>> “I talked to some physicists at work (real physicists who work on DARPA and defense projects not physics teachers). Their opinion was that the threat of EMP is greatly exaggerated and it would take a massive attack to completely blackout the US.” <<
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True. - A much larger attack than anyone but possibly Russia could ever mount.
If NK tries to use a homemade EMP device it will be detonated above the large population centers on the east or west coast. It would be much less effective over the center of CONUS.
As someone here once said.... beans, bullets and pullets. We have all three :-)