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EMP Prepping: How To Build A Reliable Faraday Cage


EMP Prepping: How To Build A Reliable Faraday CageAn electromagnetic pulse that knocks out power across the country is one of the most terrifying disasters that could happen. Millions of people would slowly die of thirst, hunger, or disease, and millions more would die at the hands of starving looters.

There are many things you should do to prepare for an EMP, and one of the most important is building a Faraday cage. With it, you can keep certain items safe from the EMP. For example, two-way radios, shortwave radios, LED flashlights, solar battery chargers, and so forth. Radios, in particular, would be helpful, as you’d be able to figure out the nearest area that wasn’t affected by the EMP and head that direction.

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A Faraday cage could be as simple as a microwave, an ammo can, or a metal trash can. But how well would a makeshift Faraday cage-like that actually work? It depends. If you are too close to ground zero and your cage isn’t very good, it might not work at all. The Faraday cage in this video, however, would probably work perfectly no matter where you are.

The video is by Canadian Prepper, and in it, he shows off what he calls his “EMP box”. He made it with a cheap aluminum crate, which you can see below.

Faraday Cage Box

It’s important that your Faraday cage has a good seal. If there is even a tiny slit between the lid and the container, the pulse could get through and fry your electronics.

To make sure that doesn’t happen, you’ll want to start by using sandpaper or a Dremel to remove any paint and smooth out any rough spots where the lid closes against the box. You can see what I mean in the image below.

Faraday Cage Edges

Next, add some conductive copper tape around the edges that you sanded. You can probably get away with using aluminum tape, but better safe than sorry. See below.

Faraday Cage Seal

Next, you need an inner liner that is non-conductive. Canadian Prepper got some custom molded laser cut foam. If that is something you’re willing to pay for, go for it. Otherwise, you could use something like cardboard or cloth.

Be sure to watch the video below for more information. Shortly after the 7-minute mark, he starts discussing the specific items he keeps in his Faraday cage.

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  1. Dan on August 23, 2019 at 11:21 pm

    Re: “try the cell phone test to see if everything is sealed”.

    A better test is a portable AM radio, preferably tuned to the strongest local station station you can find.

    Turn it on, loud, and put it in the box and seal it. If you can still hear station, the Faraday cage is leaking. (There is more energy in the EMP at the low end of the RF spectrum.)

    For a better test, drag it out to the transmitter site (in your car, like), and repeat.

    Shielding MAY be improved if the cage is connected to a GOOD low-impedance ground. You are trying to counteract something that has the characteristics of a direct lightning strike. Heavier (thicker metal) is usually better.

    • Alan on August 24, 2019 at 5:13 am

      Good advice. Thanks for sharing!

  2. pete dickson on May 27, 2019 at 11:53 am

    One goal but so many variations. Ask 10 people, get 10 answers. Adhesive: yes/no? Ground: yes/no? Copper vs aluminum? ETC. Oh hell N. Korea just launched. Hurry, someone confirm best solution other than kiss your ass goodbye.

  3. Elbert Jones on May 4, 2019 at 8:16 pm

    The #1 way to create an E.M.P. blast is with an air burst NUCLEAR WEAPON.They’ve been around for over 70 years. WHY HASN’T ANYONE DONE IT YET?

    • Alan on May 5, 2019 at 7:47 am

      I don’t know. Let’s hope it doesn’t happen.

    • Hugh on August 18, 2020 at 11:00 am

      We have done it, in a nuclear test over the Pacific in the mid-1950’s. I think it was called Operation Starfish, and it fried electrical equipment and power transmission systems in Hawaii. That’s how we learned that setting off an upper atmospheric nuclear burst yielded an EMP. EMP can also result from a powerful solar flare, which has happened a few times in the past. In the early 1980’s, an X-Class solar flare damaged several segments on a communications satellite that the Army was using for distance learning, prompting (in part) the shift to web-based distance learning.

  4. Richard on May 3, 2019 at 3:12 pm

    NAY! Best is” Double trash can, 20 gallon inside 30 gallon with both cans interior lined: sides, bottom, and lid lined with corregated works best. I have built 3 sets. Try the cell phone test to make sure all is sealed.
    As Dave says above adhesive creates voids in seal.

  5. Dave on May 3, 2019 at 10:27 am

    Problem is the metal tape is not contacting the metal box because of the adhesive. So the box is useless. Any seal used must be in contact and form a continuous electrical path.

    • Caleb on May 3, 2019 at 9:18 pm

      weld the metal on then

      • James Hoefer on May 4, 2019 at 11:19 am

        Just to be a nit-pick, welding, too, can leave voids!

        But let’s face reality – so long as the gaps in your seal are smaller than the wave length of a micro-wave, your cage should work just fine.

        For example, look at the screen in the door of a micro-wave oven. Those holes are so small that water tends to flow off rather then through. (I’ve taken a few blown ovens apart to use the screens as extremely fine sifters) – but the holes are so close together that you can see through them almost “as if” the screen didn’t exist – light waves get through, but not radio waves, not even MICRO-waves. (Otherwise, why have a light bulb inside the oven?)

        However, a simple solution is a wrap around lid. It doesn’t have to be AIR tight, just light tight, like the door-less entrance to a dark room. You know, the kind where you make two right angle and one “U” turn. Of course, in restrooms, the walls are painted to reflect light – often there IS a light in the tunnel. Just you TRY to navigate one of those when the lights are out!

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