The Emergency Action Message you heard may have been from the 121st ARW Command Post at Rickenbacker ANGB, or it may have been from an aircraft, likely an airborne command post. Sometimes you can kinda tell by characteristics of the transmission. The 121st ARW has KC-135s, which do have a wartime mission, which means their CP has an emergency actions controller who can receive EAMs & Force Direction Messages & retransmit them as-necessary, ID'ing with a tactical callword or basic ID like "Rickenbacker" or "Command Post." At other bases that have combat-coded aircraft on some semblance of alert, that's done routinely, but at others, it's just occasional or during some sort of exercise.
Airborne command posts, as part of their mission and frequent training, generate & broadcast or re-broadcast EAMs & FDMs frequently over the spectrum.