GB450150A - Improvements in or relating to radio receiving systems - Google Patents

Abstract

450,150. Valve circuits for wireless reception. PADDLE, L. H., 6, Graham Road, Purley, Surrey. Jan. 5, 1935, No. 412. [Class 40 (v)] A method of high frequency reception comprises mixing the signal with locally generated oscillations, extracting from the mixture oscillations of the local frequency now modulated by the audio frequency signal, and demodulating the local frequency oscillations. The mixing stage may be a gridleak rectifier, the local oscillations being applied to the anode circuit. A filter may be inserted between the mixing stage and demodulator to pass only oscillations of the local frequency. A limiting stage may also be provided to limit the amplitude of the local frequency thereby increasing modulation depth. Fig. 4 shows the application to a super-regenerative receiver comprising a reacting rectifier V3, the quenching frequency being generated by the triode oscillator OSC in the anode circuit of V3. The grid of V3 is connected over a filter 15, 19, tuned to the quenching frequency, to a further stage V4. In this case the quenching frequency is the frequency passed by the filter and subsequently demodulated. Fig. 5 shows a receiver for use on wavelengths of the order of 4 metres, in which the dipole 27 is coupled to the anode circuits of a pair of triodes V5, V6, coupled as described in Specification 450,967, and tending to oscillate at the frequency of tuned circuits 25, 26 in grid and anode circuits respectively, oscillation being controlled by resistance 23. The output at this oscillation quenching frequency, modulated by the signal, may be taken from couplings at 28 or 29. With this arrangement, a separate local oscillator may be employed in the anode circuit 26 of the valves V5, V6 ; and a subsequent valve may be provided, connected exactly as V4 of Fig. 4, (Fig. 6 not shown). Specification 285,108, [Class 40 (v)], is referred to.