Actually it is both. I've installed and serviced both. If you have a short
run of not too large heliax such as 7/8 inch, pressurizing the feedline (and
often the antenna depending on the design) with nitrogen is not a problem.
If the system is in pretty good shape, I've seen the tank of nitrogen last
for a couple years. Of course...one bad o ring on the antenna joints, or
some physical damage to the heliax and that tank will go in a hurry.
At any rate, both are used in the broadcast industry.
73
N7HQR
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Gene Smar
Sent: Thursday, February 14, 2008 7:25 AM
To: Gene Smar; Towertalk List; Martin Ewing AA6E
Subject: Re: [TowerTalk] water in coax
TT:
Sorry - it's dry, pressurized air and not nitrogen that is used in
commercial pressurized coax systems. Even more complex when driers are
included. My apologies.
73 de
Gene Smar AD3F
From: Gene Smar <ersmar@verizon.net>
Date: 2008/02/14 Thu AM 09:19:32 CST
To: Towertalk List <towertalk@contesting.com>,
Martin Ewing AA6E <aa6e@ewing.homedns.org>
Subject: Re: [TowerTalk] water in coax
Martin et al:
Commercial pressurization systems are pretty complex and cannot be used
with just ANY coax. Air dielectric cables, typically used for QRO microwave
sysems, require nitrogen under pressure to preserve their dielectric
strength by keeping atmospheric moisture out. The coax runs are monitored
for pressure leaks, etc. - a real PITA. I doubt there are many Amateur
installations using air dielectric hardline, hence even fewer will need
pressurization systems.
FYI - here's the Andrew page showing the index for such pressurization
systems in their catalog:
http://www.andrew.com/products/pressurization/default.aspx .
73 de
Gene Smar AD3F
From: Martin Ewing AA6E <aa6e@ewing.homedns.org>
Date: 2008/02/14 Thu AM 08:57:01 CST
To: Towertalk List <towertalk@contesting.com>
Subject: Re: [TowerTalk] water in coax
The pros often pressurize their lines, I believe, to keep water out.
Have amateurs done this? What would be involved? PL-259's aren't going
to help.
73 Martin AA6E
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