How To Build A Faraday Cage


How To Build A Faraday Cage – Protect Your Electronics From An EMP

Finding reliable information on how to build a faraday cage on the internet is extremely difficult. There are tons of varying opinions and very few “experts” on the subject. Most of the research that has been done into this subject has been accomplished by various military forces and most of them have not been forthright in sharing the information with the public.  With that in mind I set out to do the best I could to filter through as much information on faraday cages as I could find and bring together the best information I could on how to build a faraday cage.

What Is A Faraday Cage?

Wikipedia defines a Faraday Cage as follows:

Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields. A Faraday shield may be formed by a continuous covering of conductive material or in the case of a Faraday cage, by a mesh of such materials. Faraday cages are named after the English scientist Michael Faraday, who invented them in 1836.[1] 

Video of a Faraday cage shielding a man from electricity

A Faraday cage operates because an external electrical field causes the electric charges within the cage’s conducting material to be distributed such that they cancel the field’s effect in the cage’s interior. This phenomenon is used to protect sensitive electronic equipment from external radio frequency interference (RFI). Faraday cages are also used to enclose devices that produce RFI, such as radio transmitters, to prevent their radio waves from interfering with other nearby equipment. They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes through the interior.

Faraday cages cannot block static or slowly varying magnetic fields, such as the Earth’s magnetic field (a compass will still work inside). To a large degree, though, they shield the interior from external electromagnetic radiation if the conductor is thick enough and any holes are significantly smaller than the wavelength of the radiation. For example, certain computer forensic test procedures of electronic systems that require an environment free of electromagnetic interference can be carried out within a screened room. These rooms are spaces that are completely enclosed by one or more layers of a fine metal mesh or perforated sheet metal. The metal layers are grounded to dissipate any electric currents generated from external or internal electromagnetic fields, and thus they block a large amount of the electromagnetic interference. See also electromagnetic shielding. They provide less attenuation from outgoing transmissions versus incoming: they can shield EMP waves from natural phenomena very effectively, but a tracking device, especially in upper frequencies, may be able to penetrate from within the cage (e.g., some cell phones operate at various radio frequencies so while one cell phone may not work, another one will).

A common misconception is that a Faraday cage provides full blockage or attenuation; this is not true. The reception or transmission of radio waves, a form of electromagnetic radiation, to or from an antenna within a Faraday cage is heavily attenuated or blocked by the cage, however, a Faraday cage has varied attenuation depending on wave form, frequency or distance from receiver/transmitter, and receiver/transmitter power. Near-field high-powered frequency transmissions like HF RFID are more likely to penetrate. Solid cages generally provide better attenuation than mesh cages.

Why Do Prepper’s Build Faraday Cages?

Many preppers build faraday cages to house some of their electronics just in case there is an Electromagnetic Pulse attack on the USA.  There are a couple of different types of EMP’s. To learn more about EMPs and to understanding some of the misconceptions about EMPs check out this video I did on the subject not long ago.

Click here to watch on Youtube:

What Items Should You Put In A Faraday Cage?

This is obviously a personal choice but I will go ahead and make a few recommendations based on what I plan to put into my own faraday cage.

  1. A Shortwave Radio
  2. A Solar Panel Battery Charger
  3. A USB AA and AAA Battery Charger – That hooks up to the solar panels
  4. Rechargeable AA and AAA Batteries
  5. Head lamps and flashlights that run off of AA or AAA batteries
  6. 2 way radios that run off of AA or AAA batteries
  7. LED Lantern that runs on AA or AAA batteries
  8. Old Laptop or tablet or cell phone that is loaded with survival and disaster preparedness material, music and entertainment. Plus a 12 volt USB Charger that can connect to the solar panels.
  9. A Lithium Ion USB Rechargeable Battery Pack
  10. A night vision device that runs off of AAA batteries.

Having these items after an EMP attack would make life  much easier and would give you an edge over many other people in the preparedness realm. What other items would you put in a faraday cage? Let us know in the comments below.

Should You Ground A Faraday Cage?

The question of whether or not to ground a faraday cage is probably the most debated aspect of this topic.  From the research I conducted it appears that the community is divided on the matter. Personally I fall into the category of NOT grounding small faraday cages that are less than 2 foot x 2 foot.  Anything larger should probably be grounded. Room size or building sized faraday cages should definitely be grounded.  The best reason I found for not grounding smaller faraday cages is that during an EMP a long ground wire will act as an antennae and will actually attract more electromagnetic energy and funnel it towards the cage, instead of helping to direct the energy toward ground.  Independent of a ground the smaller faraday cages will only attract a relatively small amount of electromagnetic energy and the skin effect of a properly nested faraday cage will reduce and cancel out the EM energy effectively enough to protect your small electronics.  Adding a long ground just attracts additional energy and may serve to overwhelm the capability of the “skin effect” to dissipate the EM energy.

In a normal environment it makes sense that you would ground a faraday cage in order to help quickly route the energy to the ground and not into the electronic device.  But the pulse produced by an EMP does not produce a “normal” electrical environment.  The pulse will be all consuming and all surrounding, the electromagnetic energy will be all around the device and even absorbing several feet into the earth depending on your distance from the epicenter of the EMP.  And sense electricity follows the quickest path to ground, the energy from an EMP will disguise where exactly “ground” is.  Meaning that the electromagnetic energy will not “flow” as normal Alternating Current electricity does during the EMP event.

What Parts Are Needed To Construct A Nested Faraday Cage:

When building my faraday cage I used the parts listed below. Support this site by purchasing your gear through my Amazon link! It won’t cost you anything and helps me out a lot! Amazon Affiliate Link:

Copper Mesh:
Aluminum Foil:
3M Metallic Tape:
Copper Tape:
Gallon Zip Lock Bags:
Faraday Defense Bags:
Behrens 10 Gallon Galvanized Steel Can:
Glad Press N Seal Wrap:
Quart Size Zip Lock Bags:

How To Build A Nested Faraday Cage

Click here to watch on Youtube:

How did you build your faraday cage to protect your electronics? Let us know in the comments below!


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3 thoughts on “How To Build A Faraday Cage

  1. Do NOT ground your Faraday cage but make it as solid as possible and without holes, slits, open seams or gaps of any size or shape. Insulate the contents with as much distance from the interior walls as is possible and isolate each item from the other items in this container. An EMP event will have a magnitude and frequency range strong and broad enough to pass through any chicken wire cage as if it were non existent. Grounding will allow flow of electrons and thence magnetic fields to form inside and outside this cage…magnetic fields of great power which will likely harm the contents. Further, the mass of an object does not “attract” electrons from the air as much as they are incidental in contact as they travel (or more precisely, vibrate). The Faraday cage would act more like a capacitor if grounded thereby effectively rendered invisible if the electrons within the mass of the cage material were Pushed by the incidental electron fields provided by the pulse.
    Sooo, THAT is basically why a Faraday cage should NOT be grounded.

  2. Just realized that you can keep your cell phone safe from lightning with the help of these specialized cages; well thanks to your post!

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