Topband: A Big Mess!

[Charles Bibb]

Hi, Topbanders

I'm posting this so that others may benefit from my mistake and not 
repeat it. I use small PVC boxes
to house the matching transformers of my Beverage antennas.  These 
are electrical enclosures
available at Lowes's, etc. They seal tight with a rubber gasket and 
have no pre-drilled holes. When I
get them I drill two holes for the ceramic feed-through insulators, 
one for the Beverage wire and one for
the ground. The I drill another hole for the feedline connector. It 
all works very well.

Sometimes, however, I found that when I opened one up for one reason 
or another, I noticed some
beads of condensation had formed on the inside walls of the box, even 
though the seal is pretty tight.
This would cause any zinc-plated hardware inside to develop a coating 
of white oxide, and cause any
un-plated steel to eventually rust.

I set out then to eliminate that small amount of moisture remaining 
inside. I acquired some commercial
silica gel drying agent, which seemed ideally suited for the task. 
After all, keeping things dry in the
presence of moist air confined within a small space is the very 
situation for which this stuff was
invented. I place a 5 gram size perforated packet into two of my 
Beverage transformer boxes, sealed
them back up, and forgot about them.

Today, several months later, I had to go inside one of the boxes to 
tighten the nut on the backside of
one of the ceramic feed-throughs after re-attaching a broken antenna 
wire. WHAT A MESS! As I
removed the cover, liquid (water plus ??) ran out. Most of the metal 
hardware (all except the stainless
steel) was covered by a patina of oxidation or other corrosion. This 
stuff had exacerbated the very
problem(?) it was supposed to correct. And, once the silica gel 
became saturated with as much water
vapor as it could hold, it apparently released it as liquid water. 
Once saturated, the gel appears to
create a mildly corrosive atmosphere inside the enclosure, though it 
is not nearly as bad as Calcium
Chloride, which was used for the same purpose years ago.

I would strongly recommend NOT using silica gel in any outdoor 
"sealed" enclosures. I think maybe
I'll try Ed's grains of rice approach to moisture removal. Maybe he 
can give us an update on how it
worked out for him.

73,
Charles - K5ZK