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#90498 - 04/05/07 09:38 PM Re: The definitive EMP effects thread [Re: ironraven]
Russ Offline
Geezer

Registered: 06/02/06
Posts: 5357
Loc: SOCAL
Another issue to consider is in-band vs out of band equipment. An AM/FM radio is in-band and it has a real antenna. The EMP doesn't need to couple through the powerline, it can enter through the antenna. IIRC both an FM/AM radios RF and IF frquencies are in-band to an EMP so it's an easy target.

But talking about losing small electronics is really trivial compared to losing the power grid. We can all hide small cheap radios and other electronics (laptop computers) as back-ups, but when the grid goes down because those big-ass transformers have been fried, we'll all be living off grid for a long long time.

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#90500 - 04/05/07 09:54 PM Re: The definitive EMP effects thread [Re: garland]
Arney Offline
Pooh-Bah

Registered: 09/15/05
Posts: 2485
Loc: California
Originally Posted By: garland
Planes are also faraday cages, far more so than a car actually.


I'm thinking about this...a Faraday cage needs to be grounded...and it also doesn't allow EM signals to pass through...I think cars and planes fail on both counts. Well, a car is grounded but not well grounded. But I can definitely make a cell phone call from inside each vehicle, so EM can pass in and out.

Cars and planes may survive EMP, but I think it's inaccurate to say it's because they are natural Faraday cages. The electronics on both are shielded against normal EM interference, and that may be enough to save them depending on the particular EMP.

Actually, aren't most open-mesh Faraday cages insufficient to protect against EMP, although they may be sufficient against things like lightning? I know I read that somewhere.

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#90501 - 04/05/07 10:09 PM Re: The definitive EMP effects thread [Re: Arney]
Russ Offline
Geezer

Registered: 06/02/06
Posts: 5357
Loc: SOCAL
Since most of the EMP power is below 30KHz, open mesh should work, as long as it meets other faraday cage requirements. I've heard different theories on grounding, I'm not sure a faraday cage needs to be grounded to protect the contents.

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#90502 - 04/05/07 10:32 PM Re: The definitive EMP effects thread [Re: Russ]
Arney Offline
Pooh-Bah

Registered: 09/15/05
Posts: 2485
Loc: California
I was thinking some more...if a live powerline that falls on your car doesn't electrocute the occupant, is that because of a Faraday cage effect specifically, or because of the charge simply being channelled through the car body to the ground, which sounds similar perhaps to a Faraday cage but is not technically the same thing?

I mean, in a true Faraday cage, doesn't the interior of the cage technically have zero charge? And yet we're warned that if we're inside a car that a power line falls on, not to touch anything metal inside the car. That would seem to violate a characteristic of a Faraday cage, wouldn't it?

OK, now I'm thinking too much about this. crazy

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#90504 - 04/05/07 11:12 PM Re: The definitive EMP effects thread [Re: Russ]
Arney Offline
Pooh-Bah

Registered: 09/15/05
Posts: 2485
Loc: California
Originally Posted By: RAS
Since most of the EMP power is below 30KHz...


Did I remember this formula correctly? So, 30 KHz would be a wavelength of...10,000 m? So a mesh with openings spaced less than 10,000 m apart should protect/attentuate EMP? Did I do that right?

Well, in that case, practically any enclosed space made of some conductor, like a car or plane, would act as a Faraday cage against EMP. Wait, then we're right back where we started!


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#90505 - 04/05/07 11:33 PM Re: The definitive EMP effects thread [Re: garland]
ironraven Offline
Cranky Geek
Carpal Tunnel

Registered: 09/08/05
Posts: 4642
Loc: Vermont
When listening to experts who have a new revelation that contradicts what has been the generally agreed upon answer to a question for 20+ years, uhmm... Yeah, I want to know who signs their pay check, and I want it proof read.

I'm saying that because my track in college was computers and electronics, and I had profs who had either been in the space program or worked on defense contracts who agreed with everything I've always learned about EMP. This flies in the face of it, particularly when you realize that we are deploying non-nuclear EMP devices and the effects are slowly becoming declassified and emperical data supports the general consensus.
_________________________
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When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.

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#90507 - 04/05/07 11:44 PM Re: The definitive EMP effects thread [Re: Arney]
Eugene Offline
Carpal Tunnel

Registered: 12/26/02
Posts: 2997
Something to think about. Modern transistors and IC's are a lot more complicated than they used to be. A simple transistor is no longer a simple transistor but inside that package contains all sorts of protection, over voltage, surge, over current, thermal, short circuit, etc. So while they may be smaller than older ones they have a lot more robustness.
Vehicles are the same way, even though they have a dozen computers they also have extra protection. Nearly every device in my truck is protected by three levels of fuses for example. Then there are more grounds, I've counted over 30 ground points and don't even have the complete schematics for mine. So they do act somewhat as a farady cage. Then the modern tires are somewhat conductive to keep the vehicle grounded as well.

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#90508 - 04/06/07 12:14 AM Re: The definitive EMP effects thread [Re: Eugene]
LED Offline
Veteran

Registered: 09/01/05
Posts: 1474
Not to deviate from the topic but i just read this article about the recent solar burst that apparently effected all GPS units (to a varying degree) on the sun side of the earth.

Quote:

The cause for their concern, Johnson said, was an unexpected solar radio burst on December 6 that affected virtually every GPS receiver on the lighted half of Earth. Some receivers had a reduction in accuracy while others completely lost the ability to determine position, he said.


Quote:

In addition to the GPS system, the December solar flare affected satellites and induced unexpected currents in the electrical grid, Johnson said.

"The effects were more profound than we expected and more widespread than we expected," added Kintner.

Dale E. Gary, chairman of the physics department of the New Jersey Institute of Technology, said the burst produced 10 times more radio noise than any burst previously recorded.


sorry for my ignorance but is a solar burst similar to EMP?


http://www.cnn.com/2007/TECH/04/05/gps.solar.ap/index.html






Edited by LED (04/06/07 12:14 AM)

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#90512 - 04/06/07 01:48 AM Re: The definitive EMP effects thread [Re: LED]
ironraven Offline
Cranky Geek
Carpal Tunnel

Registered: 09/08/05
Posts: 4642
Loc: Vermont
Same thing.
_________________________
-IronRaven

When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.

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#90529 - 04/06/07 03:30 AM Re: The definitive EMP effects thread [Re: falcon5000]
AROTC Offline
Addict

Registered: 05/06/04
Posts: 604
Loc: Manhattan
So if I get this right tin whiskers is like having metal stalactites build up by electroplating and (I'm assuming) some sort of self organization until they contact another surface and short out?
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A gentleman should always be able to break his fast in the manner of a gentleman where so ever he may find himself.--Good Omens

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