GB650592A - Improvements in or relating to radio aerial arrangements for use on aircraft - Google Patents

Abstract

650,592. Aerials. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. April 1, 1948, No. 9257. [Class 40 (vii)] Relates to aircraft open aerials which are substantially in or sunk below the level of the aircraft skin. When such an aerial is coupled to a receiver through a long feeder the signal pick-up is reduced due to the capacity of the feeder and according to the present invention this effect is prevented by coupling the aerial to the feeder by a valve buffer stage. The invention is described as applied to a rotatable loop D.F. system in which the open aerial constitutes the sense aerial, the buffer stage also serving to decouple the two aerials. As shown, a flattened iron cored loop L rotatable by a motor (not shown) is mounted in a depression K formed in the conductive skin A of the aircraft which is covered by a removable insulating lid so as to maintain a smooth surface and the open aerial comprises a folded conductor O mounted by insulators S on the floor of the depression. One end of the conductor O is coupled to the grid of a buffer valve, Fig. 2 (not shown), mounted on the back of the floor' of the depression, Fig. 4 (not shown), and the valve anode is coupled by a toroidal matching transformer to a coaxial feeder. The other end of the open aerial is earthed and a 5 megohm resistor is connected across the two ends to disperse any static charges which may accumulate on the aerial. At the receiver end of the feeder the inner conductor is coupled to the receiver input through a capacitor which is adjusted so that the reactance presented to the receiver and hence the phasing of the input signal is the same as that produced by a conventional open aerial. If the reactance of the capacitor is high enough the buffer valve may be a cathode follower. Alternatively the open aerial may be carried by the lid or embedded in the insulating material thereof. If the depression is rectangular or square the open aerial may comprise a plurality of parallel spaced wires lying in a plane or curved surface and joined together by a cross-wire at one end or with a circular or annular depression it may comprise a central ring with a plurality of evely-spaced radial wires.