There was some nihilist creed that convinced people to destroy technological society and attempt to kill off the few survivors who were not affected. The story line centers on their survival and research. It took place in the USA.
This is the "Daybreak" series of novels by John Barnes, starting with Directive 51 (very recent -- 2010).
The followers of Daybreak bring about the end of technological civilization using nanotechnology and engineered viruses that break down rubber, plastic, petroleum fuels and metal conductors. Some airplane combustion engines remain, but need to be carefully maintained and decontaminated. Navy ships at sea survive for a while, but gradually start falling victim to Daybreak.
Nuclear "pure fusion" detonations from pre-placed weapons in key cities are used; later, pure fusion weapons are launched from a moon base, targeting (as you note) radio transmissions from survivors.
In the second book, we start to find out that Daybreak
appears to be an emergent property of a complex system... also, taking the meme "thought virus" concept to heart, if you think about Daybreak too much, you become susceptible to it, and can also be mind controlled by other Daybreak followers. It starts to get screwy, I didn't feel compelled to read the third book.