Topband: Desiccant in Beverage Boxes

[Mike Waters]

If you want to use dessicant, then you should use a suitable
hermetically-sealed pressure equalizer. This keeps the pressure inside the
box always the same as on the outside, regardless of air temperature or
barometric pressure. Thus, no water vapor can enter.

These are available commercially.
 (Sorry that I don't have a source, p/n, or price.)

But you can make your own pressure equalizer. The way I've always done that
is to fill the tip jacks full of silicone dielectric grease. This
non-hardening grease acts like a piston, moving in and out as the
barometric pressure changes.

These tip plugs are connected to the Beverage antenna itself with a short
length of #18 flexible copper wire. After you fill the jacks full, then
fill the inside of the tip plug as you assemble it to prevent corrosion.
Finally, slather more of it both on top of the jack and on the plug itself
just before you plug it in.

I've done that for ten years now, and only had to replace the dessicant bag
once. That was after lighting damaged the jacks and blew the cover off
(before I started using 90v GDTs).

I don't know why banana connectors wouldn't work just as well as tip plugs.
I just used tip connectors because that's what I had. Banana plugs are
sturdier.

In lieu of --or perhaps in addition to-- these plugs, one could use a short
length of 3/16" or 1/4" UV-proof tubing filled with this non-hardening
grease.

Note that the box should not be too large inside, lest too great a quantity
of air --from both temperature or atmospheric air pressure changes-- move
the equalizer "piston" too far, thus ruining the hermetic seal.

For my Beverage boxes, I use those Hammond enclosures with a rubber seal
between the box and the clear polycarbonate cover.

73, Mike
W0BTU