Question 1-15C1

Receiving vessel traffic lists from high seas shore stations typically involves long-distance communication over high frequencies (HF). * **SSB (Single Sideband)** is the standard modulation mode used for voice and digital data over long distances on HF marine bands. It is efficient in bandwidth and power, making it ideal for communication with stations far out at sea or shore stations covering large areas. * **FEC (Forward Error Correction)** is a crucial technique used within digital transmission modes to ensure reliable reception of text and data over noisy HF channels. It adds redundant data to the transmission, allowing the receiver to detect and correct errors without needing retransmissions. Modes like NAVTEX and SITOR-B (AMTOR-FEC), which transmit marine safety information and traffic lists, utilize FEC for robust communication. Therefore, you would select SSB on your receiver, and the data mode being used (which relies on FEC) would then be decoded. **Why other options are incorrect:** * **A) AM and VHF-FM:** AM is less efficient than SSB for HF and rarely used for modern data. VHF-FM is limited to line-of-sight communication, typically less than 30 nautical miles, making it unsuitable for "high seas" range. * **B) ARQ and FEC:** While both are error control techniques, they are not primary RF modulation "modes" that you would select directly on a radio receiver. They are components of digital transmission protocols that run on an underlying RF mode like SSB. * **C) VHF-FM and SSB:** As explained, VHF-FM is incorrect due to its limited range for high seas communication.