EMP protection

[veggie]

"The cell phone does not operate in the same band as the 2450 MHz of the microwave oven.  So much for shielding!  An EMP, and these are broadband by nature, will penetrate that oven."


DARN !  

[deeiche]

rm /

[rcavictim]

Here you go EMP Note Series at UNM.

I worked on MX missile EMP testing in the early 80's.  We built a fullscale mockup of an MX laying horizontal in an ABQ warehouse, direct drove it with a pulse generator.

man, that was a looooong time ago

I think mike90045 would be more interested if that work had been done instead in a BBQ warehouse! 

deeiche,

Did you ever work with "the trestle"?

[rcavictim]

Here you go EMP Note Series at UNM.

I worked on MX missile EMP testing in the early 80's.  We built a fullscale mockup of an MX laying horizontal in an ABQ warehouse, direct drove it with a pulse generator.

man, that was a looooong time ago

I think mike90045 would be more interested if that work had been done instead in a BBQ warehouse! 

deeiche,

Did you ever work with "the trestle"?  OOPS didn't see your link until after I replied.  I guess YOU DID!

[deeiche]

rm /

[wagspe208]

Wow, look what a simple little question turned into.
So, my pole barn is ok? The seams are not bonded. They overlap. It is an old barn, so galvanized metal, not powder coated/ painted stuff, so should be pretty good conductivity between panels.
So, if you wanted to do a cover all scenario.. would you use a small mesh as opposed to chain link fence? Something like expanded metal.
Does metal thickness or gauge matter?
Just wondering.
Wags

[rcavictim]

Wow, look what a simple little question turned into.
So, my pole barn is ok? The seams are not bonded. They overlap. It is an old barn, so galvanized metal, not powder coated/ painted stuff, so should be pretty good conductivity between panels.
So, if you wanted to do a cover all scenario.. would you use a small mesh as opposed to chain link fence? Something like expanded metal.
Does metal thickness or gauge matter?
Just wondering.
Wags

Chain link fence would be awfully poor.  Expanded metal is very good, especially aluminum if you bond the edges properly. Brass is better because you can solder one sheet to the next for a perfect continuous ground plane effect. In the kind of thicknesses you would find available to builders and industry it will be fine thickness wise. Steel expanded metal sheets could be brazed together with a torch. Chicken wire with the small 1/2" holes is pretty effective up to microwave frequencies, inexpensive and can be soldered. Heavy BBQ aluminum foil works well also.  The trick is connecting to the edges because aluminum has an insulating oxide layer.

Outfits that service communications gear like mobile telephones and taxicab radios often have an RF tight room inside which they do their work.  This keeps interference out and transmitted tests inside.  Most that I have seen use fine copper or brass mesh and the door with the continuous finger strip placed over a room made of open 2x4 wooden skeleton frame. The mesh is stapled to the wood and soldered at all the seams. They use a especially good mains filter bonded to the cage at point of entry to get the power into the room.

Your pole barn will not protect you with the panels just laid overlapping.  You need excellent continuous contact wherever the separate sheets meet, everywhere.  Wherever the contact is not perfect is where the RF pulse can get in.

Guys, I run an RF and microwave lab in support of an astronomical radio observatory and I do related microwave antenna design.  I also do occasional very high voltage pulse work, or at least used to and have ruined equipment by accident in my lab due to EMP.  You often never know where the pulse may end up. Many conductive objects and shapes can become resonant at the wavelength where the pulse energy is present and ring like a tuning fork developing dangerous voltage across themselves and sparking or suffering fatal overvoltage of components.  It doesn't take much voltage to jump sub micron gaps in modern miniature electronics.  I blew a wall socket out of a trailer once 100 feet from the lab building from a pulse that got into the mains.  My place is protected better against lightning strikes than anywhere I know that isn't a big money government facility.  I have no phobia or protection plan for a wartime type EMP attack.  I was totally kidding about my tinfoil hat.  That is just a terrific joke that pokes fun at kind of an urban legend.  A solar EMP coming in on the power lines OTOH IS something I am taking measures to protect my property against, as well as local lightning hits to Mr.Utility beyond my own property where I have no control.

[deeiche]

rm /

[mike90045]

So I realized, no one ever asked "What are you trying to protect?".

I have this nice clock radio with big LED numbers,  All the new ones have little LCD digits.

[wagspe208]

Sure, a little off topic maybe. I drive a lot, so I have time to think about strange stuff.
I was wondering if a metal building if properly grounded would serve as a Faraday Cage. Or if you have to do the expanded metal/ chain link fence thing??
Oh, of course this means would a metal building protect against an EMP? N. Korea just annouced they have a functioning one. What can go wrong?
Wags

So I realized, no one ever asked "What are you trying to protect?".

Well, excellent question. Answer... everything I believe I need to function if an EMP occurs.
Be prepared. Boy Scouts, you know.
Wags

Ok, really was just an interesting subject. Knowledge is precious.

[deeiche]

rm /

[cognos]

I'm not concerned with EMP protection, but I have had my issues with surges coming down my rural power line. So I equipped my main panel with a whole-house surge protector - this one here: http://74.53.140.226/~sycomsur/products/SYC_120_240_T2-4-3.html

In the past, I've had under-voltage problems, and this won't correct that. But it will take care of over-voltage and lightning strikes. I hope... it's been there for about ten years, must be working. Or is it... 

In the early 80's, I had one particularly scary under-voltage event, courtesy of Ontario Hydro. They allowed a factory on my main feeder to install a robot welder that taxed the limits of the power available (they made refirgeration coils - bend all day, weld 'em at night)... and they only ran it at night to take advantage of lower rates. So every night at 9 PM, my lights would flicker - for one second, every ten seconds - until about 11:30 every weeknight. My TV would "dim", and sometimes the screen would shrink... I made them aware of my issues, and those of my neighbors on the same line, and they put some sort of power logger device in my basement hooked up to my panel. They eventually put in a giant capacitor bank on the line about a mile away... didn't work...

The data logger showed that my power was being pulled down to 85 volts occasionally... my light bulbs burned out frequently, a fridge died, my Apple II+ computer died one night... Hydro paid for these things...

One morning, I came home after a night shift - I walked into the house, and smelled an electrical fire. Very characteristic smell. No smoke in the house, just the smell. I looked everywhere, I couldn't find anything... but I was a bit afraid to go to bed.. sat down in the living room, had a cup of tea - looked up at the ceiling fan, it wasn't turning, but all the paint on the motor housing had turned black, and the drywall around the sconce was discoloured. It was too hot to touch... On investigation, all the wiring inside was melted and black...

Turns out I had left the fan on "Low" the night before when I went to work. At some time during the evening, the voltage had dropped so low that the fan had stopped turning. Later, when the voltage had come back up to normal, the fan didn't have enough "ooomph" to get turning again - so it sat there, stalled, and just heated up...

Hydro paid for that, too - and got read the riot act by my insurance company, and eventually, spent several million dollars running new lines. Of course, the factory went out of business years ago...

Since that incident, I am very diligent about turning off all appliances before leaving the house...

[rcavictim]

Well, excellent question. Answer... everything I believe I need to function if an EMP occurs.
Be prepared. Boy Scouts, you know.
Wags

Ok, really was just an interesting subject. Knowledge is precious.

Well, so I don;t know what you are trying to protect may I suggest you consider tubes for any of your electronics, throw them nasty semi-conductor devices away. 

and for those folks who like their LED alarm clocks build one with Nixie Tubes.

I have always liked the looks of nixie tubes very much.  I have an old General Radio 500 MHz frequency counter with about 10 nixie tubes in the readout and it looks awesome.

[rcavictim]

<snippage>
Since that incident, I am very diligent about turning off all appliances before leaving the house...

I make it a policy that when I leave the house I consider the consequences of "What if I have an accident or Department of Homeland Security crosses the border to protect me and I cannot return to my home?".  I then thoughtfully turn off devices or disconnect that which ought not be left running without supervision.  I will not leave a diesel generator, washing machine, clothes dryer oven or woodstove running while I am away.

[Horsepoor]

I've been reading and thinking about EMP protection. I like the idea of using a metal trash can, and insulating the interior with cardboard so nothing will touch any of the metal surfaces. Bag all internal storage objects in Mylar bags and heat seal the opening of the bags closed. Finally, bury the trash can under about 3 feet of dirt. This accomplishes two things, prevents theft and I believe it will help with EMP shielding. I would appreciate comments and thoughts on the concept of burying the metal trash can in an effort to mitigate EMP effects.

Additionally, I live in South Florida so assume a high-altitude EMP (HEMP) detonation somewhere a few hundred miles over the central US. If my understanding of the E1, E2, & E3 pulses is correct, then the EMP effect travels in a straight line from the HEMP detonation (line of sight). If I figure an angle of 2 degrees formed by 3 feet underground in south Florida to the HEMP detonation height this would create a line of sight of perhaps 86 feet through dirt to the top of trash can and several hundred feet to the bottom. Your thoughts please.