GB675463A - Amplifier circuits for radio communication - Google Patents

Abstract

675,463. Reflex amplifier circuits. MURPHY RADIO, Ltd., BAKER, G. B., CULLEN, P. C., and SMITH, R. B. Nov, 8, 1946 [March 27, 1945], No. 7692/45. Class 40 (vi). In a superheterodyne radio receiver having at least one reflex stage for amplifying two or all of the radio, intermediate and audio frequencies negative feed-back is provided by means of an impedance appropriate to the frequency fed back to the reflexed stage, connected in the cathode circuit. In Fig. 1, valve 3 acts as a cathode follower R.F. stage and as an amplifier for reflexed intermediate frequency. The R.F. oscillations are fed to the grid through the tuned circuit of transformer 9 which has negligible impedance at radio frequencies. The circuit 6, which possesses rejector resonance at signal frequency and acceptor resonance at image frequency as described in Specification 670,851, is connected in the cathode circuit. The output from circuit 6 is fed to the grid of frequency changer valve 8. The intermediate frequency produced by this valve is coupled by tuned transformer 9 to the grid of valve 3, the impedance of transformer 2 being negligible at intermediate frequency. The secondary winding of the transformer connected in the cathode circuit of valve 3, is tuned to intermediate frequency and connected to a further amplifying or detecting valve 10. Fig. 2 shows an R.F. stage valve 11 with reflexed audio frequency fed back from audio amplifier valve 16 via transformer 17 and across condenser 18. The audio output is taken from transformer 19. Negative feed-back for audio frequencies is provided by an inductance 20 in the cathode circuit of valve 11.