mergency ction essage. Coded messages broadcast periodically by USSTRATCOM ground stations. The code used is changed daily and has never been completely broken, despite the fact that hundreds if not thousands of hobbyists and others around the world can listen to EAM broadcasts every day on shortwave. EAM transmissions can be heard on 311.000 MHz by anyone within range of a ground station. They are reportedly preceded by a warbling tone.