GB406708A - Improvements in or relating to modulated carrier wave transmitters - Google Patents

Abstract

406,708. Valve modulating circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, London, and QUILTER, W. A. E., 19, Bournehall Avenue, Bushey, Hertfordshire. Sept. 2, 1932, No. 24526. [Class 40 (v).] A transfer circuit, between a wave amplifier V1, V2 and the aerial or other load F, includes one or more thermionic valves V3, V4 whose internal resistance is varied by signal voltages applied to their grids. The amplifier V1, V2 preferably comprises a push-pull pair biassed to the point of cut-off. A point on the oscillatory output circuit A is connected to a point of the aerial or other load circuit F through two parallel paths each including a valve V3, V4 the two valves being connected in opposite directions. The return for this transfer circuit is afforded by earth connections. Signal voltages are applied to the grids of the valves V3, V4 from a source J through a transformer K or other coupling, the signal-carrying leads including high-frequency choke coils L. The filaments of the valves V3, V4 may be heated by high-frequency currents derived from coils G, G1 coupled to the circuits A, F. Screens E, E1 prevent undesired coupling between the circuits A, F. The effect of inter-electrode capacity in the valves V3, V4 may be neutralized ; or the valves V3, V4 may be of low resistance and connected at low-potential points on the circuits A, F so that the effect of inter-electrode capacity is unimportant. The plate voltage of the amplifiers V1, V2 should be supplied by low-impedance apparatus, e.g. mercury-vapour rectifiers. Alternatively the plate supply voltage may be kept steady by any known means.