Faraday Cage

[angie_nrs]

The CME thread got me thinking about this. I have no doubt that foreign enemies have the technology to to launch an EMP type of weapon over our country. The more dependent upon technology we become, the more our enemies will be foaming at the mouth to cause devestation. I can only hope that our military and Space Force has us covered on this front. I have no idea how this would all shake out as far as 'blast' impact on a nation would go. If an EMP was launched over the middle of the states, how would if affect those on the perimeter? Or those over many miles away? Or would the launch be so far up in the atmosphere that there would not really be any type of natural shield, such as a mountain range or natural flora?

I've heard that a Faraday cage can be made from a metal trash can by putting insulation on the interior and closing the can with it's lid and sealing with aluminum tape. Does anyone know if that would be sufficient? Also, would a metal building be a good thing or bad thing? We have a metal roof that makes it difficult sometimes to get cell signal, so I'm thinking a metal roof or building would offer some protection, but that is just my guess. I'm also thinking a basement in a 2 or 3 story building might be a safer place to store electronics?

I'd love to hear some discussion, since I have much to learn on this topic.

 

[INresponse]

The CME thread got me thinking about this. I have no doubt that foreign enemies have the technology to to launch an EMP type of weapon over our country. The more dependent upon technology we become, the more our enemies will be foaming at the mouth to cause devestation. I can only hope that our military and Space Force has us covered on this front. I have no idea how this would all shake out as far as 'blast' impact on a nation would go. If an EMP was launched over the middle of the states, how would if affect those on the perimeter? Or those over many miles away? Or would the launch be so far up in the atmosphere that there would not really be any type of natural shield, such as a mountain range or natural flora?

Just my opinion, and speculation, but if I was on their planning team I wouldn't be aiming for the center of the country. The majority of the population, and big cities and infrastructure, is near the east and west coasts. I think the main target on the west coast would be central California. A quick check showed one article claiming a high altitude EMP radius of about 700 miles, and a low altitude radius of about 400 miles, based on a device of 100 kilotons. It is about 1200 miles from California's southern border to Washington's northern border, and about 800 miles from Sacramento, California to Grand Junction, Colorado. Soooo, a high altitude EMP over the Sacramento area could possibly effect all of California, Oregon, Washington, Idaho, Nevada, Arizona and Utah, plus most of the boats and ships off the west coast.
On the east coast a high altitude EMP over Washington DC (a prime target in and of itself despite any safety measures it may have in place) would reach from Jacksonville, Florida to Quebec, Canada and as far west as Nashville, Tennessee and across Michigan's entire lower peninsula.
The central portion of the country would be spared, but the effects would still cause them quite a bit of trouble. Targeting the center of the country would be a bit harder due to the increased reaction time to the incoming missile, plus the majority of the population would not be effected.
Again, just my opinion.

I've heard that a Faraday cage can be made from a metal trash can by putting insulation on the interior and closing the can with it's lid and sealing with aluminum tape. Does anyone know if that would be sufficient? Also, would a metal building be a good thing or bad thing? We have a metal roof that makes it difficult sometimes to get cell signal, so I'm thinking a metal roof or building would offer some protection, but that is just my guess. I'm also thinking a basement in a 2 or 3 story building might be a safer place to store electronics?

I'd love to hear some discussion, since I have much to learn on this topic.

My thoughts on a faraday cage would be to frame up a small room, possibly inside a garage or maybe a spare walk in closet, and use aluminum window screen a to wrap the entire framework, including the entire floor. It would need a simple frame for a door to allow access but that would be covered with the same aluminum screen plus an extra foot or so as an overlap to ensure the door jam was completely covered. If I ever get around to this it will be in the garage, or a shed in the yard, and it would be big enough to store my generator, back up computer, a TV and DVD player, toaster oven, a spare medium sized fridge and freezer, spare ignition parts for my old (64 and 72) vehicles, a few 2 way radios, a 200 watt solar system, and several other things. Maybe even a spare ATV if I had room and had one available. Debating the items anyone chooses to safeguard is topic for another thread.

In my opinion it wouldn't be a major project, and you could easily find any item you want to protect at a garage sale or moving sale, at very affordable prices.

 

[Caribou]

A metal trash can wit a tight lid should do well. Heavy cardboard or some other insulation should line the bottom, sides and top. Some claim that you should have three layers so if you had a radio inside a cardboard box or plastic marketing display, that has been wrapped in foil, and you have your second barrier. I'd put each foil wrapped item inside a plastic bag so you don't conduct from one package to another.

The metal roof on your house reduces some of the signal. Likewise it would reduce some of the EMP. That would help but much like getting hit in the head with a softball beats getting hit in the head with a baseball, you still get hurt. The more you reduce the signal the better.

There are books on this stuff. I can't cover this fully in a post and others here can do a better job than I. I hope this gives you something till they step forward. Short answer, yes the trash can idea could work for you if done properly.

 

[bkt]

A very powerful blast - megaton(s?) - over northern North Dakota or southern Manitoba and well into space - more than 67 miles up - would wash an EMP over pretty much the entire U.S. including the coasts. Such a blast could fry most electronics very quickly. Or so the scary websites say. Very few countries have the ability to do that.

What's true? Who the heck knows - this hasn't ever been tried before. Maybe some stuff would be fried and other stuff will still work. You can probably count on the power grid and mobile phone communications going down. You can count on point-of-sale going down. That means fuel and food will soon dry up. And those things are pretty big.

If you stash some electronics in a metal trashcan that you keep in the basement and properly grounded, will those devices still work after a devastating EMP attack? Maybe. But depending on what devices you're storing in the can, it's possible the infrastructure they'd rely on in order to work would be down rendering those devices worthless.

The idea of a Faraday cage is to provide a shield for electronic devices. The copper (or other metal) mesh absorbs an electro-magnetic pulse and sends it into the ground before it can enter the electronic device inside the cage. You would need to insulate your gear from the potential transfer of electrical power from the sides of the cage.

What sorts of things would you folks want to put in a Faraday cage?

 

[backlash]

If you are one of the few with working electronics they won't be of much use.

 

[Neb]

The Navy did conduct at least one test where the effects were noticed in Hawaii.

Years ago I had heard of a large number of missile tests by N Korea were all blowing at about the same altitude. I had also heard of N Korea working on sub launched missiles. Enough to get me thinking.

At about the same time we had run out of room to store the potatoes we harvested and needed a root cellar. So I killed 2 birds with many stones and built this.

5 of those cans are the root cellars and the lids have a small at the bottom of the lid covered with a fine mesh screen to provide ventilation and allow for fluids to get out if any spuds go bad.

The top left is intact and has a very tight fitting cover. In it I have stashed things that would help me recover after an EMP.

Multiple multi meters
Batteries for the meters
5000 W inverter capable of 220V
Guts of a wind turbine
Battery charge controller

Note the rust at the bottom was from this can was used for spuds and some of the spuds had frozen over the winter since this can is the most exposed to cold temperatures.

Someday I will get around to painting the lides to blend in with the stone wall.

I have learned that what I have is not ideal but I can report an AM radio inside one of these cans does NOT work.

For what it is worth...

Ben

 

[Neb]

If you are one of the few with working electronics they won't be of much use.

Yes but...

You have a large assortment of electronic components (harvested from dumpsters ) and test equipment to troubleshoot, one could be a very powerful asset to the comunity.

Ben

 

[backlash]

I have learned that what I have is not ideal but I can report an AM radio inside one of these cans does NOT work.

We installed an MRI scanner and had an artifact in the images. We took an AM radio in the room and closed the door. When we were able to hear a station we knew there was an RF leak. The contractor had left some shielding off.

 

[Neb]

We installed an MRI scanner and had an artifact in the images. We took an AM radio in the room and closed the door. When we were able to hear a station we knew there was an RF leak. The contractor had left some shielding off.

Thaks for that report!

Independent confirmation that an AM radio can be used as a poor man's RF detector.

Ben

 

[backlash]

Put a cell phone in your cage, call it, and if it rings it's not protected.

 

[Neb]

I'

Put a cell phone in your cage, call it, and if it rings it's not protected.

l'll report back to you.

Ben

 

[SheepDog]

In order to protect against something you have to know what it is. There are two very different types of EMP's to consider and how they work and what they do is very different.
A solar EMP is a chunk of solar energy in a band of ionized particles that push against the earth's magnetic field. The bending and twisting field breaks (returns to normal) causing the magnetic field to jump rapidly. That movement induces a current flow in the wires that we use to transmit electrical power all over the world. At least some of the grid has suppressors and electronic fuses that will disconnect the power lines from the transformers and generators to prevent widespread damage. If the current can't flow it isn't dangerous. Solar EMP's are a threat only to long transmission lines that are unprotected. The damage caused will be overloaded transformers and generators that will overheat and short out. Once a short occurs it wil then burn the wires. The affected part of the grid will have to be replaced.

The other type of EMP is made with the help of a nuclear bomb detonated at high altitude. "High" altitude is anything from about 30 miles above sea level to orbital altitudes. The limit of altitude (effective altitude) is dependent on the height of the inner Van Allen belt and it's saturation.
The man made EMP (HEMP) causes three pulses in succession for different reasons. In the order of generation they are the E1, E2, and E3 pulses. What causes the pulses are;
E1 is caused by the release of gamma particles (free neutrons) by the bomb as it detonates. These neutrons knock electrons off air molecules ionizing the atmosphere and into the ground and water to a voltage of 50,000 volts per meter. This isn't really a pulse like a radio wave it is a cascade voltage rise that happens in the time it takes the neutrons to travel the distance from the bomb to the point where the neutrons are stopped. The neutrons are travelling very close to the speed of light so the event reaches maximum voltage in about 500 billionths of a second. It will affect the area from horizon to horizon in all directions of the earth from the "bombs point of view". The less "efficient" the bomb is the more free neutrons are released and the higher the voltage and amperage is. Since the voltage rise is caused locally (throughout the entire area) it doesn't diminish with distance like a radio transmission does. The E1 pulse will not affect electronics implanted in the body of animals but it will affect all electronic junctions that have terminals exposed to the atmosphere. This is why Faraday cages and metal containers offer very little to no protection. The air in the container is charged by the electrons being knocked off the molecules just like the rest of the environment. There are two possible ways to protect semiconductors from the E1 pulse. The first is a specifically designed wave guide that excludes the penetration of the ionized air and the other way is to slow down the absorption of the charge so it dissipates before it can get to the semiconductors. To slow down the propagation of the charge you can use the capacitive reactance of multiple layers of plates and insulators.

 

[Alaskajohn]

What is everyone’ thoughts on those large 120mm ammo cans with intact rubber gaskets that seal tight? My thought is that this is a perfect faraday cage. I just picked up 4 of these and can get some more. While the intent was to use as a cache, I am thinking some of the items I can cache are electronic communication devices and solar charging items.

 

[SheepDog]

Continued:

E2 is a reaction to the electrons that are trapped in the magnetic lines of force and their gradual release. This E2 pulse follows the E1 pulse by about 1 second and acts like a lightning bolt spread out over the entire area.It has a relatively slow rise time and is dissipated by anything that conducts into the ground. IT helps to remember that the E1 pulse has made everything positive polarity and the E2 pulse is a negative polarity. Damage from the E2 pulse will be limited to small transformers and unprotected low watt devices. (these things would normally be protected electronically but the E1 pulse destroyed those electronics)

Neither the E1 nor the E2 pulses is effected by the yield of the bomb. The 10 Kiloton Hiroshima and 15 Kiloton Nagasaki bombs would be "perfect" to produce damage from the E1 and E2 pulses. A modern hydrogen bomb of 1 Megaton might produce less E1 and E2 pulses because they use neutron reflectors to increase the explosive yield. That brings us to the E3 pulse.

E3 is much like the solar EMP. The blast from the bomb distorts the earth's magnetic field and when it snaps back high current is induced in long transmission lines. The E3 pulse is the only pulse that is directly resultant from the yield of the bomb. The higher the yield the more push is exerted on the magnetic field and the larger the inductance when it snaps back.

No more than one device can be effective for a period of time because once the first blast ionizes the atmosphere it will take time (up to a week) for the atmosphere to return to normal.

Because these bombs are detonated outside the atmosphere there is no blast, heat or radiation on the surface. No radiation sickness or burns will happen. Deaths will be the result of the loss of infrastructure and possible violence that grips those trying to survive.

 

[SheepDog]

What is everyone’ thoughts on those large 120mm ammo cans with intact rubber gaskets that seal tight? My thought is that this is a perfect faraday cage. I just picked up 4 of these and can get some more. While the intent was to use as a cache, I am thinking some of the items I can cache are electronic communication devices and solar charging items.

Ask yourself how it will handle a lightning strike. A Faraday cage must be a relatively good conductor that provides a good path to a good ground. The ammo box is covered with paint to keep the rust out and the gasket is made to be water tight but not a good conductor or insulator. To make it a good Faraday box you need to add conductors to ground. If you are trying to protect some electronics from the E1 pulse of an HEMP you will need multiple layers of high voltage insulation and good conductors all isolated from each other and the box. An excellent Faraday cage can be made from 1/2" hardware cloth formed into a box. That won't protect from an E1 pulse either but it would handle a lightning strike better.

 

[Haertig]

I think we have an EMP expert on the forum! Thanks for that info SheepDog. I'll have to reread what you said a couple of times for it to sink in though.

 

[INresponse]

If you are one of the few with working electronics they won't be of much use.

As long as you still had a source for electricity, either solar or generator, you could still use your electronics. You could still watch DVD's on the television, or video games. You could still access all saved information on your computer, play games on the computer, play music on the computer, write a daily summary so after things return to normal you could publish a book about what you experienced and how you survived. A stereo could play CD's. Two way radios would be very helpful. There are plenty of electronics you could store that would be very helpful as long as you also plan a way to have electricity.

 

[Haertig]

It's starting to sound like a good way to protect your stuff from an EMP might be to buy a plot in a cemetery, put your gear into a sealed grave liner, and bury the whole mess.

 

[Alaskajohn]

Ask yourself how it will handle a lightning strike. A Faraday cage must be a relatively good conductor that provides a good path to a good ground. The ammo box is covered with paint to keep the rust out and the gasket is made to be water tight but not a good conductor or insulator. To make it a good Faraday box you need to add conductors to ground. If you are trying to protect some electronics from the E1 pulse of an HEMP you will need multiple layers of high voltage insulation and good conductors all isolated from each other and the box. An excellent Faraday cage can be made from 1/2" hardware cloth formed into a box. That won't protect from an E1 pulse either but it would handle a lightning strike better.

Thanks for the response, but let's say I'm an idiot who needs additional clarification.

What if the 120MM was stored in a basement with a large log cabin overhead, an the basement is 10 foot deep below ground. The basement walls are thick poured concrete. What if I seal the 120MM with aluminum foil and run a conductive wire to a grounding rod driven 2 feet into the earth below the basement floor. Would that work?

I'll start a new thread sometime soon about what to store in a faraday cage so as to not derail this thread...

 

[SheepDog]

Thanks Haertig, but I am a student of the causes and effects of EMP and HEMP.
There are few to no experts because there is only one way to generate an E1 pulse and they frown at detonating nuclear bombs at high altitudes.
I have read everything the military releases and the studies done by universities but most of the data has one very big error. They can't reproduce the fast rise times. In addition to that their tests are limited to powers "below failure" of function. Car manufacturers have to destroy their cars to show crash resistance and survivability but folks who make EMP safety gear only have to show that they are built to a testing standard of one test.

I can take a triode designed with a 200 volt reverse blocking rating and break it with a fast rise time 150 volts or show it will handle a reverse voltage of 300 volts if I raise the voltage over a five minute time.

The math says that capacitive reactance stands the best chance of preventing damage from a fast rise single pulse that lasts less than 5 nanoseconds from start to finish. 1/2 nanosecond to max volts and 7 times that long to dissipate. The testing equipment produces rise time in milliseconds or thousands of times slower.

I do hope that folks are helped by the "simple" fix that uses plastic bags and heavy duty tin foil.

 

[SheepDog]

If you stand barefoot on concrete and touch a 120 volt hot wire can you feel the electricity?

DON'T DO IT!
Yes you will.
To protect your electronics place them in a zip-lock bag. Wrap that in a heavy duty aluminum foil with the edges double folded.
put that in another bag and wrap that in heavy duty foil double folding the edges.
One more time, into a plastic zip-lock bag and wrap it in heavy duty aluminum foil sealing the edges with double folds. Set it in storage where it won't get torn and after the HEMP open it up to use.

If you need to keep files and such up to date like I do with my laptop then use zip-lock bags and make envelopes from the foil so they can be opened and reclosed. As long as it doesn't tear it can be reused. If one or more of the foil envelopes tears then just fold a new one.

 

[UrbanHunter]

@Alaskajohn I think you would need to insulate what ever is inside your ammo can from the walls of the can, so the things inside the can need to be in plastic bags or something non-conductive, the seams of the can need to be sealed with aluminum tape. and the can needs to be grounded.

I've been told that one big problem with Faraday cages is when people want to run power into the cage and the wire acts like an antenna, defeating all of the work done to control the EMF.

 

[Alaskajohn]

@Alaskajohn I think you would need to insulate what ever is inside your ammo can from the walls of the can, so the things inside the can need to be in plastic bags or something non-conductive, the seams of the can need to be sealed with aluminum tape. and the can needs to be grounded.

I've been told that one big problem with Faraday cages is when people want to run power into the cage and the wire acts like an antenna, defeating all of the work done to control the EMF.

Thanks. I certainly would not want to run a wire into the cage. That sounds like a very bad idea.

 

[angie_nrs]

SheepDog, do you have a faraday cage that you put your tinfoil wrapped products in to? Or do you just wrap them? Would a 'fireproof document bag' provide even more protection since it is made of insulative materials?
How would you ground a metal trash can on a concrete floor?
What do you think the chances of a 'do it yourself faraday cage' (such as a metal trashcan) has of being successful since there is minimal testing to prove it's efficacy? One of your posts suggest that it's likely a losing battle.
Also in one of your posts it states it will take the atmosphere at least a week to return to normal. Does that mean things should be left in the faraday cage at least that long after the 'event' to protect those items from damage after the initial blast? Of coarse, that's assuming that they weren't fried along with everything else.

 

[SheepDog]

SheepDog, do you have a faraday cage that you put your tinfoil wrapped products in to? Or do you just wrap them? Would a 'fireproof document bag' provide even more protection since it is made of insulative materials?
How would you ground a metal trash can on a concrete floor?
What do you think the chances of a 'do it yourself faraday cage' (such as a metal trashcan) has of being successful since there is minimal testing to prove it's efficacy? One of your posts suggest that it's likely a losing battle.
Also in one of your posts it states it will take the atmosphere at least a week to return to normal. Does that mean things should be left in the faraday cage at least that long after the 'event' to protect those items from damage after the initial blast? Of coarse, that's assuming that they weren't fried along with everything else.

Lots of good questions...
No I don't use Faraday cage. they don't work for E1 pulses.
No a fire-proof document bag insulates from heat and has no capacitance to slow the voltage rise.
A metal trash can sitting on a concrete floor is grounded. All Faraday cages must be grounded but the protective envelopes and boxes for E1 pulse should not be grounded.
I think there is 0 (zero) chance of a do-it-yourself Faraday cage working at all. I think any commercial Faraday cage has the same 0 chance as well.
Yes I said it could take up to a couple of weeks before another HEMP would be possible but the E1 pulse only lasts a few milliseconds. It is safe to remove the electronics from their protection before you realize the HEMP has happened.

Let me stress this: Faraday cages are made to provide a clean path for electricity to flow to the ground. Every skyscraper is a Faraday cage. They are designed to allow lightning strikes to be grounded through the steel in the building to keep the people from getting a shock. Faraday cages will not protect anything from an E1 pulse.
E1 protection requires multiple layers of insulation and good conductors completely sealed at the perimeters so that no two conductors touch each other and there are no holes in the insulation or the conductors.

This is how it works;
the charge hits the first plate and the charge is stopped by the insulator until the entire plate becomes saturated (or 90%). Through capacitive reactance the charge is transferred through the insulator and onto the next plate in the opposite polarity. The plate has to fully charge because the next layer of insulator stops it. Once the next plate is charged then the charge is transferred to the next metal plate by capacitive reactance with the charge reversed again. The charge stops there because of the insulator until that plate charges.

At some point along that path the pulse is over and the charges regress which saves your electronics inside.
Why not just use an insulator? Because of the fast rise time the charge will travel through the insulator due to capacitive reactance. The charge on the outside of the insulator will be transferred to your goodies inside with an opposite polarity - which will still burn the junctions of semiconductors making them worthless.

Believe it or not this is pretty basic stuff. There is a capacitor in most communication devices to trap or pass electrical "noise". Capacitors are used to bring the phase angles of amps and volts back into alignment when they go through a transformer or coil. More on point to this application capacitors are used in timer circuits. The power goes through a conductor (usually a resistor) to a capacitor that takes time to charge to delay the power from getting to a switch or transistor.
In our example a resistor would be useless because the power would just hit both sides but with plates separated with insulators it slows the charge down the needed milliseconds to allow the charge to dissipate before it gets to the stuff we want to protect.

 

[Neb]

I found the attached pdf interesting.

I had to study electricity and magnetism in many classes for my physics degree.

One of the principles we could use to establish boundry conditions was;

The electrical field inside a conductor is zero.

https://byjus.com/jee-questions/can-electric-field-inside-a-conductor-be-non-zero/
So is the capacitor inside a capacitor... intended to deal with the magnetic wave?

Ben

 

[angie_nrs]

No I don't use Faraday cage. they don't work for E1 pulses.

So, to clarify....you wrap your electronics several times with plastic bags and tin foil? Would that work when a Faraday cage would fail? Do you just place them in an area and don't worry about them being in any type of insulative container?

Believe it or not this is pretty basic stuff.

LOL! None of this is in my wheelhouse at all! There's things I'm fairly clever at, but electronics is definitely NOT one of them. I had an electronics class many years ago. I did OK with it, but it was definitely not my thing. I couldn't wait to move on to something else.

It kinda sounds like if an evil country wanted to break us and use a weapon to take out our grid, then we'd likely all be screwed......even those with Faraday cages. It's not really what I wanted to hear, but better to know now than to find out later.....at the worst possible time.

 

[SheepDog]

There is no capacitor INSIDE a capacitor. The capacitors are in series and in three dimensions.
The E1 "pulse" is a positive electric field (plasma) produced by the displacement of the electrons and their capture by the magnetic field lines of the earth's magnetic field. The E1 is a "singular" pulse, it is not a wave. It doesn't propagate rather it is formed in place.

A plasma is any gas that is stripped of polarizing particles. In this case the atmosphere, ground, and water is stripped of electrons by neutrons that are not used in the cascade from the nuclear material in the bomb. It all becomes positively charged from the upper atmosphere to a depth of about 7 to 10 meters below the surface. This is why you don't want to ground your protective box or envelope and why a Faraday box won't work.

 

[SheepDog]

So, to clarify....you wrap your electronics several times with plastic bags and tin foil? Would that work when a Faraday cage would fail? Do you just place them in an area and don't worry about them being in any type of insulative container?


LOL! None of this is in my wheelhouse at all! There's things I'm fairly clever at, but electronics is definitely NOT one of them. I had an electronics class many years ago. I did OK with it, but it was definitely not my thing. I couldn't wait to move on to something else.

It kinda sounds like if an evil country wanted to break us and use a weapon to take out our grid, then we'd likely all be screwed......even those with Faraday cages. It's not really what I wanted to hear, but better to know now than to find out later.....at the worst possible time.

OK, not basic stuff for a lot of people, I have been called an alien since I was very young and less than an hour ago...
Yes, use freezer bags or the heavy black garden bags. If it doesn't have a ziplock then double fold the seams and tape over the folded seam to hold it closed. Start by putting your gear in the plastic bag. Wrap that in the heavy duty foil and seal the seams with a double fold and press it to seal.
Duplicate that process three times with the outside being foil. You can put it in a box or drawer of any material. You just don't want any holes or tears in any of the layers.

 

[UrbanHunter]

I like @Neb 's metal trash can, put it on a concrete floor or run a wire from the handles to a grounding stake, line it 3 times with heavy black contractor bags, put your stuff inside the bags and tie them off, put the lid on the trash can and seal the lid using aluminum tape.

I thought about using metal filing cabinets but they have got too danged many holes to ever be sure that it is sealed......