GB781773A - Improvements relating to aerials - Google Patents

Abstract

781,773. Aerials. ANTIFERENCE, Ltd., and BEST, N. M. Aug. 19, 1955 [Aug. 20, 1954], No. 24346/54. Class 40 (7). An aerial arrangement for the reception of radio signals in two distinct frequency bands consists of two first aerial elements forming a dipole for the lower frequency band and two additional parallel elements for the reception of the higher frequency band each secured on an exposed part of one of the first elements. The additional elements preferably form a half-wave dipole at the higher frequency and may be attached on either side of the dipole junction-box and extend a short distance outwards from the dipole before extending parallel thereto as shown at 2 (Fig. 3). The lower and higher frequency dipoles can be backed by reflector elements if required and these need not necessarily be arranged for reception from the same direction. In a modification of the arrangement of the higher frequency elements 2 these are made L-shaped with the part of the L at right-angles to the first aerial elements #/4 long at the higher frequency. The first aerial elements in this case have an end fire array effect (Fig. 2, not shown). Figure 4 shows additional elements 2 applied to the dipole elements 1 of an X aerial. The other arms 5 of the X affect the performance at the higher frequency and are provided with cylindrical coaxial stubs 6. The length of the stub and the distance of its open end from the inner end of its carrying arm 5 are each made approximately #/4 long at the higher frequency. The stubs need not be cylindrical but may be made V or U-shaped or even as single elements (Fig. 5, not shown). In a modification (Fig. 7) the additional elements 2 are #/4 long and are secured on the dipoles elements 1 #/2 from the junction-box, the dimensions being in wavelengths of the higher frequency. This modification can also be applied to the dipole elements of an X aerial. The additional elements may be capacitively coupled to the first aerial elements through a layer of insulating material as described in Specification 745,437. Although the additional elements may be formed of rod or tube a convenient construction is shown in Fig. 6 where the element is a shaped length of semicvlindrical sheet material. The end 9 is shaped to fit the element 1 and may be secured thereto by a suitable clip (not shown).