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Bob Wood wrote:
V Beam antenna question I want to put up a 40M V Beam antenna to enhance communication in one direction only. From the limited design information that I have found, I am thinking of 3/4 wavelength on each side with a horizontal separation angle of either 72 degrees or 120 degrees. I have seen both separation angles listed as optimum for maximum gain. I was wondering if anyone knew for sure which angle would produce the best result. Also, and actually most important, I need to have some idea of what the feed point impedance might be. I can feed it with ladder line or good coax and a balun but I am not sure what balun to use or would it be better to use ladder line? I sure would appreciate any guidance on this antenna project. Bob W5QCP A true V beam is a minimum of one wave per side. And that minimum is not much of a V beam...I'd have to double check, but with 3/4 wave per leg, IE: about the same as an extended double zepp, I think you would have the most gain with it straight like a normal EDZ. appx 5.1 dbi bidirectional. I bet your gain will drop off if you try to set it up like a V beam. As far as the feed impedance, it will vary per band. Not really a major issue. Just treat it like any other balanced antenna fed with ladder line. If if tunes, fine. If not, you might need to vary tyhe feedline length a bit. You could feed with coax for a 3/4 wave per leg antenna, "also 1/4 wave per leg on whatever band.." , but it would be better to use a ladder line for all band use. MK -- http://web.wt.net/~nm5k |
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