GB536377A - Improvements in or relating to direction finding systems - Google Patents

Abstract

536,377. Directive wireless systems. STANDARD TELEPHONES & CABLES, Ltd., BEATTY, W. A., and CHATTERJEA, P. K. Nov. 10, 1939, No. 29805. [Class 40 (v)] A beam rotated constantly at frame-scanning frequency, is modulated with television signals which are derived from a diagram so as to indicate in sequence their compass orientation, whereby a distant mobile receiver is given an indication of its bearings. The transmitted signals are derived by scanning the screen of a cathode ray tube which is prepared as shown in Fig. 2, so that each quarter-section develops signals characteristic of its compass bearing. The scanning movement of the electron stream is controlled horizontally by voltages derived from a saw-toothed oscillator and vertically by voltages derived from a potentiometer, Fig. 3, in which a rotating arm 38 moves constantly over a circular winding 33 connected across a battery 41. The received signals are of the kind shown in Fig. 6, and comprise the letter A and its equivalent Morse code, together with a timemodulated signal 56 in which the leading or trailing edge is typical of the compass sector in question. Synchronous signals for the receiver are transmitted from the beacon either omnidirectionally or on a wider beam than that used to transmit the bearing indications. The brightest horizontal line 56, Fig. 6, of the signals is selected, and its trailing edge then indicates the bearing of the receiver on a calibrated scale (Fig. 7 not shown). Specifications 523,575 and 524,671 are referred to.