[TowerTalk] Old Coax and cable questions

[Jim Brown]

On 9/28/2025 1:19 PM, kq2m at 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