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Counterpoise for an end-fed wire antenna
"Art Unwin" wrote in message
... On Aug 3, 5:24 am, Richard Fry wrote: On Aug 2, 3:01 pm, Art Unwin wrote: An end fed antenna cannot be of a fractional wavelength... _________________ ? ? Art, note that the vertical monopoles used by MW broadcast stations are ALL fractional-wavelength radiators, and probably 99% of them are end fed. I regard a radiator with a counterpoise as being center fed of a given impedance to connect to regardles whether the counterpoise is above ground or not. If a radiator is of a closed cuircuit form it may be fed at any point in physical terms. Other peoples definitions may vary. This is a simplified way of looking at things. It only works if he is to use a horizontal loop, but doesn't address matching the antenna to the line and in the case of "two pieces of wire", you won't have a clue where the electrical "center" is. One of the original posts was about a dipole where the coax would have to follow one of the legs because it would hang down where it shouldn't be. That makes the feed point NOT in the center and prone to common mode currents on the line. It took me a couple of posts to realize the Poster has made multiple posts questioning different aspects of his problem and we get the whole scenario from chasing down all his threads. It looks to me that his real estate won't allow a balanced antenna anyway, so he will have to deal with the issues of an unbalanced radiator anyway. I first thought of an Inverted L as an optimal antenna for his situation, with remote matching for multi-band operation to keep RF out of the shack. An elevated horizontal loop or off center fed dipole with ladder line to a tuner at the entrance of the shack would also be an answer to the problem. A multi-band vertical would be a good choice for 30-10 meters. Although they work for 40 and 80, the pattern is not as good as a horizontal antenna for exploiting the shorter skip. |
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