| 摘要 |
807,674. Aerials. SHARDLOW ELECTRIC WIRES Ltd. and JONES, P. June 22, 1956 [May 18, 1955], No. 14351/55. Class 40 (7). The invention relates to an aerial structure capable of receiving signals at two widely separated frequencies. According to the invention the structure includes dipoles effective at the two frequencies and combined in a single unit with a feeder attached to the central point of the unit. A second dipole, which may be parasitic or coupled is provided for the higher frequency and, with the other dipole for this frequency, forms an array capable of angular adjustment relative to the parts of the structure effective at the lower frequency. It is also proposed to provide a set of parts for attachment to an aerial operative at the lower frequency to convert it into a two-frequency aerial as described above. In one embodiment the lower-frequency part of the structure may comprise a dipole 1, 1a connected to a feeder in junction box 3 and supported, together with reflector 2, 2a, on a cross-arm 5 mounted on a mast 6. The first higher-frequency dipole is formed by arms 7, 7a attached to the dipole 1, 1a close to the centre thereof by means of of clamps 8. The arms 7, 7a form a V dipole. Pivotally attached to cross-arm 5 by means of clamp 9 is a further support arm 10 carrying the second, and in this case parasitic, higherfrequency dipole 11. The V dipole is angularly adjustable about the elements 1, 1a, and the arm 10 is angularly adjustable so that the higher frequency array is adjustable relative to the lower-frequency elements. |
