[TowerTalk] Black coax (again)

[Roger (K8RI)]

On 9/15/2010 7:52 PM, Tom Osborne wrote:
> BlankHi All
>
> I recently took some 75 foot sections RG-8X coax off of a pair of 40 meter
> verticals and found the center and shield was all black.  I mentioned it
> here and some said it was from water ingress.
>
> I was playing with these pieces of coax yesterday and found that if I cut 5
> feet off the antenna end, the shield was nice and bright, but the center
> conductor was all black.
>
> I took the coax fittings off at the shack end and found the same thing--the
> shield was nice and shiny, but the center conductor was all black, so there
> is no way it could be from water.
Why not?
>    Also, the antennas are lower than the
> house so the water couldn't run up hill through the bulkhead to the antenna
> switch.
Again, why not?
Capilary action, particularly with find stranded center conductor can 
wick water/moisture many feet and even up hill.
>    The connectors are Amphenol.
If UHF it really doesn't matter where water/moisture is concerned.
> The center conductor is stranded, and each strand is all black.  I would
> assume that the wires are all insulated from each other due to the
> discoloration.  It almost looks like the wire got hot, but I only run 500
> watts into matched antennas, so the SWR shouldn't be a factor.
It could be moisture or a chemical reaction with the dielectric.
> What, besides water, would turn the center conductors black?  73
Don't be too quick to write off moisture.  There aren't many things that 
will do that other than brand X coax with a contaminating jacket or 
dielectric, or water.

73 and good luck,

Roger (K8RI)
> Tom W7WHY
>
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