VHF (30–300 MHz)
Very High Frequency (VHF) is the most commonly used maritime radio frequency. A VHF radio can be found on practically all vessels, from the smallest yachts to the largest supertankers, cargo ships and cruise liners. Providing reliable transmission and reception on a line-of-sight basis using around ninety different channels (the number of approved channels differs between countries), VHF radios are used for diverse applications from local navigation and Search and Rescue (SAR) to communication with coastal stations and port authorities or harbourmasters.
All VHF users must be licenced by an approved national body and are compelled to switch to channel 16, which is reserved for maintaining a watch for international distress and safety and calling, when the radio is not being used. Under GMDSS, all SOLAS vessels must be capable of transmitting and receiving distress signal between ship to ship by two methods – VHF channel 13 and DSC.