GB670231A - Improvements in antennae - Google Patents

Abstract

670,231. Aerials. BRITISH THOMSONHOUSTON CO., Ltd. May 13, 1947 [May 13, 1946], No. 12922/47. Classes 40 (v) and 40 (vii). A wide-band aerial for radiating horizontallypolarized waves omnidirectionally in the horizontal plane comprises a plurality of radiating elements forming a concentric loop about an earthed conductive mast upon which they are conductively supported, certain pairs of adjacent elements being energized at their adjacent ends and the remainder of the elements being capacitatively coupled to the adjacent ones of the energized elements. The capacity between adjacent elements and the manner of feeding the aerial is so arranged that each element carries substantially the same current both as regards amplitude and phase. The aerial comprises arcuate members 29, 30, 33, 34, 35, 36 supported from the mast 1 by arms 25, 26, 27, 28. A radiating fin, 31, 32 or 37, is attached to each arcuate member to increase the current-carrying surfaces thereof and thus improve the broad-band characteristics of the aerial. Energy is supplied to the aerial via coaxial feeders 38 and 40 which are coupled to the adjacent ends of members 33, 34 and 35, 36, respectively. Line - balance converters are mounted within the arms 26, 28 for coupling the unbalanced coaxial feeder to the balanced aerial system. Members 29 and 30 are coupled capacitatively to the adjacent ends of elements 34 and 35 and elements 33 and 36 respectively; auxiliary discs may be mounted on the ends of the members to increase the coupling between them. The line-balance converters may be set to behave as inductances in series with the aerial inputs in those cases when the aerial impedance has a capacitative component. Fig. 1 (not shown) illustrates an alternative arrangement. In this arrangement, which is electrically equivalent to that of Fig. 3, various mechanical modifications are made; thus the radiating fins shown in Fig. 3 are replaced by rod or tubular members which are attached at each end to a corresponding end of the respective arcuate members.