[Lowfer] Moisture in tuner box...

[Ralph Hartwell]

> I used to have my loop tuner box sealed tight and it got condensation
on the
> front and top clear plastic covers. I then drilled a 1/4th inch hole
in the
> bottom to let it breath. Now looking at it today, the condensation is
so bad
> that it is dripping wet on the front cover, which is where the
feedthru's

Nothing in my climate (Louisiana) is watertight unless it is potted or
welded shut.  I have given up on most anything else and now install most
of my outside hardware with the bottom of the enclosure open to the air.
Rain does not fall up (excluding hurricanes!) so that solves the rain
problem, and normal air currents keep things fairly dry.  If any great
amount of condensation does occur on the interior enclosure walls, it
just runs out onto the ground..  I do cover  the open end of the
enclosure with window screen, otherwise I find that I will have provided
a very nice little weatherproof house for a bunch of wasps.

> Should I put the tuner parts into the Hoffman box??? Are the clear
> plastic front and top covers causing the condensation with the
sunlight??

After about 5 years or so, my clear front Hoffman boxes yellowed and
developed stress cracks, allowing water to enter the boxes.  Since the
antenna changeover relays inside were activated by 120 VAC, they
promptly burned up. :(   Now I use only the grey fiberglass variety or
the steel boxes.  I also RTV the doors after shutting them tightly
against the foam rubber seals by running a bead of RTV around the top
and both sides of the door at the seal joint, but not the bottom. (Rain
does not fall up, remember...)  This allows me to use a razor blade and
slice through the RTV and easily open the door later, but keeps water
out.   I usually drop a marble into the bottom of the enclosure and see
where the low spot is, then I drill a small hole there to let any
condensed water out.

** Do NOT use RTV on the door seal or you'll never get it open again
unless your middle name is Hercules. **

ANYTHING you close it up in will let some air in and out if there are
ANY penetrations in the enclosure.  Air will get in and out through the
wires and cables, migrating between the wire and the insulation. That
means moisture will eventually get in a well.

The trick with dealing with condensed water is to keep it from getting
on the electronics.  Usually water first gets into the cabinet when the
outside temperature drops during a rainstorm.  This causes
moisture-laden air to be sucked into the cabinet where it condenses on
the interior walls first.  After the walls have cooled down enough, the
components inside the enclosure will cool below the dewpoint and water
will start to condense on them as well.  Even worse, when the walls of
the box start to heat up as the sun hits the box, all that liquid water
remaining on the walls evaporates and then re-condenses on the now
cooler components.

If you have a small hole in the bottom of the box, hopefully some of the
condensed water from the walls will be forced to exit the box as the air
inside starts to heat up and expand.  Some of the warm, wet air will
also be forced out of the enclosure. Later, as the outside air cools
down, drier( hopefully!) air will flow back into the box through the
hole as the air inside the box cools off.  If all this fails, the only
other good option is to install a small light bulb inside the box to
keep the electronics warm and cozy.

Good luck!!


73,

Ralph   W5JGV / WC2XSR / 13

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