EMP

[Skvez]

Earthing can be a route for the EMP to get coupled *to* your device, especially if you use the utility (mains) earth (rather than running a dedicated earth to an earth spike). While an earth will help drain away any charge that might build up on the surface from a prolonged (solar) EMP I'd be inclined to go not-earthed.

[Paul]

Regarding earthing, this from Wiki regarding Faraday cages:
"The metal layers are grounded in order to dissipate any electric currents generated from external or internal electromagnetic fields, and thus they block a large amount of the electromagnetic interference".

From me:
I used to work in a Faraday cage setting up parametric amplifiers.
Pain in the bum it was but nothing was insulated from the inside of the cage. Metal shelving too!

Lets talk Nuclear, instant sunshine, aka crowd pleasers!
A nuke EMP is basically a 3 part attack on electronics.

E1, Gamma wave generated energy.
Punches through just about anything.
VERY VERY VERY fast, short duration. Loads of energy.
Even a commercial Faraday cage would struggle at this one above ground.

Best solution? Loads of earth above you AND a commercial cage.
Just disconnecting the aerial lead is enough though to save a radio only don't leave the lead resting on top of the radio case.

E2, slower more like a lighting strike. Real electrical energy kick.
Cages will stop that easily.
If you have lightning protectors fitted, they'll kick in.
Probably blow out but they will help stop the thump.
Aerials, just disconnect the gear.

E3, this is the real killer as it knocks out the national power lines.
Magnetic generated power, dead slow, swirly bit.
The "pop" basically stirs the Earths magnetic field round which generates electricity as it passes through long cables.
Faraday cage, no problem. Gear Safe.
Can affect anything which is susceptible to strong magnetic fields though.

Regarding a solar surge.
It's the same BUT the real killer is the E3 pulse.
That can last for many minutes. Definitely national grid frying capability.
Faraday cage? OK as long as what's in there isn't affected by high magnetic flux.

There's been a few mentions about microwave ovens.
The metal box keeps you from frying by keeping the RF in.
No difference really just the other way round to a Faraday cage.
Whoops, nearly forgot, that's earthed too.

Problem is finding one that will keep out a wide spectrum of frequencies.
Although the metal is bonded throughout, mine still lets 27MHz through.
Stops the phone though.

[Metroyeti]

Would an emp stop batteries? Like aa not car batteries? Not read up on emp at all. got some homework now

[Paul]

No it won't BUT you do need to disconnect batteries before a pulse.
That's because electronic components CAN be destroyed so something like filter components could short out and discharge an attached battery.