GB404349A - Improvements in or relating to frequency selective circuit arrangements for use in radio reception - Google Patents

Abstract

404,349. Impedance networks; valve circuits for wireless reception. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London, and RUST, N. M., 109, London Road, Chelinsford. July 14, 1932, Nos. 19968 and 29752. [Classes 40 (iii) and 40 (v).] In a band-pass circuit of the fixed tuned or variably tunable type one or more branched circuits are provided, each branch comprising inductance in series with capacity and being associated with negative resistance means to reduce the effective damping. In an alternative arrangement complex resonant circuits in cascade are employed. Fig. 4 (Prov. 19968 /32) shows a pair of branched circuits L1 C1, L2 C2 with associated negative resistance devices consisting of dynatron connected screen-grid valves VI. Such a branch circuit may be connected in parallel with a tuned input or intervalve circuit matching being effected by a tapping to the inductance or between two series condensers. Fig. 4 (Prov. 29752/32) shows a cascade arrangement of complex circuits A, B, coupled by an amplifying valve V3, and each associated with dynatron connected screen-grid valves V1, V2. These circuits are ganged to have a constant frequency separation and each gives a sharp cut-off on one side of the resonant frequency the overall response being shown in Fig. 3 (Prov. 29752/32). Fig. 6 shows a superheterodyne receiver in which the coupling 1b, 2b, 3b is arranged between the first detector 10 and the intermediate frequency amplifier 12. The auxiliary condensers k1, k2 are mechanically coupled so that one is maximum when the other is minimum and serve to vary the band width. Second channel interference can be removed by the use of a coupling in which the minimum response is removed from the resonance frequency by twice the intermediate frequency used. Fig. 7 shows complex cascade connected circuits A, B, tapped across part of the tuned circuits 1b and by adjustment of the tapping the isolating valve V3 may be dispensed with.