1,226,900. Pulse radar; gain control arrangements. BENDIX CORP. 21 July, 1969 [6 Aug., 1968], No. 36577/69. Headings H3Q and H4D. In a radar the echo signals in excess of a predetermined level are integrated with respect to time and the receiver gain is increased as a function of the integrated signals. The invention is applied to a known airborne weather radar which incorporates a sector P.P.I. display having bearing scale markers and cathode-ray range rings, a "contour" circuit which blanks a receiver video amplifier whenever the video level exceeds a threshold so that storm areas are shown as dark cells surrounded by a bright contour, and a swept gain circuit. In the embodiment the latter includes transistor 41 momentarily rendered conductive by a radar trigger pulse applied to its base, the conduction causes capacitor 42 to charge to a voltage determined by potentiometer 40; when the trigger pulse disappears capacitor 42 discharges through resistor 43, diode 44 and resistor 45. Diode 44 prevents retrace blanking pulses applied to amplifier 26 from affecting the charge on capacitor 42. The modification introduced by the embodiment of the invention includes transistor 48 biased to be normally non-conductive by a voltage from potentiometer 49. Echo, video signals of an amplitude sufficient to overcome the threshold set by potentiometer 49 cause transistor 48 to conduct by an amount dependent on the excess video amplitude, thereby causing capacitor 42 to discharge more rapidly, Fig. 6 (not shown).
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