| 摘要 |
A tunable dipole antenna including dipole arms formed of a pair of helical coils whose diameter is small compared to the wave length of the frequency to which the dipole antenna is tuned and whose length can be adjustably extended. The coil includes a plurality of turns of flat spring wire. When the coils are extended to a desired length, the turns of flat spring wire can be adjusted such that a number of the turns are expanded while the rest of the turns are contracted near the outer edge. The number of expanded turns can be varied at the given length of the coil to obtain tuning to the desired frequency.
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