GB426328A - Improvements in wireless direction and position finding - Google Patents

Abstract

426,328. Directive wireless signalling. WATT, R. A. W., HERD, J. F., and BELL, L. H. BAINBRIDGE-, National Physical Laboratory, Teddington, Middlesex. Aug. 2, 1933, No. 21695. [Class 40 (v)] The position of a moving craft is shown on the screen 6 of a cathode-ray tube as the intersection 14 of two lines formed by the track of the electron stream under the control of the radiation received from two land transmitters 8, 9 spaced apart. The screen of the tube is associated with a map of the locality. The deflection of the electron stream is due to the directional effect of two frame aerials, tuned to the transmitting stations. The spot on the screen formed by the impact of the electron stream when no signals are being received is rapidly and alternately zeroized at the points 8 and 9 (corresponding to the two radio transmitters) by the application of suitable control voltages. The received signals then produce the visible intersecting tracks 8, 12 and 9, 13 owing to the persistence of vision. As shown in Fig. 3, the two frame aerials 15, 151 are tuned first to one and then to the other transmitter by switches 18, 18<1>, which simultaneously change the zeroizing voltages for the spot by means of switches 27, 26 which apply different control to the electrodes 25, 24 of the cathode ray tube from a potentiometer 28. The switches are operated from a rotating disc 31 and connecting-rod 30. The two frame aerials are connected across the deflecting electrodes 21, 22, as shown. The zeroizing voltages are automatically changed, when the map of a new locality is inserted over the fluorescent screen. This is effected by means of projections such as 34, 38, Fig. 4, on the underside of the maps 33, 37, which close contacts associated with the potentiometer switches 27, 26. The method can be used at a ground station to locate the position of an aeroplane in flight. The elevation of aeroplane can also be determined from the ground by observation of the " error of bearing or " aeroplane effect," or as shown in Fig. 6 by measuring the elliptical trace produced on a cathode-ray indicator 41 by the phase-difference in the signals received on the two spaced aerials 39, 39'. Or it can be obtained on the craft by ascertaining the incident angle at which horizontally-polarized radiation from a ground transmitter reaches the machine. Specification 252,263, [Class 40 (v)], is referred to.