[topcat]

After reading about 200 pages of 'Lights Out' the EMP thought keeps jumping into my head. Yes, I have heard of it and thought of it before.

Knowing up front that there are many variables related to this question (altitude, yield, weather, etc.) I will still ask it:

Here is the question: Say we put some radios, walkie's, etc into something like a gun safe in the basement, what are the off-the-wall chances that they would still function?

Thanks.

[PrairieMule]

I believe Faraday cage on a vehicle and household/office electronics require a Faraday room.

http://en.wikipedia.org/wiki/Faraday_cage

[fireplaceguy]

I'm not convinced a faraday cage will do the job in the event of a deliberate EMP strike - at least not the mesh type. After reading Lights Out I googled EMP and found a government publication that showed preparations that were much more elaborate than a simple mesh cage - more like the wiki picture of the Faraday room. There were diagrams of airlock style entrances where you closed the outer door behind you before you could open the inner door to enter the protected area. Grounding is very imortant, as is the need to enclose the item to be protected 100%. No gaps or you're finished...

Cars are a real problm. The main black box is often under a seat but there are other electronic modules under the dash and under the hood. Modern transmissions have electronics in them, as do climate control systems. When it comes to newer automobiles, my guess at a rule of thumb is that if it has fuel injection, there are so many interacting computer chips and sensors that you would probably need to shield an entire garage to be sure of everything surviving. (All you'd need to do then is store the rest of your electronics out there as well.)

In Lights Out they had a working generator that had been stored in a metal box inside a metal shed. Whether that works in the real world is still a question but it seems like a good start. That's two layers of 100% shielding. I'm already storing things in steel cargo containers, so it will be little trouble to pick up a couple of large heavy steel job boxes and put them inside a container. I've been thinking about this anyway as an added security measure...

Here's something to ponder - static electricity is deadly to PV modules, and proper grounding is critical to a good installation. I haven't heard back from my rep yet but I should be getting a written response regarding EMP from my PV module manufacturer soon. I already know the inverters would be DOA...

High efficiency furnaces, boilers and demand water heaters have electronic controls (my wood stoves are looking better and better...). So (in almost every case) does your fridge, washer and dryer. How about the electronic ballast in the base of your screw-in CF bulbs? The list goes on and on...

[Daculling]

From what I've researched there is really no data on what would be required to defend against such an attack... depending on the size of the weapon (Nuclear).

Realise that EMP weapons that do not rely on a nuclear reaction do exist. And I'm not talking about some dude with a microwave and horn antenna, if you know what I mean.

[gg3]

What matters is the amount of energy that gets absorbed by the device. Keep in mind the inverse square law: the intensity of the pulse decreases very quickly as you get further away from ground zero. There comes a point where only devices connected to long wires (for example power and telephone lines, and rooftop TV/FM antennas (remember those?)) are affected and stand-alone devices are not harmed.

Your chances of being within the critical distance at which stand-alone devices are harmed, are about the same as your chances of being taken out by a terrorist nuclear weapon.

If the superpowers start going at it, EMP will be used as a precursor to nuclear attack. At that point, you've got bigger things to worry about than dead electroncs.

[TheDude]

How effective do they think some kind of focused EMP could be against hardened targets? Silos etc. Waste of time?
Thanks for mentioning Lights Out - didn't know about that.

[Chaparral]

$this->bbcode_second_pass_quote('gg3', 'I')f the superpowers start going at it, EMP will be used as a precursor to nuclear attack. At that point, you've got bigger things to worry about than dead electroncs.

[perdition79]

Microwave ovens are Faraday cages. Do some dumpster diving, clean a couple up and stick a few ham radios, FRS radios, CB radios, etc. inside.

[dogf]

Link

With the proper planning we should be fine.

"Campfires, horses guitars, singalongs, washboards, Barn raisers, and sitting on the porch is back in after the appropriate amount of time underground in a shelter."
I believe this is why there is so much porn on this site. It's the romance of the above.

[ChumpusRex2]

To protect against an EMP requires several measures:
1) A Faraday cage enclosure - the level of protection afforded depends on the quality of the cage.

A car body is a crude faraday cage, but the gaps where the windows are let in significant electromagnetic energy - although there is some protectino against things like lightning.

A metal cake tin, or microwave oven are very good Faraday cages. The thing that makes Faraday cages good - is lots of metal with good electrical conductivity. Copper is best. Aluminium, pretty good. Steel - less good. Stainless steel, pretty poor. The more metal the better - foil is just about functional, 1mm plate very good, 3-5 mm plating outstanding.

The thing that will destroy a Faraday cage is holes. Any holes will degrade the cage. In teh case of MW ovens, the door screen contains tiny holes - but they are much smaller than the waves, so the waves are well blocked - but nevertheless, this is less efective than if it were solid.

Where used to protect super sensitive equipment from interference - e.g. MRI scanners - the Faraday cage is made of thick copper plates (1/8 inch), that cover the entire ceilling, floor and walls of the room, and are then soldered together to form a seamless metal mat. Doors and frames have aluminum or copper foil covered rubber seals that make a sealed electrical connection between the door and rest of the room.

In defense situations - there may be air-lock style double doors, to ensure that the entire cage is never opened to the outside.

There also needs to be appropriate precautions to ensure that the cage is maintained. There have been a few incidents where hospitals ahve installed MRI scanenrs, only to find that the images produced were terrible. The cause - an electrician had run out of space in a shielded wiring conduit and had drilled a hole through the wall to run a cable - the hole breached the cage and allowed external EM interference into the room.

2) Protection of the power and communications lines
It's no good developing an excellent Faraday cage if you're channeling EM in from outside along your power lines. For various reasons, the long cables that form power lines are particularly good at absorbing the classical EMP.

If equipment has to be powered up, then various surge protection and power cleaning systems have to be installed.

Similar concerns apply to communications lines. Telephone/cable lines are susceptible (unless deeply buried) - and potentially allow EMP in. Even wireless receivers/transmitters are the same, because they have to be outside the cage.

For electronic installations which need to be safe - fiber optic is the only safe method of electronic communication. Backup power supplies (generators) may also need shielding to prevent pulses tracking in via the generator supply - and also to protect any electrical systems on the generator.

3) Physical mass shielding
Although the ground is a poor shield to EM waves - nevertheless it does have some effect.

If you've got a deep basement - then the surrounding earth will limit some of the effect, coming in from the sides. But doesn't do much about the top.

If you've got a fallout shelter, then that's as good a place as any to put any dedicated protection for high-risk items.

---

How at risk are you? If you're near a major city that is a potential target, then you might be at risk from a nuclear attack on that city. By and large, if you're well outside the blast and fallout zone, then you'll probably escape most of the EMP.

The big concern is a nuclear explosion in space. If you can get the explosion above about 200-300 miles up, then the EMP could theoretically cover an entire continent. What's not well known is how much this would dilute the EMP? Development and keeping of type of weapon is presently outlawed under a variety of treaties - but who knows what will happen if TSHTF. Given the complexity of launching a nuclear weapon into space - it's highly unlikely that terrorist groups would be able to achieve this. There are also few governments with the facilities to do this - lets just hope they don't get too pissed with each other. Nevertheless, the infrastructure impact of such a weapon (disruption of a contintent wide power grid, and communications system - even temporary) would be of immense strategic importance.

[lotrfan55345]

Just get a microwave oven and put some of your valuable electronics in there, it'll work.

[smallpoxgirl]

Wrapping stuff up tightly in aluminum foil would provide adequate protection. The actual voltages over a short conductor like that are pretty small. The longer the conductor, the higher the voltage, so power lines, phone lines, and anything hooked to them will be the most profoundly affected. There was an electromagnetic solar storm in 1989 that produced enough EM emissions to knock out the power grid in Quebec.

[I_Like_Plants]

$this->bbcode_second_pass_quote('lotrfan55345', 'J')ust get a microwave oven and put some of your valuable electronics in there, it'll work.

[gg3]

Discarded microwaves: No, no, no. Holes in the door screen. Non-conductive door seals. Please let's not propagate the myth that these things are any good for EMP shielding.

--

Chaparral: Good point, we should factor that into our design. Ideal case, a decent-sized underground shelter (one never knows, a local nuclear exchange in the Middle East or Asia could produce fallout that takes a while to come down from the clouds so it's still coming down by the time it gets overhead here), and off to the side a small room lined with copper.

We should get the electric & telecom lines further underground; this in turn will depend on the overall conduit plan including water & sewer, plus the capabilities of available excavators, plus the cost of backfill material (I prefer controlled-density fill, less susceptible to settlement and other changes that could shorten the lifespan of the buried pipes).

Electromechanical telephone switching (Strowger system) is immune to EMP (historic track record in areas near nuclear weapons tests); another good reason to have that as either a primary or as a backup. My dude back East can design & build to suit, including a planned life of 150 years.

[MD]

$this->bbcode_second_pass_quote('lotrfan55345', 'J')ust get a microwave oven and put some of your valuable electronics in there, it'll work.

[Kingcoal]

A long time ago, I worked for a company who was using heat sealers to make various ring binder books. The heat sealers used RF to make a hair thin seal on the vinyl perimeter of the book. These heat sealers were basically 27 Mhz, 10KW transmitters. We had to make faraday cages around the rooms where they were housed to comply with FCC rules. We used window screening with overlapping seams stapled together. Then we'd go around with a signal strength meter. It worked pretty well, however we didn't do the airlock style doors, even though we should have.

How powerful were these machines? I could hold a 4' florescent tube over one of them and it would light up! In fact, we used small florescent tubes as indicators for when the machine was in operation.

[ironborne]

I remember when I was in the Army they told us that 3' of soil would protect radios from EMP. I don't know if this is true or if it was someones idea to keep us busy digging holes.

[Chaparral]

Plans and components for EMP generating devices are available. It would be interesting to fabricate such a device and test the effects on things like photovoltiac panels, diodes, LEDs, older style transistors in their metal cans, simple NPN/PNP transistors, 700 series logic chips and analog chips and voltage regulators.

My idea is this: a 60 megaton thermonuke could detonate 360 miles above Omaha and we'd need to have a way of guesstimating the effect on a device in say, Warner Springs, California. Or a 3 megaton device could be airburst 3000 feet above San Diego or a multi-kiloton device detonated on a nearby Naval installation on the summit of Mt Laguna. What are the pulses from the various scenarios? Is there even a way to determine that?