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Discussion Starter · #1 ·
This might be just stupid, but here goes.

I've read pre 1982 pennies are made with copper. If I glued a layer or two into or on a shoebox, or whatever, would that work to make a small EMP proof box? Or is the copper content not high enough? Could it be used as a layer. Something like tinfoil, plastic, aluminum screen, plastic, pennies.

Any thoughts?
 

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I think you'd be better off getting some copper foil. I know it's available, but I've never purchased it by itself. It comes with some electrical connectors such as welding leads. It's fairly thin probably about 1mm thick (not as thin as aluminum foil) but should be enough for what you're planning.
 

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Patient Zero of WWZ
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Glued pennies won't work. You need a good electrical connection all the way around.

Plain old aluminum foil will work fine.

Wrap a layer of insulation around what you want to protect. A towel will work. then wrap a continuous layer of foil around that. Leave no gaps, or holes.

A second layer of insulation and foil is cheap insurance.

It is said that no grounding is needed, but if you can ground it do so.

A solid metal box with a metal lid will work also. Like the foil trick be sure the electronics is insulated from the metal.

My short wave receiver is in it's box, that is wrapped in a piece of old rubber coated canvas raincoat material. That is in a metal Christmas Cookie box. I bought them both at Goodwill for about $3 total.
 

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That's a nifty idea. You would need to electrically connect (solder/braze) all the pennies, and not have any gaps, so that means pretty much you'd need two layers of pennies. You might want to think about how many pennies you might need, though.

Aluminum foil would need to be thicker, or have multiple layers in close proximity to be good. The thicker the better. You can find industrial thickness aluminum foil, which is actually cheaper and comes in larger rolls than what's available at grocery stores. Go check out mcmaster.com and put aluminum foil in the search box. There's copper foil as well there, but, without testing, I suspect that aluminum has pretty good bang for your buck. Copper is better for EMI shielding, but aluminum is a bit cheaper and you just use a little more to make up for the loss.
 

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Not sounding rude. But as an electronic technician for 20 years in the navy and having had formal courses in EMI, EMF protection and grounding I really just have to say ???. If you really want a faraday box a large metal box with a 8 gauge copper wire run to the grounding plug of your outlet is all u need. If you want wrap it in tinfoil a couple of times mostly just for show.

2 things about your idea. Way too much work for no extra benefit and most likely if we ever do take an emp hit it will happen as a surprise and the chances that your gear is even in the box is slim.

Has anyone stopped and realized that the people you ridicule today (trailer trash) are the best equipped for an EMP. Maybe that's what the bible means when it says 'the meek shall inherit the earth'
 

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Not sounding rude. But as an electronic technician for 20 years in the navy and having had formal courses in EMI, EMF protection and grounding I really just have to say ???. If you really want a faraday box a large metal box with a 8 gauge copper wire run to the grounding plug of your outlet is all u need. If you want wrap it in tinfoil a couple of times mostly just for show.

2 things about your idea. Way too much work for no extra benefit and most likely if we ever do take an emp hit it will happen as a surprise and the chances that your gear is even in the box is slim.

Has anyone stopped and realized that the people you ridicule today (trailer trash) are the best equipped for an EMP. Maybe that's what the bible means when it says 'the meek shall inherit the earth'
Fellow Navy saying HI
 

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I have several steel cabinets, including filing cabinets, I keep the electronics in .
I have a question,.
Why would you want to attract an electric charge to the box by grounding it.
In amature radio ,the best transevers are grounded the worst (hand held ) are not .
By grounding ,one is assured that the charge will definately strike the box going through and past it.
Where as , by being ungrounded ,the magnetic pulse has no draw to it what so ever accept that it is metal, and would disapate just as quickly .
With lightening the rule is to create the least attention poassable ,and during an event unhapily being caught in it , the best move is to place your feet as close to gether as possable ,because the ground is a shunt , and the body being mostly water and minerals is a better conductor the charge will leave the ground in it route of travel and pass through the body to the leg closest to the heading it has chosen .
The closer your feet are together the less of a charge will choose the body, and of course the reverse is true. Running is very bad.
Point is, grounding insures a hit, like a lightening rod.
Any thoughts ?
 

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Cry havoc..
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Correct on the penny composition. Surprised nobody has mentioned this so far. 1982 US pennies come in two flavors. Some are COPPER, and some are ZINC (clad coins). Best way to tell is by weight. As an EMP box, I could not say, but it seems unlikey. 1981 and lower dates are all copper, 1983 and higher are zinc (clad).

Dave
 

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Who's that?
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Discussion Starter · #9 ·
Kind'a what I figured, it might work, but with easier, more efficient techniques it's not worth the work.

Thanks for the replies.
 

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Bushcraft Guy
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If your not planning to use them for the faraday cage, why not collect these copper coins in bulk as you go along for the task of barter materal? could maybe even smelt them down into bars unless this is illegal?
 

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Ok here is the easiest and the cheapest metal container.
The round metal tins flavored popcorn in at Christmas.
Be sure to sand the area where they seal.
 

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I have several steel cabinets, including filing cabinets, I keep the electronics in .
I have a question,.
Why would you want to attract an electric charge to the box by grounding it.
In amature radio ,the best transevers are grounded the worst (hand held ) are not .
By grounding ,one is assured that the charge will definately strike the box going through and past it.
Where as , by being ungrounded ,the magnetic pulse has no draw to it what so ever accept that it is metal, and would disapate just as quickly .
With lightening the rule is to create the least attention poassable ,and during an event unhapily being caught in it , the best move is to place your feet as close to gether as possable ,because the ground is a shunt , and the body being mostly water and minerals is a better conductor the charge will leave the ground in it route of travel and pass through the body to the leg closest to the heading it has chosen .
The closer your feet are together the less of a charge will choose the body, and of course the reverse is true. Running is very bad.
Point is, grounding insures a hit, like a lightening rod.
Any thoughts ?
Several key items you've touched on, and they are all very different and should not be confused with each other. While each of the above listed items has components of the other in it, the method of protection is built on different concepts and theory.
1. Lightning. Primarily an electrostatic effect. It's high voltage and current will go everywhere it feels like; with no rhyme or reason. Ground path or not, but you can help dissipate the electrostatic field that becomes the starting point for a lightning attachment by keeping all metal things grounded. Or, better, yet, have lightning rods for lightning, and electrostatic and EMI/EMP grounding for EMP. Never tie them together, or even close together, in any way, even in the ground.
2. EMI. Electromagnetic interference. Key word here is interference. It's the fuzz that finds its way onto your receiver, it's the whine in my car radio when I plug my cell phone charger in. It's a lot of things, but for the most part, it's an annoyance bordering on malfunction. In conjunction with some pretty sophisticated filtering algorithms, it can can also be a source of key information to someone else who wants to monitor your transmissions. Most EMI protection components are designed with specific frequencies and sources in mind, and only have to attenuate just enough to allow continued operation.
3. EMP. Electromagnetic Pulse. A indescribably large electromagnetic pulse whose magnetic fields generate electric currents in conductors where those magnetic lines cross. Those currents again, in turn, create magnetic fields and the process continues until it runs out, which thanks to electric lines running across the country, will go for thousands of miles and touch billions of devices even further than that. The phenomenal power generates very high frequencies and amplitudes, which overpower the EMI protections built into just about every existing electronic device. Long power lines act as antenna, retransmitting the signal even further out, hence the cause of the spread of the signal.

Got a key bit of information to understand here. There's a term used in electrostatics called isolated conductor. In a nutshell, it means a conductive object that can store an electrostatic charge, and has no external path to ground. Now, if there _is_ a path to ground, and it's a tiny wire that routes through your house wiring to the circuit breaker panel, it will drain low frequency voltage and high frequency signals of low power to ground. However, due to inductive issues, a high frequency signal of high power may not even "see" the ground path, so in essense, it acts as an isolated conductor. A ground lead needs to be short relative to its wavelength, preferably less than 1/4 wavelength, and when your wavelength is in the millimeters, you have a problem. The other thing is that high frequencies tend to travel along the outside surface of a conductor, rather than through the center (skin effect) so you want maximum _surface_ area in lieu of maximum wire cross section (such as wire gauge.) If you were to look around the cell phone towers that dot your area, you'll see wide, flat straps of copper for grounding rather than skinny wires normally used for low frequency applications like homes and TV's and such. The coaxial cables actually have hollow conductors, which, due to the skin effect, saves a ton of unnecessary copper. If you need to ground a system for high frequency and high power, you want to maximize the surface area of the conductor and minimize its inductance and imedance, and to do that, you need the widest conductor strip that's practical and have the least number of bends or direction changes in it. The longer the ground lead, the more of an antenna it will be, and the more that lead itself will retransmit electromagnetic signals.

For the record, I'm not an expert in this stuff, nor have I been trained in the field. I do, however, work with this technology for a living (among other cool physics stuff, quite often all at the same time) and have a very strong practical understanding, as well as the ability to translate the concepts into lay terms.

Some useful articles about grounding:
http://www.gacopper.com/Link.html

By the way, if any of your devices has any leads that come out of your faraday cage to go to wall power, the internet, or phone, you've just defeated the entire purpose of the cage. There are ways around that problem, but you need a very specialized education to do a good job.

Unfortunately, there is far more ignorance than understanding on the topic of EMP. Every time I do a little research on some detail or the other, I have to sift through pile of articles written by people who know just enough to be dangerous, or worse, things like folks who sell metalized plastic bags (made for EMI attentuation) as EMP shields, making money off of the ignorance of the masses. Either they're ignorant and selling what they think is a legitimate product, or they're intentionally getting rich off of the gullible masses who fall for the fluff like snake oil, cryonics, global warming, Barack Obama, and so on. Buyer's remorse may come in time, it may come with damages, or it may come too late. With doomsday oriented products, buyer's remorse will really suck, unlike still being able to vote in 2012.
 

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The 40 ft box trailer I have that has aluminum walls,roof, and a steel floor would serve as a large Faraday cage?
Perhaps it could just as easily be a nice "resonant cavity" for microwaves, cooking the occupants :eek::taped::confused:
 

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Has anyone seen an online link on how to build a Faraday cage? I've seen some really half-assed builds in my search, so what I'm referring to is a credible source, with a quality DIY design.
 

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Has anyone seen an online link on how to build a Faraday cage? I've seen some really half-assed builds in my search, so what I'm referring to is a credible source, with a quality DIY design.
The problem with that is that the folks who REALLY know how to design Faraday cages want to charge you for their effort. If you want EMP resistance, that's a whole 'nother ball of wax, and those guys are even harder to find. It all boils down to requirements, and engineers and physicists have to have requirements first.

Since there are far more people who THINK they know this stuff, and about as many who want to tell you how you can do it, I approach any sort of instructions with a jaundiced eye. I think most of what I've stumbled across doing research for work is complete baloney, and phenomenally insufficient for the broadband frequencies involved. Weird stuff happens in broadband pulses, and most of it defies explanation. If you were to look at the folks who test power distribution equipment for lightning resistance, it's still a whole lot of guess work, and lightning effects are but a tiny component of what an EMP event is (note that I said lightning effects, not lightning.)

The more YOU know, the better a job you can do of defining what your requirements are. Work out what you need, what you want (two separate things usually) and then hit the books. It's a painful learning curve; I'm warning you in advance.
 

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My cell phone doesn't work very well in my double aluminum roofed ,aluminum sided housing structure
The signal power that your cell phone works with is incredibly small and measured in microwatts, I believe (could be wrong.) If your cell phone doesn't work AT ALL, then that's a good start. Try an FM radio as the next test. EMP is broadband, which means it puts out frequencies from DC into terahertz, as well as X-rays and on up, coupled with generally power so high it's not reproducible in a laboratory of any size (and the Russians tried, believe me!)
 
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