Which channel is designated for secondary calling and general purpose calling?

Channel 9 is designated for secondary calling and general purpose calling on marine VHF radios. This channel is particularly important as it serves as a calling channel for ship-to-ship and ship-to-shore communication in non-emergency situations. It allows vessels to communicate with each other before switching to a working channel for further discussion and coordination. This designation is crucial for maintaining order on the primary channels and ensuring that emergency communications remain clear and effective on designated channels, such as Channel 16, which is reserved for distress and safety calls.

The other channels listed have different specific purposes; for instance, Channel 6 is often used for intership safety communications, Channel 70 is reserved for Digital Selective Calling (DSC), and Channel 22A is primarily used for non-commercial purposes in certain regions. Thus, Channel 9's recognition as a secondary calling channel makes it an essential tool for effective communication in boating safety practices.