GB596722A - Improvements in thermionic valve circuits, systems, or apparatus for the reception of wireless, television and the like signals - Google Patents

Abstract

596,722. Valve superheterodyne circuits. FORD, D'A. N. Aug. 1, 1945, No. 19733. [Class 40 (v)] A frequency changer comprises a local oscillator operating at the intermediate frequency, and means for modulating the local oscillations in accordance with the modulations on the incoming carrier signals. Carrier signals from input circuit LC are rectified at grid G1 by virtue of circuit C1, R5, to impress the modulation components of the signals on the electron stream in multi-electrode valve V. Grid G4 is associated with anode A in an oscillatory circuit tuned to the intermediate frequency, so that modulated signals at this frequency appear in the anode circuit which includes byepass arrangements for unwanted frequencies. The output may be fed to a similar frequency changer generating a different intermediate frequency or direct to normal I.F. amplifiers. Variable components R1, C3 are amplitude , controls for the local oscillations. Alternatively, the oscillator section may comprise grids G2, G3 and grid G4 may accept the carrier signals. In this case, a differential capacitor may provide the amplitude control and the output transformer may be associated with a tuned circuit in the anode lead, or in the oscillator section with a coupling condenser between the anode and control grid. The rectified carrier signals may be supplied to valve V from a separate detector with or without reaction.