GB1208199A - Improvements in antennas - Google Patents

Abstract

1,208,199. Aerials. COMPAGNIE FRANCAISE THOMSON HOUSTON-HOTCHKISS BRANDT. 19 Dec., 1968 [29 Dec., 1967], No. 60533/68. Heading H4A. A pylon-type M.F. aerial is supported by stays 4, 5, Fig. 4, made of conductive cables each of which is connected mechanically and electrically at one end to the earth, and at the other end to a point on the pylon which is substantially #/4 above its base (# = wavelength at the mean frequency of operation). The pylon 1 has a nominal length of #/2 and it is shunt-fed by means of wires 13 which surround its lower part and are connected to its centre, and which are secured by insulators 14, 15 to the earth. R.F. power is applied to the wires 13 at a point 16 above the insulators 14, 15, and a voltage node is developed at the points of attachment of the stays 4, 5. The said stays also function as lighting conductors. The pylon may be of uniform cross-section instead of non-uniform cross-section as shown in Fig. 4, and it may be insulated from the earth, when R.F. power may be applied directly to its base, and the shuntfeed means be omitted. Capacitive top loading may be provided by wires (10), Fig. 2 (not shown), which extend in umbrella fashion from the apex of the pylon, and which are secured by insulated cables (11), (12) to the earth. With such loading the height of the pylon may be correspondingly reduced below #/2. A group of pylon aerials as described may be used to obtain directive transmissions.