Take notes from this Marshall Project post: you’ll want to retool your radio too come the Apocalypse:
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Prisoners face numerous restrictions when communicating with one another or the outside world. But where there is a rule, there is often a workaround. At Pelican Bay State Prison in Northern California, inmates have yelled to one another through drainpipes under their cells; inmates in Texas talk through cans connected with twine; and in facilities throughout the country, little paper notes — known as “kites” — are literally handed off. As technology has developed, so have the communication methods; cell phones and iPods are regularly smuggled to inmates by visitors and guards. And occasionally, the technology is already inside the prison. Some inmates have learned how to transform their radios into devices that allow them to talk to each other and even eavesdrop on guards.
Once an inmate has purchased an analog radio from the prison commissary (they usually cost less than $30), he can open it up and pull apart a coil, which changes the range of frequency that the radio can access.