GB489486A - Improvements in frequency changers for heterodyne receivers and modulators - Google Patents

Abstract

489,486. Valve circuits for wireless reception and modulating; thermionic valves. KRAMOLIN, L. L. DE. Oct. 22, 1936, No. 28764. Convention date, Oct. 24, 1935. Addition to 409,756. [Classes 39 (i) and 40 (v)] In a frequency changer for receiving or a modulator the output of which comprises a frequency modulated signal and comprising two electron paths in series, one controlled by the signal and the other by a local oscillator, both paths are adjusted to operate within the straight parts of their characteristics instead of, as described in the parent Specification, only the path to which the signals are applied being so adjusted. Fig. 2 shows an arrangement in which an auxiliary grid of one system is connected to the cathode of the other system in which the signal path and preferably the local oscillator path are adjusted to operate within the straight part of their characteristics. The output may be taken from either anode 5 or anode 6 or from both in push-pull. The local oscillations may be applied to the two paths in push-pull and may be generated by backcoupling one or both of the discharge paths to which the local oscillations are applied Figs. 3 and 4 (not shown). Alternatively the incoming signals may be applied to paths in push-pull and in series with a path to which the local oscillations are applied. A pair of discharge paths may be arranged in push-pull and to generate the local oscillation the cathodes being connected together and to the anode of the discharge path to which the signal is applied. The capacitive leakage resistance to earth of the cathode of the discharge path remote from earth is made greater than the internal resistance of the preceding discharge path or system and the cathode is of small diameter as described in Specifications 415,079 and 427,384. The second cathode may be a " virtual cathode " comprising a space charge region formed by electrons of slow speed between a positive grid and a succeeding negative grid. Fig. 6 shows an arrangement of this kind in which the valve comprises a grid 1 and grid like anode 6 and two oscillator grids 4, 11 arranged side by side and correspondingly arranged anodes 5, 10. The electron paths 4, 5 and 10, 11 may be separated by a mica or metal foil partition which may also be utilized as the mechanical support of the electrodes. The bias of grids 4, 6, 11 is adjustable by potentiometer 13 to vary gains. The invention is particularly applicable to superheterodyne receivers having an aperiodic or semi-aperiodic input in which tuning is effected by varying the local oscillator frequency. Specification 437,726 also is referred to. Reference has been directed by the Comptroller to Specification 462,428.