[TowerTalk] UV and WX deterioration of THHN insulation, and effects

[Guy Olinger]

Bare wire up outdoors over ten years, just what I would term a patina on
the outside.

This is in contrast to what happens to bare copper used in a woven coax
shield which has become waterlogged, where cable loss increases
significantly, and sometimes stripping reveals green crumbly stuff in and
around the shield for the entire length of the coax.

The difference in the long term between the two, perhaps is that the
elevated copper wire gets wet, the water largely drips off, and then it
dries off.

The copper in the coax shield, once penetrated with water, has the water
held to the copper 24/7/365. This may be the problem with the insulation on
the THHN in question, that it becomes water porous and holds water, and
whatever breakdown compounds against the copper indefinitely

73, Guy K2AV

On Wed, Dec 28, 2016 at 8:27 AM, john at kk9a.com <john at kk9a.com> wrote:

> Bare copper oxidizes. Visibly it appears worse than wire covered with PVC.
>  Have you compared these measured THHN surface losses with bare wire that
> has been outdoors the same length of time?
>
> John KK9A
>
>
> Subject:        Re: [TowerTalk] UV and WX deterioration of THHN
> insulation,     and
> effects
> From:   Guy Olinger <k2av at contesting.com>
> Reply-to:       k2av.guy at gmail.com
> Date:   Wed, 28 Dec 2016 01:28:41 -0500
>
> Current betting money in my neck of the woods is on some actual
> deterioration of the surface of the copper caused by compounds in the
> degrading insulation. Skin effect forces some degree of current into
> the degraded copper which has a higher resistance than the non
> deteriorated good stuff in the middle of the wire.
>
> What is not in question is the higher effective resistance of the
> conductor + whatever the insulation has turned into at RF after
> degradation. That has simply been measured.
>
> 73, Guy K2AV
>
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