I know you can use a third party program to maintain communication with others but it would be nice if there was in-game way to do so.
One option could be players crafting radios and whoever they make one for and give to can then transmit and recieve the signal when equipped.
Another way it could work is everyone can craft their own radio then there would be an arbitrary number of frequencies you could choose from.
I quite like the frequency idea as this could create a new dynamic - you could essentially have a police line/food delivery service/etc. Also you could scan through the channels and try to hear other people.