Posted: 1/16/2011 6:56:13 PM EDT
| For all you gurus out there, would any electronic equipment enclosed in a Faraday cage sustain a blast from an EMP, not a direct one but if the cage and the device were within the blast radius of the EMP would the electronic equipment survive it? |
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If I was concerned about EMP I would use a solid shield - not the traditional Faraday mesh shield that was originally intended for EMI/RFI mitigation. It is important to note that you can't just slap one together - you need to know what you are doing, the implications of materials choices, how to join pieces, how to design a door, how to design and build penetrations etc etc etc.
99.8% of Arfcom members have never even SEEN a shield - let alone truly understand how to design and build one. The same number is roughly true regarding self-appointed EMP authorities here with zero minutes of experience working with EMP mitigation. So before you take advice from the armchair experts - ask about their experience (and I don't mean reading survivalist websites). |
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In the ideal case (i.e. a cage that's constructed of a material with zero resistance), I'd say maybe. But since no such thing exists, and since the field strength involved is so high, I would think it might fail. You also have to consider the xray, gamma ray, and other ionizing radiation, for which a simple cage offers no protection unless it contains a very thick layer of lead or equivalent. Any modern IC's would be destroyed or wounded unless they were rad-hardened.
But considering that we have hardened equipment on SAC bombers etc, I guess the military has tested this concept and it must work to some degree. |
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For all you gurus out there, would any electronic equipment enclosed in a Faraday cage sustain a blast from an EMP, not a direct one but if the cage and the device were within the blast radius of the EMP would the electronic equipment survive it? in principle, yes. an effective Faraday cage, however, is not trivial to construct. some of the next 25 posters will regale you with stories of old microwave ovens, or ammo boxes, but this type of approach will only provide a false confidence. btw, "blast radius" is not the correct term here, as the radius of effect can be far, far greater than the actual blast. google Compton effect and see also http://en.wikipedia.org/wiki/Electromagnetic_pulse ar-jedi |
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If I was concerned about EMP I would use a solid shield - not the traditional Faraday mesh shield that was originally intended for EMI/RFI mitigation. It is important to note that you can't just slap one together - you need to know what you are doing, the implications of materials choices, how to join pieces, how to design a door, how to design and build penetrations etc etc etc. 99.8% of Arfcom members have never even SEEN a shield - let alone truly understand how to design and build one. The same number is roughly true regarding self-appointed EMP authorities here with zero minutes of experience working with EMP mitigation. So before you take advice from the armchair experts - ask about their experience (and I don't mean reading survivalist websites). I'm glad you were here early. |
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Some very interesting and professional responses thank you, what I had in mind was constructing a Faraday cage in a pelican 1495 case to transport my laptop around, just a what if, scenario I don't know if I'll ever get around to doing it or whether it will be effective and work that's why I wanted to get a few opinions of people who know little more on the subject than me.
Also what I had in mind was not a nuclear detonation triggering an EMP but the sun giving off a huge CME and causing all sorts of disturbances and damages to electronics, my apologies in advance. -Dep |
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Faraday shielding is fairly easy to construct and effective against realistic E.M.P. (If you don't expect the 10 megaton warhead to go off 500 feet away!)
The kicker though is how to use the device while it is in the shielded area, or knowing when to position the device in the shielded area just before the E.M.P.(s) arrives. Remember in a serious situation there could be more than one. The electric feeds AC and any external antennas or cables are the main pathways of E.M.P. damage / destruction that gather the E.M.P. energy and then route it right into the heart of the electronics. ZAP!!! |
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But since no such thing exists, and since the field strength involved is so high, I would think it might fail. shielding homogeneity can be mechanically and electrically implemented such that it provides >100dB of shielding from DC to a couple of GHz –– which means that even KV/m E-fields are not going to have any effects on contained equipment. Quoted:
You also have to consider the xray, gamma ray, and other ionizing radiation, for which a cage offers no protection. Any modern IC's would be destroyed or wounded unless they were rad-hardened. an EMP event does not result in ionizing radiation. (note, we are talking here about EMP effects at a practical range from the initiating/inducing apparatus) ar-jedi |
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Some very interesting and professional responses thank you, what I had in mind was constructing a Faraday cage in a pelican 1495 case to transport my laptop around, just a what if, scenario I don't know if I'll ever get around to doing it or whether it will be effective and work that's why I wanted to get a few opinions of people who know little more on the subject than me. -Dep i doubt your laptop, assuming there are no connected metallic cables (including power, LAN, external mouse, etc), will be affected whatsoever by an EMP. ar-jedi 
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But since no such thing exists, and since the field strength involved is so high, I would think it might fail. shielding homogeneity can be mechanically and electrically implemented such that it provides >100dB of shielding from DC to a couple of GHz –– which means that even KV/m E-fields are not going to have any effects on contained equipment. Quoted:
You also have to consider the xray, gamma ray, and other ionizing radiation, for which a cage offers no protection. Any modern IC's would be destroyed or wounded unless they were rad-hardened. an EMP event does not result in ionizing radiation. (note, we are talking here about EMP effects at a practical range from the initiating/inducing apparatus) ar-jedi ar-jedi: Would a gun safe work as a faraday cage? |
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If it is properly constructed and grounded......yes. a Faraday cage need not be grounded. It is better if it is provided that it has its own ground and not one shared with other wiring or devices. define "ground" in the presence of high field strengths with fast risetimes. 
then again, you don't need one. ar-jedi |
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But since no such thing exists, and since the field strength involved is so high, I would think it might fail. shielding homogeneity can be mechanically and electrically implemented such that it provides >100dB of shielding from DC to a couple of GHz –– which means that even KV/m E-fields are not going to have any effects on contained equipment. Quoted:
You also have to consider the xray, gamma ray, and other ionizing radiation, for which a cage offers no protection. Any modern IC's would be destroyed or wounded unless they were rad-hardened. an EMP event does not result in ionizing radiation. (note, we are talking here about EMP effects at a practical range from the initiating/inducing apparatus) ar-jedi OK, I'm no expert on nukes, but the first site I googled says this: A nuclear detonation creates a severe environment including blast, thermal pulse, neutrons, x- and gamma-rays, radiation, electromagnetic pulse (EMP), and ionization of the upper atmosphere. http://www.fas.org/nuke/intro/nuke/effects.htm If you're trying to say that at long range the ionizing radiation is weak, then I guess I agree it's not an issue. . |
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Would a gun safe work as a faraday cage? a safe or an RSC?
this is a tough question because it is so very dependent on the safe construction and ultimately how bad the seams "leak" RF energy. you can have a door that is 2 feet thick but the gap between the door and surrounding frame becomes what is called a "slot antenna" and re-radiates RF energy into the inside of the safe. it is *not* trivial to evaluate this in a non-lab setting; some folks will state "well, my cell phone doesn't ring when i put it inside my safe" –– but that is an invalid test in 7 different directions. a properly shielded RF enclosure uses conductive fingers or metallic gasketing along the door jamb to provide a continuous conductive seal around the door frame. you don't get this with a gun safe designed to keep thieves at bay for 15 minutes. ar-jedi ETA 
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