GB600255A - Improvements in or relating to receivers for time modulated pulses of radio waves - Google Patents

Abstract

600,255. Pulse modulation. STANDARD TELEPHONES & CABLES. Ltd. Oct. 18, 1944, No. 20199. Convention date, May 24, 1943, [Class 40 (v)] A blocking oscillator is triggered by incoming carrier frequency pulses to produce corresponding D.C. pulses and to control a flip-flop multivibrator circuit. The output of the latter may be fed back to the oscillator to increase its sensitivity during the oscillating interval. In one embodiment time-modulated pulse radio signals in the aerial coil 18, Fig. 2, initiate oscillations in the circuit L, C which build up and are sustained by the valve 23 until the charge on condenser 26 becomes negative enough to inhibit oscillation. Thereafter the charge leaks away through resistances R1, R2 at such a rate that the next received carrier pulse can trigger the oscillator again. The free-running pulse recurrence frequency is adjusted by the screen supply potentiometer 32 so that it is lower than the meansignal pulse recurrence frequency. The voltage pulse at the anode triggers a flip-flop multivibrator (not shown) which produces output pulses of fixed amplitude and duration for the time modulated pulse demodulator which may be of the type described in Specification 600,291. A multivibrator pulse is fed back to the grid of valve 20, over the lead 37 to the junction of resistances R1, R2 during the oscillation period. The demodulator may alternatively be fed from the rectified voltage impulses in the blocking oscillator circuit.