On Wed, 31 Dec 2003 02:51:26 +0000, Dave Woolf wrote:


Just wonder what other's might do to keep moisture from getting into the
semi-hollow 9913 type low loss coax. It would seem inevitiable with
changes in temperature and pressure that moist air would eventually work
its way into the coax and then condense.

I had a fellow ham that took the precaution of pressurizing this type of
coax to maintain positive pressure and keep out outside air. Seemed like
a lot of effort but maybe it is necessary.

I have tried to seal the ends of the coax with silicone sealant but I am
not really sure that this has been effective in the long term.

What do others do? What has been your experience?

Dave - K8RSP
(to reply to me directly remove NOSPAM from above address)

Butyl rubber based self amalgamating tape, Electrical Tape, Top Coat, I
use a coat of UV Stabilized clear Spray paint Tape:
http://www.surplussales.com/Antennas/Antennas-7.html

Over the years I have cleaned up a lot of messes where they connectors
were not sealed properly. I have taken apart my connections to replace
Damaged antennas and the connections are dry as a bone. after 10 years of
more in the air.

IMHO: Take a close look at Times Microwave cables, I think it's a better
products than the equivalent Beldon.

Ron

"Ron" wrote in message
news
On Wed, 31 Dec 2003 02:51:26 +0000, Dave Woolf wrote:


Just wonder what other's might do to keep moisture from getting into the
semi-hollow 9913 type low loss coax. It would seem inevitiable with
changes in temperature and pressure that moist air would eventually work
its way into the coax and then condense.



I'd think it makes sense to seal the top, but let the connectors at the
bottom
breath, that would alleviate moisture ladden air from being drawn in at
the top. Especially during rain storms! Another idea would be having the
top sealed, and the bottom allowed to breathe through a plastic jar of
desiccant.

Pete

Uncle Peter wrote:

"Ron" wrote in message
news
On Wed, 31 Dec 2003 02:51:26 +0000, Dave Woolf wrote:


Just wonder what other's might do to keep moisture from getting into the
semi-hollow 9913 type low loss coax. It would seem inevitiable with
changes in temperature and pressure that moist air would eventually work
its way into the coax and then condense.



I'd think it makes sense to seal the top, but let the connectors at the
bottom
breath, that would alleviate moisture ladden air from being drawn in at
the top. Especially during rain storms!

That will certainly help.

Another idea would be having the
top sealed, and the bottom allowed to breathe through a plastic jar of
desiccant.

Unfortunately the desiccant doesn't last, because it absorbs moisture
from the air in the shack. However, you can easily regenerate silica gel
by baking it in a moderate oven for a few hours.

Even better is "active" pressurization - keeping a positive pressure
inside the line at all times. A very simple, low-cost method is to use a
small fish-tank aerating pump in the shack, with the far end of the line
sealed (exactly as Pete recommends) so there is *no* through flow. The
positive pressure is very effective at keeping moisture out.

In the shack, the air is connected by soldering a small brass tube
through the side of a normal coax plug. PL259/SO239 connectors will
leak, so you have to tape over them; most types of N connectors are
already well sealed.

Positive pressure is even more useful if you have a sealed box at the
far end of the line, containing preamplifiers, relays etc. In the long
term it keeps outdoor electronics in far better condition than the
alternative method using a vent hole in the box, which exposes
everything inside the box to atmospheric moisture.

To make sure the air pressure gets through into the box, you may need to
drill small holes through the insulators of some in-line connectors.
Only small holes are needed because there's very little flow. For a
deluxe job, pressurize the system with dry air, by connecting the pump
through a tube of silica gel desiccant (regenerated every few months as
above).

I can't remember who first suggested this method, but I'd like to thank
him! It worked very well indeed for me, for more than 10 years.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Ron wrote:

On Wed, 31 Dec 2003 02:51:26 +0000, Dave Woolf wrote:

snipped


IMHO: Take a close look at Times Microwave cables, I think it's a better
products than the equivalent Beldon.

Ron

I agree. Not to sound like an ad for Times Microwave but IMHO the stuff
is great and well worth the additional cost. I first started using it
for S band and above. Today, it's the only type I got installed
anywhere.

Mike

KG4RRH

On Sat, 03 Jan 2004 17:00:25 -0500, Stilz wrote:



Ron wrote:

On Wed, 31 Dec 2003 02:51:26 +0000, Dave Woolf wrote:

snipped


IMHO: Take a close look at Times Microwave cables, I think it's a better
products than the equivalent Beldon.

Ron

I agree. Not to sound like an ad for Times Microwave but IMHO the stuff
is great and well worth the additional cost. I first started using it

Additional cost? It's been pretty much a few cents below 9913 most of
the time. :-)) (admittedly I have purchased any in a couple of years,
got enough to last for a while) And it takes the same connectors.

for S band and above. Today, it's the only type I got installed
anywhere.

I pulled out well over a 1000 feet of 9913 after the lightening strike
and ordered 1500 feet of LMR-400. I gave most of the 9913 to local
club members.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com


Mike

KG4RRH