Oh yeah, I know they're fine when used properly. I just had an image
in my mind of 3" screws holding on lathe through 2" of foam board, and
then thought of how easily I can break off a screw that is hanging out
that far. Even with a good stucco mix, it seemed like it's not quite
enough for a good building- some of these things are designed to a
hair's breadth of disaster.
LOL... I often wonder it all that steel would be a problem with radio or
TV reception from indoor antennas.
That said, my house has an Aluminum roof that looks like Cedar Shakes. No
reception problems at all.
The only effective RF shield is a continuous metal grid on all sides,
top and bottom. It is called a Faraday cage. So, if you have a metal
layer in both the subfloor and ceiling, and all of those studs are
electrically connected to them and each other, and you install metal
cross braces every 16", you would reduce the strength of all signals
below about 300 MHz, so channels 7 to 13 might have more snow than the
neighbors do, but 2-6 and FM would be much weaker. The commercial AM
band would be much weaker still, which might not be a bad idea.
For any one interested in the theory, a wire mesh screen will reflect
signals whose wavelength is longer than twice the size of the space
between the wires. Twice 16" would be 32 inches, just less than one
meter. For a wavelength of 1 meter, the frequency is 300 MHz. The
reflection is not total, and the change is not instantaneous, but
gradually becomes exponentially stronger as the frequency drops. At
300 MHz, the signal would be half reflected. at 150 MHz about 3/4,
etc. FM broadcasts are grouped around 100 MHz, between TV channels 6
and 7. AM is way down at 1MHz.
On the other hand, a steel building sitting on the ground pretty much
Good explanation bob. After saying something, I started to wonder exactly
how much steel was in a house. Probably varies depending on the builder.
effective RF shield is a continuous metal grid on all sides,
As an interesting aside, my window shaker AC unit in the bedroom plays
music very softly when it's running. Took quite a few times getting
up to see which radio had been left on before I tried turning that
off, and the quiet tunes stopped. Must be some kind of wierd thing
with the fan spinning inside a farraday cage, or my brain is just
filling in the static, though it doesn't happen with a white noise
machine. I figure it's probably not me, though- it's usually stuff I
don't listen to, and comes complete with commericals.
Could be, but I'm in an awful quiet neighborhood- and the outside air
vent stays closed to keep the humidity out. Probably some oddball
combo of directional placement, circuit boards and dental fillings all
aligned "just so".
Nah- it's just weird. By the time my head hits the pillow, I'm done
for most nights, so it's really not a problem. Working 12+ hours in
the sun on a day when you *need* a/c is better than a sleeping pill-
the neighbors could be blasting heavy metal next to the window, and it
wouldn't matter a bit.
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