I have had some experience detuning a tower. In my case, I discovered
my tower was acting as a reflector element for my apex up delta loop
antenna which was adjacently located. I modeled the system, including
the tower and all adjacent structures. By setting the length and
azimuthal orientation, I was able to detune the tower, cancel the
reflector activity and turn the tower into a director. I added a relay
to the system and now can change the pattern at will, depending on
directivity required. The relay grounds and ungrounds the wire from the
tower. The reason the tower was so interactive was because of the
vertical polarization, which is predominent with an apex up loop. You
might also consider hanging the apex off a guy line. I have done this
too, but to be honest any structure within at least a 1/4 wavelength
will be possibly involved in changing patterns. As suggested in other
posts, you should model the situation first before making any serious
changes. Good luck.
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See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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