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Shielding: copper foil vs Antistatic foam (on power umbilical)

Posted by Elizabeth on April 9, 2011 at 18:45:01:
Ok the pwer suppy for my VAC Stadard puts out a ton of electromagnetic radiation (tested with non contact A/C voltage detector.
I solved the PSu itself with a VPI 'brick' on top, and a real patio brick on the side away from the wall.
I then tried to completely wrap the PSU umbilical with copper foil, then over the copper some aluminum tape (both at hand). Well the foil worked when it was loose, just blocking the direct path between the umbilical and Greenlee Votage detector, But once it was wrapped around the cord. No good. The energy was as strong radiating from the cord as before AND the sound of the tube preamp suddenly got strident. Total failure. Cut the stuff off the unbilical.
TThen i had a bit of antistatic foam left. I cut into stripes and wrapped the stripes down the umbilical cord with blue Aussie Teflon pipe tape (thick, like pink tape) So the flat foam was rolled up as a tube around the umbilical, and the teflon compressing it slightly and closed the foam gap in the open side.
This worked perfectly. Zero emmisions detectable from the PSU umbilical cable, and the sound was NOT damaged from the VAC.
So if you ever want to wrap a wire to prevent EMR radiating FROM it, forget copper or other blocking/reflective stuff, and use an absorptive thing like the antistatic foam.
(If the EMR is outside and you want to protect the wire from it, then the copper or other shield is the way to go.)
Just thought i would relate my experiment.