GB804666A - Radio aerials for aircraft - Google Patents

Abstract

804,666. Aerials; aerial couplings. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Feb. 15, 1956 [Feb. 16, 1955No. 4608/55. Addition to 704,659. Class 40 (7). An aircraft aerial system makes use of the metal skin of an aircraft member, such as a wing, as the aerial element and this is tuned and coupled to a transducer by means of a recess having a width equal or greater than its depth and conductive internal surfaces formed in a convex surface of the member. The recess contains means coupling it to a feeder and has a conductor or conductors arranged across its mouth and connecting a capacitor along the direction of flow of the radio-frequency currents. The dimensions of the recess and the value of the capacitor are chosen so as to tune the aerial system to frequencies within a required band. In one embodiment the recess 3 is formed in the leading edge of an aircraft wing 2 close to the fuselage 1. A coupling coil 4 is arranged in the recess and has a variable capacitor 7 connected across it for tuning purposes. The coaxial feeder has its inner conductor joined to the coil at an intermediate point 6 providing suitable matching and its outer conductor is earthed close to the point 30 at which the earthy side of the coil is connected to the side wall of the recess. A copper conductor 8 and capacitor 9 are connected across the mouth of the recess which may be protected by a non- conductive plastic sheet fairing 10. In a modification (Fig. 4) the tuned coil 4 is omitted and the inner conductor of the feeder led to a point 11 chosen so as to match the aerial to the feeder at a given operating frequency. In a more complex arrangement the feeder may be terminated at a switch on the side wall of the recess so arranged that the central conductor may be connected as required to any one of a number of extension wires connected to differing points 11 to provide proper matching at differing frequencies (Fig. 3, not shown). The capacitor 9 may be moved away from the recess and coupled to the side wall of the recess and the conductor 8 by a coaxial line; further, the conductor 8 may be made inductive by forming it as a coil. More than one recess may be provided to produce particular radiation patterns and the aerial may be formed from the tail fin or tail plane instead of a wing.