| 摘要 |
769,470. Aerials. WOLSEY TELEVISION, Ltd. Dec. 13, 1955 [Dec. 23, 1954], No. 37189/54. Class 40(7) An aerial system intended for the reception of signals in two frequency bands comprises a dipole 1, la, half a wavelength long at a frequency in the lower band and a folded dipole 6, 7, 8, 9 for the higher frequency band associated with the dipole 1, 1a, and supported with it on a common cross-arm 4 which also carries a least a reflector element 12 for the folded dipole. The cross-arm may also carry a reflector 2 for the dipole 1, 1a, and a suitable number of directors 14, 15, 16 for the folded dipole. The higher frequency elements may be made in V configuration, preferably with each part of the element making an angle of 60 degrees with the cross arm as shown. The various supporting brackets 5, 13 and 17 may have the arms attached to them in an angularly adjustable manner so that the angle included in the V can be varied. As shown the folded dipole is associated with the dipole 1, 1a, by the centre part of the latter (between support brackets 18 and 19 being included in the folded dipole also. A common feeder is used for the two dipoles. The coupling members 10 and 11 of the folded dipole are preferably spaced in from the ends of the elements 6, 7, 8 and 9 so that the free ends act as a resistance compensating device for reception at the higher frequency. Instead of a simple folded dipole. being used a three element type such as that shown in Fig. 3 may be used. Insulators 22 and 23 on the lower frequency dipole help to support the folded structure. In an alternative form of three element folded dipole an outer element is associated with the lower frequency dipole (Fig. 4, not shown). In any of the embodiments the extreme ends of the folded dipole members may be closed by a further pair of coupling members. |
