FEB. 15 15c NR4 ANALYZED 1930 Per Copy STABILITY OF NON -REACTIVE AF SCREEN GRID TUBES REG. U.S. PAT. UFF. COMPARED WITH OTHERS OVERALL TESTS 412th Consecutive Issue EIGHTH YEAR FOR CIRCUITS New Detector System for Non -Reactive Audio RADIO WORLD, publisbed by Hennessy Radio Publications Corporation. Roland Burke Hennessy, editor; Herman Bernard, managing editor and business manager, all of 145 West 45th Street, New York, N. Y. www.americanradiohistory.com RADIO WORLD February 15, 1930 High Impedance Audio Transformers Audio frequency coupling transformers with high impedance primaries and sec- ondaries are made in ipj two models and two ratios of each model. At left is the "Gold Bond" shielded type, at tight the "Uni- versal" unshielded type for subpanel mounting, overall height 2g". The ra- tios are 1 -to -3 and 1 -to -5, primary to secondary. The shielded "Gold Bond" model has 4,000 turns on the primary, so the 1 -to -3 model has 12,000 sec- ondary turns and the 1 -to -5 model 20,000 secondary turns. Ex- treme compactness and neatness prevail. The "Universal" Excellent reproduction of tonal values as supplied by model for subpanel of mounting has 3,200 the detector or first audio tube is assured by use primary turns. either of the transformers. The "Universal" model illus- Laminations in both trated above, is excellent for replacement purposes. A single stretch of copper wire without soldered are of best silicon Even on this model high plate voltages may be used, connections of in-between joints is used on each steel in a strong with consequent high plate currents, due to the relatively winding of both transformers. The "Gold Bond" steel frame. The coils model is illustrated. in both are vacuum large diameter of wire used. impregnated and GB -1-3 I -3 for 1 -to -3 ratio Order Cat. for -to ratio therefore moisture - Order Cat. UVS-1-3 Order Cat. GB -I-5 for 1 -to -5 ratio $ 1.50 each proof. Order Cat. UVS-1-5 for 1 -to -5 ratio $1.13 each GUARANTY RADIO GOODS Co., 143 West 45th Street, New York City FIVE-DAY MONEY -BACK GUARANTY!-C. O. D. ORDERS ACCEPTED. USE %" Extension Shaft Here is a handy aid to Aristocrat Floor Speaker salvaging condensers and coils hare LYNC that )4" diam- With Molded Wood Horn of 0 ft. $12.00 eter shafts not long enough tone travel (exponential type) with RESISTORS for your purpose. Fits on baffle and horn motor built In. 5j4" shaft and provides %" Extraordinary bargain. for new Loftin -White Set and Amplifier, auto- extension, still at 14". mobile radio sets, and new 245 resistance - Price 10e net. coupled amplifier. Write for catalog and 40- RADIO WORLD page booklet. 145 W. 45 St., N. Y. City LYNCH MFG. CO., Inc., 1775 B'way, N. Y. CONE RADIO AND OTHER ASSEMBLY TECHNICAL BOOKS WITH DOUBLE At a Glance MAGNET UNIT RADIO "Audio Power Amplifiers," by Anderson and $4.95 Bernard $3.50 "Elements of Radio Communication," by Morecroft 3.00 IIIIIIIIÌIÍ_IÌÌIIIÌIjII 'Foothold on Radio, A," by Anderson and Bernard 1001.00 Mathematics of Radio," by Rider "Practical Radio," by Moyer & Wostrel 250 "practical Radio Construction and Repairing," by Moyer & Wostrel "Principles of Radio Communication," by Morecroft "Radio Blueprint Library"-AC Hook-ups .35 "Radio Cyclopedia," by Drake 0.00 "Radio Receiving Tubes," by Moyer & Wostrel 2.50 "Superheterodyne Construction and Operation," by Lacault "Thermionic Vacuum Tube, The," by Van der Bill 5.00 osa excellent magnettc type speaker for installa- The speaker cabinet la walnut 33" "Trouble Shooter's Manual," by Rider 3.50 tion in any cabinet. The unit is a finish, high, double -magnet 241/2 ' wide, 175/" deep, with carved legs. Paratone, with two magnet coils, for utmost Golden cloth grille covers front opening. Built TELEVISION sensitivity. Each horseshoe magnet is %" thick. inside is No. 595 molded wood The coils forever horn with baffle 3.00 magnet are protected against and No. 203 driving motor unit that stands 250 "A B C of Television," by Yates dust and other foreign, injurious substances, by volts without filtration. Horn and motor re- special bakelite housings. The pin Is reverse movable. Table alone is worth price asked. drive. The cone frame is metal. The 0" cone AVIATION Is specially treated buckram. Shipped C.O.D. if desired. "A B C of Aviation," by Maj. Page 1.01. and Meterology," by All assembled, with long cord, ready "Aerial Navigation 406 to play, Shipping weight 4 lbs l9w5 Acoustical Engineering Associates Capt. Yancy .. Guide," by Maj. Page 4.00 (Cat. CAS) Net .... 143 WEST 45th STREET NEW YORK CITY "Everybody's Aviation "Ford Model 'A' Car." Its Construction, Oper- The unit alone (cord Included) II ation and Repair-by Maj. Page will operate any type sounding sur- "Modern Aircraft," by Maj. Page 5.00 face, including paper, cloth, wood, etr A PLEASE GIVE. US TWO WEEKS "Modern Aviation Engines," by Maj. Page 9.00 Shipping weight t iha. (Cat. UM $ L 9 Net for changing your address, showing new 5 renewal expiration date, etc. Subscrip- RADIO WORLD tion orders are arriving in such larga Guaranty Radio Goods Co. 145 West 45th Street numbers that it takes two weeks to N. Y. 145 45th St., New York City effectuate the change. New York, West RADIO WORLD, Broadway) 145 West 45th St., N. Y. City. (Just East of www.americanradiohistory.com February 15, 1930 RADIO WORLD 3 Attention... Highest Grade Key Tubes at Radio Service Men is compiling an international list of names of qualified service men throughout the Defiant /Radio(Faft United States and Canada, as well as in ($rofessional Servicremao-Radiotrician foreign countries. This list, which RADIO -CRAFT is trying to make the most complete one in the world, will be a connecting link Prices: radio service man. between the radio manufacturer and the RADIO -CRAFT is continuously being solicited by radio manufacturers Screen Grid Tubes for the names of competent service men; and it is for this purpose only that this list is being compiled. There is no charge for this service 224 at $1.43 to either radio service men or radio manufacturers. We are asking every reader of this magazine who is a professional 222 at 1.88 service man to fill out the blank printed below or (if he prefers not to cut the page of this magazine) to put the same information on his letterhead or that of his firm, and send it in to RADIO -CRAFT. The data Power Tubes thus obtained will be arranged in systematic form and will constitute an official list of radio service men, throughout the United States and for- 245 at 1.28 eign countries, available to radio manufacturers. This list makes possible increased cooperation for the benefit of the industry and all concerned 112A at .78 in the betterment of the radio trade. 171A at .78 Other Tubes MEN' York, N. Y 'List I OF SERVICE National Lei. 98 park Place, of your below: .90 NATIONAL/oL CRAFT' files 227 at c/o RADIO as set forth the undersigned are .68 Please enter My qualifications 226 at Service Men.(State) of Radio print) (City) . 280 at 1.13 Name (please so state) please for self, 201A at .53 Address Address in business and (If ' Firm Name Construction? in Radio The above constitute the nine most popu- Experience lar tubes used in radio today. Despite the Years'Year EX' Makes?) severely low prices the Key tubes are firsts ...... What of the very first quality. Besides, there is Servicing a five-day money -back guaranty! The above tubes are manufactured under years in licenses granted by the RCA and its Agency . affiliated companies. You All prices are net and represent extreme .... Recommend? discount already deducted. Institutions Tubes Do Y (What SpeCFollowing 228 HIGH -GAIN DETECTOR What Work from Builder Taken Radio . Increase The sensitivity of modern AC - Custom in operated circuits by substituting the new Courses ... 228 AC high mu tube (large amplification), Study for the 227 tube otherwise used as detector Makes in up - to - date circuits. The result Following is immediately obvious in the greatly in- in Servicing creased volume. Then the weak, distant Specialized stations come in stronger and tone quality is improved. Simply substitute the 228 You Own? for the 227 in the detector socket only. Equipment No wiring change of any kind is required. Testing Price, 51.88. What Professions? Trades or GUARANTY RADIO GOODS CO., 143 West What Other 45th St., N. Y. City. (Just East of Broadway). Other Qualifications? Enclosed please find $ for which ship and at once tubes marked below: Educational high mu. E 228 AC $1.88 ' ' (Signed) 0 224 AC screen grid $1.43 245 AC power tube 81.28 Comments 228 AC amplifier (RW 215) 227 AC det.-amp. .90 280 AC rectifier 51.13 D 222 battery screen arid 88 D II2A power tube SI .78 D 171A power tube .79 201A battery tube .53 Matched pair of 245s for push-pull (for SEPARATE TESTER COMBINATION both) $2.58 Matched pair 171As fer AC push-pull (fer in neat black both) 51.80 Consists of two -meter assembly Matched pair of I12As for push-pull (for metal case, with an external high resistance both) 51.80 meter. The two meters in the case read (a) 0-20, 0-100 milliamperes; (b) 0-10 volts, AC or DC, same meter reads both. The ex- Name ternal high resistance meter reads 0-600 volts, AC or DC (same meter reads both). Thus Address you can test any plate current up to 100 ma., any filament voltage, AC or DC, up to 10 V., or line voltage or other City State and any plate voltage, AC or DC voltage, up to 600 volts.