Civil Alert System Broadcast

The Civil Alert System Broadcast is a radio signal in Fallout 4. It can be received after extending the satellites at relay tower 0BB-915. The message is a pre-recorded civil alert message, warning the general public of the falling bombs.

Location
The origin of the broadcast is a ham radio in a military bunker, which can be accessed from a hatch at the base of the southwestern satellite at the Fort Hagen satellite array. Note that this is not the same bunker as the one involved in the questline of Automatron (the Fort Hagen hangar). This bunker can be accessed via the military bunker entrance, located in the base of the array dish opposite to the one that contains the Fort Hagen hangar entrance.

Behind the scenes
The narrator of this radio signal was voiced by audio director Mark Lampert.