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Faraday cages

(Radio's), (GPS), (Faraday Cages), (Other Technology)
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ranger2012
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Re: Faraday cages

Postby ranger2012 » Mon Dec 10, 2012 3:49 pm

Don't think direction if your over concrete, as concrete will bounce back a potion of that signal. That's why cities would be hit the worst if a EMP by CME or man made, regular ground, that contains moisture will absorb much of this frequency. Where as concrete will create a bounce back and efficiently almost double the damaging signal.
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"We 'Prep.' to live after a downfall, Not just to survive."

JustABear
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Re: Faraday cages

Postby JustABear » Mon Dec 10, 2012 6:19 pm

The physics behind EMP damage.... "One word:induction. When an electromagnetic pulse (EMP) hits, a big magnetic field "sweeps" everything in its path. The moving magnetic field (because it travels out from where it was created) will induce electromotive force (EMF) or voltage, if you prefer, in all kinds of stuff. There are tiny traces on circuit boards, and there are component leads and all kinds of conductors that are acting like little antennas inside electronic equipment. And these little antennae will "receive" the magnetic "signal" from the pulse and convert some of its energy into voltage. Because the pulse is so large, the voltage will be high, and will be high enough to damage components and circuits in all kinds of equipment. This will knock electronic devices out of commission. Permanently." Any magnetic field will induce an electric current when it crosses a wire or metallic surface. The purpose of shielding is to conduct this magnetically generated current "pulse" around the device in the box. If you have a break in the conductivity of your container then you have the risk of the pulse getting inside and affecting your device. Sadly in this there are no absolutes...just best gusses so that is what we do and hope for the best.
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Greenguy
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Re: Faraday cages

Postby Greenguy » Mon Dec 10, 2012 9:33 pm

I wonder if an EMP would damage a heart pacemaker. If so, my Dad (and many others) may be at risk. Not pleasant!
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nlantz
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Re: Faraday cages

Postby nlantz » Wed Dec 12, 2012 7:34 am

Hey, new to the site. This thread got me thinking. I Made an over-sized "pantry/wine cellar/gun safe while renovating the bathroom down in the basement and have an old Canadian tire gun locker stuck in there. While building the bathroom I overlooked the distance between the back wall and the furnace, now I have a chest freezer and gun locker stuck back there. May test it out then redo the inside in 3/4" plywood. I could have sworn I heard faraday cages need to be grounded. it seems the experts are 50/50 on grounding regardless of whats inside. Seeing there is a water line in the room as well anyone think there is any harm grounding off to that ? Would probably store the radios and essentials inside ammo boxes inside the locker just to keep everything tidy and double protected.
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ICRCC
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Re: Faraday cages

Postby ICRCC » Wed Dec 12, 2012 2:50 pm

Faraday cages do not need to be grounded unless you are operating equipment inside them that requires an external power source or an external antenna. Others may argue that they do but that is not the case. However proper grounding will not adversely affect your cage either. I do not ground mine as there is no need.

As far as waterlines go as long as it is a continuous copper line and buried deep enough they may be used for a ground. However you would need to consider how many joints are between your point of attachment and the point the line enters the ground and are there any brass valves or galvanised sections before the point where the copper line is buried. A couple of good ground rods are probably much better protection than a copper water line.
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nlantz
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Re: Faraday cages

Postby nlantz » Wed Dec 12, 2012 6:33 pm

That's what I figured Icrcc, It is aprox 5 ft from the point of entry into the house. I realized the clean out for the septic line is in this room also. I am probably going to drive a copper rod in there seeing as it is earth under a couple inches of stone.
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Screedcrete
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Re: Faraday cages

Postby Screedcrete » Wed Dec 12, 2012 11:02 pm

Ok I have a question for my old 78 ford. I want to shield the electronic spark control box under the hood on the inner fender. Do I make a box that has ground to the engine block or simply bolt the cage on the inner fender and insulate inside? Also what about the point of entry for the wire harness, how is this problem addressed please. I was thinking tinfoil down the wires as far as I can get to do you think this will work??
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ranger2012
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Re: Faraday cages

Postby ranger2012 » Thu Dec 13, 2012 6:24 am

Not really possible, since the wires leading into the box is what will supply the shock. The wires leading into it will act as an antenna. :evil:
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ICRCC
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Re: Faraday cages

Postby ICRCC » Thu Dec 13, 2012 4:15 pm

This is a difficult one Sceedcrete. Ranger is correct. You could build a box and you would need to ground the box (the fender would be fine) in this case because the wiring to the unit would act as an antenna. The spark control box is already likely in a plastic container. Therefore as it cannot come into electrical contact with the cage that you build so you would not need to insulate the box. The problem is that you cannot ground the "antenna" (the wiring). You could, as suggested, wrap the wiring in aluminum foil but one end would always be open so you could never complete the integrity of the cage.

If you are really worried about this and I am not sure you should be because with a 78 Ford you already have a pretty EMP proof vehicle you might consider taking the following precautions. You could acquire a spare electronic spark control box and store that in a Faraday cage at another location. Just as you might for a radio or thumb drive or external hard drive on which you have data that you want to protect. Alternatively you could go ahead with your plans as you have outlined them paying particular attention to the wiring because it is this that would pick up most of the induced charge. Also making the entry point of the wiring into the box as small as possible.

EMPS can have four or five causes. The strongest EMP would most likely be man made from a HEMP from an intentional nuclear attack or an EMP from an E-bomb. Only the separately stored control box may be effective in this case. EMP's directly from a CME will greatly affect long conducting media infrastructure like power grids and telephone lines but are unlikely to be as powerful as a HEMP. For this situation your precautions taken on the vehicle may well prove to be enough.

Personally I would pick up another control box and store it in Faraday cage with my other valuables. An easy solution that has this issue covered. You should also ask the question how likely is an EMP? Although a common theme in some good fiction books probably the chance of an EMP causing the demise of society is not very likely. There are many possibilities for the collapse of society so be sure to cover the four main pillars of prepping first before you specialize your efforts. Water, shelter, food and security, in that order are the main concerns. Cover those first and you will be in good shape.
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Grammaprepper
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Re: Faraday cages

Postby Grammaprepper » Thu Dec 13, 2012 6:24 pm

I bought a huge roll of aluminum foil from Costco. I did the garbage can with the microwave inside the can. I thought for fun, why not just wrap mycell phone in the foil and see what happens. It worked. No signal getting thru. So I wrap'd batteries, walkie talkies etc with the foil. I like the can idea just for storing the items and everyone knows where it is.
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