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Re: [TowerTalk] Strange coax failure

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Strange coax failure
From: Jim Lux <jimlux@earthlink.net>
Date: Mon, 15 Dec 2014 17:50:25 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 12/15/14, 11:19 AM, Ray Benny wrote:
Patrick,

I had a case once of a shorted coax due to a manufacturing defect. The coax
was a 100 ft piece. I had first cut off the connectors one at a time but
found the coax still shorted. I cut the coax in half, one half open, the
other shorted. I kept cutting the shorted section in half until I had about
a 6 inch shorted piece remaining. I slid off the braid and found that
during the manufacturing process the center conducted was bent outward and
through the dielectric causing a direct contact with the braid. Don't know
why the short was not caught in a QC check, but maybe only random
pieces/rolls were checked.

In the end, I still had 50ft of coax to use, plus a bunch of shorter
pieces...



That's why a TDR or a VNA or equivalent that can tell you the position of the discontinuity is useful. You'd know right away if the problem is in one connector or the other, or in the middle of the cable.

If you were real patient and had lots of time, you could do it with a SWR meter and tuning your rig around.


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