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Author Topic: EMP-Building a Faraday box  (Read 5054 times)

tex703

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EMP-Building a Faraday box
« on: July 03, 2009, 02:48:57 pm »

Does anyone know how to build a medium sized Faraday cage/box to protect medium sized radios and small electronics from a EMP strike?

I bought the book "One Second After" and it is scary to think that an EMP strike from a few nuclear warheads directly over the US would basically wipe out any and all electrical devices and all cars and trucks.

Just want to be prepared with a radio and few small electronics if this were to ever happen in the future.
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StarGazer

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Re: EMP-Building a Faraday box
« Reply #1 on: July 05, 2009, 02:18:08 pm »

Think a metal box, with no gaps.

Many ways to fabricate one, but probably the easiest is to use an old microwave oven. Be sure to clean the door and gasket seal well, then cut off the cord (so it does not get accidentally turned on). Sort of a small volume, but quick. Thrift stores often have old microwaves at reasonable prices.

Another expedient EMP box is to use milsurp ammo cans. Clean them up as usual, then sand or scrape the paint off the top lip of the can's bottom part. Next, the lid.

Peel out the rubber gasket and discard it. we need to replace this with a metal gasket that will give us metal-to-metal contact from the can lid to the can bottom. After removing the gasket, remove the paint from the recess formerly occupied by the gasket. Paint stripper works well, but be careful as it is quite caustic. After stripping the paint, clean up the lid and then create a metal gasket to fill the space.

A metal gasket can be made by pulling apart a stainless ''chore-boy" scrubbing pad. Jam the strung out chore-boy into the gasket recess (blunt end of a kabob skewer works well). Don't be cheap, make sure you have a good metal-metal connection when the lid is closed.

Now, we have a serviceable EMP box. Remember that this enclosure no longer has an airtight seal, so be certain to store it in a benign environment.

Hope this is of interest.

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icbkr

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Re: EMP-Building a Faraday box
« Reply #2 on: July 05, 2009, 08:00:16 pm »

It doesn't have to be solid metal, a Faraday cage is typically mesh.  Brass screen from the hardware store works great.  I believe any screen would do, provided it's grounded.  Build a box or drape a sheet, anything works, and it doesn't have to be seamless, it's just has to overlap, so there can be air gaps, like a tent flap.  This lets you keep equipment on and running and not have it overheat.  It can be any size, provided it's grounded.  It is incredibly easy to test.  Put your cell phone or radio inside, then try to use it.  If the comm device works, you did something wrong.  Thicker isn't better, and I'm sure there's a physical limit on the mesh hole size having to do with wavelengths, but just to stop a normal nuke jolt, all you need is mesh.  Note that if you have an antenna hooked up at the time and it's outside the mesh, your radio is probably not going to survive or at least require repairs to the reception circuits.  If you need a radio on all the time, keep a spare.

In close proximity, a nuke emp will take out everything electronic that has a circuit board whether it's powered on or not.  It will not harm a classic car with no computer, although if it's big enough, it might kill some of the guages or the clock, hard to tell, and at that point,  you don't really care, because you're history too.  It works by inducing current in the fine wiring in electronics which creates heat which melts the wires.  Wires inside a chip are extremely fine, measured in nanometers, and break or burn just by having you comment on their bad taste in clothing.

Burried items will be safe as well, provided they are far enough down, which depends on the blast size, distance, and interference.

Effects from the blast need the size to determine, but if I recall, a 50MT single atmospheric burst over Omaha waaay up on the edge of the atmosphere will take out the entire lower 48.  Any lower bursts, it all comes down to how big and how far.

Note that you don't need a nuke to do this now.  Hollywood has it right in that you can produce a large emp using big electronics and a big power source.  I've been wanting to play with one for a while.  So many fun experiments, so little time.

So, shield your electronics, buy spares, and drive a 1967 Mustang with a Cobra Jet motor.  :mellow:

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dogsledder54

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Re: EMP-Building a Faraday box
« Reply #3 on: July 05, 2009, 08:05:04 pm »

I probably don't need to worry, being within 100 miles of Omaha.  :laugh:
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icbkr

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Re: EMP-Building a Faraday box
« Reply #4 on: July 05, 2009, 08:20:53 pm »

I probably don't need to worry, being within 100 miles of Omaha.  :laugh:

Why waste a perfectly good excuse to justify the purchase, care and maintenance of a fine vintage muscle car or truck?

And drive it to the range.
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dogsledder54

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Re: EMP-Building a Faraday box
« Reply #5 on: July 05, 2009, 09:12:43 pm »

I hear you. I was not talking about the car, only the faraday cages. Even though I would like to have a Boss 302 Mustang, a Plymouth Superbird, or a 68 GTO, at the top of my list is an old pickup (1948-1953 Chev or GMC) or an old van. More practical.  :mellow:
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Who...me?

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Re: EMP-Building a Faraday box
« Reply #6 on: July 08, 2009, 08:25:40 pm »

Mutti, There is a bunch of info on faraday box or cages, some of it contradictory, but here is what I basically go by.

http://en.wikipedia.org/wiki/Faraday_cage

Read that and it should answer most of your questions. Here are a few points that merit mention.
There can't be any way for an emp wave to enter the box or cage. So if you stick something in a microwave for protection, the micro can't have a cord anymore.
The object being protected in the box can't touch the box. So if you were using a trash can as a box everything in it would need to be in a box.

After reading up on it again I think you could use 1" metal screen (like this stuff http://www.ec21.com/offer_detail/Sell_stucco_wire_netting--4612785.html ) to make an simple cheap cage or large box.

Pick a room in your house that you want protected and line the walls, ceiling and floor with the screen. Pull the circuit breaker to that room if possible to isolate it from the grid. The screen that covers the door into the room should overlap the wall to make sure you always have screen touching screen so as to have no break in the protection. Maybe a grounding strap from the door screen to the wall screen just to be safe. Don't forget to remove the door knob.

Grounding of the cage is contested and no one seems able to agree if it is necessary or not. I figure that if you ground your new room to the houses electric system already in place it cant hurt anything so what the heck. Also I think I would insulate the floor for convenience. maybe some cheap flakeboard or the like.

Now anything in the cage is protected from an EMP burst or a celestial event.



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Re: EMP-Building a Faraday box
« Reply #7 on: July 08, 2009, 08:35:47 pm »

Here is another good writeup on the subject.

http://standeyo.com/News_Files/NBC/EMP.protection.html
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"Build a politician a fire, and he will be warm for a day.
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Hollywoodgold

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Re: EMP-Building a Faraday box
« Reply #8 on: July 08, 2009, 09:49:59 pm »

Mutti, There is a bunch of info on faraday box or cages, some of it contradictory, but here is what I basically go by.

http://en.wikipedia.org/wiki/Faraday_cage

Read that and it should answer most of your questions. Here are a few points that merit mention.
There can't be any way for an emp wave to enter the box or cage. So if you stick something in a microwave for protection, the micro can't have a cord anymore.
The object being protected in the box can't touch the box. So if you were using a trash can as a box everything in it would need to be in a box.

After reading up on it again I think you could use 1" metal screen (like this stuff http://www.ec21.com/offer_detail/Sell_stucco_wire_netting--4612785.html ) to make an simple cheap cage or large box.

Pick a room in your house that you want protected and line the walls, ceiling and floor with the screen. Pull the circuit breaker to that room if possible to isolate it from the grid. The screen that covers the door into the room should overlap the wall to make sure you always have screen touching screen so as to have no break in the protection. Maybe a grounding strap from the door screen to the wall screen just to be safe. Don't forget to remove the door knob.

Grounding of the cage is contested and no one seems able to agree if it is necessary or not. I figure that if you ground your new room to the houses electric system already in place it cant hurt anything so what the heck. Also I think I would insulate the floor for convenience. maybe some cheap flakeboard or the like.

Now anything in the cage is protected from an EMP burst or a celestial event.


HM:

It makes no sense to me to not ground the box. I think that a box within a box similar to a hypercube with the outer box grounded would be ideal. The charge will get to ground eventually so why not quick and direct?
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McClarinJ

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Re: EMP-Building a Faraday box
« Reply #9 on: July 09, 2009, 07:23:10 am »

As I understand it, the burst of radio waves from an EMP or Carrington event induces a high electric potential in any conductor it strikes.  Although lightning is a different original phenomenon I suppose it also induces a high electric potential.  So my question is, how is this potential dissipated in an airborne aircraft that is struck by lightning?  Wouldn't an ungrounded Faraday cage would be similar?  What do EMP simulations suggest re grounding vs. no grounding?  Just curious.  I'd like to be sure of doing the right thing to protect my reserve electronics.
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NuclearDruid

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Re: EMP-Building a Faraday box
« Reply #10 on: July 09, 2009, 07:52:38 am »

HM:

It makes no sense to me to not ground the box. I think that a box within a box similar to a hypercube with the outer box grounded would be ideal. The charge will get to ground eventually so why not quick and direct?

According to this little powerpoint EMP and the Radio Amateur from METERS, your faraday cage should be grounded. (p. 35)

ND
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icbkr

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Re: EMP-Building a Faraday box
« Reply #11 on: July 09, 2009, 10:42:15 am »

Grounding is essential to ongoing high quality electrical operation.  Even if you operate at a military capacity, whereby the entire room and the electrical generators and such are all within the same cage so you can provide ongoing continuous electronic activity, you still have to ground, or a static difference will build up either on the cage, or in the equipment inside the box.  Then when Captain Charming enters the secured and shielded area, he is at a different potential than any of the stuff inside.  First computer or radio he grabs and WHAMO big static discharge.  You could periodically re-synch the two, but it's still a static event, and with no ground, you are risking an eventual degradation of your equipment.  Even with UPS/filters in front, you will eventually damage those to the point of failure, and if what we're after is long term operations, then you need to ground the cage and the equipment.  You also need UPS/filters in place to protect all your stuff from a nearby lightning strike.  The use of an fcage for regular operations is very tedious and costly.  and you still can't run radios inside without an externally connected antenna.

The only logical use of a cage in a normal survival gulch is to protect and shield RESERVE gear from an unexpected EMP blast.  Assuming you'll get warning in time to move equipment into the fcage is risky, it should already be in position, since most likely you'll never know its coming, and in many cases, won't even know it happened.

Any sensitive electronic spare parts or systems should be stored in a Faraday box, grounded and filtered, until they are needed.  But a practical operational faraday protected facility is of no use for radio communication.  You could push microwaves out of it though.  Mount a dish on the outside, with waveguide back through the mesh.  That would work just fine.  It's just stuff with thin metal wiring or microchips.  Even normal radio sets should still function provided they are the classic bread board, pots, and 24 guage wire.  That should survive anything that doesn't kill you outright.  The capacitors *might* not survive, but if they are stout models, it should be fine.  None of this nine volt crap though, build a radio powered by a lantern battery and that wiring will definitely survive.

icbkr
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McClarinJ

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Re: EMP-Building a Faraday box
« Reply #12 on: July 11, 2009, 12:05:37 am »

According to this little powerpoint EMP and the Radio Amateur from METERS, your faraday cage should be grounded. (p. 35)

ND

I clicked my way through the Powerpoint.  "Stout" grounding indeed is recommended.

Grounding is essential to ongoing high quality electrical operation.  Even if you operate at a military capacity, whereby the entire room and the electrical generators and such are all within the same cage so you can provide ongoing continuous electronic activity, you still have to ground, or a static difference will build up either on the cage, or in the equipment inside the box.  Then when Captain Charming enters the secured and shielded area, he is at a different potential than any of the stuff inside.  First computer or radio he grabs and WHAMO big static discharge.  You could periodically re-synch the two, but it's still a static event, and with no ground, you are risking an eventual degradation of your equipment.  Even with UPS/filters in front, you will eventually damage those to the point of failure, and if what we're after is long term operations, then you need to ground the cage and the equipment.  You also need UPS/filters in place to protect all your stuff from a nearby lightning strike.  The use of an fcage for regular operations is very tedious and costly.  and you still can't run radios inside without an externally connected antenna.

The only logical use of a cage in a normal survival gulch is to protect and shield RESERVE gear from an unexpected EMP blast.  Assuming you'll get warning in time to move equipment into the fcage is risky, it should already be in position, since most likely you'll never know its coming, and in many cases, won't even know it happened.

Any sensitive electronic spare parts or systems should be stored in a Faraday box, grounded and filtered, until they are needed.  But a practical operational faraday protected facility is of no use for radio communication.  You could push microwaves out of it though.  Mount a dish on the outside, with waveguide back through the mesh.  That would work just fine.  It's just stuff with thin metal wiring or microchips.  Even normal radio sets should still function provided they are the classic bread board, pots, and 24 guage wire.  That should survive anything that doesn't kill you outright.  The capacitors *might* not survive, but if they are stout models, it should be fine.  None of this nine volt crap though, build a radio powered by a lantern battery and that wiring will definitely survive.

icbkr

Interesting about the static differential.  Is this this present on lightning-struck planes when they land?

I agree the stuff we protect is reserve stuff, not to be used unless another reserve has been protected to take its place.  It's an added expense but what a treasure if EMP or Carrington event occurred.
« Last Edit: July 11, 2009, 12:12:16 am by McClarinJ »
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icbkr

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Re: EMP-Building a Faraday box
« Reply #13 on: July 11, 2009, 01:45:01 pm »

Interesting about the static differential.  Is this this present on lightning-struck planes when they land?

Don't confuse voltage and power.  There is frequently a static difference between any vehicle on rubber tires, lightning struck and flying or not.  Anyone with a car in winter has experienced that lovely 20KV whack when they get out of the car.  Planes get it too, but they have gear to ground it.  Ask a mechanic for specifics.

Quote
I agree the stuff we protect is reserve stuff, not to be used unless another reserve has been protected to take its place.  It's an added expense but what a treasure if EMP or Carrington event occurred.

Nice thing is, we don't all need to have everything.  If me and the surrounding five gulches have radios, and only one survives, we're still okay.  I have NO radio right now, its high on my list, but the "get me through the month" comes before the "get me through the year" stuff.  Since a Faraday box costs next to nothing, it's the spare electronics that are the PITA.  Careful shopping over time will help.

 :sign13:Idea for a poor mans Faraday cage for a well equipped gulch: take one of your plastic shelving units and wrap it completely in window screen material you can buy by the roll for about $10.  Wrap it so the front lifts up and you can get at stuff.  Make the sides bend in across the front panel when it's closed to keep everything tied together.  Don't forget the bottom, I'd just line the bottom shelf, rather than trying to get mesh under the shelf.  Solder or thread a piece of any type wire, I'd probably use 18guage or so, to the bottom of the back of the cage, and connect the other end to anything grounded like water pipes or your house ground.  Po' but viable.

Special note: hand crank gadgets are not necessarily immune to EMP, look for circuit boards and chips.  I'm not sure about LED flashlights, it would depend on the guage of the LED wires and how much other circuitry is present.  Lots of them have fancy flashing options that require a circuit board which means they are probably vulnerable.

icbkr
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Hollywoodgold

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Re: EMP-Building a Faraday box
« Reply #14 on: July 11, 2009, 02:16:38 pm »

Interesting about the static differential.  Is this this present on lightning-struck planes when they land?

Don't confuse voltage and power.  There is frequently a static difference between any vehicle on rubber tires, lightning struck and flying or not.  Anyone with a car in winter has experienced that lovely 20KV whack when they get out of the car.  Planes get it too, but they have gear to ground it.  Ask a mechanic for specifics.

Quote
I agree the stuff we protect is reserve stuff, not to be used unless another reserve has been protected to take its place.  It's an added expense but what a treasure if EMP or Carrington event occurred.

ICB:

Do you know if the points, plugs, plug wires  and condensers on a pre-computer controlled car are susceptible to an EMP attack? If so, spares would need to be kept in a cage. Correct?

Nice thing is, we don't all need to have everything.  If me and the surrounding five gulches have radios, and only one survives, we're still okay.  I have NO radio right now, its high on my list, but the "get me through the month" comes before the "get me through the year" stuff.  Since a Faraday box costs next to nothing, it's the spare electronics that are the PITA.  Careful shopping over time will help.

 :sign13:Idea for a poor mans Faraday cage for a well equipped gulch: take one of your plastic shelving units and wrap it completely in window screen material you can buy by the roll for about $10.  Wrap it so the front lifts up and you can get at stuff.  Make the sides bend in across the front panel when it's closed to keep everything tied together.  Don't forget the bottom, I'd just line the bottom shelf, rather than trying to get mesh under the shelf.  Solder or thread a piece of any type wire, I'd probably use 18guage or so, to the bottom of the back of the cage, and connect the other end to anything grounded like water pipes or your house ground.  Po' but viable.

Special note: hand crank gadgets are not necessarily immune to EMP, look for circuit boards and chips.  I'm not sure about LED flashlights, it would depend on the guage of the LED wires and how much other circuitry is present.  Lots of them have fancy flashing options that require a circuit board which means they are probably vulnerable.

icbkr
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