On 9/28/2025 1:19 PM, kq2m@kq2m.com wrote:
In the process I have been discovering old coax, some of it in possibly
re-useable and some of it ready for the landfill.
About 15 years ago, I helped the widow of a neighbor ham with a fine
station he'd built himself get rid of his stuff. In doing so, I
coordinated the extensive help from his friends and other local hams.
There was a lot of coax of varying vintage, some indoors, some outdoors.
Nearly all of it was pretty good stuff, so I took most of it to an NCCC
meeting. Everyone turned their noses up at it, so I brought it home and
made a lot of stubs from it. Virtually all of the stubs measured as good
(looking at depth of their nulls) as if they had been brand new. The
sole exceptions were a few that had obvious water intrusion and extreme
corrosion of the braid.
There is no question that a LOT of perfectly good coax ends up in the
dumpster out of stupidity and ignorance. If in doubt, open a connector
and look at it. I strongly suggest that if you find no visual signs of
corrosion that you consider it good as new, and donate it to another ham
if you don't need it yourself.
I had the experience of finding water intrusion in some RG11 that was
feedling my high dipoles. I discovered it when I pulled a cable off my
grounding panel and water leaked out. The coax was less than a year old,
and the intrusion occurred due to insufficient moisture sealing of a
very nice and very sophisticated center insulator that a friend, and
first rate engineer, had built for us.
I measured the two cables involved with a well-calibrated, high quality
VNA, and found a fractional dB increase in loss in these cables, which
were on the order of 160 ft long, in less than a year. There was obvious
corrosion, but not a lot, and the moisture was still present.
This is, of course, separate from any other issues involved with UV
exposure to certain vulnerable cable components.
73, Jim K9YC
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