GB760183A - Aerial arrangement - Google Patents

Abstract

760,183. Aerials. BELLING & LEE, Ltd. ,May 31, 1955 [Aug. 23, 1954], No. 24466/54. Class 40(7) An aerial arrangement resonant at two different frequencies comprises a dipole 10 resonant at the lower frequency and a second dipole 14 resonant at the higher frequency. The two dipoles are coupled by a transmission line 17 of such length that the second dipole and line together present a high impedance at the lower frequency at the feed point of the first dipole, the elements 17 and 14 acting as an open-circuited stub, #/2 in electrical length. The dipoles are preferably mounted in suitable insulators 11 and 15 supported by a cross-arm 13 on which directors and/or reflector elements can be arranged as required. A transmission line attached to the feed point at the centre of the dipole 10 acts as a common feeder for signals of both frequencies. Dipole 14 may be replaced by a folded dipole (Fig. 2, not shown) in which case the folded dipole and transmission line are arranged to form a short circuited stub at the lower frequency which is effective for a quarter wavelength (or an odd multiple thereof) in electrical length.