[Milsurplus] DIY Vacuum Chamber

[Jim Whartenby]

One way to easily remove water vapor is with a vacuum.  One can easily convert an old pressure cooker into a vacuum chamber for perhaps under $30 if you already have a hobby compressor / vacuum pump.  The holes in the cover are national pipe threads so just remove the old hardware and substitute a vacuum gauge, ball valve and a tubing adaptor along with a new gasket seal.  Plug any unneeded holes with the appropriate NPT plug.  I use a small Gast air compressor / vacuum pump with good results.  This example will hold a decent vacuum for well over a week.

Jim
Logic is a systematic method of coming to the wrong conclusion with confidence.  Murphy

On Monday, September 21, 2026 at 12:04:34 PM CDT, Ray Fantini <RAFANTINI at salisbury.edu> wrote:

#yiv3943579038 P {margin-top:0;margin-bottom:0;}Moisture is the enemy of all Carbon microphones.  I have a fifty-call ammo can that I keep the microphones, headset and other stuff like that in on the Mutt. Its watertight and also keep a bag of desiccant crystals in it and looks right at home with everything else. Smaller thirty-call cans can be useful but more fits in the fifty. 

Ray F/KA3EKH

From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> on behalf of Mark K3MSB via MRCA <mrca at mailman.qth.net>
Sent: Monday, September 21, 2026 11:36 AM
To: Military Radio Collectors Association (mrca at mailman.qth.net) <mrca at mailman.qth.net>; ARC5 <arc5 at mailman.qth.net>; List Milsurplus <milsurplus at mailman.qth.net>
Subject: [MRCA] Care and feeding of radios in the field

I just returned from another reenactor weekend at the Eisenhower Farms WW II weekend in Gettysburg PA.   I had a great time and will provide an AAR later.

The temps during the days varied from the mid 70s to low 80s,  but at night the temp dropped into the 60's with intermittent light rain.

Each day when I terminate operations I place a tarp over the entire display.  It completely covers all sides down to the ground.    I do this for two reasons.  Our tents are old and have small holes and I don't want the radios to get wet if it rains.   Secondly, it keeps dew from forming on the radios, even though this really doesn't happen all that much as the tents are completely closed up at night.

So, I think I've addressed rain / dew issues.

But what about overall moisture?  

I put my (carbon mic) T-17s in a plastic bag overnight.

After each reenactment event, the radios are stored in my temperature / humidity controlled shack.  If the weather was damp or rainy,  I put all radios on any available surface to ensure they are “aired -out” sufficiently for several days (with the dehumidifier running......).

What can I further do to take better care of my radios in a setup/teardown field environment?

Thanks & 73

Mark K3MSB______________________________________________________________
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