.3 one model, when making a distress call, accepted a distress acknowledgement addressed to another vessel as acknowledgment of its own distress call;
.4 all models except one allowed users to relay distress alerts that had previously been acknowledged
.5 three models appear to retain position information manually entered into radios indefinitely, although one model lost position information when unit was powered off;
.6 three models continued transmitting distress alerts on one DSC distress channel, after an acknowledgement was received on another channel; and
.7 alarms sound on all radios each time a distress alert is sent or received, a distress acknowledgement is received, a distress relay is received, or a distress relay ackowledgement is received. The impact of alarms on shipboard and RCC watchstanders can be significant. For example, one false distress alert will sound a distress alarm on a nearby ship's radio 16 times, assuming seven relays of that alert are transmitted and acknowledged.
A copy of the report is available at http://www.navcen.uscg.gov/marcomms/gmdss/hfdsc.pdf
4 The test report concluded that none of the problems found in these tests were addressed by the recommended standards for HF DSC radios (i.e. ITU-R Rec. M.493, Digital Selective Calling System for use in the Maritime Mobile Service, and IMO resolution A.806 (19), Performance standards for shipborne MF,HF Radio Installations capable of voice communication, narrow band direct printing and digital selective calling). A review of the IEC standards 61097-9, Shipborne transmitters and receivers for use in the MF and HE bands suitable for telephony, digital selective calling (DSC) and narrow band direct printing (NBDP), 61097-8, DSC MF, MF/HF and VHF Watchkeeping Receivers, and 61097-3, Digital selective calling equipment operational and performance requirements, showed that these problems were apparently unaddressed there as well. ITU-R Rec. M.541, Operational Procedures for the Use of Digital Selective Calling (DSC) Equipment in the Maritime Mobile Service, applies to operational procedures rather than to equipment design and was therefore not considered an equipment requirement. We found that variances in equipment design and operating procedures vary widely depending on the manufacturer.
Action requested of the Sub-Committee
5 the Sub-Committee is invited to:
.1 urge other administrations to conduct similar tests of DSC equipment and submit results to COMSAR 5. This will facilitate discussions with manufacturers, government agencies and/or standards committees of the problems and possible solutions to DSC equipment and operation; and
.2 review relevant IMO DSC performance standards and determine at its next session what, if any, change need be made.
