Radio today (Apr-Dec 1939)

GENERAL ELECTRIC MODEL GA-62 «g# kNT I400KC 8 1 ISTI.F Ukt\ 2NDLF fwe\ w ff} P0WER V_^ \°uy TRANS. _JlOSCI400KC ^-^ (6K7) BK6SJ 4x5 d G-£ Model GA-62 Auto Radio Mechanical push-button tuning with a 2-gang condenser is used in the G-E GA-62 auto radio. A total of 6 tubes is employed in a superhet circuit employing a radio frequency amplifier stage. Somewhat unusual is the use of an untuned transformer or coil between the 6K7 r-f tube and the 6A8 converter. This untuned stage makes it possible to have an r-f amplifier in a 2-gang receiver. The I.F. is aligned in the usual manner at 465 KC. At 1,400 KC the oscillator trimmer and antenna trimmer on the condenser gang are adjusted for maximum signal output. With the oscillator tuned to 600 KC and connected to the antenna terminal through a 100 mmf. condenser, the antenna padder is peaked while rocking the condenser gang back and forth through resonance. The padder is left at the adjustment giving maximum signal. After installation in the car, the antenna padder should be adjusted for maximum output when the set is tuned to a weak signal near 600 KC. For ease in tracing the circuits the AVC is indicated by a line of dashes and dots, the negative bias by a line made up of a dash and 2 dots. The B plus is an extra heavy line, while the arrowheads show the signal path. Insulation at High Freqs The popularity of short wave receivers and the introduction of television increases the importance of insulating materials used in antennas, coils, tube sockets, etc. When installing antennas and other parts subject to high frequency currents, an insulating material suited for the job should be used. For outdoor service, as antenna insulators, a low moisture absorbing material is necessary. In general, the lower the power factor rating of a material, the better the. insulator it is for high frequencies. For purposes of comparison, the following table gives some of the more important characteristics of the common insulating materials. Duvall Heads RSA Dielectric Material Constant Power 60 cy. Factor lkc. % Water % Absorption 1 mc. 24 hours Fibre 4-5 6-9 5 5 30 Glass (crown) 6.2 — 1 — 0 Glass (pyrex) 4.5 — 0.5 0.2 0 Mica 7.3 0.03 0.02 0.02 — M yea lex 6-8 — 0.6 0.3 0.035 Bakelite (pure phenol) 5 2 _ 1 0.15 Low-loss Bakelite (yellow phenol) 5.3 2.5 1.4 0.7 0.2 Porcelain (wet process) 6.5 2 1 0.6 Low Porcelain (dry process) 6.2 2 1 0.7 3.1-1 Quartz fused 4.2 0.03 0.03 0.03 0 Rubber, hard 2-3 1 1 0.5-0.9 0.02 Steatite 6.1 1 0.4 0.3 0.02 Shellac 2.5-4 2.5 — 0.9 0.1 Elected as National President of RSA was George F. Duvall of Brooklyn, N. Y. Mr. Duvall has been a serviceman since before the war, served as president of Metropolitan N. Y. chapter in 1938 and 1939. He is now manager of Television Technicians, Inc. His company is comprised of a group of former servicemen now doing an excellent job of television antenna installation in the New York area. Duvall succeeds T. P. Robinson, Dallas, Texas, who served two terms as first National President of RSA. In his inaugural address to the members of RSA gathered at their Convention in Chicago, June 16-17, Mr. Duvall said: "Our organization is the result of cooperation; cooperation between servicemen, cooperation with the sales managers clubs, the RMA, the trade journals, and other branches of the radio industry, and now cooperative action in the RMA-NAB campaign for the betterment of radio. Indeed, that word 'cooperation' is a grand word, a word of great potentiality, whereby servicemen gather together in mutual interest and for mutual benefit, and because of that cooperation between servicemen are invited to participate in cooperation with other branches of the radio industry, to the mutual benefit of the entire industry as well as the serviceman. Cooperation, then, is the foundation of RSA." JULY. 1939 39