How To Protect A Portable Radio From EMP

Protecting a portable Shortwave/AM/FM radio from an EMP (electro-magnetic-pulse) is (theoretically) fairly easy, and is a wise course of preventative action to take with a critical electronic piece of equipment like a radio which could provide you with critical news and information about an ongoing disaster…

An EMP event (from a solar super-storm or nuclear EMP attack) could bring down the electrical power grid — either regionally or even wider; and if strong enough, it has the potential to critically damage circuits within electronic devices…

A portable shortwave radio has the ability to receive stations all around the world, and could be your information lifeline after an EMP event — enabling you to hear communications from far away in other regions of the world that are still “up and running”, and will provide invaluable insight to your predicament.

The thing is… if your radio has been fried by the EMP, then you’re SOL…


An EMP from a nuclear atmospheric detonation is an instantaneous jolt of tens of thousands of volts per square meter that is generated from the interaction between the explosion and the Earth’s magnetic field.

The invisible but catastrophic pulse occurs instantly over an area that is within line-of-sight of the EMP-weapon detonation while its devastating electro-magnetic-pulse decays by the inverse-square-law the further away it gets form its origin.

Having said that, an EMP detonation at an altitude of 50 miles would affect an area with a diameter of 1,400 miles while a detonation altitude of 200 miles would affect an area of 2,900 miles in diameter. The area directly beneath the blast is affected the worst, while the extreme fringes are barely affected.

The EMP effects from from a massive solar flare event from the sun — similar to what happened in 1859 (the Carrington event), could also bring down the electrical power grid, although may not affect stand-alone electronics like radios, etc. as would a nuclear EMP weapon attack (the grid-down would be bad enough…).

An EMP potentially has the energy to wipe out things ‘electronic’ and could potentially send a region back to the 1800’s in the blink of an eye. An EMP weapon is a very real threat in today’s increasingly unstable world and has always been a threat from the sun.

Protect your portable radio from EMP

I will preface this opinion with the fact that none of us have ever experienced a major EMP event and there has never been an attack anywhere in the world using a nuclear EMP weapon (as of this post). Therefore any advice as to how and protect your electronics are theoretical at best. You might say that there has not been any real ‘hands-on’ experience…

First, completely wrap your portable radio in a non-conductive material being sure that no (metal) part of the radio is exposed before the next step. You can use paper, a paper bag, cardboard, or even easier…slip the radio inside a zip lock bag (if it fits). If using a Zip lock bag, ‘burp’ the bag of air for a nice snug fit.

Next firmly wrap the now-covered radio with aluminum foil — being sure not to leave any open spaces. Wrap tight and well.

Repeat the process for even more protection… another non-conductive layer or zip lock bag over the now-wrapped radio… followed by another wrapping of aluminum foil.

Lastly, place the now-wrapped radio in yet another bag so as to protect the outer foil layer from tearing.

The theory is that the pulse will enter the conductive foil and dissipate around it while not affecting (or inducing currents) within the electronic circuits which are isolated and protected inside the bag.

It is, in effect, a do-it-yourself Faraday cage. A Faraday cage is a conductive casing that prevents the electromagnetic radiation from reaching the electronic circuits contained within.

It is the opinion of many that a make-shift Faraday cage does not have to be grounded in order to prevent damaging electrical currents from an EMP getting inside the protected electronic circuits which are isolated within.

Another simple technique is to use a metal trash can with a secure metal lid. Line the trash can with cardboard or other such non-conductive material, and place your radio and other salvageable electronics inside.


    1. That may NOT be enough – especially if the cord is still there. Also many microwave ovens DO leak a little energy, so the contents may indeed still get zapped.

    2. I put my cell phone in my microwave then called it – it rang, so I guess a microwave oven is not fully shielding.

  1. The ammo cans I use have a rubber seal between the lid and can itself. This means it is not a true Faraday cage. So I’am not sure ones electronics are safe inside.

    1. I had previously thought of ammo cans, and then dismissed them for that very reason. However, I have recently been considering a resolution for that issue…remove the rubber seal, and replace it with rolled aluminum foil thick enough to ensure consistent, tight contact around the entire perimeter of the can. I would think that should work, but like has been said, you wouldn’t really know until an event proves it out…or not.

      1. That sounds reasonable. Be sure to also check for paint – which is not conductive. You may have to sand off any paint in the seams. If you have a multimeter you could check for conductivity…

      2. Wouldn’t attaching a jumper wire from the lid to the can body accomplish the same thing only more reliably?

        1. @grintch You could still have induced eddy currents, so I think the jumper wire is not as good as continuous electrical contact along the whole lid seal.

        2. You are right… Just spoke to my HAM radio guy (40 years experience and survivalist) and he said using a jump wire soldered (not tapped) on the top of the ammo box lid at one end of the wire (he said 14gauge wire) and again on the ammo box casing with the other wire end will bridge the electrical charge of an EMP.

    2. It is a true Faraday cage. The top overlaps the sides. The gasket is irrelevant. The “cage” does not have to be solid. Screen wire works just fine… the pulse doesn’t sneak through the holes.
      Lightening doesn’t strike you in your car through the windshield even though its surrounded by rubber and thus isolated from the metal. Its a Faraday “CAGE” not Faraday “solid metal box”.

      1. Also, the ammo box lid and box would be connected by the hinge and latch making it complete for circuit anyway

    3. Seal the lid to the the box of your ammo can with your electronics inside prepared as described in the article with 2”-4” self adhesive, HVAC aluminum or copper duct/sheet metal tape available at most any good hardware/home improvement store.

      1. You can also form a strip of aluminum foil around the edges of the ammo can/box so that when you close the ammo can lid on the box, you complete “the circuit” between the ammo box and it’s lid despite the rubber ammo can gasket. This will work on garbage cans too. Naturally, the “fit” between the “can” and it’s lid will be tighter so you might need to experiment a bit to get a tight fit that still seals (connects) well.

      2. I have liked the idea of the metallic tape for quite some time, but I have concerns about the adhesive that forms the sticky on one side. Basically the layers you have are the metal of the lid, the metal of the tape, the adhesive, then the metal of the bottom case. Is that adhesive an insulator or is it just as conductive as the tape. If the adhesive is conductive, temporarily remove the rubber gasket, sand the inside of the lid in that area, sand the bottom in that area, replace the gasket and then apply metal tape over the gasket ensuring the tape is also adhered to the tops metal. When closed, the gasket under the tape holds the tape firmly against the bottom.

  2. The next time you go get an MRI, ask how the room was built. The MRI puts out an EMP. When leaving the room, look at the construction of the door. It is not a regular door, the edges have copper finger leaf inserts to contain the EMP. I had a project once where one of these doors were installed back in the mid 90’s. The standard size door costs about $30K to $50,000.

    1. Or take your faraday cage in with you and put a cheap radio inside to test it out.

      1. One little, teeny, tiny problem. The MRI machine is also a huge magnet and everything ferrous gets sucked into the tube. People who have steel fragments in their eyes can have the fragments ripped out. People with embedded surgical metel like rods must wait six months or more before they can get an MRI. And worst of all, a child was killed in one when somebody inadvertantly left a fire extinguisher in the room and it was sucked in the tube at high speed and crushed the kid’s head

        1. It was actually a fire extinguisher sized oxygen tank, but yes, that did happen.

  3. I’m sure everyone knows to remove the batteries first before wrapping and storing as they corrode after a while which could ruin the radio, but how about those rechargeable radios running off solar or hand crank? Could those corrode as well even if unused and still in the unopened package? Just wondering

    1. I’ve had my crank radio stored in emp protection for 10 years without batteries in it. today,with everything going i wanted to ck it. took it out crank, everything works perfect. no corrosion at all. looks brand new.

      1. You bring up a good point in general – that it’s a good idea to check one’s storage once in awhile. Also, as you eluded, it’s very important NOT to leave batteries in the electronic device while it’s stored for a long period in order to further avoid corrosion.

        1. as for worry of corrosion, through a small silica gel pack in to keep humidity stable. I do it for my drill bit boxes and extremely minimal rust on them.

    2. Would a moisture absorber help reduce or prevent the corrosion? Especially if the batteries are disconnected or removed?

  4. Layers of shielding. Nested cages. Paper bag, tinfoil, paper bag, tinfoil – repeat until your paranoia subsides :) Multiple thin shields beat a single, thicker, shield. Check out the FutureScience site for articles on EMP.

  5. Don’t worry about that radio, what you should worry about is how you’re going to escape all those nuclear power plants melting down after an EMP. Also, if an EMP kills everything electric/motors/electronics etc. who will be broadcasting? This is the worst event that could happen to us, let’s hope it never happens!

      1. Only if your devices are not connected to external antenna when the emp goes off.. cage or not.. an externally connected antenna will bring it right in.

    1. An EMP won’t necessarily destroy all the radios in the whole world. So the recommendation is a mult-band radio that includes ‘short wave’ band. There are many ‘hams’ Amateur radio operators that are taking precaution to have radios that are protected in case of any event like this which could be naturally occurring or man made. Radio Amateurs are also emergency communication operators in the event of a regional or national disaster; so many of them are taking precautions just in case….

    2. The military has vintage equipment on standby specifically for something like this. They will still be “up and running”! It is up to you to have some means of communication or listening device. Good luck!

  6. This shows what is done to keep RF in the room, or not to let them in to start with.

    Nelco’s MRI RF Shielding is specifically designed for the MRI industry.
    Our engineers have developed a shielded enclosure made entirely of nonmagnetic materials that is unsurpassed in quality and performance. We used technology developed for our military and space industry customers (who require the most demanding RF performance) in order to design the RF shield for use with MRI. Our standard MRI RF shield exceeds all current MRI manufacturer specifications.

  7. One other thing in a shielded rooms are wave guides. You want double doors, a corridor that makes a U-Turn at the end to scatter the waves. The same for ductwork where you use a channeling design, then a u-turn at the end.

    1. You would have to remove any existing rubber gasket from the lid so that the lid makes a secure ‘electrical’ connection with the rest. You could verify this with a multi-meter for conductivity.

      Also, cover the interior with something non-conductive (cardboard, etc..) or have your electronics in a bag.

    1. Solar panels are made of silicone and will be toast if not treated the same way as portable electronics in a faraday cage. Keep smaller solar chargers with your equipment so you can use them when needed. The roof systems, etc will be useless if a nuclear device is detonated 20 to 200 miles above the earth. Good luck.

  8. My older vehicle uses a computer that is relatively easy to access and change. Could I get a spare and protect it in the same way? I’d include an ignition module and an alternator in there too. That all would fit inside an old pressure cooker easy enough.

    1. There is the likelihood sensors that communication with the computer would be damaged. In addition components that make up the electronic ignition / fuel injection may also be impacted due to the wires that lead to them.

    2. Do not forget a new starter, ignition coil for spark, a new battery, alternator, spark plugs, engine computer, transmission computer, antilock brake computer, fuel injectors, fuses, etc, etc.

      You would have better luck with an older diesel vehicle. You would only need a new starter, battery, alternator, glow plugs and fuses. No computers, no spark plugs, etc.

      Good luck

      1. How could they fry as low tech and robust an item as a spark plug? It’s a wave of electromagnetic energy, not a lightning bolt out of the blue.

  9. None of these ideas have been tested in any way, even by a simulated EMP. The NELCO information by Rick S demonstrates good engineering controls for EMI isolation and offers the best chance. While the NELCO designs are effective for MRI applications, the spectrum and distribution of energy produced by an EMP is much wider and larger. While the other methods suggested are better than doing nothing, it would be wise to locate working and repairable radio equipment that uses vacuum tubes. Even an old “All American Five”, the cheap plastic or bakelite cased 5 tube AM radio would have a better chance at survival under an EMP. Below are links to some Documents authored by known and respected scientific organizations about the EMP phenomena.





  10. Radio would not work at alot of Satellites and radio towers would be burned out from EMP.

    1. but the shortwave/Ham transmitters may not, and that’s really what I am listening for. If does happen, most of what the ‘authorities’ say will be BS. But yes, regular radio towers will be gone. As to satellites, my bet is on them being shielded because they already live in a highly radio-active environment. A microwave oven in a microwave oven anyone?

  11. What about an old refrigerator/freezer for protection of electronics?

    1. As long as a magnet sticks to all sides you’re good to go.
      Damn good idea by the way.

      BTW, it seems like there is a lot of confusion on this topic. “Electrical” is not the issue – “electronic” is the issue. EMP don’t faze vacuum tube gear, light bulbs, radio towers, transmission lines, etc. What it screws is the electronic control systems. Generally speaking, if it don’t use a computer it is immune to EMP….”Hallicrafters Short Wave rigs, older Audio Research stereos, 1967 Ford pickups,,,,, and I’ll bet that the military satellites are EMP hardened…. all that gold foil stuff. No matter what you may think of the politics of our military lately, they ain’t stupid. I’ll bet the GPS system works just fine – after all, it was built as a tool of war.

  12. Tex, Check out this link:

    Read about Starfish Prime, a U.S. nuclear test in 1962 that knocked out street lights in Hawaii and also read about Soviet Test 184.The geomagnetic storm–like E3 pulse from Test 184 induced a current surge in a long underground power line that caused a fire in the power plant in the city of Karaganda.

    Other recent studies predict that a large scale EMP such as produced by a Coronal Mass Ejection (CME) if directed toward earth (and we have had plenty of near misses) would most likely take down the national power grid by destroying the transformers at the sub-stations. Guess what; we don’t have them sittin on the shelf for replacement. And guess what else, the factories needed to manufacture them would not have power.

  13. I have a Bighorn gun safe from Rhino Steel Products that weighs about 430 pounds. Will that give full protection to a portable short wave radio?

    1. My gut instinct – yes. Even better assurance if you ground the safe (e.g. fastening a wire to a bare metal portion and attaching to a cold water pipe or the home’s electrical ground).

    2. Gun safes don’t work. The door can not form an electrically conductive seal. It’s painted, the tolerances are too loose, and there is a non conductive fire seal material. A galvanized metal garbage can is great and 3M makes an aluminum tape with a conductive adhesive that finishes the job. There are YouTube videos. Look for them.

    3. I have instaled many fariday cages over the years all have been made of mesh and steel frame

  14. A electrician told me that I could use a old power cord attached to my gun safe and cut off the power prongs but leaving the ground plug and plug it in the wall outlet. That way I would be using the ground in the house without causing a hazard for fire.
    I did it a year ago. No fire yet.

    1. I was thinking I may not be able to get into my safe if the keypad is shot.
      How to protect that?

      1. That seems like a good reason to opt for a purely mechanical lock instead of an electronic one.

  15. Perhaps 2 large plastic bags. Between these a large box. You can buy large sheets of ?, made to wrap around Water heaters or or medical wraps they use to keep the heat in for accident patients. However not much good if built into a wall.

    I think about how cars for blocks away from the Oklahoma bombed building had their wires fried.

  16. I have an aluminum tool box I put all my small electronics in, and run a metal pole 4ft into the ground and hooked a battery terminal cable between them , but I need a way to protect my 4 wheeler for some kind of transportation in the upcoming s..t storm.

  17. I advise everyone to go to the site and spend a day or two reading everything.

    An EMP is not a homogeneous event. Near sky zero there is little likelihood you can protect anything; that is the whole purpose of the event. At the fringe, you may have much surviving without any protection. The choices, strategy, bomb size, altitude and location are all variables that affect the outcome.

    Putin wants to take over the “near abroad” and mid-east. We are confronting him. When we push back unacceptably, he will neutralize us by making us blind and deaf; helpless to respond militarily and focusing on disaster mitigation to save who and what we can.

    Prepare with a steel trash can filled with your emergency and backup electronics. Seal the can and lid with 3M aluminum tape with an electrically conductive adhesive. Put a back up generator in an aluminium Fariday Box. Get a whole house surge protector and TII plug in surge protectors. Put switches on critical outlets and learn to rotate what items are plugged in or turned on at any one time. Watch the news for the crisis.

    Of course you are storing all the usual supplies.

    I think the target will be about 40 to 42 N and 99 to 101 W to maximize the pulse on NORAD at Cheyenne Mountain and still collapse the nation’s power grid. On the east coast, the outage may only last for a few weeks. From Chicago to Utah, it may be a year. That minimizes our civilian casualties, and, therefor, our probability of retaliation.

  18. I bought a galvanized garbage can with another smaller galvanized can inside, both with lids. Haven’t used the metal tape so I can get in it periodically without the hassle. Wondering what the consensus is about this doing the job. I like the storage room it provides. Thanks

  19. All the info sounds real good. Let’s pray it doesen’t happen if it does you’ll know if your theory worked be safe everyone an be ready.

  20. If it happens, and you get your vehicle to run, how will you keep people from stealing it from you, and where would you go anyway. Stockpile food and water and toilet paper, ammunition, and, hide all the women. If it’s not better in two weeks just kiss your ass goodbye…

    1. Anonymous-we have several older cars/trucks that would most likely run (70s and older), and yeah-there would be a very short period of time where we’d use them, before we’d hide them. We’d use them to get our designated ‘village’ together and strip their houses/gather it all at our place. With one exception these people are within 10 minutes of us and in rural areas, (one lives on our street down a few miles), with my dh’s grandparents living in a retirement home at a nearby town-back roads in and a quick grab and go for them.
      I think having a running vehicle in a situation like an EMP, where most others are down, is just painting a big bulls-eye on you.

  21. Semiconductors are relatively new earth technology. We know they are susceptible to emp mischief. Newer generation of this technology should be built with emp withstanding paramaters., and future infrastructure should be built with protections and redundancy. I remember the Cuban missile crisis. Fallout shelters were the rage. Houses today should be built with shielded Faraday rooms to store things. Cars should be built with a switch to change from electronic to backup just electrical, to enable minimum functionality in an emergency. My 84 GMC van only has a chip in the distributor, and the alternator, if you don’t count the radio. Maybe all those freaks with the tin foil on their heads weren’t so crazy after all?

  22. A radio in a Faraday cage is just dead weight. You don’t need it.
    A radio can’t be operated in a Faraday cage and still be protected. Because the antenna is the main EMP capturing element so you can’t put the antenna out of the cage or connect the radio to an external antenna to receive or transmit. And you can’t keep the antenna inside the cage and transmit or receive because a Faraday cage is a radio frequency shield.
    You never know when an EMP will occur so you would have to keep the radio inside all the time to protect it, and if you can’t use it you don’t need it.
    What you need is a radio that is EMP resistant so that you can keep it on all the time to listen. Most of the time you listen and only transmit when required and in a dangerous situation you may not even want to transmit at all because you may reveal your location, it is very easy to find by radio triangulation.

  23. Old Professional Engineer here: a score of nukes, two score carbon fueled power plants, pieces of the grid, designed the first US dry cask spent fuel storage facility and consulted with our government. A few thoughts on several post doctoral subjects.

    Most chips fry at less than 20 volts. An EMP is guesstimated at 50,000 volts per meter of a conductor (wire). So those high tension lines which march across the country side will pick up zillions of volts which will hit and fry a transformer rated at perhaps 500,000 volts. Some EMP frequencies are ground penetrating so if you ground to a buried water pipe, the conducting pipe may back feed large voltages. And as is well known in militaries that after the first attack, us terrified dummies will unpack everything, so the big one will come later and fry unpacked electronics.


    Unplug up all cords, antenna, power, in house telephone lines and curl them is a tight coil, minimize the induction flux (same as radio waves; they pass right through you). Wrap your electronics in a zip lock plastic bag and an outer aluminum foil. At the expected voltage and high frequencies, a tiny crack may be a problem. Have a spare.

    Get out of any city. Survive for a few days; we will win or lose. Know every seven hours, the radiation dies by a factor of ten. for each bomb. Expect several.

    You can not have too much water, food, useable energy, sewerage systems, communication or functioning weapons.

    Do not be down wind of a nuke. Fukushima is a party game.

    America is not in good shape; we will make it together or not at all. I go to church.

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