Faraday Cages

I promised to tell you how to build a Faraday cage with the foil and mylar blankets we are adding to our General Store this week. Now is the time to act to protect your electronic gear.

To be adequately shielded, electronics must be kept inside a completely enclosed metallic structure known as a Faraday cage. Nested Faraday cages offer even more protection for those closest to the attack, just in case. A Faraday cage is an enclosure surrounded by a good electrical conductor such as copper or aluminum. Large Faraday cages to protect computers and even power stations, are possible but more complicated and very expensive. For small electronics though, the task is very simple.

There are just a few simple but important points to remember.

1. Foil or metal should not touch the item placed inside or the EMP will be conducted back to the item you are trying to protect, destroying the electronic components.

2. Items must be completely covered with no gaps in the protective covering. The EMP will be conducted around the outside of the container preserving the items inside.

3. You will have no warning of an EMP attack so items will need to remain in the cage until needed and should be returned immediately after use.

4. Consider carefully which items you want to protect. Cell phone towers will be destroyed so storing a cell phone may be a waste of time. The same is true of convenience items such as hair dryers. The only reason to protect these is to avoid the cost of replacement later.

5. Adding more layers of foil or metal will do no good unless there is a layer of a non conductive material between the layers of metal. This is the same principle as layering clothing during a cold weather emergency. Simply adding more layers is not as good as adding clothing that is larger and allows air to become trapped between the layers.

6. Remember to protect cords. They must also be completely covered by a metal shield. Antennas also need complete protection.

A few options:

A Faraday cage can be built using two cardboard boxes. Place your items inside the smaller box. Be sure the box does not have any openings in the cardboard. If it does layer some more cardboard or place your items into a heavy duty plastic bag before placing in the box. Cover box completely with aluminum foil or a mylar space blanket. The blankets are great as they cover completely for much less money than the foil. Place the smaller box into the larger and again wrap the larger box completely, sealing it, with a mylar blanket or foil. Be sure the foil is taped securely to prevent tearing. Many advise to attach a ground wire at this point but the demonstrations I have seen did not include a ground. The impulse simply travels around the metal covering looking for a way in until it dissipates.

A military ammunition box can also be used as a Faraday cage. Wrap foil all the way around the gasket to form a seal, metal on metal. The inside of the can should then be lined, completely, with a non conductive material such as cardboard or foam. Do not use duct tape to seal spaces in the non conductive material. Once that is done the items can be placed inside, the lid closed and latched, and you are good to go.

You can also construct a cage using 2x4s and copper or aluminum mesh. The cage lid can be hinged for access but remember the mesh must to touching everywhere to provide protection. You cannot just staple the mesh to the wooded frame, it must touch metal to metal or a pulse can get through.

A microwave oven can also be used as a Faraday cage. Remove the power cord completely, place items inside and seal the vents and hole where the chord was with foil, mylar or metal mesh. Naturally, this is a microwave that is already dead as once you remove the chord it is no longer good for cooking.

A galvanized trash can or a large aluminum stock pot can also be used as a cage. You just need to be sure you have a good seal and there is metal touching metal all the way around the opening. As always your items being protected cannot come into contact with the metal.

Items to place in your cage may include, HAM radios, battery powdered radios, fuses, batteries, spare parts for tube radios, replacement components for your generator, and any other item which will be able to work separate from the electrical grid.

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3 Responses to “Faraday Cages”

  1. judy says:

    What’s the point of this information on Faraday cages? –I’m supposed to put all my electronic equipment in metal boxes on the chance there will be an EMP God-knows-when, with no warning? It’s just not a practical preparedness tactic. If there is an EMP, the best thing I can do is be prepared to live WITHOUT my electronics!

  2. admin says:

    Judy, I’m sorry you feel that way. I have fuses for our old car, batteries and our older HAM radio in a Faraday cage. In the event of an EMP I will be able to communicate with the outside world to let them know if we need help and also to understand what help may be coming and when to expect it. Also, when to expect the grid to be back up and where I can go to evacuate where they may still have power. You should concentrate your preparation where you see the greatest need but I believe it is my responsibility to discuss all the possible scenarios. If you have not followed the posts about EMP and Solar flares you may not realize that countries such as Iran and terrorist groups have already made threats to use these weapons so it is worth consideration. As with every aspect of preparing we must all do the things we feel are the most important and we all must pick and choose. The most important thing is that we are all doing something.

  3. Finding websites with as much information as this one is always a pleasure I wll be sure to come back and visit again real soon, keep up the good work.

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