Faraday cages (was Re: VAX 6000 3-phase conversion (was: Re: Three Phase)

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Sun Apr 22 14:43:16 2001

At 12:34 PM 4/22/01 -0600, Clint Wolff (VAX collector) wrote:
>Speaking of Faraday cages, how would one go about doing this?
...
>The cages I've seen are made from an expensive copper screen,
>like window screen, but they are for doing FCC interference
>measurements, not shielding. I can get 1/2 inch square fencing
>from the look home improvement center, but it is galvanized and
>quite a bit coarser...
...

Well the simple answer is you build a cage and you put your stuff in it
:-). Aluminum is actually a fine material to make them out of as long as
you don't allow the joints to get oxided up (Aluminum Oxide is an
insulator!) "Holes" in the screen have to be smaller than the wavelength of
the signal you are blocking. Thus if you are blocking microwaves (< 5mm)
then you need to have holes smaller than that in your screen. The biggest
issue we have at work with our cage is to make sure things transiting the
cage (like power cables) don't have any RFI on them. The power goes through
the cage to an isolation transformer then to the gear to help suppress that
stuff. You can also get conductive paint that works ok for just shielding.
(not tempest certified :-)

--Chuck
Received on Sun Apr 22 2001 - 14:43:16 BST