| 摘要 |
<p>An antenna for a portable radio device is provided, the gain of which is high regardless of whether it is extended or shortened. There are provided a metal tube having a length corresponding to the length of a quarter-wave antenna element and capable of receiving the antenna element, and a switch mechanism for switching power to the antenna element depending on whether it is extended or shortened. When the antenna element is extended, the metal tube is energized oppositely to the antenna element, and cooperates with the antenna element to functions as a dipole antenna. When the antenna is shortened, on the other hand, the antenna element is not energized and a metal tube functions as a quarter-wave antenna element.</p> |
