Peter Martinez wrote:
Incidently, Dex, have you thought about removing the wire you have
labelled 'tower grounding wire' and returning the feed to the base of
the tower instead? There should be no voltage between the bottom of the
tower and the bottom of this grounding wire, so you might as well use
the tower to 'ground itself'. Maybe you cannot rely on the tower to
conduct current!
Peter,
I initially used this antenna with a single vertical wire and the coil
grounded to the base of the tower ground system. I think this is what
you described above. There was some discussion about the capacitance
between the vertical wire and tower shunting the antenna current to
ground so I went looking for a way to feed a short grounded tower. So I
found the balanced feed method on Rik's site and give it a try.
I tried to make some meaningful field strength measurements between the
two methods of feeding the antenna but gave up when I figured out I
didn't know what I was doing. Seems I never found a place far enough
away from power lines that I could repeat the same levels from day to
day with the same antenna. I could even see as much as a 6 db change in
signal strength while watching a SLM receiving a steady carrier. These
changes could usually be associated with a click or pop which I assume
was load changed on the power grid. Conquering this problem is on my
list of things to do but right now it's microwave season :)
From the signal reports I received with both feeds I could not tell
that one way was better than the other.
The idea of using coax up the center of the tower is a possibility here.
I have a spare rung of 7/8" Heliax that would probably handle the
voltage. The tower is well bonded from top to bottom with multiple runs
of Heliax and wave guide.
Always open for suggestions,
Dex,
W4DEX / WD2XKO
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