Faraday Solutions

Discussion in 'General Survival and Preparedness' started by Hispeedal2, Mar 17, 2011.


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  1. arleigh

    arleigh Goophy monkey

    I have several LED lights in storage especially for the flash lights and other out side lighting . to day I picked up some Mylar zip loc bags I am going to use as a secondary back up to the more sensitive electronics such as ham radios and other transmitter/receiver devices .
    Until it happens there is no knowing what the intensity of the event will reveal, but I figure that having redundant systems can't hurt.
     
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  2. Ura-Ki

    Ura-Ki Grudge Monkey

    One step better is Lead lining of what ever bag or storage device you choose to use! I prefer to use anti static discharge mylar bags on the inside with discharge safe foam backing, then placed inside a lead lined and sealed box! For out door electronics that would be needed after an "event" copper wire wrapping a device and securing it inside a Gold mylar space blanket should save your devices! I'm thinking Radar/sonar sets for boat's and or light aircraft!
     
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  3. T. Riley

    T. Riley Monkey+++ Site Supporter++

    Can anyone tell be an valid effective test for a home built Faraday cage?Something I have laying around the house.
     
  4. Tempstar

    Tempstar Praeclarum Site Supporter+

    I just can't not comment here. I have worked on projects that needed total shielding from outside RF and other electromagnetic radiation. In all cases, including one that semi-trailers were pulled into, the rooms were made of steel with steel doors that had copper brushes on them to facilitate a better seal. They were NOT grounded but rather sat upon rubber isolators and ALL had megohm meters measuring ohms to ground (they wanted none). A sealed metal box with no ground path becomes invisible to RF, while a grounded steel box allows RF currents to seek a path to ground, thus energizing the skin.
    A great test is to put a radio or cell phone in your container of choice and see if it receives anything.
    An old microwave will only protect against ~2.4 ghz, the operating frequency
    Devices that are turned off will still be damaged due to the currents generated in the circuits themselves and the onslaught of the high currents punching holes in the substrate of silicone devices like transistors.
    EMP effects are logarithmic and decrease exponentially the further the device is from the source.
     
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  5. chimo

    chimo the few, the proud, the jarhead monkey crowd

    IMO you gotta either be totally isolated (very high resistance) from ground or have a good (zero resistance) common ground. Anything in between can cause unintended ground loops that may cause unintended consequences to the contents of the enclosure (heat, for example).
     
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  6. arleigh

    arleigh Goophy monkey

    Fortunately the EMP travels in a wave not a lightening bolt. it is a magnetic wave till it hits metal and a direction of flow is created.
    Some speculate that what is not grounded will maintain a capassitive charge till it is grounded .
    A ground may actually attract more energy .
    Half or more of a lightening charge comes from the ground ,but in this case the magnetic/electric charge does not exist till it hits metal.
    I postulate that large antenna like power lines and wired homes will have the most electrical influence much like an ignition coil.
    Smaller things like boxes are not spread out like wire and are a smaller target so to speak. Home fires are very likely .(More likely due to CME, but possible )
    In Albania you can see the Iron curtain Russia put up, to isolate the people form the rest of the world , it not a solid steel wall it's just a large wire antenna farm basically that's really tall.
    Now if that thing is hit with an EMP there should be a real light show .
     
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  7. Ura-Ki

    Ura-Ki Grudge Monkey

    Complex circuits would likely be the only devices effected due to the sensitivity and the intricacy. My research has shown that simple electrical systems should remain intact during an event! Even batteries and coils should servive. No one really knows, we haven't ever had a large enough test to show us! I follow what the U.S. Navy does to protect vital systems, and I also include circuit breakers in line to shut off and to isolate from any outside source of power surge be EMP directly, or a stored/Static surge as a result! Shielded circuits are also the best bet!!! Another thing I discovered is what the Aircraft Manufactures do, Build in discharge antenna to provide a fixed point of discharge for any and all potential event! This is proven to work very well at protecting against Lightning strikes! I saw an F-16 that got hit 11 times in flight, and other then some burned paint and composites at the antenna area, there was nothing wrong with it and it was ready to fly again with a re fuel and re arm!
     
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  8. Tempstar

    Tempstar Praeclarum Site Supporter+

    Remember basic physics guys. The energy will always flow to a point of lesser concentration. Grounding in an attempt to shield against EMP will just allow a potential path for the current to flow. Just like the F-16 Ura-Ki talked about, the energy can flow on the skin and continue on seeking a lesser concentration. However, EMP does not carry the instantaneous currents that lightning does, but comes in 3 distinct waves of varying strength.
     
  9. arleigh

    arleigh Goophy monkey

    Can you explain the 3 different wave lengths /strengths please ?
     
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  10. ghrit

    ghrit Bad company Administrator Founding Member

    Let me see if I can help a little here. "Nature abhors a vacuum" and will always move to fill the MT space. Energy will always move from a level of higher potential to a lower level. It doesn't care in the least whether it does harm or does useful work on the way, but if there's a path, it goes. In the case of lightning, the discharge follows a path from higher electrical potential to one that is lower, usually ground, and it will do whatever it needs to do to get there, from simply ionizing and heating the air it passes thru to blasting a house that is in the way. The heat and blast are work that isn't exactly desirable, but fall in the engineering definition of work. (If only we could readily harness lightning to charge batteries or more likely HUGE capacitors, we'd be set for a while without commercial power.)

    Lightning strikes aircraft rather often. What we do not see is that the lightning charges the aircraft skin to a higher potential than it had before. Further, what we also do not see is how that charge is dissipated, and I can't tell you for sure how. But it must, or that static jolt you get when rubbing a carpet would be a mere sample of what would hit you when you deplaned and knocked your eyes crossed. (I suspect that the charge dribbles away into the air as the plane flies along. Remember that static charges will build up on the aircraft from friction as it slithers thru the air anyway. I also suspect that ground service folks attach a ground strap to the aircraft before deplaning starts.)

    And Tempstar is right, EMP does not carry instantaneous current. In fact, EMP carries no current at all. By the nature of it, the magnetic pulse induces current in any handy nearby conductor. (And, to go a bit further, the electrical component induces magnetism in susceptible materials. But not in this case, because the electrical component has to flow, and the duration of EMP is too short for much in the way of magnetism to be induced. Or so it seems to me.)

    Addressing EMP (or HEMP) shielding: Assume a continuous conductive shield, closed on all sides, faces, top, bottom and corners and UNGROUNDED. There is no way for an EMP wave to enter the container. So, it will magnetize and absorb a charge on it's surface. Oddly enough, both magnetic fields and electrical field will accumulate on the EXTERIOR only because they will each have a common charge, positive or negative (or north and south in the case of magnetism. Bear in mind that charges are particulate in the form of electrons, or the absence thereof.) Such is the case, like charges repel each other, therefore will not penetrate, but sit on the outside trying to get away from each other. Now, ground your box, and the charge accumulated will find ground since it is at a lower potential than while on the box. Or just let it sit there, the charge will dissipate on it's own thru the air after a while.

    Sorry I cannot help with the three waves question, that's a new one on me. Now, if we are talking nuclear bombs, there are a shit load of different things that will get chez vous, and I don't see limiting it to three.
     
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  11. Tempstar

    Tempstar Praeclarum Site Supporter+

    Yeah Ghrit, that's what I said....
     
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  12. arleigh

    arleigh Goophy monkey

    Something to remember is that, it is likely that there are no public radio stations that are hardened against EMP,which leaves military and radio amatures .
     
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  13. T. Riley

    T. Riley Monkey+++ Site Supporter++

    NOAA
     
  14. oil pan 4

    oil pan 4 Monkey+++

  15. fedorthedog

    fedorthedog Monkey+++

    Bruce would using a grounded plug and only wiring to the ground circuit then attaching to the safe complete the necessary ground
     
  16. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    In normal House Wiring, likely NO.... It would dissipate "some" of an EMP Pulse, but certainly NOT All of the Pulse. Also it will very much depend on the Distance, from the Event, and the Height above Ground, that the Box was, and the WireFeet from the Grounded Plug to the actual Grounding Rod or source of Ground..... Low Impedance means very short Ground Distance, and BIG Wire.... Another thing that needs to be understood, is that the contents of the BOX needs to be insulated from the inside of Metal BOX, itself.... Much of the Energy of the Pulse travels as a Surface Effect, over the Earth Ground. SO the higher, and more distance (Resistance) between Earth Ground and the Cage, places the Cage in line for More Energy to try and dissipate. Much better to put you cage Under the Surface of the EarthGround, by a few feet. In this way the contents only see the energy that is Directly from the Event itself, and NOT from the Pulse Wave that travels as a Surface Effect Wave, which passes horizontally above the EarthGround. Inverse Square Law applies to Energy Dissipation, and Induced Energy coupled on to the Cage.
     
  17. ghrit

    ghrit Bad company Administrator Founding Member

    Exactly. Being a surface effect is what it allows the charge to slither thru gaps in the metal enclosure, and why HEMP shielding must be continuous. To say, if there is a gap, the inside surfaces are RIGHT DAMN NOW at the same potential as the outer surface and you might as well leave the sensitive things on top of the cabinet.
     
  18. fedorthedog

    fedorthedog Monkey+++

    So grounded in a basement room would be close to an ideal?
     
  19. BTPost

    BTPost Stumpy Old Fart Snow Monkey Moderator

    Well, Grounded, in a Metal Box, that had all it's seams RF Tight, up thru, Oh say, 60Ghz.... and in your Basement//// would be ideal...
     
  20. oil pan 4

    oil pan 4 Monkey+++

    Problem is in your "house ground" is the neutral and ground are bonded at the main panel.
    Then that neutral in your main panel extends out to the utility, at the very least back to the substation and likely all the way back to the power plant.
    Then installing a proper ground may not be that easy depending on where you are and how dry the ground is.
     
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