| 摘要 |
PROBLEM TO BE SOLVED: To provide a nondirectional antenna with an adjustment element which is easy to adjust, can obtain a desired impedance characteristic and is provided with an indirect lightning stroke prevention function. SOLUTION: An upper cylindrical antenna element 11 with a bottom and a lower antenna element 12 are attached to a metal support pole 10. Insulating material 14 insulates between the upper antenna element 11 and the metal support pole 10, and the lower antenna element 12 is electrically connected to the metal support pole 10. Power is fed to the antenna elements 11 and 12 from a feeding point 16 near the peripheral parts of the bottom parts 11a and 12a. An adjustment element 17 for impedance adjustment is arranged along the metal support pole 10 inside the upper antenna element 11, and its upper end part is electrically connected to the metal support pole 10 and its lower end part is electrically connected to the bottom part 11a of the upper antenna element 11. The length of the adjustment element 17 is adjusted in accordance with an impedance characteristic. In addition, the adjustment element 17 operates as a short circuit in a direct current manner and acts as a protective circuit for an indirect lightning stoke. COPYRIGHT: (C)2004,JPO
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