GB965802A - Improvements in or relating to aerials - Google Patents

Abstract

965,802. Aerials. MARCONI CO. Ltd. May 15, 1962 [Nov. 3, 1961], No. 39424/61. Heading H4A. The invention relates to wideband aerials similar to known logarithmically periodic aerial arrays such as disclosed in Specification 884,889, but in which the taper ratio, that is the ratio of the length and spacing of adjacent elements, is not a constant thus allowing the gain of the array to be greatest at the frequency where this is required. For example, in television reception band III usually requires more gain than band I, thus the taper ratio is preferably greatest at the higher frequency end of the frequency band. One embodiment, Fig. 1, comprises an array of dipoles connected to a two-wire feeder F1, F2 fed at one end, the taper ratio decreasing from a value of approximately 0.95 at the higher frequency (feed) end to a value of approximately 0.8 at the lower frequency end and the dipole spacing varying from approximately #/6 at the higher frequency end to approximately #/8 at the lower frequency end. Fig. 2 shows an array of folded unipoles connected to a single feeder and supported by a guy W from a mast M to hang as a catenary. Fig. 3 shows an array of parallel horizontal dipoles D hung on a feeder F between two masts to also form a catenary, the effective height, in wavelengths, of the higher frequency dipoles being greater than that of the lower frequency dipoles, thereby reducing the elevation of the main beam. Fig. 4 shows a twin zig-zag array each zig-zag Z consisting of coplanar parallel lengths of conductor at right angles to the back bone wire F and joined in series by longitudinal lengths of conductor, the two backbone wires forming a flared twin-wire feeder.