GB726392A - Improvements relating to radio directional apparatus - Google Patents

Abstract

726,392. Radar. GENERAL ELECTRIC CO. Aug. 4, 1953 [Aug. 9, 1952], No. 21532/53. Class 40 (7). In a ground radar displaying the plan position of aircraft, the bearing of a particular aircraft transmitting a frequency different from that of the radar is displayed as an intensified radial line on the P.P.I. by a separate directionfinder whose aerial rotates at a speed of f2= 1800 r.p.m., which is greater than the speed of rotation, f1 = 30 r.p.m., of the radar aerial, the signals from the direction-finder being recorded on an annular magnetizable strip or wire recording element 34 by a recording head 32 rotating relative to the element at a speed of f2 and the recorded signals being applied to the cathode-ray tube by a pick-up head 43 rotating relative to the element at a speed of f r.p.m. As described, the pick-up head is stationary and the recording head and element rotate in opposite directions at speeds of (f2 - f1) and f1 respectively, but alternatively the element may be stationary and the two heads rotated in the same direction at speeds of f2 and f1 respectively. As shown, the radar aerial 10 and the D.F. loop aerial 21 are rotated by motors 18, 24 controlled from a power supply 19 by units 20, 25, the magnetic element 34 and time-base coil 16 of the display cathode-ray tube 14 being rotated synchronously with aerial 10 at a speed off and the radial arm 33 carrying the recording head 32 being rotated at a speed of (f2 - f1 ) by the output shaft 42 of a differential 38 whose input shafts 39, 37 rotate synchronously with aerials 10 and 21 at speeds of f1 and f2 respectively. The output B from the D.F. receiver 23 is applied via amplifier 27, rectifier 28, clipper 29 (pulse output D), and slip-rings 31 to the recording head 32 and the output from the pick-up head 43 is shaped and differentiated at 45, 46 (outputs E and F) to trigger a monostable flip-flop 47 giving a pulse output G of duration twice that of the sweep waveform A, which is applied to intensify the cathode-ray trace. Alternatively the waveform F may condition the flip-flop 47 so that it is triggered by the succeeding sweep waveform, the duration of the output G being then equal to the sweep waveform A. An erasing head 49 energized from A.C. source 50 is located adjacent the pick-up head. Magnetic recorder. As shown in Fig. 2, the magnetic tape 34 is wound round the cylindrical flange 58 of a disc 55 attached to a shaft 51. The pick-up head 43 is fixed outside the flange 58 and the recording head 32 is mounted inside the flange 58 on a disc 59 rotated by the output from differential 38 via gearing 67, 63, 65 and 66, the head 32 being dynamically balanced by a counterweight 61. In a modification, Fig. 3 (not shown), the magnetic tape is replaced by a wire embedded in the flange 58.