Herb, you can feed any number of bands through one gamma arm or wire as long
as the highest frequency to be used is less than 1/4 wave length on the
gamma arm or wire. The appropriate matching is still required for each
band. I fed my 70ft grounded tower for 160, 80 and 40 meters with a gamma
of 27ft length...de gary
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Herbert
Schonbohm
Sent: Tuesday, February 25, 2014 11:52 AM
To: topband@contesting.com
Subject: Re: Topband: In search of resonance
On 1/30/2014 11:03 PM, Carl Braun wrote:
> If I can't get the antenna to resonate using the L I'd say that I'd
consider shunt feeding the tower and work out an (omega) matching scheme to
match the tower to my target freq. If that's the case, do I mount my upper
shunt arm on the tower at 67' or at 90'?
>
> Can I run a single drop wire into my panel and then switch the feed
between two matching networks? One for 160 and one for 80?
>
> Please advise
>
> Thanks
>
> Carl AG6X
>
>
>
Carl,
Why not just run a slant wire to your shack and feed the bottom against
a ground system through an ATU. Don't expect any real drama on 80 meters
as the tower is probably to long electrically. ut a slant on any
frequency could be modeled to see what you choices are. The only way
this could change if you made a decoupling sleeve on the tower so the
radiator appear to be between 1/4 and 3/8 wave length. It can work as a
duo bander but it will require some extra work and a good vacuum switch
since the voltages may be high at the in/out switch point. Some
directive in the direction of the slant may occur but it should be be
slight. As far as a drop wire shunt is concerned: There should not be
any advantage of having the drop wire shunt arm much higher than the
approximated sweet point for you tower.
Herb Schoenbohm, KV4FZ
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