🔍 Key Concepts

• GMDSS (Global Maritime Distress and Safety System) equipment technical standards • Frequency stability and tolerance requirements for MF-HF distress and safety radiotelephone/DSC transmitters • Which tolerance value is realistic for high-frequency (HF) radio equipment in service, not laboratory-perfect gear

💭 Think About

• Compare each option (10 Hz, 15 Hz, 20 Hz, 30 Hz) with what you know about typical HF radio operating frequencies (in kHz/MHz). Which tolerance makes practical sense as a regulatory requirement? • Think about why SOLAS and GMDSS rules set a specific maximum frequency error: what happens to distress and safety communications if the transmitter is too far off-frequency? • Ask yourself whether the tolerance is usually expressed as an absolute number of Hz or as a percentage of the assigned frequency, and what that suggests about the likely numerical size.

✅ Before You Answer

• Verify in your reference material (Radio/GMDSS section) the specified maximum frequency tolerance for MF-HF transmitters used for distress and safety under GMDSS. • Check whether the requirement is for all MF-HF GMDSS transmitters, including both radiotelephone and DSC, or just one type — the number should match the general MF-HF GMDSS standard. • Make sure you are not confusing this with VHF transmitter tolerance or older pre‑GMDSS standards, which may have different values.