I'll double check the transmission line tomorrow. Surprisingly, no
water got into the PL-259 and it was dry when I removed it. The tower
is an HDBX-48 so it doesn't "shake" very well.. While I was doing
this, I yanked on the shunt feed and wiggled it around very
energetically. Nutin'.
I wish I had an analyzer, but I don't. I used a friend's unit
initially so I'll have to go beg his again.
Kim Elmore, N5OP
At 05:25 PM 12/29/2008, Michael Germino wrote:
>Have you tried a analyzer at the matching device? Perhaps you have
>a corroded ground that looks OK at DC but not RF. While you are
>looking at the analyzer you can move and shake the parts. (of
>course, see if there was a change after you remove you hand or tighten a nut.)
>
>Are you sure your PL-259 at the end of the coax is good? How did
>you check your transmission line? With a dummy load connected to
>the PL-259? Just a wild guess, but I would really suspect the
>shield solder connection to the PL-259.
>
>Good Luck.
>
>Mike
>AD6AA
>
>
>--- On Mon, 12/29/08, Kim Elmore <cw_de_n5op@sbcglobal.net> wrote:
>
> > From: Kim Elmore <cw_de_n5op@sbcglobal.net>
> > Subject: [TowerTalk] Now this is maddening...
> > To: towertalk@contesting.com
> > Date: Monday, December 29, 2008, 2:23 PM
> > I've been shunt-feeding my tower for awhile now using an
> > L-network
> > and a motor-drive to adjust a vacuum variable. Until
> > recently, all
> > has been just hunky-dory. However, last night it appeared
> > that my
> > motor drive no longer worked as I couldn't adjust the
> > match. What's
> > more, the match started to act flaky, with variations that
> > appeared
> > to act randomly.
> >
> > Today I opened up the box that holds the matching network
> > and found
> > that there was some water inside and that the nuts holding
> > the SO-239
> > connectors had corroded on the inside. Water had deposited
> > some dirt
> > and detritus on the inside of the SO-239 and it was wet.
> > So, I
> > cleaned everything out with alcohol (91% isopropyl).
> >
> > Found the motor drive was a bit cranky, so I lubed it up
> > and assured
> > my self that it worked as it was supposed to. But, no
> > matter how I
> > adjust things, I no longer can get a match. I checked the
> > vacuum
> > variable and it appears ok -- the mechanism works and all
> > and it's
> > not shorted. All the wiring is intact. The shunt is still
> > connected,
> > the grounds good, the antennas up top still work and are
> > intact, etc.
> > The capacitor that's in there is a 5-500 pF, so as a
> > sanity check I
> > substituted in a 7-1000 pF that I have laying around. Still
> > no match
> > can be found. The transmission line checks good, so
> > that's not it, either.
> >
> > Anybody else ever seen this? What have I missed?
> >
> > Kim Elmore, N5OP
> >
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk@contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
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