GB1153253A - Improvements in or relating to V.H.F. Directional Aerial Systems - Google Patents

Abstract

1,153,253. Aerials. SIEMENS A.G. 24 April, 1967 [25 April, 1966], No. 18707/67. Heading H4A. An aerial array comprises a number of pairs of parallel dipoles in front of a common reflector, each pair being attached to a carrier which is rotatable about a horizontal axis. At least two walls of the reflector are in the form of short-circuited quarter-wave lines, which extend to enclose the array, and which act as current traps to reduce back radiation. As described, each pair of dipoles is mounted on a forked carrier 25 which is fixed at its centre to the back wall 27 of a box reflector, stops being provided so that the dipoles may be either horizontal or vertical, according to the kind of polarization required in the radiation. The upper and lower walls 28, 29 of the reflector 9 are provided with inner walls 30, 31 which are open in front and closed at the back by the wall 27. Adjustment bars 21, 22 between the walls 28, 30 and 29, 31 are set at a distance of a quarter wavelength from the front of the reflector, which may be covered by a protective sheet 33 of dielectric material. A vertical metallic dividing wall 23 in the centre of the reflector 9 serves to de-couple dipole pairs on its right from those on its left. The dipoles are connected to a common feeder by coaxial lines, and the arms of the carriers 25 may act as outer conductors thereof, and be slotted at their ends to provide balanced slot-feeding arrangements for the said dipoles.