GB516567A - Improvements in radio navigational systems for aircraft or watercraft - Google Patents

Abstract

516,567. Directive wireless signalling. SMITH & SONS (MOTOR ACCESSORIES), Ltd., S., and MEREDITH, F. W. May 25, 1938, No. 15641. [Class 40 (v)] [Also in Group XXXV] In a receiver for a radio-navigational beam in which the received signals corresponding to the overlapping characteristics are combined in opposition, the indicator is modified to give true guide-path indications, e.g., a central zero reading, when the receiver is moving in a direction convergent with the guide-path. As shown in Fig. 3, the double modulated signals from the transmitter are received on the open aerial 10 and separated in the filters 12, 13, the two signals being then rectified and com bined in opposition in the device 14 to give a direct current having a polarity which depends upon the side of the guide path OX, Fig. 2, the receiver happens to be positioned, and the amplitude of which depends upon the bearing angle a, Fig. 2, of the receiver from the transmitter. This current is applied to the moving coil of the indicator 19, a second coil being supplied from the loop aerial which is mounted athwart the aeroplane. The output from it is applied to the receiver 21 to give a direct current the amplitude of which depends upon the bearing angle # of the transmitter from the receiver and the polarity of which depends upon the sense of this bearing. If the two outputs are applied to the indicator coils in the correct sense, the indicator reading will be proportional to the two bearing angles, and will be zero for a certain direction of approach convergent with the guide-path OX. The sharpness of the approach can be adjusted by regulating the output from receiver 21 by means of a resistance 22. Indications corresponding to the angle alpha only, or to the angle # only, may be obtained by disconnecting receiver 21, or receiver 11, by means of a switch. In conditions of wind-drift, the aeroplane does not reach the course line OX, but eventually approaches the transmitter along a linear path at an angle alpha to the guide-path. The angle of drift can be calculated, or measured by an instrument connected to the output of receiver 21, so that it measures the angle # directly. The drift is then compensated by rotating the loop 20 through the drift-angle, when the course followed will lead to the guide-path. The compensatory rotation of the loop 20 may be effected automatically by means of an electric motor 41 having oppositelywound field-coils 42, 43 one of which is energized through the needle of the indicator 27 depending on the sense of the needle deflection. The aeroplane may be automatically steered by applying the outputs from receivers 11 and 21 in opposition to the coil 50 of a polarized relay 51, which controls the directional gyroscope 52 and so operates the rudder-bar 58. Specification 357,968 is referred to.