Random Wire Antenna Lengths
Author: University of Delaware.
Accessed on 30 October 2017, 2055 UTC, Post #1296.
When you're on the trail, at the annual Field Day, or wherever a good antenna is unavailable, a random wire antenna "can save the day" if you know its limitations. This article does an excellent job of describing the theory, construction, and use of random wire antennas and the wire lengths you should avoid if you want an efficient, effective operation without excessive SWR.
Of particular note is the series of graphs showing various wire lengths to avoid for different sets of amateur radio bands. The basic guidance is clear: "The fewer bands, the fewer high impedance regions to avoid."
According to the article, you want the wire antenna to be at least 1/4 wavelength long for each band you want to use. For example, to work the 40 meter amateur radio band (7 mHz), make sure the antenna is at least 33-feet/10 meters long. If you want to cover 80 meters and up, perhaps the W3EDP antenna, with a length of 84-feet/25.60 meters and a counterpoise measuring 17-feet/5.18 meters is the way to go. In any case, a good antenna transmatch (i.e. "tuner") will help you reduce rf and SWR problems in your shack. Properly designed and cut, a random wire antenna can give you hours of enjoyment in portable operations.
For the latest Amateur Radio News and Information, please visit these websites:
http://www.arrl.org/arrl-audio-news (a weekly podcast which is updated each Friday afternoon).
https://paper.li/kh6jrm/1430289353 (Amateur Radio News & Information).
Other sites of interest:
Hawaii Science Digest (https://paper.li/f-1476233615).
Hawaii Intelligence Digest (https://hawaiiintelligencedigest.com).
Hawaii Intelligence Daily (https://paper.li/f-1482109921).
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Opinions expressed in this blog are mine unless otherwise stated.
Thanks for joining us today.
Aloha es 73 de Russ (KH6JRM).