If the vessel is experiencing atmospheric interference with NAVTEX broadcasts, especially in the tropics, the GMDSS operator should:

Correct Answer: Option C — Select one of the 8 HF MSI frequencies and set-up the transceiver in FEC TELEX mode.

High-frequency (HF) bands are utilized for long-range MSI when MF/NAVTEX coverage is insufficient or degraded by atmospheric noise. There are eight designated HF MSI frequencies globally. The operator must set the transceiver to FEC mode to receive these one-way broadcasts, which are designed for wide-area dissemination.