GB850974A - Improvements relating to composite aerials - Google Patents

Abstract

850,974. Aerials. McCAIG, J. S. July 29, 1958 [Aug. 9, 1957], No. 25132/57. Class 40(7). A multi-band aerial system consists of two spaced support units disposed in parallel planes, one of them carrying two or more separate loop aerials each tuned for operation in separate bands and the other a like number of similar loops used as reflectors. In one embodiment the aerial system is supported by a mast 10, capable of rotation and carrying a cross-arm 11 secured in a bracket 12. At one end of the cross-arm is a casting 16 to which are fixed four bamboo canes 15 supporting three aerials 17, 18, and 19 in the form of concentric squares of conductor one wavelength long at the required operating frequencies; e.g. for the ten, fifteen and twenty metre bands. Insulators 22 inserted in the lower sides of the squares form feed points to which the feeders 21 are connected. On the opposite end of the cross-arm a similar casting 24 carries four further bambo canes 23 supporting like conductors 25, 26, 27 acting as reflectors for the three aerials. These conductors also have insulators, 29, in their lower sides and across each is provided an adjustable tuning stub 28. The ends of the stubs 28 and the feeder 21 are conveniently attached to an auxiliary cross-arm supported between a pair of insulators as shown and releasably attached to the mast at 31. The two units may be rotated about the axis of the cross-arm through 90 degrees to convert the system for use with vertically polarized signals. When this is done the auxiliary cross-arm is no longer in contact with the mast at 31. The length of the cross-arm is made about one-fifth of the mid-wavelength to be used. The aerials and reflectors may be made circular instead of square and may be any number of half wavelengths in circumference at the frequencies at which they are to be used. Directors and additional reflectors may be added.