GB557105A - Switching arrangement for circuits carrying radio-frequency energy - Google Patents

Abstract

557,105. Valve circuits for wireless reception. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and RYN, B. VAN. April 2, 1942, No. 4428. [Class 40 (v)] A switching arrangement for a radio-frequency circuit includes, connected across the circuit, a rectifier, a source of direct current energy, and a switch for connecting the source to the anode of the rectifier to cause it to become conducting so as to present a low impedance to radio frequency energy. In Fig. 1, a valve V has the anode coupled to the grid through condensers C2, C3 and tuned circuit TC to form the second or beatfrequency oscillator of a superheterodyne receiver, the anode potential being fed in through high and low frequency chokes HFC, LFC respectively. As an amplifier, an audio frequency signal is fed in at AI and the audio output is taken at AO. To enable the second oscillator to be switched out, when receiving modulated carrier waves, a rectifier W is connected between a point X and earth, and can be made conducting at will by the anode being connected through resistance R and switch S to H.T. +. In a modification, Fig. 2 (not shown), the rectifier is a diode in the same envelope as the triode, a second diode serving for signal detection and A.V.C., the valve comprising the oscillator and low frequency stages of a superheterodyne receiver.