GB538030A - Improvements in navigational devices - Google Patents

Abstract

538,030. Directive wireless systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Jan. 31, 1940, No. 1935. Convention date, Jan. 31, 1939. [Class 40 (v)] The heading of a moving craft with respect to (a) an earth compass, (b) a radio compass, (c) the bearing of the craft with respect to a radio transmitter are separately shown on a single indicator. A frame aerial 1, a local generator 3, and an earth inductorwinding 5 are mounted in fixed relation on a common shaft, which is continuously rotated by a motor 9. Signals from the aerial 1, and from a non-directive aerial 15, are combined in a receiver 13, the output from which is fed directly to a centre terminal 14, and through a phase-shifter 16 to the lower terminal 17, of a three-position switch 19. The output from the generator 3 is connected to the upper and centre terminals of a switch 23, whilst the earth inductor 5 is connected to the'upper terminal 27 of switch 19 and to the lower terminal of switch 23. The hinge contact of switch 23 is connected through a phasesplitter 35 to the deflecting plates of a cathode ray tube 41, the other electrodes of which are connected through switches 47, 49, 51 to a potentiometer 43. The hinge contact of switch 19 is connected to a saturation transformer 31 which also feeds the control grid 57 of the cathode ray tube through the hinge contact of the switch 51. All the switches are driven through reduction gearing 61 from the aerial shaft 7. The arrangement allows the phase of the signal current to be compared (a) with that generated by the inductor 5, and (b) with the " standard " phase from the generator 5. For instance, when the craft is heading due North, there will be no phase-difference between two of these currents, and similarly when the craft is heading directly on to the distant radio transmitter. For other directions of flight, the relative phase-differences, indicating the headings and bearings, will be shown as radial traces on three concentric scales 61, 63 and 65, Fig. 2 on the screen of the cathode ray tube. The inductor winding may be replaced by a gyro compass (Fig. 3 not shown) which is connected to a small coil located in a rotating field derived from the generator of the " standard " or reference current. A " fix " of the craft's position at any time can be obtained by observing the intersecting traces formed in a double-stream indicator tube. Reference has been directed by the Comptroller to Specification 532,854.