An Iowa National Guard exercise in late April for the first time saw the use of a common digital mode among military, Amateur Radio, and Military Auxiliary Radio System (MARS) participants on the 60-meter interoperability channels. Military standard communications mode MilStd 188-110 was pressed into service to pass digital messages during Exercise Stable Mercury. Because Amateur Radio operators on 60 meters are not symbol-rate limited, all parties were able to use a common digital mode at a higher data rate to pass traffic. For RTTY or digital operation, radio amateurs must transmit on the center frequency of 60-meter channels with a bandwidth no wider than that of a USB signal.
The April 23 – 24 communications exercise involved the deployment of Guard units across numerous incident command posts to operate cooperatively with federal, state, local, and auxiliary units. The scenario for the drill was based on an actual severe weather event that occurred 20 years ago, and the April exercise used radar feeds and storm spotter reports taken from the June 29, 1998, Iowa Derecho to inform this training event. A derecho is an extended straight-line windstorm associated with a fast-moving cluster of severe thunderstorms.