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Jet_Li wrote: best is any vertical from Force 12 - I got one on 75 meters that beats everything else I have put up. got one on 40 meters from Force 12 - beats everything else I have put up. I went to the Force 12 website and clicked on the "Flagpole antennas" link http://force12inc.com/F12-flagpole-ants-003.htm. I read the "New 40 Meter Coil" portion of the page with interest -- sounded too good to be true. A moment's use of the calculator showed that the VSWR figures and the quoted feed point impedances were very inconsistent -- orders of magnitude wrong. The claimed SWR of 16 for the unloaded antenna worked out really to be about 850 -- close enough to infinity for me! If that's what the "useful A.R.R.L. TLW software" actually indicates, then the League should withdraw the software. But somehow I suspect that the software (which I do not have) doesn't predict what the web page says it does. I leave it to someone with a copy of EZNEC to see if an 1/8 wave monople on 40 metres made out of 2 inch diameter tubing really has an input impedance of about 5 - j460. That part, at least, sounds reasonable to me David, ex-W8EZE, who hasn't forgotten the formulas for SWR -- David Ryeburn To send e-mail, use "ca" instead of "caz". |
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