GB685073A - Improvements in or relating to radio aerial systems for use on ultra short wave lengths - Google Patents

Abstract

685,073. Aerials. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. March 2, 1951 [May 25, 1950], No. 13206/50. Class 40 (vii). A short-wave aerial system for horizontally polarized waves having a substantially omnidirectional polar radiation diagram concentrated in a predetermined plane comprises an outer conductor of circular section, a plurality of inner circular conductors coaxially within the outer conductor, the common axis of the conductors being at right-angles to the predetermined plane and each of the inner conductors extending beyond the end of the conductor next surrounding it and being provided at its end with an outwardly extending flange portion. The conductors are so dimensioned and spaced that energy may be propagated in the spaces between them in the HO 1 mode, radiation being effected substantially omnidirectionally outwards through the spaces between the flanged portions. As no standing wave patterns are produced in the feed arrangement the aerial system is not sharply frequency critical. Fig. 1 shows a simple embodiment in which all the flanges extend to the cylindrical plane of the outer conductor and 45 degrees corner pieces such as 4 are provided to effect the change in the direction of energy propagation in steps. Right-angled corners may also be avoided by providing a smooth radius at the junction of the conductor and flange. In a modification, Fig. 2 (not shown), the outer conductor carries a flange, the edges of all the flanges being on a cylindrical surface coaxial with the conductors, and the flanges are made thick at their inner ends and then at their edges to provide internal coned surfaces to the radiating elements. Another embodiment, Fig. 4 (not shown), shows centrally apertured discs of solid dielectric material fitted between the flanged portions. These discs may extend outwardly beyond the flanges and may be tapered down towards their peripheries to assist in concentrating energy in the predetermined plane. In any of the embodiments described, radial conducting fins 7 may be provided between the flanges to provide mechanical support and to act as mode filters. The feed at the non-radiating end of the system may be from a single circular guide and it is stated to be desirable to keep the length of the nest of coaxial conductors as short as possible and the electrical length of the separate conductors equal.