The VHF marine radio operates on a frequency band from 156 to 174MHz. These marine radios are transceivers capable of both transmitting and receiving. Most transceivers operate simplex where the radio is either transmitting or receiving but not both at the same time. A "push to talk" button on the microphone controls the transmit/receive function. Coast Guard regulations only require commercial boats and boats over 20 meters to be equipped with a VHF marine radio, but most sailboats and charter boats are also VHF equipped.
Channel Monitoring Procedure
All VHF-equipped boats must monitor channel 9 or 16 anytime the transceiver is on but not in use. This includes boats that are VHF-equipped even if it is not required. Each VHF channel has a specific use. Some of the channels are reserved for specific geographical areas. Dredges, barges and floating plants are also required to monitor channel 13 (channel 67 in the lower Mississippi river).
Non-Emergency Call Procedure
There is a standard procedure for the non-emergency use of a VHF marine radio. It is designed to make the communications as efficient as possible. When calling another boat or a marina, the procedure is as follows:
Call the boat or marina on channel 9 or 16.
Repeat the station you are calling three times.
Follow with "this is" and your boat's name and radio call sign.
Follow with "Over."
For example: "Marlin Marina, Marlin Marina, Marlin Marina. This is the Four Bells, FL O12090. Over." The responding radio operator should respond the same way.
Distress Transmission Procedure
When sending a distress communication, speak clearly, calmly and slowly. The transmission procedure is as follows:
"MAYDAY -- MAYDAY -- MAYDAY, this is (provide your boat's name)."
Give your location and the nature of your distress.
State the number of people on the boat and information on any injuries.
Describe the seaworthiness of the boat, its type and description.
End the communication with "Over."
Repeat this call until receiving a response.