The "EMP" mystery revisited...

Discussion in 'General Survival and Preparedness' started by dragonfly, May 28, 2009.


  1. dragonfly

    dragonfly Monkey+++

    I had a couple of phone calls following the movie here; "One Second After".
    Those inquiries were in regards to the factual parts of the movie, (which I have not seen), and just what they do, how they act, and what a person can do to protect their equipment and themselves.

    Then I went to 'survivalblog.com' by 'James Wesley Rawles,' and found this tiny tidbit of info: (in his own words!)
    "just to be safe, when your compact refrigerator is not in use, you should store it in a galvanized steel garbage can (with a tight-fitting lid), to act as a protective Faraday cage."

    Ah, yeah...ok.....
    JWR has missed a small piece of info. here, and he should have been a LOT more precise/specific, and clear about his "posted" statement.

    Just to more specific, I have to add:

    1) Most any "closed" metal "container" will suffice....

    2) The "container" MUST have no openinings larger than 1 cm in any dimension. ( that's effectively stated as being "CLOSED")

    3) Each "container" used must be "grounded" to either a metal (copper or galvanized) water pipe, or at the least, one- 8 Ft. copper-coated, steel grounding rod, made specifically for the purpose of grounding. 7 1/2 foot depth-depending on your soils moisture content, (They won't work well in dry soils or sand!) ( do your 'homework' before proceeding!) (PVC pipes wont work at all.)

    4) The wire/s used to connect the "container/s" to the grounding rod/s, or water pipe/s, should be of a considerably heavier gauge than say a 12-2w/gnd. type electrical house wiring. I suggest either 8 gauge, or better yet, the heavier 6 gauge solid copper. ( or, twist 6 or more of the 12-2 'romex' ground wires into a single wire mass.)

    5) The connections to the rod 'should always be soldered', along with the "specialized" clamps, made for that purpose. (any corrosion will destroy a good ground and solder prevents that oxidation from occurring) ( I also coat mine with 50 year GE silicone following cleaning the soldered areas.) (epoxy works good too!)

    6) The EMP cage/container-Faraday cage MUST be GROUNDED, by way of copper or silver wire, (silver is far too expensive for me!), in such a way as to be able to dissipate the equivalent of a lightning strike, in the area of some 10,000 Kv. without losing it's ground or it's continuity.
    It is imperative that the ground is never broken, nor any holes are allowed to be opened to the exposure. ( That also means: put into the cage/container, what electronic devices you want to keep safe, close it, and leave it there. Don't open it until you are sure that any EMP danger has passed.)

    7) ALL items, inside either an EMP cage/container-Faraday Cage, MUST be INSULATED from the container/cage itself. It has been suggested that there is no less than a 3-4 inch spacing, from any and all sides,top, and bottom, and the items are placed on either a rubber, silicone, or wooden shelf, to insulate them from any metal contact.
    Some people "think" that their Home Depot or Walmart brand, aluminum, yard/storage sheds will work.
    They would, "IF", you were to cover 'all openings' with a fine mesh screen of either brass or aluminum, and ground the sheds properly.
    Remember, there must be NO contact at all, with any elecrical device's, wires, cables, plugs, etc., on the inside, to any wall or flooring, that is NOT made of a non-insulating material. ( best to keep them tied up)
    Those wooden and Plastic sheds just won't work.

    The whole concept, is to make a completed electrical circuit to hold or contain the EMP wave or charge, and send it to ground.

    Now as far as that movie, well it's just a "movie".
    Supposedly, in one scene, the EMP or SOLAR FLARE takes place, and the people are "supposed" to remain in their vehicles, or die?
    Like I said, I haven't seen it!
    In the movie, a man dies, from an EMP like electrical wave that stops his "pacemaker". I can see that!
    IF it has some "micro-circuitry".

    Very few people understand the concept of what an EMP does, or how it acts.
    It's like when you are outside and lightning strikes close, and you feel the hairs stand up on the back of your neck, or, a better scenario: an extremely strong static electricity discharge, as you slide across the vinyl seat of a car, or if you ever got close to high tension poles and held up a fluorescent light bulb in one hand, and watch it light up from the EMP generated from the wires and electrical flow through them.

    Now I seriously doubt, that UNLESS you have a pacemaker or some other type of electrical components inside of your body cavity, or leads into it from any such device, that any EMP would place anyone at risk.
    I have seen sheets, clothes, and mosquito type netting, made to cover peoples beds, in case of an EMP.
    They may have a place, but unless you have a serious medical condition, I sincerely doubt it.

    I have had a few people ask of me how to use an EMP or Faraday Cage, and stiil be able to use their radios, connected to an electrical power supply and connected to their antenna's.
    It cannot be done.
    Period.
    They MUST be isolated, and they must be insulated.
    That is why WE have what is known as redundancy. If 1 is good, 2 is so much better.
    I have four complete sets, consisting of 4 different radios each.
    3 of those "stacks" as I call them, are in separate EMP/Faraday Cages.
    No sense in taking any chances.
    Antennas are generally NOT affected, as they are mostly aluminum tubes and a copper wire coil.
    Coaxial cables are NOT affected at all.
    Solar panels themselves are relatively safe, unless they have some form of a controller or invertor connected.
    Invertors are filled with all sorts of sensitive transistors, etc.
    Want a 24/7 remedy for "constant" radio communications?
    Get any old tube type radio's that runs off 12 volt dc. (ebay?)
    The 1970's "Johnson Courier" 23 channel CB radio was one, but it ran off 110 vac, but it can be easily adapted with a simple invertor to run on 12vdc.
    But, there's that "invertor" thing again!

    But that's all just my opinion, and not much more!
    Bill
     
  2. dbever

    dbever Monkey++

    Thanks for the explanation, I've been feeling like I need to make a faraday cage. 2 quick questions, please -
    1. What about the microwaves? I've found people who say that that absolutely work, and others that say they only work for certain frequencies. I haven't found any source that really seems to pin it down. Also,
    2. What about the jump/thumb drives? Will an EMP affect them also?

    Thanks!
     
  3. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    1) EMP is broad spectrum, that includes microwaves. The finer the mesh in the screen, the better against all. A solid screen will do for all frequencies. For absolute screening of EMP, solid is the way to go. As noted above, keep the thing you want to protect isolated from the screen, and make sure the screen is grounded.
    2) Yes.

    It is possible to arrange things to allow (say) radar and radio waves to pass thru the screen as is done in hardened stations. It is a pretty sophisticated system involving the use of wave guides. This is not trivial science and engineering, and far beyond anything us lowlifes want or really need to get thru a situation.
     
  4. Cephus

    Cephus Monkey+++ Founding Member

    I'm not the sharpest knife in the drawer .

    So let see what I got, if I have a metal building
    that is grounded and I have all my things in it that could get fried by an EMP
    chances are good that it would make it through intact .

    Is that about it or did I miss this completely.
     
  5. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    You are close. Put in a metal floor and make sure all the gaps between wall, roof and floor panels are closed off with a conductive metal, make sure the windows and doors are likewise shielded, and you might make it. Aluminum is questionable in my mind, steel would be preferable. At least two and preferanbly three ground rods, more or less equally spaced around the building (more is better.) I've heard it said that concrete floors are sufficiently conductive to work, but it is not something I would count on.
     
  6. Cephus

    Cephus Monkey+++ Founding Member

    OK I have a 30x50 building that is all steal covered and at the rafters I have screen (aluminum) on them to keep the birds and bees out.
    The floor is 6" thick concert with rebar every two feet the one door is steal covered ,no windows .
    One door is 10x8 old barn type so if I cover that with say chicken wire and tie that into the building would it work.

    I have my generator,car,radios,and machinery in there ,so if I'm doing something wrong I want to know .

    And THANKS for putting up with these questions .
     
  7. Cephus

    Cephus Monkey+++ Founding Member

    Double post
    Big thunder storm here .
     
  8. QuietOne

    QuietOne Monkey++

    Rawles has some basic electrical stuff in his book Patriots very wrong (you DO NOT test a circuit with electric blasting caps by using an ohmmeter) and "One Second After" is a book on how to do everything wrong after TSHTF.

    Faraday cages do not have to be grounded except for low frequencies. Example: airplanes get hit by lightning all the time. See http://spacepug.wordpress.com/2008/05/27/lucky-strike/ . They're Faraday cages made of aluminum; the current passes over the outside of the plane. Or make a call on your cell phone, then wrap it in aluminum foil. You've lost the signal because you put it in a Faraday cage. You didn't ground it.

    Aluminum is fine. Copper is better. Steel will work. It's the resistance to current that degrades the efficiency of a Faraday cage; if you use steel (higher resistance) you need a thicker enclosure than if you use copper (lower resistance).

    You do not have to insulate the objects inside from the metal of the cage. RF currents will flow on the outside and not the inside. See the famous picture of Tesla standing inside one of his lightning generators http://www.kerryr.net/pioneers/gallery/ns_tesla12.htm .

    Concrete will not conduct well enough to close a Faraday cage. Damp earth underneath will if your metal container is touching the ground all around. Which will cause it to rust. Mylar space blankets are covered with non-conductive plastic and are lousy Faraday cages because they can't make metal to metal connection without scraping off the plastic.

    Easy to make Faraday cages; aluminum foil lined boxes, ammo cans, metal lockers, shipping containers with added metal flooring, underground missile bases (OK, they're a bit more work).

    Just correcting some errors. Didn't we have a thread on this a month ago?
     
  9. Cephus

    Cephus Monkey+++ Founding Member

    OK ,so the building is grounded all the way around but you say I'll have to do something with the floor .
    What will work for this because I always thought that with the rebar and the ties that are 2 feet in the ground every 2 feet that that would be grounded .

    Now I am total lost .
    And I thought I figured out .
     
  10. QuietOne

    QuietOne Monkey++

    I was reading Ghrit's post. Ties in the ground every 2 feet is fine. Just remember that wire runs into the building (electric power, antenna) will conduct EMP past your shielding and into any connected appliances.

    Let's not get too crazy about this. I keep an old shortwave radio and a scanner in an ammo box. I don't think I'll have much spare time to listen after TSHTF.
     
  11. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Longer than a month, but yes.

    Re: Chicken wire. IIRC, the mesh is about 1". That is OK for wavelengths in excess of 5 cm. Not for shorter, the pulse waves will zip right thru. No shielding at all for microwaves at that mesh size.

    QO is right about shielding small stuff, putting it in things like ammo boxes is OK and will work, as long as the lids are in good contact with the rest of the box thru the hinges and the gasket is sound (no gaps for microwave leakage.) There will be a residual charge on the can that should be dissipated by grounding before opening the box. Again, the wavelength of the pulse governs the gap that can be tolerated. And again, that is power dependent. If close, a sheet of rubber under the stored items is extra insurance.

    I'm planning to use a welder's box to contain a few items I don't want damaged. (At least as soon as I get some ammo used up and no longer need the concealment for it.) It will sit on a concrete basement floor with wire mesh rebar in it at 10 inch spacing. I'll run the risk of rust on rubbed off spots, and may go so far as to smear some conductive goop (dielectric automotive connection stuff) on them to help with corrosion and improve contact efficiency. Not ideal, but should work.

    One thing you might do if there is advance notice of the pulse, as for example with an air raid or incoming ballistic missle. Flood the floor where your ammo cans are sitting, to the extent of running over the sills. If really paranoid, make that salt water. Or put a steel plate under the sensitive stuff, and ground it directly thru the slab, not thru the building wall. One guy I know parks his car on a plate and grounds the frame to the plate with a welder's clamp to a shipping tie down on the car. I ain't so sure that will work since the ECM is exposed, but paranoia runs deep in that lad.

    The National Electric Code has a method of testing building grounds, and specs for resistance. The specs are too loose for EMP grounding, but it's a place to start the research for the real worry warts.
     
  12. The Expendable

    The Expendable Bread and Circus Master

    As far as aluminum vs. steel, I've read that while copper is the best material to build a Faraday cage out of, aluminum is a good second choice. Although I'm not an expert by any means, I've experimented with both steel and aluminum and found aluminum to work better.

    I placed a cell phone in a cardboard box, then placed the cardboard box inside a steel box. When I called the cell phone it rang. Then I took the cardboard box out of the steel box and wrapped it in aluminum foil. When I called it I was sent directly to voicemail (i.e., no signal was reaching the phone). I did the same test using FRS walkie-talkies and got the same results.

    I know this may not be conclusive, but I've ditched my steel boxes and built some Faraday cages using sturdy cardboard boxes covered with heavy duty aluminum foil and wrapped with aluminum Shurtape.
     
  13. dragonfly

    dragonfly Monkey+++

    Sorry all,
    I was "out" for a bit and unable to get back here....
    I was and stand corrected, and was not sure what the heck people were referring to, as the "NOVEL is not yet a movie, but, I have just heard that there are some talks about it, for the future.
    I have not even seen the book myself!
    I wonder what those 4 people were referring to?
    Maybe something on TV about Solar Flares?
    Why on earth was I told it was from a movie?
    That's JUST Weird!
    I have no idea, and I have been unable to reach 1 of them or get a response since my posting!
    ( Maybe their "mother ship" came and took them all home?)!!!

    Anyway!
    Back to the drawing board.....
    I use aluminum screen over a 2 x 2 wooden framing made to sizes I need for the Faraday cage. I also use 1/4" thick perf board, or peg board, for the shelving inside. As it's light and easier to work with than solid wood or plastic sheets. ( and a heck of a lot cheaper too!)
    1) Aluminum screen is cheap!
    2) It is more conductive, than copper in the way of resistance, but as you may well know, it has been illegal to use it for wiring due to it's frequency of home fires! Especially in those made in the mid to late ? 60's?
    I am no electrician, but there was some problem there!

    Anyway....
    Aluminum screen is CHEAP, easy to use, fold, staple, and lightweight, compared to all the rest of the really good conductive metals: copper, brass, silver, gold, and lead.
    I insulate my radios from each other, by using plastic dowel rods cut into 3/4 inch pieces, then silicone them as feet to each radio unit, then I "stack" them up, and silicone them one on top of the others, solely as a matter of convenience. It is easier to "house" and control a taller stack of radios in a cage 24" high by 16" wide by 16" deep, than each radio separately. ( since I have so many!)

    (testing blasting caps with an ohmmeter? WOW! Now that's gonna mess somebody's day up ROYALLY!!!) Sheesh!

    I also use several ground rods,(at least 4, one at each corner on my "commo" trailer, that was specifically designed and built for just this purpose.)
    (Diamond plate aluminum, sheeting) and if the area is dry, (as in Arizona deserts/sand)
    I lay them horizontally in a ditch and soak them down with water as I bury them.
    I see today there are companies that actually make the ground rods in an "L" configuration for just that purpose.
    Bill
    (I am sorry for the post, if this topic was covered just recently!)
     
  14. The Expendable

    The Expendable Bread and Circus Master

    Dragonfly, my understanding is that the movie rights have been sold already, so it may be a movie one day.
     
  15. dragonfly

    dragonfly Monkey+++

    Figures!
    I'm gone but a few minutes/hours/etc., and I lose all track of what is happening!
    I guess I'd better go buy the book, but I already know how it ends....
    By candlelight !
    LOL!
    Too many books to buy, no time to read them all, and most are "fiction", based on reality!
    I need to CLONE myself!
    Bill
     
  16. The Expendable

    The Expendable Bread and Circus Master

    When I read it, I kept thinking that it was like a movie. It may not be the most well-written book, but then again, I'm not an English teacher. I did find a few factual and logical errors in the book, but I won't go into them here. I don't want to spoil the book for those who haven't read it yet.
    Overall I thought the book was entertaining and it gave me a lot to think about. I've even changed a couple of my SHTF strategies thanks to ideas that the book gave me.
     
  17. The Expendable

    The Expendable Bread and Circus Master


    Don't clone yourself! Most clones are a mere shadow of the original, and of highly dubious character!
     
  18. Galactus

    Galactus Monkey+++ Founding Member

    Sorry about EMP's...happens after I eat a gas giant.
     
  19. E.L.

    E.L. Moderator of Lead Moderator Emeritus Founding Member

    Just to stir the pot, what are y'all putting in your Farady cages? I know electronics, but specifically what do you consider being of high enough priority that you buy an extra or two just to put in the box?
     
  20. The Expendable

    The Expendable Bread and Circus Master

     
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