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Re: Preventing a REALLY expensive mistake.
Original poster: "Steve Cook by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Steve-at-g8cyerichmond.freeserve.co.uk>
One of our local computer centres was modified a few yeasr back to tunr the
whole building into a faraday cage. They used a carbon fibre woven material
over the outside of the building and then re-clad it.
As to hole size, provided that the holes are smaller than a 1/4 wavelength
long at the highest frequency of interest you should be ok. Now as the
amount of energy in a Tesla coil output is relatively low once you get up
into the Gigahertz region, 1/2 chicken wire should be ok, it is necessary to
make sure that you have an effectively continuous surface by linking
As to cables fed into and out of the cage, you need to make a lossy choke,
rated at a high enough current loading. One method that I have heard of has
been to make a large co-axial choke by feeding the cable through a tube
filled with ferromagnetic material.
----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
Sent: Thursday, February 22, 2001 2:57 PM
Subject: Re: Preventing a REALLY expensive mistake.
> Original poster: "Christopher Boden by way of Terry Fritz
> >Hey Boss!
> Matt! :)
> >Back in my school days (before brother Noah and his ark) There was a HV
> >across from the Engineering computer center. The "brain rooms" contained
> >IBM 7094, a 1620, and a new System-360.
> he he he "NEW"
> Just to be on the safe side, the
> >brain rooms had metal screening behind the wallboard, above the drop
> >under the floor panels, and on the backs of the doors (there were no
> >windows). this screening was all grounded. The HVEEs claimed that the
> >reinforcing rods in the lab made the screening unnecessary, the CIS
> >were never convinced.
> >Eventually, a new computer center was built and the HV lab abandoned.
> >Matt D. G1-1085
> Ok....several people have addressed wire in the walls, etc so I'm going to
> see if I can pass/fail that one right now. I'm hoping I'm wrong....
> Doesn't a Faraday cage only work if it's a COMPLETELY ENCLOSED room? I
> mean airtight (but there is a specific maximum size hole for a given
> frequency protection limit)?
> And if I do spend the time/money in caging my High Voltage Lab, Computer
> labs, or both the second I plug the computers in to the AC, Ethernet, or
> other antenna (wire) that passes outside the cage (into the wall or
> room) haven't I just defeated the cage?
> If there is a way around the wire issue and a secure cage can be built. I
> need a DEFINATE size maximum hole. Chicken wire is great, but the HOLES in
> chicken wire vary considerably. I know the math Gods can help on this. :)
> ok, on to the next one. Sorry to play Devils advocate guys, but I need to
> SURE on this one.
> Christopher A. Boden Geek#1
> President / C.E.O. / Alpha Geek
> The Geek Group
> Because the Geek shall inherit the Earth!
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