GB439206A - Improvements in or relating to radio receivers - Google Patents

Abstract

439,206. Valve circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, London, and WRIGHT, G. M., Lordlands, Little Baddow, Chelmsford. June 2, 1934, No. 16505. [Class 40 (v)] In order to reduce interference due tc curvature of char acteristic of a homo dyne rectifier the time of traversal of the curved portior is reduced (1) by employing a synchronized pulse gen erator in place of the usual homodyne oscillator (2) by giving the oscillator output a square-topped wave-form (3) by arranging that only the tips of the local oscillations are utilized. An embodiment of method (1) is shown in Fig. 4, and comprises a cross-coupled multi-vibrator 18, 19 triggered by an oscillator 20 and feeding into a homodyne diode rectifier 14 biassed back by battery 21. Method (2) may be carried out by inserting a limiter stage between the oscillator and the detector, Fig. 2 (not shown). Fig. 3 shows an embodiment of method (3) in which the homodyne diode 14, tuned circuit 3 and output resistance-condenser combination 15, 16 form a series loop circuit, the time constant of 15, 16 being large compared with that of the oscillator 11 and small compared with the highest audio frequency dealt with. High negative voltage across resistance 15 due to the oscillator input results in only the tips of the oscillations passing to the filter 9.