GB839062A - Signal amplitude analyzer - Google Patents

Abstract

839,062. Voltage measurement. COLLINS RADIO CO. Jan. 28, 1958 [April 8, 1957], No. 2854/58. Class 37. In an arrangement for analysing variations in the amplitude of a signal which may be the A.V.C. voltage of a radio receiver being used for a field strength survey, either an indication of the amplitude exceeded by the signal for a predetermined percentage of the time or the percentage of time that the signal exceeds a preselected amplitude, or both is continuously generated. The signal which is applied to a terminal 58, Fig. 2, of a chopper 11 vibrated at 400 cycles per sec. and a reference voltage applied at terminal 59 produce, when they differ, a square wave output which is amplified and applied over a transformer 33 to a comparator comprising valves 13a, 13b wherein the phase relative to a 400-cycle supply synchronous with that driving chopper 11 is detected to energize coil 35 or 36 of a relay 14 according to whether the input voltage is above or below the reference. Voltages applied to the contacts 37, 38 of the relay for pick-up by the tongue are preselected by potentiometer 15 and are of such a ratio to give a required charge/discharge ratio to condenser 42, Fig. 3, of the integrator circuit to which the relay output is applied, whereby a voltage sufficient to actuate relays 20, 21 in later stages, is developed only if the percentage of time which the signal exceeds the reference varies from the percentage set by the potentiometer 15, for which a graph is to be traced. The relays 20, 21 are actuated through a further chopper 17 and phase detector 19 energized from a 60-cycle supply, and drive a bi-directional slipping switch 22 in one direction or the other respectively, to change the reference voltage from a potentiometer 23 to a new value whereat the percentage of time it is exceeded corresponds to that required. A punched card information switch 24 and an automatic timer or recorder are also driven by switch 22. The relays 20, 21 are arranged to short the condenser 42 on each actuation.