So I finally got Carl to pick up the radio calls and unlocked him today. So how does his hero trait actually work? I was trying him out and didn't really understand. I know it might not always get activated, but what events precipitate its activation? Like how Negans survival instinct doesn't work until in the red. Does he have to be the leader for it to work on himself, like Governor? Is he useful in the distance or just better in general for difficult missions?