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Re: [TowerTalk] Sealed container needed for tuner

Subject: Re: [TowerTalk] Sealed container needed for tuner
From: jeff millar <>
Date: Fri, 15 Apr 2011 09:19:09 -0400
List-post: <">>
Agree about the drain holes.

The tower mounted Cellular Filter/Preamps use a metal box with a small
threaded insert at the bottom.  The threaded insert looked like a threaded
shaft with a 1/8 inch hole through it.  The hole was filled with small round
pebbles and the ends capped with a small enough opening to hold in the
  pebbles.  They didn't use screens for some reason.  The inside of the box
had a sloped bottom with small groves to guide the water to the drain hole.

"Sealed" boxes act like like pumps to pull in moisture and cause it to 
unless hermetically sealed with welded joints, ceramic to metal boned coax
connectors, etc.

jeff, wa1hco

On 04/14/2011 01:23 AM, K8RI on TT wrote:
> You may find that sealed might not be the way to go.  The pressure
> inside a sealed container changes with temperature and barometric
> pressure. With Temperature it can change substantially.   Most coax
> connectors are not sealed resulting in alternating positive and negative
> pressure on those cables which will cause them to breathe. Eventually
> moisture will be pulled in through the coax or other cables with no way
> out.  So most of us give in to the inevitable and create screened drain
> holes so the compartment can breathe naturally without trapping moisture.
> 73
> Roger (K8RI)


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