GB520081A - Improvements in or relating to navigation aiding directional radio receiving installations - Google Patents

Abstract

520,081. Directive wireless systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., SMITH, S. B., and FORBES, I. S. Oct. 6, 1938, No. 29030. [Class 40 (v)] In a direction-finding receiver, the pick-ups from a directional aerial and an omni-directional aerial are combined by a continuously-variable cyclic coupling and applied through a receiver proper to one deflection system of an oscillograph, deflections in another direction being produced by means actuated for a short period once per cycle of the variable coupling, the position of the period of actuation in the cycle being adjustable. In Fig. 1 the pick-up from the open aerial 28 is coupled by means of the coils 9, 11 with the output from the search coil 3 of a goniometer connected to a crossed Adcock aerial system, the combined output being applied through a receiver proper 22 to one deflection system 23 of a cathode-ray tube. Coil 11 is, constantly rotated by the motor 13 so that the coupling between the coils 9, 11 is varied sinusoidally and a linear sweep-voltage is applied to the other deflection system 20 of the cathode-ray tube from the time-base 19 for a short period per revolution of the coil 11 by means of the rotary switch 14, 16. The phase of the actuation of the time-base may be adjusted by varying the position of the slip-rings of the rotary switch. When the output from the search coil 3 is zero a symmetrical trace, Fig. 2a, is obtained on the cathode-ray tube but when the coil is rotated from this zero position, unsymmetrical traces, Figs. 2b and 2c, are obtained the asymmetry of which depends upon the sense of rotation. The sense is determined by observing whether the symmetrical trace changes to the form shown in Fig. 2b or Fig. 2c on rotating the goniometer coil 3 in a given direction. The search coil 3 is mechanically coupled to an indicating needle 7 and the bearing of the transmitter is. accordingly given by the reading of this needle when the coil 3 is adjusted to give the symmetrical trace. Telephones 24 are connected to the receiver 22 to enable communication signals to be received during the D.F. operation. In a modification (Fig. 3, not shown) the variable coupling is provided in the input from the directional aerial, the open aerial being constantly coupled to the receiver, in which case the symmetrical trace is of rectangular shape. It is stated that the systems also provide an aural indication of the bearing.