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Old 04-11-2012, 12:16 PM
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lazyluke lazyluke is offline
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Default So, is my gun safe also a Faraday box?



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Will my safe protect my electronics during an EMP?

Also, I have to pay $ to use the General Discussion forum? Really?





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Old 04-11-2012, 02:34 PM
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Just the VIP general discussion you have to pay for from what I understand.
Old 04-11-2012, 02:54 PM
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So, is my gun safe also a Faraday box?

Probably....Maybe.

A Faraday box is a metal box, all 6 sides are metal. A good tight metal to metal fit is needed for electrical connection between door and sides, and to prevent EMP from getting in through the cracks.

Does your gun safe have two layers of metal, like outside wall, plus inside wall?

EMP is RF energy and propagates like radio waves. So radio wave of a wave length shorter than the width of the crack could get in.

Also best to have two layers of metal between your electronics and the EMP.

Generally accepted practice is to wrap the item in an insulating layer. I use a piece of an old rubberized raincoat.

Then cover that with a layer of aluminum foil, then another layer of insulating material, then put it inside your Faraday Box.

You need the insulating layer between your device and the metal layers.

There's really no guarantee. The only way you will know if your Faraday box worked is if your radio still works after an EMP.

Chapter 8 and 10 are relevent
http://tscm.com/MIL-HDBK-419A.PDF

RADIO FREQUENCY SHIELDED ENCLOSURES
http://www.wbdg.org/ccb/NAVFAC/DMMHNAV/1195.pdf

Electromagnetic Pulse and the Radio Amateur - Part 1
http://www.arrl.org/files/file/Techn.../pdf/88615.pdf

Electromagnetic Pulse and the Radio Amateur - Part 2
http://www.arrl.org/files/file/Techn...pdf/118630.pdf

Electromagnetic Pulse and the Radio Amateur - Part 3
http://www.arrl.org/files/file/Techn...pdf/108638.pdf

Electromagnetic Pulse and the Radio Amateur - Part 4
http://www.arrl.org/files/file/Techn...pdf/118630.pdf
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Old 04-11-2012, 08:07 PM
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I believe it will protect from emp,but if it's like mine with an electronic only lock it won't matter because you won't be able to get into it.
Old 04-11-2012, 08:24 PM
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Quote:
Originally Posted by Majorpayne View Post
I believe it will protect from emp,but if it's like mine with an electronic only lock it won't matter because you won't be able to get into it.
Don't you have a set of keys to bypass the electronic lock. I thought all they all did. Mine does.
Old 04-11-2012, 11:47 PM
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Quote:
Originally Posted by lazyluke View Post

Also, I have to pay $ to use the General Discussion forum? Really?
when you see the screen that says that, it usually means a post has been deleted.
Old 04-12-2012, 12:51 AM
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This question about the use of a Faraday cage comes up way too often and seems to cause much confusion.
Perhaps if it were replaced with the term RF Anachoic chamber, it would be more helpful.
An RF Anachoic chamber is used to house sensitive electronics such as active antennas while testing. this prevents stray RF energy from messing with local radios and also protects the antenna from being blown by the doomsday prepper whose testing out his 1000 Watt linear.
It is still not a 100 percent EMP shielded enclosure but it does address some of the concepts that sem to get lost in these discussions, mainly that of RF transparency, or the ability of an RF signal to get through the enclosure through the tiny seams and cracks which most Faraday cages have.
Also look into the work needed to make the Stealth fighter and bomber stealth.
Its a complex problem that the military solved, much of the basic EMP shielding requirements are very similar.
Alan
Old 04-12-2012, 02:51 AM
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id put a strip of aluminum tape over the cracks to be sure
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Old 04-12-2012, 12:50 PM
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Quote:
Originally Posted by ShellbackBill View Post
.
.
.
Electromagnetic Pulse and the Radio Amateur - Part 1
http://www.arrl.org/files/file/Techn.../pdf/88615.pdf

Electromagnetic Pulse and the Radio Amateur - Part 2
http://www.arrl.org/files/file/Techn...pdf/118630.pdf

Electromagnetic Pulse and the Radio Amateur - Part 3
http://www.arrl.org/files/file/Techn...pdf/108638.pdf

Electromagnetic Pulse and the Radio Amateur - Part 4
http://www.arrl.org/files/file/Techn...pdf/118630.pdf
Those look like useful links but they don't work...
Old 04-12-2012, 12:59 PM
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I read somewhere that you can test your faraday cage by putting a cell phone inside and then calling it. If the signal doesnt go through to the phone then it will work for a faraday cage.

Does anyone know if this is true?
Old 04-12-2012, 01:00 PM
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Quote:
Originally Posted by ShellbackBill View Post
Electromagnetic Pulse and the Radio Amateur - Part 1
http://www.arrl.org/files/file/Techn.../pdf/88615.pdf

Electromagnetic Pulse and the Radio Amateur - Part 2
http://www.arrl.org/files/file/Techn...pdf/118630.pdf

Electromagnetic Pulse and the Radio Amateur - Part 3
http://www.arrl.org/files/file/Techn...pdf/108638.pdf

Electromagnetic Pulse and the Radio Amateur - Part 4
http://www.arrl.org/files/file/Techn...pdf/118630.pdf
http://www.arrl.org/files/file/Techn.../pdf/88615.pdf

That link is to part 1. It has links to the other parts on the first page. And the shortened part of that link is Technology/tis/info/pdf/88615.pdf in case the link stops working again. The forum seems to auto-shorten it.
Old 04-12-2012, 01:19 PM
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Quote:
Originally Posted by caveman8541 View Post
I read somewhere that you can test your faraday cage by putting a cell phone inside and then calling it. If the signal doesnt go through to the phone then it will work for a faraday cage.

Does anyone know if this is true?

that makes sense.
Old 04-12-2012, 01:40 PM
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Quote:
Originally Posted by Savinkov View Post
Those look like useful links but they don't work...
These should work

http://www.arrl.org/files/file/Techn.../pdf/88615.pdf
http://www.arrl.org/files/file/Techn.../pdf/98622.pdf
http://www.arrl.org/files/file/Techn...pdf/108638.pdf
http://www.arrl.org/files/file/Techn...pdf/118630.pdf
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Old 04-12-2012, 01:55 PM
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Quote:
Originally Posted by caveman8541 View Post
I read somewhere that you can test your faraday cage by putting a cell phone inside and then calling it. If the signal doesnt go through to the phone then it will work for a faraday cage.

Does anyone know if this is true?
Yes, it is true. Cell Phone RF has a wavelength of about 1.2295 feet. So any mesh with holes smaller than that will stop cell phone signals. You can also put it in a Microwave and the same thing will happen.

Higher frequency RF that has a wave length shorter than the width of the holes in the mesh could get through.

1/4 inch wavelength RF will pass through a 1/2 inch mesh like it wasn't there.

3/4 in wavelength RF will bounce off like it was a brick wall.


Most people recommend a Faraday Box made of solid sheets of metal. Because EMP is a broad band RF pulse ranging from very high to very low frequencies.

If you are trusting this Faraday Box to protect things that may be needed to save your life, go the extra inch and just get a metal box.

Any metal box will do even a metal trash can, or a metal cookie box. See my earlier post for the how-to.
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Old 04-12-2012, 02:48 PM
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The problem with EMP is location, location, location.
The closeer you are to the source, the more difficult it is going to be to prevent dammage.
And vise versa.
the speed of the magnetic field is the determining strength building a voltage across any metal being passed, size and volume all play a part .
Theoreticlly electricity is looking for a path . a battery for instance has the energy configned , but given the least excuse will find a path and disapate neutralizing it's self.
But it is not just the flow of electricity but the making of it the magnetic field is producing .
Some believe that providing a ground provides a path to disapate the energy ignited.
Some are of the opinion that, like lightening half the charge response is comming from the ground thus insuring a hit, not preventing one.
They sell pouches to house your credit cards to prevent radio signals from exciting the chip thus revealing your credit information to unscrupulous charricters.
This is a radio signal , not a magnetic field. It is not grounded to any thing , the foil alone is the shielding .
It is likely , that your safe has enough shielding in the door and the stop the door rests, the signal is not like water. Air is a good insulator for electricity , as wel as plastic and other non conductive materials .
I would avoid papers that can hold moisture and here's the rub, nothing is guarenteed to absolutely prevent some magnetic field from intrusion.
The best you can hope for is to dilute the effect, speculating on your proximity from a EMP blast.
By the way besides the magnetic field the alternator in your car uses to make electricity charging the battery. There is a wire in the road you pass that trigger the signal lighting equipment at each intersection. look for it ,usually it is in a circle. right where you stop your car waiting for the light.
I have 16 lb lift magnet on my motor cycle 8" from the ground, that excites that wire to actuate the signal.
With out it, many do not respond.
Calculate your distance from a probable emp target and make you best guess at shielding, that's the best any of us are going to do .
Old 04-12-2012, 03:14 PM
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Quote:
Originally Posted by arleigh View Post
The problem with EMP is location, location, location.
The closeer you are to the source, the more difficult it is going to be to prevent dammage.

You are correct. The closer you are to the source the worse the damage.

Strategists who try to guess these things, say the most likely scenarios would be either one warhead or three.

Some guesstimates at the probable aim point, for a single EMP warhead say south central Kansas. About 150 miles from me. That is the geographical center of the US.

Some guesstimates for a three warhead strike say one in south central Kansas, and one more in each direction half way to the coast.
Old 04-12-2012, 06:00 PM
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So I put my cellphone in my safe and called it. I could hear it ringing in there so I answered it. Hello, who's this? It's me. It can't be me, I'm me. Liar!

Same thing with the microwave. I guess we'll go to "Plan B". (start over)

I'm not answering my phone anymore though, I'm afraid it'll be that idiot "Me".
Old 04-13-2012, 12:21 AM
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Well, those are just damn interesting, and obviously the phenomenon is just
damn complicated.

I don't see anything specific in there w/r/t how EMP field strength depends
on distance from the detonation... In fact, now I'm not even convinced that
an enemy could understand the phenomenon enough to be able to predict
the damage well enough that they could count on its being effective as a
weapon. So if anything I'm less paranoid about somebody trying it on
us, than previously.

One thing that finally sank in is that a Faraday cage will not protect your
equipment from induced voltage in the antenna. So you'd better have that
well protected. Since presumably there won't be any warning of an
impending EMP attack so all the hams can scramble to pack all their gear
away into ammo cans before the detonation (and I'd PAY to watch those
fat old geezers try to move fast), protecting equipment right where
it sits when in use, sounds like time better spent... and there was quite
a bit on that in those articles.

Thanks for posting those...
Old 04-14-2012, 08:25 AM
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The simple answer is probably. So many hypotheticals with EMP. Don't get one with an electronic lock.
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Old 04-14-2012, 09:18 AM
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Quote:
Originally Posted by lazyluke View Post
So I put my cellphone in my safe and called it. I could hear it ringing in there so I answered it. Hello, who's this? It's me. It can't be me, I'm me. Liar!

Same thing with the microwave. I guess we'll go to "Plan B". (start over)

I'm not answering my phone anymore though, I'm afraid it'll be that idiot "Me".
did you set the microwave for 2 minutes? that aught to do it...
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