Faraday cage or Faraday shield

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  • HRDWRK

    ΜΟΛΩΝ ΛΑΒΕ
    Jan 7, 2013
    2,638
    39°43′19.92216″ N
    A Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields. A Faraday shield may be formed by a continuous covering of conductive material, or in the case of a Faraday cage, by a mesh of such materials.

    Has anyone built one or has a "friend" who has?

    I can read about them and see videos, but having someone who has built one and is sure of its ability to protect a few items!

    My thoughts are to store for later just a few needed items Jic!
    I have an older truck without a computer, but it has a coil that I would need inside cage.
    A couple of baofengs!
    Maybe my backup drives for computer, ( I know it may not be needed because the network would be dead?)

    Not sure of anything else needed.. So the cage could be small.
    Thoughts?
     

    JimNorth

    Active Member
    May 4, 2018
    140
    The Cloud
    I would start by analyzing the threat, then thinking about the design. TEMPEST comes to mind. I'm pretty sure many of the defensive techniques are now unclassified and published on the Internet. There's more to it than just Faraday shielding, depending on your application.
     

    K31

    "Part of that Ultra MAGA Crowd"
    MDS Supporter
    Jan 15, 2006
    35,632
    AA county
    How old is the truck?

    I think a gun safe will probably block EMP. Of course having a power cable for lights or a goldenrod may bring some current inside. And discussed ad nauseam before here, electronic locks will need some shielding but I think a pie plate with some rare earth magnets epoxied to it would solve that issue.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    Faraday cages are not rocket science.

    They are basically a grounded conductive enclosure.

    Mesh works, but the mesh openings will determine what frequencies will be blocked or passed. The larger the mesh openings, the lower the frequencies that will be allowed in.

    Big thing is, it needs to be grounded. There is some protection without grounding, but best protection requires good grounding.

    And from my ham radio, for higher frequencies, grounding should be larger diameter. My ground conductor for my ham shack uses AC tubing, not wire.
     

    mac1_131

    MSI Executive Member
    MDS Supporter
    Jan 31, 2009
    3,280
    A galvanized trash can is easy, cheap and quite functional.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,673
    Start with a dead microwave.

    This. To OP, you’d need to store the entire computer in it. An EMP will fry any small electronics.

    There are two different things to worry about, EMP which produces a current based upon the length of the conductor perpendicular to the pulse. Very small conductors will be fried. It doesn’t introduce currents of thousands of volts. But small conductors and electronics can’t handle tens or hundreds of volts.

    CME events produce magnetic field changes high also produce currents in conductors, but it is largely based on the length of the conductor. It takes conductors miles long to produce meaningful currents and won’t impact small conductors (might still cause computers to error out or shut down, but extremely unlikely
    to cause damage or even errors).

    That’ll fry transformers, transmission lines and things connected to the grid depending on breakers and fuses acting fast enough. But because it is a voltage overload, not a current overload, breakers won’t work well.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,673
    Would a mylar bag work for say a handful of flashlights and a solar charger?

    Depends.

    As pointed out, grounding provides the most protection. Significantly more than not being grounded.

    That said, it depends on the exposure. Within the blast zone of a nuke, but physically protected it might protect what is in it. Outside the physical blast zone, it would certainly provide protection if still close enough to see EMP effects. Though for a ground or low air blast, EMP is primarily going to be within the physical blast zone. Outside it’ll cause soft errors in computers and stuff (IE reboots, memory errors, etc. not physical damage. Restart the computer and it is fine).

    The real EMP danger is an upper atmosphere detonation where the EMP travels downward. Atmosphere stops and EMP pretty quick (dozen or two miles), but the EMP will basically travel field lines and have less atmosphere to travel through as it isn’t passing horizontal through the thickest part to get to you.

    Why the upper atmospheric test hundreds of miles from Hawaii in the 60s blacked out the big island. Similarly in atmosphere bursts would have a hard time causing similar damage to electronics at a score of miles.
     

    Threeband

    The M1 Does My Talking
    MDS Supporter
    Dec 30, 2006
    25,231
    Carroll County
    Start with a dead microwave.

    I just retried a test I've run before.

    I stuck my phone in the microwave and called myself from a different phone.

    The microwave did not block the signal: the call went through.


    I am not an electrical engineer. What does this tell us about microwave ovens as ready-made Faraday cages?
     

    dblas

    Past President, MSI
    MDS Supporter
    Apr 6, 2011
    13,087
    I just retried a test I've run before.

    I stuck my phone in the microwave and called myself from a different phone.

    The microwave did not block the signal: the call went through.


    I am not an electrical engineer. What does this tell us about microwave ovens as ready-made Faraday cages?

    Most microwaves have some inherent leakage, but most electrical waves generated y either an EMP or a solar flare are not in the GHz range like your phone call, or the microwaves used by the TWT in the microwave.

    That is why a microwave is a good, simple starting point.
     

    Bolts Rock

    Living in Free America!
    Apr 8, 2012
    6,123
    Northern Alabama
    I just retried a test I've run before.

    I stuck my phone in the microwave and called myself from a different phone.

    The microwave did not block the signal: the call went through.


    I am not an electrical engineer. What does this tell us about microwave ovens as ready-made Faraday cages?

    It illustrates what a slot antenna is. The only 100% sure Faraday Cage is a grounded, solid shield with all openings sealed by welding, soldering, conductive epoxy, mechanical layering and crimping, etc. You can achieve home brewed by using several layers of lead foil and then folding and crimping the edges and grounding it.
     

    G O B

    Ultimate Member
    Nov 17, 2007
    1,940
    Cen TX
    Get a cookie tin. Solder a wire (16-18ga stranded) from the top to the bottom leave room to take the top off, solder a longer wire to the bottom, connect that wire to the GROUNDING conductor (U shaped) green terminal of a replacement 3 prong plug. NOTHING goes on the copper or silver screws. Plug it in and put your devices in the tin, put the top on.
     

    TexasBob

    Another day in Paradise
    MDS Supporter
    Oct 25, 2012
    2,485
    Space Coast
    Back in the late 70's I was stationed in up state New York, my "Shop" was in a old "PMEL" building a Precision measurement equipment laboratory, The whole building was in a Faraday Cage. We had to run an Antenna out the widows to get a Radio to work which brake the rules of a Faraday cage.

    The building was wrapped in copper screen, walls, windows, ceiling, floor etc that was grounded every few feet to a near zero ohm earth ground. All incoming power lines had some high end filters and were shielded. It was only place I had every felt safe from Lighting storms or was pesky mind probing Aliens.

    For those in the security world SCIF's have a Faraday type RFI shielding. :cool:
     

    welder516

    Deplorable Welder
    MDS Supporter
    Jun 8, 2013
    27,297
    Underground Bunker
    I have done many complete buildings back in the 70's with wire mesh welded to the building , now they have foils to put on buildings a building in College Park has foil everywhere
     

    HRDWRK

    ΜΟΛΩΝ ΛΑΒΕ
    Jan 7, 2013
    2,638
    39°43′19.92216″ N
    How old is the truck?

    I think a gun safe will probably block EMP. Of course having a power cable for lights or a goldenrod may bring some current inside. And discussed ad nauseam before here, electronic locks will need some shielding but I think a pie plate with some rare earth magnets epoxied to it would solve that issue.

    1981 K20
     

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