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Topband: Shunt Fed Tower Info

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Subject: Topband: Shunt Fed Tower Info
From: w8ji at (Tom Rauch)
Date: Mon Aug 4 10:45:10 2003
> concerned about the height of the tower being used as a radiator.  A rough
> is that the top loading of the tower by the boom of the KLM 40 meter
> would make the tower around 230 feet or so.

I see two problems Bill. First, a half-wave grounded structure is
anti-resonant when grounded. Grounding detunes the entire structure. That
means you can excite it with current, which is a good thing when you have a
four square around it.

You could sectionalize the tower, run a wire up the side and feed it a few
feet away, or detune the tower somehow. (Or it may not be half-wave
resonant, and then it would work.)

The other problem is the antennas. Insulation in the elements can be an
issue at high power. I'd ground the elements through an inductor that is
several hundred ohms reactance on 14MHz.

73 Tom

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