Radio Broadcast (May 1929-Apr 1930)

"Z_ .RADIO BROADCAST ADVERTISER. A Finer Screen -Grid Instrument Browning & Millen Designed — NATIONAL Built The NATIONAL VELVETONE AMPLIFIERPOWER SUPPLY is especially designed foi use with the NATIONAL MB-29 Tpl_ TV /f" U ^ {^\ with its 4 A. C. Screen Grid X llC 1V1D"Z y Tubes and 227 detector, with its beautiful shielded alum.mm chassis in frosted finish — with the Newest NATIONAL Weld-Built Condensers and the 1930 Model Velvet Vernier Projector Dial — offers the Large Scale Custom Set Builder, as well as the Radio owner and the Experimenter, a fine, engineered, R. F. Tuner of enormous gain and selectivity — ready for combination with power supply and audio — especially suited for consoles, and radio-phonograph combinations. Write for Bulletin RB-7, to-day. SCREEN-GRID MB-29 TUNER NATIONAL CO. INC., Maiden, Mass. Est. <j£> 1914 A Good SUMMER SELLER! VUlcAN Lightning Arrester List $1.00 The C0RWIC0 VULCAN LIGHTNING ARRESTER not only protects a radio receiver against lightning but it also dissipates accumulated static charges. Corwico Vulcan is the best value lightning arrester on the market. It is big — it is colorful, an attractive dark green shade, and it is packed in an eye-catching, two-color box. $100 GUARANTEE Inclosed in every box is [a guarantee to repair up to a cost of $100, any radio set protected by a CORWICO VULCAN LIGHTNING ARRESTER that is damaged by lightning. Stock this item now for quick sales and profits. If Your Jobber Cannot Supply You, Order A Sample Direct. CORNISH WIRE COMPANY 30 Church Street, New York city Makers ot Corwico BRAIDITE Hook-Up Wire The HAMMARLUND R. F. CHOKE COIL Is Better Built Diagram shows the Hammarlund B. F. Choke in the detector plate circuit of a radio receiver, blocking R. F. currents from the audio transformer and preventing distortion. A specially developed method of xjL winding and impregnating gives the Hammarlund R. F. Choke an extremely high impedance to all frequencies in the broadcast range. Having no pronounced natural period, its action is uniform throughout the broadcast frequencies. Compact and completely shielded with a handsome Bakelite case. Current capacity, 60 milliamperes. Two sizes: 85 and 250 millihenries. Write Dept. RB7 for special R. F. Choke data, showing important uses in modem receivers HAMMARLUND MANUFACTURING CO. 424-438 W. 33rd St., New York, N. Y. ammarlund f «£C ISION PRODUCTS Potter Condensers Potter Dynamic n C Speaker Filter . . • ° POTTER FILTER BLOCKS T9Qftfl Condenser Block for the single tfOA flft -£9UU 25Q type tube arnpl,fier.. .... ^U.UU TOQCfk Condenser for the push-pull $00 C(\ -LVOV 2SO type tube amplifier T9ftQ2 Condenser Block for single COfl flfS -£U»0 210 type tube amplifier «p£U.UU T-280-171 power pack with 280 type $18.00 tube rectifier. Cll/I f74 Condenser Block for Silver ft_ OM-073 Marshall power amplifier $£U.U9 and power supply units.... nn iiih Condenser Block for single tfln i\I\-Z4«) and push-pull 24.5 type tube <piy. /j amplifier. The Potter Co. North Chicago, Illinois A National Organization at Your Service attention service men A quality replacement audio transformer for the service man. Possesses the same high degree of performance which characterizes all Thordarson audio units. Provides highest amplification consistent with quality reproduction. Unique Mounting Feature — The mounting bracket of this transformer is designed to fit all standard mountings without the necessity of drilling additional holes. May be mounted either on end or side or may be used as bracket to support sub-panel. Remember: Thordarson radio transformers are Supreme in musical performance. R-100 List Price S2.25 THORDARSON ELECTRIC MFG. CO. Transformer Specialists Since 1895 Huron, Kingsbury & Larrabee Sts., Chicago DAR replacement audio transformer 126* IULY ■ 1929 •