> the body of a surefire is part of the circuit. So, if EMP could/would/will blow it out, then it
> would travel through the flashlight body.

I've come to the same conclusion. I think it would be fairly easy to design a hardened flashlight, though. It'd need a metal "lens cap" to shield the bulb/LED, and it'd need to not make the shell part of the circuit. But it's probably not worth it: cheaper and as effective to keep it in a metal biscuit tin when it's not being used. Don't let it touch the sides.


> The altoids tin on the other hand might.

Yep. I'm now fairly sure of this. The metal is opaque to the EMP and will sheild anything inside it. The EMP will induce current in the tin itself and in anything touching the tin, but something like a Photon Microlight which has a plastic shell keeping it away from the tin ought to be OK. The tin doesn't need to be thick, nor do small holes in it matter much, but it does need to be made of a conductor with the lid shut.

The controversial issue is whether a Faraday shield needs to be earthed. I've found several references which say it does (including some in this thread), but I don't believe them. I've also found references which don't mention it and some which flatly say earthing is not needed. I'd need to see more argument and more physics before I believe earthing is needed.

Earthing provides a favourable route to ground. If you don't earth the tin, the current will reach ground by some other route. If you are holding it, it might go to ground through you. But whatever the effect that has on you, it's not going to affect what's inside the tin. A charge may build up and take a while to dissapate, and the tin might be dangerous to touch meanwhile - but again that's about protecting people outside the tin, not the contents (and of course the danger, if any, applies to touching anything big and metal and unearthed). Aircraft can be EMP hardened and presumably are not earthed.

Some references: This was given earlier. It doesn't say earthing is required. Duncan Long is very clear about Faraday cages, says earthing is not required, and makes a lot of sense to me.

Overall, I reckon EMP shielding is an advantage for building a PSK in a tin instead of a plastic pouch. And for keeping other electrical equipment in a tin when it's not being used. Torches, GPS devices, your spare watch, I suspect simple magnetic compasses too.