The room was amazingly simple, constructed of wood, 2x4s and such. The entire thing was latticed with thick copper screen, triple thick. Air could just barely get in through the screen. The exterior shell of the room was essentially a huge diffuser, anything hitting it was spread out and attenuated over the grid, the grid was tied to ground.
An internet search using the keywords "copper cloth" produced several suppliers that have such in various materials. This is the first I've heard of such a project to shield from EMP.
The best way of protecting electronic equipment from electromagnetic impact is to use brass or some other non-magnetic metal, as this will prevent the radiation to get to the sensitive chips. Make a brass box and put the PC inside. (Fill your brother's trumpet or tuba with your floppy diskettes and seal it off, hehe!)
Mumetal is an unusual alloy that provides the only known method of shielding from electromagnetic radiation. Mumetal is the only truly mechanical shield from electromagnetic radiation, and has an usually a high Nickel content alloy. Mumetal is used in industry today for this purpose to form shielding for components, instruments, and in some instances to protect people from electromagnetic radiation Even a single sheet placed between the instrument or person to be protected and the source/direction of the radiation will greatly reduce the effect. It is especially good in 50/60hz type applications where all else fails. Mumetal can be used to eliminate radiation from the back and side of a monitor in work stations. Two bands made from Mumetal curved around the back of the cathode tube on your monitor will knock out almost all electromagnetic radiation. Mumetal works, unlike the fake monitor screens that do zero with electromagnetic radiation. Try a Milligauss meter in front of those screens and you will soon discover that they do nothing despite their claims.
Of course lead shields protect from ionizing radiation sources such as Gamma and Beta types but only Mumetal can work effectively on the lower non ionizing frequencies that may present by far the greatest threat to electronic equipment in any violent electromagnetic storms. One might protect a computer by building a Faraday cage, but even better is a lead-lined Mumetal box to slip the computer into in times of high electromagnetic radiation.
Magnetic fields either emanate out from a permanent magnetic source, such as a permanent magnet or they are momentarily created by raising or falling electric fields. The 60 Hz A/C electricity coming into your house on wires or the 600 Kilo Hz radio signal coming into your AM radio through the atmosphere, are being propagated as electromagnetic waves. Waves penetrate things that they are able to pass through and are deflected or absorbed from things that they can't pass through. Here shielding can be useful.
Here are two experiments you could try out for yourself, one with a permeant magnet and a floppy the other with a bulk cassette tape eraser. Not everyone will have a bulk cassette tape eraser. The easiest test is to use a readable formatted floppy with some files coped to it. Find a large strong enough permeant magnet, so as to make the floppy un-readable when doing a preliminary air test. Place a piece of cardboard the same thickness as your steel, or copper plate (or best conductor being tested) between the floppy, and the magnet. This will insure a constant distance. Move the magnet around at between 1-10 cycles/second. Check for readability, if you can still read it, go find a stronger magnet. Once you have a strong enough magnet, then, test each shielding maternal checking the readability of the floppy after each test. This test can be done by anyone wanting to test the effectiveness of their shielding. The bulk tape eraser test gives a shielding comparison of different materials at one test ELF of 60 cycles/sec. This indicates a trend that says Iron-steel is many times better than Aluminum at this frequency. A Fourier series analysis of any given "asymmetric pulse" to find the amplitude and frequency of all of the harmonic components that make up the pulse would give the fact that: The lowest frequency component would have the highest amplitude. If we shield for that low frequency, then the other higher frequency components with the much lower amplitudes will not be an issue, being easily shielded using the same material.
The following has been quoted from Frequently Asked Questions about Magnetic Shielding Provided by: Magnetic Shield Corporation 740 North Thomas Drive Bensenville, Illinois 60106 Telephone: 630-766-7800 What is ELF? ELF stands for Extremely Low Frequency and usually refers to magnetic fields at 0.5 to 100 Hertz. This range includes the 60 Hertz power line frequency commonly used in the United States. In other countries, the power line frequency might be 50 Hertz. What is the difference between RF and Magnetic shielding? Radio frequency (or RF) shielding is required when it is necessary to block high frequency - 100 kilohertz and above - interference fields. These shields typically use copper, aluminum, galvanized steel, or conductive rubber, plastic or paints. These materials work at high frequencies by means of their high conductivity, and little or no magnetic permeability. Magnetic shields use their high permeability to attract magnetic fields and divert them through themselves. Magnetic shielding alloys have the ability to become broadband shields, performing shielding of both frequency ranges, when properly constructed." Note well, this last sentence answers your request for confirmation.
Ferromagnetic substances including iron, steel, nickel, cobalt, and magnetic alloys, have relative permeabilities greatly in excess of unity. Under certain conditions the relative permeability of steel may exceed 2000. All the other elements air included are close to a permeability of 1. Thus, at frequency of zero the comparison of the magnetic conductivity is over 2000 times that of other elements. What this means is the lines of magnetic force will try and stay within the ferromagnetic substance and not go back into the air unless it can help it. Thus, the easiest magnetic path from one side of box to the other is through the outer shell. This reduces the internal field strength thus the shielding effect. This does not happen with non-ferromagnetic substances like copper, brass, aluminum, lead and etc. As the frequency rises eddy currents start gradually to take effect and the electrical conductivity properties begins to take over. By using a ferromagnetic substance that is a good conductor you have the best of both worlds some shielding at both high and low frequencies ELF.
At high frequencies "best conductors" are "best shielding". However, Iron and steel should not be under estimated they are not that bad a conductor compared to air. The electrical conductivity of iron is much much closer to Copper than air. So the shielding at high frequencies is not that bad for Iron. If you look into your TV or Radio you will often see iron or steel used as shielding for the RF frequencies. Note the tin plated iron box around the RF tuner section. Why, because it's cheaper and easier to use and works almost as well at high frequencies for the same thickness. Note: Copper and brass screens are used in laboratories to build Faraday's cages to shield for electromagnetic nose. Why is this used? Usually the main interest is in shielding the higher frequencies and budget and availably are not an issue. Why use a screen over a solid plate - this is so the room can be made small and the lab technician doesn't get claustrophobia inside it. A thicker iron screen or plate would work just as well. Any conductor would work at higher frequencies as long as you adjusted the thickness to simulate what a good conductor like gold, silver, and copper can do. Shielding results of testing Aluminum compared to Iron at 60 Hz: I used a "bulk cassette tape eraser" that puts out a strong 60 cycle/sec electromagnetic field as a source transmitter. I took a coil from a transformer and hooked it to a volt meter as a receiver. Cardboard and several .2" thick plastic sheets were used as spacers on both sides of the test sample (centered) so that the distance from the source to receiver was the same (.5") for all tests. The voltage was measured for each test shielding material. The positioning of the receiver was adjusted for maximum voltage for each test. This turned out to be the centered on the source. Measured voltage for each sample: Air (cardboard) - measured 19.4 Volts AC Aluminum (.100" thick) - measured 16.5 Volts AC Iron ammo box (.032" thick) - measured 6.5 Volts AC Note: The higher the voltage the more the amount of electromagnetic field that got through the sample. Analysis of results: The Aluminum being 3 times thicker than iron only dropped the electromagnetic field by 2.9 volts as compared to iron dropping it 12.9 volts. This gives a net result of (12.9/2.9) * 3 = 13.3 times thicker aluminum would be needed to shield the same amount as the Iron (or steel) ammo box material. I didn't have any copper or bass available to test, however the result should be some what similar. Summary: Conservatively speaking, Iron is more than 10 times more effective shielding than Aluminum at 60 cycles/sec. This will get even better at lower frequencies. The point is, the lower the frequency the better the shielding properties of Iron as compared to other non-ferrous conductors. At low frequencies magnetic shielding is more effective. At high frequencies electrical conductive shielding is more effective. The audio industry for years used iron shielding over tubes when needed. A further test will confirm this for you if you take a permeant magnet and wave it (1-10 cycles/sec) close to a iron plate with a floppy on the other side. Then do the same test with Gold, Silver, Copper, Brass, or Aluminum plate of the same thickness using another floppy. Then try and read each floppy. During core movement, possibly generating strong localized magnetic fields, I believe the lower frequencies are what needs to be shielded against. I believe the bigger the event, the stronger the field, and the lower the frequency. We should experience lots of random noise spikes getting stronger and stronger as one goes below 10 and even 1 cycle/sec. Now with all factors taken into account a good solution needs to be cost effective, available to all, and technologically sound. I believe Iron or steel satisfies all these conditions much better than the alternatives. Annealed cold rolled Iron plate would work slightly better than steel but not enough to worry about. The only thing I don't know for sure is how thick does it need to be to effectively work for us in all cases. I suspect one box thickness of .032" will be enough to knock the edge off any strong electromagnetic bursts, however, if you really want to be safe use one box within another for those really critical magnetic medium. If one has a Iron or steel safe or lock box that would work also. Just make sure it is fully covered with Iron or steel the thicker the better.
The static discharges of lightning produce static interference on a AM radio that will overwhelm the reception of a station on a simple radio receiver. This is propagated electromagnetic waves from the lightning, stronger at the lower frequencies. Less amplitude at the higher frequencies. For big discharges near by - a low frequency electromagnetic pulse (EMP) is generated that could produce some large changing magnetic fields - this induces a strong current in any conductor present (the longer the conductor the higher the voltage) and in the past could potentially harm sensitive receivers and electronics equipment. This is not so much the case these days with the tougher hardened electronics available. However, to be safe some shielding could be used. So if sensitive equipment is hidden away in a highly magnetic and electrical conductive box then no current will be induced - thus the protection. This is just a bonus not the main thing we are tying to shield for.
Another idea to protect computers or any sensitive electronic equipment you may want to EMF protect is mumetal shielding. It is a metal compound composed of 80% nickel, 20% iron.
Mumetal when compared to iron at low magnetic field strengths can be up to 3-4 times more effective for the same thickness. However, at 3 times stronger fields then iron is 3-4 times more effective in shielding. Mumetal cost is high and availability is low. Mumetal is usually used where field strength is low, weight is a factor and the size is small. Since we wish to shield for strong magnetic fields then I recommend use of soft (annealed) iron instead of Mumetal. Our application does not warrant the cost of Mumetal.
I recommend the use of only iron shielding such as is found in surplus used ammunition sealed containers. Iron or steal works for low and high frequency electromagnetic fields and for static magnetic fields. EMP from lightning would also be shielded. Conductors like copper, aluminum, Brass, etc. do not magnetically shield well at low electromagnetic frequencies and not at all for static magnetic fields. Of prime importance floppies, hard disks, backup tapes, and other magnetic medium to include music, training, cassette tapes, etc. would be best kept in one of these water tight iron-steal ammunition boxes. These boxes are made in different sizes some big enough to put a PC CPU in along with other sensitive electronics. A typical small ammunition box is 7" high by 11" wide by 5.5" deep with a hinged top, weight of 6 lb. and typically sells for $2.50 to $5.00. The Northern Pro catalogue has across ammo boxes, offering 4 different types. Prices range from $ 5.00,6.00,9.00 and 22.00 for a large 25"lx6 in height. Their number is 800-533-5545.
DR. BECK'S NOTES ON THE MPG Suggestions for Acquiring and Using an Inductively Coupled Magnetic Pulse Generator for Theoretical Lymph and Tissue HIV Neutralization Revision December 18, 1995. Note: These data are for informational and instructional purposes only and are not to be construed as medical advice. Consult with your licensed health practitioner. IS IT WORKING PROPERLY? A good way to test for strength of pulsed magnetic energy is to lay a thin steel washer (one strongly attracted to magnet) flat on top of coil, H" off center. A 1" dia. "fender" washer with J" center hole works well. Let the flash unit charge for about ten seconds plus or until the strobe's "ready light" comes on then push flash button and see how high the washer is "kicked" by Eddy current repulsion. A 35 watt-second strobe repels a washer about 14 inches vertically. Think of your pulsed coil as the "primary" of a transformer and anything conductive nearby (living tissue included) as the "secondary" into which current is induced when cut by coil's time-varying magnetic lines of flux. Your do-it-yourself magnetic pulse generator delivers a measurable output intensity SEVERAL THOUSAND TIMES more powerful during each cycle than $7,000.00 German "Magnetotrons", Elecsystem "Biotrons", or Canada's "Centurion" devices widely exhibited at holistic medical expos, none of which is NEARLY powerful enough for HIV, herpes, hepatitis or Epstein-Barr neutralization or adequate electroporation. It is also functionally similar to the "Diapulse" miracle-working healing modality when coil is applied over liver and other organs. Magnetic fields and therefore induced currents penetrate ALL body cells, bones and tissues in proximity to coil (effective approx. 4 inches deep) and can theoretically neutralize electro-sensitive viruses such as herpes B, HIV, hepatitis, Epstein-Barr and possibly many others as yet undiscovered that can hide WITHIN nerve sheaths and are therefore untouchable via immune system, white cells, or injectables. This may account for the impossibility of curing many known chronic infections via pharmaceuticals, antibiotics, or any presently known conventional treatments other than electrotherapy. Use pulser on body sites daily concurrently with blood clearing. This pulser is considered safe to use anywhere on the head, chest, and body except with cardiac pacemaker users. SEE GRAY'S ANATOMY for lymph gland locations. TO USE Press fully insulated coil flat against body over lymph glands and other selected locations such as shown on page 11. Let strobe build up to full charge (about 10 seconds or longer between pulses) and fire coil while contacting each site. Subjects will feel no physical sensations except for light "thumps" during this phase of treatment. Exposure levels are considered safe because intensity of this magnetic pulser is much lower than Magnetic Nuclear Resonance Imaging in routine use on tens of thousands of patients. But should subject feel "headachy", nauseous, sluggish, or display flu-like symptoms after exposures with either of these two devices, reduce number of pulses or duration of blood clearing process and drink more water. If immune system is very badly damaged, you may need to repeat all routines after several months to insure permanent and complete neutralization. WHEN USING, KEEP COIL SEVERAL FEET AWAY FROM CREDIT CARDS, WATCHES, MAGENTIC TAPE, COMPUTERS, FLOPPY DISKS, HOMEOPATHIC REMEDIES, ETC., since its powerful magnetic field can de-gauss and erase magnetic data as well as subtle energy potentized medicines. As an unanticipated serendipity, pulsers are reported to erase deeply rooted lymph and tissue pathology and possibly even classical "miasma's" as well as many other microbes, fungi, bacteria, parasites, and viruses. Flash should preferably be used with AC power to save battery costs since you'll only get about 40 full pulses per new set of alkaline batteries. For sanitary purposes, enclose coil in plastic zip-lock sandwich bag discarded after each user. When treating numerous subjects if there's no AC adapter it is economical to purchase and utilize a small rechargeable 6V lead-acid "motorcycle" type storage battery.

For basic considerations and formulas about shielding at low intensity field levels can be studied at EMF Fundamentals