GB721582A - Improvements in or relating to short wave radio aerials and aerial systems - Google Patents

Abstract

721,582. Aerials; radio navigation. MAR. CONI'S WIRELESS TELEGRAPH CO., Ltd. March 2, 1951 [April 27, 1950], No. 10431/50. Class 40 (7). An aerial arrangement for use in a system operating on a wavelength A consists of a pair of mutually perpendicular aerials mounted inside a slotted screening tube, each aerial comprising a pair of bent elements each half of the operating wavelength long and each having end portions at right angles to their centre portion, the elements being arranged so as to be substantially mirror images of each other. In one form the extremities of the two elements are arranged to join physically and electrically to form a loop (Fig. 1) which is a wavelength round. For adjustment purposes the top arm S (Fig. 2) of a rectangular loop may be made movable along the side arms. The aerial feeder F may be arranged as shown in Fig. 1 or as in Fig. 2 for any embodiment. Two rectangular loops at right angles, symmetrical about a centre axis, and inside a screening tube form a system according to the invention which may be connected to a transceiver through a goniometer for beacon or direction-finding purposes, Fig. 3 (not shown). Four loops may be symmetrically arranged round a vertical prism and so energized that the currents in conductors forming a gapped loop round the axis are all in the same direction round the loop. This arrangement (Fig. 4) results in an omnidirectional radiation pattern; Radiation from closely adjacent conductors of adjacent loops tends to cancel out and such conductors may be enclosed in pairs in tubular screens SC. The additional capacity due to the screens involves reducing the physical length of the screened conductors. In another form of multiple loop omnidirectional system, Fig. 6 (not shown), the mid-points of adjacent parallel conductors are coupled by coupling condensers. A crossed-loop directional aerial system may be mounted on the same axis as, and either inside or displaced from, an omnidirectional aerial of the general type described with reference to Fig. 4 to form the aerial arrangement for a direction finder or phase beacon. One form of slotted screening tube in which the aerial arrangements may be mounted is a vertical cylindrical wave-guide T having a ring of vertical slots SL round it. It is preferred to mount a horizontal earth counterpoise CP half a wavelength below the midpoints of the slots. The invention also includes systems using H aerials of the type shown in Fig. 8, wherein the two central portions of the half wavelength bent elements are one conductor. The feed may be across a gap in the conductor as shown, or the conductor may be continuous, or the gap may be bridged by a capacity, Figs. 9 and 10 (not shown). Crossed H aerials may be formed and also omnidirectional aerials by symmetrically arranging a plurality of H aerials round a prism, Figs. 11 and 12 (not shown).