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Faraday cages

(Radio's), (GPS), (Faraday Cages), (Other Technology)
prepperhelen
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Re: Faraday cages

Postby prepperhelen » Wed Nov 21, 2012 4:00 am

alrighty, so what would i insulate my garbage or cookie tin with?
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ICRCC
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Re: Faraday cages

Postby ICRCC » Wed Nov 21, 2012 4:43 am

First your metal garbage can or cookie tin needs to have continuous conductivity around the lid. Once you have this you need to insulate the inside of the container so that the contents do not touch the container. In theory any electrical insulating material will do. However I would tend to go with thicker rather than thinner. Cardboard could be used but any form of flexible plastic or Styrofoam would probably be better. Also grounding the cage is not necessary unless you are planning on operating electronic equipment within the cage that will be using an external power source or antenna (not recommended). Although not up to anywhere near military specs such a Faraday cage would be more than adequate for home use.
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prepperhelen
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Re: Faraday cages

Postby prepperhelen » Sun Nov 25, 2012 4:32 am

so garbage can lined with cardboard but the lid has to touch metal all around. so after sealing wrap that tape the other guy was talking about around the outside lip where the lid meets container?
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ICRCC
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Re: Faraday cages

Postby ICRCC » Sun Nov 25, 2012 5:49 am

If you have continuous electrical contact around the lid you do not need the conducting electrical tape. However it would not hurt to have it.
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ranger2012
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Re: Faraday cages

Postby ranger2012 » Mon Nov 26, 2012 12:30 pm

Thats why I have been prompting the use of fine steel wool as a gasket.
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Dakota
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Re: Faraday cages

Postby Dakota » Wed Nov 28, 2012 10:00 pm

Mechanic friend of mine suggested using our garage as one big faraday. I'm thinking this would take a lot, windows, doors.
Any ideas on this?
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Denob
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Re: Faraday cages

Postby Denob » Wed Nov 28, 2012 10:42 pm

Metal garage?
Maybe, but there would be a heck of a lot of holes & cracks to deal with.
The idea is to create a metal container that would conduct the power around and away from the inside.
Metal cans using steel wool gaskets and conductive tape around the cover sound like great ideas.
I think I heard about using the earth itself to shield, but I can't remember just how deep it needs to be.
Also, has anyone come up with a definite answer on the grounding question?
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ICRCC
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Re: Faraday cages

Postby ICRCC » Thu Nov 29, 2012 5:58 am

A metal garage would also need a metal floor and it would have to be completely sealed and conductive even at the doors. So in a word no. A Faraday cage does not need to be grounded. If you are inside the cage operating equipment such as a transceiver it should then be grounded. For storage of equipment not attached to an external power supply or antenna no grounding is needed.
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BelowTheRadar
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Re: Faraday cages

Postby BelowTheRadar » Mon Dec 10, 2012 2:41 pm

Concerning a EMP proof container, wouldn't a simple check with a Voltage Ohm Meter (VOM) measuring the resistance between the lid and body of a container (and if the resistance is zero) predict the lack of passage of electromagnetic waves to the contents of the container? If the lip of the lid extends below the top of the container would this not block electromagnetic energy from entering the container providing continuity between the lid and the body of the container? Both CME and EMP energy will come from either above or the side of the container unless you are in an aircraft or space station above the blast. Does it not stand to reason that electromagnetic energy will fail to enter a conductive, sealed container with very few exceptions?

FEMA uses chicken wire to CME (if not EMP) proof their buildings. I'm thinking the gap between the lid and body of an ammo can (for example) would be smaller that the holes in chicken wire. If the lid and body of an ammo can are electrically conductive, I see no reason to suspect the contents of the ammo can be exposed to CME's. Please correct me if I am wrong.

Just asking,
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ICRCC
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Re: Faraday cages

Postby ICRCC » Mon Dec 10, 2012 3:20 pm

In a sense you are correct. However if you can imagine a 2m x 2m conducting metal plate with a 1m diameter hole in the middle, that plate would be conductive in anywhere that you measured it but it would be totally inadequate for a side to a Faraday cage. Now if you are reasonably sure that your lid to your cage (container) is conductive all the way around the perimeter and it tests ok with a multimeter then for our purposes you should be fine.

Try not to think of direction with an EMP. An EMP is a wave and waves travel around things. Ammo cans have a rubber seal which is none conducting. If I was using an ammo can for a Faraday cage I would remove the seal grind down or otherwise expose the bare metal around the lid and the top of can where the lid makes contact as mentioned in an earlier post. That way you would be reasonably sure that that you would have effective protection.

Chicken wire (depending in the gauge of the wire and the size of the mesh) may be effective in some cases of an weak EMP. It would not cut it for an HEMP. Here a major concern would be the frequency of the EMP. Personally I would not trust my sensitive electronics to chicken wire.
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