[SBE] SBE Digest, Vol 542, Issue 1
Rolin Lintag
rolin.lintag at vtntv.com
Thu Oct 4 11:55:16 EDT 2012
Hi Dean,
Fixing the leaks is priority number one.
However, since you are looking for the second best, I suggest that you get a dehydrator, big air reservoir and an air regulator. The set-up can be similar to the third system I described in below link:
http://broadcastengineering.com/mag/pressurizing-coaxial-cable
You can pressurize the reservoir tank to 50 psi or so depending on the tank and then feed the coax through an air regulator (available at Bellofram) set at 2 psi. There are one way valves available from HVAC supply stores and they are useful in keeping the air flow one way.
Coax systems leak one way or another and becomes a concern for a tower climb if the dehydrator is running too often. "Too often" depends on the dehydrator size. We have two Andrew MT2000 that run every 25 minutes and that is still OK.
Hope this helps.
Rolin
Romualdo "Rolin" Lintag
Chief Engineer
Victory Television Network
KVTN-DT 25.1 Little Rock, AR
KVTH-DT 26.1 Hot Springs, AR
KVTJ-DT 48.1 Jonesboro, AR
www.vtntv.com
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SBE Roundtable
Today's Topics:
1. Re: "modifying co-ax" to drain moisture (Vic Jester)
2. Re: "modifying co-ax" to drain moisture (Cowboy)
3. Re: "modifying co-ax" to drain moisture (Cowboy)
4. Re: "modifying co-ax" to drain moisture (a9xw at cs.com)
5. Re: "modifying co-ax" to drain moisture (-jer)
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Message: 1
Date: Wed, 3 Oct 2012 12:14:06 -0500 (GMT-05:00)
From: Vic Jester <vjester at mindspring.com>
Subject: Re: [SBE] "modifying co-ax" to drain moisture
To: sbe member discussion mail list <sbe at sbe.org>
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Message: 2
Date: Wed, 3 Oct 2012 14:15:28 -0400
From: Cowboy <curt at cwf1.com>
Subject: Re: [SBE] "modifying co-ax" to drain moisture
To: sbe member discussion mail list <sbe at sbe.org>
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On Wednesday 03 October 2012 12:38:33 pm Dean wrote:
> I?m looking for a long range answer, without having to climb the
> tower, replace the co-ax, etc. ?
That's not going to happen.
Band-aids are exactly that.
I'd put a compressor on it and let it run, but only until you can get a competent climber up there to seal whatever, and give you your options for a permanent fix.
You're still going to have to run quite a bit of *dry* nitrogen through that line to purge it properly, when it's permanently sealed.
Where are you ?
300 isn't too tall, and I can do this sort of thing.
--
Cowboy
http://cowboy.cwf1.com
SHIFT TO THE LEFT! SHIFT TO THE RIGHT!
POP UP, PUSH DOWN, BYTE, BYTE, BYTE!
------------------------------
Message: 3
Date: Wed, 3 Oct 2012 14:55:33 -0400
From: Cowboy <curt at cwf1.com>
Subject: Re: [SBE] "modifying co-ax" to drain moisture
To: sbe member discussion mail list <sbe at sbe.org>
Message-ID: <201210031455.33297.curt at cwf1.com>
Content-Type: text/plain; charset="utf-8"
On Wednesday 03 October 2012 02:15:28 pm Cowboy wrote:
> Where are you ?
I see it now.
Not far, but your defective spam filter is preventing me from making a direct contact.
--
Cowboy
------------------------------
Message: 4
Date: Wed, 3 Oct 2012 15:35:21 -0400 (EDT)
From: a9xw at cs.com
Subject: Re: [SBE] "modifying co-ax" to drain moisture
To: sbe at sbe.org
Message-ID: <8CF6FB55C8615B0-1098-77FA9 at webmail-m135.sysops.aol.com>
Content-Type: text/plain; charset="utf-8"
Depending on how much oxidation your inner conductor has from your leak, you may have to replace the entire line. The weep hole is likely letting in more moisture than letting out because temperature changes are causing your line to "breath" Since it is causing VSWR shut down, you might even have internal arcing burning your inner conductor and that will lead to line failure. Considering thecost of labor for 2-3 trips up the tower and the low cost of coax, you are likely better off replacing the coax now before it fails and you are off the air for days/weeks. Make sure you don't have a lightning hole in the antenna. If the antenna is also pressurized from the coax line, it is much more likely you have an antenna hole than a coax hole. Having a weep hole at the bottom is never a good idea, and whomever "planned" that was no engineer. The correct method would be to have an airseal at the end of the coax and pressurize from the end to the top. You could already have insect eggs
in the line from the hole.
Henry Ruhwiedel (ret) 46 yrs CE R_TV
-----Original Message-----
From: Dean <dspencer at hpcisp.com>
To: sbe member discussion mail list <sbe at sbe.org>
Sent: Wed, Oct 3, 2012 11:48 am
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 ? 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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Message: 5
Date: Wed, 3 Oct 2012 23:00:51 +0000
From: "-jer" <jerhil at frontier.com>
Subject: Re: [SBE] "modifying co-ax" to drain moisture
To: "sbe member discussion mail list" <sbe at sbe.org>
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<1714136957-1349305246-cardhu_decombobulator_blackberry.rim.net-917454047- at b17.c14.bise6.blackberry>
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Q
-jer
-----Original Message-----
From: Cowboy <curt at cwf1.com>
Sender: sbe-bounces at sbe.org
Date: Wed, 3 Oct 2012 14:15:28
To: sbe member discussion mail list<sbe at sbe.org>
Reply-To: sbe member discussion mail list <sbe at sbe.org>
Subject: Re: [SBE] "modifying co-ax" to drain moisture
On Wednesday 03 October 2012 12:38:33 pm Dean wrote:
> I?m looking for a long range answer, without having to climb the tower,
> replace the co-ax, etc. ?
That's not going to happen.
Band-aids are exactly that.
I'd put a compressor on it and let it run, but only until you can
get a competent climber up there to seal whatever, and give
you your options for a permanent fix.
You're still going to have to run quite a bit of *dry* nitrogen through
that line to purge it properly, when it's permanently sealed.
Where are you ?
300 isn't too tall, and I can do this sort of thing.
--
Cowboy
http://cowboy.cwf1.com
SHIFT TO THE LEFT! SHIFT TO THE RIGHT!
POP UP, PUSH DOWN, BYTE, BYTE, BYTE!
_______________________________________________
The SBE Roundtable, SBE at sbe.org
To unsubscribe, go to http://seven.pairlist.net/mailman/options/sbe
http://seven.pairlist.net/mailman/listinfo/sbe
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