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Vertical HF Antennas

July 30th Fact-of-the-Day

Vertical antennas are used far less than horizontal antennas throughout most of the HF spectrum, because throughout most of the HF spectrum complex ground and sea water reflection coefficients tend to mutilate the ideal radiation patterns that could be achieved over perfectly conducting soil or water. Because ground conditions out to considerable distance from a vertical radiator significantly affect its performance, identical vertical antennas installed at different places often have substantially different performance. Buried, surface or elevated ground radials should be used near a vertical radiator, because nearby ground conditions out to about 1/2 wavelength have the greatest effect. The greater the distance between the bottom end of a vertical radiator and earth, the less important ground radials become and the longer their lengths must be if they are to be effective. ©2005 Martek International All rights reserved.


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