There's a few nationwide pager networks out there; they're quite easy to build without the task of making communication two way. Just set up a hundred or so wat

There's a few nationwide pager networks out there; they're quite easy to build without the task of making communication two way. Just set up a hundred or so watt UHF transmitter at an antenna farm, feed it with PSK or FSK from a satellite receiver, and boom! You just covered most of a large city.