GB650937A - Improved radio detecting apparatus - Google Patents

Abstract

650,937. Radio receiving circuits ; radiolocation. BRITISH THOMSON-HOUSTON CO., Ltd. May 2, 1947, No. 11889. Convention date, May 3, 1946. [Classes 40 (v) and 40 (vii)] A receiver, for use in a pulse radar system and having a gain which increases with lapse of time after the transmission of an exploring pulse, comprises a source of positive pulses synchronized with the transmitted pulses arranged in series with two condensers one of which is connected across the control grid and cathode of one of the amplifying valves in the receiver, the arrangement being such that on the application of a positive pulse grid-current flows thus providing a negative bias voltage on the grid of the valve and reducing the gain thereof, this bias voltage gradually leaking away and restoring the sensitivity of the amplifier. Source 4 which synchronizes the transmission of pulses from the transmitter 1 also applies positive pulses via condenser 39 to the grids of the I.F. amplifying valves 13 and 23 to which received signals are applied via T-R switch 2 and preliminary receiver stages 5. The passage of grid current, during the application of the pulses, charges condensers 22 and 32 negatively, thus reducing the gain of the amplifiers 13 and 23. The charge on these condensers gradually leaks away through the resistance networks shown. The grid-bias of the valves 13 and 23 is adjusted initially by means of potentiometer 37. The output of the receiver is applied to the intensitymodulating grid of a cathode-ray tube having a rotatable deflecting yoke 11 coupled to the aerial 3 to rotate therewith so that P.P.I. display is produced. On account of the increased gain at large ranges, indications of distant objects may be presented on the cathode-ray tube screen without an excessive amount of " clutter " at the centre of the screen obscuring the indications from close objects.