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Unread postPosted: Sun Jan 07, 2007 11:21 am 
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To cut a long story to almost 0:
I need an EMP proof storage solution, or at least a EMP proof Backup.
I would love to tell you the field stength, but there is no chance of predicting it.

Any ideas?
Thanks

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 Post subject: EMP proof storage
Unread postPosted: Sun Jan 07, 2007 11:33 am 
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Completely EMP proof would be punched tape, Mylar recommended for longetevity. The other thing I'd look into would be optical- either MO or writable DVD (more resistant to physical damage than CD-R).

I'm not up on designing faraday cages et al for protection against electromagnetic phenomena, but that could be used also.


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Unread postPosted: Sun Jan 07, 2007 11:47 am 
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DVD seems to be the best backup solution, but the thin metal layer could be ripped off the plastic by magnetic influencing.
MU-metal shielding is an option, however it is unclear how thick it would have to be 0.5mm-???m.


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Unread postPosted: Sun Jan 07, 2007 1:27 pm 
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Faraday cage would be the best.

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Unread postPosted: Sun Jan 07, 2007 1:45 pm 
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A giant cube of differently coloured 1x1 LEGO bricks, that would be pretty EMP-proof and would look nice too.

Am I right in guessing some over-zealous manager was writing specifications?

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Unread postPosted: Sun Jan 07, 2007 3:27 pm 
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Most devices are fairly EMP tolerant, unless you are expecting a nuclear blast or working right next to a superconductor or a big-ass generator (but we are talking megawatt to gigawatt levels).

Archival-wise, magnetic media stored inside an EMP-proof valut should just suffice (tapes, DVDs, HDDs, etc).

The computing elements can also be encaged in TEMPEST-ready enclosures (Military,industrial std for EMP-tolerant devices). But that is rather specific...

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Unread postPosted: Sun Jan 07, 2007 4:11 pm 
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R-ten-K wrote:
Most devices are fairly EMP tolerant, unless you are expecting a nuclear blast or working right next to a superconductor or a big-ass generator (but we are talking megawatt to gigawatt levels).


Don't rule out solar flares and CMEs....or an e-bomb.

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Unread postPosted: Sun Jan 07, 2007 6:16 pm 
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zahal wrote:
R-ten-K wrote:
Most devices are fairly EMP tolerant, unless you are expecting a nuclear blast or working right next to a superconductor or a big-ass generator (but we are talking megawatt to gigawatt levels).


Don't rule out solar flares and CMEs....or an e-bomb.


Unless you are out there in Space, solar flares are not an issue. If the reader has to worry about e-bombs, I assume data integrity is the least of his troubles ;-).

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Unread postPosted: Mon Jan 08, 2007 7:48 am 
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Where does the US military get its HDD/PC EMP shielding from?


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Unread postPosted: Mon Jan 08, 2007 9:24 am 
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They will probably won't tell you, and you probably don't want the prices from military contractors. If you have to ask in this forum, chances are that your company can not afford them ;-)


Here is a list of TEMPEST providers, after 9/11 a lot of security links have been removed so it is a PITA trying to get this sort of information off the net sometimes.

http://www.eskimo.com/~joelm/tempestsou ... Consulting

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Unread postPosted: Mon Jan 08, 2007 9:44 am 
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Thank you very much!
Hmm, the only usable product on that site is a 19" shielded rack vom Cabrack.
It shields 100db at 1GHz... could be sufficient

I fear I'll have to build one myself using 3mm MU-metal.


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Unread postPosted: Sat Jan 13, 2007 12:23 pm 
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DaSeitz wrote:
Thank you very much!
Hmm, the only usable product on that site is a 19" shielded rack vom Cabrack. It shields 100db at 1GHz... could be sufficient

I fear I'll have to build one myself using 3mm MU-metal.


Either way, once you've installed this "shield", you can start planning on how to prevent EMP's from being picked-up by the various antennas leading into the cage... :?

To be completely safe, you would neet to electrically insulate EVERY component from the outside world. That means power lines (a good UPS maybe?), network, FC and the works.

Reminds me of that NASA experiment, where they stretched out a tether to see if the earth's rotating magnetic field would induce a high enough current in it, to be of any use.

Well, let's just say the several mile long wire blew like a fuse. I've heard rumours that the aliens twarthed the experiment but that's taking it a bit too far methinks 8)

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Unread postPosted: Mon Jan 15, 2007 11:59 pm 
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DaSeitz wrote:
To cut a long story to almost 0:
I need an EMP proof storage solution, or at least a EMP proof Backup.
I would love to tell you the field stength, but there is no chance of predicting it.

Any ideas?
Thanks

----
Greetings from Bavaria


I've done some radio field installs, and they're designed for lightning. Used quite a bit of PolyPhaser gear, seems to work as advertised, though not sure what they're curent offerings are. They had some Ethernet supressors last time I checked (long time ago). They have lightning-rated parts and EMP rated parts, it's all in the clamping effectiveness for the risetime of the pulse, EMP being much 'faster' than lightning. And they have a mean-assed looking simulator in their labs.

The basic trick is to use supression gear for every external cable at a common entry point bonded to a common panel, thus all of the equipment in the rack can never stray any more than the rated surge voltage away from the grounding panel. The entire rack rises above ground potential and falls again after the event. Of course, this does nothing good for the external gear, but the stuff in the rack should be good.

So, with entry supressors which should allow firewire, Ethernet or USB, or Fibre Channel signals to pass unfettered, referenced against the input grounding panel, and with the AC input also referenced against this ground. If a pulse comes in through a cable, there will be a sudden voltage differential between 'outside' and 'inside', and the supressor clamps would maintain safe voltages for the equipment inside the rack, instead shunting the entire voltage differential to equipment outside the rack, more than likely destroying it.

I've personally seen a radio site in Jamaica up in the hills where the electrical panel almost got blown off the wall, and upon plugging the rack back into a live circuit, it came right up without any problems except the text on the monitor in the rack was now tilted about 30 degrees... man that had to have been some whack. The GaAsFET preamp ahead of the receiver multicoupler wasn't even damaged in the slightest, nor was the attached battery backup bank and charger.

How thick does the metal in the cabinet have to be? It would seem to me so long as the entire cabinet itself was RF tight and made of reasonable-gauge metal, it should never have to carry enough current to destroy it. It just has to be able to handle the induced current due to the propagating pulse, and if it's a flat sheet it should be able to handle a lot without failure. If the cabinet (and contents) are 'riding the pulse' so-to-speak, even less so. With a good metal cabinet, with good metal drive arrays and such all bolted together, I can't see enough of an EMP pulse getting inside to do much damage, at least compared to a direct entry via a cable. Cover the inside with copper screening, that'll likely get another 20 dB or more isolation.

Of course if you're instrumenting a blast site, then there may be issues, likely and magnificiently subsumed by what needs to be done to protect from the mechanical blast wave.

Wonder how WiFi works through 40-50 dB of isolation? Then you could just run AC into the rack, have an internal server/WiFi, and connect from outside, no wired data at all. Could be as simple as that. Paint 'er up like a British telephone booth with the time you save.

The real deal, though, is stuff like flash detectors that mechanically clamp inputs ahead of the EMP pulse.

But, no matter how you slice it, whatever's outside of the cabinet should be considered disposable in the plan, deferring to data safety instead. Otherwise the problem can't really be effectively dealt with.

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Unread postPosted: Tue Jan 16, 2007 11:16 am 
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Dr. Dave wrote:
But, no matter how you slice it, whatever's outside of the cabinet should be considered disposable in the plan, deferring to data safety instead. Otherwise the problem can't really be effectively dealt with.


Aha, so you should save some room in your EMP enclosure and also put in some biscuits and a bottle of water :).

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Unread postPosted: Tue Jan 16, 2007 11:41 am 
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Thanks again for all the replies.
I'll put everything in a MU Metal case, data transfer from outside is not soo important.
Time to start searching for the parts... .


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