Topband: Shunt Fed Tower

Earl W Cunningham k6se at
Mon Nov 20 12:49:53 EST 2006

John, W0TMM wrote:

"I have buried about 18 radials now and have my shunt fed tower up and
going.  For the time being I am tuning it through my Palstar tuner.  It
tunes up with a 1.7 SWR on 1.8 MHz and 1.4 SWR on 2.0 MHz.  I just have
to move the inductor from 8 to 41 to retune for the change in frequency."
Not sure why you're using an inductor.

"1.. Do I need to move the shunt wire away from the tower to get the SWR
down to 1.1?"
Because you're getting a lower SWR at 2.0 MHz means that you must tap the
shunt wire higher up on the tower.  Wider spacing will also bring the
frequency down, but to a lesser degree than tapping up higher.

"2. It does not tune very well on 80 meters at all. about 5.1 SWR?  What
do I need to do to get it to work on both 80 & 160?"
You will be far better off using separate shunt feeds for 160m and 80m. 
Using separate shunt feeds for those bands on my tower(s) works out quite
well.  All it takes is one more feedline and one more "gamma" capacitor
(as well as one more shunt feed wire).
"3. Is 160 used for mostly CW?"
For DXing, CW is more common due to the weak nature of DX signals.

73, de Earl, K6SE

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