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Thanks Roy for a great yet concise answer to this matter. I misunderstood
about tuned radials. I wish I would have done more then a cursory look at the matter. Basically all I saw was "tuned radials" and "you can't have too many". Had I read more I would have eventually seen that buried radials need not be tuned and that a 1/4 lambda would have been adequate. I have over 1300 ft of radials! Don't ask what my pre-cut "tuned radials" cost me!! I made sure I had plenty and now that this cabbage is boiled I am glad to see at least I did not do my station a disservice. Most importantly I learned something.I am not a new ham but am new to this vertical antenna scene. I am aware of your reputation in this field Roy and I appreciate your warm, courteous and most of all informative replies. 73 / DX -- Charlie Ham Radio - AD5TH www.ad5th.com Live Blues Music www.492acousticblues.com "Roy Lewallen" wrote in message ... Nobody's laughing at you -- it's a topic that's very poorly understood. Here's how it works with buried radials. . . It never hurts to make them longer. But beyond some distance, it doesn't help appreciably -- if the current on a radial has dropped to a negligible value at its end, extending it won't do anything. What is this distance? Well, like so many other things, the only really honest answer is that it depends. As it turns out, the current fades more rapidly if you have only a few radials. So if you only have a few, it doesn't help to make them super long. If you have a lot (say, 60 or more), increasing the length has more effect -- but your system will already be so efficient that it won't make much difference. The classic set of measurements of various ground systems was published in 1937 as "Ground Systems as a Factor in Antenna Efficiency" by Brown, Lewis, and Epstein. Their paper has many graphs of the effectiveness of various combinations of radial lengths and number of radials for various vertical heights -- for the particular ground at the place of their experiments, the characteristics of which weren't recorded. Their data have been interpreted and reorganized countless times and in countless ways -- a web search should bring you a lot of hits. But some rules of thumb (and only rules of thumb) for amateurs(*) emerge: 1. There's not much point in making radials much longer than a free-space quarter wavelength or so. 2. Increasing the number of radials from 16 to 120 or more will probably net you less than a couple of dB. That might be worth it to you, it might not. These assume more-or-less average soil. If your soil is very dry, you might benefit from more and/or longer radials. And of course, there's no point in fussing over exact lengths. There's no need to even make them the same length. Put down what you can and don't worry about it. Putting in more won't hurt, nor will making them longer. But you're not likely to notice much difference between a big installation and a fairly simple one, unless your ground is extraordinarily poor. Roy Lewallen, W7EL (*) An increase in field strength of a few percent is a worthwhile pursuit for AM broadcasters, because it increases the size of their audience and hence the value of their advertising. Small increments like that are completely useless for amateurs, though, so our goals are somewhat different. Keep that in mind when looking through various analyses and recommendations, since most are oriented toward broadcasters. Charlie wrote: I just want to thank all of you for your kindness and speediness in pointing out my error as a new vertical antenna user. I am glad several of you had a laugh on me for burying tuned radials. Thank you for your kindness and courtesy. Hope to catch each and every one of you on the bands. I am grateful for the tact and diplomacy that many of you showed me. True Ham Spirit at it's best. Based on what I have been told by the gentlemen in this great group I could have used much shorter radials than any "tuned length". If that is right then I have achieved a much more effective radial system then what I would have had I not erred. Is this right? In other words I have more wire in the ground then I need..right? Now if that is so..does that hurt or help TY Roy 73 / DX |
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