RE: Faraday Cage

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Basura, Brian by way of Terry Fritz <twftesla-at-uswest-dot-net>" <brian.basura-at-unistudios-dot-com>

Alan,

We've used digital video and digital still cameras from within my cages
without any problems or interference (YMMV)...

Check out the following links for a few images:
http://fp2.hughes-dot-net/brianb/farady.htm
http://fp2.hughes-dot-net/brianb/01222000.htm

Scope readings are another story. I'd use Terry's Fiber Probe's to isolate
things and keep all the test equipment far away from the coil...

Regards,
Brian B.

 -----Original Message-----
From: 	Tesla list [mailto:tesla-at-pupman-dot-com] 
Sent:	Friday, April 20, 2001 7:14 AM
To:	tesla-at-pupman-dot-com
Subject:	Faraday Cage

Original poster: "Kelly & Phillipa Williams by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <kellyw-at-ihug.co.nz>

Hi All!

I would like to take some pictures of my coil in operation, and other stuff
such as Ocsope waveforms, etc with a digital or electronic camera. However,
cameras with any sort of electronics in them freeze up and refuse to
function when with 20-50m of the coil in operation, and it causes our
cordless phone to beep haphazardly, and generally wreaks havoc with
electronic devices.  I am fairly sure the coil is in good tune, and it is
throwing about three 75" arcs to grounded wires at once. (crappy foil toroid
with sparp points all over it.)  It uses a single static spark gap.

Is this correct -
A metal Faraday cage blocks electromagnetic
radiation (radio waves) from penetrating it into the enclosure. The
electromagnetic radiation can get through a very thin slit in the side
of the cage, so it is the longest diagonal or horizontal or vertical
distance across a hole in the cage that determines whether or not radiation
can get in.  The frequency of the radiation determines the shortest slit
the electromagnetc wave can get through.

If this is all right (which I am not at all sure about), what is the
mathematical relationship between
frequency and slit length?

And can I make a faraday cage out of tinfoil or fine mesh such as a sieve,
but cut a hole large enough for the 5mm by 5mm arpeture of my digital
camera? That's 0.197 inches by 0.197 inches. So the longest slit (The
diagonal distance across the square) is 7mm or 0.276 inches.
Or is chicken wire fine?

My coil has a resonant frequency of 51 kHz.

I would welcome any information at all on faraday cages.

Thank you very much,

Alan Williams