The signal consists of a distress signal from a group of individuals who were hiding in an abandoned bunker, surrounded by unidentified creatures. The bunker is straight east of radio tower 3SM-U81 on the western bank of the river. The hatch down into the bunker is hidden in the bushes behind an iron barrel in a run-down campsite. There are two nearby campsites. The correct one has a picnic bench and a cooking station, the other one has some dead settlers and traders.
At higher levels, a mirelurk queen may spawn near the entrance of the bunker. Inside the bunker are two skeletons, a number of food coolers, a few first aid kits, a wooden crate, a hunting rifle, a suitcase, and the ham radio broadcasting the signal. The Sole Survivor can shut the radio off to end the broadcast.
The Greenbriar radio signal appears only in Fallout 4.
- PC Playstation 4 After doing the above steps, the radio signal keeps transmitting.[verified]