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On Sun, 14 Nov 2010 10:08:24 -0500, John Ferrell
wrote: While there is no "best solution" to most antenna configurations, understanding the decisions you make and utilizing the available resources make a big difference in the outcome. Hi John, True, this has everything to do with utility. I hope you guys can keep the thread going for a while, you are answering questions that I have been unable to ask! It's easier to keep the thread going (productively) if you could choke up a question. If I were to rummage for key points in the hopes of doing what you ask, I could as easily bore you (everyone). Fishing for just such an example, and returning to both drooping radials on a 5/8ths and how that might cause this design to suffer equally with the worst of J-Pole performances, let's look at the silhouette of the 5/8ths with drooping radials: Overall, it gives us a radiator that starts out 5/8ths tall (radials out at 90 deg), or gets "taller" as those radials droop. In the extreme (radials fallen to 0 deg), we now have a 7/8ths tall radiator (my aforementioned OCF vertical dipole). Neglecting problems of feedpoint Z, this radiator lobe pattern could be pushed beyond the two towards developing four lobes. Without checking this in EZNEC (left for the student to perform), this could result in transforming an already higher gain antenna into becoming a cloud warmer. This (the additional, higher lobes) is often the fate of the J-Pole when the line that feeds it becomes part of the radiator. We get glowing reports of how well J-Poles have been built and matched, and sometimes grief over how deaf they are (How could this be?). 73's Richard Clark, KB7QHC |
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