OP doesn't describe the mod too well imo, had to look at the code myself to figure it out completely. Could've just skipped over a word or two though.
Neat mod.
I'd make the current radio channel store on the client though, because I figure it may get annoying in a TDM or something if you have to constantly switch to a channel when you spawn. Or maybe some command that'll set an automatic channel. Just a thought.
Server hosters may benefit from the radio messages echoing into the console, too.