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Mitigating an Electro Magnetic Pulse

The chances of a nuclear war are currently reducing as we move on and our once deadly baby killing foes become our trading partners. This has reduced what once was a very likely scenario to a most unlikely event. We should all be pleased with that. Although a nuclear war would have been survivable for our species it would have had some horrific after effects. It is good for all of us that the risk is reducing.

In the early days of nuclear tests an EMP (Electro Magnetic Pulse) was predicted mathematically and the test equipment shielded as best as they could. Even so some electrical equipment was still damaged by the pulse which covered a vast area around the detonation sites. Although the effect was predicted the significance was not that apparent due to the fact there were not any electronic components in those days and the electrical equipment we had was more robust.

Now, I’m not an expert on EMPs but I do know a little bit about them. Enough to have an idea what we need to do.

First some background.

How does an EMP destroy equipment
Simply put; Basic physics shows us that a fluctuating electrical current flowing through a wire will create a magnetic field which will induce current in another wire that is in close proximity to the first but not electrical connected. This is the basis for our ordinary everyday transformers where we take 240v and transform it down to 12v for example. The current created in this unconnected coil is used to power whatever we want. It is the magnetic fluctuations in the process that creates the current in the coil.

In the same way that a rise in magnetic field causes a build up in the transformer a rise in the magnetic field from the pulse causes a current to be created in our equipment. The wires do not need to be coiled either, a straight piece of wire will also be affected. As an EMP creates a very powerful magnetic pulse significantly more than we create in our transformers we find that the resultant current created in the coil is also significant and it is this high current that burns out the wires and fries the electronics pretty much the same as if you have plugged a 12v radio into the 240v mains.

The current created is proportional to the distance from the explosion, the orientation of the item to the pulse and the length of the wire or component. As many modern day components are very small and protected against static electricity we will find that many items are unaffected by an EMP. Anything with aerials and mains wires will have the highest risk with the main grid, solar panels and aerials being particularly vulnerable.

What sort of range does an EMP have?
An EMP detonated in the upper atmosphere has the potential to destroy all electrical equipment within an area covering thousands of square miles. A large single bomb in the middle of the UK will cover our entire country.

As an aside a solar flare from the sun has the same effect, a solar flare is a massive magnetic field ejected from the sun, and solar flares have caused issues on the planet already damage worth billions of pounds mainly to the electrical grid and through that to electrical equipment. As an EMP and Solar Flare are essentially the same thing we will treat them as one risk, an EMP.

Can you stop an EMP?
Well we can’t stop EMPs as such. All we can do is ensure that susceptible equipment is protected in some way from the EMP itself. We can put the equipment in a shielded box which has no way in, we can construct the equipment so it can handle an EMP effect or we can EMP proof an area such as a building or vehicle. We have to be careful though because a hole in the shielding will allow the pulse in or if there is a wire leading into the shielded are it will be subject to the effect and take the current in along the wire. There is science behind it and it is very expensive to shield working equipment from an EMP. Way beyond the capabilities of most of us.

What is the risk?
Unfortunately, the risk of an EMP being set off somewhere is increasing. There are people who are saying when not if. Although clearly that requires someone to detonate the device in the upper atmosphere which is not easy. Solar flare activity though is currently increasing and expected to increase significantly during 2012 where damage is widely expected but solar activity seems to be being downplayed by the media and politicians. I suspect to downplay the suns influence on the planet to help the AGW scam. In addition the major powers are working on EMP bombs which are designed just for the EMP effect. These are more likely to be used than normal tactical nuclear warheads. Devastation to our Western civilisation without the bad PR of children falling apart from radiation sickness.

So we need to be aware of the risk of an EMP and what we can do to mitigate those risks. They are no different from any other risks in that respect and we should treat them as such.

Mitigating the risk
Now there is only one real way to mitigate against an EMP. EMP shielding, and there is only one way to shield from an EMP and that is to completely cover everything, the cables, equipment and aerials with conducting material. As you can imagine this is a problem for radios that need to receive RF to function and solar panels that need to be out in the sun as well as power lines which run across the country.

The military have spent a fortune shielding every bit of kit they have from an EMP. Some of this equipment is available to you and if it something you need and you can afford it you should buy it. Radios and power equipment especially.

Although we do not have the experience, equipment or skills to modify any of our equipment to be EMP proof we can build a very simple device to act as a shield. This device, called a Faraday Cage, is built to enclose the area you want to protect. A Faraday Cage is a enclosure made of conducting material with no holes in it for RF or Magnetic fields to penetrate. With no Magnetic Fields there is no current created in any equipment inside the enclosure which can be a box, room or even a building. The only issue with this is that power cables, aerials and air vents all create holes or wires that the EMP can travel along or through. It is possible to build a working Faraday Cage that is EMP proof with the right equipment; shielded wires, shielded vents. Unfortunately, as we are unable to fully test any home made items I’m not going to recommend you make any yourself for working in and rely on them exclusively. You can buy shielded equipment if you really want an EMP proof office. Bing or Google Faraday Cage.

Are all items susceptible?
Not all electrical items are susceptible to an EMP. Older items without the electronics are virtually EMP proof, cases made of metal will offer addition protection, radios with tubes and older vehicles with plugs and points will also be safe although you should still be keeping spares for the alternators and other components. Sensitive electronic equipment, plastic cased electronics and mains powered equipment are the main issues.

What can I do?
The easy solution, and my choice, is to use the equipment as normal, totally unshielded, and replace it when it is hit by an EMP. This however requires you to have spares for everything electrical that you use on a daily basis. We won’t know what will survive and what won’t. There are too many variables. These spares need to be shielded but for this a simple Faraday Cage is easily constructed that can contain our spare equipment. Switched off, boxed and not connected to anything that will conduct, it can remain perfectly safe during an EMP. This simple shielding is much easier to make and one we can easily do cheaply at home. We just enclose the complete unit, no holes or doors in the conductive material and it will be completely shielded and protected.

For a true survival situation though we need to go that extra bit further. For normal use you are not bothered if RF enters the Faraday Cage while you have the door open. In our case this is a major risk. How would you feel if you have stored radios, computers and other electronics and an EMP pulse occurred while you had the door open to do a stock check or add in a some new equipment. Our little bit further means we shield every item individually in its own Faraday Cage, store them in a Faraday Cage which is also contained in another Faraday Cage. This works on an airlock principle. You open the outer Faraday Cage door walk in. All it contains is the smaller Faraday Cage. If an EMP occurs at that point the inner cage protects the equipment. You close the outer door so the outer cage provides the protection then you open the inner cage door to enter and access the spares. Do what you need and then close the inner door before opening the outer door and exiting.

Will that fully mitigate the risk
Like everything else it is impossible to mitigate against every risk. This one is particularly difficult because you never know if another EMP will be detonated. If another is then you could lose anything outside the Faraday Cage again. You will only have a limited number of spares for each item no matter what it is and the cost.

Making a Faraday Cage
There are several ways of making Faraday Cages. We want the cheapest, easiest and most effective solution to the problem and luckily there are some out there. Relatively speaking of course.

One thing to consider is that a Microwave Oven uses RF to cook its contents. The outside is shielded by design to stop the RF getting out and microwaving people standing nearby. This means it is effectively a small Faraday Cage.

Another is simply to put your items in a solid metal box. Make sure the box is sealed all the way around and has no gaps at all. The metal lid needs to be electrically connected to the box, usually using copper braid instead of rubber seals or gaskets with lips overlapping rather than just touching the surface.

The next is to build an enclosure made of metal sheeting, no windows, slots or holes with a door that actually contact the sides of the box all the way around. Again the door is connected along the edges with copper braid.

Probably the easiest way to make a decent sized room is to take a shipping container. Ensure any gaps are sealed and that the doors seal correctly. Copper braid again for the gaps and doors. Weld where necessary. Bury it in the ground if you can as earth is an excellent shield.

My ideal storage area is a shipping container with one door, the others are welded shut. Inside is a smaller container with a single door electrically isolated from the outside container. Inside the smaller container are metal cabinets containing the individual components either wrapped in several layers of cooking foil and in the anti static bags you get computer boards in or wrapped in cooking foil or anti static bags in their own metal containers depending on what they are. Sometimes I think this may be overkill but thick cooking foil is cheaply available and you will not be able to source any equipment that is damaged in an event.

However, I can’t see that happening for a long time due to cost so at the moment I have several small boxes with small items in. These items are placed in anti static bags which are then put in small boxes which are covered in kitchen foil and stored in a large metal box. I intend to move them to a metal bin or container and weld it shut when I can fill it.

Unlike the rest of the stores I’m not that bothered about these items getting too hot. A sealed metal box in the summer is going to get quite hot but providing it is kept away from water, there is internal packing and it is stored in the shade, as much as you can, it will store electronic items OK.

EMP is a very complicated subject and one ordinary people know little about mainly because you need to be up in Physics to understand it and in that area to fully unerstand how to mitigate it. Testing is difficult and usually out of our financial reach. The best we can do to test is to put a battery powered radio in our sealed units and see if it is still receiving a signal. This is not 100% accurate though but will give you an idea if it is working or not. There are many articles out there on shielding from an EMP (Bing/Google) as well as several articles at other survival sites if you wish to know more.

Ignore all the hype and don’t panic.

  • Identify everything that could be susceptible to an EMP.
  • Buy metal cased units for your base radios and computers rather than cheap plastic ones. You should be doing this anyway where you can
  • Keep spares for those identified items as you should be doing anyway. Although you keep these spares wrapped in thick cooking foil, stored in anti static bags and store those in a sealed metal box or sealed metal bin.
  • If you have the funds seal a larger box or shipping container and insulate the inside with non conducting material. Store your sealed metal boxes in there.
  • Disconnect everything from the mains and aerials when you are not using them and store them in metal cabinets.
  • Keep you eye on the solar flare activity.(NASA and/or IPS Flare Alert)
  • Take care when adding or removing items from your shielded stores. Even after an event.

It is increasingly said an EMP is one of the most likely events that could happen to us today. More than societal collapse, more than an asteroid strike and certainly more than nuclear war. We need to prepare for it or suffer.

12 comments to Mitigating an Electro Magnetic Pulse

  • half

    I was using an old microwave as a faraday cage but after further research I’m not 100% sure they work. There seems to be two camps on this and I don’t know enough about this stuff so to be on the safe side I’m using biscuit tins with foam lining instead.

  • Skean Dhude


    With no real way to test them we cannot be certain. However, we tend to use old microwaves past their useful life. I wonder if that may be the problem we have.

    Regardless, If you wrape them up before placing in the microwave the hard case of themicrowave offers another type of protection as well. I like them.

  • moosedog

    Your advice about a possible second EMP is good. Just like the nuclear war problem there is the likelihood of retaliatory strikes and here in the UK we could be hit by both sides. Collateral damage as they call it.

    As most of my radio equipment is used daily it isn’t feasible to protect it with a Faraday cage. Reading your article I suddenly realised that I have some portable units in a drawer which could, and should, be better protected. They would likely become the equipment of choice anyway as a major EMP would probably be the end of civilisation as we know it, meaning bugging out to a safe location on foot or bicycle. That might sound overly dramatic but the consequences of an EMP on our technology-driven society would be massive.

  • Skvez

    The *Voltage* induced is proportional to the *square* of the distance from the EMP source.

    Bigger PN junctions (transistors) are less affected than smaller, thus older technology is less at risk than newer tech (transistors are shrinking so we can fit more on a chip), there is a competing effect of newer product being better designed to be less affected by Electromagnetic noise. As a result I’d have expected solar panels (with their relatively vast PN junctions) to be well down the list of vulnerable items.

    A solar flare is not a magnetic field as such; it’s a massive ejection of charged particles that carry with them a magnetic field (electric charge + movement = magnetic field)

    EMP shielding is not an absolute (magnetic fields penetrate pretty much anything, the Faraday cage is only effective at reducing the strength of the electric fields), it should be viewed like waterproofing. Splash-proof is good ‘waterproof to 3m’ is better but take either diving and they’re still going to break. How effective the Faraday cage is will be affected by how strong the EMP is, how close it is and how good the Faraday cage is. All three are variable. The good news is that a ‘fairly effective’ Faraday cage is cheap and easy to make, the bad news is a ‘highly effective’ Faraday cage is not.

    A simple test for your Faraday cage is to put your mobile phone in it and call it, if it rings it can still contact the base station and you’ve Faraday cage is poor (if it doesn’t ring you haven’t definitely got a good Faraday cage but the mobile phone test is quick and easy).

    • Skvez

      Spotted an error
      Voltage is proportionally *divided by* the square of the distance. i.e. double the distanced quarters the Voltage.

      and while I’m here a few more thoights …
      The phone test depends very much on what your normal signal strength is. If you’ve a good signal strength then it’s a worthwhile test. If your signal strength is borderline anyway then it’s not much use (since even a little shielding will stop the phone when it won’t help much in an EMP situation).

      Man-made EMPs tend to be discrete events wheras solar flares have a duration

  • Skean Dhude


    I doubt we will be hit by both sides. Hit by one and subject to the collateral damage of the other. The EMP generated being so far reaching will undoubtably effect us from both parties.


    Thanks for that. I didn’t want to get too technical because, well, I’m not that technically aware of all the details. I just know that ball of plasma, big explosion, magnetic field, current induced, destroyed kit, need shielding.

    That part about testing with a phone is a good idea. However, mobile phone stations are not that powerful and it could work for that but as you say, it depends on how close the EMP is if it will work then. We just don’t have the equipment to test it with.

    We can’t cover everything and I would suspect an EMP overhead would overload a lot of the cages, which is why I like overkill. As I said you can’t just go to the shops to replace the kit if you get it wrong.

    Go overkill. It’s the best you can do without spending a lot of money. If you have the money then get a proper room shielded.

  • AmandaK

    Love all the information this blog has given me. I heard about EMPs a few weeks ago and right away I started to look more into them and how I can prepare and protect my valuable electronics from them. I’ve come across some great, informative blogs along the way on the internet, and to be honest, this is one of my top favorites now that I’ve seen it. But what really takes the cake is a Radio Blog I came across that’s held by EMPact America. They have new guests on their show, speaking and giving out important information every Wednesday. This week the topic is on the Faraday Cages! I’m so excited for this show, because I have really been trying to figure out the best ways to protect my things. Randy Tolman is the guest that’s going to be talking about the Faraday Cages. You all seem really interested, so here’s the link if ya’ll want to check it out this Wednesday coming up!

  • Skean Dhude


    Welcome and I’m glad you like it.

    Thanks for the link. I’ll try and have a listen to that. It may be just what we are looking for.

  • AmandaK

    You’re welcome! I hope you find it helpful:)

  • Skean Dhude

    I’m sure I will if I remember. 🙂

  • bsdiem

    Do the cages need to be connected to an earth ground to be effective? Would a good quality metal screen (like screen door material) be effective as the shielding material? Assuming all of the other criterea are met. i.e no holes, cables, etc

  • Skean Dhude



    Arguments rage on this subject. I am under the understanding that it does not need grounding to be effective and I am happy to accept that answer. I can see the pulse not being able to get inside. However, being the paranoid that I am I would say ground it where you can. It doesn’t take much to do so and every little helps.

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