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## Re: Topband: Optimal radial wire type and gauge?

 To: "DAVID CUTHBERT" Re: Topband: Optimal radial wire type and gauge? "Tom W8JI" Tom W8JI Sun, 16 Dec 2012 22:25:33 -0500 mailto:topband@contesting.com>
 Tom, I think you are extrapolating one case with a particular radial length to all vertical antenna ground systems. The N6LF radial papers detail his NEC-4 simulations and measurements of vertical antennas and radial systems. If I read his papers correctly base impedance does track field strength measurements. http://www.antennasbyn6lf.com/ Hi Dave, Historically there probably have been more cases where base impedance does not directly allow loss calculations than where it does correlate. The case where feed resistance and efficiency closely agrees at all numbers of radials would be very special. One case would be where the radials are exactly 1/4 wave long electrically, so the antenna base is at a radial current maximum, and the antenna is 1/4 wave tall. In that case all of the CONDUCTED ground losses could be directly applicable as a feedpoint resistance change. Field losses from fields impinging on earth would not factor in well, but they could be small. The rule I learned to always apply to theory is where there is an exception, the theory is no longer correct or valid unless the theory includes **all** exceptions as part of the theory. If a ground system has standing waves, which even buried radials do to a significant extent in sparse radial systems, the impedance at the base is not representative of the real loss resistance. I have found that here in several cases, not just one, and others have also independently reported it without intentionally looking for it. If it is UNreliable in some case or cases, it cannot be an accurate theory for general application. To use the theory, you would have to qualify the exceptions so people could avoid them. To not use the theory do not require any qualification. An accurate field strength measurements is always right. A base resistance reading might be right or wrong..... it might be useful or not useful. 73 Tom _______________________________________________ Topband reflector - topband@contesting.com