URCP

The Uncomplicated Radio Callsign Protocol works like this: You put your UD profile number in front of all your broadcasts, then in your UD profile, you put some stuff about what group you're broadcasting for, anything that a radio listener might want to know that won't change. Coordinates are optional, so no security risk there.

The point

The point is best demonstrated with an example:
Say you're in a mall siege. You hear these, all within a few minutes:
28.64:NE corner is under attack, barricades coming down.
28.64:PK in NE corner, DieDie(341122) killed Victim.

Under URCP, you hear this:
28.64:341122: NE corner is under attack, barricades coming down.
28.64:534566: PK in NE corner, DieDie(341122) killed Victim.
So now you know that DieDie was broadcasting the first message. Later I'll come up with a better example.