GB546830A - Automatic frequency control for wave-signal receivers - Google Patents

Abstract

546,830. Valve circuits for wireless reception. HAZELTINE CORPORATION. Feb. 14, 1941, No. 2051. Convention date, Dec. 30, 1939. [Class 40 (v)] In an ultra-high frequency superheterodyne receiver having automatic frequency correction the variation of the phase angle in the thermionic reactance due to variations in the effect of the transit time of the electrons when operating at differing frequencies which would tend to impair the frequency correction is compensated by a circuit which counteracts the tendency of the phase angle to vary. The Figure shows an oscillator 23 and a 'frequency control valve 22 to which a phase displaced voltage is fed from the anode of the oscillator through the phase shifting impedances 43, 44, the capacity 44 being the input capacitance of the valve 22. The oscillator is tuned by the selected inductance 26 ... 28 and the inherent capacity 29 and the anode and screen voltages applied to valves 22, 23 is varied by resistances 39 .. 41 so as to maintain a 90 degrees phase angle between the oscillator voltage and the output voltage of valve 22. In this way incidental phase shifts produced on changing the frequency are prevented by choice of resistances 39 ... 41 and 43 and take into account variation produced by the lead inductance 37 and the phase change between the anode and screen of the valve 23.