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In article , John S wrote:
So, I had this idea. The usual monopole (or ground plane) has about 30-35 ohms resistance. To get 50 ohms it is common practice to droop the radials about 45 degrees. Since that raises the feedpoint resistance, would raising the radials lower the feedpoint resistance of the folded unipole and, if so, what effect would it have on the pattern? EZNEC said to raise the radials of the folded unipole about 23 or so degrees to get 50 ohms and the pattern would not be affected. So I built one and it works swimmingly. I had to make some minor adjustments in element lengths but that was fairly easy with the vector voltmeter. Hooray for modeling. Slick... and I bet that the appearance of it raises the occasional question and/or eyebrow! The matching approach I've usually seen for folded monopoles, is to use a quarter-wave transformer made out of (e.g.) RG-6 or another 75-ohm coax... this brings the impedance down to something not too far from 50 ohms. Your method avoids the need for this. If I were to build one I think I'd stick a fat cap over the end of each raised radial... just to reassure myself that I wasn't setting up an "automated pigeon-skewering device" of sorts :-) -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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