On further inspection of my situation with two new 15 m antennas that
seemed dissimilar, I now see the following scenario.
At a low height by the base of the tower, the antenna can be matched and
the curve centers about my design frequency of 21.2 MHz. The curve is "U"
shaped. As the antenna is raised up the side of the tower, the curve
develops two dips and a hump. The hump is approximately 21.1 MHz and is
1.5:1. The dips are 20.7 MHz and 21.45 MHz. The dips are 1.1:1 VSWR.
Those measurements are made at a height of 20'. If I go higher, I need to
snake the antenna past the guys and I can not do this alone. Previously,
when I got the antenna to its 45' mounting place, the VSWR was rather flat
and 1.7:1.
I am totally confused by this situation. Does anyone offer further
troubleshooting points?
Thanks, Dave.
David J. Rodman, MD
Assistant Clinical Professor
Department of Ophthalmology
State University of New York at Buffalo
FAX 716-859-4565
Office 716-854-1137
e-mail: rodman@acsu.buffalo.edu
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