Patent GB-696406-A (GB)
Title: Improvements in airborne equipment for use with multiple track radio ranges
IPC: G01S1/02
Filed: 1952-03-14
Abstract: 696,406. Radio navigation. COMMONWEALTH SCIENTIFIC & INDUSTRIAL RESEARCH ORGANIZATION. March 14, 1952 [April 16, 1951], No. 6670/52. Class 40 (vii). In a short-base pulse hyperbolic navigation system, employing a master station transmitting a train of closely-spaced pairs of pulses whose spacing is indicative of the station and a slave station transmitting a relatively delayed train of pulses of the same recurrence frequency, the receiver comprises means whereby small deviations of a craft carrying the receiver from a pre-selected one of a number of possible radial courses are indicated as deviations of a meter needle for a central zero position. The receiver comprises means for generating from the received pulse signals a train of double gating pulses which control a gating circuit to which the received pulses are applied after passage through an adjustable delay line whose delay is pre-selected according to the desired course, the output from the gating circuit being applied to a centre-zero meter, so that when following the desired course the gating pulses derived from the slave-station signals straddle the second pulses of the delayed pulse pairs received from the master station and a central indication is obtained upon the meter. The received demodulated pulse signals are applied to blocking-oscillator valve V whereby shaped negative Fig. 3B, and positive, Fig. 3C, pulses are developed in transformer windings 14 and 15 respectively. The negative output from winding 14 is applied to adjustable delay line DL1 which is pre-set by means of short-circuiting switch S1 according to the identity of the selected master station. The output, Fig. 3D, from the delay line which includes positive pulse signals reflected from the end of the line is applied to one input of coincidence valve F4 to another input of which positive pulses from winding 15 are applied. The negative pulse output from V4, Fig. 3E, which is obtained upon reception of signals from the appropriate master station is applied to adjustable delay line DL2 which is pre-set by means of switch S2 in accordance with the selected radial course and the output from the line, Fig. 3F, which includes positive delayed pulses is applied to the control grids of coincidence valves V5 and V6. The gating pulses controlling the operation of valves V5 and V6 are derived from blocking oscillator V3 which is triggered by the output from winding 15, and the output of the blocking oscillator V3 is applied as an " early gate," Fig. 3G, to valve V5 and, after passage through delay line DL3, as a " late gate," Fig. 3H, to valve V6. Outputs from the valves V5 and V6, which when the desired course is being followed are as shown in Figs. 3J and 3K respectively, are integrated and applied to valves V7a and V7b having a voltmeter 7, which gives a zero indication when equal inputs are applied to the two valves, connected between the valve anodes. In order to distinguish between zero readings due to accurate following of the pre-selected course and due to large departures from this course, the common anode circuit of the valves V7a and V7b includes relay winding R7 which causes the circuit of neon-lamp 38 to close, when input signals are applied to the valves V7a and V7b, due to their increased anode currents. Calibration checking.-The master station transmits a further train of pulses consisting of a series of groups of three pulses, the spacing of the first two of a group representing the " identity " of the test transmission and the spacing of the second and third pulses representing a radial course. Upon actuating switch S4 the delays introduced by delay lines DL1 and DL2 are set to corresponding values so that the meter 7 should give a zero-indication, departures from this zero-reading indicating errors in the calibration of the equipment.