GB472111A - Improvements in and relating to direction finding apparatus - Google Patents

Abstract

472, 111. Directive wireless signalling. HOOVEN, F. J. Dec. 14, 1935, No. 34710. [Class 40 (v)] Signals received on a frame aerial 10, fixed in the homing position on an aeroplane, are combined with those picked up by a non- directive aerial 12, to give a visual indication in a balanced galvanometer 36 of the course being flown. The directive and non-directive aerials are coupled to separate amplifiers 16, 17, and the output from the valve 16 is fed across the coil 27 in phase-opposition to two rectifiers 37, 38, so that the galvanometer needle remains at zero so long as the craft is travelling directly towards the transmitter beacon. The output from the valve 17 is fed from a coil 33 to the centre tapping on the coil 27 so that it is applied to the rectifiers 37, 38 in phase. When the craft yaws to one side or other, the indicator reading is independent of the characteristics of the valves used in the separate amplifiers. The non-directive signals are also supplied to a pair of headphones 48 through a separate amplifier 47. The signals may be heterodyned by a local oscillator symmetrically coupled to each aerial input. Automatic volume control can be applied from the grid current of the detector 47, in which case an ammeter is inserted in the output circuit of the last non- directive amplifier-valve to give the pilot an approximate indication of his distance from the transmitting beacon.