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## [TowerTalk] finding resonant frequency of a shunt-fed tower for 160

 To: [TowerTalk] finding resonant frequency of a shunt-fed tower for 160 n4kg@juno.com (n4kg@juno.com) Mon, 30 Jul 2001 12:44:42 -0600
 ```N4KG comments inserted below. On Mon, 30 Jul 2001 "WA9ALS - John" writes: > > I'm interested in this too, so will jump in now. My main question > now is: > > I have a C31XR at 72 ft - The elements are -not- grounded. Thus I > assume much less (or none?) capacitance hat effect. There will be LESS capacitance than if the elements were grounded. There is still the loading effect of the BOOM which I assume is electrically connected to the tower. And don't forget the capacitive coupling between the tower and the COAX which is connected to the driven elements. Tom N4KG I therefore assume I > can still work out a shunt feed for -some- frequency(s), but they will likely > be higher freq than if I had grounded elements and therefore more > capacitance at the top? TRUE > > What do you think would be reasonable to shoot for with a 70 ft > tower with the ungrounded elements of the C31? 40M? Maybe 80M? > Doubt 160M?? Your best solution for 40M is a rotary dipole or 2L40. You could also short the center of the end elements to the boom and match the boom as a 40M end loaded dipole. I have posted my method on this several times. It's a KILLER. N4KG You could make separate shunt feeds for both 80 and 160. An antenna does NOT need to be resonant to radiate. I have matched a 50 ft tower topped by a TH3 on both 160 and 80M. de Tom N4KG ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: http://dl.www.juno.com/get/tagj. ----- FAQ on WWW: http://www.contesting.com/FAQ/towertalk Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com ```
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