solar flares, and EMP's
If a solar flare is bad enough, it can do quiet a bit of damage to electronics. In the event of a nuclear war, the problem with EMP's will knock our way of life back to the 1800's
Nothing with a solid state transistor will function again--all fried. that means no communication, no computers, no radios, no nothing. Back to pre telegraph days.
I guess someone could open up Pony Express again. I do believe that tube type radio equipment would be ok, but not much of that around except in older Ham radio, and short wave stuff.
Anything else that survives would have to be in a Faraday cage to survive the pulse of energy from a nuclear device.
Hope this info helps.