Tom Kinahan, N1CPE, writes on the Wellesley ARS mailing list:
Just a reminder that tonight at 10 PM EST, there will be a DoD broadcast on 60 meters channel 1, 5330.5 khz upper sideband. This broadcast from two Department of Defense stations on the east and west coasts are a test and demonstration of DoD to amateur interoperability. For the past two weeks, MARS stations operating with their DoD callsigns have been talking to Amateur stations getting situation awareness type reports using 60 meters.
At 10 PM, the message will likely be in voice and digital modes. The message will probably request listeners to report how they heard the two broadcast stations.