Patent GB-496001-A (GB)
Title: Improvements in or relating to direct reading radiogoniometers
IPC: G01S1/02
Filed: 1937-11-20
Abstract: 496,001. Directive wireless signalling. MARIQUE, J., and SOC. ANON. INTERNATIONALE DE TELEGRAPHIE SANS FIL. Nov. 20, 1937, Nos. 31981 and 31982. Convention dates, Jan. 15 and Sept. 22. [Class 40 (v)] Relates to cathoderay indicators as used for direction finding, of the kind in which the electron beam is controlled (a) by the signal voltage picked up by a rapidlyrotating frame aerial, and (b) by a " sweeping " voltage which is a function of the orientation of the aerial relatively to a " standard " direction, which may be the lubber-line of a moving craft, or geographical North. The invention is characterized by the fact that the signal-voltage control is applied without being rectified, so that the indicating trace is not distorted near the critical minimum point, nor affected by atmospheric disturbances. The form of the trace on the fluorescent screen may be modified by slowing- down the voltage derived from the rotation of the frame aerial near the critical points, and by " limiting " the output of the amplifier. Provision is also made for indicating a course inclined to the direct " homing "-line. As shown in Fig. 1, the aerial 2 is rotated by a motor 3 and the received signals are applied through an amplifier 7 to one pair of deflecting plates 8, 9 of a cathode ray indicator. Of the other pair, one plate 11 is connected to a point 14 of fixed voltage on the battery 13, whilst the second plate 10 is connected to a pointer 15 which sweeps at the speed of the aerial around a potentiometer 12. The two open ends 21, 22 of the potentiometer wire may be kept aligned in a fixed direction by means of a gyroscope or compass repeater. The combination of the " sweeping " voltage shown in Fig. 2, and the incoming signal-voltage creates on the fluorescent screens of the cathode ray tube a curve of the shape shown in Fig. 3, which cuts a graduated scale 16 at the critical minimum points. The usual 90‹ displacement can be eliminated by shifting the relative positions of the frame aerial and the rotating contact 15 by this amount. The pick-up voltage from a vertical aerial 17 may be added to remove the 180‹ ambiguity. Alternatively, the potentiometer is made in two half-circles. This doubles the sweep frequency, and by throwing the two minima on to the same point on the indicator scale increases the brilliance and accuracy of the trace. Again by using the known polarco-ordinate type of deflection control, a directional " trace " of the form shown in Fig. 7 is produced on the screen, with " minimum " points at 18, 19. Specification 457,681 is referred to in this connection. By suitably adjusting the position of the moving contact 15 relatively to the plane of the aerial, the two critical points can be made to converge when the craft is on the " homing " line, and to diverge when the craft deviates from its direct course. A similar adjustment can be applied to set a course which is inclined at an angle to the transmitter. By using a limiter valve, or equivalent device, the trace on the screen can be confined to the regions near the critical miminum points. Again, by reducing the resistance of the potentiometer 12 over certain sections of its length, the " sweep "-voltage can be slowed down, as indicated at 28, Fig. 9, and the trace of the critical points then takes the " sharpened " forms shown in Fig. 14, in which 32 represents the homing-line, whilst 33 and 34 indicate deviations to port or starboard.