# DIY Faraday cage?



## Arklatex (May 24, 2014)

I am curious if any of you have made your own Faraday cage? An earlier thread got me to thinking of emp grid down situations similar to one second after. I have a 6 gallon galvanized bucket with a tight fitting lid. My thoughts are to line it with reflectex material that is used for sunshades in cars. Then a layer of cardboard wrapped in aluminum foil. Then keep repeating layers until a 30 cal ammo can fits snug in the middle. The goal is to protect my handheld frs/gmrs radios and a couple hand held ham radios. 

Would this work?

What else should I be trying to protect?


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## rjd25 (Nov 27, 2014)

Arklatex said:


> I am curious if any of you have made your own Faraday cage? An earlier thread got me to thinking of emp grid down situations similar to one second after. I have a 6 gallon galvanized bucket with a tight fitting lid. My thoughts are to line it with reflectex material that is used for sunshades in cars. Then a layer of cardboard wrapped in aluminum foil. Then keep repeating layers until a 30 cal ammo can fits snug in the middle. The goal is to protect my handheld frs/gmrs radios and a couple hand held ham radios.
> 
> Would this work?
> 
> What else should I be trying to protect?


just get an old microwave for your handheld stuff. I would use the cardboard idea to place over your generator when it is in storage.


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## SDF880 (Mar 28, 2013)

I won't pretend to know what the heck I'm doing just read enough to put something in place. I have 2 metal trash cans and I lined the cans inside with plastic
and foam on the bottom and sides and I completely lined the lids too! I keep all my radio equipment, walkie talkies, some LED flashlights stored in them. I have about 100 new solar LED lights in it
too. Solar lights will come in handy for night lighting and to save the candles. I'm not taking any chances with some of my LED items I think LED will be at risk in an EMP event.


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## GTGallop (Nov 11, 2012)

You can get old dead microwaves for free or damn near cheap. They are stackable and you can put electronics in them.


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## Prepadoodle (May 28, 2013)

I looked into this awhile ago, and found a Mil-Spec for EMP protection of electronic devices. Believe it or not, all they were using was an aluminumized plastic bag.

Something like these... Zip Top Metal-In Static Shielding Bag

I'll try to dig up the actual US Army data and source later if I can.

I have some of my backup devices wrapped in paper, then in foil, and sitting on top of a cardboard box in a small metal can with tight fitting lid. <shrug>

Someone on this forum knows a lot more than I do about this topic. Ripon? PaulS? Maybe they will chime in here and school us.


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## rjd25 (Nov 27, 2014)

Or you could just buy a metal storage shed and ground the metal of the building to an earth ground. It would save you a lot on tin foil and copper sheeting.


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## Prepadoodle (May 28, 2013)

rjd25 said:


> Or you could just buy a metal storage shed and ground the metal of the building to an earth ground. It would save you a lot on tin foil and copper sheeting.


The problem with that is any wire over a few feet long acts like an antenna and causes far more problems than it solves. The energy of an EMP is something like microwave-ish and can find its way into the smallest openings. (I think)


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## Dubyagee (Nov 9, 2012)

As stated above, Grounding the cage is critical. I remember running a crew that was cleaning a fuel tank on a navy ship that was at the pier. There was a lightning storm and they were all worried about it. I told them they were in the safest location in the ships tank due to it being a giant Faraday cage grounded to the ocean. They calmed down and kept working. I watched the scariest lightning I ever saw on the pier. I should have went in the tank.


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## Arklatex (May 24, 2014)

rjd25 said:


> just get an old microwave for your handheld stuff. I would use the cardboard idea to place over your generator when it is in storage.





GTGallop said:


> You can get old dead microwaves for free or damn near cheap. They are stackable and you can put electronics in them.


What are your arguments against this guy's theory?

Why Microwaves Don't work as Faraday Cages:


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## Prepadoodle (May 28, 2013)

I found this bit about EMPs from nukes. From FM 3-3-1, Nuclear Contamination Avoidance...

Appendix C
Nuclear Burst Effects on Electronics

"Shielded shelters can take many forms. A communications van or an armored fighting vehicle is what many people think of when shelters are discussed. However, _an ammunition can (with the lid tightly closed) is an expedient shelter for small items such as calculators or backup computer diskettes_, and the metal case of a radio can be an effective shelter if antennas have been removed and all access panels are closed. " (italics mine, source)

"Because they are not commonly regarded as collectors or antennas, unintended pickups may be overlooked. Potential unintended antennas include such objects as gun tubes, heating and ventilation ducts, water pipes, fuel pipelines, conduits, _grounding rods and wires_, commercial phone and power lines, missiles, guy wires, fences, railroad tracks, and power lines from generators, etc." (italics mine, same source as above)

So I'm guessing that a metal garbage can with a tight lid would work too.


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## Sasquatch (Dec 12, 2014)

I saw a show and I can't remember the name but they made a simple one and supposedly it worked. All they did was make a frame box out of wood, covered the whole thing in metal screen door material and it had a rubber mat bottom. They then grounded it with a wire to a copper rod stuck in the ground. The way they tested it was they stuck a little am/fm radio in it while it was playing music. Once they closed the lid the radio went silent thus it would be protected (their claim not mine). I've been meaning to try it out, just haven't got around to it. Figured it was cheap enough to make so if it didn't work no big loss.


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## paraquack (Mar 1, 2013)

I went to a "seminar" given by an electrical engineer about a month ago. I was under the opinion that a microwave oven would work just fine. Unfortunately he had a whole list showing how the higher the frequency of the electro-magnetic wave gets, the worse protection is offered by different types of home made "faraday" cages. The only thing that seemed to really do the job was the galvanized metal garbage can with cardboard liner to prevent equipment from touching the metal. The handles had to be removed on the can as well as on the cover and either soldered closed (galvanized metal solders pretty easily) or covered with copper foil tape with conductive adhesive. The lid was also sealed in place with the same copper foil tape. The tape was rubbed down very well eliminating any gaps between the foil tape and the can. The engineer use 1 inch tape that ran about $36 per roll with the conductive tape. The big thing he stressed was *any gap* would allow the electro-magnetic wave to get inside. And the EMP wave frequencies go way above what a microwave oven put out or a cell phone which was always being shown as evidence to support the idea that a microwave over really can do the job.

Here's the site for the foil tape.
http://www.findtape.com/product329/JVCC-CFL-5CA-Copper-Foil-Tape.aspx?idx=1&tid=25&info=copper%2bconductive


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## Illini Warrior (Jan 24, 2015)

can't believe you guys are still talking about using old microwaves .... just put 'em out in the chicken coop for nesting holes .... just some BS rumor with no technical standing .... 

and another BSer .... a radio or cell phone being blocked shows EMP effectiveness .... prepper urban legends that just don't die


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## Arklatex (May 24, 2014)

Illini Warrior said:


> can't believe you guys are still talking about using old microwaves .... just put 'em out in the chicken coop for nesting holes .... just some BS rumor with no technical standing ....
> 
> and another BSer .... a radio or cell phone being blocked shows EMP effectiveness .... prepper urban legends that just don't die


So what is your solution?


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## Spice (Dec 21, 2014)

I did some sensitive electrical recording for a project some years ago. It had to be done inside a Faraday cage. We made it ourselves; wood frame, covered with copper wire, grounded to water pipes. Didn't forget the floor, either. This worked beautifully, no noise although we were in a building Bristling with high powered electrical appliances.


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## rjd25 (Nov 27, 2014)

Illini Warrior said:


> can't believe you guys are still talking about using old microwaves .... just put 'em out in the chicken coop for nesting holes .... just some BS rumor with no technical standing ....
> 
> and another BSer .... a radio or cell phone being blocked shows EMP effectiveness .... prepper urban legends that just don't die


How can you say it has no technical standing? You are making a blanket claim on something with no evidence to back it up. A microwave is specifically designed to keep microwaves inside the microwave. The very design that keeps the microwaves in and as not to harm anyone standing next to it will keep EM out. The trick is the microwave must be grounded. Cut the power cord and take the ground wire and ground it to an earth ground. Here is some information for you.

Reader Question:
Can an old microwave oven be used as a Faraday cage?

Answer:
YES, an old microwave is perfect for use as a Faraday cage against EMP (electro magnetic pulse). In fact, it is a Faraday cage! A Faraday cage is an enclosure formed by conducting material or by a mesh of such material. A microwave oven's very design is to enclose the electro-magnetic radiation of microwaves, and keep them from getting out. The reverse will also be true - they can't get in.

Think of a Faraday cage as a reflector. A reflector of electro-magnetic waves. It reflects waves on the outside from getting in and waves on the inside from getting out.

A Faraday cage by its very definition does not have to be grounded to reflect or keep out electro-magnetic waves (they normally are not grounded). From inside the cage, it makes no difference if the conductive shell is grounded or not. The inside 'doesn't know' about the outside with regards to electro magnetic radiation.

The effectiveness of the 'reflection' properties of a Faraday cage depends upon the wavelength of the electro-magnetic radiation in question, the diameter of the holes in the cage's conductive material, and the conductivity of the material itself. Aluminum, or even steel window screen is "good enough" to prevent any significant electro-magnetic radiation.

Most purpose built "Faraday cages" that you buy are made out of copper screen instead of solid metal. As long as the holes in the screen are smaller than the wavelength of the frequencies you are trying to protect against, screen works just as well as a solid piece of metal.

An EMP is a broadband, high-intensity, short-duration burst of electromagnetic energy. In the case of a nuclear detonation, the electromagnetic pulse consists of a continuous frequency spectrum. Most of the energy is distributed throughout the lower frequencies between 3 Hz and 30 kHz. However the first effects of nuclear detonation are the very-high-frequency pulses, in the microwave range, and can work their way into Faraday cages if there are cracks, seams, or vents.

The frequency of a microwave oven is 2.45 GHz (gigahertz) and has a wavelength of 4.82 inches. Since the holes of the screen mesh of a microwave oven are small compared to the wavelength of the microwave itself, little radiation can leak out. There are also mesh screens on the sides of the oven cavity, one to protect the oven light while allowing it to shine into the cavity, the other to permit ventilation.

A microwave will indeed protect your electronic gadgets during an EMP, so long as you don't press 'START'&#8230;


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## Diver (Nov 22, 2014)

Part of the problem with the question of what will work and what won't work is there is very little experience with real EMPs, as opposed to something that is supposed to simulate the effect. Will it pass the test? Will it still pass the test with the force of a nuclear bomb behind it and the frequencies range from very long to very short? Hmmm?

As a result, you are going to have a degree of uncertainty no matter what you use.

One thing I read, that may or may not be true, was that each layer of shielding provided some reduction in force, but not total elimination of force. The suggestion was therefore multiple layers of shielding. This makes sense to me and might work even if one layer is ineffective, albeit the whole thing may get overwhelmed in a real event. The result is I have tried to go with that approach but I have no more knowledge than anyone else as to whether what I have cobbled together will work as hoped. What does any of us have to lose by trying?


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## paraquack (Mar 1, 2013)

A microwave oven can protect as a Faraday cage. But at the voltages and power of an EMP, it don't stop sufficient electro-magnet energy from getting inside. I am looking for the table. If you were far enough away from the EMP it might do the job, but the cost of the garbage can and the proper copper foil tape isn't that expensive by comparison. The engineer had a table showing the different frequencies created by and EMP and the frequencies at which different shielding methods were effective. A microwave oven was pretty high but just not high enough to really give adequate protection. But you must also remember that an EMP emission starts at <1 Hz and goes up to and including low GHz frequencies. The higher the frequency, the lower the EKV/m. Try the microwave with an AM radio tuned to a very low frequency. They seem to keep right on playing unless the station is far away. I did the cell phone in the oven and thought it would work, but... So is it worth the risk?


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## TxBorderCop (Nov 19, 2012)

Is there any way to make an entire GARAGE a giant Faraday cage?


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## Prepared One (Nov 5, 2014)

This looks pretty good and easy. I have to do more research on this subject tho.


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## LDSreliance (Sep 2, 2014)

I posted this on here a while back. Super easy and cheap to make. Will it work in theory? Yes. Will it stop a major EMP from a solar flare or something? Probably not. But it is better than nothing:


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## PaulS (Mar 11, 2013)

You need to learn the difference between a Faraday cage and an EMP shield.
A cyclone fence makes a reasonable Faraday cage. As long as you have a top and bottom and sides it will direct a high voltage electrical current around anyone inside. That same cage will not stop an EMP nor will it protect from an E1 HEMP pulse.


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## PaulS (Mar 11, 2013)

LDSreliance,
There are a couple of things wrong with your box. The first is that you only have a single layer of light duty foil to protect those items inside. You should have at least two more layers of heavy duty foil with insulating layers between them.
The other problem is that there are gaps between the lid and the rest of the box and you have the inside exposed to the foil. You have made a resonance box for the EMP to bounce around in assuring the destruction of any electronics inside.

Put your items in the box.
Wrap the outside of the box with a single sheet of heavy duty foil (turkey baking heavy duty foil) (if you need to combine two sheets to make one big enough you should align the edges, fold over one inch of both sheets and then fold over a half inch of that fold back on itself) that forms a double seem.
Place the wrapped box in a heavy garbage bag (or another box).
Wrap the outside in another single sheet of heavy duty foil.
Place that into another plastic garbage bag or another box.
wrap the entire container in one more layer of heavy duty foil. No gaps or holes and all seems doubled to prevent any penetration.

The multiple layers of protection offered by the Aluminum will conduct the current around the box without giving it time to penetrate.
one hole as small as 0.1mm is enough to let the E1 pulse through a layer of shielding. (that is about 1/15 the diameter of a sewing needle)


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## bo_leggs (Aug 8, 2015)

I live in a house with steel siding and a steel roof. If this is grounded will it work as a Faraday cage? We also have a metal garage and two metal sheds. Thanks for your assistance.


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## PaulS (Mar 11, 2013)

Your steel house will work for a Faraday cage against lightning and other static discharges but it will be a very large antenna for an E1 pulse of an HEMP (high altitude nuclear trigged EMP)

While it is theoretically possible to harden an entire house against the E1 pulse it would be very expensive (three times the cost of a similar home) and there would be no windows and all the doors would have to be sealed with interference fit copper or aluminum shielding. Door knobs would not go through the doors and would be shielded. 

It is far easier to shield an internal room from the E1 pulse but it has to have its own power supply and no connections to the outside rooms. The door has to be sealed with aluminum or copper interlocking seals.

Grounding a structure works for lightning and static discharges but aids in the transmission of the E1 pulse.


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## paraquack (Mar 1, 2013)

This is a long read but very good and from very good source. Covers the multi layer use of aluminum foil and the use of a garbage can, etc. 
Electromagnetic Pulse Protection - EMP - Futurescience.com
He has about 5 or 6 more out there. I can supply the links if you want. They are excellent reads.


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