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#70810 10/13/06 08:27 PM
Joined: Dec 2002
Posts: 228
J
JCooper Offline OP
Member
I can't I can justify the cost for this but I was trying to figure out just how I can turn my entire house into a faraday cage. I can line the walls with copper mesh, drive a whole bunch of ground rods, convert cable & telco over to fiber outside the house, but there is one piece I can't figure out, power.

My question is this, can you isloate utility power from an EMP?

I thought about a natural gas genset, fed with plastic pipe of course, inside the 'cage'. Would a simple isloation transformer provide true isolation?

#70811 10/13/06 08:29 PM
Joined: Jan 2003
Posts: 4,391
I
Moderator
I just use tin foil bed sheets.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#70812 10/13/06 08:59 PM
Joined: Sep 2001
Posts: 806
N
Member
First of all, TEMPEST shielding and EMP suppression are not exactly the same thing.

TEMPEST has to do with reducing radiation FROM equipment which could be intercepted by someone on the outside. Involves a lot of heavy shielding, broadband filtering/bypassing, etc.

EMP suppression is for the protection of your equipment. It can be achieved by LC filtering and fast-acting impulse suppressors like these:
http://www.polyphaser.com/kommerce_productdata.aspx?search_val=NEMP&x=0&y=0

Yes, utility power can be bypassed and filtered where it enters a faraday cage. It is done all the time in screen rooms used for RF equipment testing.

#70813 10/13/06 11:37 PM
Joined: Jan 2005
Posts: 5,445
Likes: 2
Cat Servant
Member
In response to a similar query.. "how can I protect my electronics from EMP?", I recall the following expert advice being given:

"Place them inside a steel ammo box. Ste this box on a block of wood, inside a larger ammo box. If the EMP still damages your electronics, you are way too close to ground zero."

#70814 10/14/06 02:51 PM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
What are you trying to protect against. That will make the difference in what you need


Greg Fretwell
#70815 10/16/06 08:44 AM
Joined: Mar 2005
Posts: 1,213
S
Member
There's an unclassified army manual for EMP-proof facilities design, EP 1110-3-2. All your answers are in there [Linked Image] The amplitudes are completely different between EMP and TEMPEST and frequencies vary a little, but the level of attentuation and design for protection for both is practically identical.

To get 90dB attentuation, you can't just use tin foil, you have to use a significant thickness of steel or copper or another conductor, otherwise a significant portion of the EMP burst will transmit straighit through it and still come out the backside at reduced but dangerous levels. The thickness depends on the frequencies and desired level of protection, and of course the material being used- welded 1/4" carbon steel will provide this protection.

You can buy filters for power and communication lines that provide > 90dB protection.

#70816 10/16/06 11:29 AM
Joined: Sep 2006
Posts: 98
A
Member
There is a cave in Newton County, Arkansas for sale for about 1.5 Million that should suit your requirements. You can't hide from all of it, forever, and then there are telemarketers...

#70817 10/16/06 11:34 AM
Joined: Dec 2003
Posts: 751
E
Member
Build your own with 4 foot thick reinforced concrete walls and ceiling, bonded to about 2 dozen ground rods. Power would be supplied by an on site generator, or a nearby set of batteries with inverter, which could be kept charged by the utility power.


Earl
#70818 10/16/06 10:36 PM
Joined: Feb 2003
Posts: 231
R
Member


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