[Premium-Rx] Faraday Shield.....To Be, or Not to Be?? Need ad vice, please!

[Carcia, Francis A HS]

I was looking at doing that but the foam panels will be a lot easier to
install and the extra R6.5 helps. Aluminum foil
might get used in the corners. Running 1500 watts 40 feet above the roof
generates a good field at 30 MHz.
The foam is two layers of shield an inch apart, even more effective.  fc

-----Original Message-----
From: Gary Geissinger [mailto:ggeissinger at digitalglobe.com]
Sent: Wednesday, January 05, 2005 5:53 PM
To: premium-rx at ml.skirrow.org
Subject: RE: [Premium-Rx] Faraday Shield.....To Be, or Not to Be?? Need
advice, please!


A couple words about building a screen room.
 
1.  Believe it or not, you can shield a room with aluminum foil.  It's best
to use a 50% overlap and fold all the corners just right.  This is described
in several NSA documents.  Done correctly, you can get at most 60 dB of
shielding effectiveness this way.  You can't get more, because you would
need mu-metal (or other magnetic material), etc for the mag shielding
required.  There is a section of this document at:
http://cryptome.quintessenz.at/mirror/emp12.htm
<http://cryptome.quintessenz.at/mirror/emp12.htm> .  If you want to trade
off other shielding materials, there is a "Perry-Graf" "shielding design
guide available from Instrument Specialties Corp (717-424-8510).
 
One additional comment.  I have seen this done almost invisibly.  You sheet
rock the room normally, with a plywood floor, but of course use EMI filters
on lights, power connections, phone etc.  Then you apply the aluminum foil
as described above.  Then, you apply another layer of sheet rock over the
aluminum foil.  If done carefully, with aluminum foil, or something
(screen?) under the tile (on top of the plywood floor), with a door as
described below, you can do this so that only a trained eye can spot it.
 
2.  For the door, a steel fire-proof door with matching steel door-jam and
kick plate work great.  Use the lighest fingerstock you can find on the
seams.  Some folks just use braid to connect the door to the jam, but I
can't believe that is adequate.  If you have room, you don't need a door at
all.  Just make a "serpentine" path to walk through and line the pathway
with RF absorber.   Frankly, for home use, the steel fire doors make more
sense.
 
Ed, feel free to email me directly on this.  I have fought this problem
several times...I think I won!
 
Gary WA0SPM
ggeissinger at digitalglobe.com
 
 
 
 

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-----Original Message-----
From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of Aidehua at aol.com
Sent: Wednesday, January 05, 2005 3:00 PM
To: premium-rx at ml.skirrow.org
Subject: [Premium-Rx] Faraday Shield.....To Be, or Not to Be?? Need
advice,please!



I am building a radio room for my Premium-Rxs and transceivers from scratch,
and was wondering the pro-and-cons of constructing a totally shielded
(screen room) approach, with bypassed 120, and multiple short grounding
paths to the earth (all bonded, of course!).  In other words, a Faraday
shielded room for ultraquiet conditions and maximum RF suppression.  I am
turning to the experts on this List, as I'd like the appropriate guidance.
Your input is appreciated!  Happy New Year!!
 
73,
Ed NI6S  


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