How to Build a Simple Faraday Cage for EMP Survival

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Of all of the reasons to prepare, one that we all need to take seriously is the possibility of a catastrophic EMP, or electromagnetic pulse. This is a frequent topic in many post-apocalyptic novels and something that most of us are aware of, even if we do not completely understand the science.

How to Build a Simple Faraday Cage for EMP Survival - Backdoor Survival

As I wrote way back when in the article Prepping for an EMP and Solar Flares:

To be blunt about it, an EMP, if large enough, would affect the entire planet.  In an instant, civilization as we know it would change as we get swept backward in time by a century or two.

Understanding the risks of an EMP goes hand in hand with threats of a cyber-attack since there is a cause and effect relationship between the two.  In this article I want to accomplish a few things:

Explain EMPs and the risks in simple, easy-to-understand language
Give you instructions to build a simple Faraday cage to protect your electronics
Provide a list of items to put inside your Faraday cage

What is an EMP?

An electromagnetic pulse or EMP, is an abrupt burst of electromagnetic radiation.

To start with, an EMP is caused by certain types of high energy explosions.  A nuclear explosion, for example, will surely cause an EMP.  Likewise, an EMP can be the result of a suddenly fluctuating magnetic field.  Or, as I have mentioned before, it can be the result of Coronal Mass Eject (CME) from solar activity.  But perhaps most sobering of all, is the possibility of a man-made EMP weapon that is purposely deployed in order to wreak devastation on our planet.  Scary stuff.

Regardless of the trigger, an EMP can be devastating to the power grid, resulting in rapidly changing electrical fields that will create fluctuating electrical currents and wild voltage surges.  Bottom line?  The electronic gizmos we have come to rely on would be toast.  The microchips would be fried or so severely damaged that they would become useless.

So what would life be like following a massive EMP event or episode?  There would be no power, no transportation systems, no communication systems, no banking, no internet, and, no surprise, no food and no water delivery systems.  This would truly be an End of The World As We Know it situation.

Ask yourself these questions:

What if the power went out and never came back on?  Could you fend for yourself?

Could you keep yourself warm in the winter and cool in the summer?

Where would you find food?

What would you use for money if credit cards and ATM’s no longer worked?

How would you get from one place to another without transportation?

How would you wash your clothes?

How would you keep yourself healthy if sanitation systems were no longer functional and medicine could no longer be manufactured.

And the biggest question of all, how would you communicate with the rest of the world?

An electromagnetic pulse could potentially fry the vast majority of all the microchips in the United States. In an instant, nearly all of our electronic devices would be rendered useless.

Back in 2004 the Wall Street Journal wrote:

“No American would necessarily die in the initial attack, but what comes next is potentially catastrophic. The pulse would wipe out most electronics and telecommunications, including the power grid. Millions could die for want of modern medical care or even of starvation since farmers wouldn’t be able to harvest crops and distributors wouldn’t be able to get food to supermarkets. Commissioner Lowell Wood calls EMP attack a “giant continental time machine” that would move us back more than a century in technology to the late 1800s.”

With that introduction, today I would like to introduce you to the Faraday cage, and further, how to build a simple Faraday cage.

The Faraday Cage

In the simplest of terms, a Faraday cage is any shielded enclosure that surrounds your electronic devices and protects them an EMP blast.  Commonly used enclosures include galvanized metal garbage cans, popcorn tins, and even tightly sealed metal filing cabinets.  In all cases, the metal container is lined with insulating material to prevent the contents from having contact with the metal.  Examples of insulating material are cardboard, Styrofoam, and even carpet scraps.

More elaborate structures can be custom built from sheet metal but for the home user, why bother?  As a matter of fact, I suspect that wrapping your devices in plain, ordinary, aluminum foil will work as well.

Factoid: Faraday cages are named after English scientist Michael Faraday, who invented them in 1836.

What About Using a Microwave Oven?

In my research I read that a microwave oven, new or used,  can be used as an effective Faraday cage.  On the surface, that seems logical since, by design, a microwave oven keeps the energy it creates confined to the interior which likewise, should prevent strong electrical pulses from getting back inside.

This was easy enough to test. I put a cell phone inside my microwave oven and tried calling it. It rang. Oops.  On the other hand, I wrapped my cell phone in aluminum foil and called it.  Nothing. Nada. No Michael Buble ringtone; the call went straight to voicemail.

Protecting Small Electronics from an EMP - Backdoor Survival

A foil-wrapped cell phone blocked the cell signal

Granted, cell phones operate at various radio frequencies so while one cell phone may not work, another one will.  Still, with this being so easy to test, why chance it?

Testing the Faraday Cage

Aside from calling a cell phone, you can test your homemade Faraday cage by putting a portable radio inside the shield after tuning it to a strong FM station.  If you can hear the FM station while the radio is inside your Faraday cage, then you need to go back to square one to ensure your shield is properly sealed.

Sealing your garbage can with duct tape will help tremendously.

A Second (Expert) Opinion

I asked my friend George Ure to comment and to offer his perspective on Faraday cages since EMP preparedness is something he covered in-depth on his subscriber site, Peoplenomics ($40 a year but worth it for the technical information on the many topics he covers.).

He was quick to point out several things about EMPs.  The definitive public information is contained In the 2004 Congressional Research Service (CRS) issued a report “High Altitude Electromagnetic Pulse (HEMP) and High Power Microwave (HPM) Devices: Threat Assessments”.  The following diagram shows how an EMP causes the complex systems we rely on to provide everyday essentials for living, to fail in a cascading manner.

EMP Cascade Effect

So, a quick inspection of the EMP failure modes, George offers, is one way to build a list of items to put in your Faraday cage.

He also told me some personal research he’s done that seems to indicate that about 90% of cars will continue to operate after an EMP event of moderate size. The problem, he points out, is that with an EMP, the grid is likely to fail, and with that, power transformers will likely fail, along with the supervisory control and data acquisition systems (SCADA) control systems for railroads, power, water, and other utility distribution.

George’s personal Faraday cage is a 33 gallon garbage can.  He considers his metal garbage effective by itself because the metal lid overlaps the can itself by an inch and radio waves don’t like to go around corners, too well. Still, the ultimate prepping device would be a metal garbage can which has the top cover sealed to the bottom of the can with aluminized duct tape such as the type found at Amazon, Lowes, Home Depot and other hardware stores.

What to Put in the Faraday Cage

The equipment you store in a Faraday cage should encompass those devices that will help you communicate with the world following a devastating loss of the grid. Short-range communications will be critical. A good starting list would include:

Multiple GMRS radios and chargers along with cables to plug in for solar charging.

Multiple 2 meter and 440 MHz ham radios (such as the portable Baofengs), again with charging cables and solar power adapters.

A laptop computer with a fresh battery, a charger, solar adapter, and all the key software on CD so if you need to bring up a fresh copy of the operating system, you’ll have the product key and then any prepping articles or references you might need.

An AM/FM/Shortwave/NOAA Weather radio that includes a solar panel charging mechanism.

High-capacity USB thumb drive holding  pertinent financial information including past year tax records, scanned copies of birth certificates, passports, marriage licenses, deeds, vehicle registrations and medical records.

George also recommends simple insulation for your electronics, so that units do not touch each other, He uses low tech insulation: a combination of cardboard and bubble-wrap works well.

Protecting Small Electronics Day to Day

This article would not be complete if I did not mention the availability of small, shielded metalized bags that can be used to provide EMP protection on a daily basis.  I am currently testing this type of bag from Mobilsec and an quite impressed.  While my phone is in the bag, it reads “no service”.

If a cell signal cannot be detected, I can only assume that an EMP would also not touch it.  Good to know and certainly an option, especially for a laptop that could be placed inside a properly sized bag when not being used.  Couple the Faraday bag with a solar charging system and if there was an EMP, you would still have a working computer.

One other thing. You may find sources online that say that when a device is turned off, it will not need EMP protection.  I reached out to Joel Ho, the developer of the Mobilesec Bagsand asked him about that.  Here is what he said:

I’m assuming you are referring to the part about devices being off not needing protection – it’s simplified a bit – essentially, devices that are off are extremely difficult to damage because there’s no existing current to piggyback on.

Imagine that an EMP is a tidal wave.  If it approaches a full reservoir (electricity and current) it can keep going. If the reservoir is empty (no juice), the tidal wave loses energy navigating the reservoir.

There are hints of this in the article Electromagnetic Pulse Protection by Jerry Emanuelson.

The major reason [most sources] don’t say “your devices are safe if off” is because most devices are usually still connected to power lines and thus susceptible – but if devices are in EMP bags (which by definition are almost always disconnected as the filters are expensive), AND the devices are off, it is unlikely, given the relatively high FCC shielding regulations to prevent excess energy from bleeding OUT into the environment, that enough can get IN to damage those electronics.

This is NOT true for every device – more like a guideline than a hard 100% rule.  Different devices have different levels of built-in shielding – a computer has much more than a $10 Radio Shack timer, for example.

The Final Word

Should a massive EMP occur, stores won’t be open, credit cards won’t work, and the gas you have in your car may be all the gas you’ll ever have for months or even possibly years. When you think about it, an EMP will become the “Ebola virus of electronics”.

That said, you know that I am not a doom and gloomer.  Quite the contrary.  I am an optimist to the nth degree.  Yet even the optimist is sobered at the ramifications of an EMP and especially at the prospect of a weapon-based EMP. If nothing else, I would like to have a mode of communication following a massive EMP.

Will the DIY Faraday cage work?  It is speculation to say for sure.  My own research plus my limited understanding of electronics tells me it will, but this premise will remain unproven until an actual EMP event occurs.

The bottom line is that I hope a catastrophic EMP never happens.  But if it does, I want to be ready to fend for myself without electronics. Sure, having communication gear and other electronic gizmos in a working Faraday cage will be a wonderful thing.  But even if it doesn’t work, the goal of preparedness is to prevail, even if that means living in an off-grid society for weeks, months, or even years.

I would like to acknowledge my pal George Ure for his assistance with this article.  His research and first hand experience with Faraday cages, along with his perspective, is appreciated.

Update:  Clearly, there are many unanswered questions and that is to be expected. Rather than answer them individually, I will compile the questions and seek answers from individuals whose technical experience and background far exceeds mine.  Please leave your questions in the comments area below.

Enjoy your next adventure through common sense and thoughtful preparation!

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Bargain Bin:  Below you will find links to the items related to today’s article.

Behrens 10-Gallon Locking Lid Can: This 10 gallon can would make a perfect Faraday cage from small electronics.  The locking lid is a bonus although I would still seal the edges with 2” duct tape. This price, by the way, is less than my local Ace Hardware store.  Also available in this larger size 20 Gallon size.

3M Duct Tape15 Ways to Limit Radiation After Nuclear Armageddon   Backdoor Survival: A good quality duct tape is an absolute necessity when sealing your DIY Faraday cage.  For slightly less, you can purchase 3M Utility Grade Duct Tape

Midland 36-Mile 50-Channel FRS/GMRS Two-Way Radios: These are the handheld radios that I own. There are lots of good uses for the these radios. Handy while hiking, traveling, or simply keeping in touch with your partner while out shopping. Just be aware that getting a 36 mile range out of any handheld FRS radio is a myth.

Pofung/Baofeng UV-5R Ham Two Way Radio: Redundancy is the name of the game.  I also have two of these inexpensive HAM radios.  Keep in mind that if you are just planning to listen, you do not need a license (I am still working on mine).  The price is right.  Also consider the NAGOYA Antenna for BAOFENG UV-5R  and the USB Programming Cable for Baofeng UV-5R UV-3R+. Note: the Pofung was formerly known as the Baofeng UV-5R).

SunJack Portable Solar Charger:  SunJack® helps mobile users stay charged on the go anywhere the sun shines. The SunJack® is able to fully charge its internal battery pack in about 5 hours of direct sunlight, or directly power any USB device. When the sun isn’t shining, users can still energize their devices from the powerful SunJack® battery, which holds enough charge to power up to 4 iPhones.

Kaito Voyager Trek Solar/Crank AM/FM/SW NOAA Weather Radio with 5-LED Flashlight: This simple to operate radio can be powered by three AAA batteries or the built-in rechargeable Ni-MH battery which in turn can be charged by hand cranking, by solar panel or even by a PC. . The 7-weather channels are pre-programmed and numbered from 1-7, you can easily and conveniently tune into the stations by adjusting the switch.  Note that not all emergency radios include the NOAA weather band so this is an important feature.

Cell Phone Faraday Cage Bag:  This is the bag I have been testing.  It is also stops hacking and the tracking of your phone.  Mobilsec also has a laptop sized Faraday Cage EMP Shield


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How to Build a Simple Faraday Cage for EMP Survival — 25 Comments

  1. I am just learning about EMP and I have one question. We have a large gun safe with an electronic lock. Does anyone know of a way to protect that so that we could open our safe?? Or would it be prudent to get a safe with a manual lock?

  2. How about the washing machine and dryer as faraday cages? Metal with large
    openings, easy to access and just about everybody has one.
    The oven also may work or the dishwasher. Any thoughts on these suggestions?

  3. I don’t know what type of dishwasher you may have but I tested mine, a built in. Didn’t work, I put my and Dahubs phones in it shut the door and called each phone. Both rang when dialed. I believe it may be that the built ins don’t have as much exterior metal around the insulation when its in the cabinet area. I think it’s to cut down on the weight and space the machine takes up when it’s built into the cabinetry. Now a portable dishwasher(if they still make them ;)) may work differently as it’s encased in a metal “box” with a lot of sound deadening insulation around the interior.

    • Interesting point which makes me wonder if a portable microwave oven would work. When I have time, I will run to the thrift store and see if they have one I can test. (My microwave oven is built in.)

  4. I am new to all of the Emp information….if we have an emp will we have time to get our electronics into the faraday cage in time…since most of our electronics always being in use….and if we do have an emp..won’t all things go down (such as towers and stations) will we have any use for our phones and radios and such….

    • Therein lies the dilemma. Once the EMP occurs, the gizmos become toast; there is no time to protect them after the fact. Many of us put spare (and even outdated) electronics in our Faraday cages. An old laptop would be a good example. As it happens, I just pulled an old laptop (Windows XP era) and have been updating it with all of my eBooks and documents before putting it back in the Faraday cage. I try to do this every six months or so.

      You are correct about cell phones and radios not working initially but current guesses (and they are just that) speculate that the military and government will work on restoring service as quickly as they can. No guarantees but it seem probable.

      Our laptops, eBook readers/Kindles should be okay though. They will become our reference library.

      • Thank you…so if I would put some old cell phones…and some electronics not really being used right now into a cage they would be ok… hubby has all kinds of ham radios and equipment…what to do with all of these very expensive equipment since they are used often…

  5. Gaye – love the simplicity of the article, but have some questions.
    I’m all for protecting my electronics, cell phone, etc. I get the use of ham radios for communication, but why am I protecting the cell phones if the network will most likely be down? There won’t be any signal or any way to reach anyone I know (because likely all their phones will be toasted). Text uses a different carrier signal, but again, its doubtful there will be an active network or phones to receive them. Same for pcs – there likely won’t be an internet to communicate through.
    OR – did I miss something in all the expert talks that says those types of things are protected at their root source – ie: Verizon has taken precautions against an EMP wave.
    If the world in general (or even just America) is set back two hundred years, what’s the point of keeping my cell phone active?

  6. Another item I would add to the list (which you also mentioned in a reply) is a tablet. Whether an iProduct or Android, with the micro-SD card, it’s an electronic library. Much easier to transport after “the event” than a shelf of books. There are also several solar chargers on the market (which would also need to be in the cage) that can support tablets and cell phones.
    Cell phones may not be useful as phones, but they have cameras. With enough storage capacity, they can be useful to record a variety of events. What did the world look like before the event, and how did it change. Pictures are also a good way to reference locations and potential stashes. Stock up on a few extra cards and the volume of pictures can be massive.
    Less expensive than a solar setup for the laptop might be a simple inverter designed for use in a car or camper. The laptop won’t like the output of the inverter much but will probably still charge.

  7. I have been waiting for this article, I have been so confused in the past about conflicting points of view about what will or wont be affected and what will or wont work for shielding. If seen the 90/10 statistic about vehicles affected from both sides of the argument. Some say 90% will fail, others say 90% will be fine. Thanks for weighing in on this Gaye. I know you put a lot of research into your articles and I know your maternal feelings for us readers means you wont steer us wrong. I have some things in a faraday cage already but there are some things that I just cant determine if need protection. Things that I deem more valuable than electronics. Will my tiller start after an emp? how bout the chainsaw? I know they are not connected to the grid but I don’t know if there is any sort of electrical component to their starting or running, and I don’t know how to find out.

  8. I’m more concerned about two way radios, small tv with omni directional antenna
    Old lap top with research material and clock radios

  9. We have a stand-by generator that automatically goes on if there is a power outage. It also starts weekly for testing. Is there a way to protect that? While we are not survivalists, we like to be prepared.

  10. To everyone who has commented and asked questions: Clearly, there are many unanswered questions and that is to be expected. Rather than answer them individually, I will compile the questions and seek answers from individuals whose technical experience and background far exceeds mine. Please leave your questions in the comments area below.

    Please continue to ask away!

  11. I am a retired contractor and use an old “gang box”. Fully enclosed in heavy steel with no openings. You can find old ones at flea markets or on the internet or local papers. It holds all of my extra FRS/GMRS, 2 meter, 440 meter, 70 cm baofungs, my HF rigs and linear amps along with windup radios, chargers for the solar array. Keep in mind that some radios like the HF have internal batteries. You might want to keep an extra set in the box. I also put in a couple of cases of MRE’s, don’t know how hungry I’ll be if I ever need to use the box.

  12. Many preppers may already have a faraday bag! Have you tried sealing your cell phone in an aluminized mylar bag? I have a one board FM transmitter that I found was radiating spurious signals and interferring with other radios. Since I was using it to listen to an audiobook I just laid a mylar bag over the transmitter (the antenna wire still outside) and it cut all the extra signals.

  13. Another good source for a faraday bag for your electronics is “Tech Protect”.
    Not certain whether or not weblinks are allowed here… but for the benefit of readers, I will try posting the weblinks for their faraday products: or

    I’ve purchased various sizes of their bags and they are high quality and do the job.

    By the way…
    much thanks to Gaye and Shelly for the great service you are providing!

  14. Not much talk about nuclear plants and meltdowns. Imagine parts of there systems would get fried. Generators would only last a few days. Gov. trucks if rolling
    might bring in some fuel. Won’t take long to leak into water table, and massive amounts of radiation. How to bug out into area away from plants when vehicles
    won’t run? 61 plants with 99 reactors in US.

  15. Some more thoughts on Faraday cages.

    You can also create a cage of any size and shape from wire mesh netting, so long as it completely surrounds the space to be protected and is fully sealed (connected along all edges with conducting materials. The wire mesh can have openings as large as an inch but not much more. Any door or hatch must electrically seal along all edges when closed.

    Increasing protection by connecting the Faraday cage to a grounded conducting post with a very thick/braided cable to drain off the received energy from the pulse. Give it a path to ground similar to lightning rod systems. The grounded post should be at least 4′ to 6′ into the earth (Not encased in concrete).

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