Faraday question

Discussion in 'Off Grid Living' started by thermax, Nov 2, 2011.


  1. thermax

    thermax Monkey+

    I've built my Faraday box for the generator. I can very easily block the cell phone signal and wifi signal, however it won't block the FM station on the radio. Does that sound normal? thanks
     
  2. Falcon15

    Falcon15 Falco Peregrinus

    No. It should block the FM radio signal as well. A test to see if your microwave is leaking is to place an FM radio inside an unpowered microwave oven. With the door shut, the signal should cut off. Microwave ovens have a Faraday cage in them to prevent radiation leakage. If the FM signal gets through, the cage is leaky.
     
  3. thermax

    thermax Monkey+

    Thank you

    I'm going to open a new post and post a video of where I'm at so far. Thanks so much for all your help.

    Faraday cage.wmv - YouTube
     
  4. BTPost

    BTPost Old Fart Snow Monkey Moderator

    I see a couple of issues already.... Why did you use aluminum screen? You do understand that aluminum is OXIDIZED, over time, and will lose it's conductivity, Right? This is why MOST Faraday Cages that use screen, use Silver Plated Copper Mesh Screen rather than aluminum. A second NOTE, here. All the different pieces of Screening are NOT electrically, BONDED, as built. As the aluminum screen oxidizes on it's surface, just having mechanical connections between the separate screen pieces will go from low resistance connections, to high resistance connection, and finally to NO Connection, as the reaction proceeds. This all means, that your good isolation, that you have demonstrated in the video, will degrade over time, to the point of non-functional. Third Note,here. I see NO Ground connection to Earth for the Screened Box. that must be remedied forthe system to be effective for EMP Pluses. Fourth Note, here. I assume, and you can correct "Me" if I am wrong, this Screened Box is JUST for Storage, and you would remove the Genset from the box to run it, Right? Therefor your Genset would NOT be protected from an EMP Burst, should it be in operation, at the time of such an Event. There are ways around this dilemma, but they get into so esoteric Design Criteria, that is beyond the scope of this discussion. ...... YMMV.....
     
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  5. thermax

    thermax Monkey+

    Thanks Bruce, You make several good points. I used Aluminum wire because that’s what every one else was using and also the expense. I tried to make sure that it was as isolated as possible from dissimilar metals to cut down on corrosion. The unit is being stored inside and that should help.
    I know I'll need to check it and look for that problem. It is only for storage. I watched several videos and what I built is the same as every one else's except its built upside down. There is no way I could lift this moose out of a box to run it. I put in an 8 ft ground rod for this system where I park it. I will leave it on the cart with the lid off and test run it and also leave it there to run when I really need it. The wheels on the rig allow me to move the unit outside for running. I realize if we get nailed with the lid off I'm in trouble. How would you solve that issue? Also could you supply me with a link where to find Silver Plated Copper Mesh Screen. Thanks Rod
     
  6. Tikka

    Tikka Monkey+++

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  7. thermax

    thermax Monkey+

    Thanks Tikka
     
  8. Tikka

    Tikka Monkey+++

    You're welcome.


    Everything known is based on one test; a test which proved their calculations were in error. ;)

    The Russian test:
    It looks as if what an even higher level of HEMP (High altitude EMP) energy will do is anyone's bet.
     
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  9. Falcon15

    Falcon15 Falco Peregrinus

    On the previous post I did note that, Tikka. I also know the government tests hardening constantly, using EMP generators, and even they admit, it is at best a guess.
     
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  10. Tikka

    Tikka Monkey+++

    Testing is so the companies who sell EMP protection to harden military equipment can prove theirs works. ;)

    However, their EMP generators are no where close to the power of 3 300 kiloton explosions.


    If it never would have happened; science would have no clue it could happen. So everything we read would be based on half the Carrington's power.
    I'm not saying go hide under the bed. However, never be so sure what we do will work.
     
  11. dragonfly

    dragonfly Monkey+++

    Ok, lets see where we are now......
    Copper corrodes, as does brass, and then aluminum oxidizes...so that leaves us with silver which tarnishes, so that ONLY leaves stuff like iron and steel which rust, or GOLD. OH Yeah, like I can afford a feet square feet of gold cloth....!
    NOT!
    You could get the metal anodized, or coated with plastic...oh wait,... there's that dang conductivity thing all over again....
    So I guess the best resolution is to dig a hole, throw your stuff in it, and bury it.....BUT make it deep! Wrapped preferably!
    No one knows exactly what will happen, as it's all based on speculations and presumptions. All you can do, is what you can do....based on any given information able to be gleaned from what little we are allowed to know!

    If there is a concern about aluminum screen turning into aluminum oxide, well it takes some time, ( normally ONLY if the aluminum is raw/bright and shiny) and exposed to moisture. It begins to oxidize the second it comes out of the mold/mill! You could wrap the whole mess with saran wrap!
    Maybe even a vacuum sealed bag?
    Or, You could spray paint it! I wonder,....will spray paint in silver ( or your favorite metallic color) oxidize rapidly enough to create even more concern? What a can of worms! Not so long ago and not too far way...someone was marketing sheets and pillow cases, and even complete coverings for beds, made of woven fine silver threads... Now I wonder, how were they cleaned? Did they tarnish from the oils and acids from contact with human skin? If not, then were they coated somehow?
    Yeah this is getting out there now!
    Lots and lots of questions and few answers....I just looked at a roll (new and unopened) of aluminum window screen and it says "Brite Kote", Brite Aluminum Screening, made by Phifer.com, made in USA. So, now I'm going to contact them and ask what the heck their meaning of "BRITE KOTE" is! It may be plastic coated! If so then there is no easy way to get any conductivity from it.
    My ohmmeter says NO coating! HUH? Ok, now this is too weird!
    I checked the roll and I just checked the outsides ( 5 sides) and the doors of 2 of my EMP cages and I have great conductivity! I doubt that I'll worry too much about it. If, these 2 are still conductive and they are 2+ years old. Setting in the house with a swamp cooler that ran for the past few months of the summers here, pumping tons of humidity in here..
    Nah, I am not going to be the least bit concerned now!
    But It was a good thing to test and see...I never gave it any thought, especially with the swamp cooler only 10-12 feet away! Not to mention the great water we have here ( very alkaline!) and unfiltered.
    But I will cover them with some sort of anti-dust covering, when I return the radio's inside!
    I liked that! It really did made me think, and it made me "test" and verify, and pay more attention to the environment than I had before!
    Interesting!
    So this thread has made a lot of good points, as far as I am concerend!
    Thanks to one and all here for the "heads up"!
    Sometimes you miss the little stuff that can sneak up and bite you in the rear end!
     
    Falcon15 likes this.
  12. dragonfly

    dragonfly Monkey+++

    Phifer - Insect Screen
    Check out Phifer.com, they have a "bronze screen" that is 90% copper and 10% zinc! Now that's different!
     
  13. BTPost

    BTPost Old Fart Snow Monkey Moderator

    DragonFly, I think you miss the point, of why some materials are better than others, here. It is NOT just because things oxidize. This issue is, getting all the pieces of screen, BONDED, mechanically, and ELECTRICALLY, into a solid conductor. If you are depending on mechanical connections between different pieces of the screen, then YES, and Oxide Layer will have significant effects on the electrical Bonding between the different pieces of material. HOWEVER, if you solder, or braze the different pieces of screen together along the seams, then it does NOT matter, AS MUCH, how well the mechanical connections are, to make the shield tight. With copper, bronze, silver plated copper, or straight silver screen, soldering or silver solder can be used to make these Electrical Connections, but with aluminum it isn't so easy to do so. Seams between pieces are where the leaks will happen, so this is a CRITICAL Failure Point that needs to be addressed. Over the years, I have built and worked in many different "Screen Rooms" with various amounts of isolation, at different Frequencies.
    A few of these were actually Calibrated, and Documented, because of the work being done inside the Faraday Cage. Doors, Openings, Power Lines, and Communications Connections, are all places that compromise, the integrity of the Faraday Shield, and need to be engineered for the best Isolation Level.
    .... YMMV....
     
  14. thermax

    thermax Monkey+

    Dragonfly, I called Phifer and they told me its a light coating of lacquer, in the sunshine it only lasts about 6 months. Brite Kote is used to take away the real shinny effect of the aluminum. I hooked an alligator clip connected to my OHM meter to one roll of screen and another one to yet another roll and laid them across each other and found I had a good connection. It appears the coating doesn't hurt anything. Even if we use a wire like Bruce talks about there is still going to be corrosion unless its welded and if its welded we won't be accessible to load and unload what we are trying to protect.
     
  15. mysterymet

    mysterymet Monkey+++

    You want to know what alloy aluminum window screen is made of? 5154a generally. So, care to make a guess about the electrical condutivity of zinc? High voltage ppwer transmission lines are usually made from aluminum 1350 alloy.
     
  16. Alpha Dog

    Alpha Dog survival of the breed

    I have a question if anyone might know and don't meen to take away from the post but Ive been looking at one of the $200.00 metal gun safe's and I was thinking about building a wooden insert wrapped in mylar and mout a ham, CB, Scanner and a few others with a cut out in the bottom covered by a metal plate for power and coax. Do yall think that would work or have anyone already tried it. Alsoit will be mounted on wheel's.
     
  17. Tikka

    Tikka Monkey+++

    Just put your stuff inside and close the door so whatever is in the box is insulated from the outside world.

    The biggest one ever did not last long. Once the EMP pulse is over you can get your gear out and use it same as always; remember, batteries not included. ;)
     
  18. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Just a NOTE, here: If you run Power or Coaxial Cables from outside the Faraday Shield, to the inside, then you have breached the shield and given EMP Pulses a path into the contents. There are ways to do this, but they are very complicated, and usually EXPENSIVE. So basically, NOT a good idea.
     
  19. thermax

    thermax Monkey+

    I talked to a guy the other day that works for the gov making shielded equipment. He told me what has been discussed at top levels is that we could be hit say on a Monday and than again later in the week with another one. The thought is that the bad guys will wait until we fix our equipment with spare parts and than take them out again, knowing we are not likely to store 3 sets of parts.
     
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