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EMP 2025-12-05 2 min read

DIY Faraday Cage: Protect Your Electronics

You can build an EMP shield with a metal trash can. We walk you through the steps of constructing a DIY Faraday cage using conductive tape and cardboard. We compare the effectiveness against professional bags.

If you read our EMP Survival Guide, you know that a Faraday cage is essential for saving your backup electronics from a high-altitude nuclear pulse or a massive solar flare. Professional Faraday bags (like those from Mission Darkness) are excellent but expensive.

For bulk storage, you can build a military-grade shield for under $50.

The Theory

A Faraday cage is simply a continuous conductive enclosure. The electromagnetic wave hits the outside metal, travels around the surface, and cancels itself out, leaving the interior "silent."

  • Rule 1: The metal must be continuous (no holes).
  • Rule 2: The contents must not touch the metal (insulation).

The Trash Can Build (Step-by-Step)

Materials

  1. Galvanized Steel Trash Can with a tight-fitting lid (Behrens brand is good).
  2. Aluminum HVAC Tape (Not duct tape. Actual metal foil tape).
  3. Cardboard or Carpet scraps.
  4. Cardboard boxes for the items.

Construction

  1. Insulate the Interior: Line the bottom and sides of the can with cardboard or carpet. This ensures your radios/solar controllers don't electrically contact the steel can.
  2. Test the Seal: Put a battery-powered bluetooth speaker inside. Put the lid on. Try to connect to it with your phone. If the music stops, you have a good seal. (Note: Bluetooth is 2.4GHz, higher frequency than an EMP, so if it blocks Bluetooth, it definitely blocks E1 pulses).
  3. Load Your Gear: Place your spare laptop, ham radios, red dot sights, and solar parts inside (wrapped in bubble wrap or their original boxes).
  4. Seal the Seams: The lid is the weak point.
    • Temporary: Just clamping the lid tight is often enough for E1.
    • Permanent: Tape over the seam where the lid meets the can with the Aluminum tape for a perfect seal.

The "Ammo Can" Method

Steel ammo cans are great small Faraday cages, BUT the rubber gasket that makes them waterproof breaks the electrical conductivity between the lid and the box.

  • ** The Fix:** You must scrape the paint off the lip where the lid touches the box, or remove the rubber gasket (sacrificing waterproofing) to ensure metal-on-metal contact.

Testing

  • Cell Phone Test: Put your phone inside. Call it. If it goes straight to voicemail, you have a shield.
  • AM/FM Radio Test: Tune a radio to a strong station. Put it in. If it goes to static instantly, you are protected.

Verdict

A DIY trash can cage is the most cost-effective way to insure your family's power and communication capability against the end of the world. Build one this weekend.

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