[TowerTalk] Water in Coax

[Roger (K8RI)]

Roger Parsons wrote:
> I have a 300' run of LMR400 going up a tower - at the top are a 900MHz bi-directional amplifier and antenna. The system stopped working properly a while ago, and I eventually (duh) found that the problem was water in the coax. There was a joint at the 220' level which I initially suspected, but decided to change the whole run to a single length of cable and this was done last Saturday. Everything now works fine again.
>
> I was interested to see what had caused the problem and proceeded to cut 20' pieces off the cable until I saw a nice shiny outer conductor. This happened at about 100' - proving (I think) that the problem was below that point. 
Did you start at the bottom and work up? If so the problem should be at 
or just below the point where the shield turns shiny.  It gradually 
turns gray with water and water *usually* works down the coax and not up 
*unless* the cable is sealed at both ends.

A "pin hole" can be very difficult to find as can a cracked jacket at times.

73

Roger (K8RI)