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Post by Cwi555 on Jul 21, 2012 16:29:14 GMT -7
This is an interesting site that (I think) was referenced by you, cwi, on the old board. They do mention the use of an older microwave for smaller items, but I'm curious what you think about there use of foil then plastic wrap, then foil, then plastic wrap, then foil etc.... I was thinking about using this method for a short wave radio. www.futurescience.com/emp/emp-protection.htmlDon't come down too hard on me, I admittedly don't know much about this stuff..... I must admit it is getting frustrating. I can technically justify that a microwave does not make an effective nuclear bomb EMP cage. I've done so on many occasions. Particularly on ST. The science of it is straightforward. What I am up against is a mountain of BS spewed on the web. A microwave satisfies the majority of people desire for simple and instant satisfaction. It is in fact a faraday cage, but not of the kind that will help you.
To your link; He claims to be an electronics engineer. That is apparent in his page. Of the pages that are out there, at least he's thought about it for himself rather than parroting outright BS. There are many things he mentions that are correct. Such as the use of a metal garbage can (if you can get the seal of the lid to work), but then again, a metal drum would work to. He mentions skin effects. Currents produced on the surface upon impact. A valid observation as well. Here is where he goes wrong. He's taking it from the perspective of an electronics engineer 'only'. He even answers his own question if he would go back and think about it. He mentions that the seal on that garbage can must be 100 percent metal to metal. He mentions that it should have an insulating material on it's internal walls. That to is correct. However; he then turns around and mentions a microwave. From an electronics engineer's perspective, microwaves are a PIA. So are high frequency interferences from welding, and other transient EMF. If he's any account as an electronics engineer, he's going to be well versed in how to mitigate those concerns. What he is not is an electromagnetic wave mechanics engineer. Why? because such a degree doesn't exist to my knowledge. His particular pedigree of engineer has a narrow window of concern when it comes to that. There are a multitude of books out there regarding the subject, but most of them are speculation. I've made a lot of money working with weld shops designing actual faraday cages that 'do' protect the computers, and other electronics found in those various operations. A high end weld shop is a mine field of strong EMF of a variety of frequencies and strength. Not only are they a strong source of EMF, they are a strong source of a variety of wave forms, wave guides, constructive and destructive interferences, wave types such as a de Broglie waves, quantum waves, the complications go on and on. I've had to weld in mission critical environments such as online nuclear power plant control rooms. Not a place you want EMF interference with the electronics. While those environments may be fraught with EMF concerns, they are still not anywhere near as strong as a nuclear driven electromagnetic pulse would be. If a microwave will not work in that environment, what gives anyone any assurance that it will magically do any better in fields that are several orders of magnitude stronger than what is found in a high end weld shop break room or front office? Specifically, what Mr. Emanuelson is missing are those little holes in the front screen of that microwave. I found that odd given that he did not miss the need for the garbage can to have 100 percent continuity in metal contact. If you get out a set of vernier calipers or optical comparator you will find those holes to be approximately 1/16". Why? That is where the vast majority fail. The reason those holes are that size is due to the wavelength of the microwave. The wavelength emitted by a microwave to cook your food has a wavelength that when divided in half, is larger than 1/16". For a wave to make it through that hole, it would be necessary for half it's wavelength to be less than 1/16". So lets just assume a rogue de Broglie wave by itself, not the thousands of other EMF interactions that would be going on. de Broglie waves are wave packets. For a propagating wave packet, in general, the envelope of the wave packet moves at a different speed than the constituent waves. Because they are propagating (moving) the particles within the packet cannot be represented in localized space. de Broglie stated that the only way to localize those particles would be if they had superpositioning in a variety of waveforms both trailing and preceding the wave packet central frequency. There would be inherent destructive and constructive interference patterns associated with that. That later destructive interference would allow that wave packet to slip through even a .010" hole, much less a 1/16", at which time it would superposition again on the inside surface. That wave packet would then impact the part. And that is only one of several thousand competing effects to deal with. Boiling all that jargon down.. You must have a solid skin for EMP protection. There is no way around it. It must be a floating ground, I.E. it cannot have a grounding stake. I've tested this personally. I have empirical results that tell me this is a 'fact'. A microwave with the standard door will not cut it. There are other problems with a microwave they don't consider either. Like the magnetron that creates the microwave to begin with. Such as skin effects on the magnetron creating a rogue microwave in the magnetron wave guide. That wave guide is specifically design to create destructive and constructive interference patterns so that the microwave coming out heats the food properly and cannot escape the front viewing grate and microwave the users brain while they are waiting on their jiffy pop. A skin effect from the EMP can create a microwave within the magnetron that is not controlled properly, and more importantly emit even thought the microwave has no power cord. That microwave can fry your electronics as well. Once again, a microwave 'will not work' for a few hundred reasons. |
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Post by woodyz on Jul 21, 2012 17:38:38 GMT -7
Good to know, thanks for clearing it up. I think the info was on the other site, but that does us no good here. Which info is that? The info that microwave ovens do not work. |
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Post by mountainmark on Jul 22, 2012 6:40:30 GMT -7
Thanks cwi for all that info. I actually beleived you the first time you said that a microwave wouldn't work. I only mentioned it as a means of questioning the validity of the article. What my question was regarding was the below quote. But if I'm understanding you correctly, it won't work either unless there is a very tight seal on the aluminum foil. Perhaps some soldering on the edges? Sorry if my first post was confusing.
From Futurescience:
"If you have a shortwave radio, it is likely to be knocked out by the EMP unless it is adequately shielded. To be adequately shielded, it needs to be kept inside of a complete metallic shielded enclosure, commonly known as a faraday cage, and preferably inside nested faraday cages. A faraday cage is an total enclosure made out of a good electrical conductor such as copper or aluminum. (Steel also works well, but it is more difficult to make a total enclosure with steel.) Large faraday cages can get extremely complicated. For small portable electronics, though, completely covering the electronic equipment in aluminum foil makes an adequate faraday cage around the equipment. The foil covering needs to be complete, without any significant gaps. Wrap the device in plastic or put it in an insulated box before wrapping the covered device in foil. (Otherwise, the foil may simply conduct the EMP energy into the device more effectively.) A single layer of foil may not be adequate. In order to enclose the equipment in a nested faraday cage, place the foil-covered device in a plastic bag, such as a freezer bag, and wrap that bag completely in aluminum foil. If you really want to protect the equipment against a large EMP, add another layer of plastic and foil. The layer of plastic need to be the thickest plastic bags that you can easily find. (They don't need to be terribly thick, but do try to find some heavy-duty bags.)
Just adding many layers of foil directly on top of foil won't do as much good, due to what is called "skin effect." I won't bother to explain skin effect here, but you can look it up if you're curious. Don't worry too much about skin effect, though. I only mention it here because many people have the misconception that when it comes to shielding, the thicker the better -- and this is definitely not true after a certain thickness is reached. Layers of shielding separated by insulation works much better. As a practical matter, though, wrapping with 2 or 3 layers of foil helps to assure that you actually have a good shield around the equipment.
Of course, any antennas or power cords need to be either disconnected or contained completely within the faraday cage."
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Post by jimmyq on Jul 22, 2012 9:54:35 GMT -7
A slight aside but if anyone needs a powerful (pun intended) visual of the principle of a farady cage, here is a video I saw a few years ago and just thought about. youtu.be/Z3q9WdjD5wc |
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Post by Cwi555 on Jul 22, 2012 10:40:41 GMT -7
Thanks cwi for all that info. I actually beleived you the first time you said that a microwave wouldn't work. I only mentioned it as a means of questioning the validity of the article. What my question was regarding was the below quote. But if I'm understanding you correctly, it won't work either unless there is a very tight seal on the aluminum foil. Perhaps some soldering on the edges? Sorry if my first post was confusing. From Futurescience: "If you have a shortwave radio, it is likely to be knocked out by the EMP unless it is adequately shielded. To be adequately shielded, it needs to be kept inside of a complete metallic shielded enclosure, commonly known as a faraday cage, and preferably inside nested faraday cages. A faraday cage is an total enclosure made out of a good electrical conductor such as copper or aluminum. (Steel also works well, but it is more difficult to make a total enclosure with steel.) Large faraday cages can get extremely complicated. For small portable electronics, though, completely covering the electronic equipment in aluminum foil makes an adequate faraday cage around the equipment. The foil covering needs to be complete, without any significant gaps. Wrap the device in plastic or put it in an insulated box before wrapping the covered device in foil. (Otherwise, the foil may simply conduct the EMP energy into the device more effectively.) A single layer of foil may not be adequate. In order to enclose the equipment in a nested faraday cage, place the foil-covered device in a plastic bag, such as a freezer bag, and wrap that bag completely in aluminum foil. If you really want to protect the equipment against a large EMP, add another layer of plastic and foil. The layer of plastic need to be the thickest plastic bags that you can easily find. (They don't need to be terribly thick, but do try to find some heavy-duty bags.) Just adding many layers of foil directly on top of foil won't do as much good, due to what is called "skin effect." I won't bother to explain skin effect here, but you can look it up if you're curious. Don't worry too much about skin effect, though. I only mention it here because many people have the misconception that when it comes to shielding, the thicker the better -- and this is definitely not true after a certain thickness is reached. Layers of shielding separated by insulation works much better. As a practical matter, though, wrapping with 2 or 3 layers of foil helps to assure that you actually have a good shield around the equipment. Of course, any antennas or power cords need to be either disconnected or contained completely within the faraday cage." He is for the most part correct in that. Which is why I still am lost as to why he threw in the microwave when it will not work. The problem with aluminum foil is getting a good seal. That is followed by it's propensity to tear. I have a shippment of ammo cans inbound, they work well. I've been short on time lately, but i'll try to get something together for it. |
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Post by hunter63 on Jul 22, 2012 17:55:59 GMT -7
Years ago, 1972 to be exact, I had purchased a brand new Volkswagen, one of the first with a "brain" and fuel injection.
Well at the time, actually a few years later early 1980's....the "breaker, breaker, 19 good buddy, CB craze was on.
When a truck running a 1k linear amp would key up, it would literary shut down the engine. EMP, don't know for sure but did cause enough interference that it did this real regular.
The brain was located in the passenger side side panel, and had a little foil in the panel.
I found that the fix was simply wrapping the whole box, was about the size of a cigar box, if anyone remembers them, in a couple of layers of alum foil...then didn't have a problem after that.
So I'd go with the foil and ammo boxes rather than spending the bucks for a trick bag.
Besides it would be my luck that some one would push the button on a microwave and fry everything..
Beside the fact that at our house the microwave is the "bread box" (kind expensive, but hey...) so there isn't any room in it anyway.....
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Post by olebama on Jul 24, 2012 18:34:17 GMT -7
"Boiling all that jargon down..
You must have a solid skin for EMP protection. There is no way around it. It must be a floating ground, I.E. it cannot have a grounding stake. I've tested this personally. I have empirical results that tell me this is a 'fact'."
CWI, I am sorry that you have to deal with a dummy like me. But can you explain a floating ground? I am referring to using a garbage can faraday cage. I looked up floating ground, but not quite sure what it meant...
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Post by Cwi555 on Jul 25, 2012 2:12:24 GMT -7
"Boiling all that jargon down.. You must have a solid skin for EMP protection. There is no way around it. It must be a floating ground, I.E. it cannot have a grounding stake. I've tested this personally. I have empirical results that tell me this is a 'fact'." CWI, I am sorry that you have to deal with a dummy like me. But can you explain a floating ground? I am referring to using a garbage can faraday cage. I looked up floating ground, but not quite sure what it meant... First your not a dummy, and thats a fair question. "Common connection in a circuit that provides a return path for current but is not connected to an earth ground." Examples of floating grounds would be an airplane, cell phone, mobile gps system, hand held radio etc. A loose definition, if your not dragging a grounding cable around with you, its a floating ground. Edit; of the questions I've received, that one is one of the more intelligent ones. Understanding that particular concept and why it is necessary, is about 3/4 of the battle. |
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Post by woodyz on Jul 25, 2012 11:40:15 GMT -7
I still don't understand the floating ground.
In his example he is looking at a trash can type cage.
How would he floating ground it, it is metal and it would be in contact with some that eventually is grounded.
A motor in a car has to be grounded to the frame, the car doesn't touch the ground due to its rubber tires. Is that it?
So on a trash can cage you would not ground the cage, but the objects in the cage would ground to it?
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Post by twicebitten on Jul 25, 2012 12:24:37 GMT -7
I have a ? about the ammo boxes.....don't they have a rubber seal, and wouldn't that negate the complete seal you're looking for?
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Post by Cwi555 on Jul 25, 2012 15:14:47 GMT -7
I have a ? about the ammo boxes.....don't they have a rubber seal, and wouldn't that negate the complete seal you're looking for? The box is a starting point. The rubber seal has to go for it to work. The to-do-list is a long one for me, but I'm going to try and put together one for example this weekend. |
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Post by woodyz on Jul 25, 2012 15:22:36 GMT -7
Works for me.  Thanks! |
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Post by Cwi555 on Jul 25, 2012 15:25:21 GMT -7
I still don't understand the floating ground. In his example he is looking at a trash can type cage. How would he floating ground it, it is metal and it would be in contact with some that eventually is grounded. A motor in a car has to be grounded to the frame, the car doesn't touch the ground due to its rubber tires. Is that it? So on a trash can cage you would not ground the cage, but the objects in the cage would ground to it? The rubber on the tires insulates the car from the ground. Think about it for a minute. How does all the electric devices in your car work? Your not dragging a copper rope down the road sparking off. Regarding the trash can, sitting on the ground without any insulation, yes it would be earth grounded but poorly so. An old tire will fix that problem fast. |
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Post by olebama on Jul 25, 2012 17:10:26 GMT -7
Thank you, sir. That is what I thought you meant.
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Thanks!