GB517909A - Interference suppression circuit for radio receiving apparatus - Google Patents

Abstract

517,909. Wireless receiving systems. MAGYAR WOLFRAMLAMPA GYAR KREMENEZKY JANOS, R. T. Sept. 26, 1938, Nos. 27994 and 27995. Convention dates. Sept. 24, 1937, and March 18, 1938. [Class 40 (v)] A circuit for deriving a voltage for muting a receiver during atmospherics &c. comprises two signal rectifiers with opposed outputs and different time-constants, or a single rectifier giving two outputs of differing characteristics. In one embodiment, Fig. 1, the signal across resistance 2 is fed to a diode rectifier circuit 6, 7, 8 of long time-constant and a fraction, preferably half, of the same signal voltage is fed from the tapping 9 to the diode circuit 3, 4, 5 of short time-constant. There is thus produced between the control points a, b connected to the diode anodes a voltage which changes in sign when, due to a disturbance, the peak voltage from the system 3, 4, 5 exceeds the smoothed voltage from system 6, 7, 8. This voltage may be used to disable an amplifying stage or detector or to close a signal path by rendering conducting a diode shunted thereacross or non-conducting a diode in series therewith. The latter arrangement is shown in Fig. 7, in which the control points a, bare connected to the grids 52, 53, respectively, of a double triode d.c. amplifier valve 50, the anodes of which are connected through a load resistance 57 the terminals c, d of which feed the signal component thereacross to the output terminals 41, 42 through a diode 34. When, during interference, the point c becomes positive relative to the point d the diode 34 becomes non-conducting. A.V.C. potentials are derived from the point b in the circuit of the diode of long time constant being fed to the lead 45 over filter 38, 39, 43. In a further embodiment, Fig. 9 (not shown) a single diode is arranged to produce control points the difference of potential between which changes in sign when interference occurs.