GB596612A - Radio direction finder systems - Google Patents

Abstract

596,612. Radio direction-finding. STANDARD TELEPHONES & CABLES, Ltd. June 29,' 1945, No. 16653.. Convention date, Aug. 9, 1944. [Class 40 (v)] [Also in Group XXXVI] In a cathode-ray tube indicator for a radio direction-finder, when the direction-finder is aligned with the direction of the incoming signals the cathode-ray trace comprises a single linear trace or two separate colinear traces and the direction-indicating signals are applied to displace two portions of the single trace or the two separate traces relative to one another out of alignment when the directionfinder departs from alignment with the incoming signals. The invention is described as applied to a homing system in which the pick-up from a loop aerial 1, Fig. 1, is alternately combined in phase and phase-opposition with the pick-up from an open aerial 2 by means of two switching valves 3 and 4 which are alternately rendered conductive by push-pull voltages from the sinusoidal control source 8. The A.C. component of the rectified output from the receiver 5 which is applied to the Y plate 6 of the cathode-ray tube 7 thus comprises a sinusoidal voltage 23 or 24, Fig. 2, which is in phase or phase-opposition with the control voltage 10 according to the sense of the homing misalignment, the amplitude depending upon the magnitude of the misalignment. A sinusoidal wave 10 from the source 8 is applied to X-plate 15A and a square wave 14 derived from the sine wave is applied to the other X plate 15; these two waves are in phase, i.e. coincident positive half-cycles, and the resultant effect is equivalent to applying the composite waveform 16, Fig. 2, to X plate 15A so that in the absence of any signal on the Y plate two colinear traces 21, 22 are produced which are displaced out of alignment into position 21A, 22A when the output from the receiver comprises the voltage 23. The flybacks produced by the portions 17 and 19 of the composite waveform may be suppressed by blanking signals. In a modification, Fig. 3 (not shown), the composite waveform 16 is actually produced by mixing the waveforms 10 and 14 and applying the resultant to a single X plate. The switching valves 3 and 4 may be operated by the square wave 14 in which case the A.C. output from the receiver comprises a square wave, Fig. 7 (not shown), and the traces are displaced into positions 21B, 22B as shown in Fig. 4. In another modification, Fig. 5 (not shown), the two traces 21, 22 are produced by saw-tooth voltages and in Fig. 6 (not shown) a single trace is produced by a saw-tooth waveform of duration equal to a complete cycle of the control voltage 10, the two halves of the trace being then displaced as above.