GB406674A - Improvements in or relating to modulated carrier wave transmitting systems - Google Patents

Abstract

406,674. Valve modulating circuits ; impedance networks. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London.-(Assignees of Crosby, M. G. ; Riverhead, Long Island, New York, U.S.A.) Aug. 31, 1932, No. 24323. Convention date, Sept. 19, 1931. [Classes 39 (i), 40 (iii), and 40 (v).] To effect phase modulation the effective length of an artificial line intermediate a source of carrier current and an output circuit is varied in accordance with the signals to be transmitted. In one embodiment a carrier current source 1 is coupled through an artificial line 20, limiter L, frequency multiplier and power amplifier PAM, to an aerial 10. Part of the distributed capacity of the line is constituted by glow discharge tubes 19 which comprise an external electrode and two internal electrodes, the intensity of the discharge between which varies the effective capacity between the internal and external electrodes, this variation being effected by changing potentials across the output choke MC of a modulating valve 11 controlled by a microphone 16. Radio frequency choke coils 21 are connected between each tube 19 and the choke MC. In a modification a single glow discharge tube 21, Fig. 2, has an artificial line helically wound therein or round the outside of the tube in close proximity thereto. The capacity of the line to earth is varied by changing the glow tube current. In other modifications the effective inductance per unit length of the line is modulated by varying the modulating valve impedance shunted across inductances coupled to the line at various points, or the plate impedance of the modulator valve is in series with the capacity of the line to earth. The Specification as open to inspection under Sect. 91 comprises also the phase modulation of a carrier current by utilizing capacitive and inductive couplings between the modulating device and the output of a carrier current amplifying valve. Thus the tuned output circuit 12, 13, Fig. 3 (Cancelled) of a carrier amplifying valve 3 has coupled theretothe output circuits of a pair of push-pull modulating valves 23, 24, one capacitively through condenser 14 and the other inductively through inductance 18, to effect phase modulation. Single capacitive and inductive coupling circuits are also described. This subject-matter does not appear in the Specification as accepted.