| 摘要 |
An elongated rod 11 of dielectric material, for example fiberglass-plastic or the like, has a central conductor (12) located coaxially therein, the conductor having a length L=3/2 lambda ; in the central lambda /2 range, the insulating rod is surrounded by a conductive layer (13, 16, 20, 25), for example of conductive lacquer, a mesh or braid of conductive material, a conductive foil or tube or the like. In the lower lambda /2 region of L1, the bottom terminal of the central conductor will provide a high resistance output for the higher one of the frequency ranges which, for example, can be a radio telephone, or vehicular communication frequency of between 450-470 MHz. The entire antenna is suitable as an AM-FM/radio-telephone combination antenna. lambda is the median operating wave length of the higher one of the frequency ranges for which the antenna is suitable. Preferably, the antenna is covered with a sleeve of insulating material, for example a heat shrinkable plastic (27). The band width of the antenna can be extended by placing a further electrically conductive layer (513, 619, 722, 828) on the rod, spaced by a gap (a) physically and electrically from the conductive layer (13, 16, 20, 25) in the middle of the elongated rod. The further conductive layer is lambda /2 long, and connected to the inner coaxial conductor (12, 512), which in turn can be coupled to an antenna input, for example the center conductor of a coaxial cable of a radio apparatus.
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