Grounding / Shielding Question

[Christopher_List at sonymusic.com]

Hi guys -

Couple of questions on the black art of shielding...

I was using my portable modular at a friend's studio this weekend. My stuff
was setup on a window ledge on the 15th floor of a building about 5 blocks
from the Empire State building (one of the radio antenna capitols of NYC).
Seems that my 3320 filter module picked up WPLJ (95.5FM) better than my
stereo at home, and noise in general seemed to be a bigger problem than in
my studio. Seemed strange that it would only be this module - some kind of
capacitor tuning I guess (?). With the module inputs grounded, I'd hear the
interference, turn the filter freq. down and it would filter the radio
sound.....

I've recently lined the inside of the (wooden) road case housing the
modular with a thick aluminum foil, connected from a single point to the
power supply ground. My hope was that this would help prevent these kinds
of problems, so I was a little frustrated....

Question - can shielding work like an antenna rather than a shield? What if
you're using a dual supply and the ground for the power supply isn't
connected to earth ground (like the power cable has a ground lifter on it).

Does the thickness of the material used for the shielding make a
difference?

Any other tips in this area of the synth builder's art would be very
welcome....

Thanks,
CList