Topband: Need help feeding tower on 160 AND 80

[Brian Machesney]

Thanks for all the responses.

One respondent recalled hearing of success with a similar setup on the
Towertalk reflector. By searching the archives for "shunt bands" I found an
"existence theorem" at:

http://lists.contesting.com/archives//html/Topband/1997-12/msg00194.html

I followed the prescription to connect the gamma wires for the two bands to
different tower legs, then realized that I had made a serious mistake by
failing to reduce the tower-to-gamma wire
spacing for the 80m feed.

With these two changes, I am able to get the desired behavior on both bands,
by switching from one series cap to the other.

73 -- Brian -- K1LI

On Tue, Oct 25, 2011 at 10:07 AM, Brian Machesney <nekvtster at gmail.com>wrote:

> Gang,
>
> I have an 80-ft tower topped by an KT34XA (elements insulated from 32-ft
> boom) and 40-2CD (only reflector electrically connected to 22-ft boom). I
> have 8 x 50-ft lengths of 4-ft wide welded, galvanized steel fence for a
> ground screen. No other radials.
>
> I have successfully matched this on 160 with about 350-pF series capacitor
> to a 45-ft #12 gamma wire spaced about 3-ft from the tower.
>
> I also want to feed the tower on 80. I have been hoping that the 160 gamma
> wire would "disappear" electrically when it is open-circuited. Given the
> complex configuratino of the GAP vertical antennas, this may be but a faint
> hope. I'm having trouble creating a good match on 80 with a simple gamma
> feed scheme.
>
> Has anyone on the reflector tried to feed the same tower on two bands?
>
> Please reply off-reflector.
>
> Thanks and 73,
>
> Brian K1LI
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>



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