IEC 61097-9:2025

IEC 61097-9 ®
Edition 2.0 2025-06
INTERNATIONAL
STANDARD
Global maritime distress and safety system (GMDSS) –
Part 9: Shipborne transmitters and receivers for use in the MF and HF bands
suitable for telephony, digital selective calling (DSC) and reception of maritime
safety information and search and rescue related information – Operational and
performance requirements, test methods and required test results
ICS 33.060.20; 47.020.70 ISBN 978-2-8327-0466-0

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– 2 – IEC 61097-9:2025 © IEC 2025
CONTENTS
FOREWORD . 13
1 Scope . 15
2 Normative references. 15
3 Terms and definitions and abbreviated terms . 16
3.1 Terms and definitions . 16
3.2 Abbreviated terms . 19
4 Performance requirements . 20
4.1 General . 20
4.2 Power supplies . 21
4.3 Control and indicators . 21
4.3.1 Operational controls . 21
4.3.2 Transmitter controls . 21
4.3.3 Receiver controls . 22
4.3.4 DSC controls and indicators . 22
4.4 Interfaces . 22
4.5 Distress controls . 25
4.6 Control panel priority . 26
4.7 Labels . 26
4.8 Safety precautions . 26
4.9 Manuals . 26
4.10 Software maintenance . 27
4.11 Bridge alert management (BAM) . 27
5 Transmitter . 27
5.1 Frequencies and classes of emission . 27
5.2 Frequency accuracy and stability . 28
5.3 Output power . 28
5.4 Transmitter input . 28
5.5 Permissible warming-up period . 29
5.6 Continuous operation . 29
5.7 Safety precautions . 29
5.8 Power of out of band emissions . 29
5.9 Power of conducted spurious emissions . 29
5.10 Residual hum and noise . 30
5.11 Residual frequency modulation on DSC . 30
5.12 Modulation rate of DSC . 30
6 Receiver . 30
6.1 Frequencies and classes of emission . 30
6.2 Frequency tolerance and accuracy . 31
6.3 Usable sensitivity . 31
6.4 Receiver output . 31
6.5 Permissible warming-up period . 31
6.6 Immunity to interference . 31
6.7 Antenna static protection . 31
6.8 Noise reducer . 32
6.9 Audiofrequency gain control and automatic gain control (AGC) . 32
6.10 Unwanted frequency modulation . 32

6.11 Audiofrequency pass band . 32
6.12 Conducted spurious emissions into the antenna . 32
7 Digital selective calling facility . 32
7.1 DSC capabilities . 32
7.2 Distress message storage . 33
7.3 DSC characteristics . 33
8 Facility for the reception of MSI . 33
8.1 General . 33
8.2 Controls and indicators . 33
8.3 Receiver . 34
8.4 Display device and printer . 35
8.5 Storage . 35
8.5.1 Non-volatile message memory . 35
8.5.2 Message identifications . 36
8.5.3 Programmable control memories . 36
8.6 Alert . 36
8.7 Test facilities . 36
8.8 Interfaces . 37
9 Automatic connection system . 37
9.1 General . 37
9.2 Transmitter . 37
9.3 Receiver . 37
10 Test methods and required test results . 38
10.1 Test conditions . 38
10.1.1 Normal and extreme test conditions . 38
10.1.2 Procedure for tests at extreme temperatures . 38
10.1.3 Test power source . 38
10.2 General requirements . 38
10.3 General conditions of measurement . 39
10.3.1 Arrangements for test signals applied to the receiver input . 39
10.3.2 Normal test signals applied to the receiver input . 39
10.3.3 Arrangements for test signals applied to the transmitter input . 39
10.3.4 Normal test signals applied to the transmitter input . 39
10.3.5 Artificial antennas . 39
10.3.6 Testing frequencies . 39
10.3.7 Bit error rate testing . 40
10.3.8 Measurement uncertainty . 40
10.4 Tests by inspection . 40
10.4.1 General . 40
10.4.2 Power supplies . 41
10.4.3 Operational controls . 41
10.4.4 Transmitter controls . 42
10.4.5 Receiver controls . 42
10.4.6 DSC controls and indicators . 42
10.4.7 Interfaces . 43
10.4.8 Distress controls . 44
10.4.9 Control panel priority . 45
10.4.10 Labels . 45

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10.4.11 Safety precautions . 45
10.4.12 Software maintenance . 46
10.4.13 DSC capabilities . 46
10.4.14 Distress message storage . 46
11 Transmitter . 47
11.1 Frequencies and classes of emission . 47
11.2 Frequency error . 47
11.2.1 General . 47
11.2.2 Test methods . 47
11.2.3 Required results . 47
11.3 Output power and intermodulation products . 47
11.3.1 General . 47
11.3.2 Test methods . 48
11.3.3 Required results . 48
11.4 Unwanted frequency modulation . 49
11.4.1 General . 49
11.4.2 Test methods . 49
11.4.3 Required results . 50
11.5 Sensitivity of the microphone . 50
11.5.1 General . 50
11.5.2 Test methods . 50
11.5.3 Required results . 50
11.6 Automatic level control and/or limiter for SSB telephony . 50
11.6.1 General . 50
11.6.2 Test methods . 50
11.6.3 Required results . 51
11.7 Audiofrequency response using SSB telephony . 51
11.7.1 General . 51
11.7.2 Test methods . 52
11.7.3 Required results . 52
11.8 Power of out-of-band emissions using SSB telephony . 52
11.8.1 General . 52
11.8.2 Test methods . 53
11.8.3 Required results . 53
11.9 Power of conducted spurious emissions of SSB telephony . 53
11.9.1 General . 53
11.9.2 Test methods . 53
11.9.3 Required results . 53
11.10 Residual hum and noise power using telephony . 53
11.10.1 General . 53
11.10.2 Test methods . 54
11.10.3 Required results . 54
11.11 Residual frequency modulation on DSC . 54
11.11.1 General . 54
11.11.2 Test methods . 54
11.11.3 Required results . 54
11.12 Carrier suppression . 55
11.12.1 General . 55
11.12.2 Test methods . 55

11.12.3 Required results . 55
11.13 Continuous operation . 55
11.13.1 General . 55
11.13.2 Test methods . 55
11.13.3 Required results . 55
11.14 Protection of the transmitter . 56
11.14.1 General . 56
11.14.2 Test methods . 56
11.14.3 Required results . 56
11.15 Standing wave ratio control . 56
11.15.1 General . 56
11.15.2 Test methods . 56
11.15.3 Required results . 56
11.16 Residual RF noise power . 57
11.16.1 General . 57
11.16.2 Test methods . 57
11.16.3 Required results . 57
11.17 Modulation rate of DSC . 57
11.17.1 General . 57
11.17.2 Test methods . 57
11.17.3 Required results . 58
12 Audio receiver . 58
12.1 Audiofrequency output levels . 58
12.1.1 General . 58
12.1.2 Test methods . 58
12.1.3 Required results . 58
12.2 Frequency error . 58
12.2.1 General . 58
12.2.2 Test methods . 58
12.2.3 Required results . 59
12.3 Unwanted frequency modulation . 59
12.3.1 General . 59
12.3.2 Test methods . 59
12.3.3 Required results . 59
12.4 Audiofrequency pass band . 59
12.4.1 General . 59
12.4.2 Test methods . 59
12.4.3 Required results . 60
12.5 Maximum usable sensitivity . 60
12.5.1 General . 60
12.5.2 Test methods . 60
12.5.3 Required results . 60
12.6 Harmonic content in output . 61
12.6.1 General . 61
12.6.2 Test methods . 61
12.6.3 Required results . 61
12.7 Adjacent channel selectivity . 61
12.7.1 General . 61
12.7.2 Test methods . 61

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12.7.3 Required results . 62
12.8 Blocking . 62
12.8.1 General . 62
12.8.2 Test methods . 62
12.8.3 Required results . 63
12.9 Cross-modulation . 63
12.9.1 General . 63
12.9.2 Test methods . 63
12.9.3 Required results . 63
12.10 Intermodulation . 63
12.10.1 General . 63
12.10.2 Test methods . 64
12.10.3 Required results . 64
12.11 Spurious response rejection ratio . 64
12.11.1 General . 64
12.11.2 Test methods . 64
12.11.3 Required results . 65
12.12 Audiofrequency intermodulation . 65
12.12.1 General . 65
12.12.2 Test methods . 66
12.12.3 Required results . 66
12.13 Conducted spurious emissions into the antenna . 66
12.13.1 General . 66
12.13.2 Test methods . 66
12.13.3 Required results . 66
12.14 Internally generated spurious signals . 66
12.14.1 General . 66
12.14.2 Test methods . 66
12.14.3 Required results . 67
12.15 Improvement in signal-to-noise ratio with AGC . 67
12.15.1 General . 67
12.15.2 Test methods . 67
12.15.3 Required results . 67
12.16 AGC range . 67
12.16.1 General . 67
12.16.2 Test methods . 67
12.16.3 Required results . 67
12.17 AGC time constants (attack and recovery time) . 68
12.17.1 General . 68
12.17.2 Test methods . 68
12.17.3 Required results . 68
12.18 Reciprocal mixing . 68
12.18.1 General . 68
12.18.2 Test methods . 68
12.18.3 Required results . 69
12.19 Protection of input circuits . 69
12.19.1 General . 69
12.19.2 Test methods . 69
12.19.3 Required results . 69

13 DSC receiver . 69
13.1 DSC test signals . 69
13.1.1 References to standard DSC signals . 69
13.1.2 Standard test signal No. 1 (STS-1) . 69
13.1.3 Standard test signal No. 2 (STS-2) . 69
13.1.4 Symbol error rate at the DSC receiver . 69
13.2 Maximum usable sensitivity . 70
13.2.1 General . 70
13.2.2 Test methods . 70
13.2.3 Required results . 70
13.3 Adjacent channel selectivity . 70
13.3.1 General . 70
13.3.2 Test methods . 70
13.3.3 Required results . 71
13.4 Co-channel rejection . 71
13.4.1 General . 71
13.4.2 Test methods . 71
13.4.3 Required results . 71
13.5 RF intermodulation response . 71
13.5.1 General . 71
13.5.2 Test methods . 71
13.5.3 Required results . 72
13.6 Spurious response rejection . 72
13.6.1 General . 72
13.6.2 Test methods . 72
13.6.3 Required results . 73
13.7 Blocking immunity . 73
13.7.1 General . 73
13.7.2 Test methods . 73
13.7.3 Required results . 73
13.8 Dynamic range . 73
13.8.1 General . 73
13.8.2 Test methods . 74
13.8.3 Required results . 74
13.9 Conducted spurious emissions into the antenna . 74
13.9.1 General . 74
13.9.2 Test methods . 74
13.9.3 Required results . 74
13.10 Protection of receiver antenna input circuits . 74
13.10.1 General . 74
13.10.2 Test methods . 75
13.10.3 Required results . 75
13.11 Stop/start of scanning efficiency . 75
13.11.1 General . 75
13.11.2 Test methods . 75
13.11.3 Required results . 75
14 MSI receiver . 75
15 Automatic connection system . 75
Annex A (normative) DSC operation . 76

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A.1 General . 76
A.2 Naming convention of DSC message types . 76
A.3 Test setup . 77
A.3.1 General . 77
A.3.2 Test methods . 78
A.4 Non-automated features . 78
A.4.1 Non-automated features requirements . 78
A.4.2 Non-automated features tests . 83
A.5 Standby . 97
A.5.1 Standby requirements . 97
A.5.2 Standby tests . 98
A.6 Sending distress automated procedure . 99
A.6.1 Sending distress automated procedure requirements . 99
A.6.2 Sending distress automated procedure tests . 105
A.7 Received distress automated procedure . 113
A.7.1 Received distress automated procedure requirements . 113
A.7.2 Received distress automated procedure tests . 116
A.8 Sending non-distress automated procedure . 126
A.8.1 Sending non-distress automated procedure requirements . 126
A.8.2 Sending non-distress automated procedure tests . 129
A.9 Received non-distress automated procedure . 133
A.9.1 Received non-distress automated procedure requirements . 133
A.9.2 Received non-distress automated procedure tests . 136
A.10 Communications automated procedure . 140
A.10.1 Communications automated procedure requirements . 140
A.10.2 Communications automated procedure tests . 141
A.11 Multiple automated procedures and parallel event handling . 141
A.11.1 Multiple automated procedures and parallel event handling
requirements . 141
A.11.2 Multiple automated procedures and parallel event handling tests . 142
A.12 Error handling in the automated procedures . 152
A.12.1 Error handling requirements . 152
A.12.2 Error handling tests . 154
Annex B (normative) DSC message composition . 158
B.1 Default values . 158
B.2 The default DROBOSE . 159
B.3 Allowable non-distress DSC message parameters . 159
Annex C (normative) Radius-centre point conversion and rounding algorithm . 160
C.1 Radius-centre point conversion . 160
C.2 Rounding . 161
C.3 Special cases for either form of area data entry . 161
Annex D (normative) Audible annunciation and BAM alert signalling . 162
D.1 Audible alert specifications . 162
D.2 Alerting with critical errors . 164
D.3 Default audible alert sounds . 164
Annex E (normative) MSI receiver for HF NBDP, test methods and required test
results . 166
E.1 General . 166
E.2 Test conditions . 166

E.2.1 Standard test signal . 166
E.2.2 Standard test file . 167
E.2.3 Arrangement for test signal applied to the receiver input . 167
E.2.4 Artificial antenna . 167
E.2.5 Character error rate . 167
E.3 Serial interface tests . 167
E.3.1 INS interface performance tests . 167
E.3.2 Printer tests . 168
E.4 General and signal processing tests .
...