How to build a faraday cage in a few easy steps

by blogRot

What is a “Faraday Cage” and How You Can Build Your Own Cheaply and Easily from Common Everyday Items.

This is a bubba-fied explanation of what it is, what it does, and how to build an effective one.  If you’re going to cite this as a source in your college research paper, you’re nuts.

Electromagnetic Pulse (aka EMP) or a Coronal Mass Ejection (CME) from our sun produce high powered electromagnetic ‘rays’ that are very damaging to electrical and electronics based equipment.

Rubbing your bare feet across the carpet generates a significant electro static potential that you feel when you then touch something metal like a door handle – that spark is a discharge of roughly 4,000 volts to 35,000 volts.  Lightning cracks across the sky are 10,000 volts and more .  YES, the voltages created from you rubbing your feet and lightning is roughly the same but there is an ‘umph’ factor behind the voltages that I could explain but do not want to have anyone’s eyes cross.

Ever tried to heat up some Earl Grey with your DW’s gold trim porcelain tea cups in the microwave?  Did you notice the fireworks from that boneheaded move? For comparison EMP is both similar and different to the above but much more powerful the closer to ground zero one is, and CME could not only be up to EMP powerful but is also sustained – the Earth could be in the sun’s blast zone for hours or days whilst an EMP burst is miliseconds.  EMP from a nuclear detonation can still be higher than 100,000 volts hundreds of miles away.

What this electromagnetic energy does is to create (‘induce’) energy potential (voltage) in equipment even when it is not plugged in.  This is bad, as not only is this not controlled (like plugging something in backwards the energy doesn’t go in the correct pathways and it burns up) but also that that energy could very easily exceed tolerances of the components of the equipment – something as low as 30V inducement could irreparably damage electronics.  And electronics are everywhere, and are needed for/included in electrical systems like your car, generators, central air conditioners, etc.

If that electronic control goes kaput it is hard if not impossible to get that electrical system it controls/manages to work.  Furthermore, susceptibility of electronic memory components needs to be considered: even if the electronic memory component physically survives the inducement there is a strong chance that the critical programming codes it contains may be altered enough to ‘break’ it!  Your Kindle or laptop may survive undamaged but the software it needs to power up and run would be corrupted enough to make it useless and its data irretrievable.

To be honest, until there is a detailed study of a modern day nuclear detonation near a population center I do not believe the magnitude of EMP effects are truly understood, anticipated or expected – I can only fantasize about what the results are and believed that most experts just don’t know every cause-and-effect nor the true extent of the damage (the good-stuff data is Classified). Yeah, there was Project Starfish Prime in Hawaii, but that was more of an incidental byproduct and not specifically set up to be monitored – “uugh… Honolulu just called and said their streetlights all went out; did we just do that?  Yes, but let’s call it part of a study so Congress will fund it. Ka-ching!”  I do recognize EMPs and CME events as being catastrophic no matter what.

So how does one protect his precious ham radio, her dc/ac inverter, or their computer from these high energy discharge events?  While some special equipment can be ‘hardened’ by design the chances of you acquiring this military-grade engineering or old-school manufacturing is not expected.  Automobiles and airplanes used to be made without electronics; today nearly everything is and today’s products are soundly engineered using the least amount of material necessary in its construction.  Great for cost savings, but no wiggle room for extra capacity.

Grandpa’s wire wound antenna I inherited in his vacuum-tube based radio weighs more than my entertainment center – this is the old-school manufacturing that I am referring to.  The wiring in those old electrical systems would be considered over-engineered in today’s standards; they were bigger back then and those bigger wires can conduct more power through them before overheating and burning out.  Hardening and modern RF shielding is a whole ‘nuther bag of beans topic-wise, and this is just a brief snippet to show contrast to the other option.

…and that other option is to Shield it.  There is a reason UFO nutters wear tinfoil hats – it is actually sound physics in shielding from electrical waves; however, unless it is properly Grounded then it is useless.  So do you truly know what ‘grounding’ is?

Earth ground is special in that it is ASSUMED to be able to absorb an unlimited amount of Current without changing its potential (Voltage).  Another way of saying it is that earth ground is always ASSUMED to have zero volts, no matter how much current/power it is subjected to. Electromagnetic radiation continues to propagate until dissipated through earth ground… err… it travels until stopped by the earth.

Let us assume the equipment is plugged into the wall outlet and is exposed to EMP.  This means that is being zapped and induced with ~100,000 volts of energy, more than likely turning whatever was plugged in into a heavy paperweight.  Light bulbs will explode, electronics will pop n fizzle, and if it was already running then it may catch fire.

Not to mention that the power lines are already saturated with its own induced energy, causing further mayhem and destruction.  “But I had it turned OFF” you say; well, unfortunately most On/Off switches only opens one leg of the circuit loop so that induced power will flow through the ‘neutral’ just like if it was running (and destroying it) or it will flow at the speed of light through the ‘hot’ and then to another piece of equipment you have running and THEN back to earth ground.

It still go ‘poof’.  Or it may even arc the distance across the leads of the On/Off switch.  Multiply this effect by all of the items you have plugged into the walls of your house, then all of the houses tied in to your electrical grid.  Many, many ‘poofs’.  Even if the mains breaker on your house trips you’re still left with 100,000v inducement in the house wiring.

“So just leaving it unplugged will protect it, right,” you ask?  Not really.  Let us say you’ve got a nice 1000W dc inverter tucked away on a shelf.  It will still get zapped by 100,000 volts, but that induced energy potential doesn’t go anywhere until that energy potential is great enough to overcome the resistance of air(!) to get to Ground.  And since we know from the paragraphs waaaay up there at the beginning that lighting can arc through air at somewhere around 10,000, we’re still turning that nice 1000W inverter into a paperweight as that induced energy somehow, someway discharges itself to ground.  Or it might not immediately, and stay at 100,000 volts potential; but then you touch it… ouch, or plug it in.. ‘poof’.

“But I want my eyes even further crossed – what else you got?”  You are masochistic, my friend.  Let us continue to Shielding.

Electromagnetic radiation wants to go to earth Ground – it is its destiny, that’s its sole purpose in the universe, its feelings would be hurt if it couldn’t.  To protect equipment we either need to “hide” it ten feet or more underground or “shield” it before the energy waves find it.  Hiding doesn’t mean putting it in the basement or the storm cellar – you need at least ten feet of earth above your abode; we’re talking underground bunkers here.

By surrounding it with – but not touching – a grounded conductive enclosure the electromagnetic waves and/or static discharges are harmlessly shunted around the sides of the enclosure.  Some dead dude name Benjamin Franklin (I’ve never heard of him either) noted as the discoverer of this but some other dead dude named Faraday codified it, thusly the Faraday Cage.

Almost anything can be made in to an effective faraday cage, provided it is:

  • conductive (“Yay!” screams the tinfoil hat crowd),
  • properly Earth Grounded (“Hissss!” boos the tinfoils),
  • adequately surrounds whatever is trying to be enclosed (“Hey, we need to breathe yo!” the tinfoils’ excuse is),
  • whatever is inside is sufficiently insulated from this cage. (“I got nothing.” Me either.)

Microwave ovens are designed and built as faraday cages and continue to function as such even if it doesn’t work anymore. Ever loose cell phone reception in an elevator?  That is the faraday cage effect my friend.  A grounded safe or vault.  Properly grounded tinfoil around a box.  You can use a military surplus ammunition can, drill and tap a hole, screw in a lugged ground wire and clip it to the metal shelf support next to the other ammunition cans you’re using as such, and tie that shelf into earth ground.

“But what about using bird cages, chicken wire, and/or DW’s heirloom spaghetti strainer bowl?” Depends, and this is where the lack of public information comes in to play.  The spacing of the electromagnetic permeable conduits acts as a wave-guide of sorts and determines what frequency of electromagnetic radiation is rejected, attenuated or passed.  WAIT- Please don’t leave, I didn’t mean to get too technical!  Think of an EMP burst as a golf ball passing through a faraday minefield of putting holes of different sizes – too small a hole and the ball will roll over it and too big a hole the ball will bounce out and continue on.

Complicate that further by not knowing what size of the golf ball is to begin with.  So it might just be that the hole spacing in a bird cage and chicken wire won’t be able shield out enough of the EMP.  I can’t say for sure that these materials would be 100% effective against EMP or CME events, but something is better than nothing and this something is *significant*.  I use chicken wire over certain things I’ve got in the shed; if you think the holes are too widely spaced then add another wrap around it.

There is no Prepper Law that says you can’t have DW’s spaghetti strainer covered by chicken wire over a bird cage.  Solid cage is best, next is the smaller the spacing of the holes the better off you are.  Just make sure whatever you use is properly grounded to earth ground.

“So what does properly earth grounded mean?” A good earth ground is a conductive rod that is driven into the ground 10 feet or so – and the depth is dependent on where the damp earth starts; Texas building code is 10 feet so that’s what I stuck to.  The licensed electricians I work with say some houses have copper plumbing that acts as the earth ground.  The shield has to be connected to it and you need to make sure the grounding wire is thick enough to handle the ‘funneled’ energy (if you’re covering an entire safe room then tiny 24ga speaker wire will not be sufficient – use a battery jumper cable) and makes a good, solid contact to whatever earth ground you are using as well as the shielding material.

“Properly insulated?” If the equipment you want to shield is actually touching the cage then there is a conductive path for the energy burst to follow that could compromise your equipment; it becomes part of the shield therefore it is fully exposed.  Put that inverter in a cardboard box, wrap it in a garbage bag, then put it in that properly grounded junky microwave.  Throw in a desiccant bag for good measure.

“’Conductive’; you keep using this word.  I do not think it means what you think it means.” Copper is the best common material that conducts electricity and the higher the content of the copper in the conductor the better it does that job.  Aluminum (probably the worst), steel, brass, tinfoil and other commonly available alloys do work but are not as efficient as copper.  But those *do* work as conductors, so don’t disregard them if that’s what you’ve got available.

EMP or CME related puns welcome in the comments; I enjoy electrifying conversations.  (<- see what I did there?  Hah! I kill me!)

About M.D. Creekmore

M.D. Creekmore is the owner and editor of He is the author of four prepper related books and is regarded as one of the nations top survival and emergency preparedness experts. Read more about him here.


  1. Annie Nonymous says:

    I find these shocking revelations electrifying… it did answer a lot of the questions I had, thank you!

    I was told that if you use something like a safe, you also need a conductor of some sort (the same 0 gauge wire, etc.) between the safe door and the safe body to make sure it’s -electrically- connected, otherwise you may have a weak spot in your defenses. Also make sure the ground lead is attached to bare metal, not to a painted surface…

    All in all, an illuminating article… we look forward to more flashes like this one!


    • “Also make sure the ground lead is attached to bare metal, not to a painted surface…”
      Excellent point, bookended on both ends by properly grounded puns!

    • Annie Nonymous,
      Yes, any lid or door must be electrically connected to the main container. Heavy wire mesh or stranded wire works better than a solid wire, both electrically and mechanically.

  2. I think you should read up on EMP en CME before writing about it.
    They are two different beasts and do not have the same consequences.
    Protection for both is also different.
    Try this resource for some real info:

    Oh, and electromagnetic radiation does not care about grounding at all. A faraday cage will protect against electromagnetic radiation even without grounding. Grounding is only to avoid the buildup of an electrostatic charge on the cage such that you would get shocked when touching it.

    • Lots of snark in your comment; most unappreciative. Change your attitude and I am more than open to the full exchange of my reseearch and knowledge – which was abbreviated for the purpose of merely presenting a primer of the topic at hand.

      I look forward to reading your submission, Rein.

      • Wel yes. I have had it with people who spread FUD.
        Prepping is a serious business, and spreading disinformation does not help anyone. No matter how well/popularly written it is.

        You might want to tackle “Electromagnetic radiation wants to go to earth Ground – it is its destiny, that’s its sole purpose in the universe, its feelings would be hurt if it couldn’t.” first. Its complete BS.

        Grounding is a good idea, but not because of that. The sole purpose in grounding is avoiding an electric potential buildup between the object and ground. Thereby avoiding you getting shocked when touching the object while standing in contact with ground. It has absolutely nothing to do with shielding from electromagnetic radiation.

        Another thing: An EMP generated by a CME will not destroy electronics that are not connected to the grid (or any other really long wire) For example a handheld transceiver will survive a CME just nicely.

        • Rien,
          +10 on grounding. Seems to be one of the most misunderstood things on the subject.
          I also didn’t see anything snarky here, just facts.

        • Well, since there is a difference of opinion, and grounding isn’t a bad thing, then if in doubt, I’d ground it.

          40 years of “playing with” electricity, has shown be that if you want to protect an item from spurious electricity you ground it.

        • Warmongerel says:

          From what I’ve read on the subject, an EMP can destroy electronics that are not connected to the grid. Antennas on radios, metal screws holding cases together, etc. can act as “inlets” for the EMP voltage to funnel the voltage to the electronic components.

          It makes sense: after all, that is exactly how the EMP pulse gets introduced into the grid, too. Why should it be any different for a smaller scale item?

          Please explain why I’m wrong.

          • You may be talking about slightly different animals here. Rien mentions that CME based EMPs are less likely (or won’t) damage electronics not attached to the grid (i.e., plugged in). Nuclear bomb EMPs have (if I’m not mistaken) 3 phases; E1, E2, and E3. CME-EMPs have only 1 or maybe 2 of these phases. My guess is this is the truth behind Rien’s statement – while still a serious threat, CME-EMPs appear to have less impulse-devastation-potential than Nuke-EMPs.

  3. Fantastic!!!! Yura speakin my language.
    I giggled the whole time I was reading. Even after your glorious explanation I am going to ask this question anyway. Because anything with volts and amps and sparking feet tending to make my eyes roll uncontrollably into their sockets.
    I have a large grounded to the ground safe. In the safe I have my radios. one extra cell phone, (you never know what will make it). My old laptop that has all my useful info on it, with solar powered battery chargers and batteries.
    Also, drumroll please…….My pride and joy, which are the pre programmed chips for my Duramax Diesel truck. The ignition, main, and transmission chips with boxes of fuses. You should have seen me trying to convice the parts manager at the dealership why I needed those. I finally gave up, just flirted and handed over cash.
    Each is put into a smaller metal box (like a popcorn tin kinda box) inside a cardboard box, sitting on top of a styrofoam block. Do I still need to wrap the cardboard in foil?
    Is this over kill, under kill, or pat Mama on the back skill?
    My husband begrudgingly put the safe and ground in but I had to threaten, browbeat, stomp feet, beg and promise a never ending sea of tears if he didn’t do it. The safe stayed in the back of my truck for a week, onto the porch for two weeks, and in the house for a month before he finally grounded it.
    My pride pleads for affirmation of success. Please?

    • Mama J,
      First of all the safe does not need to be grounded.
      If each of your items are in a separate box and are wrapped in foil, then you’re probably as good as it will get, with each box acting as its own little Faraday cage. If you have any doubt, then rewrap any of them you’d like in several continuous layers of aluminum foil from a single sheet of foil. Foil is inexpensive, and makes for cheap insurance.

  4. I’d get rid of all of the styrofoam asap; that stuff is a major static electricity generator in itself. Rubber matting would work better – I’ve got peices of a car floorboard mat I use as cheap insulation material. I personally don’t ground stuff inside a grounded container – there is still a very small likelyhood that energy could go up from earthground (that whole ‘ASSUMED to have zero volts’ thing).

    • Will do! I don’t where I read the styrofoam idea. I have lots of rubber matting.
      I still don’t understand not grunding stuff inside a grounded container.
      So I need to make sure the door is connected somehow to the body of the safe. Check.
      But, I should get rid of the Faraday boxes inside the safe? Or just make sure everything is sitting on a rubber mat? The inside walls and shelves are metal.
      I have alot of money in this stuff, I dont’ want to lose it. Thanks again.

      • Mama J,
        Don’t worry about the ground. You can replace the foam with something non-conductive like dry cardboard; however rubber mats can also be use to generate static electricity, so I’d avoid them also. Keep the individual cages (foil wrapping) for the items. Insulating them from each other (with cardboard) will do the trick.

        • OhioPrepper,
          Oh thank you! I had cardboard as the insulator in the begininng and changed it. I am going to to stick with what I started with. I understand the principle but I get confused and panic when I hear different opinions.
          So, I can take a christmas tin with a tight fitting lid, put cardboard in the bottom, set my electronics on that, not touching the sides, and it should work.

          • Warmongerel says:

            There is spray-on rubber out there that is pretty cheap. I’d coat the entire inside of the tin with it. Just don’t do the lid or the voltage won’t have a path along the outside of the container.

            Also, there is foil tape out there that could be used to seal the lid. It’s mostly used for duct work, so Home Depot should have it (has anyone ever used “duct tape” for duct work”?).

  5. Hello. I’ve been absorbing a lot of information from this site over the last several months. Thanks to all who contribute. EMP is a particular interest item of mine. I’m currently in the emergency management career field. Something like this event would SERIOUSLY jeopardize the country and, potentially for the long term. Some further links below may be of interest.

    Happy New Year and Happy Prepping

  6. Rodney Langley says:

    Thanks for the article. I have a question. Can you EMP proof your whole house if you have a metal roof?

    • I assume you are only talking about en EMP from an atomic blast.
      Sorry, but no you cannot. The frequency of the pulse is in the sub-inch range. Thus every hole (even elongated slits) bigger than, say, half an inch will let the pulse through.
      Of course it will be less strong, but still, the risk of damage remains high.

    • Short answer No. think of it as a cage or a square box. Much like a filinh cabinet or a safe or a square metal box all metal touching all metal as to complete the continuity.
      Long answer – yes if you wall up the sides with metal also solid, no gap, no holes no bars some speculate if you cannot recieve a radio signal like on a AM radio then you are in affect inside a faraday cage …..but I think that is only the initial test.

  7. Tactical G-Ma says:

    Interesting in a simplistic way. You said a microwave oven was a faraday. What about a refrigerator?

    • No deal, any slit bigger than half an inch will let a part of the pulse slip through. A refrigerator, and even a microwave, has slits all along its doors. And will let some through.

      Try this simple test: If you have a strong mobile phone signal in your home, put a mobile phone in the fridge/microwave. Then call the phone from another one. If the phone in the fridge/microwave rings the shielding is inadequate.

      • georgeislearning says:

        Hey that’s an easy test. gonna go call my fridge and microwave right now 🙂

        • georgeislearning says:

          well both of them failed if that test is valid. I made a faraday shield out of a galvanized steal garbage can when I first came to this site. I will test that and see if it stops the phone signal.

          • georgeislearning says:

            well poop if that test is a valid test then the galvanized garbage can lined with rubber and then lined with cardboard didn’t work either. or perhaps I need to line the can with rubber then metal then rubber then cardboard then rubber again will work?

            Honestly who gives a crap if the grid is down and computers are blown all over the place and cars wont work what would I need to put in the cage anyways?

          • georgeislearning,
            If it doesn’t, then there is a leak in the cage. For a trash can it would most likely be the lid not fitting snugg enough and leaving a gap, or a portion of the soldered or welded seam not being complete.

      • In the case of the Microwave oven, the shielding is specifically designed for the 2400 MHz range, which is where the oven operates; Even then, some energy leaks from the oven; however, it’s at low enough power level as to be non-harmful. If you’re looking for an off the shelf, cheap solution, then a 30 gallon galvanized metal trash can with a tight fitting lid, is a good starting point.

        • A few months ago I put my cell phone in a manila envelope and into one of my 1.5 gal maylar bags and it rang when I called. Rolled it up and put into another bag and it would not ring when called. Understand the basics of everything but need to do some more research and emperimenting but need to since this is one hole in the preps I need to work on.

          • Nested cage example there. Insulator, conductor, insulator, conductor. Repeat until satisfied. You could put the item(s) in a paper bag, wrap with tinfoil, put that in a paper bag, wrap that with tinfoil again. Put that inside a ammo can or a cookie tin if you’re really paranoid (like me). Multiple cages beat a single thicker one. Each layer doesn’t have to be perfect, the goal is just to attentuate the voltage below the point where the protected item would be damaged (which varies by the strength of the pulse, and the sensitivity of the device).

      • Encourager says:

        Cool! Failure on the ‘frig but the phone did not ring in the microwave! So the secret when hunting for a non-functioning humungous microwave to use as a Faraday box is the take two cell phones with you. Put one in the microwave and call it. Such a sizzling idea!

        • Of course there is no guarantee with this test. See it as a negative test, not a positive one. I.e. if the phone inside rings, it is definitely not a good shield. But if it does not ring, you still have to doubt its effectiveness. (Especially since the mobile phone signal can be pretty weak in some regions)

  8. Thanks, but I still can’t get any of this through my pea brain! I don’t understand it much better now. Sorry.

    • Aunt B, try this….

      You put a loaf of bread in a wrapper,
      then put the wrapped bread in a bread box.
      If the bread box has any little holes the creepie crawlies get
      inside and eat the bread, so you make sure there are no holes.

      The bread is the electronics,
      the wrapper is anything you would put around the electronics to keep them from touching the bread box,
      the bread box is the faraday cage,
      the creepie crawlies is the EMP pulse.

  9. Whats all the buzz about rien? (See what I did there)?

    If I may offer my enlightened (and there?) opinion and before we go any further …your welcome!

    Now blogrot I appreciate the post it is difficult to explain farady, grounding, shielding and yes Rien even CME. Although Rien is correct a CME (a really big solar flare) and an emp are two different things but (sckreeeeech) the results can be the same.For the attitud-inaly challenged know it alls outthere, let me break it down for you homey. (I dont even know if I spelled that right, there goes my street cred!)

    If a really big solar flare were to actually do harm, it would do more damage by over whelming the electrical grid by enormous energy burst thus causing transformers of all sizes and sub station to be overwhelmed and then creating a pretty fireworks display and at the end of that display leaving everyone in the dark and given a large enough ” KABOOM ” it would dish out what is refered to as an E.M.P. yep just that very thing blogrot was referring to in the post.

    While they are two differing entities they do at some point intersect with the protective measures people could take.

    Rien dont be so shocked that (wait did you see that one?) This One article couldn’t cover everything that you had wanted or apparently expected it to be.

    BE happy that someone wrote it and now more people are learning about what they can do to prepare. Then you take the opportunity to enlighten ( ooops, already used that one) people on your knowledge that you can politely offer to share. This exchange of information contributes to the continuity , (hahaha just had to) of civil preparedness thus keeping us out of the dark ages…..(does that one count?)

    • IMO no information is better than faulty information. At least then you know you don’t know. Wrong information leads you down the path of thinking to have prepared correctly while in fact you did not. Either you did not prepare at all (not in this case) or you paid too much (likely in this case).
      Though I have to say that storing valuable electronics in an EMP hardened case is always a good idea.

    • Encourager says:

      SaltyDawg, yes the dark ages one counts, as far as I am concerned. You win for all the sparkling word plays!

  10. Thanks blogrot for some electromagnetically correct information. It has brought some of my questions into harmonic balance…..(I have more!)

  11. Another interesting point in all this discussion is how communities would deal with an event of this magnitude. To some degree, we’ve seen this happen whenever there’s a power outage. Sandy, Katrina, and other storms can cause localized grid failures. Reading some of the first-hand accounts by affected preppers in these areas has been interesting. A few years ago, my city’s 911 network went down and the local emergency management office actually utilized a response plan called “Y2K”. It worked with the help of ham radio operators strategically placed throughout the city.

    Regretfully, the greater part of the DoD community’s Emergency Management crowd, for a long time, has treated the EMP component as a parenthetical aspect of a nuke strike. (My opinion based on my observation and training experiences.) It tends to be the elephant in the room. All agree that it could be really bad. It boggles the mind when one considers the worst case.
    This is compounded when one considers that our nations power grid sustainment doesn’t maintain an ample amount of the LARGE transformers needed to replace the one’s that would be potentially damaged should an EMP event take place NOR do we currently MANUFACTURE them.

    • This is what I don’t understand…..If all the electronic communications are knocked out, what good would a cell phone, radio or any other electronic gadgit do? I can understand the very real usefulness of ham radios but are they not electrical too? I feel that the “grid” has made us all helpless. Maybe I just don’t get it!!

      • Aunt B,
        I am NOT the expert here and have felt as helpless with this subject also. But, I can tell you why we store our electronics in faraday cages.
        I put our walkie talkies, radios and CB radios in the box in the hopes that we can use them to talk to ourselves when patroling and maybe others that have saved their electronics also. We do not have a Ham Radio yet, I am pretty sure that those are safe.
        I have a laptop in the box because I have a way to charge it with solar and I have alot of information stored on it. I also would use it to monitor our security system and to watch movies.
        I bought the pre programmed computer chips for my vehicle in the hopes that we can just switch them out and still have a functioning vehicle.
        I love Papabears breadbox explanation on the Faraday cage!

      • Aunt B,
        You are currect about cell phones and other systems reliant on a large infrastructure; however, properly protected and functioning personal electronic items like ham radio, FRS and CB radios, computers or mp3/mp4 players with local documents, audio, and video, can still be personally useful, even when the larger interconnected systems no longer function.

      • Warmongerel says:

        I have a lot of prepping literature on my Kindle and laptop. Things (canning, gardening, etc.) that I may or may not have time to learn before TSHTF. All of that literature would probably take up 10 – 20 three-ring binders.

        If I should ever have to bug out, it’s much easier to transport a 1-pound, 6″ x 8″ kindle than a library full of binders.

        • Warmongerel,
          Copying this information to some thumb drives or SD cards and having some older kindles or laptops around could also be inexpensive insurance. After all, two is one and one is none, so have at least three, LOL.

  12. My car insurance company just sent me out a revised policy. Apparently they think that CME is a big enough threat to exclude it from policy.

  13. georgeislearning says:

    Thanks for the article. I enjoyed the read.

  14. gnasher49 says:

    This is probably why electricians, and electrical engineers in the UK have the colloqial nickname of “sparks”,……… Happy New Year to all the Wolf Pack and try to keep your powder dry.

  15. livinglife says:

    The wavelength (frequency) makes the difference in shielding equipment whether it be a Farady cage or coated glass. a Microwave transmits at 300 MHz-300GHz. On the small end 1 MM and 1 meter at the high end. The width of a microwave oven beam is about 5mm so the holes in the window do not allow it to pass through so it bounces back inside.
    A CME is akin to taking a magnet to a piece of wire and inducing a current as it passes by. With varying degrees of CME’s strength I won’t take the position that they won’t hurt something not on the grid. Anything that can conduct electricity is subject to induction.
    End of the day, some protection is better than no protection. its a great article that is feasible and easy enough be a primer for those interested in furthering their knowledge with more research.
    One note on grounding, I would recommend having a voltmeter or power testing device to check the ground to see if it is active. No activity is good, you may be picking up power from a neighbors house or your own, possibly buried power lines that are leaking (skinned cable, bad joints).

    • livinglife,
      You make some very good points. It seems to me that the government or at least the politicians would much rather build a new bridge or road than maintain the current ones. The same seems to apply to the tariffs allowed for financing and maintaining the electric grid. Repair and maintenance simply isn’t sexy enough I guess.

    • Yes, wavelength is the key to understanding, as is electro-magnetic propagation.
      In order for an electro magnetic wave to induce power into something, there must be an antenna. For the longer wavelengths, the antenna must also be long. A CME induced EMP has a long wavelength (tens of feet) and will thus not induce power into small antenna’s (like you find in any electronics). A nuclear blast induced EMP has a relatively high frequency and thus a short wavelength (1 to 5 inches) and will induce power in nearly every scrap of metal. Enough power to destroy semiconductors.

      Electro magnetic propagation is something else to take into consideration. If a high frequency induces currents in some piece of metal, these current will also radiate electro magnetic frequencies themselves. While part of this secondary pulse will be opposite to the incoming pulse and thus effectively annihilate the incoming signal (hence the shielding) some of this pulse will propagate inward. Thus a single layer of shielding may not be sufficient. For best short wave EMP protection you will need multiple layers of shielding.

      Another problem may arise (I am not 100% sure on this part, so please anyone correct me if I am wrong here) if only the electro part of the “electro-magnetic” collapses. The magnetic part could travel through the shielding and induce enough power to destroy the device in the box. I think this could happen with very thin non-magnetic foils (alu?). But I do hope somebody here knows more about this. (I got this from a HAM operator, so I assume he knows what he is talking about. But I have never found other references to this effect.)

  16. Texanadian says:

    Here is an interesting look at a faraday cage.

    • Texanadian,
      Interesting video. I know a lineman that used to do this kind of work and says that although it’s safe, you do get kind of a tingle accross your skin. My response was something like, “No kidding!!!”.

  17. First of all, grounding a circuit is not a panacea and if done improperly can cause more problems when the ground path acts more like an antenna than a ground. A faraday cage does not need to be grounded, period!! Anyone who actually understands the physics will understand that. If a ground were required, then it would be impossible to protect aircraft or satellites from these hazards.

    An ungrounded item could have a voltage induced onto it during an event, and if you were unlucky enough to be physically touching the item during the event, you could receive a potentially nasty shock. However, even ungrounded, the induced voltage will not stay with the item for any length of time. For instance, when something is struck by lightning, you can touch it almost immediately, and although you could get burned from the heat, you will not get shocked.

    If using military ammunition cans you would need to remove the rubber gasket and replace it with a metal mesh like copper, aluminum, or in a pinch, even steel wool. The key is to have a completely sealed environment with the best material being solid copper sheet, foil, or extremely fine mesh screen.

    When storing electronic equipment, break it into pieces and disconnect all external cables, which act as antennas. This means unplugging microphone or speaker cables, etc; that can have a high voltage induced onto them and deliver that voltage directly back to the unit, potentially causing damage.

    And finally, you can look at the archive of this blog, for another EMP article I penned a few years ago. And BTW, the physics hasn’t changed in all of this time:

    • FarmerKin says:

      Terrific article OP!!

      • FarmerKin says:

        OP, What are your thoughts on any possible EMP protection afforded by an aluminum shed? I’m pretty sure the floor is all wood leading me to believe it would not provide any protection. But it’s only a couple of inches off of the ground and it’s also attached to the ground to secure it in a hurricane (not sure what that entails or if it is of any consequence), but was thinking that the shed may provide some shielding. What do you think? Just wondering if the stuff I keep out there (generator, riding lawn mower etc.) has any chance of surviving. If I can’t protect them, at least I can prepare mentally … not that I am particularly worried about being able to mow the yard, just thought the mower may have a better chance of being operational, post event, than my car.

        • FarmerKin,

          Personally, I am of the opinion, that most modern electronics that are not connected to either the power grid or another grid or antenna system (e.g., cable TV system) will in general be safe. In EMP tests most vehicles survived with no additional shielding. I think that most modern unconnected equipment and older equipment like autos or magneto based engines will have no issues. Your metal shed probably does offer some shielding, but how much and how necessary will take an EMP event to determine.
          This opinion is based on my engineering background and understanding of the physics involved, as well as the tests that have been conducted that I have read about. Keep in mind also, that since all of this is theoretical, it could be wrong.
          When I look at the current fiscal situation around the world, and the potential chaos, I would go back to my threat matrix and realize that an EMP event is well down the list. It is worth making some preparations against it just in case; however, these preps should have the 3 B’s and your own skill set well above them. Remember that a Faraday cage merely protects “stuff”, while your long term food preps, gardening supplies, and backups of other life essentials, along with your skills, are what really count in the end.

          • FarmerKin says:


            Thank you for the opinion. I have many shtf concerns, with EMP just being the one that scares me the most. This is the scenario I feel the most vulnerable/helpless in, because 1) so much of it is theory, and 2) I really can’t seem to grasp a lot of the technical stuff. Heck, I just had to Google “magneto based engine”.

            I also just learned the other day that the hood of my car is fiberglass. Crap! I don’t think that’s going to make it.

            What you have shared gives me a little hope/peace of mind. Not complacency, just hope. I still have work to do.
            I have the 3B’s, it’s the “W” I’m most worried about. I store some water, but need to work on back-up solutions. The generator would be useful on a short-term basis for running the well pump … for as long as the fuel supply lasts, or the mower to fetch and transport water.

            Ah, if money were no object.

  18. To ground or not ground the cages to protect against EMP ranks up there with “the best gun to have is …” arguments in survivalist circles. I used to ground mine, then decided to go with nested cages and not ground them. Right or wrong, I used the info here as my guide

    One thing I’ve taken from what I’ve read is that grounding for electromagnetic radiation is not the same as grounding for DC or 60 hz AC. Pounding a copper rod in the ground and attaching a unshielded wire between it and your cage does not create a good ground at EMP freqs, or at least that’s my take on it.

  19. blogRot:

    Any opinion on using a spray-on coating (like truck bed liner” as insulation?

  20. Great post on current events! (sorry, couldn’t resist.)

  21. rev. dave says:

    Folks, even after the Emp commission’s report, the nation has done nada to protect the grid from an EMP or CME event. So it doesn’t matter if you protect your electronic stuff or not – the commission said the grid could be down for years. YEARS, mind you. Without the grid, you can’t pump fuel into your vehicle, can’t run the freezer or computer or heat, can’t get money from the bank.

    If you can’t learn to live without your electronics and vehicles while it’s down, you’ll be gone. If you can, it won’t matter if they fried or not so long as you didn’t try to eat them with mac and cheese.

    • Warmongerel says:

      “Without the grid, you can’t pump fuel into your vehicle, can’t run the freezer or computer or heat, can’t get money from the bank.”

      Sorry, Rev, but you can do most of those things if you have a power source.

      I can live without electronics. I just prefer not to. Hence, the solar chargers,etc. As long as they last and the sun still shines and the trees keep dropping branches, I have access to at least some of those things.

      Technology isn’t a bad thing if you understand it and use it correctly.

      And, as far as money goes, might be nice not to have to chase the paper for a change. 😉

      • rev. dave says:

        Well, sure, you can do all those things, IF you have the power source. And IF you have a fuel tank at home that you can pump fuel from, you can even siphon it without power. But if you have to drive to town to a station, like most people do, you’re walking or biking for a few years.

        Let’s just say that my caution message was for those folks, and not you Warmongerel. It might make more sense for people to spend time and money setting up their own power and fuel supplies first, and worrying about Faraday cages and grounding for everything later. Putting a lot of money and effort into ‘protection’ will be useless if there’s no power.

        • rev. dave,

          The two things that I want to protect most from EMP are my shortwave radio and two way radios…

        • Warmongerel says:

          Good point, Rev. If you can’t power it, it’s nothing. I’m relatively new as a prepper, but I sometimes forget that I was doing it for a long time without even realizing it, and that some people on this site don’t know what their priorities should be, yet.

          And I guess that I’m somewhat sensitive to some people who seem to be Luddites and can’t wait for the end of anything that “reeks” of technology. If I read that into your comment, I apologize. Pavlovian reaction. 😉

          Personally, I’m not planning to count on anything that has to do with petroleum-based fuel (other than LP). Gasoline or diesel will only last a year at the most. I’m planning for much longer, God forbid.

    • Tactical G-Ma says:

      Rev. Dave,
      I know that DOD has a contingency plan and have taken steps to shield certain aspects but that is a matter of national security. I also know that gov. agencies have been briefed as to the effects of EMT and CME.

      • rev. dave says:

        G-Ma – You seem to have faith that the government is going to ‘take care of us’. I don’t.

        Shielding ‘certain aspects’ doesn’t cover what the people in this nation need to stay alive, unless you know that it’s all covered and just can’t say. But given our government’s tendency to protect themselves (Continuity of Gov’t program, e.g.) with no thought for the rest of us, I’d suggest that the ‘certain aspects’ probably only maintain the government – again, not providing for any of us.

        And ‘briefing’ an agency is useless unless it turns into some kind of action program. We’re all ‘briefed’ on EMP and CME already, which is why we’re concerned. Big deal – only action helps. What’s more, given the recent tendencies of our government – I’d bet a Benjamin that any ‘action programs’ are going to be 90% ‘citizen control’ programs to keep everybody quietly starving when the grocery trucks don’t run. (Do I sound cynical? I hope so. They built Greenbriar and Denver Airport underground, but the rest of us are supposed to go to the local schools.)

        How many turbines have we bought to store for power plants under these ‘certain aspects’? How much power will get to your residential neighborhood? How much will be available to run coolers in grocery stores and pump gas a the local Sunoco?

        Sure, you can’t say. Nobody who might know is permitted to say – which tells me it’s pretty close to ‘totally insufficient’. Why? Because national security is something to put on parade when it’s there, and something to hide when it’s not. And we hide it all now. Besides, it’s not as if an EMP bomb is a threat if the enemy knows all your systems are protected from it, is it?

        • Tactical G-Ma says:

          Rev. Dave,
          I never said, inferred, implied, or even hinted that the govt will take care of us ( the people). I stated fact and you misinterpreted it. My statement was to let people know there are plans in place. I do not know what they are. Even if no one else on the continent can communicate, the military will be able to.

          Since the military will still be operational, and the govt will be up and running, what do you think they will do?

          • Tactical G-Ma,
            At least at the local level, the emergency managers are doing their best to serve the people of the communities. I volunteer with our local county EMA and we have not only discussions and presentations, but both practical and tabletop drills for incidents from active shooter, to natural disasters, to terrorist threats. I participated in a POD (Point of Dispensing) drill a while back which looked at how to get antibiotics to all residents of our county, in the case of a biological attack like anthrax. There are large enough stores of materials and equipment spread around the country, to do something like this in a timely fashion if required.
            I think the further you get away from Washington DC, the better things get, due to less political influence, more volunteers trying to do things with less funding, making more creative solutions and better use of money.
            One of the things I’ve always stressed for new preppers is to create a personal threat matrix, listing threats, sorted first by likelihood, and then by severity. The government also has to do this on a much larger scale, and I think the non-politicians do a pretty good job in general, considering the size of the task. Unfortunately, when the political folks get involved, they see reelection as something that needs to be added to the matrix, which shifts things in often unexpected and illogical ways.

          • Tactical G-Ma says:

            Ohio Prepper
            The local emergency management groups, communities coming together, neighbors helping neighbors, churches, and local civic organizations are what will get us thru, if anything. I don’t expect any aid from the DOD initially but I am certain the military has made provisions for emp.

          • Tactical G-Ma says:

            Rev. Dave
            MY best guess is…the govt will provide for the govt.
            NG will be called on to quell civil disorder in largest troubled areas and any aid will never make it to my neck of the woods.

            Weeks, maybe months later, there might be distribution of water and some MREs or C/K Rats from WWll to some of the metropolitan areas.

            There will be radio broadcasts telling the State of the Nation and locations of relief camps.. They will probably air repeating segments on body and waste disposal and the need for cleanliness. Everyone will be promised aid. Few will get it in time.

            I see how much help storm victims get from the feds. We are on our own.

        • rev. dave,
          “I’d bet a Benjamin”. Getting pretty spendthrift with those new $2.00 bills, eh? LOL

  22. Warmongerel says:

    From what I understand, the goal of a Faraday cage is to have the voltage travel over the outside of the vessel. Therefore, I’d warn against tapping a hole to attach a ground. Soldering or brazing a lead to the outside might be better.

    Personally, I believe that a ground is unnecessary and, as Ohio Prepper pointed out above, may be the very thing that induces a voltage back into the vessel.

    And, here’s a tip: you can find old, vacuum-tube radios at most antique shops and/or auctions. They should be immune from an EMP pulse and many of them have shortwave radio bands, which may at least allow you to have some news about what’s going on in the outside world if you have power to run them.

    I have about 12 of the old, wooden radios from the 1930’s and 40’s. I collected them for years until I ran out of room just because I thought they were cool. Most of them work, and I think I paid about $100 – $150 for most of them. The shortwave ones may be worth more than their weight in gold.

    • vacuum-tubes are not a guaranteed protection against an EMP.
      If you are in the blast centre, they will most likely be destroyed if unprotected. Though if you are far from the source you do stand a chance.
      Be aware that some (later model) vacuum tube radio’s do use semiconductors in the power supply.
      And do not forget that you will need power to operate any device. Especially the old power hogs may prove challenging to operate when electricity is at a premium.

      • Warmongerel says:

        Nothing is guaranteed, Rien. You can only increase your odds, which, if my understanding is correct, is what prepping is about.

        The perfect world of engineering will be useless when TSHTF. 😉

  23. Warmongerel says:
  24. I’ve been worried about the whole EMP issue, and after reading this I went to ask my two science buddies from college (one is now a nuclear scientist, the other a physics major with a focus on electrical engineering). Their reponse was that if I had to worry about an EMP blast, I probably had to worry about nuclear fallout except for a very small range. Or to put it another way, they have yet to found a way to effective weaponize an EMP outside of a nuclear bomb.

    Though..they weren’t sure about the Sun. They both admitted that was outside their field of expertise.

    Just tossing that into the mix.

  25. It seems that people with pacemakers might have a serious problem with an EMP. True or not true?

    • Yes. They will die.

    • Papabear,
      The answer, like it is with a lot of these EMP related things is it depends. It depends on how far from the EMP generation source, the angle of their body and the lead wires to that source whether or not they have some partial shielding from the EMP like a metal building or a vehicle with limited windows. If however, the EMP does stop the pacemaker from functioning, then they are very likely to be a casualty. This is slightly different from a Implanted Cardiac Defibrillator, which in many cases runs for years and never fires; however, in the case of the ICD, if it is damaged and then needed (perhaps years later), then it’s owner would also most likely be toast.

  26. Texanadian says:

    Here is thought I’ve been kicking around. I have 5500 watt generator that will run my whole house. I plan, as I live in the country, to stay put. I am going to buy a propane converter, an idea I got from here, and convert my generator. Then I am going to buy a farm size propane tank, fill and use it if SHiFT happens. I figure with careful use, cooking mostly, that will last for years. My place is 100% electric. The gen will run lights the well, whatever. I am remote enough that the gen won’t attract zombies.

    • Texanadian,
      Sounds like a good idea to me, but I’m one of those propane supporters with two 1000 gallon farm size tanks and hopefully another one coming this calendar year. I can run the entire house in normal (non-austerity) mode for perhaps 16-18 months with the two tanks (1600 gallon propane capacity), which includes heating, cooking, and heating domestic hot water, but NOT the generator for any extended period of time. In austerity mode, we would limit the heating and the use of hot water (fewer baths, heating bulk water with a wood stove) and could probably go for more than 2 years. I have not calculated what the effect of running a generator on propane to provide other services would be, but this is something you should know, especially with an all electric home. For instance, using propane to run a generator, to operate your electric water heater would be a real energy waster. My generator plans in a SHTF scenario would be to run the generator a few hours per day or every few days in order to charge batteries and pump water. This would allow us to operate the homestead with relatively little interruption for 18 months or more, at which point things will either be getting better, or we will be going back to a more primitive style of living. Little house on the prairie anyone?

      As for your situation, the bottom line with an all electric house would mean you really need to think things through, what equipment will be used and how often. How much electric energy this will take, and how that reflects back on your generators efficiency and the amount of propane required. A 1000 gallon tank (which holds 800 gallons of propane) seems like a large and inexhaustible fuel source, but can be used up quite quickly if you haven’t planned well.

  27. Texanadian says:

    I am not any kind of an expert on electricity but I tend to agree with warmongrel, let the current go around your stuff and let if find it’s own ground. The video shows that. Birds sit on charged wires because it’s easier for the electricity to go straight than through their bodies. A farday as I understand it is like a raincoat for you stuff. Keep it inside and covered and it will stay dry (will work). Just my two cents.

  28. Yes, that’s right, I am a nerd. Specifically a radio or RF nerd.

    An even simpler way to describe EMP is that it is a high energy pulse of RF. This is important because anything that shields you from RF also shields you from EMP. You can make use of this by using the radio test on your planned Faraday cage. Turn the radio on and tune to a nearby FM station. Stick it in the Faraday cage. If you can still hear the radio, it probably isn’t shielded enough. Repeat the test using a nearby AM station. You may find that some AM stations still get in, if so reject the Faraday cage. The reason is that much of the energy of a nuclear EMP will be closer in frequency to the AM band, so you really want to make sure this is blocked.

    A Faraday cage is a continuous metal enclosure with minimum resistance. In theory, the best one would be a box that is welded shut, but this would not be too practical as it would not be possible to access the contents. In professional Faraday cages, the doors will have metal fingers all the way around to make good electrical contact and minimize the resistance.

    Grounding is useful in discharging static electricity. It is also useful when used with a surge suppressor in giving an alternate destination to electrical surges other than your electronics. It is largely pointless to ground Faraday cages as RF does not cause a static buildup and there is no surge as the minimal electrical resistance prevents any voltage from building up.

    Surprisingly enough, microwave ovens fail the radio test. Turns out that the FCC regulations allow up to a 1/4 Watt of leakage, which means that a 1000 Watt microwave only needs to have 36 dB of shielding to meet the standard, which isn’t all that much. I have to admit, I always wondered why there was no electrical connection between the door and body of the oven. Chicken wire did seem to be partially effective in that it blocked FM radio, but not AM radio. The best I found was aluminum foil and ammo cans. In fact, the ammo can was so effective it blocked the RF without the lid even being closed. As such if I were to want to put all my stuff in Faraday cages (I don’t), I would put the electronics into a paper bag, then aluminum foil, another paper bag, and into the ammo can. I would not remove the rubber gasket on the ammo can as I would give up the extra protection in favor of keeping it watertight.

    So now I am betting that the question you are all asking is why is all my stuff not in Faraday cages, after all I know all about this stuff. The answer is that I have run the numbers on how much energy is in a nuclear explosion, how much of that is actually able to generate EMP, how much of that is blocking by shielding in the device, and then spreading the remaining energy over the lowest altitude of a high altitude burst and it is a very small amount energy per square foot. As such I expect that almost nothing that is not plugged in or turned on when it occurs will not be affected. They are simply too small to pick up enough energy. However, the bigger something is, the more it will pick. Where I do expect problems is that anything connected to long wires like power lines, telephone lines and cable and I expect anything connected there to be toast and have backups accordingly.

    • Oops, meant to say: “As such I expect that almost nothing that is not plugged in or turned on when it occurs will be affected”

      • a-nerd,

        +10 – Some very good points
        “It is largely pointless to ground Faraday cages as RF does not cause a static buildup and there is no surge as the minimal electrical resistance prevents any voltage from building up.”
        Bingo & well said. If we remember basic Ohms law, where E = IR (Voltage equals current in amperes times resistance in ohms); therefore, if ‘R’ is zero, or very close to zero, the no matter how high the current ‘I’, the voltage ‘E’ will also be low. It’s not physically possible for ‘R’ to be zero, but if it was, then a current of 50,000 amps or 5,000,000 amps would still yield an induced voltage of zero.
        “I have run the numbers on how much energy is in a nuclear explosion, how much of that is actually able to generate EMP, how much of that is blocking by shielding in the device, and then spreading the remaining energy over the lowest altitude of a high altitude burst”
        This brings into the mix, another phenomenon which is easily explained and easy to calculate, like Ohms law. It is the Inverse Square Law, which simply states that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source, so, if you received a certain intensity of energy (radio energy, heat, etc) at 1 foot, you will receive only ¼ of that energy at 2 feet, or 1/100 of the energy at 10 feet. Therefore, as you get farther away from the source of the EMP, the amount of energy you receive get smaller exponentially. This Wikipedia page has a graphic representation that explains this rather well:

    • We would all be better off for knowing some nerds. Communications are going to be very important in the coming hard times.

  29. OK Folks, this is what I’m going to do. I’ll put my CB radio and a AM/FM radio with the batteries out into an old microwave I have, with a piece of wood between them. Then I’ll wrap the microwave in alluminum foil and store it on ahigh shelf out of the way. Later, if it works OK, If not that’s OK too.

    • FarmerKin says:

      Aunt B,

      It may be easier to wrap the radios with foil and put them in the microwave. I can’t imagine getting the foil wrapped microwave on a high shelf without ripping the foil.

      • FarmerKin, Thanks, Iwas really careful. I had to use my stepladder since I’m “vertically chalenged”. The reason for the high shelf is so it wouldn’t accidently get snagged or ripped.

  30. I am about EMPed, CMEed, etc out. For me and most of my folks, if it’s nuclear generated, it’s not going to matter much (unless we’re under ground when it happens) as we live too close to the number 3 target of the cold war. Maybe in a few years (when the radation dies down) some of you folks can come in a make use of our stores that may still be good. In the mean time, I recon we’ll keep on prepping for anything but nuclear.
    Be good to one another,

  31. Very well written article! Both informative and entertaining. I laughed out loud several times. And it was easily understood by complete electrical incompetents like myself! You’re an electrician? Man, you should be a regular blogger or start your own prepper newspaper column (remember newspapers?).

  32. Rein is 100% correct. He sounds like he’s the real deal. Grounding does not matter. For example, to protect a portable radio, simply wrap it in two layers of aluminum foil and hand crimp the seams. Otherwise, the radio’s ferrite antenna could pick up and conduct the pulse into the electronics inside the radio. Don’t worry about grounding, it doesn’t matter.

  33. I have been reading the responses here and they are all quite interesting. I have a n MS in Electrical Engineering an retired from Power generation. My considered opinion in this matter is that everyone is right since there are too many variables for the average citizens pocketbook to cover. When the Chinese pulled that bullshit off the California coast with their EMP missile in hopes of knocking out the aircraft carrier, they only knocked out the cruise ship. The carrier was still functional enough to deliver SPAM to the cruise ship which was refuse. Uncle Sugar has our money to protect these systems and a profit orientated entity such as the cruise line will not since the occurrences are few.
    By the way, the earth is not at zero electrical potential but a constantly changing potential. Observe if you will a typical lightening strike. When the negative potential at a pint in the earths surface rises to a great enough potential to mallow the positive potential of the static electricity generated by the clouds to close the distance gap between them a lightening strike will occur. If you catch this on film you will see the arc reaching up into the sky where it meets the downward arc. If the earths potential were consistently neutral over the surface instead of heightned potential at that one particular spot, there would be no strike.

  34. Hey guys! I have a military training background in EMP, and this is a great starting read for anyone new to the joys of EMP protective works. One this that I think should be added is the acronym IPSAT as a memory jogger. It stands for Insulate, Pad, Scrape, Apply, Tape. What it’s used for is to remember how to protect sensitive components from Electro Magnetic Radiation EMR (which both EMP/CME are derivatives of). Insulate the item you with to protect by covering it in any non conductive material (vinyl tape, card board box, rubber case), then Pad stands for pad any sharp corners that could possibly poke through the insulating material (the cardboard box is the insulator and the styrofoam packing is the padding in the articles example). Then scrape stands for scraping to remove paint or coatings from the shielding cage or edges of openings that will connect together so that a grounding wire can be bolted or soldered/bolted on to it for a solid electro/mechanical connection. Apply stands for applying the shield, and this would be placing the item into a cage or ammo can, or as the author indicates, an old microwave. Tape stands for the application of electrically conductive duct tape (regular will work too) to all edges where there is a break in the shield (the break between the lid and box of an ammo can). The actual foil duct tape works really well as a shielding tape, but you should scrape the paint off of the edges of the box and lid where the tape will be applied so that it can make an electrical connection.

    One note that I don’t think was hit upon enough was the fact that EMP can reach over 100,000 volts and that it only takes 10,000v of energy for a large discharge to leap through the air. If the voltage is high enough to energize your shield to 10,000+ volts and there is a potential that an arc will occur from the inside of your shield to the components inside that you’re trying to protect. Shielding and grounding are methods of REDUCING THE LIKLIHOOD of damage NOT ELIMINATING IT. Be sure that your ground wires are of sufficient gauge to handle the excessive voltage and current. Use at least 8ga heavy stranded wire for all of your ground wires and copper ring lugs. Use a through bolt (soldered) with a wing nut to ground the wires to you ammo cans, and use ground lug bars on each shelf all connected to a main grounding wire. If you’re handy, you can buy a three prong appliance plug from the hardware store and connect your grounding wire to the ground lug (ONLY CONNECT TO THE GROUND LUG, LEAVE THE HOT AND COMMON UNUSED), that way you can plug your EMR shelf into any household outlet and it will be grounded to your homes ground wire through the wiring in the wall. Have fun, be safe!!! Great read!! 🙂

  35. @Rein: Come on friend, try to grow a sense of humor. The author is offering a light hearted approach to a technical topic to keep readers interested. I have a military background in EMP/EMR and I think the article was great for the purpose that it was written to cover. There are no incorrect facts in it. The BS you are citing was an obvious light hearted inference regarding the FACT that electricity seeks the path of least resistance, and that it wants to equalize itself out against the ground of the Earth. That’s why it is called a “difference in potential energy”. The positive wants to get to the negative and vice-versa. Don’t turn a light hearted entry level discussion into a crappy technical argument over semantics that will miss its targeted audience. Author: great job +1 vote from me.

  36. I keep seeing comments regarding “grounding doesn’t matter” and this couldn’t be farther from the truth. If the faraday cage voltage builds to a high enough level and has nowhere to go it is possible that it could arc through the air into the components inside if not provided a path to ground through which to dissipate. 100,000V shield on the outside, 0v conductor on the inside. The conductors on the inside of the can have less potential energy than the shield and are therefore less positive aka: negative by comparison. This can lead to a situation where a discharge arc leaps to the component circuitry inside the the cage, letting the magic smoke out.

    Take this common sense example and base your decision whether to ground your cage or not on it. I work with electro explosive devices (EED’s are electric blasting caps and other devices). The military REALLY DOESN’T want a stray EMR current to initiate the devices. The devices are therefore stored in a metal ammo can (insulated and padded from the can, the metal can sits on a metal shelf inside of a metal safe. The door to explosives locker is grounded to the frame, and the frame is grounded to… That’s right, you guessed it, good ole earth ground plane.

    Grounding lessens the risk of an EMR initiating the blasting caps. The point of EMP/CME/EMR protective works is to LESSEN THE LIKLIHOOD of a negative effect on critical electrical assets. Ground your stuff. Rein and all you other technical argueknots – you’re smart, is that what you needed to hear? Go away now because EOD says so!

    • Tactical G-Ma says:

      Why not take the one final step of telling us how to create an ideal ground field …you know iron rods, water, salt, characteristic impedance, and all that jazz . The electrician has put in a ground at the breaker box but if I went to all the trouble of building faraday cages, I would make certain a more aggressive approach to grounding.

  37. TacG,
    Not being smart here, but You say “all the trouble” as if soldering a ground strap from the lid to the box and bolting a through bolt and wingnut to an 8ga wire is akin to installing an underground bunker as an entire faraday cage. It doesn’t have to be rocket surgery! I have made very effective faraday cages with ground wires out of the 20mm ammo cans in less than 30 minutes. If I wanted to use 1/2″ plywood as the insulator inside the box make it 60 minutes. I mean come on, we’re not building a skyscraper. It’s 3 holes [email protected]/8″ and [email protected]/4″, three quick wire wheel clean offs to remove the paint at those points, 3 crimped and soldered 8ga lugs, 2 rivets and solder, a 1/4-20 hex bolt and nut through the 1/4″ hole, and screw on the ground lug with a wingnut. Bolt the other end down to your ground rod (or even just add a heavy 120V plug to the end of the ground wire so you can plug it into a wall outlet for ground). That’s like half an hour if you’re motivated! 😉

    • Tactical G-Ma says:

      All the trouble was referring to how I thought your remarks were more arrogant and condescending than instructional.

  38. Yes, well I was merely standing in the gap for the author who obviously chose to take the high road in regards to some of the “snarky” comments above. The commentary from a few of the individuals above was very sharpshooterish and condescending. Especially the “my professionally written paper is in Dutch, hold your breath on me translating it.” That crap irritates me and serves absolutely no positive function. The guy was just trying to make the author look bad and make himself sound smart (which he probably is). My point is, if the military feels that grounding the explosives locker reduces the liklihood of an an inadvertent initiation of an EED, then it makes sense that the chances of an EMP inadvertently smoking electronic devices. The difference is that the military has implemented this protective work in reality and the comments above we’re based in theory. If the guys above don’t want someone to be mean to them and hurt their little feelings then they should not be so condescending and “snarky” themselves. I can have a polite discussion if the commentary remains polite, but when the commentary turns I have no problem challenging it either. The author did a great job on this article.

  39. Omegamann says:

    Sorry, but I am getting conflicting information. Some say that the edges of the Faraday cage container must meet metal to metal. Some say that GI ammo cans work. Yet, these cans are painted top to bottom. How do I resolve this conflict? Sand the cans?

  40. I think that many of you need to research the Carrington Event, and read about all of the damage that was caused and then argue amongst yourselves about what can and cannot happen. The event happened in 1859, at that time we were just infants in the technology race. If you take into account the events described then and cross it into current knowledge and technology and add into it the works of Nicola Tesla and his theory on broadcasting electricity, you will see that there is an immeasurable number of variables that are unknown. Rather than fighting amongst yourselves on who is right, just combine the knowledge that you have with that of others. Petty in fighting (and the undue need for measuring of private parts) is going to do nothing for anyone. “PREPPERS”, are supposed to be a community of people that want to survive, overcome, and maintain throughout a disaster. That can never happen if ego gets in the way. I thought that this article was well designed to inspire thought in those that may have not considered these preps before, so if you have constructive additions, then great, if not then perhaps you should contain your arguments to your own tight knit, prepper community and allow others to openly communicate and learn from eachother.

    • TFX,
      First of all, the article was a well written, if a bit tongue-in-cheek presentation and primer on EMP.
      Both the Carrington event and Starfish prime have been discussed in the past and are well known events, as are the reasons they were destructive. The damage in both cases came from the fact that the affected systems, telegraphs in Carrington and street lights in Starfish, were part of a long antenna system, which collected the energy and delivered it to ground reference points along the wiring.
      As for Nicola Tesla (one of my historical engineering heroes), his broadcast of electricity is in use today for transmitting radio and television signals; however, use for power distribution was/is not feasible, due to physics )the inverse square law).
      As for preppers helping (and learning from) each other, that is why most of us are here; however, presenting bad information helps no one, needs to be corrected, and often is.
      If for instance, someone was discussing canning and mentioned low acid vegetables and meats being canned in a boiling water bath, then I am sure many here would jump in, since that would be a potentially dangerous thing to do. I don’t personally see ego involved, just that sometimes there are folks here who know more about a subject that others, and impart their knowledge to the rest of us. That is the primary reason I come here, to learn from others; while teaching what I know, and correcting things I know to be incorrect, especially when dangerous.

  41. davesolfinger says:

    what about more comment on what to actually put in your farraday cage. what specific electronics will i need to get my toyota running, that is other than the obvious radios a wish list if you will.

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