GB741911A - Improvements in aerials - Google Patents

Abstract

741,911. Aerials. BELLING & LEE, Ltd. Oct. 25, 1954 [Oct. 23, 1953], No. 29357/53. Class 40 (7). An aerial assembly comprising two aerials which are mechanically inter-related for mounting on a single support, the aerials being capable of receiving signals in different frequency bands and having only a small effect on each other, includes a halfwave dipole for operation at the lower frequency and a plurality of closely spaced conductors forming a reflective surface which is part of the higher frequency aerial. Each conductor is arranged to lie wholly in a plane perpendicular to the half-wave dipole. In a first embodiment a half-wave dipole 1 backed by a parasitic reflector 2 is provided for operation at the lower frequency and the conductors 6 forming the reflective surface are supported by but insulated from the upper parts of the elements 1 and 2. A stouter conductor 7 forms the support bar for a broadside array 5 of elements working at the higher frequency. These elements are spaced a quarter of a wavelength in front of reflective surface by members 8. Where the half-wave dipole 1 is specially mounted in a rotatable coupling 10 and the conductive rods 6 supported through insulators at their centres the whole higher frequency aerial may be rotated for directional adjustment. The ends of the conductors 6 are held in vertical insulating supports 11 and the reflecting surface may be a plane one (Fig. 2, not shown) or parabolic as in Fig. 3. The array of elements 5 may be stacked vertically so as to lie along the focal line of the parabolic reflector. In Fig. 4 the lower frequency dipole 1 is horizontal and the conductors 6 are insulated and mounted so as to extend horizontally in a vertical plane, an array of higher frequency elements 5 being arranged as described with reference to Fig. 1. The top and bottom of the reflecting surface may extend forward so that a parabolic reflector with a horizontal focal line is formed (Fig. 5, not shown). In a modification of the Fig. 4 embodiment the conductors 6 and elements 5 may be arranged to extend vertically and in this case the reflector surface need not be a plane perpendicular to the dipole 1 but may make an angle other than 90 degrees with it in the horizontal direction. In the modification, too, the reflector may be parabolic.