Maker Pro
Maker Pro

Building Faraday room

M

MassiveProng

Jan 1, 1970
0
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.
 
M

MassiveProng

Jan 1, 1970
0
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
 
M

Meat Plow

Jan 1, 1970
0
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


--
#1 Offishul Ruiner of Usenet, March 2007
#1 Usenet Asshole, March 2007
#1 Bartlo Pset, March 13-24 2007
#10 Most hated Usenetizen of all time
Pierre Salinger Memorial Hook, Line & Sinker, June 2004
COOSN-266-06-25794
 
M

MassiveProng

Jan 1, 1970
0
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.
 
N

Neimadre

Jan 1, 1970
0
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?


Usenet lits score:
GIT-R-DONE!
#20 Usenet asshole
#6 Lits Slut
#11 Most posting trolls/hunters/flonkers 2007
 
M

Meat Plow

Jan 1, 1970
0
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.

--
#1 Offishul Ruiner of Usenet, March 2007
#1 Usenet Asshole, March 2007
#1 Bartlo Pset, March 13-24 2007
#10 Most hated Usenetizen of all time
Pierre Salinger Memorial Hook, Line & Sinker, June 2004
COOSN-266-06-25794
 
§

§ñühw¤£f

Jan 1, 1970
0
Date: 08 Apr 2007 15:03:49 GMT
Lines: 29
Message-ID: <[email protected]>
NNTP-Posting-Date: 08 Apr 2007 10:03:49 CDT
X-Trace: DXC=Poed>lB1BiA^U?2PSQ;N\E]AGWjF5PjPI465Ue@WB_5O5cm?k:2\:HE]nK=3`F;XSKY9S_[G10WaJQ>k10okE<LLnXbS:e>mh2H
Xref: number1.nntp.dca.giganews.com alt.usenet.kooks:1499483 sci.electronics.design:772773 aus.legal:196996 aus.electronics:137667

Meat Plow <[email protected]> pinched out a steaming pile
of said:
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*...
 
D

Demon Lord of Confusion

Jan 1, 1970
0
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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Remove all the confusion and k00ks from my posting addy to send me your
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Message-ID: <[email protected]>

"You are the GOD-DAMNED, IGNORANT LIAR here.
Now, that is not me taking the Lord's name in vain."
-- John Wentzky: Living proof of the Death of Irony, in Message-ID:
<[email protected]>

I mourned:
The Mop Jockey did most oddly state:

Alas, all I get for my trouble is a Monkey that's trained to hurl shit
under several of my nyms.

"DevMcKinHole, you also get the pleasure of sucking off my doggy and
cleaning out his butthole with your tongue." -- He's not so much a
*Porch*Monkey as a _Fire_Monkey, as in one who's on fire due to his
own tendency to mess with lighter fluid while standing beside a hot
stove. Message-ID: <77Uxh.1996$384.1135@trnddc05>

Said I:
You, Monkey-man, are quite possibly the only usenetter in existence
who does not and cannot own Hatter.

"[...] What's the matter fagboi, am I beating your as$ so badly that
you're no seeking an alliance with the diaperboi?...YOu really don't
know how dumb you are, do ya?" -- I guess I don't, Monkey.
Message-ID: <gHVIh.1760$Bi2.1639@trnddc01>

"Ok, but I am not stalking Teh Mop Jockey, I seem to be building a
relationship with him. Remember, I am a Christian so the secular rules
do not apply to me. I strive to be amoral, which I think applies to this
situation. Keep this in mind, please. Since I am currently mentally ill
and since I can not nominate, that is what I am doing at this time." --
Olympiada: Teh amoral "Christian", in Message-ID:
<[email protected]>

"You're like some kind of rabid attack-gerbil." -- Lionel Lauer to Joxer
in MID: <[email protected]>

"I say you are out of your fucking mind." -- Ying Guo, posting as
"SameAsB4" <[email protected]>, tells PorchMonkey4Life, posting
as the same nick but a slightly different morph, the score, in MID:
<[email protected]>

"in the holy spirit i know you would satisfy every single person in a
room if you were the only person present." -- ~tanya, to Crazy Andy II,
in MID: <[email protected]>

If you never read anything else in any of my sigs, read this:
http://www.msnbc.msn.com/id/15321167/
http://borealin.livejournal.com/15104.html
Or watch it here:
Then, if you manage to read/watch all that, try this:
http://www.newamericancentury.org/RebuildingAmericasDefenses.pdf
And Molly Ivins had a few choice words to say about it, weeks before:
http://www.truthout.org/docs_2006/092906B.shtml
Here's Chris Floyd: Fatal Vision: The Deeper Evil Behind the Detainee
Bill: http://www.truthout.org/docs_2006/100206A.shtml

"Q: What's the difference between the Vietnam War and the Iraq War?
A: George W. Bush had a plan to get out of the Vietnam War." -- Anon.

Thread where outing begins: http://tinyurl.com/hojf8
George Pickett Memorial Trophy, Special Ops Cody Memorial Purple Heart,
and the Order of the Holey Sockpuppet winner <[email protected]> on
outing personal contact info in x-poasted subject lines:
"Plenty of people post under their real names and do not attempt to hide
their contact info. You are scared of being 'outed' because you are a
pathological abuser of usenet, and people rightly despise you for it.
You're afraid of being reported to the authorities or, better, visited
by a couple of guys with baseball bats. Other people don't have this
obsessive fear. Ward Hardman himself has posted plenty of personal
information - nothing that anyone else added was hidden in any way.
You're so fucking scared you've built up this whole sick mythology about
different categories of bad dudes who 'out' scum like you.

"Meanwhile you are the ugliest pigfucker in the universe. You are the
coward without ethics. You call me a 'newbie' - ha! what an asshole you
are. Those who want to remain anonymous do so. There is absolutely no
way you could identify me, not unless you had the sort of subpoena power
that only gets turned on for big-time terrorists. That's because I chose
to be anonymous. Some people don't. Only really stupid dicks like you
choose the sort of semi-anonymity which leaves you in constant fear.

"What a dickless wonder you are 'Snarky' you fat asshole."
-- in MID: <[email protected]>

"I am the only one who has outer filthed Ward" -- James C. "Crackhead"
Cracked voluntarily self-immolates, in MID:
[email protected]

"When I told Abbie Hoffman that he was the first one who made me laugh
since Lenny Bruce died, Hoffman said, "Really? He was my god." The
combination of satirical irreverence and sense of justice that Bruce and
Hoffman shared was the real spirit behind the Yippies--a term I coined
to describe a phenomenon that already existed: an organic coalition of
stoned hippies and political activists who engaged in such actions as
throwing money on the floor of the New York Stock Exchange, then
explaining to reporters the meaning of that symbolism. Folksinger Phil
Ochs summed it up: "A demonstration should turn you on, not turn you
off." So when journalists link the Yippies with misleading bedfellows,
at best it's careless shorthand; at worst it's deliberate demonization.
Osama bin Laden wanted an aircraft to crash into the Pentagon. Abbie
Hoffman merely wanted to levitate it." -- Paul Krassner,
http://tinyurl.com/ehu3v

To Whom It May Concern: Michael J. Cranston attorney kook is a dogfucker
 
I

Ian

Jan 1, 1970
0
Paul Mathews said:
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
 
M

MooseFET

Jan 1, 1970
0
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

g

Jan 1, 1970
0
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
 
G

GregS

Jan 1, 1970
0
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

Jan 1, 1970
0
Date: 09 Apr 2007 15:10:13 GMT
Lines: 46
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
steaming pile of said:
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!!!

:)
 
W

whit3rd

Jan 1, 1970
0
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

Jan 1, 1970
0
Date: 09 Apr 2007 15:10:13 GMT
Lines: 46
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
steaming pile of said:
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!!!

:)
 
J

jasen

Jan 1, 1970
0
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
 
B

Barry Lennox

Jan 1, 1970
0
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
 
J

John E.

Jan 1, 1970
0
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.
 
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