"Spike" wrote in message
...
On Tue, 1 Feb 2005 10:40:22 -0000, Airy R.Bean wrote:

This is thin coax which has been installed for about 22 years.

I was intrigued to find that both the braid and the inner conductor
were blackened, despite being on a section of the cable that could
not have had water ingress.

The problem is not '(liquid) water ingress' but diffusion of water
molecules from the atmosphere through the cable sheathing.

Perhaps is time to replace with some larger diameter coax?

The cable sheathing may not be that much thicker than that of the
'thin' coax, and so will not significantly slow the diffusion, and in
addition you will have mechanical problems due to the much heavier
coax.

Your thin coax probably blackened years ago.

You can try to reduce the effect by covering the cable sheathing with
a light coating at regular time-intervals of something water-resistant
such as wax furniture spray or WD40 - not as '(liquid) water' is the
problem, but that the light fractions of the wax or oil will tend to
fill the pores in the sheathing material and so delay the diffusion
effect. You could move to the Arctic or a desert of your choice ;-)

For thin (RG58 etc) coax, it is cheap and running it not normally and issue-
so just replace every 12 mths or so (it really does not like the sun!).

For RG213, run inside new hose pipe (B&Q cheap stuff is ideal). Seems to
last 'forever'- well over 10 years without visible deteriotion of the coax,
or measureable change in loss at 430MHz. Not so much about saving money as
hassle lowering masts etc to replace.

--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898