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Re: [CQ-Contest] oxidized inner conductor when coax carries DC power

To: cq-contest@contesting.com
Subject: Re: [CQ-Contest] oxidized inner conductor when coax carries DC power
From: Jim Brown <k9yc@audiosystemsgroup.com>
Reply-to: k9yc@arrl.net
Date: Mon, 31 Oct 2016 18:38:23 -0700
List-post: <cq-contest@contesting.com">mailto:cq-contest@contesting.com>
Hi Franki,

I would not be so sure that it is not moisture. A few years ago, I replaced a center insulator on one of my high dipoles with one that my neighbor had built. Less than a year later, I noticed moisture at the SO239 on the panel where that feedline is grounded. I opened up the coax and found the braid almost solid black. The entry point for the water was at the new insulator, and it flowed all the way down the coax. I later confirmed that when I replaced the coax and cut it at the top. That dipole is up 140 ft, so the water flowed 160 ft down to the shack entry point. The coax was Belden 8213, which has a foam dielectric and a heavy copper braid shield.

I don't recall whether the center conductor was also black or not, but the center conductor is molded to the dielectric, so I suspect it was not.

73, Jim K9YC


On Mon,10/31/2016 3:51 AM, Franki ON5ZO wrote:
Much to my surprise I found the inner conductor black from corrosion. I cut off a few centimeters at a time, but after having cut off two meters, it still was black. I have been working with these things for ages and I can tell you: it is NOT water ingress.


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