Topband: Sealing closures

Tom W8JI w8ji at
Wed Mar 20 10:48:37 EDT 2013

> Being in outside repair with ATT for 40 years, I had plenty of experience 
> with attempting to seal closures. First of all if the closure, splice or 
> what have you is NOT encapsulated it will get wet. Either from 
> condensation or from weather exposer. Taping a splice or connection will 
> only retain moister and get worse, it is better to leave a splice open to 
> the weather than try to tape it, better yet encapsulate it. Temperature 
> changes cause condensation inside closures and it will stay there. The 
> best thing to do is allow the closure to breath. Put a hole (3/8) at the 
> low point of the closure and cover with a piece of screen (to keep bugs 
> out). You connections will be much happier.
> _________________

Good information above. I was going to make a similar post, before my power 
outage (36 hours and counting).

The biggest mistake is trying to seal something non-sealable. It either has 
to be 100% encapsulated with no air leakage ever, or it has to breathe at 
the lowest dry spot. Both ladder lines and coax (unless 100% bonded 
internally or flooded) will breath.

If we look at commercial two-way antennas, they either seal flooded or 
pressurized cables or they use rain boots or lower weather-shielded drain 
holes. They don't try to seal.

I probably have hundreds of connectors and dozens of outdoor boxes, and 
virtually none are sealed at the low spots. They are booted or hooded (open 
at the bottom) or flooded with a dielectric compound.

Sealing things not properly designed to be sealed, like standard coax or 
ladder line, is a mistake. As said above, it is much better to leave 
something not flooded or pressurized open.

73 Tom 

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