this TELEVISION CONVERSION KIT circuit two disc thermistors are added to correct 16- the error. The disc type is affected chiefly by 117V AC TO MODERNIZE YOUR 10" RECEIVER ambient temperature rather than current flow. LATEST VOLTAGE DOUBLER CIRCUIT When the room temperature drops, for ex- Wired sub -assembly chassis ample, the resistance of thermistor A is increased. Set of mounting brochets A greater portion of the d.c. battery voltage IttEG Coil, resistors á condensers is applied to the bridge, and the resistance of the Wirewound 750 ohm potentiometer bead is reduced to normal. I MEG Flyback transformer =211 T5 S 4v 6 .61 This solves one but creates another. 183 Tube problem CI I voltage Plastic sleeve & ring ALL The greater bridge increases the sensi- Complete with instructions FOR tivity. Thermistor B is added in series with the meter to compensate by limiting current flow and maintaining constant bridge sensitivity. R4 50 2 PARTS FOR =630 IN COMPLETE SETS R2 SMEG + 5 VIDEO & I.F. KIT (19 iterrn'. S 7.84 HARMONIC GENERATOR ELECTROLYTIC CONDENSER KIT (6conde -, 6.97 Patent No. 2,455,824 PAPER CONDENSER KIT 138 Conde, , 3.72 Joseph C. Tellier and Harry H. Wilson, Jr. II -3V R3 SK - 6.3VFIL TRANS CERAMIC CONDENSER KIT (28 condense. 2.86 Philadelphia, Pa. MICA CONDENSER KIT (12 condensers 1.90 flashes. Also, charged difficult (assigned to Philco Corp.) tiny sheets are to CARBON RESISTOR KIT '108 resisto s 3.34 because they tend to adhere to 3lure efficient harmonic is claimed handle nearby WIREWOUND RESISTOR KIT 4 resis): 1.98 generation nonconductors. This simple discharger includes OCTAL WAFER SOCKET KIT ,3 sockets .64 for this modification of the Colpitts crystal os- MINIATURE MOLDED cillator. an indicator to show when correct discharge is SOCKET KIT ( 2 sockets'. .38 taking place. MINIATURE WAFER Referring to the figure, static from sheet S SOCKET KIT (IO sockets) .66 may be discharged to ground by bringing near it a CATHODE RAY TUBE SOCKET ( I socket) .39 static accumulator A with u comb of fine metal KNOB KIT, decal included ( 8 knobs) .98 T. points. The charges are transferred to the comb BRACKET & SHIELD KIT (12 brackets) 8.63 VOLUME CONTROL KIT (10 controls) 6.19 and grounded after flowing through Rl, R2, and COMPLETE TV TUBE KIT, less CRT (29 tubes 21.27 R3. The filter RI -C1 bypasses a.c. such as line - H.V. RECTIFIER SOCKET ASSEMBLY .79 frequency pickup ; therefore only d.c. can flow through 182. The drop across R2 is applied to the REPLACEMENT PARTS&ACCESSORIES pentode grid. 123 is the bias control. A portion of the filament voltage appears across PUNCHED CHASSIS PAN. makes any =630.S 4.87 114. Part of it is applied to the pentode grid POWER TRANSFORMER. 295 ma 9.97 through Cl. Therefore the plate current has an HORIZONTAL OUTPUT TRANS. 211 T3 3.44 a.c. component as well as a d.c. component. How. HORIZONTAL OUTPUT TRANS., 211 T5 3.97 obvious a.c. component dis- 1.32 A coil LI is added to accentuate the higher - ever, it is that the VERTICAL BLOCKING TRANSFORMER zero HORIZONTAL DISCRIM. TRANSFORMER 1.66 order harmonics. With the usual capacitor alone appears when the plate current is (as at VERTICAL OUTPUT TRANSFORMER 2.64 these higher frequencies are bypassed to cathode cutoff) or when the tube is operated past its RCA FRONT END TUNER, complete w tubes 26.67 and lost. A second coil L2 is added in the cathode saturation point. 27.19 STANDARD TURRET TUNER, " circuit instead of a bias resistor. Here again the The pentode tube is a limiter because of the FOR TUNER .85 ESCUTCHEON PLATE ANY harmonics are strengthened. very low filament and plate potentials. It saturates DEFLECTION YOKE, 83 M.H. VERT. 50 M.M 3.48 goes by a few volts. and its D.C. resistance 2.94 Dotted lines indicate the distributed capaci- if its grid positive FOCUS COIL. 247 ohms, plate current cut off if the grid goes negative ION TRAP BEAM BENDER .98 tances of the two coils. t CATHODE TRAP COIL .89 by a few volts. Therefore no a.c. plate component VOLTAGE DIVIDER, 1360, 250 ohms, 17 á 10w .87 exists during a static discharge which produces 12" PM SPEAKER, heavy alnico =5 magnet 6.85 VOLTAGE REGULATOR more than a few volts across R2. This is true 5" x 7" OVAL PM SPEAKER, top quality 3.63 Potent No. 2,475,613 regardless of the polarity of the static charge. AUDIO OUTPUT TRANSFORMER, (6K6) .87 The second tube is a thyratron. for example, LINE w both safety plugs .29 Allen E. Hastings, Washington, D. C. 6 FOOT TV CORD type 2050. It conducts when its plate voltage is 16 SLEEVE á RING 3.78 (May be used by the U.S. Government PLASTIC provided the grid is not negative at the SET OF BRACKETS, for mounting 16" tube 2.92 positive, without royalty payments) same time. No signal appears across its input of a supply is stabilized by FREE -1630 Circuit Diagram, with every order The output d.c. during the discharge of static, and because its regulator at any voltage value up to the 10' CATHODE RAY TUBE =108P4 S 24.95 this grid is returned to ground, the bias must be zero metal 54.25 limit of the regulator tube. It compensates for 16' CATHODE RAY TUBE = 16AP4, during a discharge. Therefore. the thyratron fires TUÉE 16CP4, glass 57.50 load current or source potential. 16 CATHODE RAY = changes in and the lamp is on. TV ROOF CONICAL ANTENNA, 10' upright. 7.97 The regulation is provided by resistors R and quick rig 5.95 If the discharge stops for any reason. the a.c. TV WINDOW CONICAL ANTENNA, grid. TWIN LEAD -IN, 300 ohms, 100' hank 1.39 component appears across the thyratron =RG59U CO -AX., 72 ohms, 100' hank 3.99 The phase of this voltage is chosen to make the the plate is If nec- C negative while positive. IMMEDIATE DELI:ERY - 2) . DEPOSIT, BALANCE 0. 0. grid essary, the filament transformer connections may he reversed to bring about this condition. With BROOKS RADIO DIST. CORP. the correct connections the thyratron cannot fire and the lamp remains dark to warn that dis- 80 VESEY ST., DEPT. A NEW YORK 7, N. Y. charge is not taking place. CORTLANDT 7 -2359 RADIO -ELECTRONICS for 7:t \ bQndoas / Gionlli-c Colossal BARCA/HM RADIO FOt//PHENT

I -aó WIMPtlo CONNECTORS SOS EMERGENCY A. N. ELECTRICAL TRANSMITTER lS Fano us Gibson Girl Transmitter that ' A. N. electrical connectors provide a fast, easy way to connect during or disconnect one or many electrical circuits. This offering is tieaola, ny a dresallists° ter onp and airplanes. No es. of intense intern( to ALL manufacturers of electrical equip- power ment inasmuch as we have a huge supply of these connectors al ont It isamu ely necessarytó rn very reasonable prices on a slid- the crank on `the top of the trans. and can dispose of them at nutter and power is generated and the ing scale. The more you need, the lower the price. Plugs and distress signal I sent receptacles supplied with either male or female contacts. All raioases en . Brand New. Gibson Girl Trans. cgp,p built to rigid Army & Navy specs. mutt complet, with tubes. CHASSIS E 3100 , r3100 3106 3106 125-45 20-19P 18_205 22-25 28-12P SS_1s 105-25 24_7s 22 -125 ANTENNA 36_75 28-165 125-IP 16-12P 20 -23P 3e-7P 2U-8S 22-las 20-23$ KIT 20-Is Gerson Gid tr 20-1 3102 18-22 24-4F nutter. 300 ft. 20-24P 24-10P (crane wire. 2 bal 32-6 Is-los 20-11P 20-15 12-S bona, 2 hydrogen 20-225 18-Ils 20-3P 22-145 22-3OY ee 24-105 20-245 18-135 22-10 22-85 kite ftorOe`windy 2e-168 14-35 165-7P 24-285 us-35 SINGLE -GANG w a 21-70 16-75 165-1P Is-11.5 16-115 `light. 18-2P 16-1IP 16-75 20-22P INSULATED -VARIABLE Complete kit. s \\ 24-40 24-11P ?Ó-1Ss 20-135 24-45 85-15 12-Sp 16-85 CONDENSERS 18-85 18-11P 22-30P 22-30P $995 ;O-9Pe-1 145-1 20-275 22-85 22-115 8-45 14-3P 20-95 120-3s I25-/P be 165-4s 20-9P 16-I15 145_25 aM UNk 36-15S 16s-16 Ï(.rsïóti.5i,arayi_iüoiiói51a'ov `Ptf1 ;M ur1 T1 s1.a 22-16P 165-SP 12-55 22- F',11m1f?`dn j 18.125 165-IOP 28-125 10-155 I65_SS .ioi: i4_iiipiÖ. t . 12-SP I8-12P 18-4 1a-95 18_125 a euntrol. oura L 20-3P 28-15P iili,nt... 10 00 20-i9S 32-15 22-30P 145-2S ervtre. I8-4P 20-8P 18-35 22-145 100 sung i ,. 24-55 3-180 16-115 125-4P 165-85-_ I swot fix 1.40- ;0i i°: 24-7P 32-4 16.11P 165-1s I65.-R5-_2 j i n. I.. 1e1 mml l. lo 10. Li.aO-t0Ó for .00 OS 20-115 32-9P 18 125 28-IP LINE 20-35 145-7P 20-3P 28-15 20-85 3106 18-15 18-ss FILTERS 32-95 32 -1015 le-lP la_19 197.5107 I suPPresalneresalne 32-18P 28-9P 145-15 165-4a 28-7$ noisetor nd appliances. ESrit contains 4 mfd oil Inquiries invited from manufacturers, foreign governments, idled condensers, 50 hichoke In ll distributors, etc. Prices quoted on boys of quantity! ampeldeed and TWIN COAXIAL CABLE heavy current co 7a., .12 ndedn nduot- t' actors. 5 1 7.00 shitlded, i YI-lacket. value for 55.00. .iivethylene core. 70 to ¶12 e . ohms. Rea. 72e per ft. íßu price 1115 pe 100 I t tinder R0 -5711. Also P.M. SPEAKERS 3 -FOR -1 t! 72.00m Coas. SALE 15 4.60 per loo ft. Latest (prat PM SPeclk er to a full% - orlo. ALL 3 ITEMS ONLY 57.00 metal rah ht,. i.'Speakter and case tilt corn- 0 ALUMINUM GEAR log l8t.e : ntdrullatI °8 callers. 1unlc two IW erful el artrie Moto, RT 1579 in t addition make per- O lit :itclieti gee It2 yag: cot WITH TUBES, fect intercom emiro. diame in size from .;o 4 Inches DIAGRAM AND ions. 54.50. l m ter. Iteadliv r' tared t n rtudln¢ rout trans. beam antenna or , otter aSS PARTS LIST former 54-7.95. Oe 514.95 HEAT GUN SIGNAL CORP INTER - lied plastic. streamlined. pistol grip heal gun. Blasts lotls hot CONNECTOR RELAY BOX 130A air at 20 Cu. ft. per 1 o ute. Big rugge.I -tai. t.duu lilt, 11(lí l ti. 11 t I , lea Dull, I. .,,i I highly Iirl i.ne DDC motor that also` fil lltttinom lcacase : 1t a Ill g 21:. an 5 cold air. tine to contains Sn of c ,tenser e sensitive relat n. lenlators. n ra ltO basil - and terni,.,, eat r8 tturetors. dry Ignitions. strips. Order several at the givenw,n Consists of three stages leasode 0827.5 nuirk- nd BFe uull,ut s el high galt,, high 1 dry thaw out radiators or Price of only 01.95. Paint,. wafer Sam cycle pine,. . Guaranteed ..r money - fidelity amplfier BO 11111' a Inre g funded it timed. prenant. suppiY onn same 13íy ICI.. ehasile, protected by Slays. S1Ì.95 REMOTE which upatan CONTROL -al steel over tunes and mortal UNIT -Aluminum < Made Imo Western Electric with typical ISOLATION 4 a 3 ii 2 e tanins uallformer°OnentaHuth as TRANSFORMERS I resolution counter, 2 nnsers this Eliminate fireworksradio Itotentiometers. triple units is obviously Intended to give years he atlluatmental knobs of trouble-free service with no more blhs ótlnñe Jack. and t anti °TV sets that requirea O,, tiros Ñe

BUFFALO RADIO SUPPLY, 219 -221 Genesee St., Dept. DECEMBER, 1949 76 Ihecstion Box

PORTABLE AMPLIFIER FOR RELUCTANCE PICKUP ? Please show an amplifier I can use A. The schematic shows the amplifier with the General Electric variable-re- you want. The 6SC7 input stage, espe- Like peas luctance pickup. It should be a high- cially designed for the GE pickup, fidelity unit using 2A3's in the output should be well shielded. Adjust the 2A3 stage. -M. L. G.. Charlotte, N. C. filament pot R for minimum hum.

6SC7 .I 6SN7 6N7 2A3(2) SKaPTOP SEE in a pod 2 NOTE 47011 VAR. PE LUCT. .2S PICKUP .05 3 4 IOOK ti

1701( 47a ia SPAR

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6 a0T450V NOTE- SEC. TAPPED AS rOLLOeS LIMP. IN OHMS 1:- l6 500, 333, 250, 200,125, 50, 30, 20,15,10, 7.5. S. 2.5,1.2 QUAM TO PM SPEAKER 4 5U4-G /

' `o PILOT 6.3V/2A TO FILS Only Quam offers morel The U- Shaped Coil Pot, providing an un- broken path for the magnetic lines of force, thus producing a stronger MASTER -TO- MASTER INTERCOM AMPLIFIER magnetic field with higher efficiency and improved performance, is an ? Please show and amplifier I can use end of the input lead to permit fasten- exclusive Quam feature. plifier for use in a master-to-master ing under one of the screws on the The Quam Adjustable Voice Coil, intercommunication system. I want to terminal board. This lug connects to the permitting accurate centering after use five master stations connected so output terminal corresponding to the assembly and virtually eliminating one station can call any of the others number of the station. rubbing voice coils, is also found even when their amplifiers are turned The input transformer should have only on Quam Speakers. off. I hare several 5Y3's, 6SN7's, and a ti-ohm primary and a high -impedance No other speaker offers such out- tiV6's which I would like to use. - secondary. Shielded intercom cable standing extra features -such extra IV.B.S., Inglewood, California. should be used on long runs. It may be value. For all your replacements, A. This diagram is for a single ampli- necessary to connect the common con- specify Quam. fier. You will need one for each station. ductor to the chassis of each of the Mail This Coupon A spade lug may be soldered to the free amplifiers. For Free Catalog

N/a50V 10K 1 I 6B A 6P .01 I OUT TRANS 6SN7 lf 6V6 Z= 5.511 . TALK It e >e INTERCOM 500K VC .7 2.5 ~- o - - 6 a Ì LISTEN SPEAKERS TRANS INPUT Q o r 1 1 amNichols Co. r_41 PM L DPDTaPRIN6 o 521 E. 33rd Place 1 RETURN SW Chicago 16. Illinois 270Á Please send me Ouam catalog. t i I Name I Address ot-la City State GOVERNMENT SURPLUS!

WORLD'S LOWEST PRICE TERM.NALSTRF. 6154 7 OFF COMM 5V /2A 60MA OR MORE 70 oll oe 4 D7Vc STATION SELECTOR 20/45 VV 10--0 L` 13 INPUT LEAD.CONNECT TO OUTPUT TERMINAL CORRESPONDING TO COMPLETE WITH ä COMES 5V3 STATION N° ON STATION N °3 IT EDGERTON 6.3V/2A V10- -0 SNW10 BE CONNECTED TO FLASH TUBES TERMINAL N °3. 4 615 PINS- SN7:7-6; 6vó:2 -7 F SFLECTOSS 1)I.1 15- EASY TO CONVERT INTO J A 2 -WAY PHOTO ItY FLASH UNIT OPERATES ON 110V. AC & 12V. BATTERY CONVERTING RECEIVER OF BC -654 -A Brand new at a fraction of origina cost. Contains finest component parts available. All necessary have acq,r,,,d the receiver sec- Pont batteries. -L.P., Ojai, Calif. After ? I parts and complete instructions included. A. was controlled by a conversion. works on 110V AC or tion of a BC -654 -A transmitter-receiver The receiver 12V battery by a Nick of a switch. $68. radio set. This receiver has a 12 -point CW- OFF-PHONE switch on the transmitter Immediate delivery on all mail orders COMPLETE terminal strip on one end. Please show panel; therefore it will be necessary to 165 W. 46th St., N. Y. It, N. Y., De1t.RE s CINEX, INC., how the receiver can be made to operate replace some sections of this switch be- RADIO- ELECTRONICS for 77

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= OC 71: cc 6 41" IM 1314.5 o 0 a. El] IM Lid ;7 = 3 -- U 45.; 7, DECEMBER, 1949 Question nos 78 fore the receiver can be used. A three - position, five -pole switch and A- and B- batteries should be connected to the JAcQN numbered terminals as shown in the DIAL LIGHT

DIAL LIGHT SW

N°lo A +1.5V

559 B 90V

N°7 o B+90V N°II

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' 50 Band Width to 4.5 megacycles! 510 High Sensitivity of .018 volts-per-in. N°3 vs-0 o Now, for the first time-thanks to an amazing N°I N°2 has in electronic discovery- Jackson combined PHONE o wide width one oscilloscope both band and err o 220 High deflection sensitivity. By merely flipping CW N°4 N II a switch you can choose from one of three sensitivity ranges, or one of three other band NOTE- NUMBERED LEADS GO TO TERMINAL ON STRIP ON RIGHT SIDE OF CHASSIS width ranges. Here is a fine instrument, perfectly suitable for laboratory analysis, yet well diagram. A heavy -duty A- battery is within the price range of the average radio required. A 2 -volt storage battery and serviceman. a suitable series dropping resistor The new Jackson Model CRO -I is in produc- should last much longer than dry cells. tion right nowt It is priced at only $195.00 net. A special high -frequency signal tracing de- THE CIRCUIT modulation probe is also available at $9.95. OSCILLOnXR?E Get your order in today! Please print a circuit of the famous one -tube Oseillodyne receiver along with coil data. I built one of these sets a long time ago and found it to perform t zYreoe troiueeo better than any other 1 -tube set I hare feeotedifrea constructed.-L.E.P., Dayton, Ohio Wide Bond Amplifier: Easily usable to a cycles to 50 kilocycles in 5 steps. full 5 megacycles. flat within plus or minus Special Features: All controls on front pone?. A. The Oscillodyne circuit is shown. 1.5 db. from 20 cycles to 4 megacycles. Provision for 60 cycles or external sweep. The performance of this circuit depends Deflection Sensitivity: Vertical amplifier, Also has provision for grid modulation at on overcoupling between Ll and L2 and 60 cycles or with external voltage. Full 5- .018 RMS volts -per -inch on narrow band. on critical values of resistance and ca- Horizontol amplifier .55 RMS volts- perinch inch CRT. Same height as new Jackson TVG -I TV Sweep Generator. Rear terminal strips for pacitance in the grid circuit. The coils Input Impedance: Direct balanced, 6 meg - direct connection, through capacitors, for are wound on 11/2 -inch, low -loss, plug - ohms shunted by 11 uufd; unbalanced 3 meg A.C. voltages to CRT deflection plates. light The tickles' L2 is wound ohms shunted by 22 std. Horizontal ampli- weight, easy to carry. Provided with leather in coil forms. 1.5 megohms. fier carrying handle. Attractive all steel cabinet s%1 inch below the grid coil Ll. The out- Sweep Frequencies: Saw tooth wove, 20 with gray Ham -R -Tes finish. side ends of the windings go to plate and grid circuits and the inside ends Dynamic Tube Testers RF Oscillators go to phones and ground, respectively. jAC SON ranges are Vacuum -Tube Voltmeters TV Sweep Genera- Coils for different tuning wound as follows: Service -Engineered tors AM -FM Sweep Generators Condenser Tuning range L1 L2 Test Equipment Checkers Audio Generators Oscilloscopes. (approximate) (turns) (turns) 550 -850 kc 105 105 800 -1,500 kc 67 67. Jackson Electrical Instrument Company Dayton 1, Ohio 1.5 -2.5 me 36 36 2.4-3.5 me 23 23 3.4 -7.5 me 14 12 7.2 -14.5 me 7 9 14.0 -28.0 me 4 6 Both windings are made with No. 36 d.sc. wire. The tuning capacitor and coil and tube sockets should be designed Your T.V. set is no better than its antenna. Gel pictures day -in day out with 6C5 /6J5 strong, crystal -clear ... u ANT ETC t Tel -a- Ray -video reception -master. g2-25Hyt Extremely rugged ... yet lightweight Quick, trouble -free assembly Guaranteed against corrosion ... weather damage Made of Dural; stainless steel fittings Absolute lightning protection 0005 Very high front to back ratio. L2 son r meet every requirement for PHONES Twenty -two models to REGI NI CONT both fringe and service areas. B+ 90V for further 0 GND OB Write a A-ct oq+ facts and prices to: TEL -A -RAY ENTERPRISES, INC., BOX 332, HENDERSON, KY. RADIO -ELECTRONICS for Question Box 7! for good high -frequency performance. The original circuit was designed for a type 27 or 37 tube. Modern medium - 11/F 0//ti 011 Of /TS OW mu triodes such as the 6C5 and 6J5 may be used. Dual -purpose tubes having a medium -mu triode can also In used in the circuit. FOR PERFORMANCE! If the set does not oscillate smoothly over its tuning range, try using a smaller grid capacitor and experiment with grid resistors between 1 and 7 megohms. A good outside antenna is required for best results. The antenna trimmer will have to be adjusted to eliminate

Another great any dead spots that may appear in tim tuning range. UNIVERSITY FIRST! SHORTWAVE CONVERTER HANDLES 30W CON- I have a small a.c. -d.c. broadcast re- TINUOUS INTEGRATED ceiver to which I want to add short - PROGRAM MATERIAL wave coils to increase the tuning range to 14 mc. The receiver has a 6SS7 r.f. EASILY ACCESSIBLE, amplifier, 12SA7 converter, 6SS7 i.f. ALWAYS VISIBLE TERMI- detector and amplifier, 12SQ7 second NAL BLOCK first a.f., 501,6 power amplifier, and .1:;7.5 rectifier. It has a loop antenna TAPS MARKED IN BOTH and rut -plate tuning eapacitor.-T. P., IMPEDANCE AND WATTS Monmouth, Ore. A. We do not feel that your receiver SHATTERPROOF BAKE- is for conversion to all -wave suitable LITE BODY, ENDURINGLY reception. We recommend that you construct a small converter similar to BEAUTIFUL diagram. Plug -in the one shown in the SUPER- EFFICIENT "W" coils are used in the antenna and oscillator circuits. SHAPED ALNICO 5 The plate of the mixer tube is con- MAGNET nected to the antenna post of your receiver through a 1600 -kc converter output transformer. Cl and C2 are handset capacitors and can be fitted with standard bar -type knobs. The handspread capacitor C3 should be fitted with a slow -speed dial. A B -sup- MODEL ply delivering from 180 to 250 volts PA-30 can be used. DRIVER +250V WOK CONVERTER OUTPUT - - - -1 TRANS UNIT FIL PINS 2 -1 r- 10 RCVR i `KANT POST - - J -NCO -Ax 6K8 L4 S BUILT -IN, MULTI -TAP LINE MATCHING TRANSFORMER

L3 These rugged drivers represent the first high power continuous duty, completely waterproof units available with built -in line matching trans- 3000 140)00 formers. New type W- shaped Alnico 5 magnets result in the elimination of stray fields and a greater concentration of magnetic energy in the with 22 en- Coils are wound No. voice coil gap. Exclusive UNIVERSITY "rim centering" assures per- wire on 1%-inch plug -in forms. ameled fect alignment and concentricity always. Units may The number of turns per winding is - be used with shown in the table. equal facility on constant voltage and constant impedance output sys- Turns tems. Transformer and voice coil terminals are brought out at the Coil 1.7 -3.5 3.5 -6.5 6.5 -14.5 bottom of the unit to a terminal block which is an integral part of the mc mc mc molded housing. A translucent cover plate provides ready access to LI 22 7 5 the 16, 165, 250, 500, 1000, 2000 ohm terminals and their equivalent L2 70 25 12 wattages based on 70 volt line. L :: 55 22 9 L4 18 6 3 WRITE DEPT. D FOR ILLUSTRATED CATALOG All coils are closewound except for the highest range. Here, it may be a necessary to space L2 and L3 to cover the desired tuning range and to make the coils track. Spacing between LI and L2 and L3 and L4 should be approxi- LOUDSPEAKERS V INC mately Ms inch, except for the 6.5-14.5 - 11 80 SO. KENSICO AVE., WHITE PLAINS, N. Y. mc range for which L4 is interwound with the ground end of L3. Famous World -Wide for LOUDSPEAKERS DRIVER UNITS TWEETERS PORTABLE POWRMIKES DECEMBER, 1949 !t0 Radio-Electronic :ircuits REGULATED POWER SUPPLY WIDE -RANGE SWEEP Voltage -regulated power supplies In this circuit, the 6B4 -G acts as a The over -all usefulness of oscillo- have many applications in radio and variable resistor between the filter and scopes is, in many instances, limited by electronic fields. Gaseous voltage -regu- the B -plus output terminal. The re- the highest frequency of its sweep gen- lator tubes such as the 0A2, OB3, and sistance of this tube is controlled by erator, usually in the order of 100 kc. 0C3 perform well in circuits in which the bias applied to its grid by the High -frequency sweep circuits have the load current does not vary over too 6SJ7 d.c. amplifier. The tubes are con- wide a range, but are not suitable when nected so a decrease in output will a variable regulated output is desired. lower the bias on the 6B4 and decrease A circuit of a variable- output regu- its internal resistance to restore the lated supply was presented recently in output to its present value. The output voltage is controlled by varying The C -D Capacitor. This supply, shown the voltage on the control grid in output of the d.c. the diagram, maintains the am,difier. This stage is stabilized by voltage within 1 volt with input voltage passing its cathode current through the or output current variations up to 30'4 . 0C3 hV R105. The output voltage can be set at any Oscillations of a relaxation type may desired level between 175 and 300 with occur in this (and other voltage-regu- a front -panel control. The maximum lated power supplies) if the voltage drain is 60 and 110 ma when the output across the gas tube is too low. Keep it been developed, but they are seldom voltage is 300 and 175, respectively. well above the extinction point. used in low -cost equipment because they require several tubes. A new wide - atat- 1011/130MA 6SJ7 s1tEEti range sweep generator having a range EnSV/ 3A 0C3/VRI05 from 15 cycles to 500 kc was described 1511 2w 1011 114 The ®SW. 350v 5Z4 in Review of Scientific Instru- 117VAC é te 120MA 2 ments. The circuit is shown here.

t e 6 The frequency ranges are changed .350Y by I T16 16 switching in different values for 120MA ton /IW capacitor C. The frequency is varied within a given range by the FINE FRE-

!6.3V 7 QUENCY control. The ranges are: 15 -60, .1A ISV -WW CT 45 -180, 130 -500, 400 -1, 700, 1,200 -5,000 OUTPUT VOLTAGE CONI cycles, and 4 -6, 11 -42, 40 -200, 100 -500 STANDBY SW 1011 /1W kc, when C is 0.5, 0.15, .05, .015, .005, OFF - cl .0015 (If, and 500, 150, and 50 µµf, re- ON PE's'.' A -EP DC OUTPUT spectively. A 20 -volt sawtooth is available at the the NEW Of RAD10 - ELECTRONICS MAGAZINE LIBRARY

INGENIOUS, CUSTOM -BUILT STORAGE FILE Another WALTER ASHE Value Scoop! sch plus 6c each to cover 1- asking and postage (any. .here in U. S.) Holds 12 complete issues of magazine in its present 82 to M25t 98 page size. Measures 12" x 8r/a" x 2;,s" Here s the brand new, grand new way to preserve each issue of RADIO -ELECTRONICS Magazine! Made of high quality Kraft fibre board, printed and constructed to look like a Buckram -bound book. Affords neat, orderly, flick -of-the -finger convenience. Handy Refer- ence Index, printed on back, records the location of selected articles, wiring diagrams, etc. A "must" for every bargain -conscious reader of Radio -Electronics Magazine. At the low price you'll want several of these serviceable. attractive Magazine Libraries. Order now for immediate delivery. Walter Ashe Radio Co. RE-12-49 Use the handy coupon. 1125 Pine St., St. Louis 1, Mo. FREE! Rush my order for: Radio- Electronics Magazine Library at NEW _ (q a 1ity) 25c each (plus 6c each to cover postage and packing) 1950 Remittance for $ is enclosed Catalog (amount) of Radio, Electronics O Mail my Free Copy of new 1950 Walter Ashe Catalog and Television. 160 pages. The Treasure Name .. - -.. Chest of Values' Address a Urd,-r your copy Zone__ State today. RADIO -ELECTRONICS for Radio-Electronic Circuits 81 output terminal- over the entire range. The generator may be synchronized by applying a 0.2 -volt peak signal to the grid of the right -hand triode, which is normally grounded. The 1,000 -ohm variable resistor in the cathode return of this triode should be adjusted for short flyback time on one of the low ranges. Flyback time is decreased and BRAND NEW! IMMEDIATE DELIVERY! INDIVIDUALLY CARTONED! GUARAN- the upper frequency raised as this re- TUBES TEED! sistor is reduced. Do not set the value too low as this may cause the lower TAKE ADVANTAGE OF SPECIAL QUANTITY DISCOUNT OF- DUAL HEADSETS FER. Order 25 or More Assorted Tubes and Deduct 5e from the Tube. portion of the output signal to be U. S. Signal Corps. 6 n. cord Price of Each clipped. and tips. 2.000 ohms. Indi- 1Se Each 5X40 soss 46 SOLB vidually cartoned. S23G 57 50260 2050 SY3GT 76 53 2051 1,°."Priced amazingly low 202e SY4G 75 Se 3506 FF al $1.49 2C34 6534 6ar5G 80 CAPACITOR ANALYZER 162e 66146 11723 75 1644 6AT6 85 by 7193 2C24 6AU6 084 The capacitor analyzer, designed FINE QUALITY 6946 50e Each 59e Each viás° 66E6 Mr. Henry Levine and described in ecsar 45e Each 1.50T 6C6 01A lA6 074 ARSNY News (New York), is some- 19e Each 6r6G 195 25S lA7GT SPEAKERS 65607 ices , LA4 what from de- 617 1L4 LC6 different these usually Buy More . 57AS IRS 1C7G 656aT ]07G ILDS Save Mere! err70 154 ILE3 scribed. Provisions are made for testing v94 687GT Iss 1D8G ILM4 Guaranteed! Check %99 "TSOT 1570 ILNS capacitors under static and dynamic BSA70T 265 1.4 INGO these for magnet 'Sc, 2.6 iSa 174 conditions, the type of test being deter- sizes and check 29e Each 650707 1040 .uSaT 3056' 105 SVaG mined by the setting of the double -pole, them for price .. . 6S.7 GAAS .SGT 6An7G 2A7 6517 601e IN4G 2 %2 SAGS five -position selector switch. ALL ALNICO V of 6557GT 607 I.SGT 614 5 Bceo 8807GT 6.367 1N6G 68r6 Ea. Ea. 6ueaT ease 1J6G 68G6G APpgax 117Z8 OR 117Z4 65.707 6V6GT 1NSGT 3" P.M. -.68 oz, .99 S .95 65R70T 56507 68116 f 8.7. 6X4 e670T 106 616 3" P.M.-I.47 oz. 1.15 1.05 724 exSaT 306 6.186 4" P.M. .99 .95 126e 126U6 A5L70T 3.4 6,S 6GS 4" 12...T 126V6 354 6W4 P.M.-I.47 oz. 1.15 1.05 12 i SOT I2JS 655707 3V4 ówe 4" s 6" P.M. 1.69 1.59 12.6 12J7GT 695 6Y3 26 /2N7GT 524 5" P.M. -I oz. .99 .95 3e 6260 6ASO 12a : 2.70T 764 t2AT7 5" P.M.-1.47 oz. 1.15 1.05 TS670T XXL 6.6 '4A7 6" P.M.-I.47 oz. 1.55 1.45 é 125i5 7.5 6.0S 4G7 sI.VT90 125.7 7.6 6660 1467 6" s 9" P.M. 112415 2.39 2.25 6572 IT5K7aT 7r3 1201 22 8" P.M.-2.15 ex- 12s1]GT 7K7 608 70L7GT 2.75 2.59 1255707 606 r P.M. -1.64 oz. 2.95 2.74 12.07.2 12.76 ái°0 8" P.M. -6.8 oz. V.á517 1928 12AÚ7 I.Sa 69e Each 3.69 3.39 121.6 6.70 10" P.M. -6.8 oz. 3.75 3.43 24. 390 Each 2526aT 120E6 6T70 AAC7 1652 27 1251707 747 8AG7 w BINDING POSTS, 32 1223 7CS 6A55 5" P.M. with 5016 output IA3 14.7 87 trans- I04 35 SI ,17Z6GT former. Large magnet. tus 35L6QT 25.60 707 2SLSOT Only S1.24 ea. 35W4 1200 89v Each MAC CAPACITOR UNDER TEST 26e 3525 325,767 1/2511I 3.4 3526 34 UN 352407 25aC5 Lots 4.6 41 1BIGT 8016 MAGNAVOX 5.40 42 43 SOCS 65.6E When the selector is in position 1, of 4 S104 47 4525 SOCS A308 Ea. Ea. d.c. is applied to the capacitor under HARD TO GET TUBES: Our tube stock is constantly being expandni. 8" 680 ohms field with 11 your tube is not listed, write us! test to check for shorts and leakage. 6V6 P.P. output, cord Reject the capacitor if the neon lamp and plug S3.69 53.29 VM NO. 405 SPEED INTERMIX CHANGER 12" P.M. -21 oz. mag- -2 glows continuously or flashes more than net, 6V6 P.P. output, Sensationally Lew Priced! Intermixes 10" and 12" records once each second. Alternating current cord and plug . 5.95 5.50 t< Long Playing Needle . . 12" 1 000 ohms field, All Adjust- is applied when . to the capacitor the 6V6 P P. output, cord ments mode at Factory comes selector is in position 2. A good unit and Plug 5.95 5.50 complete with 2 GE Reluctance Cart- will cause neon lamp to l2" 680 ohms field, 6V6 ridges, one for 33.1/3 RPM. and one the glow con- P P. output, cord and for 78 RPM. Overall size 12" s 10". tinuously while an intermittent capaci- plug 5.95 5.50 Practically a gift from Santa till IIC at tit' before low price 1.577 4saa tor will cause the lamp to flicker RCA SPEAKERS l spasmodically. If the lamp glows con- E 50 CONDENSER -RESISTOR COLOR CODE 2" x 3" P.M. Alnico V S .79 CHARTI Just send us your name and address on a

stantly, tap or press the capacitor to 12" . P.M. Alnico V .. 3.95 FREE penny Fpost card. Say send me Senco's new 1950 con - make sure it is not intermittent. The 12" P.M. -6.8 oz. Alnico V. 4.75 denser color code chart. indicator does not glow when a capaci- Minimum Order 82.5e: Send 25"; deposit for all C.O.D. shipments. Include sufficient postage-excess will be refunded. Orders without postage will be shipped express collect. All prices F.O.B. New tor is open. The analyzer becomes a York City. relaxation oscillator when the switch Radio Men Who Know PEC for FREE is on position 3 or 4. Position 3 "SPECI ALS THE is for S A V E AT OF capacitors up to 0.5 Id and 4 for larger SENCO- MONTH BULLETIN- units. In either position, a good capaci- SENCO RADIO. INC., Dept. P. 73 West Broadway, Now York tor produces a constant glow. Good 7. N. T. Tel: BEeckman 34498 capacitors of approximately .0005 µf or smaller will produce a halo around one of the electrodes. Electrolytics are tested with the selector in position 5. 30-44 Megacycles F M Open capacitors will not produce a glow. The lamp will glow brightly and PR -30 Receiver For then taper off as a good electrolytic charges. MOBILE CALLS Emergency thrills ... hear "news in CORRECTION the making" . . . as if happens.

An error was made in describing the 6 Tube superheterodyne, 115 volts, Hopax Circuit Breaker Plug in the AC or DC. Now you may enjoy . August issue. It was stated that on POLICE MARITIME '4495 overload the small lever between FIRE FORESTRY LIST the HIGHWAY TELEPHONE prongs "springs up and pushes the PRICE plug out of the socket." Under any ordi- PR -7 POLICALARM tunes 152 -142 mc. $39.95 nary overload the lever does not spring See your dealer or write Dept. RE -2 up and push out the plug, its only func- RADIO APPARATUS tion being to reset the contact of the CORP. circuit breaker. QALaRM 303 FOUNTAIN SQ. THEATER BLDG. *PoLIc INDIANAPOLIS 3. INDIANA DECEMBER. 1949 82 'rechliote. - INTERMITTENTS IN AUTO SETS Intermittent operation or oscillator failure in Zenith radios in Hudson auto- mobiles can be caused by a leaky cou- GERN SBAUK pling capacitor between the plate of the r.f. amplifier and the control grid (pin No. 6) of the 7B8 converter. The control grid draws so much current that the oscillator section is paralyzed. U 3 RARI The same trouble occurs frequently in Philco UN6 -550 models. In this set, Each of these books supplies the coupling capacitor is one of the two usable information mica trimmers in the can housing the No. 29 -HANDY KINKS arid i.f. rejector and wideband coupling cir- SHORT CUTS. :\ cor0011v edited compilation of tittle savet -. KMk. cuits. on Antennas - -Power Supplies --feet Bunhnnent- Serdcitia in the Situp Failure of the muting switch to open - Phonographs and Amplifiers-Coils and 'rran.ronners -- NI i.eellaneuu. when the push- button is released is an- Subjects. 500 each. other cause of intermittent operation No. 30- UNUSUAL PATENTED of the Zenith sets. CIRCUITS. 1944 -46..5 sold tome to new honk -ups' A selection ut unusual T. M. FERREIRA, circuits. many a suit ur watti m, mlemit'll --tir great retains Port Rlizuhrt /,.South Africa sled lin el elW miesm 1.01111 d l'Imufia Iteteclura and \naditlrr- l'owr . ritmi, his yh.rrllaneuu. cir- MOTOROLA V1105, VK106, VT107 r loti ('heuita. 50e each. cuits -Fate Check the focus coil for shorted turns 0 No. 31 -RADIO QUESTIONS II AND ANSWERS. An.orn to mua or short to chassis when the focus and mos. ! ell Irryli.'1111) asked durst ('trar O circuit diagrams. Ampluiels itr brightness controls do not function timers -'ll auunÍliefa Mom. ami coil has a resistance of Test EWtluulem- -Inter phone. -- ''utter properly. The Supplies -Phonograph Atoull0era- 345 ohms in sets using chassis TS -9, Syalemx. each. VITAL I,. 4. 50e -9A, and -9B; and 540 ohms on chassis No. 32- ADVANCED SERVICE TECHNIQUE. An up -lo -dam vol. TS -9C and TS -9D. Check the chassis lechou of inhnmutlml lid the ad imuced ae titer il: \' um,al number to be sure of the correct resist- Fenl- l ln. Be FOR TV SERVICING 'flaekr,lg ma 'torde Ac-at ance. eedback 'fine 1'otihul i- nus l dims yllcoambmmes I 5elr tm'eh- T. S. PARKER, ul:nmor .Juke A new and highly important hook! Gives a complete understand ina Lund.tieakrl. - t 01,i I'hnul:el oscilloscope operation, and how Iluses -Sel u'uig lits Hartford, Conn. ins of working principles behind - Ilum Elimination FsI Set o rig to use the instrument effectively. Clearly written with a single 500 each. purpose -to help you use and understand Ihr oscilloscope. No man HEIGHT AND WIDTH ADJUSTMENTS servicing television receivers can afford to he without this knowl- No. 33-AMPLIFIER BUILDER'S edge. Insaluable for anyone who uses the oscilloscope. GUIDE. hnaivablr rot the dtvigins Upon removing the average TV set and bit I liter of audio epupunnt. 'I eus hit , build lite from its cabinet, you will probably find amplifiers i olio puoet uritpSis l S :tel tt m1 the C -R tube covered with a film of ALL ANGLES COVERED IIIg r, nitr to hcl., Ie,l sign inhuminhumation l'uni 1mdL.. for the portion pro- Phase Imershui -ISass a Ti Ode dirt and dust except Chapter l- Direct Current and Alternating Current. Visual observa. Boosters Volume Expanders - Ile- tected by the mask. If you outline the tion and measurement of varying voltages and currents on the atm., l'o'ading - Internal Feed- cathode -ray tube. Chapter 2 -How beam from electron "gun" back. 500 each. mask area with wax crayon, you will prolects image of curment and vonoge variations 000 fluorescent No. 34 - RADIOELECTRONIC he able to check the operation of the is screen, and how beam deflected by e'ectrostotic and eleCtromag CI RUC ITS. .\n c stein its collection netic means. Chapter 3 -How signal neflec,s electron beam vertu. of dirndl diagrams. wills brief. to- width and height controls before the cally in c.r tube rod seen vo tone des errs beom horizontally. Role the moon h.er ipr ions of each. In- set is returned to its cabinet. of the oscillator -the gas discharge tube -the multi. cludiug: iiin rcemmu icat Iona Sys- sow-tooth Balao vibrator -s, nchronizahon- lacking. Chapter 4 -The cathode -ray tube mua - furet mitotic. - CHRISTIE URBACK. t'iKUlls- V. T. \ till tnee is .s mph - -accelerating and focussing power supplies -the sweep generator- tiers -Kmri ers -11ím Amptiders- Pliilnrlrlf,ßin. PcIrtea. the horizontal and vertical amplifiers-contrms on oscilloocope -how SbutI W1111.\d:Will.v Klrcln runic Re. to operate o 'scope. Chapter S- Aligning TV i.f. channels -1V front. lays. 50e each. of i.f. in AM and FM sets. Use end alignment- Alignment amplifiers No. 35 AMATEUR RADIO ZENITH M -790 -Z (FORD -MERCURY) generators-i.f. alignment of o.c. d.c. receivers- bondposs - of signal BUILDER'S GUIDE. brat nie -h:nn" muted intermittently and the alignment -aligning the discriminator -the ratio detector -r.f. align. xlm builds his pan. l'tartirot. duwm The set ment of AM and FM receivers. Chapter 6 -Audio output measure. 10 earth it tells how to Ihdld .\ 2 touch -tuning failed to operate. The ment- voltage gain -power cutout -audio response curve plotting - Meier hand Acorn Tube Set- -yiittla - measurements. Checking saw -tooth amplifiers-mognetie Iure t 'ono nanirallnna Receive, - trouble was traced to dirt jamming the peak a.c. Lunt times l'ransmitter-- Iteginnrr's -ctian circuits -svnchronizinq courses. Hom transmitter me.is, - moving parts of the tuning solenoid. A Transat i her - l'reaclerl Ir - Rotait modulation. hum- incorrect r se- s -over and under Locotmq Beam Aerial - Puiser Supplies -and shield was fitted around the of ,ibr,tor rower supplies. Phase shill in audio amplifiers other hang gear. 501 each. cardboard prevent further trouble after No. 36-RADIO TEST INSTRU parts to RENTS. A 5ItST for every radie the unit had been cleaned with carbon 112 PAGES 103 ILLUSTRATIONS man. This latest book on titi hung lest equipment places cnutharia m tetrachloride. Pram l,wl malrutuon nf: Signal Tracers-rr -rapacity Mlet. Portal 1. ROBERT E. WHALLON, and Beneh Multi- checker -Signal Troy, N. Y. Only 75c Brper:t ol. - Tube Clie -kers - Elec- tronic \ nil aueera -and nia fly others. See your jobber todas or send for THE CATHODE -RAY 50e each. GI:RNSBACK OSCILLOSCOPE along with other titles in the No. 37- ELEMENTARY RADIO LIBRARY. SERVICING. Fur thv alto n,an ono know. little abran I servicing. Bow to get started. and even mure inauatam how to keep going: Plan- MAIL THIS COUPON NOW ning the Service Shop -Equipping the Shop-Systematic 1'ircuit Cheeks - Signal Tracing Slelhodu - Serriemg %1'I' Pl 151.11' 1.1'111\S Inc.. -- Soldering Sere icing It Dull 11 OTHER BOOKS ibr Midge - Dept. 1211, 27, Went Ilruadway. Codons. Foolrola- -'low to Service Speakers. 50e each. New 1 ark T, N. Y. Nu. 29 - bUc No. 38 -HOW TO BUILD RADIO Send me the books checked. postpaid. No. 30 - 50e RECEIVERS. This buck contains .udlclenr t iety of arts tu appeal

CATHODE -RAY : O NO. 90-THE No. 31 - 50e lu e n ailla Ian. Includes Shot t- OSCILLOSCOPE, 75c \\ate,,IL,agiosd. Iuttaile. .\. t'. No. 32 - 50c iineraied. Mhpalitte n nd Stapdard Ihrrtt rra, t'ulrtplite cull -w indura 6 each. I enclose No. 33 - 50e Baia is fill-Dialled. 50e No. 39- PRACTICAL DISC RE- Your Niune No. 34 - 500 CORDING. Whether you're Inter- I clearly) Print ested in amateur tir mutrastonal re- No. 35 - 50e ordlna. you'd tlnd this tnuk Invaltl- Address aile. Tell. how la stake good record.. No. 36 - 500 Each important component a fuit Town State aqui'nn tms No. 37 - 50c hapter. explaining ira IISG and Jobber's Name No. 38 500 the praRtir-al pluses off recording for - eted as ".dl as line underlying prim "John likes a speaker Ilia1 gist's lots of No. 39 75e Moles. 75e each. Address - bass.- RADIO -ELECTRONICS for 'iec1111i/teN

CROSLEY MODEL 52T9 This partial schematic shows a meth- ` Dynamic Mutual od of eliminating the power transformer in this model. All paris shown in the OConductance

PIN 4 OF 5016 TUBE Bt TUBE TESTERS 35 e1 15 IS 16A 168 HSERT47n; I RES o SPAR SOCKET L

ON SOCKET CONNECT LUG 3 f LUGS 35Z5-6 / 12507 RED 1 v 4.7.0\-a 5016 t6 HEY . /iiá'SP -REPLACE I50n/1/2W RES A5 12 WITH the 37 PHONO CONNECTOR Experts 328 BLACK for 117v AC shaded area are either removed or mere- Accuracy ly disconnected. and CROSLEY DIVISION, Avco MFG. Co., Speed Cincinnati, Ohio

SLOW FADE ON OLD SETS A slow fade in older models, particu- sp(en(11(1 í,ttaJ ttt ervt cent a It larly Phiicos, can often be traced to corroded terminals on the tube sockets. Never in the history of radio serv- Clean and bend them to restore positive MODEL 600 icing have HICKOK Tube Testers pressure on the tube pins. If the socket ever been excelled. Their Dynamic has been subjected to heat, its fiber 1. New, smaller, portable, lower Mutual Conductance Circuit has an exclusive HICKOK should be cost tester. long been may be weakened, and it development. Available in a com- replaced. 2. Tests for gas content. plete line of portable. counter, and J. G. DODD, display models. Specially designed Chicago, Ill. 3. Reads directly in micromhos. professional features. The choice 4. Separate voltage applied to of leading radio service techni- throughout the world. SHORTWAVE INTERFERENCE each element. cians A.c -d.c. receivers are particularly See them at your jobber's now, or bad offenders in cases of shortwave in- 5. Detects more weak tubes. write for latest free literature on terference or BCI. This is especially this most dependable year -round true of sets on which the grid of the income builder. first a.f. amplifier, usually a 12SQ7 or similar tube, is returned to ground through an 8- or 10- megohm resistor. * OELECTRICAL INSTRUMENT COMPANY This leaves the grid floating for r.f. le-----x-1O531 DUPONT AVENUE CLEVELAND 8, OHIO and causes grid rectification which produces the interference. Please send me latest literature on To effect a cure, bypass one side of your line of Hickok Tube Testers: the heater to ground with a 100 -visf NAME__ _ mica capacitor; reduce the grid resistor to 3 to 5 megohms and bypass ADDRESS it at the socket with a 100- or 250 -µµf CITY.. STATE_ mica capacitor. WILBUR HANTZ, Ohio ELIABLE 1 -STOP SOURCE MOTOROLA 67L11 If this set distorts when operated EVERYTHING z, from power lines, check the operation iô on batteries. If it plays OK on a good RADIO - TELEVISION - ELECTRONICS battery, replace the selenium rectifier. Catalog No. 501, 144 big pages now bring mailed to A bad selenium rectifier will result Dealers, Servicemen, Broadcast Stations, Schools, Fac- in low heater and filament voltages and tories, Public Utilities, Laboratories, Engineers, Ama- distortion will take place in the 3V4 teurs, Experimenters. It's FREE...Write us if you haven't received it. output stage. In most 3 -way sets, with low operating voltages,the oscillator cuts out before distortion occurs so may r BURSTEIN-APPLEBEE CO. this Kansas City 6, Mo. he overlooked as a source of trouble. 1012 McGee St., This does not hold true in this model Send me your FREE catalog. as severe distortion occurs when the NAME B- voltage drops below 75 volts. JOHN W. TURNER, ADDRESS Newark, N. J. TOWN STATE DECEMBER, I949 84 Try This One

TRINE TUN/NC HEADS

e BC 450 triple remote control box for \o (` `- Command Receivers (SCR 274 N Se- N Co\\P`` p °j5a\o4 Ne Npo ries). Equipped with 3 tuning dials, 3 N \3\P volume controls, and 6 selector swit- nt°AQsta9c i bes'teo r / ches. Used, but in excellent condition. Ncb}o a steal at only $1.50 Each. (Add 25c ar 44'C_ CN each to cover postage and handling). AR CdHw óonéurtooPYr/1 ar8.ga/ od C30/ ?Jo co^tr olrtone 60 tv;r6 sTgid tor

CATHODE RAY TUBE New2volt S BARCA/NS eW e Battery ALL NEW GUARANTEED e 3 CP I (Indicator Screen) $ .75 New Willard 2 y volt Storage 3FP7 -A 1.00 r4/dee/e'arosea' ré o Bée//y Band Po 6 or. Batteries, built in Hydro- we made 3 HP 7 1.25 meter. clear Plastic case. $/ SS ,rte! All New in factory cartons. 5 BP I 2.45 Pdna Shipped dry, just add acid. 5 CP I 1.95

Add 35c each to cover Pos- 5FP7 . . . . . 1.00 tage and Handling. 5 HP I 2.45 BRAND NEW FLAMEPROOF 7 BP 7 2.50 TELEGRAPH KEY 95e POSTPAID 7 CP I 3.25 908 2.45 A/ 9 GP 7 3.50 e All merchandise subject to prior sale, or- minimum order $2.00. No C.O.D. Add 25c ..ch to cor., postage and handling 6532 ECM/Chois der. accepted. Michigan residents en .Il 3" tubas, 35c socls on all 5'- tubas, 50c each an 7 tubes. 9GP7 shipped Esp...., Detroit-ark }p must add 3 Percent State Sales Tax. chews caw.

OVERMODULATION INDICATOR tarily and thus producing a sharp mark the location of each hole. Drill Construltd well below the cost of pulse. The diode plates are connected holes through the wall or chimney. most C -R -tube or meter -type modulation to a 6AG7 amplifier through a stand- Bolt the pipe to the surface with toggle indicators, the flasher -type overmodula- ard step -up interstage a.f. transformer. bolts; then insert the mast in the pipe. tion indicator shown in the diagram The amplified pulse causes the neon lamp to flash. 1% bias does not require calibration or con - The -volt battery MAST tinual. visual concentration and moni- increases the sensitivity of the diode toring to prevent overmodulation. It and causes it to conduct just before the causes a neon lamp to flash each time class -C stage swings negative. the modulating voltage carries the The values of RI and R2 are suitable for transmitters with no more than 500 CLASS C AWL volts on the class -C stage. They are selected to drop the modulated voltage to between 70 and 90 volts-well below the inverse peak voltage and peak heater -cathode voltage ratings of the NEON 61I6. The 6H6 and 6AG7 may take their .1.25 plate and filament voltages from a +300 - speech amplifier or from the transmit- 400+ ter power supply. FRANK S. GUE, VE6BH, 20K Edmonton, Alta. 6AG7 NOVEL ANTENNA MOUNT This method of mounting TV, FM, and lightweight amateur beams does A 10 -meter beam, on a 15 -foot mast, not require straps, turnbuckles, guys, supported in this way, stayed up or other hardware normally used to through -out the winter without guying. class -C plate voltage below zero on mount antennas. Furthermore, the an- G. SAMKOFSKY, W2YSF, peaks. If the indicator is allowed to tenna can be taken down in a few sec- Brooklyn, N. Y. protrude from the panel of the indi- onds without using tools. cator, it will be visible over a wide Select a length of iron pipe which (Better drill the first hole at least angle and some distance away-a fea- has an inside diameter equal to or a foot below the top of the pipe to give ture not possible with other types of slightly larger than the outside diam- the mast ample supporting surface. indicators. eter of the antenna mast. Drill several Or possibly saw a slot in the mast so When the class -C stage is overmodu- holes through the pipe, each large that it will slide down past the toggle lated, its plate voltage goes negative, enough to pass a toggle bolt. Place the bolts, thus affording additional sup- causing the 6110 to conduct momen- pipe against the chimney or wall, and port.-Editor) RADIO -ELECTRONICS for Try This One ue: HANDY BENDING TOOL Experimenters and constructors will find this tool useful for bending light sheet metal for mounting brackets, P" BETTER, BRIGHTER PICTURES" shields, and panels used in radio and electronic devices. Ovv insuline new "BI -CON" ,.rj%

TELEVISION ANTENNA 4IHeavy duty, specially de- signd, all aluminum Single Type and Stacked Array for fringe areas cast ingsfor low -resistance An engineering triumph by Insuline .. . electrical contact and rigid dipole clamping. proved outstanding by actual test. Pre - assembled sections for quick installation.

Take two pieces of doorknob rods Peak ALL- Channel reception. and weld them to the jaws of a pair Suitable for ANY make TV of lineman's pliers as shown in the receiver. drawing. Exclusive - separate High BILLY R. POGUE, frequency and low Fre- The INDOOR The Dallas, Ore. quency dipole -reflector ANTENNA elements. with AMAZING CRO AS STROBOSCOPE Popularly priced. RECEPTION A cathode -ray oscilloscope can be used QUALITIES Write for complete TELEVISION as a stroboscope to "stop" motion. The on ALL CHANNELS catalog of TV antennas and is must have a only requirement that it accessories. competitively priced short -persistence screen. Disconnect the saw -tooth generator from the deflection circuits and connect insuline CORPORATION OF AMERICA it to the Z -axis input (the electrode INSULINE BUILDING 36-02 35th AVENUE LONG ISLAND CITY, N Y which controls the intensity of the pat- West Cuost Branch and Warehouse 1335 South flower Street. Los Angeles, Calif tern). With the sweep generator op- QUALITY PRODUCTS SINCE 1921 erating at a low frequency, adjust the brightness control so that the spot appears on the screen only at the peak of the saw -tooth wave. Then apply external signals to the deflection plates to get as large a light pattern as possible. O . S The frequency of the external signals o should be high compared to that of the 10 ny" --`, sweep generator. N;: fror i CHARLES ERWIN COHN, Chicago, Ill. SIC 'SI utian SI S , u b s t it Signal r b fecesve TV PREAMP ON HIGH BAND Speed Servicing Dynamic OA-WM.MMV. The cascode preamplifier for channels Modern, problems,ro e s , SS.S tells HOW - in The Simple, 2-6 described by I. Queen on page 60 of and allotment to leo simple, direct language. alignment chosc the October, 1948, RADIO- ELECTRONICS complev 10 Pur Nothing New 9th edition now off the press. FM calva equipmentobsolescent can be used on channels above the Equipment 100 pages of valuable information. band. L2, the 6AK5 grid coil, is a Na- e Employs Basc lest tional AR-5, which has a center tap e ....._...... Available from all leading radio ports and (not used in the original diagram). If a equipment distributors or directly from factory switch is connected between the center at only 40c per copy. tap and ground, half of the coil can be COMPANY, Inc. 92-27 Horace Harding Blvd., Elmhurst 4, N. Y. shorted out and the circuit will tune to PRECISION APPARATUS the higher- frequency television channels. Be sure to use short switch leads AUGUSTINE MAYER, Tiffin, Ohio WHERE RADIOMEN MEET, EAT and SLEEP Visit the CAUSE OF SHORTED FILTERS FAMOUS FIESTA Be sure to check the contacts on the LOUNGE OT l'; 1: 45 TRALRr`7) speaker plug and socket before replac- Renowned for _ - - -- ing shorted filter Fine Food - capacitors in a receiver or amplifier with electrodynamic Atlantic City's Hotel of Distinction speakers. When the contacts open, a The Ideal Hotel for Rest and Relaxation voltage surge -produced by the collaps- Beautiful Rooms Salt Woter Baths Gloss ing field about the speaker field -may inclosed Sun Porches Open Sun Decks be high enough to break down the filter atop Delightful Cuisine Garage on capacitor. premises. Moderate Rate Schedule. JAMES R. LIMBECK, OPEN ALL rue Exclusive Pennsylvania Ave. and Boardwalk Glendale, Calif. DECEMBER, 1949 86 Association News IOWA RADIO TECHNICIANS STUDY TV

Learn How fo Simplify Rodio Repairs!

FREE MANUAL Nothing complex to learn. uu ealcolal Ing. Ised by beginners and experts. Send for FREE manual. "THE INSIDE STORY." today. 32 pates -Illustrated -easy to read! Slimes how obsolete methods prevent full use od your real ability. Explains use of NEW teehntoue. lots onee II In yollraelf and your future to get out In l on!in' yont work. Members of the Radio Technicians of of the deflection assemblies. The mem- SEND COUPON OR PENNY Iowa Association recently attended two bers meet on the second Tuesday of POSTCARD FOR FREE television lectures given by David G. each month at the Worden Hotel in Ft. MANUAL TODAY: Sinclair of KVFD and Ken Stienhogel Dodge. The photograph was ti taken at FEILEN ENGINEERING CO. Dept. 12 -RCS of Ken -El's Radio Supply. The subjects a recent gathering which combined a 545 George SI.. Chieato 14, Illinois were receiver layouts and adjustments banquet and a meeting. Please RUSH my h'RE :E: ropy of The In -tie mote "

N ante

Add rest Ime Starv ity TO ALL RADIO TECHNICIANS' ASSOCIATIONS! 4

SUB -MINIATURE Don't fail to report any and all of your noteworthy activities, campaigns, social affairs, radio or television classes or CIRCUITS extraordinary meet- PRINTED ELECTRONIC ings. Publicizing your activities will help your association by advertising on ceramics. phonic and paper boses from your it to prospective members, and will help all attention given to small associated radiomen by call- schematics. Special ing to in orders. All service and correspondence held attention activities areas far from their own. If you haven't strictly confidential. already elected a publicity agent to supply RADIO -ELECTRONICS and local Write for full details and our latest bulletins newspapers with news of your activities, elect one at your next meeting! on printed circuit components and ossemblies available from stock. PLASTICS & ELECTRONICS COMPANY 272 NarfMlaud Ave. Buffalo B, New York ROCHESTER HAS LECTURE TV CLASS IN BOSTON Rochester technicians listened to the A one -night -a -week television class first lecture of the Television Tech- was opened for members of the Ra- nicians Lecture Bureau on September dio Technicians Guild in Boston this 11. Speakers were F. C. W. Lazenby, who September. Students are working in a discussed electronic equipment, Walter laboratory supplied with test equipment R. Jones, whose subject was basic cir- of all the better manufacturers as well cuits and basic test equipment, and as a complete variety of television receivers. Total value of laboratory equip- A. C. W. Saunders, who told the as- ment is estimated at $30,000, according sembled technicians how to maintain to Albert C. W. Saunders, chairman of their equipment and how to calibrate it the Education Committee. for accuracy. He the man who can Before handle any television Prob- the formal lecture period. N. Y. TECHNICIANS MEET lem ... and get well paid fur it. Learn there was an informal lime -saving, (rouble- shooting methods discussion of Technicians of New York State niet with this new. up Io-date hook of down - Solovox circuits and servicing. to-eases television ers'IrInc. written so October 9 in New York City, at a reg- men can work from It' 401 iutur- mailioalinn- parked pages. aka valuable Id ular meeting of the Empire State Fed- utt al,It you how ur HOLD ANNUAL OUTING o kst tenewst testing luingiuutnu. eration of Electronic Technicians As- THE FACTS YOU NEED TO GO PLACES! The Whaling City Chapter of the sociations (ESFETA). Delegates to the The l'll.st"r11U. TEt.t :s !SHIN SI:115 Isles .hNtl Radio Technicians Guild of New Eng- meeting, which was held -rtllII'ItLE: SHIMMING NI 1NI' %I. slats ritlit mtl with at the River- ouble .homing. trod instruments. adjustment. repair. re- land held its annual outing recently in side Plaza Hotel, represented Roches- placement. 'ITtvl completely rovers tuner,. Inlet ision soottud. alignment. picture lobes. other important phase.. Edited New Bedford, Mass. Features of the ter, Ithaca, Binghamton, Poughkeepsie, non have worked on radio soil tel., isinn for -o sear. -mm who know television the famous ('OYNE .staff: event were a softball game and a clam- Fishkill, Kingston, Westchester, New SEND NO MONET FOR 7 DAY TRIAL bake. York City and Long Island. The Kings- art this great hook. needed loy every radio and television man. on t days trial. Send no marry. List till out and Members of the chapter took part in ton and Fishkill delegates represented ail coupon today and pay postman. Or enclm,- 51.21 and recommendations on proposed new new member associations. Endicott, tase postage. Positive money -hark guarantee. AI'T NOW the city regulations on television antenna Corning, and Cortlandt were not repre- MAIL COUPON TODAY! installations. New Bedford is believed sented. Educational Rook Peel .Ring D.vis.on to be the first New England city to list Chief business of the meeting was the COTRE ELECTRICAL & RADIO SCHOOL SOO S. Paulina St., Dept. 99 -T1. Chicago 12. III. specific requirements. The Guild adoption to convention ap- hush your new PRACTI('A1. Te1.1.4'I SII IS StRPlr- felt (subject INt: and Tm Shooting) MamlI :,t. I 1.01 me. it not eat,I,edl.x,ltma that their cooperation with the city's proval) of the Federation's new consti- return.t , po st ge. refund.copletely special committee on building codes tution, smoothing out the final rough - Name A:e would help to bring about a set of regu- nesses on the winter lecture program, Address lations that would be reasonable and and preparation for the Federation crate ...... -. about which there would be no later meeting and banquet at Rochester. No- 1 ,'II' I am enclosing 54 25. yaw ,mate. S:une Money-Rork Cuar antra. complaints. vember 12 and 13. RADIO -ELECTRONICS for Electronics 1R7

Messages Printed IN - l:athid4a-RaN Tube

AN interesting new type of electronic In response to a series of input signal communication is reported from potentials, lines of information will be the West. Called Electrontype, it prints Electrontyped across the viewing screen Announcing- words on the face of a viewing screen of the tube. lise E /YI C with the help of a special coding tube. An 8 -inch screen could accommodate Sonic of its features remind one of fac- 60 or more lines, or approximately 150 Economy Line of simile, others of Ultrafax, and yet words. Such presentations would be in- other.; of the Bell pulse -code system. tended for projection on larger screens, VOLOMETERS But it resembles none of these and op- or for recording purposes. By increas- erates on an entirely new principle. In- ing the size of characters (consequently MODEL I 0 2 vented by J. T. McNaney of Consoli- reducing the number of lines) messages dated Vultee be (1000 ohms per volt Aircraft Corp., it has can read directly from the fluores- meter) reached the development stage and is ex- cent screen. pected to replace many older nr.ethods of Provisions within the tube allow for 3' SQUARE METER sending and recording printed material. a selection from 40 different characters, 3 AC CURRENT RANGES The main element in the Electrontype which include the letters of the alpha- (0.30'150600 ma.) is the Charactron, a new type of cath- bet, digits 1 to 9, and various punctua- Same zero adjustment Ir r ode -ray tube. The operating principles tion marks. The number of different both resistance anges (0 -1000 ohms, 0- Imeg-r of one type of Charactron can be un- characters employed in a single tube ohms1 derstood from Fig. 1. does not necessarily The tube is present any par- 5 DC & 5 AC Voltage equipped with means by which an elec- ticular problem. Several hundred may Ranges to 3,000 Volts. Also d tron beam can be converted into shapes be incorporated in a tube if desired, DC Current of predetermined characters. There is and it is not necessary that they be Ranges. an electron gun at one end and a fluor- arranged in a single straight line as in- MODEL 103 Midway dicated. escent screen at the other. (1000 ohms per volt down the tube is a character- shadowing One version of a complete Electron - meter/ disc. type recorder is shown diagramatically 4Va' SQUARE METER 3 AC CURRENT in Fig. 2. The Charactron displays a RANGES single line of symbols, with space for 10 -30 150 600 ma.) Same zero adjustment for 70 per line. The fluorescent screen is both resistance ranges (0-1000 ohms. 0 -I met'. 71/2 inches across the face of the tube ohms) UN in in CHARACTRO N and ]t; inch height. The screen same Ranges as Model t02 Also 5 DB this case is a short -persistence, zinc - Ranges. 7.50 SELECTOR PLATE oxide type. IN VIEW SHOWN C D HORR.DEFL.PLATES Model 103 -S With plastic ARE BEHIND PLATES Other major units of the complete carrying strap .517.95 i VERT.DEFL. ON PLATES recorder include servo -controlled film CHATER supply and film take -up mechanisms MODEL 104 SHADOWING DISC (with the servos actuated by the posi- (20,000 ohms per volt tion of the supply an take -up idlers), meter) 4' I" SQUARE METER 150 micro-amperes-alnico magnet) ELECTRONTYPE RECORDER Includes carrying strap 5 DC Voltage Ranges at SCREEN 20.000 ohms volt to 3.000 V.; S AC Voltage Ranges to 3.000 V. 3 Resi PAR'a VIEW OF PLATES Ranges to 20 ens. Also (UPPERMOST PLATES) Current Rana s524.95 k 5 DB Rances. Fig. 1- Construction of the Charactron. All of the above have round cornered, bake- life, molded cases. The individual character openings in Write Dept. 8 -12 For Free Catalog the disc are arranged vertically, in a Gives More Measurement line one above the other. Their respec- Value per Dollar! tive shapes and quantity depend on the ELECTRONIC intended application of the Charactron. MEASUREMENTS CORP. Any character is selected for presenta- tion by means of a voltage applied to a 423 BROOME STREET, NEW YORK 13, N. Y. pair of selector plates. After the beam is directed through an opening in the disc, its cross section will represent $10,000 REWARD a message character, such as a letter Fig. 2- Complete Electrontype recorder Rwn rnr yea .rnrnrnl r,n.,, L:, lernhny lb,.n. Act tre t/r a

of the alphabet. Then, with a set of , horizontal and vertical deflection plates, film- synchronizing circuits and control P.R.I. GEIGER COUNTER the character- shaped beam can be di- mechanisms, lens system, Charactron Weight only 2 Ibn. Priced from $49.50 rom- rected to any part of the fluorescent input selector circuits, and input sweep . c '1 hr most sensitive portable (Selo.,r ('numers made. screen. PRECISION RADIATION INSTRUMENTS, INC. control circuits. 1101 -L N. Poulina St. Chicago 22, III. An enlarged portion of the deflector With 70 exposures per line, when tl` Dea.er Inquiries Inv.ted assembly is shown in Fig. 1. Charac- using 35 -mm film, it is possible to ex- ters C, D, and E represent openings in pose 10,000 characters on 150 mm of the shadowing disc. Vertical deflection film. At input signal speeds of 20,000 plates consist of two sets a and b, and characters per second, for instance, the horizontal plates consist of a single film will be traveling through the You'll find complete specs for 30 pair. There is, essentially, a pair of printer at only approximately 300 mm new exciting models, including just plates for each character. Each vertical per second. Equipment can be designed the one you want, in our IA -page plate, however, is common to two indi- to produce messages in printed form catalog. Write today for your copy. vidual characters, while the horizontal the rate of one million words per min- plates are common to all characters. ute. 398-IO 880ADWAV N vnn8 13. N DECEMBER. 1949 88 Misccllagy DOUBLE -STREAM AMPLIFIER An improvement on the travelling - wavelengths long at the frequency being wave tube, an interesting double -stream amplified may have a gain of over 40 amplifier depends for its gain on the db. The amplified signal is picked up by interaction of two streams of electrons the output helix. A third coil around travelling at different speeds. The two the tube helps to guide the streams of electron streams flow from the two electrons straight down the cylindrical ring -shaped cathodes Cl and C2 in the tube. drawing through the length of the tube Though the scientists say there is no to the collector C. The streams are ac- simple physical explanation of the V Having trouble deciphering the color celerated coding on tubular molded capacitors in new to different speeds by differ- tube's action, it is well know that -like TV and Radio sets? There's no need to con- ing voltages on the screen -like, disc - the earlier travelling-wave tube -it is sult complicated wall charts or tables! shaped grids and further accelerated by able to amplify over a startlingly broad The Sprague Capacitor Indicator gives you the needed data in a jiffy. Just alck the dials the accelerating grid G. band. There may be a gain variation of to the color bands and read the capacitance. The signal is impressed on the stream only 3 db over the whole range between voltage directly. tolerance, and by feeding it to the input helix. It then 200 and 310 mc. show This slick plastic service help fits your Experiments that pocket. Always on hand, it saves time and travels down the stream, increasing in the amplification in the tube takes place avoids mistakes and it's only 1 Sc. Ask for amplitude as it goes. All other one at your Sprague distributor today! things in the central portion and depends to being equal, the longer the tube, the some extent on the velocity difference greater the amplification. A tube 16 between the two beams. SPRAGUE PRODUCTS COMPANY Sprague Electric Dúrriburors' Dias/on of the Co ELECTRON STREAMS: NORTH ADAMS, MASS. CATHODES: ACCELERATING Gut INNER OUTER INNER OUTER (G) AMPLIFICATION (50 (s2) (CO (C2) N THIS h REGION !el AMPLIPISO INPUT OUTPUT SIGNAL .. ï, SURPLUS EQUIPMENT i% SIGNAL T TROUBLE SHOOTING MANUALS (Includes Schematics) BC -348 Receiver INPUT BEAU-GUIDING OUTPyT - BC -779 (Super -Pro) Receiver NEL.i COIL IIFIx SCR -522 Transmitterreceiver BC-610 Transmitter ANY BOOK $1.00 EACH (Add tot toe postage) Quantity Discount. FL-8A Filter -$1.37 PANORAMIC FREQUENCY METER Weise for catalog LECTRONIC RESEARCH LABS. 11121 -E. (:llosehill St. Philad.lphi 23. Pa. An effective frequency meter can be 'scope trace. The frequency values are quickly set up with the aid of an r.f. read off from the oscillator dial. dog? teeeíue out sweep generator, an oscilloscope, and a The advantage of this type of fre- Tiro mixer as in Fig. 1. The sweep gener- quency meter is that a wide spectrum BARGAIN ator is set to the desired r.f. range is visible at one time. All beats and t \ and its 60 -cycle output fed to the hori- harmonics which occur within the range 1 ° L CATALOGS zontal plates of the 'scope. A horizontal of the sweep may be observed. and rel- you to mosey 1 trace is produced on the 'scope. ative amplitude is apparent. -Nathan- (uú9 i When the output from an oscillator iel Rhita is coupled to the mixer, it produces a A RADIONIC CITIZENS RADIO SPECIAL! pip if its frequency is within the sweep Stacked, All Band Conical The FCC, in release range. This pip moves along the hori- No. 39460 -8/49, TY Array...at Lowest Cost - 1 states that because highly specialized zontal 'scope trace as its frequency is Ira here! Selentillcalty designed. experience in u.h.f. techniques is re- nreeielon made. alltb.nd conical adjusted. An unknown frequency may Tr area,- giving tremendous quired to successfully design or modify gain and sbsolule minimum In- be measured or calibrated by checking lerfrfenee at a cost no equipment to meet the greater a pip from a oscil- technical require- titan the usual dipole. Permits with marker crystal ments of Citizens Radio Service rules, direct coupling to 72. 150 or lator. When the two pips coincide, they 300 ohm line with minimum IoM. All dues! toe - there is no simple method by which the atruction. 10 loot man Included. Amazingly have the same frequency. Of course low pries of only home constructor experimenter can situ beats and harmonics also produce pips or In Iota at 5 $11.43 saes meet these requirements. Furthermore, Rest II II, 100 ohnl twin-101M 500 (if they have sufficient amplitude) ; feet. slag. 1000 feel ilia.. the possibility of complying with the _n r y LL wöh Order. b..lavc.. r'. fa.D. therefore it is necessary to use care in requirements is remote if the designer identifying them. or constructor does not have auxiilary R A D I O N I C The method may be used to measure equipment for measuring voltages, cur- EQUIPMENT CORPORATION the limits of the r.f. sweep. A cali- rents, frequency, bandwidth, percent- Tribune Theater Entrance brated oscillator is adjusted to produce age of modulation, and spurious and 17nI Nassau Street Neu Ynr1, 1. N. Y. a pip at the beginning and end of the wilrlh 2 -0421 Open o-:, tar g n t__ I rdav 9-5 harmonic radiation. In applying for license of equipment MAIL TODAY! which has not been type- approved (see VOW. RADIO -ELECTRONICS, Sept. 49, p. 36) , ,,Ax 5 _. a,rtaa0u orr 103114M the applicant should specify the measuring equipment used in conducting all tests, giving the manufacturer's name, 4 N. 1 - -- - - EQUtrTAS gor1C S the type number, and the percentage j RAVluNlO Ne a t1 I Ftre

ELECTRONIC LITERATURE KNOWLEDGE Any or all of these catalogs, bulletins. THAT HAS - and periodicals are available to you if you SHORT -WAVE write to us on your use ENDURED WITH ' letterhead (do not in THE PYRAMIDS postcards) and request them by number. your It is necessary to send only the number of item you want. We will forward the request CAR! to the manufacturers, who in turn will send the literature directly to you. This offer A SECREtit void after six months. GONSET "3 -30" Converter FOR THE D -I- SELENIUM RECTIFIERS Westinghouse has issued a catalogue attaches to your automobile radio OF LIFE listing its standard and high -voltage continuous coverage 3 ro 30 mc. selenium rectifiers. Circuits, character- WHENCE came the knowledge that á istic curves, and general application four woking (c.f.) tubes did built the Pyramids? Where notes are included. extremely compact the first builders in the Nile Valley acquire -Gratis started man their astounding wisdom that D -2- RECORDER CATALOGUE converter $39 95 no.,. ,denier SS 25 on his upward climb? Did their knowledge beneath This 16 -page booklet lists all models see your dealer come from a race now submerged of the Twin -Trax the sea? From what concealed source came tape recorder made GONSET CO. the wisdom that produced such characters by Amplifier Corp. of America. There C® BURBANK, CALIF ®,J as Amenhotep IV, Leonardo da Vinci, Isaac are portables, table models, rack Newton, and a host of others? mounts, long- and short -playing mod- Today it is known that they discovered els, single- and dual -speed mechanisms and used certain Secret Methods for the and several accessories.-Gratis SENSATIONAL! development of their inner power of mind. truly learned to master life. This D -3 -TV SET TUBE CHART ., TORCH They FAST: snap in fuel secret of living has been preserved and This chart of television receivers -is- d tight. art CLEAN: no smoke. the ages and to- sued by Sylvania -shows all tubes used mbun. or spilling. handed down throughout inutesnon-implosive fuel is extended to those who dare use its in each. One hundred ten receivers of fer:ut. i,siwe°sold: r day Inn-wherever clean hot Genre Is n le.! to meet and solve the Ued e model makers. service ,anon. profound principles 44 manufacturers are listed. The three bylsts. Jewelers.51.39 postwld Incw,n life in these complex times. I Torch. 12 Fuel Tableta. problems of pages are folded and punched for filing AMAZING! New Type SOLDER It's modem? in a standard 8% x 11 -inch loose -leaf Industry s It! It's easy This Sealed Book FREE lealeIin.tt.nlni- eliminates dux Ìn.ÌiE1 ,n h uy - book. t the keg-you buy It In 31n es. ,.jar. -- Gratis 51.1Q. The Rosicrucians (not a religious organi- Speel Combination Oaer -Toech and Solder Past.. 52.39 D-4-VARNISHED INSULATION BOOK No C.O D.'e -In 096a Add 37 Salem Taz zation) have prepared an unusual book, IMM a SONS, 111241 E. lith Et..Chmeland, Ohio. which will be sent free to sincere inquirers, The V.I. Story -Varnished Insula- in which the method of receiving these tions in Electrical Engineering, by principles and natural laws is explained. David O. Woodbury, is published by Write today for your copy of this the National Electrical Manufacturers FIX ANYTHING ELECTRICAL! sealed book. Possibly it will be the Association. The 88 -page book tells in Insure gaInst hard times with amazing new electrical first step whereby you can accom- nontechnical terms the ampliante repair method. Even beginners can he elec- plish many of your secret ambitions history of var- bical appliances double quick. At sensational low nished insulation and its application. price, you Eel training course and n simplified elec. and the building of personal - !WING tester. Send postal card for details. No obligation. achievements. Address in- your D-5- TELEVISION PICT -O -GUIDE FEILER ENGINEERING CO. quiry to: Scribe Q. 1t. K. A 100 -page loose -leaf book, 4% x 6% Dept. 12RC9E, 945 George St., Chicogo 14, 111. The ROSICRUCIANS inches, put out by RCA, contains about 50 photographs of test patterns illus- (AMORC) áLRRN San Jose, California trating most of the possible faults in a receiver. With each picture is a brief explanation of the trouble and of what to do about it.- Given. to RCA dealers with purchase of 100 RCA tubes D- 6-RECTIFIER HANDBOOK GREYLOCK Federal Telephone and Radio Corp. RADIO TUBE BARGAINS! GT. Glass and Miniature Types has published a highly useful booklet IRS SATs 12IÁ1 of 48 pages listing applications and dr- ILIA 6aE6E7 1251,aT 34 s570T 12511 cuits for selenium rectifiers. All stand- 304 b52707. 12.01 TRAIN QUICKLY! 354 ard circuits are shown with actual corn 6500T 25c6ci per 100 ponent values, OLDEST, BEST EQUIPPED Also available In smaller quantities at 390 each. with the correct rectifiers listed for each. A SCHOOL of ITS KIND in U.S. SPEAKER SPECIALS! separate page is also G.. 4. 3. PM. las output. A19cc devoted to each rectifier type in much 2 Oppoiihur4 lrelds 5 gor In cartons of 30. each 97e the same manner as in a tube man - Come to the Great Shops of COYNE in Chicago dur- G. a 9' Oval PM. Alnico e. E.tse ca. ing oily 50th Anniversary Year! Get quick practical ual. -25* training in RADIO- TELEVISION ELECTRIC- In cannons of 24. 52.39 or ITY. G I Approved. Finance plan for non -veterans. TERMS: Net C.O.D., F.O.U. NYC. Mall Coupon Today for complete details. D MICROPHONE MINIMUM ORDER $10.00. -7- CATALOG NOT Write for CR tuba and Garman Ca41oq C.12 "HOME- STUDY COURSES! Iswnle pee.. Four -page bulletin No. 104 gives in- You learn on real, full -size equipment. not by moll. Greylock Electronics Supply Co. Finest staff of trained instructors to help you get formation and prices on Electro -Voice ready quickly for a better a fine 30 Church Street New York 7, N. Y. Sob, future. microphones and stands, as well as the Clip coupon for big illustrated FREE BOOKS Coyne book on either ELEC- speech clipper and matching trans- TRICITY or RADIO -TELEVISION. Both book. sent FREE If you wish. No obligation; no salesman former.- Gratis will call. Act NOW! HEADQUARTERS FOR ELECTRONIC TUBES D DURANITE DECODER IN ALL QUANTITIES -8- CHART U. W. COOKE, Pre.. Aerovox COYNE Electrical á Radio School. Dept. 99 -8 I N 5000 Magnetrons, 1000 Kylstrons Corp., New Bedford, Mass., 500 S. Paulin Street, Chicago 12, Illinois 500.000 other tubes Write for has issued a decoder chart showing the Send FREE BOOK and full detail. on: our Bulletin and prices RMA color coding for molded tubular ID ELECTRICITY U RADIO- TELEVISION TY ELE RONICS, INC. paper capacitors. Colors on a given ca- NAME 135 LIBERTY wSTREET 111W YORK 6, N. Y. pacitor are compared with those on the ADDRESS chart and the values read off. -Gratis ,CITY STATE DECEMBER, 1949 Miscellany

itabío tZlbirtpaiTibe OtarT% logo Stop listening to u Oernsbartt Publirations Technical Bulletins DISTORTED HUGO GERNSBACK EACH S1.00 Postpaid Foreign S1.25 Founder Modern Electrics 1908 Simplified technical information on many Electrical Experimenter 1913 of usefulness, written The connoisseur of music Radio News 1919 subjects everyday Science & Invention 1920 in simple, easy -to-understand language. listening wants to recog- Television 1927 RadioCraft 1929 They contain no complicated mathema- nize the clear brilliance ShortWeve Craft 1930 electrical theories, and Television News 1931 tics, chemical and of symphonic sound and Wireless Association of Awerlea 1908 are not based on the assumption that the reader has had a technical training.

B R O O K Some of the larger librarles in the country still have epics of ELECTRICAL EXPERIMENTER on filo for (102) Cleaning Products for Many Pur- All Triode High Quality merest tl readers. poses -Oyer 35 effective chemical cleaner+ that IN THE DECEMBER 1915 ISSUE OF you can make and sell. AUDIO AMPLIFIER ELECTRICAL EXPERIMENTER (110) Electroplating Non -Metallic Ob- Cives It To Him The Radio League of America IlCts- Includes wood, leather, plaster, glas , By Wireless 'Phone from Arlington to flowers, insects, fabrics. Complete directions. Paris (114) Thermostats Easily Made -Designing and making automatic control units of many Audion Bulbs as Producers of Pure Mu- types for maintaining uniform temperatures, sical Tones, by Dr. Lee de Forest automatic furnace regulation. safety controls to Wireless Telegraphy Aids the Teutonic prevent overheating, etc. Allies (11S) Glue Molds for Casting Novelties -Making flexible glue molds for casting small Dr. de Forest to Help Detect Zeppelins objects, using plastics, magnesite. The Radio Transmitting Set at Arling- (1191 Electroplating with Alloys-Bronze_ ton, Va. brass and cadmium -silver. Improves finish and provides durable coating. (711xs. Jlodrl soû-uo shits) U.S. Army Field Radio Set Also AM ..MOdd t7..0.10 Mwtts. New 2 -KW (123) Mirror Silvering -Make money re- Marconi Company Develops silvering old mirrors and making new ones. with Radio Panel Set Colored. front- surface, transparent and photo Distortion and intermodulation at a now leu,. A Huge Oil Type Radio Condenser mirrors. Reduction of listening fatigue. Photographing Radio Waves (124) Soldering All Metals- Includes alumi- Brilliant, clear tone. Reed Radio Ampli- num and die-cast alloys. Secrets of using the Separate controls- stepped -for Bass and Treble. A New Vibrating right flux and correct technique. fier, by Homer Vanderbilt Extremely low volume without any loss of quality. (1251 Buffing S Polishing -All details on cor- Mlle TODAY for 7y.££ Tecbnicaf Bulletin The Telefunken Permanent Crystal De- rect polishing. How to select the right abrasive and Dewitt' Distortion Analysis tector for different kinds of metal. Gives wheel speeds, BROOK ELECTRONICS.Inc. Spiral Antennae for Radio Purposes types and sizes of motors for best results. Saks A9edl The Resistance of Wireless Antennas (1291 Coloring Metals Chemically- Tested Dept. EL-9, 34 De Hart Place, Elizabeth, N.J. formulas and directions to produce durable fin- A Neatly Designed Radio Receiving ishes in many colors on brass, copper, iron. Set, by J. L. Green aluminum and their alloys by chemical processes. "Pocket" Wireless Receiving Outfit, by (130) Glass -Working Technique -How to W111111 W W W// I \\A l Wi cut, drill, grind and mount glass correctly ; in- FOR Percy M. Roope eludes cutting of circles and internal openings. A Sensitive Galena Detector, by Hans UNS YOUR SOY'S (132) Working with Plastics- Covers all de- RSAZ Helle tails of cutting, tooling. bending, cementing and International Radio Code polishing. Enumerates various kinds. Shows how 54VE5 XMAS Official to design articles. Includes using liquid plastics. %/11//7WIP/IITMin PRESENT (13e) Rubber Molds for Casting Novel- TV ANTENNA ties- Used for same purpose as glue molds but NONOTUBE SPEAKER -RADIO KIT PREASSEMBLED where greater elasticity is required. This kit contains a one tulle rrro mr m..._ (141) Recording Thermometer -How to .nmplete coverage of the broadcast band oil make device to record room temperatures over J lent Dower to operate the speaker conta Mel It 12 -hour periods on a disk. Has alarm -clock ..nerved for portability. Pimple. eats mechanism. -tractions for the beginner. all coos (146) Simplified Casting Methods -Mak- rvmenn Included. Nothing else to bus. ing small castings of soft metals without use of ss described In this Issue. fob want sand molds. For novelties, toys, etc. ,rd money to eoorr poslape -oree amt. returned. (147) Drills and How to Use Them -How to use drills in different metals, plastics and f CODE OSCILLTATOR other PRACTICE KI materials. How to sharpen correctly. Includes notplete kit with ton lobes. key and O smoker charts giving speeds and rate of drilling. ,ir D phones (specify which t -simple easy -to- follow (149) Electroplating with Copper. u ras inns enclosed -NOTIII NG ELSE TO BUY. Nickel, Chromium, Zinc, Lead and Cad - mium Enables anyone to do this fascinating w,,rk no a small scale. Universal general corp (156) Home -Maint Formulas & Repairs - Includes a large number of simple. effective solutions for everyday household problems. Minute Mun t .tuna made by Cleveland, Frank Ward Products Corp.. TECHN I FAX 110 N. Ila comes preassembled (right). Chico, . Spreading arms for installation Enclosed find S for which sand the following Technical Bulletin of S1.00 each (Foreign 31.25) as (above) takes few seconds. indicated by numbers:

RADIO AMATEUR NEWCOMER KO Ideal for those just getting stoned for interested) in rodio. You need no other book to Inc., 5. Wood St., Chicago 12, III Saines Industries. 329 get your license and get on the air. How-to - bu;ld simple equipment for a complete station; U.S.A. Amateur radio regulations. Nore 41 V' 11 iP k AT YOUR DEALER - On mad Address $1.00 orders from us, 1.10 postpaid. City & Stata RE 1. AND HOW! SEE PAGE 15! EDITORS Ali ENGINEERS, Ltd. SANTA raga CAUP RADIO -ELECTRONICS for People !0 I Dr. Adolph E. Rosenthal, physicist and inventor, was appointed director of physics of FREED RADIO CORP. recently. according to Freed's director of research and development, Joshua Sieger. 2,000,000 Dr. Rosenthal has secured many patents for inventions in color and three - SERVic IN dimensional television. He is particularly well known for his Skiatron or dark - N trace tube (which he described in the AND March, 1949, issue of RADIO- ELECTRON- RADIO Ics). Dr. Rosenthal and Mr. Sieger have worked together before -in the British Scophony Corp. TELEVISION! Robert A. Seidel, formerly vice presi- JUU ULf ULIL dent and comptroller of the W. T. Grant Co., has joined the RCA VICTOR Dtvt- SION, Camden, N. J., as vice president -ISeletronl- in charge of distribution, it was an- rvnn n nr nounced by J. G. Wilson, executive vice SELENIUM RECTIFIERS president of the Radio Corp. of Amer- ica, in charge of the division. Mr. Seidel For dependable service in oll Electronic will make his headquarters at the divi- and Radio applications always specify sion's home office in Camden, N. J. Mr. SELETRON Selenium Rectifiers. Seidel joined the W. T. Grant Co. in 1940 as comptroller Model No. and was appointed vice president in 1944. He is well known 54 5M1 5P1 SRI 501 531 for his activities in the National Retail Dry Goods Associa- Plate Size tion, where he served as a member of the board of direc- I "se. 1"al. lié Iye'xl,a t % "se. 2' se. tors, chairman of the executive committee, and chairman of Mao. D.C. Output Current the association's Committee on Government Affairs. He was 75 MA. 100 MA. 150 MA. 200 MA. 250 MA. 300 MA.

awarded the Gold Medal of Honor of the NRDGA in Jan- Maw. input Voltage RMS: 130 V. uary of 1946, and a special citation of merit in January, Mao. Peak Inv. Voltage: 380 V. 1949. Approx. Rectifier Drop: 5 V. Write Dept. RS -23 for Bulletin! Joseph F. Bozzelli was recently appointed assistant sales manager of L. S. BRACH MFG. CORP., Newark, N. J., í RADIO RECEPTOR ('O11PANYe hc. alp maker of television antennas, according sw. err,. e.... n ...... ,., awn fneu s qnvp i to G. Philip Galloway, sales manager. M WM IN IL. WNW. 1I, e. V. 1.1.1 o.r.n...c 15 eu1 iIN 1L en 9eN II, II. I. Mr. Bozzelli was recently sales engineer for JFD Mfg. Co., and has been in electronics for J, SOMETHING REALLY NEW -A TV -FM ANT. KIT many years. WEAVER TV -FM ANTENNA Dr. E. M. Honan, an authority on the BROAD BAND. HIGH GAIN ALL CHANNELS ' Prefabricated construction makes compie. NET development of sound in the motion pic- tion of assembly very fast. All aluminum POST PAID $6.95V ture field, who until his retirement on elements, most and crossbar. Plastic insulators assure ee September 30 was engineering manager cellent all- weather reception. Instructions supplied. COMPLETE KIT includes antenna, 75 ft. of Electrical Research Products Divi- lead, lightning NET arrestor, mounting bracket, POST PAID $9.95 sion of Western Electric, joined the stand off insulators and hardware. Every- thing needed for an installation. ALTEC COMPANIES on October 1 in the capacity of engineering manager, ac- 267 Kings Rood J. M. . Madison, N. J. cording to an announcement by G. L. i WEAVER CO Carrington, president of Altec Service and Altec Lansing Companies. "ALL -SEE" TRANSPARENT Louis G. Pacent. veteran radio engi- BOXES! SIX TUBE SUPER neer and president and technical di- Safe and Loss -Proof Three Gang Condenser rector of Pacent Engineering Co.. New Containers for Screws e Nuls York, has been appointed consulting en- Small Pads

,:nard those small , U , gineer by Plessey International nark ,. I $33.30 of II- . ford n replace--with set of three "A II -S ?taru NET (England). transparent nntabler and toter, Assure easy .i.. i Crowe Panel are storage. Pat for Dimel Each set contains: one box. hoses. Kif Included Percy L. Spencer, RAYTHEON l's" sq.: Ire I'.' veteran 17.1.'; four hoses. IS /IO" sn. 10 loses in aiI tube expert and manager of Raytheon's T'.. 'litter a set for ynnrsell only power tuber division, Waltham, Mass.. Inkering pal of . NII. unusnul gift. $ l .00 ILao11 was given the Navy's Distinguished 81 for curl, order melete set ..,il for kIIF.t: leaflet Public Service Award, the highest RCI2. CARGILLE, RCI2,116 honor the Navy can bestow on a Dept. Liberty St. civil- New York, ian, at the Waltham plant. Rear -Ad- N. Y. miral Hewett Thebaud made the award. Admiral Thebaud cited Mr. Spencer for ANOTHER OUTSTANDING JOBBER his work as a scientist, his creative GREEN RADIO DISTRIBUTORS genius, and his ability as a leader of 482 SUTTER AVENUE Panel kit to fit most all makes (Please specify men. Particular mention was made of Brooklyn 7, N. Y. make of car and year model). New up to -dose latest priced Catalog available to dealers Mr. Spencer's work in microwave mag- HAS THE netron development, with special refer- rÍ+- I SENSATIONAL NEW Bill #4IItlUn'x I:I`e 400.K ence to the improved methods J I! s Wholesale Electronics for vol- $39.95 5" Scope Kit ume magnetron production. IN STOCK! 5th at Commerce Fort Worth, Ten.

DECEMBER. I 9 4 9 CIIInW wilco tiolls

OPPORTUNITY AD -LETS WANTS MORE SET DATA something more suitable for the aver- Advertisements in this section cost 255 word for Dear Editor: age technician. each insertion. Name, address and initials must be I suppose you included at the hors rate. Cash should accompany I was much interested in your August must publish a certain all elanlfied advertisements unless placed by an amount of TV material to keep up to accredited advertising agency. No advertisement for editorial, "Squeezing the Service Tech- leu than ten words accepted. Ten percent discount date, but I personally believe TV pic- six issues, twenty percent for twelve issues. (Shlec- nician," as well as the article, "Manu- tionaide or Ibtruding .elverti..nients not accepted facturers versus Service Technicians," ture quality and program material are Advertisements for January. 1950, issue, must reach an insult to anyone's intelligence. How us not later than November 24. 1949. on page 50 of the same issue. This Nadi.. Electronics. 25 W. Broadway. New York 7, N.V. spring I had to service a receiver which anyone can gaze at those blurred black required a new tube socket. The socket and white blobs that jump and flicker AMATEUR R.41,10 LICENSES. COMPLETE THEORY like the old -time movies is beyond me. ureparation for passing amateur radio examination. Home was not standard, so I ordered it from yludy and resident cosines. American Radin Institute. I've seen all the best receivers, and 101 Weal 63rd St., New York City. See our ad in Page 94. the maker (through the distributor). It took five months, four unanswered they're all stinkeroos. Until a high MAGAZINES (BACK DATES)- FOREIGN, DOMESTIC. scanning rate and higher frequencies arts. Hook, booklets. soharintlong oln -ups. ele. Catalog. letters, three long -distance phone calls, loo Irefundedi. Cicerone's, 86.29 Northern Blvd., Jackson are developed, TV will amount to Heights, N. Y. and some frayed tempers before I obtained the simple little tube socket that nothing. It's little better today than it WE REPAIR ALL T1PES OF ELECTRICAL INSTRU- was 10 years ago. usents, tube checken and analyssn. Hazleton Instrument I needed. Co. (Electric Meter Laboratory). 140 Liberty Street. NOW ROBERT O. BARG lark. N. f. telephone- B.4nlay 7.4239. Another instance was six Emerson TV receivers, all with the same model Rochester, N. Y. BARGAINS: NEW AND RECONDITIONED BALLI- crafters. National. Collins. Hammeriund, Meissner. ILEA number but with no two chassis alike, other receivers. tuners, leler'ISlon receivers, tratasmitlers, and no service data available. You can tic. Wholesale prices. Te . Shipped on trial. Liberal Dade -in allowance. Write. Henry Radio. Buller, Móaud imagine the grief! STATEMENT OF THE OWNERSHIP. MAN- and 11240 West Olympic, Los Angeles, California. AGEMENT, CIRCULATION, ETC., REQUIRED Manufacturers may feel that contact BY THE ACT OF CONGRESS OF AUGUST 24. BARGAIN HUNTING? RADIO SERVICEMEN WRITE. 1912, AS AMENDED BY ACTS MARCH Supply, 3619 Troost. with service technicians is beneath their THE OF Sensational catalog. Henshaw Radio 3, 1933, AND JULY 2, 1946 Kansas City 3. Missouri. dignity, but with the increasing popu- Of Radio -Electronics, published monthly at HERMAN LEWIS GORDON. REGISTERED PATENT larity of television they will have to Philadelphia, Pa. for October 1st, 1949. Attorney. Patent Investigations and Opinions. Warner State of New York I Washington. D. C. cooperate in some sort of parts replace- es Building. ment and data procurement or the set County of New York LANCASTER, ALLWINE & ROMMEL. 436 BOWEN Before me, a Notary Public in and for the Building, Washington 5, D.C. Registered Patent Attorneys. owners will rise up in arms against all State and county aforesaid. personally appeared Practice before United States Patent Office. Validity and Hugo Gernsback, who, having been duly sworn Infringement Investigations and Opinions. Booklet and of us. according to law. deposes and says that he is the form "Evidence of Conception" forwarded upon request. I am guaranteeing sets for 90 days editor of the Radio-Electronics, and that the following is. to the best of his knowledge and belief, Audio problems? Expert advice. ear- tested circuits to your (in cooperation with the dealer) but am specifications. James Lanetam, 727 Sunset Cliffs. San a true statement of the ownership, management, Diego. Celli. making only three free calls during that etc., of the aforesaid publication for the date period others are charged for at shown in the above caption. required by the act RADIOMEN, SERVICEMEN. BEGINNERS - MAKE -all of August 24, 1912, as amended by the acts more money. easily, quickly. $250 weekly possible. We $5 apiece. I have no intention of con- of March 3, 1933, and July 2, 1946 (section 537, show you how. Information free. Merit Products. 216 -32L Postal Laws and Regulations), to wit: 132nd Avenue. Springfield Gardens 13. New York. tracting for a year's service as so many 1. That the names and addresses of the pub- organizations do, as I know it can't be lisher, editor, managing editor. and business ! I ENGINEERS I ! interested in a top. TECHNICIANS Publications, paling electronic position? ? t Send post card for informa- profitable. managers are: Publisher, Radcraft tion on HOW. WHY, WHERE. MID CO.sTINENT RE- Inc., 25 West Broadway, New York 7, N. Y.: SEARCH BUREAU. P. 0. Box 121. W'Ichita, Kansas. I think trade papers such as the one Editor, Hugo Gernsback, 25 West Broadway, Sylvania sends out (Sylvania News) New York '7, N. Y. : Managing Editor. Fred BEST DISTANCE RECORD CRYSTAL circuit, Crystal. Shunaman, 25 West Broadway, New York 7, eatwhiskers. "Radlobullder," Catog -all 25e. Labora- show good cooperation with the techni- tories. 578 -B. San Cubs. California. N. Y. Business Manager, none. cian and help both parties. If set manu- 2. That the owner is: Radcraft Publications, PHONOGRAPH RECORDS 15c. Catalogue. Paramount Inc., 25 West Broadway. New York 7, N. Y.: T41-313 East Market. Wilkes -Barre, Penna. facturers adopted this plan, they could H. Gernsback, 25 West Broadway, New York 7, tell us about production changes, serv- N. Y. GEIGER COUNTER PLANS-Pocket site weighs one 3. That the known bondholders, mortgagees, complete. Proven design. Send one dollar for parts else would pound ice hints, and anything that and other security holders owning or holding 1 list, directions. photos. l'earse, 1619 Cypress, Vancouver, British Columbia. help not only to facilitate our work. percent or more of total amount of bonds, mort- boost own reputations and gages. or other securities are: None. TELEVISION -Bright and clear. Adlust present aerial. but to their 4. That the two paragraphs next above, giving Build low -cost precision antennae. Instructions. charts. sales. the names of the owners, stockholders, and se- diagrams, dimensions, plans. Free -Television stations. LYMAN E. GREENLEE curity holders, if any, contain not only the list alloanus. toner heights. l'ropson Company, Lumberton. N. J. of stockholders and security holders as they appear upon the books of the company but also, High Band $6.75. Anderson, Indiana FIVE ELEMENT TV YAM/ BEAMS. in cases where the stockholder or security holder Low Band $8.50. Aluminum Tubing, Etc. Willard Rad- cliff. Fostoria, Ohio. appears upon the books of the company as trustee LIKES TV ARTICLES or in any other fiduciary relation, the name of the AMPLIFIER for guitar or microphone. Attractive case. person or corporation for whom such trustee is completely wired, guaranteed. 5W- $20.00. 8W- 225.00. Dear Editor: acting, is given : also that the said two paragraphs 12W- $40.00. Sadler Radio. Clayton. New Mexico. contain statements embracing afidant's full knowl- I notice that you have recently in- edge and belief as to the circumstances and con- "TAB" SENSATIONAL 13.5KV/18' Television IliVolt- creased your attention to television and ditions under which stockholders and security Flbak Transformer Similar RCA211T5 ONLY $2.49.. . holders who do not appear upon the books of the 6V CARTER Hynansotors 400V/150ma. $8.!tß;'50V /I00ma. hope you will keep up this good work, company as trustees, hold stock and securities in . Guaranteed Tested Tube SPE- $4.98; BOTH $12.49. a capacity other than that of a bona fide owner: 954. 14e 16e- 1'1192. í'K1005. perhaps adding a little more on test CIALS! -955. WE215A, and this affiant has no reason to believe that any 9006, es. 18e -IR5. 155. 6A115. 614660. 65116. 626. equipment. I was a rabid high -fidelity 6SN 7 GT. 71'4, 12AP7. 117Z3, EA('ll 37e -388A. 40e ... other person, association, or corporation has any G E /2J1G1 SELSYNS Tested Pervert Used PAIR 21.49.. . fan, but since the advent of television interest direct or indirect in the said stock, bonds, 30('m 12- l'HF Mobile IIAMRAND Antenna AT5 /AI1RI. or other securities than as so stated by him. 9ße Circular de- age; 4 for $1.00 ... Tuning Meter. 5Ma, ... I have dropped some of my intense Signed, H. Gernsback, publisher. Slide Rule. 98e ... Excellent Fidelity Dynamic Micro - phone PLUS Matching 111 -Gain Transformer. BOTH $1.49. votion to audio. Write for Bargain "TABOGI(AM." "TAB ", 111 ',Werth, More case histories on video receiver Sworn to and subscribed before me this 27th S t.. N. 1'. C. day of September, 1949. Maurice Coyne, Notary faults and reports of the modifications Public. [Seal) GEIGER COUNTER KITS. BUILD YOUR OWN-save in money' Write for free illustrated 'penture. Woodwid that have been incorporated commer- Industries, 5217 -G Hollywood Boulevard. Hollywood 27. cially produced receivers would do BE YOUR OWN BOSS! California. much to help the repair technician's 101 RADIO REPAIRING TIPS (BOOKLET). SEND MAKE MORE MONEY 50 rente U.S. Radio. 135 E. 28 St.. New York 16. N. Y. daily work. POUND lo "CASH IN" fou HARRIS D. $1.00 now sa THE real Montreal, Canada VALUE - dos- aaseymakersa of profitable tented Print Your Own mall order plans, con- Cards, Stationery. Advertising, Circulars and ntlea. Sava menez Print lue Others. Good Pro\ fidential business se- ea., ale.. have horn. print ehup. Raised printinAlite TELEVISION IS NO GOOD crete dozens of prac- naavina. tee. Sold asset from factory unir. Write 25c tical tested formula, inr rr.e sealer or oomPand rI M et. successful tasted NELaEY Paafa[f, P-ey. Dear Editor: 40.000 schema - actual ex- You have published many good ar- WORDS periences of men who hove started an shoe - ticles in the past year which have been IN string --with las than $10 capita 25e DON'T MISS THE useful to me in part -time servicing and TEXT sesy postpaid. Send U. S. stamps. mossy ANNUAL JANUARY construction. However, material like NO ADS seder. or sels. TELEVISION NUMBER. the "Electronics in Medicine" series, ALL Money Back Geiger counters, and microwaves mere- "MEAT"! Guarantee R If nowl ly wastes space that could be used for NATIONAL PLANS COMPANY RADIO- ELECTRONICS for Communications

BRITISH GIMMICKER we feel free to call on each other for Dear Editor: data, hints, or other assistance. December Leotone's is to see I enjoyed your correspondence with It a pleasure that you are Dennison of the Better Business Bu- attempting to fill the gap between the Specials ! service technician and the manufac- NERE', A METER YOU CAN AFFORD!!! PORTAELE reau! Many years ago, when a friend DC AMMETER. 0.15 AMPS WITH DATA FOR turer, by seeing that the manufacturer EASY CONVERSION TO "VOLT.ONMMILLIAMMETER. was boasting of his skill in tracking 31 ï fan. mirror scale, Ent. shunt. PERFECT AS IS supplies technical data well in advance. FOR TFs'rING Electric AlPlianres latter,e., Auto- faults, I bet him five shillings that he motive. In4nstrtal A Medical Eqpt. With :to' Even the association cannot fill that leads h hinged lid metal east'.ea BRAND 39i95 would not spot in 15 minutes a "gim- NEW!! Shoe. D lack -calls to the best available sources wt. lbs mick" that I'd put into a single -tube GENERATOR VOLTAGE CAINET t CHASSIS FOUNDATION . . Modern of information that our group can REGULATOR tGEI NO,',, set with headphones. I won the bet .. d IOe BTurn,or Walllud reach are no good when the data hasn't type GIIO- I -A1$. With 24 easily. act add. relay. Shpt. fitted eb seas. eralh9 l been released by the manufacturer. wt. IM. 1.49 7x1112'. Slug wt. 4 (All I did was remove the receiver Iba. 1.9 We thank you for your consideration N EARING AID AMPLIFIER ASSEMELY ISon,lone diaphragms ! ) vaum tubebe type, Overall: 2,1/2.245*. WEIGHS ONLY and hope that your efforts will help 31g OZS.!! , . MAKE. A REAL VEST POCKET RADIO RALPH W. HALLOWS inkling Only sneaker or phone 4: Meanie tuner. Read, - bring about a better understanding be- wired components include: Tone k Vol. a rots. choke. Berkhamsted, Herts, England output, switch. etc. COMPLETE WITH SCNF: 49 tween the manufacturer and service MATIC E011 BUILDING 2 OR 3 TUBE: SET. Less tltbes ONLY technician. N EARING AID TUSES for amplifier. Set of 2.... 2.49 APPROVES OF VARIETY FRANK J. MOORE MIDGET OUTPUT TRANS- FORMER ..I:ta- x:a.,x 1. i, MIDGET AUDIO CHOKES Dear Editor: Secretary -Treasurer, 1l lgli tntped. to Voice Coil. to jxn ax 1$'' 45th For ortable.. Intercom.. olmu DC.. .49. 5 for 1.9E I agree with Mr. Goodstern (page Radio & Electronic etc . 5 for $1.9E N IGH FIDELITY CRYSTAL MICROPHONE. Sen.11 i,e 75, September issue) that you have Technicians Assn. ;diap,hragm type. high lipped. . 13'x 98. deep. Rubber sMwk mtd. Lees published many one- and two -tube set of Indiana, Inc. housing ALUMINUM HOUSING for crystal mike 19 diagrams. But I do not agree that this South Bend, Ind. EXPERIMENTAL .. D.P.D.T. TGGGLIS .. Bat rs, ested. is bad -after all, RADIO -ELECTRONICS is handle. luminous lip. For a. rx, Students. aaFsll.Ell. tested. 20A.I _5V. 1 ¡mlg.S tirl itg ! 20 . td. not published for the service technician ELECTROENCEPHALOGRAPHER r,turn..ea..39. 3 for 1.00 Kees 1.00 alone. In fact, I wish you would give us BACK AGAIN . BY POPULAR DEMAND!!! Dear Editor: L EOTONES '1U14E0 RADIO KID.-For the complete articles on these subjects once It AOItt'I AN ".w :,who s THE MOST FOR HIS MONEY! I read with much interest your July, 17 FEI.L POUNDS of aelectal new disnanlled in a while to help beginners. Radio Electronic parts: COILS, TRANSFORMERS, 1949, editorial, "Biological Electron- It. :SIS1'ORS. WIRE, HARDWARE. CONDENSERS. On the other hand I do not agree SPEAKER ACCESSORIES. ETC., FTC. All e0( ics," as well as Eugene Thompson's se- these Mhos. wt. 21 Ibs.l AND MUCH MORE Lv+ with Mr. Jeffries (same page) that you ries on medical electronics. My own FOIL ONLY should avoid 10 -tube receivers and RADIO WARETREAS- field is electroencephalography and I URE FULL POUND RSSSCARSONNANDMIKI other large projects. Even if the builder of NUTS. SCREWS. WASH- . RAND NEW with cord have been doing research on its his- Efts. LUGS. ETC. All In A pl11g. press -lo talk does not use entire circuits, he can use HANDY SF.LF.SEAI.INo ewllrh. Bakelite tory; the following may interest you. HINGED 1.1D ease. sling WI. 98_s7 parts of them. In any case, reading CAN.. hpg. wt. 49 alp. You said in your editorial that as far 2 Ills. adds to his knowledge. WRITE FOR LATEST ARGAIN SUPS. such articles back as 1911 you suspected that the I'd like to see an article on audio "FACTORY SPEAKER REPAIRS SINCE 1927" animal brain electricity. In Mtn. order deposit re. all COIF s and design proce- generates Ax imclenpl ytage-excess rfundedet equalizers- formulas an article published in 1937, Dr. H. H. dure, not just typical circuits. Jasper shows that early neuropsychol- IRADIO CO. LEON G. WILDE E7 Dry Street. ogists proved this in 1875. The first New York 7, N. Y. North Andover, Mass. LIE N work done on the human brain was in 1924 but in 1902 Dr. Hans Berger THE COMMON GOOD worked on dogs. - PEN -OSCIL -LITE Dear Editor: The first crude electroencephalo Extremely convenient test oscillator for all radio Our association is backing you 100x/(, graph was made by Dr. Berger's servicing; alignment Small as a pen Self powered Range from 700 cycles audio to over in your fight to help the electronic bother -in -law, I don't know just when. 600 megacycles u.h.f. Output from zero to 125 Low in cost Used by Signal Corps technician. By forming an association, Washington University has an instru- Write for Information. we have bridged part of the gap be- ment, made, I think, in 1922. About GENERAL TEST EQUIPMENT tween us and the owners of the re- the same time Dr. Alexander Forbes of 38 Argyle Ave. Buffalo 9, N. Y. ceivers we service. Harvard made a Hindle string galva Before we had an association, every nometer which, with a one -stage am- one of us was, a competitor. Now, know- plifier, was used to record cortical ing our competitors as good fellows responses to afferent stimulation. Re- TELEVISION RECEIVER-SI.00 problems own, Complete Instructions for building your own television with the same as our sponses were indistinct, largely ob- fertile... 16 pages -11'117 of pictures. 01(101 1 die- grams. clarified schematics. 17'122' complete echemtIt scured by what we now call alpha diagram t chalets layout. Alm booklet of alignment waves. Mr. Lovett Garcea of Electro- 1 nructlons. voltage t resktence tables and trouble- shooting Mils. -All fee 91,OS. Medical Laboratory, Holliston, Mass., CERTIFIED TELEVISION LABORATORIES has written that he believes himself to Dept. C. 5507 -13th Ave., Brooklyn 19. N. Y. be the first man to develop an instru ment in the U. S. He demonstrated the first portable machine in 1935. Incidentally, the first name of Dr. EASY TO LEARN CODE Davis, whom you mentioned in the edi- 1t Is easy to learn or Wrens. speed torial, is Hallowell, not Hollowell. with an Instructograph Code Teacher. Affords the Quickest and most prac- C. DAVID HELLMAN tical method yet developed. For beginners or advanced students. Melt- Caro, Mich. able tapes from beginner's alphabet to typical messages on all subjects. Speed range 5 to 90 WEM. Always BRITON LIKES LANGHAM ready -Ibo QRM. Dear Editor: ENDORSED BY THOUSANDS! The In.true ln:(rai,n Code Teacher rd We shall look forward to receiving literally takes entaileol an nee r- -- torte srut r and our subscription copies of RADIO -ELEC- learn ana masterm code without ur c. thee aslstal Thou.nle or successfulu operators have TRONICS. Special mention should be acquired use cmfe' with the instruc ioZrapn s em made of contributor Langham's arti- Write today for convenient rental and purcha.eplanv.y' cles, which we find instructive as well INSTRUCTOGRAPH as enjoyable for their undercurrent of COMPANY humor. 4701 Sheridan Rd., Dept. RC, Chicago 40. 111. BERNARD J. BROWN Suggested by Robe. W. Glueekstein, Menominee Falls, Wise. Director, Cole -Bernard RESERVE THE RADIO -ELECTRONICS Sore we're a hundred miles front the Productions, Ltd. JANUARY ANNUAL TV NUMBER NOW! TV transmitter and we pick it up easily." London, England

DECEMBER, I 9 4 9 Al RADIO SCHOOL DIRECTORY

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RADIOTELEVISION TECHNICIAN may be earned in 24 additional Free Placement Service. APPROVED FOR VETERANS. To young men interested specifi- months. ENROLL NOW FOR NEW CLASSES Apply Doily 9.9; Sot. 9 -2 cally in radio and television: VISIT, WRITE or PHONE Prepare here for a career in tele- A SPECIAL. PREPARATORY RADIO- TELEVISION vision -the field which business PROGRAM is offered for men leaders predict will be among lacking high school diplomas. INSTITUTE Pioneers in Television Training Since 1931 - America's top ten industries by TRAIN in modern, well 480 Lexington Ave., N. Y. 17 146th St.) 1951. In 18 months you become equipped laboratories, shops and Prose 3 -4535 2 blotto from Grand Central a Radio -Television Technician, classrooms. Faculty of 85 spe- ready for positions in receiver cialists -over 1500 students and and transmitter testing, servicing, 30,000 graduates. TRAINED MEN MILWAUKEE -011° AVAILABLE - ei Solve your trained man- cCHmL ENGINEERING power shortage by employ- Founded s Ost.tr u'erw.,th ing C.T.I. graduates. These men hove completed a rigid course of training. What they've learned has Send Coupon for free 48 -page Pic- been practical. because most of their training torial Bulletin, "Your Career", and period was spent in the shop. We probably hove 110 -page Catalog. NEXT TERMS OPEN JAN. ]- graduates from your area Write for prospectus APRIL 3 Electrical Engineer. on available men. (No employment tees). i months Electro Major COMMERCIAL TRADES INSTITUTE Electronic Technic.- " ..sa month. P108 26 ^. Raelevisio 1400 Greenleaf Dept. -11, Chicago Technician ....le months MILWAUKEE SCHOOL OF ENGINEERING Dept. RE1249, N. Broadway and E. State. Milwaukee. Wis. Without obligation send me the Bulletin, Your Career ", and your catalog. I am interested in course. Ile .a "kev" .t...arn how to send and emseive by tele1 NAME AGE t.WnwFe needs of men for Int t AVeture. - teresting omit.l.w Learn a at borne aulrkly ADDRESS through fu:o on. randier goal- Vete, an of ley for or . cence. Write for FIIIInnl,Klal l.. CITY .._. STATE...... DIX'nlld War II CANDLER SYSTEM CO. DenL3-O.1lna02 6.Denverl.COlo..V.S.A. RADIO -ELECTRONICS for Book Reviews 9; RADIO -TELEVISION QUESTIONS AND AN- Make Your Career SWERS, Elements 2. 3, and 4, by Woodrow Smith. Published by Editors and Engineers. Ltd., Santa RADIO MINDED? - Barbara. Calif. Three volumes. 5'.íír x 8'/_ inches. - Price: single volume $1; two or three column. 95e each. RADIO and TV LEARN CODE NOW!! A complete In no other industry does the future hold brighter code oscillator, plug These books contain questions taken in and use. AC Handal promise and security in AM and FM or DC. Small I than compact chassis. Variable tone. Radio. Television. These fields need and want men from the FCC's Study Guide and Ref- Operates or small - trained as annoancen, phones speak \..' script writers. disc jockeys, and erence Material for Commercial Radio er. With tube and $3.45 sL+ radio technicians. It will pay you to Investigate the - key. Guaranteed ,iHa - - lion Martin Reboot of Radio Arts, eatablished In 1937. Operator Examinations. Each question Complete day and night classes ... the latest egalp is enswered by the author, and what- BUILD YOUR OWN. ment . and a stare of 30 nationally known In- A BROADCAST RECEIVER . structors. Over 97% of the comhlnation .. men graduates ever background is deemed necessary is Postwar Development. One tube drives Y PM Speaker are placed on Jobe Immediately through the free Permeability tuned . NOTHING ELSE TO placement service. Approved for veterans. given. is While the reader not likely RUY . . Simple step by step instructions and tor- a tures. All parts, tube. speaker. batteries $5.95 FREE -Write for Free Booklet' Your Future ig Radia" to learn radio from the books, study included. Manufacturers Guarantee of them will equip the prospective ex- BUILD YOUR OWN. Den Martin Scheel et Radio Arts aminee with the knowledge specifically ELECTRONIC TIMER 1855 Me. Cherokee. Nellyemd, Calif. NUdsee 23261 required for the FCC examinations. Automatically shuts o6 devices . Photo enlargers. gadgets. etc. Variable time control. 3 Ranges avail- The present volumes cover Element 2 able ... 1'104 see. 7 -13 ace.: 13.20 see. Handle 100 watts. Schematic and all parts included. $5.95 (Basic Theory and Practice), Element NOTHING ELSE TO BUY ia 3 (Radiotelephony), and Element 4 BUILD YOUR OWN. All purpose D.C. Supply Variable 0.12 volts -1.75 (Advanced Radiotelephony). They are amps- Filtered Metered . - . Operate relays-Small surplus e sly based on the recently revised study v eratile.LSENOTHING 4e TO BUY Na95 guide, which obsoletes older books of FOB -NY Rated firms 10 days quantity discounts this type.-R.H.D. GREENWICH SALES CO. 59 Cortland? Sf. New York City 7 Preparatory Mathematics, Serv- ATOMIC MEDICINE. edited by Charles F. Beh- ice, Broadcast, Television, Ma- rens. M. D.. Captain. U. S. Navy. Published by Thomas Nelson & Sons. New York. 6% z 33.4 rine Operating, Aeronautical, inches. 416 pages. Price $7.50. Frequency Modulation. Radar. ler 20 us Irruf Ike Mid -ye, leai Fab. Id. Containing contributions by of the LEARN RADIO! Mum mm. Jab. Ike. country's most knowledgable medico - Veterans. Literature. neucleonic specialists, this book is said PREPARE FOR A GOOD JOB! COMMERCIAL OPERATOR (CODE) COMMERCIAL RADIO INSTITUTE to be "the first text on atomic medicine (PeoMN 1920/ in atomic While RADIO SERVICEMAN West Diddle Street. Baltimore written the age." cov- Si I. Ma. ering much ground of general interest TELEVISION SERVICING to those concerned with neucleonics, its BROADCAST ENGINEER special slant is toward the prevention Y.A. Furnishes Books and Tools and cure of radiation-caused damage to SEND FOR FREE LITERATURE the human body and to the use of radio- BALTIMORE TECHNICAL INSTITUTE activity as a medical tool. 1425 Eutaw Place. Dept. C. Baltimore 17. Md. RADIO ENGINEERING The opening chapters are devoted to Co a surprisingly complete explanation of FM-Television-Broadcast nuclear fission itself and a verbal pic- Servicing. Avia- AUDIO ENGINEERING SCHOOL Police Radio, Marine Radio. Radio Practical tion Radio and Ultra High mobile applications. ture of the manner in which the atomic engineering training in Audio fundamentals. Thorough training in all branches of Radio aid Elec- Disc. Film. Magnetic Recording. and Audio fre- tronics. Modern laboratories and equipment. Old es- bomb does its damage. Then follow quency Studio tmeasurements.aining simulates tablished school. Ample housing facilities. 7 acre on the biology, pathology, Broadcast. Motion Picture. campus. Small classes, enrollments limited. Our chapters and Television. and Commercial Recording work. graduates are In demand. Write for catalog. hematology of ionizing radiations, cu- Approved for Veterans Approved for Veterans HOLLYWOOD SOUND INSTITUTE, Inc. mulative effects, pathogenesis and ther- 1040 -E North Kenmore. Hollywood 27. Calif. VALPARAISO TECHNICAL INSTITUTE Correspondence Courses Available Dept. C VALPARAISO. INDIANA apy of radiation sickness, radiation de- Specify If Veteran or Non -Veteran tection, safety precautions, and disaster planning. The character of isotopes is discussed, with several chapters on TRAIN FOR ALL TYPES their manufacture and use. A chapter on radiation effects in dentistry is in- RADIO COURSES FCC (RADIO OPERATOR) LICENSES RADIO OPERATING CODE Complete Raytheon AM and FM broadcast trans- cluded, and one outlining problems RADIO SERVICING ELECTRONICS F.M. mitters and studio control equipment. Also TV earn - which are still in the research stage. TELEVISION era chain unit. 30th anniversary year. Please send The appendix includes a 21 -page table REFRIGERATION SERVICING for catalog R. Write for Catalog TE and Picture Brochure MASS. RADIO SCHOOL of isotopes and a glossary of terms. - ECM i TRADE & TECH. 229 W. 66 St., N. Y. 23 271 Boston 15. R. H. D. Huntington Ave., Mass. 4Ndieett 2 -8117 Lie. he comes Moen. Dept. Ed. SCHOOL EXPLORING ELECTRICITY, by Hugh Hildreth Skilling. Published by Ronald Press Co.. New York. 6 s 8% inches, 277 pages. Price $1.50. Written by a professor of electrical engineering at Stanford University, ELECTRICAL TRAINING Complete Radio Engineering Intensive 32 weeks' Course this volume of Ronald's Humanizing residence course in funda- including Television mentals of industrial electrical engineering, in- Bachelor of Science Degree. Science series is entirely unprofessor- cluding radio, ehctronics. Prepares for technician. Courses also in Civil, Electrical. Mechanical, ial. Covering the progress of electrical engineering aides. Approved for veteran training. Chemical. Aeronautical Engineering; Business 57th year. Enter Mar. 6. Catalog. Administration. Accounting. Secretarial Science. development from the time of Thales Graduates successful. 66th year. Enter Jan.. March, (the first electrician) to the explosion BLISSELECTRICAL E0L Sept.. June. Visitors welcome. See beautiful cam- WASHINGTON t2. D. C. pus, well equipped In h,mnti'ries. Write for catalog. of the first atom bomb, the book is TRI -STATE COLLEGE 0.1.0,OO11INDIANa more a tale of people than of science It is written in narrative fashion, with dialogue, descriptions of places. and CORRESPONDENCE COURSES IN RADIO and TELEVISION many excerpts from personal letters RADIO sod ELECTRICAL ENGINEERING Thorough Training in All and other sources. ELECTRICAL ENGINEERING (ICI gond grasp of Technical Phases To wide electrical field the novice the book presents an l'reprr witirself at Low Cost. for secure future. Modern APPROVED FOR VETERANS course So simplified anyone can understand quickly. DAYS- EVENINGS interestingly written story. To those W Extra fine RCA GRADUATES ARE IN DEMAND familiar with the science of electricity, RADIO ENGINEERING course In unit°. For F. Catalog Dent. CC-49 Wit. it humanizes work. Trains you to be super-service mean. real RCA INSTITUTES, Inc. the subject and presents technician. Servicemen needed badly. Dlnlom on A Service of Radio Corporation of America some of the historical background ev- completion Mane graduates earning big pay. 350 WEST 4TH STREET NEW YORK 14. N. Y. LINCOLN ENGINEERING SCHOOL ery worker ought to have. -R. H. D. Box 931 -E -12. Lincoln 2. Neb. DECEMBER, 1949 ADVERTISING INDEX UNITED'S SAVINGS PARTS KITS DON'T BUILD ANY Allied Radio Corporation 5I, 61 RADIO Amplifier Corporation of America 87 (All Parts New Amsterdam Sales 65 Walter Ashe Radio Company 80 and Guaranteed) TELEVISION KITS! Bell Telephone Laboratories, Inc. 19 Boland B Boyce, Inc. 52 (Unless Otherwise Specified) -When you can pick up a factory wired and Brook Electronics, Inc. 90 tested 630TV Television Set, complete with Brooks Radio Dist. Company 72, 75 RESISTORS tubes, ready to operate -at the same price as Buffalo Radio Supply 73 No. 100- Carbon, Ins., 1/5 W. to 2 W. 100 Ass't. SI.93 a kit!-Why fuss or have headaches? Burstein -Applebee 83 101- Wireweund, 2 W. to 50 W. ..25 Ass't. $1.95 This is the famous type 630TV 31 -tube Voltage Rodio Engineering Institute 7 102 -free, W.W. t 2% I W. Even Values. Capitol 6 Asst. 51.00 Doublet chassis which has proved to bet su- Corgille 91 yet 103 -Pree. W.W. ! 8% I W. Odd Values. perior to anything developed. W. need hot Certified Television Laboratories 93 12 Asst. $1.00 ) describe the 630TV chassis-you alr.ody know Cines, Incorporated 76 about it. The design and operation is excellent Cleveland Institute of Radio 20 CONDENSERS -and its fully guaranteed! Complete with Coyne Electrical School 86, 89 No. 104 -Mica, Receiving. 100 to 1000 V. ) 100 Ass't. tubes, ready for cabinet installation.-Price, DeForest's Training Incorporated II $1.95 complete with Glass 105-Mies, Kmtg. 600 to 3000 V. 15 Ass't. $1.35 199.50 Eastern Telephone Company 97 106-Ceramic. Tub. 200 to 500 V. 100 Asst. $1.95 16" Tub. Editors and Engineers 90 107- Ceramic, Buttons 200 to 500 V. Etecrro-Technical Industries 8 100 Ass't. $1.95 DUAL SPEED AC /DC Electronic Instrument Company 54 108- Trimmer Cond.. I, 2 6. 3 Unit Strips. Measurements Corporation 87 15 Ass't. $1.00 Electronic 10 51.15 ... 57, 58, 59 I09 -Air Trimmers. Asst. Styles. Ass't. PORTABLE RECORD PLAYERS Esse Radio Company 110-Variables, I, 21 3 Gang, AM, FM. SW 86, 89 These units were manufactured for the United Feller Engineering Company 5 Ass't. 62.45 States Government. Used, but reconditioned General Elecron,c Dist. Company 53, 67 for resale at a sensationally low price. General Test Equipment Company 93 HARDWARE 82 No. III -Solder Lugs. Various Types. Ass't. The motors are of the duol speed type- 33 -I/3 Gernsback Library for 89 3 Lbs. $1.29 and 78 RPM with fully adjustable speed control Gomel} Company 112- Screws. Nuts, Washers, Etc. Asst. 91 and will operate on either 110 Volts AC or DC. Green Radio Di butors 3 Lbs. for $1.29 No noisy inverters required for DC use. Smooth Greenwich Saes Company 95 113 -Rivets, Alum. Assi. types. 3 Lbs. for SI.29 silent operation. Greylock Electronic Supply Company 89 I14 -Tie Lug Strips. Asst. types. 50 for S .95 Heath Company 13, 14, 15, 16, 17, 18 115 -Insulators. Ceramic. Ass's. types. Cabinets are solidly constructed for portable 50 for $1.29 use ore covered with leather- Hershel Radio 7l and attractive I16 -Tube Sockets. All types. .. .. 25 for S .95 ette. Complete with an electrodynamic loud- Hickok Electrical Inst. Company 83 speaker, built-in pickup and amplifier, just Hotel Strand es COILS plug -in and play. Hudson Specialties .. 60 No. 1i7-Coils. R.F., Osc., I.F. F.M. T.V., etc. Asst tar Priced Ridiculously Low While They Immerman 8 Sons 89 50 $1.45 Last -Only $16.95 Instructograph Company 93 VOLUME CONTROLS America 115 Insuline Corporation of No. I18-W W. Carbon, Etc. 15 Asst. for 51.00 International Resistance Company WIRELESS AUTOMATIC Inside Front Cover SWITCHES RECORD PLAYER Jackson Electrical Inst. Company 78 Na. II'-- H!tar, Water. Asst. Types. Jensen Industries 90 15 Asst. for $1.00 A fortunate purchase hos permitted us to offer Jersey Specialty Company 97 MISCELLANEOUS these high quality single post automatic record The Kelsey Company 92 changers AT LESS THAN FACTORY COST. N, .. 120- Transformers, Chokes, Audios, Ete. Some Lafayette -Concord S5 New, Some Used, All Good. Express only. Nothing to connect, simply plug into wall out- 93 Leotone Radio Corporation Shpg. Wt, A . 45 Lbs. IO for $3.95 let, load up a stock of records and turn on any Lectronic Research Laboratories 88 12IFiller Cond. Kmitilne. I Mid. to 4 Mid. 600 radio within 50 feet. Liberty Electronics 89 V. to 1500 V.D.C. Oil Filled, Rect. Can. The record player will take ten 12" or twelve 63 6 Ain't. $1.95 McGee Radio Company to 10" standard records. The built -in wireless 62 122- Filter Cond. Receiving. 150 450 V.D.C. Metropolitan Electric 4 Inst. Company Lytles, F.P.. Cartridge, Tub., Ete. - two tubes in a stable oscillator con of Mid -America Company 56 10 for $1.95 high -quality circuit which con be easily ad- Midwest Radio Corporation Back Cover 123 -Binding Posts. Metal Atol. Styles. justed for operation in any quiet spot on the Murray Hill Books, Inc. 10 30 for $ .95 rodio. Notional Company 4 124- Knobs. Military and Civilian. 25 Ass't. S .95 125 Glass. Push Back. Etc, Ain't. Mounted on an attractive leatherette covered Rodio 3 -Hookup Wire. National Institute lengths and colors. 3 Lbs. for $1.00 base and sold complete, ready to oper- National Schools ate. $12.95 National Union Rodio Corporation 60 TUBES (Express Only) Order today -while they last. New Jersey Radio & Television Tube Co. W 3CP1 (With Altimeter Scale) New S .89 Niagara Radio Supply 69 PHONO MOTORS Opportunity Adlets 92 58P4 2.95 AC /DC 84 5FP7 1.25 Plastics & Elecrronics Company 2.45 85 GPI DUAL SPEED Precision Apparatus Company 872 -A $1.19 Ea. 2 for 2.00 "Green Flyer G. I." type reconditioned and Precision Radiation Inst. Inc. 87 1625 3 for 1.00 guaranteed. Complete with 12" $7.95 Progressive Electronics Company 77 turntable. MICROAMMETERS RADIO SCHOOL DIRECTORY 2" Beedo 0 -200 Bakelite Case. New $3.75 AC PHONO MOTOR 33 1/3 POWER TRANSFORMER (Pages 94 -95) 117 V. 60 Cyc. Prim. (Thord. 701161) Upright Mtg. RPM ONLY 750 V.C.T. a 110 Ma. 6.3 V. M 2.5 Amp. 5 V. $1.95 American Radio Institute 14 2 Amp- Like New! While they last! $2.49 Price Baltimore Technical Institute FILTER CHOKE Bliss Electronic School ( Thord.) 10 H. 75 Ma. Universal Mte. Like New. TELEVISION TRANSFORMER Candler System Company While they last. S .59 Commercial Radio Institute I ISV/60 cycles, secondary 2500 volts at 2 MA., Trades PRECISION DIAL 4.3V at .6A, 2.5 volts at I.7SA. Commercial Institute Don Martin School of Radio Arts National Type N Velvet Vernier. 0.100 Counter- slock- Price wise, with decimal scale. 5 to I Ratio. Like new. 51.69 Hollywood Sound Institute Lincoln Engineering School HEAVY CABLE G. E. 9" TELEVISION TUBE Massachusetts Radio School White screen electromagnetic deflection and Milwaukee School of Engineering 14 CONDUCTOR focus. Brand new, type MW 22-2. Complete RCA Institutes WEATHER PROOF with instruction booklet. Rodio Television Institute 513.95 14 conductors, rubber and fabric covered. =14 stranded Price Tri -Stat College H,d tinned. Enlosed i., heavy outer rubber jacket. Valparaiso Technical Institute eav, brass 14 contact plugs on either end. Cable KIT YMCA Trade & Technical Schools is I. O.D. Shpt. Wt. Approx. 110 Lbs. Eaprese TUBE CHECKER FOUNDATION only. New IOC foot cells. Sensitivity 2000 ohms /volt. Large 4" Scale -has three color "Good -Bad" markings and cali- Guam Nichols 76 ANTENNA ROTATOR brated 0 -100. Radio Apparatus Corporation 81 Inc. 9 -RL -42 Radio City Products Company, FM or TV. Antenna's. Special Price $3.95 96 Ideal Irr Lightweight Beams. Radio Dealers Supply 24 V.D.C. Reversible Motor. 5.5 Amps. May be Radio Receptor Company, Inc. 91 used on AC with modification. $2.95 TUBE CHECKER TRANSFORMER Radio Supply 8 Engineering Co. 66 C -161 TELEPHONE Has voltage taps from 1.4 through 117 volts for Radionic Equipment Corporation 88 types of tubes. all The Rosicruciens 89 REPEATER COIL

1 1 for feeding he ". Price $1.95 Howard W. Sams 6 Co., Inc. 6 to ratio. One side center.tapned 81 ins lines Into telephone circuits. Completely Senco Rodio, Inc. shielded. Shell. Wt. 3'.a Lbs. New $1.49 SPECIAL N. Silverstine 84 Products Company 88 ELECTRONICS PACKAGE Mammoth assortment of radio & electronic Sprague Sprayberry Academy of Radio. ...Inside Back Cover 10 Lbs. of assorted electronic units and parts. $1.29 parts of such items as transformers, chokes, Minimum order Sutton's Wholesale Electronics 91 Quantities are limited -Order now. - condensers, resistors, wire, coils, hardware Bill There be 25, packing eharee for all or- 18 $2.00. will etc. of not less than 10 pounds. Sylvania Electric Products ders under $2.00. 25 °. deer l' required. balance C O I' Price $1.25 Technifos 90 All orders shipped F.O.B. Chicago, Illinois. Any order, 78 received without shipping I strucoions will be shinned Tel -A -Roy - - Railway (sprees. Minimum foreign order *25.00. For complete listings of special buys for es- Transvision ... 64 perimenters, radio technicians, laboratories, United Surplus Materials 96 schools and engineers. Write for catalog R12. Universal General Corporation 90 UNITED SURPLUS University Loudspeakers, Inc. 79 MATERIALS SUPPLY CO. Company 91 RADIO DEALERS J. M. Weaver 6. III. Incorporated 98 314 S. Halsted St. Ch'cago 154 GREENWICH ST. NEW YORK 6, N. Y. Wells Sales, Wholesale Radio Parts Co., Inc. 70 RADIO .ELECTRONICS f o r Book Reviews I97 NEW ADVANCES IN PRINTED CIRCUITS. is not Proceedings of the First Technical Symposium on available in coordinated form Printed Circuits. Published by the United States anywhere else. Department of Commerce. Miscellaneous Publi- In addition cation 192 (available from the Superintendent of to theory, the author has Documents. Government Printing Office. Washing- included a chapter describing repre- ton 25, D.C.) 8 i 10 inches, 73 pages. Price 40 cents. sentative recorders in detail, another on instrumentation and measurements, TELEVISION This is a sequel to the Bureau of and a third on applications, as well as Standards Circular 468, Printed Circuit a glossary of terms. Techniques. Since it is the report of a More and more is appearing in the symposium, there is a certain amount of current technical press on magnetic re- overlapping, but there is much new in- cording. This book does a fine job of MANUFACTURERS formation in the later book, which is supplying the background for a com- roughly twice the size of the earlier one. plete understanding of new develop- DISTRIBUTORS Considerable attention is given to ments and techniques and for the read- the various methods of applying con- er's own work in the field.-R.H.D. INSTALLERS!!! ductive and resistive elements, and to the materials on which they may be applied. A number of typical com- We Manufacture RADIO COMPONENT HANDBOOK. Published mercial applications are described and by Technical Advertising Associates, Cheltenham, illustrated, and some interesting infor- Pa. 6 x 9V., inches, 210 pages. Price $2.50. 300 OHM TV TWIN mation is brought out in the questions This is asked and answers given during the a data handbook on the char- LEAD TRANSMISSION discussion. acteristics of the major electronic equipment components, with some ap- WIRE plication information on each. The first chapter covers design in general. The ELECTRONIC TIME MEASUREMENTS. edited by Britton Chance, Robert I. Hulsiser. Edward F. others deal with transformers and in- MacNichol, and Frederick C. Williams. (Volume ductors, capacitors, resistors, speakers, 20 of the Massachusetts Institute of Technology Radiation Laboratory Series.) Published by switches, insulators, and tubes and me- McGraw -Hill Book Co. 6 a 9 inches, 538 pages. tallic rectifiers. AT THE WORLD'S Price $7.00. Radar made the problem of accurate LOWEST PRICES!!! measurement of small time intervals RADIO -TELEVISION QUESTIONS AND AN- a decisive one. There are other im- SWERS. Elements 2, 3, and 4, by Woodrow Smith. Published by Editors and Engineers. Ltd.. Santa portant fields in which accurate meas- Barbara, Calif. Three Volumes, 5'/ x 8,4 inches. urement of short time intervals is of Price: single volume II great importance, as, for example, We supply over 50% study of the velocity of nuclear par- These books contain questions taken from the FCC's Study Guide and Ref- ticles in nucleonic research. of all Twin Lead used in While the pulse methods of radar are erence Material for Commercial Radio most common, measurements of other Operator Examinations. Each question the Metropolitan Area time intervals, such as the phase in- is answered by the author, and what- tervals of the absolute altimeter and ever background is deemed necessary is the Decca distance and position finding added. While it would not be possible to system, have wide application and are learn radio from the book, a study of discussed, as well as equipment, tech- them will equip the prospective ex- niques, systems and methods for the aminee with the knowledge specifically WRITE FOR QUANTITY various types of time measurements. required for the FCC examinations. The present volumes cover Element 2 PRICES TODAY!!! (Basic Theory and Practice), Element 3 MAGNETIC RECORDING, by S..1. Begun. Pub- (Radiotelephony), and Element 4 lished by Murray Hill Books. Inc., New York. (Advanced Radiotelephony). They are 6% a 9% inches, 242 pages. Price $5. based on the recently revised study As a good, solid background in mag- guide, which obsoletes older books of JERSEY SPECIALTY netic recording, this volume should be this type. -R.H.D. CO. of great value to both amateurs and Little Falls. New Jersey workers in the sound field. Dr. Begun, vice -president and chief engineer of the REFERENCE DATA FOR RADIO ENGINEERS, Brush Development Co., has written a third edition. Published by Federal Telephone and Phones: L.F. 4- 0784 -1258 Radio book of unusual - Corp.. New York. 5% x By inches, 640 clarity and complete pages plus index. Price ness on a field in which he is an out- $3.75. standing figure. The first two editions of this valuable Starting with a chapter on the his- book should be familiar by now to most tory of magnetic recording, the book radiomen. This, the third, is twice as WALL MODEL takes up the TELEPHONES subject technically even large as the second (1946). Like its N 'l'elen Hunes of Dure at low ,rires before its beginning -with the char- predecessors it contains a wealth of de- éorpori latest improvements In' de tech. acter of sound and the devices used to sign data in skeleton form -formulas, Moue. .mata goodness first andd Rn transform it to electrical impulses. The tables, graphs, basic 1 est workmanship. circuits, outline cost due to Increased vol. introduction to recording takes the drawings, It possible for and so on- intended, not to clmakesto sell at the ial form of an low price of 517.95 efor explanation of the relevant instruct, hut to remind. Two ,f either model. r plete ith wire. power sup. principles of magnetism. From that The additional material, not only Ply and Instructions. point Dr. Begun leads his readers to brings the book up to date, but also $1735,... 2 Mó rc a smooth, step -by -step understanding adds much that was omitted Common talking and rom. because of mo ringing. Any number of the entire subject. restrictions on book production. of nhones can be connected Notable in same circuit. Simple In. It is impossible to include all infor- additions are: frequency allocations; absolutely mation available in 242 technical re. y pages. The principal atomic constants; radar fun- mitred. 25of deposit ree- treatment qulred on all orders. F.0.11. is principally qualitative, damentals; AM, FM, and TV broad- Brooklyn. therefore, though the mathematical casting data; servo mechanisms; and EASTERN TELEPHONE CO. ir basis is given for each of the im- expansions of previously included ma- 320 lath St.. Dept. RC3 portant phases Much of the material terial- R.H.D. Nneklya, N. Y. DESK MODEL DECEMBER, 1949 WELLS RADIO- ELECTRONIC COMPONENTS

COAX -- CABLES AND CONNECTORS -- TWINAX TRANSMITTING MICA CONDENSERS USI 11.11 10 L COMPUT/ LIMY OF LOON -LOSS COSPICTOU 045 ADA1T1 3 10$ CASIU. ÚO015 CONSTSRCTION DEI CAST UPC LOO 34CNINSC SILOS 111775 1111114 LOI DÉCA FILM AND POLTSTTSIPI. '''.31:131311 LLLLLL 30939 ILL $105$ ARE IN STOCK FOR INN E111TC 35105751. 10 14o. SNLLL HINRLO CONTACT CONIICTOLS SNLLL Toll CONTACT CONN.CT015 3021 C .303 0. S031 .0- 0.0205 -113415 PUN- MIA la-lax 410 CI WA e 350 TUMOR n116- With =NW filled dielectric Mart MIS le-Ixe Sice Ixw NO filled MC0 13-211 AKIN MUM YCVnCIt- I PIECE PLUO I411I(0 YCI Ma 13 65 ee 13-00 .55 0. 620 DOLL 155 .105' 0.0.80140 .40 031 r 10001. CASI. .00025 Y-Il -r C036ECT55 for 53-11 1,4 0.4 IS 2133 fetter( -,x 1.5 11004- 14. IS cYlx. S/U. ;73 61-11 IECIrt1CIS CYIIn Y S55 21/11. 4s/61, rte0 i4. UM. etc. 03.7 41 L04-1443 408 14 CAP- mos7 NCO nP[- .,1 Ter cxxctex U-II. t:i.0 5E0PIICLE 016331I 36 SN S3-1In. 33-221. etc lo. no Teel- 781.41m. I 444 .65 ANn15- for ed20 N-IH 1.03 99 t te eee4040.44 563/11 .20 aó]W. uCIE PUIG 055P701- Po1c011 .% MATO- far edertlM 11.1-11r WM no 5351- 31. 4 50031 40 4.0.014 II 53/O Z J4.1K1155- For ex .I8 -TS TABLE CUM 11-21r7 144 413 Y-15A Or 41-130 .1 CawSttx. .IS

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