GB536259A - Improvements in radio receiving aerial systems - Google Patents

Abstract

536,259. Aerials; wireless signalling. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and STEWART, J. Nov. 3, 1939, No. 29362. [Class 40 (v)] The fore-and-aft and lateral trim of an aeroplane in flight are indicated by variations in the signal strength received by vertical and horizontal aerials from vertically-polarized waves. The effect depends upon the change in signal strength when an open aerial is connected either to the centre, as at A, Fig. 1, or to one side or the other as at A1, A2 of the fuselage B acting as a counterpoise. In Fig. 2, a vertical aerial OA supplies a constant signal to a centre-zero indicator M through two rectifiers R, R1, which are alternately switched into circuit at S so that the needle is kept at zero. Simultaneously an horizontal aerial A (the disposition of which has previously been adjusted to give zero pick-up when the craft is on a level trim) is synchronously switched at S1 from one end to the other of a centre-tapped coil CC, so as to feed equal signals of opposite phase to the indicator. Any alteration in trim will upset the balance of these signals, and the indicator will move accordingly to one side or other of the zero point. An aerial for showing fore-and-aft trim is preferably arranged parallel to the length of the fuselage ; or two horizontal aerials, one for showing the lateral and the other for fore-and-aft trim, may be coupled to the indicator through separate amplifying channels ; by using a " flicker " system, the two switching operations can be combined, and the signals passed through a common amplifier. A radiogoniometer may be used to adjust the relative disposition or coupling between two horizontal aerials, one mounted above the fuselage and the other below for balanced flight, Figs 3 and 4 (not shown).