Wernher's distress signal

 is the distress signal picked up on your Pipboy shortly after you download The Pitt DLC.

It is a call for help received by a runaway slave named Werhner who has just escaped from the treacherous industrial slaving town The Pitt. Tracking down the origins of this broadcast leads you to Werhner at the north end of the map in a fight with 3 Pitt Raiders. This also triggers the quest Into the Pitt. If you are inside Operation: Anchorage's Anchorage Reclamation simulation, this radio signal is the only one available.