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Homebrew copy of 70cm antenna	Reply
by KE6WNH on June 25, 2008	Mail this to a friend!
I have a 3-element broadband Yagi rated for 420-470 mhz which I bought at the TRW swap meet, and I later just happened to find a blueprint for a 9-element Yagi whose reflector and driver elements are the same dimensions. Building the reflector and parasitic elements was easy because of my background in machining, but the blueprint calls for some manufactured part for use as a tuner on the driven element. The tuner on the 3-element, however, is nothing more than a 3/16" center rod which slides into a 1/4" i.d. aluminum tube about 3" long, insulated from each other by a polyethylene sleeve. I can easily make a duplicate of this part, but the only stock I can use for a center rod is 1/4, with a 3/8" o.d. poly sleeve. In a case like this, is there an equation to find out whether I should make my [fatter] tuner shorter than the original, or should I just go ahead and make it the same length as the original and keep moving it until I get the lowest SWR on 440?

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