Building Faraday room

[MassiveProng]

The skin depth is proportional to 1/sqrt(freq*mu*sigma), where sigma is
the conductivity. Iron's high permeability is a help at low frequency,
but not by as much as one would think from this calculation.

To think about shielding effectiveness, it's important to remember that
the concept of skin depth comes out of a perturbation theory problem.
The zero-order solution you start with is a perfectly conducting
boundary, i.e. E and H are zero at the metal surface. We often think of
RF shielding as a perturbation on the free-space problem, which leads
to underestimation of shielding effectiveness, because it assumes that
the fields on the metal surface are the same as the unperturbed free
space fields, which is far from true.

We also tend to get confused by analogies with light shields, which
makes us underestimate the importance of keeping the shield electrically
continuous. A truly continuous copper shield of any reasonable
thickness will eliminate all electromagnetic radiation from inside.

Iron is mostly important for quasistatic magnetic fields, e.g. from
power transformers.

I'd bet that you used to do "tempest" shielding work.

 

[MassiveProng]

The skin depth is proportional to 1/sqrt(freq*mu*sigma), where sigma is
the conductivity. Iron's high permeability is a help at low frequency,
but not by as much as one would think from this calculation.

To think about shielding effectiveness, it's important to remember that
the concept of skin depth comes out of a perturbation theory problem.
The zero-order solution you start with is a perfectly conducting
boundary, i.e. E and H are zero at the metal surface. We often think of
RF shielding as a perturbation on the free-space problem, which leads
to underestimation of shielding effectiveness, because it assumes that
the fields on the metal surface are the same as the unperturbed free
space fields, which is far from true.

We also tend to get confused by analogies with light shields, which
makes us underestimate the importance of keeping the shield electrically
continuous. A truly continuous copper shield of any reasonable
thickness will eliminate all electromagnetic radiation from inside.

Iron is mostly important for quasistatic magnetic fields, e.g. from
power transformers.

http://www.thehowlandcompany.com/index.htm

 

[Meat Plow]

Meat Plow <[email protected]> pinched out a steaming pile

Hmmm...whats that word...describes a bit of early audio-visual
equipment that displayed a moving picture on a screen...hmmm...oh
yeah...a *projector*...

heh


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[Neimadre]

http://www.thehowlandcompany.com/index.htm

Stop spamming my group asshole.


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[MassiveProng]

Stop spamming my group asshole.

There is not one soul in all of Usenet that could afford ANY of the
products or services that company provides, idiot.

Most certainly not your retarded ass.

 

[Neimadre]

There is not one soul in all of Usenet that could afford ANY of the
products or services that company provides, idiot.

I don't eat peanuts foolboy. But I see you do.

Most certainly not your retarded ass.

Nice, copy/paste?


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[Meat Plow]

Always believe that only you know the TRVTH.
You are the only sane one. -- from Teh Way of Teh K0Ok.

I know, I was just trying to point it out to him in a way he might
understand it better. Apparently that isn't possible.

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[§ñühw¤£f]

Date: 08 Apr 2007 15:03:49 GMT
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Meat Plow <[email protected]> pinched out a steaming pile

Why is everyone to you (but not you) a:

Kootard
Retarded Twit
Idiot
Dipshit
Pathetic
Total Loser

Why is it that you think you are the only rational/viable entity while
exactly the opposite is glaringly evident?

Hmmm...whats that word...describes a bit of early audio-visual
equipment that displayed a moving picture on a screen...hmmm...oh
yeah...a *projector*...

 

[Demon Lord of Confusion]

I know, I was just trying to point it out to him in a way he might
understand it better. Apparently that isn't possible.

I was just being blunt. Some people need that sort of treatment...

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Then, if you manage to read/watch all that, try this:
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To Whom It May Concern: Michael J. Cranston attorney kook is a dogfucker

 

[Ian]

There was a really good article in Compliance Engineering or one of
the ITEM publications a few years back comparing various low-cost
approaches to building screened rooms. Galvanized steel actually came
out the overall winner in the estimation of the authors, but some of
the really low-cost options considered were nearly as good at most
frequencies. The resistivity of the steel provides some benefits,
IIRC.
Paul Mathews

Years ago I came across some material that was being used for
a commercial screened room. It was 3/4" plywood with galvanised
steel sheet bonded to both surfaces. I don't know how they made
electrical connection between the sheets. Boy, was that stuff heavy!
I assume the sheeting is available off the shelf somewhere.

Regards
Ian

 

[MooseFET]

Years ago I came across some material that was being used for
a commercial screened room. It was 3/4" plywood with galvanised
steel sheet bonded to both surfaces. I don't know how they made
electrical connection between the sheets. Boy, was that stuff heavy!
I assume the sheeting is available off the shelf somewhere.

It was likely soldered. You use acid to etch the zinc off the surface
and then use an active flux.

 

[g]

I would like to build afaradaycage large enough to work in. Can
anyone please advise on the following points.

1. Will aluminium window screen work as well as brass? Are there any
more cost-effective materials?

2. How much does grounding influence the degree of shielding? I would
assume grounding is more effective for lower frequencies where
reflection is not as much of a factor. Can anyone quantify this effect
in Hz?

3. Now-a-days most aluminium screen is anodized. Does the insulation
this adds between each strand diminish its overall effectiveness in
grounded applications?

Thank you for any advice along these lines.

Steve

Most of the cages and rooms here are aluminum. New buildings were also
constructed of aluminum backed drywall. Aluminum frames are used for
the supports. I have no idea what question #3 is or
means. Please explain. You did not explain the degree of shielding
necessary and if there are strong RF fields around. Most cages here
are made to surpress 60 Hz static fields, however the new buildings
were made of aluminum drywall to help get rid of channel 13 TV across
the street.

greg

 

[GregS]

Most of the cages and rooms here are aluminum. New buildings were also
constructed of aluminum backed drywall. Aluminum frames are used for
the supports. I have no idea what question #3 is or
means. Please explain. You did not explain the degree of shielding
necessary and if there are strong RF fields around. Most cages here
are made to surpress 60 Hz static fields, however the new buildings
were made of aluminum drywall to help get rid of channel 13 TV across
the street.

Change that to Question #2.


greg

 

[§ñühw¤£f]

Date: 09 Apr 2007 15:10:13 GMT
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Message-ID: <[email protected]>
NNTP-Posting-Date: 09 Apr 2007 10:10:13 CDT
X-Trace: DXC=<\WNAF2hI:I1BR:d@Vje=C]AGWjF5PjPI465Ue@WB_5O:V8bn`42h4H]nK=3`F;XSKY9S_[G10WaJV@@>>hej[4G9Z[D\NW1OEK

The Ugliest Pigfucker In The Universe <[email protected]> pinched out a

I was just being blunt. Some people need that sort of treatment...

Yeah...anyway...the easiest way to build a faraday cage is with brass
screen and 1x2" lumber and a staple gun.
IT HEPLS KEEP TEH GUBAMINY FROM BEEMING RAYZ ITO MY BRANE!!!!111!!!

 

[whit3rd]

I would like to build a faraday cage large enough to work in.

1. Will aluminium window screen work as well as brass?

Some fittings (and sealing flanges on the doors) may be brass,
but the classic screen room is bronze wire cloth. Same as
used for screen windows on seacost locations (until
cheap fiberglass came out).

 

[§ñühw¤£f]

Date: 09 Apr 2007 15:10:13 GMT
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Message-ID: <[email protected]>
NNTP-Posting-Date: 09 Apr 2007 10:10:13 CDT
X-Trace: DXC=<\WNAF2hI:I1BR:d@Vje=C]AGWjF5PjPI465Ue@WB_5O:V8bn`42h4H]nK=3`F;XSKY9S_[G10WaJV@@>>hej[4G9Z[D\NW1OEK
Xref: number1.nntp.dca.giganews.com alt.usenet.kooks:1500884 sci.electronics.design:773358 aus.legal:197367 aus.electronics:138013

The Ugliest Pigfucker In The Universe <[email protected]> pinched out a

I was just being blunt. Some people need that sort of treatment...

Yeah...anyway...the easiest way to build a faraday cage is with brass
screen and 1x2" lumber and a staple gun.
IT HEPLS KEEP TEH GUBAMINY FROM BEEMING RAYZ ITO MY BRANE!!!!111!!!

 

[jasen]

galv sheet is avalable by the roll (in various widths) from the makers and, available cut to
length from resellers, maximum width is probably 2.4m (same as plate),
1.2M wide to match the ply wouldn't be a problem.

It was likely soldered. You use acid to etch the zinc off the surface
and then use an active flux.

Don't need to etch, just use acid flux.

Bye.
Jasen

 

[Barry Lennox]

I would like to build a faraday cage large enough to work in. Can
anyone please advise on the following points.

1. Will aluminium window screen work as well as brass? Are there any
more cost-effective materials?

2. How much does grounding influence the degree of shielding? I would
assume grounding is more effective for lower frequencies where
reflection is not as much of a factor. Can anyone quantify this effect
in Hz?

3. Now-a-days most aluminium screen is anodized. Does the insulation
this adds between each strand diminish its overall effectiveness in
grounded applications?

Thank you for any advice along these lines.

There was an interesting aticle in "RF Design" about 10+ years ago on
a very low cost screened room using aluminium foil.

Have you seen it? I believe I have the article somewhere, but could
take a while to dig it out.

Barry

 

[John E.]

Don't need to etch, just use acid flux.

And a *really* good filter mask and/or air supply. That galv stuff is nasty.
If you're going to torch it up, be sure you're not going to breathe it.