Building a Faraday cage

[monkeylizard]

Forget about the likelihood of an EMP, whether or not a Faraday cage would help, and what you'd put in one. I want to know about building one.

 

I've done some reading and it seems like for every "expert" who swears up and down to do X, another "expert" says X won't work, you should do Y. For example, one says ground it, another says never ground it and another says it doesn't matter. Some say a microwave works, others say they do no good, and others say they're partly good.

 

Would it hurt to do multiple "layers" for protection? I'm thinking of something simple like say an ammo can. For simplicity, let's just say I want to protect a radio in my cage.

 

What if I put the radio in an anti-static bag, wrapped the bag in aluminum foil, placed that in a Ziploc, wrapped that in aluminum foil, placed that in a plastic bag? And then I lined the ammo can with aluminum foil and thin sheets of Styrofoam. Placed the bag in the can, then taped it shut with aluminum foil air duct tape (not rubbery duck tape)?

 

Is that sufficient or do I need the fancier stuff like brass or copper mesh? Or are those multiple layers somehow hurting the effectiveness?

 

What if I put the ammo can (or several cans) inside a metal garbage lined with Styrofoam to insulate it and taped the lid shut with aluminum tape?

Edited May 10, 2016 by monkeylizard

[Omega]

http://www.amazon.com/EMP-Shield-Protection-Desiccant-Electronics-Anti-static/dp/B00L2HMVYS

[monkeylizard]

Those aren't exactly world-ending EMP level protection and it says so in the description. It's basically an olive drab static bag with a Ziploc strip. Thanks though.

[Omega]

I guess it depends on the level of protection you need, sun spot vs nuclear etc  I am not versed on what actual waves are emitted by either. 

 

These guys offer these: http://techprotectbag.com/

 

They fry a cell in a microwave, but again not sure how that compares to a nuclear EMP.  Of course you will have to do your homework because there are many sites selling these type of bags and faraday cages that may of not done theirs.  Many sites advertise them as if they were doomsday protection when all they are, are Mylar bags.

 

http://www.disasterstuff.com/store/pc/EMP-Bags-c128.htm

 

 

[peejman]

I'm certainly no expert, but all the discussion and variations are because a Faraday cage is typically designed for a very specific set of circumstances.  It's designed to provide shielding from a known energy source (lightning, RF, electromagnetic, etc.), that may be inside or outside the cage.   Cages work both ways.... sometimes they're to protect what's outside the cage, sometimes they're to protect what's inside it, so they're inherently different. 

 

I assume what you want is to protect your electronics from an EMP generated by a nuclear explosion.  That would be a large source of electromagnetic energy.  The only people who've researched that and really know the answer of what works is the government, and they're not talking about it.  So unless you know the energy signature (amplitude, frequency, etc.) of an EMP, you can't really make one specifically to block it. 

 

Your idea of layering a few metallic containers with insulation will work as well as anything else.  The aluminum foil would probably repel a pretty low energy EMP.  The higher the energy you wish to repel, the more massive the metal structure needs to be so it has enough electrons to effectively block/transmit the energy away from what's inside the cage.  

[monkeylizard]

Thanks. That's sort of what I was deriving from reading around the web.

[enfield]

I wonder how effective a steel building would be?

[monkeylizard]

I've wondered that too. I also wonder how effective the ground would be. Would burying a cache of sealed containers work? If so, I wonder how deep they'd need to be.

[peejman]

I wonder how effective a steel building would be?

 

 

As effective as it is now at blocking your cell phone signal.  That's why phones don't work real well in some metal buildings... the building is effectively a faraday cage. 

 

 

 

I've wondered that too. I also wonder how effective the ground would be. Would burying a cache of sealed containers work? If so, I wonder how deep they'd need to be.

 

 

Dirt will work as well as it conducts electricity.... so, you'd need a really, really long post hole digger. 

[mikegideon]

[Fourtyfive]

As effective as it is now at blocking your cell phone signal.  That's why phones don't work real well in some metal buildings... the building is effectively a faraday cage. 

 

 

 

 

 

Dirt will work as well as it conducts electricity.... so, you'd need a really, really long post hole digger. 

If the towers will not work, what good is the phone in a $50.00 bag ?

Edited May 10, 2016 by Fourtyfive

[Alleycat72]

Of the few hundred faraday cages I've been around, every one of them was grounded. Think of a big aluminum cage inside of a big aluminum box.

[Jonnin]

If the towers will not work, what good is the phone in a $50.00 bag ?

 

the survival guide you downloaded onto it.  Your backup external hard disk with all your cool info.   Your antique watch.  A ham radio.  Whatever it is that YOU think is worth saving for when the lights come back on (assuming it is  a terrorist attack and not a total meltdown, of course).  

 

These things are hard to build right.  a big metal (conductive..!) box with a plastic box inside that with your stuff inside that with at least 6 inches between your items and the outside walls, and ground the box.  That will stop a fair amount of juice.   What you MUST do is divert the energy pulse around your items and prevent it jumping the gap between the cage and the stuff.   The more potent the gap, the farther it can jump.   Think lightning.  It can jump a very long way thru the air, and it stops cold if it hits something and is grounded.

Edited May 10, 2016 by Jonnin

[Fourtyfive]

And the cell towers are built this way ? NOT

[peejman]

If the towers will not work, what good is the phone in a $50.00 bag ?

Not much, unless you've downloaded a bunch of useful info onto it such that it will function without signal. Wasn't there a survival iPhone thread?

[Fourtyfive]

Not really worried, if it happens I've got lawyers , guns and money ! Go Warren Zevon and Hank Jr. !

 

https://www.youtube.com/watch?v=sgRfxTG1Rg8

Edited May 11, 2016 by Fourtyfive

[quietguy]

Of the few hundred faraday cages I've been around, every one of them was grounded. Think of a big aluminum cage inside of a big aluminum box.

We have used copper faraday cages around electrical transformers for decades to eliminate interference with sensitive electronics nearby.  They were always grounded as well.  

[mikegideon]

And the cell towers are built this way ? NOT

 

The only EMP shielded radio buildings I'm aware of are government owned. They are really designed to protect the equipment from EMP. AFIK, cell buildings (when they use buildings), are just reinforced concrete. Of course, the cell engineers didn't see the movie either. :).

 

The real vulnerability is in the power grid, specifically the very large components with replacement lead times of 6 months plus.

[Jonnin]

The only EMP shielded radio buildings I'm aware of are government owned. They are really designed to protect the equipment from EMP. AFIK, cell buildings (when they use buildings), are just reinforced concrete. Of course, the cell engineers didn't see the movie either. :).

 

The real vulnerability is in the power grid, specifically the very large components with replacement lead times of 6 months plus.

 

if its online and able to send signals, its probably not protected enough.  

therein lies the real issue...  its exceedingly difficult to protect a live system.  Its aggravating but not difficult to protect a backup unit esp for small items.

 

The company I was with worked on the issue for a while.   Fixing a live system is *extremely* expensive -- almost every wire and indeed, almost everything made of metal has to be examined. 

[mikegideon]

if its online and able to send signals, its probably not protected enough.  

therein lies the real issue...  its exceedingly difficult to protect a live system.  Its aggravating but not difficult to protect a backup unit esp for small items.

 

The company I was with worked on the issue for a while.   Fixing a live system is *extremely* expensive -- almost every wire and indeed, almost everything made of metal has to be examined. 

 

It's my area. I'm not all that worried, except for long term outages on the core of the power grid infrastructure.

[Jonnin]

It's my area. I'm not all that worried, except for long term outages on the core of the power grid infrastructure.

 

Yep.   The civil unrest caused by the masses who go 3 months without power is a bit of a concern.   But honestly, I can't see it happening.. the countries that CAN are not likely to do so.  To emp on a grand scale you need a second or third level of nuke tech.  And if the idiots had the first level, they would have blown something up by now just because.   Its pretty far down the list of things to worry about for me.

[monkeylizard]

Yeah, me too, but if I could make a small cache for a few hundred bucks, that seems a small price to pay for a "just in case" scenario.

[nightrunner]

Yep. The civil unrest caused by the masses who go 3 months without power is a bit of a concern. But honestly, I can't see it happening.. the countries that CAN are not likely to do so. To emp on a grand scale you need a second or third level of nuke tech. And if the idiots had the first level, they would have blown something up by now just because. Its pretty far down the list of things to worry about for me.

While the next world war will be fought in the Middle East, I believe our enemy will likely be an alliance of Russia, China, possibly N. Korea as well. Those together would have the capability and willingness to at least try either a full nuclear attack or an EMP blast then occupy. Not really highly likely though and I think our foreign relations would have to get quite a bit worse from now.

My primary concern is a solar based event that deals moderate to severe damage that takes many months if not years to repair. The civil unrest and lack of grid and structure, not to mention if the government can't continue handouts due to fixing the grid, will be significant.

[enfield]

How would old tube-based electronic equipment fare in an EMP?

[mikegideon]

How would old tube-based electronic equipment fare in an EMP?

 

Much better. Excessive voltage is the enemy of solid state junctions. Tubes are higher voltage devices. So, the voltages induced in the circuits are less likely to exceed the normal voltages in tube circuits.

 

That has been tested, BTW.