GB586578A - Improvements in or relating to aerials for radiating or receiving electromagnetic waves in a wide range of frequencies - Google Patents

Abstract

586,578. Aerials. CORK, E. C. May 2, 1944, No. 8299. [Class 40 (v)] A wide band resonant aerial comprises a conductor of large transverse dimensions provided with series capacities along its length, the values of the capacities and the length of the aerial being such that the band - width substantially exceeds 8 per cent of the centre operating frequency. The transverse dimensions of the conductor should be such that its charateristic impedance is not greater than 500 ohms, and the intervals between the series capacities are smaller than a quarter, and preferably of the order of one-twelfth, or less, of the operating wavelength. The length of the aerial may be approximately a half-wavelength, or may be made of greater length by choice of the capacities in order to increase the radiation resistance. The directive properties of the aerial are stated to be more sharply defined, compared with a normal dipole. The aerial may comprise tubular conductors of large diameter, or be of other forms such as bi-conical or ellipsoidal, the conductors being arranged in sections with ends overlapping to form the series capacities. In the arrangement illustrated, the portions 1 and 2 of a dipole aerial, which is fed from a feeder 3 by a rejector circuit of the type described in Specification 438,506, comprise tubular conductors of large transverse dimensions formed by cages of small conductors to reduce windage. The portions 1 and 2 are divided into sections 4, 5, 6, 7, 8 and 9, comprising conductors a and' b, supported by conducting rings 10-21. The conductors a are of differing cross-sections, the end of conductor a in one section being received within the end of the corresponding conductor in the next section and insulated therefrom to form the series capacities. The two halves 1 and 2 of the dipole are separated by insulated supports 22.