Why and how to protect your gear from EMP

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EMP protection

One of the scarier survival events that preppers need to be concerned about is an attack involving a High-altitude ElectroMagnetic Pulse, also called HEMP.  All nuclear weapons create EMP, but when detonated high in the atmosphere, the EMP generated is so massive that it can destroy electronics and permanently knock out the power grid across the entire country.

While there have been several venues of entertainment to come out recently that highlight this type of event, typical of Hollywood, changes in physics and reality were made to better suit the plot.  Let’s take a look at some facts and how you can protect your sensitive electronic gear from an EMP attack.

Factual information is hard to come by

The first thing that we need to look at is the distinct lack of information available about EMP and its effects.  Most of what we know is from nuclear tests, both American and Soviet, in the 1960s.  Data and information after that period is still highly classified, so all we have to go on is what has been declassified from this earlier era of tests.  However, this information, along with a few pieces of recent data, is enough to make some reasonable projections.

The second thing we need to understand is that a HEMP attack on the United States is about as bad as it gets.  Experts predict that 70% – 90% of Americans would be dead within 12 – 18 months after an EMP attack.  The reason for this is the extreme dependence on electricity and the delocalization of resources, like food, water and sanitation abilities.

EMP is survivable, but you need to start preparing for it now.  Unlike other disasters, there is no warning or precursor, and no ability to, “finish prepping,” once it occurs.  EMP is an instantaneous event.  One second after an EMP attack, it’s lights out forever.

Just as deadly, the Coronal Mass Ejection

A Coronal Mass Ejection, or CME, is another event that can take out the entire power grid.  When highly charged plasma particles from the surface of the sun crash into the Earth’s magnetosphere, it induces electrical current in long lines of metal, like wires and pipes.  This induction of current will destroy the transformers needed for power transmission on the grid, essentially wiping out the ability for power grid to remain operational.

However, unlike EMP, a CME event does not destroy electronic devices, unless they happen to be connected to the power grid or long lines that will collect the induced current.  For more on the differences between EMP and CME, you can read about it here.

Why bother protecting electronics?

In this article, we’re going to be covering how to make a simple Faraday cage to protect your electronic devices.  There are two main reasons why you want to protect your gear from EMP.  The first is that having the ability to communicate via radio and generate power, both can give you a huge tactical advantage when trying to survive in a powerless world.

The second is the massive amount of information that you can store in digital format.  As hardly anyone today remembers how to do things the, “old world,” way, this information will allow you to restart your life at a mid-1800s level.

What is a Faraday cage?

The Faraday cage is named after Michael Faraday, the scientist who discovered its properties for shielding against electromagnetic waves, including electricity.  You can build simple Faraday cages at home at a very low cost that will work just as well as the expensive ones that the government uses.  All it takes is some common household items.

A Faraday cage protects its contents by preventing electromagnetic energy from getting inside.  Expensive Faraday units use a combination of a fine copper mesh and solid aluminum.  You can build your own at home using aluminum foil and a galvanized steel trash can.  By the way, Faraday shielding doesn’t actually have to be a cage, it’s simply anything that blocks electromagnetic radiation.

There are lots of places on the Internet claiming that all you need to do is put your gear into a microwave oven or Mylar bag and it will be protected from EMP.  It would be wonderful if these worked, but unfortunately, I am highly skeptical of them.  You can easily to test these and see for yourself.

The frequencies for EMP range from approximately AM radio to approximately FM radio (actually, EMP frequencies have a much broader range, but the AM/FM radio comparison is close enough).  AM signals go as low as 540 kHz and the FM radio band stops at 108 MHz.  Don’t worry if those frequencies don’t mean anything to you. The important thing to know is that you can test how effective a container will work at shielding electromagnetic frequencies, simply by using an AM/FM radio.

First, tune the radio to a strong FM station and turn up the volume.  Put it into the Faraday cage you’re testing and listen to see if the radio station is still being picked up by the radio.  Don’t get too excited if it doesn’t, as FM signals are very easy to shield against.

Next, tune the radio to a strong AM station and retest.  The low frequency of AM signals are very good at penetrating objects.  If you can’t hear the AM station anymore, that’s a good sign.  Anything that can block strong AM and FM radio signals would probably make a good Faraday cage.  Keep in mind, though, that the power of these signals in your home are relatively weak (unless you happen to live under a radio tower).

This is important to know because you will see videos online where people put their cell phones into a microwave, Mylar bag or some other type of “Faraday” protection and demonstrate the effectiveness by showing how the cell phone loses the WiFi and cell tower signals.

Cell signals are extremely weak to begin with and are very easy to block.  These demonstrations are not good tests for protecting against EMP.  A food grade Mylar bag won’t even stop 11 watts of WiFi signal (a 2.4 GHZ frequency) from reaching my iPhone when it’s right next to the wireless router.  It certainly won’t stop the destructive pulse from EMP.

I conducted EMP-protection tests myself

When looking for an inexpensive way to protect my electronic gear from EMP, this author personally tested several methods.  As I mentioned, the tests are imperfect because we’re only testing for a certain range of frequencies, but we can get really good information from these tests.

One test involved being on top of a mountain that was filled with radio antennas.  The collective power of all these radio towers was 9,000,000 watts of RF (Radio Frequency) energy!  Another test was standing at the base of a 50,000 watt AM station.

So, what worked?

Using the AM/FM radio test, it was found that both Mylar bags and microwave ovens were not good Faraday cages.  Both of these failed inside my home.  They simply did not work well at all.  When I tuned an AM radio to a strong station and put it in the microwave, I could still here the station.  The shielding on a microwave oven is tuned to block out signals in the 2.4 GHz range, which is the same as most WiFi routers (most cell phones are close to this range, too).  Thus, when you put your cell phone in them, it’s not surprising that they lose signal.  They can also block out most FM radio stations.  However, because of the nature of longer radio waves, AM signals pass right through the shielding found in the modern microwave oven.

Because Mylar bags are a lot easier to transport than a microwave oven, they were tested at the radio antennas sites.  Even tightly wrapping the radio in two Mylar bags, the signals still got through.  In fact, the Mylar bags didn’t seem to reduce the RF radiation at all.

It turns out that a very effective shielding can be made from aluminum foil.  Common heavy duty aluminum foil successfully blocked all nine million watts of RF energy from reaching the radios.  The radio needed to be wrapped in three layers, but it worked!  For AM signals though, I needed five layers to successfully block out the RF energy.

This means that you should be able to easily protect your electronic gear from EMP simply by wrapping it in aluminum foil.  I also found that placing the foil-wrapped radio inside a galvanized steel trash can greatly increased the effectiveness of the shielding.

Here’s how to do it

To start, here’s a few things to keep in mind:

  • There needs to be a minimum of 3 layers of aluminum foil completely surrounding the device.
  •  Use a minimum of 5 layers if you’re not going to be using a second layer of shielding, e.g. the metal trash can.
  •  The foil must not contact the device directly, so first wrap it in paper or cloth. I use cloth.
  •  The foil-wrapped device must not touch the inside of the outer Faraday container.
  •  In order for the Faraday cage to be effective, the metal needs to completely surround the device being protected.
  •  Use heavy duty aluminum foil, the thicker the better.

When you wrap your electronic device, it’s important to prevent it from touching the foil. Otherwise, it’s like making an antenna for the EMP to get right to the item you’re trying to protect.  You can protect this by wrapping the device in paper, wax paper, an envelope or cardboard box.  Whichever works best for whatever you’re wrapping in foil.  If the device has protrusions, it’s best to wrap it in something thicker than thin plastic wrap or paper.  Use a box or envelope of some sort.  This will help keep the item from poking through the foil.

protect your gear from EMP

Remove batteries from electronics.

If your device has an antenna that does not retract or fold into the device and can be removed, go ahead and remove it.  Likewise for any cords or wires.  It’s not necessary to remove these, but can make it more difficult to wrap.  You don’t want to have any risk of protruding parts poking through the foil, as this will void any Faraday protection.  Just make sure that any wires, cords and antennas are completely within the foil.

If the device has a removable battery, remove it and store it separately.  The last thing you want is to find out that the batteries leaked and ruined the equipment that you went to so much trouble to protect.

You can use anything non-conductive to wrap the devices, here I used an old sheet and plastic wrap.  The cloth sheet prevents “pointy” parts of the device from poking through the foil and the plastic wrap keeps cloth to hold the fabric in place.  I could have used tape, but the plastic wrap is reusable and I can see through it to make sure that the cloth is in place.  I don’t use plastic wrap directly on devices, as I don’t want any letters or print on the device to get stuck to the plastic in long term storage and come off when I remove the wrap.

All wrapped up.

Wrap the device in the foil, making sure that all areas around the device have a minimum of 3 layers.  If you’re not going to be storing these foil-wrapped items in another Faraday container, then make sure to wrap 5 layers of foil around the device.  In tests that I’ve done, it seems that wrapping each layer individually seems to work better than folding the foil into a double layer and then wrapping.

You don’t have to wrap up every item individually.  You can save time and space, and avoid the need for cloth and plastic wrap by putting several devices into a small bag, cloth pouch or box.

Combine gear into a bag.

What if you want to protect devices that have internal batteries that can’t be removed?  Many of these items would be helpful in a post-EMP world, but you’ll need to determine a way to store them and periodically recharge the batteries.

Once you have all of your devices wrapped in several layers of aluminum foil, you’ve taken a big step in protecting them from EMP.  However, you should place all of these foil-wrapped items into another layer of Faraday protection, as EMP is an extremely powerful pulse and every layer between it and the device diminishes its ability to destroy electronics.

One of the easiest ways to do this second layer is to put them into a galvanized steel trash can.  With a tight fitting lid, it’s surprising how well this works.protect gear from EMP

Because you need to keep the items inside the can from touching the inside metal of the can, line the trash can with cardboard.  If a foil wrapped item touches the inside of the can, it’s like there’s only one level of protection, and could end up focusing the EMP directly towards the device.  Not a good thing.

Once you have your items wrapped and your can lined, place the items in the can and put the lid on.  You may want to duct tape the lid in place, so that it doesn’t get accidentally knocked loose.  Any gap between the lid and the can and it looses its ability to function as a Faraday cage.  If you have space, go ahead and wrap the items in more cloth, to further protect them from accidentally shifting and causing a tear or hole in the foil when you move the can.

As you can see from the picture above, there is a lot of room in a 31 gallon trash can.  Pack the items that can be left sealed in foil indefinitely on the bottom and place on top the items that need to be checked on or have their batteries charged.  If you happen to fill the can with equipment, make sure you place cloth or other non-conductive material on top so that nothing can touch the inside of the can lid or the top around the sides.  Also, make sure that you have a metal to metal contact between the lid and the can.  Don’t put paint, tape or anything that would get between the can and the lid, as this would likely render the can ineffective as a Faraday cage.

One final note.  Should an EMP attack ever happen, don’t rush to open your Faraday cage and start pulling out your gear.  The enemy may pop off the first EMP and then wait a few days or a week before popping off another one.  This way they could ensure that they are destroying as much as possible.

Consider having two sets of gear in separate Faraday cages.  The first one would be small and only have a few items, like an AM/FM/Shortwave radio and a few walkie-talkies.  Your second one would be larger and contain all of your main gear, which you would open only after a reasonable amount of time, or when you needed the equipment inside.

As you can see, protecting your electronic gear isn’t difficult.  While EMP will destroy most electronic equipment and take out the power grid, by taking simple precautions now, you can ensure that you have functioning equipment to make the transition to a whole new way of life a little easier.



There may be links in the post above that are “affiliate links.” This means if you click on the link and purchase the item, I will receive an affiliate commission, which does not affect the price you pay for the product. Regardless, I only recommend products or services I use personally and believe will add value to my readers. 

© Copyright 2012 The Survival Mom, All rights Reserved. Written For: The Survival Mom
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Rob Hanus is the author of several books, including, “The Preparedness Capability Checklist” and "Surviving EMP." He is also founder and host of the http://ThePreparednessPodcast.com/, where he teaches well organized reasons for preparedness, and manages the Prepper News Watch, highlighting news and articles relevant to preppers.

(53) Readers Comments

  1. Thanks for the info! Sounds so much easier than I thought. Any advice on protecting vehicles from an EMP? it is my understanding that car ignitions won’t work after such an attack.

    • I know a guy that insists that simply disconnecting a cars battery will protect the cars computer from an EMP. Is there any truth to this?

      For Anne, battery backups, solar power tied to battery banks and generators will still run a lot of electronic equipment. Think HAM radios and the ability to connect with others over great distances. The more info from the outside the better.

      • The hardest thing to protecting your gear against EMP is actually doing it. Followed closely, I think, by how to manage those devices that don’t have removable batteries, but you want to store anyway. Things like old iPhone or Androids, ebook readers, and so on. For these devices, I think it’s just a matter of having to have the discipline to take these out every 30 to 60 days and charge them up.

        As for vehicles, there is no way to know for sure. There has been no hard-core conclusive testing on vehicles, so a lot of what scientists and engineers talk about are only educated guesses. Granted, these are very educated guesses, but there’s enough dispute among them to be able to derive a conclusive answer from it.

        There’s also a lot of variables: Is the car running when EMP hits? Is it parked under a metal roof or underground? How well shielded is the computer on the vehicle from the manufacturer? Etc.

        Best answer we have: Some cars will be toast, some won’t. You may be able to reset the computer by disconnecting the battery for a few minutes.

        • Thank you!

  2. What I don’t understand is, if there is going to be no power for a very long time or maybe indefinitely, why protect electronic devices that you will then be unable to use becasue there is no power? I get the walkie talkies and a radio, but what else are people thinking of? Exactly what devices are people trying to shield, and are they things that would be able to run on batteries? My thinking has run along the lines of just adjusting to life without power and do everything possible to be able to survive and thrive without it. Am I missing the point?

    • Receiving information over AM or Shortwave would be good to have, but so would the ability to communicate with others, especially for defense purposes. Far easier for a group or neighborhood with a few CB radios to be able to warn each other about intruders, than clanging on a large bell.

      Many modern flashlights, including LED lights, are very susceptible to EMP.

      If you live on a farm or retreat, I’m sure having some spare parts to keep your alternate energy system working and/or your well pump working would be incredibly handy.

      Night vision and perimeter monitoring would give you the tactical advantage to stay alive as you try to defend your home or retreat.

      The ability to have massive amounts of information in a digital format allows for you to search for specific information far faster and more efficient than with paper books. You should have paper books, but having additional books in digital form, is a huge plus. Not to mention having thousands of novels, videos and songs that you wouldn’t otherwise have.

      For more info: http://www.thepreparednesspodcast.com/what-to-store-in-your-faraday-cages or http://thesurvivalmom.com/2012/07/16/whats-in-your-faraday-cage-a-common-sense-guide-to-preparing-for-an-emp/

  3. Why do you have to shield disconnected power cords? I get that they can act as antennas, but if not connected to anything, what damage can EMP do to them?

    Thanks for the great, practical info!

    • I don’t think the article said to wrap these by themselves. If you cannot remove cords and antennas from devices, then they need to be completely contained in the same container as the device they’re connected to. If they can be removed and do *not* have any electronics in them, they don’t need to be protected, though you’ll want to keep all parts together so you don’t lose or misplace these removed parts.

      Keep in mind, though, that some cords, especially those like charging cords, have chips in them. This includes cords you wouldn’t expect to have chips in them like Apple’s cords for iOS devices. These would also need to be protected to ensure that they will function after an EMP.

  4. Thanks for the informative post. Question: what about the charge controller for my off-grid power system? We live off the solar panels, charge controller, inverter and batteries (Edison batteries are amazing, by the way!) with a back up generator for long stretches of cloudy weather. We are about 7 miles from the nearest utility pole. I can’t figure out if this system is vulnerable to what you are describing. I need to know if I should be wrapping my power shed with tinfoil! Thanks! – Z

  5. First, keep in mind that anything that is connected to wires or metal is more susceptible to an EMP. The metal in wires and pipes acts like a collector for the EMP and directs it into whatever is connected. If what is connected contains semiconductors, they’ll probably be damaged of not outright destroyed. Small devices not connected to wires or metal might survive, or they might not; it depends on how strong the EMP is at your location (i.e., are you directly under the blast or at the edge of the line-of-site radius).

    Charge controllers, inverters, blocking diodes are all very susceptible to an EMP. I think there are some ways to protect using MOVs, but I have no experience with these. The only way to make sure that you’ll have all your systems working after an EMP event is to have safely squirreled away replacements for them. Likewise with your generator; store whatever electronic parts are needed for it to run.

    Wrapping your shed in foil might work, but unless there was no gaps in the metal sheathing, it would probably only be marginal protection. However, that doesn’t mean that you shouldn’t do it. Since we don’t know exactly how an EMP will behave, particularly for a given location, every step you take is like adding another layer.

    So, putting tin metal sheeting on your shed, storing often used items in a sealed metal trash can when not in use, deep storing in Faraday containers replacements and spare parts, and even unplugging devices and appliances from the wall outlet when not in use would all help to decrease your susceptibility to an EMP.

    • Thanks! – Z

  6. I would suggest that you wrap your laptop battery seperate, the newer batteries are controlled using micro circuits that are built into the battery pack.

  7. One Item I’ve found that works well are 20mm ammo cans. I line the inside with AL foil then 1/2 expanded foam (as an insulator) put my items inside and then a wrap of foil around the seam of the can and lid. It is both water tight and EMP proof.

  8. After an EMP, how long do you wait for pulling your items out of the first trash can? A couple of hours?

    • Some people have conjectured that a second EMP could be used to further destroy electronic capabilities, so it might be wise to wait even a couple of weeks or more unless an item is absolutely necessary for survival. You could always re-package your Faraday container contents and open them at a later date.

  9. A Faraday cage is nothing more than a ‘lightning rod’. And as such, NEEDS TO BE GROUNDED properly to work effectively, just like a lightning rod.

  10. Thanks for the article. This issue of EMP events needs to be made an issue regularly. People need to know how bad it will be if the grid goes down even in a relatively small region. Families need to prepare accordingly. They need to be able to make informed decisions. How bad will it be?



  11. Thanks for the article.. Just wondering though.. How do you know when to start wrapping your electronics? Will we get an email saying that an EMP is about hit?
    Good info !

  12. Here is the instructable for a Faraday cage that is easy to make (modify) and will look good in the house. No longer will people need to have a galvanized trash can in their den to have the convenience of having a faraday cage in the house. It also doubles as a file cabinet


  13. Suppose you want to go an extra step besides making a Faraday Cage. Could taking the batteries out of an electronic device, disabling or cutting the current, until after a CME or God forbid an HEMP. Would that device, such as a battery powered flashlight, would still work if you put the batteries back in? Would the light turn on?

  14. What about batteries? AA, AAA, C, D….. I have a small solar charger that can recharge rechargeable batteries, but do you need to protect them from EMP? Also, if I stock pile a whole bunch of store purchased disposable batteries, do they need to be protected from EMP? Car batteries? Thank you!

  15. Protecting Yourself from EMP(why? Because you can set up afterwards with solar or generators which are not so susceptable– and NO George.. Its not a lightning rod.)

    © 1989 by Duncan Long

    EMP. The letters spell burnt out computers and other electrical systems and perhaps even a return to the dark ages if it were to mark the beginning of a nuclear war. But it doesn’t need to be that way. Once you understand EMP, you can take a few simple precautions to protect yourself and equipment from it. In fact, you can enjoy much of the “high tech” life style you’ve come accustomed to even after the use of a nuclear device has been used by terrorists—or there is an all-out WWIII.

    EMP (Electro-Magnetic Pulse), also sometimes known as “NEMP” (Nuclear Electromagnetic Pulse), was kept secret from the public for a long time and was first discovered more or less by accident when US Military tests of nuclear weapons started knocking out phone banks and other equipment miles from ground zero.

    EMP is no longer “top secret” but information about it is still a little sketchy and hard to come by. Adding to the problems is the fact that its effects are hard to predict; even electronics designers have to test their equipment in powerful EMP simulators before they can be sure it is really capable of with standing the effect.

    EMP occurs with all nuclear explosions. With smaller explosions the effects are less pronounced. Nuclear bursts close to the ground are dampened by the earth so that EMP effects are more or less confined to the region of the blast and heat wave. But EMP becomes more pronounced and wide spread as the size and altitude of a nuclear blast is increased since the ground; of these two, altitude is the quickest way to produce greater EMP effects. As a nuclear device is exploded higher up, the earth soaks up fewer of the free electrons produced before they can travel some distance.

    The most “enhanced” EMP effects would occur if a nuclear weapon were exploded in space, outside the Earth’s atmosphere. In such a case, the gamma radiation released during the flash cycle of the weapon would react with the upper layer of the earth’s atmosphere and strip electrons free from the air molecules, producing electromagnetic radiation similar to broad-band radio waves (10 kHz-100 MHz) in the process. These electrons would follow the earth’s magnetic field and quickly circle toward the ground where they would be finally dampened. (To add to the confusion, we now have two more EMP terms:

    “Surface EMP” or “SEMP” which refers to ground bursts with limited-range effects and “High-altitude EMP” or “HEMP” which is the term used for a nuclear detonation creating large amounts of EMP.)

    Tactically, a space-based nuclear attack has a lot going for it; the magnetic field of the earth tends to spread out EMP so much that just one 20-MT bomb exploded at an altitude of 200 miles could—in theory—blanket the continental US with the effects of EMP. It’s believed that the electrical surge of the EMP from such an explosion would be strong enough to knock out much of the civilian electrical equipment over the whole country. Certainly this is a lot of “bang for the buck” and it would be foolish to think that a nuclear attack would be launched without taking advantage of the confusion a high-altitude explosion could create. Ditto with its use by terrorists should the technology to get such payloads into space become readily available to smaller countries and groups.

    But there’s no need for you to go back to the stone age if a nuclear war occurs. It is possible to avoid much of the EMP damage that could be done to electrical equipment—including the computer that brought this article to you—with just a few simple precautions.

    First of all, it’s necessary to get rid of a few erroneous facts, however.

    One mistaken idea is that EMP is like a powerful bolt of lightning. While the two are alike in their end results—burning out electrical equipment with intense electronic surges—EMP is actually more akin to a super-powerful radio wave. Thus, strategies based on using lightning arrestors or lightning-rod grounding techniques are destined to failure in protecting equipment from EMP.

    Another false concept is that EMP “out of the blue” will fry your brain and/or body the way lightning strikes do. In the levels created by a nuclear weapon, it would not pose a health hazard to plants, animals, or man PROVIDED it isn’t concentrated.

    EMP can be concentrated. That could happen if it were “pulled in” by a stretch of metal. If this happened, EMP would be dangerous to living things. It could become concentrated by metal girders, large stretches of wiring (including telephone lines), long antennas, or similar set ups. So—if a nuclear war were in the offing—you’d do well to avoid being very close to such concentrations. (A safe distance for nuclear-generated EMP would be at least 8 feet from such stretches of metal.)

    This concentration of EMP by metal wiring is one reason that most electrical equipment and telephones would be destroyed by the electrical surge. It isn’t that the equipment itself is really all that sensitive, but that the surge would be so concentrated that nothing working on low levels of electricity would survive.

    Protecting electrical equipment is simple if it can be unplugged from AC outlets, phone systems, or long antennas. But that assumes that you won’t be using it when the EMP strikes. That isn’t all that practical and—if a nuclear war were drawn out or an attack occurred in waves spread over hours or days— you’d have to either risk damage to equipment or do without it until things had settled down for sure.

    One simple solution is to use battery-operated equipment which has cords or antennas of only 30 inches or less in length. This short stretch of metal puts the device within the troughs of the nuclear-generated EMP wave and will keep the equipment from getting a damaging concentration of electrons. Provided the equipment isn’t operated close to some other metal object (i.e., within 8 feet of a metal girder, telephone line, etc.), it should survive without any other precautions being taken with it.

    If you don’t want to buy a wealth of batteries for every appliance you own or use a radio set up with longer than 30-inch antenna, then you’ll need to use equipment that is “hardened” against EMP.

    The trick is that it must REALLY be hardened from the real thing, not just EMP-proof on paper. This isn’t all that easy. The National Academy of Sciences recently stated that tailored hardening is “not only deceptively difficult, but also very poorly understood by the defence-electronics community.” Even the US Military has equipment which might not survive a nuclear attack, even though it is designed to do just that.

    That said, there are some methods which will help to protect circuits from EMP and give you an edge if you must operate ham radios or the like when a nuclear attack occurs. Design considerations include the use of tree formation circuits (rather than standard loop formations); the use of induction shielding around components; the use of self-contained battery packs; the use of loop antennas; and (with solid-state components) the use of Zener diodes. These design elements can eliminate the chance an EMP surge from power lines or long antennas damaging your equipment. Another useful strategy is to use grounding wires for each separate instrument which is coupled into a system so that EMP has more paths to take in grounding itself.

    A new device which may soon be on the market holds promise in allowing electronic equipment to be EMP hardened. Called the “Ovonic threshold device”, it has been created by Energy Conversion Devices of Troy, MI. The Ovonic threshold device is a solid-state switch capable of quickly opening a path to ground when a circuit receives a massive surge of EMP. Use of this or a similar device would assure survival of equipment during a massive surge of electricity.

    Some electrical equipment is innately EMP-resistant. This includes large electric motors, vacuum tube equipment, electrical generators, transformers, relays, and the like. These might even survive a massive surge of EMP and would likely to survive if a few of the above precautions were taking in their design and deployment.

    At the other end of the scale of EMP resistance are some really sensitive electrical parts. These include IC circuits, microwave transistors, and Field Effect Transistors (FET’s). If you have electrical equipment with such components, it must be very well protected if it is to survive EMP.

    One “survival system” for such sensitive equipment is the Faraday box.

    A Faraday box is simply a metal box designed to divert and soak up the EMP. If the object placed in the box is insulated from the inside surface of the box, it will not be affected by the EMP travelling around the outside metal surface of the box. The Faraday box simple and cheap and often provides more protection to electrical components than “hardening” through circuit designs which can’t be (or haven’t been) adequately tested.

    Many containers are suitable for make-shift Faraday boxes: cake boxes, ammunition containers, metal filing cabinets, etc., etc., can all be used. Despite what you may have read or heard, these boxes do NOT have to be airtight due to the long wave length of EMP; boxes can be made of wire screen or other porous metal.

    The only two requirements for protection with a Faraday box are:

    (1) the equipment inside the box does NOT touch the metal container (plastic, wadded paper, or cardboard can all be used to insulate it from the metal) and
    (2) the metal shield is continuous without any gaps between pieces or extra-large holes in it.

    Grounding a Faraday box is NOT necessary and in some cases actually may be less than ideal. While EMP and lightning aren’t the “same animal”, a good example of how lack of grounding is a plus can be seen with some types of lightning strikes. Take, for example, a lightning strike on a flying airplane. The strike doesn’t fry the plane’s occupants because the metal shell of the plane is a Faraday box of sorts. Even though the plane, high over the earth, isn’t grounded it will sustain little damage.

    In this case, much the same is true of small Faraday cages and EMP. Consequently, storage of equipment in Faraday boxes on wooden shelves or the like does NOT require that everything be grounded. (One note: theoretically non-grounded boxes might hold a slight charge of electricity; take some time and care before handling ungrounded boxes following a nuclear attack.)

    The thickness of the metal shield around the Faraday box isn’t of much concern, either. This makes it possible to build protection “on the cheap” by simply using the cardboard packing box that equipment comes in along with aluminium foil. Just wrap the box with the aluminium foil (other metal foil or metal screen will also work); tape the foil in place and you’re done. Provided it is kept dry, the cardboard will insulate the gear inside it from the foil; placing the foil-wrapped box inside a larger cardboard box is also wise to be sure the foil isn’t accidentally ripped anywhere. The result is an “instant” Faraday box with your equipment safely stored inside, ready for use following a nuclear war.

    Copper or aluminium foil can help you insulate a whole room from EMP as well. Just paper the wall, ceiling and floor with metal foil. Ideally the floor is then covered with a false floor of wood or with heavy carpeting to insulate everything and everyone inside from the shield (and EMP). The only catch to this is that care must be taken NOT to allow electrical wiring connections to pierce the foil shield (i.e., no AC powered equipment or radio antennas can come into the room from outside). Care must also be taken that the door is covered with foil AND electrically connected to the shield with a wire and screws or some similar set up.

    Many government civil defence shelters are now said to have gotten the Faraday box, “foil” treatment. These shelters are covered inside with metal foil and have metal screens which cover all air vents and are connected to the metal foil. Some of these shelters probably make use of new optical fibre systems—protected by plastic pipe—to “connect” communications gear inside the room to the “outside world” without creating a conduit for EMP energy to enter the shelter.

    Another “myth” that seems to have grown up with information on EMP is that nearly all cars and trucks would be “knocked out” by EMP. This seems logical, but is one of those cases where “real world” experiments contradict theoretical answers and I’m afraid this is the case with cars and EMP. According to sources working at Oak Ridge National Laboratory, cars have proven to be resistant to EMP in actual tests using nuclear weapons as well as during more recent tests (with newer cars) with the US Military’s EMP simulators.

    One reason for the ability of a car to resist EMP lies in the fact that its metal body is “insulated” by its rubber tires from the ground. This creates a Faraday cage of sorts. (Drawing on the analogy of EMP being similar to lightning, it is interesting to note that cases of lightning striking and damaging cars is almost non-existent; this apparently carries over to EMP effects on vehicles as well.)

    Although Faraday boxes are generally made so that what is inside doesn’t touch the box’s outer metal shield (and this is especially important for the do-it-yourself since it is easy to inadvertently ground the Faraday box—say by putting the box on metal shelving sitting on a concrete floor), in the case of the car the “grounded” wiring is grounded only to the battery. In practice, the entire system is not grounded in the traditional electrical wiring sense of actually making contact to the earth at some point in its circuitry. Rather the car is sitting on insulators made of rubber.

    It is important to note that cars are NOT 100 percent EMP proof; some cars will most certainly be affected, especially those with fibreglass bodies or located near large stretches of metal. (I suspect, too, that recent cars with a high percentage of IC circuitry might also be more susceptible to EMP effects.)

    The bottom line is that all vehicles probably won’t be knocked out by EMP. But the prudent survivalist should make a few contingency plans “just in case” his car (and other electrical equipment) does not survive the effects of EMP. Discovering that you have one of the few cars knocked out would not be a good way to start the onset of terrorist attack or nuclear war.

    Most susceptible to EMP damage would be cars with a lot of IC circuits or other “computers” to control essential changes in the engine. The very prudent may wish to buy spare electronic ignition parts and keep them a car truck (perhaps inside a Faraday box). But it seems probable that many vehicles WILL be working following the start of a nuclear war even if no precautions have been taken with them.

    One area of concern are explosives connected to electrical discharge wiring or designed to be set off by other electric devices. These might be set off by an EMP surge. While most citizens don’t have access to such equipment, claymore mines and other explosives would be very dangerous to be around at the start of a nuclear box if they weren’t carefully stored away in a Faraday box. Ammunition, mines, grenades and the like in large quantities might be prone to damage or explosion by EMP, but in general aren’t all that sensitive to EMP.

    A major area of concern when it comes to EMP is nuclear reactors located in the US. Unfortunately, a little-known Federal dictum prohibits the NRC from requiring power plants to withstand the effects of a nuclear war. This means that, in the event of a nuclear war, many nuclear reactors’ control systems might will be damaged by an EMP surge. In such a case, the core-cooling controls might become inoperable and a core melt down and breaching of the containment vessel by radioactive materials into the surrounding area might well result. (If you were needing a reason not to live down wind from a nuclear reactor, this is it.)

    Provided you’re not next door to a nuclear power plant, most of the ill effects of EMP can be overcome. EMP, like nuclear blasts and fallout, can be survived if you have the know how and take a few precautions before hand.

    And that would be worth a lot, wouldn’t it?

    Some initial thoughts on EMP protection from the US military packaging division.

    A continuously sealed metal barrier has proven to be very effective in preventing EM/HPM energy from reaching susceptible electronic or explosive components. Exterior packaging fabricated from plastic, wood or other fibre materials provides almost no protection form EM/HPM threats. The metal enclosure can be very thin provided there are no openings (tears, pin holes, doors, incomplete seams) that would allow microwaves to enter. Sealed barrier bags that incorporate a thin layer of aluminium foil and are primarily used to provide water vapour proof protection to an item, can add a great deal of resistance to EM/HPM penetration.

    A number of cylindrical and rectangular steel containers have been developed by the Packaging Division for a wide range of munitions, weapon systems and associated components. The cylindrical containers are end opening and the rectangular containers are top opening. All the containers have synthetic rubber gaskets that allow them to maintain a +3 psi environmental seal to the outside environment. The containers are constructed using seam welding to provide for continuous metal contact on all surfaces of the body assembly. The cover openings have been held to a minimum and the sealing gaskets positioned in a manner to allow overlapping metal parts to add additional protection to these areas. Microwaves are very adept at bouncing around and working their way into even the smallest opening. Tests of the cylindrical and rectangular steel containers used by this organization have demonstrated a high level of protection in preventing EM/HPM energy from entering the container.

    The key is to use a metal enclosure and eliminate or minimize any openings. Where openings are needed they should be surrounded to the greatest extent possible by continuous metal and in the case of a gasket, metal sheathing or mesh can be placed around the elastometer material or conductive metal moulded into the gasket. The closer the surrounding container comes to a continuous metal skin the more protection that will be provided.

    High quality gaskets, utilizing either a mesh or embedded conductive metal design, are very expensive. They add a magnitude of cost to a normal gasket and can easily double the price of a container similar to the ones mentioned above.

    URL: http://standeyo.com/News_Files/NBC/EMP.protection.html

  16. I’ve been looking into investing on a galvanized corrugated steel pipe bunker to help serve as a fallout shelter. Would you think that galvinized steel pipe would protect the power systems in my bunker from EMP? I just want to be sure that my generator will stay running so I have light in my shelter, if you think it won’t protect against EMP then I think I will build a faraday cage for it and any other electronics in the bunker but I just want to have a general idea about this before I invest in such a big “prep”.

  17. I’ve used this technique with several devices, such as an iPod shuffle, it would probably get boring,a kindle, good info, usbs with an old laptop, and a radio, and several charge packs for all of them. Thanks!

  18. Good article but just a thought. If there was a serious EMP I suspect the least of my worries would be my radio or ipad. The grid would be down in which case nothing would work including running water. Humans really have painted themselves into an impossible corner with our reliance on electricity. We have no backup plan. It will be a reset back to the stone age.

  19. As a woman trying to protect her own kids I am also a foster parent so I have a lot riding on my shoulders. I take my responsibility very seriously. I know the obvious items that would be effected by an EMP but what are some of the other NOT so obvious items that need to be protected. Example: solar panels? Generator? What about just the batteries for the solar back up? I hope to very soon purchase an RV refrigerator that runs on propane would this need to be protected? like I said I got the obvious but it’s the not so obvious that I am concerned about can we maybe get a list of these items and maybe a general idea or suggestion on how to protect the BIGGER items? I live not far from Nellis Air force base and yes there is an actual area 51 so an EMP is a definite concern.
    Thank you so much for taking the time to help those of us who want to help themselves!! To those who don’t well God Bless!!

  20. I just purchased a portable solar generator. I am unsure as to how I would secure said generator along with accompanied solar panels. I have not taken it out of the box and basically know nothing pertaining to its operation. I did note that the article mentioned several times to place backup components into a Faraday cage however again I have zero knowledge of the mechanical aspects of the generator. Any ideas or thoughts? Thanks much!

  21. Well I was thinking since I live in a mobile with a metal roof, and aluminum siding that I would probably be safe. But I get radio signals in the house : (

  22. Will a micro wave act as protection from an EMP

    • I’ve heard that it’s possible for EMP waves to enter the microwave through the area around the cord, but many people believe that a microwave WILL work.

  23. I don’t understand why a little crack or pinhole defeats a Faraday cage. If the effect is line of sight, then MAYBE a crack would be a problem if it lined up exactly with the source of the pulse, but even then, wouldn’t it only allow a tiny sliver of the pulse to pass? If a screen (which has a lot of holes) is effective why does a crack matter?

  24. Pingback: What the Heck does that Even Mean!? A Glossary of Preparendess & Homesteading Terms - Mom with a PREP

  25. Testing on cars actually HAS been done. I need to find the report from the UK, but it basically said that most cars would be easily restarted after the end of an EMP attack. Unless, of course, everything in your car is computerized, including the starter. Mine is not. Anybody buying a computer for a car that can be hacked and tracked is an idiot anyway. Also, here’s some better info about automobiles after EMP atatcks: http://www.futurescience.com/emp/vehicles.html

  26. It makes a difference because electricity travels in waves. So with the hole, the waves get in. You have to think of it like water. It won’t let alot in, but enough to be a problem. Additionally, this is a good reason why we shouldn’t let the gov’t eliminate important thinks like PHYSICS from public education.

  27. Take an AM radio, tune it to the strongest AM station in your area, and place it in your microwave. Does it still pick up the radio station? Most likely, it will (unless you happen to be a good distance from an AM station).

    Microwaves are designed to shield the ~2.4 Ghz waves from escaping. They do not shield for frequencies above or below those used by the microwave itself. Thus, it is a very poor EMP shield.

    Same with Mylar bags. They may block 1 Ghz and up, but most of the energy of EMP frequencies are well below this range, and they too, won’t work.

  28. EMP does its damage by inducing large voltage differences into sensitive devices. It seems to me that removing the batteries from electronic devices may be half of the solution and may actually create an additional problem. Without the battery, the ‘hot’ side of the circuitry is floating and any induced voltage may actually be greater due to the high impedance of the internal circuitry. The internal impedance of the battery may actually lower the overall ‘hot-ground’ impedance and any induced voltage.
    I believe, where practical, I would actually remove the battery and short the ‘hot-ground’ inputs to sensitive equipment while in storage. In the case of an AC input that uses a step-down transformer (as opposed to a chopping power supply) removing the AC and shorting the input would actually prevent the primary winding from inducing any voltage into the secondary. At a minimum, the device may have a greater chance at common-mode rejection wherein any induced voltage is induced into the hot and common sides of the circuitry equally, in-phase at least at lower frequencies, and self-canceling.
    I ‘m not speaking from any real-world testing, just thinking about alternate possibilities and issues for further discussion/evaluation.

  29. Addition to last — To have any positive effect (if there is one to be had) the equipment would have to be turned ‘on’ in storage. I understand this would make minimal difference in much of the solid-state equipment out there, but would it hurt?

  30. Um I have some questions . I’ve been all over the internet looking up things like this , but you and one two other sites are the only one that make since to me. I’ve read your article but I still have questions since there is a lot of miss information out there .
    I wish to protect some of my electronic devices , I know that the devices I wish to protect would be useless without power ,I’m just doing it for reasureance .
    Here’s what I need to know. –
    Will cds and DVDs / games be affected ( those on disc)
    I’ve read that yes they’ll be fine , no they won’t be fine .
    ( I have a CD player for CDs)
    Will headphones be fine if they aren’t in use . ( I have more than one pair but I’m just curious )
    I wish to protect my game systems just for the sake of making me feel better .
    Do I need to put power cords in the cage too or can I just leave them one the floor or something.
    I’ve read that you can use holiday popcorn tins and others say you can’t .
    I can’t really ground the cage because i live on the upper level , do I need to do something special because I have carpet . Some say that the batteries will explode, others say no.
    I know that I cannot protect everything , but that doesn’t me I can’t protect some . And I know that the game systems will be useless without power . But the reason I’m doing it is because if things ever go back to normal I have something , things that I can call my own , things that work. Things that bring me comfort .

  31. Great questions, Holly.

    “Will cds and DVDs / games be affected ( those on disc)”
    No. Optical discs have no electronics and won’t be affected by EMP.

    “Will headphones be fine if they aren’t in use”
    It depends. If they are simply wires and speakers, they should be fine. If they have any electronics in them, they will probably be affected. Better to assume they will be susceptible to EMP.

    “I wish to protect my game systems just for the sake of making me feel better”
    Who wouldn’t?! They will need to be protected in a Faraday box, as they are very susceptible to EMP, especially if they are plugged in.

    “Do I need to put power cords in the cage too or can I just leave them one the floor or something.”
    Unless the cord has electronics in it, it will be fine. However, it’s probably best to keep everything together.

    “I’ve read that you can use holiday popcorn tins and others say you can’t ”
    I wouldn’t use them. They’re too thin to provide a lot of EMP protection. I have put an AM radio into one and it still was able to pick up the AM station. How is it going to protect against the much stronger pulse of EMP if it can’t block a weak AM radio signal?

    “I can’t really ground the cage because i live on the upper level , do I need to do something special because I have carpet”
    You do not want to ground your EMP Faraday containers. Not to be mean, but anyone saying different doesn’t understand EMP. Common electricity theory does not apply to EMP, so there are those that will argue for grounding, because it’s what you do for safety with electricity.

    “I know that I cannot protect everything , but that doesn’t me I can’t protect some . And I know that the game systems will be useless without power . But the reason I’m doing it is because if things ever go back to normal I have something , things that I can call my own , things that work. Things that bring me comfort .”
    Agreed. I think large gaming systems might be a bit much to try and protect, as you also need to protect the controllers and an entire television, which is probably difficult. But, tablets, smartphones and small gaming systems (like DS, PSP, etc.) would be easier to protect.

    Although, I don’t think you would have too much time to play games after an EMP event, as you’ll be struggling to survive nearly every minute of the day. Having electronics to provide information (books, PDFs, text, videos), entertainment (audio, books, videos, pictures, games), and security (CO monitors, night vision, perimeter detection, alarms) can give you a force multiplier over the next guy, which is why they’re worth protecting.

  32. I don’t really have any intention of playing games after and emp . I just want the comfort in knowing my stuff is safe. But really a big thing of mine is music and as long as I have that I’ll be fine . Which is why I asked about the CDs .
    But would they be fine is I stored them in a cardboard box anyway ?
    (Cause I have a box that I can wrap in foil and put them in .)
    Though they might do better if I moved them over to the wooden book case instead of havering them sit
    On a metal stand .
    One thing i cannot get right is the lining.
    I have a 6 gallon galvanized steel trash can , but I can’t get the card board to line up right .
    Is it supposed to flush with the can ?
    That’s the one part I have a hard time with , getting it adjusted right.
    ( but I’m also using cut cardboard boxes , and I don’t think I can tape the pieces together)
    Um one final thing my house has an old tv antenna on top of the chimney , would that pose a problem?

  33. I hate to keep bothering you Rob but I have one more question .
    My mom took the trash can I was going to use as a cage.
    Now I’ve read that you can use boxes (which I hope work just as well)
    The box I’m hoping to use is the kind that you get from staples ( the white folded ones)
    Since that would fit what I want in there nicely .
    I’m gonna add extra cardboard to the inside of the box . How many layers of foil should I use?
    The items that I put in the box will be in cardboard boxes wrapped in foil . ( at least two layers )
    In a way I think this might work better in my room space wise .
    ( I hope that box works because the only other ones I have are the basic ones with the flaps at the top.)
    I know that a steel trash can would work better but you do with what you have I guess. And maybe with this done I can go back to my studies . ( though I wish I had my sisters attitude , if it happens it happens if it doesn’t , then it doesn’t . ) my family worries about the here and now , don’t get me wrong we’ve prepped and have things stored away . And thankfully we don’t live in the city , we live in the country will cows and such and farm equipment running up and down the road . ( the well water took some getting used to ). Sorry for the ramble , but please let me know if that box works .
    Please and thank you.

  34. Does anyone know if the preparednesspro.com site is accurate ?
    Cause he says foil boxes won’t work , that it’s not adequate or whatever.
    He says batteries will be fine then he turns around and says batteries won’t be fine.
    Futurescience.com seems pretty accurate .
    He told me that I needed to ground , but how can I do that if I have carpet ?

  35. I haven’t had much luck with foil lined boxes or envelopes. They might work if you were able to get enough layers of foil around them, but personally, I’d avoid them.

    If you don’t have access to a single container you can use, then wrapping each device in multiple layers of foil is probably the next best solution. Five layers of HD foil at the minimum. And make sure you first wrap the device with a non-conductive material.

    FutureScience.com is a good site to reference.

    Batteries will probably be fine, unless they have electronics in them (some do). Better to protect any that you will be depending on, as you won’t get a second chance with EMP.

    Faraday containers for EMP should not be grounded.

    I have available extensive information on my website and podcast about EMP Preparedness and suggest you read over that information, as I think you’ll find most of your questions answered in it. I also have a book, if you’re looking for a concise source of the info. You can find access to all of that here: EMP Preparedness/.

  36. Thank you very much for your help . I greatly appreciate it.
    I found another trash can , but it’s different than the other one .
    It says it galvanized sheet steel . The one I was going to use was a brehens , and it says high quality steel . ( I can feel a slight difference in thickness) but it’s the same thing right .
    The only thing is the sheet steel can isn’t a locking lid .
    But is there a steel difference ?
    One a small note I’m going to make a temp emp cage , which will be for items that I use every day. It will be a foil wrapped box that can fit other wrapped boxes inside . This is just for when I’m out or away.
    I know it’s not a lot of protection but it’s something . I might keep some cds in a small cardboard box ( cant hurt can it?) . But thank you for you help . Though I hope and pray that we are never attacked in this fashion. And I pray that we never have to use our prepp gear . As grandma said better to have it and not need it , then to need it and not have it . Nothing wrong in praying that you never need it.

  37. I know I asked this already , but I actually forgot to add this with my first post about cds .
    I know that CDs / DVDs from the store would be safe .
    So that means my game discs should be too.
    However the question I would like to know is are
    CD-R discs safe as well . I forgot to ask a long time ago and I hate to be a bother.
    I keep being told to ‘put the cd in the microwave and find out . Or that the metal layer is a conductor and will fry the disc or erase the data . Or super – emps will wipe or melt them’
    ( the reason I ask about the CD-R disc is because me and my sis have a lot of them. )
    But I’m sorry for asking a repeat question I just want to make sure I don’t have to put them in the cage ,
    And was trying to find scientific facts on optical data emp testing but I guess no ones done that .

  38. I don’t know specifically about CD-Rs, but as they’re not electrical based, I would think they would be fine. I wouldn’t put them in a microwave, as they’re likely to melt or warp. Microwave energy found in a microwave oven is not the same thing as EMP.

  39. When I was young the rule was; 3 minutes to breathe, 3 days to drink water, 3 weeks to eat in survival.
    Provided you survive an attack, the next most important and critical event is to have clean water to drink, without electricity. An old fashion point well and hand pump will be crucial, and a good water filter will keep you alive and healthy, and possibly all your neighbors. Food storage and preparation is next. As any camper from the 1950’s knows fuel and a spot to cook becomes the next most important item, again no electricity means no refrigaration. All meats need to be cooked immediately or it will spoil. Stock pile wood, kerosene, and gasoline. Survival of the first 3 months will give you time for the people to organize to the new realities and start the rebuild process. If you live in the suburbs you may meet your neighbors for the first time, some not so friendly, be prepared, need I say more!

  40. You must ground the container acting as a Faraday cage to earth with a direct, low resistance ground – or it will NOT work at ALL. Any metal shielding that is not connected to ground will inductively couple and become a secondary radiator of the RF impulse, putting your equipment at even more risk by concentrating local electromagnetic fields.

    If the cage/can/container is grounded to earth (IE 8 foot copper clad ground rod, heavy gauge, low impedance wire) the induced RF current will shunt to ground, and the cage will not become an antenna. The aluminum foil you have wrapped on devices inside the faraday cage is not doing anything, as it is not connected to a ground. If, during your test, you would have grounded your trash can with an old piece of copper waterpipe or a ground rod, the grounded trash can and the cardboard insulator would have blocked out virtually all RF, aluminum foil is completely unnecessary. The cloth is good thinking, it will allow the devices to breathe as temperature and relative humidity changes. Thank you for the article!

  41. Rich, a small gap will not necessarily defeat your Faraday cage, it has to do with the size of the gap and the frequency of the radiation. So long as the gap is smaller than the wavelength(this depends on frequency) of the RF field/EMP, the wave will not be able to pass through the hole without being captured by the metallic shield. Kind of like the shape blocks from when we were kids, for example if the wavelength of the frequency of the EMP burst was 5mm, any gap larger than 5mm will allow RF to pass through it – the inverse is also true. That is to say that any gap smaller than 5mm will attenuate the radio wave (emp). As long as you have a metallic container and a ground wire soldered onto it connected to an earth ground rod, any wave that strikes the outside of the container (being conducted into it) will shunt to ground.

  42. See this is why I have anxiety. Some say ground , others say don’t .
    I can’t bury anything because the yard floods . My cage is a galvainzed steel trash can that’s sitting in my room on a carpeted floor . I have no place to ground it too.
    My cage is lined with cardboard , sides ,top and bottom, the stuff in the cage is in a cardboard
    Box wrapped in two layers of HD aluminum foil.
    And not to be a bitch , but how do you know that a cage needs a wire . For all you know grounding could have the opposite effect, and the ones that aren’t grounded are safe. I’m sorry I don’t mean to question your knowledge, it’s just I’m so frustrated and confused, that I actually get anxiety .
    I though I was doing it right but now I don’t know .

  43. Has anyone tested the effect that a grid of rare-earth magnets would have on EMP? Close enough together to create a magnetic bottle to shield against the induction caused by the EMP. No wires near the magnet, just a grid of multiphase permanent magnets spaced equally distant and not connected to each other electrically. Is there an effect? Would it shield EMP?

  44. Holly, I believe the danger in grounding a faraday cage lies in the length of the wire used to connect to the ground. If the wire is more than 30 inches long, it would act as an antenna and actually increase the effect. Obviously, in your scenario, if the ground spike is in the same spot as the faraday cage, then the wire connecting to it would be short and a ground would be beneficial. However, if it is at the other end of the house, then the wire leading to it would induct a voltage. Causing the cage to be charged more than if it had never been grounded. Hope that helps.

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