Faraday cage or Faraday shield

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  • brownspotz

    Ultimate Member
    Oct 22, 2013
    1,765
    you need tinfoil....for your head.
     

    ED302

    Member
    Feb 14, 2020
    10
    It really depends on what you are trying to protect, and against what threat. I have seen some of the posts referencing CME events. Those are no danger to anything that you own.

    TEMPEST countermeasures are to protect against eavesdropping, not to protect from an EMP-type nuclear blast.

    As for the EMP blast, it really depends on how close it is. It it is nearby, not sure that reasonable protections will do much for you.
     

    Mark75H

    MD Wear&Carry Instructor
    Industry Partner
    MDS Supporter
    Sep 25, 2011
    17,173
    Outside the Gates
    It really depends on what you are trying to protect, and against what threat. I have seen some of the posts referencing CME events. Those are no danger to anything that you own.

    TEMPEST countermeasures are to protect against eavesdropping, not to protect from an EMP-type nuclear blast.

    As for the EMP blast, it really depends on how close it is. It it is nearby, not sure that reasonable protections will do much for you.

    Facts and logic will get you nowhere
     

    Beskee

    Member
    Feb 14, 2010
    4
    Accokeek
    TEMPEST deals mostly with RF signals. Specs are still classified. NSTISSAM 1-92 is the regulation. NSA forbids sales to non Government/Military. The concept would be if it prevents the signals from coming out, it would protect from signals coming in. I’m not an EE. I’ve worked around it for a while.


    Sent from my iPhone using Tapatalk
     
    These have always fascinated me. I know how they work but it's always cool to see them in action.
    I built a refrigerator sized one in high school for some particularly sensitive theatre equipment but I just can't remember any more details than that (it was some time and many chemicals ago). More recently, my stepdad worked for Verizon in middle-of-nowhere Northern Michigan and his field office was this small building that had beautiful copper weave wall materials (think that fancy homemade paper with irregular copper mesh showing here and there) and it was always fun to watch my cell phone signal completely disappear walking inside.
    It might be fun to make one again just for fun. Would a grounded box lined with a few layers of store tinfoil work for the most part?
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    It really depends on what you are trying to protect, and against what threat. I have seen some of the posts referencing CME events. Those are no danger to anything that you own.

    TEMPEST countermeasures are to protect against eavesdropping, not to protect from an EMP-type nuclear blast.

    As for the EMP blast, it really depends on how close it is. It it is nearby, not sure that reasonable protections will do much for you.

    If you have things plugged in, your stuff is at risk to a CME. It induces a voltage in conductors. The longer, the higher the voltage. Short conductors like in a computer would be micro volts for the most part. Wouldn’t even cause a soft error.

    Building wiring it might be a few volts. Residential power lines you might see dozens of
    Volts. Long distance transmission lines it can be tens of thousands of volts. That’s sufficient to burn out transformers.

    But it carries over to the stuff through the grid. It is still stepped down, but unless it is going through a solid state voltage transformer, the voltage difference will carry over. Some magnetic core transformers will have their core saturated and damaged. Others are going to overheat and be damaged.

    But down stream you might see that voltage spike (most likely), so you might end up seeing your voltage spike from 220/110 to 250-300+/125-150+ volts.

    Depends on where you are, what your grid looks like, how powerful a CME it is, etc. a lot of stuff won’t be damaged by a few second over voltage on the scale of 10-50%. Some things will be, even in just a few seconds.

    Things on solid state transformers are likely fine. Motors would probably be fine for seconds to even possibly a minute or a few minutes (if they don’t over rev and damage themselves). Things like incandescent bulbs, resistance circuits, etc. likely are toast in a few seconds.

    And of course there is the issue of massive parts of the grid going down with destroyed high voltage transformers (and all of the lower voltage ones that are damaged or destroyed).
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    Oh, to add, not that much uses it anymore, but the real issue is going to be all of the phone lines fried and everything connected. The wiring is 40v (48?) but it is very low amperage. It’s thin wiring and can be really long. It isn’t the diameter of the wire, but the length. A few hundred volts added on to a several mile long telephone line is going to burn it. Cable is possibly going to be fried also (same problem). Physical damage to power transmission lines is unlikely.

    Most powerful CME since the Carrington event was in the 1980s IIRC. It destroyed a handful of major transformers and dropped the grid for awhile. Took a few days to fully restore power. It was estimated at 10-30% of the power of the Carrington event (which is estimated at a 1 in 300 year event IIRC).
     

    Docster

    Ultimate Member
    Jul 19, 2010
    9,768
    I built a popcorn tin sized one based on a YouTube video from an electrical engineer who's written several books on the subject. He tested it as much as possible without an actual solar event but explained the theory of why his tests were valid. I find prepper sites on the web the best places to get expert advice and education on technical subjects
     

    photoracer

    Competition Shooter
    Oct 22, 2010
    3,318
    West Virginia
    Might be the old R&D lab of NSA. I don't know exactly where it is but a buddy of mine worked there for many years. I worked at their FANX location at BWI and I am pretty sure that building was also a full Faraday cage.
     

    dblas

    Past President, MSI
    MDS Supporter
    Apr 6, 2011
    13,087
    Might be the old R&D lab of NSA. I don't know exactly where it is but a buddy of mine worked there for many years. I worked at their FANX location at BWI and I am pretty sure that building was also a full Faraday cage.

    Come over to College Park, I can show you exactly where the "toy factory" was. It is currently being used by UMD as a computer sciences build over by College Park airport.
     

    Boom Boom

    Hold my beer. Watch this.
    Jul 16, 2010
    16,834
    Carroll
    Any metal box with a good metal seal will work. For example, use a tin cookie container with a good seal. The kind with a cover that tightly slides on. Or an ammo can. Put your phone in there. The phone is not going to get a signal and will be protected from an EMP, especially if the phone is in a rubber case that isolates the phone body from the inside surfaces of the box.

    The other way is a paper box (shoe boxes work well), tightly wrapped with two layers of commercial-grade (thick) aluminum foil. Do not use generic aluminum foil that tears easily. Using epoxy or spray-on adhesive rated for metal will help.
     

    tjaw

    Member
    Nov 14, 2014
    81
    Monkton, MD.
    Be very conscious of *quallity* in "Faraday" devices...

    I rarely mention brand names, but in this case I will mention one. BlackBag Technolgies is/was an InQtel funded startup at one time. I develop and teach grad-level mobile device forensics in my part-time gig. I have tested several devices for incoming and outgoing signals from a variety of smartphones. There are some very inexpensive, but poor quality "Faraday" devices on the market (by poor, I mean some signals that should be blocked are not). With such devices, someone could be in the land of the False Negative, a pernicious error and state.

    The BlackBag devices have performed well, in my admittedly limited number of experiements.
     

    HRDWRK

    ΜΟΛΩΝ ΛΑΒΕ
    Jan 7, 2013
    2,641
    39°43′19.92216″ N
    I rarely mention brand names, but in this case I will mention one. BlackBag Technolgies is/was an InQtel funded startup at one time. I develop and teach grad-level mobile device forensics in my part-time gig. I have tested several devices for incoming and outgoing signals from a variety of smartphones. There are some very inexpensive, but poor quality "Faraday" devices on the market (by poor, I mean some signals that should be blocked are not). With such devices, someone could be in the land of the False Negative, a pernicious error and state.

    The BlackBag devices have performed well, in my admittedly limited number of experiements.

    Thanks I will check them out!
     

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