On 20 Feb 01, at 10:37, K7LXC@aol.com wrote:
> In a message dated 2/20/01 7:22:45 AM Pacific Standard Time,
> w2up@mindspring.com writes:
>
> > I purchased this TH7 used about 2 years ago. I was told it was just
> > a few years old and appeared to be in excellent condition. I am
> > using a Palomar BA-2000 balun with it.
> >
> > Recently, the antenna has developed a higher than usual SWR on 15
> > and 20 meters, running between 2:1 and 2.5:1. It is just about flat
> > across both bands. 10m seems to be fine. Has anyone else had
> > similar problems? Is the most likely source the traps on one of the
> > driven elements? Comments appreciated.
>
> Sounds like a trap problem. Is the swr constant across the whole
> band?
YES, on 15 and 20. On 10, it has its expected curve.
> With 2 driven elements, one DE might work and the other have a
> problem.
>
> Have you put an antenna analyzer on the feedpoint?
Not yet. Hopefully this weekend, weather permitting.
>That's the first thing
> you need to do. If the antenna's okay, start working down the feedline
> to the shack. If you're measuring the swr at the shack, make sure you
> go to the feedline directly when you measure. MANY shack 'antenna'
> problems turn out to be bad jumpers, bad switch, etc.
>
> If this was a feedline problem, you'd have high swr (5:1 or so)
> everywhere.
>
> Cheers, Steve K7LXC
> Tower Tech
>
Tnx info Steve. I've never had the traps apart, so any tips on what
to look for, and disassembly appreciated.
Tnx/Barry
--
Barry Kutner, W2UP Internet: w2up@mindspring.com
Newtown, PA FRC alternate: barry@w2up.wells.com
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