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

[Jim Thomson]

UV and weather degraded THHN wire was replaced with new bare wire and
60 ohms resistance disappeared that was visible only at RF. The wires
were all pulled between posts, and the old wire was NOT sagging. The
old wire was never subjected to the stresses of having an end fastened
to a tree.

The term resistance refers to the R value from an RF analyzer that
supplies a value for X separately. E.g. R + jX .

The missing consideration here *might* be the presumption of a smooth
surface between a conducting and non-conducting layer. Close
examination of the degraded wire taken from our radial replacement
experience did NOT reveal a smooth surface.

Instead the surface resembled the surface of a football or basketball,
the small "bumps" that constitute an aid to gripping. Except the
mounds and valleys between them were smaller in size, and more easily
seen with a magnifying glass.

What if, from the viewpoint of inside the un-degraded copper the
transition from copper to degraded copper looked more like the roof of
a cave, with stalactites, with a very irregular roof. Then what
happens to the effective resistance of a glued-to-the-skin current
forced to transit all these irregularities. Stated differently, what
if a layer between absolutely conducting and absolutely not conducting
actually exists and is not smooth and monolithic, but crumbly and
irregular as all-get-out.

N6LF has agreed to make some space in his schedule and analyze some
samples of the wire in question, which I will be supplying to him
shortly.

We have some other experiments planned with some of the old wire.

We are hardly done.

73 and a prosperous New Year to all.
Guy K2AV ###  Wind a coil, say 10-20 uh, with the bad THHN, then another identical coil,but with brand new THNN.   Perhaps close wind it, then measure the UH at various freqs.My B+K  875B  LCR meter does the uh readings at just 1 khz.  Some will also take the readings at 100 khz and higher.  Then take a HP Q meter, and measure the Q of each coil,at various RF freqs, say in the middle of each of the 9 HF bands... perhaps 6m as well.  That should end the argument one way or the other, right then and there. Jim   VE7RF Jim   VE7RF