19.14 Protection against electromagnetic pulse (EMP): what is known

An electromagnetic pulse from a high-altitude nuclear detonation or an extreme solar storm is an unlikely scenario. What the official guidance says, without exaggeration:

• Small devices without cables are relatively resilient, according to the U.S. Cybersecurity and Infrastructure Security Agency (CISA). The greatest risk is to whatever is plugged in and on or charging at that moment.
• Cables act like antennas: they carry the pulse's energy into the equipment. That's why a device that is unplugged and off has a better chance.
• Even if your phone survives, it's of little use if the cell network goes down. That's why radios that don't depend on infrastructure matter.
• For spare equipment, CISA suggests disconnecting power, data, and antenna cables; turning off whatever you can't disconnect; and wrapping spare electronics in aluminum foil or storing them in Faraday-type containers.

Homemade Faraday bag or box

1. Wrap the device (spare radio, handheld radio, small power bank) in an insulating material: a plastic bag or cloth.
2. Cover it with several layers of aluminum foil with no gaps, or put it in a commercial “Faraday” bag.
3. Store the whole bundle in a metal container with a tight-fitting lid (a sheet-metal can, a metal toolbox).
4. Test it: put a powered-on phone inside and call it. If it rings, the protection isn't good (although if it doesn't ring, that doesn't guarantee protection against a pulse either).