Just thought I would pass along a discovery and troubleshooting technique,
and wonder if anyone else has experience here...
Our 50 ohm copper hardline feed to our Log Periodic has given us
trouble,
periodically. A fault 6 months ago, revealed a low resistance bridge
between the center conductor and shield. I noticed though, that the
resistance was significantly different when I switched the leads of the
VOM. AND, the resistance slowly creeped upward. I thought it might
be some moist, ion filled connection, trying to be a diode....like copper
oxide....As an interim fix, (2 hrs before a contest start weekend) Tony,
AE0M, suggested zapping the disconnected coax (both ends) with a low,
stiff voltag source...so I used
an isolation transformer, and a variac and zapped the coax. The short was
no more, and the system worked...though it is now giving me trouble
again....I'm afraid I will have to possibly replace a section of the
hardline, most likely the part that goes vertical up the pole, as I think
the water probably got in at the top connector, where the splice to RG-213
rotor loop is....Question: If I saw a section of the hardline some
distance back (75 feet back on a 350 ft run) and still find oxidized
copper inside, is it likely that the cable at that point is still lossy?
Should I continue to cut back until I find clean copper? I have some 7/8"
heliax that I can replace the bad section with, and also wonder if a
stepped increase in size of 2 50 ohm cables causes any reflections, (not
that they would be important at HF....)
BTW, anyone know a hardcore, retired contester type, who is not deeply
rooted somewhere, who yearns to build
and maintain a potentially top west coast contest station? 10 acres of
hilltop with a 2 mile view to Monterey Bay, complete with hamshack, dozens
of yagis, 70 foot poles, discones, etc, thrown in at no extra charge....
We have hookups and room to park a Mobile home/RV.....on site...Us
working stiffs, are realizing that this site is such a time sink...though
very enjoyable, it is hard to keep up with it and keep another
life....This would be a dream QTH/avocation for the right guy...and you
can have a real address of 599 DX Drive too.....what say? Check out
www.vcr.com/N6IJ for some pics...
73, DX de Pat, AA6EG/N6IJ
"The Contest Station from the Government"
Marina Amateur Radio Contest Station; N6IJ
599 DX Drive
Marina CA 93933
aa6eg@tmx.com
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