"ml" wrote in message
...
hi

i have a general shielding question i realize that overall it
might be a impractical thing to build but looking at it i wonder...

ontop of my roof is elevator room it's about 20x20

flat roof

lets suppose the motor controller throws out 1.7 to 30mhz at
s9+ (all over)

lets say i take a single 20x20 sheet of copper put it on the top
roof (assume i could ground it if need be)

lets say before i put the copper i measured s9

what shielding if any might i see "S" wise??

i understand interference would still be radiating form the rest
of the unshielded structure but wondering if measuring ontop of the
copper sheeting id' observe any attenuation?? meaning would the
signal penatrate that copper? -- and if so around how
much??(alot/very little)


tnx
the copper sheet would likely not help shielding of the rf. it would
conduct the currents nicely and maybe redirect the fields a bit, but the
current would conduct out to the edge, right on around to the bottom and
radiate just as well down toward you as up away from you. I would assume
from your reference of an elevator room that this is a relatively tall
structure, so grounding is not going to help. the lengths of the ground
leads would make them also nice radiators for the rf from the motor, perhaps
making it worse if they were close to your antenna. Better to filter power
lines to the motor and controller and stop the noise inside the case... once
its out there is very little you can do to stop it.