GB454259A - Improvements in or relating to modulated carrier wave transmitters - Google Patents

Abstract

454,259. Valve modulating circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, London, and DITCHAM, W. T., Tudor House, Broomfield Road, Chelmsford. March 27, 1935, No. 9575. [Class 40 (v)] The output of a carrier-wave generator or amplifier V1 is modulated by two valves V2, V3 which are excited in opposite phase by the modulating voltage and are connected respectively in shunt and in series with the valve V1. Both valves V2, V3 are biassed back to zero plate current, and they pass current alternately during the respective half-cycles of the modulating voltage applied to their grids by the transformers T1, T2. When the valve V2 is conductive the carrierwave output of the amplifier V1 is reduced by virtue of the iron-cored choke L in the plate supply circuit both of valve V1, and of valve V2, and connected between a D.C. source El and the cathodes. When the valve V3 is conductive, the second source E2 contributes to the plate current of the valve V1 and the carrier output rises. No current passes in the valves V2 V3 in the absence of modulating signals. Several valves in parallel may replace any of the valves V1, V2, V3.