[TowerTalk] Blackened Sheild on Belden Coax?

[Guy Olinger, K2AV]

Hmmm...

>
> Tom Rauch wrote:

> >As for current causing it, I've even melted some lines that had the
> >unfortunate luck of being in the wrong SWR at the wrong time and
> >never seen the braid change color. I can't imagine the braid getting
> >so hot as to discolor and not having the dielectric melt!
>

Well, I split the coax jacket (some old RG8U, not foam) for over a
hundred feet to check it out. The black gradually reoccurred every 21,
22 feet, with clean copper in the middle. What do you think caused that?

I figured I did it during an early mis-informed period when I was
running 400 watts on 20 meters to a tuner, then thru that coax to a 40
meter ground plane. It had a 1.5 to one swr on 40 cw straight through
and took a kW matchbox to tame it on 20. I worked people on 20.

Maybe heat to some degree accelerated the contamination process?

- - . . .   . . . - -     .   . . .     - - .   . - . .

73, Guy
k2av@contesting.com
Apex, NC, USA




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