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Old January 2nd 07, 01:08 AM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jul 2006
Posts: 199
Default Auto tuners & verticals

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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