A. Your GPS has been set to accept differential corrections from an external DGPS receiver and the unit is not receiving valid data. Go to the input/output or Interface Setup Page in the unit's main menu and select something other than RTCM in/NMEA out.

If your unit has a built in differential or if you are using an external differential receiver, this message indicates that you need to tune in the frequency and bit rate of the closest Coast Guard station. For a list of frequencies and coverage areas, please see www.navcen.uscg.mil.