What is true regarding HF SITOR (NBDP) under GMDSS?

In the context of GMDSS and HF SITOR (Station to Station) communications, it is important to understand how safety communications are typically managed. The correct answer highlights that safety communications should utilize Automatic Repeat reQuest (ARQ) mode when communicating with coast stations.

ARQ mode is designed to ensure reliable data transmission by allowing for the automatic retransmission of data packets that may have been lost or corrupted during transmission. This reliability is crucial for safety communications, as it helps ensure that vital information and instructions are received accurately. Therefore, using ARQ mode allows for better error correction and error detection, making it more suitable for safety-related messages, which are critical to maritime operations.

The other options do not accurately describe the appropriate procedures for distress and safety communications. Distress communications have specific protocols that focus on urgency and efficient transmission, while the different modes (FEC and SSB) are utilized for different types of broadcasts and may not necessarily apply to safety communications specifically. Understanding the role and function of ARQ in safety messages is key to adhering to GMDSS regulations and ensuring effective communication at sea.