Greenbriar radio signal

The Greenbriar radio signal is a radio station in the Commonwealth in Fallout 4. It can be picked up after extending the satellites at radio tower 3SM-U81.

Characteristics
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 camp site. There are two nearby camp sites. The correct one has a picnic bench, the other one has some dead settlers/traders.

Once you go near the bunker, a Mirelurk Queen will spawn near you.

Inside are two skeletons, a number of food coolers, a few first aid kits, a wooden crate, a short hunting rifle, a suitcase and the ham radio broadcasting the signal.

Behind the scenes
The Greenbrier Resort, in West Virginia, was home to the "Continuity of government" bunker designated for members of congress, and their families.