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On Mon, 04 Dec 2006 09:18:47 -0500, chuck wrote:
John Ferrell wrote: I am considering purchasing a remote auto tuner for my continuing As others have noted, the auto tuners will have no trouble matching a 33 foot vertical on either 80 or 160 meters, even over sea water. Using one at the antenna may reduce losses in your coax since the swr will always be low. The auto tuners will introduce their own losses, as will any antenna tuners, although with shorter antennas the losses may be greater. QST had an article in which auto tuner losses and matching ranges were measured and I think compared with conventional tuners. If I recall, the results were less unfavorable toward auto tuners than I had expected. To reduce auto tuner matching losses to insignificant levels, you might consider adding some lumped inductance at the base of your vertical (or even better, part way up as in center-loading). You can add a capacitance hat as well. If you cause the 33 foot antenna to appear resonant at either 80 or 160, you will see reduced auto tuner matching losses on both bands. Just a rough approximation to the required number of turns ought to work. You're only trying to provide enough external loading to reduce the tuner's losses. Resonance really doesn't matter much. If you do this, you should be able to enjoy the ease of QSY without a serious loss penalty and without a need to switch taps or retune manually. Of course your 33 foot vertical resonant at 80 or 160 meters may not perform well at 40 meters and above, or worse, may not provide an impedance your tuner can handle at those frequencies. Chuck, NT3G I have updated the 28 foot vertical web page for those who may be interested in my experience. I is at http://www.dixienc.us/28FtVert/SGC237.htm I am very pleased with the results using the tuner but it has only been a few days, I am still in the "honey moon" phase. I outline the considerations for me and a larger vertical at the web site. John Ferrell W8CCW |
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