Coast Guard warns of problems with VHF DSC distress alerts

USCGstripeAs the Rescue 21 marine radio network  becomes operational throughout the U.S., Coast Guard rescue centers can now receive instant distress alerts from commonly used DSC-capable VHF marine radios. However, approximately 90 percent  of VHF DSC distress alerts received by the Coast Guard do not contain position information, and approximately 60 percent do not contain a registered identity. The Coast Guard cannot effectively respond to a DSC distress alert sent from such a radio.  

This means that search and rescue efforts may normally be suspended when:

  • no communications with the distressed vessel can be established,
  • no further information or means of contacting the vessel can be obtained from other sources, and
  • no position information is known.

The Coast Guard has issued a marine safety alert that advises:

FIRST Obtain a Maritime Maritime Mobile Installation Identity (MMSI) and enter it into your radio. MMSI numbers are issued by the Federal Communications Commission if your vessel otherwise requires a station license, or BOATUS, (, Sea Tow (, or the U.S. Power Squadrons ( Ensure any information originally provided is updated as changes occur. FCC regulations require that DSC-equipped radios "use MMSIs assigned by the Commission or its designees" (47 CFR 80.103(b)).  

THEN Interconnect your radio to a GPS receiver using a two-wire NMEA 0183 interface on all DSC-equipped marine radios and on most GPS receivers.  Instructions should be provided in the radio and GPS operators manual.  Further information is provided and will be routinely updated in

September 2, 2011

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