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[TowerTalk] Alternate 80m antenna thoughts

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Subject: [TowerTalk] Alternate 80m antenna thoughts
From: (Bill Ralston)
Date: Thu, 24 Jan 2002 17:06:49 -0700
Of course, the obvious thing to do is shunt feed my planned 100' tower for
80 & 160.  But, I am planning a C31XR on a ring rotor at about 55' in
addition to a second C31XR at 95' and a 40m above that.

If the shunt feed attaches to the tower below 55', it seems like the lower
C31XR would effectively choke off the vertical at that height with the C31XR
acting as capacitive end loading. Maybe OK for 80m, not too cool on 160m.

If the shunt feed attaches above 55' (using some interesting contortion
around the ring rotor), I'm not sure how the thing will behave.

This got me to thinking - would it be possible to do something similar to
feeding the boom on a yagi for a different band?  With a C31XR at 55' and at
95', might it be possible to feed the tower through a suitable feed (L or
Omega) at around 75' - just like one would feed the boom of a yagi, but
oriented vertically?  The 40' of tower plus capacitance of the antennas just
might look close to resonant at 80m!  Of course, the tower above and below
the antenna will also contribute some.

One problem seems to be the feedline, but this might be solved by placing
the feedline inside the tower; the skin effect should hide it.


-- Bill N7VM

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