Depends on the environment and the use to which you're going to put it....
Here's the theory behind pressurizing:
If you don't pressurize it, then as the temperature and barometric pressure
change, outside air moves in and out of the cable. The particular problem is
moist air moving in and then the moisture condensing out as it cools, then
the water causes problems: change in impedance/loss in the short run;
corrosion in the long run.
One can seal the cable, but, finding all the small pinholes and microscopic
leaks is a pain, so if you just put a small positive pressure with dry air,
you're all set. There's no such thing as perfectly sealed, particularly on
something physically large and subject to mechanical abuse.
That said, I'll bet there are literally hundreds of runs of air dielectric
cable without pressurization running just fine..
There are also (mostly) air dielectric cables which support the center
dielectric on disks/beads of dielectric at periodic distances. Most of the
dielectric is air, so the loss is low, etc. The disks DO form a seal
between little compartments, so the migration of water through the ends is
reduced.
Moisture infiltration is a problem with ordinary solid/foam coax too.. How
obsessive are you going to be about the deleterious effects.
----- Original Message -----
From: <dick.hoff@kodak.com>
To: <towertalk@contesting.com>
Sent: Sunday, September 07, 2003 5:20 AM
Subject: [TowerTalk] Air dielectric cable
> Is it necessary to pressurize air dielectric ? Are there any problems
> using it unpressurized?
>
> Dick AA5NT
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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