Patent GB-1161460-A (GB)
Title: Steerable Antenna System
Inventor: ALFANO WILLIAM ALBERT
IPC: H01Q25/00
Filed: 1967-08-04
Abstract: 1,161,460. Aerials. GRANGER ASSOCIATES. 4 Aug., 1967 [25 Nov., 1966], No. 36014/67. Addition to 1,021,727. Heading H4A. [Also in Division H1] An aerial system of the kind described in the parent Specification, in which a vertical monopole is surrounded by poles supporting tubular reflectors, each reflector having a series of switches along its length which when not actuated divide it into sections which are individually ineffective as reflectors, is characterized by said switches being of tubular vacuum type actuated by compressed air controlled by solenoid-operated valves. As described, a system comprises two monopole aerials 2, 3, Fig. 1, of broad-band " birdcage " construction, covering adjacent bands of frequencies, e.g. 4-11 Mc/s. and 11-30 Mc/s., respectively. The aerials are fed from a transmitter 10 via a main coaxial line 9 and branching coaxial lines 7, 7<SP>1</SP>, either of the latter being selectable by a remotely-controlled switch 8. Tuning units 12, 12<SP>1</SP> at the aerial ends of the lines 7, 7<SP>1</SP> are also remotely controlled. Each aerial 2, 3 is surrounded by a ring of poles 28, 28<SP>1</SP> supporting tubular reflectors 29. Earth screens comprise radial wires 26, 26<SP>1</SP> extending to circumferential wires 27, 27<SP>1</SP> and fences 58, 58<SP>1</SP> enclose the aerials and reflectors. A vertically-extending reflector 29, Fig. 3, consists of sections of copper tube 29<SP>1</SP> interconnected by five high vacuum switches 33 and is joined at its lower end to a pipe 24 for supplying compressed air. The reflector 29 is supported on a wooden pole 28 by means of insulating brackets 30, which allow relative movement for taking up thermal expansion. A vacuum switch 33, Fig. 4, comprises a glazed ceramic hollow cylindrical housing 34 sealed at its ends to copper tubes 35, 36 carrying respectively a spring-loaded movable contact 40 having a flexible, corrugated sealing bellows 41, and a fixed contact 39. The space within the housing 34 is evacuated, and when compressed air is admitted below the contact 40 it is forced upwards to the contact 39. A by-pass connection 47 comprising a tube 47<SP>1</SP> of insulating plastics material allows compressed air to flow to and actuate other switches in series along the reflector 29. Housings 14, 14<SP>1</SP>, Fig. 1, between the aerials contain compressors, dehydrators, air storage tanks, and batteries of remotely-controlled solenoid-operated valves. Sixteen air pipes lead from each housing to a respective set of reflectors, and any reflector of a set may be made effective by operating the appropriate valve. By making eight adjacent reflectors of a set effective, radiation from the associated monopole aerial may be beamed in a desired direction, and by reducing the number of effective reflectors the beam may be broadened. The pipes outgoing from the solenoid-operated valves may be provided with pneumaticelectrical interlocks for preventing the supply of energy to a monopole aerial until the air pressure is sufficient to operate the switches in the reflectors. Dry air released into the housing when the solenoid-operated valves are deenergized may be coupled into the coaxial feeder lines, to maintain a pressure therein slightly above atmospheric.