Badlands Fieldcraft: 10 Minute Farraday Cage

I haven’t written much on subjects pertaining to communications, yet. To be honest, there’s better sources than me, like the Brushbeater blog for one. Off grid communications are a big interest of mine though, and I do have a fair amount of lessons learned I can share. If these subjects are of interest to you as well, I can’t recommend the Brushbeater communications courses enough.
Tonight I built my first Farraday cage/ signal blocker and thought it was an interesting and easy project. A Farraday cage is basically a container to block harmful electromagnetic pulses, either natural or man made, from damaging sensitive electronics. It is a sealed metallic, electrically continuous container line with electrically insulating materials. While all that might be a mouthful, it was actually simple to build with household items.
The items you will need are as follows:

  • A metal container. I picked up a 12” diameter bow tin from Wally World on clearance for $.87.
  • Aluminum Duct (not duck) tape. This is a special metal tape for sealing seams in duct work, it’s in the hardware section. Cost me about $4.
  • If your container is painted, a sheet of sand paper.
  • Insulating material to line the container with. I used some left over foam mat and vinyl cove base that I had left over from a construction project. I’ve been told you can even do this with card board so any insulator will work.
  • Some sort of glue or silicone to stick the insulating material to the container lid.
  • Tools to do it

First prepare the container. In my case I removed the bow and ribbon and scraped off the excess glue. I then taped all the seams with the duct tape.

Next I sanded the paint off the top of the container so it had good metal on metal contact with the lid.

Once this was done I added more tape to the area I just sanded to add a very tight seal that is electrically continuous. At this point I checked it with a meter. This is an optional step but I was curious. A reading of 0 ohms indicates no resistance at all. My probes measured 0.1 before the test, and in the photo you can see that I am getting that same measurement. This means there is zero resistance, indicating I have a very solid connection between the lid and the container.

This tight connection is important because as a signal blocker it has to have a very tight seal to block out signals. I tested this by placing my phone inside then trying to call it. Before I taped the top of the container I could still reach my phone, but after I couldn’t.
It was now time to line the container. First I measured and cut the cove base to length and width.

Then I traced the outline of the container on the foam pieces and cut them to fit as well.

After this I used my liquid nails and glued the top piece to the lid and placed some handy weights I had laying around on it to help get the glue stuck on.

I now have a completed Farraday cage to store my sensitive electronics in. This is my first build and if anyone reading this has more experience I would appreciate any advice if you see something I could do better.

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About the Author: NC Scout

NC Scout is the nom de guerre of a former Infantry Scout and Sergeant in one of the Army’s best Reconnaissance Units. He has combat tours in both Iraq and Afghanistan. He teaches a series of courses focusing on small unit skills rarely if ever taught anywhere else in the prepping and survival field, including his RTO Course which focuses on small unit communications. In his free time he is an avid hunter, bushcrafter, writer, long range shooter, prepper, amateur radio operator and Libertarian activist. He can be contacted at [email protected] or via his blog at brushbeater.wordpress.com .

10 Comments

  1. Andrew January 4, 2021 at 06:40

    Very nice – thanks for sharing. I will have to test to see if this can be done with a larger can of some sort.

    • JackalopeinTN January 4, 2021 at 08:53

      Walmarts has the larger popcorn tins that can be set-up like above. A galvanized garbage can can also be used.

  2. Cold Warrior January 4, 2021 at 08:53

    Respectfully recommend not using aluminum boxes, if possible. While they will work as a Faraday cage, and provide some RF blocking, a ferrous metal would be far more effective, especially against electro-magnetic challenges. If you find some old steel screen material, it is highly effective for lining boxes, and works as a Faraday cage.

    • wwes January 4, 2021 at 09:50

      Steel screen material can sometimes be found at beekeeping suppliers, although it won’t be inexpensive.

  3. Anonymous January 4, 2021 at 09:48

    5

  4. Ordinary Warrior January 4, 2021 at 12:18

    Most scientific articles say that copper mesh is the best material for your cage. I use ammo cans with a liner. These are all called ‘nested faraday cages.’ If you really want to protect your stuff, wrap your items in foam, then wrap it in mesh, then put it in a lined box/container.

  5. Johnny Paratrooper January 4, 2021 at 18:03

    I bought some used mortar cans. I stand my radios up with the antennas on inside of the cans.
    I used two extra thick mylar bags to line my cans. It’s not perfect, but it seems to work.
    I store the cans in a cheap gun safe I bought.2 across and two high.
    With a rifle and pistol. Plus some ammo in separate cans.
    I bought two decent matching headlamps and mounted them inside the gun safe for use as lamps.
    The headlamps have alligator teeth helmet pad stickers on them, and they stick to the felt lining the gun safe. They can easily be moved, or mounted to a tactical hat with fuzzing patch on the front.
    Works pretty well in my opinion.
    I cannot get a signal in, or out, of this setup. Even at point blank range.
    The one weakness is that it is obviously a permanent fixture.
    Though the cans can be moved individually.
    I have each can divided between radio types.

  6. James January 4, 2021 at 19:28

    I remember in the distant past when those “handy weights”were about 10 bucks or so a weight.
    They are still a reasonably priced weight compared to others but I miss the past!

  7. Oldhen January 5, 2021 at 03:07

    What does a kitchen microwave shield you from? Asking for a friend?

  8. ApoloDoc January 11, 2021 at 14:52

    I also suggest picking up some cloth with metal woven in. Here is a source, I think this is the one I bought fabric from a few years ago (need to look at my old receipt). Phones & radios can have a small pouch that you custom make to fit. Sew it (I bought a sewing machine for these projects, should I turn in my man card?!) or even use some sort of glue – shoe goo would work.
    Obviously tablets & laptops can benefit as well. I need to revamp a SMALL packet radio setup, package it with this stuff.
    The anticipated collapse has lagged for YEARA from what I expected, and so some areas I am woefully out of date & practice with.

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