[SBE] "modifying co-ax" to drain moisture

[Gary Stewart]

Blow it out. Then pressurize it at a very low pressure.  There is a chance that the leak at the top will minimize at the lower pressure.  Instead of 3 to 5 lbs, which might keep the leak wide open, use 1 lb or so.  Just enough to keep that little hole leaking out instead of in and hopefully minimizing the size of the leak at the same time.

Yes on the air compressor with dryer.  If you want to save nitrogen that is the way to go.


gary

________________________________
From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of Dean
Sent: Wednesday, October 03, 2012 12:39 PM
To: sbe member discussion mail list
Subject: [SBE] "modifying co-ax" to drain moisture

I have a 300 foot run of 1-5/8" air-filled coax up one of our towers that apparently has a bad seal at the top end, and it seems to be admitting water (sort of like an open drinking straw) which is collecting at the bottom in a "loop" of co-ax we left deliberately when it was installed to collect water outside the transmitter and transmitter building.  The "low point" is collecting water as we planned, but eventually it "fills" the insulation space where the drip loop is, and causes the transmitter to drop way back in power, due to high reflected power through the water route.

I can give the co-ax a blast of compressed nitrogen, and after about 15 seconds the water is "forced out" through a small drain hole we have drilled in the co-ax jacket and outer conductor, and the reflected power drops to a normal value, the transmitter output current and power return to normal and we're off and running.

My problem is:  I cannot leave the co-ax pressurized or the leaky seals at the top will bleed down my bottle of nitrogen in a short time (about an hour or so).  So, whenever it looks like a rainy siege is coming, I give the co-ax a "blast" of nitrogen, and hope it will keep the water out for the duration of the rain storm.

What if I increased the size of my co-ax "weep hole" to about ½ inch diameter.  Would this cause any problems?

What if I coupled a small air compressor (with a dryer attached) operating off 120 volts to the co-ax and left it running (cycling on and off on pressure)?  Would this work?

I'm looking for a long range answer, without having to climb the tower, replace the co-ax, etc.

Any suggestions?


DEAN SPENCER
WBIW/WQRK/WPHZ
dspencer at hpcisp.com
P.O. Box 1307
Bedford, IN.
Ph.812-275-7555  Fax 812-279-8046
Cell 812-797-3612
wbiw.com  superoldies.net


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