GB413646A - Improvements in and relating to ultra short wave modulated carrier wave radio communication systems - Google Patents

Abstract

413,646. Wireless transmitting systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, and LINSELL, A. A., 43, West Hill, Sydenham, both in London. Jan. 17, 1933, No. 1553. [Class 40 (v).] Ultra-short radio waves, of the order of 60 cm. wave-length, are modulated by one or more absorbing conductors placed in the path of the radiated wave the resistance of the conductors being varied by the modulating signal. The absorbing conductor 3, Fig. 2, is placed at a distance greater than a wave-length from the radiating dipole 1. At its centre or at two or more points in its length, a valve is connected so that its anode-filament path completes the circuit of the conductor. The resistance of the valve is varied by a microphone M coupled to its grid circuit, which thus causes the conductor to absorb varying amounts of energy from the passing wave. The valve capacity is prevented from shunting the valve resistance by connecting across the valve a non- radiating line 8 in series with a blocking- condenser 9. The conductors 3 may each comprise several parallel rods. As shown in Fig. 6, the modulating-valve 4 has a fixed bias on its grid, and the signal voltage, amplified by a valve 10, is applied to the anode circuit, either by a transformer 11 or by a choke coil. Several conductors 3, 3<1>, Fig. 5, may be arranged at different distances from the dipole radiator 1, and the signal may vary the resistance of all the valves 4, 4<1> jointly.