GMDSS GOC Worksheet for HF Distress Frequencies
6312 kHz and 12290 kHz are both GMDSS distress frequencies. Put them together in one row and you've mixed two bands. A good recall check asks you to name the band and the mode for each number.
This worksheet is for General Operator's Certificate (GOC) trainees studying the Global Maritime Distress and Safety System (GMDSS). Use these fictional high-frequency (HF) readouts as a paper exercise or as a reference-table check in a classroom simulator.
Five HF distress frequency pairs
DSC stands for digital selective calling. The DSC column gives the frequency for digital distress and safety calling, and the radiotelephony column gives the frequency for voice distress and safety traffic. Each row groups the two frequencies for one band. IMO MSC.1/Circ.1658, annex · ITU Radio Regulations, 2024 edition, Appendix 15, Table 15-1
| Band | DSC (kHz) | Radiotelephony (kHz) |
|---|---|---|
| HF4 | 4207.5 | 4125 |
| HF6 | 6312 | 6215 |
| HF8 | 8414.5 | 8291 |
| HF12 | 12577 | 12290 |
| HF16 | 16804.5 | 16420 |
Check a mixed-band readout
Suppose an HF6 practice row says DSC 6.312 MHz and voice 12290 kHz. The band label is fixed. Check the two fields separately.
- Put both values in kHz. Multiply 6.312 by 1000 to get 6312 kHz. The voice field is already in kHz. BIPM SI prefixes
- Compare each number with its column in the HF6 row. The DSC field matches. The voice field shows the HF12 voice frequency, so the error is the band of that entry.
- Write the corrected HF6 row on paper. DSC 6312 kHz, voice 6215 kHz.
Mark up five practice rows
For each row, keep the stated band and write both frequencies in kHz. Fill any blank and explain any change beyond converting the units. One row already has the correct frequencies. Try the exercise with the reference table covered, then use it to check your work.
| Row | Band | DSC field | Voice field |
|---|---|---|---|
| A | HF4 | 4125 kHz | 4207.5 kHz |
| B | HF8 | 8414.5 kHz | 16420 kHz |
| C | HF16 | 16.8045 MHz | 16420.0 kHz |
| D | HF6 | 6312 kHz | 6.251 MHz |
| E | HF12 | Blank | 12290 kHz |
Worked answers
- A · DSC 4207.5 kHz, voice 4125 kHz. Both numbers belong to HF4. The voice frequency was in the DSC field and the DSC frequency was in the voice field.
- B · DSC 8414.5 kHz, voice 8291 kHz. The DSC value matches HF8. The voice entry belongs to HF16.
- C · DSC 16804.5 kHz, voice 16420 kHz. 16.8045 MHz converts to 16804.5 kHz. The voice value, 16420.0 kHz, already matches HF16.
- D · DSC 6312 kHz, voice 6215 kHz. 6.251 MHz converts to 6251 kHz. The last two digits are reversed in the MHz display. The correct value is 6.215 MHz.
- E · DSC 12577 kHz, voice 12290 kHz. 12290 kHz is the HF12 voice frequency. Its partner in the DSC column is 12577 kHz.
If you missed a pair, try recalling it both ways in a later session. Given the DSC value, name the voice value and band. Given the voice value, name the DSC value and band. Recalling the answer before you check it and spacing your reviews over several sessions can help you remember the pairs longer. Retrieval practice study · Spacing study
The 24 English HF distress frequency flashcards by Open Study Contributor cover both directions and include more readout checks.
For the wider syllabus and worked questions on VHF, MF, and other radio concepts, see the general GMDSS GOC revision guide.
This independent, unofficial worksheet was researched and drafted with AI assistance. It uses public IMO and ITU references and an AI-generated illustration.