On what frequency should a ship station call a coast station when using radiotelephony?

The correct frequency for a ship station to call a coast station when using radiotelephony is actually 2182 kHz, a frequency designated for distress and calling. This frequency is part of the global maritime distress and safety system, specifically allocated for calling ships and coast stations.

When a ship needs to contact a coast station, it is essential that it uses a frequency that is recognized and standardized for such communications, like 2182 kHz, especially in emergencies. The frequency ensures that calls can be heard by coast stations that monitor maritime communications for safety and assistance.

The other options do not provide a suitable or designated method for initiating contact. While ITU Region 2 includes several approved frequencies, it is not specific to emergency calling and could lead to confusion on which exact channel to use. Using any vacant radio channel does not guarantee that the coast station will be monitoring that specific frequency, which could result in missed communication. Calling on the appropriate ship-to-shore working frequency is applicable, but only after initial contact has been made on 2182 kHz, which serves as the primary distress and calling frequency. Hence, it is crucial for communication safety protocols to follow established guidelines, such as using 2182 kHz for initial calls.