[TowerTalk] Co-ax,

[Tom Rauch]

Hi Kelly,

As long as we are beating up on things like cables:

> Regarding coaxial cable: unless I had extremely long runs,
or had excess
> monetary capacity, I think it's pretty hard to beat
brand-name RG-213 for
> most HF applications. Flexible, UV resistant, centre
conductor not prone to
> migration, solid dielectric to avoid water wicking to the
extent of 9913 and
> once you get to the top of the tower, no need to worry
about pigtails.

I agree with you on the selection.

But I've never in my life seen a cable wick up water in the
dielectric. I've never had a center conductor migrate
either, except in that horrid spiral core hollow cable or
when I ran 1500 watts into a grossly misterminated cable and
melted it down.

All water migration is along the center conductor or shield.
You prevent water migration by having the area between the
shield and jacket flooded with goo, and a solid center that
is bonded to the foam. With semi-rigid shields like heliax
or CATV hardline, they bond the dielectric to the shield and
the center. No chance of water migration then. Should it
develop a water leak, you just fix the bad spot and the rest
of the cable is good.

You prevent the center conductor from migating by not
radiusing the cable too sharply and by not exceeding
temperature limits. I have just as much success with foam
cables in a coil as I do solid dielectrics.

The long-term loss in cable from water ingress mainly comes
from the shield corroding. Not from water soaking into the
foam. The migration comes from excessive heat, an
excessively sharp radius, or junk foam in the cable.

73 Tom