Question of the Week - EM Shielding

The following is an email conversation I had with a friend who knows a lot about copper and electromagnetic energy. Just thought I would share the exchange with you.

Jan: Hi Rick,
I have a question for you. Do you know if copper stops the radiation from solar flares. If it does not, are you aware of anything that does. Thanks

Rick: Hi Jan,
Yes and no.
It would depend on the intensity of the solar flare and on how the copper is installed.

Here is an excerpt from an article to consider:
If you have a shortwave radio, it is likely to be knocked out by the EMP unless it is adequately shielded. To be adequately shielded, it needs to be kept inside of a complete metallic shielded enclosure, commonly known as a faraday cage, and preferably inside nested faraday cages. A faraday cage is an total enclosure made out of a good electrical conductor such as copper or aluminum. Large faraday cages can get extremely complicated. For small portable electronics, though, completely covering the electronic equipment in aluminum foil makes an adequate faraday cage around the equipment. The foil covering needs to be complete, without any significant gaps. Wrap the device in plastic or put it in an insulated box before wrapping the covered device in foil. (Otherwise, the foil may simply conduct the EMP energy into the device more effectively.) A single layer of foil may not be adequate. In order to enclose the equipment in a nested faraday cage, place the foil-covered device in a plastic bag, such as a freezer bag, and wrap that bag completely in aluminum foil. If you really want to protect the equipment against a large EMP, add another layer of plastic and foil. The layer of plastic need to be the thickest plastic bags that you can easily find. (They don't need to be terribly thick, but do try to find some heavy-duty bags.) Just adding many layers of foil directly on top of foil won't do as much good, due to what is called "skin effect." I won't bother to explain skin effect here, but you can look it up if you're curious. Don't worry too much about skin effect, though. I only mention it here because many people have the misconception that when it comes to shielding, the thicker the better -- and this is definitely not true after a certain thickness is reached. Layers of shielding separated by insulation works much better. As a practical matter, though, wrapping with 2 or 3 layers of foil helps to assure that you actually have a good shield around the equipment. Of course, any antennas or power cords need to be either disconnected or contained completely within the faraday cage.

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Comments   

0 #6 Michael 2011-12-31 08:15
There appears to be some confusion concerning Faraday cages – a structure, an enclosure made from metal, be it solid or wire mesh construction. If you choose a metal wire mesh consider using one with very small spaces – a sixteenth of an inch (2 millimeters) or smaller is adequate. The tighter the mesh, the more effective it’s shielding to higher frequency radiation like microwaves. (Of course, the best construction is a cage made from solid metal, steel sheets but unfortunately, they do not flex like a wire mesh, are difficult to form, and require some welding.) Also ensure that the cage is bonded to ground or physically in contact with the earth, moist not dry. Wet earth behaves exactly like an unplugged sewer drain eliminating waste, quickly negating the harmful effect of induced current; and induced current is the flow of electrons initiated by an external source with an “expanding/cont racting,” “reversing poles” magnetic field, or EM fields/radiatio n.
0 #5 Butttercup 2011-08-01 22:06
Would love to know more about these cages and how to make them. Perhaps you have some sites with simple information you recommend? Thanks for bringing this topic up!
0 #4 Howard 2011-07-25 11:46
What about protecting standing Solar Panels? Is 'hardware' cloth, well connected, (let's the sunlight in) going to help protect them? The wire to the inside inverters is buried under 12 inches of earth to the abode. (3 layers of rebar and 1 - 5 ft of earth?)
0 #3 Ann 2011-07-24 11:13
Excuse me for my ignorance but you have discussed protecting equipment, how do we protect ourselves for radation, solar flares, etc. Is it just staying at a very high vibration and out of fear
0 #2 Alan 2011-07-23 12:59
Like what was said about EMP protection. I have a question about microwaves. Sence microwaves are designed to prevent there waves from getting out I think they should in turn prevent anything from getting into a microwave. So,I was wondering if putting electronic equipment into a microwave would protect that equipment at all?
-1 #1 4earthwise 2011-07-23 00:31
Yes to most of these comments, Even a 'faraday cage needs to be grounded. I can speak much about this, only ask!

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