Hmm... try this trigger out to see if it has the desired effect:
TriggerRadius: 0,0
Condition: none (repeatedly)
Condition Field: "_x hasweapon ""
BAS Radio""" count (units
group) > 0
OnActivation Field: 1 setradiomsg "Call Airstrike"; 2 setradiomsg "Helicopter Extraction"
OnDeactivaton Field: 1 setradomsg "null"; 2 setradiomsg "null"
Where
BAS Radio is the weapon name for the BAS Radio, and
group is the group the player is in.
You'll also want to change the radio message to the exact message you want
What that'll do is when your guy with the radio dies, the trigger will
deactivate, turning off your radio messages. Then if another guy in your group picks up the radio, the trigger will actiavte again, and the radio messages will be added in.
Anyway, that's the theory ;D
Try it and see if it solves your problem...