15 Things You Think You Know About Faraday Cages But You Don’t

By Anne January 13, 2017 14:40

15 Things You Think You Know About Faraday Cages But You Don’t

This article takes into consideration only the effects of a nuclear EMP, not a solar flare. A solar flare would only affect any electronics connected to the grid.

#1. Will a microwave work as a Faraday cage?

No. If an EMP strikes, you will notice that all your electronic devices that you stored in a microwave oven will be rendered useless. The microwave is not a Faraday cage.

#2. Will a refrigerator work as a Faraday cage?

No, most refrigerators do not work as a Faraday cage. I tested mine, and it’s definitely not a Faraday cage.

#3. If I keep a backup mobile phone in my Faraday cage, will it work when I need it?

Yes, your phone will work perfectly. However, it will be rendered almost useless because the network will not be functional. The only form of communication after an EMP will be the radio. Click here to find out what radio you should keep in your Faraday cage. 

#4. Do I need to store batteries in a Faraday cage?

No. They will continue to work regardless and will just take up space in your Faraday cage. Here are the best batteries for survival situations.

#5. Do Faraday cages need grounding?


#6. Do I need to keep my solar panels in a Faraday cage?

No. The only part of the system you have to worry about is your solar panel inverter. Don’t worry about your solar panels; they will be fine. It’s best to buy an extra inverter and keep it in your Faraday cage so you can replace the useless one after the EMP.

#7. If I wrap electronic devices in heavy duty aluminum foil, will that work?

No. But if you wrap the cardboard box in which you bought them in heavy duty aluminum foil, this would be an effective Faraday cage. Here are the step-by-step instructions.

#8. Will flashlights continue to function after an EMP Strike?

Some flashlights will continue to function, and some will burn out. It all depends on the power and distance from the blast.

#9. Is a shipping container a Faraday cage?

Yes, but just remember that you can’t just put the electronic devices directly in contact with the metal. Some people board the interior of the container with wooden panels.

#10. Can I use this shipping container as a “Faraday garage” for my car?

Yes, you can definitely do that. Most cars fit in a standard shipping container, but just to make sure, go ahead and take the measurements before buying a shipping container.

#11. If you turn off your devices, will they be EMP-proof?


#12. Are airplanes Faraday cages?

No. Planes operate on the basic principles of lift and thrust, so they will become more or less gliders. They will be very difficult to control and most of them will fall from the sky and crash.

#13. How do I test an object to see if it will work as a Faraday cage?

You can test any device that you think might work as a Faraday cage with a radio. Simply turn on the radio and place it inside the device. If the radio is still receiving a signal, then it’s not a Faraday cage. If you don’t have a radio, you can use a mobile phone, but the results won’t be 100% accurate in the sense that if your mobile phone still rings, then it’s definitely not a Faraday cage, but if it does not, you can’t really be sure. You need to test it with a radio to be 100% sure you have a Faraday cage.

#14. Can you EMP-proof a car?

emp carYou could build a Faraday cage, but this would mean that you will either never use your car or will need to buy a new one. I’ve seen some pictures online of people wrapping them in aluminum, but as I said previously, it’s pointless.

Instead of making your car EMP-proof, I think you would be better off buying an old, cheap car that has an electric system that is a lot less vulnerable. Here are the top 10 EMP proof vehicles.

#15. Will a galvanized steel trash can make a good Faraday cage?

Yes, but the can has to close perfectly, and you will have to line the walls with cardboard.

You may also like:

You Will Not Survive an EMP Strike Without This

The Only Way To Get Antibiotics When SHTF (Video)

Where Not To Be During an EMP

7 Actions to Take Immediately Following an EMP Strike

9 Places Where You Could Recharge Your Electronics After An EMP


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By Anne January 13, 2017 14:40
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  1. Sam6 January 13, 16:17

    I was thinking of buying a metal garbage can and lining it with flex seal a rubber sealant. Would that work in a Faraday cage?

    Reply to this comment
    • dougnicholson January 13, 17:27

      As long as the top of the can makes perfect contact with the rim, yes. The FlexSeal would take the place of the cardboard mentioned in question 15.

      Reply to this comment
    • JDC January 13, 18:05

      You could do that, but it would be the expensive way. The most important thing is to ensure that nothing you are storing is in direct contact with the metal inside, and that the lid is fully seated. I use a slightly smaller round plastic trash can inside the metal can. You could even leave items in their original cardboard boxes, though I might check to ensure no metal staples in the box.

      Reply to this comment
      • Beachcomber August 22, 16:54

        So, are you saying you could place anything that would fit into the plastic can inside the metal trash can with lid , without wrapping any of the items placed inside, and seal the metal can and it’s EMP proof?

        Reply to this comment
    • Illini Warrior June 14, 15:46

      lab testing on metal garbage cans have shown that the lid to body connection point is open to wave penetration – testing with a metal tape overlap at the junction point proved effective – for the re-usability factor a joint fill with 000Fine steel wool was also effective ….

      Reply to this comment
  2. bugjuice January 13, 17:15

    If I put a metal roof and metal siding on my house, what else do I need to do to make it EMP proof?

    Reply to this comment
    • BillH January 14, 17:08

      Unfortunately, to make a proper Faraday cage, it has to conduct on all sides. So it would need a metal floor. Also, it is critical that there are no seam gaps, as they actually act as antennas to draw the EMP into your cage. The entire surface has to conduct with no breaks so that the currents induced on the surface of the cage are free to exactly match the EMP wave.

      Reply to this comment
      • CapitalistPig January 16, 22:40

        My man camp house I bought has a metal roof,walls and a metal frame and studs with the interior being a plywood floor and sheet rock walls. I’ve tried to pick up my Wi-Fi outside and its not possible. Could I be protected from EMP?

        Reply to this comment
        • BillH February 23, 02:53

          Not likely. Floor that doesn’t conduct, windows that don’t conduct, and any seams that don’t conduct are issues. It might help protect from EMP some from blocking the waves, but that does not constitute a Faraday Cage.

          Reply to this comment
  3. Don January 13, 17:37

    Will my very heavy Browning gun safe make a suitable faraday cage?

    Reply to this comment
    • Kirk January 20, 00:10

      It will help a little but there needs to be a proper metal seal on the safe instead of the rubber one safe makers use.

      Reply to this comment
  4. Sertbro January 13, 17:46

    Just a quick Thank you for providing the many tips and pointers. It’s always better to obtain knowledge and devices, then to wish you did if all hell happens.

    Reply to this comment
  5. Hamgeneral January 13, 18:20

    YES absolutely, the faraday cage needs to be grounded!!!

    Reply to this comment
    • Fc January 13, 19:27

      I used to work in communications in the USAF. Our faraday cage was grounded.

      Reply to this comment
      • Rod January 13, 22:06

        I am involved in EMP preparedness and grounding can be a very tricky thing with shielded containers. If the ground wire/strap is too long it can actually become a very good antenna for the pulse. Since the pulses are in the microwave range, you can see that the connection is going to have to be very short to be effective, hence not having things grounded might be better for the civilian. I also have grounded containers but the grounding schemes for those are very elaborate and not easily accomplished by the normal DIY’er.

        Reply to this comment
      • SailorSam January 13, 22:18

        The larger the cage, the larger the cable needs to be and the deeper the ground. You will need to dissipate a lot of current.. The closer to the EMP the stronger the field, the more current generated.

        For US Navy SatComm tech.

        Reply to this comment
      • BillH January 14, 17:13

        If the primary objective of a Faraday cage is to prevent leakage of information out of the cage (a very common military need), then grounding is a good idea. But the Faraday principle does not require grounding, only an unbroken conductive surface. Grounding causes the currents induced by the EMP to NOT mimic the wave correctly. Grounding uses a different principle to provide protection — bleeding all of the power into the ground. Which is very different from, and somewhat inconsistent with, the way a Faraday cage works. See also Rod’s remarks below, which is another way of looking at it.

        Reply to this comment
    • Kirk January 20, 00:11

      No, it doesn’t. A faraday cage does not need to be grounded. See how much bad information is floating around?

      Reply to this comment
  6. Outlaw Josey Wales January 13, 19:38

    How about computer anti-static bags? Logically I think they should work but you’d probably need to wrap them around the devices a few times. I work for a computer company so they are literally everywhere and free to take after they’ve been used.

    Reply to this comment
  7. don January 13, 20:30

    What do you recommend for a reliable Walkie Talkie, a CB, and a HAM radio?

    Reply to this comment
  8. N. Tesla January 13, 23:56

    Why don’t airplanes fall from the sky when hit by lightning?

    Reply to this comment
    • BillH January 15, 01:47

      An airplane is, to a significant degree, a Faraday cage. It has a conductive surface. However, there are sizable gaps in that conductive surface. Certainly the windows. And the doors may not be designed to allow conduction all around the edge with the adjacent surface of the plane. These problems can be solved and are solved for Air Force One, for example. But not for private aircraft.

      A lightning bolt will be conducted around the windows and doors and not enter the plane, as it is seeking the best conductive road to ground. But an EMP wave will enter through the openings, as it is a wave traveling in a straight line from its inception. It is not seeking ground any more than any radio wave is seeking ground.

      Reply to this comment
  9. Dave O January 14, 02:03

    What about army surplus ammo canisters, they are metal and close very secure, also come in many different sizes.

    Reply to this comment
    • dougnicholson January 14, 02:22

      The link in tip #7 discusses this.

      Reply to this comment
    • BillH January 15, 01:55

      Unfortunately, the info in the link from #7 above is incorrect. An ammo can does not normally have a conductive connection between the can and the lid all the way around. Which is a requirement. The entire surface must be conductive, with no non-conductive seams. Conductive tape all around the lid would help, but only if the paint was removed from the surface where the tape sticks to the lid and the sides. The only real alternative to make it work correctly would be to remove the rubber gasket and replace it with a conductive gasket.

      So the basic answer is no.

      Reply to this comment
  10. RayD January 14, 03:02

    Some good information here, but a few that are incorrect. Faraday cages and shielding must consider the frequency they are protecting against. High frequency signals are protected just fine with aluminum (or copper or silver). Seams in the seal are leakage paths. Low frequency can couple through aluminum magnetically despite this and need a ferritic shield (nickel, iron, or steel). Your best bet is an aluminized shield within a steel container, i.e. a metallized plastic bag inside a gun safe. Note that the seals on the gun safe can allow leakage, however. This is what probably killed your refrigerator idea. Aluminum or copper tape on the seals can solve this. Also, grounding is NOT required with a good Faraday shield. (PhD Electrical Engineering)

    Reply to this comment
  11. Ron January 14, 05:04

    Does a Faraday cage need to be grounded at the bottom? Is the EMP line of sight and will not reflect from below the burst?

    Why would aluminum not work as shielding?

    One of you commenters said you need to ground the cage. You said you do not need to ground it. Which is correct?

    Reply to this comment
    • BillH January 15, 02:05

      Does not need grounded. See comments by myself and others. EMP is line of sight. It will not travel through a hill or mountain or over the horizon. Aluminum will work fine as shielding for high frequencies, which is the main concern from EMP.

      Reply to this comment
      • Johnny D September 19, 06:50

        Hey BillH,
        I agree and disagree with your Line of Sight. I agree the effect is line of sight, but disagree with where that line of sight is measured from. Since the Compton effect is generated in the Ionosphere and regenerated downward I think the EMP effect will be horizon to horizon where the blast meets the Ionosphere and then downward toward earth… making mountains for the most part ineffective. I am stretching my mind here… but I think that is the way it works.

        Reply to this comment
  12. RadD January 14, 07:48

    A Faraday cage does not need to be grounded. Grounding provides a discharge path for the Faraday cage, but neither helps or hurts the items protected inside (unless the internal item is touching the cage at more than one point). Reflections occur from everything, creating both constructive (hot spots) and destructive (null spots) interference patterns.

    Electromagnetic radiation is attenuated by distance and material (shielding) in the path. So it is more attenuated when not a direct line of sight, but is still present at a lower power level.

    Electromagnetic radiation has both an E-field (electric) and an H-field (magnetic) component. E-field dominates at higher frequencies, H-field at lower. Aluminum works fine for higher frequencies, steel for lower frequencies. The item inside the cage can be in contact with the cage, but only at a single point. Otherwise, a voltage divider is created and part of the energy flashes through the device you are protecting.

    Reply to this comment
  13. MKS January 14, 10:40

    More self proclaimed experts who don’t learn anything. At the very least read MIL-STD-464 and 188.

    Reply to this comment
    • BillH January 14, 17:50

      Um, MIL-STD-464 is related to electronic safety. MIL-STD-188 is related to electronic communication standards. Neither addresses EMP at all, except by reference. MIL-STD-2169 is the EMP standard, and it is classified. You negative attitude toward your fellow bloggers appears without foundation.

      Reply to this comment
  14. Samp January 14, 12:41

    There are few absolutes when discussing EMP and things used to protect devices from its effects. Some of your 15 points are not necessarily true. There are some very good videos out there that are made by SCIENTISTS using SCIENTIFIC TESTING METHODS that put EMP into perspective. I encourage folks to do more research on the topic and not rely on this article for direction.

    Reply to this comment
  15. steven January 16, 19:28

    and right there show this tech is trash and we need to get back to the old .not tech shit that will soon fry .grr

    Reply to this comment
    • Rod January 16, 21:31

      While I sympathize with your sentiments, having been involved in EMP preps shows me the downfall of this idea. Yes, the equipment would most probably survive, but it is also extremely power inefficient, which would require a larger power source (genset, since no commercial power available) which would also require more fuel, which will be hard to come by since many of the pumps would no longer function. Best is shielded solid state with a smaller shielded genset and as much fuel as you can get your hands on, yet still keep viable.

      Reply to this comment
  16. KP January 16, 22:16

    If I store a spare computer for a 1992 Ford Ranger (pre-programmed) in a Faraday cage will my truck run after an EMP?

    Reply to this comment
    • Rod January 16, 22:32

      Best answer I can give is “Maybe” because when you are talking about EMP there are as many variables as there are when you deal with lightning. If you are right under the burst (assuming nuclear device) then you will probably lose the alternator and starting motor and other things with coils of wire. Farther away from ground zero the effects diminish. It also depends on the strength of the pluse. There is also a school of thought that says that computers in vehicles are shielded, but I take that with a grain of salt, personally. My choice is an early ’80’s model diesel before the advent of electronics, all mechanical fuel system. With a spare starter, solenoid, and alternator stored in a protected enclosure, you should be able to get it going after a few hours work.

      Reply to this comment
  17. CapitalistPig January 16, 22:41

    My man camp house I bought has a metal roof,walls and a metal frame and studs with the interior being a plywood floor and sheet rock walls. I’ve tried to pick up my Wi-Fi outside and its not possible. Could I be protected from EMP?

    Reply to this comment
    • Rod January 16, 22:49

      I would say no. I have seen an EMP protected shelter and walls, ceiling, and floor are all conductive. Door is VERY special and built to seal when closed. Other openings in the building as well are closed with finger stock grounding. When you are thinking of EMP think of an extremely close and powerful microwave dish pointed directly at you with many, many watts of power. You can see that it would punch right through any unsealed gaps in metal and would go through glass and wood as well. Sealing a building for EMP is a study in engineering, both mechanical and electrical.

      Reply to this comment
  18. vocalpatriot January 24, 16:24

    Lots of incorrect and plain dumb information in this article. I don’t recall news of any airplanes falling from the sky when hit with lightning or C.M.E.s .The skin effect, which is the principle of how a Faraday cage works, does protect the electronics on planes and in cars to some degree, you will find that cars are better protection than most believe. it isn’t an all or none situation…further..just buy spare modules in case the ones in your car DO fail, maybe the radio, too. The rest of the car will likely not be affected..but, cheap insurance. HOWEVER, because of the windows and doors on these vehicles, anything stored in them won’t be protected enough. Microwaves actually ARE Faraday cages BUT are designed to keep specific frequencies inside and E.M.P.s are broad spectrum bursts with HUGE levels of power. So, a chicken wire Faraday cage will not work. There must be no gaps in the conductive cover. even a small pinhole or slit can allow some damage. This is why a metal trashcan or altered ammo can would be the best bet. Also I’m not buying the tinfoil on the box trick, because the amount of power involved may render it “invisible” to the emp. It could act as a capacitor and simply pass the energy right through. Mass will your friend..thick metal boxes and cans would be your best bet. Insulate the stored items with plastic or cardboard form the inside surfaces of the cage and the further from the side wall the better.
    Good luck danger rangers!

    Reply to this comment
  19. Johnny D February 3, 07:10

    After reading the 15 and the comments… for the most part I think the information is accurate (especially as corrected in the posts). What I was surprised by was the comment indicating Solar Panels would stand a chance against the E1 emissions of an EMP. Fundamentally, solar panels are arrays of semiconductors where the gate lengths are quite small (not as small as communication equipment or computers…but I would think still susceptible without protection. Thoughts?

    Reply to this comment
    • Rod February 3, 17:11

      I have seen this same idea in a number of venues and have my doubts as well for exactly the reasons you stated. I would really like for someone to do some 3rd party testing so we would know for sure. It is possible to do this with EMP generators made specifically for the purpose and used every day testing EMP shielded facilities. Not sure I would trust a manufacturer’s claims without seeing the test methods and data.

      Reply to this comment
      • Johnny D February 23, 04:56

        Hey Rod,
        I haven’t seen any manufacturer spec out a semiconductor for EMP. Keep in mind that the very physical characteristics that define modern semiconductors for fast/low power use (gate-length) is the very characteristic that E1 attacks. Normal zenar diode protection (for anti-static damage) is too slow for an E1. static electricity damage is more E2, or lightning effects (much easier to protect against…oh and the principle reason why planes are fine in a lightning storm). With respect to Faraday Cages… The casual enthusiast really just doesn’t get it. A screen room (a real Faraday cage, spec’ed out and tested for emissions) is a big deal. A metal box (electrically) is not that easy to accomplish to protect against a broad spectrum event. I like the metal trash can, but even with that, seal all metal junctions with aluminum tape and a non-conductor liner on the inside AND a shield bag for your goodies. I am figuring that combo should give the enthusiast about 50dB of protection.For the cost benefit, I have seen nothing that even comes close.

        Reply to this comment
        • Rod February 23, 16:50

          Johnny D. I agree, but have to tell you that the professionally made shielding that I am familiar with is nothing more than a steel box with fingerstock on the doors and the items inside are bonded to this box without any insulating material at all. I have been suggesting to those without a lot of real world EMP experience to use a galvanized trash can, sealed with aluminum tape, stored in the lowest part of the building, such as a basement. Depending on their distance from the detonation (if it an EMP device) that should get them by unless they are right underneath and then most things will be toast anyway, even the professional stuff.

          Reply to this comment
  20. riverrat February 25, 17:18

    Unfortunately the author seems to have inaccurate data For instance, shipping containerss have a wood floor which does not allow for protection. Solar panels have a diode that requires special connections after an EMP. Flashlights using bulbs not LED will work after an EMP. and much more.

    Reply to this comment
    • Richy December 2, 17:28

      Shipping containers are all steel with a wood floor on top of the steel floor.

      Reply to this comment
      • Bob June 10, 14:28

        Sorry, Richy. I’ve been in the shipping business +40 years and riverrat is correct. Shipping containers have a wood floor (treated plywood), screwed to metal cross braces on the bottom of the container. They are NOT solid steel boxes. Steel is heavy and shipping companies are not going to transport several hundred extra pounds of steel for no reason. Additionally, the double doors compress a thick gasket to seal them. Even compressed this gasket is about 1/4″ thick, so between the four sides and the split between the doors, you have a 40′ long, by 1/4″ ‘opening’ sealed only with compressed (non-electrically conductive) gasket material. That’s almost a one square foot ‘hole’ but it’s worse than that, because it is a long narrow slit which ANY wavelength will go through. Don’t believe me? Get a good AM/FM radio with good strong stations for both bands. Then have someone seal you in a shipping container and I’m pretty sure you’ll find you can listen to either station without interruption. Shipping containers CAN be made into Faraday cages, but only with a great deal of modification.

        Reply to this comment
  21. riverrat February 25, 17:23

    I forgot about the solar EMP, under the potential of a plasma blast, it would cause more damage than a nuclear blast from an electronics perspetive. Search on the plasma blast crater in northern Africa that many thought was a meteor crater!

    Reply to this comment
  22. Illini Warrior June 14, 15:37

    Rarely ever mentioned in regard to Faraday cages …

    since both EMPs & solar flares will undoubtedly have secondary followup events – the stored electronic items will have to be used on a “use & scoot” basis – quikly re-protected within the cage – Faraday cages need to built to an eazy access design …

    Reply to this comment
  23. Bruce September 7, 16:28

    I have a battery backup system with solar inverters located in a faraday cage. The room has several large wires that enter on three sides and the floor. The system is active, not just storage. I assume the wires are “conductive penetrations” that lower or negate the effects of the shielding. How can I mitigate the effects of these conductive penetrations?

    Reply to this comment
    • Rod September 7, 20:21

      Given the equipment available to the general public, there is no way to provide protection with outside connections like you are describing. Only complete disconnection will ensure maximum protection against EMP.

      Reply to this comment
      • Bruce November 10, 22:43

        Complete disconnection is not an option. How else can I mitigate the effects of these conductive penetrations?

        Reply to this comment
        • Rod November 10, 22:56

          Considering that EMP is of varying levels depending on distance from the generation mechanism, you plan for the worst. I know of no way to reliably and economically protect anything that has connections to the outside, power, ant, phone line, etc.

          Reply to this comment
    • Magi November 14, 21:22

      To deal with AC I suppose you could set something up to induce power from inside the cage wall to the outside, the coupling would be poor and the efficiency would be low but it would could work.

      The DC from the solar panels, however, is a big problem and I have no idea how it could be done.

      Reply to this comment
  24. Johnny D September 19, 07:04

    It might be benefitial to describe the components of EMP. E1 – fast pulse, E2 – slower but more intense, E3 – slowest pulse, but a titalwave of energy. When a nuclear detination occurs, all three are generated.
    E2 is probably the easiest to understand, it is similar to lightning…. well understood and most devices have protection in them for ESD (electrostatic discharge)… basically a small lightning bolt generated on the surface of our bodies.
    E3 – This is the slowest pulse (with reference to the raise time of the energy being transmitted), but it is generated in overhead power lines. The longer the line, the bigger the titalwave. With long transmission lines accross the country, each one will create huge electrical surges, they will pass right through transformers (destroying them in the process) and continue on down the line into each of our homes. It is this E3 that will destroy most anything plugged into your home outlets. Conversely, anything not plugged in will likely not be affected by E3. With a small amount of money (maybe $300) you can buy a whole house suppressor that will (by its specifications) protect your home electronics from E2 and E3. Further, CME only generate E2 and E3 pulses.
    E1 – These are the really nasty pulses. They are not very large (in energy content), but they are large (peak) and very very fast. As such most semiconductors will be susceptible to them regardless if they are plugged in or not. Since almost anything these days have semiconductors in them (transistors, diode, etc) they are all in danger. Keep in mind that LCDs are large arrays of semiconductors, solar panels are arrays of semiconductors, almost anything that gives off light these days are semiconductors. Semiconductor items need to be in a faraday cage for protection.

    Reply to this comment
  25. Johnny D September 19, 07:20

    I might also mention, most lay persons really don’t understand shielding. Keep in mind, it is not to shield or not to shield, but how good of a shielding job you do vs the susceptibility of what you are trying to shield. In order to make computers faster, the semiconductive area of the device is made smaller and smaller (last I checked commercial processes had the gate length of semiconductors down to 1/10th a micron (1 X 10-7 m). the smaller it is, the more susceptible it becomes to damage to energy. This might be the reason why cars (especially 90’s cars) might be OK. They are using robust semiconductors with fat gate lengths and a light amount of engine shielding. Having a spare car computer in your faraday cage is still a good idea!.

    Modern communication equipment has small gate lengths and thus are highly suseptable to E3. Thus they need to be well protected. In my faraday cage, I also put sensitive items in an ESD bag… keep in mind that for cage within cage protection to be effective, none of the individual cages (ESD bags or faraday cages) can conductively touch one another. Thus a design might be…metal trash can (with taped seams and cardboard insert), then an ESD bag, then a ziplock bag with your radio in it. Notice that the pattern is conductor, insulator, conductor, insulator… I figure 30dB on the can, and another 20 dB on the bag… giving me 50dB. I think the MIL-SPEC is talking to between 60-70 dB, but getting that next 10-20 dB is REALLY hard. With all my preps, I try to match cost with reality. Hope this helps everyone.

    Reply to this comment
  26. Billy October 3, 04:01

    What material defeats a faraday cage?

    Reply to this comment
  27. Johnny D October 3, 04:19

    Not sure I understand the question. the purpose of a faraday cage is to provide isolation from one environment to another. In the case of EMP, it is to isolate our normal electrical environment (where the damaging pulse is located) to a protected environment (where we want to protect items against the EMP).

    So, if you want to defeat a faraday cage, don’t build one and don’t put your electronics in it.

    IF you are asking what construction techniques undermine the effectiveness of a faraday cage, then I would respond that it is far easier to have an ineffective shielding than not. Any wholes in the in the container, any gaps that are not electrically sealed would contribute to the cage ineffectiveness.

    Did I answer your question?

    Reply to this comment
  28. Magi November 10, 22:12

    Speaking shielding containers, a very good container i a new and empty paint can (Home Depot), all joints are electrically good seals and the lid forms an excellent electrical seal, once closed the can is even water tight. All you have to do cover the inside with an insulator or wrap whatever you put in the can in an insulator. Of course, nothing is perfect, you have a limit on the the size or the items you can put in the container.

    Reply to this comment
  29. Magi November 10, 22:38

    A question for those in the know, how well does water work a an EMP shield? For example, if you submerge sensitive equipment in a lake/pond in a watertight container, would it be protected/safe from an EMP burst?

    Reply to this comment
    • Rod November 10, 22:58

      Now that is a question I have never heard before, and does raise an interesting point. I am going to ask those that know more than I do about this one!!!!

      Reply to this comment
    • Johnny D November 11, 04:30

      Hey Magi,
      What a great question. I’m not sure how water would work. My knee jerk response is that it should work great (assuming the water is conductive). I wonder what they do for EMP on submarines when submerged.

      Let me spend some time researching it a little.

      Reply to this comment
    • Magi November 14, 21:12

      My “gut feeling” is that the protection would be dependent on the depth. Submarines have to rise close to the surface to transmit higher frequencies, i understand they’re able to receive very low frequencies at higher depths but EMP frequency should not penetrate very deep, but my gut’s been wrong before.

      Reply to this comment
      • Johnny D November 20, 04:59

        Hey Magi,
        Agreed… in fact, I think normal communication on subs, have antennas that are mounted in the parascope mast (getting the antenna out of the conductive water for use). ELF (Extremely Low Frequency) hugs the earth and can be received at depth.
        I still think that water (conductive water) would work well as an EMP protective device, just be sure to use an insulator on the inside of the container that is submerged. I haven’t looked into it yet, but it is on my list to research.

        Reply to this comment
  30. uncle December 5, 01:21

    What am I missing here, you talk about actual cages. cell phones under metal screens foil on the bottom and it will survive an EMP. okay you can see the items, that is not sealed correct, you can see the actual radio or cell phone? then you say metal trash cans will work as long as you have non conducive liner is between the can and the item you are storing in the can.will work great as long as it is a tight seal, I read as long as gaps are not more that 2″ you will be okay. There is an awful lot of [my perceived inconsistency here] how can a metal screen protect better than a trash can that might have a very tiny gap in the can . when it is stated the waves are 2″to 4″ and keep the gap less than?
    bird cages. 1/4″ inch wire fencing. some thing is not adding up here

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    • Rod December 5, 01:46

      Uncle, I can understand your confusion and I work with this stuff every day. What it boils down to is physics and the electromagnetic spectrum. Light, what allows us to see, has a very small wave length. EMP, all types, have much longer wave lengths. The copper screen in particular is a good example. Yes, you can see it because the light waves pass through the screen, and a grounded item, like the screen, does not absorb light, so all kinds of light squeezes through the holes giving you a discernible, but distorted, representation of the item behind the screen. EMP on the other hand IS absorbed and/or deflected by the grounded screen depending on the size of the holes in the screen. As long as the holes are small enough to block the entire wavelength of the EMP there will be protection behind the screen. As to the trash can, the can itself is not a bad field expedient shield, however it should have the lid sealed with aluminum tape to cover any gaps between the lid and can. Again, making sure any gaps are smaller than the EMP wavelength. Grounding these shields, screen, can, or whatever, is a highly debatable subject by even the learned. While grounding done absolutely correctly enhances the shield, done incorrectly it can turn the shield itself into an antenna, NOT something you want to have happen. My advice to the general prepping audience is trash cans, aluminum tape, and no grounding. I did not include insulating the inside of the can in that because the insulation itself can cause problems too. I have professionally shielded equipment that is not insulated on the inside but is grounded in a very specific fashion. I have no worries about it. One thing everyone needs to remember is that EMP lies between electricity that we use every day and light that we see every day. The physics displayed at each of these levels are very different and need to be dealt with in completely different ways. What might be a dead short using either DC or 120VAC, will look like an open circuit at higher frequencies. Vice versa is also true. All one needs to do is spend most of a lifetime studying and working with this to start to get an inkling of what is going on!!!

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      • uncle December 5, 15:16


        Very Very kind of you to reply so soon. My wife’s brother is in the army and his commanders are telling them to privately get their acts together. 13 Months ago he held an meeting with all of is siblings. bottom line we have about 3-5 month’s food. we bougth Mylar bags and a sealer. bought all sorts of beans of of amazon. bagged, beans and oxygen ab sobers then sealed the beans and rice. 115 gallons of water, various small solar panels and RAVstorage batteries and lights that are both battery operated or can charge another device. 30 rechargeable batteries solar cookers and today UPS delivered our Inergy kodiak. solar panels on the way I do want to protect those items. We have a heck of lot invested in the last 13 months that we never planned for. I have been looking a Lowes and home depot this weekend. the large tool boxes AKA job boxes heavy steel then use the copper door seals for the small gap even thought the gap is diverted in that it has a lip so the wave would not go directly into a box.
        I bought gun cabinet just steel cheap to store items. I tried the cell phone in it Yesterday to my dismay the phone rang while in the box. Do you think a jobber box will be any more effective. We live in a small place it has become very crowded with food, water, tents, at least 3 each bug out bags each, canopy’s [ not the delicious ones], 4 wheel carts, sling shots 5 flash lights each etc. I have terabyte drives with all of our stuff on them triple back up, We need to protect this stuff! The emp bags seem like more money out of our pocket and into others. I need some sanity in this .

        Thank for your kindness.

        Reply to this comment
        • Rod December 5, 19:18

          WOW! Sounds like you are definitely getting things together. As to the “gaps” in job boxes and gun safes, without going into exorbitant expense using copper fingerstock and other such items, I suggest using aluminum tape wherever there is gap in an item you are using to store things. A friend (who deals with this every day) has been experimenting with steel wool as a gasketing material. He has been getting mixed results.

          I also read through your list and would suggest that you make sure you have a variety of foods and ingredients so that you do not end up eating the same thing every day. That can lead to food apathy, which can lead to malnutrition, which leads to decreased mental facilities. I would also suggest you get a water filter so once your stores run out you can replenish them.
          Make sure you have a windup/solar radio as well. I use the C.Crane Solar Observer. I like the performance of the receiver in this radio, but I am a radio guy and that is extremely important to me!
          One other thing to remember is the prepper’s mantra. 3 is 2, 2 is 1, and 1 is None.
          I do wish you and yours luck in our uncertain future!

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          • uncle December 12, 04:19

            Rod, thank you I have many things you mentioned , C cranes radio no. I actually had a page open about it. but amazon reviews rated it below par. as many other crank radios it is getting frustrating too be honest.

            we do have different foods. from mountain house and others. water filters etc. ON EMP boxes we scored on the JOB box at HOME DEPOT walked out the store at $113.00 with wheels. someone returned it after a job and said it did not work . I hate that at the same time we did good. I have read, line it with cardboard. understanding the reasoning. I have read if you can put aluminum foil between 2 pieces of cardboard for better effect. (with that in mind) do you keep the aluminum foil how far for the edge of the 2 sandwich pieces of cardboard to give you EMP protection with out having the aluminum come in contact with that you are trying to protect?

            Reply to this comment
            • Rod December 12, 15:10

              Uncle, as far as putting cardboard or any other non-conductor on the inside of a metal box for EMP shielding, I am not entirely sold on that concept and I will tell you why. By doing that you are actually building a capacitor. Capacitors can pass RF right through them. When EMP strikes a metal surface the wave travels along the outside of the surface. This is called Skin Effect and is a well known phenomenon. Just because there is EMP on the outside of a container wall does not mean that the same EMP is on the inside. This is why dealing with EMP/RF is not intuitive. Different frequencies display different properties. If you have 120VAC on the outside wall of a container, you will have 120VAC on the inside because the frequency is so low. In my professional preps I have shielded equipment that is bonded to the shielding container by wide copper straps that are also grounded. These have been tested by professional, on site methods and do work. My best advice is to not get too fancy. Just make sure that any cracks or crevices are covered in aluminum tape. That should be sufficient without going to extraordinary lengths, like my professional equipment has to be done.

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              • Johnny D December 13, 06:02

                Hey Rod/Uncle,

                I agree that a cardboard insert, with a foil extra layer of protection would likely be more detrimental than beneficial. Sealing that second layer of protection properly would be a nightmare. I am a supporter of cardboard (only) to keep any metal inside of the box from potentially coming in contact with the inside of the outer shielding. As long as there is not a inside layer (or sandwiched layer) of a conductor, then there will be no appreciable capacitive effects (capacitors are two parallel plates separated by an insulator).

                You Tube shows (https://www.youtube.com/watch?v=uYWhTMmv6bs) the detail with which care must be taken when sealing a metal container and the effects of a poorly sealed cage. I use shielded bags inside my cage to improve isolation (isolation is additive in dB, so 40dB for my can + 15dB from my bag gives me better than 55dB of Isolation).

                Reply to this comment
                • uncle December 13, 19:59

                  Rod / Johnny D
                  Thank you! I am glad I found this site. You read so many things. it is hard to decipher which is good info and what is not.
                  I will watch video later tonight.

                  Reply to this comment
  31. uncle December 18, 03:04

    Are candy tins, cookie tins insulated with cardboard good protection? I would like to have my pen drives, cards, pocket battery devices like USB charger for phone, tablet or LED lamp available daily however protected. I know a phone is useless after an emp but the charger is still good for LED lights and charging handheld radios. until its dead in a few Years. I am seeing technology will be good for a short period of time in a long long time out of the electrical grid. candles and kerosene need to be looked into.

    Reply to this comment
  32. Johnny D December 18, 05:13

    Hey Uncle,
    I think that is a pretty good idea. To be safe, I would suggest using aluminum tape around the edges of the cookie tin (you can re-use it a few times). Also with small items like that, if you could get a few ESD bags, that would provide a significant amount of isolation (be sure to coat the inside of the tin with an insulator (thin cardboard, to keep the outside of the ESD bag from making contact with the inside of the tin). Don’t forget the inside top of the tin should be insulated too. I like the idea for LED flashlights and maybe rechargeable batteries and charger.

    Reply to this comment
  33. uncle December 22, 00:00

    As I learn I hope I too can assist others. SO! 🙂 I have lined the the metal box with cardboard non metallic duct tape to hold the seams. I have int he back of mind all your guys words [Antenna]. that the EMP would stay on the outside, your goods safe inside.

    This box has a folding hinge to keep it open. two blades on the lid that would catch a lock to secure the box to the locks. With Antenna in my mind. will these features bring the EMP into the box? We purchased the ridgid 32R-OS to store our items. homedepot this should give you visual of what I am speaking of. I have covered these items in NON metallic duct tape. will this suffice or should I cut them off?

    Reply to this comment
    • Rod December 28, 19:44

      Sorry to be late in replying but life has kept me busy! I would use Aluminum duct around any making surfaces, but the Rigid box should be OK otherwise. Sounds like you are on the right track!

      Reply to this comment
  34. uncle January 2, 00:50

    Happy New Year all

    EMP BAGS which bag did you finally choose which company has the best price?

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  35. CDR Sam April 25, 18:15

    You mention the inverter of a solar power system being susceptible to an EMP, but wouldn’t that also apply to the controller?

    Reply to this comment
  36. Kirk April 25, 19:57

    The Canna Bay Faraday cage provides up to 2X the attenuation protection of the , so called, “EMP bags” and cost just $75 for 20+ liters of storage.

    Reply to this comment
  37. uncle June 10, 20:21

    I can only imagining that I am not the only one totally frustrated about the lack of solid collaboration . on effective ways to protect your electronics. I have been reading since since DEC 17. I walk away from the computer more confused that when I first sat down. :)’ Now I read you should follow a method called ” use and scoot” after a first EMP. My assumption is to open your stuff use it then reseal before a secondary strike… WHY?

    We purchased a construction box. to put electronics in we lined it with cardboard. We purchased EMP bags to also put the stuff in. we purchase ammo cans and have used copper tape to seal all of the above. . I read the paint should be removed for the copper tape to work. ( I get the basics of that for an electrical connection). Why sand, a seal is a seal how would a “wave” get though a copper taped bond?

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