GB234816A - Improvements in receivers employing the heterodyne principle - Google Patents

Abstract

234,816. Marconi's Wireless Telegraph Co., Ltd., (Assignees of Dyck, A. F. van). May 27, 1924, [Convention date]. Thermionic heterodyne receivers. - In a superheterodyne system, the same oscillatory circuit serves to couple the received signal energy to the local oscillator and also to control the frequency of the latter, the first high-frequency stage 3 is coupled to the combined detector and local oscillator 5 by a tuned circuit 4, 7 which at the same time serves to determine the frequency of the local oscillations, the latter being of the same order as the received signals, and not an harmonic thereof. The resultant intermediate frequency is amplified by the tube 11, and the low frequency components are separated by a second detector tube 14, and are finalty passed through two stages 18, 19 of low frequency amplification. The supersonic frequency may be reflexed from the plate of the first detector 5 to the grid of the first tube 3, and thence to the grid of the tube 11. Fig. 3, shows such a reflexed circuit combined with balancing or stabilizing means consisting of a coil 63 closely coupled to the plate coil 57 and connected in series with a balancing condenser 62 across the grid of the tube 52 and the negative end of the plate battery B1. The amplified signal currents pass from the tube 52 to the autodyne detector 55. The resultant supersonic frequencies are fed back across the transformer 60 to the grid of the first tube and thence through the transformer 54 to the grid of the tube 64, and then through the subsequent tubes as before.