GB527380A - Load stabilizing means for modulating systems - Google Patents

Abstract

527,380. Modulating systems; directive wireless systems. INTERCONTINENTAL SERVICE CORPORATION. April 11, 1939, No. 10896. Convention date, April 4, 1938. [Class 40 (v)] In a modulating system, particularly for an overlapping-beam directional system in which a common carrier frequency modulated at different frequencies is supplied to separate aerials, crossmodulation in the carrier source is prevented by providing each aerial with a dummy load modulated in opposite sense, so that each aerial with its associated dummy load presents an approximately-constant impedance to the carrier source. The output of coil 5, coupled to the tank circuit 1, 4, is connected to two shielded transmission lines 10, 11, connected to supply current to an aerial 2 and a dummy load 13. A rotary condenser 14, 15, 18, connected through transmission lines 16, 17, impresses a characteristic modulation upon the carrier radiated by 2, and modulates the energy supplied to resistance 13 in opposite sense, so that the sum of the radiated energy and the energy dissipated in resistance 13 is approximately constant over the modulation cycle. The short-circuited lines 20, 21 are for the purpose of tuning. A similar aerial 3 and load 30 are fed from the circuit 1, 4, by coupling coil 6, and the modulation is performed by the rotary condenser 35, 36, 37, which is arranged to produce a different characteristic modulation.