What is the primary frequency used for distress communications under the Global Maritime Distress and Safety System (GMDSS)?

The primary frequency used for distress communications under the Global Maritime Distress and Safety System (GMDSS) is 156.800 MHz. This frequency is specifically designated for maritime VHF communications and serves as the international calling and distress frequency. It allows for distress alerts to be sent by vessels in situations where they are in need of immediate assistance, ensuring that they can communicate effectively with nearby vessels and shore stations.

The 156.800 MHz frequency operates within the VHF band and is capable of covering a range suitable for maritime operations, facilitating quick and reliable communication in emergencies. Transitioning to other frequencies or channels is typically done based on specific communication needs, such as routine or non-distress messages, but 156.800 MHz remains the critical frequency for GMDSS distress alerts.

The other frequencies mentioned have specific functions but do not serve this primary distress purpose within the GMDSS framework. For instance, while 406 MHz is associated with satellite-based distress beacons and 121.5 MHz was historically used for aviation emergencies and is still used in some search and rescue operations, they are not the designated primary frequency for maritime distress communications under the GMDSS. 27.255 MHz is a frequency often used for personal and recreational communication