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EMP and the Faraday Cage

Discussion in 'General Survival and Preparedness' started by melbo, Apr 4, 2010.

  1. melbo

    melbo Hunter Gatherer Administrator Founding Member

    Faraday Cage & EMP Protection - What You Should Know
    article removed at request of original author

    <EMBED src=http://www.youtube.com/v/t23iXhEiQUc&hl=en_US&fs=1& width=480 height=385 type=application/x-shockwave-flash allowfullscreen="true" allowscriptaccess="always"></EMBED>
  2. dragonfly

    dragonfly Monkey+++

    It's fun stuff!
    I did the phones, radios-AM/FM/CB/Ham, and such with new galvanized trash cans...it didn't work at all for me!
    The more the metal surrounding the items, the greater the concentrations....from EMP's anyways.
    I tried using aluminum foil, it worked better than the ammo and trash cans.. 2 complete wraps stopped all signals from getting thru (RX only!)
    Also I tried using a roll of chicken wire...that had open ends...danged thing worked the best!
    But, it won't protect against the EMP, those end holes are the problem there.
    From what I have found, is that the sizes of any openings must be smaller than 1mm in any dimension. ( lots of variants in the wavelengths from emps)
    Aluminum, window screen over a frame of wood, works very well, as long as it's connected to a ground, NOT a water pipe. That only enhances the problems....
    It's like the ground in the houses today, all are "LONG WIRE" systems that will defeat the cages.
    Whatever is inside the EMP/faraday cage, must be insulated from the cage screen or metal/whatever itself. The cage itself must be grounded to an earth ground by either copper clad steel rods, or using copper pipe. They should be 4-8 ft deep in moist ground, or some say, use an 8ft piece of just copper pipe buried in an "L" shape configuration, at least 4 ft depth. The connections should also be soldered, not just clamped....No wires going in or out of the cages/boxes, so the items inside cannot be connected to anything, power cords, antennas, etc.
    One of the biggest problems is the length of time in the EMP itself...
    If there is a large concentration of metal ( mobile homes for instance) or wires, or steel beams, and such hold the "charge" in place as it slowly dissipates or bleeds off. Then, you have the ionospheric conditions, the height of the burst and the size of the device used.
    Wow, what a nightmare!
    I do know a LOT o fpeople consider that a conex box will syop EMP from causing havoc...We tested this in a 20 ft and a 40 ft conex box with good fitting/closing doors. It didn't work at all. I guess it may also depend on what the radio frequencies being used for testing, to determine the best to evaluate the situation.
    I'm not sure what it would take anymore.....I'm just hoping my cages work!
    So far, everything we threw at them, nothing managed to penetrate!
    Now, the "point" made in the video is very good...it clearly shows that some radio waves of varied frequencies do penetrate. ( the cage was not perfectly sealed, due to the doorway not being tightly closed on the frame) But, here is the "catch"..
    The am/fm radio was shielded from receiving outside transmissions, but his microphone was not stopped from transmitting thru it! Also, the energy field was delivered by a Van deGraf (generator) which is of the "STATIC" type of energy, NOT, the "electro-magnetic" type that is released from an EMP!
    Hence the term EMP = electromagnetic pulse.
    Due to the nearly impossible task of testing this pulse, without a true discharge from a nuclear device...Clearly not what we want to be testing in our backyards!
  3. dragonfly

    dragonfly Monkey+++

    5/2009 post:
    <HR style="BACKGROUND-COLOR: #d1d1e1; COLOR: #d1d1e1" SIZE=1>
    <!-- google_ad_section_start -->Last but not least, an "oldie but a goodie"....

    Copyright (C) Duncan Long 1989. All rights reserved.


    EMP. The letters spell burnt out computers and other electrical systemsand perhaps even a return to the dark ages if it were to mark the beginning ofa nuclear war. But it doesn't need to be that way. Once you understand EMP,you can take a few simple precautions to protect yourself and equipment fromit. In fact, you can enjoy much of the "high tech" life style you've comeaccustomed to even after the use of a nuclear device has been used by ter-rorists--or there is an all-out WWIII. EMP (Electro-Magnetic Pulse), also sometimes known as "NEMP" (NuclearElectromagnetic Pulse), was kept secret from the public for a long time and wasfirst discovered more or less by accident when US Military tests of nuclearweapons started knocking out phone banks and other equipment miles from groundzero. EMP is no longer "top secret" but information about it is still a littlesketchy and hard to come by. Adding to the problems is the fact that itseffects are hard to predict; even electronics designers have to test theirequipment in powerful EMP simulators before they can be sure it is reallycapable of with standing the effect. EMP occurs with all nuclear explosions. With smaller explosions theeffects are less pronounced. Nuclear bursts close to the ground are dampenedby the earth so that EMP effects are more or less confined to the region of theblast and heat wave. But EMP becomes more pronounced and wide spread as thesize and altitude of a nuclear blast is increased since the ground; of thesetwo, altitude is the quickest way to produce greater EMP effects. As a nucleardevice is exploded higher up, the earth soaks up fewer of the free electronsproduced before they can travel some distance. The most "enhanced" EMP effects would occur if a nuclear weapon wereexploded in space, outside the Earth's atmosphere. In such a case, the gammaradiation released during the flash cycle of the weapon would react with theupper layer of the earth's atmosphere and strip electrons free from the airmolecules, producing electromagnetic radiation similar to broad-band radiowaves (10 kHz-100 MHz) in the process. (therein lies one of the big concerns and problems, the varied wave lengths!-Bill) These electrons would follow theearth's magnetic field and quickly circle toward the ground where they would befinally dampened. (To add to the confusion, we now have two more EMP terms: "Surface EMP" or "SEMP" which refers to ground bursts with limited-rangeeffects and "High-altitude EMP" or "HEMP" which is the term used for a nucleardetonation creating large amounts of EMP.) Tactically, a space-based nuclear attack has a lot going for it; themagnetic field of the earth tends to spread out EMP so much that just one 20-MTbomb exploded at an altitude of 200 miles could--in theory--blanket thecontinental US with the effects of EMP. It's believed that the electricalsurge of the EMP from such an explosion would be strong enough to knock outmuch of the civilian electrical equipment over the whole country. Certainlythis is a lot of "bang for the buck" and it would be foolish to think that anuclear attack would be launched without taking advantage of the confusion ahigh-altitude explosion could create. Ditto with its use by terrorists shouldthe technology to get such payloads into space become readily available tosmaller countries and groups. But there's no need for you to go back to the stone age if a nuclear waroccurs. It is possible to avoid much of the EMP damage that could be done toelectrical equipment--including the computer that brought this article to you--with just a few simple precautions. First of all, it's necessary to get rid of a few erroneous facts, however. One mistaken idea is that EMP is like a powerful bolt of lightning. Whilethe two are alike in their end results--burning out electrical equipment withintense electronic surges--EMP is actually more akin to a super-powerful radiowave. Thus, strategies based on using lightning arrestors or lightning-rodgrounding techniques are destined to failure in protecting equipment from EMP. Another false concept is that EMP "out of the blue" will fry your brainand/or body the way lightning strikes do. In the levels created by a nuclearweapon, it would not pose a health hazard to plants, animals, or man PROVIDEDit isn't concentrated.
    EMP can be concentrated. That could happen if it were "pulled in" by a stretch of metal. If thishappened, EMP would be dangerous to living things. It could become concen-trated by metal girders, large stretches of wiring (including telephone lines),long antennas, or similar set ups. So--if a nuclear war were in the offing--you'd do well to avoid being very close to such concentrations. (A safedistance for nuclear-generated EMP would be at least 8 feet from such stretchesof metal.)


    (Think of Conex boxes in the 20 ft + lengths as well as any MOBILE HOMES in the 60 to 70 ft lengths, and just think of the electrical wiring in the walls on BOTH sides!- Bill)
    This concentration of EMP by metal wiring is one reason that most e-lectrical equipment and telephones would be destroyed by the electrical surge. It isn't that the equipment itself is really all that sensitive, but that thesurge would be so concentrated that nothing working on low levels of electric-ity would survive.
    Protecting electrical equipment is simple if it can be unplugged from AC outlets, phone systems, or long antennas. But that assumes that you won't beusing it when the EMP strikes.
    That isn't all that practical and--if a nuclearwar were drawn out or an attack occurred in waves spread over hours or days--you'd have to either risk damage to equipment or do without it until things had settled down for sure.
    One simple solution is to use battery-operated equipment which has cordsor antennas of only 30 inches or less in length.
    This short stretch of metalputs the device within the troughs of the nuclear-generated EMP wave and willkeep the equipment from getting a damaging concentration of electrons.
    Provided the equipment isn't operated close to some other metal object (i.e.,within 8 feet of a metal girder, telephone line, etc.), it should survive without any other precautions being taken with it. If you don't want to buy a wealth of batteries for every appliance you ownor use a radio set up with longer than 30-inch antenna, then you'll need to use equipment that is "hardened" against EMP.
    The trick is that it must REALLY be hardened from the real thing, not just EMP-proof on paper.
    This isn't all that easy; the National Academy of Sciences recently stated that tailored hardening is "not only deceptively difficult, but also very poorly understood by the defense-electronics community." Even the US Military has equipment which might not survive a nuclear attack, even though it is designed to do just that.
    That said, there are some methods which will help to protect circuits from EMP and give you an edge if you must operate ham radios or the like when a nuclear attack occurs.
    Design considerations include the use of tree formation circuits (rather than standard loop formations); the use of induction shielding around components; the use of self-contained battery packs; the use of loop antennas; and (with solid-state components) the use of Zener diodes. These design elements can eliminate the chance an EMP surge from power lines or long antennas damaging your equipment.
    Another useful strategy is to use grounding wires for each separate instrument which is coupled into a system so that EMP has more paths to take in grounding itself. A new device which may soon be on the market holds promise in allowing electronic equipment to be EMP hardened. Called the "Ovonic threshold device",it has been created by Energy Conversion Devices of Troy, MI. The Ovonic threshold device is a solid-state switch capable of quickly opening a path to ground when a circuit receives a massive surge of EMP. Use of this or asimilar device would assure survival of equipment during a massive surge ofelectricity. Some electrical equipment is innately EMP-resistant. This includes large electric motors, vacuum tube equipment, electrical generators, trans-formers, relays, and the like. These might even survive a massive surge of EMP and would likely to survive if a few of the above precautions were taking in their design and deployment.
    At the other end of the scale of EMP resistance are some really sensitive electrical parts.
    These include IC circuits, microwave transistors, and FieldEffect Transistors (FET's). If you have electrical equipment with such com-ponents, it must be very well protected if it is to survive EMP.

    One "survival system" for such sensitive equipment is the Faraday box. A Faraday box is simply a metal box designed to divert and soak up the EMP. If the object placed in the box is insulated from the inside surface of the box, it will not be effected by the EMP traveling around the outside metal surface of the box. The Faraday box simple and cheap and often provides more protection to electrical components than "hardening" through circuit designs which can't be (or haven't been) adequately tested. Many containers are suitable for make-shift Faraday boxes: cake boxes, ammunition containers, metal filing cabinets, etc., etc., can all be used. Despite what you may have read or heard, these boxes do NOT have to be air-tight due to the long wave length of EMP; boxes can be made of wire screen or other porous metal.
    The only two requirements for protection with a Faraday box are: (1) the equipment inside the box does NOT touch the metal container (plastic, wadded paper, or cardboard can all be used to insulate it from the metal) and (2) the metal shield is continuous without any gaps between pieces or extra-large holesin it.
    Grounding a Faraday box is NOT absolutely necessary, and in some cases actually may be less than ideal. While EMP and lightning aren't the "same animal", a good example of how lack of grounding is a plus can be seen with some types of lightning strikes. Take, for example, a lightning strike on a flying air-plane. The strike doesn't fry the plane's occupants because the metal shell of the plane is a Faraday box of sorts. Even though the plane, high over the earth, isn't grounded it will sustain little damage. In this case, much the same is true of small Faraday cages and EMP. Consequently, storage of equipment in Faraday boxes on wooden shelves or the like does NOT necessarily require that everything be grounded. (One note: theoretically non-grounded boxes might hold a slight charge of electricity; take some time and care before handling ungrounded boxes following a nuclear attack.)
    The thickness of the metal shield around the Faraday box isn't of much concern, either.
    This makes it possible to build protection "on the cheap" by simply using the cardboard packing box that equipment comes in along with aluminum foil. Just wrap the box with the aluminum foil (other metal foil or metal screen will also work); tape the foil in place and you're done. Provided it is kept dry, the cardboard will insulate the gear inside it from the foil placing the foil-wrapped box inside a larger cardboard box is also wise to be sure the foil isn't accidentally ripped anywhere.
    The result is an "instant" Faraday box with your equipment safely stored inside, ready for use following a nuclear war.
    Copper or aluminum foil can help you insulate a whole room from EMP as well. Just paper the wall, ceiling and floor with metal foil. Ideally thefloor is then covered with a false floor of wood or with heavy carpeting to insulate everything and everyone inside from the shield (and EMP). The only catch to this is that care must be taken NOT to allow electrical wiring connections to pierce the foil shield (i.e., no AC powered equipment or radio antennas can come into the room from outside). Care must also be taken that the door is covered with foil AND electrically connected to the shield with a wire and screws or some similar set up.
    Many government civil defense shelters are now said to have gotten the Faraday box, "foil" treatment. These shelters are covered inside with metal foil and have metal screens which cover all air vents and are connected to the metal foil. Some of these shelters probably make use of new optical fiber systems--protected by plastic pipe--to "connect" communications gear inside the room to the "outside world" without creating a conduit for EMP energy to enter the shelter. Another "myth" that seems to have grown up with information on EMP is that nearly all cars and trucks would be "knocked out" by EMP. This seems logical,but is one of those cases where "real world" experiments contradict theoretical answers and I'm afraid this is the case with cars and EMP.
    According to sources working at Oak Ridge National Laboratory, cars have proven to be resistant to EMP in actual tests using nuclear weapons as well as during more recent tests (with newer cars) with the US Military's EMP simulators. One reason for the ability of a car to resist EMP lies in the fact that its metal body is "insulated" by its rubber tires from the ground. This creates a Faraday cage of sorts. (Drawing on the analogy of EMP being similar to lightning, it is interesting to note that cases of lightning striking and damaging cars is almost non-existent; this apparently carries over to EMP effects on vehicles as well.)
    Although Faraday boxes are generally made so that what is inside doesn't touch the box's outer metal shield (and this is especially important for the do-it-yourselfer since it is easy to inadvertently ground the Faraday box--say by putting the box on metal shelving sitting on a concrete floor), in the case of the car the "grounded" wiring is grounded only to the battery. In practice, the entire system is not grounded in the traditional electrical wiring sense of actually making contact to the earth at some point in its circuitry. Rather the car is sitting on insulators made of rubber. It is important to note that cars are NOT 100 percent EMP proof; some cars will most certainly be effected, especially those with fiberglass bodies or located near large stretches of metal. (I suspect, too, that recent cars with a high percentage of IC circuitry might also be more susceptible to EMP effects.) The bottom line is that all vehicles probably won't be knocked out by EMP.
    But the prudent survivalist should make a few contingency plans "just incase" his car (and other electrical equipment) does not survive the effects of EMP. Discovering that you have one of the few cars knocked out would not be agood way to start the onset of terrorist attack or nuclear war. Most susceptable to EMP damage would be cars with a lot of IC circuits orother "computers" to control essential changes in the engine. The very prudent may wish to buy spare electronic ignition parts and keep them a car truck, (perhaps inside a Faraday box). But it seems probable that many vehicles WILL be working following the start of a nuclear war even if no precautions have been taken with them.
    One area of concern are explosives connected to electrical discharge wiring or designed to be set off by other electric devices. These might be set off by an EMP surge. While most citizens don't have access to such equipment, claymore mines and other explosives would be very dangerous to be around at the start of a nuclear war, if they weren't carefully stored away in a Faraday box. Ammunition, mines, grenades and the like in large quantities might be prone to damage or explosion by EMP, but in general aren't all that sensitive to EMP. A major area of concern when it comes to EMP is nuclear reactors locatedi n the US. Unfortunately, a little-known Federal dictum prohibits the NRC from requiring power plants to withstand the effects of a nuclear war. This means that, in the event of a nuclear war, many nuclear reactors' control systems might well be damaged by an EMP surge. In such a case, the core-cooling controls might become inoperable and a core melt down and breaching of the containment vessel by radioactive materials into the surrounding area might well result. (If you were needing a reason not to live down wind from a nuclear reactor, this is it.) Provided you're not next door to a nuclear power plant, most of the illeffects of EMP can be over come. EMP, like nuclear blasts and fallout, can besurvived if you have the know how and take a few precautions before hand. And that would be worth a lot, wouldn't it?

    Read more: http://www.survivalmonkey.com/forum...75-emp-mystery-revisited-2.html#ixzz0k7yLVItK
  4. cpr_metro

    cpr_metro Monkey+

    You might be able to pick up a shielded room cheap. They are made by companies like Lindgren and Universal Shielding to name a few. I have first hand experience with both. The Lindgren are the best since they are modular, Super easy to erect and double shielded. They use a mesh screen.

    Universal Shielding rooms are a real pain in the ass to assemble and are like bomb shelters. THey use solid wall panels that weigh a ton.

    Ever think of using an oversized microwave oven to store a laptop??
    The theory is that if they don't let microwaves OUT they won't let them in.
    In theory, if microwaves are highy attenuated, the performance of such an oven
    should be even better on the lower freq. range.
  5. dragonfly

    dragonfly Monkey+++

    I'm still mystified about the companies that make those sheets out of silver thread! That's got to cost a few pennies, and I can't imagine having to clean them, much less have one over myself!
  6. -06

    -06 Monkey+++

    Seems that a great ground is the key to discharging the surge. We have a few spare parts isolated in a box and actually pegged to the earth. The diesel and old Jeep Wagoneer are the only vehicles I am concerned about keeping able to travel.
  7. James McKinley

    James McKinley Monkey+

    I've seen high powered AM radio stations in the Middle East use 2 foot thick solid copper to shield the antenna tuning unit and other equipment so it wouldn't interfere with their equipment. I can't say I'd be surprised by what people choose to make a faraday cage out of.
  8. Country_boy

    Country_boy Monkey+

    Why would you shield an antenna tuning unit? Most here in the US are in wood structures. 2' of copper wouldn't change the level , the ATU will radiate just fine. You mightwant to shield the transmitter building, but you don't need copper plate for that, with AM freqs (.5-30 MHz if you include HF short wave stations plus US broadcast bands), reenforced concrete works fine. Ever notice how you loose AM radio stations going under a bridge or tunnel?
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