My Faraday Cage Test

[The Expendable]

I've heard people talking about using steel filing cabinets as Faraday cages. Sounds logical, but how effective is it? I had some steel boxes that I was planning to use as Faraday cages, and I wanted to test them for myself. I've read that while copper is the best material to build a Faraday cage out of, aluminum is a good second choice. Although I'm not an expert by any means, I've experimented with both steel and aluminum and found aluminum to work better.

My testing used cell phones and FRS radios. I have read that the frequencies found in the E1 pulse of an EMP are similar to those found in cell phone signals. I'm not 100% sure this is true, but I needed a starting point so that is what I used.

I placed a cell phone in a cardboard box, then placed the cardboard box inside a sealed steel box. When I called the cell phone it rang. Then I took the cardboard box out of the steel box and wrapped it in aluminum foil. When I called it I was sent directly to voicemail (i.e., no signal was reaching the phone). I did the same test using FRS walkie-talkies and got the same results... I was able to send a signal to the radio in the steel box, but no signal was passed to the radio wrapped in aluminum foil.

I know this may not be conclusive, but I've ditched my steel boxes and built some Faraday cages using sturdy cardboard boxes covered with heavy duty aluminum foil and wrapped with aluminum Shurtape for strength.

This is a small Faraday cage I made out of a cell phone box. The good thing about this one is I can keep often used items in it and take them out as needed. Note how I wrapped the foil inside the lip of the box, on both the top and bottom. The inside of the box is uncovered cardboard, forming an insulating barrier between my small electronics and any EMP surge. When the box is closed, it makes a "full metal jacket", so to speak. The aluminum Suretape was used to strengthen the foil, but I could have used duct tape as well.

The bottom line is this: If you are planning on using a steel filing cabinet, or your washing machine, or your oven, or your microwave oven as a Faraday cage, put your cell phone inside it and try to call it. If it rings that means that cell signals can breach the steel structure. If cell signals can get through, your makeshift Faraday cage is not giving you any protection.

[Brownwater Riverrat 13]

OK I'll bite, "more input Johnny Five!" So that (in theory) should sheild from an EMP burst? Serious question, I would like to see some alternatives. Funny we spent much time worrying about CBR that EMP reallywent by the wayside.

Be safe............the night is your friend.

[The Expendable]

I am not guaranteeing that my aluminum foil Faraday cage will protect your external hard drive from an EMP blast, but I can almost guarantee that a steel filing cabinet won't.

[Brownwater Riverrat 13]

And I can garantee that if I bury it four feet underground with the front end loader of my tractor that it "will" protect it from an EMP burst. But my tractor won't be running when it's all said and done because of the eletronics, go figure. But hey, it sounds like you are on to something. Keep up the research.

Be safe............the night is your friend

[ak474u]

I may be bringing home some of the material we use at work to test it out, I work for a foil radiant barrier contractor, so I've got lots of uhhhhh, Samples laying around. I know a phone call gets thru after we do a house, and I have a bag that was made to show people radiant barrier doesn't ruin cell reception, but the phone is in contact with the bag when it's inside, so I may test that and post a result as well.

[The Stig]

Fantastic stuff. I love it when people test things out for themselves.

I love it even more when they share it with us.

[izzyscout21]

Expendable,

I think your experiment was very well thought out and informative. Thanks for the info.

[Alas Babylon]

Ex:
like you I too think about EMP, natural or man made.
Things are only protected when they are in the box, so what types of things do you think you would keep in the box all the time?
For me, it would be FRS radios, my shortwave reciever..?
What other things should I be thinking of protecting? Space would be limited,so what do you, and all the rest of you, consider important electronics to protect?

[izzyscout21]

I'm thinking of making several of these, lining them with hobby foam and putting all my sensitives in them,. Be a lot easier to store, protect, and stack them.

[Evolver]

Nice!!! for those that don't know what Shurtape is... it's a Aluminum Foil tape to seal Ac and heating ducting that has been joined together and is found at most hardware stores in the AC/heating ducting section.