The tower is well over 1/4 wave length and the beam on top makes it loaded
to appear longer than that.
There was an article in QST some time back for computing the cap. hat load
of variout beams.
I would guess ( GUESS) YOUR somewhere near a 1/2 wave antenna for 80. you
might find that your just going to have to continue testing at various
points untill you find a place that it will load.
I use the OMEGA match also known as modified gamma and do well with my
shunt feed.
The tower is 130 foot with a full size 2 el 40 for a cap hat. I estimate it
to be about 3/8 wave on 160 and it gets out well on that band with vy
little in a ground radial system because part of the tower is serving as the
ground plane.
If you have the caps try the modified gamma and see if that will make it
load. you might be supprized at how low on the tower or how high you might
have to go with a regular gamma match.
Quack aka rex
----- Original Message -----
From: "Stephen M. Murphy" <murphys@comcast.net>
To: <cq-contest@contesting.com>
Sent: Monday, November 15, 2004 20:54
Subject: Re: [CQ-Contest] Adding 80m Shunt feed w/160
> Have you tried tapping it lower? I'm probably wrong, but 50-60' seems kind
> of high for an 80m tap on that tower...
>
> I'm building a pair of 40m verticals using the TT tubing. Not sure what
> info you're looking for, but the tubing I got from them matched the specs
in
> their catalog and I don't see anything to complain about as far as quality
> is concerned.
>
> 73-GL,
> Steve N8NM
>
> ----- Original Message -----
> From: "Scott Bauer" <w2lc@ix.netcom.com>
> To: <cq-contest@contesting.com>
> Sent: Monday, November 15, 2004 12:51 AM
> Subject: [CQ-Contest] Adding 80m Shunt feed w/160
>
>
> Has anyone out there combined an 80m shunt feed on a tower that already
has
> a shunt feed for 160m ?
>
> I have an 76 foot tower, with a 160m shunt feed, with the shunt wire
> connected at about 60 feet. It works very well for me on 160m, or at
least
> it seems to. I only run 100W on 160m, since my amplifier does not have
160.
>
> I tried adding an 80m shunt feed, first with the shunt wire connected at
> about 50 feet, which didn't work then moved it to 60 feet, which also
didn't
> work. I am using an L network, with a shunt roller inductor and a series
> variable capacitor to the shunt wire. I have more than enough inductance
> and capacitance to work with, both value and tuning range.
>
> The 160m shunt feed took all of 30 seconds to tune. On 80m I can't even
get
> it close.
>
> The tower has a PRO-67 on top at 77 ft (40m thru 10m), with three other
> yagis at 64, 50 and 37 feet, and an 80m dipole.
>
> Since the dipole I have on 80m doesn't seem to do well, I want to shunt
feed
> the tower on 80m and take advantage of the radials already installed for
> 160.
>
> The only other option is to buy tubing and make an 80m vertical and put
down
> another set of radials. Anyone have experience with the tubing that Texas
> Towers sells ? I don't really want to use irrigation tubing, looks like
it
> is harder to support.
>
> Thanks in advance for the help.
>
> 73 Scott W2LC
>
>
>
>
>
> _______________________________________________
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>
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>
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