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Faraday Cage / Room

08/09/2017 1:15 AM

I'm studying EMP issues and have a few questions. Can anyone narrow down simplest design to build an effective faraday room and or cage for protection against solar and man made EMPs ? Also , would an earth berm such as a root cellar give protection if the above ground area had ferraday cage design . Thanks

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#1

Re: Farraday cage / room

08/09/2017 1:37 AM

It's basically a grounded wire cage made out of conducting metal wire....I think you have to be in the cage to be shielded from EM waves...

http://snallabolaget.com/building-a-faraday-cage-why-and-how/

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#2

Re: Ferraday cage / room

08/09/2017 1:41 AM

Make up your mind between Faraday and Ferraday and possible other misspellings. And don't let the bedbugs bite.

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#3

Re: Ferraday cage / room

08/09/2017 2:53 AM

How about covering the walls, floor, ceiling and doors with baking foil?

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#4
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Re: Ferraday cage / room

08/09/2017 3:45 AM

Read things like that on the Internet, might work on cell phones, I was looking for something more substantial . What does the military use to protect electronics etc?

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#5
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Re: Ferraday cage / room

08/09/2017 4:03 AM

Countermeasures.

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#6
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Re: Ferraday cage / room

08/09/2017 4:23 AM

...which are secret.

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#7
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Re: Ferraday cage / room

08/09/2017 4:38 AM

...for obvious reasons!

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#8
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Re: Ferraday cage / room

08/09/2017 7:45 AM

What does the military use to protect electronics etc?

Copper mesh, the rest is classified.

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#9
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Re: Ferraday cage / room

08/09/2017 9:24 AM

Did you really think you could discover military grade engineering here.

Wikileaks would be a plausible place to look for secrets.

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#12
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Re: Ferraday cage / room

08/09/2017 9:34 AM

Did you really think you could discover military grade engineering here.

That depends on how much money you have....

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#34
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Re: Ferraday cage / room

08/10/2017 2:13 PM
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#11
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Re: Ferraday cage / room

08/09/2017 9:30 AM

One way that the Russians discovered by accident was to stick with valves.

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#40
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Re: Ferraday cage / room

08/14/2017 5:13 AM

And just how far under the cell do you want me to go if i answer?

I worked on this at Boeing Aerospace.

Lets say multiple ground points with an isolated cage with banks of capacitors to leak away the charge slower.

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#10

Re: Ferraday Cage / Room

08/09/2017 9:27 AM

Hiding inside a Faraday cage won't help much if the power grid and electronics on the outside get fried.

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#13

Re: Ferraday Cage / Room

08/09/2017 9:41 AM

Keep in mind that as soon as you penetrate the Faraday cage with something conductive (electric supply wiring, telephone/landline cable, etc.), you provide a path for the EMP to be carried into your cage. It will only be fully effective for whatever you have fully enclosed in the cage.

The military may use shielding, but more than that they use hardening, which makes components and systems resistant to outside disturbances to varying degrees. That was one of the reasons (back in my aerospace career days) that we often used ICs in ceramic DIPs that were MIL-spec and cost hundreds of dollars vs. the plain jane commercial version in a molded DIP form costing cents. There were real differences in what was inside the IC that made them much more expensive due to their construction to be more reliable and resistant to interference, radiation, etc..

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#14

Re: Faraday Cage / Room

08/09/2017 10:00 AM

There's no magic to Faraday Cage Design, just a lot of math, little of which is a military secret. Your biggest challenge is to choose the design parameters for your particular usage since, as in all physically realizable devices, there are upper and lower limits to its performance.

There's plenty available on Google, you can start with this 2015 paper.

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#15
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Re: Faraday Cage / Room

08/09/2017 11:00 AM

Thanks, I was also wondering if a couple feet of dirt would offer any protection

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#16
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Re: Faraday Cage / Room

08/09/2017 11:16 AM

To a coffin, certainly.

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#19
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Re: Faraday Cage / Room

08/09/2017 2:30 PM

simply put...no.

Earth, no matter how thick, can always be penetrated. A berm wouldn't do much at all.

We wouldn't need Faraday cages if dirt and depth was good enough.

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#20
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Re: Faraday Cage / Room

08/09/2017 3:39 PM

It all depends on the wavelength of the photons one wishes to stop. A thin piece of plastic can easily stop 400nm to 800nm photons. However greater than a 100m and less than 1nm photons do get difficult to block.

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#17

Re: Faraday Cage / Room

08/09/2017 11:54 AM

EMP upset is mainly connecting wires to a "black box". This induces large voltages, which the box being grounded, has induced via these connection wires. This is the issue with solar flares and power transmission, as the transmission lines are very long, under a 'moderate' level field, which can become very large induced voltages. The other effect is the induced voltages at the silicon level in ICs. This causes upset of microprocessors, as it flips bits and such. A shield room to be effective, needs to have multiple layers of mu-metal. You can try just soft steel (ferromagnetic) shielding. But it all depends on how sensitive your device is to stray fields. Most hardening I've worked on was transient suppressors on connection cabling pins. Power connections being the most difficult, as by design are very low resistance to the power source.

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#18

Re: Faraday Cage / Room

08/09/2017 12:41 PM

It's really not a huge government secret.

Start with the Unified Facilities Criteria from the Whole Building Design Guide site, WDBG.org.

You'll eventually end up with CNSSAM TEMPEST/1-13 RED/BLACK Installation Guidance which gets you going in the right direction.

MIL-HDBK-232, MIL-HDBK-411, MIL-HDBK-419, etc., are all references throughout the scheme, as well as the Green and Emerald books from the IEEE. Pay attention to the references in all pubs.

You may end up with a heavily exceptioned installation with regard to the NEC, but a lot of things in the gov/mil sector are.

Of course, this is just the non-physical nature of the beast. If you get a nuke dropped on you it all gets squashed like a bug anyway.

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#21

Re: Faraday Cage / Room

08/09/2017 4:46 PM

Back years ago, when I worked on covert government satellites, we considered 1/8 inch of accumulated, bonded aluminum thickness adequate for EMP protection. Most electronic modules and structural members were Al.

Of course, the EMP we were hardening against were pretty intense.

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#22

Re: Faraday Cage / Room

08/09/2017 10:55 PM

It's Faraday (19th century scientist much-about electricity).

The simplest cage is all about electric fields, as you would want to protect yourself against lightening (a mini-EMP). It is usually constructed of a wire mesh screen, usually a copper mesh heavier than window screening. But the nuclear EMP is hypothetically much stronger than lightening, and implicitly includes a strong electromagnetic field as would be experienced right next to a lightening bolt into the ground right next to you. To protect electronics equipment against that strong transient magnetic field, an iron box (like a sheet steel tool box or an old-fashioned steel safe) is needed. The Mark 1 EMP shield is an ordinary sheet steel tool box! Then you scale up from that to enclose whatever your heart desires.

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#23

Re: Faraday Cage / Room

08/10/2017 4:13 AM

Buy a shipping container & make sure the doors are bonded.

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#24
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Re: Faraday Cage / Room

08/10/2017 9:56 AM

I have several shipping containers , what do you mean by bonding the doors

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#25
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Re: Faraday Cage / Room

08/10/2017 10:03 AM

Electrically connect the doors and panels to ground. Do not rely on an electrical connection through a bearing.

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#27
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Re: Faraday Cage / Room

08/10/2017 10:39 AM

Correct, usually a couple of pieces of heavy braid between each door & the body of the container.

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#26

Re: Faraday Cage / Room

08/10/2017 10:36 AM

Any insulated electrical conductor that penetrates the cage would be a source of damaging overvoltage/overcurrent that is picked up outside the cage. Any connected equipment would likely still be damaged.

The cage would be good as a storage location for disconnected equipment, but would not be functional as a "safe haven" for connected and functioning electronics.

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#28
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Re: Faraday Cage / Room

08/10/2017 11:29 AM

The containers would only be used for storage . What would be the best way to ground the containers , I know some soils don't offer adequate grounding conditions and what's the best way to test for proper ground Thanks

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#29
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Re: Faraday Cage / Room

08/10/2017 11:34 AM

Depends on your local authority & rules. The one I use has 2 earth straps connected to buried ground plates. These have to be tested every 11 months & must show a reading of less than 10 Ohms to ground.

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#30
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Re: Faraday Cage / Room

08/10/2017 11:44 AM

Follow your local codes for grounding. In some places this involves one or a series of 2 meter long copper clad steel rods driven into the ground. In some places a copper mesh is buried. In some cases the metal of (water) utility piping is used. (This is now frowned upon as plastic piping is getting used by utilities and ground currents get suspected of inducing pinhole leaks.) One of the main reasons that grounding techniques vary is that local geology varies considerably.

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#32
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Re: Faraday Cage / Room

08/10/2017 12:35 PM

I know here the codes for grounding have changed over the years . The containers are in a pasture on a farm , and soil conditions vary dramaticly , I will follow the 10 ohm rule . Ground rods may not work depending on where they are placed . Do you have a suggestion on how to enhance grounding to optimize chances of proper grounding from the start

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#39
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Re: Faraday Cage / Room

08/11/2017 11:53 AM

"Do you have a suggestion on how to enhance grounding to optimize chances of proper grounding from the start"

This is a 2 part question: Obtaining a good Earth Ground, and Making a Secure Bonding to Earth Ground.

Obtaining a good Earth Ground means getting a point where electrical charges will be quickly discharged into the surrounding terrain. This is a matter of geology, depending on the soil and the expected, you may be able to use a 6 foot copper stake, or you might require a buried mesh of conductors. Check with a local Licensed Electrician, that person will either have the answer, or else that person will know exactly who in that municipality to ask to get the right info.

Making a Secure Bonding to Earth Ground means having an electrical connection from the item you want to ground to the Grounding Point. This is the section where you are concerned about the '10 ohm or less' rule; there should be no more than 10 ohms of measured resistance between the grounding point and the grounded item.

If you follow these instructions your equipment will be properly grounded.

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#41
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Re: Faraday Cage / Room

08/15/2017 6:52 AM

Tipping a large quantity of seawater into the area around the earthing rods will have an effect. In the absence of seawater, try copious amounts of mammalian urine instead.

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#31
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Re: Faraday Cage / Room

08/10/2017 12:22 PM

Grounding isn't really an issue. The faraday cage acts like the outer jacket on a coaxial cable. When a transient magnetic field strikes the cage, the cage generates a current that generates an opposite magnetic field, cancelling out the original magnetic field. If you ground at a specific location on the cage, a localized current is generated because the cage is acting like an antenna. That current flowing from the ground connection has potential to generate a localized field of it's own, which could penetrate the cage.

I'm not entirely certain, but I think you might want to let the cage float electrically to let it cancel out the high frequency transient magnetic fields. I used electrically floating copper shields to protect magnetic recording tapes with good success against 60 Hz magnetic fields.

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#33
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Re: Faraday Cage / Room

08/10/2017 1:57 PM

Would just the steel container with electrically bonded doors as mentioned before be enough for a cage or would the contents need to protected. I'm storing things like extra generator , electric tools, water pumps etc and possible older diesel vehicle that has minimal electric components, extra solar panels and batteries

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#36
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Re: Faraday Cage / Room

08/10/2017 2:31 PM

A bonded steel container would not work as well as the same geometry in copper or aluminum, due to the electrical resistance of steel. A heavier wall thickness could compensate for this. Depending on the waveform of the pulse, the steel could become magnetized, which would be unlikely to be an issue, but possible. I have not been able to find references on residual magnetism from various types of EMP.

I expect that a bonded steel container would work as a shielding cage.

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#37
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Re: Faraday Cage / Room

08/11/2017 3:12 AM

Er, and why does any of that require any sophistication in the way of protection?

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#38
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Re: Faraday Cage / Room

08/11/2017 4:06 AM

Our container is grounded, not because it helps any with the protection, but because the local authority rules say that it must be grounded.

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Re: Faraday Cage / Room

08/10/2017 2:26 PM
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