GB503876A - An improved superheterodyne radio receiver - Google Patents

Abstract

503,876. Thermionic valves; valve circuits for wireless reception. COLE, Ltd., E. K., and BRADFIELD, G. Oct. 19, 1937, No. 28420. [Classes 39 (i) and 40 (v)] In a superheterodyne radio receiver utilizing a local oscillator and mixer valve the valve is caused to provide one or more electron beams, which together constitute an electron stream, and the valve has grids and electrodes so situated with respect to the beams that the output to different electrodes may be varied by controlling the bias on certain other electrodes while maintaining the stream substantially constant in intensity, and potentials applied to grid for deflecting the electron beams are used for effecting automatic frequency control of the local oscillator circuit. Input is fed to the grid g11. Electrons from the cathode k are focused by grids g1, g2, which are at high and low potentials respectively, pass through g3 at a low fixed potential, and are deflected by the grid g4, to which automatic frequency control voltage is applied, so as to be affected by either g6 or g7, after having been accelerated by g5. The grid g9, acting as the anode of a local oscillator circuit L1, is coupled at L2 to a circuit R, C, C1, C2, to which the grids g6 and g7 are connected in such a manner that g6 and g7 are in phase quadrature, and g7 is in phase opposition to g9. Thus as the voltage on g4 is varied the reactance of the valve and the tuning of the oscillator vary. A further accelerating grid g8, is provided, and grids g10 and g11 which respectively accelerate and retard the electrode so as to provide a virtual cathode, the current from which is modulated by g11 passes through screen grid g12 before it reaches the anode. The valve thus acts both as oscillator and mixer. An automatic volume control potential may be applied to the grid g11. The grids g3 and g5 may be omitted.