Topband: Desiccant in Beverage Boxes

[Mike Waters]

CORRECTION:
"blew the cover off" should have read "damaged the cover gasket".

On Thu, Oct 31, 2019, 12:13 PM Mike Waters <mikewate at gmail.com> wrote:

> 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
>