Signal Yankee Bravo is a radio transmission just south of Canterbury Commons, southwest of robot repair center, and north of Corvega factory, which is activated by a switch on a transformer there. Although identified as "Signal Yankee Bravo", it actually broadcasts the sound of labored, heavy breathing.
Just west-southwest of the tower, at the base of the drop-off, is a sewer grate to a drainage chamber. On entering, the door to the right leads to level dependent feral ghouls hovering around a ham radio, making them responsible for the broadcast. The ghoul sounds can still be heard in the signal even after the ghouls are killed, even if you turn the radio off ("click"), then back on (you have to select the station on your Pip-Boy again).
There is also a large hole in the wall to the left from the entrance that leads to a small cavern with several feral ghouls or glowing ones (also depending on level). There is nothing of note in this room except a toolbox to the left of the entrance, near a light, and a very strongly radioactive junk pile in the far corner.
A copy of Grognak the Barbarian, on the same metal shelf underneath the ham radio, the signal of the Yankee Bravo radio broadcast.
- You may also encounter heavy Enclave resistance when coming from the southwest of the radio tower. There is an outpost there with multiple turrets under a defense system called the Experimental Rho ID chip. The ID is given to an Enclave officer for experimentation on the technology, it allows the grid to ignore his existence thus not firing upon him.