🔍 Key Concepts

• MSI (Maritime Safety Information) services in the GMDSS, and how HF fits in compared to NAVTEX and SAT-C • Difference between HF voice safety broadcasts and HF NBDP/SITOR safety broadcasts • What frequencies are normally assigned for routine coast station contact vs. dedicated safety-information services

💭 Think About

• First, decide which system normally carries HF MSI: is it voice, NAVTEX-like on MF, or an HF data mode similar to telex? • Think about whether coast radio calling frequencies are always the same as safety broadcast frequencies, or if safety information tends to use specially designated channels. • Ask yourself: is NAVTEX mainly MF (and some HF) text broadcasts at 518/490/4209.5 kHz, or is HF MSI more closely tied to another digital text mode?

✅ Before You Answer

• Verify which GMDSS component handles HF MSI: is it HF voice safety channels or HF NBDP/SITOR (Narrow‑Band Direct Printing) channels. • Check whether NAVTEX frequencies are MF-specific and if they are explicitly labeled for NAVTEX, not generic HF MSI. • Confirm if routine HF contact with a coast station using FEC uses the exact same frequencies as scheduled safety broadcasts, or if safety broadcasts use their own specified HF channels.