Very interesting.

There's a little data on the RF properties of such things, but it's
pretty sparse and limited in scope.

Seems to me that the thing to do would be wind a big air core coil, and
measure its inductance and Q. Compare that to the inductance and Q with
the material under test inserted into the center of the coil. Given
similar size samples, that should at least give an indication of
comparitive loss and dielectric constant of the materials. Quantitative
results could probably be had with a bit of thought and calculation.

Or maybe just stick a plate on each side of the sample to make a
capacitor, and measure the capacitance and Q. One method would probably
work better for some materials and the other for others.

There's no doubt that water is really bad stuff at HF.

Roy Lewallen, W7EL

Crazy George wrote:
Roy:

I get the impression that building materials survive by being full of water.
I had the chance to measure cinder blocks which had been dehydrated ( poor
RF) and watch them gather moisture over a year or so (really, really bad
after a year). And that was inside an air conditioned lab. I suspect the
process would have taken only days outside in our 90%+ humidity.

Sheetrock = bad, moisture
Clay tile = better, glazed to prevent moisture penetration
wood = bad, moisture, even after years in 100 degree attics, interestingly
enough.
Styrofoam with a thin polymer coating (various proprietary wall systems), =
pretty good, unless the interface wicks moisture in because the wrong glue
is used.
ad nauseum
--
Crazy George
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