On Sat, 20 Mar 2010 21:49:42 -0700 (PDT), Art Unwin
wrote:

If on places a am/fm radio inside a box made of thin aluminum foil the
radio will be able to hear am broadcast band but not the fm band.
(Experiment by Harvard in Boston)
Intuition tells me that when using a perforated plate the lower the
frequency then the smaller the perforations in the shield to create a
blocking effect. This would, I believe, opposes the progression of
skin depth with respect to frequency.
The books state for a mesh shield the perforations should be less
than 1/10 of a WL which on the surface opposes the results obtained by
the box experiment! Is the difference involved with calculations
changes for sheets that are thinner than skin depth such as circuit
board traces or something else?
Where has my intuition gone wrong in opposing the books?


Shielding and grounding is a secret science, so secret and of military
importance that Don White Consultants would not teach foreigners
(damned furriners) how to shield a building from EMP.

w.