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Re: [TowerTalk] water in coax-DAVIS RF Co. Response

To: "Tower Talk" <>
Subject: Re: [TowerTalk] water in coax-DAVIS RF Co. Response
From: "Steve Davis -Davis RF Co." <>
Date: Sun, 17 Feb 2008 20:44:37 -0500
List-post: <">>
 Hi Folks, I would like to echo Roger's K8RI note:  "just pitch" any coax
 that has gotten water into it.  Unless you cut back the coax and check the
 center conductor, the braid shield, and the foil shield (if there is one)
 for contamination and get back to an uncontaminated point, you don't want 
 use the cable.  Also, when I say "check", this is a visual, very subjective
 process.  Also, the dielectric:  if solid polyethylene (PE,  usually a 
 grey color and used on RG-213,etc), likely water or moisture will not
 penetrate it, but the presence of water/moisture poses an electrical 
 effect.  If the diel. is closed cell PE  (white foamed PE which has a 
 VP) moisture that gets to it will migrate into the PE and you may see
 discolorization but if not, you won't "see" the contaminating moisture. If
 you do cut back to where you (subjectively) think you have passed the
 migrating problem area, then the only way to be sure is to use an
 appropriate cable testing device.  When I designed Bury-Flex (Tm Davis RF
 Co.) I used a second foil shield, bonded to the low loss dielectric, as 
 as tinned braid to protect against mild moisture attack, BUT, As I'm sure
 you know, it is extremely important at the outset of coax installation to
use good sealing material (preferably "waterproof", instead of "moisture
 proof") over the connector and up  and over the connector receptacle and
 back over the coax to prevent any water on the antenna input or on the 
 from entering the connector.  Roger mentions flooded heat shrink, otherwise
 ref'd to as adhesive backed HS, a good sealing technique (be sure it is UV
 resistant) and there are good tapes (which have been discussed here in 
 as well as AMP Fusion tape, which I prefer.
I had an inquiry due to my last post as to what  AMP Fusion tape is and I 
will post that in a few minutes, subj. "AMP Fusion tape for sealing/water 

 73,   Steve Davis   K1PEK   DAVIS RF Co.

 ~ Davis RF Co., Div. of Orion Wire Co.,Inc.
 Distribution to numerous industries,  Andrew
 Heliax; Times Microwave LMR; RFS Celwave and others.
 Cable design engineering. RF Peripherals.
 Tel: 1-800-328-4773 (1-800-DAVIS RF) Tech'l: 1-978-369-
 1738, Fax: 1-978-369-3484

> ----- Original Message ----- 
> From: <>
> To: <>
> Sent: Saturday, February 16, 2008 10:43 PM
> Subject: TowerTalk Digest, Vol 62, Issue 28
>> ----- Original Message ----- 
>> From: "Roger (K8RI)" <>
>> To: <>
>> Sent: Wednesday, February 13, 2008 3:00 PM
>> Subject: Re: [TowerTalk] water in coax
>> wrote:
>>> OK...I did it...I kept saying, "I'll get some coax seal on that joint
>>> when..."
>>> Well, the ice storm hit before "when" hit.
>>> Does Coax dry?  If not, is there a good way to figure out how deep the
>>> water has wicked?
>> Not usually and it all depends.
>> If the leak is at the top of a run it'll migrate a 100 feet in just a
>> couple of days.  If on the level  it  varies a lot and it depends on the
>> type of coax. Bury flex? No problem. 9913? big problem.  If the far end
>> is flooded (not normally a  good idea) and well sealed the migration
>> could/might be quite slow.  IF you know there's water  in it,  the
>> easiest and most reliable is to just pitch it. I've had horizontal runs
>> of LMR 400 get nicked with very little migration. I think I mentioned a
>> few weeks back I had some 9913 get nicked/abraded. Two days after an ice
>> storm and warmer weather left me with water running out the other end
>> and this was through the braid.
>> If the connection (splice?  you didn't describe it) is taped  there
>> should be little problem. If it's N-connectors, there may not be a
>> problem. UHF? I don't even put them in temporary without tape. Coax
>> Seal. Never use it-don't like it. I normally just use  flooded heat
>> shrink tubing.
>> Good Luck es 73
>> Roger (K8RI)
>>> Thanks!
>>> Art, K?RO
>> _______________________________________________
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>> End of TowerTalk Digest, Vol 62, Issue 28
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