[TowerTalk] Now this is maddening...

[Michael Germino]

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 at sbcglobal.net> wrote:

> From: Kim Elmore <cw_de_n5op at sbcglobal.net>
> Subject: [TowerTalk] Now this is maddening...
> To: towertalk at 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
> 
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