GB598672A - Improvements in or relating to radio receivers for radar echo signals - Google Patents

Abstract

598,672. Automatic gain control ; radiolocation. DUNWORTH, J. V. June 28, 1945, No. 16558. [Class 40 (v)] In a radio receiver for radar echo signals there is provided a normally-blocked A.V.C. unit, which is opened by means of gating impulses coincident with the chosen echo signals. In a branched A.V.C. amplifier, recurrent trains of negative-going echo signals are applied to the grid of the valve VI, the amplitude being adjusted by means of the variable resistance R1. The valve V1 is run at saturation level, signal pulses of above a predetermined amplitude causing positive-going impulses to be applied to the inner grid of the valve V2. The resistances R3, R4, R5 apply positive bias to the cathode of the valve V2 from the H.T. line, the outer grid being grounded over the resistance R6. The anode of the valve V2 is normally non-conductive, conduction occurring when a positive pulse on the inner grid coincides with a positive strobe pulse which is applied to the outer grid via the terminal 2. The outer grid is prevented from becoming positive relative to the cathode by means of the diode V3. Successive negative pulses are passed over the diode V4 4 to the circuit C1, R7, the steady potential being applied over the smoothing network C2, R8, R9 to the grid of the cathode follower V5. The cathode of the valve V5 is connected to the negative line 4 over the resistance R12, A.V.C. potentials being taken off over the smoothing network C3, R10, R11, R12. The A.V.C. potential is limited to negative values by means of the diode V6, and in the absence of signals is determined by the potentiometer P1. The switch 3 and adjustable potentiometer P2 permit of alternative manual control. Specifications 581,996, 582,325, 582,503 and 598,649 are referred to.