In which case can a vessel use channel 16 for a full radio check?

A vessel can use channel 16 for initial contact but should not conduct a full radio check on this channel. Channel 16 is designated as an international distress and calling frequency, primarily used for emergency situations and urgent communications. The purpose of this channel is to ensure that it remains clear for distress messages and immediate communications.

While initial contact may be permitted to quickly ascertain whether a vessel's radio equipment is functioning correctly, conducting a full radio check can disrupt emergency communications and is not in line with the intended use of channel 16. Therefore, utilizing channel 16 just for a brief contact to check the radio's operational status aligns with current protocols, while a full test should be performed on a different channel designated for routine or non-distress traffic. This guidance helps maintain the integrity of emergency channels and ensures that they are available for critical communications.