1) fire the radio message with this syntax:
leader myGroup sideRadio "myRadioMessage"; leader myGroup sideChat "bla, bla, bla, etc"
This will make the message come from the current leader, no matter who was leader at the start of the mission. Delete the sideRadio thing if you only use text and no sound. You also have to name the group with:
myGroup = GROUP this
in the init line of the original commander.
2) enableRadio true/false toggles the radio on and off.