GB612329A - Improvements in and relating to directional aerials - Google Patents

Abstract

612,329. Electric control systems. BRITISH THOMSON-HOUSTON CO., Ltd. March 6, 1946, No. 6995. Convention date, March 27, 1943. [Class 40 (ii)] [Also in Group XL (c)] A gyroscopically - stabilised aerial designed for mounting upon a ship is carried by a turntable upon which is journalled a frame having an axis perpendicular to the vertical plane containing the directive axis of the aerial system, and gyroscopic means for maintaining the intersection of the plane of the frame with the said vertical plane horizontal, means being provided to maintain the elevation angle of the directive beam at a predetermined value relative to the gyroscopically-stabilised frame. The antenna comprises a radiator 4 connected to a transmission line 3 and a parabolic reflector 5 mounted in trunnions 6 carried by' supports 7 mounted on a rotatable carriage 1 and adjustable in elevation by a toothed sector 28 secured to the reflector. The turntable 1 is driven by a motor 8 which is controlled by a selsyn follow-up system, Fig. 4 (not shown), to position the directive axis of the aerial in azimuth in accordance with the preset position of a control handle. The elevational motion is controlled by a motor 25 driving the toothed sector 28 and rotating the stator 31 of a selsyn 32, Figs. 3 and 6, so that the position of the stator corresponds to the elevation of the directive axis of the antenna. The stator 31 is journalled in a housing 34 fixed to a U-shaped frame 35 bolted to the turn-table 1. Rotatably mounted in the frame 35 is a frame 36 having a shaft 37 fixed to the rotor 38 of the selsyn 32. The frame 36 is held horizontal in a plane parallel to the vertical plane, including the directive axis of the antenna by a gyroscope which is carried by a frame 39 pivoted to the frame 36 on a horizontal axis parallel to the directive axis of the antenna and which includes a stator fixed to the frame 39 and a rotor 40 surrounding the stator and provided at its lower end with a hemispherical damper 41 associated with a permanent magnet 42 supported for universal motion from the frame 39. The magnet has a short period of oscillation and if the axis of the rotor 40 deviates from the vertical, the drag, due to eddy current in the damper 41, causes the gyroscope to process towards the vertrical, thus bringing the frame to the horizontal position. The elevation of the antenna is controlled by a selsyn 43, having its stator 44 connected to the stator 31 and having its rotor 45 adjusted by handle 46 so that any phase displacement of the.rotor 38 relative to its stator 31, as compared with the preset selsyn 43, generates a voltage which is amplified and rectified at 47 and supplied to the fields 48 of the generator 30 to produce a control voltage for the motor 25 to rotate the stator 31 and to move the antenna to decrease the displacement.