On Mar 22, 6:20*am, Richard Fry wrote:
On Mar 20, 11:49*pm, Art Unwin wrote:

*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. ...* 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! ... Where has my intuition
gone wrong in opposing the books?

If reality will help shape your intuition, then you may be interested
in this paste-up from an IEEE paper linked below.

Note that the spacing of the conductors in the mesh forming these
cavities is much greater than your intuition says is required "to
create a blocking effect."

http://i62.photobucket.com/albums/h8...Cavity_Radiato...

RF

Interesting. thank you.It would appear that they are using approx .1
lamda sections but the beam pattern appears to be what is expected
other than the differential between E and H
as shown on my page.
Ofcourse it doesnt show how it is fed which can make a lot of
difference.The size of the squares really determine whether the
currents slides across the surface or follow a paths per a normal
radiator. I certainly would not feel comfortable using such openings
as protection against lightning.