GB488480A - Antenna systems - Google Patents

Abstract

488,480. Wireless signalling; aerials. STANDARD TELEPHONES & CABLES. Ltd. Feb. 4, 1938, No. 3583. Convention date, April 15, 1937. [Class 40 (v)] To prevent radiation from the coaxial feeder of a short-wave aerial, the feeder is enclosed in a " counterpoise " or quarter-wave tube, which acts as a high impedance or tuned blocking circuit to leakage or " reflected " currents of the working frequency. As shown in Fig. 1, the dipole aerial 1 is fed through a coaxial line 4, 5, which passes through the quarter-wave hollow tube or counterpoise 2, and is connected to it at a current node 12. The various parts are supported by a tube 8 and insulators 9, 10 as shown in section in Fig. 1A. Fig. 1B shows the equivalent electrical circuit, in which the aerial constants are represented at 17, 18, 19, and those of the counterpoise as a blocking circuit 23 which prevents leakage of current along the feed-line 5. Instead of the tube 2, the counterpoise may take the form shown in Fig. 2 ; or it may be made as a rectangular cage. A second tubular shield may be arranged coaxially with the first to screen it from inductive pick-up. The tubular counterpoise may be connected to ground through a quarter-wave shortcircuited coaxial transformer, Fig. 5 (not shown). U.S.A. Specification 1,963,723 is referred to.