GB400268A - Improvements in or relating to radio and other high frequency receivers - Google Patents

Abstract

400,268. Valve circuits for wireless reception. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London, RUST, N. M., 109, London Road, and O'NEILL, R. F., Lindorel, Fourth Avenue, both in Chelmsford. April 22, 1932, No. 11674. [Class 40 (v).] In a super-regenerative radio receiver, the quenching oscillations are derived from a screen grid valve adjusted to oscillate round one of the bends at the ends of the downwardly sloping portion of its characteristic. A screen grid valve 26, Fig. 1 (Comp.), has its screen at a higher potential than its anode and generates quenching oscillations of a supersonic frequency determined by a tuned circuit 5A, 6A in its anode circuit. Received high-frequency oscillations are applied to the circuit 5, 6 tuned to radio frequency and connected to the grid of detector 1. The tuned circuit 5A, 6A has a variable resistance 28 introducing a damping effect to control the degree of quenching. Since the sum of the screen grid and anode currents remains approximately constant, the detector 1 may be dispensed with and the telephones connected in the plate or screen grid circuits of valve 26. In a modification, signals are applied to a tuned circuit 5, 6, Fig. 1 (Prov.), in the grid circuit of a detector 1, and also in the anode circuit of a screen grid valve 9 whose screen grid is at a higher potential than its anode. A periodic circuit comprising a neon tube 16 in series with a condenser 17 and resistance 18 in parallel produces an intermittent current flow in resistance 11. A tapping 10 on resistance 11 produces a cyclic variation of grid bias of valves 9, 14, a current flow in resistance 11 causing valve 14 to become conductive and reducing the negative resistance of valve 9 so producing quenching, while when no current flows in resistance 11, valve 14 is non-conductive and valve 9 has maximum negative resistance. In Fig. 2 (Prov.) the damping valve 14 is dispensed with, the oscillatory circuit comprising neon tube 16, resistance 18 and condenser 17 periodically reducing the potential of the screen grid of valve 9 to a value sufficient to obtain the quenching action. The anode potential of the screen grid valve may be varied in a similar manner, Fig. 3 (Prov.) (not shown), or the neon tube oscillatory circuit may control the cathode potential, Fig. 4 (Prov.) (not shown), varying the effective grid bias of the screen grid valve.