I had similar problems when I converted my one of my KT34XA's into a KT36XA.
To isolate the problem, I ended up removing each element from the boom, opening
up the center shorting strap, and measuring the resonant frequency of each
element on each band. In my case, the problem was the front driven element. To
bring that element into "spec" required some significant changes to the
published dimensions. I still don't know why I had this problem, and no one
else
did.
I have put together a spreadsheet showing the element resonant frequencies, as
measured by K6MYC, W4EF, and my final resonant frequencies. It can be
downloaded
from http://www.kkn.net/~n2ic/kt36xa.xls .
Good luck !
73,
Steve, N2IC
-------------------------------------------------------------------------------
I have begun doing the final assembly for my three stack of KT36XAs. The
first was hauled up to 30 feet on the side of the tower and I ran some SWR
tests on it. All three bands had SWR pretty close to what was expected. 20
was
skewed just a tad low, but that is to be expected with the height. No
problem.
The second was hauled up for testing and was a disaster. SWR was sort of OK
on 10. 15 skewed low (out of band, and bandwidth not all that wide) and 20
was over 2:1 across the band, rising as freq was increased. It was more
resonant out of the low end of the band.
Of course I checked all dimensions (six times eventually) and made sure all
obvious things were gone over (cap tubes on the right elements, orientation of
the elements) and even switched out the balun form the other "good
antenna".
Basically, the antenna behaves as though the elements are longer than they
should be even though they are not. Had the first antenna behaved this way I
might attribute it to close proximity to ground. However, the first antenna
was just fine when tested at the same height. SWR was taken right at the
feedpoint of the antenna with an MFJ259 and was also checked using the Yaesu
450
feet away on hardline, so there is no cable problem.
Mike at M2 as always has been very helpful and I'm sure we'll get this thing
up and running...eventually!
However, the combined heads of towertalk are better than just the two of us.
So...does anyone have any suggestions for what is going on. As I said, all
the obvious things have been covered. HELP!
Bill KH7XS/K4XS
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