This end was the worst, cut 1ft from the fitting which connected to the hard
line, at the tower.COAX CONTAMINATION
In January 2009 our repeater began exhibiting a crackling noise. During our investigation we discovered a length of bad coax. It had become contaminated and had significantly reduced the receiver sensitivity. It had not, however, induced the crackling noise, proven by it's replacement with new RG-213. This is temporary as we're working on permanent length of hard line as a replacement, in addition to working on the crackling problem, weather permitting.
Due to the short hard line length compared to a longer distance run, the coax was required to make up the distance to reach the cavities. Below are the problems we found with the old length of RG-8 A/U coax, which had been in use since 1997. All fitting connections were properly taped and weatherized. No moisture was present when the weatherizing was removed to disconnect the coax.
This end was the worst, cut 1ft from the fitting which connected to the hard
line, at the tower.
This sample was taken about 30ft from the end. Notice the fractures in the
dielectric.
There were no noticeable cracks or breaks in the outer jacket.
This is the center conductor with the fractured dielectric removed, (the nick
in the copper was made during the dielectric removal). Notice how the amount of
contamination is much less, but certainly not acceptable.
Noise Problem Update
January 31, 09
In attempts to isolate the noise problem to the tower antenna system, we disconnected it and temporarily replaced it with a low altitude level collinear antenna.
This has proven positive. With the tower antenna system disconnected, all noise interference has been eliminated. As of today, 2-13-09, there has been no noise other than a storm moving through, that has been experienced. We'll continue running the repeater with this low level antenna until the wx warms up long enough to get the tower equipment down for inspection.
I'm suspect of the coax which connects the hard line to the antenna, it's been in service for over ten years and is probably contaminated as the coax in the above pics. What ever it's condition, it will be replaced with new. The GP-9 antenna will be taken down and inspected also. Stay tuned! End of update.
since 1-25-2009