Monday, October 30, 2017

Random Wire Antenna Lengths. Post #1296


Random Wire Antenna Lengths
(https://udel.edu/~mm/ham/radio/randomWire/
Author:  University of Delaware.
Accessed on 30 October 2017, 2055 UTC, Post #1296.
Comment:

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.

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Hawaii Intelligence Daily (https://paper.li/f-1482109921).

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Aloha es 73 de Russ (KH6JRM).

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Aloha es 73 de Russ (KH6JRM).