GB500481A - Improvements in or relating to direction finding radio receiving installations - Google Patents

Abstract

500,481. Directive wireless signalling. MARCONI'S WIRELESS. TELEGRAPH CO., Ltd., and COCKERELL, C. S. Aug. 7, 1937, No. 21796. [Class 40 (v)] The bearing, as well as the "sense," of a distant transmitter is determined by combining the signals from a directional aerial with signals in phase-quadrature derived fromone or more non-directional aerials, under the control of a local low-frequency oscillation, and applying them to a cathode-ray indicator. As shown in Fig. 1, the input circuit of the valve 1 includes the search-coil 3 of a radiogoniometer (not shown) in series with a coil 2, the latter being coupled directly to one " open " aerial 7, and through an amplifier 8 to a second "open" aerial 10. A transformer 13 applies a 50-cycle local oscillation. The arrangement is such that the "open" aerial components are in phase-opposition with each other, and in phase-quadrature with the directive signal components, in the combining circuit 2, 3, 4, when no signals are being received. They then give the cathode-ray trace shown in Fig. 2, when the output from valve 1 is fed to one pair of deflector plates, and the local oscillations from a 50-cycle source 13 are fed to the other pair. When the directional aerial is in the minimum position, the trace takes one or other of the forms shown in Figs. 6 and 7, the " sense " being in the direction of the smaller triangle. No other manual control is necessary. Automatic volume control, having a time-period greater than that of the oscillations from 13, is applied to exclude fortuitous signals received by the " open " aerials 7, 10. In a modified arrangement each of the open aerials feeds into a variable-mu valve, the two valves being arranged in parallel as regards the valve input circuit, but in pushpull to the local oscillations, Fig. 8 (not shown). One open aerial may be used instead of two, this being connected in parallel to the grids of a pair of screen-grid or heptode valves to which the 50-cycle source is applied in pushpull, Fig. 9 (not shown). In another modification, Fig. 11 (not shown), the operation of a " sense " switch gives a trace which shows a constricted part only if the sense is correct and not otherwise.