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Multiple Dipole Multiband Antennas

April 24th Fact-of-the-Day

Several halfwave dipoles that are resonant at different frequencies can be center-fed from a common feedline to achieve multiband operation. However, their performance will be highly dependant upon their physical orientations with respect to each other. The performance of three such dipoles installed at right angles to each other, for example with one vertical, one running east to west, and the third running north to south, will be almost identical to the performance of three independent dipoles with the same orientations that are fed by separate feedlines if none of the dipoles resonate on odd harmonics of any dipole fundamental resonant frequency. However, that is not the case if three or more dipoles that are resonant at different frequencies run closely parallel to each other. Mutual coupling between parallel dipoles that are resonant at different frequencies will cause the useful bandwidth at each resonant frequency to be substantially less than if separate dipoles are used. ©2005 Martek International All rights reserved.


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