Ye, I think that I would rather install an "outside" antenna tuner
in the attic. One trick used in some military equipment is to seal
the enclosure with gaskets and have a schraeder valve on the case
to allow the entire enclosure to be pressurized with dry air,
or dry Nitrogen. This would be a bit of a "science project" for most of
us, though. Better to just keep the tuner inside and run low-loss line
like ladder line or good quality coax to the antenna.
73,
Bob WB2VUF
Tim Long wrote:
>
> Hi All,
> Some comments for the group:
> It would be difficult to put enough silica gel inside an enclosure to
> absorb all of the moisture over the lifetime of the outside tuner. I
> don't care how fine a screen you find, there's a critter or baby critter
> who will crawl through it. The solution to that problem is to use a
> cotton ball. It breathes and critters absolutely cannot get through
> it. (There's a cotton ball allowing your electric meter to breathe and
> keep out critters right now.) I wouldn't recommend sealing an
> enclosure. Even if you seal it on a dry day, the atmosphere that gets
> trapped inside will eventually reach the dew point and it will "rain"
> inside the enclosure. Better to vent it to the atmosphere, keep rain
> from getting inside, and keep the critters out with cotton balls. The
> real worry is what surface finishes are used inside the tuner and how
> resistant are those finishes to normal humidity. 73, Tim, W2UI
>
> Dr. Gerald N. Johnson, electrical engineer wrote:
>
> > The enclosure needs a vent else there can be a condensation problem. The
> > vent needs to be effectively screened so insects and critters don't call
> > the enclosure home. Power to operate the logic of the tuner made for
> > indoor use may be a slight bother, though the 120 volt outlet with GFCI
> > should be reasonably safe.
> >
> > Alternatively, the tuner enclosure can be tightly sealed but then needs
> > some humidity control like a handful of silica gel to prevent
> > condensation on the circuits at low air temperatures. Or some external
> > heat applied to keep the enclosure above a condensation temperature.
> >
> > Where there's fog and a vent, a bit of heat in the enclosure might not
> > be a bad idea either to keep the circuits dry.
> >
> > 73, Jerry, K0CQ
> >
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> >
> >
>
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